Table of contents

To determine the effect of cross-linking in polymer binders on gravimetric capacity and retention in charge/discharge cycling of lithium-ion batteries containing silicon anodes, polymers with a varied chemiophysical characters have been studied as electrode binders. Here we report the utilization of cross-linked polyborosiloxanes and a boron-modified organosilicate as binders for nanoparticulate silicon-containing anodes for lithium-ion batteries. We show that highly cross-linked binders enable a large degree of capacity to be accessed and that capacity retention is greater when the electrodes are cycled in half cells. More extensive analysis of the boron-modified organosilicate is further explored.

In this paper, the pristine and hydrofluoric acid (HF) modified MgO porous fibers are investigated as an immobilizing agent for LiF-LiCl-LiBr molten salt electrolytes. The electrochemical performance of as prepared thermal batteries is evaluated. Compared to pristine MgO porous fibers, significantly reduced electrolyte leakages and the highest ionic conductivity (1.427 S·cm^-1) of the electrolyte are obtained when the MgO porous fiber is modified by using 40 mol% (of the MgO fiber) HF solution. Accordingly, the discharge capacity of 456 mAh·g^-1 at 1.0 V voltage plateau is obtained. At the same time, the influence of HF modification on the ion transportation is discussed, based on element diffusion and properties of newly formed MgF₂. It can be concluded that HF modification is a promising method to improve the performance of MgO porous fibers used as an immobilizing agent for the molten salt electrolyte in thermal batteries.

Despite having the capability of achieving high energy densities, low cost and environment friendliness, the rechargeable Lithium-Sulfur (Li-S) batteries still suffer from many inherent disadvantages such as poor electrical conductivity and polysulfide shuttle effect. To address these issues, we have successfully designed a freestanding graphitic porous carbon nanofibers piece, which can accommodate high sulfur loading up to 70%, and be served as the polysulfides reservoirs to alleviate shuttle effect. Furthermore, the 3D graphitic porous carbon nanofibers can facilitate the diffusion and transport of electrons and ions owing to the superior electrical conductivity and interconnected porous nature resulting in improved electrochemical performance. The obtained sulfur and porous carbon nanofibers (S@P-CNFs) composite cathode shows high rate capability of 670 mAh g⁻¹ at 2 C and excellent cycling stability of 720 mAh g⁻¹ after 200 cycles at 1C.

A carbon-polytetrahydrofuran double-coated Na₃V₂(PO₄)₂F₃ composite has been prepared by synthesis of carbon coated Na₃V₂(PO₄)₂F₃ followed by in situ polymerization of tetrahydrofuran on its surface. Thermal gravimetry analysis, Fourier transform infrared spectrum and high-resolution transmission electron microscopy are used to confirm the encapsulation structure of the inner carbon layer and the outer polytetrahydrofuran layer on Na₃V₂(PO₄)₂F₃. Electrochemical tests show that electrochemical performance and electronic conductivity of the composite are significantly improved due to the polytetrahydrofuran coating, and a reversible capacity of 123.6 mAh g⁻¹ at a moderate 2 C rate is obtained with a high capacity retention of 98.5% after 250 cycles. Even at an extremely high rate of 10 C the discharge capacity is still as high as 115.8 mAh g⁻¹ with a capacity retention of 80% over 400 cycles. Interestingly, sodium ion distribution in augmented triangular prismatic sites of Na₃V₂(PO₄)₂F₃ is not unchanged, but shifts from the high energy Na(2)' site to the low energy Na(3)' site after a certain cycle, thus Na₃V₂(PO₄)₂F₃ could obtain a higher energy density. The full cell coupled with the composite cathode and Na metal anode constructed with Na-Sn alloy substrate exhibits excellent rate discharge capability and good cycling stability. The nano-level carbon-PTHF double-coating developed in this work could provide a new way to improve Na⁺-storage and rate performance of Na-based materials.

Due to the sluggish oxygen reduction reaction (ORR) process of an O₂ cathode, the power delivery of aprotic Li-O₂ batteries (A-LOBs) is widely considered to be very poor. However, this work demonstrates the transient high-power output of A-LOBs based on the capacitive feature of the O₂ cathode, including the intrinsic capacitance of cathode material and the ORR pseudocapacitance of the absorbed O₂ on the cathode surface, by using graphene with high specific surface area. The O₂ cathode delivers a high specific power of 12 026 W kg_graphene⁻¹ while also providing a large specific energy of 1216 Wh kg_graphene⁻¹. Pulse-discharge tests show that A-LOBs can achieve the transient high power output at high current via the "capacitor-type", while maintaining the high energy output at low current due to the "battery-type" (ORR). This work indicates that A-LOBs can deliver both high energy density and high transient power, which may be an appeal for the next-generation electric vehicles.

Titanium niobium oxide (TiNb₂O_7, TNO) has emerged as a competitor for Li₄Ti₅O₁₂ (LTO) anode material for the next-generation high energy solid-state batteries. However, the usage of TNO is mainly limited by its low electronic conductivity and low lithium-ion diffusivity, which need to be improved for efficient electrochemical kinetics. Amorphous energy storage materials have been widely considered as alternatives. Here, we report the fabrication of amorphous TNO thin films and their electrochemical performance in half-cell rechargeable Li-ion thin film batteries. The amorphous TNO thin films exhibit: a high discharging capacity of 226 μAh/μm cm² (∼460 mAh/g) at 17 μA/cm² current density, the high coulombic efficiency of ∼99%, fast kinetics and stable structure. The amorphous TNO thin films further show a high discharge capacity than amorphous LTO thin films, which is twice greater than crystalline TNO thin films. They offer Li-ion diffusion coefficient of ≈10⁻¹³ cm²/s, better electron-transfer reaction and high electronic conductivity (≈1 × 10⁻⁹ S/cm) during electrochemical cycling process. The superior electrochemical performance of amorphous TNO thin films are attributed due to their unique disordered structure and morphology features.

Vehicle-to-grid (V2G) and Grid-to-vehicle (G2V) strategies are often cited as promising approaches to mitigate the intermittency of renewable energy on electric power grids. However, their impact on vehicle battery degradation have yet to be investigated in detail. Since battery degradation is path dependent, i.e. different usage schedules lead to different degradation mechanisms, it is essential to investigate batteries under realistic V2G and G2V scenarios. The aim of this work is to understand the effect of bidirectional charging on the degradation mechanisms of commercial Li-ion cells used in electric vehicles today. Results showed that an extra V2G step during cycle-aging accelerated capacity loss and degraded the kinetics at the negative electrode. Moreover, for all cycling duty cycles, the loss of active material at the negative electrode was higher than the loss of lithium inventory. This condition could trigger lithium plating and shorten cell lifetimes. In the calendar-aging experiments, state of charge was shown to be an important factor and interacted with temperature to accelerate the loss of active material at the positive electrode and the loss of lithium. It was also found that high state of charge values caused loss of active material at the negative electrode and kinetic limitations.

In this article, Ni-Al LDHs/graphene composite is successfully fabricated via exfoliation and restacking method. As fabricated composite exhibits ultrathin nature of exfoliated LDHs deposited onto surface of graphene, yielding special chiffon like structure. Such structure can effectively overcome the agglomeration of initial LDHs and graphene sheets. The results of electrochemical performance confirm that Ni-Al LDHs/graphene composite exhibit enhanced performance in comparison with LDHs, which is related to the special chiffon like structure and high conductivity of graphene nanosheets. High performance of as-fabricated material can be identified via various electrochemical tests. In addition, an assembled asymmetric supercapacitor based on Ni-Al LDHs/graphene and active carbon exhibits a maximum energy density of 46.4 Wh kg⁻¹ as well as a maximum power density of 6080 W kg⁻¹, which indicates the potential of composite applied in energy storage-conversion devices.

An electrochemical cell for in-situ neutron powder diffraction studies of electrode materials for lithium-ion batteries is presented. The device has a coin cell geometry, consisting of 8.4 cm diameter, circular components that can be stacked together and clamped tight using sixteen polyetheretherketone (PEEK) screws. The background issue associated with incoherent scattering from hydrogen within the organic electrolyte was addressed by replacing the normal electrolyte with a deuterated analogue, significantly improving the peak-to-background ratio of the in-situ neutron data. Initial in-situ studies showed clear structural evolution within Li_xCoO₂ during charge in a half-cell with lithium metal as the counter electrode, in agreement with previous studies. In addition, the in-situ cell was shown to provide electrochemical performance comparable to that of equivalent coin cells of the commercial design and, following these demonstration studies, is available for in-situ structural studies of other lithium cathode and anode materials during charge/discharge cycling.

The role of dimethallyl carbonate (DMAC), which has a multiple functional group, as an additive in electrolyte have been studied for improving thermal stability of lithium ion batteries (LIB). During the initial charging of the negative electrode with an electrolyte that contains the DMAC additive, film formation occurs near 1 V vs. Li/Li⁺. Furthermore, increases in the amount of DMAC additive are accompanied by increases in the height of the dq/dV peaks and film formation progresses. The time-of-flight secondary ion mass spectrometry (TOF-SIMS) results show that increasing the amount of DMAC additive promotes the formation of aliphatic hydrocarbons of C5 or more in the Solid-Electrolyte-Interfase (SEI) and polymerization proceeds. The temperature programmed desorption mass spectrometry (TPD-MS) results show that the DMAC additive raises the peak temperature for CO₂ generation to 100°C or higher. The DMAC additive suppresses self discharge of LIB and suppresses the increase in direct current resistance (DCR) after storage at 50°C.

To develop a long-lifetime metal-air battery, oxygen reduction electrodes with improved mass-transfer routes are designed by adjusting the mass ratio of the hydrophobic polytetrafluoroethylene (PTFE) to carbon nanotubes (CNTs) in nickel foam. The oxygen reduction catalyst MnO₂ is grown on the nickel foam using a hydrothermal method. Scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Brunauer–Emmett–Teller analysis are employed to characterize the morphology, crystal structure, chemical composition, and pore structure of the electrodes, respectively. The air electrodes are evaluated using constant-current tests and electrochemical impedance spectroscopy. A PTFE:CNT mass ratio of 1:4–2:1 with 3-mm-thick nickel foam yields the optimal performance due to the balance of hydrophilicity and hydrophobicity. When the electrodes are applied in primary zinc–air batteries, the electrode with a PTFE:CNT mass ratio of 1:4 achieves the maximum power density of 95.7 mW cm⁻² with a discharge voltage of 0.8 V at 100 mA cm⁻², and completes stable discharge for over 14400 s at 20 mA cm⁻².

In this contribution, we investigate the initial surface chemistry on fully lithiated LiCoO₂ thin film model electrodes in the electrolyte solvent diethyl carbonate (DEC) and the LiPF₆-electrolyte by means of soaking experiments. The interfacial layer composition is analyzed by X-ray photoelectron spectroscopy (XPS), and possible layer morphologies and spontaneous formation mechanisms are discussed in detail. Upon decomposition of DEC a layered system of surface-bound semi-organic components (inner layer) and cross-linked organic moieties (outer layer) is formed, while a change of the Co³⁺ oxidation state and thus a surface corrosion of LiCoO₂ was not observed. In contrast, the solid electrolyte interface (SEI) film of the LiPF₆-electrolyte soaked electrode showed an inner layer, containing predominantly corroded LiCoO₂, i.e. Co(II,III)_xO_y(OH)_z and LiF as well as aliphatic fluoroorganic species. The outer SEI layer consists mainly of a poly-organic network and randomly distributed Li_xPO_yF_z domains. The thickness of the deposit on the electrolyte soaked electrode surface was only half as thick due to the significantly lower amount of organic and semi-organic compounds. Our investigation indicates that the solvent decomposition is related to the catalytically active LiCoO₂ surface, which is passivated by reaction products such as LiF originating from HF induced processes.

In this contribution, we investigate the solid electrolyte interface (SEI) layers' composition depending on the spatial location within LiCoO₂ composite cathode of a commercial Li-Ion battery. The surface chemistry is analyzed by X-ray photoelectron spectroscopy (XPS), and possible SEI morphology and the differences in the SEI composition are discussed in detail. Finally, related SEI formation reactions and the controlling processes are characterized as a function of the depth in the composite cathode. The SEI is assumed to be a multi-component, layered system. The inorganic inner SEI layer consists of LiF and degraded LiCoO₂, confirmed as Co(II,III)_xO_y(OH)_z. The much thicker outer SEI layer is mainly composed of a poly-organic network with a significantly smaller portion of, presumably, randomly distributed macroscopic Li_xPO_yF_z/Li_xPO_y-1F_z+1 and Li_xPO_y domains. A higher content of Co(II,III)_xO_y(OH)_z, and especially of the poly-organic deposit, was found on the outer cathode surface compared to the analysis position near the current collector, resulting in a 4 nm thicker SEI and indicating a stronger decomposition of LiCoO₂ and solvents. These differences in SEI composition and thickness are attributed to a significantly higher cathode polarization at the outer electrode surface during cell operation leading to a higher rate of electrochemically induced decomposition reactions.

Diffusion coefficients are important parameters for the characterization of new electrode materials, but they are also essential for the study of cell aging and as input parameters in battery modeling. In this report, the applicability of the galvanostatic intermittent titration technique (GITT) on commercial cells is studied. A GITT protocol is applied on a set of commercial cells with graphite anodes and various cathode materials. The cell response is then compared with the ones of the individual electrodes, obtained in three-electrode and half-cell configurations. In particular, mostly due to the particular potential profile of graphite, the full cell GITT response corresponds to the anode and cathode response at low and high state of charge, respectively. Therefore, it is possible to estimate the diffusion coefficients of the individual electrodes by a simple experiment on commercial cells, although only in limited ranges of SOC. If the experiments are performed at different temperatures, it is also possible to determine the activation energies of the diffusion coefficients. In conclusion, GITT allows an estimation of the diffusivity data in commercial cells, and can be therefore used as fast analytical tool for the study of aging and for the modeling of lithium-ion batteries.

From the practical application of supercapacitors, the development of carbon materials with high volumetric performance is highly desired. We report the synthesis of B/N/O co-doped carbon by a facile one-step carbonization method of polyvinylpyrrolidone/melamine formaldehyde resin with boric acid/urea treatment and a subsequent washing process. It is shown that a boric acid/urea treatment is an effective approach to incorporating B into N/O enriched carbon and effectively restraining the generation of inert B-O and B-N species. Moreover, a boric acid/urea treatment and washing process can increase specific surface area, optimize pore structure, and retain many active heteroatoms without lowering density, contributing to good conductivity, fast charge transfer and electrolyte ion diffusion, and high volumetric performance. The fabricated B/N/O co-doped carbon shows high active heteroatoms of 8.69 at.% (N-5, N-6, B-C and O-I), moderate surface area, and pore volume (778.02 m² g⁻¹ and 0.341 cm³ g⁻¹), high density (1.3 g cm⁻³), high specific volumetric, and gravimetric capacitances (309 F cm⁻³ and 238 F g⁻¹ at 0.5 A g⁻¹) and superior cycling stability. The assembled symmetric supercapacitor delivers relatively high volumetric energy density (11.5 Wh L⁻¹ at 622 W L⁻¹) in 6 M KOH electrolyte. The B/N/O co-doped carbon has great potential for applications in supercapacitors.

The formulation of solvent systems can have a severe impact on the lifetime, rate performance, and temperature performance of lithium ion cells. Methyl acetate (MA) has been found to increase rate and temperature performance of carbonate solvents, but decreased cell lifetime. This work used ultra-high precision coulometry, in-situ gas analysis, and isothermal microcalorimetry to investigate a recently reported promising high rate additive blend of fluoroethylene carbonate (FEC) and 1,3,2-dioxathiolane-2,2-dioxide (DTD) in LiNi_0.5Mn_0.3Co_0.2O₂/graphite pouch cells. Solvent systems composed of blends of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were investigated, with additions of 0%, 20% and 40% wt MA. MA was found to decrease the coulombic efficiency and increase slippage, parasitic heat flow, and gas volume. The addition of just 1% wt of DTD to 2% FEC improved the performance of cells containing 20% and 40% MA to that of cells containing no MA and 20% MA, respectively, under 4.3 V. Results suggest the negative impact of MA originates from increased electrolyte oxidation at the positive electrode. Additionally, blends of MA in EC:EMC and EC:DMC (3:7 wt) were tested head-to-head, yielding a small improvement to parasitic heat flow and UHPC performance when cells used EC:EMC.

In situ Raman microscopy was used to study polysulfide speciation in the bulk ether electrolyte during the discharge and charge of a Li-S electrochemical cell to assess the complex interplay between chemical and electrochemical reactions in solution. During discharge, long chain polysulfides and the S₃⁻ radical appear in the electrolyte at 2.4 V indicating a rapid equilibrium of the dissociation reaction to form S₃⁻. When charging, however, an increase in the concentration of all polysulfide species was observed. This highlights the importance of the electrolyte to sulfur ratio and suggests a loss in the useful sulfur inventory from the cathode to the electrolyte.

In-suit grown composite materials have received much attention on scientific communities in recent years owing to their unique physicochemical properties for applications such as energy storage devices. Herein, we report freestanding in-situ grown Ni(OH)₂ nanosheets on Ni foam by a facile one-step hydrothermal approach using aqueous nickel nitrate as precursor solution without any additives. The influence of concentration of nickel nitrate on morphology and electrochemical properties of the synthesized Ni(OH)₂/Ni foam (NHNF) was investigated. Binder-free 0.12-NHNF electrode material exhibited a high gravimetric capacity of 340 mAh g⁻¹ at a current density of 1 A g⁻¹, excellent cycling stability (81.1% capacity retention after 3000 cycles) and good flexibility (89.2% capacity retention after folding in a roll). A hybrid supercapacitor (HSC) based on the synthesized 0.12-NHNF as positive electrode and commercial active carbon as negative electrode delivered a high energy density of 39.2 Wh kg⁻¹ at a power density of 598 W kg⁻¹ at a working voltage of 1.6 V. Long-term cycling stability test shows that the capacity retention of 84.3% was achieved with the HSC after 3000 cycles. The excellent electrochemical performance of the NHNF material indicates that it can be an appealing candidate electrode material in energy storage devices.

The effect of LiPO₂F₂ as an electrolyte additive in Li[Ni_0.5Mn_0.3Co_0.2]O₂ (NMC532)/graphite pouch cells was examined using ultra high precision coulometry (UHPC), electrochemical impedance spectroscopy (EIS), storage testing, gas evolution measurements, isothermal calorimetry and long term charge-discharge cycling. Comparisons to the well-known additive, vinylene carbonate (VC) were made. LiPO₂F₂ is an effective additive for NMC532/graphite pouch cells since it was found to improve coulombic efficiency, decrease parasitic heat flow, improve charge-discharge cycle lifetime and decrease impedance growth. The composition of the solid electrolyte interphases (SEI) on both electrodes was examined by X-ray photoelectron spectroscopy in cases where LiPO₂F₂ was used or not used. The effect of combining methyl acetate, as a co-solvent to improve rate capability, and LiPO₂F₂ was also investigated using long term cycling testing at 20°C. Overall, LiPO₂F₂ is shown to be an extremely valuable electrolyte additive, more effective than VC in these cells.

The suitability of steam activated, coconut shell derived carbon (CSC) and its three variants obtained by acid washing of the CSC is investigated in detail for high power super capacitor applications using in depth electrochemical characterization. The CHNS and PIXE analysis is used to verify the purity of the samples. The structural and surface studies using Raman spectroscopy and BET techniques reveal that, after washing with acids, the structural features of the activated carbon get improved to a significant extent. Out of the three acid washing procedures, washing with HF is found to yield the activated carbon sample AC4 with maximum purity, structural order and surface morphology with optimum ratio of micropores to mesopores, suitable to facilitate fast electrolyte ion diffusion and transport. The two electrode measurements with organic electrolyte using symmetric AC4 electrode based supercapacitor test cells give an electrode capacitance of 162 F g⁻¹ and an energy density of 35.2 Wh kg⁻¹ at a current density of 1 A g⁻¹, and a power density of 3967 W kg⁻¹ at 10 A g⁻¹ along with good cycling stability. It is also observed that 96% of the initial capacitance is retained after 5000 cycles at a current density of 10 A g⁻¹.

Porous spherical α-Ni(OH)₂/C composites were successfully synthesized via an in-situ one-pot hydrothermal method using glucose as carbon source for the first time. By contrast, pure α-Ni(OH)₂ was also prepared under the same conditions without glucose. Aging experiments demonstrate that the prepared α-Ni(OH)₂/C samples have better stability than the synthesized pure α-Ni(OH)₂ toward alkaline medium. Owing to unique α-Ni(OH)₂/C composites and ultrahigh surface area the prepared α-Ni(OH)₂/C composites deliver a super high specific capacitance of 383 mAh g⁻¹ at current density of 0.8 A g⁻¹ in Ni/Zn aqueous secondary battery and good cycling stability (85% retention after 500 cycles) under three-electrode configuration in 6 M KOH. These suggest that the prepared α-Ni(OH)₂/C samples could be a new promising cathode material candidate for Ni/Zn alkaline secondary battery.

In this paper, the porous nitrogen-doped carbon nanospheres (N-CNSs) and carbon nanoboxes (CNBs) with high electrical conductivities of 244 and 329 S^.cm⁻¹ and large surface area of 558 and 306 m^2.g⁻¹ are prepared by magnesium (Mg) triggered self-propagating high-temperature synthesis (SHS) using urea and fructose as precursors. Differing from traditional time-consuming calcination technique, the obtained samples are composed of porous and 3D structure with particle size of a few tens of nanometer. Such unique structure can lead to short diffusion paths of ions, abundant active sites for charge-transfer reactions and reasonable electrical/ionic conductivity. The rapid prepared and novel structure of N-CNSs and CNBs electrodes offer a satisfactory specific capacitance (124 and 84 F^.g⁻¹ at 0.5 A^.g⁻¹), good rate performance (103 and 71 F^.g⁻¹ at 10 A^.g⁻¹), and excellent cycling stability (96.2% and 98.6% after 8000 cycles). Most importantly, N-CNSs provides larger surface area and as much as 5.67 wt% of nitrogen incorporation, due to its high content of nitrogen in urea precursors. Thus, it presents higher specific capacitance of 47.6% than CNBs. Therefore, such particularly designed 3D porous carbon provides a promising strategy to ameliorate electrode materials for advanced energy storage systems.

Development of electrical double layer capacitors using vertically oriented graphene nanosheets with fast response continues. The inherent open morphology of the nanosheets allows efficient access to charge storage surfaces, making them suitable for AC line filtering. However, since the overall surface area is only about a factor of ∼310x over the geometric area, the specific capacitance available remains limited. This work presents utilization of the conventional growth of vertically oriented graphene nanosheets on Ni substrates as the underlying architecture for coating with high surface area carbon black to substantially increase the specific capacitance while retaining the open morphology to allow good frequency response at 120 Hz. The carbon black coating was deposited on ∼1.2 μm and ∼2.5 μm high nanosheets using an aerosol spray method. Deposition times from 0–8 s, in 1 s intervals, provided coatings which translated into a specific capacitance of 2.3 mF/cm² at 120 Hz (8 s coating) and a volumetric capacitance of 4.6 F/cc (energy storage elements). Improvements in the uniformity of the carbon black coatings suggest that much higher specific capacitances are possible. COMSOL models of high density VOGN grown to 10 μm high and covered uniformly with 100 nm of carbon black coating suggest a capacitance of ∼42 mF/cm² with acceptable frequency response at 120 Hz can be achieved.

Sulfonated carbon nanotubes (CNTs) was prepared by direct hydrothermal treatment in chlorosulfonic acid and employed as electrocatalysts for V³⁺/V²⁺ redox reaction for vanadium redox flow battery. The sulfonic groups introduced on the surface of CNTs not only significantly promote the accessibility of vanadium electrolyte, but also provide more active sites for V³⁺/V²⁺ redox reaction. Therefore, a series of sulfonated CNTs exhibit higher electrochemical activity and reversibility toward V³⁺/V²⁺ redox reaction compared with pristine CNTs. In particular, sulfonated CNTs treated for 10 hrs (CNTs-10) demonstrate the best electrocatalytic performance. The cell using CNTs-10 as negative catalysts achieves excellent charge-discharge performance with voltage efficiency and energy efficiency of 68.34% and 65.56% at a current density of 120 mA cm⁻², respectively, which are higher than those (60.74% and 60.50%) for the pristine cell. The excellent electrocatalytic performance of sulfonated CNTs toward V³⁺/V²⁺ redox reaction is ascribed to the promoted electrochemical kinetic process of V³⁺/V²⁺ redox reaction and the accelerated mass transfer of vanadium ions.

The thermal stability of a separator is extremely important for the safety of lithium-ion batteries (LIBs). Poly(ether ether ketone) (PEEK) is a potential material for use as a separator due to its good heat resistance and chemical stability. However, PEEK has inferior solubility, and is not easy to be prepared a porous separator. Herein, we report a novel soluble PEEK derivative containing polar and bulk groups and a series of porous separators prepared via an electrospinning technique. The synthesis of the PEEK was confirmed by Fourier transform infrared spectroscopy (FTIR), and the morphology of the membrane was examined by scanning electron microscopy (SEM). Several important properties, such as the thermal stability, liquid electrolyte uptake, contact angle, and lithium-ion conductivity, were measured. These electrospun PEEK separators including PEEK-5, PEEK-8 and PEEK-10 exhibited better thermal stability and wettability than a commercial polypropylene (PP) separator. Notably, the PEEK-8 separator exhibited the largest liquid electrolyte uptake of 524% and the highest ionic conductivity of 3.81 mS cm⁻¹. More notably, the electrospun PEEK separators did not exhibit shrinkage at 150°C, and a coin cell assembled with the electrospun PEEK-8 separator possessed a discharge capacity of 118.9 mAh g⁻¹ (LiFePO₄/Li⁺) after 200 cycles at an elevated temperature of 60°C. Thus, the obtained electrospun PEEK separators can effectively enhance the safety and electrochemical performance of LIBs.

In this work, a flexible three-dimensional nanoporous bimetallic Cu-Ag (NPCuAg) has been fabricated by a simple electrochemically dealloying Zr₄₅Cu₃₅Ag₂₀ glassy ribbon in HF aqueous solution. The influence of dealloying treatment time on the thickness of nanoporous layer and the flexibility of the dealloyed ribbon was investigated. It is found that the thickness of NPCuAg is approximately proportional to dealloying treatment time, and the NPCuAg shows a maximum nanoporous layer ∼9 μm (one side) while possessing good flexibility. Furthermore, nanoporous CuOAg (NPCuOAg) was obtained through a simple oxidation treatment. The NPCuOAg shows a hierarchical structure where CuO nanosheets are uniformly embedded in 3D nanoporous Ag skeleton. The NPCuOAg battery-type electrode exhibits superior electrochemical performance, which has great potential application in flexible high-performance energy storage devices.

To increase the energy density of a vanadium redox flow battery (VRFB), the Mn(II)/Mn(III) system was used as a positive reaction and its effect on the performance and cycle life were investigated. The discharge voltage of the V/Mn system increased due to the higher redox potential of Mn(II)/Mn(III), which led to a 47% increase in initial energy density from 21 Wh L⁻¹ to 31 Wh L⁻¹. However, Mn(III) ions in the positive electrolyte are converted to MnO₂ upon charging and remain in the precipitate without being reduced upon discharge, thus decreasing the energy density of the V/Mn system up to the 10^th cycle. As cycles progressed further, the number of vanadium ions permeating to the positive electrolyte increased, and the particle size of MnO₂ decreased. As a result, MnO₂ could participate in the reduction reaction without precipitating, resulting in increased energy density. These results show the possibility of using Mn ions for the positive reaction by appropriately controlling the particle size of MnO₂.

Development of a tangible solid state battery has received great attention but there are various engineering challenges to overcome, especially for the scalable processing and the use of Li metal anode. In order to tackle these issues, we first evaluated the electrochemical stability of thio-LISICON solid electrolytes, i.e., Li₁₀GeP₂S₁₂ (LGPS), Li₇P₃S₁₁ (LPS), and Li₇P₂S₈I (LPSI), where the glass-ceramic LPSI electrolyte showed a superior compatibility with Li metal. Moreover, a superionic conductivity of 1.35 × 10⁻³ S/cm could be achieved by optimizing the wet mechanical milling and the low-temperature annealing processes. Using this superior LPSI solid electrolyte, we evaluated the electrochemical performance of pellet-type and slurry-type all-solid-state cells with LiNbO₃-coated LiNi_0.6Co_0.2Mn_0.2O₂ (LNO-NCM622)/LPSI composite cathode and Li metal anode. The initial discharge capacity of ∼150 mAh/g was achieved for the pellet-type test cell and ∼120 mAh/g for the slurry-type cell. Comparing the interfacial resistances of the two types of cells, strategies to enhance the performance and realize a scale-up fabrication of all-solid state Li-ion batteries are discussed.

Graphite-polypropylene bipolar plates (BPP) were subjected to galvanostatic treatment in highly charged positive and negative vanadium electrolyte solutions. The tests were performed in an ex-situ three-electrode electrochemical cell in order to simulate aging under harsh overcharging conditions in a vanadium redox flow battery (VRFB). Non-destructive computed microtomography (microCT) technique was employed to study the post aging morphological changes. The investigations revealed that even under massive hydrogen evolution conditions in the negative electrolyte the BPP is stable. However, the BPP suffers from intense corrosion associated with morphological deformations during aging by galvanostatic overcharging in the positive electrolyte. The CO/CO₂ gas evolution leads to formation of an open pore network, development of micro-cracks and meso-fractures. These morphological changes cause an expansion of the corroded bulk material. The results show that the corrosion starts at the electrolyte/BPP interface and propagates with time in plane-parallel direction to the back side of the BPP.

Grid-scale energy storage systems are of interest as the world increases reliance on renewable energy sources. Redox flow batteries are a type of grid-scale energy storage technology that shows exceptional promise for accommodating the dynamic output of wind and solar power sources. The research community employs dozens of diagnostic techniques to investigate nearly all facets of these devices. Material properties, operational losses, transport, and integrated system properties are studied through the lens of electrochemical, physical, and chemical phenomena that ultimately dictate cost by influencing efficiency, durability, power, and capacity. These diagnostic techniques can, if applied correctly, elucidate not only the types of losses in redox flow batteries, but also tie those losses to fundamental driving forces in such systems so that next generation systems and models can be designed. This review details various diagnostic techniques used in flow battery analysis. The benefits, unique insights, and limitations of these techniques are discussed. Recommendations are also made to assist researchers in identifying the diagnostics that can advance their particular investigations. The review concludes with a summary of opportunities for new diagnostics that are needed to enable solution of persistent issues in redox flow battery research and development.

Novel and highly structured materials have been pursued as sulfur-hosting materials to enhance the specific capacity and cycling stability of lithium-sulfur (Li-S) batteries. Herein, structured titanium nitride nanotubes with tunable dimensions are investigated for their performance on Li-S batteries. We firstly develop a facile method to synthesize TiN nanotubes through anodization of Ti foils and nitridation. Surface morphology and BET surface area are characterized. The change of interfacial resistance, electrochemical performance and stability of batteries are evaluated as a function of nanotube length and diameter. The best electrochemical performance in Li-S batteries observed is for the 30 μm long and 65 nm diameter TiN nanotubes, which has a high discharge capacity of 1338 mAh g⁻¹ after 180 cycles at 0.1 C, and with only 0.064% average capacity decay per cycle. Furthermore, increase in nanotube length from 4.5 to 30 μm and decrease in nanotube diameter from 100 to 35 nm of titanium nitride enhance capacity by 19.1% and 24.7% after 180 discharge/charge cycles, respectively. This study suggests nano-structure with tunable geometry can play a significant role in battery performance and cyclability, and that TiN nanotubes could serve as a very promising cathode material for advanced Li-S batteries.

The high nickel layer cathode LiNi_0.80Co_0.15Al_0.05O₂ (NCA) has excellent discharge capacity and better cycling performance. However, the NCA cathode still has the following disadvantages such as harsh synthesis conditions, cation mixing and poor thermal stability. A spherical fluorine modified gradient NCA is successfully prepared by a simple solid phase method. The F-modification NCA has a good spherical shape which shows a gradient distribution with high surface F and Al contents, and high nickel content in the core. XRD results reveal that F-modification NCA sample has well-ordered layer structure. However, there is a slight decrease in the cell parameters and interlayer spacing with the F doping into the NCA crystal lattice, due to the small F⁻ radius and the largest electronegativity. Energy Dispersive X-Ray Spectroscopy (EDX) analysis reveals that fluorine ions are successfully substituted in the lattice. The cycling stability of the F-modification NCA samples are enhanced, especially at high rates. At 2C rate, the initial discharge specific capacity is 142.34 mAh g⁻¹, and compared with that of 107.73 mAh g⁻¹ after 200 cycles, the capacity losses only 24%. Electrochemical impedance spectroscopy (EIS) further indicates that F-modification could help inhibit the increasing of polarization and change the kinetics of NCA cathode.

One goal of researchers focusing on lithium-ion batteries for electric vehicles is to decrease the time required for charging. This can be done by several methods, including increasing the electrolyte transport properties. Methyl acetate, used as a co-solvent in the electrolyte, has been shown by a number of researchers to increase cell rate capability dramatically but careful considerations of the impact of methyl acetate on cell lifetime have not been published to our knowledge. The impacts of methyl acetate as a co-solvent in NMC532/ graphite cells were systematically studied in this work. Ex-situ gas evolution measurements, electrochemical impedance spectroscopy, high rate charging tests, ultra-high precision coulometry, isothermal microcalorimetry and long term cycling at both 20 and 40°C were used to probe the impacts of including methyl acetate as a co-solvent. This work will be of great interest to Li-ion battery scientists developing cells that can support rapid charge and still maintain long lifetime.

Single crystal LiNi_0.5Mn_0.3Co_0.2O₂ (NMC532) was shown to have superior stability at high voltages and elevated temperatures compared to conventional polycrystalline NMC532 by the authors. Conventional LiNi_0.6Mn_0.2Co_0.2O₂ (NMC622) usually offers more capacity than NMC532 when charged to the same upper cutoff voltage so NMC622 is attractive. It is expected that single crystal NMC622 could also provide better performance than typical polycrystalline NMC622 materials. This work explores the synthesis of single crystal LiNi_0.6Mn_0.2Co_0.2O₂ and preferred synthesis conditions were found. A washing and reheating method was used to remove residual lithium carbonate after sintering. The synthesized single crystal NMC622 material worked poorly after the washing-heating treatment without the use of electrolyte additives in the electrolyte. However, with selected additives, single crystal cells outperformed the polycrystalline reference cells in cycling tests. It is our opinion that single crystal NMC622 has a bright future in the Li-ion battery field.

Using chitosan as the carbon and nitrogen source, highly-crystalline lithium titanate nanoparticles with N-doped carbon-coating (N-C/LTO) have been successfully synthesized via a facile refluxing and microwave-assisted hydrothermal processes followed by a subsequent calcination step. Due to the effect of chitosan-confined, the fabricated N-C/LTO composites crystallized into well-defined cubic spinel structure with an average size of ∼50 nm, leading to a significantly enhanced specific surface area. The successful doping of nitrogen into the carbon layer of the N-C/LTO has been confirmed by XPS technology. The porous LTO with nitrogen-doped carbon coating fabricated with chitosan exhibits superior electrochemical performance (a high reversible capacity of 194 mAh g⁻¹ was achieved at 1 C). This work therefore reveals that the N-doped carbon coating realized by chitosan confinement is an effective way for enhancing the surface lithium storage capability of LTO as the anode materials for lithium-ion batteries (LIBs).

Biomass derived porous carbon have attracted more and more attention for the application of energy storage. More effective activation strategy is required for production of biomass derived porous carbon. In this work, "pickle method" inspires the incorporated strategy of the activation agent, because it can realize more effective and uniform mixture between activation agent and precursor. Based on the cell structure, the tomato pickled with ZnCl₂ is transferred into natural nitrogen doped (1.2%) porous carbon materials using the one-step annealing. Porous analysis based on density functional theory (DFT) confirms that the materials possess well-defined distributions of mesopores and micropores and high specific surface area (863.6 m² g⁻¹). The synergetic effects of the hierarchical porous monolithic structure, natural nitrogen doping and high specific area results in the high specific capacitance (347.4 F g⁻¹ at 0.5 A g⁻¹). The ultimate symmetric supercapacitor exhibits ultrahigh specific energy density (142.6 Wh Kg⁻¹) based on the active materials mass. Meanwhile, the materials exhibit less impurities (such as the oxygen of ultralow content (1.1%)), which benefits safer energy storage. Finally, drop, bending and nondestructive temperature tests demonstrate the stable and safe capacitive performance of the supercapacitors.

Diffusion induced stress, due to repeated intercalation/deintercalation of lithium during cycling, causes mechanical degradation in graphite active particles used as an anode in lithium-ion batteries. The microcracks formed in the active particles hinder diffusion of lithium. On the other hand, flow of electrolyte through the accessible microcracks in the active particles leads to additional electrochemically active surfaces and effectively reduces the diffusion length. In this work, stochastic modeling of electrochemistry-mechanics interaction is presented which introduces the influence of electrochemically active microcracks on electrochemical reactions. Enhanced electrochemically active surface area further results in the formation of solid electrolyte interphase (SEI), which decreases the cell capacity due to the consumption of cyclable lithium. This stochastic model successfully predicts the formation of non-uniform and spanning cracks in active particles, which are typically observed in scanning electron micrographs. The impact of coupled electrochemical and mechanical interaction in graphite active particles on capacity fade is elucidated.

Novel cathode, electrolyte and separator concepts are expected to improve the capacity retention and cycle life of lithium-sulfur batteries by avoiding the dissolution of polysulfide-intermediates into the electrolyte or preventing their diffusion to and reaction with the lithium metal anode. However, their intrinsic evaluation is obscured by ill-defined degradation mechanisms of the lithium counter electrode due to electrolyte and polysulfide consumption during reformation of the solid electrolyte interface. Herein, we introduce symmetric lithium sulfide – sulfur cells to study the "cathode" specific degradation mechanisms of the cathode/electrolyte/separator-system in order to differentiate cathode-, separator, and electrolyte and lithium metal anode degradation. Two identical carbon/sulfur-composite cathodes, either of them one at first lithiated versus lithium, are assembled in a coin cell versus each other. The virtue of this test cell design is demonstrated evaluating prime shuttle-suppression concepts, namely a Nafion-coated polyolefin separator and a sparingly polysulfide-solvating electrolyte. We conclude that symmetric lithium sulfide – sulfur cells provide a valuable methodology to analyze the intrinsic capacity decay and cycle life of cathodes for lithium-sulfur cells with limited solvation and/or blocking of polysulfides, and it is an essential strategy to distinguish cathode from lithium anode degradation.

Currently, only two types of hybrid Mg-Na electrolytes are known. Herein, we report a new hybrid Mg-Na electrolyte, based on Mg(TFSI)₂ and NaBF₄ salts in diglyme solvent, which engenders non-dendritic cycling of Mg metal when used in hybrid Mg-Na cells. Using NaTi₂(PO₄)₃ as sodium intercalation-type cathode, NaTi₂(PO₄)₃/C vs Mg cell delivered discharge capacity approaching 120 mAh/g with flat plateau at 1.25 V vs Mg/Mg²⁺, along with relatively good rate performance and cycling stability.

High voltage positive electrodes for lithium ion batteries have suffered from continuous oxidation of the electrolyte during cycling, which largely offsets the benefits of high energy and power densities. In this work, the electrolyte oxidation and concomitant film deposition/dissolution behaviors were investigated on Pt electrode by using linear sweep voltammetry (LSV), electrochemical quartz crystal microbalance (EQCM), and X-ray photoelectron spectroscopy (XPS). Two characteristics were identified. First, film deposition is relatively unfavorable at higher potentials (>4.7 V vs. Li/Li⁺) because the oxidation products are mostly gaseous or soluble species. Second, the concentration of inorganic species decreases in the surface film as the potential increases, which is likely dissolved by HF or polar species. The dominance of gaseous or soluble products and the partial dissolution of the surface film, are two characteristics which hamper passivation of the electrode surface, leading to severe electrolyte oxidation at the high potentials.

Spinel LiNi_0.5Mn_1.5O₄ (LNMO) is a promising cathode material for high energy density lithium-ion batteries (LIBs), but further enhancement of LNMO electrochemical performance requires a better understanding of its intrinsic surface properties. Herein, we employ first-principles calculations to obtain insights into the transition-metal disproportionation reactions and oxidation states at the LNMO (001) and (111) surfaces examining the role of crystal surface, state of charge (lithium content), oxygen vacancies, and protonation of surface oxygen atoms. Our results reveal possible coexistence of multiple transition-metal oxidation states on the (001) facet promoted by surface protonation and presence of oxygen vacancies. This should facilitate Mn dissolution, while it is not the case for the (111) surface.

Graphite, which is the most wildly used anode material for lithium ion batteries, has a limited power performance at high charging rates (Li-ion input), while its alternatives, such as silicon and tin alloys, show an even inferior rate capability. Here, we describe a multi-channel graphite anode with channels etched into the graphite surface that enables lithium ions to quickly access graphite particles for fast chargeable lithium ion batteries. As a result, the multi-channel graphite anode showed an excellent charging rate capability of 83% for 6C charging and 73% for 10C charging, which is much better than pristine graphite material. Moreover, the multi-channel graphite anode showed a great enhanced discharge rate capability than pristine graphite. In addition, it showed excellent cyclability with a capacity retention of 85% at 6C after 3000 cycles without any additives. The multi-channel graphite anode is proposed for use in fast chargeable lithium ion batteries for electric vehicles and plug-in hybrid vehicles.

Silicon/graphite composites have the potential to improve the practical energy density of Li-ion batteries to enable mass-market penetration of electric vehicles. However, they require polymeric binders that are compatible with both silicon and graphite and can sustain alloying and intercalation reactions as well as the associated interfacial reactions. In this work, chitosan, a natural cellulose, is crosslinked with either molecular (citric acid) or polymeric (poly (acrylic acid), PAA) carboxylic acids to form networks with maximum interaction with the composite as evidenced by infrared spectroscopy. Li-ion half-cells of graphite-rich, silicon/graphite negative electrodes using crosslinked chitosan binders show higher initial Coulombic efficiency (ICE) and more stable cycling performance than pristine chitosan. This could be due to the polymeric network produced from the crosslinking reaction between chitosan and carboxyl acids as well as the strong interactions between polymeric network and surface of silicon and graphite as evidenced by adhesion tests. The crosslinked chitosan network can effectively accommodate large volume change of silicon particles and keep other electrode components connected during cycling as evidenced by scanning electron microscope (SEM) images leading to excellent cycling stability. This makes it very attractive for use as a binder in Si/graphite electrodes for Li-ion batteries.

The electrochemical performance of porous graphite anodes in lithium ion battery applications is limited by the lithium ion concentration gradients in the liquid electrolyte, especially at high current densities and for thick coatings during battery charging. Beside the electrolyte transport parameters, the porosity and the tortuosity of the coating are key parameters that determine the electrode's suitability for high power applications. Here, we investigate the tortuosity of graphite anodes using two water as well as three n-methyl-2-pyrrolidone based binder systems by analysis of symmetric cell impedance measurements, demonstrating that tortuosities ranging from ∼3–10 are obtained for graphite anodes of similar thickness (∼100 μm), porosities (∼50%) and areal capacity (∼3.4 mAh/cm²). Furthermore, selected electrodes with tortuosities of 3.1, 4.3, and 10.2 were cycled in cells with reference electrode at charging C-rates from 0.1-20 1/h, illustrating the clear correlation between electrode tortuosity and its rate capability.

Prelithiation is a strategy of increasing importance for high energy density, long cycle life cells. This paper provides a thorough understanding of the implications of prelithiation on cell design and a phenomenological understanding of the behavior of prelithiated negative electrodes in full cells. In a first part, an idealized electrode stack model is derived showing the variation of energy density with prelithiation. Two regimes are identified, the first where prelithiation allows increased energy density by compensating the irreversible capacity of the negative electrode and a second where further prelithiation provides a lithium reservoir to compensate ongoing cycling losses. In a second part coin and cylindrical full cells are used to demonstrate the two regimes. Full coin cells are used to show the impact of the lithium reservoir and the impact of the coulombic efficiency of the negative electrode on the cycle life of a prelithiated cell. Cylindrical 2Ah cells are used to demonstrate the impact of accurate and repeatable roll to roll prelithiation combined with an engineered Si alloy. A cylindrical cell with a prelithiated negative electrode containing 55 wt% Si alloy demonstrated 80% capacity retention at 500 cycles and a coulombic efficiency of over 99.9% up to 700 cycles.

A sulfonated poly (ether ether ketone) (sPEEK) was tested as the separator in a full alkaline flow battery with 2,6-dihydroxyanthraquinone-ferro/ferricyanide, DHAQ-FeCy, redox couples. Cell performance was compared to that of an identical cell utilizing a perfluorosulfonic acid (PFSA) membrane. Replacement of the PFSA membrane with sPEEK resulted in a 10% power density increase, a 40% decrease in capacity loss per day and an 85-fold decrease in ferricyanide permeation. Though long-term stability of sPEEK in alkaline media requires improvement, these results highlight the potential to produce non-fluorinated membranes with better performance in organic redox flow batteries than the commercially available PFSAs.

An aqueous mixture of poly(vinyl alcohol) (M.W. ∼ 8.9 × 10⁴–9.8 × 10⁴ g mol⁻¹, 14% w/v) and disodium terephthalate (Na₂TP) powders (6% w/v) was electrospun at 14 kV with a fiber collection distance and a feed rate of 12 cm and 0.5 mL h⁻¹. Then, the obtained fibers were calcined at 350°C with a heating rate of 1°C min⁻¹ under air for 7 h. Diameters of hollow Na₂TP fibers, composed of grains with sizes of 76 ± 27 nm, are 189 ± 32 nm. Na₂TP fibers are composed of ∼16% w/w Na₂CO₃. Na₂TP structure is orthorhombic and can be indexed in a space group of Pbc2₁. Degree of crystallinity of Na₂TP fibers is less than that of Na₂TP powders. Galvanostatic curves display stable reversible capacities of Na₂TP powders and fibers at ∼140 mA h g⁻¹ and ∼110 mA h g⁻¹, respectively, after 50 cycles at 25.5 mA g⁻¹. On the other hand, at 255 mA g⁻¹ and after 100 cycles, those of the powders and the fibers are ∼48 mA h g⁻¹ and ∼70 mA h g⁻¹, respectively. Thus, the eco-friendly Na₂TP fibers are potentially used as anode materials of sodium-ion batteries under high current density.

Plating in lithium-ion batteries not only reduces their lifetime, but also raises safety concerns. Preventing metallic lithium from forming is difficult, as the heterogeneity of materials typically used in batteries can create transport non-uniformities, which can lead to unanticipated local plating. Therefore, being able to predict the occurrence of plating due to a non-uniformity of a certain shape and size becomes essential. In this study, we probe the importance of the size scale and geometry on localized plating through numerical simulations and experiments. Using modified separators to create transport non-uniformities, we show that certain geometric features lead to more vulnerability to plating, and localization strongly depends on size. A single large feature in a separator induces more plating than a collection of smaller features with same total area. Our findings help elucidate the fundamentals behind heterogeneous plating, which can provide practical insights into battery safety and product control.

Highly soluble active materials, such as iodine, are of great potential to develop the research of rapid charge-discharge performance for Li-ion batteries. In this work, a new facile method is applied to construct the iodine/carbon electrode system, which is composed of a thin cathode film, prepared by directly mixing pure commercial iodine and superconducting carbon black, and a carbon nanotubes (CNTs) interlayer. The CNTs interlayer is inserted between pure iodine cathode and separator in the lithium-iodine battery. Electrochemical data reveals that the iodine cathode demonstrates a high capacity of 100 mAh g⁻¹ and ∼100% columbic efficiency after 5000 cycles at a rate of 100C, which shows a great cycle stability and superior high-rate capability, based on the contributions from both the confinement effect of iodine species in CNTs interlayer and the quick liquid-phase diffusion of Li ions in Li-I₂ battery.

The graphite anode of commercial lithium-ion batteries is a typical granular material embedded in a soft binder. To investigate its mechanical properties, a combined experimental/theoretical/numerical study is proposed and performed. On the experimental side, a systematic procedure is established, including graphite anode slurry preparation, cylindrical sample manufacturing, axial/lateral compression tests of the sample, and data analysis. On the theoretical side, the Drucker-Prager cap model, which has been widely used in the powder industry, is adopted. The inter-particle portion of the yields surface of the model is calibrated using the experimental results. On the numerical side, a model in Abaqus/explicit is established with the discrete element method. The Young's modulus of particles and the surface energy per unit area are identified as the two dominant factors that control the contact property of the particles in the discrete element method simulation. By adjusting the two factors together with iterations, a set of optimal values are determined so as to render satisfactory simulation result that can predict the deformation pattern as well as the strength of the granular anode material. At last, the deformation mechanisms of the material are discussed based on the experimental and numerical results.

A potentiometric CO₂ gas sensor was fabricated using the compound Li₃PO₄-Li₂SiO₃ thin film as electrolyte, and its sensing performances were compared with the conventional Li₃PO₄-based sensor. The Li₃PO₄-Li₂SiO₃ electrolyte was prepared by RF magnetron sputtering while the Li₃PO₄ electrolyte by thermal evaporation. The microstructures and phase composition of both sensors were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The sensors were examined in CO₂ atmosphere at a large temperature range from 350°C to 500°C. As the testing results revealed, both sensors' electromotive force (emf) have a good linear relationship with logarithmic gas concentrations, and the Li₃PO₄-Li₂SiO₃-based sensor showed higher sensitivity, shorter response and recovery times, and more stable output emf. The novel sensor exhibited sensitivity as high as 90.80 mV/dec, response and recovery times as short as 6.5 s and 17 s at 500°C. After comparison, it is quite clear that the characteristics of the electrolyte have great influence on the sensor's properties. The improvement is considered to be caused by the electrochemical properties of the Li₃PO₄-Li₂SiO₃ thin film, whose micro morphologies and higher ionic conductivity help to enhance lithium-ion transmission in the chemical reactions.

A novel electrochemical sensor was fabricated by simply screen printing reduced graphene oxide (rGO) paste on F-doped tin oxide (FTO) (rGO-SP-FTO) followed by sintering at 450°C in Argon and employed for detecting dopamine (DA) and uric acid (UA) simultaneously. The rGO film was characterized by using Raman spectroscopy, field emission scanning electron microscope (FE-SEM), and Fourier transform infrared spectroscopy (FTIR). The surface sensing features of rGO-SP-FTO were studied with electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The rGO-SP-FTO electrode exhibited foremost sensitivity in simultaneous detection of DA and UA without any interference from ascorbic acid (AA). The rGO-SP-FTO electrode showed a good linear response in the range of 0.5–50.0 μM and 5.0–300 μM with detection limits (S/N = 3) of 0.07 μM and 0.39 μM for DA and UA, respectively. The interactions between screen printed rGO with FTO electrode and their influence on how rGO-SP-FTO electrode interacted with UA, DA, and AA were analyzed from experimental observations. The rGO-SP-FTO electrode was able to detect DA in dopamine hydrochloride injection (DAI) and UA in urine sample effectively. Moreover, the designed electrochemical sensor exhibited excellent stability and reproducibility.

A compact portable nanofluidic pump that enables precise manipulation of ultra-small amount of liquid is highly desirable for the trend in miniaturization. Here we develop an integrated micro/nanofluidic pumping device utilizing nanopillar structures with diminishing intervals and locally controlled evaporation. A continuous and steady flow rate of 2.7 pL/s was achieved for more than 12 h without external mechanical power source. The liquid transports in the nanofluidic channels were controllable by adjusting the temperature of evaporation surface. The picoliter-scale flow rates meet the demands for performing nanofluidic immunoassays and other interdisciplinary applications.

The presented study is focused on the development of repetitive, fast and versatile "on-off" signaling electrochemical genosensor for detection of pagA gene of Bacillus anthracis. Such a sensor will be further used in the portable devices dedicated to molecular diagnostic. The DNA molecular beacon probe was immobilized onto gold electrodes in its folded state through the alkanethiol linker at the 5'-end, while the 3'-end was labeled with methylene blue redox molecule. Initial optimization was conducted for HPLC purified cDNA. Nonetheless application of such prepared biosensor for unpurified PCR product required further investigations. As the sensor response was significantly dependent on the stem-loop architecture, the three different hairpin probes were analyzed. The detected sequence was interior to amplicon, identical as in case of cDNA. The developed "on-off" genosensor allows for detection, in 5 minute, the pagA gene sequence at the level of 5.7 nM with 22.9–86.0 nM linear detection range also in the great excess of other DNA presented in the sample. Both LOD and linear range were significantly improved in case of longer assay time. The biosensor proved its applicability also in detection of pagA gene of Bacillus anthracis in PCR samples amplified with reduced number of cycles.

A novel dual-coreactants electrochemiluminescent (ECL) immunosensor based on CdS-MoS₂ nanocomposites was designed for detection of procalcitonin (PCT). The CdS-MoS₂ nanocomposites were synthesized through a simple one-pot hydrothermal method, and served as highly efficient luminescent material for the ECL immunosensor. In addition, we used H₂O₂ and K₂S₂O₈ as dual-coreactants, generating stronger ECL emission than that of K₂S₂O₈ or H₂O₂ as an individual coreactant, which could improve sensitivity of the immunosensor. Under optimum conditions, the ECL assay for PCT detection was developed with excellent sensitivity of a concentration variation from 0.0001 to 10 ng mL⁻¹ and limit of detection down to 33 fg mL⁻¹(RSD = 0.10). Additionally, the proposed immunosensor showed high specificity, good reproducibility, and long-term stability.

The present research was conducted to develop a potent electrochemical sensor based on multi-walled carbon nanotubes and TiO₂ nanoparticles in chitosan matrix (CS-MWCNTs+TiO₂NPs). In the CS-MWCNTs+TiO₂NPs nanocomposite film with excellent catalytic activities, good electrical conductivities and high surface areas of MWCNTs and TiO₂NPs, the simultaneous determination of hydroquinone (HQ), catechol (CC) and resorcinol (RS) with proper analytical performance was realized in the individual or triple-components solution in comparison with the bare glassy carbon electrode (GCE) and the single component modified GCE. The linear response of HQ, CC and RS were obtained in the ranges of 0.4–276.0 μmol dm⁻³, 0.4–159.0 μmol dm⁻³ and 3.0–657 μmol dm⁻³ and the detection limits (S/N = 3) were 0.06 μmol dm⁻³, 0.07 μmol dm⁻³, and 0.52 μmol dm⁻³, respectively. In the real water sample analysis by the developed sensor, satisfactory results were obtained.

For the first time, we have synthesized hollow nitrogen-doped mesoporous carbon spheres decorated graphene (NMC-G) and applied it in the simultaneous determination of hydroquinone (HQ) resorcinol (RC) and catechol (CC) in real samples. In the composite of NMC-G, hollow mesoporous carbon spheres possess high surface area and graphene have shown high electro-catalytic activity to many electroactive substances. As a result, the oxidation overpotentials of HQ, RC and CC decreased and the potential separations were 0.38, 0.49 and 0.11 V for CC and RC, RC and HQ, and HQ and CC, respectively. A linear response was obtained from 5 μM to 150 μM for the simultaneous determination of HQ, RC and CC, the linear equation was I - I₀ = 0.7695 + 0.08751C_HQ for HQ, I - I₀ = 0.00858 + 0.02243C_RC for RC and I - I₀ = 0.5027 + 0.07829C_CC for CC, respectively. Furthermore, the concentration of HQ, RC, and CC were assayed in tap water samples, the recoveries were from 95.0% to 106.6%.

Temperatures during ultrafast microwelding processes are very difficult to be measured timely and accurately. Here, we develop a self-contained temperature sensing approach using thermoelectric voltages between dissimilar welded materials. This approach can offer response speeds ranging from kilohertz to megahertz (temporal resolution of sub-millisecond scales) without requiring external thermocouples. Thus, it was successfully used to monitor temperature profiles for the resistance microwelding processes accomplished within 1 millisecond. This approach provides a promising tool for micro/nanoscale ultrafast welding methods to control the welding quality as well as explore the welding mechanism in micro/nanosystem integration and packaging.

In this work, a novel electrochemical assay was constructed based on acid-induced dissolution of nanoparticles to trigger enzyme-free cleavage for thrombin (TB) detection. First, the magnetic bioconjugates Fe₃O₄/Au/s1 could link with ZnO/Au/TBA bioconjugates via complementary base pairing. Once target TB was introduced in this system to react with thrombin binding aptamer (TBA), the formed ZnO/Au/TBA/TB biocomplex could separate from Fe₃O₄/Au/s1 bioconjugates which could be removed by magnetic separation and further dissolved by acidolysis to turn ZnO nanoparticles (ZnO NPs) into Zn²⁺. Finally, the released Zn²⁺ was adopted into the modified electrode and cleaved the substrate sequence of the Zn²⁺-dependent DNAzyme, resulting in the removing of labeled ferrocene (Fc) and the decrease of electrochemical signal. In this way, the target TB detection is transferred to monitor large numbers of DNA fragments labeled with Fc cleaved by Zn²⁺-dependent DNAzymes, resulting in hundreds of thousands-fold amplification effect, further realizing the sensitive detection of TB. And the proposed electrochemical assay exhibited good sensitivity with the detection limit of 8.6 fM in a desirable dynamic range from 0.01 pM to 10 nM. With such design, this proposed electrochemical approach based on acid-induced dissolution of nanoparticles to trigger enzyme-free cleavage provides a simple and sensitive method for detection of other analysts.

Novel two-dimensional Ti₃C₂ MXene nanosheets were successfully prepared by etching Al from Ti₃AlC₂ in LiF/HCl system. In order to further improve the dispersing property and electrical conductivity of Ti₃C₂ nanosheets, Ti₃C₂/graphene oxide (Ti₃C₂-GO) nanocomposites were synthesized and applied for the fabrication of inkjet-printed hydrogen peroxide (H₂O₂) sensor. The results of electrochemical characterization show that the prepared sensor maintains the biological activity of hemoglobin (Hb) and can be applied to the practical detection. The printed sensors display a dynamic range from 2 μM to 1 mM and a detection limit of 1.95 μM with a high sensitivity and excellent selectivity for H₂O₂ determination. Therefore, the printable Ti₃C₂-GO nanocomposites are an excellent sensing platform for electrochemical determination.

We have demonstrated here that graphene quantum dots (GQD) bind to cobaltous ion giving it a flowery structure. As a result of this binding the cyclic voltammetric peak potential shows a cathodic shift with reference to unbound cobaltous ion. From the electrochemical data, it is estimated that Co²⁺ is hexa coordinated with GQD to form the bound species. The electrochemical reduction of cobaltous ion is carried out using four baths. A spectrophotometric examination of aquo cobaltic solution shows a characteristic maximum at 508 nm that is absent when cobaltous ion is in GQD bath. Co composite has been galvanostatically deposited on metal substrates. Fourier transform infrared spectroscopy (FTIR) of Co bound GQD shows distinct peaks at 3246(broad) cm⁻¹, 2089 cm⁻¹, 1639 cm⁻¹, 1392 cm⁻¹, 1274 cm⁻¹, 1099 cm⁻¹, 536 cm⁻¹ that can be attributed to Co-C stretching and C-C stretching. The thermogravimetric analysis (TGA) of the composite shows that it is thermally stable from decomposition up to 600°C. The energy dispersion analysis (EDAX) of the deposited Co shows the presence of carbon and cobalt at 0.25 keV and 7.0 eV respectively. The electrochemically deposited graphene composite responds rapidly to a flowing hydrogen gas stream.

The development of novel and simple active sensing materials is still interested to fabricate a new and improved sensing devices for many industrial, medical and environmental applications. In this work, we have synthesized a new type of pectin (PT) and reduced graphene oxide (RGO) hydrogels (PT/RGO) by using simple sonochemical methods and further used as an active sensing material for simultaneous electrochemical detection of dopamine (DA) and paracetamol (AC). In general, PT and RGO have substantial electrocatalytic activity due to the presence of active functional groups. Herein, the successful formation of PT wrapped RGO was studied by using various analytical techniques. Subsequently, the electrochemical performance of PT/RGO modified glassy carbon electrode (GCE) toward the detection of DA and AC were systematically examined by using cyclic voltammetry (CV) and linear sweep voltammetry (LSV) techniques. As the results, PT/RGO/GCE exhibits the excellent electrochemical activity with a low detection limit (LOD) of 1.5 nM and 1.8 nM, for DA and AC respectively. Especially, the possible mechanism behind the proposed sensor (PT/RGO/GCE) toward detection of DA and AC was clearly scrutinized. In addition, the observed excellent stability, and selectivity of PT/RGO/GCE greater support for the real time detection of DA and AC in human serum and pharmaceutical samples. Thus, the proposed PT/RGO is believed as an exclusive active sensing material with desired properties for future electrochemical sensor applications.

High purity (80 ppm iron) magnesium immersed in aqueous sodium chloride solution exhibits a filiform pattern of localized corrosion in which hydrogen is evolved at local (filament head) and remote (filament tail and uncorroded surface) cathode sites. Transition metal cations in solution are shown to significantly accelerate rates of corrosion, principally by activating (catalyzing) the remote cathode sites. The degree of activation is cation concentration dependent and efficiency increases in the order Mn²⁺ < Fe²⁺ < Zn²⁺ < Cu²⁺. It is proposed that activation occurs as a result of transition metal electrodeposition through a displacement reaction. It is also shown that precipitation of insoluble transition metal (hydr)oxides through time-dependent cation hydrolysis competes with, and reduces the efficiency of, electrodeposition-induced cathodic activation.

The metallic fuel in a nuclear reactor is composed of an alloy of uranium and zirconium (5–10 wt%). To understand the feasibility of using room-temperature ionic liquids for reprocessing of spent metallic fuels, the electrochemical behavior of U(IV) and Zr(IV) was studied in the room-temperature ionic liquid, N-butyl-N-methylpyrrolidinium bis(trifuoromethylsulfonyl)imide (C₄MPyNTf₂). The U(IV) and Zr(IV) ions were introduced into the ionic liquid medium by anodic oxidation of metallic uranium or zirconium as working electrode in the presence of bis(trifuoromethylsulfonyl)imide acid (HNTf₂). The U(IV) present in C₄MPyNTf₂, in the presence and absence of C₄MPyCl, was characterized by visible absorption spectroscopy. The voltammetric behavior of U(IV) and Zr(IV) in ionic liquid medium was studied by cyclic voltammetry and chronoamperometry. The U(IV) in ionic liquid was found to undergo a two-step reduction to metallic form at −3.2 V, and Zr(IV) underwent a single-step reduction to metallic form at −1.5 V. The study showed the possibility of using C₄MPyNTf₂ ionic liquid for electrorefining of metallic fuels.

Aluminum alloy AA7075-T6 is most commonly used in the aircraft and automotive industries. Due to the presence of intermetallic particles, AA7075-T6 is susceptible to localized corrosion in chloride solutions. In the present work multilayer hybrid sol-gel coatings, based on silane precursors 3-glycidyloxypropyl(trimethoxysilane) (GPTMS) and tetraethoxysilane (TEOS), were used to protect AA7075-T6 from corrosion. To enrich the barrier properties of the coating, SiO₂ nanoparticles were added to the GPTMS/TEOS sol-gel solution. Inhibition and a self-healing effect were achieved by doping Ce(NO₃)₃ in the coating. A multi-layer system was applied on the substrate composed of a first layer doped with Ce(NO₃)₃ and the second, undoped sol-gel layer. The addition of cerium increases the lifespan of hybrid sol-gel coating and has a role in self-healing if it is locked within the first layer of the multilayer coating. The self-healing effect was confirmed by immersion of unscribed and scribed coated substrates in 0.1 mol/L NaCl by using the immersion test, electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy with chemical analysis.

The corrosion of metallic nickel was studied in eutectic LiCl-KCl at 773 K while bubbling argon into the salt with a fixed concentration of H₂O. The corrosion process was monitored electrochemically by using continuous open circuit potentiometry (OCP) and intermittent cyclic voltammetry (CV). The OCP of the Ni rod increased with time while H₂O was bubbling into the molten salt. CV measurement results were consistent with a proposed mechanism which results in formation of NiCl₂ based on matching the potentials of observed oxidation/reduction peaks. OCP reached a maximum plateau after prolonged bubbling, likely due to hydrolysis of the NiCl₂. No solubility for NiO was measured in the eutectic LiCl-KCl, thus Ni concentrations in the salt stop rising once there is a balance between NiCl₂ generation from corrosion and dissipation via hydrolysis.

The corrosion behavior of selective laser melted (SLM) 304L was investigated and compared to conventional wrought 304L in aqueous chloride and acidic solutions. Through immersed electrochemical testing and exposure in acidic solutions, the SLM 304L exhibited superior pitting resistance in the polished state compared to wrought 304L. However, the surface condition of the SLM material had a great impact on its corrosion resistance, with the grit-blasted condition exhibiting severely diminished pitting resistance. Local scale, capillary micro-electrochemical and scanning electrochemical microscopy investigations, identified porosity as a contributing factor to decreased corrosion resistance. Preferential corrosion attack was not observed to be related to the characteristic underlying cellular microstructure produced through SLM processing. This study highlights the effects of SLM microstructural features on corrosion resistance, specifically the substantial influence of surface finish on SLM corrosion behavior and the need for development and optimization of processing techniques to improve surface finish.

A pH sensing channel flow double electrode was developed for pH detection of magnesium dissolution during anodic polarization. Because the hydroxide ions generated during the anodic polarization of a magnesium working electrode (Mg-WE) flow to a tungsten pH sensor (W-pH) downstream of the Mg-WE, pH changes can be detected by measuring the rest potential of the W-pH. A video recording of the Mg-WE surface was performed during the measurement, indicating that increase of pH was related to the film breakdown on Mg-WE surface. The hydrogen evolution rate of the order of 10⁻⁸ mol cm⁻² s⁻¹ was estimated from pH values.

Electrochemical impedance spectroscopy (EIS) is a very popular technique to investigate the corrosion behavior of metals and alloys in electrolytes. To interpret the EIS data, an equivalent electrical circuit (EEC) is built and the corrosion behavior can be explained on the basis of the values obtained for each element of the EEC after fitting the impedance data. Hence, the reliability of the interpretation greatly depends on the selection of the EEC for the impedance modeling. In this work, odd random phase electrochemical impedance spectroscopy (ORP-EIS) is used to investigate the corrosion behavior of Zn, Zn-Al and Zn-Al-Mg hot dip coated steel wires in 0.1 M NaCl. ORP-EIS uses a multisine excitation signal to obtain the impedance response of the electrochemical system. It is faster than conventional EIS as well as provides accurate information about linearity, stationarity and noise distortions of the system during the measurement. This is used to optimize the experimental conditions and to evaluate the correctness of the data modeling. The corrosion behavior of the metallic coated steel wires is quantified by EIS modeling. The validity of the proposed EEC is assessed based on the physical phenomena as well as the statistical evaluation of the modeling results.

Ta and Nb are group V valve metals which resist corrosion. Anodic dissolution of Ta and Nb in acidic fluoride media of varying HF concentration is investigated using potentiodynamic polarization and electrochemical impedance spectroscopy. Polarization curves showed a clear active and passive region in all the solutions employed in this study. At a given HF concentration, Nb anodic polarization currents are larger compared to those of Ta. EIS of Ta and Nb exhibited a low frequency capacitive loop in active region, and a low frequency negative differential resistance in the passive region. The surface of Ta and Nb was characterized using XPS, and it reveals the presence of both sub oxide and pentoxide. The electrochemical results could be explained by a four step mechanism involving sub-oxide and pentoxide intermediates. The analysis shows that direct dissolution of sub-oxide occurs via an electrochemical pathway and is facilitated by HF⁻₂ species and HF in undissociated form. On the other hand, chemical dissolution of pentoxide, which occurs in parallel, is facilitated by the HF species in undissociated form.

There is great interest in elucidating the corrosion mechanism of magnesium, and different experimental methods and techniques are explored with this purpose. Among the scanning probe techniques, scanning electrochemical microscopy (SECM) is delivering some promising results in recent years. In particular, the use of ion selective microelectrodes (ISME) as SECM sensing probes allow monitoring of the temporal and spatial distribution of different ionic species related to the corrosion reactions. However, a serious disturbance in the measured potential can be observed when it comes to galvanic coupling or polarization of the samples. This work explores the factors that affect the magnitude of the electrical field effects associated with the galvanic coupling, and describes an experimental arrangement for potentiometric SECM able to avoid the unwanted contribution of the potential field. The performance of a double barrel electrode assembly comprising an ion selective microelectrode and an internal reference electrode was compared to that of a conventional single barrel ISME in order to establish its applicability for the investigation of corrosion systems presenting electrical field distributions.

The effects of micro-alloying of plain carbon steel with Cr and Mo on the corrosion behavior in CO₂-saturated (sweet) brine (0.5 M NaCl, pH 6.6) environment, under hydrodynamic conditions, at 80°C were investigated. Crystalline siderite/chukanovite scales formed on all the alloys. Analysis of potentiostatic current transient data suggest that there exists a synergistic interaction between Cr and Mo, which induces more rapid crystallization of the scale compared to Mo-free steels. Increasing the Mo content also suppressed the transport-dependent dissolution current passing through the initially-present amorphous surface film. TEM images of the FIB-sectioned corrosion scales confirm that the corrosion scale formed on 1Cr0.7Mo is comparatively thinner and yet offers greater protectiveness when compared to the plain carbon steel.

In situ electrochemical studies on the oxidation behavior of pyrite in 0.1 M H₂SO₄ solution in the temperature range of 160 to 240°C were performed by measurements of electrochemical impedance spectroscopy (EIS), linear polarization, potentiodynamic polarization and potentiostatic polarization. Results showed that with the increase of temperature, the anodic current density increased, while the corrosion potential (E_corr), polarization resistance, charge transfer resistance (R_ct) and pore resistance (R_pore) decreased. The change of these electrochemical parameters indicated that the increase of temperature promoted the dissolution of pyrite by accelerating the electrochemical step and weakening of the porous passive film. EIS studies with different applied potentials at 240°C revealed that both R_ct and R_pore decreased with increasing applied potential. As the potential increased to 400 mV, the time constant relating to the porous passive film disappeared. These changes demonstrated that sulfur yield was dependent on the potential, and the sulfur yield approached zero at 400 mV at the temperature of 240°C. The values of E_a indicated that pyrite oxidation kinetics were limited by the rate of electrochemical reaction.

Bismuth electroplating and fabrication efforts for its incorporation as an absorber in Superconducting Transition Edge X-ray Sensor devices are summarized. The bismuth films, a few microns thick, are grown using both aqueous and non-aqueous solutions. They are characterized by optical imaging, profilometry, X-ray diffraction, SEM, and by electrical transport (resistivity and Hall Effect) measurements from 30 to 310 K. While aqueous solutions produce an irregular rough and polycrystalline material, with very little chance to tune transport properties, films grown in non-aqueous solvents improve considerably homogeneity, surface roughness, and density. It is also demonstrated how the crystal texture of the films can be controlled with electroplating parameters. This allows orienting anisotropy axes directly during electroplating and thus tune electrical and thermal conductance depending on device requirements. This a significant step toward direct electrodeposition of Bi films with good transport properties, still a significant technological challenge. In order to have reasonable quantitative objectives for physical properties such as surface roughness, crystalline texture, electrical conductivity, etc. Bismuth films are also grown by Physical Vapor Deposition, characterized and compared with the electroplated.

Flexible multi-color electrochromic V₂O₅ thin films have been prepared by electrochemical deposition on the double-layer Graphene/PET substrates. The deposited films have a layered structure with nano-crystals in the amorphous matrix, which contributes to an ultrahigh coloration efficiency of ∼555.83 cm² C⁻¹@800 nm and a large transmittance modulation of 68.94% @800 nm. The large interlayer distance of 1.20 nm, good electrolyte penetration, and short lithium ion diffusion distance make some key electrochromic parameters competitive in our proposed devices. The low-temperature-processed V₂O₅ thin films on Graphene would provide us an opportunity to design and prepare flexible electrochromic devices.

The two-dimensional (2-D) multilayer structured TiC and carbide-derived carbon (CDC) have been prepared by electrochemical etching of ternary layered carbide–Ti₃SiC₂ in molten CaCl₂ at 900°C with 2.5 V and 3.0 V, respectively. Ti₃SiC₂ powder was pressed to form a pellet which was then served as the anode, and a graphite rod was used as the cathode. The obtained TiC product possesses a specific surface area of 653 m² g⁻¹ and a total pore volume of 0.56 cm³ g⁻¹ with a narrow pore size distribution (average pore diameter of 2.0 nm). The obtained CDC material shows a layer graphene-like nanosheets structure, and amorphous carbon coexists with graphitic carbon ribbon in the product. The Raman analysis confirms that the I_D/I_G ratio of the CDC nanosheets is 1.17, indicating the lower degree of graphitization. The layered CDC nanosheets possess a specific surface area of 623 m² g⁻¹ and a total pore volume of 2.06 cm³ g⁻¹ with an average pore diameter of 20–70 nm. It is suggested that the molten salt electrochemical etching process is a novel method for the production of 2-D multilayer material with tuned pores, and have penitential to be used for a variety of applications.

In this research, the cisplatin has been successfully deposited on pure Mg specimen, degradable and promising for the tumor treatment by its local sustained release to prevent the cancer from metastasis and even to achieve its apoptosis. The cathodic polarization tests coupled with electrochemical reactions in various concentrations of cisplatin solutions were qualitatively and quantitatively analyzed to speculate the deposition mechanism of cisplatin by UV visible spectrometer, Fourier transform infrared spectroscopy, field emission scanning electron microscope coupled with energy-dispersive spectroscopy, focused ion beam, and X-ray diffractometer. The drug, cisplatin, is deposited on the pure Mg through exchanging Cl⁻ with OH⁻, produced by the electrochemical method, to form strong hydrogen bonds for attracting one another. The FESEM images of cisplatin coated Mg specimens reveal that the diameter of cisplatin particle is around 50–150 nm with sphere-like shape. While that on cisplatin/HAp composite is less than 30 nm. Due to the high porosity, the drug loading on cisplatin/HAp coated one can be enhanced from 34.65 to 84.93 μg/cm². Also, the drug release duration can be elongated from one day burst to 3 weeks sustained release, which is promising for future clinical applications.

This paper describes experimental investigations on electroless deposition of silver from an aqueous bath containing AgNO₃ and N₂H₄ as the precursor for silver and the reductant, respectively. The kinetics and mechanism of the electrochemical oxidation and reduction processes are studied through the partial polarization plots using the concept of mixed potential theory. Behaviors of cathodic and anodic equilibrium potentials were determined with respect to [Ag⁺] and [N₂H₄], respectively. Thermodynamic expressions for the mixed potential E_m and kinetic expressions for the mixed current i_m were derived by considering specific segments in superimposed cathodic and anodic partial polarization curves and from it to understand the mechanism of the process.

Electrodeposited Ni-Fe-Graphene composite coatings have been prepared on the aluminum alloy substrate from alkaline Ni-Fe alloy electrolyte with varied graphene nanoplatelets (GNPs) concentrations from 0.05 g L⁻¹ to 3 g L⁻¹. The effect of graphene concentration on the microstructure, element composition and mechanical property of Ni-Fe-Graphene composite coating has been investigated. The results indicate that the incorporation of GNPs into the coatings promotes the co-deposition of Ni²⁺ in the electrolyte. Graphene content presents a negative correlation with the iron content in the composites. Graphene content and dispersion in the coatings both play a key role in the properties and when graphene concentration is 1 g L⁻¹, Ni-Fe-Graphene composite coating exhibits the highest hardness (912.6 HV) and best wear resistance (friction coefficient of 0.1990). It is attributed to the grain refinement, excellent mechanical property and self-lubricant of GNPs. The morphology, microstructure and element composition of deposited composites have been characterized using scanning electron microscopy (SEM), energy disperse spectroscopy (EDS), X-ray diffraction (XRD). Raman spectrum is used to characterize the presence of GNPs in the composites.

Obtaining titanium (Ti) coatings on industrially relevant materials at room temperature would be beneficial due to its excellent corrosion resistance and strength. Ionic liquids (ILs) have been discussed as electrolytes for this purpose, but, efforts to electrodeposit titanium from its halide sources in ILs failed due to titanium subhalide formation. Herein, we have investigated the electrode/electrolyte interface (EEI) of TiCl₄ in 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide, [Py_1,4]TFSA, with a focus on the changes in the nanostructure at varying concentrations of the Ti precursor using Atomic Force Microscopy (AFM). Furthermore, the solution species of varying TiCl₄ concentrations were investigated by Raman Spectroscopy. The AFM results reveal that the concentration of TiCl₄ influences strongly the interfacial nanostructure of the Au(111)/electrolyte interface. A typical 'IL' multilayered structure can be seen upon adding 0.1 M TiCl₄ to the IL, which disrupts completely upon further increasing the concentration to ≥ 0.25 M. Furthermore, the AFM force-distance profiles showed that quite soft films have been formed on the electrode surface under electrolysis conditions, which could influence the reduction processes to obtain elemental Ti. Our results reveal that the concentration of TiCl₄ can influence strongly the EEI nanostructure and can provide some new fundamental insights into the double layer structure of TiCl₄ in [Py_1,4]TFSA.

In copper-plating baths for filling of submicron features, a combination of additives regulates the distribution of deposition rate, and in the proper concentrations produces superconformal filling. The present study is built on the competitive adsorption model of superconformal filling in which an adsorbed suppressor, in this instance benzyl viologen or polyethylene glycol, is displaced from the surface by the accelerant 3-mercapto-1-propane sulfonic acid (MPS) during copper electrodeposition. The change in deposition current after progressive additions of suppressor or accelerant was used to determine the surface coverage of each additive as a function of its concentration in solution and of temperature. The data were fitted to the Langmuir isotherm, and the free energy and enthalpy of adsorption or displacement were determined. It was shown that adsorption of PEG or BV is a spontaneous exothermic process, and the displacement of PEG or BV by MPS is a spontaneous endothermic process. Although the suppressors form stronger bonds with the surface, the accelerant displaces them due to the resulting increase in surface-excess entropy.

Material properties of electroless deposited copper film suitable for electronic circuits have been studied on Silver nanoparticle inkjet-printed polyimide substrate. The optimized process includes silver nanoparticle seed printing, sintering at 300°C, followed by electroless deposition. The result was a highly conducting copper metallization with an improved resistivity of 2.1μΩ.cm compared to only printed silver. We also present composition analysis by XPS and structural characterization by FIB-SEM and profilometry. FIB-SEM, XPS, and XRF were integrated together to deduce the kinetics of electroless deposition on the highly porous silver nanoparticle seed. The results and the model indicate that the copper deposition is in two consecutive stages: (a) copper deposited inside the seed silver layer to fill the porous channels formed after annealing (b) the copper deposited uniformly on top of the filled pores. The effective conductance is a result of the two elements, silver and copper, the composite formed in the seed and the dense polycrystalline copper thin film deposited on the top of the seed.

A novel method using an all-wet process to reduce the cost of material in Si-based devices is described, called the electroless and electrodeposit-assisted stripping (E²AS) process. In this approach, a highly adhesive electroless Ni nanorod seed layer is formed on the Si substrate in place of a conventional high-cost physical vapor deposition (PVD) process. Then, a highly stressed Ni film is electrodeposited as the stress layer for lift-off of the Si thin film. Using the E²AS method, a thin Si film can be repetitively detached from a Si substrate without kerf loss, reducing the solar cell manufacturing cost.

Oxygen reduction reaction (ORR) not only needs the excellent electrode materials, but also requires quick mass transfer of dissolved oxygen. To strengthen the ORR and O₂⁻ oxidation desulfurization, pressurized water electrolysis was carried out in this work. The results showed that the desulfurization ratio increased with increasing pressure, indicating that the pressure has strengthened the O₂⁻ generation. As expected, the ORR initial potential shifted from −0.034 V to −0.030 V with increasing pressure from 0.1Mpa to 2Mpa. The peak current, the limit current density and the peak integral area all increased with increasing pressure. On the other hand, the reduction in solution resistance (R_s) and reaction resistance (R_ct) further verified that the pressure can strengthen the transfer of dissolved oxygen and the ORR dynamics. More importantly, the pressure has improved O₂⁻ generated potential in a large parameter window (the width of the metastable zone, the difference between the initial potential and the peak potential of the ORR). The pressure could enhance the O₂⁻ formation, and improve the desulfurization process.

Metal oxide coated carbon materials were shown to have increased ion removal over many of the uncoated carbons when used in capacitive deionization; however, the influence of the coating was dependent on the carbon material used as the substrate. Specifically, four different carbon materials, coated and uncoated, were tested. During removal, the negative electrode was coated with SiO₂ and the positive with γ-Al₂O₃. The SiO₂ coatings improved Ca²⁺ removal for 3 of the 4 carbon materials tested and the γ-Al₂O₃ coatings improved Cl⁻ removal for 2. The mechanism for this increase in removal appeared to be carbon dependent, and could be associated with the addition of new surface groups, improved wettability, or for the low surface area carbon, an increase in specific surface area of the composite material. Moreover, it was also shown that the surface area of the carbon material was not the only factor that determined the electrosorption capacities of the electrode. In addition, certain electrodes had large improvements in ion removal with increases in the applied potential. However, the stability of the electrodes, as well as faradaic reactions that may evolve at high potentials, must be considered when increasing the potential to improve ion removal.

With the rapid development of precision casting technology, more and more casted parts are used for critical components in aero-engines, such as turbine blades, supporting-case and other high-temperature engine parts. However, machining such alloy is very difficult by conventional mechanical methods. Previous studies have shown that electrochemical machining (ECM) is very suitable for efficient material removal of K423A, but is also vulnerable to stray corrosion. In this research, electrochemical turning (ECT), which is an extended form of ECM, is employed to process K423A cast revolving parts. The way of electrolyte-jet is implemented by an inter-jet cathode to improve machining localization and reduce stray corrosion. Simulation results show that the use of electrolyte-jet could effectively suppress the stray corrosion on non-machining areas. The diameter and outlet of the inter-jet cathode, and the cathode feed rate were designed, respectively. Experiments were conducted to verify the proposed method. It was confirmed that the stray corrosion of the non-machining area can be reduced significantly and the cathode feed rate can also be enhanced by using the proposed method. Finally, a simulated sample of a particular model of cartridge receiver with a larger machining height of 30 mm was fabricated successfully.

Ramie is a typical low-cost and sustainable natural biomass resource in China. In this study, we fabricated nitrogen-doped activated carbon with high surface area from ramie biomass as a highly efficient electrocatalyst for hydrogen peroxide production. Electrochemical characterizations revealed that the as-prepared catalyst showed superior oxygen reduction reaction activity through a two-electron pathway and extraordinary long-term stability. The current density and onset potential of AC700 was greater than that of other as-prepared samples. The nitrogen atoms on the catalyst surface was derived from the biomass and deconvoluted by XPS techniques, which is beneficial for the enhancement of electrocatalytic performance. The present work furthers the development of biomass-derived carbon material for environmental applications.

Roles of ultrasound on the hydroxyl radical generation from water electrolysis were examined in this work. Results indicated that the ultrasound could not only strengthen the mass transfer of liquid phase, but also could improve the electron gain and loss for hydroxyl ion, and thus improve the hydroxyl radical generation. Results from ESR signal indicated that, ultrasonic strengthened hydroxyl radical formation from water electrolysis in whatever in alkaline or acidic solution. Ultrasound improved the equilibrium potential and current of OER, indicating that ultrasound inhibited the thermodynamics conditions in OER. Ultrasound inhibited the oxygen gas release, and thus resulting in the increase in the amount of hydroxyl radicals. The R_ct of OER increased with ultrasound addition, while the R_s for water electrolysis decreased. Whatever platinum (Pt) or nickel (Ni) electrode, bauxite electrolysis desulfurization all were improved by ultrasound, and the desulfurization of Ni under ultrasound was higher than Pt without ultrasound. That is, electrolysis desulfurization with Ni electrode in presence of ultrasound could replace electrolysis desulfurization with Pt electrode in absence of ultrasound.

The electrochemical and tribological performance of cobalt during electrochemical-mechanical polishing (ECMP) was investigated in situ. Effects of polishing conditions such as applied loads and rotating speeds on frictional behavior and potentiodynamic polarization were studied. Results showed that the friction coefficient decreased slightly with the increase in applied load and polishing speed indicating the boundary lubrication regime during cobalt ECMP. The corrosion current declined firstly and then increased with the increase in mechanical power input. Further analysis revealed that the cobalt surface electrochemistry was interrelated to mechanical impact and corrosive environment, and it is not simply a linear relationship. The synergy of mechanically induced material removal and oxidation in the polishing process depends on the mechanical power and electrochemical reaction. This finding is beneficial to uncovering the mechanism of cobalt ECMP and guiding the process optimization.

In this work we demonstrate the validity of a multi-physics model using COMSOL to predict the local current density distribution at the cathode of a copper electrowinning test cell. Important developments utilizing Euler-Euler bubbly flow with coupled Nernst-Planck transport equations allow additional insights into deposit characteristics and topographies.

A titanium-base nano-coating Sb-doped SnO₂ electrode with a nano-scaled sphere-stacking structure was successfully fabricated using a solvothermal synthesis approach to enhance electrochemical performance through the formation of a nano-sized catalyst layer. Based on scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis, the nano-coated SnO₂-Sb electrode had very small (23 nm) catalyst grains that had a stacked sphere appearance, and thus a much greater specific surface area than the control electrode (SnO₂-Sb prepared by a dip-coating method, 106 nm grain size). X-ray photoelectron spectroscopy (XPS) analysis showed that the nano-coated electrode possessed a higher concentration of oxygen vacancies, which provided many more active centers for the formation of adsorbed Oxygen (Oads), which increased the production of •OH radicals and therefore the catalytic activity of organic pollutant degradation. Linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) showed that the electrode with a nano-structure coating had a higher oxygen evolution potential (2.1 V, vs. Ag/AgCl) and smaller charge transfer resistance (49 Ω) than the control (1.95 V and 93 Ω). A kinetic analysis of the electrochemical degradation of phenol showed that the first-order kinetic rate constant for the nano-coated electrode was 1.72 times higher than the control. Accelerated service life testing showed that the stability of this novel fabricated electrode was 15 h, which was nearly 11 times longer than that of non-nano SnO₂-Sb electrode.

In this paper, a new modified quantitative method for order evaluation of porous AAO (Anodic Aluminum Oxide) was proposed. Using this method, the regional order of structural cells of porous AAO can be defined as a specific value. Based on it, the critical temperature (T_c) and optimum temperature (T_o), which correspond to the order/disorder critical point and the best order point, have been investigated in detail. The effect of anodization voltage (U_a) and temperature of electrolyte (T_e) on the regional order of structural cells of porous AAO has also been studied in 0.3 M oxalic acid electrolyte (U_a: 40–50 V, T_e: 5–50°C). Moreover, the influence of current density (J_a), growth rate of porous AAO (v_a), and the internal stress in AAO on the self-ordering of porous AAO has been systematically investigated. The new modified quantitative method can also be used to evaluate other close-packed patterns, and the above mentioned mechanism findings may also be applicable to other valve metal anodization processes.

The potential biomedical application near β-type Ti-35Nb-7Zr alloy with different CPP ceramic additions were evaluated in vitro using electrochemical method and osteoblasts co-cultured. A small amount addition of calcium pyrophosphate (CPP) ceramic induced the formation of oxide film on the surface of the composites that can withstand passive layer breakdown and the onset of localized forms of corrosion. But localized breakdown of the oxide layer occurred on composites as the CPP exceeded 20 wt%. Ti-35Nb-7Zr-10CPP exhibits a wide passive range in the polarization curve and gets a higher potential for inducing growth of bone-like apatite and proliferation of osteoblasts on its surface compared to that of the Ti-35Nb-7Zr, CP Ti and Ti6Al4V (TC4) alloys. The favorable cell viability and growth inside the pores of the composites arise from the rough micro-porous surface and the release of bioactive metal-ceramic phase ions into the physiological environment.

In order to study the formation process of the pore embryos in porous anodic alumina (PAA) and compact aluminum oxide (CAO), a new three-tier structure (PAA-CAO-PAA) was designed and fabricated in 3 wt% H₂C₂O₄ and 8 wt% ammonium sebacate aqueous solutions. By exactly controlling the time of the third anodization in 3 wt% H₂C₂O₄ solution, the formation process of the pore embryos is explicitly seen for the first time. The hemispherical pore bottom and hemispherical barrier-oxide base generated in the first anodization. After the second anodization, two hemispherical structures disappear and two interfaces become flat. When the third anodization finished under given voltage and anodizing time, the hemispherical structures reappear. A bigger hemispherical barrier-oxide base and spiny oxide formed in the third anodization. Besides, the newly formed pore embryos are not connected with the above pores and the channels cannot be observed in the compact oxide layer. All these facts cannot be explained by the traditional field-assisted dissolution model. Based on the oxide flow model and the electronic current theory, the formation process of pore embryos under the compact layer can be elucidated by the oxygen bubble mould effect.

A previous experiment showed that the rate of the electropolishing of a copper anode may be increased by twofold when generating a 60 KHz to 1.7 MHz frequency vibration in the anode. In this work we use theory to elucidate the mechanisms by which the vibration may enhance the transport of ions in the electrolyte solution and support the formation of dents in the anode, which was observed in experiment. We find that in the limit of weak ion convection the transport of ions mainly supports the formation of dents in the anode. However, in the limit of prominent ion convection we find an appreciable contribution of the vibration to the efficiency of the electropolishing process, in accordance with the previous experimental findings. The contribution of the vibration to ion transport is given by , in which the Peclét number, Pe, quantifies the ratio between the convective and diffusive fluxes of ions, and D, k, and C_s are the diffusion coefficient of the ions, the wavenumber of the vibration, and the solubility limit of the ions in the electrolyte.

A very promising method for extraction of high pure titanium is electro-refining it from molten salt. Thus, a critical work for researchers is finding a molten salt which is impurity free. In order to clarify the behavior of the impurity element (oxide) in molten salt, the electrochemical behavior of oxide ions has been investigated in an equimolar NaCl-KCl by square wave voltammetry (SWV) and electrochemical titration technique (ETT) at 750°C. The purpose is to determine the residual content of oxide in the molten NaCl-KCl by using above in-situ methods. A distinct oxidation peak with a height proportional to the oxide content was observed from square wave voltammograms. The titrations of O²⁻ were applied by sodium oxide additions. The results obtained through electrochemical titration technique show that the oxide content in the melt and the free oxide ions (O²⁻) detected content have a good linear relationship. The residual contents of oxide in the melt are around 700 ppm and the relationship between current density and concentration of oxide was determined by SWV method which is according to that obtained by using ETT method.

The electrochemical performance of thin film boron-doped diamond (BDD) electrodes deposited on either single crystal p-type Si (Si/BDD) or Nb (Nb/BDD) substrates have been investigated for the electrooxidation of azo-dye Acid Violet 7 (AV7). Both electrodes were characterized by linear voltammetry and the production of hydroxyl radicals (^•OH) at their surfaces was assessed by spin trap experiment using N,N-dimethyl-p-nitrosoaniline (RNO) as a spin trap molecule. Slightly higher O₂ evolution reaction (OER) potential was observed with Nb/BDD compared to Si/BDD in both 0.05 M Na₂SO₄ and AV7 solutions. Enhanced bleaching of RNO was always observed when an increased current density was applied and a significant decay of the adsorption band of RNO was attained with Nb/BDD compared to Si/BDD electrode, indicating higher generation of ^•OH on its surface. Complete decolorization of 200 mg L⁻¹ of AV7 was achieved with either electrodes at current density of 30 and 60 mA cm⁻² in 120 min or less. Quite similar degradation efficiency was attained at both electrodes but Si/BDD showed better results than Nb/BDD. Nevertheless, lower energy requirements was achieved by Nb/BDD, demonstrating that it can be a suitable electrode for an efficient electrochemical oxidation process.

Single-layer MoS₂ and Ni₈₀Cr₂₀, as well as a double-layer Ni₈₀Cr₂₀/MoS₂, films were fabricated on pure iron substrate by magnetron sputtering, and their hydrogen permeation properties were investigated by electrochemical hydrogen permeation experiments. It was found that the single-layer MoS₂ or Ni₈₀Cr₂₀ could act as a barrier effectively retarding hydrogen permeation toward the substrate due to their lower diffusion coefficient. Using the overpotential stepping hydrogen permeation test (OSHPT), the lattice diffusion coefficient (D_L) of hydrogen in MoS₂ and Ni₈₀Cr₂₀ films was determined to be 8.35 × 10⁻⁸ and 1.76 × 10⁻⁹ cm²/s, respectively. Furthermore, it was observed that the use of Ni₈₀Cr₂₀ as the intermediate layer not only could improve the surface state of MoS₂ after hydrogen permeation but also enhanced the effect of retarding hydrogen permeation in the double-layer Ni₈₀Cr₂₀/MoS₂ film. In addition, the influences of MoS₂ and Ni₈₀Cr₂₀ films on the hydrogen evolution reaction (HER) were also investigated.

In this work, it was studied the treatment of soil washing effluents coming from the remediation of a soil spiked with atrazine by using photolysis, sonolysis, electrolysis as well as photo- and sono- electrochemical technologies using diamond anodes. Results clearly showed that both irradiated technologies were more efficient than the single electrolytic technology and these can become a good alternative for the treatment of these effluents. Main characteristic of the effluents produced in the soil washing depended strongly on the ratio surfactant/soil. And, as a novel catalytic effect, the production of persulfate from the sulfate released during the oxidation of SDS played an important role in the oxidation mechanisms of this type of pollutants. Then, SDS can be proposed as an auxiliary reagent to be introduced in the effluent when emulsion is present to increase the efficiency of the electrochemical approach used.

Tailoring chemical architecture of precious-metal based materials provides the opportunity to improve their catalytic activity, which is important for various kinds of fuel cells. Herein, we show that iron/cobalt/nitrogen codoped carbon (FeCo/C/N) substrate can greatly promote electrocatalytic oxygen reduction reaction (ORR) activity of platinum by modifying its' electronic structure in comparison to those of nitrogen/carbon and carbon supports. FeCo/C/N substrate induces the negative shift of Pt 4f binding energy and increases the electron density of Pt outer orbital, which is used for the optimization of absorption energy between ORR intermediates and Pt surface. The experiments and theoretical simulation confirm the change of Pt electronic structure and enhancement of ORR kinetic, which provide a guiding principle for rational design of Pt-based ORR catalysts.

This work is a study of the impact of short-term strong cathodic polarization in a Ni|YSZ model system using Ni probes as working microelectrodes in a high temperature scanning probe microscope at 650°C in humidified 9% H₂ in N₂. Impedance spectroscopy revealed one to three orders of magnitude decrease in the high frequency resistance and four to five orders of magnitude decrease in the low frequency impedance with polarization from −1.06 V to −3.06 V vs E°(O₂), indicating introduction of electronic conductivity and expansion of the reaction zone around the Ni microelectrode. The effect on the Ni|YSZ interface included formation of electronic conductance, reaction between Ni and YSZ and accumulation of impurities around the Ni|YSZ contact as verified by conductance scans of the polarized area. Cyclic voltammetry was used to compare three systems with different impurity levels and showed that the presence of silicates reduces the current, i.e. lowers the performance of the electrode reaction.

Catalyst layer inks are examples of biphasic material systems composed of a solid material, a polymer, and a solvent. Nanoscale interactions between the individual constituents can alter macroscopic properties that are relevant for coating and manufacturing processes (i.e. viscosity, surface tension, aggregation, and rheology). Control over these macroscale properties are important for controlled electrode formation during scalable roll-to-roll manufacturing. The underlying interactions include polymer|particle, particle|solvent, and polymer|solvent interactions. In this work we systematically investigate polymer|particle interactions via studying a range of formulated inks composed of different solvents (methanol, isopropyl alcohol, octanol, and water), varying polymer loadings, and particles with different surface charges. Ink aging is also addressed and over short time periods (<1 hr shelf life) the addition of a perfluorosulfonic acid ionomer was shown to stabilize the ink and also decrease the aggregation size. However, over long time periods (168 hrs) the aggregation size is independent of polymer loading, and approaches a steady state aggregation size around 350 nm. This equilibrium point suggests that the polymer is free to diffuse, adsorb, and relax within the excluded volume region. Furthermore, these results suggest that primary aggregates can be broken up with the addition of very low polymer loadings (15% I:C). A semi-empirical model is used to describe polymer|particle interactions within the ink, and the polymer coverage at the surface of the carbon was found to be the most sensitive parameter dictating ink stability. Finally, coating and rheology experiments are completed on all inks.

Significant effort has been devoted to reduce the cathode platinum loading for proton exchange membrane fuel cells (PEMFCs). To achieve this, it is imperative to have a comprehensive understanding of the polarization behavior for the low-Pt-loading electrodes, and to reduce the polarization loss due to oxygen transport limitation. Herein, a systematic breakdown of six types of polarization sources is presented to elaborate the effect of cathode Pt loading and the catalyst layer fabrication process. Four modifications are applied to accommodate low cathode Pt loading. GORE PRIMEA catalyst-coated membranes (CCMs) were used as a baseline and tested with 0.4 and 0.1 mg cm⁻² cathode Pt loading. A novel electrode fabrication method, reactive spray deposition technology (RSDT), was employed to fabricate 0.1 mg cm⁻² Pt loading cathode using Ketjen black carbon as catalyst supports. Non-electrode concentration overpotential is determined by the cathode Pt loading and the type of diffusion medium, while cathode electrode concentration overpotential is determined by the ionomer thin film and ionomer/Pt interface which are dependent on the fabrication process. It is shown that the RSDT process can improve fuel cell performance at 0.1 mg cm⁻² cathode Pt loading by reducing the cathode electrode concentration overpotential.

A novel synthetic process was developed to synthesize nano-sized core-shell catalysts through atomic rearrangement by heat-treatment. Agglomeration of nanoparticles caused by the high-temperature heat-treatment was alleviated by using a modified protective coating method. In this method, the carbon layer formed by the carbonization of polydopamine serves as a protective coating layer, which suppresses the sintering of the catalyst particles continuously until the high-temperature heat-treatment is completed. Later, the carbonized carbon layer is removed by ozone treatment because it blocks the active site of the catalyst. Since ozone is a highly oxidative gas, it can selectively remove the carbon layer at room temperature in just 7 minutes without affecting the physical properties of the catalyst itself, which makes this method suitable for mass production. The Pt-based alloy catalyst was prepared by this unique process was proved to have a Pt-rich shell structure, and the particles can remain small (∼5 nm) even after high-temperature heat-treatment, thus exhibiting high oxygen reduction reaction (ORR) activity in fuel cells.

We report a novel approach to processing of impedance spectra of a PEM fuel cell. We split the cell into N virtual segments and let each segment to have its own set of transport and kinetic parameters. The impedance of a single segment is calculated using our recent physics–based impedance model; the segments are "linked" by equation for the oxygen mass balance in the cathode channel transporting the local phase and amplitude information from one segment to another. Thanks to this transport, the total cell impedance contains information on the local transport and kinetic properties of the cell. We show that fitting the model cell impedance to the experimental spectra yields the parameters of individual segments, i.e., the shape of the cell physical parameters along the cathode channel.

A mixed Fe+CoO precursor was successfully utilized to synthesize a dense CoFe₂O₄ spinel coating on the Crofer 22 APU interconnect via reactive sintering at 900°C for 2 h in air without the use of any reduction treatment. Both the uncoated and coated samples were subject to thermal oxidation at 850°C for 500 h in air. Phase constituents, microstructure, and area specific resistance (ASR) of the uncoated and coated samples before and after the oxidation testing were evaluated. The CoFe₂O₄ layer effectively reduced the Cr₂O₃ scale growth and lowered the scale ASR.

We have studied the factors affecting the performances of one-compartment hydrogen peroxide photofuel cell (H₂O₂-PFC) consisting of TiO₂ photoanode, cathode, and an aqueous electrolyte solution. As the photoanode, a dense TiO₂ film was formed on fluorine-doped tin oxide by a dip-coating method (d-TiO₂/FTO) with the thickness controlled below ∼0.5 μm, and a mesoporous TiO₂ nanocrystalline film with a thickness of 3.6 μm was coated on FTO (mp-TiO₂/FTO) by a doctor blade method. The d-TiO₂/FTO provides performances superior to mp-TiO₂/FTO in spite that the decrease in the surface area. Building a compact TiO₂ underlayer by a spray method (d-TiO₂/s-TiO₂/FTO) results in further improvement of the cell performances. On the other hand, the replacement of glassy carbon cathode by Prussian Blue-electrodeposited FTO drastically increases the cell performances due to its excellent electrocatalytic activity for the H₂O₂ reduction. A one-compartment H₂O₂-PFC with the structure of d-TiO₂/s-TiO₂/FTO (photoanode) | 0.1 M NaClO₄ and 0.1 M H₂O₂ (pH 3, electrolyte solution) | PB/FTO (cathode) exhibits short-circuit current (J_sc) of 1.57 mA cm⁻² and open-circuit voltage (V_oc) of 787 mV.

In this study, the influence of catalyst loading on the performance of a proton exchange membrane (PEM) water electrolyzer is investigated (Nafion 212 membrane; IrO₂/TiO₂ (anode) and Pt/C (cathode)). Due to the fast kinetics of the hydrogen evolution reaction (HER) on platinum (Pt), the Pt loading on the cathode can be reduced from 0.30 mg_Pt cm⁻² to 0.025 mg_Pt cm⁻² without any negative effect on performance. On the anode, the iridium (Ir) loading was varied between 0.20–5.41 mg_Ir cm⁻² and an optimum in performance at operational current densities (≥1 A cm⁻²) was found for 1–2 mg_Ir cm⁻². At higher Ir loadings, the performance decreases at high current densities due to insufficient water transport through the catalyst layer whereas at Ir loadings <0.5 mg_Ir cm⁻² the catalyst layer becomes inhomogeneous, which leads to a lower electrochemically active area and catalyst utilization, resulting in a significant decrease of performance. To investigate the potential for a large-scale application of PEM water electrolysis, the Ir-specific power density (g_Ir kW⁻¹) for membrane electrode assemblies (MEAs) with different catalyst loadings is analyzed as a function of voltage efficiency, and the consequences regarding catalyst material requirements are discussed.

CeO₂-C(Vulcan) catalyst materials activated with Pt nanoclusters have been synthesized using different methods comprising microwave synthesis, reduction with hydrogen and reduction with NaBH₄. The materials have been analyzed using low temperature nitrogen adsorption, X-ray diffraction and scanning electron microscopy with energy-dispersive X-ray spectroscopy methods. Methanol oxidation has been studied using cyclic voltammetry, chronoamperometry and impedance methods. Very noticeable influence of catalyst surface structure and porosity, depending on the complex catalyst preparation conditions, has been demonstrated. High electrochemically active surface area values have been calculated. High current densities of MeOH oxidation have been established for several catalysts. Fitting of the impedance data has been performed, and the results have been discussed.

Cracking of α-LiAlO₂ matrices in molten carbonate fuel cells (MCFC) leads to reduction in the performance. It was demonstrated in this work that the mechanical strength of α-LiAlO₂ matrices is improved by heat-treating at 800°C under ambient gas atmosphere. The mechanical strength (2.91MPa) of the heat-treated matrix was enhanced more than 5 fold compared to the non-heat-treated matrix (0.58MPa). The porosity and crystal structure of the α-LiAlO₂ matrices were not changed after the heat-treatment. The wetting behavior and distribution of carbonate in the heat-treated and the non-heat-treated matrix were investigated and compared. Both non-heat-treated and heat-treated α-LiAlO₂ matrices were completely wetted by molten carbonate. The molten carbonate distribution was concentrated right underneath the circular region formed by the molten carbonate drop in the matrix. Non-heat-treated α-LiAlO₂ samples cracked as a result of the complete absorption of molten carbonate, however, the heat-treated α-LiAlO₂ matrices did not crack, presumably due to their enhanced mechanical strength.

The detailed density functional theory calculations were performed to screen the oxygen reduction reaction (ORR) catalytic activity of several kinds of Fe−S_x/C catalysts such as Fe−S₂/C, Fe−S_2×2/C, Fe−S₃/C, Fe−S₄/C, and Fe−S₆/C. The results suggest that only the Fe−S₂/C structure could maintain its initial planar structure after the geometry optimization, indicating that it is most likely to have ORR catalytic ability. Further investigations find that the O₂ molecule is firstly chemisorbed on the Fe−S₂ active site with a stable side-on mode, and then is gradually reduced to H₂O following a 4e⁻ OOH dissociation pathway. Both thermodynamic adsorption energies of ORR intermediates and kinetic activation energies of proton transfers indicate that the current Fe−S₂/C catalytic site possesses the comparable catalytic activity to that of precious Pt catalysts. Furthermore, compared with Pt(111) surface, it also has very excellent tolerance to some impurities such as sulfur compounds (SO₂, H₂S), carbon compounds (CO), and nitrogen compounds (NO, NH₃).

Fuel cells have important applications in recent decades due to high-energy demands, fossil fuel depletions, and environmental pollution throughout world. Pt/Pd nanoparticles/polyoxometalate/ionic liquid (ILs) nanohybrid synthesized for the first time and characterized by transmission electron microscope, scanning electron microscope, X-ray photo electron spectroscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction method. A cost-effective catalyst has been developed on Pt/Pd nanoparticles/polyoxometalate/ionic liquid nanohybrid. The developed catalyst based on bimetallic nanoparticle demonstrates effective methanol oxidation in comparison with catalysts on monometallic nanoparticle and polyoxometalate/ionic liquid nanohybrid.

Anodic reaction pathways in proton-conducting solid oxide electrolyzer cells (H⁺−SOECs) were investigated using electrochemical impedance spectroscopy with a cell structure of Sm_0.5Sr_0.5CoO₃ (anode) | BaZr_0.4Ce_0.4Y_0.2O_3-δ | Pt (cathode). Densely sintered BaZr_0.4Ce_0.4Y_0.2O_3-δ ceramics (>97% relative density) were fabricated by a reactive sintering process with a 2 mol% Zn(NO₃)₂ additive and were applied as the electrolyte. The impedance spectra were measured while the oxygen (p_O2) and water partial pressures (p_H2O) in the anode side were systematically varied, which revealed that the SOECs have two polarization resistances at the anode side, one proportional to p_O2^−1/4 and p_H2O⁰ and another insensitive to p_O2 and p_H2O. A comparison between the experimental results and elementary step modeling revealed that the actual anode reactions could be described by the reverse mode H⁺-SOFC cathode reactions, and, thus, the elementary steps dominating the anodic polarization resistance were assigned.

Quaternization of poly(2,6-dimethyl-1,4-phenylene oxide)s (PPOs) with a series of saturated heterocyclic compounds was carried out via the Mannich reaction to fabricate anion exchange membranes (AEMs) with high alkaline chemical stability and ion conductivity. The heterocyclic quaternary ammonium cations include 1-methylpyrrolidinium (MPy), 1-ethylpyrrolidinium (EPy), 1-butylpyrrolidinium (BPy), 1-methylpiperidinium (MPrD), 1-ethylpiperidinium (EPrD) and N-methylmorpholinium (NMM). For comparison, trimethylammonium (TMA) and 1-methylimidazolium (MeIm) functionalized PPO membranes were fabricated as well. The physicochemical properties of the prepared membranes were investigated in terms of water uptake, swelling, ion exchange capacity, mechanical properties, conductivity and tolerance to alkalies. The AEMs having saturated heterocyclic quaternary ammonium groups exhibited better resistance to nucleopholic attack of hydroxide ions than PPO-TMA and PPO-MeIm membranes, especially the PPO-MPy membrane, which retained its initial conductivity of 87.5% after immersed in 1M KOH at 80°C for 508 h.

A long-term test with a two-layer solid oxide electrolyzer stack was carried out for more than 20 000 hours. The stack was mainly operated in a furnace environment in electrolysis mode, with 50% humidification of H₂ at 800°C, a current density of −0.5 Acm⁻² and steam conversion rate of 50%. After ∼18 000 hours of operation in electrolysis mode, the voltage and area specific resistance degradation rates were ∼0.6%/kh and 8.2%/kh, respectively. A detailed post mortem analysis of cells including ICP-OES and microstructural analysis was conducted. Two main degradation phenomena were observed in the cells: In the fuel electrode, the depletion and agglomeration of nickel were visible. At the air electrode, demixing of the air electrode and diffusion of strontium took place. This was observed in the formation of strontium zirconate at the interface between the electrolyte and the GDC barrier layer as well as in the formation of strontium oxide and strontium chromate on top of the cells. Strontium oxide was even found in pores on top of the electrolyte.

Transport of reactants and products to/from reactions sites affects the electrochemical energy conversion performance of fuel cells substantially. At high reactant utilization rates, mass transport can be the performance limiting factor, resulting in significant variations of current and temperature, etc. in the active field. To overcome mass transport limitations, reactants can be supplied at high rates and proper flow fields can be designed, for both of which numerical simulations are quite valuable. In these regards, although the highest care is put on the transport of species within active area of cells/stacks, herein we show the onset of mass transport limitation in the inlet periphery, i.e., extension of the concentration gradient of reactants from reactions sites inward the inlet periphery at high reactant utilization rates. We clarify this phenomenon leaning upon the computational error appearing in the concentration profile of a microtubular Solid Oxide Fuel Cell (SOFC) while simulating its electrochemical performance. For eliminating this error in numerical studies of fuel cells, we propose and demonstrate a practical method. We also determine the critical ratio of consumed/supplied mass fluxes for evaluating relevant (reactant species) SOFC systems in terms of the mass transport limitation in their inlet peripheries.

We have reported the formation of a thin manganese cobalt sulfide (MCS) film on a fluorine-doped SnO₂ (FTO) substrate by a facile electrodeposition method for fabricating quantum-dot-sensitized solar cells (QDSSCs). The resulting FTO/MCS films are subsequently employed as counter electrodes (CEs) for cadmium selenide-based QDSSCs. The QDSSC with the FTO/MCS CE provided significantly enhanced short circuit current and fill factor, resulting in very high overall energy conversion efficiency (3.22%) compared to that with the Pt CE (1.08%) under 1-sun illumination. This can be attributed to the significantly enhanced electrocatalytic activity and superior electrical conductivity of the binary transition metal sulfide in addition to the excellent electrical contact at the interface between the electrodeposited MCS film and the FTO. Furthermore, the FTO/MCS exhibit excellent electrochemical stability, unlike the conventional Pt CE. These findings suggest that FTO/MCS should be a promising electrocatalytic electrode material for practical energy conversion applications.

Incorporation of short-side chain (SSC) ionomers in the catalyst layers (CL) of proton exchange membrane fuel cells (PEMFCs) can improve performance, particularly at low relative humidities. We attempt to understand this effect by comparing PEMFCs with cathode CLs containing Pt on carbon-black (CB) and either SSC Aquivion ionomer or a standard long-side-chain (LSC) Nafion ionomer at 50% and 100% RH. The CL microstructures are characterized for their micro- and mesoporosity. The CLs are formed into PEMFCs and probed with polarization curves, cyclic voltammetry, O₂ gain, limiting current measurements, and electrochemical impedance spectroscopy. PEMFCs containing the SSC ionomer in the cathode CL have superior polarization curves compared to those containing the LSC ionomer in the mass transport region under all conditions. We find that the SSC ionomer imparts lower proton transport resistances, lower charge transfer resistance to the cathode near 0.60 V, and lower mass transport resistance at 0.40 V. We attribute some of the performance improvements to the superior proton conductivity of the SSC ionomer, and the remainder to the higher micropore volume in the SSC-containing CLs which can more effectively evaporate water to the gas phase, improving both the availability of catalyst sites for charge transfer and mesopores for gas transport.

Iron is unstable as an oxygen evolution electrode in alkaline media. Thus, relatively expensive nickel-based electrodes are used in industrial alkaline water electrolysis. We show that an iron substrate can be rendered stable and electrocatalytically active for the oxygen evolution reaction by nano-scale surface modification with nickel. The electrocatalytic activity of such a surface-modified iron electrode is comparable to the recently-reported nickel-based catalysts. The electrocatalytic activity is due to a 50-nanometer layer of a high-surface area α-nickel hydroxide on the iron electrode. The nickel modification renders the iron electrode electrically-conductive, prevents dielectric breakdown, and thus endows anodic stability. The electrocatalytic activity is unchanged even after 1000 hours of continuous operation. The temperature of preparation is critical, as excessive dehydration of the hydroxide layer results in nickel ferrite formation and a drastic reduction in electrocatalytic activity. We report significant insight into the surface chemical composition and structure of the catalyst layer by X-ray Absorption Spectroscopy, Photoelectron Spectroscopy, and Transmission Electron Microscopy. Electrochemical kinetics analysis suggests that surface hydroxo-intermediates react with the hydroxide ions from the solution to evolve oxygen. Thus, the surface-modified iron substrates present an opportunity for improving the performance and reducing the cost of alkaline water electrolysis systems.

As a widely investigated category of non-precious metal electrocatalysts for the oxygen reduction reaction (ORR), metal-N_x-C materials are gaining increasing attention both in the rational synthesis of catalysts and in the study of structure-activity relationships. Carbon supports are important to the performance of these catalysts toward the ORR. Graphene has been used in many electrocatalysts due to its notable characteristics, such as large specific surface area, and high conductivity, but it is further limited by the tendency to agglomerate. Here, carbon nanotubes (CNTs) were employed to effectively suppress the agglomeration of graphene. The binary carbon complex was loaded with iron phthalocyanine (FePc), achieving better activity than commercialized Pt/C (30 wt%) with a positive shift of half-wave potential of 20 mV after heat-treatment at 750°C. SEM, TEM, XPS and XAS measurements revealed that the insertion of CNTs not only suppressed the stacking of graphene layers, but also enhanced the catalytic performance during the RRDE and Zn-air battery tests in alkaline electrolyte by exposing more ORR active sites in the Fe-N_x structure.

A novel electrochemical system for sulfenylation of indoles with disulfides to generate 3-sulfenylindoles via C-S bond formation mediated by potassium iodide at a low potential was developed. Iodine was electrogenerated from iodide ions at a graphite anode and showed a high catalytic activity for the electrochemical sulfenylation reactions. A variety of aromatic, heteroaromatic and aliphatic disulfides could react with 2-methlyindole to synthesize the corresponding 3-sulfenylindoles in good to excellent yields. In addition, protected and unprotected indoles with various groups, especially electron-donating groups, also performed well in the sulfenylation reactions. The transformation, which proceeded through the redox of iodine and the generation of intermediate 3-iodoindole, provided an efficient and environmentally benign protocol for the synthesis of 3-sulfenylindoles under mild conditions.

To overcome the short lifetime and low electrochemical activity of dimensionally stable anodes, we developed a novel anode material, the (Ru,Ir,Sn)O₂/G electrode, for chlorine evolution reaction. The (Ru,Ir,Sn)O₂/G electrode was prepared by introducing a graphene layer into the (Ru,Ir,Sn)O₂ coating via thermal decomposition. energy-dispersive spectroscopy results revealed that graphene was successfully retained in the (Ru,Ir,Sn)O₂ coating. In contrast to the (Ru,Ir,Sn)O₂ electrode, the microstructure of the (Ru,Ir,Sn)O₂/G electrode was flat, and there were fewer surface cracks. Linear sweep voltammetry showed values of the chlorine and oxygen evolution overpotentials of the prepared (Ru,Ir,Sn)O₂/G electrode of 1.076 V and 1.290 V, respectively. This indicates that the electrocatalytic activity of the (Ru,Ir,Sn)O₂/G electrode is better than that of the (Ru,Ir,Sn)O₂ electrode. Moreover, electrochemical impedance spectroscopy and an accelerated service lifetime experiment were conducted to study the stability of (Ru,Ir,Sn)O₂/G electrodes. The results indicate that the resistance of the (Ru,Ir,Sn)O₂/G electrode for the oxygen evolution reaction increased and the accelerated lifetime was 3.35 times longer than that of the (Ru,Ir,Sn)O₂ electrode at 2 A/cm² in 0.5 mol/L H₂SO₄.

A new phenylthiophene-containing 2,5-dithienylpyrrole derivative, namely 2,5-di(thiophen-2-yl)-1-(4-(thiophen-2-yl)phenyl)-pyrrole (DTTPP), was synthesized and its corresponding homopolymer (PDTTPP) and copolymers (P(DTTPP-co-DTP (dithieno[3,2-b:2',3'-d]pyrrole)) and P(DTTPP-co-DTC (3,6-di(2-thienyl)carbazole))) were prepared using electrochemical polymerization. Spectroelectrochemical studies showed that the PDTTPP film was yellowish-green, bluish purple, and deep bluish violet in neutral, oxidized, and highly oxidized states, respectively. The P(DTTPP-co-DTP) film exhibited a conspicuous color transition between five colors (orange brown at 0 V, coffee at 0.8 V, bluish gray at 1.0 V, bluish purple at 1.2 V, and deep bluish violet at 1.4 V). The maximum optical contrast (ΔT_max) of the PDTTPP, P(DTTPP-co-DTP), and P(DTTPP-co-DTC) films were estimated as 36.7% at 970 nm, 63.5% at 1216 nm, and 46.2% at 932 nm, respectively, and the coloration efficiency (η) of the PDTTPP and P(DTTPP-co-DTP) films were determined as 303.84 cm² C⁻¹ at 970 nm and 260.65 cm² C⁻¹ at 1216 nm, respectively, in an ionic liquid solution. A dual type PDTTPP/PProDOT-Et₂ (poly(3,3-diethyl-3,4-dihydro-2H-thieno[3,4–b][1,4]dioxepine)) electrochromic device (ECD) attained a high ΔT_max (43.5%) and a high coloration efficiency (895.53 cm² C⁻¹) at 594 nm, whereas a P(DTTPP-co-DTP)/PProDOT-Et₂ ECD realized a high ΔT_max (52.4%) at 592 nm and satisfactory long-term cycling stability and open circuit memory.

Catalytic oxidation of ferrous sulfate with molecular oxygen in 0.5 M H₂SO₄ has been studied on carbon supported platinum catalyst. Analysis of this catalytic chemical reaction as two distinct electrochemical half reactions proceeding on the catalyst surface is presented. Further, it is proposed that the catalytic chemical reaction can be studied based on mixed potential theory. Pertinent results for the proposal are presented in terms of conversions to ferric ions and the potential acquired by the electrode when immersed in an oxygen saturated solution of ferrous sulfate (mixed potential). The two individual half reactions have been studied separately to obtain key electrochemical parameters through rotating disk electrode experiments. A theoretical approach is also presented that would enable analysis of the catalytic chemical reaction through few electrochemical parameters. The results obtained clearly demonstrate that a greater understanding of various mechanistic aspects of a catalytic chemical reaction can be achieved if it is studied as two or more distinct electrochemical half reactions connected through an electron transfer mechanism.

A new system for ultra-trace detection of imipramine (IMI) in urine and whole blood samples was designed by coupling fast Fourier transformation square wave voltammetry (FFTSWV) and electromembrane extraction (EME). This is the first report of the modification carbon paste electrode (CPE) through the Sr(VO₃)₂ nanoparticles doped with phytic acid for the FFTSWV determination of IMI. The extraction of IMI molecules from the solution of phosphate buffer was performed by using 2-Nitrophenyl octyl ether as the supported liquid membrane in the pores of the hallow fiber (HF). The optimal important parameters for the EME-FFTSWV response were determined as follow: frequency: 5670 Hz, amplitude: 30 mV, pH of the sample solution: 4.5, pH of the acceptor solution: 4; EME time: 15 min; EME potential: 150 V. According to the calibration curves plotted for urine and whole blood samples, two wide linear ranges of 0.02–1000 and 0.2–1000 ng/mL with determination coefficient of 0.982 and 0.990 were obtained. The LODs of 0.001 and 0.01 ng mL⁻¹, and also LOQs of 0.02 and 0.2 ng mL⁻¹, were calculated for urine and whole blood, respectively. In addition, relative standard deviation (RSD) within the range of (4.3–5.5) and (5.2–6.1) were achieved in urine and whole blood samples.

Accurate monitoring of an electroplating bath's chemical balance is a key factor for maintaining its performance during a long-term plating operation. In this paper, a method is suggested to measure the concentration of iodide ion (I⁻), an inorganic leveler for through-silicon via (TSV) filling, based on its electrochemical response. During the operation of plating, I⁻ was consumed via the reaction with Cu⁺ (Cu⁺ + I → CuI), an oxidation reaction (2I⁻ → I₂ + 2e), as well as a physical incorporation. The I⁻ concentration decrease resulted in a degradation of the bath, while the major byproducts (CuI and I₂) rarely influenced on bath performance. In order to monitor the I⁻ concentration by cyclic voltammetry stripping (CVS) analysis, the electrochemical response of I⁻ was examined at various conditions. I⁻ suppressed the Cu electrodeposition rate; this response was dependent on the mass transport of I⁻ and the applied potential of cathode. A subsequent effective coverage analysis revealed that not only I⁻ but also Cu(I) iodide (CuI) was a key inhibitor, demonstrating that the inhibition of I⁻ becomes weaker at a negative potential. With a responsive curve (RC)-CVS analysis conducted at an optimized condition, a linear relationship between the real and measured concentrations could be found, irrespective of other additives' concentrations. The method suggested in this paper enabled the direct monitoring of the I⁻ concentration in a Cu plating bath.

The determination of the real, or active, area of a catalytic surface is a key requirement to understand or quantify parameters related to its electrochemical behavior. There are several experimental methods available, but none of them seems to be universally applied in literature. The choice of method is particularly important when evaluating electrodes made from materials that may interact with the analyte such as gold (Au) and palladium (Pd). A comparable analysis has therefore been made which includes four in situ methods (oxide formation, double layer capacitance, iodine adsorption and electrocatalysis of the Hexacyanoferrate (II/III) reductant-oxidant couple), and two ex situ methods (scanning electron microscopy and atomic force microscopy). It was found that measurements of oxide formation and the double layer capacitance gave the largest real surface area whereas scanning electron microscopy gave the smallest. Considering nanoporous Pd electrodes, the surface area ratio (the ratio between the real and geometric surface area) ranged from 0.8 (scanning electron microscopy) to 75.4 (oxide formation) and 76.5 (double layer capacitance). The corroboration between the results suggests that oxide formation and double layer capacitance provide the most accurate way of determining the real surface area for the electrode system investigated in this paper.

Compared to Pt/C, the HOR activity of Pt-Ru alloys in alkaline electrolyte is exceptionally high. Nevertheless, it remains unknown whether this enhancement is due to a bifunctional mechanism involving Pt and Ru as active sites or an electronic effect of Ru on Pt. In this study, we distinguish between those fundamental differences using Ru@Pt core-shell nanoparticles as a model system. Ru@Pt catalysts were prepared from submonolayer to multilayer Pt coverage. The exposure of Ru on the surface of the catalyst was analyzed by cyclic voltammetry, showing that Ru is solely exposed on the surface of Ru@Pt particles with low Pt-coverage. The thickness of the Pt-shell was characterized by CO stripping in H₂SO₄, allowing to distinguish between single and bilayered Ru@Pt catalysts. Determining the HOR/HER activity of these catalysts in 0.1 M NaOH revealed that fully Pt-covered Ru is more active than partially covered Ru@Pt nanoparticles. Hence, the participation of Ru as active site in a bifunctional mechanism is of minor importance with respect to the HOR/HER activity compared to its influence on the electronic structure of Pt. Similar to Pt-Ru alloys, the most active Ru@Pt core-shell nanoparticles show a 4 to 5-fold enhancement of the surface-normalized HOR/HER activity compared to Pt/C.

In this work, a 3-mercaptopropionic acid self-assembled monolayer (3-MPA SAM) was constructed as a reliable artificial membrane to investigate the intermolecular forces between the SAM and the redox species using scanning electrochemical microscopy. The results presented here reveal that the redox species, FcCH₂OH, is initially adsorbed on 3-MPA SAM by hydrogen bonding between the hydroxyl group of the former and the carboxyl group of the latter. Then, when FcCH₂OH is transformed to Fc⁺CH₂OH by electrochemical oxidation, the dominant intermolecular force in the reaction system changes from hydrogen bonding to electrostatic interaction. Increase in pH and surface coverage of the 3-MPA SAM can enhance the change behavior observed, however, adding ion strength will weaken this behavior. Our findings may help to improve the understanding of the interaction between effector proteins and phospholipid bilayer on cellular surface.

Sarcosine is a newly discovered effective biomarker for prostate cancer. However, the low concentration of sarcosine in tissue cells, plasma or urine blocks the development of sarcosine biosensors. In this manuscript, porous zeolitic imidazolate framework-8 (ZIF8) was synthesized and was used as carriers to load nano platinum (Pt@ZIF8). The porous structure of ZIF8 helped to stabilize the nano platinum and keep its high catalytic activity. The Pt@ZIF8 modified sarcosine biosensor had good response toward sarcosine due to its unique structure and morphology. The linear range of the as prepared biosensor is from 5 to 30 μM, which is consistent with the detection demand. The prepared sarcosine biosensor is suitable to be developed as a kind of portable diagnostic facilities for prostate cancer.

The on-line, self-powered monitoring of the organic carbon content in hypersaline solutions (e.g. chemical oxygen demand, COD) based on a microbial biosensor would avoid the generation of toxic waste, originated by common COD analytical methods, and reduce the release of pollutants into the environment. Herein, a disposable cathode was applied to microbial fuel cells (MFCs) for the environmental friendly monitoring of the COD reaching a sensitivity one order of magnitude higher compared to the MFC with an air breathing cathode. Additionally, the entrapment of bacterial cells in alginate-capsules ensured a considerable linear range (up to approximately 10,000 mg COD L⁻¹), providing opportunities for the wide application of the device to hypersaline solutions characterized by different origins and contamination levels.

Cypermethrin ([RS]-alpha-cyano-3-phenoxybenzyl [1RS, 3RS; 1RS, 3SR]-3-[2,2-dichlorovinyl]-2,2-dimethylcyclopropanecarboxylate) is a crucial pyrethroid and it is generally used as poison against crop pests, domestic insects and ectoparasites in farmed fish. A new molecular imprinted sensor approach based on core-shell type nanoparticles (Fe@AuNPs) incorporated two-dimensional (2D) hexagonal boron nitride (2D-hBN) nanosheets was presented for cypermethrin (CYP) detection in wastewater samples. All nanomaterials' formation and properties were highlighted with scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) method, energy dispersive X-ray analysis (EDX), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). CYP imprinted voltammetric sensor was improved in presence of 80.0 mM phenol containing 20.0 mM CYP by CV. 1.0 × 10⁻¹³ - 1.0 × 10⁻⁸ M and 3.0 × 10⁻¹⁴ M were founded as the linearity range and the detection limit (LOD). Finally, CYP imprinted glassy carbon electrode (GCE) was used for wastewater sample analysis in presence of the other competitor agents such as deltamethrin (DEL), tetrametrin (TET) and permethrin (PER). In addition, the prepared sensor was investigated in terms of stability and repeatability.

This study examines the applicability of electrochemical methods to the in situ determination of the water content in proton-conducting ionic liquids (PILs). Two proton-conducting ionic liquids with different acidities and hygroscopicities of the cations, sulfoethylmethylammonium trifluoromethanesulfonate, [2-Sema][TfO] and N,N-diethylmethylammonium trifluoromethanesulfonate, [Dema][TfO], were used. At first, PIL water electrolytes with known water concentrations ([2-Sema][TfO]: 0.64-6.1 wt%, [Dema][TfO]: 0.18-99.5 wt%) were prepared. Then, the influence of the water content on the electrochemical properties, namely the electrical conductivity, charge of hydrogen oxidation, charge of Pt oxide reduction and onset potential of Pt oxidation, were investigated. The four parameters were plotted as a function of the water concentration and fitted by exponential, linear or asymptotic functions. These fits serve as calibration curves that can be used to determine the actual water concentration by measuring one or more of the four parameters investigated. It was found that the measurement of specific ion conductivity is a fast and simple method across a wide range of water concentrations. The evaluation of the Pt oxide reduction charge from cyclic voltammograms is more time-consuming, but provides higher accuracy at low water concentrations, although the accuracy also depends on the nature of the ionic liquid.

Electrochemical water splitting is a promising method for sustainable energy conversion without environmental contamination. Developing active, stable, and low-cost electrocatalysts is important for practical applications with requirements such as scalability and durability. Herein, an efficient method for the electrodeposition of high-activity cobalt iron-phosphorus (Co_xFe_1-x-P) films as bi-functional electrocatalysts is presented. For films with a cobalt/iron atomic ratio of 1.07, the electrodeposited Co_xFe_1-x-P films showed outstanding electrocatalytic performance for both the H₂ and O₂ evolution reactions (HER and OER, respectively). In the HER, the overpotential and Tafel slope of the Co_xFe_1-x-P film on the copper plate were 169 mV at 10 mA/cm² and 56.9 mV/dec, respectively. In the case of the OER, the Co_xFe_1-x-P film on dendritic copper exhibited superior performance with an overpotential of 290 mV and a Tafel slope of 39.2 mV/dec. In the two-electrode system consisting of Co_xFe_1-x-P film on the copper plate without (HER) and with dendritic copper (OER) for full water splitting, the electrodes exhibited a low overpotential of 1.64 V at 10 mA/cm² and excellent long-term stability over several days under alkaline conditions.

Sensitive determination of actinides is of utmost importance to maintain regular surveillance over the environment in the vicinity of nuclear power plants. The noble metal nanoparticles (NPs) exhibit high electrocatalytic activity, and could be employed for the sensitive and rapid quantifications of plutonium (Pu) and neptunium (Np) ions in the aqueous matrices. Therefore, the Ru NPs decorated glassy carbon electrode (RuNPs/GCE) was examined towards the electrocatalytic redox reaction of Pu and Np respectively. Differential pulse voltammetric (DPV) technique was used for rapid and sensitive quantification of Pu and Np. The RuNPs/GC based DPV technique could be used to determine the concentration of Pu and Np in a few minutes. Both Pu and Np gave sensitive oxidation peaks at 470mV and 840 mV respectively in 1M H₂SO₄ versus silver/silver chloride electrode. The detection limits were found to be 1.5 μM for Pu and 6.5 μM for Np. The investigated method showed good stability, reproducibility, and repeatability.

A cobalt (Co)-doped ZnO film electrode was facilely fabricated via a one-step liquid phase deposition process. It was found that many rhombus-like nanoparticles with wurtzite crystal structure were uniformly deposited on the surface of electrode, and the doped Co in the film was at bivalent state. Moreover, the as-deposited film was investigated by UV-visible diffuse reflectance spectroscopy, photoluminescence, and cyclic voltammetry. Under visible light illumination, the Co-ZnO film electrode showed higher photocurrent than pure ZnO film electrode. It was explored as photoanode for visible light-driven photoelectrocatalytic (PEC) degradation of ofloxacin (OFL). The amount of Co doped in ZnO film for PEC degradation of OFL was optimized as 7.5% (at.%). Compared with other degradation methods such as direct photolysis, photocatalysis and electrochemical oxidation, PEC exhibited the highest degradation efficiency for OFL which reached 86.7% after 6-h treatment. Furthermore, the major intermediate products during the PEC process of OFL were identified by high-performance liquid chromatography-mass spectrometry; and a possible degradation mechanism for OFL on the Co-ZnO film electrode was proposed.