Table of contents

Thick Li-ion battery electrodes with high ion transport rates could enable batteries that cost less and that have higher gravimetric and volumetric energy density, because they require fewer inactive cell-components. Finding ways to increase ion transport rates in thick electrodes would be especially valuable for electrodes made with graphite platelets, which have been shown to have tortuosities in the thru-plane direction about 3 times higher than in the in-plane direction. Here, we predict that bi-tortuous electrode structures (containing electrolyte-filled macro-pores embedded in micro-porous graphite) can enhance ion transport and can achieve double the discharge capacity compared to an unstructured electrode at the same average porosity. We introduce a new two-dimensional version of porous-electrode theory with anisotropic ion transport to investigate these effects and to interpret the mechanisms by which performance enhancements arise. From this analysis we determine criteria for the design of bi-tortuous graphite anodes, including the particular volume fraction of macro-pores that maximizes discharge capacity (approximately 20 vol.%) and a threshold spacing interval (half the electrode's thickness) below which only marginal enhancement in discharge capacity is obtained. We also report the sensitivity of performance with respect to cycling rate, electrode thickness, and average porosity/electroactive-material loading.

Ethylene carbonate (EC)-free electrolyte composed of sulfolane (SL), ethylmethyl carbonate (EMC) and vinylene carbonate (VC) was studied in Li(Ni_0.42Mn_0.42Co_0.16)O₂ (NMC442)/graphite pouch cells using in situ measurements of gas evolution, ultra high precision coulometry (UHPC), automated storage experiments, long-term cycling and electrochemical impedance spectroscopy (EIS). Although cells using 1 M LiPF₆ in SL:EMC 3:7 (w:w) do not function at all, the addition of only 1% VC allows the cells to operate normally. In situ gas measurements show that NMC442/Graphite pouch cells containing SL:EMC:VC electrolyte produce less gas during formation than cells containing control (1 M LiPF₆ EC:EMC 3:7 (w:w)) electrolyte or 2% VC in control electrolyte. Cycling and storage experiments show that cells containing SL:EMC:VC electrolytes can provide better performance than control electrolyte without additives and similar performance to state-of-the-art electrolyte with the ternary additive blend 2% prop-1-ene-1,3-sultone (PES) +1% methylene methanedisulfonate (MMDS) +1% tris(trimethylsilyl) phosphite (TTSPi) ("PES-211") in EC:EMC 3:7 (w:w). The SL:EMC:VC system needs to be further explored with additional additives and from a safety perspective.

In this work, we designed two redox shuttles with high solubility (up to 1 M) in conventional carbonate-based lithium-ion battery (LIB) electrolytes. At this high concentration, redox shuttles ensure improved overcharge protection than lower concentrations. We developed electroactive imidazolium salts by modifying imidazolium with 2,5-di-tert-butyl-1,4-dimethoxybenzene. Two salts with the cation 1-(3-(2,5-di-tert-butyl-1,4-methoxyphenoxy)propyl)-3-methyl-1H-imidazol-3-ium (EMIm) were synthesized using either hexafluorophosphate (DDB-EMIm-PF₆) or bis(trifluromethanesulfonyl)amide (DDB-EMIm-TFSI)) anions. The electrochemical properties of DDB-EMIm-PF₆ and DDB-EMIm-TFSI dissolved in ethylene carbonate : diethyl carbonate (EC:DEC), in the presence of either LiPF₆ or LiTFSI, were evaluated. Cyclic voltammetry showed a compatible potential (∼3.85 V vs. Li/Li⁺) for use in LIBs using LiFePO₄ as cathodes. Electrolytes using 0.1 M of DDB-EMIm-PF₆ or 0.3, 0.7 and 1 M of DDB-EMIm-TFSI were prepared and evaluated in Li/LiFePO₄ (LFP) test cells to demonstrate overcharge protection. Electrochemical cycling at C/10 showed an overcharge protection for all concentrations of the redox ionic salts under 100% overcharge conditions. Among these salts, DDB-EMIm-TFSI, at a concentration of 0.7 M, was effective in shuttling excess current for over 200 cycles, representing over 6000 operating hours, while maintaining nominal values for the discharge capacity of LiFePO₄.

A novel composite anode is prepared by mixing zinc particles with activated carbon (AC) to improve the cycle performance of the neutral rechargeable zinc ion batteries. Galvanostatic charge/discharge cycling tests indicate that the capacity retention of the cell with adding 12 wt% activated carbon in Zn anode is 85.6% after 80 cycles, which is much higher than that of 56.7% for the cell using unmodified Zn anode. X-ray diffraction analysis indicates that the addition of activated carbon can suppress the formation of inactive basic zinc sulfates (Zn₄SO₄(OH)₆·nH₂0). Morphology, elemental mapping and N₂ adsorption and desorption measurements indicate that the pores of activated carbon can accommodate the deposition of Zn dendrites and insoluble anodic products. As a result, the cycle stability of the Zn anode has been greatly enhanced by activated carbon modification.

In this study, synthesized carbon black powder (SC) was obtained from benzene via a liquid phase plasma (LPP) process. This powder was then activated by KOH to obtain activated SC (A-SC). Both of SC and A-SC powders were compared with commercial carbon black powder (CCB) and activated commercial carbon black (A-CCB) via Brunauer–Emmett–Teller surface area analysis, Raman spectroscopy, scanning electron microscopy, and X-ray diffraction for physical and chemical investigations. SC, A-SC, CCB and A-CCB powders were used as active materials of electrochemical double-layer capacitors (EDLC), which were studied via cyclic voltammetry, galvanostatic measurements, and impedance spectroscopy. Their electrochemical performance shows that SC electrode has higher specific capacitance, capacity, and energy than CCB electrode. Non-aqueous electrolyte EDLC using A-SC electrode, especially exhibited suitable cyclic stability over 8000 cycles at various charge–discharge current densities from 250 mA g⁻¹ to 2000 mA g⁻¹. This study indicates that the LPP process successfully created specific nano-scaled CB particles supported by KOH activation process, which are noteworthy electrode materials for supercapacitor applications.

Influence of the electrode formulation on the cyclability of LiNi_0.5Mn_1.5O₄ was studied for industry-relevant surface capacities (i.e. up to ∼3 mAh cm⁻²) with two mixing methods at the lab scale: ball milling and magnetic stirring. The inactive binder and carbon additives content were varied, as well as the type of those. A more homogeneous distribution of additives is observed in ball milled electrodes compared to stirred ones. The cycle life of the former is degraded with lower coulombic efficiency at first cycle, as a consequence of higher specific surface area of the electrodes and increased parasitic reactions. The coulombic efficiency stabilizes at 99.25% after several cycles, irrespective of the electrode formulation used. The fading of the capacity is minimized by increasing the amount of conductive additives or by substituting part of carbon black for carbon nanofibers. However, the cyclability of the electrodes with high active mass loading is severely decreased. The best result found is capacity retention of 85% after 300 cycles. The electrodes prepared in water with carboxylmethyl cellulose (CMC) exhibit poorer cyclability compared to the ones prepared in N-Methylpyrrolidone (NMP) with Polyvinylidene Fluorine (PVdF). Finally, electrodes with optimized formulation was prepared at the pilot scale and evaluated.

1,1,2,2-Tetrafluoroethyl 2,2,2-Trifluoroethyl Ether (TFTFE) as electrolyte co-solvent was applied in lithium/sulfur (Li/S) battery for the first time. The ether with partially fluorinated structure reduces the conductivity of the electrolyte but increases distinctly the reversible capacity and coulombic efficiency of the cell, meanwhile decreases the self-discharging loss at the rest period of the cell. The limited dissolution of polysulfides into electrolyte due to the presence of TFTFE is an important factor for the improvement of overall cell performance. Moreover, TFTFE is found to modify the surface film on Li anode greatly, blocking the access of polysulfides to metallic Li and side-reactions between them. TFTFE acts as both polysulfides-restraining solvent and film-forming agent in a Li/S cell system, reflecting the particular functions of the fluorinated ether.

The H₂ bubbles resulting from the reaction of freshly prepared Si powders with water were found to impede the large-scale preparation of aqueous-based Si/CMC (Na-Carboxy-Methyl-Cellulose)/C slurries and could consequently prevent the large-scale production of composite electrode films. To understand and possibly control this reaction, silicon particles (Si_ref) have been partially oxidized either by contact with water or by air heating at elevated temperatures. By coupling kinetics, XRD, (HR)TEM/EELS, TGA/DSC, IR and gas adsorption data, the porosity/texture/surface chemistry of the resulting silica-based coating layers were found to be highly dependent on the oxidation process, while the extent of oxidation is tuned by the time-temperature of the treatment. Although fully oxidized samples are totally inactive vs. Li, the high porosity of the water-formed silica coating contrasts with the dense air-formed one that can limit access to the Si core and can block its reactivity if too thick. Controlled and optimized air-oxidative pre-treatments can prevent the H₂ evolution during the slurry preparation, hence enabling the reproducible production of high-quality electrode coatings on Cu current collectors. Such treatments do not impact the reversibility of the Si-Li electrochemical reaction, even with no capacity constraints and with or without FEC addition in commercial EC/DMC/LiPF₆ electrolytes.

In this computational study, we demonstrate the use of a high-fidelity multiphysics model to predict the effects of operational parameters and the performance of a new Solid Oxide Iron-Air Redox Battery (SOIARB) operated at 800°C. The results show explicitly that the operating current density has the most pronounced effect on the H₂ concentration distribution, Nernst potential, specific energy and round-trip efficiency. The initial porosity in the Redox Cycle Unit (RCU) must be >0.50 at high current density in order to avoid significant diffusion limitation. Also, the distance between the RSOFC (reversible Solid Oxide Fuel Cell) and the RCU has little effect on the performance of the SOIARB, but has an appreciable effect on the chamber pressure. The simulations indicate that a high round-trip efficiency (RTE) can be achieved at the expense of useful capacity. Enhancement of the electrolysis electro-kinetics of RSOFC and FeO-reduction kinetics of RCU is a key to achieving high capacity with high efficiency.

The structure of solid and liquid electrodes strongly affects the performance of Lithium batteries and of Semi-solid Redox-Flow cells. Thus understanding the formation of the structure of electrodes is an important issue. This paper proposes to study the aggregation processes that occur in electrode slurries by means of numerical simulations. For that Brownian dynamics simulations are developed and applied to a suspension composed of silicon nanoparticles and carbon black. Special attention is paid to the effects of the size of nanoparticles and of the interactions between the different components. The percolation of the carbon network and the number of contacts between the active mass and the conductive additive particles are quantified. Simulations results are found in good agreement with our previous experimental studies, showing that they can be used to improve the formulation of the slurry of electrodes.

In this work, nickel and cobalt binary sulfide nanoparticles are successfully decorated on the surface of multi-walled carbon nanotubes to form a composite (Ni-CoS/MWCNT) via a facile glucose-assisted hydrothermal method. By introducing the conductive MWCNT and tuning the Ni/Co molar ratio for the Ni-CoS/MWCNT composites, the optimized one shows a high capacity up to 153 mAh g⁻¹, superior rate capability and excellent electrochemical stability. On this basis, advanced hybrid supercapacitor (HSC) is assembled by using the Ni-CoS/MWCNT composite as the cathode and reduced graphene oxide as the anode. As-fabricated HCS is able to be operated reversibly in a full voltage region of 0–1.6 V and achieves a high specific capacity of 33 mAh g⁻¹ at 1 A g⁻¹, therefore delivering a maximum energy density of 23 Wh kg⁻¹ at a power density of 684 W kg⁻¹. Furthermore, the HSC still retains 90% of its initial discharge capacity after 2000-cycle consecutive charge/discharge test at 4 A g⁻¹.

Material degradation is an issue limiting the life-time of Lithium-ion batteries. This study conducts quantitative observations of performance and material degradation in a commercial high-power Lithium-ion battery as a function of aging time and ambient temperature. Batteries are cycled until different states-of-health (SOHs) in the range of 100% to 78% are obtained before being disassembled. Inductively coupled plasma (ICP-OES) analysis of the electrodes from cells in different SOHs reveals a linear increase in Li, P, and Mn on anodes with aging time and thus allows conclusions on the kinetics of the aging reactions. The vertical distribution of these decomposition products in the anode is investigated by glow discharge optical emission spectroscopy (GD-OES) depth profiling. Following this, the chemical data from Post-Mortem analysis are correlated to the electrochemical performance of the cells. Combining chemical data sets from aged cells in different SOHs with data from cells aged at different ambient temperature reveals an Arrhenius-like behavior of chemical changes on the anodes.

Classical models are not successful in describing discharge characteristics of a lead-acid battery when the current density is varied over a wide range. A model is developed in this work to overcome this lacuna by introducing into the standard models two mechanisms that have not been used earlier. Lead sulfate particles nucleate and grow on active materials of electrodes during discharge, resulting in coverage of active area. Increasing rate of discharge builds supersaturation of lead sulfate rapidly, and causes increased extents of nucleation and coverage. Electrodes behave almost like an insulator due to deposition of lead sulfate when active materials are converted to a critical extent, and this can stop discharge process. Influence of this mechanism is also rate dependent. The new model developed is tested against data on polarization behavior, and capacity drawn as a function of current. The model successfully predicts both polarization curves and Peukert behavior. The model is used to predict charge that can be drawn at a current after partial discharge at a different current. Model suggests that altering nucleation behavior can be useful in enhancing capacity available for discharge.

The interfacial reactions, especially the gas evolution, between carbon conductive agents and the electrolyte at the positive electrode in high-voltage batteries (potentials over 4.5 V) have been investigated. The amount of gas generated was quantified for various conductive agents: acetylene black (AB), furnace black, specially customized AB, and graphite (GR). The experiments revealed that in the high-voltage system, the specific gas evolution was induced by both the cathode active material and the conductive agent, with the carbon conductive agents resulting in the generation of 8 to 15 times more gas than the cathode active material LiNi_0.5Mn_1.5O₄ (LNMO) itself. The high-voltage properties of the carbon conductive agents, such as the anion intercalation and self-discharging properties, were evaluated for each carbon electrode. The results implied the existence of a local battery composed of the conductive agent and LNMO; this redox couple appears to play a key role in the gas evolution.

The spinel Li₄Mn₅O₁₂ has been considered as a prospective 3 V cathode material for the next generation of lithium-ion batteries (LIBs) due to its high energy density and excellent cycling stability. However, the low operating voltage (∼3 V) makes Li₄Mn₅O₁₂ impractical for high-energy high-power LIBs. To address this issue, Ni and Fe dual doped Li₄Mn_5-x-yNi_xFe_yO₁₂ has been prepared via a facile sol-gel method combined with post-heat-treatment. The effects of dual-cations doping on the crystal structure, morphology and electrochemical properties were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and galvanostatic charge/discharge analysis. As a result, Li₄Mn₄Ni_0.5Fe_0.5O₁₂ exhibits the highest reversible specific capacity of 133 mAh/g at a specific current density of 25 mA/g after 100 cycles and exhibits a significantly improved high voltage performance with corresponding capacity of ∼80 mAh/g at an average voltage of 4.7 V vs. Li/Li⁺ and ∼122 mAh/g at above 4.0 V. These results indicate the dual doping of Ni and Fe can effectively improve both the operating voltage and reversible specific capacity of Li₄Mn₅O₁₂ with excellent cycling stability, demonstrating a promising high-voltage cathode material for high-energy high-power LIBs.

Novel Si@double-shelled carbon (Si@DC) yolk-like powders have been fabricated by using the reinvented Si@void@mesoporous silica nanostructures as templates for the first time. The fabrication is quite economical without special equipment and using cheap glucose as the carbon source. In this special architecture, commercial Si nanoparticles are completely sealed inside the ultrathin and intact double-shelled carbon with rationally designed void spaces between the cores and shells, which can accommodate the volume fluctuation of Si cores. When tested as an anode material in lithium-ion batteries (LIBs), the resulting Si@DC yolk-like powders exhibit outstanding cycling stability and enhanced lithium storage capacity.

The electrochemical reduction of Ag_0.48VOPO₄ • 1.9H₂O is accompanied by vanadium and silver oxidation state changes, characterized with X-ray absorption spectroscopy (XAS), and by structural changes, characterized with X-ray powder diffraction (XRD). The XAS data suggest that the initial reduction process, involving 0 to 0.5 electron equivalents, involved primarily the reduction of vanadium cations, while most of the silver cations are reduced between 0.5 to 1.0 electron equivalents. The XRD data display significant intensity decreases of absorbances associated with the 004 and 006 planes upon electrochemical reduction, consistent with a reduction-displacement of Ag⁺ with insertion of Li⁺. Retention of intensity of the absorbance associated with the 002 plane, with only minor decrease in interlayer spacing, indicates retention of the VOPO₄ sublattice structure. Uncovering the details of the discharge mechanism of bimetallic cathode materials such as Ag_0.48VOPO₄ should enable the design of future high current cathodes for secondary batteries displaying an enhanced current capacity based on a reduction-displacement strategy.

Results of computational study of few-layer graphene (FLG) nanostructures as storing cells for Li are presented. Results of modeling revealed some features of these systems, which can cause dimensional instabilities and shortening of the life time of Li-based power sources. Some peculiarities of lithium diffusion motion in structural defect zones and near the edges of few-layer graphene planes have been studied. Simulations and density functional theory calculations performed allow of predicting that dimensional stability and stiffness of FLG can be in significant measure improved by the structural bridge-like radiation defects.

Cyclic voltammetry and electrochemical impedance spectroscopy were used to examine several types of carbon electrodes in V^IV/V^V in H₂SO₄. The materials investigated included glassy carbon, graphite, carbon paper, reticulated vitreous carbon and carbon fibers. In all cases the electrode kinetics of the V^IV/V^V oxidation-reduction reactions are enhanced by cathodic treatment of the electrode and inhibited by anodic treatment. Pronounced activation typically occurs at potentials more negative than +0.1 V (vs. Hg/Hg₂SO₄); the effect begins to saturate at about –0.6 V. Pronounced deactivation typically occurs at potentials more positive than +0.7 V. Both activation and deactivation occur rapidly during the first ∼10 s at the most negative and most positive potentials, respectively. The activation effect saturates quickly at the most negative potentials but the deactivation effect does not saturate on the time scales investigated. There is a considerable shift (∼1.1 V) between the potentials for activation and deactivation. Activated electrodes showed no significant loss of activity after standing in the electrolyte for 3 weeks; deactivated electrodes regained about 50% of their activity. The activation and deactivation effects were observed regardless of whether vanadium was present in the electrolyte and are attributed to oxygen-containing functional groups on the electrode surface.

The enhancement in rate performance of LiMnPO₄ cathode material for Li ion batteries has not been established for practical high power use, mainly because of its extremely poor electron and Li ion conductivities. In order to overcome this problem, we have developed a novel hybrid-coated LiMnPO₄, where very thin amorphous hybrid-coated layers of Li ion-conductive phosphate with electro-conductive pyrolytic carbon are formed on surfaces of solvothermally synthesized nano-particles of LiMnPO₄. The hybrid-coated LiMnPO₄ realizes excellent rate-capabilities and good cyclability at 25°C, enabling discharge capacities as high as 159 mAh g⁻¹ at 0.1C, 147 mAh g⁻¹ at 1C and 111 mAh g⁻¹ even at 10 C, which surpass those ever reported for LiMnPO₄. These performances could be promoted by high 3D conductivities both of electron and Li ion in the hybrid-coated layers.

Graphene-TiO₂ nanocomposites are a promising anode material for Li-ion batteries due to their good high-rate capacity, inherent safety, and mechanical and chemical robustness. However, despite a large number of scientific reports on the material, the mechanism of the enhanced high-rate Li⁺ storage capacity that results from the addition of graphene to TiO₂ – typically attributed to improved electrical conductivity – is still not well understood. In this work, we focus on optimizing the processing of surfactant-templated graphene-TiO₂ hybrid nanocomposites. Towards this end, we examine the influence of various processing parameters, in particular the surfactant-mediated colloidal dispersion of graphene, on the material properties and electrochemical performance of graphene-TiO₂. We investigate the influence of electrode mass loading on Li⁺ storage capacity, focusing mainly on high-rate performance. Furthermore, we demonstrate an approach for estimating power loss during charge/discharge cycling, which offers a succinct method for characterizing the high-rate performance of Li-ion battery electrodes.

With significant improvements in electrical energy storage, researchers could change the way energy is generated and used. One emerging approach is to change the cation that shuttles charge from lithium to calcium. Calcium cations, roughly the same size as Na⁺, have many attributes that make them a desirable charge carrier for energy storage applications, including deposition voltage and a porous passivation layer. However, system level issues, such as corrosion, have yet to be investigated. Corrosion of the current collectors must be considered whenever you change the electrolyte and we show that this is particularly true for calcium based systems. Reversible charge/discharge behavior that is due to corrosion can be seen with stainless steel in electrolytes containing calcium salts. This reversible behavior is similar to what might be expected from materials that are intercalating Ca, making the interpretation of electrochemical data challenging. We have found that this corrosion reaction requires either carbon black and/or a transition metal oxide to catalyze the reaction, making it more difficult to detect. Unlike stainless steel, Graphite foil electrodes do not show high voltage reactions and can be used as a tool for testing Ca-ion cathode materials, although some reactions at low potentials have been observed.

A novel calculation model is devised to quantitatively assess two irreversible capacities evolved in Si negative electrodes: electrolyte decomposition and Li trapping. In this model, the capacity of the electrode reaction (Li-Si alloy formation, Qⁿ_alloy), which is the only implicit value on the galvanostatic charge/discharge voltage profiles, is calculated with the data obtained from GITT (galvanostatic intermittent titration technique) experiment. When the calculation model is applied to two Si electrodes of different particle sizes, the particle size is found to significantly affect the nature of the irreversible reactions. In the bulk-sized Si electrode, Li trapping is dominant over electrolyte decomposition. This feature must be due to an electrical contact loss that is caused by crack formation, which is more vulnerable to bulk-sized Si particles. The hump behavior in the Coulombic efficiency profiles is also explained by the Li trapping. In the nano-sized Si electrode, electrolyte decomposition is the major irreversible reaction because of its larger surface area. Because of a stronger endurance against mechanical stress, crack formation and subsequently Li trapping are less severe than that of the bulk-sized one.

Various materials display a constant phase impedance, Z∝[iω]^−u, over a wide frequency range. In this paper, we show that this behavior is a natural consequence of charge transport in the macroscopic limit, and that in contrast to the common belief, no assumptions on the "relaxation functions" are required. Our unifying view of the constant-phase-element (CPE) is then employed for analyzing impedance spectra that were recorded during the aging of Li_xFePO₄ cells. We find and explain a significant correlation between their capacity loss and changes in the exponent (u) of the CPE describing cathodic Li-intercalation. Changes in u with the state of charge are also discussed. CPE exponents are shown to be valuable performance indicators for Li-ion batteries.

Demand for portable electronic and electrical devices has led to considerable growth in production of lithium-ion battery cells and the number of manufacturers thereof. However, due to lack of supplied information or independent verification, it is frequently difficult to compare cells based on available data. In this study, we conduct a comparative testing study on five types of 18650-format lithium-ion cells from three different commercial manufacturers, ranging from budget to high-performance cells. Key insights gathered in the comparison were that the tested budget cells frequently offer less than 20% of their rated capacity, that the budget cells degrade at a significantly higher proportional rate than other cells, and that certain high-performance cells exceed the size dimensions of the 18650-format by over 3%. Electrochemical impedance spectroscopy testing showed the budget cells to have internal impedances several times higher than other cells, leading to notably increased heat generation and a significantly reduced cell efficiency. Differential capacity analysis found this high internal resistance to notably impede lithium intercalation processes. The presented methodology is intended as a base framework for conducting subsequent comparative testing studies for Li-ion cells.

Na₃MnCO₃PO₄ with a potential to deliver two-electron transfer reactions per formula via Mn²⁺/Mn³⁺ and Mn³⁺/Mn⁴⁺ redox reactions and a high theoretical capacity (191 mAh/g) can play an important role in Na-ion batteries. This study investigates the dependence of the electrochemical performance of Na₃MnCO₃PO₄-based sodium-ion batteries on processing, structural defects and ionic conductivity. Na₃MnCO₃PO₄ has been synthesized via hydrothermal process under various conditions with and without subsequent high-energy ball milling. Particle sizes, structural defects and ionic conductivity have been studied as a function of processing conditions. It is found that Na₃MnCO₃PO₄ nanoparticles (20 nm in diameter) can be produced from hydrothermal synthesis, but the reaction time is critical in obtaining nanoparticles. Nanoparticles exhibit a higher ionic conductivity than agglomerated particles. Further, structural defects also have a strong influence on ionic conductivity which, in turn, affects the charge/discharge capacities of the Na₃MnCO₃PO₄-based sodium-ion batteries. These results provide guidelines for rational design and synthesis of high capacity Na₃MnCO₃PO₄ for Na-ion batteries in the near future.

Amorphous oxide thin films in the pseudobinary system Li₄SiO₄-Li₃PO₄ and Li₄GeO₄-Li₃PO₄ were fabricated using pulsed laser deposition (PLD) with a KrF excimer laser. The ionic conductivities of obtained thin films were 10⁻⁸ to 10⁻⁶ S cm⁻¹ at room temperature. Bulk-type all-solid-state batteries using LiCoO₂ particles surface-modified with ortho-oxosalt thin films were constructed to assess the influence of oxide coatings on cell performances. Higher ion-conductive oxide thin films studied here are useful for decreasing the interfacial resistance of all-solid-state cells. The interfacial resistance was lowest in the cell using Li_3.5Si_0.5P_0.5O₄ coatings as a buffer layer with estimated thickness of ca. 45 nm. We investigated the dependence of interfacial resistance on film thickness for the oxide systems fabricated in this study. Among them, much lower interfacial resistance was achieved in the cells using Li₃PO₄ coatings with film thickness of less than 45 nm. All-solid-state cells using Li₃PO₄-coated LiCoO₂ charged and discharged without marked capacity-fading during 30 cycles. Larger discharge capacity after cycling tests was achieved in a cell with a smaller interfacial resistance. The cell using Li₃PO₄-coated LiCoO₂ operated at a high current density of 6.4 mA cm⁻² with a capacity of 54 mAh g⁻¹.

In this research, the performance of Al–air batteries based on pure Al and Al-0.5 wt%In anodes in 4M NaOH solutions with or without different concentrations of additives was investigated by galvanostatic discharge test. The characteristics of the anodes after discharge were investigated by electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and energy dispersive analysis of X-ray (EDAX). The corrosion behavior of the anodes was researched by self-corrosion rate test and potentiodynamic polarization test. The results show that the Al–In alloy exhibits a low self-corrosion rate and high anodic efficiency when ZnO or Na₂SnO₃ is added to 4M NaOH. The results of galvanostatic discharge at 20 mAcm⁻² indicate that the Al–air battery based on Al-0.5 wt%In anode shows excellent discharge performance. The Al–air battery based on the alloy anode has an operating voltage of 1.3 V and anodic efficiency of 75.2% in 4M NaOH with 0.02M Na₂SnO₃, and an operating voltage of 1.01 V and anodic efficiency of 82.5% in 4M NaOH with 0.2M ZnO. SEM and EDAX results prove that zinc oxide or sodium stannate could inhibit the corrosion of the Al–In anode by the deposition of zinc or tin on the anode surface.

In this study, the separator coated with reduced graphene oxide (rGO) layer is prepared via doctor blading. The lithium-sulfur (Li-S) battery with rGO-coated separator exhibits much smaller impedance and much better electrochemical performance. After coated rGO, the initial discharge capacity can be as large as 1067 mAh g⁻¹ at 0.2 C which can retain 878 mAh g⁻¹ after 100 cycles, and the discharge capacity can reach 710 mAh g⁻¹ even at 2 C. The significant performance enhancement can be attributed to the bi-functionality of rGO; the rGO coating layer has unique porous structure, high conductivity and various kinds of functional groups, which can not only effectively prevent the diffusion of polysulfide through the separator, but also significantly increase the conducting surface between cathode and separator. It is promising to use rGO-based slurry to continuously produce large-scale, low-cost, and bi-functional rGO coated separator for high-performance Li-S batteries.

Bismuth (Bi) anodes for Magnesium-ion (Mg-ion) cells were studied for their electrochemical performance and thermal stability. The Bi anodes exhibited reversible capacities over 300 mAh/g with high coulombic efficiencies of > 98%, when cycled between 0.05 and 0.5 V (vs. Mg/Mg²⁺). Rate capability tests showed that the Bi anodes could be cycled successfully up to a 1C rate. To further understand the magnesiation and demagnesiation processes, the Bi anode was examined using a transmission electron microscope (TEM) at various states. TEM images highlighted impressive morphological changes with the formation of a Bi nanocomposite during cycling, supporting the collected electrochemical data. Additionally, an isotherm micro-calorimetric technique (IMC) was used to record the in-situ heat profile, in an attempt to identify the heat sources contributing at the Bi anode during cycling. The experimental data collected for IMC showed good agreement with the calculated results at a low cycling rate of C/10. Irreversible heat (Q_irrev) was found to be the main contributor to the overall in-situ heat generated during magnesiation and demagnesiation of Bi.

This study develops a statistics model that investigates the microstructural evolution of porous electrodes and couples the micro structural changes with a computational fluid dynamics model to simulate the discharge performance of an 800-μm-thick electrode at 1 A/m². This study considers the fact that pores that are too small to hold reactants, smaller than a critical pore size, do not contribute to the discharge of the battery. It is found that when the pore size of the electrode increases, the discharge capacity of the electrode first increases due to the improved mass transfer and then decreases due to the decrease of the effective surface area. For instance, when the critical pore size is set as 10 nm, the discharge capacity gradually increases from 86.6 to 214.8 mAh/g_carbon when the mean pore size of the electrode increases from 10 to 50 nm, followed by a capacity decrease to 150.8 mAh/g_carbon when the mean pore size further increases to 100 nm. This study also finds that alternating the discharge current between 0 (open circuit condition) and the setting current rate can increase the discharge capacity of the lithium-oxygen battery because the oxygen concentration in the electrode increases during the open circuit condition.

Oxygen reduction reaction (ORR) and oxygen evolution reactions (OER) on glassy-carbon-supported platinum electrodes (Pt/GCs), which are partially immersed in alkaline electrolytes, are investigated as a model of the triple phase boundary (TPB) in air electrodes for metal-air secondary batteries. ORR currents are measured with changing the vertical position of Pt/GCs, and OER currents are measured by linear sweep voltammetry. Based on the electrochemical results, it is found that thin liquid film on Pt/GCs effectively serves to expand TPB regions for ORR, but the liquid film hardly increases OER currents. Therefore, we conclude that the most effective TPB form are determined by the electrode reactions (ORR or OER), which are corresponding to discharge and charge processes for metal-air secondary batteries. In practice, it is strongly necessary to control the wettability of electrode inside, in order to construct high-performance bifunctional air electrodes.

In this paper, a MnO₂/activated carbon (AC) composite with high electrochemical performance is synthesized through a novel synthesis method (Grafting Oxidation Method). The structure and morphology are analyzed using X-ray diffraction, Fourier transmission infrared spectra, scanning electron microscopy and transmission electron microscopy. Additionally, the electrochemical properties are evaluated through cyclic voltammetry, electrochemical impedance spectra and galvanostatic cycling measurements. The results demonstrate this MnO₂/AC composite owes homogeneous particle size of nanometer dimension. The quasi-rectangular and symmetric cyclic voltammetry curves of the composite, which are measured under a three-electrode electrochemical system with a 0.5 mol L⁻¹ Na₂SO₄ solution at room temperature, indicate it has an ability of rapidly reversible Faraday reaction and good electrochemical behavior. Compared to the MnO₂/AC prepared through liquid-phase method, the composite prepared by grafting oxidation method exhibits a much higher specific capacitance which is up to 332.6 F g⁻¹ at scanning rate of 2 mV s⁻¹. A laboratory capacitor assembled with this MnO₂/AC composite electrode shows an average capacitance attenuation rate of just 0.0068% after 2000 cycles. Besides, the impedance tests results show that the charge transfer resistance of this composite is 0.92 Ω, which is much lower than the composite (2.52 Ω) synthesized through liquid-phase method.

The effects of various cationic substitutions in lithium-rich layered Li[Li_0.2Mn_0.4Co_0.4-xM_x]O₂ (M = Cr, Fe, and Ni) on the electrochemical behavior and oxygen loss have been systematically investigated. Fe substitution dramatically decreases the reversible capacity of Li[Li_0.2Mn_0.4Co_0.4-xFe_x]O₂ due to the reduced oxygen loss from the lattice caused by a decrease in the metal-oxygen covalence and an irreversible migration of Fe³⁺ ions. With increasing Cr substitution, the reversible capacity of Li[Li_0.2Mn_0.4Co_0.4-xCr_x]O₂ first increases due to the multi-electron transfer reaction of the Cr^3+/6+ redox couple and then decreases due to reduced oxygen loss and irreversible migration of the smaller Cr⁶⁺ ions from octahedral to tetrahedral sites. With increasing Ni substitution, the reversible capacity of Li[Li_0.2Mn_0.4Co_0.4-xNi_x]O₂ also first increases because Ni³⁺ can be fully oxidized to Ni⁴⁺ before the oxygen loss begins while Co³⁺ can be oxidized only to around Co^3.6+ and then decreases due to suppressed oxygen loss caused by the decrease in metal-oxygen covalence. Also, the Ni substitution raises the average discharge potential as Ni³⁺ ions will be reduced to Ni²⁺ before the Mn⁴⁺ ions are reduced to Mn³⁺. The study demonstrates the sensitivity and intricacies associated with the nature of the cations in lithium-rich layered oxide cathodes.

130 nm FeF₂ films were deposited on AISI 304 steel substrates by pulsed laser deposition for use as cathodes in lithium ion batteries (LIBs). Aluminum and steel leads pouch cells as well as coin cell battery configurations were used to determine the effect of cell materials on galvanostatic and cyclic voltammetry tests. It was observed that there is a large increase in measured capacity for FeF₂ films cycled using pouch cells with steel leads relative to pouch cells using aluminum leads. Transmission electron microscope (TEM) imaging showed similar microstructural behavior of the cycled FeF₂ films irrespective of the use of steel leads or aluminum leads. Results of X-ray photoelectron spectroscopy and galvanostatic testing on bare stainless steel substrates suggest that the increase in capacity for cell configurations using steel components is due to the cycling of surface iron oxides and this can be avoided through the use of Al leads.

A new method for the direct fabrication of nitrogen-doped graphite felt has been developed, the study of which demonstrates that the felt is an excellent positive electrode for vanadium redox flow batteries (VRFBs). Nitrogen-doped graphite felt was synthesized by the controlled deposition of a thin layer of polydopamine on the surface of graphite felt followed by pyrolysis in an Ar atmosphere. Taking advantage of the versatile capabilities of the coating, as well as its high nitrogen content, dopamine was demonstrated to be an effective precursor for the preparation of nitrogen-doped graphite. The dopamine-derived graphite felt exhibited outstanding electrochemical performance when employed as a positive electrode in a VRFB. It exhibited 236% and 44% increased discharge capacity at a current density of 150 mA cm⁻² compared to pristine graphite felt and thermally oxidized graphite felt, respectively. The enhanced performance of the VRFB could be caused by the improved catalytic activity of dopamine-derived graphite felt, resulting from the formation of nitrogen functional groups active in the VO²⁺/VO₂⁺ redox reaction and the increased specific surface area.

A novel modified glassy carbon electrode was prepared as an electrochemical voltammetric sensor based on molecularly imprinted polymer film for serotonin detection. The sensitive film was prepared by co-polymerization of 5-hydroxy tryptophan (5-HTP) and acrylamide (AM) on the carbon nanotubes modified glassy carbon electrode. The surface morphologies of the modified electrodes were characterized by scanning electron microscope. The electrochemical behavior of serotonin molecules on the imprinted electrode was studied by differential pulse voltammetry (DPV), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Under the optimum conditions, the linear relationships between current and concentration were obtained in the range from 1.8 × 10⁻⁶ to 5.4 × 10⁻⁹ mol L⁻¹, with the linear regression equation Ip = 1.552 C + 8.778 × 10⁻⁸ (I: μA, C: μmol L⁻¹), correlation coefficient 0.9997. The detection limit of 1.8 × 10⁻¹⁰ mol L⁻¹ was achieved (S/N = 3). The applicability of the modified electrode was demonstrated by determination of serotonin in human serum. Moreover, the possible oxidation mechanism of 5-HT was discussed.

An immunosensing-chip was developed for ultrasensitive and specific detection of morphine (MO) with the Δf of a quartz crystal microbalance (QCM) as read-out signal. After self-assembly modified the QCM-chip with 3-mercaptopropionic acid, activated by 1-ethyl-3-(3-dimethylaminoprephyl) carbodiimide and n-hydroxysulf- succinimide to immobilize the MO-antibody, the responding property of MO on this sensing-chip was studied. The specific affinity between antibody and antigen benefits the selective response to the label-free detection of MO. The detection limit is 0.11 pg/ml and the linear range is 2 to 50 pg/ml. The developed sensing-chip was successfully applied for determination of MO in spiked human urine with the recoveries from 98.2% to 120%.

The objective of the current work was to investigate the performance of a carbon paste electrode (CPE) modified by TiO₂ for the analytical detection of trace lead (II) in drinking water by square wave voltammetry. The results showed that TiO₂ plays an important role in the accumulation process of Pb (II) on the modified electrode surface. The electroanalytical procedure employed for the determination of Pb (II) comprised two steps: chemical accumulation of the analyte under open-circuit conditions, followed by the electrochemical detection of the pre-concentrated species using square wave voltammetry. The analytical performance of this system has been explored by studying the effects of preconcentration time, potential scan rates and various concentrations of lead ions, as well as interferences due to other ions. The determined detection and quantification limits were 4.5 × 10⁻⁸ M and 9.5 × 10⁻⁵ M. The reproducibility for three replicate measurements at 25 μM lead level was 4.4%. The results indicated that this electrode is sensitive and effective for the determination of Pb²⁺.

This work focuses on the effect of multiwall carbon nanotubes (MWCNTs) purification methods for their application as conductive materials in the development of MWCNTs/epoxy amperometric nanocomposite (bio)sensors. For this purpose, three different MWCNTs samples with distinctive purities were characterized by Termogravimetric Analysis, X-Ray Fluorescence Spectroscopy and Transmission Electron Microscopy. Subsequently, the samples were used to fabricate three different series of MWCNTs dispersed into resin epoxy. These series contained from 1% to 12% of the MWCNT sample. Composition ratios were modelled by percolation theory and characterized by different electrochemical techniques including Cyclic Voltammetry and Electrochemical Impedance Spectroscopy. After accurate electrical and electrochemical characterization, it has been demonstrated that the purification method affects the electrochemical behavior of the nanocomposite electrodes; however the optimum MWCNT/epoxy ratio was not modified. Furthermore, morphological experiments corroborated that the electrochemical performance of the electrodes closely depends on the physical properties of the different MWCNTs used. The optimized-sensors (near-percolation sensors) were tested by hydrodynamic amperometry, using ascorbic acid as a model analyte. Interestingly, the sensors containing non-purified MWCNTs exhibited the best electroanalytical response. This fact demonstrates the beneficial effects of metal impurities being present in MWCNTs to enhance the analytical response of MWCNT-based amperometric nanocomposite (bio)sensors.

Diamond has long been of interest as a biomaterial due to its expected biocompatibility and chemical stability. Progress in surface functionalization of diamond and diamond electrochemistry has extended this interest to use as a biosensor platform. The sensitivity and selectivity of the diamond surface can be enhanced by covalently attaching carbon-based biochemicals. In this communication, an amine-thiol molecule was attached to a boron-doped diamond (BDD) surface to produce an enhanced ability to detect NO species. In the case of hydrogen terminated BDD, it was found that NO (aqueous) oxidation was insufficiently distinct to electrochemically detect NO. However, the amine-thiol functionalized BDD surface provided a distinct oxidation peak from 65 nanomolar to 236 nanomolar concentrations. Multiple cyclic voltammagrams with amine-thiol functionalized BDD electrode in (HPLC-quality) purified water indicated that the covalently attached surface molecules resisted decomposition during both anodic and cathodic polarization.

A lytic phage-based magnetoelastic (ME) biosensor method was firstly employed for on-site detection of methicillin-resistant Staphylococcus aureus (MRSA) on spinach leaves. Due to the virulent activity of this lytic phage, the effect of time and temperature on the extent of MRSA lysis was examined by incubating a mixture of the MRSA and lytic phage at various times (0, 15, 30, 45, 60, 75, and 90 min) and temperatures (0, 4, 15, 22, 37, and 45°C). After optimization of incubation time and temperature, spinach leaves were spiked with serial concentration of MRSA and the attachment of MRSA was confirmed using SEM. The phage-immobilized sensor and control (devoid of the lytic phage) sensor were placed on the surface of the leaves and the resonant frequency shifts of both sensors were compared. The optimal incubation time and temperature for contact of the phage-immobilized ME biosensor with the MRSA were determined to be ≤ 30 min and ≤ 22°C. The attachment of the lytic phage on the sensor was observed and the density of lytic phage on the sensor was determined to be 26 ± 3 particles/μm². The resonant frequency shifts of the phage-immobilized sensor linearly increased with the increase in the MRSA concentration and had a correlation coefficient and slope of 0.819 and 840.9 Hz/log CFU, respectively. Detection limit was determined to be 1.76 log CFU/25 mm² surface of spinach.

Corrosion protection by ultra-thin (≤ 50 nm) alumina films deposited by atomic layer deposition (ALD) on copper at 250°C was studied in 0.5 M NaCl aqueous solution by combining electrochemical and surface analytical methods. Time-of-Flight Secondary Ion Mass Spectrometry revealed a homogenous in-depth stoichiometry of the alumina coatings and their residual bulk contamination by organic and water precursor fragments. Trace contamination by a spurious Cu oxide was evidenced at the interface with the Cu substrate despite a reducing pre-treatment. Atomic force microscopy images revealed conformal substrate coverage and a granular-like coating morphology at the nanometer scale. Linear Sweep Voltammetry (LSV) and Electrochemical Impedance Spectroscopy (EIS) showed no electrochemical activity of the coating and a corrosion decrease reaching 4 orders of magnitude for coated samples in comparison with bare copper. Uncoated surface fraction was quantified by application of three different methods using the LSV and EIS data which led to results in excellent agreement. The uncoated surface fraction for 50 nm Al₂O₃ layers was ∼0.01%, confirming ALD alumina as an excellent coating for corrosion protection with spectacularly low residual corrosion activity restricted to the bottom of channel defects connecting the substrate to environment through the coating.

The corrosion kinetics of a carbon steel cylindrical band concentrically positioned in an annular flow cell exposed to a flow of concentrated unbuffered NaCl solution was investigated using linear sweep voltammetry and scanning electron microscopy techniques. These experiments employed a set of conditions of high NaCl concentration and low Reynolds number values. Assuming that the corrosion reaction is entirely under conditions of mixed charge transfer plus diffusion control mechanism on a bare metal surface, the corrosion process and local surface pH were simulated by applying mixed potential theory and a mass and charge balance on the metal surface, respectively. Changes in the corrosion rates, electrochemical parameter values for partial corrosion reactions, surface pH, and morphological attributes are discussed.

Iron (Fe) is an unintentional impurity present in pure magnesium (Mg) and Mg alloys, albeit nominally in low and innocuous concentrations (< 100 ppmw). Since Fe, like most metals, is more noble than Mg, the presence of Fe impurities can serve as cathodic sites within the Mg matrix. During anodic polarization of Mg, incongruent dissolution can lead to undissolved Fe impurities accumulating upon the Mg surface, permitting an increase in the overall rate of hydrogen evolution. The experimental manifestation of the incongruent dissolution of Mg, has not yet been clarified, wherein, the extent and efficiency of Fe enrichment during anodic polarization is not known, and also the increase in the hydrogen evolution rate due to Fe enrichment has not been quantified. In this work, Mg specimens with Fe concentration between 40 to 13,000 ppmw were examined in 0.1 M NaCl to obtain a quantitative relation between the Fe concentration and the rate of cathodic hydrogen evolution. These base-line alloys were then anodically polarized to facilitate surface Fe enrichment, and subsequently again cathodically polarized to determine the impact of prior dissolution and Fe enrichment on the subsequent hydrogen evolution. A simple model to predict Fe enrichment was used to analyze the electrochemical data and predict the extent and efficiency of Fe enrichment.

Benzotriazole (BTA), an effective corrosion inhibitor for Cu or Cu-containing Al alloys, was added to 0.1 M NaCl to study its potential role in suppressing corrosion of the commercial Mg alloy, AMlite. In particular, the impact of pH and BTA concentration was investigated, indicating that BTA was effective at restricting corrosion of AMlite in weakly alkaline NaCl solution, i.e. pH 10.0. The degree of the protection afforded was a function of BTA concentration. The best corrosion inhibition was found in the NaCl containing 15 g/L BTA, however, the mechanism of inhibition was not a classical function, nor related to the inhibition mechanism of BTA for Cu-bearing alloys. Instead it is posited that BTA⁻ anions act as a nucleating agent to stimulate the formation of a dense and highly crystalline Mg(OH)₂ surface film with a uniform nano-structure capable of passivating the Mg-alloy, in contrast to say, the insoluble Cu-BTA complex via Cu-N coordination bonds for Cu-alloys. The magnitude of this effect of BTA on Mg corrosion was not anticipated, but effective, with beneficial implications to utilization of Mg alloys as anode materials, where in such cases, when dissolution occurs, the anode can passivate with little change in its potential.

Effect of weak carbide formers, Mo, Mn and Si, on intergranular corrosion (IGC) of low-Cr ferritic stainless steel is analyzed after IGC test using TEM and three dimensional atom probe. The co-addition of Mo, Mn and Si to low-Cr ferritic stainless steel effectively prevents IGC by forming along grain boundaries CMn₄MoSi intermetallic compounds, which act not only as carbon trap sites but also as diffusion barrier against solute Cr diffusion toward grain boundaries. The low solubility of Cr in the CMn₄MoSi intermetallic compound results in replenishing Cr in the Cr-depleted area.

A hierarchical rough Cu film constructed by nanosheet-like clusters is electrodeposited on Fe and Mg alloy substrates from a deep eutectic solvent based electrolyte containing CuCl₂ and NaH₂PO₂ at 75°C (CuP-75°C). After modifying by stearic acid for 5 min, the film turns from superhydrophilic to superhydrophobic with a water contact angle (CA) of 161° and a sliding angle of ∼1.0°. For comparison, the electrodeposited Cu film from the electrolyte only containing CuCl₂ (Cu-75°C) exhibits more hydrophilic. Smaller CA value is obtained at lower deposition temperature due to the decrease in surface roughness. The CA value of the CuP-75°C film increases with increase of the surface modification time. Amazingly, only 3 min of stearic acid modification at room temperature can make the CuP-75°C film superhydrophobic with a CA of 155°. Such a fast process is attributed to the chemical reactions of the native CuO formed on the film surface with stearic acid and physical absorptions caused by larger specific surface area. The superhydrophobic CuP-75°C film exhibits a positively shifted E_corr (−356 mV vs. Ag/AgCl) and a decreased i_corr (7.07 μA cm⁻²) compared with the hydrophilic counterpart film, thus providing effective protections for active substrates.

The electrodeposition of aluminum (Al) on copper (Cu) substrate was investigated in [Bmim]Cl/AlCl₃ (33.3/66.7 mol%) ionic liquid using three pyridine derivatives, nicotinic acid, methyl nicotinate, and 3-methyl pyridine as additives at 303 K, respectively. It was found that bright Al coatings could be electrodeposited with nicotinic acid and methyl nicotinate as additives. SEM and XRD characterizations revealed that the bright coatings were very smooth, composed of nanocrystalline and with a strong (200) preferential orientation. By contrast, a matte and lusterless Al coating was obtained from the ionic liquid with 3-methyl pyridine. Furthermore, the effect of the three additives was investigated by means of cyclic voltammetry, chronopotentiometry and Raman spectroscopy. It was demonstrated that nicotinic acid and methyl nicotinate could absorb on electrode surface more easily and thus served as very effective brighteners producing highly uniform and smooth Al coatings. However, 3-methyl pyridine had no such effect.

Zn alloys are considered an alternative to replace Cd in protective coatings. Among Zn alloys, Zn-Ni are those with the higher corrosion resistance and better mechanical characteristics. Although Zn-Ni alloy can be electrodeposited from eutectic-type ionic liquid the morphology of the deposits needs to be improved. The effect of ethylamine and ethylenediamine on the electrodeposition of Zn-Ni alloy was investigated from a eutectic-type ionic liquid (ethaline). The presence of the amines in the plating bath modified the CV and j-t profiles. The nucleation mechanism was also influenced by adding the amines to the solution and the deposition of Zn-Ni in the presence of ethylenediamine followed the 3D progressive mechanism. Electrodeposition of Zn-Ni alloy from ethaline gives origin to a deposit with small grain particles with partial coverage of the electrode. Using the same electrodeposition conditions, the addition of amines allowed the full coverage of the electrode surface. In the presence of ethylamine deposit was formed by globular particles and by hexagonal platelets for deposits obtained in the presence ethylenediamine. Corrosion of the Zn-Ni metallic films was evaluated by potentiodynamic polarization experiments. The lowest value for the corrosion potential was obtained for the deposit prepared in the presence of ethylenediamine.

In order to explore the possible surfactant effect of Ag on the formation of electrodeposited multilayers, Co/Cu(Ag) multilayers were prepared by this technique and their structure and giant magnetoresistance (GMR) were investigated. The multilayers were deposited from a perchlorate bath with various amounts of Ag⁺ ions in the solution for incorporating Ag atoms into the multilayer stack. Without Ag addition, secondary neutral mass spectroscopy (SNMS) indicated a well-defined composition modulation of the undermost Co/Cu bilayers. However, already at an Ag content as low as 1.8 at.% incorporated, SNMS showed a deterioration of the periodic multilayer structure. In agreement with the SNMS results, superlattice satellites were visible in the X-ray diffraction (XRD) patterns of the multilayers with up to 0.3 at.% Ag. The satellites were, however, very faint even for multilayers without Ag addition, indicating that the multilayers have high interface roughness and/or poor periodicity. In the absence of Ag and at the smallest Ag content investigated by XRD, a strong central multilayer peak and the weak superlattice satellites were complemented by weak diffraction maxima from non-periodic Co and Cu domains. In the Co/Cu(Ag) multilayer containing about 25 at.% Ag, i.e., nearly as much as Cu, XRD found a separate Ag(Cu) phase. In spite of the imperfect layered structure, a multilayer-type GMR behavior was observed in all samples up to about 10 at.% Ag incorporated in the multilayer stack. The GMR magnitude increased for Ag contents up to about 1 at.%, which implies that a small amount of Ag may have a beneficial effect through a slight modification of the layer growth and/or interface formation. However, for higher Ag contents beyond this level, the GMR was reduced in line with the structural degradation revealed by XRD and SNMS. For the highest Ag contents (above about 10 at.%), the GMR exhibited a behavior characteristic of a granular magnetic alloy, in agreement with the results of the structural study.

In₂O₃ nanoparticles (<100 nm) up to 5 wt% are incorporated into Ni-Fe alloy matrix by electrodeposition which enhance both corrosion resistance and hardness. Plating parameters like current density, concentration of metal ions and In₂O₃ particles, agitation and the temperature of the bath were optimized to achieve acceptable quality of the coatings. Effect of current density on the development of Ni-Fe/In₂O₃ nanocomposites and their physical properties was mainly studied. Coatings thus obtained were characterized by SEM-EDAX, XRD, TEM and AFM and surface morphology, crystal structure, microhardness, corrosion resistance, magnetic behavior and electrical resistivity of the nanocomposites were studied. The incorporation of conducting In₂O₃ particles in a alloy matrix resulted in a higher electrical conductivity than the matrix. X-ray diffraction results showed that the incorporation of In₂O₃ particles does not affect the Ni-Fe alloy fcc structure but alters the texture of the deposits favoring (111) crystallographic orientation and is independent of the applied current density for deposition. The crystallite size of the nanocomposites is found in the range of 5–13 nm with almost negligible strain.

We investigated the influence of antimony (Sb) dopants (6 ∼ 11 at%) with multivalent metal ions (Sb³⁺/Sb⁵⁺) on the electrical properties of ZnO nanorods for application in photoelectronic devices. More vertically aligned and more conductive n-type ZnO nanorods were effectively prepared via the electrochemical deposition process. The addition of a small amount of Sb in the ZnO nanorods induced a faster growth rate and high aspect ratio. The remarkable enhancement of electrical conductivity resulting from Sb doping was confirmed by photoelectrochemical performance and current-voltage measurements in all oxide n-type ZnO/p-type Cu₂O heterojunctions, which was ascribed to the substitution of Sb for Zn sites without defect complexes. These results demonstrate the feasibility of using Sb as an n-type dopant in ZnO nanorods in a wet-based electrodeposition process.

The electrolyte for Cu superfilling generally consists of copper sulfate, sulfuric acid, a chloride ion, an accelerator, and a suppressor. In this study, the characteristics of citric acid-based electrolytes and the interaction between citrate species and accelerators are investigated, with the ultimate goal being the replacement of both sulfuric acid and the suppressor with citric acid. Electrochemical impedance measurements were adopted to measure the changes in solution and charge transfer resistances with respect to citric acid and accelerator concentrations. In addition to a decrease in solution resistance resulting from the addition of citric acid, charge transfer inhibition was observed during Cu electrodeposition, which is likely the result of adsorption of citrate species onto Cu surface. A competitive adsorption between the citrate species and the accelerator was also observed and the new additive system was applied to the feature filling in the absence of the conventional polyethylene glycol suppressor. Using this new copper sulfate, citric acid, chloride ion, and accelerator system, trenches were successfully bottom-up filled, resulting in no internal defects.

Methanesulfonic acid (MSA) is an interesting supporting electrolyte with many desirable properties such as high salt solubility, high conductivity, low corrosivity and toxicity. Various additives or complexing agents such as brighteners, antioxidants, and surfactants are required for deposition of Sn and Cu-Sn alloys. It has been shown that the simplest electrolyte for successful Cu-Sn deposition can contain just an antioxidant and a fluorosurfactant. In this work we have further examined the role of fluorosurfactant in shifting the electrochemical reduction potential for the more noble metal. The surface adsorption and desorption processes of the surfactant has been inferred through the use of an electrochemical quartz crystal nanobalance (EQCN). Cu and Sn have been deposited individually and simultaneously from MSA electrolytes. Mass changes at the quartz crystal have been compared against those calculated from charge consumption. These data show that in MSA electrolytes the adsorption and desorption of the fluorosurfactant to the surface is potential dependent and it suppresses Cu deposition but facilitates Cu-Sn alloy deposition.

Copper foams with various pore structures have been prepared using hydrogen bubbles as templates by electrodeposition method. By adjusting deposition time and incorporating different additives, the pore structures of copper deposit layers were effectively tuned as the results of controlled nucleation, growth, coalescence and detachment of hydrogen bubbles on the deposition interfaces. According to the analysis of experimental results, a tentative templating mechanism of hydrogen bubbles has been proposed, in which the well-grown hydrogen bubbles on the deposition interface are believed to contribute mostly to the formation of pore structures in the copper deposit layers, while the bubbles enlarged through interconnection and coalescence make no templating contributions due to their easy detachment from the interface. A larger average size of templating hydrogen bubbles at the upper layer than at the lower layer should arise from the quasi close-packing of growing hydrogen bubbles with their nucleation sites confined to the areas unoccupied by the pre-existing bubbles. In terms of this templating mechanism of hydrogen bubbles, the influences of relative concentrations of Cu²⁺ and H⁺ in the electrolyte solutions, deposition current density, chemical species and concentrations of additives on the evolution of pore-structures in the electrodeposited copper foams may be well explained and understood.

Electrochemical reactions of Ni(II)/Ni and Fe(II)/Fe were investigated in a hydrophobic room-temperature ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide (BMPTFSA) containing Ni(TFSA)₂ and Fe(TFSA)₂. The optimal conformation of high-spin metal ion (M(II) = Fe(II) and Ni(II)) with three trans-TFSA⁻ were obtained using the theoretical calculations. The bigger molecular volume of Fe(II) species in BMPTFSA may lead to a smaller reduction peak current. The cyclic voltammetric results showed that the cathodic peaks of Ni(II) and Fe(II) emerged into one wave, which is close to the cathodic waves of individual metals and favorable for the co-electrodeposition of Ni-Fe. A non-anomalous codeposition behavior was found from BMPTFSA with Ni(TFSA)₂ and Fe(TFSA)₂. Ni-Fe deposits with different morphology and composition were obtained at various applied potentials and metal ion concentrations.

Tin (Sn) films have been prepared on a molybdenum substrate covered with copper (Mo/Cu) by the electrodeposition method from the electrolyte solutions of tin sulfate (SnSO₄) and trisodium citrate (C₆H₅Na₃O₇). The formation mechanism and microstructures of the films were investigated by cyclic voltammetry (CV), chronoamperometry (CA), scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). The CV and CA measurements show the electrodeposition is controlled by the diffusion process of tin ions. By means of Scharifker-Hills model and microstructural analysis, the Sn nucleation mechanism is clarified to be an instantaneous nucleation mechanism. The influence of deposition time, solution concentration and the potential on microstructures of Sn films has been systematically investigated and the optimal growth parameters for preparing dense Sn films are obtained.

An electrodeposition replacement to the commonly used physical vapor deposition methods used in enhancing the coercivity of Nd-Fe-B sintered magnets has been proposed. Dysprosium was galvanostatically electroplated on Nd-Fe-B sintered magnets that were previously electrochemically coated with copper. Electroplated dysprosium films were characterized by X-ray photoelectron spectroscopy, depth profiling, scanning electron micrographs, and energy dispersive X-ray spectroscopy. XPS analysis after argon ion sputtering indicates that minor impurities are only superficial as their atomic fractions in the sample nearly disappear with increasing etching time. The electrochemistry of synthesized dysprosium bis(trifluromethylsulfonyl)imide dissolved in the air- and water-stable ionic liquid 1-butyl-3-methylpyrrolidinium bis(trifluoromethylsuflonyl)imide was studied by cyclic voltammetry. Electroplating of metallic dysprosium was followed by a heat-treatment above the melting temperature of the Nd-rich phases of the sintered magnet base body whose magnetic characterization was performed in a hysteresis loop tracer for hard magnetic materials.

We prepared less volatile and halide-free electrolytes for room temperature non-dendritic magnesium (Mg) electrodeposition by mixing a Mg²⁺-amide-containing ionic liquid (IL) with equimolar glyme (Mg²⁺+IL : glyme = 1:1). Raman spectroscopy suggested that in the equimolar mixture most glyme molecules are coordinated to Mg²⁺ cations and/or IL cations, which is also supported by a single crystal X-ray diffraction study. The glyme-coordinated IL electrolytes showed sizable redox currents (order of mA cm^–2), while aging deterioration of electrochemical properties was observed for the triglyme mixture due to partial bath decomposition. The tetraglyme-coordinated IL electrolyte enabled flat electrodeposition of Mg with a metallic luster and showed with very high anodic stability (ca. +4 V vs. Mg) because of decrease in uncoordinated glymes, which can be used for high-voltage Mg ion batteries.

The TSV filling using the dialyl-amine and the Br⁻ and Cl⁻ halogen ions to a copper electrodeposition bath is reported. The TSV bottom acceleration and TSV outside inhibition have been measured by an electrochemical method using the rotating disk electrode and numerical computation of the fluid dynamics. A perfect TSV filling is achieved with 1 ppm P(DAMA[HBr]/SO₂) + 1 ppm of Br⁻ and the electrodeposited morphology is fine and bright. This shows acceleration at the lower rotation speeds of the rotating disk electrode and an inhibition at the higher speeds, if compared to 1 ppm P(DAMA[HCl]/SO₂) + Cl⁻1 ppm. Br⁻ 1 ppm shows a stronger inhibition at the higher rotation speeds, if compared to Cl⁻1 ppm. The addition of SPS in addition to Br⁻ 1 ppm shows acceleration at the lower speeds. No voids formed at the higher current density of 3.5 mA/cm² with SPS.

Two kinds of dendritic Te crystals were successfully prepared by electrodepositing TeO₂ in pH = 3, 8 and 11 solutions respectively. The parameter of pH played an important role in growth rate. Moreover, the nucleation of Te in pH = 3 and 8 solutions were conformed to progressive type while in pH = 11 solution was conformed to instantaneous type. By systematically studying the morphologies evolution of Te crystals with different deposition times in pH = 3, 8 and 11 solutions, the structure of crystal was confirmed directly decided by nucleation type. Base on this, a growth mechanism for two kinds of dendritic crystals was proposed. Moreover, this mechanism may provide a reference for predicting the morphology of Te crystals in electrodeposition process.

Taking bromophenol blue as pollutant model, the role of sulfate electrolytes during the anodic oxidations was investigated in a wide range of concentrations (0.1–500 mM). Trials were performed with an electrochemical cell containing boron-doped diamond anode and stainless steel cathode. The impact of sulfate concentration on the degradation performance was assessed by comparing the color removal efficiencies at various time intervals. The results revealed a significant and peculiar influence of this parameter on the degradation efficiency. Thus, we emphasize the importance of selection of operating levels in electrolytic oxidations, especially when certain activators (from the cathode) may be formed in the treated solutions.

In this paper we present a novel single-step RIE process for InP membrane optical waveguide etching. The optimization of the process is focused on the sidewall verticality and surface roughness of the etched profile. Significant improvement on the etched profile is achieved for the first time in a single-step RIE process. Loss measurement on fabricated membrane waveguides etched with the proposed RIE process results in a record low waveguide propagation loss (2.5 dB/cm).

The effect of manganese and ammonium sulfate concentrations, temperature, selenium composite additives and cathode current density on the current efficiency of metallic manganese was studied. This was done for the simultaneous production of compact electrolytic manganese dioxide at the anode in a laboratory electrochemical reactor by anion exchange membrane using AMI 7001S (Membrane International Inc., USA). The experimental results obtained from the large scale laboratory electrochemical reactor are discussed. A version of this technology that could be used for the simultaneous production of metallic manganese and electrolytic manganese dioxide is also discussed.

One significant contribution to the anodic potential during aluminum electrolysis is the formation of CO₂ bubbles that screen the anode surface. This effect creates an additional ohmic resistance as well as an increased reaction overpotential, hyperpolarization, as the effective surface area decreases.  This work aims to improve the understanding of how anode properties - including isotropy at the optical domain level, wettability (toward electrolyte), surface roughness and porosity - affect bubble evolution.  Pilot anodes, made with single source coke types varying in isotropy, were used to study bubble evolution by electrochemical methods. In order to retain bubbles during experiments, anodes were designed to have only horizontal surface area. Bubble formation and release were monitored at different current densities, and were tracked by measuring the oscillations in anode potential and series resistance.  Anodes made from different cokes were found to have different bubble evolution properties, possibly due to variation in the density of nucleation sites at the surface of each anode and varying anode-electrolyte wettability.

A newly-designed continuous flow photoelectrochemical reactor (CFPR) was applied to the solar photoelectrosynthesis of alcohols from carbon dioxide (CO₂) dissolved in aqueous media. Hybrid p-type CuO/Cu₂O semiconductor nanorod arrays, prepared by a three-step synthesis method (sol-gel synthesis, thermal anneal, and cathodic electrodeposition) were used as photocathodes. Scanning electron microscopy and powder X-ray diffraction were used to characterize these hybrid materials at various stages of the preparation protocol as well as before and after being subjected to photoelectrolysis for selected periods of time. The performance of the CFPR with the hybrid photocathode was analyzed in CO₂-saturated aqueous bicarbonate solution at −0.3 V vs Ag/AgCl under simulated AM 1.5 solar irradiation for periods up to 5 h. The hybrid photocathode formulation facilitated efficient photoelectron injection to CO₂ while its robustness and high photoelectrochemically active surface area enhanced the formation of alcohols. Gas chromatographic analyses of the photoelectrolysis solutions under a flow rate of 5 ml/h revealed ethanol to be the main product followed by isopropanol and methanol. The amounts of alcohol assayed indicated a faradaic efficiency ranging from 75 to 96%. The formation of C-C bonds in the products is a significant finding in this study and a mechanistic hypothesis is presented to account for products such as ethanol instead of methanol as is usually seen. Finally, the CFPR performance was numerically simulated to unravel the influence of flow rate and channel geometry on CO₂ conversion and consumption rate.

For this study, porous anodic alumina thin films with annular structural colors were fabricated in a phosphoric acid electrolyte by the one-step oxidation of an aluminum (Al) sheet. In this case, small carbon balls were used as the cathode and an Al sheet used as the anode, with the distance between cathode and anode remaining adjustable. Electron microscopy shows that the different parts of films are different in microstructure. Results additionally reveal that the depth and aperture of nano-holes diminished symmetrically outward from the center of the films. It is possible to control ring density by changing the oxidation time and voltage. These experimental results, conducted using point electrode, are consistent with a theoretical study of the oxidation process and formation mechanism of anodic alumina thin films with annular structural colors.

Fundamentals of synthesis, sintering issues, and chemical stability of BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3-δ (BZCYYb) proton conducting electrolyte material were studied. Solid state reaction (SSR) and glycine nitrate process (GNP) methods were used to synthesize BZCYYb powders. The GNP method produced powders with higher purity and smaller particle size in reduced heat-treatment time and temperature. It was found that BZCYYb material, despite its high proton conductivity, has surprisingly high tendency to react with common substrate materials including alumina, zirconia, and even ceria during high temperature sintering. This led to significant barium loss and even disintegration of the perovskite phase. In addition, during sintering, BZCYYb also lost Ba through gas phase. The barium loss and unwanted side reactions with substrates could be suppressed either using enclosure of a platinum substrate and a cover or protective layers of BZCYYb powders. On the other hand, using metal oxide sintering aids such as NiO helps reducing sintering time and temperature which mitigates the extent of unwanted reactions. Finally, isothermal exposure experiments showed that at 750°C, chemical stability limits for BZCYYb in CO₂ and H₂S contaminated atmospheres are below ∼50 vol. % of CO₂ and between 50 and 100 ppm of H₂S, respectively, and they shift to lower values for Ba-deficient BZCYYb.

Tb and Sm cation binary co-doped ceria films were deposited using the ultrasonic atomizing spray pyrolysis method. Crack-free homogenous films with different dopant concentrations were deposited and thereafter annealed at fixed temperatures T = 900, 1200 and 1300°C, respectively. It was demonstrated that several microstructural parameters of oxide films are controlled by the sintering temperature. The Ce_0.9Sm_0.1-xTb_xO_2-δ films formed were analyzed using X-ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy, atomic force microscopy and a four probe DC technique at different pO₂ and temperature conditions. Based on the SEM analysis the average thickness of the Ce_0.9Sm_0.1-xTb_xO_2-δ films was approximately 700 nm. The XRD patterns for the Ce_0.9Sm_0.1-xTb_xO_2-δ films annealed at 1200°C indicated a high degree of crystallinity. Tb dopant ions influence the microstructural properties like median diameter of grains, microstrain, lattice parameter and electrical properties like activation energies of ionic and electronic part of conductivity for the Ce_0.9Sm_0.1-xTb_xO_2-δ film. A significantly higher microstrain value for the lowest Tb dopant concentration with accompanied change in electrical properties was observed.

In the present computational study, a thermal flow analysis is performed on a large-scale (10 × 10 cm) planar Solid Oxide Iron-Air Redox Battery (SOIARB) operated at 800°C. The results explicitly indicate that the heat generated during the discharge cycle is more than what is needed for the charge cycle. Use of air as a working fluid to regulate the heat flow and heat balance within the battery is a practical engineering solution to maintain the desirable operating temperature and high energy efficiency for the battery system. Air utilization and inlet temperature are the two most important parameters that can be adjusted to regulate the heat flow between cycles. The analysis also shows that operating at a higher current density, around 1500 A/m², the battery becomes thermally self-sustainable, but at the expense of lowered electrical cycle efficiency.

A one-dimensional model is developed and validated to study platinum degradation and the subsequent electrochemical surface area (ECA) loss in the cathode catalyst layer (CL) of polymer electrolyte fuel cells (PEFCs). The model includes two mechanisms of Pt degradation: Ostwald ripening on carbon support and Pt dissolution-re-precipitation through the ionomer phase. Impact of H₂ | N₂ or H₂ | Air operation, operating temperature, and relative humidity (RH) on Pt degradation during voltage cycling is explored. It is shown that ECA loss is non-uniform across the cathode CL with a zone of exacerbated Pt degradation and hence much lower ECA found near the membrane. This non-uniform Pt degradation is caused by consumption of Pt ions by crossover H₂ in both H₂ | N₂ and H₂ | Air systems. An important consequence is that thinning the cathode electrode in a fuel cell would lead to more ECA loss as a higher fraction of the thin CL would fall in this exacerbated degradation zone. We have quantified the effect of thin cathode CLs on Pt degradation for the first time.

We report an analytical solution for the membrane potential in a PEM fuel cell which consist of a half-plane (semi-infinite) anode and a large-area (infinite) cathode. Mathematically, the problem is analogous to the Gouy–Chapman problem for the potential distribution inside the diffuse double layer at a flat metal/electrolyte interface. An expression for the characteristic length l_* of the membrane potential variation in the anode-free domain is derived. This expression suggests a minimum distance 3l_* between the anode edge and a reference electrode at which the potential of the reference electrode yields the cathode overpotential in the working domain of the cell.

Palladium (Pd) nanotubes are synthesized by the spontaneous galvanic displacement of copper (Cu) nanowires, forming extended surface nanostructures highly active for the hydrogen oxidation reaction (HOR) in base. The synthesized catalysts produce specific activities in rotating disk electrode half-cells 20 times greater than Pd nanoparticles and about 80% higher than polycrystalline Pd. Although the surface area of the Pd nanotubes was low compared to conventional catalysts, partial galvanic displacement thrifted the noble metal layer and increased the Pd surface area. The use of Pd coated Cu nanowires resulted in a HOR mass exchange current density 7 times greater than the Pd nanoparticles. The activity of the Pd coated Cu nanowires further nears Pt/C, producing 95% of the mass activity.

A low platinum loading model, considering both the platinum loading and platinum particle distribution on carbon support, is developed. This model takes into account the interfacial transport resistances at ionomer, water film and Pt particle surfaces in order to capture the effects of Pt loading and electrode composition on fuel cell performance. After coupling this electrode model into a comprehensive PEM fuel cell model, i.e. M2 model, experimental validation is performed for a wide range of Pt loading from 0.2 to 0.025 mg/cm² for two electrode compositions with and without carbon dilution. Good agreement between the predicted and measured polarization curves is achieved under wide-ranging operating conditions. The agglomerate size effect is also examined and it is shown that the agglomerates have virtually no effect on cell performance for agglomerate radius smaller than 150 nm. Since in realistic fuel cell catalyst layers, agglomerates may not exist, or may only exist with sizes no larger than 150 nm based on SEM observations, the present work suggests that the standard homogeneous electrode model is suitable and sufficient for analyses of transport losses in PEM fuel cell electrodes where interfacial transport resistances exist.

Rechargeable fuel-cell batteries (RFCBs) operate by hydrogen storage and release at the anode, while oxygen evolution and reduction reactions occur at the cathode. High-surface-area porous carbon was treated with HNO₃ to produce an anode material with carbonyl and phenol groups on the surface, thereby providing redox sites for hydrogen storage and release. The HNO₃-activated carbon anodes were characterized with respect to use in a RFCB operated from room temperature to 75°C with a voltage range of 0–2.0 V. The quantity of carbonyl groups and the corresponding reduced phenol groups increased with the O/C atomic ratio of the oxygenated carbon, by which the electrical capacity was increased to reach a maximum of 125 mAh g⁻¹ at an O/C atomic ratio of 0.114. The optimal temperature and charge voltage for performance and cyclability were determined to be 50°C and 1.25 V, respectively. The charge and discharge times remained at ca. 93% of the respective initial values after 300 cycles. The RFCB with the modified porous carbon anode provided energy densities of 2.5–13.8 Wh kg⁻¹ and power densities of 46.4–296.3 W kg⁻¹ (normalized according to the mass of the entire cell).

A transient 1+1 D model has been developed for carbon corrosion during fuel cell start-up. The model considers the species transport in the anode channel and catalyst layer, the double-layer and pseudo capacitances, and the multiple species coverage on carbon and Pt which influences reaction kinetics. Model simulations and analysis have been performed focusing on the reaction kinetics including carbon corrosion rate, the contributions from double-layer and pseudo capacitances, and the effects of initial Pt state at anode and cathode, temperature, and anode O₂ diffusivity. It has been found that the remaining O₂ amount in the anode catalyst layer, rather than the H₂ front, is the key factor for cathode carbon corrosion rate. There exists a charge balance in anode oxygen reduction reaction (ORR) which is the driver for cathode carbon corrosion, cathode oxygen evolution reaction (OER), cathode carbon corrosion reaction (COR), and multiple capacitive currents. Among all capacitive currents, cathode pseudo capacitance contributes most to the protons for anode ORR. Enhancing cathode OER is preferred over cathode pseudo capacitance to reduce COR since the latter approach can increase cathode PtO coverage and Pt dissolution. Higher cathode initial bare Pt surface leads to less cathode carbon corrosion, whereas higher anode initial bare Pt surface enhances anode ORR rate as well as cathode carbon corrosion in the beginning but reduces both afterwards due to faster consumption of the remaining O₂. Both reduced temperature and anode O₂ diffusivity are shown to decrease the cathode carbon corrosion during start-up, the former being highly effective.

The oxygen reduction reaction (ORR) at the interface between platinum and Nafion 1100 equivalent weight was studied as a function of temperature (20–80 °C), humidity (10–100%), scan rate, the manner in which Nafion film was deposited, and the state of the Pt surface using ultramicroelectrodes employing cyclic voltammetry and chronoamperometry. ORR on smooth electrodes was strongly inhibited under specific conditions dependent on temperature, humidity, and scan rate. From the data presented, we postulate that dynamic changes in the molecular structure of the ionomer at the platinum interface result in differences in ORR voltammetry for films prepared and equilibrated under different conditions. The lack of similar changes for rough, platinized electrodes has been attributed to differences in initial ionomer structure and a higher energy barrier for ionomer restructuring. These model system studies yield insight into the ionomer-catalyst interface of particular interest for polymer electrolyte fuel cells.

In the present work, a 40 wt% Pt₃Cr/C alloy catalyst showed enhanced activity under both half-cell and full-cell conditions as well as excellent corrosion stability compared to those of the 40 wt% Pt/C benchmark catalyst. In half-cell experiments at 2 mA cm⁻², Pt₃Cr/C catalyst exhibited 10 mV less over-potential and twofold higher specific and mass activity for ORR than Pt/C. The average particle size grew from 4.5 nm up to "only" 6–8 nm after 7000 degradation cycles. For comparison, average particle size of Pt/C increased from 4.5 up to 10–30 nm. After 1000 degradation cycles in full-cell, MEA with Pt₃Cr/C cathode exhibits an excellent maximum power density retention of about 94% compared to only 59% for the MEA with the commercial catalyst.

A Solid Oxide Electrolysis (SOE) short stack consisting of anode-supported cells (ASCs in fuel cell mode) was assembled in JÜLICH's F10-design. ASCs are based on Ni/8YSZ (8 mol-% yttria-stabilized zirconia) with an LSCF air electrode (La_0.58Sr_0.4Co_0.2Fe_0.8O_3-δ) and 8YSZ electrolyte. A gadolinium-doped ceria (GDC) (Ce_0.8Gd_0.2O_1.9) barrier layer was deposited between 8YSZ and LSCF by means of physical vapor deposition (PVD). The stack was mainly characterized in a furnace environment in both fuel cell and electrolysis modes, with 50% humidified H₂ at 700 and 800°C. An endothermic long-term electrolysis operation was carried out at 800°C with a current density of −0.5 Acm⁻² and steam conversion rate of 50%. After 2300 h of operation, the stack showed an average voltage degradation rate of 0.7%/kh. Electrochemical impedance spectroscopy (EIS) and analysis of the distribution function of relaxation times (DRT) showed that the degradation was primarily due to the increase in ohmic resistance.

This work compares the methanol oxidation performance and stability of a commercial PtRu/Carbon catalyst post modified with nitrogen against an unmodified counterpart in alkaline media. Commercially available Hi-Spec JM10000 (PtRu) was modified with nitrogen via ion implantation in order to modify those areas not shielded by the pre-existing catalyst. The effects of this process on the structure and chemical composition of the catalyst and carbon support were explored using X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM), while the electrochemical performance and stability of the catalyst were then investigated using rotating disk electrode experiments. Compared to the unmodified catalyst, the N-modified sample had a higher initial electrochemical surface area, likely resulting from the ablation and redeposition of PtRu during the implantation process. Accelerated degradation test (ADT) results showed that nitrogen modification reduced surface area loss, helped to retain ruthenium, and improved methanol oxidation performance by nearly double. The benefits of nitrogen doping to improve state-of-the-art electrocatalysts combined with advantages of alkaline media improve the viability of widespread commercialization of direct methanol fuel cells.

The regenerative H₂-Br₂ fuel cell has been a subject of notable interest and is considered as one of the suitable candidates for large scale electrical energy storage. In this study, the preliminary performance of a H₂-Br₂ fuel cell using both conventional as well as novel materials (Nafion and electrospun composite membranes along with Pt and Rh_xS_y electrocatalysts) is discussed. The performance of the H₂-Br₂ fuel cell obtained with a conventional Nafion membrane and Pt electrocatalyst was enhanced upon employing a double-layer Br₂ electrode while raising the cell temperature to 45°C. The active area and wetting characteristics of Br₂ electrodes were improved upon by either pre-treating with HBr or boiling them in de-ionized water. On the other hand, similar or better performances were obtained using dual fiber electrospun composite membranes (PFSA/PPSU) versus using Nafion membranes. The Rh_xS_y electrocatalyst proved to be more stable in the presence of HBr/Br₂ than pure Pt. However, the H₂ oxidation activity on Rh_xS_y is quite low compared to that of Pt. In conclusion, a stable H₂ electrocatalyst that can match the hydrogen oxidation activity obtained with Pt and a membrane with low Br₂/Br⁻ permeability are essential to prolong the lifetime of a H₂-Br₂ fuel cell.

Highly Pr-doped Ba₂In₂O₅ (PBI) was successfully fabricated and its ionic conduction and power generation characteristics were studied in this work. Two PBI materials of different concentration ratio were evaluated: Pr:Ba:In = 0.9:1.1:1 (PBI910) and Pr:Ba:In = 1:1:1 (PBI000). PBI910 material was confirmed as single phase with cubic perovskite structure. However, PBI000 had both cubic phase and impurity phase. In a hydrogen concentration cell, the measured proton transfer number of PBI910 at 500°C was 0.81 and then decreased with increasing temperature, whereas the oxide ion transfer number was 0.07 and then increased with increasing temperature. Power generation experiments were evaluated at 500°C to 900°C using PBI as electrolyte and H₂ as fuel. Results revealed that and showed different dependency on temperature and significantly affected the power density. Proton conduction dominated from 500°C∼600°C, and power density increased with increasing operating temperature due to improved proton conductivities. However, at 600∼800°C, proton conductivities decreased, which caused a decrease in power density. Further increase in temperature into the 800°C∼900°C range showed oxide ion conduction to then dominate, and the consequent improved oxide ion conductivity again increased the power density despite a decrease in open current voltage (OCV).

Advanced oxidation processes are an efficient method of treating many industrial wastewaters. This study investigated the treatment of olive mill wastewater with the electro-oxidation method. This study investigated data obtained from chemical oxygen demand (COD), total organic carbon (TOC) and total phenol (TP) removal efficiencies for this wastewater. The anode material was Ti/Pt while the cathode material was Ti. The experiments using a batch reactor examined the effects of mixing rate (0–600 rpm), dilution factor (1/5-5/5), pH (2–8), type of support electrolyte (Na₂SO₄, KCl and NaCl), concentration of support electrolyte (0.25–1.25 M) and current density (2.5–15 mA/cm²) on COD, TOC and TP removal efficiencies. The study found the COD, TOC and TP removal rates under optimum conditions were 100%, 78% and 100%.

Electrical properties of core–shell nanoparticles with protein shell layers have not been fully surveyed, although such nanoparticles have been studied widely as model biomimetic particles. In this study, we demonstrated that the capacitance changes of a silica (SiO₂)/bovine serum albumin (BSA) core–shell nanoparticle (SiO₂@BSA) could be monitored with variation of BSA shell thickness using AC impedance spectroscopy combined with conductive atomic force microscopy (c-AFM). Impedance spectra showed that the resistance and capacitance of SiO₂@BSA core–shell nanoparticles increased with increasing BSA shell thickness. Within the range of experimental conditions studied, the capacitance of SiO₂@BSA increased linearly with increasing number of BSA layers, corresponding to a 5.4 pF rise per single layer of BSA after the first two layer deposition of BSA. This result demonstrated that the minute changes of the electrical properties that were induced by the shell protein layer can be monitored and quantified using impedance spectroscopy.

A novel conducting polymer, poly(aniline-co-N-methylthionine), is synthesized in a mildly acidic aqueous solution using cyclic voltammetry. The rate of copolymerization and the electrochemical properties of the obtained copolymers are substantially affected by pH, upper potential limit and comonomer concentration ratio. The copolymer possesses a high electrochemical activity in an aqueous solution up to pH 10.0. The copolymer formed on an indium-tin oxide glass electrode exhibits a black-to-transmissive electrochromism under relatively low potentials. The results from the Fourier transformed infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) of the copolymer show that NMTh units and Cl⁻ ions were incorporated into the copolymer backbone during the electrosynthesis. The scanning electron microscopy (SEM) micrograph demonstrates that the copolymer film is composed of polymeric flower-like microparticles with an average diameter of 1μm.

The electrochemical behavior of tetrafluoro-p-quinone, TFQ, at bare and activated glassy carbon electrodes (BGCE and AGCE) was studied in aqueous solution by cyclic voltammetry. The effects of scan rate, pH and concentration on the electrochemical behavior of TFQ indicate that the reduced form of TFQ (tetrafluoro-p-hydroquinone, TFHQ) is adsorbed weakly at the AGCE surface whereas the oxidized form does not show any adsorption at this surface. The temperature dependency of the TFQ redox potential has been used for determination of the changes of entropy, enthalpy and Gibbs free energy of the electrochemical reaction of TFQ. Theoretical calculations have been also carried out by means of standard ab initio modern composite methods (G3B3 and G4 theories). Theoretical and experimental values for the standard redox potential of TFQ are in good agreement with each other.

In this paper, a titanium electrode was used in the electrochemical synthesis of 2,2^'-dichlorohydrazobenzene (DHB) from o-chloronitrobenzene (o-CNB). The catalytic activity of four different catalysts PbO, Bi₂O₃, Sb₂O₃, and SnO₂ on the titanium electrode was investigated. Both PbO and Bi₂O₃ demonstrated high catalytic activity. The chemical yield of DHB was 93.9% in 6 hours using PbO and 95.5% in 6.5 hours using Bi₂O₃, respectively. A new catalyst loading method on the titanium electrode was explored by cyclic voltammetry (CV). The CV method formed smaller and more uniform size PbO crystals at a scanning rate of 10 mv/s and, ultimately, the yield of DHB reached 93% within a shorter reaction time. A possible reaction mechanism was presented and the origin of the by-product o-CA was found.

The Li-ion battery electrode materials generally experience significant volume change during lithium diffusion. These volume changes lead to diffusion induced stress. Diffusion induced stress(DIS) will cause fracture and nucleation in the electrode. Many electrode materials undergo formation of two or more phases during lithium insertion. By analyzing the process of lithiation, the DIS in phase transforming electrodes using a core-shell model structural is investigated. The new model considering the misfit dislocation effect is established to analyze the stress distribution in the nanoparticle electrode. We observe that the magnitude of DIS can be affected by the misfit dislocation. In addition, the concentration jumps is also affected by the misfit at phase boundaries that result in stress discontinuities, which in turn can cause cracking. The influence of the mechanical properties of the two phases on stress evolution, stress discontinuity, and misfit dislocation effect are clarified. What's more, the Tresca stress is also expounded in the Li-ion battery. The effect of misfit dislocation and the phase transforming on the Tresca stress is clarified. The trends obtained with the model may be used to help tune electrode materials with appropriate interfacial and the misfit dislocation so as to increase the durability of battery electrodes.

Electrode reactions of tris(1,10-phenanthroline)iron complexes, [Fe(phen)₃]^3+/2+, were investigated in some amide-type ionic liquids. The diffusion coefficients of [Fe(phen)₃]²⁺ and [Fe(phen)₃]³⁺ were smaller than those of tris(2,2^'-bipyridine)iron complexes, [Fe(bpy)₃]²⁺ and [Fe(bpy)₃]³⁺, in each ionic liquid, reflecting the phen complexes are larger than the bpy complexes. The ratio of diffusion coefficient of the trivalent species to that of the divalent one for [Fe(phen)₃]^3+/2+ was smaller than that for [Fe(bpy)₃]^3+/2+, indicating the coulombic interaction between the charged species and the ions composing the ionic liquid is dependent on the charge densities of complexes. The rate constants for [Fe(phen)₃]^3+/2+ were close to those for [Fe(bpy)₃]^3+/2+, suggesting the outer components of reorganization energies for both complexes are similar to each other. On the other hand, the apparent reaction entropies for [Fe(phen)₃]^3+/2+ were smaller than those for [Fe(bpy)₃]^3+/2+, reflecting the difference in the charge densities of complexes.

Room temperature ionic liquids (RTILs) provide an ionic, solvent-free medium for electrochemical reactions. RTILs are appreciated for their many unique properties; nevertheless, it is precisely these qualities that can be very easily debased by water and organic impurities. Water, as a major contaminant in hygroscopic RTILs, has a strong effect on the physical and electrochemical properties (e.g., viscosity and dielectric constant, hence the background voltammetric current, diffusion coefficient of redox analytes and electron-transfer kinetics). In this work, a simple and relatively rapid purification process was investigated that involves sparging ultrahigh purity Ar through the RTIL while being heated at 70°C (so-called sweeping). A more conventional vacuum drying method at 80°C was used for comparison. The electrochemical properties of two RTILs, [BMIM][BF₄] and [EMIM][BF₄], were assessed voltammetrically using a nitrogen-incorporated tetrahedral amorphous carbon (ta-C:N) thin-film electrode. We found the sweeping purification method to be superior to vacuum drying in terms of more timely and effective removal of water. In addition, we present for the first time some of the basic electrochemical properties of novel ta-C:N electrode in contact with a RTIL.

Pd nanocubes (∼10 nm) and Pd nanocubes coated with multi-armed Pt shells have been successfully prepared. Their microstructures are determined from their electron diffraction patterns and line scan energy-dispersive X-ray measurements taken on a single particle. These Pd nanocubes and the Pd-Pt nanocubes are applicable as catalysts for the alkaline oxygen reduction reaction. On the basis of the same loading mass of catalyst, the results of rotating ring-disk electrode measurements indicate that the cubic Pd nanoparticles and particles coated by multi-armed Pt shells display activities of 1.47 × 10⁻² and 9.22 × 10⁻³ mA μg⁻¹, respectively. These values are greater than the 6.79 × 10⁻³ mA μg⁻¹ observed for Pt nanoparticles. The prepared Pd nanocubes and the Pd-Pt core-shell catalysts, as well as Pt nanoparticles, show 98% efficiency in the production of OH⁻ via an approximate four-electron pathway. Additionally, a fair comparison supported by transmission electron microscopy and electrochemical data shows that the shapes of Pd nanocubes coated with multi-armed Pt shells are nearly unchanged by the ORR and that these core-shell catalysts show stabilities superior to Pd nanocubes.

Mg-Al layered double hydroxide (LDH), a two-dimensional layered material, has been added in composite gel electrolyte for quasi-solid dye-sensitized solar cells (DSSCs), resulting in enhanced power conversion efficiency (PCE) from 0.69% to 2.05%. Herein, we demonstrated that using stearic acid-intercalated LDH (LDH-St) as additives instead of pristine LDH in composite gel electrolyte achieved even higher PCE of 2.86%. XRD analysis revealed that the interlayer spacing of LDH-St has been enlarged from 0.77 nm to 4.41 nm, which is highly favorable for iodide/triiodide ions transportation. The enhancement in photovoltaic performance was primarily explained by a decrease of charge transfer resistance (R_ct), an increase of limiting current density (j_lim) and the suppressed dark current density for electrolyte containing LDH-St compared with that containing LDH.

This study applied a methodology for defining the threshold voltage shift (ΔV_TH) transient of AlGaN/GaN heterostructure field-effect transistors (HFETs) to observe the influence of traps in AlGaN/GaN HFETs with different buffer layers: a carbon-doped (C-doped) buffer and an Al_0.05Ga_0.95N back barrier layer. This methodology involves synchronous switching of gate-to-source voltage (V_GS) and drain-to-source voltage (V_DS). Two HFETs demonstrated similar transient behaviors but different trends by enduring various V_DS stress level. For devices with a C-doped buffer layer, the amount of threshold voltage shift becomes saturated with increasing V_DS stress; however, a device with an Al_0.05Ga_0.95N back barrier layer does not. A simulation tool was used to analyze the trap behaviors and close agreement was seen between measured and simulated.

A new star shape monomer, 2,4,6-tris((9H-carbazol-2-yl)oxy)-1,3,5-triazine (CTR) was synthesized. It was electrochemically polymerized in boron trifluoride diethyl etherate (BFEE)/acetonitrile (ACN) solvent couple. The interaction between BFEE and the CTR lowers the oxidation potential of the monomer and the catalytic effect of BFEE facilitated the formation of high quality polymer film. Electrochemically prepared P(CTR) film was characterized via CV, SEM, FTIR, TGA and UV-vis spectroscopy. Spectroelectrochemical analysis revealed that P(CTR) has high band gap energy which provide it colorless in the neutral state. Electronic transitions of the P(CTR) were observed at 327 and 650 nm, revealing π to π^* transitions, and polaron band formation. The polymer switches between dark turquoise and transparent with a switching time of 1.5 s and an optical contrast (%ΔT) of 50%. Electrochromic studies revealed that P(CTR) has opposite properties to EDOT in terms of redox color. In addition to a dual-type complementary colored polymer electrochromic device based on P(CTR) and P(EDOT) was constructed in sandwich configuration. Spectroelectrochemical studies disclosed that the oxidized state of the device shows a blue color and it is transparent in the reduced state. Switching time and maximum contrast (%ΔT) of the device was measured as 3 s and 32% for 615 nm.

Boron-doped diamond (BDD) films were subjected to cathodic or anodic pre-treatments to achieve hydrogen-terminated (BDD-H) or oxygen-terminated (BDD-O) surfaces and then used as supports for surfactant-assisted anodic deposition of titanium oxide. Cyclic voltammetry and EIS experiments have shown that, unlike BDD-O case, at the BDD-H surface a stable layer of sodium dodecyl sulfate (SDS) is formed, which hinders TiO₂ overall deposition process, as demonstrated by linear sweep voltammetry. SEM measurements revealed that this sluggish process leads to a better uniformity and to a higher roughness of the oxide coatings. When deposited on BDD-H, TiO₂ also exhibited a light to dark current ratio with ca. 28% higher than that enabled by the use of a BDD-O substrate, indicating a better efficiency of charge carrier separation.

The voltammetric behavior of Ciprofloxacin (CIP) was investigated in different buffer solutions using cyclic voltammetry. It exhibited a single irreversible anodic peak with shift in peak potential with pH value which indicates proton dependent reaction. In a pH 4.0 phthalate buffer, a poorly defined oxidation peak current (i_p) is observed using carbon paste (CP) electrode for the determination of CIP using linear sweep adsorptive stripping voltammetric method (LS-AdASV). However, in the presence of low concentration of Cetyltrimethylammonium bromide (CTAB), i_p enhancement occurs. Moreover, the usage of mesoporous carbon-modified carbon paste (MC/CP) electrode exhibits a significant enhancement in the i_p. The enhancement of the i_p of CIP at MC/CP electrode in the presence of CTAB [1.0 × 10⁻⁴ M], was ascribed to two factors: (1) CTAB facilitates electron transfer of CIP; and (2) the high surface area of MC, which accumulates adsorptive CIP on the MC/CP electrode surface. All experimental parameters, were optimized for the determination of CIP. LS-AdASV method is observed to possess the following good qualities: high sensitivity (detection limit is 1.5 × 10⁻⁹ M), wide linearity (5.0 × 10⁻⁹–2.0 × 10⁻⁵ M), rapid response, low cost and simplicity. In conclusion, this method was employed to successfully detect CIP in pharmaceutical formulation and human serum.

In this report, we examine the origin of photocurrent produced by irradiating single layer poly(3-hexylthiophene) (P3HT) films deposited on ITO-coated glass, in aqueous solutions. The photocurrent is found to be largely due to reduction of trace molecular oxygen, which decreases significantly in the presence of an oxygen scavenger. Residual current, < 1 μA cm⁻², is observed in acidic media that may be attributed to proton reduction. The addition of a catalyst to aid proton reduction is achieved through photoelectrochemical deposition of Pt nanoparticles from K₂PtCl₆. Photocurrents at single layer films in aqueous solution increase significantly and bubble formation is observed on the P3HT film that is confirmed to be hydrogen gas. While the photocurrents produced are smaller than those devices employing sophisticated multilayer architectures, the results hold promise that, with further studies, H₂ can be evolved at technologically-simple single layer systems with substantially higher rates.

To extend the photo response of TiO₂ further into the visible light region, TiO₂ nanotube arrays codoped with vanadium and nitrogen were synthesized by anodization process, followed by impregnation and calcination process. X-ray photoelectron spectroscopy (XPS) revealed the existence of interstitial N and V (V⁴⁺ and V⁵⁺) in V, N codoped TiO₂ catalysts, which was beneficial to narrow the bandgap and separating charges. Higher photocurrent density displayed by the V, N codoped TiO₂ nanotube arrays showed that more photo-induced electrons were generated, therefore effectively improved the catalytic activity. V, N codoped samples were used for the photodegradation of methyl orange (MO) in aqueous solution in presence of H₂O₂. H₂O₂ is used to serve as an electron scavenger and a precursor for •OH radicals, thus significantly accelerating the photodegradation of MO under visible light irradiation. A synergistic effect between V, N codoped TiO₂ catalyst and H₂O₂ contributed to the high degradation activity toward MO.

By thermally reducing platinum onto the surface of Graphene Nanoplatelet (GNP) particles the catalytic activity of the iodide/triiodide reaction in dye-sensitized solar cells (DSC) can be improved significantly. The GNP-Pt particles can be used to formulate a highly catalytic yet transparent ink, which can be deposited by a number of different technologies such as flexographic printing, K-bar, slot-die and spin coating. The catalytic performance of the ink has been characterized using impedance spectroscopy, the impedance spectra show a high frequency impedance curve often seen in carbon electrodes. The origin of this impedance has a number of opposing hypotheses which are critically examined. The data supports the hypothesis that the high frequency curve is due to a contact resistance between the GNP-Pt ink and the FTO. In addition to the high frequency curve, a previously unresolved low frequency impedance is identified. When fabricated into DSCs the ink catalyst demonstrates cell efficiencies up to 5.2% and is shown to have a similar performance to conventional sputtered platinum when used in a reverse illuminated DSC (through the counter electrode). The first flexible reverse illuminated DSC with a GNP-Pt ink catalyst, suitable for roll-to-roll deposition is reported with an efficiency of 2.6%.