Focus on Functional Materials for Energy Applications

MXene materials have become a competitive candidate for electrochemical energy storage due to their unique two-dimensional layered structure, high density, metal-like conductivity, fast ion intercalation, tunable surface terminal groups, and good mechanical flexibilities, showing unique application advantages in the field of supercapacitors. With widely research of MXene in energy storage applications, plenty of studies in synthesis strategies of MXene, including etching, intercalation and exfoliation processes, and its charge storage mechanism in supercapacitors have been conducted. However, the restacking of two-dimensional MXene nanosheets severely affects their electrochemical performance. To prevent the stacking of MXene, MXene-based nanocomposite electrode materials have been developed with remarkable electrochemical performance by incorporating conventional active capacitive materials, including metal oxides/sulfides and conductive polymers, with MXene. This review summarizes the etching strategies of MXenes and selection of intercalants, also discusses the charge storage mechanism of MXenes in aqueous and nonaqueous electrolytes. It mainly expounds the preparation strategies and applications of MXene-based nanocomposites in supercapacitors, including MXene/metal oxide, MXene/metal sulfide, MXene/conducting polymer, and MXene/carbon-based composites. Additionally, the advantages of combining MXene with other active materials in supercapacitor applications, which support its promising prospects, are discussed. Finally, the critical challenges faced by MXene-based nanocomposites in long-term research are mentioned.

Passive radiative cooling involves the emission of thermal radiation into cold space and the reflection of solar radiation, which aims to cool and lower the temperature of objects. However, currently most radiative coolers have a white appearance which restricts their potential applications. We develop a coloured bilayer radiative cooling membrane using polyvinylidene fluoride/tetraethoxysilane (PVDF/TEOS) fibres, with incorporation of phase change materials (PCMs) and active dyes through a simple and large-area electrospinning process. In comparison to traditional emitters, PCM-incorporated colourful coolers provide energy storage capacity and colourful appearances. Our phase-transition-based colourful flexible film (PCFF) achieves a total solar reflectance of 0.81 and a mid-infrared (8–13 μm) emissivity of 0.85 with superior mechanical strength and good hydrophobicity. We experimentally demonstrate that our PCFF can significantly reduce the temperature of objects exposed to direct sunlight, with a cooling effect of up to 9 °C compared to commercial fabrics of similar materials and colours. Our work provides a promising starting point for the design and manufacture of colourful and flexible thermal control films.

Considering the advantages of MOF-based, CdSe-based, and rGO-based materials, CdSe nanoparticles encapsulated with rGO (CdSe@rGO) were synthesized by a metal-organic framework derived method. CdSe nanoparticles encapsulated with rGO can effectively tolerate volume expansion and improve electrical conductivity, leading to excellent cycling stability (396 mAh g⁻¹ at 0.3 A g⁻¹ after 200 cycles, 311 mAh g⁻¹ at 0.5 A g⁻¹ after 500 cycles), and rate performance (562 mAh g⁻¹ at 0.1 A g⁻¹ and 122.2 mAh g⁻¹ at 4 A g⁻¹) for lithium-ion storage. This strategy for preparing metal selenides protected by carbon layers can be extended to the design of other high-performance materials.

We report the formation of Mo_1−xW_xO₃-CdS (0 ≤ x ≤1) nanophotocatalysts by a combination of solid-state and solution-impregnation processes. The formation of 2D+1D heterostructured composite was revealed by electron microscopy and the structure of ternary co-catalyst and photocatalysts were confirmed by spectroscopic analyses. The H₂ evolution activity of the nanocomposites was assessed via photocatalytic splitting of water under the irradiation of visible light. All the nanocomposites studied here exhibit notable catalytic activity and good photostability using lactic acid as the sacrificial electron donor compared to a pristine compound. Among these nanocomposites, WO₃-CdS shows superior activity with H₂ evolution rates of 15.19 mmolg⁻¹h⁻¹, 28 times higher than the pure CdS. The WO₃-CdS photoactivity is not only superior among all the composites studied here but also highest among the reported WO₃ composite catalysts to date. The novel construction of the oxide-based nanocomposite photocatalyst shown here efficiently enhances the catalytic activity by effective separation of charge carriers and inhibits photocorrosion of CdS nanorods. The apparent quantum yield of the hydrogen evolution for WO₃-CdS was found to be 8% in the visible spectral range. The disparity of the catalytic ability between MoO₃ and WO₃ and the variance among the compositions was unraveled through optical band-offset alignment with respect to CdS. Though the 2D+1D novel fabrication is common to all the composites, the difference in the type of band alignment MoO₃ (type-I) and WO₃ (type-II) with CdS plays a highly significant role in the co-catalytic activity.

A multilayer structure with a high-quality (Bi,La)(Fe,Co)O₃ multiferroic thin film/[Co/Pd] perpendicular magnetic thin film dots was fabricated for demonstrating magnetization reversal of [Co/Pd] dots under an applied electric field. Although the magnetization direction of the multiferroic thin film was reversed under the electric field, the magnetic properties of the multiferroic thin films were generally low. If the multiferroic thin film in this structure can control the magnetization direction of the highly functional magnetic thin film under an electric field, high-performance magnetic devices with low power consumption are easily obtained. The magnetic domain structure of the [Co/Pd] dots fabricated on the (Bi,La)(Fe,Co)O₃ thin film was analyzed by magnetic force microscopy (MFM). The structure was de-magnetized before the local electric-field application and magnetized after applying the field, showing reduced magnetic contrast of the dot. The line profile of the MFM image revealed a downward magnetic moment of 75%, which reversed to upward under the local electric field. Magnetic interaction between the (Bi,La)(Fe,Co)O₃ and [Co/Pd] layers was also observed in magnetization hysteresis measurements. These results indicate that the magnetization direction of the [Co/Pd] dots was transferred through the magnetization reversal of the (Bi,La)(Fe,Co)O₃ layer under a local electric field. That is, the magnetization of [Co/Pd] dots were reversed by applying a local electric field to the multilayer structure. This demonstration can potentially realize high-performance magnetic devices such as large capacity memory with low power consumption.

3D-ordered porous CdS/AgI/ZnO nanostructures were designed to perform as high-performance photoelectrodes for photoelectrochemical (PEC) water-splitting applications. They rely on the advantages of an extremely large active surface area, high absorption capacity in the visible-light region, fast carrier separation and transportation caused by the intrinsic ladder-like band arrangement. These nanostructures were fabricated by employing a three-stage experiment in a sequence of hard mold-assisted electrochemical deposition, wet chemical method and deposition–precipitation. First, 3D-ordered ZnO nanostructures were electrochemically deposited using a polystyrene film as the sacrificed template. AgI nanoparticles were then decorated on the interfacial ZnO nanostructures by deposition–precipitation. Finally, these binary AgI/ZnO nanoporous networks were thoroughly wet-chemically coated with a CdS film to form a so-called 'ternary interfacial CdS/AgI/ZnO nanostructures'. The PEC water-splitting properties of the fabricated 3D nanostructures were systematically studied and compared. As a result, the highest efficiency of the fabricated 3D-ordered porous CdS/AgI/ZnO measured under the irradiation of solar simulation is about 5.2%, which is relatively 1.5, 3.5 and 11.3 times greater than that of the corresponding CdS/ZnO (3,4%), AgI/ZnO (1.5%) and pristine porous ZnO (0.46%) photoelectrodes, respectively. The significant improvement in the PEC activity is attributed to the enhanced charge separation and transport of ternary photoelectrodes caused by an unconventional ladder-like band arrangement formed between interfacial CdS-AgI-ZnO. Our study provides a promising strategy for developing such ternary photoelectrode generation that possesses higher stability and efficiency towards water-splitting processes.

Oxygen doping strategy is one of the most effective methods to improve the electrochemical properties of nickel–cobalt phosphide (NiCoP)-based capacitors by adjusting its inherent electronic structure. In this paper, O-doped NiCoP microspheres derived from porous nanostructured nickel metal–organic frameworks (Ni-MOFs) were constructed through solvothermal method followed by phosphorization treatment. The O-doping concentration has a siginificant influence on the rate performance and cycle stability. The optimized O-doped NiCoP electrode material shows a specific capacitance of 632.4 F-g⁻¹ at 1 A-g⁻¹ and a high retention rate of 56.9% at 20 A g⁻¹. The corresponding NiCoP-based asymmetric supercapacitor exhibits a high energy density of 30.1 Wh kg⁻¹ when the power density is 800.9 W kg⁻¹, and can still maintain 82.1% of the initial capacity after 10 000 cycles at 5 A g⁻¹.

Extensive investigations have been devoted to nitrogen-doped carbon materials as catalysts for the oxygen reduction reaction (ORR) in various conversion technologies. In this study, we introduce nitrogen-doped carbon materials with hollow spherical structures. These materials demonstrate significant potential in ORR activity within alkaline media, showing a half-wave potential of 0.87 V versus the reversible hydrogen electrode (RHE). Nitrogen-doped hollow carbon spheres (N-CHS) exhibit unique characteristics such as a thin carbon shell layer, hollow structure, large surface area, and distinct pore features. These features collectively create an optimal environment for facilitating the diffusion of reactants, thereby enhancing the exposure of active sites and improving catalytic performance. Building upon the promising qualities of N-CHS as a catalyst support, we employ heme chloride (1 wt%) as the source of iron for Fe doping. Through the carbonization process, Fe-N active sites are effectively formed, displaying a half-wave potential of 0.9 V versus RHE. Notably, when implemented as a cathode catalyst in zinc-air batteries, this catalyst exhibits an impressive power density of 162.6 mW cm⁻².

We investigated the structural evolution of electrochemically fabricated Pd nanowires in situ by means of grazing-incidence transmission small- and wide-angle x-ray scattering (GTSAXS and GTWAXS), x-ray fluorescence (XRF) and two-dimensional surface optical reflectance (2D-SOR). This shows how electrodeposition and the hydrogen evolution reaction (HER) compete and interact during Pd electrodepositon. During the bottom-up growth of the nanowires, we show that β-phase Pd hydride is formed. Suspending the electrodeposition then leads to a phase transition from β-phase Pd hydride to α-phase Pd. Additionally, we find that grain coalescence later hinders the incorporation of hydrogen in the Pd unit cell. GTSAXS and 2D-SOR provide complementary information on the volume fraction of the pores occupied by Pd, while XRF was used to monitor the amount of Pd electrodeposited.

In this work, we report a vertical contact-separation mode triboelectric nanogenerators (TENG) comprising of Ni₃C/PDMS composite and Nylon Nanofibers for self-powering a nichrome wire-based thermal patch for muscular/joint relaxation. An optimised composition of Ni₃C (25 wt%) and PDMS as a tribo-negative material and Nylon Nanofibers synthesised via electrospinning on copper electrode foil as a tribo-positive material were used to fabricate the TENG. The fabricated TENG exhibits outstanding output generating an average open circuit voltage of ∼252 V, an average short circuit current of ∼40.87 μA and a peak power of ∼562.35 μW cm⁻² at a matching resistance of 20 MΩ by manual tapping. Enhancement in contact area due to electrospun nylon and micro capacitive Ni₃C flakes in dielectric PDMS contribute to the exceptional performance of the TENG. The optimised TENG is then connected to a full bridge rectifier with a 100 nF filtering capacitor to convert the AC voltage to a DC output with a peak voltage of ∼5.4 V and a ripple voltage of ∼1.04 V to recharge an ICR 18650 Li-ion battery, which functions as a medium to improve electrical energy flow to the heat patch. The electrical energy is converted into heat energy by a wounded nichrome wire placed inside the heat patch. The nichrome wire of length 3 cm with appropriate number of windings was employed in the heat patch. An increment of 45 °F can be observed by switching the charged Li-ion battery-based circuit ON for just 30 s. The strategy of self-powering a heat patch using this TENG finds enormous applications in physiotherapy and sports to relieve muscle and joint pains.

Triboelectric nanogenerators (TENGs) have emerged as a promising alternative for powering small-scale electronics without relying on traditional power sources, and play an important role in the development of the internet of things (IoTs). Herein, a low-cost, flexible polyvinyl alcohol (PVA)-based TENG (PVA-TENG) is reported to harvest low-frequency mechanical vibrations and convert them into electricity. PVA thin film is prepared by a simple solution casting technique and utilized to serve as the tribopositive material, polypropylene film as tribonegative, and aluminum foil as electrodes of the device. The dielectric-dielectric model is implemented with an arch structure for the effective working of the PVA-TENG. The device showed promising electrical output by generating significant open-circuit voltage, short-circuit current, and power . Also, PVA-TENG is subjected to a stability test by operating the device continuously for 5000 cycles. The result shows that, the device is mechanically durable and electrically stable. Further, the as-fabricated PVA-TENG is demonstrated to show feasible applications, such as charging two commercial capacitors with capacitances 1.1 and 4.7 μF and powering green light-emitting diodes. The stored energy in the 4.7 μF capacitor is utilized to power a digital watch and humidity and temperature sensor without the aid of an external battery. Thus, the PVA-TENG facilitates ease of fabrication, robustness, and cost-effective strategy in the field of energy harvesting for powering lower-grid electronics by demonstrating their potential as a sustainable energy source.

Multi-shell transition metal oxide hollow spheres show great potential for applications in energy storage because of their unique multilayered hollow structure with large specific surface area, short electron and charge transport paths, and structural stability. In this paper, the controlled synthesis of NiCo₂O₄, MnCo₂O₄, NiMn₂O₄ multi-shell layer structures was achieved by using the solvothermal method. As the anode materials for Li-ion batteries, the three multi-shell structures maintained good stability after 650 long cycles in the cyclic charge/discharge test. The in situ transmisssion electron microscope characterization combined with cyclic voltammetry tests demonstrated that the three anode materials NiCo₂O₄, MnCo₂O₄ and NiMn₂O₄ have similar charge/discharge transition mechanisms, and the multi-shell structure can effectively buffer the volume expansion and structural collapse during lithium embedding/delithiation to ensure the stability of the electrode structure and cycling performance. The research results can provide effective guidance for the synathesis and charging/discharging mechanism of multi-shell metal oxide lithium-ion battery anode materials.

Fe–N–C materials have emerged as promising alternatives to precious metals for oxygen reduction reaction/oxygen evolution reaction (ORR/OER). In this study, a strategy is presented to investigate the influence of different chemical states of iron species in Fe–N–C materials on their electrocatalytic performance. Three Fe–N–C catalysts, containing either zero-valent Fe or Fe₃O₄ nanoparticles, are synthesized using acid pickling, high-speed centrifugation and ultrasound-assisted hydrothermal methods, respectively. The findings manifest that the chemical state of iron significantly affects the electrocatalytic activity of Fe–N_X active sites, namely zero-valent Fe enhancing Fe–N_X activity while Fe₃O₄ weakening its activity. Notably, the Fe@FeNC catalyst containing only zero-valent iron, demonstrates the only 0.621 V potential difference between the ORR half-wave potential and the OER potential at 10 mA cm⁻². Furthermore, the rechargeable Zn–air battery assembled with Fe@FeNC as the air cathode exhibits a remarkable peak power density of 179.0 mW cm⁻², excellent cycling stability over 210 h (with a cycle frequency of one every 10 min), and the minimal voltage gap of 0.710 V. These results reveal the significance of different chemical states of metal-based nanoparticles in Fe–N_X activity of Fe–N–C catalysts and offer insights into the rational design of electrocatalysts with exceptional activity and versatile applications.

Electrodeposited polyaniline over the carbon nanotubes fiber (CNTF) has been investigated as potential candidate to substitutes the Pt based auxiliary electrodes in unidimensional fibrous solar cells. CNTF, with excellent electrical and mechanical properties, modified with conducting polymer (polyaniline) via facile electrodeposition process which employed as cathodic materials showed efficient electrochemical reduction of triiodide ions in the fiber shaped dye-sensitized solar cells. Scanning electron microscopic analysis showed the efficacious integration of conducting polymer over the CNTF surface. The admirable electrocatalytic behavior of the fabricated electrode has investigated by electrochemical impedance spectroscopy and cyclic voltammetry. Current density and voltage (J–V) curves are used to quantify the photovoltaic performance of devices with different counter electrodes with fixed photoanode. With lower peak to peak separation, improved current density and better fill factor, exhibited the superior efficiency of modified electrode (PANI@CNTF). As compared to pristine fiber, polyaniline modification showed the outstanding performance with improved photovoltaics and electrochemical parameters measured by the J–V and CV curves, respectively.

Annealing step is a critical step in the hydrothermal assisted synthesis of La/Ni oxides such as LaNiO_3−δ (LNOA) and La₂NiO_4+δ (LNON). In the current study, we have discovered the interlink between the atmosphere and temperature conditions which dictate the product formed. La/Ni nitrate precursors were subjected to a hydrothermal synthesis followed by an annealing step at appropriate temperature and varying atmosphere resulting in the synthesis of the corresponding oxides. The annealing temperature was varied in the range between 650 °C and 800 °C and also the annealing was carried out either in pure N₂ atmosphere or air. From the x-ray diffraction analysis, it was inferred that annealing in air invariably resulted in the rhombohedral LaNiO₃ (LNOA) perovskite phase, while annealing in N₂ atmosphere resulted in an orthorhombic Ruddlesden–Popper phase La₂NiO₄ (LNON), a layered oxide containing traces of NiO phase. Typically, iodometric titrations substantiate the presence of Ni (III) which further can be correlated to the presence of oxygen vacancies (δ). Iodometric test results demarcated the difference between the two phases with absolutely minimal I₂ liberated from the LNON samples proving that negligible amount of Ni (III) was present in LNON Scanning electron microscopy (SEM) images showed an agglomeration of particles annealed at higher temperatures irrespective of the atmosphere. Temperature dependent oxygen non-stoichiometry (Δδ) was analyzed through thermogravimetric analysis, wherein Δδ was inversely proportional to the annealing temperature for all of the LNOA samples. Considering that large δ values favor pseudocapacitive behaviour, it was observed LNOA oxides showed excellent pseudocapacitive behaviour compared to the LNON oxides. Dunn deconvolution of the cyclic voltammograms of LNOA 800 °C at 5 m Vs⁻¹ indicated that diffusive contribution (66%) was predominant over capacitive contributions. The LNOA sample annealed at 800 °C displayed the highest specific capacitance of 100.3 F g⁻¹ at 1 A g⁻¹ current density.

The demand for a facile approach for synthesizing multifunctional nanocomposites is increasingly vital across diverse applications. In this study, a polymerizable sol–gel synthesis has been reported to obtain nanocomposites of magnetic iron oxide deposited over alumina nanopowder. The synthesis is mediated by the deposition of a calculated amount of iron(III) methacrylate, along with ethylene glycol dimethacrylate crosslinker, over alumina nanopowder, followed by thermally-inducing free radical polymerization at 125 °C for 30 min. The powder thus obtained has been subjected to calcination at 400 °C for 150 min and the resultant nanocomposites were characterized using wide-angle x-ray scattering, attenuated total reflectance—Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy, field-emission scanning electron microscopy, ultraviolet-diffuse reflectance spectroscopy, vibrating sample magnetometer and Brunauer–Emmett–Teller surface area measurements. The nanocomposites containing 15 and 20 wt% of iron oxide have been found to exhibit a saturation magnetization (M_s) value ranging from 12 to 14 emu g⁻¹. To the nanocomposite containing 20 wt% of iron oxide, 5 wt% of AgBr was loaded through thoroughly mixing a surfactant-based precursor, silver-tetraoctyl ammonium bromide (Ag-TOAB), followed by thermolysis. All the nanocomposites have been studied for their antibacterial activity against a representative gram-negative bacterium, Escherichia coli, under dark and visible light conditions. While a 3 mg ml⁻¹ loading of the AgBr-loaded nanocomposite has exhibited complete clearance of the bacterial growth by 90 min in the dark, a similar activity has been observed in 60 min under light. The study has revealed the multifunctionality and high potential of the AgBr-loaded iron oxide/alumina nanocomposite as a promising dual-mode antibacterial and magnetically recoverable photocatalyst material.

Polyethylene glycol (PEG) is widely used as a phase change material (PCM) in thermal energy storage systems due to its high latent heat and chemical stability. However, practical application has been hindered by its low thermal conductivity and leakage issues. Therefore, developing shape-stable high thermal conductivity PCM is of great importance. In this study, new shape-stable composite PCM with high thermal conductivity and leak-prevention capabilities were designed. The porous carbon skeleton of diamond foam (DF) and dual-3D carbon nanotube-diamond foam (CDF) were prepared using the microwave plasma chemical vapor deposition method. The composite materials (DF/PEG and CDF/PEG) were produced by vacuum impregnation with PEG and skeletons. The results showed that CDF/PEG had the highest thermal conductivity, measuring 2.30 W·m⁻¹·K⁻¹, which is 707% higher than that of pure PEG. The employing of 3D networks of CNTs, which can improve the phonon mean free path in DF/PEG (1.79 W·m⁻¹·K⁻¹) while reducing phonon dispersion.The phonon vibration of dual-3D CDF plays an important role in heat transfer. PEG was physically absorbed and well-distributed in CDF, alleviating leakage of liquid PEG. The weight loss of CDF/PEG was only 25% at 70 °C for 120 s. Using CDF is an attractive and efficient strategy to increase the heat transfer of PEG and improve heat storage efficiency, alleviate the problem of poor shape-stability.

By using a simple device architecture along with a simple process design and a low thermal-budget of a maximum of 100 °C for passivating metal/semiconductor interfaces, a Schottky barrier MOSFET device with a low subthreshold slope of 70 mV dec⁻¹ could be developed. This device is enabled after passivation of the metal/silicon interface (found at the source/drain regions) with ultra-thin SiO_x films, followed by the e-beam evaporation of high- quality aluminum and by using atomic-layer deposition for HfO₂ as a gate oxide. All of these fabrication steps were designed in a sequential process so that a gate-last recipe could minimize the defect density at the aluminum/silicon and HfO₂/silicon interfaces, thus preserving the Schottky barrier height and ultimately, the outstanding performance of the transistor. This device is fully integrated into silicon after standard CMOS-compatible processing, so that it could be easily adopted into front-end-of-line or even in back-end-of-line stages of an integrated circuit, where low thermal budget is required and where its functionality could be increased by developing additional and fast logic.

We investigate the effect of hydrogen passivation of dangling bonds in silicon oxide passivating contacts with embedded silicon nanocrystals (NAnocrystalline Transport path in Ultra-thin dielectrics for REinforced passivation contact, NATURE contact). We first investigated the differences in electrical properties of the samples after hydrogen gas annealing and hydrogen plasma treatment (HPT). The results show that the NATURE contact was efficiently passivated by hydrogen after HPT owing to the introduction of hydrogen radicals into the structure. Furthermore, we examined the dependence of process parameters such as HPT temperature, duration, and H₂ pressure, on the electrical properties and hydrogen depth profiles. As a result, HPT at 500 °C, 15 min, and 0.5 Torr resulted in a large amount of hydrogen inside the NATURE contact and the highest implied open-circuit voltage of 724 mV. Contact resistivity and surface roughness hardly increased when HPT was performed under the optimized condition, which only improved the passivation performance without deteriorating the electron transport properties of the NATURE contact.

Constructing heterojunction to adjust the electronic structure of catalysts is a promising strategy for synergistically improving electrocatalytic activity. In addition, RuSe₂ is recognized as an effective alternative to Pt for boosting alkaline hydrogen evolution reaction (HER) on account of its outstanding catalytic properties. Herein, novel RuSe₂/CeO₂ heterojunction electrocatalysts are fabricated through hydrothermal and thermal treatment methods. The optimal 50% RuSe₂/CeO₂ heterojunction electrocatalyst exhibits a low HER overpotential of 16 mV to attain 10 mA cm⁻² current density and Tafel slope of 66.1 mV dec⁻¹ for hydrogen evolution in 1.0 M KOH. At the same time, the 50% RuSe₂/CeO₂ heterojunction electrocatalyst also maintains a stable HER activity for 50 h or 3000 CV cycles. The experimental results show that formation of heterogeneous interface between RuSe₂ and CeO₂ results in the redistribution of electrons at the RuSe₂/CeO₂ interface, thereby changing the electronic structure of RuSe₂ and enhancing the performance of the RuSe₂/CeO₂ electrocatalyst. This work may provide a feasible way to design efficient hydrogen evolution heterojunction electrocatalysts by modulating the electronic structure in alkaline electrolytes.

Flexible solid-state zinc–air batteries as a wearable energy storage device with great potential, and their separators, which control ion permeability, inhibit zinc dendrite generation, and regulate catalytic active sites, have been developed as gel electrolyte separators with high retention of electrolyte uptake. However, the gel electrolyte separator still has problems such as poor affinity with the electrolyte and poor ionic conductivity, which limits its further application. In order to further improve the electrolyte absorption, ionic conductivity and mechanical strength of cellulose acetate(CA)/polyvinyl alcohol (PVA) nanofibers, TiO₂ was added to CA/PVA to increase the porosity, and glutaraldehyde (GA) was used to modify the CA/PVA/TiO₂ separator by acetal reaction with CA and PVA to make the molecules closely linked. The results shows that the optimal mass fractions of TiO₂ and GA were 2% and 5%, respectively. At this time, the porosity and absorption rate of the separator increased from 48% to 68.2% and 142.4% to 285.3%, respectively. The discharge capacity reached 179 mA cm⁻³, and the cycle stability rate was 89% after 7 stable constant current charge/discharge cycles.

A novel 3D hierarchical TiO₂/CaIn₂S₄/C₃N₄ arrays with dual heterojunctions photoanode is constructed by stepwise deposition of CaIn₂S₄ nanosheets and ultrathin C₃N₄ onto the well-aligned TiO₂ nanorods arrays. Integrating the merit of the superior ability of CaIn₂S₄ and C₃N₄ to harvest visible light, dual type-Ⅱ heterojunction band structure and one-dimensional ordered nanostructures, the TiO₂/CaIn₂S₄/C₃N₄ photoanode exhibits simultaneous significant improvements in visible-light harvesting, charge separation and electron transfer capability. At 1.23 V (versus reversible hydrogen electrode) under AM 1.5 G irradiation, the TiO₂/CaIn₂S₄75/C₃N₄ photoanode exhibits a photocurrent density of 4.5 mA cm⁻², which is 5.2 and 51.1-fold higher than that of TiO₂/CaIn₂S₄75 and pristine TiO₂ photoanode, respectively. Moreover, the applied bias photo-to-current efficiency (ABPE) of the TiO₂/CaIn₂S₄75/C₃N₄ photoanode reaches 3.5% at 0.36 V (versus reversible hydrogen electrode). These results are helpful for fabricating more efficient heterostructure photoelectrodes.

The global COVID-19 pandemic has led to an increase in the importance of implementing effective measures to prevent the spread of microorganisms. Consequently, there is a growing demand for antimicrobial materials, specifically antimicrobial textiles and face masks, because of the surge in diseases caused by bacteria and viruses like SARS-CoV-2. Face masks that possess built-in antibacterial properties can rapidly deactivate microorganisms, enabling reuse and reducing the incidence of illnesses. Among the numerous types of inorganic nanomaterials, copper oxide nanoparticles (CuO NPs) have been identified as cost-effective and highly efficient antimicrobial agents for inactivating microbes. Furthermore, biosurfactants have recently been recognized for their potential antimicrobial effects, in addition to inorganic nanoparticles. Therefore, this research's primary focus is synthesizing biosurfactant-mediated CuO NPs, integrating them into natural and synthetic fabrics such as cotton and polypropylene and evaluating the resulting fabrics' antimicrobial activity. Using rhamnolipid (RL) as a biosurfactant and employing a hydrothermal method with a pH range of 9–11, RL-capped CuO NPs are synthesized (RL-CuO NPs). To assess their effectiveness against gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli) microorganisms, the RL-CuO NPs are subjected to antibacterial testing. The RL-capped CuO NPs exhibited antimicrobial activity at much lower concentrations than the individual RL, CuO. RL-CuO NPs have shown a minimum inhibitory concentration (MIC) of 1.2 mg ml⁻¹ and minimum bactericidal concentration (MBC) of 1.6 mg ml⁻¹ for E. coli and a MIC of 0.8 mg ml⁻¹ and a MBC of 1.2 mg ml⁻¹ for S. aureus, respectively. Furthermore, the developed RL-CuO NPs are incorporated into cotton and polypropylene fabrics using a screen-printing technique. Subsequently, the antimicrobial activity of the coated fabrics is evaluated, revealing that RL-CuO NPs coated fabrics exhibited remarkable antibacterial properties against both gram-positive and gram-negative bacteria.

We report a study to improve the ternary oxide Ni₃V₂O₈'s electrochemical energy storage capabilities through correct surfactanization during hydrothermal synthesis. In this study, Ni₃V₂O₈ nanomaterials were synthesized in three different forms: one with a cationic surfactant (CTAB), one with an anionic surfactant (SLS), and one without any surfactant. FESEM study reveals that all the synthesized Ni₃V₂O₈ nanomaterials had a small stone-like morphology. The electrochemical study showed that anionic surfactant-assisted Ni₃V₂O₈ (NVSLS) had a maximum of 972 F g⁻¹ specific capacitance at 1 A g⁻¹ current density, whereas cationic surfactant-assisted Ni₃V₂O₈ (NV_CTAB) had the lowest specific capacitance of 162 F g⁻¹. The specific capacitance and the capacitance retention of the NV_SLS (85% after 4000 cycles) based electrode was much better than that of the NV_CTAB (76% after 4000 cycles) based electrode. The improved energy storage properties of the NV_SLS electrode are attributed to its high diffusion coefficient, high surface area, and enriched elemental nickel, as compared to the NV_CTAB electrode. All these excellent electrochemical properties of NV_SLS electrode indicates their potential usage in asymmetric supercapacitor application.

The effects of pH, MNP concentration, and medium viscosity on the magnetic fluid hyperthermia (MFH) properties of chitosan-coated superparamagnetic Fe₃O₄ nanoparticles (MNPs) are probed here. Due to the protonation of the amide groups, the MNPs are colloidally stable at lower pH (∼2), but form aggregates at higher pH (∼8). The increased aggregate size at higher pH causes the Brownian relaxation time (τ_B) to increase, leading to a decrease in specific absorption rate (SAR). For colloidal conditions ensuring Brownian-dominated relaxation dynamics, an increase in MNP concentrations or medium viscosity is found to increase the τ_B. SAR decreases with increasing MNP concentration, whereas it exhibits a non-monotonic variation with increasing medium viscosity. Dynamic hysteresis loop-based calculations are found to be in agreement with the experimental results. The findings provide a greater understanding of the variation of SAR with the colloidal properties and show the importance of relaxation dynamics on MFH efficiency, where variations in the frequency-relaxation time product across the relaxation plateau cause significant variations in SAR. Further, the in vitro cytotoxicity studies show good bio-compatibility of the chitosan-coated Fe₃O₄ MNPs. Higher SAR at acidic pH for bio-medically acceptable field parameters makes the bio-compatible chitosan-coated Fe₃O₄ MNPs suitable for MFH applications.

Binary metal oxides possess unique structures and multiple oxidation states, making them highly valuable in electrochemical analysis. This study aims to determine the effect of annealing temperature on the electrochemical properties of magnesium ferrite when used as an electrode material in a neutral aqueous electrolyte. We utilized the sol–gel technique to synthesize the material and annealed it at various temperatures. Our analysis of the material using different characterization techniques reveals significant changes in its structural and electrochemical properties. We found that the material exhibited a range of phases, and higher annealing temperatures led to improved electrochemical properties. The electrochemical measurements showed reversible and redox pseudo-capacitance behavior, with the material annealed at 500 °C exhibiting the highest specific capacitance of 117 F g⁻¹ at a current density of 0.5 A g⁻¹. Capacitive and diffusion-controlled processes govern the total charge storage mechanism, and their contribution changes significantly as the annealing temperature varies. The capacitance retention of 500 °C annealed sample was 58% and it remained stable. This work establishes a correlation between annealing temperature on structural, morphological, and electrochemical behavior, thereby opening up avenues for tailoring them effectively. These findings can be useful in the development of future electrode materials for electrochemical applications.

In the face of increasing energy demand, the approach of transformation that combines energy restructuring and environmental governance has become a popular research direction. As an important part of electrocatalytic reactions for gas molecules, reduction reactions of oxygen (ORR) and carbon dioxide (CO₂RR) are very indispensable in the field of energy conversion and storage. However, the non-interchangeability and irreversibility of electrode materials have always been a challenge in electrocatalysis. Hereon, nickel and nitrogen decorated biomass carbon-based materials (Ni/N-BC) has been prepared by high temperature pyrolysis using agricultural waste straw as raw material. Surprisingly, it possesses abundant active sites and specific surface area as a bifunctional electrocatalyst for ORR and CO₂RR. The three-dimensional porous cavity structure for the framework of biomass could not only provide a strong anchoring foundation for the active site, but also facilitate the transport and enrichment of reactants around the site. In addition, temperature modulation during the preparation process also optimizes the composition and structure of biomass carbon and nitrogen. Benefit from above structure and morphology advantages, Ni/N-BC-800 exhibits the superior electrocatalytic activity for both ORR and CO₂RR simultaneously. More specifically, Ni/N-BC-800 exhibits satisfactory ORR activity in terms of initial potential and half wave potential, while also enables the production of CO under high selective. The research results provide ideas for the development and design of electrode materials and green electrocatalysts, and also expand new applications of agricultural waste in fields such as energy conversion, environmental protection, and resource utilization.

We report the growth, structural characterization, and transport studies of Bi₂Se₃ thin film on single crystalline silicon (Si), Si/SiO₂, quartz, and glass substrates by thermal evaporation method. Our results show that 300 °C is the optimum substrate temperature to obtain the c-axis (001) oriented Bi₂Se₃ films on all the substrates. The film grown on the Si substrate has the minimum crystalline disorder. The energy-dispersive x-ray spectroscopy results show that film on Si substrate is bismuth deficient, the film on Si/SiO₂ substrate is selenium deficient, and the film on quartz substrate is near perfect stoichiometric providing a way to tune the electronic properties of Bi₂Se₃ films through substrate selection. The film grown on quartz shows the highest mobility (2.7 × 10⁴ cm² V^-1s⁻¹) which drops to 150 cm² V^-1s⁻¹ for Si, 60 cm² V^-1s⁻¹ for Si/SiO₂, and 0.9 cm² V^-1s⁻¹ for glass substrate. Carrier concentration is n-type for Bi₂Se₃ films on Si (∼10¹⁸ cm⁻³), quartz (∼10¹⁸ cm⁻³) and Si/SiO₂ (∼10¹⁹ cm⁻³) substrate with a clear indication of frozen out effect around 50 K for Si/SiO₂ and Si substrate. Longitudinal resistivity of Bi₂Se₃ film on Si/SiO₂ substrate shows different behavior in three different temperature regions: temperature dependent resistivity region due to electron–phonon scattering, a nearly temperature independent resistivity region due to electron–phonon and electron–ion scattering, and a quantum coherent transport region.

Two-dimensional (2D) van der Waals materials in-plane anisotropy, caused by a low-symmetric lattice structure, has considerably increased their applications, particularly in thermoelectric. MoS₂ and MoS₂/reduced graphene oxide (rGO) thin films were grown on SiO₂/Si substrate by atmospheric chemical vapor deposition technique to study the thermoelectric performance. Few layered MoS₂ was confirmed by the vibrational analysis and the composition elements are confirmed by the x-ray photoelectron spectroscopy technique. The continuous grains lead to reduced phonon life time in A_1g and low activation energy assists to enhance the electrical property. The MoS₂/rGO has achieved the highest σ of 22 622 S m⁻¹ at 315 K due to an electron-rich cloud around the electrons in S atoms near the adjacent layer of rGO.

Permanent magnets generate magnetic fields that can be sustained when a reverse field is supplied. These permanent magnets are effective in a wide range of applications. However, strategic rare-earth element demand has increased interest in replacing them with huge energy product (BH)_max. Exchange-coupled hard/soft ferrite nanocomposites have the potential to replace a portion of extravagant rare earth element-based magnets. In the present, we have reported the facile auto combustion synthesis of exchange-coupled Ba_0.5Sr_0.5Fe₁₀Al₂O₁₉ and Ni_0.1Co_0.9Fe₂O₄ nanocomposites by increasing the content of soft ferrite over the hard from x = 0.1 to 0.4 wt%. The XRD combined with Rietveld analysis reflected the presence of hexaferrite and spinel ferrite without the existence of secondary phases. The absorption bands from the Fourier transform infrared spectrum analysis proved the presence of M–O bonds in tetrahedral sites and octahedral sites. Rod and non-spherical images from TEM represent the hexaferrite and spinel ferrite. The smooth M–H curve and a single peak of the switching field distribution curve prove that the material has undergone a good exchange coupling. The nanopowders displayed an increase in saturation magnetization and a decrease in coercivity with the increases in the spinel content. The prepared nanocomposites were showing higher energy products. The composite with the ratio x = 0.2 displayed a higher value of (BH)_max of 13.16 kJ m⁻³.

Graphene and its derivatives are widely used in the field of energy conversion and management due to their excellent physical and chemical properties. In this paper, ultra-thin graphite film (GF) with thickness of 100–150 nm prepared by chemical vapor deposition was transferred to oxygen plasma-treated polyimide (PI) substrate as flexible heating film. The electrothermal and photothermal properties of GF on PI substrates with different treatment time were studied. The experimental results show that the PI substrate pretreated by oxygen plasma can change the surface morphology of GF, increase its electrical conductivity and light absorption capacity, and significantly improve the electrothermal and photothermal properties of GF heater. Under the low applied voltage of 5 V (power density of 0.81 W cm⁻²), the surface temperature of GF on 40 min plasma-treated PI substrate can rise to 250 °C, which is nearly 50 °C higher than that of GF on untreated PI substrate. When 100 nm thick commercial multilayer graphene film (MLG) is used, plasma-treated PI substrate can increase the electric heating temperature of MLG by 70 °C. In terms of photothermal performance, the surface temperature of GF on 50 min plasma-treated PI substrate can reach 73 °C under one Sun irradiation, which is 8 °C higher than that on untreated substrate. The experimental results are in good agreement with the simulation research. Our strategy has important implications for the development of efficient and energy-saving graphene/graphite-based heating films for advanced electrothermal and photothermal conversion devices.

Cadmium selenide (CdSe) quantum dots (QDs) with different size, 2.5 and 3.2 nm, were successfully deposited on mesoporous titanium dioxide (TiO₂) (Degussa-P25) nanostructures by electrophoretic deposition method (EPD) at the applied voltage 100 V for 120 s deposition time. In this study, the morphology of CdSe films deposited by EPD and the performance of the film when assembled into a solar cell were investigated. From the field emission scanning electron microscopy cross-section, the thickness of the CdSe nanoparticles with size 2.5 nm films were 3.4 and 3.0 μm for CdSe 3.2 nm nanoparticles film. The structure of 2.5 nm is denser than compare of 3.2 nm CdSe nanoparticles. From UV visible spectroscopy, the band gap calculated for 2.5 nm CdSe nanoparticles is 2.28 eV and for 3.2 nm is 2.12 eV. Photovoltaic characterization was performed under an illumination of 100 mW cm⁻². A photovoltaic conversion efficiency of 1.81% was obtained for 2.5 nm CdSe and 2.1% was obtained for 3.2 nm CdSe nanoparticles. This result shows that the photovoltaic efficiency is dependent on CdSe nanoparticle size.