Applications In Energy Devices Research Articles

A Review of Perovskite-based Lithium-Ion Battery Materials

Lithium-ion batteries (Li-ion batteries or LIBs) have garnered significant interest as a promising technology in the energy industry and electronic devices for the past few decades owing to their superior energy and power density profiles, small size, long cycle life, low self-discharge rate, no memory effect, long-lasting power properties, and environmental friendly. The ongoing advancement of electrode and electrolyte materials has contributed significantly to enhancing and spreading the application of lithium-ion battery technology. Among the non-precious metal-based materials, perovskites have emerged as attention over the last decade, holding a prominent position in materials and energy. Due to their unique physical and chemical properties, these materials have garnered particular interest for their potential application in electrochemical energy devices. Perovskite oxides have piqued the interest of researchers as potential catalysts in Li-O₂ batteries due to their remarkable electrochemical stability, high electronic and ionic conductivity, and the ability to modify their properties through doping and element substitution. The purpose of this article is to provide an overview of recent developments in the application of perovskites as lithium-ion battery materials, including the exploration of novel compositions and structures, optimization of fabrication methods, and a deeper understanding of the fundamental mechanisms that can unveil the potential of perovskite materials.

Comparative analysis of thermoelectric properties in bulk 2H and monolayer MoS2: a first-principles study at high temperatures

The pursuit of high-efficiency heat-to-electricity conversion is one of the indispensable driving forces toward future renewable energy production. The two-dimensional (2D) transition metal dichalcogenide, such as molybdenum disulfide (MoS2), is at the forefront of research due to its outstanding heat propagation features and potential applications as a thermoelectric material. Using the first-principles density functional theory coupled with the semi-classical Boltzmann transport equation within the constant relaxation time approximation, we present the thermoelectric and energy transport in the bulk 2H and monolayer MoS2 material system. In order to advance the underlying physics, we calculate several crucial transport parameters such as electrical conductivity, electronic thermal conductivity, Seebeck coefficient, and power factor as a function of the reduced chemical potential for different doping types and temperatures, in addition to the electron energy dispersion relation of the material system. Our comprehensive study employs the Shankland interpolation algorithm and the rigid band approximation to attain a high degree of accuracy. This thorough investigation reveals the high Seebeck coefficient of 1534 and 1550 μ V/K at 500 K for the bulk 2H and monolayer MoS2, respectively. Furthermore, the ultrahigh power factor values of 9.21 × 1011 and 3.69 × 1011 Wm −1 K −2 s −1 are shown at 800 K in the bulk 2H and monolayer MoS2, respectively. Based on the power factor results, our in-depth analysis demonstrates that the bulk 2H MoS2, when compared to monolayer MoS2, exhibits great potential as a promising semiconducting thermoelectric material for advanced high-performance energy device applications.

Bacterial cellulose materials in sustainable energy devices: A review.

This article provides a comprehensive review of the processing and applications of bacterial cellulose (BC) for energy conversion and storage devices. These emerging technologies enable the transformation of sustainable energy sources into electricity. Once converted, energy storage devices are vital for stable energy supply. To promote green manufacturing practices in this field, bio-based materials are explored as alternative materials for energy devices, addressing the growing demand for sustainable solutions. From a research and development perspective, the materials chosen for energy devices must exhibit exceptional mechanical, electrical, and thermal properties, along with the necessary chemical reactivity to unlock new applications. Furthermore, for successful commercialization and industrialization, these materials must be suitable for large-scale production within practical timeframes. BC fulfills all of these requirements. The review begins with an overview of BC growth, detailing the composition and operating parameters of the culture medium and the design of bioreactors for large-scale production. It then defines and summarizes both in-situ and ex-situ modifications and processing strategies, offering a comprehensive perspective on these techniques. Unique and interesting properties linking BC's structure to its properties are reviewed to demonstrate its potential as a substitute for benchmark materials. The exceptional performance and synergistic effects of BC-derived hybrid materials highlight their potential for state-of-the-art applications in energy devices, and are suitable for the next-generation energy devices. The papers reviewed in this work have gained significant attention and been widely cited over the past 10years for their relevance to various practical applications, allowing readers to have a better understanding in development of BC based materials for energy conversion and conversion devices.

Compositional dependence of electrochemical properties in biopolymer blend-based solid electrolytes doped with sodium perchlorate for EDLC applications

Biopolymer-based blends of solid electrolytes capable of conducting sodium ions were prepared via solution casting by incorporating sodium carboxymethyl cellulose (NaCMC) and polyvinyl alcohol (PVA) with varying concentrations of sodium perchlorate monohydrate (NaClO4.H2O), which was used as the dopant. The prepared electrolytes were characterized to reveal their structural, vibrational, electrical, and electrochemical properties that make them promising as solid polymer electrolytes (SPEs). X-ray diffraction (XRD) analysis showed that the amorphous nature of the sample increased with the addition of NaClO4.H2O salt concentrations of up to 30 wt.%. The complexation between the polymers and salt was confirmed by Fourier-Transform Infrared (FTIR) analysis. The SPE exhibited an optimal ionic conductivity of (1.90 ± 0.05) ×10−5 S cm−1, which is three orders higher than that of the pristine polymer blend with (5.31 ± 0.61) ×10−8 S cm−1, as determined by electrochemical impedance spectroscopy (EIS) analysis. Scaling studies conducted based on AC conductivity and tangent loss revealed that these measurements could be represented by a single master curve, which suggests that the optimal sample adheres to the time-temperature superposition principle (TTSP). The temperature dependence of Jonscher's exponent indicates that the conduction mechanism can be effectively represented by the Quantum Mechanical Tunneling model (QMT). Both transference number measurement (TNM) and linear sweep voltammetry (LSV) analyses validated the electrolyte's suitability for energy device applications by demonstrating its high ion transference number and electrochemical potential window of 3.93 V. The optimized SPE film was subsequently utilized in an electrochemical double-layer capacitor (EDLC) device to evaluate its performance as both an electrolyte and separator. The supercapacitor exhibited an impressive energy density of 15.18 Wh kg−1 and a power density of 4512.5 W kg−1, along with remarkable stability in terms of cycle life.

Solution-Free Melt-Grown CsGeI3 Polycrystals for Lead-Free Perovskite Photovoltaics: Synthesis, Characterization, and Theoretical Insights

Inorganic lead-free metal halide perovskites are being rigorously explored as a substitute for organic lead-based materials for various energy device applications. Germanium as a replacement for lead has been proven to give exemplary results theoretically, and there have been promising results. The current work presents the investigation of CsGeI3 (CGI) polycrystals grown using a solution-free melt-growth technique with low-cost precursors. A soak-ramp profile was designed to synthesize polycrystalline powders, which were evaluated for stability. X-ray diffraction and Raman spectroscopy analysis suggest the formation of CsGeI3 perovskite powders, matching the reported literature. Diffuse reflectance spectroscopy measurements showed the bandgap of the polycrystals to be around 1.6 eV. A prominent photoluminescence peak was obtained at 767 nm. The powders were examined using thermogravimetric analysis to assess the thermal degradation pathways. The as-grown inorganic perovskite polycrystals were relatively stable during storage under ambient conditions. Theoretical studies were also carried out to support the experimental data. Calculations were performed with different approximations, including local density approximation (LDA), generalized gradient approximation (GGA), and Heyd–Scuseria–Ernzerhof (HSE) approximation, out of which the HSE approximation yielded the most accurate results that matched the experimental findings. Moreover, for the CGI device with Ag electrodes simulated using SCAPS-1D software, highest incident photon-to-electron conversion efficiency was observed. The obtained optical and structural properties indicate the suitability of the synthesized CsGeI3 perovskite polycrystals for photovoltaic applications, specifically solar cells and light-emitting diodes.

On-Water Surface Synthesis of Two-Dimensional Polymer Membranes for Sustainable Energy Devices.

ConspectusIon-selective membranes are key components for sustainable energy devices, including osmotic power generators, electrolyzers, fuel cells, and batteries. These membranes facilitate the flow of desired ions (permeability) while efficiently blocking unwanted ions (selectivity), which forms the basis for energy conversion and storage technologies. To improve the performance of energy devices, the pursuit of high-quality membranes has garnered substantial interest, which has led to the exploration of numerous candidates, such as polymeric membranes (e.g., polyamide and polyelectrolyte), laminar membranes (e.g., transition metal carbide (MXene) and graphene oxide (GO)) and nanoporous 2D membranes (e.g., single-layer MoS2 and porous graphene). Despite impressive progress, the trade-off effect between ion permeability and selectivity remains a major scientific and technological challenge for these membranes, impeding the efficiency and stability of the resulting energy devices.Two-dimensional polymers (2DPs), which represent monolayer to few-layer covalent organic frameworks (COFs) with periodicity in two directions, have emerged as a new candidate for ion-selective membranes. The crystalline 2DP membranes (2DPMs) are typically fabricated either by bulk crystal exfoliation followed by filtration or by direct interfacial synthesis. Recently, the development of surfactant-monolayer-assisted interfacial synthesis (SMAIS) method by our group has been pivotal, enabling the synthesis of various highly crystalline and large-area 2DPMs with tunable thicknesses (1 to 100 nm) and large crystalline domain sizes (up to 120 μm2). Compared to other membranes, 2DPMs exhibit well-defined one-dimensional (1D) channels, customizable surface charge, ultrahigh porosity, and ultrathin thickness, enabling them to overcome the permeability-selectivity trade-off challenge. Leveraging these attributes, 2DPMs have established their critical roles in diverse energy devices, including osmotic power generators and metal ion batteries, opening the door for next-generation technology aimed at sustainability with a low carbon footprint.In this Account, we review our achievements in synthesizing 2DPMs through the SMAIS method and highlight their selective-ion-transport properties and applications in sustainable energy devices. We initially provide an overview of the SMAIS method for producing highly crystalline 2DPMs by utilizing the programmable assembly and enhanced reactivity/selectivity on the water surface. Subsequently, we discuss the critical structural parameters of 2DPMs, including pore sizes, charged sites, crystallinity, and thickness, to elucidate their roles in selective ion transport. Furthermore, we present the burgeoning landscape of energy device applications for 2DPMs, including their use in osmotic power generators and as electrode coating in metal ion batteries. Finally, we conclude persistent challenges and future prospects encountered in synthetic chemistry, material science, and energy device applications within this rapidly evolving field.

(Invited) Scalable 2-Step Fabrication of Core-Shell GaN Micropillars

Group III-Nitride three-dimensional structures have gained substantial interest for application in optoelectronic, energy, and sensor devices with non-planar geometries [1-4]. The benefits of 3D structures, such as GaN-based nano-/micro-rods, compared to planar films include large surface area, high structural quality, non-polar-surface utilization, small footprint, mechanical flexibility, and enhanced light absorption/extraction efficiency. To advance the technology of non-planar III-Nitride semiconductors, it is necessary to optimize and scale up the fabrication of such structures with controlled geometries and desired electronic and optical properties. Here, we report the fabrication of wafer-scale periodic arrays of vertically aligned GaN core-shell micropillars using a combination of top-down etch and epitaxial overgrowth.The two-step process consists of inductively coupled plasma (ICP) etching of lithographically patterned GaN-on-Si substrate to produce an array of micropillars followed by selective growth of GaN shells over these pillars using Hydride Vapor Phase Epitaxy (HVPE). The most significant aspect of the study is the demonstration of the sidewall facet control in the shells, ranging from truncated hexagonal pyramids with the (1-101) semi-polar sidewalls to hexagonal prisms with the (1-100) non-polar sidewalls, by employing a post-ICP wet chemical etch and by tuning the HVPE growth temperature. Optimization of both ICP etching and epitaxial overgrowth reduced dislocation density in the GaN shells, thus enhancing the transport and optical characteristics of these device platforms. Photo- and cathodoluminescence showed a substantial reduction of parasitic yellow luminescence as well as strain-relaxation in the core-shell structures, supported by Raman scattering, electron-backscatter-diffraction (EBSD), and X-ray-diffraction measurements. Transmission electron microscopy revealed improved crystal quality with reduced dislocation density in the epitaxially grown shells. This work demonstrates the feasibility of selective epitaxy on micro/nano-engineered 3D templates for realizing high-quality GaN-on-Si devices such as LEDs and p-i-n photodetectors.

Enhancement of photovoltaic efficiency in BiVO4 films through Zr4+-W6+ Co-doped

Using a cost-effective and simple sol-gel process, BiVO4 films and Zr4+-W6+ co-doped BVO films were prepared on Pt/Ti/SiO2/Si substrates. The influence of Zr4+-W6+ co-doped on the photovoltaic properties of the synthesized BiVO4 films was systematically investigated. When the doped amount of Zr4+-W6+ is 6 %, the optical band gap of the film decreases from 2.58 eV to 2.31 eV. The increased strength of the built-in electric field of the films help to improve the separation of photogenerated charge carriers. The Zr4+-W6+ co-doped BiVO4 films demonstrated a significant increase in photocurrent density from 0.284 mA/cm2 to 1.04 mA/cm2. These findings highlight the potential of Zr4+-W6+ co-doped in advancing the performance of BiVO4-based photovoltaic materials and suggest avenues for future applications in solar energy devices.

Pyrolysis-free coupling strategy to synthesize two-dimensional oxygen reaction electrocatalysts for rechargeable Zn-air batteries

Although rechargeable Zn-air batteries (ZABs) representing one of the most prospective energy devices, their practical applications are primarily restricted by sluggish oxygen reduction and evolution reactions (ORR/OER). We herein propose a pyrolysis-free coupling strategy to prepare two-dimensional ORR/OER bifunctional electrocatalysts, in which atomic Fe-N4 moieties from planar iron phthalocyanine molecules for ORR and ultrathin FeCo hydroxides for OER are anchored on graphene by ultrasound-assisted coupling interactions. The obtained catalyst exhibits a small OER-ORR potential difference of 0.64 V. When used in ZABs, excellent performance is achieved such as a large power density (216 mW cm−2), a high specific capacity (743 mAh g−1), and stable charge–discharge voltage platform, demonstrating its great potential in the applications of energy devices.

Structure and ionic conduction enhancement mechanisms at CeO2/SrTiO3 heterointerfaces

Fluorite-perovskite heterointerfaces garner great interest for enhanced ionic conductivity for application in electronic and energy devices. However, the origin of observed enhanced ionic conductivity as well as the details of the atomic structure at these interfaces remain elusive. Here, systematic, multi-stoichiometry computational searches and experimental investigations are performed to obtain stable and exact atomic structures of interfaces between CeO2 and SrTiO3—two archetypes of the corresponding structural families. Local reconstructions take place at the interface because of mismatched lattices. TiO2 terminated SrTiO3 causes a buckled rock salt CeO interface layer to emerge. In contrast, SrO terminated SrTiO3 maintains the fluorite structure at the interface compensated by a partially occupied anion lattice. Moderate enhancement in oxygen diffusion is found along the interface by simulations, yet evidence to support further significant enhancement is lacking. Our findings demonstrate the control of interface termination as an effective pathway to achieve desired device performance.

Control of spin on ferromagnetism and thermoelectric properties of Sr(V/Cr)2S4; emergent spintronic aspirant

Strontium-based spinel chalcogenides are promising materials for energy harvesting and spintronics. Therefore, the electronic, ferromagnetic, and thermoelectric properties of SrZ2S4 (Z = V, Cr) spinels are thoroughly investigated. The formation energy and energy released during optimization demonstrate the stability of the cubic phase in a ferromagnetic state. The spin polarisation and the Curie temperature have been calculated using the density of states (DOSs) and the Heisenberg model. To explore ferromagnetism, exchange energies, the double exchange mechanism, exchange constants, and the hybridization process have all been used. The decrease in the magnetic moment for V/Cr and its shift to nonmagnetic (Sr, S) sites show that ferromagnetism is caused by electron exchange rather than V/Cr atom clustering. In the end, electrical and thermal conductivities, Seeback coefficient (S), and power factor have been used to explain the thermoelectric analysis for energy applications. Ultralow thermal conductivity values lessen the impact of heat on electron spin, extending the device’s useful life. All of these aspects, when taken together, provide a comprehensive picture of the role electron exchange plays in ferromagnetism and its application in energy devices.

First-principles calculations to investigate electronic, magnetic, and optical properties at (110) and (111) surfaces of Ni adsorption on CdO

In this study, we utilised the GGA+U method via the WIEN2k software to investigate the structural, magnetic, and optoelectronic responses of two distinct surfaces, (111) and (110), to Ni adsorption on CdO at the Cd site. The analysis revealed that Ni/CdO (111) demonstrates properties akin to a semimetal or a zero-gap semiconductor across both spin orientations, while Ni/CdO (110) exhibits a metallic nature under similar conditions. These phenomena are predominantly ascribed to the orbital contributions from Ni-d, Cd-d, and O-p for the Ni/CdO (111), and Ni-d, Cd-d, and O-s for the Ni/CdO (110), respectively. A notable blue shift in the optical absorption spectra was observed for both materials. Utilising the Dielectric function, we calculated the dispersion of energy bands along with essential optical properties, including the absorption coefficient, energy loss function, and reflectivity, refractive index, and extinction coefficient. Magnetisation values for Ni/CdO (110) and Ni/CdO (111) were recorded at (−0.11794) µB and (2.17926) µB, respectively, influenced by the absorption spectrum's blue shift. Additionally, transport properties were evaluated using the BoltzTraP software over a temperature range of 0 to 800 K. Our findings suggest that Ni/CdO (110) and Ni/CdO (111) are significant for applications in spintronics and energy devices.

A computational approach to study the halides-based double perovskites Cs2InAuX6 (X=Cl, Br) for low-cost energy technologies

Using the computer-based simulations in the framework of WIEN2K, we have investigated the structure, optoelectronic, and thermoelectric properties of lead-free double perovskite halides Cs2InAuX6 (X = Cl, Br). These materials stabilize in the cubic phase due to lower formations energies. Interestingly, the Cs2InAuCl6 (Eg = 0.7 eV) exhibits a narrow band gap while the Cs2InAuBr6 (Eg = 0 eV) shows metallic behavior. Our calculated optical parameter values unambiguously reveal that the infrared (IR) regions exhibit the greatest light absorption, proving that these halides are suitable for application in transistors-based devices. Concerning the transport qualities, the Seebeck coefficient, electrical conductivity, thermal conductivity, and figure of merit are all investigated. Our findings will benefit future experiments on Cs2InAuX6 (X = Cl, Br) for application in renewable energy devices.

Regulating atomic Fe/Cu dual sites with unsymmetrical Fe-N6 and Cu-N1S2 coordination for promoting bifunctional oxygen electrocatalysis in advanced zinc-air batteries

Dual-metal single-atom catalysts with heteronuclear active sites exhibit superior oxygen catalysis performance than their single-atom counterparts, facilitating the practical applications in advanced electrochemical energy devices. Herein, a Fe-Cu dual-metal single-atom catalyst with Fe-N6 and Cu-N1S2 coordination environment (FeCu-DSAs/NSC) is reported. Due to the synergism of bimetallic active sites and asymmetric heteroatom coordination, the resultant FeCu-DSAs/NSC displays better bifunctional catalytic performance (a small potential gap between the Eη10 and E1/2, ΔE=0.647 V) when compared with the counterparts (Pt/C+IrO2 and Cu-ISAs/NSC), as well as surpassing most of bifunctional metal atom-based catalysts reported to date. As expected, FeCu-DSAs/NSC based rechargeable zinc-air battery shows remarkable superiority than commercial Pt/C+IrO2 benchmark, resulting in a high peak power density (230.66 mW cm−2), open-circuit voltage (1.464 V) and long-term cycling stability (up to 350 h at 10 mA cm−2).

Chitosan as a suitable host for sustainable plasticized nanocomposite sodium ion conducting polymer electrolyte in EDLC applications: Structural, ion transport and electrochemical studies

The challenge in front of EDLC device is their low energy density compared to their battery counter parts. In the current study, a green plasticized nanocomposite sodium ion conducting polymer blend electrolytes (PNSPBE) was developed by incorporating plasticized Chitosan (CS) blended with polyvinyl alcohol (PVA), doped with NaBr salt with various concentration of CaTiO3 nanoparticles. The most optimized PNSPBE film was subsequently utilized in an EDLC device to evaluate its effectiveness both as an electrolyte and a separator. Structural and morphological changes were assessed using XRD and SEM techniques. The PNSPBE film demonstrated a peak ionic conductivity of 9.76×10−5 S/cm, as determined through EIS analysis. The dielectric and AC studies provided further confirmation of structural modifications within the sample. Both TNM and LSV analyses affirmed the suitability of the prepared electrolyte for energy device applications, evidenced by its adequate ion transference number and an electrochemical potential window of 2.86 V. Electrochemical properties were assessed via CV and GCD techniques, confirming non-Faradaic ion storage, indicated by the rectangular CV pattern at low scan rates. The parameters associated with the designed EDLC device including specific capacitance, ESR, power density (1950 W/kg) and energy density (12.3 Wh/kg) were determined over 1000 cycles.

Single-Atom Catalysts on Covalent Organic Frameworks for Energy Applications.

Single-atom catalysts (SACs) have been investigated and applied to energy conversion devices. However, issues of metal agglomeration, low metal loading, and substrate stability have hindered realization of the SACs' full potential. Recently, covalent organic framework (COF)-based SACs have emerged as promising materials to enable highly efficient catalytic reactions. Here, we summarize the representative COF-based SACs and their wide application in clean energy devices and conversion reactions, such as hydrogen evolution reaction, carbon dioxide reduction reaction, nitrogen reduction reaction, oxygen reduction reaction, and oxygen evolution reaction. Based on their catalysis conditions, these reactions are categorized into photocatalyzed and electrocatalyzed reactions. We also summarize their design strategies, including heteroatom inclusion, donor-acceptor pairs, pore engineering, interface engineering, etc. Although COF-based SACs are promising, more efforts, such as linkage engineering, functional groups, ionization, multifunctional sites for cocatalyzed systems, etc., could improve them to be the ideal SAC materials. At the end, we provide our perspectives on where the field will proceed in the next 5 years.

Dual‐Float‐Based Triboelectric Nanogenerator for Low‐Frequency Wave Energy Harvesting

Electromagnetic induction generator is not the best choice for collecting low frequency wave energy, since waves have the characteristics of low frequency and variable amplitude. In contrast, triboelectric nanogenerator (TENG) has an absolute advantage in collecting low‐frequency mechanical energy. Based on this, a dual‐float‐based triboelectric nanogenerator (DF‐TENG) for harvesting low‐frequency wave energy is proposed in this article. In this device, the TENG is mounted in the lower float, and its slider component is connected to the upper float by a cable. On the one hand, the motion of the slider is consistent with the relative motion of the dual floats, which is easy to analyze; on the other hand, the TENG is located in the lower float, which avoids damage to the TENG caused by extreme sea conditions. The physical model of the device was established, and the motion characteristics, electrical output characteristics, and its influencing factors of TENG were analyzed using finite element simulation software. The numerical calculations were verified by experimental tests. The calculated results show that the optimal matching resistance of the system is 500 MΩ. The research work in this article provides a research basis and reference for the development and application of such wave energy devices.

Recent Advances in Dispersant Technology for Carbon Nanotubes toward Energy Device Applications

Carbon nanotubes (CNTs) are of interest in various industries owing to their high aspect ratio, electrical conductivity, and other properties. By maximizing the number of CNTs in their solvents or matrices, the electrical and mechanical performance in applications such as batteries, sensors, and transistors can be enhanced. However, the hydrophobicity of CNTs’ surface induces aggregation that adversely impacts their performance. To overcome this obstacle, many researchers have been designing novel dispersants with performances exceeding that of existing commercial dispersants. This article reviews contemporary studies on CNT dispersants from 2015 to 2022, along with the comprehensive features of CNTs depending on their chirality, number of walls, synthesis methods, and functionalization. Studies of CNT dispersants are primarily organized according to whether aqueous or organic solvents are used. This review article provides a clear perspective of CNT dispersants development today and how to design new CNT dispersants depending on the solvents. A conclusion is given to identify major challenges to the implementation of CNT dispersion and an outlook on future avenues of research.

Electrocatalytic Activation in ReSe2-VSe2 Alloy Nanosheets to Boost Water-Splitting Hydrogen Evolution Reaction.

It is challenging to control the electronic structure of 2D transition metal dichalcogenides (TMD) for extended applications in renewable energy devices. Here, ReSe2-VSe2 (Re1- xVxSe2) alloy nanosheets over the whole composition range via a colloidal reaction is synthesized. Increasing x makes the nanosheets more metallic and induces a 1T″-to-1T phase transition at x = 0.5-0.6. Compared to the MoSe2-VSe2 and WSe2-VSe2 alloy nanosheets, ReSe2 and VSe2 are mixed more homogeneously at the atomic scale. The alloy nanosheets at x = 0.1-0.7 exhibit an enhanced electrocatalytic activity toward acidic hydrogen evolution reaction (HER). In situ X-ray absorption fine structure measurements reveal that alloying caused the Re and V atoms to be synergically more active in the HER. Gibbs free energy (ΔGH*) and density of state calculations confirm that alloying and Se vacancies effectively activate the metal sites toward HER. The composition dependence of HER performance is explained by homogenous atomic mixing with the increased Se vacancies. The study provides a strategy for designing new TMD alloy nanosheets with enhanced catalytic activity.

Improved Superconductivity and Structural Mechanism Analysis of Y0.55Gd0.45Ba2Cu3O7–x/SrTiO3/Y0.55Gd0.45Ba2Cu3O7–x Tri-layer

ABSTRACT REBa2Cu3O7–ä (REBCO) coated conductors has great potential in the field of energy transmission and device applications. However, one of the main obstacles is the limitation of critical current and critical current density of REBCO coated conductors, which restricts its wide application in the above fields. Herein a method to improve the thickness effect based on sandwich structure and SrTiO3 (STO) interlayer has been proposed. The sandwich structural coated conductor displayed better superconductivity. Compared with single-step and multi-step Y0.55Gd0.45Ba2Cu3O7–x (YGdBCO) film, the critical current of YGdBCO/STO/YGdBCO increased by 52.4% and 25.3%, respectively. Meanwhile, the micro-mechanism of current transport in the superconducting film has been investigated and discussed in detail. The segregation and diffusion of elements in the superconducting film and the metallic parts formed within the STO interlayer connected the top and bottom layers and provided channels for current transport. Thickness effect was significantly improved through this method under the mechanism discussed, which should help to improve the large-scale application of REBCO coated conductors.