Abstract ：

This study investigates the electrocatalytic reduction of nitrates using three novel electrodes: Cu@CNFs/NF, Cu@CNTs/NF, and Cu@CB/NF, synthesized via an impregnation-calcination-electrodeposition technique. The emphasis is on the role of different carbon materials, which serve as the base or matrix for Cu, and their influence on nitrate reduction and nitrogen selectivity. Experimental results indicated that all three-electrode variants outperformed the conventional Cu/NF electrode in nitrate reduction and nitrogen selectivity. Among these, the Cu@CNFs/NF electrode emerged as the standout performer, achieving an impressive nitrate reduction rate of up to 98 % and a nitrogen selectivity of 51 % under the optimized experimental conditions (pH 7, nitrate concentration of 100 mg center dot L-1 as NO3--N, a current density of 8 mA cm- 2, a sodium sulfate concentration of 0.5 g center dot L-1, 120 min, anode: Ti/RuO2-IrO2). Stability tests confirmed that the Cu@CNFs/NF electrode maintained over 97 % nitrate removal efficiency across ten cycles, highlighting its robustness and potential for practical water treatment applications. A significant enhancement in nitrogen selectivity of Cu@CNFs/NF to 96 % was observed when using 0.75 g center dot L-1 NaCl as the electrolyte during an extended electrolysis period of 180 min, underscoring its potential to optimize catalytic efficiency. Characterization data from SEM, XRD, and other analyses substantiate that the incorporation of carbon materials augments the active sites of copper; Nitrogen adsorption-desorption experiments further illustrate that the integration of carbon materials leads to an increase in mesoporous volume. This increase promotes adsorptive interactions, enhances the conversion of intermediates, and contributes to the improvement of nitrate reduction and nitrogen selectivity. These results highlight the potential of tailored carbon material integration for enhancing the electrocatalytic performance of electrodes in practical water treatment applications.

Keyword ：

Carbon material based N2 selectivity Electrocatalytic nitrate reduction

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Abstract ：

Metal-organic frameworks (MOFs) as emerging material have drawn much attention to apply to the field of water splitting. In this paper, layered NiFe-MIL-53 and nanoflower-like CoFe-MOF-74 were sequentially grown on nickel foam through two-step in -situ growth to construct a MOF-74/MIL-53 heterojunction. On this basis, we used the localized surface plasmon resonance (LSPR) effect of gold nanoparticles (Au NPs) to significantly improve the oxygen evolution reaction performance of MOF-74/MIL-53 heterojunction. Under illumation, the obtained Au-MOF-74/MIL-53 exhibits a lower overpotential of 218 mV, which is far superior to commercial catalyst. The reaction kinetics are significantly enhanced due to the lower charge transfer resistance and the higher electric double layer capacitance. We confirmed the existence of charge transfer between Au NPs and MOFs, and at the same time, the deposition of Au NPs significantly reduced the charge transfer resistance of MOF-74/MIL-53. On the basis of our work, we provide a novel MOF-based electrocatalytic nanocomposite structure for efficient water splitting.

Keyword ：

Water electrolysis MOF Plasmonic Au Heterojunction Oxygen evolution reaction

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Abstract ：

Tungsten coatings have unique properties such as high melting points and hardness and are widely used in the nuclear fusion and aviation fields. In experiments, compared to pure Na2WO4 molten salt, electrolysis with Na2WO4-WO3 molten salt results in a lower deposition voltage. Herein, an investigation combining experimental and computational approaches was conducted, involving molecular dynamics simulations with deep learning, high-temperature in situ Raman spectroscopy and activation strain model analysis. The results indicated that the molten salt system's behaviour, influenced by migration and polarization effects, led to increased formation of Na2W2O7 in the Na2WO4-WO3 molten salt, which has a lower decomposition voltage and subsequently accelerated the cathodic deposition of tungsten. We analyzed the mechanism of the effect of the electric field on the Na2W2O7 structure based on the bond strength and electron density. This research provides crucial theoretical support for the effect of electric field on tungsten in molten salt and demonstrates the feasibility of using machine learning-based DPMD methods in simulating tungsten-containing molten salt systems.

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Hydrogen by electrolysis with solar PV and nuclear are regarded as the most promising zero-carbon hydrogen production technologies to replace conventional fossil-fuel-based hydrogen production technologies. This study evaluates the levelized cost of hydrogen (LCOH) of conventional technologies with and without carbon price, solar and nuclear electricity-based technology, and the nuclear high temperature gas cooled reactor (HTGR) in China, and analyzes the effects of energy storage on the LCOH of solar electricity-to-hydrogen in different photovoltaic resource regions. The results show that when considering carbon price, the LCOH of conventional technologies will rise to 1938-2564 $/tH2 in 2050. The LCOH of HTGR will be 1149 $/tH2 in 2050, much lower than that of coal gasification, which is widely used in China today. In the photovoltaic resource-rich region, solar PV electrolysis shows strong competitiveness, particularly for PEM_PV, whose LCOH could reduce to 1154 $/tH2 in 2050. While energy storage only serves solar PV electrolysis, it fails to increase the cost competitiveness of solar PEM. Therefore, zero carbon hydrogen could have cost advantage by 2040 in rich photovoltaic resource area and by HTGR.

Keyword ：

HTGR Solar PV electrolysis Energy storage assisted Green hydrogen LCOH China

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Abstract ：

Hydrogen production by the electrolysis of water is a green and efficient method, which is of great significance for achieving sustainable development. Molybdenum disulfide (MoS2) is a promising electrocatalyst for hydrogen evolution reaction (HER) due to its high electrochemical activity, low cost, and abundant reserves. In comparison to the noble metal Pt, MoS2 has poorer hydrogen evolution performance in water electrolysis. Therefore, further modifications of MoS2 need to be developed aiming at improving its catalytic performance. The present work summarizes the modification strategies that have been developed in the past three years on hydrogen evolution from water electrolysis by utilizing MoS2 as the electrocatalyst and following the two aspects of internal and external modifications. The former includes the strategies of interlayer spacing, sulfur vacancy, phase transition, and element doping, while the latter includes the heterostructure and conductive substrate. If the current gap in this paper's focus on modification strategies for electrocatalytic hydrogen evolution in water electrolysis is addressed, MoS2 will perform best in acidic or alkaline media. In addition to that, the present work also discusses the challenges and future development directions of MoS2 catalysts.

Keyword ：

modification strategies molybdenum disulfide hydrogen evolution reaction

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Abstract ：

The slow kinetics of water dissociation on electrocatalysts lacking platinum hinders the advancement of cost-effective hydrogen production via alkaline water electrolysis. Herein, a hierarchically peach-flower-shaped electrocatalyst consisting of copper-restructured cobalt–nickel/cobalt–nickel oxide heterostructure anchored on copper nanowires (Cu-CoNiO/CoNi@Cu NWs) is developed for efficient hydrogen evolution reaction (HER). Benefiting from the optimized electronic configuration and geometric structure, this Cu-CoNiO/CoNi@Cu NWs catalyst performs an outstanding alkaline HER activity of 29 mV at 10 mA cm−2 and 98 mV at 100 mA cm−2, which is comparable with the state-of-the-art Pt/C catalyst (26 mV at 10 mA cm−2 and 117 mV at 100 mA cm−2). Our findings rank among the topmost catalytic efficiencies when compared to all previously reported non-noble metal catalysts and numerous noble metal catalysts. The combined experimental exploration and theoretical studies reveal that the incorporation of Cu dopant into CoNiO/CoNi heterostructure enhances electron transfer from metal atoms to O atom, leading to the formation of the polarized electric field to accelerate water dissociation and H evolution, eventually facilitating the overall alkaline HER process. The boosted electron exchange and mass transportation deriving from the introduction of Cu NWs and hierarchically peach-flower-shaped nanostructure further reinforce the HER activity of the Cu-CoNiO/CoNi catalyst. © 2024 Elsevier Ltd

Keyword ：

Nickel oxide Cobalt Copper compounds Surface discharges Bioremediation Platinum alloys Mass transportation Palladium Copper Platinum compounds Catalytic oxidation

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Abstract ：

Molten salt electrolysis is an innovative technology applied to recover tungsten from the scrap of cemented carbide, which enables the realization of energy saving and consumption reduction goals. Currently, numerous studies have focused on the molten salt electrolysis of chlorine salt systems, but still face challenges including low electrolysis efficiency and salt volatilization. Here, we propose to employ the FLiNaK molten salt system for recovering tungsten from the scrap cemented carbide and analyze the feasibility of the dissolution of WC occurring at the anode from the perspective of thermodynamics and electrochemical polarization curves. Moreover, the influence of electrolysis temperature on the dissolution of the anode is also investigated and the productions are identified as nano-flake tungsten powder by characterizing the cathode product using XRD, SEM, EDS, and XPS. A two-step reduction mechanism of W ions was analyzed by electrochemical means such as CV, SWV, etc., and the ionic groups stabilized by W6+ and W4+, and F- in the molten salts were deduced to be WF33+ and WF3+ by DFT simulation calculations. This work provides new guidance for the application of molten salt electrolysis in the recovery of tungsten from scrap cemented carbide.

Keyword ：

Anodic dissolution Molten salt electrolysis DFT FLiNaK Tungsten metal extraction

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In this study, a hybrid ion exchange membrane (IEM) electrolysis process incorporating AEM/CEM electrolysis was implemented to investigate the removal efficiency and the underlying mechanism of IEM fouling in removing organic matter and ions (Ca2+, Mg2+, SO42-) from nanofiltration concentrate (NFC). The results reveal that Ca2+ and Mg2+ were removed through the formation of CaCO3 and Mg(OH)2 precipitates in the cathode chamber of AEM electrolysis (ACC), whereas SO42- was enriched in the anode chamber (AAC). The addition of Ca (OH)2 and NaAlO2 led to ettringite precipitation in the cathode chamber of the CEM electrolysis (CCC), along with CaCO3 and Mg(OH)2 precipitates. Meanwhile, the oxidation and the precipitation adsorption led to effective removal of organic matter. A comparison of the current density demonstrated that the optimum conditions for removal were 10 mA/cm2 in AEM electrolysis and 15 mA/cm2 in CEM electrolysis. Notably, in IEM fouling, the Zeta potential, XDLVO and other results showed the AEM fouling was more aggravated than CEM.

Keyword ：

Electrochemical oxidation Membrane fouling Ion exchange membrane electrolysis Precipitation adsorption Nanofiltration concentrate

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Abstract ：

In the process of molten salt electrolysis of spent tungsten carbide for the separation of tungsten and cobalt, the nature of the molten salt has a crucial impact on product quality and efficiency. In this study, the microscopic and macroscopic models of the diffusion layer of Na2WO4-WO3-CoO molten salt were developed. The structure, transport properties and electroanalytical behavior of Na2WO4-WO3-CoO molten salt were investigated by combining molecular dynamics and finite element simulation under different CoO and WO3 molar ratios and different applied electric field conditions. The cost of this approach is relatively low compared to experiments. It was found that the addition of CoO hinders the mass transfer and increases the electrochemical impedance. The reason for this is that the addition of CoO leads to an increase in the entropy of the molten salt. The change in external electric field does not affect this law. The calculated results are in general agreement with the available experimental data. In the study of the structure of molten salts, the vacancy volume factor, which is a metric for evaluating the size of the vacancy volume of molten salts, was proposed for the first time. The addition of CoO also affects the microstructure, which can be used to infer changes in the electrodeposition products. Experimental results of electrodeposition support this speculation. This study confirms that a combination of macroscopic and microscopic, molecular dynamics and finite element simulations can theoretically aid the development of molten salt electrolysis processes.

Keyword ：

Molten salt Electroanalysis Na2WO4-WO3-CoO Transport properties Molecular dynamics

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Although the acidic oxygen evolution reaction (OER) plays a crucial role in proton-exchange membrane water electrolysis (PEMWE) devices, challenges remain owing to the lack of efficient and acid-stable electrocatalysts. Herein, we present a low-iridium electrocatalyst in which tensile-strained iridium atoms are localized at manganese-oxide surface cation sites (TS-Ir/MnO2) for high and sustainable OER activity. In situ synchrotron characterizations reveal that the TS-Ir/MnO2 can trigger a continuous localized lattice oxygenmediated (L-LOM) mechanism. In particular, the L-LOM process could substantially boost the adsorption and transformation of H2O molecules over the oxygen vacancies around the tensile-strained Ir sites and prevent further loss of lattice oxygen atoms in the inner MnO2 bulk to optimize the structural integrity of the catalyst. Importantly, the resultant PEMWE device fabricated using TS-Ir/MnO2 delivers a current density of 500mA cm(-2) and operates stably for 200 h.

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