Design,Synthesis And High Efficiency Electrocatalytic Performance Of Tungsten-Based Electrode Materials

With high energy density and environmentally friendly properties,hydrogen is considered a promising sustainable energy carrier.Electrically driven overall water splitting is an important pathway for largescale hydrogen production,including reduction reactions on the cathode（hydrogen evolution reaction,HER）and oxidation reactions on the anode（oxygen evolution reaction,OER）.HER is a multistep process and it is usually very slow due to the limitations of reaction kinetics.Pt and its complexes are promising HER electrocatalysts,but their high cost and scarcity limit largescale development and application.Tungsten is abundant in the earth’s crust,and density functional theory（DFT）calculates that it has high intrinsic activity.Tungsten-based materials are thought to be attractive candidates to replace the costly Pt-based catalysts,employed in electrochemical HER.The electrochemical performance of HER depends largely on the hydrogen adsorption configuration,chemical composition,and surface structure.The introduction of metal cations is an effective way to improve HER performance,which can redistribute electron density and change the electronic structure,thereby regulating the adsorption/desorption energy of reactants,intermediates and products during the reaction,thereby improving catalytic activity.This paper studies the following:（1）W/Mo-Ni₃S₂ nanowires were successfully synthesized on nickel foam（W/Mo-Ni₃S₂/NF）by hydrothermal method,and the HER performance was explored in alkaline electrolyte.The results show that W/Mo-Ni₃S₂/NF can reach 10 m A·cm^-2 with only 136 m V,and its morphology and composition do not change significantly after hydrogen discharge at10 m A·cm^-2 for 20 h.It is mainly attributed to two factors:bimetallic W/Mo co-doping changes the morphology of Ni₃S₂ and creates more active sites;The three-dimensional integrated frame of the self-supporting substrate is highly conductive and provides many channels for electron transfer,thereby accelerating the catalytic reaction process.（2）Two-dimensional rGO nanosheet composite W-Ni₃S₂ three-dimensional nanorod electrocatalyst（W-Ni₃S₂/rGOn@NF）was successfully synthesized on nickel foam by hydrothermal method.Under alkaline conditions,W-Ni₃S₂/rGO_1.0@NF exhibited excellent HER performance,reaching 10 m A·cm^-2 and small Tafel slope(87 m V·dec^-1)with only 91m V,and its morphology and composition did not change significantly after hydrogen discharge at 10 m A·cm^-2 for 24 h.It is mainly attributed to the following points:W doping Ni₃S₂ effectively regulates the electronic structure and helps to enrich the electrocatalytic active site;The characterization of rGO showed large surface area,open edge and high conductivity,which was conducive to hydrogen evolution reaction.The superhydrophilic characteristics make the electrode fully in contact with the electrolyte to accelerate electron transfer,and the superaerophobic characteristics reduce the adhesion of hydrogen bubbles to the electrode surface and improve the efficiency of the HER reaction.（3）Three-dimensional conical structures were designed on the surface of nickel plate（Ni-plate）using femtosecond laser micro-nano processing technology.The self-supported electrode of nanoneedle arrays and nanowires（W-Ni₃S₂/Ni-fs）was obtained by hydrothermal sulfuration on the processed nickel plate（Ni-plate）.The electrode synthesized by this method exhibits superhydrophilic and superaerophobic characteristics,and can continuously discharge hydrogen for 47 h at high current density(100 m A·cm^-2).Moreover,the HER performance of W-Ni₃S₂/Ni-fs is better than that of Ni₃S₂/Ni-fs and W-Ni₃S₂/Ni-plate,which once again proves that W doping improves the catalytic performance of Ni₃S₂,while femtosecond laser processing technology improves the surface roughness of the substrate and adds the active site for subsequent synthesis（structural defects of the Ni-fs substrate）.This superhydrophilic and superaerophobic self-supporting electrode construction method provides a new scheme for the selection of electrocatalyst substrates for hydrogen evolution reaction.