Study On The Construction And Performance Of Vanadium-based Catalysts For High-efficiency Electro-photocatalytic Decomposition Of Water To Hydrogen

In recent years,with the advancement of hydrogen storage technology and the rapid development of hydrogen fuel cells,the lack of demand for hydrogen will stimulate the supply-side market of hydrogen.At present,the production of hydrogen is mainly derived from fossil energy,but the preparation process will cause problems such as the greenhouse effect and environmental pollution.Green electrocatalysis and photocatalytic water splitting hydrogen production technology is considered to be the most potential hydrogen production method.At present,platinum-based catalysts are the most excellent catalysts in the process of splitting water to produce hydrogen.However,they face problems such as high prices and low reserves in actual large-scale applications,making them unable to be widely used in industry.In this context,non-noble metal-based catalysts have received extensive attention.Among them,vanadium-based compounds such as hydroxides and carbides stand out among many catalysts due to their better catalytic properties and good stability.It has important practical significance for the research of electric and photocatalytic decomposition of water to produce hydrogen.The main research contents of this subject are as follows:（1）Vanadium-based electrocatalyst:Cobalt and vanadium double hydroxides（LDHs）are loaded on carbon cloth by a simple one-step hydrothermal method to obtain an electrocatalyst with a uniform three-dimensional nanosheet structure（denoted as Co₂V₁-LDH/CC）.In an alkaline electrolyte,when the current density is 10 m A cm^-2,the overpotential is 82 m V,which is a nearly 46.4%improvement in performance compared to pure Co（OH）₂/CC（overpotential of 153 m V）.The electric double layer capacitance of Co₂V₁-LDH/CC(75 m F cm^-2)is 10.7 times that of pure Co（OH）₂/CC(7.04 m F cm^-2).At the same time,the hydrogen evolution activity of Co₂V₁-LDH/CC was not significantly weakened after 60 h of stability test.Its excellent performance of hydrogen evolution from electrolyzed water is mainly due to the following two points:the carbon cloth matrix used can improve the overall conductivity,while providing a three-dimensional framework to promote hydrogen precipitation;the three-dimensional nanosheets that grow perpendicular to each other can expose more active sites.And shorten the distance of charge transfer to obtain excellent hydrogen evolution performance.Therefore,this study provides a reference for the design and preparation of low-cost,high-efficiency non-noble metal-based electrocatalysts.（2）Vanadium-based photocatalyst:Nitrogen-doped vanadium carbide（denoted as NVC）is prepared by chemical vapor carbonization method,graphite phase carbon nitride（g-C₃N₄）is used as the photocatalyst,combined with heat treatment and in-situ light deposition The method loads NVC and Pt together on g-C₃N₄ to obtain the g-C₃N₄ photocatalytic material co-modified by Pt and NVC double co-catalyst.The photocatalytic performance test showed that the photocatalytic hydrogen evolution rate of g-C₃N₄ co-modified with Pt and NVC reached 40μmol/h,which was about 3 times and 100 times that of Pt/C₃N₄ and NVC/C₃N₄,respectively.At the same time,the study found that the loading of NVC can greatly promote the separation of photogenerated carriers,while the loading of Pt can accelerate the proton reduction process;further comparing the catalytic performance of pure VC and NVC,it is speculated that the NVC promoter is beneficial to activate water molecules,thereby providing a reaction the required protons.Therefore,the excellent photocatalytic activity of Pt/NVC/C₃N₄ is mainly attributed to the good synergy between Pt and NVC.This study provides ideas for the design of multifunctional co-catalysts for efficient photolysis of water to produce hydrogen.