| Hydrogen production from water electrolysis is an ideal clean chemical fuel preparation method with excellent gravity energy density and high energy conversion efficiency,which can solve the problems of depletion of traditional fossil fuels and environmental pollution.In fact,a water cell requires an effective catalyst to facilitate the simultaneous hydrogen evolution（HER）and oxygen evolution（OER）reactions,so two catalysts are needed for HER and OER reactions respectively.The use of two catalysts in one reaction system is not only costly in preparation,but also complicated in design of experimental system.This paper aims to use the same catalyst to achieve HER and OER reaction at the same time,extract the advantages of HER and OER catalysts,and construct the two catalysts into one catalyst.The newly synthesized catalyst has a binding force for both hydrogen-containing and oxygen-containing intermediates,which is very favorable to achieve complete hydrolysis of water with high activity.In recent years,transition metal sulfides（TMS）have been widely explored and applied as catalysts for water electrolysis,which can eliminate the presence of precious metals to a large extent.In this paper,nickel sulfide is used as the base catalyst,which is modified,and two kinds of system catalysts are constructed for complete water hydrolysis.The details are as follows:（1）Through a simple hydrothermal reaction,using NF as the base to react with thiourea of different concentrations,when the amount of thiourea was 0.5M,NixSy-0.5 M electrode carried out HER and OER reaction in 1.0M KOH solution,the required overpotential to achieve the current density of 10 m A cm-2 was 148 m V and 111 m V,respectively.The prepared catalyst NixSy-0.5M with the best performance has the following characteristics:First,the three-dimensional nanoarray structure is conducive to the exposure of more active sites,which is conducive to the precipitation of H2 and O2.Second,the synergistic effect of different active sites and the enhanced electronic interaction between the interface of nickel polyphase sulfide are more advantageous to HER and OER catalytic activity.Third,in the strong alkali environment,sulfide in the process of OER will occur autoxidation phenomenon,that is,is oxidized into the corresponding oxygen（hydroxide）compounds,the role of sulfur element in the catalyst is to promote the formation of real active substances.（2）In order to further improve the performance of OER and confirm the role of metal hydroxide in OER reaction,the surface of nickel sulfide was coated with amorphous nickel-iron hydroxide by electrodeposition.According to the experimental results,the catalytic performance of Ni coated with NiFe-OH in the process of OER reaction has been greatly improved,and the improvement of NiFe-OH@NixSy-0.3 M catalyst is the most obvious.The reaction of HER and OER in 1.0 M KOH solution is conducted.To achieve a current density of 10 m A cm-2,the required overpotential is 178 m V and 121 m V,respectively.The surface of Nix Sy catalyst coated with metal hydroxide makes the synergistic effect between multiple crystals unable to play,so NiFe-OH@NixSy-0.3 M has the best electrolytic performance of water. |
