The Preparation,Modification And Catalytic Performance Of Cobalt And Molybdenum-Based Nanomaterials For Electrolysis Of Water

With the frequent occurrence of global climate extremes,the energy crisis and greenhouse effect have become more pronounced,and countries are advocating new clean energy sources to solve the growing carbon emission problem.Hydrogen energy has a high calorific value of combustion,and the combustion product is water,which is the cleanest energy in the world.Hydrogen production by electrolysis of water from renewable energy sources has become one of the most promising solutions in the future.At present,although Pt-based noble metal catalysts have excellent hydrogen evolution performance,the scarcity of resources and high cost severely limit their large-scale commercial applications（hydrogen production from water electrolysis accounts for only4%）.Therefore,it is the most urgent research direction to find non-precious metal-based hydrogen evolution catalysts with high catalytic activity and high stability to replace noble metal-based catalysts to realize large-scale and low-cost hydrogen production in industry and to strive for carbon neutrality.In this paper,the preparation,modification and performance of non-noble metal Co and Mo-based electrocatalysts for hydrogen evolution were investigated.The main research results obtained are as follows:（1）Cobalt molybdate precursor was synthesized by hydrothermal method using nickel foam as the conductive substrate.By controlling the subsequent surface phosphating,the cobalt molybdate core-shell electrocatalyst（Co Mo O₄@a-Co P_x）with incomplete surface amorphous phosphating was obtained.The electrochemical test showed that the overpotential of the catalyst is only 76 m V at a current density of 10m A cm^-2,the Tafel slope is 64 m V dec^-1,and the stability of the catalyst can reach 16hours.The good catalytic activity originates from the large amount of amorphous a-Co P_x in the shell layer,which provides highly active catalytic sites,and at the same time contains a large number of defects,exposing more catalytic sites,while the existence of crystalline Co Mo O₄ can effectively regulate The electron transfer inside the material makes it have more suitable water dissociation energy and hydrogen adsorption and desorption energy,and prevents the deactivation of the active site,thereby promoting its catalytic process.（2）Using nickel foam as the conductive substrate,Cr-doped cobalt molybdate was synthesized by using hydrothermal method,combined with alkali etching and surface phosphating treatment,PE-Cr-Co Mo O₄ catalyst was obtained.Electrochemical tests show that the catalyst has an overpotential of only 52.7 m V and a Tafel slope of 71.5m V dec^-1 at a current density of 10 m A cm^-2,with a 24-hour catalytic reaction stability.Structural characterization and analysis of experimental results show that the addition of Cr inhibits the further oxidation of Co²⁺,regulates the internal electron transfer of the material,and is beneficial to improve the intrinsic catalytic activity and stability of the material.Alkali etching not only increases the specific surface area,but also helps to adsorb water molecules and promote the Volmer process.Finally,the phosphating process greatly improves the catalytic performance and stability of the material.In addition,the presence of Mo O₂ increases the electron transfer rate on the surface of the material and weakens the adsorption strength of P component to H,which is beneficial to the desorption process of hydrogen molecules.The research in this thesis proves that the catalytic activity of the material can be greatly improved by appropriate surface phosphating modification,and the catalytic performance of the material can be effectively improved by means of surface alkali etching or element doping.At the same time,the experimental scheme is simple,the energy consumption is low,and it is beneficial to large-scale commercial application.It is expected to replace the noble metal-based hydrogen evolution electrocatalyst.At the same time,combined with characterization and analysis,the changes and effects of surface modification on the material itself were deeply discussed,which provided new ideas for designing advanced hydrogen evolution catalysts with high activity and high stability...