The Synthesis And Performance Study Of Self-supported Transition Metal Oxides For Oxygen Evolution Reaction

Water electrolysis technology is the most effective means to deal with the increasingly severe global energy and environmental problems,and the oxygen evolution reaction at anode has become a limiting step in water electrolysis technology due to its slow kinetic process.Transition metal oxides show great potential in electrochemical oxygen evolution reactions due to their low price,abundant reserves,and controllable structure,composition,valence and morphology.The type and exposure degree of active sites of transition metal-based oxide catalysts and their own electrical conductivity are important factors that determine the oxygen evolution reaction activity of catalysts.By changing the electronic structure of transition metal-based oxides,increasing the specific surface area,Effective strategies such as increasing the exposure of active sites and coupling active materials to different substrates,rationally designing catalyst structures can improve their catalytic activity.In this dissertation,the main research object is transition metal-based oxides.Based on the existing experiments,combined with the advantages of self-supported catalysts,new and efficient electrochemical oxygen evolution catalysts are explored and synthesized through effective strategies.The main contents are as follows:1.In this work,nickel-iron bimetallic oxides are used as the research object,and metal-organic framework materials are used as the precursor.Ni Fe-MOFs precursors are first synthesized on a nickel foam substrate,and then Rod-like nanosheet array OER electrocatalysts Ni_0.6Fe_2.4O₄ is synthesized by annealing in air.Various experimental test data show that the structure of the rod-shaped nanosheet array exposes more catalytic sites and optimizes the electronic structure advantage.At the same time,the introduction of the metal substrate also improves the overall conductivity of the nickel-iron bimetallic oxide material.Due to these designs,the Ni_0.6Fe_2.4O₄ rod-like nanosheet array electrocatalyst exhibits a small overpotential of 215 m V(current density of 10m A cm^-2)and a Tafel slope as low as 40.7 m V dec^-1.2.This work takes nickel-cobalt double-metal oxides as the research object,and achieves the purpose of improving the catalytic activity of nickel-cobalt double-metal oxides by introducing defect engineering and design strategies of self-supporting structures.In the experiment,layered double metal hydroxide is used as the basic material,and metal aluminum element is introduced into the precursor.In the later synthesis process,it is removed by an alkaline etching step,thereby introducing a variety of vacancy defects.At the same time,the foamed nickel substrate enhanced the electrical conductivity of the material and the structural advantages of 2D nanosheets made the Ni Co₂O₄/NF material exhibit excellent OER catalytic performance under alkaline conditions.The Ni Co₂O₄/NF catalyst has an overpotential of only 265 m V at a current density of 10 m A cm^-2,and a lower Tafel slope value of 61.4 m V dec^-1.