Construction Of Iron-based Composite System And Its Derivation Behavior In Electrocatalytic Oxygen Evolution Process

In order to solve the problems of energy depletion and environmental pollution caused by the combustion of traditional fossil fuels,the development of clean and renewable energy is imminent.Among various alternatives,hydrogen is considered to be one of the most ideal energy carriers.Compared with traditional fossil fuel hydrogen production,hydrogen production by electrolysis of water has the advantages of environmental protection,low cost,large-scale production,and high purity hydrogen.Its core process includes the hydrogen evolution reaction（HER）at the cathode and the oxygen evolution reaction（OER）at the anode.Among them,the OER process has become a bottleneck in the development of electrolyzed water due to the multi-electron transfer involved and slow kinetics.Therefore,efficient catalysts are needed to accelerate the reaction process and lower the kinetic energy barrier of the water splitting reaction.Currently,Ru O₂and Ir O₂have been considered as benchmark catalysts for OER,but these noble metal catalysts are costly and unstable under alkaline conditions.However,transition metal compounds have the characteristics of low cost and abundant content,and have become strong candidates for OER catalysts,but there are still problems of low stability and OER catalytic activity that still need to be improved.In view of this,this thesis takes iron-based composites as the research object to explore the method of preparing high-performance OER catalysts,and at the same time explore the relationship between its catalytic behavior,catalytic performance and structure and components.The main work is as follows:（1）Using cobalt chloride and 1,1’-ferrocenedicarboxylic acid（Fc）as raw materials,two-dimensional sheet-like Co Fc-MOF/NF materials were prepared on the surface of nickel foam（NF）by hydrothermal synthesis.As an oxygen evolution reaction catalyst,it has a low overpotential of only 268 m V at a current density of 50 m A cm^-2in 1 mol L^-1KOH.This performance exceeds that of most bimetallic catalytic materials.Characterization results analysis surface:During the catalytic process,Co Fc-MOF undergoes obvious phase evolution behavior,forming oxyhydroxide or hydroxide.This synergistic effect between the in situ-derived active species and the Co and Fe sites is responsible for the excellent electrocatalytic performance of this material.（2）Using Fe³⁺and[Mo₇O₂₄]^6-as raw materials,amorphous Fe-POMo/NF materials were synthesized by solvothermal method,and the diffusion leaching of[Mo₇O₂₄]^6-anions led to phase reconstruction during the oxygen evolution process.The obtained low-crystalline oxyhydroxides with a large number of vacancies are supported on the electrode surface,and this in situ-derived active species exposes more active sites,leading to an increase in catalytic activity.In 1 mol L^-1KOH,it only has a low overpotential of 216 m V at a current density of 10 m A cm^-2and can still maintain 94.1%of the initial current density after 48 hours of reaction,showing excellent catalytic activity and high stability.（3）Amorphous Co Fe-B materials were facile and scalable prepared by using sodium borohydride as a reducing agent.As an oxygen evolution reaction catalyst,it has only a small Tafel slope of 38.8 m V dec^-1and a low overpotential of 274 m V at a current density of10 m A cm^-2in 1 mol L^-1KOH.This performance exceeds that of most bimetallic powder-like catalytic materials.Characterization results analysis surface:Co Fe-B has obvious phase derivation behavior.During the oxygen evolution process,the diffusion and leaching of B⁺cations lead to the oxidation of the catalyst surface and the reconstruction process of oxyhydroxide promotes the electron transfer and mass transfer process.