Preparation Of ZIF-derived Metal Oxides And Their Electrocatalytic Oxygen Evolution Performance Study

Hydrogen is a clean energy carrier with high energy density and various applications.It is considered as the most ideal substitute for fossil fuels and able to alleviate the climate and energy crisis caused by extensive use of fossil fuels.Hydrogen production from proton exchange membrane water electrolysis is one of the most popular methods.In the acidic electrolytic water hydrogen production process,the oxygen evolution reaction（OER）at the anode involves multiple proton-coupled electron transfer,which leads to slow thermodynamic and kinetic processes that seriously affect the energy conversion efficiency of the entire hydrolysis electrolyzer.In addition,the highly corrosive acidic environment also requires the catalyst itself to be highly resistant to acidic corrosion in order to ensure that it can act as a catalyst for a long time.Therefore,the development of OER catalysts that can work efficiently in acidic media for a long time is of great significance and value to advance the upgrading of electrolytic water to hydrogen technology and large-scale industrial applications.Cobalt-based zeolite imidazolate framework（ZIF-67）is a porous material with both metal-organic framework and zeolite properties.Its derived cobalt-based metal oxide inherits its structural properties and is considered as one of the most promising non-precious metal OER catalysts,but its catalytic performance still needs to be enhanced to meet practical needs.This thesis focuses on a ZIF-67-derived cobalt-based metal oxide catalyst with excellent acid corrosion resistance,which is modified by introducing a series of transition metal atoms（Mn,Cu,Zn,Ru）using a cation exchange-pyrolysis process,and investigates the electrocatalytic oxygen precipitation performance of the catalyst in acidic media.The main works of this thesis are as follows:（1）A series of transition metal-doped cobalt-based metal oxides were prepared by using ZIF-67 nanoparticles synthesized via surfactant-mediated method as precursors for acidic OER catalysts.Electrochemical test results show that the best performing Ru-doped Co₃O₄ has an overpotential of 250 m V@10 m A cm^-2,which is better than commercial Ru O₂.The large surface area of ZIF-67-derived Co₃O₄ greatly improves the utilization of precious metal Ru,and the electronic coupling between Co and Ru also makes an important contribution to the improvement of catalyst OER activity.In addition,the optimal Ru-doped Co₃O₄ catalyst has a stability of more than 100 h.（2）First-principles theoretical calculations of the oxygen evolution performance of ZIF-67-derived cobalt-based metal oxide catalysts in acidic media were carried out.The relevant reaction path energy calculations show that the introduction of Ru can further enhance the non-electrochemical kinetic rate of water dissociation based on the reduction of the thermodynamic Gibbs free energy of the electrochemical step and the enhancement of the adsorption of the OER reaction intermediate OOH*,and the two factors synergistically enhance the oxygen precipitation reaction activity under acidic conditions.The structure-activity relationship between the surface electronic structure of the catalyst and the reaction activity of the catalyst was studied by coupling experimental characterization with first-principles theoretical calculation,which provided valuable reference for guiding the design and preparation of high-efficiency oxygen evolution reaction catalyst.