Study On The Regulation Mechanism Of Electrocatalytic Performance Of Cobalt Oxide For Oxygen Evolution Reaction

Electrolytic water reaction is an effective way to convert renewable energy into hydrogen energy.However,the high overpotential and reaction barrier of anodic oxygen evolution reaction（OER）,as well as the high cost of commercial precious metal catalysts,hinder the further development and application of water electrolysis technology.Therefore,it is necessary to develop efficient and low-cost OER electrocatalysts.Cobalt oxide is one of the most promising catalysts due to its excellent electrochemical performance and stability.Introducing oxygen vacancy and doping are important methods to improve the intrinsic activity of cobalt oxides.Based on this background,this paper took cobalt oxides as the research object.The micro mechanism of the oxygen vacancy（V_O）effect on the OER electrocatalytic performance of cobalt oxide（CoO）was studied.Considering that metal oxides are easily oxidized to hydroxyl oxides in alkaline electrolyte,the effect of（Fe,Co）co-doping on the OER electrochemical performance of cobalt oxyhydroxide（CoOOH）was further studied.The surface reconstruction and its effect on the V_Oformation and OER performance of CoO（111）surface were studied using the first principles calculations.The surface reconstruction from the CoO₆octahedrons to the CoO₄tetrahedrons was revealed at CoO（111）surface,which enhanced the OER activity and the stability of V_Oat the surface of CoO（111）.The existence of V_Ochanged the electron accumulation around the Co atoms and the bonding state between Co and O atoms,and thus,affected the adsorption of hydroxyl group and deprotonation process.By analyzing the electron structure,the nature of the activity changed at Co sites due to the surface reconstruction and the introduction of V_Owas revealed.The underlying mechanism of Fe Ni-codoping effect on the OER performance of CoOOH was studied by both experiments and first principles calculations.The Fe Ni-codoped CoOOH as oxygen evolution reaction（OER）electrocatalyst was prepared successfully by simple electrodeposition and anodic oxidation methods,which exhibited a 247 m V low overpotential at 10 m A cm^-2and good stability after100 h.It was revealed that the reaction kinetics increased after doping Fe and Ni.Thermodynamically,Fe-doping changed the active site from Co to Fe and the Gibbs free energy change of adsorbing hydroxyl group decreased.However,the strong adsorption of the hydroxyl group made the next deprotonation step difficult.Ni doping benefited the electron transfer between Fe and intermediates and further balanced the two steps by enhancing the Fe-O covalent components.The results provided a theoretical basis for the rational design and application of Co-based OER catalysts.