Study On The Effect Of Doping On The Electrocatalytic Oxygen Evolution Performance Of ZnO And Co₃O₄

With the development of the times and the continuous progress of human society,industrialization is also gradually accelerating its pace of progress.However,the development of industrialization has made the energy crisis and environmental pollution two major problems increasingly prominent.Fossil energy,as the main source of energy at present,is non renewable and polluting,which requires us to find other energy sources to replace the use of fossil energy.Hydrogen,as a pollution-free,highly thermal and renewable new energy source,is an ideal alternative to fossil fuels.As one of the main methods for hydrogen production,electrocatalytic water decomposition involves two and a half reactions,HER and OER.Compared to HER,the kinetic process of OER is slower,therefore,studying OER catalysts is currently a hot topic.Transition metal oxides are widely used in the study of OER catalysts due to their unique structure and excellent electrical properties.ZnO has attracted extensive attention due to its good properties such as easy growth,high cost efficiency,appropriate oxidation reduction potential and good electrochemical stability.In particular,under different growth parameters and technologies,the morphology of ZnO can be transferred from 1D nanostructures to 3D nanostructures,namely nanowires,nanorods,nanosheets,Nanoflower,nanosheets and nanospheres.Therefore,ZnO is widely used as a sacrificial template in cation exchange technology to obtain different crystal structures.Due to its unique spinel structure and different oxidation valence states,Co₃O₄ plays an excellent catalytic effect and good stability in OER reactions.However,compared to IrO₂ and RuO₂,their catalytic performance is still much worse.In this paper,doping method is used to change the original electronic structure of materials to improve the OER catalytic efficiency,as follows:Based on first principles calculations,the ZnO（001）surface was used as the research surface,and Co was doped into ZnO using cation exchange technology.The concentration of Co ranged from 0%to 100%.The results show that the introduction of Co can adjust the electronic structure of ZnO.With the increase of Co concentration,the band gap is greatly reduced.The system is tuned from semiconductor to metal,and the conductivity is significantly improved,which is conducive to OER.The introduction of Co has changed the charge arrangement,and the electrons are gradually concentrated at the active site.The combination between the oxygen-containing intermediate and the surface is greatly improved,so the OER overvoltage is reduced.The rate determination step has changed from the first step in pure ZnO to the third step in Co exchanged ZnO.In addition,Co_0.5Zn_0.5O exhibited the most popular OER activity with an overpotential of 0.4 V.Based on first-principles calculations,the Co₃O₄（100）surface was used as the research surface,and Zn was doped into Co₃O₄.The results showed that Zn doping changed the charge distribution,which led to the aggregation of electrons to the Co active site,and the combination between the oxygen containing intermediate and the surface was more suitable for OER catalysts.The incorporation of Zn not only reduces the overpotential of the Co octahedron at the active site,but also the overpotential of the Co tetrahedron at the non active site.However,Zn is not the active site,and the overpotential is high.