Preparation And Properties Of Cobalt Oxide Based Oxygen Reaction Electrocatalyst

Energy is one of the biggest challenges during the development of human society.With the growing demand for energy consumption,the use of renewable energy can reduce CO₂emissions and mitigate climate change.Metal-air batteries,as a new type of electrochemical energy storage device,have attracted extensive attentions due to their high energy density,low cost,and environmental friendliness.Oxygen reduction reaction（ORR）and oxygen evolution reaction（OER）are key steps for oxygen electrodes in metal-air batteries,but their slow kinetics hinder the large-scale commercialization of metal-air batteries.The development of efficient and low-cost oxygen reaction catalysts is crucial for the application of metal-air batteries.Herein,three types of cobalt oxide-based catalysts were prepared and their oxygen catalytic performance was studied.The specific research contents are as follows:（1）A simple room temperature acid etching strategy was used to fabricate V_oon the surface of Co₃O₄.By changing the acid etching time,a series of Co₃O₄-V_owith different oxygen vacancy concentrations were prepared.It was found that the concentration of oxygen vacancies in Co₃O₄-V_ogradually increased with the prolongation of acid etching time.Moderate V_oconcentration caused by controlled acid capture time（less than 32 h）can elevate the electrical conductivity and optimize the electronic structure,while excessive V_oinduced by overlong acid capture time（reaching 64 h）will lead to enlarged energy band gap and declined electrical conductivity.In addition,lengthy acid capture treatment also results in the structure collapse of Co₃O₄microspheres,which is detrimental to the exposure of catalytic sites and accessibility of electrolyte.Consequently,the resultant Co₃O₄-V_o-32（32 represents acid capture time）achieves a good balance on V_oconcentration and structure stability,thus displaying much better OER performance than the counterparts.（2）The original Co₃O₄is treated by acid etching,and the obtained oxygen vacancy（V_o）decorated Co₃O₄（Co₃O₄-V_o）was used as the precursor to synthesize P-doped Co₃O₄（P-Co₃O₄-V_o）through low-temperature pyrolysis process.It is found that acid etching can create V_oin Co₃O₄,and the as-formed V_oas active doping sites is conducive to more efficient P doping effect.Doping P element into Co₃O₄can not only effectively improve its intrinsic conductivity,but also optimize its electronic structure and chemical composition,thereby improving its oxygen evolution（OER）performance.（3）Home-made defective carbon fibers（CNFs-D）/Co O hybrid electrocatalyst is successfully prepared by a simple impregnated adsorption method followed by pyrolysis process using CNFs-D as carbon precursor.The results show that the as-prepared CNFs-D/Co O hybrid electrocatalyst shows much better bi-functional oxygen catalytic performance when compared to other comparison samples.And this excellent oxygen catalytic performance is mainly due to the fact that CNFs-D possesses larger specific surface area,higher defect degree and stronger interaction with cobalt source.