Study Of Preparation Of Co Based Catalyst And Its Electrocatalytic Oxygen Reduction And Oxygene Evolution Reaction Performances

Zinc-air battery is widely concerned because of its high energy density,abundant raw materials,environmental protection,safety and low cost.However,the sluggish kinetics of oxygen reduction reaction?ORR?and oxygen evolution reaction?OER?processes in Zinc-air battery leads to high overpotential and low catalytic efficiency.Platinum and iridium/ruthenium based noble metal catalysts are considered to be highly efficient electrocatalysts for ORR and OER,but their scarcity and high cost greatly limit their practical application.It is of great significance for the development of Zinc-air batteries to study the bifunctional catalytic activity and low cost electrocatalysts.Co based catalysts have attracted wide attention due to their excellent ORR and OER performance.The Co microspheres coated with porous carbon,the sea urchin like spinel Ni Co₂O₄ and ZIFs-Co NC polyhedron catalysts were prepared by a simple synthesis method through this article,its elements composition,structure and mechanism were analyzed,and its electrocatalytic performance was studied to improve the performance of Co based non noble metal catalyst.The research contents are as follows:?1?Study of preparation and electrocatalytic performances of Co microspheres coated with porous carbon.Firstly,Co precursor spheres were prepared by hydrothermal method,and then porous carbon coated Co microspheres?Co/PC?were obtained by carbonization through self polymerization of dopamine hy drochloride.The phase and morphology of the samples were analyzed by XRD and SEM characterization techniques.The electrochemical test shows that Co/PC has a high ORR performance,with an initial potential of 0.886 V,a half-wave potential of 0.712 V,a limiting current density of 5.50 m A cm^-2 and a Tafel slope of 81 m V dec^-1.When the current density is 10 m A cm^-2,the overpotential of Co/PC is 438 m V.The structure of porous carbon coated Co microspheres make the catalyst disperse independently,effectively avoid the agglomeration and loss of Co,and increase the stability and durability of the catalyst.The porous structure and high specific surface area of carbon are conducive to mass transfer,and obtain the catalyst with both catalytic activity and stability.?2?Study of preparation and electrocatalytic performances of sea urchin like spinel Ni Co₂O₄.The sea urchin like spinel Ni Co₂O₄ was prepared by hydrothermal method with cobalt nitrate and nickel nitrate as raw materials.XRD characterization proved that the synthesized Ni Co₂O₄ was spinel structure,and its morphology was sea urchin like structure by SEM observation.The electrochemical performance test showed that sea urchin like spinel Ni Co₂O₄obtained by hydrothermal reaction for 10 h has high ORR activity,with an initial potential of 0.905 V,a half-wave potential of 0.796 V,and a limiting current density of 5.475 m A cm^-2.At the same time,it also has a good OER activity.At the current density of 10 m A cm^-2,the overpotential is 421 m V,and the Tafel slope is 72 m V dec^-1.Its unique structure has abundant active sites,and Ni doping improves the conductivity and promotes the charge transfer in the electrocatalytic process,showing good ORR and OER bifunctional catalytic activity.?3?Study of preparation and electrocatalytic performances of ZIFs-Co NCwas prepared by one pot solvent method with cobalt nitrate and zinc nitrate provided the metal source and 2-methylimidazole as the organic linker,then the ZIFs-Co NC-x:y polyhedron was obtained by calcination at high temperature.The elemental composition and morphology of the elements were analyzed by XRD and TEM.The results of electrochemical performance test showed that the ZIFs-Co NC-3:1 polyhedron has good ORR activity,with an initial potential of0.935 V and half wave potential of 0.846 V.ZIFs-Co NC-3:1 polyhedron showed higher OER activity,with an overpotential of 372 m V at current density of 10m A cm^-2,and a lower Tafel slope(76 m V dec^-1).The porous structure and high specific surface area of ZIFs-Co NC-3:1 polyhedron are conducive to the exposure of more active sites and promote the progress of the reaction,showing higher electrocatalytic oxygen reduction and oxygen evolution performance.