The Fabrication Of Cobalt-nickel Oxide Nanomaterial And Its Electrocatalytic Properties

Oxygen reaction?OER/ORR?plays a pivotal role in application of the new energy devices such as metal-air batteries.Recently,bifunctional oxygen catalysts have received extensive attention.Pt,RuO₂ and IrO₂ are considered to be the best catalysts for the catalytic oxygen reaction,but their further development is obstructed by several factors such as higher cost and poor cycle stability.Therefore,preparaing highly active,stable catalysts that can replace precious metals is a valuable research.Nickel-cobalt oxide is a spinel-type transition metal oxide.Its two-dimensional structure can provide a large reaction area and more active sites for catalytic reactions,besides,there are two oxygen gaps in its microscopic crystal structure and a variety of metal ion oxidation states.Therefore,it is very meaningful to prepare two-dimensional nickel-cobalt oxide material to optimize the number of active sites on the surface and improve the electrocatalytic performance.?1?A shape-control of hexagon nickel cobalt oxide spinel nanosheets was prepared via co-precipitation and sintering process and the atomic ratio of Ni and Co in raw materials was 0/1 in Co₃O₄ or 1/4.Through simply tuning annealing temperature,different Ni³⁺/Ni²⁺and Co³⁺/Co²⁺atomic configurations on nickel cobalt oxide surface were controllably synthesized.In detail,the oxide treated at250°C has highest value of Ni³⁺/Ni²⁺sites and lowest value of Co³⁺/Co²⁺sites and the oxide treated at 450°C has lowest value of Ni³⁺/Ni²⁺sites and highest value of Co³⁺/Co²⁺sites.Electrochemical results show that the oxide with highest value of Ni³⁺/Ni²⁺sites and lowest value of Co³⁺/Co²⁺sites own the best bifunctional electrocatalytic performance.Besides,it has a longer stable catalytic performance,comparing to RuO₂ and Pt/C.Overall,the remarkable electrocatalytic activity can be ascribed to the following reasons.First,the enriched Ni³⁺and Co²⁺species provide more active sites for OER/ORR,which optimizes the adsorption/desorption energy barrier of molecular oxygen,so accelerating the overall reaction kinetics.Second,the considerable electrical conductivity ensures the efficient electron transfer during the catalytic process.Third,the 2D nanosheets and pore structure offer larger specific surface area,which facilitates the diffusion of oxygen and electrolyte.?2?The graphene-like nickel-cobalt oxide nanofilm was prepared by a one-step hydrothermal method.The effect of different Ni doping amounts on OER/ORR electrocatalytic performance was studied on alkaline conditions.The test results showed that when the atomic ratio of Ni/Co is 1/1 has the best bifunctional catalytic performance.At this Ni/Co ratio,the nickel-cobalt element achieves the optimal ratio,and the special structure of the film also provides a powerful condition for catalysis.The Zn-air battery was tested under simulated reality conditions.The Zn-air battery cycling charge and discharge can work exceed 60 h,showing its relatively stable cycle charge and discharge performance.