The Preparation And Electrocatalytic Performances Study Of Doping Transition Metal Cobaltates

Fuel batteries own the advantages of high energy conversion efficiency,wide applications and environment friendly as the new candidate of traditional fossil power.As determined steps of the performance of batteries,the oxygen reduction reaction and oxygen evolution reaction that happen at electrode react slowly and hider the practical applications.The electrocatalytic materials can accelerate the electrode reaction and improve the performance of batteries.So,the exploration of superior electrocatalysts is of great significance.The representative spinel-type materials AB2O4(Both of A and B are transition metals)electrocatalysts for oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)have been investigated widely and significant improvements have been achieved in the activity and durability.But FeCo2O4 was not explored widely like ZnCo2O4 or NiCo2O4 as the electrocatalyst for its relatively complicated atomic site occupation.FeCo2O4 has a tylpical cubic spinel structure with Co2+ in the tetrahedron and Co3+ and Fe3+ in the octahedron.A mixture of Co3+ and Fe3+ in the B site makes the oxide has a wider overlap between transition metal 3d orbit and O 2p orbit,which can lead to an effective charge transfer in the rate-determining steps of ORR process and then enhance the electrocatalytic activity.The high electronic conductivity and specific surface area of rGO can accelerate charger transfer and provide more catalytic sites,which would contributes to a faster ORR process.Meanwhile,as a valence alterable element,Mn shows outstanding performance in electrocatalysis area according to the pervious reports.The above conditions provide the possibility for optimizing the electrocalytic performance of spinel-type FeCo2O4 material.The paper chooses electrolytic tank as experimental environment for oxygen catalytic tests and controls the experimental conditions rigorously to obtain reliable experimental results.The work of the paper is as follow:(1)The CoFeCoO4 microparticles that synthesized by hydrothermal technology were characterized by XRD to obtain the information of crystal structure.The spindle micromorphology and porous structure were characterized by SEM and Nitrogen adsorption-desorption isotherm,respecitively.The CoFeCoO4 microparticles were assembled on the rGO surface to obtain the CoFeCoO4/rGO composite,which exhibited enhanced ORR activity and catalytic stability comparable to that of Pt/C.On the other hand,the oxygen evolution reaction catalytic activity of the prepared samples was also studied.The results demonstrated the potential of CoFeCoO4/rGO as a bifunctional oxygen catalyst.(2)A part of Co element at B site in FeCo2O4 was doped by Mn to prepare the FeCo1.6Mn0.4O4 microspheres.The characterization methods were used to test the information of crystal structure,micromorphology and so on.The oxygen reduction reaction catalytic performances and stability of sample and Pt/C were tested.The results showed that the sample can be an ORR electrocatalyst.The work found an enhanced performance CoFeCoO4/rGO catalyst for bifunctional reaction and a superior FeCo1.6Mn0.4O4 catalyst for oxygen reduction reaction,respectively.