KHCO3 activated carbon microsphere as excellent electrocatalyst for VO2+/VO2~+ redox couple for vanadium redox flow battery

In this paper,carbon microsphere prepared by hydrothermal treatment was activated by KHCOat high temperature,and employed as the catalyst for VO/VO~+redox reaction for vanadium redox flow battery(VRFB).Carbon microsphere can be etched by KHCOdue to the reaction between the pyrolysis products of KHCOand carbon atoms.Moreover,KHCOactivation can bring many oxygen functional groups on carbon microsphere,further improving the wettability of catalyst and increasing the active sites.The electrocatalytic properties of carbon microsphere from hydrothermal treatment are improved by high temperature carbonization,and can further be enhanced by KHCOactivation.Among carbon microsphere samples,the VO/VO~+redox reaction exhibits the highest electrochemical kinetics on KHCOactivated sample.The cell using KHCOactivated carbon microsphere as the positive catalyst demonstrates higher energy efficiency and larger discharge capacity,especially at high current density.The results reveal that KHCOactivated carbon microsphere is an efficient,low-cost carbon-based catalyst for VO/VO~+redox reaction for VRFB system.