Mesoporous graphitic carbon on graphene oxide: A high-performance catalyst for vanadium redox flow batteries

Abstract

Graphene oxide templated carbon framework (GOTCF) was synthesized on the surface of graphene oxide (GO) as a highly efficient catalyst for vanadium redox flow batteries (VRFBs). A two-step synthesis involving microwave irradiation and post-treatment resulted in enhanced catalytic performance towards vanadium ion redox reactions (VIRR) through the formation of graphitic carbon with porous structure and high oxygen-containing functional group content. Subsequent to post-treatment, a 15-fold increase in surface area with a predominantly mesoporous feature compared to pristine GO was observed without a significant decrease in oxygen content, optimizing electron and ion transport, thereby enhancing catalytic activity towards VIRR. Electrochemical evaluations demonstrated the superior performance of the GOTCF electrodes for VIRR, as evidenced by the greater than 50 % reduction in charge transfer resistance and approximately 30 % higher peak current densities compared to those of the electrode utilizing pristine GO. Single-cell VRFB tests revealed that the GOTCF-based electrodes achieved significantly higher energy efficiencies and stable capacity performance, even under high current density conditions (400 mA cm⁻²). Moreover, after 500 cycles, the GOTCF electrodes retained over 89.3 % of their initial capacity, surpassing the durability of GF and GF/GO electrodes, thus confirming their potential as robust catalysts for VRFB applications.