Accessing the electrocatalytic activity of two-dimensional carbons for vanadium redox reactions using Ti as a stable and inert substrate electrode
摘要
The performance of graphene, nanocrystalline graphene, and nitrogen-doped graphene (NG) towards the V(IV)/V(V) redox couple of the vanadium redox flow battery was assessed using Ti as an inert and stable substrate electrode. Graphene and nitrogen-doped graphene were synthesized by atmospheric pressure chemical vapor deposition on Cu substrates and transferred to the Ti electrode, while it is shown that nanocrystalline graphene can be grown directly on Ti. Raman spectroscopy, X-ray photoelectron spectroscopy, and Raman mapping analysis of the sp2 carbons provide insights into the physical features of these electrodes. Irreversible cyclic voltammetry results reveal remarkable electrochemical activity towards the V(IV) → V(V) redox reaction compared to the bare Ti support. Density functional theory calculations simulate the probable growth pattern of nanocrystalline graphene on Ti and the possible sources of the redox properties of nanocrystalline graphene and nitrogen-doped graphene. The combination of the defect-rich nature of NCG and the enhanced active sites provided by nitrogen doping in NG leads to significantly improved redox reaction kinetics. These results will guide future studies in developing both catalytically active and stable materials for large-scale energy storage systems.