An electrochemically activated graphite electrode with excellent kinetics for electrode processes of V(II)/V(III) and V(IV)/V(V) couples in a vanadium redox flow battery

An electrochemically activated graphite electrode (EAGE) was obtained by a simple and moderate method of anodic potentiostatic polarization. The composition, microstructure, and electrochemical properties of the EAGE were characterized by high-resolution X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. The results show that the electrochemical activity and the reversibility for electrode processes of V(II)/V(III) and V(IV)/V(V) couples on the EAGE are significantly improved due to the introduced CO and COOH groups. The rate constant of charge transfer for the anodic oxidation of V(IV) on the EAGE was determined to be 8.17 × 10⁻⁴ cm s⁻¹, which is about 20 times larger than the 4.09 × 10⁻⁵ cm s⁻¹ rate constant on the pristine graphite electrode.