Characteristics of graphite felt electrode electrochemically oxidized for vanadium redox battery application

The graphite felt was oxidized at a positive electrode potential in sulfuric acid solution. The electrochemical performance of the treated graphite felt served as electrode for vanadium redox battery was investigated with FT-IR, SEM, XPS, BET, cyclic voltammetry and testing VRB system, respectively. The results show that the molar ratio of O to C increases from 0.085 to 0.15 due to the increase of —COOH functional groups during electrochemical oxidation treatment, and the GF surface is eroded by electrochemical oxidation, resulting in the surface area increase from 0.33 m2/g to 0.49 m2/g. The VRB with modified GF electrode exhibits excellent performance under a current density of 30 mA/cm2. The average current efficiency reaches 94% and average voltage efficiency reaches 85%. The improvement of electrochemical activity for the electrode is ascribed to the increase of the number of —COOH group and the special surface of GF.