Investigations on the Thermal and Acid Treatment of Graphite Felt for Vanadium Redox Flow Battery Application

In this paper, the effects of thermal treatment and acid treatment on the performance of graphite felt for vanadium redox flow battery (VRB ) were investigated by cyclic voltammograms, polarization curves and AC impedance measurements. Both thermal treatment and acid treatment can improve the activity of graphite felt and the thermally treated graphite felt exhibited better activity and reversibility for both positive and negative electrodes of vanadium redox flow batteries. Results from polarization curves analysis showed that the polarization resistivity of thermally treated graphite felt was reduced by 45.5% compared to raw graphite felt while the polarization resistivity of graphite felt became larger after acid treatment. The results of AC impedance measurement revealed that charge transfer process were the control step of the electrode reaction and the thermally treated graphite felt had a lower reaction resistance compared to graphite felt with acid treatment.