Modification of graphite electrode materials for vanadium redox flow battery application—I. Thermal treatment

The thermal activation of graphite felt was investigated at a range of temperatures and treatment times so as to enhance the electrochemical performance of this material for use in the vanadium redox cell. Graphite felt treated thermally at 400°C exhibited the greatest improvement in performance of the vanadium cell. Energy efficiencies of over 88% were obtained after this treatment compared with only 78% for the untreated felt. Results from XPS analysis showed that surface functional groups of CO and C  O increased dramatically compared with untreated samples, suggesting that these functional groups behave as active sites for the vanadium redox reactions.