Electrochemical Evaluation of Different Graphite Felt Electrode Treatments in Full Vanadium Redox Flow Batteries

The use of flow batteries for energy storage has attracted considerable attention with the increased use of renewable resources. It is well known that the performance of a flow battery depends, among other factors, on the properties of the electrodes, which are generally composed of graphite felt (GF). In this work, thermal, chemical and plasma treatments have been employed to modify the surface of the graphite felt to improve the electrochemical activity of the redox flow cell. The influence of the variables of each of these processes on the generation of surface functional groups and on changes in the obtained surface area have been examined. In this work, the kinetics of redox reactions relevant to the VO2+/VO2+ reaction have been studied with these treated electrodes and the relationship between the nature of the surface and electrochemical activity of the GF is discussed. As a result, an enhanced electrochemical performance (reduction over 200 mV of the separation between anodic and cathodic peaks and 110 mV of the onset potential) in comparison to the untreated GF is obtained for those GF treatments with low oxygenated groups concentration.