Graphite Felt Coated with Dopamine-Derived Nitrogen-Doped Carbon as a Positive Electrode for a Vanadium Redox Flow Battery

A new method for the direct fabrication of nitrogen-doped graphite felt has been developed, the study of which demonstrates that the felt is an excellent positive electrode for vanadium redox flow batteries (VRFBs). Nitrogen-doped graphite felt was synthesized by the controlled deposition of a thin layer of polydopamine on the surface of graphite felt followed by pyrolysis in an Ar atmosphere. Taking advantage of the versatile capabilities of the coating, as well as its high nitrogen content, dopamine was demonstrated to be an effective precursor for the preparation of nitrogen-doped graphite. The dopamine-derived graphite felt exhibited outstanding electrochemical performance when employed as a positive electrode in a VRFB. It exhibited 236% and 44% increased discharge capacity at a current density of 150 mA cm−2 compared to pristine graphite felt and thermally oxidized graphite felt, respectively. The enhanced performance of the VRFB could be caused by the improved catalytic activity of dopamine-derived graphite felt, resulting from the formation of nitrogen functional groups active in the VO2+/VO2+ redox reaction and the increased specific surface area.