Thermally reduced graphite oxide as positive electrode in Vanadium Redox Flow Batteries

Two graphene-like materials, obtained by thermal exfoliation and reduction of a graphite oxide at 700 and 1000 degrees C, were studied as active electrodes in the positive half-cell of a Vanadium Redox Flow Battery (VRFB). In particular, that obtained at 1000 degrees C exhibited an outstanding electrochemical performance in terms of peak current densities (30.54 and 30.05 mA cm(-2) for the anodic and cathodic peaks at 1 mV s(-1), respectively) and reversibility (Delta E-p = 0.07 V). This excellent behavior is attributed to the restoration of sp(2) domains after thermal treatment, which implies the production of a graphene-like material with a high electrical conductivity and accessible surface area. Moreover, the residual functional groups, -OH, act as active sites towards the vanadium redox reactions. This represents a significant step forward in the development of highly effective VRFB electrode materials. (C) 2011 Elsevier Ltd. All rights reserved.