In common with most aqueous batteries, the vanadium redox flow battery generates a small amount of hydrogen during operation. Over the lifetime of the battery this leads to a gradual imbalance in the state-of-charge (SoC) of the positive and negative electrolytes, with a consequent loss in discharge energy. To slow the rate of capacity fade to an acceptable level commercial vanadium redox flow batteries operate with a rather restricted maximum SoC. Increasing this SoC limit would improve the electrolyte utilisation, but also increase the rate of hydrogen evolution. Therefore a novel approach to alleviate this imbalance is examined, namely by reacting the evolved H-2, from the parasitic reaction at the negative electrodes, with the charged positive electrolyte. Due to the very slow native rate of reaction between VO2+ and H-2 at room temperature a series of potential catalysts are examined. Finely dispersed Pt, Ir and Pt-Ru on carbon paper are found to accelerate the reaction, with Pt-Ru being the most active. (C) 2012 Elsevier B.V. All rights reserved.