The zinc–cerium redox flow battery has the highest open circuit cell voltage (E cell = 2.4 V) of all the common redox flow battery (RFB) systems being investigated. In this paper, carbon polymer composite materials based on polyvinyl ester and polyvinylidene difluoride are investigated as the negative electrode for this RFB system. Electrolyte composition, particularly on the negative side, is found to play a key role in maintaining high (∼90%) coulombic efficiencies for the different charge durations, from 10 min to 4 h, examined. Energy efficiencies >60% are obtained for temperatures in the range 45 °C–55 °C when the zinc ion concentration in the methanesulfonic acid electrolyte is 2.5 mol dm−3. No dependence of the energy efficiency on the flow velocity is found, over the range 7.5 cm s−1–13.5 cm−1.