We, for the first time, demonstrate a facile preparation of N, O dual-doped carbon felt (CF) as electrodes in all-vanadium redox flow batteries (VRFB). N-2 and O-2 plasma was employed to treat the CF, introducing nitrogen and oxygen atoms doped into the carbon felt to result in the improved electrocatalytic activity and enhanced interaction of CF-electrolyte during the battery operation. The energy efficiency of the as-assembled VRFB is improved from 65% (pristine) to 78% (doped) at a current density of 50 mA cm(-2) with excellent cycling stability. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.