Nitrogen-Functionalized Metal Carbide-Modified Graphite Felt As a High Performance Electrocatalyst for an All-Vanadium Redox Flow Battery

Abstract

To improve the electrochemical performance of graphite felt (GF) electrodes in vanadium redox flow batteries (VRFBs), we synthesize nitrogen-doped tungsten carbide nanowires (N-WC NWs), which are grown on the surface of GF through the two-step approach. When applied to VRFBs, the prepared electrode exhibits an apparent electrocatalytic effect toward the VO2+/VO2 + and V3+/V2+ redox reaction compared with pristine GF. The presence of negatively charged density on nitrogen promotes the absorption of vanadium ions. The nanowire structure exposes more active sites for the redox reaction of vanadium ions. The prepared N-WC NWs-GF electrode displays the best electrochemical performance with energy and voltage efficiencies of 74.8% and 78.9%, respectively, which is much higher than those of 59.8% and 63.2% obtained from the pristine GF at 100 mA cm−2. The N-WC NWs-GF exhibited durability and stability in an acidic electrolyte during long-term operation for 100 cycles at the higher current density of 100 mA cm−2.