The effect of water activation on the electrochemical activity of GF is investigated. A high content of oxygen-containing groups improves the performance of VRFB. Improved wettability due to increased surface-active oxygen functional groups. WA-GF-5 min improves battery energy efficiency from 69.84% to 78.12% at 80 mA cm-2. WA-GF-5 min acts as more powerful positive electrode for the VO2+/VO2+ redox couple.