Influence of the Oxygen Surface Functionalities Introduced by Electrochemical Treatment on the Behavior of Graphite Felts as Electrodes in VRFBs

Graphite felts act as electrodes in VRFBs thanks to their properties such chemical strength and electrical conductivity or 3D-structure. However, there are significant drawbacks be overcome, low wettability, sluggish kinetic reversibility electroactivity towards faradaic processes related vanadium electroactive species. As a consequence, it is key alter the fibres enhance electrochemical performance during battery operation. Most of previously reported modifications have been focused on incorporating surface oxygenated functional groups, even though role those groups electrocatalytic activity still not clear. Aiming gain knowledge this issue, work investigates influence electro-oxidation electro-reduction treatments, performed different acidic media (H2SO4 HNO3 solutions), subsequent response VO2+/VO2+ V3+/V2+ processes. The modified were analyzed understand two parameters that affect reaction catalysis: depth oxidation degree fibres. A treatment with HNO3, strong oxidizing agent, leads deep fibre development high density mainly C=O, which hinder redox reactions vanadium, especially for from catholyte.