Titanium oxide covers graphite felt as negative electrode for vanadium redox flow battery by liquid phase deposition

Abstract

Using a mixed solution of (NH₄)₂TiF₆ and H₃BO₃, this study performed liquid phase deposition (LPD) to deposit TiO₂ on graphite felt (GF) for application in the negative electrode of a vanadium redox flow battery (VRFB). The results revealed that LPD-TiO₂ uniformly coated GF, effectively transforming the original hydrophobic nature of GF into a superhydrophilic nature. After annealing at 500 ℃ in an atmospheric environment, the oxygen vacancies in the TiO₂ thin film were optimized, considerably enhancing its mass transfer efficiency and electrochemical activity. The VRFB comprising the LPD-TiO₂/GF negative electrode achieved a coulombic efficiency, voltage efficiency, and energy efficiency of 96.2%, 71.8%, and 69.3%, respectively, at 125 mA/cm², which were significantly superior to the corresponding efficiencies of 95.7%, 60.3%, and 57.7%, respectively, achieved by the VRFB with the acid cleaned GF. These findings demonstrate that the proposed technology has great potential for application in VRFBs.