Enhanced vanadium redox reaction catalytic properties enabled by tunning oxygen vacancy in rutile tio2 coated graphite felt electrodes

Abstract

Abstract Catalyzing vanadium redox reactions in VRFBs with transition metal oxides is an effective and affordable approach. In this study, the surface electron distribution of TiO2 was regulated by introducing oxygen vacancies into its lattice, enabling the electrode to exhibit outstanding catalytic efficacy in VO2 +/VO2+ and V3+/V2+ redox transformations and suppress the detrimental side reaction (HER and OER) simultaneously. Benefiting from the enhanced catalytic activity and selectivity, the 1000-TiO2-GF electrode sustained a stable operation for 100 cycles at 120 mA cm−2 with no discernible efficiency degradation. The DFT results indicate that oxygen vacancy in TiO2 provides more extra electrons to its neighboring titanium, further strengthening the interaction between the electron-rich titanium and oxygen in VO2 +/VO2+, thus enhancing its catalytic performance. The enhanced catalytic activity for V3+/V2+ on oxygen vacancy-rich TiO2 coating can be attributed to the effective suppression of hydrogen evolution reaction, which can occupy active sites exclusively and produce detrimental H2 bubbles. This insight provides valuable guidance for the innovative design of catalysts in vanadium redox flow batteries.