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

Catalyzing vanadium redox reactions in VRFBs with transition metal oxides is an effective and affordable approach. In this study, the surface electron distribution of TiO 2 was regulated by introducing oxygen vacancies into its lattice, enabling the electrode to exhibit outstanding catalytic efficacy in VO 2 + /VO 2+ and V 3+ /V 2+ redox transformations and suppress the detrimental side reaction (HER and OER) simultaneously. Benefiting from the enhanced catalytic activity and selectivity, the 1000-TiO 2 -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 TiO 2 provides more extra electrons to its neighboring titanium, further strengthening the interaction between the electron-rich titanium and oxygen in VO 2 + /VO 2+ , thus enhancing its catalytic performance. The enhanced catalytic activity for V 3+ /V 2+ on oxygen vacancy-rich TiO 2 coating can be attributed to the effective suppression of hydrogen evolution reaction, which can occupy active sites exclusively and produce detrimental H 2 bubbles. This insight provides valuable guidance for the innovative design of catalysts in vanadium redox flow batteries.