Nature of oxygen vacancy in accelerating redox kinetics of V2+/V3+in flow batteries

The rational design of oxygen vacancy in metal oxide based catalysts is an effective strategy to enhance their intrinsic activity by influencing the microelectronic structure. However, the impact of oxygen vacancy on the reaction kinetics and the catalytic mechanism in vanadium redox flow batteries (VRFBs) remains under-explored. Herein, a novel approach is developed to regulate the concentration of oxygen vacancy in TiO2 nanoplates for high performance VRFBs. The oxygen vacancy-rich TiO2 efficiently facilitates the desorption and electron transfer process of V3+ during the electrochemical oxidation process. Owing to the enhanced electrochemical oxidation of V2+ to V3+, the inherently sluggish reaction kinetics of V2+/V3+ is significantly accelerated. The battery assembled with oxygen vacancy-rich TiO2 achieves an energy efficiency of 79.81 % at 200 mA cm- 2 and outstanding long-term durability. This work not only elucidates the nature of oxygen vacancy in accelerating the redox kinetics of V2+/V3+ but also offers insights for rationally designing efficient catalysts for VRFBs.