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 TiO 2 nanoplates for high performance VRFBs. The oxygen vacancy-rich TiO 2 efficiently facilitates the desorption and electron transfer process of V 3+ during the electrochemical oxidation process. Owing to the enhanced electrochemical oxidation of V 2+ to V 3+ , the inherently sluggish reaction kinetics of V 2+ /V 3+ is significantly accelerated. The battery assembled with oxygen vacancy-rich TiO 2 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 V 2+ /V 3+ but also offers insights for rationally designing efficient catalysts for VRFBs.