Function regionalized catalyst promoted bromine redox kinetics for bromine-based flow battery.

Bromine-based flow batteries are considered as ideal large-scale energy storage devices, due to their attractive high energy density and low cost. However, the inferior redox activity of the Br 3 −/Br− couple leads to limited power density, which cannot meet the practical application requirements. Herein, a flexible catalytic electrode is constructed by interweaving a nitrogen-doped porous carbon (NPC) coated TiO 2 (TiO 2 @NPC) nanofiber, via electrospinning technique. In the electrode, the NPC component with superior affinity to the reactant Br−, could assistant rapid charge transfer, and facilitate the conversion from Br− to Br 3 −, which plays an excellent catalytic function. With a stronger adsorption for the oxidation product Br 3 − than NPC, the TiO 2 component can transfer Br 3 − from NPC, releasing the catalytic active sites on NPC timely and enabling the reaction smoothly proceeded. Consequently, the regional differentiation strategy of the catalysis and adsorption functions significantly boosts the redox kinetic of the bromine chemistry. The Zinc-bromine flow batteries equipped with TiO 2 @NPC can run 200 cycles stably at 80 mA cm−2, with the voltage efficiency and energy efficiency of 82.8 % and 81.6 %, respectively. This design provides a brand-new improvement strategy for bromine cathode from the perspective of accelerating the reaction rate-determining step. • Root cause for the sluggish kinetics of Br 2 / Br ‐ is intensively studied. • The concept of the functional regionalization catalyst is proposed. • Specific functions are confirmed by the combination of theory and experiment. • ZBFBs operate stably for 200 cycles with EE of 81.6 % at 80 mA cm−2. [ABSTRACT FROM AUTHOR]