Regulated adsorption capability by Interface–Electric–Field enabling promoted electrochemical kinetics of Zinc–Bromine flow batteries

Zinc–bromine flow batteries (ZBFB) are gaining significant attention for large–scale energy storage due to the high energy density and affordable cost. Nevertheless, the diffusion of Br 2 and the relatively low activity of Br 2 /Br − impede their broader application. Herein, a bi–phasic rutile/anatase–TiO 2 embedded in carbon composite with hollow sphere structure (R/A–TiO 2 @HCS) is proposed as the catalyst for the Br 2 /Br − electrode. The internal electric field (IEF) formed between rutile–TiO 2 and anatase–TiO 2 regulates the adsorption capability for active bromine species. The appropriate adsorption capability can rapidly transfer the generated Br 2 complex (QBr n ) to the adsorbent component R/A–TiO 2 during charging, liberating the carbon active sites, and release QBr n back to the carbon reaction sites timely during discharging, satisfying the both adsorption and desorption requirements of QBr n in different processes. The kinetics for oxidation and reduction are simultaneously enhanced. Moreover, the hollow construction offers storage space for QBr n , relieving its penetration problem. Under the synergistical cooperation, the ZBFB assembled with R/A–TiO 2 @HCS demonstrates the energy efficiency (EE) of 83.6 % at 80 mA cm −2 , without significant decay over 500 cycles. And the EE still maintains 70.0 % even under 160 mA cm −2 . This work highlights the significance of tailored electrocatalyst for ZBFB.