Dual-Pathway Redox-Targeting Catalysis Promoting Electrochemical Kinetics for Bromine-Based Flow Batteries

Bromine-based flow battery (BFB) boasts numerous merits of high energy density, intrinsic safety, and low cost, making it highly promising in the field of large-scale energy storage. However, the inferior activity and significant permeation of the bromine cathode severely hinder its commercialization. Herein, a Prussian blue analogue Co₂Fe(CN)₆ (CoHCF) coated with a nitrogenous carbon composite (CoHCF@NC) is designed to catalyze the redox-targeting reactions at the bromine cathode. The cationic pairs of Co^III/Co^II and the anionic pairs of Fe^III(CN)₆/Fe^II(CN)₆ in CoHCF are both coupled with Br₂/Br^- in the redox potential range, which enables a two-pathway redox-targeting catalysis for the bromine cathode, thereby remarkably promoting the electrochemical kinetics. Besides, the ZIF-derived nitrogenous carbon (NC) framework guarantees smooth electron transmission for the uniformly embedded CoHCF catalyst. Consequently, the zinc-bromine flow battery assembled with CoHCF@NC catalyst delivers an ultrahigh energy efficiency of 86.1% and 65.3% at 80 and 200 mA cm^-2, respectively, and maintains a stable operation for 300 cycles at 80 mA cm^-2. This work proposes a design strategy to enhance the redox-targeting catalysis, effectively improving the practical performance of BFB.