Decoupling Activation and Transport by Electron‐Regulated Atomic‐Bi Harnessed Surface‐to‐Pore Interface for Vanadium Redox Flow Battery

Abstract Vanadium redox flow battery (VRFB) promises a route to low‐cost and grid‐scale electricity storage using renewable energy resources. However, the interplay of mass transport and activation processes of high‐loading catalysts makes it challenging to drive high‐performance density VRFB. Herein, a surface‐to‐pore interface design that unlocks the potential of atomic‐Bi‐exposed catalytic surface via decoupling activation and transport is reported. The functional interface accommodates electron‐regulated atomic‐Bi catalyst in an asymmetric Bi─O─Mn structure that expedites the V³⁺/V²⁺ conversion, and a mesoporous Mn₃O₄ sub‐scaffold for rapid shuttling of redox‐active species, whereby the site accessibility is maximized, contrary to conventional transport‐limited catalysts. By in situ grafting this interface onto micron‐porous carbon felt (Bi₁‐sMn₃O₄‐CF), a high‐performance flow battery is achieved, yielding a record high energy efficiency of 76.72% even at a high current density of 400 mA cm⁻² and a peak power density of 1.503 W cm⁻², outdoing the battery with sMn₃O₄‐CF (62.60%, 0.978 W cm⁻²) without Bi catalyst. Moreover, this battery renders extraordinary durability of over 1500 cycles, bespeaking a crucial breakthrough toward sustainable redox flow batteries (RFBs).