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

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 Mn3 O4 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 -sMn3 O4 -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 sMn3 O4 -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).