"Fence" Effect Enabling a Metal-Organic Framework-Derived Single-Atom Co-N-C Catalyst for High-Performance Zn-Air Batteries.

It offers bright prospects to develop non-Pt group metal (non-PGM) electrocatalysts in the area of energy storage and conversion. Herein, we reported a simple spatial isolation strategy to synthesize Co-based electrocatalysts, using partially substituted Zn atoms in a ZnCo-ZIF precursor. The "fence" effect that originated from the partially substituted Zn atoms can yield a better isolation of Co atoms, achieving selective loading of Co species on nitrogen-doped porous carbon varying from nanoparticles to single atoms. The low boiling point of Zn enables abundant porous structures to the N-doped carbon substrate after pyrolysis. The best performing single-atom Co catalyst (Co-SAs/N-C) exhibits excellent oxygen reduction reaction activity in alkaline media. As an illustration, the rechargeable liquid Zn-air battery incorporating the Co-SAs/N-C catalyst demonstrates a substantial open circuit voltage of 1.49 V, a high specific capacity of 689.3 mAh g, and remarkable cycling stability over 200 h. This study paves the way for the strategic development of non-PGM electrocatalysts in battery applications.