Defect-engineered amorphous MnO2/Co-N-C composites derived from CoZn-ZIF via mild KMnO4 etching for high-performance rechargeable zinc-air batteries

Developing low-cost, durable bifunctional electrocatalysts is essential for scalable rechargeable zinc-air batteries (ZABs). Though hierarchically porous MOF-derived carbon boosts oxygen reduction/evolution reaction (ORR/OER) kinetics, integrating abundant exposed sites, fast mass transport and stable conductive networks remains challenging. Herein, this study synthesize defect-rich hierarchical porous a-MnO 2 /Co@CNT-XM via CoZn-ZIF/CNT pyrolysis followed by mild KMnO 4 etching. Pyrolytic Zn volatilization suppresses Co sintering and generates abundant Co-N-C sites; subsequent etching introduces carbon defects, oxygen groups and in-situ grown amorphous MnO 2 (a-MnO 2 ). Benefiting from synergy between Co-N-C, carbon defects and a-MnO 2 , optimized a-MnO 2 /Co@CNT-0.01M delivers outstanding bifunctional activity: ORR half-wave potential (0.84 V), onset potential (0.96 V), OER overpotential (393 mV@10 mA cm −2 ), 3.92 electron-transfer number for 4e − pathway, robust durability and methanol tolerance. The assembled ZAB attains 1.44 V open-circuit voltage, 119.1 mW cm −2 peak power density, 756.8 mA h · g Zn ‐ 1 specific capacity and ultra-long 280 h cycling stability. This work offers a universal strategy for high-performance non-noble-metal air cathode catalysts.