Synergistic Co-Mn Interaction-Induced Built-In Electric Field Modulates Electron Redistribution for Efficient Oxygen...

Developing highly efficient oxygen electrocatalysts to boost the kinetics of ORR and OER is essential to promoting the commercialization of Zn-air batteries. Co and Mn-based catalysts have been widely investigated in electrochemistry due to their variable valence states. Herein, Co-MnO-Mn₃(PO₄)₂ synergetic composites (denoted CMO@NPC) are fabricated via phosphorylation pyrolysis of urea-treated Co-Mn-MOF as ORR and OER catalysts for the rechargeable ZAB. Due to differences in diffusion coefficients, Mn²⁺ is more readily transported to the surface, where it forms Mn₃(PO₄)₂ outer framework to mitigate structural degradation during cycling. Moreover, the construction of Co-Mn heterojunctions can modulate the electron distribution, break the original electronic symmetry, and thereby optimize the adsorption strength of reaction intermediates. As a result, the optimal CMO@NPC-800 exhibits outstanding ORR and OER performance, delivering a potential difference of 0.701 V. DFT calculations reveal that the generation of a built-in electric field in the Co-MnO-Mn₃(PO₄)₂ system, and the Co-Mn synergy optimizes the d-band center, thereby significantly reducing the reaction barriers for both ORR and OER. The aqueous ZAB based on the CMO@NPC-800 catalyst exhibits outstanding performance with a high peak power density (203.8 mW cm^-2), a large specific capacity (793.5 mAh g^-1), and long-term charge-discharge durability (1695 cycles).