Synergistic Spin-Polarization Effect and Magnetic Exchange Interaction of Core/Shell Structure for Bifunctional Oxygen Electrocatalysis.

Abstract

Rechargeable zinc-air batteries (RZABs) are hindered by sluggish oxygen reduction and evolution (ORR/OER) kinetics. While core/shell nanostructures can enhance bifunctional electrocatalysis via synergy, achieving precise interfacial electronic modulation and scalable synthesis for ampere-hour-level RZABs remain challenging. Herein, we report a scalable synthesis of nitrogen-doped carbon-supported CoCuNi/ZnMn₂O₄ core/shell nanoparticles (CoCuNi/ZnMn₂O₄-NC) as an efficient bifunctional electrocatalyst. Leveraging electronegativity differences among transition-metals, controlled morphology during gram-scale production is achieved. The core/shell interaction elevates the spin state of surface Mn cations, enabling an antiferromagnetic-to-ferromagnetic transition. The dynamic equilibrium of *OH adsorption/desorption is facilitated, and the rate-determining energy barrier is reduced by 0.17 and 0.15 eV compared to individual ZnMn₂O₄ and CoCuNi, respectively. The catalyst exhibits outstanding bifunctional performance (ORR half-wave potential = 0.941 V; OER overpotential = 430 mV at 10 mA cm^-2) and robust stability. Liquid RZABs using CoCuNi/ZnMn₂O₄-NC achieve a peak power density of 244.4 mW cm^-2, a specific capacity of 802.5 mAh g^- ¹, and stable cycling over 450 h. Practical viability is further confirmed by an 8.4 Ah quasi-solid-state pouch cell with an output power of 369 mW and a lifespan of 200 h. This work sheds light on designing and scaling core/shell electrocatalysts toward high-energy, practical metal-air batteries.