Three-dimensionally ordered mesoporous Co₃O₄ decorated with Mg as bifunctional oxygen electrocatalysts for high-performance zinc-air batteries

Developing low-cost and high-efficiency bifunctional catalysts for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is critical to expedite the widespread implementation of rechargeable zinc-air batteries. Herein, a unique Mg-decorated three-dimensionally ordered mesoporous (3DOM) Co₃O₄ electrocatalyst is engineered and evaluated as cathodic material for zinc-air batteries. The modulation of electronic structure and bonding configuration of Co sites through coordination with substituted Mg atoms effectively enhance the interaction with oxygen species and, therefore, the ORR/OER activity. Meanwhile, the substitution of Co²⁺ with Mg²⁺ creates abundant, more catalytically active octahedral sites (Co³⁺) in 3DOM-Mg_xCo_3−xO₄. Moreover, the tailored 3D interpenetrating porous structure endows the electrocatalyst with large diffusion channels for oxygen species and highly accessible active sites. The as-prepared catalyst retains 99% and 98% of its initial ORR and OER current, respectively, after 16 h under chronoamperometric measurement. The zinc-air battery assembled with 3DOM-Mg_xCo_3−xO₄ exhibits a high power density of 253 mW cm⁻² and long-term cyclability over 236 h, outperforming the commercial noble-metal based catalysts in terms of performance and stability. This work offers a straightforward and promising design strategy for development of robust bifunctional electrocatalysts toward practical applications of zinc-air batteries.