Bifunctional electrocatalysts of MOF-derived Co-N/C on bamboo-like MnO nanowires for high-performance liquid- and solid-state Zn-air batteries

Exploration of cost-effective electrocatalysts that could replace noble metals to promote the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) holds great potential for large-scale applications in energy storage devices such as metal-air batteries. Metal-organic frameworks (MOFs) provide a new route to design highly active catalysts owing to their adjustable composition, morphology and surface area. Herein, a highly efficient bifunctional catalyst was fabricated by forming an interconnected and conducting Co-N/C framework on bamboo-like hollow MnO nanowires. The hybrid demonstrates prominent ORR/OER activity and promising potential in rechargeable Zn-air batteries. Especially, when assembled into solid-state Zn-air batteries, high open-circuit potential and stable discharge-charge cycling platforms were achieved. The outstanding performances stem from the synergistic effect of the two composites in one-dimensional nanowires, facilitating the convenient and sustainable diffusion of electrolytes to active sites. This work provides a new guideline to optimize MOF-derived materials as substitutes for Pt/C and RuO2 noble-metal catalysts for air cathodes in both liquid- and solid-state Zn-air batteries.