Recent Advances in Metal-Organic Framework Derivatives as Oxygen Catalysts for Zinc-Air Batteries

Electrochemical energy storage systems with high power output, large energy density, and stable performance are urgently needed. Zn- air batteries are one of the most promising candidates owing to abundant and inexpensive resources used, decent energy density, and the high reduction potential of Zn. The most significant challenge of primary and rechargeable aqueous Zn- air batteries is the relatively high overpotential due to the sluggish kinetics of oxygen reactions on the air cathode. Highly efficient oxygen catalysts derived from metal- organic framework ( MOF) precursors have demonstrated remarkable capabilities for facilitating the oxygen reactions. In this contribution, we review the recent progress in state- of- the- art MOF- derived materials for use as oxygen catalysts in primary and rechargeable Zn- air batteries. We first summarize the development of several important MOF derivatives, including transition metal- nitrogen- carbon ( TM N C) composites, carbon- based transition metal compounds, and metal- free carbons. The advantages and disadvantages of these MOF- derived catalysts are also discussed. Strategies for optimization of the gas- liquid diffusion and the long- range electronic transportation on the air cathode with these MOF- derived catalysts are also demonstrated. Finally, the main challenges and some perspectives for developing advanced MOF- derived catalysts applied in Zn- air batteries are provided.