Mesoporous ZnMn2O4 Nanospheres as a Nonprecious Bifunctional Catalyst for Zn-Air Batteries

The rapid and effective transfer of chemical reactants to solid surfaces through a mesoporous structure is essential for enhancing the catalytic performance of nanomaterials. Such materials are essential for realizing durable, nonpreciousmetal-based bifunctional electrocatalysts for rechargeable Zn-air batteries. Herein, highly reactant-accessible and mesoporous ZnMn2O4 nanospheres have been prepared via solvothermal synthesis. The nanospheres demonstrate excellent catalytic activity toward the oxygen reduction reaction and the oxygen evolution reaction in an aqueous alkaline solution. Moreover, compared with commercial 20 wt % platinum on carbon black, IrO2, and RuO2, the mesoporous ZnMn2O4 catalyst exhibits lower charge- discharge voltage gaps, good cycling stability, and improved round-trip efficiency. The enhanced electrochemical performance of the developed catalyst is attributed to the high specific surface area, numerous reaction sites by defective O-2(-) (O-ads) species, and sufficient structural stability of the ZnMn2O4 material. The achievements presented in this work are of great importance for the development of outstanding non-noble spinel electrocatalysts for Zn-air batteries.