Enhancing zinc-air battery performance by constructing three-dimensional N-doped carbon coating multiple valence Co and MnO heterostructures

Developing highly-efficient bifunctional oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) electrocatalysts is crucial for the widespread application of rechargeable Zn-air batteries (ZABs). Herein, an efficiency electrodeposition and pyrolytic strategy to synthesize the three-dimensional (3D) N-doped carbon coating multiple valence Co and MnO heterostructures supported on carbon cloth substrate (Co-MnO@NC/CC). It contains Co-Co, Co-N, and Co-O bonds, which synergistically enhance the oxygen reaction activity with MnO. It exhibits a working potential of 1.473 V at 10 mA center dot cm-2 for OER and onset potential of 0.97 V for ORR. Theory calculations demonstrate that the synergy between cobalt and manganese species could optimize the d-band center and reduce the energy barrier of Co-MnO@NC/CC for both OER and ORR processes. Besides, the MnO acts as the main OER active site could significantly optimize the energy barrier of O* -> OOH*, thus further promoting the OER activity. It can be directly used as the air-cathode for both liquid-state and solid-state ZABs, which could afford a small voltage gap of 0.75 V at 10 mA center dot cm-2, a high power density of 172.5 mW center dot cm-2 and a long-term durability for 400 h, surpassing those of the Pt/C + RuO2-based ZAB. Importantly, the assembled batteries show potential applications in portable devices.