High-performance bifunctional oxygen electrocatalysts for zinc-air batteries over nitrogen-doped carbon encapsulating CoNi nanoparticles

The nitrogen doped carbon (NC) encapsulating metal particles (metal/NC) are promising low-cost bifunctional oxygen electrocatalysts for rechargeable Zn-air batteries. However, the states of the art catalytic performance are still significantly restricted by the limited content of active sites for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, a series of NC encapsulating CoNi samples as a bifunctional catalyst for both ORR and OER were synthesized via a simple pyrolysis method. Large surface area and high content M-N (x) active sites promote the ORR activity and accelerate the surface reconstruction layer for high OER performance. The NC encapsulating CoNi with optimized Co/Ni ratio (2:1) shows high ORR activity with a half-wave of potential (0.85 V) and a low overpotential of 309 mV for OER. Rechargeable Zn-air battery assembled by an air cathode with the NC encapsulating CoNi exhibits a power density of 143 mW cm(-2) and good cyclability over 100 h at 10 mA cm(-2). This mechanism work provides a feasible strategy for developing high activity and low cost bifunctional oxygen electrocatalysts.