CoNi alloy catalyzed N-doped carbon nanotube-anchored CoMn2O4 as highly efficient oxygen electrocatalysts for rechargeable Zn-air battery

The development of high-efficiency and low-cost catalysts is the key to the large-scale application of Zn-air batteries (ZABs). Herein, highly conductive CoNi/NCNTs were synthesized by high-temperature pyrolysis and then the valence-rich CoMn2O4 was anchored on CoNi/NCNTs by solvothermal method. Benefiting from the highly conductive CoNi/NCNTs for efficient electron transfer, the hollow bamboo-like carbon nanotube structure for electrolyte ion and oxygen diffusion, the large accessible surface area for exposure of abundant active sites, and the abundant Co2+/Co3+, Mn2+/Mn3+, and Mn3+/Mn4+ redox pairs, the as-prepared CoMn2O4/NCNTs/CoNi exhibited impressive catalytic activity for oxygen reduction reaction (ORR)/oxygen evolution reaction (OER). The CoMn2O4/NCNTs/CoNi catalyst demonstrated a half-wave potential of 0.822 V for ORR and a low overpotential of 420 mV at 10 mA cm- 2 for OER. Moreover, such a bifunctional catalyst endowed a homemade ZAB with an open-circuit potential of 1.50 V, a power density of 138.41 mW cm- 2, and excellent long-term stability. Density functional theory (DFT) further indicated that the improved catalytic property of CoMn2O4/NCNTs/CoNi could be attributed to its small energy barrier, high reactivity, and fast electron transfer. This study provides a practical strategy to develop multifunctional electrocatalysts to facilitate the application of rechargeable ZABs.