Facile synthesis of MnO/NC nanohybrids toward high-efficiency ORR for zinc-air battery

The development of inexpensive non-precious metal materials as high-efficiency stable oxygen reduction reaction (ORR) catalysts holds significant promise for application in metal-air batteries. Here, we synthesized a series of nanohybrids formed from MnO nanoparticles anchored on N-doped Ketjenblack carbon (MnO/NC) via a facile hydrothermal reaction and pyrolysis strategy. We systematically investigated the influence of pyrolysis temperature (600 to 900 °C) on the ORR activities of the MnO/NC samples. At the optimized pyrolysis temperature of 900 °C, the resulting MnO/NC (referred to as MnO/NC-900) exhibited superior ORR activity (onset potential = 0.85 V; half-wave potential = 0.74 V), surpassing other MnO/NC samples and nitrogen-doped Ketjenblack carbon (NC). Additionally, MnO/NC-900 demonstrated better stability than the Pt/C catalyst. The enhanced ORR activity of MnO/NC-900 was attributed to the synergy effect between MnO and NC, abundant surface carbon defects and surface-active components (N species and oxygen vacancies). Notably, the Zinc-air battery (ZAB) equipped MnO/NC-900 as the cathode catalyst delivered promising performance metrics, including a high peak power density of 146.5 mW cm^-2, a large specific capacity of 795 mA h g_Zn ^-1, and an excellent cyclability up to 360 cycles. These results underscore the potential of this nanohybrid for applications in energy storage devices.