Study of NiMnO3-based oxide catalysts for efficient oxygen reduction reactions and alkaline Al-air batteries

The oxygen reduction reaction of the cathode in an Al-air battery plays a key role in the performance of the entire battery. Generally, Pt and its alloys are recognized as catalysts with high oxygen reduction catalytic performance, but their application is limited by the rare earth content and high cost. In this paper, alpha-MnO2 nanotubes are prepared using a hydrothermal method and used as a template. Nano-Ni-Mn bimetallic oxides with different compositions are prepared with different NiO and alpha-MnO2 ratios by calcination. The effects of morphology, phase, and Mn3+/Mn4+ and Ni3+/Ni2+ ratios on electrochemical performance and battery discharge performance are analyzed. The results show that the contents of alpha-MnO2 and Ni6MnO8 in NM-12 catalyst are low, and the molar ratio of Mn3+/Mn4+ and Ni3+/Ni2+ is high. Also, the specific surface area of NM-12 is relatively high. Finally, the catalyst prepared with a NiO to alpha-MnO2 ratio of 1:2 shows better electrochemical catalytic performance and battery discharge performance that is comparable to that obtained for a commercial 20 wt% Pt/C catalyst.