nγ-MnO2 nanorod-assembled hierarchical micro-spheres with oxygen vacancies to enhance electrocatalytic performance toward the oxygen reduction reaction for aluminum-air batteries

Abstract γ-MnO2 nanorod-assembled hierarchical micro-spheres with abundant oxygen defects are synthesized by a simple thermal treatment approach as oxygen reduction electrocatalysts for Al (aluminum) - air batteries. The rich oxygen vacancies on the surface of γ-MnO2 are verified by morphology, structure, electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS) results. The oxygen reduction reaction (ORR) electrocatalytic activity of γ-MnO2 is significantly improved by the incoming oxygen vacancies. The γ-MnO2 nanorod-assembled hierarchical micro-spheres calcined under 300 °C in Ar atmosphere show the best ORR performance. The primary Al-air batteries using γ-MnO2 catalysts as the cathode, which demonstrates excellent peal power density of 318 mW cm−2 when applying the γ-MnO2 catalysts with optimal amount of oxygen vacancies.