Nickel-hydroxide decorated trimanganese-tetroxide nanorods supported on graphene as bifunctional electrocatalyst for metal–air batteries

Abstract

Manganese oxide, such as Mn3O4, is one of promising material as electrocatalyst in air–cathode for metal–air battery due to low cost, high catalytic activity and good stability. Although pure Mn3O4 material exhibits excellent catalytic activity to ORR, it is severely limited by its intrinsically low conductivity and high over-potential toward OER. In this work, the hybrid materials of nickel-hydroxide-decorated nanorods of trimanganese-tetroxide supported on reduced-graphene have been prepared by one-step hydrothermal method. The composite materials are used as bifunctional cathode catalysts to ORR/OER, and investigated by the technologies of rotating disk electrode and metal–air batteries. The results indicate that the hybrid material of Mn-Ni/rGO use as catalyst in air–cathode for Al/Zn–air battery has good catalytic activity. Based on analysis of scanning electron microscope and X-ray photoelectron spectroscopy, the composite material shows good performance owing to the improvement of conductivity supported on graphene, more Mn4+ on the surface of hybrid material, the coexistence of Mn3+/Mn4+ redox couple, and the synergism between nickel-hydroxide and graphene.