Reduced graphene oxide supported hierarchical flower like manganese oxide as efficient electrocatalysts toward reduction and evolution of oxygen

Abstract

The slow kinetics of the electrochemical oxygen reduction reaction (ORR) is a major bottleneck for the development of alkaline fuel cells. Herein, a facile and effective hydrothermal route has been developed to synthesize hierarchical with controllable structures of manganese oxides (Mn2O3) and reduced graphene oxides supported Mn2O3 composites. The hierarchal metal oxides were formed by self-assembly of very small Mn2O3 nanoparticles as evident from transmission electron microscopy. The nature of chelating agents has found to be the key factor whose subtle variation can effectively control the morphology of the Mn2O3. Electrochemical investigations indicate that the both pure and supported Mn2O3 demonstrate bifunctional catalytic activity toward the four-electron electrochemical reduction of oxygen and evolution reaction in alkaline media. Due to the 3D assembled hierarchical architecture of Mn2O3 composed of rose- and petal-like nano-particle arrays and the interconnection of reduced graphene oxides (rGO) network, as well as the synergetic effects of rGO as a support, revealing the pronounce impact on the electrocatalytic activity the Mn2O3 composites with high current density and excellent durability as cathode material which is comparable with other electrocatalysts. The synthetic approach provides a general platform for fabricating well-defined pure and supported metal oxides with prospective applications as low-cost catalysts for alkaline fuel cells.