Hierarchical MnO₂/rGO hybrid nanosheets as an efficient electrocatalyst for the oxygen reduction reaction

Electrocatalysts for the oxygen reduction reaction (ORR) play a crucial role in renewable-energy technologies, including metal-air batteries and fuel cells. However, development of novel catalysts with high activity and low cost remains a great challenge. Here, we present hierarchical MnO₂/reduced graphene oxide (MnO₂/rGO) hybrid nanosheets by using a facile method and study its electrocatalytic performance. Cyclic voltammograms, and rotating disk electrode and rotating ring/disk electrode measurements demonstrate that the hierarchical MnO₂/rGO hybrid nanosheets exhibit excellent electrocatalytic activity for the ORR in an alkaline medium, as evidenced by their higher cathodic current density, more positive onset potential, lower H₂O₂ yield, and higher electron transfer number compared to pure rGO. The excellent catalytic activity of the MnO₂/rGO hybrid nanosheets highlights the importance of the synergetic chemical coupling effect between the ultrathin MnO₂ nanosheets and the graphene layer.