High-Performance Manganese Nanoparticles on Reduced Graphene Oxide for Oxygen Reduction Reaction

Non-noble-metal nanostructure materials represent an emerging class of electrocatalysts for oxygen reduction reaction (ORR) in fuel cells, but their applications have been limited by catalytic activity and durability. Herein the composite of manganese oxide nanoparticle supported on reduced graphene oxide (Mn3O4/rGO) was synthesized via a simple circulation reflux method with oxide graphene and MnCl2 center dot 4H(2)O as precursors. The Mn3O4/rGO sample exhibited high ORR activity with a positive onset potential of -0.12 V (vs. SCE) and high limiting current of 4 mA/cm(2) (close to that of 20 % Pt/C, -0.09 V; 3.9 mA/cm(2)). Moreover, the durability and tolerance to methanol of as-prepared products are compared with commercial 20 % Pt/C. The results showed that Mn3O4 supported on rGO displays promising stability characteristics for applications as oxygen catalysts. When it comes to the reaction theory for ORR pathway, the Mn3+/Mn4+ center metal ion and O-2 ligand are involved, and the four-step principle is shown in the follow figure. In this study, methods to further increase the catalytic activity of Mn3O4 were created by increasing conductivity compared with rGO, hence the improvement of unpaired e.g. electron transfer to the O-O pi* orbital during ORR.