Engineering manganese oxide/nanocarbon hybrid materials for oxygen reduction electrocatalysis

Manganese oxides are cost-effective and green materials with rich electrochemical properties. Continuous research efforts have been undertaken to obtain MnO (x) materials with improved activity and stability for catalyzing the oxygen reduction reaction (ORR). Here, we have developed a novel ORR catalyst by nucleation and growth of Mn3O4 nanoparticles on graphene oxide (GO) sheets interconnected by electrically conducting multi-walled carbon nanotubes (MWCNTs). X-ray near edge absorption structure (XANES) spectroscopy revealed the partially reduced nature of GO and strong chemical coupling between the nanoparticles and the GO sheets. Incorporation of MWCNTs was found to improve the activity and stability of the hybrid by imparting higher conductivity to the hybrid material. Furthermore, surface oxidation of the manganese oxide nanoparticles through a calcination step was found to increase the density of ORR active sites. The strongly coupled and electrically interconnected Mn3O4/nanocarbon (Mn3O4/Nano-C) hybrid is one of the most active and stable manganese oxide-based ORR catalysts and shows promise for electrochemical energy conversion applications.