Transition metal oxide nanocatalysts for oxygen reduction reaction

[Display omitted] Oxygen reduction reaction (ORR) is the most important reaction that occurs in the cathode surface of fuel cells. Its sluggish kinetics stimulated the researchers towards the development of inexpensive as well as efficient alternatives, to the precious and low abundant Pt-based catalysts. Recently, transition metal-oxide (TMO) based electrocatalysts have attracted tremendous attention as suitable electrocatalyst towards ORR due to its high activity and better stability. Other factors that promote the utilization of TMOs include low cost, high availability and the presence of variable oxidation states. Mixed transition metal oxides (MTMOs) show even better ORR performance due to their enhanced electrical conductivity as compared to that of single TMOs. This review article highlights the recent progress in the design and synthesis of TMO based electrocatalysts with various size and morphology for ORR. Special importance has been given to cobalt oxides, copper oxides, manganese oxides and iron oxides throughout the study. Moreover, the effects of using conductive materials like carbon nanotubes, carbon nanofibres, mesoporous carbon, graphene etc. have also been reviewed.