Efficiently Enhancing Oxygen Reduction Electrocatalytic Activity of MnO2 Using Facile Hydrogenation

Improving the electrocatalytic oxygen reduction reaction (ORR) activity of transition metal oxides is important for the development of non-noble metal catalysts that are used in metal-air batteries and fuel cells. Here, a novel facile strategy of hydrogenation to significantly enhance the ORR performance of MnO2. The hydrogenated MnO2 (H-MnO2), which is prepared through a simple heat treatment in hydrogen gas, shows characteristics of modified lattice/surface structures and increased electrical conductivity. In 0.1 M KOH aqueous solution, the prepared H-MnO2 exhibits high activity toward the oxygen electrocatalysis with more positive onset potential (approximate to 60 mV), approximate to 14% larger of limiting current, lower yield of peroxide species, and better durability than the pristine oxide. Further conductivity testing and density functional theory (DFT) studies reveal the faster kinetics of ORR after hydrogenation is due to the formation of hydrogen bonds and altered microstructure and improved electronic properties. These results highlight the importance of hydrogenation as a facile yet effective strategy to improve the catalytic activity of transition metal oxides for ORR-based applications.