MnO₂-Based Nanostructures as Catalysts for Electrochemical Oxygen Reduction in Alkaline Media

This paper reports a systematical study on the electrochemical properties of MnO 2 -based nanostructures as low-cost catalysts for oxygen reduction reaction (ORR) in alkaline media. The results show that the catalytic activities of MnO 2 depend strongly on the crystallographic structures, following an order of α- > β- > γ-MnO 2 . Meanwhile, morphology is another important influential factor to the electrochemical properties. Among various micro and nanostructures, α-MnO 2 nanospheres and nanowires outperform the counterpart microparticles. Furthermore, a new nanocomposite catalyst by depositing Ni nanoparticles on α-MnO 2 nanowires (denoted as MnO 2 -NWs@Ni-NPs) was prepared and characterized. The as-prepared MnO 2 -NWs@Ni-NPs nanocomposite exhibits an onset potential of 0.08 V, a specific current of 33.5 mA/mg, and an overall quasi 4-electron transfer involved in oxygen reduction reaction, indicating its potential application as the electrocatalyst of oxygen reduction reaction.