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

This paper reports a systematical study on the electrochemical properties of MnO2-based nanostructures as low-cost catalysts for oxygen reduction reaction (ORR) in alkaline media. The results show that the catalytic activities of MnO2 depend strongly on the crystallographic structures, following an order of (alpha- > beta- > gamma-MnO2. Meanwhile, morphology is another important influential factor to the electrochemical properties. Among various micro and nanostructures, alpha-MnO2 nanospheres and nanowires outperform the counterpart microparticles. Furthermore, a new nanocomposite catalyst by depositing Ni nanoparticles on alpha-MnO2 nanowires (denoted as MnO2-NWs@Ni-NPs) was prepared and characterized. The as-prepared MnO2-NWs@Ni-NPs nanocomposite exhibits an onset potential of 0.08 V, a specific current of 33.5 mA/mg, and all overall quasi 4-electron transfer involved in oxygen reduction reaction, indicating its potential application as the electrocatalyst of oxygen reduction reaction.