Development of improved MnOx nanoparticles for the oxygen reduction reaction†

Manganese oxides (MnO_x) present interesting properties for the oxygen reduction reaction (ORR), but little is known about the influence of their properties on this application. In this work, MnO_x nanostructures were synthesized with different chemical states (MnO₂ and Mn₂O₃) with or without pore ordering. The samples were used in the ORR at 500 °C before and after reduction treatment at this same temperature. The results point to an improved performance of Mn₃O₄ in comparison with MnO₂ or Mn₂O₃ compounds. These results are further verified with kinetic Monte Carlo simulations. Furthermore, it is demonstrated that the samples without pore ordering present better results towards H₂O production. This means that pore ordering is not important for this reaction, which simplifies the future design of MnO_x nanostructures for ORR application.