1D-MnO2, 2D-MnO2 and 3D-MnO2 for low-temperature oxidation of ethanol

Abstract

1D-MnO2 synthesized using the hydrothermal method was a single-crystal nano-rod with a tetragonal structure. 2D-MnO2 and 3D-MnO2 prepared by the hard template method possess 2D and 3D pore channels, respectively, good pore size distributions and orderly polycrystalline walls due to perfect replication of their templates containing hexagonal (p6mm) pore channel structures and symmetrical cubic (ia3d) structures, respectively. The physicochemical properties of these samples were characterized, and their low-temperature activities for ethanol oxidation were evaluated. 3D-MnO2 exhibited the best catalytic properties for ethanol oxidation due to better low-temperature reducibility and more abundant surface-adsorbed oxygen species and Mn4+ ions. The complete oxidation of ethanol to CO2 was achieved at 150°C on 3D-MnO2. The turnover frequency (TOF) of 3D-MnO2 was the highest (i.e., 0.019h−1 at 40°C, 0.047h−1 at 70°C and 0.17h−1 at 110°C), and its apparent activation energy for the reaction was the lowest (i.e., 28.2kJ/mol). After the addition of 10vol.% H2O, the complete oxidation of ethanol to CO2 was obtained at 190°C on 3D-MnO2. There was no obvious decrease after the sample was run for 160h. The mesoporous MnO2 catalysts, especially 3D-MnO2, are very promising materials for the efficient elimination of ethanol.