Efficient α-MnO with (2 1 0) facet exposed for catalytic oxidation of toluene at low temperature: A combined in-situ DRIFTS and theoretical investigation.

The α-MnO catalysts with (1 1 0), (2 1 0) and (3 1 0) crystal facets exposed were prepared via hydrothermal method and studied for the catalytic oxidation of toluene. Some characterization technologies and DFT theoretical calculation were combined to analyze the as-synthesized catalysts. The α-MnO catalyst exposed with the (2 1 0) plane displayed best catalytic performance and attained complete toluene conversion at 140 °C. The O-TPD and XPS results exhibited the amount of surface lattice oxygen on α-MnO-210 catalyst was largest. Lower accumulation and faster disintegration of intermediates which was characterized by in-situ DRIFTS could be discovered on the surface of α-MnO-210 catalyst. The results of DFT calculation showed that the unique atomic arrangement of α-MnO-210 catalyst enhanced the charge separation and conversion, promoting the formation of active oxygen and the activation of toluene. The E of α-MnO-210 catalyst was 24.75 kJ mol, lowest among the three catalysts. This work highlights the facet effects on catalytic property and provides new insight into the understanding of catalytic oxidation reaction mechanism of toluene.