Manganese oxides with different crystalline structures: Facile hydrothermal synthesis and catalytic activities

Manganese oxides with different crystalline structures, namely alpha-, beta-, and gamma-, were synthesized by a facile hydrothermal method and characterized by X-ray powder diffraction (XRD), surface area analyzer, scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and hydrogen temperature-programmed reduction (H-2-TPR) techniques. The dimethyl ether combustion was used as a probe reaction to explore the crystalline phase effect of the manganese oxides. The results revealed that alpha-MnO2 with nanorod shape possesses higher catalytic activity compared to the other two manganese oxides. Their different catalytic activities for dimethyl ether combustion have also been discussed in terms of surface areas, crystalline structures and oxygen mobilities. (C) 2012 Elsevier B.V. All rights reserved.