X-RAY ABSORPTION SPECTROSCOPY STUDY OF Mn2O3 AND Mn3O4 NANOPARTICLES SUPPORTED ON MESOPOROUS SILICA SBA-15

Abstract

Mn K-edge absorption measurements were carried out on α-Mn2O3 and Mn3O4 nanocrystals supported on a mesoporous silica, SBA-15. The X-ray absorption near edge structure (XANES) spectra demonstrate the existence of the oxidation states of Mn (2+ and 3+) in Mn3O4 and Mn (3+) in Mn2O3, those ions were present in different octahedral environments. Meanwhile, XANES data demonstrate that some Mn atoms that are bonding to the inner wall of the channels as isolated species, may exist as Mn4+ in Mn2O3/SBA-15. In addition, the structure, texture, and electronic properties of nanocomposites were also studied using various characterization techniques including X-ray diffraction (XRD) and laser Raman spectroscopy (LRS). The formation of the hausmannite Mn3O4 and bixbyite Mn2O3 structures has been confirmed clearly by XRD. The prepared nanocomposites of MnOx showed significant catalytic activity towards CO oxidation below 523 K.