Morphology evolution and quantitative analysis of β-MoO ₃ and α-MoO ₃

Abstract

Abstract The morphology evolution from monoclinic molybdenum trioxide (β-MoO 3 ) to orthorhombic molybdenum trioxide (α-MoO 3 ) and quantitative analyses of their mixtures were examined. It was found that the morphology (from spherical to elliptical shape) and color (from green to white) displayed obvious changes when β-MoO 3 converted to α-MoO 3 in ambient air at 773 K. The transformation from β-MoO 3 to α-MoO 3 resulted from a change of the internal crystalline structure. The mass percent of β-MoO 3 in MoO 3 mixtures showed an excellent linear relationship with the relative intensity ratio of the strongest peaks in X-ray diffraction patterns. This approach provides a simple and time-saving method to evaluate the amount of β-MoO 3 , which is a promising material in catalyst and electrochemical applications, in such mixtures. This finding may provide guidance for the analysis of catalytic performance of MoO 3 mixtures. In addition, it was found that β-MoO 3 can be easily decomposed into suboxides such as MoO 2 and Mo 4 O 11 in pure argon gas atmosphere. The possible decomposition mechanism of β-MoO 3 is discussed.