Electron structure and photocatalytic activity of new compounds CsMxW2-xO6 (M = Sn, V and Mo, x=0–0.5) with β-pyrochlore structure

The new CsMxW2-xO6 (M = Sn, V and Mo, x = 0–0.5) solid solutions with β-pyrochlore structure have been prepared by sol-gel synthesis. The chemical composition has been investigated by SEM with X-ray microanalysis and X-ray photoelectron spectroscopy. It was found that the W atom in structure has mixed valence state 5+ and 6+, Sn and Mo has only 4+ and 6+, respectively, and V possesses mix of 5+ and 3+ dependence on composition. Thus the crystal structure has been determined by X-ray diffraction analysis, and the CsMxW2-xO6 (M = Sn and Mo, x = 0–0.5) compounds have the monotonous changing in unit cell parameter, whereas CsVxW2-xO6 (x = 0–0.25) has complex dependence due to different V atom ratio. The electronic structure has been studied by UV–vis spectroscopy and XPS analysis and approximated by simple theoretical calculation based on atomic electronegativity. The photocatalytic activity has been investigated using reaction of methylene blue decomposition under visible and UV irradiation, and the possible degradation pathway was supposed by HR-LCMS analysis. The relation between electronic structure and photocatalytic activity has been discussed.