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. The new β-pyrochlore compounds with composition of CsMxW2-xO6 (M = Sn, V and Mo, x = 0–0.5) have been prepared by sol-gel method. The highest MB conversion degree in visible light was observed for CsSn0.25W1.75O6, CsMo0.25W1.75O6, CsMo0.5W1.5O6 and CsMo0.1W1.9O6. According to HR-LCMS analysis, the composition of CsSn0.25W1.75O6 shows the deepest MB decomposition, without any peaks of initial molecules, and leads to formation simple aromatic and non-aromatic compounds. [Display omitted] •The new β-pyrochlore compounds with composition of CsMxW2-xO6 (M = Sn, V and Mo, x = 0–0.5) have been prepared by sol-gel method.•The valence state of W, Sn, V atoms in octahedral framework was determined by XPS method.•The electronic structure of obtained compounds has been investigated experimentally.•The phototcatalytic decomposition of MB has been investigated under UV and visible light.•The MB decomposition products have been defined.