Crystal Structure and Photocatalytic Properties of the CsV_0.625Te_1.375O₆ Mixed‐Valence β‐Pyrochlore Compound

Abstract

A new β‐pyrochlore compound with complex composition of Cs(V3+0.0625V5+0.5625Te4+0.34375Te6+1.03125)O6 has been synthesized by a solid‐state reaction and characterized by single‐crystal X‐ray diffraction and thermal analysis. The compound possesses the typical cubic symmetry with space group , however some of the oxygen atoms shift from the special position 48 f to the general crystallographic positions 32e, 96 g and 96 h. This shift is caused by complex B‐site composition with mixed‐valence vanadium and tellurium atoms, especially the presence of the large Te4+ ion. The locations of the valence band and conduction band edges were determined experimentally under vacuum conditions by X‐ray photoelectron spectroscopy, UV‐visible and impedance spectroscopy and evaluated theoretically for water solutions. The photocatalytic ability of the compound under visible light irradiation was determined using the methylene blue decomposition process as an example. The nature of the active radical species and possible dye degradation pathway were suggested according to experimental data.

Effects of Oxygen Vacancies with Different Valence States on the Photo(electro)catalytic Performance of a 2D TiO2:N (001) System

“…In TiO 2 , when N element doping and different V o valence states coexist, the structure changes and the middle of gravity of charges deviates, resulting in electrostatic interactions between atoms and generating a local electric field and an electric dipole moment, which changes the carrier activity. In accordance with the Debye equation, 48 the electric dipole moment is = nqR (6) where n stands for the electron number; q represents the amount of charge; and R indicates the distance about charges. Lattice deformation occurred in the 2D ) systems, resulting in electric dipole moments.…”

“…Their results showed that Mn valence states considerably influence the SCR activity of the MnO x /TiO 2 surface, and Mn 4+ is essential for low-temperature SCR activity. Fukina 6 studied the photocatalytic ability of CsV 0.625 Te 1.375 O 6 materials containing valence states V 3+ , V 5+ , Te 4+ , and Te 6+ via the solidphase reaction method. They discovered that the photocatalytic ability improves when the Te 4+ ion content increases.…”