Structural transformation of Bi1−x/3V1−xMoxO4 solid solutions for light-driven water oxidation

Abstract

The influence of molybdenum content in the solid solutions of Bi_1−x/3V_1−xMo_xO₄ (x = 0.05–0.20) on the morphology, band gap, structure and light-driven water oxidation properties has been studied by scanning electron microscopy, X-ray powder diffraction and vibrational spectroscopy (Raman and infrared). To find out the peculiarities of structural changes for bismuth scheelite-related oxides containing both vanadium and molybdenum crystals of Bi_0.98V_0.93Mo_0.07O₄ have been grown from a K–Bi–V–Mo–O high-temperature melt and characterized by single crystal X-ray diffraction. For the scheelite-related framework both V and Mo were found to occupy the same positions lowering the point group symmetry of tetrahedra from 4/m to 2/m giving monoclinic distortion for solid solutions with x = 0.05–0.10. The most promising photocatalytic performance was obtained for Bi_0.96Mo_0.10V_0.90O₄, in which the oxygen evolution could reach 21 μM in 50 s under visible light of LEDs, λ = 470 ± 10 nm, and 820 μE cm⁻² s⁻¹. The changes in catalytic properties are shown to be governed by a crystal structure strain with a maximum obtained for the boundary sample between the monoclinic and tetragonal phase.