Structural transformation of Bi sub(1-x/3)V sub(1 -x)Mo sub(x)O sub(4) solid solutions for light-driven water oxidation

The influence of molybdenum content in the solid solutions of Bi sub(1-x/3)V sub(1-x)Mo sub(x)O sub(4) (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 sub(0.98)V sub(0.93)Mo sub(0.07)O sub(4) 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 sub(0.96)Mo sub(0.10)V sub(0.90)O sub(4), in which the oxygen evolution could reach 21 mu M in 50 s under visible light of LEDs, lambda = 470 plus or minus 10 nm, and 820 mu E cm super(-2) s super(-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.