Substitution-induced band modification and developmental changes of optical properties in Bi_6−xTe_xMo_2−xV_xO₁₅ (0  ⩽  x  ⩽  1) solid solutions

Bi_6−xTe_xMo_2−xV_xO₁₅ (0  ⩽  x  ⩽1) solid solutions with loosely aggregated ball-like profiles were prepared via sol–gel synthesis. X-ray powder diffraction was used to investigate the crystal phase and structural characteristics. The UV–vis absorption measurements concluded that Te⁴⁺/V⁵⁺ co-doping could greatly modify the band gap of Bi_6−xTe_xMo_2−xV_xO₁₅ (0  ⩽  x  ⩽  1), i.e. the band energies possessed a decreasing trend with the increase of doping concentration. Consequently, the Te/V-doped samples could harvest more visible light in the longer-wavelength region. This is most favorable for photocatalytic performance. The improved photocatalysis was verified by Rhodamine B photodegradation in the presence of Bi_6−xTe_xMo_2−xV_xO₁₅ (0  ⩽  x  ⩽  1) under visible-light irradiation (λ  ⩾  420 nm). X-ray photoelectron spectroscopy measurements and impedance spectra were measured to elucidate the photocatalytic mechanisms. The improved photocatalysis was related to the microstructural changes and multivalent V and Mo ions. (paper)