Heterovalent substitution of Nb5+, Ta5+ on Te4+ sites and induced modification on luminescence and photocatalysis of Te-V mixed oxide Te2V2O9

Abstract

Materials combining d0 and p cations with stereo-active lone pair electrons have excellent polarization for photoelectric applications. This work reports the modifications of photochemical properties via Nb5+-, Ta5+-doping in Te-V mixed oxide Te2V2O9 with d0-(V5+) and p-(Te4+) cations. Nb5+-, Ta5+-doped Te2V2O9 nanobelts were prepared using the sol-gel method. The structure, morphologies, and optical absorption properties were reported. The calculation and experimental results indicate that the Te-V mixed oxide Te2V2O9 has an indirect transition with band energy of 2.19 eV. The photodegradation of RhB dye solutions was conducted under the irradiation of visible-light irradiation (λ ≥ 420 nm). The conductivity properties, lifetime of charge carriers were characterized via impedance spectra and decay curves, respectively. The multivalent cations were confirmed via XPS measurements. The experiments concluded that both Nb5+ and Ta5+ ions can depressed the luminescence, and enhanced photocatalysis to some extent. While, compared with Ta5+, the Nb5+ doping shows much more significant improvement of photodegradation. It was concluded that the redox couples V5+/4+ induced by Nb5+ doping attribute to the photocatalysis. This work offers an effective method to modify the photochemical properties via the redox couples and defects induced by heterovalent substitution on the cations.