Efficient hydrogen evolution under visible light irradiation over BiVO4 quantum dot decorated screw-like SnO2 nanostructures

Abstract

Nanostructured photocatalysts are often attractive due to their enhanced photocatalytic performance by the quantization effect. In this study, BiVO₄ quantum dots were decorated on the surface of screw-like SnO₂ nanostructures by successive ionic layer absorption and reaction method. The distinctions from bulk materials and the role of BiVO₄ quantum dots were investigated in their function as a water splitting photoanode. It was demonstrated that the band-gap of BiVO₄ could increase to 2.6 eV when the particle size decreased to about 5 nm, but the band gap of the bulk was only 2.4 eV. Moreover, the decrease in particle size and the coupling with screw-like SnO₂ nanostructures enhanced the photocurrent density up to two times under visible light irradiation. The incident photon to current conversion efficiency also increased up to 13.47% at 400 nm. Furthermore, by depositing Pt as cocatalyst, splitting water into hydrogen was realized on the BiVO₄ quantum dot/screw-like SnO₂ nanostructures under visible light irradiation, and the generation rate is up to 1.16 μmol h⁻¹ cm⁻². The improved photoelectrochemical properties and the enhanced photocatalytic activity for hydrogen evolution are attributed to the effective electron-transfer between BiVO₄ quantum dots and screw-like SnO₂ nanostructures, and the accordingly prolonged photogenerated charge carrier lifetime, as well as the elevated conduction band bottom level of BiVO₄ and SnO₂ due to the band-gap widening and energy level realignment.