Highly active photocatalyst BixTiyVxO 4x+2y (x ≈ y) for oxygen evolution under visible-light illumination

Abstract

A coupled TiO2-BiVO4 system, BixTi yVxO4x+2y (x ≈ y), with modified TiO 2 and BiVO4 crystals through their interaction, was prepared in the form of powder by solid-state reaction under the concept of combining properties of active photocatalysts. Experiments of photocatalytic oxygen evolution from an aqueous powder suspension under visible-light irradiation (λ ≥ 420 nm) have shown that BixTi yVxO4x+2y (x ≈ y) exhibits activity much higher than that of BiVO4, which is known as one of the most active visible-light-responsive photocatalysts, indicating the effectiveness of the interaction and the modification of TiO2 and BiVO4. XRD experiments showed that BixTiyVxO 4x+2y (x ≈ y) was composed of BiVO4 and TiO2 crystals slightly modified probably by partial exchange of V5+ and Ti4+ ions. Photocurrent vs. wavelength for a particulate Bi xTiyVxO4x+2y (x ≈ y) film electrode demonstrated several components, in agreement with the conclusion that BixTiyVxO4x+2y (x ≈ y) consisted of modified BiVO4 and TiO2 crystals. A possible band model was tentatively proposed to explain observed characteristics such as photocurrent density (j ) vs. potential (U), j vs. illumination wavelength (λ), the U dependence of j vs. λ, and the effect of the addition of a reductant such as I-, MeOH, SCN- and Br- on j vs. U and j vs. λ. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.