TiO 2/V–TiO 2 composite photocatalysts with an n–n heterojunction semiconductor structure

Abstract

Highly active TiO 2/V–TiO 2 composite photocatalysts with an n–n heterojunction semiconductor structure have been prepared by mixing TiO 2 sol with sol–gel derived V–TiO 2 powders that have adsorbed ammonium oleate in advance, followed by drying and calcination. These composite photocatalysts were characterized by XRD, TEM, BET, XPS, UV–vis and PL spectroscopy. The photodegradation of methyl orange in aqueous solution under UV–vis light irradiation has been investigated over TiO 2-based photocatalysts consisting of different TiO 2/V–TiO 2 ratios and different vanadium contents. TiO 2/V–TiO 2 composite photocatalysts were generally shown to have a much higher photocatalytic destruction rate than that of undoped TiO 2, which is ascribed mainly to the electrostatic-field-driven electron–hole separation in TiO 2/V–TiO 2 composite photocatalysts. The best TiO 2/V–TiO 2 composite with the mass ratio of TiO 2:0.5 at.%V–TiO 2 equal to 12:1 demonstrates 5.9 times the photocatalytic activity of that of undoped TiO 2 with comparable crystallite size and specific surface area. The effect of photocatalysts composition on the photoactivity was discussed.