Full visible-light absorption of TiO2 nanotubes induced by anionic S22− doping and their greatly enhanced photocatalytic hydrogen production abilities

Abstract

TiO2, as a benchmark photocatalyst for hydrogen production through water splitting, has a relatively large band gap (3.2eV for anatase and 3.0eV for rutile) requiring UV light (290–400nm) for electronic excitations from the valence band to the conduction band, hence utilizing only a small part of the solar spectrum. The construction of new electronic band gap, especially in the visible region (400–800nm), is of great importance for improving TiO2 optical and photocatalytic properties. In this work, though it is deem metastable and can induce a broad visible-light adsorption in previous literatures, anionic S22− has been successfully introduced into TiO2 nanotubes, which is different from the previous works about S-doped TiO2 that contain only cationic S4+ and S6+. Resultantly, the S22− doped TiO2 nanotubes exhibit a full visible-light absorption (from 400 to 800nm) and a greatly enhanced photocatalytic H2-production rate under visible-light irradiation (9610μmolh−1g−1, about 13.7 and 37 times of other cationic and anion S-doped TiO2 nanoparticles, respectively, almost highest in all the results reported previously in literatures of TiO2 doped with non-metal elements).