Surface analysis of N-doped TiO2 nanorods and their enhanced photocatalytic oxidation activity

We investigated the presence of Ti3+ defect sites on the surfaces of N-doped TiO2 nanorods by using scanning transmission X-ray microscopy (STXM) and high-resolution photoemission spectroscopy (HRPES). The photo-oxidation activities of different types of N-doped TiO2 nanorods were compared with each other and with their undoped nanorods. These nanorods were used to photocatalyze the oxidation of thiol molecules (i.e. 2-mercaptoethanol, benzenethiol, and 2-aminothiophenol) to disulfide and sulfonic (-SO3H) species, and the conversion of CO to CO2, and their photocatalytic activities towards these reactions were assessed using HRPES and a residual gas analyzer, respectively. Conversion to further oxidized sulfonic species was only achieved on the N-doped TiO2 surface compared to the non-doped TiO2 nanorods. In addition, we found that longer N-doped TiO2 nanorods (NTR-150) showed higher photo oxidation activity than NTR-60, which resulted from their increased number of defect sites and narrowed band-gap. (C) 2016 Elsevier B.V. All rights reserved.