A biotemplate synthesized hierarchical Sn-doped TiO2 with superior photocatalytic capacity under simulated solar light

Abstract

Despite a number of studies have been carried out on TiO2 based materials as photocatalysts for water pollutant treatment, it still needs sustained effort to extend the optical range of the photocatalysts and inhibit the recombination of photo-induced carriers to improve their catalytic activities under solar light. In this work, a series of Sn-doped TiO2 with different amounts of Sn doping (1, 5, 10 and 20 mol%) were biomimetically synthesized by a facile sol–gel method using cellulosic cotton as biotemplate. The Sn-doped TiO2 materials possess a typical three-dimensional hierarchical structure of microtubes consisting of interwoven nanofibers. The photocatalytic performance was evaluated via the degradation of methylene blue (MB) (10.0 mg L−1) under Xenon lamp simulated solar irradiation. The results show that Sn(5)-TiO2 (5 mol% Sn doping) sample exhibits an outstanding photocatalytic capacity with a superior degradation rate of higher than 98% within 30 min and a good reusability without significant decrease of activity after reused for four cycles. The most significantly improved photocatalytic capacity of TiO2 is ascribed to more extra surface hydroxyl groups and accessible active sites provided by the relatively high surface area, and a higher light capturing and utilization efficiency with less recombination of the photogenerated electron-hole pairs endowed by the good synergistic effect of the special hierarchically porous microstructure and the appropriate amount of Sn doping. Whereas, the excessive Sn doping reduces the photocatalytic activity obviously, resulting from the phase transformation of TiO2 generating more rutile phase with less reactivity, the phase separation with clear grain boundary blocking the active sites, and the extra Sn4+ acting as the recombination center. This research presents a facile biomimetic synthesis strategy combined with the traditional sol–gel method to develop various ion doped metal oxides as photocatalysts with enhanced activity.