Sn4+ and S2- co-doped N-TiO2-x nanoparticles for simultaneously efficient photocatalytic removal of multi-contaminants

Abstract: N-TiO2-x nanoparticles (NPs) were selected as a basic construction unit for its plenty of Ti3+ and O vacancies on its surface. When S2- and Sn4+ are co-doped into the N-TiO2-x lattice, the positions of O2- and Ti4+ can be replaced, respectively. Owing to formation the dopant energy level from Sn4+ and S2-, an obvious red shift to visible light for the Sn4+/S2-/N-TiO2-x was caused. The significant reduction of the recombination rate of the e-/h+ pairs was noticed due to the fast migration and separation of the electron for the energy level doping from Sn4+ and S2- and the formation of electron traps from Sn4+. The co-doping of Sn4+ and S2- into the N-TiO2-x NPs significantly narrowed the band gap of N-TiO2-x NPs (from 3.07 eV to 0.77 eV), resulting in the superior photocatalytic activity of the Sn4+/S2-/N-TiO2-x NPs. The photocatalytic reduction rate of Cr (VI) increased to 11.6 times and the photo-degradation rate of doxycycline hydrochloride (DH) achieved about 5.7 times of that original N-TiO2-x NPs. This study provided a plain means to prepare the metal and nonmetal co-doping N-TiO2-x NPs, which could greatly improve the removal efficiency of contaminants via their synergistic effect.