Improved photocatalytic performance of Sn/Cl co-doped TiO2 nanoparticles via a novel volatilization solid solution method

Sn/Cl co-doped TiO2 nanoparticles were synthesized via a novel volatile solid solution method. The effect of SnCl2·2H2O concentration (0–35.4 mol.%) and calcination temperature on thermal effect, crystal structure, morphology, composition, light absorption and photocatalytic performance of TiO2 nanoparticles was investigated by TG-DSC, XRD, SEM, EDS, TEM, HRTEM, SAED, UV–Vis, PL, photocurrent test, EIS and XPS. Results indicate that Sn and Cl are co-doped into TiO2 crystal lattice forming a mixed anatase-rutile TiO2 phase without SnO2 phase when SnCl2·2H2O concentration is below 17.7 mol.%, and excess SnCl2·2H2O caused the rutile SnO2 generation and simultaneous rutile TiO2 disappearance. The degradation efficiency of methyl orange reaches 98.7 % using 17.7 mol.% SnCl2·2H2O modified TiO2 calcined at 380 °C after 2 h of 15 W UV light irradiation, which is 19.72 % and increases by two times compared with that of pure TiO2 (8.98 %) after 2 h of 15 W visible light irradiation, both showing the maximum photocatalytic performance possibly due to the simultaneous increased active surface sites, enhanced light absorption and improved separation efficiency of photogenerated electron-hole pairs resulted from small particle size, reduced energy band gap and formation of mixed anatase-rutile TiO2 phases. Reactive species scavenging experiments revealed that O.-2 and h+ play a dominant role in photodegradation process.