Defect-induced modification of band structure by the insertion of Ce3+ and Ce4+ in SrTiO3: A high-performance sunlight-driven photocatalyst

Ce3+ and Ce4+ ions were successfully substituted in Sr2+ sites of SrTiO3 nanoparticles (NPs) synthesized by the Pechini type sol-gel process and post annealing at 750 degrees C. The resulting Ce-doped NPs, with average particle sizes up to 31.2 +/- 0.5 nm, exhibited the cubic pemvskite structure of SrTiO3. According to the analysis of crystalline structure, valence states, electronic structure, and optical properties, the surface defects induced by the Ce3+/Ce4+ pair had an important influence in improving the process of light absorption, charge transfer and surface chemisorption. Accordingly, the NPs with nominal composition Sr0.97Ce0.03TiO3 had the best balance between light absorption enhanced by surface defects and defect-induced carrier traps, exhibiting the highest photocatalytic activity with 95.10 % of methylene blue dye removal, after 120 min of simulated sunlight irradiation.