Ce-TiO 2 nanoparticles with surface-confined Ce 3+ /Ce 4+ redox pairs for rapid sunlight-driven elimination of organic contaminants from water

Industrial discharge of organic pollutants poses a severe threat to human health and aquatic life. Elimination of these pollutants from drinking and wastewater is imperative for a sustainable environment. To address this issue, pure and Ce 3+ -doped TiO 2 nanoparticles are designed with stable tetragonal (anatase) lattices by a low-temperature sol–gel process. The spectroscopic and structural analyses reveal the formation of TiO 2 and Ce-TiO 2 nanocrystals with controlled crystallite size (3–6 nm), high surface areas, and varying surface chemistry. The effect of calcination (thermal (Δ) treatment at 450 °C) on the structure and photocatalytic performance of ΔTiO 2 and ΔCe-TiO 2 nanoparticles is also investigated. Simultaneous photocatalysis experiments over a 90-min exposure to natural sunlight show 240 % and 191 % improved elimination of methylene blue (MB), an organic pollutant, by Ce-TiO 2 and ΔCe-TiO 2 nanoparticles compared to their pure TiO 2 analogs. Also, Ce-TiO 2 and ΔCe-TiO 2 nanoparticles exhibit 326 % and 229 % faster kinetics for the photocatalytic elimination of MB primarily due to the surface-confinement of Ce 3+ in Ce-TiO 2 nanocrystals, where Ce 3+ ions play a dual role as reducing agent for adsorbed oxygen species and electron trap sites via Ce 3+ /Ce 4+ interconversion. The mechanism of photocatalytic redox reactions is discussed. The study elaborates on the role of Ce-TiO 2 nanoparticles as an effective photocatalyst for the elimination of organic pollutants in wastewater.