Indium and cerium co-doped mesoporous TiO2 nanocomposites with enhanced visible light photocatalytic activity

• In3+ and Ce4+/Ce3+ on TiO2 enhanced the optical transparency in the visible region.
• In3+ on TiO2 enhanced the surface Brønsted acidity and the adsorption of cationic MB.
• Surface state energy level due to O–In–Clx species on TiO2 allowed the visible light.
• Ce4+/Ce3+ active sites efficiently extended the lifetime of electron–hole pair.
• 0.2 wt% In2O3/CeO2-TiO2 showed the enhanced photocatalytic activity.

Indium and cerium co-doped mesoporous TiO2 nanocomposites with different weight percentage were synthesized by sol–gel route using Pluronic P123 as the structure directing template. The synthesized materials were characterized by X-ray powder diffraction, high resolution transmission electron microscopy, scanning electron microscope with energy dispersive X-ray spectroscopy, N2 adsorption–desorption studies, X-ray photoelectron spectroscopy, diffuse reflectance UV–vis absorption spectroscopy, Fourier transform infrared spectroscopy, photoluminescence spectroscopy and electron paramagnetic resonance spectroscopy. Indium and cerium co-doped on TiO2 nanocomposites shifted the light absorption band-edge position to visible region and showed high surface area with large pore diameter. The optimum loading of In2O3 and CeO2 on TiO2 was 0.2 wt%. Ce4+ is good electron scavengers, which easily trapped the exited electrons and transferred the electrons to the adsorbed O2 molecules to produce O2−
• . Hence the electron–hole recombination was efficiently suppressed, which was revealed by the photoluminescence spectroscopy. The large number of structural defects by the substitution of In3+ for Ti4+ enhanced the surface Brønsted acidity and the adsorption of cationic methylene blue. Consequently, In2O3/CeO2-TiO2 exhibited promising photocatalytic activity in the degradation of methylene blue under visible light irradiation due to the formation of large number of O2−
• and
• OH radicals.

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