Strong visible absorption and excellent photocatalytic performance of brown TiO2 nanoparticles synthesized using one-step low-temperature process

Abstract

We report a facile and modified sol-gel approach to synthesize brown TiO 2 nanoparticles at low temperature (100–600 °C). The TiO 2 nanoparticles dried at 180 °C (TiO 2 -180°C) possessed a small particle size (5.0 nm), large specific surface area (213.45 m 2 /g), and efficient response to broadband light over the entire ultraviolet-visible spectrum with a narrow band gap of 1.84 eV. In addition, TiO 2 -180°C exhibited the optimal reaction rate constant for the degradation of methylene blue (0.08287 mg/(L·min)), which is six times higher than that of the mixed rutile/anatase phase TiO 2 photocatalytic standard P25 (0.01342 mg/(L·min)). Furthermore, cycling photodegradation experiments confirmed the stability and reusability of this catalyst. The unique physicochemical properties resulting from the low-temperature preparation of TiO 2 -180°C, including its broadband visible absorption associated with a high concentration of oxygen vacancies, large surface area, and enriched surface –OH/H 2 O may be responsible for this excellent photocatalytic performance. The use of as-prepared TiO 2 -180°C for practical applications is expected after further optimization. Brown TiO 2 nanoparticles synthesized using a modified sol-gel approach at 180 °C exhibited small particle size, large surface area, enhanced visible-light response, and enriched surface –OH/H 2 O, leading to the enhancement of their photocatalytic activity.