A critical structured TiO2 with enhanced photocatalytic activity during the formation of yolk-shell structured TiO2

Yolk-shell structured TiO 2 microspheres were synthesized by using a facile hydrothermal method with ammonium chloride (NH 4 Cl) as additive. Ostwald ripening mechanism was proposed to explain the growth of yolk-shell structured TiO 2 by conducting a series of time-dependent experiments, where the solid microspheres, narrow-band-like structured, wide-band-like structured and shedding structured samples were obtained. The as-synthesized samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller analysis (BET) and UV–Vis spectra. BET results showed that the as-synthesized powders displayed bimodal pore size distributions and the wide-band-like structured sample had the largest specific surface area. The photocatalytic efficiency of Rhodamine B (RhB) achieved 99.24% for wide-band-like structured TiO 2 photocatalyst, under 500 W Xe lamp irradiation, indicating that the increase of 28.0%, 11.3%, 12.2% and 7.41% was achievd compared to the photocatalytic efficiency of solid microspheres (77.53%), narrow-band-like structured (89.17%), shedding-shell structured TiO 2 (88.42%) and Degussa P25 (91.89%) as photocatalysts, respectively.