Solvothermal synthesis of TiO2 hollow nanospheres utilizing the Kirkendall effect and their photocatalytic activities

Abstract Anatase TiO 2 hollow nanospheres were prepared by solvothermal method, using polyethyleneimine (PEI) as an auxiliary agent, followed by calcination at 400, 500 and 700 °C, respectively. The samples were characterized by XRD, SEM, TEM, HRTEM, thermal gravimetric-differential thermal analysis (TG-DTA) and N 2 adsorption–desorption isotherm. The optical properties and photocatalytic reaction mechanism were investigated by means of UV–Vis diffuse reflectance spectra, radical-trapping experiments and fluorescent technique. The effect of the PEI quantity on morphologies of the products and the formation mechanism of the TiO 2 nanospheres were explored on the basis of series of control experiments. The photocatalytic activities of the samples were evaluated by degradation of rhodamine B (RhB) solutions and compared with that of the commercial TiO 2 (P25). The results clearly show that the TiO 2 hollow nanospheres were formed via the Kirkendall effect. For the first time, we find that the morphologies of the products change dramatically with slightly increasing the PEI quantity. The photocatalytic activity of the TiO 2 nanospheres calcined at 500 °C is higher than those of the other two samples and P25. The active species for the photocatalytic reactions is not ·OH.