Surface Acidity, Adsorption Capacity, and Photocatalytic Activity of SiO2 Supported on TiO2 Nanotubes for Rhodamine B Degradation

The surface acidity, adsorption capacity, and photocatalytic performance of nanotubes (NTs) superficially modified with SiO2 were analyzed. The NTs were prepared by the hydrothermal method. Photocatalysts with 1, 3 and 5 wt% of SiO2 were used to promote the adsorption and efficient removal of rhodamine B (Rh B) from water. The photocatalysts were characterized by SBET, XRD, HR-TEM, Zeta potential, FT-IR surface acidity, Raman, and UV–Vis spectroscopies. It was found that the addition of 3 wt% of SiO2 improved remarkably the photocatalytic performance and adsorptive properties of the titania nanotubes. The loading of 3 wt% of SiO2 enhanced the surface area and promoted the formation of Brönsted acid sites on the surface of the titania nanotubes. The adsorption of OH groups increased as the concentration of Brönsted acid sites increased. The OH groups triggered the formation of ·OH radicals, which promoted the oxidation pathway reaction of Rh B to CO2 and water. It was found that the Brönsted acid sites along with the electronic properties of the semiconductor materials played a major role in the photocatalytic process.