Colored TiO2 Hollow Spheres for the Photodegradation of Dyes and Drugs

Abstract

Nowadays, nanostructured titanium dioxide, TiO2, is recognized as one of the most effective photocatalysts, capable of degrading under UV light a wide spectrum of organic pollutants, from dyes to antibiotics. Recent studies have stated that by modifying the morphology of titania nanoparticles in hollow spheres it is possible to increase the photocatalytic activity, due to the increase of the surface-to-volume ratio, to the high shell permeability, the effect of void space, and the excellent optical and electronic properties. Furthermore, recent studies have shown that titania hydrogenation is another method to increase the photocatalytic efficiency of these nanoparticles, by tuning the band gap of the semiconductor. This allows the TiO2 to absorb in the visible light range, so as to better exploit all the contributions of sunlight. In this work, white titania hollow spheres have been synthesized by a sol-gel template-based synthesis and then by a calcination process they have changed their crystalline phase from amorphous to anatase. Subsequently, through a chemical reduction under annealing in different operating conditions, different hydrogenated samples were obtained. Several techniques were used to characterize the samples: SEM, TEM, XRD, Raman, FTIR, UV-Vis, and N2 Physisorption. Finally, the photocatalytic tests were carried out in aqueous solution at r.t. and Patm, under UV, visible and simulated solar light irradiation. Methylene Blue and Ciprofloxacin were used as target pollutant molecules to investigate the photoactivity of the prepared systems.