Radially organized pillars in TiO2 and in TiO2/C microspheres: synthesis, characterization and photocatalytic tests

Porous TiO 2 microspheres with robust texture and high photoactivity were prepared by inflowing a TiO 2 precursor in the confined space of polystyrene-co-divinyl benzene (PS-co-DVB) polymer, working as sacrificial scaffold. The impregnated polymer spheres, upon thermal treatments under N 2, N 2/air or pure air flow at temperatures in the 400-500 °C interval, are transformed into porous microspheres. Depending on the gas flow composition, the obtained microspheres are constituted by porous carbon, hybrid core-shell C/TiO 2 or of cemented TiO 2 nanoparticles assembled in elongated pillars. The composition of pure TiO 2 microspheres ranges from pure anatase (400°C) to the prevailing rutile phase (>475-500°C). All samples have been extensively characterized by means of SEM/AFM microscopes, N 2-volumetric porosimetry, XRD and UV-vis analyses. The photodegradation of NO has been used to check the photocatalytic activity of the TiO 2 materials. It is concluded that they exhibit higher photoactivity than the classical benchmark material (Degussa P25). This property together with porous character of the microspheres, the tunable anatase-rutile ratio and the high crystallinity makes these microspheres very interesting materials for applications in photocatalysis. From a physical point of view, the large axial pores and the columnar nature of the spheres can produce the entrapment of the light into the material.