Recyclable, hierarchical hollow photocatalyst TiO2@SiO2 composite microsphere realized by raspberry-like SiO2

TiO2@SiO2 composite microspheres (TS) were prepared by the deposition of TiO2 on the raspberry-like SiO2@polystyrene microspheres (PSS). The hollow microspheres with hierarchical microtopography possess both improved photocatalytic activity and stabilized TiO2 particle structure. The results of energy dispersion spectrum (EDS) mapping, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) showed that after calcination, anatase TiO2 nanoparticles has formed on the raspberry-like PSS template with preferred deposition among interstitials of the drupelet-like structure. The thermal degradation of the polystyrene (PS) core during calcination led to the hollow microspheres. The photocatalytic experiments indicated that the raspberry-like TiO2@SiO2 composite microspheres (TS1-T53) had higher photocatalytic efficiency than the smooth ones (TS0), due to the hierarchical and hollow structure. The sample TS2 prepared with a moderate ammonia concentration (3 %) not only had relatively more intact hollow spherical structure, but also enhanced photocatalytic activity. The hollow TiO2@SiO2 composite microspheres (TS3) prepared with 4 % ammonia showed the best photocatalytic efficiency. However, the higher ammonia concentration made the drupelet-like structure unstable and the microspheres tend to disintegrate. The raspberry-like microstructure showed a protective effect on the loaded TiO2, which resulted in better recyclability with persistent photocatalytic activity. The hierarchical composite microspheres shed light on the potential effective utilization strategy of nano-photocatalyst.