Formation of core/shell structured polystyrene/anatase TiO2 photocatalyst via vapor phase hydrolysis
The core/shell structured polystyrene/anatase TiO2 (PS/A-TiO2) photocatalyst is prepared via vapor phase hydrolysis method and characterized by X-ray diffraction, transmission electron microscopy (TEM), High resolution transmission electron microscopy (HRTEM), thermogravimetry, N2 adsorption/desorption isotherm analysis and UV–vis spectra. TEM and HRTEM show that well crystalline A-TiO2 nanocrystals are immobilized on the surface of PS microspheres with dimensions of 400 nm. The TiO2 crystallite size in the shell ranges from 7.5 nm to 13.6 nm, which is dependent on the temperature of vapor phase hydrolysis. The weight ratio of A-TiO2 in the composite can be tuned by varying the content of titanium precursor. The composite density is lower than that of bare A-TiO2 because of the light PS core, thus the composite has improved floating property. The photocatalytic performances of various catalysts in the degradation of methylene blue (MB) and phenol are evaluated, and the core/shell catalyst has a relatively higher activity than that of bare A-TiO2 due to the improved floating and light harvesting ability. However, the PS core competitively consumes some active radicals, which are generally essential to the photocatalytic oxidation of MB, phenol or their intermediate derivatives. Then an insulating coating of SiO2 between the PS core and A-TiO2 shell is also introduced via vapor phase hydrolysis process, and the long-term stability of core/shell structured composite is enhanced.
Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights▸ Anatase TiO2 nanocrystals were immobilized on the surface of PS microspheres via the vapor phase hydrolysis process. ▸ PS/TiO2 showed better suspensible ability and improved light harvesting properties in the efficient degradation the MB dye and phenol. ▸ The crystallite size and the thickness of the TiO2 shell in the composite could be tuned. ▸ The presence of SiO2 was demonstrated to be against the photocatalytic oxidation of polymer core.
Journal: Applied Catalysis B: Environmental - Volumes 123–124, 23 July 2012, Pages 127–133