Titania Coated Silica Nano-spheres as Catalyst in the Photodegradation of Hydrocarbons

摘要

Nano-scaled spherical silica particles were directly coated with titania nanoparticles by means of heterocoagulation. Silica was prepared by the Stoeber method, titania by a hydrolysis-condensation reaction of tetrapropyl-orthotitanate under acidic conditions. The photocatalytic activity of the coated spheres was investigated by a smog chamber technique, designed for the simulation of tropospheric photodegradation of hydrocarbons adsorbed on aerosol surfaces. In the chamber different solar spectra and irradiation intensities can be simulated and therefore the degradation can be monitored under different conditions. The degradation itself is dominated by OH radicals. Besides the monitoring, the reaction kinetics of particular hydrocarbon degradations was determined in the smog chamber. The steady-state concentration of OH radicals is higher in the presence of titania, and furthermore a heterogeneous photodegradation on the titania surface occurs.