Photocatalytic characterization of silica coated titania nanoparticles with tunable coatings

Photocatalytic experiments were conducted using the silica coated titania nanoparticles with tunable coatings to photocatalytically degrade methyl orange in water solutions. When the silica loading on titania nanoparticles was 4.67 wt%, the silica coating layer was incomplete and the photocatalytic activity of coated nanoparticles was higher than titania nanoparticles. However, when the silica loading on titania nanoparticles increased to 9.33 wt%, the thickness of silica coatings was 1.5 nm and the photocatalytic activity of coated nanoparticles sharply decreased. When the silica loading on titania nanoparticles increased to 25.19 wt%, the coated nanoparticles still exhibited a certain photacatalytic activity due to the porosity of silica coatings. The change of the effective tiania surface area available for methyl orange caused by silica coatings and the dispersion stability were used to explain the difference in photocatalytic activity.