Engineering an ultrathin amorphous TiO2 layer for boosting the weatherability of TiO2 pigment with high lightening power

TiO 2 pigments are typically coated with inert layers to suppress the photocatalytic activity and improve the weatherability. However, the traditional inert layers have a lower refractive index compared to TiO 2 , and therefore reduce the lightening power of TiO 2 . In the present work, a uniform, amorphous, 2.9-nm-thick TiO 2 protective layer was deposited onto the surface of anatase TiO 2 pigments according to pulsed chemical vapor deposition at room temperature, with TiCl 4 as titanium precursor. Amorphous TiO 2 coating layers exhibited poor photocatalytic activity, leading to a boosted weatherability. Similarly, this coating method is also effective for TiO 2 coating with amorphous SiO 2 and SnO 2 layers. However, the lightening power of amorphous TiO 2 layer is higher than those of amorphous SiO 2 and SnO 2 layers. According to the measurements of photoluminescence lifetime, surface photocurrent density, charge-transfer resistance, and electron spin resonance spectroscopy, it is revealed that the amorphous layer can prevent the migration of photogenerated electrons and holes onto the surface, decreasing the densities of surface electron and hole, and thereby suppress the photocatalytic activity.