Insights into the composite coating for improving the weatherability of TiO 2 white pigments

Several inorganic coatings, such as ZrO 2 , SiO 2 , Al 2 O 3 , and AlPO 4 , have been utilized in the TiO 2 pigment industry in order to reduce the natural photoactivity of TiO 2 nanoparticles. However, the different role of each material in impacting the TiO 2 photoactivity lacks comparative studies, and this is critical to provide a composite coating strategy for TiO 2 pigments to achieve optimal weatherability. Our work has shown that each of these coating materials plays a unique role in suppressing the TiO 2 photoactivity. For instance, ZrO 2 and AlPO 4 increase the rate of charge recombination, while SiO 2 reduces it. By comparing and analyzing their effects on the charge carrier processes, we have designed and created a composite-coated TiO 2 pigment that features a sequential deposition of ZrO 2 , SiO 2 , and AlPO 4 . This product has been proved to exhibit excellent weatherability.