Suppression of TiO2 Photocatalytic Activity by Low-Temperature Pulsed CVD-Grown SnO2 Protective Layer

TiO2 pigments are widely used in paint industries. Inert coating layers were usually deposited on the TiO2 pigments to suppress the photocatalytic activity of TiO2, which can prevent the degradation of surrounding polymer molecules. However, the traditional wet chemical methods normally form thick films, which would impair the pigment properties of TiO2. In this work, SnO2 and SiO2 protective layers were grown on the TiO2 particle surface by low-temperature pulsed chemical vapor deposition. At temperatures <60 °C, thin and uniform amorphous SnO2 films were obtained. The photocatalytic activities of both TiO2/SnO2 and TiO2/SiO2 core–shell particles were suppressed, and TiO2/SnO2 core–shell particles showed higher lightening power than TiO2/SiO2. According to transient fluorescence, photocurrent, and electrochemical impedance spectroscopy measurements, the low electron mobility of amorphous SnO2 and SiO2 films led to fast recombination of photogenerated electrons and holes, thus preventing their migration to the surface and suppressing the photocatalytic activity of TiO2.