(699a) ALD-Grown SiO2 Protective Layer on TiO2 Nanoparticles Under Mild Conditions for the Suppression of Photocatalytic Activity

ALD-grown SiO₂ Protective Layer on TiO₂ Nanoparticles under Mild Conditions for the Suppression of Photocatalytic Activity

Jing Guo, Shaojun Yuan, Hairong Yue, Siyang Tang, Changjun Liu, Bin Liang*

Multi-phase Mass Transfer & Reaction Engineering Lab, College of Chemical Engineering, Sichuan University, Chengdu 610065, China

*corresponding author: liangbin@scu.edu.cn

    Titanium dioxide (TiO₂), an inert and nontoxic chemical, is one of the best white pigment due to its excellent optical properties. It is widely used in the paint, plastic, and paper industries. However, the excellent photocatalytic activity of TiO₂ particles facilitates the oxidation and decomposition of organic substrates in the paint layer, which severely restrict the performance of the optical properties and the color of TiO₂ products. Therefore, it is necessary to suppress the photocatalytic activity of the TiO₂ with inert protective layers, such as SiO₂, Al₂O₃. In view of the rich surface hydroxyl group on TiO₂ particles, the gas phase atomic layer deposition (ALD)-grown method was used as an efficient approach to coat much thin and uniform protective layers on the TiO₂particles. The ALD-grown method also possesses inherent advantages, such as no solvent waste, the feasibility of continuous processing, and the potential for scaling-up.

   The experimental results indicated that SiCl₄ could easily reacts with the hydroxyl group of TiO₂ viagasification and hydrolyzation in the ALD-grown method at room temperature. The TiO₂ particles coated with SiO₂ protective layer exhibited a significant decrease of the photocatalytic activity (K_app from 0.158 to 0.017 min^-1). The shielding effect and the coating thickness were strengthened in accordance with the increase of the coating number. This simple gas phase coating process with less reaction time, no use of acid and alkali solutions and dense and uniform coating layers has the potential application in the material synthesis and catalysis.

Keywords: TiO₂coating, ALD reaction, nanoparticles

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