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: firstname.lastname@example.org
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 via gasification 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 (Kapp 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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