Preparation of SiO2@Ag@SiO2@TiO2 Core-shell Structure and Its Photocatalytic Degradation Property

Photocatalytic degradation is an eco-friendly and high-efficiency way to degrade dye pollutants which has broad application prospects in water pollution control. In this study, the multi-layer core-shell structure of SiO2@Ag@SiO2@TiO2 was synthesized by different methods as a photocatalyst for pollutant degradation, with oxidation-reduction method, modified St?ber method and hydrothermal method in turn. Effect of silver nitrate（AgNO3）, tetraethyl orthosilicate（TEOS） and tetrabutyl titanate（TBOT） on the coating effect were discussed.Microstructure, phase structure, pore structure parameters and photoelectrical properties of SiO2-based multi-layer core-shell structure were systematically analyzed by various characterization methods while its degradation performance of methylene blue（MB） was also studied and discussed. The results show that when the mass ratio of AgNO3,TEOS and TBOT to SiO2 is 5 : 2.4 : 6 : 1, each layer of the multi-layer cored shell structure achieves the optimal coating effect. Compared with Si O2@Ti O2 and Si O2@Ag@Ti O2, the core-shell structure of SiO2@Ag@SiO2@TiO2photocatalyst has the best photocatalytic activity. Its photocatalytic degradation efficiency is close to 93% after simulated visible light irradiation for 45 min, and degradation efficiency keeps at 90% after 4 cycles of recycling tests.