Development of visible light-responsive N-doped TiO2/SiO2 core–shell nanoparticles for photocatalytic degradation of methylene blue dye

A visible-light responsive Nitrogen-doped TiO2 photocatalyst (NT) is a promising photocatalyst for environmental applications. This study aimed to synthesize N-doped TiO2/SiO2 (NT/SiO2) core/shell nanoparticles and investigate the effect of SiO2 on the photocatalytic reactivity of NT. The NT photocatalyst was prepared by the solvothermal method, while the NT/SiO2 core/shell photocatalysts were prepared by the sol–gel method with and without the use of cetyltrimethylammonium bromide (CTAB) as a directing agent. The photocatalytic reactivity of the NT/SiO2 core/shell photocatalysts was examined by methylene blue (MB) photodegradation under light-emitting diode visible light irradiation. Transmission electron microscope images indicated the core/shell structure, in which NT was a core and mesoporous SiO2 was a shell. The bonding of NT and SiO2 was examined by X-ray Photoelectron Spectroscopy. Interestingly, using CTAB caused a decrease in the photocatalytic performance of NT/SiO2 due to the aggregation of NT particles. The results of MB photodegradation indicated that the NT/SiO2 core/shell catalysts (without CTAB) had higher MB photodegradation efficiency (72%) than that of the NT/CTAB/SiO2 core/shell catalysts (60%), and bare NT (30%), respectively. The role of the mesoporous SiO2 shell was not only to increase the specific surface area but also to decrease the recombination rate of photogenerated electrons and holes in the NT/SiO2 core/shell photocatalysts.