Preparation and photocatalytic degradation properties of Z-scheme Si-TiO2/g-C3N4 heterojunction modified with F-CDs

For environmental remediation, the development of innovative photocatalysts for efficient degradation of pollutants is essential. This paper construct three-dimensional (3D) Si-doped TiO₂ (Si-TiO₂) hollow material, and explores its photocatalytic reaction efficiency after composite g-C₃N₄ under F-doped carbon dots (F-CDs) modification. Silica opal template can be used to prepare Si-TiO₂ with hollow spherical structure and layered macroscopic mesoporous structure. Due to the confinement effect of template and the formation of Si-O-Ti bonds, anatase phase Si-TiO₂ hollow spheres do not undergo structural phase transition during high-temperature calcination. The incorporation of g-C₃N₄ can increase the light absorption range, and facilitate the formation of heterojunction with Si-TiO₂, thereby improving the charge carrier generation and separation efficiency. Since F-CDs contains carbon core and abundant surface functional groups, it is favorable to increase the number of active sites and adsorb more g-C₃N₄, thus increasing the heterojunction area. It can also be used as the electronic medium to accelerate carrier separation and transport rate between g-C₃N₄/Si-TiO₂ heterojunctions. Finally, thanks to the large specific surface area, abundance of active sites, excellent light absorption performance and effective charge separation and transport performance, the g-C₃N₄/F-CDs/Si-TiO₂ photocatalyst can decompose 3 mg L⁻¹ of Rh B under visible light, and the degradation rate can reach 74 % in 50 min under 10 mg conditions. The insights gained from this study could provide useful information for the development of effective photocatalysts.