Quantum dots TiO2 loaded amorphous SiO2 composite photocatalysts: Significant performance enhancement and the effect of SiO2 surface hydroxyl groups

Using amorphous SiO ₂ (A-SiO ₂ ) and tetrabutyl titanate (TBOT) as raw material, a composite photocatalyst with surface loaded quantum dot size TiO ₂ (A-SiO ₂/TiO ₂, AST) was prepared. The degradation of tetracycline hydrochloride as well as mechanism of performance improvement by A-SiO ₂ were investigated. The TiO ₂ on the composite was anatase with a content of 9.96 wt% and a size of 7–8 nm (quantum dot level). TiO ₂ was uniformly distributed and was closely bonded at the interface by chemical bonds. The degradation rate of AST was 95% after 60 min UV exposure, which was comparable to pure nano-TiO ₂. The particle size of TiO ₂ in AST was reduced from 20–50 nm to 7–8 nm comparing with pure nano-TiO ₂ and changed from a highly agglomerated to a well-dispersed state due to abundant hydroxyl groups on A-SiO ₂ surface. TiO ₂ bandgap width increased from 3.25 eV to 3.39 eV. These led to the exposing of active sites on TiO ₂ and significantly increased photogenerated carrier separation efficiency. This study provides a feasible and simple method to improve TiO ₂ nanoparticles’ photocatalytic activity, reduce the usage and achieve recycling to cut the application cost by surface coated.