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.