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

Abstract

Using amorphous SiO2 (A-SiO2) and tetrabutyl titanate (TBOT) as raw material, a composite photocatalyst with surface loaded quantum dot size TiO2 (A-SiO2/TiO2, AST) was prepared. The degradation of tetracycline hydrochloride as well as mechanism of performance improvement by A-SiO2 were investigated. The TiO2 on the composite was anatase with a content of 9.96 wt% and a size of 7–8 nm (quantum dot level). TiO2 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-TiO2. The particle size of TiO2 in AST was reduced from 20–50 nm to 7–8 nm comparing with pure nano-TiO2 and changed from a highly agglomerated to a well-dispersed state due to abundant hydroxyl groups on A-SiO2 surface. TiO2 bandgap width increased from 3.25 eV to 3.39 eV. These led to the exposing of active sites on TiO2 and significantly increased photogenerated carrier separation efficiency. This study provides a feasible and simple method to improve TiO2 nanoparticles’ photocatalytic activity, reduce the usage and achieve recycling to cut the application cost by surface coated.