Boosting photocatalytic performance and stability of CuInS^sub 2^/ZnS-TiO^sub 2^ heterostructures via sol-gel processed integrate amorphous titania gel

Semiconductor quantum dots (QDs) are interesting photocatalysts for solar fuel production and environmental pollution control. However, the poor stability and recombination probability of photogenerated electron-hole pairs prevented the practical applications of QDs based photocatalysts. Herein we demonstrated that the incorporation of amorphous titania (TiO2) coatings with CuInS2/ZnS-TiO2 heterostructures (CIS/ZnS-TiO2 gel) can markedly boost photocatalytic performance and stability for Cr (VI) reduction. The promoted photocatalytic activity of CIS/ZnS-TiO2 gel is associated with the enhanced light-absorption and distinctive heterojunction imposed by the integration of CIS/ZnS-TiO2 with amorphous TiO2 coatings, which drastically speed the separation of photogenerated electron-hole pairs. Moreover, the physical protection and photocorrosion-inhibition functions (receptors of photogenerated holes from CIS/ZnS QDs) arised from the amorphous TiO2 coatings were mainly responsible for the promoted photostability of CIS/ZnS-TiO2 gel. Our CIS/ZnS-TiO2 gel retained over 90% of its initial activity under cycle tests, while the bared CIS/ZnS-TiO2 showed a distinct reduction (approximately 35%) of its original efficiency due to the photocorrosion and weight-loss. Obviously, the incorporation of amorphous TiO2 along with its bulk appearance of gel realized the enhanced photocatalytic performance with a favorable cycling stability. This strategy could be extended to other QDs-based photocatalysts in improving photocatalytic performance toward practical application.