Controlled calcination of ZnSe and ZnTe nanospheres to prepare visible-light catalysts with enhanced photostability and photoactivity

To obtain cheap, low-toxic, efficient and robust visible-light photocatalyst, a controlled calcination strategy is proposed for converting unstable ZnX (X=Se, Te) nanospheres (NSs) to ZnX–ZnO hybrid nanospheres (HNSs) with an appropriate composition and structure. Under such a conception, ZnSe–ZnO HNSs with various compositions were prepared by calcining ZnSe NSs under different conditions. Their morphology, composition, crystal structure, and optical absorption property were found to be highly dependent on their calcination condition. When serving as the catalyst for photodegrading organic dyes, they exhibited an attractive composition/structure-dependent photocatalytic activity and enhanced photostability. Particularly, the HNSs prepared by calcining at 500 °C for 4.0 h demonstrated the highest photocatalytic activity and excellent photostability, only taking 4.5 and 5.5 h to degrade 97.3 % methylene blue (MB) and 93 % ethyl violet (EV), respectively, under visible irradiation. The reason why such HNSs possessed the best photocatalytic performance was then intensively explored from different points of view. Moreover, we also extended this calcination protocol to prepare ZnTe–ZnO HNSs, whose photocatalytic performance was proven to be much better than that of pure ZnTe NSs as expected. We believe the strategy for fabricating such hybrid nanospheres and the exploration on their excellent photocatalytic performance will definitely benefit the preparation of high-efficient visible-light catalyst as well as the better understanding of its composition/structure-dependent photocatalytic activity.