SnO2/ZnO heterostructured nanorods: Structural properties and mechanistic insights into the enhanced photocatalytic activity

Restricting electron-hole recombination addresses a bottleneck in photocatalytic processes, namely, low quantum efficiency. One way to restrict recombination is by constructing a heterostructure to spatially separate photoproduced electrons from corresponding holes. In this study, a SnO2-ZnO binary system is constructed hydrothermally to clarify the enhancement mechanism of photocatalytic activity in a heterostructure. XPS analysis confirms that the chemical state of Sn cations remains intact, while that of Zn cations gradually changes upon heterostructuring. Further in-depth analyses with XANES and EXAFS at the Zn K-edge reveal that the oxidation state of Zn cations decreases and their local structure gradually changes. The sensitivity of the oxidation state, local environment around Zn cations, and SnO2 loading amount suggest the partial replacement of Zn cations on the surface region by a small portion of Sn cations. Heterostructuring with SnO2 beneficially affects the photocatalytic activity of ZnO for mineralizing refractory organic compounds under ultraviolet light irradiation (200 < lambda < 400 nm). The enhanced photocatalytic activity is caused by the efficient restriction of electron-hole recombination, as is evidenced by light-induced infrared absorption spectroscopy. The electron population is increased by up to 17 times after the heterostructuring.

Automated summary

Constructing a SnO2-ZnO heterostructure enhances the photocatalytic activity by restricting electron-hole recombination, increasing the electron population by up to 17 times. XPS, XANES, and EXAFS analyses confirm changes in the chemical state and local structure of Zn cations upon heterostructuring.