Au‐TiO ₂ ‐ZnO sandwich‐structured composite films with enhanced ultraviolet‐light photocatalytic activity

Abstract

The rapid recombination of photogenerated electron-hole pairs is one of the main reasons for limiting the photocatalytic efficiency of semiconductor photocatalysts. This paper investigates and analyzes two methods to improve the separation and lifetimes of electronhole pairs: semiconductor heterojunction and metal electron sink. As a specific example, an Au-TiO 2 -ZnO composite film with a sandwich structure is prepared. The energy level gradient formed at the TiO 2 /ZnO heterojunction separates the electron-hole pairs effectively, and the AuNPs promote the photo-induced charge transfer. Moreover, a synergistic effect of TiO 2 /ZnO heterojunction and AuNPs, which can further improve the photocatalytic performance, has been found by the photoelectric performance measurement. The experimental results demonstrate that the UV photocurrent density of the Au-TiO 2 -ZnO composite film is almost 22 times that of the pure TiO 2 film. And a similar result has been observed in the UV light degradation of methylene blue. Such Au-TiO 2 -ZnO composite film combining semiconductor heterojunctions and metal electron sink has a potential prospect in the photo-degradation of organic pollutants.