Enhancement of Titania Photoanode Performance by Sandwiching Copper between Two Titania Layers

Vacancies in semiconductors can play a versatile role in boosting their photocatalytic activity. In this work, a novel TiO(2)/Cu/TiO(2) sandwich structure is designed and constructed. Abundant vacancies were introduced in TiO(2) lattice by Cu reduction under heat treatment. Meanwhile, Cu atom could diffuse into TiO(2) to form Cu-doped TiO(2). The synergistic effect between oxygen vacancies and Cu atoms achieved about 2.4 times improved photocurrent of TiO(2)/Cu/TiO(2) sandwich structure compared to bare TiO(2) thin film. The enhanced photoactivity may be attributed to regulated electron structure of TiO(2) by oxygen vacancies and Cu dopant from experimental results and density functional theory calculations. Oxygen vacancies and Cu dopant in TiO(2) formed through copper metal reduction can introduce impurity levels and narrow the band gap of TiO(2), thus improve the visible light response. More importantly, the Cu(2+) and oxygen vacancies in TiO(2) lattice can dramatically increase the charge density around conduction band and promote separation of photo-induced charge carriers. Furthermore, the oxygen vacancies on the surface may serve as active site for sufficient chemical reaction. This work presents a novel method to prepare doped metal oxides catalysts with abundant vacancies for improving photocatalytic activity.