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

• Main Authors: Fan Yang, Ruizhuang Yang, Lin Yan, Jiankun Wu, Xiaolin Liu, Lirong Yang, Minglong Zhong, Xuan Luo, Lin Zhang
• Format: Article
• Language: English
• Published: MDPI AG 2020-09-01
• Series: Materials
• Subjects: metal reduction; oxygen vacancies; TiO₂; electronic structure; photoanode
• Online Access: https://www.mdpi.com/1996-1944/13/19/4326

Vacancies in semiconductors can play a versatile role in boosting their photocatalytic activity. In this work, a novel TiO₂/Cu/TiO₂ sandwich structure is designed and constructed. Abundant vacancies were introduced in TiO₂ lattice by Cu reduction under heat treatment. Meanwhile, Cu atom could diffuse into TiO₂ to form Cu-doped TiO₂. The synergistic effect between oxygen vacancies and Cu atoms achieved about 2.4 times improved photocurrent of TiO₂/Cu/TiO₂ sandwich structure compared to bare TiO₂ thin film. The enhanced photoactivity may be attributed to regulated electron structure of TiO₂ by oxygen vacancies and Cu dopant from experimental results and density functional theory calculations. Oxygen vacancies and Cu dopant in TiO₂ formed through copper metal reduction can introduce impurity levels and narrow the band gap of TiO₂, thus improve the visible light response. More importantly, the Cu²⁺ and oxygen vacancies in TiO₂ 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.