A new understanding of the photocatalytic mechanism of the direct Z-scheme g-C3N4/TiO2 heterostructure. Issue 45 (7th November 2016)

• Record Type: Journal Article
• Authors: Liu, Jianjun; Cheng, Bei; Yu, Jiaguo
• Is Part Of: Physical chemistry chemical physics. Volume 18:Issue 45(2016)
• Page Start: 31175
• Page End: 31183
• Publication Date: 2016-11-07
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c6cp06147h
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : First-principles calculations help to understand the direct Z-scheme photocatalytic mechanism of the g-C3 N4 /TiO2 heterostructure. Abstract : Constructing a TiO2 based heterostructure is a very effective strategy for enhancing photocatalytic performance. The details of the electronic structure, interfacial interaction, and photogenerated carrier separation are important for explaining the photocatalytic properties of a heterostructure. Herein, the density of states, charge distribution, and the band offset of the monolayer g-C3 N4 /TiO2 heterojunction are systematically investigated through the hybrid DFT method. Results indicated that the valence band offset and the conduction band offset of the g-C3 N4 /TiO2 heterostructure were 0.40 and 0.18 eV, respectively. Interfacial interaction made the TiO2 surface with negative charge, whereas the g-C3 N4 surface with positive charge, which led to the formation of a built-in electric field at the interface. Under illumination, the built-in electric field accelerates the transfer of photoexcited electrons in the CB of TiO2 into the VB of g-C3 N4, thus resulting in the photoexcited electrons and holes naturally accumulating in the CB of g-C3 N4 and the VB of TiO2, respectively. The photoexcited electrons and holes gathering in different surface regions efficiently prolonged the lifetime of photogenerated carriers. Meanwhile, electrons in the CB of g-C3 N4 and holes in the VB of TiO2 had a stronger redox ability. Therefore, g-C3 N4 /TiO2 is a direct Z-scheme photocatalyst, and the Z-scheme heterostructure mechanism can well explain the improved photocatalytic activity of the g-C3 N4 /TiO2 heterostructure.