Critical role of the defect state in the photo-oxidation of methanol on TiO2(110). Issue 38 (25th September 2020)

• Record Type: Journal Article
• Authors: Jin, Fan; Zhang, Xiao; Wei, Min; Chen, Tingwei; Ma, Huizhong; Ma, Yuchen
• Is Part Of: Journal of materials chemistry. Volume 8:Issue 38(2020)
• Page Start: 20082
• Page End: 20090
• Publication Date: 2020-09-25
• Subjects: Materials -- Research -- Periodicals; Chemistry, Analytic -- Periodicals; Environmental sciences -- Research -- Periodicals; 543.0284
• DOI: 10.1039/d0ta05637e
• Languages: English
• ISSNs: 2050-7488

Abstract

Abstract : Photo-oxidation of CH3 OH on TiO2 has been extensively studied in order to understand the fundamental principles of heterogeneous photocatalysis. Abstract : Photo-oxidation of CH3 OH on TiO2 has been extensively studied in order to understand the fundamental principles of heterogeneous photocatalysis. However, the roles of the photogenerated hole and the energy barrier in this reaction are still controversial. Using the ab initio many-body Green's function theory, we examine the evolution of excitons along the reaction path of CH3 OH photo-oxidation on the rutile TiO2 (110) surface. We reveal the critical role of the Ti 3d defect state produced by the final product in lowering the energy barrier (by 1.3 eV) and stabilizing the product in the conversion from CH3 O to CH2 O. With the transfer of hydrogen from CH3 O to TiO2, the hole migrates gradually from the O 2p orbitals of TiO2 at the valence band edge to the Ti 3d orbitals near the conduction band bottom, with the band-gap hole state localized on the adsorbate as the bridge. We find that whether the hole is initially trapped by the reactant CH3 O is not a crucial issue for the oxidation of CH3 O to occur. Hole trapping required in photocatalytic reactions might just be an event happening in the reaction process. In the oxidation of CH3 OH to CH3 O, the hole remains within TiO2 in the whole process and this reaction is essentially thermal-driven. The critical role of the defect state clarified in this work provides new insights into understanding photochemical reactions at metal oxide surfaces. Based on our studies, we propose a convenient strategy to judge whether the hole participates in the reaction.