Excitonic Interfacial Proton-Coupled Electron Transfer Mechanism in the Photocatalytic Oxidation of Methanol to Formaldehyde on TiO2(110)
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- 作者：Annapaola Migani ; Lluís Blancafort
- 刊名：Journal of the American Chemical Society
- 出版年：2016
- 出版时间：December 14, 2016
- 年：2016
- 卷：138
- 期：49
- 页码：16165-16173
- 全文大小：599K
- ISSN：1520-5126
文摘
CH<sub>3sub>OH on a single-crystal rutile TiO<sub>2sub>(110) surface is a widely studied model system for heterogeneous photocatalysis. Using spin-polarized density functional theory with a hybrid functional (HSE06), we study the photocatalytic oxidation of CH<sub>3sub>OH adsorbed at a coordinately unsaturated Ti site as an excited-state process with triplet spin multiplicity. The oxidation to CH<sub>2sub>O is stepwise and involves a CH<sub>3sub>O intermediate. The first O–H dissociation step follows an excitonic interfacial proton-coupled electron transfer mechanism where the hole–electron (h–e) pair generated during the excitation is bound, and the h is transferred to the adsorbate. The O–H dissociation paths associated with other h–e pairs are unreactive, and the moderate experimental efficiency is due to the different reactivity of the h–e pairs. The excited-state CH<sub>3sub>O intermediate further deactivates through a seam of intersection between the ground and excited states. It can follow three different paths, regeneration of adsorbed CH<sub>3sub>OH or formation of the ground-state CH<sub>3sub>O anion or an adsorbed CH<sub>2sub>O radical anion. The third channel corresponds to photochemical CH<sub>2sub>O formation from CH<sub>3sub>OH, where a single photon induces one electron oxidation and transfer of two protons. These results expand the current view on the photocatalysis of CH<sub>3sub>OH on TiO<sub>2sub>(110) by highlighting the role of excitons and showing that adsorbed CH<sub>3sub>OH may also be an active species in the photocatalytic oxidation to CH<sub>2sub>O.