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Excitonic Interfacial Proton-Coupled Electron Transfer Mechanism in the Photocatalytic Oxidation of Methanol to Formaldehyde on TiO2(110)

CH3OH on a single-crystal rutile TiO2(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 CH3OH adsorbed at a coordinately unsaturated Ti site as an excited-state process with triplet spin multiplicity. The oxidation to CH2O is stepwise and involves a CH3O 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 CH3O intermediate further deactivates through a seam of intersection between the ground and excited states. It can follow three different paths, regeneration of adsorbed CH3OH or formation of the ground-state CH3O anion or an adsorbed CH2O radical anion. The third channel corresponds to photochemical CH2O formation from CH3OH, where a single photon induces one electron oxidation and transfer of two protons. These results expand the current view on the photocatalysis of CH3OH on TiO2(110) by highlighting the role of excitons and showing that adsorbed CH3OH may also be an active species in the photocatalytic oxidation to CH2O

We acknowledge financial support from Spanish Ministerio de Economía y Competitividad (FIS2012-37549-C05-02, UNGI10-4E-801, RYC-2011-09582, CTQ2015-69363-P), Generalitat de Catalunya (2014SGR-301, 2014SGR-1202, XRQTC), and computational time from BSC Red Española de Supercomputación and Consorci de Serveis Universitaris de Catalunya

© Journal of the American Chemical Society, 2016, vol. 138, núm. 49, p. 16165-16173

American Chemical Society (ACS)

Author: Migani, Annapaola
Blancafort San José, Lluís
Date: 2016 December 14
Abstract: CH3OH on a single-crystal rutile TiO2(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 CH3OH adsorbed at a coordinately unsaturated Ti site as an excited-state process with triplet spin multiplicity. The oxidation to CH2O is stepwise and involves a CH3O 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 CH3O intermediate further deactivates through a seam of intersection between the ground and excited states. It can follow three different paths, regeneration of adsorbed CH3OH or formation of the ground-state CH3O anion or an adsorbed CH2O radical anion. The third channel corresponds to photochemical CH2O formation from CH3OH, where a single photon induces one electron oxidation and transfer of two protons. These results expand the current view on the photocatalysis of CH3OH on TiO2(110) by highlighting the role of excitons and showing that adsorbed CH3OH may also be an active species in the photocatalytic oxidation to CH2O
We acknowledge financial support from Spanish Ministerio de Economía y Competitividad (FIS2012-37549-C05-02, UNGI10-4E-801, RYC-2011-09582, CTQ2015-69363-P), Generalitat de Catalunya (2014SGR-301, 2014SGR-1202, XRQTC), and computational time from BSC Red Española de Supercomputación and Consorci de Serveis Universitaris de Catalunya
Format: application/pdf
ISSN: 0002-7863 (versió paper)
1520-5126 (versió electrònica)
Document access: http://hdl.handle.net/10256/13721
Language: eng
Publisher: American Chemical Society (ACS)
Collection: MINECO/PE 2015-2017/CTQ2015-69363-P
Reproducció digital del document publicat a: http://dx.doi.org/10.1021/jacs.6b11067
Articles publicats (D-Q)
Is part of: © Journal of the American Chemical Society, 2016, vol. 138, núm. 49, p. 16165-16173
Rights: Tots els drets reservats
Subject: Fotocatàlisi
Photocatalysis
Funcional de densitat, Teoria del
Density functionals
Reacció d’oxidació-reducció
Oxidation-reduction reaction
Protons -- Reaccions de transferència
Proton transfer reactions
Title: Excitonic Interfacial Proton-Coupled Electron Transfer Mechanism in the Photocatalytic Oxidation of Methanol to Formaldehyde on TiO2(110)
Type: info:eu-repo/semantics/article
Repository: DUGiDocs

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