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Title: Methanol on Anatase TiO 2 (101): Mechanistic Insights into Photocatalysis

Abstract

The photoactivity of methanol adsorbed on the anatase TiO2 (101) surface was studied by a combination of scanning tunneling microscopy (STM), temperature-programmed desorption (TPD), X-ray photoemission spectroscopy (XPS), and density functional theory (DFT) calculations. Isolated methanol molecules adsorbed at the anatase (101) surface show a negligible photoactivity. Two ways of methanol activation were found. First, methoxy groups formed by reaction of methanol with coadsorbed O2 molecules or terminal OH groups are photoactive, and they turn into formaldehyde upon UV illumination. The methoxy species show an unusual C 1s core-level shift of 1.4 eV compared to methanol; their chemical assignment was verified by DFT calculations with inclusion of final-state effects. The second way of methanol activation opens at methanol coverages above 0.5 monolayer (ML), and methyl formate is produced in this reaction pathway. The adsorption of methanol in the coverage regime from 0 to 2 ML is described in detail; it is key for understanding the photocatalytic behavior at high coverages. There, a hydrogen-bonding network is established in the adsorbed methanol layer, and consequently, methanol dissociation becomes energetically more favorable. DFT calculations show that dissociation of the methanol molecule is always the key requirement for hole transfer from the substrate tomore » the adsorbed methanol. Here, we show that the hydrogen-bonding network established in the methanol layer dramatically changes the kinetics of proton transfer during the photoreaction.« less

Authors:
ORCiD logo [1];  [2];  [1];  [1];  [1];  [1]; ORCiD logo [3]; ORCiD logo [2];  [1]
  1. Institute of Applied Physics, TU Wien, Wiedner Hauptstrasse 8-10/134, 1040 Vienna, Austria
  2. Department of Chemistry, Princeton University, Frick Laboratory, Princeton, New Jersey 08544, United States
  3. Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, Via Cozzi 55, 20125 Milano, Italy
Publication Date:
Research Org.:
Princeton Univ., NJ (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES)
OSTI Identifier:
1393722
Alternate Identifier(s):
OSTI ID: 1499011
Grant/Contract Number:  
SC0007347
Resource Type:
Published Article
Journal Name:
ACS Catalysis
Additional Journal Information:
Journal Name: ACS Catalysis Journal Volume: 7 Journal Issue: 10; Journal ID: ISSN 2155-5435
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
33 ADVANCED PROPULSION SYSTEMS; anatase; DFT; methanol; photocatalysis; STM; TiO2; TPD; XPS

Citation Formats

Setvin, Martin, Shi, Xiao, Hulva, Jan, Simschitz, Thomas, Parkinson, Gareth S., Schmid, Michael, Di Valentin, Cristiana, Selloni, Annabella, and Diebold, Ulrike. Methanol on Anatase TiO 2 (101): Mechanistic Insights into Photocatalysis. United States: N. p., 2017. Web. doi:10.1021/acscatal.7b02003.
Setvin, Martin, Shi, Xiao, Hulva, Jan, Simschitz, Thomas, Parkinson, Gareth S., Schmid, Michael, Di Valentin, Cristiana, Selloni, Annabella, & Diebold, Ulrike. Methanol on Anatase TiO 2 (101): Mechanistic Insights into Photocatalysis. United States. doi:https://doi.org/10.1021/acscatal.7b02003
Setvin, Martin, Shi, Xiao, Hulva, Jan, Simschitz, Thomas, Parkinson, Gareth S., Schmid, Michael, Di Valentin, Cristiana, Selloni, Annabella, and Diebold, Ulrike. Thu . "Methanol on Anatase TiO 2 (101): Mechanistic Insights into Photocatalysis". United States. doi:https://doi.org/10.1021/acscatal.7b02003.
@article{osti_1393722,
title = {Methanol on Anatase TiO 2 (101): Mechanistic Insights into Photocatalysis},
author = {Setvin, Martin and Shi, Xiao and Hulva, Jan and Simschitz, Thomas and Parkinson, Gareth S. and Schmid, Michael and Di Valentin, Cristiana and Selloni, Annabella and Diebold, Ulrike},
abstractNote = {The photoactivity of methanol adsorbed on the anatase TiO2 (101) surface was studied by a combination of scanning tunneling microscopy (STM), temperature-programmed desorption (TPD), X-ray photoemission spectroscopy (XPS), and density functional theory (DFT) calculations. Isolated methanol molecules adsorbed at the anatase (101) surface show a negligible photoactivity. Two ways of methanol activation were found. First, methoxy groups formed by reaction of methanol with coadsorbed O2 molecules or terminal OH groups are photoactive, and they turn into formaldehyde upon UV illumination. The methoxy species show an unusual C 1s core-level shift of 1.4 eV compared to methanol; their chemical assignment was verified by DFT calculations with inclusion of final-state effects. The second way of methanol activation opens at methanol coverages above 0.5 monolayer (ML), and methyl formate is produced in this reaction pathway. The adsorption of methanol in the coverage regime from 0 to 2 ML is described in detail; it is key for understanding the photocatalytic behavior at high coverages. There, a hydrogen-bonding network is established in the adsorbed methanol layer, and consequently, methanol dissociation becomes energetically more favorable. DFT calculations show that dissociation of the methanol molecule is always the key requirement for hole transfer from the substrate to the adsorbed methanol. Here, we show that the hydrogen-bonding network established in the methanol layer dramatically changes the kinetics of proton transfer during the photoreaction.},
doi = {10.1021/acscatal.7b02003},
journal = {ACS Catalysis},
number = 10,
volume = 7,
place = {United States},
year = {2017},
month = {9}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
DOI: https://doi.org/10.1021/acscatal.7b02003

Citation Metrics:
Cited by: 9 works
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Figures / Tables:

Figure 1 Figure 1: (a) TPD spectra of methanol on the anatase (101) surface. One monolayer (ML) is defined as one molecule per surface Ti5c atom. (b) Coverage-dependent adsorption energies, obtained from the results shown in (a) by the inversion analysis method.

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