Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 107, Issue 6, Pages 2391-2396Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0911349107
Keywords
photocatalysis; STM/STS; titania; water; molecular oxygen
Categories
Funding
- Engineering and Physical Sciences Research Council [EP/C541898/1]
- EU
- Royal Society
- Engineering and Physical Sciences Research Council [EP/C541898/1] Funding Source: researchfish
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Oxygen vacancies on metal oxide surfaces have long been thought to play a key role in the surface chemistry. Such processes have been directly visualized in the case of the model photocatalyst surface TiO2 (110) in reactions with water and molecular oxygen. These vacancies have been assumed to be neutral in calculations of the surface properties. However, by comparing experimental and simulated scanning tunneling microscopy images and spectra, we show that oxygen vacancies act as trapping centers and are negatively charged. We demonstrate that charging the defect significantly affects the reactivity by following the reaction of molecular oxygen with surface hydroxyl formed by water dissociation at the vacancies. Calculations with electronically charged hydroxyl favor a condensation reaction forming water and surface oxygen adatoms, in line with experimental observations. This contrasts with simulations using neutral hydroxyl where hydrogen peroxide is found to be the most stable product.
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