Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 114, Issue 8, Pages 1801-1805Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1613756114
Keywords
adsorbate dynamics; water; dissociative adsorption; titanium dioxide; kinetic barriers
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Funding
- US Department of Energy (DOE), Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences Biosciences [KC0301050-47319]
- DOE's Office of Biological and Environmental Research
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Understanding adsorbed water and its dissociation to surface hydroxyls on oxide surfaces is key to unraveling many physical and chemical processes, yet the barrier for its deprotonation has never been measured. In this study, we present direct evidence for water dissociation equilibrium on rutile-TiO2(110) by combining supersonic molecular beam, scanning tunneling microscopy (STM), and ab initio molecular dynamics. We measure the deprotonation/ protonation barriers of 0.36 eV and find that molecularly bound water is preferred over the surface-bound hydroxyls by only 0.035 eV. We demonstrate that long-range electrostatic fields emanating from the oxide lead to steering and reorientation of the molecules approaching the surface, activating the O-H bonds and inducing deprotonation. The developed methodology for studying metastable reaction intermediates prepared with a high-energy clarify a wide range of important bond activation processes.
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