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Title: Probing equilibrium of molecular and deprotonated water on TiO 2(110)

Understanding water structure and its deprotonation dynamics on oxide surfaces is key to understanding many physical and chemical processes. In this study, we directly measure the energy barriers associated with the protonation equilibrium of water on the prototypical oxide surface, rutile-TiO 2(110) by a combination of a supersonic molecular beam, scanning tunneling microscopy, and ab initio molecular dynamics simulations. We show 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 incident energy dependent studies allow for a direct determination of the dissociation barrier. Temperature dependent imaging yields the reverse barrier and the equilibrium constant. Molecularly bound water is preferred by 0.035 eV over the surface-bound hydroxyls. In conclusion, the techniques developed in this work are readily extended to other systems where the understanding of bond-activation processes is critical.
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [2] ;  [1]
  1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Oregon State Univ., Corvallis, OR (United States)
Publication Date:
Report Number(s):
PNNL-SA-119143
Journal ID: ISSN 0027-8424; 49642; KC0302010
Grant/Contract Number:
AC05-76RL01830; KC0301050-47319
Type:
Published Article
Journal Name:
Proceedings of the National Academy of Sciences of the United States of America
Additional Journal Information:
Journal Volume: 114; Journal Issue: 8; Journal ID: ISSN 0027-8424
Publisher:
National Academy of Sciences, Washington, DC (United States)
Research Org:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 54 ENVIRONMENTAL SCIENCES; Environmental Molecular Sciences Laboratory; adsorbate dynamics; water; dissociative adsorption; titanium dioxide; kinetic barriers
OSTI Identifier:
1342803
Alternate Identifier(s):
OSTI ID: 1368129