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

Abstract

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-TiO₂(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:

Wang, Zhi-Tao ^[1]; Wang, Yang-Gang ^[2]; Mu, Rentao ^[2]; Yoon, Yeohoon ^[2]; Dahal, Arjun ^[1]; Schenter, Gregory K. ^[3]; Glezakou, Vassiliki-Alexandra ^[2]; Rousseau, Roger ^[2]; Lyubinetsky, Igor ^[2]; Dohnálek, Zdenek ^[2]

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+ Show Author Affiliations

1. Microscopy Group, Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA 99352,, Institute for Integrated Catalysis, Pacific Northwest National Laboratory, Richland, WA 99352,
2. Institute for Integrated Catalysis, Pacific Northwest National Laboratory, Richland, WA 99352,, Catalysis Group, Physical Sciences Division, Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA 99352,
3. Institute for Integrated Catalysis, Pacific Northwest National Laboratory, Richland, WA 99352,, Chemical Physics &, Analysis Group, Physical Sciences Division, Physical &, Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA 99352

Publication Date:

Mon Feb 06 00:00:00 EST 2017

Research Org.:

Pacific Northwest National Laboratory (PNNL), Richland, WA (United States). Environmental Molecular Sciences Laboratory (EMSL)

Sponsoring Org.:

USDOE

OSTI Identifier:

1342803

Alternate Identifier(s):

OSTI ID: 1368129

Report Number(s):

PNNL-SA-119143
Journal ID: ISSN 0027-8424

Grant/Contract Number:  

KC0301050-47319; AC05-76RL01830

Resource Type:

Published Article

Journal Name:

Proceedings of the National Academy of Sciences of the United States of America

Additional Journal Information:

Journal Name: Proceedings of the National Academy of Sciences of the United States of America Journal Volume: 114 Journal Issue: 8; Journal ID: ISSN 0027-8424

Publisher:

Proceedings of the National Academy of Sciences

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