Subscriber access provided by UNIVERSITY OF TOLEDO LIBRARIES
Surfaces, Interfaces, and Catalysis; Physical Properties of Nanomaterials and Materials
Visualization of Water-induced Surface Segregation of Polarons on Rutile TiO(110) 2
Chi Ming Yim, Ji Chen, Yu Zhang, Bobbie-Jean Shaw, Chi Pang, David C. Grinter, Hendrik Bluhm, Miquel Salmeron, Christopher Andrew Muryn, Angelos Michaelides, and Geoff Thornton J. Phys. Chem. Lett., Just Accepted Manuscript • DOI: 10.1021/acs.jpclett.8b01904 • Publication Date (Web): 06 Aug 2018 Downloaded from http://pubs.acs.org on August 8, 2018
Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
Page 1 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
The Journal of Physical Chemistry Letters
Visualization of Water-induced Surface Segregation of Polarons on Rutile TiO2(110)
Chi M. Yim, †,∇ Ji Chen, ‡,∇ Yu Zhang,† Bobbie-Jean Shaw,† Chi L. Pang,† David C. Grinter,† Hendrik Bluhm,§,∥ Miquel Salmeron,⊥ Christopher A. Muryn,# Angelos Michaelides,‡ and Geoff Thornton*,†
†
Department of Chemistry and London Centre for Nanotechnology, University
College London, 20 Gordon Street, London WC1H 0AJ, UK ‡
Department of Physics and Astronomy, London Centre for Nanotechnology and
Thomas Young Centre, University College London, London WC1E 6BT, UK §
Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley,
California 94720, USA ∥
Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley,
California 94720, USA ⊥
Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley,
California 94720, USA #
School of Chemistry, The University of Manchester, Manchester, M13 9PL, UK
*Corresponding author:
[email protected] 1 Environment ACS Paragon Plus
The Journal of Physical Chemistry Letters 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 2 of 24
ABSTRACT Water-oxide surfaces are ubiquitous in nature and of widespread importance to phenomena like corrosion as well as contemporary industrial challenges such as energy production through water splitting. So far a reasonably robust understanding of the structure of such interfaces under certain conditions has been obtained. Considerably less is known about how overlayer water modifies the inherent reactivity of oxide surfaces. Here we address this issue experimentally for rutile TiO2(110)
using
scanning
tunneling microscopy
and photoemission,
with
complementary density functional theory calculations. Through detailed studies of adsorbed water nanoclusters and continuous water overlayers, we determine that excess electrons in TiO2 are attracted to the top surface layer by water molecules. Measurements on methanol show similar behavior. Our results suggest that adsorbateinduced surface segregation of polarons could be a general phenomenon for technologically relevant oxide materials, with consequences for surface chemistry and the associated catalytic activity.
Table of Contents (TOC) Graphic
2 Environment ACS Paragon Plus
Page 3 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
The Journal of Physical Chemistry Letters
All real materials contain defects, ranging from atomic vacancies, to interstitials, to impurities, to excess electrons, and more. Defects greatly affect the physical and optical properties of materials and when present at the surfaces of materials can significantly alter the chemical activity of a material. Indeed, a large body of work has shown that defects at the surfaces of materials act as preferential sites for adsorbate binding; sites at which adsorbates are pinned or bonded more strongly and sites with altered catalytic properties.1-3 However, considerably less is known about the other side of this interplay between adsorbates and defects, namely how adsorbates alter the distribution of defects at the surfaces of materials.4,5 This is the issue we address in the current study through a detailed set of experiments and simulations of water on rutile TiO2, in which we focus on the interplay between water and excess electron defects. The water/rutile TiO2(110) interface has been selected for this study because of its importance to catalysis and photocatalysis and because it is one of the most widely studied and most well understood of all model oxide surface systems.3,6-8 Thanks to this earlier work we now have a broad understanding of the behavior of water on TiO2(110) at a range of temperatures and water coverages. It is known, for example, that water dissociates at defects on TiO2(110). 9-13 Higher exposure to water at
