skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Structure of Rutile TiO 2 (110) in Water and 1 Molal Rb+ at pH 12: Interrelationship Among Surface Charge, Interfacial Hydration Structure, and Substrate Structural Displacements

Abstract

The rutile (110)-aqueous solution interface structure was measured in deionized water (DIW) and 1 m RbCl + RbOH solution (pH 12) at 25 C with the X-ray crystal truncation rod method. The rutile surface in both solutions consists of a stoichiometric (1 1) surface unit mesh with the surface terminated by bridging oxygen (BO) and terminal oxygen (TO) sites. An additional hydration layer is observed above the TO site, with three distinct water adsorption sites each having well-defined vertical and lateral locations. Rb+ specifically adsorbs at the tetradentate site between the TO and BO sites, replacing one of the adsorbed water molecules at the interface. There is no further ordered water structure observed above the hydration layer. Structural displacements of atoms at the oxide surface are observed to be sensitive to the solution composition. Ti atom displacements from their bulk lattice positions, as large as 0.05 at the rutile (110)-DIW interface, decay in magnitude into the crystal with significant relaxations that are observable down to the fourth Ti-layer below the surface. A systematic outward shift was observed for Ti atom locations below the BO rows, while a systematic inward displacement was found for Ti atoms below the TO rows. Themore » Ti displacements were mostly reduced in contact with the RbCl solution at pH 12, with no statistically significant relaxations in the fourth layer Ti atoms. The distance between the surface 5-fold Ti atoms and the oxygen atoms of the TO site is 2.13 0.03 in DIW and 2.05 0.03 in the Rb+ solution, suggesting that water adsorbs mainly in molecular form to the rutile (110) surface at the TO site in DIW, while it is primarily in the form of an adsorbed hydroxyl group at pH 12.« less

Authors:
 [1];  [1];  [2];  [3];  [4];  [5]
  1. Argonne National Laboratory (ANL)
  2. University of Illinois, Chicago
  3. Northwestern University, Evanston
  4. Illinois State Water Survey, Champaign, IL
  5. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1081585
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Surface Science; Journal Volume: 601; Journal Issue: 4
Country of Publication:
United States
Language:
English

Citation Formats

Zhang, Zhan, Fenter, Paul, Sturchio, N. C., Bedzyk, Michael J., Machesky, Michael L., and Wesolowski, David J. Structure of Rutile TiO2 (110) in Water and 1 Molal Rb+ at pH 12: Interrelationship Among Surface Charge, Interfacial Hydration Structure, and Substrate Structural Displacements. United States: N. p., 2007. Web. doi:10.1016/j.susc.2006.12.007.
Zhang, Zhan, Fenter, Paul, Sturchio, N. C., Bedzyk, Michael J., Machesky, Michael L., & Wesolowski, David J. Structure of Rutile TiO2 (110) in Water and 1 Molal Rb+ at pH 12: Interrelationship Among Surface Charge, Interfacial Hydration Structure, and Substrate Structural Displacements. United States. doi:10.1016/j.susc.2006.12.007.
Zhang, Zhan, Fenter, Paul, Sturchio, N. C., Bedzyk, Michael J., Machesky, Michael L., and Wesolowski, David J. Mon . "Structure of Rutile TiO2 (110) in Water and 1 Molal Rb+ at pH 12: Interrelationship Among Surface Charge, Interfacial Hydration Structure, and Substrate Structural Displacements". United States. doi:10.1016/j.susc.2006.12.007.
@article{osti_1081585,
title = {Structure of Rutile TiO2 (110) in Water and 1 Molal Rb+ at pH 12: Interrelationship Among Surface Charge, Interfacial Hydration Structure, and Substrate Structural Displacements},
author = {Zhang, Zhan and Fenter, Paul and Sturchio, N. C. and Bedzyk, Michael J. and Machesky, Michael L. and Wesolowski, David J},
abstractNote = {The rutile (110)-aqueous solution interface structure was measured in deionized water (DIW) and 1 m RbCl + RbOH solution (pH 12) at 25 C with the X-ray crystal truncation rod method. The rutile surface in both solutions consists of a stoichiometric (1 1) surface unit mesh with the surface terminated by bridging oxygen (BO) and terminal oxygen (TO) sites. An additional hydration layer is observed above the TO site, with three distinct water adsorption sites each having well-defined vertical and lateral locations. Rb+ specifically adsorbs at the tetradentate site between the TO and BO sites, replacing one of the adsorbed water molecules at the interface. There is no further ordered water structure observed above the hydration layer. Structural displacements of atoms at the oxide surface are observed to be sensitive to the solution composition. Ti atom displacements from their bulk lattice positions, as large as 0.05 at the rutile (110)-DIW interface, decay in magnitude into the crystal with significant relaxations that are observable down to the fourth Ti-layer below the surface. A systematic outward shift was observed for Ti atom locations below the BO rows, while a systematic inward displacement was found for Ti atoms below the TO rows. The Ti displacements were mostly reduced in contact with the RbCl solution at pH 12, with no statistically significant relaxations in the fourth layer Ti atoms. The distance between the surface 5-fold Ti atoms and the oxygen atoms of the TO site is 2.13 0.03 in DIW and 2.05 0.03 in the Rb+ solution, suggesting that water adsorbs mainly in molecular form to the rutile (110) surface at the TO site in DIW, while it is primarily in the form of an adsorbed hydroxyl group at pH 12.},
doi = {10.1016/j.susc.2006.12.007},
journal = {Surface Science},
number = 4,
volume = 601,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • Detailed description is presented of molten salt synthesis, single crystal structures, and a comparison is offered of the {alpha}- and {beta}-La{sub 4}Ti{sub 9}Si{sub 4}O{sub 30} phases. The electrical property and band struture of this mixed-valence titanium (III/IV) oxosilicate series, La{sub 4}Ti(Si{sub 2}O{sub 7}){sub 2}(TiO{sub 2}){sub 4m} (m = 1,2), are discussed in terms of electronic interactions in a confined space with respect to the (110) rutile sheets. The results from the extended Hueckel tight binding calculations and the bond valence sum analysis are contrasted with regard to charge distribution. 33 refs., 9 figs., 3 tabs.
  • Adsorption, binding, and diffusion of CO2 molecules on rutile TiO2(110) model surfaces was investigated experimentally using scanning tunneling microscopy, infrared reflection adsorption spectroscopy (IRAS), temperature programmed desorption and theoretically via dispersion corrected density functional theory and ab initio molecular dynamics. In accord with previous studies, bridging oxygen (Ob) vacancies (VO’s) are found to be the most stable binding sites. Additional CO2 adsorbs on 5-coordinated Ti sites (Ti5c) with the initial small fraction is stabilized by CO2 on VO sites. The Ti5c-bound CO2 is found to be highly mobile at 50 K at coverages of up to 1/2 monolayer (ML). Theoreticalmore » studies show that the CO2 diffusion on Ti5c rows proceeds via a rotation-tumbling mechanism with extremely low barrier of 0.06 eV. The Ti5c-bound CO2 molecules are found to bind preferentially to a single Ti5c with the O=C=O axis tilted away from the surface normal. The binding energy of tilted CO2 molecules changes only slightly with changes in the azimuth of the CO2 tilt angle. At 2/3 ML, CO2 diffusion is hindered and at 1 ML an ordered (2×2) overlayer with a zigzag arrangement of tilted CO2 molecules develops along the Ti5c rows. Out of phase arrangement of the zigzag chains is observed across the rows. An additional 0.5 ML of CO2 can be adsorbed at Ob sites with a binding energy only slightly lower than that on Ti5c sites due to quadrupole-quadrupole interactions with the Ti5c-bound CO2 molecules.« less
  • Cited by 4
  • Charge transfer between metal nanoparticles and the supported TiO{sub 2} surface is primarily important for catalytic applications as it greatly affects the catalytic activity and the thermal stability of the deposited nanoparticles on the surface. Herein, systematic spin-polarized density functional and HSE06 calculations are performed to evaluate the adsorption, diffusion, and charge state of several transition metal monomers on both stoichiometric and reduced rutile TiO{sub 2} (110) surface. Although the presence of oxygen vacancy (O{sub v}) increases the binding of Au, Pt and Pd on the surface, it weakens the interaction thus enhancing the diffusion for Fe, Co, Ni, Ag,more » and Cu adatoms on the surface. For pristine reduced surface, only a small portion (around 5%) of the excess electrons occupy the topmost surface, which are mainly delocalized at the second nearest and third nearest fivefold coordinated Ti (Ti{sub 5c}) atoms. Excess electrons populating at the Ti{sub 5c} atoms on the basal plane can be transferred to strongly electronegative adsorbates like Au and Pt thus enabling a moderate adsorption at this site, whereas no stable adsorption is found for other less electronegative transition metal adatoms (Ag, Cu, Fe, Co, Ni, and Pd) on the reduced surface and for all the adatoms on stoichiometric surface. This result clarifies the origin of the experimental observation of the adsorption of O{sub 2} and CO molecules at Ti{sub 5c} sites in connection with charge transfer. In addition, the spatial redistribution of the excess electrons around the O{sub v} upon the adsorption of the monomers is thoroughly examined. Our finding of an accumulation of excess electrons at the Ti{sub 5c} sites around the monomers explains the critical role of the perimeter interface of the deposited nanoparticles in promoting the adsorption and activation of reactants observed in experiments.« less
  • No abstract prepared.