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Title: Probing the interactions of Pt, Rh and bimetallic Pt-Rh clusters with the TiO2(110) support

Abstract

Pt, Rh, and Pt-Rh clusters on TiO{sub 2}(1 1 0) have been investigated by scanning tunneling microscopy (STM), soft X-ray photoelectron spectroscopy (sXPS), and low energy ion scattering (LEIS). The surface compositions of Pt-Rh clusters are Pt-rich (66-80% Pt) for room temperature deposition of both 2 ML of Pt on 2 ML of Rh (Rh + Pt) and 2 ML of Rh on 2 ML of Pt (Pt + Rh). Pt and Rh atoms readily diffuse within the clusters at room temperature, and although diffusion is slower at 240 K, intermixing of Pt and Rh still occurs. The binding energies of surface and bulk states for Rh(3d{sub 5/2}) and Pt(4f{sub 7/2}) can be distinguished in sXPS studies, and an analysis of these spectra indicates that the surface compositions of the Pt + Rh and Rh + Pt clusters are similar at room temperature but not identical. In addition to sintering, the pure Pt, pure Rh and Pt-Rh clusters become completely encapsulated by titania upon heating to 700 K. sXPS investigations show that annealing the clusters to 850 K induces reduction of titania support to Ti{sup +2} and Ti{sup +3}, with the extent of reduction being the greatest for Pt, themore » least for Rh and intermediate for Pt-Rh. We propose that TiO{sub 2} is reduced at the metal-titania interface on top of the clusters, not at the base of the clusters. Furthermore, the extent of titania reduction is greater for metal clusters with weaker metal-oxygen bonds because oxygen atoms are less likely to migrate to the top of the clusters, and therefore the encapsulating titania is oxygen-deficient.« less

Authors:
 [1];  [2];  [3];  [2];  [4];  [4];  [2]
  1. Gebze Yuksek Teknoloji Enstitusu, Gebze-Kocaeli, Turkey
  2. University of South Carolina, Columbia
  3. Brookhaven National Laboratory (BNL)
  4. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
931021
DOE Contract Number:  
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Surface Science; Journal Volume: 601; Journal Issue: 14,15
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; PLATINUM; RHODIUM; BIMETALS; SUBSTRATES; TITANIUM OXIDES; INTERACTIONS; DIFFUSION; BINDING ENERGY; REDUCTION; TITANIUM; INTERFACES

Citation Formats

Ozturk, O., Park, J. B., Ma, S., Ratliff, J. S., Zhou, Jing, Mullins, David R, and Chen, D. A. Probing the interactions of Pt, Rh and bimetallic Pt-Rh clusters with the TiO2(110) support. United States: N. p., 2007. Web. doi:10.1016/j.susc.2007.05.030.
Ozturk, O., Park, J. B., Ma, S., Ratliff, J. S., Zhou, Jing, Mullins, David R, & Chen, D. A. Probing the interactions of Pt, Rh and bimetallic Pt-Rh clusters with the TiO2(110) support. United States. doi:10.1016/j.susc.2007.05.030.
Ozturk, O., Park, J. B., Ma, S., Ratliff, J. S., Zhou, Jing, Mullins, David R, and Chen, D. A. Mon . "Probing the interactions of Pt, Rh and bimetallic Pt-Rh clusters with the TiO2(110) support". United States. doi:10.1016/j.susc.2007.05.030.
@article{osti_931021,
title = {Probing the interactions of Pt, Rh and bimetallic Pt-Rh clusters with the TiO2(110) support},
author = {Ozturk, O. and Park, J. B. and Ma, S. and Ratliff, J. S. and Zhou, Jing and Mullins, David R and Chen, D. A.},
abstractNote = {Pt, Rh, and Pt-Rh clusters on TiO{sub 2}(1 1 0) have been investigated by scanning tunneling microscopy (STM), soft X-ray photoelectron spectroscopy (sXPS), and low energy ion scattering (LEIS). The surface compositions of Pt-Rh clusters are Pt-rich (66-80% Pt) for room temperature deposition of both 2 ML of Pt on 2 ML of Rh (Rh + Pt) and 2 ML of Rh on 2 ML of Pt (Pt + Rh). Pt and Rh atoms readily diffuse within the clusters at room temperature, and although diffusion is slower at 240 K, intermixing of Pt and Rh still occurs. The binding energies of surface and bulk states for Rh(3d{sub 5/2}) and Pt(4f{sub 7/2}) can be distinguished in sXPS studies, and an analysis of these spectra indicates that the surface compositions of the Pt + Rh and Rh + Pt clusters are similar at room temperature but not identical. In addition to sintering, the pure Pt, pure Rh and Pt-Rh clusters become completely encapsulated by titania upon heating to 700 K. sXPS investigations show that annealing the clusters to 850 K induces reduction of titania support to Ti{sup +2} and Ti{sup +3}, with the extent of reduction being the greatest for Pt, the least for Rh and intermediate for Pt-Rh. We propose that TiO{sub 2} is reduced at the metal-titania interface on top of the clusters, not at the base of the clusters. Furthermore, the extent of titania reduction is greater for metal clusters with weaker metal-oxygen bonds because oxygen atoms are less likely to migrate to the top of the clusters, and therefore the encapsulating titania is oxygen-deficient.},
doi = {10.1016/j.susc.2007.05.030},
journal = {Surface Science},
number = 14,15,
volume = 601,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}