Au-Core/Pt-Shell Bimetallic Cluster-Loaded TiO2. 1. Adsorption of Organosulfur Compound

Hiroaki Tada,*† Fumiaki Suzuki,‡ Seishiro Ito,‡ Tomoki Akita,§ Koji Tanaka,§ Tetsuro Kawahara, and Hisayoshi Kobayashi
Molecular Engineering Institute, Kinki University, 3-4-1, Kowakae, Higashi-Osaka, Osaka 577-8502, Japan, Department of Applied Chemistry, Faculty of Science and Engineering, Kinki University, 3-4-1, Kowakae, Higashi-Osaka, Osaka 577-8502, Japan, National Institute of Advanced Industrial Science and Technology, Midorigaoka 1-8-31, Ikeda, Osaka 563-8577, Japan, Nippon Sheet Glass Co. Ltd., 1-7, 2-Chome, Kaigan, Minato-Ku, Tokyo 105-8552, Japan, and Department of Chemical Technology, Kurashiki University of Science and Arts, 2640 Nishinoura, Tsurajima, Kurashiki 712, Japan
J. Phys. Chem. B, 2002, 106 (34), pp 8714–8720
DOI: 10.1021/jp0202690
Publication Date (Web): August 1, 2002
Copyright © 2002 American Chemical Society
*

 Author to whom correspondence should be addressed:  Tel:  +81-6-721-2332. Fax:  +81-6-721-3384. E-mail:  h-tada@apsrv.apch.kindai.ac.jp.

,
†

 Molecular Engineering Institute, Kinki University.

,
‡

 Department of Applied Chemistry, Faculty of Science and Engineering, Kinki University.

,
§

 National Institute of Advanced Industrial Science and Technology.

,

 Nippon Sheet Glass Co. Ltd.

,

 Kurashiki University of Science and Arts.

Abstract

Au-core/Pt-shell bimetallic clusters have been loaded on the surface of TiO2 (Au(x wt %)−Pt(y wt %)−TiO2(Pt/Au atomic ratio, z)) in a highly dispersed state by a two-step method consisting of the Au deposition and the subsequent Pt photodeposition. The mean diameter of the metal particles increases as a result of the Pt deposition from 3.6 (x = 0.39, y = 0, z = 0) to 4.3 nm (x = 0.37, y = 0.74, z = 2.0), while their number density hardly changes. High-resolution transmission electron spectroscopy directly confirms an Au-core/Pt-shell structure for a sample (z = 0.82). Adsorption experiments of bis(2-dipyridyl) disulfide, selected as a sulfur-containing compound, clarify that it adsorbs preferentially on the metal surfaces and the saturated adsorption amount on Au−Pt/TiO2 significantly decreases as compared to those on Au/TiO2 and Pt/TiO2. From X-ray photoelectron spectroscopic measurements, the Pt4f7/2 binding energy for the Au−Pt/TiO2 sample has been found to shift to a lower energy relative to that for bulk Pt by 1.4 eV. Also, the Pt photodeposition causes a red shift in the absorption maximum of the Au plasmon band. These spectroscopic results are rationalized in terms of the partial electron transfer from Au to Pt, which is also suggested by the calculations of a model cluster (Au2−Pt2/TiO2) using the density functional theory (DFT). Further, the DFT calculations indicate that the bonding and antibonding metal−sulfur orbitals are formed and the latter contribution is more significant to the bond for the Pt-containing clusters.

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History

  • Published In Issue August 29, 2002
  • Received January 29, 2002
    Revised June 2, 2002

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