AVS 51st International Symposium
    Surface Science Tuesday Sessions
       Session SS-TuP

Paper SS-TuP40
Growth and Reactivity of Pt, Rh and Pt-Rh Nanoparticles on TiO@sub 2@(110)

Tuesday, November 16, 2004, 4:00 pm, Room Exhibit Hall B

Session: Poster Session
Presenter: S. Ma, University of South Carolina
Authors: S. Ma, University of South Carolina
J.S. Ratliff, University of South Carolina
D.A. Chen, University of South Carolina
Correspondent: Click to Email
Pt, Rh and Pt-Rh nanoparticles have been deposited on TiO@sub 2@(110) at room temperature and have been characterized by scanning tunneling microscopy (STM). The deposition of a small amount of Pt on the surface (0.12 ML) results in particles with an average diameter of 22.7+4.2 Å and height of 4.4+1.2 Å. In contrast to the growth of Cu and Ni on TiO@sub 2@(110), the Pt particles do not exhibit a preference to reside at the step edges. At higher Pt coverages (2 ML), the average size of the particles increases to 30.4+4.6 Å in diameter and 8.5+2.0 Å in height. Larger particles with roughly the same size distribution could be produced by depositing at room temperature and annealing to elevated temperatures. For example, after annealing the 2 ML coverage of Pt to 500 K, particles sizes ranged from 40-45 Å in diameter and ~10 Å in height. Further heating to 700 K increased the sizes of the particles to ~50 Å in diameter and 10-12 Å in height, and the largest particles were prepared by annealing at 1000 K (60 Å in diameter, 15 Å in height). Since Pt particles on TiO@sub 2@ are known to encapsulate with a TiO@sub x@ species upon annealing, X-ray photoelectron studies were carried out on the Pt particles annealed to 1000 K. However, there was no evidence for Ti@super +4@ reduction or Pt oxidation in the Ti(2p) and Pt(4f) regions. Possible encapsulation of the nanoparticles by TiO@sub x@ will be further studied by low energy ion scattering as well as grazing angle X-ray photoelectron spectroscopy experiments. The reduction of NO by CO on the monometallic and bimetallic clusters of different sizes will be investigated by temperature programmed desorption.