AVS 53rd International Symposium
    Surface Science Wednesday Sessions
       Session SS1-WeM

Paper SS1-WeM12
Adsorption of Gas-Phase Oxygen Atoms on Pt(100)-hex-R0.7°

Wednesday, November 15, 2006, 11:40 am, Room 2002

Session: Reactions on Metal & Bimetallic Surfaces
Presenter: R.B. Shumbera, University of Florida
Authors: R.B. Shumbera, University of Florida
H.H. Kan, University of Florida
J.F. Weaver, University of Florida
Correspondent: Click to Email
We investigated the adsorption of gaseous oxygen atoms on Pt(100)-hex-R0.7° at surface temperatures of 450 and 573 K using temperature programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS), electron energy loss spectroscopy (ELS), and low energy electron diffraction (LEED). Differences in the O@sub2@ TPD spectra reveal that the types and relative populations of the oxygen phases that develop on Pt(100) are strongly dependent on the surface temperature during adsorption. At 573 K, oxygen atoms initially adsorb into disordered (3x1) domains up to a coverage of about 0.32 ML (monolayers), and then arrange into a complex, ordered phase until the surface saturates at a coverage of 0.63 ML. In contrast, chemisorption at 450 K results in the simultaneous growth of the disordered (3x1) phase as well as a "high-concentration" phase that populates at the expense of the complex, ordered phase up to a coverage of about 0.50 ML. The temperature dependence of the oxygen phase distribution suggests that slow kinetics hinders formation of the complex, ordered phase, and forces oxygen atoms to become trapped in the high-concentration phase at 450 K. Further atomic oxygen uptake at 450 K produces an additional disordered phase that acts as a precursor to the growth of three-dimensional Pt oxide particles that saturate at approximately 3.6 ML for the incident fluxes employed. Finally, thermal decomposition of the Pt oxide is characterized by an explosive O@sub2@ desorption peak that shifts to higher temperature and intensifies dramatically as the initial oxygen coverage is increased, similar to prior observations on Pt(111).