AVS 50th International Symposium
    Surface Science Monday Sessions
       Session SS2-MoM

Paper SS2-MoM9
The Correlation between the Electronic Structure and the Energetics of CO Chemisorption on Pd/Re (0001) Surfaces

Monday, November 3, 2003, 11:00 am, Room 327

Session: Catalysis I: Adsorption and Reactions of Small Molecules at Surfaces
Presenter: B.S. Mun, Lawrence Berkeley National Laboratory
Authors: B.S. Mun, Lawrence Berkeley National Laboratory
C.M. Lee, Lawrence Berkeley National Laboratory
V. Stamenkovic, Lawrence Berkeley National Laboratory
N.M. Markovic, Lawrence Berkeley National Laboratory
P.N. Ross, Lawrence Berkeley National Laboratory
Correspondent: Click to Email
We explored the nature of CO chemisorption on a Pd thin film electrode by utilizing ex-situ x-ray photoelectron spectroscopy (XPS) and in-situ Fourier transform infrared (FTIR) spectroscopy. The Pd film was deposited on Re (0001) single crystal by evaporation in UHV. Upon the deposition of the Pd thin film, the valence band (VB) photoemission spectrum shows a significant change from the bulk Re VB spectrum, yet also unlike the VB of bulk Pd(111). The morphology of the Pd thin film on the Re surface is discussed from LEED measurements. Careful analysis and comparison of lineshape and peak positions of the VB spectrum of the monolayer Pd film revealed a valence band spectrum similar to that of Ag(111), implying a filling of the Pd d-band from the intermetallic bonding with the Re substrate. Analysis of FTIR spectrum on this same sample transferred from UHV to the in-situ electrochemical cell indicated direct evidence of a modified (unlike Pd) CO bonding state consistent with reduced back-bonding from the Pd d-band to the CO π* antibonding orbitals. It is also found that this "weakly bonded" CO is oxidized to CO2 at a much lower (ca. 0.2 V) electrode potential than on the Pd multilayer film.