Interactions of Hydrogen and Carbon Monoxide on Pd-Au Bimetallic Surfaces
Journal
Journal of Physical Chemistry C
Journal Volume
118
Journal Issue
4
Pages
2129-2137
Date Issued
2014
Author(s)
Abstract
Pd–Au bimetallic catalysts have shown potential applications in numerous heterogeneous reactions in which hydrogen and CO act as reactants, intermediates, or products. A fundamental understanding of the interplay between coadsorbed H and CO on the Pd–Au surface is necessary for improving the understanding of catalytic performance. In this study, the interactions of hydrogen and CO with Pd/Au(111) model surfaces were investigated by temperature-programmed desorption (TPD) and molecular beam scattering (MBS) experiments, carried out under ultra-high-vacuum conditions. Our results reveal that CO adsorbs competitively on the hydrogen-precovered Pd–Au surface, causing surface H adatoms to diffuse away from stronger-binding sites (e.g., Pd(111)-like islands) to weaker-binding sites (e.g., Pd–Au alloy sites and subsurface), as evidenced by a shift of the H2 desorption feature to lower temperatures in TPD measurements. Additionally, evolution of H2 was observed when a CO molecular beam was impinged onto the H-precovered Pd–Au surface, providing direct evidence that CO induces recombinative desorption of H adatoms. The presence of H adatoms on the Pd–Au surface was found to decrease the initial sticking probability of CO during MBS experiments but had little influence on CO desorption during subsequent TPD measurements.
SDGs
Type
journal article