Graphene-Supported
Pd Nanoclusters Probed by Carbon Monoxide Adsorption
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Abstract
The
adsorption of CO on graphene-supported Pd nanoparticles was studied
in situ with high-resolution synchrotron-based X-ray photoelectron
spectroscopy. At 150 K, CO adsorbs mainly in bridge and 3-fold-hollow
sites. The nanoparticles are considered as a mixture of low-index
facets. The variation of the amount of deposited Pd revealed identical
CO adsorption behavior for all investigated cases, confirming a similar
average cluster size over a wide range of Pd coverages. The desorption
characteristics were studied with temperature-programmed XPS. The
observed desorption maxima at 230 and 430 K are in good agreement
with temperature-programmed desorption data on stepped Pd single crystals.
At 500 K, CO is completely desorbed from the Pd clusters. The adsorption
and desorption of CO are found to be not fully reversible as the Pd
particles undergo restructuring upon heating