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2019 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 123, no 36, p. 22172-22180Article in journal (Refereed) Published
Abstract [en]
Reduction of Cu2O by hydrogen is a common preparation step for heterogeneous catalysts; however, a detailed understanding of the atomic reaction pathways is still lacking. Here, we investigate the interaction of atomic hydrogen with the Cu2O(100):(3,0;1,1) and Cu2O(111):(root 3 x root 3)R30 degrees surfaces using scanning tunneling microscopy (STM), low-energy electron diffraction, temperature-programmed desorption (TPD), and X-ray photoelectron spectroscopy (XPS). The experimental results are compared to density functional theory simulations. At 300 K, we identify the most favorable adsorption site on the Cu2O(100) surface: hydrogen atoms bind to an oxygen site located at the base of the atomic rows intrinsic to the (3,0;1,1) surface. The resulting hydroxyl group subsequently migrates to a nearby Cu trimer site. TPD analysis identifies H-2 as the principal desorption product. These observations imply that H-2 is formed through a disproportionation reaction of surface hydroxyl groups. The interaction of H with the (111) surface is more complex, including coordination to both Cu+ and O-CUS sites. STM and XPS analyses reveal the formation of metallic copper clusters on the Cu2O surfaces after cycles of hydrogen exposure and annealing. The interaction of the Cu clusters with the substrate is notably different for the two surface terminations studied: after annealing, the Cu clusters coalesce on the (100) termination, and the (3,0;1,1) reconstruction is partially recovered. Clusters formed on the (111) surface are less prone to coalescence, and the (root 3 x root 3)R30 degrees reconstruction was not recovered by heat treatment, indicating a weaker Cu cluster to support interaction on the (100) surface.
Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2019
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-261961 (URN)10.1021/acs.jpcc.9b03888 (DOI)000486360900036 ()2-s2.0-85072714617 (Scopus ID)
Note
QC 20191015
2019-10-152019-10-152022-06-26Bibliographically approved