Reaction
of CO with Preadsorbed Oxygen on Low-Index
Copper Surfaces: An Ambient Pressure X‑ray Photoelectron Spectroscopy
and Scanning Tunneling Microscopy Study
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Abstract
The
reaction of CO with chemisorbed oxygen on three low-index faces
of copper was studied using ambient pressure X-ray photoelectron spectroscopy
(XPS) and high-pressure scanning tunneling microscopy. At room temperature,
the chemisorbed oxide can be removed by reaction with gas-phase CO
in the 0.01–0.20 Torr pressure range. The reaction rates were
determined by measuring the XPS peak intensities of O and CO as a
function of time, pressure, and temperature. On Cu(111) the rate was
found to be one order of magnitude faster than that on Cu(100) and
two orders of magnitude faster than that on Cu(110). The apparent
activation energies for CO oxidation were measured as 0.24 eV for
O/Cu(111), 0.29 eV for O/Cu(100), and 0.51 eV for O/Cu(110) in the
temperature range between 298 and 473 K. These energies are correlated
to the oxygen binding energies on each surface
