Abstract
We investigate the oxidation of, and the reaction of ethylene with, Ni(111) with and without
sub-monolayer Ag adlayers as a function of temperature. The addition of Ag to Ni(111) is shown
to enhance the activity towards the ethylene epoxidation reaction, and increase the temperature at
which ethylene oxide is stable on the surface. We present a systematic study of the formation of
chemisorbed oxygen on the Ag–Ni(111) surfaces and correlate the presence and absence of O1
and O2 surface species with the reactivity towards ethylene. By characterizing the samples with
low-energy electron microscopy (LEEM) in combination with X-ray photoelectron spectroscopy
(XPS), we have identified specific growth of silver on step-edge sites and successfully increased the
temperature at which the produced ethylene oxide remains stable, a trait which is desirable for
catalysis.