F. Boccuzzi et al., FTIR STUDY OF CARBON-MONOXIDE OXIDATION AND SCRAMBLING AT ROOM-TEMPERATURE OVER GOLD SUPPORTED ON ZNO AND TIO2 .2., Journal of physical chemistry, 100(9), 1996, pp. 3625-3631
An FTIR and quadrupole mass spectroscopic study of CO adsorption and o
xidation with O-16(2) and O-18(2) is presented together with coadsorpt
ion experiments of CO and water on gold supported on ZnO and TiO2. The
experimental results are closely related to those presented in the pa
rallel paper on copper catalysts supported on the same oxides. The mos
t important points are as follows: (i) CO is found to be activated on
the metallic particles on two kinds of sites, the normal terrace sites
and sites at the borderline of the particles; (ii) there is evidence
that on the examined samples there are metallic sites which are able t
o adsorb both oxygen and carbon monoxide molecules at the same time; (
iii) carbon dioxide and carbonate-like species are formed; the asymmet
ric stretching frequencies of CO2, the quadrupole mass spectroscopic a
nalysis, and the IR spectra analysis reveal that with O-18(2), differe
nt isotopic molecular CO2 is formed while the carbonate-like species h
ave the same frequencies of those produced in O-16(2); (iv) there are
two independent pathways for CO oxidation, a rapid direct oxidation of
CO at the surface of the metallic particles and a slow induced oxidat
ion with the surface lattice oxygen species of the supports; (v) evide
nce is found that CO-H2O coadsorption experiments produce atomic hydro
gen on Au/ZnO, not on Au/TiO2.