The electrochemical oxidation of carbon monoxide and the interfacial
structure of the CO adlayer (COads) on platinum low index single crystals,
Pt(111), Pt(100) and two reconstruction of Pt(110), were examined using the
rotation disk electrode method in combination with the in situ surface X-ray
diffraction scattering technique. The mechanism of CO oxidation is discussed
on the basis of the findings that, depending on the potential, two energetic
states ofCOads exist on the platinum surfaces. Thus, at lower potentials,
weakly bonded states (COads,w) and at higher potentials strongly bonded
states (COads,s) are formed. The mechanism of the oxidation of
hydrogen-carbon monoxide mixtures is also proposed.