CO Chemisorption on Oxide Surfaces: Bonding and Vibrations

The surface chemistry of metal oxides is of considerable importance in catalysis. A large fraction of industrial catalytic processes involves reactions occuring at the surface of transition metal oxides.1,2 For this reason, there is a need for the development of analytical surface techniques for the determination of the physico-chemical properties of the oxide surfaces. An important problem is the determination of the formal oxidation state of the surface cations. This can be indirectly deduced from measures of the Lewis’s acidity of the cationic surface sites. A variety of physico-chemical methods have been used to characterize the surface of an oxide: thermal desorption, microcalorimetry, Potentiometric titrations, spectroscopy. Usually, these techniques make use of a probe molecule adsorbed on the surface. The response of this adsorbed molecule to the experimental technique applied provides a measure of the chemical nature of the adsorption sites.