Infrared study of interactions between the carbon monoxide and support in platinum-supported catalysts

Infrared study of interactions between the carbon monoxide and support in platinum-supported catalysts

Blog Article

Interactions between chemisorbed carbon monoxide molecules and surface hydroxyl groups of the support in Pt/ Al2O3 skull bride and groom and Pt/SiO2 catalysts were studied by using FTIR spectroscopy.Infrared spectra of the catalysts were measured both before and after the adsorption of CO.Due to the adsorption of CO, the intense 3700-3000 cm-1 band, corresponding to O-H stretching vibration of hydroxyl groups which are involved in hydrogen-bonding, was broadened towards lower frequencies and decreased in its intensity.The 1630 cm-1 band assigned to bending vibration of H-O-H angle decreased in its intensity for the hydrogen saturate catalysts and increased for the catalysts without hydrogen.

These changes depend on the amount of adsorbed carbon monoxide.The 3743 cm-1 band, attributed to O-H stretching vibration of isolated silanol groups, was not modifed by chemisorbed CO.The spectral changes observed in the absorption bands of the bonded hydroxyl groups can be explained by a strong interaction through hydrogen bonding between the chemisorbed carbon monoxide and these hydroxyl groups.In the hydrogen-saturated samples, this interaction takes place mainly with the adsorbed water on the support, and in the hydrogen-depleted samples, with the structural hydroxyl groups.

The chemisorbed CO molecules that interact u11-200ps with the surface hydroxyl groups vibrates at lower frecuency, causing the assymetry of the CO linear band.