Comparison of the Coverage of the Linear CO Species on Pt/Al2O3 Measured under Adsorption Equilibrium Conditions by Using FTIR and Mass Spectroscopy

There is controversy in the literature about the relationship between the IR band area (denoted by A) of the adsorbed CO species (i.e., linear (denoted by L) and bridged (denoted by B) CO species) on noble-metal-containing solids (supported metal catalysts and single crystals) and the coverage (denoted by θ) of the surface by CO. Usually, a straight line is observed at low coverages (θ550 K) the two analytical methods give the same coverage values in the range θ=1–0.6. This leads to the conclusion (a) that there is a proportionality between the IR band area of the L species and its amount on the Pt surface and (b) that quantitative studies involving the L species can be performed by using FTIR spectroscopy (i.e., determination of the heats of adsorption of the L species at several coverages).