Calorimetric Measurement of the Heat of Adsorption of Benzene on Pt(111)

The heat of adsorption of benzene on clean Pt(111) at 300 K is measured calorimetrically and found to decrease with coverage (θ) as (197 − 48θ − 83θ 2 ) kJ/mol. Saturation coverage (θ = 1.0) is 2.3 × 10 14 molecules/cm 2 . Sticking probabilities of benzene on Pt(111) were measured by mass spectrometry, giving an initial value of 0.97 and showing Kisliuk-type behavior with increasing coverage that implies there is a precursor to sticking with a ratio of its hopping rate to its desorption rate of ∼28. Benzene adsorbs transiently on the benzene-saturated surface at 300 K with a trapping probability of 0.90 and a heat of adsorption of 63−73 kJ/mol.