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Single crystal adsorption calorimetry on Pt(111) surfaces allows us to study the influence of different functional groups on heats of adsorption. At zero coverage we find 103, 194, and 325 kJ/mol for acetonitrile, benzene, and benzonitrile, respectively. This leads to the idea of summing up the heats of adsorption of acetonitrile and benzene, assuming that the total heat of adsorption of benzonitrile is due to the combined effect of isolated functional groups. This idea is discussed in light of the recent literature regarding nitrile adsorption on metal surfaces and further investigated theoretically by density functional theory. In order to figure out the importance of dispersive effects on the heats of adsorption, van der Waals corrected calculations are performed considering different binding modes and surface reconstructions.

Here we present the modification of an already existing Single Crystal Adsorption Calorimetry (SCAC) apparatus which has been extended by a compact cooling system to measure the coverage dependent heats of adsorption of gaseous compounds on thin metal substrates in a temperature range from 80 K to 430 K. The setup is characterized and its performance is tested by studying the adsorption of CO on Pt(111) at 150 K and 300 K. Coverage dependent sticking probabilities and heat of adsorption measurements are compared to previous experimental and theoretical studies proving the reliability of our compact low-temperature-SCAC setup.

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