Energetics of adsorbed benzene on Ni(111) and Pt(111) by calorimetry

Abstract

The heat of adsorption and sticking probability of benzene were measured on Ni(111) and Pt(111) at 90 K using single crystal adsorption calorimetry (SCAC). Benzene adsorbs molecularly with a heat of 208 kJ/mol on terrace sites in the low-coverage limit on Ni(111) and has a standard enthalpy of formation (∆Hf0) of C6H6,ads of −251 kJ/mol at a coverage of 1/9 ML. These results are compared to calorimetric results on Pt(111), where the standard enthalpy of formation (∆Hf0) of C6H6,ads was found to be −244 kJ/mol at a coverage of 1/9 ML. The slightly stronger bonding to Ni is attributed to stronger CNi covalent bonding partially compensated by weaker van der Waals (vdW) attractions to Ni compared to Pt. The measured energetics for benzene are compared to Density Functional Theory (DFT) calculations from previous literature, showing that functionals that do not contain corrections for vdW interactions badly underestimate the bond energies of benzene to both Ni(111) and Pt(111), while many of those that correct for vdW interactions are much more accurate.