and measured a reaction enthalpy for the dissociative adsorption on Pt(111) of -212 kJ mol -1 with SCAC 120 . ∆ f H* CH 3 can then be derived using a thermodynamic cycle as displayed in Fig. . The experimental determination of the accurate ∆ f H of adsor- bates is challenging since single-crystal adsorption calorimeters are expensive and intricate systems. Creating single crystals and ensuring no transformation during the operation is challenging. Additionally, ∆ f H of the co-adsorbates have to be known with high accuracy 122 , and coverage effects caused by self-or crossinteraction can distort the measurement 120,121 . Another challenge for more complex adsorbates is finding suitable gas-phase precursors and preventing unwanted dissociation of the adsorbate. Due to all these factors, only a few dozen experimental adsorption enthalpies exist for a limited number of systems, summarized by Silbaugh and Campbell . Consequently, it is fair to assume that most adsorbate ∆ f H will never be experimentally determined, and they have to be derived from QM data instead.