For ethylene-Pt7, there are multiple low-lying configurations with di-σ ethylene binding modes that favor dehydrogenation. The branching between intact ethylene desorption vs. dehydrogenation leading to coking should be related to the relative barriers for desorption (ΔE(C2H4)) and decomposition (ΔE(C-H)) of adsorbed ethylene, both shown in Fig. and Figs. S16-S18. For Pt7, the ΔE(C-H) values range from 1.86 to 1.36 eV, i.e., well below the 2.0 to 2.2 eV ΔE(C2H4) values, favoring decomposition over desorption, and accounting for the substantial coking and rapid deactivation observed in the ethylene TPD experiments (Fig. ).