According to the Sabatier principle, the interactions between a catalyst and a substrate should be neither too strong nor too weak. Our results suggest that the dopant concentration is a tool to modulate the binding of ethane, and therefore the reactivity of platinum. To further probe this conjecture, we compute the barriers for ethane dehydrogenation reactions on Pt 4 , Pt 4 Ge, and Pt 4 Ge 2 , i.e. clusters predicted to have appreciable dehydrogenation activity due to their greater adsorption energies. Upon ethane adsorption the Pt 4 Isomer II becomes predominant, and the dehydrogenation proceeds barrierlessly. Evidently, the GM of the monometallic cluster is not the most catalytically active isomer. Isomer I (configuration 4) has an energy barrier of 0.50 eV toward the first dehydrogenation of ethane (Fig. ), which is widely accepted to be the rate-determining step. This step proceeds via a higher-lying ethane binding mode. Finally, on Isomer III a small energy barrier of ca. 0.08 eV needs to be surmount for the first dehydrogenation step. On Pt 4 Ge, barriers of 0.40 and 0.46 eV are found (see Fig. ). In the latter, starting from the configuration 2, the geometry of the product exhibits a second C-H bond that is already activated. For Pt 4 Ge 2 , we find a similar barrier of 0.47 eV. Note that the addition of a second Ge decreases the ethane adsorption energy from -0.53 eV to -0.47 eV relative to Pt 4 Ge. Overall, our results suggest that the addition of Ge at low concentrations does not significantly harm its activity toward ethane dehydrogenation. Next, we study ethylene adsorption on Pt 4 Ge x /MgO (Fig. ), to elucidate the possible influence of Ge concentration in the clusters on the selectivity, and therefore coking resistance of Pt nanoclusters. Note that once dehydrogenation proceeds beyond ethylene, it is not going to stop. Ethylene can bind to Pt in the 𝜋-or the di-𝜎 fashion, and it has been shown the former configuration is the likely precursor to desorption, whereas the latter is more likely to undergo dehydrogenation. Therefore, the bonding mode can serve as a reactivity descriptor.