The binding energy (BE) of ethylene is reduced as the Ge concentration increases (Fig. ). Thus, larger Ge concentrations would lead to a weaker interaction with the desired product, with a reduction of the BE ranging from 7% (-0.14 eV) in Pt 4 Ge to 43% in Pt 4 Ge 4 (-0.88 eV). A similar behavior was recently observed for freestanding PtGe clusters, where equimolar clusters showed the weakest interaction with CO, due to the formation of multiple Pt-Ge bonds that stabilize such compositions. It is evident that Ge in PtGe has an effect on the ethylene binding and activation, which exhibit a decline with the increased Ge concentration. The reaction pathways for the first dehydrogenation event of ethylene on Pt 4 Ge x (x = 0 -3) are calculated for the GM configurations (Pt 4 Ge 4 is excluded from our study since it is mostly unable to bind ethane). As can be seen in Fig. , adding Ge systematically increases the barriers for the undesired dehydrogenation of ethylene, improving the selectivity with respect to pure Pt. The largest improvement is found for Pt 4 Ge, which exhibits a barrier of 1.16 eV vs 0.6 eV for Pt 4 . Moreover, Pt 4 is able to spontaneously dehydrogenate ethylene; the configuration is highlighted in red in Figure . Pt4Ge2 shows a lower barrier than Pt4Ge, which we attribute to the fact that the ethylene binding mode is di-σ. Interestingly, it remains quite a bit higher than the di-σ mode of Pt, indicating that the change in barrier cannot be attributed to a change in preferred binding mode alone. For Pt 3 Ge 3 , we see that it has a similar C-H activation barrier to Pt 4 Ge; if we were considering the ethylene dehydrogenation ability alone, it would appear to be competitive. However, we also see that it hardly binds ethane, indicating that in assessing the selectivity of the catalyst, it is crucial to also assess the activity. Hence, our results suggest that the Pt:Ge ratio in the cluster catalysts appears to be a lever of activity, selectivity, and stability. Overall, Pt 4 Ge/MgO is predicted to be the winning composition among the studied clusters, as it maintains a good activity (low barriers for ethane dehydrogenation), and exhibits a significantly enhanced selectivity (large barriers for ethylene dehydrogenation), along with an improved sintering resistance.