b,H indicates that the surface properties, including the interaction of surface and subsurface with carbon and hydrogen, are crucial for the selectivity towards ethylene. This might be related to the formation of surface carbides and the availability of surface hydrogen. Indeed, the formation of Pd x C y surface layers has been shown to lower the desorption barrier of ethylene while the low availability of surface hydrogen atoms can prevent the undesired further hydrogenation of ethylene to ethane, both enhancing S C2H4 . Additionally, the relevance of D µ and w metal could be related to the type and relative amount of surface sites available, which depend on the distribution of NP sizes and on the metal loading. Interestingly, the t OS -independent term of Eq. 2 contains the parameters E sub d,C , w metal , and D µ , whereas the t OS -dependant terms of Eq. 2 contain the parameters ϵ d , ∆W surf H , E surf b,H , and E sub b,H . Therefore, the stability of the subsurface carbon and the loading and size of metal NPs mainly determine the initial value of ethylene selectivity at t OS = 0 min, while the stability of surface and subsurface hydrogen is the key factor modulating the evolution of the selectivity with t OS . No elemental or metal bulk candidate descriptive parameters are selected by SISSO in Eq. 6. This suggests that the ethylene selectivity is governed by processes related to the NP surface and subsurface rather than its bulk. We note that many analytical expressions considered by SISSO may provide a similar description compared to Eq. 6. Thus, the expressions and operators themselves might not have physical meaning. However, the parameters entering the expressions do have a physical meaning, as they correlate with relevant underlying physical processes. We have also trained SISSO models for the selectivity towards ethane. These results are discussed in the ESI.