The key parameters identified in Eq. 7 are t OS , ϵ d , E surf b,H , E sub d,C , composition-averaged distance expansion due to subsurface carbon (δ sub C ), d closest , compositionaveraged electron affinity (EA), and specific surface area (s BET ). The microscopic parameters ϵ d , E surf b,H , E sub d,C , and δ sub C , indicate that (sub)surface processes, including the participation of carbon and hydrogen, are crucial for the formation of C 4 molecules. Additionally, the parameters d closest and EA show that properties of the bulk of NP are important. Finally, the key parameter s BET reflects that the surface area also impacts the formation of C 4 products. The relevance of the (sub)surface parameters ϵ d , E surf b,H , E sub d,C , and δ sub C can be related to the influence of surface-carbon binding and hydrogen availability on the reaction pathways that lead to C 4 products. Indeed, it had been argued that surface sites that provide strong palladium-carbon binding are more prone to oligomerize acetylene and other surface intermediates during the reaction. The relevance of the bulk parameters d closest , EA, in turn, could be related to the de-alloying of the NPs. This de-alloying process in palladium-based materials, for instance, results in the creation of palladium-rich surface sites, which could more efficiently oligomerize acetylene compared to sites containing both palladium and other metals such as silver. Indeed, the X-ray diffraction (XRD) analysis of some of the palladium-silver alloys after the reaction indicates the segregation of palladium to the surface. In case of a fixed particle size, s BET is correlated with the distances between NPs. The relevance of this parameter could point at the importance of average distances between particles in the oligomerisation side reaction. However, the average particle sizes in the investigated data set vary between 3 to 9 nm. Thus, this interpretation has to be handled with care. Interestingly, the time-dependent term of Eq. 7, which captures the S C4 increase with t OS (see Fig. ), contains the parameters E surf b,H and s BET . Thus, the availability of hydrogen as well as underlying processes related to the specific surface area modulate the evolution of the formation of C 4 molecules over time and are likely associated to catalyst deactivation.