Our next and final case study addresses the effect of alloying. Alloying is often exploited in catalyst design as a tool that allows to manipulate the electronic properties, and hence reactivity, of active site. This concept was recently invoked to rationalize the increased selectivity towards acetate (Ac) that was measured during CO electroreduction (eCORR) on two different Cu-based alloys, namely Cu-Pd 40 and Cu-Ag. The authors of both these studies in fact found that there exists an optimal alloying ratio for which maximal selectivity towards this C 2 product is reached (SI, Sec. S3.3). They explained this on the basis of active site binding strengths. We argue here that modifying the density of active sites within the "desorption-re-adsorption-reaction" mechanism provides again an alternative, or at least complementary, reasoning to explain the reported selectivity changes.