The SmSI case deserves special attention too. As in the previous two cases, surface wetting is predominant. Nonetheless, in Pt10/SmSI some of the Pt atoms detach from the cluster and diffuse to the center of the Sm3S3 chair units. Until the catalytic activity is tested, this may not necessarily indicate an adverse effect, since Pt active sites remain accessible to the reactants. Even more, this detachment may result in the formation of new active sites with different catalytic properties from the original cluster owing to synergistic effects, acting as single atom catalysts (SACs). Additionally, the same effect occurs in the opposite direction. Some of the I atoms have migrated from the support to the cluster. On Pt10 the I atoms occupy bridge positions with no Sm-I bonds. We hypothesize that this is a consequence of a SMSI effect and under given electrocatalytic conditions the cluster may be encapsulated by an I layer. The Eads is significantly greater than in 5-8-5-DV and 2H-MoS2, although not as large as in phosphorene, silicene and germanene. Overall, the Eads is decreased to half its value or more in equimolar clusters compared to the pure ones for all supports. Overall, the most stable adsorption configuration is found to be atop ( Pt-C-O 180º), where CO ∠ is always bonded to Pt. The only exception is Pt7Ge where CO adsorbs in a bridge configuration. In general, single CO adsorption has little impact on the cluster geometry, and the charge transfer from the cluster to the molecule is rather small. Interestingly, the CO affinity is found to depend non-continuously on size and composition, as indicated in Figure . Among the pure Pt clusters, Pt4 shows the weakest affinity to CO. Phosphorene helps improve the CO tolerance of Pt. In fact, Ptn/phosphorene have low ΔGCO* compared with other typical Ptn/oxide supports. For example, Pt4/MgO has a BE[CO] of -3.13 eV. For comparison with our previous work, the CO binding energies (electronic energy) are also given in Figure . Ge alloying also has a beneficial effect hindering the CO poisoning tendency. In a similar fashion to gas-phase, the CO adsorption energy decreases with increasing Ge content. The improvement becomes more evident as the Ge concentration increases.