Surprisingly, Pt11Ge4 was less stable than the smaller clusters in terms of the stability of strong CO binding sites, both in repeated CO TPD runs, and after three C2D4 TPD runs. Since all the clusters had similar Pt:Ge ratios, it is not clear why stability was lower for the largest cluster size, but unfortunately it is not feasible to attempt detailed DFT for a system with the size and complexity of Pt11Ge4C2, which is expected to have a very large number of thermally accessible isomers. Note that both TPD and ISS suggest that Pt11 has a 3D structure, unlike the 2D structures for the smaller clusters, and both the increased Pt-Pt coordination, and reduced footprint might reduce the cluster-support binding strength, facilitating ripening at high temperatures.