Density functional theory calculations are performed to investigate oxygen dissociation on 38-atom truncated octahedron platinum-based particles. This study progresses our previous work (Jennings et al. Nanoscale, 2014, 6, 1153), where it was shown that flexibility of the outer Pt shell played a crucial role in facilitating fast oxygen dissociation. In this study, the effect of forming M@Pt (M core, Pt shell) particles for a range of metal cores (M = 3d, 4d, and 5d transition metals) is considered, with respect to O2 dissociation on the Pt(111) facets. We show that forming M@ Pt particles with late transition metal cores results in favorable shell flexibility for very low O2 dissociation barriers. Conversely, alloying with early transition metals results in a more rigid Pt shell because of dominant M−Pt interactions, which prevent lowering of the dissociation barriers.