This trend is also reported for other metals, such as Pd, Rh, and Cu. Similarly, Takagi et al. reported the same behavior experimentally on similarly sized Pt nanoparticles using HAXPES. However, in these studies, nanoparticles are only partially oxidized, e.g. oxygen atoms are only located on the outer shell. This strengthens our conclusion that the features observed in our PDOS are due to a progression towards complete oxidation of the nanoparticle.