Traditionally, surface restructuring of Pt(111) electrodes during oxidation and reduction cycles in pure acidic electrolytes (with an UPL larger than 1.2 V) was rationalized by an irreversible place exchange process between adsorbed atomic oxygen and surface Pt atoms. More recently, this picture was supplemented by a reversible O insertion / partial Pt extraction process, which occurs before irreversible Pt and O exchange. In a simple picture, one would expect that both reversible and irreversible restructuring of the Pt surface layer(s) set in once a critical coverage of adsorbed OH/O species is reached. For Pt layers on Ru(0001), it is known that the binding energy of OH/O is lowest on the monolayer and increases with increasing Pt layer thickness, until reaching the binding energy of Pt(111) for thick layers. In that case, the onset of restructuring should shift to lower potentials with increasing Pt layer thickness, and the critical potential for the onset of a possible irreversible place exchange process would then always be more positive than that for Pt(111), i.e., 1.2 V. Hence, the Pt films on Ru(0001) should, in principle, be intrinsically more stable than Pt(111) with respect to reversible Pt extraction and irreversible place exchange, with monolayer Pt films presenting the most stable structure. Since the Pt-3 electrodes are stable under present reaction conditions, the potential for irreversible place exchange processes must be beyond the explored potential limit of 1.35 V for the COOR or 1.4 V for the MOR. Furthermore, considering that both irreversible place exchange and dissolution lead to a restructuring of the surface, this also means that the Pt dissolution potential should shifts to more positive potentials. Nevertheless, once the critical potential for the formation of a dense O adlayer is reached, we expect that the Pt films on Ru(0001) restructure similarly to Pt(111) electrodes. Indeed, we found similar structures as for restructured Pt(111) on Pt-3 electrodes, induced by potential cycles to high potentials in pure supporting electrolyte shown (in Section S1).