We investigated the electrochemical stability of a Pt/Pd(111) model core-shell structure for oxygen reduction reaction catalysts in 0.1MHClO(4) at 80 degrees C by performing potential cycles (PCs) between 0.6 and x V vs. RHE (x = 0.8- 1.0; xV-PCs). Pristine Pt/Pd(111) shows an ORR activity four times higher than that of Pt(111), which considerably decreased after 5000 cycles of 0.9-and 1.0 V-PCs and remained nearly unchanged for the 0.8-and 0.85 V-PCs samples. These results suggest that the atomic-scale structural changes at the Pt/Pd interface that depend on PC windows determine the durability of Pd-Pt core-shell structures. (C) The Author(s) 2017. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. All rights reserved.