Kinetic Monte Carlo simulations are performed to study the dealloying of Pt-based nanoparticles typically used as oxygen reduction reaction catalysts. The Kirkendall effect is represented to emulate the synthesis of hollow nanoparticles by removing the Ni core in a Ni-core/Pt-shell nanoparticle. It is found that initial shell vacancies are required to completely dissolve the non-noble core. The evolution of porosity is followed by dealloying Ni0.75Pt0.25 and Co0.63Pt0.37 nanoparticles. Two critical potentials define regions where the bimetallic particles may exist as core-shell, porous, and hollow structures, accompanied with clear variations in the dissolution rates. The phenomena are characterized by the dynamic evolution of the surface coordination numbers, and that of the surface area per platinum mass. (C) 2013 Elsevier Ltd. All rights reserved.