The sluggish reaction of oxygen reduction in proton-exchange membrane fuel cells (PEMFCs) and the durability of platinum-based catalysts have been major economical and technological barriers to the widespread application of PEMFCs. We report here on two Pt-surface-enriched nanosize structure (Pt-SENS) catalysts with iridium core, synthesized with the use of single-step and successive step-by-step electroless deposition of platinum. The synthesized catalysts were studied by energy-dispersive X-ray spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS), and transmission scanning electron microscopy (STEM). Electrochemical analysis demonstrated improved oxygen reduction reaction (ORR) mass activity of the homemade catalysts by 25–30% compared with commercial 50%Pt/C catalyst and improved durability, by a factor of ~ 3, of the catalyst synthesized by successive step-by-step deposition following accelerated stress test (AST). Higher mass activities are attributed to better platinum utilization as a result of a Pt-surface-enriched structure, while greater durability is attributed to the stabilization of surface platinum by stronger Pt–Ir bonds induced by iridium atoms in the core.