Support‐Free, Connected Core–Shell Nanoparticle Catalysts Synthesized via a Low‐Temperature Process for Advanced Oxygen Reduction Performance

Nanostructured Pt‐based catalysts have attracted considerable attention for fuel‐cell applications. This study introduces a novel one‐pot and low‐temperature polyol approach for synthesizing support‐free, connected nanoparticles with non‐Pt metal cores and Pt shells. Unlike conventional heat treatment methods, the developed support‐free and Fe‐free connected Pd core @Pt shell (Pd@Pt) nanoparticle catalyst possesses a stable nanonetwork structure with a high surface area. This approach can precisely control the atomic‐level structure of the Pt shell on the Pd core at a low deposition temperature. The optimized Pd@Pt catalyst with a Pt/Pd atomic ratio of 0.8 and a Pt shell thickness of 1.1 nm exhibits a threefold improvement in oxygen reduction reaction (ORR) mass activity compared to that of commercial carbon‐supported Pt nanoparticle catalyst (Pt/C). Durability evaluation demonstrated 100% retention of specific activity after 10,000 load cycles, owing to the stable nanonetwork and uniform coverage of the Pt shell. In addition, the support‐free, connected core–shell nanoparticle catalyst overcomes the carbon corrosion issues commonly associated with conventional carbon‐supported catalysts while simultaneously improving both ORR activity and load cycle durability. These findings highlight the potential of this innovative approach to develop support‐free catalysts for polymer electrolyte fuel cells and other energy devices.