Highly Active and Durable PdAg@Pd Core-Shell Nanoparticles as Fuel-Cell Electrocatalysts for the Oxygen Reduction Reaction

By controlling the surface structure and composition at the atomic level, the catalytic properties of bimetallic alloy catalysts can be precisely and effectively tuned, and their activity and durability can be enhanced. Here, a class of highly active and durable PdAg bimetallic alloy nano-electrocatalysts is demonstrated by tuning the surface composition through a simple electrochemical treatment process in acid medium. Transmission electron microscopy, X-ray photoelectron spectroscopy, and cyclic voltammogram measurements clearly show the well-defi ned core-shell structure that consists of a PdAg alloy core and a few atomic layers of Pd as the shell (PdAg@Pd). Compared to pure Pd and Ag catalysts, the prepared PdAg@Pd/C exhibits enhanced electrocatalytic activity and durability for the oxygen reduction reaction in alkaline media. According to the theoretical and experimental results, the enhanced electrocatalytic activity can be attributed to the synergistic effects between the Pd and the Ag, while the durability is ascribed to the unique alloy core-ultrathin-Pd-shell structure of the PdAg@Pd/C catalyst. This study not only proposes a simple and straightforward approach for preparing highly monodisperse PdAg alloy nanoparticles and designing advanced electrocatalysts for fuel cells, but also demonstrates the crucial effect of electrochemical treatment on the electrocatalytic properties of catalysts.