Aqueous-Phase Synthesis of Sub 10 nm Pd_core@Pt_shell Nanocatalysts for Oxygen Reduction Reaction Using Amphiphilic Triblock Copolymers as the Reductant and Capping Agent

Abstract

Sub 10 nm Pdcore@Ptshell nanocrystals (NCs) were prepared by a facile and green reduction method in aqueous solutions using commercially available and nontoxic poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) amphiphilic triblock copolymers as the reductant, stabilizer, and capping agent. The growth mode and morphology of the Pt shell on the Pd surface can be adjusted simply by the Pt/Pd molar ratio. The activity of carbon-supported Pd@Pt NCs toward oxygen reduction reaction exhibited a Pt shell morphology dependence, with Pd2@Pt1 (Pt/Pd molar ratio 1/2) having the highest mass activity and Pd1@Pt2 (Pt/Pd molar ratio 2/1) having the best area-specific activity, and both of them were significantly enhanced in comparison with that of commercial Pt/C catalysts. Moreover, single-fuel-cell testing indicated superior activity and durability of Pd2@Pt1 NCs, which made Pd2@Pt1 NCs promising cathode catalysts for fuel cell applications.