Ultrasound-assisted polyol synthesis and electrocatalytic characterization of Pd x Co alloy and core–shell nanoparticles

Carbon supported Co–Pd nanocomposites with two different surface compositions and various Co/Pd ratios have been synthesized by an ultrasound-assisted polyol process. Sonochemical treatment of palladium acetylacetonate and cobalt acetylacetonate in ethylene glycol in the presence of a carbon support without added surfactant, pH adjuster, or stabilizer has produced 4–7nm PdxCo nanoparticles dispersed on the carbon support. The absence of additives has led to purer nanoparticles than produced by conventional wet methods. The structures of nanoparticles – pure Pd, Co–Pd alloy, and core–shell – have been characterized by XRD, TEM, EELS, and STEM. Electrocatalysis of oxygen reduction reactions of the materials have been measured using rotating disk electrodes and are compared with pure Pd/C and commercial Pt/C. The Co–Pd mixed phase samples show higher specific activity than pure Pd/C and comparable performance to commercial Pt/C. The Pd4Co core–shell structure shows significantly enhanced catalytic activity.