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A novel nanoparticle-stacking thin film (NPSTF) of Pt–Ni alloy for highly active oxygen reduction reaction (ORR) electrocatalyst was synthesized. The Pt mass activity of the synthesized Pt–Ni NPSTF were 10-fold higher than commercial carbon-supported Pt catalysts. The remarkable ORR activity enhancement of the Pt–Ni NPSTF was attributed to the modified electronic properties of the surface Pt-enriched layers induced by underlying Ni atoms and to the increased active surface area achieved by stacking of Pt–Ni nanoparticles.

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The oxygen reduction reaction (ORR) activity and durability of various Au(x)/Pt100 nanoparticles (where x is the atomic ratio of Au against Pt) are evaluated herein. The samples were fabricated on a highly-oriented pyrolytic graphite substrate at 773 K through sequential arc-plasma depositions of Pt and Au. The electrochemical hydrogen adsorption charges (electrochemical surface area), particularly the characteristic currents caused by the corner and edge sites of the Pt nanoparticles, decrease with increasing Au atomic ratio (x). In contrast, the specific ORR activities of the Au(x)/Pt100 samples were dependent on the atomic ratios of Pt and Au: the Au28/Pt100 sample showed the highest specific activity among all the investigated samples (x = 0-42). As for ORR durability evaluated by applying potential cycles between 0.6 and 1.0 V in oxygen-saturated 0.1 M HClO4, Au28/Pt100 was the most durable sample against the electrochemical potential cycles. The results clearly showed that the Au atoms located at coordinatively-unsaturated sites, e.g. at the corners or edges of the Pt nanoparticles, can improve the ORR durability by suppressing unsaturated-site-induced degradation of the Pt nanoparticles.

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