Understanding the effect of ultrathin AuPd alloy shells of irregularly shaped Au@AuPd nanoparticles with high-index facets on enhanced performance of ethanol oxidation

In this study, irregularly shaped, concave cuboidal Au@AuPd nanoparticles (ISCC-Au@AuPd NPs) with high-index facets were synthesized via Pd overgrowth on pre-formed ISCC-Au NPs with a concentration of Pd precursors as low as 2%. The AuPd alloy nature of the resulting shells was confirmed by X-ray photoelectron spectroscopy, cyclic voltammogram analysis, and energy dispersive X-ray spectroscopy. Among the irregularly shaped NPs obtained, the ISCC-Au-97.5@Au0.5Pd2.0 NPs display the largest electrochemically active surface area (up to 92.11 m(2) g(-1)), as their closed-packed agglomeration was prevented, and the best long-term stability with respect to ethanol oxidation (0.50 M) in alkaline media (0.30 KOH) by efficiently removing intermediates. Their mass-and ECSA-normalized current densities (4.15 A mg(Pd)(-1) and 4.51 mA cm(-2)) are about 20.7 times and 6.9 times higher than those of commercial Pd/C catalysts (0.20 A mg(Pd)(-1) and 0.65 mA cm(-2)), respectively.