Pd skin on AuCu intermetallic nanoparticles: A highly active electrocatalyst for oxygen reduction reaction in alkaline media

Core-shell structured catalysts have been widely investigated for fuel cell applications in the recent decade. The skin-substrate interaction has provided a well tunable basis for the design of better catalysts. Herein, we report an implementation of fabricating a Pd skin onto the AuCu intermetallic nanoparticles (denoted as (PdAuCu)-Au-S iNPs), and its exceptionally high activity towards the oxygen reduction reaction (ORR) in alkaline media. The structure of (PdAuCu)-Au-S iNPs was well characterized through combining a variety of techniques, including high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) and energy dispersive X-ray (EDX) line scanning analysis, synchrotron X-ray diffraction patterns (SXRD), X-ray photoelectron spectra (XPS), X-ray fluorescence analysis (XRF), and electrochemical measurements. The AuCu intermetallic core was identified to be fully wrapped by a Pd skin with 2-3 atomic layers. The catalytic activity of (PdAuCu)-Au-S iNPs towards the ORR in alkaline is more than 8-times higher in surface-specific activity (SA), and 20-times higher in mass-specific activity (MA), than that of the commercial Pt/C catalyst, and remains reasonably stable in thousands cycles of potential sweep. Such an outstanding performance is attributed to the reduction in the oxygen affinity of the Pd skin caused by a proper and stable shrink in Pd lattice induced by the AuCu intermetallic substrate. (C) 2016 Elsevier Ltd. All rights reserved.