Pd–Ni ellipsoidal nano-alloys with excellent catalytic performance for oxygen reduction reaction.

A Pd–Ni ellipsoidal nano-alloy catalyst with a long diameter of 5 ± 0.1 nm and short diameter of 3 ± 0.1 nm supported on carbon black (PdNi EN/CB) was successfully prepared via a facile one-pot synthesis route. During the synthetic process, cetyl trimethyl ammonium chloride (CTAC) was used as a structure-directing agent, which induced the ellipsoidal morphology. As compared with commercial Pt/C, Pd/C and Pd–Ni catalyst without special morphology supported on carbon black (PdNi NW/CB), PdNi EN/CB demonstrated both ultrahigh catalytic activity towards oxygen reduction reaction (ORR) and favorable long-term durability in alkaline solutions. According to X-ray photoelectron spectra (XPS) analysis and density functional theory (DFT) calculation results, a down-shift of the Pd d-band center, which weakens the adsorption strength for oxygen-containing species, along with a reaction path closer to the ideal free energy due to the small particle size and special morphology of Pd–Ni ellipsoidal nano-alloys contribute to the excellent activity of the PdNi EN/CB catalyst. [Display omitted] • A Pd–Ni ellipsoidal nano-alloy catalyst supported on carbon black was prepared. • Formation of ellipsoid is due to the addition of CTAC as a structure-directing agent. • PdNi EN/CB has superb catalytic activity for ORR and favorable durability in KOH. • A down-shift of d-band center owing to special morphology leads to the high activity. • The reaction path of PdNi EN/CB is closer to the ideal free energy. [ABSTRACT FROM AUTHOR]