Abstract:

We designed and synthesized carbon-supported cubic Pt₃Ni nanoparticles (NPs) with Pd monolayer shells (Pt₃Ni@Pd/C) by a two-step method: generally, CO-assisted preparation of cubic Pt₃Ni NPs, Pd monolayer deposition through underpotential deposition of a Cu monolayer, and displacement of Cu with Pd. The as-synthesized Pt₃Ni@Pd/C catalyst was characterized with inductively coupled plasma elemental analysis, X-ray diffraction, and transmission electron microscopy. Most Pt₃Ni NPs had a cubic nanostructure enclosed by {100} facets, on which the Pd monolayer shells were deposited epitaxially via electrodeposition, by which the Pd monolayers gained the crystallographic orientation of the {100} facets. We then used Pt₃Ni@Pd/C as an electrocatalyst for formic acid oxidation (FAO), comparing it with commercial Pd/C and the pristine Pt₃Ni/C catalysts. The Pt₃Ni@Pd/C exhibited superior electrocatalytic performance because of its monolayer structure and exposed Pd{100} facets. The noble-metal mass activity of the Pt₃Ni/C with the deposited Pd monolayer shell was 7.5 times greater than that of the Pt₃Ni/C catalyst alone. Moreover, the area-specific and Pd mass activities of Pt₃Ni@Pd/C were 2.5 and 8.3 times greater than those of the commercial Pd/C catalyst, respectively.

Key words: Electrocatalyst, Formic acid oxidation, Palladium monolayer, Cubic structure, Core-shell structure