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Nano Lett. 2015 Dec 9;15(12):7808-15. doi: 10.1021/acs.nanolett.5b02960. Epub 2015 Nov 3.

Epitaxial Growth of Twinned Au-Pt Core-Shell Star-Shaped Decahedra as Highly Durable Electrocatalysts.

Author information

1
State Key Laboratory of Silicon Materials, School of Materials Science & Engineering, and Cyrus Tang Center for Sensor Materials and Applications, Zhejiang University , Hangzhou, Zhejiang 310027, People's Republic of China.
2
State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University , 800 Dongchuan Rd, Shanghai, 200240, People's Republic of China.
3
Department of Chemical & Biomolecular Engineering, University of Illinois at Urbana-Champaign , 600 South Mathews Avenue, 206 Roger Adams Laboratory, Urbana, Illinois 61801, United States.

Abstract

Pt epitaxial layer on a nanoparticle with twinned structure and well-defined shape is highly desirable in order to achieve high performance in both catalytic activity and durability toward oxygen reduction reaction (ORR). However, it remains tremendously challenging to produce conformal, heterogeneous, twinned nanostructures due to the high internal strain and surface energy of Pt. In addition, these twinned nanostructures may be subject to degradation in highly corrosive ORR environments due to the high energy of twin boundary. Here we report the synthesis of Au-Pt core-shell star-shaped decahedra bounded mainly by {111} facets, in which Pt shells with controlled thickness epitaxially grew on Au cores with a 5-fold twinned structure. The incorporation of the amine group decreases the surface energy of Pt by strong adsorption and thus facilitates the epitaxial growth of Pt on Au core instead of the dendritic growth. In addition, Br(-) ion could largely stabilize the {111} facets of Pt, which prevent the formation of spherical nanoparticles. The Au-Pt core-shell decahedra with thicker Pt shell exhibited enhanced ORR properties in terms of activity and durability. Specifically, AuPt1.03 star-shaped decahedra achieved the highest mass activity (0.94 mA/μg(Pt)) and area activity (1.09 mA/cm(2)(Pt)), which is ∼6.7 and 5 times, respectively, as high as those of the commercial Pt/C (ETEK). Significantly, such star-shaped decahedra were highly stable with ∼10% loss in area activity and ∼20% loss in mass activity after 30,000 CV cycles in O2 saturated acid solution.

KEYWORDS:

Bimetallic nanocrystals; electrocatalysis; epitaxial growth; star-shaped decahedra; ultrathin shell

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