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Synthesis of Pd−Pt Bimetallic Nanocrystals with a Concave Structure through a Bromide-Induced Galvanic Replacement Reaction

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journal contribution
posted on 20.04.2011, 00:00 by Hui Zhang, Mingshang Jin, Jinguo Wang, Weiyang Li, Pedro H. C. Camargo, Moon J. Kim, Deren Yang, Zhaoxiong Xie, Younan Xia
This article describes a systematic study of the galvanic replacement reaction between PtCl62− ions and Pd nanocrystals with different shapes, including cubes, cuboctahedrons, and octahedrons. It was found that Br ions played an important role in initiating, facilitating, and directing the replacement reaction. The presence of Br ions led to the selective initiation of galvanic replacement from the {100} facets of Pd nanocrystals, likely due to the preferential adsorption of Br ions on this crystallographic plane. The site-selective galvanic replacement resulted in the formation of Pd−Pt bimetallic nanocrystals with a concave structure owing to simultaneous dissolution of Pd atoms from the {100} facets and deposition of the resultant Pt atoms on the {111} facets. The Pd−Pt concave nanocubes with different weight percentages of Pt at 3.4, 10.4, 19.9, and 34.4 were also evaluated as electrocatalysts for the oxygen reduction reaction (ORR). Significantly, the sample with a 3.4 wt.% of Pt exhibited the largest specific electrochemical surface area and was found to be four times as active as the commercial Pt/C catalyst for the ORR in terms of equivalent Pt mass.