title: Epitaxial overgrowth of platinum on palladium nanocrystals.
abstract: This paper describes a systematic study on the epitaxial overgrowth of Pt on well-defined Pd nanocrystals with different shapes (and exposed facets), including regular octahedrons, truncated octahedrons, and cubes. Two different reducing agents, i.e., citric acid and L-ascorbic acid, were evaluated and compared for the reduction of K₂PtCl₄ in an aqueous solution in the presence of Pd nanocrystal seeds. When citric acid was used as a reducing agent, conformal overgrowth of octahedral Pt shells on regular and truncated octahedrons of Pd led to the formation of Pd-Pt core-shell octahedrons, while non-conformal overgrowth of Pt on cubic Pd seeds resulted in the formation of an incomplete octahedral Pt shell. On the contrary, localized overgrowth of Pt branches was observed when L-ascorbic acid was used as a reducing agent regardless of the facets expressed on the surface of Pd nanocrystal seeds. This work shows that both the binding affinity of a reducing agent to the Pt surface and the reduction kinetics for a Pt precursor play important roles in determining the mode of Pt overgrowth on Pd nanocrystal surface.
authors.affiliation: Department of Chemistry, Washington University, St. Louis, Missouri 63130, USA.
authors.forename: Majiong
authors.initials: M
authors.lastname: Jiang
authors.forename: Byungkwon
authors.initials: B
authors.lastname: Lim
authors.forename: Jing
authors.initials: J
authors.lastname: Tao
authors.forename: Pedro H C
authors.initials: PH
authors.lastname: Camargo
authors.forename: Chao
authors.initials: C
authors.lastname: Ma
authors.forename: Yimei
authors.initials: Y
authors.lastname: Zhu
authors.forename: Younan
authors.initials: Y
authors.lastname: Xia