title: Element-specific anisotropic growth of shaped platinum alloy nanocrystals.
abstract: Morphological shape in chemistry and biology owes its existence to anisotropic growth and is closely coupled to distinct functionality. Although much is known about the principal growth mechanisms of monometallic shaped nanocrystals, the anisotropic growth of shaped alloy nanocrystals is still poorly understood. Using aberration-corrected scanning transmission electron microscopy, we reveal an element-specific anisotropic growth mechanism of platinum (Pt) bimetallic nano-octahedra where compositional anisotropy couples to geometric anisotropy. A Pt-rich phase evolves into precursor nanohexapods, followed by a slower step-induced deposition of an M-rich (M = Ni, Co, etc.) phase at the concave hexapod surface forming the octahedral facets. Our finding explains earlier reports on unusual compositional segregations and chemical degradation pathways of bimetallic polyhedral catalysts and may aid rational synthesis of shaped alloy catalysts with desired compositional patterns and properties.
authors.affiliation: Electrochemical Energy, Catalysis and Materials Science Laboratory, Department of Chemistry, Chemical Engineering Division, Technical University Berlin, 10623 Berlin, Germany. Division of Energy and Environment, Graduate School at Shenzhen, Tsinghua University, 518055 Shenzhen, PR China.
authors.forename: Lin
authors.initials: L
authors.lastname: Gan
authors.affiliation: Electrochemical Energy, Catalysis and Materials Science Laboratory, Department of Chemistry, Chemical Engineering Division, Technical University Berlin, 10623 Berlin, Germany.
authors.forename: Chunhua
authors.initials: C
authors.lastname: Cui
authors.affiliation: Ernst Ruska Center for Microscopy and Spectroscopy with Electrons, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany.
authors.forename: Marc
authors.initials: M
authors.lastname: Heggen
authors.affiliation: Electrochemical Energy, Catalysis and Materials Science Laboratory, Department of Chemistry, Chemical Engineering Division, Technical University Berlin, 10623 Berlin, Germany.
authors.forename: Fabio
authors.initials: F
authors.lastname: Dionigi
authors.affiliation: Electrochemical Energy, Catalysis and Materials Science Laboratory, Department of Chemistry, Chemical Engineering Division, Technical University Berlin, 10623 Berlin, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Rudi
authors.affiliation: Electrochemical Energy, Catalysis and Materials Science Laboratory, Department of Chemistry, Chemical Engineering Division, Technical University Berlin, 10623 Berlin, Germany. pstrasser@tu-berlin.de.
authors.forename: Peter
authors.initials: P
authors.lastname: Strasser