title: Elemental Anisotropic Growth and Atomic-Scale Structure of Shape-Controlled Octahedral Pt-Ni-Co Alloy Nanocatalysts.
abstract: Multimetallic shape-controlled nanoparticles offer great opportunities to tune the activity, selectivity, and stability of electrocatalytic surface reactions. However, in many cases, our synthetic control over particle size, composition, and shape is limited requiring trial and error. Deeper atomic-scale insight in the particle formation process would enable more rational syntheses. Here we exemplify this using a family of trimetallic PtNiCo nanooctahedra obtained via a low-temperature, surfactant-free solvothermal synthesis. We analyze the competition between Ni and Co precursors under coreduction "one-step" conditions when the Ni reduction rates prevailed. To tune the Co reduction rate and final content, we develop a "two-step" route and track the evolution of the composition and morphology of the particles at the atomic scale. To achieve this, scanning transmission electron microscopy and energy dispersive X-ray elemental mapping techniques are used. We provide evidence of a heterogeneous element distribution caused by element-specific anisotropic growth and create octahedral nanoparticles with tailored atomic composition like Pt1.5M, PtM, and PtM1.5 (M = Ni + Co). These trimetallic electrocatalysts have been tested toward the oxygen reduction reaction (ORR), showing a greatly enhanced mass activity related to commercial Pt/C and less activity loss than binary PtNi and PtCo after 4000 potential cycles.
authors.affiliation: Instituto de Electroquímica, Universidad de Alicante , Apartado 99, 03080 Alicante, Spain.
authors.forename: Rosa M
authors.initials: RM
authors.lastname: Arán-Ais
authors.affiliation: The 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: The Electrochemical Energy, Catalysis, and Materials Science Laboratory, Department of Chemistry, Chemical Engineering Division, Technical University Berlin , 10623 Berlin, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Merzdorf
authors.affiliation: Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, Forschungszentrum Jülich GmbH , 52425 Jülich, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Gocyla
authors.affiliation: Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, Forschungszentrum Jülich GmbH , 52425 Jülich, Germany.
authors.forename: Marc
authors.initials: M
authors.lastname: Heggen
authors.affiliation: Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, Forschungszentrum Jülich GmbH , 52425 Jülich, Germany.
authors.forename: Rafal E
authors.initials: RE
authors.lastname: Dunin-Borkowski
authors.affiliation: The Electrochemical Energy, Catalysis, and Materials Science Laboratory, Department of Chemistry, Chemical Engineering Division, Technical University Berlin , 10623 Berlin, Germany.
authors.forename: Manuel
authors.initials: M
authors.lastname: Gliech
authors.affiliation: Instituto de Electroquímica, Universidad de Alicante , Apartado 99, 03080 Alicante, Spain.
authors.forename: José
authors.initials: J
authors.lastname: Solla-Gullón
authors.affiliation: Instituto de Electroquímica, Universidad de Alicante , Apartado 99, 03080 Alicante, Spain.
authors.forename: Enrique
authors.initials: E
authors.lastname: Herrero
authors.affiliation: Instituto de Electroquímica, Universidad de Alicante , Apartado 99, 03080 Alicante, Spain.
authors.forename: Juan M
authors.initials: JM
authors.lastname: Feliu
authors.affiliation: The Electrochemical Energy, Catalysis, and Materials Science Laboratory, Department of Chemistry, Chemical Engineering Division, Technical University Berlin , 10623 Berlin, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Strasser
keywords: PtNiCo octahedra; anisotropic growth; intraparticle composition; oxygen reduction reaction