title: Rh-Doped Pt-Ni Octahedral Nanoparticles: Understanding the Correlation between Elemental Distribution, Oxygen Reduction Reaction, and Shape Stability.
abstract: Thanks to their remarkably high activity toward oxygen reduction reaction (ORR), platinum-based octahedrally shaped nanoparticles have attracted ever increasing attention in last years. Although high activities for ORR catalysts have been attained, the practical use is still limited by their long-term stability. In this work, we present Rh-doped Pt-Ni octahedral nanoparticles with high activities up to 1.14 A mgPt(-1) combined with improved performance and shape stability compared to previous bimetallic Pt-Ni octahedral particles. The synthesis, the electrocatalytic performance of the particles toward ORR, and atomic degradation mechanisms are investigated with a major focus on a deeper understanding of strategies to stabilize morphological particle shape and consequently their performance. Rh surface-doped octahedral Pt-Ni particles were prepared at various Rh levels. At and above about 3 atom %, the nanoparticles maintained their octahedral shape even past 30,000 potential cycles, while undoped bimetallic reference nanoparticles show a complete loss in octahedral shape already after 8000 cycles in the same potential window. Detailed atomic insight in these observations is obtained from aberration-corrected scanning transmission electron microscopy (STEM) and energy dispersive X-ray (EDX) analysis. Our analysis shows that it is the migration of Pt surface atoms and not, as commonly thought, the dissolution of Ni that constitutes the primary origin of the octahedral shape loss for Pt-Ni nanoparticles. Using small amounts of Rh we were able to suppress the migration rate of platinum atoms and consequently suppress the octahedral shape loss of Pt-Ni nanoparticles.
authors: Electrochemical Energy, Catalysis, and Material Science Laboratory, Department of Chemistry, Technical University Berlin , 10623 Berlin, Germany.
authors: Vera
authors: V
authors: Beermann
authors: Ernst-Ruska Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich GmbH , 52425 Jülich, Germany.
authors: Martin
authors: M
authors: Gocyla
authors: Department of Inorganic Chemistry, Fritz-Haber-Institut der Max-Planck-Gesellschaft , Faradayweg 4-6, 14195 Berlin, Germany.
authors: Elena
authors: E
authors: Willinger
authors: Electrochemical Energy, Catalysis, and Material Science Laboratory, Department of Chemistry, Technical University Berlin , 10623 Berlin, Germany.
authors: Stefan
authors: S
authors: Rudi
authors: Ernst-Ruska Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich GmbH , 52425 Jülich, Germany.
authors: Marc
authors: M
authors: Heggen
authors: Ernst-Ruska Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich GmbH , 52425 Jülich, Germany.
authors: Rafal E
authors: RE
authors: Dunin-Borkowski
authors: Department of Inorganic Chemistry, Fritz-Haber-Institut der Max-Planck-Gesellschaft , Faradayweg 4-6, 14195 Berlin, Germany.
authors: Marc-Georg
authors: MG
authors: Willinger
authors: Electrochemical Energy, Catalysis, and Material Science Laboratory, Department of Chemistry, Technical University Berlin , 10623 Berlin, Germany.
authors: Peter
authors: P
authors: Strasser
mesh_terms: D000497:Alloys / Q000737:chemistry*; D002384:Catalysis; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D008958:Models, Molecular; D009532:Nickel / Q000737:chemistry*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D010316:Particle Size; D010984:Platinum / Q000737:chemistry*; D012428:Ruthenium / Q000737:chemistry*
chemical_list: D000497:Alloys; D010984:Platinum; D009532:Nickel; D012428:Ruthenium; D010100:Oxygen
keywords: PtNi alloy; Rh-doped; anisotropy; octahedral nanoparticles; oxygen reduction reaction; stability