title: Peptide-Directed PdAu Nanoscale Surface Segregation: Toward Controlled Bimetallic Architecture for Catalytic Materials.
abstract: Bimetallic nanoparticles are of immense scientific and technological interest given the synergistic properties observed when two different metallic species are mixed at the nanoscale. This is particularly prevalent in catalysis, where bimetallic nanoparticles often exhibit improved catalytic activity and durability over their monometallic counterparts. Yet despite intense research efforts, little is understood regarding how to optimize bimetallic surface composition and structure synthetically using rational design principles. Recently, it has been demonstrated that peptide-enabled routes for nanoparticle synthesis result in materials with sequence-dependent catalytic properties, providing an opportunity for rational design through sequence manipulation. In this study, bimetallic PdAu nanoparticles are synthesized with a small set of peptides containing known Pd and Au binding motifs. The resulting nanoparticles were extensively characterized using high-resolution scanning transmission electron microscopy, X-ray absorption spectroscopy, and high-energy X-ray diffraction coupled to atomic pair distribution function analysis. Structural information obtained from synchrotron radiation methods was then used to generate model nanoparticle configurations using reverse Monte Carlo simulations, which illustrate sequence dependence in both surface structure and surface composition. Replica exchange with solute tempering molecular dynamics simulations were also used to predict the modes of peptide binding on monometallic surfaces, indicating that different sequences bind to the metal interfaces via different mechanisms. As a testbed reaction, electrocatalytic methanol oxidation experiments were performed, wherein differences in catalytic activity are clearly observed in materials with identical bimetallic composition. Taken together, this study indicates that peptides could be used to arrive at bimetallic surfaces with enhanced catalytic properties, which could be leveraged for rational bimetallic nanoparticle design using peptide-enabled approaches.
authors: Applied Chemical and Materials Division, National Institute of Standards and Technology , Boulder, Colorado 80305, United States.
authors: Nicholas M
authors: NM
authors: Bedford
authors: Department of Physics, University of Notre Dame , Notre Dame, Indiana 46556, United States.
authors: Allison R
authors: AR
authors: Showalter
authors: Applied Chemical and Materials Division, National Institute of Standards and Technology , Boulder, Colorado 80305, United States.
authors: Taylor J
authors: TJ
authors: Woehl
authors: Institute for Frontier Materials, Deakin University , Geelong, Victoria 3216, Australia.
authors: Zak E
authors: ZE
authors: Hughes
authors: X-ray Sciences Division, Argonne National Laboratory , Argonne, Illinois 60439, United States.
authors: Sungsik
authors: S
authors: Lee
authors: X-ray Sciences Division, Argonne National Laboratory , Argonne, Illinois 60439, United States.
authors: Benjamin
authors: B
authors: Reinhart
authors: Department of Polymer Science and Engineering, University of Massachusetts , Amherst, Massachusetts 01003, United States.
authors: S Piril
authors: SP
authors: Ertem
authors: Department of Polymer Science and Engineering, University of Massachusetts , Amherst, Massachusetts 01003, United States.
authors: E Bryan
authors: EB
authors: Coughlin
authors: X-ray Sciences Division, Argonne National Laboratory , Argonne, Illinois 60439, United States.
authors: Yang
authors: Y
authors: Ren
authors: Institute for Frontier Materials, Deakin University , Geelong, Victoria 3216, Australia.
authors: Tiffany R
authors: TR
authors: Walsh
authors: Department of Physics, University of Notre Dame , Notre Dame, Indiana 46556, United States.
authors: Bruce A
authors: BA
authors: Bunker
keywords: X-ray absorption spectroscopy; atomic pair distribution function analysis; bimetallic nanoparticles; electrocatalysis; peptide-enabled nanoparticles