title: Adsorbate-induced structural changes in 1-3 nm platinum nanoparticles.
abstract: We investigated changes in the Pt-Pt bond distance, particle size, crystallinity, and coordination of Pt nanoparticles as a function of particle size (1-3 nm) and adsorbate (H2, CO) using synchrotron radiation pair distribution function (PDF) and X-ray absorption spectroscopy (XAS) measurements. The ∼1 nm Pt nanoparticles showed a Pt-Pt bond distance contraction of ∼1.4%. The adsorption of H2 and CO at room temperature relaxed the Pt-Pt bond distance contraction to a value close to that of bulk fcc Pt. The adsorption of H2 improved the crystallinity of the small Pt nanoparticles. However, CO adsorption generated a more disordered fcc structure for the 1-3 nm Pt nanoparticles compared to the H2 adsorption Pt nanoparticles. In situ XANES measurements revealed that this disorder results from the electron back-donation of the Pt nanoparticles to CO, leading to a higher degree of rehybridization of the metal orbitals in the Pt-adsorbate system.
authors.affiliation: Energy Systems Division, ‡X-ray Science Division, §Chemical Sciences and Engineering Division, Argonne National Laboratory , Lemont, Illinois 60439, United States.
authors.forename: Yu
authors.initials: Y
authors.lastname: Lei
authors.forename: Haiyan
authors.initials: H
authors.lastname: Zhao
authors.forename: Rosa Diaz
authors.initials: RD
authors.lastname: Rivas
authors.forename: Sungsik
authors.initials: S
authors.lastname: Lee
authors.forename: Bin
authors.initials: B
authors.lastname: Liu
authors.forename: Junling
authors.initials: J
authors.lastname: Lu
authors.forename: Eric
authors.initials: E
authors.lastname: Stach
authors.forename: Randall E
authors.initials: RE
authors.lastname: Winans
authors.forename: Karena W
authors.initials: KW
authors.lastname: Chapman
authors.forename: Jeffrey P
authors.initials: JP
authors.lastname: Greeley
authors.forename: Jeffrey T
authors.initials: JT
authors.lastname: Miller
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Chupas
authors.forename: Jeffrey W
authors.initials: JW
authors.lastname: Elam