Formation and Thermal Stability of Platinum Oxides on Size-Selected Platinum Nanoparticles: Support Effects

    Authors

    L. K. Ono; B. Yuan; H. Heinrich;B. R. Cuenya

    Comments

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    Abbreviated Journal Title

    J. Phys. Chem. C

    Keywords

    RAY PHOTOELECTRON-SPECTROSCOPY; RESOLUTION ELECTRON-MICROSCOPY; SINGLE-CRYSTAL SURFACES; THIN-FILMS; CATALYTIC-PROPERTIES; ZRO2 FILMS; MICELLE ENCAPSULATION; GOLD NANOPARTICLES; SUBSURFACE OXYGEN; CO; OXIDATION; Chemistry, Physical; Nanoscience & Nanotechnology; Materials Science, ; Multidisciplinary

    Abstract

    This article presents a systematic study of the formation and thermal stability of Pt oxide species on size-Selected Pt nanoparticles (NPs) supported on SiO(2), ZrO(2), and TiO(2) thin films. The studies were carried Out in ultrahigh vacuum (UHV) by temperature-dependent X-ray photoelectron spectroscopy (XPS) measurements and ex situ transmission electron microscopy and atomic force microscopy. The NPs were synthesized by inverse micelle encapsulation and oxidized in UHV at room temperature by an oxygen plasma treatment. For a given particle size distribution, the role played by the NP support on the stability of Pt oxides was analyzed. PtO(2) species are formed on all supports investigated after O(2)-plasma exposure. A two-step thermal decomposition (PtO(2) - > PtO - > Pt) is observed from 300 to 600 K upon annealing in UHV. The stability of oxidized Pt species was found to be enhanced on ZrO(2) under annealing treatments in O(2). Strong NP/support interactions and the formation of Pt-Ti-O alloys are detected for Pt/TiO(2) upon annealing in UHV above 550 K but not under an identical treatment in O(2). Furthermore, thermal treatments in both environments above 700 K lead to the encapsulation of Pt by TiO(x). The final shape of the micellar Pt NPs is influenced by the type of underlying support as well as by the post-deposition treatment. Spherical Pt NPs are stable on SiO(2), ZrO(2), and TiO(2) after in situ ligand removal with atomic oxygen at RT. However, annealing in UHV at 1000 K leads to NP flattening on ZrO(2) and to the diffusion of Pt NPs into TiO(2). The stronger the nature of the NP/support interaction, the more dramatic is the change in the NP shape (TiO(2) > ZrO(2) > SiO(2)).

    Journal Title

    Journal of Physical Chemistry C

    Volume

    114

    Issue/Number

    50

    Publication Date

    1-1-2010

    Document Type

    Article

    Language

    English

    First Page

    22119

    Last Page

    22133

    WOS Identifier

    WOS:000285236800033

    ISSN

    1932-7447

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