Oxygen Chemisorption, Formation, and Thermal Stability of Pt Oxides on Pt Nanoparticles Supported on SiO2/Si(001): Size Effects

    Authors

    L. K. Ono; J. R. Croy; H. Heinrich;B. R. Cuenya

    Comments

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    Abbreviated Journal Title

    J. Phys. Chem. C

    Keywords

    ENVIRONMENTAL ELECTRON-MICROSCOPY; ATOMIC OXYGEN; MICELLE ENCAPSULATION; ADSORBED OXYGEN; PARTICLE-SIZE; PLATINUM NANOPARTICLES; MEOH; DECOMPOSITION; PD NANOPARTICLES; PT(111) SURFACE; OXIDATION-STATE; Chemistry, Physical; Nanoscience & Nanotechnology; Materials Science, ; Multidisciplinary

    Abstract

    The changes induced in the structure and chemical state of size-selected Pt nanoparticles (NPs) supported on ultrathin SiO2 films upon exposure to oxygen have been investigated by atomic force microscopy (AFM), transmission electron microscopy (TEM), in situ X-ray photoelectron spectroscopy (XPS), and temperature-programmed desorption (TPD). For low atomic oxygen exposures, chemisorbed oxygen species were detected on all samples. Exposure to higher atomic oxygen coverages at room temperature leads to the formation and stabilization of PtOx species (PtO2 and PtO). On all samples, a two-step thermal decomposition process was observed upon annealing in ultrahigh vacuum: PtO2 - > PtO - > Pt. For NPs in the 2-6 nm range, the NP size was found to affect the strength of the O binding. Contrary to the case of Pt(111), where no oxides were detected above 700 K, 10-20% PtO was detected on the NP samples via XPS at the same temperature, suggesting the presence of strongly bound oxygen species. In addition, for identical atomic oxygen exposures, decreasing the NP size was found to favor their ability to form oxides. Interestingly, regardless of whether the desorption of chemisorbed oxygen species or that of oxygen in PtOx species was considered, our TPD data revealed higher O-2-desorption temperatures for the Pt NPs as compared with the Pt(111) surface. Furthermore, a clear size-dependent trend was observed, with an increase in the strength of the oxygen bonding with decreasing NP size.

    Journal Title

    Journal of Physical Chemistry C

    Volume

    115

    Issue/Number

    34

    Publication Date

    1-1-2011

    Document Type

    Article

    Language

    English

    First Page

    16856

    Last Page

    16866

    WOS Identifier

    WOS:000294146700017

    ISSN

    1932-7447

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