title: Facile fabrication of Ag-Pd bimetallic nanoparticles in ultrathin TiO(2)-gel films: nanoparticle morphology and catalytic activity.
abstract: Ag-Pd bimetallic nanoparticles were prepared directly in ultrathin TiO(2)-gel films by a stepwise ion-exchange/reduction approach. Ion-exchange sites were created in ultrathin films using Mg(2+) ions as template. Ag(+) ion was then incorporated by ion exchange, and converted into metallic nanoparticles by low-temperature H(2) plasma, regenerating ion-exchange sites. The same procedure was then carried out for Pd(2+) ion, producing Pd-on-Ag bimetallic nanoparticles, as TEM observation and plasmon resonance absorption indicate. By contrast, reversed metal incorporation procedure appeared to give a mixture of individual Ag and Pd nanoparticles, as confirmed by TEM, absorption spectroscopy and X-ray photoelectron spectroscopy. For hydrogenation of methyl acrylate, the catalytic activity of the Pd-on-Ag nanoparticle is 367 times as large as that of commercial Pd black and 1.6 times as large as that of Pd monometallic nanoparticle. The outstanding catalytic activity was explicable by the large fraction of the surface-exposed Pd atoms. The formation process of the bimetallic nanoparticle and their general morphological feature are discussed.
authors.affiliation: Frontier Research System and Surface Science Division, The Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
authors.forename: Junhui
authors.initials: J
authors.lastname: He
authors.forename: Izumi
authors.initials: I
authors.lastname: Ichinose
authors.forename: Toyoki
authors.initials: T
authors.lastname: Kunitake
authors.forename: Aiko
authors.initials: A
authors.lastname: Nakao
authors.forename: Yukihide
authors.initials: Y
authors.lastname: Shiraishi
authors.forename: Naoki
authors.initials: N
authors.lastname: Toshima