| Abstract
| - Silica-supported bimetallic MSn (M = Ni, Pd, Pt) samples havebeen prepared by twoconsecutive impregnation steps with solutions of[MCl2(PPh3)2] complexes andSnCl2,respectively. After treatment in H2 at 673 K, thesematerials were characterized in detailby X-ray diffraction (XRD), conventional transmission electronmicroscopy, combined withenergy-dispersive X-ray microanalysis, high-resolution transmissionelectron microscopy(HRTEM), and X-ray photoelectron spectroscopy (XPS). In addition,their performance inCO oxidation at temperatures ranging from 298 to 623 K was examinedafter activationprocesses under O2 and/or CO/O2 mixtures.XRD, HRTEM, electron diffraction, and XPSdata of the Pt- or Pd-containing samples revealed that MSn alloys areformed upon H2treatment but that they are inactive in CO oxidation at lowtemperature. However, anoxidizing pretreatment produced alloys enriched in Pt or Pd(Pt3Sn, Pd3Sn2) andSnOx phases,which gave satisfactory catalytic performance in the CO oxidation.The behavior of the NiSnsystem was different. Although a Ni-enrichedNi3Sn2 phase was identified inreducedsamples, further O2 treatment at 673 K led to a mixture ofphases including NiO and Ni-rich particles embedded in Sn-rich structures. ThisNiSn/SiO2 sample gave poor performancein CO oxidation, which was similar to that of the Ni-freeSn/SiO2 counterpart.
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