文摘
This work reports on the hydrogen interaction with a 3 wt % Au/Ce0.62Zr0.38O2 (Au/CZ) catalyst prepared bydeposition-precipitation. As deduced from X-ray powder diffraction, electron microscopy (scanningtransmission electron microscopy-high-angle angular dark field and high-resolution electron microscopy),and CO volumetric/Fourier transform IR (FTIR) adsorption studies, the investigated catalyst shows a goodmetal dispersion. By combining FTIR spectroscopy and volumetric chemisorption studies, it is shown thatupon treating the Au/CZ catalyst with 40 Torr of H2 at room temperature a fast and very intense spillovereffect occurs. As determined from the recorded isotherm, very high values of the apparent H/Au ratio (>8.0)and of the atomic hydrogen surface density (>11.0 H/nm2) are reached. In parallel with this observation, theonset of a characteristic IR band at 2133 cm-1 shows the occurrence of significant support reduction withinherent appearance of Ce3+ species. Moreover, the simultaneous growth of the IR band at 1630 cm-1 due tomolecular water strongly suggests that even at room temperature oxygen vacancies are also formed. AdditionalFTIR spectroscopy studies have shown that the hydrogen spillover is strongly inhibited by either co-adsorptionof CO or a reducing pretreatment with flowing 5% H2/Ar at 673 K. These deactivation effects, however, maybe reverted by very mild regeneration treatments at room temperature.