X線吸収スペクトルによる吸着水素の定量

We investigated Γt andΓd L-edge X-ray absorption near edge structure（XANES）spectra for the metal particles supported on some inorganic oxides（Si0_2，Al_20_3，MgO and Ti0_2）with and without adsorbed hydrogen. The new peaks appeared at 6-8eV above the Pt L-edge in difference spectra between those in vacuum and with adsorbed hydrogen. The intensity of the new peak was decreased by evacuation at room temperature，and then intensity of peak was found to be proportional to the hydrogen coverages but independent of the kind of the supports We also measured XANES spectra at Pt L-edge for Pt particles supported on Si0_2 under CO adsorption and CO＋H_2coadsorption. Coadsorption of hydrogen and CO broadened and shifted the peak in Pt L-XANES to the higher energy side. It was found that the peak can be represented by two components due to adsorbed hydrogen and CO. It was found that the fitting component with respect to adsorbed hydrogen was proportional to the amount of adsorbed hydrogen and this linear relationship was same as hydrogen mono-adsorption. In Pd L-edgeXANES spectra，new peak appeared after hydrogen adsorption and it was found that their intensity of peak can be related with amount of adsorbed hydrogen and ratio of adsorbed hydrogen or Pd atoms in subsurface region to total Pd atoms. XANES changes its structure with interaction between catalysts and adsorbates sensitively，so XANES is expected as new method for in-situ characterization.