Site-Selective X-Ray Absorption Fine Structure (XAFS) Spectroscopy (2). XAFS Spectra Tuned to Surface Active Sites of Cu/ZnO and Cr/SiO2 Catalysts

Abstract Site-selective XAFS spectra were measured by tuning the Rowland-type fluorescence spectrometer to each site of Cu/ZnO and Cr/SiO2 catalysts. The chemical shifts between Cu0 and CuI sites and between CrIII and CrVI sites were relatively large for model compounds (ΔE = 1.6 eV), and were utilized as the tune energies of site-selective XAFS. Site-selective XANES tuned to Cu0, CuI, and CrIII sites were successfully obtained. Based on the correlation between the chemical shift and the peak width (energy resolution of the fluorescence spectrometer), site-selective XANES spectra were analyzed. The population ratio of Cu metal, Cu2O, and CuI atomically dispersed on ZnO was estimated to be 70(±23) : 22(±14) : 8(±5). The contribution of the CrIII site to site-selective XANES tuned to the CrIII site was 94(±3)%.