Site-selective XAFS spectroscopy tuned to surface active sites of Cu/ZnO and Cr/SiO<sub>2</sub> catalysts

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<jats:p>XAFS (X-ray absorption fine structure) spectra were measured by using the fluorescence spectrometer for the emitted X-ray from sample. The chemical shifts between Cu<jats:sup>0</jats:sup> and Cu<jats:sup>I</jats:sup> and between Cr<jats:sup>III</jats:sup> and Cr<jats:sup>VI</jats:sup> were evaluated. Tuning the fluorescence spectrometer to each energy, the Cu<jats:sup>0</jats:sup> and Cu<jats:sup>I</jats:sup> site-selective XANES for Cu/ZnO catalyst were measured. The first one was similar to the XANES of Cu metal and the second one was the 5 : 5 average of XANES for Cu<jats:sup>I</jats:sup> sites + Cu metal. The population ratio of copper site of the Cu/ZnO catalyst was found to be Cu metal : Cu<jats:sub>2</jats:sub>O : Cu<jats:sup>I</jats:sup> atomically dispersed on surface = 70(±23) : 22(±14) : 8(±5). Site-selective XANES for Cr<jats:sup>III</jats:sup> site of Cr/SiO<jats:sub>2</jats:sub> catalyst was also studied.</jats:p>

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