Deconvolution analysis of Cu L-edge XANES for quantification of copper (II) coordinations in copper-aluminate catalysts

Cu L-3-edge XANES spectra of Cu-aluminate catalysts were recorded to clarif y the local structure of Cu2+ cation in alumina matrix. XANES spectra of Cu -aluminate exhibited two different peaks, which were assigned, by compariso n with those of reference compounds, to Cu2+ in tetrahedral and octahedral sites. To estimate the fraction of these Cu2+ species, a deconvolution anal ysis of XANES spectra was carried out. For CuAl2O4 (stoichiometric spinel), the ratio of the peak areas of the deconvoluted spectrum was in good agree ment with the ratio of tetrahedral/octahedral previously determined by X-ra y diffraction method. Thus, it is concluded that the fraction of Cu2+ ions on tetrahedral and octahedral sites can be estimated quantitatively from Cu L-3-edge absorption spectra. This method was applied to a series of copper -aluminate catalysts, and it was shown that the fraction of Cu2+ On tetrahe dral sites increased as Cu content increased.