X-Ray absorption spectroscopic studies on copper-containing hydrotalcite

Abstract

EXAFS and XANES spectra have been recorded at the copper K-absorption edge on hydrotalcite samples, which contain 10 mol% copper, in order to determine the local environment of the copper ions. The vanishingly small magnitude of the pre-edge peak in the XANES region of the spectra indicates a centrosymmetric coordination of copper. The analysis of the EXAFS region results in a set of four oxygen ligands, 1.98 Åapart from copper as well as two oxygen ligands, which are 0.26 Åfurther apart. This is consistent with an octahedron, elongated by Jahn–Teller effects. The best fit of the third coordination shell is obtained with 4.6 aluminium or magnesium ions at a distance of 3.05 Åfrom the copper.