Elucidation of copper environment in a Cu–Cr–Fe oxide catalyst through <i>in situ</i> high-resolution XANES investigation
Tahmin Lais, Liliana Lukashuk, Leon G. A. van de Water, Timothy I. Hyde, Matteo Aramini, Gopinathan Sankar
Abstract
Copper containing materials are widely used in a range of catalytic applications. Here, we report the use of Cu K-edge high resolution XANES to determine the local site symmetry of copper ions during the thermal treatment of a Cu-Cr-Fe oxide catalyst. We exploited the Cu K-edge XANES spectral features, in particular the correlation between area under the pre-edge peak and its position to determine the local environment of Cu2+ ions. The information gained from this investigation rules out the presence of Cu2+ ions in a tetrahedral or square planar geometry, a mixture of these sites, or in a reduced oxidation state. Evidence is presented that the Cu2+ ions in the Cu-Cr-Fe oxide system are present in a distorted octahedral environment.