Extended X-ray Absorption Fine Structure Studies of Bimetallic ${Cu-Ni/ \gamma -$Al_2O_3$}$ Catalysts

The nature of the species and their local structure in reduced $Cu-Ni/ \gamma -Al_20_3$ catalysts have been investigated over the entire composition range. Nickel is present in the form of $Ni$ metal as well as $Ni^{2+}$ , the latter in both octahedral and tetrahedral environments; copper is present as Cu metal and as a $Cu_2O$-like phase. Analysis of the $EXAFS$ of these multiphasic catalysts has been carried out employing an additive relation for the EXAFS function and making use of residual spectra. The concentration of $Ni^0$ relative to $Ni^{2+}$ increases with increase in copper content; similarly, the concentration of $Cu^0$ relative to $Cu^+$ increases with the proportion of nickel