CHIMIE-DOUCE REACTIONS - A NEW ROUTE TO OBTAIN WELL CRYSTALLIZED LAYER DOUBLE HYDROXIDES

Layer double hydroxides (LDHs) have been obtained by chimie douce reactions from the NaNi1-yCoyO2 cobalt substituted sodium nickelate (0 ≤ y ≤ 0.5). These materials exhibit the general formula Ni1-y Coy(OH)2Xy/n, zH2O, Xn- = CO2-3, NO-3, Cl-, OH-, SO2-4 …. The Xn- anions and the water molecules are inserted between the hydroxide slabs. The Ni1-yCoyO2 slabs are built up during the high temperature preparation of the sodium nickelate, while the anions are inserted later on during the chimie douce reaction. It follows that a wider range of materials can be obtained than in the case of classical precipitation reactions. Moreover, the materials are well crystallized. The LDHs have been characterized by X-ray diffraction and by IR spectroscopy. The observed anion selectivity is discussed on the basis of electrostatic interactions and steric effects. © 1993 Academic Press, Inc.