New (Ni, Co)-based layered double hydroxides with intercalated oxometalate (Mo, W) species, obtained by chimie douce reactions

Layered double hydroxides (LDHs), containing intercalated oxometalate (Mo, W) species, were obtained by chimie douce reactions from NaNi1-yCoyO2 cobalt substituted sodium nickelates (0.10 less than or equal to y less than or equal to 0.40). The X-ray diffraction (XRD), infrared (IR) and extended X-ray absorption fine structure (EXAFS) studies show that, in both cases, M2O72- anions (M=Mo, W), made of corner-sharing tetrahedra, are intercalated. In these MO4 tetrahedra, the M-O bond with the bridging oxygen is elongated compared to the other ones, and the M-O-M angle is close to 115degrees. Oxygen atoms belonging to water molecules are pointing to some faces of the MO4 tetrahedra. The presence of such peculiar intercalated species, as well as the existence of an hydrogen bond network, leads to local distortions within the slabs, which entails a turbotratic type'' shape of the XRD patterns.