New (Ni, Co)-based layered double hydroxides with intercalated oxometalate (Mo, W) species, obtained by chimie douce reactionsElectronic supplementary information (ESI) available: parameters obtained after refinement of the EXAFS data at the Ni and Mo K-edges for LDH0.30(Mo) (Table S1) and parameters obtained after refinement of the EXAFS data at the W L(III)-edge for LDH0.30(W) (Table S2). See http://www.rsc.org/suppdata/jm/b1/b107791k/

Abstract

Layered double hydroxides (LDHs), containing intercalated oxometalate (Mo, W) species, were obtained by chimie douce reactions from NaNi_{1 − y}Co_yO₂ cobalt substituted sodium nickelates (0.10 ≤ y ≤ 0.40). The X-ray diffraction (XRD), infrared (IR) and extended X-ray absorption fine structure (EXAFS) studies show that, in both cases, M₂O₇ ²⁻ anions (MMo, 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 115°. 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.