Evidences of segregated SnO 2 type nanoparticles coating layered double hydroxide at moderate temperature

Abstract

A series of layered double hydroxide (LDH) materials prepared by classical coprecipitation in the presence of divalent Co 2+, trivalent Al 3+, and tetravalent Sn 4+ cations have been investigated as a function of the temperature. As illustrated for the cation composition (Co; Al; Sn) of (0.75; 0.175; 0.075), the segregation of SnO 2-type nanodomains in an interphasing LDH sand-rose region is directly evidenced by transmission electron microscopy and selected area electron diffraction (TEM/SAED). At moderate temperature (⩽400 °C) the local environment around the cobalt cations is strongly modified, whereas the local structure is found to be unchanged in the vicinity of the tin cations. It is explained on the basis of the breakdown of the lamellar assembly and of the partial oxidation of Co 2+ cations and that tin dioxide domains are still segregated from LDH particles. Even if the tin dioxide component does not participate from a structural point of view in the LDH composition, its beneficial effect on the textural properties is significant, increasing the specific surface area and narrowing the pore size distribution.