Layered double hydroxides with the hydrotalcite-type structure containing Cu2+, Ni2+ and Al3+

Abstract

Layered double hydroxides (LDHs) with the hydrotalcite-like structure have been prepared containing different amounts of Ni2+, Cu2+ and Al3+ in the brucite-like layers by a coprecipitation method. The samples have been characterized by elemental chemical analysis, powder X-ray diffraction, differential thermal analysis and thermogravimetric analysis, FT-IR and UV–VIS diffuse reflectance spectroscopies, temperature-programmed reduction, and specific surface area and porosity assessment by N2 adsorption at −196 °C. The nature of the phase obtained, crystallinity of the HT-like phase and thermal behaviour of these materials were influenced by MII/Al atomic composition and concentration of bivalent metal ion. Calcination at 500 °C leads to mostly amorphous solids containing NiO, and also CuO (tenorite) for large Cu2+ contents (Cu/Ni molar ratio equal to 4). When the calcination temperature is increased to 850 °C, crystallization of well defined phases (NiO, CuO and NiAl2O4, depending on the relative amounts of Ni, Cu and Al) takes place. Reduction of Cu2+ species in these samples takes place at a lower temperature than that for Ni2+, while the temperature of reduction of nickel is increased with an increase in aluminium and copper content of the samples.