Time-resolved, in situ X-ray diffraction studies of intercalation in lamellar hosts

Abstract

Energy dispersive X-ray diffraction (EDXRD) has been used to perform in situ kinetic studies on the intercalation of a range of guest molecules in layered lattices. The kinetics of the intercalation of cations (K +, PyH + (Py=C 5H 5N), NMe 4 +) and the long chain ammonium ions C 12TMA, C 16TMA, C 18TMA (C 12TMA=dodecyltrimethylammonium, C 16TMA=hexadecyltrimethylammonium and C 18TMA=octadecyltrimethylammonium) into crystals of MnPS 3 have been determined. These reactions are very fast, and in some cases novel transient phases are observed. The rate of cobaltocene, Co(η-C 5H 5) 2, intercalation in layered metal dichalcogenides ZrS 2, 2H-SnS 2, 2H-SnSe 2, 2H-TaS 2, 2H-NbS 2, 1T-TaS 2 and TiS 2 has also been investigated. Integrated intensities of the Bragg reflections have been used to determine the extent of reaction ( α) versus time for each of these reactions. A number of kinetic models have been considered, including the Avrami–Erofeyev ( m=1.5) deceleratory nuclei-growth model and statistical simulation. The concentration and solvent dependence of the rate of Co(η-C 5H 5) 2 intercalation into 2H-SnS 2 has also been determined. Surprisingly, we find that the rate of intercalation is invariant to the initial Co(η-C 5H 5) 2 concentration over a wide concentration range. The rate of intercalation of the lithium salts (LiX; X=Cl, Br, NO 3 and OH) into Gibbsite (γ-Al(OH) 3) giving the layered double hydroxides [LiAl 2(OH) 6]X· nH 2O (X=Cl, Br, NO 3 and OH) and [LiAl 2(OH) 6] 2SO 4· nH 2O has been studied. The temperature dependence of the rate of intercalation of LiCl yields an activation energy of 27 kJ mol −1. The reaction was also found to be half order with respect to the initial concentration of LiCl. Time-resolved in situ energy dispersive X-ray powder diffraction (EDXRD) spectra have been recorded following the addition of an aqueous solution of hexadecyltrimethylammonium chloride (C 16H 33N +Me 3Cl −=C 16TMACl) to kanemite (NaHSi 2O 5·3H 2O). The diffraction data suggest that initially a layered phase forms due to intercalation of the alkylammonium ions which then transforms into a silicate-organic mesophase which is the precursor to the hexagonal mesoporous silicate, FSM-16.