Mechanism of n-alkylammonium ion intercalation into the layered host α-VOPO4·2H2O

Abstract

The mechanism of redox intercalation reactions between alkylammonium iodides and the layered host α-VOPO₂·2H₂O has been investigated by synthesis of mixed- and single-ion intercalates, by ion-exchange experiments, and by EPR study of in situ reactions. Intercalation was found to occur first at the edge of crystallites. With alkyl chains of butyl and longer, intercalation of ions was seen to proceed throughout the interlayer galleries, resulting in a bilayer arrangement, with the chains making an average angle of 39° to the host layers. Smaller ions were not intercalated to any great degree, with reaction occurring only on crystal edges and faces. Intercalation of these smaller ions at crystal edges in mixed intercalation reactions prevented larger, co-present octylammonium ions from intercalating, indicating that they represented a barrier to free interlayer diffusion of further reactant. This barrier is suggested as being the result of smaller ions intercalating parallel to the host layers at crystallite edges.