Hexacyanoferrate (III) as an electroactive probe for the investigation of the interlayer basicity of the layered double hydroxide (LDH) of Mg with Al

Hexacyanoferrate on intercalation within the interlayer region of the layered double hydroxide (LDH) of Mg with Al retains its electroactivity. Within the confined region of the interlayer, the redox potential of the intercalated ion, as estimated from cyclic voltammetric studies, is shifted by almost 126 mV higher than that of the free ion in solution. We attribute this to the activity of hydroxyl ions in the interlayer. By comparing the shifts of the redox potential of the free ion in solutions containing different concentrations of hydroxyl ions, we estimate the concentration of hydroxyl ions in the interlayer to be in the vicinity of ∼11.8 M. This corresponds to 20% of the crystallographically defined number density of hydroxyl ions (equilibrium dissociation constant ∼0.2) and shows that the chemical environment of the interlayer is very similar to that in solution. The LDH of Mg with Al thereby behaves like a strong base.