Layered double hydroxides, layer lattice

There are two major subdivisions of layer lattice silicates a single layer type based on a condensation of a hydroxide layer structure with one silica plane and a double layer unit in which a further inverted silica plane completes a sandwich-like structure above the hydroxide unit. Each layer lattice is theoretically complete within itself and although similar layers can stack above each other there can be no formal inter-layer ionic or covalent bond formation. 

There are a number of techniques that have been successfully applied to synthesize modified hydrotalcites (48). The most commonly method used is the co-precipitation of two metal salts in alkaline solution at a constant pH value of about 10. Another method uses the classical ion exchange process in which the guest anions are exchanged with the anions in the interlayer spaces of preformed layered double hydroxides to produce specific anion intercalated modified hydrotalcites. StiU another method is a lattice reconstruction after heating, i.e., calcination, which is based on the structural memory effect of these materials, due to which the original structure is reproduced after rehydration. 

Water molecules will be adsorbed on metal oxide surfaces to compensate the oxygen defects in the lattice. Afterwards, water molecules will dissociate and the surface of mthenium oxide is covered with hydroxide groups. When this layer is exposed to an electrolyte a Helmholtz double layer is formed at the electrodeelectrolyte interface which is responsible for the electrochemical potential of the electrode attributed to the pH of the solution. 

---