From Libiola's natural woodwardite to the energy storage systems: a journey through the Layered Doubled Hydroxides (LDHs)

Layered doubled hydroxides (LDHs) belong to the hydrotalcite supergroup, their crystal structure is composed of brucite-type layers in which a trivalent cation partially substitutes a divalent cation, generating a net positive charge balanced by an anionic species in the interlayer giving the general formula: [M2+ 1-x N3+x (OH)2]x+(Anx/ n)x- * mH2O Where M and N are respectively a divalent and a trivalent cation, A is an anion with n charge, x is the molar ratio N/(M+N) and m is a value between 1 and 4. The interlayer is very flexible and could host different compounds both anions, cations and not charged ones; fourthermore the whide range of possible combination of M,N and A lead to a lot of different applications for those class of compounds. This work reports the results obtained starting from the synthesis of the analogue of the natural woodwardite (AlCu-SO4 LDH and its affinity for rare earths elements. Moreover a number of synthetic LDHs have been properly planned and synthesised for the adsorption of dangerous pollutants such as Cr(VI) and electrochemical purposes, to be appliable as active materials in metal ions batteries.