Facile proton conduction in a new 2D layered vanadoborate

Abstract

A new 2D vanadoborate, (enH2)4Na2[V12B18O54(OH)6(H2O)]·7H2O (1, en = enthylenediamine), has been successfully synthesized under hydrothermal conditions. The structure of 1 contains the [V12B18O54(OH)6(H2O)]10− clusters which are built from two triangular [V6O18] units and one puckered [B18O36(OH)6] ring. These clusters are linked by NaO6 polyhedra into the 2D layer, which are further connected by hydrogen bonds to form the 3D vanadoborate architecture. The voids formed in the structure are filled with protonated enH22+ and free H2O molecules. Such structural features are particularly desirable for the development of proton conductors. This material shows a high proton conductivity of 1.64 × 10−4 S cm−1 at 333 K under the condition of 100% relative humidity, and the activation energy is estimated to be 0.75 eV.