Structural and electronic properties of ion-exchangeable layered perovskites

Abstract

The modification of metal oxide surfaces with organic moieties has been widely studied as a method of preparing organic-inorganic hybrid materials for various applications. Among inorganic oxides, the ion-exchangeable layered perovskites, materials composed by perovskite-like slabs (ABO3, in which B is a small transition metal cation and A is a larger s-, d- or f-block cation) and intercalated cations, stimulated authors’ interest in reason of some encouraging electronic and reactive properties. In particular it is well known that the interlayer surface of layered-perovskites in their protonated form can be easily functionalized with organic groups, such as alcohols, organophosphonic acids, trifluoroacetate groups, D-glucopyranose derivatives, thus allowing the production of stable hybrid materials with new electronic and reactive features. With the aim to design new inorganic-organic hybrid proton conductors, in a first step, the Dion-Jacobson-type ion-exchangeable layered perovskite RbLaNb2O7 and its protonated form (HLaNb2O7) have been studied as inorganic support, by means of DFT methods, within a periodic approach. Starting from experimental evidences and with a look to the interlayer functionalization, different surfaces have been investigated for the materials, notably the ones indexed (001) and (100). Mulliken charges, band structures, and total and projected densities of states have been computed. Results show that, between the functionals tested in this study, hybrid PBE0 is the one that allows to better reproduce electronic (band structure, electronic gap) and structural features reported in literature for such materials.