The electronic structure of two-dimensional transition metal hydroxide monolayers and heterostructures

Abstract

Transition metal layered double hydroxides can be fabricated in two-dimensions. Specifically, two-dimensional monolayers, such as Fe(OH)2, Co(OH)2 and Ni(OH)2, and their corresponding heterostructure bilayers can be potentially useful for solar energy conversion. In order to determine the electronic structure properties of these unique materials, we perform Density Functional Theory calculations. We find that the adhesion energy between the monolayers is small and should allow separating the layers. Furthermore, the calculated band gaps are in the range of 1.4–2.3eV, which is suitable for good optical absorption of solar energy. All of the studied hydroxides have different chemical character at the band edges, i.e. transition metal states at the valence band and oxygen states at the conduction band, which may allow good charge separation after optical excitation.