Computational investigation of two-dimensional LDHs and the modification of their electronic structure induced by defects

Abstract

The exfoliation of layered double hydroxides was studied using DFT calculations with periodic boundary conditions. F−, Cl−, Br−, NO3− and CO32− were chosen as the counteranions to estimate their influence on the exfoliation energies. Two surfactants (dodecyl sulfate and dodecylbenzene sulfonate) were also considered for the simulations. The binding energies demonstrated that both NO3− and dodecyl sulfate favor the exfoliation over the other anions. Regarding the electronic structure, the band gaps were altered upon exfoliation. The comparison between the structural and energetic features of the hydrated and dehydrated 2D forms showed that the hydration degree is a relevant factor for the fabrication of novel composites. Band gap modifications were also observed after dehydration. The energetic and electronic aspects of the formation of vacancy defects were also analyzed. The defect formation energies showed that the removal of clusters (M(OH)x) is less costly than the formation of single atom vacancies. The band structures of the defective structures presented significant band gap changes. In certain cases, metallic states appeared as the divalent species were removed from the LDH layers. These results highlight the importance of 2D LDHs for photocatalytic applications, since many degrees of freedom are available for the tuning of the electronic structure.