Exfoliation, Point Defects and Hydrogen Storage Properties of Monolayer TiS3: an Ab Initio Study.

The possibility of H2 molecule adsorption on the basal plane of monolayer TiS3 at various sites has been studied. Among the studied adsorption sites, few sites were found to be suitable for physisorption with binding energy up to 0.10 eV per H2. To increase the activity of hydrogen sorption, the possibility of generating S-vacancies, by removing sulfur atoms from the basal plane of monolayer TiS3, was investigated. Despite the fact that the structures containing vacancies were found to be stable enough, there was no increase in the activity towards hydrogen adsorption. The same effect was obtained with the use of common methods of increasing of the H2 adsorption energy: the decoration of the two-dimensional material with alkali metals (Li, Na). This might be caused by the negatively charged surfaces of single layer TiS3, which hinder the increase in binding by alkali metals through a weak electrostatic interaction.