Ab initio study of hydrogen storage on metal-decorated GeC monolayers

Abstract

Bidimensional nanostructures have been proposed as hydrogen-storage systems owing to their large surface-to-volume ratios. Germanium carbide monolayers (GeC-MLs) can offer attractive opportunities for H2 adsorption compared to graphene. However, this possibility has not been explored in detail. In this work, the adsorption of H2 molecules on GeC-MLs decorated with alkali metal (AM) and alkaline earth metal (AEM) adatoms was investigated using the density functional theory. Results showed that the AM adatoms were chemisorbed on the GeC-ML, whereas AEM adatoms were physisorbed. The H2 molecules presented negligible adsorption energies on the weakly adsorbed AEM adatoms. Conversely, the AM adatoms improved the H2 adsorption, possibly due to a large charge transfer from the adatoms to the GeC-ML. The potassium-decorated GeC-ML exhibited the most optimal H2 storage capacity, adsorbing up to six molecules and with a lower possibility of forming metal clusters than the other studied cases. These results may aid in the development of new efficient hydrogen-storage materials.