First-principles study of hydrogen adsorption on two-dimensional C2N sheet

Abstract

First-principles calculations based on density functional theory (DFT) are carried out to study the adsorption behaviours of molecular H2 on the graphene-like material C2N. The plausible adsorption sites on top of bonds, on carbon atom and nitrogen atom and the center of C-C hexagon and the C-N hexagon are considered. The calculated adsorption energies are found to be in the physisorption regime. We find that the most favourable site of H2 is above the center of C-N hexagon. In addition, we demonstrate the inclusion of the Van der Waals interactions through the DFT-D2 method via the generalized gradient approximation (GGA) functional gives the consistent trend of H2 adsorption with that obtained via the local-density approximation (LDA) functional. The effects of Van der Waals interactions on the adsorption energies and equilibrium distance between H2 and C2N are discussed.