Density functional theory calculations of hydrogen molecule adsorption on monolayer molybdenum and tungsten disulfide

Abstract

In this work, we report a theoretical study on the adsorption of molecular hydrogen (H2) on monolayer molybdenum disulfide (MoS2) and tungsten disulfide (WS2) using a first-principles van der Waals functional (vdW-DF) method. Our calculations show that the most favorable configuration for the adsorption of a H2 molecule on monolayer MoS2 is similar to that for the monolayer WS2 surface. The H2 molecule is physisorbed on the surface of the monolayers MoS2 and WS2 with adsorption energies of −131.61 and −169.44meV, respectively. Analysis of the electronic structures and charge confirmed that no significant hybridization between the respective orbitals occurs, and quantitative analysis revealed that a small interaction was obtained in terms of binding energies. Furthermore, adsorption of two H2 molecules on one and both sides of the monolayer MoS2 and WS2 was examined. The obtained results indicated that, with the adsorption of the second H2 molecule on one- and both-side of WS2, the binding energies were decreased to −155.2 and −153.6meV, respectively. However, the values for adsorption of the second H2 on monolayer MoS2 remained nearly constant compared to the adsorption of the first H2 molecule. In addition, we calculated the binding energy between the H2 molecule and the substrate (MoS2 and WS2) under axial strain of −10% to 10%, which revealed that the binding energy between the H2 molecule and the substrate was enhanced by axial strain. Our results also indicated that applying compression to monolayer WS2 yields higher reactivity with the hydrogen molecule than applying compression to monolayer MoS2.