DFT study of MoS2 and hydrogen adsorbed on the (100) face of MoS2

Abstract

DFT calculations were employed to investigate the properties of the catalytically important (100) edge of MoS₂ and the adsorption of hydrogen thereon. The electronic properties of the bulk and surface as well as the relaxed positions of surface atoms are calculated by two different techniques, namely all-electron and plane wave pseudo-potential DFT methods. Hydrogen adsorption is studied by means of a (2 × 1) surface cell to account for H–H interactions and the different configurations of adsorbed hydrogen atoms. Our calculations demonstrate that the electronic structure and the positions of the relaxed surface atoms obtained by the two methods are identical, with the exception of minor discrepancies which are attributed to the different relaxation procedures. The (100) surface of MoS₂ contains weakly coupled S–S pairs formed by relaxation of its sulfur atoms. The results of the hydrogen adsorption show that hydrogen is adsorbed on the sulfur pairs but not on Mo atoms on the surface. Only one of the possible configurations of adsorbed H atoms on a (2 × 1) cell is energetically favoured, while the energy of the other configurations is higher with respect to the energy of H₂ and MoS₂ .