Methane adsorption on strained 1T′-MoS2 monolayer: insights from density functional theory calculations

In this work, the adsorption mechanism of methane on strained 1T'-MoS2 monolayer was investigated using density functional theory calculations. Motivated by a recent finding on the role of strained 1T'-MX2 transition metal dichalcogenide monolayers on hydrogen evolution reaction (Putungan et al 2015 Phys. Chem. Chem. Phys. 17, 21702-21708), we probed methanes's binding properties on three selected sites: S1 (elongated bond lengths with Mo), S2 (shortened bond lengths with Mo) and Mo-Top. It is found that methane does not bind with S1 and S2, but rather adsorbs on Mo-Top with relatively weak adsorption energy. Application of isotropic tensile biaxial strain tend to improve methane's adsorption, but not until a seemingly 'turn on' strain is reached (at 10%) that a significant increase in the binding energy is reached. It is suggested that strain reinforces states in the vicinity of the Fermi level, thereby improving states hybridization leading to better adsorbate-substrate interaction. Furthermore, strain helps enhance charge transfer from 1T'-MoS2 to methane, improving ionic interaction between the two. These results and insights are of significance in the design of future devices for methane sequestration, storage and release that can be controlled and fine-tuned using strain.