Molybdenum disulfide as a highly efficient adsorbent for non-polar gases

Abstract

Molybdenum disulfide (MoS₂), a kind of graphene-like, two-dimensional material, has attracted great interest because of its unique properties and potential applications in electronics and sensors. In this paper, first-principle calculations and grand canonical Monte Carlo (GCMC) simulations are performed and used to show that the MoS₂ layer is efficient at absorbing non-polar gases. Compared with the popular gas sorbents (metal organic frameworks and carbon-based materials), MoS₂ has additional advantages, including large surface to volume ratio and tunable properties. The non-polar gas [carbon dioxide (CO₂) and methane (CH₄)] adsorption on the MoS₂ layer with and without vacancies has been systematically studied. The perfect MoS₂ shows little or no adsorption for CO₂ and CH₄ molecules, but the MoS₂ with a single S vacancy and double S vacancies exhibits an excellent adsorption ability for CO₂ and CH₄ gases. The adsorption energies were 65 kJ mol⁻¹ for CO₂ and 47 kJ mol⁻¹ for CH₄ (van der Waals-D2), respectively. An orbital coupling between the p orbital of the CO₂ (or CH₄) molecule and the d orbital of the Mo atom was observed. GCMC simulation results show that MoS₂ with a single S vacancy could absorb 42.1 wt% of CO₂ and 37.6 wt% of CH₄ under a pressure of 80 bar at room temperature. The results given in this paper indicate that monolayer MoS₂ with defects is a highly efficient absorbent for non-polar gases.