Modulation effects of S vacancy and Mo edge on the adsorption and dissociation behaviors of toxic gas (H2S, SO2) molecules on the MoS2 monolayer

Abstract

This study focuses on the modulation effects of S vacancy and Mo edges on the adsorption and dissociation behaviors of toxic gases (H₂S and SO₂) on MoS₂ by first-principles calculations. Both molecules are found to chemisorb at the S vacancy (SV) and pristine Mo edge and physisorb at the Mo edge with a 50% sulfur coverage (Mo-50 edge). Among them, SO₂ has larger adsorption energy than H₂S on both S vacancy and pristine Mo edge, which is related to a more electronegative O than S atom and electronically rich for the pristine Mo edge. The defective states of MoS₂ induced by SV can be removed by forming Mo–S, Mo–O and Mo–H bonds upon the adsorption of SO₂ and the dissociation of H₂S, which is applicable in designing MoS₂ based nano-electronics devices in the future. The dissociations of H₂S and SO₂ on pristine Mo edges are found to be more favorable than those on S vacancies due to the catalytically active Mo⁴⁺ states at edge sites. H₂S is found to dissociate on the Mo-50 edge more easily than SO₂. The adsorptions and dissociations of toxic gas on MoS₂ with SV or Mo edges suggest MoS₂ is a potential candidate in detecting and removal of toxic gases.