N-doping enabled defect-engineering of MoS₂ for enhanced and selective adsorption of CO₂: A DFT approach

A density functional theory study was conducted to analyze CO₂ adsorption on defective and non-defective MoS₂ surfaces with or without nitrogen doping. The MoS₂_1V_S and MoS₂_1V_Mo_3N_S were found exhibiting outstanding adsorption activity and stability, which is linked to an enhanced electron charge on the surface in the presence of vacancies and N species that alters strength and type of interactions with CO₂ molecules. Results showed the dissociative chemisorption of CO₂ on the MoS₂_1V_s and a significantly enhanced physisorption of CO₂ on the MoS₂_1V_Mo_3N_S, which displays an adsorption energy of −1.818 eV compared with −0.139 eV of the pristine MoS₂ surface. Meanwhile, the MoS₂_1Vs exhibits an excellent selective adsorption of CO₂ over N₂ and H₂O, with the highest adsorption ratio of 5.1 and 3.5, respectively. Partial dissociation of CO₂ to CO over the MoS₂_1Vs is also observed and attributed to increased covalent attractions at the vacant site, while the improved CO₂ physisorption over the MoS₂_1V_Mo_3N_S is attributed to the enhanced electrostatic interactions at the vacancy site due to N doping. These findings are confirmed by the computed vibrational frequencies of CO₂ bound on these surfaces. The N-doping enabled defect engineering of MoS₂ is proved effective and enhanced selective adsorption of CO₂.