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

Abstract

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_1VS and MoS2_1VMo_3NS 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_1Vs and a significantly enhanced physisorption of CO2 on the MoS2_1VMo_3NS, 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_1VMo_3NS 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.