DFT based investigations on inherent CO2 adsorption and direct dissociation capability of Ti2C and Nb2C mxenes

Abstract

Transition metal carbide MXenes, specifically Ti2C and Nb2C, have been investigated for their ability to efficiently adsorb and dissociate CO2 using First Principles Calculations based on Density Functional Theory (FPS-DFT). Pure Ti2C and Nb2C sheets were studied with the adsorption of 1 to 4 CO2 molecules, and the results were analyzed for each case. For 4 CO2 molecules adsorbed on Ti2C and Nb2C sheets, the weight percentage (wt%) ratio was found to be 21.39% and 14.33%, respectively. The Density of States (DOS) analysis revealed that, upon CO2 adsorption, the CO2 molecule dissociates into CO and O atoms on the MXene surface. The CO molecule showed no significant hybridization with the host sheet atoms, whereas the O atom exhibited strong hybridization with the MXene surface. Transition State (TS) profiles illustrated the dissociation steps on both Ti2C and Nb2C surfaces. Phonon calculations confirmed the dynamic stability of both pure and CO2 adsorbed MXenes. Molecular Dynamics (MD) simulations conducted at 900 K indicated uniform temperature and Mean Square displacement (MSD) profiles, suggesting the stability of both pure and CO2 adsorbed MXenes at elevated temperatures, as well as uniform CO2 adsorption behavior. The adsorption energies for Ti2C and Nb2C sheets were calculated to be in the range of -1.89 to -2.77eV, suggesting that the adsorption process is favorable, spontaneous, and predominantly involves chemisorption. These findings indicate that Ti2C and Nb2C MXenes, in their intrinsic forms, are promising candidates for CO2 adsorption and dissociation technologies.