Adsorption and Activation of CO2 on Nitride MXenes: Composition, Temperature, and Pressure effects

The interaction of CO2 with nitride MXenes of different thickness is investigated using periodic density functional theory-based calculations and kinetic simulations carried out in the framework of transition state theory, the ultimate goal being predicting their possible use in Carbon Capture and Storage (CCS). We consider the basal (0001) surface plane of nitride MXenes with Mn+1Nn (n=1-3; M=Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W) stoichiometry and also compare to equivalent results for extended (001) and (111) surfaces of the bulk rock-salt transition metal nitride compounds. The present results show that the composition of MXenes has a marked influence on the CO2-philicity of these substrates, whereas the thickness effect is, in general, small, but not negligible. The largest exothermic activation is predicted for Ti-, Hf-, and Zr-derived MXenes, making them feasible substrates for CO2 trapping. From an applied point of view, Cr-, Mo-, and W-derived MXenes are especially well suited for CCS as the interaction with CO2 is strong enough but molecular dissociation is not favored. Newly developed kinetic phase diagrams are introduced supporting that Cr-, Mo-, and W-derived MXenes are appropriate CCS substrates as they are predicted to exhibit easy capture at mild conditions and easy release by heating below 500 K.

Automated summary

The study reveals that the composition of MXenes significantly influences their CO2-philicity, while the effect of thickness is generally small but not negligible. Ti-, Hf-, and Zr-derived MXenes are predicted to exhibit the largest exothermic activation, making them feasible substrates for CO2 trapping. Cr-, Mo-, and W-derived MXenes, which show strong interaction with CO2 but do not favor molecular dissociation, are particularly suitable for CCS applications.