Two-dimensional Sc₂N MXenes as efficient solid catalysts for CO₂ adsorption and conversion: a density functional theory study

We have employed density functional theory (DFT) calculations to explore the catalytic potential of scandium nitride (Sc₂N) MXenes for CO₂ capture and hydrogenation to methane. The Sc₂N surface exhibits a strong affinity for CO₂ with an adsorption energy of –3.627 eV, surpassing values reported for other MXenes, such as Ti₂N and V₂N, and even outperforming conventional catalysts like Pt(111). Charge density difference and COHP analyses reveal significant back-donation from Sc d-orbitals to the antibonding orbitals of CO₂, resulting in the formation of activated CO₂δ− species. AIMD simulations confirm the thermal stability of Sc₂N under ambient conditions. The hydrogenation pathway to CH₄ proceeds via eight elementary steps, with the CH₂OH + H → CH₃OH reaction identified as the rate-determining step due to its high activation barrier (2.916 eV). Sc₂N effectively stabilizes key intermediates, such as COOH, HCOOH and CH₂OH, and facilitates H₂ dissociation with moderate energy requirements. Compared with other MXenes, Sc₂N shows superior ability to stabilize intermediates, particularly HCOOH, which plays a crucial role in the conversion pathway. However, large negative adsorption energies for H and O atoms suggest potential surface poisoning, which may limit catalytic turnover unless regeneration strategies are implemented. These findings highlight Sc₂N MXenes as robust and efficient materials for CO₂ capture and conversion, although further optimization is necessary for sustained catalytic performance.