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. This article is part of the theme issue 'Surfaces, interfaces and heterogeneous catalysis'.