Single-Atom Catalysts Based on Two-Dimensional Transition Metal Carbides for Efficient Carbon Dioxide Reduction

The electrochemical reduction of carbon dioxide (CO 2 RR) into value-added products is a promising route toward carbon neutrality, yet its efficiency is often limited by the weak activity and instability of conventional catalysts. Single-atom catalysts (SACs) anchored on two-dimensional transition metal carbides (MXenes) offer a tunable platform with high atomic utilization and strong metal-support interactions. However, the fundamental understanding of how coordination geometry and electronic coupling jointly regulate CO 2 activation remains insufficient. This study integrates density functional theory (DFT) calculations with experimental electrochemical characterization to investigate MXene-supported SACs. The Fe 1 /Ti 3 C 2 O 2 system exhibits a pseudo-square-planar coordination environment with strong Fe-O bonding, leading to an optimized d-band alignment and enhanced σ-back-donation to CO 2 π* orbitals. The calculated free-energy barrier for COOH formation is only 0.41 eV, resulting in high Faradaic efficiency (91.2%) and a partial current density of 34.8 mA·cm - 2 . These findings reveal that ligand field stabilization and interfacial charge transfer are key to achieving efficient CO 2 reduction. The proposed coordination-electronic coupling framework provides actionable guidelines for the rational design of high-performance catalytic materials in sustainable energy conversion.