Rational Design of MXene-Supported Single-Atom Catalysts for Electrochemical CO _<b>2</b> Reduction with Tunable Activity and Product Selectivity

The electrochemical CO 2 reduction reaction (CO 2 RR) represents a promising pathway for the sustainable conversion of CO 2 into energy-dense fuels and commodity chemicals, thereby contributing to carbon neutrality. Nevertheless, achieving simultaneously high catalytic activity and product selectivity remains a formidable challenge. Herein, a comprehensive first-principles investigation integrating density functional theory (DFT) and ab initio molecular dynamics (AIMD) was conducted to elucidate the structure–stability–reactivity correlations of transition metal (TM)-doped Mo 2 TiC 2 single-atom catalysts (SACs) in the context of CO 2 RR. The results demonstrate that the efficient activation of CO 2 originates from the strong orbital hybridization between TM d-states and the CO 2 antibonding orbitals, accompanied by pronounced charge redistribution at the catalytic centers. The TM–Mo 2 TiC 2 catalysts exhibit intrinsic selectivity toward CH 3 OH formation, among which Ni–, Cu–, Os–, and Pt–Mo 2 TiC 2 display remarkably low limiting potentials of −0.39, −0.52, −0.37, and −0.49 V, respectively, outperforming the benchmark Mo 3 C 2 O 2 catalyst (−0.54 V). These findings unveil the fundamental origin of product selectivity and provide atomistic design guidelines for the development of next-generation CO 2 RR electrocatalysts featuring enhanced CH 3 OH selectivity and superior activity.