S and N coordinated single-atom catalysts for electrochemical CO₂ reduction with superior activity and selectivity

As the energy crisis and global warming become ever more serious, the electrochemical reduction of carbon dioxide (CO₂RR) using single-atom catalysts (SAC) is a potential strategy to solve these problems by converting notorious CO₂ into high value-added products. The electronic structures and the catalytic activity of SAC can be adjusted through changing the coordination environment. In this paper, 28 TM@S_xN_y SACs (TM = Fe, Co, Ni, Cu; x + y = 4) are constructed and the CO₂RR performances toward C1 products are exploited. The calculations based on spin-polarized density functional theory (DFT) show that Cu@S₃N₁ has the best catalytic performance toward CO, CH₃OH and CH₄, with the favorable limiting potentials of −0.20 V, −0.36 V, and −0.36 V, respectively. Fe@S₁N₃ exhibits the best catalytic activity and selectivity toward HCOOH, with the limiting potential of −0.25 V. Electronic structure analysis reveals the catalytic origin of excellent Cu@S₃N₁ SAC toward CO product. S_xN_y coordination can partially weaken the scaling relationship between *COOH and *CO, especially for S₃N₁. Furthermore, the solvation effect and the selectivity of Cu@S₃N₁ and Fe@S₁N₃ under the applied potential are illustrated. The results provide a theoretical reference to regulate the CO₂RR activity using coordinated SAC.