Single-Atom Catalysts for CO2 Reduction to Oxalate: Theoretical Design and Reaction Condition Prediction

The electrochemical conversion of carbon dioxide (CO2) into high-value-added products under mild conditions is crucial for achieving carbon neutrality. Oxalate (C2O42–) is one of the most important industrial raw materials and is widely used as a reducing agent in the fields of medicine, dyeing, and plastics yet faces challenges in efficient C–C bond formation under mild conditions. In this study, we investigate the reduction of CO2 to C2O42– using single-atom catalysts (SACs) with M–Nx–C configurations, employing density functional theory (DFT) to assess their catalytic performance under varying reaction conditions. Our findings demonstrate that the catalytic activity of Ti–N3–C is highly sensitive to the choice of solvent and electrode potential. Lower solvent dielectric constants and more negative electrode potentials promote oxalate formation with Ti–N3–C, exhibiting a remarkably low-energy barrier (0.31 eV) for the rate-determining step at −0.7 V in acetonitrile, alongside high selectivity. By systematically tuning the coordination environment of single metal atoms, we identify Ti–N2C–C, Cr–N2C–C, and Cr–N3–C as promising catalysts, operating efficiently at potentials of −0.7, −0.7, and −0.6 V, respectively. This work not only offers theoretical guidance for designing high-performance SACs for CO2 conversion but also deepens the mechanistic understanding of the electrochemical CO2 reduction pathways.