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.