Temperature-Induced Regulation of the Local Mn-N Coordination Environment for Efficient CO2 Electroreduction

The catalytic activity of single-atom catalysts (SACs) is strongly influenced by their local coordination environment. In this study, a series of Mn-N-C SACs with tunable coordination structures were synthesized via pyrolysis of Mn-doped metal-organic frameworks (MOFs) at different temperatures. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and X-ray absorption spectroscopy (XANES and EXAFS) confirmed the atomic dispersion of Mn and the formation of Mn-N 4 moieties as the active sites. Among the catalysts, Mn-NC-1000°C with high Pyridine-N content exhibited the best performance, achieving a maximum Faradaic efficiency (FE) of 94.9% for CO at –0.47 V vs. RHE in an H-type cell, along with a current density of ∼15 mA . cm −2 . And in a flow cell, the current density increased significantly to ∼100 mA . cm −2 while maintaining high CO selectivity (FE CO =95%) and operational stability (24 h). The density functional theory (DFT) studies further reveal that the Mn-NC-1000°C with high Pyridine-N content effectively reduces the reaction barriers for the formation of *COOH and thus accelerates the reduction of CO 2 .This work provides a controllable strategy for regulating the coordination microenvironment of SACs and offers valuable insights for the development of efficient CO 2 electroreduction system.