Fourteen-Membered Macrocyclic Cobalt Complex for Low-Concentration CO2 Electrolysis with High Faradic Efficiency Towards CO

CO2 electrolysis is a promising solution for creating a carbon-neutral society in the near future. Lowering the overpotential for CO2 reduction is crucial for the practical application of CO2 electrolysis in industrial scenarios. In this study, a fourteen-membered macrocyclic cobalt complex (Co−14 membered ring complex: Co−14MR) was found to be a superior cathode catalyst for the reduction of CO2 to CO, achieving a large current density (101 mA cm−2 at −2.05 V (Ag/AgCl)), high Faradic efficiency (>99%), small overpotential (onset potential of CO formation: −0.13 V (RHE)), and great durability (stable performance until turn over number (TON): 2.2×104 per Co atom) in gas diffusion electrode-type CO2 electrolysis. Moreover, CO was generated with a Faradic efficiency of 95% during CO2 electrolysis when using the Co−14MR catalyst under a low CO2 concentration (10% CO2). Single-atom Co site in the Co−14MR catalyst enables near-complete surpession of undesired H2 evolution.