CuCATCO2 · Halogen-Axially Coordinated Cu–N4 Single-Atom catalyst as a Self-Standing Electrode for Scalable CO2 Reduction Reaction

Electrochemical CO2 reduction (CO2RR) utilizing self-standing electrodes with copper single-atom catalysts (Cu–N₄) axially coordinated with halogens (Cl/F) integrated into carbon nanotube (CNT) scaffolds exemplifies a cutting-edge method for scalable CO2 valorization. Axial halogen ligation alters the d-band configuration of the copper center, stabilizing *COOH/*CO intermediates and reducing the C–C coupling barrier, thus improving selectivity for C2⁺ products. The CNT backbone provides a binder-free, porous, and conductive structure that facilitates swift electron transfer, effective CO2 diffusion, and mechanical stability during high-current operation. This approach addresses the significant limitations of traditional Cu catalysts, specifically inadequate durability, nanoparticle agglomeration, and restricted multi-carbon selectivity, while facilitating flow-cell testing under conditions relevant to industrial applications. The integrated electrode achieves current densities exceeding 200 mA cm⁻², with Faradaic efficiencies surpassing 70% for C2⁺ species (ethylene, ethanol, acetate). It demonstrates stability for over 50 hours of continuous operation, parameters that exceed the majority of documented Cu-N₄ benchmarks. This performance showcases both the structural integrity of halogen-coordinated Cu single atoms under cathodic polarization and their capacity to bridge fundamental catalysis with practical applications in sustainable CO2 utilization.