Extrinsic hydrophobicity-controlled silver nanoparticles as efficient and stable catalysts for CO₂ electrolysis

To realize economically feasible electrochemical CO₂ conversion, achieving a high partial current density for value-added products is particularly vital. However, acceleration of the hydrogen evolution reaction due to cathode flooding in a high-current-density region makes this challenging. Herein, we find that partially ligand-derived Ag nanoparticles (Ag-NPs) could prevent electrolyte flooding while maintaining catalytic activity for CO₂ electroreduction. This results in a high Faradaic efficiency for CO (>90%) and high partial current density (298.39 mA cm^‒2), even under harsh stability test conditions (3.4 V). The suppressed splitting/detachment of Ag particles, due to the lipid ligand, enhance the uniform hydrophobicity retention of the Ag-NP electrode at high cathodic overpotentials and prevent flooding and current fluctuations. The mass transfer of gaseous CO₂ is maintained in the catalytic region of several hundred nanometers, with the smooth formation of a triple phase boundary, which facilitate the occurrence of CO₂RR instead of HER. We analyze catalyst degradation and cathode flooding during CO₂ electrolysis through identical-location transmission electron microscopy and operando synchrotron-based X-ray computed tomography. This study develops an efficient strategy for designing active and durable electrocatalysts for CO₂ electrolysis.