Unlocking the Activity of Molecular Assemblies for CO2 Electroreduction in Zero-Gap Electrolysers via Catalyst Ink Engineering

In recent years, CO2 electrolysis, particularly the electrochemical reduction of CO2 to CO in zero-gap systems, has gained significant attention. While Ag-coated gas diffusion electrodes are commonly used in state-of-the-art systems, heterogenized molecular catalysts like bis-coordinated homoleptic silver(I) N,N-bis(arylimino)-acenaphthene (Ag-BIAN) complexes are emerging as a promising alternative due to their tunability and high mass activity. In this study, the influence of ink composition on the performance of Ag-BIAN-based GDEs in zero-gap electrolyzers (ZGEs) are systematically explored at 60 °C and 600 mA cm⁻2. Sedimentation analyses across various solvents informed the selection of optimal solvent-catalyst and solvent-carbon additive combinations, streamlining the GDE optimization process and reducing associated costs and time. These results demonstrate that solvent choice and dilution state of the ink are critical factors impacting CO2 reduction, achieving faradaic efficiencies for CO production (FECO) up to 67% at 600 mA cm⁻2 with catalyst loadings as low as 0.2 mg cm⁻2. These findings lay the groundwork for advancing from homogeneous H-type cells to industrial ZGE systems through tailored ink engineering.