Electrocatalysts Derived from Copper Complexes Transform CO into C 2+ Products Effectively in a Flow Cell.

Electrochemical reactors that electrolytically convert CO 2 into higher-value chemicals and fuels often pass a concentrated hydroxide electrolyte across the cathode. This strongly alkaline medium converts the majority of CO 2 into unreactive HCO 3 - and CO 3 2- byproducts rather than into CO 2 reduction reaction (CO2RR) products. The electrolysis of CO (instead of CO 2 ) does not suffer from this undesirable reaction chemistry because CO does not react with OH - . Moreover, CO can be more readily reduced into products containing two or more carbon atoms (i. e., C 2+ products) compared to CO 2 . We demonstrate here that an electrocatalyst layer derived from copper phthalocyanine (CuPc) mediates this conversion effectively in a flow cell. This catalyst achieved a 25 % higher selectivity for acetate formation at 200 mA/cm 2 than a known state-of-art oxide-derived Cu catalyst tested in the same flow cell. A gas diffusion electrode coated with CuPc electrolyzed CO into C 2+ products at high rates of product formation (i. e., current densities ≥200 mA/cm 2 ), and at high faradaic efficiencies for C 2+ production (FE C2+ ; >70 % at 200 mA/cm 2 ). While operando Raman spectroscopy did not reveal evidence of structural changes to the copper molecular complex, X-ray photoelectron spectroscopy suggests that the catalyst undergoes conversion to a metallic copper species during catalysis. Notwithstanding, the ligand environment about the metal still impacts catalysis, which we demonstrated through the study of a homologous CuPc bearing ethoxy substituents. These findings reveal new strategies for using metal complexes for the formation of carbon-neutral chemicals and fuels at industrially relevant conditions.