Electrocatalysts Derived from Copper Complexes Transform CO into C <sub>2+</sub> Products Effectively in a Flow Cell
Shaoxuan Ren, Zishuai Zhang, Eric W. Lees, Arthur G. Fink, Luke Melo, Camden Hunt, David Dvořák, Wen Yu Wu, Edward R. Grant, Curtis P. Berlinguette
Abstract
Abstract 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.