Electrochemical CO2 Reduction over Copper Phthalocyanine Derived Catalysts with Enhanced Selectivity for Multicarbon Products

Metal complexes have shown impressive selectivity and activity as catalysts for electrochemical CO2 reduction (CO2RR), yet the nature of their active sites under operating conditions remains elusive. Herein, by using in situ Raman, X-ray photoelectron spectroscopy, and advanced electron microscopy in combination with density functional theory calculations, we reveal that copper phthalocyanine (CuPc) reconstructs during the CO2RR, which proceeds through the demetalation of CuPc to Cu atoms followed by the agglomeration of Cu atoms to Cu clusters and finally Cu nanoparticles (NPs). Further, we find that the size of the Cu NPs is highly dependent on several key experimental parameters, and more importantly, the selectivity of multicarbon products is positively correlated with the size of the Cu NPs because large NPs are rich in grain boundaries. Specifically, at −0.73 V vs RHE and 800 mA cm–2, the CuPc-derived Cu NPs catalyst shows a maximum Faradaic efficiency for multicarbon products of 70%. These insights provide vital information for future applications of metal complex catalysts in the CO2RR and are expected to inspire researchers to design advanced electrocatalysts for other electrochemical reactions.