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

Metal complexes have shown impressive selectivity andactivityas catalysts for electrochemical CO2 reduction (CO2RR), yet the nature of their active sites under operatingconditions remains elusive. Herein, by using in situ Raman, X-rayphotoelectron spectroscopy, and advanced electron microscopy in combinationwith density functional theory calculations, we reveal that copperphthalocyanine (CuPc) reconstructs during the CO2RR, whichproceeds through the demetalation of CuPc to Cu atoms followed bythe agglomeration of Cu atoms to Cu clusters and finally Cu nanoparticles(NPs). Further, we find that the size of the Cu NPs is highly dependenton several key experimental parameters, and more importantly, theselectivity of multicarbon products is positively correlated withthe 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 efficiencyfor multicarbon products of 70%. These insights provide vital informationfor future applications of metal complex catalysts in the CO2RR and are expected to inspire researchers to design advanced electrocatalystsfor other electrochemical reactions.