Identification of dual-active sites in cobalt phthalocyanine for electrochemical carbon dioxide reduction

Abstract Cobalt phthalocyanine (CoPc) as a typical transition metal complex catalyst for electrochemical CO2 reduction is able to produce CO with high selectivity and activity. However, the reaction mechanism remain unclear because of the ambiguity in catalytic active sites between Co center atom and Pc ligand. Herein, synchrotron-based X-ray photoelectron spectroscopy (XPS) and soft X-ray absorption spectroscopy (XAS) were employed to elucidate the catalytic active site evolution during the reaction process. We found that the electrochemical reduction reaction of CO2 on CoPc follows a dual-active sites process. The CO2 molecule is initially protonated on the N atom site of Pc ligand forming *COOH intermediate and then is further reduced to *CO at the center Co site.