Water Facilitated Electrochemical Reduction of CO2 on Cobalt-Porphyrin Catalysts

Cobalt-porphyrin catalyzed reductive decomposition of CO2 to CO is investigated based on Koper's water facilitated CO2 reduction mechanism using a simple but accurate protocol based on thermodynamics. In our protocol, accurate predictions of standard redox potentials and free energy differences are achieved by combining strengths of both density functional theory and experimental observations. With the proposed protocol, we found that the proton transfer from H2O takes place at -0.80 V vs. RHE at pH=3 through a concerted pathway and, as a result, the key intermediate for the CO generation, i.e., [CoP-COOH]- is formed. Since the redox potential of the proton transfer agrees well with experimentally observed CO2 reduction potential, we successfully clarified that H2O plays an important role in the reductive decomposition of CO2 to CO. This result is valuable not only for understanding the cobalt-porphyrin catalyzed reductive decomposition of CO2 but also as a guide for the development of new catalysts.