Water Facilitated Electrochemical Reduction of CO2 on Cobalt-Porphyrin Catalysts

TL;DR

This study combines computational and experimental methods to elucidate how water facilitates CO2 reduction to CO on cobalt-porphyrin catalysts, providing insights for designing improved catalysts.

Contribution

It introduces a protocol integrating density functional theory and experimental data to accurately predict redox potentials and elucidate water's role in CO2 reduction on cobalt-porphyrin catalysts.

Findings

Proton transfer from H2O occurs at -0.80 V vs. RHE at pH=3.

The key intermediate [CoP-COOH]- is formed during CO2 reduction.

Water plays a crucial role in the reductive decomposition of CO2 to CO.

Abstract

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.