The electrocatalytic CO2 reduction suffers from poor selectivity and high overpotential. Product selectivity is suppressed by competitive proton reduction to hydrogen evolution. A linear relationship between formation energy of HCOO- with first reduction potential of the catalyst poses a limitation to reduce overpotential. Herein, we investigated porphyrin-based complexes with Rh, Ir, Pd, Al, Ga, In, Tl, Sn, and Bi as the metal ions for CO2 reduction to HCOO- and proton reduction to HER, based on free energy calculations using density functional theory. In this study, we demonstrated that the linear relationship of HCOO- formation energy with the first reduction potential of the catalyst can be broken on porphyrin-based catalysts with main group elements as metal ions. Furthermore, we found that porphyrin with Rh, Ir, Al, Ga, Sn, Tl, and Bi metal ions are selective to HCOO- while suppressing hydrogen evolution. Based on calculated free energies an overpotential of 0.14 V for Al porphyrin, 0.19 V for Ga porphyrin, and 0.16 V for Tl porphyrin is reported. We hope that our study can help to design selective and efficient catalysts for CO2 reduction from other classes of metal complexes.

Electrochemical reduction of CO2 to HCOO- catalyzed by metalloporphyrins: Suppression of hydrogen evolution and reduction of overpotential

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.