High current density microkinetic and electronic structure analysis of CO2 reduction using Co and Fe complexes on gas diffusion electrode

Reactionmechanisms of electrocatalytic CO2 reduction into COover Co or Fe complexes were examined using gas diffusion electrodes to meet the requirement of high current densities for industrial deployment. Our experimental and theoretical calculation results consistently revealed that the Fe-based molecular catalysts exhibited more positive redox potentials relevant to CO2 electrocatalysis but disfavored the desorption of generated CO, especially at high overpotentials, failing to achieve appreciable reaction rates. Distinctively, the heterogenized Co- based molecular complexes were found to be tolerant to the high coverage of COat steady state on the active site and achieved rates exceeding 100 mA cm(-2) toward exclusive CO evolution. Density-functional theory calculations not only disclosed the redox non-innocent tetraphenylporphyrins and phthalocyanines during electrocatalytic CO2 reduction but also corroborated the energetics, especially for CO2 and COadsorption, accounting for distinctive reaction pathways between Co and Fe complexes.

Automated summary

The reaction mechanisms of electrocatalytic CO2 reduction into CO over Co or Fe complexes were studied using gas diffusion electrodes. Experimental and theoretical calculations showed that Fe-based molecular catalysts had more positive redox potentials but were less effective in desorbing CO, especially at high overpotentials. In contrast, heterogenized Co-based molecular complexes were found to tolerate high coverage of CO and achieved higher reaction rates.