Selectivity of CO2, carbonic acid and bicarbonate electroreduction over Iron-porphyrin catalyst: A DFT study

Reza Khakpour, Kari Laasonen, Michael Busch*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

2 Citations (Scopus)

Abstract

Carbon dioxide reduction is a promising approach to convert CO2 to value-added products. Carbon dioxide electroreduction is commonly performed at neutral pH where CO2, H2CO3, HCO3, and CO3−2 are in equilibrium. Despite this, only CO2 is commonly considered as the active species while H2CO3, HCO3, and CO3−2 (carbonate species) are neglected. Using density functional theory (DFT), we investigate the contribution of carbonate species in the CO2 electroreduction reaction over a Fe-porphyrin (Fe(ppy)) model system. We find that the hydrogen evolution reaction (HER) is blocked by a high activation barrier of 1.54 eV associated with the Fe("I")(ppy)-H formation. This is opposed to the reduction of H2CO3 and HCO3 whose rate-limiting step requires significantly lower activation energies of approximately 0.4 eV. Direct CO2 reduction on the other hand requires to overcome a rate-limiting barrier of 0.95 eV for the CO2 adsorption step. Based on these results we suggest that H2CO3 and HCO3 are the true reactants for the electrochemical "CO2"RR over Fe(ppy).

Original languageEnglish
Article number141784
JournalElectrochimica Acta
Volume442
DOIs
Publication statusPublished - 20 Feb 2023
MoE publication typeA1 Journal article-refereed

Keywords

  • Active species
  • Bicarbonate reduction
  • CO reduction
  • DFT
  • Electrocatalysis
  • Fe-porphyrin
  • Homogeneous catalysis

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