What question did this study set out to answer?

The aim is to assess how impurities in flue gas affect carbon dioxide reduction using a molecular catalyst.

March 28, 2026ChemSusChem1 citationsOpen Access

Electroreduction of CO 2 From Flue Gas: Impurity Tolerance and Mechanistic Insights in Molecular Catalysis

YSYutzil Segura‐RamirezCentre National de la Recherche Scientifique ASAlbert Solé‐DauraInstitut Català d'Investigació Química GMGomez‐Mingot MariaCentre National de la Recherche Scientifique

Key Points

The aim is to assess how impurities in flue gas affect carbon dioxide reduction using a molecular catalyst.
Experimental data collection using a model Re molecular catalyst during CO2 reduction under varying impurity conditions.
Density functional theory (DFT) calculations to understand the interaction between the catalyst and impurities.
Cyclic voltammetry and ion chromatography to verify low affinity of the catalyst for impurities.
Maintained high selectivity toward CO production with faradaic efficiencies above 90% and 70% under different CO2 concentration conditions.
O2 reduction reaction competes significantly, consuming ≈80% of the charge in realistic flue gas scenarios.
NO2 and SO2 impurities do not significantly decrease CO production, with faradaic efficiency remaining ≥ 82% in their presence.

Abstract

Direct utilization of diluted CO2 from industrial flue gas containing SO2, NO2 and O2 impurities is economically appealing and circumvents capture and purification prior to conversion. We present experimental data and density functional theory (DFT) calculations for understanding the effect of those impurities during CO2RR catalyzed by a model Re molecular catalyst, Re(bpy)(CO)3Cl (bpy = bipyridine). Under both 10% and 1% v/v CO2 gas streams, high selectivity toward CO production was maintained, with faradaic efficiency (FECO) above 90% and 70%, respectively. O2 reduction reaction (ORR) on the electrode surface represents a substantial competitive reaction that accounts for ≈80% of the charge consumed when a realistic CO2 source mimicking an industrial waste-incinerator stream (10% v/v CO2, 10% v/v O2, 100 ppm NO2, and 50 ppm SO2 in N2 matrix) is used. Neither NO2 nor SO2 incorporated in the diluted CO2 stream provoke a significant decrease in the CO production (FECO ≥ 82%). DFT calculations indicate low affinity of the catalyst for impurities, because they are in their reduced form at the CO2RR potential. This is experimentally proven by cyclic voltammetry and ion chromatography. These findings call for new strategies that enhance the moderate O2-tolerance exhibited by Re complex on CO2RR from flue gas.

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