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

Direct utilization of diluted CO 2 from industrial flue gas containing SO 2 , NO 2 and O 2 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 CO 2 RR catalyzed by a model Re molecular catalyst, [Re(bpy)(CO) 3 Cl] (bpy = bipyridine). Under both 10% and 1% v/v CO 2 gas streams, high selectivity toward CO production was maintained, with faradaic efficiency (FE CO ) above 90% and 70%, respectively. O 2 reduction reaction (ORR) on the electrode surface represents a substantial competitive reaction that accounts for ≈80% of the charge consumed when a realistic CO 2 source mimicking an industrial waste‐incinerator stream (10% v/v CO 2 , 10% v/v O 2 , 100 ppm NO 2 , and 50 ppm SO 2 in N 2 matrix) is used. Neither NO 2 nor SO 2 incorporated in the diluted CO 2 stream provoke a significant decrease in the CO production (FE CO ≥ 82%). DFT calculations indicate low affinity of the catalyst for impurities, because they are in their reduced form at the CO 2 RR potential. This is experimentally proven by cyclic voltammetry and ion chromatography. These findings call for new strategies that enhance the moderate O 2 ‐tolerance exhibited by Re complex on CO 2 RR from flue gas.