Unveiling the Effect of Flue Gas Contaminants on Electrochemical Reduction of CO₂ to Methyl Formate in Dual Methanol/Water Electrolysis System

Abstract

Exploiting renewable energy sources to drive CO2 reduction electrochemically into value-added products has gained tremendous attention towards reducing the greenhouse effect. Upstream processes for capturing and purifying the CO2 raise the overall cost of the electrolysis system. Direct reduction of flue gas into value-added C2+ products has attained much consideration in recent years. However, the sensitivity of the cathode catalyst performance in the presence of flue gas contaminants, particularly O2, and strong competition from the hydrogen evolution reaction in aqueous electrolyte are major challenges for such an approach. Herein, the influence of flue gas contaminants on electrochemical reduction of CO2 in acidic nonaqueous methanol to a methyl formate product has been investigated on a Pb-catalyzed electrode in conjunction with aqueous anolyte for the promotion of a sustainable water oxidation half-reaction. The presence of 4% O2, 0.05% SO2, and 0.05% NO is shown to have minimal effect on the total faradaic efficiency of CO2 reduction products. CO2 concentration-dependent measurements reveal declining CO2 reduction faradaic efficiencies corresponding to the decrease in partial pressure, which is attributed to CO2 mass transfer limitations to the electrode surface. XPS analysis displays the relative stability of the Pb working electrode before and after the electrochemical operation during exposure to flue gas components, which further highlights the promising tolerance of this system for direct flue gas conversion. Figure 1

Metal–Ligand Cooperativity Promotes Reversible Capture of Dilute CO2 as a Zn(II)-Methylcarbonate

“…The CuL 1 (MeOH) is significantly less effective as it binds only 2−3% of these dilute CO 2 streams. At higher CO 2 concentrations associated with flue gas exhaust (15% CO 2 ) 48 or pure CO 2 streams (1 atm) the percentage of CO 2 sequestered from these sources is very low (≤1%) as the metal complexes in solution are saturated with CO 2 , Figure 6B. In summary, thiosemicarbazonato− hydrazinatopyridine metal complexes provide a novel route for reversible CO 2 capture from dilute sources with high CO 2 capture efficiency up to 90% from air.…”