Insights into the Role of Electrolyte Ionophore on Electrochemical Reduction of CO2

Monday, 10 October 2022
T. Tran, L. Zhang, N. Xu, G. Xia, S. Sahu, Y. Wang, X. Yu, and X. D. Zhou (University of Louisiana at Lafayette)
Electrochemical reduction of carbon dioxide (CO2) to value-added chemicals and fuels offers a sustainable route to utilize CO2 by exploiting renewable energy source. The electrolyte plays a significant role by taking advantage of the interaction between electrocatalytic surface and electrolyte. In this work, we present a CO2 conversion flow cell with an external compartment for a reference electrode (AgCl/Ag) to investigate the effect of alkaline electrolyte composition on the direct conversion of CO2 to fuels and commodity chemicals under ambient conditions. In this flow cell, a catalytic Ag-based gas diffusion electrode (GDE) was employed for CO2 reduction reaction, while an anode electrode was prepared with a RuO2 catalytic GDE. The gaseous products generated from the cell were analyzed with a Gas Chromatography (GC), while the liquid products were analyzed with Nuclear Magnetic Resonance Spectroscopy (NMR). Electrolytes with various cations (Li+, Na+, K+) and anions (OH-, HCO3-, CO32-) were investigated. With a KOH electrolyte (combination of the cation K+ and anion OH-), high faradaic efficiency (~ 97%) was achieved at -1.115 V vs SHE toward the formation of syngas (CO + H2) and ~ 60% faradaic efficiency was obtained toward the product of ethanol. The overall energy conversion efficiency could be up to ~ 45%. In consideration of faradaic efficiency, energy conversion efficiency, and the production of CO and ethanol, the preferable option of anions followed the order of OH- > HCO3- > CO32-, while the option for cations was in the order of K+ > Na+ > Li+.