Electrochemical conversion of pressurized CO2 at simple silver-based cathodes in undivided cells: study of the effect of pressure and other operative parameters

Abstract

Electrochemical reduction of pressurized CO2 is proposed as an interesting approach to overcome the main hurdle of the CO2 electrochemical conversion in aqueous solution, its low solubility (ca. 0.033 M), and to achieve good faradaic efficiency in CO using simple sheet silver cathodes and undivided cells, thus lowering the overall costs of the process. The effect on the process of CO2 pressure (1–30 bar), current density, nature of the supporting electrolyte and other operative conditions, such as the surface of the cathode or the mixing rate, was studied to enhance the production of CO. It was shown that pressurized conditions allow to improve drastically the current efficiency of CO (CECO). Furthermore, at relatively high pressure (20 bars), the utilization of simple sheet silver cathodes and silver electrodes with high surfaces gave similar CECO. The stability of the system was monitored for 10 h; it was shown that at a relatively high pressure (15 bar) in aqueous electrolyte of KOH using a simple plate silver cathode a constant current efficiency of CO close to 70% was obtained. Graphic abstract

Elucidating Mass Transport Regimes in Gas Diffusion Electrodes for CO2 Electroreduction

“…F is Faradays' constant, R is the ideal gas constant, T is the temperature, i 0 is the exchange current density, α is the charge transfer coefficient, c CO 2 ref is a reference concentration fixed at 1 M, and η is the overpotential. There is some uncertainty regarding the underlying reaction mechanism for COER on Ag; 5,16,17 however, the first-order dependence on the CO 2 concentration in eq 5 is consistent with experimental data taken at varying CO 2 pressures, 16,18,19 and eqs 5 and 6 may be viewed as empirical fits to the available data. Relevant parameters are listed in Table 1, and further details are provided in Section S2.…”

Enriching Surface‐Accessible CO2 in the Zero‐Gap Anion‐Exchange‐Membrane‐Based CO2 Electrolyzer

“…This demonstration reveals the immense potential of high‐pressure (>10 bar) CO 2 electrolysis. [ 3a , 15 ] Operating at higher pressures does increase capital costs, so other approaches to increase local [CO 2 ] would also be helpful. Thus, another general strategy based on a pulsed electrochemical (EC) method was developed.…”

Enriching Surface‐Accessible CO2 in the Zero‐Gap Anion‐Exchange‐Membrane‐Based CO2 Electrolyzer

“…These features result in a high [CO 2 ] SA allowing for better CO 2 R performance. This demonstration reveals the immense potential of high‐pressure (>10 bar) CO 2 electrolysis [3a, 15] . Operating at higher pressures does increase capital costs, so other approaches to increase local [CO 2 ] would also be helpful.…”