(326d) Electrochemical Bicarbonate Conversion into Chemicals and Fuels

Electrochemical CO₂ reduction converts CO₂ and water into chemicals and fuels such as carbon monoxide, methane, and ethylene. Pure CO₂ gas (>99% v/v) is often used as the feedstock for low-temperature electrochemical reactors (electrolyzers); however, pure CO₂ gas must be captured from the atmosphere or an industrial source via a series of energy-intensive thermal desorption steps before it is converted.¹ The direct electrochemical conversion of carbon capture sorbents, as opposed to CO₂ gas, presents an opportunity to electrochemically synthesize carbon chemicals and fuels without the need for CO₂ thermal desorption.

This presentation will discuss the science and engineering behind “bicarbonate electrolyzers”—devices that convert bicarbonate-based carbon capture solutions into reduced carbon products in a single-step. Bicarbonate electrolyzers use H⁺ generated electrochemically to trigger the in situ release of CO₂ gas from bicarbonate near a CO₂ reduction catalyst. This acid-base mechanism enables high product formation rates without the need to isolate pure CO₂ gas upstream. Since the first report of bicarbonate electrolysis,² we systematically investigated the effect of electrode properties (e.g., hydrophobicity and surface area),³ operating conditions (e.g., pressure and temperature),⁴ CO₂ capture promoters,⁵ and ionic surfactants⁶ on product formation rates. The use of hydrophilic silver electrodes and elevated pressures enabled CO formation rates >200 mA cm^-2, and the addition of cetrimonium bromide to the bicarbonate feedstock enabled >100 mA cm^-2 of methane formation when using a porous copper electrode. 1D multi-physics models were used to quantify the rate-limiting in situ CO₂ formation step and show how a high H⁺ flux from the membrane increases methane selectivity with copper catalysts. Finally, the electrolyzer was integrated with a CO₂ absorption column and tested with different CO₂ capture promoters. This talk will overview these studies and establish guidelines for converting reactive carbon capture solutions into valuable products.

References

1. Keith, D. W.; Holmes, G.; Angelo, D. S.; Heidel, K., A Process for Capturing CO2 from the Atmosphere. Joule 2018, 2 (8), 1573-1594.
2. Li, T. F.; Lees, E. W.; Goldman, M.; Salvatore, D. A.; Weekes, D. M.; Berlinguette, C. P., Electrolytic Conversion of Bicarbonate into CO in a Flow Cell. Joule 2019, 3 (6), 1487-1497.
3. Lees, E. W.; Goldman, M.; Fink, A. G.; Dvorak, D. J.; Salvatore, D. A.; Zhang, Z. S.; Loo, N. W. X.; Berlinguette, C. P., Electrodes Designed for Converting Bicarbonate into CO. Acs Energy Lett 2020, 5 (7), 2165-2173.
4. Zhang, Z. S.; Lees, E. W.; Habibzadeh, F.; Salvatore, D. A.; Ren, S. X.; Simpson, G. L.; Wheeler, D. G.; Liu, A.; Berlinguette, C. P., Porous metal electrodes enable efficient electrolysis of carbon capture solutions. Energ Environ Sci 2022, 15 (2), 705-713.
5. Fink, A. G. G.; Lees, E. W. W.; Gingras, J.; Madore, E.; Fradette, S.; Jaffer, S. A. A.; Goldman, M.; Dvorak, D. J. J.; Berlinguette, C. P. P., Electrolytic conversion of carbon capture solutions containing carbonic anhydrase. J Inorg Biochem 2022, 231.
6. Lees, E. W.; Liu, A.; Bui, J. C.; Ren, S. X.; Weber, A. Z.; Berlinguette, C. P., Electrolytic Methane Production from Reactive Carbon Solutions. Acs Energy Lett 2022, 7 (5), 1712-1718.