New Study Could Help Advance Electrocatalytic Reduction of CO2

The electrocatalytic reduction of carbon dioxide (CO₂), or CO₂ER, provides an ideal path for realizing green CO₂ cycling and mitigating the greenhouse effect. A majority of the studies on CO₂ER in the recent past have focused on the inherent performance of the catalysts.

In general, bicarbonate — an electrolyte or negatively charged ion used by the body to help maintain its pH balance — is used in CO₂ER. However, a group of researchers from China set out to perform an investigation of its role and behavior. The findings have been reported in the KeAi journal Fundamental Research.

Bicarbonate, as a common electrolyte anion, can enhance CO₂ER activity via its rapid equilibrium exchange with dissolved CO₂. We found that higher concentrations of bicarbonate in the electrolyte provided higher energy efficiency.

Jinlong Gong, Study Corresponding Author and Professor, School of Chemical Engineering and Technology, Tianjin University

According to Dr. Wanyu Deng, the lead author of the study, “The new knowledge gained in this work guides the direct electroreduction of bicarbonate and provides valuable insights into CO₂ER with high-concentration electrolytes. This finding is expected to help save abundant energy in the CO₂ER process and can pave the way for advancing the progress of CO₂ER towards commercialisation.”

The researchers performed in-situ experimental observations and found an accumulation of negatively charged bicarbonate anions close to the electrode surface. The enriched bicarbonate anions transformed into CO₂ to offer reactants.

Moreover, the local concentration of bicarbonate anions was regulated by both the bulk concentration of bicarbonate electrolyte and the cathodic potential. This finding helped account for the dependency of CO₂ER activity on the local bicarbonate concentration, where the limited cathodic potential led to a plateau in the CO₂ER activity.

This hinders the use of high-concentration electrolytes to enhance activity. Further research is required to systematically explore the intrinsic relationship between CO₂ER activity and bicarbonate concentration to achieve better CO₂ER performance.

Jinlong Gong, Study Corresponding Author and Professor, School of Chemical Engineering and Technology, Tianjin University

Journal Reference:

Deng, W., et al. (2021) Effect of bicarbonate on CO₂ electroreduction over cathode catalysts. Fundamental Research. doi.org/10.1016/j.fmre.2021.06.004.