Advancing the Anode Compartment for Energy Efficient CO2 Reduction at Neutral pH

Energy efficient CO2 reduction in neutral pH requires the development of electrochemical devices operating with minimal energy input. To reach this objective, we propose an original approach focused on the anode compartment where the oxygen evolution reaction (OER) takes place. Different anode catalysts, anolytes and membranes were tested, and the components resulting in the most energy efficient and stable CO2 reduction reaction device were selected. A stainless-steel-based anode with significant OER activity and stability in a wide pH range was used to compare symmetric (neutral catholyte and anolyte) and asymmetric (neutral catholyte and alkaline anolyte) configurations. The gain in energy efficiency for carbon products of 6-8 % in the asymmetric configuration highlighted the advantages of a pH gradient. Although a Nafion membrane gave the highest energy efficiencies, the pH was unstable. Therefore, bipolar membranes that can maintain a pH gradient emerge as the best option for long-term electrolysis. This work paves the way for the development of highly energy efficient CO2-reduction devices with cathodes operating in low pH conditions.

Automated summary

Efficient CO2 reduction at neutral pH requires the development of electrochemical devices with minimal energy input. An original method focusing on the anode compartment was proposed, testing different catalysts, anolytes, and membranes to select components for the most energy efficient and stable CO2 reduction device. Asymmetric configurations with alkaline anolytes showed a gain in energy efficiency for carbon products, highlighting the advantages of a pH gradient.