No abstract

Energy efficient CO 2 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 CO 2 reduction reaction device were selected. A stainless-steelbased 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 CO 2 -reduction devices with cathodes operating in low pH conditions.