Continuous Electro-Alkali Coproduction via the Low-Temperature Na-Ion- Exchange Membrane Direct Formate Fuel Cell

Metal hydroxides are capable of capturing atmospheric carbon dioxide and further converting it into value-added chemicals or fuels, which is considered one of the most promising CO 2 capture and utilization (CCU) technologies. However, the production and regeneration of metal hydroxides are extremely challenging due to their process defects, including high energy consumption and environmental pollution. Herein, a Na-ion exchange membrane direct formate fuel cell (Na-DFFC) was developed that can achieve the continuous production and collection of alkali while simultaneously generating electricity. The polarization curves indicate that the peak power density of the electro-alkali-coproducing Na-DFFC reaches 8 mW cm –2 under ambient temperature without supplying alkaline electrolyte to the anode. The Na-DFFC operates stably at 10 mA cm –2 with a NaOH production efficiency higher than 95%, which demonstrates the conceptual feasibility and durability of this electro-alkali coproducing device. In addition, the concentration of the collected NaOH solution, up to 3.63 M, is obtained in this work through the adjustment of the water flow rate and flow mode, confirming the Na-DFFC’s capability for concentrated NaOH production. More importantly, unlike the traditional chlor-alkali process, the Na-DFFC provides a more energy-efficient and environment-friendly pathway to produce green alkali.