A Sodium-Ion-Conducting Direct Formate Fuel Cell: Generating Electricity and Producing Base

A barrier that limits the development of the conventional cation-exchange membrane direct liquid fuel cells (CEM-DLFCs) is that the CEM-DLFCs need additional base to offer both alkaline environment and charge carriers. Herein, we propose a Na⁺ -conducting direct formate fuel cell (Na-DFFC) that is operated in the absence of added base. A proof-of-concept Na-DFFC yields a peak power density of 33 mW cm^-2 at 60 °C, mainly because the hydrolysis of sodium formate provides enough OH^- and Na⁺ ions, proving the conceptual feasibility. Moreover, contrary to the conventional chlor-alkali process, this Na-DFFC enables to generate electricity and produce NaOH simultaneously without polluting the environment. The Na-DFFC runs stably during 13 hours of continuous operation at a constant current of 10 mA, along with a theoretical production of 195 mg NaOH. This work presents a new type of electrochemical conversion device that possesses a wide range of potential applications.