A cation-exchange membrane direct formate-CO2 fuel cell: Enabling simultaneous hydrogen production and CO2 utilization

The carbon-neutral and carbon-negative energy utilization technologies have long been people pursued to realize the strategic objective of carbon neutrality. Herein, we propose a cation-exchange membrane (CEM) direct formate-CO₂ fuel cell that possesses the capability of simultaneously generating electricity and producing hydrogen, as well as continuously transforming carbon dioxide into pure sodium bicarbonate. Using the CO₂-derived formate fuel, the roof-of-concept CEM direct formate-CO₂ fuel cell exhibits a peak power density of 38 mW cm⁻² at 80 °C without the assistance of additional electrolyte. The fairly stable constant-current discharge curve along with the detected hydrogen and pure sodium bicarbonate prove the conceptual feasibility of this electricity‑hydrogen-bicarbonate co-production device. By adding alkaline electrolyte to the anode, we achieved a higher peak power density of 63 mW cm⁻² at the corresponding hydrogen production rate of 0.57 mL min⁻¹ cm⁻². More interestingly, the concentrations of pure NaHCO₃ solution can be controlled by adjusting the cathode water flow rate and fuel cell discharge current density. This work presents a theoretically feasible avenue for coupling hydrogen production and CO₂ utilization.