Microbial Water Electrolysis Cells for Efficient Wastewater Treatment and H₂ Production

The world is facing severe environmental pollution and energy shortages. Microbial electrolysis cells (MECs) provide a promising solution by producing H₂ from wastewater. However, MECs face limitations, such as low current densities, slow H₂ production, and electrogenic bacteria deactivation at high voltages. In this study, we developed microbial water electrolysis cells (MWECs), a new device that couples MECs with water electrolysis (WE). At an applied voltage of 2.2 V, MWECs achieved an industrial-level high current density of 400 mA/cm², a fast H₂ production rate of 121 L-H₂/L/d, and a low energy consumption of 5.93 kWh/m³. Moreover, the protective effect of the abiotic anode in water electrolysis enabled microorganisms to maintain robust activity at high voltages in MWECs, with Geobacter, Azospirillum, and Paracoccus as the dominant genera. This led to a 2-fold increase in chemical oxygen demand (COD) removal, reaching 1.51 kg/m³/d, compared to MECs. This study demonstrated the feasibility and advantages of integrating MECs with water electrolysis to achieve high current densities, fast H₂ production rates, and efficient COD removal rates, making practical applications possible.