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 rates, 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. 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 m3-H2/m3/d, and a low energy consumption of 5.95 kWh/m3. Moreover, MWECs exhibited a two-fold increase in COD removal (1.51 kg/m3/d) compared to MECs, attributed to enhanced microbial activity. It is notable that microorganisms could maintain robust activity at high voltages in MWECs with Geobacter, Azospirillum and Paracoccus as the dominant genera, likely due to the synergistic effects of the abiotic anode used in water electrolysis. This study demonstrated that it is feasible to integrate MECs with water electrolysis to achieve high current densities, fast H2 production rates, and efficient COD removal rates, making practical applications possible.