Connecting Conductive Dynamic Membrane to Biocathode Enables Net Energy Generation from Buffer-Free Artificial Wastewater

Microbial fuel cells (MFCs) utilize electroactive microbes to oxidize organics for electricity generation, yet their wastewater treatment application is still hindered by inefficient energy recovery, high cost, and hydraulic limitations, with separator configurations crucially influencing system viability. This study developed a cost-effective conductive dynamic membrane separator (CDMS) with carbon felt, stainless-steel mesh, and fiberglass cloth as a bifunctional separator-biocathode, enhancing MFC's performance through increased electrode surface area and optimized hydrodynamics for continuous-flow treatment. Integrating CDMS as a biocathode significantly boosted power output, achieving 24.5 ± 1.5 W/m³ volumetric and 2.5 ± 0.2 W/m² areal power densities at the steady stage, with advantages persisting despite degradation due to cathode performance being the principal determinant of MFC functionality. Comparative analysis indicated that both CDMS and carbon brush cathodes played indispensable roles in sustaining dual-cathode MFC high-performance and stability. The bifunctional CDMS in dual-cathode MFC established a self-reinforcing cycle of substrate limitation, oxygen allocation, and electron transfer optimization, fundamentally addressing the stability-performance trade-off in the MFC system. Material-energy balance analysis revealed that the dual-cathode MFC system achieved net positive energy production (+3.12 Wh/m³) from artificial wastewater with much lower capital costs than traditional configurations, advancing scalable MFC design for energy-positive wastewater treatment and practical applications.