High power density redox-mediated Shewanella microbial flow fuel cells

Microbial fuel cells (MFCs) utilize exoelectrogenic microorganisms to directly convert organic matter into electricity, offering a compelling approach for simultaneous power generation and wastewater treatment. However, conventional MFCs typically require thick biofilms for sufficient metabolic electron production rate, which inevitably compromises mass and electron transport, posing a fundamental tradeoff of limiting the achievable power density (<1 mW cm-2). Herein, we report a new concept of redox mediated microbial flow fuel cells (MFFCs) by exploiting artificial redox mediators in flowing medium to efficiently transfer metabolic electrons from bacteria to electrodes, which effectively overcomes mass transport limitations and markedly reduces internal resistance. The biofilm-free MFFC thus breaks the inherent tradeoff in dense biofilms, resulting in a maximum current density surpassing 40 mA cm-2 and a highest power density exceeding 10 mW cm-2, approximately one order of magnitude higher than those of state-of-the-art MFCs, to the best of our knowledge.