Bridging Microbial and Electrochemical Redox Systems for Sustainable Wastewater Treatment and Energy Storage

The limited power output (<10 W/m2) of microbial fuel cells (MFCs) remains a major barrier to their industrial deployment, prompting research to shift toward alternative applications and hybrid systems. These include the integration of MFCs into constructed wetlands, bioelectro-Fenton systems, or photocoupled MFCs for applications in wastewater and recalcitrant pollutant remediation to compensate for the inherent power output limitations of MFCs. This review highlights recent advances in the use of bioanodes and biocathodes beyond conventional electricity generation. We place particular emphasis on their integration with redox flow batteries (RFBs), exploring the synergistic potential of such pairings for energy harvesting from MFCs and delivering higher power densities (>1000 W/m2). The fundamental principles of RFBs are outlined, followed by an in-depth discussion of how they can be coupled with bioelectrodes. We also survey key electroactive microbial strains and redox-active species to evaluate promising MFC–RFB configurations.