Conductive Polymers in Microbial Fuel Cells for Bioelectricity Generation

Abstract

Microbial fuel cells (MFCs) offer simultaneous wastewater treatment and electricity generation, but their practical performance is limited by inefficient extracellular electron transfer (EET) and interfacial losses at the electrode–biofilm interface. Conductive polymers (CPs), particularly polyaniline (PANI), polypyrrole (PPy), and poly(3,4-ethylenedioxythiophene) (PEDOT), have therefore been investigated as electrode modifiers because their electrical, electrochemical, and surface properties can be tailored to support biofilm development and electron transfer. This review critically evaluates reported evidence for CP-modified MFC electrodes, with emphasis on electrochemical performance, EET-related mechanisms, microbial interactions, real-wastewater applications, stability, and scale-up limitations. Laboratory studies demonstrate substantial performance improvements under controlled conditions. For example, PANI nanofiber-modified carbon cloth reached 1,091 mW m⁻², PPy/MXene-modified graphite felt reached 264 mW m⁻² (vs. 45 mW m⁻² for bare graphite felt), and a PEDOT-modified graphite-felt system treating palm oil mill effluent reported a maximum current density of 3.5 A m⁻² and a Coulombic efficiency of 51%. However, these results are difficult to compare directly because studies differ in electrode architecture, reactor configuration, substrate, inoculum, and performance normalization. Evidence for specific CP-mediated EET mechanisms also remains limited, particularly for distinguishing direct, mediated, and long-distance electron-transfer contributions. More importantly, long-term operation with real wastewater and pilot-scale CP-modified systems remains insufficiently investigated. Existing pilot-scale MFC studies without CP modification demonstrate that performance under real wastewater conditions can differ substantially from laboratory results. Future research should therefore prioritize standardized performance reporting, matched real-wastewater comparisons, long-term stability testing, pilot-scale validation, mechanistic EET characterization, and fabrication-cost assessment. Overall, CPs show considerable potential for improving MFC electrode performance, but their practical and economic advantages over conventional electrodes remain to be established under realistic operating conditions.