Modified graphene oxide-coated stainless-steel bioanodes for enhanced electrode-biofilm charge transfer and aromatic pollutant degradation in microbial fuel cells

Inefficient extracellular electron transfer and weak anode–biofilm coupling remain major limitations to the bioelectrochemical performance of microbial fuel cells (MFCs). In this study, stainless-steel (SS) anodes were engineered with graphene oxide (SS-GO) and reduced graphene oxide (SS-rGO) to regulate the electrode–biofilm interface and improve charge-transfer efficiency during MFCs operation. The three anodes were evaluated as model biointerfaces in single-chamber MFCs operated for 50 days using spoiled Bei-Bei pumpkin juice as a waste-derived substrate and 4-hydroxybenzyl aldehyde (4-HBA) as a model aromatic aldehyde pollutant. Surface modification markedly improved the electrochemical response. The SS-rGO anode delivered the highest maximum power density of 29 mW/m² at a current density of approximately 95 mA/m², followed by SS-GO with 17 mW/m² at approximately 90 mA/m², whereas bare SS produced 6.6 mW/m² at approximately 85 mA/m². Charge-storage performance improved with graphene coatings, with specific capacitance increasing from 9.7 × 10⁻² F/g (SS-GO) to 1.29 × 10⁻¹ F/g (SS-rGO), consistent with stronger biofilm–electrode coupling. In parallel, 4-hydroxybenzyl aldehyde degradation reached 95.15% on SS-rGO, compared with 90.29% on SS-GO and 75.79% on SS. Community profiling indicated Achromobacter enrichment on GO-modified anodes, whereas Pseudomonas-related taxa were more prominent on bare SS.