Facile and binder free nano-architecturing of anode with biocompatible g-C3N4-PPy for bacterial community enrichment and green energy generation in microbial fuel cells

The adoption of microbial fuel cells (MFCs) as waste-to-power solution for green energy generation while treating wastewater has attracted considerable attention. However, their wide-scale expansion requires further improvements, particularly by anode modifications which necessitates the development of anodes with large surface area, high electrical conductivity, and biocompatibility. Thus, herein, we present a novel and facile approach for the modification of carbon felt (CF) with graphitic carbon nitride (g-C3N4) and polypyrrole (PPy) to create a highly biocompatible anode following a binder-free route. Increased surface area with microporous rough surface of modified electrodes was confirmed through scanning electron microscopy (SEM) and atomic force microscopy (AFM). The g-C3N4@PPy-CF anode exhibited minimal water contact angle of 0.9°, in contrast to g-C3N4-CF (53.5°) and pristine CF (123.8°), indicating enhanced hydrophilicity essential for biofilm formation. The synergy between g-C3N4 and polypyrrole results in remarkable 80.7% higher power output (205.8 ± 7.36 mW/m2) and 47% higher current response (8.24 mA) as compared to pristine-CF. Efficient extracellular electron transport (EET) was enacted through better interfacial contact between electrode and electroactive bacteria (EAB), as evidenced by the minimal charge transfer resistance in g-C3N4@PPy-CF (4.21 Ω) and g-C3N4-CF (6.47 Ω), while 68% higher resistance (7.06 Ω) with pristine-CF. Microbial characterization of biofilms showed enrichment of electroactive bacteria, mainly the Proteobacteria phylum comprised 79–82% of total microbial community in modified electrodes while it was 74% in pristine CF. Acinetobacter (25.9%) and Desulfuromonas (17.9%) emerges as major electroactive genera on g-C3N4@PPy-CF contributing to its excellent bio-electrogenic performance. Thus, the low-cost, binder-free and facilely fabricated novel anode with stable electrogenic efficiency provides solution to longstanding challenge of suboptimal anode performance and opens new avenues for scale-up of sustainable energy generation from wastewater using MFCs.