Synergistic Enhancement of Microbial Fuel Cell Performance via Hierarchical NiCo2O4/Polypyrrole-Modified Carbon Felt Anode

In this study, a carbon felt (CF)-based ternary composite anode was developed through the decoration of nickel cobaltite (NiCo2O4) nano-needles and subsequent in situ electropolymerization of polypyrrole (PPy). The structural and electrochemical properties of the modified electrodes were systematically characterized. The CF/NiCo2O4/PPy anode demonstrated significantly enhanced bioelectrochemical activity, achieving a peak current density of 96.0 A/m2 and a steady-state current density of 28.9 A/m2, which were 4.85 and 5.90 times higher than those of bare carbon felt, respectively. Geobacteriaceae is a type of electrogenic bacteria. It was hardly detected on the bare CF substrate; however, in the ternary CF/NiCo2O4/PPy electrode, the relative abundance of Geobacteriaceae significantly increased to 43%. Moreover, the composite electrode exhibited superior charge storage performance, with a total charge (Qt) of 32,509.0 C/m2 and a stored charge (Qs) of 3609.0 C/m2 measured under a 1000 s charging/discharging period. The MFC configured with the CF/NiCo2O4/PPy anode reached a maximum power density of 1901.25 mW/m2 at an external resistance of 200 Ω, nearly six times that of the unmodified CF-based MFC. These improvements are attributed to the synergistic interaction between the pseudocapacitive NiCo2O4 and conductive PPy, which collectively facilitate electron transfer, promote microbial colonization, and enhance interfacial redox kinetics. This work provides an effective strategy for designing high-performance MFC electrodes with dual functionality in energy storage and power delivery.