Transition metal sulfide/oxide nanoflowers decorated on poly (aniline-2-sulfonic acid) modified polyacrylamide derived carbon cathode catalyst for bioenergy generation in microbial fuel cells

Microbial fuel cells (MFCs) are promising carbon-free energy devices with the potential to harvest power and treat wastewater simultaneously, which is crucial to meet the emerging energy challenges. Despite the high theoretical power output, the performance of MFCs is dependent on the cathodic oxygen reduction reaction (ORR) to generate electricity. Herein, a hybrid nanostructure of nickel-cobalt sulfide (NiCo2S4) nanosheets over NiCo2O4 nanoflowers on in-situ nitrogen and sulfur-doped carbon (NSC) is prepared by direct pyrolysis. Deposition of NiCo2S4 nanosheets improves the effective contact with the electrolyte and increases the catalytic sites for ORR. NiCo2S4/NiCo2O4@NSC shows an oxygen reduction peak at 0.150 V, limiting current of -0.093 mA, close to -0.107 mA for Pt/C and generates optimal power density of 831.74 mW m−2 comparable to Pt/C (857.92 mW m−2) and higher than NiCo2O4@NSC (665.86 mW m−2), NSC (650.28 mW m−2) and NC (485.98 mW m−2) air cathodes. This could be attributed to the high degree of graphitization, appropriate N and S content, a synergistic effect between the metal species and the heteroatoms, and better catalytic surface area utilization. The results suggest that M-N-S-based carbons could be potential cathodes for microbial fuel cells and similar energy devices.