Porous Co, N co-doped carbon derived from tea residue as efficient cathode catalyst in microbial fuel cells for swine wastewater treatment and the microbial community analysis

The rapid increase of swine wastewater (SW) has posed great threat to the environment and traditional processes also suffered from a high operational cost. In this study, porous Co, N co-doped carbon derived from tea residue was synthesized through a green, low-cost method combining the NaCl/KCl eutectic salt and a little KOH as activator at different temperature for microbial fuel cells to treat the SW. The catalyst prepared at 700 °C (TC-700) displayed high specific surface area (1009.5 m2/g) and appropriate porous structure, high Co-Nx and pyridinic-N content, which endowed it with good oxygen reduction reaction activity. When used in the MFC to treat SW, a higher maximum power density (748.9 mW/m2) and maximum output voltage (0.529 V) was obtained with better stability, compared to the Pt/C cathode MFC (588.7 mW/m2 and 0.513 V). Besides, it can also achieve high coulombic efficiency of 6.18 ± 0.38%, chemical oxygen demand removal of 81.8 ± 1.86%, and ammonia removal of 35.0 ± 2.0%, total nitrogen removal of 33.5 ± 2.4%. Microbial community analysis revealed the functional bacteria for electricity generation and pollutant removal. This work demonstrated the feasibility of development on MFC cathode catalysts and its application in SW treatment.