Tofu gel-derived nitrogen and trace iron co-doped porous carbon as highly efficient air-cathode electrocatalyst for microbial fuel cells

A highly efficient biomass derived nitrogen (N) and trace iron (Fe) co-doped oxygen reduction reaction (ORR) catalyst (NFeC-3) is synthesized through a facile method. Trace Fe doped into carbons plays important roles in physical characteristics of carbons in which the specific surface area (655 m2 g−1), degree of graphitization (ID/IG = 1.023), and content of ORR-related N (N-ORR/C = 2.67%) for NFeC-3 are all higher than that of NC. As expected, NFeC-3 exhibits excellent ORR electrocatalytic performances with more positive ORR peak potential (0.024 V), onset potential (0.157 V) and half-wave potential (−0.026 V) than that of other prepared carbons and even commercial Pt/C catalyst. Also, when NFeC-3 is chosen as air-cathode ORR electrocatalyst for single-chamber air-cathode MFC (AC-MFC), the AC-MFC coated with NFeC-3 runs steadily for ∼ 400 h. The corresponding maximum power density of AC-MFC coated with NFeC-3 (863.40 ± 13.19 mW m−2) is 23.61% and 30.62% higher than that of AC-MFCs coated with NC (698.51 ± 17.89 mW m−2) and Pt/C catalyst (661.02 ± 12.19 mW m−2), respectively. Amazingly, three AC-MFCs in series can drive an LED work properly. Therefore, NFeC-3 is a promising carbon-based ORR electrocatalyst in the practical application of MFCs and related devices.