Nitrogen-doped activated carbon as metal-free oxygen reduction catalyst for cost-effective rolling-pressed air-cathode in microbial fuel cells

To increase the performance of MFCs, nitrogen-doped activated carbon (AC) for rolling-pressed air-cathode was synthesized using inexpensive melamine as nitrogen source by pyrolysis. The ratio of melamine to activated carbon (N/C) and pyrolysis temperature were optimized to be 10 and 900 °C. To clarify how the structure and active nitrogen content in different preparations influence the ORR performance, series of characterizations were carried out, and a good agreement between the content of pyridinic type N and high ORR activity was observed. As a dominant four electron cathode catalyst, AC-N10-900 exhibited the best performance both in electrochemical and MFCs tests in comparison with AC and Pt/C. The maximum power density was 1042 mW m−2, which was 65.4% and 116.2% higher than that of AC and Pt/C. Therefore, AC-N10-900, one of cost-effective and metal-free MFCs cathode catalysts towards ORR, is expected to alternate precious metal for high performance in MFCs.