Air Cathode Catalysts of Microbial Fuel Cell by Nitrogen-Doped Carbon Aerogels

Microbial fuel cell (MFC) has been attracting extensive interest, because it can be used for electricity generation and concurrently wastewater treatment. Yet, the MFC performance has remained limited due to the sluggish electron-transfer kinetics and hence high overpotential of oxygen reduction reaction (ORR) at the cathode. In the present study, nitrogen-doped carbon aerogels (NCAs) were prepared by pyrolysis of polyacrylonitrile at controlled temperatures (600 to 900 °C). Electrochemical tests showed apparent electrocatalytic activity by the NCAs toward ORR in alkaline media, and among the series the sample prepared at 800 °C exhibited the best performance, with a half-wave potential of +0.80 V versus reversible hydrogen electrode and the number of electron transfer ∼3.9. The electrocatalytic performance was ascribed to nitrogen doping that generated catalytic active sites that led to improved ORR kinetics. An MFC using the best NCA as cathode catalysts achieved a maximum power density of 1048 ± 47 mW m–2, close to that (1051 ± 28 mW m–2) based on state-of-the-art Pt/C, and a mass specific power of 52.4 mW g–1. These results demonstrate that cost-efficient NCAs can be used as a viable, platinum-free, ORR catalyst for MFC applications.