Metal-free cathodic catalyst with nitrogen- and phosphorus-doped ordered mesoporous carbon (NPOMC) for microbial fuel cells

Nitrogen- and phosphorus-doped, ordered mesoporous carbon (NPOMC) is a novel metal-free cathode catalyst for the oxygen reduction reaction (ORR). The electrochemical performance of NPOMC is compared with that of a Pt/C catalyst for the ORR in two different type microbial fuel cell (MFC) configurations: single-chamber MFC (SMFC) without an ion exchange membrane, and two-chamber MFC (TMFC) with an ion exchange membrane. The NPOMC shows approximately 60–75% of the ORR activity observed with the Pt/C catalyst in an ion exchange membrane implementing TMFC (OCV 0.42 V and power density of 245.8 mW m−2). In contrast, the membrane-less SMFC produces approximately 30% of the ORR activity of Pt/C (154.0 mW m−2). The mesoporous catalyst with NPOMC shows not only higher electrochemical charge transfer performance, but also improves electrical capacitance due to the larger surface area and morphology of the mesoporous structure. Biofilm formation on mesoporous NPOMC reduces the ORR activity in the SMFC significantly, whereas the decrease is less severe in the TMFC because of the ion exchange membrane. The material cost of the NPOMC is estimated to be approximately 5% of the cost of Pt/C. Therefore, NPOMC is a cost-effective alternative catalyst for MFC applications. [Display omitted] •Nitrogen- and phosphorus-doped ordered mesoporous carbon (NPOMC) was developed.•The performance of NPOMC was compared in different types of MFC configurations.•Metal-free NPOMC produced approximately 75% of the ORR activity compared to Pt/C.•Biofilm formation on the NPOMC surface may hinder the ORR activity during operation.•NPOMC is a cost effective alternative catalyst for the MFC cathode.