Nitrogen-doped MoS2/carbon as highly oxygen-permeable and stable catalysts for oxygen reduction reaction in microbial fuel cells

Developing non-noble metal catalysts with high oxygen-permeability and activity for oxygen reduction reaction (ORR) is crucial for microbial fuel cells (MFCs). In this study, nitrogen-doped molybdenum disulfide/carbon (N-MoS2/C) is prepared using melamine as nitrogen and carbon sources. Ammonium molybdate, thiourea and Pluronic F127 are used as Mo source, S source and surfactant, respectively. Mo-S-melamine complex precursor is obtained through the evaporation-induced self-assembly route, which is then carbonized at 800, 900 and 1000 °C to fabricate N-MoS2/C. Defect-rich N-MoS2/C has a large number of exposed active sites and a high oxygen permeability. N-MoS2/C (900 °C) with regular honeycomb structure shows the maximum power density of 0.815 W m-2, which is far higher than that of Pt/C (0.520 W m-2) and only has a decline of 1.23% after 1800 h operation in MFCs. Four-electron (4e−) reduction of O2 is the main ORR pathway for N-MoS2/C (900 °C), attributing to the efficient permeation, adsorption, activation and reduction of O2 on the active sites. The synergy among abundant defects, N-species (pyridinic N, graphitic N and Mo−Nx) and high conductivity contributes to the promising ORR activity. This simple synthetic route of N-doped metal sulfides/carbon composites displays a new prospect for preparation of ORR catalyst.