Graphite/MnO2and MoS2Composites Used as Catalysts in the Oxygen Reduction Cathode of Microbial Fuel Cells

In this study, mixtures of graphite, γ-MnO 2 and MoS 2 with different weight proportions (20:1:1, 30:1:2 and 30:2:1) were used in microbial fuel cells (MFCs) and the catalysts were also subjected to ultrasonication to study its influence. The data suggest that the MFC fabricated with the catalyst prepared using graphite, γ-MnO 2 and MoS 2 in a weight proportion of 20:1:1 exhibited the highest optimal power density of 120 mW/m 2 . However, after ultrasonic treatment, the power density was significantly improved, which was 183 mW/m 2 . It can also be observed that after using ß-MnO 2 , the optimal power density of the MFC fabricated with the catalyst prepared with graphite, ß-MnO 2 and MoS 2 in a proportion of 20:1:1 higher (158 mW/m 2 ) than that of the MFC fabricated with γ-MnO 2 in the same proportion, showing that the performance of ß-MnO 2 with a whisker structure was better than that of γ-MnO 2 owing to its higher surface area, larger pore diameter and great pore volume. The long term performances of the MFCs fabricated using catalysts prepared with the different graphite, γ-MnO 2 (ß-MnO 2 ) and MoS 2 proportions decreased finally in the order of 20:1:1 (ß-MnO 2 ) > 20:1:1 (ultrasonicated γ-MnO 2 ) > 10:1 (ß-MnO 2 ) >20:1:1 (γ-MnO 2 ) > 30:2:1 (γ-MnO 2 ) >30:1:2 (γ-MnO 2 ).