Developments of metallic anodes with various compositions and surfaces for the microbial fuel cells

Factors that affect the power performance of microbial fuel cells (MFCs) are well known to be very complex because of their multidisciplinary character, especially with respect to the electrode. In this study, for the first time, specimens of different metallic materials with smooth and rough surfaces, including Cu-based alloys and porous Ni plates whose sintering temperature was in the range of 900 °C-1100 °C, were investigated with regard to their possible application as anodes in MFCs. The results show that MFCs equipped with a Cu-Ag alloy anode could produce a higher power performance with an open-circuit voltage of 0.65 V and a power density of 1141.69 mW m^-2 compared to the other anodes of Cu-Zn and Cu-Ni-Zn alloys. The reason is that the performances of anodes are proportional to the electrical conductivity of the various alloys. In addition, the porosity of the specimens is 20.3% for the Ni-1100 °C and 58.4% for the Ni-900 °C anode material. The conductivity of the anodes decreases with increasing porosity, which, in turn, will result in a lower power performance. Here, the Ni-1100 anode applied in MFCs displays a better performance with an open-circuit voltage of 0.56 V, a limiting current density of 3140 mA m^-2, and a corresponding maximum power density of 448 mW m^-2. The output power density could be maintained at 450 mW m^-2 after a test of 50 h.