Serially Connectable Sediment Microbial Fuel Cells using Dipole Graphite Solids and Voltage Reversal Suppression

Sediment microbial fuel cells (SMFCs) are installed in natural water systems for the on-site power source of aquatic devices; however, the power generated from single unit is not enough to operate certain devices. To overcome this drawback, the series connection of SMFCs is indispensable. We describe a dipole-electrode-containing stacked SMFC system operated in series connection mode. Two SMFC units were fabricated, which produced maximum current densities of 492 and 302 mA m⁻², respectively. They were connected in series and operated at 1.45 V, which is close to the sum of the individual voltages. Even though voltage reversal inevitably occurred in the connected mode, it was suppressed by adjusting the internal resistance of each SMFC to be very close within a few Ω. We achieved a maximum power density at a high voltage over 123 mW m⁻² at 0.6 V and enhanced the available maximum current density (i.e., no voltage reversal) by 269 to 320 mA m⁻². We have developed a serially connectable SMFC system with an improved maximum power at a higher voltage than that of a single SMFC and we suggest a method for voltage reversal control for the further test of multistacked SMFCs.