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

Abstract

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 inevita-bly occurred in the connected mode, it was suppressed by adjusting the internal resistance of each SMFC to be very close within a few Omega. 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.