Effect of Electrode-Surface Area on Electricity Generation in Microbial Fuel Cells

Abstract

Abstract. Microbial fuel cells (MFCs) are prospective biodevices for the purification and energy recovery from organic wastewater. In this study we examined the effect of surface areas of anode and cathode on electrical power output in MFCs. Hydrogen, produced by anaerobic bacteria, is one of the possible mediators for electricity generation in MFCs. A reactor consisted of an anode, air cathode, and proton-exchange membrane was filled with a phosphate buffer without inoculation of bacteria, and hydrogen gas as a fuel for electricity generation was dissolved in the buffer. The cathode contained Pt catalyst, but the anode did not it. When the surface areas of anode and cathode were changed from 6 to 25 cm 2 , the electrical power outputs were proportional to the cathode area but not to the anode area. To examine the electricity generation by bacterial, an artificial wastewater containing peptone and beef extract was filled in the reactor, and activated sludge was inoculated as the seed bacteria. The reactor was operated at room temperature over two months, and the electricity generation was monitored. The electrical power output by bacteria with regard to the change in the surface areas of anode and cathode showed a similar tendency to those with hydrogen in the absence of bacteria, i.e., it was dependent on only the cathode area. These results suggest that the power output of the MFC can be increased by enlarging the cathode area.