2013 Volume 11 Issue 5 Pages 453-461
A microbial fuel cell (MFC) is defined as a system in which microorganisms function as catalysts to convert chemical energy into electrical energy. A typical MFC acts with a couple of reactions; anodic bioreactions by exoelectrogenic bacteria and a cathodic reaction of oxygen reduction. This research focused on the cathodic reaction of a single chamber MFC with a cathode exposed to the air (air-cathode), and the pH of water attached on air-cathode (air-cathode pH) was actively controlled for the enhancement of the cathodic reaction. The active control of the air-cathode pH successfully improved the coulombic efficiency of the MFC due to the enhancement of proton supply to the air-cathode, which accelerated the cathodic reaction. The enhancement effect at the acidic condition of the air-cathode pH was larger than that at neutral and alkaline conditions. However, the long-term operation revealed that the power generation almost stopped at the acidic condition due to the inactivation of exoelectrogenic bacteria on the anode. Consequently, pH 7.0 was the most effective condition in this study. In this condition, no bad influence was observed on the biofilm. The observed electric current and coulombic efficiency were 2.9 and 2.7 times higher than those without the air-cathode pH control, respectively.
