Increased power from a two-chamber microbial fuel cell with a low-pH air-cathode compartment

Pt-supported air-cathodes still need improvement if their application in MFC technology is to be sustainable. In this context, the efficiency of an air-cathode was studied with respect to the pH of the solution it was exposed to. Voltammetry showed that oxygen reduction was no longer limited by H+ availability for pH lower than 3.0. A new MFC was designed with a catholyte compartment setup between the anode compartment and the air-cathode. With a catholyte compartment at pH 1.0, the MFC provided up to 5 W/m2, i.e., 2.5-fold the power density obtained with the same anode and cathode in a single-chamber MFC working at pH 7.5. Current density exceeded 20 A/m2. The benefit of low-pH in the catholyte chamber largely counterbalanced the mass transfer hindrance due the membrane that separated the two compartments. The MFC kept 66% its performance during nine days of continuous operation.