Simultaneous pH self-neutralization and bioelectricity generation in a dual bioelectrode microbial fuel cell under periodic reversion of polarity

In order to overcome pH membrane gradient and minimize dosage of buffer, a dual bioelectrode microbial fuel cell (MFC) with periodic reversion of polarity is conducted. The performances of the MFC before and after polarity reversion are compared to the MFC without polarity reversion and the mechanisms of the polarity reversion are investigated using electrochemical impedance spectroscopy and cyclic voltammetry. The MFC has been run continuously and stably for more than four months under periodic reversion of polarity with extreme low phosphate buffer of 5 mM. The accumulated proton in the anode and hydroxyl in the cathode are neutralized after polarity reversion but the acidification of the anode more serious than the alkalization of the cathode. Polarity reversion improve the anodic and cathodic performance due to in situ use of the accumulated proton and hydroxyl in the same electrode chamber which result in 58.3% and 36.0% increases in power density as compared to that produced before polarity reversion and by the MFC without polarity reversion, respectively. Cathode performance can be adversely affected by residual soluble organic carbons during polarity reversion due to oxygen consumption by heterotrophic bacteria in the presence of residual soluble organic carbons.