(27d) Electron Transfer and Local pH Variations in Anodic Biofilms

Proton transport out of the anodic biofilms is a limiting factor of current in microbial fuel cells. It has been demonstrated that the limitation of proton transport causes local pH changes inside biofilms. However, the correlation between local pH changes and current is not quantified. In this study, we have quantified local pH changes in biofilms with current generated from a microbial fuel cell. A two compartment microbial fuel cell was used where biofilms of Shewanella oneidensis MR ? 1 were grown on the graphite plate anode. In the cathodic, oxygen was used as the electron acceptor. The local pH changes inside the biofilms were measured using pH microelectrode. We found that there is a linear correlation between current and local pH. Our results also showed that the pH variation was higher near the electrode surface compare to that in the bulk solution and that the direction of pH change depended on the polarization potential relative to the equilibrium potential of the anode.