The maximum current and power densities were 6.98 mA/cm2
and 0.818 mW/cm2 (at 3.41 mA/cm2), respectively (Fig. 1a). The
electrode potentials for the MFC obtained from the ieV
relationship are shown in Fig. 1b. The measured cathode potential
at the OCV, 0.401 V vs. SHE, was smaller than the theoretical
value for oxygen reduction (0.815 V vs. SHE).