Abstract
Changes in the anode, cathode, and solution/membrane
impedances during enrichment of an anode microbial consortium
weremeasuredusing electrochemicalimpedancespectroscopy.
The consortium was enriched in a compact, flow-through
porous electrode chamber coupled to an air-cathode. The anode
impedance initially decreased from 296.1 to 36.3 Ω in the
first 43 days indicating exoelectrogenic biofilm formation. The
external load on the MFC was decreased in a stepwise
manner to allow further enrichment. MFC operation at a final
load of 50 Ω decreased the anode impedance to 1.4 Ω, with a
corresponding cathode and membrane/solution impedance
of 12.1 and 3.0 Ω, respectively. An analysis of the capacitive
element suggested that most of the three-dimensional anode
surface was participating in the bioelectrochemical reaction. The
power density of the air-cathode MFC stabilized after 3
months of operation and stayed at 422 ( 42 mW/m2 (33 W/m3)
for the next 3 months. The normalized anode impedance for
theMFCwas 0.017 kΩcm2, a 28-fold reduction over that reported
previously. This study demonstrates a unique ability of
biological systems to reduce the electron transfer resistance
in MFCs, and their potential for stable energy production over
extended periods of time.
