Microbial Fuel Cells in Power Generation and Extended Applications - Biotechnology in China: Biofuels and Bioenergy - page 168

Fig. 2 Schematic diagram of a typical two-chamber MFC

column setup in that tubular-type electrodes are adopted. This design confers
several extra benefits, such as great compactness, superior scalability and generally
low internal resistance due to the common use of a separator electrode assembly
(SEA) that decreases electrode spacing and increases the proton exchange area [ 8 ].
You et al. [ 9 ] developed a tubular air-cathode MFC with graphite granules packed
inside as the anode, which demonstrated a low internal resistance of only 27 X and
enhanced power generation. In such systems, cathode reactions are usually the
limiting factors. To further enlarge the biocathode area, a tubular MFC with
graphite fiber packed into the cathode chamber reactor was recently developed
[ 10 ], and a maximum power density of 15 W/m 3 was achieved. The tubular
configuration of MFC reactor enables more flexible choices of separator and
electrode materials. Considering the constrained proton transfer by the use of a
proton-exchange membrane (PEM), efforts have also been made to substitute the
PEM with more porous and cost-effective separators. Zuo et al. (2007) manufac-
tured a SEA by coating a layer of graphite paint and non-precious metal catalyst
onto a tubular ultrafiltration membrane, and a high power density of 17.7 W/m 3
was achieved, attributed to improved proton transfer. Likewise, Zhuang et al. [ 11 ]
developed a tubular SEA-MFC that used canvas cloth as the separator. To enhance
its electrical conductivity and catalytic activity, the canvas cloth was coated with a
mixture of nickel-based conductive paint and MnO 2 . Under the fed-batch opera-
tion using brewery wastewater, this tubular MFC generated a maximum power
density of 9.87 W/m 3 . While the use of coarse-porous separators significantly
reduces internal resistance, it also increases oxygen intrusion to anode chamber
and substrate leakage to cathode chamber. In an effort to prevent such oxygen