Development of carbon free diffusion layer for activated carbon air cathode of microbial fuel cells

The fabrication of activated carbon air cathodes for larger-scale microbial fuel cells requires a diffusion layer (DL) that is highly resistant to water leakage, oxygen permeable, and made using inexpensive materials. A hydrophobic polyvinylidene fluoride (PVDF) membrane synthesized using a simple phase inversion process was examined as a low cost ($0.9/m2), carbon-free DL that prevented water leakage at high pressure heads compared to a polytetrafluoroethylene/carbon black DL ($11/m2). The power density produced with a PVDF (20%, w/v) DL membrane of 1400 ± 7 mW/m2 was similar to that obtained using a wipe DL [cloth coated with poly(dimethylsiloxane)]. Water head tolerance reached 1.9 m (∼19 kPa) with no mesh supporter, and 2.1 m (∼21 kPa, maximum testing pressure) with a mesh supporter, compared to 0.2 ± 0.05 m for the wipe DL. The elimination of carbon black from the DL greatly simplified the fabrication procedure and further reduced overall cathode costs.