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/m(2)), carbon-free DL that prevented water leakage at high pressure heads compared to a polytetrafluoroethylene/carbon black DL ($11/m(2)). The power density produced with a PVDF (20%, w/v) DL membrane of 1400 +/- 7 mW/m(2) was similar to that obtained using a wipe DL [ cloth coated with poly(dimethylsiloxane)]. Water head tolerance reached 1.9 m (similar to 19 kPa) with no mesh supporter, and 2.1 m (similar to 21 kPa, maximum testing pressure) with a mesh supporter, compared to 0.2 +/- 0.05 mfor the wipe DL. The elimination of carbon black from the DL greatly simplified the fabrication procedure and further reduced overall cathode costs. (C) 2015 Elsevier Ltd. All rights reserved.