Poly(vinyl alcohol) separators improve the coulombic efficiency of activated carbon cathodes in microbial fuel cells

High-performance microbial fuel cell (MFC) air cathodes were constructed using a combination of inexpensive materials for the oxygen reduction cathode catalyst and the electrode separator. A poly(vinyl alcohol) (PVA)-based electrode separator enabled high coulombic efficiencies (CEs) in MFCs with activated carbon (AC) cathodes without significantly decreasing power output. MFCs with AC cathodes and PVA separators had CEs (43%–89%) about twice those of AC cathodes lacking a separator (17%–55%) or cathodes made with platinum supported on carbon catalyst (Pt/C) and carbon cloth (CE of 20%–50%). Similar maximum power densities were observed for AC-cathode MFCs with (840 ± 42 mW/m²) or without (860 ± 10 mW/m²) the PVA separator after 18 cycles (36 days). Compared to MFCs with Pt-based cathodes, the cost of the AC-based cathodes with PVA separators was substantially reduced. These results demonstrated that AC-based cathodes with PVA separators are an inexpensive alternative to expensive Pt-based cathodes for construction of larger-scale MFC reactors.