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

a r t i c l e i n f o 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/m 2) or without (860 ± 10 mW/m 2) 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. Microbial fuel cells (MFCs) that use exoelectrogenic microorganisms [1] to generate electricity from biomass have received much attention as a promising technology for energy recovery and wastewater treatment [2–4]. However, the high cost of the materials used in the construction of the MFCs has been a limitation for practical applications. Since the air cathode accounts for the largest percentage of the total cost of MFC electrode materials [5], identifying inexpensive cathode materials and architectures that maintain high cell performance is important for widespread deployment of larger-scale MFCs. Inexpensive activated carbon (AC)-based air cathodes have been shown to be a good alternative to metal catalyst-containing electrodes in MFCs. AC-based cathodes have been fabricated in several ways. One method is cold-pressing AC and polytetrafluoroethylene (PTFE) powder onto a nickel mesh to form a catalytic layer on the electrolyte side of the cathode and using a porous PTFE diffusion layer on the air side to reduce water leakage out of the MFC chamber [6,7]. MFCs with these PTFE-based AC air cathodes are lower in cost than previous designs by avoiding the use of expensive porous carbon cloth and precious metal catalysts. MFC tests with these AC cathodes showed similar or slightly higher maximum power densities than MFCs made with Pt/C catalysts and carbon cloth cathodes [8,9]. Costs of AC cathodes have been reduced by using stainless steel mesh instead of Ni mesh and poly(dimethylsiloxane) (PDMS) diffusion layers …