Maximum power densities of wastewater-fed microbial fuel cells (MFCs) are limited by low buffer capacities and conductivities. To address these challenges, a continuous flow MFC was constructed using a thin flow channel and an anion exchange membrane (AEM) in a novel configuration. The electrodes were separated only by a thin AEM (∼100 μm), reducing the solution resistance while facilitating transport of hydroxide ions from the cathode into the anolyte (no catholyte). The flow-MFC produced 1.34 ± 0.03 W m–2 using an artificial wastewater specifically designed to have a low buffer capacity (alkalinity of 360 mg L–1), compared to only 0.37 ± 0.01 W m–2 using a more typical cubic-shaped MFC. Internal resistance (Rint = 34 ± 1 mΩ m2) was 83% lower than that of the cubic MFC (202 ± 2 mΩ m2) due to the better mitigation of pH imbalances between the electrodes by using the AEM and zero-gap electrodes. Performance was benchmarked against a higher buffer concentration (50 mM) solution which showed that the maximum power density with additional buffering increased to 2.88 ± 0.02 W m–2. These results show that MFCs designed for selective hydroxide ion transport will enable improved power production even in low conductivity and poorly buffered solutions such as domestic and industrial wastewater.
Bibliographical noteKAUST Repository Item: Exported on 2021-02-10
Acknowledgements: The authors acknowledge funding by the Environmental Security Technology Certification Program via cooperative research agreement W9132T-16-2-0014 through the US Army Engineer Research and Development Center and funding by the Pennsylvania State University.