Polymer coatings as separator layers for microbial fuel cell cathodes

Type
Article

Authors
Watson, Valerie J.
Saito, Tomonori
Hickner, Michael A.
Logan, Bruce E.

KAUST Grant Number
KUS-I1-003-13

Date
2011-03

Abstract
Membrane separators reduce oxygen flux from the cathode into the anolyte in microbial fuel cells (MFCs), but water accumulation and pH gradients between the separator and cathode reduces performance. Air cathodes were spray-coated (water-facing side) with anion exchange, cation exchange, and neutral polymer coatings of different thicknesses to incorporate the separator into the cathode. The anion exchange polymer coating resulted in greater power density (1167 ± 135 mW m-2) than a cation exchange coating (439 ± 2 mW m-2). This power output was similar to that produced by a Nafion-coated cathode (1114 ± 174 mW m-2), and slightly lower than the uncoated cathode (1384 ± 82 mW m-2). Thicker coatings reduced oxygen diffusion into the electrolyte and increased coulombic efficiency (CE = 56-64%) relative to an uncoated cathode (29 ± 8%), but decreased power production (255-574 mW m-2). Electrochemical characterization of the cathodes ex situ to the MFC showed that the cathodes with the lowest charge transfer resistance and the highest oxygen reduction activity produced the most power in MFC tests. The results on hydrophilic cathode separator layers revealed a trade off between power and CE. Cathodes coated with a thin coating of anion exchange polymer show promise for controlling oxygen transfer while minimally affecting power production. © 2010 Elsevier B.V. All rights reserved.

Citation
Watson VJ, Saito T, Hickner MA, Logan BE (2011) Polymer coatings as separator layers for microbial fuel cell cathodes. Journal of Power Sources 196: 3009–3014. Available: http://dx.doi.org/10.1016/j.jpowsour.2010.11.105.

Acknowledgements
This research was supported under a National Science Foundation Graduate Research Fellowship, National Science Foundation Grant CBET-0730359, and the King Abdullah University of Science and Technology (KAUST) (Award KUS-I1-003-13). Thanks to Solvay Advanced Polymers for the donation of Radel (R) and Udel (R) polymer and to Justin Tokash for insights into EIS theory and application.

Publisher
Elsevier BV

Journal
Journal of Power Sources

DOI
10.1016/j.jpowsour.2010.11.105

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