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Title: Microbial Fuel Cell Performance with a Pressurized Cathode Chamber

Author
item FORNERO, JEFFREY - WASHINGTON UNIV
item Rosenbaum, Miriam
item Cotta, Michael
item ANGENENT, LARGUS - WASHINGTON UNIV

Submitted to: Environmental Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/25/2008
Publication Date: 10/1/2008
Citation: Fornero, J.J., Rosenbaum, M., Cotta, M.A., Angenent, L.T. 2008. Microbial Fuel Cell Performance with a Pressurized Cathode Chamber. Environmental Science and Technology. 42(22):8578-8584.

Interpretive Summary: Interest in the production of hydrogen to power engines and/or fuel cells has increased markedly in recent years in response to concerns over the high cost and limited supply of petroleum. Currently, hydrogen is produced from fossil fuels like natural gas and petroleum. Hydrogen can also be produced by fermentation of a wide variety of agricultural materials, but current technologies suffer from low yields and productivity. An alternative biological approach would be to use microbial fuel cells (MFCs) modified to produce hydrogen which would overcome the limitations imposed using fermentation. MFC power densities are often constrained by the oxygen reduction reaction rate on the cathode electrode. One important factor for this is the normally low solubility of oxygen in the aqueous cathode solution creating mass transport limitations, which hinder oxygen reduction at the electrocatalyst (platinum, Pt). Here, we pressurized the cathode chamber to increase the solubility of air and consequently the availability of oxygen, which is a function of the partial pressure. Increasing the cathode pressure above atmospheric pressure (17.24 kPa) resulted in a 69.9% increase in the power density. Results from this study demonstrate that higher MFC power densities can be realized by increasing the cathode air pressure and point forward to a MFC design that can exploit this capability.

Technical Abstract: Microbial fuel cell (MFC) power densities are often constrained by the oxygen reduction reaction rate on the cathode electrode. One important factor for this is the normally low solubility of oxygen in the aqueous cathode solution creating mass transport limitations, which hinder oxygen reduction at the electrocatalyst (platinum, Pt). Here, we pressurized the cathode chamber to increase the solubility of air and consequently the availability of oxygen, which is a function of the partial pressure. Under stable anode and cathode conditions, a MFC was tested with an anion exchange membrane (AEM) and a cation exchange membrane (CEM) at atmospheric pressure, +17.24 kPa (2.5 psig) and +34.48 kPa (5.0 psig) overpressure of air. The cell potential at an external resistance of 100 ohms increased from 0.423 V to 0.553 V by increasing the cathode pressure from atmospheric pressure to 17.24 kPa for a MFC with AEM, and this resulted in a 69.9% increase in the power density (4.29 versus 7.29 W/m3). In addition, the MFC produced 65-108% more power with AEM in comparison to CEM under the same operating conditions. Results from this study demonstrate that higher MFC power densities can be realized by increasing the cathode air pressure and point forward to a MFC design that can exploit this capability.