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Research Papers

Analysis of a Permselective Membrane-Free Alkaline Direct Ethanol Fuel Cell

[+] Author and Article Information
Amir Faghri

e-mail: faghri@engr.uconn.edu

Department of Mechanical Engineering,
University of Connecticut,
Storrs, CT 06269

1Corresponding author.

Contributed by the Advanced Energy Systems Division of ASME for publication in the JOURNAL OF FUEL CELL SCIENCE AND TECHNOLOGY. Manuscript received August 5, 2013; final manuscript received October 22, 2013; published online December 5, 2013. Editor: Nigel M. Sammes.

J. Fuel Cell Sci. Technol 11(2), 021009 (Dec 05, 2013) (10 pages) Paper No: FC-13-1071; doi: 10.1115/1.4025931 History: Received August 05, 2013; Revised October 22, 2013

A physical model is developed to study the coupled mass and charge transport in a permselective membrane-free alkaline direct ethanol fuel cell. This type of fuel cell is not only free of expensive ion exchange membranes and platinum based catalysts, but also features a facile oxygen reduction reaction due to the presence of alkaline electrolyte. The proposed model is first validated by comparing its predictions to the experimental results from literature and then used to predict the overall performance of the cell and reveal the details of ion transport, distribution of electrolyte potential and current density. It is found that: (1) KOH concentration lower than 1 M notably impairs cell performance due to low electrolyte conductivity; (2) the concentration gradient and electrical field are equally important in driving ion transport in the electrolyte; (3) the current density distributions in the anode and cathode catalyst layers keep nonuniform due to different reasons. In the anode, it is caused by the ethanol concentration gradient, while in the cathode it is because of the electrolyte potential gradient; and (4) at low cell voltage, current density distribution in the catalyst layer shows stronger nonlinearity in the anode than in the cathode.

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References

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Figures

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Fig. 1

Structure of a PMF-ADEFC

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Fig. 2

Possible scenarios of electrolyte potential and electrolyte concentration distribution at the reservoir-ADL boundary

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Fig. 3

Comparison of the predictions by this study and the experimental results of Ref. [2] (CE,res = 2.4 M, CKOH,res = 1 M, ambient air, 313 K)

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Fig. 4

Influence of ethanol concentration on performance

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Fig. 5

Influence of KOH concentration on polarization

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Fig. 6

Overpotential breakdown

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Fig. 7

Distribution of ethanol concentration for various cell voltages

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Fig. 8

Distribution of oxygen concentration for various cell voltages

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Fig. 9

Distribution of normalized (a) oxidation reaction rate in the ACL and (b) reduction reaction rate in the CCL

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Fig. 10

Distribution of electrolyte potential

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Fig. 11

Distribution of KOH concentration

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Fig. 12

Diffusion and migration molar flux of (a) K+ and (b) OH ions under various voltages

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Fig. 13

Change of fuel utilization with different cell voltage

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Fig. 14

Influence of separator thickness

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