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Research Papers

Water Transport in a PEMFC Based on the Difference in Capillary Pressure Between the Cathode Catalyst Layer and Microporous Layer

[+] Author and Article Information
Enju Nishiyama

Department of Electrical and Electronic Engineering,
Fukui University of Technology,
3-6-1 Gakuen,
Fukui, Fukui 910-9409, Japan
e-mail: jp2e-nsym@asahi-net.or.jp

Masaya Hara

Department of Electrical and Electronic Engineering,
Fukui University of Technology,
3-6-1 Gakuen,
Fukui, Fukui 910-9409, Japan
e-mail: toraneko0523@gmail.com

Toshiaki Murahashi

Department of Electrical and Electronic Engineering,
Fukui University of Technology,
3-6-1 Gakuen,
Fukui, Fukui 910-9409, Japan
e-mail: murahashits@eva.hi-ho.ne.jp

Kazushige Nakao

Department of Electrical and Electronic Engineering,
Fukui University of Technology,
3-6-1 Gakuen,
Fukui, Fukui 910-9409, Japan
e-mail: nakao@fukui-ut.ac.jp

Contributed by the Advanced Energy Systems Division of ASME for publication in the JOURNAL OF FUEL CELL SCIENCE AND TECHNOLOGY. Manuscript received January 21, 2014; final manuscript received October 11, 2015; published online October 27, 2015. Assoc. Editor: Abel Hernandez-Guerrero.

J. Fuel Cell Sci. Technol 12(5), 051005 (Oct 27, 2015) (7 pages) Paper No: FC-14-1009; doi: 10.1115/1.4031774 History: Received January 21, 2014; Revised October 11, 2015

The water transport behavior of the cathode catalyst layer (CCL) in a proton exchange membrane fuel cell (PEMFC) was investigated by comparing the performance of several cells containing different microporous layers (MPLs). The capillary pressure and effective diffusivity of the cathode gas diffusion layer (GDL) and the CCL play an important role in the transport of water generated in the PEMFC. Experimental data for various inlet humidities and air stoichiometries were evaluated using the modified water vapor activity with the capillary pressure of the MPL. The capillary pressures in the MPLs and CCL are approximated using a polynomial function of liquid saturation. There was a significant increase in the diffusion resistance of oxygen in the CCL, while that in the MPLs and CCL was moderate, which indicates that the CCL is susceptible to flooding.

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References

Figures

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Fig. 1

SEM images of MPL surfaces for cells (b)–(d)

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Fig. 2

I–V characteristics and O2 gains for different MPL configurations using dry inlet air (Tcell = 70 °C, RHa/RHc = 64%/0, and ξa/ξf = 2.0/1.43). The cathode GDL properties of cells (a)–(d) are given in Table 1.

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Fig. 3

I–V characteristics and O2 gains for different MPL configurations using wet inlet air (Tcell = 70 °C, RHa/RHc = 64/64%, and ξa/ξf = 2.0/1.43). The cathode GDL properties of cells (a)–(d) are given in Table 1.

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Fig. 4

Cell output voltage and internal resistance versus oxygen stoichiometry for dry (solid line: Tcell = 70 °C and RHa/RHc = 64/0%) and wet (dotted line: Tcell = 70 °C and RHa/RHc = 64/64%) inlet air conditions. The cathode GDL properties of cells (a) and (b) are given in Table 1.

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Fig. 5

Relation between capillary pressure and liquid saturation for MPLs and CCLs. For simplicity, only the MPL curve for cell (b) is shown. The saturation levels for MPL and CCL are marked as slmpl and slccl, respectively. Balance of Pc and sl between MPLs and CCL is shown as horizontal lines in the case of slmpl = 0.045. If the contact angle of CCL is 91.4 deg, then slccl for cells (b)–(d) corresponds to 0.73, 0.66, and 0.79, respectively.

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Fig. 6

Change in the gas diffusion resistance and cathode overpotentials as a function of current density for an MPL, GDL, and CCL

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Fig. 7

Schematic diagram of the model for the GDL, MPL, and CCL

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Fig. 8

Comparison of the experimental and calculated cell output voltages for dry and wet inlet conditions (Tcell = 70 °C, iav = 0.3 A cm −2, RHa = 64%, and ξf = 1.43). Experimental (▪, RHc = 64%, curve e; •, RHc = 0%, curve f). Calculated (, RHc = 0%, curve d; □ (θc = 91.5 deg), curve a; □ (θc = 91.4 deg), curve b; □ (θc = 91.3 deg), RHc = 64%, curve c).

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Fig. 9

Cell voltage versus water activity for dry and wet inlet air conditions (Tcell = 70 °C, RHa = 64%, iav = 0.3 A cm − 2, and ξf = 1.43). The solid vertical line for water activity ac of 1.04 represents the onset of flooding in cell (b). Curves (a) and (b) show the calculated cell output voltages for cells (a) and (b), respectively, under wet inlet air conditions.

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