Journal of The Electrochemical Society, 156 ͑1͒ B16-B21 ͑2009͒
B21
Greek
the greater increase in pressure-driven flux of water through the
membrane with increasing pressure differential than water diffusion
due to an increase in the temperature.
␦
M
thickness of the catalyst coated membrane, cm
water content of the membrane on the anode side
water content of the membrane on the cathode side
a
c
Conclusions
3
M
density of Nafion, g/cm
We have developed a mathematical model, in conjunction with
experimental data, to predict water transport in a PEM electrolyzer
References
1
2
3
4
5
. M. A. Rosen, Int. J. Hydrogen Energy, 21, 349 ͑1996͒.
. M. A. Rosen and D. S. Scott, Int. J. Hydrogen Energy, 23, 653 ͑1998͒.
. M. A. Rosen, Int. J. Hydrogen Energy, 20, 547 ͑1995͒.
. S. Z. Baykara, Int. J. Hydrogen Energy, 29, 1451 ͑2004͒.
. E. Varkaraki, N. Lymberopoulos, E. Zoulias, D. Guichardot, and G. Poli, Int. J.
Hydrogen Energy, 32, 1589 ͑2007͒.
. M. B. Gorensek, Paper presented at the AIChE Spring 2005 Meeting, Session 73,
April 11, 2005.
. Y. Shin, W. Park, J. Chang, and J. Park, Int. J. Hydrogen Energy, 32, 1486 ͑2007͒.
. J. S. Herring, J. E. O’Brien, C. M. Stoots, G. L. Hawkes, J. J. Hartvigsen, and M.
Shahnam, Int. J. Hydrogen Energy, 32, 440 ͑2007͒.
9. Department of Energy ͑DOE͒ Energy Information Administration, Hydrogen Use,
Petroleum Consumption and Carbon Dioxide Emissions, Washington, DC ͑2008͒.
0. Nuclear Hydrogen R&D Plan Draft, Department of Energy, Office of Nuclear
Energy, Science and Technology, 2004.
fed with gaseous SO . We predicted the combined effects of diffu-
2
sion, permeation, and electro-osmotic drag and show how these in-
fluence cell performance. We now understand how water transport
affects the sulfuric acid concentration, which influences the cell
voltage. There is a trade-off between low voltages ͑large water
transport͒ and high sulfuric acid concentrations ͑low water trans-
port͒ in that a higher sulfuric acid concentration is desired for down-
stream decomposition, but concentrated sulfuric acid increases the
cell voltage and hence the power required to drive the electrolyzer.
A full, system-level optimization is needed to determine the desired
electrolyzer operating conditions. The model developed here can aid
in this optimization. The model also reveals how the water transport
rate can be manipulated by independently varying design ͑e.g.,
membrane thickness͒ and operating conditions ͑e.g., temperature,
current, pressure differential͒.
6
7
8
1
1
1. Nuclear Hydrogen Initiative: Ten Year Program Plan, Office of Advanced Nuclear
Research, DOE Office of Nuclear Energy, Science and Technology, March 2005.
12. A. Hauch, S. H. Jensen, S. Ramousse, and M. Mogensen, J. Electrochem. Soc.,
1
53, A1741 ͑2006͒.
Acknowledgment
13. P. W. Lu, E. R. Garcia, and R. L. Ammon, J. Appl. Electrochem., 11, 347 ͑1981͒.
1
1
4. P. W. Lu and R. L. Ammon, J. Electrochem. Soc., 127, 2610 ͑1980͒.
5. P. Sivasubramanian, R. P. Ramasamy, F. J. Freire, C. E. Holland, and J. W.
Weidner, Int. J. Hydrogen Energy, 32, 463 ͑2007͒.
The authors thank the U.S. DOE for funding this work ͑grant no.
DE-FC07-06ID14752͒.
1
6. J. A. Staser, R. P. Ramasamy, P. Sivasubramanian, and J. W. Weidner, Electrochem.
University of South Carolina assisted in meeting the publication costs of
this article.
Solid-State Lett., 10, E17 ͑2007͒.
1
7. M. B. Gorensek and W. A. Summers, Int. J. Hydrogen Energy, In press. ͓DOI:
/
10.1016/j.ijhydene.2008.06.49͔.
1
1
2
8. F. Jomard, J. P. Feraud, and J. P. Caire, Int. J. Hydrogen Energy, 33, 1142 ͑2008͒.
9. P. Batamack and J. Fraissard, Catal. Lett., 49, 129 ͑1997͒.
0. S. Motupally, A. J. Becker, and J. W. Weidner, J. Electrochem. Soc., 149, D63
List of Symbols
2
A1,A2 pre-exponential factor in Eq. 7 and 8, respectively, cm /s
aw activity of water
͑
2002͒.
1. S. Motupally, A. J. Becker, and J. W. Weidner, J. Electrochem. Soc., 147, 1371
2000͒.
22. T. E. Springer, T. A. Zawodzinski, and S. Gottesfeld, J. Electrochem. Soc., 138,
334 ͑1991͒.
2
2
Dw,F Fickian diffusion coefficient of water, cm /s
͑
2
iH2SO4 current density, A/cm
MM molecular weight of membrane, g/mol
2
2
Nw flux of water, mol/cm s
23. T. A. Zawodzinski, T. E. Springer, J. Davey, R. Jestel, C. Lopez, J. Valerio, and S.
⌬
P
pressure differential across the membrane, kPa
Gottesfeld, J. Electrochem. Soc., 140, 1981 ͑1993͒.
PM membrane permeability, mol/cm s/kPa
24. Y. W. Rhee, S. Y. Ha, and R. I. Masel, J. Power Sources, 117, 35 ͑2003͒.
25. F. F. Stewart and C. J. Orme, Annual Meeting of the American Institute of Chemi-
cal Engineers, Nov. 2006.
T
x
temperature, K
distance perpendicular to the membrane, cm