Results

The performance data were obtained in the form of current-potential relationships under various experimental conditions. All cells and stacks operate in self-humidified mode with dry reactants. Figure 1 shows the performance of a 50 cm2 fuel cell operated with air at 2.35 atm at two different Pt loadings. The performance achieved was 0.716 V and 0.756 V at 0.5 A-cm'2 for 0.5 and 1.0 mg-cm"2 of Pt catalyst, respectively. This cell is based on Nafion 1100 electrolyte deposit technology. Other experimental conditions are given in the figure's caption. Figure 2 shows similar data obtained with larger, 108 cm2 cell based on Nafion 115 membrane. Presented graph shows the performance of such cell with both, air and oxygen, at the atmospheric pressure. Figure 3 and Figure 4 show similar data to the above, but obtained for the three- and four-cell stacks, respectively. Complementing Figure 5 presents stability data collected from somewhat smaller cell of 25 cm2 active area for few different current densities.

The presented data show that self-humidification phenomena is not limited to small fuel cell units, but can easily be incorporated into larger fuel cells and stacks. It's worth to note that performance is not sacrificed. On the contrary, the technology allows not only to take advantage of the cell simplification (the absence of humidification unit and associated auxiliaries) but also achieve vety high performance levels.

1. H. P. Dhar. 29th IECEC Conference Proceedings, Monterey, CA, Aug. 7-11,1994. Vol. 2, pp. 865-870.

2. K. A. Lewinski and H. P. Dhar, Report Submitted to National Science Foundation (NSF), Arlington, VA, Contract U DMI-9460292, 1995.

3. H. P. Dhar, U.S. Patent Nos. 5,242,764 (1993) and 5,318,863 (1994).

4. M. Watanabe, H. Uchida, Y. Seki, and M. Emori. Extended Abstract No. 606. Electrochemical Society Meeting. October 9-14, 1994. Miami Beach, FL.

5. A. Cisar, A. Gonzalez-Martin, O. J. Murphy, S. F. Simpson, and C. Salinas. 30th IECEC Conference Proceedings, Lake Buena Vista, FL, July 30-Aug. 4, 1995.

6. M. Watanabe, Y. Satoh, and C. Shimura. J. Electrochem. Soc. 140, (1993), 3190-3193.

Figure 1. Fuel cell performance with Pt loading of 0.5 and 1.0 mg-cm'2 (lower and higher curve, respectively). Experimental conditions: electrolyte. Nafion 1100 deposit; electrolyte loading, 10 mg-cm'2; temperature, 50°C; electrode active area, 50 cm2; air as the oxidant at 2.35 atm pressure.

Current Density I A*cm~

Figure 1. Fuel cell performance with Pt loading of 0.5 and 1.0 mg-cm'2 (lower and higher curve, respectively). Experimental conditions: electrolyte. Nafion 1100 deposit; electrolyte loading, 10 mg-cm'2; temperature, 50°C; electrode active area, 50 cm2; air as the oxidant at 2.35 atm pressure.

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