Current Density (mA/cm*)

Current Density (mA/cm*)

Figure 3. Comparison of PEMFC Performance of PtRuPc/vulcan with State-of-the-Art catalysts.

a terminal voltage of 610 mV. In comparison to this, the fuel cell built with a 15% (Pt-RuPc)n /Vulcan anode and a 20% Pt/Vulcan cathode has a terminal voltage only 60 mV lower, namely 550 mV vi 610 mV. We have also evaluated the performance of the cobalt transition metal phthalocycanine complex ((CoPc)„) on heat treated Black Peal 2000. The catalyst exhibits good catalytic activity for hydrogen oxidation. Further studies of these nonprecious metal macrocyclic complexes are currently in progress and the data will be reported in future publications.

The stability characteristics of a PEM fuel cell using a 40 cm2 MEA composed of a 15% (Pt-RuPc)„/Vulcan anode and a 20% Pt/Vulcan cathode were evaluated at 80°C and 500 mA/cmJ. In Figure 4 the terminal voltage as a function of time for continuous operation over 800 hours is shown. As seen, the voltage observed is relatively constant at about 600 mV. The minor variations in voltage are attributed to changes in the degree of membrane hydration. A second cell was built and tested under similar conditions in order to evaluate the performance reproducibility. This cell was continuously operated at 500 mA/cm2 for 102 hours and was then shutdown for 48 hours. The cell was then restarted and the testing continued for another 98 hours, for a total testing time of200 hours. It should be noted that this discontinuous operation of the cell did not adversely affect its performance. The cell also displayed stable operating characteristics, and this can be seen in the polarization behavior of this cell measured before and after 200 hours of operation. These results are shown in Figure 5 on the following page. One thing that can be seen upon examination of this data is that fuel cell terminal voltage has increased after operation. This improved performance could be the result of increased hydration of the assembly.

Studies of the effect of carbon monoxide contamination of the fuel have been initiated. Preliminary results have shown voltage drops of 25mV, 30mV, and 325mV for CO levels of lOppm, 20ppm, and lOOppm in the H2 fuel, respectively. Los Alamos National Laboratory (LANL) has reported (7) values of 90mV and 390-400mV for CO levels of 5ppm and 20ppm, respectively. No results were reported at higher CO levels. The LANL results were obtained using Pt/Vulcan anode formed into a thin-film having a Pt loading of 0.14 mg/cm2. This is four times the noble metal loading of the s

(PtRuPc)„/Vulcan. We believe that the voltage drop in the (Pt-RuPq) /Vulcan can be reduced by optimization of the electrode, including removal of the small amounts of uncomplexed noble metal which could be present. Future work will be made on pure (Pt-RuPc)„ complex catalyst.

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