Fuel cell membrane electrode assemblies with improved power outputs and poison resistance
A fuel cell and electrode technology, which is applied to fuel cell parts, fuel cells, battery electrodes, etc., can solve the problems of fuel cells without teaching, explaining or proposing, achieve good inter-surface contact, improve power output, improve Effect of Poison Resistance
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[0182] normal processing
[0183] In each instance, unless otherwise stated, the ion-conducting membrane (proton exchange membrane, PEM) was approximately 20 microns thick. The membrane is a high Gurley number (>10000 sec) fully impregnated membrane, and was prepared by using perfluorinated sulfonic acid resin (FLEMION®, EW950) as described in U.S. Patent Nos. 5,547,551; 5,635,041 and 5,599,614 (to Bahar et al. Extended PTFE impregnated to formulate high ionic conductivity. This membrane is known as GORE-SELECT(R) and is available from W.L. Gore and Associates, Inc. (Elkton, MD). These patents are hereby incorporated by reference in their entirety.
[0184] Unless otherwise mentioned, electrodes comprising the first catalytically active metal were prepared as described above in Procedure A to generate the target metal loading. The electrode includes Pt supporting carbon, an ion-conducting polymer membrane, and a solvent. The electrode has a range from 0.05mg Pt / cm 2 to 0....
example 1
[0192] Example 1 illustrates an indirect method in which the second catalytically active metal region is first deposited on the substrate prior to transfer from the substrate to the membrane or electrode.
[0193] By EB-PVD, a 50 Å platinum coating area (0.01 mg / cm 2 ). The catalytic zone was then transferred to the membrane by decals, leaving a 50 Å catalytic layer bonded to one side of the membrane and centrally located. The membrane area calibrated by the transferred catalyst is the active area. Catalyzed electrodes (0.3 mg Pt / cm 2 ) are attached to each side of the catalytic membrane so as to cover the active area. Thus, one side of the MEA has a Z-gradient region at the membrane / electrode interface.
[0194] at 25cm 2 Active area fuel cell test fixtures or between gaskets in the cell are loaded with a 25cm 2 Active area of prepared MEA. This electrode containing the Z-gradient zone is placed towards the cathode where it will be in contact with the oxidant (air). ...
example 2
[0201] In this example, direct deposition of regions on electrodes was performed at two region thicknesses. Deposition is performed by EB-PVD. A catalyzed electrode with a deposited Z-gradient thereon had 0.1 mgPt / cm 2 load rate. For a sample, the deposition rate is 0.2-0.3 Å / sec to reach the 50 Å region (0.01mg Pt / cm 2 ). The second electrode is deposited at a rate of 0.1 Å / sec to reach the 5 Å region (0.001mgPt / cm 2 ). Contains 0.05mg / cm 2 An electrode (anode) was used in both samples.
[0202] The performance of the MEA was again estimated at cell pressures of 0 psig and 15 psig. In all experiments, the cells were operated at 65°C with hydrogen and air supplied at 0 psig and humidified to a 60°C dew point. The flow rates of hydrogen and air were set at 1.2 and 3.5 times, respectively, the stoichiometric values required to produce a given cell current output.
[0203] Figure 9 shows the improved power output at 0 psig. At 0.6V, the improvement in current density ...
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