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1) As known, when the start and stop of the fuel cell are repeated, the platinum catalyst in the cathode (oxygen electrode) is dissolved as Pt ions. The Pt ions diffuse from the cathode into the polymer electrolyte membrane (PEM) and deposits inside the PEM. The platinum deposition inside PEM deteriorates the performances of the MEA, resulting in increase of the internal resistance of the fuel cell and decrease of the output power of the fuel cell. Hitachi Maxell has solved this problem by creating a metal ion trapping agent which is capable of trapping the Pt ions, and adding it to the cathode. The metal ion trapping agent added to the cathode successfully suppresses Pt deposition inside PEM (see figure). This technology was presented in "The 48th Battery Symposium in Japan.
2) The current fuel cell has another problem. When the fuel cell stops, hydrogen and oxygen coexist in the anode. The fact leads to oxidation of the cathode carbon of the cathode which supports the platinum catalyst. The carbon oxidation leads to deterioration of the MEA performances. Hitachi Maxell has solved the problem by developing a new technology to remove the hydrogen from the anode.
The technology succeeds in completely suppressing the carbon oxidation.

Platinum Dissolving:
The amount of the dissolved platinum (Pt ions) increases when start/stop operations of the fuel cell are repeated, the pt ions
deposit again in the cathode, and also deposits in the Polymer Electrolyte Membrane (PEM). The platinum deposited in the cathode will contribute again to the power generation reaction. The platinum deposited in the PEM never contributes to the power generation reaction, however. More adversely, the platinum deposited in the PEM impedes the hydrogen ion conduction of the PEM. This results in increase of the internal resistance of the fuel cell and lowering of the output power of the cell. In the fields of the vehicle and residential fuel cells, the methods to cope with the problem have been applied to the entire fuel cell system. For example, the hydrogen purge and/or the nitrogen purge are carried out to remove the oxygen from the cathode every time the cell is stopped. In the field of the fuel cells for mobile devices, the measures having been taken are still in unsatisfactory levels since the device size is small. In those devices, a frequency of the occurrence of the power generation stops is also high. This results in producing a remarkable amount of Pt ions. As described above, Hitachi Maxell has succeeded in considerably lessening the MEA performance deterioration, which is due to the dissolution of the platinum as the catalyst, and substantially completely suppressing the carbon oxidation in the cathode. As a result, the MEA life is substantially extended and the continuous run of the fuel cell of 4,000 hours or over is achieved. Incidentally, Hitachi Maxell is making efforts of commercializing the small PEFC using a hydrogen generator, which is based on aluminum and water. The PEFC will be used for 10 to 100 W power sources in use for mobiles devices for emergency and outdoor uses.

Source: Press release from Hitachi Maxell

Keywords: metal ion trapping agent, platinum dissolving, platinum catalyst, cathode, oxygen electrode, MEA, PEM, carbon oxidation, MEA life, 4,000 hours, Hitachi Maxell