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Polymer electrolyte fuel cell
| Details |
Inventors: Hirano, Shinichi; Fujikawa, Futoshi;
Assignee: Mazda Motor Corporation (Hiroshima-ken, JP)
Primary Examiner: Valentine; Donald R.
Assistant Examiner:
Attorney, Agent or Firm: Nixon Peabody LLP, Studebaker; Donald R.
A polymer electrolyte fuel cell comprising a polymer electrolyte membrane, an anode catalytic electrode disposed at one side of the polymer electrolyte membrane, a fuel gas being supplied to the anode catalytic electrode, a cathode electrode disposed at another side of the polymer electrolyte, an oxidation gas being supplied to the cathode catalytic electrode, control means for controlling a reduction amount of water from the cathode electrode accompanying with the oxidation gas to a sum of a water amount increased at the cathode electrode transported from the anode electrode through the polymer electrolyte membrane during a redox reaction of the fuel cell and a water amount produced by an oxidation reaction in the cathode electrode. A compact fuel cell system with a high cell performance can be accomplished. |
|
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG.
3, there are shown relationships between the water transportation amount J.
sub.
M, the maximum water supply amount J.
sub.
A(MAX) at the anode side and the maximum water amount J.
sub.
C(MAX) removed from the cathode side with regard to the temperature.
The water transportation amount was obtained based on the net flux of water per mole of electrons S which is cited from an article entitled as "a water transportation during an operation of the polymer electrolyte fuel cell" by Mizuhata et al.
Collections of Abstracts of The 61th Meeting of Electro-Chemical Association in 1994.
The value of S below 60.
degree.
C.
is substituted by the value S at 70.
degree.
C.
From these relationships, it is found that a desirable water balance in the fuel cell can be obtained at a temperature lower than about 80.
degree.
C.
, preferably at around 70.
degree.
C.
In this case, a temperature lower than about 50.
degree.
C.
would cause the dry out at the anode side due to the fact that the maximum water supply amount J.
sub.
A(MAX) at the anode side is less than the water transportation amount J.
sub.
M.
Thus, it is desirable to operate the fuel cell between about 50.
degree.
C.
and 80.
degree.
C.
Thickness of the polymer electrolyte membrane Referring to FIG.
4, it is shown a fuel cell output characteristics as the air supply amount and the operating condition are changed.
Membranes with the thickness of 100 and 50 .
mu.
m are employed.
The current density is 5 A/cm.
sup.
2 and the fuel cell output characteristics is provided as a cell output voltage for a single fuel cell structure.
According to FIG.
4, the membrane with 50 .
mu.
m thickness exerts a greater output voltage or as the membrane is thin, the fuel cell generates a greater voltage.
As the operating temperature increases, the cell performance is reduced.
This is because the dry out would occurs at the cathode side.
As aforementioned, it is easy to establish the water balance between the anode side and the cathode side as the membrane becomes thin
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MEMS 
