JP4884589B2 - Operation method of polymer electrolyte fuel cell - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for operating a polymer electrolyte fuel cell (hereinafter also referred to as PEFC).
[0002]
[Prior art]
A fuel cell obtains an electromotive force by a cell reaction that obtains water from hydrogen and oxygen. The raw material hydrogen is obtained by reacting raw fuel such as methanol and water in the presence of a reforming catalyst. Among such fuel cells, PEFC is attracting attention as being able to exhibit excellent performance.
Such PEFC is humidified in order to keep the water content in the polymer of the PEFC cell appropriate. However, the supplied humidified water condenses and stays in the PEFC cell, which inhibits the gas supply and causes deterioration of the cell, and there is a problem in properly supplying the humidified water. .
That is, if humidified water is supplied excessively, the amount of water condensation increases and the water tends to stay. On the other hand, when the humidified water is insufficient, the water content in the polymer of the PEFC cell is reduced, and the proton transfer resistance is increased, leading to a decrease in performance of the PEFC cell.
Therefore, there has been a demand for an improvement that appropriately controls such agglomeration and retention of water, maintains a PEFC cell well, and operates the PEFC stably.
[0003]
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and provides a method for operating a polymer electrolyte fuel cell in which the aggregation and retention of water is appropriately controlled and the PEFC cell can be stably operated. The purpose is to do.
[0004]
[Means for Solving the Problems]
As a result of intensive studies to achieve the above object, the present inventors have found that the thickness of the ion exchange membrane used in the PEFC cell, the operating temperature of the PEFC cell, the humidity of the fuel gas (water content), the humidity of the air ( By setting the five parameters of moisture content) and temperature distribution in the groove length direction to the optimized ranges in relation to each other, water does not coagulate and stay in the polymer in the PEFC cell due to lack of humidified water. It has been found that the fuel cell can be operated while maintaining high performance without reducing the water content.
[0005]
That is, in order to achieve the above object, the present invention provides a method for operating a polymer electrolyte fuel cell, wherein the film thickness of the polymer membrane is controlled to be 30 μm or more and less than 100 μm, the cell temperature is controlled to be constant throughout the cell, When the humidity at the temperature is 100%, the relative humidity with respect to the cell temperature of the fuel gas is Y%, and the relative humidity with respect to the cell temperature of the air is X%, Y ≦ −3 / 10X + 140, Y ≧ −11 / 10X + 130, Y A range surrounded by ≦ 20X-270 and Y ≧ 20X-1600 was defined, and the humidity was controlled to be within these ranges .
[0006]
In another embodiment, the solid polymer fuel cell operation method according to the present invention is such that the film thickness of the polymer membrane is 10 μm or more and less than 30 μm, the cell temperature is controlled to be constant throughout the cell, and the operation cell temperature is When the humidity is 100%, the relative humidity with respect to the cell temperature of the fuel gas is Y%, and the relative humidity with respect to the cell temperature of the air is X%, Y ≦ −3 / 10X + 140, Y ≧ −9 / 10X + 100, Y ≦ 20X− 270, a range surrounded by Y ≧ 20X-1600 is defined, and the humidity is controlled to be within these ranges .
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the operation method of the PEFC according to the present invention will be described in more detail with reference to the accompanying drawings.
1 to 3 show an embodiment of PEFC operated by the PEFC operating method according to the present invention.
The PEFC 1 is composed of a cell 2, separators 3a and 3b disposed on both ends of the cell 2 to sandwich the cell 2, and a diffusion layer 4 disposed between the cell 2 and the separators 3a and 3b. Yes.
[0010]
The cell 2 includes a solid polymer film 5 and reaction layers 6 a and 6 b disposed on both sides of the film 5. The diffusion layer 4 includes a carbon paper 7 and a slurry layer 8 formed on one main surface. A groove 9 for flowing hydrogen gas is formed in the cell of the separator 3a, and a groove 10 for flowing air is formed in the other separator 3b.
[0011]
The cell 2 will be described more specifically. As shown in FIG. 2, the reaction layer 6a includes a fuel electrode 11 and, for example, a platinum catalyst layer 12 formed on the solid polymer film 5 side. The reaction layer 6b includes an air electrode 13 and, for example, a platinum catalyst layer 12 formed on the solid polymer film 5 side. Here, the following reaction is performed in the fuel electrode 11 and the air electrode 13.
[0012]
The following reaction is caused to occur in the fuel electrode 11 by the platinum catalyst layer 12.
H ₂ → 2H ⁺ + 2e ⁻
H ⁺ produced by this reaction diffuses.
On the other hand, the platinum catalyst layer 12 causes the following reaction in the air electrode 13.
2H ⁺ + 2e- + 1 / 2O ₂ → H ₂ O
A battery reaction is constituted by combining these reactions, and an electromotive force can be obtained.
[0013]
This reaction will be further described with reference to the configuration of FIGS.
First, fuel gas (hydrogen-containing gas, hydrogen gas) passes through the diffusion layer 4. Then, hydrogen ions (cations) are generated at the fuel electrode 11 of the reaction layer 6a. The hydrogen ions move through the solid polymer film 5 to the air electrode 13 of the reaction layer 6b. At the air electrode 13, hydrogen ions react with oxygen in the air (oxygen-containing gas, oxidant) to generate water.
[0014]
In this PEFC, the planar shape of the separator 3a (or 3b) is such that grooves are formed in a meandering shape as shown in FIG. That is, in the present embodiment, for example, when hydrogen gas is sent from the introduction hole 14 at the corner of the separator 3a to the discharge hole 15 on the diagonal line, the direction of the gas is changed a plurality of times. In addition, although it is 3 times in FIG. 3, the frequency | count of changing is not specifically limited.
[0015]
In the PEFC of the embodiment as described above, water is generated at the same time as power is obtained as described above, so that this does not stay, and the moisture content in the cell is appropriately maintained to appropriately control the proton migration resistance. Need to keep.
Hereinafter, an embodiment of an operation method for appropriately operating a PEFC obtained as a result of intensive studies by the present inventors will be described. According to the following embodiments, the water content in the cell is appropriately maintained, and the electromotive force can be maintained well.
[0016]
First Embodiment In the method of operating a solid polymer fuel cell, the present inventors controlled the film thickness of the solid polymer film to be 30 μm or more and less than 100 μm and the cell temperature to be constant throughout the cell. When the humidity at the operating cell temperature is 100%, the relative humidity with respect to the cell temperature of the fuel gas is Y%, and the relative humidity with respect to the cell temperature of the air is X%, Y ≦ −3 / 10X + 140, Y ≧ −11 / It has been found as an appropriate control method to control the humidity so that it is in a range surrounded by 10X + 130, Y ≦ 20X-270, and Y ≧ 20X-1600.
[0017]
Here, the fuel gas is a concept including a hydrogen-containing gas and a hydrogen gas. In addition, the expression “air” can be replaced with oxygen or an oxygen-containing gas. The same applies to other descriptions in the present specification.
In order to control the humidity within the above range, it is possible to adjust the temperature of the humidifying pot or the amount of steam added by the injector according to the gas temperature using a humidifying pot or a steam producing device and an injector. .
[0018]
FIG. 4 shows the result of appropriately controlling the water content in the cell by implementing the first embodiment and the result of appropriately controlling the water content in the cell outside the range of the first embodiment. In comparison with
As shown in the figure, the following was confirmed.
(1) In the range where Y ≦ −3 / 10X + 140 (dotted line (1) in the figure) is deviated, the voltage drop was within 4%. It will lead to cell damage.
(2) In the range where Y ≧ −11 / 10X + 130 (one-dot chain line (2) in the figure), the water retention phenomenon did not occur, but the water content of the solid polymer component and the solid polymer film in the electrode decreased. The voltage drop exceeded 4% due to the lower ionic conductivity.
(3) If Y ≦ 20X-270 (dot-dash line (3) in the figure) is deviated, there is no water pool phenomenon, but the water content of the solid polymer component and the solid polymer film in the electrode is reduced, and the ionic conductivity The voltage drop exceeded 4% due to the low nature.
(4) Y ≧ 20X-1600 (dotted line (4) in the figure) The voltage drop was within 4%. However, the phenomenon of water retention occurred and the uniform gas supply to the electrode was hindered, leading to cell damage.
(5) The region surrounded by the lines {circle around (1)} to {circle around (4)} according to the present embodiment showed good power generation characteristics.
From the above, in the operation method according to the present embodiment, it is understood that the parameters are in a range optimized in relation to each other.
[0019]
Second embodiment In the operation method of the polymer electrolyte fuel cell, the present inventors controlled the film thickness of the polymer film to 10 μm or more and less than 30 μm, the cell temperature to be constant throughout the cell, When the humidity at the operating cell temperature is 100%, the relative humidity with respect to the fuel gas cell temperature is Y%, and the relative humidity with respect to the air cell temperature is X%, Y ≦ −3 / 10X + 140, Y ≧ −9 / 10X + 100 , Y ≦ 20X-270, Y ≧ 20X-1600, it was found as an appropriate control method to control the humidity so that it is in the range surrounded.
[0020]
In order to control the humidity within the above range, it is possible to adjust the temperature of the humidifying pot or the amount of steam added by the injector according to the gas temperature using a humidifying pot or a steam producing device and an injector. .
[0021]
FIG. 5 shows the result of appropriately controlling the water content in the cell by implementing the second embodiment and the result of appropriately controlling the water content in the cell outside the range of the second embodiment. In comparison with
As shown in the figure, the following was confirmed.
(1) In the range where Y ≦ −3 / 10X + 140 (dotted line (1) in the figure) is deviated, the voltage drop was within 4%. It will lead to cell damage.
(2) In the range where Y ≧ −9 / 10X + 100 (one-dot chain line (2) in the figure), there was no water retention phenomenon, but the water content of the solid polymer component and the solid polymer film in the electrode decreased. The voltage drop exceeded 4% due to the lower ionic conductivity.
(3) If Y ≦ 20X-270 (dot-dash line (3) in the figure) is deviated, there is no water pool phenomenon, but the water content of the solid polymer component and the solid polymer film in the electrode is reduced, and the ionic conductivity The voltage drop exceeded 4% due to the low nature.
(4) Y ≧ 20X-1600 (dotted line (4) in the figure) The voltage drop was within 4%. However, the phenomenon of water retention occurred and the uniform gas supply to the electrode was hindered, leading to cell damage.
(5) The region surrounded by the lines {circle around (1)} to {circle around (4)} according to the present embodiment showed good power generation characteristics.
From the above, in the operation method according to the present embodiment, it is understood that the parameters are in a range optimized in relation to each other.
[0028]
【Effect of the invention】
As is clear from the above, according to the present invention, there is provided a method for operating a polymer electrolyte fuel cell that appropriately controls the aggregation and retention of water and enables the PEFC cell to operate stably. Is done.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view conceptually showing an embodiment of a PEFC that implements a PEFC operating method according to the present invention.
FIG. 2 is a conceptual diagram for explaining the power generation principle of a PEFC that implements the PEFC operation method according to the present invention.
FIG. 3 is a plan view for explaining a cell structure in one embodiment of PEFC for carrying out the PEFC operation method according to the present invention.
FIG. 4 is a graph showing the optimum control range of the first embodiment for the PEFC operation method according to the present invention.
FIG. 5 is a graph showing the optimum control range of the second embodiment for the PEFC operation method according to the present invention.

Claims (2)

The film thickness of the polymer film is 30 μm or more and less than 100 μm, the cell temperature is controlled to be constant throughout the cell, the humidity at the operating cell temperature is 100%, the relative humidity of the fuel gas to the cell temperature is Y%, and the air cell When the relative humidity with respect to the temperature is X%, a range surrounded by Y ≦ −3 / 10X + 140, Y ≧ −11 / 10X + 130, Y ≦ 20X−270, Y ≧ 20X-1600 is defined, and these ranges are set. A method for operating a polymer electrolyte fuel cell, characterized by controlling humidity. The film thickness of the polymer film is 10 μm or more and less than 30 μm, the cell temperature is controlled to be constant throughout the cell, the humidity at the operating cell temperature is 100%, the relative humidity of the fuel gas to the cell temperature is Y%, and the air cell When the relative humidity with respect to the temperature is X%, a range surrounded by Y ≦ −3 / 10X + 140, Y ≧ −9 / 10X + 100, Y ≦ 20X-270, Y ≧ 20X-1600 is defined, and these ranges are set. A method for operating a polymer electrolyte fuel cell, characterized by controlling humidity.

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