JP2006331731A - Film-electrode assembly and polymer electrolyte fuel cell using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem of a film-electrode assembly that a calculation on simulation is carried out, a thermocouple is put on a gas flow passage, or temperature is measured by using a thermography for measuring in face temperature of the film electrode assembly of a polymer electrolyte fuel cell, but the temperature of the inside of the film-electrode assembly where actually the reaction is generated can not be measured accurately. <P>SOLUTION: A temperature measuring sensor is embedded in the film-electrode assembly of the solid electrode type fuel cell composed of an anode electrode and a cathode electrode arranged in opposition to each other through an electrolyte film, and a pair of catalyst layer containing electrolyte arranged on the anode electrode and the cathode electrode respectively. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a membrane-electrode assembly particularly suitably used for a polymer electrolyte fuel cell or the like provided with a temperature measuring sensor, a polymer electrolyte fuel cell using the same, a fuel cell evaluation method using the same, and the same The present invention relates to a fuel cell system using

  The fuel cell is attracting attention as a power generation system that directly converts the energy of the fuel into electricity, and has been rapidly developed both at home and abroad. The fuel cell has the advantage of not polluting the environment because the product of power generation is only water. For example, attempts are being made to use it for household cogeneration and automobile driving power. .

For example, in the case of a polymer electrolyte fuel cell, the electrode reaction of the fuel cell is H ₂ → 2H ⁺ + 2e ⁻ at the anode electrode and 1 / 2O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O at the cathode electrode. The standard potential E ₀ obtained from the Gibbs free energy of the water production reaction is 1.23 V. The voltage actually generated decreases as the current increases, and this voltage decrease is called polarization. The polarization component that is not converted into electrical energy becomes thermal energy.

  As described above, since the fuel cell generates heat during operation, it needs to be cooled in order to maintain the fuel cell in a good operating state. In a fuel cell stack, a method of inserting a cooling plate for circulating a cooling medium every few cells is common.

  For the problem that a high temperature part (about 85 ° C) and a low temperature part (about 75 ° C) are generated in the cell surface depending on the flow direction of the cooling medium, the oxidizing gas flow direction is changed from the high temperature side to the low temperature side of the distribution in the cell surface. An example using a means such as installing in a direction to go is disclosed (see Patent Document 1).

Also, a fuel cell having a structure in which the temperature distribution in the surface direction generated in the oxidant gas supply groove and the temperature distribution in the surface direction generated in the cooling medium flow groove are orthogonal to each other is cited as an issue of in-plane temperature distribution. Yes. It is considered that it is very important to accurately grasp the in-plane temperature distribution of the fuel cell from these prior documents (see Patent Document 2).
JP 2002-42844 A JP 2002-289219 A

  In order to grasp the temperature distribution inside the cell, it is common to perform a simulation using parameters such as gas flow rate, gas flow path, and current value. In addition, a method of inserting a thermocouple into the gas flow path or measuring from the outside by thermography is also used.

  However, in the simulation, there is a problem that the amount of heat and temperature calculated by calculation do not necessarily match the actual conditions due to the influence of side reaction or deterioration phenomenon occurring in the cell. In addition, the external temperature measurement method such as thermocouple or thermography inserted into the gas flow path has the advantage that the electrode itself is not damaged, but it is greatly affected by the members that make up the cell and the stack, and the temperature inside the cell is reduced. There was a problem of not being able to measure. The present invention has been made to solve the above-described problems, and its object is to determine the in-plane temperature distribution of a membrane-electrode assembly of a polymer electrolyte fuel cell by using a membrane-electrode junction in which a reaction actually occurs. It is an object of the present invention to provide a membrane-electrode assembly that can be accurately grasped as the temperature inside the body, a fuel cell evaluation method using the membrane-electrode assembly, and a fuel cell system.

  In order to solve such a problem, a polymer electrolyte fuel cell of the present invention includes an anode electrode and a cathode electrode, which are disposed to face each other via an electrolyte membrane, and an electrolyte provided on each of the anode electrode and the cathode electrode. A membrane-electrode assembly of a polymer electrolyte fuel cell having a pair of gas diffusion electrodes each including a catalyst layer containing a temperature measurement sensor embedded in the membrane-electrode assembly It is characterized by.

  The membrane-electrode assembly according to claim 2 is characterized in that the temperature measurement sensor is embedded in the electrolyte membrane.

  In the membrane-electrode assembly according to claim 3, in order to solve the above-described problem, the temperature measurement sensor is provided between the catalyst layer, the gas diffusion layer, the catalyst layer and the electrolyte membrane, and between the catalyst layer and the diffusion layer. Embedded in at least one location selected from the group consisting of:

  According to the above configuration, for example, by embedding a temperature measurement sensor in the catalyst layer, a temperature change due to a reaction occurring inside the catalyst layer can be detected more accurately.

  The membrane-electrode assembly according to claim 4 is characterized in that the temperature measuring sensor is at least one detector selected from the group consisting of a thermocouple, a temperature measuring element, and a temperature measuring body.

  According to said structure, by selecting from this group, it becomes possible to measure the temperature inside a membrane-electrode assembly directly rather than from the outside of a membrane-electrode assembly.

  The membrane-electrode assembly according to claim 5 is characterized in that at least one of a diameter and a thickness of the temperature measurement sensor is smaller than an electrolyte film thickness in order to solve the above-described problem.

  In the above configuration, the diameter or thickness of the temperature measurement sensor is not particularly limited, but when considering a commonly used electrolyte film thickness, it is more than 0 and 100 μm or less, preferably more than 0 and 50 μm or less, more preferably 0. And not more than 25 μm.

  The membrane-electrolyte assembly according to claim 6 is characterized in that the surface of the temperature measurement sensor is covered with a corrosion-resistant insulating coating in order to solve the above-mentioned problems.

  In order to measure the temperature distribution during power generation of the fuel cell, the temperature measurement sensor needs to be electrically insulated. Further, since the electrolyte of the solid oxide fuel cell has proton conductivity, there is a concern that the acid strength is strong and corrodes. For the above reasons, it is desirable that the temperature measurement sensor is coated with a corrosion-resistant insulating coating. In order not to impair the accuracy of temperature measurement, it is desirable that the corrosion-resistant insulating coating is applied as thin as possible. Specifically, as the corrosion-resistant insulating coating material, for example, polyimide, PTFE (polytetrafluoroethylene), PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), PVdF (polyvinylidene fluoride), FEP ( And tetrafluoroethylene-hexafluoropropylene copolymer) and ETFE (tetrafluoroethylene-ethylene copolymer).

  In order to solve the above problems, a polymer electrolyte fuel cell according to a seventh aspect has the membrane-electrode assembly according to any one of the first to sixth aspects. When the polymer electrolyte fuel cell is configured as a stack, it is preferable to have at least one membrane-electrode assembly in which the temperature measurement sensor of the present invention is embedded.

  A fuel cell evaluation method according to an eighth aspect is characterized in that the membrane-electrode assembly according to the seventh aspect is used in order to solve the above-described problems.

  According to said structure, it is applicable to evaluation of the temperature rise part by deterioration phenomena, such as initial temperature distribution, the temperature distribution after an endurance test, and a cross leak.

  In order to solve the above problems, the fuel cell system according to claim 9 detects a temperature distribution of the fuel cell by the temperature measurement sensor, and includes a cell temperature, a gas flow rate, a gas pressure, a cooling water flow rate, and a current. It is characterized by adjusting at least one selected parameter.

  According to the above configuration, it is possible not only to control the operation of the fuel cell system but also to stop the fuel cell system urgently by detecting a rapid temperature rise in the cell.

  According to the present invention, the in-plane distribution of reactions occurring inside the fuel cell can be grasped in-situ using temperature as a parameter. For example, it is possible to detect where in the cell a temperature change due to a phenomenon other than the original fuel cell reaction, such as cross-leakage, by-product generation, reaction of mixed impurities, etc. Applicable. In addition, by embedding a temperature measurement sensor in the catalyst layer, diffusion layer, interface between the catalyst layer and the electrolyte membrane, interface between the catalyst layer and the diffusion layer, more detailed temperature measurement is possible. It is possible to guess the phenomenon that will occur. Furthermore, the fuel cell system itself can be controlled using the measured temperature, and the reliability of the fuel cell system can be improved.

  Hereinafter, a membrane-electrode assembly embedded with a temperature measurement sensor of the present invention and a fuel cell evaluation method using the same will be described with reference to the drawings. In addition, this invention is not limited to the following description, In the range which does not deviate from the summary of this invention, it can change suitably.

  FIG. 1 is an explanatory view showing the membrane-electrode assembly used in the present embodiment. The membrane-electrode assembly 4 includes a gas diffusion electrode 2 coated with a catalyst layer, an electrolyte membrane 3, and a temperature sensor 1 (temperature measurement sensor) embedded in the electrolyte membrane 3. The gas diffusion electrode used in the present embodiment was a substantially square with a size of 50 mm square, and Nafion (trade name) manufactured by Du Pont was used as the electrolyte membrane. The temperature sensor 1 has a diameter or thickness of 10 to 40 μm, and has a polyimide insulating coating on the surface.

  FIG. 2 shows temperature measurement points (measurement points) of the membrane-electrode assembly used in the present embodiment. In FIG. 2, nine temperature measurement points 5 are provided as indicated by numerals (1) to (9).

  FIG. 3 shows an external view when the membrane-electrode assembly in which the temperature sensor 1 is embedded is incorporated in the cell holder. The cell holder 10 includes a carbon plate 6, a clamping plate 7, a gas introduction port 8, a gas discharge port 9, and the like having a gas flow path on the surface. The membrane-electrode assembly 4 in which the temperature sensor 1 is embedded is sandwiched by a carbon plate 6 having a gas flow path on the surface, and is further sandwiched by a clamping plate 7. The reaction gas is introduced from the gas inlet 8 and the gas is discharged from the gas outlet 9, whereby the gas is allowed to flow through the cell and the electric current can be taken out to generate power.

In the present embodiment, Table 1 shows the temperature measurement results when the power generation test was performed at a cell temperature of about 60 ° C., an H ₂ utilization rate of 70%, an Air utilization rate of 40%, and 200 mA / cm ² . Nine temperatures could be measured.

  Fig. 4 shows the in-plane temperature distribution when the power generation test was conducted under the same conditions. The temperature distribution in the cell plane could be visualized.

Fig. 5 shows the IV characteristic test results at a cell temperature of about 60 ° C, an H ₂ utilization rate of 70%, and an Air utilization rate of 40%, and the temperature change at that time. The temperature measurement points were three points: gas inlet (measurement point (2)), center (measurement point (5)), and air outlet (measurement point (8)). It can be seen that as the current density increases, the temperature rise at the center and the air inlet is remarkable, and the difference from the air outlet is increased. The number of measurement points and the arrangement position are not particularly limited, and may be appropriately determined depending on the scale of the fuel cell used, and may be one or more, but the number of measurement points per electrode surface area to be measured. Is more preferably 0.01 / cm ² to 1 / cm ² , and still more preferably 0.04 / cm ² to 1 / cm ² .

  As described above, by embedding the temperature measurement sensor in the membrane-electrode assembly, it has become possible to measure the temperature distribution in the cell surface and the temperature change due to the fuel cell operation parameters such as the current density.

It is explanatory drawing which shows the membrane-zygote used for this Embodiment. It is a figure which shows the temperature measurement point of the membrane-electrode assembly used for this Embodiment. It is an external view when the membrane-electrode assembly in which the temperature measurement sensor is embedded is assembled in the cell holder. It is a figure which shows cell surface temperature distribution when a power generation test is implemented at a cell temperature of about 60 ° C., an H ₂ utilization rate of 70%, an Air utilization rate of 40%, and 200 mA / cm ² . Cell temperature of about 60 ° C., H ₂ utilization rate of 70% is a graph showing the IV characteristics test results and the temperature change at that time in the Air utilization of 40%.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Temperature sensor 2 Gas diffusion electrode 3 Electrolyte membrane 4 Membrane-electrode assembly 5 Temperature measurement point 6 Carbon plate (carbon plate provided with a gas channel on the surface)
7 Clamping plate 8 Gas inlet 9 Gas outlet 10 Cell holder

Claims (9)

  A solid polymer comprising an anode electrode and a cathode electrode arranged opposite to each other via an electrolyte membrane, and a pair of gas diffusion electrodes provided on the anode electrode and the cathode electrode, each having a catalyst layer containing an electrolyte. A membrane-electrode assembly of a fuel cell, wherein a temperature measurement sensor is embedded in the membrane-electrode assembly.   The membrane-electrode assembly according to claim 1, wherein the temperature measurement sensor is embedded in the electrolyte membrane.   The temperature measurement sensor is embedded in at least one location selected from the group consisting of a catalyst layer, a gas diffusion layer, a catalyst layer and an electrolyte membrane, and a catalyst layer and a diffusion layer. The membrane-electrode assembly according to claim 1. 4. The membrane-electrode according to claim 1, wherein the temperature measuring sensor is at least one detector selected from the group consisting of a thermocouple, a temperature measuring element, and a temperature measuring body. Joined body. 5. The membrane-electrode assembly according to claim 1, wherein at least one of a diameter and a thickness of the temperature measurement sensor is smaller than an electrolyte film thickness.   6. The membrane-electrode assembly according to claim 1, wherein the surface of the temperature measurement sensor is coated with a corrosion-resistant insulating coating.   A polymer electrolyte fuel cell comprising the membrane-electrode assembly according to any one of claims 1 to 6.   A fuel cell evaluation method using the membrane-electrode assembly according to any one of claims 1 to 6.   A temperature distribution of the fuel cell is detected using the membrane-electrode assembly according to any one of claims 1 to 6, and at least selected from the group consisting of cell temperature, gas flow rate, gas pressure, cooling water flow rate, and current. A fuel cell system which adjusts one kind of parameter.