JP3841732B2 - Surface treatment method for fuel cell separator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface treatment method of the separators for a fuel cell.
[0002]
[Prior art]
In general, a fuel cell is provided with a separator so as not to mix fuel gas (such as hydrogen) and air (such as oxygen). This separator is plate-shaped, and a groove serving as a fuel gas flow path is formed on one surface, and a groove serving as an air flow path is formed on the other surface. The separator is made of an impermeable material obtained by processing a graphite block to make it impermeable, or a liquid resin impregnated material obtained by impregnating and hardening a liquid resin in an expanded graphite sheet laminated molded body.
[0003]
In the power generation process of the fuel cell, generated water is generated on the fuel gas channel side or the air channel side depending on the type of the fuel cell. Therefore, one of the functions required of the separator is a function of ensuring that a flow path for fuel gas or air is obtained by quickly discharging the generated water from the groove formed on the surface. This is because the performance of the fuel cell can be improved if the generated water is discharged quickly to secure the flow path of the fuel gas and air.
[0004]
[Problems to be solved by the invention]
However, since the separator made of the above material is easy to repel the generated water, the generated water is present as water droplets in the groove, and the generated water is not discharged quickly. This has been an obstacle to improving the performance of the fuel cell.
[0005]
Therefore, it is conceivable to form a silicon oxide thin film, which is used in a wide range of fields as a hydrophilic film, on the surface of the groove. This conventionally known silicon oxide thin film is formed by a sol-gel method, a sputtering method or the like. However, the sol-gel method has a high-temperature process, and the sputtering method has a vacuum (decompression) process. Moreover, the hydrophilicity of the silicon oxide thin film thus formed has a contact angle with pure water of about 40 to 50 degrees, and does not exhibit a very high hydrophilicity. The reason seems to be that a component having a hydroxyl group exhibiting hydrophilicity was removed by a high temperature process or the like. Therefore, even if a silicon oxide thin film is formed by a sol-gel method or the like, the discharge of generated water in the groove is not so fast.
[0006]
The present invention has been made in view of such circumstances, the surface of the separator for fuel cell, to provide a surface treatment method of the separators for a fuel cell can be discharged produced water fast and its object.
[0007]
[Means for Solving the Problems]
To achieve the above object, the surface treatment method of the first aspect separator for a fuel cell of the present invention, a gel film by coating a sol solution composed mainly of oxidation of silicon on the surface of the separator body for a fuel cell And a step of forming a hydrophilic film containing a component having a hydroxyl group by irradiating the gel film with vacuum ultraviolet light. The second gist of the present invention The surface treatment method for a fuel cell separator includes a step of forming a hydrophilic film containing a component having a hydroxyl group by subjecting the gel film to an atmospheric pressure plasma treatment .
[0008]
The inventors of the present invention have made extensive studies in order to speed up the discharge of generated water on the surface of the fuel cell separator. In the course of the research, it was found that if the surface of the separator is hydrophilized, the generated water is discharged faster. It was also found that surface hydrophilization can be achieved by forming a thin film (hydrophilic film) mainly composed of silicon oxide on the surface. And further earnest research was repeated. As a result, when the thin film (hydrophilic film) is formed, if the gel film containing silicon oxide as a main component is irradiated with vacuum ultraviolet light or atmospheric pressure plasma treatment, the formed thin film (hydrophilic film) Then, it discovered that the component provided with the hydroxyl group which exhibits hydrophilicity remained without being removed. As a result, the hydrophilicity of the thin film (hydrophilic film) was dramatically improved, and the generated water was discharged faster on the surface of the separator. Thus, the present inventors have reached the present invention.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described in detail with reference to the drawings.
[0010]
FIG. 1 shows an embodiment of a fuel cell separator treated by the surface treatment method for a fuel cell separator of the present invention. In this embodiment, the fuel cell separator includes a plate-shaped fuel cell separator body 1 and a hydrophilic film 2 formed on the surface of the separator body 1. This hydrophilic film 2 contains silicon oxide as a main component and contains a component having a hydroxyl group such as silicon hydroxide that exhibits hydrophilicity. Further, the separator body 1 has a plurality of grooves 1a and 1b formed on the front and back surfaces (in FIG. 1, three on the front surface and four on the back surface). Each of the separators is also uneven by forming a plurality of strip grooves 2a and 1b (three on the front surface and four on the back surface) on the front and back surfaces, respectively. And the groove | channel 2a, 1b in the separator is a flow path of fuel gas or air.
[0011]
More specifically, the material of the separator body 1 is not particularly limited, and is used for a normal separator as described in the above-described conventional technique. A material mainly composed of carbon is preferable in that it has both corrosion resistance and corrosion resistance. Examples of the material mainly composed of carbon include glassy carbon and graphite. And the manufacturing method of the said separator main body 1 is although it does not specifically limit, Usually, it produces by shaping | molding. Further, the grooves 1a and 1b on the surface of the separator body 1 may be formed by transferring a molding die, or may be formed by machining after the substrate of the flat separator body 1 is formed.
[0012]
Unlike the silicon oxide thin film formed by the sol-gel method, the hydrophilic film 2 contains a component having a hydroxyl group such as silicon hydroxide, and since this component is a component that exhibits hydrophilicity, the sol-gel Compared with a silicon oxide thin film formed by the method, it exhibits dramatically higher hydrophilicity. That is, the contact angle between the silicon oxide thin film by the sol-gel method and pure water is about 40 to 50 degrees as described above, whereas the contact angle between the hydrophilic film 2 and pure water is 10 degrees. Depending on the formation conditions of the hydrophilic film 2, it can be as close to 0 degrees as possible. Furthermore, the hydrophilic film 2 can maintain its hydrophilicity for a long time. The thickness of the hydrophilic film 2 is not particularly limited, but is preferably 10 nm or more. It is because there exists a possibility that hydrophilicity may not fully be exhibited as it is less than 10 nm. Further, since the hydrophilic film 2 contains a component having a hydroxyl group such as silicon hydroxide, when an infrared absorption spectrum is measured for the hydrophilic film 2, an absorption band appears in the wave number belonging to each component. . For example, in the case of silicon hydroxide, an absorption band appears at a wave number of 940 cm ⁻¹ .
[0013]
Moreover, formation of the said hydrophilic film 2 (surface treatment of a separator) can be performed as follows, for example. That is, first, a sol solution (sol solution containing silicon oxide as a main component) used when forming a silicon oxide thin film by the sol-gel method is applied to the surface of the separator body 1 to form a gel film. Next, the hydrophilic film 2 is formed by irradiating the gel film with vacuum ultraviolet light using an excimer lamp or the like.
[0014]
In the formation of the hydrophilic film 2, the sol solution is not particularly limited as long as the sol solution can form a silicon oxide thin film by a sol-gel method. Tetraethoxysilane or the like is hydrolyzed under an acidic catalyst. And a sol solution obtained by condensation polymerization. Moreover, the method of apply | coating a sol solution is not specifically limited, The method used by normal sol-gel methods, such as a dip method, a spin coat method, and a spray method, is employable.
[0015]
In addition, irradiation with vacuum ultraviolet light can usually be performed at room temperature (25 ° C.), but if the fuel cell separator body 1 does not change in quality and the gel film does not react with heat, it is heated. May be. In this way, in the step of forming the hydrophilic film 2 by irradiating the gel film with vacuum ultraviolet light, unlike the sol-gel method, heat that causes the gel film to react is not applied, so the water contained in the gel film At least a part of the component having a hydroxyl group such as silicon oxide remains in the hydrophilic film 2 without reacting. Therefore, the hydrophilic film 2 formed by such a separator surface treatment method exhibits a significantly higher hydrophilicity than the hydrophilicity of the silicon oxide thin film prepared by the sol-gel method. As a result, in the groove 2a formed on the surface of the separator, the generated water is discharged quickly. The time for irradiation with vacuum ultraviolet light is not particularly limited, but is preferably 15 seconds or longer in order to dramatically increase the hydrophilicity.
[0016]
Thus, according to the separator of the above embodiment, the hydrophilic film 2 formed on the surface of the separator contains a component having a hydroxyl group such as silicon hydroxide, so that the hydrophilic film 2 is dramatically improved. Since the discharge of the generated water in the groove 2a formed on the surface of the separator can be accelerated, a large flow path of fuel gas or air can be secured, and the performance of the fuel cell can be improved. Can be improved.
[0017]
In addition, according to the separator surface treatment method of the above embodiment, the hydrophilic film 2 can be formed by irradiating the gel film with vacuum ultraviolet light. Therefore, unlike conventional sol-gel methods and sputtering methods, There is no process or vacuum (decompression) process, and the hydrophilic film 2 can be formed easily and inexpensively. In particular, if the irradiation with vacuum ultraviolet light is performed using an excimer lamp, the irradiation operation can be performed easily and inexpensively, so that the formation of the hydrophilic film 2 can be performed more easily and inexpensively.
[0018]
Next, another embodiment of the fuel cell separator treated by the surface treatment method for a fuel cell separator of the present invention will be described. In this embodiment, as the formation of the hydrophilic film 2 (surface treatment of the separator), atmospheric pressure plasma treatment is performed instead of vacuum ultraviolet light irradiation in the above embodiment. That is, the hydrophilic film 2 is formed by subjecting the gel film formed in the same manner as described above to atmospheric pressure plasma treatment.
[0019]
The atmospheric pressure plasma treatment is not particularly limited, and can be performed using, for example, an atmospheric pressure plasma treatment apparatus in which electrodes facing each other are provided in a chamber. That is, the separator main body 1 on which the gel film is formed is disposed between the electrodes, a gas used for atmospheric pressure plasma is supplied into the chamber, and then a voltage is applied between the electrodes to apply atmospheric pressure. Generate plasma. Thereby, the active species in the plasma act directly on the gel film, and form the hydrophilic film 2 in a short time.
[0020]
The atmospheric pressure plasma treatment can also be performed at room temperature (25 ° C.) as in the case of the vacuum ultraviolet light irradiation, and the hydrophilic film 2 has the same functions and effects as those of the embodiment. . Further, even in the atmospheric pressure plasma treatment, there is no high temperature process or vacuum (decompression) process as in the case of the irradiation with the vacuum ultraviolet light, and the formation of the hydrophilic film 2 can be performed easily and inexpensively.
[0021]
In the atmospheric pressure plasma treatment, the voltage applied between the electrodes is not particularly limited as long as atmospheric pressure plasma is generated, but is usually in the range of 1 to 10 kV. Also, the frequency of the power source is not particularly limited as long as atmospheric pressure plasma is generated, but is usually in the range of 1 to 20 kHz. The time for performing the atmospheric pressure plasma treatment is not particularly limited, but is preferably 5 seconds or longer in order to dramatically increase the hydrophilicity. Further, the gas used for the atmospheric pressure plasma is not particularly limited as long as atmospheric pressure plasma is generated. Usually, an inert gas group consisting of helium, neon, argon, krypton, xenon, radon and nitrogen is used. At least one selected from is used.
[0022]
In each of the above embodiments, as shown in FIG. 1, the hydrophilic film 2 is formed on the entire surface of the separator body 1, but the surface of the groove 1 a formed on the surface of the separator body 1 (the groove). The hydrophilic film 2 may be formed only on the bottom surface and both side surfaces of 1a. Further, although the hydrophilic film 2 is formed only on the surface of the separator body 1, the hydrophilic film 2 may be formed on the back surface of the separator body 1 in the same manner.
[0023]
Next, examples will be described together with comparative examples.
[0024]
[Example 1]
In the same manner as in the above embodiment, a hydrophilic film 2 containing silicon oxide as a main component and a component having a hydroxyl group such as silicon hydroxide that exhibits hydrophilicity was formed. That is, first, a sol solution (manufactured by High Purity Chemical Research Laboratory) used when a silicon oxide thin film is formed on the surface of a fuel cell separator body 1 made of a glassy carbon substrate (GL100, manufactured by Tokai Carbon Co., Ltd.). MOD coding agent Si-05S) was applied by spin coating to form a gel film. The gel film was then irradiated with Ar excimer light (wavelength: 126 nm) for 10 minutes to form a hydrophilic film 2 having a thickness of 130 nm, thereby obtaining a fuel cell separator.
[0025]
[Example 2]
The vacuum ultraviolet light applied to the gel film was Xe excimer light (wavelength: 172 nm). Other than that was carried out similarly to the said Example 1, the 130-nm-thick hydrophilic film 2 was formed, and the separator for fuel cells was obtained.
[0026]
[Example 3]
In the same manner as in the other embodiments described above, a hydrophilic film 2 containing silicon oxide as a main component and a component having a hydroxyl group such as silicon hydroxide that exhibits hydrophilicity was formed. That is, in Example 1 above, instead of irradiating the gel film with Ar excimer light, atmospheric pressure plasma treatment was performed for 1 minute. Argon was used as the gas used for the atmospheric pressure plasma. Then, an AC power source having a frequency of 5 kHz was used as a power source, and a voltage of 3 kV was applied between the electrodes. As a result, a hydrophilic film 2 having a thickness of 130 nm similar to that of Example 1 was formed to obtain a fuel cell separator.
[0027]
[Comparative Example 1]
A fuel cell separator made of the same glassy carbon substrate as in Examples 1 to 3 was prepared. No hydrophilic film 2 was formed on the surface.
[0028]
And 1 drop of pure water was dripped with the dropper on the surface of each said separator for fuel cells, and the contact angle with pure water was measured using the contact angle measuring machine (The Elma company make, G-1-1000 type | mold). The measurements for the fuel cell separators of Examples 1 to 3 were performed twice immediately after the formation of the hydrophilic film 2 and after storage for 30 days at room temperature (25 ° C.).
[0029]
As a result, in each of Examples 1 to 3, the contact angle immediately after the formation of the hydrophilic film 2 was 0 degree (wet spread state), and the contact angle after 30 days was 0 degree (wet spread state). On the other hand, in Comparative Example 1, it was 110 degrees.
[0030]
From the above results, the gel film is irradiated with excimer light to form the hydrophilic film 2 as in Examples 1 and 2, or the gel film is subjected to atmospheric pressure plasma treatment to form the hydrophilic film 2 as in Example 3. If it is formed, the contact angle with pure water is drastically reduced and the hydrophilicity is drastically improved, and the hydrophilicity is maintained for a long time.
[0031]
[Example 4]
In order to make it easy to measure the infrared absorption spectrum of the hydrophilic film 2, the hydrophilic film 2 was formed in the same manner as in Example 1 above on a substrate having gold plated on the surface of a stainless steel plate. This is because a good infrared absorption spectrum cannot be measured with a glassy carbon substrate. And the result of having measured the infrared absorption spectrum of the hydrophilic film | membrane 2 was shown in FIG.
[0032]
In FIG. 2, an absorption band appears at a wave number of 940 cm ⁻¹ belonging to silicon hydroxide that is not found in a normal silicon oxide thin film formed by the sol-gel method. From this result, it can be seen that, as in Example 4, silicon hydroxide that exhibits hydrophilicity remains in the hydrophilic film 2 formed by irradiating the gel film with excimer light.
[0033]
【The invention's effect】
As described above, the fuel cell separator treated by the surface treatment method for a fuel cell separator of the present invention contains a component mainly composed of silicon oxide and a hydroxyl group on the surface of the fuel cell separator body. Since the hydrophilic film is formed, the hydrophilic film exhibits extremely high hydrophilicity, and the generated water can be discharged quickly on the surface of the fuel cell separator. As a result, a large flow path for fuel gas and air can be secured, and the performance of the fuel cell can be improved.
[0034]
According to the surface treatment method for a fuel cell separator of the present invention, a sol solution mainly composed of silicon oxide is applied to the surface of the fuel cell separator body to form a gel film; Forming a hydrophilic film containing a component having a hydroxyl group by performing irradiation with vacuum ultraviolet light or atmospheric pressure plasma treatment on the surface of the fuel cell separator. Discharge can be fast. As a result, a large flow path for fuel gas and air can be secured, and the performance of the fuel cell can be improved. Furthermore, since the hydrophilic film can be formed by a simple process of irradiating the gel film with vacuum ultraviolet light, the hydrophilic film can be formed at a low cost.
[0035]
In the surface treatment method for a fuel cell separator according to the present invention, when irradiation with vacuum ultraviolet light is performed using an excimer lamp, the irradiation operation can be performed easily and inexpensively. The above-mentioned hydrophilic film can be formed.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an embodiment of a separator for a fuel cell of the present invention.
FIG. 2 is a graph showing an infrared absorption spectrum of a hydrophilic film formed by a surface treatment method for a fuel cell separator according to the present invention.
[Explanation of symbols]
1 Separator body 2 Hydrophilic membrane

Claims (3)

  A step of forming a gel film by applying a sol solution containing silicon oxide as a main component to the surface of a separator body for a fuel cell, and by irradiating the gel film with vacuum ultraviolet light, a component having a hydroxyl group is formed. A surface treatment method for a fuel cell separator, comprising: forming a hydrophilic film contained therein. The surface treatment method of a separator for a fuel cell according to claim 1, wherein the performed irradiation of vacuum ultraviolet light using an excimer lamp.   A step of forming a gel film by applying a sol solution containing silicon oxide as a main component to the surface of a separator body for a fuel cell, and a component having a hydroxyl group contained by subjecting the gel film to atmospheric pressure plasma treatment A surface treatment method for a separator for a fuel cell, comprising: forming a hydrophilic film.

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