JP2016030845A - Conductive member, method for manufacturing the same, and separator for fuel cell and solid polymer fuel cell using the conductive member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide means (a manufacturing method) that, while sufficiently ensuring the excellent conductivity of a conductive member having a boundary layer located between an intermediate layer and a conductive carbon layer and having good adhesiveness with both layers, can improve corrosion resistance of a metal substrate and suppress an increase in contact resistance between a separator and other members such as MEA.SOLUTION: A conductive member manufacturing method according to the present invention includes the steps of: forming on a metal substrate an intermediate layer comprising at least one selected from the group consisting of a group 4 metal of the periodic table, a group 5 metal, a carbide, nitride, or carbonitride of a group 6 metal in a dry film deposition method; and forming a conductive carbon layer on the intermediate layer. The step of forming the conductive carbon layer on the intermediate layer includes changing a negative bias voltage from a lower value to a higher value.SELECTED DRAWING: Figure 5A

Description

  The present invention relates to a conductive member, a method for producing the same, and a fuel cell separator and a polymer electrolyte fuel cell using the same. Especially in a separator having a high potential corrosion resistance intermediate layer and a surface carbon layer on a metal substrate, it is possible to improve the adhesion between the intermediate layer and the conductive carbon layer while ensuring high potential corrosion resistance. The present invention relates to a method for producing a conductive member.

  A polymer electrolyte fuel cell (PEFC) has a structure in which a plurality of single cells that exhibit a power generation function are stacked. Each of the single cells includes a polymer electrolyte membrane, a pair of (anode, cathode) catalyst layers sandwiching the polymer electrolyte membrane, and a pair of (anode, cathode) gas diffusion layers sandwiching them for dispersing the supply gas. It has a membrane electrode assembly containing. And MEA which each single cell has is electrically connected with MEA of an adjacent single cell through a separator. In this way, a single cell is stacked and connected to form a fuel cell stack. The fuel cell stack can function as power generation means that can be used for various applications. In such a fuel cell stack, the separator exhibits a function of electrically connecting adjacent single cells as described above. In addition to this, a gas flow path is usually provided on the surface of the separator facing the MEA. The gas flow path functions as gas supply means for supplying fuel gas and oxidant gas to the anode and the cathode, respectively.

  Briefly explaining the power generation mechanism of the PEFC, during operation of the PEFC, a fuel gas (for example, hydrogen gas) is supplied to the anode side of the single cell, and an oxidant gas (for example, air or oxygen) is supplied to the cathode side. As a result, in each of the anode and the cathode, an electrochemical reaction represented by the following reaction formula proceeds to generate electricity.

  As separators for fuel cells that require electrical conductivity, replacement of conventional carbon separators and conductive resin separators with metal separators is progressing. This is because the size of the stack can be reduced because the metal separator has excellent strength and conductivity. In recent years, a separator in which a layer having corrosion resistance is laminated on a metal substrate has been developed in order to prevent a decrease in conductivity due to corrosion, which is a problem of a metal separator, and a decrease in output of a stack accompanying this. For example, a technique has been proposed in which a negative bias voltage is changed from a low value to a high value on a metal substrate, an intermediate layer is formed by a dry film forming method, and a conductive carbon layer is formed on the intermediate layer. (For example, refer to Patent Document 1). In this document, at the initial stage of intermediate layer deposition in the dry deposition method, deposition is started at a low bias voltage to reduce the roughness of the interface with the substrate, and then the bias voltage is shifted to a higher value. The columnar crystal grows thick. Here, the conductive carbon film grows with the column diameter of the columnar crystals in the intermediate layer. In this way, by increasing the column diameter of the columnar crystals of the intermediate layer, the gaps in the intermediate layer and the defects of the conductive carbon film existing thereon are reduced, and the oxidation at each interface is prevented by preventing the ingress of water. And the increase in contact resistance can be suppressed.

JP 2010-287542 A

  However, when the intermediate layer is formed of titanium nitride, carbide, or carbonitride having excellent high-potential corrosion resistance, adhesion with the conductive carbon layer is not sufficient. For this reason, the further improvement of the corrosion resistance of a separator and the further reduction of the increase in contact resistance were calculated | required.

  Therefore, the present invention has been made in view of the above prior art, and is a conductive member having high adhesion between the intermediate layer and the conductive carbon layer, which has excellent high-potential corrosion resistance, and has sufficient excellent conductivity. It aims at providing the manufacturing method of the electrically-conductive member which can suppress the increase in contact resistance, ensuring.

  The inventors of the present invention have examined the cause of low adhesion to an intermediate layer such as titanium nitride, which is excellent in high potential corrosion resistance in the conventional conductive carbon layer. The conventional conductive carbon layer is formed under a high bias voltage, so the conductive carbon layer is formed on the assumption that carbon will bounce off by an intermediate layer such as hard titanium nitride, making it difficult to form the film. The method was examined. As a result, it has been found that the above problem can be solved by changing the bias voltage from a low value to a high value in the conductive carbon layer forming step, and the present invention has been completed.

  In other words, the conductive member manufacturing method of the present invention is characterized in that the negative bias voltage is changed from a low value to a high value to form the conductive carbon layer on the intermediate layer.

According to the method of the present invention, the adhesion between the intermediate layer and the conductive carbon layer can be improved. Therefore, the conductive member manufactured according to the method of the present invention can suppress an increase in contact resistance while sufficiently ensuring its excellent conductivity, and has a low contact resistance with other members (for example, MEA). (Separator 5) can be provided. Here, although the mechanism which can improve the adhesiveness of an intermediate | middle layer and a conductive carbon layer by the method of this invention is unknown, it estimates as follows. Note that the present invention is not limited to the following estimation. That is, when a film is formed at a low bias voltage, a DLC carbon film containing a large amount of flexible sp ³ carbon is formed on an intermediate layer of hard titanium nitride, carbide, carbonitride, etc., and a surface layer portion is formed at a high bias voltage. When this occurs, the collision of carbon is alleviated and a stable film can be produced. In addition, when the bias voltage is low, the deposition of carbon on the unevenness of titanium nitride can be improved, and a dense film can be obtained. On the other hand, when the bias voltage is high, it becomes difficult to contribute to the adhesion with the intermediate layer due to rebound and graphitization due to collision. Therefore, according to the method of the present invention, a conductive member having low contact resistance and good adhesion between the intermediate layer and the conductive carbon layer can be obtained.

It is a section schematic diagram showing the basic composition of the cell unit of the polymer electrolyte fuel cell (PEFC) which uses the separator to which the conductive member concerning the present invention is applied. FIG. 2 is a cross-sectional view showing another embodiment of the schematic configuration of the separator portion in FIG. 1, and has an intermediate layer and a boundary layer on both surfaces of the metal substrate of the separator used in the fuel cell unit of FIG. 1. It is a section schematic diagram showing typically the composition provided with a conductive carbon layer. It is the schematic which shows the fuel cell (stack) including the current collection board of the fuel cell to which the electrically-conductive member of this invention is applied. FIG. 4 is a perspective view of the fuel cell (stack) of FIG. 3. FIGS. 5A to 5D are diagrams showing various patterns obtained by changing the negative bias voltage during the formation of the intermediate layer from a low value to a high value in the dry film forming method. Among these, FIG. 5A shows the bias voltage. It is drawing which showed one example of the pattern formed by changing the value from a low value to a high value in one step. FIG. 5B is a diagram showing an example of a pattern obtained by continuously changing the negative bias voltage during the formation of the intermediate layer from a low value to a high value in the dry film forming method. FIG. 5C is a diagram showing an example of a pattern obtained by changing the negative bias voltage during the formation of the intermediate layer in a dry film formation method from a low value to a high value in multiple steps. FIG. 5D is a drawing showing an example of a pattern in which the negative bias voltage during intermediate layer formation in the dry film forming method is continuously changed in multiple steps from a low value to a high value. The conductive member of the present invention, in particular, at least one of each of the intermediate layer and the conductive carbon layer, preferably each of these layers is sequentially formed by sputtering (for example, unbalanced magnetron sputtering (UBMS)). FIG. 2 is a schematic plan view of a manufacturing apparatus for forming (however, an example in which an existing disk-shaped wafer is set in place of a flat plate-shaped metal separator before pressing of unevenness) is shown. Manufacturing apparatus for forming (forming) at least one of the conductive members of the present invention, particularly the intermediate layer and the conductive carbon layer, preferably using the arc ion plating (AIP) method in order. FIG. 2 is a schematic plan view of an example in which an existing disk-shaped wafer is set in place of a flat plate type metal separator before uneven pressing. It is an external appearance photograph of the electrically-conductive member shown in Example 1 of this invention. It is an external appearance photograph of the electrically-conductive member shown in the comparative example 1 of this invention. It is a surface SEM observation photograph of the electrically-conductive member shown in Example 1 of this invention. 4 is a surface SEM observation photograph of a conductive member shown in Comparative Example 1. It is a schematic diagram which shows the outline | summary of the measuring apparatus used in measuring the contact resistance in an Example.

(Method for producing conductive member)
In the method for producing a conductive member of the present invention, a group 4 metal (e.g., Ti, Zr, Nf), a group 5 metal (e.g., V, Nb, Ta) of the periodic table on a metal substrate, A step of forming an intermediate layer made of at least one selected from the group consisting of carbides, nitrides and carbonitrides of Group 6 metals (for example, Cr, Mo, W), and conductive on the intermediate layer Forming a conductive carbon layer, and forming the conductive carbon layer on the intermediate layer includes changing a negative bias voltage from a low value to a high value. is there. As a method for producing a conductive member according to the present invention, a simple method of changing the set value of a dry film forming method (sputtering etc.) used at the time of film formation, while sufficiently ensuring its excellent conductivity, A conductive member capable of suppressing an increase in contact resistance can be realized.

  The present embodiment is characterized in that the negative bias voltage at the time of forming the conductive carbon layer in the dry film forming method is changed from a low value to a high value.

  Here, changing the bias voltage in the dry film forming method from a low value to a high value does not include a process of changing from a high value to a low value in the middle, for example, a pattern such as FIG. 5A to FIG. 5D. Is mentioned. Specifically, it is changed in one step from a low value to a high value (FIG. 5A), continuously changed from a low value to a high value (FIG. 5B), or changed in multiple steps from a low value to a high value. Pattern (FIG. 5C). Further, it may be continuously changed in multiple steps from a low value to a high value (FIG. 5D). As described above, in the present specification, “change the negative bias voltage from a low value to a high value” means that the bias voltage is changed from a low value to a high value continuously or stepwise within a predetermined range. Change to. For this reason, the process of changing the bias voltage may include a steady state (a state in which the bias voltage is held) in the middle. However, the change of the bias voltage always takes a rising or steady state, and the change process of the bias voltage does not include the state where the bias voltage decreases.

When the film is formed at a low bias voltage, a flexible DLC carbon film containing a large amount of sp ³ carbon is formed on the hard intermediate layer, and the collision of carbon when forming the surface layer part at a high bias voltage is mitigated to form a film. It becomes easy. Further, when the bias voltage is low, the contact of the intermediate layer with the unevenness can be improved. On the other hand, if a high bias voltage of 200 V or more is used from the beginning, a film cannot be formed due to rebound due to collision, or it becomes difficult to contribute to adhesion with the intermediate layer due to graphitization.

  Therefore, in the conductive carbon layer thickness, the vicinity of the intermediate layer is formed with a low bias voltage, and the adhesion with the intermediate layer is improved by suppressing the formation of the graphite structure. The initial bias voltage in the conductive carbon layer forming step may be a voltage higher than 0V, and usually in the range of higher than 0V and lower than or equal to 50V, it can improve the adhesion between the intermediate layer and the conductive carbon layer. An effect is obtained.

  As a method for obtaining a conductive carbon layer in the vicinity of the intermediate layer that is denser and has higher adhesion to the intermediate layer, the conductive carbon layer is formed after the intermediate layer is formed, and the conductive carbon layer is being formed. Controlling the material temperature within a certain range can be mentioned. Here, the carbon film is graphitized at about 400 ° C. or higher, and it is difficult or impossible to maintain the form of the film. For this reason, it is preferable to keep the temperature during the film-forming process from the start of film formation of the intermediate layer to the end of film formation below the above temperature. In addition, the surface layer temperature during film formation may increase due to collision between carbons. Considering the above points, the substrate temperature during the film forming step is preferably less than 350 ° C., more preferably 300 ° C. or less, and even more preferably 270 ° C. or less. In addition, although the minimum in particular of the said temperature range is not restrict | limited, For example, 100 degreeC or more is preferable and 150 degreeC or more is more preferable. If it is such a temperature range, it can suppress that the conductive carbon layer formed on the intermediate | middle layer graphitizes with temperature.

  When the conductive carbon layer is formed as described above, a conductive carbon layer region exhibiting good adhesion with the intermediate layer is formed between the surface layer portion and the intermediate layer of the conductive carbon layer. This region is referred to as a “boundary layer” in the present application.

The boundary layer of the conductive carbon layer of the present invention preferably has an R value (= _ID / _IG ) of less than 1.3, more preferably 1.2 or less, and even more preferably 1 .1 or less. The lower limit of the R value of the boundary layer in the conductive carbon layer is not particularly limited, but is preferably 0.6 or more, and more preferably 0.7 or more. If R value is such a range, it is preferable from a viewpoint which can fully suppress the inhibition of adhesiveness by formation of a graphite structure. Here, the “boundary layer in the conductive carbon layer” intends a layer formed by applying a low bias voltage, and the thickness thereof is not particularly limited, and the adhesion between the intermediate layer and the conductive carbon layer is determined. It can be prepared accordingly. In the present specification, the R value (= I _D / I _G ) means a value measured in the following examples.

  The R value of the conductive carbon layer is preferably gradually increased from the outermost surface of the intermediate layer toward the surface layer portion from the viewpoint of ensuring high adhesion between the intermediate layer and the conductive carbon layer. The R value of the surface layer part is preferably 1.3 or more, more preferably 1.4 or more, and further preferably 1.5 or more. If the R value of the surface layer portion is 1.3 or more, the conductivity of the surface layer portion can be ensured and the contact resistance can be sufficiently reduced. In addition, although the upper limit of the R value of the surface layer part in the conductive carbon layer is not particularly limited, for example, 2.0 or less is preferable and 1.9 or less is more preferable. Here, the “surface layer portion in the conductive carbon layer” means a layer formed by applying a high bias voltage. The thickness of the surface layer portion in the conductive carbon layer is not particularly limited as in the case of the boundary layer, and can be appropriately adjusted according to the conductivity, adhesiveness to the intermediate layer, and the like.

  The above is an explanation of the main features of the method for manufacturing a conductive member according to the present invention, and other manufacturing methods (processes, etc.) can be manufactured by appropriately referring to conventionally known methods. . Hereinafter, although preferable embodiment for manufacturing an electroconductive member is described, the technical scope of this invention is not limited only to the following form. Various conditions such as the material of each component of the conductive member constituting the separator will be described in the section of the conductive member to be described later, and the description is omitted here.

  First, an aluminum plate, a titanium plate, a stainless plate, or the like having a desired thickness is prepared as a constituent material of the metal base 31. Subsequently, the surface of the constituent material of the prepared metal substrate 31 is degreased and washed using an appropriate solvent (for example, ethanol, ether, acetone, isopropyl alcohol, trichlorethylene, and a caustic agent). Examples of the treatment include ultrasonic cleaning. As conditions for ultrasonic cleaning, the processing time is about 1 to 10 minutes, the frequency is about 30 to 50 kHz, and the power is about 30 to 50 W.

  Subsequently, the oxide film formed on the surface (both sides) of the constituent material of the metal base 31 is removed. Examples of the method for removing the oxide film include a cleaning treatment with an acid, a dissolution treatment by applying a potential, or an ion bombardment treatment.

  Next, in the present invention, in order to manufacture a conductive member (separator 5) having the conductive carbon layer 33 having the form shown in FIG. A step of forming an intermediate layer 32 on at least one main surface of 31, preferably both surfaces, is performed. At this time, as a method for forming the intermediate layer 32, a method similar to that described later for forming the conductive carbon layer 33, preferably a dry film forming method, can be employed. However, it is necessary to change the target to the constituent material of the intermediate layer 32. Particularly preferably, the intermediate layer 32 is preferably formed according to a method described in JP 2010-287542 A. The intermediate layer formed by this method is excellent in corrosion resistance and can suppress an increase in contact resistance.

  In particular, in the present invention, the negative bias voltage at the time of forming the conductive carbon layer 33 is changed from a low value to a high value by a dry film forming method. Thereby, the R value of the conductive carbon layer 33 can be controlled, a boundary layer having an R value of less than 1.3 is formed in the vicinity of the intermediate layer, and an R value of 1.3 or more is formed on the opposite side of the intermediate layer. The surface layer portion is formed. The initial low bias voltage may be a voltage higher than 0V as described above, and may be a range higher than 0V and not higher than 50V. The high bias voltage is preferably 200 V or more, more preferably 200 to 500 V, and still more preferably 200 V to 300 V. That is, it is preferable to change the negative bias voltage when forming the conductive carbon layer from 50 V or less to 200 V or more. Within such a range, a surface layer portion having a sufficiently high R value can be obtained, and a conductive member having a low contact resistance can be obtained. Thus, by changing the bias voltage from a low value to a high value, the conductive carbon layer 33 in which the R value gradually changes from a low value to a high value from the vicinity of the intermediate layer toward the surface layer portion is obtained.

  The lower the bias voltage, the smaller the pushing effect during the film formation by Ar + ions, and the lower the energy of collision of carbon atoms. Therefore, carbon atoms can be stacked on the intermediate layer 32 of hard, chemically stable titanium nitride, carbide, carbonitride, etc., and the form as a film can be maintained. When the bias voltage is increased, the carbon energy by Ar + ions increases, so that carbon atoms bounce off without being stacked on the film, so that the form of the film cannot be maintained and becomes powdery and remains on the surface. Alternatively, even if the shape as a film can be maintained, a non-dense film structure having a gap at a grain boundary or the like may cause a poor adhesion.

  Therefore, by forming the film in the vicinity of the intermediate layer 32 while controlling the bias voltage to a low value, it is possible to suppress the change to graphite that does not contribute to the adhesion with the intermediate layer, and thus conductive carbon having high adhesion to the intermediate layer. A layer can be obtained.

  In the subsequent film formation, a high bias voltage is applied as it approaches the surface layer portion, and a surface layer portion having a graphite structure with high conductivity is formed, thereby having high adhesion to the intermediate layer and high conductivity. A conductive carbon layer can be obtained.

  In the step of forming the intermediate layer 32 using the method of changing the negative bias voltage from a low value to a high value after polishing the surface of the metal base 31 described above, the intermediate layer 32 is formed by sputtering. It is preferable to perform a method (a coating process for forming a film) to form by a method. In order to form a conductive member composed of the metal substrate 31 having the structure of the present invention, the intermediate layer 32, and the conductive carbon layer 33, the conductive carbon layer 33 is preferably formed by a sputtering method. This is because the intermediate layer 32 to be formed is preferably formed by a similar dry process, particularly by a sputtering method. Such an intermediate layer 32 makes it possible to form the conductive carbon layer 33 without poor adhesion, so that high conductivity and corrosion resistance can be obtained. Further, since the film can be formed in the same manner as the conductive carbon film, the manufacturing process cost can be reduced.

  In addition, when including a step of forming the intermediate layer 32 by changing the negative bias voltage from a low value to a high value, the substrate 31 is subjected to a pretreatment such as a polishing treatment on the surface of the metal substrate 31. It is desirable to perform a coating process for forming a film on the surface of the film by sputtering. This is because when the intermediate layer 32 is made of columnar crystals or the like, if the substrate roughness is reduced by the polishing treatment, the number of columnar crystal nucleation sites is reduced and the individual columnar crystals can be made thicker. By using such an intermediate layer, the metal substrate can be prevented from coming into contact with the acidic solution, and the corrosion resistance can be improved. Here, as the pre-treatment, in addition to the polishing treatment, generally implemented items can be widely adopted. For example, electrolytic polishing, lapping treatment, microshot treatment, etc. can be applied.

  Next, the intermediate layer 32 and the conductive carbon layer 33 are sequentially formed on the surface of the constituent material of the metal base 31 subjected to the above treatment. As a target to be used, for example, the constituent material of the intermediate layer 32 (for example, titanium metal) and the constituent material of the conductive carbon layer 33 (for example, solid graphite) can be used. First, titanium metal is used as a target, and sputtering is performed by applying a negative bias voltage to the metal substrate while introducing nitrogen gas into the system, so that the titanium nitride film is formed on both surfaces of the metal substrate 31. To form. Next, the conductive carbon layer 33 having the boundary layer 33a and the surface layer portion 33b can be obtained by using solid graphite as a target and changing the bias voltage from a low value to a high value. In this way, the intermediate layer 32 and the conductive carbon layer 33 can be sequentially formed on the metal substrate 31.

  As a method suitably used for laminating (depositing) the intermediate layer 32 and the conductive carbon layer 33, as a dry deposition method, for example, physical vapor deposition (PVD) such as a sputtering method or an ion plating method is used. Or ion beam deposition such as filtered cathodic vacuum arc (FCVA) method. Examples of the sputtering method include a magnetron sputtering method, an unbalanced magnetron sputtering (UBMS) method, a dual magnetron sputtering method, and an ECR sputtering method. Examples of the ion plating method include an arc ion plating method. Among these, it is preferable to use a sputtering method and an ion plating method which are dry film forming methods. According to such a technique, a graphite structure having a turbulent structure with a small hydrogen content can be formed as the surface layer portion. As a result, the R value of the surface layer portion can be increased, and excellent conductivity can be achieved. In addition to this, the film can be formed at a relatively low temperature, and there is an advantage that damage to the metal substrate 31 can be minimized. Further, the sputtering method has an advantage that the crystal structure of the intermediate layer 32 can be controlled and the film quality of each layer can be controlled by controlling the bias voltage and the like.

  Here, when the intermediate layer 32 and the conductive carbon layer 33 are formed by the sputtering method, which is a dry film formation method, as described above, when a negative bias voltage is applied to the metal substrate 31 during the sputtering. Good. According to such an embodiment, the crystal structure can be controlled like the above-described intermediate layer 32 by the ion irradiation effect, and the structure of the conductive carbon layer 33 can be changed between the boundary layer and the surface layer portion. Thereby, it is possible to obtain a conductive carbon layer that can achieve both high adhesion and low contact resistance, such as formation of an intermediate layer contributing to improvement of corrosion resistance and the conductive carbon layer in the present invention.

  The intermediate layer 32 can enhance the anticorrosion effect of the metal substrate 31 as described above, and can be applied as the metal substrate 31 of the separator even in the case of an easily corroded metal such as aluminum. In the embodiment, the magnitude (absolute value) of the negative bias voltage to be applied is not particularly limited, and a voltage capable of forming the intermediate layer 32 can be adopted. As an example, the magnitude of the applied voltage is preferably 50 to 500V, more preferably 100 to 300V.

  The conductive carbon layer 33 according to the present invention has high adhesion to the intermediate layer by the boundary layer, and the surface layer portion can exhibit excellent conductivity. Therefore, the conductive carbon layer 33 can be used with other members (for example, MEA). A conductive member (separator 5) having a low contact resistance can be provided. As described above, the conductive carbon layer 33 uses a method of changing the negative bias voltage when forming the conductive carbon layer 33 from a low value to a high value. Specifically, at the initial stage when the conductive carbon layer 33 is formed as in the embodiments described later, a low bias voltage (higher than 0 V, 0 V is required so as not to cause a gap or a defect with the intermediate layer 32. The film formation is started at ultra high to 50 V, and then the bias voltage is shifted to a high value (usually 200 to 500 V, preferably 200 to 300 V) to change to graphite having a high conductivity.

  In addition, specific forms, such as other conditions at the time of film-forming of the intermediate | middle layer 32 and the conductive carbon layer 33, are not restrict | limited, A conventionally well-known knowledge can be referred suitably. Further, when the conductive carbon layer 33 is formed by the UBMS method, it is preferable to form the intermediate layer 32 in advance by the same apparatus and manufacturing method, and form the conductive carbon layer 33 thereon. Thereby, the intermediate | middle layer 32 and the conductive carbon layer 33 which are excellent in adhesiveness with a base layer can be formed. However, the intermediate layer 32 may be formed by other methods, and the conductive carbon layer 33 may be formed by a different apparatus or manufacturing method. Even in this case, the intermediate layer 32 and the conductive carbon layer 33 having excellent adhesion to the metal substrate 31 can be formed.

  According to the above-described method, a conductive member in which the intermediate layer 32 and further the conductive carbon layer 33 are formed on both surfaces of the metal base 31 can be manufactured. In order to manufacture a conductive member in which the intermediate layer 32 and further the conductive carbon layer 33 are formed on both surfaces of the metal base 31, a commercially available appropriate film forming apparatus (both sides simultaneous sputter film forming apparatus and the same) was used. Sputter film formation method) may be used, or separately, a sputtering apparatus or a film forming apparatus capable of forming the intermediate layer 32 and further the conductive carbon layer 33 on both surfaces of the metal substrate 31 is formed and subjected to film formation. There are no particular restrictions. Although not advantageous in terms of cost, an intermediate layer 32 and further a conductive carbon layer 33 are formed on one main surface of the metal substrate 31, and then the other main surface of the metal substrate 31. On the other hand, the intermediate layer 32 and the conductive carbon layer 33 may be sequentially formed by the same method as described above. Alternatively, first, an intermediate layer 32 is formed on one main surface of the metal base 31 in an apparatus targeting a metal material such as chromium, and then the intermediate layer 32 formed by the above process is opposed. The intermediate layer 32 is formed on the main surface different from the main surface to be formed. Subsequently, the target is switched to carbon, and the conductive carbon layer 33 is formed on the intermediate layer 32 formed on one main surface of the metal base 31 in the same apparatus, and subsequently formed by the above process. What is necessary is just to perform the process of forming the conductive carbon layer 33 on the main surface different from the main surface opposite to the main surface different from the main surface facing the formed conductive carbon layer 33. As described above, even when the intermediate layer 32 is formed on both surfaces of the metal substrate 31 or the conductive carbon layer 33 is formed on the surface of the intermediate layer 32, the intermediate layer 32 on one surface of the metal substrate 31 may be used. There is no particular limitation such that the same method as described above (however, the number of man-hours can be halved) can be adopted for the formation of the layer 32 and the conductive carbon layer 33.

(Conductive member)
In the conductive member of the present invention, a metal base material and an intermediate layer containing metal nitride, carbide, or carbonitride are provided on the metal base material, and a conductive carbon layer is coated on the intermediate layer. It is a conductive member. The conductive carbon layer is characterized in that the forming step includes a step of changing from a low bias voltage to a high bias voltage. By this step, a boundary layer having good adhesion with the intermediate layer is formed in the vicinity of the intermediate layer, and the outermost layer portion has high conductivity. The use of titanium nitride and other Group 4 metals, Group 5 metals, Group 6 metal carbides, nitrides and carbonitrides as the intermediate layer material improves the corrosion resistance of the conductive member. It is effective from.

  However, when a conductive carbon layer is formed on the intermediate layer to reduce contact resistance with other members, it is difficult to ensure adhesion between the intermediate layer and the conductive carbon layer. . This is because a constant high bias voltage is applied in the conventional process of forming the conductive carbon layer. The conductive carbon layer produced by such a method has a high R value due to the large proportion of graphite having a turbostratic structure, and high adhesion to the above materials such as titanium nitride cannot be obtained.

Therefore, the present invention includes a step of changing the bias voltage from a low value to a high value in the conductive carbon layer forming step. Thus, when the conductive carbon layer is formed at a low initial bias voltage, a conductive carbon layer in which a large amount of sp ³ carbon remains is obtained. Becomes precise and precise. By stacking a surface layer portion having a low contact resistance with a high bias voltage on such a soft carbon layer containing a large amount of sp ³ carbon, collision of carbon is mitigated and a stable film can be manufactured. Therefore, it is possible to obtain a conductive member having low contact resistance and good adhesion between the intermediate layer and the conductive carbon layer. When the surface of the conductive member according to the present invention is observed by SEM, it can be seen that there are very few gaps in the grain boundary portion of the intermediate layer as shown in FIG. 9A. On the other hand, in the conventional manufacturing method, when the intermediate layer is made of a material such as hard titanium nitride, the conductive carbon layer is graphitized, so that a dense film cannot be formed on the surface of the intermediate layer. As a result, as shown in FIG. 9B, a gap is generated between the intermediate layer and the conductive carbon layer.

  As described above, according to the configuration of the conductive member of the present invention, by providing a boundary layer having good adhesion between the intermediate layer and the surface layer portion of the conductive carbon layer, the intermediate layer and the conductive layer are provided. Gaps and defects formed between the carbon layers can be reduced. Furthermore, the function which suppresses the penetration | invasion of water can be provided by suppressing peeling of a conductive carbon layer and generation | occurrence | production of a clearance gap. As a result, the anticorrosion effect of the metal substrate can be enhanced. By having such anti-corrosion performance, the conductive member according to the present invention can be used stably as a separator for a long period of time even when a metal that is easily corroded is used as a metal substrate, while being lightweight and inexpensive such as aluminum. . That is, by providing a boundary layer between the intermediate layer and the surface layer portion of the conductive carbon layer, high adhesion between the intermediate layer and the conductive carbon layer can be obtained while having high conductivity of the surface layer portion. . Furthermore, by suppressing generation of gaps and defects between the intermediate layer and the conductive carbon layer, entry of water can be prevented, oxidation of each member can be suppressed, and increase in contact resistance can be suppressed.

  Hereinafter, embodiments to which the present invention is applied will be described with reference to the accompanying drawings. In addition, this invention is not restrict | limited only to the following embodiment. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may be different from the actual ratios.

FIG. 1 shows a basic configuration of a fuel cell using a metal separator, which is a typical embodiment of a conductive member according to the present invention, specifically a basic configuration of a cell unit of a polymer electrolyte fuel cell (PEFC). In the cell unit 1 of the fuel cell (PEFC) shown in FIG. 1, catalyst layers 3 (anode 3 a and cathode 3 b) are arranged on both surfaces of the solid polymer electrolyte membrane 2. Yes. The laminate of the solid polymer electrolyte membrane 2 and the catalyst layer 3 (3a, 3b) is further provided with a gas diffusion layer 4 (anode 4a and cathode 4b) so as to sandwich them, A membrane electrode assembly (MEA) 9 is formed. The MEA (Mebrane Electrode Assembly) 9 is finally sandwiched by a pair of conductive metal separators 5 (anode 5a and cathode 5b) to form a single cell unit 1 of PEFC. In FIG. 1, the metal separator 5 (the anode 5 a and the cathode 5 b) is illustrated so as to be located on both surfaces (both sides) of the MEA 9. However, in the fuel cell stack in which a plurality of MEAs 9 are stacked, the metal separator 5 is generally used as the metal separator 5 for the adjacent PEFC cell unit 1 (see FIG. 3). In other words, in the fuel cell stack, the MEAs 9 are sequentially stacked via the metal separator 5 to constitute a stack. In an actual fuel cell stack, between the metal separator (5a, 5b) and the solid polymer electrolyte membrane 2, or between the PEFC cell unit 1 and another adjacent PEFC cell unit 1. Although a gas seal part is arrange | positioned, these description is abbreviate | omitted in FIG. 1 (refer FIG. 3, FIG. 4).

The convex part seen from the MEA 9 side of the metal separator 5 (5a, 5b) is in contact with the MEA 9. Thereby, the electrical connection with MEA9 is ensured. In addition, the concave portion (the space between the metal separator 5 and the MEA 9 generated due to the uneven shape of the metal separator 5) viewed from the MEA 9 side of the metal separator 5 (5a, 5b) is a gas during the operation of the PEFC 1. It functions as a gas flow path for circulating. Specifically, a fuel gas 5ag (eg, hydrogen or a hydrogen-containing gas) is circulated through the gas flow path 5aa of the anode separator 5a, and an oxidant gas 5bg (eg, air) is passed through the gas flow path 5bb of the cathode separator 5b. Or gas containing O ₂ ).

  On the other hand, the concave portion viewed from the side opposite to the MEA 9 side of the metal separator 5 (5a, 5b) is a refrigerant for circulating the refrigerant 8w (for example, cooling water, water) for cooling the PEFC during operation of the PEFC 1. The channel 8 is used. Further, the metal separator 5 (5a, 5b) is usually provided with a manifold (not shown). This manifold functions as a connecting means for connecting each cell (unit 1) of the PEFC when a stack is formed. With such a configuration, the mechanical strength of the fuel cell stack 200 can be ensured (see FIGS. 3 and 4).

In an actual fuel cell (PEFC), a gas seal is provided between the metal separator 5 and the periphery (periphery) of the end of the electrolyte membrane 2 and between the cell unit 1 of the fuel cell and another cell unit 1 adjacent thereto. Arranged but not shown in this schematic diagram. The separator 5 for a fuel cell is a metal separator 5 that is an embodiment of a conductive member according to the present invention. For example, by pressing a thin plate having a thickness of 0.5 mm or less, an uneven shape as shown in FIG. Shaped (wave-shaped) gas flow paths 5aa, 5bb and a refrigerant flow path 8 are formed, and fuel gas 5ag (hydrogen or hydrogen-containing gas) or oxidant gas 5bg (air or O gas) is formed there (gas flow paths 5aa, 5bb). ₂ containing gas) and cooling water 8w.

  As described above, in addition to the function of electrically connecting each MEA 9 in series, the metal separator 5 has gas flow paths 5aa, 5bb and refrigerant flow through which different fluids such as the fuel gas 5ag, the oxidant 5bg gas, and the refrigerant 8w flow. A path 8 and a manifold are provided, and further, there is a function of maintaining the mechanical strength of the stack. Since the electrolyte membrane 2 is usually a perfluorosulfonic acid type membrane, various acidic ions eluted from the membrane and a humidified gas are introduced into the battery. In the environment.

  In the present embodiment shown in FIG. 2, the conductive member constituting the metal separator 5 has a configuration in which an intermediate layer 32 and a conductive carbon layer 33 are sequentially laminated on a metal base 31. The conductive carbon layer includes a boundary layer 33a and a surface layer portion 33b in the vicinity of the intermediate layer. In the PEFC cell unit 1, the metal separator 5 is disposed such that the conductive carbon layer 31 is located on the MEA 9 side (see FIGS. 2, 3, and 4).

  As shown in FIG. 2, as a cross-sectional configuration of the metal separator 5 of the fuel cell (PEFC) which is a typical embodiment of the conductive member according to the present invention, both main surfaces of the metal base 31 of the metal separator 5 ( The intermediate layer 32 and the outermost conductive carbon layer 33 are disposed on the surface). When stainless steel with excellent corrosion resistance such as SUS316L is used for the metal base 31, for example, the metal base 31 itself can withstand the acidic environment in the fuel cell, so that the main purpose is to prevent acid corrosion. Then, the requirements of the intermediate layer 32 are not so strict. However, a high potential may be locally generated in the cell when the fuel cell is started or stopped. Considering the anticorrosion property against high potential, the material such as titanium nitride is more suitable than the conventional intermediate layer made of metal.

  However, when a material such as titanium nitride having excellent high-potential corrosion resistance is used as the intermediate layer, the adhesion with the conductive carbon layer formed on the intermediate layer is reduced for reducing contact resistance. As a cause of this, it was considered that the graphite having a turbulent layer structure contained in a large amount of the conductive carbon layer having a high R value does not contribute to the adhesion to the intermediate layer.

  Therefore, in the present invention, a boundary layer having high adhesion to an intermediate layer material such as titanium nitride is formed by controlling the R value of the conductive carbon layer near the intermediate layer to be lower than that of the surface layer portion. Yes.

  As a result, it is possible to obtain a conductive member having low contact resistance and high adhesion to the intermediate layer. In addition, the conductive member according to the present invention can suppress the peeling of the conductive carbon layer, and can suppress the penetration of water into the separator leading to an increase in contact resistance of the conductive carbon layer and corrosion of the metal substrate. As a result, the expected excellent battery performance can be expressed and maintained stably for a long period of time.

  Hereinafter, each component of the metal separator 5 of this embodiment is explained in detail.

[Metal base material]
The metal substrate 31 is a main layer of a conductive member that constitutes the metal separator 5 and contributes to securing conductivity and mechanical strength.

  There is no restriction | limiting in particular about the metal which comprises the metal base material 31, The thing conventionally used as a constituent material of the metal separator 5 can be used suitably. Examples of the constituent material of the metal base 31 include iron, titanium, aluminum, and alloys thereof. These materials can be preferably used from the viewpoint of mechanical strength, versatility, cost performance, or processability. Here, the iron alloy includes stainless steel. Especially, it is preferable that the metal base material 31 is comprised from stainless steel, aluminum, or an aluminum alloy. When stainless steel is used as the metal substrate 31, the conductivity of the contact surface with the gas diffusion substrate that is a constituent material of the gas diffusion layer (GDL) 4 can be sufficiently ensured. As a result, even if moisture enters the gaps between the rib shoulder film and the like, durability can be maintained by the corrosion resistance of the oxide film formed on the metal base 31 itself made of stainless steel. Here, GDL4 consists of a portion where the surface pressure is directly applied to GDL4 (4a, 4b) (metal separator 5 and contact portion; rib portion) and a portion that is not directly applied (non-contact portion; flow path portion). The rib shoulder portion refers to a contact portion with the metal separator 5; a shoulder portion (corner portion) of the rib portion.

  Examples of stainless steel include austenite, martensite, ferrite, austenite / ferrite, and precipitation hardening. Examples of austenite include SUS201, SUS202, SUS301, SUS302, SUS303, SUS304, SUS305, SUS316 (L), and SUS317. Examples of the austenite-ferrite type include SUS329J1. Examples of the martensite system include SUS403 and SUS420. Examples of the ferrite type include SUS405, SUS430, and SUS430LX. Examples of the precipitation hardening system include SUS630. Among these, it is more preferable to use austenitic stainless steel such as SUS304 and SUS316. Moreover, the content rate of iron (Fe) in stainless steel becomes like this. Preferably it is 60-84 mass%, More preferably, it is 65-72 mass%. Furthermore, the content of chromium (Cr) in the stainless steel is preferably 16 to 20% by mass, and more preferably 16 to 18% by mass.

  On the other hand, examples of the aluminum alloy include pure aluminum, aluminum / manganese, and aluminum / magnesium. The elements other than aluminum in the aluminum alloy are not particularly limited as long as they are generally usable as an aluminum alloy. For example, copper, manganese, silicon, magnesium, zinc and nickel can be included in the aluminum alloy. Specific examples of the aluminum alloy include A1050 and A1050P as the pure aluminum system, A3003P and A3004P as the aluminum / manganese system, and A5052P and A5083P as the aluminum / magnesium system. On the other hand, since the mechanical strength and formability are also required for the metal separator 5, in addition to the above alloy types, the tempering of the alloy can be selected as appropriate. In addition, when the metal base material 31 is comprised from the simple substance of titanium or aluminum, the purity of the said titanium or aluminum becomes like this. Preferably it is 95 mass% or more, More preferably, it is 97 mass% or more, More preferably, it is 99 mass % Or more.

  The thickness of the metal substrate 31 is not particularly limited. From the viewpoint of ease of processing and mechanical strength, and improvement of the energy density of the battery by thinning the separator 5 itself, it is preferably 50 to 500 μm, more preferably 80 to 300 μm, and still more preferably 80 ~ 200 μm. In particular, the thickness of the metal substrate 31 when stainless steel is used as the constituent material is preferably 80 to 150 μm. On the other hand, the thickness of the metal substrate 31 when aluminum is used as a constituent material is preferably 100 to 300 μm. In the above range, the metal separator 5 has a sufficient strength, but is excellent in workability and can achieve a suitable thickness.

  For example, from the viewpoint of providing sufficient strength as a constituent material for the fuel cell separator 5 or the like, the metal substrate 31 is preferably made of a material having a high gas barrier property. Since the separator 5 of the fuel cell plays a role of partitioning cells, different gas flows on both sides of the separator 5 (see FIG. 3). Therefore, from the viewpoint of eliminating the mixing of adjacent gases in each cell of the PEFC cell unit 1 and the fluctuation of the gas flow rate, the higher the gas barrier property, the more preferable the metal substrate 31 is.

[Conductive carbon layer]
The conductive carbon layer 33 is a layer containing conductive carbon. The presence of this layer can improve the corrosion resistance as compared with the case of only the metal substrate 31 while ensuring the conductivity of the conductive member constituting the metal separator 5. In the present invention, by changing the bias voltage from a low value to a high value when forming the conductive carbon layer, a boundary layer having good adhesion with the intermediate layer is formed at the interface of the intermediate layer, and the surface of the conductive carbon layer is formed. A surface layer portion having high conductivity can be formed.

The conductive carbon layer 33 is defined by an intensity ratio R (I _D / I _G ) between the D band peak intensity (I _D ) and the G band peak intensity (I _G ) measured by Raman scattering spectroscopy. By controlling the R value of the boundary layer and the surface layer portion to a certain region, effects such as improvement in adhesion between the intermediate layer and the conductive carbon layer, reduction in contact resistance, and corrosion resistance are increased. This will be described in more detail below.

When the carbon material is analyzed by Raman spectroscopy, peaks are usually generated around 1350 cm ⁻¹ and 1584 cm ⁻¹ . Highly crystalline graphite has a single peak near 1584 cm ⁻¹ , and this peak is usually referred to as the “G band”. On the other hand, a peak near 1350 cm ⁻¹ appears as the crystallinity decreases (crystal structure defects increase). This peak is usually referred to as the “D band” (note that the peak of diamond is strictly 1333 cm ⁻¹ and is distinct from the D band). The intensity ratio R (I _D / I _G ) between the D band peak intensity (I _D ) and the G band peak intensity (I _G ) is the graphite cluster size of the carbon material and the disorder of the graphite structure (crystal structure defect), Used as an index such as sp ² bond ratio. That is, in the present invention, it can be used as an index of the contact resistance of the conductive carbon layer 33 and can be used as a film quality parameter for controlling the conductivity of the conductive carbon layer 33.

The R (I _D / I _G ) value is calculated by measuring the Raman spectrum of the carbon material using a microscopic Raman spectrometer. Specifically, the peak intensity of 1300～1400Cm ^-1 called the D band _{(I D),} the relative intensity ratio of the peak intensity of 1500～1600Cm ^-1 called G band _{(I G)} (peak area ratio ( I _D / I _G )).

  As described above, in the present embodiment, the R value of the surface layer portion is preferably 1.3 or more, more preferably 1.4 to 2.0, and further preferably 1.4 to 1.9. Yes, particularly preferably 1.5 to 1.8. If this R value is 1.3 or more, a surface layer part with sufficient conductivity can be obtained. Moreover, if R value is 2.0 or less, the reduction | decrease of a graphite component can be suppressed. Furthermore, an increase in internal stress of the conductive carbon layer 33 itself can be suppressed, and the adhesion with the boundary layer can be further improved.

Moreover, it is preferable that R value of a boundary layer is less than 1.3, More preferably, it is 1.2 or less, More preferably, it is 1.1 or less. If the R value is less than 1.3, a boundary layer containing a large amount of sp ³ carbon can be obtained, and a surface layer portion can be formed on the boundary layer with a high bias voltage.

  In addition, the mechanism by which the above-described effect is obtained by setting the R value of the surface layer portion to 1.3 or more or the R value of the boundary layer to less than 1.3 as in the present embodiment is estimated as follows. Yes. However, the following estimation mechanism does not limit the technical scope of the present invention in any way.

In polycrystalline graphite, since the graphene surface is formed by the bonding of sp ² carbon atoms constituting the graphite cluster, conductivity is ensured in the plane direction of the graphene surface. Therefore, the conductive carbon layer according to the present invention has high adhesion between the intermediate layer and the conductive carbon layer while ensuring low contact resistance.

  Here, the size of the graphite cluster constituting the polycrystalline graphite which is the surface layer portion of the conductive carbon layer according to the present invention is not particularly limited. As an example, the average diameter of the graphite cluster is preferably about 1 to 50 nm, more preferably 2 to 10 nm. When the average diameter of the graphite cluster is within such a range, it is possible to prevent the conductive carbon layer 33 from being thickened while maintaining the crystal structure of the polycrystalline graphite. Here, the “diameter” of the graphite cluster means the maximum distance among the distances between any two points on the contour line of the cluster. Moreover, the average diameter value of the graphite cluster is expressed as an average value of the diameter of the cluster observed in several to several tens of fields using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). Can be calculated.

  In the present embodiment, the conductive carbon layer 33 may be composed of only polycrystalline graphite, but the conductive carbon layer 33 may include materials other than polycrystalline graphite. Examples of carbon materials other than polycrystalline graphite that can be included in the conductive carbon layer 33 include carbon black, fullerene, carbon nanotubes, carbon nanofibers, carbon nanohorns, and carbon fibrils. Specific examples of carbon black include, but are not limited to, ketjen black, acetylene black, channel black, lamp black, oil furnace black, or thermal black. Carbon black may be subjected to a graphitization treatment. Examples of materials other than the carbon material that can be included in the conductive carbon layer 33 include gold (Au), silver (Ag), platinum (Pt), ruthenium (Ru), palladium (Pd), rhodium (Rh), and indium. Examples thereof include noble metals such as (In); water-repellent substances such as polytetrafluoroethylene (PTFE); and conductive oxides. As for materials other than polycrystalline graphite, only 1 type may be used and 2 or more types may be used together.

  The thickness of the conductive carbon layer 33 (however, excluding the protruding particles 33a; the average value) is not particularly limited. However, Preferably it is 1-1000 nm, More preferably, it is 2-500 nm, More preferably, it is 5-200 nm. If the thickness of the conductive carbon layer 33 is a value within such a range, sufficient conductivity can be secured between the gas diffusion base material and the separator 5. Moreover, the advantageous effect that a high corrosion-resistant function can be given with respect to the metal base material 31 can be produced. In the present embodiment, the conductive carbon layer 33 may exist only on one main surface of the conductive member (separator 5), but preferably, as shown in FIG. It is desirable that the conductive carbon layer 33 exist on the other main surface (that is, on both surfaces of the conductive member). This improves the anticorrosion effect of the base material while ensuring the adhesion between the metal base material 31 and the conductive carbon layer 33 via the intermediate layer 32 on both surfaces of the conductive member (conductive carbon layer 33). This is because it can be further maintained.

  In the present embodiment, the entire metal base 31 is covered with the conductive carbon layer 33 via the intermediate layer 32. In other words, in this embodiment, the ratio (coverage) of the area where the metal base 31 is covered with the conductive carbon layer 33 is 100%. However, it is not limited only to such a form, and the coverage may be less than 100%. The coverage of the metal substrate 31 by the conductive carbon layer 33 is preferably 50% or more, more preferably 80% or more, still more preferably 90% or more, and most preferably 100%. By setting it as such a structure, the fall of electroconductivity and corrosion resistance accompanying the formation of the oxide film in the exposed part of the metal base material 31 which is not coat | covered with the electroconductive carbon layer 33 can be suppressed effectively. In addition, when the intermediate layer 32 is interposed between the metal base 31 and the conductive carbon layer 33 as in the present embodiment, the coverage is obtained when the conductive member (metal separator 5) is viewed from the stacking direction. The ratio of the area of the metal substrate 31 overlapping with the conductive carbon layer 33 is meant.

[Middle layer]
As shown in FIG. 2, in this embodiment, the conductive member constituting the separator 5 has an intermediate layer 32. The intermediate layer 32 has a function of preventing contact between the acidic aqueous solution and the metal substrate and preventing elution of ions from the metal substrate 31. In particular, when the R value of the conductive carbon layer exceeds the upper limit value of the preferable range described above, the effect of providing the intermediate layer 32 is remarkably exhibited. However, it is a matter of course that the intermediate layer 32 can be provided even when the R value is included in the preferred range described above. From another point of view, the above-described operation and effect due to the installation of the intermediate layer 32 is more noticeable when the metal base 31 is made of a material having low corrosion resistance under acidic conditions such as aluminum or an alloy thereof. Hereinafter, a preferable mode when the intermediate layer 32 is provided on the conductive member will be described.

  The material constituting the intermediate layer 32 is not particularly limited as long as it provides the above adhesion. For example, Group 4 metals (Ti, Zr, Nf), Group 5 metals (V, Nb, Ta), Group 6 metals (Cr, Mo, W) carbides, nitrides and And carbonitride. Among these, a metal nitride, carbide, or carbonitride with less ion elution such as tungsten (W), titanium (Ti), molybdenum (Mo), niobium (Nb), or hafnium (Hf) is preferably used. More preferably, titanium nitride, carbide or carbonitride having high high-potential corrosion resistance is used in addition to the anticorrosive effect of the underlying metal substrate. By using these materials, the conductive member can be protected from a local high potential generated at the time of starting and stopping. In addition, these metal materials are particularly useful in that even if an exposed portion exists due to the formation of a passive film, the elution of the metal material itself is hardly observed. In particular, when the metal base material is a metal base material 31 made of a metal having low corrosion resistance such as aluminum or an alloy thereof, corrosion proceeds due to moisture reaching the vicinity of the interface. As a result, the conductivity in the film thickness direction of the entire metal base 31 is deteriorated. For this reason, providing the intermediate layer is effective for imparting corrosion resistance to the conductive member.

  The film thickness of the intermediate layer 32 is not particularly limited. However, from the viewpoint of making the size of the fuel cell stack as small as possible by making the separator 5 thinner, the thickness of the intermediate layer 32 is preferably 0.01 to 10 μm, more preferably 0. 0.05 to 5 μm, more preferably 0.02 to 5 μm, and particularly 0.1 to 1 μm. If the thickness of the intermediate layer 32 is 0.01 μm or more, a uniform layer is formed, and the corrosion resistance of the metal substrate 31 can be effectively improved. On the other hand, if the thickness of the intermediate layer 32 is 10 μm or less, an increase in the film stress of the intermediate layer 32 can be suppressed, and a decrease in film followability to the metal substrate 31 and occurrence of peeling / cracking associated therewith can be prevented. .

  Further, the surface of the intermediate layer 32 on the conductive carbon layer 33 side is preferably rough at the nano level. According to such an embodiment, the adhesion between the boundary layer densely formed on the intermediate layer 32 and the intermediate layer 32 can be further improved. Examples of such an intermediate layer include an intermediate layer having a columnar crystal structure.

Furthermore, when the thermal expansion coefficient of the intermediate layer 32 is a value close to the thermal expansion coefficient of the metal constituting the metal substrate 31, the adhesion between the intermediate layer 32 and the metal substrate 31 is improved. However, in such a form, the adhesion between the intermediate layer 32 and the conductive carbon layer 33 may be reduced. Similarly, when the thermal expansion coefficient of the intermediate layer 32 is close to the thermal expansion coefficient of the conductive carbon layer 33, the adhesion between the intermediate layer 32 and the metal substrate 31 may be lowered. Taking these into consideration, the thermal expansion coefficient (α _mid ) of the intermediate layer 32, the thermal expansion coefficient (α _sub ) of the metal substrate 31, and the thermal expansion coefficient (α _c ) of the conductive carbon layer 33 are expressed by α _sub It is preferable that the relationship of> α _mid > α _c is satisfied.

  The intermediate layer 32 is preferably present on both surfaces of the metal base 31, but in the case of use in an application location that does not impair the intended effect of the present invention, on either surface. May exist only. However, when the conductive carbon layer 33 exists only on one main surface of the metal substrate 31, the intermediate layer 32 exists between the metal substrate 31 and the conductive carbon layer 33. In addition, the conductive carbon layer 33 may exist on both surfaces of the metal base 31 as described above. In such a case, the intermediate layer 32 is preferably interposed between the metal base 31 and both conductive carbon layers 33, respectively. When the intermediate layer 32 exists only between the metal substrate 31 and one of the conductive carbon layers 33, the intermediate layer 32 is disposed on the MEA 9 side in the PEFC 1. It is preferable that it exists between 33 and the metal base material 31 (refer FIG.1, FIG.3, FIG.4 etc.).

  FIG. 6 shows a manufacturing apparatus for forming (forming) at least one of the conductive members of the present invention, particularly the intermediate layer 32 and the conductive carbon layer 33, preferably using the sputtering method in order to form each of these layers. FIG. Here, as a sputtering apparatus, an apparatus applicable to the unbalanced magnetron sputtering (UBMS) method used in the examples is shown.

  7 shows at least one of the conductive members of the present invention, in particular, the intermediate layer 32 and the conductive carbon layer 33, preferably each of these layers is formed (formed) using the arc ion plating (AIP) method in order. It is the plane schematic diagram of the manufacturing apparatus for carrying out. However, FIG. 6 and FIG. 7 show an example in which an existing disk-shaped wafer is set instead of the flat metal separator 5 before the uneven pressing.

  When sputtering is performed using the apparatuses 300 and 400 shown in FIG. 6 and FIG. 7, one or more metal separators 5 are arranged on the rotating tables 301 and 401, and the films are formed on the front and back of each metal separator 5. Each metal separator 5 itself also rotates in a direction perpendicular to the rotating surface (rotating shaft) of the rotating table. The arrow method of each of the metal separators 5 of the rotating tables 301 and 401 indicates the direction of rotation in which the rotation surfaces (axes) are orthogonal to each other.

The vacuum chambers 303 and 403 shown in FIGS. 6 and 7 are held at a level of 10 ⁻¹ to 10 ⁻² Torr, and as necessary. Gases (not shown) such as N ₂ and Ar can be introduced from the air supply ports 305 and 405. Unnecessary atmospheric gas and excess gas source are appropriately exhausted from the exhaust ports 307 and 407 in order to control a predetermined pressure (vacuum pressure or the like) in the vacuum chambers 303 and 403.

  Temperature control equipment is connected to the vacuum chambers 303 and 403 and the tables 301 and 401 themselves holding the metal separators 5 so that the temperature can be adjusted.

  First, the surface of each metal separator 5 shown in FIGS. 6 and 7 is removed with an Ar ion bombardment (reverse sputtering) to remove the oxide film present on the surface layer portion of the metal separator 5. Since the oxide film is formed with a thickness of several angstroms, the removal time may be several seconds to several minutes. In the present embodiment, titanium nitride is disposed as the intermediate layer 32 before the conductive carbon layer 33 is formed. For this reason, Ti targets (sputtering targets (Ti)) 309 and 409 are disposed in the chambers 301 and 401, and sputtering is performed in a nitrogen atmosphere. After the formation of the intermediate layer 32 of titanium nitride, the conductive carbon layer 33 is formed by using the carbon (target) (sputtering target (C)) 311 and 411 disposed in the same chambers 301 and 401. As shown in FIG. 6, the conductive carbon layer 33 may be formed in various patterns in which the negative bias voltage at the time of forming the conductive carbon layer is changed from a low value to a high value. In addition, it can be formed continuously by changing the bias voltage, temperature, degree of vacuum, etc. of each metal separator 5. The formation of the intermediate layer 32 may be performed without changing the bias voltage or the like at a predetermined value, or may be performed twice or more (or may be changed continuously). good. In addition, it can be formed continuously by changing the bias voltage, temperature, degree of vacuum, etc. of each metal separator 5.

  When the conductive carbon layer 33 is formed by arc ion plating (AIP) using the apparatus shown in FIG. 7, the target (sputtering target (C)) 411 is used as in the case of FIG. However, by disposing another vapor deposition source 413 for arc discharge, it is possible to form a film in the same chamber 401 without reducing the degree of vacuum. Even in the formation of the conductive carbon layer 33 by the AIP method using the apparatus shown in FIG. 7, in order to obtain the conductive carbon layer 33 having predetermined characteristics, the conditions (voltage / current) of the arc power source 415, the degree of vacuum, The temperature, bias voltage, etc. may be constant without changing them at predetermined values, or can be formed by changing them as appropriate.

  The conductive carbon layer 33 is formed by, for example, using the apparatus shown in FIGS. 6 and 7, after the deposition of the intermediate layer 32, after changing the target, and after that, the bias (voltage), temperature, vacuum degree, supply gas amount (min. It is desirable to form the same batch or process using the same apparatus and method by changing at least one of the pressure. This is because the conductive carbon layer 33 can be continuously formed after the formation of the intermediate layer 32 and can be formed on the same film formation process, which is excellent in terms of low cost.

  In the present invention, the intermediate layer 32 and the conductive carbon layer 33 are formed by sputtering using the apparatus shown in FIG. 6, or are formed by AIP or ECR sputtering using the apparatus shown in FIG. desirable. This is because a conductive path from one surface of the conductive carbon layer 33 to the other surface is secured by using a sputtering method or an AIP method, which is a dry film formation method, for the intermediate layer 32 and the conductive carbon layer 33. By this, it is excellent in that a conductive member having further improved corrosion resistance can be provided while sufficiently ensuring excellent conductivity. Further, in the conductive member having the intermediate layer 32 between the metal substrate 31 and the conductive carbon layer 33, a means for suppressing an increase in contact resistance while sufficiently ensuring the excellent conductivity can be provided. Is excellent.

  In forming the intermediate layer 32 and the conductive carbon layer 33, a solid source (eg, graphite carbon) is desirable. With a gas source, it is difficult to produce a good gas type that is currently used. This is because hydrogen enters the film (resulting in a decrease in conductivity).

  Note that the size and number of the targets 309, 311, 409, 411, and 413 can be adjusted as appropriate depending on the size and the processing amount of the metal separator 5.

  In the present invention, not only the metal separator 5 but also the surface of a component that requires conductivity and corrosion resistance can be applied anywhere. For example, current collecting plates 30 and 40 (see FIG. 3) disposed at both ends of the stack 20 in which a plurality of cells are stacked, a gas diffusion layer (GDL) 4, and terminal connection portions for monitoring voltage (not shown). And output terminals 37 and 47 in FIG. 4).

  In the present embodiment, when the intermediate layer is formed on the metal substrate in the dry film forming method, the dry film forming method is preferably a sputtering method or an ion plating method. However, the present invention is not limited to these, and various conventionally known film forming techniques described above can be used.

  Hereinafter, the components of the PEFC using the separator formed of the conductive member of the present embodiment will be described with reference to FIGS. However, the present invention is characterized by the conductive member constituting the separator. Therefore, specific forms such as the shape of the separator in the PEFC and specific forms of members other than the separator constituting the fuel cell can be appropriately modified with reference to conventionally known knowledge. 3 is a schematic cross-sectional view for explaining an example of a fuel cell stack configuration in which a plurality of unit cell configurations of the fuel cell of FIG. 1 are stacked, and FIG. 4 is a perspective view of the fuel cell stack configuration of FIG. It is.

[Electrolyte layer]
The electrolyte layer is composed of a solid polymer electrolyte membrane 2 as shown in FIGS. 1 and 3, for example. This solid polymer electrolyte membrane 2 has a function of selectively permeating protons generated in the anode catalyst layer 3a during operation of the PEFC composed of a plurality of cell units 1 and the like to the cathode catalyst layer 3b along the film thickness direction. Have The solid polymer electrolyte membrane 2 also has a function as a partition wall for preventing the fuel gas 5ag supplied to the anode side and the oxidant gas 5bg supplied to the cathode side from being mixed.

  The solid polymer electrolyte membrane 2 is roughly classified into a fluorine-based polymer electrolyte membrane and a hydrocarbon-based polymer electrolyte membrane depending on the type of ion exchange resin that is a constituent material. Examples of ion exchange resins constituting the fluorine-based polymer electrolyte membrane include Nafion (registered trademark, manufactured by DuPont), Aciplex (registered trademark, manufactured by Asahi Kasei Co., Ltd.), Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.), and the like. Perfluorocarbon sulfonic acid polymer, perfluorocarbon phosphonic acid polymer, trifluorostyrene sulfonic acid polymer, ethylene tetrafluoroethylene-g-styrene sulfonic acid polymer, ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride- Examples include perfluorocarbon sulfonic acid polymers. From the viewpoint of improving power generation performance such as heat resistance and chemical stability, these fluorine-based polymer electrolyte membranes are preferably used, and particularly preferably fluorine-based polymer electrolytes composed of perfluorocarbon sulfonic acid polymers. A membrane is used.

  Specific examples of the hydrocarbon electrolyte include sulfonated polyethersulfone (S-PES), sulfonated polyaryletherketone, sulfonated polybenzimidazole alkyl, phosphonated polybenzimidazole alkyl, sulfonated polystyrene, and sulfonated poly. Examples include ether ether ketone (S-PEEK) and sulfonated polyphenylene (S-PPP). These hydrocarbon polymer electrolyte membranes are preferably used from the viewpoint of production such that the raw material is inexpensive, the production process is simple, and the material selectivity is high. In addition, as for the ion exchange resin mentioned above, only 1 type may be used independently and 2 or more types may be used together. Moreover, it is not restricted only to the material mentioned above, Other materials may be used.

  The thickness of the electrolyte layer may be appropriately determined in consideration of the characteristics of the obtained fuel cell, and is not particularly limited. The thickness of the electrolyte layer is usually about 5 to 300 μm. When the thickness of the electrolyte layer is within such a range, the balance between the strength during film formation, durability during use, and output characteristics during use can be appropriately controlled.

[Catalyst layer]
The catalyst layers 3 (the anode catalyst layer 3a and the cathode catalyst layer 3b) shown in FIGS. 1 and 3 are layers in which the cell reaction actually proceeds. Specifically, the oxidation reaction of hydrogen proceeds in the anode catalyst layer 3a, and the reduction reaction of oxygen proceeds in the cathode catalyst layer 3b.

  The catalyst layer 3 includes a catalyst component, a conductive catalyst carrier that supports the catalyst component, and an electrolyte. Hereinafter, a composite in which a catalyst component is supported on a catalyst carrier is also referred to as an “electrode catalyst”.

  The catalyst component used in the anode catalyst layer 3a is not particularly limited as long as it has a catalytic action in the hydrogen oxidation reaction, and a known catalyst can be used in the same manner. The catalyst component used for the cathode catalyst layer 3b is not particularly limited as long as it has a catalytic action for the oxygen reduction reaction, and a known catalyst can be used in the same manner. Specifically, it may be selected from metals such as platinum, ruthenium, iridium, rhodium, palladium, osmium, tungsten, lead, iron, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, aluminum, and alloys thereof. .

  Among these, those containing at least platinum are preferably used in order to improve catalyst activity, poisoning resistance to carbon monoxide and the like, heat resistance, and the like. Although the composition of the alloy depends on the type of metal to be alloyed, the content of platinum is preferably 30 to 90 atomic%, and the content of the metal to be alloyed with platinum is preferably 10 to 70 atomic%. In general, an alloy is a generic term for a metal element having one or more metal elements or non-metal elements added and having metallic properties. The alloy structure consists of a eutectic alloy, which is a mixture of the component elements as separate crystals, a component element completely melted into a solid solution, and a component element composed of an intermetallic compound or a compound of a metal and a nonmetal. There is what is formed, and any may be used in the present application. At this time, the catalyst component used for the anode catalyst layer 3a and the catalyst component used for the cathode catalyst layer 3b can be appropriately selected from the above. In the present specification, unless otherwise specified, descriptions of the catalyst components for the anode catalyst layer and the cathode catalyst layer have the same definition for both. Therefore, they are collectively referred to as “catalyst components”. However, the catalyst components of the anode catalyst layer 3a and the cathode catalyst layer 3b do not have to be the same, and can be appropriately selected so as to exhibit the desired action as described above.

  The shape and size of the catalyst component are not particularly limited, and the same shape and size as known catalyst components can be adopted. However, the shape of the catalyst component is preferably granular. At this time, the average particle diameter of the catalyst particles is preferably 1 to 30 nm. When the average particle diameter of the catalyst particles is within such a range, the balance between the catalyst utilization rate related to the effective electrode area where the electrochemical reaction proceeds and the ease of loading can be appropriately controlled. The “average particle diameter of catalyst particles” in the present invention is the average of the crystallite diameter determined from the half-value width of the diffraction peak of the catalyst component in X-ray diffraction or the average particle diameter of the catalyst component determined from a transmission electron microscope image. It can be measured as a value.

  The catalyst carrier functions as a carrier for supporting the above-described catalyst component and an electron conduction path involved in the transfer of electrons between the catalyst component and another member.

  Any catalyst carrier may be used as long as it has a specific surface area for supporting the catalyst component in a desired dispersion state and sufficient electron conductivity, and the main component is preferably carbon. Specific examples include carbon particles made of carbon black, activated carbon, coke, natural graphite, artificial graphite and the like. “The main component is carbon” means that the main component contains carbon atoms, and is a concept that includes both carbon atoms and substantially carbon atoms. In some cases, elements other than carbon atoms may be included in order to improve the characteristics of the fuel cell. Note that “substantially consisting of carbon atoms” means that contamination of about 2 to 3 mass% or less of impurities can be allowed.

The BET specific surface area of the catalyst carrier may be a specific surface area sufficient to carry the catalyst component in a highly dispersed state, but is preferably 20 to 1600 m ² / g, more preferably 80 to 1200 m ² / g. When the specific surface area of the catalyst carrier is in such a range, the balance between the dispersibility of the catalyst component on the catalyst carrier and the effective utilization rate of the catalyst component can be appropriately controlled.

  The size of the catalyst carrier is not particularly limited, but from the viewpoint of controlling the ease of loading, the catalyst utilization, and the thickness of the catalyst layer within an appropriate range, the average particle size is about 5 to 200 nm, preferably 10 to 10 nm. About 100 nm is preferable.

  In the electrode catalyst in which the catalyst component is supported on the catalyst carrier, the supported amount of the catalyst component is preferably 10 to 80% by mass, more preferably 30 to 70% by mass with respect to the total amount of the electrode catalyst. When the supported amount of the catalyst component is within such a range, the balance between the degree of dispersion of the catalyst component on the catalyst support and the catalyst performance can be appropriately controlled. The amount of the catalyst component supported on the electrode catalyst can be measured by inductively coupled plasma emission spectroscopy (ICP).

  The catalyst layer 3 contains an ion conductive polymer electrolyte in addition to the electrode catalyst. The polymer electrolyte is not particularly limited, and conventionally known knowledge can be referred to as appropriate. For example, the ion exchange resin which comprises the electrolyte layer 2 mentioned above can be added to the catalyst layer 3 as a polymer electrolyte.

[Gas diffusion layer (GDL)]
The gas diffusion layer 4 (gas diffusion layer 4a, cathode gas diffusion layer 4b) shown in FIG. 31 is a gas channel (fuel gas channel 5aa, oxidant gas channel) of the metal separator 5 (anode separator 5a, cathode separator 5b). 5bb) has a function of promoting diffusion of the gas (fuel gas or oxidant gas) supplied to the catalyst layer 3 (the anode catalyst layer 3a and the cathode catalyst layer 3b) and a function as an electron conduction path.

  The material which comprises the base material of the gas diffusion layer 4 (4a, 4b) is not specifically limited, A conventionally well-known knowledge can be referred suitably. For example, a sheet-like material having conductivity and porosity such as a carbon woven fabric, a paper-like paper body, a felt, and a non-woven fabric can be used. The thickness of the base material of the gas diffusion layer 4 may be appropriately determined in consideration of the characteristics of the obtained gas diffusion layer, but may be about 30 to 500 μm. If the thickness of the base material of the gas diffusion layer 4 is within such a range, the balance between the mechanical strength and the diffusibility of gas, water, etc. can be controlled appropriately.

  The gas diffusion layer 4 preferably contains a water repellent for the purpose of further improving water repellency and preventing a flooding phenomenon or the like. Although it does not specifically limit as a water repellent, Fluorine-type high things, such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), polyhexafluoropropylene, and tetrafluoroethylene-hexafluoropropylene copolymer (FEP), are included. Examples thereof include molecular materials, polypropylene, and polyethylene.

  In order to further improve the water repellency, the gas diffusion layer 4 includes a carbon particle layer (microporous layer; MLP, not shown) made of an aggregate of carbon particles containing a water repellent agent on the catalyst layer side of the substrate. You may have.

  The carbon particles contained in the carbon particle layer are not particularly limited, and conventionally known materials such as carbon black, graphite, and expanded graphite can be appropriately employed. Among them, carbon black such as oil furnace black, channel black, lamp black, thermal black, acetylene black and the like can be preferably used because of excellent electron conductivity and a large specific surface area. The average particle diameter of the carbon particles is preferably about 10 to 100 nm. Thereby, while being able to obtain the high drainage property by capillary force, the contact property with the catalyst layer 4 can also be improved.

  Examples of the water repellent used in the carbon particle layer include the same water repellent as described above. Among these, fluorine-based polymer materials can be preferably used because of excellent water repellency, corrosion resistance during electrode reaction, and the like.

  The mixing ratio of the carbon particles to the water repellent in the carbon particle layer is about 90:10 to 40:60 (carbon particles: water repellent) in terms of mass ratio in consideration of the balance between water repellency and electron conductivity. It is good. The thickness of the carbon particle layer is not particularly limited and may be appropriately determined in consideration of the water repellency of the obtained gas diffusion layer, but is preferably 10 to 1000 μm, more preferably 50 to 500 μm. Good.

[Separator]
The metal separator 5 shown in FIGS. 1 and 3 is as described in the examples described later.

The conductive member of this embodiment can be used for various applications. A typical example is the PEFC separator 5 shown in FIG. However, the use of the conductive member of the present embodiment is not limited to this. For example, in addition to PEFC, various fuel cell separators such as phosphoric acid fuel cell (PAFC), molten carbonate fuel cell (MCFC), solid electrolyte fuel cell (SOFC) or alkaline fuel cell (AFC) Can also be used. In addition to the fuel cell separator, the separator can be used in various applications that require both conductivity and corrosion resistance. Examples of uses other than the fuel cell separator in which the conductive member of the present embodiment can be used include other fuel cell components (current collector plate, bus bar, gas diffusion base material, MEA), contacts of electronic components, and the like. . In another preferred embodiment, the conductive member of the present embodiment is used in a wet environment and an energized environment. When used in such an environment, the effect of the present invention of achieving both conductivity and corrosion resistance can be remarkably exhibited.
[Basic configuration of cell unit]
1 and 3, the basic structure of a single cell (cell unit) 1 of a solid polymer fuel cell is that a fuel electrode side electrode catalyst layer 3a and a fuel electrode side gas are formed on both sides of a solid polymer electrolyte membrane 2. The fuel electrode composed of the diffusion layer 4a and the oxygen electrode composed of the oxygen electrode side electrode catalyst layer 3b and the oxygen electrode side gas diffusion layer 4b each have an MEA 9 disposed opposite to each other. It is sandwiched between the fuel electrode side separator 5a and the oxygen electrode side separator 5b. Further, the fuel gas 5ag (hydrogen-containing gas) and the oxidant gas 5bg (air) supplied to the MEA are supplied to the fuel electrode side separator 5a and the oxygen electrode side separator 5b, to the fuel electrode side electrode catalyst layer 3a and the oxygen electrode side electrode. The gas is supplied through a fuel gas flow path 5aa and an oxidant gas flow path 5bb formed at a plurality of locations on the surface facing the catalyst layer 3b.

  In order to use the cell unit (single cell) 1 for the fuel cell (stack) 20, a single cell 1 or a stack in which two or more single cells 1 are stacked (stacked stack) is further used in the thickness direction of the single cells 1 to the stacked stack Are used by fastening with a pair of end plates, ie, a fuel electrode side end plate 70 and an oxygen electrode side end plate 80 from both sides (both ends) (see FIG. 4).

  More specifically, as a configuration of the fuel cell stack 20 (a portion sandwiched between the current collector plates 30 and 40), as shown in FIG. 3, a plurality of single cells (cell units) 1 of fuel cells are stacked. It has a stack unit 20 and is used as a power source. Applications of the power source include, for example, stationary devices, consumer portable devices such as mobile phones, emergency devices, outdoor devices such as leisure and construction power sources, and mobile objects such as automobiles with limited mounting space. In particular, the mobile power supply is preferably applied because a high output voltage is required after a relatively long period of shutdown. Further, in a vehicle equipped with the fuel cell of the present invention, the thickness can be reduced and the cost can be reduced through components (conductive members) such as the metal separator 5 and current collector plates 30 and 40 of the fuel cell (PEFC). This can contribute to an improvement in the output density of the fuel cell. Therefore, the vehicle weight can be reduced and the vehicle cost can be reduced, and when a fuel cell having the same volume is mounted, the vehicle can run for a longer distance and the acceleration performance can be improved.

  In the single cell (cell unit) 1 of the fuel cell according to the present invention, the thickness can be reduced and the cost can be reduced through components (conductive members) such as the metal separator 5 and current collector plates 30 and 40 of the fuel cell (PEFC). When 20 is formed, it can contribute to the improvement of the output density of the fuel cell stack 20. In addition, the corrosion resistance of the components (conductive members) such as the metal separator 5 and the current collector plates 30 and 40 of the fuel cell is excellent, and the durability (long life) of the fuel cell stack 20 can also be achieved.

  On both sides of the stack part 20, current collecting plates 30, 40, insulating plates 50, 60 and end plates 70, 80 are arranged. The current collecting plates 30 and 40 are made of a gas impermeable conductive member such as dense carbon, copper plate, or aluminum plate, and are provided with output terminals 37 and 47 for outputting the electromotive force generated in the stack portion 20. It has been. The insulating plates 50 and 60 are formed from an insulating member such as rubber or resin.

  Here, instead of the above-described carbon or the like, the current collector plates 30 and 40 are made of a copper plate, an aluminum plate, or the like having poor corrosion resistance while being thinner and lighter than stainless steel from the viewpoint of thinning and cost reduction. When used for the electric plates 30 and 40, the configuration of the present invention can be adopted. With this configuration, it is possible to form a conductive member in which resistance is reduced on the outermost surface of the conductive carbon layer 33 while preventing the base material 31 from being corroded by the ingress of droplets in the intermediate layer 32. As a result, the chemical stability can be maintained even if the metal current collector plates 30 and 40 are exposed to an acidic atmosphere while maintaining the conductivity. Specifically, the surface treatment can effectively suppress the ion elution property against defects such as pinholes without increasing the electrical resistance (here, contact resistance with the separator 5 as shown in FIG. 3). The applied current collecting plates 30 and 40 can be provided.

  As shown in FIGS. 1 and 4, the end plates 70 and 80 are made of a material having rigidity, for example, a metal material such as steel. The end plates 70 and 80 are provided with a fuel gas flow path (hydrogen-containing gas flow path) 5aa and an oxidant in order to circulate the fuel gas 5ag (for example, hydrogen), the oxidant gas 5bg (for example, oxygen), and the cooling water 8w. A fuel gas inlet 71, a fuel gas outlet 72, an oxidant gas inlet 74, and an oxidant gas outlet that communicate with the gas passage (oxygen gas passage) 5 bb and the cooling water passage (refrigerant passage) 8. 75, a cooling water introduction port 77, and a cooling water discharge port 78.

  As shown in FIG. 4, through holes through which the tie rods 90 are inserted are arranged at the four corners of the stack unit 20, current collector plates 30 and 40, insulating plates 50 and 60, and end plates 70 and 80. The tie rod 90 is screwed with a nut (not shown) to a male screw portion formed at an end portion thereof, and the inside of the fuel cell stack 200 (stack portion 20) is fastened by the end plates 70 and 80. The load for forming the stack acts in the stacking direction of the single fuel cell (cell unit) 1 (MEA 9), and holds the single fuel cell (cell unit) 1 in a pressed state.

As shown in FIG. 4, the tie rod 90 is formed of a rigid material, for example, a metal material such as steel, and an insulated surface to prevent electrical short circuit between the fuel cell unit cells 201. Part. The number of tie rods 90 installed is not limited to four (four corners). The fastening mechanism of the tie rod 90 is not limited to screwing, and other means can be applied. As shown in FIG. 1 and FIG. 3, the fuel cell single cell (cell unit) 1 is as described above. It is desirable to have an MEA 9, separators 5a and 5b, and a gasket (not shown). The MEA 9 includes an electrolyte membrane 2, a fuel electrode side electrode (catalyst layer 3 a and gas diffusion layer 4 a) and an oxygen electrode side electrode (catalyst layer 3 b and gas diffusion layer 4 b) disposed with the electrolyte membrane 2 interposed therebetween. Separator 5a, 5b is arrange | positioned on the outer surface of MEA9. The separator 5 a has a flow path 5 aa for circulating the fuel gas 5 ag and is connected to a fuel gas inlet 71 and a fuel gas outlet 72 arranged in the end plate 70. The separator 5 b has a flow path 5 bb for allowing the oxidant gas 5 bg to flow, and is connected to an oxidant gas inlet 74 and an oxidant gas outlet 75 arranged in the end plate 80.

  As shown in FIGS. 1 and 3, the separators 5 a and 5 b have a flow path 8 for circulating the cooling water 8 w, and a cooling water inlet 77 disposed in the end plates 70 and 80 and The cooling water discharge port 78 is connected.

  Next, the gasket is a seal member disposed so as to surround the outer periphery of the electrode positioned on the surface of the MEA 9 and is fixed to the outer surface of the electrolyte membrane 2 of the MEA 9 via an adhesive layer (not shown). You may have a structure. The gasket has a function of ensuring the sealability between the separator 5 and the MEA 9. Note that the adhesive layer used as necessary preferably corresponds to the shape of the gasket and is arranged in a frame shape on the entire peripheral edge of the electrolyte membrane in consideration of securing adhesiveness.

  Further, as shown in FIG. 4, in the fuel cell stack 200 using the conductive member of the present invention, a manifold (anode (fuel gas 5ag), cathode (oxidation) formed through the current collector plates 30 and 40 is formed. In the preferred embodiment, the intermediate layer 32 is also formed on the inner wall of the penetrating portion of the agent gas 5bg) and the inlet and outlet of each of the cooling water 8w for a total of six locations. In other words, since no electrical conductivity is required on the inner wall of the penetrating portion of the manifold, it is desirable to form the intermediate layer 32 without providing a surface treatment layer such as gold plating. This is extremely effective in that corrosion of the base material at the penetrating portion of the manifold can be effectively prevented.

  The above is the outline of the configuration of the fuel cell stack 200 using the conductive member of the present invention. In addition to the metal separator 5 and the current collector plates 30 and 40, the components of the fuel cell that require conductivity and corrosion resistance About (conductive member), the structure of this invention can be employ | adopted. As a result, it is possible to reduce the thickness and weight of the fuel cell component (conductive member), and thus the fuel cell stack, and contribute to improving the output density. Furthermore, since it leads to cost reduction, it is also useful as a battery element technology to be mounted on a fuel cell vehicle that is strongly demanded for price reduction.

  The manufacturing method of the fuel cell of the present invention is not particularly limited (except for the manufacturing method of the intermediate layer 32 described above) in particular, and can be manufactured by appropriately referring to conventionally known knowledge in the field of fuel cells. It is.

  The type of the fuel gas 5ag (hydrogen-containing gas) used when operating the fuel cell has been described by taking hydrogen as an example in the above description, but is not particularly limited. In addition to hydrogen, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, secondary butanol, tertiary butanol, dimethyl ether, diethyl ether, ethylene glycol, and diethylene glycol can be used. Of these, hydrogen and methanol are preferred because they can increase the output.

  Furthermore, a fuel cell stack 200 having a structure in which a plurality of membrane electrode assemblies (MEA 9) are stacked and connected in series via a metal separator 5 may be formed so that a desired voltage or the like can be obtained by the fuel cell ( (See FIGS. 3 and 4). The shape of the fuel cell is not particularly limited, and may be determined as appropriate so that desired battery characteristics such as voltage can be obtained.

  Although it does not restrict | limit especially as a use of the fuel cell of this invention, Since it is excellent in electric power generation performance, it is preferable to use as a drive power supply in vehicles, such as a motor vehicle.

  The PEFC cell unit 1 and the fuel cell stack 200 described above use a metal separator 5 made of a conductive member having excellent conductivity and corrosion resistance. Therefore, the cell unit 1 and the fuel cell stack 200 of the PEFC are excellent in output characteristics and durability, and can maintain good power generation performance over a long period of time. In the PEFC cell unit 1 in the form shown in FIG. 1, the metal separator 5 is formed in a concavo-convex shape by subjecting a flat conductive member to a press treatment. However, it is not limited only to such a form. For example, the concave and convex shapes constituting the gas flow paths 5ag and 5bg and the refrigerant flow path 8 are formed in advance by performing a cutting process on a flat metal plate (metal base 31), and the above-described technique is formed on the surface thereof. By forming the conductive carbon layer 33 (and the intermediate layer 32 if necessary), the metal separator 5 may be used.

  The PEFC cell unit 1 of this embodiment and the fuel cell stack 200 using the same can be mounted on a vehicle as a driving power source, for example.

  In order to mount the fuel cell stack 200 on a vehicle such as a fuel cell vehicle, for example, the fuel cell stack 200 may be mounted under the seat at the center of the vehicle body of the fuel cell vehicle. If it is installed under the seat, the interior space and the trunk room can be widened. Depending on circumstances, the place where the fuel cell stack 200 is mounted is not limited to the position under the seat, but may be a lower part of the rear trunk room or an engine room in front of the vehicle. Thus, a vehicle equipped with the PEFC cell unit 1 and the fuel cell stack 200 of the above-described form is also included in the technical scope of the present invention. The above-described PEFC cell unit 1 and fuel cell stack 200 are excellent in output characteristics and durability. Therefore, a highly reliable fuel cell vehicle can be provided over a long period of time.

  Hereinafter, although the effect by this invention is demonstrated using an Example and a comparative example, the technical scope of this invention is not limited to these Examples.

[Example 1]
A separator plate made of austenitic stainless steel with a thickness of 100 μm was used, and as a pretreatment, ultrasonic cleaning was performed in ethanol solution for 3 minutes, a metal substrate was then placed in a vacuum chamber, and ion bombardment with Ar gas was performed. The oxide film was removed. The pretreatment and the ion bombardment treatment were both performed on both surfaces of the metal substrate.

  Next, by using an ion ion plating method (or sputtering method), Ti is used as a target, a negative bias voltage is applied to the metal substrate while introducing nitrogen gas, and a 0.5 μm thick TiN film is applied. The resulting intermediate layer was formed on both sides of the metal substrate. The temperature at the time of forming the intermediate layer is 200 ° C., and the voltage application pattern is constant at 50V.

  Next, on the intermediate layer, while applying a negative bias voltage to the metal substrate by sputtering, the solid graphite is used as a target, and the film thickness is formed on both surfaces of the metal substrate on which the intermediate layer is formed. A 0.02 μm conductive carbon layer was deposited. The temperature and voltage application pattern during the formation of the conductive carbon layer was maintained at the initial bias voltage value of 50 V for 5 minutes, then increased to 7 minutes until the final voltage of 200 V, and maintained at the final voltage of 200 V for 3 minutes. The peel test and contact resistance values are shown in Table 1 below.

  In this example, as is clear from the appearance photograph shown in FIG. 8A, the front surface of the conductive member is glossy, and the entire surface can be formed. Moreover, as shown in Table 1, it can be understood that the obtained conductive carbon layer has high adhesion to the intermediate layer while having low contact resistance.

  In addition, as apparent from the surface SEM observation photograph shown in FIG.

[Example 2]
In the step of forming the conductive carbon layer of Example 1, the holding time at the initial value of the bias voltage of 50 V is 15 minutes, the boosting time to the final voltage of 200 V is 10 minutes, and the holding time at the final voltage of 200 V is 5 A conductive member was prepared in the same manner except for the minute.

  Adhesion with the intermediate layer can be improved while maintaining a low contact resistance of the conductive carbon layer by taking a long film formation time at a low voltage and taking time for boosting as in this embodiment.

[Example 3]
In the step of forming the conductive carbon layer of Example 1, a conductive member was produced in the same manner except that the final voltage was 300V.

  Setting the final voltage high as in this embodiment can increase the degree of graphitization of the surface layer portion, which is advantageous from the viewpoint of reducing the contact resistance of the surface layer portion.

[Comparative Example 1]
A conductive member was produced in the same manner except that the bias application pattern for forming the conductive carbon layer of Example 1 was set at 150 V for 15 minutes.

  In this comparative example, as is apparent from the appearance photograph of FIG. 8B, it is powdery near the center and no film is formed. This is presumably because the value of the bias voltage is too high to form the boundary layer.

  Further, as can be seen from FIG. 9B showing a surface SEM observation photograph of a portion not in powder form in FIG. 8B, it can be seen that there is no gap in the grain boundary or the like and the film form is dense.

[Comparative Example 2]
In Comparative Example 1, a conductive member was produced in the same manner except that the substrate temperature immediately before forming the conductive carbon layer was 350 ° C. and the value of the bias voltage was 50V.

  The bias voltage value of this comparative example is preferable for forming a carbon layer as a boundary layer having a low R value and good adhesion to the intermediate layer. However, since the temperature is high, graphitization proceeds and the adhesion between the intermediate layer and the conductive carbon layer cannot be ensured.

[Comparative Example 3]
A conductive member was produced in the same manner except that the bias application pattern for forming the conductive carbon layer of Comparative Example 1 was 50V.

  In this comparative example, a carbon layer that can function as a boundary layer having a low R value and good adhesion to the intermediate layer can be formed on the intermediate layer. However, since such a carbon layer has a low degree of graphitization, the contact resistance is high.

[Measurement of contact resistance]
For the conductive members prepared in Examples 1 to 3 and Comparative Example 3, the contact resistance in the stacking direction of the conductive members was measured. Specifically, as shown in FIG. 10, a pair of gas diffusion substrates (gas diffusion layers 4a) are formed on both sides of the conductive members (metal separators 5) formed in Examples 1 to 3 and Comparative Example 3 above. 4b), the both sides of the obtained laminate are further sandwiched by a pair of electrodes (catalyst layers 3a, 3b), power is connected to both ends thereof, and the entire laminate including the electrodes is loaded with 1 MPa. The measurement device was configured by holding. The contact resistance value of the laminate was calculated from the energization amount and voltage value when a constant current of 1 A was passed through the measuring apparatus and a load of 1 MPa was applied.

As shown in Table 1, the contact resistances of the conductive members produced in Examples 1 to 3 were all 1 mΩ · cm ² . On the other hand, in Comparative Example 3, it was 5 mΩ · cm ² .

[Measurement of R value]
About the electrically-conductive member produced in each said Examples 1-3 and the comparative example 3 which could form the electroconductive carbon layer, R value of the electroconductive carbon layer 33 was measured about the surface layer part and the intermediate | middle layer. Specifically, first, the Raman spectrum of the conductive carbon layer 33 was measured using a microscopic Raman spectrometer. Then, the peak intensity of the bands (D-band) located 1300~1400cm ^-1 _{(I D),} the peak area ratio of the peak intensity _{(I G)} of band (G-band) located 1500~1600cm ^-1 ( I _D / I _G ) was calculated and used as the R value. The obtained results are shown in Table 1 below.

  As shown in Table 1, all of the R values of the surface layer portion 33b in the conductive members produced in Examples 1 to 3 were 1.3 or more. The R values of the boundary layers of Examples 1 to 3 and Comparative Example 3 were all less than 1.3.

1,201 Single polymer fuel cell (PEFC) single cell (unit cell),
2 electrolyte membrane (solid polymer electrolyte membrane),
3 catalyst layer,
3a Anode catalyst layer (fuel electrode side electrode catalyst layer),
3b Cathode catalyst layer (oxygen electrode side electrode catalyst layer),
4 Gas diffusion layer (GDL),
4a Anode gas diffusion layer (fuel electrode side gas diffusion layer),
4b Cathode gas diffusion layer (oxygen electrode side gas diffusion layer),
5 Separator (metal separator),
5a Anode separator (fuel electrode side separator),
5b Cathode separator (oxygen electrode side separator),
5aa anode side gas flow path,
5bb cathode side gas flow path,
5ag fuel gas,
5 bg oxidant gas,
8 Cooling water channel (refrigerant channel),
8w cooling water (refrigerant),
9 Membrane-electrode assembly (MEA),
20 stack part (stacked stack),
30, 40 current collector plate,
31 metal substrate,
32 middle class,
33 conductive carbon layer,
33a boundary layer,
33b surface layer part,
37, 47 output terminals,
50, 60 insulation plate,
70 fuel electrode side end plate,
80 oxygen electrode side end plate,
71 Fuel gas inlet,
72 Fuel gas outlet,
74 Oxidant gas inlet,
75 Oxidant gas outlet,
77 Cooling water inlet,
78 Cooling water outlet,
90 tie rods,
200 Fuel cell (stack).

Claims (8)

In the dry deposition method,
An intermediate comprising at least one selected from the group consisting of Group 4 metals, Group 5 metals, Group 6 metal carbides, nitrides and carbonitrides of the periodic table on a metal substrate Forming a layer;
Forming a conductive carbon layer on the intermediate layer,
Forming a conductive carbon layer on the intermediate layer,
A method for producing a conductive member, comprising changing a negative bias voltage from a low value to a high value. The step of forming the conductive carbon layer includes
The method for producing a conductive member according to claim 1, comprising changing a negative bias voltage when forming the conductive carbon layer from 50 V or less to 200 V or more. In the step of forming the conductive carbon layer,
The method for producing a conductive member according to claim 1 or 2, wherein a temperature immediately before and during formation of the conductive carbon layer is 300 ° C or lower. A metal base material, and a metal group selected from the group consisting of a group 4 metal, a group 5 metal, a group 6 metal carbide, nitride and carbonitride of the periodic table on the metal base. An electrically conductive member provided with an intermediate layer comprising at least one kind, and a conductive carbon layer coated on the intermediate layer,
The conductive carbon layer is a conductive member having a boundary layer in contact with the intermediate layer. The conductive member according to claim 4, wherein the surface layer portion of the conductive carbon layer has an I _D / _IG of 1.3 or more. The conductive member according to claim 4 or 5, wherein the boundary layer of the conductive carbon layer has a region where I _D / I _G is less than 1.3.   The separator for fuel cells comprised from the electrically-conductive member of any one of Claims 4-6. A polymer electrolyte membrane, a pair of anode catalyst layer and cathode catalyst layer sandwiching the polymer electrolyte membrane, and a membrane electrode assembly including a pair of anode gas diffusion layer and cathode gas diffusion layer sandwiching them;
A polymer electrolyte fuel cell having a pair of anode separator and cathode separator sandwiching the membrane electrode assembly,
8. At least one of the anode separator or the cathode separator is the fuel cell separator according to claim 7, wherein the fuel cell separator is formed in a concavo-convex shape, and the convex portion is the membrane electrode joint. A solid polymer fuel cell, wherein the solid polymer fuel cell is in contact with a body, and the concave portion serves as a gas flow path for circulating fuel gas or oxidant gas.