JP5332550B2 - Conductive member, method for producing the same, fuel cell separator and polymer electrolyte fuel cell using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive member capable of suppressing and preventing the corrosion of a separator base material for a fuel cell, by suppressing and preventing permeation of water molecules to a separator base-material side. <P>SOLUTION: The conductive member includes a base material layer, made of metals, a dense barrier layer 53 formed on the metallic base material layer 52, an intermediate layer 54 formed on the dense barrier layer, and a conductive thin film layer 55 formed on the intermediate layer. Since permeation of water molecules generated in an electrode to a separator base material side is suppressed and is prevented by using the conductive member, superior conductivity is ensured, and corrosion resistance is further improved. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

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.

  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 single cell includes a polymer electrolyte membrane; a pair of (anode, cathode) catalyst layers (electrode catalyst layer) sandwiching the polymer electrolyte membrane; and a pair (anode, cathode) for dispersing the supply gas sandwiching them A membrane electrode assembly (MEA) including a gas diffusion layer (GDL); 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.

  Conventionally, metals, carbon, or conductive resins are known as constituent materials for fuel cell separators that require electrical conductivity. Among these, in the carbon separator and the conductive resin separator, it is necessary to set the thickness relatively large in order to secure the strength after forming the gas flow path to some extent. As a result, the overall thickness of the fuel cell stack using these separators also increases. Such an increase in the size of the stack is not preferable particularly in an in-vehicle PEFC that requires a reduction in size.

  On the other hand, since the metal separator has a relatively high strength, the thickness can be made relatively small. Moreover, since it is excellent also in electroconductivity, when a metal separator is used, there also exists an advantage that contact resistance with MEA can be reduced. On the other hand, in metal materials, there may be a problem that the conductivity is lowered due to corrosion (for example, due to generated water or a potential difference generated during operation), and the output of the stack is lowered accordingly. Therefore, the metal separator is required to improve the corrosion resistance while ensuring its excellent conductivity.

For example, Patent Document 1 discloses a technique for forming an oxide film on a base material between the base material and a conductive thin film. Thereby, while ensuring electroconductivity, melt | dissolution of the metal which comprises a base material is suppressed, and it is supposed that the separator for fuel cells excellent in electroconductivity and durability can be provided. Patent Document 1 discloses forming an intermediate layer that enhances adhesion between an oxide film of a substrate and a conductive thin film. This describes that the adhesion between the oxide film of the substrate and the conductive thin film can be enhanced. Here, the intermediate layer is formed by a sputtering method.
JP 2004-185998 A

  However, as disclosed in Patent Document 1, the intermediate layer produced by the sputtering method is a layer having high crystal orientation. For this reason, in the fuel cell using the separator of Patent Document 1, water molecules generated by the electrodes easily enter the separator substrate side through the gaps between the crystals, and the separator substrate is easily corroded. Moreover, since the oxide film disposed on the substrate surface itself is a highly insulating layer, the conductivity in the thickness direction of the separator is lowered.

  Accordingly, the present invention provides a separator base material by suppressing and preventing water molecules from entering the separator base side in a conductive member having a base layer made of metal and a conductive thin film layer disposed on the surface thereof. It aims at providing the means which can suppress and prevent the corrosion of.

  The present inventors have found that the above problem can be solved by arranging a dense layer between the metal substrate layer and the intermediate layer, and have completed the present invention.

  The conductive member of the present invention is formed on the metal base layer, the dense barrier layer formed on the metal base layer, the intermediate layer formed on the dense barrier layer, and the intermediate layer. A conductive thin film layer. The dense barrier layer has a lower crystal orientation than the intermediate layer.

  According to the present invention, the corrosion resistance is further improved while sufficiently securing the excellent electrical conductivity of the metal separator by suppressing / preventing the penetration of water molecules into the separator substrate side of the water molecules generated by the electrode. An electrically conductive member can be provided.

(Conductive member)
The conductive member of the present invention includes a metal base layer, a dense barrier layer formed on the metal base layer, an intermediate layer formed on the dense barrier layer, and a conductive formed on the intermediate layer. The dense barrier layer is a conductive member having a lower crystal orientation than the intermediate layer.

  Conventionally, in order to improve the adhesion between the metal substrate layer and the conductive thin film layer, an intermediate layer is provided between these layers by sputtering (Patent Document 1, paragraph “0023”). However, when the intermediate layer is formed by a sputtering method, the intermediate layer has a columnar structure with high crystal orientation, and many gaps are generated between crystals (columns). On the other hand, when the conductive thin film layer is formed of a carbon material, the conductive thin film layer easily passes water generated on the electrode side. Further, the water that has passed through the conductive thin film layer in this way comes to the intermediate layer, and as described above, the intermediate layer has a columnar structure with high crystal orientation. For this reason, the water molecules that have passed through the conductive thin film layer easily pass through the gaps between the crystals (columns) and reach the metal substrate layer. The metal substrate layer is generally made of a metal including iron, titanium, aluminum and copper and alloys thereof. For this reason, although the metal substrate layer has a certain degree of corrosion resistance, the metal substrate layer is gradually corroded by water when exposed to an electric potential for a long period of time, resulting in a problem in durability.

  On the other hand, the present invention is characterized in that a dense barrier layer having a low crystal orientation is disposed between the metal substrate layer and the intermediate layer. As a result, water generated on the electrode side passes through the conductive thin film layer but hardly passes through the dense barrier layer having low crystal orientation. For this reason, there are almost no water molecules that pass through the dense barrier layer, that is, the metal substrate layer has almost no risk of being exposed to water. For this reason, the conductive member of the present invention is hardly corroded by water even when it is exposed to an electric potential for a long time. For this reason, the fuel cell using the conductive member of the present invention as a separator can exhibit excellent durability while sufficiently securing the excellent conductivity of the metal separator.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, exemplary embodiments to which the 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 is a schematic diagram showing a basic configuration of a polymer electrolyte fuel cell (PEFC) 1 according to one embodiment of the present invention. The PEFC 1 first includes a solid polymer electrolyte membrane 2 and a pair of catalyst layers (an anode catalyst layer 3a and a cathode catalyst layer 3c) that sandwich the membrane. The laminate of the solid polymer electrolyte membrane 2 and the catalyst layers (3a, 3c) is further sandwiched between a pair of gas diffusion layers (GDL) (anode gas diffusion layer 4a and cathode gas diffusion layer 4c). Thus, the polymer electrolyte membrane 2, the pair of catalyst layers (3a, 3c), and the pair of gas diffusion layers (4a, 4c) constitute a membrane electrode assembly (MEA) 10 in a stacked state.

  In PEFC1, the MEA 10 is further sandwiched between a pair of separators (anode separator 5a and cathode separator 5c). In FIG. 1, the separators (5 a, 5 c) are illustrated so as to be positioned at both ends of the illustrated MEA 10. However, in a fuel cell stack in which a plurality of MEAs are stacked, the separator is generally used as a separator for an adjacent PEFC (not shown). In other words, in the fuel cell stack, the MEAs are sequentially stacked via the separator to form a stack. In an actual fuel cell stack, a gas seal portion is disposed between the separator (5a, 5c) and the solid polymer electrolyte membrane 2, or between the PEFC 1 and another adjacent PEFC. These descriptions are omitted in FIG.

  The separators (5a, 5c) are obtained, for example, by forming a concavo-convex shape as shown in FIG. 1 by subjecting a thin plate having a thickness of 0.5 mm or less to a press treatment. The convex part seen from the MEA side of the separator (5a, 5c) is in contact with the MEA 10. Thereby, the electrical connection with MEA10 is ensured. Further, a recess (space between the separator and the MEA generated due to the concavo-convex shape of the separator) viewed from the MEA side of the separator (5a, 5c) is a gas for circulating gas during operation of the PEFC 1 Functions as a flow path. Specifically, a fuel gas (for example, hydrogen) is circulated through the gas flow path 6a of the anode separator 5a, and an oxidant gas (for example, air) is circulated through the gas flow path 6c of the cathode separator 5c.

  On the other hand, the recess viewed from the side opposite to the MEA side of the separator (5a, 5c) serves as a refrigerant flow path 7 for circulating a refrigerant (for example, water) for cooling the PEFC during operation of the PEFC 1. . Further, the separator is usually provided with a manifold (not shown). This manifold functions as a connection means for connecting cells when a stack is formed. With such a configuration, the mechanical strength of the fuel cell stack can be ensured.

  FIG. 2 is a cross-sectional view showing a schematic configuration of the separator 5 in FIG. In the present embodiment, the conductive member constituting the separator 5 includes a metal base layer 52, a dense barrier layer 53, an intermediate layer 54, and a conductive thin film layer 55. In PEFC1, the separator 5 is disposed such that the conductive thin film layer 55 is located on the MEA 10 side.

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

[Metal base material layer]
The metal base layer 52 is a main layer of a conductive member that constitutes the separator 5 and contributes to ensuring conductivity and mechanical strength.

  There is no restriction | limiting in particular about the metal which comprises the metal base material layer 52, What was conventionally used as a constituent material of a metal separator can be used suitably. As a constituent material of a metal base material layer, iron, titanium, aluminum, and these alloys are mentioned, for example. 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 a metal base material layer is comprised from stainless steel, aluminum, or an aluminum alloy. Furthermore, in particular, when stainless steel is used as the metal base material layer, the conductivity of the contact surface with the gas diffusion base material which is a constituent material of the gas diffusion layer 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 due to the corrosion resistance of the oxide film formed on the metal base layer itself made of stainless steel.

  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 separator is also required to have mechanical strength and formability, the tempering of the alloy can be appropriately selected in addition to the above alloy types. In addition, when the metal base material layer 52 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, 99 It is at least mass%.

  The thickness of the metal base layer 52 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 itself, it is preferably 50 to 500 μm, more preferably 80 to 300 μm, still more preferably 80 to 200 μm. In particular, the thickness of the metal base layer 52 when stainless steel is used as the constituent material is preferably 80 to 150 μm. On the other hand, the thickness of the metal base layer 52 when aluminum is used as a constituent material is preferably 100 to 300 μm. When it is within the above range, it has excellent strength as a separator and is excellent in processability and can achieve a suitable thickness.

  For example, from the viewpoint of providing sufficient strength as a constituent material for a fuel cell separator or the like, the metal base layer 52 is preferably made of a material having a high gas barrier property. Since the separator of the fuel cell plays a role of partitioning cells, different gas flows on both sides of the separator. Therefore, from the viewpoint of eliminating the mixing of adjacent gases in each cell and the fluctuation of the gas flow rate, the metal base layer 52 is preferably as the gas barrier property is higher.

[Dense barrier layer]
The dense barrier layer 53 is disposed on the metal base layer 52. Due to the presence of this layer, it is possible to suppress / prevent water generated by the electrode from entering the metal substrate layer 52 side. Therefore, due to the arrangement of the dense barrier layer 53, the conductive member constituting the separator 5 is more conductive than the conductive member having only the metal base layer 52, the intermediate layer 54, and the conductive thin film layer 55 while ensuring conductivity. Corrosion resistance can be improved.

  By disposing the dense barrier layer having low crystal orientation in this manner between the metal base material layer and the intermediate layer, the water generated on the electrode side can easily pass through the conductive thin film layer 55, although The barrier layer hardly passes. For this reason, since water hardly reaches the intermediate layer 54 and the metal base layer 52, the corrosion of the conductive member can be effectively suppressed / prevented.

  In the present specification, the “dense barrier layer” means a layer that is so dense that water molecules and eluted ions do not pass through. Specifically, the porosity is 10% or less, more preferably 7% or less. It means a certain layer. The lower limit of the porosity of the dense barrier layer is not particularly limited as long as water molecules do not pass therethrough. Specifically, the lower limit of the porosity of the dense barrier layer can be about 0.5%, more preferably 0.7%. Here, the “porosity” refers to the area ratio of the metal, semimetal, metal carbide, or metal nitride constituting the dense barrier layer in the layer by performing image analysis on the surface and cross section of the layer with SEM ( %).

  In the present invention, the dense barrier layer preferably has a lower crystal orientation than the intermediate layer. By adopting such a structure, the dense barrier layer has a structure in which water molecules generated on the electrode side are difficult to pass through. Here, “crystal orientation” refers to the degree of orientation of crystal axes in a polycrystalline structure. Therefore, “high crystal orientation” means that each crystal axis exists in the same direction (in parallel) in a polycrystalline structure. On the other hand, “low crystal orientation” means that each crystal axis exists in various directions in a polycrystalline structure. The degree of crystal orientation (degree of crystal orientation) is generally determined by using JCPDS (ASTM) data, which is standard data by powder X-ray diffraction, which is considered to have substantially no orientation, as an index. sell. For example, “degree of crystal orientation (%)” is obtained from the peak intensity of the Debye intensity distribution on the (121) plane by WAXD measurement.

In the case where the dense barrier layer has a lower crystal orientation than the intermediate layer, the method for forming the dense barrier layer is not particularly limited so that the dense barrier layer has a lower crystal orientation than the intermediate layer. For example, it can be appropriately adjusted by appropriately selecting the average crystallite size and the forming method of each dense barrier layer. More specifically, the dense barrier layer according to the present invention can be formed by making the average crystallite size of the dense barrier layer smaller than the average crystallite size of the intermediate layer. Here, the magnitude relationship between the average crystallite size of the dense barrier layer and the average crystallite size of the intermediate layer is not particularly limited as long as the crystal orientation can be achieved. Preferably, the ratio (D ₂ / D ₁ ) of the average crystallite diameter [D ₂ (nm)] of the dense barrier layer to the average crystallite diameter [D ₁ (nm)] of the intermediate layer is 0.1 or more and 1 It is less than 0.1, More preferably, it is 0.1-0.5. Within such a range, the crystal orientation of the dense barrier layer can be lowered to the extent that water molecules do not substantially reach the metal substrate layer. Moreover, the average crystallite diameter of each layer is not particularly limited as long as the above-described size relationship is satisfied. The “average crystallite diameter” in this specification was measured with an X-ray diffractometer manufactured by Mac Science. Preferably, the average crystallite diameter [D ₂ (nm)] of the dense barrier layer is 10 to 30 nm, more preferably 10 to ₂₀ nm. Moreover, the average crystallite diameter [D ₁ (nm)] of the intermediate layer is preferably 30 to 100 nm, more preferably 30 to 50 nm. Here, the “crystallite diameter” means the crystallite size calculated by the Scherre method in the X-ray diffraction method.

  In the present invention, the material constituting the dense barrier layer is not particularly limited. Specifically, the materials constituting the dense barrier layer include metals of Group 4 metals (Ti, Zr, Nf), Group 5 metals (V, Nb, Ta), and Group 6 metals of the periodic table. Metals such as (Cr, Mo, W); semimetals such as Si and B; alloys, carbides and nitrides of the above metals. Among these, metals with low ion elution such as chromium (Cr), tungsten (W), titanium (Ti), molybdenum (Mo), niobium (Nb) or hafnium (Hf), or nitrides, carbides or carbonitrides thereof. The product is preferably used. More preferably, Cr or Ti, or a carbide or nitride thereof is used. In particular, when the above-described metal with little ion elution or a carbide or nitride thereof is used, the corrosion resistance of the separator can be significantly improved. In addition, the material which comprises the said dense barrier layer may be used independently, or may be used with the form of 2 or more types of mixtures.

  Here, the material constituting the dense barrier layer is preferably equal to or less than the thermal expansion coefficient of the material (metal, metal carbide or metal nitride) constituting the intermediate layer described in detail below. In general, the conductive thin film layer is hardly thermally expanded, and the metal substrate layer is hardly thermally expanded. For this reason, by selecting the material constituting the dense barrier layer and the intermediate layer so as to have the above-described thermal expansion coefficient, each of the metal base material layer, the dense barrier layer, the dense barrier layer, and the conductive thin film layer is formed. A difference in expansion and contraction due to heat can be suppressed, and peeling of each layer can be prevented. In such a case, the adhesion between the intermediate layer and the dense barrier layer can also be improved.

  Alternatively, the material constituting the dense barrier layer is metally noble to the same extent as the material (metal, metal carbide or metal nitride) constituting the intermediate layer described in detail below, or of the intermediate layer It is preferable that the metal is noble compared to the material. Thereby, a potential difference is hardly generated between the dense barrier layer and the intermediate layer, the metal base material layer is more effectively protected, and the corrosion resistance of the conductive member can be improved.

  The thickness of the dense barrier layer 53 is not particularly limited. However, from the viewpoint of making the fuel cell stack as small as possible by making the separator 5 thinner, the thickness of the dense barrier layer 53 is preferably 0.01 to 10 μm, more preferably 0. 0.05 to 5 μm, and more preferably 0.1 to 2 μm. If the thickness of the dense barrier layer 53 is 0.01 μm or more, a uniform layer is formed, and the corrosion resistance of the metal base layer can be effectively improved. On the other hand, if the thickness of the dense barrier layer 53 is 10 μm or less, an increase in the film stress of the dense barrier layer can be suppressed, and the follow-up performance of the intermediate layer and the metal substrate layer may be deteriorated, and peeling / cracking associated therewith may occur. Can be prevented.

  In the present embodiment, all of the metal base layer 52 is covered with the dense barrier layer 53. In other words, in the present embodiment, the ratio (coverage) of the area where the metal base layer 52 is covered with the dense barrier layer 53 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 base layer 52 by the dense barrier layer 53 is preferably 60% or more, more preferably 80 to 100%, still more preferably 90 to 100%, and most preferably 100%. . By adopting such a configuration, it is possible to effectively suppress / prevent water molecules from entering the exposed portion of the metal base layer 52 that is not covered with the dense barrier layer 53, and to prevent the conductive member (in particular, the metal base layer). ) Can be effectively suppressed. In addition, the said coverage shall mean the ratio of the area of the metal base material layer 52 which overlaps with the dense barrier layer 53, when a conductive member (separator 5) is seen from a lamination direction.

[Middle layer]
The intermediate layer 54 is disposed on the dense barrier layer 53. Here, the intermediate layer 54 has a function of improving adhesion between the dense barrier layer 53 and the conductive thin film layer 55 and a function of preventing elution of ions from the metal base layer 52. In particular, the above-described operation and effect due to the installation of the intermediate layer 54 is remarkably exhibited when the dense barrier layer 53 is made of the above-described metal or alloy thereof. In addition, as will be described in detail below, the intensity ratio between the D band peak intensity (I _D ) and the G band peak intensity (I _G ) measured by Raman scattering spectroscopic analysis in which the conductive thin film layer 55 contains conductive carbon. In the case where the conductive carbon layer has a large R (I _D / I _G ) (for example, R value exceeds 2.0), the adhesion effect with the conductive thin film layer 55 can be obtained by providing the intermediate layer 54. It can be remarkably expressed.

  The material constituting the intermediate layer 54 is not particularly limited as long as it provides the above adhesion. For example, Group 4 metals (Ti, Zr, Nf) of the periodic table, Group 5 metals (V, Nb, Ta), Group 6 metals (Cr, Mo, W), and their carbides, Examples thereof include nitrides and carbonitrides. Among these, metals with low ion elution such as chromium (Cr), tungsten (W), titanium (Ti), molybdenum (Mo), niobium (Nb) or hafnium (Hf), or their nitrides, carbides or charcoal are preferable. Nitride is used. More preferably, Cr or Ti, or a carbide or nitride thereof is used. In particular, when the above-described metal with little ion elution or a carbide or nitride thereof is used, the corrosion resistance of the separator can be significantly improved. In addition, the material which comprises the said intermediate | middle layer may be used independently, or may be used with the form of 2 or more types of mixtures.

  The thickness of the intermediate layer 54 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 54 is preferably 0.01 to 10 μm, more preferably 0.00. It is 05-5 micrometers, More preferably, it is 0.1-1 micrometers. If the thickness of the intermediate layer 54 is 0.01 μm or more, a uniform layer is formed, and the corrosion resistance of the metal substrate layer can be effectively improved. On the other hand, if the thickness of the intermediate layer 54 is 10 μm or less, an increase in the film stress of the intermediate layer can be suppressed, and a decrease in film followability with respect to the metal substrate layer and the occurrence of peeling / cracking associated therewith can be prevented.

  In addition, the surface of the intermediate layer 54 on the conductive thin film layer 55 side is preferably rough at the nano level. According to such a form, the adhesiveness of the conductive thin film layer 55 formed on the intermediate layer 54 to the intermediate layer 54 can be further improved.

As described above, when the thermal expansion coefficient of the material constituting the intermediate layer 54 is equal to or lower than the thermal expansion coefficient of the material constituting the dense barrier layer 53, adhesion between the intermediate layer and the dense barrier layer is improved. Can do. However, in such a form, the adhesion between the intermediate layer 54 and the conductive thin film layer 55 may decrease. Similarly, when the thermal expansion coefficient of the intermediate layer 54 is equal to or less than the thermal expansion coefficient of the conductive thin film layer 55, the adhesion between the intermediate layer 54 and the conductive thin film layer 55 may decrease. Considering these, the coefficient of thermal expansion (α _sub ) of the material constituting the metal base layer, the coefficient of thermal expansion (α _den ) of the material constituting the dense barrier layer, the coefficient of thermal expansion ( It is preferable that (α _mid ) and the coefficient of thermal expansion of the material constituting the conductive thin film layer (α _c ) satisfy the following relationship.

[Conductive thin film layer]
The conductive thin film layer 55 is disposed on the intermediate layer 54. Here, the material constituting the conductive thin film layer 55 is not particularly limited. Specifically, the conductive thin film layer 55 includes a metal thin film layer and a conductive carbon layer formed from carbon. Among these, as a material which comprises a metal thin film layer, copper (Cu), gold (Au), silver (Ag), platinum (Pt), palladium (Pd), etc. are mentioned. The conductive carbon layer is a layer containing conductive carbon. Of these, a conductive carbon layer is preferred. The presence of the conductive carbon layer can improve the corrosion resistance as compared with the case where the conductive carbon layer is not included while ensuring the conductivity of the conductive member constituting the separator 5. Hereinafter, a preferred embodiment when a conductive carbon layer is used as the conductive thin film layer 55 will be described.

Conventionally, while applying a negative high voltage to the separator substrate in an inert gas atmosphere, carbonized material is applied to one surface of the metal base of the metal separator using a carbon-based material by a dry film forming method on the substrate surface. A technique for forming a carbon layer comprising: Although the fuel cell separator having this carbon layer is said to be excellent in corrosion resistance and conductivity, the crystal structure of the carbon layer is various, and if the crystal structure of the carbon layer is different, this causes the separator itself. Corrosion resistance and conductivity can also vary. Therefore, it cannot be said that the conventional fuel cell separator still has sufficient corrosion resistance and conductivity. On the other hand, by adjusting the crystallization structure of the conductive carbon layer to a specific structure, a conductive path from one surface of the conductive carbon layer to the other surface can be secured. By using such a conductive carbon layer for a conductive member (especially a separator), it is possible to provide a conductive member with further improved corrosion resistance while sufficiently ensuring excellent conductivity. That is, the crystalline structure of the conductive carbon layer is determined by the 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. Stipulate. Specifically, the intensity ratio R (I _D / I _G ) is preferably set to 1.3 or more. Hereinafter, the configuration requirement will be described in more detail.

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 bm ⁻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), It is used as an indicator such as sp2 bond ratio. That is, in this embodiment, it can be used as an index of contact resistance of the conductive carbon layer, and can be used as a film quality parameter for controlling the conductivity of the conductive carbon layer.

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 is preferably 1.3 or more. The R value is more preferably 1.4 to 2.0, still more preferably 1.4 to 1.9, and particularly preferably 1.5 to 1.8. If this R value is 1.3 or more, a conductive carbon layer having sufficient conductivity in the stacking direction can be obtained. Moreover, if R value is 2.0 or less, the reduction | decrease of a graphite component can be suppressed. Furthermore, the increase in internal stress of the conductive carbon layer itself can be suppressed, and the adhesion with the intermediate layer as the base can be further improved.

  In addition, the mechanism by which the above-mentioned effect is acquired by making R value 1.3 or more like this embodiment is estimated as follows. However, the following estimation mechanism does not limit the technical scope of the present invention in any way.

  As described above, increasing the D-band peak intensity (that is, increasing the R value) means an increase in crystal structure defects in the graphite structure. In other words, it means that the sp3 carbon increases in the highly crystalline graphite composed of almost only the sp2 carbon. Here, a photograph (magnification: 400,000 times) of a cross section of a conductive member (conductive member A) having a conductive carbon layer of R = 1.0 to 1.2 observed with a transmission electron microscope (TEM) is shown in FIG. 3A. Shown in Similarly, the photograph (magnification: 400,000 times) which observed the cross section of the electrically-conductive member (conductive member B) which has the conductive carbon layer of R = 1.6 by TEM is shown to FIG. 3B. The conductive member A and the conductive member B use SUS316L as a metal base layer, and an intermediate layer (thickness: 0.2 μm) made of Cr and a conductive carbon layer (thickness: 0.00) on the surface. 2 μm) was sequentially formed by sputtering. In addition, the bias voltage applied to the metal base layer at the time of producing the conductive carbon layer in the conductive member A is 0V. The bias voltage applied to the metal base layer during the production of the conductive carbon layer in the conductive member B was −140V.

  As shown in FIG. 3B, it can be seen that the conductive carbon layer of the conductive member B has a structure of polycrystalline graphite. On the other hand, such a structure of polycrystalline graphite cannot be confirmed in the conductive carbon layer of the conductive member A shown in FIG. 3A.

  Here, “polycrystalline graphite” microscopically has an anisotropic graphite crystal structure (graphite cluster) in which graphene surfaces (hexagonal network surfaces) are laminated, but macroscopically, a large number of such graphite structures. Is an isotropic crystal. Therefore, it can be said that the polycrystalline graphite is one type of diamond-like carbon (DLC). Normally, single crystal graphite has a disordered structure in which graphene surfaces are laminated even when viewed macroscopically, as represented by HOPG (highly oriented pyrolytic graphite). On the other hand, the polycrystalline graphite has a graphite structure as an individual cluster, and has a turbostratic structure. By controlling the R value to the above-mentioned value, this degree of disorder (graphite cluster amount, size) can be ensured appropriately, and a conductive path from one surface to the other surface of the conductive carbon layer can be secured. As a result, it is considered that a decrease in conductivity due to the separate provision of a conductive carbon layer in addition to the metal substrate layer can be prevented.

  In polycrystalline graphite, since the graphene surface is formed by the bonding of sp2 carbon atoms constituting the graphite cluster, conductivity is ensured in the plane direction of the graphene surface. Polycrystalline graphite is substantially composed of only carbon atoms, has a small specific surface area, and a small amount of bonded functional groups. For this reason, polycrystalline graphite has excellent resistance to corrosion by acidic water or the like. In addition, even in powders such as carbon black, primary particles are often formed by aggregates of graphite clusters, thereby exhibiting electrical conductivity. However, since the individual particles are separated, there are many functional groups formed on the surface, and corrosion due to acidic water or the like is likely to occur. In addition, even when a conductive carbon layer is formed with carbon black, there is a problem that the denseness as a protective film is lacking.

  Here, when the conductive carbon layer of the present embodiment is made of polycrystalline graphite, the size of the graphite cluster constituting the polycrystalline graphite 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 from becoming thick 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 may be composed of only polycrystalline graphite, but the conductive carbon layer may include materials other than polycrystalline graphite. Examples of carbon materials other than polycrystalline graphite that can be included in the conductive carbon layer 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 include gold (Au), silver (Ag), platinum (Pt), ruthenium (Ru), palladium (Pd), rhodium (Rh), indium ( A noble metal such as In); a water repellent material such as polytetrafluoroethylene (PTFE); and a conductive oxide. 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 thin film layer 55 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. When the thickness of the conductive thin film layer is a value within such a range, sufficient conductivity can be secured between the gas diffusion base material and the separator. Moreover, the advantageous effect that a high corrosion-resistant function can be given with respect to a metal base material layer can be show | played. In the present embodiment, the conductive thin film layer 55 exists only on one main surface of the conductive member (separator 5). However, in some cases, the conductive thin film layer 55 may also exist on the other main surface of the conductive member (separator 5).

  Hereinafter, although more preferable embodiment in the electroconductive thin film layer 55 of this embodiment is described, the technical scope of this invention is not limited only to the following form.

  First, with respect to Raman scattering spectroscopy when the conductive thin film layer 55 is a conductive carbon layer, from another viewpoint, the average peak measured by rotational anisotropy measurement of Raman scattering spectroscopy is a two-fold symmetrical pattern. It is preferable to show. Hereinafter, the measurement principle of rotational anisotropy measurement will be briefly described.

  The rotational anisotropy measurement of the Raman scattering spectroscopic analysis is performed by performing the Raman scattering spectroscopic measurement while rotating the measurement sample 360 degrees in the horizontal direction. Specifically, the surface of the measurement sample is irradiated with laser light, and a normal Raman spectrum is measured. Next, the measurement sample is rotated by 10 °, and the Raman spectrum is measured in the same manner. This operation is performed until the measurement sample rotates 360 °. And the average peak is obtained by calculating the average value of the peak intensities obtained in the measurement at each angle and displaying the 360 ° polar coordinate with one peak at the center. For example, when the graphite layer is present on the sample surface so that the graphene surface is parallel to the surface direction of the sample, a three-fold symmetry pattern as shown in FIG. 4A can be seen. On the other hand, when the graphite layer is present on the sample surface so that the graphene surface is perpendicular to the surface direction of the sample, a two-fold symmetry pattern as shown in FIG. 4B can be seen. When an amorphous carbon layer having no clear crystal structure is present on the surface of the sample, a pattern having no symmetry as shown in FIG. 4C is seen. Therefore, the fact that the average peak two-fold symmetry pattern measured by rotational anisotropy measurement indicates that the plane direction of the graphene surface constituting the conductive carbon layer is substantially coincident with the stacking direction of the conductive carbon layer. Means that. According to such a form, the conductivity in the conductive carbon layer is ensured by the shortest path, which is preferable.

  Here, the results of the rotational anisotropy measurement are shown in FIGS. 5A and 5B. FIG. 5A shows a Raman spectrum when the conductive member B is used as a measurement sample, and the rotation angles of the sample are 0 °, 60 °, and 180 °, respectively. FIG. 5B shows the average peak of the rotational anisotropy measurement for the conductive member B obtained by the method described above. As shown in FIG. 5B, in the measurement of rotational anisotropy of the conductive member B, peaks were observed at 0 ° and 180 ° positions. This corresponds to the two-fold symmetry pattern shown in FIG. 4B. In this specification, the average peak measured by rotational anisotropy measurement of Raman scattering spectroscopic analysis “shows a two-fold symmetric pattern” means that, as shown in FIG. 4B and FIG. This means that there are two peaks that are 180 ° opposite to each other with the intensity being zero. Since the peak intensity seen in the 3-fold symmetrical pattern and the peak intensity seen in the 2-fold symmetrical pattern are supposed to show the same value in principle, such a definition is possible.

  In a preferred embodiment, the Vickers hardness of the conductive thin film layer 55 is defined. “Vickers hardness (Hv)” is a value that defines the hardness of a substance, and is a value inherent to the substance. In this specification, the Vickers hardness means a value measured by a nanoindentation method. The nanoindentation method is a method in which the diamond indenter is continuously loaded and unloaded with a very small load on the sample surface, and the hardness is measured from the obtained load-displacement curve. Larger means that the substance is harder. In a preferred embodiment, specifically, the Vickers hardness of the conductive thin film layer 55 is preferably 1500 Hv or less, more preferably 1200 Hv or less, further preferably 1000 Hv or less, and particularly preferably 800 Hv or less. . When the Vickers hardness is within such a range, excessive mixing of sp3 carbon having no conductivity can be suppressed, and a decrease in conductivity of the conductive thin film layer 55 can be prevented. On the other hand, the lower limit value of the Vickers hardness is not particularly limited, but if the Vickers hardness is 50 Hv or more, the hardness of the conductive thin film layer 55 is sufficiently ensured. As a result, it is possible to provide a conductive member (separator) that can withstand impacts such as external contact and friction and has excellent adhesion to other layers. From such a viewpoint, the Vickers hardness of the conductive thin film layer 55 is more preferably 80 Hv or more, further preferably 100 Hv or more, and particularly preferably 200 Hv or more.

  Here, SUS316L is prepared as a metal base layer of the conductive member, and an intermediate layer (thickness: 0.2 μm) made of Cr and a conductive carbon layer (thickness: 0.2 μm) are sequentially formed on the surface by a sputtering method. It produced by forming. At this time, the Vickers hardness of the conductive carbon layer was changed by controlling the bias voltage and the film formation method. FIG. 6 shows the relationship between the Vickers hardness of the conductive carbon layer in the conductive member thus obtained and the value of the sp3 ratio in the conductive carbon layer. In FIG. 6, diamond has an sp3 ratio = 100%, which is Hv10000. From the results shown in FIG. 6, it can be seen that when the Vickers hardness of the conductive carbon layer is 1500 Hv or less, the value of the sp3 ratio is greatly reduced. Moreover, it is estimated that the value of the contact resistance of a conductive member also falls along with this, when the value of sp3 ratio falls.

  From another viewpoint, it is preferable that the amount of hydrogen atoms contained in the conductive thin film layer 55 is also taken into consideration. That is, when the conductive thin film layer 55 contains a hydrogen atom, the hydrogen atom is bonded to a carbon atom. Then, the hybrid orbital of carbon atoms bonded with hydrogen atoms changes from sp2 to sp3 and loses conductivity, and the conductivity of the conductive thin film layer 55 decreases. Further, when the C—H bond in the polycrystalline graphite is increased, the continuity of the bond is lost, the hardness of the conductive thin film layer 55 is lowered, and finally the mechanical strength and corrosion resistance of the conductive member are lowered. . From such a viewpoint, the content of hydrogen atoms in the conductive thin film layer 55 is preferably 30 atomic percent or less, more preferably 20 atomic percent or less, based on all atoms constituting the conductive thin film layer 55. More preferably, it is 10 atomic% or less. Here, as the value of the hydrogen atom content in the conductive thin film layer 55, a value obtained by elastic recoil scattering analysis (ERDA) is adopted. In this method, a measurement sample is tilted, and a helium ion beam is incident shallowly, thereby detecting an element ejected forward. Since the nucleus of a hydrogen atom is lighter than the incident helium ion, if a hydrogen atom is present, the nucleus is ejected forward. Since such scattering is elastic scattering, the energy spectrum of the ejected atom reflects the mass of the nucleus. Therefore, the content of hydrogen atoms in the measurement sample can be measured by measuring the number of nuclei of ejected hydrogen atoms with a solid detector.

  Here, FIG. 7 is a graph showing the results of measuring the contact resistance of several conductive members having conductive thin film layers having different hydrogen atom contents although the R value is 1.3 or more. is there. As shown in FIG. 7, when the content of hydrogen atoms in the conductive thin film layer is 30 atomic% or less, the value of the contact resistance of the conductive member is significantly reduced. In the experiment shown in FIG. 7, SUS316L was used as the metal base material layer of the conductive member, and an intermediate layer (thickness: 0.2 μm) made of Cr and a conductive thin film layer (thickness: 0.2 μm) on this surface. ) Were sequentially formed by a sputtering method. At this time, the hydrogen atom content in the conductive thin film layer was changed by controlling the film formation method and the amount of hydrocarbon gas.

  In the present embodiment, all of the metal base layer 52 (although through the dense barrier layer 53 and the intermediate layer 54) is covered with the conductive thin film layer 55. In other words, in the present embodiment, the ratio (coverage) of the area where the metal base layer 52 is covered with the conductive thin film layer 55 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 base layer 52 by the conductive thin film layer 55 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 layer 52 which is not coat | covered with the electroconductive thin film layer 52 can be suppressed effectively. In addition, the said coverage shall mean the ratio of the area of the metal base material layer 52 which overlaps with the electroconductive thin film layer 55, when a conductive member (separator 5) is seen from a lamination direction.

(Method for producing conductive member)
There is no restriction | limiting in particular about the method of manufacturing the electrically-conductive member of embodiment mentioned above, It can manufacture by referring a conventionally well-known method suitably. 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. In addition, since various conditions such as the material of each component of the conductive member constituting the separator 5 are as described above, the description thereof is omitted here.

  That is, the manufacturing method of the electrically-conductive member of this invention which has the following process is provided. First, a dense barrier layer is formed on a metal substrate layer (main surface of the metal substrate layer) by plating, thermal spraying, CVD, or coating [Step (1)]. Next, an intermediate layer is formed on the dense barrier layer (main surface of the dense barrier layer) by sputtering or ion plating [Step (2)]. Furthermore, a conductive thin film layer is formed on the intermediate layer (main surface of the intermediate layer) by sputtering and ion plating [Step (3)].

[Step (1)]
First, a metal plate such as a stainless plate or an aluminum plate having a desired thickness is prepared as a constituent material of the metal base layer. Next, the surface of the constituent material of the prepared metal base layer is degreased and washed using an appropriate solvent (for example, ethanol, ether, acetone, isopropyl alcohol, trichlorethylene, and 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 layer is removed. The technique for removing the oxide film is not particularly limited, and examples thereof include an acid cleaning process, a dissolution process by applying a potential, and an ion bombardment process.

  Alternatively, a method in which alkali immersion cleaning, removal of an oxide film with alkali (alkali etching), surface activation with a hydrofluoric acid mixed acid solution, and subsequent zincate treatment in a zinc replacement bath are preferably used. Although the zincate treatment conditions are not particularly limited, for example, the bath temperature is 10 to 40 ° C. and the immersion time is 20 to 90 seconds. Note that the oxide film removal step may be omitted.

  The treatment (degreasing / cleaning treatment or oxide film removal treatment on the surface of the metal plate) is preferably performed on at least the surface of the metal plate on which the dense barrier layer is formed, but more preferably on both surfaces of the metal plate.

  Next, a dense barrier layer is formed (deposited) on the surface of the constituent material of the metal base layer subjected to the above treatment. Here, the method for forming (depositing) the dense barrier layer is not particularly limited as long as the crystal orientation is low as described above, but plating, thermal spraying, CVD (Chemical Vapor Deposition), and coating are not limited. used. Preferably, the dense barrier layer is formed (formed) on the surface of the constituent material of the metal base layer by plating.

The plating conditions are not particularly limited as long as the above-described dense barrier layer can be formed (film formation), and known conditions are used, and the type of constituent material of the dense barrier layer to be used. It depends on the amount and quantity. For example, Cr plating treatment conditions are a current density of 3 to 10 A / dm ² , a bath temperature of 20 to 60 ° C., and an electrodeposition time of 30 to 120 minutes. Under such conditions, the dense barrier layer as described above can be easily formed.

  By such a method, a dense barrier layer having a spherical or granular structure (surface convex portion) with low crystal orientation can be formed on the metal substrate layer. Here, the size of the spherical / granular structure of the dense barrier layer is preferably fine enough not to pass water molecules. Specifically, the average crystallite diameter of the spherical / granular structure (surface protrusion) of the dense barrier layer is preferably 10 to 30 nm, more preferably 10 to 20 nm. With such a size, the penetration of water molecules can be effectively suppressed / prevented. In this specification, the “average crystallite diameter of the spherical / granular structure of the dense barrier layer” was calculated from the half width of the peak intensity ratio by X-ray diffraction.

[Step (2)]
Next, an intermediate layer is formed (film formation) on the dense barrier layer formed (film formation) in the step (1). Here, the method for forming (depositing) the intermediate layer is not particularly limited as long as the crystal orientation is improved to some extent as described above, but a sputtering method and an ion plating method are used. A sputtering method is preferred.

  As a method suitably used for forming (depositing) the intermediate layer, there is a physical vapor deposition (PVD) method such as a sputtering method or an ion plating method. The intermediate layer can also be formed (film formation) by other methods, for example, an ion beam evaporation method such as a filtered cathodic vacuum arc (FCVA) method. However, in view of high crystal orientation, it is preferable to use a sputtering method and an ion plating method, and it is particularly preferable to use a sputtering method. Here, examples of the sputtering method include a magnetron sputtering method, an unbalanced magnetron sputtering (UBMS) method, and a dual magnetron sputtering method. Examples of the ion plating method include an arc ion plating method. According to such a method, a layer having high crystal orientation can be formed. In addition to this, the film can be formed at a relatively low temperature, and there is an advantage that damage to the dense barrier layer can be minimized. Further, the sputtering method has an advantage that the film quality of the deposited film can be controlled by controlling the bias voltage and the like.

  When the intermediate layer is formed on the dense barrier layer by sputtering or ion plating, the boundary portion between the dense barrier layer and the intermediate layer is a dense and low crystallinity portion derived from the dense barrier layer, There may be a structure in which a columnar portion having high crystallinity derived from the intermediate layer coexists. Even if such coexisting portions exist, if the dense barrier layer having a low crystallinity and the intermediate layer having a columnar structure having a high crystallinity are arranged with the thickness as described above, the effect of the present invention is sufficient. Can be achieved.

  By such a method, an intermediate layer having a columnar structure having higher crystal orientation than the dense barrier layer can be formed on the dense barrier layer. Here, the size of the columnar structure of the intermediate layer is not particularly limited, but considering the adhesion to the dense barrier layer or the conductive thin film layer, the spherical / granular structure (surface convex portion) of the dense barrier layer is considered. It is preferable that it is larger than the size. Specifically, the average size of the columnar structure (surface convex portion) of the intermediate layer is preferably 10 to 100 nm, more preferably 30 to 100 nm. With such a size, sufficient adhesion with the dense barrier layer and the conductive thin film layer can be achieved. In this specification, “the average size of the columnar structure of the intermediate layer” is calculated from image analysis of the cross section of the intermediate layer by SEM.

[Step (3)]
Next, a conductive thin film layer is formed (deposited) on the intermediate layer formed (deposited) in the step (2). Here, the method for forming (depositing) the conductive thin film layer is not particularly limited. For example, when the conductive thin film layer is a conductive carbon layer, a layer containing conductive carbon is laminated on the intermediate layer at the atomic level using the above-described constituent material of the conductive thin film layer (for example, graphite) as a target. By conducting (film formation), a conductive thin film layer can be formed. As a result, the adhesion between the directly attached conductive thin film layer and the intermediate layer or the interface between the dense barrier layer and the intermediate layer and the vicinity thereof is maintained for a long period of time due to intermolecular force and slight carbon atoms entering. sell.

  As a method suitably used for laminating (depositing) conductive carbon, for example, physical vapor deposition (PVD) methods such as sputtering or ion plating, or filtered cathodic vacuum arc (FCVA) And ion beam deposition methods. 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. Of these, the sputtering method and the ion plating method are preferably used, and the sputtering method is particularly preferably used. According to such a method, a carbon layer with a low hydrogen content can be formed. As a result, the ratio of bonds between carbon atoms (sp2 hybrid carbon) 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 intermediate layer can be minimized. Further, the sputtering method has an advantage that the film quality of the deposited film can be controlled by controlling the bias voltage and the like.

  Here, when the conductive thin film layer is formed by sputtering, a negative bias voltage may be applied to the intermediate layer during sputtering. According to such a form, a conductive thin film layer having a structure in which graphite clusters are densely assembled can be formed by the ion irradiation effect. Since such an electroconductive thin film layer can exhibit the outstanding electroconductivity, the electroconductive member (separator) with small contact resistance with another member (for example, MEA) can be provided. In this embodiment, the magnitude (absolute value) of the negative bias voltage to be applied is not particularly limited, and a voltage capable of forming a conductive thin film layer can be adopted. As an example, the magnitude of the applied voltage is preferably 50 to 500V, more preferably 100 to 300V. In addition, specific forms, such as other conditions at the time of film-forming, are not restrict | limited, A conventionally well-known knowledge can be referred suitably.

  In order to manufacture the conductive member (separator) having the form shown in FIG. 2, an intermediate layer is formed on at least one main surface of the metal base layer before the conductive carbon layer forming step described above. Perform the process. At this time, as the method for forming the intermediate layer, the same method as described above for the formation of the conductive carbon layer may be employed. However, it is necessary to change the target to the constituent material of the intermediate layer.

  According to the above-described method, a conductive member in which the metal base layer 52, the dense barrier layer 53, the intermediate layer 54, and the conductive thin film layer 55 are sequentially formed can be manufactured. In the above method, the dense barrier layer 53, the intermediate layer 54, and the conductive thin film layer are formed only on one side of the metal base layer 52. However, the conductive layer is formed by forming the above layers on both sides of the metal base layer 52. In order to manufacture the member, the same method as described above may be applied to the other surface of the metal base layer 52.

  The conductive member of this embodiment can be used for various applications. A typical example is the PEFC separator 5 shown in FIG. That is, the present invention provides 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, 6. A polymer electrolyte fuel cell comprising a pair of anode separator and cathode separator sandwiching a membrane electrode assembly, wherein at least one of the anode separator or the cathode separator is a fuel cell separator according to claim 5. In this case, the fuel cell separator is formed in a concavo-convex shape, the convex portion comes into contact with the membrane electrode assembly, and the concave portion circulates fuel gas or oxidant gas. Thus, a polymer electrolyte fuel cell is provided.

  When the conductive member of the present invention is used for a PEFC separator, the conductive member of the present invention may be used for any one of an anode and a cathode. However, considering the fact that a large amount of water is generated particularly on the cathode side, it is preferable to use the conductive member of the present invention as at least a cathode separator. More preferably, the conductive member of the present invention is used for both the cathode separator and the anode separator. In the present invention, the dense barrier layer does not need to be covered over the entire surface of the metal substrate layer for both separators. However, in consideration of the effect of suppressing / preventing water permeation into the metal substrate layer, the coverage with the cathode separator is preferably equal to or higher than the coverage with the anode separator. This effectively suppresses / prevents intrusion of water molecules on the cathode side where a larger amount of water is generated, and effectively suppresses the decrease in conductivity / corrosion resistance of the conductive member (particularly the metal substrate layer). sell. Specifically, the magnitude relationship of the coverage of the metal base material layer with the dense barrier layer on the anode separator side with respect to the cathode separator side is preferably 60 to 60 on the cathode side, assuming that the coverage on the anode separator side is 100. 100, more preferably 80-100.

  Further, the dense barrier layer does not necessarily have to be formed over the entire surface of the metal base layer (with a coverage of 100%) in the respective surface directions of the cathode side and anode side separators. Preferably, the dense barrier layer has a metal base layer so that the in-plane distribution of each separator is continuously or in divided regions of two or more regions, so that the downstream side of the gas flow direction has a higher coverage. Formed on top (film formation). This considers that a large amount of water is generated at the cathode and the anode toward the downstream side with respect to the gas flow direction. Therefore, by adopting such an arrangement, a dense barrier layer is formed on the metal substrate layer according to the amount of water generated, and more effectively suppresses / prevents intrusion of water molecules, The decrease in conductivity and corrosion resistance of the (metal substrate layer) can be more effectively suppressed.

  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.

  Hereinafter, with reference to FIG. 1, components of the PEFC using the separator constituted by the conductive member of the present embodiment will be described. 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.

[Electrolyte layer]
The electrolyte layer is composed of, for example, a solid polymer electrolyte membrane 2 as shown in FIG. The solid polymer electrolyte membrane 2 has a function of selectively permeating protons generated in the anode catalyst layer 3a during operation of the PEFC 1 to the cathode catalyst layer 3c along the film thickness direction. The solid polymer electrolyte membrane 2 also has a function as a partition wall for preventing the fuel gas supplied to the anode side and the oxidant gas 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 of strength during film formation, durability during use, and output characteristics during use can be appropriately controlled.

[Catalyst layer]
The catalyst layers (the anode catalyst layer 3a and the cathode catalyst layer 3c) 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 3c.

  The catalyst layer 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 is not particularly limited as long as it has a catalytic action in the oxidation reaction of hydrogen, and a known catalyst can be used in the same manner. The catalyst component used in the cathode catalyst layer 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 in the anode catalyst layer and the catalyst component used in the cathode catalyst layer 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 and the cathode catalyst layer 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 includes 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 mentioned above can be added to a catalyst layer as a polymer electrolyte.

[Gas diffusion layer]
The gas diffusion layers (anode gas diffusion layer 4a, cathode gas diffusion layer 4c) are catalyst layers (3a, 3c) of gas (fuel gas or oxidant gas) supplied via the gas flow paths (6a, 6c) of the separator. ) And a function as an electron conduction path.

  The material which comprises the base material of a gas diffusion layer (4a, 4c) 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 substrate 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 substrate is within such a range, the balance between mechanical strength and diffusibility such as gas and water can be appropriately controlled.

  The gas diffusion layer 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 has a carbon particle layer (microporous layer; MPL, 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, it becomes possible to improve contact property with a catalyst layer.

  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. In addition, there is no restriction | limiting in particular also about the thickness of a carbon particle layer, What is necessary is just to determine suitably in consideration of the water repellency of the gas diffusion layer obtained.

  The manufacturing method of the fuel cell is not particularly limited, and conventionally known knowledge can be appropriately referred to in the field of the fuel cell.

  The fuel used when operating the fuel cell is not particularly limited. For example, hydrogen, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, secondary butanol, tertiary butanol, dimethyl ether, diethyl ether, ethylene glycol, diethylene glycol and the like can be used. Of these, hydrogen and methanol are preferably used in that high output is possible.

  Furthermore, a fuel cell stack having a structure in which a plurality of membrane electrode assemblies are stacked and connected in series via a separator may be formed so that the fuel cell can exhibit a desired voltage. 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.

  The PEFC 1 and the fuel cell stack described above use the separator 5 made of a conductive member having excellent conductivity and corrosion resistance. Therefore, the PEFC 1 and the fuel cell stack have excellent output characteristics and durability, and can maintain good power generation performance over a long period of time. In addition, in PEFC1 of the form shown in FIG. 1, the separator 5 is shape | molded by the uneven | corrugated shape by performing a press process with respect to a flat conductive member. However, it is not limited only to such a form. For example, an uneven shape constituting a gas channel or a coolant channel is formed in advance by cutting a flat metal plate (metal substrate layer), and the conductive thin film is formed on the surface by the above-described method. It is good also as a separator by forming a layer (and intermediate | middle layer as needed).

  The PEFC 1 of the present embodiment and the fuel cell stack using the PEFC 1 can be mounted on a vehicle as a driving power source, for example. Thus, a vehicle equipped with the PEFC 1 and the fuel cell stack of the above-described form is also included in the technical scope of the present invention. The above-mentioned PEFC1 and fuel cell stack are excellent in output characteristics and durability. Therefore, a highly reliable fuel cell vehicle can be provided over a long period of time.

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

  FIG. 11 is a conceptual diagram of a vehicle equipped with the fuel cell stack of the above-described embodiment. As shown in FIG. 11, in order to mount the fuel cell stack 61 on a vehicle such as the fuel cell vehicle 60, for example, the fuel cell stack 61 may be mounted under the seat at the center of the vehicle body of the fuel cell vehicle 60. If it is installed under the seat, the interior space and the trunk room can be widened. Depending on the case, the place where the fuel cell stack 61 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 1 and the fuel cell stack 61 of the above-described form is also included in the technical scope of the present invention. The PEFC 1 and the fuel cell stack 61 described above 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.

[Reference Example 1]
An aluminum plate (thickness: 0.2 mm) was prepared as a constituent material of the metal base layer constituting the conductive member. The aluminum plate was immersed and washed in an alkaline aqueous solution having a pH of 10 at 50 ° C. for 10 minutes. Next, this aluminum plate was etched with nitric acid (acid) to remove the oxide film. Further, the aluminum plate was subjected to surface activation with a hydrofluoric acid mixed acid solution and then subjected to a zincate treatment in a zinc substitution bath. In this case, the zincate treatment conditions are a bath temperature of 25 ° C. and an immersion time of 30 seconds. Moreover, the said process was performed about both surfaces of the aluminum plate.

Next, the aluminum plate subjected to the above pretreatment was subjected to chromium (Cr) plating in a sergeant bath to form a dense barrier layer. At this time, plating conditions were a current density of 4 A / dm ² , a bath temperature of 35 ° C., an electrodeposition time of 1 hour, and a dense barrier layer (Cr plating) made of Cr having a thickness of 2 μm was formed.

  With respect to the dense barrier layer thus formed, the average crystallite diameter was measured using an X-ray diffractometer (manufactured by Mac Science) by the method of Scherre in the X-ray diffraction method.

  Further, for the dense barrier layer formed in this manner, the cross section was subjected to image analysis by SEM, and the area ratio occupied by Cr constituting the dense barrier layer in the layer was determined to determine the porosity, 1% or less.

[Reference Example 2]
An aluminum plate (thickness: 0.2 mm) was prepared as a constituent material of the metal base layer constituting the conductive member. This aluminum plate was subjected to ultrasonic cleaning in an aqueous ethanol solution for 3 minutes as a pretreatment. Next, the cleaned aluminum plate was placed in a vacuum chamber, and ion bombardment with Ar gas was performed to remove the oxide film on the surface. The pretreatment (cleaning) and ion bombardment described above were both performed on both surfaces of the aluminum plate.

  Next, an unbalanced magnetron sputtering (UBMS) method is used to apply a negative bias voltage of 50 V to the aluminum plate using Cr as a target, and from 0.2 μm thick Cr to the aluminum plate. An intermediate layer was formed.

  With respect to the intermediate layer thus formed, the average crystallite size was measured in the same manner as in Reference Example 1. As a result, it was 30 nm. Further, when the porosity of this intermediate layer was determined in the same manner as in Reference Example 1, it was 7%.

Here, by comparing the result of Reference Example 1 and the result of Reference Example 2, the dense barrier layer formed in Reference Example 1 has a lower porosity than the intermediate layer formed in this example. I understand. The average crystallite diameter [D ₂ (nm)] of the dense barrier layer formed in Reference Example 1 is smaller than the average crystallite diameter [D ₁ (nm)] of the intermediate layer formed in this example. _{(D 2 / D 1 = 0.5} ). On the other hand, since there is a correlation between the degree of crystal orientation (crystal orientation) and the average crystallite diameter, the dense barrier layer formed in Reference Example 1 has a higher crystal orientation than the intermediate layer formed in this example. It is considered low. It is also considered that the degree of crystal orientation (crystal orientation) of each layer can be easily adjusted by adjusting the average crystallite diameter.

  In addition to the above, the results of image analysis of the cross sections of the dense barrier layer and the intermediate layer prepared in Reference Examples 1 and 2 by TEM are shown in FIG. 8A (Reference Example 1) and FIG. 8B (Reference Example 2). Shown in 8A and 8B, the dense barrier layer of Reference Example 1 has a granular structure, whereas the intermediate layer of Reference Example 2 has a columnar structure. Also from this figure, it can be seen that the dense barrier layer of Reference Example 1 is denser than the intermediate layer of Reference Example 2, and this result is consistent with the above-described porosity result. .

  Similarly, for the dense barrier layer and the intermediate layer prepared in Reference Examples 1 and 2, the surface of each layer was subjected to image analysis by SEM, and the results are shown in FIG. 9A (Reference Example 1) and FIG. 9B (Reference Example 2). ). From FIGS. 9A and 9B, it can be seen that the fine barrier layer of Reference Example 1 has a fine granular structure, whereas the intermediate layer of Reference Example 2 has convex portions with gaps of constant intervals. . Further, from FIG. 9B, it was found that the average size of the columnar structure of the intermediate layer was about 50 nm.

[Example 1]
In the same manner as described in Reference Example 1, a dense barrier layer (Cr plating, average crystallite diameter = 15 nm) made of Cr having a thickness of 2 μm was formed on both surfaces of the metal substrate layer. Next, with respect to the formed dense barrier layer, in the same manner as the method described in Reference Example 2, while applying a negative bias voltage (50 V) using Cr as a target by UBMS method, 0.2 μm An intermediate layer (average crystallite diameter = 30 nm) made of Cr having a thickness was formed. The same operation was repeated to form an intermediate layer made of Cr having a thickness of 0.2 μm on both dense barrier layers. Thus, an intermediate layer made of Cr with a thickness of 0.2 μm; a dense barrier layer made of Cr with a thickness of 2 μm; a metal substrate layer; a dense barrier layer made of Cr with a thickness of 2 μm; a thickness of 0.2 μm A laminate of five intermediate layers made of Cr was produced.

  The laminate was cut into a size of 30 mm × 30 mm in the surface direction, and the side surface was masked with a silicon material to prepare sample (1).

[Comparative Example 1]
In the same manner as described in Reference Example 1, a dense barrier layer (Cr plating) made of Cr having a thickness of 2 μm was formed on both surfaces of the metal substrate layer. This was cut into a size of 30 mm × 30 mm in the surface direction, and the side surface was masked with a silicon material to prepare a sample (2).

[Comparative Example 2]
In the same manner as described in Reference Example 2, an intermediate layer made of Cr having a thickness of 0.2 μm was formed on both surfaces of the metal substrate layer. This was cut into a size of 30 mm × 30 mm in the surface direction, and the side surface was masked with a silicon material to prepare a sample (3).

[Evaluation: Corrosion resistance test]
For the samples (1), (2), and (3) prepared in Example 1 and Comparative Examples 1 and 2, the following experiment was conducted to test the elution amount of aluminum ions. That is, the samples (1), (2) and (3) were each immersed in 70 mL of an aqueous sulfuric acid solution (pH 4) at 80 ° C. for 100 hours. The sulfuric acid aqueous solution simulates the environment where the separator is exposed in the fuel cell. In general, since the temperature during operation of the fuel cell is 80 ° C., the test temperature was set to 80 ° C.

  After 100 hours, the amount (ppm) of aluminum ions eluted in the sulfuric acid aqueous solution was analyzed by ICP-MS (Inductively-Coupled Plasma-Mass Spectrometry) -mass spectrometry). The results are shown in Table 1 below.

[Example 2]
In the same manner as described in Reference Example 1, a dense barrier layer (Cr plating, average crystallite diameter = 15 nm) made of Cr having a thickness of 2 μm was formed on one surface of the metal base layer. Next, with respect to the formed dense barrier layer, in the same manner as the method described in Reference Example 2, while applying a negative bias voltage (50 V) using Cr as a target by UBMS method, 0.2 μm An intermediate layer (average crystallite diameter = 30 nm) made of Cr having a thickness was formed.

  Further, a conductive thin film layer having a thickness of 0.2 μm was formed on the intermediate layer by applying a negative bias voltage of 100 V to the intermediate layer by using the solid graphite as a target by the UBMS method. . Thus, the conductive member of this example was produced.

  FIG. 10 shows the result of image analysis of the cross section of the conductive member by TEM. From FIG. 10, in the conductive member of the present invention, the dense barrier layer is formed in a granular structure, whereas the intermediate layer is formed in a columnar structure, and the dense barrier layer is more in comparison with the intermediate layer. It turns out that it is precise. This result is consistent with the porosity result.

1 is a schematic diagram showing a basic configuration of a polymer electrolyte fuel cell (PEFC) 1 according to one embodiment of the present invention. It is sectional drawing which shows schematic structure of the part of the separator 5 among FIG. It is the photograph (magnification: 400,000 times) which observed the cross section of the electrically-conductive member (electrically-conductive member A) which has the electroconductive thin film layer of R = 1.0-1.2 with the transmission electron microscope (TEM). It is the photograph (magnification: 400,000 times) which observed the section of the conductive member (conductive member B) which has the conductive thin film layer of R = 1.6 by TEM. It is a schematic diagram which shows the 3 times symmetrical pattern of an average peak in the rotational anisotropy measurement of a Raman scattering spectroscopy analysis. It is a schematic diagram which shows the 2 times symmetrical pattern of an average peak in the rotational anisotropy measurement of a Raman scattering spectroscopy analysis. It is a schematic diagram which shows the pattern which does not show the symmetry of an average peak in the rotational anisotropy measurement of a Raman scattering spectroscopy analysis. It is a graph which shows the Raman spectrum when the electrically conductive member B is used as a measurement sample and the rotation angles of the sample are 0 °, 60 ° and 180 °, respectively. 5 is a graph showing an average peak of rotational anisotropy measurement for conductive member B. Values of the Vickers hardness of the conductive carbon layer and the sp3 ratio of the conductive carbon layer in several conductive members having different Vickers hardness of the conductive carbon layer by changing the bias voltage and the film formation method by sputtering. It is a figure which shows the relationship. It is a graph which shows the result of having measured the contact resistance about several electrically-conductive members which have an electroconductive thin film layer from which content of hydrogen atom differs although R value is 1.3 or more. It is a photograph which shows the result of having image-analyzed the cross section of the dense barrier layer produced in Reference Example 1 by TEM. It is a photograph which shows the result of having image-analyzed the cross section of the intermediate | middle layer produced in Reference Example 2 by TEM. It is a photograph which shows the result of having image-analyzed the surface of the dense barrier layer produced in Reference Example 1 by SEM. It is a photograph which shows the result of having image-analyzed the surface of the intermediate | middle layer produced in Reference Example 2 by SEM. It is a photograph which shows the result of having image-analyzed the cross section of the electrically-conductive member produced in Example 2 by TEM. It is a conceptual diagram of the vehicle carrying the fuel cell stack of one Embodiment of this invention.

Explanation of symbols

1 Polymer electrolyte fuel cell (PEFC),
2 solid polymer electrolyte membrane,
3a anode catalyst layer,
3c cathode catalyst layer,
4a Anode gas diffusion layer,
4c cathode gas diffusion layer,
5a anode separator,
5c cathode separator,
6a Anode gas flow path,
6c cathode gas flow path,
7 Refrigerant flow path,
10 Membrane electrode assembly (MEA),
5 separator,
52 metal substrate layer,
53 dense barrier layer,
54 Middle layer,
55 conductive thin film layer,
60 Fuel cell vehicle,
61 Fuel cell stack.

Claims (9)

A metal substrate layer, a dense barrier layer formed on the metal substrate layer, an intermediate layer formed on the dense barrier layer, and a conductive thin film layer formed on the intermediate layer. And
The dense barrier layer has a lower crystal orientation than the intermediate layer, and the average crystallite diameter [D ₂ ( D) of the dense barrier layer with respect to the average crystallite diameter [D ₁ (nm)] of the intermediate layer. nm)] in a ratio (D ₂ / D ₁ ) of 0.1 or more and less than 1 . The dense barrier layer is at least one selected from the group consisting of a metal selected from Cr, W, Ti, Mo, Nb and Hf, a nitride of the metal, a carbide of the metal, and a carbonitride of the metal. It becomes conductive member according to claim 1.   The intermediate layer is selected from the group consisting of a metal selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W, a carbide of the metal, a nitride of the metal, and a carbonitride of the metal. The conductive member according to claim 1 or 2, comprising at least one of the above.   The conductive member according to any one of claims 1 to 3, wherein the constituent material of the metal base layer is at least one selected from the group consisting of iron, titanium, aluminum, copper, and alloys thereof.   The conductive member according to claim 1, wherein the conductive thin film layer is a conductive carbon layer. Forming a dense barrier layer on the metal substrate layer by plating, spraying, CVD or coating;
Forming an intermediate layer on the dense barrier layer by sputtering or ion plating; and forming a conductive thin film layer on the intermediate layer;
The manufacturing method of the electrically-conductive member of any one of Claims 1-5 which has a thing.   The manufacturing method according to claim 6, wherein the conductive thin film layer is formed by a sputtering method, and a negative bias voltage is applied to the intermediate layer at the time of sputtering.   The separator for fuel cells comprised from the electrically-conductive member of any one of Claims 1-5, or the electrically-conductive member manufactured by the method of Claim 6 or 7. 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 pair of anode separator and cathode separator sandwiching the membrane electrode assembly;
A polymer electrolyte fuel cell comprising:
9. At least one of the anode separator or the cathode separator is the fuel cell separator according to claim 8, 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, which is in contact with a body, and the recess is a gas flow path for circulating fuel gas or oxidant gas.