JP5493341B2 - Conductive member, method for producing the same, fuel cell separator and polymer electrolyte fuel cell using the same - Google Patents

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.

  In addition, while providing an intermediate layer on the metal substrate to improve corrosion resistance, it is possible to ensure conductivity by coating the conductive carbon film thereon. However, in such a case, since the hydrophilization is not sufficient, the drainage is inferior. As a method for imparting hydrophilicity, there are a method of imparting a functional group by applying a hydrophilic material, plasma treatment, and the like. In any case, a film having low conductivity is formed so as to cover the outermost surface of the carbon film. For this reason, contact resistance increases and electroconductivity falls.

Here, a technique for forming a carbon-based film containing a metal oxide of an element having a high oxide forming ability such as Si or Ti in a composite state on a separator substrate has been proposed (for example, Patent Documents). 1). In this document, while applying a negative high voltage to a separator substrate in an inert gas atmosphere, a carbon-based film and a composite metal are formed on the surface of the substrate by a dry film forming method, and then a composite film is formed. It describes that the metal halide is subjected to a dry / wet hydrophilization treatment. By such a hydrophilization treatment, the metal oxide fine particles exhibit hydrophilicity and drain excess water near the separator. As a result, a fuel cell separator excellent in durability and power generation performance can be provided (paragraph “0029”).
JP 2007-134107 A

  In a fuel cell separator having a carbon layer provided by a conventional technique, there are various crystal structures of the carbon layer. When the crystal structure of the carbon layer is different, the corrosion resistance and conductivity of the separator itself may vary due to this. In any case, however, the fuel cell separator provided by the conventional technology still has sufficient corrosion resistance and conductivity even if it is subjected to a surface treatment such as arrangement of a carbon layer. That's not true. Further, in the technique described in Patent Document 1, an oxide in the carbon-based film may increase contact resistance.

  Accordingly, an object of the present invention is to provide means capable of improving hydrophilicity while maintaining low contact resistance in a conductive member having a metal base layer, an intermediate layer, and a conductive carbon layer.

  In the conductive member having a metal base layer, an intermediate layer, and a conductive carbon layer, the present inventors can solve the above problem by partially exposing the intermediate layer to the surface layer of the conductive carbon layer. As a result, the present invention has been completed.

  ADVANTAGE OF THE INVENTION According to this invention, the electroconductive member excellent in electroconductivity and hydrophilicity can be provided because the intermediate | middle layer is exposed to the surface layer of an electroconductive carbon layer.

(Conductive member)
The conductive member of the present invention includes a metal base layer, an intermediate layer formed on the metal base layer, and a conductive carbon layer containing conductive carbon located on the intermediate layer. And it is a conductive member which has an intermediate | middle layer exposure part in a part of said conductive carbon layer.

  Conventionally, conductivity has been ensured by providing an intermediate layer on a metal substrate and forming a conductive carbon film thereon, but hydrophilicity is not sufficient. For this reason, various hydrophilization treatment methods have been studied, but a film having low conductivity is formed on the outermost surface of the conductive carbon film. For this reason, the contact resistance of the conductive member is increased and the conductivity is lowered.

  In contrast, the present invention is characterized in that a part of the intermediate layer is exposed on the surface layer of the conductive carbon layer. Here, the intermediate layer is responsible for imparting hydrophilicity, and the conductive carbon layer is responsible for imparting conductivity. For this reason, the electroconductive member of this invention can improve hydrophilicity, maintaining low contact resistance. 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.

  2A is a cross-sectional view showing a schematic configuration of a separator 5 portion in FIG. FIG. 2B is an image view of the separator 5 viewed from the MEA 10 side. In the present embodiment, the conductive member constituting the separator 5 includes a metal base layer 52, an intermediate layer 53, and a conductive carbon layer 54, and the intermediate layer 53 is exposed on the outermost surface of the conductive carbon layer 54. Part 55 is present. In PEFC 1, the separator 5 is arranged so that the conductive carbon layer 54 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, copper, 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. These materials are excellent in conductivity and moldability. 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.

[Middle layer]
The intermediate layer 53 is formed (arranged) on the metal base layer 52. Here, the intermediate layer 53 has hydrophilicity. For this reason, by disposing the intermediate layer 53, the metal base layer 52 functions as a corrosion prevention layer that suppresses the corrosion of the metal base layer 52 and the formation of an oxide film at the interface between the metal base layer and the intermediate layer. The excess water generated at the electrode is efficiently discharged. The intermediate layer 53 also has a function of improving adhesion with the conductive carbon layer 54 and a function of preventing elution of ions from the metal base layer 52. 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 carbon layer 54 includes 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 carbon layer 54 can be obtained by providing the intermediate layer 53. It can be remarkably expressed.

The material constituting the intermediate layer 53 is not particularly limited as long as it provides the above adhesion. For example, Group 4 metals (Ti, Zr, Hf ) 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 53 is not particularly limited. Specifically, the thickness of the intermediate layer 53 is preferably 30 nm or more, more preferably 100 nm or more, and further preferably 200 nm or more. With such a thickness, the contact resistance can be made sufficiently low. Also, with such a thickness, the metal used for the intermediate layer generally has a higher sputtering rate than carbon, and the conductive carbon layer can be thinner (less) than the intermediate layer. Can be shortened. Note that the upper limit of the thickness of the intermediate layer 53 is not particularly limited. In consideration of the manufacturing process and the stack size of the fuel cell, the thickness condition of the intermediate layer is appropriately 20 μm or less, and more preferably 10 μm or less. Thereby, the raise of the film | membrane stress of an intermediate | middle layer is suppressed, and the fall of the film followable | trackability with respect to a metal base material layer and generation | occurrence | production of peeling and a crack accompanying this can be prevented.

  Further, the surface of the intermediate layer 53 on the conductive carbon layer 54 side is preferably rough at the nano level. According to such an embodiment, the adhesion of the conductive carbon layer 54 formed on the intermediate layer 53 to the intermediate layer 53 can be further improved.

Furthermore, when the thermal expansion coefficient of the intermediate layer 53 is a value close to the thermal expansion coefficient of the metal constituting the metal base layer 52, the adhesion between the intermediate layer 53 and the metal base layer 52 is improved. However, in such a form, the adhesion between the intermediate layer 53 and the conductive carbon layer 54 may decrease. Similarly, when the thermal expansion coefficient of the intermediate layer 53 is close to the thermal expansion coefficient of the conductive carbon layer 54, the adhesion between the intermediate layer 53 and the metal base layer 52 may be lowered. Considering these, the thermal expansion coefficient (α _mid ) of the intermediate layer, the thermal expansion coefficient (α _sub ) of the metal base material layer, and the thermal expansion coefficient (α _c ) of the conductive carbon layer are expressed by α _sub > α It is preferable to satisfy the relationship of _mid > α _c .

  In addition, the intermediate | middle layer should just exist on the surface of at least one of a metal base material layer. However, when the conductive carbon layer exists only on one main surface of the metal base material layer, the intermediate layer exists between the metal base material layer and the conductive carbon layer. In addition, the conductive carbon layer may be present on both sides of the metal base layer as described above. In such a case, the intermediate layer is preferably interposed between the metal substrate layer and both conductive carbon layers. When the intermediate layer exists only between the metal substrate layer and one of the conductive carbon layers, the intermediate layer is disposed on the MEA side in the PEFC with the conductive carbon layer and the metal group. It is preferable to exist between the material layers.

  In the present invention, another layer may be provided between the intermediate layer 53 and the metal base layer 52. Here, as another layer, the dense layer which can suppress and prevent that the water produced | generated with the electrode permeates the metal base material layer side is mentioned. By disposing such a layer between the intermediate layer 53 and the metal base layer 52, the conductive member constituting the separator 5 can further improve the corrosion resistance while ensuring the conductivity. In particular, when the dense layer is made of a metal or an alloy thereof, the above-described operational effects due to the installation of the intermediate layer can be remarkably exhibited. The characteristics of the dense layer in the case of arranging the dense layer are not particularly limited, but it is preferable that water molecules do not pass through. Specifically, the dense layer has a porosity of 10% or less, more preferably 7% or less. Here, the “porosity” refers to the area ratio (%) of the metal, metalloid, metal carbide, or metal nitride constituting the dense layer in the layer after image analysis of the surface and cross section of the layer by SEM. ) Is measured.

[Conductive carbon layer]
The conductive carbon layer 54 is formed (arranged) on the intermediate layer 53. The conductive carbon layer 54 is a layer containing conductive carbon. The presence of this layer can improve the corrosion resistance as compared with the case of the metal base layer 52 alone, while ensuring the conductivity of the conductive member constituting the separator 5. In the present invention, as is apparent from FIGS. 2A and 2B, the conductive carbon layer 54 is not necessarily configured as an integral layer. However, in the present specification, portions where conductive carbon exists are collectively referred to as “conductive carbon layer”.

  In the present invention, the conductive carbon layer 54 does not cover the entire surface of the intermediate layer 53 and there is an exposed portion of the intermediate layer. Since the intermediate layer bears hydrophilicity and the conductive carbon layer bears conductivity, hydrophilicity can be improved while maintaining low contact resistance. That is, the intermediate layer is more hydrophilic than the conductive carbon layer. For this reason, hydrophilicity improves rather than a conductive carbon layer single-piece | unit because the exposed part of such a hydrophilic intermediate | middle layer exists in the outermost surface of a conductive carbon layer. Although the intermediate layer has a higher contact resistance than the conductive carbon layer, the increase in the contact resistance can be suppressed as much as possible by ensuring the conductive path.

  Here, the coverage of the intermediate layer with the conductive carbon layer is preferably 30% or more and less than 100%. Thus, if the intermediate layer is covered with a conductive carbon layer in an area ratio of 30% or more, the conductive member surface is sufficiently hydrophilic while ensuring a conductive path by the conductive carbon layer, and drainage performance is improved. improves. Therefore, when the conductive member of the present invention is used for a separator, the separator surface exhibits hydrophilicity while maintaining sufficient conductivity, and excess water near the separator can be drained efficiently. More preferably, the coverage of the intermediate layer with the conductive carbon layer (the exposure rate on the outermost surface of the conductive carbon layer) is 50 to 90%. In addition, the said coverage is the ratio of the area of the conductive carbon layer 54 overlapping with the intermediate layer 53 when the conductive member (separator 5) is viewed from the stacking direction {= [(total area of the conductive carbon layer 54) / (Area of the intermediate layer 53)] × 100 (%)}.

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. With such an R value, the graphite bond ratio in the conductive carbon layer increases, so that π electrons increase, and the conductivity can be ensured. 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 this specification, “R value” was measured according to the following method.

[Measurement of R value]
For the conductive member, the R value of the conductive carbon layer was measured. Specifically, first, the Raman spectrum of the conductive carbon layer was measured using a microscopic Raman spectrometer. Then, the peak intensity of the bands (D-band) located 1300~1400cm ^-1 _{(I D),} the peak area ratio of the peak intensity _{(I G)} of band (G-band) located 1500~1600cm ^-1 ( I _D / I _G ) was calculated and used as the R value.

  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 carbon layer 54 is not particularly limited. However, Preferably it is 1-1000 nm, More preferably, it is 2-500 nm, More preferably, it is 5-200 nm. If the thickness of the conductive carbon layer is within such a range, sufficient conductivity can be ensured between the gas diffusion base material and the separator. In the present embodiment, the conductive carbon layer 54 exists only on one main surface of the conductive member (separator 5). However, in some cases, the conductive carbon layer 54 may also exist on the other main surface of the conductive member (separator 5).

  Hereinafter, although more preferable embodiment in the conductive carbon layer 54 of this embodiment is described, the technical scope of this invention is not limited only to the following form.

  First, regarding the Raman scattering spectroscopic analysis of the conductive carbon layer 54, from another viewpoint, it is preferable that the average peak measured by the rotational anisotropy measurement of the Raman scattering spectroscopic analysis shows a two-fold symmetry pattern. 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. Accordingly, the fact that the average peak measured by the rotational anisotropy measurement shows the twofold symmetry pattern, the plane direction of the graphene planes constituting the electrical conductive carbon layer is substantially coincident with the laminating 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 carbon layer 54 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 carbon layer 54 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 carbon layer 54 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 carbon layer 54 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 carbon layer 54 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. The conductive member was 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 point of view, it is preferable to consider the amount of hydrogen atoms contained in the conductive carbon layer 54 as well. That is, when the conductive carbon layer 54 includes a hydrogen atom, the hydrogen atom is bonded to the carbon atom. Then, the hybrid orbital of the carbon atom to which the hydrogen atom is bonded changes from sp2 to sp3 and loses conductivity, so that the conductivity of the conductive carbon layer 54 is lowered. Further, when the C—H bond in the polycrystalline graphite is increased, the continuity of the bond is lost, the hardness of the conductive carbon layer 54 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 carbon layer 54 is preferably 30 atomic percent or less, more preferably 20 atomic percent or less, with respect to all atoms constituting the conductive carbon layer 54. More preferably, it is 10 atomic% or less. Here, as the value of the hydrogen atom content in the conductive carbon layer 54, 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. More specifically, the “hydrogen atom content” in the present specification is a value measured according to the following method.

  Here, FIG. 7 is a graph showing the results of measuring the contact resistance of several conductive members having conductive carbon layers having different hydrogen atom contents although the R value is 1.3 or more. is there. As shown in FIG. 7, when the hydrogen atom content in the conductive carbon 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 carbon layer (thickness: 0.2 μm) on the surface. ) Were sequentially formed by a sputtering method. At this time, the hydrogen atom content in the conductive carbon layer was changed by controlling the film formation method and the amount of hydrocarbon gas.

(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 (henceforth "method 1") of the electrically-conductive member of this invention which has the following process is provided. First, an intermediate layer is formed on a metal substrate layer [Step (1-1)]. Next, a conductive carbon layer is formed on the intermediate layer formed in the step (1-2) by sputtering or ion plating, and a metal base layer, an intermediate layer, and a conductive carbon layer are stacked. A body is formed [step (1-2)]. Subsequently, the laminate obtained in the step (1-2) is formed by pressing [step (1-3)].

  Or the manufacturing method (henceforth "method 2") of the electrically-conductive member of this invention which has the following process is also provided. First, a metal substrate layer is formed by pressing [step (2-1)]. Next, an intermediate layer is formed on the metal substrate layer formed in the above step (2-1) [step (2-2)]. Subsequently, a conductive carbon layer is formed on the intermediate layer obtained in the step (2-2) by a sputtering method or an ion plating method [step (2-3)].

  Conventionally, for example, in the method described in Japanese Patent Application Laid-Open No. 2007-134107, there is a concern that the process becomes complicated due to the composite of the metal element into the carbon-based film. On the other hand, according to the above method 1 and method 2, it is possible to easily manufacture the conductive member of the present invention.

  First, method 1 will be described.

[Step (1-1)]
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 above 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 intermediate layer is formed, but more preferably on both surfaces of the metal plate.

  Next, an intermediate layer is formed (film formation) on the surface of the constituent material of the metal base layer subjected to the above treatment. 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. According to such a method, the intermediate layer can be formed (film formation) without causing poor adhesion between the intermediate layer and the conductive carbon layer. For this reason, the obtained electroconductive member can achieve high electroconductivity and corrosion resistance.

  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 excellent hydrophilicity 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 metal base 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 intermediate layer is formed by sputtering, a negative bias voltage may be applied to the metal base layer during sputtering. According to such a form, an intermediate layer having a structure in which constituent materials are densely assembled can be formed by the ion irradiation effect. Since such an intermediate layer exhibits high crystal orientation, adhesion with the conductive thin film layer can be improved. Moreover, the intermediate layer thus obtained is excellent in hydrophilicity. 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 carbon 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.

[Step (1-2)]
Next, a conductive carbon layer is formed (deposited) on the intermediate layer formed (deposited) in the above step (1-1). Here, the formation (film formation) method of the conductive carbon layer is not particularly limited. For example, the conductive carbon layer is formed by laminating (depositing) a layer containing conductive carbon on the intermediate layer at the atomic level using the above-described constituent material of the conductive carbon layer (for example, graphite) as a target. be able to. Thereby, the adhesion between the interface between the conductive carbon layer and the intermediate layer directly attached and the vicinity thereof can be maintained for a long period of time due to intermolecular force or slight carbon atom intrusion.

  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 carbon layer is formed by a sputtering method, a negative bias voltage may be applied to the intermediate layer during sputtering. According to such a form, a conductive carbon layer having a structure in which graphite clusters are densely assembled can be formed by the ion irradiation effect. Since such a conductive carbon layer can exhibit excellent conductivity, a conductive member (separator) having a low contact resistance with other members (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 carbon 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 the present invention, the conductive carbon layer is formed on the intermediate layer so as not to completely cover the intermediate layer. Thus, the method for forming the conductive carbon layer is not particularly limited so that the conductive carbon layer does not cover the entire surface of the intermediate layer and there is an exposed portion of the intermediate layer. For example, (a) a method of forming a conductive carbon layer by previously controlling the amount of target material (a constituent material of a conductive carbon layer such as graphite); (a) a target material (of a conductive carbon layer such as graphite) A method of forming a conductive carbon layer by appropriately controlling the film formation time of the constituent material); (c) ionization by an inert gas after forming the conductive carbon layer on the intermediate layer A method of removing a part of the outermost conductive carbon layer by performing a bombardment process; (D) masking the intermediate layer before forming the conductive carbon layer, and then placing the conductive carbon layer on the intermediate layer. A method of forming a film and further removing the masking to expose the intermediate layer; (e) a mask that is incompatible with the conductive carbon layer and cannot maintain the adhesion of the carbon layer before forming the conductive carbon layer After coating the layer so that the intermediate layer is exposed, conductive Forming a arsenide layer on the intermediate layer, and further removing the mask layer, a method of exposing the intermediate layer, and the like. In addition, although it explains in full detail in the following process (1-3), it press-processes after forming into a film so that a conductive carbon layer may be coat | covered on an intermediate | middle layer, without using the method of said (a)-(e). The exposed portion of the intermediate layer can be formed on the outermost surface layer of the conductive carbon layer. Among the above methods, in (a), the constituent material in an amount of about 110 to 120% by mass with respect to the amount of the constituent material of the conductive carbon layer used to form the conductive carbon layer with a predetermined thickness. Can be used. In (A), the film formation time varies depending on the film formation conditions such as the film formation speed and the area, but the film formation time is preferably about 0.05 to 1 minute. In (c), the inert gas is not particularly limited, but argon gas, helium gas, nitrogen gas, preferably argon gas is used. In (d), a solvent such as xylene or methoxypropanol is applied as a masking agent, fluorine resin (PTFE (polytetrafluoroethylene), FEP (fluorinated ethylene propylene copolymer), PFA (tetrafluoroethylene-perfluoroalkylvinyl ether copolymer)). Films such as can be used. In (e), a coating film such as Al or Al alloy having low adhesion to the conductive carbon layer can be used. Among the above methods, the methods (a), (c), (d), and (e) are preferably used, and (a) and (c) are more preferable. Although the said method may be used independently, depending on the coverage of a conductive carbon layer, you may carry out combining the 2 or more types, or repeating the same method. Further, the above methods (a) to (e) may be performed in combination with the following process (1-3).

[Step (1-3)]
In the said process (1-3), the laminated body obtained at the said process (1-2) is shape | molded by press. Thus, by applying a press treatment to the flat laminate, the conductive member of the present invention can be manufactured by being formed into a desired shape such as an uneven shape. Moreover, after producing the laminated body obtained at the said process (1-2), by performing a press process, a crack arises in a conductive carbon layer surface, and an intermediate | middle layer is exposed from the outermost layer of a conductive carbon layer. .

  Here, the conditions similar to the conditions generally applied when manufacturing a separator from a metal substrate can be used for the press treatment conditions for the laminate. For example, the laminate obtained in the above step (1-2) is pressed at room temperature.

  Next, method 2 will be described.

[Step (2-1)]
In this step, the metal substrate layer is formed by pressing. Thereby, a flat metal base material layer can be shape | molded in desired shapes, such as uneven | corrugated shape which is the final target shape.

  Here, the press treatment conditions for the metal base material layer can be the same conditions as those generally applied when producing a separator from the metal base material, and preferable conditions are the above-mentioned step (1-3). It is the same as described in.

[Step (2-2)]
In this step, an intermediate layer is formed on the metal base material layer formed in the above step (2-1). At this time, the method for forming the intermediate layer is the same as that described in the above step (1-1), and thus the description thereof is omitted here.

[Step (2-3)]
In this step, a conductive carbon layer is formed on the intermediate layer obtained in the above step (2-2) by a sputtering method or an ion plating method. At this time, since the method for forming the conductive carbon layer is the same as that described in the above step (1-2), the description thereof is omitted here.

  Of the above methods 1 and 2, method 1 is preferably used. This is because, in the method of coating after pressing in Method 2, since the shape of the conductive member is not a flat plate but a complicated shape, each operation such as coating treatment and jig setup is performed by a metal base layer (metal plate). It is necessary to carry out one by one. On the other hand, in the method of pressing after coating in Method 1, since each layer is formed first, it is possible to carry out at once by coating a roll material on a large-area metal base material layer (metal plate). . Next, the laminated body thus obtained may be cut into a desired size, and a pressing process may be performed to a desired shape in the process (1-3). For this reason, the method 1 is more advantageous in terms of labor and productivity.

  In addition to the above advantages, as described above, when the laminate obtained in the step (1-2) is subjected to the pressing process by the method 1, the conductive carbon layer is partially broken by the pressing pressure, Cracks occur on the surface of the conductive carbon layer. For this reason, even if the conductive carbon layer covers the entire surface of the intermediate layer in step (1-2), the exposed portion of the intermediate layer can be easily formed on the outermost layer of the conductive carbon layer by a simple operation such as pressing. Can be formed. Further, the formation direction of the cracks formed in this way can be easily controlled by a pressing method or the like. For this reason, for example, when the conductive member is applied to the separator, it is preferable to generate a crack so as to be parallel to the gas flow path. Accordingly, excess water generated at the electrode can be efficiently discharged through the crack portion, and the crack can work advantageously with respect to the discharge.

  According to the above-described method, the metal base layer 52, the intermediate layer 53, and the conductive carbon layer 54 are sequentially formed, and the conductive carbon layer 54 does not cover the entire surface of the intermediate layer 53 and there is an exposed portion of the intermediate layer. The conductive member thus manufactured can be easily manufactured. In the above method, the intermediate layer 53 and the conductive carbon layer are formed only on one side of the metal base layer 52. However, to manufacture a conductive member in which the above layers are formed on both sides of the metal base layer 52. May be applied to the other surface of the metal base layer 52 in the same manner as described above.

The conductive member of the present invention as described above is excellent in hydrophilicity because the intermediate layer is partially exposed on the outermost surface of the conductive carbon layer. Here, the degree of hydrophilicity of the conductive member when expressed as a contact angle (an index indicating hydrophilicity) is preferably about 20 to 60 °, and more preferably 20 to 50 °. If it is such a range, hydrophilicity sufficient to drain the excess water | moisture content near the separator produced | generated with the electrode can be exhibited. In the conductive member of the present invention, the conductive carbon layer is disposed on the outermost surface. Since an electroconductive carbon layer can exhibit the outstanding electroconductivity, when using the electrically conductive member of this invention for a separator, contact resistance with another member (for example, MEA) can be reduced. Here, the contact resistance of the conductive member of the present invention is preferably about 2 to 15 (mΩ · cm ² ), and more preferably ^{2 to} 8 (mΩ · cm ² ). In the present specification, “contact angle” and “contact resistance” are values measured according to the methods described in the following examples.

  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.

  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.

  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.

  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. 8 is a conceptual diagram of a vehicle equipped with the fuel cell stack of the above-described embodiment. As shown in FIG. 8, 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.

[Example 1]
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.

  Subsequently, by applying an unbalanced magnetron sputtering (UBMS) method and applying a negative bias voltage of 50 V to the aluminum plate with Cr as a target, both surfaces of the aluminum plate have a thickness of 200 nm. An intermediate layer consisting of

  Further, by applying a negative bias voltage of 140 V to the aluminum plate with UBMS method as a target, a thickness of 2 nm was applied on each of the intermediate layers on both sides of the aluminum plate for 0.5 minutes. A conductive carbon layer was formed to obtain a conductive member. Thus, the conductive member of this example was produced. In this example, since the application time was as short as 0.5 minutes, as shown in FIGS. 2A and 2B, the conductive carbon layer does not cover the entire surface of the intermediate layer, and the intermediate layer is formed on the outermost surface of the conductive carbon layer. It was in an exposed state.

[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.

  Subsequently, by applying an unbalanced magnetron sputtering (UBMS) method and applying a negative bias voltage of 50 V to the aluminum plate with Cr as a target, both surfaces of the aluminum plate have a thickness of 200 nm. An intermediate layer consisting of

  Furthermore, by applying a negative bias voltage of 140 V to the aluminum plate by using UBMS method and applying a negative bias voltage of 140 V to the aluminum plate, the conductive material having a thickness of 20 nm on the intermediate layer on both sides of the aluminum plate for 5 minutes. A carbon layer was formed to obtain a conductive member. Here, the conductive carbon layer almost entirely covered the intermediate layer.

  Next, while applying a negative bias voltage of 50 V, ion bombardment with Ar gas was performed. By this ion bombardment, a part of the outermost conductive carbon layer was removed, and the intermediate layer was exposed on the surface layer.

[Comparative Example 1]
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.

  Subsequently, by applying an unbalanced magnetron sputtering (UBMS) method and applying a negative bias voltage of 50 V to the aluminum plate with Cr as a target, both surfaces of the aluminum plate have a thickness of 200 nm. An intermediate layer consisting of

  Furthermore, by applying a negative bias voltage of 140V to the aluminum plate by using UBMS method and applying a negative bias voltage of 140V to the aluminum plate, the thickness is 20 nm on each of the intermediate layers on both sides of the aluminum plate. A conductive carbon layer was formed to obtain a conductive member. Here, the conductive carbon layer substantially covered the entire intermediate layer (the coverage of the intermediate layer by the conductive carbon layer was 100%).

[Comparative 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.

  Subsequently, by applying an unbalanced magnetron sputtering (UBMS) method and applying a negative bias voltage of 50 V to the aluminum plate with Cr as a target, both surfaces of the aluminum plate have a thickness of 200 nm. An intermediate layer made of was formed to obtain a conductive member.

  With respect to the conductive members produced in each of the above examples and comparative examples, the contact resistance and contact angle in the stacking direction of the conductive members were measured. The contact resistance and contact angle were measured according to the following method. The results are shown in Table 1 below and FIG.

[Measurement of contact resistance]
With respect to the conductive members produced in each of the above Examples and Comparative Examples, the contact resistance in the stacking direction of the conductive members was measured. Specifically, as shown in FIG. 9, the produced conductive member 100 is sandwiched between a pair of gas diffusion base materials 200, and the obtained laminate is further sandwiched between a pair of catalyst layers 300, at both ends thereof. A power supply was connected and held at a load of 1 MPa to constitute a measuring device. A constant current of 1 A was passed through this measuring apparatus, and the contact resistance value (mΩ / cm ² ) of the laminate was calculated from the voltage value at that time.

[Measurement of contact angle]
As shown in FIG. 11, water droplets were deposited on the conductive carbon layer, and after 90 seconds, the shape of the water droplets was image-analyzed, and the contact length (r) and height (h) of the water droplets were measured. The contact angle θ is calculated according to the formula. In addition, hydrophilicity is so high that the value of a contact angle is small.

  From Table 1 and FIG. 10, it can be seen that the conductive member of the present invention has a low contact resistance (excellent conductivity) and a small contact angle (excellent hydrophilicity). On the other hand, the conductive member of Comparative Example 1 has a low contact resistance because the conductive carbon layer is present on the entire outermost layer, but is inferior in hydrophilicity because of a high contact angle. Moreover, since the conductive member of Comparative Example 2 is an intermediate layer only and does not have a conductive carbon layer, it is excellent in hydrophilicity but has high contact resistance and poor conductivity.

[Example 3]
In Example 1, a conductive member was produced in the same manner as in Example 1 except that the thickness of the intermediate layer was 25 nm, 50 nm, 100 nm, and 200 nm.

  The obtained conductive member was subjected to a corrosion resistance test according to the following method. The results are shown in FIG. From FIG. 12, it can be seen that the contact resistance decreases as the number of intermediate layers increases, and that the contact resistance before and after immersion has a substantially constant low value when the thickness of the intermediate layer is 30 nm or more. From this, if the film thickness of the intermediate layer is 30 nm or more, the intermediate layer is sufficiently corrosive to the metal base material layer and sufficiently serves as a corrosion prevention layer that suppresses the formation of an oxide film at the interface between the base material and the intermediate layer. It is considered that it can be accomplished.

[Corrosion resistance test]
For the conductive member, the contact resistance in the stacking direction of the conductive member was measured. Specifically, as shown in FIG. 9, the produced conductive member is sandwiched between a pair of gas diffusion base materials, the obtained laminate is further sandwiched between a pair of catalyst layers, and a power source is connected to both ends thereof. And it hold | maintained with the load of 1 MPa, and comprised the measuring apparatus. A constant current of 1 A was passed through this measuring device, and the contact resistance value of the laminate was calculated from the voltage value at that time.

  Moreover, after measuring a contact resistance value above, the immersion test with respect to acidic water was done, and the contact resistance value was measured similarly. In addition, as an immersion test, specifically, each conductive member was cut into a size of 30 mm × 30 mm and immersed in acidic water (pH 4 or less) at a temperature of 80 ° C. for 100 hours.

[Example 4]
A stainless steel (SUS316L) plate (thickness: 0.1 mm) was prepared as a constituent material of the metal base layer constituting the conductive member. This stainless steel plate was ultrasonically cleaned in an aqueous ethanol solution for 3 minutes as a pretreatment. Next, the cleaned stainless steel 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 stainless steel plate.

  Subsequently, by applying an unbalanced magnetron sputtering (UBMS) method and applying a negative bias voltage of 50 V to the stainless steel plate with Cr as a target, both surfaces of the stainless steel plate have a thickness of 200 nm. An intermediate layer consisting of

  Furthermore, by applying a negative bias voltage of 140 V to the stainless steel plate by using the UBMS method and applying a negative bias voltage of 140 V to the stainless steel plate, the conductive material having a thickness of 20 nm on the intermediate layer on both surfaces of the stainless steel plate for 5 minutes. A carbon layer was formed to produce a laminate. Here, the conductive carbon layer almost entirely covered the intermediate layer.

  The laminate thus produced was pressed at room temperature to obtain a conductive member. The surface of the conductive member thus obtained was observed with an SEM, and the result is shown in FIG. As can be seen from FIG. 13, it is understood that a crack is generated on the surface of the conductive carbon layer by the press treatment, and the intermediate layer is exposed from the crack. When the SEM photograph was subjected to image processing and the coverage of the intermediate layer with the conductive carbon layer was calculated, it was about 70%. Moreover, from FIG. 13, in the conductive member of Example 4, the crack has arisen in parallel with the flow path (the convex part in FIG. 13). From this, when such a conductive member is applied to the separator, it is considered that excess water generated in the electrode can be efficiently discharged through the crack portion, and the crack works advantageously with respect to the discharge. Is done.

[Example 5]
A stainless steel (SUS316L) plate (thickness: 0.1 mm) was prepared as a constituent material of the metal base layer constituting the conductive member. This stainless steel plate was pressed at room temperature. This stainless steel plate was ultrasonically cleaned in an aqueous ethanol solution for 3 minutes as a pretreatment. Next, the cleaned stainless steel 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 stainless steel plate.

  Furthermore, by applying a negative bias voltage of 140 V to the stainless steel plate by using the UBMS method and applying a negative bias voltage of 140 V to the stainless steel plate, the conductive material having a thickness of 20 nm on the intermediate layer on both surfaces of the stainless steel plate for 5 minutes. A carbon layer was formed to produce a laminate. Here, the conductive carbon layer almost entirely covered the intermediate layer.

The conductive members obtained in Examples 4 and 5 were subjected to the corrosion resistance test described in Example 3 above, and the results are shown in Table 2 and FIG. Further, the conductive members obtained in Examples 4 and 5 are shown in Table 2 and FIG. , Measure the ion elution amount according to the following method,
[Measurement of ion elution amount]
The conductive member was immersed in an aqueous sulfuric acid solution (pH 4) of 70 mL 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 is analyzed by ICP-MS (Inductively-Coupled Plasma-Mass Spectrometry) -mass spectrometry).

  From Table 2 and FIG. 14, it can be seen that both of the conductive members obtained in Example 4 (press after coating) and Example 5 (coating after press) have low values of contact resistance and ion elution. I understand. In the conductive member of Example 4, as described above, cracks occurred in the carbon-based conductive layer from the SEM photograph of the surface, and a part of the intermediate layer was exposed, but the contact resistance after immersion in the corrosion resistance test and Regarding the ion elution amount, both values are low, and it is considered that high corrosion resistance is maintained.

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 image figure which looked at the part of the separator 5 from FIG. 1 from the MEA10 side. It is the photograph (magnification: 400,000 times) which observed the section of the conductive member (conductive member A) which has the conductive carbon 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 carbon 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 contact resistance about several electrically-conductive members which have a conductive carbon layer from which content of hydrogen atoms differs although R value is 1.3 or more. It is a conceptual diagram of the vehicle carrying the fuel cell stack of one Embodiment of this invention. It is a schematic diagram which shows the outline | summary of the measuring apparatus used in measuring the contact resistance in an Example. It is a graph which shows the result of having measured the contact resistance and the contact angle about the electrically-conductive member produced in the Example and the comparative example. It is a figure which shows the evaluation method of the contact angle of a conductive carbon layer. It is a graph which shows the relationship between the thickness of an intermediate | middle layer, and contact resistance about the electrically-conductive member produced in Example 3. FIG. It is the photograph which observed the part (left figure) which took the SEM photograph about the surface of the conductive member produced in Example 4, and the part concerned by SEM. It is a graph which shows the result of having measured the contact resistance before and after an immersion test about the electrically conductive member produced in Example 4, 5. FIG.

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 Middle layer,
54 conductive carbon layer,
60 Fuel cell vehicle,
61 Fuel cell stack.

Claims (14)

A metal substrate layer;
An intermediate layer formed on the metal substrate layer;
A conductive carbon layer comprising conductive carbon located on the intermediate layer;
A conductive member having
An intermediate layer exposed portion in a part of the conductive carbon layer;
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. A conductive member comprising at least one of the above.   The conductive member according to claim 1, wherein the coverage of the intermediate layer by the conductive carbon layer is 30% or more and less than 100%.   The conductive member according to claim 2, wherein the coverage of the intermediate layer by the conductive carbon layer is 50 to 90%.   The conductive member according to any one of claims 1 to 3, wherein a degree of hydrophilicity of the conductive member when expressed as a contact angle is 20 to 60 °. The conductive member according to claim 1, wherein the conductive member has a contact resistance of 2 to 15 (mΩ · cm ² ).   The thickness of the said intermediate | middle layer is a conductive member of any one of Claims 1-5 which is 30 nm or more. 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 of the conductive carbon layer is 1.3 or more. The conductive member according to any one of claims 1 to 6. The conductive member according to claim 7, wherein the conductive carbon layer has a structure of polycrystalline graphite. The constituent material of the said metal base material layer is 1 type, or 2 or more types selected from the group which consists of iron, titanium, copper, aluminum, and these alloys, The any one of Claims 1-8. Conductive member. Forming an intermediate layer on the metal substrate layer;
A conductive carbon layer is formed on the intermediate layer by sputtering or ion plating to form a laminate of a metal base layer, an intermediate layer and a conductive carbon layer,
Forming the laminate by pressing;
With the method for manufacturing a conductive member according to any one of claims 1-9. The metal substrate layer is formed by pressing,
Forming an intermediate layer on the metal substrate layer;
Forming a conductive carbon layer on the intermediate layer by sputtering or ion plating;
With the method for manufacturing a conductive member according to any one of claims 1-9. The manufacturing method according to claim 10 or 11 , wherein the conductive carbon layer is formed by a sputtering method, and a negative bias voltage is applied to the intermediate layer at the time of sputtering. Composed of claims 1-9 conductive member is produced by a method according to any one of the conductive member or claim 10-12 of any one of, the fuel cell separator. 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:
14. At least one of the anode separator or the cathode separator is the fuel cell separator according to claim 13 , 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.