JP5287180B2 - Laminated structure, manufacturing method thereof, and fuel cell using the same - Google Patents

Description

  The present invention relates to a laminated structure, a method for producing the same, and a 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 of the single cells is also referred to as (1) a polymer electrolyte membrane (for example, a Nafion (registered trademark) membrane) and (2) a pair of (anode, cathode) catalyst layers (an “electrode catalyst layer”) sandwiching the membrane. ), And (3) a membrane electrode assembly (MEA) including a pair of (anode, cathode) gas diffusion layers (GDL) for dispersing the supply gas sandwiching them. 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.

  On the other hand, it is known that water generated during the power generation of the fuel cell (the above reaction formula (2)) may hinder the smooth flow of the fuel gas and greatly affect the cell characteristics. Therefore, in order to increase the output of the fuel cell, it is required to improve the water discharge performance in the flow path of the fuel gas.

As a technology for that purpose, for example, Patent Document 1 discloses a separator in which a carbon-based film containing a metal oxide in a composite form is formed on a base material. In this method, drainage is improved by hydrophilizing the separator surface with a metal oxide. Moreover, it is said that it is excellent in corrosion resistance by using a carbon-type film | membrane.
JP 2007-134107 A

  However, in the technique described in Patent Document 1, since the metal oxide contained in the carbon film exhibits insulating properties, the conductivity in the thickness direction of the separator is reduced, or the contact resistance with the gas diffusion layer is increased. Resulting in.

  Therefore, the present invention provides a separator for a fuel cell in which a metal base material layer and a conductive carbon layer are laminated, and a gas diffusion layer including a gas diffusion base material having a plurality of pores. An object of the present invention is to provide means for further improving the conductivity and drainage performance while ensuring corrosion resistance in a laminated structure laminated so as to face the diffusion layer.

  The present inventors have found that the above problem can be solved by imparting conductivity and hydrophilicity to the surface of the conductive carbon layer by dispersing hydrophilic conductive particles on the surface of the conductive carbon layer. The present invention has been completed.

  That is, the present invention provides a separator for a fuel cell in which a metal base material layer and a conductive carbon layer are laminated, and a gas diffusion layer including a gas diffusion base material having a plurality of pores. The present invention relates to a laminated structure that is laminated so as to face a gas diffusion layer. In the laminated structure of the present invention, hydrophilic conductive particles are dispersed in a contact region that is in contact with the gas diffusion layer on the surface of the conductive carbon layer. The distance between the active particles is not more than the distance between the holes of the gas diffusion base material.

  According to the present invention, the hydrophilic conductive particles are dispersed on the surface of the conductive carbon layer, thereby sufficiently ensuring the excellent electrical conductivity and corrosion resistance of the metal separator having the carbon layer, and more excellent drainage on the separator surface. A further improved laminated structure can be provided.

(Laminated structure)
In one embodiment of the present invention, a separator for a fuel cell in which a metal base material layer and a conductive carbon layer are laminated, and a gas diffusion layer including a gas diffusion base material having a plurality of pores are the conductive carbon layer. And a laminated structure in which the gas diffusion layers are laminated so as to face each other. In the laminated structure of the present invention, hydrophilic conductive particles are dispersed in a contact region that is in contact with the gas diffusion layer on the surface of the conductive carbon layer. The distance between the active particles is not more than the distance between the holes of the gas diffusion base material.

  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). That is, the separators (5a, 5c) are disposed adjacent to the gas diffusion layers (4a, 4c), and the adjacent separators (5a, 5c) and the gas diffusion layers (4a, 4c) are laminated structures (8a, 8c). Configure. 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 separators (5a, 5c) are in contact with the gas diffusion layers (4a, 4c) at the convex portions (contact region 9) viewed from the MEA side. 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.

  In addition, in embodiment shown in FIG. 1, the separator (5a, 5c) is shape | molded by the uneven | corrugated shape. However, the separator is not limited to such a concavo-convex shape, and may be any form such as a flat plate shape and a partially concavo-convex shape as long as the functions of the gas flow path and the refrigerant flow path can be exhibited. Also good.

  FIG. 2 is a cross-sectional view showing a schematic configuration of the laminated structure 8 in FIG. In the present embodiment, the laminated structure 8 includes the gas diffusion layer 4 and the separator 5. The separator 5 has a metal base layer 52 and a conductive carbon layer 54. Then, hydrophilic conductive particles 57 are dispersed in the contact region 9 on the surface of the conductive carbon layer 54 and in contact with the gas diffusion layer 4. An intermediate layer 56 is interposed between the metal base layer 52 and the conductive carbon layer 54. 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 laminated structure 8 of this embodiment is explained in detail.

(Separator)
[Metal base material layer]
The metal base layer 52 is a main layer of 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. Here, the iron alloy includes stainless steel. Especially, it is preferable that a metal base material layer is comprised from stainless steel, aluminum, or aluminum alloy from viewpoints, such as corrosion resistance, mechanical strength, versatility, cost performance, or workability. 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.

[Conductive carbon layer]
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 only the metal substrate layer 52 while ensuring the conductivity of the separator 5.

  The carbon material that can be used as the conductive carbon is not particularly limited as long as the contact resistance as a separator is not increased. For the crystallinity and crystalline composition of the carbon material, for example, the ratio of the G band peak intensity and the D band peak intensity (intensity ratio R value: ID / IG) calculated by Raman scattering spectroscopy can be used. .

When the carbon material is analyzed by Raman spectroscopy, peaks are usually generated around 1350 cm ⁻¹ and 1584 cm ⁻¹ . Highly crystalline graphite has a single peak near 1584 cm ⁻¹ , and this peak is usually referred to as the “G band”. On the other hand, a peak near 1350 cm ⁻¹ appears as the crystallinity decreases (crystal structure defects increase). This peak is usually referred to as the “D band” (note that the peak of diamond is strictly 1333 cm ⁻¹ and is distinct from the D band). The intensity ratio R (I _D / I _G ) between the D band peak intensity (I _D ) and the G band peak intensity (I _G ) is the graphite cluster size of the carbon material and the disorder of the graphite structure (crystal structure defect), It is used as an indicator such as sp2 bond ratio. That is, in the present invention, it can be used as an index of contact resistance of the conductive carbon layer 54 and can be used as a film quality parameter for controlling the conductivity of the conductive carbon layer 54.

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 )).

  Here, when the strength ratio (R value) of the conductive carbon layer is within a predetermined range, an increase in contact resistance can be remarkably suppressed. Therefore, the carbon material used as the conductive carbon is preferably selected so that the conductive carbon layer has a strength ratio within the predetermined range. Specifically, the predetermined range relating to the strength ratio (R value) of the conductive carbon layer is not limited to the following, but is preferably 1.3 or more, more preferably 1.4-2. 0.0, 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, an increase in internal stress of the conductive carbon layer itself can also be suppressed, and adhesion with a metal base layer (an intermediate layer in the case where an intermediate layer described later) exists can be further improved.

  In addition, the mechanism by which the above-mentioned effect is acquired by making R value 1.3 or more 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, the photograph (magnification: 400,000 times) which observed the cross section of the separator A which has the conductive carbon layer of R = 1.0-1.2 with the transmission electron microscope (TEM) is shown to FIG. 3A. Similarly, the photograph (magnification: 400,000 times) which observed the cross section of the separator B which has the electroconductive carbon layer of R = 1.6 by TEM is shown to FIG. 3B. These separator A and separator 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: 0.2 μm) on this surface. Were prepared by sequentially forming the layers by sputtering. Also, the bias voltage applied to the metal substrate layer during the production of the conductive carbon layer in the separator A was 0 V, and the bias voltage applied to the metal substrate layer during the production of the conductive carbon layer in the separator B. The voltage was -140V.

  As shown in FIG. 3B, it can be seen that the conductive carbon layer of the separator 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 separator 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 of the conductive carbon layer 54 to the other surface can be ensured. As a result, it is considered that a decrease in conductivity due to the separate provision of the conductive carbon layer 54 in addition to the metal base layer 52 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 54 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 in such a range, it is possible to prevent the conductive carbon layer 54 from being thickened while maintaining the crystal structure of the polycrystalline graphite. Here, the “diameter” of the graphite cluster means the maximum distance among the distances between any two points on the contour line of the cluster. Moreover, the average diameter value of the graphite cluster is expressed as an average value of the diameter of the cluster observed in several to several tens of fields using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). Can be calculated.

  The conductive carbon layer 54 is preferably composed of polycrystalline graphite having the above-mentioned predetermined R value. However, the conductive carbon layer 54 may be other than polycrystalline graphite instead of or in addition to polycrystalline graphite. The conductive carbon may be included. Examples of such conductive carbon other than polycrystalline graphite include graphite block (highly crystalline graphite), carbon black, fullerene, carbon nanotube, carbon nanofiber, carbon nanohorn, and carbon fibril. 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. These conductive carbons may be used alone or in combination of two or more. Further, conductive carbon may be used in combination with a resin such as a polyester resin, an aramid resin, or a polypropylene resin.

  The average particle diameter when the conductive carbon material is particulate is not limited to the following, but is preferably 2 to 100 nm, more preferably 5 to 20 nm, from the viewpoint of suppressing the thickness of the conductive carbon layer. is there. In the present specification, the “particle diameter” means the maximum distance among the distances between any two points on the particle outline. In addition, as the value of “average particle diameter”, particles 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) unless otherwise specified. A value calculated as the average value of the particle diameters of the particles is adopted. The particle diameter and average particle diameter of conductive particles described later can be defined similarly.

  The diameter when the conductive carbon material is in the form of a fiber such as a carbon nanotube is not limited to the following, but is preferably 0.4 to 100 nm, more preferably 1 to 20 nm. On the other hand, although the length in the case of the said fibrous form is not specifically limited, 5-200 nm, More preferably, it is 10-100 nm. And although the aspect ratio in the case of the said fibrous form is not restrict | limited to the following, it is 1-500, More preferably, it is 2-100. When it exists in the above-mentioned range, the thickness of a conductive carbon layer can be restrained suitably.

  Examples of materials other than the carbon material that can be included in the conductive carbon layer 54 include gold (Au), silver (Ag), platinum (Pt), ruthenium (Ru), palladium (Pd), rhodium (Rh), indium (In ); Water-repellent substances such as polytetrafluoroethylene (PTFE); and conductive oxides. Only 1 type may be used for these 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. Moreover, the advantageous effect that a high corrosion-resistant function can be given with respect to a metal base material layer can be show | played. In the present embodiment, the conductive carbon layer 54 exists only on one main surface of the separator 5. However, in some cases, the conductive carbon layer 54 may also exist on the other main surface of the 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. Therefore, the average peak measured by rotational anisotropy measurement shows a two-fold symmetry pattern. This means that the surface direction of the graphene surface constituting the conductive carbon layer 54 is substantially the same as the stacking direction of the conductive carbon layer 54. Means you are doing it. According to such a form, the conductivity in the conductive carbon layer 54 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 separator B is used as a measurement sample and the rotation angles of the sample are 0 °, 60 °, and 180 °, respectively. Moreover, FIG. 5B shows the average peak of the rotational anisotropy measurement about the separator B obtained by the method mentioned above. As shown in FIG. 5B, in the measurement of rotational anisotropy of separator 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 symmetry pattern” means that the average peak is an average as shown in FIGS. 4B and 5B. This means that there are two peaks that are 180 ° opposite each other with respect to a point where the peak intensity is 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 separator that can withstand impacts such as external contact and friction, and has excellent adhesion to the metal base layer 52 that is the base. 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 was prepared as a metal base layer of the separator, and an intermediate layer (thickness: 0.2 μm) made of Cr and a conductive carbon layer (thickness: 0.2 μm) were sequentially formed on this surface by a sputtering method. It produced by doing. 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 separator 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 separator also falls in connection with the fall of the value of sp3 ratio.

  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 separator 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.

  Here, FIG. 7 is a graph showing the results of measurement of contact resistance for several separators having conductive carbon layers having different hydrogen atom contents although the R value is 1.3 or more. . As shown in FIG. 7, when the hydrogen atom content in the conductive carbon layer is 30 atomic% or less, the contact resistance value of the separator is significantly reduced. In the experiment shown in FIG. 7, SUS316L was used as the metal substrate layer of the separator, and an intermediate layer (thickness: 0.2 μm) made of Cr and a conductive carbon layer (thickness: 0.2 μm) were formed on this surface. Were prepared by sequentially forming the layers by sputtering. 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.

  In this embodiment, all of the metal substrate layer 52 is covered by the conductive carbon layer 54 (although through the intermediate layer 56). In other words, in the present embodiment, the ratio (coverage) of the area where the metal base layer 52 is covered with the conductive carbon layer 54 is 100%. However, it is not limited only to such a form, and the coverage may be less than 100%. The coverage of the metal base layer 52 by the conductive carbon layer 54 is preferably 50% or more, more preferably 80% or more, still more preferably 90% or more, and most preferably 100%. By adopting such a configuration, it is possible to effectively suppress a decrease in conductivity and corrosion resistance due to the formation of an oxide film on the exposed portion of the metal base layer 52 that is not covered with the conductive carbon layer 54. Note that when the intermediate layer 56 described later is interposed between the metal base layer 52 and the conductive carbon layer 54 as in this embodiment, the above-described coverage is determined when the separator 5 is viewed from the stacking direction. The ratio of the area of the metal base material layer 52 overlapping with the carbonaceous layer 54 is meant.

[Hydrophilic conductive particles]
The hydrophilic conductive particles 57 (hereinafter also simply referred to as “conductive particles”) are conductive particles having hydrophilicity, and are formed on the surface of the conductive carbon layer 54 and in the contact region 9 in contact with the gas diffusion layer 4. Is distributed. Due to the presence of the conductive particles 57, hydrophilicity is imparted to the conductive carbon layer 54, conductivity is further improved, and contact resistance with the gas diffusion layer substrate can be reduced. In addition to the contact region 9, the conductive particles may be present on the surface of the conductive carbon layer other than the contact region 9 or inside the conductive carbon layer. However, the conductive particles 57 are preferably present in the surface layer of the conductive carbon layer 54 in order to effectively exhibit the effect of reducing contact resistance and the effect of improving hydrophilicity and reduce the manufacturing cost. More specifically, it is preferable that uniform dispersion is performed in a plane with a minimum thickness. For this reason, the thickness and dispersibility largely depend on the manufacturing method and conditions. The average thickness of the conductive carbon layer that can be confirmed in the present invention is preferably 0.005 to 1 μm.

The conductive particle is not particularly limited as long as it is a material having conductivity and hydrophilicity. In this specification, the hydrophilic property means that the contact angle with water is less than the contact angle of the conductive carbon layer of 85 to 100 °, preferably 70 ° or less, more preferably 60 ° or less. Say. Specifically, it is preferable to include at least one selected from the group consisting of noble metals, alloys containing noble metals, conductive nitrides, and conductive oxides. The noble metal is selected from the group consisting of gold (Au), silver (Ag), platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), ruthenium (Ru), and osmium (Os). At least one is preferably mentioned. The alloy containing the noble metal is not particularly limited, and examples thereof include a gold-cobalt alloy (Au—Co), a gold-nickel alloy (Au—Ni), and a palladium-nickel alloy (Pd—Ni). Examples of the conductive nitride include CrN, TiN, ZrN, and HfN. As the conductive oxide, MBa ₂ Cu ₃ O _7-x (M is a rare earth element except Y or Ce, Pr, Tb), SnO ₂ , In ₂ O ₃ , CrO ₂ , Fe ₃ O ₄ , IrO _2. , OsO ₂ , PtO ₂ , ReO ₂ (β), ReO ₃ , RhO ₂ , RuO ₂ , WO ₂ , W ₁₈ O ₄₉ , V ₂ O ₃ , V ₇ O ₁₃ , V ₈ O ₁₅ , V ₆ O ₁₃ Preferably, at least one selected from the group consisting of: Among these, platinum (Pt), gold (Au), and silver (Ag) are preferable from the viewpoint of high conductivity, and silver (Ag) is more preferable from the viewpoint of cost. Gold (Au) is also preferably used in terms of cost in consideration of utilization including recycling. In addition, about the kind of these noble metals, the alloy containing noble metal, electroconductive nitride, and electroconductive oxide, you may use individually by 1 type, and may mix and use 2 or more types.

  In the present invention, the particle diameter of the conductive particles and the distance between the conductive particles are not more than the distance between pores of the gas diffusion base material. In such a case, a contact point between the conductive particles and the gas diffusion base material can be secured, and the contact resistance with the gas diffusion layer can be reduced. In the present specification, the “distance between conductive particles” means the distance between the centers of the two closest conductive particles. The “inter-hole distance” means the distance between the centers of the two closest holes. “Distance between conductive particles” is, for example, an average of particle diameters of particles observed in several to several tens of fields using observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). A value calculated as a value is adopted. Similarly, the “inter-hole distance” is observed in several to several tens of fields in the cross section of the gas diffusion substrate using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). It can be calculated as an average value of the distance between holes.

  Specifically, when the gas diffusion base material is composed of fibers (fiber assembly), the distance between the holes corresponds to the fiber diameter. For example, as shown in FIG. 8A, when the gas diffusion base material is composed of carbon fibers 58, the particle diameter of the conductive particles 57 and the distance between the conductive particles 57 are equal to or smaller than the diameter of the carbon fibers 58. Preferably there is. When the gas diffusion base material is composed of particles (particle aggregate), the distance between the holes corresponds to the diameter of the particles. For example, as shown in FIG. 8A, when the gas diffusion base material is composed of carbon particles 58, the particle diameter of the conductive particles 57 and the distance between the conductive particles 57 are not more than the diameter of the carbon particles 58. Preferably there is. Thus, when a gas diffusion base material is comprised from a fiber and particle | grains, the contact of an electroconductive particle and carbon fiber or a carbon particle can be ensured reliably. When the gas diffusion substrate is made of a porous metal such as a metal mesh or a punched press plate having a through hole, this corresponds to the shortest distance between the centers of the holes. For example, as shown in FIG. 8B, when the gas diffusion base material is composed of a porous metal 60 having through-holes 61, the particle diameter of the conductive particles 57 and the distance between the conductive particles 57 are the porous It is preferable that it is below the distance between holes of the conductive metal 60. In such a case, since the fine particles exist at intervals smaller than the width of the base metal in the distance between the holes in the porous metal, a large number of contacts can be secured. As an example, the particle diameter of the conductive particles and the distance between the conductive particles are 1 nm to 7 μm.

  The coverage of the contact area with the conductive particles is preferably 1% or more. If it is 1% or more, the effect of improving hydrophilicity and conductivity by the conductive particles can be obtained. More preferably, it is 2-100%, More preferably, it is 3-100%, Most preferably, it is 10-100%. If it is more than this lower limit, hydrophilicity and electroconductivity will improve notably. On the other hand, the upper limit is preferably as large as possible from the viewpoint of improving hydrophilicity and conductivity, and is preferably 100% (complete coverage). However, in consideration of cost, as long as hydrophilicity and conductivity are ensured. A smaller coverage is preferred.

Here, the contact resistance between the two elements is calculated from the sum of the volume resistivity (ρ ₁ , ρ ₂ ) of the two members constituting the contact and the reciprocal of the contact radius (1 / a _n ).

(Wherein, R: contact resistance _{[Ω], ρ 1, ρ} 2: volume resistivity _{[Ω · cm], a n} : radius of the contact [cm], n: number of contact points)
ρ ₁ and ρ ₂ are values specific to the material. For example, when gold (Au) is used as the conductive particles and carbon fiber is used as the gas diffusion base material, ρ ₁ and ρ ₂ are each gold (Au). And the volume resistivity of the carbon fiber. Therefore, it can be seen that the contact resistance depends on the number of contacts and the radius of the contacts.

  As the coverage of the conductive particles increases, the number of conductive particles dispersed on the surface of the conductive carbon layer increases, so the number of contacts with the gas diffusion substrate can be increased, thereby reducing the contact resistance. can do.

  The present inventors have found that when the coverage of the conductive particles is not less than the above lower limit, the contact with the gas diffusion substrate can be significantly increased and the contact resistance can be reduced. It was. In the present invention, when conductive particles such as the noble metals exemplified above, alloys containing noble metals, conductive nitrides, and conductive oxides are used, the coverage by the conductive particles is not less than the above lower limit value. If so, it was found that the contact resistance was reduced. However, the contact point between the gas diffusion substrate and the conductive particles depends on the material and size of the conductive particles and the gas diffusion substrate, and the surface roughness and material of the contact region of the conductive carbon layer. For example, when the surface roughness of the contact area of the contact area is small, the contact between the conductive particles dispersed in the contact area and the gas diffusion base material can be increased, and thus the contact resistance can be reduced. . On the other hand, it is generally known that the hydrophilic surface has a higher hydrophilicity as the surface roughness is larger. On the hydrophilic surface with a high coverage, the larger the surface roughness, the more hydrophilic effect. Can be demonstrated. For this reason, it is preferable to appropriately adjust the coverage of the conductive particles according to the conductive particles, gas diffusion base material, and conductive carbon layer (contact region) to be used.

  Moreover, the contact angle of water in the contact region in which the conductive particles are dispersed is preferably 70 ° or less, more preferably 0 to 60 °, and further preferably 45 to 50 °. In such a case, since the drainage performance of the separator surface serving as a water flow path is further improved, the narrow flow path in the separator having a small rib pitch (having a fine uneven shape) in particular, which is a problem of water discharge performance. Even so, it can be drained efficiently. In the present invention, the contact angle is measured based on the wettability test method described in JIS K6768.

  In addition, the electroconductive particle should just exist on the surface of the electroconductive carbon layer formed in at least one of the metal base material layer. However, when conductive carbon layers are present on both main surfaces of the metal substrate layer, conductive particles may be dispersed on the surfaces of both conductive carbon layers. When exhibiting, it is preferable that electroconductive particle exists in the surface of the electroconductive carbon layer which will be arrange | positioned at the MEA side (reaction surface side) in PEFC.

[Middle layer]
As shown in FIG. 2, in the present embodiment, the separator 5 has an intermediate layer 56. The intermediate layer 56 has a function of improving the adhesion between the metal base layer 52 and the conductive carbon layer 54 and a function of preventing elution of ions from the metal base layer 52. In particular, when the R value exceeds the upper limit value of the preferable range described above, the effect of providing the intermediate layer 56 is remarkably exhibited. However, it is a matter of course that an intermediate layer can be provided even when the R value is included in the preferred range described above. From another point of view, the above-described operation and effect due to the installation of the intermediate layer 56 are also significantly manifested when the metal base layer 52 is made of aluminum or an alloy thereof. In the present invention, the intermediate layer is an arbitrary layer, and the intermediate layer does not necessarily exist. Hereinafter, a preferable form in the case where the separator includes an intermediate layer will be briefly described.

  The material constituting the intermediate layer 56 is not particularly limited as long as it provides the above adhesion. For example, Group 4 metals (Ti, Zr, Nf) of the periodic table, Group 5 metals (V, Nb, Ta), Group 6 metals (Cr, Mo, W), and their carbides, Examples thereof include nitrides and carbonitrides. Among these, metals with low ion elution such as chromium (Cr), tungsten (W), titanium (Ti), molybdenum (Mo), niobium (Nb) or hafnium (Hf), or their nitrides, carbides or charcoal are preferable. Nitride is used. More preferably, Cr or Ti, or a carbide or nitride thereof is used. In particular, when the above-described metal with little ion elution or a carbide or nitride thereof is used, the corrosion resistance of the separator can be significantly improved.

  The thickness of the intermediate layer 56 is not particularly limited. However, from the viewpoint of making the size of the fuel cell stack as small as possible by making the separator 5 thinner, the thickness of the intermediate layer 56 is preferably 0.01 to 10 μm, more preferably 0.00. It is 05-5 micrometers, More preferably, it is 0.1-1 micrometers. If the thickness of the intermediate layer 56 is 0.01 μm or more, a uniform layer is formed, and the corrosion resistance of the metal base layer can be effectively improved. On the other hand, if the thickness of the intermediate layer 56 is 10 μm or less, an increase in the film stress of the intermediate layer can be suppressed, and a decrease in film followability to the metal substrate layer and the occurrence of peeling / cracking associated therewith can be prevented.

  In addition, the surface of the intermediate layer 56 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 56 to the intermediate layer 56 can be further improved.

Furthermore, when the thermal expansion coefficient of the intermediate layer 56 is a value close to the thermal expansion coefficient of the metal constituting the metal base layer 52, the adhesion between the intermediate layer 56 and the metal base layer 52 is improved. However, in such a form, the adhesion between the intermediate layer 56 and the conductive carbon layer 54 may decrease. Similarly, when the thermal expansion coefficient of the intermediate layer 56 is close to the thermal expansion coefficient of the conductive carbon layer 54, the adhesion between the intermediate layer 56 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.

[Gas diffusion layer]
The gas diffusion layers (anode gas diffusion layer 4a and cathode gas diffusion layer 4c) are composed of a gas diffusion base material having a plurality of pores, and are disposed adjacent to the separators (anode separator 5a and cathode separator 5c). The gas diffusion layer has a function of promoting diffusion of gas (fuel gas or oxidant gas) supplied through the gas flow paths (6a, 6c) of the separator to the catalyst layers (3a, 3c), and an electron conduction path. As a function.

  The gas diffusion substrate is not particularly limited as long as it is a material having a plurality of pores (porous material), and conventionally known knowledge can be appropriately referred to. Examples thereof include sheet-like materials having conductivity and porosity, such as carbon fabrics, paper-like paper bodies, felts, non-woven fabrics, and porous metals (such as wire mesh and press plates). Preferably, paper-like paper bodies made of carbon fibers, woven fabrics and non-woven fabrics, porous metals (such as wire mesh and press plates) are generally used.

  The thickness of the gas diffusion base material 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.

(Manufacturing method of laminated structure)
There is no restriction | limiting in particular about the method of manufacturing the laminated structure of embodiment mentioned above, It can manufacture by referring a conventionally well-known method suitably. Hereinafter, although preferable embodiment for manufacturing a laminated structure is described, the technical scope of this invention is not limited only to the following form. Moreover, since various conditions, such as the material of each component of the separator 5 which comprises the laminated structure 8, and the gas diffusion layer 4, are as above-mentioned, description is abbreviate | omitted here.

  One embodiment of the present invention includes a step of forming a conductive carbon layer on at least one main surface of a metal base layer, a step of dispersing hydrophilic conductive particles on the surface of the conductive carbon layer, and the conductive And a step of disposing the gas diffusion layer in contact with the region in which the conductive particles are dispersed, and a method for producing a laminated structure, wherein the conductive particles are dispersed by a sputtering method. This is a method for manufacturing a laminated structure.

  First, a stainless 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. Examples of the method for removing the oxide film include a cleaning treatment with an acid, a dissolution treatment by applying a potential, or an ion bombardment treatment.

  Next, a conductive carbon layer is formed on the surface of the constituent material of the metal base layer subjected to the above treatment. For example, the conductive carbon layer is formed by stacking (forming) a layer containing conductive carbon on the metal base layer at the atomic level using the above-described constituent material of the conductive carbon layer (for example, graphite) as a target. Can be formed. Thereby, the adhesiveness of the interface between the conductive carbon layer and the metal base material layer directly attached thereto 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, and a dual magnetron 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 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 conductive carbon layer is formed by sputtering, a negative bias voltage may be applied to the metal substrate 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 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. Further, when the conductive carbon layer 54 is formed by the UBMS method, it is preferable to form an intermediate layer in advance and form the conductive carbon layer thereon. Thereby, the conductive carbon layer excellent in adhesiveness with the underlayer can be formed. However, when the conductive carbon layer is formed by another method, a conductive carbon layer having excellent adhesion to the metal substrate layer can be formed even when the intermediate layer is not present.

  According to the above-described method, a separator in which the conductive carbon layer 54 is formed on one main surface of the metal base layer 52 can be manufactured. In order to manufacture a separator in which the conductive carbon layer 54 is formed on both surfaces of the metal base layer 52, the other main surface of the metal base layer 52 is made conductive by the same method as described above. A carbon layer may be formed.

  Next, conductive particles are dispersed on the whole or a part of the surface of the conductive carbon layer subjected to the above treatment. As described above, the conductive particles only have to be dispersed in a region in contact with the gas diffusion layer on the surface of the conductive carbon layer. In order to disperse the conductive particles only on a part of the surface of the conductive carbon layer, for example, a mask may be formed and the conductive particles may be selectively dispersed in a desired portion. Methods for dispersing conductive particles include physical vapor deposition (PVD) methods such as plating, sputtering or ion plating, or ion beam deposition methods such as filtered cathodic vacuum arc (FCVA). Can be mentioned. 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. Of these, the sputtering method and the ion plating method are preferably used, and the sputtering method is particularly preferably used. Among these, it is preferable to use a sputtering method or a plating method.

  When the sputtering method is used, a dispersed structure of conductive particles having high adhesion can be obtained. Moreover, it is preferable because the conductive particles can be dispersed continuously by simply changing the target following the formation (sputtering) of the conductive carbon layer. The sputtering conditions are not particularly limited as long as the above-described conductive particle dispersion structure can be formed. However, a negative bias voltage may be applied to the metal base layer during sputtering. As an example, the magnitude of the applied voltage is preferably 50 to 500V, more preferably 100 to 300V. Note that specific forms such as other conditions are not particularly limited, and conventionally known knowledge can be appropriately referred to.

On the other hand, when the plating method is used, the conductive particles can be dispersed with a high coverage. In addition, since the process can be performed in a roll-to-roll system, mass production is possible. The plating conditions are not particularly limited as long as the above-described conductive particle dispersion structure can be formed. Known conditions are used, and vary depending on the type and amount of the conductive particles used. For example, the plating treatment conditions are a current density of 0.25 to 5 A / dm ² , a bath temperature of 45 to 55 ° C., and an electrodeposition time of about 10 seconds to about 100 minutes. However, since the deposition time varies depending on the size and shape of the counter electrode, it can be adjusted as appropriate. Under such conditions, a desired dispersed structure of conductive particles can be easily formed.

  Note that the coverage and particle size of the conductive particles can be set in a desired range by previously grasping the relationship between the sputtering conditions such as sputtering time or plating time and the amount of dispersion in advance and controlling them. it can. In addition, as described above, since the coverage varies depending on the material of the conductive carbon layer in which the conductive particles are dispersed and the method of dispersing the particles, it is necessary to grasp the relationship between the material of the conductive carbon layer and the coating form in advance. There is. For example, in the case of using a composite material in which conductive carbon and a resin are combined, if the conductive particles are dispersed using a plating method, the conductive particles are adsorbed on the surface of the carbon, but the resin surface is adsorbed. Does not adsorb. For this reason, when such a composite material is used, it is necessary to control the coverage rate in consideration of the amount of resin contained in the composite material.

  By conducting the above treatment on the surface of the conductive carbon layer 54 formed on one or both main surfaces of the metal substrate layer 52, the conductive carbon layer is formed on one or both main surfaces of the metal substrate layer 52. 54, and a separator in which hydrophilic conductive particles 57 are dispersed on the surface of the conductive carbon layer 54 can be manufactured.

  In order to manufacture the separator having the intermediate layer 56 shown in FIG. 2, the intermediate layer is formed on at least one main surface of the metal base layer before the conductive carbon layer forming step described above. A film forming step is performed. At this time, as the method for forming the intermediate layer, the same method as described above for the formation of the conductive carbon layer may be employed. However, it is necessary to change the target to the constituent material of the intermediate layer.

  Subsequently, the step of forming the conductive carbon layer and the step of dispersing the conductive particles may be performed on a main surface different from the main surface facing the conductive carbon layer of the intermediate layer formed by the above step. . As a method for forming the conductive carbon layer on the surface of the intermediate layer, the same method as described above for the formation of the conductive carbon layer on the surface of the metal base layer may be employed.

  And the laminated structure formed by laminating | stacking a separator and a gas diffusion layer is obtained by laminating | stacking a gas diffusion base material on the separator obtained by said method. At this time, the gas diffusion layer is laminated so that the gas diffusion layer is in contact with the region where the conductive particles are dispersed.

The laminated structure of this embodiment can be used for various applications. A typical example is a PEFC laminated structure 8 shown in FIG. However, the use of the laminated structure of the present embodiment is not limited to this. For example, in addition to PEFC, various fuel cells such as phosphoric acid fuel cell (PAFC), molten carbonate fuel cell (MCFC), solid electrolyte fuel cell (SOFC) or alkaline fuel cell (AFC) are configured. It can also be used as a laminated structure. In addition to the laminated structure, it can be used for various applications that require both conductivity and corrosion resistance. In another preferred embodiment, the laminated structure 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 drainage can be remarkably exhibited. The “wet environment” in which the laminated structure of the present embodiment is used refers to an environment where the relative humidity of the atmosphere in contact with the laminated structure is 30 RH or higher. The relative humidity is preferably 30% RH or more, more preferably 60% RH or more, and particularly preferably 100% RH or more. Further, the “energization environment” in which the laminated structure of the present embodiment is used refers to an environment in which current flows through the laminated structure at a current density of 0.001 A / cm ² or more. The current density is preferably 0.01 A / cm ² or more.

  Hereinafter, the components of the PEFC using the laminated structure of the present embodiment will be described with reference to FIG. However, the present invention is characterized by a laminated structure. Therefore, the specific form of the members other than the laminated structure 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 can 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.

  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 member. However, it is not limited only to such a form. For example, a concave and convex shape constituting a gas flow path and a refrigerant flow path is formed in advance by cutting a flat metal plate (metal base material layer), and conductive carbon 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.

  FIG. 9 is a conceptual diagram of a vehicle equipped with the fuel cell stack of the above-described embodiment. As shown in FIG. 9, in order to mount the fuel cell stack 101 on a vehicle such as the fuel cell vehicle 100, for example, the fuel cell stack 101 may be mounted under the seat at the center of the vehicle body of the fuel cell vehicle 100. If it is installed under the seat, the interior space and the trunk room can be widened. In some cases, the place where the fuel cell stack 101 is mounted is not limited to the position under the seat, but may be the lower part of the rear trunk room or the engine room in front of the vehicle. Thus, a vehicle equipped with the PEFC 1 and the fuel cell stack 101 of the above-described form is also included in the technical scope of the present invention. The PEFC 1 and the fuel cell stack 101 described above are excellent in output characteristics and durability. Therefore, a highly reliable fuel cell vehicle can be provided over a long period of time.

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

[Reference Example 1]
A stainless steel (SUS316L) plate (thickness: 100 μm) was prepared as a constituent material of the metal base layer constituting the separator. This stainless steel plate was subjected to ultrasonic cleaning in an ethanol solution for 3 minutes as a pretreatment. Next, the cleaned stainless steel plate was placed in a vacuum chamber (degree of vacuum: about 10 ⁻³ Pa), and ion bombarding with Ar gas (about 0.1 to 1 Pa) 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, each of the stainless steel plates has a thickness of 0.2 μm. An intermediate layer made of Cr was formed.

  Next, by applying a negative bias voltage of 100 V to the stainless steel plate with a solid graphite as a target by the UBMS method, a thickness of 0.2 μm is formed on each intermediate layer on both surfaces of the stainless steel plate. The conductive carbon layer (polycrystalline graphite layer) was formed.

  Furthermore, by applying a negative bias voltage of 100 V to the stainless steel plate with Au serving as a raw material of the conductive particles as a target by the UBMS method, on the conductive carbon layers on both surfaces of the stainless steel plate, Conductive particles were dispersed. This produced the separator (1).

[Reference Example 2]
A separator (2) was produced by the same method as in Reference Example 1 described above, except that the sputtering time of the conductive particles (Au) was changed.

[Reference Example 3]
A separator (3) was produced in the same manner as in Reference Example 1 described above, except that the sputtering time of the conductive particles (Au) was changed.

[Comparative Reference Example 1]
A separator (4) was produced by the same method as in Reference Example 1 described above, except that the conductive particles were not dispersed on the surface of the conductive carbon layer.

[Reference Example 4]
A separator (5) was produced in the same manner as in Example 1 except that a graphite block (highly crystalline graphite) was used as it was as the conductive carbon layer.

[Comparative Reference Example 2]
A separator (6) was produced by the same method as in Reference Example 4 described above, except that the conductive particles were not dispersed on the surface of the conductive carbon layer.

[SEM observation / coverage measurement]
With respect to the separators (1) to (6) prepared in each of the above Reference Examples and Comparative Reference Examples, the surface of the conductive carbon layer was photographed with a scanning electron microscope (SEM).

  Among these, FIGS. 10 and 11 show SEM photographs of the surface of the conductive carbon layer in which the conductive particles (Au) in the separators (1) and (2) are dispersed. 10 and 11 confirm that the conductive particles (Au) are uniformly dispersed on the surface of the conductive carbon layer. As for the separators other than the separator (4) in which the conductive particles and the metal oxide are not dispersed, the conductive particles (Au) are uniformly dispersed on the surface of the conductive carbon layer as in FIGS. I confirmed.

  Moreover, from the SEM photograph, the average particle diameter of the dispersed particles (conductive particles or metal oxide) existing on the surface of each separator and the average distance between the dispersed particles were calculated.

  Then, using EDX (energy dispersive X-ray analyzer), the in-plane distribution of elements present on the surface of the conductive carbon layer is investigated, and the area occupied by carbon is green and the area occupied by conductive particles (Au) is red. Binarization was performed, and the ratio of red by image processing was calculated, and this value was determined as the coverage (%).

  Table 1 shows the particle diameter and coverage of the conductive particles in each separator.

[Element concentration profile analysis by AES (Auger electron spectroscopy)]
For the separators (2) and (4) produced in Reference Example 2 and Comparative Reference Example 1, the element concentration profile in the stacking direction of the separator was measured by AES. 12A and 12B show the element distribution in the depth direction from the surface of the conductive carbon layer by Auger electron spectroscopy analysis (AES) in the separators (2) and (4). In the separator (4) of Comparative Reference Example 1, no conductive particles are present on the surface of the conductive carbon layer, but in the separator (2) of Reference Example 2, the conductive particles (Au) are present on the surface layer of the conductive carbon layer. It was confirmed that it existed. The conductive particles (Au) were present on the surface layer of the conductive carbon layer (C). The AES measurement was performed under the following conditions.

AES apparatus name: Field emission type Auger electron spectrometer PHI Model-680
The number of data points is 256 × 256 Electron beam acceleration voltage 10 kV
[Measurement of contact resistance]
For the separators produced in the above Reference Examples and Comparative Reference Examples, the contact resistance in the stacking direction of the separators was measured. Specifically, as shown in FIG. 13, the manufactured separator 200 is sandwiched between a pair of gas diffusion base materials 210, and the obtained laminate is further sandwiched between a pair of catalyst layers 220, and power supplies are connected to both ends thereof. Were connected and held at a load of 1 MPa to constitute a measuring apparatus. As the gas diffusion base material, carbon fiber (manufactured by Toray, average fiber diameter: 7 μm) was used. 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. The obtained results are shown in Table 1 below. Moreover, the graph corresponding to the result regarding the contact resistance shown in Table 1 is shown in FIG.

  As shown in Table 1 and FIG. 14, in the case of the separator produced in the reference example, the contact resistance is suppressed to a smaller value than in the comparative reference example, and the coverage is 1% or more. It can be seen that the contact resistance is significantly reduced. Furthermore, it was confirmed that the contact resistance can be suppressed to a very small value when the coverage is 10% or more.

  In addition, when polycrystalline graphite was used (Reference Examples 1 to 3), it was confirmed that the contact resistance can be significantly reduced at a low coverage compared to the case where a graphite block is used (Reference Example 4). The In the case of polycrystalline graphite, the surface roughness is smaller than that of the graphite block, so it is possible to secure many contacts with the gas diffusion base material, and this is thought to be due to the further resistance reduction effect. Is done.

[Measurement of contact angle]
For the separators (1) to (6) prepared in each of the above Reference Examples and Comparative Reference Examples, the contact angle of water on the surface of the conductive carbon layer in which conductive particles were dispersed was measured based on JIS K6768. The results obtained are shown in Table 1 below. Moreover, the graph corresponding to the result regarding the contact angle shown in Table 1 is shown in FIG.

  From this result, in the case of the separator having a coverage of 1% or more produced in each reference example, the contact angle of water on the surface of the conductive carbon layer is suppressed to 70 ° or less compared to the case of the comparative example. You can see that Furthermore, it was confirmed that when the coverage is 10% or more, the value of the contact angle is decreased and the hydrophilicity is extremely improved.

  Regarding the contact angle, when polycrystalline graphite was used (Reference Example 1), it was confirmed that the contact angle could be reduced to 70 ° or less with a low coverage of about 4%. Further, it was confirmed that the contact angle could be lowered to 70 ° or less with a low coverage of about 4% even when a graphite block was used (Reference Example 4).

[Measurement of R value]
About the separator produced in said each reference example and comparative reference example, 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. The results obtained are shown in Tables 1 and 2 below.

  As shown in Table 1, the R values of the conductive carbon layers in the separators produced in Reference Examples 1 to 3 and Comparative Reference Example 1 were all 1.3 or more. On the other hand, the R values of the conductive carbon layers in the separators produced in Reference Example 4 and Comparative Reference Example 2 were both less than 1.3. From Table 1, when the separator produced in Reference Example 1 having an R value of 1.3 or more was used, the R value produced under the same conditions except for the R value was less than 1.3. Compared to the case, it was confirmed that the contact resistance can be suppressed to a smaller value.

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. FIG. 2 is a cross-sectional view illustrating a schematic configuration of a portion of a laminated structure 8 in FIG. It is the photograph (magnification: 400,000 times) which observed the cross section of the separator (separator A) which has the electroconductive thin film layer of R = 1.0-1.2 with the transmission electron microscope (TEM). It is the photograph (magnification: 400,000 times) which observed the cross section of the separator (separator B) which has an electroconductive thin film layer of R = 1.6 by TEM. It is a schematic diagram which shows the 3 times symmetrical pattern of an average peak in the rotational anisotropy measurement of a Raman scattering spectroscopy analysis. It is a schematic diagram which shows the 2 times symmetrical pattern of an average peak in the rotational anisotropy measurement of a Raman scattering spectroscopy analysis. It is a schematic diagram which shows the pattern which does not show the symmetry of an average peak in the rotational anisotropy measurement of a Raman scattering spectroscopy analysis. It is a graph which shows a Raman spectrum when the separator B is used as a measurement sample and the rotation angles of the sample are 0 °, 60 ° and 180 °, respectively. 6 is a graph showing an average peak of rotational anisotropy measurement for separator B. In some separators in which the Vickers hardness of the conductive carbon layer is varied by changing the bias voltage and the film formation method by sputtering, the values of the Vickers hardness of the conductive carbon layer and the sp3 ratio in the conductive carbon layer It is a figure which shows the relationship. It is a graph which shows the result of having measured contact resistance about several separators which have an electroconductive thin film layer from which content of hydrogen atom differs although R value is 1.3 or more. It is a schematic cross section which shows the contact area | region of the conductive carbon layer in which the gas diffusion base material comprised from carbon fiber or carbon particle and the electroconductive particle were disperse | distributed. It is a schematic cross section which shows the contact region of the gas diffusion base material comprised from a porous metal, and the electroconductive carbon layer in which electroconductive particle was disperse | distributed. It is a conceptual diagram of the vehicle carrying the fuel cell stack of one Embodiment of this invention. It is drawing which shows the SEM photograph of the surface of the electroconductive carbon layer in which electroconductive particle (Au) in the separator (1) was disperse | distributed. It is drawing which shows the SEM photograph of the surface of the electroconductive carbon layer in which the electroconductive particle (Au) in the separator (2) was disperse | distributed. It is drawing which shows the element concentration profile of the lamination direction of the separator (2) measured by AES. It is drawing which shows the element concentration profile of the lamination direction of the separator (4) measured by AES. 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 contact resistance about the separator produced in the reference example and the comparative reference example. It is a graph which shows the result of having measured the contact angle about the separator produced in the reference example and the comparative reference example.

Explanation of symbols

1 Polymer electrolyte fuel cell (PEFC),
2 solid polymer electrolyte membrane,
3a anode catalyst layer,
3c cathode catalyst layer,
4 Gas diffusion layer,
4a Anode gas diffusion layer,
4c cathode gas diffusion layer,
5,200 separator,
5a anode separator,
5c cathode separator,
6a Anode gas flow path,
6c cathode gas flow path,
7 Refrigerant flow path,
8 Laminated structure,
8a Anode laminated structure,
8c cathode laminated structure,
9 contact area,
10 Membrane electrode assembly (MEA),
52 metal substrate layer,
54 conductive carbon layer,
56 middle class,
57 hydrophilic conductive particles,
58 carbon fibers or carbon particles,
59 holes,
60 porous metal,
61 through hole,
100 fuel cell vehicle,
101 fuel cell stack,
210 gas diffusion substrate,
220 catalyst layer.

Claims (13)

A separator for a fuel cell formed by laminating a metal base layer and a conductive carbon layer, and a gas diffusion layer including a gas diffusion base having a plurality of pores are opposed to the conductive carbon layer and the gas diffusion layer. In the laminated structure formed by laminating,
Hydrophilic conductive particles are dispersed in a contact region on the surface of the conductive carbon layer and in contact with the gas diffusion layer,
A laminated structure in which a particle diameter of the conductive particles and a distance between the conductive particles are equal to or less than a distance between pores of the gas diffusion base material. 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 laminated structure according to claim 1. The gas diffusion base material is composed of carbon fiber;
The laminated structure according to claim 1 or 2, wherein a particle diameter of the conductive particles and a distance between the conductive particles are equal to or less than a diameter of the carbon fiber. The gas diffusion base material is composed of a porous metal;
The laminated structure according to claim 1 or 2, wherein a particle diameter of the conductive particles and a distance between the conductive particles are equal to or less than a distance between pores of the porous metal.   The laminated structure according to any one of claims 1 to 4, wherein a coverage of the contact region with the conductive particles is 1% or more.   The laminated structure according to any one of claims 1 to 5, wherein a contact angle of water in the contact region is 70 ° or less.   The laminated structure according to any one of claims 1 to 6, wherein the conductive particles include at least one selected from the group consisting of a noble metal, an alloy including a noble metal, a conductive nitride, and a conductive oxide. body.   The laminated structure according to any one of claims 1 to 7, wherein an intermediate layer is interposed between the metal base material layer and the conductive carbon layer.   The laminated structure according to claim 1, wherein a particle diameter of the conductive particles and a distance between the conductive particles are 1 nm to 7 μm. Forming a conductive carbon layer on at least one main surface of the metal substrate layer;
Dispersing hydrophilic conductive particles on the surface of the conductive carbon layer;
Arranging a gas diffusion layer so as to come into contact with the region in which the conductive particles are dispersed;
A method for producing a laminated structure comprising:
A method for producing a laminated structure, wherein the conductive particles are dispersed by a sputtering method. Forming a conductive carbon layer on at least one main surface of the metal substrate layer;
Dispersing hydrophilic conductive particles on the surface of the conductive carbon layer;
Placing a gas diffusion layer on the surface of the conductive carbon layer;
A method for producing a laminated structure comprising:
A method for producing a laminated structure, wherein the conductive particles are dispersed by a plating method.   A polymer electrolyte fuel cell comprising the laminated structure according to any one of claims 1 to 9 or the laminated structure produced by the production method according to claim 10 or 11.   A vehicle equipped with the polymer electrolyte fuel cell according to claim 12.