JP2016143596A - Conductive member, manufacturing method thereof and fuel cell separator using the same, and polymer electrolyte fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive member having sufficient corrosion resistance.SOLUTION: A conductive member of the present invention includes: a metal base material; at least one intermediate layer formed on the metal base material; and a noble metal layer formed on the intermediate layer. The noble metal layer includes at least one noble metal selected from the group consisting of Au, Ru, Rh, Pd, Ir, Os and Pt. The intermediate layer includes M doped TiO(M represents at least one doping element selected from the group consisting of Nb, Ta, Mo, W, Fe, Ge, Sn, Bi, Al, Si, Zr, Co, Cr, Ni, V, Mn, P and B).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a conductive member, a method for producing the same, and a fuel cell separator and a polymer electrolyte fuel cell using the same. More specifically, the present invention relates to a technique for improving the corrosion resistance of a conductive member used for a fuel cell separator or the like.

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

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

  As separators for fuel cells that require electrical conductivity, replacement of conventional carbon separators and conductive resin separators with metal separators is progressing. This is because the size of the stack can be reduced because the metal separator has excellent strength and conductivity.

  In recent years, a separator in which a layer having corrosion resistance is laminated on a metal substrate has been developed in order to prevent a decrease in conductivity due to corrosion, which is a problem of a metal separator, and a decrease in output of a stack accompanying this.

  For example, Patent Document 1 proposes a fuel cell separator material in which a hardened layer made of titanium nitride or titanium carbide and a conductive film made of noble metal are sequentially laminated on a titanium base material. According to the document, by using such a material to constitute a fuel cell separator, it is possible to improve the strength of the separator while achieving both corrosion resistance and conductivity.

JP 2008-251296 A

  However, when the present inventors manufactured and operated a fuel cell using a separator made of the material described in Patent Document 1, the hardened layer made of titanium nitride or titanium carbide may corrode. It turned out to be.

  Accordingly, an object of the present invention is to provide a conductive member having sufficient corrosion resistance.

As a result of intensive studies by the present inventors, it has been found that the above problem can be solved by providing an intermediate layer containing TiO ₂ doped with a specific element between the metal substrate and the noble metal layer. The present invention has been completed.

That is, the conductive member of the present invention has a metal substrate, at least one intermediate layer formed on the metal substrate, and a noble metal layer formed on the intermediate layer. The noble metal layer includes at least one noble metal selected from the group consisting of Au, Ru, Rh, Pd, Ir, Os, and Pt. And the intermediate layer is made of M-doped TiO ₂ (M is Nb, Ta, Mo, W, Fe, Ge, Sn, Bi, Al, Si, Zr, Co, Cr, Ni, V, Mn, P and B) It represents at least one doping element selected from the group consisting of:

According to the present invention, an intermediate layer containing TiO ₂ doped with a specific doping element and a noble metal layer are sequentially laminated on a metal substrate, thereby suppressing corrosion under a condition where a potential is applied. Is done. Therefore, it is possible to provide a conductive member having sufficient corrosion resistance that can be applied to uses such as a separator of a fuel cell.

It is a section schematic diagram showing the basic composition of the conductive member concerning one embodiment of the present invention. 1 is a schematic cross-sectional view showing a basic configuration of a polymer electrolyte fuel cell according to an embodiment of the present invention. It is an external appearance photograph of the test piece before and after a corrosion test. It is a graph showing the relative current density value in a corrosion test (constant potential application). It is a schematic diagram which shows the outline | summary of the measuring apparatus used in measuring contact resistance.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may be different from the actual ratios.

  In the present specification, “metal substrate” is also simply referred to as “substrate”, and “fuel cell separator” is also simply referred to as “separator”.

<Conductive member>
According to an aspect of the present invention, there is provided a conductive member having a metal base, at least one intermediate layer formed on the metal base, and a noble metal layer formed on the intermediate layer. The noble metal layer includes at least one noble metal selected from the group consisting of Au, Ru, Rh, Pd, Ir, Os, and Pt. And the intermediate layer is made of M-doped TiO ₂ (M is Nb, Ta, Mo, W, Fe, Ge, Sn, Bi, Al, Si, Zr, Co, Cr, Ni, V, Mn, P and B) It represents at least one doping element selected from the group consisting of:

FIG. 1 is a sectional view showing a basic configuration of a conductive member according to an embodiment of the present invention. According to FIG. 1, the conductive member 20 has a configuration in which an intermediate layer 23 made of Nb-doped TiO ₂ and a noble metal layer 25 made of Au are sequentially laminated on both surfaces of a metal base material 21 made of stainless steel.

  In the embodiment shown in FIG. 1, an intermediate layer 23 and a noble metal layer 25 made of the same material are formed on both surfaces of the metal base material 21, but an intermediate made of different materials on one surface and the other surface. The layer 23 and the noble metal layer 25 may be formed, or the intermediate layer 23 and the noble metal layer 25 may be formed only on one surface, and the other surface may have another configuration.

  In FIG. 1, the metal base material 21 and the intermediate layer 23, and the intermediate layer 23 and the noble metal layer 25 are laminated so as to be in contact with each other. Another layer may be provided between the layer 25. However, from the viewpoint of reducing contact resistance, the intermediate layer 23 and the noble metal layer 25 are preferably laminated so as to be in contact with each other. Further, two or more intermediate layers 23 made of the same or different materials may be provided between the metal substrate 21 and the noble metal layer 25.

  Hereinafter, each structure of the electrically-conductive member of this form is demonstrated. In the following, description will be made assuming that the conductive member is applied as a separator material for a fuel cell. However, the use of the conductive member of the present embodiment is not limited to this, and various types of high corrosion resistance are required. Applicable for use.

[Metal base material]
The metal substrate 21 is a main layer of the conductive member, and contributes to ensuring conductivity and mechanical strength.

  The metal which comprises the metal base material 21 is not restrict | limited in particular, The metal etc. which were conventionally used as a constituent material of a metal separator can be used suitably. Examples of the constituent material of the metal substrate 21 include iron, titanium, aluminum, and alloys thereof. These materials can be preferably used from the viewpoint of mechanical strength, versatility, cost performance, or processability. Here, the iron alloy includes stainless steel. Especially, it is preferable that the metal base material 21 is comprised from stainless steel, aluminum, or aluminum alloy. In particular, when stainless steel is used as the metal substrate 21, the conductivity of the contact surface with the gas diffusion substrate, which is a constituent material of the gas diffusion layer (GDL), is sufficiently secured when the conductive member is applied to the separator. sell.

  Examples of the 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%. Further, 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. When a conductive member is applied to a separator, mechanical strength and formability are also required, so that in addition to the above alloy types, alloy tempering can be selected as appropriate. In addition, when the metal base material 21 is comprised from the simple substance of titanium or aluminum, the purity of the said titanium or aluminum becomes like this. Preferably it is 95 mass% or more, More preferably, it is 97 mass% or more, More preferably, it is 99 mass % Or more.

  The thickness of the metal substrate 21 is not particularly limited. From the viewpoints of ease of processing, mechanical strength, and improvement of the energy density of the battery when a conductive member is applied to the separator, it is preferably 50 to 500 μm, more preferably 80 to 300 μm, and still more preferably 80 ~ 200 μm. In particular, the thickness of the metal substrate 21 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 material 21 when aluminum is used as a constituent material is preferably 100 to 300 μm. In the case of the above-described range, it is possible to achieve a suitable thinness with excellent processability while having sufficient strength.

[Middle layer]
The intermediate layer 23 contributes mainly to securing corrosion resistance and conductivity in the conductive member.

In this embodiment, the intermediate layer 23 essentially contains M-doped TiO ₂ . In this specification, “M-doped TiO ₂ ” means TiO ₂ doped with the doping element M. Here, the doping element M is selected from the group consisting of Nb, Ta, Mo, W, Fe, Ge, Sn, Bi, Al, Si, Zr, Co, Cr, Ni, V, Mn, P, and B. At least one. Especially, it is preferable that it is at least 1 type which consists of Nb, Ta, Mo, and W. Since these elements have more valence electrons than Ti, excellent conductivity can be exhibited by doping these elements into TiO ₂ .

The upper limit of the content of the doping element M contained in the M-doped TiO ₂ is not particularly limited, but is preferably 30% by mass or less with respect to the total mass of the M-doped TiO ₂ and more preferably from the viewpoint of reducing costs. Is 10% by mass or less. In addition, it is preferable that a minimum shall be 2 mass% or more from a viewpoint of ensuring sufficient electroconductivity.

The intermediate layer 23 may contain other components other than the M-doped TiO ₂ , but from the viewpoint of exhibiting sufficient corrosion resistance and conductivity, the content of the M-doped TiO ₂ is based on the total mass of the intermediate layer 23. Preferably, it is 90 mass% or more, More preferably, it is 95 mass% or more, More preferably, it is 98 mass% or more, Especially preferably, it is 99 mass% or more, Most preferably, it is 100 mass%.

The composition of the intermediate layer 23 (especially the elemental composition of M-doped TiO ₂ ) should be confirmed by cutting out the intermediate layer 23 and dissolving it in sulfuric acid, followed by inductively coupled plasma mass spectrometry (IPC-MS). Can do.

The electrical resistivity of the intermediate layer 23 is required to be 5 × 10 ² Ω · cm or less, and preferably 1 × 10 ⁻¹ Ω · cm or less. On the other hand, the lower limit is not particularly limited, but is generally about 1 × 10 ⁻⁵ Ω · cm or more. Such an electrical resistivity can be easily achieved by converting the crystal structure of M-doped TiO ₂ into an anatase type by an annealing process in the manufacturing method described later.

  The thickness of the intermediate layer 23 is not particularly limited, but is preferably 100 to 1000 nm, more preferably 150 to 400 nm, and further preferably 150 to 300 nm. When the thickness is 100 nm or more, sufficient corrosion resistance can be ensured. On the other hand, the cost can be suppressed by setting the thickness to 1000 nm or less.

[Precious metal layer]
The noble metal layer 25 contains a noble metal and contributes mainly to securing conductivity in the conductive member. In particular, when the noble metal layer 25 is present in the outermost layer, it has a function of reducing the contact resistance of other members.

  The noble metal constituting the noble metal layer 25 includes at least one of Au, Ru, Rh, Pd, Ir, Os, and Pt. Especially, it is preferable that at least 1 sort (s) of noble metals selected from the group which consists of Au, Ir, and Pt is included from a viewpoint of being excellent in corrosion resistance.

  The thickness of the noble metal layer 25 is not particularly limited, but is preferably 10 to 100 nm, and more preferably 20 to 50 nm. When the thickness is 10 nm or more, sufficient conductivity can be ensured. On the other hand, the cost can be suppressed by setting the thickness to 100 nm or less.

  The conductive member of this embodiment can be used for various applications that require both conductivity and corrosion resistance. Applications of the conductive member include a fuel cell separator described later, other fuel cell components (current collector plate, bus bar, gas diffusion substrate, MEA), electronic component contacts, and the like. In another preferred embodiment, the conductive member of the present embodiment is used in a wet environment and an energized environment. When used in such an environment, the effect of the present invention of exhibiting a high level of corrosion resistance can be remarkably exhibited.

<Method for producing conductive member>
Although the manufacturing method of the electrically-conductive member of this form is not restrict | limited in particular, Although it can manufacture with reference to a well-known knowledge suitably, the following methods are mentioned as an example of a preferable manufacturing method. That is, the method for manufacturing a conductive member according to one embodiment of the present invention is formed on a metal base, an intermediate layer precursor containing M-doped TiO ₂ formed on the metal base, and an intermediate layer precursor surface. A step of annealing the laminate having the noble metal layer at 250 to 500 ° C. under vacuum. Here, the M-doped TiO ₂ constituting the intermediate layer and the noble metal constituting the noble metal layer are the same as described in the conductive member described above. In the following, first, a method for manufacturing a laminate having a metal substrate, an intermediate layer precursor, and a noble metal layer in order will be briefly described, and then a step of annealing the laminate will be described.

The laminate includes a metal substrate, an intermediate layer precursor containing M-doped TiO ₂ formed on the metal substrate, and a noble metal layer formed on the surface of the intermediate layer precursor. In the present specification, the “interlayer precursor” means a layer containing M-doped TiO ₂ and having a high electrical resistivity (1 × 10 ³ Ω · cm or more). The M-doped TiO ₂ film is formed using a known method such as sputtering, but immediately after the formation, it is amorphous and has poor conductivity. When such an amorphous M-doped TiO ₂ film is annealed under predetermined conditions, the M-doped TiO ₂ undergoes a phase transition to an anatase type crystal structure, thereby obtaining sufficient conductivity. That is, the M-doped TiO ₂ in the intermediate layer precursor is amorphous, and the M-doped TiO ₂ in the intermediate layer has an anatase crystal structure. The crystal structure of the intermediate layer precursor or the intermediate layer M-doped TiO ₂ contained in the intermediate layer can be confirmed by XRD.

The method for forming the intermediate layer precursor on the metal substrate is not particularly limited, and a known M-doped TiO ₂ film forming method can be appropriately employed. Examples of the M-doped TiO ₂ film forming method include sputtering, arc ion plating, chemical vapor deposition (CVD), and the like. Among these, it is preferable to form the intermediate layer precursor using a sputtering method from the viewpoint of denseness of the film and mixing of other elements. By using the sputtering method as the M-doped TiO ₂ film forming method, the film becomes dense and other elements are less likely to be mixed due to the treatment in vacuum.

  Next, a noble metal layer is formed on the surface of the intermediate layer precursor. The method for forming the noble metal layer is not particularly limited, and a known method can be appropriately employed. Examples of the method for forming the noble metal layer include sputtering, vacuum evaporation, arc ion plating, plating, and the like. Among these, it is preferable to form a noble metal layer using a vacuum evaporation method and sputtering from a viewpoint of the denseness of a film | membrane, and economical efficiency. When sputtering is used as the method for forming the noble metal layer, a dense noble metal film with few defects can be formed, and the film thickness can be controlled at the nm level.

  Next, the laminated body obtained by the above method is annealed at 250 to 500 ° C. under vacuum conditions. The apparatus used for the annealing treatment is not particularly limited, and a sheath heater, a lamp heater, or the like can be used.

The annealing process is performed under vacuum conditions. In this specification, “under vacuum” means that the degree of vacuum is 1 × 10 ⁻¹ Pa or more, preferably 1 × 10 ⁻³ Pa or more. When the annealing treatment is performed at a lower degree of vacuum than the above, oxygen (O) may enter the M-doped TiO ₂ and the conductivity may be reduced. On the other hand, the upper limit of the degree of vacuum is not particularly limited, but is generally 10 ⁻⁸ Pa or less.

The temperature of annealing treatment is 250-500 degreeC, Preferably it is the range of 300-450 degreeC. If the temperature is lower than 250 ° C., the crystallinity of M-doped TiO ₂ may be deteriorated. On the other hand, if the temperature exceeds 500 ° C., the crystal of M-doped TiO ₂ may be rutile, and the mechanical properties of the metal substrate may be adversely affected.

The annealing time is not particularly limited, but is preferably 0.5 to 60 minutes, and more preferably 1 to 30 minutes. When the time is 60 minutes or more, the processing time is long and the productivity is deteriorated. On the other hand, if the time is 0.5 minutes or less, the crystallinity of M-doped TiO ₂ is deteriorated. The annealing time can be appropriately adjusted depending on the annealing temperature. When a lamp heater is used as the annealing treatment apparatus, M-doped TiO ₂ of anatase crystals can be obtained in a relatively short time. However, when a sheath heater is used, a relatively long time is required to obtain an anatase crystal.

In the manufacturing method of the present embodiment, the annealing process is performed after the noble metal layer is laminated on the surface of the intermediate layer precursor as described above (that is, the M-doped TiO ₂ remains amorphous). It is said. Through this sequence, the intermediate layer and the noble metal layer are more adhesive than the intermediate layer precursor formed immediately after the intermediate layer precursor is formed, and the intermediate layer is formed on the surface. The contact resistance can be reduced.

<Fuel cell separator, polymer electrolyte fuel cell>
Since the above-mentioned conductive member has a characteristic that it is not easily corroded even under a condition where a potential is applied, it is suitably used as a separator for a fuel cell (especially for a polymer electrolyte fuel cell). . That is, according to another embodiment of the present invention, there is provided a fuel cell separator composed of the conductive member. According to still another embodiment of the present invention, there is provided a solid polymer fuel cell having a membrane electrode assembly and a pair of anode separator and cathode separator sandwiching the membrane electrode assembly. Here, the fuel cell separator is applied to at least one of the anode separator and the cathode separator. The membrane electrode assembly includes a polymer electrolyte membrane, a pair of anode catalyst layers and a cathode catalyst layer sandwiching the polymer electrolyte membrane, and a pair of anode gas diffusion layers and a cathode gas diffusion layer sandwiching them. Further, the fuel cell separator is formed in a concavo-convex shape, the convex portion comes into contact with the membrane electrode assembly, and the concave portion serves as a gas flow path for circulating fuel gas or oxidant gas. In the fuel cell separator and the polymer electrolyte fuel cell of this embodiment, by using the above-described conductive member as the separator material, corrosion is unlikely to occur due to the potential during operation, and the contact resistance can be kept low. Therefore, it is possible to exhibit excellent battery performance over a long period of time.

  FIG. 2 is a cross-sectional view schematically showing a basic configuration of a polymer electrolyte fuel cell (PEFC) 1 according to an 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 an electrolyte membrane-electrode assembly (MEA) 10 in a stacked state. To do.

  In PEFC1, the MEA 10 is further sandwiched between a pair of separators (anode separator 5a and cathode separator 5c). In FIG. 2, the separators (5a, 5c) are illustrated so as to be located at both ends of the illustrated MEA. 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) can be obtained by forming the concavo-convex shape as shown in FIG. The convex part seen from the MEA side of the separator (5a, 5c) is in contact with the MEA 10. Thereby, the electrical connection with MEA10 is ensured. Further, a recess (space between the separator and the MEA generated due to the concavo-convex shape of the separator) viewed from the MEA side of the separator (5a, 5c) is a gas for circulating gas during operation of the PEFC 1 It functions as the flow path 6. 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 1 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. 2, 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 or a partially concavo-convex shape as long as the functions of the gas flow path 6 and the refrigerant flow path 7 can be exhibited. There may be. Hereinafter, each member constituting the solid polymer fuel cell will be described.

[Electrolyte layer]
The electrolyte membrane is composed of a solid polymer electrolyte membrane 2. 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 between the strength during film formation, durability during use, and output characteristics during use can be appropriately controlled.

[Catalyst layer]
The catalyst layer 3 (the anode catalyst layer 3a and the cathode catalyst layer 3c) is a layer 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 3 includes a catalyst component, a conductive catalyst carrier that supports the catalyst component, and an electrolyte. Hereinafter, a composite in which a catalyst component is supported on a catalyst carrier is also referred to as an “electrode catalyst”.

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

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

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

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

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

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

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

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

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

[Gas diffusion layer (GDL)]
The gas diffusion layer 4 (gas diffusion layer 4a, cathode gas diffusion layer 4c) passes through the gas flow path 6 (fuel gas flow path 6a, oxidant gas flow path 6c) of the separator 5 (anode separator 5a, cathode separator 5c). The function of promoting the diffusion of the gas (fuel gas or oxidant gas) supplied to the catalyst layer 3 (the anode catalyst layer 3a and the cathode catalyst layer 3c) and the function of an electron conduction path are provided.

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

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

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

  The carbon particles contained in the carbon particle layer are not particularly limited, and conventionally known materials such as carbon black, graphite, and expanded graphite can be appropriately employed. Among them, carbon black such as oil furnace black, channel black, lamp black, thermal black, acetylene black and the like can be preferably used because of excellent electron conductivity and a large specific surface area. The average particle diameter of the carbon particles is preferably about 10 to 100 nm. Thereby, while being able to obtain the high drainage property by capillary force, the contact property with the catalyst layer 3 can be improved.

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

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

[Separator]
The separator 5 (anode separator 5a, cathode separator 5c) has a function of electrically connecting each cell in series when a plurality of single polymer electrolyte fuel cells are connected in series to form a fuel cell stack. Have The separator 5 also has a function as a partition that separates the fuel gas, the oxidant gas, and the coolant from each other. In order to secure these flow paths, it is preferable that each of the separators 5 is provided with a gas flow path 6 and a cooling flow path 7 as described above.

  The separator 5 of this embodiment is composed of the above-described conductive member. The thickness and size of the separator 5 and the shape and size of each flow path provided are not particularly limited, and can be appropriately determined in consideration of the desired output characteristics of the obtained fuel cell.

  The method for producing the solid polymer fuel cell of this embodiment is not particularly limited, and can be produced by appropriately referring to conventionally known knowledge in this technical field.

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

  In addition, since the separator for fuel cells of this embodiment has excellent corrosion resistance and conductivity, it can be applied to fuel cells other than the above-described polymer electrolyte fuel cells. Examples of other types of fuel cells include phosphoric acid fuel cells (PAFC), molten carbonate fuel cells (MCFC), solid electrolyte fuel cells (SOFC), and alkaline fuel cells (AFC). Among them, a polymer electrolyte fuel cell (PEFC) is preferable because it is small and can achieve high density and high output. The fuel cell is useful as a stationary power source in addition to a power source for a moving body such as a vehicle in which a mounting space is limited. Among them, it is particularly preferable to use as a power source for a mobile body such as an automobile that requires a high output voltage after a relatively long time of operation stop.

  The present invention is described in further detail by the following examples and comparative examples. However, the technical scope of the present invention is not limited to the following examples.

<Manufacture of conductive members>
[Example 1]
A thin plate (SUS316, thickness 100 μm) made of stainless steel was prepared as a metal substrate. The base material was placed in a vacuum chamber, Ar gas was introduced under vacuum conditions (10 ⁻³ Pa), Ar ions were generated, and the surface of the base material was beaten to remove the surface oxide film (ion bombardment). processing). Such a treatment was performed on both surfaces of the substrate.

Next, the degree of vacuum was adjusted to 0.3 to 1.0 Pa, and an intermediate layer precursor (thickness 400 nm) made of Nb-doped TiO ₂ was formed on both surfaces of the substrate by sputtering.

  Further, a noble metal layer (thickness: 50 nm) made of Au was formed on both surfaces of the intermediate layer precursor by sputtering.

And the vacuum degree in a chamber was adjusted to 10 ^<-3 > Pa, temperature was adjusted to 300 degreeC, and the annealing process was performed for 10 minutes. After the annealing treatment was completed, the inside of the chamber was returned to atmospheric pressure, and the conductive member was taken out.

The intermediate layer of the obtained conductive member were analyzed by ICP-MS, the content of Nb is based on the total weight of Nb-doped TiO _2, it was 4% by weight. Moreover, when the electrical resistivity of the intermediate layer was measured with a resistivity meter, it was 1 × 10 ⁻¹ Ω · cm.

  In addition, the measuring method of the electrical resistivity of an intermediate | middle layer was performed with the following method. That is, an intermediate layer was formed on an insulating glass substrate under the same film formation conditions as in this example, and the electrical resistivity was measured by a four-terminal method using a Mitsubishi Chemical Analytech Loresta GP MCP-T610 type resistivity meter.

[Comparative Example 1]
A thin plate (SUS316, thickness 100 μm) made of stainless steel was prepared as a metal substrate. The base material was placed in a vacuum chamber, Ar gas was introduced under vacuum conditions (10 ⁻³ Pa), Ar ions were generated, and the surface of the base material was beaten to remove the surface oxide film (ion bombardment). processing).

Next, the degree of vacuum is adjusted to 0.3 to 1.0 Pa by introducing Ar gas and N ₂ gas into the chamber, and a layer made of TiN (thickness 500 nm) is formed on the surface of the substrate by sputtering. A film was formed.

  Further, a noble metal layer (thickness 50 nm) made of Au was formed on the surface of the TiN layer by vapor deposition.

  Then, the inside of the chamber was returned to atmospheric pressure, and the conductive member was taken out.

<Corrosion test>
The conductive members produced in the above examples and comparative examples were cut into 3 cm × 3 cm squares, and the cut surfaces were masked using silicon rubber to obtain test pieces. Then, the test piece is immersed in a test solution (pH 3 dilute sulfuric acid aqueous solution, 80 ° C.), a constant potential exceeding 1.2 V is applied to the test piece, and the appearance of the test piece is observed over 18 hours. Current characteristics were measured. For the measurement, a potentiostat was used as an electrochemical measurement system.

  Further, for the conductive member produced in the comparative example, the same observation and measurement were performed when the constant potential applied to the test piece was 1.2V.

  The electromotive force of the chemical reaction of the fuel cell is generally about 1.2 V, and may exceed 1.2 V when starting at a temperature of 0 ° C. or lower such as in a cold district. Therefore, in order to apply the conductive member as a separator material for a fuel cell, it is considered necessary to have sufficient corrosion resistance even in a situation where such a potential is applied.

  The results are shown in FIGS. According to the appearance photograph of the test piece in FIG. 3, the surface of the conductive member of Comparative Example 1 was discolored and corrosion progressed, whereas the surface of the conductive member of Example 1 was slightly discolored. It was confirmed that almost no corrosion occurred.

  FIG. 4 shows a graph showing current characteristics at a constant potential. The vertical axis of the graph shows the relative current density value when the largest value among the observed current density values is 1, and the horizontal axis shows the elapsed time from the start of the corrosion test. Since current flows when ions are eluted from the conductive member due to corrosion, the larger the value, the more the corrosion has progressed. From the graph, in the conductive member of Comparative Example 1, current was observed throughout the test period, and it was confirmed that corrosion progressed continuously. On the other hand, the conductive member of Example 1 had a relative current density value of approximately 0 during the test period, and it was confirmed that there was almost no corrosion compared to Comparative Example 1. In Table 1 below, the relative current density values at the time points 0.5 hours, 9 hours, and 18 hours after the start of the humus test (the value in the case of applying over 1.2 V in Comparative Example 1 is 1). ).

<Contact resistance measurement>
For the conductive members before and after the corrosion test, the contact resistance in the stacking direction was measured by the following method. Specifically, as shown in FIG. 5, both sides of each conductive member (separator 5) are sandwiched between a pair of gas diffusion base materials (gas diffusion layers 4a and 4c), and both sides of the obtained laminate are further A measuring apparatus was configured by sandwiching between a pair of electrodes (catalyst layers 3a, 3c), connecting a power source to both ends thereof, and holding the entire laminate including the electrodes with a load of 1 MPa. The contact resistance value of the laminate was calculated from the energization amount and voltage value when a constant current of 1 A was passed through the measuring apparatus and a load of 1 MPa was applied. The results are shown in Table 2 below. Each numerical value in Table 2 is a relative value where the value after the corrosion test in the case of applying a voltage exceeding 1.2 V in Comparative Example 1 is 1.

  As shown in Table 2, the contact resistance value of Comparative Example 1 was smaller than that of Example 1 before the corrosion test, but Example 1 with less corrosion after the test was more than Comparative Example 1 with much corrosion. In addition, it was shown that the contact resistance value becomes small. In particular, when the applied potential in the corrosion test is higher than 1.2 V, it was confirmed that the contact resistance value after the test was extremely high because the corrosion progressed remarkably in Comparative Example 1.

1 Polymer electrolyte fuel cell (PEFC),
2 solid polymer electrolyte membrane,
3 catalyst layer,
3a anode catalyst layer,
3c cathode catalyst layer,
4a Anode gas diffusion layer,
4c cathode gas diffusion layer,
5 separator,
5a anode separator,
5c cathode separator,
6a Anode gas flow path,
6c cathode gas flow path,
7 Refrigerant flow path,
10 Membrane electrode assembly (MEA),
20 conductive member,
21 metal substrate,
23 middle layer,
25 Noble metal layer.

Claims (7)

A metal substrate;
At least one intermediate layer formed on the metal substrate;
A noble metal layer formed on the intermediate layer;
Have
The intermediate layer includes M-doped TiO ₂ , where M is Nb, Ta, Mo, W, Fe, Ge, Sn, Bi, Al, Si, Zr, Co, Cr, Ni, V, Mn, Represents at least one doping element selected from the group consisting of P and B;
The noble metal layer includes at least one noble metal selected from the group consisting of Au, Ru, Rh, Pd, Ir, Os, and Pt,
The electrically conductive member whose electrical resistivity of the said intermediate | middle layer is 5 * 10 < ² > ohm * cm or less.   The conductive member according to claim 1, wherein M represents at least one doping element selected from the group consisting of Nb, Ta, Mo, and W.   The conductive member according to claim 1, wherein the noble metal is at least one selected from the group consisting of Au, Ir, and Pt. The conductive member according to claim 1, wherein the content of M is 30% by mass or less with respect to the total mass of M-doped TiO ₂ . A metal substrate;
M-doped TiO ₂ (M is Nb, Ta, Mo, W, Fe, Ge, Sn, Bi, Al, Si, Zr, Co, Cr, Ni, V, Mn, formed on the metal substrate. An intermediate layer precursor comprising at least one doping element selected from the group consisting of P and B);
A noble metal layer comprising at least one noble metal selected from the group consisting of Au, Ru, Rh, Pd, Ir, Os and Pt formed on the surface of the intermediate layer precursor;
The manufacturing method of the electrically-conductive member including the process of annealing at 250-500 degreeC the laminated body which has this.   The separator for fuel cells comprised from the electrically-conductive member of any one of Claims 1-4, or the electrically-conductive member manufactured by the manufacturing method of Claim 5. A polymer electrolyte membrane, a pair of anode catalyst layer and cathode catalyst layer sandwiching the polymer electrolyte membrane, and a membrane electrode assembly including a pair of anode gas diffusion layer and cathode gas diffusion layer sandwiching them;
A polymer electrolyte fuel cell having a pair of anode separator and cathode separator sandwiching the membrane electrode assembly,
At least one of the anode separator or the cathode separator is a fuel cell separator according to claim 6,
At this time, the fuel cell separator is formed in a concavo-convex shape, the convex portion is in contact with the membrane electrode assembly, and the concave portion is a gas flow path for circulating fuel gas or oxidant gas. A polymer electrolyte fuel cell.