JP2006172720A - Separator for fuel cell and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal separator for a fuel cell having both excellent corrosion resistance and conductivity, and to provide its manufacturing method. <P>SOLUTION: After an oxide coating layer formed on a base body surface layer by using a lightweight and inexpensive metal material as a base body is removed, an intermediate layer having conductivity is formed and a π-conjugate system conductive polymer film is formed on the upper layer on a surface thereof. The intermediate layer is at least one kind selected from a group comprising C, Ni, Co, Zr, Sn, Pt, Au, Ag, Pd, Ir, Ru, a Ni-based alloy, a Fe-based alloy, a Co-based alloy, a Zr-based alloy, a Sn-based alloy, a Pt-based alloy, a Au-based alloy, a Ag-based alloy, a Pd-based alloy, an Ir-based alloy, a Ru-based alloy, an Ru oxide, a Zn oxide, an Ir oxide and an Sn oxide. The π-conjugate system conductive polymer formed on the upper layer of the base body with the intermediate formed thereon is formed by an electrolytic polymerization method or the electrolytic polymerization method after chemical polymerization. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell separator, and more particularly to a fuel cell separator provided adjacent to an electrode of a polymer electrolyte fuel cell and a method for producing the same.

  A polymer electrolyte fuel cell is configured by sandwiching a proton conductive electrolyte membrane between two catalyst-supporting porous electrodes, and further stacking a plurality of cells made of separators disposed on both sides thereof. In the separator, a gas flow path for supplying water such as fuel gas such as hydrogen and oxidizer such as air or oxygen gas or discharging water generated by a chemical reaction is formed on both electrodes, and in contact with the electrodes. It has a current collecting function for deriving current.

  The performance required for the separator is a gas sealing property that completely separates the oxidant gas and the fuel gas of the adjacent cell, a current collecting property that suppresses a decrease in output due to a voltage drop, and a stress that accompanies swelling contraction of the proton conductive electrolyte membrane. Examples include mechanical properties for preventing breakage, and corrosion resistance in a low acid atmosphere at high temperatures. In addition, since one fuel cell stack is usually composed of several tens to several hundred cells, a similar number of separators are required, so that it is required to be inexpensive and excellent in productivity.

  The separator is generally made of a carbon material such as a resin-impregnated isotropic carbon or a carbon / resin composite material, or a metal material such as stainless steel. However, since resin-impregnated isotropic carbon has high electrical conductivity but is a hard and brittle material, machining such as cutting is required to form a gas flow path, and the processing cost is high. There is a problem that it is inferior in productivity. Carbon / resin composite materials can be manufactured by injection molding and compression molding methods that are inexpensive and highly productive. However, since they are composite materials of porous insulating resin and carbon particles, they have the disadvantage of low gas sealability. To solve this problem, increasing the thickness of the separator increases the internal resistance, which causes a voltage drop in the fuel cell.

  On the other hand, a separator made of a metal material has high mechanical strength, is excellent in ductility, has excellent gas sealability, and can easily form a gas flow path by press work with high productivity. Furthermore, it is possible to reduce the weight of the fuel cell by using a low specific gravity metal material such as aluminum, which is a promising material as a fuel cell separator. However, since the operating environment in the fuel cell is a high temperature of 80 ° C. to 120 ° C. and an acidic atmosphere with a pH of 2 to 3, the metal substrate is corroded and metal ions are eluted, and the proton conductive electrolyte There is a problem that the film deteriorates. Therefore, it is conceivable to use a metal material having excellent corrosion resistance such as stainless steel and titanium for the separator, but this corrosion resistance is derived from a passive film having electrical insulation formed on the surface of the metal substrate, As a compensation, there is a problem that the contact resistance between the separator and the electrode increases.

  Various methods have been proposed in order to maintain low contact resistance and volume resistance and improve the corrosion resistance of the metal separator. For example, in the fuel cell separator disclosed in Patent Document 1, an alumite film is formed on a gas flow path on an aluminum metal substrate, and a metal such as nickel is formed on the first layer by plating or the like, and the uppermost layer is formed. A method for achieving high corrosion resistance and low volume resistance by coating a metal such as gold has been proposed.

  In addition, in the fuel cell separator disclosed in Patent Document 2, the conductive polymer film is very minute by forming an oxide film on aluminum and forming the conductive polymer film by electrolytic polymerization. There has been proposed a method that prevents corrosion of a metal that causes deterioration of a proton conductive electrolyte membrane and has low contact resistance even if it has defects.

  However, when nickel plating and further gold plating are performed on the aluminum metal by the method of Patent Document 1, when a pinhole is formed, a local battery is formed by nickel and gold, and the dissolution of nickel proceeds and finally Corrosion of aluminum occurs. In order to prevent this, a method of increasing the thickness of the gold plating is also conceivable, but the cost is increased and it is not practical. In Patent Document 2, in which an electroconductive polymer film is formed by electropolymerization after an oxide film is formed on aluminum, electropolymerization proceeds by an anodic reaction, so that an oxide film formation of aluminum also proceeds simultaneously. However, the surface resistance of the aluminum substrate is increased and the contact resistance is increased.

JP 2001-351642 A JP 2004-139951 A

  The objective of this invention is providing the metal separator for fuel cells which has the outstanding corrosion resistance, and electroconductivity, and its manufacturing method.

The present invention is a fuel cell separator constituted by at least one item of (1) to (7), or a method for manufacturing the same.
(1) A fuel cell separator, wherein a conductive intermediate layer is formed on a surface of a substrate made of a metal material, and a π-conjugated conductive polymer is formed on the intermediate layer.

  (2) The substrate made of a metal material is at least one selected from the group consisting of Mg, Al, Ti, Fe, Mg-base alloy, Al-base alloy, Ti-base alloy, and Fe-base alloy (1 The separator for fuel cells described in the above.

  (3) The π-conjugated conductive polymer is at least one selected from the group consisting of polypyrrole and derivatives thereof, polythiophene and derivatives thereof, polyaniline and derivatives thereof, and (1) or (2) Fuel cell separator.

  (4) The intermediate layer having conductivity is C, Ni, Co, Zr, Sn, Cu, Pt, Au, Ag, Pd, Ir, Ru, Ni base alloy, Fe base alloy, Co base alloy, Zr base alloy, Sn base alloy, Cu base alloy, Pt base alloy, Au base alloy, Ag base alloy, Pd base alloy, Ir base alloy, Ru base alloy, Ru oxide, Zn oxide, Ir oxide, In oxide, Sn oxidation The high corrosion-resistant material for electric conduction according to (1) to (3), which is at least one selected from the group consisting of:

  (5) The fuel cell according to any one of (1) to (4), wherein an intermediate layer having conductivity is formed after the step of removing the oxide film layer on the surface of the substrate made of a metal material. Separator and manufacturing method thereof.

  (6) The fuel according to any one of (1) to (5), wherein the π-conjugated conductive polymer formed on the upper surface of the base material made of a metal material is formed by an electrolytic polymerization method. Battery separator and method for producing the same.

  (7) In any one of (1) to (5), the π-conjugated conductive polymer formed in the upper layer of the substrate surface made of a metal material is formed by chemical polymerization after chemical polymerization The separator for a fuel cell according to the description and the production method thereof.

  According to the present invention, by forming a conductive intermediate layer on the surface of a metal material and then forming a separator having a conductive polymer layer, corrosion of the metal substrate can be suppressed, and the metal separator excellent in durability. Can be provided. Further, by forming a conductive intermediate layer and forming a conductive polymer film on the conductive intermediate layer, oxidation erosion of the metal substrate is caused during the formation of the conductive polymer film or in the fuel cell operating environment. Thus, a separator having low interface resistance between the substrate and the coating film and low surface resistance and excellent contact resistance with the electrode can be obtained over a long period. In addition, since it can be coated on a metal material having good workability by an inexpensive and simple method, a fuel cell separator excellent in productivity and a method for producing the same can be provided.

  The present invention will be described with reference to the drawings. As shown in FIG. 1, a substrate 1 made of a plate-shaped metal material is prepared. As the metal material used for the substrate of the present invention, any metal such as Mg, Al, Ti, Fe having current collecting ability can be used, but Mg, Al, Ti which are low specific gravity metals are used from the viewpoint of light weight. It is preferable to use it. Further, an alloy or an intermetallic compound containing the metal at 50 atomic% or more may be used. For example, Mg alloys include Mg—Zn alloys, Mg—rare earth elements alloys, Mg—Al—Zn alloys, Mg—Zn—Zr alloys, and Al alloys include Al—Cu alloys, Al -Mn alloys, Al-Si alloys, Al-Mg alloys, Al-Mg-Si alloys, Al-Zn-Mg alloys, etc. Ti alloys include Ti-Ni alloys, Ti-Ni -Ru-based alloy, Ti-Pd-based alloy and the like are mentioned, and it is more preferable to use Al or Al alloy from the viewpoint of cost and lightness. The base body 1 is subjected to press working so as to form a groove-like gas flow path 1a.

  Next, the oxide film formed on the surface of the substrate 1 is removed. As a removal method, for example, a well-known method such as a wet etching method, an electrolytic etching method, an electrolytic polishing method, a mechanical polishing method, a reverse sputtering method, a blast method, or a displacement plating method can be used. Is preferred. This removal treatment has the effect of reducing the surface resistance of the substrate and improving the adhesion between the substrate to be coated and the substrate.

  Next, the conductive intermediate layer 2 is formed on the substrate surface. In the present invention, when the π-conjugated conductive polymer is formed, the conductive intermediate layer 2 is formed in order to suppress the formation of an oxide film on the metal substrate. As a metal substrate that can be used, any metal having current collecting ability can be used. However, in the present invention, it is effective when applied to Mg, Al, Ti, Fe, alloys having them as a main component, etc. having high reaction activity. Especially, it is effective for Mg, Al, Ti and alloys containing them as main components. That is, when direct electropolymerization is performed using a metal substrate such as Mg, Al, Ti, and Fe having high reaction activity as an electrode, a conductive polymer layer is formed on the substrate, and at the same time, an insulating oxide film or passive film is formed. Formation also occurs, and the interface resistance between the metal substrate and the conductive polymer layer increases. Even when the chemical polymerization method is used, the formation of an oxide film similarly occurs when the oxidant solution used for polymerization and the metal substrate come into contact with each other.

  Further, the conductive intermediate layer 2 suppresses the formation of an oxide film or a passive film on the surface of the substrate in a fuel cell operating environment at a high temperature of 80 ° C. to 120 ° C. and in an acidic atmosphere having a pH of 2 to 3. Has a working effect.

As this conductive intermediate layer, C, Ni, Co, Zr, Sn, Cu, Pt, Au, Ag, Pd, Ir, Ru, Ni-based alloy, Fe-based alloy, Co-based alloy, Zr-based alloy, Sn-based Alloy, Cu base alloy, Pt base alloy, Au base alloy, Ag base alloy, Pd base alloy, Ir base alloy, Ru base alloy, Ru oxide, Zn oxide, Ir oxide, In oxide, Sn oxide, etc. From the viewpoint of productivity, heat resistance, and acid resistance, C, Ni, Co, Au, Ag, Ir, Ru, Ni base alloy, Fe base alloy, Co base alloy, Au base alloy, Ag base alloy, Ir-based alloys and Ru-based alloys are preferably used, but C, Ni, Co, Au, Ag, Ni-based alloys, Fe-based alloys, Co-based alloys, Au-based alloys, and Ag-based alloys are more preferably used. Examples of Ni-based alloys include Ni-Mo alloys, Ni-W alloys, Ni-P alloys, Ni-Co alloys, Ni-Sn alloys, Ni-Co-B alloys, Ni-Fe-P alloys, and the like. Examples of the base alloy include Fe—Cr alloy, Fe—Mo alloy, Fe—W alloy, Fe—P alloy, Fe—Co alloy, Fe—Sn alloy, Fe—Co—B alloy, and Fe—Ni—P alloy. Examples of the Co-based alloy include a Co—Mo alloy, a Co—W alloy, a Co—P alloy, a Co—Ni alloy, a Co—Sn alloy, a Co—Ni—B alloy, and a Co—Fe—P alloy. Zr-based alloys include Zr-Ni alloys, Zr-Fe alloys, Zr-Co alloys, Zr-Cu alloys, etc., and Sn-based alloys include Sn-Ni alloys, Sn-Cu alloys, Cu-based alloys. As an alloy, Cu-Ni alloy, Cu-Fe alloy Cu-Zn alloy, Cu-Al alloy, and Pt-based alloy include Pt-Ir alloy, Pt-Pd alloy, Pt-Fe alloy, Pt-Pd-Ag alloy, Pt-Rh alloy, Pt-Au alloy, Pt- Examples of the Au base alloy include an Au—Ir alloy, an Au—Pd alloy, an Au—Sn alloy, an Au—Ag alloy, an Au—Ag—Cu alloy, and the like. Examples thereof include Ag-Pd alloy, Ag-Au alloy, Ag-Pd-Cu alloy, Ag-Mg alloy, Ag-Sn alloy, Ag-Ir alloy, etc. Examples of the Pd-based alloy include Pd-Au alloy, Pd-Ag. Alloy, Pd—Au—Ag alloy, Pd—Pt alloy, Pd—Cu alloy, Pd—Ir alloy and the like, and Ir-based alloys include Ir—W alloy, Ir—Ni—Al alloy, Ir—Mo alloy. Ir-Pt alloy, r-Rh alloy, Ir-Ta alloy, Ir-Ti alloy and the like. Examples of the Ru-based alloy include Ru-Ta alloy, Ru-Ti alloy, Ru-W alloy, Ru-W alloy, Ru-Rh alloy, Ru-Ir alloy, Ru-Pt alloy, Ru-Ag alloy, Ru-Au alloy, _IrO 2, in oxide as _RuO 2, Zn as oxide _{ZnO-Al 2} O 3, Ir oxide as Ru oxide Examples of the material include In ₂ O ₃ —SnO ₂ , and examples of the Sn oxide include SnO ₂ —Sb ₂ O ₃ and SnO ₂ —F.

  Conventionally known methods can be used as the method for forming the conductive intermediate layer 2 described above. For example, there are plating methods, electroless plating methods, physical vapor deposition methods, ion plating methods, vacuum deposition methods, thermal spraying methods, chemical vapor deposition methods, etc., but inexpensive and highly productive plating methods or electroless plating methods. The method is preferred.

  The thickness of the conductive intermediate layer 2 is preferably 0.01 μm to 20 μm, more preferably 0.01 μm to 10 μm in order to increase the corrosion resistance and reduce the volume resistance.

  As shown in FIG. 2, when the conductive intermediate layer 2 is formed using a liquid phase method typified by a plating method or the like, the gas flow path is molded by bending the substrate before the formation. By doing so, the conductive intermediate layer can be formed without damaging at the time of forming the flow path. Further, when the conductive intermediate layer 2 made of a ductile metal such as Au or a ductile metal alloy is formed, as shown in FIG. 3, it can be pressed after the formation of the conductive intermediate layer.

  Next, a π-conjugated conductive polymer film 3 is formed on the substrate 1 provided with the conductive intermediate layer 2. As the conductive polymer forming method of the present invention, an electrolytic polymerization method is preferable. Since the π-conjugated conductive polymer film obtained by the electrolytic polymerization method is dense and highly regular, it has high electrical conductivity. As a result, a film having excellent corrosion resistance and good contact resistance is formed on the upper layer of the substrate. As the electrolytic polymerization method, a π-conjugated conductive polymer film can be formed on the upper layer of the substrate by electrolysis using a conductive intermediate layer as an anode in a solution containing a conductive polymer monomer and a supporting electrolyte. it can.

  However, since this electrolytic polymerization method is a method of forming a π-conjugated conductive polymer film using the intermediate layer as an anode, it is excellent in corrosion resistance, like a Ni-based alloy, but is generated during electrolysis in a solution. When a metal or alloy that easily reacts with oxygen and forms a passive film is used for the intermediate layer, the contact resistance value may increase. In such a case, as shown in FIG. 3, after forming the conductive intermediate layer 2, a thin π-conjugated conductive polymer layer 4 is provided using a chemical polymerization method, and the π-conjugated conductive property is provided. It is preferable to perform electropolymerization using the polymer layer 4 as an anode to form the electropolymerized conductive polymer layer 3.

  As the chemical polymerization method, a π-conjugated conductive polymer film can be formed by bringing a π-conjugated conductive polymer monomer and an oxidant solution into contact with each other on the surface of the substrate after the formation of the conductive intermediate layer 2. it can. However, a π-conjugated conductive polymer film generally obtained by chemical polymerization is composed of porous fine particles, is not a dense film, and has poor electrical conductivity. Therefore, it is necessary to form a π-conjugated conductive polymer film having a dense and high electric conductivity by chemical polymerization after chemical polymerization.

  Examples of the π-conjugated conductive polymer to be formed include polypyrrole and derivatives thereof, polythiophene and derivatives thereof, polyaniline and derivatives thereof, polyphenylene and derivatives thereof, polyacetylene and derivatives thereof, polyfuran and derivatives thereof, polyphenylene vinylene and derivatives thereof, polyacene In addition, polypyrrole and derivatives thereof, polythiophene and derivatives thereof, polyaniline and derivatives thereof are particularly preferable.

  When the conductive intermediate layer has a defect, the π-conjugated conductive polymer film is partially self-passivated by releasing the dopant contained in the polymer film, thereby suppressing local battery formation. It also has an effect.

  As shown in FIG. 2, in order that the separator and the electrode exhibit good contact resistance when stacked as a fuel cell, the electrical conductivity of the π-conjugated conductive polymer film provided on the upper layer of the substrate is 1 S / Physical properties of cm or more are preferable. If it is less than this, the contact resistance value increases, which is not suitable.

  Moreover, although electrical conductivity is expressed when a dopant is contained in the π-conjugated conductive polymer, the dopant is an anion or a cation. Therefore, even if the conductive filler made of metal corrodes and becomes a metal cation, it is trapped in the π-conjugated conductive polymer film, thereby preventing the proton conductive electrolyte film from being adversely affected. Also has.

  Unlike the conventional plating method, the π-conjugated conductive polymer film formed in this way can form an organic polymer film that is uniform and free of pinholes and is excellent in corrosion resistance and electrical conductivity.

  The separators 7 and 8 shown in FIGS. 1 and 3 are manufactured by the processes described above. As shown in FIGS. 2 and 4, the separators 7 and 8 are arranged between cells composed of an electrolyte 5 made of a proton conductive electrolyte membrane and electrodes 6a and 6b provided on both sides thereof. By stacking, a polymer electrolyte fuel cell is obtained. In this configuration, the separators 7 and 8 supply a fuel gas such as hydrogen and an oxidant gas such as air to the electrodes 6a and 6b via the gas flow path 1a, respectively. Further, it also functions as a current collecting member that draws a current in contact with the electrodes 6a and 6b.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited at all by the Example.

Example 1
Al alloy 6063 was used as the metal substrate. The Al alloy 6063 is a cold rolled material having a size of 190 × 260 mm and a thickness of 1 mm. A gas flow path was formed by pressing the substrate. Thereafter, in order to remove the natural oxide film of the substrate, the substrate was immersed in a 2% by mass hydrofluoric acid aqueous solution for 1 minute, washed with ethanol, and sufficiently dried with nitrogen gas.

The pressed substrate is immersed in a Zn displacement plating solution (sodium hydroxide 120 g / L, zinc oxide 20 g / L, potassium sodium tartrate 50 g / L, ferric chloride 2 g / L, sodium nitrate 1 g / L). Thereafter, Cu strike plating (copper sulfate pentahydrate 21 g / L, ammonium sulfate 2.2 g / L, diethylenetriamine 10 g / L, bath temperature 60 ° C., current density 300 mA / cm ² ) was performed. Subsequently, Ni plating to a thickness of 20 μm (nickel sulfate hexahydrate 330 g / L, nickel chloride hexahydrate 45 g / L, boric acid 40 g / L, bath temperature 60 ° C., current density 500 mA / cm ² ) To form a conductive intermediate layer.

Next, a π-conjugated conductive polymer film was formed by electrolytic polymerization. Using a pure water solvent, an electrolyte containing 0.45 mol / L of pyrrole as a monomer and 0.20 mol / L of sodium salicylate as a supporting electrolyte, the conductive intermediate layer is an anode, SUS304 is a cathode, and the electropolymerization time is 1 hour Electropolymerization was carried out at a current density of 5 mA / cm ² to form a polypyrrole film and 10 separators were produced.

About 10 obtained separators, the contact resistance with the carbon sheet at a load of 5 to 10 kg / cm ² was measured, and the results of calculating the average value under each load were shown in Table 1, and the electricity of the polypyrrole film itself Table 2 shows the results of measuring the conductivity by a four-terminal measurement method. Furthermore, in order to confirm the corrosion resistance of the substrate, it was immersed in a sulfuric acid aqueous solution adjusted to a temperature of 90 ° C. and pH 3 for 2000 hours, the weight reduction rate due to dissolution of the substrate was measured, and the average value was calculated. Indicated.

From the results of Tables 1 to 3, the electrical conductivity of the polypyrrole film is 63 S / cm, the contact resistance at a load of 10 kg / cm ² is 15 mΩ · cm ² or less, the weight reduction rate is 5% or less, and good contact resistance. It was confirmed that it has high corrosion resistance.

Example 2
Al alloy 6063 was used as the metal substrate. The Al alloy 6063 is a cold rolled material having a size of 190 × 260 mm and a thickness of 1 mm. A gas flow path was formed by pressing the substrate. In order to remove the natural oxide film of this substrate, it was removed by sandblasting using glass beads, washed with ethanol, and sufficiently dried with nitrogen gas.

The pressed substrate is immersed in a Zn displacement plating solution (sodium hydroxide 120 g / L, zinc oxide 20 g / L, potassium sodium tartrate 50 g / L, ferric chloride 2 g / L, sodium nitrate 1 g / L). Thereafter, Cu strike plating (copper sulfate pentahydrate 21 g / L, ammonium sulfate 2.2 g / L, diethylenetriamine 10 g / L, bath temperature 60 ° C., current density 300 mA / cm ² ) was performed. Subsequently, Ni-W plating (nickel sulfate hexahydrate 79 g / L, sodium tungstate dihydrate 66 g / L, tartaric acid dihydrate 69 g / L, pH 3, bath temperature 25 ° C. to a thickness of 2 μm , A current density of 50 mA / cm ² ) was performed to form a conductive intermediate layer.

  Next, a π-conjugated conductive polymer film was formed by chemical polymerization. After the pyrrole monomer is uniformly applied to the substrate on which the conductive intermediate layer has been formed by a spraying method, 0.20 mol / L of ammonium peroxodisulfate as an oxidant and sodium dodecylbenzenesulfonate as a dopant in an ethanol / water mixed solvent The polypyrrole film | membrane was formed by spraying the oxidizing agent solution which melt | dissolved 20 mol / L and adjusted pH to 7 by the spraying method.

Subsequently, a π-conjugated conductive polymer film was formed by electrolytic polymerization using the polypyrrole film previously formed by chemical polymerization as an electrode. Using an electrolytic solution containing 0.45 mol / L of pyrrole as a monomer and 0.20 mol / L of sodium p-toluenesulfonate as a supporting electrolyte using pure water as a solvent, an electroconductive intermediate layer as an anode, SUS304 as a cathode, and electropolymerization The time was 1 hour, the current density was 5 mA / cm ² , electropolymerization was performed to form a polypyrrole film, and 10 separators were produced.

About 10 obtained separators, the contact resistance with the carbon sheet at a load of 5 to 10 kg / cm ² was measured, and the results of calculating the average value under each load were shown in Table 1, and the electricity of the polypyrrole film itself Table 2 shows the results of measuring the conductivity by a four-terminal measurement method. Furthermore, Table 3 shows the results of measuring the weight reduction rate after 2,000 hours of immersion in a sulfuric acid aqueous solution adjusted to a temperature of 90 ° C. and pH 3, and calculating the average value.

From the results of Tables 1 to 3, the electrical conductivity of the polypyrrole film is 58 S / cm, the contact resistance at a load of 10 kg / cm ² is 15 mΩ · cm ² or less, the weight reduction rate is 5% or less, and the good contact resistance. It was confirmed that it has high corrosion resistance.

Example 3
Al alloy 6063 was used as the metal substrate. The Al alloy 6063 is a cold rolled material having a size of 190 × 260 mm and a thickness of 1 mm. A gas flow path was formed by pressing the substrate. Thereafter, in order to remove the natural oxide film of the substrate, the substrate was immersed in a 2% by mass hydrofluoric acid aqueous solution for 1 minute, washed with ethanol, and sufficiently dried with nitrogen gas.

The pressed substrate is immersed in a Zn displacement plating solution (sodium hydroxide 120 g / L, zinc oxide 20 g / L, potassium sodium tartrate 50 g / L, ferric chloride 2 g / L, sodium nitrate 1 g / L). Thereafter, Cu strike plating (copper sulfate pentahydrate 21 g / L, ammonium sulfate 2.2 g / L, diethylenetriamine 10 g / L, bath temperature 60 ° C., current density 300 mA / cm ² ) was performed. Subsequently, Ag electroless plating (Ag plating solution: silver nitrate 20 g / L, ammonia water about 45 g / L, reducing solution: sodium potassium tartrate 100 g / L, bath temperature 10 ° C.) is performed so that the thickness becomes 2 μm. An intermediate layer was formed.

Next, the conductive intermediate layer was formed into an anode by using an electrolyte containing ethanol as a solvent, 0.40 mol / L of 3,4-ethylenedioxythiophene as a monomer, and 0.30 mol / L of sodium dodecylbenzenesulfonate as a supporting electrolyte. SUS304 was used as the cathode, the electropolymerization time was 1 hour, and the current density was 0.25 mA / cm ² to conduct the electropolymerization to form a poly-3,4-ethylenedioxythiophene film, and 10 separators were produced.

About 10 obtained separators, the contact resistance with the carbon sheet at a load of 5 to 10 kg / cm ² was measured, and the results of calculating the average value under each load were shown in Table 1, and Poly-3, 4 -The results of measuring the electrical conductivity of the ethylenedioxythiophene film itself by a four-terminal measurement method are shown in Table 2. Furthermore, Table 3 shows the results of measuring the weight reduction rate after 2,000 hours of immersion in a sulfuric acid aqueous solution adjusted to a temperature of 90 ° C. and pH 3, and calculating the average value.

From the results of Tables 1 to 3, the electrical conductivity of the poly-3,4-ethylenedioxythiophene film is 89 S / cm, the contact resistance at a load of 10 kg / cm ² is 15 mΩ · cm ² or less, and the weight reduction rate is 5 %, It was confirmed that it had good contact resistance and high corrosion resistance.

Example 4
Mg alloy AZ91D was used as the metal substrate. The Mg alloy AZ91Z is a cold rolled material having a size of 190 × 260 mm and a thickness of 1 mm. Thereafter, in order to remove the natural oxide film on the substrate, the substrate was immersed in a 5% by weight hydrochloric acid aqueous solution for 1 minute, washed with ethanol, and sufficiently dried with nitrogen gas.

After forming an Ag-Pd alloy having a thickness of 0.3 μm as a conductive intermediate layer by an O ₂ —Ar sputtering method (film formation temperature: 250 ° C.) using an Ag—Pd target, the substrate is subjected to a gas flow path by pressing. Formed.

Next, a π-conjugated conductive polymer film was formed by electrolytic polymerization. Using an electrolytic solution containing 0.45 mol / L of pyrrole as a monomer and 0.20 mol / L of sodium p-phenolsulfonate as a supporting electrolyte, the conductive intermediate layer is an anode, SUS304 is a cathode, and electropolymerization is performed using pure water as a solvent and 0.45 mol / L as a supporting electrolyte. The time was 1 hour, the current density was 5 mA / cm ² , electropolymerization was performed to form a polypyrrole film, and 10 separators were produced.

About 10 obtained separators, the contact resistance with the carbon sheet at a load of 5 to 10 kg / cm ² was measured, and the results of calculating the average value under each load were shown in Table 1, and the electricity of the polypyrrole film itself Table 2 shows the results of measuring the conductivity by a four-terminal measurement method. Furthermore, Table 3 shows the results of measuring the weight reduction rate after 2,000 hours of immersion in a sulfuric acid aqueous solution adjusted to a temperature of 90 ° C. and pH 3, and calculating the average value.

From the results of Tables 1 to 3, the electrical conductivity of polypyrrole is 69 S / cm, the contact resistance at a load of 10 kg / cm ² is 15 mΩ · cm ² or less, and the weight reduction rate is 5% or less. It was confirmed that it has high corrosion resistance.

Example 5
Mg alloy AZ91D was used as the metal substrate. The Mg alloy AZ91Z is a cold rolled material having a size of 190 × 260 mm and a thickness of 1 mm. A gas flow path was formed by pressing the substrate. Thereafter, in order to remove the natural oxide film on the substrate, the substrate was immersed in a 5% by mass aqueous hydrochloric acid solution for 1 minute, washed with ethanol, and sufficiently dried with nitrogen gas.

After forming an Ag—Au alloy having a thickness of 0.5 μm as a conductive intermediate layer by an O ₂ —Ar sputtering method (deposition temperature: 350 ° C.) using an Ag—Au target, the base is pressed into a gas flow path. Formed.

Next, a π-conjugated conductive polymer film was formed by electrolytic polymerization. The solvent is pure water, the pH is adjusted to 3 with sulfuric acid, an electrolytic solution containing aniline 0.30 mol / L as a monomer and tetraethylammonium dodecylbenzenesulfonic acid 0.20 mol / L as a dopant is used to form a conductive intermediate layer as an anode, Electropolymerization was performed with SUS304 as the cathode, electrolytic polymerization time of 1 hour, and current density of 5 mA / cm ² to form a polyaniline film, and 10 separators were produced.

For the 10 separators obtained, the contact resistance with the carbon sheet at a load of 5 to 10 kg / cm ² was measured, and the results of calculating the average value under each load were shown in Table 1, and the electricity of the polyaniline film itself Table 2 shows the results of measuring the conductivity by a four-terminal measurement method. Furthermore, Table 3 shows the results of measuring the weight reduction rate after 2,000 hours of immersion in a sulfuric acid aqueous solution adjusted to a temperature of 90 ° C. and pH 3, and calculating the average value.

From the results of Tables 1 to 3, the electrical conductivity of polyaniline is 9 S / cm, the contact resistance at a load of 10 kg / cm ² is 15 mΩ · cm ² or less, and the weight reduction rate is 5% or less. It was confirmed that it has high corrosion resistance.

Comparative Example 1
In accordance with JP 2001-351642 A, an Al plate (190 × 260 mm, thickness 1 mm) having a purity of 99.6% was used as the metal substrate. A gas flow path was formed by pressing the substrate. This was anodized in an aqueous oxalic acid solution, then immersed in boiling water for 30 minutes and dried to form an alumite film having a thickness of 13 μm on the substrate surface as a gas channel protective film. Next, the electrode contact surface of the substrate was lapped and cleaned.

  A glossy Ni layer having a thickness of 5 μm was formed as a first layer on the treated substrate by a wet electroplating method, and an Au layer having a thickness of 0.1 μm was similarly formed by a wet electroplating method. Ten separators were produced by the above method.

Table 1 shows the results of measuring the contact resistance of each of the obtained separators with the carbon sheet at a load of 5 to 10 kg / cm ² and calculating the average value under each load. Furthermore, Table 3 shows the results of measuring the weight reduction rate after 2,000 hours of immersion in a sulfuric acid aqueous solution adjusted to a temperature of 90 ° C. and pH 3, and calculating the average value.

From the results of Tables 1 and 3, good results were obtained when the contact resistance at a load of 10 kg / cm ² was 15 mΩ · cm ² or less, but the weight reduction rate was 30% or more, and Au plating caused by pinholes Two pieces of partial peeling of the layer were confirmed, and it was confirmed that there was a problem in corrosion resistance.

Comparative Example 2
Al alloy 6063 was used as the metal substrate. The Al alloy 6063 is a cold rolled material having a size of 190 × 260 mm and a thickness of 1 mm. A gas flow path was formed by pressing the substrate. As a base treatment before forming the oxide film, the substrate was immersed in a 2 wt% hydrofluoric acid aqueous solution for 1 minute, washed with pure water, and dried.

  The oxide film was formed by anodizing in an oxalic acid aqueous solution, then dipping in boiling water for 30 minutes, and drying to form an alumite film having a thickness of 11 μm as a gas channel protective film on the substrate surface. Thereafter, the oxidation-treated substrate was sufficiently washed with water and dried.

Next, a π-conjugated conductive polymer film was formed by electrolytic polymerization. According to Japanese Patent Application Laid-Open No. 2004-139951, the electrolyte solution was degassed 1% by mass aniline aqueous solution. Electrolyte temperature was 20 ° C., Pt was cathode, electropolymerization time was 20 minutes, current density was 0.25 mA / cm ² , electropolymerization was performed to form a polyaniline film, and 10 separators were produced.

For the 10 separators obtained, the contact resistance with the carbon sheet at a load of 5 to 10 kg / cm ² was measured, and the results of calculating the average value under each load were shown in Table 1, and the electricity of the polyaniline film itself Table 2 shows the results of measuring the conductivity by a four-terminal measurement method. Furthermore, Table 3 shows the results of measuring the weight reduction rate after 2,000 hours of immersion in a sulfuric acid aqueous solution adjusted to a temperature of 90 ° C. and pH 3, and calculating the average value.

From the results of Tables 1 to 3, the polyaniline film had an electric conductivity of 0.4 S / cm and a weight reduction rate of 5% or less, but the contact resistance at a load of 10 kg / cm ² was 900 mΩ · cm ² or more. There was a problem with contact resistance.

The flowchart which shows an example of the manufacturing process of the separator of this invention. The fuel cell sectional view using the separator of the present invention. The flowchart which shows an example of the manufacturing process of the separator of this invention. Sectional drawing of the fuel cell using the other separator of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 1a Gas flow path 2 Conductive intermediate layer 3 π-conjugated system conductive polymer film formed by electrolytic polymerization method 4 π-conjugated system conductive polymer film formed by chemical polymerization method 5 Proton conductive electrolyte film 6a Electrode 6b Electrode 7 Separator 8 Separator

Claims (7)

A fuel cell separator, wherein a conductive intermediate layer is formed on a surface of a substrate made of a metal material, and a π-conjugated conductive polymer is formed on the intermediate layer. 2. The substrate made of a metal material is at least one selected from the group consisting of Mg, Al, Ti, Fe, Mg-base alloy, Al-base alloy, Ti-base alloy, and Fe-base alloy. Fuel cell separator. 3. The fuel cell according to claim 1, wherein the π-conjugated conductive polymer is at least one selected from the group consisting of polypyrrole and derivatives thereof, polythiophene and derivatives thereof, polyaniline and derivatives thereof. Separator. Conductive intermediate layer is C, Ni, Co, Zr, Sn, Cu, Pt, Au, Ag, Pd, Ir, Ru, Ni base alloy, Fe base alloy, Co base alloy, Zr base alloy, Sn base alloy , Cu base alloy, Pt base alloy, Au base alloy, Ag base alloy, Pd base alloy, Ir base alloy, Ru base alloy, Ru oxide, Zn oxide, Ir oxide, In oxide, Sn oxide The conductive high corrosion-resistant material according to claim 1, wherein the material is at least one selected from the group consisting of: 5. A fuel cell separator and a method for producing the same according to claim 1, wherein an intermediate layer having conductivity is formed after the step of removing the oxide film layer on the substrate surface made of a metal material. 6. The fuel cell separator according to claim 1, wherein the π-conjugated conductive polymer formed on the upper surface of the base material made of a metal material is formed by electrolytic polymerization. 6. The fuel cell separator according to claim 1, wherein the π-conjugated conductive polymer formed in the upper layer of the substrate surface made of a metal material is formed by chemical polymerization after chemical polymerization and the fuel cell separator. Production method.

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