JP4534033B2 - Current collector for fuel cell and electrolyte composite using the same - Google Patents

Description

  The present invention relates to a current collector for a fuel cell that requires gas permeability and conductivity, and particularly relates to a current collector suitable for a solid polymer electrolyte fuel cell and an electrolyte composite using the current collector.

  The fuel cell is a technology that has been attracting attention in recent years as a device that generates clean energy with little environmental impact. Four types of fuel cells have been developed, mainly phosphoric acid type, solid polymer type, molten carbonate type and solid oxide type, depending on the type of electrolyte used.

As shown in FIG. 3, the basic structure of the fuel cell is such that a fuel electrode 102 (functioning as an anode) and an air electrode 103 (functioning as a cathode) are joined to both sides of the electrolyte 101, and hydrogen (H ₂ ) is connected to the fuel electrode 102. ) And air containing oxygen (O ₂ ) is supplied to the air electrode 103. Each electrode is formed with a catalyst layer in which platinum as a reaction catalyst is dispersed between the electrode 101 and the electrolyte 101. On the fuel electrode 102 side, the presence of hydrogen, catalyst, and electrolyte generates protons (H ⁺ ) and electrons (e −). The electrons are taken out from the fuel electrode 102 and supplied to the load 104, Moves in the electrolyte 101 and moves toward the air electrode 103 side. On the other hand, on the air electrode 103 side, oxygen, a catalyst, and an electrolyte exist, so that electrons supplied from the load 104 to the air electrode 103, protons that have moved in the electrolyte 101, and oxygen in the air react to water. Will be generated.

In order to perform the reaction efficiently, the fuel electrode 102 and the air electrode 103 need to have gas permeability so that hydrogen and air can come into contact with the electrolyte 101 and the catalyst, respectively. Conductivity is necessary to move. Various electrodes have been proposed from this viewpoint. For example, in Patent Document 1, in the fuel electrode and the oxidation electrode provided on both sides of the solid polymer electrolyte, the current collector provided on the gas supply side is formed of a porous metal material such as nickel foam, It describes that a carbon layer is interposed between the current collector and the catalyst layer. Further, in Patent Document 2, three-dimensional network structure nickel and thermally expanded graphite are compression-molded, and uneven grooves are formed on the surface of the structured nickel, and thermally expanded graphite is compressed in the voids inside. The point to be filled is described. Patent Document 3 describes that a sheet material having a porous structure mainly composed of a fibrous conductive material is used as an electrode substrate.
JP-A-6-223836 JP-A-8-213035 JP 2001-283878 A

  In the above-described prior art, the catalyst layer is formed separately from the current collector (see Patent Document 1), or a paste in which platinum as a catalyst is mixed with an electrolyte is applied to the current collector to form a catalyst layer (patent However, there is a problem whether the catalyst is uniformly dispersed in the catalyst layer and whether gas permeability is kept good. In addition, the manufacturing process is a complicated process, such as the need to prepare a catalyst layer separately.

  Accordingly, an object of the present invention is to provide a current collector for a fuel cell that has gas permeability and conductivity suitable for an electrode of a fuel cell and can simplify the manufacturing process, and an electrolyte composite using the same. Is.

A fuel cell current collector according to the present invention is formed so as to cover a base material made of a porous nickel material or a porous nickel-based alloy material, and a surface including the inner surface of the base material, and has high water repellency. And a metal plating layer containing fine particles made of a fluorine-based resin, and the substrate on which the metal plating layer is formed is pressure-molded to form a groove serving as a flow path . Further, the metal of the metal plating layer is made of Ni, Ni alloy, Cu, Cu alloy, Sn, Cr, Zn, Co, Ti, Al, Au, Ag, Pt, Pt alloy, Pd, Rh, Ru. One metal selected from the group. Furthermore, the metal of the metal plating layer is one metal selected from the group consisting of Ni-P, Ni-B, Ni-Cu-P, Ni-Co-P, and Ni-Cu-B.

An electrode for a fuel cell according to the present invention comprises the current collector for a fuel cell and an electrode catalyst layer formed on a surface opposite to the surface on which the groove of the current collector for the fuel cell is formed. It is characterized by being.

An electrolyte composite according to the present invention includes the above-described fuel cell electrode and a solid electrolyte membrane formed on the electrode catalyst layer of the fuel cell electrode .

  Since the current collector for a fuel cell according to the present invention uses a porous nickel material or a porous nickel-based alloy material, gas permeability and conductivity can be ensured evenly throughout and the characteristics can be adjusted by a metal plating layer. It becomes possible to do. For example, since the metal plating layer is coated on the surface including the inner surface of the substrate, the porosity of the substrate can be easily adjusted, and further, the substrate can be changed by changing the metal plating layer in a part of the substrate. It is also possible to change the porosity for a part of.

  In addition, by appropriately selecting the metal of the metal plating layer and the material of fine particles other than the metal, it is possible to impart necessary characteristics to the current collector. For example, it becomes possible to improve the corrosion resistance of the current collector or to improve the adhesion to other members.

  As described above, since necessary characteristics can be imparted to the current collector in advance by the metal plating layer, it is possible to easily manufacture the electrode and the electrolyte composite. For example, if characteristics are imparted so as to enhance the adhesion to the electrolyte, the production of the electrolyte composite is facilitated, and at that time, the catalyst should be uniformly dispersed in the current collector by plating or the like in advance. Well, it is not necessary to mix the catalyst and the electrolyte in advance to improve the adhesion.

  Hereinafter, embodiments according to the present invention will be described in detail. The embodiments described below are preferable specific examples for carrying out the present invention, and thus various technical limitations are made. However, the present invention is particularly limited in the following description. Unless otherwise specified, the present invention is not limited to these forms.

  FIG. 1 shows one cell of a polymer electrolyte fuel cell equipped with an embodiment of the present invention. On both surfaces of the solid polymer electrolyte membrane 1 formed in layers, catalyst layers 2 and 12 in which a catalyst is dispersed are formed, and current collectors 3 and 13 are joined. The separators 4 and 14 are joined to the outer surfaces of the current collectors 3 and 13. A plurality of grooves are formed in the joint portions of the current collectors 3 and 13 with the separators 4 and 14, and flow paths 5 and 15 through which gas flows are formed by these grooves.

  Then, hydrogen gas is supplied to the flow path 5 from an external supply device (not shown), and air containing oxygen is supplied to the flow path 15 so that the catalyst layer 2 and the current collector 3 function as a fuel electrode. The catalyst layer 12 and the current collector 13 function as an air electrode. Therefore, similarly to the known fuel cell, electrons are taken out from the current collector 3 and supplied to the current collector 13. The current collectors 3 and 13 are formed by forming a metal plating layer on a material such as a porous nickel material, for example, nickel foam, nickel expanded mesh, or a porous nickel-based alloy material, for example, a stainless steel metal porous body. ing. The metal of the metal plating layer includes Ni, Ni alloy, Cu, Cu alloy, Sn, Cr, Zn, Co, Ti, Al, Au, Ag, Pt, Pt alloy, Pd, Rh, Ru. It may be selected from among these, or may be selected from alloys of Ni—P, Ni—B, Ni—Cu—P, Ni—Co—P, and Ni—Cu—B. In particular, these alloys are excellent in corrosion resistance to sulfonic acid groups possessed by Nafion (manufactured by DuPont) used in electrolytes.

  Moreover, various characteristics can be provided by including fine particles other than metal in the metal plating layer described above. As fine particles, polytetrafluoroethylene (PTFE), polyethylene (PE), polypropylene (PP), ABS resin, polyamide (PA), polysulfone (PSU), AS resin, polystyrene (PS), vinylidene chloride resin (PVDC) , Vinylidene fluoride resin, PFA resin, polyphenylene ether (PFE), methylpentene resin, methacrylic acid resin, carbon (C), catalyst-supporting fine particles, and thermosetting resin. For example, if a metal plating layer of the current collector 13 having a large water repellency is selected as fine particles, water generated at the air electrode can be efficiently discharged from the current collector 13. In addition, when a fluorine resin such as PTFE is used, when a fluorine resin such as Nafion is used as the electrolyte, the fluorine resin can be bonded to each other on the bonding surface with the electrolyte of the current collector to obtain a good bonded state. it can.

  When plating a porous nickel material or a porous nickel-based alloy material, if the thickness of the metal plating layer on the separator side is thinner than the electrolyte side of the current collector, the porosity on the separator side Is set large to improve gas permeability, and if the thickness of the metal plating layer on the electrolyte side is increased, the corrosion resistance can be further improved.

  Further, by stacking a plurality of porous nickel materials or porous nickel-based alloy materials plated and press-molding, the fine particles of the metal plating layer can be bonded together and easily formed integrally. For example, when PTFE is used as the fine particles, it can be integrally molded at a pressure of about 1 MPa at 200 to 400 ° C. Furthermore, since the surface of the metal plating layer containing the fine particles is formed to be porous, the metal formed in a large number of protrusions on the pressure contact surface is entangled with each other, so that sufficient electrical conductivity is ensured. As described above, since a plurality of layers can be easily pressure-formed, various thicknesses can be formed, and various shapes such as formation of grooves can be easily formed.

  As the catalyst used for the catalyst layers 2 and 12, a known catalyst can be used, and is not particularly limited, and examples thereof include platinum, gold, palladium, ruthenium, and iridium. Such a catalyst is dispersed and attached to the entire surface of the current collectors 3 and 13 on the electrolyte membrane 1 side. There are various adhesion methods such as plating and coating, but it is possible to deposit uniformly and thinly by depositing by plating.

  As the material of the electrolyte membrane 1, a known electrolyte can be used, and examples thereof include those having a sulfonic acid group as a proton exchange group, those having a carboxylic acid group, and those having a phosphoric acid group, such as Nafion described above. It is done. The electrolyte membrane may be a membrane formed in advance or reinforced with a nonwoven fabric or the like, but may be directly applied to the current collector surface on which the catalyst layer is formed.

  When the cell shown in FIG. 1 is manufactured, a porous nickel material or a porous nickel-based alloy material is first plated to form a metal plating layer, and then a groove is formed by pressure forming to form a channel serving as a flow path. Mold. An electrode is formed by forming a catalyst layer by dispersing and adhering the catalyst to the entire surface opposite to the surface on which the groove of the current collector is formed. When an electrolyte solution is formed on the catalyst layer to form an electrolyte membrane, a structure as shown in FIG. 2 is completed. And the electrolyte composite_body | complex shown in FIG. 1 is manufactured by joining two electrolyte membranes of this structure, and crimping | bonding them.

  As the porous nickel material, a three-dimensional mesh metal porous body (trade name; Celmet, model No. 7) manufactured by Sumitomo Electric Industries, Ltd. was used. First, the surface treatment (degreasing etc.) of porous nickel material is performed, and a metal plating layer is formed by electrolytic plating.

  The composition of the plating bath, the plating conditions, the thickness of the obtained metal plating layer, etc. when electrolytic plating is shown below.

[Example 1] Electrolytic nickel plating (Watt bath)
NiSO ₄ · 6H ₂ O 250 g / liter NiCl ₂ · 6H ₂ O 45 g / liter H ₃ BO ₃ 40 g / liter Surfactant 1.0 g / liter PTFE 100 g / liter pH 4.0
Cathode current density 10A / dm ²
Temperature 50 ℃
Anode Ni plate
Stirring circulation
Plating time 30 minutes (energization time 15 minutes)
Layer thickness 3μm

[Example 2] Electrolytic nickel plating (sulfamic acid bath)
_{Ni (NH 2 SO 3) 2} · 4H 2 O 350g / l NiCl ₂ · 6H ₂ O 45g / l H ₃ BO ₃ 40g / l surfactant 1.0 g / l PTFE 100 g / l pH 4.0
Cathode current density 10A / dm ²
Temperature 50 ℃
Anode Ni plate
Stirring circulation
Plating time 30 minutes (energization time 15 minutes)
Film thickness 3μm

[Example 3] Electrolytic copper plating
Cu ₂ P ₂ O ₇ .3H ₂ O 80 g / liter K ₄ P ₂ O ₇ 300 g / liter Surfactant 1.0 g / liter PTFE 100 g / liter pH 8.5
Cathode current density 4A / dm ²
Temperature 50 ℃
Anode Cu plate
Stirring circulation
Plating time 75 minutes (energization time 37.5 minutes)
Film thickness 3μm

[Example 4] Electrolytic Ni-P plating
NiSO ₄ · 6H ₂ O 250 g / liter NiCl ₂ · 6H ₂ O 45 g / liter H ₃ BO ₃ 40 g / liter H ₃ PO ₄ 40 g / liter Surfactant 1.0 g / liter PTFE 100 g / liter pH 1.5
Cathode current density 4A / dm ²
Temperature 50 ℃
Anode Ni plate
Stirring circulation
Plating time 150 minutes (energization time 75 minutes)
Film thickness 3μm

[Example 5] Electrolytic Co plating
CoSO ₄ .7H ₂ O 250 g / liter CoCl ₂ .6H ₂ O 45 g / liter H ₃ BO ₃ 40 g / liter Surfactant 1.0 g / liter PTFE 100 g / liter pH 4.0
Cathode current density 10A / dm ²
Temperature 50 ℃
Anode Co plate
Stirring circulation
Plating time 30 minutes (energization time 15 minutes)
Film thickness 3μm

  Next, an example in which a metal plating layer is formed by electroless plating will be described below.

[Example 6] Electroless Ni-P plated NiSO ₄ .6H ₂ O 30 g / liter Sodium hypophosphite 10 g / liter Sodium citrate 10 g / liter Surfactant 0.5 g / liter PTFE 50 g / liter pH 5
Temperature 90 ° C
Stirring Circulating plating time 20 minutes Film thickness 3μm

[Example 7] Electroless Ni-B plating NiSO ₄ .6H ₂ O 30 g / liter Dimethylamine borane 10 g / liter Sodium citrate 20 g / liter Surfactant 0.5 g / liter PTFE 50 g / liter pH 5.5
60 ° C
Stirring Circulating plating time 15 minutes Film thickness 3μm

  The content ratio of PTFE in the metal plating layer obtained by the above example was about 40% by volume. After the plating treatment, the plate was sufficiently washed with water and vacuum-dried under reduced pressure for 5 hours.

  The current collector thus prepared by plating was flat pressed using a mold and pressure-molded to form a channel groove on one side. And after making platinum adhere to the whole surface of the other side by an electroplating process, the alcohol dispersion liquid of Nafion (fluorine-type solid electrolyte resin which has a sulfonic acid group; Du Pont company) was apply | coated, and the electrolyte membrane was formed.

  The structure shown in FIG. 2 is produced by the above steps, and two electrolyte membranes having this structure are joined to each other, and crimped with carbon separators from both sides of the joined parts, as shown in FIG. A cell was manufactured.

  Using this single cell, hydrogen gas was supplied to the fuel electrode, air was supplied to the air electrode, and the performance as a battery was tested. As a result, an electromotive force of about 0.9 V was obtained.

  It is suitable as a current collector and electrolyte composite used in a solid polymer electrolyte fuel cell.

It is sectional drawing which shows typically the cell structure of the solid polymer electrolyte fuel cell provided with embodiment which concerns on this invention. It is sectional drawing which shows the electrode structure used for the cell of FIG. It is a figure explaining the principle of a fuel cell.

Explanation of symbols

1 Electrolyte membrane 2, 12 Catalyst layer 3, 13 Current collector 4, 14 Separator 5, 15 Flow path

Claims (5)

A base material made of a porous nickel material or a porous nickel-based alloy material, and a metal plating layer formed so as to cover the surface including the inner surface of the base material and containing fine particles made of a fluorine-based resin having high water repellency ; And a groove for forming a flow path is formed by pressure-molding the base material on which the metal plating layer is formed .   The metal of the metal plating layer is made of Ni, Ni alloy, Cu, Cu alloy, Sn, Cr, Zn, Co, Ti, Al, Au, Ag, Pt, Pt alloy, Pd, Rh, Ru. The composite sheet body according to claim 1, wherein the composite sheet body is one metal selected from the inside.   The metal of the metal plating layer is one metal selected from the group consisting of Ni-P, Ni-B, Ni-Cu-P, Ni-Co-P, and Ni-Cu-B. The collector for fuel cells as described. 4. A fuel cell current collector according to claim 1, and an electrode catalyst layer formed on a surface of the fuel cell current collector opposite to the surface on which the groove is formed. An electrode for a fuel cell. An electrolyte composite comprising the fuel cell electrode according to claim 4 and a solid electrolyte membrane formed on the electrode catalyst layer of the fuel cell electrode.

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