WO2013137187A1

WO2013137187A1 - Method for producing membrane electrode assembly

Info

Publication number: WO2013137187A1
Application number: PCT/JP2013/056620
Authority: WO
Inventors: 松岡　孝明; 川村　剛平; 河南　博
Original assignee: 東京エレクトロン株式会社
Priority date: 2012-03-14
Filing date: 2013-03-11
Publication date: 2013-09-19
Also published as: TW201403934A; JP5995468B2; JP2013191441A

Abstract

The present invention is a method for forming a membrane electrode assembly (7) within a processing vessel that has been evacuated. The method for production includes a film formation step for forming the membrane electrode assembly (7) consistently in a vacuum without exposure to the atmosphere. The membrane electrode assembly (7) is formed by forming, in the given order, a cathode layer (3) on a lower separator (2) that is a substrate, an electrolyte layer (4) and an anode layer (5) or an anode layer (5), an electrolyte layer (4), and a cathode layer (3). In the method for production, the membrane electrode assembly (7) including the cathode layer (3) and the anode layer (5) and not just the electrolyte layer (4) is formed consistently in a vacuum in a processing vessel that has been evacuated, and so it is possible to protect the interfaces between the electrolyte layer (4), the cathode layer (3) and the anode layer (5) from oxidation or contamination resulting from exposure to the atmosphere.

Description

Manufacturing method of membrane electrode assembly

Various aspects and embodiments of the present invention relate to a method of manufacturing a membrane electrode assembly.

Patent Document 1 describes a method for producing a kind of electrolyte layer used in a solid fuel battery cell. The manufacturing method described in Patent Document 1 is a method of forming an electrolyte layer by performing film deposition by CVD using an organometallic material containing metal while performing plasma spraying using a thermal spraying powder containing metal. is there. Plasma spraying is performed using microwaves. Film formation by CVD is performed in an atmosphere of about 500 Torr to atmospheric pressure.

JP 2007-299686 A

The power generation performance of the solid fuel battery cell is not limited to the above-described ion conduction characteristics of the electrolyte layer itself, but also a membrane electrode assembly (MEA: Membrane Electrode) in which the electrolyte layer is sandwiched between an air electrode (anode layer) and a fuel electrode (cathode layer). Assembly) depends on the catalytic reactivity. For example, the bonding state at the interface between the electrolyte layer and the electrode affects the catalytic reactivity of the membrane electrode assembly, that is, the power generation performance of the solid fuel cell. For this reason, in this technical field, it is desired to improve the catalytic reactivity of the membrane electrode assembly.

The method for producing a membrane electrode assembly according to one aspect of the present invention is a method of forming a membrane electrode assembly in a vacuum evacuated processing container. This manufacturing method includes a film forming step of forming a membrane electrode assembly in a consistent vacuum without being exposed to the atmosphere. The membrane electrode assembly is formed by forming a cathode layer, an electrolyte layer and an anode layer, or an anode layer, an electrolyte layer and a cathode layer in this order on a substrate.

According to this manufacturing method, in order to form not only the electrolyte layer but also the membrane electrode assembly including the cathode layer and the anode layer in a vacuum consistently in the evacuated processing container, the electrolyte layer, the cathode layer, and the anode layer are formed. The interface can be protected from oxidation or contamination associated with atmospheric exposure. For this reason, it becomes possible to reduce the resistance loss of the whole membrane electrode assembly. Furthermore, since it is possible to easily change the film quality in the depth direction, for example, compared to the wet method which is a conventional manufacturing method, the film quality can be easily controlled and the film thickness can be reduced. Therefore, the catalytic reactivity of the membrane electrode assembly can be improved.

Here, in the film forming step, at least one layer selected from a cathode layer, an electrolyte layer, and an anode layer may be formed by plasma CVD. By manufacturing in this way, film thickness control and composition control of at least one film selected from the cathode layer, the electrolyte layer, and the anode layer can be facilitated. For example, a high-performance layer can be formed. it can.

In one embodiment, a film forming apparatus including a processing container, a mounting table, a microwave generator, an antenna, a dielectric window, and a material gas supply unit may be used in the film forming process. The processing container defines a processing space. The mounting table mounts a substrate. The antenna radiates the microwave generated by the microwave generator. The dielectric window is provided between the processing space and the antenna. The material gas supply unit supplies a material gas for forming at least one layer selected from a cathode layer, an electrolyte layer, and an anode layer. In the film forming process, the substrate is placed on a mounting table, a plasma excitation gas is supplied from the gas supply unit, a microwave is emitted from the antenna to excite the plasma, and a material gas is supplied from the material gas supply unit. Then, the material gas may be reacted with plasma to generate at least one layer selected from the cathode layer, the electrolyte layer, and the anode layer. By manufacturing in this way, at least one layer selected from a cathode layer, an electrolyte layer, and an anode layer can be formed with low damage by high-density and low electron temperature plasma excited using microwaves. Therefore, the film quality can be improved.

In one embodiment, the material gas for forming the electrolyte layer may be a gas containing CF _x and a gas containing SO _x as a doping material. With this configuration, it is possible to form a membrane electrode assembly having a low resistance interface and an ultrathin film by using high-density and low electron temperature plasma excited using microwaves.

In one embodiment, in the film forming process, the film forming apparatus may further include a high frequency power source that applies high frequency power for bias to the mounting table, and a dope gas supply unit that supplies a dope gas containing SO _x. . In the film forming step, after any one of the cathode layer, the electrolyte layer, and the anode layer is laminated, high frequency power is applied to the mounting table by a high frequency power source, and a gas for plasma excitation is supplied from the gas supply unit. Doping may be performed on the layer located on the most surface by exciting the plasma by radiating microwaves from the antenna, supplying the dope gas from the dope gas supply unit, and drawing the element in the dope gas to the mounting table by high frequency power .

In one embodiment, in the film forming step, the electrolyte layer may be doped with SO ₃ ^— or SO ₂ ^— . By manufacturing in this way, an electrolyte layer that conducts hydrogen ions better can be formed.

In one embodiment, the material gas for forming the anode layer or the cathode layer may be a gas containing C _x H _y . Alternatively, in one embodiment, a raw material in which carbon nanotubes are dispersed in a solution may be used as a material gas for forming the anode layer or the cathode layer. In one embodiment, the anode layer or the cathode layer may be formed by depositing an organic raw material or an inorganic raw material containing Pt or Pt on the amorphous carbon film by a CVD method. With such a configuration, the low-resistance interface and the ultrathin film electrode assembly hydrogen ions can be formed by the high-density and low-electron temperature plasma excited using microwaves.

Further, in one embodiment, the anode layer or the cathode layer may be formed by forming an organic raw material or an inorganic raw material containing Pt or Pt on the amorphous carbon film by the PVD method.

As described above, according to various aspects and embodiments of the present invention, a method for producing a membrane electrode assembly capable of improving the catalytic reactivity of the membrane electrode assembly is provided.

It is a perspective view of the fuel cell containing the membrane electrode assembly manufactured with the manufacturing method concerning one embodiment. FIG. 2 is a cross-sectional view taken along line II-II of the fuel battery cell shown in FIG. It is a whole schematic diagram of a processing system for manufacturing a membrane electrode assembly. It is an example of the CVD apparatus contained in the processing system of FIG. It is a flowchart which shows the flow of the manufacturing method which concerns on one Embodiment.

Hereinafter, various embodiments will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

(First embodiment)
FIG. 1 is a perspective view of a fuel cell 1 including a membrane electrode assembly manufactured by a manufacturing method according to an embodiment. FIG. 2 is a sectional view taken along line II-II of the fuel cell 1 shown in FIG. The fuel cell 1 generates power by propagating hydrogen ions (protons). The fuel cell shown in FIGS. 1 and 2 is employed, for example, as a polymer electrolyte fuel cell, and includes a lower separator 2, a lower electrode layer 3a, a lower catalyst layer 3b, an electrolyte layer 4, an upper catalyst layer 5b, An upper electrode layer 5a and an upper separator 6 are provided.

The lower separator 2 has a substantially plate shape and includes a first main surface and a second main surface facing the first main surface. Grooves serving as fluid flow paths are formed in the first main surface and the second main surface. The groove formed on the first main surface is formed to extend in a direction orthogonal to the direction in which the groove formed on the second main surface extends. As shown in FIGS. 1 and 2, the lower separator 2 is arranged so that a groove 2 a for circulating oxygen (air) is positioned on the upper surface side thereof. The groove 2b functions as a flow path for flowing hydrogen (fuel gas) supplied to the other fuel cells when the other fuel cells are connected to the lower side of the fuel cell 1 via the separator 2. .

The lower electrode layer 3 a is formed on the lower separator 2. The lower electrode layer 3a is an electrode member having electrical conductivity, and is formed as amorphous or porous. The lower electrode layer 3a also functions as a catalyst carrier contained in the lower catalyst layer 3b. For example, amorphous carbon is used as the lower electrode layer 3a. The lower electrode layer 3a has a thickness of about 100 nm, for example.

The lower catalyst layer 3b is formed on the lower electrode layer 3a and is formed in the same manner as the lower electrode layer 3a. The lower electrode layer 3a and the lower catalyst layer 3b may be configured as the cathode layer 3. The electrolyte layer 4 is formed on the cathode layer 3. The electrolyte layer 4 is a so-called ion exchange membrane, and here has a function of conducting hydrogen ions from the anode layer 5 side described later to the cathode layer 3 side.

The upper catalyst layer 5b, the upper electrode layer 5a, and the upper separator 6 are configured in the same manner as the lower catalyst layer 3b, the lower electrode layer 3a, and the lower separator 2. That is, the upper catalyst layer 5b contains a catalyst metal that ionizes the fuel gas. The anode layer 5 includes an upper catalyst layer 5b. The anode layer 5 may further include an upper electrode layer 5a. The flow path 6b of the upper separator 6 circulates hydrogen gas. A membrane electrode assembly 7 is configured to include the cathode layer 3, the electrolyte layer 4, and the anode layer 5 described above. As will be described later, the membrane electrode assembly 7 is formed in a consistent vacuum without being exposed to the atmosphere. In addition, you may comprise the fuel cell 1 connected in multiple numbers. In this case, the lower separator 2 also serves as the upper separator 6.

Hydrogen gas and air are supplied to the fuel cell 1 having the above configuration. Hydrogen supplied to the flow path 6 b is ionized in the anode layer 5, conducts through the electrolyte layer 4, and reaches the cathode layer 3. At this time, electrons are taken out from the anode layer 5 and generated. On the other hand, oxygen in the air supplied to the flow path 2 a chemically reacts with hydrogen ions conducted through the electrolyte layer 4 in the cathode layer 3 to generate water.

Next, a method for manufacturing the fuel battery cell 1 will be described. FIG. 3 shows a film forming system for manufacturing the fuel battery cell 1. As shown in FIG. 3, the processing system 107 includes a carry-in / out section 108, a load lock chamber 109, a transfer chamber 100, and processing apparatuses 101 to. In the processing system 107, the substrate is carried into and out of the transfer chamber 100 from the carry-in / out unit 108 via the two load lock chambers 109, and the substrate is carried into and out of each processing apparatus 101 to 106 by the transfer chamber 100. It is like that. The number and arrangement of processing devices provided in the processing system are arbitrary.

The processing apparatuses 101 to 106 are configured as film forming apparatuses, for example. Note that the processing apparatuses 101 to 106 may include not only a film forming apparatus but also a doping apparatus or an etching apparatus. The processing apparatuses 101 to 106 may include a chamber for forming an anode layer, a chamber for forming an electrolyte layer, a chamber for forming a cathode layer, a pretreatment chamber, and a posttreatment chamber. Both chambers are vacuum vessels connected to a vacuum pump. These chambers are transported in vacuum and are not exposed to the atmosphere. In addition, any or all of a gas supply function, a pressure control function, a film formation temperature control function, a substrate adsorption function, and a plasma generation mechanism can be mounted in any chamber. For example, a CVD apparatus is used as the film forming apparatus. That is, at least one layer selected from the cathode layer, the electrolyte layer, and the anode layer may be formed by plasma CVD. In some cases, any of the chambers can be changed to a film forming apparatus having a sputtering function (a film forming apparatus using a PVD method).

Hereinafter, details of the CVD apparatus will be described. FIG. 4 is an example of a CVD apparatus included in the processing system of FIG. Here, a case where a radial line slot antenna (RLSA: Radial Line Slot Antenna) type planar antenna member is used as a CVD apparatus will be described as an example. That is, this is a case where surface wave plasma (SWP: Surface Wave Plasma) is used.

4 includes a processing vessel 12, a stage (mounting table) 14, a microwave generator 16, an antenna 18, and a dielectric window 20. The CVD apparatus 10 shown in FIG.

The processing container 12 defines a processing space S for performing plasma processing on the substrate W to be processed. The processing container 12 may include a side wall 12a and a bottom 12b. The side wall 12a has a substantially cylindrical shape extending in the axis X direction (that is, the extending direction of the axis X). The bottom 12b is provided on the lower end side of the side wall 12a. The bottom 12b is provided with an exhaust hole 12h for exhaust. The upper end of the side wall 12a is open.

The upper end opening of the side wall 12 a is closed by the dielectric window 20. An O-ring 21 may be interposed between the dielectric window 20 and the upper end portion of the side wall 12a. The O-ring 21 ensures the sealing of the processing container 12 more reliably.

The microwave generator 16 generates a microwave of 2.45 GHz, for example. In one embodiment, the CVD apparatus 10 further includes a tuner 22, a waveguide 24, a mode converter 26, and a coaxial waveguide 28.

The microwave generator 16 is connected to the waveguide 24 via the tuner 22. The waveguide 24 is, for example, a rectangular waveguide. The waveguide 24 is connected to a mode converter 26, and the mode converter 26 is connected to the upper end of the coaxial waveguide 28.

The coaxial waveguide 28 extends along the axis X. The coaxial waveguide 28 includes an outer conductor 28a and an inner conductor 28b. The outer conductor 28a has a substantially cylindrical shape extending in the axis X direction. The inner conductor 28b is provided inside the outer conductor 28a. The inner conductor 28b has a substantially cylindrical shape extending along the axis X.

The microwave generated by the microwave generator 16 is guided to the mode converter 26 via the tuner 22 and the waveguide 24. The mode converter 26 converts a microwave mode and supplies the microwave after the mode conversion to the coaxial waveguide 28. Microwaves from the coaxial waveguide 28 are supplied to the antenna 18.

The antenna 18 radiates a microwave for plasma excitation based on the microwave generated by the microwave generator 16. The antenna 18 may include a slot plate 30, a dielectric plate 32, and a cooling jacket 34.

The slot plate 30 has a plurality of slots arranged in the circumferential direction around the axis X. The slot plate 30 can be a slot plate constituting a radial line slot antenna. The slot plate 30 is made of a metal disc having conductivity. A plurality of slot pairs 30 a are formed in the slot plate 30. Each slot pair 30a includes a slot 30b and a slot 30c extending in a direction intersecting or orthogonal to each other. The plurality of slot pairs 30a are arranged at predetermined intervals in the radial direction, and are arranged at predetermined intervals in the circumferential direction.

The dielectric plate 32 is provided between the slot plate 30 and the lower surface of the cooling jacket 34. The dielectric plate 32 is made of, for example, quartz and has a substantially disk shape. The surface of the cooling jacket 34 may have conductivity. The cooling jacket 34 cools the dielectric plate 32 and the slot plate 30. For this purpose, a coolant channel is formed in the cooling jacket 34. The lower end of the outer conductor 28 a is electrically connected to the upper surface of the cooling jacket 34. Further, the lower end of the inner conductor 28 b is electrically connected to the slot plate 30 through a hole formed in the cooling jacket 34 and the central portion of the dielectric plate 32.

The microwave from the coaxial waveguide 28 is propagated to the dielectric plate 32 and is introduced into the processing space S from the slot of the slot plate 30 through the dielectric window 20. The dielectric window 20 has a substantially disc shape and is made of, for example, quartz. The dielectric window 20 is provided between the processing space S and the antenna 18. In one embodiment, the dielectric window 20 is provided immediately below the antenna 18 in the axis X direction. A conduit 36 passes through the inner hole of the inner conductor 28 b of the coaxial waveguide 28. The conduit 36 extends along the axis X and can be connected to the gas supply system 40.

The gas supply system 40 supplies argon gas to the conduit 36. The gas supply system 40 may include a gas source 40a, a valve 40b, and a flow rate controller 40c. The gas source 40a is a gas source of argon gas. The valve 40b switches supply and stop of supply of argon gas from the gas source 40a. The flow rate controller 40c is, for example, a mass flow controller, and adjusts the flow rate of argon gas from the gas source 40a.

The CVD apparatus 10 may further include an injector 41. The injector 41 supplies the gas from the conduit 36 to the through hole 20 h formed in the dielectric window 20. The gas supplied to the through hole 20 h of the dielectric window 20 is supplied to the processing space S. In the following description, the gas supply path constituted by the conduit 36, the injector 41, and the through hole 20h may be referred to as a “central gas introduction unit”.

The CVD apparatus 10 may further include a gas supply unit 42. The gas supply unit 42 supplies gas from the periphery of the axis X to the processing space S between the stage 14 and the dielectric window 20. In the following description, the gas supply unit 42 may be referred to as “peripheral gas introduction unit”. The gas supply unit 42 may include a conduit 42a. The conduit 42 a extends annularly around the axis X between the dielectric window 20 and the stage 14. A plurality of gas supply holes 42b are formed in the conduit 42a. The plurality of gas supply holes 42 b are arranged in an annular shape, open toward the axis X, and supply the gas supplied to the conduit 42 a toward the axis X. The gas supply unit 42 is connected to a gas supply system 45 through a conduit 46.

The material gas supply system (material gas supply unit) 44 supplies the material gas to the gas supply unit 42. The material gas supply system 44 may include a gas source 44a, a valve 44b, and a flow controller 44c. The gas source 44a is a gas source of material gas. The valve 44b switches between supply and stop of gas supply from the gas source 44a. The flow rate controller 44c is a mass flow controller, for example, and adjusts the flow rate of the gas from the gas source 44a. As the material gas, CFx gas is used. Alternatively, a raw material having a SO _x bond in a part of CF _x may be used. That is, the material gas may be a gas containing CF _x and a gas containing SO _x as a doping material. Alternatively, a raw material in which carbon nanotubes are dispersed in a solution may be used as a material gas.

The dope gas supply system (dope gas supply unit) 45 supplies the dope gas to the gas supply unit 42. The dope gas supply system 45 may include a gas source 45a, a valve 45b, and a flow rate controller 45c. The gas source 45a is a gas source of dope gas. The valve 45b switches supply and stop of supply of the dope gas from the gas source 45a. The flow rate controller 45c is, for example, a mass flow controller, and adjusts the flow rate of the dope gas from the gas source 45a. For example, a gas containing SO _x is used as a doping gas for the electrolyte layer. Alternatively, H ₂ SO ₄ or the like may be used as a dope gas for the electrolyte layer.

The stage 14 is provided so as to face the dielectric window 20 in the axis X direction. The stage 14 is provided so as to sandwich the processing space S between the dielectric window 20 and the stage 14. A substrate to be processed is placed on the stage 14. In one embodiment, the stage 14 may include a table 14a, a focus ring 14b, and an electrostatic chuck 14c.

The base 14 a is supported by a cylindrical support portion 48. The cylindrical support portion 48 is made of an insulating material and extends vertically upward from the bottom portion 12b. A conductive cylindrical support 50 is provided on the outer periphery of the cylindrical support 48. The cylindrical support portion 50 extends vertically upward from the bottom portion 12 b of the processing container 12 along the outer periphery of the cylindrical support portion 48. An annular exhaust passage 51 is formed between the cylindrical support portion 50 and the side wall 12a.

An annular baffle plate 52 provided with a plurality of through holes is attached to the upper part of the exhaust passage 51. An exhaust device 56 is connected to the lower portion of the exhaust hole 12 h via an exhaust pipe 54. The exhaust device 56 has a vacuum pump such as a turbo molecular pump. The exhaust device 56 can depressurize the processing space S in the processing container 12 to a desired degree of vacuum.

The stand 14a also serves as a high-frequency electrode. A high frequency power source 58 for RF bias is electrically connected to the base 14 a via a matching unit 60 and a power feeding rod 62. The high frequency power supply 58 outputs a predetermined frequency suitable for controlling the energy of ions drawn into the substrate W to be processed, for example, high frequency power of 13.65 MHz at a predetermined power. The matching unit 60 accommodates a matching unit for matching between the impedance on the high-frequency power source 58 side and the impedance on the load side such as electrodes, plasma, and the processing container 12. This matching unit includes a blocking capacitor for generating a self-bias.

An electrostatic chuck 14c is provided on the upper surface of the table 14a. The electrostatic chuck 14c holds the substrate to be processed W with an electrostatic attraction force. A focus ring 14b that surrounds the periphery of the substrate W to be processed is provided on the outer side in the radial direction of the electrostatic chuck 14c. The electrostatic chuck 14c includes an electrode 14d, an insulating film 14e, and an insulating film 14f. The electrode 14d is made of a conductive film, and is provided between the insulating film 14e and the insulating film 14f. A high-voltage DC power supply 64 is electrically connected to the electrode 14 d via a switch 66 and a covered wire 68. The electrostatic chuck 14c can attract and hold the substrate W to be processed by the Coulomb force generated by the DC voltage applied from the DC power source 64.

An annular refrigerant chamber 14g extending in the circumferential direction is provided inside the table 14a. A refrigerant having a predetermined temperature, for example, cooling water, is circulated and supplied to the refrigerant chamber 14g from a chiller unit (not shown) via

pipes

70 and 72. Depending on the temperature of the refrigerant, the heat transfer gas of the electrostatic chuck 14 c, for example, He gas, is supplied between the upper surface of the electrostatic chuck 14 c and the rear surface of the substrate W to be processed via the gas supply pipe 74.

In the CVD apparatus 10 configured in this way, gas is supplied along the axis X into the processing space S from the through hole 20h of the dielectric window 20 through the conduit 36 and the through hole 41h of the injector 41. Further, gas is supplied from the gas supply unit 42 toward the axis X below the through hole 20h. Further, microwaves are introduced from the antenna 18 through the dielectric window 20 into the processing space S and / or the through hole 20 h. Thereby, plasma is generated in the processing space S and / or the through hole 20h. Thus, according to the CVD apparatus 10, it is possible to generate plasma without applying a magnetic field.

Hereinafter, an embodiment of a manufacturing method (film formation process) using the above-described processing system 107 will be described. First, an anode layer (anode electrode) is formed in a chamber for forming an anode layer. For example, a highly conductive amorphous carbon film is formed by plasma CVD, and then an organic solvent (organic raw material) or inorganic solvent (inorganic raw material) containing vaporized Pt is attached to the amorphous carbon film. The amorphous carbon of the electrode is formed by selecting a raw material of C _x H _y (CH ₄ , C ₂ H ₄ , C ₂ H ₂ , C ₃ H ₆ , C ₃ H ₈ or C ₄ H ₆ ), for example. May be. As the organic solvent, for example, (CH ₃ ) ₃ (CH ₃ C ₅ H ₄ ) Pt, Pt (CF ₃ COCHCOCF ₃ ) ₂ or the like is used. At this time, Pt contained in the organic solvent may be formed by a plasma CVD method. Furthermore, in order to remove organic substances contained in the organic solvent, unnecessary organic substances may be reduced and removed by, for example, irradiation with H ₂ plasma. Alternatively, Pt may be formed in a sputtering chamber different from this without using the CVD method. Unlike conventional wet methods, these processes make full use of control parameters such as pressure, flow rate, and time to control the desired film thickness, composition, and structure in the depth direction of the film. Can do. In particular, since it is easy to make a thin film, it is an inexpensive manufacturing method that can significantly reduce the consumption of expensive Pt, which has been conventionally consumed in large quantities. A film containing CF _x and SO _x as an ionomer in the electrode is formed and supported on the anode electrode carbon film by a CVD method. The ionomer film formation may be performed simultaneously with the carbon electrode film formation, or the carbon electrode film formation and the ionomer film formation may be performed alternately.

Next, it transfers from the chamber which forms an anode layer to the chamber which forms an electrolyte layer, and forms an electrolyte layer into a film. It is needless to say that oxidation or contamination from the atmosphere does not occur even during transfer because the path for transferring between chambers can be evacuated. As a result, the resistance between the anode and the electrolyte does not increase due to deterioration such as oxidation. In this chamber, for example, an amorphous fluorocarbon film is formed by plasma CVD. The amorphous fluorocarbon of the electrolyte layer is CF ₄ , C ₂ F ₄ , C ₂ F ₆ , C ₃ F ₆ , C ₃ F ₈ , C ₄ F ₆ , C ₄ F ₈ , C ₅ F ₈ , C ₅ F ₁₀ or The film may be formed using a gas containing C and F, such as C ₆ F ₆ . Next, a raw material such as SO ₂ or H ₂ SO _{4 that} functions as a sulfone group (SO ³⁻ ) is bonded to the terminal portion of the previously formed amorphous fluorocarbon film by plasma CVD. By this method, it is possible to provide performance equal to or higher than that of a polymer compound represented by conventional Nafion (registered trademark) and Flemion (registered trademark). In addition, since this plasma CVD method can be made thinner by several orders of magnitude than Nafion and Flemion, which can be made only with micron or more, the electric resistance of the electric field can be greatly reduced.

Next, the cathode layer is transferred from the chamber for forming the electrolyte layer to the chamber for forming the cathode layer. In this chamber, almost the reverse process of the chamber for forming the anode layer is performed. First, an organic solvent containing vaporized Pt is deposited on the amorphous fluorocarbon film previously formed. As the organic solvent, those similar to those used when forming the above-described anode layer are employed. At this time, Pt contained in the organic solvent may be formed by plasma CVD, or may be transferred to another chamber and formed by sputtering. Further, in order to remove organic substances contained in the organic solvent, for example, H ₂ plasma is irradiated to reduce and remove unnecessary organic substances. Thereafter, for example, an amorphous carbon film having high conductivity is formed by plasma CVD. Similar to the anode electrode, a film containing CF _x and SO _x as an ionomer is formed and supported on the cathode electrode carbon film by a CVD method in the cathode electrode. The ionomer film formation may be performed simultaneously with the carbon electrode film formation, or the carbon electrode film formation and the ionomer film formation may be performed alternately.

At this time, the interface between the anode layer and the cathode layer is covered with an amorphous fluorocarbon film containing a sulfone group so as to cover the Pt surface. At these interfaces, the amorphous fluorocarbon film containing a sulfone group plays the role of an ionomer, and can promote the permeation of hydrogen and oxygen and promote the catalytic reaction on the Pt surface.

In this way, the film can be formed in a vacuum consistent process that is never exposed to the atmosphere, and a low-resistance interface and an ultra-thin membrane electrode assembly, which has not been obtained by conventional methods, are configured.

Hereinafter, details of a manufacturing method (film formation process) using the above-described processing system 107 will be described. FIG. 5 is a flowchart showing a manufacturing method according to an embodiment. In the manufacturing method shown in FIG. 5, first, a substrate is carried in. That is, the substrate is loaded into the processing apparatus 101 via the loading / unloading unit 108, the load lock chamber 109, and the transfer chamber 100 (S10). The substrate is the lower separator 2, and here,

grooves

2a and 2b are formed in advance.

Next, the lower electrode layer 3a is formed on the lower separator 2 (S12). For example, an amorphous carbon film is formed on the lower separator 2 by plasma processing in an Ar atmosphere in the processing apparatus 101. For example, the film is formed with a microwave power of 2000 W as a power source, a flow rate of C ₄ H ₆ gas of 200 sccm, a pressure of a processing space of 50 mTorr (65 Pa), and a processing time of 20 seconds.

Next, the lower catalyst layer 3b is formed on the lower electrode layer 3a (S14). For example, an organic or inorganic material containing Pt is continuously formed on the amorphous carbon film on the processing apparatus 101. For example, film formation is performed with a microwave power of 200 W, a flow rate of a raw material containing Pt of 5 sccm, a pressure of a processing space of 100 mTorr (130 Pa), and a processing time of 20 seconds. At this time, adsorption may be performed simply by flowing a gas without using a microwave. After the Pt material is adsorbed, the Pt organic matter is reduced and removed using H ₂ plasma. At this time, for example, the processing is performed with a microwave power of 200 W, a flow rate of a raw material containing Pt of 5 sccm, a processing space pressure of 100 mTorr (130 Pa), and a processing time of 20 seconds. Further, Pt may be formed by sputtering instead of the above method.

Next, the electrolyte layer 4 is formed on the lower catalyst layer 3b (S16). For example, it is assumed that the processing apparatus 103 is the CVD apparatus shown in FIG. In this case, the processing body is transferred from the processing apparatus 102 to the processing apparatus 103 via the transfer chamber 100. A CF _x film is formed using plasma excited by RLSA in the apparatus 103. For example, a microwave power of 2000 W, a microwave frequency of 2.45 GHz, an output RF power of 0 W of the high-frequency power supply 58, an argon gas flow rate of 200 sccm, a CFx gas flow rate of 200 sccm, a flow rate ratio (a gas flow rate at the central gas inlet: peripheral gas) Gas flow rate of introduction part) 1: 1.5, pressure of processing space S 60 mTorr, processing time 30 seconds, temperature of processing space S Upper: 100 ° C., side wall 12a inner surface: 80 ° C., temperature of stage 14 Center: 200 ° C., Film formation is performed at the peripheral edge: 200 ° C. and the refrigerant temperature of the stage 14: 80 ° C. After laminating the CF _x film, a doping gas is introduced to dope the sulfone group. A high frequency power is applied to the stage 14 by the high frequency power source 58, a gas for gas excitation is supplied from the gas supply unit 42, a microwave is emitted from the antenna 18 to excite the plasma, and a dope gas is supplied from the gas supply unit 42. Then, the element located in the most surface is doped by drawing the element in the doping gas into the stage 14 by high frequency power. For example, doping is performed at an output RF power of 300 W from the high-frequency power source 58, an argon gas flow rate of 200 sccm, and an SO ₂ gas flow rate of 50 sccm. As a result, the electrolyte layer is doped with SO ³⁻ or SO ²⁻ .

Next, the upper catalyst layer 5b is formed on the electrolyte layer 4 (S18). For example, the processing body is transferred from the processing apparatus 103 to the processing apparatus 102 via the transfer chamber 100. In the apparatus 102, an organic material containing Pt is formed. The film forming conditions are the same as S14.

Next, the upper electrode layer 5a is formed on the upper catalyst layer 5b (S20). For example, the processing body is transferred from the processing apparatus 102 to the processing apparatus 101 via the transfer chamber 100. In the apparatus 101, an amorphous carbon film is formed on the upper catalyst layer 5b by plasma treatment in an Ar atmosphere. The film forming conditions are the same as in S12.

Next, this membrane electrode assembly is unloaded (S22). It is unloaded from the processing apparatus 101 via the transfer chamber 100, the load lock chamber 109, and the loading / unloading unit 108. When the process of S22 ends, the control process shown in FIG. 5 ends.

According to the manufacturing method shown in FIG. 5, not only the electrolyte layer 4 but also the membrane electrode assembly 7 including the cathode layer 3 and the anode layer 5 is formed in a consistently vacuum without being exposed to the atmosphere in a evacuated processing container. Therefore, the interface between the electrolyte layer 4, the cathode layer 3, and the anode layer 5 can be formed with good consistency. That is, an interface with reduced roughness can be realized. For this reason, the resistance loss of the whole membrane electrode assembly 7 can be reduced. Therefore, the catalytic reactivity of the membrane electrode assembly 7 can be improved.

Moreover, since the film thickness control and composition control of the electrolyte layer 4 can be facilitated by forming the electrolyte layer 4 by plasma CVD, it is possible to form the electrolyte layer 4 having a uniform film thickness and composition. It becomes. Further, by using plasma CVD, the electrolyte layer 4 can be formed with a thickness of 1 μm or less instead of the electrolyte layer of several tens μm to several hundreds μm as in the prior art.

Although various embodiments have been described above, various modifications can be made without being limited to these embodiments. For example, in the above-described embodiment, the example in which the lower separator 2 in which the

grooves

2a and 2b are formed in advance has been described in the process of S10, but the

grooves

2a and 2b may be formed with an etching apparatus or the like. Alternatively, the lower separator 2 and the upper separator 6 on which an amorphous carbon film is formed in advance may be used. In this case, the processes of S12 and S20 are not necessary. Moreover, although the manufacturing method of 1 cell was demonstrated in embodiment mentioned above, it is good also considering the upper separator 6 as the lower separator 2 of the following fuel cell. Thereby, the fuel cell of a plurality of cycles can be formed in a consistent vacuum. In the above-described embodiment, the example in which the cathode layer 3, the electrolyte layer 4, and the anode layer 5 are formed in this order on the lower separator 2 that is the substrate has been described. However, the anode layer 5, the electrolyte layer 4, and the cathode are formed. The layers 3 may be formed in this order.

DESCRIPTION OF SYMBOLS 1 ... Fuel cell, 2 ... Lower separator (substrate), 3 ... Cathode layer, 3a ... Lower electrode layer, 3b ... Lower catalyst layer, 4 ... Electrolyte layer, 5 ... Anode layer, 5a ... Upper electrode layer, 5b ... Upper part Catalyst layer, 6 ... upper separator (substrate), 7 ... membrane electrode assembly, 10 ... CVD apparatus, 12 ... processing vessel, 14 ... stage (mounting table), 16 ... microwave generator, 18 ... antenna, 20 ... dielectric Body window, 30 ... slot plate, 32 ... dielectric plate, 40 ... gas supply system, 44 ... material gas supply system (material gas supply unit), 45 ... dope gas supply system (dope gas supply unit), S ... processing space, W ... Substrate to be treated.

Claims

A method for producing a membrane electrode assembly having a cathode layer, an electrolyte layer and an anode layer,
The substrate is introduced into the evacuated processing container, and the cathode layer, the electrolyte layer and the anode layer, or the anode layer, the electrolyte layer and the cathode layer are sequentially exposed to the atmosphere on the substrate without being exposed to the atmosphere. Including a film-forming process for consistent film formation,
Manufacturing method of membrane electrode assembly.
The method of manufacturing a membrane electrode assembly according to claim 1, wherein in the film formation step, at least one layer selected from the cathode layer, the electrolyte layer, and the anode layer is formed by plasma CVD.
In the film forming step, as a film forming apparatus,
A processing vessel defining a processing space;
A mounting table for mounting the substrate;
A microwave generator;
An antenna for radiating microwaves generated by the microwave generator;
A dielectric window provided between the processing space and the antenna;
A gas supply unit for supplying a gas for plasma excitation;
A material gas supply unit for supplying a material gas for forming at least one layer selected from the cathode layer, the electrolyte layer, and the anode layer;
Using a film forming apparatus comprising:
The substrate is placed on the mounting table, the gas for plasma excitation is supplied from the gas supply unit, microwaves are emitted from the antenna to excite plasma, and the material gas is supplied from the material gas supply unit. 3. The method of manufacturing a membrane electrode assembly according to claim 2, wherein the material gas is supplied and reacted with the plasma to form at least one layer selected from the cathode layer, the electrolyte layer, and the anode layer.
Wherein said material gas for forming the electrolyte layer, the manufacturing method of the membrane electrode assembly according to claim 3 is a gas containing a gas containing SO x as CF x and doped materials.
In the film forming step, as the film forming apparatus,
A high frequency power source for applying a high frequency power for bias to the mounting table;
A dope gas supply unit for supplying a dope gas containing SO x ;
Further comprising
After laminating any one of the cathode layer, the electrolyte layer, and the anode layer, the high-frequency power is applied to the mounting table by the high-frequency power source, and the gas for plasma excitation is supplied from the gas supply unit. And by exciting microwaves from the antenna to excite plasma, supplying the dope gas from the dope gas supply unit, and drawing the elements in the dope gas into the mounting table by the high frequency power, the layer located on the most surface The method for producing a membrane electrode assembly according to claim 4, wherein doping is performed on the electrode.
6. The method of manufacturing a membrane electrode assembly according to claim 5, wherein in the film forming step, the electrolyte layer is doped with SO 3 − or SO 2 — .
The method for producing a membrane electrode assembly according to any one of claims 3 to 6, wherein the material gas for forming the anode layer or the cathode layer is a gas containing CxHy.
The method for producing a membrane electrode assembly according to any one of claims 3 to 6, wherein the material gas for forming the anode layer or the cathode layer is a raw material in which carbon nanotubes are dispersed in a solution.
The membrane electrode junction according to any one of claims 2 to 8, wherein the anode layer or the cathode layer is formed by depositing Pt or an organic material or an inorganic material containing Pt on the amorphous carbon film by a CVD method. Body manufacturing method.
The method for producing a membrane electrode assembly according to claim 1, wherein the anode layer or the cathode layer is formed by depositing Pt or an organic or inorganic raw material containing Pt on the amorphous carbon film by a PVD method.