JP2003317740A - Thin film functioning structural body, single cell for solid electrolyte fuel cell using it, and method for manufacturing it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin film functioning structural body having excellent durability, a thin film functioning structure precursor, a hydrogen separating cell causing a small loss in a generated power output, hydrogen separating efficiency and the like even if the flow rate and the feeding pressure of gas are fluctuated, and a single cell for solid electrolyte fuel cell, and to provide a method for manufacturing it. <P>SOLUTION: In this thin film functioning structural body, a porous supporting body having an opening is coated with a coating film, porosity of the porous supporting body is 30-97%, the ratio of communicating holes among total holes is 80-100%, and the maximum film thickness of the coating film is 0.1-100 μm. The maximum opening diameter a of the hole and the maximum film thickness d of the coating film satisfy 0.01≤d/a≤10. The maximum opening diameter of the hole is 1 μm-10 mm, and the non-contact area ratio of the porous supporting body is 10-90%. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a thin film functional structure,
TECHNICAL FIELD The present invention relates to a thin film functional structure precursor, a hydrogen separation cell using the thin film functional structure, a single cell for a solid oxide fuel cell and a method for producing the same, and more specifically, pores of a porous support suitable for gas diffusion. The present invention relates to a thin film functional structure having an opening covered with a functional thin coating film, a thin film functional structure precursor, a hydrogen separation cell using the thin film functional structure, a single cell for a solid oxide fuel cell, and a method for producing the same.

[0002]

2. Description of the Related Art Applications of a structure having a functional support film formed on a porous support include a filter, a gas separation membrane structure (cell), a gas sensor and a solid oxide fuel cell. When applied to these, the porous support is required to have a function of supporting a functional coating film, a function of diffusing a gas, and a function of a gas flow path.

When a functional coating film is required to have a function of transmitting gas molecules and conducting ions and electrons, generally, the thinner the film is, the more film defects such as pinholes occur. The more dense there is, the better the characteristics such as permeability and conductivity. Further, as the film becomes thinner, a support for holding the film is required. However, on the surface of the porous support,
It is extremely difficult to form a dense and thin film. In addition, the larger the porosity of the porous support near the interface with the coating film, the thicker the coating film in order to reduce film defects. On the other hand, when reducing the film thickness, the porosity of the porous substrate must be reduced.
Further, the surface smoothness of the contact surface of the porous support with the coating film is also important. That is, even if the coating film is thin, if the surface of the support is rough and there are large irregularities, it is difficult to form a film with a uniform thickness, and an extremely thin portion is formed around the irregularities. However, film cracks may occur and cause film defects.

The function of diffusing the gas is a function of uniformly supplying the gas to the entire functional coating film. If a gas with a biased component concentration or pressure is supplied to a part of the coating film, the coating film will be damaged, and the efficiency and characteristics of the entire system incorporating these functional structures will decrease. .

Further, the function as the gas flow path is a ventilation function for supplying gas through the porous support to the interface between the coating film and the porous support. From the viewpoint of introducing gas into a system incorporating these functional structures, it is important to control the gas flow and reduce the gas ventilation resistance (gas pressure loss). In general, the larger the porosity, the better. If the porosity is small, the rate of supplying the gas to the functional coating film is rate-determining, and the efficiency and the characteristics decrease. Further, in order to reduce the ventilation resistance, the ratio of open pores, the pore diameter, and the pore shape that are connected so as to function as a gas flow path are important even with the same porosity. When the ratio of open pores is low or the diameter of pores is small, ventilation resistance increases. Further, if the pore size is extremely thin on the way from the upstream side to the downstream side of the gas flow, or if the hole has a complicated mesh structure, the ventilation resistance tends to increase. In particular, in the case of a vehicle-mounted functional structure in which the gas flow rate and gas pressure fluctuate, it is likely to cause damage. Therefore, not only the porosity of the porous support but also the pore shape plays an important role in improving the function of diffusing the gas and the function of the gas passage.

A solid electrolyte fuel cell is an example of a structure in which a functional coating film is formed on such a porous support. In recent years, solid oxide fuel cells have been attracting attention as a clean energy source that has high power generation efficiency, generates almost no harmful exhaust gas, and is environmentally friendly. A solid electrolyte type fuel cell uses an ion conductive solid electrolyte as an electrolyte, attaches porous electrodes to both surfaces thereof, and supplies a fuel gas such as hydrogen or hydrocarbon to one electrode side using the solid electrolyte as a gas partition wall, This is a fuel cell of the type that supplies air or oxygen gas to the other electrode side.

Further, the following constitution has been proposed for the purpose of increasing the output of the solid oxide fuel cell. 1) A structure in which a porous cell substrate is used as a support, and an electrode, an electrolyte, and an electrode are laminated in that order on the support. 2) The electrode itself also serves as a cell support, on which an electrolyte and an electrode are laminated in order.

Further, when the electrolyte layer, which is a functional coating film, becomes thicker, the internal resistance (especially IR resistance) of the cell in the thickness direction becomes large, and there is a drawback that the output of the fuel cell is lowered. Is preferable to be thinner. In the solid oxide fuel cell, as the operating temperature is lowered,
Reducing IR resistance is a particularly important issue. Furthermore, since the electrolyte layer also functions as a gas partition wall, denseness is required. Further, the cell substrate or the electrode itself, which is a porous support, has a function of supporting the electrolyte thin film and is suitable for allowing fuel gas or air to reach the three-phase interface formed at the interface between the electrolyte layer and the electrode layer. It is important to have porosity, that is, to have a gas diffusion function and a gas flow path function. For example,
When the gas is unevenly supplied to the interface with the electrolyte layer, a power generating reaction locally generating heat occurs at that portion, and the electrolyte layer is destroyed. Further, when not only hydrogen gas but also hydrocarbon fuel gas such as natural gas or gasoline having a large molecular weight is used as the fuel gas, if the porous support is not provided with suitable pores for ventilation, the gas is not supplied. The power generation output is reduced due to lack or uneven distribution of components. Furthermore, in the case of a structure in which water is generated on the side of the porous support, unnecessary water is not efficiently removed, resulting in a decrease in power generation output.

Therefore, in order to form a high-power cell, 1) an electrolyte layer is formed on a substrate that has a shape suitable for gas supply and diffusion and is as porous as possible, 2) an electrolyte layer that is as thin and dense as possible It is desirable to have such a configuration.

Another example of the structure having a functional coating film is a hydrogen separation cell for purifying and recovering hydrogen gas. From the viewpoints of energy saving, separation efficiency, miniaturization of equipment, etc., a membrane separation method has been attracting attention. Among them, a hydrogen separation cell in which a membrane made of palladium or a palladium alloy is formed as a hydrogen separation membrane on a porous metal support. Is proposed. The hydrogen separation membrane has a function of permeating and purifying only hydrogen gas from a mixed gas containing hydrocarbon gas, carbon monoxide, steam and the like in hydrogen gas. If the hydrogen separation membrane becomes thicker, the hydrogen permeation resistance increases, and the hydrogen separation efficiency decreases. Therefore, it is desirable that the hydrogen permeable film be thinner. Further, since the hydrogen permeable film also functions as a gas partition wall for gas molecules other than hydrogen, it is required that the hydrogen permeable film be dense without any film defects such as pinholes. It is important that the porous support used with the hydrogen separation membrane has, in addition to the function of supporting the hydrogen separation membrane, a porosity suitable for the gas containing hydrogen to reach the surface of the hydrogen separation membrane. For example, when the ventilation resistance is high, the rate of supplying or exhausting gas to or from the coating film is slower than the rate of hydrogen separation of the coating film, so that the hydrogen separation efficiency is reduced.

From such a background, the following fuel cells and hydrogen separation cells have been proposed. <Fuel Cell I> As a known fuel cell production method, there is a method of forming an electrolyte layer on a porous substrate by a slurry coating method and performing a sintering heat treatment. By adjusting the particle size and composition of the raw material powder in the slurry, an extremely thin and dense film can be formed. FIG. 2 is a SEM of a fuel battery cell using a fuel electrode support manufactured by a slurry coating method.
An observation photograph is shown [SOFC (VII), 16,1002
(2001)]. This fuel cell is characterized in that the thickness of the electrolyte film is as very thin as 5 μm.

<Fuel Cell II> In Japanese Patent Laid-Open No. 4-92369, a porous substrate made of a sintered body having a porosity of 30 to 50% is spin-coated with an organic material to seal the pores near the surface. A method has been proposed in which pore treatment is performed to form an electrolyte layer having a thickness of 20 μm or less, and an organic material is heat-treated and removed.

<Fuel Cell III> JP-A-10-6456
Japanese Unexamined Patent Publication No. 5 (1994) proposes a method in which a porous support and a green body of an electrolyte layer are laminated and produced by a co-sintering method. By examining the green body components and co-sintering conditions of both layers, it has become possible to simultaneously sinter a porous support and a dense electrolyte layer. FIG. 3 shows an SEM observation photograph of the manufactured solid oxide fuel cell [SOFC
(VII), 16, 94 (2001)]. A dense electrolyte is formed on a porous support that also serves as an electrode layer having a relatively high porosity.

<Fuel Cell IV> A method is known in which an electrolyte layer is formed on a porous support by a thermal spraying method. The thermal spraying method has a feature that the film can be formed while the sealing treatment is performed to some extent by optimizing the raw material powder particle size and the film forming conditions, and the film forming speed is high. However, a sprayed film that is usually formed has several percent of pores, and the film is not dense enough. Therefore, JP-A-9
Japanese Patent No. 50818 proposes a method in which an electrolyte layer is formed by a thermal spraying method, and then an organometallic solution containing a constituent element of the electrolyte is applied to seal and densify.

<Hydrogen Separation Cell I> JP-A-6-91144
In the publication, by plasma spraying method on a porous support,
A manufacturing method has been proposed in which, after forming a film made of a palladium alloy, the film surface is blasted and then subjected to high temperature heat treatment to densify the film.

[0016]

However, the above-mentioned fuel cell and hydrogen separation cell have the following problems. <Fuel Cell I> It is necessary to adjust the particle size of the raw material powder, the slurry component, and the porous shape of the support so that the slurry does not soak into the pores of the porous fuel electrode support. Therefore, since the porosity of the support does not reach 30%, the gas supply and diffusion are insufficient.

<Fuel Cell II> The thinner the film is formed, the more important it is to make the surface of the substrate sealed with the organic material smooth and pinhole-free. In the step I of forming the fuel electrode before spin coating, if the support can be sealed to some extent, the sealing treatment can be performed by the spin coating method.
However, when the porosity is relatively high, the more excellent the gas permeability, such as a high ratio of open pores or a large pore size, the more difficult it is for the spin-coated organic material to remain on the surface of the substrate, and it is difficult to seal the organic material. Poor holes. When a thin film that is thinner than the surface irregularities is formed on it, it is difficult for the film to cover the entire surface of the substrate, and there is a problem that an extremely thin portion is formed or a film defect that a film is not formed occurs. In a fuel cell, gas leakage causes a problem in that the power generation output is reduced and the electrolyte layer is damaged. Further, there is a problem that the combination of the support and the fuel electrode material is limited in order to form a cell having high characteristics as a fuel electrode, which can be sealed to some extent before spin coating.

<Fuel Cell III> A dense electrolyte is formed on an electrode layer / porous support having a relatively high porosity, but the thickness of the electrolyte is as thick as several tens of μm. This is insufficient for thinning the coating film. Therefore, the effect of reducing the IR resistance of the electrolyte layer is insufficient, which causes a problem that the power generation output decreases.

<Fuel Cell IV / Hydrogen Separation Cell I> Since the raw material powder particle size in the thermal spraying method is as large as several to several tens of μm, the film can be formed while the support is sealed to some extent.
There is a problem that the film thickness becomes as thick as several tens to several hundreds μm. Further, since the support is irradiated with the raw material powder melted at a high temperature to form a film, the film formation surface of the support is locally rapidly heated and rapidly cooled. Therefore, there is a problem that cracks easily occur at the interface between the support and the film, for example, when the thermal expansion coefficient of the support and the film differ greatly. In the case of a functional coating film, the interface sometimes fulfills the function, so that there is a problem that an intermediate layer for improving the adhesion cannot be inserted.

The present invention has been made in view of the above problems of the prior art, and an object thereof is to provide a thin film functional structure having excellent durability, a thin film functional structure precursor, and a gas flow rate. Another object of the present invention is to provide a hydrogen separation cell, a single cell for a solid oxide fuel cell, and a method for producing the same, in which power generation output, hydrogen separation efficiency, and other losses are small even when supply pressure changes.

[0021]

As a result of intensive studies to solve the above problems, the present inventors have found that a porous support having communicating pores suitable for gas supply and diffusion has excellent functional characteristics. By coating a dense and thin coating film,
The inventors have found that the above problems can be solved and completed the present invention.

That is, in the thin film functional structure of the present invention, a coating film is provided so as to cover the openings provided on the front surface and / or the back surface of the porous support, and the porosity of the porous support is 30 to 97.
%, The ratio of communicating holes penetrating to the front and back of all the holes is 80 to 100%, and the thickness of the coating film is 0.1 to 0.1%.
It is 100 μm.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION The thin film functional structure and its precursor of the present invention will be described in detail below. In the present specification, “%” indicates a mass percentage unless otherwise specified.
Further, for convenience of description, one surface of the porous support, the electrolyte and the electrode is described as “front surface” or “upper surface”, and the other surface is described as “rear surface” or “lower surface”, but these are equivalent elements. However, configurations in which they are mutually replaced are also included in the scope of the present invention.

The thin film functional structure of the present invention is formed by coating the front surface and / or the back surface of the porous support with a coating film. Here, the porous support has pores, and the porosity is 30.
~ 97%. If it is less than 30%, the function as a gas flow path or the gas diffusion function becomes insufficient. If it exceeds 97%, the mechanical strength as a support decreases. In addition, the ratio of communication holes penetrating to the front and back of all the holes is 80 to 10
It is 0%. By having the communicating pores at such a ratio, the porous support functions as a gas flow path, and gas can be supplied from the outside to the coating film (electrolyte layer or the like). When the continuous porosity is less than 80%, not only the function of the gas flow channel cannot be achieved, but also the strength as a support is lowered. The communicating holes are not limited to the case where one hole communicates with the front and back surfaces, and includes the case where the plurality of holes communicate with each other as a result of communication with each other. The porous support means a foaming method,
A general structure having a certain proportion of pores formed by a sintering method, an elution method, a phase separation method or the like is shown.

As the above-mentioned porous support, a general sintered body can be used, and for example, a mixture of metal powder, surfactant water, a water-soluble resin binder and a non-water-soluble organic solvent is used.
A sintered body having a three-dimensional network structure obtained by evaporating and foaming a non-water-soluble organic solvent and sintering it can be used, and in this case, the porosity can be made extremely high. Further, a porous body obtained by laminating and sintering a metal felt using a fibrous metal wire, a metal cloth, a metal net, or the like can be used. In this case, the porosity and the pore diameter are relatively easy to adjust. Further, a board-shaped punching material in which through holes are formed by regularly patterning a metal thin plate or a ceramic thin plate by an etching method or a machining method can be used. In this case, 100% open porosity (open pores) Is obtained. Furthermore, it is also possible to use a ceramics substrate that has been sintered after being subjected to hole processing with a green body. In particular, since a high open-pore ratio is required in order to function as a gas flow path, it is preferable that the porous support is made of a foam material or a punching material. The shape of the porous support is not particularly limited, and it may be a flat plate, a cylinder or the like.

Further, the porous support has communicating pores, and there are a plurality of openings on the front surface and the back surface, and these openings are covered with a coating film. In the present invention, the maximum film thickness of this coating film is 0.1 to 100 μm. The film thickness is 0.
When it is less than 1 μm, it is not sufficient to fulfill the function of the gas partition wall. If it exceeds 100 μm, for example, when used in a fuel cell, the internal resistance of the cell in the thickness direction (particularly I
R resistance) becomes large, and when used in a hydrogen separation cell, hydrogen permeation resistance becomes large, and the performance of the device deteriorates. An electrode layer, an electrolyte layer, a hydrogen separation membrane, or the like, which will be described later, can be used as the coating film.

Further, it is preferable that the maximum film thickness d of the coating film satisfies the relationship expressed by the following equation 0.01 ≦ d / a ≦ 10 with the maximum opening diameter a of the holes. In this case, it means that the coating film is dense even when the porous support has a high porosity and a large opening diameter. d / a is 0.
When it is less than 01, the film thickness depends on the material of the coating film, but the film thickness is too thin with respect to the opening diameter, so that the gas flow rate and the gas pressure fluctuate, and the thermal shock between the operating temperature and room temperature is reduced. Repeated addition may reduce durability and damage the coating film. When d / a is greater than 10, the film thickness is large with respect to the opening diameter, and therefore, when used in a fuel cell or a hydrogen separation cell, the characteristics are likely to deteriorate.

Furthermore, the maximum opening diameter of the holes is 1 μm.
10 to 10 mm is preferable, and the non-contact area ratio of the porous support to the film formation area of the coating film is 10 to 9 mm.
It is preferably 0%. If the opening diameter of the pores is 1 μm, gas diffusion tends to be insufficient, and if it exceeds 10 mm, the durability of the coating film is lowered and the coating film is easily damaged. Here, the non-contact area ratio is the area ratio of the porous support pores to the film formation surface of the coating film laminated on the porous support. When the non-contact area ratio is less than 10%, the area in which the coating film and the support are bonded is large, and gas diffusion tends to be insufficient. When it exceeds 90%, the coating film has a high proportion of being self-supporting without being adhered to the support, and thus the durability is lowered, and the coating film is easily damaged when the gas flow rate or the gas pressure changes.

The thin film functional structure precursor is formed by coating the coating film on the front surface or the back surface of the porous support having the openings of the pores impregnated with the filler. With such a structure, the thin film functional structure can be easily obtained by removing the filler. Examples of the filler include imide resin, triazine resin, acrylic resin, vinyl resin, epoxy resin, silicon resin, styrene resin, phenol resin, urethane resin, polyolefin resin, and fluororesin. Materials such as the resin material, low-melting glass such as chalcogenide glass, halide glass, chalcogenide glass and oxyhalide glass, low-melting alloy such as solder, and inorganic salt can be appropriately used. Further, the roughness Ra of the surface formed by the opening of the pores impregnated with the filler and the front surface or the back surface of the porous support has a relationship satisfying the following formula Ra ≦ d / 10 with the film thickness d of the coating film. It is preferable that the above condition be satisfied from the viewpoint of the adhesion of the coating film, the strength of the coating film, the gas diffusibility, and the like. If the above formula is not satisfied, a portion where the film thickness becomes extremely thin or a pinhole may be formed.

Next, the single cell for a solid oxide fuel cell of the present invention will be described in detail. First, the first single cell for a solid oxide fuel cell of the present invention (hereinafter abbreviated as “single cell”)
Is formed by using the thin film functional structure, covers an electrolyte layer as the covering film, and coats an air electrode layer or a fuel electrode layer thereon, and a fuel electrode layer on the back surface of the porous support. Alternatively, the air electrode layer is coated so as to be in close contact with the electrolyte layer through the communication holes. In this case, the porous support has a function of supporting the electrolyte layer, a function of diffusing gas, and a function as a gas flow path. Further, in particular, the thin film structure of the electrolyte layer reduces IR resistance and electrode reaction resistance, and improves the output density and power generation efficiency of the fuel cell. For example, as shown in FIG. 4, a large number of patterned communication holes (through holes) are provided on the surface of a porous support which is a punching material, and an electrolyte layer is formed so as to cover the communication holes. A fuel cell layer is formed on the electrolyte layer, while an air electrode layer is formed on the back surface of the porous support, and a single cell that contacts the back surface of the electrolyte layer through an opening in the communicating pores can be mentioned. In the fuel cell using the above single cell, when the porous support also serves as the electrode layer, and when the non-contact area ratio is not within the range of 10 to 90%, the three-phase interface where the electrode reaction takes place decreases. And the reaction resistance of the electrode increases and the output of the fuel cell tends to decrease.

A second unit cell of the present invention is formed by using the thin film functional structure, wherein the surface of the porous support is coated with an air electrode layer or a fuel electrode layer as a coating film, An electrolyte layer and a fuel electrode layer or an air electrode layer are sequentially coated thereon. For example, as shown in FIG. 5, a large number of patterned communication holes (through holes) are provided on the surface of a porous support which is a punching material, and an air electrode layer is formed so as to cover the communication holes. An electrolyte layer is formed on this air electrode layer,
Further, a single cell formed by forming a fuel electrode layer can be mentioned. Further, in this unit cell, a current collector layer is formed on the back surface of the porous support and is in contact with the back surface of the air electrode layer through the opening at the communicating pores. An electrically conductive material such as metal can be used as the current collector. Further, when the porous support has a current collecting function, the coating film may include a layer functioning as a layer mainly responsible for an interfacial reaction at the three-phase interface.
For example, the coating film can be composed of a mixture of lanthanum cobalt oxide generally used as an air electrode material and a ceria-based oxide generally used as an electrolyte material.

The thickness of the coating film (electrolyte layer in the first unit cell, electrode layer in the second unit cell) in the first unit cell and the second unit cell is preferably 1 to 20 μm. Is. If the film thickness is less than 1 μm, for example, the electrolyte layer may be permeable to hydrogen gas or the like, in which case the electrolyte does not function sufficiently and the output decreases when used in a fuel cell. In addition, the catalytic reaction cannot be sufficiently performed on the electrode surface, and the overvoltage increases. On the other hand, when it exceeds 20 μm, the internal resistance of the cell (especially IR resistance) depending on the thickness direction of the electrolyte.
Becomes larger and the output may decrease when used in a fuel cell. Further, the supply and diffusion of the gas becomes rate-determining, and the function deteriorates. Particularly, in the fuel electrode, it takes time to reduce the electrode, and the startability deteriorates.

In the first unit cell and the second unit cell of the present invention, the electrode layer, the electrolyte layer or the porous support as the coating film is used in a conventionally known solid oxide fuel cell. All the materials such as the air electrode material and the fuel electrode material can be mentioned, and the materials are not particularly limited. For example, as the cathode material, strontium, calcium-doped lanthanum manganese oxide, calcium- or strontium-doped lanthanum cobalt oxide, praseodymium cobalt oxide, strontium-doped praseodymium manganese oxide, bismuth-doped lanthanum nickel. Oxide, indium oxide doped with tin,
Examples thereof include lanthanum manganese oxide doped with strontium and cobalt, and lanthanum manganese oxide doped with strontium and chromium. Further, as the electrolyte material, stabilized zirconia added with ruthenia or yttria or samaria, cerium oxide added with gadria or yttria or samaria, strontium,
Examples thereof include lanthanum gallium oxide doped with magnesium, cobalt, copper or iron, and any combination thereof, bismuth oxide solid solution doped with yttria, gadria, and the like. Further, as the fuel electrode material, an alloy containing nickel, cobalt, platinum, palladium, ruthenium, a mixture of the above electrolyte material and these metals, cermet, or the like can be used. Furthermore,
Examples of the porous support that does not serve as an electrode include Ni-based alloy, N
Metals such as i-Cr alloys, iron-nickel alloys, SUS and Si, ceramics such as alumina, titania, zirconia, quartz, cordierite, or glass can be used.

The coating film can function as an electrolyte layer or an electrode layer as described above, and can also increase the film strength, adjust the film stress, increase the adhesive force with the support, Furthermore, although it can exert a function of adjusting the difference in thermal expansion coefficient from the support, various additives can be mixed in order to exert these functions.

Next, the hydrogen separation cell of the present invention will be described in detail. The hydrogen separation cell of the present invention comprises the thin film functional structure, uses a metal as the porous support, and the coating film has a hydrogen separation function. With such a configuration, the hydrogen separation cell has good hydrogen separation efficiency.
As the coating film, for example, palladium or palladium alloy can be used. Examples of the metal include Ni-based alloys, Ni-Cr alloys, iron-nickel alloys,
Metals such as SUS and Si can be used.

Next, the method for producing the single cell for a solid oxide fuel cell of the present invention will be described in detail. In the present manufacturing method, as shown in FIG. 1, the following steps 1) a step of forming a porous support 2) a step of impregnating a porous support with a filler 3) a step of polishing the surface of the porous support 4) Step of forming coating film on porous support 5) Step of removing filler to join porous support, air electrode layer, fuel electrode layer and electrolyte layer to form solid electrolyte described above A unit cell for a fuel cell of a type is obtained. By such a manufacturing method, it is possible to manufacture by making the porosity and the pore diameter of the porous support supporting the coating film extremely large, and further providing an electrode layer or an electrolyte layer which is extremely thinner than the conventional product as the coating film. It will be configured. Therefore, in the fuel cell using the obtained single cell, the gas permeability, the adsorption area and the adsorption rate required for the porous support and the electrode layer are improved, and the fuel utilization rate is increased. Further, the obtained single cell structure realizes weight reduction of the fuel cell. Furthermore, since a single cell can be manufactured by a simple process, it is economical in terms of cost and industrially effective.

Here, in the step of forming the porous support, for example, a known foaming method, sintering method, elution method, phase separation method or the like can be adopted. Specifically, there is a method of sintering raw material powder of metal or ceramics. Further, in order to obtain a porous body having an extremely high porosity, a mixture of metal powder, surfactant water, a water-soluble resin binder and a non-water-soluble organic solvent is used, and the water-insoluble organic solvent is vaporized and foamed. There is a method of sintering into a sintered body having a three-dimensional network structure. Further, as a method for easily adjusting the porosity and the pore diameter (opening diameter), there is a method of laminating and sintering a metal felt made of fibrous metal wire, a metal cloth, a metal net, and the like. Furthermore, as a method of making the open porosity 100%, there is a method of forming a punching board-like support body in which through holes are formed by regularly patterning a metal thin plate or a ceramic thin plate by an etching method or a machining method. is there. Further, it is also possible to use a ceramics substrate or the like, which is sintered after the holes are formed in the green body.

In the step of impregnating the porous support with the filler, for example, a vacuum impregnation method, a melt impregnation method, a dipping method or the like can be adopted. As the filler, for example,
Resin materials such as imide resin, triazine resin, acrylic resin, vinyl resin, epoxy resin, silicon resin, styrene resin, phenol resin, urethane resin, polyolefin resin and fluororesin, chalcogenide glass Materials such as low melting point glass such as halide glass, chalcohalide glass and oxyhalide glass, low melting point alloy such as solder, and inorganic salt can be used. These fillers are appropriately selected depending on the material of the porous support, the surface state and shape of the pores, the thickness of the coating film, the temperature of the porous support at the time of film formation, and the method conditions of the polishing step. It is desirable to be selected.

Since the filler is polished in the polishing step,
It is important that the vicinity of the surface where the coating film is formed is smooth without any filling defect. However, it is not necessary that the support is uniformly filled in the thickness direction. Specifically, the monomer or prepolymer can be impregnated into the pores, and a curing treatment can be performed after the impregnation. At this time, the impregnation step and the curing treatment are repeated twice or more to reduce the filling defects near the surface. Further, during the curing treatment, it is possible to sequentially cure the surface by forming a temperature gradient from the surface on which the coating film is formed to the surface on the opposite side. In addition, the filler can be mixed with various additives, which allows adjustment of the difference in hardness between the support and the cured filler, and the wettability of the support and the cured filler. Alternatively, the viscosity of the filler before curing can be adjusted.

It should be noted that with a porous support alone, it is difficult to process fine grooves and perforations because the processed edge becomes brittle and cracks or cracks occur as the porosity increases.
Therefore, after the impregnation step, a mechanical processing step such as groove processing or perforation processing can be inserted. As a result, it is possible to secure a gas flow path in the porous support impregnated with the filler and to process the flange when assembling the stack. Further, when the functional structure (cell) is incorporated into the fuel cell stack or the hydrogen separation membrane system by the groove processing or the hole processing, the flange processing for joining with the supporting member or the gas manifold can be easily performed. This can simplify the assembly parts of the stack and significantly reduce joints using dissimilar materials. For example, in a hydrogen separation membrane stack or a fuel cell stack that is used at a high temperature of about 500 ° C. or higher, by reducing the number of dissimilar joints, it is possible to obtain an excellent effect that damage due to thermal shock or high temperature can be significantly improved.

Further, in the step of polishing the surface of the porous support, for example, a known lapping method or polishing method,
Mechanochemical polishing methods can be adopted. In this case, it is important that the surface roughness Ra is d / 10 or less with respect to the film thickness d of the coating film formed thereafter. When it is larger than d / 10, a portion where the film thickness becomes extremely thin and pinholes are formed, which is not preferable. The impregnation step and the polishing step can be repeated twice or more.

Furthermore, in the step of forming the coating film on the porous support, a dry method and a wet method can be appropriately adopted. As a dry method, for example, a PV method such as a sputtering method, a vacuum deposition method, an ion plating method, or a laser ablation method is used.
D method (physical vapor deposition method), plasma spraying method, AD method (aerosol deposition method), gas deposition method (GD method), CVD method (chemical vapor deposition method) and the like can be mentioned. Examples of the wet method include a method in which an electrode material or an electrolyte material is applied to the surface of a support by a screen printing method, a slurry coating method, or the like, and then sintered at 1000 to 1500 ° C. Further, a conventionally known electrode forming method such as a sol-gel method may be mentioned, and the method is not particularly limited. By such a film forming method, it is possible to form a dense and thin film having an increased three-phase interface on a porous support having a large porosity and a large pore size by using a raw material powder having a small particle size. .

In the step of removing the filler, the filler can be removed by appropriately combining wet etching with acid, alkali, organic solvent or the like, dry etching, thermal decomposition or melting, and these methods. Prior to the step of removing the filler, a step of forming an electrode layer or a current collector layer is continuously performed, and a reforming catalyst or the like is added to the surface of the support, the opening, the surface of the coating film or the like to perform various functions. It is also possible to perform a step of applying.

[0044]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. In addition, although the single cells for fuel cells are obtained in Examples 1 to 8 and the hydrogen separation cells are obtained in Example 9, each of them is formed by using the thin film functional structure of the present invention.

Example 1 First, LSM (LaSr _0.3 Mn _0.7 O ₃ ) which is a porous electrode as a cell support is used.
Was used. The particle size of LSM was several tens of μm, the porosity was 40%, and the pore size was about 100 μm. LS
The M sintered body was placed in a polyimide raw material before polymerization, vacuum impregnated, and then cured. Such a process was repeated twice to obtain an impregnated body. The obtained impregnated body film-forming surface was mirror-polished to adjust the surface of the sintered body to Ra = 0.1 μm. After that, the substrate temperature is set to room temperature and the electrolyte material Y is formed by the EB deposition method.
A 1 μm film of SZ was formed. After removing the resin by etching the formed impregnated body with hydrazine, as shown in FIG. 6, a thin YSZ having a porosity of 40% is formed on the LSM electrode.
A film was obtained. In addition, a Ni electrode (5μ
m) was formed by a sputtering method to prepare a cell. As a result of conducting a power generation test on such a single cell at 700 ° C., an open circuit voltage is 1.0 V and an output density is 0.2 W / cm.
It was ² .

(Example 2) The polyimide resin impregnated body of the LSM sintered body obtained in Example 1 was mirror-polished to form a 5 μm film of the electrolyte material YSZ by the sputtering method.
A Ni / YSZ electrode (5 μm) as a fuel electrode material was formed thereon by a sputtering method. Then, it was etched with hydrazine to prepare a cell. As a result of performing a power generation test on such a single cell at 700 ° C., the open circuit voltage was 1.0 V and the output density was 0.15 W / cm ² .

Example 3 A cell was prepared by repeating the same operation as in Example 1 except that the chalcogenide glass was melt-impregnated as the filler, and a power generation test was conducted. As a result, the open circuit voltage was 1.1 V and the power density was 0.20.
It was W / cm ² .

Example 4 The porosity of the cell support is 30%.
A cell was prepared by repeating the same operation as in Example 1 except for the above, and a power generation test was performed. As a result, the open circuit voltage was 1.1 V and the power density was 0.15 W / cm ² .

Example 5 The porosity of the cell support is 30%.
Then, the same operation as in Example 1 was repeated except that the YSZ film thickness was set to 5 μm to fabricate a cell, and a power generation test was performed. As a result, the open circuit voltage was 1.1 V and the power density was 0.15 W / cm ² .

(Comparative Example 1) As an electrode support, LSM was used.
A sintered body of (LaSr _0.3 Mn _0.7 O ₃ ) was used.
The particle size was several tens of μm, and the porosity was 20%. A YSZ electrolyte is formed by a printing method, and Ni is used as a fuel electrode on the YSZ electrolyte.
/ YSZ was formed. As a result of SEM observation, the film thickness of the YSZ electrolyte was 20 μm. Other than these, the same operation as in Example 1 was repeated to fabricate a cell, and a power generation test was performed. As a result, the open circuit voltage was 0.8 V and the power density was 0.1 W / cm ² .

(Example 6) A SUS punching board was used as a cell support, and an electrolyte YSZ and a fuel electrode N were provided above the support.
The same operation as in Example 1 was repeated except that i / YSZ was laminated in this order, and the air electrode LSC was formed from the back surface of the punching pod, and a cell as shown in FIG. 7 was produced and a power generation test was conducted. . As a result, the open circuit voltage was 1.0 V and the power density was 0.2 W / cm ² .

Example 7 Porous Ni-C was used as a cell support.
Using an r alloy substrate, an air electrode LSM on the support,
A cell was prepared by repeating the same operation as in Example 1 except that the electrolyte LSGM and the fuel electrode Ni / YSZ were laminated in this order, and a power generation test was performed. As a result, the open circuit voltage is 1.1
V, and the power density was 0.18 W / cm ² .

(Embodiment 8) Foam metal was used for the cell support, and the fuel electrode Ni / SDC, electrolyte SDC, and
The same operation as in Example 1 was repeated except that the laminated air electrodes were laminated in the order of the air electrode LSC to fabricate a cell and a power generation test was performed. As a result, the open circuit voltage was 1.0 V and the power density was 0.16 W / cm ² .

Example 9 A support was used in the same manner as in Example 6, and a palladium film as a coating film was formed by EB vapor deposition.
μm formed. Remove the filler in the same manner as in Example 6,
A hydrogen separation cell was formed. The cell was installed in an evaluation device at 400 ° C., and mixed gas (H ₂ : 70%, CH ₄ : 2%, C
O: 1%, CO ₂ residue) was introduced from the support side, and the flow rate and composition of the gas passing through the membrane were measured by gas chromatography. The permeation gas is 100% hydrogen and the permeation rate is 90 cm.
^{It was 3} / (cm ² · min).

[0055]

[Table 1]

[0056]

[Table 2]

From Table 1, it can be seen that the unit cells obtained in Examples 1 to 5 have an extremely thin coating film in spite of the higher porosity as compared with Comparative Examples 1 and 2. Also,
It can be seen that the output density is also large. In addition, from Table 2, in Examples 6 to 8, although other materials are used for the porous support, since they have d / a ratios within the preferred range of the present invention,
It can be seen that the output density is high. Further, it can be seen that only hydrogen is permeated into the hydrogen separation cell obtained in Example 9 at an excellent permeation rate.

Although the present invention has been described in detail with reference to the embodiments, the present invention is not limited to these, and various modifications can be made within the scope of the gist of the present invention. For example, in the present invention, the shape and the like of the single cell and the hydrogen separation cell can be arbitrarily selected, and a fuel cell can be manufactured according to the target output. Also, a desired battery circuit can be formed by combining the porous support and the insulator. Further, the fuel electrode and the air electrode of the single cell can be arbitrarily arranged according to the gas species (hydrogen, air, etc.) flowing through the gas flow path.

[0059]

As described above, according to the present invention, a porous support having communication pores suitable for gas supply and diffusion is provided with a dense and thin coating film having excellent functional characteristics. Since it is covered, a thin film functional structure with excellent durability, a thin film functional structure precursor, a hydrogen separation cell and a solid electrolyte with little loss in power generation output and hydrogen separation efficiency even when the gas flow rate and supply pressure change A single cell for a fuel cell and a method for manufacturing the same can be provided.

[Brief description of drawings]

FIG. 1 is a flowchart showing a manufacturing process of a fuel cell unit cell.

FIG. 2 is an SEM observation photograph showing an example of a conventional fuel cell (slurry coating method).

FIG. 3 is an SEM observation photograph showing another example of a conventional fuel cell (co-sintering method).

FIG. 4 is a schematic view showing a configuration example of a single cell for a fuel cell of the present invention.

FIG. 5 is a schematic view showing another configuration example of the unit cell for fuel cells of the present invention.

FIG. 6 LSM porous support obtained in Example 1 and Y
It is a SEM observation photograph which shows a SZ coating film.

FIG. 7 is a schematic diagram showing the structure of a fuel cell single cell obtained in Example 6.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01M 8/12 C25B 9/00 L (72) Inventor Keiko Kushibiki 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. Incorporated (72) Inventor Yoshiko Nishitani 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. (72) Inventor Bunki Sato 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa (72) Inventor Makoto Uchiyama 2 Takara-cho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. (72) Inventor Mitsugu Yamanaka 2 Takara-cho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. F-term (reference) 4K011 AA04 AA07 AA12 BA04 BA07 CA04 CA13 DA11 4K021 DB40 DB53 5H018 AA06 AS02 AS03 BB01 BB05 BB07 BB09 BB12 DD01 DD08 EE13 EE17 HH02 HH03 HH04 HH05 5H026 AA06 BB03 BB04 CC05 CX01 CX04 HH02 HH03 HH04

Claims (11)

[Claims] 1. A thin film functional structure comprising a front surface and / or a back surface of a porous support having a plurality of openings on the front surface and a back surface thereof, which is covered with a coating film, wherein the porosity of the porous support is high. Is 30 to 97%, and the ratio of communicating holes penetrating to the front and back of all the holes is 80 to 100.
%, And the maximum film thickness of the coating film is 0.1 to 100 μm. 2. The maximum opening diameter a of the holes and the maximum film thickness d of the coating film satisfy the relation expressed by the following equation 0.01 ≦ d / a ≦ 10. Item 3. The thin film functional structure according to item 1. 3. The maximum opening diameter of the holes is 1 μm to 10 m.
3. The thin film functional structure according to claim 1 or 2, wherein the porous support has a non-contact area ratio of 10 to 90% with respect to the film formation area of the coating film. 4. The thin film functional structure according to claim 1, wherein the porous support is made of a foam material or a punching material. 5. A thin film functional structure precursor which becomes the thin film functional structure according to any one of claims 1 to 4 by removing the filler, wherein the porous support has front and back surfaces. Has multiple openings in
A thin film functional structure precursor characterized in that the opening is impregnated with a filler, and only one of the front surface and the back surface is covered with a coating film. 6. The roughness Ra of the surface formed by the opening of the pores impregnated with the filler and the front surface or the back surface of the porous support is such that the film thickness d of the coating film and the following formula Ra ≦ d / 10. The thin film functional structure precursor according to claim 5, wherein the precursor satisfies the following condition. 7. A single cell for a solid oxide fuel cell comprising the thin film functional structure according to claim 1, wherein the coating film is an electrolyte layer. The surface thereof is coated with an air electrode layer or a fuel electrode layer, and on the back surface of the porous support,
A single cell for a solid oxide fuel cell, characterized in that a fuel electrode layer or an air electrode layer is coated so as to be in close contact with the electrolyte layer through communicating pores. 8. A single cell for a solid oxide fuel cell, which comprises the thin film functional structure according to claim 1, wherein the coating film is an air electrode layer or a fuel. A single cell for a solid oxide fuel cell, which is an electrode layer and is formed by successively coating an electrolyte layer and a fuel electrode layer or an air electrode layer on the surface thereof. 9. The unit cell for a solid oxide fuel cell according to claim 7, wherein the coating film has a thickness of 1 to 20 μm. 10. A hydrogen separation cell using the thin film functional structure according to any one of claims 1 to 4, wherein the porous support is a metal, and the coating film is hydrogen. A hydrogen separation cell having a separation function. 11. A porous support, an air electrode layer, a fuel electrode layer, and an electrolyte layer are joined together to manufacture the unit cell for a solid oxide fuel cell according to any one of claims 7 to 9. A step of forming a porous support, a step of impregnating the porous support with a filler, a step of polishing the surface of the porous support, a step of forming a coating film on the porous support, and a filler. A method for producing a single cell for a solid oxide fuel cell, which comprises performing a removing step.