JP2002313357A - Single-chamber fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a single-chamber fuel cell having a low internal resistance and emitting a high output. SOLUTION: The single-chamber fuel cell 10 is composed of a base board 12, a first electrode 14 highly active to the oxidation reaction of hydrocarbons formed on the base board 12, a solid oxide electrolyte film 16 of porous nature formed on the first electrode 14, and a second electrode 18 formed on the electrolyte film 16 being low active or inert to the oxidation reaction of hydrocarbons. The electrolyte film 16 has a columnar structure such that columnar crystals 16b have grown in the direction to penetrate the film and should preferably be of porous nature such that voids exist between the columnar crystals 16b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single-chamber fuel cell, and more particularly, to a large-sized power generator for an electric utility business, a small-sized power generator for business or home use, a fuel cell used for a cogeneration system, and the like. The present invention relates to a single-chamber fuel cell suitable for a hydrocarbon sensor or the like.

[0002]

2. Description of the Related Art A fuel cell is provided with a fuel supply from outside,
This is a battery that takes out changes in free energy when fuel is oxidized directly as electric power while continuously discharging combustion products. Fuel cells are classified into various types depending on the type of electrolyte used.
A fuel cell using an oxygen ion conductive solid electrolyte such as partially stabilized zirconia is called a solid oxide fuel cell. Since the solid oxide fuel cell has no problem of electrolyte dissipation and has a high operating temperature (600 to 1000 ° C.), the electrode reaction proceeds rapidly, high-temperature waste heat can be used, and high output and high power can be obtained. There is a feature that conversion efficiency can be expected.

Various proposals have been made for the specific structure of the solid oxide fuel cell. Focusing on the reaction gas supply method, a solid oxide fuel cell generates electricity in a state in which a fuel gas and an oxidant gas are separated (hereinafter, this is referred to as a “membrane type”), and a fuel gas and an oxidant are used. It is classified into a type that generates power using a gas mixture (hereinafter, this is referred to as a “single-chamber type”).

A membrane-type solid oxide fuel cell has an anode and a cathode formed on one side and the other side of an electrolyte membrane, respectively, and a fuel gas supplied to the anode side and an oxidant supplied to the cathode side. The power is generated in a state where the gas and the gas are separated by an electrolyte membrane. The diaphragm type solid oxide fuel cell further depends on the type of separating the reaction gas,
A cylindrical type in which electrodes are formed on both sides of a cylindrical electrolyte, an electrode is formed on both sides of a flat electrolyte, and a flat plate type in which the electrodes are sandwiched by separators, and the electrolyte is made into a honeycomb shape, and the electrodes are formed on both sides of the partition walls. It is roughly divided into the formed integral type.

On the other hand, in a single-chamber solid oxide fuel cell, an anode and a cathode having different catalytic performances for an oxidation reaction of a fuel gas are formed on the same surface or different surfaces of a solid oxide electrolyte. Electric power is generated using a mixed gas of a fuel gas and an oxidizing gas. The reason why an output is obtained by supplying a mixed gas to a single-chamber solid oxide fuel cell is that an oxygen concentration cell is formed due to a difference in catalytic performance between a cathode and an anode.

For example, Solid State Ionics 91 (1996) 6
9, and Japanese Patent Application Laid-Open No. 8-264195 disclose that a solid oxide electrolyte of BaCe _0.8 Gd having a thickness of 1 mm is used.
A single-chamber solid oxide fuel cell using a _0.2 O _{3 -α} plate and forming a palladium electrode (anode) and a gold electrode (cathode) on the same surface of the plate is disclosed.

[0007]

In a diaphragm type solid oxide fuel cell, oxygen ions generated at a cathode are:
Conducted to the anode side through the inside of the electrolyte membrane. Therefore, in order to obtain a high output, it is necessary to reduce the resistance of the electrolyte membrane, and for that purpose, it is necessary to make the electrolyte membrane thin. However, since the electrolyte membrane also functions as a diaphragm for separating a reaction gas, there is a limit in reducing the thickness of the electrolyte membrane.

Further, a membrane type solid oxide fuel cell is
Many components are required, such as an electrolyte, an anode, a cathode, and a separator for separating a reaction gas. Moreover, it is necessary to integrate them so that a sufficient gas seal can be obtained in a high temperature state. However, since these components mainly use fragile ceramics, there is a problem that they are easily broken by thermal stress. Conventionally, in order to solve this problem, means such as matching the thermal expansion coefficients of the electrolyte and other components or using a high-strength material have been used. , No material has been established.

On the other hand, a single-chamber solid oxide fuel cell does not require a separator for separating a reaction gas, and thus has an advantage that the structure is simplified as compared with a diaphragm type. Also, when electrodes are formed on the same surface of the electrolyte,
Oxygen ions generated at the cathode move to the anode side mainly by conducting ions on the surface and the surface layer. Therefore, in order to reduce the resistance of the electrolyte,
It is not always necessary to reduce the thickness. That is, in order to obtain high output in a single-chamber solid oxide fuel cell having electrodes formed on the same surface of the electrolyte, it is necessary to shorten the distance between the electrodes, increase the electrode area, or optimize the electrode shape. Valid (see SolidState Ionics
91 (1996) 69).

[0010] However, for example, when electrodes are formed on the surface of the electrolyte by screen printing, the distance between the electrodes is limited to about 0.5 mm. Further, the electrode area and the electrode shape are limited by the size of the fuel cell. In particular, when forming the anode and the cathode on the same surface of the electrolyte, the area and shape of one electrode are limited by the other electrode. Therefore, in the conventional method, there is a limit in reducing the internal resistance.

An object of the present invention is to reduce the internal resistance of a single-chamber fuel cell and increase the output of the single-chamber fuel cell.

[0012]

Means for Solving the Problems In order to solve the above-mentioned problems, a single-chamber fuel cell according to the present invention comprises a first electrode having a high activity with respect to a hydrocarbon oxidation reaction, and a first electrode provided on the first electrode. A porous solid oxide electrolyte membrane formed, and a porous second electrode formed on the solid oxide electrolyte membrane and having low activity or no activity with respect to a hydrocarbon oxidation reaction. The point is that

In the single-chamber fuel cell according to the present invention, since the first electrode and the second electrode are formed on both surfaces of the solid oxide electrolyte membrane, the distance between the electrodes can be reduced to about the film thickness. Also,
The electrode area and / or shape of the first electrode and the second electrode can be arbitrarily selected without being restricted by the other electrode. Further, since the solid oxide electrolyte membrane is porous, the surface and the surface layer of the pores inside the electrolyte membrane function as an ion conduction path. Therefore, the internal resistance of the single-chamber fuel cell is reduced, and a large current can be obtained. Also,
If the single-chamber fuel cell according to the present invention is applied to a hydrocarbon sensor, it becomes possible to detect low-concentration hydrocarbons with high sensitivity.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a single-chamber fuel cell according to a first embodiment of the present invention. FIG.
1, the single-chamber fuel cell 10 includes a substrate 12, a first electrode 14, a solid oxide electrolyte membrane 16, and a second electrode 18. On the substrate 12, a first electrode 14, a solid oxide electrolyte film 16 and a second electrode 18 are laminated in this order. Further, a lead wire 22 and a lead wire 26 for extracting output are attached to the end of the first electrode 14 and the end of the second electrode 18, respectively.

First, the substrate 12 will be described. The substrate 12 is for supporting the solid oxide electrolyte membrane 16, and is made of a material having sufficient strength and electrical insulation at the operating temperature of the single-chamber fuel cell 10. As a material of the substrate 12, specifically, quartz, alumina, or the like is preferably mentioned as an example.

The thickness of the substrate 12 is not particularly limited.
Can be arbitrarily selected according to the strength required for the above, or the use environment of the single-chamber type fuel cell 10. In FIG. 1, the substrate 12 has a rectangular shape. However, the shape of the substrate 12 is not particularly limited, and can be arbitrarily selected according to the use environment of the single-chamber fuel cell 10. .

Next, the first electrode 14 will be described. The first electrode 14 is an anode of the single-chamber fuel cell 10,
As the material, a material having high activity against the hydrocarbon oxidation reaction is used. Preferable examples of the material of the first electrode 14 include platinum, palladium, nickel, and rhodium.

The thickness of the first electrode 14 is not particularly limited, and the material, forming method, durability,
An optimum thickness may be selected according to cost or the like. For example, a platinum thin film formed by sputtering is
When used as the electrode 14, the thickness is preferably 10 nm or more and 5000 nm or less, more preferably 10 nm or more.
It is not less than 0 nm and not more than 1000 nm.

The area and shape of the first electrode 14 are not particularly limited. Generally, the higher the area of the first electrode 14 is, the higher the output is obtained. However, substrate 1
When the first electrode 14 is formed on the entire surface of the second electrode 2, when the lead wire 26 is attached to the second electrode, the first electrode 14 and the second electrode 1
8 may be short-circuited. Therefore, the first electrode 14
It is desirable that the shape is determined so that a margin is left at least in a portion where the lead wire 26 is attached to the second electrode. In the example shown in FIG. 1, the first electrode 14 is
It is formed on the substrate 12 so as to have a rectangular shape slightly smaller than 2 and leave a margin around the substrate 12.

Next, the solid oxide electrolyte membrane 16 will be described. The solid oxide electrolyte membrane 16 only needs to exhibit oxygen ion conductivity, and its material is not particularly limited. As a material of the solid oxide electrolyte 16,
Specifically, yttria-stabilized zirconia (hereinafter referred to as “YSZ”), calcia-stabilized zirconia,
Scandia-stabilized zirconia, ceria, bismuth oxide and the like are mentioned as preferable examples.

In the present invention, a porous membrane is used as the solid oxide electrolyte membrane 16. The microstructure of the solid oxide electrolyte membrane 16 is not particularly limited, as long as it can diffuse the reaction gas to the first electrode 14 side. However, to get high output,
The solid oxide electrolyte membrane 16 is preferably a porous membrane having a columnar structure in which columnar crystals have grown in a direction penetrating the membrane, and having gaps between the columnar crystals.

When the solid oxide electrolyte membrane 16 is a porous membrane having a columnar structure, the smaller the diameter of each columnar crystal, the better. This is because the smaller the diameter of the columnar crystal, the larger the surface area of the entire solid oxide electrolyte membrane 16 and the lower the resistance. Specifically, the diameter of the columnar crystal is preferably 2 μm or less, more preferably 0.2 μm or less.
μm or less.

The spacing between the columnar crystals is not particularly limited as long as the spacing allows the reaction gas to pass therethrough. The spacing of the gap varies depending on the manufacturing conditions of the solid oxide electrolyte membrane 16, but, for example, when the solid oxide electrolyte membrane 16 having a columnar structure is formed using a sputtering method, the spacing of the gap between the columnar crystals is It is about a fraction of the diameter of the columnar crystal.

The growth direction of the columnar crystals may be any direction as long as it penetrates the solid oxide electrolyte membrane 16. That is, the growth direction of the columnar crystal may be a direction perpendicular to the film surface, or may be a direction in which the angle between the columnar crystal and the film surface is less than 90 ° (hereinafter, referred to as an “oblique direction”). good. However, when forming the second electrode 18, the first electrode 14 and the second
In order to prevent a short circuit with the electrode 18, the growth direction of the columnar crystal is preferably an oblique direction. This will be described later.

The thickness of the solid oxide electrolyte membrane 16 is
The thinner the better, as long as no short circuit occurs between the first electrode 14 and the second electrode 16. This is because as the thickness of the solid oxide electrolyte membrane 16 decreases, the distance between the first electrode 14 and the second electrode 18 decreases, and the resistance of the solid oxide electrolyte membrane 16 decreases. Solid oxide electrolyte membrane 16
Is preferably 5 μm or less, more preferably 1 μm or less.

The shape of the solid oxide electrolyte membrane 16 is as follows.
The substrate 12 and the first electrode 1 are not particularly limited.
4 can be arbitrarily selected according to the use environment of the single-chamber fuel cell 10 and the like. However, when the entire surface of the first electrode 14 is covered with the solid oxide electrolyte film 16,
It becomes difficult to attach the lead wire 22 to the wire. Therefore, it is preferable that the shape of the solid electrolyte membrane 16 be determined so as not to hinder the attachment of the lead wire 22.

In the example shown in FIG. 1, the solid oxide electrolyte film 16 has a rectangular shape in which only the length of the long side is shorter than the substrate 12, and the solid oxide electrolyte film 16 is formed so that one side edge of the first electrode 14 is exposed. 12 and the first electrode 14. The lead wire 22 is attached to a side edge of the first electrode 14 exposed from the solid oxide electrolyte membrane 16.

Next, the second electrode 18 will be described. The second electrode 18 is a cathode of the single-chamber fuel cell 10,
As the material, a material having low activity or no activity with respect to hydrocarbon oxidation reaction is used. Second electrode 1
As a material of No. 8, specifically, gold is a preferred example.

In the present invention, a porous electrode is used as the second electrode 18. The microstructure of the second electrode 18 is not particularly limited as long as the reaction gas can be introduced into the solid oxide electrolyte membrane 16 and conduction can be ensured. Specifically, as the second electrode 18, a porous electrode having a mesh-like microstructure having a large number of isolated through holes is preferable.

The thickness of the second electrode 18 is not particularly limited, and the material, forming method, durability,
An optimum thickness may be selected according to cost or the like. For example, when a gold thin film formed by a sputtering method is used as the second electrode 18, the thickness is 50 nm or more and 1
000 nm or less, more preferably 100 nm or less.
nm or more and 300 nm or less.

The area and shape of the second electrode 18 are not particularly limited. Generally, the higher the area of the second electrode 18 is, the higher the output is obtained. However, when the entire formation region of the second electrode 18 is included in the formation region of the first electrode 14, the first electrode 14 and the second electrode 18 are short-circuited when the lead wire 26 is attached to the second electrode. There is a risk. Therefore, the shape of the second electrode 18 is preferably determined so that the lead wire 26 can be attached in a region where the first electrode 14 is not formed.

In the example shown in FIG. 1, the second electrode 18
Are connected to the rectangular main electrode 18a by a narrow lead wire attaching portion 18;
The main electrode 18a is formed substantially at the center of the substrate 12 in a T-shape provided with a b. The lead wire attaching portion 18b has a length reaching the side edge of the board 12, and the first
The lead wire 26 can be attached in a blank portion of the substrate 12 where the electrode 14 is not formed.

The material of the lead wire 22 attached to the end of the first electrode 14 and the material of the lead wire 26 attached to the end of the second electrode 18 are the same as those of the first electrode 14 and the second electrode 18. The optimum material may be selected according to the use environment, required characteristics, and the like of the single-chamber fuel cell 10, and is not particularly limited.

FIG. 2 is a schematic sectional view of a single-chamber fuel cell 10 according to the present embodiment. In FIG. 2, the second electrode 18 formed on the outermost surface of the single-chamber fuel cell 10 is a porous electrode having a large number of through holes 18c. Also,
The solid oxide electrolyte membrane 16 is an aggregate of columnar crystals 16b grown in an oblique direction, and is a porous film in which gaps having predetermined intervals are formed between the columnar crystals 16b.

Next, the operation of the single-chamber fuel cell according to this embodiment will be described. Predetermined temperature (600 ° C-10
When a mixed gas of a fuel gas containing a hydrocarbon such as methane and an oxidizing gas containing oxygen is supplied to the single-chamber fuel cell 10 heated to (00 ° C.), a part of the mixed gas becomes porous. Second electrode 18 and porous solid oxide electrolyte membrane 16
And diffuses to the first electrode 14 side.

Since the first electrode 14 is made of a material having a high activity with respect to the oxidation reaction of the hydrocarbon, the oxidation reaction of the hydrocarbon contained in the mixed gas proceeds near the first electrode 14. Then, the oxygen concentration in the atmosphere decreases. on the other hand,
Since the second electrode 18 is made of a material having low activity or inactivity with respect to the oxidation reaction of hydrocarbons, the second electrode 1
In the vicinity of 8, the oxygen concentration in the atmosphere does not decrease significantly.

As a result, the first electrode 14 and the second electrode 18
An oxygen concentration cell is formed between them, and a driving force for moving oxygen ions from the second electrode 18 toward the first electrode 14 acts. When a driving force acts between the electrodes, oxygen near the second electrode 18 is dissociated at the second electrode 18 to become oxygen ions, and the generated oxygen ions pass through the solid oxide electrolyte 16 to the first electrode 14. Ion conduction to the side. Thus, a change in free energy when the fuel is oxidized can be extracted as electric energy.

At this time, as the solid oxide electrolyte membrane 16,
When a porous membrane is used, the inner surface and the surface layer of pores inside the electrolyte membrane function as an ion conduction path. In particular, in the case of a porous film having a fine columnar structure, the total surface area becomes extremely large when the surface areas of the columnar crystals are added. Therefore, as compared with a conventional single-chamber fuel cell in which a pair of electrodes face each other on the same surface of a dense electrolyte membrane, the area of the ion conduction surface is significantly increased, and the solid oxide electrolyte membrane 16
Can be reduced in electric resistance.

Further, in the present invention, since the first electrode 14 and the second electrode 18 are formed on both surfaces of the solid oxide electrolyte film 16, the distance between the electrodes can be reduced to about the film thickness. Further, the first electrode and the second electrode can be arbitrarily selected in electrode area and / or shape without being restricted by the other electrode. Therefore, the internal resistance of the single-chamber fuel cell 10 is reduced, and a large current is obtained.

Further, since the internal resistance of the single-chamber fuel cell 10 is reduced, a relatively large output current can be obtained even when the concentration of the hydrocarbon contained in the mixed gas is low. Therefore, if the single-chamber fuel cell according to the present invention is applied to a hydrocarbon sensor, a sensor capable of detecting low-concentration hydrocarbons with high sensitivity can be obtained.

Next, a method for manufacturing the single-chamber fuel cell according to the present embodiment will be described. The single-chamber fuel cell 10 according to the present embodiment can be manufactured by the following procedure. First, a first electrode having a predetermined shape is formed on the substrate 12. The method for forming the first electrode 14 is not particularly limited, and various methods can be used depending on the material of the substrate 12 and the first electrode 14 and the like. For example,
When using platinum as the first electrode 14, a sputtering method is preferable.

Next, a solid oxide electrolyte film 16 having a predetermined shape is formed on the first electrode 14. Since the solid oxide electrolyte film 16 needs to be a porous film, it is preferable to select an optimum film formation method according to the material, the microstructure to be formed, and the like. For example, when a porous YSZ thin film having a columnar structure is used as the solid oxide electrolyte film 16, a sputtering method is preferable.

When a YSZ thin film is formed by a sputtering method, when the film forming conditions, particularly, the temperature and the gas pressure of the substrate 12 are optimized, the YSZ thin film is formed of an aggregate of fine columnar crystals grown in one direction, and Thus, a porous film is obtained in which the gap between the columnar crystals is about a fraction of the diameter of the columnar crystals. In this case, the growth direction of the columnar crystal can be arbitrarily controlled by changing the direction of sputtering.

The growth direction of the columnar crystal is not particularly limited, and may be either a vertical direction or an oblique direction. However, if the columnar crystal is grown in a direction perpendicular to the film surface, the first electrode 14 and the second electrode 18 may be short-circuited when the second electrode 18 is formed. It is preferable to grow them. When the columnar crystal is grown in an oblique direction, the growth direction is not particularly limited as long as the film can be easily formed and a short-circuit between the electrodes can be prevented. 6
A direction of 0 ° is preferred.

Next, a second electrode having a predetermined shape is formed on the solid oxide electrolyte membrane 16. Since the second electrode 18 also needs to be porous, it is preferable to select an optimal film forming method according to the material, the microstructure to be formed, and the like. For example, when a porous gold electrode having a large number of isolated through holes is used as the second electrode 18, a dense film is formed on the surface of the solid oxide electrolyte film 16 using a sputtering method, and then an annealing process is performed. Is preferred.

When the gold thin film formed by the sputtering method is annealed in air at a predetermined temperature for a predetermined time, a porous electrode having a large number of isolated through holes formed in the gold thin film is obtained. . The number and size of the through-holes vary depending on the processing conditions (particularly, the processing temperature and the processing time). Therefore, in the annealing process, the optimal processing time is set so that the desired air permeability and conductivity are secured. It is desirable to choose.

In the case where the solid oxide electrolyte film 16 is a porous film having a columnar structure, when forming the second electrode 18 by sputtering, it is preferable to perform sputtering from a direction different from the growth direction of the columnar crystal. preferable. From the direction parallel to the growth direction of the columnar crystal, the second electrode 1
8, the component particles of the second electrode 18 penetrate into the gaps between the columnar crystals, and the first electrode 14 and the second electrode 1
8 is not preferable because it may cause a short circuit. For example,
When the solid oxide electrolyte membrane 16 is sputtered from an oblique direction, it is preferable that the second electrode 18 be sputtered from the opposite direction (a direction in a mirror image with respect to a plane perpendicular to the membrane).

According to the above procedure, on the substrate 12
After laminating a first electrode 14, a solid oxide electrolyte film 16, and a second electrode 18 having a predetermined shape in this order, a lead wire 22 and a lead wire 26 are provided on the first electrode 14 and the second electrode 18, respectively. When attached, a single-chamber fuel cell 10 according to the present invention is obtained.

In this case, the method of attaching the lead wires 22 and 26 is not particularly limited, but a method of applying a paste containing an electrode component to the electrode and baking the lead wires 22 and 26 using the paste is preferable. .

When the lead wire 22 is baked on the first electrode 14 using a paste, the place where the lead wire 22 is attached is not particularly limited. It can be a place.

On the other hand, when the lead wire 26 is baked on the second electrode 18, the lead wire 26 is baked on the first electrode 14.
Is preferably performed in a portion where is not formed. this is,
Since the second electrode 18 and the solid oxide electrolyte film 16 are both porous films, when the lead wire 26 is baked at the portion where the first electrode 14 is formed, the paste is applied to the surface of the second electrode 18. When applied and heated, the electrode components contained in the paste diffuse inside the solid oxide electrolyte membrane 16,
This is because the first electrode 14 and the second electrode 18 may be short-circuited.

In the single-chamber fuel cell 10 obtained by such a method, the distance between the electrodes is reduced to about the film thickness. In addition, since electrodes are formed on both surfaces of the solid oxide electrolyte membrane 16, the electrode area can be increased. Further, since the solid oxide electrolyte membrane 16 is a porous membrane, the inner surface and surface layer of pores inside the solid oxide electrolyte membrane 16 function as an ion conduction path for oxygen ions. In particular, when the solid oxide electrolyte membrane 16 is a porous membrane having a fine columnar structure, the ion conduction area is dramatically increased as compared with a conventional single-chamber fuel cell. Therefore, a single-chamber fuel cell having a small internal resistance and a large current can be obtained.

Next, a single-chamber fuel cell according to a second embodiment of the present invention will be described. FIG. 3 shows a single-chamber fuel cell according to the present embodiment. In FIG. 3, the single-chamber fuel cell 30 includes a first electrode 34 and a solid oxide electrolyte membrane 3.
6 and a second electrode 38. On the first electrode 34, a solid oxide electrolyte membrane 36 and a second electrode 38 are stacked in this order.

First, the first electrode 34 will be described.
The first electrode 34 is the anode of the single-chamber fuel cell 30, and is made of a material having a high activity with respect to the oxidation reaction of hydrocarbons. In addition, the first electrode 34
At the same time as being an anode, it also has a role as a substrate for supporting the solid oxide electrolyte membrane 36 and the second electrode 38. This point is different from the single-chamber fuel cell 10 according to the first embodiment.

In the present embodiment, a cermet of a catalyst metal and a solid oxide electrolyte having high activity against the oxidation reaction of hydrocarbon is used for the first electrode 34. Specifically, nickel, platinum, palladium, rhodium, and the like are preferable examples of the catalyst metal constituting a part of the first electrode 34. Further, as the solid oxide electrolyte constituting another part of the first electrode 34, specifically,
Preferred examples include YSZ, calcia-stabilized zirconia, scandia-stabilized zirconia, ceria, bismuth oxide, magnesia, and alumina.

The ratio between the catalyst metal and the solid oxide electrolyte contained in the first electrode 34 is determined so that a predetermined activity for the oxidation reaction of hydrocarbons and a predetermined electron conductivity are obtained. May be selected according to the material of the above. For example, when a Ni-YSZ cermet is used as the first electrode 34, the Ni ratio is 40 wt% or more and 80 wt% or more.
wt% or less, more preferably 60 wt% or more and 70 wt% or less.

The first electrode 34 may be a dense body,
Alternatively, it may be a porous body. However, the first
When a porous body is used as the electrode 34, the supply of the reaction gas to the interface between the first electrode 34 and the solid oxide electrolyte membrane 36 is promoted, and thus there is an advantage that a high output can be obtained.

When a porous body is used as the first electrode 34,
The porosity is preferably 5% or more and 70% or less. Porosity of 5
%, It is not preferable because the effect of promoting the supply of the reaction gas is reduced. On the other hand, if the porosity exceeds 70%, the strength of the first electrode 34 decreases, which is not preferable. The porosity of the first electrode 34 is more preferably 10%.
Not less than 50%.

The thickness of the first electrode 34 is set so that the solid oxide electrolyte membrane 36 and the second electrode 38 can be supported with sufficient strength to support the single-chamber fuel cell 30 and the first electrode 3.
4 may be appropriately selected according to the material or the like. For example, the first
When a Ni-YSZ cermet having a porosity of 25% is used as the electrode 34, its thickness is preferably 0.05 mm or more and 5 mm or less, more preferably 0.1 mm or more and 3 mm or less.
It is as follows.

In the example shown in FIG. 3, the first electrode 3
Although 4 has a disk shape, the shape and area of the first electrode are not particularly limited, and are arbitrary depending on the material of the first electrode 34, the use of the single-chamber fuel cell 30, the required characteristics, and the like. Can be selected.

Next, the solid oxide electrolyte membrane 36 will be described. The solid oxide electrolyte membrane 36 is a porous membrane made of a material having oxygen ion conductivity. Further, in the present embodiment, the solid oxide electrolyte membrane 36 is
4 except for an arcuate region located at one end of the first electrode 34.
Is formed on the entire surface of the substrate. The arc-shaped region where the solid oxide electrolyte film 36 is not formed is a region for joining a lead wire (not shown) to the first electrode 34.

When a lead wire is bonded to the back surface of the first electrode 34, a solid oxide electrolyte film 36 may be formed on the entire surface of the first electrode 34. The other configuration of the solid oxide electrolyte membrane 36 is the same as that of the solid oxide electrolyte 16 of the single-chamber fuel cell 10 according to the first embodiment, and a description thereof will be omitted.

Next, the second electrode 38 will be described. The second electrode 38 is a cathode of the single-chamber fuel cell 30,
As the material, a material having low activity or no activity with respect to the hydrocarbon oxidation reaction is used. Also, the second electrode 38
, A porous electrode is used.

In the present embodiment, the second electrode 38
It has a rectangular shape and is formed substantially at the center of the solid oxide electrolyte membrane 36. Further, the second electrode 38 and the solid oxide electrolyte membrane 36
A short-circuit prevention layer 39 is formed on a part of the interface. The short circuit prevention layer 39 is a layer for preventing a short circuit between the second electrode 38 and the first electrode 36 when a lead wire (not shown) is joined to the second electrode 38. Therefore, the short-circuit prevention layer 39
It may be formed at least in a region including a portion to which the lead wire is joined.

The material of the short-circuit prevention layer 39 may be any material as long as a short-circuit between the electrodes can be prevented, and an optimum material may be selected according to the material of the lead wire, the mounting method, and the like. For example, a paste containing an electrode component is applied to the second electrode 38,
When the method of baking the lead wire is used, the short-circuit prevention layer 3
Specific examples of the material of No. 9 include porous Aron ceramics, alumina and the like.

The same applies to the thickness of the short-circuit preventing layer 39, as long as the short-circuit between the electrodes does not occur. The optimum thickness may be selected according to the material of the lead wire, the mounting method, and the like. . For example, when a porous Aron ceramic is used as the short-circuit preventing layer 39, its thickness is 0.5 μm.
Not less than 500 μm, more preferably not more than 1 μm.
m or more and 50 μm or less.

The second electrode 38 may be formed on the entire surface of the solid oxide electrolyte film 36. Also, the second
The other configuration of the electrode 38 is the same as that of the second electrode 18 of the single-chamber fuel cell 10 according to the first embodiment, and thus the description is omitted.

Next, the operation of the single-chamber fuel cell 30 according to the present embodiment will be described. In the single-chamber fuel cell 30 according to the present embodiment, the first electrode 34 and the second electrode 38 having different activities with respect to the oxidation reaction of hydrocarbon are formed on both surfaces of the porous solid oxide electrolyte membrane 36. The electrical resistance of the solid oxide electrolyte membrane 36 can be reduced;
The distance between the electrodes can be reduced to about the film thickness. Further, the first electrode 34 and the second electrode 38 can arbitrarily select the electrode area and / or shape without being restricted by the other electrodes. Therefore, the internal resistance of the single-chamber fuel cell 30 is reduced, and a large current is obtained.

Further, in this embodiment, since the first electrode 34 also serves as the substrate, the structure is simplified and the degree of freedom in selecting the position where the lead wire is to be attached is large. Furthermore, the first
When a porous body is used as the electrode 34, the first electrode 34
Both the reaction gas diffused from the second electrode 38 side and the reaction gas diffused from the first electrode 34 side are supplied to the interface between the solid oxide electrolyte membrane 36 and the solid oxide electrolyte membrane 36, so that the oxidation reaction of the fuel gas is It can proceed efficiently and obtain a high output.

In the single-chamber fuel cell 30 according to the present embodiment, a cermet composed of a catalyst metal and a solid oxide electrolyte is prepared in the usual manner to form the first electrode 34, and then the above-described procedure is followed. It can be manufactured by forming the solid oxide electrolyte membrane 36 and the second electrode 38.

[0071]

EXAMPLE 1 A single-chamber fuel cell 10 having the structure shown in FIG. 1 was manufactured according to the following procedure. First, a Pt electrode (first electrode 14) having a thickness of 400 nm was formed on an alumina substrate (substrate 12) by using a sputtering method. Then, a 1 μm thick YSZ thin film (solid oxide electrolyte film 16) is formed on the Pt electrode by performing sputtering under the conditions of a substrate temperature: 90 ° C. and a gas pressure: 0.4 Pa.
Was formed. The obtained YSZ thin film has a diameter of about 0.2 μm.
Was grown in one direction, and there was a gap between the columnar crystals.

Next, YSZ is formed by sputtering.
After forming an Au thin film having a thickness of 200 nm on the thin film, annealing was performed at 800 ° C. for 1 hour in the air to form a porous Au electrode (second electrode 18). Furthermore, Pt
Pt paste and Au paste were applied to the ends of the electrode and the Au electrode, respectively, and a Pt wire (lead wire 22) and an Au wire (lead wire 26) were baked.

The output characteristics of the obtained single-chamber fuel cell 10 were evaluated. The test conditions were as follows: electrode area: 0.
045 cm ² , cell temperature: 600 ° C., and a mixed gas of methane: oxygen = 2: 1 was used as a reaction gas. As a result, under the condition of a current density of 60 mA / cm ² ,
An output voltage of 0.89 V was obtained.

(Example 2) A single-chamber fuel cell 30 having the structure shown in FIG. 3 was manufactured according to the following procedure. First,
Y containing 64 wt% of NiO powder and 8 mol% of Y ₂ O ₃
After mixing with SZ36wt% in a ball mill for 24 hours,
Dried. Next, the mixture was press-molded at a press pressure of 20 MPa, and the molded body was subjected to 1300 in air.
The resultant was fired at 4 ° C. for 4 hours to obtain a sintered body of NiO and YSZ having a thickness of 1.5 mm. Further, the obtained sintered body is subjected to a reduction treatment in Ar + 20% H ₂ at 900 ° C. for 2 hours to obtain Ni-YSZ having electron conductivity.
I got a cermet.

Next, a YSZ thin film (solid oxide electrolyte film 36) having a thickness of 1 μm was formed on the surface of the Ni-YSZ cermet under the same conditions as in Example 1. Then Y
100 μm thick in the lead wire mounting area of the SZ surface
After the Aron ceramics of the above was formed by the screen printing method, the porous A was formed thereon under the same conditions as in Example 1.
A u electrode (second electrode 38) was formed. Furthermore, Ni-Y
Lead wires were baked on the SZ cermet and the porous Au electrode, respectively.

The output characteristics of the obtained single-chamber fuel cell 30 were evaluated. The test conditions were as follows: electrode area: 0.
045 cm ² , cell temperature: 600 ° C., and a mixed gas of methane: oxygen = 2: 1 was used as a reaction gas. As a result, under the condition of a current density of 75 mA / cm ² ,
An output voltage of 0.9 V was obtained.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various modifications are possible without departing from the gist of the present invention. is there.

For example, in the first embodiment, a single-chamber fuel cell including the first electrode, the solid oxide electrolyte membrane, and the second electrode is formed on one surface of the substrate. A single-chamber fuel cell may be formed, and these may be connected in series or in parallel. Further, the shape of the substrate is not limited to a rectangular flat plate shape, and various shapes such as an arc shape and a cylindrical shape can be used depending on the use of the single-chamber fuel cell.

[0079]

In the single-chamber fuel cell according to the present invention, the first electrode and the second electrode are formed on both surfaces of the porous solid oxide electrolyte, so that the distance between the electrodes can be reduced and the electrode area can be reduced. Can be greatly increased. Further, since the solid oxide electrolyte membrane is porous, the surface and the surface layer of the pores inside the electrolyte membrane function as an ion conduction path, and the resistance of the electrolyte membrane is reduced. Therefore, there is an effect that the internal resistance of the single-chamber fuel cell is reduced and a large current is obtained.

In particular, when a porous film having a columnar structure in which columnar crystals are grown in a direction penetrating the film and a gap is present between the columnar crystals is used as the solid oxide electrolyte membrane, Since the conduction area is dramatically increased, there is an effect that the internal resistance is further reduced and a large current is obtained.

When the first electrode supports the solid oxide electrolyte membrane and the second electrode, and a porous material is used as the first electrode, the reaction gas flows to the interface between the first electrode and the solid oxide electrolyte membrane. There is an effect that the supply is promoted and a high output is obtained.

[Brief description of the drawings]

FIG. 1A is a plan view of a single-chamber fuel cell according to a first embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along line AA ′. .

FIG. 2 is a schematic cross-sectional view of a single-chamber fuel cell including a solid oxide electrolyte membrane having a columnar structure.

FIG. 3A is a plan view of a single-chamber fuel cell according to a second embodiment of the present invention, and FIG. 3B is a cross-sectional view taken along the line AA ′. .

[Explanation of symbols]

 Reference Signs List 10 single-chamber fuel cell 12 substrate 14 first electrode 16 solid oxide electrolyte membrane 16b columnar crystal 18 second electrode 30 single-chamber fuel cell 34 first electrode 36 solid oxide electrolyte membrane 38 second electrode

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Tatsuo Fukano 41-Yokomichi Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture Inside Toyota Central Research Laboratory Co., Ltd. 41, Yokomichi, Toyota Central Research Laboratory Co., Ltd. (72) Inventor Katsunori Yamada 41, Ochi-Cho, Yoji, Nagakute-cho, Aichi-gun, Aichi Prefecture F-term in Toyota Central Research Laboratory Co., Ltd. 4K029 BA43 BA50 BB07 BD00 CA05 5H018 AA06 AS01 BB01 BB07 CC06 DD08 EE03 EE04 EE12 EE13 5H026 AA06 BB04 CX04 EE02 EE08 EE12 EE13

Claims (5)

[Claims] 1. A first electrode having a high activity with respect to an oxidation reaction of a hydrocarbon, a porous solid oxide electrolyte film formed on the first electrode, and a first electrode formed on the solid oxide electrolyte film. And a porous second electrode having low activity or no activity with respect to a hydrocarbon oxidation reaction. 2. The method according to claim 1, wherein the first electrode is a porous body.
2. The single-chamber fuel cell according to 1. 3. The single-chamber fuel cell according to claim 1, further comprising a substrate, wherein the first electrode is formed on the substrate. 4. The solid oxide electrolyte membrane is a porous membrane having a columnar structure in which columnar crystals grow in a direction penetrating the membrane, and wherein a gap exists between the columnar crystals. 4. The single-chamber fuel cell according to 2 or 3. 5. The single-chamber fuel cell according to claim 4, wherein the solid oxide electrolyte membrane is a porous membrane obtained by a sputtering method.