JPH0987880A - Electrochemical element and manufacturing method thereof - Google Patents

Abstract

(57) [Summary] [Purpose] To efficiently decompose a small amount of NO _x in the presence of O ₂ . [Structure] An electrolyte, a porous cathode and an anode provided to face the electrolyte, and a porous catalyst layer sandwiched between the electrolyte and the cathode, the catalyst layer being a noble metal complex oxide. Included catalyst.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrochemical element for electrochemically decomposing a small amount of nitrogen oxide (NO _x ) in the presence of oxygen (O ₂ ) and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, NO _X emitted from internal combustion engines such as domestic combustors and automobiles is not only harmful to humans, but also causes environmental pollution such as air pollution and acid rain. Therefore, the establishment of a technique for decomposing NO _X is strongly desired, and NO _X is electrochemically converted into nitrogen (N) by using an electrolyte.
₂ ) and an electrochemical device that decomposes into O ₂ are being studied.

Conventionally, an electrochemical element of this kind has been disclosed in Japanese Patent Laid-Open No. 61-61
The configuration as shown in Japanese Patent Publication No. 78421 has been general. As shown in FIG. 6, this is composed of a bottomed cylindrical oxygen ion conductive solid electrolyte 1, a cathode 2 and an anode 3 which are provided on the inner surface and the outer surface of the electrolyte 1 so as to face each other by a method such as printing. By using at least one kind of noble metal for the cathode 2, NO _x is dissociated and adsorbed on the cathode 2, and a DC voltage is applied between the cathode 2 and the anode 3 to coexist in the presence of O ₂ . NO _X
Is electrochemically decomposed into N ₂ and O ₂ .
Further, a catalyst layer made of a catalyst in which a noble metal or a rare earth element is supported on a porous carrier such as alumina (Al ₂ O ₃ ) is provided on the surface of the cathode 2 to accelerate the decomposition of NO _X.

[0004]

However, in the above-mentioned conventional electrochemical device, N which can be decomposed in the coexistence of O ₂ is used.
O _X is very small. For example, a cathode and an anode made of platinum (Pt) are formed on a solid electrolyte made of yttria (Y ₂ O ₃ ) stabilized zirconia (ZrO ₂ ), and rhodium (R) is made on a γ-Al ₂ O ₃ carrier on the cathode.
The electrochemical element provided with a catalyst layer composed of a catalyst supporting h) is heated to 700 ° C. by a heater, and the current density is increased in a gas to be treated containing 1000 ppm of nitric oxide (NO) and 1% of O _2. Has a problem that even when a DC voltage is applied so as to be 200 mA / cm ² , only 0.4% of NO _x can be decomposed and the decomposition efficiency in the coexistence of O ₂ is poor.

The present invention solves such a conventional problem, and its first object is to efficiently decompose even a small amount of NO _{x in the} presence of O ₂ .

Further, when the cathode is laminated on the catalyst layer, if the areas of the catalyst layer and the cathode are equal, the cathode may be displaced and the catalyst layer may protrude, so that the area effective for decomposing NO _X may be reduced. Therefore, a second object is to provide an electrochemical device in which the area effective for decomposing NO _X does not decrease even if the cathode is displaced.

Further, when the size and material of the cathode and the anode are the same, it may not be possible to visually distinguish the cathode and the anode. Therefore, even if the materials of the cathode and the anode are the same, the cathode and the anode can be visually distinguished. A third object is to provide an electrochemical device.

Further, by the process contents in the fabrication of an electrochemical device, or increased work time, not only it may take time and cost, because there are cases where the efficiency of decomposition of the NO _X becomes poor, the efficiency of A fourth object is to provide a good method for manufacturing an electrochemical device.

[0009]

In order to achieve the above first object, an electrochemical device according to a first aspect of the present invention comprises an electrolyte,
A porous cathode and an anode provided facing the electrolyte, and a noble metal sandwiched between the electrolyte and the cathode with LA ₂ M ₃ O _7-X (L is selected from Y, Bi and rare earth elements) At least one element, A is at least one element selected from alkaline earth elements, M
Represents at least one element selected from transition elements, and has a porous catalyst layer to which a composite oxide represented by 0 ≦ X ≦ 1) is added. .

In order to achieve the first object, an electrochemical device according to a second aspect of the present invention has an electrolyte, a porous cathode and an anode provided so as to face the electrolyte, and the electrolyte and the cathode. LA ₂ M ₃ O sandwiched between
_And a porous catalyst layer made of a composite oxide represented by _7-X .

In order to achieve the first object, the electrolyte of the invention of claim 3 has an electrolyte, a porous cathode and an anode provided facing the electrolyte, and between the electrolyte and the cathode. A porous catalyst layer in which a complex oxide having a perovskite type crystal structure is added to the sandwiched noble metal is provided.

In order to achieve the first object, an electrochemical device according to a fourth aspect of the present invention provides an electrolyte, a porous cathode and an anode provided facing the electrolyte, and an electrolyte and a cathode. And a porous catalyst layer made of a composite oxide having a perovskite type crystal structure, which is sandwiched therebetween.

In order to achieve the second object, the electrochemical element of the invention of claim 5 is the same as the electrochemical element of any one of the inventions of claims 1 to 4, and is further provided with an electrolyte and facing the electrolyte. And a porous catalyst layer sandwiched between the electrolyte and the cathode and having a smaller area than the cathode.

In order to achieve the third object, the electrochemical element of the invention of claim 6 is further provided with an electrolyte and the electrolyte element facing the electrolyte according to any one of the inventions of claims 1 to 4. And a porous catalyst layer sandwiched between the electrolyte and the cathode and having a larger area than the cathode.

The electrochemical element of the invention of claim 7 is the electrochemical element of any one of claims 1 to 6, wherein the electrolyte is composed of an oxygen ion conductive solid electrolyte.

An electrochemical device according to an eighth aspect of the present invention is the electrochemical device according to any one of the first to sixth aspects, wherein the cathode is made of a porous precious metal.

In order to achieve the above-mentioned fourth object, the method for manufacturing an electrochemical device according to the ninth aspect of the present invention comprises forming an anode on one surface of an electrolyte and then forming a porous catalyst on the other surface. The layer is printed, dried and fired, and the porous cathode is printed, dried and fired on the catalyst layer.

In order to achieve the fourth object, the method for manufacturing an electrochemical device according to the tenth aspect of the present invention is such that an anode is printed on one surface of the electrolyte and dried, and then the other surface is printed. This is a manufacturing method in which a porous catalyst layer is printed and dried, the anode and the catalyst layer are simultaneously fired, and then a porous cathode is printed, dried and fired on the catalyst layer.

Further, in order to achieve the fourth object, the method for manufacturing an electrochemical element according to the eleventh aspect of the present invention comprises printing, drying and firing a porous catalyst layer on one surface of the electrolyte, It is a manufacturing method in which a porous cathode is printed and dried on the catalyst layer, and then an anode is printed and dried on the other surface with the same material as the cathode, and the cathode and the anode are simultaneously fired.

In order to achieve the fourth object, the method for producing an electrochemical element according to the twelfth aspect of the invention is characterized in that a porous catalyst layer is printed on one surface of the electrolyte, dried, and heated at a temperature of T ₁ . After firing, a porous cathode was printed on the catalyst layer and dried, and then an anode was printed and dried on the other side, and the cathode and the anode were simultaneously heated to a temperature T ₂ (T
It is a manufacturing method in which ₂ ≦ T ₁ ).

[0021]

According to the above-mentioned structure of the electrochemical device of the present invention, LA ₂ M ₃ O _7-X (L is Y, Bi and rare earth) provided in the noble metal sandwiched between the electrolyte and the cathode. At least one element selected from elements, A represents at least one element selected from alkaline earth elements, M represents at least one element selected from transition elements, and 0 ≦ X
A catalyst layer to which a complex oxide represented by
Alternatively, a catalyst layer made of LA ₂ M ₃ O _7-X , or a catalyst layer obtained by adding a perovskite complex oxide to a noble metal,
Or alternatively each of the catalyst layer containing the perovskite-type composite oxide has a characteristic of adsorbing nitrogen oxides in O ₂ presence, any NO _X in trace amounts O ₂ presence selectively adsorbed nitrogen And can be decomposed into oxygen efficiently.

In the above-mentioned structure of the electrochemical device of the fifth aspect of the present invention, since the area of the catalyst layer is smaller than that of the cathode in one of the first to fourth aspects of the invention, when the cathode is laminated on the catalyst layer. never catalyst layer protrudes from the cathode be deviated cathode, NO by protruding _X
There is no reduction in the effective area for the decomposition.

In the above-mentioned structure of the electrochemical device according to the sixth aspect of the present invention, since the area of the catalyst layer is larger than that of the cathode in one of the first to fourth aspects of the present invention, the catalyst layer can be visually observed and the cathode and the anode are separated. Even if the materials are the same, they can be easily distinguished.

[0024] In the above configuration of the electrochemical device of the invention of claim 7, further characterized in that in the invention of claim 6, when applying a DC voltage between the anode and the cathode, NO _X adsorbing the catalyst layer on the cathode side The oxygen that is adsorbed and decomposed by is given an electron to be ionized, but since the electrolysis value is an oxygen ion conductive solid, this is transferred from the cathode to the anode side to release an electron and release it as re-transformed O ₂ . Therefore, the decomposition of NO _X can be further promoted.

In the above-mentioned structure of the electrochemical element of the invention of claim 8, in the invention of claims 1 to 7, the oxygen adsorbed and decomposed when the cathode is a porous noble metal is transferred to the anode side by ionization. It can facilitate and further accelerate the decomposition of NO _x .

In the above-described structure of the method for manufacturing an electrochemical device according to the present invention, since the catalyst layer and the cathode are formed after forming the anode, the anode can be formed by a method such as plating, sputtering, vapor deposition, etc. When manufacturing a large number of chemical elements, the cost can be saved and the electrochemical elements can be efficiently manufactured.

In the above-mentioned structure of the method for producing an electrochemical device according to the tenth aspect of the present invention, since the anode and the catalyst layer are fired at the same time, the number of firing steps is reduced, working time and cost can be saved, and the electrochemical device can be efficiently produced. .

In the above-mentioned structure of the method for manufacturing an electrochemical element according to the eleventh aspect of the present invention, after the catalyst layer is formed, the anode and the cathode are printed with the same material, dried, and fired at the same time, which saves working time and cost. The electrochemical device can be efficiently manufactured.

In the above-mentioned structure of the method for producing an electrochemical device according to the twelfth aspect of the present invention, since the cathode and the anode are fired at a temperature lower than that of the catalyst layer, the catalytic activity of the cathode and the catalyst layer is improved, and in the presence of O ₂ . A minute amount of NO _x can be decomposed more efficiently.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will now be described with reference to the drawings along with some examples.

FIG. 1 shows, in cross section, one embodiment of an electrochemical device according to the present invention. As shown in FIG. 1, a porous cathode 2 and an anode 3 are provided on opposite surfaces of an electrolyte 1 made of an oxygen ion conductive solid, and a porous catalyst layer 4 is formed between the electrolyte 1 and the cathode 2. Has been done.

When the gas to be treated is exposed to such an electrochemical device, NO _x in the gas to be treated diffuses through the porous cathode 2 to the catalyst layer 4, and NO _x coexists in the presence of O _2. Is selectively adsorbed by the catalyst layer 4 having the property of adsorbing and is dissociated into nitrogen and oxygen. When a direct current voltage is applied between the cathode 2 and the anode 3, the oxygen dissociated and adsorbed receives the electron and becomes an oxygen ion, which moves from the cathode to the anode in the electrolyte 1 which is an oxygen ion conductive solid, and emits the electron on the anode. It becomes O ₂ again and desorbs. On the other hand, the dissociatively adsorbed nitrogen becomes N _{2 and} is desorbed. That is, with the above structure, NO _x can be selectively and efficiently decomposed in the coexistence of O ₂ .

Example 1 A first example of this embodiment will be described below. Vertical 25 mm × horizontal 12.5mm firstly the Y ₂ O ₃ was added 8 mol% consists of ZrO ₂ which is stabilized
× Electrolyte 1 having a thickness of 0.5 mm was thoroughly washed, Pt paste was screen-printed on one surface, dried at 100 ° C., and then baked at 820 ° C. for 10 minutes in the air, 23 mm in length × 1 in width
The anode 3 having a thickness of 0.5 mm and a thickness of about 20 μm was formed.
Next, a paste obtained by adding 20 wt% yttrium barium copper oxide (YBa ₂ Cu ₃ O _7-X ) to Pt was screen-printed on the other surface, dried at 100 ° C., and then at 820 ° C. in the atmosphere for 10 minutes. Fired 23 mm long x 10.5 wide
A porous catalyst layer 4 having a size of mm × thickness of about 40 μm was formed.
Next, screen-print a Pt paste on the catalyst layer 4,
After being dried at 100 ° C., it was baked at 820 ° C. for 10 minutes in the atmosphere to form a porous cathode 2 having a length of 23 mm × width of 10.5 mm × thickness of about 20 μm.

Since Pt paste is laminated as the cathode 2 on the porous catalyst layer 4 by a printing method, Pt which is a component of the cathode 2 is partially diffused into the catalyst layer 4 when the cathode 2 is fired, and Some of them are considered to form compounds effective for NO _X decomposition.

The electrolyte 1 is Y ₂ O ₃ in this embodiment.
Stabilized ZrO ₂ was used, but Y ₂ O was added to stabilize it.
_In addition to ₃ , calcium (Ca), strontium (S
r), magnesium (Mg), ytterbium (Y
b), scandium (Sc), lanthanum (La), or other oxides may be added. In addition to ZrO ₂ , ceria (CeO ₂ ), thoria (ThO ₂ ), bismuth oxide (B) may be added.
An oxygen ion conductive solid electrolyte such as i ₂ O ₃ ) may be used.

The sizes of the electrolyte 1, the cathode 2, the anode 3, and the catalyst layer 4 may be different from those used.

Further, although the anode 3 was formed by screen-printing a Pt paste in this embodiment, a conductive metal such as gold (Au) may be used in addition to Pt, and the anode 3 may be formed as in this embodiment. If it is formed before the catalyst layer 4 and the cathode 2, methods other than screen printing such as plating, sputtering, and vapor deposition can be used, which is cost-efficient and efficient when manufacturing a large number of electrochemical elements. Further, the firing temperature and time may be other than those used.

Further, the catalyst layer 4 is composed of Pt and Y in this embodiment.
A catalyst containing Ba ₂ Cu ₃ O _7-X was used, but Au, Rh, palladium (Pd), iridium (I
Other noble metals such as r) may be used. Also YBa ₂ Cu
_{In addition to 3} O _7-X , gadolinium barium copper oxide (GdB
a ₂ Cu ₃ O _7-X ), yttrium strontium copper oxide (YSr ₂ Cu ₃ O _7-X ), etc. LA ₂ M ₃ O
_7-X (L is at least one element selected from Y, B and rare earth elements, A is at least one element selected from alkaline earth elements, and M is at least one element selected from transition elements. Other composite oxides, which represent an element and are represented by 0 ≦ X ≦ 1, may be used. The amount of the noble metal added to the composite oxide may be other than that used.

Further, the cathode 2 is formed by using Pt paste in the present embodiment, but Au, Rh, P other than Pt is used.
Other porous noble metals such as d and Ir may be used.

Next, a Pt lead wire having a diameter of 0.1 mm and a length of 20 mm was fixed on the cathode 2 and the anode 3 with Au paste, and baked in the air at 700 ° C. for 10 minutes. In addition,
Although Pt is used as the lead wire in this embodiment, other conductive metal such as Au may be used. The paste for fixing the lead wire may be other conductive metal such as Pt other than Au.

It is preferable that the electrochemical device obtained as described above is previously energized at a predetermined temperature as a pretreatment. In this example, the electrochemical device is heated by a heater.
It was heated to ℃, connected to the DC power supply through the lead wire between the anode 3 and the cathode 2, 10% O ₂ 100ppm NO
Pretreatment was performed by passing a current for 10 minutes in an atmosphere containing _X so that the current density was about 10 mA / cm ² .
The pretreatment conditions may be temperature, atmosphere, current density and energization time other than those in this embodiment.

Next was measured NO _X amount of decomposition of O ₂ presence by using this electrochemical device.

The electrochemical element was heated to about 450 ° C. with a heater, a direct current power source was connected between the anode 3 and the cathode 2 via a lead wire, and in a gas to be treated containing 10% O ₂ and 70 ppm NO _x. electric current, NO with NO _X scale _X
The amount of decomposition was measured. FIG. 2 shows the relationship between the current density and the NO _X decomposition amount. As shown in FIG. 2, the current density is about 5 mA / cm.
About 40% of the NO _X when the ² is reduced. NO due to stoichiometric N ₂ detected by gas chromatography
_It is considered that _X was decomposed into N ₂ and O ₂ by passing a current. That is, even a small amount of NO _x in the presence of O ₂ can be efficiently decomposed.

(Embodiment 2) In the electrochemical device as the second embodiment, LA ₂ M ₃ is formed on the catalyst layer 4 in the first embodiment.
The same except that a complex oxide represented by O _7-X was used. In this example, YBa ₂ Cu ₃ O _7-X was used for the catalyst layer 4.

Using this electrochemical device, the amount of NO _x decomposed in the coexistence of O ₂ was measured in the same manner as in the first embodiment. When the current density was about 5 mA / cm ² , about 10% NO was obtained.
_X is decomposed, and the decomposition rate is lower than that of the first embodiment, but a small amount of NO _X can be decomposed efficiently in the coexistence of O ₂ .

(Third Embodiment) The electrochemical device of the third embodiment is the same as the first embodiment except that the catalyst layer 4 uses a catalyst in which a complex oxide having a perovskite type crystal structure is added to a noble metal. Are the same. In this embodiment, Pt is 2
0 wt% barium platinum oxide (BaPtO _3-X ) was used. In addition to the above, lanthanum strontium cobalt oxide (La) having a perovskite type crystal structure was used.
_0.6 Sr _0.4 CoO ₃ ), lanthanum cobalt oxide (L
Other complex oxides such as aCoO ₃ ) may be used. Further, the amount of the composite oxide added to the noble metal may be other than that used.

Hereinafter, the electrochemical device of the third embodiment will be described more specifically with reference to FIG. First, BaP
Barium oxide (BaO) to prepare powder of tO _3-X
Powder and Pt powder are mixed, and the temperature is 1000 ° C., 30
After that, it was baked at 800 ° C. for 45 minutes, and then naturally cooled. The powder of BaPtO _3-X thus obtained is sieved so that it can be printed, and particles having a particle size of 50 μm or less are mixed in the Pt paste so that the added amount is about 20 wt%. It was a paste.

In the preparation of BaPtO _3-X , the raw materials other than those used may be used, for example, other barium (Ba) compounds and Pt compounds may be used. Further, the firing temperature and time may be other than the above. Further, the amount added to the Pt paste may be other than the amount used.

Next, the electrolyte 1 composed of Y ₂ O ₃ -stabilized ZrO ₂ was thoroughly washed, and a catalyst paste obtained by adding BaPtO ₃ -X having a perovskite type crystal structure to Pt prepared on one side was screened. After printing and drying at 100 ° C., the catalyst layer 4 was formed by firing in air at 720 ° C. for 10 minutes. Next, a Pt paste was screen-printed on the catalyst layer 4, dried at 100 ° C., and the same P was formed on the other surface.
After the t paste was screen-printed and dried at 100 ° C., the anode 3 and the cathode 2 were exposed to the atmosphere at 720 ° C. for 10 minutes.
Simultaneous firing for minutes.

According to the manufacturing method of the present embodiment, the number of firing steps is one less than that of the first embodiment, so that the working time is reduced,
Not only is the cost low, but because the cathode and anode materials are the same, it is possible to print continuously with the same mask, saving labor, and efficient.

Using this electrochemical device, the amount of NO _x decomposed was measured in a gas to be treated containing 500 ppm NO and 10% O _{2 in the same} manner as in the first embodiment, and the current density was 10 mA / When it is cm ² , about 20% of NO _x is decomposed, and even a small amount of NO _x can be efficiently decomposed even in the coexistence of O ₂ .

(Embodiment 4) The electrochemical element of the fourth embodiment is the same as that of the first embodiment except that the catalyst layer 4 has the perovskite type crystal structure. In this example, La _0.6 Sr _0.4 CoO ₃ was used for the catalyst layer 4.

Using this electrochemical device, the amount of NO _X decomposed in the coexistence of O ₂ was measured in the same manner as in Example 1, and when the current density was 10 mA / cm ² , NO of about 5% was obtained.
_X decomposes, and a small amount of NO _X can be decomposed more efficiently than before even in the coexistence of O ₂ .

(Embodiment 5) The electrochemical element of the fifth embodiment has a catalyst layer 4 formed on one surface of an electrolyte 1 and having a larger area than that of the catalyst layer 4 as shown in the cross section of FIG. This is the same as the first embodiment except that the large cathode 2 is laminated. In this embodiment, the size of the catalyst layer 4 is 21 mm in length × 8.5 m in width.
m × thickness about 40 μm, the size of the cathode 2 is 23 mm in length
The width of the cathode 2 was 10.5 mm and the thickness was about 20 μm, and the cathode 2 was laminated so as to cover the catalyst layer 4. In the first embodiment, since the catalyst layer 4 and the cathode 2 have the same size, it is very difficult to form the cathode 2 on the catalyst layer 4 without shifting as shown in FIG. As catalyst layer 4
NO _X in O ₂ presence in the area of less than the cathode 2
Since it can be decomposed efficiently, the formation of the electrochemical element is simplified, and the cathode is not displaced so that the area effective for NO _X decomposition is not reduced.

(Embodiment 6) In the electrochemical device of the sixth embodiment, as shown in a cross section in FIG. 4, a catalyst layer 4 is formed on one surface of an electrolyte 1 and an area larger than that of the catalyst layer 4 is formed thereon. This is the same as the first embodiment except that the small cathode 2 is laminated. In this embodiment, the size of the catalyst layer 4 is 23 mm in length × 10.5 in width.
mm × thickness about 40 μm, the size of the cathode 2 is 21 m vertically
The cathode 2 was laminated on the catalyst layer 4 with m × 8.5 mm × thickness of about 20 μm. In the first embodiment, the catalyst layer 4 and the cathode 2 have the same size, and since the anode 3 and the cathode 2 are made of the same material, the catalyst layer 4 is formed on either side of the electrolyte 1.
It is difficult to determine whether or not the cathode 2 is formed, and it is difficult to distinguish the cathode 2 and the anode 3. By making the area of the catalyst layer 4 larger than that of the cathode 2 as in the present embodiment, the catalyst layer 4 can be seen, so that the cathode 2 and the anode 3 can be easily distinguished.

(Embodiment 7) The electrochemical element of the seventh embodiment is the same as that of the first embodiment except the manufacturing method.

In this example, the electrolyte was thoroughly washed, the anode was printed and dried on one side, the catalyst layer was printed and dried on the other side, and then baked at 820 ° C. for 10 minutes in the atmosphere. Next, a cathode was printed on this catalyst layer, dried, and then baked in the atmosphere at 820 ° C. for 10 minutes.

When the amount of NO _x decomposition of this electrochemical device was measured in the coexistence of O ₂ as in the case of the first embodiment, almost the same results as in the first embodiment were obtained, and the firing process was performed in the first embodiment. Compared with, there is one less process, so the work time is shorter and the cost is lower.

(Embodiment 8) In the electrochemical device of the eighth embodiment, 20 wt% YBa ₂ Cu ₃ O _{7-X was} added to Pt in the catalyst layer.
This catalyst layer was printed using a catalyst added with, dried, and baked in air at a temperature T ₁ = 820 ° C. for 10 minutes, after which the same Pt paste was used to print the anode and cathode,
Temperature T ₂ lower than the temperature T ₁ at which the catalyst layer was dried and calcined
It was baked at 720 ° C. for 10 minutes.

The electrochemical element thus obtained and, for comparison, both the catalyst layer, the cathode and the anode were 82
Regarding the electrochemical device of the first embodiment baked at 0 ° C. O
_The amount of NO _X decomposition under the coexistence of ₂ was measured. The electrochemical device was heated to 450 ° C., a direct current voltage was applied between the anode and the cathode in a gas to be treated containing 500 ppm NO and 10% O ₂ , and the NO _X decomposition amount was measured by a NO _X meter. FIG. 5 shows the relationship between the current density and the amount of NO _X decomposition. FIG.
In the figure, a circle indicates the present embodiment, and a cross indicates the first embodiment.
As compared with the electrochemical device of the first embodiment, as shown in FIG.
The electrochemical device of this example has a larger amount of NO _X decomposition. That is, as described above, the production method of firing the cathode and the anode at a temperature lower than the temperature at which the catalyst layer is fired seems to improve the activity of the cathode and the catalyst layer,
A small amount of NO _x can be decomposed more efficiently in the coexistence of O ₂ .

[0061]

According to the electrochemical device of the present invention, the catalyst layer provided on the noble metal sandwiched between the electrolyte and the cathode is LA ₂ M ₃ O _7-X (L is Y, At least one element selected from Bi and rare earth elements, A is at least one element selected from alkaline earth elements, M
Represents at least one element selected from the transition elements, and 0 ≦ X ≦ 1) is added to the catalyst layer, LA ₂ M ₃ O _7-X , or a noble metal with By comprising the catalyst layer to which the buskite-type composite oxide is added, or the perovskite-type composite oxide, the catalyst layer can be efficiently decomposed in the presence of O ₂ and even with a small amount of NO _x .

According to the electrochemical element of the invention of claim 5, the area of the catalyst layer is smaller than that of the cathode in any one of the inventions of claims 1 to 4, and therefore when the cathode is laminated on the catalyst layer. The cathode is displaced and the catalyst layer protrudes N
Thereby preventing such an effective area in the degradation of O _X decreases.

The electrochemical element of the invention of claim 6 is the electrochemical element of any one of claims 1 to 4, wherein the area of the catalyst layer is larger than that of the cathode. The same can be easily distinguished.

According to the electrochemical element of the invention of claim 7,
Further, in the inventions of claims 1 to 6, the ionized oxygen adsorbed on the cathode side and decomposed due to the fact that the electrolysis value is an oxygen ion conductive solid is transferred from the cathode to the anode side to emit electrons and re-transform O Since it is released as ₂ , the decomposition of NO _X can be further promoted.

According to the electrochemical element of the invention of claim 8,
Further, in the inventions of claims 1 to 7, since the cathode is a porous noble metal, it facilitates the transfer of the adsorbed and decomposed oxygen to the anode side by ionization.
The decomposition of _X can be further promoted.

According to the method of manufacturing an electrochemical element of the ninth aspect of the present invention, since the catalyst layer and the cathode are formed after forming the anode, the anode can be formed by a method such as plating, sputtering or vapor deposition. When manufacturing a large number of devices, the electrochemical device can be manufactured efficiently with low cost.

According to the method of manufacturing an electrochemical element of the tenth aspect of the invention, since the anode and the catalyst layer are simultaneously fired,
The number of firing steps is reduced, working time and cost can be saved, and an electrochemical element can be efficiently manufactured.

According to the eleventh aspect of the method for producing an electrochemical element of the present invention, after forming the catalyst layer, the anode and the cathode are printed with the same material, dried, and fired at the same time, which saves working time and cost. An electrochemical device can be manufactured efficiently.

According to the method for producing an electrochemical element of the twelfth aspect of the present invention, since the cathode and the anode are fired at a temperature lower than that of the catalyst layer, the catalytic activity of the cathode and the catalyst layer is improved, and a trace amount is present in the presence of O _2. NO _x can be decomposed more efficiently.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first example of one embodiment of an electrochemical device according to the present invention.

FIG. 2 is a current density characteristic diagram of NOx decomposition amount according to the first embodiment of the present invention.

FIG. 3 is a sectional view of an electrochemical device according to a fifth embodiment of the present invention.

FIG. 4 is a sectional view of an electrochemical device according to a sixth embodiment of the present invention.

FIG. 5 is a current density characteristic diagram of NO _X decomposition amount according to a ninth embodiment of the present invention.

FIG. 6 is a cross-sectional view of a conventional electrochemical device.

[Explanation of symbols]

 1 Electrolyte 2 Cathode 3 Anode 4 Catalyst Layer

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kenzo Ochi 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Akio Fukuda 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (12)

[Claims] 1. An electrolyte, a porous cathode and an anode provided so as to face the electrolyte, and a noble metal sandwiched between the electrolyte and the cathode with LA ₂ M ₃ O.
_7-X (L is at least one element selected from Y, Bi and rare earth elements, A is at least one element selected from alkaline earth elements, and M is at least one element selected from transition elements. And a porous catalyst layer to which a complex oxide represented by the formula 0 ≦ X ≦ 1 is added. 2. An electrolyte, a porous cathode and an anode provided so as to face the electrolyte, and LA ₂ M ₃ O _7-X (L is sandwiched between the electrolyte and the cathode).
At least one element selected from Y, Bi and rare earth elements, A is at least 1 selected from alkaline earth
The element M represents at least one element selected from transition elements, and 0 ≦ X ≦ 1), and a porous catalyst layer made of a composite oxide. An electrochemical device that does. 3. An electrolyte, a porous cathode and an anode provided so as to face the electrolyte, a noble metal sandwiched between the electrolyte and the cathode, and a porous oxide obtained by adding a complex oxide having a perovskite type crystal structure. An electrochemical device comprising a high quality catalyst layer. 4. A porous catalyst comprising an electrolyte, a porous cathode and an anode provided facing the electrolyte, and a composite oxide having a perovskite type crystal structure sandwiched between the electrolyte and the cathode. An electrochemical device comprising a layer. 5. The electrochemical device according to claim 1, wherein the catalyst layer has a smaller area than the cathode. 6. The electrochemical device according to claim 1, wherein the catalyst layer has a larger area than the cathode. 7. The electrochemical element according to claim 1, wherein the electrolyte is an oxygen ion conductive solid electrolyte. 8. The electrochemical device according to claim 1, wherein the cathode is a porous precious metal. 9. After forming an anode on one surface of the electrolyte, printing, drying and firing a porous catalyst layer on the other surface, printing and drying a porous cathode on the catalyst layer,
A method of manufacturing an electrochemical device for firing. 10. Printing an anode on one side of the electrolyte,
After drying, then printing and drying a porous catalyst layer on the other side, and simultaneously firing the anode and the catalyst layer,
A method of manufacturing an electrochemical device, comprising printing, drying and firing a porous cathode on the catalyst layer. 11. A porous catalyst layer is printed, dried and fired on one surface of the electrolyte, a porous cathode is printed and dried on the catalyst layer, and then the cathode is formed on the other surface. A method for manufacturing an electrochemical device, in which an anode is printed with the same material as in 1. above, dried, and the cathode and the anode are simultaneously fired. 12. A porous catalyst layer is printed on one surface of the electrolyte, dried, and calcined at a temperature of T ₁ , and then a porous cathode is printed on the catalyst layer, dried, and then the other catalyst layer is printed. A method for producing an electrochemical element, comprising printing an anode on a surface, drying the anode, and simultaneously firing the cathode and the anode at a temperature T ₂ (T ₂ ≤T ₁ ).