JPH06160344A - Electrochemical element - Google Patents

Abstract

(57) [Summary] [Object] To provide an electrochemical device for detecting nitrogen oxides by measuring an electric current generated by a chemical reaction with nitrogen oxides. A pair of electrodes 2a and 2b are formed on both surfaces of an oxygen ion conductive solid electrolyte 1, and the cathode electrode 2a contains one or more kinds of tungsten oxide or copper-based superconducting metal oxide 4 and a noble metal. The pair of electrodes 2a and 2b form a closed circuit by connecting a DC voltage source 5 in series via a lead wire 6. Nitrogen oxides are selectively adsorbed by the tungsten oxide or the copper-based superconducting metal oxide 4 on the cathode electrode 2a and decomposed into oxygen and nitrogen by an electric field by a DC voltage source, and the oxygen molecules of the decomposition products are converted into noble metals. Since the detection is performed with high sensitivity, the generated current value becomes large. According to this configuration, it is not necessary to raise the temperature of the electrochemical element at the time of measurement, and it is possible to provide a NOx sensor having a simple structure and a long life.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention utilizes the current generated when a nitrogen oxide such as nitric oxide or nitrogen dioxide chemically reacts with an electrode material to detect the concentration of nitrogen oxide in combustion gas, for example. The present invention relates to an electrochemical device.

[0002]

2. Description of the Related Art In recent years, an electrochemical element using an oxygen ion conductive solid electrolyte has been widely used as an oxygen sensor and a nitrogen oxide sensor for controlling combustion in automobile engines and combustion equipment.

The structure of a conventional electrochemical device, for example, a device of a limiting current type oxygen sensor is shown in FIG. In the figure, 11 is an oxygen ion conductive solid electrolyte, and a pair of electrodes 12a and 1 are provided on both surfaces of this oxygen ion conductive solid electrolyte 11.
2b is formed. The electrodes 12a and 12b
Is composed of a noble metal 13 as a main component, and has a pair of electrodes 12.
DC voltage source 14 is connected in series to a and 12b.
5 to form a closed circuit.

After oxygen in the air is adsorbed on the cathode electrode 12a, it reacts with the electrons from the DC voltage source 14 to become oxygen ions, and further diffuses in the oxygen ion conductive solid electrolyte 11 as oxygen ions to form the anode electrode. At 12b, electrons are removed by the DC voltage source 14 to become oxygen, which is desorbed and returns to the air again.

Therefore, the pair of electrodes 12a and 12b
In order to realize the above-mentioned flow of oxygen species, (1) it is porous to accelerate the diffusion of oxygen gas, and (2) for adsorption / desorption of oxygen molecules and reduction / oxidation to oxygen ions. Are required to be active and (3) to be electrically conductive to take out an electric current, and a noble metal such as platinum is generally used as an electrode material satisfying these requirements.

Further, it is different from the limiting current type oxygen sensor in that a closed circuit is not formed by connecting a DC voltage source.
A pair of electrodes 1 on both sides of the oxygen ion conductive solid electrolyte 11
There is a solid oxide fuel cell having a similar structure as an electrochemical device formed with 2a and 12b. In this fuel cell, a perovskite-based composite oxide is used as an electrode material as disclosed in Japanese Patent Laid-Open No. 2-96650, and electrons are obtained by a chemical reaction between oxygen ions and fuel, and the electrons are exposed to the outside. I got it out and got a battery.

On the other hand, tungsten oxide is known as a semiconductor whose electric resistance changes greatly when it comes into contact with nitrogen oxides such as nitric oxide and nitrogen dioxide. This tungsten oxide is an n-type semiconductor, and has the property that when it comes into contact with nitric oxide or nitrogen dioxide, its electrical resistance increases, and the gas sensitivity thereof increases as the concentration of these nitrogen oxides increases. Further, a copper-based superconducting metal oxide is known as a material that adsorbs nitric oxide at a high temperature.

[0008]

However, in the case of an electrochemical device having the above structure, for example, a limiting current type oxygen sensor,
In order to detect the concentration of nitrogen oxides such as nitric oxide and nitrogen dioxide, it is necessary to decompose nitrogen oxides once in an electric field to generate oxygen and detect the generated oxygen. In contrast,
Since the conventional oxygen sensor uses a platinum electrode having high sensitivity to oxygen as an electrode, a generated current value is large for oxygen. However, regarding nitrogen oxide concentration detection,
The amount of oxygen generated by the decomposition of nitrogen oxides is small, and the generated current value is also small because the electrode has no gas selective adsorption. Therefore, to detect the concentration of nitrogen oxides such as nitric oxide and nitrogen dioxide, increase the temperature of the sensor element to increase the amount of oxygen generated by decomposition of nitrogen oxides and increase the generated current value. It was necessary to increase the sensitivity. However, increasing the temperature of the sensor element causes a problem of shortening the life of the element.

On the other hand, in order to decompose nitrogen oxides into oxygen using a metal oxide catalyst, direct decomposition with a catalyst is about 80.
A high temperature of 0 ° C is required. Raising the temperature of the sensor element to this temperature causes a problem that the life of the element is shortened. Further, there is a problem that reducing gas such as hydrocarbon or carbon monoxide is required for decomposition at a low temperature of 500 ° C. or less, which is not practical.

Further, in the constitution in which the perovskite type composite oxide used as the electrode material in the fuel cell is used for the electrode, the complex oxide is a catalyst for promoting the reduction reaction of oxygen molecules to oxygen ions in the cathode electrode. Although it is active for adsorption and reduction of oxygen molecules, it has no ability to decompose nitrogen oxide gas and selective adsorption, and its electron conductivity is inferior to that of precious metals. Therefore, even if the conventional perovskite-based composite oxide electrode is applied to the detection of the concentration of nitrogen oxides in the limiting current type oxygen sensor, the oxygen production due to the decomposition of nitrogen oxides has a completely different reaction form, and the amount of oxygen produced is reduced. . Moreover, since the electron conductivity of the electrode is inferior to that of the noble metal, the generated current value becomes small. Therefore, when these metal oxide electrodes are applied to the concentration detection of nitrogen oxides as limiting current type oxygen, the amount of oxygen generated due to the decomposition of these nitrogen oxides is increased by increasing the temperature of the sensor element to increase the generated current value. Needs to be increased, which causes a problem that the life of the sensor element is shortened.

On the other hand, there is tungsten oxide as a semiconductor whose electric resistance changes when it is brought into contact with nitrogen oxides such as nitric oxide and nitrogen dioxide. However, the sensor resistance in the atmosphere is as high as 10 ⁶ Ω, and the nitrogen oxide is also present. When it comes into contact with an object, the electrical resistance changes in the direction of becoming even higher, which makes it difficult to distinguish between the insulating part generation and the nitrogen oxide detection in the sensor detection circuit, and the problem that the concentration of nitrogen oxide cannot be detected with high accuracy. is there.

Further, as a high temperature adsorbing material for nitric oxide, there is a copper-based superconducting metal oxide, but its electric conductivity is remarkably superior to that of a noble metal. There is a problem that the concentration of nitrogen oxides is so small that it is hardly detectable.

The present invention is intended to solve such a problem, and is capable of selectively adsorbing nitrogen oxides on an electrode, generating a large amount of oxygen due to decomposition of the nitrogen oxides, and having high sensitivity and long life. It is intended to provide an electrochemical device for detection.

[0014]

In order to solve the above problems, the electrochemical device of the present invention comprises a pair of electrodes formed on the surface of an oxygen ion conductive solid electrolyte, and a DC voltage source connected in series to the pair of electrodes. These are connected to form a closed circuit, and at least the cathode electrode material contains at least one of tungsten oxide or copper-based superconducting metal oxide and a noble metal.

[0015]

According to the above structure, nitrogen oxides such as nitric oxide are selectively adsorbed by the tungsten oxide or the copper-based superconducting metal oxide on the cathode electrode of the electrochemical device, where the DC voltage source The formed electric field decomposes into oxygen and nitrogen. Therefore, many oxygen molecules are generated on the electrodes of the electrochemical device due to the decomposition of nitrogen oxides. Moreover, since the electrode is composed of a noble metal electrode having a high electronic conductivity and a high sensitivity to the adsorption / reduction reaction of oxygen molecules, the generated current value is increased and the detection sensitivity is improved. Therefore, it is not necessary to raise the temperature of the electrochemical element during use, and the life can be improved. In addition, since nitrogen oxides are efficiently decomposed into oxygen and nitrogen on the electrode, a practical and easy-to-use sensor can be obtained without the need for reducing agents such as hydrocarbons and carbon monoxide as nitrogen oxide decomposers. Becomes

[0016]

EXAMPLE An electrochemical device of an example of the present invention will be described below with reference to the drawings.

FIG. 1 shows the structure of an electrochemical device according to one embodiment of the present invention. In FIG. 1, 1 is an oxygen ion conductive solid electrolyte, and this oxygen ion conductive solid electrolyte 1
A pair of electrodes 2a and 2b are formed on both surfaces of. The cathode electrode 2a is made of either tungsten oxide or copper-based superconducting metal oxide 4, or both, and the noble metal 3.
Contains. A direct voltage source 5 is connected in series to the pair of electrodes 2a and 2b via a lead wire 6 to form a closed circuit. Tungsten oxide or a copper-based superconducting metal oxide (for example, YBa ₂ Cu ₃ O ₇ or Ba) is used as the noble metal 3.
₂ CuO _3.5 , Gd—Ba—Cu—O) is the only constituent electrode that needs to be the cathode electrode 2a, and the anode electrode 2b is an electrode composed of a noble metal 3 mixed with tungsten oxide or a copper-based superconducting metal oxide 4. , Or an electrode containing only the precious metal 3 or an electrode containing only these metal oxides 4 may be used.

A more detailed description will be given below with reference to specific examples. (Example 1) 92Z as an oxygen ion conductive solid electrolyte
A 10 mm square plate (thickness 0.4 m) formed by using rO ₂ · 8Y ₂ O ₃ (hereinafter referred to as ZrO ₂ · 8 mol Y ₂ O ₃ ).
The electrodes 2a and 2b (area 80 mm ² ) having a thickness of about 10 μm were formed on both surfaces of m) using the thick film printing method. Electrode 2
Samples a and 2b were prepared by mixing sample powder with glass frit (a few%) and a polyvinyl alcohol aqueous solution to form a paste, screen-printing on a zirconia plate, and then firing in air at 800 ° C. for 10 minutes. After that, this pair of electrodes 2
Lead wires were attached to a and 2b, and a DC voltage source was further connected in series to form a closed circuit to obtain an electrochemical element.

The cathode electrode 2a comprises 80% by weight of platinum and 20% by weight of superconducting metal oxide 4 (YBa ₂ Cu ₃ O ₇ ).
Three types were prepared, one using the mixed powder, one using only the platinum powder, and one using only the powder of the superconducting metal oxide (YBa ₂ Cu ₃ O ₇ ) and applied to the cathode electrode 2a. On the other hand, as the anode 2b, an electrode containing only platinum powder was used.

The evaluation of the electrochemical device constructed as described above was carried out by holding the electrochemical device in an electric furnace at 700 ° C., and including a current generated in helium gas containing 5% of nitric oxide and 200 ppm of oxygen. The current generated in the helium gas was measured by changing the applied voltage. The measurement result of this element is shown in FIG. The current shown in the figure was the value after 20 minutes when the measured value was stable.

Platinum and superconducting oxide (YBa ₂ Cu ₃ O
The mixed electrode of ₇ ) generates a larger current than an electrode formed of only platinum or an electrode formed of only superconducting metal oxide.

The reason for this is considered as follows. The platinum-only electrode is active in adsorbing oxygen molecules and reducing it to oxygen ions, but is not active in decomposing nitrogen oxides, and as a result, the amount of decomposed oxygen is reduced and the generated current is thought to be smaller. . On the other hand, an electrode containing only superconducting metal oxide has an excellent selective adsorption property for nitric oxide, but its activity for adsorption of oxygen molecules and reduction to oxygen ions is low, resulting in a small generated current. It is considered to be. On the other hand, the mixed electrode of platinum and superconducting metal oxide (YBa ₂ Cu ₃ O ₇ ) has high activity for adsorption of oxygen molecules and reduction to oxygen ions of the platinum electrode and nitrogen oxide of the superconducting metal oxide electrode. It is considered that the excellent selective adsorption property for nitric oxide coexists, resulting in a large generated current. In particular, the generated current obtained from this mixed electrode is larger than the sum of the generated currents in each of the two electrodes, and a synergistic effect can be seen by using the mixed electrode. This synergistic effect is due to the rapid movement of oxygen due to the high activity of adsorption of oxygen molecules on the platinum electrode and the reduction thereof to oxygen ions, and that YBa ₂ C
It is considered that since the u ₃ O ₇ -based superconducting material has an excellent selective adsorption property for nitric oxide even in the presence of oxygen, a large amount of oxygen is generated.

Comparing the currents in 5% nitric oxide and 200 ppm oxygen, the current in 5% nitric oxide is higher in all electrodes. The reason for this is considered to be that the amount of oxygen generated by the decomposition of nitric oxide by an electric field is considerably larger than 200 ppm of oxygen, so that the electronic conductivity thereof increases and a large amount of current flows.

The electrochemical device with a mixed electrode is
It has been confirmed from this example that nitrogen monoxide is decomposed to generate oxygen and nitrogen, and when a large amount of current flows through the element, the decomposition reaction of nitric oxide is accelerated.

Moreover, platinum and superconductivity (YBa₂Cu₃O
₇) The mixing ratio with the metal oxide is platinum: superconductivity (YB
a₂Cu₃O₇) = 0.1 to 100: 1 wt%
It In particular, superconductivity (YBa₂Cu₃O₇) Metal oxide
Platinum powder 0.1 parts by weight or more per 1 part by weight of powder
Compared to electrodes made only of superconducting metal oxide
The generated current is large. Superconductivity for 1 part by weight of platinum powder
Sex (YBa₂Cu₃O ₇) Metal oxide powder 0.1-9 weight
Compared to an electrode containing only platinum, the electrode containing mixed parts generated current
Was great. Furthermore, superconducting metal oxide (YBa₂C
u₃O₇) Laminate the electrode on top and the platinum only electrode on the bottom
However, a large current was obtained. In addition, copper-based superconducting metal oxide
YBa as a thing₂Cu₃O₇Besides Ba₂CuO_3.5Or
A high current was obtained even with GdBaCuO.

On the other hand, the anode is made of platinum and a superconducting metal.
Oxide (YBa₂Cu₃O₇) With mixed electrode white
The generated current is about the same as when using the gold-only anode electrode.
It decreased by about 15%. In addition to platinum, gold and silver
Similar measurements for electrodes made of rhidium or ruthenium
However, noble metals and superconducting metal oxides (YBa₂Cu ₃
O₇) Mixed electrodes are electrodes containing only precious metals or superconducting metal acids.
The generated current was larger than that of the electrode containing only the oxide.

Further, as the oxygen ion conductive solid electrolyte, other than ZrO ₂ .8Y ₂ O ₃ , (Bi ₂ O ₃ ) _0.85 (N
b ₃ O ₅ ) _0.15 or (Bi ₂ O ₃ ) _0.78 (WO ₃ ) _0.22 ,
Furthermore, oxygen vacancy perovskite-type metal oxide (La
_{Even if} a solid electrolyte such as _1.6 Sr _0.4 CuO ₆ ) is used, noble metal and superconducting metal oxide (YBa ₂ Cu
The mixed electrode of ₃ O ₇ ) generated a larger current than the electrode containing only noble metal or the electrode containing only superconducting oxide.

(Embodiment 2) In this embodiment, the cathode electrode 2 is used.
The powder was formed by adding a powder of tungsten oxide (WO ₃ ) to a, and the effect was measured. The production of the electrode and the measurement of the current were performed in the same manner as in Example 1. Prepare three types of powder, 80% by weight of platinum and 20% by weight of tungsten oxide, powder of only platinum, and powder of only tungsten oxide, and mix each sample powder with several% of glass frit and polyvinyl alcohol aqueous solution. To form a paste, screen-printed on the cathode electrode of a zirconia plate, and baked in air at 800 ° C. for 10 minutes to prepare a cathode electrode. On the other hand, the anode electrode 2
For b, an electrode made of only platinum powder was used.

The evaluation was performed by holding the electrochemical device in an air furnace at 700 ° C. and applying a current generated in helium gas containing 5% of nitric oxide and a current generated in helium gas containing 200 ppm of oxygen. The voltage was changed and each measurement was performed. The results of this measurement are shown in FIG. 3. As the current shown in the figure, the value after 20 minutes when the measured value was stable was used.

A mixed electrode containing platinum and tungsten oxide produces a larger current than an electrode containing only platinum or tungsten oxide. The reason for this is considered as follows. The platinum-only electrode is active in adsorbing oxygen molecules and reducing it to oxygen ions, but has low activity in decomposing nitrogen oxides and lacks selective adsorption of nitric oxide. It is thought that the generated current decreases and the generated current decreases. On the other hand, the electrode containing only tungsten oxide has an excellent selective adsorption property with respect to nitric oxide, but it is considered that the generated current is small due to its low activity with respect to adsorption of oxygen molecules and reduction to oxygen ions.
On the other hand, the mixed electrode of platinum and tungsten oxide coexists with high activity for adsorption of oxygen molecules and reduction to oxygen ions of the platinum electrode and excellent selective adsorption property of tungsten oxide for nitric oxide. It is considered that the generated current becomes large. In particular, the generated current obtained from this mixed electrode is larger than the sum of the generated currents in each of the two electrodes, and a synergistic effect can be seen by using the mixed electrode. This synergistic effect is due to the rapid movement of oxygen due to the high activity of adsorption of oxygen molecules on the platinum electrode and the reduction to oxygen ions, and the excellent selective adsorption of nitric oxide even when tungsten oxide is present in the presence of oxygen. It is considered that this is because a large amount of oxygen is generated because it has

Comparing the currents in 5% nitric oxide and 200 ppm oxygen, a larger current is shown in 5% nitric oxide for all electrodes. The reason for this is considered to be that the amount of oxygen generated by the decomposition of nitric oxide by an electric field is considerably larger than 200 ppm of oxygen, so that the electronic conductivity thereof increases and a large amount of current flows.

The electrochemical device with a mixed electrode is
It was confirmed from this example that nitrogen monoxide is decomposed to generate oxygen and nitrogen, and the reaction of nitric oxide is promoted when a large amount of current flows.

The mixing ratio of platinum and tungsten oxide is platinum: tungsten oxide = 0.5 to 90: 1% by weight.
Is. In particular, a mixed electrode containing 0.5 parts by weight or more of platinum powder with respect to 1 part by weight of tungsten oxide powder produces a larger current than an electrode containing only tungsten oxide.
In the mixed electrode of 0.5 to 9 parts of tungsten oxide powder, the generated current was larger than that of the electrode containing only platinum. Furthermore, a large current was obtained even when the tungsten oxide electrode was laminated on the upper layer and the platinum electrode was laminated on the lower layer.

On the other hand, when the mixed electrode of platinum and tungsten oxide was used as the anode electrode, the generated current was reduced by about 10% as compared with the case of using the electrode of only platinum. Further, in addition to platinum, gold, silver, iridium, and ruthenium electrodes were also evaluated in the same manner. However, the mixed electrode of noble metal and tungsten oxide generated a larger current than the electrode of noble metal alone or tungsten oxide alone.

(Embodiment 3) In this embodiment, a limiting current type sensor was experimentally manufactured using an electrode made of a mixture of platinum and a superconducting oxide (YBa ₂ Cu ₃ O ₇ ). As shown in FIG. 1, the limiting current type sensor of this embodiment encloses the cathode electrode 2a on one side of the solid electrolyte 1 of ZrO ₂ .8Y ₂ O ₃ having electrodes 2a and 2b formed on both sides, and the starting end and the terminating end are In this configuration, glass spiral spacers (not shown) are arranged so as to be spaced apart from each other, and a seal plate (not shown) is further arranged on the spiral spacers. The diffusion-controlling body is composed of a spiral spacer and a seal plate, and the oxygen diffusion passage is formed by a spiral space surrounded by the partition walls of the spiral spacer facing each other, the solid electrolyte 1 and the seal plate.
Oxygen diffuses into the cathode electrode 2a via the oxygen diffusion passage and exhibits limiting current characteristics. The element of this example was evaluated as follows. The limiting current type sensor was held in an electric furnace at 500 ° C., and the current generated in helium gas containing 5% of nitric oxide was measured by changing the applied voltage. The measurement results are shown in FIG.

Superconducting metal oxide (YBa ₂ Cu
_The mixed electrode composed of ₃ O ₇ ) and platinum had a wider voltage range in which a limiting current value was obtained compared with an electrode containing only platinum, and was shifted to a lower voltage side than an electrode containing only platinum. Therefore, it is not necessary to raise the temperature of the sensor element to detect the concentration of nitrogen oxides.

Example 4 In this example, a limiting current type sensor was prepared by using an electrode made of a mixture of platinum and tungsten oxide. The limiting current type sensor is configured in the same manner as in Example 3, and surrounds the cathode electrode 2a on one side of the solid electrolyte 1 of ZrO ₂ .8 mol Y ₂ O ₃ having electrodes formed on both sides as shown in FIG. A spiral spacer (not shown) made of glass is arranged so that the start end and the end are spaced from each other, and a seal plate (not shown) is further arranged above the spiral spacer to form an oxygen diffusion passage. Is formed. The element of this example was evaluated as follows.
The limiting current type sensor was held in an electric furnace at 500 ° C., and the current generated in helium gas containing 5% of nitric oxide was measured by changing the applied voltage. The measurement result is shown in FIG.

The mixed electrode composed of tungsten oxide and platinum had a wider voltage range in which the limiting current value was obtained and shifted to the low voltage side as compared with the electrode containing only platinum. Therefore,
It is not necessary to raise the temperature of the sensor element to detect the concentration of nitrogen oxides.

According to the above examples, the cathode electrode 2a is made of a material containing at least one kind of tungsten oxide or copper-based superconducting metal oxide and a noble metal, so that oxygen generated by decomposition of nitric oxide is produced. Therefore, it was confirmed that the electrochemical device of this example can be applied to the limiting current type sensor for detecting the concentration of nitrogen oxides. Further, this electrochemical element can be applied not only as a nitrogen oxide sensor but also for decomposing nitrogen oxides.

In this embodiment, an example in which platinum is used as the noble metal of the electrode material has been described, but the same effect can be obtained by using palladium.

[0041]

As is apparent from the above description, according to this embodiment, a pair of electrodes are formed on both surfaces of the oxygen ion conductive solid electrolyte plate, and a DC voltage source is connected in series to the pair of electrodes. A closed circuit was constituted so that at least the electrode material of the cathode electrode contained one or more kinds of tungsten oxide or copper-based superconducting metal oxide and a noble metal. According to this structure, nitrogen oxides such as nitric oxide are selectively adsorbed on the cathode electrode by the tungsten oxide or the copper-based superconducting metal oxide, and further decomposed into oxygen and nitrogen by the electric field by the DC voltage source. It Therefore, many oxygen molecules are generated on the electrodes of the electrochemical device due to the decomposition of nitrogen oxides. Moreover, since the electrode uses a noble metal electrode having high sensitivity to adsorption / reduction of oxygen molecules, the generated current value is increased and the detection sensitivity can be improved. Therefore, it is not necessary to raise the temperature of the electrochemical element at the time of measurement, and since it operates at low temperature, the life can be improved. Further, since nitrogen oxides are decomposed into oxygen and nitrogen on the cathode electrode, reducing agents such as hydrocarbons and carbon monoxide are not required,
Simple structure and easy to use.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration of an electrochemical device according to an embodiment of the present invention.

FIG. 2 is a diagram showing nitrogen oxide detection characteristics of the electrochemical device of Example 1.

FIG. 3 is a diagram showing nitrogen oxide detection characteristics of the electrochemical device of Example 2.

FIG. 4 is a diagram showing nitrogen oxide detection characteristics of the electrochemical device of Example 3;

FIG. 5 is a diagram showing nitrogen oxide detection characteristics of the electrochemical device of Example 4.

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

[Explanation of symbols]

 1 Oxygen Ion Conductive Solid Electrolyte 2a Cathode Electrode 2b Anode Electrode 3 Noble Metal 4 Metal Oxide 5 DC Voltage Source

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takahiro Umeda 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Kenzo Koike, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] 1. An electrode which forms a closed circuit by forming a cathode electrode and an anode electrode on the surface of a plate-like oxygen ion conductive solid electrolyte and connecting a direct current power source in series to the electrodes to form at least a cathode electrode. The material contains one or more kinds of nitrogen oxide adsorbing metal oxides and a noble metal, and the electrode material forming the anode electrode is a nitrogen adsorbing metal oxide or noble metal,
Alternatively, an electrochemical device containing the metal oxide and the noble metal. 2. The electrochemical device according to claim 1, wherein the metal oxide is tungsten or a copper-based superconducting metal oxide. 3. The electrochemical device according to claim 1, wherein the noble metal is platinum or palladium.