WO2018182324A1

WO2018182324A1 - Ammonia sensor

Info

Publication number: WO2018182324A1
Application number: PCT/KR2018/003699
Authority: WO
Inventors: 박진수; 김정민; 이태훈; 박준형
Original assignee: 주식회사 코멧네트워크
Priority date: 2017-03-30
Filing date: 2018-03-29
Publication date: 2018-10-04
Also published as: KR101851281B1; JP2020512524A

Abstract

Provided is an ammonia sensor capable of improving detection responsiveness of an ammonia concentration. The ammonia sensor comprises: a plate-shaped sensor element in which a pair of electrodes (2) having different reactivities to ammonia are formed on a plate-shaped surface of a solid electrolyte (1) having oxygen ion conductivity; and a measurement device (12) for measuring at least one of a potential difference or a current between the pair of electrodes (2), wherein both of the pair of electrodes (2) are formed so as to be exposed to a gas to be measured (E); the solid electrolyte (1) is formed to be porous; and a plurality of gas flow holes, through which the gas to be measured (E) flows from one side of the solid electrolyte (1) of the plate-shaped sensor element (20) to the other side opposite to the one side, are formed, in the thickness direction of the plate-shaped sensor element (20).

Description

Ammonia sensor

The present invention provides a measuring device for measuring one of a plate-like sensor element having a pair of electrodes having different reactivity with ammonia on a surface of a plate-like solid electrolyte having oxygen ion conductivity and a potential difference or current between the pair of electrodes. It is related with the ammonia sensor provided with both and a pair of electrodes formed so that it may expose to the gas to be measured.

In such an ammonia sensor, when a pair of electrodes are exposed to the gas to be measured, a reaction for ionizing oxygen contained in the gas to be measured at one electrode proceeds, and oxygen ions generated by the reaction are in the solid electrolyte. The reaction proceeds by oxidizing ammonia contained in the gas to be measured by oxygen ions at the other electrode. With such a pair of electrode reactions, an electromotive force according to the ammonia concentration in the measurement target gas is generated between the pair of electrodes. Therefore, by measuring such electromotive force, it is possible to detect the ammonia concentration contained in the measurement target gas.

As such an ammonia sensor, there exists a thing which detects the ammonia density | concentration of the waste gas discharged | emitted to air | atmosphere from the automobile etc. provided with the urea SCR system (for example, refer patent document 1). This patent document 1 describes adjusting the amount of urea injected into the exhaust gas in the urea SCR system to the amount of urea in which ammonia emission is suppressed in accordance with the ammonia concentration detected by the ammonia sensor. Therefore, in order to reduce the ammonia emitted to the atmosphere from an automobile or the like equipped with such an element SCR system, excellent response of the ammonia sensor is required.

[Preceding technical literature]

(Patent Document 1) Japanese Patent Application Laid-Open No. 2013-40959

Recently, from the viewpoint of environmental protection, the concentration regulation on ammonia emitted from automobiles and the like has been tightened. In order to cope with such a tightening of concentration regulation and to reduce ammonia emitted to the atmosphere from automobiles and the like equipped with the urea SCR system, it is desired to improve the ammonia sensor response.

This invention is made | formed in view of the said situation, and the objective is to provide the ammonia sensor which can improve ammonia concentration detection responsiveness.

Ammonia sensor according to the present invention,

A plate-shaped sensor element having a pair of electrodes having different reactivity with respect to ammonia on the surface of the plate-shaped solid electrolyte having oxygen ion conductivity;

A measuring device for measuring one of a potential difference or a current between the pair of electrodes,

As the ammonia sensor in which all of the pair of electrodes are formed to be exposed to the measurement target gas, the characteristic configuration is

The solid electrolyte is formed of a porous,

The pair of electrodes comprises a first electrode having an oxidation activity for ammonia and a second electrode having a lower oxidation activity for ammonia than the first electrode,

The first electrode includes a material having a high oxidation activity against ammonia, including at least one of ZnO, SnO ₂ and In ₂ O ₃ , 50 to 90 Wt%, 1 to 15 Wt% glass,

In the thickness direction of the said plate-shaped sensor element, many gas flow holes through which the said object gas flows are formed from one side of the solid electrolyte of the said plate-shaped sensor element to the other side facing the said one side.

According to the above characteristic configuration, the gas to be measured passes through the solid electrolyte and flows from one side to the other side of the solid electrolyte of the sensor element. For this reason, the measurement target gas rapidly reaches the entire interface between the solid electrolyte and the electrode where the electrode reaction of the measurement target gas becomes active. As a result, since the electrode reaction of ammonia contained in the measurement target gas proceeds, electromotive force according to the concentration of ammonia is rapidly generated between the pair of electrodes. Since the ammonia concentration can be detected by measuring the electromotive force generated thus quickly by the measuring device, the ammonia concentration detection responsiveness can be improved.

For example, when the solid electrolyte is dense, since one surface of the electrode on which the solid electrolyte is formed is blocked by the solid electrolyte, the flow of the gas to be measured is hindered. In this case, it is inhibited that the gas to be newly introduced from outside reaches the entire interface between the solid electrolyte and the electrode quickly, and the ammonia concentration detection response cannot be improved. In contrast, according to this characteristic configuration, as described above, since the measurement target gas quickly reaches the entire interface between the electrode and the solid electrolyte in which the electrode reaction of the measurement target gas becomes active, the ammonia concentration detection responsiveness can be improved. Can be.

Further, according to the above characteristic configuration,

Since the electrode reaction for oxidizing ammonia in the first electrode is promoted, it is possible to generate electromotive force between the pair of electrodes in a state where the first electrode is an anode and the second electrode is a cathode.

In addition, according to the characteristic configuration, ZnO, SnO ₂ Since In ₂ O ₃ has a high oxidation activity against ammonia, it is possible to accelerate the electrode reaction of oxidizing ammonia contained in the gas to be measured as the first electrode serving as an anode. As a result, since a large electromotive force is generated between the pair of electrodes, it is possible to more accurately detect the ammonia concentration contained in the measurement target gas based on the electromotive force.

Moreover, according to the said characteristic structure, since the 1st electrode contains glass, it is possible to improve the sintering property of a 1st electrode.

Further characteristic configuration of the ammonia sensor according to the present invention,

One of the pair of electrodes is formed on one side of the solid electrolyte, and the sensor element is provided with the other one of the pair of electrodes formed on the other side opposite to one side of the solid electrolyte.

According to the above characteristic configuration, since the gas to be measured passes through the solid electrolyte after passing through the interface between one electrode and the solid electrolyte, and reaches the interface between the other electrode and the solid electrolyte, the electrode reaction of the gas to be measured is It quickly reaches the interface between the solid electrolyte and one electrode which becomes active and the interface between the solid electrolyte and the other electrode. Thereby, since the electrode reaction of ammonia contained in the measurement target gas is promoted, the detection response of ammonia concentration can be improved. In addition, since electrodes are provided on each of one side and the other side of the solid electrolyte, the electrode area can be formed on each of one side and the other side of the solid electrolyte to be wide. Thereby, the electrode reaction of ammonia contained in the measurement object gas can be promoted to each electrode.

A further characteristic configuration of the ammonia sensor according to the invention is that

One side of the solid electrolyte is provided with the sensor element in which the pair of electrodes are formed.

According to the above characteristic configuration, since all the electrodes of the pair of electrodes are formed on one side of the solid electrolyte, the measurement target gas reaches one side of the solid electrolyte provided with all the electrodes, so that it is included in the measurement target. Electromotive force is generated by the electrode reaction of ammonia. Therefore, the electromotive force generated by the electrode reaction of the ammonia contained in the gas to be measured can be measured without the gas to be measured reaching the other side of the solid electrolyte. Thereby, ammonia concentration can be detected quickly.

The second electrode includes a noble metal.

According to the above characteristic configuration, since the noble metal has a high decomposition activity for decomposing oxygen molecules into oxygen ions, it is possible to promote an electrode reaction for oxygen ionizing oxygen contained in the measurement target gas at the second electrode serving as a cathode. Do. As a result, since a large electromotive force is generated between the pair of electrodes, the ammonia concentration contained in the measurement target gas can be detected more accurately based on the electromotive force.

The second electrode includes a material having a decomposition activity for nitrogen oxide gas.

According to the above characteristic configuration, the nitrogen oxide gas contained in the measurement target gas acts on the electrode reaction for oxidizing ammonia, thereby preventing the decrease in the electromotive force generated between the pair of electrodes.

In other words, when the gas to be measured contains nitrogen dioxide as a nitrogen oxide gas, the nitrogen dioxide acts on an electrode reaction for oxidizing ammonia at the first electrode, which is an anode, whereby the electromotive force generated between the pair of electrodes is reduced. Can be. In this case, according to this characteristic configuration, since it is possible to accelerate the electrode reaction for decomposing oxygen ions from nitrogen dioxide contained in the measurement target gas in the cathode, the electromotive force generated between the pair of electrodes Is increased. Therefore, the above-mentioned electromotive force fall can be prevented.

As the concentration of nitrogen dioxide contained in the gas to be measured increases, the amount of decrease in electromotive force generated by the action of nitrogen dioxide on the electrode reaction of the first electrode increases, and similarly, the nitrogen dioxide acts on the electrode reaction of the second electrode. This increases the amount of electromotive force generated. Therefore, at any concentration of nitrogen dioxide, the reduction in electromotive force generated by the action of nitrogen dioxide on the electrode reaction of the first electrode can be prevented by the increase in electromotive force generated by the action of nitrogen dioxide on the electrode reaction of the second electrode. Can be. Therefore, even when nitrogen dioxide is contained in the measurement target gas, it is possible to prevent a decrease in the electromotive force generated between the pair of electrodes.

The material having a decomposing activity for the nitrogen oxide gas is NiO, CuO, Cr ₂ O ₃ , WO _3, 2CuO-Cr ₂ O _3, LaNiO ₃ , LaCoO ₃ , La ₀ _. ₆ Sr ₀ _. ₄ Co ₀ _. ₈ Fe ₀ _. ₂ O ₃ , La ₀ _. ₈ Sr ₀ _. ₂ MnO ₃ or La ₀ _. ₈₅ Sr ₀ _. ₁₅ CrO ₃ At least one of the materials.

According to the above characteristic configuration, as described above, the nitrogen oxide gas contained in the measurement target gas acts on the electrode reaction for oxidizing ammonia, thereby preventing the decrease in the electromotive force generated between the pair of electrodes.

Each of the pair of electrodes comprises at least one of an oxygen ion conductive solid electrolyte, alumina, zirconia and glass.

According to the above characteristic configuration, when each of the pair of electrodes contains a solid electrolyte of oxygen ion conductivity, the interface between the electrode material and the solid electrolyte in which the electrode reaction in the electrode is activated is increased. Therefore, the electrode reaction can be promoted to each of the pair of electrodes.

In addition, when each pair of electrodes contains alumina or zirconia, the electrical resistance value of each pair of electrodes can be adjusted. Specifically, by adjusting the content of alumina or zirconia, which is an insulator, the electrical resistance of each of the pair of electrodes can be adjusted to the desired resistance. For example, by adjusting the electrical resistance of each electrode, the influence of moisture and oxygen, which are coexisting gases contained in the measurement target gas, on the electromotive force generated between the pair of electrodes can be reduced as much as possible.

Furthermore, when each pair of electrodes contains glass, the sinterability of an electrode can be improved. In other words, by containing alumina or zirconia having a high sintering temperature, it is necessary to increase the sintering temperature of the electrode. However, since the glass can be included in the electrode, the sinterability of the electrode can be improved. Even when zirconia is included in the electrode, it is possible to prevent the sintering temperature of the electrode from becoming high.

The solid electrolyte is formed of any one of yttria stabilized zirconia (YSZ), scandia stabilized zirconia (ScSZ), samarium doped ceria (SDC), gadolinium doped ceria (GDC) or thorium dioxide (ThO ₂ ). Is that it is.

According to the above characteristic configuration, since the solid electrolyte has good oxygen ion conductivity, it is possible to efficiently transport oxygen ions generated at the electrode serving as the cathode into the solid electrolyte. And by measuring the large electromotive force which arises with favorable movement of oxygen ion, the ammonia density | concentration contained in the gas to be measured can be detected correctly.

The non-combustible oxidation catalyst layer for oxidizing carbon monoxide and hydrocarbons contained in the measurement target gas is provided on at least one of the one side and the other side of the plate-shaped sensor element.

According to the above characteristic configuration, carbon monoxide and hydrocarbons are oxidized and removed before they enter the pair of electrodes because carbon monoxide and hydrocarbons that may inhibit the electrode reaction in the pair of electrodes are reacted at the pair of electrodes. Can be prevented. Thereby, the fall of the detection precision of ammonia concentration can be prevented.

The unburned oxidation catalyst layer comprises a porous ceramic in which at least one of Pt, Pd, Rh, Ir, Ru or Ag is dispersed and supported.

According to the above characteristic configuration, since it is possible to prevent the carbon monoxide and the hydrocarbon from inhibiting the electrode reaction at the pair of electrodes, it is possible to prevent the decrease in the detection accuracy of the ammonia concentration.

An ammonia oxidation catalyst layer for oxidizing ammonia contained in the measurement target gas is provided on the one side or the other side of the plate-shaped sensor element.

According to the above characteristic configuration, part or all of the ammonia contained in the measurement target gas can be oxidized and removed before the measurement target gas flows into the pair of electrodes. For example, by providing an ammonia oxidation catalyst layer which oxidizes and removes ammonia of a predetermined concentration, when ammonia contained in the measurement target gas is less than or equal to the predetermined concentration, ammonia contained in the measurement target gas is not detected. When exceeding, ammonia can be detected.

The ammonia oxidation catalyst layer is Co ₃ O ₄ , MnO ₂ , V ₂ O ₅ , Ni-Al ₂ O ₃ , Fe-Al ₂ O ₃ , Mn-Al ₂ O ₃ , CuO-Al ₂ O ₃ , Fe ₂ O ₃ -Al ₂ O ₃ , Fe ₂ O ₃ -TiO ₂ , Fe ₂ O ₃ -ZrO ₂ Or at least one of the metal ion exchange zeolites.

According to the above characteristic configuration, as described above, since it is possible to oxidize and remove some or all of the ammonia contained in the measurement target gas before the measurement target gas flows into the pair of electrodes, for example, If ammonia contained in the target gas is below a predetermined concentration, ammonia can be detected without exceeding the predetermined concentration.

The support body which supports the said plate-shaped sensor element is provided in the said one side surface or the said other side surface of the said plate-shaped sensor element,

The said support body is equipped with the heater which heats the said plate-shaped sensor element.

According to the said characteristic structure, since the plate-shaped sensor element is supported by the support body, the mechanical strength of a plate-shaped sensor element can be reinforced. Moreover, since the heater which heats a plate-shaped sensor element is provided, a plate-shaped sensor element can be heated to predetermined optimal temperature.

A support for supporting the plate sensor element is provided on the one side of the plate sensor element, and the carbon monoxide and the hydrocarbon contained in the measurement target gas are provided on the other side of the plate sensor element on which the first electrode is formed. An unburned oxide oxidation catalyst layer for oxidizing and an ammonia oxidation catalyst layer for oxidizing ammonia contained in the gas to be measured are provided in a stacked state.

According to the above characteristic configuration, when the gas to be measured flows in from the other side of the plate sensor element, it passes through the unburned oxidation catalyst layer and the ammonia oxidation catalyst layer and flows into the plate sensor element, thereby inhibiting the electrode reaction of ammonia. Since potential carbon monoxide and hydrocarbons are oxidized and removed before entering the first electrode, a decrease in detection accuracy of the ammonia concentration can be prevented. In addition, since some or all of the ammonia contained in the measurement target gas is oxidized and removed before entering the first electrode, for example, when ammonia contained in the measurement target gas is below a predetermined concentration, ammonia is not detected. Instead, ammonia can be detected when it exceeds a predetermined concentration. In addition, since the plate-shaped sensor element is supported by the support, the mechanical strength of the plate-shaped sensor element can be reinforced.

There is provided a power supply device for applying a constant voltage or a constant current between the pair of electrodes.

According to the above characteristic configuration, the electrode reaction can be promoted in the pair of electrodes by applying a constant voltage or a constant current between the pair of electrodes. Thus, for example, even when the electromotive force generated by the electrode reaction of ammonia is small and it is difficult to detect the ammonia concentration contained in the measurement target gas from the electromotive force, a constant voltage or a constant current is applied between the pair of electrodes. By promoting the ammonia electrode reaction, a large potential difference or current based on the ammonia electrode reaction is generated between the pair of electrodes. By measuring one of this potential difference or an electric current, the ammonia density | concentration contained in the measurement object gas can be detected correctly.

Between the pair of electrodes, there is provided a power supply device for applying a voltage or a current in a state in which the first electrode becomes an anode and in a state in which the second electrode becomes a cathode.

According to the above characteristic configuration, an electrode reaction for oxidizing ammonia contained in the gas to be measured at the first electrode by applying a voltage or a current by a power supply such that the first electrode is an anode and the second electrode is a cathode. This is accelerated, and the electrode reaction which ionizes oxygen contained in the measurement target gas is accelerated in the second electrode. Therefore, as described above, even when the electromotive force generated based on the electrode reaction of ammonia is so small that it is difficult to detect the ammonia concentration contained in the gas to be measured from the electromotive force, the ammonia concentration contained in the gas to be measured is accurately determined. Can be detected.

In the ammonia sensor according to the present invention, the gas to be measured passes through the solid electrolyte and flows from one side to the other side of the solid electrolyte of the sensor element. For this reason, the measurement target gas rapidly reaches the entire interface between the solid electrolyte and the electrode where the electrode reaction of the measurement target gas becomes active. As a result, since the electrode reaction of ammonia contained in the measurement target gas proceeds, electromotive force according to the concentration of ammonia is rapidly generated between the pair of electrodes. Since the ammonia concentration can be detected by measuring the electromotive force generated thus quickly by the measuring device, the ammonia concentration detection responsiveness can be improved.

In addition, the ammonia sensor according to the present invention improves the sinterability of the electrode because a glass component is added to the electrode. The improvement of the sintering property of the electrode can minimize the difference in thermal expansion coefficient between the electrode and the solid electrolyte, thereby improving the mechanical bonding strength. In addition, the addition of the glass component may improve the interfacial stability of the electrode and the solid electrolyte to improve the sensor signal stability. Charge exchange reaction of NH ₃ in the ammonia sensor according to the present invention is the sum of reactions in a plurality of micro-cells, and the interfacial stability of the electrode and the solid electrolyte minimizes the change of the micro-cells. Sensor signal changes can be suppressed.

In addition, the addition of the glass component can improve the signal size of the ammonia sensor according to the present invention. The signal of the ammonia sensor according to the invention is generated by an electrochemical catalyst (with charge exchange) reaction at the electrode of the non-equilibrium target gas. However, the electrode can also play the role of a chemical catalyst (no charge exchange), and when the measurement target gas is an unbalanced gas, the concentration decreases due to the chemical catalysis in the process of passing the electrode through the electrode. The signal from the sensor is reduced because it reaches. Therefore, as the porosity of the electrode increases, the sensitivity decreases, so that the porosity decrease due to the improvement of sinterability due to the addition of the glass component may improve the sensitivity (signal size) of the sensor.

1 is a schematic diagram of an ammonia sensor according to a first embodiment of the present invention.

2 is a cross-sectional view of the ammonia sensor according to the first embodiment of the present invention.

3 is an exploded perspective view of the ammonia sensor according to the first embodiment of the present invention.

4 is a diagram showing a relationship between voltage and current of the ammonia sensor according to the first embodiment of the present invention.

5 is a diagram showing the responsiveness of the ammonia sensor when the ammonia concentration is increased according to the first embodiment of the present invention.

Fig. 6 is a diagram showing the responsiveness of the ammonia sensor when the ammonia concentration is reduced according to the first embodiment of the present invention.

7 is a view showing the effect of the coexistence gas on the electromotive force according to the first embodiment of the present invention

8 is a diagram showing a relationship between ammonia concentration and electromotive force according to the first embodiment of the present invention.

9 is an exploded perspective view of the ammonia sensor according to the second embodiment of the present invention.

10 is a cross-sectional view of the ammonia sensor according to the second embodiment of the present invention.

11 is an exploded perspective view of the ammonia sensor according to the third embodiment of the present invention.

12 is a cross-sectional view of the ammonia sensor according to the third embodiment of the present invention.

13 is a schematic diagram of an ammonia sensor according to another embodiment of the present invention.

[First Embodiment]

EMBODIMENT OF THE INVENTION The 1st Embodiment of the ammonia sensor which concerns on this invention is described below based on drawing. Ammonia sensor according to one embodiment of the invention, e.g., as an element the gas to measure the exhaust gas discharged from the SCR system with a diesel engine, and is used to detect the concentration of ammonia NH ₃ contained in the exhaust gas. In addition, the measurement target gas which the ammonia sensor of this embodiment uses as a measurement target gas is not limited to the discharge gas discharged | emitted from the urea SCR system, and can also use the discharge gas containing other ammonia as a measurement target gas.

As shown to FIG. 1 and FIG. 2, the ammonia sensor 100 which concerns on this embodiment is equipped with the plate-shaped sensor element 20. As shown in FIG. In addition, as shown in FIG. 2, the plate-shaped sensor element 20 includes a plate-shaped solid electrolyte 1 having oxygen ion conductivity and a pair of electrodes 2 formed on the surface of the solid electrolyte 1. One side of the plate-shaped sensor element 20 is provided with a support 3 for supporting the plate-shaped sensor element 20, and the other side of the plate-shaped sensor element 20 is an unburned oxidation catalyst layer 4 for oxidizing carbon monoxide and hydrocarbons contained in the gas to be measured. Is provided. 1 and 2, in the thickness direction of the plate-shaped sensor element 20, the lower side of the drawing toward the support 3 from the plate-shaped sensor element 20 is referred to as one side, and the upper side of the drawing toward the plate-shaped sensor element 20 from the support 3 is referred to as the other side. It is called.

In addition, as shown in FIG. 1, the ammonia sensor 100 is provided with a measuring device 12 that measures either the potential difference or the current between the pair of electrodes 2. This measuring device 12 is connected to a pair of terminals 6 provided in the support 3. The measuring device 12 measures the electromotive force generated between the pair of electrodes 2 with respect to the concentration of ammonia contained in the measurement target gas. Although details are mentioned later, a pair of terminal 6 is connected to the pair of electrode 2 by the lead wire 5 with which the support body 3 was equipped.

When the ammonia sensor 100 exposes the pair of electrodes 2 to the measurement target gas, the exhaust gas ammonia concentration can be detected. For example, when the ammonia sensor 100 is disposed in an exhaust pipe or the like through which the gas to be measured flows, the ammonia concentration of the gas to be measured is detected.

Based on FIG. 2 and FIG. 3, the plate sensor element 20 will be described in detail. Solid electrolyte 1 is formed in a rectangular plate shape. In addition, the solid electrolyte 1 is made of porous material, and the porosity of the porous material is formed to be any porosity between 10% and 80%. In this embodiment, the porosity of the solid electrolyte 1 is formed to be 23%. Moreover, the solid electrolyte 1 is provided with many through-holes from which the gas to be measured reaches from one side of the solid electrolyte 1 to the other side facing the one side. This through hole is formed by connecting fine pores in the solid electrolyte 1.

In addition, the solid electrolyte 1 is made of one of yttria stabilized zirconia (YSZ), scandia stabilized zirconia (ScSZ), samarium-doped ceria (SDC), gadolinium-doped ceria (GDC), or thorium dioxide (ThO ₂ ). It is formed.

A pair of electrodes 2 will be described. In the ammonia sensor 100 according to the present embodiment, one electrode 2a (referred to as one electrode) of a pair of electrodes 2 is formed on one side of the plate-shaped solid electrolyte 1 so as to face one side of the plate-shaped solid electrolyte 1. The plate-shaped sensor element 20 in which the other electrode 2b (called the other electrode) of the pair of electrodes 2 is formed in the other side. That is, one pair of electrodes 2 is provided on each of one side and the other side of the solid electrolyte 1. One electrode 2a and the other electrode 2b are formed in a thin plate shape, and at the same time, are formed in a rectangular shape in a plan view from the thickness direction of the solid electrolyte 1. Moreover, it is formed so that it may be slightly smaller than the solid electrolyte 1 in the planar viewpoint seen from the thickness direction of the solid electrolyte 1.

As indicated by the broken arrow in FIG. 2, for example, the measurement target gas E flows in from the other side of the plate-shaped sensor element 20 and is inside the other electrode 2b, the solid electrolyte 1, and the one electrode 2a. It passes through and flows to one side of the plate-shaped sensor element 20. And the measurement object gas E which flowed to the other side from the other side of the plate-shaped sensor element 20 flows out of the plate-shaped sensor element 20 from the one side side of the plate-shaped sensor element 20. Thus, both of the pair of electrodes 2 provided on one side and the other side of the plate-shaped sensor element 20 are formed to be exposed to the measurement target gas E. In addition, although not shown, the measurement object gas E flows in from one side of the plate-shaped sensor element 20, passes through one electrode 2a, the solid electrolyte 1 and the other electrode 2b, and flows to the other side of the plate-shaped sensor element 20. You may.

The pair of electrodes 2 are a first electrode C having an oxidation activity with respect to ammonia contained in the measurement target gas, and a second electrode D having a lower oxidation activity with respect to ammonia contained in the measurement target gas than the first electrode C. Consists of. In this embodiment, one electrode 2a is referred to as the second electrode D and the other electrode 2b is referred to as the first electrode C. FIG.

Specifically, the first electrode C is ZnO, SnO ₂ and In ₂ O ₃ which are materials having high oxidation activity against ammonia. The second electrode D is formed of a noble metal containing at least one of the above, and having a lower oxidation activity to ammonia than a material having a higher oxidation activity to these ammonias. In this embodiment, the first electrode C is formed including ZnO, and the second electrode D is formed of platinum.

An electrode reaction occurring at the first electrode C and the second electrode D will be described in detail. At the interface between the cathode, the second electrode D, and the solid electrolyte 1, a cathode reaction occurs in which oxygen gas contained in the gas to be measured becomes oxygen ions.

At the interface between the first electrode C, which is an anode, and the solid electrolyte 1, an anode reaction occurs in which oxygen ions contained in the gas to be measured become oxygen gas. In addition, when ammonia is contained in the gas to be measured, an anodic reaction by ammonia occurs as shown in the following formula (2).

Therefore, even if both of the pair of electrodes 2 of the ammonia sensor 100 are exposed to the gas to be measured, the above-described electrode reaction occurs at the first electrode C and the second electrode D, so that the electromotive force according to the concentration of ammonia contained in the gas to be measured is reduced. It occurs between the pair of electrodes 2. When the electromotive force is measured by the measuring apparatus 12, the ammonia concentration contained in the measurement target gas can be detected.

In addition, the first electrode C is formed including one or more of a solid electrolyte, alumina, zirconia, and glass of oxygen ion conductivity. In this embodiment, the 1st electrode C is formed including the solid electrolyte of oxygen ion conductivity, alumina, and glass.

Since the first electrode C contains yttria stabilized zirconia (YSZ), in the first electrode C, the interface between the electrode material and the solid electrolyte increases, so that the electrode reaction is activated. As a result, in the first electrode C, the electrode reaction is promoted. It is preferable that the solid electrolyte of oxygen ion conductivity is contained in the range of 5-30 Wt% in the 1st electrode C. In this embodiment, the oxygen ion conductive solid electrolyte is yttria stabilized zirconia (YSZ) similarly to solid electrolyte 1.

In addition, since the 1st electrode C contains alumina, each said resistance value of the 1st electrode C can be adjusted to desired resistance value. Thereby, the said resistance value of the 1st electrode C can be adjusted so that the bad influence which moisture and oxygen which are coexistence gases contained in the measurement object gas have on ammonia concentration detection as possible as possible can be minimized. It is preferable that alumina is contained in the 1st electrode C in the range of 1-30 Wt%.

In addition, since the first electrode C contains glass, it is possible to improve the sinterability of the first electrode C when the ammonia sensor 100 is made. It is preferable that the glass is contained in the range of 1 to 15 Wt% in the first electrode C. In this embodiment, glass has silicon dioxide as a main component.

In the first electrode C, a material having a high oxidation activity against ammonia is preferably contained in a range of 50 to 90 Wt%. In the present embodiment, the first electrode C contains ZnO, yttria stabilized zirconia, alumina, and glass in a weight ratio of 65: 27: 6: 2, which has a high oxidation activity against ammonia.

The method for detecting ammonia concentration by the ammonia sensor 100 is, for example, before detecting the ammonia concentration of the gas to be measured by the ammonia sensor 100, using an ammonia mixed gas having a known ammonia concentration. The electromotive force generated between the pair of electrodes 2 is measured. Next, based on the measurement results, a relation curve of ammonia concentration and electromotive force is prepared. When detecting the ammonia concentration of the gas to be measured by the ammonia sensor 100, the ammonia concentration corresponding to the electromotive force measured by the measuring device 12 can be detected by referring to the relation curve between the ammonia concentration and the electromotive force created.

In order to implement such a method for detecting ammonia concentration, a detection device (not shown) for detecting the ammonia concentration may be provided. That is, an electromotive force measured by the measuring device 12 is input, and at the same time, the relationship curve between the ammonia concentration and the electromotive force is stored, and a detection device for detecting the ammonia concentration from the input power force and the stored relationship curve is provided. , Ammonia concentration can be detected.

The unburned oxidation catalyst layer 4 shown in FIGS. 1 to 3 is formed in a porous material through which the gas to be measured is permeable, and in order to oxidize carbon monoxide and hydrocarbons contained in the gas to be measured, Pt, Au, Pd, Rh, Ir, Ru, or Ag It is formed of one or more materials selected from precious metals such as these, porous ceramics in which these precious metals are dispersed and supported. In the present embodiment, the unburned oxidation catalyst layer 4 is formed of a porous ceramic dispersedly supported by platinum.

The unburned oxidation catalyst layer 4 is formed in the same dimension as the solid electrolyte 1 from the planar view point viewed from the thickness direction of the solid electrolyte 1. Therefore, the unburned oxidation catalyst layer 4 covers the entirety of the other side surface of the other electrode 2b formed on the other side of the solid electrolyte 1, and at the same time, the periphery of the unburned oxidation catalyst layer 4 is provided at the periphery of the solid electrolyte 1. It is laminated | stacked on the other side surface of the plate-shaped sensor element 20 in close contact.

Based on FIG. 2 and FIG. 3, the support 3 will be described. The support body 3 is formed by stacking the first support plate 3a and the second support plate 3b formed in an elongated shape. The plate-shaped sensor element 20 is provided in the other side surface of the front end side part of the 1st support plate 3a in the longitudinal direction. The plate-shaped sensor element 20 is formed on the other side of the first support plate 3a in a state where one electrode 2a is sandwiched between the solid electrolyte 1 and the support 3, and the peripheral portion of the solid electrolyte 1 is in close contact with the support 3. It is stacked.

A pair of terminals 6 are provided on the other side of the rear end side portion in the longitudinal direction of the first supporting plate 3a. A pair of terminals 6 are connected to the measuring device 12. Moreover, the lead wire 5 which connects a pair of electrode 2 of the plate-shaped sensor element 20 to a pair of terminal 6 is provided in the other side surface of the 1st support plate 3a. Lead wire 5 is made of platinum.

The heater 8 which heats the plate-shaped sensor element 20 is provided between the 1st support plate 3a and the 2nd support plate 3b. The heater 8 is located between the first support plate 3a and the second support plate 3b and at the same time at the front end side portion in the longitudinal direction of the first support plate 3a and the second support plate 3b, and viewed from the thickness direction of the solid electrolyte 1. It is provided in the position which overlaps with the plate-shaped sensor element 20. As shown in FIG. Moreover, the pair of heater terminals 9 is provided in the rear end side part of the 2nd support plate 3b in the longitudinal direction. The heater 8 and the pair of heater terminals 9 are connected by a heater connecting line 10. The pair of heater terminals 9 are provided on one side of the second support plate 3b and are connected to a heater power supply (not shown). The heater 8 can be heated to a predetermined temperature by this heater power supply.

The first support plate 3a and the second support plate 3b are made of dense alumina and yttria stabilized zirconia (YSZ). In addition, when formed from yttria stabilized zirconia (YSZ), an insulating layer such as alumina or zirconia (not shown) is formed between the first support plate 3a and the heater 8 and between the second support plate 3b and the heater 8.

4 shows the relationship between the voltage and the current of the ammonia sensor 100 of the present embodiment. In the figure, the voltage on the horizontal axis is an applied voltage applied between the pair of electrodes 2, and the current on the vertical axis is a current generated between the pair of electrodes 2 due to the applied voltage. The relationship between the voltage and the current is a voltage between -5V and 5V between the pair of electrodes 2 in a state where the ammonia sensor 100 is heated to 700 ° C in a dry mixed gas of 21% oxygen and 79% nitrogen. The relationship between the voltage and the current obtained by the application of the voltage interval. In addition, the thickness of the solid electrolyte 1 is 50 µm.

In Fig. 4, the change in the current when the applied voltage is reciprocated between -5V and 5V is shown, but it can be seen that the relationship between the voltage and the current shown in the figure does not show hysteresis. Therefore, even when the ammonia concentration contained in the measurement target gas changes, the ammonia concentration can be detected accurately.

The change in electromotive force (EMF) shown in FIG. 5 and FIG. 6 shows a change in electromotive force output from the ammonia sensor 100 when the ammonia concentration contained in the measurement target gas changes, and the response of the ammonia sensor 100 of the present embodiment is changed. It is a surname. In addition, the electromotive force shown in FIG. 5 and FIG. 6 uses the mixed gas which mixed ammonia with the combustion gas containing 13% of oxygen which generate | occur | produced by the combustion of LP gas as a measurement object gas, and uses the ammonia sensor 100 as a measurement object gas. It is an electromotive force obtained by arrange | positioning in the exhaust pipe through which the ammonia sensor 100 was heated at 700 degreeC. The temperature of the combustion gas was 250 ° C, and the ammonia concentration of the measurement target gas was changed by adjusting the amount of ammonia mixed in the combustion gas.

The change in electromotive force of the ammonia sensor 100 shown in FIG. 5 is a change in electromotive force when the ammonia concentration of the measurement target gas is increased from 0 ppm to 42 ppm, and the voltage change shown in FIG. 6 is 208 ppm of the ammonia concentration of the measurement target gas. The change in electromotive force when reduced from 0ppm to.

5 and 6 show changes in electromotive force output from ammonia sensors composed of conventional dense solid electrolytes. In the figure, the electromotive force of the ammonia sensor 100 of this embodiment was shown by the solid line, and the electromotive force of the conventional ammonia sensor was shown by the broken line. In addition, in FIG. 5 and FIG. 6, the time when the start of the rise or fall of the electromotive force output from the ammonia sensor 100 was confirmed by the change of the ammonia density | concentration of the measurement object gas was shown to 0 horizontal axis.

From the change in electromotive force shown in FIGS. 5 and 6, as described above, the ammonia sensor 100 of the present embodiment has a solid electrolyte in which the solid electrolyte 1 is made of porous, and the measurement target gas is active in the electrode reaction of the measurement target gas. Since the entire electrode including the interface between the electrode 1 and electrode 2 is reached quickly, the electromotive force according to the ammonia sensor concentration was output faster than the conventional ammonia sensor in both the increase in the ammonia concentration and the decrease in the ammonia concentration. Therefore, it turns out that the responsiveness of the ammonia sensor 100 improves compared with the conventional ammonia sensor. In addition, the electromotive force shown in FIG. 5 and FIG. 6 is measured by the measuring apparatus 12, and ammonia concentration is detected by this detection apparatus from this electromotive force.

FIG. 7 shows the results of investigating the influence of moisture and oxygen contained in the measurement target gas on the electromotive force of the ammonia sensor 100 of the present embodiment. The electromotive force (EMF) shown in FIG. 7 is obtained by arranging the ammonia sensor 100 in an exhaust pipe through which the gas to be measured flows, and changing the water concentration and oxygen concentration of the gas to be measured in a state where the ammonia sensor 100 is heated to 700 ° C. It is the electromotive force obtained.

Specifically, in each of the periods a to d shown in FIG. 7, ammonia gas was added to the measurement target gas so that the ammonia concentration of the measurement target gas was 250 ppm. In the period P1 including the period a and the period b, an oxygen concentration of 21%, a water concentration of 1% and a nitrogen balance target gas are used, and in a period P2 including the period c and the period d, the oxygen concentration is 15%. , Measurement target gas of moisture concentration 3% and nitrogen balance was used. In addition, in periods other than periods a to d, ammonia was not included in the measurement target gas.

As shown in Fig. 7, it can be seen that in the periods a to d, electromotive force of the same magnitude is obtained. Accordingly, it can be seen that the ammonia sensor 100 does not affect the electromotive force generated with respect to the ammonia concentration even when the water concentration and the oxygen concentration change at least in the above concentration range. Thereby, even when the water concentration and oxygen concentration contained in the measurement target gas change, the ammonia concentration of the measurement target gas can be detected accurately. In addition, the electromotive force shown in FIG. 7 is an electromotive force obtained by making the measurement object gas of the flow volume smaller than the electromotive force shown in FIG. 5 and FIG. 6 as a measurement object gas. Therefore, the responsiveness of the ammonia sensor 100 shown in FIG. 7 differs from the responsiveness of the ammonia sensor 100 shown in FIGS. 5 and 6.

8 shows the relationship between the ammonia concentration and the electromotive force (EMF) of the ammonia sensor 100 of the present embodiment. The relationship between the ammonia concentration and the electromotive force shown in FIG. 8 is a measurement gas using a mixed gas in which ammonia is mixed with a combustion gas containing an oxygen concentration of 13% generated by combustion of LP gas. It is a relationship between the ammonia concentration and electromotive force obtained in the state which arrange | positioned at the flowing exhaust pipe and heated the ammonia sensor 100 to 700 degreeC. The temperature of the combustion gas was 135 ° C, and the ammonia concentration of the measurement target gas was changed by adjusting the amount of ammonia mixed in the combustion gas. 8, it can be seen that the electromotive force increases with the increase of the ammonia concentration. The relationship between the ammonia concentration and the electromotive force shown in the drawing is an example of a relationship curve between the ammonia concentration and the electromotive force, and by referring to this relationship curve, the ammonia concentration corresponding to the electromotive force measured by the measuring apparatus 12 can be detected.

Second Embodiment

Hereinafter, a second embodiment of the ammonia sensor according to the present invention will be described based on FIGS. 9 and 10. The ammonia sensor 100 according to the second embodiment differs from the first embodiment described above in that the plate-shaped sensor element 20 in which a pair of electrodes 2 are formed on one side of the solid electrolyte 1 is provided. 9 is an exploded perspective view of the ammonia sensor 100 according to the present embodiment, and FIG. 10 is a cross-sectional view of a portion in which the plate-like sensor element 20 is provided in the longitudinal direction of the ammonia sensor 100 according to the present embodiment.

In the second embodiment, as shown in Figs. 9 and 10, a pair of electrodes 2 are provided between the solid electrolyte 1 and the support 3 in a state in which the pair of electrodes 2 are arranged in a short direction that runs straight in the longitudinal direction of the support 3. . The pair of electrodes 2 are composed of the right electrode 2c provided on the right side and the left electrode 2d provided on the left side from the rear end side in the longitudinal direction of the support body 3 to the front end side. In this second embodiment, the right electrode 2c is the first electrode C and the left electrode 2d is the second electrode D. FIG.

The right electrode 2c and the left electrode 2d are formed in a thin plate shape and, in a plan view viewed from the thickness direction of the solid electrolyte 1, are formed in a rectangular shape having a long side in the longitudinal direction of the support 3.

In addition, similarly to the first embodiment, since the solid electrolyte 1 is formed of porous material having a through hole, one side and the other side surface of the solid electrolyte 1 of the plate-shaped sensor element 20 in the thickness direction of the plate-shaped sensor element 20. A large number of gas through holes through which the measurement target gas flows are formed in the plate-shaped sensor element 20 during the period.

For example, as indicated by the broken arrow in FIG. 10, the measurement target gas E flows from the other side of the plate-shaped sensor element 20, passes through the solid electrolyte 1, the right electrode 2c, and the left electrode 2d, and forms a plate. It flows to one side of the sensor element 20. The measurement target gas E that flowed from the other side of the plate sensor element 20 to one side flows out of the plate sensor element 20 from one side side of the plate sensor element 20. Thus, both of the pair of electrodes 2 provided on one side and the other side of the plate-shaped sensor element 20 are formed to be exposed to the measurement target gas E. Although not shown, the measurement target gas E flows into one side of the plate-shaped sensor element 20, passes through the right electrode 2c, the left electrode 2d, and the solid electrolyte 1, and can flow to the other side of the plate-shaped sensor element 20. have.

On the other side of the plate-shaped sensor element 20, the unburned oxidation catalyst layer 4 formed porous is provided. Specifically, the unburned oxidation catalyst layer 4 is formed in the same dimension as that of the solid electrolyte 1 in a plan view from the thickness direction of the solid electrolyte 1. The unburned oxidation catalyst layer 4 is laminated on the other side of the plate-shaped sensor element 20 in such a state that one side of the unburned oxidation catalyst layer 4 is in close contact with the other side of the solid electrolyte 1.

Moreover, the support body 3 which supports the plate-shaped sensor element 20 is provided in one side surface of the plate-shaped sensor element 20. As shown in FIG. Specifically, the plate-shaped sensor element 20 is a state in which the right electrode 2c and the left electrode 2d are sandwiched between the solid electrolyte 1 and the support 3, and the peripheral portion of one side of the solid electrolyte 1 is the other side of the first support plate 3a. It is laminated | stacked on the 1st support plate 3a in the state contact | adhered to the side surface.

Third Embodiment

Hereinafter, a third embodiment of the ammonia sensor according to the present invention will be described based on FIGS. 11 and 12. The ammonia sensor 100 according to the third embodiment differs from the first embodiment described above in that the plate-shaped sensor element 20 is provided with an ammonia oxidation catalyst layer 7 for oxidizing ammonia contained in the measurement target gas. FIG. 11 shows an exploded perspective view of the ammonia sensor 100 according to the present embodiment, and FIG. 12 shows a cross-sectional view of a part provided with the plate-like sensor element 20 in the longitudinal direction of the ammonia sensor 100 according to the present embodiment.

As shown in FIGS. 11 and 12, the ammonia sensor 100 according to the third embodiment is provided with a support 3 supporting the plate sensor element 20 on one side of the plate sensor element 20, and the plate electrode on which the first electrode C is formed. On the other side of the sensor element 20, the unburned oxidation catalyst layer 4 and the ammonia oxidation catalyst layer 7 are provided in a stacked state. Specifically, the ammonia oxidation catalyst layer 7 is formed so as to have the same dimensions as the unburned oxidation catalyst layer 4 in a plan view from the thickness direction of the solid electrolyte 1, and is laminated on the other side of the unburned oxidation catalyst layer 4. The ammonia oxidation catalyst layer 7 is formed of a porous material through which the gas to be measured can flow, similar to the unburned oxidation catalyst layer 4. Accordingly, as shown in FIG. 12, the measurement target gas E flows in from one side of the ammonia oxidation catalyst layer 7, passes through the ammonia oxidation catalyst layer 7 and the unburned oxidation catalyst layer 4, and reaches one side of the plate-shaped sensor element 20. .

In addition, the ammonia oxidation catalyst layer 7 includes Co ₃ O ₄ , MnO ₂ , V ₂ O ₅ , Ni-Al ₂ O ₃ , Fe-Al ₂ O ₃ , Mn-Al ₂ O ₃ , CuO-Al ₂ O ₃ , Fe ₂ O ₃ -Al ₂ O ₃ , Fe ₂ O ₃ -TiO ₂ , Fe ₂ O ₃ -ZrO ₂ Alternatively, the metal ion exchange zeolite is formed of at least one material.

Thus, by providing the ammonia oxidation catalyst layer 7, it is possible to oxidize and remove some or all of the ammonia contained in the measurement target gas before the measurement target gas flows into the pair of electrodes 2. For example, by adjusting the material of the ammonia oxidation catalyst layer 7 and the thickness of the ammonia oxidation catalyst layer, it is possible to oxidize and remove ammonia at a predetermined concentration from the measurement target gas passing through the ammonia oxidation catalyst layer 7. Therefore, the ammonia sensor 100 provided with the ammonia oxidation catalyst layer 7 does not detect ammonia when the ammonia contained in the measurement target gas is below a predetermined concentration, and ammonia when the ammonia contained in the measurement target gas exceeds the predetermined concentration. Can be detected.

Fourth Embodiment

Hereinafter, a fourth embodiment of the ammonia sensor according to the present invention will be described. The ammonia sensor 100 according to the fourth embodiment differs from the first embodiment described above in that the second electrode D is formed including a material having a decomposition activity with respect to nitrogen oxide gas.

Specific materials having a decomposition activity with respect to the nitrogen oxide gas included in the second electrode D include NiO, CuO, Cr ₂ O ₃ , WO ₃ , 2CuO-Cr ₂ O ₃ , LaNiO ₃ , LaCoO ₃ , and La _0. _. ₆ Sr ₀ _. ₄ Co ₀ _. ₈ Fe ₀ _. ₂ O ₃ , La _0.8 Sr _0.2 MnO ₃ or La ₀ _. ₈₅ Sr ₀ _. ₁₅ CrO ₃ Of at least one material.

In addition, the second electrode D is formed including at least one of an oxygen ion conductive solid electrolyte, alumina, zirconia, and glass. That is, each of the pair of electrodes 2 includes at least one or more of an oxygen ion conductive solid electrolyte, alumina, zirconia, and glass. Specifically, the second electrode D is formed including a solid electrolyte, alumina, and glass of oxygen ion conductivity. In the second electrode D, the oxygen ion conductive solid electrolyte is preferably contained in the range of 2 to 25 Wt%, and the alumina is preferably contained in the range of 5 to 60 Wt%. Moreover, it is preferable that glass is contained in the range of 1-15 Wt%, and it is preferable that the material which has a decomposition activity with respect to nitrogen oxide gas is contained in the range of 50-90 Wt%. In the present embodiment, the second electrode D contains LaCoO ₃ , yttria stabilized zirconia, alumina, and glass in a weight ratio of 60: 10: 25: 5 as a material having decomposition activity with respect to nitrogen oxide gas.

In the ammonia sensor 100 according to the fourth embodiment, the nitrogen dioxide as the nitrogen oxide gas included in the measurement target gas prevents the electromotive force generated by the electrode reaction oxidizing ammonia from being lowered, thereby reducing the amount of ammonia contained in the measurement target gas. The concentration can be detected accurately.

That is, when nitrogen dioxide is included in the gas to be measured, the nitrogen dioxide acts on the electrode reaction of oxidizing ammonia at the first electrode C serving as the anode, thereby reducing the electromotive force generated between the pair of electrodes 2. Since the second electrode D serving as a cathode contains a material having a decomposition activity with respect to nitrogen dioxide which is nitrogen oxide gas, an electrode reaction for decomposing oxygen ions from nitrogen dioxide contained in the measurement target gas is promoted. By the oxygen ions generated in the second electrode D electrode reaction, the electromotive force generated between the pair of electrodes 2 increases.

The decrease in the electromotive force generated by the action of nitrogen dioxide on the electrode reaction of the first electrode C and the increase in the electromotive force generated by the action of nitrogen dioxide in the electrode reaction of the second electrode D depend on the concentration of nitrogen dioxide contained in the gas to be measured. It is either an increase or a decrease. That is, the higher the concentration of nitrogen dioxide contained in the gas to be measured, the greater the decrease in electromotive force generated by the action of nitrogen dioxide on the electrode reaction of the first electrode C. Similarly, the nitrogen dioxide is caused by the electrode reaction action of the second electrode D. The increase in generated electromotive force also increases. Thus, for example, the second electrode such that the amount of decrease in the electromotive force generated by the action of the unit concentration of nitrogen dioxide in the first electrode C and the increase in the amount of increase in the electromotive force generated by the action of the unit concentration of nitrogen dioxide in the second electrode D are the same. By adjusting in advance the mixing rate of the material having a decomposing activity with respect to nitrogen dioxide for D, the reduction in the electromotive force generated by the action of the electrode reaction of the first electrode C with respect to the concentration of nitrogen oxides is achieved. Nitrogen dioxide can be offset by an increase in the electromotive force generated by the action of the electrode reaction of the second electrode D.

Therefore, by appropriately including a material having a decomposition activity with respect to nitrogen oxide gas in the second electrode D, even when nitrogen dioxide is included in the measurement target gas, the electromotive force generated between the pair of electrodes 2 is reduced. It can detect the density | concentration of the ammonia contained in the gas to be measured accurately, preventing it.

[Separate embodiment]

Hereinafter, another embodiment is listed.

(1) In the above embodiment, a measuring device 12 for measuring at least one of a potential difference or a current between a pair of electrodes is provided between a pair of electrodes 2, but as shown in FIG. 13, a pair of electrodes Between 2, in addition to the measuring apparatus 12, the power supply apparatus which applies a constant current or voltage between a pair of electrodes 2 can be provided. In this case, the power supply 11 can be provided in a state where the first electrode C becomes an anode and at the same time a second electrode D becomes a cathode.

(2) In the above embodiment, the first electrode C is ZnO or SnO ₂ , which is a material having a high oxidation activity with respect to ammonia. And at least one material of In ₂ O ₃ , which includes an oxygen ion conductive solid electrolyte, alumina, and glass, but is not limited thereto. The first electrode C may be a ZnO material having a high oxidation activity with respect to ammonia; It may be formed of only at least one material of SnO ₂ and In ₂ O ₃ .

(3) In the first embodiment, the second electrode D is formed of only a noble metal, but the present invention is not limited thereto, and the second electrode D is formed of an oxygen ion conductive solid electrolyte, alumina, zirconia, and glass in addition to the noble metal. It may be formed including at least one.

(4) In the first embodiment, the unburned oxidation catalyst layer 4 is a noble metal such as Pt, Au, Pd, Rh, Ir, Ru, or Ag, which oxidizes carbon monoxide and a hydrocarbon contained in the gas to be measured, It is formed of at least one material selected from a porous ceramic, etc., which is dispersed and supported, but is not limited thereto. The non-flammable oxidation catalyst layer 4 may include a material for oxidizing ammonia included in the gas to be measured. In addition, as a material for oxidizing ammonia, Co ₃ O ₄ , MnO ₂ , V ₂ O ₅ , Ni-Al ₂ O ₃ , Fe-Al ₂ O ₃ , Mn-Al ₂ O ₃ , CuO-Al ₂ O ₃ , Fe At least one material of ₂ O ₃ -Al ₂ O ₃ , Fe ₂ O ₃ -TiO ₂ , Fe ₂ O ₃ -ZrO _2, or a noble metal ion exchange zeolite may be used. Thereby, in addition to the carbon monoxide and the carbon hydrogen contained in the measurement target gas, the ammonia included in the measurement target gas can be oxidized by the unburned oxidation catalyst layer 4.

(5) In the first embodiment, one electrode 2a is used as the second electrode D and the other electrode 2b is used as the first electrode C. However, the present invention is not limited thereto, and one electrode 2a is used as the first electrode C. The other electrode 2b can be used as the second electrode D.

(6) In the second embodiment, the right electrode 2c is the first electrode C, and the left electrode 2d is the second electrode D, but the present invention is not limited thereto, and the right electrode 2c is the second electrode D, and the left electrode is 2d can be used as the first electrode C. In addition, although the right electrode 2c and the left electrode 2d are provided on one side of the solid electrolyte 1, the present invention is not limited thereto, and the right electrode 2c and the left electrode 2d may be provided on the other side of the solid electrolyte 1.

(7) In the third embodiment, a support body 3 supporting the plate sensor element 20 is provided on one side of the plate sensor element 20, and the non-flammable material is on the other side of the plate sensor element 20 on which the first electrode C is formed. Although the oxidation catalyst layer 4 and the ammonia oxidation catalyst layer 7 are provided in a stacked state, the present invention is not limited thereto, and the unburned oxidation catalyst layer 4 and the ammonia oxidation catalyst layer 7 may be provided on one side of the plate sensor element 20. In this case, the support body 3 can be provided in one side surface of the plate-shaped sensor element 20 in the state which the unburned oxidation catalyst layer 4 and the ammonia oxidation catalyst layer 7 are pinched | interposed between the one side surface of the plate-shaped sensor element 20, and the support body 3. As shown in FIG.

(8) In the third embodiment, although the ammonia oxidation catalyst layer 7 is laminated on the unburned oxidation catalyst layer 4 included in the plate sensor element 20, the ammonia oxidation catalyst layer 7 is provided on the plate sensor element 20 without being limited thereto. The unburned oxidation catalyst layer 4 can be laminated on the ammonia oxidation catalyst layer 7.

(9) In the third embodiment, the flammable oxidation catalyst layer 4 and the ammonia oxidation catalyst layer 7 are provided on one side of the plate sensor element 20 in a stacked state, but the present invention is not limited thereto, and the flammable oxidation catalyst layer 4 is not provided. Instead, the ammonia oxidation catalyst layer 7 can be provided on one side of the plate sensor element 20. In this case, the ammonia oxidation catalyst layer 7 may include a material for oxidizing carbon monoxide and hydrocarbons included in the gas to be measured. In addition, as a material for oxidizing hydrocarbons, one or more materials selected from precious metals such as Pt, Au, Pd, Rh, Ir, Ru, or Ag, porous ceramics in which these precious metals are dispersed and supported, and the like can be used. Thereby, the ammonia oxidation catalyst layer 7 can oxidize carbon monoxide and hydrocarbons contained in the measurement target gas in addition to ammonia included in the measurement target gas.

(10) In the fourth embodiment, the second electrode D is formed of an oxygen ion conductive solid electrolyte, alumina, zirconia, and glass, in addition to a material having a decomposition activity with respect to nitrogen oxide gas. The second electrode D can be formed of only a material having a decomposition activity with respect to the nitrogen oxide gas, without limitation.

(11) Always-on embodiment provided the nonflammable oxidation catalyst layer 4 in the other side surface of the plate-shaped sensor element 20, It is not limited to this, It is not necessary to provide the unflammable oxidation catalyst layer 4. In addition, one side surface and the other side surface of the plate-shaped sensor element 20 can be provided with the unburned oxidation catalyst layer.

(12) In the above embodiment, the non-flammable oxidation catalyst layer 4 is provided on the other side of the plate sensor element 20. However, the present invention is not limited thereto, and the flammable oxidation catalyst layer 4 may be provided on one side of the plate sensor element 20. In this case, the support 3 can be provided on one side of the plate-shaped sensor element 20 while the nonflammable oxidation catalyst layer 4 is sandwiched between one side of the plate-shaped sensor element 20 and the support 3, and the other side of the plate-shaped sensor element 20. The support 3 can be provided in a side surface.

(13) Although the said embodiment provided the support body 3 on one side surface of the plate-shaped sensor element 20, it is not limited to this, The support body 3 can be provided in the other side surface of the plate-shaped sensor element 20.

(14) Although the said embodiment provided the support body 3 in one side surface of the plate-shaped sensor element 20, it is not limited to this, The support body 3 does not need to be provided. In this case, in order to connect the pair of electrodes 2 and the measuring device 12, the lead wire 5 and the heater terminal 9 can be provided in the solid electrolyte 1.

(15) In the above embodiment, the solid electrolyte 1 is formed in a flat state, but is not limited thereto, and the solid electrolyte 1 may be formed in a curved state.

(16) In the embodiment, each of the pair of electrodes 2 is formed by including an oxygen ion conductive solid electrolyte, alumina, and glass, but the present invention is not limited thereto, and each pair of electrodes includes oxygen ions. And at least one or more of a conductive solid electrolyte, alumina, zirconia, and glass. For example, it may include only an oxygen ion conductive solid electrolyte, and may include only an oxygen ion conductive solid electrolyte and alumina. In addition, it may include an oxygen ion conductive solid electrolyte, zirconia, and glass.

(17) In the above embodiment, the oxygen ion conductive solid electrolyte contained in each of the pair of electrodes 2 is yttria stabilized zirconia (YSZ), but is not limited thereto, and the oxygen ion conductivity included in the pair of electrodes 2 The solid electrolyte may be any of Scandia stabilized zirconia (ScSZ), samarium-doped ceria (GDC) or thorium dioxide (ThO ₂ ).

In addition, the structure disclosed by the said embodiment (including another embodiment, is the same below) can be applied in combination with the structure disclosed by another embodiment, unless a contradiction arises, and also the embodiment disclosed by this specification The form is an illustration, and embodiment of this invention is not limited to this, It can modify suitably within the range which does not deviate from the objective of this invention.

As described above, an ammonia sensor capable of improving the ammonia concentration detection response can be provided.

Claims

A plate-shaped sensor element in which a pair of electrodes having different reactivity with respect to ammonia is formed on a surface of a plate-shaped solid electrolyte having oxygen ion conductivity;

A measuring device for measuring at least one of a potential difference or a current between the pair of electrodes,

An ammonia sensor configured to expose all of the pair of electrodes to a gas to be measured,

The solid electrolyte is formed of a porous,

The pair of electrodes comprises a first electrode having an oxidation activity for ammonia and a second electrode having a lower oxidation activity for ammonia than the first electrode,

The first electrode includes a material having a high oxidation activity against ammonia, including at least one of ZnO, SnO 2 and In 2 O 3 , 50 to 90 Wt%, 1 to 15 Wt% glass,

An ammonia sensor in which a plurality of gas flow holes through which the measurement target gas flows are formed from one side of the solid electrolyte of the plate sensor element to the other side facing the one side in the thickness direction of the plate sensor element.
The method of claim 1,

An ammonia sensor provided with one of said pair of electrodes formed on one side of said solid electrolyte, and said plate-shaped sensor element formed with the other of said pair of electrodes on the other side opposite said one side of said solid electrolyte .
The method of claim 1,

The ammonia sensor provided with the said sensor element in which the said pair of electrode was formed in one side of the said solid electrolyte.
The method of claim 1,

The second electrode, the ammonia sensor containing a noble metal.
The method of claim 1,

And the second electrode comprises a material having a decomposition activity with respect to nitrogen oxide gas.
The method of claim 5,

NiO, CuO, Cr 2 O 3 , WO 3 , 2CuO-Cr 2 O 3 , LaNiO 3 , LaCoO 3 , La 0 . 6 Sr 0 . 4 Co 0 . 8 Fe 0 . 2 O 3 , La 0 . 8 Sr 0 . 2 MnO 3 , La 0 . 85 Sr 0 . Ammonia sensor made of at least one of 15 CrO 3 .
The method of claim 1,

Wherein each of the pair of electrodes comprises at least one of an oxygen ion conductive solid electrolyte, alumina, zirconia, and glass.
The method of claim 1,

The solid electrolyte is an ammonia sensor formed of one of yttria stabilized zirconia (YSZ), scandia stabilized zirconia (ScSZ), samarium doped ceria (SDC), gadolinium doped ceria (GDC) or thorium dioxide (ThO 2 ).
The method of claim 1,

The ammonia sensor provided with at least one of the said one side surface and the said other side surface of the said plate-shaped sensor element with the unburnt oxidation catalyst layer which oxidizes carbon monoxide and a hydrocarbon contained in the said measurement object gas.
The method of claim 9,

The ammonia sensor, wherein the unburned oxidation catalyst layer comprises a porous ceramic in which at least one of Pt, Pd, Rh, Ir, Ru or Ag is dispersed and supported.
The method of claim 1,

The ammonia oxidation catalyst layer which oxidizes ammonia contained in the said measurement object gas is provided in the said one side surface or the said other side surface of the said plate-shaped sensor element.
The method of claim 11,

The ammonia oxidation catalyst layer is Co 3 O 4 , MnO 2 , V 2 O 5 , Ni-Al 2 O 3 , Fe-Al 2 O 3 , Mn-Al 2 O 3 , CuO-Al 2 O 3 , Fe 2 O An ammonia sensor comprising at least one of 3 -Al 2 O 3 , Fe 2 O 3 -TiO 2 , Fe 2 O 3 -ZrO 2 , or a metal ion exchange zeolite.
The method of claim 1,

The support body which supports the said plate-shaped sensor element is provided in one side surface or the said other side surface of the said plate-shaped sensor element,

The ammonia sensor with which the said support body is equipped with the heater which heats the said plate-shaped sensor element.
The method of claim 1,

On one side of the plate sensor element, a support for supporting the plate sensor element is provided, and on the other side of the plate sensor on which the first electrode is formed, oxidation of carbon monoxide and hydrocarbons contained in the measurement target gas is performed. And ammonia oxidation catalyst layer for oxidizing ammonia contained in the measurement target gas in a stacked state.
The method of claim 1,

An ammonia sensor having a power supply device that applies a constant voltage or a constant current between the pair of electrodes.
The method of claim 1,

An ammonia sensor having a power supply device for applying a constant voltage or current between the pair of electrodes in a state where the first electrode becomes an anode and the second electrode becomes a cathode.