JP2009128127A - Hydrogen gas sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrogen gas sensor having a sensitivity higher than those of the conventional types. <P>SOLUTION: The hydrogen sensor 100 includes a sensor section 10 having a thermoelectric material section 2 constituted of a thermoelectric material, and a catalyst section 6 located on a pair of electrodes 4a, 4b provided on the thermoelectric material section 2 and on one electrode side 4a of the pair of electrodes 4a, 4b and which are in contact with the thermoelectric material section 2, for catalyzing reaction by hydrogen; and a voltage measuring section 20 for measuring the voltage generated across the pair of electrodes 4a, 4b. At least a part of the catalyst section 6 is located in a concave section 8, formed on the thermoelectric material section 2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a hydrogen gas sensor, and more particularly to a thermoelectric hydrogen gas sensor.

  As a hydrogen gas sensor for detecting hydrogen in the atmosphere, a thermoelectric hydrogen gas sensor is expected to be able to be efficiently applied to, for example, a power generation system such as a fuel cell because of its low power consumption and low cost. Yes. This thermoelectric hydrogen gas sensor detects hydrogen by causing an exothermic reaction due to hydrogen in a part of the thermoelectric element and generating an electromotive force based on a temperature difference from the part where the exothermic reaction did not occur.

  Such a thermoelectric hydrogen gas sensor includes, for example, a catalyst (catalyst component) that causes a catalytic reaction in contact with a non-detection gas, and a thermoelectric conversion material film that converts a local temperature difference due to this reaction into a voltage signal. What has a structure is known (refer patent document 1, 2).

JP 2003-156461 A JP 2006-201100 A

  The conventional thermoelectric hydrogen gas sensor having the above-described configuration has an operation principle of generating a temperature difference in the thermoelectric conversion material film using heat generated by the reaction in the catalyst portion, thereby generating an electromotive force. Therefore, unless the reaction heat generated by the reaction in the catalyst is reliably conducted to the thermoelectric conversion material film, it is difficult to generate a temperature difference between both ends of the thermoelectric conversion material film, and as a result, the sensitivity of the hydrogen gas sensor is lowered.

  However, the thermoelectric hydrogen gas sensors described in Patent Documents 1 and 2 often cannot achieve the expected sensitivity. This is considered to be partly because part of the reaction heat escapes from the catalyst part to the outside air and the reaction heat is not sufficiently conducted to the thermoelectric conversion material film.

  Therefore, the present invention has been made in view of such circumstances, and an object thereof is to provide a hydrogen gas sensor having higher sensitivity than before.

  In order to achieve the above object, the hydrogen gas sensor of the present invention is unevenly distributed on a thermoelectric material portion made of a thermoelectric material, a pair of electrodes provided on the thermoelectric material portion, and one of the pair of electrodes, and A sensor unit provided in contact with the thermoelectric material unit and having a catalyst unit for catalyzing a reaction by hydrogen; and a voltage measuring unit for measuring a voltage generated between the pair of electrodes, at least a part of the catalyst unit being It is arranged in a recess formed in the thermoelectric material part. That is, in the hydrogen gas sensor of the present invention, at least a part of the catalyst part is embedded in the thermoelectric material part.

  The hydrogen gas sensor according to the present invention generates heat based on a catalytic reaction of hydrogen in the catalyst portion, thereby causing a temperature difference between the portion in contact with the catalyst portion and the other portion in the thermoelectric material portion. It is a thermoelectric hydrogen gas sensor that detects hydrogen gas by generating electric power and measuring the electromotive force with a voltage measurement unit.

  In this hydrogen gas sensor, at least a part of the catalyst part is disposed in a recess formed in the thermoelectric material part, and is surrounded by the inner wall of the recess. Therefore, in the present invention, the heat of reaction is less likely to escape from the catalyst portion to the outside air than in the case where the catalyst portion is installed on the outer surface of the flat thermoelectric material portion where no recess is formed as in the prior art. . That is, in the present invention, since the heat conducted to the thermoelectric material part of the reaction heat generated in the catalyst part without escaping to the outside air can be increased compared to the conventional case, the sensitivity of the hydrogen gas sensor can be improved compared to the conventional case. It becomes possible.

  In the present invention, the catalyst part is preferably in contact with the inner wall of the recess, and more preferably the catalyst part is in contact with the entire inner wall of the recess. Thereby, compared with the case where the catalyst part is installed on the flat surface of the thermoelectric material part in which no recess is formed as in the prior art, the contact area between the catalyst part and the thermoelectric material part is increased, and the catalyst part Since the reaction heat generated in step 1 is more reliably conducted to the thermoelectric material part, the sensitivity of the hydrogen gas sensor can be further improved.

  In the said invention, it is preferable that the contact interface of a catalyst part and a thermoelectric material part is uneven | corrugated. Thereby, compared with the case where the contact interface of a catalyst part and a thermoelectric material part is planar like before, the contact area of a catalyst part and a thermoelectric material part becomes large, and the reaction heat generated in the catalyst part, Since it more reliably conducts to the thermoelectric material part, it becomes possible to further improve the sensitivity of the hydrogen gas sensor.

  In the said invention, the penetration part which penetrates a thermoelectric material part to the surface on the opposite side to a recessed part may be formed in a part of recessed part. If it carries out like this, the hydrogen gas which penetrate | invaded into the inside of the thermoelectric material part through this penetration part can be made to react in a catalyst part. That is, it is possible to detect hydrogen gas that has entered the thermoelectric material portion from the side opposite to the concave portion. Moreover, when a part of catalyst part is arrange | positioned in a penetration part and the inner wall of a penetration part and a part of catalyst part contact, the contact area of a catalyst part and a thermoelectric material part can be enlarged further. Moreover, when a part of the catalyst part is filled in the penetration part, that is, when a part of the catalyst part is fitted in the penetration part, the catalyst part is hardly detached from the thermoelectric material part.

  According to the present invention, it is possible to provide a hydrogen gas sensor having higher sensitivity than before.

  Preferred embodiments of the present invention will be described below with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant descriptions are omitted. Further, the dimensions and positional relationships shown in the drawings are not limited to those illustrated.

(First embodiment)
FIG. 1 is a schematic view showing the configuration of the hydrogen gas sensor according to the first embodiment of the present invention. As shown in FIG. 1, the hydrogen gas sensor 100 according to the first embodiment includes a sensor unit 10 and a voltage measurement unit 20.

  FIG. 1 schematically shows a cross-sectional configuration of the sensor unit 10. FIG. 2 is a plan view of the sensor unit 10 as viewed from above. 1 and 2, the sensor unit 10 includes a thermoelectric material unit 2, a pair of electrodes 4a and 4b provided on the thermoelectric material unit 2, and one electrode 4a of the pair of electrodes 4a and 4b. And a catalyst part 6 that is provided so as to be in contact with the thermoelectric material part 2 and catalyze a reaction by hydrogen. For example, the sensor unit 10 has a length of about 10 mm, a width of about 7 mm, and a thickness of about 0.2 mm.

  In the present embodiment, the entire catalyst portion 6 is disposed in the recess 8 formed in the thermoelectric material portion 2, and the catalyst portion 6 is in contact with the entire inner wall of the recess 8. That is, the entire catalyst portion 6 is fitted in the recess 8 formed in the thermoelectric material portion 2 and is embedded in the thermoelectric material portion 2. In addition, the surface of the catalyst unit 6 that is exposed to the outside without being in contact with the thermoelectric material unit 2 is the surface of the thermoelectric material unit 2 on which the pair of electrodes 4a and 4b are provided (hereinafter referred to as “electrode installation of the thermoelectric material unit 2”). It is written as “face”.)

  The catalyst portion 6 is provided on the same surface side where the electrodes 4a and 4b of the thermoelectric material portion 2 are formed, and is unevenly distributed on one electrode 4a side of the pair of electrodes 4a and 4b. The catalyst unit 6 has a catalytic ability to cause a reaction between hydrogen gas and oxygen in the air. As the catalyst part 6, what has the structure which made the catalyst support body carry | support the catalyst component which has the said catalyst ability is mentioned, for example. Specifically, it is preferable that the catalyst support is made of porous alumina and platinum is supported on the catalyst support. Platinum can selectively cause a reaction by hydrogen gas, and this is efficiently supported on the surface of the catalyst part 6 by being supported on a porous catalyst support having a large surface area.

  As described above, the catalyst portion 6 is provided unevenly on the one electrode 4a side, but it is preferable that the catalyst portion 6 be as far as possible from the electrode 4b on the side where the catalyst portion 6 is not formed. As the catalyst unit 6 is further away from the electrode 4b, the temperature gradient in the thermoelectric material unit 2 as described later can be increased, and a larger electromotive force can be obtained. However, from the viewpoint of balance with the calorific value of the catalyst unit 6, the catalyst unit 6 necessary for efficiently causing a reaction in the catalyst unit 6 and giving a sufficient temperature difference to the thermoelectric material unit 6. It is preferable that the catalyst part 6 is unevenly distributed on the electrode 4a side as much as possible.

  The catalyst unit 6 may or may not be in contact with the electrode 4a on the side where it is provided. For example, by providing the catalyst portion 6 so as to be in contact with the electrode 4a, the distance between the catalyst portion 6 and the electrode 4b can be increased as compared with the case where the catalyst portion 6 and the electrode 4a are not in contact with each other. The temperature gradient generated in 2 can be further increased, and a large electromotive force can be obtained between the electrodes 4a and 4b. Whether or not the catalyst unit 6 is brought into contact with the electrode 4a may be appropriately selected according to the desired characteristics of the hydrogen gas sensor.

  The catalyst unit 6 may be formed so as not to cover the electrode 4a, or may be formed so as to cover the electrode 4a. In particular, if the catalyst portion 6 is formed so as not to cover the electrode 4a, the heat generated in the catalyst portion 6 is directly transmitted to the thermoelectric material portion 2 without passing through the electrode 4a. A larger temperature gradient can be generated.

  The thermoelectric material part 2 is a plate-like member having a thickness of about 10 to 500 μm and a rectangular planar shape. This thermoelectric material part 2 is comprised from the thermoelectric material which has the property (thermoelectric conversion capability) which an electromotive force generate | occur | produces by Seebeck effect, when a local temperature difference arises. As the thermoelectric material, a material that has such properties sufficiently and has little change in resistance and electromotive force due to gas or the like is preferable. Examples thereof include thermoelectric materials such as BiTe, PbTe, FeSi, SiGe, scuttaldide, half-Heusler intermetallic compound, cobalt layered compound, and metal oxide. Moreover, NiO system doped with an alkali metal or the like is also applicable.

  The pair of electrodes 4 a and 4 b are provided on one surface of the thermoelectric material portion 2 so as to be separated from each other, and specifically, are formed along the sides of both ends of the thermoelectric material portion 2. These electrodes 4a and 4b have a function as terminals for connecting the thermoelectric material portion 2 to an external circuit or the like, and are made of a conductive material such as metal.

  The voltage measuring unit 20 is connected to the pair of electrodes 4a and 4b included in the sensor unit 10, and can measure the voltage between the electrodes 4a and 4b. As the voltage measuring unit 20, a known voltmeter corresponding to the detected voltage can be applied.

  Detection of hydrogen gas by the hydrogen gas sensor 100 having the above configuration is performed according to the following operation principle. That is, first, in the sensor unit 10, when hydrogen gas comes into contact with the catalyst unit 6, the reaction between the hydrogen gas and oxygen in the air is catalyzed on the catalyst unit 6. In this reaction, water is generated and heat is generated by the reaction between hydrogen and oxygen. With this heat, the portion of the thermoelectric material portion 2 that is in contact with the catalyst portion 6 is heated. On the other hand, since the part where the catalyst part 6 is not provided is not easily heated even if the above reaction occurs, the temperature before the reaction is easily maintained. As a result, when a reaction of hydrogen gas occurs in the catalyst unit 6, a temperature gradient is generated in the thermoelectric material unit 2. Since the thermoelectric material part 2 has thermoelectric conversion ability, an electromotive force is generated in the thermoelectric material part 2 due to such a temperature gradient.

  The electromotive force generated in the thermoelectric material part 2 generates a voltage between the pair of electrodes 4 a and 4 b provided at both ends of the thermoelectric material part 2. Since the voltage measuring unit 20 is connected to the electrodes 4a and 4b, the voltage measuring unit 20 measures the voltage between the electrodes 4a and 4b. Based on the voltage value obtained, the hydrogen gas in the atmosphere can be detected, and the concentration of the hydrogen gas in the atmosphere can be quantified.

  In the first embodiment, since the catalyst portion 6 is disposed in the recess 8 formed in the thermoelectric material portion 2 and is surrounded by the inner wall of the recess 8, it is flat without a recess as in the prior art. Compared with the case where the catalyst part is installed on the outer surface of the thermoelectric material part, the reaction heat is less likely to escape from the catalyst part 6 to the outside air. That is, since the total amount of reaction heat generated in the catalyst unit 6 is easily conducted to the thermoelectric material unit 2 without escaping to the outside air, the sensitivity of the hydrogen gas sensor 100 can be improved as compared with the conventional case.

  Further, in the first embodiment, since the catalyst portion 6 is in contact with the entire inner wall of the recess 8, the catalyst portion is installed on the flat surface of the thermoelectric material portion where no recess is formed as in the prior art. Compared with the case where it exists, the contact area of the catalyst part 6 and the thermoelectric material part 2 becomes large, and the reaction heat generated in the catalyst part 6 is more reliably conducted to the thermoelectric material part 2. As a result, the temperature gradient generated in the thermoelectric material portion 2 is likely to be large, and the electromotive force generated between the electrodes 4a and 4b is likely to be large, so that the sensitivity of the hydrogen gas sensor 100 can be further improved.

(Second Embodiment)
Next, a hydrogen gas sensor according to a second embodiment of the present invention will be described with reference to FIG. In addition, below, description is abbreviate | omitted suitably about the matter which is common in 1st Embodiment and 2nd Embodiment mentioned above.

  As shown in FIG. 3, the hydrogen gas sensor of the second embodiment is composed of a sensor unit 10 and a voltage measurement unit 20 as in the first embodiment. The sensor unit 10 includes a thermoelectric material unit 2 and a thermoelectric material. A pair of electrodes 4a and 4b provided on the part 2, and one electrode 4a of the pair of electrodes 4a and 4b, which is unevenly distributed on the side of the thermoelectric material part 2 and catalyzes the reaction by hydrogen And a catalyst part 6 to be used.

  In the second embodiment, as in the first embodiment, the entire catalyst portion 6 is embedded in the recess 8 formed in the thermoelectric material portion 2, but as shown in FIG. The contact surface 12 between the surface of the thermoelectric material portion 2 side and the bottom surface of the recess 8 of the thermoelectric material portion 2 is uneven, which is different from the first embodiment in which the interface is planar. ing.

  Thus, in 2nd Embodiment, the contact surface with respect to the thermoelectric material part 2 of the catalyst part 6 and the contact surface with respect to the catalyst part 6 of the thermoelectric material part 2 are uneven | corrugated, respectively, Moreover, both these contact The surface irregularities are in mesh. The uneven shape of the contact interface is not particularly limited, and may be any of a shape in which groove-like unevenness is arranged in parallel, a shape in which the unevenness is alternately repeated in the vertical and horizontal directions, a shape that is irregularly roughened, and the like. Good. In 2nd Embodiment, the space | interval of the unevenness | corrugation (distance between the top parts of a convex part etc.) of this contact interface is preferable in it being 0.01-1 mm, for example, and it is more preferable in it being 0.05-0.5 mm. . In this way, it is possible to improve the thermal conductivity at the contact interface particularly well.

  In 2nd Embodiment which has such a structure, since the catalyst part 6 is arrange | positioned in the recessed part 8 formed in the thermoelectric material part 2 similarly to 1st Embodiment, the reaction heat which generate | occur | produced in the catalyst part 6 is shown. Can be easily conducted to the thermoelectric material portion 2. In particular, in the second embodiment, the contact interface 12 between the catalyst portion 6 and the bottom of the recess portion 8 formed in the thermoelectric material portion 2 is uneven, so that the catalyst portion 6 and the thermoelectric device as in the first embodiment. Compared with the case where the contact interface with the bottom of the recess 8 formed in the material portion 2 is planar, the contact area between the catalyst portion 6 and the thermoelectric material portion 2 is increased, and the reaction heat generated in the catalyst portion 6 is reduced. Further, it becomes easier to conduct to the thermoelectric material portion 2, and as a result, the sensitivity of the hydrogen gas sensor 100 can be further improved.

(Third embodiment)
Next, a hydrogen gas sensor according to a third embodiment of the present invention will be described with reference to FIG. In addition, below, description is abbreviate | omitted suitably about the matter which is common in 1st Embodiment and 3rd Embodiment mentioned above.

  As shown in FIG. 4, the hydrogen gas sensor 100 of the third embodiment is the first in that a penetrating part 14 that penetrates the thermoelectric material part to the opposite side of the concave part 8 is formed in a part of the concave part 8. This is different from the hydrogen gas sensor 100 of the embodiment. That is, in the third embodiment, a through portion 14 that penetrates the thermoelectric material portion 2 in the depth direction of the concave portion 8 is formed at the bottom of the concave portion 8.

  In the third embodiment, as in the first embodiment, the entire catalyst portion 6 is disposed in the recess 8 formed in the thermoelectric material portion 2, and inside the recess 8 formed in the thermoelectric material portion 2. And is embedded in the thermoelectric material portion 2. Further, the surface exposed to the outside without being in contact with the thermoelectric material portion 2 in the catalyst portion is made to coincide with the electrode installation surface of the thermoelectric material portion 2. Furthermore, in the third embodiment, the catalyst portion 6 is formed by filling the through portion 14 with the catalyst component.

  In 3rd Embodiment which has such a structure, since the catalyst part 6 is arrange | positioned in the recessed part 8 formed in the thermoelectric material part 2 similarly to 1st Embodiment, the reaction heat which generate | occur | produced in the catalyst part 6 is shown. Can be reliably conducted to the thermoelectric material portion 2. And especially in 3rd Embodiment, the catalyst part 6 is arrange | positioned also at the penetration part 14, and the inner wall of the penetration part 14 and a part of catalyst part 6 contact, Thereby, the catalyst part 6 and the thermoelectric material part The contact area with 2 can also be increased. Further, the catalyst part 6 is also formed in the through part 14, that is, a part of the catalyst part 6 is fitted to the through part 14, so that the catalyst part 6 is hardly detached from the thermoelectric material part 2. .

  The inner diameter of the penetrating portion 14 can be appropriately set according to the desired characteristics of the hydrogen gas sensor 100. For example, the inner diameter and shape of the penetrating portion 14 may be the same as that of the concave portion 8. In this case, the concave portion 8 has a shape that penetrates to the opposite side surface.

  The hydrogen gas sensors of the first, second, and third embodiments have been described above. However, the present invention is not necessarily limited to the above-described embodiments, and can be appropriately changed without departing from the spirit of the present invention.

  For example, in the first, second, and third embodiments, the surface exposed to the outside without contacting the thermoelectric material unit 2 in the catalyst unit 6 coincides with the electrode installation surface of the thermoelectric material unit 2. However, the catalyst unit 6 may protrude from the electrode installation surface of the thermoelectric material unit 2. That is, the height of the catalyst part 6 in the depth direction of the recess 8 may be larger than the distance from the bottom of the recess 8 to the electrode installation surface of the thermoelectric material part 2. Conversely, the height of the catalyst part 6 in the depth direction of the recess 8 may be smaller than the distance from the bottom of the recess 8 to the electrode installation surface of the thermoelectric material part 2. Further, the catalyst unit 6 may be in contact with the thermoelectric material unit 2 only at the bottom of the recess 8.

  Furthermore, in the second embodiment, only the contact interface at the bottom surface of the recess 8 is uneven, but this is not a limitation, and the side surface of the contact portion (contact interface at the side surface of the recess 8) may be uneven. . Further, the inner wall of the recess 8 may be a curved surface instead of a flat surface.

  Furthermore, in the third embodiment, the catalyst portion 6 is formed even in the through portion 14 formed on the bottom surface of the recess 8, but the catalyst portion 6 may not necessarily be formed in the through portion 14. Good. Even in this case, hydrogen can be ventilated from the surface of the thermoelectric material portion 2 opposite to the surface on which the concave portion 8 is formed, so that detection of hydrogen gas is advantageous. That is, it is possible to detect the hydrogen gas that has entered the inside of the thermoelectric material portion 2 from the opposite surface of the recess 8 through the through portion 14.

  Moreover, although the thermoelectric material part 2 in the hydrogen gas sensor 100 has a plate shape, the thermoelectric material part 2 has a shape other than the plate shape as long as the pair of electrodes 4a, 4b and the catalyst part 6 can be arranged on the surface. It may be. The electrodes 4a and 4b and the catalyst part 6 are all provided on the same surface of the thermoelectric material part 2, but for example, only one of the electrodes 4a and 4b may be provided on the other surface. Good.

It is a schematic sectional drawing which shows the structure of the hydrogen gas sensor which concerns on 1st Embodiment. It is the top view which looked at the sensor part 10 shown in FIG. 1 from upper direction. It is a schematic sectional drawing which shows the structure of the hydrogen gas sensor which concerns on 2nd Embodiment. It is a schematic sectional drawing which shows the structure of the hydrogen gas sensor which concerns on 3rd Embodiment.

Explanation of symbols

2 ... Thermoelectric material part, 4a, 4b ... Electrode, 6 ... Catalyst part, 8 ... Recessed part, 10 ... Sensor part, 20 ... Voltage measuring part, 100 ... Hydrogen gas sensor .

Claims (4)

A thermoelectric material portion made of a thermoelectric material, a pair of electrodes provided on the thermoelectric material portion, and unevenly distributed on one electrode side of the pair of electrodes and in contact with the thermoelectric material portion; A sensor part having a catalyst part for catalyzing the reaction by
A voltage measuring unit for measuring a voltage generated between the pair of electrodes;
With
At least a part of the catalyst part is disposed in a recess formed in the thermoelectric material part,
A hydrogen gas sensor characterized by that.   The hydrogen sensor according to claim 1, wherein the catalyst portion is in contact with the entire inner wall of the recess.   The hydrogen sensor according to claim 1, wherein a contact interface between the catalyst portion and the thermoelectric material portion is uneven. The hydrogen according to any one of claims 1 to 3, wherein a penetration part that penetrates the thermoelectric material part to a surface opposite to the depression is formed in a part of the depression. Sensor.

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