JP2009133636A - Hydrogen gas sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrogen gas sensor having higher sensitivity than before. <P>SOLUTION: The hydrogen gas sensor 100 is equipped with a sensor part 10, which has a thermoelectric material part 2 comprising a porous thermoelectric material, a pair of the electrodes 4a and 4b provided on the thermoelectric material part 2 and the catalyst part 6, which catalyzes the reaction by hydrogen, provided so as to be unevenly distributed on the side of one electrode 4a of a pair of the electrodes 4a and 4b on the thermoelectric material part 2, and a voltage measuring part 20 for measuring the voltage produced across a pair of the electrodes 4a and 4b. <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 gas to be detected, 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

  In the conventional thermoelectric hydrogen gas sensor having the above-described configuration, the operation principle is to generate a temperature difference in the thermoelectric conversion material film by using heat generated by the reaction in the catalyst, thereby generating an electromotive force (voltage). Therefore, the greater the temperature difference generated in the thermoelectric conversion material film, the greater the electromotive force generated in the thermoelectric conversion material film, resulting in higher sensitivity of the hydrogen gas sensor.

  However, the thermoelectric hydrogen gas sensors described in Patent Documents 1 and 2 often cannot achieve the expected sensitivity. This is considered to be due to the fact that the temperature difference generated in the thermoelectric conversion material film cannot be made sufficiently large.

  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, a hydrogen gas sensor according to a first invention includes a thermoelectric material portion made of a porous thermoelectric material, a pair of electrodes provided on the thermoelectric material portion, and a pair of electrodes on the thermoelectric material portion. It is provided with the sensor part which is provided unevenly by the one electrode side, and has a catalyst part which catalyzes the reaction by hydrogen, and the voltage measurement part which measures the voltage which generate | occur | produced between a pair of electrodes.

  The porous thermoelectric material in the first invention means a thermoelectric material having many fine pores (porous thermoelectric material). The pore diameter of the porous thermoelectric material is about 0.1 to 20 μm.

  The hydrogen gas sensor according to the first aspect of the present invention generates a heat by generating a catalytic reaction of hydrogen in the catalyst portion, so that the temperature difference between the portion in contact with the catalyst portion and the other portion in the thermoelectric material portion is obtained. The thermoelectric hydrogen gas sensor detects hydrogen gas by generating an electromotive force based thereon and measuring the electromotive force (voltage) with a voltage measuring unit.

  Since the thermoelectric material part provided in the hydrogen gas sensor of the first invention is made of a porous thermoelectric material that is less likely to conduct heat than the dense thermoelectric material conventionally used in hydrogen gas sensors, the heat generated in the catalyst part is In the thermoelectric material part, it becomes difficult to conduct from the part in contact with the catalyst part to other parts. As a result, in the first invention, the temperature difference between the portion where the electrode on the side where the catalyst portion is unevenly distributed in the thermoelectric material portion is arranged and the portion where another electrode is arranged becomes large. Since the electromotive force generated between both electrodes is increased, the sensitivity of the hydrogen gas sensor can be improved as compared with the conventional case.

  A hydrogen gas sensor according to a second aspect of the present invention is provided with a thermoelectric material portion made of a porous thermoelectric material, a pair of electrodes provided on the thermoelectric material portion, and unevenly provided on one electrode side of the pair of electrodes. A sensor part having a catalyst part formed by supporting a catalyst component that catalyzes a reaction by a pore of the porous thermoelectric material, and a voltage measuring part for measuring a voltage generated between a pair of electrodes, It is characterized by providing.

  The hydrogen gas sensor according to the second aspect of the invention is similar to the first aspect of the invention, in which a catalytic reaction of hydrogen is caused in the catalyst part to generate heat, so that the part in contact with the catalyst part in the thermoelectric material part This is a thermoelectric hydrogen gas sensor that detects hydrogen gas by generating an electromotive force based on a temperature difference from other portions and measuring the electromotive force (voltage) with a voltage measurement unit.

  The thermoelectric material part provided in the hydrogen gas sensor of the second invention is made of a porous thermoelectric material that is less likely to conduct heat than the dense thermoelectric material conventionally used in hydrogen gas sensors, as in the first invention. The reaction heat generated in the catalyst part is difficult to conduct from the part where the catalyst part is formed in the thermoelectric material part to other parts. As a result, in the hydrogen gas sensor according to the second aspect of the present invention, the temperature difference between the portion where the electrode on the side where the catalyst portion is unevenly provided in the thermoelectric material portion and the portion where another electrode is placed is arranged. Since the electromotive force generated between the two electrodes is increased, the sensitivity of the hydrogen gas sensor can be improved as compared with the prior art.

  In the hydrogen gas sensor of the second invention, since the catalyst part is formed by supporting the catalyst component in the pores of the porous thermoelectric material, the catalyst part is the outer surface of the thermoelectric material part as in the prior art. The contact area between the catalyst component and the thermoelectric material can be increased as compared with the case where the catalyst component is installed only in the case. Therefore, the reaction heat generated in the catalyst part is easily conducted to the thermoelectric material part, and in particular, the side where the catalyst part is unevenly distributed in the thermoelectric material part is easily heated. As a result, in the second invention, the temperature difference between the portion where the electrode on the side where the catalyst portion is unevenly distributed in the thermoelectric material portion and the portion where another electrode is disposed is large. Since the electromotive force generated between both electrodes is increased, the sensitivity of the hydrogen gas sensor can be improved as compared with the conventional case.

  Furthermore, in the hydrogen gas sensor according to the second aspect of the invention, since the catalyst component is supported on the inner wall of the pores of the porous thermoelectric material, the catalyst component is on the surface of the thermoelectric material portion (surface on which a pair of electrodes are provided). The active surface area of the catalyst part is increased compared to the case where the catalyst part is disposed in the catalyst part, and the catalytic activity of the entire catalyst part is improved. Therefore, in the second invention, the sensitivity of the hydrogen gas sensor can be improved.

  Furthermore, in the hydrogen gas sensor according to the second aspect of the invention, since the catalyst component is supported in the vacancies that exist in large numbers inside the thermoelectric material portion, the hydrogen catalytic reaction also proceeds inside the thermoelectric material portion. Therefore, in the hydrogen gas sensor of the second invention, the reaction heat generated in the catalyst part is less likely to escape to the outside air than in the conventional case where the catalyst part is installed only on the outer surface of the thermoelectric material part. Can be efficiently conducted to the thermoelectric material part, so that the sensitivity of the hydrogen gas sensor can be improved.

  In the said 1st and 2nd invention, it is preferable that the porosity of a porous thermoelectric material is 30 to 80%.

  By setting the porosity of the porous thermoelectric material within the above preferred range, the sensitivity of the hydrogen gas sensor can be further improved.

  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)
<Hydrogen gas sensor 100>
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. As shown in FIGS. 1 and 2, the sensor unit 10 includes a thermoelectric material unit 2, a pair of electrodes 4 a and 4 b provided on the thermoelectric material unit 2, and a pair of electrodes 4 a and 4 b on the thermoelectric material unit 2. And a catalyst portion 6 that is provided unevenly on one of the electrodes 4a and catalyzes 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.

The thermoelectric material part 2 is a plate-like member having a thickness of about 10 to 500 μm and a rectangular planar shape. The thermoelectric material portion 2 has a property (thermoelectric conversion ability) that generates an electromotive force due to the Seebeck effect when a local temperature difference occurs, and is composed of a porous thermoelectric material having many fine pores. The pore diameter of the porous thermoelectric material is about 0.1 to 20 μm. As the porous thermoelectric material, those having such a property and having little change in resistance and electromotive force due to gas or the like are preferable. For example, Ca ₃ Co ₄ O ₉ , Na _x CoO ₂ ( x is an arbitrary real number satisfying 0 <x <1.0, for example. Among these, the porous thermoelectric material made of Ca ₃ Co ₄ O ₉ is preferable as the porous thermoelectric material. By using a porous thermoelectric material made of Ca ₃ Co ₄ O ₉ , the effects of the present invention can be easily obtained.

Ca ₃ Co ₄ O ₉ is a substance having large crystal anisotropy, and its crystal grains have a plate-like shape that is long in the plane direction perpendicular to the c-axis of the crystal axis. The resistivity of Ca ₃ Co ₄ O ₉ is about 10 ⁻⁵ Ω · m, the thermoelectromotive force is about 0.12 mV · K ⁻¹ , and the thermal conductivity is about 2 W · m ⁻¹ · K ⁻¹ , especially c In the surface direction perpendicular to the axis, the resistivity of Ca ₃ Co ₄ O ₉ is small and the thermoelectromotive force is large. A porous thermoelectric material made of Ca ₃ Co ₄ O ₉ is, as will be described later, for example, a large number of Ca ₃ Co ₄ O ₉ crystal particles are stacked in the c-axis direction of the crystal axis, pressed, and then fired. Can be obtained.

In Ca ₃ Co ₄ O ₉ thermoelectric material part 2 is constituted of a porous shaped thermoelectric material _consisting, Ca 3 _Co 4 and a plane direction perpendicular to the c axis of the crystal axes of the crystal grains of _{O 9,} a pair of electrodes 4a, 4b is The facing direction is preferably substantially parallel. In this way, since Ca ₃ Co ₄ O ₉ has a large thermoelectromotive force in the plane direction perpendicular to the c-axis of the crystal axis, the temperature difference and the electromotive force between the electrodes 4a and 4b are likely to increase, As a result, the sensitivity of the hydrogen gas sensor 100 can be further improved.

An example of Ca ₃ Co ₄ consisting O ₉ porous shaped thermoelectric material of the thermoelectric material part 2 constructed from the SEM image shown in FIG. 6 (a) and 6 (b). 6A is an SEM image obtained by photographing the surface of the thermoelectric material portion 2 on the side where the catalyst portion 6 is provided from a direction perpendicular to the surface, and FIG. 6B is a view where the catalyst portion 6 is provided. The thermoelectric material portion 2 was cut in a direction perpendicular to the surface of the thermoelectric material portion 2 on the side formed (a direction in which many crystal grains of Ca ₃ Co ₄ O ₉ were stacked along the c-axis direction of the crystal axis). It is a SEM image of a section. In FIG. 6A and FIG. 6B, the white portion with contrast is Ca ₃ Co ₄ O ₉ crystal particles constituting the porous thermoelectric material, and the black portion with porous contrast is the porous thermoelectric material. The hole which has. As shown in FIG. 6A and FIG. 6B, each crystal grain of Ca ₃ Co ₄ O ₉ has a plate shape that is long in the plane direction perpendicular to the c-axis of the crystal axis, and in the c-axis direction. It is in a state where a large number of layers are laminated along. In the porous thermoelectric material, a large number of pores are formed along the plane direction perpendicular to the c-axis of the crystal particles of Ca ₃ Co ₄ O ₉ .

  The porous thermoelectric material preferably has a porosity of 30 to 80%. The porosity of the porous thermoelectric material can be measured with a mercury intrusion pore distribution measuring device (porosimeter).

  The sensitivity of the hydrogen gas sensor 100 can be further improved by setting the porosity of the porous thermoelectric material within the above preferable range. Note that the smaller the porosity, the more easily heat is conducted in the thermoelectric material part 2 and the effect of the present invention tends to be reduced. The larger the porosity is, the lower the mechanical strength of the thermoelectric material part 2 is. Although there is a tendency to become brittle, these tendencies can be suppressed by setting the porosity of the porous thermoelectric material within the above preferred range.

  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 catalyst portion 6 is provided on the same surface as the electrodes 4a and 4b of the thermoelectric material portion 2 so as to be unevenly distributed on the 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 carrier is made of porous alumina and platinum is supported on the catalyst carrier. 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 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, a reaction between the hydrogen gas and oxygen in the air occurs 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, the thermoelectric material part 2 is made of a porous thermoelectric material that is less likely to conduct heat than the dense thermoelectric material conventionally used in hydrogen gas sensors. It is possible to make it difficult for the material portion 2 to conduct from the portion in contact with the catalyst portion 6 to the portion where the electrode 4b is provided. As a result, in the hydrogen gas sensor 100 of the first embodiment, the portion where the electrode 4a on the side where the catalyst portion 6 is provided unevenly in the thermoelectric material portion 2 is disposed, and the portion where another electrode 4b is disposed. Since the temperature difference between the electrodes 4a and 4b increases, the sensitivity of the hydrogen gas sensor 100 can be improved as compared with the prior art.

<Method for Manufacturing Hydrogen Gas Sensor 100>
Next, the manufacturing method of the hydrogen gas sensor 100 of 1st Embodiment is demonstrated. Hereinafter, the case of forming the thermoelectric material part 2 with a porous shape thermoelectric material consisting of Ca ₃ Co ₄ O _9.

First, the manufacturing method of the thermoelectric material part 2 is demonstrated. In the production of the thermoelectric material part 2, the raw material CaCO ₃ powder and Co ₃ O ₄ powder are weighed so that the molar ratio of Ca atoms to Co atoms is about 3: 4, and these are measured with a ball mill or the like. After mixing, the obtained mixture is heated to about 700 to 900 ° C. in the air and calcined to obtain a calcined body. The calcined body is crushed and further finely pulverized with a ball mill or the like to obtain a pulverized powder of Ca ₃ Co ₄ O ₉ .

A pulverized powder of Ca ₃ Co ₄ O ₉ , a binder resin, a solvent, and the like are mixed to prepare a slurry. Next, a sheet is formed from the slurry using a sheet method or the like. According to the seat method, in the thickness direction of the _sheet, the crystal grains of Ca 3 _Co 4 _{O 9} is, many laminated along the c-axis direction of the crystal axis in the surface direction of the _sheet, Ca 3 _Co 4 _{O 9} It becomes easy to obtain a sheet having a structure in which a large number of crystal grains are arranged along a plane direction perpendicular to the c-axis.

  Next, the sheet is punched to a predetermined size, a plurality of punched sheets are stacked to form a stacked body, and the stacked body is hot pressed at about 40 to 150 ° C. in the stacking direction of the stacked body. The thermoelectric material part 2 is obtained by heating and baking the laminated body after hot pressing at 800-920 degreeC.

  Next, an electrode forming paste for forming the electrodes 4 a and 4 b is applied to a predetermined position of the thermoelectric material portion 2. As the electrode forming paste, a mixture of a conductive material such as metal, a binder resin, a solvent, and the like can be used. The electrodes 4a and 4b are formed by baking the electrode forming paste applied to the thermoelectric material portion 2 on the thermoelectric material portion 2 at 300 to 800 ° C.

  And the catalyst part 6 is formed in the thermoelectric material part 2 in which the electrodes 4a and 4b were formed, and the sensor part 10 is obtained. In addition, as a formation method of the catalyst part 6, you may use the method of adhere | attaching the catalyst part 6 formed separately separately to the thermoelectric material part 2 in which electrode 4a, 4b was formed, and the above-mentioned catalyst component and catalyst carrying | support are mentioned. A method of forming the catalyst part 6 by applying a paste containing a body to a predetermined position of the thermoelectric material part 2 and drying it may be used. In the first embodiment, the paste including the catalyst component and the catalyst carrier is prepared to have a viscosity that can be easily applied onto the thermoelectric material portion 2.

  And the hydrogen gas sensor 100 is completed by connecting the voltage measurement part 20 to a pair of electrode 4a, 4b with which the sensor part 10 is provided.

(Second Embodiment)
Next, a hydrogen gas sensor according to a second embodiment of the present invention will be described. 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 100 of the second embodiment includes a thermoelectric material portion 2 made of a porous thermoelectric material, a pair of electrodes 4 a and 4 b provided on the thermoelectric material portion 2, and a pair of electrodes 4 a, Sensor part having catalyst part 6 which is formed by being unevenly provided on one electrode 4a side of 4b and formed by supporting a catalyst component catalyzing a reaction due to hydrogen in the pores of the porous thermoelectric material 10 and a voltage measuring unit 20 that measures a voltage generated between the pair of electrodes 4a and 4b. 3 indicates a part of the thermoelectric material portion 2, and the catalyst component is supported in the pores of the porous thermoelectric material constituting the thermoelectric material portion 2. It is a part.

  As described above, the hydrogen gas sensor 100 of the second embodiment is such that the catalyst portion 6 is formed by supporting the catalyst component that catalyzes the reaction by hydrogen in the pores of the porous thermoelectric material. This is different from the first embodiment in which 6 is provided on the surface of the thermoelectric material portion 2. That is, in 2nd Embodiment, the part of the catalyst part 6 in a figure becomes a structure which the thermoelectric material part 2 and the catalyst part 6 integrated.

  In the catalyst unit 6 in the hydrogen gas sensor 100 of the second embodiment, for example, a catalyst component is supported in the pores in the thermoelectric material unit 2 having a porous structure as shown in FIG. In such a catalyst part 6, the aspect with which the catalyst component was filled in the void | hole and the aspect in which the catalyst component adhered to the inner wall of a void | hole can be considered, and either may be sufficient. In the catalyst unit 6, both the thermoelectric material and the catalyst component can function. That is, the portion of the catalyst portion 6 in the drawing can also function as the thermoelectric material portion 2 and the catalyst portion 6.

  In the catalyst part 6, it is preferable that the pores of the porous thermoelectric material constituting the thermoelectric material part 2 can be vented to the outside. As a result, the catalyst component supported on the inner walls of the pores can easily come into contact with the external hydrogen gas and oxygen, and the catalytic reaction of hydrogen by the catalyst component is advantageous.

  Further, in the catalyst unit 6, the larger the total amount of the catalyst component with respect to all the pores of the porous thermoelectric material of this part, the larger the contact area between the catalyst component and the thermoelectric material, and the catalyst unit 6 generated It becomes easy to conduct reaction heat to the thermoelectric material part 2. On the other hand, the smaller the total amount of catalyst components in the pores of the porous thermoelectric material of the catalyst part 6 is, the easier it is to vent the holes located inside the thermoelectric material part 2 and the outside of the thermoelectric material part 2. The catalytic component carried in the pores of the thermoelectric material portion 2 facilitates the catalytic reaction of hydrogen.

  The porous thermoelectric material preferably has a porosity of 30 to 80%. The porosity of the porous thermoelectric material can be measured by the same method as in the first embodiment.

  By setting the porosity of the porous thermoelectric material within the above-mentioned preferable range, the sensitivity of the hydrogen gas sensor 100 can be further improved. When the porosity is less than 30%, the catalyst component tends to be difficult to be supported in the pores of the porous thermoelectric material. When the porosity exceeds 80%, the electrode 4a is provided in the thermoelectric material portion 2. It is difficult to support the catalyst component so that it is unevenly distributed only on the other side, and the mechanical strength of the thermoelectric material portion 2 tends to be reduced and become brittle. By setting the inside, these tendencies can be suppressed.

  The thermoelectric material unit 2 included in the hydrogen gas sensor 100 according to the second embodiment, like the first embodiment, is a porous thermoelectric material that is less likely to conduct heat than a dense thermoelectric material conventionally used in hydrogen gas sensors. Since it consists of material, the reaction heat generated in the catalyst part 6 becomes difficult to conduct from the part where the catalyst part 6 is formed in the thermoelectric material part 2 to other parts. As a result, the temperature difference between the portion where the electrode 4a on the side where the catalyst portion 6 is provided unevenly in the thermoelectric material portion 2 and the portion where the other electrode 4b is arranged increases, and both electrodes Since the electromotive force generated between 4a and 4b is increased, the sensitivity of the hydrogen gas sensor 100 can be improved as compared with the conventional case.

  Further, in the hydrogen gas sensor 100 of the second embodiment, since the catalyst portion 6 is formed by supporting the catalyst component on the inner wall of the pores of the porous thermoelectric material, the catalyst portion is the thermoelectric material as in the prior art. Compared with the case where it is installed only on the outer surface of the part, the contact area between the catalyst part 6 and the thermoelectric material part 2 is increased. Therefore, the reaction heat generated in the catalyst unit 6 is easily conducted to the thermoelectric material unit 2, and in particular, the side where the catalyst unit 6 is unevenly provided in the thermoelectric material unit 2 is easily heated. As a result, the temperature difference between the portion where the electrode 4a on the side where the catalyst portion 6 is provided unevenly in the thermoelectric material portion 2 and the portion where the other electrode 4b is arranged increases, and both electrodes Since the electromotive force generated between 4a and 4b is increased, the sensitivity of the hydrogen gas sensor 100 can be improved as compared with the conventional case.

  Furthermore, in the hydrogen gas sensor 100 of the second embodiment, since the catalyst component is supported on the inner walls of the pores of the porous thermoelectric material, the catalyst component is provided on the surface of the thermoelectric material portion 2 (a pair of electrodes 4a and 4b are provided). The active surface area of the catalyst part 6 is increased compared to the case where the catalyst part 6 is disposed on the surface, and the catalytic activity ability of the catalyst part 6 as a whole is improved. Therefore, the sensitivity of the hydrogen gas sensor 100 can be improved.

  Furthermore, in the hydrogen gas sensor 100 of the second embodiment, a catalyst component is supported in a large number of holes in the thermoelectric material portion 2. That is, since the catalyst part 6 is also located inside the thermoelectric material part 2, the hydrogen catalytic reaction also proceeds inside the thermoelectric material part 2. Therefore, in the hydrogen gas sensor 100 of the second embodiment, the reaction heat generated in the catalyst unit 6 is less likely to escape to the outside air as compared with the conventional case where the catalyst unit 6 is installed only on the outer surface of the thermoelectric material unit 2. The reaction heat can be efficiently conducted to the thermoelectric material part 2 and the sensitivity of the hydrogen gas sensor 100 can be improved.

  The hydrogen gas sensor 100 of the second embodiment is formed by forming the thermoelectric material part 2, the electrodes 4a and 4b, and the voltage measuring part 20 by the same method as in the first embodiment except that the formation method of the catalyst part 6 is different. Can be manufactured. The catalyst unit 6 in the hydrogen gas sensor 100 of the second embodiment is preferably manufactured as follows, for example. That is, as shown in FIG. 4, after applying a paste 6 a containing a catalyst component to a predetermined position on the thermoelectric material portion 2, the paste 6 a is soaked into the thermoelectric material portion 2. That is, the paste 6 a is caused to enter the holes in the thermoelectric material portion 2. Next, by drying the paste 6a, the catalyst part 6 having a structure in which the catalyst component is supported in the pores of the thermoelectric material part 2 can be formed.

  In this case, the paste containing the catalyst component is a mixture of a catalyst component, a catalyst carrier, a binder resin, a solvent, and the like, and a paste whose viscosity is adjusted so as to easily penetrate into the thermoelectric material portion 2 is used. be able to. In the second embodiment, since the thermoelectric material part 2 made of a porous thermoelectric material also functions as a catalyst carrier, the catalyst part 6 is made by carrying a catalyst component on a carrier such as porous alumina. It is not necessary to use it.

  Moreover, in 2nd Embodiment, as shown in FIG. 5, the catalyst part 6 immerses a part of the thermoelectric material part 2 in the solution 6b of the catalyst component with which the tank was filled, and 1 part of the thermoelectric material part 2 is immersed. Alternatively, the solution 6b may be soaked in the part, and then the solution 6b soaked in the thermoelectric material part 2 may be dried. By doing so, the penetration of the catalyst component tends to be more advantageous.

  The hydrogen gas sensors of the first and second 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 thereof.

  For example, in the hydrogen gas sensor 100 of the first embodiment, the catalyst unit 6 is provided on the thermoelectric material unit 2, but a part of the catalyst unit 6 may penetrate into the thermoelectric material unit 2.

  Moreover, the formation position of the catalyst part 6 in 2nd Embodiment is not limited to the above-mentioned thing. For example, the catalyst component constituting the catalyst part 6 may be further carried in the holes of the thermoelectric material part 2 located immediately below the electrode 4a. Further, a part of the catalyst unit 6 may be further formed at a position adjacent to the electrode 4 a on the surface of the thermoelectric material unit 2.

  Furthermore, in the first and second embodiments, the thermoelectric material portion 2 in the hydrogen gas sensor 100 has a plate shape, but any one that can arrange the pair of electrodes 4a, 4b and the catalyst portion 6 on the surface. It may have a shape other than a plate shape. 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 figure which shows an example of the formation method of the catalyst part with which the hydrogen gas sensor which concerns on 2nd Embodiment is provided. It is a figure which shows an example of the formation method of the catalyst part with which the hydrogen gas sensor which concerns on 2nd Embodiment is provided. Ca is ₃ Co ₄ SEM image showing an example of the structure of the porous shaped thermoelectric material consisting of O _9.

Explanation of symbols

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

Claims (3)

A thermoelectric material portion made of a porous thermoelectric material, a pair of electrodes provided on the thermoelectric material portion, and provided unevenly on one electrode side of the pair of electrodes on the thermoelectric material portion, and by hydrogen A sensor part having a catalyst part for catalyzing the reaction;
A voltage measuring unit for measuring a voltage generated between the pair of electrodes;
A hydrogen gas sensor comprising: A thermoelectric material part made of a porous thermoelectric material, a pair of electrodes provided on the thermoelectric material part, and a catalyst component that is provided unevenly on one electrode side of the pair of electrodes and catalyzes a reaction by hydrogen Is a sensor part having a catalyst part formed by being carried in the pores of the porous thermoelectric material,
A voltage measuring unit for measuring a voltage generated between the pair of electrodes;
A hydrogen gas sensor comprising: The hydrogen gas sensor according to claim 1 or 2, wherein a porosity of the porous thermoelectric material is 30 to 80%.