Hydrogen gas concentration sensor

Abstract

To provide an electromotive force (EMF)-type hydrogen gas concentration sensor inhibiting disturbance gas from contacting a hydrogen detection electrode of a hydrogen gas sensor while maintaining sensor functions.SOLUTION: A hydrogen gas concentration sensor comprises: a first electrode piece and a second electrode piece; electrolyte in which the electrode pieces are separately disposed; and a container storing the first electrode piece, the second electrode piece and the electrolyte. The first electrode piece contains a first electrode material of which a cell composed of H2(-)|50 mol / m3H2SO4| material sample (+) has a reference electromotive force value of 0.8 V or greater, while the second electrode piece contains a second electrode material of which the cell composed of the same has the reference electromotive force value of less than 0.8 V. One end of the container is sealed by a porous material including pores having a diameter of 0.25 nm to 0.45 nm.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a hydrogen gas concentration sensor. [Background technology]

[0002] In the future society that utilizes hydrogen energy, it is desirable to construct a hydrogen energy utilization system that eliminates the risk of hydrogen explosions, is highly safe, and is highly convenient. The specifications of the hydrogen gas sensor must be able to instantly detect the amount of hydrogen that has leaked into the atmosphere with high accuracy, have an extremely simple structure, and be highly reliable.

[0003] Conventional hydrogen gas concentration sensors are based on detection methods such as semiconductor, ionization, combustion, etc. The measurement principle of these is to detect the amount of hydrogen indirectly as "extensive physical quantities" such as "carrier concentration (semiconductor type)," "ion concentration (ionization type)," or "reaction heat (combustion type or burning and measuring the water vapor pressure)," and convert these into electrical quantities to use as sensors.

[0004] As a hydrogen gas concentration sensor that shortens the detection time, for example, an electromotive force (EMF) type hydrogen gas sensor has been proposed which has a first electrode and a second electrode made of materials with different chemical potentials with respect to hydrogen, and an electrolyte in contact with these electrodes, and detects hydrogen gas based on the electromotive force value generated between these electrodes (Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 4035848 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the hydrogen gas sensor described in Patent Document 1, the surface of the hydrogen detection electrode has a property of promoting chemical reactions, and this property is explained by the electronic structure of the surface. In other words, it is required not to come into contact with gases that interfere with the sensor function described in the necessity of the application. To achieve this purpose, it is possible to use a hydrogen selective permeable thin film (Pd thin film), but since it takes time to release hydrogen dissolved in the Pd thin film, there is an issue that it takes time to respond to hydrogen gas compared to the above-mentioned EMF-type hydrogen gas concentration sensor.

[0007] An object of the present invention is to provide an EMF type hydrogen gas concentration sensor that suppresses contact of interfering gases with a hydrogen detection electrode in a hydrogen gas sensor and maintains sensor function. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention provides: a first electrode piece and a second electrode piece, an electrolyte in which the electrodes are disposed apart from each other, and a container that contains the first electrode piece, the second electrode piece, and the electrolyte; The first electrode piece is H2(-)|50mol / m 3 The cell includes a first electrode material having a standard electromotive force value of 0.8 V or more, the standard electromotive force value being 0.8 V or more. The second electrode piece includes a second electrode material that exhibits a standard electromotive force value of less than 0.8 V in a cell having the same configuration, The present invention relates to a hydrogen gas concentration sensor, characterized in that one end of the container is sealed with a porous body having pores with diameters of 0.25 nm to 0.45 nm. Effect of the Invention

[0009] According to the present invention, one end of the container constituting the hydrogen gas concentration sensor is sealed with a porous body having pores with a diameter of 0.25 nm to 0.45 nm. This porous body does not allow interfering gases such as carbon dioxide (CO2) to pass through, but allows hydrogen gas to pass through. Therefore, interfering gases such as carbon dioxide (CO2) do not enter the container, and only hydrogen gas is selectively introduced and reaches the hydrogen detection electrode. Therefore, in combination with the characteristics of the first electrode piece and the second electrode piece, it is possible to provide an EMF type hydrogen gas concentration sensor that suppresses contact of interfering gases with the hydrogen detection electrode in the hydrogen gas sensor and maintains sensor function. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic configuration diagram of a hydrogen gas concentration sensor according to an embodiment. [Diagram 2] 4 is a graph showing hydrogen gas concentration and EMF value when a platinum wire is used as a first electrode piece of the hydrogen gas concentration sensor in the example. [Diagram 3] 1 is a graph showing the EMF value of an interfering gas (CO2 gas). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] FIG. 1 is a schematic diagram of a hydrogen gas concentration sensor according to the present embodiment.

[0012] As shown in FIG. 1, the hydrogen gas concentration sensor 10 of this embodiment comprises a linear first electrode piece 11, a linear second electrode piece 12, an electrolyte 14 in which these electrodes are arranged at a distance from each other, and a container 15 that contains the first electrode piece 11, the second electrode piece 12, and the electrolyte 14.

[0013] One end of the container 15 is sealed with a porous body 16 having pores with a diameter of 0.25 nm to 0.45 nm, preferably 0.29 nm to 0.33 nm. The pore diameter is the average value of 10 pore diameters when the porous body 16 is observed with a transmission electron microscope (TEM). The one end of the container 15 is inserted and disposed in a system to be measured. The porous body 16 can be composed of, for example, a microporous ceramic filter such as alumina or zeolite, or a membrane such as a microporous metal filter or polymer filter, but is not limited thereto.

[0014] In addition, since the detection sensitivity of the hydrogen gas concentration sensor 10 of this embodiment changes depending on the environmental temperature, a linear temperature compensation third electrode piece 13 is provided to eliminate the influence of the environmental temperature. This third electrode piece 13 is also provided so as to be spaced apart from the first electrode piece 11 and the second electrode piece 12 with respect to the electrolyte 14.

[0015] In addition, the first electrode piece 11, the second electrode piece 12, and the third electrode piece 13 are arranged to extend outside the container 15 from the rear end opening of the container 15 opposite the sealed portion of the container 15 in order to measure the electromotive force associated with the detection of hydrogen gas concentration.

[0016] The first electrode piece 11 functions as a detection electrode for hydrogen gas, and the chemical potential of (atomic) hydrogen changes significantly when it comes into contact with hydrogen gas. The second electrode piece 12 functions as a reference electrode for hydrogen gas, and the chemical potential of the second electrode piece 12 changes very little or only slightly when it comes into contact with hydrogen gas.

[0017] The first electrode piece 11 can be made of a first electrode material having a relatively high chemical potential, specifically, H2(-)|50 mol / m 3 The first electrode material includes a cell formed of H2SO4|substance sample (+) that exhibits a standard electromotive force value of 0.8 V or more.

[0018] The above-mentioned materials include platinum, platinum alloys, and other materials that have a relatively high adsorption activity for hydrogen gas. The first electrode piece 11 can be made of these materials themselves, or these materials can be supported on a predetermined substrate. However, as long as it functions as a detection electrode for hydrogen gas without departing from the scope of the present invention, it can be used in any form.

[0019] The above-mentioned materials may also be made of materials with relatively high adsorption activity for hydrogen gas, such as palladium and palladium alloys. As in the above, the first electrode piece 11 may be made of these materials themselves, or these materials may be supported on a predetermined substrate. However, as long as they function as a detection electrode for hydrogen gas without departing from the scope of the present invention, they may be used in any form.

[0020] Furthermore, when the first electrode piece 11 is made of a platinum-based material, hydrogen molecules are dissociated, and the hydrogen gas adsorbed on the first electrode piece 11 is quickly released, making it suitable as a detection electrode for a fast-responding hydrogen gas concentration sensor, such as a fuel cell control sensor or a hydrogen gas concentration sensor for hydrogen gas dissolved in medical fluids, etc.

[0021] On the other hand, when the first electrode piece 11 is made of a palladium-based material, it dissolves an amount of hydrogen according to the hydrogen partial pressure, but the dissolved hydrogen has a property of being difficult to escape, and it takes time to recover after hydrogen gas detection. Therefore, when the first electrode piece 11 is made of a palladium-based material, the first electrode piece 11 has a memory function and can be used as a detection electrode suitable for checking the deterioration of transformer oil, for example. However, it is not suitable as a hydrogen detection electrode for an EMF-type hydrogen gas concentration sensor.

[0022] The second electrode piece 12 can be made of a material with a relatively low chemical potential. Specifically, H2(-)|50 mol / m 3 The second electrode material contains H2SO4|, and the standard electromotive force value of the cell constructed with the substance sample (+) is less than 0.8 V.

[0023] The above-mentioned materials include materials with relatively low adsorption activity for hydrogen gas, such as tungsten, tungsten alloys, nickel, nickel alloys, titanium, titanium alloys, copper, copper alloys, iron, iron alloys, aluminum, aluminum alloys, and organic conductive materials. However, as long as they function as a reference electrode for hydrogen gas without departing from the scope of the present invention, they can be used in any manner.

[0024] The third electrode piece 13 is an electrode piece for temperature compensation and is arranged to offset changes in the environmental temperature of the hydrogen gas concentration sensor 10, i.e., the environmental temperature of the first electrode piece 11, which is the detection electrode, and therefore it is preferable for the third electrode piece 13 to be made of the same material as the first electrode piece 11.

[0025] Furthermore, the electrolyte 14 can be made of an electrolyte such as phosphotungstic acid that has excellent adhesion to the first electrode piece 11 and the second electrode piece 12. The electrolyte 14 can contain a structural reinforcing material such as glass wool in addition to an electrolyte material such as phosphotungstic acid. In this case, the strength of the electrolyte 14 can be increased, and the adhesion to the first electrode piece 11 and the second electrode piece 12 can be further increased.

[0026] In order to ensure insulation between the first electrode piece 11 and the second electrode piece 12, the container 15 is preferably made of glass, resin, ceramics, or the like.

[0027] When the container 15 is made of an electrically conductive material such as metal, it is preferable to insulate the first electrode piece 11 from the container 15 by coating it with resin or ceramic.

[0028] The hydrogen gas concentration sensor 10 of this embodiment includes a first electrode piece 11, a second electrode piece 12, an electrolyte 14 between which the electrodes are spaced apart, and a container 15 that contains the first electrode piece 11, the second electrode piece 12, and the electrolyte 14. The first electrode piece 11 has a concentration of H2(-)|50 mol / m 3The container includes a first electrode material having a standard electromotive force value of 0.8 V or more when configured with H2SO4|substance sample (+), and the second electrode piece 12 includes a second electrode material having a standard electromotive force value of less than 0.8 V when configured with the same cell, and one end of the container is sealed with a porous body having pores with diameters of 0.25 nm to 0.45 nm.

[0029] Interfering gases such as carbon dioxide (CO2) do not permeate the porous body 16, but hydrogen gas does. Therefore, interfering gases such as carbon dioxide (CO2) do not enter the container 15, and only hydrogen gas is selectively introduced and reaches the hydrogen detection electrode, i.e., the first electrode piece 11. Therefore, in conjunction with the characteristics of the first electrode piece 11 and the second electrode piece 12, it is possible to provide an EMF type hydrogen gas concentration sensor 10 that suppresses contact of interfering gases with the hydrogen detection electrode in the hydrogen gas sensor and maintains sensor function.

[0030] The hydrogen concentration of the hydrogen gas concentration sensor 10 of this embodiment is detected by the electromotive force generated between the first electrode piece 11 and the second electrode piece 12, and this electromotive force is generated based on the following relational expression.

[0031]

number

number

number

number

number

[0032] In view of the above embodiment, the present application also includes the following inventions. [1] A battery comprising a first electrode piece and a second electrode piece, an electrolyte in which the electrodes are disposed apart from each other, and a container for accommodating the first electrode piece, the second electrode piece, and the electrolyte; The first electrode piece is H2(-)|50mol / m 3 The cell includes a first electrode material having a standard electromotive force value of 0.8 V or more, the standard electromotive force value being 0.8 V or more. The second electrode piece includes a second electrode material that exhibits a standard electromotive force value of less than 0.8 V in a cell having the same configuration, A hydrogen gas concentration sensor, characterized in that one end of the container is sealed with a porous body having pores with diameters of 0.25 nm to 0.45 nm. [2] The hydrogen gas concentration sensor according to [1], characterized in that the porous body is a membrane. [3] The hydrogen gas concentration sensor according to [1] or [2], characterized in that the first electrode material includes at least one of platinum, a platinum alloy, and materials containing these. [4] A hydrogen gas concentration sensor as described in any one of [1] to [3], characterized in that the second electrode material includes at least one of tungsten, tungsten alloy, nickel, nickel alloy, titanium, titanium alloy, copper, copper alloy, iron, iron alloy, aluminum, aluminum alloy, and materials containing these. [5] A hydrogen gas concentration sensor as described in any one of [1] to [4], characterized in that it comprises a third electrode piece housed in the container and disposed in the electrolyte. EXAMPLES

[0033] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these.

[0034] A hydrogen gas concentration sensor 10 shown in Fig. 1 was prepared and a simple hydrogen gas detection test was carried out. Note that a platinum wire with a diameter of 0.2 mm was used for the first electrode piece 11, and a tungsten wire with a diameter of 0.2 mm was used for the second electrode piece 12. For simplification, the third electrode piece 13 was omitted.

[0035] Next, the first electrode piece 11 and the second electrode piece 12 were disposed in an electrolyte 14 made of cesium tungsten phosphate at an interval of 0.2 mm, and the first electrode piece 11, the second electrode piece 12 and the electrolyte 14 were housed and disposed in a glass tube 15 having a diameter of 6 mm and a length of 25 mm, and an alumina membrane 16 having a pore size of 0.3 nm was disposed at one end of the glass tube 15, and the glass tube 15 was sealed with the alumina membrane 16. When sealing, the alumina membrane 16 portion of the glass tube 15 was covered with a silicon tube, and the alumina membrane 16 was pressed against the inner wall surface of the glass tube 15 to seal it.

[0036] FIG. 2 is a graph showing the hydrogen gas concentration and the EMF value when a platinum wire is used as the first electrode piece, and FIG. 3 is a graph showing the EMF value of an interfering gas (CO2 gas).

[0037] The hydrogen gas concentration was adjusted by filling a sealed container with hydrogen gas, which had an opening through which the glass container 15 could be inserted, and the detected electromotive force was measured at the rear end opening of the glass tube 15.

[0038] As shown in FIG. 2, when a platinum wire is used as the first electrode piece 11, the detection voltage decreases from about 0.5 V to about -0.5 V as the hydrogen gas concentration changes from 0 to 50 volume % at a temperature of 20°C, but when contact with hydrogen gas is cut off, the electromotive force immediately recovers to about 0.5 V. In other words, it is found that hydrogen gas is quickly released and the electrode is suitable as a detection electrode for a hydrogen gas concentration sensor with fast response. In addition, in the measurement using a platinum wire as the first electrode piece 11, the value of the spontaneous electromotive force of the sensor, which is a characteristic of an EMF type hydrogen sensor, was measured by an electrometer at the rear end opening of the glass tube 15.

[0039] On the other hand, as shown in FIG. 3, when the interfering gas (CO2 gas) concentration exceeds 20 volume %, the interfering gas shielding effect of the alumina film 16 is slightly deteriorated, but it can be seen that a sufficiently high interfering gas shielding effect is achieved between 5 volume % and 20 volume %.

[0040] Therefore, it is understood that the hydrogen gas concentration sensor 10 of the present invention can provide an EMF type hydrogen gas concentration sensor that suppresses contact of interfering gas with the hydrogen detection electrode and maintains sensor function.

[0041] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0042] 10 Hydrogen gas concentration sensor 11 First electrode piece 12 Second electrode piece 13 Third electrode piece 14 Electrolytes 15 Container 16 Porous bodies

Claims

1. a first electrode piece and a second electrode piece, an electrolyte in which the electrodes are disposed apart from each other, and a container that contains the first electrode piece, the second electrode piece, and the electrolyte; The first electrode piece is H ２ (-)|50mol / m ３ H ２ SO ４ | A first electrode material having a standard electromotive force value of 0.8 V or more when the cell is made of the substance sample (+), The second electrode piece includes a second electrode material that exhibits a standard electromotive force value of less than 0.8 V in a cell having the same configuration, A hydrogen gas concentration sensor, characterized in that one end of the container is sealed with a porous body having pores with diameters of 0.25 nm to 0.45 nm.

2. 2. The hydrogen gas concentration sensor according to claim 1, wherein the porous body is a membrane.

3. 2. The hydrogen gas concentration sensor according to claim 1, wherein the first electrode material includes at least one of platinum, a platinum alloy, and a material containing these.

4. 2. The hydrogen gas concentration sensor according to claim 1, wherein the second electrode material includes at least one of tungsten, a tungsten alloy, nickel, a nickel alloy, titanium, a titanium alloy, copper, a copper alloy, iron, an iron alloy, aluminum, an aluminum alloy, and materials containing these.

5. 2. The hydrogen gas concentration sensor according to claim 1, further comprising a third electrode piece housed in the container and disposed in the electrolyte.

Images