JP2006162365A - Hydrogen gas detection sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrogen gas detection sensor capable of improving poisoning resistance of a catalyst, removing humidity dependency, and obtaining high-speed responsiveness. <P>SOLUTION: This sensor for detecting hydrogen gas is equipped with: an electrically insulating substrate 1; a detection film 3 for detecting the hydrogen gas by dissociating hydrogen gas laminated on the substrate 1; a pair of electrodes 2 in contact with either of the substrate 1 and the detection film 3; and a heating means 4 arranged on the insulating substrate 1 side, for heating the detection film 3 to a prescribed temperature. The detection film 3 comprises the catalyst having an action adsorbing the hydrogen gas and dissociating the gas into protons (H<SP>+</SP>) and electrons (e), and a metal oxide whose conductivity is increased by a reaction between protons (H<SP>+</SP>) and electrons (e) generated by the action. Consequently, the poisoning resistance of the catalyst is improved, and the humidity dependency is removed, and the high-speed responsiveness becomes possible. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a hydrogen gas detection sensor using a detection film in which a catalyst is dispersedly supported on a metal oxide, and by reaction of protons (H ⁺ ) generated by dissociating hydrogen gas with a catalyst and electrons (e), The present invention relates to a hydrogen gas detection sensor that utilizes the property that electrical resistance changes due to reduction of metal oxides. In particular, containers, pipes, automobiles, fuel cells, hydrogen that require monitoring of gas leakage including hydrogen gas for safety The present invention relates to a hydrogen gas detection sensor installed in a fuel reformer or the like.

  In recent years, from the viewpoint of protecting the global environment and preventing the depletion of fossil fuels, it is desired to use clean and recyclable energy, and hydrogen gas is attracting attention as a substitute. Hydrogen gas is a potentially abundant fuel and has the advantage of low environmental impact, but is highly explosive (explosion limit concentration is wide from 4% to 75%) and is known to be a dangerous gas. It has been. In order to spread hydrogen gas as an energy source in the future, safety measures for using the system with confidence are indispensable. Therefore, a hydrogen gas detection sensor having high-speed response, high sensitivity, and excellent reliability is desired.

  Currently, there are a catalytic combustion method, a semiconductor method, a solid electrolyte method, a light detection method, and the like as a hydrogen gas detection sensor, and a semiconductor method using a metal oxide is representative.

In a conventional semiconductor-type hydrogen gas detection sensor, two electrodes are provided on a substrate, tungsten trioxide (WO ₃ ) as a detection layer is provided across the electrodes, and a catalyst layer is further provided thereon. A hydrogen gas detection sensor (for example, see Patent Document 1) formed with platinum (Pt) or palladium (Pd), a detection film mainly composed of tungsten trioxide (WO ₃ ), and a surface of the detection layer And a detection layer provided with a heater to prevent a decrease in sensitivity due to a decrease in the temperature of the atmosphere, and a catalyst layer that dissociates hydrogen gas provided on the surface of the detection film. A stacked hydrogen gas detection sensor in which a catalyst layer is stacked is known. (For example, see Patent Document 2.)
Further, a platinum dispersion in which a detection film in which a platinum (Pt) catalyst is dispersedly supported on tungsten trioxide (WO ₃ ) is formed on an insulating substrate, and an electrode is formed on the tungsten trioxide (WO ₃ ) with platinum (Pt). Research has been conducted on hydrogen gas detection sensors of type tungsten oxide. (For example, refer nonpatent literature 1.)
These hydrogen gas detection sensors dissociate hydrogen gas into protons (H ⁺ ) and electrons (e) by a catalyst, and protons (H ⁺ ), electrons (e) and tungsten trioxide (WO ₃ ) generated by the catalyst. As a result, tungsten bronze is formed, and the conductivity of the detection film changes accordingly, and hydrogen gas is detected by detecting the conductivity.
JP-A-60-212348 JP 2003-240746 A Nanako Yamamoto, 3 others, “Detection characteristics and optimization of room-temperature hydrogen sensor using Pt / WO3 film”, Chemical Sensors, Chemical Society of Electrochemical Society, Vol. 18, Supplement A (2002)

  However, the above hydrogen gas detection sensor has the following problems.

In the sensor in which the detection film and the catalyst film are laminated, when palladium (Pd) is used for the catalyst film, the property changes irreversibly, such as cracking in the palladium (Pd) film when hydrogen exposure is repeated. There is a problem that sensor characteristics deteriorate. In addition, when platinum (Pt) is used for the catalyst film, platinum (Pt) has a property of strongly binding to carbon monoxide (CO). Therefore, if carbon monoxide (CO) is present in the atmospheric gas, platinum (Pt) There is a problem in that the surface of Pt) is poisoned by carbon monoxide (CO), hydrogen gas cannot be dissociated into protons (H ⁺ ) and electrons (e), and hydrogen gas cannot be detected.

  In addition, platinum dispersed tungsten oxide is greatly affected by the humidity of the atmosphere in which the hydrogen gas detection sensor is installed. When only the humidity is changed with the hydrogen concentration kept constant, the conductivity is high at low humidity and high humidity. Sometimes there is a humidity dependency problem that the conductivity is low. It is also possible to install a humidity sensor or the like to detect the humidity of the installation atmosphere and make corrections based on the result, but this hinders downsizing the sensor and also increases costs.

  Furthermore, the response time for detecting hydrogen gas generally needs to be high-speed response to ensure safety, but there is also a problem that the response time is very slow.

  The present invention solves the above-described conventional problems, and an object thereof is to provide a hydrogen gas detection sensor that improves the poisoning resistance of a catalyst, removes humidity dependency, and enables high-speed response. .

In order to solve the conventional problems, a hydrogen gas detection sensor according to the present invention is a hydrogen gas detection sensor for detecting hydrogen gas, comprising an electrically insulating substrate and a hydrogen gas laminated on the substrate. A detection film that dissociates and detects the hydrogen gas; and a pair of electrically conductive electrodes that are formed in contact with the substrate or the detection film in a structure that is not exposed to atmospheric gas, the detection film comprising: , metal conductivity increases by the reaction of adsorbed hydrogen gas and protons (H ⁺⁾ and electrons protons generated in the catalyst and the effect it has the effect of dissociation in (e) (H ⁺⁾ and electrons (e) The catalyst comprises an oxide, and the catalyst has a particle structure in which particles having a diameter smaller than that of the metal oxide constituting the detection film are dispersedly supported on the metal oxide particles.

Further, the hydrogen gas detection sensor of the present invention is a hydrogen gas detection sensor for detecting hydrogen gas, an electrically insulating substrate, a detection film for detecting hydrogen gas laminated on the substrate, An electrode made of a metal that is formed in contact with the sensing film to measure the conductivity of the sensing film and has no catalytic activity against a reducing gas such as hydrogen gas, hydrocarbon gas, or carbon monoxide gas When, wherein the sensing layer comprises a catalyst having an action to dissociate adsorbed hydrogen gas and protons (H ⁺⁾ to the electronic (e), protons generated in the acting and (H ⁺⁾ electronic (e) The catalyst has a particle structure in which particles having a diameter smaller than the metal oxide particles constituting the detection film are dispersed and supported on the metal oxide particles. It is characterized by .

The hydrogen gas detection sensor of the present invention is a hydrogen gas detection sensor that detects hydrogen gas, and dissociates the electrically insulating substrate from the hydrogen gas stacked on the substrate to remove the hydrogen gas. A detection film for detection, and a pair of electrically conductive electrodes formed in contact with the substrate or the detection film in a structure not exposed to atmospheric gas, the detection film adsorbing hydrogen gas proton (H ⁺⁾ and a metal oxide conductivity is increased by reaction of protons generated in the catalyst and the effect of having an effect of dissociation and (H ⁺⁾ and electrons (e) to an electronic (e), the detection A heating means for heating the film to a predetermined temperature is provided.

Further, the hydrogen gas detection sensor of the present invention is a hydrogen gas detection sensor for detecting hydrogen gas, an electrically insulating substrate, a detection film for detecting hydrogen gas laminated on the substrate, An electrode made of a metal that is formed in contact with the sensing film to measure the conductivity of the sensing film and has no catalytic activity against a reducing gas such as hydrogen gas, hydrocarbon gas, or carbon monoxide gas When, wherein the sensing layer comprises a catalyst having an action to dissociate adsorbed hydrogen gas and protons (H ⁺⁾ to the electronic (e), protons generated in the acting and (H ⁺⁾ electronic (e) And a heating means for heating the detection film to a predetermined temperature.

The hydrogen gas detection sensor of the present invention is a hydrogen gas detection sensor that detects hydrogen gas, and dissociates the electrically insulating substrate from the hydrogen gas stacked on the substrate to remove the hydrogen gas. A detection film for detection, and a pair of electrically conductive electrodes formed in contact with either the substrate or the detection film, wherein the detection film absorbs hydrogen gas and absorbs protons ( H ⁺ ) and a catalyst having a function of dissociating into electrons (e) and a metal oxide whose conductivity is increased by the reaction of protons (H ⁺ ) and electrons (e) generated by the action, A heating means for heating to a predetermined temperature from 50 ⁰ C to 150 ⁰ C is provided.

According to the hydrogen gas detection sensor of the present invention, a hydrogen gas detection sensor for detecting hydrogen gas, which is a structure that is not exposed to an electrically insulating substrate and an electrically conductive atmospheric gas. And a detection film for dissociating and detecting hydrogen gas, the detection film adsorbing hydrogen gas and finally dissociating into protons (H ⁺ ) and electrons (e) and the catalyst The catalyst comprises a metal oxide whose conductivity is increased by a reaction between protons (H ⁺ ) and electrons (e) generated by the action, and the catalyst has particles smaller in diameter than the metal oxide particles constituting the detection film. By having a particle structure dispersed and supported on metal oxide particles, a hydrogen gas detection sensor with excellent poisoning resistance that does not deteriorate in hydrogen gas sensitivity even if the hydrogen gas detection sensor is exposed to carbon monoxide gas. Realize It can be.
Further, according to the hydrogen gas detection sensor of the present invention, the hydrogen gas detection sensor detects hydrogen gas and has a structure that is not exposed to an electrically insulating substrate and an electrically conductive atmospheric gas. A catalyst having a pair of electrodes and a detection film for dissociating and detecting hydrogen gas, the detection film adsorbing hydrogen gas and finally dissociating into proton (H ⁺ ) and electron (e) And a hydrogen oxide gas comprising a heating means for heating the detection film to a predetermined temperature, comprising a metal oxide whose conductivity is increased by a reaction between protons (H ⁺ ) and electrons (e) generated by the above action. It is not affected by the humidity dependency in the installation atmosphere of the detection sensor, and high-speed response can be achieved.

  Embodiments of the hydrogen gas detection sensor of the present invention will be described below in detail with reference to the drawings.

  In Example 1, the structure, material, operation principle, and preparation method of the hydrogen gas detection sensor of the present invention are described, and the poisoning resistance, humidity dependency, and responsiveness were evaluated using the hydrogen gas detection sensor of the present invention. State the results.

  The structure of the hydrogen gas detection sensor will be described with reference to FIGS.

The main components of the hydrogen gas detection sensor of the present invention include an electrically insulating substrate 1, an electrically conductive electrode 2, an adsorbed hydrogen gas, and finally a proton (H ⁺ ) And a catalyst having a function of dissociating into electrons (e), and a detection film 3 made of a metal oxide whose conductivity is increased by a reaction between protons (H ⁺ ) and electrons (e) generated by the above-described actions. Yes. Actually, as shown in FIG. 1, an electrically insulating substrate 1, a pair of electrodes 2 provided on the same substrate 1, and a detection film 3 formed so as to cover the electrodes 2. The metal used for the electrode 2 is required to use a metal having a heat resistance of 350 ° C. or higher for the use of the hydrogen gas detection sensor. Such a metal includes hydrogen gas, hydrocarbon-based gas, It has activity against reducing gases such as carbon monoxide gas. Therefore, in order to realize a hydrogen gas detection sensor having selectivity for hydrogen gas and high reproducibility, the electrode 2 needs to have a structure that is not exposed to the atmospheric gas. As another structure, as shown in FIG. 2, a detection film 3 is provided on an electrically insulating substrate 1, and a pair of electrodes having a low catalytic activity against hydrogen gas on the detection film 3 May be formed.

  Alternatively, as shown in FIG. 2, when the electrode 2 made of a metal catalyst active in gas is used on the detection film 3, the electrode 2 is not directly exposed to the atmospheric gas as shown in FIG. In addition, it is only necessary to be covered with a protective film 9 that does not allow the passage of reducing gas that causes poisoning of the sensor. If the electrode 2 is inert to the gas, the protective film 9 may or may not be provided.

  In the case where the heating means 4 is provided, as shown in FIGS. 4 and 5, in the hydrogen gas detection sensor having the structure shown in FIGS. 1 and 2, heating is performed on the surface of the substrate 1 on which the electrode 2 and the detection film 3 are not stacked. Means 4 are formed. In addition, as shown in FIG. 6, a heating means 4 is provided on an electrically insulating substrate 1, an insulating film 5 is formed so as to cover the heating means 4, and a pair of electrodes is formed on the insulating film 5. The detection film 3 may be formed so as to cover the electrode 2.

  Further, the heater as the heating unit 4 may have a configuration similar to that in FIG. 6 and the electrode 2 may be formed on the detection film 3. That is, as in FIG. 6, the heating means 4 is provided on the electrically insulating base material 1, the insulating film 5 is formed so as to cover the heating means 4, and the detection film 3 is formed on the insulating film 5. Then, a pair of electrodes 2 may be formed on the detection film 3 (not shown). The structure is not limited to the above structure. Further, although similar to FIG. 6, as shown in FIG. 7, the heating means 4 is formed on the insulating substrate 1 on the side where the detection film 3 is not laminated, and the heating means 4 is further covered with the insulating layer 5. It may be a structure.

  Next, the structure of the detection film will be described. In FIG. 8, the detection film 3 is composed of an aggregate of particulate metal oxides 18 having a particle diameter of 15 nm to 100 nm and has a gap. The gap is formed by evaporating a solvent component of water or alcohol contained in a sol-gel solution that is a synthetic material of the metal oxide 18 described later when heat treatment is performed when the detection film 3 is formed. The gap between the metal oxide 18 aggregates is related to gas adsorption, and the larger the gap, the larger the hydrogen gas adsorption area, and the higher the hydrogen gas sensitivity. A catalyst 19 having a particle diameter of 1 nm to 35 nm is dispersed and supported on the surface of the metal oxide 18. As shown in FIG. 8, the dispersion support indicates a state in which the catalyst 19 is scattered as particles in the metal oxide 18 and the metal oxide 18 and the catalyst 19 in the catalyst 19 are adsorbed.

The catalyst 19 particles adsorbed on the metal oxide 18 particles preferably have a smaller catalyst 19 particle diameter than the metal oxide 18 particle diameter. The catalyst 19 has an area exposed on the surface of the metal oxide 18 particles. The wider, the greater the adsorption / dissociation action of hydrogen gas, and the more proton (H ⁺ ) production occurs. Although FIG. 8 shows that a plurality of catalysts 19 exist on the particle surface of the metal oxide 18, the number of the catalysts 19 on the particle surface of the metal oxide 18 is not limited.

  Next, materials that constitute the hydrogen gas detection sensor will be described.

The substrate 1 may be made of any material as long as it has insulating properties. However, since the heating temperature at the time of sintering the detection film 3 is 350 ° C. or higher, the substrate 1 needs to be a material having high heat resistance. Preferably, quartz (SiO ₂ ), surface-insulated (eg, silicon oxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), aluminum nitride (AlN), alumina (Al ₂ O ₃ ), or these A silicon substrate (SiO ₂ ), aluminum nitride (AlN), alumina (Al ₂ O ₃ ) or the like on which a composite film is formed can be used.

  Next, as shown in FIGS. 1, 4, 6, and 7, the electrode 2 has a structure in which the electrode 2 is formed on the substrate 1 or between the insulating film 5 and the detection film 3. Since it is not exposed to the atmospheric gas, it is possible to use a material that is electrically conductive and is stable at about 350 ° C. or higher, which is the sintering temperature of the detection film 3. Preferably, aluminum (Al), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), nickel (Ni), copper (Cu), niobium (Nb), molybdenum (Mo), ruthenium ( Use metals and alloys such as Ru), rhodium (Rh), silver (Ag), tantalum (Ta), osmium (Os), iridium (Ir) platinum (Pt), gold (Au), carbon (C), etc. Is possible.

  As shown in FIGS. 2 and 5, when the electrode 2 is formed on the detection film 3 and exposed to the atmospheric gas, the electrode 2 is electrically conductive and has a sintering temperature of about 350, which is the sintering temperature of the detection film 5. Any metal that is stable at a temperature higher than or equal to ° C., is less likely to oxidize itself, and is inert to hydrogen gas in the atmosphere gas can be used. Preferably, gold (Au), silver (Ag), copper (Cu), and aluminum (Al) are used. Moreover, silver (Ag) can be used as a metal inert to reducing gas, such as hydrocarbon gas and carbon monoxide gas. If the electrode 2 is active in a reducing gas such as a hydrocarbon gas or carbon monoxide gas, a protective film 9 may be provided so that the electrode 2 is not directly exposed to the atmospheric gas as shown in FIG. Even active metals can be used.

Then sensing film 3 of protons generated by the action with a catalyst having an action to dissociate the final protons by adsorbing hydrogen gas (H ⁺⁾ and electrons (e) and (H ⁺⁾ and electrons (e) Dispersed and supported on a metal oxide whose conductivity is increased by the reaction, and the catalyst material in the detection film 3 is one that adsorbs hydrogen gas and dissociates into protons (H ⁺ ) and electrons (e). And preferably palladium (Pd), iridium (Ir), or platinum (Pt) can be used. The metal oxide material in the detection film 3 may be any material as long as the conductivity is increased by protons (H ⁺ ) and electrons (e) dissociated by the catalyst. Preferably, by injecting protons (H ⁺ ) and electrons (e), a non-stoichiometric compound is formed, and molybdenum trioxide (MnO ₃ ) or tungsten trioxide (WO ₃ ), titanium dioxide (TiO ₂ ), vanadium pentoxide (V ₂ O ₅ ), nickel oxide (NiO ₂ ), iridium hydroxide (Ir (OH) _n ), and the like can be used.

  Next, as the heating means 4, it is possible to use a method of directly heating or a method of indirectly heating from the outside, and the heating method described in FIGS. 4 to 7 is a method of directly heating. Specifically, the heater uses a thin film. The present invention is not limited to this, and a commercially available ceramic heater or the like may be used by being fixed on the insulating substrate on the side where the detection film is not laminated (not shown).

Also, as shown in FIGS. 4 to 6, when a heater is used as the heating means 4, it is sufficient that the detection film 3 can be heated from room temperature to 350 ° C. or less. As shown in FIGS. When a heater is exposed to atmospheric gas, it is preferable to use a material that is not easily oxidized. Specifically, metals such as nickel (Ni), platinum (Pt), tungsten (W), molybdenum (Mo), and alloys containing these metals can be used. In addition to the above, as shown in FIGS. 6 and 7, by covering the heater with the insulating film 5, the heater is prevented from being oxidized, and a heater material that is easily oxidized can be used. As the insulating film 5 material, silicon dioxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), aluminum nitride (AlN), alumina (Al ₂ O ₃ ), or the like can be used.

As shown in FIG. 3, the protective film 12 of the electrode 2 is an inorganic film such as silicon dioxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), aluminum nitride (AlN), alumina (Al ₂ O ₃ ), or Any heat-resistant organic film such as epoxy, polyimide, or polyfluorinated ethylene, or an insulating protective film containing these films may be used as long as the gas permeability is low.

  The operation principle of the hydrogen gas detection sensor of the present invention will be described.

As a principle of operation, when hydrogen gas is present in the atmospheric gas, first, the hydrogen gas is dissociated and adsorbed on the catalyst particles to become adsorbed hydrogen atoms (H _ad ) as shown in the following equation.

H ₂ → 2H _ad
As shown in the following equation, the adsorbed hydrogen atoms diffuse from the catalyst particles onto the metal oxide which is the main component of the detection film 3 by spillover, and finally become protons (H ⁺ ) and electrons (e). And injected into the oxide.

H _ad → H ^{+ +} e ^{-
_{XH + + Xe - + M y}} O z → H x M y O z (M: metal)
The main component metal oxide which is a detection film 3 (M _y O _z) is substantially an insulator, in the atmosphere there is no hydrogen, detection film 3 has an electrically high resistance. On the other hand, the reaction occurs in the presence of hydrogen, the non-stoichiometric compound is a good conductor (H _x M _y O _z) is produced, the conductivity of the sensing film 3 is increased.

On the other hand, Returning to the atmosphere there is no hydrogen, as shown in the following equation, non-stoichiometric compound with oxygen gas in the atmosphere (H _x M _y O _z) is oxidized, a metal oxide (M _y O _z) is Reproduce. Along with this, the conductivity of the detection film 3 becomes low and returns to the original insulating state.

_{H x M y O z + (} X / 4) O 2 → M y O z + (X / 2) H 2 O
Based on the principle of operation as described above, hydrogen gas can be detected by measuring the conductivity of the sensing film 3 that changes in accordance with the concentration of hydrogen gas contained in the atmospheric gas.

  As a method for forming the electrode 2, a printing method, a vapor deposition method, or the like can be used. This time, the electrodes were formed by sputtering deposition. The shape of the electrode 2 can be formed by physical etching such as ion milling or dry etching or chemical etching after pattern formation by photolithography after film formation. Alternatively, lift-off for forming a desired pattern before film formation can be used. Alternatively, a metal mask can be attached at the time of film formation, and the film can be formed through the metal mask. Alternatively, after a pattern is formed by a printing method or an ink jet method using a metal paste containing the above metal, the pattern can be formed by a predetermined heat treatment. This time, an arbitrary shape is obtained using a metal mask having an arbitrary electrode shape. The film thickness of the electrode 2 was adjusted by the sputtering time and the sputtering power to be 100 nm to 1000 nm.

Next, as a method of forming the detection film 3, any method may be used as long as it is a method in which a catalyst is dispersedly supported on a metal oxide and can form such a structure. For example, a vapor deposition method, a dipping method, a sol-gel method, etc. can be raised. In this case, sodium ion (Na ⁺ ) and proton (H ⁺ ) aqueous solution of metal acid salt (for example, sodium salt) is used as a precursor for forming metal oxide using sol-gel method. A solution in which a metal complex salt as a catalyst precursor is dissolved in pure water is added and uniformly dispersed and mixed, and this mixed sol-gel solution is formed into a detection film 3. It was applied to the surface. Thereafter, the applied film was baked to form. As a coating method, a spin coating method, a dip coating method, a dispensing method, or the like can be used.

  Further, as a method for forming the heater which is the heating unit 4, a printing method, a vapor deposition method, or the like can be used. This time, a heater pattern of the heating means 4 is formed on the substrate 1 by using a screen printing method, and after that, the heater 4 pattern of the heating means 4 formed on the substrate 1 is sufficiently dried at room temperature, and then in an electric furnace. Firing was performed for 1 hour at a high temperature. The film thickness may be 0.5 μm to 500 μm.

  The experimental results of poisoning resistance using the hydrogen gas detection sensor of the present invention are shown below.

  The hydrogen gas detection sensor used in this experiment is shown in FIG. The hydrogen gas detection sensor was created as follows.

A quartz (SiO ₂ ) substrate 1 was used as the substrate 1. As the size of the substrate 1, a substrate 1 having a length of 10 mm, a width of 30 mm, and a thickness of 1 mm was used. The substrate 1 is subjected to ultrasonic cleaning using a neutral detergent (trade name: Schumma), rinsed several times with pure water, and then immersed in boiling isopropyl alcohol (IPA) for cleaning. It was.

  Next, a pair of gold (Au) electrodes 2 was formed on one surface of the substrate 1 by sputtering deposition. For the electrode 2, a comb-shaped electrode having an interelectrode distance of 0.5 mm and an electrode length of 39 mm was formed using a metal mask. The film thickness of the electrode 2 was 100 nm.

Next, with respect to the detection film 3, the detection film 3 made of platinum-dispersed tungsten oxide was formed by using platinum (Pt) as a catalyst and tungsten oxide (WO3) as a metal oxide so as to cover the pair of electrodes 2. . A sol-gel method was used as a forming method. Specifically, first, 41.2 g of sodium tungstate dihydrate (Na ₂ WO ₄ .2H ₂ O: Junsei Kagaku Co., Ltd.) was placed in a volumetric flask, and purified water was added to prepare 250 mL. A 5 mol / L colorless and transparent aqueous solution of sodium tungstate (Na ₂ WO ₄ ) was obtained. Next, a cation exchange resin (Amberlite IR120B Na: Organo Co., Ltd.) is packed in a column tower, and an aqueous solution of sodium tungstate (Na ₂ WO ₄ ) is passed through to form sodium in the aqueous solution of sodium tungstate (Na ₂ WO ₄ ). Ions (Na ⁺ ) were exchanged for protons (H ⁺ ) to obtain a pale yellow tungstic acid (H ₂ WO ₄ ) aqueous solution. An aqueous solution obtained by dissolving 0.5 mol / L of hexachloroplatinic acid (H ₂ PtCl ₆ .6H ₂ O: Wako Pure Chemical Industries, Ltd.), which is a catalytic metal, in 13 mL of an aqueous solution of tungstic acid (H ₂ WO ₄ ) in pure water. 4 mL and 8 mL of ethanol were added and uniformly dispersed and mixed to synthesize a sol-gel solution of platinum-dispersed tungsten oxide. The sol-gel solution was uniformly dropped so as to cover one surface of the substrate 1 provided with the electrode 2, and the uniform sol-gel solution was applied using a spin coater. Then, after drying at room temperature for 1 hour, using an electric furnace, pre-baking at 200 degreeC for 1 hour, and also baking at 500 degreeC for 1 hour, Then, it cooled to room temperature. At this time, the thickness of the detection film 3 was 250 nm.

  As a method for measuring the conductivity of the detection film 3, a measurement lead wire 6 was connected from the electrode 2, and an LCR meter (Agilent Technologies product number: 4263B) 8 was connected for measurement. This time, the conductivity of the detection film 3 was measured by applying a high frequency of 1 V and a frequency of 1 kHz by the LCR meter 8.

  Next, an experiment was conducted using the following equipment as experimental equipment.

  The hydrogen gas detection sensor is installed in a sealed container 11 as shown in FIG. The container 11 has a gas inlet 12 and a gas outlet 13, and a hydrogen gas cylinder 15, a compressed air cylinder 16, and a carbon monoxide gas cylinder are connected to the container 11. Further, the gas introduced from each cylinder is piped so as to flow into the container after being adjusted to an arbitrary humidity by the humidifier 14.

  First, FIG. 10 shows the experimental results of the poisoning resistance of the hydrogen gas detection sensor.

In order to clarify the poisoning resistance of the hydrogen gas detection sensor having the structure shown in FIG. 1, for comparison, tungsten trioxide (WO ₃ ) is used for the detection layer 21 and platinum (Pt) is used for the detection layer 22 as shown in FIG. The conventional stacked hydrogen gas detection sensor used was prepared and compared. The experimental results are shown in FIG.

  As shown in FIG. 9, the measurement conditions were that each hydrogen gas detection sensor 20 was installed in a container 11 maintained at room temperature, and 100 vol. % Pure carbon monoxide gas was introduced from the gas inlet 12 and each hydrogen gas detection sensor was exposed in the above atmosphere for 12 hours, and then the carbon monoxide was exhausted, and then the hydrogen gas concentration was 1 vol. The conductivity was measured when exposed to% air dilution gas. The vertical axis of FIG. 13 shows the hydrogen gas concentration of 1 vol. After exposure to carbon monoxide, based on the output before exposure to the carbon monoxide atmosphere. It represents the rate of decrease in conductivity when exposed to%.

  In FIG. 10, the conventional stacked hydrogen gas detection sensor is exposed to carbon monoxide (CO), and the conductivity is reduced by 80% compared to the conductivity before the exposure. This hydrogen sensor confirmed that the conductivity did not change before and after exposure.

In order to investigate the mechanism of poisoning resistance, the detection film 3 of the hydrogen gas detection sensor of the present invention was observed with a scanning electron microscope (SEM). Observation with SEM, detection film 3, it is confirmed that an aggregate of particles of tungsten oxide (WO _3), tungsten trioxide (WO ₃₎ platinum in the particles (Pt) catalyst is scattered becomes particles The platinum (Pt) catalyst particles were adsorbed on the tungsten trioxide (WO ₃ ) particles. As a result of calculating the particle size of the tungsten oxide (WO ₃ ) particles from the particle size frequency distribution of about 100 particles by SEM, the particle size of the tungsten trioxide (WO ₃ ) particles was 15 nm to 100 nm. Similarly, the particle diameter of the platinum (Pt) catalyst was 1 nm to 35 nm.

In addition, platinum (Pt) catalyst particles adsorbed on tungsten trioxide (WO ₃ ) particles were adsorbed with platinum (Pt) catalyst particle sizes smaller than tungsten trioxide (WO ₃ ) particle sizes. .

  The mechanism of anti-toxicity is estimated as follows. The sensing film 3 in which tungsten oxide (WO3) particles are sintered is a porous film having dense pores, which is considered to have a kind of molecular sieving effect. Accordingly, since carbon monoxide gas having a molecular size larger than hydrogen cannot reach the inside of the detection film 3, it is considered that the platinum catalyst inside the film is not poisoned.

  As described above, by using the hydrogen gas detection sensor of the present invention, it is possible to create a hydrogen gas detection sensor that is highly resistant to poisoning.

  Next, the humidity dependence experiment of the hydrogen gas detection sensor according to the present invention will be described.

  The hydrogen gas detection sensor used in this experiment is shown in FIG. The hydrogen gas detection sensor shown in FIG. 4 was prepared as follows.

  The substrate 1, the electrode 2 and the detection film 3 were formed in the same manner as in the poisoning resistance experiment.

  In addition, as the heater as the heating means 4, a heater was made of platinum (Pt) on one surface of the substrate 1. As a production method, platinum (Pt) paste was used, and a heater pattern was formed by screen printing. Thereafter, the heater pattern was sufficiently dried at room temperature and then baked in an electric furnace at about 900 ° C. for 1 hour. The film thickness of platinum (Pt) as a heater was 100 μm.

  As a heater temperature control method, the heating means lead wire 7 was connected from the heater pattern, and the temperature control of the detection film 3 was performed by the DC power supply 10. About temperature control, the value of the heater current and voltage and the temperature of the surface of the detection film 3 were measured in advance with a thermocouple, a temperature calibration curve was prepared, and an arbitrary temperature was obtained.

  In addition, as a method for measuring the conductivity of the detection film 3, as in the case of the poisoning resistance experiment, a lead wire 6 for conductivity measurement is connected from the electrode 2, and an LCR meter (Agilent Technologies product number: 4263B) 8 is connected. The conductivity of the detection film 3 was measured by applying an AC signal having a voltage of 1 V and a frequency of 1 kHz.

  As the experimental equipment, the equipment shown in FIG. 9 was used as in the poisoning resistance experiment.

  Using the hydrogen gas detection sensor having the structure shown in FIG. 4, the electrical conductivity at high and low humidity is measured by changing the temperature of the heater, and the experimental result of humidity dependence is shown in FIG.

  The measurement was performed as follows. The surface temperature of the detection film 3 is set to normal temperature (20 ° C.), 50 ° C., 80 ° C., 120 ° C., 150 ° C., 200 ° C., 250 ° C., 300 ° C., 350 ° C., and the humidity is set to low humidity (20% or less). Hydrogen gas concentration of 1 vol. % Air dilution gas was introduced from the gas inlet 12 and the conductivity of the detection film 3 was measured.

  From FIG. 11, when no voltage was applied to the heater, the low humidity conductivity showed a high value while the low humidity conductivity showed a low value at room temperature (20 ° C.). . However, as the voltage is applied to the heater, the surface temperature of the detection film 3 increases, and as the surface temperature of the detection film 3 increases, the difference in conductivity between high humidity and low humidity decreases, and is 50 ° C. or higher. By doing so, the same conductivity is exhibited. Further, as the upper limit heating temperature, when the temperature of the detection film 3 is increased, it also responds to a reducing gas such as a hydrocarbon-based gas or carbon monoxide gas, which causes erroneous detection. Therefore, it is necessary to improve the selectivity of hydrogen gas with respect to reducing gas such as hydrocarbon gas and carbon monoxide gas as a hydrogen gas detection sensor three times or more, and the heating temperature is preferably 350 ° C. or less. As described above, by heating the heater from 50 ° C. to 350 ° C., the measurement can be performed without being affected by the humidity dependence in the installation atmosphere of the hydrogen gas detection sensor. Further, in order to further improve the selectivity of the hydrogen gas with respect to the reducing gas such as hydrocarbon gas and carbon monoxide gas by 10 times or more, the temperature is preferably 50 ° C. to 150 ° C.

  In general, platinum (Pt) catalysts are poisoned by carbon monoxide when the catalyst temperature is 150 ° C. or lower. However, when the catalyst temperature is 150 ° C. or higher, carbon monoxide is oxidized on the platinum (Pt) catalyst. Since it is discharged as carbon dioxide, poisoning can be avoided. However, the use of the detection film 3 as shown in the present invention enables a hydrogen gas detection sensor that is not poisoned even at 150 ° C. or lower.

Further, even if an aqueous solution in which 0.1 mol / L of hexachloroplatinic acid (H ₂ PtCl ₆ .6H ₂ O: Wako Pure Chemical Industries, Ltd.), which is a catalyst of platinum dispersion type tungsten oxide, is dissolved in pure water, is used. Although the rate level was changed, the humidity dependence was removed by heating at 50 ° C. or higher.

In the hydrogen gas detection sensor according to the present invention, first, dissociative adsorption and spillover of hydrogen gas occur on the catalyst of platinum (Pt) particles, and protons (H ⁺ ) and electrons (e) generated thereby are detected in the detection film 3. Reaction occurs with tungsten trioxide (WO ₃ ), which is the main component, to form tungsten bronzes (H _x WO ₃ ). The fact that this reaction strongly depends on the humidity of the atmospheric gas indicates that water molecules are deeply involved in the rate-determining step of the above reaction process, and the water molecules adsorb to tungsten trioxide (WO ₃ ). It is presumed that the generated surface hydroxyl group acts as a reactive site. In this case, the coverage of the surface hydroxyl group on tungsten trioxide (WO ₃ ) greatly affects the reaction rate. However, when the temperature of the detection film 3 is 50 ° C. or higher, the coverage is saturated. It is considered that the dependency disappears.

  Next, a response experiment of the hydrogen gas detection sensor according to the present invention will be described.

  This time, the hydrogen gas detection sensor used in the experiment was the same as in the humidity dependence experiment.

  Using the hydrogen gas detection sensor having the structure shown in FIG. 4, the response time of high humidity and low humidity when the temperature of the heater was changed was measured. The experimental results are shown in FIG.

  The measurement was performed as follows. The surface temperature of the detection film 3 is set to normal temperature (20 ° C.), 50 ° C., 80 ° C., 120 ° C., 150 ° C., 200 ° C., 250 ° C., 300 ° C., 350 ° C., and the humidity is set to low humidity (20% or less). Hydrogen gas concentration of 1 vol. % Air dilution gas was introduced from the gas inlet 12. At that time, the time from the introduction of hydrogen gas to the stabilization of the conductivity was taken as the response time, and the response time was measured.

From FIG. 12, it can be seen that when no voltage is applied to the heater, the response time is 1000 seconds or more at room temperature (20 ° C.), and the response time is very slow. However, as the voltage is applied to the heater 4, the surface temperature of the detection film 3 increases, and the rate at which tungsten trioxide (WO ₃ ), proton (H ⁺ ), and electrons (e) react to generate tungsten bronze is increased. Increasing the response speeds up the response speed at both high and low humidity. By setting the surface temperature of the detection film 3 to 50 ° C. or more, the response time becomes about 10 seconds, and further, by setting the surface temperature of the detection film 3 to 100 ° C. or more, the response time is within 5 seconds. Made sex possible. In general, the response time of the hydrogen gas detection sensor is preferably within 10 seconds from the viewpoint of safety.

A hydrogen gas detection sensor according to the present invention is a hydrogen gas detection sensor that detects hydrogen gas, and is a pair of structures that are not exposed to an electrically insulating substrate and an electrically conductive atmospheric gas. An electrode and a detection film for dissociating and detecting hydrogen gas, the detection film adsorbing hydrogen gas and finally having a function of dissociating into protons (H ⁺ ) and electrons (e) and the action The catalyst is made of a metal oxide whose conductivity is increased by the reaction of protons (H ⁺ ) and electrons (e) generated in the catalyst, and the catalyst uses particles smaller in diameter than the metal oxide particles constituting the detection film. It has a particle structure that is dispersed and supported on oxide particles, and is a hydrogen gas detection sensor that is excellent in anti-toxicity and that detects hydrogen gas. Electrically conductive A pair of electrodes is a structure that is not exposed to囲気gas, dissociated hydrogen gas, and a detection film which detects the detection film by adsorbing hydrogen gas finally protons (H ⁺⁾ and electrons (e) A heating means for heating the detection film to a predetermined temperature, comprising a catalyst having a dissociating action and a metal oxide whose conductivity is increased by the reaction of protons (H ⁺ ) and electrons (e) generated by the action It has the feature that enables high-speed response without being affected by the humidity dependence in the installation atmosphere of the hydrogen gas detection sensor, and stable high-speed hydrogen gas in any environment. It is useful as a hydrogen gas detection sensor that can detect leakage.

The figure which shows an example of the structure of the hydrogen gas detection sensor in Example 1 of this invention The figure which shows an example of the other structure of the hydrogen gas detection sensor in Example 1 of this invention The figure which shows an example of the further another structure of the hydrogen gas detection sensor in Example 1 of this invention. The figure which shows an example of the structure of the hydrogen gas detection sensor which has a heating means in Example 1 of this invention. The figure which shows an example of the structure of the other hydrogen gas detection sensor which has a heating means in Example 1 of this invention. The figure which shows an example of the structure of the other hydrogen gas detection sensor which has a heating means in Example 1 of this invention. The figure which shows an example of the structure of the further another hydrogen gas detection sensor which has a heating means in Example 1 of this invention. The figure which shows typically the structure of the detection film | membrane of the hydrogen gas detection sensor in Example 1 of this invention. The figure which shows typically the experimental installation of the hydrogen gas detection sensor in Example 1 of this invention The figure for demonstrating the poisoning resistance of the hydrogen gas detection sensor in Example 1 of this invention The figure which shows the humidity dependence of the hydrogen gas detection sensor in Example 1 of this invention The figure which shows the responsiveness of the hydrogen gas detection sensor in Example 1 of this invention Diagram showing the configuration of a conventional stacked hydrogen gas detection sensor

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Electrode 3 Detecting film 4 Heating means 5 Insulating film 6 Conductivity measuring lead wire 7 Heating means lead wire 8 LCR meter 9 Protective film 10 DC power source 11 Container 12 Gas inlet 13 Gas outlet 14 Humidifier 15 Hydrogen Gas cylinder 16 Compressed air cylinder 17 Carbon monoxide cylinder 18 Metal oxide 19 Catalyst 20 Hydrogen gas detection sensor 21 Detection layer 22 Catalyst layer

Claims (22)

A hydrogen gas detection sensor for detecting hydrogen gas,
An electrically insulating substrate;
A detection film for dissociating hydrogen gas stacked on the substrate and detecting the hydrogen gas;
A pair of electrically conductive electrodes formed in contact with the substrate or sensing film in a structure not exposed to atmospheric gas;
With
The sensing film, the conductivity by the reaction of the adsorbed hydrogen gas and protons (H ⁺⁾ and electrons protons generated in the catalyst and the effect it has the effect of dissociation in (e) (H ⁺⁾ and electrons (e) Consisting of increasing metal oxides,
The hydrogen gas detection sensor, wherein the catalyst has a particle structure in which particles having a diameter smaller than the metal oxide particles constituting the detection film are dispersedly supported on the metal oxide particles. A hydrogen gas detection sensor for detecting hydrogen gas,
An electrically insulating substrate;
A sensing film for detecting hydrogen gas laminated on the substrate;
An electrode made of a metal that is formed in contact with the sensing film to measure the conductivity of the sensing film and has no catalytic activity against a reducing gas such as hydrogen gas, hydrocarbon gas, or carbon monoxide gas When,
The detection film has a function of adsorbing hydrogen gas and dissociating it into protons (H ⁺ ) and electrons (e);
It consists of a metal oxide whose conductivity is increased by the reaction of protons (H ⁺ ) and electrons (e) generated by this action,
The hydrogen gas detection sensor, wherein the catalyst has a particle structure in which particles having a diameter smaller than the metal oxide particles constituting the detection film are dispersedly supported on the metal oxide particles. The detection film has a particle structure in which the catalyst has a particle size of 1 nm to 35 nm,
The hydrogen gas detection sensor according to claim 1 or 2, wherein the catalyst particles have a structure in which the catalyst particles are dispersed and supported on metal oxide particles having a particle diameter of 15 nm to 100 nm. The hydrogen gas detection sensor according to claim 2, wherein the electrode includes any one of gold (Au), silver (Ag), copper (Cu), and aluminum (Al). The catalyst is one of palladium (Pd), iridium (Ir), and platinum (Pt), or a mixture containing at least one of these. The hydrogen gas detection sensor according to claim 1 or 2. The main components of the metal oxide are molybdenum trioxide (MoO ₃ ), tungsten trioxide (WO ₃ ), titanium dioxide (TiO ₂ ), iridium hydroxide (Ir (OH) _n ), vanadium pentoxide (V 2 O 5), The hydrogen gas detection sensor according to claim 1, wherein the hydrogen gas detection sensor is made of any one of nickel oxide (NiO ₂ ). In the detection film, the main component of the catalyst is platinum (Pt),
The hydrogen gas detection sensor according to claim 1 or 2, wherein the main component of the metal oxide is tungsten trioxide (WO ₃ ). A hydrogen gas detection sensor for detecting hydrogen gas,
An electrically insulating substrate;
A detection film for dissociating hydrogen gas stacked on the substrate and detecting the hydrogen gas;
A pair of electrically conductive electrodes formed in contact with the substrate or sensing film in a structure not exposed to atmospheric gas;
With
The sensing film, the conductivity by the reaction of the adsorbed hydrogen gas and protons (H ⁺⁾ and electrons protons generated in the catalyst and the effect it has the effect of dissociation in (e) (H ⁺⁾ and electrons (e) Consisting of increasing metal oxides,
A hydrogen gas detection sensor comprising heating means for heating the detection film to a predetermined temperature. A hydrogen gas detection sensor for detecting hydrogen gas,
An electrically insulating substrate;
A sensing film for detecting hydrogen gas laminated on the substrate;
An electrode made of a metal that is formed in contact with the sensing film to measure the conductivity of the sensing film and has no catalytic activity against a reducing gas such as hydrogen gas, hydrocarbon gas, or carbon monoxide gas When,
The detection film has a function of adsorbing hydrogen gas and dissociating it into protons (H ⁺ ) and electrons (e);
It consists of a metal oxide whose conductivity is increased by the reaction of protons (H ⁺ ) and electrons (e) generated by this action,
A hydrogen gas detection sensor comprising heating means for heating the detection film to a predetermined temperature. The detection film has a particle structure in which the catalyst has a particle diameter of 1 nm to 35 nm,
The hydrogen gas detection sensor according to claim 8 or 9, wherein the catalyst particles have a structure in which the catalyst particles are dispersed and supported on metal oxide particles having a particle diameter of 15 nm to 100 nm. The hydrogen gas detection sensor according to claim 8 or 9, wherein a heating temperature of the detection film is set to 50 ° C to 350 ° C. 10. The hydrogen gas detection sensor according to claim 8, wherein a heating temperature of the detection film is preferably set to 50 ° C. to 150 ° C. 10. The hydrogen gas detection sensor according to claim 9, wherein the electrode includes any one of gold (Au), silver (Ag), copper (Cu), and aluminum (Al). The catalyst is one of palladium (Pd), iridium (Ir), and platinum (Pt), or a mixture containing at least one of these. The hydrogen gas detection sensor according to claim 8 or 9. The main components of the metal oxide are molybdenum trioxide (MoO ₃ ), tungsten trioxide (WO ₃ ), titanium dioxide (TiO ₂ ), iridium hydroxide (Ir (OH) _n ), vanadium pentoxide (V 2 O 5), The hydrogen gas detection sensor according to claim 8 or 9, comprising any one of nickel oxide (NiO ₂ ). In the detection film, the main component of the catalyst is platinum (Pt),
The hydrogen gas detection sensor according to claim 8 or 9, wherein a main component of the metal oxide is tungsten trioxide (WO ₃ ). 10. The hydrogen gas detection according to claim 8, wherein heating means for heating the detection film to a predetermined temperature is formed on the insulating substrate on the side where the detection film is not laminated. Sensor. The hydrogen gas detection according to claim 8 or 9, wherein the heating means is formed on the insulating substrate on the side where the detection film is not laminated, and the heating means is further covered with an insulating layer. Sensor. The hydrogen gas detection sensor according to claim 8, wherein the heating unit is provided between the substrate, the electrode, and the detection film. The heating means is one of nickel (Ni), platinum (Pt), tungsten (W), and molybdenum (Mo), or a mixture containing at least one of these. The hydrogen gas detection sensor according to claim 8 or 9, wherein The hydrogen gas detection sensor according to claim 8 or 9, wherein the heating means is platinum (Pt) or a mixture containing the same. A hydrogen gas detection sensor for detecting hydrogen gas,
An electrically insulating substrate;
A detection film for dissociating hydrogen gas stacked on the substrate and detecting the hydrogen gas;
A pair of electrically conductive electrodes formed in contact with one of the substrate or the sensing film,
The sensing film, the conductivity by the reaction of the adsorbed hydrogen gas and protons (H ⁺⁾ and electrons protons generated in the catalyst and the effect it has the effect of dissociation in (e) (H ⁺⁾ and electrons (e) Consisting of increasing metal oxides,
A hydrogen gas detection sensor comprising heating means for heating the detection film to a predetermined temperature of 50 ⁰ C to 150 ⁰ C.

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