JP2005265546A - Hydrogen gas detecting material and hydrogen gas sensor using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrogen gas detecting material excellent in hydrogen gas detecting sensitivity and hydrogen gas selectivity and suitably used in a fuel cell vehicle or the like, its manufacturing method and a hydrogen gas sensor using the hydrogen gas detecting material. <P>SOLUTION: The hydrogen gas detecting material contains zinc oxide particles and a chlorine conpound present on the surfaces zinc oxide particles. The hydrogen gas sensor is equipped with the hydrogen gas detecting material as a hydrogen gas detection part. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a hydrogen gas detection material for detecting hydrogen gas in the air and a hydrogen gas sensor using the same.

  In recent years, research and development of fuel cell vehicles using hydrogen, methanol or the like as fuel has been actively conducted. In the fuel cell vehicle, a hydrogen gas sensor is used for hydrogen gas fuel concentration control and hydrogen gas leak detection. Further, hydrogen gas sensors for fuel cell vehicles are required to be further improved in terms of detection sensitivity, hydrogen gas selectivity, durability, manufacturing cost, and the like.

  As hydrogen gas sensors that have already been put into practical use, those using a platinum-based catalyst as a hydrogen gas detection material and those using tin oxide that is a metal oxide are known (for example, see Patent Document 1). .

On the other hand, zinc oxide has a large change in electrical resistivity before and after contact with hydrogen gas, a high detection sensitivity is obtained, and the time required for recovery to the initial state after contact with hydrogen gas is short. It has been known that it has advantageous performance compared to tin oxide and the like.
Japanese Patent No. 3438978

  However, since zinc oxide has little difference in the rate of change in electrical resistance before and after contact with gas between hydrogen gas and other reducing gases such as carbon monoxide gas, However, there is a problem that the so-called hydrogen gas selectivity for separating and detecting only the gas is not always sufficient. In particular, in the case of a hydrogen gas sensor for a fuel cell vehicle or the like, it is required to detect hydrogen gas and carbon monoxide gas separately. However, since the above problems have not been solved for many years, It has been considered extremely difficult to use a hydrogen gas sensor using zinc for a fuel cell vehicle or the like.

  The present invention has been made in view of the above circumstances, and has excellent hydrogen gas detection sensitivity and hydrogen gas selectivity, and a hydrogen gas detection material that can be suitably used for fuel cell vehicles and the like, and hydrogen using the same An object is to provide a gas sensor.

  In order to solve the above-described problems, the hydrogen gas detection material of the present invention is characterized by containing zinc oxide particles and a chlorine compound present on the surface of the zinc oxide particles.

  In this way, the presence of a chlorine compound on the surface of zinc oxide particles significantly improves the hydrogen gas selectivity without substantially detracting from the excellent performance such as high detection sensitivity of zinc oxide. The present inventors have found.

  Here, it is preferable from the point of hydrogen gas selectivity that a chlorine compound is a compound which produces | generates a chlorine ion by contact with water.

  Moreover, in the hydrogen gas detection material of this invention, it is preferable that the quantity of the chlorine atom which a chlorine compound has is 0.01 to 3.0 weight% with respect to 100 weight% of zinc oxide particles. If the amount of chlorine atom is less than 0.01% by weight, the hydrogen gas selectivity tends to decrease, and if it exceeds 3.0% by weight, the hydrogen gas selectivity decreases or the mechanical strength of the hydrogen gas detection material is low. It tends to decrease.

The hydrogen gas detection material of the present invention preferably further has a BET specific surface area (value of specific surface area measured by the BET method) of 0.1 to 100 m ² / g. If the BET specific surface area is less than 0.1 m ² / g, the detection sensitivity to hydrogen gas may not be sufficient, and if it exceeds 100 m ² / g, the mechanical strength as a material may not be sufficient.

  Moreover, in the hydrogen gas detection material of this invention, it is preferable that the zinc oxide particle is mutually connected and forms the porous body. In such a porous body, since a large number of zinc oxide particles adhere to each other to form a connected aggregate and are integrated as a whole, the contact area is reduced while maintaining the overall shape. The detection sensitivity can be increased efficiently, and the detection sensitivity can be further increased.

  The hydrogen gas detection material as described above includes a precipitation method in which an aqueous zinc chloride solution is brought into contact with aqueous ammonia to form a precipitate, and a heating step in which the precipitate is heated. It can obtain efficiently by the manufacturing method provided with the adhesion process which attaches aqueous solution, and obtains an adhering body, and the removal process which removes water from this adhering body.

  The hydrogen gas sensor of the present invention includes a hydrogen gas detection unit made of the hydrogen gas detection material of the present invention and a heating unit for heating the hydrogen gas detection unit. By this heating unit, the hydrogen gas detection unit can be maintained at a high temperature, and a hydrogen gas sensor excellent in hydrogen gas detection sensitivity and stability of the hydrogen gas detection operation can be obtained.

  ADVANTAGE OF THE INVENTION According to this invention, the hydrogen gas detection material which is excellent in the detection sensitivity and hydrogen gas selectivity of hydrogen gas, and can be used suitably for fuel cell vehicles etc., and a hydrogen gas sensor using the same are obtained.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings as the case may be. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted.

(Hydrogen gas detection material)
The hydrogen gas detection material of the present invention is characterized by containing zinc oxide particles and a chlorine compound present on the surface of the zinc oxide particles.

  The hydrogen gas detection material of the present invention may further contain other metal oxides and the like different from zinc oxide as other components. When the hydrogen gas detection material contains another metal oxide, it is preferable to form particles in which zinc oxide and another metal oxide coexist. Moreover, it is preferable that the quantity in which another metal oxide is contained is 0.1-5 mol% with respect to 100 mol% of the whole quantity of zinc oxide and another metal oxide.

  The chlorine compound is present on at least the surface of the zinc oxide particles. By being present on the surface of the zinc oxide particles, the effect of improving the hydrogen gas selectivity is remarkably exhibited. This is presumably because, in a hydrogen gas detection material using a metal oxide, the electrical resistance changes mainly in the region near the surface when it comes into contact with hydrogen gas. In addition, the hydrogen gas detection material of this invention may have further the chlorine compound which exists in the inside of a zinc oxide particle.

  Although the chlorine compound should just be a compound which has a chlorine atom, it is preferable from the point of hydrogen gas selectivity that it is a compound which produces | generates a chlorine ion by contact with water. In a chlorine compound that generates chlorine ions by contact with water, the chlorine atom is present in an ionic or ionic state with a negative charge due to ionic bonds with other atoms, etc. It is thought that this contributes to the improvement of hydrogen gas selectivity by some action.

  The generation of chlorine ions by contact of the chlorine compound with water can be confirmed, for example, by detecting the presence of chlorine ions eluted in water when the hydrogen gas detection material is immersed in water.

  The amount of chlorine atoms contained in the chlorine compound is preferably 0.01 to 3.0% by weight and more preferably 0.1 to 1.0% by weight with respect to 100% by weight of the zinc oxide particles. Making the amount of chlorine atoms in such a range means, for example, optimizing the amount of chlorine-containing compound used as a raw material when manufacturing a hydrogen gas detection material, the heating temperature in the production method described later, etc. This can be achieved. The amount of chlorine atoms contained in the hydrogen gas detection material can be quantified by, for example, fluorescent X-ray analysis.

The hydrogen gas detection material preferably has a BET specific surface area of 0.1 to 100 m ² / g in order to further increase detection sensitivity. By making the hydrogen gas detection material a porous body in which fine pores are formed, the surface area can be increased efficiently, and a material having a BET specific surface area in such a range can be obtained. It becomes easy.

  This porous body can be suitably obtained as an aggregate formed by connecting zinc oxide particles to each other, for example, by heating the aggregated zinc oxide particles.

  In addition to the above components, the hydrogen gas detection material of the present invention includes at least one additive selected from the group consisting of Zr, In, Nb, La, Re, Yb, Ho, Er, Hf, Dy, Ga, and Al. It may further contain other components such as elemental oxides and platinum group elemental compounds.

  As a method for obtaining the hydrogen gas detection material described above, for example, the following two production methods can be suitably employed.

  The first production method includes a precipitation step in which a zinc chloride aqueous solution is brought into contact with aqueous ammonia to generate a precipitate, and a heating step in which the precipitate is heated.

  In the precipitation step, first, an aqueous zinc chloride solution and aqueous ammonia are prepared, and both aqueous solutions are mixed and brought into contact with each other, thereby generating a precipitate mainly composed of zinc hydroxide. Specifically, for example, a zinc chloride aqueous solution and ammonia water are uniformly mixed to generate a precipitate.

  The zinc chloride aqueous solution used as a raw material preferably has a zinc ion concentration of 0.01 to 1 mol / L, and the aqueous ammonia preferably has an ammonia concentration of 0.01 to 1 mol / L. At this time, in order to sufficiently reduce the solubility of the precipitate, it is preferable to mix the two aqueous solutions while adjusting the pH so that the pH of the mixed solution is 6.5 to 7.5.

  Next, in the heating step, the obtained precipitate is preferably decanted, centrifuged, filtered, etc., and then heated, so that the zinc oxide particles and the chlorine compound present on the surface of the zinc oxide are A hydrogen gas detection material containing can be obtained. The heating temperature is preferably 400 to 800 ° C, more preferably 500 to 700 ° C. By heating in such a temperature range, a hydrogen gas detection material in which zinc oxide particles are connected to each other to form a porous body can be obtained. If the heating temperature is less than 400 ° C., the material characteristics may not be stable when heated for hydrogen gas detection. If the heating temperature exceeds 800 ° C., volatilization or alteration of the chlorine compound or the hydrogen gas detection material In some cases, the specific surface area tends to decrease.

  The second production method includes an attachment step of attaching an ammonium chloride aqueous solution to zinc oxide particles to obtain an attachment, and a removal step of removing water from the attachment.

  In the second production method, first, in the attaching step, the zinc oxide particles are attached by impregnating an aqueous ammonium chloride solution to obtain an attached body. The concentration of chlorine ions in the aqueous ammonium chloride solution used at this time is preferably 0.1 to 2 mol / L. The amount of the ammonium chloride aqueous solution to be deposited is preferably such that the chlorine ions are 0.01 to 3.0% by weight with respect to 100% by weight of zinc oxide. In this adhesion process, ammonium chloride and water may be mixed with the zinc oxide particles instead of the ammonium chloride aqueous solution to produce an ammonium chloride aqueous solution in the adherent.

  Next, a hydrogen gas detection material containing zinc oxide particles and a chlorine compound present on the surface of the zinc oxide particles is obtained by a removing step of removing water from the obtained adherent. The removal of water can be performed by a method such as spray drying under normal pressure or reduced pressure, or by heating the adherent. The heating temperature is preferably 50 to 200 ° C, and more preferably 100 to 150 ° C. At this time, the water adhering to the adhering body may not necessarily be completely removed, and a trace amount of water may remain in the obtained hydrogen gas detection material.

  You may provide the heating process which heat-processes the zinc oxide particle from which the water was removed after the said removal process. In this case, the removal step is preferably performed at 50 to 200 ° C, and the heating step is preferably performed at 400 to 800 ° C.

  In addition to the above-described method, the hydrogen gas detection material of the present invention is prepared by adding ammonium chloride on the surface of a zinc oxide thin film formed on a substrate such as an insulating substrate by a vapor phase synthesis method such as a sputtering method or a CVD method. It can also be produced by a method comprising an attaching step of attaching an aqueous solution to obtain an attached body, and a removing step of removing water from the attached body. In the case of this method, for example, the substrate temperature and the supply amount of the source gas are controlled so that the surface of the thin film is roughened, or the film is relatively dense by sputtering or CVD. A flat zinc oxide thin film is formed, and this thin film is etched with an etching solution (for example, an aqueous solution of ammonia, sulfuric acid, acetic acid, sodium hydroxide, potassium hydroxide, etc.) to roughen the surface. For example, a zinc oxide thin film having a large number of irregularities formed on the surface and a zinc oxide thin film made of a porous body having a form in which particulate zinc oxide (zinc oxide particles) are connected to each other can be obtained. Moreover, the adhesion process and the removal process in this manufacturing method can be suitably performed using the same raw materials, conditions, and the like as described above.

  The hydrogen gas detection material of the present invention as described above is, for example, a hydrogen gas that is detected on the basis of a change in electrical resistance by forming a film on the surface of an electrically insulating substrate to form a hydrogen gas detector. It can be used for a gas sensor or the like.

(Hydrogen gas sensor)
FIG. 1 is a cross-sectional view schematically showing the basic configuration of the first embodiment of the hydrogen gas sensor of the present invention.

  A hydrogen gas sensor 100 shown in FIG. 1 includes an electrical insulating substrate 1, a hydrogen gas detection material film 2 that is a hydrogen gas detection portion provided on one surface (upper side in the drawing) of the electrical insulating substrate 1, and electrical insulation. A resistive film 3 that is provided on the other surface (lower side in the drawing) of the conductive substrate 1 and that heats the hydrogen gas detection material film 2, and the electrically insulating substrate 1 so as to cover the resistive film 3. And a protective layer 5 provided on the electrically insulating substrate 1 so as to cover the diffusion preventing layer 4.

  Further, the hydrogen gas sensor 100 includes an electrode 30 provided on the electrically insulating substrate 1 so as to be in contact with the hydrogen gas detection material film 2 and an electrode provided on the electrically insulating substrate 1 so as to be in contact with the resistor film 3. 31.

  In the hydrogen gas sensor 100, the hydrogen gas is detected based on the change in the electrical resistance of the hydrogen gas detection material film 2 due to the contact with the hydrogen gas measured through the electrode 30. Since the change in electrical resistance due to contact with hydrogen gas is small near room temperature, the hydrogen gas detection material film 2 is heated by the resistor film 3 through the insulating substrate 1 by heating the hydrogen gas detection material film 2. It is maintained at a predetermined temperature in the high temperature region. The predetermined temperature is preferably 200 to 550 ° C, and more preferably 300 to 500 ° C. If the predetermined temperature is lower than 200 ° C, sufficient detection sensitivity may not be obtained. If the predetermined temperature exceeds 550 ° C, the surrounding materials are rapidly deteriorated and the hydrogen is close to the ignition temperature (about 570 ° C) in the atmosphere. , Hydrogen gas explosion may easily occur.

  The hydrogen gas detection material film 2 is formed by depositing the hydrogen gas detection material of the present invention, and the thickness thereof is preferably 1 to 200 μm, and more preferably 10 to 100 μm. If this thickness is less than 1 μm, the hydrogen gas detection sensitivity tends to be reduced, and if it exceeds 200 μm, the film tends to crack due to heating.

  The electrically insulating substrate 1 is composed of a base material 10 and insulating layers 11 provided on both surfaces of the base material 10 to insulate the hydrogen gas detection material film 2 and the resistor film 3 and as a hydrogen gas sensor. The main purpose is to maintain the shape. In order to increase the efficiency of heat transfer from the resistor film 3 to the hydrogen gas detection material film 2, the material constituting the base material 10 includes the hydrogen gas detection material film 2, the resistor film 3, and the electrically insulating substrate 1. It is preferable to select the thermal conductivity in consideration of the mutual positional relationship.

  In the case of a structure in which the hydrogen gas detection material film 2 and the resistor film 3 are formed on one surface and the other surface of the electrically insulating substrate 1 as in the hydrogen gas sensor 100 shown in FIG. A material having a relatively high thermal conductivity is preferred. For example, metals such as tungsten, molybdenum, platinum, iron, various stainless materials, alumina, beryllium oxide, silicon carbide, tungsten carbide, tungsten nitride, aluminum nitride, boron nitride, and the like can be suitably used.

  On the other hand, in the case of a structure in which the hydrogen gas detection material film 2 and the resistor film 3 are formed on one surface of the electrically insulating substrate 1 as in the hydrogen gas sensor 120 shown in FIG. The material of the substrate 10 is preferably a material having a relatively low thermal conductivity. For example, gypsum, silica, borosilicate glass, mullite, zirconia and the like can be suitably used.

  By using the base material 10 as described above, the heat conduction from the resistor film 3 to the hydrogen gas detection material film 2 can be more reliably increased. Moreover, since the material of said electrically insulating board | substrate 1 is excellent also in mechanical strength, the hydrogen gas sensor which is more excellent in durability is obtained.

  The thickness of the substrate 10 is preferably 0.1 to 1.5 mm, and more preferably 0.5 to 1.0 mm, in order to achieve both heat conduction efficiency and mechanical strength. Moreover, the shape of the main surface is not specifically limited, It can be set as the desired shape according to a use, such as a rectangular shape.

  The insulating layer 11 is preferably made of an insulating material such as silica, alumina, zirconia, carbon nitride, or silicon nitride. The thickness of the insulating layer 11 is preferably 50 to 500 nm, and more preferably 100 to 300 nm.

  The resistor film 3 generates heat when energized through the electrode 31 and functions as a heating unit that heats the hydrogen gas detection material film 2.

  The resistor film 3 is preferably a thin film obtained by a thin film process such as sputtering or CVD. The thickness is preferably 0.05 to 1 μm, and more preferably 0.1 to 0.8 μm. If the thickness is less than 0.05 μm, the amount of heat generation and durability tend to be insufficient, and if it exceeds 1 μm, it is difficult to reduce the size of the hydrogen gas sensor and the power consumption tends to increase.

  As a material constituting the resistor film 3, metal, nitride, cermet, silicide, polysilicon, silicon carbide, carbon, or the like can be suitably used.

Examples of the metal include Fe—Cr—Al, Ni—Cr, Pt, Mo, Ta, and W. Examples of the nitride include BN, Ta ₂ N, TiN, and AlN. Examples of the cermet include TaSiO. TaSiC, NbSiO, and CrSiO, and examples of the silicide include TaSi, CrSi, and MoSi, respectively.

  Among these, the use of at least one selected from the group consisting of TaSiO, TaSiC, NbSiO and polysilicon for the resistor film 3 can shorten the time required to reach a predetermined temperature after startup, This is preferable because it is excellent in that durability against heat history accompanied by temperature change is enhanced. It is particularly important that these characteristics are excellent in the case of a hydrogen gas sensor for a fuel cell vehicle.

  The diffusion prevention layer 4 is a layer provided so as to cover the resistor film 3 while being interposed between the resistor film 3 and the protective layer 5. The diffusion preventing layer 4 has a function of suppressing the diffusion of the substance from the protective layer 5 to the resistor film 3. If a substance diffused from the protective layer 5 enters the resistance film 3 as an impurity, the temperature stability is impaired and the measurement operation of the hydrogen gas sensor becomes unstable. Therefore, it is preferable to provide this diffusion prevention layer 4. In particular, when the material constituting the resistor film 3 is at least one selected from the group consisting of metal, nitride, cermet, silicide, polysilicon, silicon carbide, and carbon as described above, Since a thin film is easily affected by impurities, it is important to provide such a diffusion prevention layer.

  The diffusion prevention layer 4 is preferably composed of at least one selected from the group consisting of silica, silicon nitride, and alumina, and the thickness is preferably 10 to 100 nm.

  The protective layer 5 mainly improves the efficiency of heat conduction to the hydrogen gas detection material film 2 by suppressing heat conduction from the resistor film 3 to the opposite side of the hydrogen gas detection material film 2. It is a layer provided for the purpose.

  Although the thickness of the protective layer 5 should just be thickness which can ensure required heat insulation, specifically, it is preferable that it is 100-1500 micrometers.

  The protective layer 5 is preferably formed of a material having low thermal conductivity, such as at least one material selected from the group consisting of refractory cement, gypsum, silica, mullite, zirconia and borosilicate glass. More preferably, it consists of a porous body made of a material. Furthermore, it is preferable to mix inorganic hollow beads in these materials because the heat insulation effect can be further enhanced. Among these, it is preferable to use refractory cement for the protective layer 5 in terms of heat insulation, moldability, and the like.

  The hydrogen gas sensor 100 can be manufactured by the following method, for example.

  First, the insulating layer 11 is formed on both surfaces of the substrate 10 by a thin film process such as sputtering or CVD to obtain the electrically insulating substrate 1.

  Next, the electrode 30 is formed in a predetermined pattern on the surface of one insulating layer 11 (upper side in the figure) opposite to the substrate 10 by etching or the like, and then the hydrogen gas detection material of the present invention is formed by coating or the like. The hydrogen gas detection material film 2 is formed.

  Subsequently, the electrode 31 is formed in a predetermined pattern on the surface of the other (lower side in the drawing) insulating layer 11 opposite to the substrate 10 by etching or the like, and then the resistor film 3 is formed by a thin film process. Then, the diffusion prevention layer 4 is formed by a thin film process so as to cover the exposed region of the resistor film 3. Further, the protective layer 5 is formed by a method such as a dip coating method so as to cover the exposed region of the diffusion prevention layer 4, thereby obtaining the hydrogen gas sensor 100.

  As a modification of the first embodiment, the electrically insulating substrate 1 may be composed of a single layer made of an electrically insulating material having both a function as a base material and a function as an insulating layer. . In the hydrogen gas sensor according to this embodiment, the electrode 30 and the hydrogen gas detection material film 2 are formed on one surface of an electrically insulating substrate composed of a single layer, and the electrode 31 is disposed on the other surface of the electrically insulating substrate. After the formation, the resistor film 3, the diffusion preventing layer 4, and the protective layer 5 are obtained in this order.

  FIG. 2 is a cross-sectional view schematically showing the basic configuration of the second embodiment of the hydrogen gas sensor of the present invention.

  A hydrogen gas sensor 110 shown in FIG. 2 includes an electrically insulating substrate 1 and is formed on one surface (upper side in the drawing) of the electrically insulating substrate 1 so as to cover the temperature detecting film 6 and the temperature detecting film 6. 1 and a hydrogen gas detection material film 2 as a hydrogen gas detection part are laminated in this order, and the other surface (lower side in the figure) of the electrically insulating substrate 1 is the same as the hydrogen gas sensor 100 of FIG. The structure includes a resistor film 3, which is a heating unit, a diffusion prevention layer 4, and a protective layer 5.

  Further, the hydrogen gas sensor 110 is electrically insulated from the hydrogen gas detection material film 2 through the insulation layer 7 and the electrode 30 provided on the insulation layer 7 so as to be in contact with the hydrogen gas detection material film 2. Thus, the electrode 32 provided on the temperature detection film 6 and the electrode 31 provided on the electrically insulating substrate 1 so as to be in contact with the resistor film 3 are provided.

  The temperature detection film 6 is provided close to the gas detection material film 2 as a temperature detection unit that detects the temperature of the gas detection material film 2. Based on the temperature information detected by the temperature detection film 6, the fluctuation of the temperature of the hydrogen gas detection material film 2 due to a sudden change in the gas flow rate or the ambient temperature is suppressed, thereby improving the stability of the hydrogen gas measurement operation. Is done. For this purpose, the temperature of the gas detection material film 2 is preferably maintained within a range of ± 5 ° C. of the predetermined temperature.

  The temperature detection film 6 is preferably a thin film obtained by a thin film process such as sputtering or CVD, and its thickness is preferably 0.05 to 1 μm.

  Materials used for the temperature detection film 6 include metal oxides such as Cu, Ni, Co, Fe, Mn, Sn, and Zn, SiC, Pt, Rh, Ni, Cr, Fe, Cu, Ir, Re, and Mo. , Au, Pd, W and the like can be used, and these can be used alone or in combination.

  The insulating layer 7 is a layer made of the same electrically insulating material as the insulating layer 11, and the hydrogen gas detecting material film 2 and the temperature detecting film 6 are electrically insulated and the temperature detecting film 6 and the outside air are in contact with each other. To prevent its deterioration.

  The hydrogen gas sensor 110 includes temperature control means (not shown in FIG. 2) that controls the temperature of the gas detection material film 2 based on temperature information detected by the temperature detection film 6.

  As the temperature control means, for example, based on the temperature information detected by the temperature detection film 6, an electric circuit or the like that controls the energization amount to the resistor film 3 so that the gas detection material film 2 is maintained at a predetermined temperature. Can be used.

  The hydrogen gas sensor 110 can be manufactured by sequentially laminating each layer using a thin film process or the like using the same material as the hydrogen gas sensor 100.

  FIG. 3 is a cross-sectional view schematically showing the basic configuration of the third embodiment of the hydrogen gas sensor of the present invention.

  A hydrogen gas sensor 120 illustrated in FIG. 3 includes a base material 10 and an electrically insulating substrate 1a having an insulating layer 11 provided on one surface (upper side in the drawing) of the base material 10. On the insulating layer 11, the resistor film 3, which is a heating part, the insulating layer 8, the temperature detection film 6, the insulating layer 7, and the hydrogen gas detection material film 2 which is a hydrogen gas detection part are laminated in this order. A laminate is formed with the electrically insulating substrate 1a. Further, the hydrogen gas sensor 120 protects the diffusion preventing layer 4 and the protective layer 4 on the outer surface of the laminate so as to cover the laminate while exposing the surface of the hydrogen gas detection material film 2 opposite to the insulating layer 7. The layer 5 is laminated in this order from the inside.

  In addition, the hydrogen gas sensor 120 is electrically insulated from the hydrogen gas detection material film 2 through the insulation 7 and the electrode 30 provided on the insulating layer 7 so as to be in contact with the hydrogen gas detection material film 2. The electrode 32 provided on the temperature detection film 6 and the electrode 31 provided on the resistor film 3 so as to be electrically insulated from the temperature detection film 6 with the insulating layer 8 interposed therebetween. ing.

  In the case of the hydrogen gas sensor 120, the resistor film 3 and the hydrogen gas detection material film 2 are both provided on one surface of the electrically insulating substrate 1a. Like the hydrogen gas sensors 100 and 110, the resistor film 3 and the hydrogen gas sensor 120 are provided. The efficiency of heat conduction from the resistor film 3 to the hydrogen gas detection material film 2 can be further increased as compared with the case where an electrically insulating substrate is disposed between the gas detection material film 2 and the gas detection material film 2.

  The insulating layer 8 is a layer made of the same electrically insulating material as that of the insulating layer 11, whereby the resistor film 3 and the temperature detection film 6 are electrically insulated.

  Similarly to the hydrogen gas detection material 110 described above, the hydrogen gas sensor 120 is a temperature control unit (shown in FIG. 3) that controls the temperature of the gas detection material film 2 based on the temperature information detected by the temperature detection film 6. Not).

  The hydrogen gas detection material 120 can be manufactured by a method similar to that of the hydrogen gas sensor 100, preferably using the same material as the hydrogen gas detection materials 100 and 110.

  The hydrogen gas sensor described above is excellent in hydrogen gas detection sensitivity and hydrogen gas selectivity by using the hydrogen gas detection material of the present invention, and can be suitably used for hydrogen gas leak detection in a fuel cell vehicle.

  EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

(Example 1)
A hydrogen gas detection material was prepared according to the following procedure and evaluated.

<Preparation of hydrogen gas detection material 1>
First, an aqueous solution of zinc chloride in which 10 g of zinc chloride (manufactured by Kanto Chemical Co., Ltd.) is dissolved in 990 g of water is mixed with aqueous ammonia while adjusting the pH to around 7, and a white precipitate mainly composed of zinc hydroxide. Product was produced. The generated precipitate was washed several times with water by decantation, water was removed with a spray dryer, and then heat treatment was performed at 600 ° C. for 1 hour to obtain a hydrogen gas detection material 1.

  A part of the hydrogen gas detection material 1 is put into neutral water and left at room temperature, and then the filtrate obtained by filtering this is analyzed by an ion chromatogram method. It was confirmed that the chlorine compound that was present in the water contacted with water to produce chlorine ions.

<Evaluation of hydrogen gas selectivity>
On the glass substrate, a pair of opposed platinum electrode thin films having a rectangular main surface is formed so that a groove having a width of 1 cm is formed between them, and then hydrogen gas detection material 1 (10 g) A paste obtained by mixing 0.5 g of polyvinyl alcohol (manufactured by Kanto Chemical Co., Inc.) and 10 g of water was applied at a thickness of 100 μm so as to fill the groove formed on the glass substrate. Subsequently, this was heated at 600 ° C. for 1 hour and then allowed to cool to form a hydrogen gas detection material film in which zinc oxide particles were connected to each other to form a porous body. At this time, the BET specific surface area of the hydrogen gas detection material 1 forming the hydrogen gas detection material film was 6.6 m ² / g, the theoretical particle size was 162 nm, and the chlorine atom content was 0.72 wt%.

  In this example, the BET specific surface area was measured using NOVA2000 (trade name, manufactured by Cantachrome) after vacuum drying the sample at 300 ° C. for 30 minutes. The BET specific surface area and the true specific gravity of the material were The theoretical particle size was calculated from the value. The chlorine atom content was measured using a fluorescent X-ray analyzer.

  This hydrogen gas detection material film was heated to 500 ° C. through a glass substrate in the atmosphere. In this state, while measuring the electric resistance of the hydrogen gas detection material film through the platinum electrode, the hydrogen gas detection material film was brought into contact with 1% by volume of hydrogen gas and carbon monoxide gas, respectively, and in the process of contact with these gases. The change in electrical resistance with time was measured. The peak width (half-value width) of the electrical resistance over time was 6 sec for hydrogen gas and 16 sec for carbon monoxide.

Based on the measured change over time, R ₀ is the electrical resistance before contact with hydrogen gas or carbon monoxide gas, and R ₁ is the minimum value of electrical resistance when contacted with hydrogen gas or carbon monoxide gas. The value calculated by equation (1) was defined as the resistance change rate.
(Resistance change rate) = R ₀ / R ₁ (1)

Furthermore, the ratio (H ₂ / CO) of the resistance change rate with respect to hydrogen gas and the resistance change rate with respect to carbon monoxide gas was calculated, and this was used as an index of hydrogen gas selectivity.

(Example 2)
<Preparation of hydrogen gas detection material 2>
10 g of zinc oxide (manufactured by Kanto Chemical Co., Inc.) was mixed with 0.1 g of ammonium chloride and 10 g of water to obtain an adherent that was a paste in which an aqueous ammonium chloride solution was adhered to zinc oxide. Subsequently, this adhering body was heated at 600 ° C. for 1 hour to obtain a hydrogen gas detection material 2.

<Evaluation of hydrogen gas selectivity>
The adhering body is applied onto a glass substrate on which a platinum electrode thin film is formed, as in Example 1, and heated at 600 ° C. for 1 hour to form a hydrogen gas detection material film made of the hydrogen gas detection material 2. I let you. At this time, the BET specific surface area of the hydrogen gas detection material 2 forming the hydrogen gas detection material film was 6.7 m ² / g, the theoretical particle size was 160 nm, and the chlorine content was 0.59 wt%. Subsequently, the hydrogen gas selectivity of this hydrogen gas detection material film was evaluated by the same method as in Example 1. The peak width (half-value width) of the electrical resistance with time was 55 sec for hydrogen gas and 50 sec for carbon monoxide.

(Example 3)
<Preparation of hydrogen gas detection material 3>
First, a zinc nitrate aqueous solution in which 10 g of zinc nitrate (manufactured by Kanto Chemical Co., Ltd.) is dissolved in 990 g of water and ammonia water are mixed while adjusting the pH to be around 7, and precipitation mainly composed of zinc hydroxide. Product was produced. The generated precipitate was decanted and washed several times with water, and then water was removed to obtain particulate zinc oxide.

  10 g of the zinc oxide obtained above was mixed with 0.1 g of ammonium chloride and 10 g of water to obtain an adherent that was a paste in which an aqueous ammonium chloride solution was adhered to zinc oxide. Subsequently, this adhering body was heated at 600 ° C. for 1 hour to remove water, whereby a hydrogen gas detection material 3 was obtained.

<Evaluation of hydrogen gas selectivity>
A hydrogen gas detection material film was produced using the hydrogen gas detection material 3 in the same manner as in Example 1, and the hydrogen gas selectivity was evaluated. The peak width (half-value width) of the electrical resistance over time was 21 sec for hydrogen gas and 26 sec for carbon monoxide. At this time, the BET specific surface area of the hydrogen gas detection material 3 forming the hydrogen gas detection material film was 4.4 m ² / g, the theoretical particle size was 244 nm, and the chlorine content was 0.48 wt%.

(Comparative Example 1)
Commercially available zinc oxide (manufactured by Kanto Chemical Co., Inc.) used as a raw material in Example 2 was used as the hydrogen gas detection material 4 as it was.

A hydrogen gas detection material film was prepared by using the hydrogen gas detection material 4 in the same manner as in Example 1, and the hydrogen gas selectivity was evaluated. The peak width (half-value width) of the electrical resistance with time was 20 sec for hydrogen gas and 25 sec for carbon monoxide. At this time, the BET specific surface area of the hydrogen gas detection material 4 forming the hydrogen gas detection material film was 5.9 m ² / g, the theoretical particle size was 182 nm, and chlorine was not detected.

(Comparative Example 2)
The zinc oxide produced in Example 3 before the aqueous ammonium chloride solution was attached was used as the hydrogen gas detection material 5.

Using the hydrogen gas detection material 5 (10 g), a hydrogen gas detection material film was produced in the same manner as in Example 1, and the hydrogen gas selectivity was evaluated. The peak width (half-value width) of the electrical resistance over time was 40 sec for hydrogen gas and 35 sec for carbon monoxide. At this time, the BET specific surface area of the hydrogen gas detection material 5 forming the hydrogen gas detection material film was 9.4 m ² / g, the theoretical particle size was 114 nm, and chlorine was not detected.

  The measurement results in Examples 1 to 3 and Comparative Examples 1 and 2 are collectively shown in Table 1.

FIG. 1 is a cross-sectional view schematically showing a first embodiment of the hydrogen gas sensor of the present invention. FIG. 2 is a cross-sectional view schematically showing a second embodiment of the hydrogen gas sensor of the present invention. FIG. 3 is a cross-sectional view schematically showing a third embodiment of the hydrogen gas sensor of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electrical insulation board | substrate, 1a ... Electrical insulation board | substrate, 2 ... Hydrogen gas detection material film | membrane, 3 ... Resistor film | membrane, 4 ... Diffusion prevention layer, 5 ... Protection layer, 6 ... Temperature detection film | membrane, 7 ... Insulation layer, DESCRIPTION OF SYMBOLS 10 ... Base material, 11 ... Insulating layer, 100, 110, 120 ... Hydrogen gas sensor

Claims (8)

  A hydrogen gas detection material comprising zinc oxide particles and a chlorine compound present on the surface of the zinc oxide particles.   The hydrogen gas detection material according to claim 1, wherein the chlorine compound is a compound that generates chlorine ions by contact with water.   The hydrogen gas detection material according to claim 1 or 2, wherein the amount of chlorine atoms contained in the chlorine compound is 0.01 to 3.0 wt% with respect to 100 wt% of the zinc oxide particles. The hydrogen gas detection material according to claim 1, wherein the BET specific surface area is 0.1 to 100 m ² / g.   The hydrogen gas detection material according to any one of claims 1 to 4, wherein the zinc oxide particles are connected to each other to form a porous body. A precipitation step in which a zinc chloride aqueous solution is brought into contact with aqueous ammonia to form a precipitate;
A hydrogen gas detection material according to any one of claims 1 to 5, which is obtained by a production method comprising a heating step of heating the precipitate. An attachment step of attaching an ammonium chloride aqueous solution to the zinc oxide particles to obtain an attachment;
A hydrogen gas detection material according to any one of claims 1 to 5, which is obtained by a production method comprising a removal step of removing water from the adherent. A hydrogen gas detector comprising the hydrogen gas detection material according to any one of claims 1 to 7,
A hydrogen gas sensor comprising: a heating unit that heats the hydrogen gas detection unit.

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