Hydrogen gas sensor and method for producing hydrogen gas sensor

Abstract

To provide a hydrogen gas sensor that achieves high-sensitivity detection of hydrogen gas and offers advantages in durability.SOLUTION: A hydrogen gas sensor 1a includes a substrate 10, a sensing layer 20, a catalyst layer 30, and a protective layer 40. In a thickness direction of the sensing layer 20, the substrate 10, the sensing layer 20, the catalyst layer 30, and the protective layer 40 are arranged in this order. The sensing layer 20 has optical properties that vary by adsorption of hydrogen atoms. The catalyst layer 30 dissociates hydrogen molecules into hydrogen atoms. The protective layer 40 protects the catalyst layer 30. The protective layer 40 contains silicon oxide having a density of 2.20 g / cm3 or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a hydrogen gas sensor and a method for manufacturing the hydrogen gas sensor. [Background technology]

[0002] In recent years, interest in the use of hydrogen has been growing. The use of hydrogen requires sufficient safety measures, and technology that can detect hydrogen gas is important.

[0003] For example, Patent Document 1 describes a hydrogen gas detector. This hydrogen gas detector has a laminated structure of palladium and tungsten oxide. Palladium adsorbs molecular hydrogen gas and dissociates it into hydrogen atoms. The light transmittance of this hydrogen gas detector changes significantly due to the adsorption of hydrogen.

[0004] Patent Document 2 describes a hydrogen sensor. This hydrogen sensor has a substrate, a thin film layer, and a catalyst layer. The thin film layer is formed on the substrate. The catalyst layer is formed on the surface of the thin film layer and hydrogenates the thin film layer with hydrogen gas contained in the atmosphere, thereby changing the optical reflectance of the thin film layer. For example, a protective film is formed on the surface of the catalyst layer. The thin film layer is a magnesium-nickel alloy thin film layer or a magnesium thin film layer. The catalyst layer is made of palladium or platinum. The protective film is made of, for example, silicon dioxide (SiO2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-278744 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-248424 Summary of the Invention [Problem to be solved by the invention]

[0006] In the hydrogen gas detecting material described in Patent Document 1, the laminated structure of palladium and tungsten oxide is considered to be exposed to the outside of the hydrogen gas detecting material. With such a configuration, it is expected that physical or chemical deterioration will occur in the laminated structure depending on the environment in which the hydrogen gas detecting material is placed.

[0007] In the hydrogen sensor described in Patent Document 2, a protective film is formed on the surface of the catalyst layer, which prevents the catalyst layer from absorbing moisture or oxygen in the atmosphere and prevents deterioration of the catalyst layer. According to Patent Document 2, the thickness of the protective film formed on the surface of the catalyst layer is set in consideration of the trade-off between the hydrogen gas detection time and the lifespan required of a hydrogen sensor. For example, if the protective film is thick, it is difficult to shorten the hydrogen gas detection time, and it is thought that highly sensitive detection of hydrogen gas becomes difficult.

[0008] In view of the above circumstances, the present invention provides a novel hydrogen gas sensor that is advantageous in terms of high-sensitivity detection of hydrogen gas and durability, and a method for manufacturing the same. [Means for solving the problem]

[0009] The present invention provides A substrate; a sensitive layer having optical properties that change upon adsorption of hydrogen atoms; a catalyst layer that dissociates hydrogen molecules into hydrogen atoms; a protective layer that protects the catalyst layer, the substrate, the sensitive layer, the catalyst layer, and the protective layer are arranged in this order in a thickness direction of the sensitive layer; The protective layer has a density of 2.20 g / cm 3 and silicon oxide having a density of at least A hydrogen gas sensor is provided.

[0010] The present invention also provides forming a sensitive layer, a catalytic layer, and a protective layer in this order on a substrate successively in a vacuum by sputtering; the sensitive layer has optical properties that change upon adsorption of hydrogen atoms; The catalyst layer dissociates hydrogen molecules into hydrogen atoms, the protective layer protects the catalyst layer, The protective layer has a density of 2.20 g / cm 3 and silicon oxide having a density of at least A method for manufacturing a hydrogen gas sensor is provided. [Effects of the Invention]

[0011] The above-described hydrogen gas sensor is advantageous in terms of high sensitivity in detecting hydrogen gas and durability. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a cross-sectional view showing an example of a hydrogen gas sensor. [Figure 2] FIG. 2 is a diagram schematically illustrating an example of a method for manufacturing a hydrogen gas sensor. [Figure 3] FIG. 3 is a diagram schematically showing an apparatus used to create calibration curves for evaluating the sensitivity characteristics of samples according to the examples and comparative examples. [Figure 4] FIG. 4 is a diagram schematically showing an apparatus for evaluating the sensitivity characteristics of the samples according to the examples and comparative examples. [Figure 5] FIG. 5 is a diagram schematically showing another device for evaluating the sensitivity characteristics of the samples according to the examples and comparative examples.

[0013] As shown in FIG. 1, the hydrogen gas sensor 1a includes a substrate 10, a sensitive layer 20, a catalytic layer 30, and a protective layer 40. In the thickness direction of the sensitive layer 20, the substrate 10, the sensitive layer 20, the catalytic layer 30, and the protective layer 40 are arranged in this order. The sensitive layer 20 has optical properties that change with the adsorption of hydrogen atoms. The catalytic layer 30 dissociates hydrogen molecules into hydrogen atoms. The protective layer 40 protects the catalytic layer 30. The protective layer 40 has a density of 2.20 g / cm. 3The protective layer 40 contains silicon oxide having a density of at least 1000 MPa. This prevents the catalytic layer 30 from deteriorating due to the environment of the hydrogen gas sensor 1a, and the hydrogen gas sensor 1a is likely to have high durability. In this specification, silicon oxide is a compound in which one silicon atom is bonded to at least one oxygen atom, such as silicon dioxide (SiO2).

[0014] When hydrogen gas is present around the hydrogen gas sensor 1a, the hydrogen gas can permeate the protective layer 40 and reach the catalytic layer 30. The hydrogen molecules contained in the hydrogen gas are dissociated into hydrogen atoms in the catalytic layer 30 and diffuse through the catalytic layer 30 toward the sensitive layer 20. The hydrogen atoms that reach the sensitive layer 20 can be adsorbed onto the sensitive layer 20. As described above, the sensitive layer 20 has optical properties that change due to the adsorption of hydrogen atoms, and therefore hydrogen gas can be detected based on the optical changes in the sensitive layer 20. Therefore, it is understood that for highly sensitive detection of hydrogen gas, it is important that the protective layer 40 has high hydrogen gas permeability.

[0015] On the other hand, according to the inventors' investigations, even if a protective layer containing silicon oxide has desirable properties from the viewpoint of preventing deterioration of the catalyst layer, it does not necessarily have high hydrogen gas permeability. Patent Document 2 also explains that the thickness of the protective film is set in consideration of the trade-off between the hydrogen gas detection time and the lifespan required of a hydrogen sensor, and it is understood that if the thickness of the protective film is increased in consideration of the lifespan, the sensitivity of hydrogen gas detection will be sacrificed.

[0016] In light of these circumstances, the present inventors have conducted extensive research into the configuration of a protective layer that can exhibit high hydrogen gas permeability while preventing deterioration of the catalyst layer, and have undertaken a great deal of trial and error. As a result, they have found that the density of silicon oxide contained in the protective layer is 2.20 g / cm 3 It was found that the above-mentioned conditions make it easy for the protective layer to have high hydrogen gas permeability and for hydrogen gas to be detected with high sensitivity. Therefore, the hydrogen gas sensor 1a is easy to have high durability and to detect hydrogen gas with high sensitivity.

[0017] If the hydrogen ion permeability of the protective layer containing silicon oxide is high, it may affect the reliability of the sensor as a sensor that detects hydrogen molecules. Therefore, in order to improve the reliability of hydrogen gas detection, it is advantageous for the protective layer to have a low hydrogen ion permeability. According to the study by the inventors, the hydrogen ion permeability of the protective layer containing silicon oxide is not necessarily low. On the other hand, when the density of the silicon oxide contained in the protective layer is 2.20 g / cm 3 If this is the case, the hydrogen ion permeability of the protective layer containing silicon oxide is likely to be low, and therefore the hydrogen gas sensor 1a is likely to have high reliability in detecting hydrogen molecules.

[0018] The density of silicon oxide contained in the protective layer 40 is 2.21 g / cm 3 More than 2.23g / cm 3 or more, or 2.25 g / cm 3 Its density may be, for example, 2.40 g / cm 3 The density of silicon oxide contained in the protective layer 40 can be determined, for example, by X-ray reflectometry (XRR). The density of silicon oxide contained in the protective layer 40 can be determined, for example, by the method described in the Examples.

[0019] The thickness of the protective layer 40 is not limited to a specific value. The thickness is, for example, 30 nm or more and 200 nm or less. When the thickness of the protective layer 40 is 30 nm or more, the catalyst layer 30 is less likely to deteriorate. When the thickness of the protective layer 40 is 200 nm or less, the productivity of manufacturing the hydrogen gas sensor 1a is likely to be high.

[0020] The thickness of the protective layer 40 may be 40 nm or more, or 50 nm or more, and the thickness of the protective layer 40 may be 190 nm or less, or 180 nm or less.

[0021] As long as the hydrogen gas sensor 1a can detect hydrogen gas, the substrate 10 is not limited to a specific substrate. The substrate 10 is, for example, transparent in a predetermined wavelength range including a specific wavelength. For example, the average transmittance of the substrate 10 in the predetermined wavelength range is 50% or more. The substrate 10 may include, for example, an organic material such as an organic polymer, or an inorganic material such as quartz glass. Examples of organic polymers are polycarbonate, polyethylene, polyethylene terephthalate (PET), polypropylene, and polyvinylidene chloride. The substrate 10 is, for example, a glass substrate. In this case, the hydrogen gas sensor 1a is more likely to have high durability. The substrate 10 may also be a flexible substrate. In this case, the hydrogen gas sensor 1a can be easily deformed along a curved surface. The substrate 10 preferably includes PET.

[0022] The shape of the substrate 10 is not limited to a particular shape, and may be, for example, a shape having a flat surface such as a plate, a sheet, or a film.

[0023] The thickness of the substrate 10 is not limited to a specific value. The thickness is, for example, 10 μm or more and 5 cm or less. In this case, the sensitive layer 20, the catalyst layer 30, and the protective layer 40 can be easily formed by sputtering.

[0024] The sensitive layer 20 is not limited to a specific layer as long as it has optical properties that change due to the adsorption of hydrogen atoms. For example, the optical property that changes due to the adsorption of hydrogen atoms in the sensitive layer 20 is the transmittance of light at a specific wavelength. In this case, the hydrogen gas sensor 1a can detect hydrogen gas based on the change in the transmittance of light at the specific wavelength through the sensitive layer 20.

[0025] The specific wavelength is, for example, a wavelength included in the visible light range, and can be included in the wavelength range of 400 to 700 nm or the wavelength range of 500 to 700 nm.

[0026] The sensitive layer 20 contains, for example, tungsten oxide. Tungsten oxide has a dimming function as a reduction coloring material in electrochromic and gasochromic applications. When hydrogen atoms are adsorbed onto tungsten oxide, the transmittance of the sensitive layer 20 at a specific wavelength decreases. This can be used to detect hydrogen gas.

[0027] There is no particular limitation to the thickness of the sensitive layer 20. From the viewpoint of evaluating the optical properties of the sensitive layer 20 with high sensitivity, the thickness of the sensitive layer 20 is preferably 50 to 2000 nm, more preferably 100 to 1000 nm, even more preferably 200 to 800 nm, and particularly preferably 350 to 700 nm.

[0028] The catalyst layer 30 is not limited to a specific layer as long as it can dissociate hydrogen molecules into hydrogen atoms. The catalyst layer 30 may contain, for example, palladium. In this case, hydrogen molecules that come into contact with the catalyst layer 30 are more likely to dissociate into hydrogen atoms, making it easier to detect hydrogen gas with high sensitivity. In addition, components contained in the catalyst layer 30 are less likely to diffuse into the sensitive layer 20, making it easier to maintain the properties of the sensitive layer 20.

[0029] The thickness of the catalyst layer 30 is not limited to a specific value. The thickness is, for example, 3 to 20 nm. In this case, the amount of catalyst such as palladium used can be reduced, while the catalyst layer 30 tends to be uniform. The thickness of the catalyst layer 30 is preferably 3 to 10 nm, more preferably 3 to 7 nm, and even more preferably 4 to 6 nm.

[0030] The method for manufacturing the hydrogen gas sensor 1a is not limited to a specific method. The hydrogen gas sensor 1a can be manufactured, for example, by a method including successively forming the sensitive layer 20, the catalytic layer 30, and the protective layer 40 in this order on a substrate in a vacuum by sputtering. According to such a method, the hydrogen gas sensor 1a is likely to have high durability and is likely to detect hydrogen gas with high sensitivity. For example, the vacuum used in sputtering can be a medium vacuum (0.1 Pa or more but less than 100 Pa) or a high vacuum (1×10 -6The pressure can be adjusted to a state corresponding to a pressure of 0.1 Pa or more and less than 0.1 Pa.

[0031] FIG. 2 is a diagram schematically illustrating an example of a method for manufacturing a hydrogen gas sensor. As shown in FIG. 2, a sensitive layer 20 is formed on a substrate 10 by sputtering. When the sensitive layer 20 contains tungsten oxide, a layer containing tungsten oxide can be formed on the substrate 10 by, for example, reactive sputtering using metallic tungsten as a target. In this reactive sputtering, for example, argon gas and oxygen gas can be supplied. The ratio of the flow rate of oxygen gas to the total flow rate of gas can be adjusted to, for example, 20 to 90%. This makes it easier for the sensitive layer 20 to have the desired sensitivity to hydrogen gas. This ratio is preferably adjusted to 50 to 90%, more preferably 70 to 90%.

[0032] Next, after the formation of the sensitive layer 20 is completed, the catalyst layer 30 is formed by sputtering while the environment around the laminate including the substrate 10 and the sensitive layer 20 is kept in vacuum.

[0033] Next, after the formation of the catalyst layer 30 is completed, the protective layer 40 is formed by sputtering while the environment surrounding the laminate including the substrate 10, the sensitive layer 20, and the catalyst layer 30 is kept in a vacuum. In this way, the hydrogen gas sensor 1a can be manufactured. The conditions for sputtering the protective layer 40 are not limited to specific conditions. For example, sputtering is performed by supplying gas at a pressure of 2 Pa or less. As a result, the density of silicon oxide contained in the protective layer becomes 2.20 g / cm. 3 The gas supply pressure during sputtering is preferably 1 Pa or less. [Example]

[0034] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0035] Example 1 DC sputtering was performed on a quartz glass substrate using metallic tungsten (W) as the target material. In this DC sputtering, the vacuum around the ITO-coated quartz glass substrate was 8.0 × 10 -4 The pressure was adjusted to 3.0 Pa, and argon gas and oxygen gas were supplied. The gas supply pressure (total pressure) was 3.0 Pa, the ratio of the oxygen gas flow rate to the total gas flow rate was 80%, and the ratio of the argon gas flow rate to the total gas flow rate was 20%. The input power for DC sputtering was 100 W. In this way, the sensitive layer according to Example 1 containing tungsten oxide was formed on the quartz glass substrate.

[0036] The degree of vacuum around the quartz glass substrate was 8.0×10 -4 While maintaining the pressure at 0.5 Pa, DC sputtering was then performed using metallic palladium (Pd) as a target material. In this DC sputtering, only argon gas was supplied at a pressure of 0.5 Pa. The input power in the DC sputtering was 10 W. In this way, a catalyst layer containing palladium according to Example 1 was formed on the sensitive layer.

[0037] The degree of vacuum around the quartz glass substrate was 8.0×10 -4 While maintaining the pressure at 0.5 Pa, RF sputtering was then performed using silica (SiO2) as a target material. In this RF sputtering, argon gas and oxygen gas were supplied. The gas supply pressure (total pressure) was 0.5 Pa, the ratio of the oxygen gas flow rate to the total gas flow rate was 95%, and the ratio of the argon gas flow rate to the total gas flow rate was 5%. The input power in the DC sputtering was 200 W. In this way, the protective layer containing silicon oxide according to Example 1 was formed on the catalyst layer. In this way, the sample according to Example 1 was obtained.

[0038] A stylus-type step profiler DekTak manufactured by Bruker was used to measure the thicknesses of the sensitive layer, catalyst layer, and protective layer according to Example 1. The results are shown in Table 1.

[0039] <Examples 2 and 3> Samples according to Examples 2 and 3 were prepared in the same manner as in Example 1, except that the sputtering time was adjusted so that the thicknesses of the sensitive layer, catalyst layer, and protective layer were as shown in Table 1.

[0040] <Comparative Example 1> A sample of Comparative Example 1 was prepared in the same manner as Example 1, except that the sputtering time was adjusted so that the thicknesses of the sensitive layer and catalyst layer were as shown in Table 1, and no protective layer was formed.

[0041] <Comparative Example 2> A sample according to Comparative Example 2 was prepared in the same manner as in Example 1, except that the pressure of the RF sputtering for forming the protective layer was changed to 3.0 Pa and the time of each sputtering was adjusted so that the thicknesses of the sensitive layer, catalyst layer, and protective layer would be as shown in Table 1.

[0042] <Comparative Example 3> A sample according to Comparative Example 3 was prepared in the same manner as in Example 1, except that in the RF sputtering for forming the protective layer, alumina (Al2O3) was used as the target material instead of silica, and the time for each sputtering was adjusted so that the thicknesses of the sensitive layer, catalytic layer, and protective layer would be as shown in Table 1.

[0043] [Evaluation of the density of the protective layer] Using a fully automated multipurpose X-ray diffractometer SmartLab manufactured by Rigaku Corporation, the density of the protective layer of the samples according to each of Examples, Comparative Examples 2 and 3 was measured by X-ray reflectometry (XRR). The results are shown in Table 1.

[0044] [Evaluation of protective properties] For the samples of each Example and Comparative Example, the sheet resistance was measured 50 times at 1 mm intervals in a measurement zone including 51 measurement points positioned at 1 mm intervals along a straight line 5 cm long on the outermost surface of the laminate structure formed on the ITO layer of the ITO-coated quartz glass substrate. The sheet resistance was measured using a sheet resistance measuring device NC-80LINE manufactured by Napson Corporation. For example, the average sheet resistance in the measurement zone of each sample of Example 1 was approximately 100 Ω / □. Steel wool #0000 was applied to a pressure of 9.81 kPa (100 gf / cm 2 A reciprocating test was performed in which the sample was brought into contact with the outermost surface of the laminated structure at a pressure of 1000 psi (0.01 psi) and moved back and forth 20 times in a direction perpendicular to the 5 cm long straight line so as to cross the center position of the measurement zone. The sheet resistance in the measurement zone before and after the reciprocating test was measured, and the ratio R1 / R0 of the sheet resistance R1 after the reciprocating test to the sheet resistance R0 before the reciprocating test was calculated at each measurement position. The maximum value of the ratio R1 / R0 for each sample (R1 / R0) was calculated. max The results are shown in Table 1.

[0045] As shown in Table 1, the maximum values ​​(R1 / R0) of the samples according to each Example and Comparative Examples 2 and 3 were max The values ​​of R1 / R0 were all 1, and the sheet resistance hardly changed during the reciprocating test, suggesting that the protective layers of the samples according to each example could exhibit the desired protective properties. On the other hand, in the sample according to Comparative Example 1, the maximum value (R1 / R0) max The value of the reciprocating test exceeded 10, indicating that the sheet resistance can increase significantly due to the reciprocating test. Since the sample according to Comparative Example 1 does not have a protective film, it is believed that the catalyst layer on the outermost surface deteriorated due to the reciprocating test.

[0046] [Sensitivity characteristics rating A] FIG. 3 is a schematic diagram illustrating an apparatus used to create calibration curves for evaluating the sensitivity characteristics of samples according to the examples and comparative examples. As shown in FIG. 3, the apparatus A1 includes a three-electrode cell B1 and a controller C1. The three-electrode cell B1 includes a working electrode WE, a reference electrode RE, and an auxiliary electrode CE. The controller C1 includes a potentiostat and a galvanostat, and adjusts the voltage between the working electrode WE and the reference electrode RE to a predetermined value. In addition, the controller C1 measures the current between the auxiliary electrode CE and the working electrode WE.

[0047] The working electrode WE was fabricated as follows. An indium tin oxide (ITO) layer was formed on a quartz glass substrate. DC sputtering was performed on the ITO layer of the quartz glass substrate using metallic tungsten (W) as the target material. During this DC sputtering, the vacuum around the quartz glass substrate was 8.0 × 10 -4 The pressure was adjusted to 3.0 Pa, and argon gas and oxygen gas were supplied. The gas supply pressure (total pressure) was 3.0 Pa, the ratio of the oxygen gas flow rate to the total gas flow rate was 80%, and the ratio of the argon gas flow rate to the total gas flow rate was 20%. The input power for DC sputtering was 100 W. In this way, a sensitive layer containing tungsten oxide was formed on the ITO layer of the ITO-coated quartz glass substrate. The thickness of this sensitive layer was 598 nm.

[0048] The degree of vacuum around the ITO-coated quartz glass substrate was 8.0×10 -4 While maintaining the pressure at 0.5 Pa, DC sputtering was then performed using metallic palladium (Pd) as a target material. In this DC sputtering, only argon gas was supplied at a pressure of 0.5 Pa. The input power in the DC sputtering was 10 W. In this way, a catalyst layer containing palladium was formed on the sensitive layer, and a sample according to Example 1 in the device A1 was obtained. The thickness of this catalyst layer was 5 nm.

[0049] Using the above-described apparatus A1, the relationship between the change in optical density (OD) at a wavelength of 600 nm at the working electrode WE and the amount of injected charge per unit area was determined. An Ag / AgCl electrode was used as the reference electrode RE, and a Pt electrode was used as the auxiliary electrode CE. In the three-electrode cell B1, 0.1 M HCl was used as the electrolyte E1. The change in OD at a wavelength of 600 nm at the working electrode WE was measured while sweeping the voltage between the working electrode WE and the reference electrode RE from -0.5 V to 0.5 V at a rate of 20 mV / s. Charge injection into the working electrode WE caused electrochromism, resulting in a color change in the sensitive layer. The OD at a wavelength of 600 nm at the working electrode WE was measured using a Shimadzu UV-3600 Plus spectrometer. The amount of injected charge per unit area Q was calculated by dividing the time integral of the reduction current between the auxiliary electrode CE and the working electrode WE by the surface area of ​​the working electrode WE.

[0050] 0~30mC / cm 2 A calibration curve was created using the least squares method from a graph showing the relationship between the change in optical density (OD) at a wavelength of 600 nm of the working electrode WE and the amount of injected charge in the range of injected charge Q. As a result, the calibration curve expressed by the following formula (1) was obtained. In formula (1), ΔOD is the change in optical density, and Q is the amount of injected charge per unit area [mC / cm 2 ]. ΔOD=0.046500×Q Equation (1)

[0051] FIG. 4 is a schematic diagram illustrating an apparatus for evaluating the sensitivity characteristics of samples according to the examples and comparative examples. The apparatus A2 shown in FIG. 4 includes a pair of quartz glass plates W1, a supply pipe P1, and an exhaust pipe P2. The space between the pair of quartz glass plates W1 is sealed. Samples Sa according to the examples and comparative examples were placed between the pair of quartz glass plates W1 of the apparatus A2. In this state, a mixed gas of argon gas and hydrogen gas was supplied around each sample Sa from the supply pipe P1 at a flow rate of 50 standard cc / min (sccm). The mixed gas was discharged through the exhaust pipe P2. The hydrogen gas concentration in the mixed gas was 3% by volume. Before supplying the mixed gas and after a predetermined time had elapsed since the start of the mixed gas supply, light L1 containing a wavelength of 600 nm was transmitted from one side of the pair of quartz glass plates W1 to the other, and the OD at a wavelength of 600 nm of each sample Sa was measured. A Shimadzu UV-3600 Plus spectrometer was used to measure the OD at a wavelength of 600 nm of the sample Sa. This allows us to measure the change in optical density (OD) at a wavelength of 600 nm before and after the supply of the mixed gas. g The change in ΔOD was measured. g Substituting into equation (1) gives the corresponding injected charge Q g The film quality of the sensitive layer of the working electrode WE of the device A1 is considered to be equivalent to that of the sensitive layers of the samples according to the examples and comparative examples. g The value of Q is considered to be correlated with the amount of hydrogen atoms adsorbed on the sensitive layer by the supply of the mixed gas. Since the sample according to Comparative Example 1 does not have a protective layer, the injected charge amount Q g and the injected charge Q in the other samples g By comparing the injected charge Q of the other samples, the hydrogen gas permeability of the protective layer can be evaluated. g is the injected charge amount Q in the sample according to Comparative Example 1 g It is understood that the closer the value is to , the higher the hydrogen gas permeability of the protective layer of the sample. g The injected charge amount Q in the samples according to each example and comparative examples 2 and 3 g The ratio of rQ The percentage values ​​are shown in Table 1.

[0052] As shown in Table 1, in the samples according to each example, the ratio r Q On the other hand, in Comparative Examples 2 and 3, the ratio r Q The hydrogen gas permeability of the protective layer in the samples according to Comparative Examples 2 and 3 was low, and it was difficult to say that it was high. Comparing each example with Comparative Example 2, the density of silicon oxide contained in the protective layer was 2.20 g / cm 3 From the above, it was suggested that the hydrogen gas permeability of the protective layer is likely to be high, and that highly sensitive detection of hydrogen gas is likely to be achieved.

[0053] [Sensitivity characteristics rating B] FIG. 5 is a schematic diagram illustrating another apparatus for evaluating the sensitivity characteristics of samples according to the examples and comparative examples. As shown in FIG. 5, the apparatus A3 includes a three-electrode cell B3 and a controller C3. The three-electrode cell B3 includes a working electrode WE, a reference electrode RE, and an auxiliary electrode CE. The controller C3 includes a potentiostat and adjusts the voltage between the working electrode WE and the reference electrode RE to a predetermined value. In addition, the controller C3 measures the current between the auxiliary electrode CE and the working electrode WE.

[0054] The hydrogen ion permeation characteristics of the samples according to each Example and Comparative Example were evaluated using the above-mentioned device A3. The samples according to each Example and Comparative Example were used as the working electrode WE in the device A3, an Ag / AgCl electrode was used as the reference electrode RE, and a Pt electrode was used as the auxiliary electrode CE. In the three-electrode cell B3, HCl with a concentration of 0.1 M was used as the electrolyte E1. Cyclic voltammetry was performed while sweeping the voltage between the working electrode WE and the reference electrode RE in the range of -0.5 V to 0.5 V at a rate of 20 mV / sec. In this cyclic voltammetry, the time integral of the reduction current between the auxiliary electrode CE and the working electrode WE was divided by the surface area of ​​the working electrode WE to determine the charge injection amount per unit area Q [mC / cm]. 2The number of hydrogen ions that reached the sensitive layer, N, was calculated according to the following formula (2): H [pcs / m 3 The results are shown in Table 1. In formula (2), e is the elementary charge of 1.602 × 10 -19 [C] and d is the thickness of the sensitive layer. N H =Q×10 -3 / (e×d) Equation (2)

[0055] As shown in Table 1, the number of hydrogen ions that reached the sensitive layer of the sample according to each Example was significantly smaller than the number of hydrogen ions that reached the sensitive layer of the samples according to Comparative Examples 1 and 2. This indicates that the protective layer of the sample according to each Example is less permeable to hydrogen ions. Comparing each Example with Comparative Example 2, it is clear that the density of silicon oxide contained in the protective layer was 2.20 g / cm 3 These findings suggest that the hydrogen ion permeability of the protective layer is likely to be low, and the reliability of hydrogen gas detection is likely to be high.

[0056] [Table 1]

[0057] A first aspect of the present invention is A substrate; a sensitive layer having optical properties that change upon adsorption of hydrogen atoms; a catalyst layer that dissociates hydrogen molecules into hydrogen atoms; a protective layer that protects the catalyst layer, the substrate, the sensitive layer, the catalyst layer, and the protective layer are arranged in this order in a thickness direction of the sensitive layer; The protective layer has a density of 2.20 g / cm 3 and silicon oxide having a density of at least A hydrogen gas sensor is provided.

[0058] A second aspect of the present invention is The protective layer has a thickness of 30 nm or more and 200 nm or less. According to a first aspect, there is provided a hydrogen gas sensor.

[0059] A third aspect of the present invention is The optical property is the transmittance of light at a specific wavelength. A hydrogen gas sensor according to the first or second aspect is provided.

[0060] A fourth aspect of the present invention is the sensitive layer comprises tungsten oxide; The present invention provides a hydrogen gas sensor according to any one of the first to third aspects.

[0061] A fifth aspect of the present invention is The catalyst layer contains palladium. The present invention provides a hydrogen gas sensor according to any one of the first to fourth aspects.

[0062] A sixth aspect of the present invention is forming a sensitive layer, a catalytic layer, and a protective layer in this order on a substrate successively in a vacuum by sputtering; the sensitive layer has optical properties that change upon adsorption of hydrogen atoms; The catalyst layer dissociates hydrogen molecules into hydrogen atoms, the protective layer protects the catalyst layer, The protective layer has a density of 2.20 g / cm 3 and silicon oxide having a density of at least A method for manufacturing a hydrogen gas sensor is provided. [Explanation of symbols]

[0063] 1a Hydrogen gas sensor 10 Base material 20 Sensitive Layer 30 Catalyst layer 40 protective layer

Claims

1. A substrate; a sensitive layer having optical properties that change upon adsorption of hydrogen atoms; a catalyst layer that dissociates hydrogen molecules into hydrogen atoms; a protective layer that protects the catalyst layer, the substrate, the sensitive layer, the catalyst layer, and the protective layer are arranged in this order in a thickness direction of the sensitive layer; The protective layer has a density of 2.20 g / cm 3 and silicon oxide having a density of at least Hydrogen gas sensor.

2. The protective layer has a thickness of 30 nm or more and 200 nm or less.

2. The hydrogen gas sensor according to claim 1.

3. The optical property is the transmittance of light at a specific wavelength.

2. The hydrogen gas sensor according to claim 1.

4. the sensitive layer comprises tungsten oxide; 2. The hydrogen gas sensor according to claim 1.

5. The catalyst layer contains palladium.

2. The hydrogen gas sensor according to claim 1.

6. forming a sensitive layer, a catalytic layer, and a protective layer in this order on a substrate successively in a vacuum by sputtering; the sensitive layer has optical properties that change upon adsorption of hydrogen atoms; The catalyst layer dissociates hydrogen molecules into hydrogen atoms, the protective layer protects the catalyst layer, The protective layer has a density of 2.20 g / cm 3 and silicon oxide having a density of at least A method for manufacturing a hydrogen gas sensor.

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