JP2013068567A - Signal processing method of hydrogen gas sensor, and signal processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a signal processor of a hydrogen gas sensor capable of properly detecting hydrogen gas without using an expensive humidity sensor even when there is an influence of environmental fluctuation in the hydrogen gas sensor.SOLUTION: A hydrogen gas sensor includes: a proton conductive layer 2: a catalytic layer 3; a first electrode 4a joined to the proton conductive layer via the catalytic layer; and a second electrode 4b joined to the proton conductive layer without interposing the catalytic layer. A signal processor is constituted by including: a measurement processing part 11 which applies voltage of a predetermined pattern which gradually changes between both positive and negative polarities between both the electrodes of the hydrogen gas sensor, to measure values of currents which flow between both the electrodes; a normalization processing part 12 which normalizes the respective measured current values by a current value corresponding to a preset predetermined applied voltage to calculate voltage current characteristics; a temperature measurement processing part 13 which measures ambient temperature of the hydrogen gas sensor; a hydrogen gas detection processing part 14 which calculates the concentration of hydrogen gas based on the correlation between the normalized voltage current characteristics and the ambient temperature; and an output processing part 15 which outputs a processing result.

Description

  The present invention relates to a signal processing method and a signal processing apparatus for a hydrogen gas sensor.

  In configuring a hydrogen energy system typified by a fuel cell, there is an extremely high need for a hydrogen gas sensor that can accurately detect the presence or concentration of hydrogen gas, and it is compact when measuring hydrogen in the gas phase or liquid phase. A hydrogen gas sensor that can be reduced in weight is desired.

  As disclosed in Patent Document 1, in this background, the applicant of the present application used a solid polymer electrolyte membrane such as perfluorosulfonic acid or perfluorocarboxylic acid that exhibits high proton conductivity. A hydrogen gas sensor is proposed.

  In the hydrogen gas sensor, a catalyst layer is formed on at least one surface of a substrate made of a solid polymer electrolyte, a first electrode is formed on one surface via the catalyst layer, and a first electrode is formed on the other surface. Two electrodes are formed. Further, Patent Document 1 discloses that a base material in which carbon is added to the solid polymer electrolyte is suitably used in order to improve hydrogen gas detection characteristics, particularly output falling characteristics.

  In addition, since the hydrogen gas sensor has temperature and humidity dependence in its output characteristics, Patent Document 2 properly detects hydrogen gas regardless of changes in output caused by fluctuations in environmental factors such as humidity and temperature. An improved hydrogen gas sensor is disclosed for the purpose of doing so.

  The hydrogen gas sensor is provided with a measurement circuit that measures the impedance characteristics of the substrate, and a signal processing circuit that detects hydrogen gas based on the correlation between the output change of the hydrogen gas sensor and the impedance change.

WO / 2008/093813 JP 2009-145328 A

  However, in the hydrogen gas sensor described in Patent Document 1, the proton conductivity of the solid polymer electrolyte membrane used in the sensitive part varies under the influence of fluctuations in temperature, humidity, etc., so that its output characteristics are environmentally dependent. The problem is that even if hydrogen gas has the same concentration, the output of the hydrogen gas sensor fluctuates depending on the environment such as the humidity around the hydrogen gas sensor, and it is difficult to accurately detect hydrogen gas under conditions where the environmental change is large. was there.

  In addition, as described in Patent Document 2, a method of separating a signal change due to hydrogen and a signal change due to temperature and humidity by a method of changing the impedance signal is a gas leak detector that detects the presence or absence of hydrogen near room temperature. Although it is effective for applications, it has not been sufficient for hydrogen detection and hydrogen concentration measurement in any stable state over a wide temperature and humidity range.

  In order to detect the environment of the hydrogen gas sensor, a temperature sensor and a humidity sensor may be provided separately to correct the sensor output based on the detected temperature and humidity. When the processing circuit is provided, there arises a problem that the cost of the hydrogen gas sensor increases.

  Conversely, it is conceivable to provide a temperature / humidity adjusting mechanism to maintain the environment of the hydrogen gas sensor constant, but there is also a problem that a large-scale device for that purpose is required.

  In view of the above-described problems, an object of the present invention is to provide a hydrogen gas sensor signal processing method and signal processing capable of properly detecting hydrogen gas without using an expensive humidity sensor even if the hydrogen gas sensor is affected by environmental fluctuations. The point is to provide a device.

  In order to achieve the above object, a first characteristic configuration of a signal processing method for a hydrogen gas sensor according to the present invention includes a proton conductive layer and a proton conductive layer as described in claim 1 of the claims. A signal processing method for a hydrogen gas sensor comprising a first electrode and a second electrode joined to each other, wherein the predetermined pattern gradually changes between positive and negative polarities between the first electrode and the second electrode. A voltage step by measuring a current value flowing between both electrodes by applying a voltage, and normalizing each current value measured in the measurement step with a current value corresponding to a predetermined applied voltage set in advance A normalization step for determining characteristics, and a hydrogen gas detection step for determining the presence or absence of hydrogen gas based on the voltage-current characteristics obtained in the normalization step or for determining the concentration of hydrogen gas. That.

  When a voltage of a predetermined pattern that gradually changes between positive and negative polarities is applied between the first electrode and the second electrode in a state where hydrogen gas of a constant concentration is exposed to the hydrogen gas sensor, the current value flowing between the two electrodes is Observed, this current value fluctuates to a degree that cannot be ignored depending on temperature and humidity.

  As a result of intensive studies, the inventors of the present application have found that when each current value at this time is normalized with a current value corresponding to a predetermined applied voltage set in advance, the voltage-current characteristics almost overlap in a certain temperature range. A new finding is that it is not affected by humidity fluctuations, and that if the same normalization is applied to the current value measured in an atmosphere that does not contain hydrogen gas, the voltage-current characteristics will almost overlap regardless of temperature and humidity. I got it. According to such new knowledge, if the temperature fluctuation is within a predetermined range, even in an environment where the humidity fluctuates, it is possible to measure the hydrogen based on the normalized voltage-current characteristics without measuring the humidity for correction. The presence or absence of gas can be determined, or the concentration of hydrogen gas can be determined.

  The second characteristic configuration is a signal processing method of a hydrogen gas sensor comprising a proton conductive layer and a first electrode and a second electrode respectively joined to the proton conductive layer, as described in claim 2. A measuring step of measuring a current value flowing between both electrodes by applying a voltage of a predetermined pattern that gradually changes between positive and negative polarities between the first electrode and the second electrode; A normalizing step for obtaining a voltage-current characteristic by normalizing each current value measured in step 1 with a current value corresponding to a predetermined applied voltage set in advance, a temperature measuring step for measuring the ambient temperature of the hydrogen gas sensor, and Hydrogen gas that determines the presence or absence of hydrogen gas based on the correlation between the voltage-current characteristics obtained in the normalization step and the ambient temperature measured in the temperature measurement step, or obtains the concentration of hydrogen gas It lies in including a step out, the.

  According to the first characteristic configuration described above, if the temperature fluctuation is within a predetermined range, the presence or absence of hydrogen gas can be determined based on the normalized voltage-current characteristics, or the concentration of hydrogen gas can be obtained. When the temperature fluctuation is large, the influence of temperature appears in the normalized voltage-current characteristic, so that it is difficult to accurately obtain the hydrogen gas concentration. The present inventors have obtained a new finding that even in such a case, a correlation is found between the normalized voltage-current characteristic and the ambient temperature. Therefore, if the ambient temperature of the hydrogen gas sensor is measured, the presence or absence of hydrogen gas can be accurately determined based on the correlation, or the hydrogen gas concentration can be obtained. Since such a temperature sensor is usually available at a very low cost, the cost is not increased so much.

  In the third feature configuration, as described in claim 3, in addition to the first or second feature configuration described above, the hydrogen gas sensor is provided between the proton conductive layer and the first electrode, and / Or a catalyst layer is provided between the proton conductive layer and the second electrode.

  According to the above-described configuration, hydrogen is efficiently decomposed into protons by the catalytic action of the catalyst layer, and good hydrogen gas detection sensitivity can be ensured.

  In the fourth feature configuration, in addition to any one of the first to third feature configurations described above, in the measurement step, the second electrode is compared with the first electrode as described in claim 4. A voltage of a predetermined pattern including a portion that gradually changes from an initial voltage at which becomes positive to a transition voltage at which the second electrode becomes negative with respect to the first electrode is applied.

  When the first electrode is exposed to hydrogen gas, the hydrogen gas is decomposed by the action of the first electrode or catalyst layer having catalytic action, protons move to the second electrode through the proton conductive layer, and electrons are Since one electrode flows to the external circuit, the presence or concentration of hydrogen gas can be detected by measuring the current value at this time. That is, in the first electrode, an oxidation reaction in which hydrogen molecules are decomposed into protons and electrons proceeds.

  However, at this time, when an initial voltage that makes the second electrode positive with respect to the first electrode is applied, electrons are supplied to the first electrode to promote a reduction reaction in which hydrogen molecules are generated from protons and electrons. Thus, an equilibrium state is reached and almost no current can be detected. When the applied voltage gradually changes from this state to a transition voltage at which the second electrode becomes negative with respect to the first electrode, the equilibrium state of the oxidation-reduction reaction collapses and the oxidation reaction proceeds, and the generated protons are directed toward the second electrode. Moving. Therefore, by applying a voltage having a predetermined pattern including a portion that gradually changes from the initial voltage to the transition voltage, the generation of protons can be detected with high sensitivity even when the hydrogen gas concentration is low.

  In the fifth feature configuration, in addition to any one of the first to third feature configurations described above, in the measurement step, the second electrode may be the second electrode with respect to the first electrode. A voltage of a predetermined pattern including a portion that gradually changes from an initial voltage at which becomes positive to a transition voltage at which the second electrode becomes negative with respect to the first electrode is repeatedly applied at a predetermined period.

  When the application of the voltage in the predetermined pattern described above is repeated between the first electrode and the second electrode at a predetermined cycle, the movement toward the reduction reaction side and the movement toward the oxidation reaction side in the first electrode are performed in the first electrode. Repeated at a predetermined cycle. As a result, generation of protons corresponding to the hydrogen gas concentration can be periodically detected with good sensitivity.

  In the sixth feature configuration, as described in claim 6, in addition to the fourth or fifth feature configuration described above, the voltage of the predetermined pattern includes a portion in which the initial voltage continues for a certain period of time. There is in point.

  By continuing the initial voltage for a certain period of time, the reduction reaction is promoted at the first electrode, the movement of protons to the second electrode is sufficiently blocked, and the applied voltage changes from that state to the transition voltage, thereby oxidizing the reaction. Then, the generation of protons corresponding to the hydrogen gas concentration can be detected with high sensitivity.

  In the seventh feature configuration, as described in claim 7, in addition to any of the fourth to sixth feature configurations described above, in the hydrogen gas detection step, the transition voltage is minimized. The hydrogen gas concentration is obtained based on the correlation between the current value of the voltage-current characteristic and the ambient temperature.

  Of the voltage-current characteristics, the current value at which the transition voltage is minimum is in a state in which protons can be detected with the maximum sensitivity because the oxidation reaction is most accelerated.

  A first characteristic configuration of a signal processing apparatus for a hydrogen gas sensor according to the present invention includes a proton conductive layer, and a first electrode and a second electrode respectively joined to the proton conductive layer. A signal processing apparatus for a hydrogen gas sensor, wherein a voltage having a predetermined pattern that gradually changes between positive and negative polarities is applied between the first electrode and the second electrode, and a current value flowing between the two electrodes is determined. A measurement processing unit for measuring, a normalization processing unit for obtaining a voltage-current characteristic by normalizing each current value measured by the measurement processing unit with a current value corresponding to a predetermined application voltage set in advance, and the normalization A hydrogen gas detection processing unit that determines the presence or absence of hydrogen gas based on the voltage-current characteristics obtained by the processing unit or obtains the concentration of hydrogen gas; and an output processing unit that outputs a processing result by the hydrogen gas detection processing unit; ,including Located in.

  The second characteristic configuration is a signal processing device for a hydrogen gas sensor comprising a proton conductive layer, and a first electrode and a second electrode respectively joined to the proton conductive layer, as described in claim 9. A measurement processing unit that measures a value of a current flowing between both electrodes by applying a voltage of a predetermined pattern that gradually changes between positive and negative polarities between the first electrode and the second electrode, and the measurement A normalization processing unit that obtains a voltage-current characteristic by normalizing each current value measured by the processing unit with a current value corresponding to a predetermined applied voltage, and a temperature measurement process that measures the ambient temperature of the hydrogen gas sensor A hydrogen gas detection processing unit for obtaining a concentration of hydrogen gas based on a correlation between a voltage-current characteristic obtained by the normalization processing unit and an ambient temperature measured by the temperature measurement processing unit, and the hydrogen gas Depending on the detection processor In that it includes an output processing unit that outputs the management result.

  As described above, according to the present invention, there is provided a signal processing method and a signal processing apparatus for a hydrogen gas sensor that can properly detect hydrogen gas without using an expensive humidity sensor even if the hydrogen gas sensor is affected by environmental fluctuations. Can now be offered.

(A) is an example of a hydrogen gas sensor used in the present invention, and is a block diagram of a self-supporting film type hydrogen gas sensor, and (b) is a block diagram of a signal processing device according to the present invention. (A) shows the signal processing method of the hydrogen gas sensor by this invention, and is explanatory drawing of the voltage application state to the reductive reaction side, (b) explanatory drawing of the voltage application state to the oxidation reaction side, (c) is an applied voltage pattern (D) is an explanatory diagram of other applied voltage patterns It is a voltage-current characteristic diagram of a hydrogen gas sensor when a predetermined voltage pattern is applied to different hydrogen gas concentrations under different environmental conditions, and (a) is a voltage-current characteristic before normalization when not exposed to hydrogen gas. Figure, (b) is a voltage-current characteristic diagram after normalization with the maximum current value when not exposed to hydrogen gas, (c) is normalized with the maximum current value, including when exposed to hydrogen gas of a certain concentration Voltage-current characteristics after FIG. 4 is a hydrogen gas detection characteristic diagram calculated based on the voltage-current characteristic diagram of FIG. 3C, where FIG. 3A is a hydrogen gas concentration detection characteristic based on the minimum current value of the voltage-current characteristic diagram normalized by the maximum current value. (B) is a hydrogen gas concentration detection characteristic diagram based on the total integral value of the voltage-current characteristic diagram normalized by the maximum current value. It is a voltage-current characteristic diagram of a hydrogen gas sensor when a predetermined voltage pattern is applied to different hydrogen gas concentrations under different environmental conditions, and (a) is a voltage-current characteristic before normalization when not exposed to hydrogen gas. (B) is a voltage-current characteristic diagram after normalization with a current value at 0 V applied voltage when not exposed to hydrogen gas, and (c) includes a case where it is exposed to a constant concentration of hydrogen gas and applied with 0 V Voltage-current characteristics after normalization with current value at voltage FIG. 6 is a hydrogen gas detection characteristic diagram calculated based on the voltage-current characteristic diagram of FIG. 5C, and FIG. 5A is a hydrogen gas concentration detection characteristic based on the maximum current value of the voltage-current characteristic diagram normalized by the maximum current value. (B) is a hydrogen gas concentration detection characteristic diagram based on the total integral value of the voltage-current characteristic diagram normalized by the maximum current value. It is a voltage-current characteristic diagram of a hydrogen gas sensor when a predetermined voltage pattern is applied to different hydrogen gas concentrations under different environmental conditions, and (a) is a voltage-current characteristic before normalization when not exposed to hydrogen gas. Figure, (b) is a voltage-current characteristic diagram after normalization with the minimum current value when not exposed to hydrogen gas, (c) is normalized with the minimum current value, including when exposed to a constant concentration of hydrogen gas Voltage-current characteristics after FIG. 8 is a hydrogen gas detection characteristic diagram calculated based on the voltage-current characteristic diagram of FIG. 7C, where FIG. 7A is a hydrogen gas concentration detection characteristic based on the total integrated value of the voltage-current characteristic diagram normalized by the maximum current value. FIG. 4B is a hydrogen gas concentration detection characteristic diagram based on the integral value in the negative region of the current in the voltage-current characteristic diagram normalized by the maximum current value. (A) is a voltage-current characteristic diagram before normalization of a hydrogen gas sensor when a predetermined voltage pattern is applied to different hydrogen gas concentrations at different temperatures and constant temperatures, and (b) is when the applied voltage is maximum. (C) is a hydrogen gas concentration detection characteristic diagram based on the minimum current value of the voltage-current characteristic diagram of (b). Configuration diagram of substrate type hydrogen gas sensor used in the present invention Configuration diagram of substrate type hydrogen gas sensor used in the present invention Another configuration example of a hydrogen gas sensor used in the present invention and a block configuration diagram of a signal processing apparatus corresponding thereto

  Hereinafter, a signal processing method and a signal processing apparatus for a hydrogen gas sensor according to the present invention will be described with reference to the drawings.

  FIG. 1 (a) shows an example of a hydrogen gas sensor used in the present invention. The hydrogen gas sensor 1 includes a proton conductive layer 2 made of a solid polymer electrolyte, a first electrode 4 a joined via the proton conductive layer 2 and the catalyst layer 3, and a second joined to the proton conductive layer 2. The electrode 4b is laminated and formed.

  As the proton conductive layer 2, a solid polymer electrolyte that is an organic electrolyte can be employed. Perfluorosulfonic acid-based, perfluorocarboxylic acid-based perfluoropolymers having high proton conductivity, Poly ( It is preferable to use a hydrocarbon-based solid polymer electrolyte membrane made of partially sulfonated styrene-olefin copolymer such as styrene-ran-ethylene), sulfonated, etc., and Nafion (registered trademark: NAFION) or Aciplex (registered by Asahi Kasei Corporation) (Trademark: ACIPLEX) can be preferably used. The proton conductive layer 2 can be formed by casting such a solid polymer electrolyte solution on the substrate 8.

  The catalyst layer 3 is configured such that a catalyst 3 a made of a metal having a catalytic function by being brought into contact with hydrogen gas is supported on the upper surface of the proton conductive layer 2.

  As the catalyst 3a, platinum Pt or a platinum alloy is preferably used. Besides, gold Au, silver Ag, iridium Ir, palladium Pd, ruthenium Ru, osmium Os, cobalt Co, nickel Ni, tungsten W, molybdenum Mo, manganese A metal containing at least one selected from Mn, yttrium Y, vanadium V, niobium Nb, titanium Ti, and a rare earth metal can be used.

  The second electrode 4b does not require air permeability, and can use a metal such as copper, aluminum, stainless steel, or a carbon material, but it is desirable to select a material that does not corrode even under high humidity. Such an electrode layer can be formed on the substrate 8 by a known film forming method such as coating, screen printing, plating, sputtering, or vacuum deposition.

  For the first electrode 4a and the second electrode 4b, metals such as copper, aluminum, and stainless steel and carbon materials can be used, but it is desirable to select materials that do not corrode even under high humidity. The first electrode 4a needs to ensure air permeability, and a metal porous body, carbon paper, or the like can be suitably used. The second electrode 4b does not need to have air permeability. Other specific embodiments of the hydrogen gas sensor that can be used in the present invention will be described in detail later.

  When the electrode 4a on the catalyst layer 3 side is exposed to hydrogen gas, hydrogen is decomposed into protons and electrons by the action of the catalyst, and the generated protons diffuse into the proton conductive layer 2 and are separated from the electrons. The remaining electrode 4a has a negative potential with respect to the electrode 4b.

  That is, the electrode 4a on the side where the catalyst layer 3 is formed becomes a negative electrode, and at this time, the voltage value or current value having a correlation with the hydrogen gas concentration is detected by the signal processing circuit, so that the hydrogen gas concentration can be detected. . This value is a value based on the electromotive force due to the equilibrium electrode potential of the hydrogen oxidation-reduction reaction represented by Equation 1, and since this is represented by the Nernst equation represented by Equation 2, the value depends on the hydrogen gas concentration. .

Formula 1: H ₂ ⇔ 2H ⁺ + 2e ⁻
Formula 2: E = Eo + (RT / nF) lna
Where Eo is the standard electrode potential, R is the gas constant, T is the temperature (K), n is the number of mobile electrons, F is the Faraday constant, a is the activity (a = γ · c), and c is the hydrogen gas concentration. .

  In such a hydrogen gas sensor 1, proton conductivity fluctuates due to the influence of fluctuations in temperature, humidity, etc., so that its output characteristics are environmentally dependent, and even with the same concentration of hydrogen gas, the ambient humidity, etc. As the environment changes, the output of the hydrogen gas sensor changes.

  However, as will be described below, by applying the cyclic voltammetry method, the hydrogen gas concentration can be accurately detected regardless of the surrounding humidity environment.

  As shown in FIG. 1B, the signal processing device 10 of the hydrogen gas sensor 1 includes a measurement processing unit 11, a normalization processing unit 12, a temperature measurement processing unit 13, a hydrogen gas detection processing unit 14, and an output process. Part 15 is provided. These are constituted by an electronic circuit such as FPGA or ASIC or a microcomputer and its peripheral circuits, and are configured to execute predetermined processing described below based on a preset program.

  The measurement processing unit 11 includes a variable voltage generator VR, a current detection unit A, and a voltage detection unit V. The voltage detection unit V adjusts the variable voltage generator VR while monitoring the voltage between the electrodes 4a and 4b. Then, a voltage of a predetermined pattern that gradually changes between positive and negative polarities is applied between the first electrode 4a and the second electrode 4b, and the value of the current flowing between the electrodes 4a and 4b is measured. The voltage of a predetermined pattern is a repetitive voltage of a pattern as shown in FIGS. 2 (c) and 2 (d), for example.

  The normalization processing unit 12 normalizes each current value measured by the measurement processing unit 11 with a current value corresponding to a predetermined application voltage set in advance, for example, a current value when the application voltage becomes maximum, etc. An arithmetic process for obtaining current characteristics is executed.

  The temperature measurement processing unit 13 measures the voltage from the element TS having different characteristics depending on the temperature of a thermistor, a diode, etc., and calculates the ambient temperature of the hydrogen gas sensor 1.

  The hydrogen gas detection processing unit 14 calculates the concentration of hydrogen gas based on the correlation between the voltage-current characteristics obtained by the normalization processing unit 12 and the ambient temperature measured by the temperature measurement processing unit 13. Therefore, the hydrogen gas detection processing unit 14 includes a memory in which the correlation measured in advance by test is stored.

  The output processing unit 15 is a block that outputs a processing result from the hydrogen gas detection processing unit 14, and includes a liquid crystal display unit that displays the processing result, a signal transmission unit that outputs the processing result to an external device, and the like.

  The signal processing method of the hydrogen gas sensor according to the present invention is executed by the signal processing apparatus 10 described above. In other words, measurement is performed by the measurement processing unit 11 and a voltage of a predetermined pattern that gradually changes between positive and negative polarities is applied between the first electrode and the second electrode to measure a current value flowing between the two electrodes. A normalization step that is executed by the normalization processing unit 12 and obtains a voltage-current characteristic by normalizing each current value measured in the measurement step with a current value corresponding to a predetermined application voltage set in advance, and a temperature A temperature measurement step that is executed by the measurement processing unit 13 and measures the ambient temperature of the hydrogen gas sensor, and a voltage-current characteristic that is executed by the hydrogen gas detection processing unit 14 and obtained in the normalization step and the ambient that is measured in the temperature measurement step A hydrogen gas detection step for obtaining a hydrogen gas concentration based on the correlation with temperature.

  As shown in FIG. 2A, when a positive voltage is applied to the second electrode 4b of the hydrogen gas sensor 1 and a negative voltage is applied to the first electrode 4a as a bias voltage by the measurement processing unit 11, an oxidation reaction is caused in the catalyst layer 3. The decomposed protons move from the electrode 4b to the electrode 4a by the reverse bias voltage, and the detected current is reduced because the equilibrium state of the oxidation-reduction reaction shifts to the reduction reaction side.

  As shown in FIG. 2B, conversely, when a negative voltage is applied to the electrode 4 b of the hydrogen gas sensor 1 and a positive voltage is applied to the electrode 4 a by the measurement processing unit 11, protons decomposed by the oxidation reaction in the catalyst layer 3. Is moved from the electrode 4a to the electrode 4b by the forward bias voltage, and the detected current increases because the equilibrium state of the oxidation-reduction reaction shifts to the oxidation reaction side.

  As described above, when the voltage of a predetermined pattern that gradually changes between positive and negative polarities is applied between the first electrode 4a and the second electrode 4b by the measurement processing unit 11, the current value that changes with the voltage is changed. It is measured.

  For example, as shown in FIG. 2 (c), the voltage drops linearly from an initial voltage of 250 mV (point A) to 0 mV (point B) to -250 mV (point C) and further to 0 mV (point D) to 250 mV. When a voltage having a linearly rising pattern is applied to the hydrogen gas sensor 1, voltage-current characteristics as shown in FIG.

  For example, as shown in FIG. 2 (d), the voltage drops linearly from the initial voltage 0 (point B) to −250 mV (point C), further increases linearly to 250 mV (point E), and then returns to the initial voltage. When a pattern voltage is applied to the hydrogen gas sensor 1, a voltage-current characteristic as shown in FIG.

  Both are voltages having a cycle of 4 seconds in a range of ± 250 mV. However, the maximum-minimum voltage range and cycle are not limited to these values, and may be set as appropriate depending on the sensitivity of the hydrogen gas sensor 1 used. The applied voltage only needs to change gradually, and does not need to be changed linearly. The measurement processing unit 11 repeatedly applies such a constant pattern voltage to the hydrogen gas sensor 1 and measures each current value at that time.

  Such voltage-current characteristics fluctuate depending on temperature and humidity, but when each current value at this time is normalized with a current value corresponding to a predetermined applied voltage set in advance, in a range where the temperature difference is small. Even if the humidity fluctuates greatly, the voltage-current characteristics almost overlap each other, so that it is not affected by the humidity fluctuation. When the same normalization process is performed on the current value measured in an atmosphere (air) that does not contain hydrogen gas, the normalized voltage-current characteristics almost overlap regardless of temperature and humidity.

  The predetermined applied voltage value set in advance for the normalization process is the minimum voltage value indicating the maximum current value as indicated by point C in FIG. 2C and the maximum indicating the minimum current value as indicated by point E. A zero voltage value that passes when the voltage is swept, such as the voltage value, the B point, and the D point, can be preferably used. Furthermore, the present invention is not limited to these values, and appropriate values can be adopted.

  Regardless of the value of the applied voltage for normalization, the voltage-current characteristic after normalization is hardly affected by humidity. A certain correlation is obtained between the normalized voltage-current characteristics and the ambient temperature of the hydrogen gas sensor at that time. Accordingly, the hydrogen gas concentration is uniquely determined by the voltage-current characteristics after normalization and the ambient temperature of the hydrogen gas sensor at that time. Such knowledge has been obtained as a result of extensive research by the inventors of the present application.

  For example, the hydrogen gas concentration can be obtained using the correlation between the minimum current value and the temperature with respect to the voltage-current characteristic after normalization with the current value with respect to the maximum voltage value. Further, the hydrogen gas concentration can be obtained using the correlation between the maximum current value and the temperature with respect to the voltage-current characteristic after normalization with the current value with respect to the minimum voltage value.

  Further, the hydrogen gas concentration can be obtained by utilizing the correlation between the integrated value and the temperature with respect to the voltage-current characteristic after normalization with the current value for any voltage value. As the integral value at this time, the area of the whole area on the two-dimensional coordinate indicating the voltage-current characteristics, the area of either positive or negative area, the area of a specific quadrant (for example, the third quadrant), or the like can be used.

  If the temperature of the environment where the hydrogen gas sensor 1 is installed is substantially constant, it is not necessary to provide the temperature measurement processing unit 13. In this case, a voltage of a predetermined pattern that gradually changes between positive and negative polarities is applied between the first electrode and the second electrode, and a measurement step for measuring a current value flowing between the two electrodes and a measurement step are used. A normalization step that normalizes each current value with a current value corresponding to a preset applied voltage to obtain a voltage-current characteristic, and determines the presence or absence of hydrogen gas based on the voltage-current characteristic obtained in the normalization step Alternatively, a hydrogen gas detection step for obtaining the concentration of hydrogen gas may be executed.

  According to the normalized voltage-current characteristics, the voltage-current characteristics in the absence of hydrogen gas and the voltage-current characteristics in the presence of hydrogen gas are significantly different, so the presence or absence of hydrogen gas can be easily determined. is there.

  As shown in FIG. 2C, in the measurement step, a transition voltage at which the second electrode 4b is negative with respect to the first electrode 4a from an initial voltage at which the second electrode 4b is positive with respect to the first electrode 4a. It is preferable to apply a voltage having a predetermined pattern including a gradually changing portion. Here, the transition voltage refers to a voltage at which the second electrode 4b is negative with respect to the first electrode 4a.

  When the first electrode 4a is exposed to hydrogen gas, the hydrogen gas is decomposed by the action of the catalyst layer 3, protons move to the second electrode 4b through the proton conductive layer 2, and electrons are externally transmitted from the first electrode 4b. Since the current flows through the circuit, the current value corresponding to the presence or absence or concentration of hydrogen gas can be efficiently detected by measuring the current value at this time. That is, in the first electrode 4a, an oxidation reaction in which hydrogen molecules are decomposed into protons and electrons proceeds.

  At this time, when an initial voltage at which the second electrode 4b is positive with respect to the first electrode 4a is applied, electrons are supplied to the first electrode 4a and hydrogen molecules are generated from protons and electrons on the reduction reaction side. The equilibrium state is reached, and the current becomes almost undetectable. When the applied voltage gradually changes from this state to a transition voltage at which the second electrode 4b becomes negative with respect to the first electrode 4a, the equilibrium state of the oxidation-reduction reaction breaks down and proceeds to the oxidation reaction side, and the generated protons are transferred to the second electrode. Move towards Therefore, by applying a voltage having a predetermined pattern including a portion that gradually changes from the initial voltage to the transition voltage, the generation of protons can be detected with high sensitivity even when the hydrogen gas concentration is low.

  It is possible to change the applied voltage rapidly from the initial voltage to the transition voltage. However, if the applied voltage changes suddenly, the sensitivity may decrease, so the hydrogen gas responsiveness (sensitivity) of the hydrogen gas sensor may be reduced. ). Further, if the change in applied voltage is too slow, the change in current value may be small. That is, it is preferable to change the applied voltage along the hydrogen gas responsiveness (sensitivity) of the hydrogen gas sensor.

  In the current detection step, a predetermined pattern including a portion that gradually changes from an initial voltage at which the second electrode 4b is positive with respect to the first electrode 4a to a transition voltage at which the second electrode 4b is negative with respect to the first electrode 4a. It is preferable to repeatedly apply this voltage at a predetermined cycle.

  When the application of the voltage in the predetermined pattern described above is repeated between the first electrode 4a and the second electrode 4b in a predetermined cycle, the first electrode 4a moves to the reduction reaction side in the equilibrium state and moves to the oxidation reaction side. The movement is repeated at the predetermined cycle. As a result, the generation of protons corresponding to the hydrogen gas concentration can be detected with high sensitivity.

  Furthermore, as indicated by a broken line in FIG. 2C, it is preferable that the voltage of the predetermined pattern includes a portion where the initial voltage continues for a predetermined time. By continuing the initial voltage for a certain period of time, the reduction reaction is promoted in the first electrode 4a, the movement of protons to the second electrode 4b is sufficiently blocked, and the applied voltage changes from that state to the transition voltage. As the oxidation reaction proceeds, the generation of protons corresponding to the hydrogen gas concentration can be detected with high sensitivity.

  In the hydrogen gas detection step, it is particularly preferable to obtain the concentration of hydrogen gas based on the correlation between the current value of the voltage-current characteristic when the transition voltage is minimized and the ambient temperature. This is because, among the voltage-current characteristics, the current value when the transition voltage is minimum is in a state in which protons can be detected with the maximum sensitivity because the oxidation reaction is most accelerated.

Hereinafter, experimental examples will be described.
Change the environment at 3 levels of temperature 20, 40, 80 ° C and 2 levels of humidity 40, 80% Rh, respectively for the state where hydrogen is not supplied and the state where it is exposed to hydrogen gas with a concentration of 0.4% The current value when a voltage having a pattern as shown in FIG. 2C was repeatedly applied was measured.

A hydrogen gas sensor as a sample was produced by the following procedure.
As a substrate made of a solid polymer electrolyte, a 100 μm thick perfluoro polymer, Nafion membrane (NRE-212) (purchased from DuPont) is cut into 5 cm square, and the cut Nafion membrane is sandwiched between filter papers. Then, it was pressed with an iron heated to 130 ° C., and water was repeatedly blown until water did not penetrate into the filter paper.

  In this way, platinum Pt as a catalyst was supported on one side of a Nafion film from which water had been sufficiently removed within a 4 cm square range with a sputtering time of 30 seconds to form a catalyst layer 3 having a thickness of 20 nm. The sputtering conditions for platinum Pt were as follows: output RF 300 W, gas flow rate Ar Ar 20 cc / min. It is.

  The Nafion membrane 21 on which the catalyst layer 3 is formed is sandwiched between a pair of copper-nickel electrodes 4 having a large number of pores, and is further sandwiched by an acrylic resin plate-shaped body 5 having a large number of openings 5a. The hydrogen gas sensor 1 was produced by fixing the plate-like body 5 with bolts.

  After mounting the hydrogen gas sensor in a cylindrical glass tube, the hydrogen gas sensor was installed in an oven for adjusting the environment, and air or air-based hydrogen gas was supplied from one end of the glass tube and was discharged from the other end. Measurements were made 1 minute after the supply of air or air-based hydrogen gas (r2) and again after 2 minutes (r3).

  FIG. 3A shows the voltage-current characteristics during the initial measurement (r2) in which only air that does not contain hydrogen gas is supplied. The symbols A, B, C, D, and E in the figure correspond to the voltages in FIG. It can be seen that the hydrogen gas sensor is affected by temperature and humidity even when hydrogen is not present. FIG. 3B shows the voltage-current characteristics after normalizing each voltage-current characteristic with the maximum current value at the maximum applied voltage of 250 mV (the value in the area surrounded by an ellipse indicated by symbol E). (The values at the point E surrounded by circles are equal). According to FIG. 3B, it can be seen that, in the case of only air that does not contain hydrogen gas, the effects of temperature and humidity are eliminated, and the voltage-current characteristics are almost the same.

  FIG. 3 (c) shows the voltage-current characteristics during initial measurement (r2) and re-measurement (r3) when 0.4% hydrogen gas based on air is supplied. The voltage-current characteristic after normalizing each voltage-current characteristic with the maximum current value is shown.

  It can be seen from FIG. 3C that when the temperature is constant, the voltage-current characteristics after the normalization process are almost the same even when the humidity is different, and that the voltage-current characteristics after the normalization process are different when the temperature is different. In the figure, the group G1 shows voltage-current characteristics of 20 ° C., the group G2 of 40 ° C., and the group G3 of 80 ° C.

  FIG. 4 (a) shows a calibration curve showing the correlation between the normalized minimum current value and the hydrogen gas concentration in FIGS. 3 (b) and 3 (c). From this, it can be understood that if the ambient temperature of the hydrogen gas sensor is known, the hydrogen gas concentration can be specified based on the normalized voltage-current characteristic (minimum current value). In the figure, only a calibration curve for 0.4% hydrogen gas concentration is shown, but it is confirmed that the same is true for 1% hydrogen gas concentration. The same applies to the following description.

  FIG. 4B shows a calibration curve showing the correlation between the total integrated value (internal area) of the voltage-current characteristic after normalization in FIGS. 3B and 3C and the hydrogen gas concentration. Similarly, if the ambient temperature of the hydrogen gas sensor is known, it can be seen that the hydrogen gas concentration can be specified based on the normalized voltage-current characteristic (integrated value).

  FIG. 5A is the same voltage-current characteristic diagram as FIG. FIG. 5 (b) corresponding to FIG. 3 (b) shows an example of normalization with the current value when the voltage becomes zero when the applied voltage is swept from positive to negative. Similarly, in FIG. 5C corresponding to FIG. 3C, the voltage-current characteristics at the initial measurement (r2) and remeasurement (r3) when 0.4% hydrogen gas based on air is supplied are normalized. The voltage-current characteristics are shown.

  FIG. 6 (a) shows a calibration curve showing the correlation between the normalized minimum current value and the hydrogen gas concentration in FIGS. 5 (b) and 5 (c). From this, it can be understood that if the ambient temperature of the hydrogen gas sensor is known, the hydrogen gas concentration can be specified based on the normalized voltage-current characteristic (minimum current value).

  FIG. 6B shows a calibration curve showing the correlation between the total integrated value (internal area) of the voltage-current characteristic after normalization in FIGS. 5B and 5C and the hydrogen gas concentration. Similarly, if the ambient temperature of the hydrogen gas sensor is known, it can be seen that the hydrogen gas concentration can be specified based on the normalized voltage-current characteristic (integrated value).

  FIG. 7A is the same voltage-current characteristic diagram as FIG. FIG. 7B corresponding to FIG. 3B shows an example of normalization with the current value when the applied voltage becomes the minimum value. Similarly, in FIG. 7C corresponding to FIG. 3C, the voltage-current characteristics at the initial measurement (r2) and remeasurement (r3) when 0.4% hydrogen gas based on air is supplied are normalized. The voltage-current characteristics are shown.

  FIG. 8A shows a calibration curve indicating the correlation between the total integrated value (internal area) of the voltage-current characteristics after normalization in FIGS. 7B and 7C and the hydrogen gas concentration. From this, it can be seen that if the ambient temperature of the hydrogen gas sensor is known, the hydrogen gas concentration can be specified based on the normalized voltage-current characteristics (total area).

  FIG. 8B shows the integral value of the negative region of the voltage-current characteristics after normalization of FIGS. 7B and 7C (current value and current when the applied voltage is swept from the maximum value to the minimum value). A calibration curve showing the correlation between the area between the axis and the hydrogen gas concentration is shown. Similarly, if the ambient temperature of the hydrogen gas sensor is known, it can be seen that the hydrogen gas concentration can be specified based on the normalized voltage-current characteristic (integrated value).

  That is, if the ambient temperature of the hydrogen gas sensor is known, the hydrogen gas concentration can be accurately obtained based on the correlation between the temperature and the normalized voltage-current characteristic. Such correlation may be acquired in advance by a test or the like.

  Next, the environment is changed at two levels of 40 and 80% Rh with a constant temperature of 40 ° C., in a state where hydrogen is not supplied and in a state where the gas is exposed to hydrogen gas having a concentration of 0.4% and a concentration of 1.0%. For each, a current value was measured when a voltage having a pattern as shown in FIG. 2D was repeatedly applied. As described above, the first measurement (r2) was performed 1 minute after the supply of air or air-based hydrogen gas, and the remeasurement (r3) was performed after 2 minutes. In the figure, solid lines without triangles, squares, and circles indicate characteristics with respect to air.

  FIG. 9A shows voltage-current characteristics at that time. FIG. 9B shows a current-voltage characteristic normalized by a current value at 250 mV at which the applied voltage is maximum.

  FIG. 9C shows a calibration curve for the hydrogen gas concentration based on the minimum current value in FIG. 9B. If the temperature is constant, the hydrogen gas concentration can be accurately measured even if the environment changes. I understand that I want it.

  Furthermore, the same experiment was performed on the methane gas and the carbon monoxide gas as the gas to be detected using the hydrogen gas sensor described above, but none of the characteristic changes in output appeared. From this, it was confirmed that gas selectivity to hydrogen gas was also provided.

  In the embodiment described above, the measurement step for measuring the current value flowing between the first electrode 4a and the second electrode 4b is a predetermined step that gradually changes between positive and negative polarities between the first electrode 4a and the second electrode 4b. Although the case where the pattern voltage is directly applied has been described, the reference electrode 4c is interposed between the first electrode 4a and the second electrode 4b and sandwiched between the proton conductive layers 2 as shown in FIG. The voltage may be applied between the first electrode 4a and the second electrode 4b while monitoring the voltage between the first electrode 4a and the reference electrode 4c.

  If the voltage is applied between the first electrode 4a and the second electrode 4b so that the monitor voltage between the first electrode 4a and the reference electrode 4c at this time has the above-described predetermined pattern, Accurate measurement is possible. The reference electrode 4c can be made of the same material as the second electrode 4b.

  That is, according to the configuration shown in FIG. 1B, the concentration of the redox species at the interface of the first electrode 4a changes due to the current flowing between the first electrode 4a and the second electrode 4b, and the reference potential Although the device itself may fluctuate, if the configuration shown in FIG. 12 is adopted, a desired voltage can be applied between the first electrode 4a and the second electrode 4b while reducing the influence of such current. it can.

  That is, in the measurement step included in the signal processing method of the hydrogen gas sensor according to the present invention, between the first electrode 4a and the second electrode 4b, or between the first electrode 4a, the first electrode 4a, and the second electrode 4b. A voltage of a predetermined pattern which gradually changes between positive and negative polarities is applied between the reference electrode 4c formed so as to be sandwiched between the proton conductive layers 2 and a current value flowing between the electrodes is measured. Measurement steps to be included.

Below, the other aspect of a hydrogen gas sensor is explained in full detail.
FIG. 10A shows one embodiment of a substrate-type hydrogen gas sensor. First electrode layer 4a and second electrode layer 4b formed on substrate 8 to be separated from each other, catalyst layer 3 laminated on first electrode layer 4a, second electrode layer 4b and catalyst layer The counter electrode substrate type hydrogen gas sensor 1 can be configured by including the proton conductive layer 2 laminated so as to cover 3. If necessary, a reference electrode layer 4c may be formed on the substrate 8 and between the first electrode layer 4a and the second electrode layer 4b.

  As long as the substrate 8 can stably hold the proton conductive layer 2 formed on the upper surface, the substrate 8 is made of a resin material such as glass epoxy resin or phenol resin from a substrate using an inorganic material such as glass, ceramic, or silicon. The substrate can be formed using various materials, such as a shape-retaining substrate using a substrate and a flexible film-like substrate using a resin material such as polyimide resin.

  As resin materials that compose the substrate, polyethylene terephthalate, polyethylene naphthalate, nylon, cyclic olefin, polyethylene sulfonate, polysulfone, polyimide, polyamideimide, polycarbonate, polybutylene terephthalate, urethane, acrylic, polyethylene, polystyrene, polypropylene, fluorine Examples thereof include PTFE (PTFE, PFA, ETFE, FEP, PVDF, etc.).

  As the proton conductive layer 2, it is possible to use a solid ionic conductor having a ionic liquid as a main component and a mixture of an ionic liquid and a resin as a main component in addition to the above-described solid polymer electrolyte as a main component. . The solid ionic conductor is obtained by mixing an ionic liquid with any one of a photo-curing resin, a thermosetting resin, and a thermoplastic resin, followed by curing treatment.

  As the ionic liquid, a cation moiety selected from one or more of imidazolium ions, pyridinium ions, aliphatic amine ions, alicyclic amine ions, and aliphatic phosphonium ions, a halogen ion, a halogen ion, One having one or more types of anion sites selected from any of system ions, phosphonate ions, borate ions and triflate ions can be suitably selected.

  As the photocurable resin, methyl methacrylate, epoxy acrylate, urethane acrylate, polyester acrylate, unsaturated polyester resin, diazo resin, azide resin, silicone resin, or the like can be used. Here, the photocurable resin means a broad concept including an ultraviolet curable resin, a visible light curable resin, and an electron beam curable resin. A film-like solid ionic conductor can be obtained by irradiating ultraviolet rays or the like after stirring and mixing the ionic liquid and the photocurable resin into a film shape.

  As the thermosetting resin, polyimide, polyamideimide, epoxy, urethane, silicone resin, or the like can be used. A film-like solid ionic conductor is obtained by stirring and mixing the ionic liquid, the thermosetting resin, and the reactant, and then forming into a film shape and heat-treating.

  As the thermoplastic resin, fluorine resin (PTFE, PFA, ETFE, FEP, PVDF, etc.), nylon, cyclic olefin, polyethylene sulfonate, polysulfone, or the like can be used. In particular, a fluororesin having water repellency and high heat resistance is suitable. Among them, a resin such as PVDF (polyvinylidene fluoride) or a copolymer thereof can be suitably used. A film-like solid ionic conductor is obtained by stirring and mixing an ionic liquid and a thermoplastic resin in a molten state at a high temperature, and then forming into a film shape and cooling.

  In any case, a mixing step of mixing and stirring the ionic liquid in the resin, a step of dropping and casting the ion conductor subjected to the stirring and mixing process in the mixing step on the substrate 8, and a cast ion conductor The film is formed by a curing process step for curing the film.

  Furthermore, an organic-inorganic composite electrolyte can be employed as the proton conductive layer 2. Organic-inorganic composite electrolytes are those in which various organic and inorganic electrolytes are nano-dispersed in ceramics such as silica, titania, zirconia, alumina, etc., while leaving organic substances as required, using a sol-gel method. is there. Examples of organic electrolytes include polymer electrolytes such as urea, polyethylene oxide, and perfluorosulfonic acid polymers. Examples of the inorganic electrolyte include various acid and alkali salts such as phosphoric acid and sulfuric acid, ion conductive glass, and ceramics.

In particular, a urea-based silica composite electrolyte prepared from urea and silica alkoxide by a sol-gel method, a composite electrolyte composed of a phosphosilicate (P ₂ O ₅ —SiO ₂ ) gel prepared from phosphoric acid and silica alkoxide by a sol-gel method, or A composite solid polymer electrolyte in which these electrolytes are dispersed in a polymer can be suitably employed.

  These organic-inorganic composite electrolytes are produced by a sol-gel method. For example, a sol solution can be obtained by adding and mixing an inorganic electrolyte to a solution obtained by mixing water containing an acidic condensation catalyst and silica alkoxide and partially hydrolyzing the silica alkoxide, followed by hydrolysis and condensation. The organic-inorganic composite electrolyte gel membrane is obtained by dropping the sol solution of the organic-inorganic composite electrolyte thus obtained onto the target for film formation, drying the solvent, and then performing a predetermined heat treatment to obtain the above-described proton conductivity. Layer 2 can be formed.

  In addition, the organic-inorganic composite electrolyte gel membrane thus obtained has poor impact resistance due to its brittleness, and the inorganic electrolyte dissolves in condensed water under high temperature and high humidity conditions, etc., and is detached from the gel. There is a problem that water resistance is poor because it is easy. Therefore, impact resistance and water resistance can be improved by pulverizing the organic-inorganic composite electrolyte gel and combining it with a polymer component, and further, it can be easily processed into a film of any size. It becomes like this. Such a polymer component is not particularly limited, and the above-described thermoplastic resin, thermosetting resin, UV curable resin, and the like can be used.

  For example, VdF-HFP copolymer resin (Kyner # 2801, manufactured by Arkema: HFP 11 mol%), which is a copolymer of vinylidene fluoride (VdF) and hexafluoropropylene (HFP), is converted to N, N-dimethylacetamide (DMAC). To obtain a composite polymer electrolyte solution by stirring and mixing the solution and the organic-inorganic composite electrolyte gel in a DMAC (dimethylacetamide) solvent. The above-described proton conductive layer 2 can be formed by dropping on a film formation target such as a substrate or a mold and drying.

As the catalyst, a carbide such as molybdenum carbide Mo ₂ C, or an oxide such as zirconia oxide or tantalum oxide can be used instead of the metal catalyst already described.

  One kind of these catalysts 3a may be used alone, a plurality of them may be used in combination, or a part or all of them may be used in the form of an alloy.

  It is also possible to use a catalyst 3a made of an organic metal or an organic substance having catalytic activity by contacting with hydrogen gas. Examples of such organometallic catalysts include N, N'-Bis (salicylidene) ethylene-diamino-metal (= Ni, Fe, V, etc.), N, N'-mono-8-quinoly-σ-phenylenediamino-metal. (= Ni, Fe, V, etc.) can be used, and examples of organic substances include pyrrolopyrrole red pigments and dipyridyl derivatives.

  The catalyst layer 3 is formed by sputtering, vacuum deposition, electron irradiation, CVD, PVD, impregnation, spray coating, spray pyrolysis, kneading, spraying, coating with a roll or iron, screen printing, kneading method, photoelectrolysis method, coating method. It can be formed by employing a sol-gel method, a dip method or the like.

In particular, it is preferable to form the catalyst layer 3 by sputtering. The sputtering treatment time is preferably less than 90 seconds, and more preferably 60 seconds or less. The DC and RF output values during sputtering are not particularly limited, but are preferably 1.2 W / cm ² or more.

  The second electrode 4b does not require air permeability, and can use a metal such as copper, aluminum, stainless steel, or a carbon material, but it is desirable to select a material that does not corrode even under high humidity. Such an electrode layer can be formed on the substrate 8 by a known film forming method such as coating, screen printing, plating, sputtering, or vacuum deposition.

  In the case of this embodiment, the first electrode 4a does not need to be a material having air permeability, and can be composed of the same material as the second electrode layer 4b. The hydrogen gas passes through the proton conductive layer 2 and comes into contact with the catalyst layer 3.

  Either the first electrode layer 4 a or the second electrode layer 4 b can be used also as the substrate 8. In this case, as shown in FIG. 10B, the other electrode layer 4b needs to be laminated on the substrate 8 via the insulating layer 4c.

  In the hydrogen gas sensor 1 described above, the first electrode 4a and the second electrode layer 4b are formed on the substrate 8 by screen printing or the like, and the catalyst 3a is supported on the upper portion of the first electrode 4a. 3, a step of forming the proton conductive layer 2 on top of the catalyst layer 3 and the second electrode layer 4 b so as to cover the catalyst layer 3, and a step of cutting the laminate through each step into a predetermined size Manufactured by.

  FIG. 11A shows another aspect of the substrate-type hydrogen gas sensor. The proton conductive layer 2 formed on the substrate 8, the catalyst layer 3 and the second electrode layer 4 b stacked on the upper surface of the proton conductive layer 2, and the first electrode stacked on the catalyst layer 3 The substrate 4 type hydrogen gas sensor 1 can be configured by including the layer 4a.

  In this case, the first electrode layer 4a needs to have air permeability. The first electrode 4a needs to be made of a gas-permeable material so that hydrogen gas contacts the catalyst layer 3, and carbon paper, carbon fiber nonwoven fabric, or the like can be suitably used. Furthermore, it is also possible to comprise a copper-nickel alloy thin film in which a large number of pores are formed, or a metal porous sintered body having good conductivity. The second electrode layer 4b need not have air permeability.

  As shown in FIG. 11B, wiring patterns 5a and 5b for extracting the output of the hydrogen gas sensor 1 are formed on the substrate 8, and the electrode layers 4a and 4b are connected to the wiring patterns 5a and 5b, respectively. It is also possible to constitute each electrode layer 4a, 4b.

  FIG. 11C shows a third embodiment of the substrate type hydrogen gas sensor. The second electrode layer 4b formed on the substrate 8, the proton conductive layer 2 stacked on the second electrode layer 4b, the catalyst layer 3 stacked on the proton conductive layer 2, and the catalyst layer 3 are stacked. The substrate vertical hydrogen gas sensor 1 can be configured with the first electrode layer 4a.

  In this case, the 1st electrode layer 4a needs to be equipped with air permeability similarly to the case of the 2nd mode. The second electrode layer 4b need not have air permeability.

  Further, as shown in FIG. 11 (d), the substrate 8 and the second electrode layer 4b can be used together to form a metal substrate 8 (4b) such as stainless steel. For this metal substrate, it is desirable to select a material that does not corrode even at high humidity at least at the interface with the electrolyte membrane.

  Further, when a gas diffusion layer made of carbon paper, carbon nonwoven fabric, or the like is provided on either the front or back surface of the electrode layer 4a, hydrogen gas can be brought into contact with the catalyst layer 3 evenly, and the sensitivity is improved. Further, by interposing a gas diffusion layer made of carbon paper, carbon non-woven fabric or the like between the electrode layer 4a and the catalyst layer 3 or between the electrode layer 4b and the proton conductive layer, the corrosion resistance of the electrode layers 4a and 4b is improved. improves.

  Although the configuration in which the catalyst layer 3 is interposed only between the proton conductive layer 2 and the first electrode 4a has been described as the hydrogen gas sensor 1 according to the present invention, the above-described configuration is also provided between the proton conductive layer 2 and the second electrode 4b. A catalyst layer using the prepared catalyst may be interposed.

  That is, the hydrogen gas sensor 1 according to the present invention may be configured to include the catalyst layer 3 between the proton conductive layer 2 and the first electrode 4a and / or between the proton conductive layer 2 and the second electrode 4b. Good.

  Furthermore, the catalyst layer and the first electrode layer and / or the catalyst layer and the second electrode layer may be integrated so that each electrode layer functions as a catalyst layer. In this case, it is not necessary to form a separate catalyst layer, and for example, the electrode layer 4a can be configured using a metal such as platinum which is an example of the catalyst described above.

  It has been confirmed that the hydrogen gas detection apparatus described above can selectively detect hydrogen gas not only in the atmosphere but also in an environment where oxygen is not present.

  The hydrogen gas detection device according to the present invention is extremely useful for a fuel cell system (stationary type, in-vehicle type, mobile type, etc.) using hydrogen gas as an energy source and its peripheral equipment (hydrogen station etc.). As a hydrogen gas concentration meter, it can be used by being incorporated into a system device, or can be used as a handy portable gas measuring device. Moreover, it can be suitably used when it is necessary to detect the hydrogen gas concentration in the absence of oxygen gas, such as detection of hydrogen concentration in a hydrogen gas tank or hydrogen gas supply pipe or leakage detection.

  Moreover, it can be suitably used for hydrogen concentration monitoring and hydrogen gas leak detection in a heat treatment apparatus of a semiconductor manufacturing plant. For example, it can be used for monitoring the hydrogen gas concentration in a heat treatment process for interfacial treatment using hydrogen gas or a mixed gas of hydrogen gas and nitrogen gas.

1: hydrogen gas sensor 2: proton conductive layer 3: catalyst layer 3a: catalyst 4, 4a, 4b: electrode 4c: reference electrode 8: substrate 11: measurement processing unit 12: normalization processing unit 13: temperature measurement processing unit 14: hydrogen Gas detection processing unit 15: output processing unit

Claims (9)

A signal processing method of a hydrogen gas sensor comprising a proton conductive layer, and a first electrode and a second electrode respectively joined to the proton conductive layer,
A measurement step of applying a voltage of a predetermined pattern gradually changing between positive and negative polarities between the first electrode and the second electrode, and measuring a current value flowing between the two electrodes,
A normalizing step of normalizing each current value measured in the measuring step with a current value corresponding to a predetermined application voltage set in advance to obtain a voltage-current characteristic;
A hydrogen gas detection step for determining the presence or absence of hydrogen gas based on the voltage-current characteristics obtained in the normalization step, or for determining the concentration of hydrogen gas;
A signal processing method for a hydrogen gas sensor including: A signal processing method of a hydrogen gas sensor comprising a proton conductive layer, and a first electrode and a second electrode respectively joined to the proton conductive layer,
A measurement step of applying a voltage of a predetermined pattern gradually changing between positive and negative polarities between the first electrode and the second electrode, and measuring a current value flowing between the two electrodes,
A normalizing step of normalizing each current value measured in the measuring step with a current value corresponding to a predetermined application voltage set in advance to obtain a voltage-current characteristic;
A temperature measuring step for measuring an ambient temperature of the hydrogen gas sensor;
A hydrogen gas detection step for determining the presence or absence of hydrogen gas based on the correlation between the voltage-current characteristics obtained in the normalization step and the ambient temperature measured in the temperature measurement step;
A signal processing method for a hydrogen gas sensor including:   The signal of the hydrogen gas sensor according to claim 1 or 2, wherein the hydrogen gas sensor includes a catalyst layer between the proton conductive layer and the first electrode and / or between the proton conductive layer and the second electrode. Processing method.   In the measurement step, a predetermined pattern including a portion that gradually changes from an initial voltage at which the second electrode is positive with respect to the first electrode to a transition voltage at which the second electrode is negative with respect to the first electrode. The signal processing method of the hydrogen gas sensor according to any one of claims 1 to 3, wherein a voltage is applied.   In the measurement step, a predetermined pattern including a portion that gradually changes from an initial voltage at which the second electrode is positive with respect to the first electrode to a transition voltage at which the second electrode is negative with respect to the first electrode. The signal processing method for a hydrogen gas sensor according to any one of claims 1 to 3, wherein the voltage is repeatedly applied at a predetermined cycle.   6. The signal processing method for a hydrogen gas sensor according to claim 4, wherein the voltage of the predetermined pattern includes a portion where the initial voltage continues for a predetermined time.   The hydrogen gas concentration is obtained in the hydrogen gas detection step based on a correlation between a current value of a voltage-current characteristic when the transition voltage is minimized and the ambient temperature. Signal processing method for hydrogen gas sensor. A hydrogen gas sensor signal processing device comprising a proton conductive layer, and a first electrode and a second electrode respectively joined to the proton conductive layer,
A measurement processing unit that applies a voltage of a predetermined pattern that gradually changes between positive and negative polarities between the first electrode and the second electrode, and measures a current value flowing between the two electrodes,
A normalization processing unit that obtains a voltage-current characteristic by normalizing each current value measured by the measurement processing unit with a current value corresponding to a predetermined application voltage set in advance,
A hydrogen gas detection processing unit that determines the presence or absence of hydrogen gas based on the voltage-current characteristics obtained by the normalization processing unit, or obtains the concentration of hydrogen gas;
An output processing unit for outputting a processing result by the hydrogen gas detection processing unit;
A signal processing device for a hydrogen gas sensor. A hydrogen gas sensor signal processing device comprising a proton conductive layer, and a first electrode and a second electrode respectively joined to the proton conductive layer,
A measurement processing unit that applies a voltage of a predetermined pattern that gradually changes between positive and negative polarities between the first electrode and the second electrode, and measures a current value flowing between the two electrodes,
A normalization processing unit that obtains a voltage-current characteristic by normalizing each current value measured by the measurement processing unit with a current value corresponding to a predetermined application voltage set in advance,
A temperature measurement processing unit for measuring the ambient temperature of the hydrogen gas sensor;
A hydrogen gas detection processing unit that obtains the concentration of hydrogen gas based on the correlation between the voltage-current characteristics obtained by the normalization processing unit and the ambient temperature measured by the temperature measurement processing unit;
An output processing unit for outputting a processing result by the hydrogen gas detection processing unit;
A signal processing device for a hydrogen gas sensor.