JP2009198410A - Hydrogen gas sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately sense a change in a concentration of a hydrogen gas by using a possibly simple constitution. <P>SOLUTION: A hydrogen gas sensor includes: a sensor head 100 including a proton conductivity solid polymer electrolyte film 101 in which a carbon material is dispersed, a catalyst layer 102 fixed to a main surface of the solid polymer electrolyte film, an electrode 103 attached to the catalyst layer, and an electrode 104 attached to the solid polymer electrolyte film; and a control section 205 for determining that the hydrogen gas is contained in the atmosphere around the sensor head if an output voltage as a potential of the electrode 104 is positive when a potential of the electrode 103 is reference potential, and determining that the hydrogen gas is not contained in the atmosphere around the sensor head if the output voltage is negative. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a hydrogen gas sensor that is less susceptible to environmental factors.

  In recent years, hydrogen gas sensors are employed in hydrogen energy systems typified by fuel cells and hydrogen engines to ensure the safety of systems that handle hydrogen gas, which is a combustible gas. Various methods for detecting hydrogen gas have been proposed so far.

  For example, Patent Document 1 discloses a technique for detecting hydrogen gas by employing an oxide semiconductor for a sensor head and measuring impedance characteristics of the oxide semiconductor. This utilizes a phenomenon in which impedance characteristics of an oxide semiconductor change when hydrogen gas is adsorbed on the surface of the oxide semiconductor.

  Patent Document 2 discloses a technique for deriving the concentration of a flammable gas containing hydrogen atoms in a molecule by employing a solid electrolyte zirconia in a sensor head and measuring the impedance of zirconia or the phase angle of the impedance. Yes.

Patent Document 3 discloses a technique for detecting hydrogen gas by employing a thermistor element in the sensor head and measuring the resistance of the thermistor element. This is due to the fact that the thermal conductivity differs between hydrogen gas and air, so that the heat dissipation characteristic varies depending on the hydrogen gas concentration around the sensor head, and the thermal equilibrium temperature of the thermistor element varies accordingly.
Japanese Patent Laid-Open No. 7-103924 JP 2006-90812 A JP 2004-37235 A

  However, although the technique described above can detect the concentration of hydrogen gas or a combustible gas containing hydrogen atoms in the molecule, the following problems also exist.

  In the techniques disclosed in Patent Documents 1 and 2, the temperature at which the sensor head operates properly is high (for example, typical operating temperatures are 400 ° C. in Patent Document 1 and 500 to 1000 ° C. in Patent Document 2). It is necessary to provide a heater for heating the sensor head to the operating temperature. In the technique disclosed in Patent Document 3, since the heat radiation characteristic of the atmosphere around the sensor head is influenced not only by the hydrogen gas concentration but also by the humidity, the sensor using four thermistor elements is used to cancel the influence of the humidity. It constitutes the head. Thus, if a heater is provided around the sensor head or the sensor head is configured using a plurality of thermistor elements, the structure of the hydrogen gas sensor becomes complicated, which hinders downsizing and cost reduction.

  Therefore, in view of the above problems, an object of the present invention is to provide a hydrogen gas sensor that can detect hydrogen gas with the simplest possible configuration.

  A hydrogen gas sensor according to the present invention includes a proton conductive solid polymer electrolyte membrane in which a carbon material is dispersed, a catalyst layer deposited on the solid polymer electrolyte membrane, a first electrode attached to the catalyst layer, and A sensor head including a second electrode attached to the solid polymer electrolyte membrane, and the sensor head if the output voltage that is the potential of the second electrode when the potential of the first electrode is a reference potential is a positive voltage A control unit that determines that the surrounding atmosphere contains hydrogen gas and determines that the atmosphere around the sensor head does not contain hydrogen gas if the output voltage is a negative voltage.

  A sensor head of a type in which a catalyst layer is attached to a proton conductive solid polymer electrolyte membrane can operate at room temperature. Therefore, it is not necessary to provide a sophisticated heat-resistant structure and a heater for heating the sensor head. Therefore, the configuration of the hydrogen gas sensor can be simplified as much as possible. As a result of the inventors' experiment, if a solid polymer electrolyte in which a carbon material is dispersed is adopted, the voltage value changes depending on environmental factors such as temperature and humidity, but the atmosphere around the sensor head contains hydrogen gas. It is found that the output voltage shows a positive voltage when it is present, and the output voltage shows a negative voltage when the atmosphere around the sensor head does not contain hydrogen gas. By utilizing such characteristics, hydrogen gas detection independent of environmental factors can be realized.

The best mode for carrying out the present invention will be described in detail with reference to the drawings.
<Configuration of hydrogen gas sensor>
FIG. 1 is a cross-sectional view showing a configuration of a sensor head that is a part of a hydrogen gas sensor according to an embodiment of the present invention.

  In the sensor head 100, a catalyst layer 102 is attached to all or a part of the main surface of a proton conductive solid polymer electrolyte membrane 101 in which a carbon material is dispersed. The electrode 104 is attached to the molecular electrolyte membrane 101.

  The solid polymer electrolyte is not particularly limited as long as it exhibits proton conductivity. However, perfluorosulfonic acid-based and perfluorocarboxylic acid-based perfluoropolymers having high proton conductivity, poly (styrene) -ran-ethylene), sulfonated, and other partially sulfoneted styrene-olefin copolymers are preferably used, and Nafion (registered trademark of DuPont: NAFION) and Aciplex (registered trademark of Asahi Kasei Corporation: ACIPLEX) can be suitably used. is there.

  As the carbon material, one or more of carbon nanotubes, fullerenes, graphite, carbon black, carbon nanofibers, and carbon nanohorns can be selected. Specific examples of carbon black include furnace black, channel black, and graft carbon. The size (particle size, length, or diameter) of the carbon material is not particularly limited, but the longer the length, the more preferable, and the length of 1 μm to 1 mm and the diameter of 5 to 30 nm are particularly preferable.

  Moreover, if the state in which the carbon material is dispersed in the solid polymer electrolyte membrane can be secured, the mixing ratio of the solid polymer electrolyte and the carbon material is not particularly limited, but is preferably 10: 1 to 10:10.

  The catalyst layer 102 may be any material that promotes a hydrogen decomposition reaction by contacting with hydrogen gas. For example, a metal, a metal compound, an organic metal, or an organic substance can be used. Examples of the metal include platinum, molybdenum carbide, gold, silver, iridium, palladium, ruthenium, osmium, nickel, tungsten, molybdenum, manganese, yttrium, vanadium, niobium, titanium, zirconia, and rare earth metals. Examples of the metal compound include molybdenum carbide. Organic metals 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 as the organic substance, for example, a pyrrolopyrrole red pigment or a pyridyl derivative can be used.

  The electrode 103 has a large number of pores 103c for allowing the gas in the atmosphere to flow from one main surface 103a to the other main surface 103b. The same applies to the electrode 104. As these materials, metal materials having good conductivity, for example, copper-nickel alloy thin films can be used. Note that the pores 103c and 104c are not indispensable configurations, and any configuration may be used as long as it has gas flowability inside and good conductivity. Therefore, for example, in addition to the metal porous sintered body, it can be composed of carbon-containing fibers such as carbon paper and carbon cloth. Carbon paper, carbon cloth, and the like are suitable as electrode materials because they have electrical conductivity and particularly good air permeability.

  FIG. 2 is a diagram showing a system configuration of the hydrogen gas sensor according to the embodiment of the present invention.

  The hydrogen gas sensor 200 includes a sensor head 100, a resistance R, an amplification circuit 201, an AD conversion circuit 202, a thermometer 203, an AD conversion circuit 204, a control unit 205, a table storage unit 206, a buzzer 211, a lamp 212, an output terminal 213, and a reset. A switch 214 is provided.

The sensor head 100 is considered to work as follows in an atmosphere containing hydrogen gas. When hydrogen gas comes into contact with the catalyst layer 102, a hydrogen decomposition reaction occurs, and hydrogen molecules (H ₂ ) are decomposed into hydrogen ions (protons) and electrons (H ₂ → 2H ⁺ + 2e ⁻ ). Electrons obtained by the decomposition move from the electrode 103 to the electrode 104 through the resistor R. On the other hand, hydrogen ions (protons) obtained by the decomposition move in the solid polymer electrolyte membrane 101 and combine with oxygen in the atmosphere near the main surface 101b of the solid polymer electrolyte membrane 101 to cause a water generation reaction ( 2H ⁺ + 2e ⁻ + 1 / 2O ₂ → H ₂ O). Thus, since a current flows through the resistor R, a voltage corresponding to the current is induced at the N point. The voltage at the point N is amplified as an output voltage of the sensor head 100 by the gain variable amplifier circuit 201, converted into a digital signal by the AD conversion circuit 202, and input to the control unit 205.

  The thermometer 203 measures the temperature of the atmosphere around the sensor head. For example, a platinum resistance thermometer, a thermocouple, a thermistor, or the like can be used. The output signal of the thermometer 203 is converted into a digital signal by the AD conversion circuit 204 and input to the control unit 205.

  The control unit 205 determines whether the atmosphere around the sensor head includes hydrogen gas based on the output voltage of the sensor head 100 and the temperature of the thermometer 203, and if hydrogen gas is included, Derivation of concentration. For deriving the hydrogen gas concentration, a humidity table 207 and a hydrogen gas concentration table 208 stored in the table storage unit 206 are used. The humidity table 207 is a table for deriving humidity using the output voltage and temperature as parameters, and a specific example thereof is shown in FIG. The hydrogen gas concentration table is a table for deriving the hydrogen gas concentration using the output voltage, temperature and humidity as parameters, and a specific example thereof is shown in FIG. The specific numerical values that make up the humidity table and the hydrogen gas concentration table vary depending on the specifications of the sensor head material, composition ratio, shape, size, etc., and the resistance value of the resistance R. Therefore, in the design stage of the hydrogen gas sensor It is determined appropriately.

If the hydrogen gas concentration is equal to or higher than the threshold value, the control unit 205 notifies the hydrogen gas detection by operating the buzzer 211 and the lamp 212 as alarm means, and outputs an alarm signal to the outside via the output terminal 213. By doing this, a hydrogen gas detection report is made. The hydrogen gas detection notification is stopped by operating the reset switch 214.
<Operation of hydrogen gas sensor>
The hydrogen gas sensor of the present embodiment periodically detects the output voltage and temperature after turning on the power, and determines whether or not hydrogen gas is contained in the atmosphere every time the output voltage and temperature are detected. Furthermore, the hydrogen gas sensor derives the hydrogen gas concentration when hydrogen gas is contained, activates an alarm if the hydrogen gas concentration is greater than or equal to the threshold, and returns to normal operation when a reset operation is performed during the alarm operation. Return. The flow for realizing such specifications is shown below.

  3 and 4 are flowcharts showing the operation of the hydrogen gas sensor according to the embodiment of the present invention.

  The hydrogen gas sensor detects the output voltage and temperature after turning on the power (step S11), and determines whether the output voltage is positive or negative (step S12). If the output voltage is a negative voltage (step S12: NO), the hydrogen gas sensor refers to the humidity table, specifies the humidity corresponding to the detected output voltage and temperature (step S13), and sets the specified humidity. A corresponding hydrogen gas concentration table is selected (step S14). Here, the hydrogen gas concentration table used when the output voltage becomes a positive voltage is simply selected in advance, and the hydrogen gas concentration is not derived at this stage. If the detection cycle of the output voltage and temperature has elapsed (step S15: YES), the hydrogen gas sensor repeats the operation from step S11. As a result, the output voltage and temperature are periodically detected. In this specification, the term “periodic” simply means continuous execution. Therefore, it may be anything that is continuously and repeatedly detected, and does not necessarily have a fixed period.

  On the other hand, if the output voltage is a positive voltage (including zero) (step S12: YES), the hydrogen gas sensor determines whether the hydrogen gas concentration can be derived (step S21), and the hydrogen gas concentration can be derived. If the output voltage has changed from a negative voltage to a positive voltage (step S22: YES), the output voltage and temperature are detected (step S23). Further, the hydrogen gas sensor refers to the hydrogen gas concentration table previously selected in step S14, identifies the hydrogen gas concentration corresponding to the detected output voltage and temperature (step S24), and the identified hydrogen gas concentration is a threshold value. It is determined whether or not the above is true (step S25). If the hydrogen gas concentration is equal to or higher than the threshold value (step S25: YES), the hydrogen gas sensor activates an alarm (step S26), and if the hydrogen gas concentration is less than the threshold value (step S25: NO), the processing after step S11 is performed. repeat. When the hydrogen gas sensor is reset during the alarm operation (step S27: YES), the process after step S11 is repeated.

Note that the hydrogen gas sensor of the present embodiment needs to select a hydrogen gas concentration table in step S14 in advance. For this reason, when the output voltage is a positive voltage since the power is turned on (that is, when hydrogen gas is already leaked when the power is turned on), the hydrogen gas concentration cannot be derived. In such a case (step S21: NO), an immediate alarm is activated without deriving the hydrogen gas concentration (step S26).
<Possibility of hydrogen gas sensor>
The inventors conducted an experiment for grounding the feasibility of the hydrogen gas sensor of the present embodiment. Below, the procedure for producing the sensor head used in this experiment, the validity of the process for determining whether the atmosphere contains hydrogen gas (hydrogen gas detection process) based on whether the output voltage of the sensor head is positive or negative, The validity of the process for deriving the hydrogen gas concentration based on the output voltage, temperature and humidity of the sensor head (hydrogen gas concentration deriving process) will be described.
(1) Preparation procedure of sensor head First, 10 g of Nafion solution (containing 5% Nafion) and 0.2 g of carbon nanotubes were prepared. Carbon nanotubes were put into the Nafion solution and stirred for 45 minutes with a stirrer. EC-NS-05-250 manufactured by ElectroChem, Inc. was used as the Nafion solution, and Multi-Wall Carbon nanotubes L MWNTs-10 purchased from New Metals End Chemical Corporation was used as the carbon nanotube. .

  Next, 3 mL of Nafion solution in which carbon nanotubes were dispersed was poured into a 5 cm × 5 cm mold placed on a stainless steel plate, and placed in an oven at 120 ° C. for 40 minutes to evaporate the solvent. Thereby, a Nafion film in which carbon nanotubes are dispersed is obtained.

  Next, a platinum layer having a thickness of 20 nm was formed on the upper surface of the Nafion film (the surface not attached to the stainless steel plate). The sputtering conditions are an output of 300 W, a gas flow rate of 20 cc / min, and a time of 30 seconds.

Next, stainless steel washers as electrodes were attached to both surfaces of the Nafion membrane on which the platinum layer was formed.
(2) Appropriateness of hydrogen gas detection processing The inventors used a digital multimeter (IWASU VOAC 7411) for the sensor head produced by the above process, connected the platinum layer side electrode to GND, and the atmosphere around the sensor head. The change in the output voltage before and after the introduction of 5200 ppm of hydrogen gas was observed.

  FIG. 7 is a diagram showing a temporal change in the output voltage of the sensor head at a temperature of 30 ° C., and FIG. 8 is an enlarged view of a part of FIG. In this experiment, hydrogen gas is introduced into the atmosphere around the sensor head approximately 20 seconds after the detection of the output voltage is started. The hydrogen gas concentration in the atmosphere before the introduction of hydrogen gas is zero, and the hydrogen gas concentration in the atmosphere after the introduction of hydrogen gas is about 5200 ppm. FIG. 9 is a diagram showing temporal changes in the output voltage of the sensor head at a temperature of 40 ° C., and FIG. 10 is an enlarged view of a part of FIG. In this experiment, hydrogen gas is introduced into the atmosphere around the sensor head approximately 10 seconds after the detection of the output voltage is started. The hydrogen gas concentration in the atmosphere before the introduction of hydrogen gas is zero, and the hydrogen gas concentration in the atmosphere after the introduction of hydrogen gas is about 5200 ppm.

  7 to 10, in any environment, if hydrogen gas is not included in the atmosphere around the sensor head, the output voltage of the sensor head becomes a negative voltage, and at least 5200 ppm of hydrogen gas is present in the atmosphere around the sensor head. If it is included, it indicates that the output voltage of the sensor head is a positive voltage. According to another experiment, it has been found that the output voltage of the sensor head becomes a positive voltage even when the hydrogen gas concentration is 2600 ppm (see FIGS. 12 and 13). From these experimental results, it can be seen that whether or not hydrogen gas is contained in the atmosphere can be determined based on whether the output voltage of the sensor head is positive or negative.

In FIGS. 9 and 10, four consecutive data have the same value, and the output voltage rises stepwise. This is because there is some setting mismatch in the output voltage measurement system. Conceivable. Note that when the raw data of the output voltage is monitored with an oscilloscope, it can be confirmed that the output voltage rises smoothly.
(3) Validity of Hydrogen Gas Concentration Derivation Process FIG. 11 is a graph showing the relationship between humidity and output voltage when hydrogen gas is not included in the atmosphere. Here, the output voltage when the humidity is 30% RH, 60% RH, and 90% RH at a temperature of 30 ° C and the output voltage when the humidity is 30% RH, 60% RH, and 90% RH at a temperature of 40 ° C are plotted. ing. According to FIG. 11, when the temperature is fixed, there is a tendency of a simple increase in that the absolute value of the output voltage increases as the humidity increases. That is, the two curves described in FIG. 11 can be used as a calibration curve for deriving humidity from the output voltage and temperature. Therefore, it can be seen that the humidity table shown in FIG. 5 can be created by measuring the output voltage at each combination of temperature and humidity at the design stage of the hydrogen gas sensor.

  FIG. 12 is a graph showing the relationship between the hydrogen gas concentration in the atmosphere and the output voltage. FIG. 13 is a graph in which the vertical axis of FIG. 12 is expressed on a logarithmic scale. Here, the output voltage when the hydrogen gas concentration is 2600 ppm, 5300 ppm, 10700 ppm, and 21300 ppm at a temperature of 40 ° C. and a humidity of 90% RH, the output voltage when the hydrogen gas concentration is 2600 ppm, 5300 ppm, and 10700 ppm at a temperature of 30 ° C. and a humidity of 80% RH, and a temperature of 10 The output voltage at a hydrogen gas concentration of 2600 ppm, 5300 ppm, and 10700 ppm at a temperature of 30 ° C. and 30% RH is plotted. According to FIGS. 12 and 13, when temperature and humidity are fixed, there is a simple increase tendency that the output voltage increases as the hydrogen gas concentration increases. That is, the three curves described in FIGS. 12 and 13 can be used as a calibration curve for deriving the hydrogen gas concentration from the output voltage, temperature, and humidity. Therefore, it can be seen that the hydrogen gas concentration table shown in FIG. 6 can be created by measuring the output voltage at each combination of temperature, humidity and hydrogen gas concentration at the design stage of the hydrogen gas sensor.

  From these experimental results, when the sensor head output voltage is negative, the humidity is derived from the output voltage, and when the sensor head output voltage is positive, hydrogen gas is derived from the derived humidity, temperature, and output voltage. It can be seen that the concentration can be derived.

  Although the hydrogen gas sensor according to the present invention has been described based on the embodiments, the present invention is not limited to the above configuration. For example, the following modifications may be adopted.

  In the embodiment, if the output voltage is a negative voltage, the hydrogen gas sensor specifies the humidity each time the output voltage is detected (step S13), and selects the hydrogen gas concentration table corresponding to the specified humidity. (Step S14), the present invention is not limited to this. For example, the history of detected output voltage and temperature is stored in the memory, and when the output voltage changes from negative voltage to positive voltage, the humidity is specified based on the past history, and the specified humidity is Alternatively, a hydrogen gas concentration table may be selected.

  In the embodiment, the output voltage and the temperature are detected after waiting for a predetermined period from the time when the output voltage changes from the negative voltage to the positive voltage (steps S22 and S23). However, the present invention is not limited to this. For example, in step S23, only the output voltage may be detected, and the temperature used when the hydrogen gas concentration table is selected may be used. The length of the predetermined time may be a time sufficient for the output voltage to rise and saturate. Further, as shown in FIGS. 7 to 10, since it takes a certain time for the output voltage of the sensor head to saturate, it takes time to derive the hydrogen gas concentration if waiting for the saturation of the output voltage. End up. Therefore, the output voltage and temperature may be detected without waiting for the output voltage to saturate. In this case, it can be said that the temporal change rate of the output voltage is observed. Alternatively, the voltage value may be periodically detected while the output voltage is rising, and the voltage value when the output voltage is saturated may be predicted from the amount of change in the voltage value in each cycle.

  In the embodiment, the humidity is specified based on the voltage value and temperature when the output voltage of the sensor head 100 is a negative voltage. That is, when hydrogen gas is not contained in the atmosphere, the sensor head 100 is also used as a hygrometer. However, the present invention is not limited to this, and a hygrometer may be provided separately. In this case, when the output voltage of the sensor head 100 changes from a negative voltage to a positive voltage, the hydrogen gas concentration is derived based on the output voltage of the sensor head, the temperature of the thermometer, and the humidity of the hygrometer. . As the hygrometer, for example, popular products such as a polymer film humidity sensor, a ceramic humidity sensor, and an electrolyte humidity sensor can be used.

  In the embodiment, the catalyst layer is deposited on one main surface of the solid polymer electrolyte membrane, but the present invention is not limited to this. For example, a catalyst layer may be deposited on all or part of both main surfaces of the solid polymer electrolyte membrane. When the catalyst layers are deposited on both main surfaces of the solid polymer electrolyte membrane, both the electrodes 103 and 104 are attached to the catalyst layer. In this case, a structure in which only the main surface to which the electrode 103 is attached is in contact with hydrogen gas (for example, the main surface to which the electrode 104 is attached is sealed with a container so as not to be exposed to hydrogen gas) is adopted. Then, the same effect as the embodiment can be obtained.

  The hydrogen gas sensor of the present invention can be used as a means for detecting leakage of hydrogen gas in, for example, automobile, facility, and portable fuel cell systems.

Sectional drawing which shows the structure of the sensor head which is a part of hydrogen gas sensor which concerns on embodiment of this invention The figure which shows the system configuration | structure of the hydrogen gas sensor which concerns on embodiment of this invention The flowchart which shows operation | movement of the hydrogen gas sensor which concerns on embodiment of this invention. The flowchart which shows operation | movement of the hydrogen gas sensor which concerns on embodiment of this invention. The figure which shows the specific example of the humidity table which concerns on embodiment of this invention The figure which shows the specific example of the hydrogen gas concentration table which concerns on embodiment of this invention The figure which shows the time change of the output voltage of a sensor head in the temperature of 30 degreeC An enlarged view of a part of FIG. The figure which shows the time change of the output voltage of a sensor head in the temperature of 40 degreeC. An enlarged view of a part of FIG. Graph showing the relationship between humidity and output voltage when hydrogen gas is not included in the atmosphere Graph showing the relationship between the hydrogen gas concentration in the atmosphere and the output voltage The graph which expressed the vertical axis | shaft of FIG. 12 on the logarithmic scale

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Sensor head 101 Solid polymer electrolyte membrane 102 Catalyst layer 103, 104 Electrode 103c, 104c Pore 200 Hydrogen gas sensor 201 Amplifying circuit 202 AD conversion circuit 203 Thermometer 204 AD conversion circuit 205 Control part 206 Table memory | storage part 207 Humidity table 208 Hydrogen Gas concentration table 211 Buzzer 212 Lamp 213 Output terminal 214 Reset switch

Claims (11)

A proton conductive solid polymer electrolyte membrane in which a carbon material is dispersed, a catalyst layer deposited on the solid polymer electrolyte membrane, a first electrode attached to the catalyst layer, and an attached to the solid polymer electrolyte membrane A sensor head including a second electrode formed;
If the output voltage, which is the potential of the second electrode when the potential of the first electrode is a reference potential, is positive, it is determined that hydrogen gas is contained in the atmosphere around the sensor head, and the output voltage is A hydrogen gas sensor, comprising: a controller that determines that hydrogen gas is not contained in the atmosphere around the sensor head if the voltage is negative. The control unit periodically detects the output voltage, and determines whether or not hydrogen gas is contained in an atmosphere around the sensor head each time the output voltage is detected. 2. The hydrogen gas sensor according to 1. The hydrogen gas sensor further includes a thermometer,
The controller further detects the temperature of the thermometer periodically, and when the output voltage changes from a negative voltage to a positive voltage, at least a voltage value and a temperature when the output voltage is a negative voltage. The hydrogen gas sensor according to claim 2, wherein a concentration of hydrogen gas contained in an atmosphere around the sensor head is derived based on a voltage value when the output voltage is a positive voltage. The control unit derives the humidity of the atmosphere around the sensor head based on the voltage value and temperature if the output voltage is a negative voltage, and at least in advance when the output voltage changes from a negative voltage to a positive voltage. Deriving the hydrogen gas concentration in the atmosphere around the sensor head based on the derived humidity and the voltage value of the output voltage when a predetermined time has elapsed since the output voltage changed from a negative voltage to a positive voltage. The hydrogen gas sensor according to claim 3. The hydrogen gas sensor further includes a table storage unit that stores a table in which voltage values of temperature, humidity, and output voltage are adopted as parameters for deriving the hydrogen gas concentration,
The hydrogen gas sensor according to claim 4, wherein the control unit derives a hydrogen gas concentration with reference to the table. The hydrogen gas sensor further includes a table storage unit that stores a table in which voltage values of temperature and output voltage are adopted as parameters for deriving humidity.
The hydrogen gas sensor according to claim 4, wherein the control unit derives humidity by referring to the table. The hydrogen gas sensor further includes alarm means,
The hydrogen gas sensor according to claim 3, wherein the control unit further operates the alarm unit when the derived hydrogen gas concentration is equal to or greater than a threshold value. The hydrogen gas sensor further includes a thermometer and a hygrometer,
When the output voltage changes from a negative voltage to a positive voltage, the control unit is included in the atmosphere around the sensor head based on the voltage value of the output voltage, the temperature of the thermometer, and the humidity of the hygrometer. The hydrogen gas sensor according to claim 2, wherein the concentration of hydrogen gas is derived. The hydrogen gas sensor further includes alarm means,
The hydrogen gas sensor according to claim 8, wherein the control unit further operates the alarm means when the derived hydrogen gas concentration is equal to or greater than a threshold value. The hydrogen gas sensor according to claim 1, wherein the carbon material includes at least one of carbon nanotubes, fullerenes, graphite, carbon black, carbon nanofibers, and carbon nanohorns. A proton conductive solid polymer electrolyte membrane in which a carbon material is dispersed, first and second catalyst layers deposited on both main surfaces of the solid polymer electrolyte membrane, and a first attached to the first catalyst layer A sensor head including one electrode and a second electrode attached to the second catalyst layer;
If the output voltage, which is the potential of the second electrode when the potential of the first electrode is a reference potential, is positive, it is determined that hydrogen gas is contained in the atmosphere around the sensor head, and the output voltage is A hydrogen gas sensor, comprising: a controller that determines that hydrogen gas is not contained in the atmosphere around the sensor head if the voltage is negative.

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