JP2018124211A - Hydrogen detection method and hydrogen detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydrogen detection method with which it is possible to easily detect the generation of a hydrogen gas in a liquid that contains water, and a hydrogen detection device that uses the hydrogen detection method.SOLUTION: The hydrogen detection method involves a hydrogen generation member and a hydrogen detection member immersed in a liquid arranged in a container, the liquid containing water, the hydrogen generation member generating a gas that contains hydrogen by an electrochemical reaction, the hydrogen detection member containing at least one kind of compound selected from the group consisting of tungsten oxide, molybdenum oxide, cobalt oxyhydroxide and nickel oxyhydroxide. The hydrogen generation member and the hydrogen detection member are electrically connected, with hydrogen ions supplied from the liquid to the hydrogen detection member and electrons supplied from the hydrogen generation member to the hydrogen detection member, at least one of the color and electric conductivity of the hydrogen detection member changing in accordance with the hydrogen ions and electrons supplied to the hydrogen detection member. Hydrogen in the liquid is detected by measuring a change of at least one of the color and the electric conductivity.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a hydrogen detection method and a hydrogen detection device.

  Currently, reduction of greenhouse gas emissions such as carbon dioxide is required worldwide from the viewpoint of preventing global warming. As a specific approach, the introduction of clean energy (renewable energy) such as wind power or sunlight is being promoted. Under such circumstances, hydrogen can be cited as an energy following the renewable energy.

  Carbon dioxide is not generated even when hydrogen gas is burned. Therefore, hydrogen gas is expected as clean energy that can solve environmental problems and resource problems. Hydrogen gas is expected to be used as fuel for fuel cells, for example.

  As an industrial method for producing hydrogen gas, a method for extracting hydrogen gas from fossil fuel such as natural gas or petroleum is mainly used. However, there are concerns about exhaustion of fossil fuels. In addition, carbon dioxide is discharged in the hydrogen production process using fossil fuel. In recent years, research for producing hydrogen gas by reforming methanol, ethanol, or biomass fuel without using fossil fuel has been advanced. Actually, a reforming method of methanol is adopted in domestic hydrogen stations (hydrogen supply facilities).

Examples of other hydrogen gas production methods include water electrolysis, thermochemical decomposition, and underwater crystal photosynthesis. For example, hydrogen gas can be produced by electrolyzing water using a photovoltaic power generated when a metal oxide semiconductor such as titanium dioxide (TiO ₂ ) absorbs light energy. A search for a material that can proceed even when the light is visible light having a long wavelength has been underway. In the underwater crystal photosynthesis method, a surface of a metal material immersed in water is irradiated with light, whereby oxide or hydroxide nanocrystals are formed, and highly pure hydrogen gas is easily obtained.

  In addition to the above method, hydrogen gas may be generated as a by-product. For example, in an iron making process using coal and iron ore as raw materials, gas containing hydrogen is generated when coal is converted into coke in a coke oven.

  Other examples in which hydrogen gas is generated as a by-product are secondary batteries such as lead-acid batteries and redox flow batteries. In a secondary battery equipped with an electrolyte, during charging or discharging, if the potential difference between the positive electrode and the negative electrode is higher than the voltage required for water electrolysis, apart from the original battery reaction during charging and discharging, A reaction that generates hydrogen gas may proceed.

In the lead acid battery, the positive electrode is lead oxide (PbO ₂ ), the negative electrode is lead (Pb), and the electrolyte is an aqueous sulfuric acid solution. In the positive electrode during charging / discharging, the reaction shown in the following reaction formula (1) occurs. In the negative electrode during charging / discharging, the reaction shown in the following reaction formula (2) occurs. In the following reaction formulas (1) and (2), the charging reaction proceeds from right to left, and the discharging reaction proceeds from left to right.
<Positive electrode> PbO ₂ + 4H ⁺ + SO ₄ ^{2 −} + 2e ⁻ ⇔2PbSO ₄ + 2H ₂ O (1)
<Negative electrode> Pb + SO ₄ ²⁻ ⇔PbSO ₄ + 2e ⁻ (2)

At the end of charging, an electrolysis reaction of water occurs as shown in the following reaction formula (3). Then, as shown in the following reaction formula (4), hydrogen gas (H ₂ ) is generated from the negative electrode.
<Positive electrode> 2H ₂ O → O ₂ + 4H ⁺ + 4e ⁻ (3)
<Negative electrode> 2H ⁺ + 2e ⁻ → H ₂ (4)

  When an electrolysis reaction of water occurs in a lead-acid battery, the water in the electrolytic solution is reduced, and the battery characteristics may be deteriorated. Depending on the type of battery, measures such as replenishing water according to the capacity of the electrolyte or regenerating water by attaching a control valve to the battery and absorbing oxygen gas generated from the positive electrode at the negative electrode Has been taken.

  The redox flow battery includes a positive electrode and a negative electrode that perform a battery reaction, a positive electrode electrolyte and a negative electrode electrolyte, a positive electrode electrolyte reservoir and a negative electrode electrolyte reservoir, a liquid feed pump, and piping. In the redox flow battery, the electrolytic solution is circulated between the electrode and the storage part, so that charging / discharging is performed. Since the positive electrode and the negative electrode are separated by the diaphragm, mixing of the positive electrode electrolyte and the negative electrode electrolyte is prevented. Active material candidates in a redox flow battery are ions whose valence changes. From the viewpoint of safety and the like, vanadium (V / V) redox flow batteries have been put into practical use.

The electrode reaction of the V / V redox flow battery is shown in the following reaction formulas (5) and (6). In the following reaction formulas (5) and (6), the charging reaction proceeds from left to right, and the discharging reaction proceeds from right to left.
<Positive> ^{VO 2+ _{(4-valent) + H 2 O⇔VO 2 + (}} 5 ^{valence) + 2H + + e - (} 5)
<Negative> ^{V 3+} (3-valent) + e ^- ⇔V ²⁺ (2-valent) (6)

Also in the redox flow battery, at the end of charging, the reactions shown in the above reaction formulas (3) and (4) occur, and hydrogen gas (H ₂ ) is generated from the negative electrode.

  By the way, the explosion range of hydrogen gas is as wide as 4% to 75% by volume. Moreover, since hydrogen gas is tasteless, odorless and light, handling is difficult. For this reason, hydrogen gas is currently used only in industrially limited places. Whether hydrogen gas is produced industrially or hydrogen gas is produced as a by-product, care must be taken in handling hydrogen gas to prevent explosions and fires.

  By detecting the hydrogen gas, the hydrogen gas can be appropriately managed. As a method for detecting hydrogen gas, a catalytic combustion type, a gas heat conduction type, a semiconductor type, and the like are known. Existing methods such as catalytic combustion are used in commercially available hydrogen gas sensors. However, in the existing method, heating and combustion are necessary to increase detection sensitivity, and there is a problem in safety. In addition, the existing method consumes a large amount of energy during standby. Furthermore, the existing method has problems such as insufficient reliability because the hydrogen detection element deteriorates quickly and the characteristics are likely to become unstable.

As a method for detecting hydrogen gas at room temperature, for example, there is a method using a chromic reaction of transition metal oxides such as tungsten oxide (WO ₃ ) and molybdenum oxide (MoO ₃ ). A chromic reaction is a phenomenon in which the optical properties of a material change reversibly in response to external stimuli. The chromic reaction is mainly divided into an electrochromic reaction and a gas chromic reaction. The electrochromic reaction is accompanied by an oxidation-reduction reaction by applying a voltage. In the gaschromic reaction, reduction and oxidation of gas molecules in the atmosphere occur. For example, when transparent or ocherous tungsten oxide is disposed in a hydrogen gas atmosphere, dark blue tungsten bronze (H _x WO ₃ ) is formed.

  Non-Patent Document 1 below discloses a thin film gas sensor using a chromic reaction. The thin film gas sensor described in Non-Patent Document 1 is manufactured by the following method. First, metallic tungsten is deposited on quartz glass. Next, the tungsten metal is oxidized to form tungsten oxide. Tungsten oxide is activated with platinum.

The following Patent Document 1 discloses a selective thin film gas sensor made of a thin film of tungsten oxide formed on a substrate such as silicon oxide or ceramics. The tungsten oxide thin film described in Patent Document 1 has a composition of WO _3−δ (δ <0.2) in an atmosphere having a low oxygen concentration (1 to 10%).

Patent Document 2 listed below discloses a hydrogen gas detection member including a cerium oxide (CeO ₂ ) -containing layer, a tungsten oxide-containing layer, and a catalytic metal element-containing layer. In the hydrogen gas detection member described in Patent Document 2, the combination of tungsten oxide and cerium oxide having oxygen attraction makes the crystal structure of tungsten oxide unstable. Therefore, when atomic hydrogen (H) derived from hydrogen gas enters tungsten oxide, the crystal structure change from tungsten oxide to tungsten bronze (H _x WO ₃ ) occurs rapidly, and the detection sensitivity of hydrogen gas is improved.

  The following Patent Documents 3 to 6 disclose a thin film for a hydrogen gas sensor using a solid compound semiconductor. The thin film for hydrogen gas sensors described in Patent Documents 3 to 6 is manufactured by the following method. First, a solution containing a raw material for a solid compound semiconductor such as tungsten oxide is applied onto a substrate. Next, the substrate coated with the solution is baked to form an oxide thin film having a desired composition on the substrate.

  Patent Documents 7 and 8 listed below disclose a thin film for a hydrogen gas sensor using a solid compound oxide. The thin film for a hydrogen gas sensor described in Patent Documents 7 and 8 is manufactured by the following method. First, a solution containing a raw material of a solid compound oxide such as tungsten oxide is applied on a substrate. Next, instead of baking the substrate coated with the solution, the target oxide thin film is formed on the substrate by irradiating the substrate with ultraviolet rays.

P. J. et al. Shaver, “Activated Tungsten Oxide Gas Detectors”, Applied Physics Letters, vol. 11, no. 8, pp. 255-257, 1967.

Japanese Examined Patent Publication No. 63-51501 International Publication No. 2016/143385 Japanese Patent No. 3781354 JP 2005-331364 A JP 2005-345338 A JP 2007-71866 A Japanese Patent Laid-Open No. 2006-161507 JP 2010-2346 A

  In the thin film gas sensor described in Non-Patent Document 1, the time (rise time) from contact with the hydrogen gas atmosphere until the change in characteristics is recognized is about 1 second. However, the recovery time of the thin film gas sensor in dry atmosphere is about 10 minutes and is slow. Therefore, the thin film gas sensor described in Non-Patent Document 1 is not practical as a hydrogen gas sensor.

In the method for producing a hydrogen gas sensor described in Patent Documents 1 and 2, an amorphous phase WO ₃ film or a CeO ₂ / WO ₃ composite film exhibiting good chromic characteristics can be obtained according to sputtering conditions. However, in order to exhibit good characteristics as a hydrogen gas sensor, it is necessary to form a metal catalyst such as platinum in the form of fine particles on the surface of the hydrogen detection element (WO ₃ film). Actually, in order to make a hydrogen gas sensor using tungsten oxide or the like respond to hydrogen gas in a temperature range of room temperature (for example, around 20 ° C.), the hydrogen gas is highly adsorbed and the adsorbed gas is activated. A noble metal catalyst that can be retained at

  In the method for producing a thin film for a hydrogen gas sensor described in Patent Documents 3 to 6, a solid compound oxide such as tungsten oxide is formed by a so-called sol-gel method. This method is considered to overcome problems peculiar to the amorphous phase formed by the sputtering method. The problems are (1) difficulty in density control, (2) large variation in detection sensitivity, and (3) being susceptible to humidity. Depending on conditions such as the composition of the raw material solution used in the sol-gel method and the temperature, fine open pores can be provided in the film. As a result, it is considered that the reaction rate and detection sensitivity for hydrogen gas are improved. However, the above-described metal catalyst is indispensable for improving the characteristics. Therefore, the thin film for hydrogen gas sensors described in Patent Documents 3 to 6 includes a metal catalyst such as platinum (Pt) in the form of fine particles or a thin film.

  The method for producing a thin film for a hydrogen gas sensor described in Patent Documents 7 and 8 essentially does not include a heating step when a solid compound oxide such as tungsten oxide is formed. Therefore, for example, a solid compound oxide can be formed on a substrate having low heat resistance. However, even when these methods are used, a metal catalyst is required to obtain good characteristics as a hydrogen gas sensor.

  From the above, when applying the chromic reaction to the hydrogen gas sensors described in Non-Patent Document 1 and Patent Documents 1 to 8, it is necessary to support an expensive metal catalyst such as platinum (Pt). Therefore, the cost of the material for the hydrogen gas sensor is high, and the process for manufacturing the hydrogen gas sensor is complicated. In particular, the metal catalyst added to the solid compound oxide is buried in the film (solid compound oxide) except when the metal catalyst layer is supported in the form of fine particles on a solid compound oxide (tungsten oxide, etc.). As a result, the activation of hydrogen gas essentially does not occur.

  In addition, the hydrogen gas sensors described in Non-Patent Documents and Patent Documents 1 to 8 are all intended to detect hydrogen gas in the atmosphere, and depending on the environment in which the hydrogen gas sensor is used, an accurate hydrogen concentration This is considered difficult to detect. In particular, it has been difficult to detect hydrogen gas generated in a liquid with a conventional hydrogen gas sensor.

  When hydrogen gas is generated in water or an aqueous solution, it is required not only to grasp the concentration of the generated hydrogen gas, but also to be able to monitor the generation location of the hydrogen gas derived from the photocatalytic reaction or the photochemical reaction.

In tungsten bronze (H _x WO ₃ ) formed by tungsten oxide taking in hydrogen ions and electrons (e ⁻ ), the taken electrons (e ⁻ ) become carriers, and thus show electrical conductivity. In addition to the color change described above, it is also possible to detect the concentration of hydrogen gas by measuring the change in electrical resistance of the hydrogen detection element (tungsten oxide). In particular, when a part of the battery has a sealed structure, such as a lead storage battery or a redox flow battery, and the appearance of the electrode where the charge / discharge reaction of the battery occurs cannot be confirmed from the outside, the change in the electric resistance of the hydrogen detection element is used. Thus, by monitoring the concentration of hydrogen gas and the presence / absence of generation, it is required to identify the location where hydrogen gas is generated in the battery and obtain feedback for optimizing the material and battery operating conditions.

  The present invention has been made in view of the above circumstances, and provides a hydrogen detection method capable of easily detecting the generation of hydrogen gas in a liquid containing water, and a hydrogen detection device used in the hydrogen detection method. With the goal.

  In the hydrogen detection method according to one aspect of the present invention, the hydrogen generation member and the hydrogen detection member are immersed in the liquid disposed in the container, the liquid contains water, and the hydrogen generation member is electrochemical. A gas containing hydrogen is generated with a reaction, and the hydrogen detection member contains at least one compound selected from the group consisting of tungsten oxide, molybdenum oxide, cobalt oxyhydroxide and nickel oxyhydroxide, and a hydrogen generation member And the hydrogen detection member are electrically connected, hydrogen ions are supplied from the liquid to the hydrogen detection member, electrons are supplied from the hydrogen generation member to the hydrogen detection member, and hydrogen ions and electrons supplied to the hydrogen detection member In response, at least one of the color and electrical conductivity of the hydrogen detection member changes, and at least one of the color change and the electrical conductivity measurement is measured. It allows to detect hydrogen in a liquid.

  In the hydrogen detection method according to one aspect of the present invention, the hydrogen generation member and the hydrogen detection member are immersed in the liquid disposed in the container, the liquid contains water, and the hydrogen generation member is electrochemical. A gas containing hydrogen is generated with a reaction, and the hydrogen detection member contains at least one compound selected from the group consisting of tungsten oxide, molybdenum oxide, cobalt oxyhydroxide and nickel oxyhydroxide, and a hydrogen generation member And the hydrogen detection member are electrically connected, hydrogen ions are supplied from the liquid to the hydrogen detection member, electrons are supplied from the hydrogen generation member to the hydrogen detection member, and the hydrogen detection member is irradiated with light to generate hydrogen. The intensity of the transmitted light that has passed through the detection member is measured, and the physical property value of at least one of the hydrogen detection member among the light absorption coefficient, the transmittance, and the optical band gap is calculated from the intensity of the transmitted light. And, based on a change in physical properties in response to the supply of the hydrogen ions and electrons of the hydrogen detecting member detects the hydrogen in the liquid.

  In the hydrogen detection method according to one aspect of the present invention, the compound may be at least one selected from the group consisting of polycrystals, oriented crystals, and amorphous substances.

  In the hydrogen detection method according to one aspect of the present invention, the hydrogen detection member further includes at least one metal catalyst selected from the group consisting of platinum, palladium, rhodium, iridium, ruthenium, osmium, cobalt, nickel, and copper. May be included.

  In the hydrogen detection method according to one aspect of the present invention, the shape of the hydrogen detection member is at least one selected from the group consisting of a plate, a block, a ribbon, a rod, a wire, a sheet, a mesh, a lump, a particle, and a thin film. It may be.

  In the hydrogen detection method according to one aspect of the present invention, the hydrogen generation member may be a member that generates the gas by at least one of a photocatalytic reaction and a photochemical reaction. In the hydrogen detection method according to one aspect of the present invention, the hydrogen generation member may be an electrode material for a battery that involves an electrochemical reaction.

  In the hydrogen detection method according to one aspect of the present invention, in the photochemical reaction, the hydrogen generation member containing a metal material may be irradiated with light to generate the gas from the hydrogen generation member.

  In the hydrogen detection method according to one aspect of the present invention, the metal material may include at least one selected from the group consisting of iron, copper, zinc, tin, and titanium.

  In the method for detecting hydrogen according to one aspect of the present invention, the battery may be any one type of secondary battery of a lead storage battery, a nickel-zinc battery, and a redox flow battery.

  In the hydrogen detection method according to one aspect of the present invention, the hydrogen generation member and the hydrogen detection member may be in direct contact with each other.

  In the hydrogen detection method according to one aspect of the present invention, the conductive material connecting the hydrogen generation member and the hydrogen detection member is copper, silver, gold, platinum, aluminum, chromium, nickel, iron, tin, lead, and brazing. It may be at least one selected from the group consisting of materials.

  In the hydrogen detection method according to one aspect of the present invention, in the liquid, each of the plurality of hydrogen detection members may be electrically connected to different portions of the hydrogen generation member, and the gas is generated in the hydrogen generation member. You may monitor the location.

  A hydrogen detection device according to one aspect of the present invention is a hydrogen detection device used in the above-described hydrogen detection method, and includes a container, a hydrogen generation member, and a hydrogen detection member electrically connected to the hydrogen generation member. .

  The hydrogen detection device according to one aspect of the present invention may further include a wiring portion that applies a current or a voltage to the hydrogen detection member, and an electrical measurement device that measures the electrical conductivity of the hydrogen detection member.

  A hydrogen detection device according to one aspect of the present invention is a hydrogen detection device used in the above-described hydrogen detection method, and includes a container, a hydrogen generation member, a hydrogen detection member electrically connected to the hydrogen generation member, and a hydrogen A light source unit that irradiates light to the detection member and an optical measurement device that measures the intensity of transmitted light are provided.

  ADVANTAGE OF THE INVENTION According to this invention, the hydrogen detection method which can detect simply the production | generation of hydrogen gas in the liquid containing water, and the hydrogen detection device used for the said hydrogen detection method can be provided.

(A) in FIG. 1 is a schematic diagram illustrating a hydrogen detection method according to an embodiment of the present invention, and (b) in FIG. 1 illustrates a hydrogen detection method according to an embodiment of the present invention. It is a schematic diagram shown. FIG. 2 is a schematic diagram illustrating a hydrogen detection method according to an embodiment of the present invention. FIG. 3 is a schematic diagram showing a crystal structure of a perovskite oxide. FIG. 4 is a perspective view showing a hydrogen detection member according to an embodiment of the present invention. FIG. 5 is a diagram illustrating an appearance and an optical band gap of the hydrogen detection member before being used for detection of hydrogen. FIG. 6 is a diagram illustrating an appearance and an optical band gap of the hydrogen detection member after being used for hydrogen detection. FIG. 7 is a schematic diagram of a redox flow battery according to an embodiment of the present invention.

  Hereinafter, preferred embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiment. In this specification, the term “process” is not limited to an independent process, and is included in the term if the purpose of the process is achieved even when it cannot be clearly distinguished from other processes. In this specification, the numerical range indicated using “to” indicates a range including the numerical values described before and after “to” as the minimum value and the maximum value, respectively. In the present specification, the content of each component in the composition means that when there are a plurality of substances corresponding to each component in the composition, the contents of the plurality of substances present in the composition unless otherwise specified. It means the total amount. In the drawings, the same components are denoted by the same reference numerals.

In this specification, the term “hydrogen gas” means a gas composed of hydrogen molecules (H ₂ ). The term “hydrogen ion” means a cation (H ⁺ ) in which a hydrogen atom has lost an electron. The term “atomic hydrogen” means a state (H) in which a hydrogen molecule (H ₂ ) is changed to a single atom. The term “hydrogen” is used when the above-described hydrogen gas, hydrogen ion, and atomic hydrogen are used collectively, or when expressed as a kind of element.

  In the hydrogen detection method according to this embodiment, as shown in FIG. 1A, the hydrogen generation member 16 and the hydrogen detection member 18 are immersed in the liquid 14 disposed in the same container 12. ing. The liquid 14 includes water. The liquid 14 may be water or an aqueous solution in which an electrolyte is dissolved in water. The hydrogen generating member 16 generates a gas 20 containing hydrogen with an electrochemical reaction. The hydrogen detection member 18 contains at least one compound selected from the group consisting of tungsten oxide, molybdenum oxide, cobalt oxyhydroxide, and nickel oxyhydroxide. The hydrogen generation member 16 and the hydrogen detection member 18 are electrically connected. Hydrogen ions are supplied from the liquid 14 to the hydrogen detection member 18. When an electrochemical reaction occurs, electrons are supplied from the hydrogen generation member 16 to the hydrogen detection member 18. At least one of the color and electrical conductivity of the hydrogen detection member 18 changes according to the hydrogen ions and electrons supplied to the hydrogen detection member 18. Hydrogen in the liquid 14 is detected by measuring at least one of a change in color of the hydrogen detection member 18 and a change in electrical conductivity of the hydrogen detection member 18. Or in the modification of this embodiment, as shown in FIG. 2, the light L1 is irradiated to the hydrogen detection member 18, and the intensity | strength of the transmitted light L2 which permeate | transmitted the hydrogen detection member 18 is measured. A physical property value of at least one of the hydrogen detection member 18 among the light absorption coefficient, the transmittance, and the optical band gap is calculated from the intensity of the transmitted light L2. Hydrogen in the liquid is detected based on changes in physical property values according to the supply of hydrogen ions and electrons to the hydrogen detection member.

  A hydrogen gas detection method using a conventional hydrogen gas sensor directly detects hydrogen gas in the atmosphere by using a chromic reaction in the atmosphere. For the chromic reaction in the atmosphere, a metal catalyst such as platinum (Pt) is essential. On the other hand, the method for detecting hydrogen according to the present embodiment detects the generation of hydrogen gas in a liquid by using a chromic reaction in the liquid. In contrast to the conventional hydrogen gas detection method, the hydrogen detection method according to the present embodiment does not directly detect the hydrogen gas itself. In the hydrogen detection method according to the present embodiment, hydrogen gas is indirectly detected by detecting a part of hydrogen ions and a part of electrons generated in a hydrogen gas generation process (electrochemical reaction) with a hydrogen detection member. To do. Moreover, a metal catalyst is not essential for the chromic reaction according to the present embodiment. Thus, the mechanism by which the chromic reaction occurs in the present embodiment is different from the mechanism by which the chromic reaction occurs in the conventional atmosphere. Below, the chromic reaction in air | atmosphere is demonstrated first. Next, the chromic reaction according to this embodiment will be described.

(Chromic reaction in the atmosphere)
FIG. 3 shows a crystal structure of a general perovskite oxide. The composition of the perovskite oxide is represented by ABO ₃ . The A site is a rare earth element or an alkaline earth metal. B site is a transition metal. The perovskite oxide is, for example, tungsten oxide (WO ₃ ). The A site of the tungsten oxide crystal is a vacancy. The B site is a tungsten (W) ion. Oxygen (O) is coordinated around tungsten (W) ions to form an octahedron. Tungsten oxide is linked by sharing oxygen at the apexes of the octahedron. Tungsten oxide can accept many elements at the A site, which is a void. Hereinafter, in a hydrogen gas atmosphere, the chromic reaction is described in the case where a WO ₃ film comprising platinum (Pt) catalyst.

When a WO ₃ thin film comprising platinum is placed in a hydrogen gas atmosphere, the hydrogen gas is adsorbed on platinum and activated to generate atomic hydrogen (active hydrogen). WO ₃ then takes up atomic hydrogen (H). Next, in the skeleton of WO ₃ , atomic hydrogen (H) is separated into hydrogen ions (H ⁺ ) and electrons (e ⁻ ). Then, as shown in the following reaction formula (7), tungsten bronze _(H x WO ₃₎ is produced. The color of the WO ₃ thin film is transparent. The color of the H _x WO ₃ thin film is dark blue. Note that when WO ₃ is a bulk material, the color of the WO ₃ is ocher.
WO ₃ (transparent or ocher) + xH ⁺ + xe ⁻ → H _x WO ₃ (dark blue) (7)

The reason why the color of tungsten bronze (H _x WO ₃ ) is dark blue is considered as follows. Electrons (e ⁻ ) taken into tungsten oxide (WO ₃ ) reduce part of tungsten ions from hexavalent (W ⁶⁺ ) to pentavalent (W ⁵⁺ ), so that W ⁶⁺ / W ⁵⁺ mixed valence is reduced. A state arises. As a result, tungsten bronze absorbs visible light of about 600 to 800 nm due to intervalence transfer absorption by electrons transitioning between W ⁶⁺ and W ⁵⁺ . Therefore, tungsten bronze appears dark blue.

Tungsten bronze (H _x WO ₃ ) exhibits electrical conductivity when the taken electrons (e ⁻ ) become carriers. Therefore, the concentration of hydrogen gas can be detected by monitoring the electrical resistance of the hydrogen detection element containing tungsten oxide.

As described above, in the chromic reaction in the atmosphere, it is essential to incorporate atomic hydrogen into the oxide. Therefore, for example, in order to make tungsten oxide (WO ₃ ) respond to hydrogen in the atmosphere at room temperature, an expensive noble metal catalyst must be used in combination. A typical noble metal catalyst is a platinum (Pt) catalyst. Platinum has a high adsorptivity to hydrogen molecules (H ₂ ) and oxygen molecules (O ₂ ). Therefore, hydrogen molecules and oxygen molecules can maintain an atomized (activated) state on the surface of platinum.

(Chromic reaction according to this embodiment (chromic reaction in water))
Below, the mechanism in which the chromic reaction which concerns on this embodiment occurs is demonstrated. However, the mechanism by which the chromic reaction according to this embodiment occurs is not limited to the following reaction mechanism. The hydrogen generating member immersed in the liquid containing water generates hydrogen gas with an electrochemical reaction represented by the following reaction formula (8). A mechanism by which the hydrogen generating member generates hydrogen gas will be described later. The hydrogen ion (H ⁺ ) in the following reaction formula (8) is a hydrogen ion present in the liquid. Hydrogen ions are present in the liquid regardless of whether the liquid is acidic, neutral or alkaline. Hydrogen ions present in the liquid are taken into the hydrogen detection member. When the electrochemical reaction proceeds in the hydrogen generation member, a part of hydrogen ions in the following reaction formula (8) is supplied to the hydrogen detection member via the liquid without becoming hydrogen molecules. That is, the more the electrochemical reaction is promoted, the more hydrogen ions are supplied to the hydrogen detection member via the liquid. Further, since the hydrogen generation member and the hydrogen detection member are electrically connected, electrons (e ⁻ ) that are not used in the reaction shown in the following reaction formula (8) are also taken into the hydrogen detection member. When hydrogen ions and electrons are supplied to the hydrogen detection member, the following chromic reaction occurs. As a result, at least one of the color and electrical conductivity of the hydrogen detection member changes.
2H ⁺ + 2e ⁻ → H ₂ (8)

The chromic reaction when the hydrogen detection member includes a perovskite oxide is different from the chromic reaction when the hydrogen detection member does not include a perovskite oxide. Of the compounds contained in the hydrogen detection member, tungsten oxide and molybdenum oxide are both perovskite oxides. When hydrogen ions and electrons are supplied to tungsten oxide, as described above, hydrogen ions are taken into the A site, and the electrons reduce tungsten ions. As a result, tungsten bronze (H _x WO ₃ ) is formed as shown in the reaction formula (7). The mechanism of chromic reaction in molybdenum oxide is the same as the mechanism of chromic reaction in tungsten oxide. When hydrogen ions and electrons are supplied to molybdenum oxide, molybdenum bronze (H _x MoO ₃ ) is formed as shown in the following reaction formula (9). When MoO ₃ is a thin film, the color of MoO ₃ is transparent. When MoO ₃ is a bulk material, the color of MoO ₃ is yellow. The color of the H _x MoO ₃ thin film is dark blue.
MoO ₃ (transparent or yellow) + xH ⁺ + xe ⁻ → H _x MoO ₃ (dark blue) (9)

On the other hand, neither cobalt oxyhydroxide nor nickel oxyhydroxide is a perovskite oxide. When hydrogen ions and electrons are supplied to cobalt oxyhydroxide (CoOOH) contained in the hydrogen detection member, cobalt hydroxide (Co (OH) ₂ ) is generated by the reaction shown in the following reaction formula (10). The color of CoOOH is dark brown. When Co (OH) ₂ is a thin film, the color of Co (OH) ₂ is yellowish and transparent. When Co (OH) ₂ is a bulk material, the color of Co (OH) ₂ is blue-green. When hydrogen ions and electrons are supplied to nickel oxyhydroxide (NiOOH) contained in the hydrogen detection member, nickel hydroxide (Ni (OH) ₂ ) is generated by the reaction shown in the following reaction formula (11). The color of NiOOH is dark brown. When Ni (OH) ₂ is a thin film, the color of Ni (OH) ₂ is yellowish and transparent. When Ni (OH) ₂ is a bulk material, the color of Ni (OH) ₂ is green.
CoOOH (dark brown) + H ⁺ + e ⁻ → Co (OH) ₂ (clear or white) (10)
NiOOH (dark brown) + H ⁺ + e ⁻ → Ni (OH) ₂ (transparent or white) (11)

As described above, unlike the conventional chromic reaction in the atmosphere, the chromic reaction according to this embodiment does not require generation of atomic hydrogen (H) from hydrogen gas (H ₂ ). Therefore, an expensive noble metal catalyst is not essential in the chromic reaction according to this embodiment.

In the chromic reaction according to the present embodiment, in addition to the mechanism in which the hydrogen detection member takes in hydrogen ions (H ⁺ ) and electrons (e ⁻ ), the hydrogen detection member generates atomic hydrogen (H) generated in the liquid. The inventors speculate that it can also occur by incorporation. However, in the present embodiment, the mechanism by which the hydrogen detection member takes in atomic hydrogen is not a dominant mechanism, and as described above, the mechanism by which the hydrogen detection member takes in hydrogen ions and electrons is dominant. Think. Below, the mechanism in which a hydrogen detection member takes in atomic hydrogen is demonstrated.

In the present embodiment, hydrogen gas is generated in the liquid by the reaction of the above reaction formula (8) (electrochemical reaction in the hydrogen generating member). The reaction shown in the above reaction formula (8) can be mainly divided into the following three stages.
-Hydrogen ions are reduced to produce atomic hydrogen (active hydrogen);
H ⁺ + e ⁻ → H (12)
-Atomic hydrogen (active hydrogen) forms hydrogen molecules in the liquid;
2H → H ₂ (13)
・ Hydrogen molecules are generated as gas in the liquid;
H ₂ → H ₂ (gas) (14)

In the process of generating hydrogen gas (H ₂ ) in the liquid, atomic hydrogen (H) is formed as shown in the reaction formula (12). In the process in which the atomic hydrogen is taken into the hydrogen detection member, the atomic hydrogen is separated into hydrogen ions and electrons. Therefore, it is considered that a chromic reaction occurs even when a metal catalyst is not used.

(Change in characteristics of hydrogen detection member)
In this embodiment, at least one of the color and electrical conductivity of the hydrogen detection member changes according to the hydrogen ions and electrons supplied to the hydrogen detection member. Hydrogen in the liquid is detected by measuring at least one of a change in color and a change in electrical conductivity of the hydrogen detection member. The amount of change in the color of the hydrogen detection member depends on the amount of hydrogen ions and electrons taken up by the hydrogen detection member. The more hydrogen ions and electrons taken into the hydrogen detection member, the more the color of the hydrogen detection member changes. The amount of change in the electrical conductivity of the hydrogen detection member depends on the amount of hydrogen ions and electrons taken up by the hydrogen detection member. The more hydrogen ions and electrons taken into the hydrogen detection member, the greater the electrical conductivity of the hydrogen detection member changes. Moreover, in the modification of this embodiment, light is irradiated to a hydrogen detection member, and the intensity | strength of the transmitted light which permeate | transmitted the hydrogen detection member is measured. A physical property value of at least one of the hydrogen detection member among the light absorption coefficient, the transmittance, and the optical band gap is calculated from the intensity of the transmitted light. Hydrogen in the liquid is detected based on changes in physical property values according to the supply of hydrogen ions and electrons to the hydrogen detection member. The amount of change in the physical property value depends on the amount of hydrogen ions and electrons taken in the hydrogen detection member. As the number of hydrogen ions and electrons taken into the hydrogen detection member increases, the physical property value of the hydrogen detection member also changes greatly. Below, the change of each characteristic of a hydrogen detection member and the measuring method are demonstrated.

  The change in the color of the hydrogen detection member may be confirmed visually, for example. In the case of tungsten oxide, as shown in the above reaction formula (7), it changes from transparent or ocherous tungsten oxide to deep blue tungsten bronze. In the case of molybdenum oxide, as shown in the above reaction formula (9), it changes from transparent or yellow molybdenum oxide to dark blue molybdenum bronze. In the case of cobalt oxyhydroxide, as shown in the above reaction formula (10), it changes from dark brown cobalt oxyhydroxide to yellowish transparent or blue-green cobalt hydroxide. In the case of nickel oxyhydroxide, as shown in the above reaction formula (11), it changes from dark brown nickel oxyhydroxide to yellowish transparent or green nickel hydroxide.

  When the hydrogen generation member and the hydrogen detection member are arranged in a sealed structure like a secondary battery, it is not easy to visually observe the color of the hydrogen detection member. For example, in the case of a redox flow battery, the electrode part (hydrogen generation member) and the hydrogen detection member are electrically connected in a sealed battery container, and the electrolyte solution is not transparent. It cannot be observed from the outside. However, by measuring the change in electrical conductivity of the hydrogen detection member, it is possible to detect hydrogen generated in the sealed structure. For example, as shown in FIGS. 1A and 1B, the hydrogen detection member 18 and the electric measurement device 22 are connected via a conductive wiring portion 24, and the hydrogen detection member is used using a four-terminal method. It is possible to measure the change in electrical conductivity. When hydrogen gas is generated in the liquid and a chromic reaction occurs, the electrical conductivity of the hydrogen detection member increases. By measuring this change in electrical conductivity, the presence or absence of hydrogen gas generation in the liquid can be evaluated.

When measuring the physical property values of the hydrogen detection member such as the light absorption coefficient, the transmittance, and the optical band gap, for example, as shown in FIG. 2 or 4, the hydrogen detection member 18 includes the substrate 28 and the surface of the substrate 28. And the compound thin film 30 formed thereon may be provided as long as the substrate 28 is transparent. The compound thin film 30 is made of at least one compound selected from the group consisting of tungsten oxide, molybdenum oxide, cobalt oxyhydroxide, and nickel oxyhydroxide. The physical property values can be measured, for example, by the following method. As illustrated in FIG. 2, the light detection unit 18 is used to irradiate the hydrogen detection member 18 with light L1 (incident light) having a specific wavelength. Using an optical measuring device 34 such as a spectrophotometer, the light L2 (transmitted light) transmitted through the hydrogen detecting member 18 is detected. When the intensity of incident light is I ₀ , the intensity of transmitted light is I, and the thickness of the hydrogen detection member is x, Lambert-Beer's law shown in the following formula (A) is established.
I = I ₀ exp (−αx) (A)

In the above formula (A), α is a light absorption coefficient. The unit of α is (cm ⁻¹ ), for example. Α can be calculated from the measured value of I, the measured value of I ₀ , and the value of x by the above mathematical formula (A). When the hydrogen detection member is colored by a chromic reaction with hydrogen gas, the intensity I of the transmitted light decreases, so the value of α increases. That is, the value of α increases as the amount of hydrogen gas generated increases.

The light transmittance τ in the hydrogen detection member 18 can be calculated by the following mathematical formula (B). In a chromic reaction in a hydrogen gas sensor used in the atmosphere, the high-speed response of the hydrogen detection element is defined as the time required for the transmittance τ of the thin film sample to change to 50% in a high concentration (100%) hydrogen atmosphere. May be.
τ = I / I ₀ (B)

The optical band gap (E _g ) means a band gap of a semiconductor material obtained by measuring optical characteristics. When the hydrogen detection member is a semiconductor, the optical band gap of the hydrogen detection member can be obtained by the following procedure. First, using a spectrophotometer, the hydrogen detection member is individually irradiated with light divided for each wavelength, and the intensity of transmitted light that has passed through the hydrogen detection member is measured. The transmittance τ is calculated by the same method as described above. The relationship between the wavelength of the irradiated light and the transmittance τ is converted into a Tauc plot. The Tauc plot uses the fact that the density of states of electrons in the conduction band and valence band of a semiconductor is proportional to the square root of energy in a three-dimensional material. The Tauc plot is expressed by the following mathematical formula (C).
(Hνα) ⁿ = A (E _g −hν) (C)

In the above formula (C), h is a Planck constant (4.135 × 10 ⁻¹⁵ eVs). ν is the light frequency (s ⁻¹ ). α is a light absorption coefficient (m ⁻¹ ). A is absorbance. E _g is the optical band gap (eV). The index n on the left side varies depending on the type of semiconductor. n is 2 if the semiconductor is a direct transition type, and 0.5 if the semiconductor is an indirect transition type. By using the relationship of E = hν, the above formula (C) can be rewritten into the following formula (D). When the following mathematical formula (D) is represented by a graph of a coordinate system in which the horizontal axis is E and the vertical axis is (αE) ⁿ , the intersection of the graph and the horizontal axis is the optical band gap E _g .
(ΑE) ⁿ = A (E _g −E) (D)

FIG. 5 shows the appearance and optical band gap of the hydrogen detection member before being used for hydrogen detection. The hydrogen detection member in FIG. 5 includes a SiO ₂ substrate, an ITO film formed on the SiO ₂ substrate, and a WO ₃ thin film formed on the ITO film. The hydrogen detection member of FIG. 5 does not appear transparent in FIG. 5, but is actually transparent. FIG. 6 shows an appearance and an optical band gap of the hydrogen detection member after being used for detection of hydrogen. The hydrogen detection member of FIG. 6 is colored by the hydrogen detection member (transparent tungsten oxide) taking in hydrogen ions (H ⁺ ) and electrons (e ⁻ ), and is close to dark blue tungsten bronze (H _x WO ₃ ). It is in a state of transition to the composition. The value of the optical band gap E _g of the hydrogen detection member in FIG. 5 is 2.9 eV. The value of the optical band gap E _g of the hydrogen detection member in FIG. 6 is 2.1 eV, which is clearly smaller than the value of the optical band gap E _{g in} FIG. Thus, it can be seen that the crystal structure and the optical band gap of the hydrogen detection member changed during the transition from WO ₃ to H _x WO ₃ . It can be said that calculating and detecting the change of the optical band gap by the above method is an effective means as the hydrogen detection method in the present embodiment.

  Physical property values such as light absorption coefficient, transmittance, and optical band gap vary depending on the measurement environment. That is, when measuring directly in a liquid, it is necessary to consider physical properties such as the refractive index of the liquid existing between the hydrogen detection member and the photodetector in the optical measurement apparatus. Even when the colored hydrogen detection member is taken out from the liquid and measured, it is preferable to appropriately consider the optical properties of the transparent substrate on which the compound thin film is mounted.

The method for detecting hydrogen in a liquid by measuring the physical property values can be summarized as follows. As shown in FIG. 2, the hydrogen generation member 16 and the hydrogen detection member 18 are disposed so as to be electrically connected. The hydrogen detection member 18 takes in hydrogen ions (H ⁺ ) and electrons (e ⁻ ), thereby causing a chromic reaction. Incident light L <b> 1 is irradiated on the surface of the hydrogen detection member 18. Incident light L <b> 1 is emitted from the light source unit 32. The transmitted light L <b> 2 that has passed through the hydrogen detection member 18 enters the optical measurement device 34. The optical measuring device 34 measures the intensity of the transmitted light L2. Physical property values such as a light absorption coefficient, transmittance, and optical band gap are calculated from the intensity of the transmitted light L2.

(Details of hydrogen detection device)
The hydrogen detection device according to the present embodiment is a hydrogen detection device used in the hydrogen detection method according to the present embodiment. As shown in FIG. 1A, the hydrogen detection device 100 a includes a container 12, a hydrogen generation member 16, and a hydrogen detection member 18 that is electrically connected to the hydrogen generation member 16. The hydrogen detection device 100 a may further include a wiring unit 24 that applies a current or voltage to the hydrogen detection member 18 and an electrical measurement device 22 that measures the electrical conductivity of the hydrogen detection member 18. Each of the four wiring parts 24 may be connected to a different location of the hydrogen detection member 18. The hydrogen detection device 100 a includes the wiring unit 24 and the electric measurement device 22, thereby monitoring the change in the electrical conductivity of the hydrogen detection member 18 due to the electrochemical reaction in the hydrogen generation member 16.

  As shown in FIG. 2, the hydrogen detection device 200 irradiates light L <b> 1 to the container 12, the hydrogen generation member 16, the hydrogen detection member 18 electrically connected to the hydrogen generation member 16, and the hydrogen detection member 18. The light source part 32 and the optical measuring device 34 which measures the intensity | strength of the transmitted light L2 are provided. The light source unit 32 and the optical measurement device 34 measure the intensity of the transmitted light L2. Based on the measured value of the intensity of the transmitted light L2, physical property values such as the light absorption coefficient, transmittance, and optical band gap of the hydrogen detection member 18 are calculated, and changes in the physical property values are monitored. The hydrogen detection device 200 is a hydrogen detection device that replaces a conventional hydrogen gas sensor and has high sensitivity and quick response speed.

  In FIG. 2, when the hydrogen generating member 16 is a member that generates a gas containing hydrogen by at least one of a photocatalytic reaction and a photochemical reaction, as will be described later, when the hydrogen generating member 16 is irradiated with light. Hydrogen gas is generated. Therefore, in this case, the hydrogen generation member 16 is irradiated with light necessary for the photocatalytic reaction or the photochemical reaction separately from the light L1 for measuring optical characteristics in FIG. That is, when at least one of the photocatalytic reaction and the photochemical reaction is caused in the hydrogen generation member, the hydrogen generation member is irradiated with light different from the light L1 from a light source different from the light source 32. The wavelength and intensity of light necessary for the photocatalytic reaction or photochemical reaction can be appropriately selected according to the photocatalytic reaction or photochemical reaction.

  The hydrogen detection device may further include a device that issues an alarm or a warning when a physical property value of the water detection member such as a light absorption coefficient, transmittance, or optical band gap exceeds a specified value. Thereby, the hydrogen detection device can notify leakage of hydrogen gas.

(Details of hydrogen detection member)
The hydrogen detection member contains at least one compound selected from the group consisting of tungsten oxide, molybdenum oxide, cobalt oxyhydroxide, and nickel oxyhydroxide. The hydrogen detection member may consist only of the above compound. The compound contained in the hydrogen detection member may be a composite oxide in which two or more kinds of oxides are combined.

  The compound contained in the hydrogen detection member is preferably at least one selected from the group consisting of polycrystals, oriented crystals, and amorphous substances. When the compound contains at least one of polycrystal, oriented crystal, and amorphous material, the crystal structure of the hydrogen detection member is likely to change with the incorporation of hydrogen ions and electrons. As a result, the sensitivity of the hydrogen detection member with respect to hydrogen is further improved. On the other hand, when the compound has a dense structure such as a single crystal, the amount of hydrogen ions and electrons taken up by the hydrogen detection member tends to decrease. As a result, the response speed of the hydrogen detection member to hydrogen gas generation tends to be slow. The above compound is more preferably an amorphous substance from the viewpoints of sensitivity to hydrogen gas generation and response speed.

The hydrogen detection member may further contain at least one metal catalyst selected from the group consisting of platinum, palladium, rhodium, iridium, ruthenium, osmium, cobalt, nickel and copper. By including a metal catalyst in the hydrogen detection member, in addition to the chromic reaction, hydrogen gas (H ₂ ) generated from the hydrogen generation member can be transitioned to atomic hydrogen (H) in the liquid. As a result, the sensitivity and response speed of the hydrogen detection member with respect to hydrogen gas generation can be further improved. As the metal catalyst, platinum and palladium are more preferable from the viewpoint of the selectivity of hydrogen gas (H ₂ ) adsorption.

  The shape of the hydrogen detection member is not particularly limited. The shape of the hydrogen detection member may be at least one selected from the group consisting of a plate, a block, a ribbon, a rod, a wire, a sheet, a mesh, a lump, a particle, and a thin film, for example. The line may be a round line, for example. A thin film means the film | membrane formed in the surface of a sheet-like base material. The shape of the hydrogen detection member is preferably a plate, rod, particle, or thin film from the viewpoint of the sensitivity and response speed of the hydrogen detection member with respect to hydrogen gas generation.

  The method for producing the hydrogen detection member is not particularly limited. For example, when the hydrogen detection member is made of a metal oxide, the oxide can be obtained by heating a metal material having a predetermined shape at a high temperature to oxidize the metal material. . The oxidation temperature of the metal material varies depending on the type of the metal material. For example, when forming tungsten oxide, the temperature which heats metallic tungsten may be 650-900 degreeC. When forming molybdenum oxide, the temperature which heats metal molybdenum may be 450-700 degreeC.

  When the hydrogen detection member is composed of a thin film compound (compound thin film), the compound thin film can be produced by a known method such as a sol-gel method, a vapor deposition method, or a sputtering method. In particular, compound thin films formed by sputtering tend to have an amorphous structure, and the chromic reaction is promoted by the amorphous structure. In addition, the oxide thin film may be formed by heating a metal thin film formed by sputtering at a high temperature.

  As shown in FIG. 4, the compound thin film 30 is preferably formed on the substrate 28. That is, the hydrogen detection member 18 may include the substrate 28 and the compound thin film 30.

  The material of the substrate 28 is not particularly limited. The substrate 28 is preferably a ceramic substrate, a glass substrate, or the like from the viewpoint of the mechanical strength, heat resistance, water resistance, etc. of the hydrogen detection member. In particular, when measuring the color of the hydrogen detection member, the substrate 28 is preferably transparent. When the substrate 28 is transparent, the material of the substrate 28 may be quartz, glass, or the like. When measuring the change in electrical conductivity, a conductive thin film may be formed on the substrate 28 in advance before the compound thin film 30 is formed on the substrate 28. That is, the hydrogen detection member 18 may include a substrate 28, a conductive thin film formed on the substrate 28, and a compound thin film 30 formed on the conductive thin film. The material of the conductive thin film is preferably tin-doped indium oxide (ITO), fluorine-doped tin oxide (FTO), or the like.

  The thickness of the compound thin film 30 is not particularly limited. From the viewpoint of improving the efficiency of the chromic reaction, the thickness of the compound thin film 30 may be, for example, 15 nm to 5 μm, and preferably 50 nm to 1 μm.

  The method for supporting the metal catalyst on the compound constituting the hydrogen detection member may be appropriately selected according to the shape of the compound and the production method. Since the chromic reaction occurs on the surface of the hydrogen detection member, it is preferable that at least a part of the metal catalyst is exposed on the surface of the compound. For example, after forming a compound such as a plate, rod, particle, or thin film, a metal catalyst may be applied to the compound by sputtering. In the case of using the sol-gel method, for example, the substrate may be heated at the same time that a metal alkoxide solution in which a compound containing a metal catalyst is dissolved is applied to the substrate.

  In the liquid, each of the plurality of hydrogen detection members may be electrically connected to a different location of the hydrogen generation member, and the location where hydrogen-containing gas is generated in the hydrogen generation member may be monitored. For example, if there is a difference in the amount of hydrogen gas generated in the hydrogen generation member, the hydrogen gas generation location can be specified by placing multiple hydrogen detection members at different locations on the hydrogen generation member. Can be monitored.

After the hydrogen detection member is colored by the chromic reaction, the hydrogen detection member may be restored to a state before the chromic reaction occurs by heat treatment of the hydrogen detection member. For example, when the compound contained in the hydrogen detection member is tungsten oxide (WO ₃ ), tungsten bronze (H _x WO ₃ ) is formed by the chromic reaction as shown in the above reaction formula (7). By stopping the supply of hydrogen gas or keeping the hydrogen gas atmosphere low, it is considered that a reaction occurs in which hydrogen ions (H ⁺ ) in the tungsten bronze are extracted as shown in the following reaction formula (15). As a result, tungsten bronze returns to tungsten oxide.
2H _x WO ₃ → 2WO ₃ + xH ₂ (15)

The reaction shown in the above reaction formula (15) proceeds efficiently by heating tungsten bronze in the atmosphere. For example, when the rod-like tungsten bronze after the chromic reaction is heated at about 400 ° C. for about 1 minute, a transition from H _x WO ₃ to WO ₃ occurs. That is, the color of the hydrogen detection member changes from dark blue to ocher.

  The conditions for the heat treatment can be appropriately selected according to the type of the hydrogen detection member. The heat treatment conditions are, for example, preferably 200 to 700 ° C. for 2 seconds to 15 minutes, more preferably 250 to 600 ° C. for 5 seconds to 10 minutes, and further preferably 300 to 500 ° C. for 10 seconds to 5 minutes.

  The state before the chromic reaction can also be restored by allowing the hydrogen detection member to stand at room temperature in the atmosphere instead of the heat treatment. In this case, hydrogen escapes from the compound contained in the hydrogen detection member in the atmosphere. The standing time may be, for example, 50 hours or more, and preferably 72 hours or more.

(Details of hydrogen generating members)
The hydrogen generation member may be a member that generates a gas containing hydrogen by at least one of a photocatalytic reaction and a photochemical reaction. The hydrogen generating member may be a battery electrode material that involves an electrochemical reaction. As shown in FIGS. 1A and 1B, the hydrogen generation member 16 generates a gas 20 containing hydrogen while being immersed in the liquid 14.

The photocatalytic reaction is a reaction in which water is electrolyzed using a photovoltaic power generated when a metal oxide semiconductor such as titanium dioxide (TiO ₂ ) absorbs light energy. Specifically, when a platinum electrode and a titanium dioxide electrode are disposed in water and the titanium dioxide electrode is irradiated with ultraviolet rays, the water is decomposed into hydrogen gas and oxygen gas.

Hydrogen generating members that generate hydrogen gas by photocatalytic reaction are TiO ₂ , zinc oxide (ZnO), zirconium oxide (ZrO ₂ ), copper oxide (CuO or Cu ₂ O), tantalum oxide (Ta ₂ O ₅ ), tin oxide. (Sn ₃ O ₄ ), zinc sulfide (ZnS), cadmium sulfide (CdS), bismuth vanadate (BiVO ₄ ), calcium titanate (CaTiO ₃ ), strontium titanate (SrTiO ₃ ), lanthanum titanate (La ₂ TiO ₂ ) ₅ , La ₂ Ti ₃ O ₉ , or La ₂ Ti ₂ O ₇ ), sodium titanate (Na ₂ Ti ₆ O ₁₃ ), barium titanate (BaTiO ₄ or BaTi ₄ O ₉ ), gadolinium titanate (Gd ₂ Ti ₂ O ₇ ), yttrium titanate (Y ₂ Ti ₂ O ₇ ), potassium niobate (K ₄ N) b ₆ O _12), niobate rubidium _{(Rb 4 Nb 2 O 7)} , calcium niobate _{(Ca 2 Nb 2 O 7)} , niobate, strontium _{(Sr 2 Nb 2 O 7)} , barium niobate _(Ba 5 Nb ₄ O ₁₅ ), zinc niobate (ZnNb ₂ O ₆ ), tin niobate (SnNb ₂ O ₆ ), lithium tantalate (LiTaO ₃ ), sodium tantalate (NaTaO ₃ ), potassium tantalate (KTaO ₃ or K ₂ Ta ₂ O ₆ ), silver tantalate (AgTaO ₃ ), nickel tantalate (NiTa ₂ O ₆ ), rubidium tantalate (Rb ₄ Ta ₆ O ₁₇ ), calcium tantalate (Ca ₂ Ta ₂ O ₇ ), strontium tantalate _(Sr 2 _Ta 2 _{O 7} or _Sr 5 _Ta 4 _{O 15),} barium tantalate (Ba Ta ₄ O _15), tantalum lanthanum (LaTaO ₄ or _La 3 _TaO 7), lead tungstate (PbWO _4), tantalum nitride (TaON), tantalum - barium oxynitride (BaTaO ₂ N), tantalum - calcium oxy At least one selected from the group consisting of nitride (CaTaO ₂ N) and tantalum nitride (Ta ₃ N ₅ ) may be included. Moreover, you may use what gave the catalyst containing a noble metal, nickel, etc. to the said material.

  In the photochemical reaction, a hydrogen generation member containing a metal material may be irradiated with light to generate a gas containing hydrogen from the hydrogen generation member. A mechanism for generating a gas containing hydrogen by a photochemical reaction is, for example, an underwater crystal photosynthesis (SPSC) method. The method for producing hydrogen gas using the SPSC method includes a light irradiation step of generating a gas containing hydrogen by irradiating light on the surface of a hydrogen generation member (metal material) immersed in water. Below, the production | generation mechanism of the hydrogen gas by SPSC method is demonstrated. Note that the generation mechanism of hydrogen gas by the SPSC method is not limited to the following mechanism.

First, when a metal material containing metal M is immersed in water, a reaction in which metal M corrodes proceeds. That is, the metal M is ionized in water, and the metal M ion (M ^{n +} ) is generated as shown in the following reaction formula (16). In general, a metal corrosion reaction is a combination of an anode reaction in which a metal is dissolved as a metal ion and a cathode reaction in which an oxidizing agent in water is reduced. The reaction shown in the following reaction formula (16) is an anodic reaction. The reaction shown in the following reaction formula (17) and the reaction shown in the following reaction formula (18) are both cathode reactions. The reaction shown in the following reaction formula (17) occurs when water is acidic. The reaction shown in the following reaction formula (18) occurs when water is neutral or alkaline, or when dissolved oxygen is contained in water. Here, when the standard electrode potential of the metal is positive, it is generally considered that the anode reaction shown in the following reaction formula (16) does not occur. However, depending on the concentration of hydrogen ions (H ⁺ ) in water or the concentration of dissolved oxygen, the metal is ionized to generate M ^{n +} as shown in the following reaction formula (19). M ^{n +} dissolved in water by the reaction shown in the following reaction formula (16) or the reaction shown in the following reaction formula (19) is generated by the reaction shown in the following reaction formula (18) in water containing dissolved oxygen, for example. Reacts with hydroxide ions (OH ⁻ ). As a result, a hydroxide (M (OH) _n ) is produced as shown in the following reaction formula (20). Thereafter, water molecules are detached from the hydroxide, thereby generating an oxide (MO _x ) as shown in the following reaction formula (21).
M → M ^{n +} + ne ⁻ (16)
2H ⁺ + 2e ⁻ → H ₂ (17)
O ₂ + 2H ₂ O + 4e ⁻ → 4OH ⁻ (18)
2M + O ₂ + 2nH ⁺ → 2M ^{n +} + 2H ₂ O (19)
M ^{n +} + nOH ⁻ → M (OH) _n (20)
M (OH) _n → MO _x + (nx) H ₂ O (21)

In the general metal corrosion reaction described above, the generated hydroxide and oxide form a film. On the other hand, in the method for producing hydrogen gas using the SPSC method, nanocrystals containing oxides grow from the hydroxides on the surface of the metal material in the light irradiation step, and not only water molecules as by-products. Hydrogen gas (H ₂ ) is generated with an electrochemical reaction.

The metal material used for the SPSC method is not particularly limited. The metal material preferably contains at least one selected from the group consisting of iron, copper, zinc, tin and titanium from the viewpoint of promoting the generation of hydrogen gas (H ₂ ) and the productivity of nanocrystals. The metal material may contain an alloy.

The purity of the metal material is not particularly limited. The purity of the metal material is preferably 10.0 to 100.0% by mass from the viewpoint of promoting the generation of hydrogen gas (H ₂ ) and the productivity of nanocrystals, and 15.0 to 100.0% by mass. % Is more preferable, and 20.0 to 100.0 mass% is still more preferable. As the purity of the metal material is higher, hydrogen gas (H ₂ ) is more likely to be generated, oxides or hydroxides are more likely to be generated, and the composition of the oxides or hydroxides is more easily controlled.

  When an alloy is used for the metal material, the composition of the alloy is not particularly limited as long as it contains a metal element constituting the target oxide. The alloy may be an iron alloy, for example.

  Examples of iron alloys include Fe-C alloys, Fe-Au alloys, Fe-Al alloys, Fe-B alloys, Fe-Ce alloys, Fe-Cr alloys, Fe-Cr-Ni alloys. Fe-Cr-Mo alloy, Fe-Cr-Al alloy, Fe-Cr-Cu alloy, Fe-Cr-Ti alloy, Fe-Cr-Ni-Mn alloy, Fe-Cu alloy, Fe -Ga alloy, Fe-Ge alloy, Fe-Mg alloy, Fe-Mn alloy, Fe-Mo alloy, Fe-N alloy, Fe-Nb alloy, Fe-Ni alloy, Fe-P Alloy, Fe-S alloy, Fe-Si alloy, Fe-Si-Ag alloy, Fe-Si-Mg alloy, Fe-Ti alloy, Fe-U alloy, Fe-V alloy, Fe -W system alloy, Fe-Zn system alloy, etc. are mentioned.

  The metal material may further contain other atoms that are inevitably mixed. The content of other atoms inevitably mixed may be, for example, 3% by mass or less based on the total mass of the metal material. It is preferable that the content rate of the said atom contained in a metal material is 1 mass% or less from a viewpoint of productivity of a nanocrystal.

The shape of the metal material is not particularly limited. Examples of the shape of the metal material include a plate, a block, a ribbon, a round wire, a sheet, a mesh, or a combination of these. The shape of the metal material is preferably a plate, a block, or a sheet from the viewpoint of recoverability of hydrogen gas (H ₂ ) and nanocrystals and workability of immersion in water.

In the spectral radiation distribution (spectrum) of the light used in the light irradiation step, the wavelength of light having the maximum spectral irradiance (intensity) is preferably 185 nm or more and less than 8000 nm. The unit of the spectral irradiance (intensity) of light may be, for example, W · m ⁻² · nm ⁻¹ . In the spectrum of light used in the light irradiation step, the wavelength having the maximum intensity is preferably 380 to 600 nm, and preferably 400 to 580 nm, from the viewpoint of hydrogen gas (H ₂ ) purity and prevention of damage to the metal material due to heat. It is more preferable that

  The light source for irradiating the metal material is not particularly limited as long as it can irradiate the light. The light source may be, for example, the sun, an LED, a xenon lamp, a mercury lamp, a fluorescent lamp, or the like. The light applied to the metal material may be, for example, sunlight or pseudo-sunlight. Sunlight can be suitably used from the viewpoint that it can be used as a renewable energy that flows infinitely on the earth and does not emit greenhouse gases. Pseudo-sunlight means light that does not use the sun as a light source and whose light spectrum matches the spectrum of sunlight. The simulated sunlight can be emitted by a solar simulator using a metal halide lamp, a halogen lamp, or a xenon lamp, for example. Pseudo sunlight is generally used for the purpose of evaluating the strength of a material against ultraviolet rays, evaluating solar cells, or evaluating weather resistance. Also in this embodiment, simulated sunlight can be used suitably.

In this embodiment, when using the photochemical reaction by SPSC method, you may further provide the surface roughening process which roughens the surface of a metal material before a light irradiation process. That is, in the light irradiation step, the surface of the roughened metal material may be irradiated with light. By performing the surface roughening step, irregularities are formed on the surface of the metal material, the generation of hydrogen gas is easily promoted, and the growth rate of the nanocrystal is easily improved. When irregularities are formed on the surface of the metal material, the electron density at the tip of the nanocrystal tends to increase. Thereby, it is estimated that formation of hydrogen gas (H ₂ ) and formation of nanocrystals are promoted.

The size of the irregularities on the surface of the metal material formed by the surface roughening process is not particularly limited.
From the viewpoint of promoting the photochemical reaction, promoting the generation of hydrogen gas (H ₂ ), and promoting the growth of nanocrystals, the average value of the size of the bottoms of the protrusions is preferably 10 nm or more and 500 nm or less. And it is preferable that the average value of the space | interval of adjacent convex parts is 2 nm or more and 200 nm or less. The average value of the sizes of the bases of the protrusions is more preferably 15 nm or more and 300 nm or less, and the average value of the interval between adjacent protrusions is more preferably 5 nm or more and 150 nm or less. The average value of the sizes of the bottoms of the protrusions is more preferably 20 nm or more and 100 nm or less, and the average value of the interval between adjacent protrusions is more preferably 10 nm or more and 100 nm or less. The size of the base of the convex portion means the maximum width of the convex portion in a direction perpendicular to the height direction of the convex portion.

  The surface roughening step may be performed, for example, by machining, chemical treatment, or discharge treatment in a liquid of the surface of the metal material. The submerged discharge process means a process of discharging in a conductive liquid. Examples of the mechanical processing include grinding using a polishing paper, buff, or grindstone, blasting, processing using a sandpaper, and the like. Examples of the chemical treatment include etching with acid or alkali. As the in-liquid discharge treatment, for example, as described in International Publication No. 2008/099618, a voltage is applied to a counter electrode composed of an anode and a cathode disposed in a conductive liquid, and the vicinity of the cathode This may be done by generating a plasma and locally melting the cathode. In the submerged discharge treatment, by using a metal material for the cathode, irregularities can be formed on the surface of the metal material.

The submerged discharge treatment may be performed using, for example, the following apparatus. An apparatus that performs an in-liquid discharge process includes a cell that contains a conductive liquid, a non-contact electrode pair disposed in the cell, and a DC power source that applies a voltage to the electrode pair. The electrode pair is a cathode and an anode. A metal material is used for the cathode. The material of the anode is not particularly limited as long as it is stable in a conductive liquid without being energized. The material of the anode may be platinum or the like, for example. The surface area of the anode may be greater than the surface area of the cathode. The liquid having conductivity may be, for example, an aqueous potassium carbonate (K ₂ CO ₃ ) solution.

  The surface of the metal material after the surface roughening step may be exposed to the outside or may be covered with a natural oxide film.

The water in which the metal material is immersed is selected from the group consisting of pure water, ion exchange water, rain water, tap water, river water, well water, filtered water, distilled water, reverse osmosis water, spring water, spring water, dam water, and seawater. May be at least one kind. As water, pure water, ion-exchanged water, and tap water are preferable from the viewpoint of promoting the generation of hydrogen gas (H ₂ ), controlling the composition of nanocrystals, and productivity. However, river water, well water, dam water, seawater, etc. can be used suitably as naturally derived water.

  The hydrogen generation member may be a battery electrode material that involves an electrochemical reaction. The battery may be a secondary battery of any one of a lead storage battery, a nickel-zinc battery, and a redox flow battery.

In the secondary battery, depending on operating conditions, a reaction that generates hydrogen gas (H ₂ ) may proceed separately from the original charge / discharge reaction. Except for lead-acid batteries provided with a control valve, it may be necessary to detect unintentional generation of hydrogen gas (H ₂ ) with a hydrogen gas sensor or the like. In this embodiment, since hydrogen gas (H ₂ ) generated in the liquid can be detected, it is possible to detect hydrogen gas (H ₂ ) with higher sensitivity than a method using a conventional hydrogen gas sensor. In addition, when a part of the battery has a sealed structure and the electrode in the battery where the charge / discharge reaction occurs cannot be visually observed from the outside, the hydrogen gas concentration can be monitored using the change in the electric resistance of the hydrogen detection member. . Then, it is possible to determine where of hydrogen gas (H ₂₎ in the battery, obtain feedback for optimization of the electrode material and the cell operating conditions.

The compound contained in the hydrogen detection member can be appropriately selected according to the type of secondary battery. For example, a nickel-zinc battery uses a strong alkaline aqueous solution (potassium hydroxide aqueous solution). Lead acid batteries and redox flow batteries use acidic or neutral electrolytes. On the other hand, oxides such as tungsten oxide (WO ₃ ) and molybdenum oxide (MoO ₃ ) are easily dissolved in an alkaline aqueous solution and tend to have resistance to acids. Accordingly, oxides such as tungsten oxide (WO ₃ ) and molybdenum oxide (MoO ₃ ) are suitable for hydrogen detection members of lead-acid batteries or redox flow batteries. On the other hand, nickel oxyhydroxide (NiOOH) can be stably present in an alkaline aqueous solution and is therefore suitable for a hydrogen detection member of a nickel-zinc battery.

The following describes how to detect the generation of hydrogen gas (H ₂₎ in a redox flow battery. FIG. 7 is a schematic diagram of a redox flow battery according to the present embodiment. The redox flow battery 300 includes a positive electrode cell 40a, a negative electrode cell 40b, a positive electrode electrolyte storage part 52a, and a negative electrode electrolyte storage part 52b. The upper part of the positive electrode cell 40 a and the upper part of the positive electrode electrolyte storage part 52 a are connected via a pipe 56. The lower part of the positive electrode cell 40 a and the lower part of the positive electrode electrolyte storage part 52 a are connected via a pipe 56. The upper part of the negative electrode cell 40 b and the upper part of the negative electrode electrolyte storage part 52 b are connected via a pipe 56. The lower part of the negative electrode cell 40 b and the lower part of the negative electrode electrolyte storage part 52 b are connected via a pipe 56.

  A positive electrode 42a, a bipolar plate 46, and a current collector plate 48 are disposed in the positive electrode cell 40a. A bipolar plate 46 is disposed on the surface of the positive electrode 42a. A current collecting plate 48 is disposed on the surface of the bipolar plate 46. A negative electrode 42b, a bipolar plate 46, and a current collector plate 48 are disposed in the negative electrode cell 40b. A bipolar plate 46 is disposed on the surface of the negative electrode 42b. A current collecting plate 48 is disposed on the surface of the bipolar plate 46. The positive electrode 42 a and the negative electrode 42 b are separated by a diaphragm 44.

  A positive electrode electrolyte solution 50a containing a positive electrode active material is stored in the positive electrode electrolyte reservoir 52a. The positive electrode electrolyte 50a circulates between the positive electrode cell 40a and the positive electrode electrolyte reservoir 52a via the pipe 56 and the liquid feed pump 54, and continues to be supplied into the positive electrode 42a in the positive electrode cell 40a. A negative electrode electrolyte solution 50b containing a negative electrode active material is stored in the negative electrode electrolyte storage part 52b. The negative electrode electrolyte 50b circulates between the negative electrode cell 40b and the negative electrode electrolyte reservoir 52b via the pipe 56 and the liquid feed pump 54, and continues to be supplied into the negative electrode 42b in the negative electrode cell 40b. Charging / discharging is controlled by the power supply 58 and the external load 60.

  The hydrogen detection member 18a is disposed, for example, in a range surrounded by a dotted line in FIG. 7, and is electrically connected to the positive electrode 42a. The hydrogen detection member 18a and the positive electrode 42a may be in direct contact. The hydrogen detection member 18a detects the generation of hydrogen gas by the positive electrode 48a at the end of charging. The hydrogen detection member 18b is disposed, for example, in a range surrounded by a dotted line in FIG. 7, and is electrically connected to the negative electrode 42b. The hydrogen detection member 18b and the negative electrode 42b may be in direct contact. The hydrogen detection member 18b detects the generation of hydrogen gas by the negative electrode 42b at the end of charging. In order to suppress an increase in pressure loss of the electrolyte solution of the redox flow battery, the shape and size of the hydrogen detection member may be adjusted as appropriate.

  The electrodes 42a and 42b of the redox flow battery may be a metal such as aluminum, copper, or zinc, or carbon (graphite). The shape of the electrodes 42a and 42b may be a plate, a mesh, or the like.

  The electrodes 42a and 42b preferably contain carbon fibers in order to increase a reaction field, ie, an electrode area, as an electron transfer with the positive electrode active material or the negative electrode active material.

  From the viewpoints of handling, processability, manufacturability, and surface area, the electrodes 42a and 42b are preferably porous bodies made of carbon fibers. The porous body made of carbon fiber may be carbon felt, carbon cloth, carbon paper or the like. Especially, it is preferable that the porous body which consists of carbon fiber is a carbon felt from a viewpoint of the reaction activity and surface area during charging / discharging.

  The raw fiber of carbon fiber may be carbonizable. The carbon fiber raw fiber may be a cellulose fiber, an acrylic fiber, a rayon fiber, a phenol fiber, an aromatic polyamide fiber, a pitch fiber, a polyacrylonitrile fiber, or the like.

  The diaphragm 44 is not particularly limited as long as it can withstand the use conditions of the redox flow battery. The diaphragm 44 may be an ion conductive polymer film capable of conducting ions, an ion conductive solid electrolyte film, a polyolefin porous film, a cellulose porous film, or the like. Examples of the ion conductive polymer membrane include a cation exchange membrane and an anion exchange membrane. Examples of the ion conductive polymer membrane include Selemion APS (registered trademark) (manufactured by AGC), Nafion (registered trademark) (manufactured by DuPont), Neoceptor (registered trademark) (manufactured by Astom).

Each of the positive electrode active material and the negative electrode active material preferably contains ions whose valence changes, and known materials can be used. Each of the positive electrode active material and the negative electrode active material can contain, for example, an oxidant / reducer that satisfies the following reaction formula (22). Hereinafter, the oxidant / reductant is also referred to as a redox pair. In the following reaction formula (22), n ≧ x.
A ^{n +} + xe ⁻ ⇔A ^{(n−x) +} (22)

As redox pairs, Fe ²⁺ / Fe ³⁺ , Cr ²⁺ / Cr ³⁺ , Ga ²⁺ / Ga ³⁺ , Ti ²⁺ / Ti ³⁺ , Co ²⁺ / Co ³⁺ , Cu ⁺ / Cu ²⁺ , V ²⁺ / V ³⁺ , V ⁴⁺ / V ⁵⁺ , Ce ³⁺ / Ce ⁴⁺ , Cl ⁻ / Cl ³⁻ , Br ⁻ / Br ³⁻ , I ⁻ / I ₃ ⁻ , S ₂ ²⁻ / S ₄ ²⁻ , Zn ²⁺ / Zn, Pb ²⁺ / Pb , Fe ²⁺ / Fe, Cr ²⁺ / Cr, Ga ²⁺ / Ga, Ti ²⁺ / Ti, Mn ²⁺ / Mn, Mg ²⁺ / Mg, Mg ⁺ / Mg, Ag ⁺ / Ag, Cd ²⁺ / Cd, Co ²⁺ / Co Cu ²⁺ / Cu, Cu ⁺ / Cu, Hg ²⁺ / Hg and the like.

  Each of the positive electrode electrolyte solution 50a and the negative electrode electrolyte solution 50b may further contain a dispersion medium. The dispersion medium is not particularly limited as long as it is a solvent for dispersing or dissolving the positive electrode active material and the negative electrode active material.

  Examples of the solvent include acetone, methyl ethyl ketone, methyl n-propyl ketone, methyl isopropyl ketone, methyl n-butyl ketone, methyl isobutyl ketone, methyl n-pentyl ketone, methyl n-hexyl ketone, diethyl ketone, and dipropyl. Ketone solvents such as ketone, diisobutyl ketone, trimethylnonanone, cyclohexanone, cyclopentanone, methylcyclohexanone, 2,4-pentanedione, acetonylacetone; diethyl ether, methyl ethyl ether, methyl-n-propyl ether, diisopropyl ether , Tetrahydrofuran, methyltetrahydrofuran, dioxane, dimethyldioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol Di-n-propyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol methyl n-propyl ether, diethylene glycol methyl n-butyl ether, diethylene glycol di-n-propyl ether, diethylene glycol di- n-butyl ether, diethylene glycol methyl-n-hexyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol methyl ethyl ether, triethylene glycol methyl-n-butyl ether, triethylene glycol di-n-butyl ether, triethylene Glycol meth -N-hexyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetradiethylene glycol methyl ethyl ether, tetraethylene glycol methyl-n-butyl ether, diethylene glycol di-n-butyl ether, tetraethylene glycol methyl-n-hexyl ether, tetra Ethylene glycol di-n-butyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol di-n-propyl ether, propylene glycol dibutyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, dipropylene glycol methyl ethyl ether, di Propylene glycol methyl -N-butyl ether, dipropylene glycol di-n-propyl ether, dipropylene glycol di-n-butyl ether, dipropylene glycol methyl-n-hexyl ether, tripropylene glycol dimethyl ether, tripropylene glycol diethyl ether, tripropylene glycol methyl ethyl Ether, tripropylene glycol methyl-n-butyl ether, tripropylene glycol di-n-butyl ether, tripropylene glycol methyl-n-hexyl ether, tetrapropylene glycol dimethyl ether, tetrapropylene glycol diethyl ether, tetradipropylene glycol methyl ethyl ether, tetra Propylene glycol methyl-n-butyl ether, dipropylene glycol Ether solvents such as -n-butyl ether, tetrapropylene glycol methyl-n-hexyl ether, tetrapropylene glycol di-n-butyl ether; carbonates such as propylene carbonate, ethylene carbonate, diethyl carbonate, methyl acetate, ethyl acetate, n acetate -Propyl, isopropyl acetate, n-butyl acetate, isobutyl acetate, sec-butyl acetate, n-pentyl acetate, sec-pentyl acetate, 3-methoxybutyl acetate, methylpentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, acetic acid 2- (2-butoxyethoxy) ethyl, benzyl acetate, cyclohexyl acetate, methyl cyclohexyl acetate, nonyl acetate, methyl acetoacetate, ethyl acetoacetate, diethylene glycol methyl ether acetate, vinegar Diethylene glycol monoethyl ether, acetic acid dipropylene glycol methyl ether, acetic acid dipropylene glycol ethyl ether, diacetic acid glycol, acetic acid methoxytriglycol, ethyl propionate, n-butyl propionate, isoamyl propionate, diethyl oxalate, di-oxalate n-butyl, methyl lactate, ethyl lactate, n-butyl lactate, n-amyl lactate, ethylene glycol methyl ether propionate, ethylene glycol ethyl ether propionate, ethylene glycol methyl ether acetate, ethylene glycol ethyl ether acetate, propylene glycol Methyl ether acetate, propylene glycol ethyl ether acetate, propylene glycol propyl ether acetate, γ-butyl Ester solvents such as rolactone and γ-valerolactone; acetonitrile, N-methylpyrrolidinone, N-ethylpyrrolidinone, N-propylpyrrolidinone, N-butylpyrrolidinone, N-hexylpyrrolidinone, N-cyclohexylpyrrolidinone, N, N-dimethylformamide , N, N-dimethylacetamide, dimethylsulfoxide and the like aprotic polar solvents; methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, t-butanol, n-pentanol, isopen Tanol, 2-methylbutanol, sec-pentanol, t-pentanol, 3-methoxybutanol, n-hexanol, 2-methylpentanol, sec-hexanol, 2-ethylbutanol, s ec-heptanol, n-octanol, 2-ethylhexanol, sec-octanol, n-nonyl alcohol, n-decanol, sec-undecyl alcohol, trimethylnonyl alcohol, sec-tetradecyl alcohol, sec-heptadecyl alcohol, phenol, Alcohol solvents such as cyclohexanol, methylcyclohexanol, benzyl alcohol, ethylene glycol, 1,2-propylene glycol, 1,3-butylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol; ethylene glycol monomethyl ether , Ethylene glycol monoethyl ether, ethylene glycol monophenyl ether, diethylene glycol monomethyl ether Diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol mono-n-hexyl ether, ethoxytriglycol, tetraethylene glycol mono-n-butyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol mono Glycol monoether solvents such as ethyl ether and tripropylene glycol monomethyl ether; α-terpinene, α-terpineol, myrcene, allocymene, limonene, dipentene, α-pinene, β-pinene, terpineol, carvone, osimene, ferlandylene, etc. Terpene solvent; water and the like. A solvent may be used individually by 1 type, or may use 2 or more types together. The solvent is preferably water from the viewpoint of the viscosity of the electrolytic solution.

  Each of the positive electrode electrolyte solution 50a and the negative electrode electrolyte solution 50b may further contain a supporting electrolyte salt. When the electrolytic solutions 50a and 50b contain the supporting electrolyte salt, the ionic conductivity in the electrolytic solutions 50a and 50b can be increased, and the internal resistance of the redox flow battery system tends to be reduced.

(Electrical connection method between hydrogen generating member and hydrogen detecting member)
The electrical connection method between the hydrogen generation member and the hydrogen detection member is not particularly limited. For example, as shown to (a) in FIG. 1, the hydrogen production | generation member 16 and the hydrogen detection member 18 may contact directly. The hydrogen generation member 16 and the hydrogen detection member 18 may be welded. As shown in (b) of FIG. 1, the hydrogen generation member 16 and the hydrogen detection member 18 may be electrically connected via a conductive material 26. The electrical connection between the hydrogen generation member 16 and the hydrogen detection member 18 does not mean an electrical connection through water.

  The conductive material connecting the hydrogen generation member and the hydrogen detection member may be at least one selected from the group consisting of copper, silver, gold, platinum, aluminum, chromium, nickel, iron, tin, lead, and brazing material. . The conductive material may be a wiring material containing copper, silver, gold, platinum, aluminum, chromium, nickel, iron, tin, or lead.

  Connection using brazing material is effective when electrical conductivity is required. When at least one of the hydrogen generation member and the hydrogen detection member is thin and it is difficult to weld the hydrogen generation member and the hydrogen detection member, connection using a brazing material is particularly effective. As the brazing material, those having a known composition can be suitably used. The brazing material may be solder. The brazing material is silver brazing (Ag—Cu—An alloy), brass brazing (Cu—Zn alloy), phosphor copper brazing (Cu—P alloy), aluminum brazing (Al—Si alloy), etc. Good.

  The solder may be Sn—Pb solder, Sn—Pb—Ag solder, Sn—Ag—Cu solder, or the like. Considering the influence on the environment, the solder is preferably Sn—Ag—Cu based solder which does not substantially contain lead. When electrical connection is made using solder, the solder may be heated to a temperature higher than the melting point. Specifically, when the solder is Sn—Pb solder, the solder may be heated to a temperature range of 230 to 300 ° C. to melt the solder.

  Hereinafter, although the content of the present invention is explained in detail using an example and a comparative example, the present invention is not limited to the following examples.

<Example 1>
(Hydrogen detection member)
Tungsten powder having a purity of 99.5% was filled in a rubber mold and molded by isotropic pressure molding at 100 MPa to obtain a molded body. The compact was heated at 1300 ° C. for 20 minutes in a hydrogen stream to pre-sinter the compact. Next, the compact was heated at 3000 ° C. while energizing to sinter the compact, thereby obtaining a tungsten sintered compact. Next, the tungsten sintered body was processed by forging and drawing to obtain rod-shaped tungsten. The rod-shaped tungsten had a diameter of 2.0 mm and a length of 35.0 mm. Next, using a muffle furnace (KDF F-70) manufactured by Denken Hydental Co., Ltd., rod-shaped tungsten was annealed at 800 ° C. for 2 hours in the atmosphere to obtain tungsten oxide. The dimensions of tungsten oxide were the same as those of the rod-shaped tungsten described above. The color of tungsten oxide was ocher. By the above method, a hydrogen detection member made of rod-shaped tungsten oxide was manufactured.

(Hydrogen detection)
A hydrochloric acid aqueous solution having a hydrogen chloride concentration of 1 mol / L was placed in a glass container. The hydrogen detection member and the hydrogen generation member were immersed in an aqueous hydrochloric acid solution. In the hydrochloric acid aqueous solution, the hydrogen detection member and the hydrogen generation member were in direct contact. The hydrogen generating member was a zinc plate. The purity of the zinc plate was 99.5% by mass. The surface dimension of the zinc plate was 20 mm × 5 mm, and the thickness of the zinc plate was 0.5 mm. Immediately after the hydrogen detection member and the hydrogen generation member are immersed in an aqueous hydrochloric acid solution, hydrogen is generated from the surface of the hydrogen generation member with the electrochemical reaction shown in the following reaction formula (23) and the electrochemical reaction shown in the following reaction formula (24). Gas was generated. 30 seconds after the generation of hydrogen gas, the hydrogen detection member was taken out of the container.
2H ⁺ + 2e ⁻ → H ₂ (23)
Zn → Zn ²⁺ + 2e ⁻ (24)

[color]
The color of the hydrogen detection member after being used for detection of hydrogen was confirmed visually. As a result, the color of the hydrogen detection member was changed to dark blue.

<Example 2>
(Hydrogen detection member)
A laminate including a quartz glass substrate and a conductive thin film formed on one side of the quartz glass substrate was prepared. The conductive thin film was a tin-doped indium oxide (ITO) film formed by sputtering. The thickness of the conductive thin film was 100 nm. The size of the quartz glass substrate was 15 mm × 15 mm. A tungsten thin film was formed on the conductive thin film included in the laminate. The thickness of the tungsten thin film was 300 nm. The tungsten thin film was formed by sputtering for 15 minutes under the conditions of a high frequency voltage of 500 W and a degree of vacuum of 1 Pa. Next, the laminated body including the tungsten thin film was annealed at 800 ° C. for 1 hour to form a tungsten oxide thin film on the laminated body. The color of the tungsten oxide thin film was transparent. By the above method, a hydrogen detection member including a quartz glass substrate, a conductive thin film, and a tungsten oxide thin film was manufactured. The entire color of the hydrogen detection member before being used for hydrogen detection was transparent.

(Hydrogen detection)
A hydrochloric acid aqueous solution having a hydrogen chloride concentration of 1 mol / L was placed in a glass container. The hydrogen detection member and the hydrogen generation member were immersed in an aqueous hydrochloric acid solution. In the hydrochloric acid aqueous solution, the tungsten oxide thin film included in the hydrogen detection member and the hydrogen generation member were in direct contact. The hydrogen generating member was a zinc plate. The purity of the zinc plate was 99.5% by mass. The surface dimension of the zinc plate was 20 mm × 5 mm, and the thickness of the zinc plate was 0.5 mm. Immediately after immersing the hydrogen detecting member and the hydrogen generating member in an aqueous hydrochloric acid solution, hydrogen is generated from the surface of the hydrogen generating member with the electrochemical reaction shown in the reaction formula (23) and the electrochemical reaction shown in the reaction formula (24). Gas was generated. 30 seconds after the generation of hydrogen gas, the hydrogen detection member was taken out of the container.

[color]
The color of the hydrogen detection member after being used for detection of hydrogen was confirmed visually. As a result, the color of the hydrogen detection member was changed to dark blue.

[Electric conductivity]
Using an electric conductivity meter, the electric conductivity of the hydrogen detection member before being used for hydrogen detection was measured by a four-terminal method. In the measurement of electrical conductivity, four locations on the surface of the tungsten oxide thin film included in the hydrogen detection member were connected to an electrical conductivity meter. As the electric conductivity meter, a wide range DC power supply (PWR1600H) manufactured by Kikusui Electronics Co., Ltd. was used. The electric conductivity of the hydrogen detection member before being used for detection of hydrogen was 2.0 × 10 ⁻⁵ S / cm.

By the same method as described above, the electric conductivity of the hydrogen detection member after being used for detection of hydrogen was measured. As a result, the electric conductivity of the hydrogen detection member after being used for detection of hydrogen was 4.5 × 10 ⁻⁴ S / cm.

[Optical band gap]
Using a spectrophotometer, light was irradiated to the hydrogen detection member before being used for hydrogen detection, and the intensity of the transmitted light that passed through the hydrogen detection member was measured. As a spectrophotometer, V-630 Spectrophotometer manufactured by JASCO was used. The optical band gap was calculated from the intensity of transmitted light by the method described above. The optical band gap of the hydrogen detection member before being used for hydrogen detection was 3.0 eV.

  The optical band gap of the hydrogen detection member after being used for hydrogen detection was calculated by the same method as described above. As a result, the optical band gap of the hydrogen detection member before being used for hydrogen detection was 2.5 eV.

<Example 3>
(Hydrogen detection member)
In Example 3, the same hydrogen detection member as in Example 1 was prepared.

(Hydrogen detection)
Pure water was put into a glass container. The hydrogen detection member and the hydrogen generation member were immersed in pure water. In pure water, the tungsten oxide thin film included in the hydrogen detection member and the hydrogen generation member were in direct contact. The hydrogen generating member was an iron plate. The surface of the iron plate was roughened in advance by submerged discharge treatment. The purity of the iron plate was 99.0% by mass. The dimension of the surface of the iron plate was 50 mm × 10 mm, and the thickness of the iron plate was 0.5 mm. Next, using a UV lamp, the surface of the iron plate was irradiated with light continuously for 24 hours. As the UV lamp, a Lighting Cure LC8 type lamp manufactured by Hamamatsu Photonics was used. The wavelength of light was 332 nm. About 1 hour after irradiation with light, hydrogen gas was generated from the surface of the hydrogen generating member with the electrochemical reaction shown in the following reaction formula (25) and the electrochemical reaction shown in the following reaction formula (26). It was. The present inventors consider that the generation of this hydrogen gas is due to the SPSC method. 24 hours after irradiation with light, the hydrogen detection member was taken out of the container.
2H ⁺ + 2e ⁻ → H ₂ (25)
Fe → Fe ²⁺ + 2e ⁻ (26)

[color]
The color of the hydrogen detection member after being used for detection of hydrogen was confirmed visually. As a result, the color of the hydrogen detection member was changed to dark blue.

<Example 4>
(Hydrogen detection member)
A laminate including a quartz glass substrate and a conductive thin film formed on one side of the quartz glass substrate was prepared. The conductive thin film was a tin-doped indium oxide (ITO) film formed by a sputtering method. The thickness of the conductive thin film was 100 nm. The size of the quartz glass substrate was 50 mm × 50 mm. A molybdenum thin film was formed on the conductive thin film included in the laminate. The thickness of the molybdenum thin film was 300 nm. The molybdenum thin film was formed by sputtering for 15 minutes under the conditions of a high frequency voltage of 500 W and a degree of vacuum of 1 Pa. Next, the laminate including the molybdenum thin film was annealed at 650 ° C. for 2 hours to form a molybdenum oxide thin film on the laminate. The color of the molybdenum oxide thin film was transparent. By the above method, a hydrogen detection member including a quartz glass substrate, a conductive thin film, and a molybdenum oxide thin film was manufactured. The entire color of the hydrogen detection member before being used for hydrogen detection was transparent.

(Detection of hydrogen)
In Example 4, the hydrogen detection member of Example 4 was used instead of the hydrogen detection member of Example 3. In Example 4, the molybdenum oxide thin film included in the hydrogen detection member and the hydrogen generation member were in direct contact with each other in pure water. Except for the above points, hydrogen was detected by the same method as in Example 3. In Example 4, about one hour after irradiation with light, hydrogen was generated from the surface of the hydrogen generating member with the electrochemical reaction shown in the reaction formula (25) and the electrochemical reaction shown in the reaction formula (26). Gas was generated. The present inventors consider that the generation of this hydrogen gas is due to the SPSC method. 24 hours after irradiation with light, the hydrogen detection member was taken out of the container.

[color]
The color of the hydrogen detection member after being used for detection of hydrogen was confirmed visually. As a result, the color of the hydrogen detection member was changed to dark blue.

[Optical band gap]
In the same manner as in Example 2, the optical band gap of the hydrogen detection member before being used for hydrogen detection was calculated. The optical band gap of the hydrogen detection member before being used for hydrogen detection was 2.9 eV.

  In the same manner as in Example 2, the optical band gap of the hydrogen detection member after being used for hydrogen detection was calculated. The optical band gap of the hydrogen detection member after being used for detection of hydrogen was 2.5 eV.

<Example 5>
(Hydrogen detection member)
In Example 5, the same hydrogen detection member as in Example 1 was prepared.

(Detection of hydrogen)
In Example 5, the hydrogen detection member and the hydrogen generation member were not brought into direct contact. In Example 5, the hydrogen detection member and the hydrogen generation member were connected via a copper wire. Specifically, one end of the copper wire was wound around the hydrogen detection member, and the other end of the copper wire was wound around the hydrogen generation member. The diameter of the copper wire was 0.5 mm. The purity of the copper wire was 99.9% by mass. Except for the above points, hydrogen was detected by the same method as in Example 1. In Example 5, immediately after the hydrogen detection member and the hydrogen generation member are immersed in an aqueous hydrochloric acid solution, the hydrogen generation is performed with the electrochemical reaction shown in the reaction formula (23) and the electrochemical reaction shown in the reaction formula (24). Hydrogen gas was generated from the surface of the member. 30 seconds after the generation of hydrogen gas, the hydrogen detection member was taken out of the container.

[color]
The color of the hydrogen detection member after being used for detection of hydrogen was confirmed visually. As a result, the color of the hydrogen detection member was changed to dark blue.

<Comparative Example 1>
(Hydrogen detection member)
An alumina powder having a purity of 99.8% was molded by a rubber press method to obtain a molded body. As the alumina powder, 160SG-3H manufactured by Showa Denko KK was used. The dimensions of the molded body were 4.0 mm in diameter and 60.0 mm in length. Subsequently, the molded body was heated at 1620 ° C. for 4 hours to sinter the molded body to obtain a sintered body. Next, the sintered body was processed by cutting to obtain rod-shaped aluminum oxide (Al ₂ O ₃ ). The rod-shaped aluminum oxide had a diameter of 2.0 mm and a length of 35.0 mm. The color of aluminum oxide was white. By the above method, a hydrogen detection member made of rod-shaped aluminum oxide was manufactured.

(Hydrogen detection)
In Comparative Example 1, the hydrogen detection member of Comparative Example 1 was used instead of the hydrogen detection member of Example 1. Except for this point, hydrogen was detected by the same method as in Example 1. In Comparative Example 1, immediately after the hydrogen detection member and the hydrogen generation member are immersed in the hydrochloric acid aqueous solution, the hydrogen generation is accompanied by the electrochemical reaction shown in the reaction formula (23) and the electrochemical reaction shown in the reaction formula (24). Hydrogen gas was generated from the surface of the member. 30 seconds after the generation of hydrogen gas, the hydrogen detection member was taken out of the container.

[color]
The color of the hydrogen detection member after being used for detection of hydrogen was confirmed visually. As a result, the color of the hydrogen detection member was white and did not change.

<Comparative example 2>
(Hydrogen detection member)
In Comparative Example 2, the same hydrogen detection member as in Example 1 was prepared.

(Hydrogen detection)
In Comparative Example 2, no hydrogen generating member was used. In Comparative Example 2, only the hydrogen detection member of Comparative Example 2 was immersed in an aqueous hydrochloric acid solution. Except for the above points, hydrogen was detected by the same method as in Example 1. In Comparative Example 2, no gas was generated even when the hydrogen detection member was immersed in an aqueous hydrochloric acid solution. 30 seconds after the hydrogen detection member was immersed in the hydrochloric acid aqueous solution, the hydrogen detection member was taken out of the container.

[color]
The color of the hydrogen detection member after being used for detection of hydrogen was confirmed visually. As a result, the color of the hydrogen detection member was ocher and did not change.

<Comparative Example 3>
(Hydrogen detection member)
In Comparative Example 3, the same hydrogen detection member as in Example 1 was prepared.

(Detection of hydrogen)
In Comparative Example 3, the hydrogen detection member and the hydrogen generation member were not electrically connected. In Comparative Example 3, the hydrogen detection member and the hydrogen generation member were separated and immersed in the liquid. Except for the above points, hydrogen was detected by the same method as in Example 1. In Comparative Example 3, immediately after immersing the hydrogen detecting member and the hydrogen generating member in the aqueous hydrochloric acid solution, the hydrogen generation is accompanied by the electrochemical reaction shown in the reaction formula (23) and the electrochemical reaction shown in the reaction formula (24). Hydrogen gas was generated from the surface of the member. 30 seconds after the generation of hydrogen gas, the hydrogen detection member was taken out of the container.

[color]
The color of the hydrogen detection member after being used for detection of hydrogen was confirmed visually. As a result, the color of the hydrogen detection member was ocher and did not change.

<Comparative example 4>
(Hydrogen detection member)
In Comparative Example 4, the same hydrogen detection member as in Example 1 was prepared.

(Detection of hydrogen)
High-purity hydrogen gas was blown onto the hydrogen detection member for 10 seconds at 25 ° C. in an air atmosphere. The purity of hydrogen gas was 99.9% by mass. In Comparative Example 4, generation of hydrogen gas accompanied by an electrochemical reaction did not occur.

[color]
The color of the hydrogen detection member after being used for detection of hydrogen was confirmed visually. As a result, the color of the hydrogen detection member was ocher and did not change.

<Comparative Example 5>
(Hydrogen detection member)
In Comparative Example 5, the same hydrogen detection member as in Example 1 was prepared.

(Detection of hydrogen)
Pure water was put into a glass container. Only the hydrogen detection member was immersed in pure water. In pure water, high-purity hydrogen gas was blown onto the hydrogen detection member for 10 seconds. The purity of hydrogen gas was 99.9% by mass. Subsequently, the hydrogen detection member was taken out from the container. In Comparative Example 5, generation of hydrogen gas accompanied by an electrochemical reaction did not occur.

[color]
The color of the hydrogen detection member after being used for detection of hydrogen was confirmed visually. As a result, the color of the hydrogen detection member was ocher and did not change.

  Table 1 shows hydrogen detection members and hydrogen generation members of Examples 1 to 5 and Comparative Examples 1 to 5 used for detection of hydrogen. Table 2 shows changes in the characteristics of the hydrogen detection members of Examples 1 to 5 and Comparative Examples 1 to 5.

In Examples 1 to 5, rod-shaped or thin-film oxides functioned as hydrogen detection members. It was found that each of the hydrogen detection members of Examples 1 to 5 exhibited a chromic reaction by taking in hydrogen ions (H ⁺ ) in the liquid and electrons (e ⁻ ) emitted from the hydrogen generation member.

  In Comparative Example 1, aluminum oxide was used. Aluminum oxide did not cause a chromic reaction even in an environment where hydrogen gas was generated in the liquid, and did not show a change in color.

In Comparative Example 2, no hydrogen generating member was used. As a result, no chromic reaction of tungsten oxide occurred. In Comparative Example 2, even if the liquid contains abundant hydrogen ions (H ⁺ ), almost no electrons (e ⁻ ) are generated. Therefore, it is considered that the valence does not essentially change in the tungsten oxide, and the color of the tungsten oxide does not change.

In Comparative Example 3, since the hydrogen detection member (tungsten oxide) and the hydrogen generation member (zinc plate) are not electrically connected, electrons (e ⁻ ) are not taken into tungsten oxide and the chromic reaction does not proceed. It is thought.

  In Comparative Example 4, hydrogen gas was sprayed onto a rod-shaped tungsten oxide simple substance in an air atmosphere. In Comparative Example 4, since the hydrogen detection member did not include a metal catalyst, the hydrogen gas did not change to atomic hydrogen. Therefore, it is considered that there was no supply of hydrogen ions and electrons to tungsten oxide, and the chromic reaction did not proceed.

  In Comparative Example 5, hydrogen gas was sprayed onto tungsten oxide immersed in pure water. In Comparative Example 5, as in Comparative Example 4, since the hydrogen detection member did not include a metal catalyst, the hydrogen gas did not change to atomic hydrogen. Therefore, it is considered that hydrogen ions and electrons were not taken into tungsten oxide and chromic reaction did not occur essentially.

  DESCRIPTION OF SYMBOLS 12 ... Container, 14 ... Liquid, 16 ... Hydrogen production | generation member, 18, 18a, 18b ... Hydrogen detection member, 20 ... Gas containing hydrogen, 22 ... Electric measurement apparatus, 24 ... Wiring part, 26 ... Conductive material, 28 ... Substrate 30 ... Compound thin film, 32 ... Light source unit, 34 ... Optical measuring device, 40a ... Positive electrode cell, 40b ... Negative electrode cell, 42a ... Positive electrode, 42b ... Negative electrode, 44 ... Separator, 46 ... Bipolar plate, 48 ... Current collector Plate, 50a ... Positive electrode electrolyte, 50b ... Negative electrode electrolyte, 52a ... Positive electrode electrolyte reservoir, 52b ... Negative electrode electrolyte reservoir, 54 ... Feed pump, 56 ... Pipe, 58 ... Power source, 60 ... External load, 100a , 100b, 200 ... hydrogen detection device, 300 ... redox flow battery, L1 ... incident light, L2 ... transmitted light.

Claims (15)

The hydrogen generating member and the hydrogen detecting member are immersed in the liquid disposed in the container,
The liquid includes water;
The hydrogen generating member generates a gas containing hydrogen with an electrochemical reaction;
The hydrogen detection member contains at least one compound selected from the group consisting of tungsten oxide, molybdenum oxide, cobalt oxyhydroxide, and nickel oxyhydroxide,
The hydrogen generation member and the hydrogen detection member are electrically connected,
Hydrogen ions are supplied from the liquid to the hydrogen detection member,
Electrons are supplied from the hydrogen generation member to the hydrogen detection member,
According to the hydrogen ions and the electrons supplied to the hydrogen detection member, at least one of the color and electrical conductivity of the hydrogen detection member changes,
Detecting hydrogen in the liquid by measuring at least one of the change in color and the change in electrical conductivity;
How to detect hydrogen. The hydrogen generating member and the hydrogen detecting member are immersed in the liquid disposed in the container,
The liquid includes water;
The hydrogen generating member generates a gas containing hydrogen with an electrochemical reaction;
The hydrogen detection member contains at least one compound selected from the group consisting of tungsten oxide, molybdenum oxide, cobalt oxyhydroxide, and nickel oxyhydroxide,
The hydrogen generation member and the hydrogen detection member are electrically connected,
Hydrogen ions are supplied from the liquid to the hydrogen detection member,
Electrons are supplied from the hydrogen generation member to the hydrogen detection member,
Irradiating the hydrogen detection member with light, measuring the intensity of transmitted light that has passed through the hydrogen detection member,
From the intensity of the transmitted light, calculate a physical property value of the hydrogen detection member at least one of a light absorption coefficient, a transmittance, and an optical band gap,
Detecting hydrogen in the liquid based on a change in the physical property value according to the supply of the hydrogen ions and the electrons to the hydrogen detection member;
How to detect hydrogen. The compound is at least one selected from the group consisting of polycrystals, oriented crystals, and amorphous materials,
The method for detecting hydrogen according to claim 1 or 2. The hydrogen detection member further contains at least one metal catalyst selected from the group consisting of platinum, palladium, rhodium, iridium, ruthenium, osmium, cobalt, nickel and copper;
The method for detecting hydrogen according to any one of claims 1 to 3. The shape of the hydrogen detection member is at least one selected from the group consisting of a plate, a block, a ribbon, a rod, a wire, a sheet, a mesh, a lump, a particle, and a thin film.
The method for detecting hydrogen according to any one of claims 1 to 4. The hydrogen generating member is
A member that generates the gas by at least one of a photocatalytic reaction and a photochemical reaction;
Or
It is a battery electrode material with an electrochemical reaction,
The method for detecting hydrogen according to any one of claims 1 to 5. In the photochemical reaction, the hydrogen generating member containing a metal material is irradiated with light to generate the gas from the hydrogen generating member.
The method for detecting hydrogen according to claim 6. The metal material includes at least one selected from the group consisting of iron, copper, zinc, tin and titanium,
The method for detecting hydrogen according to claim 7. The battery is a secondary battery of any one of a lead storage battery, a nickel-zinc battery, and a redox flow battery.
The method for detecting hydrogen according to claim 6. The hydrogen generating member and the hydrogen detecting member are in direct contact;
The method for detecting hydrogen according to any one of claims 1 to 9. The conductive material connecting the hydrogen generation member and the hydrogen detection member is at least one selected from the group consisting of copper, silver, gold, platinum, aluminum, chromium, nickel, iron, tin, lead and brazing material. ,
The method for detecting hydrogen according to claim 1. In the liquid, each of the plurality of hydrogen detection members are electrically connected to different portions of the hydrogen generation member,
Monitoring the location where the gas is generated in the hydrogen generating member;
The method for detecting hydrogen according to any one of claims 1 to 11. A hydrogen detection device used in the hydrogen detection method according to claim 1,
The container;
The hydrogen generating member;
The hydrogen detection member electrically connected to the hydrogen generation member;
Comprising
Hydrogen detection device. A wiring portion for applying a current or voltage to the hydrogen detection member;
An electrical measurement device for measuring electrical conductivity of the hydrogen detection member;
Further comprising
The hydrogen detection device according to claim 13. A hydrogen detection device used in the hydrogen detection method according to claim 2,
The container;
The hydrogen generating member;
The hydrogen detection member electrically connected to the hydrogen generation member;
A light source unit for irradiating light to the hydrogen detection member;
An optical measuring device for measuring the intensity of the transmitted light;
Comprising
Hydrogen detection device.