JP5946038B2 - Method for generating hydrogen from hydrazine compounds - Google Patents

Description

  The present invention relates to a method for generating hydrogen from a hydrazine compound and a hydrogen generator used in the method.

  In recent years, hydrogen has been considered promising as a new energy source due to environmental problems and energy problems. For example, the development of hydrogen automobiles that use hydrogen directly as fuel and fuel cells that use hydrogen are being developed. The fuel cell has excellent advantages such as small size, high power generation efficiency, no generation of noise and vibration, and use of waste heat.

  When hydrogen is used as an energy source, it is necessary to supply hydrogen as a fuel safely and stably. A method for supplying hydrogen directly as compressed hydrogen or liquid hydrogen, or a hydrogen storage material such as a hydrogen storage alloy. Various methods have been proposed, such as a method for storing and supplying hydrogen by using hydrogen and a method for supplying hydrogen by steam reforming methanol or hydrocarbon.

  However, these methods can be used for production on a factory scale or generation of hydrogen to the extent that they can be used in laboratories, but the required amount of hydrogen fuel can be continuously supplied, and downsizing is required. It is unsuitable as a hydrogen supply method for automobile fuel cells; portable fuel cells for mobile phones, personal computers, and the like.

Hydrazine (H ₂ NNH ₂ ) is a compound having a high hydrogen content in addition to being a liquid at room temperature and being easy to handle, and is regarded as a promising source of hydrogen.

  As a method for generating hydrogen using hydrazine as a raw material, a method in which hydrazine or a derivative thereof is brought into contact with a metal catalyst for hydrogen generation such as nickel, cobalt, iron, copper, palladium, platinum or the like is known (patent document). 2). However, this method is a method in which an aqueous solution containing hydrazine is brought into contact with a catalyst to generate hydrogen by a chemical reaction, and it is difficult to control hydrogen generation after the reaction has started by contact with the catalyst. . In addition, when the metal catalyst described above is used, there is a problem that the selectivity of the hydrogen generation reaction is low and a sufficient amount of hydrogen generation is not obtained.

JP-A 61-42875 JP 2006-244961 A JP 2007-269514 A

  The present invention has been made in view of the current state of the prior art described above, and its main purpose is to use a hydrazine compound such as hydrazine or a hydrazine derivative as a hydrogen generation source under the conditions that can be controlled. It is an object of the present invention to provide a method capable of generating hydrogen well and a hydrogen generator suitable for this method.

  The present inventor has intensively studied to achieve the above-described object. As a result, a metal complex comprising a group 9 element or a group 8 element or group 9 element as a metal component and a nitrogen-containing polycyclic compound as a ligand is an electrochemical oxidation catalyst for a hydrazine compound. As a result, it was found that the activity of the hydrazine compound in the autolysis reaction was very low. And, by combining the electrochemical oxidation reaction of the hydrazine compound generated by using these metal complexes or metals as an anode catalyst with the hydrogen generation reaction at the cathode, it becomes possible to control the hydrogen generation rate and generation amount, Moreover, it has been found that the electrochemical energy generated during the hydrogen generation reaction can be used effectively. The present invention has been completed as a result of further research based on these findings.

That is, the present invention relates to the following hydrogen generation method and a hydrogen generation apparatus used in the method.
Item 1. A hydrogen generation method comprising immersing an anode electrode and a cathode electrode in an aqueous solution containing a hydrazine compound and electrically connecting both electrodes by an external circuit,
From the group consisting of (1) a metal comprising a group 9 element and (2) a metal complex comprising a group 8 element or a group 9 element as a metal component and a nitrogen-containing polycyclic compound as a ligand. A hydrogen generation method comprising at least one selected as an anode catalyst.
Item 2. Item 2. The hydrogen generation method according to Item 1, wherein the cathode electrode contains a metal composed of a Group 10 element as a cathode catalyst.
Item 3. Item 3. The method for generating hydrogen according to Item 1 or 2, further comprising applying a positive voltage to the anode electrode by a DC power source connected between the anode electrode and the cathode electrode.
Item 4. Item 4. The method for generating hydrogen according to any one of Items 1 to 3, wherein the hydrazine compound is at least one compound selected from the group consisting of hydrazine, hydrazine hydrate, and hydrazine derivatives.
Item 5. Item 5. The method for generating hydrogen according to any one of Items 1 to 4, wherein the aqueous solution containing a hydrazine compound is an alkaline aqueous solution having a pH of 11 or more.
Item 6. A container containing an aqueous solution containing a hydrazine compound with a hydrogen outlet;
An anode electrode and a cathode electrode installed in the container;
An external circuit that electrically connects the anode and cathode;
A hydrogen generator having an opening / closing part for opening and closing the external circuit,
The anode is composed of (1) a metal composed of a group 9 element, and (2) a metal complex including a group 8 element or a group 9 element as a metal component and a nitrogen-containing polycyclic compound as a ligand. A hydrogen generator comprising at least one selected from the above as an anode catalyst.
Item 7. A container containing an aqueous solution containing a hydrazine compound with a hydrogen outlet;
An anode electrode and a cathode electrode installed in the container;
A hydrogen generator having a direct current power source coupled between the anode and the cathode,
The anode is composed of (1) a metal composed of a group 9 element, and (2) a metal complex including a group 8 element or a group 9 element as a metal component and a nitrogen-containing polycyclic compound as a ligand. A hydrogen generator comprising at least one selected from the above as an anode catalyst.
Item 8. 8. The hydrogen generator according to 6 or 7, wherein the cathode electrode contains a metal composed of a group 10 element as a cathode catalyst.
Item 9. Item 7. The hydrogen generator according to Item 6, wherein the anode electrode catalyst is a catalyst having an anode electrode potential lower than the cathode electrode potential in an open circuit.

  Hereinafter, the hydrogen generation method of the present invention and the hydrogen generation apparatus used in the method will be described.

(1) Compound for generating hydrogen In the present invention, at least one hydrazine compound selected from the group consisting of hydrazine, hydrazine hydrate, and hydrazine derivatives is used as a compound that serves as a hydrogen generation source.

  Among these, specific examples of hydrazine derivatives include the following general formula:

(Wherein X ₁ represents a hydrogen atom or a lower alkyl group), a carbazic acid ester represented by the following general formula

(Wherein, X ₂ and X ₃ are the same or different and represent —NH ₂ , a hydrogen atom or a lower alkyl group), and the like.

  In the above general formulas, examples of the lower alkyl group include linear or branched alkyl groups having about 1 to 5 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, and n-butyl. , Isobutyl, tert-butyl, sec-butyl, n-pentyl, 1-ethylpropyl, isopentyl, neopentyl and the like.

  Specific examples of the carbazic acid ester represented by the above general formula include methyl carbazate and the like, and specific examples of the carbazic acid amide include carbohydrazide and the like.

  In the present invention, hydrazine, hydrazine hydrate, and hydrazine derivatives can be used singly or in combination of two or more as the hydrogen generation source.

(2) Hydrogen generation method The hydrogen generation method of the present invention requires the anode and cathode to be immersed in an aqueous solution containing a hydrazine compound as a raw material compound for hydrogen generation, and both electrodes are electrically connected by an external circuit. Accordingly, by connecting a DC power source between the two electrodes and applying a positive voltage to the anode electrode, an electrochemical oxidation reaction of the hydrazine compound as an anode reaction shown in the following chemical reaction formula and a water reaction as a cathode reaction are performed. This is a method of generating hydrogen by promoting a hydrogen generation reaction by an electrochemical reduction reaction. In the following reaction formula of the anode reaction, hydrazine is shown as a representative example.

Anode reaction: N ₂ H ₄ → N ₂ + 4H ⁺ + 4e ⁻
Cathode reaction: 4H ⁺ + 4e ⁻ → 2H ₂
According to this method, the amount of hydrogen generation can be controlled by opening / closing an external circuit in which the anode and cathode are electrically connected and controlling the applied voltage. For this reason, according to the required amount of hydrogen supply, hydrogen corresponding to the required amount can be generated only when necessary.

  Hereinafter, the electrode catalyst used in the hydrogen generation method of the present invention will be described.

(I) Anode catalyst In the hydrogen generation method of the present invention, the catalyst used for the anode reaction includes (1) a metal composed of a group 9 element, and (2) a group 8 element or a group 9 element as a metal component. At least one selected from the group consisting of a metal complex containing a nitrogen-containing polycyclic compound as a child is used.

  These metals and metal complexes are all active against the electrochemical oxidation reaction of hydrazine compounds, and are not active or very active against the self-decomposition reaction of hydrazine compounds. It is a very low substance.

  For this reason, by using the above-mentioned catalyst as a catalyst for the anode electrode, when the anode electrode and the cathode electrode are electrically connected, the reaction rate of the hydrogen generation reaction can be improved, and between the anode electrode and the cathode electrode. When the circuit is opened, the hydrogen generation reaction can be controlled or the hydrogen generation reaction can be stopped.

  Among the above-mentioned anode catalyst, cobalt, rhodium, iridium and the like can be exemplified as specific examples of the metal composed of a group 9 element. The form of the catalyst made of these metals is not particularly limited, and any form of metal can be used. For example, a linear metal can be used.

  Examples of the group 8 element in the metal complex include iron and ruthenium, and examples of the group 9 element include cobalt, rhodium and iridium. Examples of the nitrogen-containing polycyclic compound used as the ligand include porphyrin compounds, phthalocyanine compounds, and salen compounds.

  The anode catalyst used in the present invention may be a metal complex containing a group 8 element or a group 9 element as a metal component and a nitrogen-containing polycyclic compound as a ligand. Is not particularly limited.

  Hereinafter, preferable specific examples of the metal complex which is an active component of the anode catalyst will be shown.

  (1) Chemical formula:

(Wherein R _{1 to} R ₁₂ are the same or different and each represents an alkyl group, an aryl group which may have a substituent, a hydrogen atom or a halogen atom, and M represents a group 8 element or a group 9 element. A metal porphyrin complex represented by:

  In the above chemical formula, the central metal element represented by M is a group 8 element or a group 9 element, and specific examples thereof include iron, ruthenium, cobalt, rhodium and the like.

R _{1 to} R ₁₂ are the same or different and each represents an alkyl group, an aryl group that may have a substituent, a hydrogen atom, or a halogen atom. Among these, as an alkyl group, methyl, ethyl, isopropyl, n-propyl, t-butyl, sec-butyl, n-butyl, isobutyl, n-pentyl, etc. A branched lower alkyl group is preferred. Further, as the halogen atom, fluorine, chlorine, bromine and the like are preferable. As the aryl group which may have a substituent, a phenyl group, a phenyl group having a substituent, a pyridyl group, a pyridyl group having a substituent, and the like are preferable.

Among these, when R ₁ , R ₄ , R _7, and R ₁₀ are all aryl groups that may have a substituent, the meso position is chemically protected, so that the oxidation reaction and the like are prevented. Increases stability.

Among the aryl groups having a substituent, examples of the pyridyl group having a substituent include a 1-methylpyridyl group. Examples of the substituent in the phenyl group having a substituent include a lower alkoxy group, a lower alkyl group, a halogen atom, —SO ₃ M ¹ (wherein M ¹ is a hydrogen atom, an alkali metal, or —NH ₄ ), —COOM. ² (wherein M ² is a hydrogen atom, an alkali metal, —NH ₄ or an alkyl group), —OCH ₂ —COOM ³ (wherein M ³ is a hydrogen atom, an alkali metal, —NH ₄ or an alkyl group) And the like.

  Among these, as a phenyl group having a lower alkoxy group as a substituent, a para-methoxyphenyl group and the like, and as a phenyl group having a lower alkyl group as a substituent, a para-methylphenyl group, 2,4,6-trimethyl Examples of the phenyl group having a halogen atom as a substituent such as a phenyl group include a pentafluorophenyl group.

Among the substituents of the phenyl group, the _-SO 3 ^{M 1, M 1} is a hydrogen atom, an alkali metal or -NH _4. Among these, examples of the alkali metal include K and Na. Among the substituents of the phenyl group, in —COOM ² , M ² is a hydrogen atom, an alkali metal, —NH ₄ or an alkyl group. Among these, examples of the alkali metal include K and Na. Examples of the alkyl group include the same groups as those described above. Among the substituents of the phenyl group, in —OCH ₂ —COOM ³ , M ³ is a hydrogen atom, an alkali metal, —NH ₄ or an alkyl group. Among these, examples of the alkali metal include K and Na. Examples of the alkyl group include the same groups as those described above.

Substituents such as —SO ₃ M ¹ , —COOM ² and —OCH ₂ —COOM ³ can be substituted at the 4-position of the phenyl group, for example, but are not limited thereto.

As a representative example of the porphyrin complex represented by the above chemical formula, R ₁ , R ₄ , R ₇ and R ₁₀ are phenyl groups that may have a substituent, and R _2, R ₃ , R ₅ , R ₆ , A tetraphenylporphyrin complex in which R ₈ , R ₉ , R ₁₁ and R ₁₂ are hydrogen atoms; R ₁ , R ₄ , R ₇ and R ₁₀ are hydrogen atoms, and R _2, R ₃ , R ₅ , R ₆ , R ₈ , R ₉ , R ₁₁ and R ₁₂ are octaalkylporphyrin complexes in which a lower alkyl group is exemplified.

  (2) Chemical formula

(Wherein R _{1 to} R ₈ are the same or different and each represents a hydrogen atom, an alkyl group, a hydroxyalkyl group, an alkenyl group, a group: —SO ₃ M ₁ (wherein M ₁ represents a hydrogen atom, an alkali A metal or —NH ₄ ), or a group: —R ₉ —COOM ₂ (wherein R ₉ is a linear or branched alkylene group, and M ₂ is a hydrogen atom, an alkali metal or an alkyl group) Or at least one combination of R ₁ and R ₂ , R ₃ and R ₄ , R ₅ and R ₆ , R ₇ and R ₈ is bonded to each other, and these groups are bonded to each other. An aromatic ring which may have a substituent may be formed together with the carbon atom to perform M. M represents a group 8 element or a group 9 element, provided that at least one of R _{1 to} R ₈ is a group: metal porphyrin complex represented by -R ₉ is a -COOM _2).

  In the above chemical formula, the central metal element represented by M is a group 8 element or a group 9 element, and specific examples thereof include iron, ruthenium, cobalt, rhodium and the like.

  In the above chemical formula, the alkyl group is linear or branched having about 1 to 5 carbon atoms such as methyl, ethyl, isopropyl, n-propyl, t-butyl, sec-butyl, n-butyl, isobutyl, n-pentyl and the like. A chain-like lower alkyl group is preferred.

  As the alkyl group portion of the hydroxyalkyl group, a straight chain having about 1 to 5 carbon atoms such as methyl, ethyl, isopropyl, n-propyl, t-butyl, sec-butyl, n-butyl, isobutyl, n-pentyl or the like A branched lower alkyl group can be exemplified. The hydroxy group can be substituted on any carbon atom of the alkyl group.

  Examples of the alkenyl group include linear or branched alkenyl groups having 2 to 6 carbon atoms such as vinyl, allyl, 2-butenyl, 3-butenyl, 1-methylallyl, 2-pentenyl, 2-hexenyl and the like. Can do.

In the group: —SO ₃ M ₁ , M ₁ is a hydrogen atom, an alkali metal, or —NH ₄ . Among these, examples of the alkali metal include K and Na.

In the group: —R ₉ —COOM ₂ , as the alkylene group represented by R ₉ , for example, methylene, ethylene, trimethylene, 2-methyltrimethylene, 2,2-dimethyltrimethylene, 1-methyltrimethylene, methylmethylene C1-C6 linear or branched alkylene groups such as ethylmethylene, tetramethylene, pentamethylene and hexamethylene groups. The alkyl group and alkali metal represented by M ₂ are the same as those described above.

  (3) Chemical formula

(Wherein R _{1 to} R ₁₆ are the same or different and each represents a hydrogen atom, an alkyl group, an alkoxyl group, a halogen atom or a sulfonic acid group, or R ₂ and R ₃ , R ₆ and R _7). , R ₁₀ and R ₁₁ , and each combination of R ₁₄ and R ₁₅ are bonded to each other to form an aromatic ring which may have a substituent together with the carbon atom to which these groups are bonded. M represents a group 8 element or a group 9 element.) A metal phthalocyanine complex represented by:

  In the above chemical formula, the central metal element represented by M is a group 8 element or a group 9 element, and specific examples thereof include iron, ruthenium, cobalt, rhodium and the like.

In the above chemical formula, R _{1 to} R ₁₆ are the same or different and each represents a hydrogen atom, an alkyl group, an alkoxyl group, a halogen atom, or a sulfonic acid group. Further, among these, at least one of each combination of R ₂ and R ₃ , R ₆ and R ₇ , R ₁₀ and R ₁₁ , R ₁₄ and R ₁₅ is bonded to each other, and these groups are bonded. You may form the aromatic ring which may have a substituent with a carbon atom.

  Among these, as an alkyl group, methyl, ethyl, isopropyl, n-propyl, t-butyl, sec-butyl, n-butyl, isobutyl, n-pentyl, etc. A branched lower alkyl group is preferred. Examples of the alkoxy group include straight chain or branched chains having 1 to 6 carbon atoms such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, tert-butoxy, n-pentyloxy, n-hexyloxy group, and the like. An alkoxyl group is preferred. Further, as the halogen atom, fluorine, chlorine, bromine and the like are preferable.

Each combination of R ₂ and R ₃ , R ₆ and R ₇ , R ₁₀ and R ₁₁ , R ₁₄ and R ₁₅ is bonded to each other, and has a substituent together with the carbon atom to which these groups are bonded. As an aromatic ring-containing compound, the following chemical formula

The compound represented by these can be illustrated. In the above chemical formula, R _{17 to} R ₃₂ are the same or different and each represents a hydrogen atom, an alkyl group, an alkoxyl group, a halogen atom, or a sulfonic acid group. Specific examples of each of these groups are the same as R _{1 to} R ₁₆ .

  (4) Chemical formula:

(Wherein, M represents a group 8 element or a group 9 element).

  In the above chemical formula, the central metal element represented by M is a group 8 element or a group 9 element, and specific examples thereof include iron, ruthenium, cobalt, rhodium and the like.

  In the salen complex described above, an arbitrary substituent may be present on the salen ring.

Method for Producing Metal Complex The metal complex described above can be produced , for example, by dissolving a compound serving as a ligand of the target complex and the metal compound in a solvent and heating.

  As the solvent, a solvent capable of dissolving the ligand compound and the metal compound may be used. For example, ethanol, dimethylformamide, or the like can be used. The heating temperature may be, for example, the reflux temperature of the solvent used.

Supported Catalyst The above-described metal complex can have a high catalytic activity for an electrochemical oxidation reaction of a hydrazine compound by being supported on a conductive carrier.

  The conductive carrier is not particularly limited, and for example, various carriers conventionally used as catalyst carriers for polymer electrolyte fuel cells can be used. Specific examples of such a carrier include carbonaceous materials such as carbon black, activated carbon, and graphite. Among these, carbon black is a particularly preferable substance as a conductive carrier because it is excellent in conductivity and has a large specific surface area.

The shape of the conductive carrier is not particularly limited, and for example, a conductive carrier having an average particle diameter of about 0.1 to 100 μm, preferably about 1 to 10 μm can be used. Further, when carbon black is used, for example, is preferably one in the range BET specific surface area of about 100~800m ² / g, more is intended to be within the range of about 200 to 300 [m ² / g preferable. Specific examples of such carbon black include those marketed under the trade name Vulcan XC-72R (Cabot).

  As a method for supporting the conductive carrier, for example, a known method such as a dissolution drying method or a gas phase method can be applied.

  For example, in the dissolution drying method, a metal complex is dissolved in an organic solvent, and a conductive carrier is added to this solution. For example, the metal complex is adsorbed on the carrier by stirring for several hours, and then the organic solvent is dried. Just do it. In addition, when a large amount of metal complex is contained in the organic solvent, the metal complex that is not adsorbed on the conductive support is removed by filtering after adsorbing the metal complex on the conductive support until equilibrium is reached. Thus, only the metal complex interacting with the support can be left on the surface of the support.

  In this method, any organic solvent can be used without particular limitation as long as it can dissolve the metal complex. For example, chlorinated hydrocarbons such as dichloromethane and chloroform and lower alcohols such as ethanol can be preferably used.

  If the dispersion obtained by filtration is further washed with an organic solvent until the washing liquid becomes transparent, the metal complex having a weak interaction with the conductive carrier can be washed away and firmly adsorbed on the conductive carrier. It is possible to obtain a highly active catalyst containing only the metal complex.

  In the case of carrying by a vapor phase method, for example, a known method such as a plasma vapor deposition method, a CVD method, or a heating vapor deposition method can be adopted.

The amount of the metal complex to be supported on the conductive carrier is not particularly limited.
The amount of the metal complex to be supported on the conductive carrier is not particularly limited. For example, it is preferable to carry about 10 μmol to 1000 μmol of the metal complex with respect to 1 g of the conductive carrier, and about 20 μmol to 100 μmol. Is more preferable.

(Ii) Cathode catalyst In the hydrogen generation method of the present invention, as a catalyst for the cathode reaction, a metal, metal oxide or the like having a low overvoltage in the reaction of generating water by electrochemical reduction of water can be used. . In the present invention, it is particularly preferable to use a metal composed of a group 10 element as a cathode catalyst. A metal composed of a group 10 element is a substance that has a low overvoltage for the electrochemical reduction reaction of water and has little activity for the self-decomposition reaction of the hydrazine compound, and is only immersed in an aqueous solution containing the hydrazine compound. Then, the hydrazine decomposition reaction and the hydrogen generation reaction are scarcely advanced, and the hydrogen generation reaction can be promoted by electrically connecting to the anode electrode and applying a voltage as necessary. it can.

(Iii) Hydrogen generation method In the hydrogen generation method of the present invention, the anode electrode having the anode catalyst and the cathode electrode having the cathode catalyst are immersed in an aqueous solution containing a hydrazine compound, and both electrodes are electrically connected by an external circuit. Connect to. At this time, when the potential of the anode electrode in the open circuit is more negative than the potential of the cathode electrode, the reaction rate of the hydrogen generation reaction at the cathode electrode is reduced by closing the external circuit and electrically connecting both electrodes. It can rise and promote hydrogen generation. Further, the hydrogen generation rate can be improved by connecting a direct current power source between both electrodes and applying a positive voltage to the anode electrode.

  In addition, when the anode potential in the open circuit is more positive than the cathode potential, the hydrogen generation reaction is promoted only by electrically connecting the anode electrode immersed in the aqueous solution containing the hydrazine compound and the cathode electrode. However, it is possible to increase the hydrogen generation rate by connecting a DC power source between both electrodes and applying a positive voltage to the anode electrode. The magnitude of the voltage to be applied is appropriately determined according to the type of hydrazine compound to be used, the state of the aqueous solution, the type of anode catalyst, the type of cathode catalyst, the target hydrogen generation rate, the amount of hydrogen generation, etc. Just decide.

  The anode electrode and the cathode electrode are not particularly limited as long as they are electrodes having the above-described anode catalyst and cathode catalyst.

  For example, when a group 9 element metal is used as the anode catalyst and a group 10 element metal is used as the cathode catalyst, a metal wire made of these metals can be used as the anode electrode as it is.

Further, when using the metal complex described above as an anode catalyst or a supported catalyst in which the metal complex is supported on a conductive support, the anode catalyst is applied to a conductive substrate such as a carbon material (Vulcan XC72R, Ketjen Black, etc.). Can be used. Although there is no particular limitation on the amount of catalyst in the anode electrode, for example, be a 0.1 to 5.0 mg / cm ² or so, it is preferable to 0.1-3.0 mg / cm ² or so.

  In the hydrogen generation method of the present invention, the concentration of the hydrazine compound in the aqueous solution containing the hydrazine compound is not particularly limited, but in order to efficiently generate hydrogen, the concentration of the hydrazine compound described above is 1 mmol / L to The content is preferably about 5 mol / L, more preferably about 0.2 mol / L to 1.5 mol / L.

  Furthermore, the aqueous solution containing the hydrazine compound is preferably alkaline, and particularly preferably has a pH of about 11 or more.

  In the hydrogen generation method of the present invention, the temperature of the aqueous solution containing the hydrazine compound is not particularly limited, and the reaction can usually proceed at room temperature.

  FIG. 1 shows a schematic diagram of one embodiment of a hydrogen generator used in the hydrogen generation method of the present invention.

  The apparatus shown in FIG. 1 is connected to a container that contains an aqueous solution containing a hydrazine compound, having a hydrogen outlet, an anode electrode and a cathode electrode installed in the container, and connected between the anode electrode and the cathode electrode. The anode electrode includes (1) a metal composed of a group 9 element, and (2) a group 8 element or a group 9 element as a metal component, and a nitrogen-containing polycycle as a ligand. At least one selected from the group consisting of metal complexes containing a formula compound is included as an anode catalyst.

  The anode catalyst used in the present invention has high activity for the electrochemical oxidation reaction of the hydrazine compound, and is inactive for the autolysis reaction of the hydrazine compound, or very active. It is a low substance. For this reason, in the state which opened the external circuit which connects an anode pole and a cathode pole, hydrogen generation by the self-decomposition of hydrazine hydride can be suppressed. Also, by closing the external circuit and adjusting the voltage applied from the external power source according to the type of electrolyte used, the type of anode catalyst, the type of cathode catalyst, etc., the rate of hydrogen generation reaction, the amount of hydrogen generated, etc. Can be controlled easily. Specifically, in the hydrogen generator having the structure described above, when the potential of the anode electrode in the open circuit is lower than the potential of the cathode electrode, the hydrogen generation reaction based on the above-described reaction proceeds by closing the external circuit. Can be made. Furthermore, if necessary, a positive voltage is applied to the anode electrode using a DC power source connected between the two electrodes, and the potential is adjusted to control the hydrogen generation rate, the hydrogen generation amount, and the like. In addition, when the potential of the anode electrode in the open circuit is higher than the potential of the cathode electrode, the hydrogen generation reaction is allowed to proceed by applying a positive voltage to the anode electrode using a DC power source connected between both electrodes. Can do. For this reason, it is possible to control the hydrogen generation rate, the hydrogen generation amount, and the like by adjusting the voltage applied between the two electrodes.

  In particular, when the potential of the anode electrode in the open circuit is lower than the potential of the cathode electrode, the hydrogen generation reaction can be promoted even when the hydrogen generator not including an external power source shown in FIG. 2 is used. . The hydrogen generator shown in FIG. 2 has a hydrogen outlet and a container containing an aqueous solution containing a hydrazine compound, an anode electrode and a cathode electrode installed in the container, and the anode electrode and the cathode electrode are electrically connected. And an open / close section that opens and closes the external circuit, and has the above-described specific catalyst as an anode catalyst.

  The hydrogen generator shown in FIG. 2 can spontaneously advance the cathode reaction and the anode reaction by closing the external circuit, so no external power source is required for hydrogen generation, and the structure of the device is simplified. Is done. Furthermore, according to the hydrogen generator shown in FIG. 2, the hydrogen generation reaction proceeds by simply closing the external circuit, so that the potential difference between the cathode potential and the anode potential during the hydrogen generation reaction can be acquired as electric energy. For this reason, it becomes possible to obtain chemical energy and electric energy with high energy conversion efficiency from a hydrazine compound as a raw material as a hydrogen generator having a self-power generation action.

  Although there is no limitation in particular about the use of the hydrogen generated using the hydrogen generator of the present invention, for example, it can be used as a fuel for a fuel cell. In this case, for example, the generated hydrogen may be supplied to the fuel cell by joining the hydrogen outlet of the hydrogen generator described above to the hydrogen supply line.

  According to the hydrogen generation method and the hydrogen generation apparatus of the present invention, the amount of hydrogen generation can be controlled using hydrazine compounds such as hydrazine, hydrazine derivatives, and hydrates thereof having a high hydrogen content as a hydrogen generation source. Hydrogen can be generated efficiently under mild conditions.

  For this reason, the hydrogen generation method of the present invention is a very useful method as means for supplying hydrogen to, for example, a fuel cell.

The schematic block diagram which shows one embodiment of the hydrogen generator of this invention. The schematic block diagram which shows the other embodiment of the hydrogen generator of this invention. The current-voltage curve at the time of hydrogen generation reaction measured in Example 1 and 2. FIG. The current-voltage curve at the time of hydrogen generation reaction measured in Example 3 and 4. FIG. The graph which shows the measurement result of the cyclic voltammogram with respect to the hydrazine measured in Reference Example 1. The graph which shows the measurement result of the cyclic voltammogram with respect to the carbohydrazide measured in Reference Example 1. The graph which shows the measurement result of the cyclic voltammogram with respect to the methyl carbazate measured in Reference Example 1.

  Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1
A hydrogen generation test was conducted by the following method using the hydrogen generator having the structure shown in FIG.

  First, 10.5 mL of an aqueous solution of pH 13.8 containing 1 mol / L of hydrazine and 1 mol / L of NaOH was placed in a 25 mL glass container. A cobalt wire (0.05 cm in diameter) and a platinum wire (0.05 cm in diameter) were each immersed in this aqueous solution to a depth of 2.1 cm, and this container was sealed with a rubber stopper provided with a hydrogen outlet. The cobalt wire and the platinum wire immersed in the aqueous solution containing hydrazine were exposed to the outside of the container through the rubber plugs and connected with a copper wire to form an external circuit. The external circuit is provided with a switch for opening and closing the circuit.

With the external circuit opened using a switch installed in the external circuit, 130 minutes later, hydrogen gas in the gas phase was quantified. The amount of hydrogen generated per unit surface area of the cathode electrode was 0.0052 μmol / min · cm ² , and only slight hydrogen generation was confirmed.

Thereafter, the external circuit was closed by a switch installed in the external circuit, the cobalt wire and the platinum wire were electrically connected, and 130 minutes later, the hydrogen gas in the gas phase was quantified. The amount of hydrogen generated per unit surface area of the cathode electrode was 0.054 μmol / min · cm ² , greatly increasing the hydrogen generation rate.

  From this result, in the hydrogen generator of the above structure. Almost no hydrogen is generated when the external circuit is opened and the cobalt wire and the platinum wire are not connected, but by closing the external circuit and electrically connecting the cobalt wire and the platinum wire, It became clear that the hydrogen generation reaction was controlled by opening and closing the external circuit.

Further, in the above-described hydrogen generator, the cobalt wire exposed to the outside of the container containing the hydrazine aqueous solution and the platinum wire were connected via an external resistor, and a current-voltage curve in a state where hydrogen was generated was obtained. The results are shown in FIG. In the current-voltage curve of FIG. 3, the terminal voltage indicates the voltage of the platinum wire with respect to the cobalt wire, and the current value indicates the reduction current on the platinum as positive.
As can be seen from FIG. 3, the reduction current on platinum is positive in the region where the potential is positive, and it can be confirmed that power is generated simultaneously with the generation of hydrogen.

Example 2
A hydrogen generation test was conducted in the same manner as in Example 1 except that the NaOH concentration in the aqueous solution containing hydrazine was changed to 0.1 mol / L (pH 13.1). The results are shown in Table 1 below.

  Further, in the above hydrogen generator, a cobalt wire and a platinum wire were connected via an external resistor, and a current-voltage curve in a state where hydrogen was generated was obtained. The results are shown in Figure 3. In the current-voltage curve of FIG. 3, the terminal voltage indicates the voltage of the platinum wire with respect to the cobalt wire, and the current value indicates the reduction current on the platinum as positive.

  As can be seen from FIG. 3, the reduction current on the platinum is positive in the region where the potential is positive, and it can be seen that power is generated simultaneously with the generation of hydrogen.

Example 3
A hydrogen generation test was conducted in the same manner as in Example 1 except that a nickel wire (diameter 0.05 cm) was used instead of the platinum wire. The results are shown in Table 1 below.

In the above hydrogen generator, a cobalt wire and a nickel wire were connected via an external resistor, and a current-voltage curve in a state where hydrogen was generated was obtained. The results are shown in Figure 4. In the current-voltage curve of FIG. 4, the voltage between terminals indicates the voltage of nickel with respect to the cobalt wire, and the current value indicates the reduction current on the nickel wire as positive.

As is apparent from FIG. 4 , the reduction current on nickel is positive in the region where the potential is positive, and it can be seen that power is generated simultaneously with the generation of hydrogen.

Example 4
A hydrogen generation test was conducted in the same manner as in Example 1 except that a rhodium wire (0.05 cm in diameter) was used instead of the cobalt wire. The results are shown in Table 1 below.

In the above hydrogen generator, a rhodium wire and a platinum wire were connected via an external resistor, and a current-voltage curve in a state where hydrogen was generated was obtained. The results are shown in Figure 4. In the current-voltage curve of FIG. 4, the voltage between terminals indicates the voltage of the platinum wire relative to the rhodium wire, and the current value indicates the reduction current on platinum as positive.

As is apparent from FIG. 4 , the reduction current on platinum is positive in the positive potential region, and it can be seen that power is generated simultaneously with the generation of hydrogen.

Example 5
The following chemical formula

After dissolving 0.9 micromol of a cobalt octaethylporphyrin complex (produced by Aldrich) in 20 mL of dichloromethane, carbon black (specific surface area 250 m ² / g, trade name: Vulcan XC 72R) (Manufactured by Cabot) and carbon black was well dispersed using an ultrasonic cleaner, and then the solvent was distilled off by a rotary evaporator to support the cobalt octaethylporphyrin complex on the carbon black.

Next, 5 mg of carbon black carrying a cobalt octaethylporphyrin complex is suspended in a mixed solvent containing 0.25 mL of ethanol, 0.25 mL of water, and Nafion 0.005 mL, and this suspension is added to 0.1 mL of a glassy carbon plate. It was applied and allowed to dry (the area where the catalyst was applied was 2.25 cm ² ).

A glass container with a size of 13.8 pH 13.8 containing 1 mol / L of carbohydrazide and 1 mol / L of NaOH is placed in a 25 mL glass container, and a glassy glass in which a cobalt octaethylporphyrin complex is supported in this aqueous solution by the method described above. A carbon plate and platinum wire (diameter 0.1 cm) were immersed, and the container was sealed with a rubber stopper provided with a hydrogen outlet. The glassy carbon plate was dipped in the entire coated surface of the catalyst, and the area in which the platinum wire was dipped was 2.25 cm ² . The glassy carbon plate and the platinum wire were exposed to the outside of the container through their rubber plugs and connected with a copper wire to form an external circuit. The external circuit was provided with a switch for opening and closing the circuit, and an external DC power source was connected to the glassy carbon plate and the platinum wire.

  With the external circuit opened, hydrogen gas in the gas phase was quantified after 40 minutes, but hydrogen could not be detected.

After that, the external circuit was closed, the glassy carbon plate and the platinum wire were electrically connected, and when a voltage was applied using a potentiostat so that the glassy carbon plate was 0.5 V positive with respect to platinum, hydrogen was generated. A reaction occurred. After 40 minutes, the amount of hydrogen gas in the gas phase was quantified. As a result, the amount of hydrogen generated per surface area of the glassy carbon plate was 0.030 μmol / min · cm ² .

  From the above results, it was found that hydrogen generation can be controlled by applying a voltage from an external power source.

Reference Examples 1-9
Hereinafter, with reference examples, a metal complex containing a group 8 element or a group 9 element as a metal component and a nitrogen-containing polycyclic compound as a ligand is active against an electrochemical oxidation reaction of a hydrazine compound. It shows that it has.

(I) Production of supported carbon catalyst Each metal complex shown in Tables 2 and 3 below was used as a catalyst component, and after dissolving each metal complex in a solvent, carbon black (specific surface area 250 m ² / g, 30 mg of Vulcan XC 72R (trade name, manufactured by Cabot) was added. As the solvent, dichloromethane was used in Reference Examples 1, 3, 6, 7, and 8, distilled water was used in Reference Example 2, dimethylformamide was used in Reference Examples 4 and 5, and ethanol was used in Reference Example 9. All amounts were 20 mL. The amount of metal complex added in each solution was 0.9 micromolar.

  Next, for each solution in which the carbon black was suspended, the carbon black was well dispersed using an ultrasonic cleaner, and then the solvent was distilled off by a rotary evaporator, whereby each metal complex was supported on the carbon black. .

(Ii) Evaluation of catalytic activity The catalyst with each metal complex supported on carbon black was crushed in a mortar by the method described above, and 5 mg was suspended in 0.5 mL of a mixed solvent (water: ethanol = 1: 1). After that, 5 μL of 5% Nafion solution (manufactured by Aldrich) was added. This suspension was placed in an ultrasonic cleaner for 5 minutes to be well dispersed, and then 2 μL was placed on a rotating disk electrode (diameter 3 mm) and dried.

  Evaluation of the oxidation activity of each catalyst with respect to the hydrazine compound was performed using a potentiostat (ALS model 711B) manufactured by ALS. A glassy carbon rotating disk electrode coated with a catalyst was used as a working electrode, a platinum electrode as a counter electrode, and an Ag / AgCl / KCl (sat.) Electrode as a reference electrode.

  Hydrazine, carbohydrazide, and methyl carbazate were used as the hydrazine compound, and 1 M NaOH was used as the electrolyte. Each hydrazine compound was added to this electrolyte so as to be 1 mol / L, and dissolved oxygen was removed by bubbling argon, and then a cyclic voltammogram was measured at a sweep rate of 10 mV / s. During the measurement, oxygen gas was prevented from being mixed by blowing argon gas over the solution.

  Regarding the catalyst in which cobalt octaethylporphyrin of Reference Example 1 is supported on carbon black, the results of cyclic voltammogram measurement in an electrolytic solution in which hydrazine compounds of hydrazine, carbohydrazide, and methyl carbazate are dissolved are shown in FIG. As shown in FIG. In addition, in the cyclic voltammogram of FIGS. 5-7, an oxidation current is shown with a negative value.

FIG. 5 shows the measurement results for hydrazine. The oxidation current starts to flow around −0.6 V, and the oxidation current rapidly increases as the potential becomes positive. The current value at −0.4 V is 1.7 mA. (24 mA / cm ^{2 in} current density) was exceeded. Fig. 6 shows the measurement results for carbohydrazide. The oxidation current started to flow around -0.6 V, and the current value at -0.4 V exceeded 1.5 mA (21 mA / cm ^{2 in} current density). . Fig. 7 shows the measurement results for methyl carbazate. Current starts to flow around -0.5 V, and the current value at -0.4 V exceeds 0.13 mA (1.8 mA / cm ^{2 in} current density). It was.

  As is clear from the above results, the catalyst in which cobalt octaethylporphyrin is supported on carbon black gives an oxidation current to each hydrazine compound of hydrazine, carbohydrazide, and methyl carbazate, and these compounds are electrically connected. It became clear that it could be chemically oxidized.

  In the following Tables 2 and 3, with each metal complex in Reference Example 1 to Reference Example 9 as a catalyst component, with respect to the supported catalyst obtained by the same method as the method for preparing the supported carbon catalyst, Indicates the current value (A / g) per gram of metal obtained at -0.4 V. From this result, it was confirmed that each metal complex of Reference Examples 1 to 9 effectively acts as a catalyst for an electrochemical oxidation reaction with respect to hydrazine, carbohydrazide, and methyl carbazate.

Claims (7)

A hydrogen generation method comprising immersing an anode electrode and a cathode electrode in an aqueous solution containing a hydrazine compound and electrically connecting both electrodes by an external circuit,
From the group consisting of (1) a metal comprising a group 9 element and (2) a metal complex comprising a group 8 element or a group 9 element as a metal component and a nitrogen-containing polycyclic compound as a ligand. all SANYO containing at least one selected as the anode catalyst,
Cathode electrode, Ru der those containing metal comprising a Group 10 element as a cathode catalyst, the hydrogen generation methods. The method for generating hydrogen according to claim 1, further comprising applying a positive voltage to the anode electrode by a DC power source connected between the anode electrode and the cathode electrode. The method for generating hydrogen according to claim 1 or 2 , wherein the hydrazine compound is at least one compound selected from the group consisting of hydrazine, hydrazine hydrate, and hydrazine derivatives. The method for generating hydrogen according to any one of claims 1 to 3 , wherein the aqueous solution containing a hydrazine compound is an alkaline aqueous solution having a pH of 11 or more. A container containing an aqueous solution containing a hydrazine compound with a hydrogen outlet;
An anode electrode and a cathode electrode installed in the container;
An external circuit that electrically connects the anode and cathode;
A hydrogen generator having an opening / closing part for opening and closing the external circuit,
The anode is composed of (1) a metal composed of a group 9 element, and (2) a metal complex including a group 8 element or a group 9 element as a metal component and a nitrogen-containing polycyclic compound as a ligand. der those containing at least one as an anode catalyst selected from is,
Cathode electrode, Ru der those containing metal comprising a Group 10 element as a cathode catalyst, the hydrogen generating apparatus. A container containing an aqueous solution containing a hydrazine compound with a hydrogen outlet;
An anode electrode and a cathode electrode installed in the container;
A hydrogen generator having a direct current power source coupled between the anode and the cathode,
The anode is composed of (1) a metal composed of a group 9 element, and (2) a metal complex including a group 8 element or a group 9 element as a metal component and a nitrogen-containing polycyclic compound as a ligand. der those containing at least one as an anode catalyst selected from is,
Cathode electrode, Ru der those containing metal comprising a Group 10 element as a cathode catalyst, the hydrogen generating apparatus. 6. The hydrogen generator according to claim 5 , wherein the potential of the anode electrode in an open circuit is lower than the potential of the cathode electrode.

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