JPH0631449B2 - Hydrogen storage / release method and hydrogen storage / release device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a hydrogen storage / release method and a hydrogen storage / release apparatus.

[Prior art and its problems] Currently, primary energy is mainly fossil fuels such as petroleum, coal and natural gas, but it is estimated that non-fossil fuels such as nuclear power and natural energy will be mainly in the future. .

Therefore, hydrogen is drawing attention as a secondary energy that replaces city gas and gasoline.

Hydrogen is an abundant resource. Further, since it is clean, it does not disturb the natural environment and can economically and efficiently perform energy conversion, transportation and storage, and various energy systems centered on hydrogen are being planned.

Heretofore, a hydrogen storage alloy has attracted attention as a hydrogen storage method.

The hydrogen storage alloy is an alloy composed of a combination of special metals such as Fe-Ti and La-Ni, which enables storage and release of hydrogen by the operation of temperature and pressure. Large amount of hydrogen storage (approx. 3-5 of gas cylinder)
Double), and has the advantage of higher safety compared to storage by gas cylinder.

However, the hydrogen storage alloy has the following problems.

(1) Activation operation (heating and degassing under reduced pressure,
The step of pressurizing hydrogen gas and injecting hydrogen gas into the alloy is repeated. ) Is required and is complicated.

(2) A step of pulverizing the alloy is necessary.

(3) Durability is not yet sufficient due to changes in morphology such as pulverization of the alloy due to storage and release cycles.

(4) The price is so high that it doesn't go on a commercial basis.

(5) Temperature and pressure changes that promote storage and release of hydrogen are not smoothly transmitted to the alloy, making temperature and pressure control difficult.

[Object of the Invention] The present invention has been made based on the above circumstances.

That is, an object of the present invention is to provide a hydrogen storage / release method that does not require an activation operation, does not use a special alloy as a hydrogen storage / release material, and can efficiently store and release hydrogen with a simple operation. A hydrogen storage / release device is provided.

[Means for Achieving the Object] The gist of the first invention for achieving the object is to provide an electrode in a solution of a reducible oxyacid and / or a salt thereof, and to add the solution and hydrogen gas. Gas is separated by a gas-liquid separation membrane that is permeable to protons, and a battery is formed by connecting an electrode formed on the gas contact surface of the gas-liquid separation membrane and an electrode in the solution to form a battery. By storing hydrogen in the solution and applying a voltage between the electrode in the solution and the electrode in the gas-liquid separation membrane, it is possible to release the hydrogen stored in the solution to the outside of the gas-liquid separation membrane. A hydrogen absorption / desorption method characterized by the above, and the gist of a second invention is to store a solution of a reducible oxyacid and / or its salt and to provide a container with an electrode in the solution; When the gas containing hydrogen gas is isolated A proton-permeable gas-liquid separation membrane that together forms an electrode on the gas-side surface, and when hydrogen is stored, the electrode in the solution and the electrode in the gas-liquid separation membrane are connected, and the hydrogen stored in the solution is connected. And a wiring for applying a voltage between the electrodes when discharging hydrogen.

The method and apparatus of the present invention use a solution of a reducible oxyacid and / or a salt thereof as a hydrogen storage medium, and allow a proton permeation through a solution of the reducible oxyacid and / or a salt thereof and a gas containing hydrogen gas. A gas / liquid separation membrane is separated, and by connecting the electrode placed in the solution and the electrode formed on the gas side surface of the gas / liquid separation membrane, hydrogen gas, electrode | gas / liquid separation membrane | electrode, oxy Acid and /
Alternatively, a battery composed of a salt thereof is formed to dissociate hydrogen into protons in the vicinity of the electrode formed on the gas-liquid separation membrane, and the protons permeate the gas-liquid separation membrane to allow reduction of oxyacid and / or
Alternatively, hydrogen is absorbed as a proton in the solution containing the salt, and the voltage is applied between the electrodes to oxidize the polyanion in the solution to convert the protons as hydrogen through the gas-liquid separation membrane to the outside. The principle is to release to.

The reducible oxyacid or salt thereof is not particularly limited as long as it satisfies the above-mentioned principle, but specific examples thereof include, for example, isopoly acid and heteropoly acid.

Examples of the isopoly acid include paramolybdic acid, paratungstic acid, metavanadic acid, and the like, and examples of the isopoly acid salt include those represented by the general formula mM (I) ₂ O.nM (V) ₂ O ₅ .xH ₂ O or Represented by mM (I) ₂ O.nM (VI) O ₃ .xH ₂ O, M (I) in the general formula is mainly an alkali metal, and M (V) is vanadium or niobium of Group V on the periodic table. , Tantalum, and M (VI) include chromium, molybdenum, tungsten, and uranium of Group VI, and examples thereof include isopolymolybdate, isopolytungstate, and isopolyvanadate.

As the heteropolyacid, among polyacids, known heteronuclear condensed acids having two or more types of central ions, which can be reduced, can be appropriately used.
_{3 [HSiW 12 O 40],} H 3 [PMo
₁₂ O ₄₀ ], H ₇ [Co (II) Co (III) W
₁₂ O ₄₂ ], H ₃ [PV ₂ Mo ₁₀ O ₃₉ ] and the like can be given as typical ones.

In the present invention, a heteropoly acid or a salt thereof is preferable to an isopoly acid or a salt thereof, and in the heteropoly acid or a salt thereof, the coordination element is at least one selected from the group consisting of Mo, W and V, and the coordination The number of elements
12 and the central element is P, As, Si, Sn, Ge, S
n, Ti, Zr, Ce, Fe, Pt, Mn, Co, N
Heteropoly acids such as i, Te, Cr, Rh, Cu, and Se or salts thereof are preferable, and among these heteropoly acids, 12-molybdophosphoric acid, 12-tungstophosphoric acid, and 12-tungstosilic acid are particularly preferable. preferable.

The solution that forms the hydrogen storage material can be obtained by using the oxyacid and / or salt thereof that can be reduced and a solvent capable of dissolving them.

Examples of the solvent include water, ethers such as methyl ether and ethyl ether, and alcohols such as methanol and ethanol. Of these, water is preferable. This is because it has high proton conductivity, is chemically stable, and is easy to handle and obtain.

Generally, the oxyacids and salts thereof that can be reduced can become unstable when alkaline, and can exist stably under strongly acidic conditions.

Therefore, the pH of the solution is preferably 1 or less in order to stabilize the oxyacid and / or its salt.

For adjusting the pH, a protic acid such as sulfuric acid, phosphoric acid, hydrochloric acid or p-toluenesulfonic acid can be used, and sulfuric acid is preferable.

The concentration of the oxyacid and / or its salt in the solution may be up to the limit at which the oxyacid and / or its salt can be dissolved. When the oxyacid and / or its salt is dissolved at a high concentration that can be dissolved, the maximum amount of hydrogen occluded is reached. However, the concentration range usually employed is 10 ^{−3 to} 20 mo /, preferably 10 ^{−3.
-1 to 2} mo /.

As the hydrogen-containing gas, a gas containing 100% hydrogen and a gas containing hydrogen and other gases can be used.

Examples of the gas containing hydrogen and other gas include waste gas containing hydrogen gas and natural gas containing hydrogen gas.

When the waste gas or the natural gas is used in the method of the present invention, the method of the present invention becomes a hydrogen gas refining method for extracting pure hydrogen from the waste gas or natural gas, or a hydrogen gas extraction method.

Next, the gas-liquid separation membrane is formed of any material as long as it can separate the reductive oxyacid and / or its salt from the hydrogen-containing gas and can permeate protons. Alternatively, a phenol-sulfonic acid-based condensed cation exchange membrane having a cation exchange group such as a sulfonic acid group, a carboxyl group, and a phosphonic group, a fluororesin-based, methacrylic acid-based, styrene-
Ion exchange membranes such as divinylbenzene and vinyl-divinylbenzene polymerization cation exchange membranes; ceramic porous plates such as aluminum oxide, Vycor glass, mullite and cordierite; zirconia phosphate, β-alumina, phosphoric acid A porous plate of solid electrolyte such as uranyl hydrogen can be used.

Among the above various types, a cation exchange membrane is preferable, and a fluororesin cation exchange membrane having a sulfonic acid group is particularly preferable.

The fluororesin cation exchange membrane is commercially available under the trade name “Nafion” [manufactured by DuPont].

It is desirable to appropriately determine the thickness of the gas-liquid separation membrane so that it is not easily destroyed by the pressure of the solution of the reducible oxyacid and / or salt thereof and the pressure of the hydrogen-containing gas. However, if the film thickness is too large, it may take time for the protons to move.

In the method of the present invention, the electrode is arranged in the solution and the electrode is formed on the gas side surface of the gas-liquid separation membrane.

The electrodes are Pt, Pd, Rh, Ir, Os,
It is possible to use Ru, Ni, Fe, Co, Au, a simple substance of a metal having a hydrogen activation ability, or an alloy thereof. Further, other than metal, such as graphite may be used as long as it has a hydrogen activating ability. However, since the electrode immersed and placed in the solution is exposed to strong acidity, it is preferable that the electrode has acid resistance. Examples of such electrodes include Pt and A.
u, graphite, and the like.

The electrodes can be formed on the surface of the gas-liquid separation film by, for example, a vacuum vapor deposition method, a plasma vapor deposition method, a sputtering method, an ion plating method, an electroplating method, an electroless plating method, a hot stamping method or the like. Considering the formation of a simple and convenient electrode, for example, JP-A-55-38934
The electroless plating method described in the publication is preferred.

In the method of the present invention, when hydrogen is absorbed, it is sufficient to connect the electrode in the solution and the electrode on the gas-liquid separation membrane to bring the gas containing hydrogen into contact with the gas containing hydrogen. As a result, a battery as described above is formed, hydrogen gas is dissociated into protons by the electrodes on the surface of the gas-liquid separation membrane, and the protons pass through the gas-liquid separation membrane, while the electrons flowing through the external circuit are Reduce the oxyacid and / or its salt in solution. At this time, a current corresponding to H ₂ → 2H ⁺ + 2e flows through the electric wire between both electrodes. As a result, hydrogen is occluded in the solution.

On the other hand, when the stored hydrogen is released from the solution, a DC voltage may be applied to the electrode in the solution and the electrode on the gas-liquid separation membrane. When a DC voltage is applied, the reduced oxyacid and / or its salt is oxidized, while hydrogen gas is released from the gas-liquid separation membrane to the outside.

Next, an apparatus for carrying out the method of the present invention will be described by taking the case of using an oxyacid or a salt thereof as an example.

As shown in FIG. 1, the hydrogen storage / release device 1 has a first container 2 having an opening, and an opening of a second container 4 having a gas introduction hole 3 connected to the opening of the first container 2. Then, a gas-liquid separation membrane 5 permeable to protons, for example, a fluorinated cation exchange membrane having a sulfonic acid group, is stretched at the portions where the openings of the first container 2 and the second container 4 face each other, An electrode 6a, for example, a platinum electrode is formed on the surface of the gas-liquid separation membrane 5 on the second container 4 side, and an electrode 6b is formed in the first container 2.
For example, a platinum electrode is arranged and a solution 7 of an oxyacid and / or a salt thereof which can be reduced, for example, an aqueous sulfuric acid solution in which 12-molybdophosphoric acid is dissolved is stored, and the electrode 6 on the gas side
The electrode a and the electrode 6b in the first container 2 are connected to the DC power source E via the switch SW, or have a direct connection as they are.

In this device, first, the switch is set to the ab connection, and then a gas containing hydrogen is introduced into the second container 4 from the gas introduction hole 3, the hydrogen gas is protonated at the electrode 6a portion on the gas-liquid separation membrane 5. Is dissociated into oxyacids and / or salts thereof by reducing the oxyacid and / or its salt in the solution 7.
Alternatively, a complex of the salt and the proton is formed, and the hydrogen gas in the gas introduced into the second container 4 becomes the solution 7
It is stored inside.

On the other hand, when hydrogen is occluded in the solution 7 and the switch SW is connected to ac, the complex in the solution 7 is oxidized to dissociate the protons, and the protons pass through the gas-liquid separation membrane 5 and then the electrode 6a portion. To hydrogen gas, and as a result, the hydrogen stored in the solution 7 is released into the second container 4 as hydrogen gas.

The electrochemical reaction in this case is as follows, taking 12-molybdophosphoric acid as an example.

(Pt electrode / cation exchange membrane) H ₂ → 2H ⁺ + 2e- (Pt electrode in solution) 2e + [▲ PMo ⁶ + ₁₂ ▼ O ₄₀ ] ³ →→ [▲ PMo
^{_{5+ 2 ▼ ▲ Mo 6+ 10 ▼}} O 40] 5- ( cation exchange membrane / solution ^{interface) 2H + + [▲ PMo 5+} 2 ▼ ▲ Mo 6+ 10 ▼ O 40]
^5- → H ₂ [▲ PMo ⁵⁺ ₂ ▼ ▲ Mo ⁶⁺ ₁₀ ▼
O ₄₀ ] ₃ Incidentally, the device shown in FIG. 1 shows the present invention in principle, and it goes without saying that the present invention is not limited to the device shown in FIG.

EFFECTS OF THE INVENTION According to the present invention, when compared with a hydrogen storage alloy, (1) an electrode in a solution in which an oxyacid and / or its salt is dissolved, and a gas-liquid separation for separating the solution and a hydrogen-containing gas from each other. Hydrogen can be occluded and released by simply applying a DC voltage to the electrodes formed on the film or by directly connecting the electrodes, and at the time of release, it is only necessary to control the voltage or current. Since the release rate or release amount can be controlled, the operation and control are simple, the response is fast, and efficient storage and release can be performed, and the temperature and pressure as in the case of the hydrogen storage alloy can be maintained. (2) Hydrogen can be stored and released at room temperature and pressure without the need for complicated control and pretreatment by means of, so it is necessary to adjust the temperature and pressure like a hydrogen storage alloy. Special special (3) Hydrogen gas can be taken out by applying a voltage to a solution that dissolves a reducible oxyacid and / or its salt, so that hydrogen can be stored and stored stably. As in the case of a hydrogen storage alloy, the inside of the container must be kept in a hydrogen gas atmosphere, and there is no instability that the stored hydrogen escapes due to leakage of the hydrogen gas. (4) Hydrogen storage alloy When using, the inside of the container containing this hydrogen storage alloy must be placed under a hydrogen gas atmosphere,
If so, there is a risk of explosion due to hydrogen leakage and damage to the container due to hydrogen embrittlement, but it is easy to handle without paying particular attention to the atmosphere of the solution, and there is no damage to the container that contains the solution. 5) It is possible to provide a hydrogen storage method and a hydrogen storage device which have various excellent advantages such as being able to take out electric energy during hydrogen storage.

[Embodiment] Next, an embodiment of the present invention will be described.

In the following examples, the hydrogen storage / release device shown in FIG. 2 was used.

As shown in FIG. 2, the hydrogen storage / release device 10 has the following configuration.

An upper opening of a bottomed cylindrical container body (12) having a cylindrical side opening (11) on its peripheral side surface is sealed with a cover (13) having two ports.

A port 13a located at the center of the two ports is provided with a side tube 14 into which an argon gas flow can be introduced, and the container body
A support member (17) for supporting a platinum electric wire (16) connected to a platinum electrode (15) arranged inside (12) is attached.

The platinum electrode 15 has a size of 3 cm × 1 cm and a thickness of 0.2 mm.

Then, in the side opening 11, in the opening 19 of the hydrogen supply member 18, a fluorine-based cation exchange membrane having a sulfonic acid group.
Tighten the side opening 11 and the opening 19 of the hydrogen supply member 18 with 20 [“Nafion 117”, manufactured by DuPont Co., Ltd.] with a bolt and a nut.

In this case, the thickness of the cation exchange membrane 20 is 0.0185 cm.

On the surface of the cation exchange membrane 20 on the hydrogen supply member 18 side, a circular platinum electrode 21 having an area of 3.14 cm ² is formed by electroless plating.

The hydrogen supply member 18 has a hydrogen gas inlet 22 and a hydrogen gas outlet 23 for introducing and discharging hydrogen gas, and a platinum electrode 21 formed on the cation exchange membrane 20.
The platinum wire 24 is supported so that the end of the platinum electrode 24 connected to the hydrogen supply member 18 is led out.

The hydrogen storage / release device 10 configured as described above stores a solution of a reducible oxyacid and / or a salt thereof in the container body 12 and also supplies the side pipe 14 of the support member 17.
Argon gas can be introduced into the container body 12 from the above, and can be discharged to the outside of the container body 12 from one of the two openings 13b.

From the hydrogen inlet 22 of the hydrogen supply member 18 to the hydrogen supply member
Hydrogen gas can be supplied to the cation exchange membrane 20 in the inside 18 and discharged from the hydrogen gas discharge port 23 to the outside of the hydrogen supply member 18.

In addition, one end of the platinum electric wire 16 drawn out from the container body 12 and the platinum electrode 24 drawn out from the hydrogen supply member 18
A DC voltage source (not shown) and an ammeter are connected in series to one end of the switch, and the switch can be switched between the DC voltage source and the ammeter by a switch (not shown).

An example in which hydrogen is stored and released using the hydrogen storage and release device configured as described above is shown.

Example 1 2 × 10 12-molybdophosphoric acid was added to a 20 wt% sulfuric acid aqueous solution.
Solution obtained by dissolving to ^-3 M (pH <1) 120
m, housed in the container body. Room temperature inside the container body,
It was kept at normal pressure.

Hydrogen gas was supplied to the cation exchange membrane from the hydrogen gas inlet of the hydrogen supply member.

Electric energy with an electromotive force of 31 to 40 mV and an average current of 3.35 mA was generated, and 16.1 m of hydrogen was occluded in the solution in about 9 hours.

The storage efficiency was 77.0%, and the generated electric energy was 4.53 W hours per mol of 12-molybdophosphoric acid.

(Example 2) With respect to the solution in which hydrogen was occluded in Example 1,
When a 6-electron reduced heteropolyanion was reoxidized by applying a DC voltage, 4.6 to 4.8 mA at a cell voltage of 1.36 to 1.54 V
The electric current of 1) flows and 10.6 m of hydrogen is collected in the hydrogen supply member in about 6 hours.

The recovery efficiency was 85.7%, and the consumed electric energy was 169.0 W hours per mol of 12-molybdophosphoric acid.

Example 3 The concentration of 12-molybdophosphoric acid in Example 1 was set to 4.5 × 1.
0 ^{-3 M} and the outside, was carried out in the same manner as in Example 1.

As a result, 35.6 m of hydrogen was occluded. Further, the storage efficiency was 81.4%, and the amount of generated electric power was 6.85 W hours per mol of 12-molybdophosphoric acid.

At this time, the hydrogen absorption rate is about 1.
It was 6 times.

(Example 4) The same procedure as in Example 1 was carried out except that the concentration of the sulfuric acid aqueous solution in Example 1 was changed to 40% by weight.

As a result, 16.0 m of hydrogen was occluded. The storage efficiency was 91.1%, and the amount of generated electric power was 4.43 W hours per 1 mol of 12-molybdophosphoric acid.

Example 5 Instead of 12-molybdophosphoric acid in Example 1, 12-
The same procedure as in Example 1 was performed except that tungstic acid was used.

As a result, 7.48 m of hydrogen was stored. This is 12-
This corresponds to 1.4 mol of hydrogen per mol of tungstic acid.

Example 6 Instead of 12-molybdophosphoric acid in Example 1, 12-
The same procedure as in Example 1 was performed except that tungstosilicic acid was used.

As a result, 2.54 m of hydrogen was stored. This is 12-
This corresponds to 0.5 mol of hydrogen per mol of molybdosilicic acid.

Example 7 The same procedure as in Example ¹ was repeated except that 12-molybdophosphoric acid was dissolved in water to a concentration of 2 × 10 ⁻¹ M and 0.1 electron reduction was performed.

As a result, 25.9 m of hydrogen was stored. The storage efficiency was 98.9%, and the amount of generated electric power was 0.219 W hours per mol of 12-molybdophosphoric acid.

At this time, the hydrogen absorption rate was about 17 as compared with the first embodiment.
It was double.

[Brief description of drawings]

FIG. 1 is a principle explanatory view showing one structural example according to the present invention, and FIG. 2 is an explanatory view showing one embodiment of the present invention. 1 ... Hydrogen storage / release device, 2 ... First container, 4 ... Second
Container, 5 ... Gas-liquid separation membrane, 6a, 6b ... Electrode, 10 ...
Hydrogen storage / release device, 12 …… Container body, 15 …… Platinum electrode,
20 …… Cation exchange membrane, 21 …… Platinum electrode.

Claims (20)

[Claims] 1. An electrode is provided in a solution of a reducible oxyacid and / or a salt thereof, and the solution and a gas containing hydrogen gas are separated by a gas-liquid separation membrane permeable to protons. A battery is formed by connecting the electrode formed on the gas contact surface of the membrane and the electrode in the solution to occlude hydrogen in the gas in the solution, and the electrode in the solution and the gas-liquid separation membrane. A method for storing and releasing hydrogen, wherein hydrogen stored in a solution is released to the outside of the gas-liquid separation membrane by applying a voltage between the electrode and the electrode. 2. The hydrogen storage / release method according to claim 1, wherein the oxyacid or a salt thereof is a heteropolyacid or a salt thereof. 3. The oxyacid or a salt thereof, wherein the coordination element is at least one selected from the group consisting of molybdenum, tungsten and vanadium, and the number of coordination atoms with respect to the central element is 12. Range of the second
The method for storing and releasing hydrogen according to the item. 4. The oxy acid is 12-molybdophosphoric acid, 12-
The hydrogen storage / release method according to claim 3, wherein the method is at least one selected from the group consisting of tungstophosphoric acid and 12-tungstosilicic acid. 5. The hydrogen storage / release method according to any one of claims 1 to 4, wherein the solvent in the solution is water. 6. The hydrogen storage / release method according to any one of claims 1 to 5, wherein the solution is strongly acidic. 7. The method for storing and releasing hydrogen according to claim 6, wherein the pH of the solution is 1 or less. 8. The hydrogen storage / release method according to any one of claims 1 to 7, wherein the gas-liquid separation membrane is an ion exchange membrane. 9. The hydrogen storage / release method according to any one of claims 1 to 8, wherein the gas containing hydrogen gas is hydrogen gas itself. 10. The method for storing and releasing hydrogen according to any one of claims 1 to 8, wherein the gas containing hydrogen gas is a mixed gas of hydrogen gas and other gas. 11. A container for accommodating a solution of a reducible oxyacid and / or a salt thereof and having an electrode provided in the solution, and a surface on the gas side for separating the solution and a gas containing hydrogen gas from each other. A proton-permeable gas-liquid separation membrane forming an electrode, and an electrode in the solution and an electrode in the gas-liquid separation membrane are connected to each other when absorbing hydrogen, and both of the electrodes are connected to each other when hydrogen stored in the solution is released. A hydrogen storage / desorption device comprising: a wiring for applying a voltage between electrodes. 12. The hydrogen storage / release device according to claim 11, wherein the oxyacid or a salt thereof is a heteropolyacid or a salt thereof. 13. The oxyacid or salt thereof, wherein the coordination element is at least one selected from the group consisting of molybdenum, tungsten and vanadium, and the coordination atom number with respect to the central element is 12. Range of
Item 12. The hydrogen storage / release device according to item 12. 14. The oxyacid is 12-molybdophosphoric acid, 12
14. The hydrogen storage / release device according to claim 13, wherein the hydrogen storage / release device is at least one selected from the group consisting of -tungstophosphoric acid and 12-tungstosilicic acid. 15. The hydrogen storage / release device according to any one of claims 11 to 14, wherein the solvent in the solution is water. 16. The hydrogen storage / release device according to any one of claims 11 to 15, wherein the solution is strongly acidic. 17. The hydrogen storage / release device according to claim 16, wherein the pH of the solution is 1 or less. 18. The hydrogen storage / release device according to any one of claims 11 to 17, wherein the gas-liquid separation membrane is a sulfur exchange membrane. 19. The hydrogen storage / release device according to any one of claims 11 to 18, wherein the gas containing hydrogen gas is hydrogen gas itself. 20. The method according to claim 11, wherein the gas containing hydrogen gas is a mixed gas of hydrogen gas and another gas.
19. The hydrogen storage / release device according to any one of items 1 to 18.