JPH07109101A - Occlusion of hydrogen or lithium to sodium tungsten bronze, occlusion apparatus and sodium tungsten bronze containing occluded hydrogen or lithium - Google Patents

Abstract

PURPOSE:To enable the occlusion of hydrogen and/or lithium in a sodium tungsten bronze and enable the occlusion of a large amount of hydrogen and/or lithium in the bronze. CONSTITUTION:An occlusion apparatus consists of an electrolytic cell 1 into which a cathode 2, an anode 3 and reference electrode 3R are inserted, a voltage controlling apparatus 4 and X-Y recorder 5. Electrolytic cell 1 is filled with lithium hydroxide in the form of an alkaline aqueous solution. Cathode 2 consists of a sodium tungsten bronze (Na0.58WO3). Anode 3 is made of platinum and reference electrode 3R composes of a saturated calomel electrode(SCE). A voltage controlling apparatus 4 is controlling the voltage applied to the cathode 2, the anode 3 and the reference electrode 3R, and an X-Y recorder 5 is recording the change of electric current caused by the sweep of voltage applied to the cathode 2. Lithium is occluded in a sodium tungsten bronze by the above occlusion apparatus.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for storing hydrogen or lithium in sodium tungsten bronze which causes hydrogen or lithium to be stored in the sodium tungsten bronze by electrolysis in an alkaline aqueous solution, and hydrogen or lithium. Regarding sodium tungsten bronze.

[0002]

2. Description of the Related Art Conventionally, it is known that a tungsten bronze type crystal such as sodium tungsten bronze (Na _x WO ₃ ) has a nonstoichiometric value of x and has electrical conductivity. Sodium tungsten bronze has been reported to occlude hydrogen, which has been done by methods such as contacting sodium tungsten bronze with gaseous hydrogen.

It has also been attempted to electrolyze sodium tungsten bronze in a sulfuric acid aqueous solution as a cathode to generate hydrogen on the cathode and at the same time store hydrogen in the cathode. In comparison, it is suggested that a large amount of hydrogen can be stored.

Further, it is also known to occlude lithium in sodium tungsten bronze, and electrolysis is carried out using sodium tungsten bronze as a cathode in a molten salt containing lithium ions or in a non-aqueous solvent containing lithium ions.

[0005]

In the above conventional method of contacting with gaseous hydrogen, the amount of hydrogen that can be occluded using hydrogen gas at 1 atm is extremely small, and the composition of Na ₇₃ WO ₃ is 0.0059 (Na _0.73 H
_0.0059 WO ₃ ) has been reported. Therefore, since the hydrogen storage rate is low, it is considered that it is not suitable for the generation of excess heat disclosed in JP-A-4-506564.

Further, in the above-mentioned conventional method of electrolyzing in a sulfuric acid aqueous solution, according to the experiments conducted by us, there is no definitive evidence that a large amount of hydrogen is occluded, and the reported sodium is reported. Considering the value of the diffusion constant of hydrogen in the tungsten bronze of 10 ⁻¹¹ to 10 ⁻¹² cm ² / s, it is considered that hydrogen is absorbed only on the very surface of the electrode.

Further, the method of electrolyzing in a molten salt containing a lithium ion or a non-aqueous solvent is performed electrochemically, but is performed only in the non-aqueous solvent containing a lithium ion or in a molten state. . The reason is,
It is presumed that hydrogen was generated at a potential nobler than the penetration of lithium in the electric field in the aqueous solution.

Therefore, the inventors of the present invention believe that when platinum is used for the cathode and the anode in electrolysis in an aqueous alkaline solution, hydrogen is generated at the cathode and oxygen is generated at the anode by applying an applied voltage higher than the decomposition voltage of water. However, it was found that the behavior of sodium tungsten bronze varies greatly depending on the type of alkaline aqueous solution when it is used as a cathode. As a result of a systematic investigation, sodium tungsten bronze was used as a cathode in the alkaline aqueous solution to electrolyze sodium tungsten. Focusing on the technical idea of the present invention that hydrogen or lithium is stored in bronze, hydrogen and lithium can be stored in sodium tungsten bronze, and a large amount of hydrogen and lithium can be stored in sodium tungsten bronze. It has reached the present invention for achieving the goal of.

[0009]

The method for occluding hydrogen or lithium in sodium tungsten bronze according to the present invention (the first invention according to claim 1) is to electrolyze sodium tungsten bronze as a cathode in an aqueous alkali solution. As a result, at least one of hydrogen and lithium is occluded in the sodium tungsten bronze.

The storage device for hydrogen or lithium in sodium tungsten bronze of the present invention (the second invention according to claim 2) is an electrolytic cell filled with an alkaline aqueous solution,
A cathode that is placed in the electrolytic cell and is made of sodium tungsten bronze; an anode that is placed in the electrolytic cell; and a voltage control device that controls the voltage applied to the cathode and the anode. At least one of lithium and lithium is stored in a sodium tungsten bronze.

The hydrogen- or lithium-occluded sodium tungsten bronze of the present invention (the third invention according to claim 3) is electrolyzed with sodium tungsten bronze as a cathode in an alkaline aqueous solution to obtain hydrogen or lithium. At least one is occluded.

[0012]

The method for storing hydrogen or lithium in the sodium tungsten bronze of the first invention having the above-mentioned structure is
By electrolyzing sodium tungsten bronze as a cathode in an alkaline aqueous solution, at least one of hydrogen and lithium is occluded in the sodium tungsten bronze.

A device for storing hydrogen or lithium in sodium tungsten bronze according to the second aspect of the present invention, which has the above-mentioned structure, has the voltage control device for the cathode and the anode made of sodium tungsten bronze in the alkaline aqueous solution in the electrolytic cell. At least one of hydrogen and lithium is occluded in sodium tungsten bronze by electrolyzing by applying a voltage controlled by.

The sodium tungsten bronze containing hydrogen or lithium according to the third aspect of the present invention having the above structure,
Various uses are made of hydrogen or lithium occluded in sodium tungsten bronze depending on the application.

[0015]

The method of storing hydrogen or lithium in sodium tungsten bronze according to the first aspect of the present invention, which enables the storage of at least one of hydrogen and lithium in sodium tungsten bronze, as well as hydrogen and lithium. The effect that a large amount of at least one of them can be stored is exhibited.

The device for storing hydrogen or lithium in sodium tungsten bronze according to the second aspect of the present invention, which enables the storage of at least one of hydrogen and lithium in the sodium tungsten bronze constituting the cathode, and hydrogen and lithium The effect is that a large amount of at least one of lithium can be stored.

The sodium tungsten bronze containing hydrogen or lithium according to the third aspect of the present invention, which has the above-mentioned function, is:
Since it is possible to store a large amount of hydrogen or lithium, it is possible to use such a sodium tungsten bronze for secondary batteries, display devices, pH sensors, and also for fusion reactions. The effect that there is.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) A method and apparatus for storing lithium in sodium tungsten bronze according to the first embodiment are, as shown in FIG. 1, an electrolytic cell 1 filled with lithium hydroxide as an alkaline aqueous solution, and Sodium tungsten bronze (Na _0.58 WO
₃ ), a cathode 2 composed of ₃ ), an anode 3 composed of platinum inserted in the electrolytic cell 1, and a reference electrode composed of a saturated calomel electrode (SCE) inserted in the electrolytic cell 1. 3R, a voltage controller 4 that controls the voltage applied to the cathode 2, the anode 3, and the reference electrode 3R, and an XY recorder 5 that records the change in current when the potential acting on the cathode 2 is swept. In other words, lithium is occluded in the sodium tungsten bronze forming the cathode 2.

The electrolytic cell 1 is composed of a hollow cylindrical body 10 with a bottom and is filled with 1M lithium hydroxide.

The cathode 2 is composed of a rectangular parallelepiped of sodium tungsten bronze (Na _0.58 WO ₃ ), and is arranged substantially in the center of the bottomed hollow cylindrical body 10.

The anode 3 is coaxially and spirally arranged so as to surround the cathode 2 in the electrolytic cell 1.

The voltage controller 4 comprises a potentiostat 40 connected to a function generator 41 which outputs the signals required for electrolysis and measurement, the cathode 2,
It is connected to the anode 3 and the reference electrode 3R and regulates the potential so that hydrogen is not generated in the cathode 2 composed of sodium tungsten bronze.
It is configured so that an electric quantity of 9.62 coulombs can be controlled so as to flow during electrolysis.

The method of storing lithium in the sodium tungsten bronze of the first embodiment using the device for storing lithium in the sodium tungsten bronze of the first embodiment having the above-mentioned structure is as follows. In order to prevent hydrogen from being generated in the cathode 2 of the sodium tungsten bronze arranged in the electrolytic cell 1, the voltage control device 4 regulates the potential with respect to the reference electrode 3R so that an electric quantity of 39.62 coulomb is obtained. It is controlled so as to flow, and electrolysis is performed for about 16 hours to occlude lithium in the sodium tungsten bronze forming the cathode 2.

The method and apparatus for storing lithium in the sodium tungsten bronze of the first embodiment are different from the conventional one as shown in the cyclic voltammogram when the potential of the cathode 2 is swept at 50 mV / sec in FIG. The effect is that a large amount of lithium is occluded in the sodium tungsten bronze forming the cathode 2.

After completion of the electrolysis, the sodium tungsten bronze constituting the cathode 2 was decomposed according to the procedure shown in FIG. 3 and analyzed by atomic absorption spectrometry of high frequency plasma emission spectrometry to measure the lithium content. I got the result. Sodium Tungsten Bronze Electrode Weight: 0.7900 g Lithium amount detected after electrolysis: 0.00265 g Theoretical amount calculated from electricity amount: 0.00285 g Even from the theoretical amount of 0.00285 g, the detected lithium amount of 0.00265 g corresponds well. It can be said that they are doing.

(Second Embodiment) A method for storing hydrogen in sodium tungsten bronze according to the second embodiment is as follows. 1M potassium hydroxide is used as an electrolytic solution, sodium tungsten bronze (Na _0.67 WO ₃ ) is used as a cathode, and platinum is used. The electrode potential of the cathode as the anode was regulated to -2.0 V with respect to the saturated calomel electrode as the reference electrode, and electricity was supplied for a certain period of time to perform electrolysis.

In the second embodiment, after energization for a certain period of time, the potential of the cathode made of sodium tungsten bronze was swept at 100 mV per second as shown in FIG. 4, and then 4 hours 22 minutes, 8 hours 24 minutes, and 21 hours. The anodic voltammogram was recorded when electricity was applied for 49 minutes. As is clear from FIG. 4, the anode current increased with the energization time and reached a constant value in about 1 hour. From the pH dependence of this peak position, this peak was determined to be due to the release of absorbed hydrogen, and the hydrogen concentration on the surface of sodium tungsten bronze was calculated from the height of the peak using the following formula 1.

[Equation 1] As a result, the atomic ratio of hydrogen was estimated to be 0.3 to 0.4, and production of Na _0.67 H _0.33 WO ₃ was confirmed.

(Third Embodiment) A method of occluding hydrogen in sodium tungsten bronze of the third embodiment uses 1 M sodium hydroxide as an electrolyte, sodium tungsten bronze (Na _0.67 WO ₃ ) as a cathode, and platinum. The electrode potential of the cathode as the anode was regulated to -2.0 V with respect to the saturated calomel electrode, and electricity was supplied for a certain period of time to perform electrolysis.

In the third embodiment as well, it was confirmed that hydrogen was occluded in the same manner as in the second embodiment and that Na _0.67 H _0.33 WO ₃ was produced.

(Fourth Embodiment) A method for storing hydrogen and lithium in sodium tungsten bronze according to a fourth embodiment is as follows. Lithium ions are added to a 1 M potassium hydroxide electrolytic solution so as to have a concentration of 10 ^-6 M. Then, sodium tungsten bronze (Na _0.67 WO ₃ ) was used as the cathode, platinum was used as the anode, and the electrode potential of the cathode was regulated to -2.0 V with respect to the saturated calomel electrode and energized for 1 hour,
It was electrolyzed.

In the above fourth example, the anodic voltammogram of the cathode composed of sodium tungsten bronze was recorded as shown in FIG.
As is clear from FIG. 5, of the two peaks, the peak at the more noble potential is dependent on the concentration of added lithium, and is therefore confirmed to be due to the release of lithium occluded in the sodium tungsten bronze. Therefore, it is judged that both hydrogen and lithium are occluded in the sodium tungsten bronze.

(Comparative Example) A method of occluding hydrogen in the sodium tungsten bronze of the comparative example is as follows. 1N sulfuric acid is used as an electrolytic solution, sodium tungsten bronze (Na _0.67 WO ₃ ) is used as a cathode, and platinum is used as in the above-mentioned embodiment. As an anode, the electrode potential of the cathode was regulated to -2.0 V with respect to the saturated calomel electrode, and electricity was applied for a certain period of time to perform electrolysis.

In the above comparative example, an unclear peak was observed as shown in FIG. 6, but hydrogen storage was not observed as in the alkaline electrolytes of the examples.

(Application Example) If the intercalation of lithium by electrolytic reduction of sodium tungsten bronze in an alkaline aqueous solution in the above-mentioned example is used, an aqueous solution electrolyte is used by combining with a suitable positive electrode such as nickel hydroxide. It is also possible to fabricate a secondary battery. That is, a secondary battery was constructed by using sodium tungsten bronze Na _0.58 WO ₃ of this example as a negative electrode active material, a positive electrode of nickel oxyhydroxide, and an electrolyte of 1M lithium hydroxide. The chemical reactions of the positive electrode and the negative electrode are as shown in the following chemical formulas 1 and 2, and the battery voltage is 1.6.
It was V.

[Chemical 1]

[Chemical 2]

Further, since a clear color change occurs with a change in the amount of hydrogen stored in the sodium tungsten bronze, it can be applied to a display element, a display material and a mirror using this.

Further, since the electrode potential of the sodium tungsten bronze electrode in the aqueous solution changes depending on the hydrogen ion concentration of the aqueous solution, this is changed to a glass electrode.
Application to H sensor is also possible.

Further, as another application of the sodium tungsten bronze, it is considered that excess heat is generated by applying the Ponds-Fleishman effect, but its mechanism is not clear at present, and Pd is used for fusion.
It is considered that deuterium nuclei react with each other in a metal like this, or deuterium reacts with lithium 6 or light hydrogen reacts with lithium 7, but in any case, the presence of alkali metals is a major factor. Is believed to be doing.

Therefore, since the sodium tungsten bronze according to the above-mentioned embodiment can store a large amount of hydrogen, it can be said that it is extremely advantageous for excessive heat generation as disclosed in JP-A-4-506564. The application example will be described below.

When a lithium hydroxide electrolyte is used, both lithium and hydrogen are considered to be occluded in the tungsten bronze, and a nuclear fusion reaction such as Chemical formula 3 can be expected on the electrode surface or inside.

[Chemical 3]

When potassium hydroxide or sodium hydroxide is used as the electrolytic solution, a larger amount of occlusion can be obtained than when lithium hydroxide is used.
Lithium was occluded in a tungsten bronze using a lithium hydroxide electrolytic solution, and then potassium hydroxide or sodium hydroxide was used as the electrolytic solution to replace the electrolytic solution with hydrogen and occlude hydrogen with lithium stored in advance. It can be expected to cause a nuclear fusion reaction with hydrogen.

Further, even when sodium hydroxide or potassium hydroxide is used as the electrolytic solution, a small amount of sodium or potassium is not detected by electrochemical or ordinary elemental analysis, but a small amount of sodium or potassium is tungsten bronze. Since it is considered that they are occluded or adsorbed on the surface, a nuclear fusion reaction such as Chemical formula 4 can be expected.

[Chemical 4]

The embodiments described above are merely examples for the purpose of explanation, and the present invention is not limited to them. Those skilled in the art will recognize from the claims, the detailed description of the invention and the description of the drawings. Modifications and additions can be made without departing from the technical idea of the present invention.

[Brief description of drawings]

FIG. 1 is a block diagram showing a storage method and storage device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a cyclic voltammogram in the first embodiment.

FIG. 3 is a chart showing a sample disassembling procedure in the first embodiment.

FIG. 4 is a diagram showing anodic voltammograms in the second and third embodiments.

FIG. 5 is a diagram showing an anodic voltammogram in a fourth embodiment.

FIG. 6 is a diagram showing an anodic voltammogram in a comparative example.

[Explanation of symbols]

 1 Electrolyzer 2 Cathode 3 Anode 4 Voltage Control Device 40 Potentiostat 41 Function Generator 5 XY Recorder

Claims (3)

[Claims] 1. A method of electrolyzing sodium tungsten bronze as a cathode in an alkaline aqueous solution to occlude at least one of hydrogen and lithium in the sodium tungsten bronze. Storage method. 2. An electrolytic cell filled with an alkaline aqueous solution, a cathode which is inserted into the electrolytic cell and is made of sodium tungsten bronze, an anode which is inserted into the electrolytic cell, and the cathode and the anode. A device for storing hydrogen or lithium in sodium tungsten bronze, comprising: a voltage control device for controlling an applied voltage; and storing at least one of hydrogen and lithium in sodium tungsten bronze. 3. A sodium tungsten bronze containing hydrogen or lithium, wherein at least one of hydrogen and lithium is stored by electrolyzing sodium tungsten bronze as a cathode in an alkaline aqueous solution.