JP2004315347A - Ruthenic acid nano-sheet and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a layered ruthenic acid compound whose active area is expanded. <P>SOLUTION: The ruthenate nano-sheet is manufactured by obtaining a colloid containing a ruthenic acid nano-sheet having a thickness of not more than 1 nm from a layered ruthenic acid compound, via a proton type layered ruthenic acid hydrate and an alkyl ammonium-layered ruthenic acid intercalation compound. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a ruthenate compound having a novel structure, a method for producing the same, and an electrode for an electrochemical device using the ruthenate compound.

Conventionally, typical electrochemical elements having a storage function include electric double-layer capacitors, pseudo-double-layer capacitors, secondary batteries, and electric quantity storage elements, which are applied devices that make use of their respective characteristics. Has been put to practical use. An electric double layer capacitor has a higher output density and a longer life than a secondary battery, and is therefore used for a backup power supply or the like that requires high reliability. On the other hand, a secondary battery has a higher energy density than an electric double layer capacitor and is the most typical historical power storage device.
However, a secondary battery has a shorter service life than an electric double layer capacitor and needs to be replaced after a certain period of use. In addition, although the electric quantity storage element has been put to practical use as a timer that can be used repeatedly, the development of a long-time timer for 10 to 15 years has been a problem.

The main characteristic difference between these power storage devices is due to the power storage mechanism of the electric energy. The quasi-double-layer capacitor has a capacity that is developed by an electrochemical adsorption phenomenon at an interface between a surface of a metal oxide such as RuO ₂ , IrO ₂ and Co ₃ O ₄ and an electrolyte. This capacitance is called a pseudo capacitance and is distinguished from an electric double layer capacitance generated at the interface between the activated carbon electrode surface and the electrolyte.
In an electric double layer capacitor, an electrochemical reaction does not occur at an interface between an electrode and an electrolytic solution, and only ions contained in the electrolytic solution move during charging and discharging. For this reason, deterioration is less likely to occur as compared with the secondary battery, and the ion movement speed is high, so that the battery has a long life and a high output density.

On the other hand, a secondary battery uses an electrochemical reaction between an electrode and an electrolytic solution, and thus deteriorates due to charge and discharge. The chemical reaction rate is relatively slow, the service life is short, and the power density is relatively small. However, since the electrode material itself stores energy in the form of chemical energy, it has a feature that it has a higher energy density than an electric double layer capacitor which can store energy only at the interface between the electrode and the electrolyte.
With respect to these conventional power storage devices, a quasi-double-layer capacitor has been proposed that has both high output density and long life, which are the characteristics of an electric double-layer capacitor, and high energy density, which is a characteristic of a secondary battery. Typical examples of the electrode material used in the pseudo double layer capacitor are ruthenium, iridium and cobalt. All of these materials are expensive, and there is an issue of reducing cost and improving performance.

As a solution to such a problem, there has been proposed an electrode material in which a rutile-type ruthenium oxide is dispersed and supported in an electrode, or an electrode material in which a ruthenium compound and a vanadium compound are adsorbed on activated carbon (see Patent Document 1). There is a method in which a solid solution containing a compound and a vanadium compound is contained in an electrode.
In this connection, Non-Patent Document 1 proposes a layered ruthenate compound as a material for a pseudo double layer supercapacitor.
JP-A-11-354389 Y. Takasu et al., Electrochim, Acta 2000, 45, 4135.

When an expensive ruthenium compound is dispersed and supported on the surface of a host material such as activated carbon in the form of fine particles, the ruthenium compound crystal becomes rutile or amorphous. Therefore, although the initial performance is expected, a phenomenon in which the ruthenium compound falls off from the host material occurs when charge and discharge are repeated for a long time.
Further, when a compound such as vanadium is mixed, the bond strength with the host material is deteriorated, and the ruthenium compound is dropped off by long-term charge / discharge, which has a problem in long-term life.

In general, layered compounds such as graphite have been attracting attention as electrode materials. However, the layered compound is an easily graphite material, TiS ₂ , MoS ₂ , CoO _2, V ₆ O _{13 and the} like, and it has been difficult to synthesize a layered compound of ruthenium.
Non-Patent Document 1 also discloses a layered ruthenate compound, but here, a method of producing an electrode by applying a ruthenate compound to a current collector made of titanium metal is mainly used. The electrode obtained by this method did not have sufficient strength and was insufficient as an electrode.

Accordingly, an object of the present invention is to provide a novel layered ruthenate compound having an increased active area and further having a significantly increased charge storage ability.
Another object of the present invention is to provide an electrode that provides a high-output and large-capacity electrochemical capacitor using a layered ruthenate compound, and an electrochemical device using the same.

The present invention relates to a ruthenate nanosheet having a thickness of 1 nm or less, wherein the ruthenate nanosheet is preferably
Formula (1): [RuO _{2 + 0.5x} ] ^x- (1)
Is represented by

The present invention also relates to a layered ruthenate compound having a structure in which the ruthenate nanosheets are stacked. This layered ruthenate compound has an X-ray diffraction pattern of (00L) on each plane (where L = 1 to n in the range of 0 ≦ θ (CuKα) ≦ 90 °, where n is determined by the basic plane distance and 5 ≦ n ≤ 35).
Furthermore, the present invention also relates to a colloidal ruthenate compound comprising the ruthenate nanosheet and / or the layered ruthenate compound and a solvent.

The present invention also provides an alkali metal salt of the above-mentioned layered ruthenate compound (alkali metal-type layered ruthenate compound), and a proton-type layered ruthenium in which at least a part of the alkali metal of the alkali metal-type layered ruthenate compound is substituted with a proton. acid compounds, as well as hydrates, including of H ₂ O molecules between the layers concerns.
Above all, proton-type layered ruthenic acid hydrate is
Equation _{(2): M xy H yz} B z RuO 2 + 0.5x · nH 2 O (2)
Wherein M is an alkali metal ion such as Li, Na, K, Rb or Cs, and B is (R) _m NH _4-m or (R) _mp (R ′) _p NH _4-m (wherein R and R ′ are alkylammoniums represented by CH ₃ (CH ₂ ) _q , m = 0 to 4, p = 0 to 3, q = 0 to 18), and 0 <x <1, 0 ≦ y < x, 0 ≦ z <y, 0 ≦ n ≦ 10].

Further, the present invention provides
(A) mixing ruthenium oxide and an alkali metal compound, and calcining or melting the obtained mixture to obtain an alkali metal-type layered ruthenic acid containing a ruthenate nanosheet having a thickness of 1 nm or less;
(B) treating the alkali metal-type layered ruthenic acid in an acidic solution, and exchanging at least a part of the alkali metal with a proton to obtain a proton-type layered ruthenic acid hydrate;
(C) reacting the proton-type layered ruthenic acid hydrate with alkylammonium or alkylamine to obtain an alkylammonium-layered ruthenic acid intercalation compound; and (d) using the alkylammonium-layered ruthenic acid intercalation compound as a solvent. Provided is a method for producing a ruthenate nanosheet, comprising a step of mixing to obtain a colloid containing a ruthenate nanosheet having a thickness of 1 nm or less.

In the step (a), it is preferable that ruthenium oxide and an alkali metal salt are mixed, and the obtained mixture is fired at 700 to 900 ° C.
In the step (a), ruthenium oxide and an alkali metal hydroxide may be mixed, and the resulting mixture may be melted at 500 to 700 ° C.

In the step (c), (R) _m NH _4-m or (R) _mp (R ′) _p NH _4-m (where R and R ′ are CH _{3 (CH 2) q, m =} 0~4, p = 0~3, preferably reacted alkylammonium represented by q = 0 to 18).
In the step (c), (R) _m NH _3-m or (R) _mp (R ′) _p NH _3-m (where R and R ′ are _{CH 3 (CH 2) q,} m = 0~3, p = 0~2, may be reacted with an alkyl amine represented by q = 0 to 18).

  In the step (d), the alkylammonium-layered ruthenic acid intercalation compound is mixed with at least one solvent selected from the group consisting of water, alcohol, acetonitrile, dimethylsulfoxide, dimethylformamide and propylene carbonate to form a colloid. Is preferred.

  The layered ruthenate compound having a structure in which ruthenate nanosheets having a thickness of 1 nm or less according to the present invention are laminated has a larger charge storage ability than conventional ruthenium oxide, and is useful as an electrode of an electrochemical element. In this layered ruthenate compound, a ruthenate nanosheet, which is an electrochemically stable electron conductive layer, is laminated, and a proton conductive layer composed of water or hydrated protons exists at a molecular level between the electron conductive layers. I do. Therefore, it exhibits a greatly increased charge storage ability and is useful as a high-output, large-capacity supercapacitor.

  Further, the ruthenate nanosheet having a thickness of 1 nm or less according to the present invention obtained from the above-mentioned layered ruthenate compound has a larger charge storage ability than a conventional ruthenium oxide, and is useful as an electrode material of an electrochemical element.

  The present inventors have found that by adding a potassium salt to a ruthenium compound, it is possible to synthesize a compound having a layered structure formed by stacking layers having a thickness of 1 nm or less (layered ruthenate compound). We succeeded in making the ruthenate compound finer (larger area). This micronization resulted in a ruthenate nanosheet having a thickness of 1 nm or less. Here, the ruthenate nanosheet refers to a sheet-like crystalline ruthenate compound having a thickness on the order of nm and a length and width on the order of μm. It has been found that the ruthenate nanosheet can be used for a pseudo-double-layer capacitor, and the capacity of the pseudo-double-layer capacitor can be improved to about 10 times that of a conventional one by imparting proton conductivity.

  The present invention, in the crystal structure of the ruthenate compound, by synthesizing a layered ruthenate compound by forming a state in which a crystal layer and a water layer are stacked as separate layers at the nano level, It is based on the result of studying enabling easy proton transfer inside the solid bulk. As described above, the layered ruthenate compound in the present invention is composed of an electron conductive layer composed of an electrochemically stable nano-level sheet-like ruthenium oxide crystal and a proton conductive layer composed of water or hydrated protons. . Due to such a laminated structure of the electron conductive layer and the proton conductive layer at the molecular level, it is possible to exhibit a significantly increased charge storage ability. That is, the layered ruthenate compound is a material useful for a high-output, large-capacity supercapacitor.

  In the X-ray diffraction pattern, the layered ruthenate compound according to the present invention has (00L) planes (where L = 1 to n in the range of 0 ≦ θ (CuKα) ≦ 90 °, and n is determined by the basic plane distance. ≤ n ≤ 35). In particular, the layered ruthenium is characterized in that the diffraction intensity of the (001) plane and the (002) plane is stronger than that of the other planes. In the acid compound, the thickness of each ruthenium acid compound layer (nanosheet) is 1 nm or less. Preferably, the thickness is 0.1 nm or more.

Ruthenate nanosheet according to the present invention,
(A) mixing ruthenium oxide and an alkali metal compound, and heating or melting the resulting mixture to obtain an alkali metal-type layered ruthenate compound containing a ruthenate nanosheet having a thickness of 1 nm or less;
(B) a step of treating the alkali metal-type layered ruthenate compound in an acidic solution and exchanging at least a part of the alkali metal with protons to obtain a proton-type layered ruthenate hydrate;
(C) reacting the proton-type layered ruthenic acid hydrate with alkylammonium or alkylamine to obtain an alkylammonium-layered ruthenic acid intercalation compound; and (d) using the alkylammonium-layered ruthenic acid intercalation compound as a solvent. It can be obtained by mixing and obtaining a colloid containing ruthenate nanosheets having a thickness of 1 nm or less.

Step (a):
First, ruthenium oxide and an alkali metal compound are mixed, and the resulting mixture is heated or melted to obtain an alkali metal-type layered ruthenate compound containing a ruthenate nanosheet having a thickness of 1 nm or less.
Specific examples of the layered ruthenate compound obtained here are:
Formula (3): M _x RuO _{2 + 0.5x} · nH ₂ O (3)
(Where M is an alkali metal ion such as Li, Na, K, Rb or Cs, for example, 0 <x <1, 0 ≦ n ≦ 10) and is an alkali metal-type layered ruthenate compound.

A first method for synthesizing this alkali metal-type layered ruthenate compound is to mix an alkali metal carbonate or an alkali metal nitrate with ruthenium oxide, and to obtain the resulting mixture, preferably in an inert atmosphere at 700 to 900 This is a method of performing a heat treatment at a temperature of ° C. (solid-phase reaction method).
The second synthesis method is a method (melting method) in which an alkali metal hydroxide and ruthenium oxide are mixed, and the resulting mixture is melted at 500 to 700 ° C.

Further, the alkali metal-type layered ruthenate compound represented by the formula (3) is obtained by mixing the layered ruthenate compound and the alkali metal nitrate as a third synthesis method, and subjecting the resulting mixture to an inert atmosphere. Inside, it can also be obtained by a method of performing a melting treatment at a temperature higher than the melting point of the alkali metal nitrate (molten ion exchange method).
Furthermore, as a fourth synthesis method, a proton-type layered ruthenic acid hydrate described below is also obtained by dispersing in an aqueous solution of an alkali metal hydroxide or chloride (for example, potassium hydroxide or potassium chloride) and stirring. be able to.

Step (b):
Next, the alkali metal-type layered ruthenate compound is treated in an acidic solution, and at least a part of the alkali metal is exchanged with protons to obtain a proton-type layered ruthenate hydrate.
The proton-type layered ruthenic acid hydrate obtained by the step (b) is
Equation _{(4): M xy H y} RuO 2 + 0.5x · nH 2 O (4)
(In the formula, M is represented by, for example, an alkali metal ion such as Li, Na, K, Rb or Cs, 0 <x <1, 0 ≦ y <x, 0 ≦ n ≦ 10).
This proton-type layered ruthenic acid hydrate can be synthesized by performing a proton exchange reaction in an acidic aqueous solution using an alkali metal-type layered ruthenate compound as a starting material (proton exchange method).

Further, the proton-type layered ruthenic acid hydrate,
Equation _{(5): H xy M y} RuO 2 + 0.5x · nH 2 O (5)
(Wherein, M is a divalent metal ion such as Mg, Ca, Sr, Ba or a trivalent metal ion such as Y or Ln, 0 <x <1, 0 ≦ y <x, 0 ≦ n ≦ 10). The layered ruthenate represented may be.
This layered ruthenate is synthesized by a method of reacting a proton-type layered ruthenate hydrate represented by the above formula (4) with an aqueous solution containing M metal ions in the formula (5) (solution ion exchange method). can do.

Step (c):
In the step (c), an alkyl ammonium or an alkyl amine is reacted with the proton-type layered ruthenic acid hydrate to obtain an alkyl ammonium-layered ruthenic acid intercalation compound.
The alkylammonium-layered ruthenic acid intercalation compound obtained here is a compound having a structure in which alkylammonium is intercalated into the layered ruthenate compound,
Equation _{(2): M xy H yz} B z RuO 2 + 0.5x · nH 2 O (2)
Wherein M is an alkali metal ion such as Li, Na, K, Rb or Cs, B is (R) _m NH _4-m or (R) _mp (R ′) _p NH _4-m (R and R 'Is an alkyl ammonium represented by CH ₃ (CH ₂ ) _q , m = 0 to 4, p = 0 to 3, q = 0 to 18), and 0 <x <1, 0 ≦ y <x, 0 ≦ z <y, 0 ≦ n ≦ 10].

In the step (c), as a first method, the above-mentioned intercalation compound can be obtained by mixing the above-mentioned proton-type layered ruthenic acid hydrate with a solution containing an alkylammonium salt and reacting both. Exchange method).
Furthermore, as a second method, the above-mentioned intercalation compound can be obtained by mixing the above-mentioned proton-type layered ruthenic acid hydrate with a solution containing an alkylamine and reacting both (acid-base reaction method).
Alternatively, after the above-mentioned alkylammonium-layered ruthenic acid intercalation compound is obtained, it may be further mixed with a solution containing a second alkylammonium salt to allow them to react (guest exchange reaction method).

Step (d):
Finally, the alkylammonium-layered ruthenate interlayer compound is mixed with a solvent to obtain a colloid containing a ruthenate nanosheet having a thickness of 1 nm or less. Specifically, the alkylammonium-layered ruthenic acid intercalation compound is dispersed in a high dielectric constant solvent.
As the high dielectric constant solvent, at least one selected from the group consisting of water, alcohol, acetonitrile, dimethylsulfoxide, dimethylformamide and propylene carbonate can be used. Among them, water, alcohol, or acetonitrile is preferred because of its high dielectric constant, low viscosity, and low boiling point. Among them, methanol is particularly preferred.

When the intercalation compound is dispersed in a high dielectric solvent, the intercalation compound is isolated and dispersed in a single layer, and a colloid in which ruthenate nanosheets are dispersed is obtained. Of course, this colloid may partially contain a layered ruthenate compound which is a laminate in which several nanosheets are stacked. From this colloid, the ruthenate nanosheet according to the present invention, which is porous and has excellent electron and proton conductivity, can be recovered.
Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

<< Step (a) >>
1. Synthesis of potassium-type layered ruthenic acid Potassium-type layered ruthenic acid was synthesized by the solid phase method or the melting method as follows.
(1) Synthesis by solid phase method K ₂ CO ₃ and RuO ₂ were mixed at a molar ratio of 0.625: 1, and the resulting mixture was heated and baked at 850 ° C. for 12 hours under a flow of Ar gas. Next, the obtained fired product was washed with distilled water to remove excess potassium. Finally, a solid component was recovered from the fired product after washing by filtration or centrifugation.
Wherein the molar ratio of K ₂ CO ₃ with respect to RuO ₂ is preferably 0.2 to 1.5, more it was preferably in the range of 0.5 to 0.7. In addition, although sintering was possible in the air, it was preferable to perform sintering in an inert atmosphere such as Ar gas. Further, the firing temperature was preferably from 700 to 900C.

(2) Production Method by Melting Method KOH and RuO ₂ were mixed at a molar ratio of 3: 1 and the resulting mixture was heated and melted in air at 600 ° C. for 0.5 hour. The obtained melt was washed with distilled water to remove excess potassium. Then, solid components were recovered from the washed melt by filtration or centrifugation. Finally, the recovered solid component was air-dried to obtain a hydrate, and the hydrate was dried at a temperature of 120 ° C. or higher to obtain an anhydride.
The molar ratio of KOH with respect to RuO ₂ was preferred 2 to 3. Further, the melting temperature was preferably from 500 to 700 ° C.

(3) Production Method by Ion Exchange Method As another method, potassium-type layered ruthenic acid was synthesized by ion exchange of a proton-type layered ruthenic acid hydrate described below.
First, the proton-type layered ruthenic acid hydrate was dispersed in an aqueous solution of KOH or KCl and stirred at 60 to 80 ° C. to obtain a potassium-type layered ruthenic acid hydrate. After washing with distilled water, excess potassium was removed from the potassium-type layered ruthenic acid hydrate, and the solid component was recovered by filtration or centrifugation. A hydrate was obtained by air-drying the collected solid component, and the hydrate was dried at a temperature of 120 ° C. or higher to obtain an anhydrate.

2. Synthesis of Cesium-Type Layered Ruthenic Acid Cs ₂ CO ₃ and RuO ₂ were mixed at a molar ratio of 0.192: 1, and the resulting mixture was heated and baked at 900 ° C. for 120 hours under flowing Ar gas.
The molar ratio of Cs ₂ CO ₃ with respect to RuO ₂ is preferably from 0.1 to 1.0, more it was preferably in the range of 0.15 to 0.30. Although sintering was possible in air, it was preferable to perform sintering in an inert atmosphere such as Ar gas. Further, the firing temperature is preferably from 800 to 1000 ° C, and more preferably from 700 to 900 ° C.

3. Evaluation of Physical Properties of Potassium-Type Layered Ruthenic Acid (1) Composition The composition of the potassium-type layered ruthenic acid synthesized in 1 above was subjected to inductively coupled plasma emission spectrometry, thermogravimetric analysis, X-ray fluorescence analysis and X-ray photoelectron spectroscopy. Analysis by the method revealed that it was represented by K _x RuO _{2 + 0.5x} · nH ₂ O. Note that x varies depending on the synthesis conditions such as the firing temperature, the firing time, and the mixing ratio of the raw materials, but is a value satisfying 0 <x <1. In the case of 850 ° C., 12 hours, under Ar gas flow, and K ₂ CO ₃ : RuO ₂ = 0.625: 1 (molar ratio), x = 0.22. The water content n varied depending on the drying conditions, and was a value satisfying 0 ≦ n ≦ 10. N = 0.7 when air-dried at room temperature, and 0 ≦ n ≦ 0.4 when dried at 120 ° C. In addition, what is necessary is just to determine the optimal value for the water content n according to the target electrochemical element.

(2) Appearance The potassium-type layered ruthenic acid produced in 1 above was observed with a scanning electron microscope. The obtained scanning electron microscope (SEM) photograph (image) is shown in FIGS. 1 and 2. As can be seen from FIGS. 1 and 2, a plate-like crystal having several hundred nm in the major and minor axis directions and several tens nm in thickness was obtained.

(3) Structure _{K x RuO 2 + 0.5x · nH} 2 O (x = 0.22, n = 0.4) in powder X-ray diffraction (XRD) pattern is shown in FIG. FIG. 3 shows that a layered structure having a basic plane distance d ₀₀₁ of 0.730 nm is obtained.
Here, the basic plane interval is a repetition interval of each layer in the laminating direction of the layered structure (that is, a direction perpendicular to the plane direction of the layer), and the ruthenium oxide layers (ruthenate nanosheets) are regularly arranged. Indicates the space between layers.

As will be described later, this basic plane spacing can be changed by metal ions or organic components existing between layers of the layered ruthenate compound. The assignment of each diffraction peak is as shown in Table 1. Diffraction planes other than the (00L) plane have low peak intensities (about 1/1000) in the X-ray diffraction pattern and are difficult to assign.
_{Here, K 0.22 RuO 2.11 · 0.4H 2} O electron beam diffraction image of the (photographic) shown in FIG. 4 shows a transmission electron micrograph (image) in FIG. It is understood that the thickness of the ruthenium oxide layer is 1 nm or less, and that a regular two-dimensional array is obtained.

4. Evaluation of Physical Properties of Cesium-Type Layered Ruthenic Acid (1) Composition The composition of the cesium-type layered ruthenic acid produced in the above item 2 was analyzed by thermogravimetric analysis and X-ray fluorescence spectroscopy. The formula: Cs _x RuO ₂₊ it was found to be expressed in _0.5x · nH ₂ O. Note that x varies depending on the synthesis conditions such as the firing temperature, the firing time, and the mixing ratio of the raw materials, but is a value satisfying 0 <x <1. In the case of 900 ° C., 12 hours, Ar gas flow, and Cs ₂ CO ₃ : RuO ₂ = 0.192: 1 (molar ratio), x = 0.35. The water content n varied depending on the drying conditions, and was a value satisfying 0 ≦ n ≦ 10. N = 0.7 when air-dried at room temperature, and 0 ≦ n ≦ 0.4 when dried at 120 ° C. In addition, what is necessary is just to determine the optimal value for the water content n according to the target electrochemical element.

(2) Appearance The cesium-type layered ruthenic acid produced in 2 above was observed with a scanning electron microscope, and a scanning electron microscope photograph was taken. According to this, a plate-like crystal having several hundred nm in the major and minor axis directions and a thickness of several tens nm was obtained.

(3) Structure FIG. 6 shows a powder X-ray diffraction (XRD) pattern of Cs _x RuO _{2 + 0.5x} · nH ₂ O (x = 0.35, n = 0.4). FIG. 6 shows that a layered structure having a basic plane distance d ₀₀₁ of 0.762 nm was obtained. Table 2 shows the assignment of each diffraction line. Diffraction planes other than the (00L) plane have low peak intensities (about 1/1000) in the X-ray diffraction pattern and are difficult to assign.

<< Step (b) >>
1. Production of proton-type layered ruthenic acid hydrate Proton-type multilayered ruthenic acid hydrate was synthesized by performing a proton exchange reaction using the layered ruthenate compound synthesized in the above step (a) as a starting material.
First, potassium-type layered ruthenic acid was stirred in diluted hydrochloric acid at 60 ° C. for 48 hours. Then, excess hydrochloric acid was washed with distilled water, and a solid component was recovered by filtration or centrifugation. The acid that can be used here is not limited to hydrochloric acid. Similar results were obtained with sulfuric acid, nitric acid, hydrogen bromide and the like. Further, the stirring time and the temperature also varied depending on the amount to be synthesized. Although it is possible to synthesize at room temperature, the reaction time is longer.

2. Evaluation of physical properties of proton-type layered ruthenate hydrate (1) Composition The composition of the proton-type layered ruthenate hydrate synthesized in 1 above was analyzed by inductively coupled plasma emission spectrometry, thermogravimetric analysis, and fluorescent X-ray analysis. It was analyzed by law and X-ray photoelectron spectroscopy, the _{formula: K xy H y RuO 2 +} 0.5x · nH 2 O ( where satisfy 0 <x <1,0 ≦ y < x, 0 ≦ n ≦ 10. ).
Here, the amount y of H differs depending on the acid treatment conditions, and satisfies xy <0.05 after the acid treatment at 60 ° C. for 48 hours. The water content n was 0.4 when dried at 120 ° C., and n = 0 to 10 depending on the drying conditions.

(2) Appearance The proton-type layered ruthenic acid hydrate produced in 1 above was observed with a scanning electron microscope. FIGS. 7 and 8 show the obtained scanning electron micrographs. As can be seen from FIGS. 7 and 8, plate crystals having a length of several hundred nm in the major and minor axes and a thickness of several tens of nm were obtained.

(3) Structure FIG. 9 shows a powder X-ray diffraction (XRD) pattern of H _0.22 RuO _2.11 · nH ₂ O (n = 0.4). FIG. 9 shows that a layered structure having a basic plane distance d ₀₀₁ of 0.457 nm was obtained. Table 3 shows the assignment of each diffraction line. Diffraction planes other than the (00L) plane have low peak intensities (about 1/1000) in the X-ray diffraction pattern and are difficult to assign.

Here, the electron beam diffraction image of H _0.22 RuO _2.11 · 0.4H ₂ O shown in FIG. 10 shows a transmission electron micrograph in Figure 11. It is observed that the layers are repeated at intervals of about 0.5 nm, the thickness of one layer of ruthenium oxide (ruthenate nanosheet) can be estimated to be about 0.5 nm, and a regular two-dimensional array is obtained. You can see that it is. In addition, a clear diffraction spot is observed in the electron diffraction image, which indicates that the ruthenium oxide layer has good crystallinity.

  In general, in the structure of the proton-type layered ruthenic acid, a ruthenium oxide layer having a thickness of about 0.5 nm and water of hydration are regularly arranged two-dimensionally, and the surface of the ruthenium oxide layer is covered with hydroxyl groups. It has a crystal structure. The amount of hydration is not particularly limited by the structure, and the proton-type layered ruthenic acid can contain water up to a state close to infinite swelling. In the existing amorphous hydrated oxide and electrolytic ruthenium oxide hydrate, the amount of hydration is macroscopic because the ruthenium oxide and the structural water are arranged randomly and the water molecules are present in the gaps between the structures. To some extent dictated by the structure.

<< Process (c) >>
1. Synthesis of alkylammonium-layered ruthenic acid intercalation compound The alkylammonium-layered ruthenic acid intercalation compound was obtained by an ion exchange reaction, a guest exchange reaction or an acid-base reaction as follows.
(1) Synthesis by ion exchange reaction The proton-type layered ruthenic acid hydrate synthesized in the above step (b) was dispersed in an aqueous solution of alkylammonium and stirred at room temperature for 3 days. Subsequently, excess organic substances were washed with distilled water, and solid components were recovered by filtration or centrifugation. Here, the alkyl ammonium is represented by (R) _m NH _4-m or (R) _mn (R ′) _n NH _4-m (where R and R ′ are CH ₃ (CH ₂ ) p, m = 0 to 4, n = 0-3, p = 0-18).

(2) Synthesis by acid-base reaction The proton-type layered ruthenic acid hydrate synthesized in the above step (b) was dispersed in an alkylamine solution and stirred at room temperature for 3 days. Subsequently, excess organic substances were washed with distilled water, and solid components were recovered by filtration or centrifugation. Here, the alkylamine is represented by (R) _m NH _3-m or (R) _mn (R ′) _n NH _3-m (where R and R ′ are CH ₃ (CH ₂ ) p, m = 0 to 3, n = 0-2, p = 0-18).

(3) Synthesis by Guest Exchange Reaction The alkylammonium-layered ruthenic acid intercalation compound was dispersed in an aqueous solution of alkylammonium and stirred at room temperature for 3 days. Subsequently, excess organic substances were washed with distilled water, and solid components were collected by ultracentrifugation. Here, the alkylammonium was the same as that used for the synthesis by the ion exchange reaction in the above (1).

2. Evaluation of Physical Properties of Alkyl Ammonium-Layered Ruthenic Acid Intercalation Compound (1) Composition The alkylammonium-layered ruthenic acid intercalation compound synthesized in the above 1 was analyzed by thermogravimetric analysis and found to have the following chemical composition.
H: alkyl ammonium: Ru = yz: z: 1 (molar ratio)
Here, the organic content z differs depending on the preparation conditions and the type of the alkyl chain, and satisfies y <1.

(2) Appearance Among the intercalation compounds synthesized in 1 above, a scanning electron micrograph of a cetyltrimethylammonium-layered ruthenate intercalation compound ([CH ₃ (CH ₂ ) ₁₅ N (CH ₃ ) ₃ ] _0.2 RuO _2.1 ) is shown. As shown in FIG. The layers are repeated at intervals of about 2.8 nm, and a striped pattern is observed.

(3) Structure Among the intercalation compounds synthesized in the above 1, powder X-ray diffraction patterns of ethylammonium-layered ruthenate intercalation compound, tetrabutylammonium-layered ruthenate intercalation compound, and cetyltrimethylammonium-layered ruthenate intercalation compound are shown. 13, 14 and 15 respectively. It can be seen that each has a layered structure in which the basic plane distances are d ₀₀₁ = 0.816, 1.68, and 2.76 nm. The assignment of each diffraction line is as shown in Tables 4, 5 and 6.

<< Process (d) >>
1. Production of Colloids Containing Ruthenate Nanosheets Colloidal ruthenate nanosheets (colloids containing nanosheets) were obtained by dispersing tetrabutylammonium-layered ruthenate intercalation compound in a solvent.
Specifically, first, the tetrabutylammonium-layered ruthenic acid intercalation compound synthesized in the step (c) was dispersed in a solvent having a high dielectric constant, ultrasonically treated, and stirred. Next, the colloid component (supernatant) was collected by centrifugation (2000 rpm). Here, methanol was used as the high dielectric constant solvent.

2. Evaluation of Physical Properties of Colloidal Ruthenate Nanosheet (1) Composition The colloidal ruthenate nanosheet is composed of a high dielectric constant solvent, tetrabutylammonium and ruthenate nanosheet, and a high dielectric constant solvent: tetrabutylammonium: ruthenate nanosheet = ( 100-x): 0.075x: x (molar ratio). Here, x is the concentration of the tetrabutylammonium-layered ruthenic acid intercalation compound, and was about 2 to 100 μg / L.

(2) Appearance FIG. 16 shows a scanning electron micrograph of the ruthenate compound nanosheet contained in the colloid obtained in the above step (d). At this time, the colloidal ruthenate nanosheet was supported on a carbon material as a support and observed. From FIG. 16, it can be seen that an isolated crystalline nanosheet having a thickness of several hundred nm in the long and short major axis directions and a nanometer order was obtained.

(3) Structure The dispersion (colloid) containing the ruthenate nanosheet obtained in the above step (d) was cast on a glass substrate. As a result, the ruthenate nanosheets were re-laminated, and an oriented thin film composed of tetrabutylammonium-layered ruthenate interlayer compound was obtained. FIG. 17 shows a powder X-ray diffraction pattern of the oriented thin film. From FIG. 17, it can be seen that the alignment thin film has a layered structure with a basic plane distance d ₀₀₁ = 1.68 nm and has an extremely good c-axis alignment. Table 7 shows the assignment of each diffraction line.

In this example, an electrode for an electrochemical supercapacitor was manufactured using the proton-type layered ruthenic acid hydrate (HRO = H _0.22 RuO _2.11 · nH ₂ O, n> 0) obtained in the above step (b). The capacity of the electrochemical supercapacitor was examined.
Proton-type layered ruthenic acid hydrate is dispersed in water or a solvent such as dimethylformamide (about 40 μg / L), and the obtained dispersion is dropped on a cut surface (diameter 5 mm) of a glassy carbon rod and further fixed. A perfluorocarboxylic acid ionomer sold by DuPont under the name of Nafion is further dripped as an agent and dried to produce a glassy carbon (hereinafter referred to as HRO / GC) electrode supporting a proton-type layered ruthenic acid hydrate. Was prepared.

  Using an HRO / GC electrode, a platinum mesh counter electrode, and a Ag / AgCl reference electrode in a 0.5 M sulfuric acid electrolyte, scanning was performed at 500 to 2 mV / s to obtain a cyclic voltammogram (CV). 18 to 23 show CVs when the scanning speed is 500 mV / s, 200 mV / s, 50 mV / s, 20 mV / s, 5 mV / s and 2 mV / s, respectively.

  At the time of high-speed scanning, a square CV peculiar to the pseudo-double-layer capacitor is obtained, and at the time of low-speed scanning, an oxidation-reduction capacity due to oxidation-reduction is obtained in addition to the capacity of the pseudo-double-layer capacitor. The capacity like a pseudo double layer capacitor hardly depends on the scanning speed, and the oxidation-reduction capacity increases as the scanning speed decreases.

  Table 8 shows the capacitance of the HRO / GC electrode obtained from the CV obtained at each scanning speed. The capacitance increases slightly with decreasing scanning speed. This is due to the increase in the oxidation-reduction capacity described above. The obtained capacitance is comparable to that of hydrated ruthenium oxide synthesized by electrolytic oxidation, and is one order of magnitude higher than that of crystalline ruthenium oxide having a rutile structure.

As a pseudo double layer capacity (physical phenomenon not involving the redox reaction) of ruthenium oxide, a general value of about 80 μF / cm ² (microfarad per actual surface area) is used, and the capacitance (389 F / g) at 50 mV / s is used. ) Was 486 m ² / g. The surface area of conventional rutile RuO ₂ is 50 to 60 m ² / g (specific surface area determined by the BET method based on nitrogen adsorption / desorption measurement) even for fine particles having a particle diameter of 10 nm.

Proton-type layered ruthenic acid hydrate has characteristics different from existing amorphous ruthenium oxide hydrate and rutile-type ruthenium oxide. The features are listed below.
(i) The electrochemically active surface area is extremely large. Each layer of the proton-type layered ruthenic acid has a thickness of 1 nm or less, and protons and hydrated protons can freely move between the layers. The electrochemically active specific surface area reaches up to 508 m ² / g-RuO ₂ .

(ii) In HRO / GC, a clear redox pair appears during slow charge / discharge (slow scan or small current charge / discharge). This is a component that cannot be obtained with amorphous hydrated ruthenium oxide because it depends on the crystalline structure. The capacity due to this redox depends on the active surface area. In crystalline rutile-type ruthenium oxide, this redox capacity can be obtained only at the particle surface, and its contribution is extremely small. The active surface area of crystalline rutile-type ruthenium oxide is 50 m ² / g, and the active surface area of proton-type layered ruthenic acid is 508 m ² / g-RuO _2, which is almost ten times as large. In the case of the proton-type layered ruthenic acid, the interlayer itself is electrochemically active, so that a redox capacity that cannot be achieved with crystalline rutile-type ruthenium oxide is obtained.

(Iii) In HRO / GC, a constant capacity can be obtained even during extremely fast charging / discharging (high-speed scanning or large-current charging / discharging). This capacitance is composed of a non-Faradic electric double layer capacitance component and a Faradic redox capacitance component. These capacitive components depend on the electrochemically active surface area. In the case of crystalline rutile-type ruthenium oxide, these contributions can be obtained only on the particle surface, and thus their contribution is extremely small. The active surface area of the crystalline rutile-type ruthenium oxide is 50 m ² / g, and that of the proton-type layered ruthenic acid is 508 m ² / g-RuO _2, which is ten times as large as that. In the case of the proton-type layered ruthenic acid, since the interlayer itself is electrochemically active, a pseudo capacitance that cannot be achieved with crystalline rutile-type ruthenium oxide is obtained.

In general, in the proton-type layered ruthenic acid, the electrolyte solution could penetrate between the crystalline ruthenium oxide layers, and proton conductivity could be imparted without damaging the electron conductive network. In addition, as a result of making the ruthenium oxide layer finer to the atomic level of 0.5 nm or less, the active surface area was extremely high, and 508 m ² / g was achieved.

  As a result, an extremely fast non-faradic (physical phenomenon not involving the redox reaction) electric double layer capacitance component and a faradic redox capacitance component can be obtained on the layer surface, so that a large capacitance can be obtained even when charging and discharging a large current. can get. In addition, since a redox capacity on the layer surface derived from the crystalline structure can be obtained, a larger capacitance can be obtained during low-speed charge and discharge. Therefore, the proton-type layered ruthenic acid hydrate is a large-capacity electrochemical superelectrode material that can be rapidly charged and discharged, and has extremely high energy density and output density.

  It is presumed that the reason why both the energy density and the output density are extremely large is that the proton / electron mixed conductivity is excellent. In general, whether the proton / electron mixed conductivity is good is determined by the i-V curve ( CV characteristic). That is, the reason can be understood from the fact that the iV curve rises favorably even at a high scanning speed and maintains a square shape similar to a capacitor, and that no resistance is included. Further, from the viewpoint of numerical data, even if the scanning speed is increased in Tables 8 and 10, almost no capacitance loss is observed, so the above reason can be estimated.

  For example, assuming that the capacitance at the time of scanning at 2 mV / s is 100%, the capacitance retention of the proton-type layered ruthenic acid when the scanning speed is increased is 90% at the time of scanning at 500 mv / s. In contrast, the capacitance retention of rutile-type ruthenium oxide nanoparticles having a nano-level particle size is only 69% when scanning at 500 mV / s. This is considered to be the result of sufficient proton conductivity. Table 9 summarizes the data.

In the above Example 2, the capacitance of the proton-type layered ruthenic acid hydrate in sulfuric acid was described. However, the present invention can be applied to a potassium-type layered ruthenic acid hydrate and various alkaline electrolytes.
(1) Regarding the capacitance of a proton-type layered ruthenic acid hydrate in an alkaline electrolyte, a proton-type layered ruthenic acid hydrate was synthesized in the same manner as in Example 2 above, and instead of a 0.5M sulfuric acid electrolyte. The capacitance was examined in the same manner as in Example 2 except that a 1M KOH electrolyte was used. Table 10 shows the results. Compared to rutile-type ruthenium oxide nanoparticles having a nano-sized particle size, the capacitance is five times higher. The reason why the capacitance is smaller than that in the case of the 0.5 M sulfuric acid electrolyte is that the pseudo capacity is reduced by oxidation and reduction in the alkali electrolyte.

(2) Regarding the capacitance of potassium-type layered ruthenic acid hydrate, a dispersion of potassium-type layered ruthenic acid hydrate and polyethylene terephthalate (PTFE) as a binder (30-J manufactured by DuPont Fluorochemicals, Mitsui) ) Was mixed, and the resulting mixture was applied to a current collector to prepare a membrane electrode. Table 11 shows the capacitance when the 0.5 M sulfuric acid electrolyte and the 1 M KOH electrolyte were used. As compared with the rutile-type ruthenium oxide nanoparticles, the capacitance can be obtained up to six times.

An example in which the layered ruthenate compound in the present invention is applied to an electrochemical device will be described. The layered ruthenate compound forms extremely stable crystals as understood from a scanning micrograph and an X-ray diffraction pattern. Hereinafter, a process of manufacturing an electrochemical device will be described.
(A) Pulverization Step The layered ruthenate compound was coarsely pulverized, then finely pulverized, and classified through a classification step to a particle size of 8 to 2.5 μm.

(B) Mixing and Kneading Steps Next, 40 parts by weight of the classified layered ruthenate compound, activated carbon powder (BP-20 manufactured by Kuraray Chemical Co., Ltd., average particle size 5 μm, specific surface area 2200 m ² / g, average pore diameter 16 °) An electrode material was prepared by mixing 50 parts by weight, 4 parts by weight of a conductive material, 2 parts by weight of a primary binder, 2 parts by weight of a permanent binder, and 2 parts by weight of a rubber-based material, followed by dry mixing, wet mixing and kneading.

(C) Various electrode materials As the conductive material, a carbon black mixture in which acetylene black and ketjen black were mixed at a weight ratio of 1: 1 was used. As the primary binder, a mixture in which starch and carboxymethyl cellulose were mixed at a weight ratio of 1: 1 was used. As the permanent binder, a sol solution of polytetrafluoroethylene (PTFE) is preferably used for an aqueous solvent, and polyvinylidene fluoride (PVDF) is preferably used for an organic solvent. .

  As the rubber-based material, a mixture obtained by mixing acrylonitrile butadiene rubber (NBR) and styrene butadiene rubber (SBR) at a weight ratio of 1: 1 was preferably used. Further, as the activated carbon powder, any activated carbon such as coconut shell activated carbon, phenol-based activated carbon, coal-based pitch activated carbon, petroleum-based pitch activated carbon, and airgel carbon could be used.

(D) Molding step, drying step A press or a coater was used according to the shape and size of the electrochemical element. The electrode material was dried at 100 ° C. or less in the case of an organic solvent. Further, in the case of an aqueous solvent, water is removed from the electrode material, the primary binder is incinerated and removed, complete drying is performed to a reduced-rate drying area, and then a sheet having a thickness of about 120 μm is obtained with a rolling roller. The sheet was cut into a shape to obtain a sheet-like electrode.

  For a coin-type capacitor, an electrochemical element was obtained by laminating a pair of sheet-like electrodes via a separator (polyvinyl alcohol-based synthetic paper manufactured by Nippon Steel Pipe Co., Ltd., thickness 50 μm). For a cylindrical capacitor, a pair of sheet electrodes was sandwiched between separators, and the whole was spirally wound to obtain an electrochemical element.

(E) Housing The electrochemical element was housed in a coin-type or cylinder-type case together with an electrolytic solution to complete the electrochemical element.
(F) Evaluation The charge / discharge characteristics of the obtained electrochemical device were evaluated. The evaluation was performed at a temperature of 85 ° C., 45 ° C., 25 ° C., 0 ° C., or −20 ° C. using a discharge rate assumed for practical use.

  A conventional electrochemical element using a ruthenium compound mainly contains ruthenium oxide. However, since ruthenium oxide is expensive, ruthenium oxide is thinly dispersed and supported in an island shape. For this reason, although the electrochemical element was excellent in initial performance, a phenomenon in which activated carbon and ruthenium oxide were separated when charge and discharge were repeated was observed, and did not reach practical use. On the other hand, the layered ruthenate compound in the present invention has excellent crystallinity, and the electrochemical device using the compound has stable charge / discharge characteristics for a long period of time.

In this example, an electrode for an electrochemical supercapacitor using an alkylammonium-layered ruthenic acid interlayer compound was prepared, and the capacity of the electrochemical capacitor was evaluated.
An electrode was produced in the same manner as in Example 2 using an alkylammonium-layered ruthenic acid intercalation compound instead of the protonated layered ruthenic acid hydrate, and the capacitance when a 0.5 M sulfuric acid electrolyte was used as the electrolyte. I asked. Table 12 shows the results. As compared with the case where the proton-type layered ruthenic acid hydrate was used, twice the capacitance was obtained.

  The reason that the alkylammonium-layered ruthenic acid intercalation compound obtains a larger capacitance than the proton-type layered ruthenic acid hydrate is that the interlayer is expanded by the alkylammonium and is expanded even after ion exchange with protons in the electrolyte. This is because the penetration of the electrolyte solution is promoted by the interlayer.

In this example, an electrode for an electrochemical supercapacitor using a colloidal ruthenate nanosheet (a colloid containing a ruthenate nanosheet) was prepared, and the capacity of the electrochemical capacitor was evaluated.
By dispersing the tetrabutylammonium-layered ruthenic acid intercalation compound obtained in the same manner as in Example 1 in methanol, which is a high dielectric constant solvent, individual ruthenate nanosheets are isolated and dispersed while maintaining the crystal structure. A ruthenate nanosheet was obtained. In this colloid, the ruthenate nanosheet was stably dispersed in the dispersion medium, and had properties similar to swellable clay.

  Thus, the colloid solution containing the ruthenate nanosheet was applied to the surface of the glassy carbon rod to form an electrode modified with the ruthenate nanosheet (nanosheet-modified electrode). That is, a colloid solution containing a ruthenate nanosheet was dropped on the surface of a glassy carbon rod and dried, and then the above-mentioned perfluorocarboxylic acid ionomer was dropped and dried to prepare a product. The obtained nanosheet-modified electrode was scanned at a scanning speed of 50 mV / s under the same conditions as in Example 2 to examine the CV characteristics. The obtained CV curve is shown by a in FIG. For comparison, CVs of ordinary HRO (proton-type layered ruthenic acid hydrate) particles and rutile-type ruthenium oxide nanoparticles which are not formed into nanosheets are shown by b and c, respectively.

  The shape of the CV curve of the nanosheet-modified electrode using the ruthenate nanosheet is essentially the same as the shape of the CV curve when the layered ruthenate hydrate is used. However, in the former case, the redox capacity component due to the oxidation-reduction reaction is clearly observed even during high-speed scanning, and the contribution of the oxidation-reduction reaction to the total capacity is increasing. It is considered that in the nanosheet-modified electrode, the ruthenate nanosheets formed a disordered structure during re-lamination, the diffusion resistance of protons was reduced, and the permeation of the electrolyte between the layers was performed more smoothly. As a result, as shown in Table 13, when the ruthenic acid nanosheet is used, good supercapacitor characteristics can be obtained even at the time of high-speed charge / discharge, and it is possible to cope with high-power large-capacity applications more than layered ruthenate.

  In this example, various capacitors were compared. In order to compare a commercially available electric double-layer capacitor using an activated carbon electrode, an electrochemical capacitor using rutile-type ruthenium oxide, and typical electrochemical capacitors I and II according to the present invention, each has a diameter of 20 mm and a thickness of 1. A 6 mm coin cell was assembled, and the capacity per unit mass and per unit volume was measured. Table 14 shows the results. In Table 14, as the aqueous system, an acidic electrolyte such as sulfuric acid, hydrochloric acid, or perchloric acid, or an alkaline electrolyte such as KOH, NaOH, or LiOH can be used. Here, an 8N KOH aqueous solution was used.

  Capacitors I and II were produced by the method of Example 4. As can be seen from Table 14, the capacitor according to the present invention has a mass capacity 8 to 11 times that of the conventional rutile type, 2 to 3 times that of the electric double layer capacitor, and 5 to 8 times that of the conventional rutile type. An excellent result of having a volume capacity 9 to 12 times that of the electric double layer capacitor was obtained.

In this example, an electrode catalyst for a fuel cell using a ruthenate nanosheet was prepared, and its carbon monoxide oxidation property and methanol oxidation property were examined.
A platinum-based electrode catalyst (platinum-supported carbon) was added to the colloidal ruthenic acid solution prepared in the same manner as in Example 6 and dried to prepare a ruthenate nanosheet-supported catalyst (hereinafter, referred to as HRO-NS / Pt / C). did. A glassy carbon rod as a current collector was modified with the electrode catalyst thus prepared, and an electrode was produced in the same manner as in Example 6. For comparison, an electrode was prepared using a platinum-supported carbon (Pt / C) catalyst.

When the methanol oxidation current at 0.5 V (vs. RHE) in 0.5 M sulfuric acid in the presence of 1 M methanol was measured after 30 minutes, HRO-NS / Pt / C had a higher current than Pt / C. Density was obtained. In the case of HRO-NS / Pt / C, it was 21 A / g-Pt, whereas in the case of Pt / C, it was 2 A / g-Pt. This indicates that the nanosheet-supported catalyst according to the present invention is suitable as a methanol oxidation electrode catalyst, and it is considered that HRO-NS functions as a cocatalyst that imparts resistance to CO poisoning. This is because HRO-NS / Pt / C (RuO ₂ : Pt = 1: 1 (molar ratio), Pt: C = 30: 70 (mass ratio)) and Pt / C (Pt) in a 0.5 M sulfuric acid electrolyte solution. : C = 30: 70 (mass ratio)).

  The electro-oxidation of CO by HRO-NS / Pt / C is started at about 0.44 V (vs. RHE). In the case of Pt / C, CO is electro-oxidized at a high potential of about 0.62 V (vs. RHE) or more. Electrolytic oxidation starts. It is known that CO poisons the Pt surface when methanol is used as a fuel or when a reformed fuel such as methanol or city gas is used. It means that it is increasing. In the case of HRO-NS / Pt / C, it is considered that CO is easily oxidized because OH species that oxidize adsorbed CO are present on the HRO surface.

  The present invention provides a ruthenate nanosheet having a crystal structure with a thickness of 1 nm or less, and a layered ruthenate compound having a structure in which the nanosheets are stacked. The nanosheet and the layered ruthenate compound according to the present invention have a larger charge storage ability than conventional ruthenium oxide, and are useful as electrodes of electrochemical devices. Further, the nanosheet and the layered ruthenate compound according to the present invention can be applied not only to electrochemical devices but also to electrodes of polymer electrolyte fuel cells, photocatalysts, dye-sensitized wet solar cells, and the like.

It is a scanning electron microscope photograph of potassium type layered ruthenic acid in the present invention. FIG. 2 is an enlarged view of the scanning electron microscope photograph shown in FIG. 1. It is a powder X-ray diffraction (XRD) pattern of the potassium-type layered ruthenic acid in this invention. 3 is an electron diffraction pattern of potassium-type layered ruthenic acid in the present invention. It is a transmission electron microscope photograph of potassium type layered ruthenic acid in the present invention. 1 is a powder X-ray diffraction (XRD) pattern of a cesium-type layered ruthenic acid in the present invention. It is a scanning electron micrograph of the proton type layered ruthenic acid hydrate in this invention. FIG. 8 is an enlarged view of the scanning electron microscope photograph shown in FIG. 7. It is a powder X-ray diffraction (XRD) pattern of the proton type layered ruthenic acid hydrate in the present invention. It is an electron-beam-diffraction figure of the proton type layered ruthenic acid hydrate in this invention. It is a transmission electron micrograph of the proton type layered ruthenic acid hydrate in the present invention. It is a scanning electron micrograph of the cetyltrimethylammonium-layered ruthenic acid intercalation compound in this invention. It is a powder X-ray diffraction pattern of the ethylammonium-layered ruthenic acid intercalation compound in the present invention. It is a powder X-ray diffraction pattern of the tetrabutylammonium-layered ruthenic acid intercalation compound in the present invention. 1 is a powder X-ray diffraction pattern of cetyltrimethylammonium-layered ruthenic acid intercalation compound in the present invention. 4 is a scanning electron micrograph of a ruthenate nanosheet according to the present invention. 4 is a powder X-ray diffraction pattern of an oriented thin film obtained by re-stacking the ruthenate nanosheet according to the present invention. 5 is a cyclic voltammogram of the HRO / GC electrode according to the present invention at the time of scanning at 500 mV / s. 5 is a cyclic voltammogram of the HRO / GC electrode according to the present invention at the time of scanning at 200 mV / s. 5 is a cyclic voltammogram of the HRO / GC electrode according to the present invention at the time of scanning at 50 mV / s. 5 is a cyclic voltammogram of the HRO / GC electrode according to the present invention at the time of scanning at 20 mV / s. 5 is a cyclic voltammogram of the HRO / GC electrode according to the present invention when scanning at 5 mV / s. 4 is a cyclic voltammogram of the HRO / GC electrode according to the present invention when scanning at 2 mV / s. 5 is a cyclic voltammogram of the nanosheet-modified electrode according to the present invention at the time of scanning at 50 mV / s.

Claims (12)

  A ruthenate nanosheet having a thickness of 1 nm or less. Formula (1): [RuO _{2 + 0.5x} ] ^x- (1)
The ruthenate nanosheet according to claim 1, which is represented by the following formula:   A layered ruthenate compound formed by laminating the ruthenate nanosheets according to claim 1.   In the X-ray diffraction pattern, each plane is (00L) (provided that L = 1 to n in the range of 0 ≦ θ (CuKα) ≦ 90 °, and n is determined by the basic plane distance and satisfies 5 ≦ n ≦ 35). The layered ruthenate compound according to claim 3, which has a diffraction peak.   A colloidal ruthenate compound comprising the ruthenate nanosheet according to claim 1 and / or the layered ruthenate compound according to claim 3 and a solvent.   An electrochemical device having an electrode comprising the ruthenate nanosheet according to claim 1. (A) mixing ruthenium oxide and an alkali metal compound and calcining or melting the resulting mixture to obtain an alkali metal-type layered ruthenate compound containing a ruthenate nanosheet having a thickness of 1 nm or less;
(B) a step of treating the alkali metal-type layered ruthenate compound in an acidic solution and exchanging at least a part of the alkali metal with protons to obtain a proton-type layered ruthenate hydrate;
(C) reacting the proton-type layered ruthenic acid hydrate with alkylammonium or alkylamine to obtain an alkylammonium-layered ruthenic acid intercalation compound; and (d) using the alkylammonium-layered ruthenic acid intercalation compound as a solvent. A method for producing a ruthenate nanosheet, comprising a step of mixing to obtain a colloid containing a ruthenate nanosheet having a thickness of 1 nm or less.   The method for producing a ruthenate nanosheet according to claim 7, wherein the step (a) is a step of mixing ruthenium oxide and an alkali metal salt and firing the resulting mixture at 700 to 900 ° C.   The method for producing a ruthenate nanosheet according to claim 7, wherein the step (a) is a step of mixing ruthenium oxide and an alkali metal hydroxide and melting the resulting mixture at 500 to 700 ° C. In the step (c), (R) _m NH _4-m or (R) _mp (R ′) _p NH _4-m (where R and R ′ are CH ₃ ( _{CH 2) q, m = 0~4} , p = 0~3, q = 0~18) in the production method of the ruthenium acid nanosheets according to claim 7, wherein the alkylammonium is a step of reacting represented. In the step (c), the proton-type layered ruthenic acid hydrate is converted into (R) _m NH _3-m or (R) _mp (R ′) _p NH _3-m (where R and R ′ are CH ₃ ( _{CH 2) q, m = 0~3} , p = 0~2, q = 0~18) in the production method of the ruthenium acid nanosheets according to claim 7 wherein the alkyl amine is a step of reacting represented.   In the step (d), an alkylammonium-layered ruthenic acid intercalation compound is mixed with at least one solvent selected from the group consisting of water, alcohol, acetonitrile, dimethylsulfoxide, dimethylformamide and propylene carbonate to obtain a colloid. The method for producing a ruthenate nanosheet according to claim 7, which is a step.