JP5070483B2 - Ruthenic acid nanosheet and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ruthenic acid nanosheet derived from an MRuO<SB>2</SB>type layered ruthenic acid alkali metal compound (wherein, M is an alkali metal) and its producing method. <P>SOLUTION: The method for producing the ruthenic acid nanosheet whose formula is denoted as [RuO<SB>2</SB>]<SP>x-</SP>(0&lt;x&lt;1) comprises (a) a step that a mixture of a ruthenium oxide having an atomic valence of tetravalent or more, an alkali metal compound and the like is mixed with metallic ruthenium powder and then an alkali metal type layered ruthenic acid compound is obtained, (b) a step that the ruthenic acid compound is treated with a bromine solution and then a proton type layered ruthenic acid is obtained, (c) a step to obtain a proton type layered ruthenic acid hydrate by hydrating ruthenic acid, (d) a step to obtain an alkyl ammonium-layered ruthenic acid intercalation compound by reacting the ruthenic acid hydrate with an alkyl ammonium compound and the like and (e) a step that the ruthenic acid intercalation compound is mixed with a solvent and dispersed and then a ruthenic acid nanosheet colloid is obtained. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

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

Conventionally, typical electrochemical elements having a power storage function include electric double layer capacitors, pseudo double layer capacitors, and secondary batteries, and these have been put into practical use in application devices that make use of their respective characteristics. . Secondary batteries have a higher energy density than electric double layer capacitors, and are currently the most general-purpose power storage devices. However, since the secondary battery is charged and discharged using an electrochemical reaction between the electrode and the electrolytic solution, the cycle life is insufficient, and it is necessary to replace it after use for a certain period. On the other hand, the electric double layer capacitor based on the electric double layer capacity generated at the interface between the activated carbon electrode surface and the electrolyte solution has a high output density and a long life compared to the secondary battery, and therefore requires high reliability. Used for backup power supply. On the other hand, the pseudo double layer capacitor has a pseudo capacitance that is expressed by an electrochemical adsorption phenomenon at the interface between the surface of a metal oxide such as RuO ₂ , IrO ₂ , and Co ₃ O ₄ and the electrolytic solution. In recent years, development has been accelerated as a power storage device having both high output density and long life, which are characteristics of a multilayer capacitor, and high energy density, which is a characteristic of a secondary battery.

In particular, a pseudo double layer capacitor using RuO ₂ has been researched and developed for the longest time, and recently has been put into practical use in part. However, since ruthenium is a noble metal and expensive, further higher activation and effective utilization are desired. Recently, ruthenic acid nanosheets were synthesized by delamination of layered ruthenic acid obtained by ion exchange from layered potassium ruthenate, and high electronic conductivity and high capacitance were reported (Patent Document 1 and Non-Patent Document 1). .

However, the sheet thickness of the ruthenic acid nanosheet derived from this potassium ruthenate is estimated to be about 0.5 nm, and RuO ₂ contained in one thickness direction corresponds to two, and there is room for further thinning, A method for producing a ruthenic acid nanosheet corresponding to one RuO ₂ layer has not been known.

Recently, synthesis and structural analysis of a novel layered ruthenate NaRuO ₂ having an α-NaFeO ₂ type structure have been reported (Non-patent Document 2 and Non-patent Document 3). Since this NaRuO ₂ has one layer of RuO _{2 and} is extremely thin, if it can be delaminated and made into a colloidal nanosheet, the ruthenium acid nanosheets that have been wasted in the past ruthenium acid nanosheets Can be effectively utilized to the limit, and higher pseudo double layer capacity can be expected. However, the delamination technique applicable to layered ruthenate derived from potassium ruthenate was difficult to apply to layered ruthenate derived from sodium ruthenate.

JP2004-315347 W. Sugimoto, H .; Iwata, Y. et al. Yasunaga, Y. et al. Murakami, and Y.M. Takasu, Angew. Chem. , Int. Ed. , 42, 4092 (2003) M.M. Shikano, R.A. K. Kremer, M.M. Ahrens, H.M. J. Koo, M.M. H. Whangbo, and J.M. Inorg. Chem. , 43, 5 (2004) M.M. Shikano, C.I. Delmas, and J.M. Darriet, Inorg. Che. , 43, 1214 (2004)

It is an object of the present invention to provide an extremely thin ruthenic acid nanosheet obtained by peeling off layers of ruthenic acid derived from an alkali metal ruthenate compound of the MRuO ₂ (M = alkali metal) type, and a method for producing the same. To do.

In order to solve the above problems, the present invention has a thickness of 0.4 nm or less, and the formula (1):
[RuO ₂ ] ^x- (0 <x <1) (1)
The ruthenic acid nanosheet represented by this is provided.

  The present invention also provides an alkylammonium-layered ruthenate intercalation compound containing an alkylammonium ion between layers of the layered ruthenate compound formed by laminating the ruthenate nanosheets.

  The present invention also provides a colloid comprising the ruthenate nanosheet and / or the alkylammonium-layered ruthenate intercalation compound and a solvent.

  The present invention also provides an electrochemical device having an electrode containing the ruthenate nanosheet and / or the alkylammonium-layered ruthenate intercalation compound.

The present invention also includes the following steps (a) to (e):
(A) A mixture of ruthenium oxide having a valence of IV or higher and an alkali metal compound, or an alkali metal compound of ruthenium acid having a valence of IV or more is mixed with a metal ruthenium powder, and the resulting mixture is calcined or A step of obtaining an alkali metal layered ruthenate compound containing III-valent ruthenium by melting;
(B) treating the alkali metal-type layered ruthenate compound with a bromine solution to remove at least a portion of the alkali metal ions between the layers to obtain a proton-type layered ruthenate acid;
(C) a step of hydrating the proton-type layered ruthenium acid to obtain a proton-type layered ruthenium acid hydrate;
(D) a step of reacting the proton-type layered ruthenium acid hydrate with an alkylammonium compound and / or an alkylamine to obtain an alkylammonium-layered ruthenate intercalation compound; and (e) the alkylammonium-layered ruthenate intercalation compound. And having a thickness of 0.4 nm or less, including the step of mixing and dispersing with a solvent to obtain a delaminated ruthenic acid nanosheet colloid, and represented by the formula: [RuO ₂ ] ^x− (0 <x <1) A ruthenic acid nanosheet manufacturing method is provided.

  The ruthenic acid nanosheet of the present invention and / or the alkylammonium-layered ruthenic acid intercalation compound laminated therewith can be used as an electrode for various electrochemical devices such as redox capacitors and fuel cells. Since the sheet thickness is reduced, the utilization efficiency of ruthenium is improved, both the electronic conductivity on the sheet surface and the proton conductivity between the sheets are improved, and the electrode performance is remarkably improved. When used for a redox capacitor electrode, a high redox capacitor capacity can be obtained, which is 10 times higher than that of the conventional particulate ruthenium oxide and 10% higher than that of the conventional ruthenic acid nanosheet.

The present inventors have reported that the layer thickness is about 0.3 nm, which is as thin as possible (FIG. 3 of Non-Patent Document 3 above). Using Ru (III) -valent layered sodium ruthenate (NaRuO ₂ ), As a result of intensive studies on the delamination method, which was difficult with the conventional method, sodium ions were first deintercalated by bromine treatment to convert them into proton-type layered ruthenic acid (HRuO ₂ ), and then bulky alkylammonium ions It was found that delamination is possible by performing a guest exchange reaction of protons. By this method, we succeeded in obtaining a ruthenate nanosheet colloid with a sheet thickness of 0.4 nm or less which is unprecedented. Here, the ruthenate nanosheet refers to a sheet-like crystalline ruthenate compound having a thickness in the order of nm to sub-order and a size in the vertical and horizontal order of several hundred nm to μm. Such ruthenium acid nanosheets can be easily laminated by electrophoresis, etc., and can be used for electrodes of pseudo double layer capacitors and fuel cells, and the use efficiency of ruthenium can be increased to the limit to improve the performance of the electrodes. There was found.

The ruthenic acid nanosheet of the present invention is prepared by using a Ru (III) _-valent layered ruthenate alkali metal compound as a precursor, thereby _producing M _x RuO _{2 + 0.5x} · nH ₂ O (M is an alkali metal ion, Unlike a ruthenate nanosheet having a sheet thickness of about 0.5 nm (hereinafter referred to as ruthenate nanosheet type 1) with 0 <x <1) as a precursor, the formula (1): [RuO ₂ ] ^x− (0 <X <1) [Hereinafter, the ruthenate nanosheet of the present invention is distinguished from the ruthenate nanosheet (type 1) and is referred to as a ruthenate nanosheet (type 2)). In the present invention, the Ru (III) -valent layered ruthenate alkali metal compound is preferably NaRuO ₂ .

The present invention also provides an alkylammonium-layered ruthenate intercalation compound containing an alkylammonium ion between layers of the layered ruthenate compound formed by laminating the ruthenate nanosheets. This alkylammonium-layered ruthenate intercalation compound has (00L) faces in the X-ray diffraction pattern (provided that L = 1 to n in the range of 0 ≦ 2θ (CuKα) ≦ 90 °, and n depends on the basic plane spacing) It preferably has a diffraction peak). The alkylammonium ion has the following structural formula: (R) _m (R ′) _n (R ″) _p (R ′ ″) _q NH _{4− (m + n + p + q)} ⁺ (where R, R ′, R ′ ', And R''' each independently represent H or CH ₃ (CH ₂ ) _r , m, n, p and q are each 0 or an integer of 1 to 4, and 0 ≦ m + n + p + q ≦ 4, And a cation represented by r = 0 to 18). In particular, in order to promote delamination of ruthenate nanosheets in the step (e) described later, in the above formula, R = R ′ = R ″ = R ′ ″ = n—CH ₃ (CH ₂ ) ₃ − The ammonium compound, that is, a quaternary (n-tetrabutyl) ammonium ion is preferred. The alkylammonium-layered ruthenate intercalation compound is [(R) _m (R ′) _n (R ″) _p (R ′ ″) _q NH _{4− (m + n + p + q)} ⁺ ] _x (RuO ₂ ) (R, R ′, R ″, R ″, m, n, p and q are as described above, and x is preferably 0 <x <1. x is particularly preferably 0.05 to 0.3.

Furthermore, the present invention also relates to a colloid containing the ruthenate nanosheet and / or the alkylammonium-layered ruthenate intercalation compound and a solvent. The ruthenic acid nanosheet and / or alkylammonium-layered ruthenic acid intercalation compound colloidal solution of the present invention is composed of ruthenic acid nanosheet type 1 and the corresponding colloidal solution of alkylammonium-layered ruthenic acid intercalation compound. It can be identified by the difference in the wavelength of plasmon resonance absorption. That is, in the UV / visible absorption spectrum, the known ruthenate nanosheet (type 1) and the corresponding colloidal solution of alkylammonium-layered ruthenate intercalation compound have an absorption maximum in the λmax 357-367 nm region, whereas The inventive ruthenate nanosheet (type 2) and the corresponding colloidal solution of alkylammonium-layered ruthenate intercalation compound have an absorption maximum in the λmax 340-350 nm region. Since the ruthenate nanosheet (type 2) of the present invention is about 1/2 to 2/3 thinner than the ruthenate nanosheet (type 1), the plasmon resonance absorption wavelength as a quantum size effect is blue. Presumably shifted (shorter wavelength). Incidentally, the plasmon absorption maximum of the colloidal spherical hydrated ruthenium oxide having a particle size of 3.01 nm or 2.05 nm which is not nanosheeted is reported to be 397 nm and 394 nm, respectively [Chi-Chang Hu et al. Electrochem. Soc. , 151 (2), A281 (2004)]. Compared to these, the blue shift of the absorption wavelength of the ruthenic acid nanosheet colloid of the present invention is more remarkable.
The colloidal solvent is preferably selected from the group consisting of water, alcohol, acetonitrile, dimethyl sulfoxide, dimethylformamide and propylene carbonate, more preferably water, acetonitrile and dimethylformamide.

  The ruthenic acid nanosheet (type 2) of the present invention and / or the alkylammonium-layered ruthenic acid intercalation compound laminated therewith can be used as an electrode for various electrochemical devices such as redox capacitors and fuel cells. The electrode can be produced by coating the electrode substrate with a colloid of the ruthenate nanosheet and / or the alkylammonium-layered ruthenate intercalation compound of the present invention. In the production of the electrode containing the ruthenate nanosheet (type 2) of the present invention, a method known in the art can be used as a method of coating the colloid on the electrode substrate. For example, electrophoresis from a colloidal solution can be applied to a conductive substrate, filtration can be applied to a porous substrate, and spin coating or coating can be applied to a non-conductive / non-porous substrate. A coating layer with high adhesion strength can be obtained without a binder because of the easy lamination of nanosheets, but various binders can be used depending on the application. For example, in order to ensure proton conductivity, an ionomer of perfluorosulfonic acid, for example, Nafion solution (registered trademark of EI DuPont de Nemour) can be used. Ruthenium acid nanosheets and alkylammonium-layered ruthenium acid intercalation compound laminated therewith have reduced sheet thickness, thereby improving the utilization efficiency of ruthenium and improving both the electronic conductivity on the sheet surface and the proton conductivity between the sheets. Is improved, and the electrode performance is remarkably improved. When used for a redox capacitor electrode, the capacity of the redox capacitor is 10 times higher than that of the conventional particulate ruthenium oxide and 10% higher than that of the ruthenic acid nanosheet (type 1).

<Manufacturing method>
As described above, the ruthenic acid nanosheet (type 2) of the present invention is
(A) A mixture of ruthenium oxide having a valence of IV or higher and an alkali metal compound, or an alkali metal compound of ruthenium acid having a valence of IV or more is mixed with a metal ruthenium powder, and the resulting mixture is calcined or A step of obtaining an alkali metal layered ruthenate compound containing III-valent ruthenium by melting;
(B) treating the alkali metal layered ruthenium acid compound with a bromine solution to remove at least one part of the alkali metal ions between the layers to obtain a proton type layered ruthenium acid;
(C) hydrating the proton-type layered ruthenium acid to obtain a proton-type layered ruthenium acid hydrate;
(D) a step of reacting the proton-type layered ruthenium acid hydrate with an alkylammonium compound and / or an alkylamine to obtain an alkylammonium-layered ruthenate intercalation compound; and (e) an alkylammonium-layered ruthenate intercalation compound. It is manufactured by a manufacturing method including a step of obtaining a colloid containing a ruthenic acid nanosheet by dispersing in a solvent and delamination.

Step (a)
First, in step (a), ruthenium oxide having a high valence of IV or higher and an alkali metal salt, or an alkali metal compound of ruthenium acid is mixed with metal ruthenium powder and fired or melted. The alkali metal compound of valent ruthenium oxide or ruthenium acid is reduced to obtain an alkali metal layered ruthenium acid compound composed of trivalent ruthenium. The ruthenium oxide IV valent or higher-valent, ruthenium oxide (RuO ₂₎ of IV-valent, although V-valent Ru ₂ O _5, VIII-valent RuO ₄ and the like, RuO ₂ are preferred. Examples of the alkali metal salt used in combination with a high valence ruthenium oxide having a valence of IV or higher include sodium salts such as sodium carbonate and sodium nitrate, with sodium carbonate being preferred. As the ruthenium acid alkali metal compound, a VI-valent alkali metal ruthenate is preferably used, and sodium ruthenate (Na ₂ RuO ₄ ) is particularly preferred.

Each composition of ruthenium oxide having a high valence of IV or higher and a mixture of an alkali metal salt and a metal ruthenium, or a mixture of a ruthenium acid compound and a metal ruthenium, and the conditions for firing and melting the mixture are as follows: The composition of the mixture and the firing / melting conditions under which the alkali metal layered ruthenic acid composed of the above can be most efficiently obtained are appropriately selected. For example, when Na ₂ RuO ₄ , which is a VI-valent alkali metal ruthenate, is used as a starting material, the atomic ratio of Na ₂ RuO ₄ : Ru is 0.5: 1 to 1.5: 1, preferably about 1: By charging in No. 1, mixing and melting in an inert gas atmosphere or in a sealed tube substituted with inert gas, sodium ruthenate (NaRuO ₂ ) containing III-valent ruthenium is obtained according to the following formula.

Na ₂ RuO ₄ + Ru → 2NaRuO ₂
This production method is known from Non-Patent Documents 2 and 3.

On the other hand, when IV-valent ruthenium oxide RuO ₂ is used, an alkali metal carbonate, preferably sodium carbonate (Na ₂ CO ₃ ), is added to ruthenium oxide RuO ₂ , and this and the metal ruthenium powder are mixed with RuO ₂ : Na. _By mixing and melting an atomic ratio of ₂ CO ₃ : Ru of 2.5 to 3.5: 1.5 to 2.5: 1, preferably about 3: 2: 1, NaRuO ₂ according to the following formula: Is obtained.

3RuO ₂ + 2Na ₂ CO ₃ + Ru → 4NaRuO ₂ + 2CO ₂
This method is a novel production method that has not been conventionally known. The product NaRuO ₂ is identified by comparison with the physical properties of NaRuO ₂ (particularly the powder X-ray diffraction pattern) described in Non-Patent Document 3 above. According to Non-Patent Document 3, the RuO ₂ layer of NaRuO ₂ has only one RuO ₂ unit in the thickness direction and has a thickness of 0.4 nm or less.

  The composition of these ruthenic acid compounds and the valence state of ruthenium are determined according to conventional methods such as wet gravimetric analysis, thermobalance-suggested thermal analysis (TG-DTA), and X-ray photoelectron spectroscopy (XPS). The ruthenium concentration is completely solubilized by melting in the presence of sodium peroxide, and the solution is analyzed by inductively coupled plasma (ICP).

  The ruthenium acid compound, ruthenic acid nanosheets obtained in the following steps, the composition of their colloids and the valence state of ruthenium are also determined in the same manner. Further, the surface form and fine structure such as the layered structure and sheet structure of the ruthenic acid compound of the present invention are observed and identified according to a conventional method such as scanning electron microscope, transmission electron microscope, and electron beam diffraction combined therewith. The bulk layered structure of the layered ruthenate re-laminated from the layered ruthenate compound or its colloid is identified from the periodic structure of the diffraction pattern by the X-ray diffraction method.

The alkali metal type layered ruthenium acid compound containing trivalent ruthenium obtained in this step is preferably a layered compound having a thickness of 0.4 nm or less, and preferably composed of NaRuO ₂ . The alkali metal-type layered ruthenium acid compound containing III-valent ruthenium thus obtained is different from the layered ruthenium acid composed of [RuO _{2 + 0.5x} ] ^x- type IV-valent ruthenium reported in Patent Document 1, with water or It is difficult to perform ion exchange into proton-type layered ruthenic acid by direct ion exchange reaction with dilute hydrochloric acid aqueous solution. Although some alkali metal ions are exchanged for protons by the hydration treatment, it is about 70% at most, and the remaining alkali metal ions are firmly held between the layers. If it is forcibly treated with a strong acid, the layered structure collapses, which is not preferable. In order to obtain a proton-type layered ruthenium acid by removing most of the alkali metal ions between the layers, it is necessary to treat the alkali metal-type layered ruthenium acid compound containing the above-mentioned III-valent ruthenium with a bromine solution in the step (b). is there.

Step (b)
In order to remove most of the alkali metal ions between the layers of the alkali metal-type layered ruthenate compound obtained in the step (a) to obtain a proton-type layered ruthenate acid, the alkali metal-type layered ruthenate compound is preferably used as a bromine solution. Is treated with an organic solvent solution of bromine. As the organic solvent, polar organic solvents such as acetonitrile or dimethylformamide are particularly preferred. This bromine treatment can remove most of the alkali metal ions even once, but may be repeated multiple times to remove more thoroughly. In the bromine treatment step, the alkali cation between layers is ion-exchanged into the proton type, and at the same time, ruthenic acid undergoes partial oxidation of trivalent ruthenium, and the formula (1): [RuO ₂ ] ^x− (0 < As represented by x <1), it is oxidized to an oxidation state of (4-x) valence (0 <x <1).

  The obtained proton-type layered ruthenic acid compound is recovered from a bromine organic solvent solution by filtration and washed thoroughly with a bromine-free organic solvent, preferably a polar organic solvent, more preferably acetonitrile, until the filtrate is colorless and transparent. The By this step, the layered ruthenic acid has the alkali metal ion in the structural formula reduced to 0.2 equivalents or less, preferably 0.1 equivalents or less, per 1 ruthenium atom.

Step (c)
Next, in step (c), the brominated ruthenate compound powder is suspended in a large excess of ion-exchanged water, stirred at room temperature for 1 to 48 hours, filtered, washed with deionized water, and then washed for 24 hours to Dry at room temperature for 72 hours to obtain a brominated ruthenate compound hydrate.

  By this step, the layered ruthenic acid is such that the amount of hydrated water in the structural formula increases to 0.2 equivalents or more, preferably 0.3 equivalents or more, per ruthenium atom. In the hydration treatment of the alkali metal layered ruthenium acid without bromine treatment, the hydration water in the structural formula enters at most 0.2 equivalent per ruthenium atom, whereas the hydration water by bromine treatment. It is presumed that the amount of ruthenium is increased from the III valence to the IV valence by the bromine treatment, and the interaction between the layers is weakened to facilitate the insertion of hydrated water between the layers.

Step (d)
The proton-type layered ruthenium hydrate obtained in step (c) is then reacted with an aqueous solution of an alkylammonium compound and / or an alkylamine in step (d) to obtain an alkylammonium-layered ruthenium containing an alkylammonium ion. It is converted into an acid intercalation compound, and in some cases, through this alkylammonium-layered ruthenate intercalation compound, it is converted into a ruthenic acid nanosheet colloid causing delamination.

Examples of the alkylammonium compound include structural formulas: (R) _m (R ′) _n (R ″) _p (R ′ ″) _q NH _{4− (m + n + p + q)} ⁺ (wherein R, R ′, R ′ ', And R''' each independently represent H or CH ₃ (CH ₂ ) _r , m, n, p and q are each 0 or an integer of 1 to 4, and 0 ≦ m + n + p + q ≦ 4, And an alkylammonium compound having an alkylammonium ion represented by r = 0 to 18). In particular, in order to promote delamination of the ruthenic acid nanosheet in the step (e), R = R ′ = R ″ = R ′ ″ = n—CH ₃ (CH ₂ ) ₃ − ammonium in the above formula A compound, that is, a quaternary (n-tetrabutyl) ammonium compound, particularly a quaternary (n-tetrabutyl) ammonium hydroxide is preferably used.

In addition, as the alkylamine, (R) _m (R ′) _n (R ″) _p NH _{3− (m + n + p)} (wherein R, R ′ and R ″ are independently H or CH ₃ ( CH ₂ ) _q , m, n and p are each 0 or an integer of 1 to 3, and satisfy 0 ≦ m + n + p ≦ 3, and q = 0 to 18 is preferable. . In particular, to promote delamination of ruthenic acid nanosheets in step (e), an amine of R = R ′ = R ″ = n—CH ₃ (CH ₂ ) ₃ —, that is, tri ( n-butyl ) amine Are preferably used. Alkylamine hydrates in aqueous solution and functions as the corresponding alkylammonium hydroxide.

  The reaction between the aqueous solution of these alkylammonium compounds and / or alkylamines and proton-type layered ruthenic acid is carried out by adding the aqueous solution of alkylammonium compounds and / or alkylamines to the proton-type layered ruthenium acid powder, and the resulting slurry is kept constant. It is carried out by stirring at a temperature for a certain time. As the reaction conditions, conditions under which ion exchange reaction by proton alkylammonium ions and further delamination efficiently proceed are appropriately selected. The liquid temperature is usually room temperature to 70 ° C., preferably 30 ° C. to 60 ° C., and the reaction time is usually 2 hours to 96 hours, preferably 24 hours to 72 hours. During the reaction, the atmosphere is preferably purged with an inert gas. In particular, when using ammonium compounds or alkylamines containing hydrogen in the molecule other than quaternary ammonium compounds, the reactor containing the proton-type layered ruthenic acid powder is replaced with an inert gas in advance, and then the ammonium compounds and alkylamines are replaced. It is preferable to add. If added in the air, there is a risk of ignition by an oxidation reaction catalyzed by ruthenium acid, an amine hydrogen.

  The concentration of the alkylammonium compound and / or alkylamine, the concentration of the proton-type layered ruthenic acid in the slurry, and the molar ratio of the alkylammonium compound and / or alkylamine to the proton-type layered ruthenium acid are also determined by ions of protons due to the alkylammonium ions Conditions under which the exchange reaction and further delamination efficiently proceed are appropriately selected. The concentration of the alkylammonium compound and / or alkylamine is usually 1% to 70%, preferably 5% to 60%, more preferably 10% to 50% by mass% with respect to the slurry. The concentration of the proton-type layered ruthenium acid is usually 0.001% to 20%, preferably 0.01% to 10%, more preferably 0.05% to 5% in terms of mass% with respect to the slurry. The molar ratio of the alkylammonium compound and / or alkylamine to the protonic layered ruthenic acid is usually 1: 1 to 500: 1, preferably 5: 1 to 200: 1, more preferably 10: 1 to 100: 1. It is. If the molar ratio is too small, the ion exchange reaction by alkylammonium ions of protons between layers may be insufficient, which is not preferable. If it is too large, an excess of alkylammonium compound and / or alkylamine is required, which may increase the cost, which is not preferable.

  Moreover, after obtaining the said alkylammonium-layered ruthenate intercalation compound, this is further mixed with the solution containing a 2nd alkylammonium compound, it is made to react, and a 2nd alkylammonium-layered ruthenate intercalation compound is carried out by guest exchange reaction. You can also get

  By appropriately selecting the structure and reaction conditions of the alkylammonium compound and / or alkylamine used in this step, the product alkylammonium-layered ruthenate intercalation compound does not cause delamination after ion exchange, It is recovered as a powder. That is, preferably, an alkylammonium ion aqueous solution consisting of a relatively small molecule or a molecule that is not sterically bulky, such as ethylamine or ethylammonium hydroxide, is used, preferably under a relatively mild reaction condition of 30 ° C. or less. After ion exchange, the resulting slurry is filtered, washed with deionized water, and then vacuum-dried to obtain an alkylammonium-layered ruthenate intercalation compound powder.

On the other hand, in this step, one or more of R ¹ , R ² , R ³ and R ⁴ is an alkyl ammonium compound having an alkyl group having a chain length of 4 or more carbon atoms, or ¹ of R ¹ , R ² and R ³ . When one or more alkylamines having an alkyl group with a chain length of 4 or more carbon atoms are used and ion exchange is carried out using an aqueous solution of alkylammonium ions of a sterically bulky molecule, the produced alkylammonium-layered ruthenic acid The intercalation compound sequentially undergoes delamination in a solvent to obtain a ruthenic acid nanosheet colloid. Usually, the crude colloid containing excessive alkylammonium ions is concentrated and separated by a centrifugal separation method. In the concentrated precipitate, the ruthenate nanosheet colloid produced in the ion exchange solution is laminated again to form an alkylammonium-layered ruthenate intercalation compound. Since the concentrated precipitate contains excess alkylammonium compound and alkylamine, it is preferable to perform a washing treatment to remove these. A long-chain hydrocarbon solvent such as n-heptane or n-octane is added to the colloidal concentrated precipitate and dispersed and washed by centrifugation. The centrifugal force for concentration and washing is usually 1,000 to 100,000 g, preferably 2,000 to 10,000 g.

Step (e)
Next, in step (e), the alkylammonium-layered ruthenate intercalation compound is dispersed in a solvent and delaminated to obtain a colloid containing ruthenate nanosheets having a thickness of 0.4 nm or less. As the solvent, a high dielectric constant solvent is preferable, and at least one solvent selected from the group consisting of water, alcohol, acetonitrile, dimethyl sulfoxide, dimethylformamide, and propylene carbonate is particularly preferable. Ultrasonic dispersion can be suitably used for the dispersion treatment. The dispersion colloid of the ruthenic acid nanosheets thus obtained was subjected to a centrifugal separation treatment with a relatively weak centrifugal force, and the alkylammonium-layered ruthenic acid intercalation compound and the agglomerates of the ruthenic acid nanosheet colloid that could not be delaminated. The trace amount impurity which consists of can be removed. The centrifugal force at this time is usually in the range of 100 g to 1000 g, preferably 300 g to 800 g. The concentration of ruthenium in the ruthenic acid nanosheet colloid is not particularly limited, but is usually 0.001 to 100 g Ru / L, preferably 0.01 to 10 g Ru / L, and more preferably 0.1 to 1.0 g Ru / L. It is.

  Examples of the present invention are shown below, but the present invention is not limited to the following examples.

<Example 1> Production process of tetrabutylammonium-ruthenic acid (type 2) intercalation compound (a): Production of NaRuO ₂ by reduction of RuO ₂ 0.51 g of ruthenium powder (Fluka, average particle size 45 μm), sodium carbonate 1.06 g (Wako Pure Chemical Industries, special grade 99.5%) and ruthenium oxide (RuO ₂ ) (NE Chemcat, Ru content 75%) 2.02 g are mixed and mixed for 30 minutes using an agate mortar. And mixed in a glove box in a nitrogen atmosphere. Thereafter, the mixed powder was put in an alumina crucible and baked at 450 ° C. for 12 hours in an annular furnace under argon gas flow. After firing, the solid was once taken out and mixed again in an agate mortar for 30 minutes in a glove box under a nitrogen atmosphere. The mixture powder was again put in an alumina crucible and heated to 900 ° C. for 1.5 hours under an argon gas flow in an annular furnace, held at the same temperature for 24 hours, then cooled to room temperature, and 3.13 g of black powder was obtained. Obtained. The composition of this product is as follows: inductively coupled plasma emission (ICP) analysis method, thermogravimetric analysis (TG / DTA) method, energy dispersive X-ray emission analysis (EDX) method, fluorescent X-ray analysis method and X-ray photoelectron It was determined to be NaRuO ₂ in combination with spectroscopy (XPS) (also determined in the following steps).

The powder X-ray diffraction (XRD) pattern of the NaRuO ₂ powder obtained by this method is shown in FIG. XRD uses a rotor flex X-ray diffractometer (Rigaku Corporation, RINT2550H / PC), CuK _α (graphite monochromatization, λ = 0.15406 nm) as an X-ray source, tube voltage 40 kV, tube current 40 mA. Measured at an angular feed rate of 2 ° min ⁻¹ and a measurement range 2θ = 3 to 80 °. From FIG. 1A, it can be seen that a trace amount of unreacted Ru metal remains in the NaRuO ₂ powder obtained in this step.

The surface morphology of the product was observed with a scanning electron microscope SEM (Hitachi High-Technologies S-300). The sample was fixed to a sample stage using a conductive carbon double-sided tape (the surface morphology of the product was also observed in the following examples). An SEM image of NaRuO ₂ is shown in FIG.

The thermal decomposition process of the product was evaluated by thermogravimetry and suggested thermal analysis TG-DTA. A powder sample having the same particle size in an agate mortar was filled in an alumina pan (5φ × 2.5 mm, 5 μl), and measured using a thermal analyzer (manufactured by Rigaku Corporation, TAS-200). The measurement was performed at a temperature increase rate of 5 ° C. min ⁻¹ from room temperature to 900 ° C. under a semi-air flow.

Step (b): Deintercalation of NaRuO ₂ by bromine treatment 1.00 g of the NaRuO ₂ powder produced in step (a) was placed in a Pyrex (registered trademark) three-necked flask and bromine (Wako Pure Chemical Industries, special grade 99). .0%) 5.11 g and 100 ml of acetonitrile (made by Wako Pure Chemical Industries, special grade 99.5%) were added, and the side tube was capped and stirred at room temperature for 25 days. After completion of the stirring, suction filtration was performed, and the filter cake was washed 6 times with 50 ml of acetonitrile. The washed cake was vacuum dried at room temperature for 24 hours. Thereafter, the above operation was repeated again to carry out bromine treatment. As a second dry powder, 0.88 g of Na _n RuO ₂ (0 <n <1) was obtained.

The XRD patterns of the powders of the product Na _n RuO ₂ (0 <n <1) in the first and second bromine treatments are shown in FIGS. 1 (c) and (d), respectively. Further, an SEM image of Na _n RuO ₂ after the second bromine treatment is shown in FIG. Furthermore, the TG / DTA curve of Na _n RuO ₂ after the second bromine treatment is shown in FIG. The decrease in mass up to 150 ° C. is attributed to the disappearance of surface adhering water, and the decrease in mass at 150 to 400 ° C. is attributed to the disappearance of interlayer water. It is presumed that the mass decrease of 400 to 600 ° C. is caused by a dehydration condensation reaction represented by the following formula.

Ru—OH + Ru—OH → Ru—O—Ru + H ₂ O
From these results, the composition of the product after bromine treatment (second time) was determined to be H _0.1 RuO ₂ .0.1H ₂ O.

Step (c): Production of Brominated Na _n RuO ₂ Hydrate 150 ml of ion-exchanged water is added to 0.50 g of brominated Na _n RuO ₂ powder produced in the above step (b) and stirred at room temperature for 15 hours. did. After completion, the precipitate was collected by suction filtration. This was dried at room temperature for 48 hours to obtain 0.513 g of brominated Na _n RuO ₂ hydrate.

The resulting brominated _Na n RuO ₂ hydrate, an XRD pattern in FIG. 1 (e), the SEM image in FIG. 3 (d), and shows a TG / DTA curve in FIG. 4 (c). The decrease in mass up to 150 ° C is attributed to the disappearance of surface adhering water. The mass loss of 150-400 ° C is attributed to the disappearance of interlayer water. The mass loss of 400-600 ° C is attributed to the dehydration condensation reaction.

From these results, the composition of brominated Na _n RuO ₂ hydrate was identified as H _0.1 RuO ₂ .0.3H ₂ O.

Step (d): tetrabutoxide butyl intercalation the process brominated prepared in (c) Na _n RuO ₂ hydrate powder 0.50g 10% tetrabutylammonium hydroxide aqueous solution of ammonium (manufactured by Wako Pure Chemical Industries, 920 ml of special grade) was added and stirred at 60 ° C. for 72 hours. After allowing to cool to room temperature, stirring was stopped, and the resulting black-brown colloid was placed in a glass sedimentation tube of a sedimentation centrifuge (manufactured by Kokusan, H-103N) and centrifuged at 4000 rpm (2900 g) for 30 minutes. The precipitate was collected. 200 ml of heptane was added to the precipitate, washed and centrifuged again. This washing-centrifugation operation was repeated 5 times. The last supernatant liquid is discarded by decantation, and the precipitate remaining in the settling tube is vacuum-dried at room temperature for 24 hours to obtain tetrabubutylammonium (TBA ⁺ ) -ruthenate intercalation compound [(TBA ⁺ ) _x RuO ₂ ]. 0.571 g of a black solid was obtained.

The XRD pattern of (TBA ⁺ ) _x RuO ₂ is shown in FIG. Until this stage, contamination of unreacted Ru metal was observed even though it was very small.

An SEM image of (TBA ⁺ ) _x RuO ₂ is shown in FIG.

A TG / DDTA curve of (TBA ⁺ ) _x RuO ₂ is shown in FIG. The decrease in mass up to 150 ° C is attributed to the disappearance of surface adhering water. The rapid exotherm around 200 ° C is attributed to the disappearance of the interlayer amine. Assuming that the temperature range where the disappearance of the interlayer amine occurs is 150 to 250 ° C., the mass reduction during this period is 16%, and it is estimated that 16% of the protons between the layers were guest-exchanged to TBA ions in the treatment of this step. A mass loss of 250 to 400 ° C is attributed to the disappearance of interlayer water, and a mass loss of 400 to 600 ° C is attributed to dehydration condensation.

From these results, the composition formula of (TBA ⁺ ) _x RuO ₂ was identified as (TBA ⁺ ) _0.1 RuO ₂ .0.2H ₂ O.

Step (e): Production of ruthenic acid nanosheet (type 2) colloid In step (d), the precipitate collected by centrifugation from an aqueous solution of tetrabutylammonium hydroxide was washed with heptane, and then removed in place of vacuum drying. 600 ml of ionic water was added and ultrasonic dispersion treatment was performed for 30 minutes to obtain a uniform black-brown colloid. The colloid is centrifuged at 1600 rpm (460 g) for 30 minutes to remove the original layered ruthenic acid that has not been delaminated or aggregates of ruthenic acid nanosheets that have been once delaminated as precipitates, and a ruthenic acid nanosheet ( 600 ml of colloid containing type 2) were obtained. According to wet gravimetric analysis, the Ru concentration was 0.46 g / L.

An XRD pattern of a film obtained by casting a ruthenic acid nanosheet (type 2) colloid on a non-reflective silicon substrate and drying at room temperature is shown in FIG. The peak attributed to the incorporation of a trace amount of Ru metal observed in the XRD pattern of the (TBA ⁺ ) _0.1 RuO ₂ .0.2H ₂ O powder in the step (d) (FIG. 2 (b)) It can be seen that the ruthenic acid nanosheet colloid having undergone the above process was not detected but removed in this step.

FIG. 5 (a) shows a UV / visible absorption spectrum of a diluted colloidal aqueous solution obtained by diluting a ruthenic acid nanosheet (type 2) colloid 50 times with deionized water. The UV / visible absorption spectrum was measured using a spectrophotometer (UV-2400PC manufactured by Shimadzu Corporation) with a sample solution packed in a quartz cell having an optical path length of 10 mm at a scanning speed of 100 nm / min. A plasmon absorption peak due to the quantum size effect of the ruthenate nanosheet was detected at λ _max 346 nm.

<Example 2> Tetrabutylammonium - ruthenate (Type 2) the manufacturing process of the intercalation compound _(a): Na 2 of Example 1 NaRuO ₂ by reduction of RuO ₄ step (a) the same ruthenium dioxide as used in 1 .01 g and 0.78 g of sodium peroxide (manufactured by Wako Pure Chemical Industries, Ltd.) were mixed in a mortar in a dry box substituted with nitrogen gas. This mixed powder was put into an alumina crucible, charged in an annular furnace, and fired at 627 ° C. for 50 hours under an argon flow to obtain 1.79 g of a black powder of Na ₂ RuO ₄ .

The obtained black powder was mixed with 1.01 g of the same metal ruthenium powder used in step (a) of Example 1 in a dry box substituted with nitrogen gas, placed in an alumina crucible, and placed at 197 ° C. under argon flow. Baking for 12 hours, and further baking at 900 ° C. for 12 hours. The produced NaRuO ₂ shows the same X-ray diffraction pattern as NaRuO ₂ obtained in step (a) of Example 1. Moreover, the SEM photograph of the NaRuO ₂ powder obtained here is shown in FIG.

Using this NaRuO ₂ powder, the same treatment as in steps (b), (c), (d) and (e) of Example 1 was carried out, and then a ruthenic acid nanosheet colloid having a Ru concentration of 0.47 g / L, 600 ml. Got. XRD of the cast film on the colloidal non-reflective Si substrate was obtained in step (e) of Example 1 shown in FIG. 2 (c) (TBA ⁺ ) _0.1 RuO ₂ .0.2H ₂ O The same diffraction pattern was exhibited.

<Comparative Example 1> Production of Na _x RuO ₂ · yH ₂ O To 0.20 g of NaRuO ₂ powder produced in step (a) of Example 1, 500 ml of ion-exchanged water was added and stirred at room temperature at 25 ° C for 3 days. . After completion of stirring, the precipitate was collected by suction filtration and dried at room temperature for 48 hours to obtain 0.184 g of Na _x RuO ₂ .yH ₂ O.

The XRD pattern of the obtained Na _x RuO ₂ .yH ₂ O is shown in FIG. This XRD pattern matches the XRD pattern of Na _x RuO ₂ .yH ₂ O described in Non-Patent Document 3 except that a trace amount of Ru metal peak is detected.

An SEM image of the Na _x RuO ₂ .yH ₂ O is shown in FIG.

The TG / DTA curve of the Na _x RuO ₂ .yH ₂ O is shown in FIG. The decrease in mass up to 150 ° C is attributed to the disappearance of surface adhering water. The mass reduction of 150 to 400 ° C. is attributed to the disappearance of interlayer water, and the mass reduction of 400 to 600 ° C. is presumed to be accompanied by a change in the crystal structure from ruthenic acid to rutile-type RuO ₂ .

These results, the composition formula of the _Na x RuO ₂ · yH ₂ O was determined to _{Na 0.3 RuO 2 · 0.2H 2 O} .

Comparative Example 2 Production of Ruthenate Nanosheet (Type 1) Colloid According to the production method of Patent Document 1, the following operation was performed.
Step (a ′): Production of K _0.2 RuO _2.1 · xH ₂ O K ₂ CO ₃ (manufactured by Wako Pure Chemical Industries, 99%) 0.641 g, used in step (a) of Example 1 The same ruthenium dioxide RuO ₂ powder (1.01 g) was mixed, and the mixture was heated and fired at 850 ° C. for 12 hours under a flow of argon gas. The resulting solid was washed with deionized water until the filtrate conductivity was 100 μS / cm or less. By drying at 65 ° C. for 16 hours, 1.02 g of layered potassium ruthenate K _0.2 RuO _2.1 · xH ₂ O powder was obtained.

Step (b ′): Production of H _0.2 RuO _2.1 · yH ₂ O 100 ml of 5% hydrochloric acid was added to 1.00 g of the potassium layered ruthenic acid obtained in step (a ′), and the mixture was stirred at 60 ° C. for 48 hours. . After cooling, the mixture was filtered and washed with deionized water until the conductivity of the filtrate reached 100 μs / cm or less. The cake was dried at 65 ° C. for 16 hours to obtain 0.92 g of proton-type layered ruthenate H _0.2 RuO _2.1 · yH ₂ O powder.

Step (c ′): Production of Ethylammonium-Layered Ruthenic Acid Intercalation Compound 50 ml of 50% ethylamine aqueous solution was added to 0.50 g of proton-type layered ruthenic acid powder produced in the above step (b ′) in an argon atmosphere. The mixture was kept stirring at room temperature 25 ° C. for 24 hours. After completion, the slurry was concentrated by centrifugation at 4000 rpm (2900 g) for 30 minutes, and finally the precipitate was washed with 40 ml of acetone, centrifuged again, and the supernatant was discarded. 40 ml of acetone was again added to the precipitate, and the above washing step was repeated 4 times. The last acetone washing residue was vacuum dried at room temperature for 24 hours to obtain 0.53 g of ethylammonium-layered ruthenic acid intercalation compound (EtNH ₃ ⁺ ) _0.2 RuO _2.1 · 0.3H ₂ O powder.

Step (d ′) Production of Ruthenate Nanosheet (Type 1) 10% tetrabutylammonium hydroxide aqueous solution (special grade, manufactured by Wako Pure Chemical Industries, Ltd.) was added to 0.50 g of ethylammonium-layered ruthenate powder produced in the above step (c ′). ) 870 ml was added and stirred at 30 ° C. for 50 hours. After cooling to room temperature, stirring was stopped, and the resulting black-brown colloid was centrifuged at 4000 rpm (2900 g) for 30 minutes to collect a precipitate. 200 ml of heptane was added to the precipitate, washed and centrifuged again. This washing / centrifugation operation was repeated 5 times. The last supernatant was discarded by decantation, and 550 ml of deionized water was added to the precipitate and subjected to ultrasonic dispersion for 30 minutes to obtain a uniform black-brown colloid. The colloid was centrifuged at 1600 rpm (460 g) for 30 minutes to remove unpeeled components and aggregates. 550 ml of ruthenic acid nanosheet colloid (type 1) having a supernatant Ru concentration of 0.43 g / L was obtained.

K _0.2 RuO _2.1 · xH ₂ O, H _0.2 RuO _2.1 · yH ₂ O obtained in the steps (a ′), (b ′) and (c ′), respectively, and ( EtNH ₃ ⁺ ) _0.2 RuO _2.1 · yH ₂ O powders and ruthenium acid nanosheet (type 1) colloid obtained in the above step (d ') colloidal XRD pattern of cast film on non-reflective silicon substrate Corresponds to the XRD pattern of the product of the corresponding process of Patent Document 1 and Non-Patent Document 1, respectively.

  FIG. 5B shows a UV / visible absorption spectrum of a dilute colloidal aqueous solution in which a ruthenic acid nanosheet (type 1) colloid is diluted 50 times with deionized water. Unlike the UV / visible absorption spectrum (FIG. 5A) of the ruthenate nanosheet (type 2) colloid of Example 1, the plasmon absorption was λmax 362 nm, and (type 2) appeared 15 nm longer than the colloid.

<Comparative Example 3> Ion Exchange of Alkali Metal-Type Layered Ruthenic Acid with Mineral Acid Using 0.50 g of NaRuO ₂ powder obtained in Step (a) of Example 1 and using Step (b ′) of Comparative Example 2 50 ml of 5% sulfuric acid was added and stirred at 60 ° C. for 48 hours. After cooling, the mixture was filtered and washed with deionized water until the conductivity of the filtrate reached 100 μs / cm or less. This cake was dried at 65 ° C. for 16 hours to obtain 0.43 g of black powder. An SEM image of this powder is shown in FIG. It was found that the layered structure was no longer observed and decomposed into fine amorphous particles. In powder X-ray diffraction of this product, a regular diffraction peak of proton-type layered ruthenic acid as seen in FIGS. 1 (c), (d) and (e) was not detected. That is, unlike the case of K _0.2 RuO _2.1 in Comparative Example 2, it was found that when NaRuO ₂ was treated with mineral acid, the layered structure collapsed and the desired proton-type layered ruthenic acid could not be obtained. .

<Example 3> Electrochemical property evaluation (dispersion preparation method)
In the case of a powder sample, 10 ml of deionized water was added to 10 mg of the sample and subjected to ultrasonic dispersion treatment for 1 hour to prepare a 1.0 g / L dispersion. The ruthenic acid nanosheet colloidal solutions of Example 1 and Comparative Example 2 were used as they were.
(Electrode creation method)
A cut surface of amorphous carbon (hereinafter abbreviated as GC) (Tokai Carbon Co., Ltd., GC-20SS, φ5 mm × 30 mm) was designated No. It was smoothed by dry polishing with 3000 emery paper (manufactured by Marumoto Kogyo Co., Ltd.). Ultrasonic cleaning with ion-exchanged water and then with ethanol was repeated twice for about 3 minutes each and then dried to obtain a carbon carrier. 20 μl of the sample dispersion prepared by the above method was dropped on the GC polished surface with a micropipette and dried at 60 ° C. for 30 minutes. Then 5 wt. 1% Nafion (registered trademark) solution obtained by diluting 5% Nafion (registered trademark) solution (manufactured by Aldrich) with deionized water 5 times was added dropwise and dried again at 60 ° C. for 30 minutes to obtain a test electrode. .
(Electrochemical measurement)
The electrochemical properties of the test electrode were evaluated by cyclic voltammetry (CV). Using a beaker-type triode cell, Pt mesh (99.98%, 150 mesh manufactured by Nilaco Co., Ltd.) is used for the counter electrode, and Ag / AgCl electrode (HS-205C, manufactured by Toa Denpa Kogyo Co., Ltd.) is used for the reference electrode. It was. All the test electrodes as working electrodes were covered with Teflon (registered trademark) tape, leaving only the sample carrying surface (apparent surface area 19 mm ² ). A 0.5 MH ₂ SO ₄ aqueous solution was used as the electrolytic solution. As a measuring device, HZ3000 system and HSV100 system (both including a potentio / galvanostat, a function generator, and measurement software) (manufactured by Hokuto Denko Co., Ltd.) were used. Before measurement, install the measuring cell in a thermostatic chamber maintained at 25 ° C, and purge with nitrogen gas (Okaya Oxygen Co., Ltd., 99.99995%) for 40 minutes to remove dissolved oxygen in the electrolyte. The bubbling was continued during the measurement. First, after performing a stabilization process by scanning a potential scanning range of 0.2 to 1.2 V versus RHE for 500 cycles at a potential scanning speed of 50 mV / s, 500, 200, 50, 20, 5, and 2 mV / CV measurement was performed at a potential scanning speed of s.

Na _0.3 RuO ₂ · 0.2H ₂ O of Comparative Example 1, the cyclic of H _0.1 RuO ₂ · 0.3H ₂ O of Example 1, and Example 1 of ruthenate nanosheets colloid (type 2) Voltammograms are shown in FIGS. 6 (a), 6 (b), and 6 (c), respectively.

  Table 1 shows the relationship between potential scanning speed and specific capacitance, and Table 2 shows the relationship between potential scanning speed and specific capacitance retention.

The specific capacitance of the electrode produced from Na _0.3 RuO ₂ .0.2H ₂ O of Comparative Example 1 is 187 F / g RuO ₂ , whereas the brominated hydrate H _{0 of} Example 1 The specific capacitance of the _.1 RuO ₂ .0.3H ₂ O electrode was 435 F / g RuO ₂ (both values at a potential scanning speed of 2 mV / S), which was remarkably increased. In Example 1, it is presumed that Na ions between layers were removed by bromine treatment, proton conductivity increased, and capacitance increased. Further, an electrode manufactured from Na _0.3 RuO ₂ .0.2H ₂ O has a low specific capacitance retention, and proton conductivity is inhibited.

The specific capacitance of the ruthenate nanosheet colloid (type 2) electrode of Example 1 is 730 F / g RuO ₂ (at a potential scanning rate of 2 mV / S), and the hydrate H _0.1 after bromine treatment of Example 1 is _0.1. The specific capacitance further increased as compared with the RuO ₂ .0.3H ₂ O electrode. It is presumed that the active area was further increased as compared to H _0.1 RuO ₂ .0.3H ₂ O due to the formation of nanosheets by delamination. Moreover, the specific capacitance of the ruthenate nanosheet colloid (type 2) electrode of Example 1 was 10 to 20% higher than the previously reported ruthenate nanosheet colloid (type 1) electrode. It is presumed that the utilization efficiency of ruthenium has been improved by reducing the thickness of the ruthenium acid nanosheet.

From the cyclic voltammograms of FIGS. 6 (a), 6 (b) and 6 (c), Na _0.3 RuO ₂ .0.2H ₂ O, H _0.1 RuO ₂ .0.3H ₂ O and electric double layer capacity of the ruthenium acid nanosheet (type 2) colloids were respectively read as _{57F / g RuO 2, 201F /} g RuO 2 and 420F / g RuO _2.

Assuming that the electric double layer capacity per unit surface area of crystalline RuO ₂ is 80 μF / cm ² , Na _0.3 RuO ₂ .0.2H ₂ O, H _0.1 RuO ₂ .0.3H ₂ O, and ruthenium each active surface area of the acid nanosheet (type 2) colloid is calculated to 70,250, and 525m2 / g RuO _2.

  In addition to the electric double layer capacity, redox peaks were observed at potentials of 0.6 to 0.7 V and 0.8 to 1.0 V (vs. RHE). This redox peak is presumed to be caused by adsorption / desorption of ionic species on the front and back surfaces of the ruthenate nanosheet.

(a) is an X-ray diffraction (XRD) pattern of NaRuO ₂ obtained in step (a) of Example 1; (b) is Na _0.3 RuO ₂ .0.2H obtained in Comparative Example 1. XRD patterns of ₂ O; (c) and (d) are respectively the product Na _n RuO ₂ after one bromine treatment in step (b) of Example 1 and the product H ₀ .2 after two bromine treatments _. XRD pattern of ₁ RuO ₂ .0.1H ₂ O; and (e) shows the hydrate H _0.1 RuO ₂ .0.3H ₂ O after the bromine treatment twice in step (c) of Example 1. It is an XRD pattern. (a), (b), and (c) are bromine-treated H _0.1 RuO ₂ .0.3H ₂ O [step (c)] and (TBA ⁺ ) _0.1 RuO _2. It is an X-ray diffraction (XRD) pattern of cast films of 0.2H ₂ O [step (d)] and ruthenic acid nanosheet (type 2) colloid [step (e)]. _{2 is} a SEM image of NaRuO ₂ obtained in step (a) of Example 1. _{2 is} a SEM image of Na _0.3 RuO ₂ .0.2H ₂ O obtained in Comparative Example 1. _{2 is} a SEM image of bromine-treated H _0.1 RuO ₂ .0.1H ₂ O obtained in step (b) of Example 1. FIG. _{2 is} a SEM image of hydrated H _0.1 RuO ₂ .0.3H ₂ O after bromine treatment obtained in step (c) of Example 1. FIG. _{2 is} a SEM image of (TBA ⁺ ) _0.1 RuO ₂ .0.1H ₂ O obtained in step (d) of Example 1. _{2 is} a TG / DTA curve of Na _0.3 RuO ₂ .0.2H ₂ O obtained in Comparative Example 1. FIG. 2 is a TG / DTA curve of a product H _0.1 RuO ₂ .0.1H ₂ O [step (b)] after two bromine treatments in Example 1. FIG. 2 is a TG / DTA curve of hydrate H _0.1 RuO ₂ .0.3H ₂ O [Step (c)] after two bromine treatments in Example 1. FIG. It is a TG / DTA curve of (TBA ⁺ ) _0.1 RuO ₂ .0.1H ₂ O [Step (d)] in Example 1. 2 is a UV / visible absorption spectrum of a ruthenic acid nanosheet colloid obtained in step (e) of Example 1. FIG. 3 is a UV / visible absorption spectrum of a ruthenic acid nanosheet colloid obtained in Comparative Example 2. FIG. 4 is a cyclic voltammogram when the electrode using Na _0.3 RuO ₂ .0.2H ₂ O according to Comparative Example 1 is scanned at 2, 5, 20, 50, 200 and 500 mV / s. FIG. 3 is a cyclic voltammogram when an electrode using H _0.1 RuO ₂ .0.3H ₂ O according to Example 1 is scanned at 2, 5, 20, 50, 200 and 500 mV / s. FIG. 2 is a cyclic voltammogram when the electrode using the ruthenate nanosheet (type 2) according to Example 1 is scanned at 2, 5, 20, 50, 200 and 500 mV / s. (a) shows an electrode (□) using H _0.1 RuO ₂ .0.3H ₂ O of Example 1, an electrode (○) using a ruthenic acid nanosheet (type 2) colloid of Example 1, and A graph showing the relationship between potential scanning speed and specific capacitance in cyclic voltammetry evaluation of an electrode (Δ) using Na _0.3 RuO ₂ .0.2H ₂ O of Comparative Example 1; and (b) Are electrodes (□) using H _0.1 RuO ₂ .0.3H ₂ O of Example 1, electrodes (O) using a ruthenic acid nanosheet (type 2) colloid of Example 1, and Comparative Example 1 5 is a graph showing the relationship between the potential scanning speed and the specific capacitance retention rate of an electrode (Δ) using Na _0.3 RuO ₂ .0.2H ₂ O. _{2 is} a SEM image of NaRuO ₂ obtained in step (a) of Example 2. 4 is a SEM image of a NaRuO ₂ sulfuric acid treatment product obtained in Comparative Example 3.

Claims (16)

A ruthenate nanosheet represented by the formula : [RuO ₂ ] ^x- (0 <x <1). The ruthenic acid nanosheet according to claim 1, having a thickness of 0.4 nm or less. An alkylammonium-layered ruthenate intercalation compound comprising an alkylammonium ion between layers of a layered ruthenate compound formed by laminating the ruthenate nanosheets according to claim 1 or 2 . In the X-ray diffraction pattern, diffraction peaks on each plane of (00L) (however, L = 1 to n in the range of 0 ≦ 2θ (CuKα) ≦ 90 °, n is determined by the basic plane spacing and satisfies 5 ≦ n ≦ 35) The alkylammonium-layered ruthenate intercalation compound according to claim 3 having A colloid comprising the ruthenate nanosheet of claim 1 or 2 and / or the alkylammonium-layered ruthenate intercalation compound of claim 3 or 4 and a solvent. 6. The colloid according to claim 5 , wherein the solvent is at least one selected from the group consisting of water, alcohol, acetonitrile, dimethyl sulfoxide, dimethylformamide, and propylene carbonate. The colloid according to claim 5 or 6, which has an absorption maximum in a region of 340 to 350 nm in a UV / visible absorption spectrum. An electrochemical device having an electrode comprising the ruthenate nanosheet of claim 1 or 2 and / or the alkylammonium-layered ruthenate intercalation compound of claim 3 or 4 . The electrochemical element which has an electrode manufactured using the colloid of any one of Claims 5-7 . The following steps (a) to (e):
(A) A mixture of ruthenium oxide having a valence of IV or higher and an alkali metal compound, or an alkali metal compound of ruthenium acid having a valence of IV or more and a metal ruthenium powder, and firing or melting the resulting mixture A step of obtaining an alkali metal layered ruthenium acid compound containing trivalent ruthenium,
(B) treating the alkali metal-type layered ruthenate compound with a bromine solution to remove at least a portion of the alkali metal ions between the layers to obtain a proton-type layered ruthenate acid;
(C) a step of hydrating the proton-type layered ruthenium acid to obtain a proton-type layered ruthenium acid hydrate;
(D) a step of reacting the proton-type layered ruthenium acid hydrate with an alkylammonium compound and / or an alkylamine to obtain an alkylammonium-layered ruthenate intercalation compound; and (e) the alkylammonium-layered ruthenate intercalation compound. The method for producing a ruthenic acid nanosheet according to claim 1, comprising a step of mixing and dispersing with a solvent to obtain a delaminated ruthenic acid nanosheet colloid. The manufacturing method according to claim 10, wherein the alkali metal-type layered ruthenate compound obtained in the step (a) has a thickness of 0.4 nm or less. The method according to claim 10 or 11 wherein the alkali metal type layered ruthenate compound obtained in step (a) is a NaRuO _2. The method for producing a ruthenic acid nanosheet according to any one of claims 10 to 12 , wherein the step (b) is treatment with an acetonitrile solution of bromine. In the step (d), the proton-type layered ruthenium acid hydrate is converted to a structural formula: (R) _m (R ′) _n (R ″) _p (R ′ ″) _q NH _{4− (m + n + p + q)} ⁺ ( In the formula, R, R ′, R ″ and R ′ ″ each independently represent H or CH ₃ (CH ₂ ) _r , where (R) _m (R ′) _n (R ″) _p ( R ′ ″) _q has at least one CH ₃ (CH ₂ ) _r , m, n, p and q are each 0 or an integer from 1 to 4 and satisfy 0 ≦ m + n + p + q ≦ 4, and r The method for producing a ruthenic acid nanosheet according to any one of claims 10 to 13 , which is a step of reacting an alkylammonium compound having an alkylammonium ion represented by: In the step (d), proton type layered ruthenium acid hydrate is converted into a structural formula: (R) _m (R ′) _n (R ″) _p NH _{3− (m + n + p)} (wherein R, R ′ and R ″ each independently represents H or CH ₃ (CH ₂ ) _q , where (R) _m (R ′) _n (R ″) _p (R ′ ″) _q represents at least one CH ₃ ( CH ₂ ) _q , m, n and p are 0 or an integer of 1 to 3, and 0 ≦ m + n + p ≦ 3, and q = 0 to an integer of 18 It is a process made to react, The manufacturing method of the ruthenate acid nanosheet of any one of Claims 10-13 . In the step (e), a colloid is obtained by mixing the alkylammonium-layered ruthenic acid intercalation compound with at least one solvent selected from the group consisting of water, alcohol, acetonitrile, dimethylsulfoxide, dimethylformamide and propylene carbonate. It is a process, The manufacturing method of the ruthenic acid nanosheet of any one of Claims 10-15 .

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