JP6301705B2 - Method for supporting manganese dioxide and method for producing porous ceramic member - Google Patents

Description

  The present invention relates to a technique for supporting manganese dioxide on a porous ceramic member.

Conventionally, there are various devices and materials that use manganese dioxide (MnO ₂ ) as a catalyst, such as fuel cells, alkaline manganese dry cells, and sulfur oxide adsorbents. Manganese dioxide is also used as a catalyst for various applications such as alcohol oxidation, carbon monoxide oxidation, and NOx reduction.

Manganese dioxide is known to have crystal phases having many types of tunnel structures and layered structures such as α-type, β-type, γ-type, and δ-type. Manganese dioxide having a desired crystal structure can be made separately. For example, β-MnO ₂ is synthesized by thermal decomposition of manganese nitrate or the like. β-MnO ₂ is the most stable crystal in manganese dioxide. γ-MnO ₂ is industrially produced by an electrolytic method, and many of them are chemically active, and is suitable for a positive electrode material of a dry battery.

  In the metal-air battery disclosed in Patent Document 1, manganese dioxide having a β-type crystal structure is used for the positive electrode catalyst layer. Patent Document 1 mentions that the formation of the positive electrode catalyst layer is performed by a slurry coating method and firing, a hydrothermal synthesis method, CVD, PVD, or the like, but details thereof are not disclosed.

JP 2011-253789 A

  By the way, when carrying a manganese dioxide on a porous ceramic member, the method of apply | coating the ink and slurry containing powdered manganese dioxide to a porous ceramic member can be considered. However, in such a method, a catalyst layer becomes thick and the gas permeability of a porous ceramic member falls significantly.

  The present invention has been made in view of the above problems, and an object thereof is to support manganese dioxide on a porous ceramic member while suppressing a decrease in gas permeability.

The invention according to claim 1 is a manganese dioxide supporting method for supporting manganese dioxide on a porous ceramic member, wherein a) a porous ceramic member containing manganese atoms in a pressure-resistant container has a concentration of potassium permanganate. Is immersed in an aqueous solution of 0.014 mol / L or more and 0.14 mol / L or less and the concentration of manganese sulfate is 0.07 mol / L or less, and b) after the step a), Heating the aqueous solution, and supporting manganese dioxide on the porous ceramic member by a hydrothermal synthesis method.

Invention of Claim 2 is the manganese dioxide carrying | support method of Claim 1 , Comprising: In the said aqueous solution in the said a process, the molar ratio of manganese sulfate with respect to potassium permanganate is 0.35 or more. 36 or less.

The invention according to claim 3 is the manganese dioxide supporting method according to claim 1 or 2 , wherein the material of the porous ceramic member is lanthanum / strontium / manganite (LSM), lanthanum / strontium / manganese / Iron oxide (LSMF) or lanthanum / strontium / cobalt / manganese / iron oxide (LSCMF).

The invention of claim 4 is a method for producing a porous ceramic member, comprising the step of supporting the manganese dioxide in the manganese dioxide loading method according to any one of claims 1 to 3.

The invention according to claim 5 is a manganese dioxide supporting method for supporting manganese dioxide on a porous ceramic member, after a) immersing the porous ceramic member not containing manganese atoms in an aqueous potassium permanganate solution. A step of drying, b) before or after the step a), the porous ceramic member is immersed in a manganese sulfate aqueous solution and then dried, and c) after the steps a) and b), Dipping the porous ceramic member in an aqueous solution in which potassium permanganate is dissolved in the pressure vessel; d) after the step c), heating the aqueous solution in the pressure vessel, And a step of supporting manganese dioxide on the porous ceramic member by a synthesis method.

A sixth aspect of the present invention is the manganese dioxide supporting method according to the fifth aspect , wherein manganese sulfate is further dissolved in the aqueous solution in the step c).

The invention according to claim 7 is the manganese dioxide supporting method according to claim 6 , wherein in the aqueous solution in the step c), the molar ratio of manganese sulfate to potassium permanganate is 0.35 or more and 1. 36 or less.

The invention according to claim 8 is the manganese dioxide supporting method according to any one of claims 5 to 7 , wherein the material of the porous ceramic member is alumina, cordierite, zirconia, mullite or silica.

The invention of claim 9 is a method for producing a porous ceramic member, comprising the step of supporting the manganese dioxide in the manganese dioxide loading method according to any one of claims 5 to 8.

  In the present invention, manganese dioxide can be supported on the porous ceramic member while suppressing a decrease in gas permeability.

It is a figure which shows the flow of the supporting method of manganese dioxide to a porous ceramic member. It is a figure which shows the flow of pre-processing. 3 is a diagram showing an SEM image in Example 1. FIG. 6 is a diagram showing an SEM image in Example 2. FIG. 10 is a diagram showing an SEM image in Comparative Example 1. FIG. 10 is a diagram showing an SEM image in Comparative Example 2. FIG. FIG. 10 is a diagram showing an SEM image in Example 11. It is a figure which shows the structure of a metal air secondary battery.

  FIG. 1 is a diagram showing a flow of a method for supporting manganese dioxide on a porous ceramic member according to one embodiment of the present invention.

First, an aqueous solution in which potassium permanganate (KMnO ₄ ) and manganese sulfate pentahydrate (MnSO ₄ .5H ₂ O) are dissolved is prepared as a reaction solution (step S11). Manganese sulfate is not limited to pentahydrate. Next, the reaction solution is stored in a pressure vessel, and the porous ceramic member is immersed in the reaction solution (step S12). Of course, the reaction liquid may be injected into the pressure vessel after the porous ceramic member is disposed in the pressure vessel.

  As the porous ceramic member, one containing manganese atoms is used. For example, the material of the porous ceramic member is a lanthanum, strontium, manganite (LSM), lanthanum, strontium, manganese, iron oxide (LSMF), lanthanum, strontium, cobalt, manganese, iron oxide as perovskite type oxides. (LSCMF). The shape of the porous ceramic member may be anything. In the examples described later, the porous ceramic member is cylindrical, but may be honeycomb or monolithic.

The pressure vessel is sealed and the reaction solution is heated in the pressure vessel. The pressure vessel is heated and pressurized (step S13). As a result, manganese dioxide crystals are supported on the surface of the porous ceramic member by hydrothermal synthesis. The reaction formula is
2MnO ₄ ⁻ + 3Mn ²⁺ + 2H ₂ O → 5MnO ₂ + 4H ⁺
It is indicated by.

  Only by dissolving potassium permanganate and manganese sulfate at room temperature and normal pressure, only precipitates of manganese dioxide with low crystallinity can be obtained, but by using the hydrothermal synthesis method as described above, it becomes porous. Highly crystalline manganese dioxide is supported on the ceramic member. In hydrothermal synthesis, the pressure vessel may be swung as necessary.

  The reaction temperature in hydrothermal synthesis is preferably 120 ° C. or higher and 200 ° C. or lower, and more preferably 140 ° C. or higher and 180 ° C. or lower. When synthesized at a low temperature, a longer reaction time is required until a desired crystal structure is obtained. However, since a rapid reaction can be suppressed, manganese dioxide can be uniformly supported on the porous ceramic member. When the reaction temperature is 120 ° C. or lower, since the reaction rate is slow, heating for a long time is required, which is uneconomical and inefficient. When the reaction temperature is 200 ° C. or higher, the reaction rate is too high, and it becomes difficult to carry a uniform catalyst. In addition, the pressure vessel is also expensive. The reaction time is preferably 6 hours or more and 24 hours or less.

  As described later, by changing the conditions of the reaction solution and the hydrothermal synthesis conditions such as temperature and time, desired manganese dioxide such as α-type, β-type, and γ-type can be supported on the porous ceramic member. It becomes possible.

In the case where the porous ceramic member does not contain manganese atoms as a nucleus during the synthesis of manganese dioxide, a pretreatment is performed before the hydrothermal synthesis. FIG. 2 is a diagram showing the flow of preprocessing. The work after the pre-processing is the same as in FIG. Examples of the material of the porous ceramic member when the pretreatment is performed include alumina (Al ₂ O ₃ ), cordierite (2MgO · 2Al ₂ O ₃ · 5SiO ₂ etc.), zirconia (ZrO ₂ ), mullite (3Al ₂ O ₃ · 2SiO ₂ ) and silica (SiO ₂ ). Furthermore, examples of the perovskite oxide include lanthanum, strontium, cobalt, and iron oxide (LSCF).

  In the pretreatment, a precursor of manganese dioxide is attached to the porous ceramic member. First, a first pretreatment liquid and a second pretreatment liquid are prepared as pretreatment liquids (step S21). The first pretreatment liquid is an aqueous manganese sulfate solution, and the second pretreatment liquid is an aqueous potassium permanganate solution. The first pretreatment liquid may be a potassium permanganate aqueous solution, and the second pretreatment liquid may be a manganese sulfate aqueous solution.

  When the pretreatment liquid is prepared, the porous ceramic member is dipped in the first pretreatment liquid, pulled up (step S22), and dried (step S23). Next, it is immersed in the second pretreatment liquid and pulled up (step S24) and dried (step S25). Thereby, the precursor of manganese dioxide adheres to the surface of the porous ceramic member (including the surface in the porous void). Thereafter, step S11 and subsequent steps in FIG. 1 are executed, whereby manganese dioxide is supported on the porous ceramic member.

Example 1
A porous alumina cylindrical member was used as the porous ceramic member. The porous ceramic member has a length of 70 mm, an outer diameter of 16 mm, and an inner diameter of 12 mm. Hydrothermal synthesis was performed after pretreatment.

First, a 0.34M-KMnO ₄ aqueous solution (hereinafter referred to as “A ₁ solution”) and a 0.47M-MnSO ₄ aqueous solution (hereinafter referred to as “B ₁ solution”) were prepared. As the reagent, potassium permanganate (Kishida Chemical, special grade, model number: 000-63915) and manganese sulfate pentahydrate (Kishida Chemical, special grade, model number: 000-47525) were used.

In pretreatment, the A ₁ was the first pretreatment solution, the B ₁ liquid was second pretreatment solution. The porous ceramic member is immersed in the first pretreatment liquid for 1 minute, room temperature drying is performed for 30 minutes, and 100 ° C. drying is performed for 1 hour. Drying at 100 ° C. was performed for 1 hour.

The reaction solution used for hydrothermal synthesis was prepared by mixing A ₁ solution, B ₁ solution, and ion-exchanged water for co-washing at a ratio of 2: 2: 1. At this time, was added dropwise a mixture with stirring B ₁ liquid A ₁ solution, the beaker was filled with B ₁ was washed co a predetermined amount of ion-exchanged water, a mixed solution of A ₁ solution and B ₁ liquid The co-washed ion exchange water was added dropwise. The solution stirred for 30 minutes was used as a reaction solution. The final concentrations are 0.14M-KMnO ₄ and 0.19M-MnSO ₄ , and the concentration ratio of B ₁ solution to A ₁ solution (B solution / A solution) is 1.36. Hydrothermal synthesis conditions are a reaction temperature of 140 ° C. and a reaction time of 12 hours.

The powder obtained by washing and drying the residue obtained by hydrothermal synthesis was examined by X-ray diffraction (XRD) and found to be α-MnO ₂ . The BET specific surface area was 81.79 m ² / g, and the weight increase rate was 0.01%. The N ₂ gas permeation amount decreased from 3,117 m ³ / (m ² · h · atm) to 2,684 m ³ / (m ² · h · atm), and the gas permeation rate change rate was 0.73. The gas permeation amount was obtained by dividing the flow rate at a predetermined pressure by the area.

  FIG. 3 is an SEM image of the porous ceramic member after the reaction. Manganese dioxide is supported on the alumina particle surface of the porous ceramic member. It is considered that this is because the pretreatment liquid is likely to be accumulated in the gaps between the alumina particles.

(Example 2)
In pretreatment, the B ₁ was the first pretreatment solution, was A ₁ liquid and the second pretreatment solution. That is, the porous ceramic member B ₁ liquid immersed for 1 minute, 30 minutes at room temperature drying, after performing 100 ° C. dried 1 hour, was immersed for 1 minute in A ₁ solution, 30 minutes at room temperature drying, 100 ° C. Drying For 1 hour. The material of the porous ceramic member, the reaction solution, and the hydrothermal synthesis conditions are the same as in Example 1.

The residue was found to be α-MnO ₂ by XRD measurement. The BET specific surface area was 80.68 m ² / g, and the weight increase rate was 0.66%. The N ₂ gas permeation amount decreased from 3,431 m ³ / (m ² · h · atm) to 1,839 m ³ / (m ² · h · atm), and the gas permeation rate change rate was 0.54.

  FIG. 4 is an SEM image of the porous ceramic member after the reaction. Manganese dioxide is supported on the alumina particle surface of the porous ceramic member. Similar to Example 1, it is supported a little in the gaps between the alumina particles, which is presumably because the pretreatment liquid easily collects in the gaps between the alumina particles.

  More manganese dioxide was supported in Example 2 than in Example 1. This is because potassium permanganate is easier to dissolve than manganese sulfate. Therefore, if the porous ceramic member is immersed in the potassium permanganate aqueous solution first, it is excessive when it is immersed in the manganese sulfate aqueous solution even if it is dried. This is probably because potassium manganate is redissolved.

(Comparative Example 1)
In Comparative Example 1, the material of the porous ceramic member, the reaction liquid, and the hydrothermal synthesis conditions are the same as in Example 1 except that no pretreatment is performed. However, only in Comparative Example 1, on reaction solution preparation, which was added dropwise a mixture of A ₁ solution B ₁ liquid.

When the residue obtained in the reaction solution was subjected to XRD measurement, it was found to be α-MnO ₂ . Further, the BET specific surface area was 80.98 m ² / g, and the weight increase rate was −0.56%. The N ₂ gas permeation amount increased from 2,860 m ³ / (m ² · h · atm) to 3,038 m ³ / (m ² · h · atm), and the gas permeation rate change rate was 1.06. The decrease in weight is considered to be caused by the fact that manganese dioxide was not supported and the reaction solution before the start of the reaction was acidic, so that the sintering aid in alumina was dissolved. The pH of the reaction solution changed from 1.79 to 1.62 before and after the reaction.

  FIG. 5 is an SEM image of the porous ceramic member after the reaction. From the SEM image, it can be seen that manganese dioxide is not supported on the surface of the alumina particles when the pretreatment is not performed.

(Example 3)
As the porous ceramic member, a cylindrical member of porous LSM perovskite oxide was used. No pretreatment was performed, and only hydrothermal synthesis was performed.

The reaction liquid used for the hydrothermal synthesis was 0.034M-KMnO ₄ aqueous solution (hereinafter referred to as “A ₂ liquid”), 0.047M-MnSO ₄ aqueous solution (hereinafter referred to as “B ₂ liquid”), co-washing. Ion exchange water for mixing was prepared at a ratio of 2: 2: 1. After the B ₂ liquid is dropped and mixed into the A ₂ liquid, the beaker containing the B ₂ liquid is washed with a predetermined amount of ion exchange water, and the ion exchange water is washed with a mixed solution of the A ₂ liquid and the B ₂ liquid. Were mixed dropwise. The solution stirred for 30 minutes was used as a reaction solution. The final concentrations are 0.014M-KMnO ₄ and 0.019M-MnSO ₄ , and the concentration ratio of B ₂ solution to A ₂ solution (B solution / A solution) is 1.36. Hydrothermal synthesis conditions are a reaction temperature of 140 ° C. and a reaction time of 12 hours. In Example 3 and Examples 4 to 11 to be described later, the pressure vessel is vibrated during hydrothermal synthesis.

XRD measurement revealed that the residue was α-type and γ-type mixed crystal manganese dioxide. The BET specific surface area was 69.06 m ² / g, and the weight increase rate was −0.42%. The N ₂ gas permeation amount decreased from 1,982 m ³ / (m ² · h · atm) to 1,147 m ³ / (m ² · h · atm), and the gas permeation rate change rate was 0.58. The decrease in weight seems to be due to the fact that the reaction solution before the start of the reaction was acidic, so that LSM was dissolved more than the supported manganese dioxide (the same applies to other examples with the following decrease in weight). The pH of the reaction solution changed from 2.11 to 3.59 before and after the reaction.

Example 4
Hydrothermal synthesis was carried out in the same manner as in Example 3 except that the hydrothermal synthesis conditions were a reaction temperature of 140 ° C. and a reaction time of 24 hours. The residue was found to be β-MnO ₂ by XRD measurement. The BET specific surface area was 19.69 m ² / g, and the weight increase rate was −0.75%. The N ₂ gas permeation amount decreased from 2,231 m ³ / (m ² · h · atm) to 1,355 m ³ / (m ² · h · atm), and the gas permeation rate change rate was 0.61. The pH of the reaction solution changed from 2.11 to 3.89 before and after the reaction.

(Example 5)
Hydrothermal synthesis was carried out in the same manner as in Example 3 except that the hydrothermal synthesis conditions were a reaction temperature of 160 ° C. and a reaction time of 12 hours. The residue was found to be β-MnO ₂ by XRD measurement. The BET specific surface area was 61.01 m ² / g, and the weight increase rate was −0.74%. The N ₂ gas permeation amount decreased from 2,167 m ³ / (m ² · h · atm) to 1,341 (m ³ / m ² · h · atm), and the gas permeation rate change rate was 0.62. . The pH of the reaction solution changed from 2.11 to 3.59 before and after the reaction.

(Example 6)
Hydrothermal synthesis was carried out in the same manner as in Example 3 except that the hydrothermal synthesis conditions were a reaction temperature of 180 ° C. and a reaction time of 12 hours. The residue was found to be β-MnO ₂ by XRD measurement. The BET specific surface area was 32.04 m ² / g, and the weight increase rate was −0.57%. The N ₂ gas permeation amount decreased from 2,255 m ³ / (m ² · h · atm) to 1,248 m ³ / (m ² · h · atm), and the gas permeation rate change rate was 0.56. The pH of the reaction solution changed from 2.11 to 3.20 before and after the reaction.

(Example 7)
As a porous ceramic member, LSM was used in the same manner as in Example 3. The reaction solution used for the hydrothermal synthesis is a 0.14M-KMnO ₄ aqueous solution. Since it does not contain MnSO ₄ , (B liquid / A liquid) is zero. The hydrothermal synthesis conditions are a reaction temperature of 180 ° C. and a reaction time of 24 hours. Others are the same as in the third embodiment.

By XRD measurement, it was found that the residue was barnesite type manganese dioxide. The BET specific surface area was 69.92 m ² / g, and the weight increase rate was 2.52%. The N ₂ gas permeation amount decreased from 2,246 m ³ / (m ² · h · atm) to 1,373 m ³ / (m ² · h · atm), and the gas permeation rate change rate was 0.61. The pH of the reaction solution changed from 6.47 to 12.78 before and after the reaction.

(Example 8)
Upon preparation of the reaction solution by changing the concentration of _{B 1} liquid, _{B 1} liquid and _{A 1} solution concentration ratio of the (B solution / A solution) was 0.50. The preparation of the reaction solution is the same as in Example 1. Hydrothermal synthesis conditions are the same as in Example 7, with a reaction temperature of 180 ° C. and a reaction time of 24 hours.

The residue was found to be α-MnO ₂ by XRD measurement. The BET specific surface area was 18.28 m ² / g, and the weight increase rate was −0.39%. The N ₂ gas permeation amount decreased from 2,220 m ³ / (m ² · h · atm) to 1,618 m ³ / (m ² · h · atm), and the gas permeation rate change rate was 0.73. The pH of the reaction solution changed from 1.86 to 4.01 before and after the reaction.

(Comparative Example 2)
The reaction solution was prepared in the same manner as in Example 1, and the concentration ratio of the B ₁ solution and the A ₁ solution (B solution / A solution) was 1.36. The material of the porous ceramic member is LSM as in Example 7. No pretreatment is performed, and hydrothermal synthesis conditions are a reaction temperature of 140 ° C. and a reaction time of 12 hours.

The residue was found to be α-MnO ₂ by XRD measurement. The BET specific surface area was 54.09 m ² / g, and the weight increase rate was 0.11%. The N ₂ gas permeation amount decreased from 2,091 m ³ / (m ² · h · atm) to 0 m ³ / (m ² · h · atm), resulting in complete clogging. The pH of the reaction solution changed from 1.79 to 1.99 before and after the reaction.

  FIG. 6 is an SEM image of the porous ceramic member after the reaction. It can also be seen from the SEM image that manganese dioxide blocks the pores of the LSM perovskite oxide.

Example 9
Upon preparation of the reaction solution by changing the concentration of _{B 2} solution, _{B 2} solution and _{A 2} solution concentration ratio of the (B solution / A solution) was 0.35. The preparation of the reaction solution is the same as in Example 3. The material of the porous ceramic member and the hydrothermal synthesis conditions are the same as in Example 7. The reaction temperature is 180 ° C. and the reaction time is 24 hours.

The residue was found to be α-MnO ₂ by XRD measurement. The BET specific surface area was 97.15 m ² / g, and the weight increase rate was 0.01%. The N ₂ gas permeation amount decreased from 2,245 m ³ / (m ² · h · atm) to 1,767 m ³ / (m ² · h · atm), and the gas permeation rate change rate was 0.79. The pH of the reaction solution changed from 2.61 to 8.55 before and after the reaction.

(Example 10)
The concentration of the A ₂ solution and the B ₂ solution and the preparation of the reaction solution are the same as in Example 3. The concentration ratio of the B ₂ solution to the A ₂ solution (B solution / A solution) is 1.36. The material of the porous ceramic member and the hydrothermal synthesis conditions are the same as in Example 7. The reaction temperature is 180 ° C. and the reaction time is 24 hours.

The residue was found to be β-MnO ₂ by XRD measurement. The BET specific surface area was 33.29 m ² / g, and the weight increase rate was −0.70%. The N ₂ gas permeation amount decreased from 2,255 m ³ / (m ² · h · atm) to 1,378 m ³ / (m ² · h · atm), and the gas permeation rate change rate was 0.61. The pH of the reaction solution changed from 2.11 to 3.31 before and after the reaction.

(Example 11)
As the porous ceramic member, a LSMF perovskite oxide powder formed on the outer surface of a cylindrical alumina member by a slurry coating method and sintered by high-temperature firing was used. Hereinafter, in Table 1 described later, this material is represented as “LSMF / Al ₂ O ₃ ”. No pretreatment was performed, and only hydrothermal synthesis was performed. The reaction solution is the same as in Example 3, and the concentration ratio of the B ₂ solution and the A ₂ solution (B solution / A solution) is 1.36. The hydrothermal synthesis conditions are the same as in Example 7, with a reaction temperature of 180 ° C. and a reaction time of 24 hours.

The residue was found to be α-MnO ₂ by XRD measurement. The BET specific surface area was 79.11 m ² / g, and the weight increase rate was −1.11%. The N ₂ gas permeation amount decreased from 2,203 m ³ / (m ² · h · atm) to 1,890 m ³ / (m ² · h · atm), and the gas permeation rate change rate was 0.86. The pH of the reaction solution changed from 2.11 to 3.53 before and after the reaction.

  FIG. 7 is an SEM image of the porous ceramic member after the reaction. It can be seen that manganese dioxide is uniformly supported on the surface of the LSM particles.

  Table 1 shows the conditions and results of the above examples and comparative examples. In the "Evaluation" column, considering that manganese dioxide is supported to some extent and gas permeation after the support is ensured, the gas permeation rate change rate is 0.50 or more and less than 0.70. 0.10 or more and less than 0.50 and 0.70 or more and less than 1.00 are (circle) (possible), and less than 0.10 and 1.00 or more are x (impossible).

As can be seen from a comparison between Examples 1 and 2 and Comparative Example 1, when the porous ceramic member does not contain manganese atoms, manganese dioxide is not supported unless pretreatment is performed. Further, in the preprocessing, it is preferable that the porous ceramic member is immersed in the A ₁ solution after being immersed in the B ₁ liquid.

  From Comparative Example 2, it can be seen that the concentration of the reaction solution in Examples 1 and 2 is too high in the case of LSM. Comparing Example 3 and Example 4, it can be seen that the crystal structure of manganese dioxide changes with the time of hydrothermal synthesis. Comparing Example 3 with Examples 5 and 6, it can be seen that the crystal structure of manganese dioxide changes depending on the hydrothermal synthesis temperature.

  From Example 7, it can be said that manganese dioxide can be supported even when manganese sulfate is not dissolved in the reaction solution. From Examples 7 and 8, and Examples 9 and 10, it can be seen that the crystal structure of manganese dioxide changes depending on the concentration of manganese sulfate.

  From Example 11, it is considered that pretreatment is unnecessary in various porous ceramic members containing manganese atoms.

  As shown in the above examples, a porous ceramic member containing manganese atoms is immersed in an aqueous solution in which at least potassium permanganate is dissolved, and manganese dioxide is directly applied to the porous ceramic member by a hydrothermal synthesis method. It can be supported. The supported manganese dioxide is stable and does not fall into powder form. It is preferable that manganese sulfate is further dissolved in the reaction solution. By utilizing the hydrothermal synthesis method, manganese dioxide can be supported on the porous ceramic member easily and inexpensively. Further, manganese dioxide can be uniformly supported while ensuring the gas permeability of the porous ceramic member. In particular, when manganese dioxide particles are adhered directly to a porous ceramic member, such as a rubbing method or a slurry coating method, the adhesion layer in the pores becomes thick and the pores are blocked. However, such a problem can be avoided by the hydrothermal synthesis method.

  Furthermore, the amount of supported manganese dioxide and the crystal structure can be controlled by changing the concentration of the reaction solution and the hydrothermal synthesis conditions, that is, the reaction temperature, the reaction time, and the like. From the above examples, it can be seen that at least α-type, β-type, γ-type, and birnessite-type crystal structures can be obtained. When a stable crystal structure such as α-type, β-type or γ-type is required, the molar ratio of manganese sulfate to potassium permanganate in the reaction solution is 0.35 or more and 1.36 or less from the above examples. Is desirable.

  Further, even when the porous ceramic member does not contain manganese atoms, the pretreatment is performed to support manganese dioxide on the porous ceramic member. By performing the pretreatment, the precursor of manganese dioxide adheres to the surface of the porous ceramic member (including the surface in the porous void), and the manganese atoms are removed from the surface of the porous ceramic member to the porous void. Since it is in a state existing over the inner surface, even if it is a porous ceramic member that does not contain manganese atoms, it is considered possible to obtain the same operations and effects as in the case of a porous ceramic member that contains manganese atoms. .

  Note that the entire member immersed in the reaction solution does not have to be made of ceramic, and a part of the member may be porous ceramic.

  The porous ceramic member on which manganese dioxide is supported by the above method can be used for various applications using manganese dioxide as a catalyst. For example, when the material of the porous ceramic member is a perovskite-type oxide, a preferable example of application is a positive electrode of a metal-air battery. Further, by supporting manganese dioxide on a honeycomb-shaped porous ceramic member in which many long pores are formed, it can be used as a NOx decomposition filter.

  Further, a zeolite membrane can be formed on a porous ceramic member by a hydrothermal synthesis method, and manganese dioxide can be supported thereon, so that it can be used as a membrane reactor. In this case, manganese dioxide is indirectly supported on the ceramic of the porous ceramic member. For example, an apparatus that decomposes molecules to be decomposed with manganese dioxide and separates only molecules smaller than the pore diameter of the zeolite membrane through the zeolite membrane can be considered. A zeolite membrane may be formed on the surface of the porous ceramic member, and manganese dioxide may be supported from the back surface to the inner surface of the porous void. In this case, the substance to be decomposed permeates the porous ceramic member while being decomposed by manganese dioxide, and is separated by the zeolite membrane.

  FIG. 8 is a diagram showing a configuration of the metal-air secondary battery 1 having a porous ceramic member on which manganese dioxide is supported by the above method. Since the metal-air secondary battery 1 uses zinc ions, it is hereinafter referred to as a “zinc-air secondary battery”. The metal-air secondary battery may use other metal ions. The main body 11 of the zinc-air secondary battery 1 has a substantially cylindrical shape centered on the central axis J1, and FIG. 8 shows a cross section of the main body 11 on a plane including the central axis J1. The zinc-air secondary battery 1 includes a positive electrode 2, a negative electrode 3, an electrolyte layer 4, and an electrolytic solution 40.

  The negative electrode 3 (also referred to as a metal electrode) is a coiled member centered on the central axis J1. The negative electrode 3 in the present embodiment has a shape in which a linear member having a substantially circular cross section is spirally wound around the central axis J1. The negative electrode 3 includes a coil-shaped base material 31 formed of a conductive material, and a deposited metal layer 32 formed on the surface of the base material 31. A negative electrode current collector terminal 33 is connected to the end of the negative electrode 3 in the direction of the central axis J1.

  As a material for forming the substrate 31, a metal such as copper (Cu), nickel (Ni), silver (Ag), gold (Au), iron (Fe), aluminum (Al), magnesium (Mg), or any An alloy containing such a metal is exemplified. In the present embodiment, the base material 31 is formed of copper. From the viewpoint of increasing the conductivity of the base material 31 also serving as a current collector, the base material 31 preferably contains copper or a copper alloy. When the main body of the base material 31 is formed of copper, it is preferable that a protective film of other metal such as nickel is formed on the surface of the main body. In this case, the surface of the base material 31 is the surface of the protective film. For example, the thickness of the protective film is 1 to 20 μm (micrometer), and the protective film is formed by plating. The deposited metal layer 32 is formed by electrolytic deposition of zinc (Zn). The deposited metal layer 32 may be formed by electrolytic deposition of an alloy containing zinc.

  A cylindrical separator 41 is provided around the negative electrode 3, and a cylindrical positive electrode 2 (also referred to as an air electrode) is provided around the separator 41. That is, the inner surface of the separator 41 faces the negative electrode 3, and the outer surface of the separator 41 faces the inner surface of the positive electrode 2. The negative electrode 3, the separator 41, and the positive electrode 2 are provided concentrically with the central axis J1 as the center, and when viewed along the central axis J1, the distance between the outer edge of the negative electrode 3 and the positive electrode 2 is the central axis. It is constant over the entire circumference in the circumferential direction centered on J1. That is, between the negative electrode 3 and the positive electrode 2 in the zinc-air secondary battery 1, the interval between equipotential surfaces is constant over the entire circumference. Since the equipotential surface is not dense, the current distribution during charging and discharging is constant in the circumferential direction. If the current distribution over the entire circumference is approximately uniform, the shape of the positive electrode 2 may be, for example, a regular polygonal cylinder having six or more vertices.

The separator 41 includes a separator body 411 that is a porous cylindrical support formed of ceramic, and a porous film 412 that is formed on the inner surface of the separator body 411 facing the negative electrode 3. The separator body 411 is formed of a ceramic having high mechanical strength and insulating properties such as silica (SiO ₂ ), alumina (Al ₂ O ₃ ), zirconia (ZrO ₂ ), titania (TiO ₂ ), and hafnia (HfO ₂ ). Is done. In the present embodiment, the separator body 411 is an integrally formed ceramic sintered body, and is composed only of ceramic. The separator body 411 may be a mixture or laminate of these ceramics. The thickness of the cylindrical separator body 411 is, for example, 0.2 to 4 millimeters (mm).

  The average pore diameter of the separator body 411 may be within a range in which liquid retention, ionic conductivity, and air permeability that do not inhibit the battery reaction are ensured. The average pore diameter of the separator body 411 is preferably 15 μm or less.

  The porous film 412 is formed of ceramic, and in the present embodiment, the porous film 412 is a ceramic sintered body like the separator body 411. Specifically, the porous film 412 (in the case of a laminated film, each film of the laminated film) includes at least one of ceramics having high mechanical strength and insulating properties such as silica, alumina, zirconia, titania and hafnia. It is preferable to include a ceramic. More preferably, the porous membrane 412 is made of ceramic only.

  The porous membrane 412 has an average pore diameter that is smaller than the average pore diameter of the separator body 411. Specifically, the average pore diameter of the porous membrane 412 is 0.01 μm or more and 2 μm or less. Preferably, the porous film 412 is a laminated film in which a plurality of films are laminated. From the viewpoint of stability, zirconia is preferably used for forming the ceramic film on the surface. In the zinc-air secondary battery 1, the porous membrane 412 is formed over the entire circumference of the surface facing the negative electrode 3 in the cylindrical separator body 411.

  A space on the inner side (center axis J1 side) of the cylindrical positive electrode 2 is filled with an aqueous electrolyte solution 40. The electrolytic solution 40 is interposed between the positive electrode 2 and the negative electrode 3 and is in contact with both electrodes. About the entire negative electrode 3 is immersed in the electrolytic solution 40. The electrolyte solution 40 is also filled in the pores of the separator 41 which is a porous member. In the following description, the space between the negative electrode 3 and the positive electrode 2 when viewed along the central axis J1 is referred to as “electrolyte layer 4”. That is, the electrolyte layer 4 is a space located between the negative electrode 3 and the positive electrode 2. In the present embodiment, the electrolyte layer 4 includes a separator 41. The electrolytic solution 40 is an alkaline aqueous solution, and preferably includes a potassium hydroxide (caustic potash, KOH) aqueous solution or a sodium hydroxide (caustic soda, NaOH) aqueous solution. Further, the electrolytic solution 40 includes zinc ions or ions containing zinc. That is, the zinc ions contained in the electrolytic solution 40 may exist in various forms and may be regarded as ions containing zinc (that is, zinc atoms). For example, it may exist as tetrahydroxyzinc ions.

  The positive electrode 2 includes a porous positive electrode conductive layer 21. A positive electrode catalyst layer 22 is formed on the outer surface of the cylindrical positive electrode conductive layer 21. A positive electrode catalyst is supported on the positive electrode catalyst layer 22. Around the positive electrode catalyst layer 22, for example, a metal mesh sheet of nickel or the like is wound to form a current collecting layer 23. A positive current collecting terminal 24 is provided at an end of the current collecting layer 23 in the central axis J1 direction. Connected. The current collecting layer 23 also partially contacts the outer surface of the positive electrode conductive layer 21. An interconnector that contacts only a part of the outer surface of the positive electrode conductive layer 21 may be provided as the current collecting layer 23.

  A material having water repellency (for example, PFA (perfluoroalkoxy) is used on the outer surface of the current collecting layer 23 (including a portion of the outer surface of the positive electrode catalyst layer 22 not covered with the mesh-shaped current collecting layer 23). A porous layer made of alkane) or PTFE (polytetrafluoroethylene) is formed as the liquid repellent layer 29.

From the viewpoint of preventing deterioration due to oxidation during charging, the positive electrode conductive layer 21 preferably does not contain conductive carbon. In this embodiment, the positive electrode conductive layer 21 is a porous perovskite type having conductivity. It is a porous thin conductive film mainly formed of an oxide (for example, LSCF (LaSrCoFeO ₃ )).

The positive electrode catalyst layer 22 is a porous ceramic carrying a catalyst for promoting an oxygen reduction reaction. Examples of the catalyst include metal oxides such as manganese (Mn), nickel (Ni), and cobalt (Co). In the present embodiment, the positive electrode catalyst layer 22 is obtained by supporting manganese dioxide (MnO ₂ ) on a porous perovskite oxide (for example, LSMF (LaSrMnFeO ₃ )). Therefore, precisely, the portion of the porous ceramic where manganese dioxide is supported functions as the positive electrode catalyst layer. In the zinc-air secondary battery 1, in principle, an interface between air and the electrolytic solution 40 is formed in the vicinity of the porous positive electrode catalyst layer 22.

  As shown in FIG. 8, disc-shaped blocking members 51 are fixed to both end surfaces (upper end surface and lower end surface in FIG. 8) of the negative electrode 3, the electrolyte layer 4, and the positive electrode 2 in the direction of the central axis J1. A through hole 511 is provided at the center of each closing member 51. In the zinc-air secondary battery 1, the liquid repellent layer 29 and the closing member 51 prevent the electrolytic solution 40 in the main body 11 from leaking outside the through hole 511.

  One end of the supply pipe 61 is connected to the through hole 511 of one closing member 51, and the other end of the supply pipe 61 is connected to the supply / recovery unit 6. One end of the recovery pipe 62 is connected to the through hole 511 of the other closing member 51, and the other end of the recovery pipe 62 is connected to the supply and recovery unit 6. The supply / recovery unit 6 includes an electrolytic solution storage tank and a pump, and recovers the electrolytic solution 40 in the main body 11 to the storage tank at a flow rate (volume per unit time) instructed by a control unit (not shown). At the same time, the electrolytic solution in the storage tank is supplied to the main body 11 at the same flow rate. That is, the electrolytic solution can be circulated between the main body 11 and the storage tank of the supply and recovery unit 6. The supply and recovery unit 6 is provided with a filter, and unnecessary substances contained in the electrolytic solution are removed by the filter when the electrolytic solution is circulated.

  In the zinc-air secondary battery 1 in the present embodiment, the central axis J1 of the main body 11 is parallel to the vertical direction (gravity direction), and the through hole 511 connected to the recovery pipe 62 is connected to the supply pipe 61. It is located above the through hole 511 in the vertical direction. The supply pipe 61 and the recovery pipe 62 are provided with a supply valve and a recovery valve (not shown). In normal operation in this operation example, the electrolyte solution is circulated at a constant flow rate. The supply valve and the recovery valve can be regarded as a part of the supply recovery unit 6. The electrolytic solution may be supplied from the upper through hole 511 and recovered from the lower through hole 511. The central axis J1 of the zinc-air secondary battery 1 does not necessarily have to be parallel to the vertical direction. For example, the zinc-air secondary battery 1 may be arranged so that the central axis J1 is parallel to the horizontal direction.

  When discharge is performed in the zinc-air secondary battery 1 of FIG. 8, the negative electrode current collector terminal 33 and the positive electrode current collector terminal 24 are electrically connected via a load such as a lighting fixture, for example. Zinc included in the negative electrode 3 is oxidized to generate zinc ions, and electrons are supplied to the positive electrode 2 via the negative electrode current collector terminal 33 and the positive electrode current collector terminal 24. In the porous positive electrode 2, oxygen in the air that has passed through the liquid repellent layer 29 is reduced by the electrons supplied from the negative electrode 3 and is eluted into the electrolyte as hydroxide ions. In the positive electrode 2, the reduction reaction of oxygen is promoted by the positive electrode catalyst.

  On the other hand, when charging is performed in the zinc-air secondary battery 1, a voltage is applied between the negative electrode current collector terminal 33 and the positive electrode current collector terminal 24, and electrons are supplied from the hydroxide ions to the positive electrode 2. And oxygen is generated. In the negative electrode 3, metal ions are reduced by the electrons supplied to the negative electrode current collector terminal 33 via the current collector layer 23 and the positive electrode current collector terminal 24, and zinc is deposited.

  At this time, since the coiled negative electrode 3 has no corners, electric field concentration hardly occurs. That is, there is no significant bias in current density. Further, the negative electrode 3 is in uniform contact with the electrolytic solution 40. As a result, the generation and growth of dendrites in which zinc precipitates in a dendritic shape and whiskers in which the zinc precipitates in a whisker shape (needle shape) are greatly suppressed. Actually, dense zinc is uniformly deposited on almost the entire surface of the negative electrode 3, and a deposited metal layer 32 is formed. In the positive electrode 2, the generation of oxygen is promoted by the positive electrode catalyst contained in the positive electrode catalyst layer 22.

  As described above, in the zinc-air secondary battery 1, the electrolyte solution is circulated by the supply and recovery unit 6, and electrolysis is performed in the vicinity of the upper through hole 511 (hereinafter also referred to as “upper through hole 511”). The liquid 40 is collected from the upper through hole 511. Further, a part of the electrolytic solution 40 supplied into the main body 11 from the lower through hole 511 (hereinafter also referred to as “lower through hole 511”) is a gap (that is, shown in FIG. 8) of the coiled negative electrode 3. In the cross section of the negative electrode 3, it diffuses also in the electrolyte layer 4 (the separator 41) via circular portions separated from each other in the vertical direction. Thereby, the electrolytic solution 40 contained in the electrolyte layer 4 is replaced with the electrolytic solution in the storage tank of the supply and recovery unit 6 while discharging or charging in the zinc-air secondary battery 1.

  In the zinc-air secondary battery 1, the operation of sequentially collecting the predetermined amount of electrolytic solution from the upper through hole 511 and supplying the same amount of electrolytic solution from the lower through hole 511 may be repeated. Thereby, the electrolytic solution 40 in the main body 11 is replaced with the electrolytic solution in the storage tank of the supply and recovery unit 6 while discharging or charging. It is also possible to intermittently replace the electrolyte. For example, after the electrolytic solution is circulated for a predetermined time, the supply valve and the recovery valve are closed, and the recovery and supply of the electrolytic solution are stopped until the diffusion of the new electrolytic solution reaches an equilibrium state. As a result, the electrolytic solution 40 in the main body 11 is replaced or the deteriorated electrolytic solution and a new electrolytic solution are mixed while discharging or charging. Of course, the discharging or charging may be stopped and the electrolytic solution 40 in the main body 11 may be replaced.

  The structure of the zinc-air secondary battery 1 is a preferred example and may be variously modified. For example, in the separator 41, the porous film 412 may be formed on both the inner surface and the outer surface of the separator body 411. One or both of the separator body 411 and the porous film 412 may contain other materials such as a binder in addition to the ceramic. The separator 41 may be omitted.

  In the zinc-air secondary battery 1, it is not always necessary to circulate the electrolytic solution. The negative electrode is not limited to a coil shape. For example, it may be tubular or flat. Furthermore, the positive electrode may be located inside the negative electrode. The shape of the positive electrode is not limited to a tubular shape.

Next, manufacture of the member containing the positive electrode 2 and the separator 41 of the zinc-air secondary battery 1 will be described. First, a porous ceramic member that is the separator body 411, for example, an alumina tubular member is prepared. A slurry containing particles as a material for the porous film 412 is applied to the inner peripheral surface of the separator body 411. A porous film 412 is formed by drying and firing the slurry. A slurry containing cerium oxide (CeO ₂ ) particles is applied to the outer peripheral surface of the separator body 411, and a thin reaction preventing layer is formed by drying and firing.

  On the reaction preventing layer, a slurry containing LSCF particles is applied, and the positive electrode conductive layer 21 is formed by drying and firing. A slurry containing LSMF particles is applied onto the positive electrode conductive layer 21, and a ceramic portion of the positive electrode catalyst layer 22 is formed by drying and firing. Since LSMF contains manganese atoms, manganese dioxide is supported on LSMF, that is, on the outer peripheral surface of the porous ceramic member, by the reaction of FIG. 1 using the hydrothermal synthesis method without pretreatment. Thereby, the positive electrode catalyst layer 22 is completed. During hydrothermal synthesis, an unnecessary area such as the inner peripheral surface is appropriately masked.

  By using a porous ceramic member having manganese atoms on the outer peripheral surface and further utilizing a hydrothermal synthesis method, manganese dioxide crystals can be easily supported stably on the porous ceramic member. As a result, the manufacturing cost of the zinc-air secondary battery 1 can be reduced. Further, manganese dioxide can be uniformly supported while ensuring the gas permeability of the porous ceramic member.

  The member including the separator 41 and the positive electrode 2 can be manufactured by various other methods. For example, the separator 41 is formed by applying a slurry containing alumina particles to the inner peripheral surface of a porous tubular member formed of LSM, and drying and firing. Thereafter, the reaction shown in FIG. 1 is performed on the porous ceramic member, and manganese dioxide is supported on the outer peripheral surface by a hydrothermal synthesis method. LSM functions as the positive electrode conductive layer 21, but the portion on which manganese dioxide is supported functions as the positive electrode catalyst layer 22.

  The above-described method for supporting manganese dioxide can be variously modified.

  For example, the reaction solution and hydrothermal synthesis conditions may be variously changed according to the material of the porous ceramic member and the required gas permeation performance (including cases where gas permeation is unnecessary). The reaction solution may further contain substances other than potassium permanganate and manganese sulfate. The pretreatment liquid may further contain substances other than potassium permanganate and manganese sulfate.

  The porous ceramic member on which manganese dioxide is supported can be used for various apparatuses using manganese dioxide as a catalyst. In particular, even a porous ceramic member having a large area or an uneven porous ceramic member can easily carry manganese dioxide, and can be easily used for manufacturing parts for various applications.

  The configurations in the above-described embodiments and modifications may be combined as appropriate as long as they do not contradict each other.

DESCRIPTION OF SYMBOLS 1 Zinc air secondary battery 2 Positive electrode 3 Negative electrode 21 Positive electrode conductive layer 22 Positive electrode catalyst layer 40 Electrolytic solution 41 Separator S11-S13, S21-S25 Step

Claims (9)

A method for supporting manganese dioxide in which manganese dioxide is supported on a porous ceramic member,
a) In a pressure-resistant vessel, a porous ceramic member containing manganese atoms has a potassium permanganate concentration of 0.014 mol / L to 0.14 mol / L and a manganese sulfate concentration of 0.07 mol / L or less. A step of immersing in an aqueous solution,
b) after the step a), heating the aqueous solution in the pressure vessel, and supporting manganese dioxide on the porous ceramic member by a hydrothermal synthesis method;
A method for supporting manganese dioxide, comprising: The method for supporting manganese dioxide according to claim 1 ,
In the aqueous solution in the step a), a manganese dioxide supporting method, wherein a molar ratio of manganese sulfate to potassium permanganate is 0.35 or more and 1.36 or less. A method for supporting manganese dioxide according to claim 1 or 2 ,
The material of the porous ceramic member is lanthanum / strontium / manganite (LSM), lanthanum / strontium / manganese / iron oxide (LSMF) or lanthanum / strontium / cobalt / manganese / iron oxide (LSCMF). A feature of supporting manganese dioxide. A method for producing a porous ceramic member , comprising the step of supporting manganese dioxide by the method for supporting manganese dioxide according to any one of claims 1 to 3 . A method for supporting manganese dioxide in which manganese dioxide is supported on a porous ceramic member,
a) a step of immersing a porous ceramic member containing no manganese atom in an aqueous potassium permanganate solution and then drying;
b) Before or after the step a), the porous ceramic member is immersed in an aqueous manganese sulfate solution and then dried;
c) a step of immersing the porous ceramic member in an aqueous solution in which potassium permanganate is dissolved in the pressure vessel after the steps a) and b);
d) after the step c), heating the aqueous solution in the pressure vessel, and supporting the manganese dioxide on the porous ceramic member by a hydrothermal synthesis method;
A method for supporting manganese dioxide, comprising: The manganese dioxide carrying method according to claim 5 ,
A method for supporting manganese dioxide, wherein manganese sulfate is further dissolved in the aqueous solution in the step c). It is a manganese dioxide carrying | support method of Claim 6 , Comprising:
In the aqueous solution in step c), a manganese dioxide supporting method, wherein a molar ratio of manganese sulfate to potassium permanganate is 0.35 or more and 1.36 or less. A method for supporting manganese dioxide according to any one of claims 5 to 7 ,
A method for supporting manganese dioxide, wherein the material of the porous ceramic member is alumina, cordierite, zirconia, mullite, or silica. Method for producing a porous ceramic member which comprises a step of supporting the manganese dioxide in the manganese dioxide loading method according to any one of claims 5 to 8.