JP2005332610A - Proton conductive material, its manufacturing method, hydrogen concentration cell, hydrogen sensor and fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide proton conductive material capable of operating in a low temperature range to a middle temperature range, and being manufactured easily at low cost, and its manufacturing method. <P>SOLUTION: The proton conductive material contains elements of calcium, sulfur and hydrogen and has the room temperature proton conductivity of not less than 10<SP>-6</SP>S/cm. When expressed in terms of oxide, the proton conductive material can contain CaO of not less than 10 wt% and not more than 45 wt%, SO<SB>3</SB>of not less than 15 wt% and not more than 60 wt%, H<SB>2</SB>O of not less than 5 wt% and not more than 55 wt%, and P<SB>2</SB>O<SB>5</SB>of not less than 0.1 wt% and not more than 50 wt%. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a proton conductive material and a method for producing the same. Further, the present invention relates to a hydrogen concentration cell, a hydrogen sensor, and a fuel cell on which a proton conductive material is mounted.

  Recently, fuel cells, hydrogen concentration cells, hydrogen sensors, and the like have attracted attention from the viewpoint of prevention of environmental pollution and energy. In order for these to function satisfactorily, the electrolyte through which the hydrogen ions (protons) used must be suitable. That is, it is preferable to withstand the use conditions, have good film formability, and have as high a proton conductivity as possible.

  Today, as a proton conductive electrolyte, an organic solid polymer membrane (Nafion etc.) operating at a low temperature range of about 80 ° C. and an inorganic solid perovskite type operating at a high temperature range of about 900 ° C. are known. ing.

  The proton conductive electrolyte described above has the following drawbacks. The former is expensive and the use temperature is limited. The latter does not work unless the temperature is high. Furthermore, in order to make a film, it is necessary to sinter at a high temperature of 1200 ° C. or higher.

Among the hydrous crystalline oxygen acids as proton conductive materials, H ₃ Mo ₁₂ PO ₄₀ / 29H ₂ O (12 molybdophosphoric acid) and H ₃ W ₁₂ PO ₄₀ / 29H ₂ O (12 tungstophosphoric acid) are used at room temperature. 2 × 10 ⁻¹ S / cm, indicating high proton conductivity. However, this crystal is easily dehydrated and its conductivity is lowered. In addition, since it is a strong acid, there is a problem that it is easy to corrode surrounding materials, and attempts have been made to produce proton conductive membranes and plates, but at present, satisfactory results have not been obtained.

In addition, anhydrous compounds having hydrogen bonds, that is, solids of a type in which there is no crystal water but protons move through hydrogen bonds, C ₆ H ₁₂ N ₂ (H ₂ SO ₄ ) _1.5 and LiN ₂ H ₅ SO ₄ Quaternary amine sulfates having the chemical formula are known. These are stable up to about 200 ° C. and show a considerable proton conductivity, but the conductivity at room temperature is low, and the decomposition starts at a high temperature of 200 ° C. or higher. Solid potassium potassium (KOH) exhibits a considerable proton conductivity in the temperature range of 248 to 406 ° C., but has a hygroscopic property and easily absorbs carbon dioxide, so it cannot be used in the atmosphere.

In addition, cesium hydrogen sulfate CsHSO ₄ as a proton conductive material and its analogs increase its proton conductivity with a rise in temperature, causing a phase transition at 144 ° C. and rapidly increasing the proton conductivity. Low.

  The present invention has been made in view of the above circumstances, and can be operated from a low temperature range to a medium temperature range (for example, 200 ° C.), can be easily manufactured, and can be manufactured at low cost. To provide a manufacturing method. Furthermore, the present invention provides a hydrogen concentration cell, a hydrogen sensor, and a fuel cell equipped with the proton conductive material.

  The present inventor has been eagerly developing proton conductive materials for many years. And it discovered that the material illustrated by calcium sulfate each containing the element of calcium (Ca), sulfur (S), and hydrogen (H) was useful as a proton conductive material, and completed this invention based on this knowledge. I let you.

That is, the proton conductive material according to the present invention contains calcium (Ca), sulfur (S), and hydrogen (H) elements, respectively, and the proton conductivity at room temperature is 10 ⁻⁶ S / cm or more. It is a feature. Room temperature refers to 25 ° C.

  In general, hydrogen (H) is one of molecular water, crystal water, and mobile protons that are shared in the proton conductive material.

  The proton conductive material according to the present invention can be manufactured based on the manufacturing method exemplified below, but is not limited to the following manufacturing method, and can also be manufactured based on other manufacturing methods. .

The method for producing a proton conductive material according to the present invention includes a step of forming a mixture of calcium sulfate hemihydrate (CaSO ₄ .1 / 2H ₂ O, hemihydrate gypsum) and an aqueous solution, and curing the mixture to cure. And a step of making a body. The aqueous solution preferably contains an acid.

The method for producing a proton conductive material according to the present invention comprises mixing a mixture of calcium sulfate hemihydrate (CaSO ₄ .1 / 2H ₂ O, hemihydrate gypsum) and an aqueous solution containing phosphoric acid and / or phosphate. And a step of forming the cured product by curing the mixture.

  The method for producing a proton conductive material according to the present invention includes a step of obtaining a cured body based on gypsum hydrate and a step of introducing mobile hydrogen ions into the cured body based on gypsum hydrate. It is characterized by. In introducing mobile hydrogen ions, for example, an aqueous solution containing phosphoric acid and / or phosphate can be impregnated into a hardened body based on gypsum hydrate.

  A hydrogen concentration cell according to the present invention is a hydrogen concentration cell composed of a reference electrode facing a reference material, a measurement electrode facing a measurement object, and an electrolyte phase sandwiched between the reference electrode and the measurement electrode. The electrolyte phase is formed of the proton conductive material according to any one of the above claims. At the time of measurement, the reference substance is brought into contact with the reference electrode, and the measurement object is brought into contact with the measurement electrode. An electromotive force is generated between the reference electrode and the measurement electrode based on the hydrogen concentration of the reference substance and the hydrogen concentration of the measurement object.

  A hydrogen sensor according to the present invention is a hydrogen concentration cell type hydrogen comprising a reference electrode facing a reference material, a measurement electrode facing a measurement object, and an electrolyte phase sandwiched between the reference electrode and the measurement electrode. In the sensor, the electrolyte phase is formed of a proton conductive material according to any one of the above claims.

  At the time of measurement, the reference substance is brought into contact with the reference electrode, and the measurement object is brought into contact with the measurement electrode. An electromotive force is generated between the reference electrode and the measurement electrode based on the hydrogen concentration of the reference substance and the hydrogen concentration of the measurement object. Based on the electromotive force, the hydrogen concentration of the measurement object is detected.

  The fuel cell according to the present invention is a fuel cell comprising a fuel electrode to which fuel is supplied, an oxidant electrode to which an oxidant is supplied, and an electrolyte phase sandwiched between the fuel electrode and the oxidant electrode. The electrolyte phase is formed of the proton conductive material according to any one of the above claims.

  Fuel is supplied to the fuel electrode and an oxidant is supplied to the oxidant electrode. Hydrogen generated from the fuel is oxidized and separated into protons (hydrogen ions) and electrons. Protons move through the electrolyte phase, reach the oxidant electrode, react with the oxidant (oxygen) to generate water, and generate electricity.

  With the proton conductive material according to the present invention, good proton conductivity can be obtained at room temperature.

  According to the method for producing a proton conductive material according to the present invention, a proton conductive material having good proton conductivity at room temperature can be obtained.

  According to the hydrogen concentration cell and the hydrogen sensor of the present invention, since a proton conductive material having a good proton conductivity at room temperature is used, a good detection output can be obtained.

  According to the fuel cell of the present invention, since a proton conductive material having good proton conductivity at room temperature is used, a good power output can be obtained.

The proton conductive material according to the present invention contains calcium (Ca), sulfur (S), and hydrogen (H) elements, respectively, and has a proton conductivity at room temperature of 10 ⁻⁶ S / cm or more. Furthermore, at least one of barium (Ba) and zinc can be contained as required.

  According to the proton conductive material of the present invention, it can be formed of ceramics based on sulfate. As the sulfate, calcium sulfate and / or barium sulfate can be employed.

According to the proton conductive material according to the present invention, calcium (Ca), sulfur (S), and hydrogen (H) elements are expressed in terms of their respective oxides, as CaO, 10 wt% or more and 45 wt% or less, and as SO _3. A form containing 15 wt% or more and 60 wt% or less and H ₂ O containing 5 wt% or more and 55 wt% or less can be adopted.

  Here, “calcium is expressed in terms of oxide and contains 10% by weight as CaO” means that when the proton conductive material is 100%, in addition to CaO itself, calcium compounds other than CaO (for example, calcium sulfide) Even when calcium is contained as, etc.), when calcium is counted as CaO, it means 10% by weight.

Examples of CaO include 10 to 40% by weight, 14 to 30% by weight, 14 to 27% by weight, and 16 to 23% by weight. Examples of SO ₃ include 15 to 50% by weight, 18 to 40% by weight, and 20 to 35% by weight. Examples of H ₂ O include 10 to 55% by weight, 20 to 55% by weight, or 25 to 50% by weight. Of course, it is not limited to these.

Further, according to the proton conductive material according to the present invention, calcium (Ca), sulfur (S), hydrogen (H), and phosphorus (P) elements are expressed in terms of their respective oxides, and expressed as 10% by weight or more and 45% by weight as CaO. % Or less, 15 to 60% by weight as SO ₃ , 5 to 55% by weight as H ₂ O, and 0.1 to 50% by weight as P ₂ O ₅ Can do. Examples of P ₂ O ₅ include 0.5 to 40% by weight, 1 to 35% by weight, and 2 to 30% by weight. Of course, it is not limited to these.

Here, as the proton conductive material according to the present invention, calcium sulfate (CaSO ₄ ) can be contained in an amount of 40% by weight or more (or 45% by weight or more, 50% by weight or more). In addition, calcium sulfate dihydrate (CaSO ₄ .2H ₂ O) can be contained in an amount of 40% by weight or more (also 45% by weight or more, 50% by weight or more).

Moreover, as the proton conductive material according to the present invention, it is possible to adopt a form formed of a cured body obtained by solidifying a raw material containing calcium sulfate as a main component with water. Further, as the proton conductive material according to the present invention, a form formed by reacting a raw material containing 30 wt% or more of calcium sulfate (CaSO ₄ ) with phosphoric acid can be employed. Therefore, as the proton conductive material according to the present invention, a form mainly composed of sulfate-phosphate-water can be adopted.

Furthermore, the proton conductive material according to the present invention has a form formed of a cured body obtained by mixing and curing a calcium sulfate hemihydrate (CaSO ₄ .1 / 2H ₂ O, hemihydrate gypsum) and an aqueous solution. Can be adopted.

As the proton conductive material according to the present invention, calcium sulfate hemihydrate (CaSO ₄ .1 / 2H ₂ O, hemihydrate gypsum) and an aqueous solution containing phosphoric acid and / or phosphate are mixed and cured. The form currently formed with the hardening body is employable.

  As the proton conductive material according to the present invention, a form formed by introducing mobile hydrogen ions into a cured body based on gypsum hydrate can be employed.

  As the proton conductive material according to the present invention, a form formed by impregnating a hardened body formed of a gypsum base material with an aqueous solution containing phosphoric acid and / or phosphate can be employed.

In the proton conductive material according to the present invention, the proton conductivity at room temperature (25 ° C.) can be 10 ⁻⁶ S / cm or more, and can be 10 ⁻⁵ S / cm or more. If manufacturing conditions and use conditions are matched, the temperature should be 10 ⁻⁴ S / cm or more, 10 ⁻³ S / cm or more, 10 ⁻² S / cm or more at room temperature (25 ° C.) as in the examples described later. Can do. Further, it can be 10 ^-1 S / cm or more.

  Examples of the method for producing a proton conductive material according to the present invention include the production methods represented by the following (1) to (3).

(1) Use calcium sulfate hemihydrate (CaSO ₄ .1 / 2H ₂ O, hemihydrate gypsum = gypsum hemihydrate) before solidifying with water. The calcium sulfate hemihydrate _{(CaSO 4 · 1 / 2H 2} O, gypsum hemihydrate) forming a mixture obtained by mixing the aqueous solution, and forming a cured product by curing the mixture. It can be left to cure. Incidentally, those cured with water is 2 gypsum (gypsum _{dihydrate, CaSO 4 · 2H 2 O)} .

(2) forming a mixture of calcium sulfate hemihydrate (CaSO ₄ .1 / 2H ₂ O, hemihydrate gypsum = gypsum hemihydrate) and an aqueous solution containing phosphoric acid and / or phosphate; And curing the mixture. It can be left to cure.

  (3) A step of obtaining a cured body based on gypsum hydrate and a step of introducing mobile hydrogen ions into the cured body based on gypsum hydrate are included. In order to introduce mobile hydrogen ions, the cured body is preferably impregnated with an aqueous solution containing phosphoric acid and / or phosphate. In this case, an aqueous solution containing phosphoric acid and / or phosphate and the cured body can be brought into contact with each other, or the cured body can be immersed in the aqueous solution. As the temperature of the aqueous solution, although it varies depending on the composition, production method, size, etc. of the proton conductive material, room temperature to 120 ° C., room temperature to 100 ° C., room temperature to 80 ° C., etc. can be exemplified as appropriate. is not. Examples of the immersion time include 3 seconds to 120 minutes, 10 seconds to 60 minutes, and 1 minute to 30 minutes, although they vary depending on the composition, production method, size, and the like of the proton conductive material, but are not limited thereto. Is not to be done.

  As shown in FIG. 1, the hydrogen sensor according to the present invention includes a reference electrode 10 facing a reference gas as a reference substance, a measurement electrode 11 facing a measurement target gas as a measurement object, a reference electrode 10 and a measurement. The electrolyte phase 12 is sandwiched between the electrodes 11. The reference electrode 10 and the measurement electrode 11 are made of a material having electronic conductivity and good corrosion resistance. Examples of such materials include, but are not limited to, nickel, platinum, gold, rhodium, ruthenium and the like. The reference electrode 10 and the measurement electrode 11 can be formed by a known method exemplified by a normal coating method, coating baking method, PVD method, CVD method and the like. The electrolyte phase 12 is formed of any of the proton conductive materials described above having high proton conductivity at room temperature. In measurement, the reference gas is brought into contact with the reference electrode 10 and the measurement target gas is brought into contact with the measurement electrode 11. An electromotive force is generated between the reference electrode 10 and the measurement electrode 11 based on the hydrogen concentration of the reference gas and the hydrogen concentration of the measurement target gas, or based on the hydrogen partial pressure of the reference gas and the hydrogen partial pressure of the measurement target gas. Arise. Based on the electromotive force, the hydrogen concentration of the measurement target gas is detected.

As shown in FIG. 2, the fuel cell according to the present invention includes a fuel electrode 16 to which fuel is supplied, an oxidant electrode (also referred to as air electrode) 17 to which an oxidant is supplied, a fuel electrode 16 and an oxidant electrode. 17 and an electrolyte phase 18 sandwiched between them. The fuel electrode 16 and the oxidant electrode 17 can be formed of a material having gas permeability and electronic conductivity. The electrolyte phase 18 is formed of any of the proton conductive materials described above having high proton conductivity at room temperature. As the fuel, natural gas, hydrogen-rich hydrogen gas such as methanol, hydrogen-containing gas, or the like can be used. As the oxidizing agent, oxygen gas, oxygen-containing gas (generally air) or the like can be used. When the fuel is supplied to the fuel electrode 16 and the oxidant is supplied to the oxidant electrode 17, a fuel oxidation reaction occurs in the fuel electrode 16 to generate protons (H ⁺ ) and electrons e ⁻ . Protons (H ⁺ ) pass through the electrolyte phase 18 and reach the oxidant electrode 17. At the oxidant electrode 17, protons (H ⁺ ) react with the oxidant (generally air) and are reduced to produce water (H ₂ O). In this way, power generation is performed. The catalyst can be provided on the oxidant electrode 17 and the fuel electrode 16. The catalyst can be provided at the interface between the oxidant electrode 17 and the electrolyte phase 18 and at the interface between the fuel electrode 16 and the electrolyte phase 18.

  Examples of the present invention will be specifically described.

For Example 1, as a starting material, a mixture of gypsum hemihydrate (CaSO ₄ .1 / 2H ₂ O) powder and water in a weight ratio of 50:50 (= 1: 1) was used. Formed. The mixture was used to form a disk-shaped molded body (diameter 15 mm × thickness 1 mm). The molded body was a cured body cured by natural drying to form an oxide material as a test piece.

For Example 2, gypsum hemihydrate (CaSO ₄ · 1 / 2H ₂ O) was used as a starting material, gypsum hemihydrate (CaSO ₄ · 1 / 2H ₂ O), water and phosphoric acid (H ₃ PO). ₄ ) and water were mixed at a weight ratio of 50:40:10 to form a mixture. The mixture was used to form a disk-shaped molded body (diameter 15 mm × thickness 1 mm). The molded body was cured by natural drying to form a cured body, and an oxide material as a test piece was formed.

About Example 3, the oxide material as a test piece was formed similarly to Example 2. However, as a starting material, a mixture in which gypsum hemihydrate (CaSO ₄ .1 / 2H ₂ O), water and phosphoric acid (H ₃ PO ₄ ) are mixed at a weight ratio of 50:33:17 is used. Formed.

For Example 4, a disk-shaped molded body (diameter 15 mm × thickness 1 mm) based on gypsum hydrate was formed. A molded body based on gypsum hydrate was formed as follows. That is, as a starting material, a mixture in which gypsum hemihydrate (CaSO ₄ .1 / 2H ₂ O) and water were mixed at a weight ratio of 50:50 (ratio of 1: 1) was formed. Using the mixture, a disk-shaped molded body (diameter 15 mm × thickness 1 mm) was formed. The molded body was cured by natural drying to obtain a cured body. This cured body was immersed in a phosphoric acid solution (100 ° C. × 10 minutes), and phosphoric acid was impregnated inside the cured body. Thereafter, the molded body was taken out from the phosphoric acid solution. The concentration of the phosphoric acid solution is 85% or more by weight . Thereafter, the cured product was washed with a large amount of water and dried at room temperature. As a result, mobile hydrogen ions are introduced into the cured body based on gypsum hydrate, and proton conductivity is exhibited.

About Example 5, the oxide material as a test piece was formed similarly to Example 2. However, as a starting material, a mixture was formed by mixing zinc oxide (ZnO), water, and phosphoric acid (H ₃ PO ₄ ) in a weight ratio of 50:17:33.

About Example 6, the oxide material as a test piece was formed similarly to Example 2. However, as starting materials, gypsum hemihydrate (CaSO ₄ .1 / 2H ₂ O), water and calcium phosphate hydrate (Ca (H ₂ PO ₄ ) ₂ .H ₂ O) in a weight ratio of 45:50: A 5% mixed mixture was formed.

For Example 7, calcium sulfate dihydrate (CaSO ₄ .2H ₂ O) was dried at 50 ° C. or higher for 2 days as a starting material, and a dried powder material was used. The dried powder material and water were mixed at a weight ratio of 1: 1 to form a mixture. A disk-shaped molded body (diameter 15 mm × thickness 1 mm) was formed from the mixture. The molded body was naturally dried to obtain a cured body, and an oxide material as a test piece was formed. When calcium sulfate dihydrate (CaSO ₄ .2H ₂ O) and water were mixed at a weight ratio of 1: 1, the mixture was not sufficiently cured and a good molded product could not be obtained.

Table 1 shows the blending ratio (% by weight) of the starting materials for Examples 1 to 7. Table 2 shows the component ratio of the proton conductive material, the possibility of molding the molded body, and the proton conductivity (S / cm) at 25 ° C. The weight percentages of CaO, SO ₃ , P ₂ O ₅ , ZnO, and H ₂ O shown in Table 2 mean calculated values obtained from the blending of starting materials. H ₂ O may be in the form of being contained as water, in the form of being contained as crystal water, etc. The weight% of H ₂ O shown in Table 2 is the amount of water obtained by calculation from the blending of starting materials. means.

As shown in Table 1, Examples 1 to 7 were good with respect to proton conductivity at 25 ° C. Specifically, Example 1 shows 4 × 10 ⁻⁵ (S / cm), Example 2 shows 5 × 10 ⁻³ (S / cm), and Example 3 shows 1 × 10 ⁻² (S / cm). Example 4 shows 3 × 10 ⁻² (S / cm), Example 6 shows 4 × 10 ⁻⁶ (S / cm), and Example 7 shows 5 × 10 ⁻⁵ (S / cm). S / cm).

As shown in Table 2, for Examples 1 and 7, the elements of calcium (Ca), sulfur (S), and hydrogen (H) are 10% by weight or more and 45% by weight or less as CaO, and as SO _3. It is set in the range of 15 wt% to 60 wt% and H ₂ O in the range of 5 wt% to 55 wt%.

For Examples 2 to 6, the element of calcium (Ca) and sulfur (S) and hydrogen (H) and phosphorus (P), 10 wt% to 30 wt% as CaO, SO ₃ as 15 wt% It is set within the range of 50 wt% or less, P ₂ O ₅ of 0.1 wt% or more and 50 wt% or less, and H ₂ O of 10 wt% or more and 55 wt% or less.

Table 3 shows the formulation (wt%) of the starting materials for Examples 8-11. As shown in Table 3, according to Example 8, as a starting material, hemihydrate gypsum (CaSO ₄ .1 / 2H ₂ O) 41.7%, ammonium sulfate ((NH ₄ ) ₂ SO ₄ ) by weight ratio. 8.3%, phosphoric acid (H ₃ PO ₄ ) 10% and water (H ₂ O) 40% were mixed to form a mixture. The mixture was formed into a disk-shaped molded body (diameter 15 mm × thickness 1 mm). The molded body was cured by natural drying to obtain a cured body, thereby forming an oxide material as a test piece.

According to Example 9, as a starting material, hemihydrate gypsum (CaSO ₄ · 1 / 2H ₂ O) 41.7% by weight ratio, aluminum sulfate hydrate (Al ₂ (SO ₄ ) ₃ · 16 to 18H ₂ O) 8.3%, phosphoric acid (H ₃ PO ₄ ) 10% and water 40% were mixed to form a mixture. The mixture was formed into a molded body (diameter 15 mm × thickness 1 mm). The molded body was cured by natural drying to obtain a cured body, and an oxide material as a test piece was formed.

According to Example 10, as starting materials, by weight, hemihydrate gypsum (CaSO ₄ · 1 / 2H ₂ O) 45%, barium sulfate (BaSO ₄ ) 5%, phosphoric acid (H ₃ PO ₄ ) 10% And 40% water to form a mixture. The mixture was formed into a disk-shaped molded body (diameter 15 mm × thickness 1 mm). The molded body was cured by natural drying to obtain a cured body, and an oxide material as a test piece was formed.

According to Example 11, as starting materials, by weight ratio, hemihydrate gypsum (CaSO ₄ · 1 / 2H ₂ O) 45%, zinc sulfate hydrate (ZnSO ₄ · 7H ₂ O) 5%, phosphoric acid ( H ₃ PO ₄ ) 10% and water 40% were mixed to form a mixture. The mixture was formed into a disk-shaped molded body (diameter 15 mm × thickness 1 mm). The molded body was cured by natural drying to obtain a cured body, and an oxide material as a test piece was formed.

Table 4 shows the results of proton conductivity at 25 ° C. for the test pieces (proton conductive materials) according to Examples 8 to 11 indicating whether or not the molded body can be molded. The weight percentages of CaO, SO ₃ , P ₂ O ₅ , NO ₂ , Al ₂ O ₃ , BaO, ZnO, and H ₂ O shown in Table 4 mean calculated values obtained from the blending of starting materials. As described above, H ₂ O may be in the form of being contained as water, the form of being contained as crystal water, etc. The weight% of H ₂ O shown in Table 4 was calculated from the blending of starting materials. Means the amount of water.

In Examples 8 to 11, the molding was good and the proton conductivity was good. Specifically, a 7 × 10 ^-4 S / cm for Example 8, a 1 × 10 ^-3 S / cm for Example 9, Example 10 1 × 10 ^-3 S / cm It was 4 × 10 ⁻⁴ S / cm for Example 11.

FIG. 3 shows the relationship between measurement temperature and proton conductivity. The lower side of the horizontal axis in FIG. 3 indicates 1000 / T, and the upper side of the horizontal axis in FIG. 3 indicates absolute temperature (K) and Celsius temperature (° C.). The vertical axis in FIG. 3 represents log σ (S / cm). “−2” on the vertical axis indicates 1 × 10 ⁻² . In FIG. 3, □ indicates Example 1, ○ indicates Example 2, × indicates Example 3, ◇ indicates Example 4, ● indicates Example 6, and Δ indicates Shows Example 7. According to FIG. 3, in the temperature range of 298 K (25 ° C., 1000 / T = 3.4) to 588 K (1000 / T = 1.7), the proton conductivity was good in both Examples 1 to 7. It was. In particular, Example 4, Example 3, and Example 2 were good.

In Example 4, as described above, a cured product obtained by curing a molded product based on gypsum hydrate was used, and the cured product was impregnated with a phosphoric acid solution. Mobile hydrogen ions are introduced into the cured body. Example 3 increased the proportion of phosphoric acid (H ₃ PO ₄ ) when mixing gypsum hemihydrate (CaSO ₄ .1 / 2H ₂ O), water and phosphoric acid (H ₃ PO ₄ ). Is. Thus, it can be seen that the use of phosphoric acid is effective for increasing proton conductivity.

FIG. 4 schematically shows the measurement concept of proton conductivity. In this case, a disk-shaped test piece 10 (diameter 15 mm) made of a proton conductive material was produced. The thickness of the test piece 10 is t. The test piece 10 was sandwiched between 15 mm square platinum plates 12. A platinum wire was passed from the platinum plate 12 and connected to a resistance measurement device (Hewlett-Packard, Impedance Analyzer 4192A). In addition, when measuring at the temperature above room temperature, the whole was covered with the tubular electric furnace, and the test piece 10 was heated. The thermocouple was installed just below the test piece 10. The resistivity at each temperature was measured. The electrode area is 1.77 cm ² . From the thickness t of the test piece 10 (S = 1.5 / 2 × 1.5 / 2 × π = 1.77 cm ² ), the proton conductivity (σ) was determined based on the following equation (1).

σ = (1 / R) × (t / S) (1 formula)
FIG. 5 shows the test results of VI characteristics (room temperature, sample thickness of 1 mm) when applied to a hydrogen concentration cell. The horizontal axis in FIG. 5 indicates the current density. The vertical axis in FIG. 5 indicates the cell voltage and the output density. In FIG. 5, the characteristic line W1 indicates the cell voltage, and the characteristic line W2 indicates the output density.

  FIG. 6 schematically shows the concept of measuring the characteristics of the hydrogen concentration cell described above. The hydrogen gas sensor 20 formed of the hydrogen concentration cell described above has a reference electrode 22 facing the first atmosphere 21 to which a reference gas as a reference substance is supplied, and a second gas to which a measurement object gas is supplied as a measurement object. A measurement electrode 24 facing the atmosphere 23 and an electrolyte phase 25 sandwiched between the reference electrode 22 and the measurement electrode 24 are included. The electrolyte phase 25 is a test piece formed of a proton conductive material.

In this case, a disk-shaped test piece (diameter 15 mm, thickness 1 mm) was produced. A circle with a diameter of 8 mm was written in the center of both sides of the test piece. Further, platinum-supported carbon kneaded with an aqueous polyvinyl alcohol (PVA) solution was applied in a circle. Measurement tubes 27 and 28 made of ceramics (alumina) having a diameter of 15 mm are used, and a platinum mesh (corresponding to the reference electrode 22) is attached to the cross section of the shaft end of the measurement tube 27. (Corresponding to the measurement electrode 24) was attached. Platinum wires 29 and 30 were passed from the reference electrode 22 and the measurement electrode 24 and connected to a measurement device 31 (manufactured by Hokuto Denko, potentiogalvanostat HA-151). The continuity was confirmed and sealed with a silicone sealant to prevent gas leakage. A 10 mol% hydrogen gas (room temperature) was passed through the measuring tube 27 and a 1 mol% hydrogen gas (room temperature) was passed through the measuring tube 28. Both hydrogen gases flowed through water at room temperature. Then, the voltage was measured by the measuring device 31. When the measured value settled, the voltage was recorded. The value of the current taken out was changed and the voltage value at each time was recorded. In this case, the current density was determined from the electrode area (0.5 cm ² ).

  FIG. 7 shows a test result of VI characteristics when applied to a fuel cell. The horizontal axis in FIG. 7 represents current density, the left side of the vertical axis in FIG. 7 represents cell voltage, and the right side of the vertical axis represents output density. In this case, the fuel cell was operated at room temperature. In FIG. 7, a characteristic line X1 indicates a cell voltage, and a characteristic line X2 indicates an output density. As shown by the characteristic line X2 in FIG. 7, an output of about 0.045 mW / cm 2 was obtained.

FIG. 8 shows the concept of measuring the VI characteristics of the fuel cell described above. This fuel cell uses fuel (
A fuel electrode to which pure hydrogen gas) is supplied, an oxidant electrode to which oxidant (air) is supplied, and an electrolyte phase sandwiched between the fuel electrode and the oxidant electrode. The electrolyte phase is formed of a proton conductive material.

  First, a disk-shaped test piece 40 (proton conductive material) having a diameter of 15 mm and a thickness of 1 m is produced. A circle with a diameter of 8 mm is written in the center of both sides of the test piece 40. On one surface of the test piece 40, platinum-supported carbon (corresponding to a fuel electrode) kneaded with an aqueous polyvinyl alcohol (PVA) solution is applied in a circle. Further, on the other surface of the test piece 40, platinum-supported carbon (corresponding to an oxidizer electrode) kneaded with an aqueous polyvinyl alcohol (PVA) solution was applied in a circle. Then, a platinum net 45 is attached to the cross section of the shaft end of the ceramic (alumina) measuring tube 41 having a diameter of 15 mm, and a platinum net 46 is provided to the cross section of the shaft end of the ceramic (alumina) measuring tube having a diameter of 15 mm. Wearing. The platinum nets 45 and 46 function as current collectors. The platinum wires 47 and 48 connected to the platinum nets 45 and 46 were connected to the measuring device 49. The continuity was confirmed and sealed with a silicone sealant to prevent gas leakage between the measuring tubes 41 and 42. Pure hydrogen gas is passed through the measuring tube 41. Air is passed through the measuring tube 42. Hydrogen gas and air were both flowed through room temperature water. Then, the voltage was measured, and when the measured value settled, the voltage was recorded.

(Other)
In addition, the present invention is not limited to the embodiments described above and shown in the drawings, and can be implemented with appropriate modifications as necessary. The present invention can be understood as the following technical idea.

(Additional Item 1) In Claim 1, CaO is contained in an amount of 10% to 45% by weight, SO ₃ is contained in an amount of 15% to 50% by weight, and H ₂ O is contained in an amount of 5% to 55% by weight. Proton conductive material.

In (Note 2) according to claim 1, 10% by weight to 40% by weight as CaO, SO ₃ as 15 weight% to 60 weight%, H ₂ O as a 5 wt% to 55 wt% or less, and P ₂ O _5. A proton conductive material containing ₅ to 0.1% by weight and 50% by weight or less.

In (Note 3) according to claim 1, 15 wt% to 30 wt% as CaO, SO ₃ as 18 wt% to 50 wt% or less, and comprising H ₂ O as a 10 wt% to 55 wt% or less Proton conductive material.

In (Note 4) according to claim 1, 10 wt% to 30 wt% as CaO, a SO ₃ 15 wt% to 50 wt% or less, 10 wt% or more 55 wt% or less H ₂ O, and P ₂ O _5. A proton conductive material containing ₅ to 0.1% by weight and 50% by weight or less.

  The present invention can be used for a proton conductive material exhibiting good proton conductivity at room temperature. Furthermore, it can be used for a hydrogen concentration cell, a hydrogen sensor, a fuel cell, and the like on which a proton conductive material is mounted. For example, it can be used at room temperature to around 300 ° C.

It is a conceptual diagram which shows a hydrogen sensor typically. It is a conceptual diagram which shows a fuel cell typically. It is a graph which shows the relationship between temperature and proton conductivity. It is a conceptual diagram which shows the form which measures proton conductivity. It is a graph which shows the relationship between the current density and cell voltage in a hydrogen concentration battery. It is a conceptual diagram when using as a hydrogen concentration battery. It is a graph which shows the relationship between the current density and cell voltage in a fuel cell. It is a conceptual diagram when using as an oxyhydrogen fuel cell.

Explanation of symbols

  In the figure, 10 is a reference electrode, 11 is a measurement electrode, 12 is an electrolyte phase, 16 is a fuel electrode, 17 is an oxidant electrode, 18 is an electrolyte phase, and 20 is a hydrogen gas sensor.

Claims (19)

A proton conductive material comprising elements of calcium (Ca), sulfur (S) and hydrogen (H), respectively, and a proton conductivity at room temperature of 10 ⁻⁶ S / cm or more.   The proton conductive material according to claim 1, wherein the base material is a sulfate. 3. The element of claim 1 or 2, wherein calcium (Ca), sulfur (S) and hydrogen (H) are expressed in terms of oxides, respectively, as CaO, 10 wt% or more and 45 wt% or less, and SO ₃ as 15 wt%. % To 60% by weight, and H ₂ O containing 5% by weight to 55% by weight. In Claim 1 or Claim 2, the elements of calcium (Ca), sulfur (S), hydrogen (H), and phosphorus (P) are expressed in terms of their respective oxides, and CaO is 10 wt% or more and 45 wt% or less, Proton conductive material comprising 15 to 60% by weight as SO ₃ , 5 to 55% by weight as H ₂ O, and 0.1 to 50% by weight as P ₂ O ₅ .   The proton conductive material according to any one of claims 1 to 4, comprising 40 wt% or more of calcium sulfate. 5. The proton conductive material according to claim 1, comprising 40 wt% or more of calcium sulfate dihydrate (CaSO ₄ .2H ₂ O). A proton conductive material, characterized in that it is formed of a hardened body obtained by hardening a raw material containing calcium sulfate (CaSO ₄ ) as a main component with water. A proton conductive material formed by reacting a raw material containing 40% by weight or more of calcium sulfate (CaSO ₄ ) with phosphoric acid.   A proton conductive material formed by mixing and curing calcium sulfate hemihydrate and an aqueous solution.   A proton conductive material formed by mixing and curing calcium sulfate hemihydrate and an acid solution.   A proton conductive material formed by mixing and curing calcium sulfate hemihydrate and an aqueous solution containing phosphoric acid and / or phosphate.   A proton conductive material formed by introducing mobile hydrogen ions into a cured body based on gypsum hydrate.   A proton conductive material formed by impregnating a hardened body based on gypsum hydrate with an aqueous solution containing phosphoric acid and / or phosphate. Forming a mixture of calcium sulfate hemihydrate and an aqueous solution;
Curing the mixture, and a method for producing a proton conductive material.   A method for producing a proton conductive material, comprising: forming a mixture of calcium sulfate hemihydrate and an aqueous solution containing phosphoric acid and / or phosphate; and curing the mixture.   A method for producing a proton conductive material, comprising: obtaining a cured body based on gypsum hydrate; and introducing movable hydrogen ions into the cured body based on gypsum hydrate. . In a hydrogen concentration cell composed of a reference electrode facing a reference material, a measurement electrode facing a measurement object, and an electrolyte phase sandwiched between the reference electrode and the measurement electrode,
The said electrolyte phase is formed with the proton conductive material which concerns on any one of Claims 1-16, The hydrogen concentration battery characterized by the above-mentioned. In a hydrogen sensor formed by a hydrogen concentration cell composed of a reference electrode facing a reference material, a measurement electrode facing a measurement object, and an electrolyte phase sandwiched between the reference electrode and the measurement electrode,
The hydrogen sensor, wherein the electrolyte phase is formed of a proton conductive material according to any one of claims 1 to 16. In a fuel cell comprising a fuel electrode to which fuel is supplied, an oxidant electrode to which an oxidant is supplied, and an electrolyte phase sandwiched between the fuel electrode and the oxidant electrode,
The fuel cell, wherein the electrolyte phase is formed of a proton conductive material according to any one of claims 1 to 16.

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