JP6747778B2 - Cell for steam electrolysis - Google Patents

Description

The present invention relates to a steam electrolysis cell which has high current efficiency and can efficiently produce hydrogen gas from steam.

In recent years, a technology for preventing resource depletion and global warming has been demanded. Particularly in the electric power field, the development of renewable energy that suppresses the emission of carbon dioxide, which is one of the greenhouse gases, and does not rely on fossil resources is progressing. Renewable energy is energy obtained from renewable energy sources such as sunlight, solar heat, hydraulic power, wind power, geothermal heat, and biomass that are constantly or repeatedly supplemented from nature, for example, producing hydrogen from biomass, Electric power obtained by generating electricity from hydrogen and air using a fuel cell can be mentioned.

Recently, steam electrolysis has been widely studied as a promising technology for producing hydrogen. Steam electrolysis uses gaseous steam instead of liquid water when electrolyzing H ₂ O to obtain hydrogen and oxygen. Since it can be operated at high temperatures, the voltage required for electrolysis is small. It is characterized by high energy efficiency.

Conventionally, in steam electrolysis, oxygen ion conductive electrolytes have been used exclusively. For example, Patent Document 1 discloses a steam electrolysis technique using yttria-stabilized zirconia having oxygen ion conductivity as a solid electrolyte.

However, when steam electrolysis is performed using an oxygen ion conductive solid electrolyte, the electrode reactions occurring at the anode and the cathode are as follows.

_{^{Anode: 2O 2- → O 2 + 4e}} -
Cathode: 2H ₂ O + 4e ⁻ → 2H ₂ + 2O ^{2 −}
As shown in the above formula, in this case, there is a problem that hydrogen is generated on the cathode side and a separate step for separating coexisting water vapor is required.

As a technique capable of solving such a problem, for example, as disclosed in Patent Document 2, a technique of performing steam electrolysis using a proton conductive electrolyte has been developed. The electrode reactions occurring at the anode and cathode in the art are as follows.

Anode: 2H ₂ O → O ₂ + 4H ⁺ + 4e ^{−
Cathode: 4H + + 4e - → 2H} 2
According to the above formula, in this case, hydrogen is generated on the cathode side as in the case of using the oxygen ion conductive electrolyte, but since steam is supplied to the anode side, it is not necessary to separate hydrogen from steam. There is an advantage that.

In the steam electrolysis cell described in Patent Document 2, a perovskite type oxide containing a transition metal at the B site is used as an anode material, and Co is mentioned as the transition metal. Further, Patent Document 3 discloses a perovskite type oxide containing Ba and Co as an oxidizing electrode material.

JP, 2005-150122, A JP, 2009-209441, A JP 2001-250563 A

As described above, Patent Document 2 discloses a steam electrolysis cell containing a proton conductive solid electrolyte. However, the cell for steam electrolysis described in Patent Document 2 has a problem that although the cell terminal voltage is low, the current efficiency and the H ₂ generation rate are also low.

Further, Patent Document 3 describes that a perovskite type oxide containing Ba and Co is used as a solid electrolyte or an oxidation electrode. However, such a solid electrolyte or an oxidizing electrode is applied to a fuel cell or a gas sensor, and Patent Document 3 does not describe that it is applied to a steam electrolysis cell.

Therefore, an object of the present invention is to provide a cell for steam electrolysis that can obtain high current efficiency and efficiently produce H ₂ .

The present inventors have conducted extensive studies to solve the above problems. As a result, it was found that high current efficiency can be obtained and H ₂ can be efficiently produced by using a perovskite type oxide containing Ba and Co as a constituent component of the anode layer of the cell for steam electrolysis. Completed the invention.

The present invention will be described below.

[1] An anode layer and a cathode layer are provided, and a proton conductive solid electrolyte layer is provided between the anode layer and the cathode layer,
A cell for steam electrolysis, wherein the anode layer contains a perovskite type oxide containing Ba and Co.

[2] The cell for steam electrolysis according to the above [1], wherein the A site of the perovskite-type oxide contains Ba in a molar ratio of 30% or more, and the B site contains at least Co.

[3] Further, a part of the A site of the perovskite oxide is substituted with one or more elements selected from Sr, La, Ce, Pr, Nd, Sm, Eu, Gd and Yb [1]. Alternatively, the cell for steam electrolysis according to [2].

[4] The steam electrolysis cell according to any one of the above [1] to [3], wherein the anode layer is formed by firing at a temperature of 900° C. or lower.

[5] A perovskite type in which the proton conductive solid electrolyte layer contains an alkaline earth metal at the A site and a trivalent or tetravalent transition metal belonging to Groups 4 to 14 of the periodic table at the B site. The cell for steam electrolysis according to any one of the above [1] to [4], which contains a metal oxide.

[6] The cathode layer contains at least one metal element selected from nickel, cobalt, and iron, an alkaline earth metal at the A site, and a B site belonging to Groups 4 to 14 of the periodic table. The steam electrolysis cell according to any one of the above [1] to [5], which contains a perovskite-type metal oxide containing a trivalent or tetravalent transition metal.

In the steam electrolysis cell according to the present invention, the voltage required to obtain a predetermined current is almost the same as that of the conventional steam electrolysis cell. Nevertheless, the H ₂ generation rate per electrode area at a current density of more than 0.1 A/cm ² is higher than that of the conventional steam electrolysis cell. Therefore, the cell for steam electrolysis according to the present invention is industrially very excellent in that H ₂ can be efficiently produced with lower energy.

Hereinafter, first, a method for manufacturing a cell for steam electrolysis according to the present invention will be described.

1. Proton Conductive Solid Electrolyte Layer There are mainly electrolyte-supported cells and electrode-supported cells as cells for steam electrolysis. In the case of the electrolyte-supported cell, the firing temperature of the electrolyte layer is generally the highest among the electrolyte layer, the anode layer, and the cathode layer, so that the electrolyte layer is first prepared. In the case of the electrode-supported cell, the electrolyte layer is formed on the electrode layer which will be the support layer.

Examples of the material of the proton conductive solid electrolyte that can be used in the present invention include a metal oxide exhibiting proton conductivity, and such a proton conductive metal oxide has, for example, an ABO ₃ type structure. Perovskite type oxides, pyrochlore type oxides having an A ₂ B ₂ O ₇ type structure, ceria-rare earth oxide solid solutions or ceria-alkaline earth metal oxide solid solutions, metal oxides having a brown millerite type structure, etc. Can be mentioned.

As the material of the proton conductive solid electrolyte, a perovskite type metal oxide having an ABO ₃ type structure is preferably used since the anode layer contains a perovskite type oxide as a main component. The perovskite-type metal oxide is preferably a perovskite-type metal whose A site contains an alkaline earth metal and whose B site contains a trivalent or tetravalent element belonging to Groups 4 to 14 of the periodic table. An oxide can be mentioned, and the element contained in the B site can more preferably be Zr, Ce, Ti or Sc. Furthermore, at least a part of at least one of A site and B site is La, Ce, Pr, Nd, Sm, Gd, Eu, Yb, Sc, Y, In, Ga, Fe, Co, Ni, Zn, Ta, Nb. It is preferable to use a perovskite-type metal oxide substituted with one or more elements selected from the above. Among them, at least part of at least one of A site and B site is La, Ce, Pr, Nd, Sm, Gd, Eu, It is preferable to use a perovskite-type metal oxide substituted with one or more elements selected from Yb, Sc, Y, In, and Ga. Specifically, Sr-Zr-Y system, Sr-Zr-Ce-Y system, Ca-Zr-In system, La-Sc system, Sr-Ce-Yb system, La-Sr-Ti-Nb system perovskite. Type metal oxides and the like.

The thickness of the proton conductive solid electrolyte layer is not particularly limited and may be appropriately set according to the cell shape and the like. For example, in the case of an electrolyte-supported cell, the thickness is preferably 50 μm or more and 500 μm or less. When the thickness is less than 50 μm, proton conductivity can be ensured, but cell strength may not be sufficiently secured. On the other hand, if the thickness exceeds 500 μm, the proton conductivity may be impaired. That is, when the thickness is 50 μm or more and 500 μm or less, both cell strength and proton conductivity can be more reliably ensured. In the case of an electrode-supported cell, the thickness is preferably 1 μm or more and 50 μm or less. When the thickness is 1 μm or more, the proton conductive solid electrolyte layer can be more easily formed by an industrial process such as screen printing. On the other hand, when the thickness is 50 μm or less, the proton conductivity is more surely secured as compared with the electrode-supported cell. In the present invention, the electrode-supported cell is more preferable.

Examples of the method for producing the proton conductive solid electrolyte layer include the following methods. An organic solvent such as ethanol or terpineol, a dispersant, a plasticizer, a binder such as ethyl cellulose, etc. are added to the proton conductive metal oxide, and the mixture is wet pulverized and mixed in a ball mill or the like to form a slurry, which is then green by the doctor blade method or the like. Use as a sheet. Then, by firing, a proton conductive solid electrolyte layer can be obtained. In the case of an electrode-supported cell, the above-mentioned slurry is applied onto the electrode layer serving as a support layer and then baked to form a proton conductive solid electrolyte layer on the support electrode layer.

2. Formation of Anode Layer When the cell for steam electrolysis of the present invention is an electrolyte-supported cell, it is baked after applying the anode layer paste and the cathode layer paste to the proton conductive solid electrolyte layer. The anode layer and the cathode layer may be formed by applying each paste to the proton conductive solid electrolyte layer and then firing the paste at the same time. However, since the firing temperatures of the anode layer and the cathode layer are not always the same, it is generally preferable to first form the electrode layer having a higher firing temperature and then form the other electrode layer.

When the cell for steam electrolysis of the present invention is an electrode-supported cell, an electrolyte layer is formed on the electrode layer serving as a support layer, and the other electrode layer is further formed on the electrolyte layer. In this case, generally, since the baking temperature of the cathode layer is higher than that of the anode layer, the cathode layer or its precursor is used as a supporting layer, an electrolyte layer is formed thereon, and further, the electrolyte layer is formed on the electrolyte layer. Form the anode layer.

The anode layer of the cell for steam electrolysis according to the present invention is required to exhibit a catalytic action for promoting the reaction of 2H ₂ O → O ₂ + 4H ⁺ + 4e ⁻ and have electron conductivity. As such a material, a perovskite-type metal oxide containing a transition metal element which is a catalyst component for promoting the above reaction can be used, but in the present invention, a perovskite-type oxide containing Ba and Co is used as a main component. To use. The cell for steam electrolysis of the present invention using such a perovskite type oxide as the material for the anode layer provides high current efficiency and enables efficient production of H ₂ .

As described above, the main component of the anode layer of the steam electrolysis cell according to the present invention is the perovskite type oxide containing Ba and Co. In the present invention, “the perovskite type oxide is the main component of the anode layer” means that the components of the anode layer are excluded from the raw materials of the components except the components such as binder and solvent that are lost by firing during formation of the anode layer. The ratio of the perovskite oxide is 60 v/v% or more. The ratio is preferably 65 v/v% or more, more preferably 70 v/v% or more, still more preferably 75 v/v% or more. On the other hand, the upper limit of the ratio is not particularly limited, and substantially 100 v/v% excluding inevitable impurities and inevitable residues may be the perovskite type oxide, but as described below, other components may be included. Since it may be contained, the ratio is preferably 95 v/v% or less, more preferably 90 v/v% or less, and further preferably 85 v/v% or less.

Ba is a kind of alkaline earth metal, and in a perovskite type oxide, it is usually located at the A site and Co is located at the B site.

The proportion of Ba in the metal element located at the A site of the perovskite type oxide is preferably 30% or more in terms of molar ratio. When the molar ratio is 30% or more, the action effect of Ba together with Co is sufficiently exerted, high current efficiency can be obtained, and H ₂ can be efficiently produced by the cell for steam electrolysis according to the present invention. It will be possible more reliably. The molar ratio is more preferably 35% or more, further preferably 40% or more, particularly preferably 45% or more. On the other hand, the upper limit of the molar ratio may be 100%, more preferably 90% or less, further preferably 80% or less, particularly preferably 70% or less. Examples of the element that may be substituted for a part of the A site of the perovskite type oxide include one or more elements selected from Sr, La, Ce, Pr, Nd, Sm, Eu, Gd, and Yb. It is possible, and one or more elements selected from Sr, La, Sm, and Gd are more preferable.

The proportion of Co in the metal element located at the B site of the perovskite type oxide is not particularly limited and may be appropriately adjusted, but for example, the molar ratio is preferably 50% or more. When the molar ratio is 50% or more, the action effect of Co together with Ba is sufficiently exerted, and the cell for steam electrolysis according to the present invention can obtain high current efficiency and efficiently produce H _2. It will be possible more reliably. The molar ratio is more preferably 60% or more, 70% or more or 80% or more, and particularly preferably 90% or more or 95% or more. On the other hand, the upper limit of the molar ratio is preferably 100%. Examples of the element that may be substituted for a part of the B site of the perovskite type oxide include at least one of Ni and Fe.

Examples of the components other than the above-mentioned constituents of the anode layer include the same constituents as those of the proton conductive electrolyte material and the electronic conductive material.

In the anode layer of the cell for steam electrolysis according to the present invention, it is preferable to add an electron conductive component in addition to the perovskite type oxide. As the electronically conductive component, a metal such as silver, nickel, cobalt, iron, platinum, palladium, ruthenium or the like; an electronically conductive metal such as silver oxide, nickel oxide, cobalt oxide, iron oxide in a reducing atmosphere or an air atmosphere Metal oxides that change; or complex metal oxides such as nickel ferrite and cobalt ferrite containing two or more of these oxides. These may be used alone, or may be used in combination of two or more kinds as required. Among these, silver, metallic nickel, metallic cobalt, metallic iron or oxides thereof are preferable.

The amount of the electron conductive component used is not particularly limited and may be appropriately adjusted. For example, it is preferable that the mass ratio to the entire electrode is 2.0% by mass or more and 25% by mass or less. If the said ratio is 2.0 mass% or more, electronic conductivity will be exhibited more reliably. On the other hand, if the proportion is too large, the porosity of the electrode may be excessively reduced, so that the proportion is preferably 25% by mass or less.

The thickness of the anode layer is not particularly limited and may be appropriately determined depending on the cell shape and the like. For example, in both the electrolyte-supported cell and the electrode-supported cell, the range is preferably 5 μm or more and 100 μm or less.

The anode layer can be formed by a conventional method. For example, as in the case of the proton conductive solid electrolyte layer, a paste of the above-mentioned constituents may be prepared, coated on the proton conductive solid electrolyte layer so as to obtain a desired film thickness, and then baked. In the case of an electrode-supported cell having the electrode layer as a support layer, after forming the electrode layer also serving as a support, a proton conductive solid electrolyte layer is formed thereon, and further the electrolyte layer The other electrode layer may be formed thereover. Alternatively, a porous support layer may be formed under the electrode layer (on the side opposite to the electrolyte layer).

The firing temperature for forming the anode layer is preferably 900° C. or lower, more preferably 850° C. or lower, from the viewpoint of current efficiency.

3. Formation of Cathode Layer The cathode layer of the cell according to the present invention is required to have a catalytic action for promoting the reaction of 4H ⁺ + 4e ⁻ → 2H ₂ and have electron conductivity. Examples of such a material include a metal element such as Pt, Pd, Ni, Co, Fe, and Ru, and a mixture of the metal element and a perovskite-type oxide that is a material of the proton conductive solid electrolyte layer. A mixture of a metal element and a perovskite type oxide is preferable from the viewpoints of affinity and adhesion to the proton conductive solid electrolyte layer.

Examples of the material of the metal element include metals such as Pt, Pd, Ni, Co, Fe, and Ru; metal oxides such as nickel oxide, cobalt oxide, and iron oxide that change into electron conductive metals in a reducing atmosphere; or these. The mixed metal oxides such as nickel ferrite and cobalt ferrite containing two or more kinds of oxides of These may be used alone, or may be used in combination of two or more kinds as required. Among these, nickel, cobalt, and iron are preferable as the metal element.

As the proton conductive metal oxide, a perovskite-type metal whose A site contains an alkaline earth metal and whose B site is composed of a trivalent or tetravalent element belonging to Groups 4 to 14 of the periodic table An oxide can be mentioned, and the element contained in the B site can more preferably be Zr, Ce, Ti or Sc. Furthermore, at least part of at least one of the A site and the B site is La, Ce, Pr, Nd, Sm, Gd, Eu, Yb, Sc, Y, In, Ga, Fe, Co, Ni, Zn, Ta, Nb. It is preferable to use a perovskite-type metal oxide substituted with one or more elements selected from the group consisting of La, Ce, Pr, Nd, Sm, Gd, Eu, at least a part of at least one of the A site and the B site. It is preferable to use a perovskite-type metal oxide substituted with one or more elements selected from Yb, Sc, Y, In, and Ga. Specifically, Sr-Zr-Y system, Sr-Zr-Ce-Y system, Ca-Zr-In system, La-Sc system, Sr-Ce-Yb system, La-Sr-Ti-Nb system perovskite. Type metal oxides and the like.

When a mixture of a metal element material and a perovskite type oxide is used as the cathode material, the ratio thereof is not particularly limited, and may be appropriately adjusted in consideration of the electron conductivity and the catalytic ability of the material used specifically. However, for example, the ratio of the perovskite oxide to the total of the metal element material and the perovskite oxide can be 20 v/v% or more and 80 v/v% or less. The ratio is more preferably 25 v/v% or more and 70 v/v% or less.

The thickness of the cathode layer is not particularly limited and may be appropriately determined depending on the cell shape and the like. For example, in the case of an electrolyte-supported cell, it is preferably 5 μm or more and 100 μm or less. In the case of an electrode-supported cell having the electrode layer as a support layer, the thickness is preferably 100 μm or more and 2000 μm or less. The reason for defining the lower limit and the upper limit is the same as in the case of the electrolyte-supported cell.

The cathode layer can be formed by a conventional method. For example, as in the case of the proton conductive solid electrolyte layer, a paste of the above-mentioned constituents may be prepared, coated on the proton conductive solid electrolyte layer so as to obtain a desired film thickness, and then baked. In the case of an electrode-supported cell having the electrode layer as a support layer, after forming the electrode layer also serving as a support, a proton conductive solid electrolyte layer is formed thereon, and further the electrolyte layer The other electrode layer may be formed thereover. Alternatively, a porous support layer may be formed under the electrode layer (on the side opposite to the electrolyte layer). In addition, when a metal oxide is used as the metal element material, the metal oxide is reduced to a metal element by positively performing the reduction treatment, and the volume is reduced by that amount to make the cathode layer porous. You can A cell for steam electrolysis having such a porous cathode layer has an even higher H ₂ production capacity.

H ₂ can be efficiently produced by using the cell for steam electrolysis according to the present invention and supplying steam to the anode while applying a voltage between the electrodes and flowing a current.

The steam electrolysis cell according to the present invention has a higher current efficiency, which is the production efficiency of H ₂ with respect to the applied current, than the conventional cell, but such a difference is more remarkable as the current density is higher.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples, and appropriate changes may be made within a range that can conform to the gist of the preceding and the following. Of course, it is possible to carry out, and all of them are included in the technical scope of the present invention.

Example 1
(1) Preparation of Cathode Support Commercially available nickel oxide powder (manufactured by Shodo Kagaku Co., Ltd., product name “Green”) and SrZr _0.5 Ce _0.4 Y _0.1 O _{3 −δ} particles as electrolyte particles were added to the nickel oxide powder 50 vol%. Then, the electrolyte particles were weighed so as to be 50 vol %, and stirred and mixed in an organic solvent in a mortar to obtain a mixture. This mixture was uniaxially molded and isotropically hydrostatically pressed by a pressing machine to form a disc. This disk-shaped compact was fired at 1250° C. for 10 hours to prepare an electrode support having a diameter of 25φ and a thickness of 0.5 mm.

(2) Preparation of Proton Conductive Electrolyte Layer SrZr _0.5 Ce _0.4 Y _0.1 O _3-δ , ethyl cellulose and α-terpineol were mixed in a mortar. Then, the mixture was kneaded using a three-roll mill (manufactured by EXAKT Technologies, model “M-80S”) to obtain an electrolyte layer paste.

The paste was applied to the above electrode support by a screen printing method, dried, and then baked at 1400° C. in an air atmosphere for 2 hours to form a proton conductive electrolyte layer having a thickness of 20 μm.

(3) Preparation of La _0.5 Ba _0.5 CoO _3-δ Anode Layer Commercially available powders of La ₂ O ₃ , BaCO ₃ and Co ₃ O _{4 having} a purity of 99.9% by mass were mixed with La _0.5 Ba _0.5 CoO _3-δ . Mixed so that Ethanol was added to the obtained mixture, the mixture was wet-milled for 60 hours with a ball mill, and then dried at 120° C. for 10 hours. Then, it was fired at 1100° C. for 10 hours to obtain a fired powder. Further, ethanol was added to the obtained calcined powder, the mixture was wet pulverized with a ball mill for 100 hours, and then dried at 120° C. for 10 hours to obtain an electrode catalyst powder which can be used as an anode layer material for steam electrolysis. The composition of the obtained electrode catalyst powder was La _0.5 Ba _0.5 CoO _3-δ , and it was confirmed by X-ray diffraction that it was a single phase composed of perovskite.

The electrode catalyst powder and AgO powder (manufactured by Wako Pure Chemical Industries, Ltd.) were mixed so that the volume ratio of the electrode catalyst powder and AgO was 8:2, and further ethyl cellulose as a binder and α-terpineol as a solvent. In addition, mixed in a mortar. Then, the mixture was kneaded using a three-roll mill (manufactured by EXAKT Technologies, model “M-80S”) to obtain an anode paste.

The anode paste was applied to the opposite side of the supporting electrode layer of the proton conductive electrolyte by a screen printing method, and then baked at 850° C. in an air atmosphere for 1 hour to form an anode layer having a thickness of 30 μm. ..

Comparative Example 1
In Example 1, using commercially available powders of Sm ₂ O ₃ , SrCO ₃ and Co ₃ O _{4 having} a purity of 99.9% by mass, La _0.5 Ba _0.5 CoO _3-δ was converted into Sm _0.5 Sr _0.5 CoO _3-δ . A cell was prepared in the same manner except that the anode layer was formed instead.

Example 2
A cell was prepared in the same manner as in Example 1 except that the firing temperature of the anode layer was changed to 800°C.

Example 3
A cell was prepared in the same manner as in Example 1 except that the firing temperature of the anode layer was changed to 900°C.

Example 4
A cell was prepared in the same manner as in Example 1 except that the proportion of the perovskite oxide in the cathode layer was changed to 28 vol% and the proportion of the nickel oxide powder was changed to 72 vol %.

Example 5
A cell was prepared in the same manner as in Example 4, except that the anode layer was formed by replacing La _0.5 Ba _0.5 CoO _3-δ with La _0.6 Ba _0.4 CoO _3-δ .

Example 6
A cell was prepared in the same manner as in Example 4 except that the anode layer was formed by replacing La _0.5 Ba _0.5 CoO _3-δ with La _0.4 Ba _0.6 CoO _3-δ .

Example 7
A cell was prepared in the same manner as in Example 4 except that La _0.5 Ba _0.5 CoO _{3 -δ} was replaced with La _0.5 Ba _0.5 Co _0.9 Fe _0.1 O _3-δ to form an anode layer.

Test example 1
A glass ring was sandwiched between the cells produced in Examples 1 to 7 and Comparative Example 1 so as not to come into contact with the anode layer, and the cells were softened at 800° C. to perform gas sealing. Then, after the temperature was lowered to 600 ° C. is a working temperature, by introducing N ₂ gas containing 10v / v% H ₂ gas to reduce the NiO of the electrode support in a porous Ni-SrZr the electrode support _{As a 0.5} Ce _0.4 Y _0.1 O _3-δ cathode layer. Argon gas containing 20 v/v% of steam and 1 v/v% of oxygen was introduced into the anode layer side at a flow rate of 100 NmL/min, and argon gas containing 2 v/v% of steam and 1 v/v% hydrogen was introduced into the cathode layer side. It was introduced at a flow rate of 100 NmL/min. The current-voltage curve was obtained by measuring the voltage while changing the current using a potentiogalvanostat.

In addition, the concentration of hydrogen generated in the cathode layer was quantified by gas chromatography, and the flow rate of the cathode outlet gas was measured with a high precision precision membrane flow meter (manufactured by Horiba STEC Co., Ltd.). The H ₂ generation rate was calculated from the obtained measured value by the following formula.

H ₂ generation rate (μmol/h·cm ² )=[{(Qv0×Hc0/100)−(Qv1×Hc1/100)}]×60×10 ⁶ ]/(22400×S)
Qv0: Gas flow rate at cathode outlet when not energized (NmL/min)
Hc0: H ₂ concentration (v/v%) in the cathode outlet gas when not energized
Qv1: Cathode outlet gas flow rate when energized (NmL/min)
Hc1: H ₂ concentration (v/v%) in the cathode outlet gas during energization
S: Anode electrode area (cm ² )

Further, the theoretical H ₂ generation rate was calculated by the following formula.
Theoretical H ₂ generation rate (μmol/h·cm ² )={Electrified current (A)×3600 (s)×10 ⁶ }/{2×F×Current area (cm ² )}
F: Faraday constant

Furthermore, the H ₂ production rate based on the measured value and the theoretical H ₂ production rate was calculated current efficiency by the following equation. The results are shown in Table 1.
Current efficiency (%)=(H ₂ generation rate/theoretical H ₂ generation rate)×100

As shown in the results shown in Table 1, comparing the cells of the present invention (Examples 1 to 7) in which the anode layer contains the perovskite type oxide containing Ba and Co with the conventional cell (Comparative Example 1), the cells of the present invention were compared. The H ₂ generation rate with respect to the current density is clearly higher than that of the conventional cell, and the current efficiency is improved. From these experimental results, it was shown that by using the perovskite type oxide containing Ba and Co as the anode material, higher current efficiency than that of the conventional cell was obtained and H ₂ could be efficiently produced.

Claims (4)

It has an anode layer and a cathode layer, and has a proton conductive solid electrolyte layer between the anode layer and the cathode layer,
The anode layer contains a perovskite type oxide containing Ba and Co,
The molar ratio of Ba at the A site of the perovskite type oxide is 30% or more,
A part of the A site of the perovskite type oxide is substituted with one or more elements selected from La, Ce, Pr, Nd, Sm, Eu, Gd and Yb,
The molar ratio of one or more elements selected from La, Ce, Pr, Nd, Sm, Eu, Gd and Yb at the A site of the perovskite type oxide is 40% or more and 60% or less,
A cell for steam electrolysis, wherein Co is contained in the B site of the perovskite type oxide, and the molar ratio of Co in the B site is 90% or more. The cell for steam electrolysis according to claim 1, wherein the anode layer is formed by firing at a temperature of 900°C or lower. A perovskite-type metal oxide in which the proton conductive solid electrolyte layer contains an alkaline earth metal at the A site and a trivalent or tetravalent transition metal belonging to Groups 4 to 14 of the periodic table at the B site. A cell for steam electrolysis according to claim 1 or 2, which comprises: The cathode layer contains at least one metal element selected from nickel, cobalt and iron, an alkaline earth metal at the A site, and a trivalent group belonging to Groups 4 to 14 of the periodic table at the B site. steam electrolysis cell according to any one of claims 1 to 3 containing perovskite-type metal oxide containing tetravalent transition metal.