JP6367636B2 - Steam electrolysis cell - Google Patents

Description

The present invention relates to a cell for steam electrolysis that has a high H ₂ production rate and high current efficiency and can efficiently produce hydrogen gas from steam.

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

Recently, research on steam electrolysis has been widely promoted as a promising technique for producing hydrogen. Steam electrolysis uses gaseous water vapor instead of liquid water when electrolyzing H ₂ O to obtain hydrogen and oxygen, and can be operated at a high temperature, so the voltage required for electrolysis is small. , It is characterized by high energy efficiency.

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

However, when water vapor 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, hydrogen is generated on the cathode side, and there is a problem that a separate step for separating from coexisting water vapor is required.

As a technique that can solve such a problem, for example, as in Patent Document 2, a technique of water vapor electrolysis using a proton conductive electrolyte has been developed. The electrode reactions that take place at the anode and cathode in the art are as follows.
Anode: 2H ₂ O → O ₂ + 4H ⁺ + 4e ⁻
Cathode: 4H ⁺ + 4e ⁻ → 2H ₂
As shown in 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 water vapor is introduced on the anode side, it is not necessary to separate hydrogen from water vapor. There is an advantage.

JP 2005-150122 A JP 2009-209441 A

As described above, Patent Document 2 discloses a water vapor electrolysis cell including a proton-conductive solid electrolyte. However, although the cell for steam electrolysis described in Patent Document 2 has a low cell terminal voltage, it has a problem of low current efficiency and H ₂ generation rate.

The present invention provides high H ₂ production rate and current efficiency, and to provide a steam electrolysis cell which can be manufactured of H ₂ efficiently.

The inventors of the present invention have made extensive studies to solve the above problems. As a result, as a main raw material powder constituting the anode layer of the steam electrolysis cell, a perovskite type having a BET specific surface area of not less than a predetermined value when fired under the same firing conditions for forming the anode layer by firing by using the oxide powder, compared with a conventional steam electrolysis cell, and found that of H ₂ is efficiently producible steam electrolysis cell obtained in high H ₂ production rate and current efficiency, the present invention completed.

  Hereinafter, the present invention will be described.

[1] 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 oxide, and the BET specific surface area when the raw material perovskite oxide powder is fired under the same firing conditions as the anode layer is 2.0 m ^2. A cell for water vapor electrolysis that is formed using a material that is greater than / g.

  [2] 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] A cell for steam electrolysis as described in 1.

  [3] The proton conductive solid electrolyte layer includes a perovskite type containing 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 the above [1] or [2] containing a metal oxide.

The steam electrolysis cell according to the present invention has a higher H ₂ production rate per electrode area at a current density of more than 0.1 A / cm ² as compared with the conventional steam electrolysis cell and high current efficiency. Therefore, the steam electrolysis cell according to the present invention is very industrially excellent as it can efficiently produce H ₂ .

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

1. Proton Conductive Solid Electrolyte Layer Steam electrolysis cells mainly include an electrolyte support cell and an electrode support cell. In the case of an electrolyte-supported cell, since the firing temperature of the electrolyte layer is generally the highest among the electrolyte layer, the anode layer, and the cathode layer, the electrolyte layer is prepared first. In the case of an electrode-supported cell, an electrolyte layer is formed on the electrode layer that becomes the support layer.

Examples of the material of the proton conductive solid electrolyte that can be used in the present invention include metal oxides that exhibit proton conductivity. Examples of such proton conductive metal oxides include an ABO ₃ type structure. Perovskite oxides, pyrochlore 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 mirrorite structure, etc. Can be mentioned.

As a material for the proton conductive solid electrolyte, a perovskite metal oxide having an ABO ₃ type structure is preferably used because the anode layer contains a perovskite oxide as a main component. As the perovskite type metal oxide, for example, a perovskite type metal oxide in which the A site contains an alkaline earth metal and the B site contains a trivalent or tetravalent element belonging to Groups 4 to 14 of the periodic table. A part of at least one of the A site or the B site of the perovskite oxide is La, Ce, Pr, Nd, Sm, Gd, Eu, Yb, Sc, Y, In, Ga, Fe, Co, A perovskite metal oxide substituted with one or more elements selected from Ni, Zn, Ta, and Nb can be used. Specifically, Sr—Zr—Y, Sr—Zr—Ce—Y, Ba—Zr—Y, Ba—Zr—Ce—Y, Ca—Zr—In, La—Sc, Sr -Ce-Yb-based and Ba-Ce-Y-based perovskite metal oxides.

  The thickness of the proton conductive solid electrolyte layer is not particularly limited, and may be set as appropriate according to the cell shape and the like. For example, in the case of an electrolyte support type cell, it is preferably 50 μm or more and 500 μm or less. If the thickness is less than 50 μm, sufficient strength may not be obtained. On the other hand, when the thickness exceeds 500 μm, there is a possibility that the proton conductivity may be hindered. 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 less than 1 μm, it may be difficult to form a proton conductive solid electrolyte layer by an industrial process such as screen printing. On the other hand, if the thickness exceeds 50 μm, proton conductivity may be hindered.

  Examples of the method for producing the proton conductive solid electrolyte layer include the following methods. Add organic solvent such as ethanol and terpineol, dispersant, plasticizer and binder such as ethyl cellulose to proton conductive metal oxide, wet pulverize and mix with a ball mill etc. to make a slurry, then green by doctor blade method etc. A sheet. Next, by baking, a proton conductive solid electrolyte layer can be obtained. In the case of an electrode-supported cell, the proton-conducting solid electrolyte layer is formed on the support electrode layer by applying the slurry on the electrode layer to be the support layer and then baking the slurry.

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

  When the steam electrolysis cell 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, since the firing temperature of the cathode layer is generally higher than that of the anode layer, the cathode layer or its green sheet is used as a support layer, an electrolyte layer is formed thereon, and further on the electrolyte layer. An anode layer is formed.

The anode layer of the cell for steam electrolysis according to the present invention needs to exhibit a catalytic action for promoting the reaction of 2H ₂ O → O ₂ + 4H ⁺ + 4e ⁻ and have electronic conductivity. As such a material, a perovskite type metal oxide containing a transition metal element which is a catalyst component for promoting the reaction can be used. In the present invention, it is preferable to use a perovskite type oxide as a main component.

  As described above, the main component of the anode layer of the cell for steam electrolysis according to the present invention is a perovskite oxide. In the present invention, “perovskite-type oxide is the main component of the anode layer” means that the perovskite occupies the raw materials of the components constituting the anode layer, except for components that disappear upon firing such as a binder and a solvent during the formation of the anode layer. It shall be said that the ratio of the type oxide is 60 v / v% or more. The ratio is preferably 65 v / v% or more, more preferably 70 v / v% or more, and further 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 perovskite type oxides, but other components are included as described later. Therefore, the ratio is preferably 95 v / v% or less, more preferably 90 v / v% or less, and still more preferably 85 v / v% or less.

  Examples of the velovskite oxide constituting the anode layer include, for example, one or more elements selected from Sr, La, Ce, Pr, Nd, Sm, Eu, Gd, and Yb, and the B site is Co, Perovskite type metal oxides substituted with Ni, Fe, etc., specifically, Sm—Sr—Co, La—Sr—Co, La—Ba—Co, Pr—Sr—Co, Nd— Examples thereof include perovskite metal oxides such as Sr—Co and Ba—Sr—Co—Fe. These can be used alone, or an electrode to which the above proton conductive oxide or the like is added can also be used.

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

  Although the usage-amount of an electron-conductive component is not restrict | limited in particular, For example, it is preferable to set it as 2.0 mass% or more and 25 mass% or less by the mass ratio with respect to the whole electrode. If the said ratio is 2.0 mass% or more, electronic conductivity will be exhibited more reliably. On the other hand, if the ratio is too large, the porosity of the electrode may be excessively decreased. Therefore, the ratio is preferably 25% by mass or less.

In the present invention, the perovskite oxide powder, which is a main raw material for forming the anode layer, has a BET specific surface area of 2.0 m ² / g when fired under the same firing conditions as those for forming the anode layer. Use what is above. If the anode layer is formed using the perovskite type oxide powder having a BET specific surface area of 2.0 m ² / g or more as a main raw material powder, the H ₂ generation rate and current efficiency of the steam electrolysis cell are improved, Efficient production of H ₂ becomes possible. Preferably at least 2.1 m ² / g as the BET specific surface area, more preferably at least 2.2 m ² / g, more preferably not less than 2.4 m ² / g. It can be said that the production efficiency of H ₂ is improved as the BET specific surface area is large. However, if the BET specific surface area is excessively large, the strength of the anode layer may not be sufficiently secured. Therefore, the BET specific surface area is 15 m ² / g or less. Preferably, 10 m ² / g or less is more preferable, and 8 m ² / g or less is more preferable. The perovskite oxide powder, which is the anode layer raw material powder, is fired only to measure the BET specific surface area, which is an indicator of the present invention. The raw material perovskite used to actually form the anode layer is used. As the type oxide powder, the powder before firing is used. That is, the firing and the measurement of the BET specific surface area are separately performed independently of the formation of the anode layer.

  In order to adjust the BET specific surface area of the raw material perovskite type oxide powder fired under the same conditions as the firing conditions for forming the anode layer, for example, the constituent elements of the raw material perovskite type oxide powder before firing The composition ratio, grinding conditions, and grinding method may be adjusted. Specifically, the pulverization method may be dry pulverization, wet pulverization, or freeze pulverization, and a ball mill, bead mill, attritor, rod mill, hammer mill, freezer mill, jet mill, or the like can be used. The conditions should be appropriately selected depending on the above-described pulverization method or characteristics of the pulverizer, and cannot be generally specified. For example, when using a rotary pulverizer such as a ball mill, a bead mill, an attritor, etc. As mentioned above, it may be pulverized at 150 rpm or less for 1 hour or more and 200 hours or less, preferably wet pulverization at a rotation speed of 50 rpm or more and 100 rpm or less for 1 hour or more and 100 hours or less.

  The BET specific surface area refers to a surface area obtained by adsorbing nitrogen molecules to a measurement target substance at a liquid nitrogen temperature of −196 ° C. and obtaining the BET equation from the amount of adsorption.

  The thickness of the anode layer is not particularly limited, and may be appropriately determined according to the cell shape and the like. For example, it is preferable that both the electrolyte support type cell and the electrode support type cell have a range of 5 μm or more and 100 μm or less.

  As a method for forming the anode layer, for example, after preparing a paste of the above-described components in the same manner as in the case of the proton conductive solid electrolyte layer, the anode layer is applied so that a desired film thickness is obtained on the proton conductive solid electrolyte layer. And then firing. Preferable firing conditions for forming the anode layer are, for example, 700 ° C. or more and 900 ° C. or less, and 30 minutes or more and 2 hours or less. When the firing temperature is less than 700 ° C., the electrode adhesion becomes low, so that peeling may occur and the performance may be lowered. On the other hand, when the temperature is higher than 900 ° C., the hydrogen generation rate may be lowered. It is not preferable. The firing temperature is preferably 750 ° C. or higher and 900 ° C. or lower, more preferably 800 ° C. or higher and 900 ° C. or lower.

3. Formation of Cathode Layer The cathode layer of the cell according to the present invention needs to exhibit a catalytic action that promotes the reaction of 4H ⁺ + 4e ⁻ → 2H ₂ and has electronic 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 oxide that is a material of the proton conductive solid electrolyte layer. A mixture of a metal element and a perovskite oxide is preferable from the viewpoint of affinity and adhesion to the proton conductive solid electrolyte layer.

  Examples of metal element materials include metals such as Pt, Pd, Ni, Co, Fe, and Ru; metal oxides that change to electron conductive metals in a reducing atmosphere such as nickel oxide, cobalt oxide, and iron oxide; or these And composite metal oxides such as nickel ferrite and cobalt ferrite containing two or more of these oxides. These may be used alone or in combination of two or more as necessary. Among these, metallic nickel, metallic cobalt, metallic iron, or oxides thereof are preferable.

  Examples of proton conductive metal oxides include perovskite-type metal oxides in which the A component is an alkaline earth metal and the B component is composed of a trivalent or tetravalent element belonging to Groups 4 to 14 of the periodic table. A part of the A component and / or B component of the perovskite-type metal oxide may be La, Pr, Nd, Sm, Gd, Yb, Sc, Y, Ce, In, Ga, Fe, Co, Ni, Zn, Ta, A perovskite metal oxide substituted with one or more elements selected from Nb can be used.

  When a mixture of a metal element material and a perovskite oxide is used as the cathode material, these ratios are not particularly limited, and may be appropriately adjusted in consideration of the electron conductivity, catalytic ability, etc. 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. As the said ratio, 25 v / v% or more is more preferable, and 70 v / v% or less is more preferable.

  The thickness of the cathode layer is not particularly limited and may be appropriately determined according to 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 using 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.

As a method for forming the cathode layer, for example, a paste of the above components is prepared in the same manner as in the case of the proton conductive solid electrolyte layer, and then applied to obtain a desired film thickness on the proton conductive solid electrolyte layer. Then, it may be fired. In the case of an electrode-supported cell using the cathode layer as a support layer, after forming the cathode layer that also serves as a support, a proton conductive solid electrolyte layer is formed on the cathode layer, and the electrolyte layer An anode layer may be formed thereon. Alternatively, a porous support layer may be formed under the cathode layer (opposite 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 actively performing a reduction treatment, and the volume is reduced by that amount to make the cathode layer porous. Can do. The steam electrolysis cell having such a porous cathode layer has a higher H ₂ production capacity.

  Preferable firing conditions for forming the cathode layer can be, for example, 900 ° C. or higher and 1500 ° C. or lower and 1 hour or longer and 5 hours or shorter. When the firing temperature is less than 900 ° C., the strength is not sufficient and peeling may occur, and the performance may be deteriorated. On the other hand, when the temperature is higher than 1500 ° C., the cathode layer becomes a dense body and gas diffusion decreases. Since there is a possibility of fear, it is not preferable. The firing temperature is preferably 1000 ° C. or higher and 1500 ° C. or lower, and more preferably 1100 ° C. or higher and 1500 ° C. or lower.

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

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

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.

Example 1
(1) Production of cathode support green sheet Commercially available nickel oxide powder (manufactured by Shodo Chemical Co., Ltd., product name “Green”) and SrZr _0.5 Ce _0.4 Y _0.1 O _3-δ particles as electrolyte particles, the nickel oxide powder It weighed so that it might become 50 vol% and electrolyte particles 50 vol%. A binder and a solvent were added to these particles, and a plasticizer, a dispersant, a lubricant and an antifoaming agent were further added. A slurry was prepared by wet pulverizing and mixing the mixture with a ball mill for 30 hours. The obtained slurry was formed into a sheet by a tape casting method and then dried at 80 ° C. for 1 hour.

(2) Production of _half cell SrZr _0.5 Ce _0.4 Y _0.1 O _3-δ , ethyl cellulose and α-terpineol were mixed in a mortar. Then, it knead | mixed using the 3 roll mill (EXAKT technologies company make, model "M-80S"), and obtained electrolyte layer paste.

  The paste is applied by screen printing on the cathode support green sheet prepared in (1) above, dried at 80 ° C. for 30 minutes, and then baked at 1400 ° C. in an air atmosphere for 2 hours to conduct proton conduction. A half cell having a thickness of the conductive electrolyte layer of 20 μm and a thickness of the cathode support of 250 μm was produced.

(3) Production of anode layer Commercially available powders of Sm ₂ O ₃ , SrCO ₃ and Co ₃ O ₄ with a purity of 99.9% by mass were mixed so as to have a composition of Sm _0.5 Sr _0.5 CoO _{3 -δ} . Ethanol was added to the obtained mixture, and wet pulverization was performed for 2 hours with a bead mill, followed by drying at 120 ° C. for 10 hours. Subsequently, the powder was obtained by heat-processing at 1000 degreeC for 10 hours. Furthermore, ethanol was added to the obtained powder, wet pulverized with a bead mill for 2 hours, and then dried at 120 ° C. for 10 hours to obtain a raw material powder that can be used as an anode layer material for steam electrolysis. The composition of the obtained anode layer raw material powder was Sm _0.5 Sr _0.5 CoO _{3 -δ} , and it was confirmed by X-ray diffraction that it was a single phase composed of perovskite.

  Ethyl cellulose as a binder and α-terpineol as a solvent were added to the anode layer raw material powder and mixed in a mortar. Subsequently, kneading was performed using a three-roll mill (manufactured by EXAK technologies, model “M-80S”) to obtain an anode paste.

  The anode paste was applied to the opposite side of the cathode support in the half-cell proton-conducting electrolyte obtained in (2) above by screen printing, and then fired at 850 ° C. for 1 hour in an air atmosphere. An anode layer having a thickness of 30 μm was formed.

Separately, the wet pulverized anode layer raw material powder was calcined at 850 ° C. for 1 hour in an air atmosphere in the same manner as the calcining conditions for forming the anode layer, and then a BET specific surface area meter (“Macsorb HM” manufactured by Mountec Co., Ltd.). -1210 ") to measure the BET specific surface area. Specifically, a measurement sample was charged into a cell, and degassing was performed at 200 ° C. for 30 minutes while flowing 100 mL / min of nitrogen gas through the cell. After the deaeration treatment, while flowing 50 mL / min of nitrogen gas through the cell, the cell was immersed in liquid nitrogen to adsorb nitrogen to the measurement sample. Next, the BET specific surface area was measured by keeping the cell at room temperature and measuring the amount of nitrogen desorbed. The measurement was performed 3 times per sample, and the average value was obtained. As a result, the BET specific surface area of the obtained anode layer raw material powder was 2.5 m ² / g.

Example 2
A cell was prepared in the same manner as in Example 1 except that the composition of the anode layer was La _0.5 Sr _0.5 CoO _3-δ . When La _0.5 Sr _0.5 CoO _3-δ anode layer raw material powder for forming the anode layer of the cell was fired at 850 ° C. for 1 hour in an air atmosphere in the same manner as the firing conditions for forming the anode layer, The BET specific surface area was 2.8 m ² / g.

Example 3
Commercially available powders of La ₂ O ₃ , BaCO ₃ and Co ₃ O ₄ with a purity of 99.9% by mass were mixed so as to have a composition of La _0.5 Ba _0.5 CoO _{3 -δ} . Ethanol was added to the obtained mixture, wet pulverized with a ball mill for 60 hours, and then dried at 120 ° C. for 10 hours. Subsequently, the powder was obtained by heat-processing at 1100 degreeC for 10 hours. Furthermore, ethanol was added to the obtained powder, wet pulverized with a ball mill for 100 hours, and then dried at 120 ° C. for 10 hours to obtain a raw material powder that can be used as an anode layer material for steam electrolysis. The composition of the obtained anode layer raw material 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.

  Ethyl cellulose as a binder and α-terpineol as a solvent were added to the anode layer raw material powder, and mixed in a mortar. Then, it knead | mixed using the 3 roll mill (The product made by EXAK technologies, model "M-80S"), and obtained the paste for anodes.

  The anode paste is applied to the opposite side of the cathode support in the half-cell proton-conducting electrolyte obtained in Example 1 (2) by screen printing, and then fired at 850 ° C. in an air atmosphere for 1 hour. Thus, an anode layer having a thickness of 30 μm was formed.

In the same manner as in Example 1 (3), La _0.5 Ba _0.5 CoO _3-δ anode layer raw material powder was separately added at 850 ° C. in an air atmosphere in the same manner as the firing conditions for forming the anode layer. When the BET specific surface area was measured after baking for a time, it was 4.7 m ² / g.

Comparative Example 1
A cell was produced in the same manner as in Example 1 except that the firing temperature for forming the anode layer was changed to 950 ° C. Separately, the used Sm _0.5 Sr _0.5 CoO _3-δ anode layer raw material powder was fired at 950 ° C. for 1 hour in the air atmosphere in the same manner as the firing conditions for forming the anode layer, and then the BET specific surface area was measured. However, it was 1.5 m ² / g.

Test example 1
A glass ring was sandwiched between the cells prepared in Examples 1 to 3 and Comparative Example 1 so as not to contact the anode layer, and gas sealing was performed by softening at 800 ° C. Then, after the temperature was lowered to 600 ° C. it is operating temperature, and reduced the NiO in the cathode support by introducing N ₂ gas containing 10v / v% H ₂ gas. Argon gas containing 20 v / v% water vapor and 1 v / v% oxygen is introduced into the anode layer at a flow rate of 100 NmL / min, and argon gas containing 2 v / v water vapor and 1 v / v% hydrogen is introduced into the cathode layer side. It was introduced at a flow rate of 100 NmL / min. Using a potentiogalvanostat, a current-voltage curve was obtained by measuring the voltage while changing the current.

Further, 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 (Horiba Estec). From the obtained measured value, the H ₂ production rate was calculated by the following formula.
H ₂ production rate (μmol / h · cm ² ) = [{(Qv0 × Hc0 / 100) − (Qv1 × Hc1 / 100)}] × 60 × 10 ⁶ ] / (22400 × S)
Qv0: Cathode outlet gas flow rate when not energized (NmL / min)
Hc0: H ₂ concentration (v / v%) in cathode outlet gas when not energized
Qv1: Cathode outlet gas flow rate during energization (NmL / min)
Hc1: H ₂ concentration (v / v%) in the cathode outlet gas during energization
S: Anode electrode area (cm ² )

The theoretical H ₂ production rate was calculated from the following formula.
Theoretical H ₂ production rate (μmol / h · cm ² ) = {current applied (A) × 3600 (s) × 10 ⁶ } / {2 × F × current area (cm ² )}
F: Faraday constant

Furthermore, the current efficiency was calculated from the following formula from the H ₂ production rate and the theoretical H ₂ production rate based on the measured values.
Current efficiency (%) = (H ₂ production rate / theoretical H ₂ production rate) × 100

Table 1 shows the composition of the anode layer of each cell, the BET specific surface area, the hydrogen production rate at a current density of 0.5 A / cm ² , and the current efficiency.

As shown in Table 1, if the anode layer is formed using a raw material powder having a BET specific surface area of 2.0 m ² / g or more when fired under the same conditions as the anode layer preparation, the H ₂ production rate is increased. It was proved that a cell for steam electrolysis with significantly good current efficiency can be obtained.

Claims (2)

An anode layer and a cathode layer, and a proton conductive solid electrolyte layer between the anode layer and the cathode layer;
The anode layer contains a perovskite oxide, and the BET specific surface area when the raw material perovskite oxide powder is fired under the same firing conditions as the anode layer is 2.0 m ^2. / g all SANYO formed in it using what above,
The proton conductive solid electrolyte layer includes a perovskite-type metal oxide containing 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. steam electrolysis cell characterized that you contain.   The water vapor according to claim 1, wherein 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. Electrolysis cell.