JP6202784B2 - Hydrogen production equipment - Google Patents

Description

Embodiments described herein relate generally to a hydrogen production apparatus.

  Solid Oxide Fuel Cell (SOFC) is a reducing agent (hydrogen or hydrocarbon, etc.) through an electrolyte membrane having ionic conductivity (oxygen ions or hydrogen ions) under an operating condition of about 600 to 1000 ° C. ) And an oxidizing agent (such as oxygen) react (fuel cell reaction) and take out the energy as electricity.

  On the other hand, Solid Oxide Electrolysis Cell (SOEC) uses the reverse reaction of SOFC as the principle of operation, and electrolyzes high-temperature water vapor through an electrolyte membrane having ionic conductivity, thereby converting hydrogen and oxygen. It is a device to obtain.

  When the electrochemical cell functions as an SOFC, a reducing gas containing hydrogen is supplied to the fuel electrode. When the electrochemical cell functions as an SOEC, hydrogen corresponding to the fuel electrode is supplied. An oxidizing gas containing water vapor is supplied to the electrode.

  For this reason, when the electrochemical cell is used as SOEC for a long period of time, a metal such as nickel constituting the hydrogen electrode is oxidized and the catalytic activity is lost.

  In view of such problems, a special manufacturing method is disclosed in which Ni is dispersed by droplet penetration after formation of a samaritan-doped ceria (SDC) skeleton. However, since the electrolyte support type is the main cell structure, Although droplet permeation is possible, since a support is provided on the hydrogen electrode side, Ni-containing droplets remain on the support, and Ni is evenly and effectively dispersed uniformly in the hydrogen electrode near the electrolyte. It is difficult to make it. Therefore, the above-described problem cannot be solved.

JP 2006-283103 A

An object of the present invention is to provide, to suppress deterioration of catalytic function of the hydrogen electrode due to electrolysis reaction, to provide a hydrogen producing device capable of maintaining a high electrolytic reaction efficiency for a long period of time is there.

  The hydrogen production apparatus of the embodiment is a hydrogen production apparatus that produces hydrogen by an electrolysis reaction of water vapor using an electrochemical cell. The electrochemical cell is electrically insulating and has an oxygen ion conductive electrolyte membrane, an oxygen electrode formed on one main surface side of the electrolyte membrane, and formed on the other main surface side of the electrolyte membrane. And a hydrogen electrode made of a metal oxide containing metallic nickel and cerium. Metallic nickel is dispersed in particles made of a metal oxide containing cerium. The metal oxide is a solid solution of at least one selected from the group consisting of yttrium, lanthanum, samarium, and gadolinium. The amount of metallic nickel is larger than 40% by mass and smaller than 60% by mass with respect to the total amount of metallic nickel and metal oxide.

  ADVANTAGE OF THE INVENTION According to this invention, deterioration of the catalyst function of the hydrogen electrode resulting from an electrolytic reaction can be suppressed, and high electrolytic reaction efficiency can be maintained over a long period of time.

It is sectional drawing which shows schematic structure of the electrochemical cell in 1st Embodiment. It is sectional drawing which shows schematic structure of the electrochemical cell in 2nd Embodiment. It is a graph which shows the relationship between the operation time of the electrochemical cell in an Example, and cell voltage. It is a graph which shows the relationship between the operation time of the electrochemical cell in an Example, and cell voltage.

(First embodiment)
FIG. 1 is a cross-sectional view showing a schematic configuration of an electrochemical cell in the present embodiment.
An electrochemical cell 10 shown in FIG. 1 is electrically insulative and has an electrolyte film 11 exhibiting electronic insulation and oxygen ion conductivity, and oxygen formed on one main surface 11A side of the electrolyte film 11. The electrode 12 includes a hydrogen electrode 13 formed on the other main surface 11B side of the electrolyte membrane 11.

The electrolyte membrane 11 can be composed of, for example, stabilized zirconia. In this case, examples of the stabilizer include Y ₂ O ₃ , Sc ₂ O ₃ , Yb ₂ O ₃ , Gd ₂ O ₃ , Nd ₂ O ₃ , CaO, and MgO. Moreover, it can replace with stabilized zirconia and can also comprise perovskite type oxides, such as LaSrGaMg oxide, LaSrGaMgCo oxide, LaSrGaMgCoFe oxide, LaSrGaMgCoFe oxide. Furthermore, a ceria-based electrolyte solid solution in which Sm ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ , La ₂ O _{3 and the} like are dissolved in CeO ₂ can also be used. However, the electrolyte membrane 11 is not limited to these materials, and may be composed of other materials.

  In addition, although the thickness of the electrolyte membrane 11 can be arbitrarily set according to the objective, it can be set as the range of 0.001 mm-1 mm, for example. Further, the electrolyte membrane 11 generally has a dense structure because it mainly conducts only oxygen ions and does not allow gas to pass therethrough.

  The oxygen electrode 12 includes a LaSrMn oxide (hereinafter, LSM), a LaSrCo oxide (hereinafter, LSC), a LaSrCoFe oxide (hereinafter, LSCF), a LaSrFe oxide (hereinafter, LSF), a LaSrMnCo oxide (hereinafter, LSMC), LaSrMnCr oxide (hereinafter LSMC), LaCoMn oxide (hereinafter LCM), LaSrCu oxide (hereinafter LSC), LaSrFeNi oxide (hereinafter LSFN), LaNiFe oxide (hereinafter LNF), LaBaCo oxide (hereinafter hereafter) LBC), LaNiCo oxide (hereinafter LNC), LaSrAlFe oxide (hereinafter LSAF), LaSrCoNiCu oxide (hereinafter LSCNC), LaSr-FeNiCu oxide (hereinafter LSFNC), LaNi oxide (hereinafter LN) GdSrCo oxide (hereinafter referred to as G SC), GdSrMn oxide (hereinafter GSM), PrCaMn oxide (hereinafter PCaM), PrSrMn oxide (hereinafter PSM), PrBaCo oxide (hereinafter PBC), SmSrCo oxide (hereinafter SSC), NdSmCo oxidation (Hereinafter referred to as NSC), BiSrCaCu oxide (hereinafter referred to as BSCC), BaLaFeCo oxide (hereinafter referred to as BLFC), BaSrFeCo oxide (hereinafter referred to as BSFC), YSrFeCo oxide (hereinafter referred to as YLFC), YCuCoFe oxide (hereinafter referred to as YCCF) ), YBaCu oxide (hereinafter referred to as YBC), or other materials having electron-ion mixed conductivity.

  In this case, since the oxygen electrode 12 has electronic conductivity and oxide ion conductivity, the electrochemical reaction of oxygen ions at the oxygen electrode 12 is promoted, and oxygen can be generated efficiently. That is, the generation current, that is, the generation amount of oxygen and hydrogen when used as a solid electrolyte electrolytic cell (SOEC) can be further improved.

  In addition, when using the material which has the electron-ion mixed conductivity mentioned above, a composition ratio etc. do not ask | require. Further, a mixture of stabilized zirconia or ceria-based electrolyte solid solution may be used. Further, for example, by adding a metal component such as Pt, Ru, Au, Ag, Pd to the above-described electron-ion mixed conductive material, the above-described electron conductivity and oxide ion conductivity are improved. Oxygen and hydrogen production can be increased more efficiently.

  When the electrochemical cell 10 is used as a SOEC, the oxygen electrode 12 is generally formed as a porous body in order to take out the generated oxygen efficiently. Although the thickness of the oxygen electrode 12 can be arbitrarily set according to the purpose, it can be in a range of, for example, 0.001 mm to 1 mm.

  The hydrogen electrode 13 is composed of a metal oxide containing metallic nickel and cerium. In this case, metallic nickel has electron conductivity and oxide ion conductivity, and functions as a catalyst for the hydrogen electrode 13, so that the supplied water vapor generates hydrogen and oxygen ions by taking in electrons. . The oxygen ions reach the oxygen electrode 12 after being conducted through the solid electrolyte 11 and become oxygen through an electrochemical reaction in the oxygen electrode 12 as described above.

  The hydrogen electrode 13 also has a metal oxide containing cerium in addition to the metal nickel. The cerium oxide has electron conductivity and oxide ion conductivity so that it functions as a catalyst for the hydrogen electrode 13. Become. Therefore, the supplied water vapor takes in electrons to generate hydrogen and oxygen ions. The generated oxygen ions are converted into oxygen at the oxygen electrode 12 as described above.

  Thus, since the hydrogen electrode 13 contains the metal oxide of cerium which functions as a catalyst in addition to the metal nickel which originally functions as a catalyst, the function of the metal nickel itself as a catalyst is the above metal oxide. It will be alleviated by the presence of things. Further, by using cerium oxide, this cerium oxide is responsible for both electronic conduction and oxygen ion conduction, so that the electron conduction path is hardly cut off. Therefore, since the influence of the supplied water vapor is reduced by the presence of the metal oxide, the oxidation of the metal nickel by the water vapor can be suppressed and the electron conduction path can be secured. As a result, it is possible to provide the electrochemical cell 10 capable of suppressing deterioration of the catalytic function of the hydrogen electrode 13 over a long period of time and maintaining a high electrolytic reaction efficiency over a long period of time.

  In addition, the metallic nickel which comprises the hydrogen electrode 13 exists in the state of nickel oxide by the influence of the formation method of the metal oxide containing cerium etc. or the hydrogen electrode 13 at the time of forming the hydrogen electrode 13. However, nickel oxide is reduced to metallic nickel by supplying a reducing gas such as hydrogen as necessary under operating conditions when the electrochemical cell 10 is used as an SOEC, for example, at a temperature of 600 to 900 ° C. It becomes like this.

  Moreover, it is preferable that the amount of metallic nickel in the hydrogen electrode 13 is larger than 40 mass% and smaller than 60 mass% with respect to the whole quantity of metallic nickel and a metal oxide.

  In general, in an electrochemical cell that is practically used as an SOEC, a cell voltage after the cell has been operated for 1000 hours, that is, a change in applied voltage to the electrochemical cell 10 necessary for generating hydrogen and oxygen from supplied water vapor. The rate is required to be 1% or less. However, if the amount of metallic nickel in the hydrogen electrode 13 is 60% by mass or more, the rate of change of the cell voltage after 1000 hours exceeds 1%, which may not be suitable for practical use. This is because, when the amount of metallic nickel in the hydrogen electrode 13 is 60% by mass or more, the function of cerium in the cerium-containing metal oxide described above cannot sufficiently supplement the function of metallic nickel as a catalyst. It is considered that the influence of the oxidation of metallic nickel appears relatively remarkably.

  When the amount of metallic nickel at the hydrogen electrode 13 is 40% by mass or less, the original amount of metallic nickel is small, and the cell voltage increases even when the rate of change of the cell voltage after 1000 hours is within 1%. Resulting in. That is, since the electrolysis voltage of water vapor increases, a large amount of energy is used for electrolysis of water vapor, which is not preferable.

Note that the cerium-containing metal oxides, yttrium, lanthanum, samarium, and that at least one metal selected from the group consisting of Gadori two um is dissolved preferable. Such a solid solution exhibits electron-ion conductivity, does not impair the above-described function of cerium as a catalyst, and is structurally stable even when the electrochemical cell 10 is operated at a temperature of about 600 to 900 ° C. And sufficient strength. Therefore, the long-term reliability of the hydrogen electrode 13, that is, the electrochemical cell 10 can be enhanced.

  In the hydrogen electrode 13, it is preferable that the metal nickel and the metal oxide exist as composite metal oxide particles of the nickel and the cerium in the raw material powder at the time of manufacture (before the reduction treatment). This composite metal oxide particle has a form in which nickel metal oxide particles are dispersed in cerium metal oxide particles, a form in which cerium metal oxide particles are dispersed in nickel metal oxide particles, or nickel. It means a form in which cerium metal oxide particles are dispersed or a form in which nickel and cerium are dispersed in metal oxides. That is, it is not an open system state in which metallic nickel adheres to the surface of the cerium metal oxide, but means a form in which at least one of nickel and cerium is constrained in the metal oxide.

  When the electrochemical cell 10 including the hydrogen electrode 13 using a mixture of nickel oxide particles and cerium metal oxide particles is used as a SOEC for a long time, the metal nickel constituting the hydrogen electrode 13 is bonded to each other. Grain growth may occur, and the catalytic activity may deteriorate as the surface area of the metallic nickel decreases.

  However, as described above, when nickel is dispersed in the cerium metal oxide particles, the grain growth of the metal nickel is suppressed by the cerium metal oxide when firing is performed at the time of manufacture. Therefore, the inconvenience as described above does not occur. Therefore, the catalytic activity of metallic nickel is not deteriorated.

  The composite metal oxide particles described above can be formed by a method such as a solid phase reaction method, a coprecipitation method, a mechanochemical method, or a spray pyrolysis method.

  When the electrochemical cell 10 is used as an SOEC, the hydrogen electrode 13 is generally formed as a porous body so that the supplied water vapor can be efficiently brought into contact with metallic nickel or the like. Although the thickness of the hydrogen electrode 13 can be arbitrarily set according to the purpose, it can be set to, for example, 5 μm to 100 μm.

  As described above, according to the present embodiment, deterioration of the catalytic function of the hydrogen electrode due to the electrolytic reaction can be suppressed, and high electrolytic reaction efficiency can be maintained over a long period of time.

(Second Embodiment)
FIG. 2 is a cross-sectional view showing a schematic configuration of the electrochemical cell in the present embodiment. In addition, the same code | symbol is used about the same or same component as the electrochemical cell 10 shown in FIG.

  The electrochemical cell 20 of the present embodiment is different from the electrochemical cell 10 of the first embodiment shown in FIG. 1 in that the support material 21 is disposed on the hydrogen electrode 13. Adopts the same structure.

  The support 21 is porous and is configured such that the water vapor supplied to the hydrogen electrode 13 reaches the metal nickel and cerium-containing metal oxide constituting the hydrogen electrode 13. In addition, as described in the first embodiment, oxygen ions are converted into oxygen through an electrochemical reaction in the oxygen electrode 12.

  Moreover, the thickness of the electrolyte membrane 11 can be reduced by disposing the support 21. When the thickness of the electrolyte membrane 11 is large, it takes a long time for oxygen ions to conduct through the electrolyte membrane 11, so that the ionic conductivity resistance increases. However, when the thickness of the electrolyte membrane 11 is small, the ionic conductivity resistance is reduced. Can be small.

The support 21 needs to be made of a material having at least electronic conductivity so that a predetermined voltage can be applied between the oxygen electrode 12 and the hydrogen electrode 13, for example, a metal sintered body, a metal foam, a metal It can be composed of a fibrous body, a ceramic sintered body having conductivity, and its porosity depends on, for example, the molding pressure when forming the molded body, the sintering temperature during sintering, the type of pore forming material, etc. to cause. In particular, the amount of the three-phase interface on the side of the hydrogen electrode 13 is increased by using an electron-ion mixed conductive ceramic material. Therefore, the electrochemical reaction at the hydrogen electrode 13 is promoted, and the output characteristics of the electrochemical cell 20 can be improved. Specifically, it can be composed of at least one selected from the group consisting of _Sm 2 _{O 3} doped _CeO 2, _Gd 2 _{O 3} doped CeO _2, and _Y 2 _{O 3} doped CeO _2. Moreover, electroconductivity can also be provided by plating etc. with respect to the porous support body 21 mentioned above.

  The thickness of the support 21 can be, for example, 100 μm or more and 1000 μm or less. If the thickness of the support 21 is smaller than 100 μm, the strength of the support 21 is not sufficient, and the strength of the electrochemical cell 10 is deteriorated. On the other hand, when the thickness of the support 21 is larger than 1000 μm, the ionic conduction resistance increases.

  The porosity of the support 21 is preferably larger than 30% and smaller than 50%. In this case, the cell voltage after 1000 hours of operation, that is, the rate of change of the applied voltage to the electrochemical cell 20 required for generating hydrogen and oxygen from the supplied water vapor is kept within a practical range of 1% or less. be able to. This is because when the porosity of the support 21 is 30% or less, the amount of water vapor supplied to the hydrogen electrode 13 is small, and metallic nickel and the like constituting the hydrogen electrode 13 are oxidized by factors other than water vapor. As a result, the catalytic function cannot be achieved, and if the porosity of the support 21 is 50% or more, the amount of water vapor supplied to the hydrogen electrode 13 becomes too large, and the catalytic function of metallic nickel is lowered. This is thought to be because it becomes impossible to compensate for cerium.

  The porosity of the support 21 is made larger than the porosity of the hydrogen electrode 13 in order to prevent the supply resistance of water vapor from becoming too large at the support 21 and being supplied to the hydrogen electrode 13.

  Also in this embodiment, as in the first embodiment, since the hydrogen electrode 13 is made of a metal oxide containing metallic nickel and cerium, the deterioration of the catalytic function of the hydrogen electrode due to the electrolytic reaction is suppressed. The electrochemical cell 20 capable of maintaining high electrolytic reaction efficiency over a long period of time can be provided.

  In addition, since it is the same as that of the electrochemical cell 10 of 1st Embodiment about another structure, the characteristic, and an effect, description is abbreviate | omitted.

Example 1
In this example, an electrochemical cell 20 having a configuration as shown in FIG. 2 was produced.
The electrolyte membrane 11 uses scandia-stabilized zirconia with a thickness of 10 μm, the oxygen electrode 12 uses a composite oxide of lanthanum, strontium, cobalt, and iron with a thickness of 20 μm to 40 μm, and the hydrogen electrode 13 has a thickness. Ni-GDC (CeO ₂ and Gd ₂ O ₃ solid solution: metal nickel content 55 mass%) of 25 μm to 35 μm was used. Further, Ni-GDC having a thickness of 0.5 mm to 1 mm was also used for the support 21.

  The operation temperature of the electrode cell 20 thus obtained was set to 800 ° C., and a mixed gas of water vapor and hydrogen (water vapor: hydrogen = 50: 50) was supplied to the hydrogen electrode 13 to perform an electrolysis operation of water vapor. The results are shown in FIG.

  For comparison, FIG. 3 shows the result of the electrolysis operation of water vapor in an electrochemical cell obtained by forming the hydrogen electrode 13 from Ni having a thickness of 25 μm to 35 μm and yttria-stabilized zirconia.

  As is clear from FIG. 3, when the hydrogen electrode 13 is made of Ni-GDC having a thickness of 25 μm to 35 μm, the cell voltage, that is, the electrolysis voltage of water vapor is less than 1% even after 1500 hours. It can be seen that the oxidation of the metallic nickel of the hydrogen electrode 13 is suppressed by cerium of GDC, the deterioration of the catalytic function of the hydrogen electrode can be suppressed over a long period of time, and high electrolytic reaction efficiency can be maintained.

  On the other hand, in an electrochemical cell obtained by forming the hydrogen electrode 13 from Ni having a thickness of 25 μm to 35 μm and yttria-stabilized zirconia, the cell voltage, that is, the electrolysis voltage of water vapor increases from the start of operation, and after 300 hours have elapsed. It increased to about 1.5 times, and after that, it became impossible to operate. That is, it has been found that the oxidation of the metallic nickel at the hydrogen electrode 13 is hardly suppressed, and the catalytic function of the hydrogen electrode is immediately deteriorated and the electrolytic reaction efficiency cannot be maintained.

(Example 2)
In this example, the ratio of metallic nickel constituting the hydrogen electrode 13 in Example 1 was changed to 40% by mass, 55% by mass, 60% by mass, and 65% by mass, and water vapor electrolysis was performed under the same conditions. It was. The results are shown in FIG.

  As can be seen from FIG. 4, the cell voltage, that is, the electrolysis voltage changes depending on the proportion of metallic nickel in the hydrogen electrode 13, but when the proportion of metallic nickel is 40% by mass and 55% by mass, after 1000 hours of operation. It can also be seen that the cell voltage, that is, the variation of the electrolysis voltage of water vapor is less than 1%, while the variation of the electrolysis voltage exceeds 10% when the proportion of metallic nickel is 60% by mass and 65% by mass.

  On the other hand, when the ratio of the metallic nickel is 40% by mass, the variation in the electrolysis voltage is small, but the cell voltage, that is, the electrolysis voltage is increased because the amount of metallic nickel is small.

  Therefore, it can be seen from this example that the proportion of metallic nickel in the hydrogen electrode 13 is preferably larger than 40 mass% and smaller than 60 mass%.

(Example 3)
In this example, in Example 1, the porosity of the support 21 was changed to 30%, 35%, 40%, 45%, and 50%, and water vapor electrolysis was performed under the same conditions. The results are shown in Table 1.

  As is apparent from Table 1, when the porosity of the support 21 is 35%, 40% and 45%, the cell voltage, that is, the fluctuation of the electrolysis voltage of water vapor is less than 1% even after 1000 hours of operation. On the other hand, when the porosity of the support 21 is 30% and 50%, it can be seen that the fluctuation of the electrolysis voltage exceeds 1%. Therefore, the porosity of the support 21 is preferably larger than 30% and smaller than 50%.

  As mentioned above, although several embodiment of this invention was described, these embodiment was posted as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

10, 20 Electrochemical cell 11 Electrolyte membrane 12 Oxygen electrode 13 Hydrogen electrode 21 Support

Claims (5)

An electrolyte membrane that is electrically insulating and exhibits oxygen ion conductivity;
An oxygen electrode formed on one main surface side of the electrolyte membrane;
A hydrogen electrode formed on the other main surface side of the electrolyte membrane and made of a metal oxide containing metallic nickel and cerium;
Using an electrochemical cell Ru comprising a a hydrogen production apparatus for producing hydrogen by electrolysis reaction of water vapor,
The metallic nickel is dispersed in particles made of the metal oxide containing cerium,
The metal oxide is a solid solution of at least one selected from the group consisting of yttrium, lanthanum, samarium, and gadolinium ,
The amount of the said metallic nickel is larger than 40 mass% with respect to the whole quantity of the said metallic nickel and the said metal oxide, and smaller than 60 mass%, The hydrogen production apparatus characterized by the above-mentioned . The hydrogen production apparatus according to claim 1 , further comprising a porous support for holding at least one of the oxygen electrode and the hydrogen electrode. The hydrogen production apparatus according to claim 2 , wherein the porosity of the support is larger than 30% and smaller than 50%. Wherein the thickness of the electrolyte membrane is 0.001～1Mm, hydrogen production apparatus according to any one of claims 1-3. Wherein the thickness of the hydrogen electrode is 5 to 100 [mu] m, hydrogen production apparatus according to any one of claims 1-4.

Images