JP2008027866A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell capable of efficiently carrying out protonation, and capable of suppressing peeling-off between an electrolyte membrane and a hydrogen separation membrane. <P>SOLUTION: The fuel cell (100) is provided with the hydrogen separation membrane (10) and the electrolyte membrane (20) which is installed on the hydrogen separation membrane and which has proton productivity. The electrolyte membrane includes a first electrolyte (21) and a second electrolyte (22) on an interface between the hydrogen separation membrane and the electrolyte membrane, and proton-forming ability of the first electrolyte is higher than that of the second electrolyte while adhesiveness to the hydrogen separation membrane of the second electrolyte is higher than that of the hydrogen separation membrane of the first electrolyte. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell including a proton conductive electrolyte.

  A fuel cell is a device that generally obtains electric energy using hydrogen and oxygen as fuel. Since this fuel cell is excellent in terms of environment and can realize high energy efficiency, it has been widely developed as a future energy supply system.

  Among the fuel cells, those using solid electrolytes include solid polymer fuel cells, solid oxide fuel cells, hydrogen separation membrane cells, and the like. Here, the hydrogen separation membrane battery is a fuel cell provided with a dense hydrogen separation membrane (see, for example, Patent Document 1). The dense hydrogen separation membrane is a layer formed of a metal having hydrogen permeability and also functions as an anode. The hydrogen separation membrane battery has a structure in which an electrolyte membrane having proton conductivity is laminated on the hydrogen separation membrane. Hydrogen supplied to the hydrogen separation membrane permeates the hydrogen separation membrane, is converted into protons in the electrolyte membrane, moves through the electrolyte membrane, and combines with oxygen at the cathode.

JP 2004-146337 A

  However, in the hydrogen separation membrane battery according to the technique of Patent Document 1, the metal constituting the hydrogen separation membrane is easily terminated by oxygen in the electrolyte membrane at the interface between the electrolyte membrane and the hydrogen separation membrane. As a result, sufficient protonation ability in the electrolyte membrane cannot be obtained. Therefore, it is conceivable to dispose an electrolyte membrane having a high protonation ability. However, in that case, the adhesion between the electrolyte membrane and the hydrogen separation membrane is lowered. As a result, the electrolyte membrane and the hydrogen separation membrane may be separated.

  An object of this invention is to provide the fuel cell which can perform protonation efficiently and can suppress peeling with an electrolyte membrane and a hydrogen separation membrane.

  A fuel cell according to the present invention includes a hydrogen separation membrane and an electrolyte membrane provided on the hydrogen separation membrane and having proton conductivity, and the electrolyte membrane includes a first electrolyte at an interface between the hydrogen separation membrane and the electrolyte membrane. The first electrolyte has a higher proton generation capacity than the second electrolyte, and the second electrolyte has a hydrogen separation membrane that has a close adhesion with the hydrogen separation membrane of the first electrolyte. It is characterized by being higher than sex.

  In the fuel cell according to the present invention, since the first electrolyte is disposed at the interface between the hydrogen separation membrane and the electrolyte membrane, protonation of hydrogen can be promoted. Therefore, the power generation performance of the fuel cell according to the present invention is improved. In addition, since the second electrolyte is disposed at the interface between the hydrogen separation membrane and the electrolyte membrane, the adhesion between the hydrogen separation membrane and the electrolyte membrane is improved. Thereby, peeling between the hydrogen separation membrane and the electrolyte membrane can be suppressed. From the above, the fuel cell according to the present invention can efficiently perform protonation and suppress separation of the hydrogen separation membrane and the electrolyte membrane.

The first electrolyte and the second electrolyte may be ceramics. The first electrolyte is AB _(1-x) M _x O ₃ type perovskite, the second electrolyte is AB _(1-y) N _y O ₃ type perovskite, and the electronegativity of M is N It may be higher than the electronegativity. In this case, the proton generating ability of the first electrolyte is improved. M may be In. Furthermore, the first electrolyte and the second electrolyte may be arranged in an island shape on the hydrogen separation membrane.

  According to the present invention, protonation can be efficiently performed, and peeling between the hydrogen separation membrane and the electrolyte membrane can be suppressed.

  Hereinafter, the best mode for carrying out the present invention will be described.

  FIG. 1 is a schematic cross-sectional view of a fuel cell 100 according to a first embodiment of the present invention. As shown in FIG. 1, the fuel cell 100 has a structure in which an electrolyte membrane 20 and a cathode 30 are sequentially laminated on a hydrogen separation membrane 10. The hydrogen separation membrane 10 is made of a dense hydrogen permeable metal layer. The hydrogen separation membrane 10 functions as an anode to which fuel gas is supplied, and also functions as a support that supports and reinforces the electrolyte membrane 20. In this embodiment, the hydrogen separation membrane 10 is made of a hydrogen permeable metal such as palladium, a palladium alloy, or vanadium having palladium formed on the surface thereof. The film thickness of the hydrogen separation membrane 10 is, for example, about 80 μm. The cathode 30 is an electrode to which an oxidant gas is supplied, and is made of a conductive material such as lanthanum cobaltite, lanthanum manganate, silver, platinum, or platinum-supported carbon. The film thickness of the cathode 30 is, for example, about 30 μm.

  The electrolyte membrane 20 includes a first electrolyte 21 and a second electrolyte 22 having proton conductivity. The first electrolyte 21 is arranged in an island shape on the hydrogen separation membrane 10 with a predetermined interval. The second electrolyte 22 is disposed so as to cover the exposed portion of the hydrogen separation membrane 10 on the electrolyte membrane 20 side and the first electrolyte 21. That is, both the first electrolyte 21 and the second electrolyte 22 are in contact with the hydrogen separation membrane 10. The first electrolyte 21 is disposed, for example, with an interval of about 5 nm. The thickness of the first electrolyte 21 in the stacking direction is, for example, about 5 nm. The thickness of the electrolyte membrane 20 is, for example, about 2 μm.

  The proton generation capacity of the first electrolyte 21 is higher than the proton generation capacity of the second electrolyte 22, and the adhesion of the second electrolyte 22 to the hydrogen separation membrane 10 is higher than the adhesion of the first electrolyte 21 to the hydrogen separation membrane 10. The material of the 1st electrolyte 21 and the 2nd electrolyte 22 is selected so that it may become high. The first electrolyte 21 and the second electrolyte 22 are made of ceramics, for example.

In the present embodiment, the first electrolyte 21 is AB _(1-x) M _x O ₃ type perovskite, and the second electrolyte 22 is AB _(1-y) N _y O ₃ type perovskite. Here, x is a value that satisfies 0 <x <1, and y is a value that satisfies 0 <y <1. Metal M and metal N are doped metals having a valence smaller than +4. Metal M has an electronegativity greater than that of metal N. Thereby, the proton generating ability of the first electrolyte becomes larger than the proton generating ability of the second electrolyte 22. This is because a metal having a high electronegativity easily extracts electrons from hydrogen atoms. In addition, the adhesiveness with the hydrogen separation membrane of the electrolyte doped with the metal having high electronegativity is lower than the adhesiveness with the hydrogen separation membrane of the electrolyte doped with the metal with low electronegativity.

As the metal M, In or the like can be used. Also. As the metal N, Yb, Y or the like can be used. As the A site, Sr, Ba, Ca, or the like can be used. Zr, Ce, etc. can be used as the B site. Specific examples of the first electrolyte _{21, SrZr 1-x In x} O 3, BaZr 1-x In x O 3, CaZr 1-x In x O 3, BaCe 1-x In x O 3, SrCe 1-x In _x O ₃ or the like can be used. Specific examples of the second electrolyte _22, can be used _{SrZr 1-y Yb y O 3} , BaZr 1-y Y y O 3 or the like.

  As described above, by arranging the first electrolyte 21 at the interface between the hydrogen separation membrane 10 and the electrolyte membrane 20, protonation of hydrogen can be promoted. Therefore, the power generation performance of the fuel cell 100 is improved. Further, by arranging the second electrolyte 22 at the interface between the hydrogen separation membrane 10 and the electrolyte membrane 20, the adhesion between the hydrogen separation membrane 10 and the electrolyte membrane 20 is improved. Thereby, peeling between the hydrogen separation membrane 10 and the electrolyte membrane 20 can be suppressed. From the above, the fuel cell 100 can perform protonation efficiently and can suppress the separation between the hydrogen separation membrane 10 and the electrolyte membrane 20.

  The occupied area of the first electrolyte 21 and the second electrolyte 22 at the interface between the hydrogen separation membrane 10 and the electrolyte membrane 20 is preferably about 50% each. In this embodiment, the hydrogen separation membrane 10 is made of palladium or the like, but the metal that can be used as the hydrogen separation membrane 10 is not particularly limited as long as it has hydrogen permeability. Examples of the metal constituting the hydrogen separation membrane 10 include palladium, vanadium, titanium, tantalum, and alloys thereof.

  Further, the arrangement of the first electrolyte 21 and the second electrolyte 22 may be reversed depending on the level of proton conductivity. For example, when the proton conductivity of the first electrolyte 21 is higher than the proton conductivity of the second electrolyte 22, the second electrolyte 22 may be disposed so as to cover the first electrolyte 21 as shown in FIG. On the other hand, when the proton conductivity of the second electrolyte 22 is larger than the proton conductivity of the first electrolyte 21, the second electrolyte 22 is arranged in an island shape on the hydrogen separation membrane 10, and the second electrolyte 22 and hydrogen The first electrolyte 21 may be disposed so as to cover the separation membrane 10. This is to improve the proton conductivity of the entire electrolyte membrane 20.

Table 1 shows combinations of the first electrolyte 21 and the second electrolyte 22 when the proton conductivity of the second electrolyte 22 is larger than the proton conductivity of the first electrolyte 21. For example, if SrZr _1-x In _x O ₃ is used as the first electrolyte 21 and SrZr _1-y Yb _y O ₃ is used as the second electrolyte 22, the proton conductivity of the second electrolyte 22 is the proton of the first electrolyte 21. It becomes larger than the conductivity.

  Then, the manufacturing method of the fuel cell 100 is demonstrated. FIG. 2 is a flowchart showing the manufacturing process of the fuel cell 100. First, as shown in FIG. 2A, a hydrogen separation membrane 10 is prepared. Next, as shown in FIG. 2B, a first electrolyte 21 is formed on the hydrogen separation membrane 10 by physical vapor deposition or the like. In this case, the first electrolyte 21 can be formed in an island shape by setting the film thickness of the first electrolyte 21 to about several nm.

  Next, as shown in FIG. 2C, the second electrolyte 22 is formed on the hydrogen separation membrane 10 and the first electrolyte 21 by physical vapor deposition or the like. Thereby, the electrolyte membrane 20 can be formed. Next, as shown in FIG. 2D, a cathode 30 is formed on the electrolyte membrane 20 by physical vapor deposition or the like. The fuel cell 100 is completed through the above steps.

  The first electrolyte 21 can also be formed by applying a binder (organic binder) mixed with the electrolyte components constituting the first electrolyte 21 on the hydrogen separation membrane 10 and burning the binder. .

  Subsequently, a fuel cell 100a according to a second embodiment of the present invention will be described. FIG. 3 is a schematic cross-sectional view of the fuel cell 100a. The fuel cell 100a differs from the fuel cell 100 of FIG. 1 in that an electrolyte membrane 20a is provided instead of the electrolyte membrane 20. In the electrolyte membrane 20a, the first electrolyte 21 and the second electrolyte 22 are randomly dispersed in the form of particles. Therefore, both the first electrolyte 21 and the second electrolyte 22 are in contact with the hydrogen separation membrane 10 at the interface between the hydrogen separation membrane 10 and the electrolyte membrane 20a. The average particle diameter of the first electrolyte 21 and the second electrolyte 22 is, for example, about 10 μm.

  Since the first electrolyte membrane 21 is present at the interface between the hydrogen separation membrane 10 and the electrolyte membrane 20a, protonation of hydrogen can be promoted. Therefore, the power generation performance of the fuel cell 100a is improved. In addition, since the second electrolyte membrane 22 is interposed at the interface between the hydrogen separation membrane 10 and the electrolyte membrane 20a, the adhesion between the hydrogen separation membrane 10 and the electrolyte membrane 20a is improved. Thereby, peeling between the hydrogen separation membrane 10 and the electrolyte membrane 20a can be suppressed. From the above, the fuel cell 100a can efficiently perform protonation and can suppress the separation between the hydrogen separation membrane 10 and the electrolyte membrane 20a.

  In addition, the 1st electrolyte 21 and the 2nd electrolyte 22 should just be arrange | positioned at the interface of the hydrogen separation membrane 10 and the electrolyte membrane 20a. Therefore, an electrolyte having a relatively high proton conductivity may be disposed in the region on the cathode 30 side of the electrolyte membrane 20a.

  Then, the manufacturing method of the fuel cell 100a is demonstrated. FIG. 4 is a flowchart showing the manufacturing process of the fuel cell 100a. First, as shown in FIG. 4A, a hydrogen separation membrane 10 is prepared. Next, as shown in FIG. 4B, an electrolyte membrane 20a is formed on the hydrogen separation membrane 10 by physical vapor deposition or the like. In this case, the oxide film 20a is formed by using the oxide constituting the first electrolyte 21 and the oxide constituting the second electrolyte 22 as targets and alternately supplying energy to each target during physical vapor deposition. be able to. Next, as shown in FIG. 4C, a cathode 30 is formed on the electrolyte membrane 20a by physical vapor deposition or the like. The fuel cell 100a is completed through the above steps.

1 is a schematic cross-sectional view of a fuel cell according to a first embodiment. It is a flowchart which shows the manufacturing process of the fuel cell which concerns on 1st Example. It is typical sectional drawing of the fuel cell which concerns on 2nd Example. It is a flowchart which shows the manufacturing process of the fuel cell which concerns on 2nd Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Hydrogen separation membrane 20,20a Electrolyte membrane 21 1st electrolyte 22 2nd electrolyte 30 Cathode 100,100a Fuel cell

Claims (5)

A hydrogen separation membrane;
An electrolyte membrane provided on the hydrogen separation membrane and having proton conductivity,
The electrolyte membrane includes a first electrolyte and a second electrolyte at an interface between the hydrogen separation membrane and the electrolyte membrane,
The proton generating capacity of the first electrolyte is higher than the proton generating capacity of the second electrolyte,
The fuel cell according to claim 1, wherein the adhesion of the second electrolyte to the hydrogen separation membrane is higher than the adhesion of the first electrolyte to the hydrogen separation membrane. The fuel cell according to claim 1, wherein the first electrolyte and the second electrolyte are ceramics. The first electrolyte is AB _(1-x) M _x O ₃ type perovskite,
The second electrolyte is AB _(1-y) N _y O ₃ type perovskite,
3. The fuel cell according to claim 2, wherein the electronegativity of M is higher than the electronegativity of N. The fuel cell according to claim 3, wherein the M is In. The fuel cell according to claim 1, wherein the first electrolyte and the second electrolyte are arranged in an island shape on the hydrogen separation membrane.

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