JP6192063B2 - Composite membrane structure and fuel cell - Google Patents

Description

  The present invention relates to a composite membrane structure comprising a solid electrolyte membrane-hydrogen permeable metal membrane, a fuel cell, and a method for producing them. Such a composite membrane structure is particularly suitable for a fuel cell that operates in an intermediate temperature range.

  As fuel cells, PAFC (phosphoric acid fuel cell), MCFC (molten carbonate fuel cell), SOFC (solid electrolyte fuel cell), PEFC (solid polymer fuel cell), and the like have been proposed. The operating temperature of each fuel cell varies, for example, about 80 ° C. for PEFC (solid polymer fuel cell) and about 1000 ° C. for SOFC (solid electrolyte fuel cell).

Applicant _{is, AECeO} 3 (AE: 2-valent alkaline earth metal) proton conductivity while also maintaining, under a mixed gas atmosphere environment to overcome the vulnerability to CO ₂ of the AECeO ₃ containing CO ₂ of However, a proton conductive oxide membrane-hydrogen permeable membrane that can be used has been previously proposed (see Patent Document 1). In Patent Document 1, if such a proton conductive oxide membrane-hydrogen permeable membrane is applied to develop a fuel cell that operates in an intermediate temperature range of about 250 to 500 ° C., performance and materials are improved as compared with existing fuel cells. This indicates that there is a possibility that the fuel cell will be superior in terms of aspect.

  In order to apply the proton conductive oxide membrane-hydrogen permeable membrane disclosed in Patent Document 1 to a fuel cell that operates in an intermediate temperature range, the proton conductive solid electrolyte is thinned to reduce the internal resistance of the solid electrolyte. Is required. However, while maintaining the performance of a material having a relatively low melting point, for example, a hydrogen permeable membrane made of palladium, it has been difficult to reduce the thickness of the proton conductive solid electrolyte and maintain its characteristics.

  Also proposed are a metal substrate having hydrogen permeation performance, a hydrogen permeable structure formed thereon and a proton conductive oxide film having a thickness of 20 μm or less, and a fuel cell using this hydrogen permeable structure. (See Patent Document 2). In Patent Document 2, as a method for forming a layer of a proton conductive oxide film, a method using a wet process such as a sputtering method, an electron beam evaporation method, a laser ablation method, or a sol-gel method is cited. However, there is a problem that the production costs are high and it is difficult to form a dense proton conductive oxide film composed of a single phase while maintaining the performance of the hydrogen permeable film.

  If the proton conductive oxide film is not a single phase or a dense film, the performance of selectively permeating hydrogen may be reduced, or a desired internal resistance may not be obtained. There is a problem that power generation characteristics are deteriorated due to such problems.

  Such problems are not limited to composite membrane structures made of solid electrolyte-hydrogen permeable metal membranes used in fuel cells, but also to other electrochemical devices such as hydrogen sensors, hydrogen pumps, water vapor sensors, and exhaust gas purification devices. The same exists in the composite membrane structure used.

  Therefore, the present applicant has proposed a composite membrane structure composed of a hydrogen permeable metal membrane and a thin solid electrolyte membrane (see Patent Document 3).

JP 2006-054170 A JP 2007-026946 A JP 2011-029149 A

  The composite membrane structure of Patent Document 3 can be manufactured at low cost, has low internal resistance, and is excellent in electrochemical characteristics such as power generation characteristics and hydrogen permeability. There is a need for composite membrane structures with excellent chemical properties.

  In view of such circumstances, it is an object of the present invention to provide a composite membrane structure and a fuel cell excellent in electrochemical characteristics, and a method for producing them.

  A first aspect of the present invention is a composite membrane structure comprising a hydrogen permeable metal membrane and a solid electrolyte membrane, wherein the solid electrolyte membrane is applied on the surface of the hydrogen permeable metal membrane that has been subjected to thermal oxidation treatment. The basic structure is a perovskite-type oxide that is formed by the method and has a divalent alkaline earth metal arranged at the A site and at least one of tetravalent cerium and tetravalent zirconium arranged at the B site. And a compound having a crystal structure in which a part of the tetravalent B-site element is substituted with a trivalent rare earth element, the solid electrolyte film comprising an alkaline earth metal, at least one of cerium and zirconium, and a rare earth element And forming a first solid electrolyte precursor film by crystallizing the first solid electrolyte precursor film by a rapid heating process. In composite membrane structure comprising: a solid electrolyte membrane.

  According to this aspect, the metal oxide film is not formed between the hydrogen permeable metal film and the solid electrolyte film by crystallizing the first solid electrolyte precursor film by the rapid heating process. In addition, the adhesion between the hydrogen permeable metal membrane and the solid electrolyte membrane can be improved. Thereby, it can be set as the composite film structure excellent in the electrochemical characteristic.

  Here, the solid electrolyte membrane forms a second solid electrolyte precursor membrane by irradiating energy rays after applying the organometallic acid salt solution on the hydrogen permeable metal membrane or the first solid electrolyte membrane. It is preferable to further include a second solid electrolyte membrane formed by crystallizing the second solid electrolyte precursor membrane by rapid heating treatment.

  According to this, the 2nd solid electrolyte precursor film | membrane obtained by irradiating an energy ray can be made into a precise | minute 2nd solid electrolyte film by crystallizing by rapid temperature rising heat processing. By providing the first solid electrolyte membrane and the second solid electrolyte membrane, a composite membrane structure having more excellent electrochemical characteristics can be obtained.

  As a preferred embodiment of the present invention, the solid electrolyte membrane includes one or more first solid electrolyte membranes and one or more second solid electrolyte membranes.

  As a preferred embodiment of the present invention, the solid electrolyte membrane may be composed of the second solid electrolyte membrane and the first solid electrolyte membrane provided on both surfaces of the second solid electrolyte membrane. .

  Another aspect of the present invention is a composite membrane structure comprising a hydrogen permeable metal membrane and a solid electrolyte membrane, wherein the solid electrolyte membrane is coated on the surface of the hydrogen permeable metal membrane that has been subjected to thermal oxidation treatment. A perovskite oxide having a basic structure in which a divalent alkaline earth metal is arranged at the A site and at least one of tetravalent cerium and tetravalent zirconium is arranged at the B site; A compound having a crystal structure in which a part of a tetravalent B site element is substituted with a trivalent rare earth element, and the solid electrolyte film includes an alkaline earth metal, at least one of cerium and zirconium, a rare earth element, The solid electrolyte precursor film is formed by applying an organometallic acid salt solution containing, and after irradiating the solid electrolyte precursor film with energy rays, the solid electrolyte precursor film is subjected to rapid heating treatment. In composite membrane structure, characterized in that formed by crystallization by.

  According to this aspect, the solid electrolyte precursor film obtained by irradiating the energy beam is crystallized by a rapid temperature increase heat treatment, thereby forming a metal oxide film between the hydrogen permeable metal film and the solid electrolyte film. In addition to the above, it can be a dense solid electrolyte membrane. Thereby, it can be set as the composite film structure excellent in the electrochemical characteristic.

  Here, the alkaline earth metal is preferably at least one of barium (Ba) and strontium (Sr). According to this, it can be set as the composite film structure excellent in the electric power generation characteristic.

  The trivalent rare earth element is a group consisting of ytterbium (Yb), erbium (Er), yttrium (Y), dysprosium (Dy), gadolinium (Gd), samarium (Sm), and neodymium (Nd). It is preferable that it is at least one more selected. According to this, it can be set as the composite film structure excellent in the electric power generation characteristic.

  As a preferred embodiment of the present invention, the hydrogen permeable metal film may be a palladium metal film.

  Another aspect of the present invention includes the composite membrane structure described above, and includes a cathode on the surface of the solid electrolyte membrane opposite to the hydrogen permeable metal membrane, and the hydrogen permeable metal membrane serves as an anode. It is in the fuel cell characterized by having.

  According to this aspect, a fuel cell having excellent electrochemical characteristics can be obtained.

  Another aspect of the present invention is a method for producing a composite membrane structure comprising a hydrogen permeable metal membrane and a solid electrolyte membrane, the step of thermally oxidizing at least one surface of the hydrogen permeable metal membrane, A perovskite type oxidation in which a divalent alkaline earth metal is arranged at the A site and at least one of tetravalent cerium and tetravalent zirconium is arranged at the B site on the surface of the hydrogen permeable metal film that has been thermally oxidized. Forming a solid electrolyte film comprising a compound having a basic structure and a crystal structure in which a part of a tetravalent B-site element is substituted with a trivalent rare earth element, and forming the solid electrolyte film Applying the organic metal salt solution containing an alkaline earth metal, at least one of cerium and zirconium, and a rare earth element to form a solid electrolyte precursor film; and A method for producing a composite membrane structure comprising a step of forming a first solid electrolyte membrane by a firing step in which the solid electrolyte precursor membrane is fired at a low temperature of 900 ° C. or less by rapid thermal annealing and crystallized. It is in.

  According to this aspect, the metal oxide film is not formed between the hydrogen permeable metal film and the solid electrolyte film by crystallizing the first solid electrolyte precursor film by the rapid heating process. In addition, the adhesion between the hydrogen permeable metal membrane and the solid electrolyte membrane can be improved. Thereby, the composite film structure excellent in electrochemical characteristics can be manufactured.

  Here, the solid electrolyte membrane forming step further includes a coating / irradiating step of forming a second solid electrolyte precursor membrane by irradiating energy rays after applying the organometallic acid salt solution, and the second solid electrolyte. It is preferable to include a step of forming the second solid electrolyte membrane by a baking step of baking and crystallizing the precursor film at a low temperature of 900 ° C. or lower by rapid temperature rising heat treatment.

  According to this, the 2nd solid electrolyte precursor film | membrane obtained by irradiating an energy ray can be made into a precise | minute 2nd solid electrolyte film by crystallizing by rapid temperature rising heat processing. By providing the first solid electrolyte membrane and the second solid electrolyte membrane, a composite membrane structure having more excellent electrochemical characteristics can be obtained.

  Moreover, it is preferable that the rapid temperature increase heat treatment is performed at a rapid temperature increase rate of 50 to 200 ° C./min. According to this, the composite film structure excellent in electrochemical characteristics can be manufactured more reliably.

  The rapid temperature raising heat treatment is preferably heated to 800 ° C. or higher and 900 ° C. or lower. According to this, the composite film structure excellent in electrochemical characteristics can be manufactured more reliably.

  According to another aspect of the present invention, there is provided a solid electrolyte membrane, an anode made of a hydrogen permeable metal film formed on one side of the solid electrolyte membrane, and a cathode formed on the other side of the solid electrolyte membrane. A method of manufacturing a fuel cell comprising: a step of thermally oxidizing at least one surface of a hydrogen permeable metal membrane; and a divalent alkaline earth on the surface of the hydrogen permeable metal membrane subjected to a thermal oxidation treatment The basic structure is a perovskite oxide in which metal is arranged at the A site and at least one of tetravalent cerium and tetravalent zirconium is arranged at the B site, and a part of the tetravalent B site element is a trivalent rare earth. Forming a solid electrolyte membrane made of a compound having a crystal structure substituted with an element, and the step of forming the solid electrolyte membrane includes a small amount of alkaline earth metal, cerium and zirconium. A coating step in which an organometallic acid salt solution containing at least one element and a rare earth element is applied to form a solid electrolyte precursor film; and the solid electrolyte precursor film is heated at a low temperature of 900 ° C. or lower by rapid thermal annealing. The fuel cell manufacturing method includes a step of forming a first solid electrolyte membrane by a baking step of baking and crystallizing.

  According to this aspect, a fuel cell excellent in electrochemical characteristics can be manufactured.

  Here, a coating / irradiation step of forming a second solid electrolyte precursor film by irradiating energy rays after applying the organometallic acid salt solution, and the second solid electrolyte precursor film by rapid heating treatment 900 It is preferable to include a step of forming the second solid electrolyte membrane by a baking step of baking and crystallizing at a low temperature of not higher than ° C. According to this, a fuel cell with more excellent electrochemical characteristics can be obtained.

It is the figure which showed simply the structure of the composite film structure which concerns on Embodiment 1. FIG. 2A and 2B are a plan view and a cross-sectional view illustrating the structure of the fuel cell according to Embodiment 1. 1 is an explanatory diagram showing a structure of a fuel cell according to Embodiment 1. FIG. It is the figure which showed the structure of the composite film structure concerning Embodiment 2 simply. FIG. 5 is a plan view and a cross-sectional view showing a structure of a fuel cell according to Embodiment 2. It is the figure which showed simply the structure of the composite film structure which concerns on Embodiment 3. FIG. FIG. 5 is an explanatory diagram showing a structure of a fuel cell according to Embodiment 3. It is a cross-section backscattered electron image of Examples 1-2 and Comparative Examples 1-2. It is a graph which shows the XRD measurement result of Example 2 and Comparative Examples 1-2. It is a graph which shows the electrical conductivity of Example 2 and Comparative Examples 1-2. It is a graph which shows the electric power generation performance test result of Example 4. It is a graph which shows the electric power generation performance test result of Example 4. It is a cross-section backscattered electron image of Examples 2, 5, and 6. It is a graph which shows the XRD measurement result of Example 2, 5, 6.

(Embodiment 1)
Hereinafter, the present invention will be described in detail based on embodiments.

  FIG. 1 is a diagram simply showing the structure of the composite membrane structure of the present embodiment.

  As shown in FIG. 1, the composite membrane structure according to the present invention comprises a hydrogen permeable metal membrane 1 and a solid electrolyte membrane 2, and the interface is in a continuously joined state. The hydrogen permeable metal membrane 1 and the solid electrolyte membrane 2 are hydrogen permeable membranes capable of separating hydrogen.

The hydrogen permeable metal membrane 1 is capable of separating only hydrogen from a mixed gas such as H ₂ (hydrogen) or CO ₂ (carbon dioxide), and specifically, hydrogen molecules are converted into protons (H ⁺ ). And electrons (e ⁻ ).

The hydrogen permeable metal membrane 1 may be made of a material that can pass protons (H ⁺ ) and can separate only hydrogen from a gas containing CO ₂ . Examples of such materials include palladium, niobium, tantalum, lanthanum, titanium, zirconium, copper, nickel, and alloys thereof with silver, and palladium-based metals are preferable. As will be described in detail later, the hydrogen-permeable metal film made of a palladium-based metal can easily thermally oxidize only the extreme surface that does not impair the original hydrogen permeability when the surface is thermally oxidized. Specific examples of the palladium-based metal include palladium, an alloy of palladium and silver, an alloy of palladium and platinum, and an alloy of palladium and copper, and in particular, palladium and silver having an effect of suppressing hydrogen embrittlement. Alloys are preferred. The hydrogen permeable metal film 1 may be a single layer or a laminate of the same or different materials. In the present embodiment, the hydrogen permeable metal film 1 is made of an alloy of palladium and silver.

The solid electrolyte membrane 2 has a basic structure of a perovskite oxide (ABO ₃ ) in which a divalent alkaline earth metal is arranged at the A site and at least one of tetravalent cerium and tetravalent zirconium is arranged at the B site. And a compound having a crystal structure in which part of the B site is substituted with a trivalent rare earth element. The solid electrolyte membrane 2 is a proton conductive electrolyte membrane capable of separating only hydrogen from a hybrid gas such as H ₂ (hydrogen) or CO ₂ (carbon dioxide).

The solid electrolyte membrane 2 according to this embodiment includes a perovskite oxide (ABO) in which a divalent alkaline earth metal is arranged at the A site and at least one of tetravalent cerium and tetravalent zirconium is arranged at the B site. ₃ ) and a compound having a crystal structure in which a part of the tetravalent B site element is substituted with a trivalent rare earth element. The tetravalent B site element referred to here is tetravalent cerium or / and tetravalent zirconium arranged at the B site. This perovskite-type oxide (ABO ₃ ) is one in which proton ion vacancies are generated to express proton conductivity, and a part of the tetravalent B site element is substituted with a trivalent rare earth element. Has been. If, for example, Ce ⁴⁺ → Yb ³⁺ is substituted by a trivalent rare earth element, the electrical neutrality in the crystal lattice is lost, and in order to compensate for this, ½ oxygen in the lattice is lost. Then, the electrical neutrality in the lattice is maintained. In this manner, oxide ion vacancies can be intentionally generated (doping), and proton generation is further promoted.

  Examples of the divalent alkaline earth metal to be distributed at the B site include barium (Ba) and strontium (Sr). It is preferable to distribute barium, strontium, or any one of barium and strontium to the B site.

  Examples of trivalent rare earth elements include ytterbium (Yb), erbium (Er), yttrium (Y), dysprosium (Dy), gadolinium (Gd), samarium (Sm), and neodymium (Nd). When the membrane structure is applied to an intermediate temperature fuel cell, yttrium (Y), gadolinium (Gd), and samarium (Sm) that exhibit good proton conductivity in an intermediate temperature range and a hydrogen stream are preferable.

The solid electrolyte membrane 2 is composed of a first solid electrolyte membrane 21 formed by a method described in detail later. The first solid electrolyte membrane 21 is composed of a single phase. The single phase here refers to a main peak of carbonate (for example, BaCO ₃ ) and a main peak of perovskite (ABO ₃ ) that are easily generated from an alkaline earth metal at the A site in an X-ray diffraction (XRD) pattern. The strength ratio is less than 0.05, preferably less than 0.02. The solid electrolyte membrane 2 of the present invention is excellent in proton conductivity by being composed of a single phase.

  The solid electrolyte membrane 2 has a thickness of 30 μm or less, preferably 10 μm or less, more preferably 3 μm or less. By making the solid electrolyte membrane 2 a thin film, the internal resistance of the solid electrolyte membrane 2 can be made extremely low.

In the present embodiment, the hydrogen permeable metal film 1 is an alloy of palladium and silver having a thickness of 200 μm, and the solid electrolyte film 2 is a part of cerium trioxide (BaCeO ₃ ) cerium substituted with yttrium (Y). A 1 μm-thick film made of the BaCe _0.9 Y _0.1 O _3-α structure (hereinafter referred to as BCYO) was used.

  The above-described solid electrolyte membrane 2 is formed by a coating method on the surface of the hydrogen permeable metal membrane 1 subjected to the thermal oxidation treatment. The coating method referred to here is a method of applying a precursor solution and baking it, and examples thereof include a MOD method. Specifically, the solid electrolyte membrane 2 according to the present embodiment includes an organometallic acid salt solution containing an alkaline earth metal, at least one of cerium and zirconium, and a rare earth element. A first solid electrolyte precursor film is formed by coating on a thermally oxidized surface to form a first solid electrolyte precursor film, and the first solid electrolyte precursor film is crystallized by rapid heating treatment. .

  As described above, first, one surface of the hydrogen permeable metal film 1 is subjected to thermal oxidation treatment. At this time, the hydrogen permeable metal film 1 only needs to be subjected to thermal oxidation treatment on the one surface so that the original hydrogen permeability is not impaired, and the inside and the other surface are preferably not oxidized. This is because the original characteristics can be suitably maintained by subjecting only one surface to the thermal oxidation treatment. Note that the thermal oxidation treatment refers to heat treatment of one surface of the hydrogen permeable metal film 1 in an oxygen-containing atmosphere, for example, air.

  Then, an organometallic acid salt solution containing an alkaline earth metal, at least one of cerium and zirconium, and a rare earth element is applied to the thermally oxidized pole surface of the hydrogen permeable metal film 1 to form a first solid. An electrolyte precursor film is formed. Thereafter, the first solid electrolyte precursor film 21 is formed by crystallizing the first solid electrolyte precursor film by a rapid heating process.

  As described above, the first solid electrolyte precursor film is crystallized by rapid heating treatment to maintain the properties of the film obtained by the coating method, and between the hydrogen permeable metal film 1 and the solid electrolyte film 2. The formation of a metal oxide film can be suppressed. In other words, the solid electrolyte membrane 2 (first solid electrolyte membrane 21) in which remarkably densification is suppressed can be formed without almost oxidizing the surface of the hydrogen permeable metal membrane 1. For example, when crystallized by ordinary heat treatment, the solid electrolyte membrane 2 having many pores and a relative density of about 80% is formed, and the hydrogen permeable metal membrane 1 is slightly oxidized. On the other hand, in this embodiment, the hydrogen permeable metal film 1 is hardly oxidized and the solid electrolyte film 2 having a certain degree of pores, for example, a relative density of about 80 to 90% can be formed.

The “relative density” means a value calculated by the following equation using an experimentally obtained actual density ρ and a theoretical density ρ ₀ .
[Relative density (%)] = (ρ / ρ ₀ ) × 100 (5)

  As described above, since the solid electrolyte membrane 2 (first solid electrolyte membrane 21) is not completely densified, it can flexibly follow the thermal behavior such as thermal expansion of the hydrogen permeable metal membrane 1. it can. For this reason, the difference in thermal expansion coefficient between the hydrogen permeable metal film 1 and the solid electrolyte film 2 is alleviated, and the hydrogen permeable metal film 1 and the solid electrolyte film 2 are prevented from being peeled off to achieve adhesion. It can be excellent. In addition, by crystallization of the first solid electrolyte precursor film by rapid heating treatment, it is possible to suppress the hydrogen permeable metal film 1 from being oxidized when the first solid electrolyte precursor film is crystallized. The metal oxide film may not be formed between the hydrogen permeable metal film 1 and the solid electrolyte film 2. Thereby, the fall of the electrical conductivity resulting from an oxide film is suppressed, and it can be set as a composite film structure with high electrical conductivity.

In addition, by forming the solid electrolyte membrane 2 after thermally oxidizing the extreme surface of the hydrogen permeable metal membrane 1, the solid electrolyte membrane 2 becomes a single phase despite being formed by low-temperature firing. Incidentally, when the electrode surface is fired at a low temperature without thermal oxidation treatment, the solid electrolyte membrane 2 does not become a single phase, and crystals of an alkaline earth metal carbonate such as barium carbonate (BaCO ₃ ) or cerium oxide (CeO ₂ ) are formed. It will be mixed.

  As described above, the composite membrane structure is composed of the hydrogen-permeable metal membrane 1 that maintains its performance and the solid electrolyte membrane 2 that is a single-phase thin film. Such a composite membrane structure has excellent hydrogen permeability and excellent electrochemical characteristics such as conductive characteristics.

In the composite membrane structure described above, the hydrogen permeable metal membrane 1 and the solid electrolyte membrane 2 may be supported by a porous support. Such a porous support may be any material that does not affect the functions of the hydrogen permeable metal membrane 1 and the solid electrolyte membrane 2 for separating hydrogen from the gas, and hydrogen is permeable to hydrogen as protons (H ⁺ ). What is necessary is just to be excellent in gas diffusibility to such an extent that this reaction is not inhibited when entering the solid electrolyte membrane 2 from the metal membrane 1. When the porous support is provided, the strength of the composite membrane structure can be ensured by the porous support, and therefore the strength of the hydrogen permeable metal membrane 1 and the solid electrolyte membrane 2 may be low. That is, it is not necessary to ensure a predetermined strength with the hydrogen permeable metal film 1 or the solid electrolyte film 2, and therefore the hydrogen permeable metal film 1 or the solid electrolyte film 2 can be thinned.

  The composite membrane structure described above can be applied to, for example, a fuel cell, and can be suitably used in a fuel cell that operates in an intermediate temperature range.

  Here, a fuel cell using the composite membrane structure will be described. 2A and 2B are a plan view and a cross-sectional view showing the structure of the fuel cell using the composite membrane structure of the present embodiment, and FIG. 3 shows the structure of the fuel cell using the composite membrane structure of the present embodiment. It is explanatory drawing.

  As shown in FIGS. 2 and 3, the fuel cell 10 according to the present invention includes a solid electrolyte membrane 2, a hydrogen permeable metal membrane 1 as an anode formed on one side of the solid electrolyte membrane 2, and a solid electrolyte. The cathode 4 is formed on the other side of the membrane 2. Here, the hydrogen permeable metal membrane 1 and the solid electrolyte membrane 2 are the composite membrane structure 3 according to the present invention.

The fuel cell 10 has a structure in which the composite membrane structure 3 has a structure in which the hydrogen permeable metal membrane 1 and the solid electrolyte membrane 2 made of a proton conductive oxide film complement each other's disadvantages so that proton conductivity can be obtained. Can be used in a gas atmosphere environment containing CO ₂ by overcoming the vulnerability of the solid electrolyte membrane 2 to CO ₂ . In the present embodiment, the fuel cell 10 is in a state where another membrane (specifically, the hydrogen permeable metal membrane 1) is interposed between the solid electrolyte membrane 2 made of BCYO and the gas, in other words, BCYO. In this state, a hydrogen-permeable protective membrane element is formed on the surface of the solid electrolyte membrane 2 made of the material, and decomposition of BCYO by CO ₂ can be prevented.

In the fuel cell 10, when hydrogen moves between phases from the solid phase (hydrogen permeable metal membrane 1) to the solid phase (solid electrolyte membrane 2), it does not move as a hydrogen element or a hydrogen molecule, but in FIG. As shown, it is thought to move continuously as protons. In this case, the hydrogen permeable metal film 1 has a property of selectively transmitting only hydrogen (H ₂ ) and not transmitting other molecules (N ₂ , CO, CO _2, etc.). The metal film 1 can be regarded as a proton-electron mixed conductor. Therefore, the hydrogen permeable metal film 1 serves as an electrode and an electrolyte.

The cathode 4 is preferably made of a porous material, and preferably has a high intermediate temperature electrode reaction activity as the cathode. Specifically, the cathode 4 uses silver, an electron-oxide ion mixed conductive oxide having a perovskite structure, an electron-oxide ion mixed conductive oxide having a perovskite structure, and silver cermet. Electro-oxide ion mixed conductivity having a perovskite structure of La (Co, Fe) O ₃ system, Ba (Co, Fe) O ₃ system, and Sr (Co, Fe) O ₃ system preferably having high intermediate temperature electrode reaction activity Oxides are particularly preferred. In this embodiment, a perovskite structure of (Ba, Sr) (Co, Fe) O ₃ is used.

The fuel cell 10 may include a porous support, and examples thereof include a battery having a porous support on the gas side surface of the anode. Thereby, intensity | strength can be ensured, the hydrogen-permeable metal membrane 1 and the solid electrolyte membrane 2 can be thinned, and an electrical resistance can be reduced. The porous support is one that does not hinder gas diffusion, and a porous support having pores of 0.002 to 3 μm, preferably 0.004 to 0.5 μm, is appropriately selected and used. Specifically, for example, a Ni—YSZ cermet porous body having a pore of 0.1 to 0.5 μm, a Ni—Al ₂ O ₃ cermet porous body, and the like can be exemplified.

In the fuel cell 10, the solid electrolyte membrane 2 made of proton conductive BCYO is provided in a gas flow path in which hydrogen, carbon dioxide, or the like such as the reformed gas A is mixed, and functions as a hydrogen permeable membrane. . At this time, the anode and the cathode 4 made of the hydrogen permeable metal film 1 are provided on both surfaces of the solid electrolyte membrane 2, respectively, and a protective film is formed. Therefore, even if CO ₂ is contained in the reformed gas A flowing on the anode side made of the hydrogen permeable metal membrane 1, the gas atmosphere environment containing CO ₂ is overcome by overcoming the vulnerability of the solid electrolyte membrane 2 to CO ₂ . Can also be used below.

  Here, the heat resistant temperatures of the solid electrolyte membrane, the anode, and the cathode of this embodiment will be described. The heat-resistant temperatures of the solid electrolyte membrane, the anode, and the cathode of this embodiment are as shown in Table 1.

The sintering temperature (densification temperature) of the BaCeO ₃ BCYO bulk body is 1650 ° C., which is higher than the heat resistance temperature of the anode and the cathode. Here, the heat-resistant temperature is not the melting temperature of the metal or the decomposition temperature of the oxide, but the structure of the base material itself is thermally changed by sintering or the like, so that it cannot be practically used as a member. Temperature.

  Usually, when forming a thin solid electrolyte membrane, an anode or a cathode is used as a supporting substrate, and the solid electrolyte membrane is densely formed thereon. Therefore, it is desirable that the heat resistance temperature of the anode or cathode of the support substrate is higher than the sintering temperature necessary for densification of the solid electrolyte membrane.

  In this embodiment, the anode is an alloy of palladium and silver, and the melting point is 1360 ° C. on the Pd—Ag alloy phase diagram, but the actual heat resistance temperature as a substrate is lower than that in a reducing atmosphere. Presumed to be around 1200 ° C. Further, the cathode having a perovskite structure has a heat resistance temperature of about 900 to 1000 ° C. because Co is contained in the component element. Therefore, the support substrate needs to be an anode made of a metal having a higher heat resistance temperature. However, there is a problem that the heat-resistant temperature of the anode is considerably lower than the sintering temperature of normal BCYO of 1650 ° C.

  In the method for producing a composite membrane structure of the present invention, a thin-film solid electrolyte composed of a single phase can be formed on a hydrogen-permeable metal film at a low temperature, which may deteriorate the hydrogen-permeable metal film (anode). There is no.

  Hereinafter, the manufacturing method of the composite membrane structure will be described in detail.

  First, one surface of the hydrogen permeable metal film is subjected to thermal oxidation treatment. At this time, it is sufficient that the extreme surface of one surface is thermally oxidized to such an extent that the original hydrogen permeability of the hydrogen permeable metal film is not impaired, and the inside and the other surface side are not oxidized. Although the heating conditions for the thermal oxidation treatment are not particularly limited, for example, heating may be performed at 800 to 900 ° C. for 5 to 10 minutes. In the present embodiment, the extreme surface of one surface of the metal film made of an alloy of palladium and silver was thermally oxidized by heating at 900 ° C. for 10 minutes.

  Then, an organometallic acid salt solution containing an alkaline earth metal, at least one of cerium and zirconium, and a rare earth element is applied onto the surface of the hydrogen permeable metal film 1 that has been subjected to the thermal oxidation treatment to apply the first solid. An electrolyte precursor film is formed. Specifically, an organometallic acid salt solution containing an alkaline earth metal, at least one of cerium and zirconium, and a rare earth element is applied on the hydrogen permeable metal film 1 by spin coating or the like (application). Process). Here, the organometallic acid salt solution contains at least one of an alkaline earth metal, cerium and zirconium, and a rare earth element. For example, the divalent alkaline earth metal is arranged at the A site by firing. A crystal structure in which a perovskite oxide in which at least one of tetravalent cerium and tetravalent zirconium is arranged at the B site is a basic structure, and a part of the tetravalent B site element is substituted with a trivalent rare earth element. It can be formed. In the present embodiment, an organometallic acid salt solution in which a BaCeY organometallic acid salt containing barium (Ba), cerium (Ce), and yttrium (Y) metals in a desired molar ratio is dissolved in a solution is applied. . And this is dried at 100-300 degreeC (drying process). In this embodiment, the BaCeY organometallic acid salt solution was applied, heated at 150 ° C. for 3 minutes, and then dried by heating at 250 ° C. for 10 minutes.

  Next, on the first solid electrolyte precursor film of the first layer, a coating process and a drying process are sequentially repeated to form a solid electrolyte precursor film having a predetermined thickness composed of a plurality of layers. In the present embodiment, the first solid electrolyte precursor film having eight layers is used.

Next, the first solid electrolyte precursor film is baked and crystallized at a low temperature of 900 ° C. or less by rapid temperature increasing heat treatment, thereby arranging a divalent alkaline earth metal at the A site, tetravalent cerium and A perovskite-type oxide (ABO ₃ ) in which at least one of tetravalent zirconium is arranged at the B site is a basic structure, and a crystal structure in which a part of the tetravalent B site element is substituted with a trivalent rare earth element. 1 Solid electrolyte membrane 21 is formed. In the present embodiment, a solid electrolyte membrane having a crystal structure in which a portion of cerium (Ce) of barium cerium trioxide (BaCeO ₃ ) is substituted with yttrium (Y) is formed.

  The rapid temperature increase heat treatment may be performed by an RTA (Rapid Thermal Annealing) apparatus heated by irradiation with an infrared lamp, an RTA apparatus heated by a special silicon carbide heater, or the like. The rapid temperature increase heat treatment is preferably performed at a rapid temperature increase rate of 50 to 200 ° C./min, more preferably 50 to 100 ° C./min.

  The firing temperature of the solid electrolyte precursor film is 900 ° C. or less, preferably 800 to 900 ° C. In the present embodiment, the first solid electrolyte membrane 21 (solid electrolyte membrane) composed of a 1 μm-thick BCYO single phase was formed by firing at 850 ° C. for 30 minutes using an RTA apparatus.

  In the case of a conventional method for producing a composite membrane structure, for example, when the first solid electrolyte precursor film is fired by rapid heating at a temperature rising rate of 100 to 200 ° C./hour in a batch furnace, hydrogen permeability The metal film is slightly oxidized, and a thin metal oxide film (metal oxide film of a material constituting the hydrogen permeable metal film) is formed between the hydrogen permeable metal film 1 and the solid electrolyte film 2. There was a problem that. When the metal oxide film is formed, the electric conductivity of the solid electrolyte film 2 is lowered and the power generation characteristics are lowered. On the other hand, in the method for producing a composite membrane structure of the present invention, a composite in which a metal oxide film is not formed between the hydrogen permeable metal film 1 and the solid electrolyte film 2 is obtained by firing by rapid temperature increase heat treatment. It can be a membrane structure.

  As described above, the metal oxide film is formed between the hydrogen permeable metal film and the solid electrolyte film, while maintaining the characteristics of the solid electrolyte film formed by the coating method, by baking by the rapid temperature rising heat treatment. Can not be. That is, since the relative density is not significantly densified to about 80 to 90%, the first solid electrolyte membrane 21 can flexibly follow the thermal behavior, and the hydrogen permeable metal membrane 1 and the solid electrolyte can be obtained. It can be assumed that no metal oxide film is formed between the films 2. Thus, since the metal oxide film is not formed between the hydrogen permeable metal film and the solid electrolyte film, a composite membrane structure having high conductivity and excellent electrochemical characteristics can be obtained.

Further, by subjecting the extreme surface of the hydrogen permeable metal film to thermal oxidation in advance and forming a solid electrolyte film on the surface, a single-phase solid electrolyte film can be obtained at a low firing temperature. Moreover, by baking at a low temperature of 900 ° C. or less to form a solid electrolyte membrane, it is possible to suppress the hydrogen permeable metal film from being oxidized to the inside, and the hydrogen permeable metal film is not deteriorated. . That is, it is possible to form a solid electrolyte membrane composed of a single phase of barium cerium trioxide (BaCeO ₃ ) while maintaining the performance of the hydrogen permeable metal membrane. When firing at a temperature higher than 900 ° C., the oxidation of the hydrogen permeable metal film is promoted, and the entire hydrogen permeable metal film may be oxidized to deteriorate the electrical characteristics. However, when a solid electrolyte membrane is formed on a hydrogen permeable metal membrane whose surface is not oxidized, a solid electrolyte membrane comprising a barium cerium trioxide (BaCeO ₃ ) single phase can be obtained at a firing temperature of 900 ° C. or lower. In other words, barium carbonate (BaCO ₃ ) and cerium oxide (CeO ₂ ) are mixed.

  As described above, according to the method for manufacturing a composite membrane structure of the present invention, the metal oxide film is not formed between the hydrogen permeable metal film and the solid electrolyte film. A composite membrane structure excellent in electrochemical characteristics can be obtained, and a composite membrane structure excellent in adhesion between the hydrogen-permeable metal membrane and the solid electrolyte membrane can be obtained. In addition, a thin solid electrolyte membrane composed of a single phase can be realized while maintaining the performance of the hydrogen permeable metal membrane. Thereby, it is possible to produce a composite membrane structure having excellent mechanical characteristics, low internal resistance, excellent electrochemical characteristics such as conductive characteristics, and excellent hydrogen permeability.

  As described above, by forming the solid electrolyte membrane by the coating method, it is possible to easily cope with a large area or a complicated shape. Further, as in this embodiment, by forming a solid electrolyte membrane by a MOD (Metal-Organic Decomposition) method, not only the control of the composition becomes easy, but also a solid electrolyte membrane that is uniform at the molecular level is formed. Can do. In addition, since the MOD method is stable and does not change with time like the sol-gel method, a desired solid electrolyte membrane can be easily formed. Furthermore, since a vacuum process is not required, it can be manufactured at low cost.

(Embodiment 2)
Hereinafter, the present invention will be described in detail based on Embodiment 2. In addition, the same code | symbol is attached | subjected to the same member as Embodiment 1, and the overlapping description is abbreviate | omitted.

  FIG. 4 is a diagram simply showing the structure of the composite membrane structure of the present embodiment.

  As shown in FIG. 4, the composite membrane structure according to the present invention comprises a hydrogen permeable metal membrane 1 and a solid electrolyte membrane 2A, and the interface is continuously joined. The hydrogen permeable metal membrane 1 and the solid electrolyte membrane 2A are hydrogen permeable membranes capable of separating hydrogen.

The solid electrolyte membrane 2A has a basic structure of a perovskite oxide (ABO ₃ ) in which a divalent alkaline earth metal is arranged at the A site and at least one of tetravalent cerium and tetravalent zirconium is arranged at the B site. And a compound having a crystal structure in which part of the B site is substituted with a trivalent rare earth element.

Further, the solid electrolyte membrane 2A is composed of a second solid electrolyte membrane 22 formed by a method described in detail later. The second solid electrolyte membrane 22 is composed of a single phase. The single phase here refers to a main peak of carbonate (for example, BaCO ₃ ) and a main peak of perovskite (ABO ₃ ) that are easily generated from an alkaline earth metal at the A site in an X-ray diffraction (XRD) pattern. The strength ratio is less than 0.05, preferably less than 0.02. The solid electrolyte membrane 2A of the present embodiment is excellent in proton conductivity by being composed of a single phase.

  Further, the solid electrolyte membrane 2A has a thickness of 30 μm or less, preferably 10 μm or less, more preferably 3 μm or less. By making the solid electrolyte membrane 2A a thin film, the internal resistance of the solid electrolyte membrane 2A can be made extremely low.

In the present embodiment, the hydrogen permeable metal film 1 is an alloy of palladium and silver having a thickness of 200 μm, and the solid electrolyte film 2A is a part of cerium trioxide (BaCeO ₃ ) cerium substituted with yttrium (Y). A 1 μm-thick film made of the BaCe _0.9 Y _0.1 O _3-α structure (hereinafter referred to as BCYO) was used.

  The above-described solid electrolyte membrane 2A is formed by a coating method on the surface of the hydrogen permeable metal membrane 1 subjected to the thermal oxidation treatment. Specifically, the solid electrolyte membrane 2 </ b> A according to the present embodiment is obtained by using an organometallic acid salt solution containing an alkaline earth metal, at least one of cerium and zirconium, and a rare earth element as a hydrogen permeable metal membrane 1. A second solid electrolyte precursor film is formed by irradiating energy rays after coating on the surface subjected to thermal oxidation treatment to form a second solid electrolyte precursor film, and crystallizing the second solid electrolyte precursor film by a rapid heating process. It consists of a solid electrolyte membrane 22.

  As described above, after forming the second solid electrolyte precursor film by irradiating with energy rays, the dense solid electrolyte film 2A (second solid electrolyte film 22) is obtained by crystallization by rapid heating treatment. In addition, a metal oxide film may not be formed between the hydrogen permeable metal film 1 and the solid electrolyte film 2A. Specifically, the solid electrolyte membrane 2A (second solid electrolyte membrane 22) can be made into a dense membrane by irradiating the second solid electrolyte precursor membrane with energy rays. Thereby, the electrical conductivity of the solid electrolyte membrane 2A can be improved. In addition, by crystallization of the second solid electrolyte precursor film by rapid heating treatment, a metal is interposed between the hydrogen permeable metal film 1 and the solid electrolyte film 2A when the second solid electrolyte precursor film is crystallized. The formation of a film, specifically, an oxide film of a material constituting the hydrogen permeable metal film 1, can be suppressed, and a metal oxide film is formed between the hydrogen permeable metal film 1 and the solid electrolyte film 2A. Can be not. Thereby, the fall of the electrical conductivity resulting from an oxide film is suppressed, and it can be set as a high electrical conductivity.

  When crystallized by ordinary heat treatment, the solid electrolyte membrane 2 with many pores and a relative density of about 80% is formed, and the hydrogen permeable metal membrane 1 is slightly oxidized. On the other hand, in the present embodiment, the hydrogen permeable metal film 1 can be formed in a significantly densified state, for example, a solid electrolyte film 2A having a relative density of 95% or more without being almost oxidized.

Further, by forming the solid electrolyte membrane 2A after thermally oxidizing the extreme surface of the hydrogen permeable metal membrane 1, the solid electrolyte membrane 2A becomes a single phase despite being formed by low-temperature firing. Incidentally, when the low temperature firing is performed without thermal oxidation treatment, the solid electrolyte membrane 2A does not become a single phase, and a mixture of alkaline earth metal carbonates such as barium carbonate (BaCO ₃ ) and cerium oxide (CeO ₂ ) is mixed. End up. As described above, the composite membrane structure is composed of the hydrogen permeable metal membrane 1 maintaining performance and the thin solid electrolyte membrane 2A composed of a single phase. Such a composite membrane structure has excellent hydrogen permeability and excellent electrochemical characteristics such as conductive characteristics.

  In the composite membrane structure described above, the hydrogen permeable metal membrane 1 and the solid electrolyte membrane 2A may be supported by a porous support. Since this porous support is the same as that of Embodiment 1, the description thereof is omitted.

  The composite membrane structure described above can be applied to, for example, a fuel cell, and can be suitably used in a fuel cell that operates in an intermediate temperature range.

  Here, a fuel cell using the composite membrane structure will be described. FIG. 5 is a plan view and a cross-sectional view showing the structure of a fuel cell using the composite membrane structure of the present embodiment.

  As shown in FIG. 5, the fuel cell 10A according to the present embodiment includes a solid electrolyte membrane 2A, a hydrogen permeable metal membrane 1 as an anode formed on one surface side of the solid electrolyte membrane 2A, and a solid electrolyte membrane 2A. The cathode 4 is formed on the other side of the cathode. Here, the hydrogen permeable metal membrane 1 and the solid electrolyte membrane 2A are the composite membrane structure 3A according to the present invention.

  Hereinafter, the manufacturing method of the composite membrane structure will be described in detail.

  First, one surface of the hydrogen permeable metal film 1 is subjected to thermal oxidation treatment.

  Then, an organometallic acid salt solution containing an alkaline earth metal, at least one of cerium and zirconium, and a rare earth element is applied on the surface of the hydrogen permeable metal film 1 that has been subjected to the thermal oxidation treatment. Specifically, an organometallic acid salt solution containing an alkaline earth metal, at least one of cerium and zirconium, and a rare earth element is applied on the hydrogen permeable metal film 1 by spin coating or the like (application). Process). As this organometallic acid salt solution, the same one as in Embodiment 1 can be used. In this embodiment, an organometallic acid salt solution in which a BaCeY organometallic acid salt containing each metal of barium (Ba), cerium (Ce), and yttrium (Y) in a desired molar ratio is dissolved in the solution is used. Such BaCeY organometallic acid salt solution was applied.

  Next, an energy ray is irradiated (irradiation process). By irradiating energy rays in this way, a denser solid electrolyte membrane can be obtained. Here, the energy beam is not limited as long as it can cut the binding energy of molecules, and examples thereof include ultraviolet rays, electron beams, and laser beams. Although it does not specifically limit as an ultraviolet source, For example, a low pressure mercury lamp and a Xe excimer lamp are mentioned, An electron beam accelerator is mentioned as an electron beam source, An excimer laser apparatus is mentioned as a laser light source.

  Here, Table 2 shows chemical bond energies of main molecules and energy conversion wavelengths. Table 3 shows the emission wavelength and energy of the low-pressure mercury lamp and the xenon excimer lamp.

  As shown in Table 3, the low-pressure mercury lamp can irradiate UV having a wavelength of 185 nm and a wavelength of 254 nm, and the energy is 647 kJ / mol and 472 kJ / mol, respectively. Therefore, when irradiating UV, for example, a low-pressure mercury lamp or a Xe excimer lamp can be used, but a low-pressure mercury lamp is preferable in terms of handling. This is because 172 nm UV has a larger absorption coefficient to oxygen than 185 nm UV, and attenuates greatly even if it passes through the atmosphere several mm, whereas 185 nm UV does not attenuate so much.

  Next, it is dried at 100 to 300 ° C. to form a second solid electrolyte precursor film (drying step). In this embodiment, the drying time can be shortened by irradiating energy rays. In this embodiment, for example, after heating at 150 ° C. for 3 minutes, heating was performed at 250 ° C. for 6 minutes.

  Next, on the first second solid electrolyte precursor film, a coating process, an irradiation process, and a drying process are sequentially repeated to form a second solid electrolyte precursor film having a predetermined thickness composed of a plurality of layers. . In the present embodiment, the second solid electrolyte precursor film having eight layers is used.

Next, the second solid electrolyte precursor film is baked and crystallized at a low temperature of 900 ° C. or less by rapid temperature increase heat treatment, thereby arranging a divalent alkaline earth metal at the A site, tetravalent cerium and A perovskite-type oxide (ABO ₃ ) in which at least one of tetravalent zirconium is arranged at the B site is a basic structure, and a crystal structure in which a part of the tetravalent B site element is substituted with a trivalent rare earth element. 2 Solid electrolyte membrane 2A is formed. In the present embodiment, the second solid electrolyte membrane 2A having a crystal structure in which part of barium cerium trioxide (BaCeO ₃ ) is substituted with yttrium (Y) is formed.

  As described above, by irradiating energy rays, a denser solid electrolyte membrane can be obtained, and between the hydrogen permeable metal membrane 1 and the solid electrolyte membrane 2A by firing by rapid heating treatment. The formation of a metal oxide film can be suppressed. In other words, the dense solid electrolyte membrane 2A can be formed without oxidizing the surface of the hydrogen permeable metal membrane 1. Thereby, the electrical conductivity fall resulting from an oxide film is suppressed, and since the solid electrolyte membrane becomes dense, it can be made excellent in conductive characteristics.

  As in the first embodiment, the method for manufacturing the composite membrane structure of the present embodiment forms a metal oxide film between the hydrogen permeable metal film 1 and the solid electrolyte film 2A by firing by a rapid temperature increase heat treatment. It can be set as the composite film structure which is not made.

  Furthermore, the solid electrolyte membrane 2A is formed by irradiating with energy rays, thereby forming a dense membrane and having excellent conductive properties.

  Further, by subjecting the extreme surface of the hydrogen permeable metal film to thermal oxidation in advance and forming a solid electrolyte film on the surface, a single-phase solid electrolyte film can be obtained at a low firing temperature. Moreover, by baking at a low temperature of 900 ° C. or less to form a solid electrolyte membrane, it is possible to suppress the hydrogen permeable metal film from being oxidized to the inside, and the hydrogen permeable metal film is not deteriorated. .

  As described above, according to the method for manufacturing a composite membrane structure of the present embodiment, the solid electrolyte membrane can be made to have high conductivity, and between the hydrogen permeable metal membrane and the solid electrolyte membrane. Since the metal oxide film is not formed, a composite film structure having excellent electrochemical characteristics such as power generation characteristics can be obtained. In addition, a thin solid electrolyte membrane composed of a single phase can be realized while maintaining the performance of the hydrogen permeable metal membrane. Thereby, it is possible to produce a composite membrane structure having low internal resistance and excellent electrochemical characteristics such as conductive characteristics and hydrogen permeability.

(Embodiment 3)
Hereinafter, the present invention will be described in detail based on the third embodiment. In addition, the same code | symbol is attached | subjected to the same member as Embodiment 1, and the overlapping description is abbreviate | omitted.

  FIG. 6 is a diagram simply showing the structure of the composite membrane structure of the present embodiment.

  As shown in FIG. 6, the composite membrane structure according to the present invention comprises a hydrogen permeable metal membrane 1 and a solid electrolyte membrane 2B, and the interface is in a continuously joined state. The hydrogen permeable metal membrane 1 and the solid electrolyte membrane 2B are hydrogen permeable membranes capable of separating hydrogen.

The solid electrolyte membrane 2B has a basic structure of a perovskite oxide (ABO ₃ ) in which a divalent alkaline earth metal is arranged at the A site and at least one of tetravalent cerium and tetravalent zirconium is arranged at the B site. And a first solid electrolyte membrane 21 (21A and 21B) formed of a compound having a crystal structure in which a part of the B site is substituted with a trivalent rare earth element and formed by the same method as the solid electrolyte membrane 2 of the first embodiment. And the second solid electrolyte membrane 22 formed by the same method as the solid electrolyte membrane 2A of the second embodiment. Specifically, as shown in FIG. 6, the solid electrolyte membrane 2 </ b> B includes a second solid electrolyte membrane 22 and first solid electrolyte membranes 21 </ b> A and 21 </ b> B provided on both surfaces of the second solid electrolyte membrane 22. Is.

The first solid electrolyte membrane 21A, the second solid electrolyte membrane 22, and the first solid electrolyte membrane 21B are respectively arranged with a divalent alkaline earth metal at the A site, and tetravalent cerium and tetravalent zirconium. Of these, a perovskite oxide (ABO ₃ ) having at least one of them arranged at the B site as a basic structure and a compound having a crystal structure in which a part of the B site is substituted with a trivalent rare earth element. The first solid electrolyte membrane 21A, the second solid electrolyte membrane 22, and the first solid electrolyte membrane 21B may be made of different compounds, but are preferably made of the same composition.

  The solid electrolyte membrane 2B has a thickness of 30 μm or less, preferably 10 μm or less, more preferably 3 μm or less. By making the solid electrolyte membrane 2B a thin film, the internal resistance of the solid electrolyte membrane 2B can be made extremely low. Here, the thickness of the second solid electrolyte membrane 22 is, for example, 0.5 to 2.4 μm, and the thickness of each of the first solid electrolyte membranes 21A and 21B is greater than that of the second solid electrolyte membrane 22. Is preferably thin, for example, 0.1 to 0.3 μm.

In this embodiment, the hydrogen permeable metal film 1 is an alloy of palladium and silver having a thickness of 200 μm, and the solid electrolyte film 2B is a part of cerium trioxide (BaCeO ₃ ) with yttrium (Y). The first solid electrolyte membranes 21A and 21B each have a thickness of 0.25 μm, and the second solid electrolyte membrane 22 has a thickness of BaCe _0.9 Y _0.1 O _3-α structure (hereinafter referred to as BCYO). The thickness was 0.88 μm.

  The above-described solid electrolyte membrane 2B is formed by a coating method on the surface of the hydrogen permeable metal membrane 1 which has been subjected to thermal oxidation treatment. The coating method referred to here is a method of applying a precursor solution and baking it, and examples thereof include a MOD method. In the solid electrolyte membrane 2B according to the present embodiment, the first solid electrolyte membrane 21A is formed on the surface of the hydrogen permeable metal membrane 1 by the same method as in the first embodiment, and the hydrogen permeable metal of the first solid electrolyte membrane 21A is formed. The second solid electrolyte membrane 22 is formed on the surface opposite to the membrane 1 by the same method as in the second embodiment, and the first solid electrolyte membrane 21A on the opposite surface of the second solid electrolyte membrane 22 from the first embodiment. The first solid electrolyte membrane 21B is formed by the same method as described above.

  The composite membrane structure according to the present embodiment is not completely densified on the hydrogen permeable metal membrane 1 side, and includes a first solid electrolyte membrane 21A that can flexibly follow, thereby providing a hydrogen permeable metal. The first solid electrolyte membrane 21A of the second solid electrolyte membrane 22 is excellent in adhesiveness with the membrane 1 and can have high conductivity by including the second solid electrolyte membrane 22 which is a dense membrane. By providing the first solid electrolyte membrane 21 </ b> B on the opposite surface side, it is possible to achieve excellent adhesion with a member provided on the other surface side. That is, the composite membrane structure according to the present embodiment is a combination of excellent adhesion between the hydrogen permeable metal membrane 1 and the solid electrolyte membrane 2B and high conductivity of the solid electrolyte membrane 2B. Thereby, it can be set as what was further excellent in the electric power generation characteristic rather than Embodiment 1 and Embodiment 2.

  The composite membrane structure of the present embodiment can be applied to, for example, a fuel cell, and can be suitably used in a fuel cell that operates in an intermediate temperature range.

  Here, a fuel cell using the composite membrane structure will be described. FIG. 7 is a plan view and a cross-sectional view showing the structure of a fuel cell using the composite membrane structure of the present embodiment.

  As shown in FIG. 7, the fuel cell 10B according to the present embodiment includes a solid electrolyte membrane 2B, a hydrogen permeable metal membrane 1 as an anode formed on one side of the solid electrolyte membrane 2B, and a solid electrolyte membrane 2B. The cathode 4 is formed on the other side of the cathode. Here, the hydrogen permeable metal membrane 1 and the solid electrolyte membrane 2B are the composite membrane structure 3B according to the present invention. The fuel cell 10B has excellent adhesion between the hydrogen permeable metal membrane 1 and the solid electrolyte membrane 2B because the solid electrolyte membrane 2B includes the first solid electrolyte membrane 21A on the hydrogen permeable metal membrane 1 side. By providing the first solid electrolyte membrane 21B on the cathode 4 side, the adhesion between the cathode 4 and the solid electrolyte membrane 2B is excellent. Thereby, it becomes the thing excellent in electrochemical characteristics, such as a power generation characteristic. Further, since the solid electrolyte membrane 2B includes the second solid electrolyte membrane 22, high conductivity can be realized.

(Other embodiments)
The manufacturing method of the composite membrane structure concerning this invention is not limited to what was mentioned above.

  For example, in the above-described embodiment, the solid electrolyte precursor film composed of a plurality of layers is formed by repeating the coating process and the drying process, and then baked to form the solid electrolyte film. However, the present invention is not limited to this. Absent. After forming and firing a solid electrolyte precursor film composed of a plurality of layers, a solid electrolyte membrane is formed by firing again by forming a solid electrolyte precursor film composed of a plurality of layers by repeating the coating step and the drying step again. May be formed. Thereby, a denser solid electrolyte membrane can be formed.

  In addition, the composite membrane structure according to the present invention only needs to include at least one of the first solid electrolyte membrane 21 and the second solid electrolyte membrane 22. For example, the first solid electrolyte membrane 21 and the second solid electrolyte membrane 21 may be used. A plurality of electrolyte membranes 22 may be stacked in order.

  Further, the composite membrane structure comprising the solid electrolyte membrane and the hydrogen permeable metal membrane according to the present invention is suitable as an electrolyte in a fuel cell, but other electrochemical devices such as a hydrogen sensor, a hydrogen pump, a water vapor sensor, It is also suitable as an electrolyte in an electrochemical device for exhaust gas purification.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, these do not restrict | limit the scope of the present invention at all.

Example 1
A Pd—Ag alloy plate (Pd 75% —Ag 25%) having a thickness of 0.2 mm was cut into a diameter of 18 mm and heat-treated at 900 ° C. for 10 minutes to obtain a palladium-based metal film.

On the obtained palladium-based metal film, an acetate solution in which each metal acid salt was prepared so as to be BaCe _0.9 Y _0.1 O _3-a was applied by spin coating (600 rpm × 6 seconds, (2000 rpm × 24 seconds) (application process) After heating at 150 ° C. × 3 minutes, it was dried by heating at 250 ° C. for 10 minutes (drying step). The coating process and the drying process were repeated 8 times to form a solid electrolyte precursor film having a predetermined thickness. This solid electrolyte precursor film was crystallized by heating at 850 ° C. for 30 minutes using an RTA apparatus to form a 0.49 μm-thick solid electrolyte film, whereby the composite membrane structure of Example 1 was obtained. The rapid temperature increase heat treatment was performed at a temperature increase rate of 100 ° C./min.

(Example 2)
The composite film structure of Example 2 was obtained in the same manner as in Example 1 except that UV irradiation was performed after the coating process, heating was performed at 150 ° C. for 3 minutes in the drying process, and heating was performed at 250 ° C. for 6 minutes. . In addition, UV irradiation was performed by irradiating for 30 seconds using a low-pressure mercury lamp (manufactured by Sen Special Light Source: SSP17-110, irradiation distance 6 cm, 14 mW / cm ² ).

(Example 3)
A Pd—Ag alloy plate (Pd 75% —Ag 25%) having a thickness of 0.2 mm was cut into a diameter of 18 mm and heat-treated at 900 ° C. for 10 minutes to obtain a palladium-based metal film.

On the obtained palladium-based metal film, an acetate solution in which each metal acid salt was prepared so as to be BaCe _0.9 Y _0.1 O _3-a was applied by spin coating (600 rpm × 6 seconds, (2000 rpm × 24 seconds) (application process) After heating at 150 ° C. × 3 minutes, it was dried by heating at 250 ° C. for 10 minutes (drying step). The coating process and the drying process were repeated four times to form a solid electrolyte precursor film having a predetermined thickness. The solid electrolyte precursor film was crystallized by heating at 850 ° C. for 30 minutes using an RTA apparatus, thereby forming a first solid electrolyte film 21A having a thickness of 0.25 μm.

Next, on the surface of the first solid electrolyte membrane 21A, an acetate solution in which each metal acid salt was prepared so as to be BaCe _0.9 Y _0.1 O _3-a was applied by spin coating (600 rpm × 6 seconds, 2000 rpm × 24 seconds) (application process). Thereafter, UV was irradiated (irradiation step), heated at 150 ° C. for 3 minutes, and then dried at 250 ° C. for 6 minutes (drying step). The coating process and the drying process were repeated 12 times to form a solid electrolyte precursor film having a predetermined thickness. The solid electrolyte precursor film was crystallized by heating at 850 ° C. for 30 minutes using an RTA apparatus, thereby forming a second solid electrolyte film 22 having a thickness of 0.88 μm.

Then, the surface of the second solid electrolyte membrane _{22, BaCe 0.9 Y 0.1 O 3} -a and so as the respective metal salt is acetate solution formulated by spin coating (600 rpm × 6 Second, 2000 rpm × 24 seconds) (application process), heated at 150 ° C. × 3 minutes, and then dried by heating at 250 ° C. for 10 minutes (drying step). The coating process and the drying process were repeated four times to form a solid electrolyte precursor film having a predetermined thickness. The solid electrolyte precursor film is crystallized by heating at 850 ° C. for 30 minutes with an RTA apparatus to form a first solid electrolyte film 21B having a film thickness of 0.25 μm, and the composite film structure of Example 3 is obtained. Obtained.

  Note that the rapid temperature increase heat treatment by the RTA apparatus was performed at a temperature increase rate of 100 ° C./min.

(Comparative Example 1)
A composite membrane structure of Comparative Example 1 was obtained in the same manner as in Example 1 except that heat treatment was performed at a heating rate of 200 ° C./hour using a batch electric furnace instead of the RTA apparatus, and crystallization was performed.

(Comparative Example 2)
A composite membrane structure of Comparative Example 2 was obtained in the same manner as in Example 2 except that heat treatment was performed at a temperature increase rate of 200 ° C./hour using a batch electric furnace instead of the RTA apparatus, and crystallization was performed.

(Test Example 1)
The cross-sectional SEM observation of Examples 1-2 and Comparative Examples 1-2 was performed. 8A is a backscattered electron (BSE) image of Comparative Example 1, FIG. 8B is a backscattered electron image of Comparative Example 2, and FIG. 8C is Example 2. FIG. 8D is a reflected electron image of Example 1. All are sample cross-sections produced by a focused ion beam (FIB) apparatus (SMI3050MS2 manufactured by SII).

  As shown in FIGS. 8A and 8B, in Comparative Examples 1 and 2, a palladium-based metal oxide layer is formed on the palladium-based metal film regardless of the presence or absence of UV irradiation. It was confirmed. On the other hand, as shown in FIGS. 8 (c) and 8 (d), in Examples 1 and 2 crystallized by an RTA apparatus, that is, crystallized by a rapid temperature raising process, palladium-based metal oxides are used. It was confirmed that no layer was formed. More specifically, in Example 1, as shown in FIG. 8D, a solid electrolyte membrane in which pores existed can be formed while suppressing formation of a palladium-based metal oxide layer. Further, in Example 2, as shown in FIG. 8C, a dense solid electrolyte membrane could be formed while the formation of the palladium-based metal oxide layer was suppressed.

(Test Example 2)
The XRD diffraction patterns of the solid electrolyte membranes of Example 2 and Comparative Examples 1 and 2 were compared. For measurement, “RINT TTRIII” manufactured by Rigaku Corporation was used, CuKα ray was used as the X-ray source, and the X-ray diffraction pattern of the solid electrolyte membrane was obtained at room temperature. The results are shown in FIG.

  As shown in FIG. 9, in Comparative Example 1 and Comparative Example 2, the peak of the palladium-based metal oxide was confirmed, whereas in Example 2, the peak of the palladium-based metal oxide was not confirmed. Thus, also in XRD measurement, it was confirmed that no palladium-based metal oxide layer was formed in Example 2, which was crystallized by an RTA apparatus, that is, crystallized by a rapid heating process.

(Test Example 3)
The electrical conductivity of the solid electrolyte membrane of Example 2 and Comparative Examples 1-2 was measured. The electrical conductivity was measured using a potentiogalvano (Toyo Technica Solartron 1287) and a frequency response analyzer (FRA, Toyo Technica Solartron 1255) using the AC impedance method. The results are shown in FIG. For reference, a thickness of 600 μm described in Reference 1 (H. Iwahara, H. Uchida, K. Kondo, and K. Ogaki, J. Electrochem. Soc., 135 (1988) 529.) The bulk conductivity is also shown.

  As shown in FIG. 10, compared with the solid electrolyte membrane of Comparative Example 2, the solid electrolyte membrane of Example 2 subjected to the rapid temperature increase treatment has a conductivity increased by an order of magnitude and has a high conductivity. It was confirmed to be a thing. That is, it has been confirmed that the conductivity is improved by crystallization by the rapid heating process.

  In addition, from the results described above, it is predicted that the conductivity of the solid electrolyte membrane of Example 1 also increases when compared with the solid electrolyte membrane of Comparative Example 1.

Example 4
The composite membrane structure of Example 3 having a diameter of 7 mm made of Ba _0.5 Sr _0.5 Co _0.8 Fe _0.2 O _3-α on the surface opposite to the hydrogen permeable metal membrane of the solid electrolyte membrane. A cathode was formed by paste application to obtain a fuel cell of Example 4.

(Test Example 4)
Wet hydrogen bubbled at room temperature (23 ° C.) as a fuel gas is flowed to the anode side at a flow rate of 100 ml min ⁻¹ , and wet air (simulated gas by oxygen and nitrogen) is similarly given to the cathode side to 200 ml min ⁻¹ (O ₂ : N ₂ = 40: 160) Inflow test was performed. In the test, polarization was measured every 50 mV up to 250 mV, and constant voltage polarization measurement was performed. The results of the power generation performance test of the fuel cell of Example 4 are shown in FIG. In addition, for reference, the result of a bulk having a thickness of 600 μm described in Reference 1 is also shown.

As shown in FIG. 11, it was confirmed that the fuel cell of Example 4 can obtain 240 mWcm ⁻² (at 0.7 V), which is a battery output comparable to the performance of the high temperature SOFC. From this, it was confirmed that the composite membrane structure of Example 3 was suitable as a fuel cell operating in an intermediate temperature range.

  In addition, as shown in FIG. 12, the solid electrolyte membrane made of thin BCYO has a very small resistance value and greatly improved performance as compared with the solid electrolyte membrane made of thick BCYO. confirmed.

(Example 5)
BaCe _0.9 Y _0.1 O _3-a and so as to place the respective acetate solution metal salt is _formulated, each metal oxide to be a _BaZr 0.9 _Y 0.1 _{O 3-a} A composite membrane structure of Example 5 was obtained in the same manner as Example 2 except that the acetate solution prepared with the salt was used.

(Example 6)
Instead of the acetate solution in which each metal acid salt is prepared to be BaCe _0.9 Y _0.1 O _3-a , Ba (Ce _0.7 Zr _0.3 ) _0.9 Y _0.1 O A composite membrane structure of Example 6 was obtained in the same manner as in Example 2 except that an acetate solution in which each metal acid salt was prepared so as to be _3-a was used.

(Test Example 5)
Cross-sectional SEM observation of Examples 2, 5, and 6 was performed. FIG. 13A is a backscattered electron (BSE) image of Example 2, FIG. 13B is a backscattered electron image of Example 6, and FIG. 13C is Example 5. It is a backscattered electron image. All are sample cross-sections produced by a focused ion beam (FIB) apparatus (SMI3050MS2 manufactured by SII).

Example 2 (see FIG. 13A) composed of BaCe _0.9 Y _0.1 O _3-a , Ba (Ce _0.7 Zr _0.3 ) _0.9 Y _0.1 O _3-a In Example 6 (see FIG. 13 (b)) and Example 5 (see FIG. 13 (c)) made of BaZr _0.9 Y _0.1 O _{3-a, a} palladium-based metal oxide layer is formed. Not confirmed.

(Test Example 6)
The XRD diffraction patterns of the solid electrolyte membranes of Examples 2, 5, and 6 were compared. For measurement, “RINT TTRIII” manufactured by Rigaku Corporation was used, CuKα ray was used as the X-ray source, and the X-ray diffraction pattern of the solid electrolyte membrane was obtained at room temperature. The results are shown in FIG.

14A is an X-ray diffraction pattern of Example 2 made of BaCe _0.9 Y _0.1 O _3-a , and FIG. 14B is Ba (Ce _0.7 Zr _0.3 ) _0. 14 is an X-ray diffraction pattern of Example 6 composed of ₉ Y _0.1 O _3-a , and FIG. 14C is an X-ray diffraction pattern of Example 5 composed of BaZr _0.9 Y _0.1 O _3-a. FIG. 14D shows an X-ray diffraction pattern of the Pd—Ag alloy substrate.

  As shown in FIG. 14, no palladium metal oxide peak was observed in any of Examples 2, 5, and 6.

In Example _5, it was confirmed that the solid electrolyte film made of _BaZr 0.9 _Y 0.1 _{O 3-a} is formed. In Example _6, it was confirmed that the solid electrolyte film made of _{Ba (Ce 0.7 Zr 0.3) 0.9} Y 0.1 O 3-a is formed.

From Test Examples 5 and 6, crystallized by RTA apparatus, i.e., by rapid thermal treatment consisting of Ba formed by crystallization (Ce _{1 over x Zr x) 0.9 Y 0.1 O} 3-a (X = It was confirmed that the composite film structure of 0-1) was not formed with a palladium-based metal oxide layer. That is, even when zirconium is arranged at the B site, a desired solid electrolyte membrane can be formed by firing at a low temperature of 900 ° C. or less by rapid temperature rising heat treatment, as in the case of arranging cerium at the B site. It was confirmed that the palladium-based metal oxide layer was not formed.

1 Hydrogen permeable metal membrane (Pd-Ag membrane)
2,2A, 2B Solid electrolyte membrane (BCYO membrane)
3, 3A, 3B Composite membrane structure 4 Cathode 10, 10A, 10B Fuel cell A Reformed gas B Oxidant gas

Claims (8)

A composite membrane structure comprising a hydrogen permeable metal membrane and a solid electrolyte membrane,
The solid electrolyte membrane is formed by a coating method provided on a surface obtained by thermally oxidizing the hydrogen permeable metal membrane at 800 to 900 ° C. for 5 to 10 minutes , and a divalent alkaline earth metal is used. A perovskite oxide, which is arranged at the A site and at least one of tetravalent cerium and tetravalent zirconium is arranged at the B site, has a basic structure, and part of the tetravalent B site elements are trivalent rare earth elements. A compound having a substituted crystal structure,
The solid electrolyte membrane, A alkaline earth metal, and at least one of cerium and zirconium, in contact with a rare earth element, a first solid electrolyte membrane relative density 80-90% including said hydrogen-permeable metal membrane composite membrane structure, characterized in that it comprises Te.   2. The composite membrane structure according to claim 1, wherein the solid electrolyte membrane further includes a second solid electrolyte membrane having a relative density of 95% or more provided on the first solid electrolyte membrane.   The composite membrane structure according to claim 2, wherein the solid electrolyte membrane is composed of one or more first solid electrolyte membranes and one or more second solid electrolyte membranes.   4. The composite according to claim 2, wherein the solid electrolyte membrane includes the second solid electrolyte membrane and the first solid electrolyte membrane provided on both surfaces of the second solid electrolyte membrane. 5. Membrane structure. The alkaline earth metal is barium (Ba) and composite film structure according to any one of claims 1 to 4, characterized in that at least one of strontium (Sr). The trivalent rare earth element is selected from the group consisting of ytterbium (Yb), erbium (Er), yttrium (Y), dysprosium (Dy), gadolinium (Gd), samarium (Sm), and neodymium (Nd). The composite membrane structure according to any one of claims 1 to 5 , wherein the composite membrane structure is at least one. The composite membrane structure according to any one of claims 1 to 6 , wherein the hydrogen permeable metal membrane is a palladium-based metal membrane. A composite membrane structure according to any one of claims 1 to 7 , comprising a cathode on a surface of the solid electrolyte membrane opposite to the hydrogen permeable metal membrane, wherein the hydrogen permeable metal membrane is A fuel cell characterized by being an anode.