WO2014207993A1

WO2014207993A1 - Anode support for solid oxide fuel cell, anode-supported solid oxide fuel cell, and fuel cell system

Info

Publication number: WO2014207993A1
Application number: PCT/JP2014/002720
Authority: WO
Inventors: 佐藤　康司; 貴章谷口; 工藤　孝夫; 達也川田; 圭司八代; 橋本　真一; 大樹進藤; 浩史雨澤; 崇司中村
Original assignee: Ｊｘ日鉱日石エネルギー株式会社; 国立大学法人東北大学
Priority date: 2013-06-25
Filing date: 2014-05-23
Publication date: 2014-12-31
Also published as: JP2015008088A

Abstract

　An anode support (21) for a solid oxide fuel cell constituting an embodiment of the present invention contains metallic Ni and/or Ni oxide. The anode support has a porous base section, and a surface of the base section that comes into contact with fuel supplied at least to an anode catalyst layer (23) has particles, or an aggregate thereof, composed of at least one oxide of a single metal selected from the group consisting of Ti, Zr, Nb, Hf, Ta, and Ce. The oxide content in relation to the total mass of the anode support (21) is at least 0.5% by mass.

Description

Anode support for solid oxide fuel cell, anode supported solid oxide fuel cell, and fuel cell system

The present invention relates to an anode support for a solid oxide fuel cell, an anode supported solid oxide fuel cell, and a fuel cell system.

Solid oxide fuel cells (SOFC) generally have higher power conversion efficiency than solid polymer fuel cells (PEFC). Further, not only hydrogen but also reformed gas obtained by reforming raw fuel such as hydrocarbon, alcohol and dimethyl ether (DME) can be used as the fuel. Furthermore, carbon monoxide, unreformed methane, etc. produced as a by-product during reforming of the raw fuel can also be used as a fuel for power generation. Generally, in one thermal closed system, heat for reforming is supplied by using the amount of heat generated in SOFC or heat obtained by burning surplus gas not used for power generation in the upper part of the cell. The ability to balance heat contributes to the high efficiency of SOFC.

The operating temperature of SOFC has often been 700 ° C or higher in the past. On the other hand, operation at a lower temperature is possible by using an electrolyte material or an air electrode material which is operated at a low temperature (below 700 ° C.), which has been developed in recent years. Thereby, the practicality of SOFC can be improved, for example, an inexpensive material with low heat resistance can be adopted.

On the other hand, if the operating temperature of the cell decreases, the temperature of the reformer that is in thermal balance with the cell also decreases. As a result, fuel gas having a high methane ratio is supplied to the cell due to thermal equilibrium in the reforming reaction. In addition, when using raw fuel containing hydrocarbons having 2 or more carbon atoms (C2 or more hydrocarbons) such as natural gas or LPG with adjusted calorie, C2 or more hydrocarbons are converted to C1 species (carbon number 1) in the reformer. There is a growing concern about the occurrence of slippage of so-called C2 or higher hydrocarbons that are supplied to the cell without being converted into hydrocarbons. Furthermore, even with an SOFC that operates at a normal operating temperature (700 ° C. or higher), the reformer may not be sufficiently heated during startup or shutdown. For this reason, in addition to the increase in the methane concentration in the fuel gas, a situation may occur in which the reformed gas mixed with hydrocarbons of C2 or higher is supplied to the cell.

Incidentally, in an anode (fuel electrode) -supported SOFC, a cermet containing nickel (Ni) having high conductivity is preferably used as an anode support. When the reformed gas supplied from the reformer contains high-concentration methane and C2 or higher hydrocarbons, most of the methane and C2 or higher hydrocarbons are combined with coexisting steam by the catalytic action of Ni contained in the anode support. As the reforming reaction proceeds, the hydrogen-rich gas is used as a fuel for power generation. However, some methane and C2 or higher hydrocarbons may precipitate as carbon on the anode support.

Particularly, under the condition of low S / C (steam / carbon ratio) with a low water vapor partial pressure and a high hydrocarbon partial pressure, carbon deposition on the anode support is likely to occur. As the carbon deposition reaction, direct thermal decomposition reaction of methane (the following formula (1)), steam reforming reaction (the following formula (2)) or aqueous transfer reaction (water gas shift reaction) (the following formula (3)) The disproportionation reaction of CO produced by the above (formula (4) below) is known.

When carbon deposition occurs on the anode support, the gas supply hole of the anode support is blocked, and the supply of fuel gas to the anode active layer is interrupted, resulting in a risk of reoxidation of the cell. Also, the carbon deposited on the anode support causes the anode support to expand. As a result, there is a risk of damaging the electrode and electrolyte layer provided on the surface of the anode support. Moreover, the expansion of the anode support accompanying the carbon deposition and the occurrence of cracks in the electrolyte layer are irreversible phenomena. For this reason, a case where cracking of the electrolyte layer due to the expansion of the anode support becomes serious may become unusable as a cell. Therefore, it was very important to suppress carbon deposition on the anode support. And suppression of this carbon precipitation has been calculated | required, without implement | achieving the physical property of the existing material system, such as an electrical conductivity and a thermal expansion coefficient, changing significantly (refer nonpatent literature 1, 2).

As for the means for suppressing the carbon deposition described above, for example, a fuel electrode in which a composite oxide _SrZr _0.95 Y _0.05 O _3-0δ (SZY) having proton conductivity is added to Ni / YSZ cermet is used. There is known a research example in which the addition amount is changed to optimize the addition amount in terms of deterioration resistance, electrochemical characteristics, operational stability, and the like (see Non-Patent Document 3).

The suppression of carbon deposition in the anode support for a solid oxide fuel cell still has room for investigation from the viewpoint of improving the suppression effect.

The present invention has been made in view of such circumstances, and an object thereof is to provide a technique for suppressing carbon deposition in an anode support for a solid oxide fuel cell.

One embodiment of the present invention is an anode support for a solid oxide fuel cell. The anode support includes at least one of Ni metal and Ni oxide, and has a porous base portion. On the surface of the base portion that contacts at least the fuel supplied to the anode catalyst layer, Ti, Zr, Nb, It has particles composed of one or more oxides of a single metal selected from the group consisting of Hf, Ta and Ce, or aggregates of the particles, and the content of the oxide is the total mass of the anode support. On the other hand, it is 0.5 mass% or more.

Another embodiment of the present invention is an anode-supported solid oxide fuel cell. The anode-supported solid oxide fuel cell is provided on the surface of the anode support of the aspect described above, the anode catalyst layer provided on the surface of the anode support, and the surface of the anode catalyst layer opposite to the anode support. An electrolyte layer; and a cathode catalyst layer provided on a surface of the electrolyte layer opposite to the anode catalyst layer.

Still another aspect of the present invention is a fuel cell system. The fuel cell system includes an anode-supported solid oxide fuel cell according to the above-described embodiment, and reforming raw fuel using heat generated from the anode-supported solid oxide fuel cell, and an anode-supported solid oxide. And a reformer that generates fuel used for power generation of the fuel cell.

According to the present invention, it is possible to provide a technique for suppressing carbon deposition on an anode support for a solid oxide fuel cell.

FIG. 1A is a perspective view showing a schematic structure of a main part of the fuel cell system according to the embodiment. FIG. 1B is a vertical cross-sectional view schematically showing the structure of the main part of the fuel cell system according to the embodiment. FIG. 2A is a horizontal sectional view schematically showing the structure of the fuel cell stack. FIG. 2B is a schematic diagram showing an enlarged part of the anode support. FIG. 3A is a horizontal cross-sectional view schematically showing a partial structure of a fuel cell stack provided in the fuel cell system according to the first modification. FIG. 3B is a horizontal sectional view schematically showing the structure of the fuel cell according to Modification 2. It is a schematic diagram of an expansion measuring device. It is a graph which shows the relative carbon deposition amount in the support body sample of each Example and each comparative example. It is a graph which shows the relative linear expansion coefficient in the support body sample of each Example and each comparative example. It is a graph which shows the relationship between the relative voltage of a fuel cell, and elapsed time. It is a graph which shows the relationship between the number of the cracks which generate | occur | produced in the fuel cell, and elapsed time.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same reference numerals are given to the same components, and the description will be omitted as appropriate.

First, the knowledge found by the present inventors will be described before the embodiment is described. The present inventors have used various oxides as the third component with respect to Ni / YSZ (Yttria-Stabilized Zilconia) and Ni / GDC (Gadolinia Doped Ceria), which are general support compositions conventionally used. A carbon deposition test was conducted using a sample of the anode support to which was added with a low S / C reformed gas. As a result, the inventors have found that a specific oxide significantly suppresses carbon deposition even when added in a small amount, and have arrived at the anode support, fuel cell, and fuel cell system according to the present embodiment. Hereinafter, the anode support, the fuel cell, and the fuel cell system according to the present embodiment will be described in detail.

FIG. 1A is a perspective view showing a schematic structure of a main part of a fuel cell system according to an embodiment. FIG. 1B is a vertical cross-sectional view schematically showing the structure of the main part of the fuel cell system according to the embodiment. FIG. 1A shows a state where the inside of the module case 2 is seen through. Since FIG. 1B is a schematic diagram, the arrangement of each part, the number of installations, and the like do not necessarily match those in FIG. The fuel cell system 100 includes a hot module 1. The hot module 1 includes a module case 2, a fuel cell stack 10 accommodated in the module case 2, a water vaporizer 50, and a reformer 6.

The module case 2 is composed of a substantially rectangular parallelepiped outer frame formed of a heat-resistant metal and a heat insulating material lined on the inner surface of the outer frame. The module case 2 is provided with a supply pipe 3, a supply pipe 4 and a supply pipe 52. The supply pipe 3 is a pipe for supplying raw fuel and ATR (autothermal reforming reaction) air into the case from the outside of the case. The supply pipe 4 is a pipe for supplying cathode air (oxygen-containing gas) from the outside of the case into the case. The supply pipe 52 is a pipe for supplying reforming water used for the steam reforming reaction from the outside of the case into the case. The module case 2 is provided with an exhaust port 5. As raw fuel, city gas, LPG, methanol, dimethyl ether (DME), kerosene and the like are used.

The water vaporizer 50 and the reformer 6 are arranged in the upper part of the module case 2 and above the fuel cell stack 10. A supply pipe 52 is connected to the water vaporizer 50, and a supply pipe 3 is connected to the reformer 6. The water vaporizer 50 vaporizes the reforming water supplied from the supply pipe 52. Vaporized reforming water (steam) is supplied to the reformer 6. The reformer 6 includes a case formed of a heat-resistant metal and a reforming catalyst that is accommodated in the case and used for reforming raw fuel. The reformer 6 is a raw material supplied from the supply pipe 3 by a self-thermal reforming reaction using ATR air supplied from the supply pipe 3 or a steam reforming reaction using water vapor supplied from the water vaporizer 50. The fuel is reformed into a fuel gas rich in hydrogen (reformed gas).

One end of the reformed gas supply pipe 7 is connected to the reformed gas outlet 6 a of the reformer 6. The other end of the reformed gas supply pipe 7 is connected to the manifold 8. The manifold 8 is a fuel supply path that is supplied to the anode catalyst layer 23 described later. The manifold 8 is disposed below the fuel cell stack 10 and distributes the reformed gas supplied from the reformer 6 to the plurality of fuel cells 20 included in the fuel cell stack 10. The fuel cell stack 10 is disposed in the lower part of the module case 2, below the reformer 6 and the water vaporizer 50, and fixed on the manifold 8.

The manifold 8 includes a box-shaped main body having an opening and an upper lid that closes the opening of the box-shaped main body. The upper lid is fixed to the box-shaped main body by, for example, an inorganic glass composition. The upper lid functions as a holding member for the fuel cell stack 10. The upper lid is provided with a plurality of holes for fixing the anode support 21 of each fuel cell 20, and the lower end portion of each anode support 21 is inserted into each opening, and a fixing material such as an adhesive is provided. It is fixed by. Examples of the adhesive used as the fixing material include silica-alumina based inorganic adhesives. In this case, the anode support 21 is fixed to the upper lid by solidifying the inorganic adhesive by firing in a state where the lower end portion of each anode support 21 is held in each opening of the upper lid via the inorganic adhesive. can do. Further, an adhesive layer for fixing the anode support 21 and the upper lid is covered with a sealing material. Thereby, the junction part of the anode support body 21 and an upper cover is sealed gas tight (airtight).

The fuel cell stack 10 is an assembly of a plurality of fuel cells 20 (cells). When, for example, a cylindrical flat plate type fuel cell is used as the fuel cell 20, a plurality of (shown five for simplicity in FIG. 1) vertically long fuel cells 20 are arranged in a row in the horizontal direction. A current collecting member 30 is interposed between the side surfaces of the adjacent fuel cells 20. A plurality of fuel cells 20 in a row are arranged on a plane, so that a large number of fuel cells 20 are arranged in a matrix (see FIG. 2). The outermost current collecting member 30 in each row is electrically connected to the conductive member 40.

Each of the fuel cells 20 is provided with a plurality of gas passages 22 extending from the lower end to the upper end of the fuel cell 20. Each gas flow path 22 communicates with the manifold 8 at its lower end. The upper end portion of the gas flow path 22 is opened to a space sandwiched between the reformer 6 and the water vaporizer 50 and the fuel cell stack 10. The space constitutes a combustion portion for fuel gas discharged from the upper end portion of the gas flow path 22. Most of the fuel gas flowing from the manifold 8 into the gas flow path 22 is supplied to the fuel cell 20. Excess fuel gas that is not supplied to the fuel cell 20 is supplied from the upper end of the gas flow path 22 to the combustion unit.

Subsequently, the structure of the fuel cell stack 10 will be described in more detail. FIG. 2A is a horizontal sectional view schematically showing the structure of the fuel cell stack. As shown in FIG. 2A, in this embodiment, a cylindrical flat plate fuel cell 20 is illustrated. The fuel cell 20 is an anode-supported solid oxide fuel cell, and includes an anode support 21, a gas flow path 22, an anode catalyst layer 23 (fuel electrode layer), and an electrolyte layer 24 (solid oxide electrolyte layer). A cathode catalyst layer 25 (air electrode layer), and an interconnector 26.

The anode support 21 is a porous body containing at least one of Ni metal and Ni oxide. The anode support 21 is a plate-shaped piece having a flat oval horizontal cross-sectional shape and extending in the vertical direction (vertical direction) (see FIG. 1B). The anode support 21 has a lower surface located on the manifold 8 side, an upper surface located on the reformer 6 side, two flat side surfaces (flat side surfaces) facing each other, and two semi-cylindrical surface shapes facing each other. And side surfaces (two curved side surfaces arranged in a direction orthogonal to the direction in which the two flat side surfaces are arranged).

The anode support 21 has a plurality of gas flow paths 22 at the center thereof. The gas flow path 22 is provided along the longitudinal direction of the anode support 21. One end (lower end) of the gas passage 22 is located on the lower surface of the anode support 21, and the other end (upper end) of the gas passage 22 is located on the upper surface of the anode support 21. In the present embodiment, four gas flow paths 22 are provided in each anode support 21. The anode support 21 is fixed to the manifold 8, and one end of the gas flow path 22 is communicated with the manifold 8. The reformed gas generated in the reformer 6 is distributed to the gas flow paths 22 of the fuel cells 20 by the manifold 8 and flows from one end of the gas flow paths 22 to the other end side.

The interconnector 26 is provided on one flat side surface of the anode support 21 (on the left flat side surface in the fuel cell stack 10-1 in the first row in FIG. 2A). The interconnector 26 is a conductive member for collecting current from the anode of each fuel cell 20. The interconnector 26 can be made of, for example, a conductive ceramic.

The anode catalyst layer 23 is provided on the surface of the anode support 21. In the present embodiment, the anode catalyst layer 23 is laminated at least on the other flat side surface of the anode support 21 (on the right flat side surface in the fuel cell stack 10-1 in the first row in FIG. 2A). Is done.

The electrolyte layer 24 is provided on the surface of the anode catalyst layer 23 opposite to the anode support 21. In the present embodiment, the electrolyte layer 24 covers the entire surface of the anode catalyst layer 23. The cathode catalyst layer 25 is provided on the surface of the electrolyte layer 24 opposite to the anode catalyst layer 23. In the present embodiment, the cathode catalyst layer 25 is laminated on the main surface of the electrolyte layer 24. Therefore, the anode support 21 is disposed on the side opposite to the interconnector 26. That is, in the fuel cell 20, the anode catalyst layer 23, the electrolyte layer 24, and the cathode catalyst layer 25 are laminated in this order on one surface of the anode support 21 having the gas flow path 22, and the other surface of the anode support 21. And an interconnector 26 is formed. The constituent materials of the anode support 21, the anode catalyst layer 23, the electrolyte layer 24, and the cathode catalyst layer 25 will be described in detail later.

The plurality of fuel cells 20 are arranged in a row so that one cathode catalyst layer 25 and the other interconnector 26 in two adjacent fuel cells 20 face each other, and are joined to each other via a current collecting member 30. The That is, as shown in FIG. 2A, the interconnector 26 located on the left side of each fuel cell 20 is connected to the cathode catalyst layer 25 located on the right side of the left fuel cell 20 via the current collecting member 30. Join. As a result, a plurality of fuel cells 20 arranged in a row are connected in series to form the fuel cell stack 10. In the present embodiment, the fuel cell stack 10 includes a first row of fuel cell stacks 10-1 and a second row of fuel cell stacks 10-2. The current collecting member 30 can be composed of a member having a predetermined shape formed from a metal or alloy having elasticity, or a member obtained by performing a predetermined surface treatment on a felt made of metal fiber or alloy fiber.

In the hot module 1 having the above-described configuration, raw fuel for hydrogen production and, if necessary, ATR air are supplied from the supply pipe 3 to the reformer 6, and reforming water is supplied from the supply pipe 52 to the water vaporizer 50. Supplied. The reformer 6 reforms the raw fuel by a steam reforming reaction or an autothermal reforming reaction to generate a hydrogen-rich reformed gas used for power generation of the fuel cell 20. The generated reformed gas is supplied to the manifold 8 through the reformed gas supply pipe 7. The reformed gas supplied to the manifold 8 is distributed to each fuel cell 20 and rises in the gas flow path 22 of each fuel cell 20. In this process, hydrogen in the reformed gas permeates through the anode support 21 and reaches the anode catalyst layer 23. On the other hand, cathode air is introduced into the module case 2 from the supply pipe 4. The cathode air introduced into the module case 2 is supplied to each fuel cell 20, and oxygen in the cathode air reaches the cathode catalyst layer 25.

In the cathode catalyst layer 25 located on the outer peripheral side of each fuel cell 20, an electrode reaction represented by the following formula (5) occurs. O ²⁻ produced in the cathode catalyst layer 25 permeates the electrolyte layer 24 and reaches the anode catalyst layer 23. Further, an electrode reaction represented by the following formula (6) occurs in the anode catalyst layer 23 located on the center side of the fuel cell 20. Thereby, power generation is performed in the fuel cell 20.
1 / 2O ₂ + 2e ⁻ → O ²⁻ (5)
O ²⁻ + H ₂ → H ₂ O + 2e ⁻ (6)

Of the reformed gas flowing through the gas flow path 22, surplus reformed gas that has not been used for the electrode reaction is released into the module case 2 from the upper end of the anode support 21. This reformed gas is burned in the combustion section located between the reformer 6 and the water vaporizer 50 and the fuel cell stack 10. Predetermined ignition means (not shown) is provided in the module case 2, and when the reformed gas starts to be released to the combustion section, the ignition means is activated and combustion of the reformed gas is started. Of the cathode air introduced into the module case 2, surplus air that has not been used for the electrode reaction is used for combustion of the reformed gas. The inside of the module case 2 becomes a high temperature of, for example, about 600 ° C. to 1000 ° C. due to heat generated by the power generation of each fuel cell 20 and heat generated by combustion of the surplus reformed gas. The water vaporizer 50 and the reformer 6 perform the vaporization and reforming reaction of the reforming water using the heat generated from the fuel cell 20 and the heat generated by the combustion of the reformed gas. The exhaust gas generated by the combustion of the reformed gas in the module case 2 is discharged out of the module case 2 through the exhaust port 5.

Subsequently, the composition of each part constituting the fuel cell 20 will be described in detail. FIG. 2B is a schematic diagram showing an enlarged part of the anode support. The anode support 21 is required to have gas permeability in order to permeate fuel from the gas flow path 22 to the anode catalyst layer 23. Further, the anode support 21 is required to have conductivity in order to transmit electrons generated in the anode catalyst layer 23 to the interconnector 26.

Therefore, the anode support 21 according to the present embodiment has a base 210 that is porous. By making the base 210 porous, the reformed gas can be transmitted from the gas flow path 22 to the anode catalyst layer 23. Moreover, the base 210 contains at least one of Ni metal and Ni oxide. Ni contained in the base 210 takes the state of Ni oxide during the manufacture of the anode support 21 and the fuel cell 20 and before the fuel cell system 100 is driven, and is reduced during the driving of the fuel cell system 100 to form Ni metal. It can take a state. In FIG. 2B, Ni metal and Ni oxide are not distinguished from each other and are illustrated as a nickel portion 212. Since the base 210 has the nickel portion 212, conductivity can be imparted to the anode support 21.

The base 210 includes at least one of Ni metal and Ni oxide (that is, the nickel portion 212), and at least one oxide 214 selected from the group consisting of Y ₂ O ₃ , a zirconia-based composite oxide, and a ceria-based composite oxide. It is preferable that the composite is That is, the base 210 is preferably a cermet composed of Ni metal and / or Ni oxide and a porous conductive ceramic. Examples of the zirconia-based composite oxide include YSZ, ScSZ (Scandia Stabilized Zirconia) and the like. Examples of the ceria-based composite oxide include SDC (Samaria-Doped Ceria), YDC (Yttria-Doped Ceria), LDC (La ₂ O ₃ -doped Ceria), GDC (Gadolinia-doped Ceria), and the like.

The anode support 21 preferably has an open porosity of 20% or more, more preferably 25% to 50%. The anode support 21 preferably has a conductivity of 100 S / cm or higher, more preferably 200 S / cm or higher. In order to satisfy these requirements, the base 210 is preferably 30% by mass or more in terms of Ni oxide with respect to the total mass of the anode support 21 (for example, the total mass of the base 210 and the oxide particle part 220 described later). More preferably, it contains 30 mass% to 90 mass%, more preferably 40 mass% to 80 mass% of Ni atoms. By setting the content of Ni atoms in the base 210 to 30% by mass or more in terms of Ni oxide, desired conductivity can be more reliably imparted to the anode support 21. Moreover, a desired open porosity can be more reliably imparted to the anode support 21 by setting the content of Ni atoms in the base 210 to 90 mass% or less in terms of Ni oxide. The dimension of the anode support 21 is 7 cm to 20 cm in height (length from the upper end to the lower end), for example.

As a manufacturing method of the base 210, a composite composition containing nickel oxide and oxide 214 is processed into a support shape by means of extrusion molding or the like, and subjected to appropriate firing treatment to obtain predetermined dimensions and porosity. A preferred example is a method of forming a cermet having the same. The cermet is subjected to a reduction treatment before it is used as a fuel cell after all cell constituent layers are finally formed. This reduction treatment is usually performed by heating the fuel cell 20 or the fuel cell stack 10 to a predetermined temperature in a reducing gas stream such as hydrogen gas or hydrogen gas diluted with nitrogen. By this reduction treatment, almost all of the nickel oxide contained in the base portion 210 is reduced to Ni metal.

In addition, the anode support 21 has titanium (Ti), zirconium (Zr), niobium (Nb), hafnium (Hf), tantalum (on the surface in contact with the fuel supplied to the anode catalyst layer 23 at least in the base 210. A particle composed of one or more oxides of a single metal selected from the group consisting of Ta) and cerium (Ce) or an aggregate of the particles. The oxide of these metals alone is at least the nickel portion constituting the base 210 on the surface of the base 210 that contacts the fuel (including the surface of the base 210 as well as the surface of the internal pores). It exists as particles (primary particles) that are distinguished from 212 and oxide 214, or exists as aggregates (secondary particles) formed by aggregation of these particles.

That is, these metal single oxides exist as single compound domains on the base 210. In FIG. 2B, the oxide particles 220 are illustrated without distinction between particles and aggregates. When the oxide particle part 220 is comprised with an aggregate, the oxide particle part 220 may be layered (film | membrane form). The oxide particle portion 220 has a maximum width of 0.5 μm to 20 μm, for example, in the case of particles and particle aggregates. In addition, when the agglomerate is layered, the layer thickness is, for example, 0.1 μm to 10 μm.

The oxide constituting the oxide particle portion 220 is a single oxide in which only one type of metal selected from the group consisting of Ti, Zr, Nb, Hf, Ta, and Ce is included in the single crystal. Therefore, the oxide 214 is distinguished from a zirconia-based composite oxide or a ceria-based composite oxide in which a plurality of types of metals are included in a single crystal. For example, the oxide particle part 220 is composed of at least one single oxide selected from the group consisting of TiO ₂ , ZrO ₂ , Nb ₂ O ₅ , HfO ₂ , Ta ₂ O ₅ and CeO ₂ . The oxide particle part 220 may be a mixture in which a plurality of single oxides (for example, TiO ₂ and ZrO _2, etc.) are mixed within the range of the oxide group.

Conventionally, the operating temperature of SOFC has often been 700 ° C or higher. In contrast, in recent years, improvements in electrolyte materials and air electrode materials have progressed, and SOFCs that can operate at a low temperature of about 600 ° C. or lower are being used. However, when the operating temperature of the fuel cell 20 decreases, the temperature of the reformer 6 also decreases in the hot module 1 that performs the reforming reaction in the reformer 6 using the heat generated by the fuel cell 20. In this case, a reformed gas having a high methane ratio may be generated due to thermal equilibrium.

Further, when a raw fuel containing C2 or higher hydrocarbons is used, the reformer 6 may cause the C2 or higher hydrocarbons to be supplied to the fuel cell 20 without being converted into C1 chemical species (C2 or higher hydrocarbon slips). Occurrence). Further, the fuel cell system 100 may be stopped due to various reasons such as a user instruction, a purpose of improving the energy saving effect, and a trouble of the device. In the system stop process and the subsequent restart process, the reformer 6 may not be sufficiently heated even with a conventional SOFC operating at a high temperature. Also in this case, the above-described methane concentration increase or a situation in which the reformed gas mixed with C2 or more hydrocarbons is supplied to the fuel cell 20 may occur.

In particular, in the system stop process, after the power generation of the fuel cell 20 is stopped, the fuel cell 20 may be gradually cooled while continuing to supply the reformed gas to the fuel cell 20. The reformed gas is supplied for the purpose of preventing air from flowing into the anode support 21 and the anode catalyst layer 23 and re-oxidation of the anode support 21. In this case, the reformed gas is supplied to the fuel cell 20 for several hours even after the power generation of the fuel cell 20 is stopped. On the other hand, as the temperature of the fuel cell 20 decreases, the temperature of the reformer 6 also decreases. For this reason, there is a high possibility that high-concentration methane or unreformed C2 or higher hydrocarbon compound is supplied from the reformer 6 to the fuel cell 20.

When a high concentration of methane or C2 or higher hydrocarbon compound is supplied to the fuel cell 20, the fuel cell system having a conventional anode support made of Ni cermet (that is, only the base 210) has various forms of carbon. Precipitation may occur in various places. Such carbon deposition is likely to occur, for example, in the manifold, the upstream portion of the anode support in the fuel gas flow direction, in the pores of the anode support, or in places where the potential changes due to the external current collecting structure in the hot module. .

For example, when reformed gas containing a large amount of C2 or more hydrocarbons and low S / C is supplied to the fuel cell, fibrous carbon often grows. This fibrous carbon may cause an electrical short circuit or clogging of the pores of the anode support (gas blockage), and the fuel cell may be irreversibly disabled. Further, when a high concentration of methane is included and a low S / C reformed gas is supplied, solid carbon is deposited. Then, granular carbon is deposited in the pores of the anode support 21 and this causes dimensional expansion of the anode support. When the anode support is expanded, there is a possibility that stress deformation and cracks may occur. In addition, stress deformation occurs in the sealing material covering the joint between the anode support and the manifold, which may lead to cracking or peeling. In particular, when the raw fuel contains a hydrocarbon compound having 2 or more carbon atoms in an amount of 5 mol% or more based on the total molar amount of the raw fuel, the above-described carbon deposition tends to occur.

On the other hand, the anode support 21 according to the present embodiment has the oxide particle part 220 on the surface in contact with the reformed gas of the base part 210. The oxide particle part 220 can suppress the above-described carbon deposition on the anode support 21.

Content of the oxide particle part 220 (oxide which comprises particle | grains or an aggregate) is 0.5 mass with respect to the total mass (For example, total mass of the base 210 and the oxide particle part 220) of the anode support body 21. FIG. % Or more, preferably 1% by mass or more. By setting the content of the oxide particle part 220 to 0.5 mass% or more with respect to the total mass of the anode support 21, carbon deposition on the anode support 21 can be more reliably suppressed.

Further, the weight ratio of the single oxide particles or aggregates in the anode support 21 can be inclined along the flow direction of the fuel gas. For example, the anode support 21 has a total weight ratio of particles and aggregates in at least a part of the upstream side in the fuel flow direction, and a total weight of particles and aggregates in the at least a part of the downstream side. Greater than percentage. The total weight ratio is the total weight of the oxide particle part 220 with respect to the total weight of the base part 210 and the oxide particle part 220. The upstream region is, for example, a region including the upstream end portion of the anode support 21 in the fuel gas flow direction, and the downstream region is, for example, the downstream end portion of the anode support 21 in the fuel gas flow direction. It is an area including When the weight ratio of the particles and aggregates in the anode support 21 is inclined, the total amount of the oxide particle portions 220 on the upstream side in the fuel flow direction is equal to the total amount of the oxide particle portions 220 on the downstream side in the fuel flow direction. It is preferable that there are more. By making the addition rate of the oxide particle part 220 in the upstream region of the anode support 21 higher than that in the downstream region, deformation and expansion of the anode support 21 can be suppressed more efficiently.

Examples of the method for forming the oxide particle part 220 include the following examples. That is, as a first forming method, in the manufacturing process of the base 210, a single oxide (hereinafter referred to as “ The anode support 21 having the base portion 210 and the oxide particle portion 220 can be formed by mixing and firing this composite composition in advance. Alternatively, as a second forming method, a composite composition including the nickel portion 212 and the oxide 214 is formed and fired to form the base 210, and then a carbon deposition inhibitor is attached to the obtained base 210. Thus, the oxide particle part 220 can be formed. According to the second method, the above-described concentration distribution control of the oxide particle part 220 in the anode support 21 can be realized more easily. In any method, the oxide particle part 220 exists without changing to a constituent material of the base part 210 and a different substance by solid solution or solid phase reaction. Moreover, the state which exists as the independent particle | grains or aggregate different from the base 210 on the surface of the base 210 which is a cermet can be formed.

In the second forming method, a chemical vapor deposition method (CVD method) or the like can be used as the vapor phase process. In addition to coprecipitation method, homogeneous precipitation method, hydrolysis method, precipitation method represented by citrate method, hydrothermal synthesis method, microemulsion method, solvent evaporation method, etc. can be used as the liquid phase process. . As the solid phase process, a solid thermal decomposition method, a solid phase reaction method, a hydrothermal crystallization method, or the like can be used. For example, in the second forming method, a suspension of fine particles of a single oxide is prepared as a carbon deposition inhibitor, and this suspension is sprayed on the base 210 or impregnated with the base 210 in the suspension, and then dried. A method of immobilizing a carbon deposition inhibitor on the base 210 by treatment or baking treatment can be used. Alternatively, a soluble salt of a single oxide, for example, when the single oxide is CeO ₂ , cerium nitrate or the like is dissolved in a solvent such as water, and this solution is sprayed on the base 210 or the base 210 is impregnated with this solution. Also good. In this case, in order to form the oxide particle part 220 from the soluble salt attached to the base part 210, the anode support 21 to which the carbon deposition inhibitor is attached is heated and fired. This heating and baking may be combined with a baking process performed at the time of forming the base 210, the temporary baking or the main baking, or the formation of the anode catalyst layer 23, the electrolyte layer 24, the cathode catalyst layer 25, and the like.

The firing temperature of the carbon deposition inhibitor varies depending on the type of carbon deposition inhibitor used and the amount of adhesion to the base 210, but is generally 300 ° C to 1600 ° C, preferably 350 ° C to 1200 ° C, more preferably 400 ° C. ° C to 1000 ° C. By setting the firing temperature to 300 ° C. or higher, the carbon precipitation inhibitor can be more reliably attached to the base portion 210, and nitrate such as cerium nitrate can be more reliably denitrated, so that the oxide particle portion 220 Formation can be made more reliable. Moreover, it can avoid more reliably that decomposition | disassembly and aggregation of a carbon precipitation inhibitor occur by making baking temperature into 1600 degrees C or less. The firing time is usually 15 minutes to 48 hours, preferably 1 hour to 24 hours. By setting the firing time to 15 minutes or longer, the carbon deposition inhibitor can be fired more reliably. By setting the firing time to 48 hours or less, aggregation of the carbon deposition inhibitor can be avoided more reliably, and a decrease in industrial productivity can be suppressed.

The anode catalyst layer 23 is a composite composed of at least one of Ni metal and Ni oxide and at least one composite oxide selected from the group consisting of zirconia composite oxide, ceria composite oxide, and LSGM. Preferably there is. Specifically, the anode catalyst layer 23 is made of Ni / YSZ, Ni / ScSZ, Ni / SDC, Ni / YDC, Ni / LDC, Ni / GDC, Ni / LSGM (La—Sr—Ga—Mg composite oxide). Preferably, at least one cermet selected from the group consisting of: The layer thickness of the anode catalyst layer 23 is, for example, 0.1 μm to 50 μm.

The electrolyte layer 24 functions as an electrolyte that bridges electron conduction and ion conduction between electrodes, and also functions as a gas barrier layer for preventing leakage of fuel gas and air. The electrolyte layer 24 preferably includes at least one composite oxide selected from the group consisting of zirconia composite oxide, ceria composite oxide, and LSGM. Specifically, a solid electrolyte selected from the group consisting of YSZ, ScSZ, SDC, YDC, LDC, GDC, and LSGM is preferably used for the electrolyte layer 24. The layer thickness of the electrolyte layer 24 is, for example, 0.2 μm to 200 μm.

The cathode catalyst layer 25 can be formed using a conductive ceramic composed of a so-called ABO ₃ type perovskite oxide. The cathode catalyst layer 25 is required to have gas permeability. Therefore, the open porosity of the cathode catalyst layer 25 is preferably 20% or more, and more preferably 30% to 50%. Therefore, the cathode catalyst layer 25 preferably contains a composite oxide such as LSM (La Sr Mn), LSC (La Sr Co), or LSCF (La Sr Co Fe). The thickness of the cathode catalyst layer 25 is, for example, 2 μm to 200 μm. However, this does not apply when the cathode catalyst layer 25 has a function of electrically connecting to the current collector 30 or when the cathode catalyst layer 25 itself has a function of collecting current. Depending on the materials of the anode catalyst layer 23, the electrolyte layer 24, and / or the cathode catalyst layer 25 described above, the operation of the fuel cell 20 at a temperature of about 600 ° C. or lower can be realized.

The anode catalyst layer 23, the electrolyte layer 24, and the cathode catalyst layer 25 are laminated on the anode support 21 in this order. Further, the interconnector 26 is sintered to the anode support 21. Thereby, the fuel cell 20 is formed. In the process of forming the anode support 21 described above, by sintering the composite composition to be the anode support 21 and simultaneously sintering the anode catalyst layer 23 and the electrolyte layer 24 to the composite composition, residual stress can be reduced. A structure including the anode support 21, the anode catalyst layer 23, and the electrolyte layer 24 can be formed in a small amount.

As described above, the anode support 21 according to the present embodiment is an oxidation of a single metal selected from the group consisting of at least one of Ni metal and Ni oxide and Ti, Zr, Nb, Hf, Ta, and Ce. And at least one kind of product. More specifically, the base portion 210 includes a nickel portion 212 and is porous, and the oxide particle portion 220 is provided on at least a surface in contact with the fuel in the base portion 210. The content of the oxide is 0.5% by mass or more with respect to the total mass of the anode support. Thereby, carbon deposition in the anode support 21 can be suppressed.

The fuel cell system 100 according to the present embodiment includes an anode-supported fuel cell 20 and a reformer 6 that reforms the raw fuel using heat generated from the fuel cell 20. As described above, in the fuel cell system 100 in which heat is transferred between the fuel cell 20 and the reformer 6, methane and C2 or more hydrocarbons in the reformed gas are reduced as the operating temperature of the fuel cell 20 decreases. As the concentration increases, carbon deposition tends to occur in the anode support 21. On the other hand, since the fuel cell system 100 according to the present embodiment includes the anode support 21 having the oxide particle part 220, such carbon deposition can be suppressed. In addition, when the raw fuel contains a hydrocarbon compound having 2 or more carbon atoms in an amount of 5 mol% or more based on the total molar amount of the raw fuel, the above-described carbon deposition is likely to occur, but the fuel cell system according to the present embodiment According to 100, even if the raw fuel contains 5 mol% or more of C2 or more hydrocarbons, it is possible to effectively suppress the occurrence of cracks in the anode support 21 due to carbon deposition.

Therefore, temperature management in the start-up process and the stop process of the fuel cell system 100 can be simplified. In addition, it is possible to achieve both reduction of the operating temperature of the fuel cell 20 and extension of the life of the fuel cell 20 and thus the fuel cell system 100. Furthermore, according to the present embodiment, carbon deposition can be suppressed by adding a small amount of a single oxide to the anode support 21. Therefore, carbon deposition can be suppressed without significantly changing the composition of the anode support from the conventional composition, that is, without sacrificing the conductivity and gas permeability of the anode support 21.

The present invention is not limited to the above-described embodiments, and various modifications such as design changes can be added based on the knowledge of those skilled in the art. Embodiments to which such modifications are added Can also be included in the scope of the present invention.

FIG. 3A is a horizontal cross-sectional view schematically showing a partial structure of a fuel cell stack provided in the fuel cell system according to the first modification. As shown in FIG. 3A, in Modification 1, the anode catalyst layer 23 has a substantially plate shape, and is laminated on one flat side surface of the anode support 21. The electrolyte layer 24 is laminated on the anode catalyst layer 23 and the two curved side surfaces of the anode support 21. Both ends of the electrolyte layer 24 are joined to both ends of the interconnector 26. An intermediate layer 27 is laminated on the surface of the electrolyte layer 24 opposite to the anode catalyst layer 23. Therefore, the anode catalyst layer 23 and the intermediate layer 27 face each other with the electrolyte layer 24 interposed therebetween. The intermediate layer 27 is a layer for suppressing an interlayer reaction between the electrolyte layer 24 and the cathode catalyst layer 25. The cathode catalyst layer 25 is laminated on the surface of the intermediate layer 27. The current collecting member 30 is a substantially oval conductive member having a flat surface in contact with one interconnector 26 in two adjacent fuel cells 20 and a flat surface in contact with the cathode catalyst layer 25 on the other side. .

FIG. 3B is a horizontal sectional view schematically showing the structure of the fuel cell according to Modification 2. The fuel cell 20 according to Modification 2 is a cylindrical fuel cell. The fuel cell 20 has a cylindrical anode support 21. The anode support 21 has a gas flow path 22 along its central axis. On the peripheral surface of the anode support 21, an anode catalyst layer 23, an intermediate layer 27, an electrolyte layer 24, and a cathode catalyst layer 25 are laminated in this order. The intermediate layer 27 is a layer for suppressing an interlayer reaction between the anode catalyst layer 23 and the electrolyte layer 24. A current collecting cap (not shown) is fitted to the upper and lower ends of the cylinder of the fuel cell 20. The current collecting cap is made of, for example, an alloy subjected to silver plating. A current collecting film (not shown) is provided on the circumferential surface of the cylinder of the fuel cell 20. The current collecting member 30 (see FIG. 2A) has one end electrically connected to the current collecting cap and the other end electrically connected to the current collecting film of the adjacent fuel cell 20.

The effects of the present invention will be described more specifically with reference to the following examples, but the present invention is not limited to the following examples.

<Preparation of support sample>
NiO (trade name NiO-FP, manufactured by Sumitomo Metal Mining Co., Ltd.) and YSZ (trade name TZ8YS, manufactured by Tosoh Corporation) were wet-mixed at a volume ratio of 40:60 and dried. Thereafter, it was fired at a temperature of 873 K for 1 hour. Cross-linked polymethyl methacrylate fine particles (manufactured by Sekisui Plastics Co., Ltd.) as a pore former were mixed with the powder obtained after firing at a mass ratio of 30%, and the mixture was dry-pulverized. Thereafter, the mixture was molded by applying a hydrostatic pressure press of 100 MPa to obtain a pellet-shaped sample. The obtained green compact pellet was fired at 1300 ° C. in the air for 4 hours to produce a NiO / YSZ pellet. About 2 × 2 × 10 mm rectangular parallelepiped pellet pieces were cut out from this pellet. The pellet piece was subjected to a reduction treatment at 800 ° C. for 5 hours in hydrogen to obtain a support sample made of Ni / YSZ. This support sample was referred to as Comparative Example 1. The porosity of the pellet pieces (NiO / YSZ) before the reduction treatment was about 17%, and the porosity of the support sample (Ni / YSZ) after the reduction treatment was about 35%.

Moreover, during the mixing of the NiO and YSZ in the support body samples prepared as described above, based on the total weight of the support sample being manufactured, the Example 1 material obtained by adding TiO ₂ of 0.5 wt%, 0.5 Example 2 was obtained by adding ₂ % by mass of ZrO ₂ , Example 3 by adding 0.5% by mass of Nb ₂ O _5, and Example 3 by adding 0.5% by mass of

CeO

_2. 4, 1 wt% CeO ₂ was added as Example 5, 2 wt% CeO ₂ was added as Example 6, and 5 wt% CeO ₂ was added as Example 7. did. Further, Comparative Example 2 was obtained by adding 0.5% by mass of 8YSZ (8 mol% YSZ), and Comparative Example 3 was obtained by adding 0.5% by mass of 10 GDC (10 mol% GDC).

<Measurement of deformation due to hydrocarbon exposure treatment and carbon deposition>
Deformation evaluation of the support sample according to each example and each comparative example by carbon deposition was performed using an expansion measurement device (Dilameter, manufactured by Netzsch). First, in the expansion measurement device, the support samples of each example and each comparative example were subjected to a hydrocarbon exposure treatment. FIG. 4 is a schematic diagram of an expansion measuring device. As shown in FIG. 4, each support was set in an expansion measuring device so as to measure a change in length in the long side direction of the support sample.

The atmosphere of each support sample was a dry 5% H ₂ —N ₂ atmosphere, and the temperature was raised at 5 ° C./min to about 800 ° C. (1073 K). After confirming that the length change due to the thermal expansion of the support sample converged and its shape was stabilized, supply of hydrocarbon fuel to each support sample was started and a hydrocarbon exposure treatment was performed. In the hydrocarbon exposure process, hydrocarbon fuel was supplied at a flow rate of 100 cc / min. The amount of water vapor in the hydrocarbon fuel was adjusted by bubbling temperature-controlled water or a saturated aqueous solution of lithium chloride (LiCl). As the hydrocarbon fuel, any of methane (CH ₄ ), ethane (C ₂ H ₆ ), and propane (C ₃ H ₈ ) was used.

Then, the support samples of Examples and Comparative Examples, a change in the length of the hydrocarbon exposure treatment was measured with expansion measurement device to calculate the linear expansion rate _{(ΔL / L 0) (%} ). ΔL is the amount of change in the length of the support sample, and L ₀ is the length of the support sample before the hydrocarbon exposure treatment. After the predetermined time hydrocarbon exposure treatment was completed, dry N ₂ was supplied to the support sample to purge the hydrocarbon fuel. Then, the temperature was lowered at 5 ° C./min, and the support sample was taken out from the expansion measuring device. In addition, the microscopic structure observation and elemental analysis by SEM (Scanning Electron Microscope) and EDX (Energy Dispersive X-ray spectrometry) and the homology of Ni / YSZ and precipitated carbon by X-ray diffractometer are applied to the support sample after the test. Was carried out. As a result, it was confirmed that carbon was deposited on the support sample.

<Evaluation of carbon deposition suppression>
About the support body sample of each Example and each comparative example which performed the hydrocarbon exposure process mentioned above, the relative value of the carbon deposition amount was computed by the combustion infrared absorption method. The hydrocarbon exposure measurement conditions were a temperature of 1073 K, a hydrocarbon fuel flow rate of 100 cc / min, S / C = 0.1, and an exposure time of 1 hour. The exposure time measurement was started at the timing when the linear expansion coefficient of the support sample started to change from the start of the supply of the hydrocarbon fuel (the timing at which the linear expansion coefficient elongation rate rose). In this evaluation, the carbon deposition amount when methane was supplied to the support sample of Comparative Example 1 was used as a reference value. Further, a carbon deposition amount of 50% of the reference value was set as a threshold value, and a case where the relative carbon deposition amount was less than the threshold value was evaluated as good.

The results are shown in FIG. FIG. 5 is a graph showing the relative carbon deposition amount in the support sample of each example and each comparative example. The vertical axis in FIG. 5 indicates the relative carbon deposition amount (relativerelcarbon deposition). In FIG. 5, “none” represents Comparative Example 1, “0.5% 8YSZ” represents Comparative Example 2, “0.5% 10 GDC” represents Comparative Example 3, and “0.5% TiO 2” represents Example 1. “0.5% ZrO2” is Example 2, “0.5% Nb2O3” is Example 3, “0.5% CeO2” is Example 4, and “1% CeO2” is Example 5. “2% CeO2” indicates Example 6, and “5% CeO2” indicates Example 7. “CH4” represents methane, “C2H5” represents ethane, and “C3H8” represents propane.

As shown in FIG. 5, in the support sample of Comparative Example 1 (none), the relative carbon deposition amount increased as the carbon number of the carbon-hydrogen fuel increased. In addition, when the results of the respective support samples in which the supplied fuel is methane are compared, in Comparative Example 2 (0.5% 8YSZ) and Comparative Example 3 (0.5% 10GDC), a good carbon precipitation suppression effect is seen. In contrast to Example 1 (0.5% TiO2), Example 2 (0.5% ZrO2), Example 3 (0.5% Nb2O5) and Example 4 (0.5% CeO2). Good carbon precipitation suppression effect was observed. Further, when the results of the respective support samples in which the supplied fuel is propane are compared, Example 4, Example 5 (1% CeO2), Example 6 (2% CeO2) and Example 7 are compared with Comparative Example 1. In (5% CeO2), a good carbon precipitation suppression effect was observed. Furthermore, it was confirmed that the carbon precipitation suppression effect is improved with an increase in the CeO ₂ content.

<Evaluation of deformation of support sample>
The relative values of the linear expansion coefficients were calculated for the support samples of the examples and the comparative examples subjected to the above-described hydrocarbon exposure treatment. The hydrocarbon exposure measurement conditions were a temperature of 1073 K, a hydrocarbon fuel flow rate of 100 cc / min, S / C = 0.1, and an exposure time of 1 hour. The exposure time measurement was started at the timing when the linear expansion coefficient of the support sample started to change from the start of the hydrocarbon fuel supply. In this evaluation, the linear expansion coefficient when methane was supplied to the support sample of Comparative Example 1 was used as a reference value. Further, a linear expansion coefficient of 50% of the reference value was set as a threshold value, and a case where the relative linear expansion coefficient was less than the threshold value was evaluated as good.

The results are shown in FIG. FIG. 6 is a graph showing the relative linear expansion rates of the support samples of each example and each comparative example. The vertical axis | shaft of FIG. 6 shows a relative linear expansion coefficient (relative-extension). In FIG. 6, “none”, “0.5% 8YSZ”, “0.5% 10GDC”, “0.5% TiO2”, “0.5% ZrO2”, “0.5% Nb2O3”, “0” .5% CeO2, “1% CeO2,” “2% CeO2,” “CH4,” “C2H5,” and “C3H8” have the same meaning as in FIG.

As shown in FIG. 6, in the support sample of Comparative Example 1 (none), the relative linear expansion coefficient increased as the carbon number of the carbon-hydrogen fuel increased. Further, when comparing the results of the respective support samples in which the supplied fuel is methane in common, Comparative Example 2 (0.5% 8YSZ) and Comparative Example 3 (0.5% 10GDC) do not show a good deformation suppressing effect. In contrast, in Example 1 (0.5% TiO2), Example 2 (0.5% ZrO2), Example 3 (0.5% Nb2O5) and Example 4 (0.5% CeO2), A good deformation suppressing effect was observed. Further, when the results of the respective support samples in which the supplied fuel is propane are compared, it is better in Example 4, Example 5 (1% CeO2) and Example 6 (2% CeO2) than Comparative Example 1. A deformation suppressing effect was observed. Furthermore, it was confirmed that the deformation suppressing effect was improved with an increase in the CeO ₂ content.

<Evaluation of fuel cell durability: Voltage change>
Using the cylindrical fuel cell shown in Modification 2 described above, a durability test of the fuel cell was performed. In this test, as the anode support, the support of Example 8 in which 0.5% by mass of TiO ₂ was added to Ni / YSZ containing 50% by mass of Ni in terms of oxidized Ni, similarly 0.5% by mass. The support of Example 9 to which CeO ₂ was added, the support of Comparative Example 4 to which nothing was added, and the support of Comparative Example 5 to which 0.5% by mass of YSZ was added were used. Ni / YSZ was used for the anode catalyst layer. LSGM was used for the electrolyte layer. LSCF was used for the cathode catalyst layer. As the anode gas, 5% C ₃ H ₈ /65% H ₂ /20% H ₂ O / 30% N ₂ gas was used. The anode gas used in this test is a gas simulating the anode gas used in an actual fuel cell system. As the hydrocarbon species, only C ₃ H ₈ was assumed, and CH ₄ and CO ₂ present in the actual fuel gas were replaced with 30% N ₂ . Further, 5% C ₃ H ₈ in the anode gas was contained assuming a hydrocarbon slip from the reformer outlet in the actual fuel cell system. The cathode gas was air. The operating temperature of the fuel cell was 973K. The utilization rate of the anode gas was 75%, and the utilization rate of the cathode gas was 40%.

And, the durability of the fuel cell was evaluated from the change in the output voltage of the fuel cell with the passage of the fuel cell drive time. In this evaluation, the output voltage at the initial driving stage of the fuel cell was used as a reference value. Moreover, the output voltage which decreased 10% from this reference value was set as a threshold value, and the case where the relative voltage exceeded the threshold value was evaluated as good. Further, the output voltage that is reduced by 50% from the reference value corresponds to the actual operation limit voltage of the fuel cell system.

Results are shown in FIG. FIG. 7 is a graph showing the relationship between the relative voltage of the fuel cell and the elapsed time. The vertical axis in FIG. 7 indicates the relative voltage of the fuel cell (relative の cell voltage), and the horizontal axis indicates the elapsed time (time course). As shown in FIG. 7, in the anode supports of Comparative Example 4 (none) and Comparative Example 5 (0.5% YSZ), the relative voltage decreases with the passage of time. After 175 hours, in Comparative Example 5, the relative voltage dropped below the threshold between about 250 hours and 300 hours. On the other hand, in Example 8 (0.5% TiO2) and Example 9 (0.5% CeO2), the relative voltage does not drop below the threshold value even after 1000 hours have elapsed since the start of power generation. It was. In Comparative Example 4 and Comparative Example 5, the supply amount of the fuel gas to the fuel cell is decreased mainly due to the increase in the pressure loss of the fuel gas due to the carbon deposition on the anode support, thereby increasing the anode polarization and the output of the fuel cell. The voltage is thought to have dropped. Further, in Comparative Example 4 and Comparative Example 5, in addition to gas blockage due to an increase in the amount of carbon deposition, output is also caused by a short circuit due to precipitated carbon, reoxidation of the anode support in a fuel cell in which the supply of fuel gas is interrupted, etc. It is thought that a voltage drop occurred.

<Evaluation of fuel cell durability: Cracking>
A durability test of the fuel cell was performed using the cylindrical flat plate fuel cell shown in the above-described embodiment. In this test, as the anode support, the support of Example 10 in which 0.5% by mass of TiO ₂ was added to Ni / Y ₂ O ₃ containing 60% by mass of Ni in terms of oxidized Ni, similarly 0.5 The support of Example 11 to which mass% CeO ₂ was added, the support of Comparative Example 6 to which nothing was added, and the support of Comparative Example 7 to which 0.5 mass% of YSZ was added were used. Ni / YSZ was used for the anode catalyst layer. YSZ was used for the electrolyte layer. LSCF was used for the cathode catalyst layer. As the anode gas, 2% C ₃ H ₈ /68% H ₂ /20% H ₂ O / 30% N ₂ gas was used. The reason for setting this composition is the same as that of the anode gas at the time of voltage change evaluation described above. The cathode gas was air. The operating temperature of the fuel cell was 1023K. The utilization rate of the anode gas was 70%, and the utilization rate of the cathode gas was 35%.

Then, the durability of the fuel cell was evaluated from the number of cracks generated on the surface of the fuel cell as the fuel cell driving time passed. In this evaluation, five fuel cells were driven. Then, the driving was stopped every 50 hours, the number of cracks generated on the fuel cell surface was measured, and the number of cracks generated per fuel cell was calculated.

The results are shown in FIG. FIG. 8 is a graph showing the relationship between the number of cracks generated in the fuel cell and the elapsed time. The vertical axis in FIG. 8 indicates the number of cracks per fuel cell (crack number per cell), and the horizontal axis indicates the elapsed time (time course). As shown in FIG. 8, in the fuel cells using the anode supports of Comparative Example 6 (none) and Comparative Example 7 (0.5% YSZ), the number of cracks increased with the passage of time. In particular, in Comparative Example 6, the number of cracks increased rapidly after 150 hours passed, and in Comparative Example 7, the number of cracks increased rapidly after 300 hours passed. In contrast, in Example 10 (0.5% TiO 2) and Example 11 (0.5% CeO 2), almost no cracks were observed even after 1000 hours had elapsed since the start of power generation. In Comparative Example 6 and Comparative Example 7, it is considered that cracks occurred in the electrolyte layer and the like covering the surface of the fuel cell due to dimensional expansion of the anode support accompanying carbon deposition on the anode support.

6 reformer, 20 fuel cell, 21 anode support, 23 anode catalyst layer, 24 electrolyte layer, 25 cathode catalyst layer, 100 fuel cell system, 210 base, 220 oxide particle part.

The present invention can be used in an anode support for a solid oxide fuel cell, an anode supported solid oxide fuel cell, and a fuel cell system.

Claims

Including at least one of Ni metal and Ni oxide and having a base that is porous;
Particles composed of at least one oxide of a metal selected from the group consisting of Ti, Zr, Nb, Hf, Ta and Ce on at least the surface in contact with the fuel supplied to the anode catalyst layer in the base Or an aggregate of the particles,
The anode support for a solid oxide fuel cell, wherein the content of the oxide is 0.5% by mass or more based on the total mass of the anode support.
The base is a composite of at least one of the Ni metal and the Ni oxide and at least one oxide selected from the group consisting of Y 2 O 3 , a zirconia-based composite oxide, and a ceria-based composite oxide. The anode support for a solid oxide fuel cell according to claim 1.
The anode support for a solid oxide fuel cell according to claim 1 or 2, wherein the base contains 30 mass% or more of Ni atoms in terms of Ni oxide with respect to the total mass of the anode support.
An anode support for a solid oxide fuel cell according to any one of claims 1 to 3,
An anode catalyst layer provided on the surface of the anode support;
An electrolyte layer provided on a surface of the anode catalyst layer opposite to the anode support;
A cathode catalyst layer provided on a surface of the electrolyte layer opposite to the anode catalyst layer;
An anode-supported solid oxide fuel cell comprising:
The anode support is fixed to a fuel supply path to be supplied to the anode catalyst layer;
5. The anode support according to claim 4, wherein a total weight ratio of the particles and the aggregate is larger in at least a part of the upstream side in the fuel flow direction than in at least a part of the downstream side. An anode-supported solid oxide fuel cell.
6. The anode-supported solid oxide fuel cell according to claim 4, wherein the electrolyte layer includes at least one composite oxide selected from the group consisting of a zirconia-based composite oxide, a ceria-based composite oxide, and LSGM. .
The anode catalyst layer is a composite composed of at least one of Ni metal and Ni oxide and at least one composite oxide selected from the group consisting of zirconia composite oxide, ceria composite oxide, and LSGM. The anode-supported solid oxide fuel cell according to any one of claims 4 to 6.
An anode-supported solid oxide fuel cell according to any one of claims 4 to 7,
A reformer that reforms raw fuel using heat generated from the anode-supported solid oxide fuel cell and generates fuel used for power generation of the anode-supported solid oxide fuel cell. A fuel cell system.
The fuel cell system according to claim 8, wherein the raw fuel contains a hydrocarbon compound having 2 or more carbon atoms in an amount of 5 mol% or more based on the total molar amount of the raw fuel.
At least one of Ni metal and Ni oxide;
Containing at least one oxide of a metal alone selected from the group consisting of Ti, Zr, Nb, Hf, Ta and Ce,
The anode support for a solid oxide fuel cell, wherein the content of the oxide is 0.5% by mass or more based on the total mass of the anode support.