JP2018037329A - Solid oxide fuel battery single cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the disadvantage of the occurrence of a quality-modification reaction in the vicinity of a fuel electrode in a solid oxide fuel battery of a metal support type, which are arranged so as to perform an internal quality modification of a carbon hydride-based fuel.SOLUTION: A solid oxide fuel battery single cell of the present invention comprises a fuel electrode layer, a solid electrolyte layer, and an air electrode layer which are stacked on one face of a porous metal support plate in this order, and a gas passage on a side of the other face of the porous metal support plate. The porous metal support plate supports, on the gas passage-side surface and in pores thereof, a modification catalyst for modifying a carbon hydride-based fuel into hydrogen in quality. An amount of the modification catalyst that the porous metal support plate supports on the gas passage side is larger than that on the fuel electrode layer side.SELECTED DRAWING: Figure 2

Description

  TECHNICAL FIELD The present invention relates to a solid oxide fuel cell single cell that is used by reforming a hydrocarbon-based fuel inside a fuel cell, and more specifically, a solid oxide type having improved reforming efficiency of a hydrocarbon-based fuel. The present invention relates to a single fuel cell.

  In recent years, fuel cells have attracted attention as a clean energy source that has high power generation efficiency, generates almost no harmful exhaust gas, and is friendly to the global environment.

Among various types of fuel cells, a solid oxide fuel cell (hereinafter simply referred to as “SOFC”) is an anode electrode that transmits gas to one surface of a solid electrolyte, and a cathode that transmits gas to the other surface. It has an electrode.
The fuel cell generates power by supplying fuel gas to the anode electrode and supplying oxygen-containing gas to the cathode electrode using the solid electrolyte as a partition.

  Ideally, the fuel gas is a hydrogen gas that directly causes an electrochemical reaction. However, hydrogen gas is flammable and has poor handleability such as storage and transportability, and its use requires complicated mechanisms and devices.

  Therefore, a hydrocarbon fuel generated from natural gas, biomass, or the like is used as a fuel gas that is easy to handle, and the hydrocarbon fuel is reformed and converted into hydrogen gas and supplied to the anode electrode.

  The reforming of the hydrocarbon fuel can be performed inside the solid oxide fuel cell. As the solid oxide fuel cell for internal reforming, an anode support cell supported by an anode electrode, A metal support cell supported by a metal support is known.

  The anode support cell performs both the reforming of the hydrocarbon fuel and the cell reaction while being supported as a structure by an anode electrode in which a catalyst is supported on ceramic particles. However, since the anode electrode in which the catalyst is supported on the ceramic particles is thick and has low mechanical strength, it is difficult to improve the power generation amount per volume.

Japanese Patent Application Publication No. 2012-527068 discloses a metal support type solid oxide in which a reforming catalyst is supported on a porous metal support and the hydrocarbon-based fuel is reformed in the porous metal support. A type fuel cell is disclosed.
In Patent Document 1, the amount and concentration of the reforming catalyst supported on the porous metal support is decreased from the upstream side to the downstream side in the fuel gas flow direction, that is, from the inlet to the outlet of the fuel gas. It is described that the amount of the reforming catalyst to be used, in particular, the amount of noble metal used can be optimized or reduced to the necessary minimum.

Special table 2012-527068 gazette

  However, since the thing of patent document 1 has the same amount of reforming catalysts on the anode electrode side and the gas flow path side of the porous metal support, the reforming is an endothermic reaction in the vicinity of the anode electrode. A reaction occurs, and an anode electrode in which an exothermic reaction occurs and a local temperature gradient are generated, resulting in damage due to thermal stress.

  In the process of generating hydrogen from hydrocarbon fuel, carbon may be deposited due to insufficient supply of water vapor. When carbon is deposited in the vicinity of the anode electrode, the pores of the porous metal support from the fuel gas flow path to the anode electrode, that is, the transport path of the fuel gas in the porous metal support are blocked, and the anode electrode Decrease power generation efficiency by reducing catalytic activity.

  Furthermore, it is known that the activity of the reforming reaction changes depending on the temperature, and considering that a temperature distribution occurs from the inlet to the outlet, the amount of catalyst on the inlet side is large, as in Patent Document 1, It is not always optimal to decrease the catalyst concentration toward the downstream.

For example, there are various operating points (load, conditions, etc.). In particular, when a solid oxide fuel cell for a vehicle is assumed, the reforming reaction depends on the temperature as compared with a stationary application that is generally used regularly. The activity tends to change.
As a result, the temperature distribution in the gas flow direction in the fuel cell stack also changes greatly. Therefore, if the amount of reforming catalyst in the gas flow direction is determined in advance as in Patent Document 1 and the amount of reforming catalyst on the downstream side is reduced, the robustness (correspondence and adaptation) with respect to various operating points (operating conditions). ) Will be low.

  The present invention has been made in view of such problems of the prior art, and the object of the present invention is to provide a highly robust metal support type that eliminates the disadvantage caused by the reforming reaction in the vicinity of the fuel electrode. An object of the present invention is to provide a solid oxide fuel cell unit cell.

  As a result of intensive studies to achieve the above object, the present inventor has increased the amount of the reforming catalyst supported in the porous metal support on the fuel gas channel side than on the fuel electrode layer side, thereby The present inventors have found that the object can be achieved and have completed the present invention.

That is, in the solid oxide fuel cell single cell of the present invention, the fuel electrode layer, the solid electrolyte layer, and the air electrode layer are laminated in this order on one surface of the porous metal support plate. A fuel gas flow path is provided on the other surface side of the.
And the said porous metal support plate carries the reforming catalyst which reforms hydrocarbon fuel into hydrogen in the fuel gas channel side surface and its hole,
The amount of the reforming catalyst supported on the porous metal support plate is larger on the gas flow path side than on the fuel electrode layer side.

  According to the present invention, since the amount of the reforming catalyst supported in the porous metal support is increased on the fuel gas flow path side than on the fuel electrode layer side, there is a disadvantage caused by a reforming reaction occurring in the vicinity of the fuel electrode. It is possible to provide a metal support type solid oxide fuel cell single cell with high robustness that eliminates the above problem.

It is a schematic sectional drawing which shows an example of the state which laminated | stacked the solid oxide fuel cell single cell of this invention. FIG. 2 is an enlarged cross-sectional view of a portion surrounded by a circle in FIG. 1, and is a schematic cross-sectional view illustrating a supported state of a reforming catalyst. It is a schematic sectional drawing explaining another example of the carrying | support state of a reforming catalyst. It is a schematic sectional drawing explaining the state which carry | supported the reforming catalyst in the porous gas flow path formation member.

The solid oxide fuel cell unit cell of the present invention will be described in detail.
FIG. 1 shows a schematic cross-sectional view of a solid oxide fuel cell unit cell of the present invention.
As shown in FIG. 1, the solid oxide fuel cell single cell has a fuel electrode layer 2, a solid electrolyte layer 3, and an air electrode layer 4 laminated in this order on one surface of a porous metal support plate 1. It has been done.
A metal support type in which the gas flow path forming member 5 forms a fuel gas flow path on the other surface side of the porous metal support plate 1 and an air flow path on the opposite side of the air electrode layer from the solid electrolyte layer. It is a fuel cell.
In FIG. 1, the fuel gas or air in the gas flow path flows from the front side of the page to the back side of the page.

<Porous metal support plate>
The porous metal support plate includes a reforming catalyst that supports the fuel electrode layer, the solid electrolyte layer, and the air electrode layer, and converts the hydrocarbon-based fuel into hydrogen in the surface on the fuel gas flow path side and in the hole. The hydrocarbon fuel from the fuel gas channel is converted to hydrogen and supplied to the fuel electrode layer.

  The hydrocarbon fuel is supplied from a fuel gas passage formed on the surface of the porous metal support plate opposite to the fuel electrode layer side.

  In the present invention, the “hydrocarbon fuel” is a hydrogen generation source, and in addition to so-called hydrocarbons such as alkanes, alkenes, alkynes, aromatic hydrocarbons, etc., oxygen is bonded to the above hydrocarbons. , Alcohol, aldehyde, ketone, ether and the like.

  The hydrocarbon fuel is reformed to hydrogen by the following reaction formulas (1) and (2).

_{C n H m + nH 2 O} → nCO + (m / 2 + n) H 2 ··· reaction formula (1)
_{CO + H 2 O → CO 2} + H 2 ··· reaction formula (2)
However, in Reaction Formula (1) and Reaction Formula (2), m and n represent integers.

  In the porous metal support plate of the present invention, the amount of the reforming catalyst supported is greater on the gas flow path side than on the fuel electrode layer side. FIG. 2 shows an enlarged view of a circled portion in FIG.

  As shown in FIG. 2, the reforming catalyst 11 is supported on the fuel gas channel side of the porous metal support plate so that the hydrocarbon-based fuel can be reformed in the vicinity of the fuel gas channel. it can.

  Therefore, the hydrocarbon fuel is converted into hydrogen having a high diffusion coefficient and flows inside the porous metal support plate 1, so that the gas transport resistance is reduced.

The porous metal support plate preferably has a supporting region for supporting the reforming catalyst on the fuel gas flow path side and has a non-supporting region for the reforming catalyst on the fuel electrode layer side.
That is, the reforming catalyst 11 in the porous metal support plate does not exist at the interface between the porous metal support plate 1 and the fuel electrode layer 2 as shown in FIG. 11 and the anode catalyst 21 are preferably separated and non-contact.

As the reforming catalyst 11, a catalyst similar to the anode catalyst 21 in the fuel electrode layer can be used, and a catalytic reaction or an electrochemical reaction occurs depending on the place where it is supported. Since the electrochemical reaction does not occur in the porous metal support plate and the ion conduction function is unnecessary, the roles of the reforming catalyst and the anode catalyst can be separated.
In the present invention, as shown in FIG. 3, the porous metal support plate and the fuel electrode layer may enter each other to form an interface.

The porous metal support plate 1 is not particularly limited as long as it has communication holes through which fuel gas flows and can support the fuel electrode layer 2, the solid electrolyte layer 3, and the air electrode layer 4 and can pass an electric current. There is no.
Examples of the porous metal support plate include those obtained by solidifying metal particles or metal fibers by sintering or pressing, or those obtained by forming holes in a metal plate by etching or mechanical treatment, etc. However, it is preferably a porous body obtained by sintering metal particles.

  Examples of the metal material 12 constituting the porous metal support plate include metal materials such as stainless steel, iron (Fe), nickel (Ni), and titanium (Ti).

  The porous metal support plate 1 in which the reforming catalyst 11 is unevenly distributed on the fuel gas channel side is obtained by immersing a part of the porous metal support plate in a dispersion or suspension of the reforming catalyst to support the porous metal. It can be formed by adhering to the surface and the holes of the plate, or applying the dispersion or suspension of the reforming catalyst from one side of the porous metal support plate by spray coating or the like.

  Examples of the reforming catalyst include transition metals such as nickel (Ni), cobalt (Co), copper (Cu), lanthanum (La), ruthenium (Ru), platinum (Pt), rhodium (Rh), iridium ( Ir), silver (Ag), palladium (Pd) and the like can be used, and these can be used alone or in combination of two or more.

  The metal material 12 constituting the porous metal support plate is preferably such that at least the metal material in the region supporting the reforming catalyst has irregularities on the surface. The metal material 12 in the carrying region carrying the reforming catalyst has surface irregularities, and the surface roughness is larger than the metal material in the non-carrying region that does not carry the reforming catalyst, thereby increasing the surface area of the metal material in the carrying region. Thus, the peel resistance of the reforming catalyst is improved.

  As the method for forming the surface irregularities, the porous metal support plate is immersed in a solvent such as ethanol and ultrasonic waves are applied, or the metal particles constituting the porous metal support plate are previously fired at a high temperature. In addition to the use of, surface treatment by etching and the like can be mentioned.

Moreover, you may improve the peeling resistance of a reforming catalyst by providing the binder which improves the peeling resistance different from the binder of the metal material of the said non-supporting area | region to the surface of the metal material of a carrying | support area | region.
The binder for improving the peel resistance can be composed of an inorganic substance, and examples thereof include silicon-based oxides and hydroxides.

  The binder for improving the peel resistance may be applied in advance to metal particles and metal fibers constituting the porous metal support plate, or by impregnation in the same manner as the reforming catalyst, the metal material in the supporting region. Can be applied to the surface.

  Further, the metal material of the porous metal support plate preferably has a diffusion preventing layer on the surface of the metal material in a region supporting the reforming catalyst.

  The diffusion preventing layer prevents mutual diffusion between the metal material and the reforming catalyst. By preventing mutual diffusion, the reforming catalyst is present on the surface of the metal material, and the hydrocarbon-based fuel is used for a long time. Can be modified.

  Examples of the material constituting the diffusion prevention layer include gadolinium-doped ceria, and the diffusion suppression layer can be formed by sputtering or the like.

<Fuel electrode layer>
As the fuel electrode layer, a cermet or the like in which an anode catalyst 21 is supported on ion conductive oxide particles 22 such as YSZ can be used.

  As the anode catalyst 21, an anode catalyst made of a metal and / or alloy having hydrogen oxidation activity and stable in a reducing atmosphere can be used. For example, nickel (Ni), palladium (Pd), platinum (Pt) , Ruthenium (Ru), Ni—Fe alloy, Ni—Co alloy, Fe—Co alloy, Ni—Cu alloy, Pd—Pt alloy, and the like.

<Solid electrolyte layer>
As the solid electrolyte layer 3, an oxide having oxygen ion conductivity and functioning as a solid electrolyte can be used.

Examples of the oxide include YSZ (yttria-stabilized zirconia: Zr _1-x Y _x O ₂ ), SSZ (scandium-stabilized zirconia: Zr _1-x S _cx O ₂ ), SDC (samarium-doped ceria: Ce _1-x Sm _x O ₂ ), GDC (gadlium _- doped ceria: Ce _1-x Gd _x O ₂ ), LSGM (lanthanum strontium magnesium gallate: La _1-x Sr _x Ga _1-y Mg _y O ₃ ), etc. Can be mentioned.

<Air electrode layer>
Examples of the constituent material of the air electrode layer 4 include perovskite oxides.
Examples of the perovskite oxide include perovskite oxides (for example, LSCF (lanthanum strontium cobalt iron oxide), LSM (lanthanum strontium manganese oxide), and the like.

The solid oxide fuel cell single cell can be formed by sequentially laminating a fuel electrode layer, a solid electrolyte layer, and an air electrode layer on one surface of the porous metal support plate.
The laminating method may be either a dry method or a wet method.

  Examples of the dry method include DC heating vapor deposition, ion beam vapor deposition, reactive ion beam vapor deposition, dipole sputtering, magnetron sputtering, reactive sputtering, tripolar sputtering, ion beam sputtering, and ion plating. Examples thereof include a ting method, a hollow cathode beam method, an ion beam implantation method or a plasma CVD method, and a method in which these methods are arbitrarily combined.

  In addition, examples of the wet method include inkjet, dispenser, roll coater, screen printing, and a method in which these are arbitrarily combined. The wet method can be formed by forming a film using a slurry material or a paste material.

<Gas flow path forming member>
The gas flow path forming member 5 is in contact with the porous metal support plate, and electrically and indirectly between the porous metal support plate and the air electrode layer of the solid oxide fuel cell single cell adjacent thereto. While joining, a gas flow path is formed.

  The gas flow path forming member can be formed of a corrugated separator obtained by pressing a metal flat plate as shown in FIG. 1 into a corrugated shape, a metal porous body 51 obtained by sintering metal particles as shown in FIG. As the metal material constituting the gas flow path forming member, the same metal material as that constituting the porous metal support plate can be used.

  The gas flow path forming member 5 is preferably one in which the reforming catalyst 11 is supported at a site in contact with the hydrocarbon-based fuel. Since the gas flow path forming member 5 carries the reforming catalyst 11, the hydrocarbon fuel can be converted into hydrogen even in the gas flow path, and the reforming efficiency is improved.

  The solid oxide fuel cell unit cell of the present invention can establish a reforming reaction and an electrochemical reaction of a fuel gas at a high level and is required to be operated at a high power density. A physical fuel cell can be suitably used.

DESCRIPTION OF SYMBOLS 1 Porous metal support plate 11 Reforming catalyst 12 Metal material 2 Combustion electrode layer 21 Anode catalyst 22 Ion conductive oxide particle 3 Solid electrolyte layer 4 Air electrode layer 5 Gas flow path forming member 51 Metal porous body gas flow path forming member

Claims (5)

A solid oxide having a fuel electrode layer, a solid electrolyte layer, and an air electrode layer laminated in this order on one surface of the porous metal support plate, and having a fuel gas channel on the other surface side of the porous metal support plate Type fuel cell single cell,
The porous metal support plate carries a reforming catalyst for converting a hydrocarbon-based fuel into hydrogen in the surface on the fuel gas flow path side and in the hole thereof,
A solid oxide fuel cell single cell, wherein the amount of the reforming catalyst supported on the porous metal support plate is larger on the gas flow path side than on the fuel electrode layer side.   2. The porous metal support plate according to claim 1, wherein the porous metal support plate has a supporting region for supporting the reforming catalyst on the fuel gas channel side, and has a non-supporting region for the reforming catalyst on the fuel electrode layer side. A solid oxide fuel cell unit cell as described. The reforming catalyst is supported on a metal material constituting the porous metal support plate,
The metal material in the carrying region has a surface roughness larger than that of the metal material in the non-carrying region and / or has a binder on the surface thereof that is different from the binder of the metal material in the non-carrying region. The solid oxide fuel cell single cell according to claim 2, wherein the solid oxide fuel cell is a single cell.   The metal material constituting the porous metal support plate in the region carrying the reforming catalyst has a diffusion prevention layer on the surface thereof. A solid oxide fuel cell unit cell as described. A gas flow path forming member that is in contact with the porous metal support plate and forms a gas flow path;
The gas flow path forming member is a metal porous body and / or a corrugated separator, and the reforming catalyst is supported on a portion in contact with a hydrocarbon fuel. The solid oxide fuel cell unit cell according to any one of the items.

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