JP2011255332A - Gas decomposition element and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas decomposition element which is capable of obtaining large throughput while using the electrochemical reaction, and to provide a manufacturing method thereof.SOLUTION: The gas decomposition element 10 is provided with a tubular body of MEA 7, a heater 41 to heat MEA, Celmet(R) 11s which is inserted in the inner surface side of the tubular body of MEA and which is conductive with an anode 2, a central conductive bar 11k which is so inserted as to serve as an electrically conductive axis of the Celmet(R) 11s and a Ni mesh sheet 11a inserted between the anode 2 and the Celmet(R) 11s wherein the Ni mesh sheet 11a has a portion coming out of the end of MEA and the portion coming out from the end is conductively connected with the central conductive bar 11k.

Description

  The present invention relates to a gas decomposition element and a method for manufacturing the same, and more specifically to a gas decomposition element capable of efficiently decomposing a predetermined gas and a method for manufacturing the same.

Ammonia is an indispensable compound for agriculture and industry, but it is harmful to humans. Therefore, many methods for decomposing ammonia in water and air have been disclosed. For example, in order to decompose and remove ammonia from water containing high-concentration ammonia, a method in which atomized aqueous ammonia is brought into contact with an air stream to separate ammonia in the air and brought into contact with a hypobromite solution or sulfuric acid Has been proposed (Patent Document 1). In addition, a method of separating ammonia in the air by the same process as described above and combusting with a catalyst is also disclosed (Patent Document 2). Moreover, a method for decomposing ammonia-containing wastewater into a nitrogen and water by using a catalyst has been proposed (Patent Document 3).
Moreover, ammonia, hydrogen, and the like are usually contained in the waste gas of the semiconductor manufacturing apparatus. In order to completely remove the odor of ammonia, it is necessary to detoxify it to the ppm order. For this purpose, many methods have been used in which harmful gas is absorbed in water containing chemicals through a scrubber when discharging waste gas from a semiconductor manufacturing apparatus. On the other hand, in order to obtain an inexpensive running cost without input of energy, chemicals, or the like, there has been proposed an exhaust gas treatment of a semiconductor manufacturing apparatus in which ammonia is decomposed by a phosphoric acid fuel cell (Patent Document 4).

JP-A-7-31966 Japanese Patent Laid-Open No. 7-116650 Japanese Patent Laid-Open No. 11-347535 JP 2003-45472 A

Ammonia can be decomposed by a method using a chemical solution such as the above neutralizing agent (Patent Document 1), a combustion method (Patent Document 2), a method using a thermal decomposition reaction using a catalyst (Patent Document 3), etc. It is. However, the above-described method has a problem in that it requires chemicals and external energy (fuel), requires periodic replacement of the catalyst, and has a high running cost. In addition, the apparatus becomes large and, for example, when it is additionally provided in existing equipment, the arrangement may be difficult.
A device that uses phosphoric acid fuel cells for the removal of ammonia in the exhaust of compound semiconductor manufacturing (Patent Document 4) also solves the problem by depressing pressure loss and increasing electrical resistance, etc. The idea to do is not made. When an electrochemical reaction is used for abatement of ammonia, etc., the level of practical use is large unless an epoch-making structure prevents the increase in pressure loss and the increase in electrical resistance between the electrode and current collector in a high-temperature environment. It is in a situation where the processing ability cannot be obtained and the idea remains.

  An object of the present invention is to provide a gas decomposition element and a method for manufacturing the same, which can obtain a large processing capacity while using an electrochemical reaction.

The gas decomposition element of the present invention is used to decompose gas. This gas decomposition element is a cylindrical MEA (Membrane Electrode Assembly) composed of a first electrode on the inner surface side, a second electrode on the outer surface side, and a solid electrolyte sandwiched between the first electrode and the second electrode. : A membrane-electrode assembly), a heater for heating the MEA, a porous metal body that is inserted on the inner surface side of the MEA of the cylindrical body and is electrically connected to the first electrode, and the conductivity of the porous metal body A central conductive rod inserted so as to form an axis, and a metal mesh sheet inserted between the first electrode and the porous metal body, wherein the metal mesh sheet is a portion protruding from the end of the MEA And a portion protruding from the end thereof is conductively connected to the central conductive rod.
With the above configuration, the current collector of the first electrode has a low electrical resistance, and facilitates the gas decomposition electrochemical reaction, thereby contributing to an increase in the gas decomposition processing capacity.

  The metal mesh sheet may be formed in a cylindrical shape and disposed over the first electrode so as to cover the first electrode. As a result, a metal mesh sheet covering the first electrode located on the inner surface of the cylindrical body MEA can be interposed between the first electrode and the porous metal body to reduce electrical resistance.

  The portion protruding from the end of the metal mesh sheet can be reduced in diameter and welded to the outer periphery of the central conductive rod. Thereby, the conductive connection between the metal mesh sheet and the central conductive rod can be easily realized. The welding may be any welding method such as MIG (Metal Inert Gas) welding, TIG (Tungsten Inert Gas) welding, or resistance welding.

  The portion protruding from the end of the metal mesh sheet can be joined to the outer periphery of the central conductive rod by resistance welding at one or more points. In resistance welding, a metal mesh sheet is pressed against a central conductive rod (pressure is applied), a current is passed between the interfaces, and bonding is performed by the generated heat. For this reason, welding material, inert gas, etc. are unnecessary, and joining can be realized easily in a short time while maintaining a relatively clean environment.

  The metal mesh sheet can be conductively connected to the central conductive rod on the inlet side and / or outlet side of the MEA into which a gas containing gas is introduced. This makes it possible to select an appropriate option according to the situation.

  The gas to be decomposed can be a gas discharged from the semiconductor manufacturing apparatus and a gas containing at least ammonia. As a result, it is possible to easily remove the ammonia discharged with the production of a compound semiconductor such as GaAs to the order of several ppm where no odor is felt by a small device that does not take up space. The exhaust from the semiconductor manufacturing apparatus is intermittent, and the amount of ammonia exhaust at the peak is large. That is, the ammonia emission amount varies greatly. However, the gas decomposing element of the present invention can increase the processing capacity in accordance with the peak discharge amount, and can perform the above-described detoxification.

  Electric power can be extracted from the first electrode and the second electrode to supply electric power to the heater. Thereby, energy efficient gas decomposition can be performed. Even if the amount of power generated by the private power generation is sufficient to supplement the power supplied from the outside, the running cost of the power required for heater heating can be reduced.

  It can function as a fuel cell to supply power to an external device. As a result, power generation by the fuel cell can be performed while decomposing harmful gas.

The method for producing a gas decomposition element according to the present invention includes a metal mesh sheet disposed on the inner side of the cylindrical body, on the current collector of the first electrode, with the inner surface side of the cylindrical body MEA as the first electrode. A gas decomposition element using a porous metal body and a central conductive rod inserted through the porous metal body is manufactured. This manufacturing method includes a step of fixing and winding the porous metal sheet around a central conductive rod, and a cylindrical metal mesh sheet on the inner surface of the cylindrical body MEA. A step of disposing the center conductive rod around which the porous metal sheet is wound, a step of charging the cylindrical body MEA where the metal mesh sheet is disposed, and the wound porous body The method includes a step of conductively connecting a metal body and a metal mesh sheet, and a step of conductively connecting a portion protruding from an end of the metal mesh sheet to a central conductive rod.
By the above manufacturing method, the first electrode current collector having a low electric resistance can be formed, and a gas decomposition element having a sufficiently high processing capability can be easily manufactured.

  The portion protruding from the end of the metal mesh sheet can be joined to the central conductive rod by welding. As a result, the metal mesh sheet can be efficiently connected to the central conductive rod.

Before inserting the central conductive rod into the cylindrical body MEA so that the Ni paste is interposed between the wound porous metal body and the metal mesh sheet, the wound porous metal body Or Ni paste can be apply | coated to the metal mesh sheet | seat arrange | positioned in the cylindrical body MEA. Thereby, the electrical resistance of the portion of the first electrode / metal mesh sheet / porous metal body can be lowered.

  According to the gas decomposition element or the like of the present invention, the metal mesh sheet put in order to lower the electrical resistance in the conductive connection between the first electrode and the porous metal body is extended and conductively connected to the central conductive rod. The electrical resistance of the electrode current collector can be further reduced. As a result, it is a small apparatus, has a large gas processing capacity, and can be operated at a low running cost.

(A) It is a longitudinal cross-sectional view which shows the gas decomposition element in Embodiment 1 of this invention, especially an ammonia decomposition element, (b) is sectional drawing which follows the IB-IB line in (a). FIG. 2 shows a Ni mesh sheet in a gas decomposition element, where (a) shows a form in which a Ni sheet is punched, and (b) shows a form in which a Ni wire is knitted. It is a figure which shows the edge part of Ni mesh sheet. It is a figure which shows the electrical wiring system | strain of the gas decomposition element of FIG. It is a figure which shows the formation method of an anode electrical power collector. It is a figure which shows the connection form of the external wiring and gas conveyance path with respect to cylindrical MEA. It is a figure which shows the silver paste application | coating wiring and Ni mesh sheet | seat provided in the outer peripheral surface of the cylindrical cathode. The scanning electron microscope image which shows the surface property of a silver paste application | coating wiring is shown, (a) is image data, (b) is the explanatory drawing. It is a figure for demonstrating the electrochemical reaction in an anode. It is a figure for demonstrating the electrochemical reaction in a cathode. It is a figure for demonstrating the manufacturing method of cylindrical MEA. The arrangement | sequence form of a gas decomposition | disassembly element is shown, (a) is a structure at the time of using one cylindrical MEA, Moreover, (b) is what (a) is shown in parallel (plurality (12 pieces)). It is a figure which shows the arrange | positioned structure.

FIG. 1A is a longitudinal sectional view of a gas decomposition element, particularly an ammonia decomposition element 10, which is an electrochemical reaction apparatus according to Embodiment 1 of the present invention. Moreover, FIG.1 (b) is sectional drawing which follows the IB-IB line | wire in Fig.1 (a).
In this ammonia decomposing element 10, an anode (first electrode) 2 is provided so as to cover the inner surface of the cylindrical solid electrolyte 1, and a cathode (second electrode) 5 is provided so as to cover the outer surface. MEA 7 (1, 2, 5) is formed. The anode 2 is sometimes called a fuel electrode, and the cathode 5 is sometimes called an air electrode. In general, the cylindrical body may be wound in a spiral shape or a serpentine shape, but in the case of FIG. 1, it is a right cylindrical MEA 7. The inner diameter of the cylindrical MEA is, for example, about 20 mm, but may be changed according to the device to be applied. In the ammonia decomposing element 10 of the present embodiment, the anode current collector 11 is disposed in the inner cylinder of the cylindrical MEA 7. A cathode current collector 12 is arranged so as to wrap around the outer surface of the cathode 5.

<Anode current collector 11>: Ni mesh sheet 11a / porous metal body 11s / center conductive rod 11k
The Ni mesh sheet 11a is conductively connected to the anode 2 on the inner surface side of the cylindrical MEA 7 and conducts from the porous metal body 11s to the central conductive rod 11k. Further, as shown in FIG. 1A, on the inlet 17 side, the Ni mesh sheet 11a has a portion extending from the MEA 7, and the tip W of this portion is conductively connected to the central conductive rod 11k. For this reason, the Ni mesh sheet 11a is, in parallel, referred to as (1) Ni mesh sheet 11a / porous metal body 11s / center conductive bar 11k, and (2) Ni mesh sheet / center conductive bar 11k. And a conductive path. As a result, an increase in pressure loss can be prevented while being located on the inner surface of the cylindrical MEA 7 and maintaining a low electrical resistance. This structure forms the basis of the present invention. This point will be described later in detail.
As the porous metal body 11s, in order to reduce the pressure loss of the gas containing ammonia, it is preferable to use a metal plated body capable of increasing the porosity, for example, Celmet (registered trademark: Sumitomo Electric Industries, Ltd.). On the inner surface side of the cylindrical MEA, it is important to reduce the pressure loss of gas introduction to the anode side while lowering the overall electric resistance of the current collector 11 formed of a plurality of members.
The anode 2 and the Ni mesh sheet 11a are bonded by reduction sintering after applying the Ni paste, and the sintered Ni paste 8a is interposed therebetween. Similarly, a Ni paste 8b that is reduced and sintered is located between the porous metal body 11s and the Ni mesh sheet 11a.

<Cathode current collector 12>: Silver paste coated wiring 12g + Ni mesh sheet 12a
The Ni mesh sheet 12a contacts the outer surface of the cylindrical MEA 7 and conducts to the external wiring. The silver paste-coated wiring 12g contains silver that acts as a catalyst for promoting the decomposition of oxygen gas at the cathode 5 into oxygen ions, and contributes to lowering the electrical resistance of the cathode current collector 12. Although the cathode 5 can contain silver, the silver paste coating wiring 12g having a predetermined property is connected to the cathode current collector 12 so that the silver particles come into contact with the cathode 5 while passing oxygen molecules. It exhibits the same catalytic action as silver particles contained in. Moreover, it is less expensive than the inclusion in the cathode 5.
Said Ni mesh sheet | seat 12a may be coat | covered with the silver plating layer irrespective of the presence or absence of the silver paste application | coating wiring 12g. The silver plating layer acts as a catalyst that promotes the decomposition of oxygen molecules at the cathode 5. Moreover, since the electrical resistance is small, the electrical resistance of the cathode current collector 12 is reduced. Although it is more effective to use it together with the silver paste coated wiring 12g, the silver paste coated wiring 12g may be omitted.

<Characteristics of gas decomposition element of this embodiment>
The features of the gas decomposition element 10 of the present embodiment are as follows.
(1) An Ni mesh sheet is disposed on the entire anode 2 so as to cover the anode 2, and the Ni mesh sheet 11a is interposed between the anode 2 and the porous metal body 11s.
(2) The Ni mesh sheet 11a has a portion extending from the MEA 7, and this extended portion is resistance welded to the central conductive rod 11k. The Ni mesh sheet 11a is joined to the central conductive rod 11k at the weld W.
(3) The porous metal body 11s disposed in the gas passage P is intermittent, and the ratio of the porous metal body 11s to the entire length of the passage P is about 20%, which is very small. . The role of the porous metal body 11s is to prevent gas from passing through while maintaining a low electrical resistance in the anode current collector 11. The prevention of gas passage is realized by making the gas containing the gas to be decomposed into contact with the anode 2 by making the gas turbulent or the like. It is important that pressure loss is not increased while passing through. Setting the ratio of the porous metal body 11s to the entire length of the passage P to about 20% has a great effect on reducing the pressure loss.
Due to the above characteristics, the following remarkable effects can be obtained.
(E1) The Ni mesh sheet 11a can be interposed between the anode 2 and the porous metal body 11s to increase the conductivity between the two. This is because the Ni mesh sheet 11a is a single smooth surface and is easy to come into contact with the other party, whereas the porous metal body, particularly the cermet 11s, is spirally wound around the central conductive rod 11k. This is because it consists of a set of fine dendritic parts.
(E2) From the anode 2 to the central conductive rod 11k, in addition to the conductive path of (anode 2 / Ni mesh sheet 11a / porous metal body 11s / central conductive rod 11k), (anode 2 / Ni mesh sheet 11a / center) Conductive paths of conductive bars 11k) are added in parallel. As a result, the electrical resistance of the anode current collector 11 can be dramatically reduced.
(E3) By reducing the electrical resistance in (E2) above, the length of the porous metal body 11s in the passage P can be shortened. As described above, the total length of the porous metal body 11s can be about 20% of the total length of the passage P. As a result, the pressure loss in the passage P can be dramatically reduced. Furthermore, the porous metal body 11s is intermittent as described above, and the temperature rises to a higher temperature on the outlet side than on the gas inlet side in which the decomposition electrochemical reaction proceeds at a high rate. ) Is focused on.

Next, the Ni mesh sheet 11a will be described in more detail. First, the operation (E1) will be described.
If the Ni mesh sheet 11 a is not used, the porous metal body 11 s is in direct contact with the anode 2. In this case, even if the porous metal body 11s is made of a metal plating body such as cermet, the contact resistance becomes large. The metal plating body is a sheet having a predetermined thickness, and microscopically, a dendritic metal extends and is continuous between the dendrites. When the metal plating body is inserted as the first electrode current collector on the inner surface side of the cylindrical body MEA, the sheet-shaped metal plating body is wound in a spiral shape so that the vortex axis becomes the axial center of the cylindrical body MEA. Insert along. On the outer peripheral surface of the spiral sheet, the outermost edge of the helix or the generatrix part at a predetermined position is likely to come in contact with the inner surface of the cylinder, but the inner part is helical rather than non-concentric. There is a tendency to move away from the electrode. For this reason, it is difficult to take a sufficiently large contact area between the porous metal body and the first electrode. Similarly, with respect to the contact pressure, the predetermined busbar portion can maintain a sufficient contact pressure, but it is insufficient on the inner side. For this reason, when the porous metal body is brought into direct contact with the first electrode to establish conduction, the contact resistance is increased, and the electrical resistance of the first electrode current collector is increased. Increasing the electrical resistance of the current collector decreases the ability of the electrochemical reaction. Further, further disadvantageously, in order to increase the contact area, conventionally, the porous metal body 11s has been continuously arranged to the full length of the anode 2. Such a continuous arrangement of the porous metal body 11s full length increases the pressure loss of the introduced gas.
On the other hand, when a Ni mesh sheet is used, the contact resistance can be lowered as follows. That is, in the case of the Ni mesh sheet 11a, since it is a single sheet, it is natural that the Ni mesh sheet 11a contacts the entire circumference along the inner cylindrical surface of the first electrode. Then, by adjusting the external force (compressibility) applied to fill the cylindrical body and the increase in material for filling, the metal mesh sheet 11a and the metal plating body 11s become familiar with each other and project toward the anode 2 side. The contact area with the anode 2 can be increased. In addition, at the contact interface between the metal mesh sheet 11a and the metal plating body 11s, the dendritic metals are pressed against each other and enter the gap on the other side to contact each other, so that the state of low contact resistance is maintained.
Furthermore, the electric resistance can be further reduced by disposing Ni pastes 8a and 8b at each interface of the anode 2 / Ni mesh sheet 11a / metal plated body 11s and performing reduction sintering. The reduction sintering will be described later.
As described above, even when Celmet (registered trademark), which is a metal plating body, is used as the porous metal body 11s, when the Ni mesh sheet is not used, the contact resistance is relatively large, and the cathode current collector of the gas decomposition element 10 The electrical resistance between 12 and the anode current collector 11 was, for example, about 4-7Ω. The Ni mesh sheet 11a is inserted into this, Ni pastes 8a and 8b are arranged, and reduction sintering can be performed to about 1Ω or less. That is, it can be reduced to about 1/4 or less.

  2A and 2B are views showing the Ni mesh sheet 11a. FIG. 2A shows a woven fabric made into a mesh by punching from a single-phase Ni sheet, and FIG. 2B shows a woven fabric made into a mesh by knitting Ni wire. Moreover, although not shown in figure, the nonwoven fabric formed by making a fiber into cotton shape and applying pressure may be sufficient. Any Ni mesh sheet 11a may be used. However, it is preferable to use a woven fabric in terms of flexibility and uniform distribution of pore diameters. In FIG. 2, the Ni mesh sheet 11 a is not cylindrical, but the actual gas decomposition element 10 may have an incomplete cylindrical shape with a slightly open top.

The material of the mesh sheet will be described. As described above, the Ni mesh sheet 11a has been described, but the mesh sheet material is not limited to Ni. Ni, Ni-Fe, Ni-Co, Ni-Cr, Ni-W and the like are preferable. Moreover, the mesh sheet | seat which has said metal or alloy in a plating layer may be sufficient. For example, a woven fabric of Fe plated with Ni may be used. It is alloyed by heating to form a Ni-Fe alloy. When these metals or alloys are bonded to the first electrode, it is relatively easy to achieve a reducing atmosphere with respect to the above-mentioned metal forming the mesh sheet even if the sealing conditions are not extremely strict. It becomes easy to carry out reduction bonding with one electrode. Among these, Ni-W or the like has a particularly high catalytic action, and can promote, for example, decomposition of ammonia.
In addition, the word of Ni mesh sheet | seat used after this also means that it is a mesh sheet | seat formed with the said material.

  FIG. 3 is a view showing the shape of the end portion of the Ni mesh sheet 11a. As shown in FIG. 1A, it is necessary to reduce the diameter in order to weld the Ni mesh sheet 11a to the central conductive rod 11k. The portion W to be welded may be brought into contact with the outer periphery of the central conductive rod 11k and welded by resistance welding. The number of resistance welding points is preferably about 4 at regular intervals on the outer periphery of the central conductive rod 11k. Instead of resistance welding, TIG welding or MIG welding may be performed. However, a welding material and a shielding gas are required, and since the heat input is large, the central conductive rod may be deformed. For this reason, it is better to use resistance welding. By joining the Ni mesh sheet 11a and the central conductive rod 11k by resistance welding, a joint portion having high strength and low electrical resistance can be obtained.

FIG. 4 is a diagram showing an electrical wiring system of the gas decomposition element 10 of FIG. 1 when the solid electrolyte is oxygen ion conductive. The gas containing ammonia is introduced into the inner cylinder of the cylindrical MEA 7, that is, the space where the anode current collector 12 is disposed, with tight airtightness. When the cylindrical MEA 7 is used, it is important to use the porous metal body 11s and, as described above, a metal plating body, for example, Celmet, because gas passes through the inner surface side. As described above, in the present embodiment, the cermet 11s is intermittently arranged at intervals, and the length in the passage P is about 20%.
The gas containing ammonia contacts the anode 2 while passing through the gaps between the Ni mesh sheet 11a and the porous metal 11s, and undergoes the following ammonia decomposition reaction. Oxygen ions O ²⁻ are generated by an oxygen gas decomposition reaction at the cathode and reach the anode 2 through the solid electrolyte 1. That is, it is an electrochemical reaction when oxygen ions, which are anions, move through the solid electrolyte.
(Anode reaction): 2NH ₃ + 3O ²⁻ → N ₂ + 3H ₂ O + 6e ⁻
More specifically, a part of ammonia causes a reaction of 2NH ₃ → N ₂ + 3H ₂ , and this 3H ₂ reacts with oxygen ions 3O ²⁻ to generate 3H ₂ O.
Air, particularly oxygen gas, is introduced into the cathode 5 so as to pass through the space S, and oxygen ions decomposed from oxygen molecules at the cathode 5 are sent toward the anode 2 toward the solid electrolyte 1. The cathode reaction is as follows.
(Cathode reaction): O ₂ + 4e ⁻ → 2O ²⁻
As a result of the above electrochemical reaction, electric power is generated, a potential difference is generated between the anode 2 and the cathode 5, and a current I flows from the cathode current collector 12 to the anode current collector 11. If a load, for example, a heater 41 for heating the gas decomposition element 10 is connected between the cathode current collector 12 and the anode current collector 11, electric power for that purpose can be supplied. The supply of the electric power to the heater 41 may be partial, but in most cases, the supply amount of private power generation is often less than half of the electric power required for the entire heater.

The above is an electrochemical reaction in which oxygen ions, which are anions, move through the solid electrolyte 1. For example, barium zirconate (BaZrO ₃ ) is used as the solid electrolyte 1 to generate protons at the anode 2 to generate solid electrolyte 1. The reaction of moving the inside to the cathode 5 is also a desirable form of the present invention.
When proton conductive solid electrolyte 1 is used, for example, when ammonia is decomposed, ammonia is decomposed at anode 2 to generate protons, nitrogen molecules and electrons, and protons are transferred to cathode 5 through solid electrolyte 1. Then, it reacts with oxygen at the cathode 5 to produce water (H ₂ O). Since protons are smaller than oxygen ions, the moving speed in the solid electrolyte is large. Therefore, a practical decomposition capacity can be obtained while lowering the heating temperature. The thickness of the solid electrolyte 1 is also easily set to a thickness that can ensure strength.
Further, for example, when ammonia decomposition is performed using a cylindrical body MEA, when the inner side is an anode, the oxygen ion conductive solid electrolyte is a reaction that generates water on the inner side (anode) of the cylindrical body. Water may form water droplets at the low temperature near the outlet of the cylindrical body MEA and cause pressure loss. In contrast, when a proton conductive solid electrolyte is used, protons, oxygen molecules, and electrons react at the cathode (outside) to generate water. Since the outside is almost open, pressure loss is unlikely to occur even if water droplets adhere on the outlet side at low temperature.

Next, a method of forming the anode current collector 11 using the cylindrical MEA 7, the Ni mesh sheet 11a, the cermet (porous metal body) 11s, and the central conductive rod 11k will be described with reference to FIG. A method for manufacturing the cylindrical MEA will be described later. First, the end of the Ni mesh sheet 11a is processed as shown in FIG. 3, and after applying the Ni paste 8a, the Ni mesh sheet 11a is loaded into the cylindrical MEA 7. Immediately thereafter, the anode 2 / Ni mesh sheet 11a may be bonded by reduction sintering, or may be temporarily fixed without reduction sintering.
On the other hand, the winding start portion of the cermet sheet 11s is fixed to the central conductive rod 11 by resistance welding, and is wound and temporarily fixed. Ni paste 8b is applied to the outer surface of the wound cermet 11s, and is inserted into the cylindrical MEA 7 with the Ni mesh sheet 11a. Thereafter, the Celmet 11s and the Ni mesh sheet 11a are joined immediately by reduction sintering (RS process). When the Ni mesh sheet 11a and the anode 2 are not reduced and sintered by this (RS step), they are reduced and sintered in parallel in this (RS step). Next, (W step) An extended portion (end portion) W of the Ni mesh sheet 11a is arranged on the outer periphery of the central conductive rod 11k, and resistance welding is performed. The order of (RS process) and (W process) may be interchanged. As a result, the anode current collector 11 can be formed and transferred to the next step.
Resistance welding can be performed, for example, under the following conditions.
Resistance welder: manufactured by Miyachi Technos, welding power source: IS-120B, welding transformer: ITH-651A6W6, welding head: MH-D500C, welding conditions: current 6.0 kA × pressure 25.0 N
The conditions for reduction sintering are holding at 800 ° C. for 10 to 20 minutes in a nitrogen atmosphere containing 20% NH ₃ .

Features of other parts of the gas decomposition element 10 of the present embodiment will be described.
1. Center conductive rod 11k:
In the present embodiment, the MEA 7 has a cylindrical shape, and one of the features is that the central conductive rod 11k is used for the anode current collector 11. The center conductive rod 11k is preferably formed of a metal that does not contain Cr in at least the surface layer. For example, the Ni conductive rod 11k is preferable. This is because when stainless steel containing Cr is used, the ceramic GDC in the anode 2 malfunctions due to Cr poisoning during use. The diameter of the central conductive rod 11k is not particularly limited, but is preferably about 1/9 to 1/3 of the inner diameter of the cylindrical solid electrolyte 1. For example, when the inner diameter is 18 mm, the thickness is preferably about 2 mm to 6 mm. If it is too thick, the maximum flow rate of the gas that can be flowed will decrease, and if it is too thin, the electrical resistance will increase, leading to a voltage drop during power generation. The porous metal body 11s is resistance-welded to the central conductive rod 11k at the beginning of winding of a sheet-like material (Celmet sheet), tightly wound in a spiral shape, and the spiral state is maintained. For this reason, the electrical resistance at the interface between the porous metal body 11s and the central conductive rod 11k is small. The advantages of using the central conductive rod 11k are as follows.
(1) The overall electrical resistance between the anode 2 and the external wiring can be reduced. That is, it helps to reduce the electrical resistance of the anode current collector 11.
(2) The crying place in the case of using a conventional cylindrical MEA is that the external terminals of the current collector on the inner surface side cannot be put together in a small size with a simple structure. A porous metal body is indispensable for collecting current on the inner surface side of the cylindrical MEA. However, this porous metal body is difficult to put together the end portions, and a miniaturized terminal portion cannot be formed. For example, when the end of the porous metal is stretched to establish a conductive connection with the outside, the gas decomposition element itself becomes large, and the commercial value is greatly reduced. Also, it is not preferable to extend the porous metal body in terms of pressure loss.
Further, since a gas containing ammonia is introduced into the inside of the cylindrical MEA 7, it is important to connect the gas conveying path and the cylindrical MEA 7 with high airtightness and the connection between the anode current collector 11 and the external wiring. . At the end of the cylindrical MEA 7, both a connection part to the external wiring of the anode current collector and a connection part to the gas conveyance path are provided.
The central conductive rod 11k is easy to process such as threading and grooving, and is a solid rod, so that it is not deformed by some external stress, and its shape can be maintained stably. As a result, the connecting portion between the anode current collector 11 and the external wiring can be realized with a simple structure and in a small size.
(3) In order to operate the gas decomposing element 10 efficiently, it is necessary to heat to 300 ° C. to 1000 ° C. The heater 41 for heating can only be arranged outside the air passage. Although heat is conducted from the outside to the inside of the cylindrical MEA 7, the end portion of the cylindrical MEA 7 naturally becomes high temperature. In order to connect the external wiring and the gas transport path with high airtightness to the high temperature end, a special heat resistant resin is required at the above high temperature. In addition, since corrosion due to gas tends to increase as the temperature increases, a special material may be required for corrosion resistance. As a result, usable resin may be very expensive.
However, if the central conductive rod 11k is used, it is at a position farthest from the outside on the heater 41 side, and can be easily extended in the axial direction. For this reason, in the position extended to the location where temperature is comparatively low, the electrical connection with an external wiring and the connection with a gas conveyance path can be performed, making airtightness high. As a result, a resin having a normal level of heat resistance and corrosion resistance can be used without using a very special resin, so that economic efficiency can be improved and durability can be improved.

FIG. 6 is a diagram showing a connection form between the central conductive rod 11k and the external wiring 11e and a connection form between the cylindrical MEA 7 and the gas conveyance path 45. A tubular joint 30 made of fluororesin is fitted into the end of the cylindrical MEA 7. In the fitting, the O-ring 33 housed on the inner surface side of the fastening portion 31b extending from the main body portion 31 of the tubular joint 30 to the solid electrolyte 1 is brought into contact with the outer surface of the ceramic solid electrolyte 1 which is a sintered body. The state is maintained. For this reason, the fastening portion 31b of the tubular joint 30 is configured such that the outer diameter changes into a taper shape, a screw is cut there, and the annular screw 32 is screwed into the screw. By fastening the annular screw in the direction in which the outer diameter increases, the fastening portion 31b is tightened from the outer surface, and the airtightness by the O-ring 33 can be adjusted.
The main body portion 31 of the tubular joint 30 is provided with a conductive through portion 37c that penetrates the main body portion 31 while maintaining airtightness, and is coated with a sealing resin 38 or the like in order to maintain airtightness. The conductive penetrating portion 37c is a cylindrical rod, and a screw for screwing the nut 39 is preferably cut in order to make a reliable conductive connection with the external wiring 11e. A conductive wire 37b is bonded to the distal end of the conductive through portion 37c in the tube, and a connection plate 37a is bonded to the other end of the conductive wire 37b.
Conductive connection between the connection plate 37a and the distal end portion 35 of the central conductive rod 11k is performed by screwing the screw 34 through the protruding hole portion 31a of the tubular joint 30 using a connection tool such as a driver. . By tightening the screw 34 by the driver, the electrical resistance (contact resistance) in the conductive connection between the tip 35 and the connection plate 37a can be almost eliminated.
Further, the external wiring 12e can be wound around the outer periphery of the end portion of the Ni mesh sheet 12a of the cathode current collector 12, whereby the lead-out to the outside can be performed. Since the cathode 5 is located on the outer surface side of the cylindrical MEA 7, it is not as difficult as withdrawing from the anode current collector 11 to the outside.
For the gas conveyance path 45, it is preferable to use a tube made of an elastically deformable resin or the like. By fitting the tube 45 to the outer periphery of the protruding hole portion 31 a and fastening with the fastener 47, a connection with good airtightness can be obtained.
The connection between the anode current collector 11 and the external wiring 11e and the connection between the tubular joint 30 and the gas conveyance path 45 in FIG. 6 are both realized by a very simple and small structure. Also, the above two types of connections are separated by the central conductive rod 11k and the tip portion 35 that is an accessory thereof to a position that is out of the main stream portion of the thermal sulfur from the heater. For this reason, long-term repeated durability can be ensured by an ordinary heat-resistant resin or corrosion-resistant resin called a fluororesin. Moreover, as added for confirmation, the central conductive rod 11k is conductively connected to the porous metal body 11s with a small contact resistance as described above.

2. Silver paste coated wiring 12g:
Conventionally, it has been usual to arrange silver particles on the cathode 5 to improve the decomposition rate of oxygen molecules by the catalytic action of the silver particles. However, in the structure in which the cathode 5 contains silver particles, the price of the cathode 5 becomes high and the economy is lowered. Instead of containing silver particles in the cathode 5, wiring of silver particles can be formed on the outer surface of the cathode 5 in the form of a silver paste coating layer.
FIG. 7 is a diagram showing a silver paste coated wiring 12g and a Ni mesh sheet 12a provided on the outer peripheral surface of the cylindrical cathode 5. As shown in FIG. In the silver paste application wiring 12g, the silver paste is arranged on the outer peripheral surface of the cathode 5, for example, as shown in FIG. 5, the belt-like wiring is arranged in a lattice shape (bus line direction + annular direction).
What is important in this silver paste is to make it highly porous after drying or sintering. FIG. 8 shows an SEM (Scanning Electron Microscopy) image showing the surface of the silver paste coated wiring 12g, (a) is image data, and (b) is an explanatory diagram thereof. As shown in FIG. 8, a silver paste that becomes porous after being applied and dried (sintered) is commercially available. For example, DD-1240 manufactured by Kyoto Elex Co., Ltd. can be used. The importance of making the silver paste coated wiring 12g porous is based on the following reason.
The cathode 5 should be supplied with as many oxygen molecules O ₂ as possible, and the silver particles contained in the silver paste have a catalytic action that promotes the cathode reaction in the cathode 5 (see FIG. 10). By applying the silver paste coating wiring 12g to the cathode 5, the metal oxide such as LSM that passes oxygen ions in the cathode, silver particles, and oxygen molecules O ₂ are in contact with each other at high density (contact points). Arise. By making the silver paste coated wiring 12g porous, a large number of oxygen molecules O ₂ enter the porous pores and touch the above-mentioned contact portions, and the cathode reaction is likely to occur.
Furthermore, since the silver paste coated wiring 12g containing silver particles has high conductivity, the Ni mesh sheet 12a is assisted to lower the electrical resistance in the cathode current collector 12. For this purpose, the silver paste coated wiring 12g is preferably provided so as to be continuous in a lattice shape (bus line direction, annular direction) as described above. The outer Ni mesh sheet 12a is wound so as to be in contact with the silver paste coated wiring 12g.
In summary, the silver paste-coated wiring 12g that becomes porous can promote (1) the cathode reaction and (2) lower the electrical resistance of the cathode current collector 12.
As shown in FIG. 5, the silver paste coated wiring 12 g may be provided in a strip shape in a lattice shape, or may be formed on the entire outer peripheral surface of the cathode 5. When the silver paste is applied to the entire outer peripheral surface of the cathode 5, it is difficult to call it a wiring. . In the case of applying to the entire outer peripheral surface of the cathode 5, the Ni mesh sheet 12a can be omitted.

3. Anode 2:
-Configuration and action-
FIG. 9 is a diagram for explaining an electrochemical reaction of the anode 2 when the solid electrolyte 1 is oxygen ion conductive. A gas containing ammonia is introduced into the anode 2 and flows through the pores 2h. The anode 2 is a sintered body mainly composed of a metal particle chain 21 having a surface oxidized oxide layer and an oxygen ion conductive ceramic 22. As the oxygen ion conductive ceramic 22, SSZ (scandium stabilized zirconia), YSZ (yttrium stabilized zirconia), SDC (samarium stabilized ceria), LSGM (lanthanum gallate), GDC (gadria stabilized ceria) and the like are used. be able to.
The metal of the metal particle chain 21 is preferably nickel (Ni) or Ni containing iron (Fe). More preferably, Ti contains a trace amount of about 2 to 10000 ppm. (1) Ni itself has a catalytic action to promote the decomposition of ammonia. Further, the catalytic action can be further enhanced by containing a small amount of Fe or Ti. Furthermore, the nickel oxide formed by oxidizing this Ni can further enhance the promotion effect of these simple metals. However, since the ammonia decomposition reaction (anode reaction) is a reduction reaction, the oxide layer produced in the sintering process, etc., was formed in the Ni particle chain in the product before use. The chain is also reduced and the oxide layer disappears. However, the catalytic action of Ni itself is certain, and furthermore, in order to cover the absence of an oxide layer, Fe or Ti can be included in Ni to compensate for the reduction in catalytic action.
In addition to the above catalytic action, oxygen ions are allowed to participate in the decomposition reaction at the anode. That is, the decomposition is performed in an electrochemical reaction. In the above-mentioned anode reaction 2NH ₃ + 3O ²⁻ → N ₂ + 3H ₂ O + 6e ⁻ , oxygen ions contribute and greatly improve the decomposition rate of ammonia. (3) In the anode reaction, free electrons e ⁻ are generated. When the electrons e ⁻ stay on the anode 2, the progress of the anode reaction is hindered. The metal particle chain 21 is elongated in a string shape, and the content 21a covered with the oxide layer 21b is a good conductor metal (Ni). The electrons e ⁻ flow smoothly in the longitudinal direction of the string-like metal particle chain. For this reason, the electrons e ⁻ do not stay in the anode 2 and flow outside through the contents 21 a of the metal particle chain 21. The metal particle chain 21 makes the passage of electrons e ⁻ very good. In summary, the characteristics of the embodiment of the present invention are the following (e1), (e2) and (e3) in the anode.
(E1) Promotion of decomposition reaction by nickel particle chain, Fe-containing nickel chain, or Fe, Ti-containing nickel particle chain (high catalytic function)
(E2) Decomposition promotion by oxygen ions (decomposition promotion in electrochemical reaction)
(E3) Ensuring continuity of electrons by string-like good conductor of metal particle chain (high electron conductivity)
By the above (e1), (e2) and (e3), the anode reaction is greatly promoted.
The decomposition of the decomposition target gas proceeds only by raising the temperature and bringing the decomposition target gas into contact with the catalyst. It is disclosed in prior literature and is well known as described above. However, as described above, in the element constituting the fuel cell, oxygen ions are involved in the reaction from the cathode 5 through the ion conductive solid electrolyte 1, and as a result, the generated electrons are conducted to the outside, thereby decomposing. The reaction rate is dramatically improved. It is a major feature of the present invention to have the functions (e1), (e2), and (e3) described above, and a configuration that provides the functions.
Although the above description is for the case where the solid electrolyte 1 is oxygen ion conductive, the solid electrolyte 1 may be proton (H ⁺ ) conductive. In this case, the ion conductive ceramics 22 in the anode 2 is proton conductive. Ceramics such as barium zirconate is used.
-Formulation and sintering-
When the oxygen ion conductive metal oxide (ceramics) of the anode 2 is SSZ, the average diameter of the raw material powder of SSZ is about 0.5 μm to 50 μm. The compounding ratio between the surface-oxidized metal particle chain 21 and SSZ22 is in the range of 0.1 to 10 in terms of mol ratio. A sintering method is performed by hold | maintaining for 30 minutes-180 minutes, for example in air | atmosphere atmosphere at the temperature of 1000 to 1600 degreeC. The manufacturing method will be described later in connection with the manufacturing method of the cylindrical MEA 7 in particular.

4). Metal grain chain 21:
-Reduction precipitation method-
The metal particle chain 21 is preferably manufactured by a reduction precipitation method. The reduction precipitation method of the metal particle chain 21 is described in detail in Japanese Patent Application Laid-Open No. 2004-332047. The reduction precipitation method introduced here is a method using trivalent titanium (Ti) ions as a reducing agent, and the precipitated metal particles (Ni particles and the like) contain a small amount of Ti. For this reason, it can identify with what was manufactured by the reduction | restoration precipitation method by trivalent titanium ion by quantitatively analyzing Ti content. By changing the metal ions present together with the trivalent titanium ions, desired metal grains can be obtained. In the case of Ni, Ni ions are allowed to coexist. When a small amount of Fe ions is added, a Ni grain chain containing a small amount of Fe is formed.
In order to form a chain, the metal must be a ferromagnetic metal and have a predetermined size or more. Since both Ni and Fe are ferromagnetic metals, a metal particle chain can be easily formed. The size requirement is that the ferromagnetic metal forms a magnetic domain and bonds with each other by magnetic force, and in the combined state, the metal is deposited → the growth of the metal layer occurs, and the entire metal body is integrated. ,is necessary. Even after metal grains of a predetermined size or more are bonded by magnetic force, metal deposition continues, for example, the neck at the boundary of the bonded metal grains grows thicker together with other portions of the metal grains. The average diameter D of the metal particle chain 21 contained in the anode 2 is preferably in the range of 5 nm to 500 nm. The average length L is preferably in the range of 0.5 μm or more and 1000 μm or less. The ratio between the average length L and the average diameter D is preferably 3 or more. However, it may have dimensions outside these ranges.
-Formation of oxide layer-
When the surface oxidation treatment is used for the anode 2, the degree of importance is slightly reduced because it is reduced. The surface oxidation treatment method is as follows. Three types of (i) heat treatment oxidation by vapor phase method, (ii) electrolytic oxidation, and (iii) chemical oxidation are suitable methods. In (i), it is good to process at 500-700 degreeC for 1 to 30 minutes in air | atmosphere. Although it is the simplest method, it is difficult to control the oxide film thickness. In (ii), surface oxidation is performed by applying a potential to about 3 V with reference to a standard hydrogen electrode and performing anodization. However, the oxide film thickness can be controlled by the amount of electricity according to the surface area. However, when the area is increased, it is difficult to uniformly form an oxide film. In (iii), the surface is oxidized by being immersed in a solution in which an oxidizing agent such as nitric acid is dissolved for about 1 to 5 minutes. Although the oxide film thickness can be controlled by time, temperature, and type of oxidizer, cleaning of chemicals is troublesome. Either method is suitable, but (i) or (iii) is more preferred.
A desirable thickness of the oxide layer is 1 nm to 100 nm, and more preferably 10 nm to 50 nm. However, it may be outside this range. If the oxide film is too thin, the catalyst function will be insufficient. In addition, even a slight reducing atmosphere may cause metallization. On the other hand, if the oxide film is too thick, the catalytic property is sufficiently maintained, but on the other hand, the electronic conductivity at the interface is impaired and the power generation performance is lowered.

5). Cathode 5:
-Configuration and action-
FIG. 10 is a diagram for explaining an electrochemical reaction at the cathode 5 when the solid electrolyte 1 is oxygen ion conductive. Air, particularly oxygen molecules, is introduced into the cathode 5. The cathode 5 is a sintered body mainly composed of an oxygen ion conductive ceramic 5c. In this case, it is preferable to use LSM (lanthanum strontium manganite), LSC (lanthanum strontium cobaltite), SSC (samarium strontium cobaltite) or the like as the oxygen ion conductive ceramic 5c.
In the cathode 5 in the present embodiment, Ag particles are arranged in the form of silver paste coated wiring 12g. Among them, the Ag particles have a catalytic function for greatly promoting the cathode reaction O ₂ + 4e ⁻ → 2O ²⁻ . As a result, the cathodic reaction can proceed at a very high rate. The average diameter of the Ag particles is preferably 10 nm to 100 nm.
The above is a description of the case where the solid electrolyte 1 is oxygen ion conductive. However, the solid electrolyte 1 may be proton (H ⁺ ) conductive, and in this case, the ion conductive ceramic 5c in the cathode 5 is a proton conductive ceramic, For example, barium zirconate may be used.
-Sintering-
The average diameter of SSZ is preferably about 0.5 μm to 50 μm. The sintering conditions are maintained at 1000 ° C. to 1600 ° C. for about 30 minutes to 180 minutes in an air atmosphere.

6). Solid electrolyte 1:
As the electrolyte 1, a solid oxide, molten carbonate, phosphoric acid, solid polymer, or the like can be used, but the solid oxide is preferable because it can be downsized and easily handled. As the solid oxide 1, it is preferable to use oxygen ion conductive SSZ, YSZ, SDC, LSGM, GDC, or the like. Further, as described above, proton conductive barium zirconate can also be used.

7). Plating metal body 11s:
The porous metal body 11s, which is an important element of the current collector of the anode 2, is preferably a metal plating body. As the porous metal body 11, it is preferable to use a metal-plated porous body, particularly a Ni-plated porous body, that is, the above-mentioned Celmet (registered trademark). The Ni-plated porous body can have a large porosity, for example, 0.6 or more and 0.98 or less. This makes it possible to obtain very good air permeability while functioning as one element of the current collector of the anode 2 that is the inner surface side electrode. If the porosity is less than 0.6, the pressure loss increases, and if forced circulation by a pump or the like is performed, the energy efficiency is lowered, and bending deformation or the like occurs in the ion conductive material or the like. In order to reduce the pressure loss and prevent the ion conductive material from being damaged, the porosity is preferably 0.8 or more, and more preferably 0.9 or more. On the other hand, when the porosity exceeds 0.98, the electrical conductivity is lowered and the current collecting function is lowered.

8). Manufacturing method of cylindrical MEA7:
The outline of the manufacturing method of the cylindrical MEA 7 will be described with reference to FIG. FIG. 11 shows a step of firing for each of the anode 2 and the cathode 5. First, a commercially available cylindrical solid electrolyte 1 is purchased and prepared. Next, when the cathode 5 is formed, a solution in which the cathode constituent material is dissolved in a solvent so as to have a predetermined fluidity is prepared and applied uniformly to the outer surface of the cylindrical solid electrolyte. Next, the cathode 5 is fired under suitable firing conditions. Thereafter, the process proceeds to formation of the anode 2. There are many variations in addition to the manufacturing method shown in FIG. In the case where the number of times of firing is one time, as shown in FIG. 9, instead of firing each part, each part is formed in the applied state, and finally the greatest common divisor of each part Firing is performed under various conditions. In addition, there are many variations, and the manufacturing conditions can be determined by comprehensively considering the material constituting each part, the target decomposition efficiency, the manufacturing cost, and the like.

9. Arrangement of Gas Decomposing Elements FIG. 12 is a view showing an arrangement example of the gas decomposing elements 10. FIG. 12 (a) shows a gas abatement apparatus when one cylindrical MEA 7 is used, and FIG. 12 (b) shows a plurality (12 pieces) of those shown in FIG. 12 (a) in parallel. It is the gas abatement apparatus of the structure arrange | positioned. When the processing capacity of one MEA 7 is insufficient, the plurality of parallel arrangements can increase the capacity without troublesome processing. In any of the plurality of cylindrical MEAs 7, the anode current collector 11 (11a, 11s, 11k) is inserted on the inner surface side, and a gas containing ammonia is flowed on the inner surface side. A space S is provided on the outer surface side of the cylindrical MEA 7 so as to be in contact with hot air or hot oxygen.
Moreover, about the heater 41 which is a heating apparatus, it can provide by the aspect which bundles and bundles the whole cylindrical MEA7 arranged in parallel. By adopting such a mode in which the whole is bundled together, downsizing can be achieved.

(Other gas decomposition elements)
Table 1 is a table illustrating other gas decomposition reactions to which the gas decomposition element of the present invention can be applied. The gas decomposition reaction R1 is the ammonia / oxygen decomposition reaction described in the first embodiment. In addition, the gas decomposition element of the present invention can be used for any of the gas decomposition reactions R2 to R8. That is, it can be used for ammonia / water, ammonia / NOx, hydrogen / oxygen /, ammonia / carbon dioxide gas, VOC (volatile organic compounds) / oxygen, VOC / NOx, water / NOx, and the like. In any reaction, the first electrode is not limited to the anode, and may be a cathode. The cathodes should be paired accordingly.

Table 1 only illustrates some of the many electrochemical reactions. The gas decomposition element of the present invention is applicable to many other reactions. For example, Table 1 is limited to reaction examples of the solid electrolyte having oxygen ion conductivity, but the reaction example in which the solid electrolyte is proton (H ⁺ ) conductivity as described above is also a powerful embodiment of the present invention. is there. Even if the solid electrolyte is made proton conductive, the ionic species that permeate the solid electrolyte become protons. However, in the gas combinations shown in Table 1, it is possible to achieve decomposition of gas molecules as a result. For example, in the reaction of (R1), in the case of a proton conductive solid electrolyte, ammonia (NH ₃ ) decomposes into nitrogen molecules, protons, and electrons at the anode, and the protons move through the solid electrolyte to the cathode. The electrons move through the external circuit to the cathode. At the cathode, oxygen molecules, electrons, and protons generate water molecules. As a result, ammonia is decomposed in combination with oxygen molecules, which is the same as when the solid electrolyte is oxygen ions.

(Other application examples)
The above electrochemical reaction is a gas decomposition reaction for the purpose of removing gas. However, there are gas decomposition elements that are not mainly intended for gas removal, and the gas decomposition elements of the present invention can also be used in such electrochemical reaction devices such as fuel cells.

  Although the embodiments of the present invention have been described above, the embodiments of the present invention disclosed above are merely examples, and the scope of the present invention is not limited to these embodiments. The scope of the present invention is indicated by the description of the scope of claims, and further includes meanings equivalent to the description of the scope of claims and all modifications within the scope.

  According to the gas decomposition element or the like of the present invention, the metal mesh sheet put in order to lower the electrical resistance in the conductive connection between the first electrode and the porous metal body is extended and conductively connected to the central conductive rod. The electrical resistance of the first electrode current collector can be lowered. By reducing the electrical resistance, the length of the porous metal body in the gas passage can be shortened, so that an increase in pressure loss can be prevented. As a result, it is a small apparatus, has a large gas processing capacity, and can be operated at a low running cost.

  DESCRIPTION OF SYMBOLS 1 Solid electrolyte, 2 anode, 2h pore in anode, 5 cathode, 5c ion conductive ceramic of cathode, 8a, 8b Ni paste, 10 gas decomposition element, 11 anode current collector, 11a Ni mesh sheet, 11e anode external wiring 11g Ni paste layer, 11k center conductive rod, 11s porous metal body (metal plating body), 12 cathode current collector, 12a Ni mesh sheet, 12e cathode external wiring, 12g silver paste coating wiring, 21 metal particle chain, 21a Core part (metal part) of metal particle chain, 21b oxide layer, 22 ion conductive ceramic of anode, 30 tubular joint, 31 tubular joint body part, 31a protruding hole part, 31b fastening part, 32 annular screw, 33 O Ring, 34 screw, 35 Center conductive rod tip, 3 a connection plate, 37b conductive wire, 37c conductive through-hole, 39 nut, 45 gas conveying path, 47 fastener, 41 heater, 51 exhaust passage before decomposition, 53 exhaust passage after decomposition, 61 control panel, 63 power generation wiring, 64 External power wiring, P gas passage (inside MEA), S air space, W Ni mesh sheet weld.

Claims (11)

An element used to decompose gas,
A cylindrical MEA (Membrane Electrode Assembly) composed of a first electrode on the inner surface side, a second electrode on the outer surface side, and a solid electrolyte sandwiched between the first electrode and the second electrode;
A heater for heating the MEA;
A porous metal body that is inserted on the inner surface side of the MEA of the cylindrical body and is electrically connected to the first electrode;
A central conductive rod inserted so as to form a conductive axis of the porous metal body;
A metal mesh sheet inserted between the first electrode and the porous metal body,
The metal mesh sheet has a portion protruding from the end of the MEA, and the portion protruding from the end is conductively connected to the central conductive rod.   2. The gas decomposition element according to claim 1, wherein the metal mesh sheet has a cylindrical shape and is disposed over the first electrode so as to cover the first electrode.   The gas decomposing element according to claim 2, wherein a portion protruding from an end of the metal mesh sheet is reduced in diameter and welded to an outer periphery of the central conductive rod.   The part which protruded from the end of the said metal mesh sheet | seat is joined to the outer periphery of the said center conductive rod by the resistance welding at one or several points, The one of Claims 1-3 characterized by the above-mentioned. The gas decomposition element as described in 2.   The metal mesh sheet is conductively connected to the central conductive rod on the inlet side and / or the outlet side of the MEA into which the gas containing the gas is introduced. The gas decomposing element according to any one of the above.   The gas decomposition element according to claim 1, wherein the gas to be decomposed is a gas discharged from a semiconductor manufacturing apparatus and is a gas containing at least ammonia.   The gas decomposing element according to claim 1, wherein electric power is taken out from the first electrode and the second electrode to supply electric power to the heater.   The gas decomposition element according to claim 1, wherein the gas decomposition element functions as a fuel cell for supplying electric power to an external device. A metal mesh sheet, a porous metal body, and the porous metal body, which are disposed on the inner side of the cylindrical body, are disposed on the inner surface of the cylindrical body MEA as a first electrode. A gas decomposition element manufacturing method using a central conductive rod to be inserted,
Fixing and winding the porous metal sheet around the central conductive rod;
A step of disposing a cylindrical metal mesh sheet on an inner surface of the cylindrical body MEA so as to have a portion protruding from an end of the cylindrical body MEA;
A step of charging the central conductive rod around which the porous metal sheet is wound into the cylindrical body MEA in which the metal mesh sheet is disposed;
A step of conductively connecting the wound porous metal body and the metal mesh sheet;
And a step of conductively connecting a portion protruding from an end of the metal mesh sheet to the central conductive rod.   The method of manufacturing a gas decomposition element according to claim 9, wherein a portion protruding from an end of the metal mesh sheet is joined to a central conductive rod by welding. Before inserting the central conductive rod into the cylindrical body MEA so that Ni paste is interposed between the wound porous metal body and the metal mesh sheet, the winding is performed. 11. The method for producing a gas decomposition element according to claim 9, wherein Ni paste is applied to a metal mesh sheet disposed in the porous metal body or cylindrical body MEA.

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