JP2012011337A - Electrode connection structure, fuel cell, gas detoxifying apparatus, and method of manufacturing electrode connection structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode connection structure that can be further improved both in reduction in electric resistance of an electrode/collector, and favorable contact between the electrode and gas in a general electrochemical reaction, and to provide a fuel cell, a gas detoxifying apparatus, and a method of manufacturing the electrode connection structure.SOLUTION: In the electrode connection structure, an anode 2 is porous, including ion conductive ceramics. Moreover, the collector 11a is a metal mesh sheet 11a, and the anode 2 and the metal mesh sheet 11a are reductively joined.

Description

  The present invention relates to an electrode connection structure, a fuel cell, a gas abatement apparatus, and a method for manufacturing an electrode connection structure, and more specifically, an electrode connection that can reduce electrical resistance while ensuring sufficient contact between the electrode and gas. The present invention relates to a structure, a fuel cell, a gas abatement apparatus, a method for manufacturing an electrode connection structure, and the like.

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.
An apparatus (patent document 4) that uses a phosphoric acid type fuel cell for the elimination of ammonia in exhaust gas from the production of compound semiconductors also inhibits the improvement of the abatement capability, increases the electric resistance, and improves the gas and the electrode. There is no contrivance to solve the problems such as contact and pressure loss. When electrochemical reaction is used for the detoxification of ammonia, etc., unless an innovative structure prevents the increase in electrical resistance between the electrode and current collector in a high temperature environment, improvement in contact efficiency between gas and electrode, etc. However, it is difficult to obtain a large processing capacity at a practical level.
Not only in gas abatement devices, but also in electrochemical reaction devices that involve gas decomposition, such as fuel cells, the electrical resistance of the electrode / current collector, the good contact between the fuel gas or air and the electrode is It is essential to increase the capacity or efficiency of the reactor. For this reason, there is a demand for measures to further improve both.

  The present invention provides an electrode connection structure that can further reduce both the electrical resistance of an electrode / current collector and the good contact between the electrode and the gas in an electrochemical reaction involving gas decomposition and the like. It aims at providing the manufacturing method of a fuel cell, a gas abatement apparatus, and an electrode connection structure.

The electrode connection structure of the present invention is a connection structure between an electrode and a current collector for use in an electrochemical reaction. In this electrode connection structure, the electrode includes ion conductive ceramics and is porous, the current collector is a porous metal body, and the electrode and the porous metal body are reduction-bonded. And
In the reduction bonding, the metal oxide is reduced to a metal at a predetermined temperature and partial pressure of oxygen, and in the reduction process, the metals or the metal and the oxide diffuse to each other and bond. For this reason, no extra material is used in addition to the objects to be joined, and no part of the joined part that blocks the pores on the other side in shape is generated. For this reason, the gas which passes by the electrode and the electrode can maintain a favorable contact in the state of reduction joining. In particular, good contact with the electrode while passing through the porous metal body can be obtained.
As for conductivity, an oxide layer or the like is not interposed therebetween, so that good current collecting property can be obtained. In reduction bonding, high energy density localization (such as a thin high energy density beam) is not required for bonding, and if the porous metal body is in contact with the entire surface of the electrode, the bonding proceeds slowly over the entire surface of the electrode. . As a result, the electrode and the porous metal body are conductively connected to the porous metal body over the entire surface of the electrode, and a conductive connection with low electrical resistance can be realized.
Note that the current collector may be formed by combining a plurality of members instead of a single member. Usually, a plurality of members are combined, and in this case, the porous metal body can be considered as one of the plurality of members.

  The porous metal body can be a metal mesh sheet. The metal mesh sheet has no unevenness and has a smooth flat surface or curved surface, and good electrical conductivity can be obtained by planar contact with the electrode of the reduction bonding partner. Also, the gas can make good contact with the porous electrode through the mesh of the mesh sheet. The gas can come into contact with the electrode by freely entering and leaving through the pores of the porous electrode as well as the macroscopic surface along which the metal mesh sheet is located.

  It can be set as the structure by which a metal particle is located in the circumference | surroundings of the junction part reduced-joined, and this junction part. The metal particles are applied in the form of a metal paste at the time of reduction bonding so that the reduction bonding is performed reliably. That is, the metal paste is used to fill a gap between the electrode and the metal mesh sheet (porous metal body) to promote conductive connection. The metal particles are distributed in a discrete manner regardless of the aggregate state and the individual state, not the form covering the surface. For this reason, it is possible to ensure good contact between the gas and the electrode while obtaining high conductivity.

  The metal mesh sheet may be a metal woven fabric or a metal woven fabric that is plated. Metal woven fabrics are rich in flexibility and are thin but elastic in the thickness direction. For this reason, planar contact can be easily obtained according to the surface of the electrode.

Metal mesh sheet and / or metal particles (Ni, Ni-Co, Ni-Fe, Ni-Cr, Ni-Cu and Ni-W single phase metals, and It is possible to adopt a configuration in which the metal is formed of any one of a composite metal having a plating layer as a plating layer.
An alloy containing one or more of the above (Ni, Ni—Co, Ni—Fe, Ni—Cr, Ni—Cu, and Ni—W) has a catalytic action and promotes decomposition of gas molecules. . For this reason, it can contribute to promotion of an electrochemical reaction by distributing in the form of a mesh sheet and / or particle | grains in the position which contacts an electrode, or the position which adjoins.
Further, among these, the mesh sheet or the plating layer applied to the mesh sheet containing one or more of (Ni, Ni—Co, Ni—Fe, Ni—Cu) is reduced even if the oxygen partial pressure is relatively high. Easy to join. For this reason, a highly reliable reduction junction can be easily obtained.

The current collector includes a second porous metal body that is conductively connected to a metal mesh sheet, and the second porous metal body is positioned so as to block the flow of the gas so that the gas does not pass therethrough. Can take.
According to said structure, favorable electroconductivity and favorable contact with gas and an electrode can be obtained, keeping the pressure loss of gas low.

  The metal mesh sheet and the second porous metal body can be reduced and joined. Thus, the turbulent gas flow can easily pass through the joint between the metal mesh sheet and the second porous metal body. That is, the above-described reduction junction does not become an obstacle in the gas path between the porous metal body and the electrode. In other words, the reduction joint between the metal mesh sheet and the second porous metal body also has good air permeability and conductivity for the same reason as the reduction joint between the electrode and the (first) porous metal body. Sex can be obtained.

The metal mesh sheet is located over the entire surface of the electrode, and the second porous metal body is intermittently disposed so that there is a portion where the metal mesh sheet is not contacted by the second porous metal body. Can be configured.
With the above configuration, the pressure loss can be further reduced, and good conductivity and good electrode-gas contact can be obtained.

The second porous metal body is a plated porous body, and the plated porous body is a kind of (Ni, Ni—Co, Ni—Fe, Ni—Cr, Ni—Cu, and Ni—W). It can be formed of any one of the above-described single-phase metals and composite metals having a metal plating layer.
Plated porous bodies are known for their high porosity among porous metals. For this reason, the pressure loss of a gas flow can be made low. And the catalytic action with respect to gas decomposition | disassembly of these metals can be obtained by using said metal plating porous body or the said metal plating layer. Furthermore, reduction joining can be facilitated for Ni, Ni—Co, Ni—Fe, and Ni—Cu metals.

The fuel cell or gas abatement apparatus of the present invention is characterized by using any of the electrode connection structures described above.
This makes it possible to obtain good contact between the electrode and the gas while obtaining good conductivity between the electrode and the current collector.

The electrode connection structure manufacturing method of the present invention manufactures a connection structure between an electrode and a current collector for use in an electrochemical reaction. In this manufacturing method, the metal mesh sheet is placed in contact with the entire surface of the electrode, and at least the space where the electrode and the metal mesh sheet are located is set to a temperature at which bonding is performed by diffusion, and the mesh sheet is formed at that temperature. And an atmosphere that does not oxidize with respect to the metal, and the electrode and the metal mesh sheet are maintained for the time during which the electrode and the metal mesh sheet are reductively bonded.
By the above method, it is possible to easily obtain an electrode connection structure excellent in conductivity and contact between the electrode and gas. In this case, the partial pressure of oxygen in the space is set to about 1E-14 atm to 1E-16 atm or less. In this case, an inert gas such as nitrogen gas or argon gas is mainly flowed, a reducing gas such as ammonia is mixed to cause a chemical reaction with oxygen molecules, and the oxygen partial pressure is lowered by two kinds of gases. Is good.

  In order to realize an atmosphere that does not become oxidizing, it is possible to measure whether there is a leak in the space with a leak detector. In order to obtain an ultra-high vacuum atmosphere with an oxygen partial pressure of about 1E-14 atm to 1E-16 atm or less, it is difficult to realize if oxygen gas enters (leaks) from the atmosphere. The leak detector can perform highly accurate leak detection by flowing helium gas into the atmosphere space and measuring the leakage of the helium gas outside the space. By using this leak detector, it is possible to easily and surely obtain an atmosphere for reducing bonding while using a reducing gas such as an inert gas and / or ammonia.

Furthermore, the plating porous body for preventing the passage of the gas involved in the electrochemical reaction is brought into contact with the metal mesh sheet, and the plating porous body and the metal mesh sheet can be reduced and joined.
As a result, while reducing the pressure loss of the gas flow, the conductivity between the electrode and the combined current collector is improved, and the gas passage between the plated porous body through which the main gas flow passes and the electrode Can be better.

  The reduction bonding between the electrode and the metal mesh sheet and the reduction bonding between the metal mesh sheet and the plated porous body can proceed in parallel on the same occasion. Thereby, the electrode connection structure can be manufactured efficiently.

(Ni, Ni-Co-based, Ni-Fe-based, Ni-Cr-based, Ni-Cu-based) at the contact portion between the electrode and the metal mesh sheet and / or the contact portion between the metal mesh sheet and the plated porous body , And a single phase metal containing at least one of Ni-W, and a composite metal having a plating layer of the metal, and a paste containing metal particles of any one of them is disposed to perform reduction bonding. be able to.
This facilitates the decomposition of gas such as ammonia, and then the gas passage between the plated porous body and the electrode via the metal mesh sheet, and the conductivity between the electrode and the combined current collector Thus, it is possible to easily and reliably obtain an electrode connection structure that secures both.

The electrochemical reaction includes a process of introducing a gas containing a reducing gas to the electrode. When the electrochemical reaction apparatus is not in operation, the electrode and the metal mesh sheet are not reductively joined, and the operation is started. Thus, the reduction bonding can be realized by introducing a non-oxidizing gas into the electrochemical reaction apparatus.
In the above electrochemical reaction device, the electrode and the metal mesh sheet are not reductively bonded before the first operation. They are only in mechanical contact. Reduction bonding can be realized by flowing a reducing gas such as ammonia in the space where the electrode and the metal mesh sheet are located during the initial operation. Thereby, an electrode connection structure can be obtained easily and inexpensively. Even during the subsequent operation, the portion where the reduction bonding is performed is reinforced, and the reduction bonding is not eliminated. Moreover, although oxygen in air may be touched at the time of an operation stop, since the elapsed time at high temperature is so short that reduction joining is canceled, reduction joining is maintained without a problem.

  According to the electrode connection structure and the like of the present invention, in the electrochemical reaction accompanied by gas decomposition and the like, the reduction in the electric resistance of the electrode / current collector and the good contact between the electrode and the gas are more excellent. I can do it.

It is a figure which shows the gas decomposition apparatus in which the electrode connection structure in Embodiment 1 of this invention was used. It is a figure for demonstrating the electrochemical reaction in the gas decomposition apparatus of FIG. 1 in case the solid electrolyte 1 is oxygen ion electroconductivity. (A) is the elements on larger scale which show the metal mesh sheet | seat in an anode, when using the metal mesh sheet | seat 11a as a woven fabric. It is a figure for demonstrating the material and electrochemical reaction of an anode in case a solid electrolyte is oxygen ion electroconductivity. It is a figure for demonstrating the material and electrochemical reaction of a cathode in case a solid electrolyte is oxygen ion electroconductivity. It is a figure which shows the procedure which obtains the standard of the oxygen partial pressure for performing reductive joining using a redox equilibrium diagram (Ellingham diagram). It is a flowchart which shows the procedure for carrying out reductive joining of an anode and an anode electrical power collector. (A) is a longitudinal cross-sectional view of the gas decomposition apparatus which has the electrode connection structure in Embodiment 2 of this invention, (b) is a cross-sectional view which follows a VIIIB-VIIIB line. It is a figure for demonstrating the electrochemical reaction in the gas decomposition apparatus of FIG. 8 in case the solid electrolyte 1 is oxygen ion electroconductivity. The metal mesh sheet | seat which is interposed between an anode and a plating porous body, and carries out reduction | restoration joining to both is shown, (a) is a mesh sheet | seat (the opening part is exaggerated), (b) is a metal film A mesh sheet in which an opening is formed by punching. It is a figure which shows the outer peripheral surface by which the cathode collector on the outer side of cylindrical MEA is arrange | positioned. The SEM image which shows the surface of a silver paste application part is shown, (a) is image data, (b) is the explanatory drawing. It is a figure for demonstrating the outline | summary of the manufacturing method of cylindrical MEA. (A) is a longitudinal cross-sectional view of the gas decomposition apparatus in Embodiment 3 of this invention, (b) is a cross-sectional view which follows the XIIIB-XIIIB line in (a). In Embodiment 4 of this invention, it is a figure which shows the system which functions as a fuel cell.

(Embodiment 1)
FIG. 1 is a diagram showing a gas abatement apparatus 10, particularly an ammonia decomposition apparatus 10, in which the electrode connection structure according to Embodiment 1 of the present invention is used. In FIG. 1, an anode 2 and an anode current collector 11 are disposed on the upper side, and a cathode 5 and a cathode current collector 12 are disposed on the lower side with the solid electrolyte 1 interposed therebetween. With this as a unit, usually a plurality of units are laminated. The lamination is held by pressing with a fastener, restraint by a casing, or the like.
The point in the present embodiment is the connection structure between the anode 2 which is one electrode in the MEA 7 and the anode current collector 11 (11a, 11s). That is, in the anode 2 / metal mesh sheet ((first) porous metal body) 11a / second porous metal body (plated porous body) 11s, the anode 2 and the metal mesh sheet 11a are reduced. is conductively connected by joints a _1, also a metal mesh sheet 11a and the plating porous 11s is conductively connected by reduction junction a _2.
In the reduction bonding, the metal paste containing the metal particles 11p is used as a material for bonding, and none of the pores of the porous anode 2, the metal mesh sheet 11a, and the plated porous body 11s are blocked. . In addition, since no oxide or the like is interposed between the objects to be joined, the conductivity is excellent. The metal particles 11p are extremely effective in reducing the electrical resistance of the reduction junctions A ₁ and A ₂ by ensuring reduction junction. The average diameter of the metal particles 11p is preferably about 10 nm to 5000 nm.
By the above reduction bonding, the anode 2 that is a porous body can be in sufficient contact with gas, and the anode 2 and the metal mesh sheet 11a / plated porous body 11s constituting the current collector 11, It is possible to sufficiently reduce the electrical resistance between the two. Furthermore, the reduction junction A _1, A _2, since no thing that could block the pores, the pressure loss is largely determined by the porosity and the like of the plating porous body 11s, the reducing joint A _1, A ₂ There is no increase in pressure loss. Rather, in the relationship between the electrical resistance of the current collector and the pressure loss, which is in a trade-off relationship, the anode 2 and the metal mesh sheet 11a are reduced and joined with a very low electrical resistance. The arrangement of the second porous metal body (plated porous body) 11s can be made sparse. That is, the second porous metal body (plated porous body) 11s is intermittently arranged at intervals to reduce the pressure loss and allow an increase in the electrical resistance of the anode current collector 11 to some extent. Become.
The second porous metal body is a plated porous body 11s, and in particular, Celmet (registered trademark: Sumitomo Electric Industries, Ltd.) is preferably used in order to reduce pressure loss. It is also preferable to use Celmet (registered trademark) for the plated porous body 12 s in the cathode current collector 12 to be described later.

The current collector 12 of the cathode 5 is composed of (metal mesh sheet 12a + silver particles 12g) / plated porous body 12s. The conductive connection between the cathode 5 and the metal mesh sheet 12a and the conductive connection between the metal mesh sheet 12a and the plated porous body 12s are both mechanical contact portions B such as pressing by a fastener and restraint by a casing. ₁ and B ₂ are secured. For the contact portions B ₁ and B ₂ in the cathode 5, it is important to minimize oxidation as much as possible, and therefore it is important to use silver having a high catalytic function for decomposing oxygen molecules. The silver particles 12g contribute to the reduction of electrical resistance while contributing to the prevention of oxidation at the contact portion. For this reason, it can be useful for preventing deterioration of the cathode current collector, that is, improving durability.

The conductive connection with the current collector 11 in the anode 2 is realized by reduction bonding, while the conductive connection with the current collector 12 in the cathode 5 is realized by contact for the following reason. In the fuel cell or gas abatement apparatus, the anode 2 is called a fuel electrode, the cathode 5 is called an air electrode, and the anode 2 is a reduction of hydrogen, ammonia, VOC (Volatile Organic Compound) or the like. The cathode 5 comes into contact with an oxidizing gas to decompose the gas, and the cathode 5 comes into contact with an oxidizing gas such as oxygen to decompose the oxygen molecules. For this reason, in the anode 2, the reduction junctions A ₁ and A ₂ are stably maintained during operation at a high temperature. Since the temperature is low during the rest, the oxidation does not proceed to the extent that the reduction bonding is eliminated even though it is in contact with oxygen.
On the other hand, even if the reduction bonding is performed on the cathode 5, the reduction bonding is eliminated by oxidation, and on the contrary, the oxidation proceeds. For this reason, even if a reduction junction is formed, the reduction junction is not maintained. For this reason, the cathode 5 uses a pressing mechanism for maintaining conductive contact, restraint by a casing, etc., while relying on a catalyst for decomposing oxygen such as silver particles 12g for the conductive connection with the current collector 12, while preventing oxidation. It is good. As will be described later, in order to improve the oxidation resistance, a silver plating layer is formed on the metal mesh sheet 12a and / or the metal mesh sheet 11a is made of a metal having a strong catalytic action for oxygen molecule decomposition. It is also important to form with.

  A metal woven fabric is preferably used for the metal mesh sheets 11a and 12a. The metal woven fabric is deformed flexibly and is easily compressed in the thickness direction. For this reason, not only the reduction junction but also the conductive connection by the contact at the cathode 5 can obtain a sufficiently large surface contact, and the electrical resistance between the cathode 5 and the cathode current collector 12 can be lowered. it can. That is, by interposing the metal woven fabric 12a between the plated porous body 12s and the cathode 5, the electric resistance can be sufficiently lowered. As described above, the silver particles 12g contribute to the reduction of electric resistance.

FIG. 2 is a view for explaining an electrochemical reaction in the ammonia decomposition apparatus 10 of FIG. 1 when the solid electrolyte 1 is oxygen ion conductive.
The gas containing ammonia contacts the anode 2 while passing through the gaps between the metal mesh sheet 11a and the plated porous body 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, and oxygen ions decomposed from oxygen molecules at the cathode 5 are sent out 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 abatement apparatus 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.

Fig.3 (a) is a figure at the time of using the metal mesh sheet 11a as a woven fabric. In order to emphasize the suppleness similar to that of a normal cloth, it is shown with a slight slack. The thickness is about 100 μm to 500 μm. Needless to say, when the anode 2 is brought into contact with the anode 2, it is arranged without slack. The metal mesh sheet 11a includes (a single-phase metal including one or more of Ni, Ni-Co, Ni-Fe, Ni-Cr, Ni-Cu, and Ni-W), and the metal. It is good to form with either of the composite metal used as a plating layer. The composite metal is, for example, a woven fabric of iron (Fe) subjected to Ni plating (woven fabric). It is alloyed by heating during the production or operation of the gas abatement apparatus to form a Ni-Fe woven fabric.
The Ni-based or alloy-based woven fabric has a catalytic action for gas decomposition, and can promote gas decomposition. For this reason, the metal mesh sheet 11a, especially the woven fabric, not only lowers the electrical resistance of the electrode connection structure (E1), but can also promote gas decomposition at the electrode (E2) (catalytic action). As a result, the gas decomposition treatment capacity can be improved. The metal mesh sheet 11a in the anode 2 has another important function, which will be described later.
A metal mesh sheet 11a similar to this can be used for the current collector 12a of the cathode 5. However, since the cathode 5 comes into contact with oxygen and decomposes oxygen molecules, it is preferable to perform silver plating. Accordingly, the decomposition of oxygen molecules can be promoted together with the silver particles 12g or without the silver particles.

FIG. 3B is a partially enlarged view showing a metal mesh sheet 11a between the anode 2 and the plated porous body 11s. The metal mesh sheet 11a is interposed between the plated porous body 11s for preventing gas from passing through and the anode 2, and realizes a good conductive connection therebetween. In order to realize this low electric resistance, the reduction junctions A ₁ and A ₂ are formed. In order to assist the reduction bonding A ₁ and A ₂ , a metal paste containing the metal particles 11p is used so that the metal particles 11p are distributed at the interface and in the vicinity thereof after sintering. The metal particles 11p include (Ni, Ni—Co, Ni—Fe, Ni—Cr, Ni—Cu, and Ni—W single phase metal, and the metal as a plating layer). Or a composite metal). As a result, the same catalytic action that promotes gas decomposition can be obtained as in the case of the metal mesh sheet 11a.

FIG. 4 is a diagram for explaining the material and 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 catalyst, that is, a chain body 21 of alloy particles that are surface-oxidized and have an oxide layer, and an oxygen ion conductive ceramic 22. Here, a chain 21 of Ni—Fe alloy particles is used. The composition is preferably about Ni 60 at%, for example.
Furthermore, it is preferable to contain a trace amount of Ti of about 2 to 10000 ppm. Catalysis can be further enhanced by containing a small amount of 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 the Ni—Fe alloy itself is reliable, and furthermore, in order to cover the absence of an oxide layer, Ti can be included in the Ni—Fe system to compensate for the reduction in catalytic action.
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.

In addition to the above catalytic action, oxygen ions are allowed to participate in the decomposition reaction at the anode 2. 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 chain 21 is elongated in a string shape, and the contents 21a covered with the oxide layer 21b is a good conductor metal (Ni—Fe alloy). The electron e ⁻ flows smoothly in the longitudinal direction of the string-like chain. For this reason, the electrons e ⁻ do not stay in the anode 2, and flow outside through the contents 21 a of the chain 21. The chain 21 makes the electron e ⁻ path very good.
In addition, since ammonia which is a reducing gas is introduced into the anode 2, the oxide layer 21b of the chain 21 is also reduced, and even if the oxide layer 21b is formed before installation, it is reduced during operation. For this reason, the catalytic action of gas decomposition by the oxide layer 21b cannot be expected, but on the contrary, a smooth flow of electrons or the like can be compensated. Further, the chain metal 21a can exert a sufficiently large gas decomposition catalytic action by directly contacting the gas.
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 chain 3 (high catalytic function)
(E2) Decomposition promotion by oxygen ions (decomposition promotion in electrochemical reaction)
(E3) Ensuring continuity of electrons by the string-like good conductor 3a of the chain 3 (high electron conductivity)
The high electronic conductivity of the above (e3) has good electrical conductivity between the anode 2 and the anode current collector 11 and between the cathode 5 and the cathode current collector 12 in view of the whole electrochemical reaction. Securing contributes. There is also a contribution of a good conductive connection in each current collector 11, 12.
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. However, as described above, in the apparatus constituting the fuel cell or the like, oxygen ions are involved in the reaction from the cathode 5 through the ion conductive solid electrolyte 1, and as a result, the resulting electrons are conducted outside, The decomposition reaction rate is dramatically improved.
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.

FIG. 5 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 oxygen ion conductive ceramics 52. As the oxygen ion conductive ceramic 52 in this case, LSM (lanthanum strontium manganite), LSC (lanthanum strontium cobaltite), SSC (samarium strontium cobaltite), or the like may be used. When the oxygen ion conductive solid electrolyte 1 is used, the cathode 5 may not use a chain.
In the cathode 5 in the present embodiment, Ag particles are arranged in the form of a silver paste application part 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.
Since silver has a catalytic action for promoting the decomposition of oxygen molecules, a silver plating layer may be formed on the metal mesh sheet 12a in addition to the above-described silver paste coating portion 12g. By forming the silver plating layer on the metal mesh sheet 12a, the decomposition of oxygen molecules is further promoted.

For 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 handled easily. As the solid oxide 1, it is preferable to use oxygen ion conductive SSZ, YSZ, SDC, LSGM, GDC, or the like.
In addition, a reaction in which protons are generated at the anode 2 using, for example, barium zirconate (BaZrO ₃ ) as the solid electrolyte 1 and moved through the solid electrolyte 1 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.

As described above, the effect of forming the metal mesh sheet 11a of the anode current collector 11 with the above metal is as follows: (E1) Decrease in electrical resistance of the electrode connection structure (good conductivity), (E2) There was acceleration of gas decomposition (catalysis) at the electrode. A metal mesh sheet 11a used for the anode current collector 11 is plated with a single-phase metal containing at least one of Ni, Ni—Co, Ni—Fe, and Ni—Cu, and metals of these systems. Another effect of forming the composite metal as a layer is that (E3) the reduction junctions A ₁ and A ₂ having a low electrical resistance can be obtained.
FIG. 6 shows a metal redox equilibrium diagram (Ellingham diagram). Using this figure, it is possible to know how much the oxygen partial pressure should be reduced in the reduction junction. For example, when the reduction bonding is performed at 800 ° C. and the metal mesh sheet 11a and the metal particles 11p are Ni-based, the oxygen partial pressure can be obtained by the following procedure. The horizontal axis (temperature axis) is called the X axis, and the vertical axis (energy axis) is called the Y axis.
(T1) A straight line is established parallel to the Y axis from a temperature of 800 ° C.
(T2) The intersection (●) with the straight line (energy-temperature curve) of NiO is obtained.
(T3) Oxygen O mark on the left side) and the intersection point ● are connected by a straight line and extended.
(T4) The intersection of the extended straight line and the outside Po ₂ partial pressure scale is a measure of the oxygen partial pressure required in the reduction bonding. If the oxygen partial pressure is equal to or lower than this oxygen partial pressure, reduction bonding is possible by diffusion without being oxidized. As a result, the reduction junctions A ₁ and A ₂ having low electric resistance can be obtained.
In the case of Ni-based, the standard oxygen partial pressure is 1E-14 (atm). Other systems can be obtained in the same procedure. For example, in the Fe system, the oxygen partial pressure is 1E-16 atm. Since there is no data about the alloy, it can be considered that the oxygen partial pressure between Ni and Fe is about 1E-15 atm.
In the above system, Ni, Co, and Fe are not oxidized even at a relatively high oxygen partial pressure (reduction bonding is possible), but in the Cr system, the oxygen partial pressure must be very low. For this reason, it is difficult to say that reduction bonding is easy for Ni—Cr and Ni—W systems. However, reduction bonding is possible if the oxygen partial pressure is lowered to a predetermined level.

The metal mesh sheet 12a of the cathode current collector 11 can be considered as follows. The metal mesh sheet 12a is exposed to an oxidizing atmosphere. For this reason, the metal mesh sheet 11a is required to have oxidation resistance. For this reason, the metal mesh sheet 12a of the cathode current collector 12 is desirably formed of a Ni—Cr system or a Ni—W system. Using this Ni-Cr-based or Ni-W-based woven fabric as it is, the silver particles 12g can be used as a catalyst. You may use what formed the Ni-Cr plating layer and the Ni-W plating layer in the woven fabric of iron (Fe).
Moreover, you may use what formed the silver plating layer in the Ni-Cr type | system | group and Ni-W type | system | group woven fabric. When the silver plating layer is formed, the silver particles 12g may not be used or may be used. Moreover, when using a silver plating layer, the metal (to-be-plated material) of a woven fabric may be iron (Fe). This is because silver easily decomposes oxygen molecules, and the oxidation resistance can be greatly improved only by the silver plating layer. As a result, the electrical resistance of the cathode current collector 12 itself and between the cathode current collector 12 and the cathode 5 can be reduced.

FIG. 7 is a diagram showing a method for manufacturing the electrode connection structure of the anode 2.
First, an MEA (Membrane Electrode Assembly) 7 in which anode 2 / solid electrolyte 1 / cathode 5 is laminated is prepared. Usually, the MEA 7 is integrated. The metal mesh sheet 11a is brought into contact with the anode 2 and a metal paste containing metal particles 11p is applied. Next, after applying a metal paste to the plated porous body 11s, the metal mesh sheet 11a is laminated and laminated. This laminate, MEA 7 (anode 2) / metal mesh sheet 11a / plated porous body 11s, is placed in an atmosphere for reduction bonding. It is desirable that a metal paste is disposed at least at the boundary between the layers.
The atmosphere of the reduction bonding needs to be less than or equal to the oxygen partial pressure in the oxidation-reduction equilibrium diagram shown in FIG. For this purpose, a leak check is performed to confirm that there is no entry of air or oxygen from the outside. In order to realize the low oxygen partial pressure, an inert gas such as nitrogen gas or argon gas, or a reducing gas such as hydrogen or ammonia, or both (inert gas and reducing gas) is sufficient. It is good to flow an appropriate amount. When both an inert gas and a reducing gas are used, it is preferable that a small amount of gas such as ammonia is contained on the basis of nitrogen gas. For example, (3% NH ₃ + N ₂ ) can be used. While aiming at the realization of the low oxygen partial pressure, heating is performed at a temperature at which sufficient diffusion occurs, for example, about 950 ° C. If a sufficiently low oxygen partial pressure is realized, the reduction bonding proceeds automatically at the above 950 ° C. The holding time at 950 ° C. is preferably 20 minutes, for example. As a result, it is possible to obtain an electrode connection structure that allows good contact between the anode 2 and the gas to be decomposed and that has low electrical resistance.

(Embodiment 2)
FIG. 8 is a diagram showing a gas abatement apparatus 10 having an electrode connection structure according to Embodiment 2 of the present invention. The gas to be decomposed is ammonia. FIG. 8A is a longitudinal sectional view, and FIG. 8B is a transverse sectional view taken along the line VIIIB-VIIIB. As shown in these drawings, the gas decomposition apparatus 10 in the present embodiment is manufactured using a cylindrical MEA 7 (1, 2, 5).
An anode 2 is provided so as to cover the inner surface of the cylindrical solid electrolyte 1, and a cathode 5 is provided so as to cover the outer surface. As described above, the anode 2 is called a fuel electrode, and the cathode 5 is called an air electrode. The inner diameter of the cylindrical MEA is, for example, about 20 mm, but may be changed according to the device to be applied. An 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.

Each current collector is as follows.
<Anode current collector 11>: Metal mesh sheet 11a / plated porous body 11s / center conductive rod 11k
The metal mesh sheet 11a is reductively joined to the anode 2 on the inner surface of the cylindrical MEA ₇ to form a reductive joint A1. Furthermore, the metal mesh sheet 11a forms a reduced junction A ₂ is reduced joined with the plated porous body 11s. The plated porous body 11s is wound around the central conductive rod 11k, and a conductive connection is realized between them. Therefore, anode 2 / metal mesh sheet 11a / plated porous body 11s / center conductive rod 11k are conductively connected. For the plated porous body 11s, in order to reduce the pressure loss of a gas containing ammonia, which will be described later, the Celmet (registered trademark) that can increase the porosity is preferably used. 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. In the present embodiment, while using the above-mentioned Celmet (registered trademark), the plated porous body is not disposed over the entire length, and is disposed intermittently at intervals to reduce the pressure loss. By disposing the plated porous body 11s intermittently at intervals, the pressure loss decreases, but the electrical resistance of the anode current collector 11 increases. However, even if the metal mesh sheet 11a is used and a metal paste containing metal particles is used to form the reduction joints A ₁ and A ₂ , the electrical resistance is practical even if they are arranged intermittently at intervals. In addition, it can be suppressed to a level with no problem.
When the central conductive rod 11k uses a cylindrical MEA to flow a gas requiring airtightness such as ammonia on the inner surface side, the central conductive rod 11k can be electrically connected to the external wiring with a small and simple structure. Further, by slightly extending the center conductive rod 11k, a conductive connection structure can be formed in a region where the influence of heating of the heater is small, and no special heat resistant seal is required. For this reason, it is excellent also in economical efficiency.

<Cathode current collector 12>: Silver paste application part 12g + metal mesh sheet 12a
In the cathode 5, the metal mesh sheet 12 a contacts the outer surface of the cylindrical MEA 7 and conducts to the external wiring. The silver paste application part 12g contains silver particles that act as a catalyst for promoting the decomposition of oxygen gas at the cathode 5 into oxygen ions, and lowers the electrical resistance of the cathode current collector 12. The cathode 5 may contain silver particles. However, the silver paste coating portion 12g having a predetermined property passes through the cathode current collector 12 while the silver particles come into contact with the cathode 5 while passing oxygen molecules. The catalytic action equivalent to that of silver particles contained therein is expressed. Moreover, it is less expensive than the inclusion in the cathode 5. The metal mesh sheet 12a may be subjected to silver plating to form a silver plating layer.

FIG. 9 is a diagram showing an electrical wiring system of the gas decomposition apparatus 10 of FIG. 8 when the solid electrolyte is oxygen ion conductive. The anode current collector 11 is electrically connected to the external wiring 11e, and the cathode current collector 12 is electrically connected to the external wiring 12e, and is wired on the plus side and the minus side of the load. The load can be a heater 41 or the like for heating the MEA 7, and as a result, the energy efficiency can be increased as in the first embodiment.
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, the use of the plated porous body 11s is indispensable because gas passes through the inner surface side. From the viewpoint of reducing the pressure loss, it is important to use a plated porous body having a high porosity as described above. The gas containing ammonia contacts the anode 2 while passing through the gaps between the metal mesh sheet 11a and the plated porous body 11s, and is subjected to the above-described electrochemical reaction.

The electrochemical reaction occurring in the anode 2 and the cathode 5 is the same as that in the first embodiment. In common with the first embodiment, the solid electrolyte 1 in the MEA 7 may be oxygen ion conductive or proton conductive. The same applies to the material constituting the MEA. It is the same as described above that private power can be supplied to the heater 41.
In addition, when the solid electrolyte 1 is oxygen ion conductive as illustrated, water (H ₂ O) is generated in the anode 2. At the center of the MEA 7, the water is a gas (water vapor) because it is heated to 100 ° C. or higher, but the temperature decreases near the outlet, and the water vapor becomes water droplets that adhere to the plated porous body 11 s and close the pores, resulting in pressure loss. May increase. On the other hand, when the solid electrolyte 1 is proton conductive, ammonia decomposition occurs at the anode 2, and the protons go to the cathode 5, and react with oxygen at the cathode 5 to generate water. The cathode 5 is on the outer peripheral side of the cylindrical MEA and is open. For this reason, even if water drops near the MEA outlet (outer periphery), no problem occurs. When the solid electrolyte 1 is proton conductive, in addition to the effect of promoting the progress of the electrochemical reaction and lowering the heating temperature, the above-mentioned harmless effect of water droplets can also be obtained.

FIG. 10 shows a metal mesh sheet 11a interposed between the anode 2 and the plated porous body 11s and reduction-bonded to both, and FIG. 10 (a) shows a mesh sheet of woven fabric (with the opening exaggerated). (B) and (b) are mesh sheets obtained by punching a metal film to form openings. In terms of flexibility, the mesh sheet of the woven fabric shown in FIG. 10 (a) is excellent. However, if the properties of the metal film are selected, the mesh sheet in which the opening is formed by punching has a sufficiently high flexibility. Any one of these metal mesh sheets 11a is arranged so as to be in contact with the anode 2 in the procedure shown in FIG. At this time, it is preferable to apply a metal paste containing the metal particles 11p. Thereafter, as shown in FIG. 7, the plated porous body 11s is inserted and arranged inside the metal mesh sheet 11a. In order to suppress the pressure loss, it is preferable to dispose intermittently, that is, at intervals. In the anode current collector 12, since the plated porous body 11s is wound around the central conductive rod 11k, the plated porous body 11s is wound around the central conductive rod 11k in advance, and the central conductive rod 11k and the cylindrical MEA are made together. Insert inside. When the plated porous body 11s is formed of cermet, there are various specifications with different pore sizes and a sheet shape. For this reason, for example, a cermet sheet having a large pore size is preferably used in a portion where a main flow of a gas containing ammonia flows, and a cermet sheet having a small pore size is preferably used in a portion in contact with the anode 2. This makes it possible to obtain a low reduction junction A ₂ electrical resistance while reducing the pressure loss of the gas flow.
The conditions for the subsequent reduction bonding are the same as those in the first embodiment.
The difference is that the manufacturing method has more options. Since the anode current collector 11 is formed on the inner surface side of the cylindrical MEA, several variations appear. In addition to the above procedure, the following method can be employed.
(V1) The metal mesh sheet 11a is reduced and bonded to the anode 2 once. Thereafter, the plated porous body 11a wound around the central conductive rod 11k is inserted, and reduction bonding is performed again.
(V2) The metal mesh sheet 11a and the plated porous body 11s wound around the central conductive rod 11k are reduced and bonded in advance. The anode current collector 11 subjected to the reduction bonding is inserted into the inner surface side of the MEA 7 to perform the reduction bonding between the anode 2 and the metal mesh sheet 11a.
Considering the processing accuracy of the charge (especially the outer diameter, etc.), the mechanical friction between the charge and the cylindrical MEA, etc., how to arrange all or part of the current collector 11 on the cylindrical inner surface It is sufficient to select a variation in a state of being loaded.

The metal mesh sheet 11a to be reductively bonded to the anode 2 is made of (Ni, Ni—Co, Ni—Fe, Ni—Cr, Ni—Cu, and Ni—W) as in the first embodiment. It may be formed of any one of a single-phase metal including one or more and a composite metal having the metal as a plating layer. The composite metal is, for example, a woven fabric of iron (Fe) subjected to Ni plating (woven fabric). It is alloyed by heating during the production or operation of the gas abatement apparatus to form a Ni-Fe woven fabric.
Also, the metal particles 11p included in the metal paste used to reliably realize the reduction bonding are preferably made of the same metal as the metal mesh sheet 11a. The following effects can be obtained by forming the metal mesh sheet 11a and the metal particles 11p from the above metal.
(E1) Decrease in electrical resistance of electrode connection structure (good conductivity)
(E2) Promotion of gas decomposition at the electrode (catalysis)
Furthermore, the following (E3) can be obtained as long as it is limited to Ni, Ni—Co, Ni—Fe, and Ni—Cu.
(E3) Facilitating reduction junctions or forming reduction junctions with low electrical resistance

FIG. 11 is a view showing an outer peripheral surface on which the cathode current collector 12 outside the cylindrical MEA 7 is disposed. A metal mesh sheet 12a is conductively connected to the cathode 5 with a silver paste application part 12g.
Silver particles can be arranged 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, silver particles can be arranged on the outer peripheral surface of the cathode 5 in the form of a silver paste application part 12g. As a result, as shown in FIG. 5, the silver particles function as a catalyst in the cathode 5. What is important in this silver paste is to make it highly porous after drying or sintering.
FIG. 12 shows an SEM (Scanning Electron Microscopy) image showing the surface of the silver paste application part 12g, (a) is image data, and (b) is an explanatory diagram thereof. Silver paste that becomes porous after being applied and dried (sintered) is commercially available, and for example, DD-1240 manufactured by Kyoto Elex Co., Ltd. can be used. The importance of making the silver paste application part 12g porous is based on the following reason.
It is preferable to supply as much oxygen molecules O _{2 as possible} to the cathode 5, and the silver particles contained in the silver paste have a catalytic action that promotes the cathode reaction in the cathode 5 (see FIG. 5). By disposing the silver paste coating portion 12g on the cathode 5, the locations (contact locations) where the metal oxide such as LSM that passes oxygen ions in the cathode, the silver particles, and the oxygen molecules O ₂ are in contact with each other are high density. Arise. By making the silver paste application part 12g porous, many oxygen molecules O ₂ enter the porous pores and touch the contact points, and the cathode reaction is likely to occur.
Furthermore, since the silver paste application part 12g containing silver particles has high conductivity, the electrical resistance in the cathode current collector 12 is lowered by assisting the metal mesh sheet 12a. For this purpose, the silver paste application part 12g is preferably provided so as to be continuous in a lattice shape (bus line direction, annular direction) as described above. The metal mesh sheet 12a is wound around the cathode 5 so as to be in contact with the silver paste application part 12g and to be conducted.
As described above, since silver strongly promotes the decomposition of oxygen molecules, the metal mesh sheet 12a may be subjected to silver plating to form a silver plating layer. By forming a silver plating layer on the metal mesh sheet 12a, the amount of silver paste applied can be reduced.

  Regarding the metal mesh sheet 12 a of the cathode current collector 12, an important factor that the anode current collector 11 does not have is deterioration due to oxidation. Since oxygen is introduced into the cathode 5 at a high temperature, it is preferable to use a metal mesh sheet formed of an oxidation-resistant metal. For example, (Ni, Ni-Co-based, Ni-Fe-based, Ni-Cr-based, Ni-Cu-based and single-phase metals including one or more of Ni-W-based materials, and composites having the metal as a plating layer) Metal) mesh sheet is preferable. In particular, the oxidation resistance of the cathode current collector 12 is improved by using one or more single-phase metals of Ni—Cr and Ni—W, and composite metals having these metals as plating layers. Can do. As a result, it is possible to obtain the cathode current collector 12 itself having a low electrical resistance and the conductive connection between the cathode current collector 12 and the cathode 5.

  An outline of a method for manufacturing cylindrical MEA 7 in the present embodiment will be described with reference to FIG. FIG. 13 shows a step of performing sintering 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 sintered under appropriate sintering 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 sintering is one time, as shown in FIG. 13, instead of sintering each part, each part is formed in the applied state, and finally, the greatest promise of each part Sintering is performed under several 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.

(Embodiment 3)
FIG. 14A is a longitudinal sectional view of the gas decomposition apparatus 10 according to Embodiment 3 of the present invention, and FIG. 14B is a sectional view taken along the line XIVB-XIVB in FIG. The present embodiment is characterized in that the plated porous body 11s is directly reduction bonded to the anode 2 by applying a thick metal paste, which is a material of the metal particles 11p. That is, the metal mesh sheet is omitted, and the plated porous body 11s, which is a porous metal body, is reduction bonded to the anode 2. Therefore, the anode current collector 11 is formed by (metal particles 11p + plated porous body 11s) / center conductive rod 11k.
As described above, the plated porous body 11s, for example, Celmet (registered trademark), is commercially available in the form of a sheet in which the size of the pores varies depending on the specification. It is preferable to use a plurality of types of sheets having different pore sizes, use a cermet having large pores for the first winding around the central conductive rod 11k, and use a cermet having fine pores for the portion in contact with the anode 2 on the outer periphery. As a result, the pressure loss of the gas containing the gas flowing through the cylindrical MEA 7 is ensured while ensuring good contact between the anode 2 and the gas while reducing the electrical resistance of the portion from the anode 2 to the central conductive rod 11k. Can be reduced. The advantage that a metal mesh sheet can be omitted can also be obtained.

The plated porous body 11s includes (a single-phase metal containing at least one of Ni, Ni—Co, Ni—Fe, Ni—Cr, Ni—Cu, and Ni—W), and a plating layer of the metal. Or a composite metal). Further, for the metal particles 11p, (a single-phase metal including one or more of Ni, Ni—Co, Ni—Fe, Ni—Cr, Ni—Cu, and Ni—W), and the metal It is desirable that the metal layer is formed of any one of a composite metal as a plating layer.
In the first to third embodiments, the metal particles 11p are preferably formed of the metal used for the plated porous body 11s when the metal particles 11p are disposed at or near the portion in contact with the anode 2.
As for the plated porous body 11s, when the metal mesh sheet 11s is interposed between the anode 2 and the metal porous sheet 11s as in the first and second embodiments, the plated porous body 11s is not particularly required to have a function of enhancing the catalytic action. However, in the case of directly contacting the anode 2 as in the present embodiment, it is desirable that the metal is formed from the above metal. Normally, the cermet 11s is made of Ni, so the above condition is satisfied. In order to further enhance the catalytic action, it is preferable to form the other metal (Ni-Fe or the like).
The cathode 5 and the cathode current collector 12 are the same as those in the second embodiment, and oxidation resistance is a point. In general, the metal mesh sheet in the anode 2 is omitted, and the anode 2 and the plated porous body 11 s are the same as in the second embodiment except that the anode 2 and the plated porous body 11 s are directly reduced and joined.

(Embodiment 4)
FIG. 15 is a diagram showing a system functioning as a fuel cell in Embodiment 4 of the present invention. In this fuel cell 50, a hydrogen source that is a molecule containing hydrogen, such as ammonia, toluene, xylene, or the like, is supplied from the hydrogen source, and any one of the gas decomposition apparatus 10 or the power generation cell 10 shown in the first to third embodiments. At the anode 2. Air, that is, oxygen is introduced into the cathode 5 and decomposed. As a result, an electrochemical reaction proceeds to generate electric power. Part of this electric power is used for a heating device (heater) 41 for improving gas decomposition ability or power generation ability. The surplus power is AC / DC converted or boosted by the inverter 71 to be converted into a power form suitable for the external device. As a result, the fuel cell system of the present embodiment is used as a power source for electronic devices such as PCs and portable terminals, and a power source for electric devices with higher power consumption, using various hydrogen sources including organic substances such as sugars. Can be.
The gas that has been decomposed and exhausted from the power generation cell 10 or the gas decomposition apparatus 10 detects the residual component concentration by the post-processing device (built-in sensor) 75 and processes it safely. In this case, depending on the residual component concentration, it can be returned to the original and circulated.
In the fuel cell system 50, it is not necessary to extremely reduce the concentration of the gas component at the outlet of the MEA 7 as in the case of Embodiment 2 or the like for the purpose of gas abatement. A high power generation capacity can be obtained by performing a chemical reaction.

(Other fuel cells or gas decomposition equipment)
Table 1 is a table illustrating other gas decomposition reactions to which the electrode connection structure of the present invention can be applied. The gas decomposition reaction R1 is the ammonia / oxygen decomposition reaction described in detail in the first and second embodiments. In addition, the electrode connection structure of the present invention can be used for any of the gas decomposition reactions R2 to R20. 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.

Table 1 only illustrates some of the many electrochemical reactions. The electrode connection structure 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.
The above electrochemical reaction is a gas decomposition reaction for the purpose of gas abatement, a fuel cell or the like. However, it may be used for other purposes.

  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 electrode connection structure and the like of the present invention, in the electrochemical reaction accompanied by gas decomposition and the like, the reduction in the electric resistance of the electrode / current collector and the good contact between the electrode and the gas are more excellent. I can do it. Furthermore, by reducing the electrical resistance, a porous metal body that prevents gas flow-through can be arranged sparsely, and the pressure loss of the gas flow can be reduced.

1 solid electrolyte, 2 anode, 2h pore in anode, 5 cathode, 10 gas decomposition device, 11 anode current collector, 11a metal mesh sheet, 11e anode external wiring, 11k central conductive rod, 11p metal paste layer, 11s porous Metal body (metal plating body), 12 cathode current collector, 12a metal mesh sheet, 12e cathode external wiring, 12g silver paste coating part, 21 metal grain chain, 21a core part of metal grain chain (metal part) , 21b oxide layer, 22 ionic conductive ceramic of anode, 41 heater, 50 gas decomposition system, 52 ionic conductive ceramic of cathode, 71 inverter, 75 post-treatment device, A ₁ reduction joint of anode and metal mesh sheet , instead of the a ₂ metal mesh sheet and the second porous metal body (plated porous body) Former joint, B ₁ , B ₂ contact part (conductive connection part), S air space.

Claims (17)

A connection structure between an electrode and a current collector for use in an electrochemical reaction,
The electrode includes an ion conductive ceramic and is porous,
The current collector is a porous metal body;
The electrode connection structure, wherein the electrode and the porous metal body are reduction bonded.   The electrode connection structure according to claim 1, wherein the porous metal body is a metal mesh sheet.   3. The electrode connection structure according to claim 1, wherein metal particles are located around the joint portion that is reduction-joined and around the joint portion.   The electrode connection structure according to claim 2 or 3, wherein the metal mesh sheet is a metal woven fabric or a metal woven fabric plated.   The metal mesh sheet and / or metal particles are (a single-phase metal containing one or more of Ni, Ni-Co, Ni-Fe, Ni-Cr, Ni-Cu, and Ni-W, and 5. The electrode connection structure according to claim 2, wherein the electrode connection structure is formed of any one of a composite metal having the metal as a plating layer.   The current collector includes a second porous metal body that is conductively connected to the metal mesh sheet, and the second porous metal body is positioned so as to block the flow of the gas so that the gas does not pass therethrough. The electrode connection structure according to claim 2, wherein the electrode connection structure is provided.   The electrode connection structure according to claim 6, wherein the metal mesh sheet and the second porous metal body are reduction bonded.   The metal mesh sheet is located over the entire surface of the electrode, and the second porous metal body is intermittent so that there is a portion where the metal mesh sheet is not contacted by the second porous metal body. The electrode connection structure according to claim 6, wherein the electrode connection structure is arranged in a mechanical manner.   The second porous metal body is a plated porous body, and the plated porous body is made of (Ni, Ni-Co, Ni-Fe, Ni-Cr, Ni-Cu, or Ni-W). The electrode according to any one of claims 6 to 8, wherein the electrode is formed of any one of a single-phase metal containing one or more kinds and a composite metal having the metal as a plating layer). Connection structure.   A fuel cell using the electrode connection structure according to claim 1.   A gas abatement apparatus using the electrode connection structure according to any one of claims 1 to 9. A method for producing a connection structure between an electrode and a current collector for use in an electrochemical reaction,
Placing a metal mesh sheet in contact over the entire surface of the electrode; and
At least a space in which the electrode and the metal mesh sheet are located at a temperature at which bonding by diffusion is performed, and an atmosphere that is not oxidizing with respect to the metal of the mesh sheet at the temperature.
A method for producing an electrode connection structure, wherein the electrode and the metal mesh sheet are held for reductive bonding in the atmosphere and temperature.   13. The method for manufacturing an electrode connection structure according to claim 12, wherein in order to realize an atmosphere that does not become oxidizing, the space is measured for leakage by a leak detector.   Further, the metal mesh sheet is contacted with a plated porous body for preventing passage of gas involved in the electrochemical reaction, and the plated porous body and the metal mesh sheet are subjected to reduction bonding. The method for manufacturing an electrode connection structure according to claim 12 or 13.   The electrode connection according to claim 14, wherein the reduction bonding between the electrode and the metal mesh sheet and the reduction bonding between the metal mesh sheet and the plated porous body are performed in parallel on the same occasion. Structure manufacturing method.   The contact portion between the electrode and the metal mesh sheet and / or the contact portion between the metal mesh sheet and the plated porous body is formed of (Ni, Ni—Co, Ni—Fe, Ni—Cr, Ni— A paste containing metal particles of any one of a single-phase metal including one or more of Cu-based and Ni-W-based, and a composite metal including the metal as a plating layer), and the reduction bonding. The method for manufacturing an electrode connection structure according to any one of claims 12 to 15, wherein: The electrochemical reaction includes a process of introducing a gas containing a reducing gas into the electrode, and the electrode and the metal mesh sheet are not reductively bonded when the electrochemical reaction apparatus is not in operation. The reduction bonding is realized by starting operation and introducing a gas containing the reducing gas into the electrochemical reaction apparatus. Manufacturing method of electrode connection structure.

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