JP5621332B2 - Gas decomposition element, ammonia decomposition element, power generation device and electrochemical reaction device - Google Patents

Description

  The present invention relates to a gas decomposing element, an ammonia decomposing element, a power generation apparatus, and an electrochemical reaction apparatus, and more specifically, a gas decomposing element capable of efficiently decomposing a predetermined gas, particularly an ammonia decomposing element capable of decomposing ammonia. The present invention relates to a power generation device based on a gas decomposition reaction and an electrochemical reaction device.

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). As for the catalyst for the ammonia decomposition reaction, porous carbon particles containing a transition metal component, manganese composition, iron-manganese composition (Patent Document 3), chromium compound, copper compound, cobalt compound (Patent Document 4), and alumina 3 Platinum (Patent Document 5) and the like supported on a three-dimensional network structure are disclosed. In the method of decomposing ammonia by a chemical reaction using the above catalyst, generation of nitrogen oxides NOx can be suppressed. Furthermore, a method for promoting thermal decomposition of ammonia more efficiently at 100 ° C. or less by using manganese dioxide as a catalyst has been proposed (Patent Documents 6 and 7).
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, etc., there has also been proposed an exhaust gas treatment of a semiconductor manufacturing apparatus that decomposes ammonia with a phosphoric acid fuel cell (Patent Document 8).

JP-A-7-31966 Japanese Patent Laid-Open No. 7-116650 Japanese Patent Laid-Open No. 11-347535 JP-A-53-11185 JP 54-10269 A JP 2006-231223 A JP 2006-175376 A JP 2003-45472 A

According to the above-described method using a chemical such as a neutralizing agent (Patent Document 1), a method of burning (Patent Document 2), a method using a thermal decomposition reaction using a catalyst (Patent Documents 3 to 7), etc. Is possible. However, the above method has a problem in that it requires chemicals and external energy (fuel), and requires periodic replacement of the catalyst, resulting in high running costs. In addition, the apparatus becomes large and, for example, when it is additionally provided in existing equipment, the arrangement may be difficult.
The device that uses phosphoric acid fuel cells for the removal of ammonia in the exhaust gas from compound semiconductor manufacturing can not make the partition between the air side and the ammonia side compact because the electrolyte is liquid. There was a problem that it was difficult.

  The present invention provides a gas decomposing element, particularly an ammonia decomposing element for ammonia in particular, which can obtain a large processing capacity with a small apparatus while suppressing running cost by using an electrochemical reaction, and the decomposition of these elements. It aims at providing the electric power generating apparatus using the element which produces electric power among elements, and an electrochemical reaction apparatus.

  The gas decomposition element of the present invention is used to decompose gas. This element includes a cylindrical MEA 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, The porous metal body is inserted on the inner surface side of the MEA and is electrically connected to the first electrode, and a central conductive rod inserted so as to form a conductive axis of the porous metal body.

According to the above configuration, the current collector of the first electrode includes the porous metal body and the central conductive rod. A gas to be removed such as ammonia is usually introduced into the inner surface side of the cylindrical body. The gas containing the gas to be removed is guided from the external gas transport path to the first electrode through the inlet on the inner side of the MEA, but the portion of the inlet to the inner side of the MEA has a strict airtightness. Sex is required.
On the other hand, in the cylindrical MEA including the solid electrolyte, there is no other arrangement path of the current collector material of the first electrode than the above-described inlet. There is no choice but to connect to the external wiring from the gas inlet or the periphery of the inlet. Providing an arrangement path for the material of the current collector of the first electrode in the other part of the cylindrical MEA has to make great sacrifices such as reducing the place of electrochemical reaction and increasing the risk of gas leakage. ,Can not. For this reason, wiring for current collection passes through the end of the cylindrical MEA together with the introduction of the gas transport path.
Since the above-mentioned central conductive bar is a single solid bar, it has high rigidity, is not easily deformed by some stress, maintains a stable shape, and is easy to process. Therefore, processing such as grooving and screw hole formation can be easily performed to electrically connect the end portion of the central conductive rod to external wiring. For this reason, a connection terminal or the like having a small contact resistance can be easily disposed at the end of the central conductive rod. Regarding the electrical resistance between the central conductive rod and the porous metal body, the contact interface of (porous metal body / central conductive rod) increases. However, the interface between the porous metal and the outer surface of the central conductive rod is formed by spirally winding a sheet-like porous metal body, and if the winding is tightly bound, contact between metals rich in conductivity can be achieved. However, the interfacial resistance does not increase the electrical resistance to the level at issue.
Compared to this, when the current collection of the first electrode is performed only with the porous metal (when the central conductive rod in the present invention is not used), in the cylindrical porous metal body in which the porous metal sheet is spirally wound, etc. (D1) The ends of the spiral porous metal body are very difficult to put together. For this reason, it is not easy to form a compact structure for connecting to external wiring while maintaining the above-mentioned strict airtightness at the end. The end portion of the porous metal is not limited to a columnar shape or a spiral shape, and is easily deformed, difficult to be united, and the structure for electrical connection with the outside must be large. And a bigger problem is (D2) large contact resistance accompanying conductive connection with external wiring. Even if an in-tube (inside the tubular MEA) connecting member is disposed between the end of the above-described form of the porous metal body and the external wiring, it is difficult to conduct conductive connection with low electrical resistance at the end.
In summary, it is difficult to satisfy both the above (D1) and (D2) practically.
In the configuration of the present invention, since the central conductive rod is used as described above, the end of the cylindrical MEA where the gas conveyance path and the external wiring are concentrated can be gathered in a compact manner while suppressing the electric resistance. That is, it is possible to reduce the size and achieve a clean structure. As a result, electrical resistance in “first electrode / first electrode current collector (including porous metal body, central conductive rod) / external wiring” can be suppressed. As a result, it is possible to promote the electrochemical reaction of gas decomposition and increase the processing capacity. And size reduction of the apparatus containing a gas decomposition | disassembly element can be promoted.
Since these electrochemical reactions usually have practical reaction rates at high temperatures, it is necessary to heat the MEA to a temperature range of 600 ° C. to 1000 ° C. with a heater or the like. The power cost for this is small compared to the above-mentioned chemicals. However, no chemicals are required for operation, and the running cost is small.
In connection with this high-temperature heating, the above-mentioned central conductive rod further brings the following advantages. That is, it is difficult for general resins to maintain durability such as strength for general resins, and if it is close to the mainstream part of the heat flow from the heater, sufficient safety is required unless a special and expensive resin is used. Cannot be guaranteed. However, it is easy for the above-mentioned central conductive rod to extend the conductive connection portion with the external wiring to a position away from the main flow portion of the heat flow. When the center conductive rod itself cannot be lengthened, it is easy to connect a member extending the tip. For this reason, while the MEA main body is heated to the above temperature, the portion connected to the external wiring and the portion connected to the gas conveyance path can be considerably lowered from the above temperature range. As a result, the durability of the various connecting members at the end of the MEA can be increased, and an expensive special material can be omitted, so that the economy can be improved.
Speaking of an example in which ammonia is used in a reaction in which oxygen is decomposed by oxygen in the air, the gas supplied to the second electrode may be air, and the electrochemical reaction of ammonia decomposition involves power generation. The heater can be supplied. For this reason, some of the electric power required for heater heating can be covered by the electric power generated by the ammonia decomposition reaction.
In the case of the above ammonia decomposition, the first electrode is an anode and the second electrode is a cathode. However, in the gas decomposition element targeted by the present invention, generally, the first electrode may be an anode or a cathode, and the second electrode is a corresponding pair of electrodes.

  The central conductive rod is preferably a single-phase or composite-phase metal rod, and at least the surface layer does not contain Cr. This makes it possible to obtain an appropriate central conductive rod according to the specifications of the gas decomposition element while preventing the first electrode and the like from being poisoned by Cr and reducing its activity.

  In the MEA of the cylindrical body, a solid electrolyte protrudes at both ends and includes a tubular joint fitted to both ends of the cylindrical solid electrolyte, and the tubular joint is connected to a gas conveyance path containing a gas supplied to the first electrode In addition, a conductive member that is conductively connected to the central conductive rod and penetrates the tubular joint can be provided. As a result, the connection with the gas conveyance path and the current collector (porous metal body, central conductive rod, etc.) of the first electrode can be compactly coupled to the cylindrical MEA while maintaining airtightness. In addition, the connection mechanism connected with a gas conveyance path can be used maintaining airtightness. Moreover, it is preferable that the tubular joint of the conductive member penetrates the material of the tubular joint while maintaining airtightness. In this case, it is preferable to use a gap filler or the like so as not to cause a gap or the like in the tubular joint.

  The tubular joint can be formed of a resin having heat resistance and corrosion resistance. As a result, even when the temperature of the position of the tubular joint is lowered by using the central conductive rod, the temperature is higher than normal temperature, so the use of the above resin makes it durable even if the conditions of corrosive gas environment overlap. Have stable and airtightness.

The first electrode and / or the second electrode can be a sintered body containing a metal particle chain mainly composed of nickel (Ni) and an ion conductive ceramic. The metal particle chain refers to a bead-like elongated metal body made of a series of metal particles. Ni, Fe-containing Ni, or Ni, Fe-containing Ni may be a metal containing a small amount of Ti. When the surface of Ni or the like is oxidized, the surface of the metal particle chain is oxidized, and the contents (portion inside the surface layer) are not oxidized and retain the conductivity of the metal. For this reason, for example, when the ion moving through the solid electrolyte is an anion (which may be a cation), (A1) when the metal particle chain is contained in the first electrode (anode), the anode is separated from the solid electrolyte. The chemical reaction between the moving anion and the gas molecules in the gas led from the outside of the anode to the anode is promoted by the oxidized layer of metal particle chain (catalysis), and the anion is added to the anode. Promotes chemical reaction at the surface (accelerating action by electric charge). And as a result of the chemical reaction, the conductivity of the generated electrons can be ensured by the metal portion of the metal particle chain. As a result, the electrochemical reaction involving charge transfer at the anode can be accelerated as a whole. When the metal particle chain is contained in the first electrode (anode), a positive ion, for example, a proton is generated at the anode, and the positive ion is moved to the cathode through the solid electrolyte. Can get to.
However, the oxide layer of the metal particle chain is surely formed by sintering before use, but the oxide layer is often lost due to a reduction reaction during use. Even if the oxide layer disappears, the above-described catalytic action may or may not be reduced. In particular, Ni containing Fe or Ti has high catalytic action even without an oxide layer.
Further, (A2) When the metal particle chain is put in the second electrode (cathode), the chemical reaction of the gas molecules in the gas led from the outside of the cathode to the cathode is caused by the oxide layer of the metal particle chain. Promote (catalyst action), improve the conductivity of electrons from the external circuit, and participate in the electrons to promote the chemical reaction at the cathode (acceleration action by charge). Then, anions can be efficiently generated from the molecules and delivered to the solid electrolyte. Similarly to (A1), in the case of (A2), the electrochemical reaction between the cation that has moved through the solid electrolyte, the electrons that have flowed through the external circuit, and the second gas can be promoted. For this reason, the electrochemical reaction accompanied with transfer of the electric charge in a cathode can be accelerated as a whole like the case where it is included in the anode. In what case, the metal particle chain is included in the cathode, depending on the gas to be decomposed. (A3) When the metal particle chain is contained in the anode and the cathode, the effects (A1) and (A2) can be obtained.
The metal particle chain will be described later in the embodiment of the present invention.

In many cases, the electrochemical reaction is limited by the moving speed or moving time of the ionic solid electrolyte. In order to increase the moving speed of ions, the gas decomposition element is usually provided with a heating device such as a heater, and is usually set at a high temperature, for example, 600 ° C to 1000 ° C. By raising the temperature, not only the ion transfer speed but also chemical reactions involving charge transfer at the electrodes are promoted.
When the ions moving through the solid electrolyte are anions, they are generated and supplied by a chemical reaction at the cathode as described above. Molecules in the fluid introduced at the cathode react with electrons to generate anions. The produced anion moves in the solid electrolyte to the anode. Electrons participating in the reaction at the cathode come from an external circuit (including a capacitor, a power source, and a power consuming device) that connects the anode and the cathode. When the ions moving through the solid electrolyte are cations, they are generated by an electrochemical reaction at the anode and move through the solid electrolyte to the cathode. Electrons are generated at the anode and flow through an external circuit to the cathode and participate in the electrochemical reaction at the cathode.
The electrochemical reaction may be a power generation reaction as a fuel cell, or may be an electrolysis reaction.

The solid electrolyte can be configured to have oxygen ion conductivity or proton conductivity.
Many solid electrolytes are known for oxygen ion conductivity, and many results have been accumulated. In the case of using an oxygen ion conductive solid electrolyte, for example, electrons and oxygen molecules are reacted at the cathode to generate oxygen ions and move the solid electrolyte to cause a predetermined electrochemical reaction at the anode. In this case, since the moving speed of oxygen ions in the solid electrolyte is not large compared to protons, the temperature is sufficiently increased and / or the thickness of the solid electrolyte is sufficiently reduced to obtain a practical level of decomposition capacity, etc. This measure is necessary.
On the other hand, barium zirconate (BaZrO3) is known as a proton conductive solid electrolyte. When a proton-conducting solid electrolyte is used, for example, ammonia is decomposed at the anode to generate protons, nitrogen molecules and electrons, and the protons are transferred to the cathode through the solid electrolyte. H ₂ O). Since protons are small compared to oxygen ions, the moving speed in the solid electrolyte is high, so that the decomposition temperature at a practical level can be obtained by lowering the heating temperature.
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 forms water droplets near the outlet where the temperature is low, causing pressure loss. In contrast, when a proton conductive solid electrolyte is used, protons, oxygen molecules, and electrons are generated at the cathode (outside). Since the outside is almost open, even if it adheres as water droplets, pressure loss is unlikely to occur.

  The porous metal body can be a metal plated body. As a result, a porous metal body having a high porosity can be obtained, and pressure loss can be suppressed. Since the porous body by metal plating forms the skeleton part by metal (Ni) plating, it can be easily controlled in a range where the thickness is reduced, so that the porosity can be easily increased.

  A configuration can be adopted in which the first gas is introduced into the first electrode, the second gas is introduced into the second electrode, and electric power is extracted from the first electrode and the second electrode. Thus, the gas to be decomposed can be used as fuel, and the fuel cell can be configured by the gas decomposition element to generate electric power.

  A heater is provided, and electric power can be supplied to the heater. Thereby, gas decomposition with excellent energy efficiency can be performed.

  The ammonia decomposing element of the present invention includes any one of the gas decomposing elements described above, and can introduce a gas containing ammonia into the first electrode and introduce a gas containing oxygen molecules into the second electrode. As a result, oxygen ions generated at the second electrode (cathode) are moved to the first electrode (anode), and ammonia and oxygen ions are promoted by the catalytic action by the metal particle chain and the ions at the first electrode. By reacting under the action, electrons generated as a result of the reaction can be quickly moved.

Electric power can be supplied from the first electrode and the second electrode by introducing the third gas into the first electrode and the fourth gas into the second electrode. Thereby, electric power can be consumed and the gas to be decomposed can be decomposed. In this case, the gas decomposing element performs electrolysis of the gas in the third and fourth gases with the first electrode and the second electrode. Depending on the electrochemical relationship between the gas to be decomposed and a gas (NH ₃ , VOC, air (oxygen), H ₂ O, etc.) that supplies ions for electrochemical reaction, electrolysis or fuel cell It will be decided.

  A power generator according to the present invention includes any one of the above-described gas decomposition elements for taking out electric power, and further includes an electric power supply component for supplying electric power to another electric device. Thus, electric power can be generated using a gas decomposing element viewed from the viewpoint of a power generation device, for example, using a combination of gases that generates only exhaust gas that does not cause a load on the global environment.

  The electrochemical reaction device of the present invention is an electrochemical reaction device for a fluid (gas, liquid), and is characterized by using any of the gas decomposition elements described above. As a result, in the future, not only gas abatement, but in the field of fuel cells and unique electrochemical reactors using gas decomposition, it will be used for the electrodes that are the basis of the equipment, improving the efficiency of electrochemical reactions, This contributes to downsizing of the device and low running costs.

  According to the gas decomposing element of the present invention, a small apparatus has a large processing capacity and can be operated at a low running cost. In particular, as a result of using the combination of the central conductive rod and the porous metal body as the current collector of the first electrode, the end of the cylindrical MEA is compact while maintaining airtightness while reducing the electrical resistance. Can be structured.

(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). 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 connection form of the external wiring and gas conveyance path with respect to cylindrical MEA. FIG. 2 shows a Ni mesh sheet in the gas decomposition element according to Embodiment 1, wherein (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 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. (A) is a longitudinal cross-sectional view of the gas decomposition element in Embodiment 2 of this invention, Moreover, (b) is sectional drawing which follows the XIB-XIB line | wire in (a).

(Embodiment 1)
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 arranged so as to fill 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>: Ni mesh sheet 11a / porous metal body 11s / center conductive rod 11k
The Ni mesh sheet 11a contacts 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. For the porous metal body 11s, it is preferable to use a metal plating body capable of increasing the porosity, for example, Celmet (registered trademark: Sumitomo Electric Industries, Ltd.) in order to reduce the pressure loss of a gas containing ammonia, which will be described later. 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.
<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.

FIG. 2 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, the use of the porous metal body 11s is indispensable because gas is passed through the inner surface side. From the viewpoint of reducing the pressure loss, it is important to use a metal plated body such as Celmet as described above. 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.
Again, in the gas decomposition element described above, in the anode 2 on the inner surface side of the cylindrical MEA, it is possible to reduce the pressure loss of the gas passing therethrough while reducing the electrical resistance of the anode current collector 11. The key to On the cathode side, air does not pass through the cylinder, but the density of the contact point between the air and the cathode and the reduction in the resistance of the cathode current collector 12 are also key to success.

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.

<Characteristics of gas decomposition element in the present embodiment>:
1. Center conductive rod 11k:
The present embodiment is characterized in that the MEA 7 has a cylindrical shape, and 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. As the porous metal body 11s, a sheet-like material (Celmet sheet) is tightly wound in a spiral shape around the central conductive rod 11k, 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.
(E1) The overall electrical resistance between the anode 2 and the external wiring can be reduced.
(E2) The crying place in the case of using the conventional cylindrical MEA was that the external terminals of the current collector on the inner surface side could not be made compact 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 12 and the external wiring can be realized with a simple structure and in a small size.
(E3) In order to operate the gas decomposition element 10 efficiently, it is necessary to heat it to 600 ° 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. 3 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 transport path 45 in FIG. 3 are both realized with 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. Ni mesh sheet 11a of anode current collector:
The Ni mesh sheet 11a in the anode current collector 11 shown in FIGS. 1A and 1B is important in that the pressure loss of the gas flow is reduced by reducing the electric resistance of the anode current collector 11. Is an element. As described above, the anode current collector 11 takes a conductive path of anode 2 / Ni mesh sheet 11a / porous metal body (Celmet) 11s / center conductive rod 11k. 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 composed of a metal plating body such as cermet, the contact resistance becomes large as follows. 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. The contact resistance can be lowered when the center conductive rod 11k can be wound tightly and tightly, but the spiral outer periphery does not become the center of the spiral. 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 the metal mesh sheet 11a, particularly the 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 plated body 11s are adapted to 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.
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. By inserting the Ni mesh sheet 11a, it can be lowered to about 1Ω or less. That is, it can be reduced to about 1/4 or less.

From the above configuration, when the Ni mesh sheet 11a was used for the anode current collector 11, the following was found.
(F1) By disposing the Ni mesh sheet 11a, the porous metal body 11s may be intermittently disposed inside the cylindrical MEA, and has a sufficiently low electrical resistance by the configuration shown in FIG. Can do. That is, unlike the prior art, it is not necessary to dispose the porous metal body 11 s without any breaks over the entire length of the cylindrical MEA 7.
(F2) As a result of disposing the porous metal bodies 11s intermittently at intervals, the pressure loss in the flow of gas containing ammonia can be greatly reduced. As a result, for example, a sufficient amount of gas containing ammonia discharged from the exhaust equipment of the semiconductor manufacturing apparatus can be sucked out without applying a large pressure difference, and the power cost required for sucking out the gas can be reduced.
In addition, the specifications of the parts for the pressure difference of the piping system and the gas decomposition element can be loosened, and the risk of an accident due to a high pressure difference or the like can be reduced while improving the economy.

  4A and 4B are views showing the Ni mesh sheet 11a. FIG. 4A shows a mesh formed by punching from a single-phase Ni sheet, and FIG. 4B shows a mesh formed by knitting Ni wire. Either of the Ni mesh sheets 11a may be used. In FIG. 4, 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.

3. 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 silver paste coating.
FIG. 5 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. 6A and 6B show SEM (Scanning Electron Microscopy) images showing the surface of the silver paste coated wiring 12g. FIG. 6A is image data, and FIG. 6B is an explanatory diagram thereof. As shown in FIG. 6, 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. 8). 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. However, in this description, the case where the coating is applied without any missing area in the region of the entire outer peripheral surface is also referred to as a silver paste applied wiring. . In the case of applying to the entire outer peripheral surface of the cathode 5, the Ni mesh sheet 12a can be omitted.

Next, the configuration of each part will be described.
<Anode 2>
-Configuration and action-
FIG. 7 is a diagram for explaining the 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.

<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 are suitable methods: (i) heat treatment oxidation by a vapor phase method, (ii) electrolytic oxidation, and (iii) chemical oxidation. 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.

<Cathode>
-Configuration and action-
FIG. 8 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 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.
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 description is for the case where the solid electrolyte 1 is oxygen ion conductive. However, the solid electrolyte 1 may be proton (H ⁺ ) conductive. In this case, the ion conductive ceramic 52 in the cathode 5 is proton conductive. Ceramics such as barium zirconate is 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.

<Solid electrolyte>
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.

<Plating metal body>
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 becomes large, 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.

<Method of manufacturing cylindrical MEA>
The outline of the manufacturing method of the cylindrical MEA 7 will be described with reference to FIG. FIG. 9 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.

<Arrangement of gas decomposition elements>
FIG. 10 is a diagram illustrating an arrangement example of the gas decomposition elements 10. FIG. 10 (a) shows a gas abatement apparatus when one cylindrical MEA 7 is used, and FIG. 10 (b) shows a plurality (12 pieces) of those shown in FIG. 10 (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.

(Embodiment 2)
FIG. 11A is a longitudinal sectional view of the gas decomposition element 10 according to Embodiment 2 of the present invention, and FIG. 11B is a sectional view taken along line XIB-XIB in FIG. The present embodiment is characterized in that the anode current collector 11 is formed by the Ni paste layer 11g in contact with the anode 2, the porous metal body 11s, and the central conductive rod 11k. That is, the Ni mesh sheet 11a in the gas decomposing element 10 in FIGS. 1A and 1B is characterized by being replaced by the Ni paste layer 11g.
As described above, even when Celmet (registered trademark), which is a metal plating body, is used as the porous metal body 11s, the contact resistance is relatively large, and the cathode current collector 12 and the anode current collector 11 of the gas decomposition element 10 The electrical resistance between them was, for example, about 6Ω. By forming the Ni paste layer 11g, it can be lowered to about 2Ω. That is, it can be reduced to about 1/3. This electrical resistance reduction effect is equivalent to the Ni mesh sheet 11a. Whether to use the Ni paste layer 11g or the Ni mesh sheet 11a is preferably determined in consideration of economic efficiency, ease of manufacture, and the like.

(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 decomposing element of the present invention, it is possible to obtain a large processing capacity with a small apparatus while suppressing running cost by using an electrochemical reaction. In particular, ammonia decomposition by a cylindrical MEA especially for ammonia. The device is small and has a high processing capacity, and is excellent in durability while being used at a high temperature in order to secure a processing capacity.

  1 solid electrolyte, 2 anode, 2h pore in anode, 5 cathode, 10 gas decomposition element, 11 anode current collector, 11a Ni mesh sheet, 11e anode external wiring, 11g Ni paste layer, 11k central 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 grain chain, 21a core part (metal part) of metal grain chain, 21b Oxidation layer, 22 Ion conductive ceramic of anode, 30 Tubular joint, 31 Tubular joint body, 31a Extrusion hole, 31b Fastening part, 32 Annular screw, 33 O-ring, 34 screw, 35 Tip of central conductive rod, 37a Connection plate, 37b conductive wire, 37c conductive through-hole, 39 nut, 45 Body conveying path, 47 fastener 41 heater, 52 a cathode of the ion conductive ceramic, S air space.

Claims (12)

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 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 tubular joint that protrudes at both ends of the MEA of the cylindrical body and is fitted to both ends of the cylindrical solid electrolyte; and
The tubular joint is
A gas decomposing element comprising: a conductive member connected to a gas conveyance path containing the gas supplied to the first electrode, and conductively connected to the central conductive rod and penetrating the tubular joint .   The gas decomposition element according to claim 1, wherein the central conductive rod is a single-phase or composite-phase metal rod, and at least the surface layer does not contain Cr. The gas decomposition element according to claim 1 or 2 , wherein the tubular joint is formed of a resin having heat resistance and corrosion resistance. 2. The first electrode and / or the second electrode is a sintered body containing a metal particle chain composed mainly of nickel (Ni) and an ion conductive ceramic. The gas decomposition element according to any one of claims 3 to 4. The gas decomposition element according to claim 1 , wherein the solid electrolyte has oxygen ion conductivity or proton conductivity. The gas decomposition element according to any one of claims 1 to 5 , wherein the porous metal body is a metal plating body. The first gas is introduced into the first electrode, the second gas is introduced into the second electrode, and electric power is taken out from the first electrode and the second electrode. The gas decomposition element according to any one of claims 1 to 6 . The gas decomposition element according to claim 7 , further comprising a heater, wherein the electric power is supplied to the heater. The gas decomposition element according to claim 1 , wherein a gas containing ammonia is introduced into the first electrode, and a gas containing oxygen molecules is introduced into the second electrode. Ammonia decomposition element. The third gas is introduced into the first electrode, the fourth gas is introduced into the second electrode, and electric power is supplied from the first electrode and the second electrode. The gas decomposition element according to claim 6 . A power generator comprising the gas decomposition element according to any one of claims 7 to 9 , and comprising a power supply component for supplying the power to another electric device. An electrochemical reaction apparatus for fluid, wherein the gas decomposition element according to any one of claims 1 to 11 is used.

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