Gas recovery system

Abstract

To provide a gas recovery system whose capability of recovering gas to be recovered can be prevented from deteriorating.SOLUTION: A carbon dioxide system 1 as a gas recovery system comprises an action electrode 104, a counter electrode 106, an action electrode power collecting material 103, and a counter electrode power collecting material 105. The action electrode 104 adsorbs carbon dioxide. The counter electrode 106 gives and receives electrons to / from the action electrode 104. The action electrode power collecting material 103 comes into contact with the action electrode 104 to electrically connect the action electrode 104 to the counter electrode 106. The counter electrode power collecting material 105 comes into contact with the counter electrode 106 to electrically connect the action electrode 104 to the counter electrode 106. Opening spaces of counter-electrode opening parts 105a formed in the counter electrode power collecting material 105 are smaller than opening spaces of action electrode opening parts 103a formed in the action electrode power collecting material 103.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a gas recovery system for recovering a target gas to be recovered from a mixed gas containing the target gas to be recovered.

Background Art

[0002] Conventionally, Patent Document 1 discloses a carbon dioxide recovery system for recovering carbon dioxide, which is a target gas to be recovered, from a mixed gas containing carbon dioxide. The carbon dioxide recovery system of Patent Document 1 includes an electrochemical cell that adsorbs carbon dioxide by an electrochemical reaction.

[0003] The electrochemical cell is formed as a laminate in which a working electrode, a counter electrode, a working electrode current collector, a counter electrode current collector, etc., each formed in a flat plate shape, are laminated. The working electrode contains a carbon dioxide adsorbent that absorbs carbon dioxide from the mixed gas. The counter electrode contains an electrochemically active auxiliary material that exchanges electrons with the working electrode. The working electrode current collector is an electrode that contacts the working electrode. The counter electrode current collector is an electrode that contacts the counter electrode.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the carbon dioxide recovery system, in order to adsorb carbon dioxide to the carbon dioxide adsorbent of the working electrode, it is necessary to expose the working electrode to the mixed gas. Therefore, in Patent Document 1, the working electrode current collector is formed of a gas permeable membrane.

[0006] On the other hand, exposing the counter electrode to the mixed gas may cause the electroactivating auxiliary material of the counter electrode to oxidize. If the electroactivating auxiliary material oxidizes, the recovery capacity of the target gas in the gas recovery system will decrease. However, Patent Document 1 does not mention suppressing the oxidation of the electroactivating auxiliary material.

[0007] In view of the above, the present invention aims to provide a gas recovery system that can suppress a decrease in the recovery capacity of the gas to be recovered. [Means for solving the problem]

[0012] Furthermore, claims 1 The gas recovery system described herein is a gas recovery system that recovers a target gas from a mixed gas by an electrochemical reaction, and comprises a working electrode (104), a counter electrode (106), a working electrode current collector (103), and a counter electrode current collector (105).

[0013] The working electrode adsorbs the gas to be recovered. The counter electrode exchanges electrons with the working electrode. The working electrode current collector contacts the working electrode and electrically connects the working electrode and the counter electrode. The counter electrode current collector contacts the counter electrode and electrically connects the working electrode and the counter electrode.

[0014] The working electrode current collector has an working electrode opening (103a) that exposes the mixed gas to the working electrode. The counter electrode current collector is designed to prevent contact between the mixed gas and the counter electrode.

[0015] According to this, the counter electrode current collector (105) is formed to prevent contact between the mixed gas and the counter electrode (106). Therefore, oxidation of the counter electrode (106) can be suppressed, thereby preventing a decrease in the recovery capacity of the target gas in the gas recovery system.

[0016] The symbols in parentheses next to each means described in this section and in the claims are merely examples indicating the correspondence with the specific means described in the embodiments described later. [Brief explanation of the drawing]

[0017] [Figure 1] This is a conceptual diagram showing the overall configuration of the carbon dioxide capture system according to the first embodiment. [Figure 2] This is a perspective view of the carbon dioxide capture device according to the first embodiment. [Figure 3] This is a cross-sectional view of the electrochemical cell according to the first embodiment. [Figure 4] This is a disassembled perspective view of the electrochemical cell of the first embodiment. [Figure 5] This is an explanatory diagram illustrating the method for manufacturing an electrochemical cell according to the first embodiment. [Figure 6] This is a disassembled perspective view of the electrochemical cell of the second embodiment. [Figure 7] This is an explanatory diagram illustrating the method for manufacturing an electrochemical cell according to the second embodiment. [Figure 8] This is an explanatory diagram illustrating the manufacturing method of the electrochemical cell according to the third embodiment. [Modes for carrying out the invention]

[0018] Several embodiments for carrying out the present invention will be described below with reference to the drawings. In each embodiment, parts corresponding to matters described in a prior embodiment will be denoted by the same reference numerals, and redundant descriptions may be omitted. If only a part of the configuration is described in each embodiment, other parts of the configuration can be applied to other embodiments described in advance. Not only can parts that are explicitly shown to be combinable in each embodiment be combined, but embodiments can also be partially combined even if not explicitly shown, as long as there is no particular impediment to the combination.

[0019] (First Embodiment) A first embodiment of the gas recovery system according to the present invention will be described using Figures 1 to 5. In this embodiment, the gas recovery system according to the present invention is applied to a carbon dioxide recovery system 1 that separates and recovers carbon dioxide from a mixed gas containing carbon dioxide. Therefore, the gas to be recovered in this embodiment is carbon dioxide.

[0020] As shown in the overall configuration diagram of FIG. 1, the carbon dioxide recovery system 1 of this embodiment includes a carbon dioxide recovery device 10, a pump 11, a flow path switching valve 12, a carbon dioxide utilization device 13, and a control device 14.

[0021] The carbon dioxide recovery device 10 separates and recovers carbon dioxide from the mixed gas. As the mixed gas, air or the exhaust gas of an internal combustion engine can be used. The mixed gas also contains gases other than carbon dioxide. The mixed gas is supplied to the carbon dioxide recovery device 10. The carbon dioxide recovery device 10 discharges the mixed gas after carbon dioxide is removed or the recovered carbon dioxide. The detailed configuration of the carbon dioxide recovery device 10 will be described later.

[0022] The suction side of the pump 11 is connected to the outlet of the carbon dioxide recovery device 10. The pump 11 sucks the mixed gas after carbon dioxide is removed or the recovered carbon dioxide from the carbon dioxide recovery device 10. Further, due to the suction action of the pump 11, the mixed gas is supplied to the carbon dioxide recovery device 10.

[0023] In this embodiment, an example in which the pump 11 is arranged on the downstream side in the gas flow direction of the carbon dioxide recovery device 10 is described, but the pump 11 may be arranged on the upstream side in the gas flow direction of the carbon dioxide recovery device 10.

[0024] The inlet side of the flow path switching valve 12 is connected to the discharge port of the pump 11. The flow path switching valve 12 is a three-way valve that switches the flow path of the gas flowing out from the carbon dioxide recovery device 10. The flow path switching valve 12 switches between a flow path for allowing the gas flowing out from the carbon dioxide recovery device 10 to flow out to the atmosphere side and a flow path for allowing the gas flowing out from the carbon dioxide recovery device 10 to flow out to the carbon dioxide utilization device 13 side.

[0025] The carbon dioxide utilization device 13 is a device that utilizes carbon dioxide. The carbon dioxide utilization device 13 can include, for example, a storage tank for storing carbon dioxide or a conversion device for converting carbon dioxide into fuel. The conversion device is a device that converts carbon dioxide into a hydrocarbon fuel such as methane. The hydrocarbon fuel may be a gaseous fuel at room temperature and pressure, or a liquid fuel at room temperature and pressure.

[0026] The control device 14 consists of a well-known microcomputer including a CPU, ROM, and RAM, and its peripheral circuits. The control device 14 performs various calculations and processes based on a control program stored in the ROM, and controls the operation of various controlled devices connected to the output side. More specifically, the control device 14 in this embodiment controls the operation of the carbon dioxide capture device 10, the pump 11, and the flow path switching valve 12.

[0027] Next, the carbon dioxide capture device 10 will be described using Figures 2 to 5. As shown in Figure 2, the carbon dioxide capture device 10 has a housing 100 and a plurality of electrochemical cells 101. In this embodiment, the housing 100 is made of a metal material. The housing 100 may also be made of a resin material.

[0028] The housing 100 has a gas inlet and a gas outlet. The gas inlet is an opening for introducing the mixed gas into the housing 100. The gas outlet is an opening for releasing the mixed gas, after carbon dioxide has been removed, or the recovered carbon dioxide, from inside the housing 100.

[0029] The electrochemical cell 101 adsorbs carbon dioxide through an electrochemical reaction, separating and recovering it from the mixed gas. The electrochemical cell 101 also releases the adsorbed carbon dioxide through an electrochemical reaction. Multiple electrochemical cells 101 are housed in the enclosure 100.

[0030] The electrochemical cell 101 is formed in the shape of a rectangular flat plate. Multiple electrochemical cells 101 are stacked inside the housing 100 at regular intervals so that their plate surfaces are parallel to each other. Multiple gas channels 102 are formed between adjacent electrochemical cells 101 to allow the mixed gas flowing in from the gas inlet to circulate.

[0031] Therefore, the flow direction of the mixed gas is parallel to the plate surface of the electrochemical cell 101 and perpendicular to the stacking direction of the multiple electrochemical cells 101.

[0032] As shown in Figures 3 and 4, the electrochemical cell 101 includes a working electrode current collector 103, a working electrode 104, a counter electrode current collector 105, a counter electrode 106, a separator 107, and an electrolyte layer 108. The working electrode current collector 103, the working electrode 104, the counter electrode current collector 105, the counter electrode 106, and the separator 107 are all formed in the shape of rectangular flat plates.

[0033] The electrochemical cell 101 is formed as a laminate of a working electrode current collector 103, a working electrode 104, a counter electrode current collector 105, a counter electrode 106, and a separator 107. The lamination direction in which the working electrode current collector 103, etc., are stacked in each individual electrochemical cell 101 coincides with the lamination direction in which multiple electrochemical cells 101 are stacked inside the housing 100.

[0034] The working electrode current collector 103 is a conductive member that contacts the working electrode 104 and electrically connects the working electrode 104 and the counter electrode 106. One flat surface of the working electrode current collector 103 is exposed to the mixed gas. The other flat surface of the working electrode current collector 103 is in contact with the working electrode 104. The working electrode current collector 103 has a working electrode opening 103a that exposes the mixed gas on one flat surface side to the working electrode 104 on the other flat surface side.

[0035] More specifically, the working electrode current collector 103 in this embodiment is made of a porous metal. Therefore, the working electrode opening 103a in this embodiment is formed by multiple voids formed inside the working electrode current collector 103 communicating with each other. As the working electrode current collector 103, a porous metal with a porosity of 50% or more can be used. The porosity is defined as the ratio of the volume of voids to the apparent volume.

[0036] The working electrode 104 can adsorb and recover carbon dioxide from the mixed gas, and desorb and release the recovered carbon dioxide. The working electrode 104 comprises a carbon dioxide adsorbent, a conductive additive, and a binder. The carbon dioxide adsorbent, conductive additive, and binder are used in a mixture state. More specifically, in this embodiment, fine particles of the carbon dioxide adsorbent and fine particles of the conductive additive are used in a state held by the binder.

[0037] Carbon dioxide adsorbents are electroactive species that adsorb carbon dioxide by accepting electrons and desorb the adsorbed carbon dioxide by releasing electrons. Examples of carbon dioxide adsorbents include carbon materials, metal oxides, and polyanthraquinones.

[0038] The conductive additive forms a conductive path to the carbon dioxide adsorbent. Examples of conductive additives include carbon materials such as carbon nanotubes, carbon black, and graphene.

[0039] The binder is a binder that holds the carbon dioxide adsorbent and the conductive additive. As the binder, for example, a conductive resin made of a high-molecular-weight polymer can be used. As the conductive resin, an organic material such as epoxy resin containing Ag or the like as a conductive filler, or fluororesin such as polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVDF) can be used.

[0040] The counter electrode current collector 105 is a conductive member that contacts the counter electrode 106 and electrically connects the working electrode 104 and the counter electrode 106. One flat surface of the counter electrode current collector 105 is exposed to the mixed gas. The other flat surface of the counter electrode current collector 105 is in contact with the counter electrode 106. The counter electrode current collector 105 has a counter electrode opening 105a that exposes the mixed gas on one flat surface side to the counter electrode 106 on the other flat surface side.

[0041] More specifically, the counter electrode current collector 105 in this embodiment is formed of a porous metal, similar to the working electrode current collector 103. Therefore, the counter electrode opening 105a is formed by multiple voids formed inside the counter electrode current collector 105 communicating with each other. It is preferable to use a porous metal with a void ratio of 70% or less as the counter electrode current collector 105.

[0042] Furthermore, in this embodiment, a porous metal material with a smaller porosity than the working electrode current collector 103 is used as the counter electrode current collector 105. As a result, the opening area of ​​the counter electrode opening 105a of the counter electrode current collector 105 is smaller than the opening area of ​​the working electrode opening 103a of the working electrode current collector 103.

[0043] Furthermore, in this embodiment, multiple working electrode openings 103a and counter electrode openings 105a are formed. Therefore, the opening area of ​​the working electrode opening 103a can be the total opening area at the contact surface between the working electrode current collector 103 and the working electrode 104. Similarly, the opening area of ​​the counter electrode opening 105a can be the total opening area at the contact surface between the counter electrode current collector 105 and the counter electrode 106.

[0044] The counter electrode 106 exchanges electrons with the working electrode 104 when the carbon dioxide adsorbent adsorbs or desorbs carbon dioxide. The counter electrode 106 comprises an electroactivating agent, a conductive additive, and a binder. The electroactivating agent, conductive additive, and binder are used in a mixture state. More specifically, in this embodiment, fine particles of the electroactivating agent and fine particles of the conductive additive are used in a state held by the binder.

[0045] The basic composition of the conductive additive and binder of the counter electrode 106 is the same as that of the conductive additive and binder of the working electrode 104. The electroactivating additive is an auxiliary electroactive species that transfers electrons with the carbon dioxide adsorbent of the working electrode 104, and is an active material with redox properties. As the active material, an organic compound having a π bond, a transition metal compound that can take on multiple oxidation states, or a metal complex that enables electron transfer by changing the valence of a metal ion can be used.

[0046] Examples of such metal complexes include cyclopentadienyl metal complexes such as ferrocene, nickerosene, and cobaltocene, or porphyrin metal complexes. These metal complexes may be polymers or monomers.

[0047] The separator 107 is positioned between the working electrode 104 and the counter electrode 106, separating them. The separator 107 is an insulating ion-permeable membrane that prevents physical contact between the working electrode 104 and the counter electrode 106, thereby suppressing electrical short circuits, while also allowing ions to pass through. As the separator 107, a cellulose membrane, a polymer, a composite material of polymer and ceramic, etc., can be used.

[0048] The electrolyte layer 108 is an immersion layer in which the working electrode 104, separator 107, and counter electrode 106 are immersed. For example, an ionic liquid can be used as the electrolyte layer 108. An ionic liquid is a salt of a liquid that is non-volatile at room temperature and pressure.

[0049] Furthermore, a power supply 109 is connected to the working electrode current collector 103 and the counter electrode current collector 105 of the electrochemical cell 101. The power supply 109 can apply a predetermined voltage to the working electrode 104 and the counter electrode 106, thereby changing the potential difference between the working electrode 104 and the counter electrode 106. The working electrode 104 is the negative electrode, and the counter electrode 106 is the positive electrode.

[0050] The electrochemical cell 101 operates in a carbon dioxide capture mode, where carbon dioxide is captured at the working electrode 104, and a carbon dioxide release mode, where carbon dioxide is released from the working electrode 104, by changing the potential difference between the working electrode 104 and the counter electrode 106. The carbon dioxide capture mode is a charging mode that charges the electrochemical cell 101, and the carbon dioxide release mode is a discharge mode that discharges the electrochemical cell 101.

[0051] Specifically, in carbon dioxide capture mode, a first voltage V1 is applied between the working electrode 104 and the counter electrode 106, and electrons are supplied from the counter electrode 106 to the working electrode 104. At the first voltage V1, the working electrode potential is less than the counter electrode potential. The first voltage V1 can be, for example, in the range of 0.5 to 2.0 V.

[0052] In the carbon dioxide emission mode, a second voltage V2 is applied between the working electrode 104 and the counter electrode 106, supplying electrons from the working electrode 104 to the counter electrode 106. The second voltage V2 is different from the first voltage V1. The second voltage V2 only needs to be lower than the first voltage V1, and the relative magnitudes of the working electrode potential and the counter electrode potential are not limited. In other words, in the carbon dioxide emission mode, the working electrode potential may be less than the counter electrode potential, the working electrode potential may be equal to the counter electrode potential, or the working electrode potential may be greater than the counter electrode potential.

[0053] Next, the manufacturing method for the electrochemical cell 101 described above will be explained. The manufacturing method for the electrochemical cell 101 in this embodiment includes a working electrode side current collector attachment step in which the working electrode 104 is attached to the working electrode current collector 103, and a counter electrode side current collector attachment step in which the counter electrode 106 is attached to the counter electrode current collector 105. The working electrode side current collector attachment step and the counter electrode side current collector attachment step can be carried out separately.

[0054] The process of attaching the current collector to the working electrode and the process of attaching the current collector to the counter electrode are basically the same. Therefore, Figure 5 will explain the process of attaching the current collector to the counter electrode. Furthermore, in Figure 5, the symbols of each component in the process of attaching the current collector to the working electrode are shown in parentheses.

[0055] In the process of attaching the current collector to the counter electrode, as shown in Figure 5, a preparation step, a coating step, a drying step, and a peeling step are performed. In the preparation step, the counter electrode current collector 105 is placed on a release paper 200 that is arranged on a flat surface. The release paper 200 is a release paper used in the molding process of a substance that exhibits temporary adhesion.

[0056] In the coating process, the counter electrode 106, which is made into a paste by mixing an electroactivating agent, a conductive additive, and a binder, is applied to the upper surface of the counter electrode current collector 105 after the preparation process, i.e., the surface opposite the release paper 200, by screen printing or the like. As a result, the paste-like counter electrode 106 penetrates not only the upper surface of the counter electrode current collector 105 but also into the interior of the counter electrode opening 105a.

[0057] In the drying process, the counter electrode 106 coated on the counter electrode current collector 105 after the coating process is dried. This hardens the counter electrode 106. Thus, the counter electrode 106 is formed by solidifying fine particles of an electroactivating additive and fine particles of a conductive additive together with a binder. In the drying process, the counter electrode current collector 105 and the counter electrode 106 may be heated to speed up the drying process. Alternatively, the counter electrode current collector 105 and the counter electrode 106 may be placed in a low-pressure environment.

[0058] In the peeling process, the release paper 200 is peeled off the counter electrode current collector 105. In the peeling process, as shown in Figure 5 as an example, there is a possibility that a portion of the counter electrode 106 may peel off together with the release paper 200 as a residual portion 200a. This residual portion 200a can cause defects in the counter electrode 106. Therefore, in the peeling process, it is desirable to peel off the release paper 200 in a way that does not cause defects in the counter electrode 106.

[0059] Through the above process, in the current collector attachment process on the counter electrode side, the counter electrode 106 is attached to the counter electrode current collector 105. In the current collector attachment process on the working electrode side, where the working electrode 104 is attached to the working electrode current collector 103, the same preparation process, coating process, drying process, and peeling process are performed.

[0060] Then, a bonding process is performed in which the counter electrode current collector 105 and counter electrode 106, which were attached by the current collector attachment process on the working electrode side, and the working electrode current collector 103 and working electrode 104, which were attached by the current collector attachment process on the working electrode side, are bonded together with a separator 107 in between. In the bonding process, as is clear from Figures 3 and 4, the surfaces on the counter electrode 106 side and the surfaces on the working electrode 104 side are bonded together so that they are in contact with the separator 107.

[0061] Subsequently, the power supply 109 is connected to the working electrode current collector 103 and the counter electrode current collector 105. This manufactures the electrochemical cell 101.

[0062] Next, the operation of the carbon dioxide capture system 1 of this embodiment will be described. As described above, the carbon dioxide capture system 1 operates by alternately switching between a carbon dioxide capture mode and a carbon dioxide release mode. The operation of the carbon dioxide capture system 1 is controlled by the control device 14.

[0063] First, let's explain the carbon dioxide recovery mode. In carbon dioxide recovery mode, the pump 11 is activated. This supplies the mixed gas to the carbon dioxide recovery device 10. In the carbon dioxide recovery device 10, the voltage applied between the working electrode 104 and the counter electrode 106 of the electrochemical cell 101 is defined as the first voltage V1. This allows for the simultaneous donation of electrons to the electroactivating auxiliary material of the counter electrode 106 and the withdrawal of electrons to the carbon dioxide adsorbent of the working electrode 104.

[0064] The carbon dioxide adsorbent on the working electrode 104, having received electrons from the counter electrode 106, has increased carbon dioxide binding affinity and adsorbs carbon dioxide contained in the mixed gas. As a result, the carbon dioxide recovery device 10 can recover carbon dioxide from the mixed gas. The mixed gas, after carbon dioxide has been removed, is discharged from the carbon dioxide recovery device 10.

[0065] In carbon dioxide recovery mode, the flow path switching valve 12 switches to a flow path that allows the mixed gas discharged from the carbon dioxide recovery device 10 to flow out to the atmosphere. As a result, the mixed gas discharged from the carbon dioxide recovery device 10 is released into the atmosphere.

[0066] Next, the carbon dioxide release mode will be described. In the carbon dioxide release mode, the pump 11 is stopped. This stops the supply of the mixed gas to the carbon dioxide recovery device 10. In the carbon dioxide recovery device 10, the voltage applied between the working electrode 104 and the counter electrode 106 of the electrochemical cell 101 is set to the second voltage V2. This allows for the simultaneous donation of electrons to the carbon dioxide adsorbent of the working electrode 104 and the withdrawal of electrons to the electroactivating auxiliary material of the counter electrode 106.

[0067] The carbon dioxide adsorbent at the working electrode 104 releases electrons and enters an oxidized state. The carbon dioxide adsorbent's binding force to carbon dioxide decreases, and it desorbs and releases carbon dioxide. The carbon dioxide released from the carbon dioxide adsorbent is discharged from the carbon dioxide recovery device 10.

[0068] In carbon dioxide release mode, the flow path switching valve 12 switches to a flow path that allows carbon dioxide emitted from the carbon dioxide recovery device 10 to flow out to the inlet side of the carbon dioxide utilization device 13. As a result, the carbon dioxide emitted from the carbon dioxide recovery device 10 is supplied to the carbon dioxide utilization device 13.

[0069] As described above, the carbon dioxide recovery system 1 of this embodiment allows for the recovery of carbon dioxide from a mixed gas and the effective utilization of the recovered carbon dioxide.

[0070] In this embodiment, the electrochemical cell 101 employs a counter electrode current collector 105 with a counter electrode opening 105a. Therefore, the counter electrode 106 is exposed to the mixed gas through the counter electrode opening 105a. When the mixed gas contains oxygen, the oxygen that comes into contact with the counter electrode 106 receives electrical energy, generating reactive oxygen species such as superoxide.

[0071] These reactive oxygen species can easily oxidize the electroactivating auxiliary material and binder formed from organic materials in the counter electrode 106. When the electroactivating auxiliary material is oxidized, its ability to transfer electrons decreases. Furthermore, when the binder is oxidized, it becomes impossible to retain the electroactivating auxiliary material. As a result, the carbon dioxide recovery capacity of the working electrode 104 may decrease.

[0072] In contrast, in the electrochemical cell 101 of this embodiment, the opening area of ​​the counter electrode opening 105a of the counter electrode current collector 105 is smaller than the opening area of ​​the working electrode opening 103a of the working electrode current collector 103, making it difficult to expose the counter electrode 106 to the mixed gas. Therefore, oxidation of the electroactivating auxiliary material and binder of the counter electrode 106 can be suppressed, thereby suppressing a decrease in the recovery capacity of the target gas in the carbon dioxide recovery device system 1.

[0073] (Second Embodiment) In this embodiment, an example is described in which the configuration of the electrochemical cell 101 is modified from that of the first embodiment, as shown in Figure 6. Specifically, in this embodiment, a metal plate is used as the counter electrode current collector 115. The counter electrode current collector 115 does not have a configuration corresponding to the counter electrode opening 105a described in the first embodiment.

[0074] Therefore, the counter electrode current collector 115 is formed to prevent contact between the mixed gas and the counter electrode 106. In other words, the counter electrode current collector 115 prevents contact between the mixed gas and the counter electrode 106 by being formed of a conductive plate-like member that does not have any openings.

[0075] Furthermore, in this embodiment, as the counter electrode current collector 115, a metal plate is used in which the surface roughness Rzo of the surface on the counter electrode 106 side is equal to or greater than the average particle size φDo of the fine particles of the electroactivating auxiliary material 106a and the conductive additive 106b that form the counter electrode 106.

[0076] Surface roughness Rzo is calculated by extracting a reference length from the roughness curve in a predetermined direction, and using the distance from the highest peak to the lowest valley (i.e., the height dimension) in the extracted portion. The roughness curve is a curve obtained by removing wavelength components greater than a predetermined length from the cross-sectional polar line drawn by a cross-section perpendicular to a flat surface.

[0077] Alternatively, the surface roughness Rzo may be calculated using the average distance obtained by summing the average elevations of multiple mountain peaks and the average elevations of multiple valley bottoms (for example, the ten-point mean roughness). Alternatively, the so-called arithmetic mean roughness may be used as the surface roughness Rzo.

[0078] The surface roughness Rzo of the counter electrode current collector 115 is adjusted to the desired value by methods such as shot blasting, laser processing, machining with grinders or sanders, etching, and creasing.

[0079] The average particle size φDo of the fine particles of the electroactivating additive 106a and the fine particles of the conductive additive 106b should be the value of the one that results in the larger average particle size between the electroactivating additive 106a and the conductive additive 106b. Alternatively, the average value of all particle sizes of the fine particles of the electroactivating additive 106a and the fine particles of the conductive additive 106b may be used. The configuration and operation of the electrochemical cell 101 and the carbon dioxide recovery system 1 are the same as in the first embodiment.

[0080] Next, the manufacturing method of the electrochemical cell 101 of this embodiment will be described. The current collector attachment process on the counter electrode side of this embodiment includes a coating step and a drying step.

[0081] In the coating process of this embodiment, similar to the first embodiment, a paste-like counter electrode 106 is applied to the upper surface of the counter electrode current collector 115 by screen printing or the like. In the coating process of this embodiment, after the drying process, the counter electrode 106 is applied so that the thickness To of the counter electrode 106 in the lamination direction is greater than the surface roughness Rzo, as shown in Figure 7. The thickness To of the counter electrode 106 is defined as the distance from the lowest valley bottom on the surface of the counter electrode current collector 115 to the outer surface.

[0082] In the drying process, the counter electrode 106 coated on the counter electrode current collector 115 is dried and hardened, similar to the first embodiment. Through these steps, the counter electrode 106 is attached to the counter electrode current collector 115. The other manufacturing methods for the electrochemical cell 101 are the same as in the first embodiment.

[0083] Therefore, the carbon dioxide recovery system 1 of this embodiment can recover carbon dioxide from a mixed gas in the same manner as the first embodiment. The recovered carbon dioxide can then be effectively utilized.

[0084] Furthermore, in the electrochemical cell 101 of this embodiment, a metal plate is used as the counter electrode current collector 115, thereby preventing contact between the mixed gas and the counter electrode 106. Consequently, the counter electrode 106 is not exposed to oxygen and oxidized. As a result, a decrease in the recovery capacity of the target gas in the carbon dioxide recovery system 1 can be suppressed.

[0085] In this embodiment, if a metal plate is used as the counter electrode current collector 115, then, as in the first embodiment, the paste-like counter electrode 106 cannot penetrate into the counter electrode opening 105a during the coating process. As a result, the contact area between the counter electrode current collector 105 and the counter electrode 106 is reduced, which may cause the counter electrode 106 to peel off from the counter electrode current collector 115.

[0086] In contrast, in the electrochemical cell 101 of this embodiment, as shown in Figure 7, a metal plate is used as the counter electrode current collector 115, such that the surface roughness Rzo of the surface facing the counter electrode 106 is equal to or greater than the average particle size φDo of the fine particles of the electroactivating auxiliary material 106a and the conductive additive 106b of the counter electrode 106. This improves the adhesion between the counter electrode current collector 115 and the counter electrode 106 through an anchoring effect.

[0087] On the other hand, if the surface roughness Rzo of the counter electrode current collector 115 is larger than necessary, it may damage the separator 107 and cause a short circuit between the counter electrode 106 and the working electrode 104. In contrast, in the electrochemical cell 101 of this embodiment, as shown in Figure 7, the thickness To of the counter electrode 106 is greater than the surface roughness Rzo, so that the counter electrode current collector 115 does not damage the separator 107.

[0088] Furthermore, the current collector attachment process on the counter electrode side of the electrochemical cell 101 in this embodiment does not require the peeling process described in the first embodiment. As a result, it is possible to prevent defects from forming on the counter electrode 106 during the manufacturing process. This improves the productivity of the electrochemical cell 101.

[0089] (Third embodiment) The basic configuration of the carbon dioxide recovery system 1 in this embodiment is the same as in the second embodiment. In this embodiment, an example is described in which the manufacturing method of the electrochemical cell 101 is changed from that of the second embodiment.

[0090] In the current collector attachment process on the counter electrode side of this embodiment, as shown in Figure 8, a buffer layer formation process, a coating process, and a drying process are performed. In the buffer layer formation process, a buffer layer is formed on the surface of the counter electrode current collector 115. In this embodiment, a carbon buffer layer 110 is formed by vacuum deposition.

[0091] In the coating step, similar to the first embodiment, a paste-like counter electrode 106 is applied to the surface of the counter electrode current collector 115 where the buffer layer 110 is formed, by screen printing or the like. In the drying step, similar to the first embodiment, the counter electrode 106 applied to the counter electrode current collector 115 is dried. Through these steps, the counter electrode 106 is attached to the counter electrode current collector 115. The other manufacturing methods for the electrochemical cell 101 are the same as in the first embodiment.

[0092] Therefore, the carbon dioxide recovery system 1 of this embodiment can operate in the same manner as the first embodiment and recover carbon dioxide from the mixed gas. Furthermore, the recovered carbon dioxide can be effectively utilized. In addition, similar to the second embodiment, contact between the mixed gas and the counter electrode 106 can be prohibited, thereby suppressing a decrease in the recovery capacity of the target gas in the carbon dioxide recovery system 1.

[0093] Furthermore, in the electrochemical cell 101 of this embodiment, a carbon buffer layer 110 is formed between the counter electrode current collector 115 and the counter electrode 106. This improves the adhesion between the counter electrode current collector 115 and the counter electrode 106.

[0094] More specifically, the carbon adheres well to the metal counter electrode current collector 115 by being refined through vacuum deposition or the like. Furthermore, since the binder of the counter electrode 106 contains an organic polymer, it has a high affinity for the carbon buffer layer 110. Therefore, in the electrochemical cell 101 of this embodiment, the formation of the buffer layer 110 improves the adhesion between the counter electrode current collector 115 and the counter electrode 106.

[0095] (Other embodiments) The present invention is not limited to the embodiments described above, and can be modified in various ways without departing from the spirit of the invention. Furthermore, the means disclosed in each of the above embodiments may be combined as appropriate to the extent that they are feasible.

[0096] In the embodiments described above, an example was given in which the gas recovery system according to the present invention is applied to a carbon dioxide recovery system 1 that recovers carbon dioxide from a mixed gas. However, the application of the gas recovery system according to the present invention is not limited to this. The gas recovery system according to the present invention may also be applied to a system that recovers a specific type of gas other than carbon dioxide from a mixed gas.

[0097] In the first embodiment described above, an example was given in which the working electrode current collector 103 and the counter electrode current collector 105 were made of a porous metal material, but the invention is not limited thereto. For example, expanded metal, perforated metal, carbon fiber, carbon nonwoven fabric, or conductive polymer film may be used as the working electrode current collector 103 and the counter electrode current collector 105.

[0098] Expanded metal, perforated metal, etc., have flat sections. Therefore, when using expanded metal, perforated metal, etc. as the counter electrode current collector 105, it is desirable, as in the second embodiment, that the surface roughness Rzo of the flat section be greater than or equal to the average particle size φDo of the fine particles of the electroactivating auxiliary material 106a and the fine particles of the conductive additive 106b. Similarly, it is desirable that the thickness To of the counter electrode 106 be greater than the surface roughness Rzo of the flat section.

[0099] Furthermore, while the second and third embodiments described above describe examples in which a counter electrode current collector 115 made of a metal plate is used, the invention is not limited thereto. For example, as the counter electrode current collector 115, a current collector material having a metal foil, metal oxide, and conductive material filmed on its surface may be used, as long as the configuration corresponding to the counter electrode opening 105a described in the first embodiment is not formed.

[0100] Furthermore, although the buffer layer formation step of the third embodiment described above involved forming a carbon buffer layer 110 on the surface of the counter electrode current collector 115 by vacuum deposition, the invention is not limited to this. The buffer layer 110 may also be formed by sputtering in the buffer layer formation step.

[0101] The gas recovery systems disclosed herein can be described as follows: (Item 1) A gas recovery system that recovers a target gas from a mixed gas by an electrochemical reaction, The working electrode (104) adsorbs the gas to be recovered, The working electrode and the counter electrode (106) that exchanges electrons, A working electrode current collector (103) that contacts the working electrode and electrically connects the working electrode and the counter electrode, The system includes a counter electrode current collector (105) that contacts the counter electrode and electrically connects the working electrode and the counter electrode, The working electrode current collector has a working electrode opening (103a) formed therein, which exposes the working electrode to the mixed gas. The counter electrode current collector has a counter electrode opening (105a) formed therein that exposes the counter electrode to the mixed gas. A gas recovery system in which the opening area of ​​the counter electrode opening is smaller than the opening area of ​​the working electrode opening. (Item 2) A gas recovery system that recovers a target gas from a mixed gas by an electrochemical reaction, The working electrode (104) adsorbs the gas to be recovered, The working electrode and the counter electrode (106) that exchanges electrons, A working electrode current collector (103) that contacts the working electrode and electrically connects the working electrode and the counter electrode, The system includes a counter electrode current collector (105) that contacts the counter electrode and electrically connects the working electrode and the counter electrode, The working electrode current collector has a working electrode opening (103a) formed therein, which exposes the working electrode to the mixed gas. The counter electrode current collector is configured to prevent contact between the mixed gas and the counter electrode in a gas recovery system. (Item 3) The counter electrode is formed of multiple fine particles, The gas recovery system according to item 1 or 2, wherein the surface roughness (Rzo) on the counter electrode side surface of the counter electrode current collector is equal to or greater than the average particle size (φDo) of the fine particles. (Item 4) A gas recovery system according to any one of items 1 to 3, wherein the surface roughness (Rzo) of the counter electrode side surface of the counter electrode current collector is less than or equal to the thickness dimension (To) of the counter electrode. (Item 5) A gas recovery system according to any one of items 1 to 4, wherein a buffer layer (110) is formed between the counter electrode current collector and the counter electrode to improve adhesion between the counter electrode current collector and the counter electrode. [Explanation of Symbols]

[0102] 1. Carbon dioxide capture system (gas capture system) 10. Carbon dioxide capture device 101 Electrochemical cell 103 Working electrode current collector 103a Working electrode opening 104 Working electrode 105, 115 Counter electrode current collector 105a Counter electrode aperture 106 Opposite

Claims

1. A gas recovery system that recovers a target gas from a mixed gas by an electrochemical reaction, The working electrode (104) adsorbs the gas to be recovered, The working electrode and the counter electrode (106) that exchanges electrons, A working electrode current collector (103) that contacts the working electrode and electrically connects the working electrode and the counter electrode, The system includes a counter electrode current collector (105) that contacts the counter electrode and electrically connects the working electrode and the counter electrode, The working electrode current collector has a working electrode opening (103a) formed therein, which exposes the working electrode to the mixed gas. The counter electrode current collector is configured to prevent contact between the mixed gas and the counter electrode in a gas recovery system.

2. The counter electrode is formed of multiple fine particles, The gas recovery system according to claim 1, wherein the surface roughness (Rzo) of the counter electrode side surface of the counter electrode current collector is equal to or greater than the average particle size (φDo) of the fine particles.

3. The gas recovery system according to claim 1 or 2, wherein the surface roughness (Rzo) of the counter electrode current collector on the counter electrode side is less than or equal to the thickness dimension (To) of the counter electrode.

4. The gas recovery system according to claim 1 or 2, wherein a buffer layer (110) is formed between the counter electrode current collector and the counter electrode to improve adhesion between the counter electrode current collector and the counter electrode.

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