Carbon dioxide recovery system and working electrode

Abstract

Provided is a carbon dioxide recovery system capable of inhibiting a decrease in the amount of CO2 adsorbed by an electrochemical cell over time, and a working electrode used in the carbon dioxide recovery system. An electrochemical cell including a working electrode and a counter electrode is provided. The working electrode includes an electrode substrate, a CO2 adsorbent, and a binder. An applied voltage between the working electrode and the counter electrode causes electrons to be supplied from the counter electrode to the working electrode, and the CO2 adsorbent to bind with CO2 when the electrons are supplied. The binder is electrically conductive, and the CO2 adsorbent is held in the electrode substrate by the binder.

Description

Technical Field

[0001] The present invention relates to a carbon dioxide recovery system for recovering CO2 from a CO2-containing gas, and a working electrode used in the carbon dioxide recovery system. Background Technology

[0002] JP2018-533470A discloses a gas separation system that separates CO2 from CO2-containing gases via an electrochemical reaction. In this gas separation system, the working electrode of the electrochemical cell is equipped with a CO2 adsorbent capable of adsorbing CO2.

[0003] CO2 adsorbent is an electroactive substance that can switch between adsorbing and emitting CO2 by changing the potential difference between the working electrode and the counter electrode.

[0004] However, in the prior art construction described above, the CO2 adsorbent of the working electrode may peel off from the electrode substrate during prolonged use. Therefore, the amount of CO2 adsorbed by the electrochemical cell may decrease over time. Summary of the Invention

[0005] In view of the above, the object of the present invention is to provide a carbon dioxide recovery system capable of suppressing the reduction of the amount of CO2 adsorbed by an electrochemical cell over time, and a working electrode used in the carbon dioxide recovery system.

[0006] To achieve the above objectives, a carbon dioxide recovery system according to one aspect of the present disclosure is a carbon dioxide recovery system that separates CO2 from a CO2-containing gas by an electrochemical reaction. The carbon dioxide recovery system includes an electrochemical cell (101) having a working electrode (102) and a counter electrode (103). The working electrode includes an electrode substrate (102a), a CO2 adsorbent (102b), and a binder (102c). An applied voltage between the working electrode and the counter electrode supplies electrons from the counter electrode to the working electrode, and enables the CO2 adsorbent to bind with CO2 when electrons are supplied. The binder is conductive and retains the CO2 adsorbent in the electrode substrate by means of the binder.

[0007] According to the foregoing aspects of this disclosure, the CO2 adsorbent is retained within the electrode substrate by using an adhesive. As a result, the CO2 adsorbent is less likely to peel off from the electrode substrate, and the reduction in the amount of CO2 adsorbed by the electrochemical cell over time can be suppressed.

[0008] The reference numerals in parentheses following each of the above components indicate their correspondence with the specific apparatus described in the following embodiments. The invention according to this disclosure is not limited to any specific apparatus. Attached Figure Description

[0009] In the attached diagram:

[0010] Figure 1 This is a conceptual diagram of a carbon dioxide recovery system according to an embodiment of the present invention;

[0011] Figure 2 This is a conceptual diagram of a CO2 recovery device;

[0012] Figure 3 It is a cross-sectional view of an electrochemical cell;

[0013] Figure 4 This is a graph showing the CO2 selective permeability and hydrophobicity of the negative electrode adhesive;

[0014] Figure 5 It is an enlarged cross-sectional view showing the area near the surface of the negative electrode of an electrochemical cell;

[0015] Figure 6 It is a diagram used to describe the operation of a CO2 recovery device in both CO2 recovery and CO2 emission modes;

[0016] Figure 7 This is a diagram of a modified example of an electrochemical cell. Detailed Implementation

[0017] Hereinafter, embodiments of the present invention will be described using the accompanying drawings. Figure 1 As shown, the carbon dioxide recovery system 10 of this embodiment includes a compressor 11, a CO2 recovery device 100, a flow path switching valve 12, a CO2 utilization device 13, and a control device 14.

[0018] Compressor 11 pumps CO2-containing gas to CO2 recovery unit 100. The CO2-containing gas is a mixture of CO2 and other gases. For example, air or exhaust gases from an internal combustion engine can be used.

[0019] CO2 recovery device 100 is a device for separating and recovering CO2 from CO2-containing gas. CO2 recovery device 100 may discharge CO2-removed gas after CO2 recovery from CO2-containing gas, or discharge CO2 recovered from CO2-containing gas. The construction of CO2 recovery device 100 will be described in detail later.

[0020] The flow path switching valve 12 is a three-way valve used to switch the flow path of the gas discharged from the CO2 recovery unit 100. When CO2 removal gas is discharged from the CO2 recovery unit 100, the flow path switching valve 12 switches the flow path of the discharged gas to the atmospheric side. When CO2 is discharged from the CO2 recovery unit 100, the flow path of the discharged gas is switched to the CO2 utilization unit 13 side.

[0021] CO2 utilization device 13 is a device that utilizes CO2. Examples of CO2 utilization device 13 include a storage tank for storing CO2 and a conversion device for converting CO2 into fuel. The conversion device can be a device that converts CO2 into hydrocarbon fuels such as methane. The hydrocarbon fuel can be a gaseous fuel or a liquid fuel at normal temperature and pressure.

[0022] The control device 14 consists of a known microcomputer including a CPU, ROM, RAM, etc., and peripheral circuitry of the microcomputer. 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. In this embodiment, the control device 14 performs operation control of the compressor 11, operation control of the CO2 recovery device 100, and flow path switching control of the flow path switching valve 12, etc.

[0023] Next, we will use Figure 2 Describes a CO2 recovery device 100. (e.g.) Figure 2 As shown, the CO2 recovery device 100 includes an electrochemical cell 101. The electrochemical cell 101 includes a working electrode 102, a counter electrode 103, and an insulating layer 104. Figure 2 In the example shown, the working electrode 102, the counter electrode 103, and the insulating layer 104 are all plate-shaped. Although in Figure 2 The working electrode 102, the counter electrode 103, and the insulating layer 104 are shown in a spaced-out manner, but in reality these components are arranged to be in contact with each other.

[0024] The electrochemical cell 101 may be housed within a container (not shown). The container may include a gas inlet and a gas outlet, wherein the gas inlet is used to allow CO2-containing gas to flow into the container, and the gas outlet is used to allow CO2 to remove gas or CO2 to flow out of the container.

[0025] The CO2 recovery device 100 adsorbs and desorbs CO2 through an electrochemical reaction, and is capable of separating and recovering CO2 from CO2-containing gases. The CO2 recovery device 100 has a power supply 105 that applies a predetermined voltage to the working electrode 102 and the counter electrode 103, and is capable of changing the potential difference between the working electrode 102 and the counter electrode 103. The working electrode 102 is the negative electrode, and the counter electrode 103 is the positive electrode.

[0026] The electrochemical cell 101 operates by switching between a CO2 recovery mode (where CO2 is recovered at the working electrode 102) and a CO2 emission mode (where CO2 is emitted from the working electrode 102) by changing the potential difference between the working electrode 102 and the counter electrode 103. The CO2 recovery mode is the charging mode that charges the electrochemical cell 101. The CO2 emission mode is the discharging mode that discharges the electrochemical cell 101.

[0027] In CO2 recovery mode, a first voltage is applied between the working electrode 102 and the counter electrode 103, and electrons are supplied from the counter electrode 103 to the working electrode 102. At the first voltage, the working electrode potential is lower than the counter electrode potential. The first voltage can, for example, be in the range of 0.5 to 2.0 V.

[0028] In CO2 emission mode, a second voltage is applied between the working electrode 102 and the counter electrode 103, and electrons are supplied from the working electrode 102 to the counter electrode 103. The second voltage is lower than the first voltage, and the relationship between the working electrode potential and the counter electrode potential is not limited. That is, in CO2 emission mode, the working electrode potential can be lower than the counter electrode potential, equal to the counter electrode potential, or higher than the counter electrode potential.

[0029] like Figure 3 As shown, the working electrode 102 includes a working electrode substrate (electrode substrate) 102a and a CO2 adsorbent 102b. For convenience, Figure 3 The diagram shows the CO2 adsorbent 102b located on the outside of the working electrode substrate 102a. However, in reality, the CO2 adsorbent 102b is disposed inside the porous working electrode substrate 102a.

[0030] The working electrode substrate 102a is a porous and conductive material that allows CO2 to pass through. Examples of working electrode substrate 102a include carbonaceous materials and metallic materials. Examples of carbonaceous materials that can be used to form the working electrode substrate 102a include carbon paper, carbon cloth, nonwoven carbon pads, and porous gas diffusion layers (GDL). Examples of metallic materials that can be used to form the working electrode substrate 102a include metals (such as Al or Ni) processed into a mesh structure.

[0031] CO2 adsorbent 102b exhibits redox activity and contains electroactive substances capable of reversibly inducing redox reactions. CO2 adsorbent 102b can bind and adsorb CO2 in a reduced state and release CO2 in an oxidized state.

[0032] CO2 adsorbent 102b has functional groups that bind to CO2. These CO2-binding functional groups exchange electrons and serve as CO2 adsorption sites. Examples of CO2-binding functional groups include atoms with high electronegativity (such as F, O, N, Cl, and S). For example, a ketone group (C=O) can be used.

[0033] In this embodiment, polyanthraquinone, an organic polymer having a ketone group, is used as CO2 adsorbent 102b. Examples of polyanthraquinones include poly(1,4-anthraquinone), poly(1,5-anthraquinone), poly(1,8-anthraquinone), and poly(2,6-anthraquinone). In this embodiment, more specifically, poly(1,4-anthraquinone) as shown below can be used as CO2 adsorbent 102b.

[0034]

[0035] CO2 adsorbent 102b can be mixed with conductive materials such as carbon nanotubes, carbon black, or graphene. In other words, by using conductive materials and mixing them with CO2 adsorbent 102b, the conductive materials can form conductive pathways to CO2 adsorbent 102b.

[0036] The mixing of the CO2 adsorbent and the conductive material can be carried out by, for example, dissolving the conductive material in an organic solvent such as NMP (N-methylpyrrolidone), and then contacting the conductive material dispersed in the organic solvent with the CO2 adsorbent 102b. The contact between the conductive material and the CO2 adsorbent 102b can be achieved by methods such as wetting and coating, where the working electrode substrate 102a containing the CO2 adsorbent 102b is immersed in the solvent in which the conductive material is dispersed. As a result, the conductive material can be uniformly contacted with the CO2 adsorbent 102b.

[0037] A working electrode adhesive (adhesive) 102c is disposed between the working electrode substrate 102a and the CO2 adsorbent 102b. The working electrode adhesive 102c has adhesive force and retains the CO2 adsorbent 102b in the working electrode substrate 102a.

[0038] The working electrode binder 102c contains a conductive material with conductivity. As a result, electron transfer between the working electrode substrate 102a and the CO2 adsorbent 102b can be ensured.

[0039] In this embodiment, the CO2 adsorbent 102b and the working electrode adhesive 102c are used in the form of a mixture. That is, the CO2 adsorbent 102b exists in a dispersed state within the working electrode adhesive 102c. A mixture of the CO2 adsorbent 102b and the working electrode adhesive 102c is formed, and this mixture adheres to the working electrode substrate 102a as a mixed layer of the CO2 adsorbent 102b and the working electrode adhesive 102c. The CO2 adsorbent 102b is contained within the working electrode adhesive 102c, and the CO2 adsorbent 102b can be firmly retained within the working electrode adhesive 102c.

[0040] In this embodiment, the working electrode adhesive 102c has CO2 permeability, enabling CO2 to permeate. Furthermore, the working electrode adhesive 102c of this embodiment has CO2 selective permeability, enabling CO2 to selectively permeate among various types of gases contained in the CO2-containing gas. Additionally, the working electrode adhesive 102c of this embodiment is hydrophobic.

[0041] like Figure 4 As shown, CO2 contained in the CO2-containing gas permeates through the working electrode adhesive 102c and can reach the CO2 adsorbent 102b present inside the working electrode adhesive 102c. On the other hand, gases other than CO2 contained in the CO2-containing gas (such as N2 and O2) cannot permeate the working electrode adhesive 102c, which has CO2 selective permeability. Furthermore, when moisture (H2O) is present in the CO2-containing gas, the moisture will not permeate the hydrophobic working electrode adhesive 102c.

[0042] Non-fluid materials that do not possess flowability can be used as working electrode binders 102c. Examples of non-fluid materials include gel materials and solid materials. Examples of gel materials include ionic liquid gels. Examples of solid materials include solid electrolytes and conductive resins.

[0043] When a solid electrolyte is used as the working electrode binder 102c, it is desirable to use an ionomer made of a polymer electrolyte or the like to increase the contact area with the CO2 adsorbent 102b. When a conductive resin is used as the working electrode binder 102c, epoxy resin or fluororesins containing silver, such as polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVDF), can be used as conductive fillers.

[0044] The raw material for the working electrode adhesive 102c can be a free-flowing liquid substance. In this case, the CO2 adsorbent 102b can be dispersed and mixed into the raw material of the working electrode adhesive 102c, and can be adhered to the working electrode substrate 102a by means of impregnation, coating, etc. Then, the raw material of the working electrode adhesive 102c can be gelled or cured under predetermined conditions. The predetermined conditions can be conditions such as specific pressure, specific temperature, and specific time under which the raw material of the working electrode adhesive 102c undergoes gelation or becomes cured.

[0045] like Figure 5 As shown, the working electrode adhesive 102c enters and is fixed in the holes and gaps formed in the working electrode substrate 102a. Due to the anchoring effect, a mechanical bonding force can be generated between the working electrode adhesive 102c and the working electrode substrate 102a.

[0046] In this embodiment, the ionic liquid gel obtained by gelation of the ionic liquid can be used as the working electrode binder 102c. The ionic liquid gel is a gel-state structure in which the ionic liquid is retained in a polymer network structure.

[0047] The structure disclosed in JP2015-25056A can be preferably used as an ionic liquid gel. In this structure, the ionic liquid is held within a three-dimensional network structure composed of two different types of polymer chains. This three-dimensional network structure includes a first network structure formed by condensation polymerization and a second network structure formed by free radical polymerization.

[0048] Tetraethyl orthosilicate (TEOS) can be used as a monomer for condensation polymerization. TEOS is also used as a crosslinking agent in condensation polymerization.

[0049] N,N-Dimethylacrylamide (DMAAm) can be used as a monomer for free radical polymerization. In free radical polymerization, N,N'-methylenebisacrylamide (MBAA) can be used as a crosslinking agent, and 2,2'-azobisisobutyronitrile (AIBN) can be used as an initiator.

[0050] The ionic liquid constituting the ionic liquid gel serves as a solvent for the monomers constituting the first network structure and the monomers constituting the second network structure. Then, after the formation of the first and second network structures, the first and second network structures become entangled with each other, and the ionic liquid is incorporated into these network structures.

[0051] Examples of ionic liquids constituting ionic liquid gels include 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([EMIM][Tf2N]), 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([BMIM][Tf2N]), and 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]).

[0052] To impart hydrophobicity to the working electrode binder 102c, it is desirable to use a hydrophobic ionic liquid as the ionic liquid constituting the ionic liquid gel. [EMIM][Tf2N] or [BMIM][Tf2N] can be used as the hydrophobic ionic liquid.

[0053] The ionic liquid gel illustrated in this embodiment can be obtained by independently performing condensation polymerization of monomers constituting the first network structure (e.g., TEOS) and free radical polymerization of monomers constituting the second network structure (e.g., DMAAm) in an ionic liquid. In this embodiment, the method for preparing the ionic liquid gel includes: a step of mixing monomers constituting the first network structure and monomers constituting the second network structure with an ionic liquid; a step of forming the first network structure by condensation polymerization; and a step of forming the second network structure by free radical polymerization. Free radical polymerization can be performed after condensation polymerization, or condensation polymerization and free radical polymerization can be performed simultaneously.

[0054] Return to Figure 3 The counter electrode 103 has the same structure as the working electrode 102, and is provided with a counter electrode substrate 103a, an electroactive auxiliary material 103b, and a counter electrode adhesive 103c.

[0055] The counter electrode substrate 103a is a conductive material and may be made of the same material as the working electrode substrate 102a, or a different material. The counter electrode adhesive 103c may be a conductive material capable of retaining the electroactive auxiliary material 103b within the counter electrode substrate 103a. The counter electrode adhesive 103c may be made of the same material as the working electrode adhesive 102c, or a different material.

[0056] Electroactive auxiliary material 103b has a redox state opposite to that of CO2 adsorbent 102b and is an auxiliary electroactive material that exchanges electrons with CO2 adsorbent 102b. Examples of electroactive auxiliary material 103b include metal complexes that achieve electron transfer by changing the valence state of metal ions. Examples of such metal complexes include cyclopentadienyl metal complexes such as ferrocene, nickel dicene, and cobalt dicene, as well as porphyrin metal complexes. In this embodiment, ferrocene polyethylene, as shown below, can be specifically used as electroactive auxiliary material 103b.

[0057]

[0058] An insulating layer 104 is disposed between the working electrode 102 and the counter electrode 103, and separates the working electrode 102 and the counter electrode 103. The insulating layer 104 prevents physical contact between the working electrode 102 and the counter electrode 103 and suppresses electrical short circuits.

[0059] As the insulating layer 104, a separator or a gas layer such as air can be used. In this embodiment, a porous separator is used as the insulating layer 104. Examples of materials for the separator include separators made of cellulose membranes, polymers, and composite materials containing polymers and ceramics.

[0060] like Figure 3 As shown, an ion-conducting member 106 is disposed between the working electrode 102 and the counter electrode 103. The ion-conducting member 106 is disposed between the working electrode substrate 102a and the counter electrode substrate 103a through an insulating layer 104.

[0061] The ion-conducting component 106 is in contact with the CO2 adsorbent 102b inside the working electrode substrate 102a. The ion-conducting component 106 has ion conductivity and promotes conductivity with the CO2 adsorbent 102b. The ions contained in the ion-conducting component 106 do not directly react with the functional groups contained in the CO2 adsorbent 102b that are bound to CO2.

[0062] Non-fluid materials that do not possess flowability can preferably be used as the ion-conducting component 106. Examples of non-fluid materials include gel-state materials and solid materials such as ionic liquid gels and solid electrolytes. The ion-conducting component 106 can use the same material as the working electrode adhesive 102c, or it can use a different material than the working electrode adhesive 102c.

[0063] Next, the operation of the carbon dioxide recovery system 10 of this embodiment will be described. For example... Figure 6 As shown, the carbon dioxide recovery system 10 operates by alternately switching between a CO2 recovery mode and a CO2 emission mode. The operation of the carbon dioxide recovery system 10 is controlled by a control device 14.

[0064] First, the CO2 recovery mode will be described. In the CO2 recovery mode, compressor 11 operates to supply CO2-containing gas to CO2 recovery device 100. In CO2 recovery device 100, the voltage applied between working electrode 102 and counter electrode 103 is set to a first voltage. As a result, electron supply to the electroactive auxiliary material 103b of counter electrode 103 and electron attraction to the CO2 adsorbent 102b of working electrode 102 can be achieved simultaneously.

[0065] The electroactive auxiliary material 103b of the counter electrode 103 releases electrons and is in an oxidized state, and supplies electrons from the counter electrode 103 to the working electrode 102. The CO2 adsorbent 102b of the working electrode 102 receives electrons and is in a reduced state.

[0066] The CO2 adsorbent 102b in its reduced state has a high CO2 binding strength and binds to and adsorbs CO2 contained in the CO2-containing gas. As a result, the CO2 recovery device 100 is able to recover CO2 from the CO2-containing gas.

[0067] After CO2 is recovered by the CO2 recovery unit 100, the CO2-containing gas is discharged from the CO2 recovery unit 100 as CO2-free gas or CO2-removed gas with reduced CO2 concentration. The flow path switching valve 12 switches the gas flow path to the atmospheric side, and the CO2-removed gas is discharged from the CO2 recovery unit 100 into the atmosphere.

[0068] Next, the CO2 emission mode will be described. In the CO2 emission mode, the compressor 11 stops, and the supply of CO2-containing gas to the CO2 recovery unit 100 ceases. In the CO2 recovery unit 100, the voltage applied between the working electrode 102 and the counter electrode 103 is set to a second voltage. As a result, electron supply to the CO2 adsorbent 102b of the working electrode 102 and electron attraction to the electroactive auxiliary material 103b of the counter electrode 103 can be achieved simultaneously.

[0069] The CO2 adsorbent 102b of the working electrode 102 emits electrons and is in an oxidized state. The CO2 binding strength of the CO2 adsorbent 102b decreases, and CO2 is desorbed and emitted. The electroactive auxiliary material 103b of the counter electrode 103 receives electrons and is in a reduced state.

[0070] CO2 emitted from CO2 adsorbent 102b is discharged from CO2 recovery unit 100. Flow path switching valve 12 switches the gas flow path to the CO2 utilization unit 13 side, and CO2 emitted from CO2 recovery unit 100 is supplied to CO2 utilization unit 13.

[0071] In the CO2 recovery apparatus 100 of this embodiment as described above, the CO2 adsorbent 102b is retained in the working electrode substrate 102a by using the working electrode adhesive 102c. As a result, the CO2 adsorbent 102b is less likely to peel off from the working electrode substrate 102a, and the reduction in the amount of CO2 adsorbed by the electrochemical cell 101 over time can be suppressed.

[0072] Furthermore, the working electrode adhesive 102c of this embodiment is conductive. Therefore, it is possible to prevent the working electrode adhesive 102c from hindering the electron flow between the working electrode substrate 102a and the CO2 adsorbent 102b.

[0073] Furthermore, in this embodiment, a gel-state material or a solid material is used as the working electrode adhesive 102c. Therefore, due to the anchoring effect, a mechanical bonding force can be generated between the working electrode adhesive 102c and the pores and voids formed on the surface of the working electrode substrate 102a.

[0074] In this embodiment, an ionic liquid gel is used as the working electrode binder 102c. As described above, by using a gel-like material as the binder 102c, the CO2 adsorbent 102b and the binder 102c can more easily come into contact with each other, and conductivity can be improved.

[0075] Furthermore, in this embodiment, the working electrode adhesive 102c is CO2 permeable. Therefore, even when the CO2 adsorbent 102b is disposed inside the working electrode adhesive 102c and cannot directly contact the CO2-containing gas, CO2 can still permeate the working electrode adhesive 102c and reach the CO2 adsorbent 102b. As a result, even when the CO2 adsorbent 102b is present inside the working electrode adhesive 102c, CO2 can be recovered by the CO2 adsorbent 102b.

[0076] Furthermore, in this embodiment, the working electrode binder 102c has CO2 selective permeability. Therefore, gases other than CO2 contained in CO2-containing gases (such as N2 and O2) can be prevented from reaching the working electrode binder 102c. As a result, the CO2 concentration reaching the CO2 adsorbent 102b can be increased, and the amount of CO2 adsorbed by the CO2 adsorbent 102b can be increased.

[0077] Furthermore, in this embodiment, the working electrode binder 102c is hydrophobic. Therefore, even in the presence of moisture (H2O), H2O can be prevented from reaching the working electrode binder 102c. As a result, H2O can be prevented from preferentially reacting with the CO2 adsorbent 102b, and the amount of CO2 adsorbed by the CO2 adsorbent 102b can be increased.

[0078] Furthermore, in this embodiment, the CO2 adsorbent 102b and the working electrode adhesive 102c are used in a mixture. As a result, the CO2 adsorbent 102b is firmly retained inside the working electrode adhesive 102c, and the CO2 adsorbent 102b is unlikely to peel off from the working electrode substrate 102a.

[0079] Furthermore, in this embodiment, an ion-conducting member 106 is provided between the working electrode 102 and the counter electrode 103, and a gel-state material or a solid material is used as the ion-conducting member 106. As described above, by using a non-fluid material as the ion-conducting member 106, it is possible to prevent the ion-conducting member 106 from eluting between the working electrode 102 and the counter electrode 103.

[0080] (Other implementation methods)

[0081] This invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the invention. Furthermore, the apparatus disclosed in the embodiments described above can be appropriately combined within feasible limits.

[0082] For example, in the embodiment described above, the working electrode 102, the counter electrode 103, and the insulating layer 104 of the electrochemical cell 101 are all plate-shaped components. However, as... Figure 7 As shown, the working electrode 102, the counter electrode 103, and the insulating layer 104 can each be a cylindrical component. In this case, the working electrode 102 can be arranged on the innermost side, the counter electrode 103 can be arranged on the outermost side, and the insulating layer 104 can be arranged between the working electrode 102 and the counter electrode 103. As a result, the space formed inside the working electrode 102 can be used as a gas flow path for CO2-containing gas to pass through.

[0083] Furthermore, in the embodiment described above, a hydrophobic working electrode adhesive 102c is used. However, the working electrode adhesive 102c does not necessarily have to be hydrophobic.

[0084] Furthermore, in the embodiment described above, a working electrode adhesive 102c that selectively allows CO2 permeation is used. However, the working electrode adhesive 102c does not necessarily have to have selective CO2 permeability.

[0085] Furthermore, in the embodiment described above, a configuration is used in which the CO2 adsorbent 102b is disposed inside the working electrode adhesive 102c. However, the CO2 adsorbent 102b can also be disposed on the surface of the working electrode adhesive 102c. In this case, since the CO2 adsorbent 102b can directly contact CO2-containing gases, the working electrode adhesive 102c does not necessarily need to be CO2 permeable.

Claims

1. A carbon dioxide recovery system that separates CO2 from a CO2-containing gas containing CO2 by an electrochemical reaction, comprising: an electrochemical cell that includes a working electrode and a counter electrode; wherein the working electrode includes an electrode substrate, a CO2 adsorbent, and a binder, the carbon dioxide recovery system is configured such that an applied voltage between the working electrode and the counter electrode causes electrons to be supplied from the counter electrode to the working electrode, and the CO2 adsorbent is capable of binding to CO2 when supplied with electrons, the binder is configured to have electrical conductivity to transfer electrons between the electrode substrate and the CO2 adsorbent, and the CO2 adsorbent is held in the electrode substrate by the binder having electrical conductivity, the electrode substrate is a porous material, the binder having electrical conductivity is configured to enter and be fixed to recessed and protruding voids formed in the electrode substrate, thereby creating a mechanical binding force in combination with the electrode substrate.

2. The carbon dioxide recovery system according to claim 1, wherein the binder is a gel-like material or a solid material.

3. The carbon dioxide recovery system according to claim 2, wherein the binder is an ionic liquid gel that is obtainable from gelation of an ionic liquid.

4. The carbon dioxide recovery system according to claim 1, wherein the binder has CO2 permeability.

5. The carbon dioxide recovery system according to claim 4, wherein the CO2-containing gas includes a plurality of types of gases, and the binder has CO2 selective permeability that is capable of selectively permeating CO2 among the plurality of types of gases contained in the CO2-containing gas.

6. The carbon dioxide recovery system according to claim 1, wherein the binder has hydrophobicity.

7. The carbon dioxide recovery system according to claim 1, wherein the binder and the CO2 adsorbent form a mixture, and the mixture is held in the electrode substrate.

8. The carbon dioxide recovery system according to any one of claims 1 to 7, wherein an ionically conductive member having ion conductivity is provided between the working electrode and the counter electrode, and the ionically conductive member is a gel-like material or a solid material.

9. A working electrode for use in a carbon dioxide recovery system that separates CO2 from a CO2-containing gas containing CO2 by an electrochemical reaction, the carbon dioxide recovery system including an electrochemical cell that includes a working electrode and a counter electrode, wherein the working electrode includes an electrode substrate, a CO2 adsorbent, and a binder, the carbon dioxide recovery system is configured such that an applied voltage between the working electrode and the counter electrode causes electrons to be supplied from the counter electrode to the working electrode, and the CO2 adsorbent is capable of binding to CO2 when supplied with electrons. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The adhesive is configured to have electrical conductivity to transfer electrons between the electrode substrate and the CO2 adsorbent, and the CO2 adsorbent is held in the electrode substrate by the adhesive having electrical conductivity, The electrode substrate is a porous material, The adhesive having electrical conductivity is configured to enter and be fixed to recessed and protruding voids formed in the electrode substrate, thereby generating a mechanical bonding force in combination with the electrode substrate.

Images