WO2024014483A1 - Electrochemical cell - Google Patents

Electrochemical cell Download PDF

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WO2024014483A1
WO2024014483A1 PCT/JP2023/025744 JP2023025744W WO2024014483A1 WO 2024014483 A1 WO2024014483 A1 WO 2024014483A1 JP 2023025744 W JP2023025744 W JP 2023025744W WO 2024014483 A1 WO2024014483 A1 WO 2024014483A1
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carbon dioxide
counter electrode
working electrode
electrochemical cell
active material
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PCT/JP2023/025744
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French (fr)
Japanese (ja)
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勝真 石野
淳一 成瀬
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株式会社デンソー
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/32—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by electrical effects other than those provided for in group B01D61/00

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  • the present disclosure relates to electrochemical cells.
  • carbon dioxide recovery systems have been developed that separate carbon dioxide (CO 2 ) from a target gas containing carbon dioxide (CO 2 ) through an electrochemical reaction.
  • a carbon dioxide adsorbent capable of adsorbing carbon dioxide is provided at the working electrode of an electrochemical cell.
  • the adsorbent is an electroactive species, and by changing the potential difference between the working electrode and the counter electrode, the adsorption and release of carbon dioxide by the carbon dioxide adsorbent can be switched.
  • the counter electrode of the electrochemical cell is configured to include an active material that is an auxiliary electroactive species that exchanges electrons with the carbon dioxide adsorbent of the working electrode.
  • an active material for example, a metal complex that can transfer electrons by changing the valence of metal ions can be used.
  • ferrocene (Fc) for example, as such a metal complex has been considered.
  • ferrocene is a small molecule, it easily dissolves into the electrolyte provided between the working electrode and the counter electrode. This may reduce electrode performance.
  • Non-Patent Document 1 discloses a technique using polyvinylferrocene (PVFc) as a counter electrode active material.
  • PVFc polyvinylferrocene
  • Non-Patent Document 1 a mixed gas of carbon dioxide and nitrogen (N 2 ) is used as the gas to be treated. That is, in Non-Patent Document 1, an electrochemical cell is operated in a CO 2 /N 2 atmosphere.
  • Non-Patent Document 1 when the electrochemical cell described in Non-Patent Document 1 is used in a carbon dioxide recovery system that separates carbon dioxide from a gas containing oxygen such as the atmosphere, the active material of the electrode deteriorates due to oxygen. There is a risk. This can reduce the durability of the electrochemical cell.
  • the present disclosure aims to provide an electrochemical cell that can improve electrode performance and durability.
  • an electrochemical cell includes a working electrode that adsorbs and desorbs carbon dioxide from a gas to be treated containing carbon dioxide through an electrochemical reaction; a counter electrode that transfers electrons to and from the working electrode;
  • An electrochemical cell comprising: an electrolyte material covering a working electrode and a counter electrode;
  • the electrolyte material is an ionic liquid,
  • At least one of the working electrode and the counter electrode has an active material and carbon nanotubes, The active material is contained inside the carbon nanotube.
  • FIG. 1 is a conceptual diagram showing the overall configuration of a carbon dioxide recovery system in one embodiment. It is an explanatory view showing a carbon dioxide recovery device in one embodiment.
  • FIG. 2 is a cross-sectional view of an electrochemical cell in one embodiment.
  • FIG. 2 is an explanatory diagram for explaining the configuration of a counter electrode in one embodiment. It is a figure showing a TEM image. It is a figure showing a STEM-ADF image. It is a figure showing an EDX analysis result. It is a figure showing a cyclic voltammogram of an example. It is a figure which shows the cyclic voltammogram of a comparative example.
  • the electrochemical cell of the present disclosure is applied to a carbon dioxide recovery system that separates and recovers carbon dioxide from a gas to be treated containing carbon dioxide.
  • the gas to be treated is a carbon dioxide-containing gas containing carbon dioxide.
  • the gas to be treated also contains gases other than carbon dioxide.
  • the carbon dioxide-containing gas contains oxygen (O 2 ) as a gas other than carbon dioxide.
  • the gas to be treated is the atmosphere or a highly concentrated gas containing carbon dioxide at a higher concentration than the atmosphere. Highly concentrated gases are emitted from internal combustion engines and factories, for example.
  • the gas to be processed in this embodiment is the atmosphere.
  • the carbon dioxide recovery system 10 of this embodiment is provided with a compressor 11, a carbon dioxide recovery device 100, a flow path switching valve 12, a carbon dioxide utilization device 13, and a control device 14.
  • the compressor 11 pumps atmospheric air, which is a carbon dioxide-containing gas, to the carbon dioxide recovery device 100.
  • the compressor 11 is provided on the downstream side of the carbon dioxide recovery device 100 in the gas flow direction.
  • the carbon dioxide recovery device 100 is a device that separates and recovers carbon dioxide from a carbon dioxide-containing gas.
  • the carbon dioxide recovery device 100 discharges carbon dioxide removed gas after carbon dioxide has been recovered from the carbon dioxide-containing gas, or carbon dioxide recovered from the carbon dioxide-containing gas.
  • the configuration of carbon dioxide recovery device 100 will be described in detail later.
  • the flow path switching valve 12 is a three-way valve that switches the flow path of the exhaust gas of the carbon dioxide recovery device 100.
  • the flow path switching valve 12 switches the flow path of the exhaust gas to the atmosphere side when carbon dioxide removal gas is discharged from the carbon dioxide recovery device 100, and switches the flow path of the exhaust gas to the atmosphere side when carbon dioxide is discharged from the carbon dioxide recovery device 100.
  • the exhaust gas flow path is switched to the carbon dioxide utilization device 13 side.
  • the carbon dioxide utilization device 13 is a device that utilizes carbon dioxide.
  • a storage tank that stores carbon dioxide or a conversion device that converts carbon dioxide into fuel can be used.
  • a conversion device a device that converts carbon dioxide into hydrocarbon fuel such as methane can be used.
  • the hydrocarbon fuel may be a gaseous fuel at normal temperature and normal pressure, or may be a liquid fuel at normal temperature and normal pressure.
  • the control device 14 is composed of a well-known microcomputer including a CPU, ROM, RAM, etc., 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 operations of various devices to be controlled.
  • the control device 14 of this embodiment performs operation control of the compressor 11, operation control of the carbon dioxide recovery device 100, flow path switching control of the flow path switching valve 12, and the like.
  • Electrochemical cell 101 has a working electrode 130, a counter electrode 140, and a separator 150.
  • the working electrode 130, the counter electrode 140, and the separator 150 are each formed into a plate shape.
  • the working electrode 130, the counter electrode 140, and the separator 150 are shown spaced apart from each other in FIG. 2, these components are actually arranged so as to be in contact with each other.
  • the electrochemical cell 101 may be housed in a container (not shown).
  • the container can be provided with a gas inlet that allows the carbon dioxide-containing gas to flow into the container, and a gas outlet that allows the carbon dioxide removal gas and carbon dioxide to flow out of the container.
  • the carbon dioxide recovery device 100 adsorbs and desorbs carbon dioxide through an electrochemical reaction, and separates and recovers carbon dioxide from a carbon dioxide-containing gas.
  • the carbon dioxide recovery device 100 is provided with a control power source 120 that applies a predetermined voltage to the working electrode 130 and the counter electrode 140, and can change the potential difference between the working electrode 130 and the counter electrode 140.
  • Working electrode 130 is a negative electrode
  • counter electrode 140 is a positive electrode.
  • the electrochemical cell 101 operates by changing the potential difference between the working electrode 130 and the counter electrode 140 to switch between a recovery mode in which carbon dioxide is recovered at the working electrode 130 and a release mode in which carbon dioxide is released from the working electrode 130. I can do it.
  • the recovery mode is a charging mode in which the electrochemical cell 101 is charged
  • the discharge mode is a discharging mode in which the electrochemical cell 101 is discharged.
  • the first voltage V1 is applied between the working electrode 130 and the counter electrode 140, and electrons are supplied from the counter electrode 140 to the working electrode 130.
  • working electrode potential At the first voltage V1, working electrode potential ⁇ counter electrode potential.
  • the first voltage V1 can be within a range of 0.5 to 2.0V, for example.
  • a second voltage V2 lower than the first voltage V1 is applied between the working electrode 130 and the counter electrode 140, and electrons are supplied from the working electrode 130 to the counter electrode 140.
  • the second voltage V2 only needs to be a voltage lower than the first voltage V1, and the magnitude relationship between the working electrode potential and the counter electrode potential is not limited. That is, in the release 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.
  • the working electrode 130 in the electrochemical cell 101 has a working electrode side current collector 131 and a working electrode side electrode film 132.
  • the working electrode side current collector 131 is connected to the control power source 120 and is a porous conductive member through which carbon dioxide-containing gas can pass.
  • the working electrode side current collector 131 for example, a carbonaceous material or a metal material can be used.
  • a carbonaceous material constituting the working electrode side current collector 131 for example, carbon paper, carbon cloth, nonwoven carbon mat, porous gas diffusion layer (GDL), etc. can be used.
  • GDL porous gas diffusion layer
  • the metal material constituting the working electrode side current collector 131 a structure made of a metal such as Al, Ni, or SUS in a mesh shape can be used, for example.
  • the working electrode side electrode film 132 adsorbs and desorbs carbon dioxide from a carbon dioxide-containing gas through an electrochemical reaction.
  • the working electrode side electrode film 132 includes a carbon dioxide adsorbent, a working electrode side conductive agent, and a working electrode side binder.
  • a carbon dioxide adsorbent is an electroactive species (i.e., an active material) that adsorbs carbon dioxide by receiving electrons and desorbs the adsorbed carbon dioxide by releasing electrons.
  • an electroactive species i.e., an active material
  • carbon dioxide adsorbent for example, carbon materials, metal oxides, polyanthraquinone, etc. can be used.
  • the working electrode side conductive agent is a conductive material that forms a conductive path to the carbon dioxide adsorbent.
  • carbon materials such as carbon nanotubes, carbon black, and graphene can be used, for example.
  • the working electrode side binder holds the carbon dioxide adsorbent and the working electrode side conductive agent on the working electrode side current collector 131. Specifically, a mixture of the carbon dioxide adsorbent, the working electrode side conductive agent, and the working electrode side binder is formed, and the mixture is adhered to the working electrode side current collector 131. The carbon dioxide adsorbent and the working electrode side conductive agent are held inside the working electrode side binder.
  • a conductive resin As the binder on the working electrode side, for example, a conductive resin can be used.
  • a conductive resin an epoxy resin containing Ag or the like as a conductive filler, a fluororesin such as PTFE (polytetrafluoroethylene), PVDF (polyvinylidene fluoride), etc. can be used.
  • the counter electrode 140 has a counter electrode current collector 141 and a counter electrode film 142.
  • the configuration of counter electrode 140 will be explained in detail later.
  • the separator 150 is arranged between the working electrode film 132 and the counter electrode film 142.
  • the separator 150 separates the working electrode film 132 and the counter electrode film 142. That is, the separator 150 prevents physical contact between the working electrode film 132 and the counter electrode film 142. Moreover, the separator 150 suppresses electrical short circuit between the working electrode side electrode film 132 and the counter electrode side electrode film 142.
  • separator 150 a separator made of a cellulose membrane, a polymer, a composite material of polymer and ceramic, etc. can be used.
  • separator 150 a porous separator may be used.
  • An electrolyte material 160 (see FIG. 4 described later) is provided between the working electrode film 132 and the separator 150 and between the counter electrode film 142 and the separator 150.
  • Working electrode 130 and counter electrode 140 are covered with electrolyte material 160.
  • the electrolyte material 160 promotes electrical conduction to the carbon dioxide adsorbent.
  • an ionic liquid is used as the electrolyte material 160.
  • Ionic liquids are liquid salts that are nonvolatile at room temperature and pressure.
  • the ionic liquid used as the electrolyte material 160 has a cation containing at least one of imidazole and ammonium, and an anion containing TFSI (trifluoromethanesulfonylimide).
  • the counter electrode side current collector material 141 in the counter electrode 140 is a conductive member connected to the control power source 120.
  • the counter electrode side current collector material 141 may be made of the same material as the working electrode side current collector material 131, or may be made of a different material.
  • the counter electrode film 142 of the counter electrode 140 exchanges electrons with the working electrode film 132.
  • the counter electrode film 142 includes a counter active material 143, a counter conductive agent 144, and a counter binder (not shown).
  • the counter electrode active material 143 is an auxiliary electroactive species that exchanges electrons with the carbon dioxide adsorbent.
  • the counter electrode side active material 143 is a material that can transfer electrons in and out by changing the valence of the metal and transferring charges into and out of the ⁇ electron cloud.
  • a metal complex that enables transfer of electrons by changing the valence of metal ions can be used.
  • metal complexes include cyclopentadienyl metal complexes such as ferrocene, nickelocene, and cobaltocene, and porphyrin metal complexes. These metal complexes may be polymers or monomers.
  • a compound having a ferrocene skeleton may be used.
  • the counter electrode side active material 143 may include a substance that undergoes a redox reaction within a potential range of ⁇ 1.1 V to +0.5 V with respect to the redox potential of ferrocene.
  • the counter electrode active material 143 may contain at least one of ferrocene, ferrocene derivatives, metallocene, and phenothiazine. In this embodiment, ferrocene is used as the counter electrode side active material 143.
  • the counter electrode conductive aid 144 is a conductive material that forms a conductive path to the counter electrode active material 143.
  • the counter electrode side conductive agent 144 is used in combination with the counter electrode side active material 143.
  • carbon nanotubes are used as the counter electrode conductive aid 144.
  • the counter electrode binder is a material that can hold the counter electrode active material 143 and the counter electrode conductive agent 144 on the counter electrode current collector 141 and has electrical conductivity.
  • the binder on the opposite electrode side may be made of the same material as the binder on the working electrode side, or may be made of a different material. In this embodiment, PVDF is used as the opposite binder.
  • the counter electrode side active material 143 is contained inside the carbon nanotube as the counter electrode side conductive agent 144.
  • the present inventors conducted a TEM-EDX analysis to confirm the encapsulation state of ferrocene, which is the counter electrode side active material 143, in the carbon nanotubes.
  • TEM is a transmission electron microscope.
  • EDX is Energy Dispersive X-ray Spectroscope.
  • the following samples were prepared. First, 20 mg of carbon nanotubes were heat-treated at 350° C. in an air atmosphere. Next, 100 mg of ferrocene was encapsulated in the carbon nanotubes under an Ar atmosphere and heated at 270° C. for 48 hours to create a mixture. Thereafter, the mixture was washed with ethanol multiple times and air-dried to obtain a sample.
  • TEM-EDX analysis was performed on the sample.
  • a sample was processed into a thin section using an FIB (Focused Ion Beam System), and then a TEM image was observed. In the TEM image shown in FIG. 5, it was confirmed that some substance was contained inside the carbon nanotube.
  • an ADF (Annular Dark Field) image of the sample was observed using a STEM (Scanning Transmission Electron Microscope). Note that in this specification, an ADF image observed using STEM may be referred to as a STEM-ADF image. In the STEM-ADF image shown in FIG. 6, it was confirmed that the substance present inside the carbon nanotube appeared bright.
  • CV cyclic voltammetry
  • a three-electrode system was used, including an electrode film/glassy carbon substrate containing ferrocene inside carbon nanotubes as a working electrode, an Ag/Ag + electrode as a reference electrode, and Pt as a counter electrode.
  • the peak current value of the ferrocene oxidation wave after 20 cycles is 11% compared to the peak current value of the ferrocene oxidation wave after the first cycle. % increase.
  • the electrode film according to the comparative example was used, the peak current value of the ferrocene oxidation wave after 20 cycles was reduced by 29% compared to the peak current value of the ferrocene oxidation wave after the first cycle.
  • the peak current did not decrease.
  • the electrode film according to the comparative example was used, the peak current decreased.
  • the counter electrode side active material 143 is contained inside the carbon nanotube as the counter electrode side conductive agent 144. According to this, the counter electrode active material 143 can be protected by the carbon nanotubes. Therefore, elution of the counter electrode side active material 143 into the ionic liquid that is the electrolyte material 160 can be suppressed, so that the electrode performance of the counter electrode 140 can be improved. Further, since it is possible to suppress deterioration of the counter electrode side active material 143 due to oxygen contained in the atmosphere, durability can be improved.
  • the counter electrode side active material 143 was contained inside the carbon nanotube as the counter electrode side conductive agent 144, but the present invention is not limited to this embodiment.
  • carbon nanotubes may be used as the conductive agent on the working electrode side, and a carbon dioxide adsorbent, which is the active material of the working electrode 130, may be contained inside the carbon nanotubes.
  • an ionic liquid was used as the electrolyte material 160, but the present invention is not limited to this embodiment.
  • an ionic liquid gel obtained by gelling an ionic liquid may be used as the electrolyte material 160. According to this, it is possible to suppress the electrolyte material 160 from being eluted from the electrochemical cell 101.
  • double-walled carbon nanotubes are shown as carbon nanotubes in the TEM image shown in FIG. 5, but carbon nanotubes are not limited to double-walled carbon nanotubes.
  • the carbon nanotube a single-walled carbon nanotube or a three- or more-walled carbon nanotube may be used.
  • the characteristics of the electrochemical cell disclosed herein are as follows.
  • a working electrode (130) that adsorbs and desorbs carbon dioxide from a gas to be treated containing carbon dioxide through an electrochemical reaction
  • a counter electrode (140) that exchanges electrons with the working electrode
  • An electrochemical cell comprising an electrolyte material (160) covering the working electrode and the counter electrode,
  • the electrolyte material is an ionic liquid
  • At least one of the working electrode and the counter electrode has an active material (143) and carbon nanotubes, An electrochemical cell in which the active material is contained inside the carbon nanotube.

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Abstract

An electrochemical cell comprising a working electrode (130), a counter electrode (140), and an electrolyte material (160). The working electrode (130), by electrochemical reactions, adsorbs carbon dioxide from a carbon-dioxide-containing gas to be treated and desorbs the carbon dioxide. The counter electrode (140) performs electron transfers between itself and the working electrode. The electrolyte material (160) covers the working electrode (130) and the counter electrode (140). The electrolyte material (160) is an ionic liquid. The working electrode (130) and/or the counter electrode (140) includes an active material (143) and carbon nanotubes. The active material (143) is contained inside the carbon nanotubes.

Description

電気化学セルelectrochemical cell 関連出願の相互参照Cross-reference of related applications
　本出願は、２０２２年７月１５日に出願された日本特許出願２０２２－１１４０３９号に基づくもので、ここにその記載内容を援用する。 This application is based on Japanese Patent Application No. 2022-114039 filed on July 15, 2022, and the contents thereof are incorporated herein.
　本開示は、電気化学セルに関する。 The present disclosure relates to electrochemical cells.
　従来、電気化学反応によって二酸化炭素（ＣＯ２）を含有する被処理ガスから二酸化炭素を分離する二酸化炭素回収システムが開発されている。二酸化炭素回収システムでは、電気化学セルの作用極に二酸化炭素を吸着可能な二酸化炭素吸着材が設けられている。吸着材は電気活性種であり、作用極と対極の間の電位差を変化させることで、二酸化炭素吸着材による二酸化炭素の吸着と放出を切り替えることができる。 Conventionally, carbon dioxide recovery systems have been developed that separate carbon dioxide (CO 2 ) from a target gas containing carbon dioxide (CO 2 ) through an electrochemical reaction. In a carbon dioxide recovery system, a carbon dioxide adsorbent capable of adsorbing carbon dioxide is provided at the working electrode of an electrochemical cell. The adsorbent is an electroactive species, and by changing the potential difference between the working electrode and the counter electrode, the adsorption and release of carbon dioxide by the carbon dioxide adsorbent can be switched.
　電気化学セルの対極は、作用極の二酸化炭素吸着材との間で電子の授受を行う補助的な電気活性種である活物質を含んで構成されている。活物質としては、例えば金属イオンの価数が変化することで、電子の授受を可能とする金属錯体を用いることができる。このような金属錯体として、例えばフェロセン（Ｆｃ）を用いることが検討されてきた。 The counter electrode of the electrochemical cell is configured to include an active material that is an auxiliary electroactive species that exchanges electrons with the carbon dioxide adsorbent of the working electrode. As the active material, for example, a metal complex that can transfer electrons by changing the valence of metal ions can be used. The use of ferrocene (Fc), for example, as such a metal complex has been considered.
　しかしながら、フェロセンは小分子のため、作用極と対極との間に設けられる電解液に容易に溶出してしまう。これにより、電極性能が低下する可能性がある。 However, since ferrocene is a small molecule, it easily dissolves into the electrolyte provided between the working electrode and the counter electrode. This may reduce electrode performance.
　これに対し、非特許文献１には、対極の活物質としてポリビニルフェロセン（ＰＶＦｃ）を用いる技術が開示されている。非特許文献１では、フェロセンをポリマー化することにより、活物質の電解液へ溶出抑制を図っている。 On the other hand, Non-Patent Document 1 discloses a technique using polyvinylferrocene (PVFc) as a counter electrode active material. In Non-Patent Document 1, elution of an active material into an electrolytic solution is suppressed by polymerizing ferrocene.
　ここで、非特許文献１では、被処理ガスとして、二酸化炭素および窒素（Ｎ２）の混合ガスを用いている。すなわち、非特許文献１では、ＣＯ２／Ｎ２雰囲気において電気化学セルを作動させている。 Here, in Non-Patent Document 1, a mixed gas of carbon dioxide and nitrogen (N 2 ) is used as the gas to be treated. That is, in Non-Patent Document 1, an electrochemical cell is operated in a CO 2 /N 2 atmosphere.
　これに対し、上記非特許文献１に記載の電気化学セルを、例えば大気等の酸素が含まれるガスから二酸化炭素を分離する二酸化炭素回収システムに用いた場合、酸素により電極の活物質が劣化するおそれがある。これにより、電気化学セルの耐久性が低下する可能性がある。 On the other hand, when the electrochemical cell described in Non-Patent Document 1 is used in a carbon dioxide recovery system that separates carbon dioxide from a gas containing oxygen such as the atmosphere, the active material of the electrode deteriorates due to oxygen. There is a risk. This can reduce the durability of the electrochemical cell.
　本開示は、上記点に鑑みて、電極性能および耐久性を向上させることができる電気化学セルを提供することを目的とする。 In view of the above points, the present disclosure aims to provide an electrochemical cell that can improve electrode performance and durability.
　上記目的を達成するため、本開示の一態様に係る電気化学セルは、二酸化炭素を含有する被処理ガスから電気化学反応によって二酸化炭素の吸着と脱離を行う作用極と、
　作用極との間で電子の授受を行う対極と、
　作用極および対極を覆う電解質材料と、を備える電気化学セルにおいて、
　電解質材料は、イオン液体であり、
　作用極および対極の少なくとも一方は、活物質およびカーボンナノチューブを有しており、
　活物質は、カーボンナノチューブの内部に含有されている。 In order to achieve the above object, an electrochemical cell according to an embodiment of the present disclosure includes a working electrode that adsorbs and desorbs carbon dioxide from a gas to be treated containing carbon dioxide through an electrochemical reaction;
a counter electrode that transfers electrons to and from the working electrode;
An electrochemical cell comprising: an electrolyte material covering a working electrode and a counter electrode;
The electrolyte material is an ionic liquid,
At least one of the working electrode and the counter electrode has an active material and carbon nanotubes,
The active material is contained inside the carbon nanotube.
　これによれば、活物質が電解質材料へ溶出することを抑制できるので、電極性能を向上させることができる。また、被処理ガスに含まれる成分により活物質が劣化することを抑制できるので、耐久性を向上させることができる。 According to this, it is possible to suppress the active material from being eluted into the electrolyte material, so that the electrode performance can be improved. Furthermore, since deterioration of the active material due to components contained in the gas to be treated can be suppressed, durability can be improved.
一実施形態における二酸化炭素回収システムの全体構成を示す概念図である。1 is a conceptual diagram showing the overall configuration of a carbon dioxide recovery system in one embodiment. 一実施形態における二酸化炭素回収装置を示す説明図である。It is an explanatory view showing a carbon dioxide recovery device in one embodiment. 一実施形態における電気化学セルを示す断面図である。FIG. 2 is a cross-sectional view of an electrochemical cell in one embodiment. 一実施形態における対極の構成を説明するための説明図である。FIG. 2 is an explanatory diagram for explaining the configuration of a counter electrode in one embodiment. ＴＥＭ像を示す図である。It is a figure showing a TEM image. ＳＴＥＭ－ＡＤＦ像を示す図である。It is a figure showing a STEM-ADF image. ＥＤＸ分析結果を示す図である。It is a figure showing an EDX analysis result. 実施例のサイクリックボルタモグラムを示す図である。It is a figure showing a cyclic voltammogram of an example. 比較例のサイクリックボルタモグラムを示す図である。It is a figure which shows the cyclic voltammogram of a comparative example.
　以下、本開示における一実施形態について、図面を参照して説明する。本実施形態は、本開示における電気化学セルを、二酸化炭素を含有する被処理ガスから二酸化炭素を分離して回収する二酸化炭素回収システムに適用している。 Hereinafter, one embodiment of the present disclosure will be described with reference to the drawings. In this embodiment, the electrochemical cell of the present disclosure is applied to a carbon dioxide recovery system that separates and recovers carbon dioxide from a gas to be treated containing carbon dioxide.
　被処理ガスは、二酸化炭素を含有する二酸化炭素含有ガスである。被処理ガスは、二酸化炭素以外のガスも含有している。二酸化炭素含有ガスには、二酸化炭素以外のガスとして酸素（Ｏ２）が含まれている。被処理ガスは、大気、若しくは、大気よりも二酸化炭素含有濃度の高い高濃度ガスである。高濃度ガスは、例えば、内燃機関や工場から排出される。本実施形態の被処理ガスは、大気である。 The gas to be treated is a carbon dioxide-containing gas containing carbon dioxide. The gas to be treated also contains gases other than carbon dioxide. The carbon dioxide-containing gas contains oxygen (O 2 ) as a gas other than carbon dioxide. The gas to be treated is the atmosphere or a highly concentrated gas containing carbon dioxide at a higher concentration than the atmosphere. Highly concentrated gases are emitted from internal combustion engines and factories, for example. The gas to be processed in this embodiment is the atmosphere.
　図１に示すように、本実施形態の二酸化炭素回収システム１０は、圧縮機１１、二酸化炭素回収装置１００、流路切替弁１２、二酸化炭素利用装置１３、制御装置１４が設けられている。 As shown in FIG. 1, the carbon dioxide recovery system 10 of this embodiment is provided with a compressor 11, a carbon dioxide recovery device 100, a flow path switching valve 12, a carbon dioxide utilization device 13, and a control device 14.
　圧縮機１１は、二酸化炭素含有ガスである大気を二酸化炭素回収装置１００に圧送する。本実施形態では、二酸化炭素回収装置１００のガス流れ方向の下流側に圧縮機１１が設けられている。 The compressor 11 pumps atmospheric air, which is a carbon dioxide-containing gas, to the carbon dioxide recovery device 100. In this embodiment, the compressor 11 is provided on the downstream side of the carbon dioxide recovery device 100 in the gas flow direction.
　二酸化炭素回収装置１００は、二酸化炭素含有ガスから二酸化炭素を分離して回収する装置である。二酸化炭素回収装置１００は、二酸化炭素含有ガスから二酸化炭素が回収された後の二酸化炭素除去ガス、あるいは二酸化炭素含有ガスから回収した二酸化炭素を排出する。二酸化炭素回収装置１００の構成については、後で詳細に説明する。 The carbon dioxide recovery device 100 is a device that separates and recovers carbon dioxide from a carbon dioxide-containing gas. The carbon dioxide recovery device 100 discharges carbon dioxide removed gas after carbon dioxide has been recovered from the carbon dioxide-containing gas, or carbon dioxide recovered from the carbon dioxide-containing gas. The configuration of carbon dioxide recovery device 100 will be described in detail later.
　流路切替弁１２は、二酸化炭素回収装置１００の排出ガスの流路を切り替える三方弁である。流路切替弁１２は、二酸化炭素回収装置１００から二酸化炭素除去ガスが排出される場合は、排出ガスの流路を大気側に切り替え、二酸化炭素回収装置１００から二酸化炭素が排出される場合は、排出ガスの流路を二酸化炭素利用装置１３側に切り替える。 The flow path switching valve 12 is a three-way valve that switches the flow path of the exhaust gas of the carbon dioxide recovery device 100. The flow path switching valve 12 switches the flow path of the exhaust gas to the atmosphere side when carbon dioxide removal gas is discharged from the carbon dioxide recovery device 100, and switches the flow path of the exhaust gas to the atmosphere side when carbon dioxide is discharged from the carbon dioxide recovery device 100. The exhaust gas flow path is switched to the carbon dioxide utilization device 13 side.
　二酸化炭素利用装置１３は、二酸化炭素を利用する装置である。二酸化炭素利用装置１３としては、例えば二酸化炭素を貯蔵する貯蔵タンクや二酸化炭素を燃料に変換する変換装置を用いることができる。変換装置は、二酸化炭素をメタン等の炭化水素燃料に変換する装置を用いることができる。炭化水素燃料は、常温常圧で気体の燃料であってもよく、常温常圧で液体の燃料であってもよい。 The carbon dioxide utilization device 13 is a device that utilizes carbon dioxide. As the carbon dioxide utilization device 13, for example, a storage tank that stores carbon dioxide or a conversion device that converts carbon dioxide into fuel can be used. As the conversion device, a device that converts carbon dioxide into hydrocarbon fuel such as methane can be used. The hydrocarbon fuel may be a gaseous fuel at normal temperature and normal pressure, or may be a liquid fuel at normal temperature and normal pressure.
　制御装置１４は、ＣＰＵ、ＲＯＭおよびＲＡＭ等を含む周知のマイクロコンピュータとその周辺回路から構成されている。制御装置１４は、ＲＯＭ内に記憶された制御プログラムに基づいて各種演算、処理を行い、各種制御対象機器の作動を制御する。本実施形態の制御装置１４は、圧縮機１１の作動制御、二酸化炭素回収装置１００の作動制御、流路切替弁１２の流路切替制御等を行う。 The control device 14 is composed of a well-known microcomputer including a CPU, ROM, RAM, etc., 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 operations of various devices to be controlled. The control device 14 of this embodiment performs operation control of the compressor 11, operation control of the carbon dioxide recovery device 100, flow path switching control of the flow path switching valve 12, and the like.
　図２に示すように、二酸化炭素回収装置１００は、電気化学セル１０１が設けられている。電気化学セル１０１は、作用極１３０、対極１４０およびセパレータ１５０を有している。図２に示す例では、作用極１３０、対極１４０およびセパレータ１５０をそれぞれ板状に構成している。なお、図２では、作用極１３０、対極１４０およびセパレータ１５０を、それぞれ間隔を設けて図示しているが、実際はこれらの構成要素は接するように配置されている。 As shown in FIG. 2, the carbon dioxide recovery device 100 is provided with an electrochemical cell 101. Electrochemical cell 101 has a working electrode 130, a counter electrode 140, and a separator 150. In the example shown in FIG. 2, the working electrode 130, the counter electrode 140, and the separator 150 are each formed into a plate shape. Although the working electrode 130, the counter electrode 140, and the separator 150 are shown spaced apart from each other in FIG. 2, these components are actually arranged so as to be in contact with each other.
　電気化学セル１０１は、図示しない容器内に収容されるようにしてもよい。容器には、二酸化炭素含有ガスを容器内に流入させるガス流入口と、二酸化炭素除去ガスや二酸化炭素を容器内から流出させるガス流出口を設けることができる。 The electrochemical cell 101 may be housed in a container (not shown). The container can be provided with a gas inlet that allows the carbon dioxide-containing gas to flow into the container, and a gas outlet that allows the carbon dioxide removal gas and carbon dioxide to flow out of the container.
　二酸化炭素回収装置１００は、電気化学反応によって二酸化炭素の吸着および脱離を行い、二酸化炭素含有ガスから二酸化炭素を分離して回収する。二酸化炭素回収装置１００は、作用極１３０と対極１４０に所定の電圧を印加する制御電源１２０が設けられており、作用極１３０と対極１４０の電位差を変化させることができる。作用極１３０は負極であり、対極１４０は正極である。 The carbon dioxide recovery device 100 adsorbs and desorbs carbon dioxide through an electrochemical reaction, and separates and recovers carbon dioxide from a carbon dioxide-containing gas. The carbon dioxide recovery device 100 is provided with a control power source 120 that applies a predetermined voltage to the working electrode 130 and the counter electrode 140, and can change the potential difference between the working electrode 130 and the counter electrode 140. Working electrode 130 is a negative electrode, and counter electrode 140 is a positive electrode.
　電気化学セル１０１は、作用極１３０と対極１４０の電位差を変化させることで、作用極１３０で二酸化炭素を回収する回収モードと、作用極１３０から二酸化炭素を放出する放出モードを切り替えて作動することができる。回収モードは電気化学セル１０１を充電する充電モードであり、放出モードは電気化学セル１０１を放電する放電モードである。 The electrochemical cell 101 operates by changing the potential difference between the working electrode 130 and the counter electrode 140 to switch between a recovery mode in which carbon dioxide is recovered at the working electrode 130 and a release mode in which carbon dioxide is released from the working electrode 130. I can do it. The recovery mode is a charging mode in which the electrochemical cell 101 is charged, and the discharge mode is a discharging mode in which the electrochemical cell 101 is discharged.
　回収モードでは、作用極１３０と対極１４０の間に第１電圧Ｖ１が印加され、対極１４０から作用極１３０に電子が供給される。第１電圧Ｖ１では、作用極電位＜対極電位となっている。第１電圧Ｖ１は、例えば０．５～２．０Ｖの範囲内とすることができる。 In the recovery mode, the first voltage V1 is applied between the working electrode 130 and the counter electrode 140, and electrons are supplied from the counter electrode 140 to the working electrode 130. At the first voltage V1, working electrode potential<counter electrode potential. The first voltage V1 can be within a range of 0.5 to 2.0V, for example.
　放出モードでは、作用極１３０と対極１４０の間に第１電圧Ｖ１より低い第２電圧Ｖ２が印加され、作用極１３０から対極１４０に電子が供給される。第２電圧Ｖ２は、第１電圧Ｖ１より低い電圧であればよく、作用極電位と対極電位の大小関係は限定されない。つまり、放出モードでは、作用極電位＜対極電位でもよく、作用極電位＝対極電位でもよく、作用極電位＞対極電位でもよい。 In the emission mode, a second voltage V2 lower than the first voltage V1 is applied between the working electrode 130 and the counter electrode 140, and electrons are supplied from the working electrode 130 to the counter electrode 140. The second voltage V2 only needs to be a voltage lower than the first voltage V1, and the magnitude relationship between the working electrode potential and the counter electrode potential is not limited. That is, in the release 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.
　図３に示すように、電気化学セル１０１における作用極１３０は、作用極側集電材１３１及び作用極側電極膜１３２を有する。作用極側集電材１３１は、制御電源１２０に接続されるとともに、二酸化炭素含有ガスを通過させることができる多孔質状の導電性部材である。 As shown in FIG. 3, the working electrode 130 in the electrochemical cell 101 has a working electrode side current collector 131 and a working electrode side electrode film 132. The working electrode side current collector 131 is connected to the control power source 120 and is a porous conductive member through which carbon dioxide-containing gas can pass.
　作用極側集電材１３１として、例えば炭素質材料や金属材料を用いることができる。作用極側集電材１３１を構成する炭素質材料として、例えばカーボン紙、炭素布、不織炭素マット、多孔質ガス拡散層（ＧＤＬ）等を用いることができる。作用極側集電材１３１を構成する金属材料として、例えばＡｌ、Ｎｉ、ＳＵＳ等の金属をメッシュ状にした構造体を用いることができる。 As the working electrode side current collector 131, for example, a carbonaceous material or a metal material can be used. As the carbonaceous material constituting the working electrode side current collector 131, for example, carbon paper, carbon cloth, nonwoven carbon mat, porous gas diffusion layer (GDL), etc. can be used. As the metal material constituting the working electrode side current collector 131, a structure made of a metal such as Al, Ni, or SUS in a mesh shape can be used, for example.
　作用極側電極膜１３２は、二酸化炭素含有ガスから電気化学反応によって二酸化炭素の吸着と脱離を行う。作用極側電極膜１３２は、二酸化炭素吸着材、作用極側導電助剤および作用極側バインダを有する。 The working electrode side electrode film 132 adsorbs and desorbs carbon dioxide from a carbon dioxide-containing gas through an electrochemical reaction. The working electrode side electrode film 132 includes a carbon dioxide adsorbent, a working electrode side conductive agent, and a working electrode side binder.
　二酸化炭素吸着材は、電子を受け取ることで二酸化炭素を吸着し、電子を放出することで吸着していた二酸化炭素を脱離する電気活性種（すなわち、活物質）である。二酸化炭素吸着材としては、例えば、カーボン材、金属酸化物、ポリアントラキノン等を用いることができる。 A carbon dioxide adsorbent is an electroactive species (i.e., an active material) that adsorbs carbon dioxide by receiving electrons and desorbs the adsorbed carbon dioxide by releasing electrons. As the carbon dioxide adsorbent, for example, carbon materials, metal oxides, polyanthraquinone, etc. can be used.
　作用極側導電助剤は、二酸化炭素吸着材への導電路を形成する導電物質である。作用極側導電助剤として、例えばカーボンナノチューブ、カーボンブラック、グラフェン等の炭素材料を用いることができる。 The working electrode side conductive agent is a conductive material that forms a conductive path to the carbon dioxide adsorbent. As the conductive agent on the working electrode side, carbon materials such as carbon nanotubes, carbon black, and graphene can be used, for example.
　作用極側バインダは、二酸化炭素吸着材および作用極側導電助剤を作用極側集電材１３１に保持する。具体的には、二酸化炭素吸着材、作用極側導電助剤、および作用極側バインダの混合物が形成され、混合物が作用極側集電材１３１に接着される。二酸化炭素吸着材および作用極側導電助剤は、作用極側バインダの内部に保持された状態となっている。 The working electrode side binder holds the carbon dioxide adsorbent and the working electrode side conductive agent on the working electrode side current collector 131. Specifically, a mixture of the carbon dioxide adsorbent, the working electrode side conductive agent, and the working electrode side binder is formed, and the mixture is adhered to the working electrode side current collector 131. The carbon dioxide adsorbent and the working electrode side conductive agent are held inside the working electrode side binder.
　作用極側バインダとしては、例えば導電性樹脂を用いることができる。導電性樹脂としては、導電性フィラーとしてＡｇ等を含有するエポキシ樹脂やＰＴＦＥ（ポリテトラフルオロエチレン）、ＰＶＤＦ（ポリフッ化ビニリデン）等のフッ素樹脂等を用いることができる。 As the binder on the working electrode side, for example, a conductive resin can be used. As the conductive resin, an epoxy resin containing Ag or the like as a conductive filler, a fluororesin such as PTFE (polytetrafluoroethylene), PVDF (polyvinylidene fluoride), etc. can be used.
　対極１４０は、対極側集電材１４１及び対極側電極膜１４２を有する。対極１４０の構成については、後で詳細に説明する。 The counter electrode 140 has a counter electrode current collector 141 and a counter electrode film 142. The configuration of counter electrode 140 will be explained in detail later.
　セパレータ１５０は、作用極側電極膜１３２と対極側電極膜１４２との間に配置される。セパレータ１５０は、作用極側電極膜１３２と対極側電極膜１４２とを分離する。すなわち、セパレータ１５０は、作用極側電極膜１３２と対極側電極膜１４２との物理的な接触を防ぐ。また、セパレータ１５０は、作用極側電極膜１３２と対極側電極膜１４２との電気的短絡を抑制する。 The separator 150 is arranged between the working electrode film 132 and the counter electrode film 142. The separator 150 separates the working electrode film 132 and the counter electrode film 142. That is, the separator 150 prevents physical contact between the working electrode film 132 and the counter electrode film 142. Moreover, the separator 150 suppresses electrical short circuit between the working electrode side electrode film 132 and the counter electrode side electrode film 142.
　セパレータ１５０として、セルロース膜やポリマー、ポリマーとセラミックの複合材料等からなるセパレータを用いることができる。セパレータ１５０として、多孔質体のセパレータを用いても良い。 As the separator 150, a separator made of a cellulose membrane, a polymer, a composite material of polymer and ceramic, etc. can be used. As the separator 150, a porous separator may be used.
　作用極側電極膜１３２とセパレータ１５０との間、および対極側電極膜１４２とセパレータ１５０との間には、電解質材料１６０（後述する図４参照）が設けられている。作用極１３０および対極１４０は、電解質材料１６０により覆われている。 An electrolyte material 160 (see FIG. 4 described later) is provided between the working electrode film 132 and the separator 150 and between the counter electrode film 142 and the separator 150. Working electrode 130 and counter electrode 140 are covered with electrolyte material 160.
　電解質材料１６０は、二酸化炭素吸着材への導電を促進する。電解質材料１６０としては、イオン液体が用いられている。イオン液体は、常温常圧下で不揮発性を有する液体の塩である。電解質材料１６０として用いられるイオン液体は、イミダゾール、アンモニウムの少なくともいずれかを含むカチオンと、ＴＦＳＩ（トリフルオロメタンスルホニルイミド）を含むアニオンを有している。 The electrolyte material 160 promotes electrical conduction to the carbon dioxide adsorbent. As the electrolyte material 160, an ionic liquid is used. Ionic liquids are liquid salts that are nonvolatile at room temperature and pressure. The ionic liquid used as the electrolyte material 160 has a cation containing at least one of imidazole and ammonium, and an anion containing TFSI (trifluoromethanesulfonylimide).
　ここで、本実施形態における対極１４０について、図４を参照して説明する。 Here, the counter electrode 140 in this embodiment will be explained with reference to FIG. 4.
　対極１４０における対極側集電材１４１は、制御電源１２０に接続される導電性部材である。対極側集電材１４１は、作用極側集電材１３１と同じ材料を用いても良く、異なる材料を用いても良い。 The counter electrode side current collector material 141 in the counter electrode 140 is a conductive member connected to the control power source 120. The counter electrode side current collector material 141 may be made of the same material as the working electrode side current collector material 131, or may be made of a different material.
　対極１４０における対極側電極膜１４２は、作用極側電極膜１３２との間で電子の授受を行う。対極側電極膜１４２は、対極側活物質１４３、対極側導電助剤１４４および対極側バインダ（図示せず）を有する。 The counter electrode film 142 of the counter electrode 140 exchanges electrons with the working electrode film 132. The counter electrode film 142 includes a counter active material 143, a counter conductive agent 144, and a counter binder (not shown).
　対極側活物質１４３は、二酸化炭素吸着材との間で電子の授受を行う補助的な電気活性種である。対極側活物質１４３は、金属の価数変化やπ電子雲への電荷出入によって電子を出し入れすることができる物質である。 The counter electrode active material 143 is an auxiliary electroactive species that exchanges electrons with the carbon dioxide adsorbent. The counter electrode side active material 143 is a material that can transfer electrons in and out by changing the valence of the metal and transferring charges into and out of the π electron cloud.
　対極側活物質１４３として、例えば金属イオンの価数が変化することで、電子の授受を可能とする金属錯体を用いることができる。このような金属錯体として、フェロセン、ニッケロセン、コバルトセン等のシクロペンタジエニル金属錯体、あるいはポルフィリン金属錯体等を挙げることができる。これらの金属錯体は、ポリマーでもモノマーでもよい。対極側活物質１４３としては、フェロセン骨格を持った化合物を用いてもよい。 As the counter electrode side active material 143, for example, a metal complex that enables transfer of electrons by changing the valence of metal ions can be used. Examples of such metal complexes include cyclopentadienyl metal complexes such as ferrocene, nickelocene, and cobaltocene, and porphyrin metal complexes. These metal complexes may be polymers or monomers. As the counter electrode side active material 143, a compound having a ferrocene skeleton may be used.
　対極側活物質１４３は、フェロセンの酸化還元電位に対して－１．１Ｖ～＋０．５Ｖの電位範囲内で酸化還元反応する物質を含んでいてもよい。対極側活物質１４３は、フェロセン、フェロセン誘導体、メタロセン、フェノチアジンの少なくともいずれかを含んでいてもよい。本実施形態では、対極側活物質１４３としてフェロセンを用いている。 The counter electrode side active material 143 may include a substance that undergoes a redox reaction within a potential range of −1.1 V to +0.5 V with respect to the redox potential of ferrocene. The counter electrode active material 143 may contain at least one of ferrocene, ferrocene derivatives, metallocene, and phenothiazine. In this embodiment, ferrocene is used as the counter electrode side active material 143.
　対極側導電助剤１４４は、対極側活物質１４３への導電路を形成する導電物質である。対極側導電助剤１４４は、対極側活物質１４３と混合して用いられる。本実施形態では、対極側導電助剤１４４として、カーボンナノチューブを用いている。 The counter electrode conductive aid 144 is a conductive material that forms a conductive path to the counter electrode active material 143. The counter electrode side conductive agent 144 is used in combination with the counter electrode side active material 143. In this embodiment, carbon nanotubes are used as the counter electrode conductive aid 144.
　対極側バインダは、対極側活物質１４３及び対極側導電助剤１４４を対極側集電材１４１に保持させることができ、かつ、導電性を有する材料である。対極側バインダは、作用極側バインダと同じ材料を用いても良く、異なる材料を用いても良い。本実施形態では、対極側バインダとしてＰＶＤＦを用いている。 The counter electrode binder is a material that can hold the counter electrode active material 143 and the counter electrode conductive agent 144 on the counter electrode current collector 141 and has electrical conductivity. The binder on the opposite electrode side may be made of the same material as the binder on the working electrode side, or may be made of a different material. In this embodiment, PVDF is used as the opposite binder.
　対極側活物質１４３は、対極側導電助剤１４４としてのカーボンナノチューブの内部に含有されている。 The counter electrode side active material 143 is contained inside the carbon nanotube as the counter electrode side conductive agent 144.
　ここで、本発明者らは、対極側活物質１４３であるフェロセンのカーボンナノチューブへの内包状態を確認するためにＴＥＭ－ＥＤＸ分析を行った。なお、ＴＥＭとは、透過電子顕微鏡（Transmission Electron Microscope）である。ＥＤＸとは、エネルギ分散型Ｘ線分光法（Energy Dispersive X-ray Spectroscope）である。 Here, the present inventors conducted a TEM-EDX analysis to confirm the encapsulation state of ferrocene, which is the counter electrode side active material 143, in the carbon nanotubes. Note that TEM is a transmission electron microscope. EDX is Energy Dispersive X-ray Spectroscope.
　試料は、次のものを用意した。まず、カーボンナノチューブ２０ｍｇを、大気雰囲気下、３５０℃で加熱処理を行った。次に、カーボンナノチューブに、Ａｒ雰囲気下でフェロセン１００ｍｇを封入し、２７０℃で４８時間加熱し、混合物を作成した。その後、混合物をエタノールで複数回洗浄し、自然乾燥させて試料を得た。 The following samples were prepared. First, 20 mg of carbon nanotubes were heat-treated at 350° C. in an air atmosphere. Next, 100 mg of ferrocene was encapsulated in the carbon nanotubes under an Ar atmosphere and heated at 270° C. for 48 hours to create a mixture. Thereafter, the mixture was washed with ethanol multiple times and air-dried to obtain a sample.
　そして、試料について、ＴＥＭ－ＥＤＸ分析を行った。まず、ＦＩＢ（Focused Ion Beam System：集束イオンビーム加工観察装置）により試料を薄片化加工した後、ＴＥＭ像を観察した。図５に示すＴＥＭ像では、カーボンナノチューブの内側に何かの物質が含まれていることが確認できた。 Then, TEM-EDX analysis was performed on the sample. First, a sample was processed into a thin section using an FIB (Focused Ion Beam System), and then a TEM image was observed. In the TEM image shown in FIG. 5, it was confirmed that some substance was contained inside the carbon nanotube.
　続いて、試料について、ＳＴＥＭ（Scanning Transmission Electron Microscope：走査透過型電子顕微鏡）を使ってＡＤＦ（Annular Dark Field：環状暗視野）像を観察した。なお、本明細書ではＳＴＥＭを使って観察されるＡＤＦ像をＳＴＥＭ－ＡＤＦ像と呼ぶことがある。図６に示すＳＴＥＭ－ＡＤＦ像では、カーボンナノチューブの内側に存在する物質が明るく見えていることが確認できた。 Subsequently, an ADF (Annular Dark Field) image of the sample was observed using a STEM (Scanning Transmission Electron Microscope). Note that in this specification, an ADF image observed using STEM may be referred to as a STEM-ADF image. In the STEM-ADF image shown in FIG. 6, it was confirmed that the substance present inside the carbon nanotube appeared bright.
　また、試料についてＥＤＸ分析を行った。その分析結果を図７に示す。図５に示すＴＥＭ像や図６に示すＳＴＥＭ－ＡＤＦ像で見られたカーボンナノチューブの内側に含まれる物質が、ＥＤＸ分析結果によるフェロセン分布と一致することが確認できた。以上により、カーボンナノチューブの内部にフェロセンが含有されていることがわかった。 Additionally, EDX analysis was performed on the sample. The analysis results are shown in FIG. It was confirmed that the substances contained inside the carbon nanotubes seen in the TEM image shown in FIG. 5 and the STEM-ADF image shown in FIG. 6 matched the ferrocene distribution according to the EDX analysis results. From the above, it was found that ferrocene was contained inside the carbon nanotubes.
　ここで、本発明者らは、実施例としてカーボンナノチューブの内部にフェロセンが含有された電極膜についてＣＶ（サイクリックボルタンメトリ）測定を行い、フェロセン酸化還元波のピーク電流値の変化を調べた。具体的には、乾燥空気（Ｎ２／Ｏ２）雰囲気下にて、下記の条件でＣＶ測定を２０サイクル行った。その結果を図８に示す。 Here, as an example, the present inventors performed CV (cyclic voltammetry) measurements on an electrode film containing ferrocene inside carbon nanotubes, and investigated changes in the peak current value of ferrocene redox waves. . Specifically, CV measurement was performed for 20 cycles under the following conditions in a dry air (N 2 /O 2 ) atmosphere. The results are shown in FIG.
　・作用電極として、カーボンナノチューブの内部にフェロセンが含有された電極膜／グラッシーカーボン基板を、参照電極としてＡｇ／Ａｇ＋電極を、カウンター電極としてＰｔを備える、三電極系で行った。 - A three-electrode system was used, including an electrode film/glassy carbon substrate containing ferrocene inside carbon nanotubes as a working electrode, an Ag/Ag + electrode as a reference electrode, and Pt as a counter electrode.
　・測定は、イオン液体であるＢＭＩｍＴＦＳＩ（１－ブチル－３－メチルイミダゾリウムビス（トリフルオロメタンスルホニル）イミド）溶液中で行った。 ・Measurements were performed in an ionic liquid BMImTFSI (1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide) solution.
　・スキャンレートは０．０１Ｖ／ｓとした。 ・The scan rate was 0.01V/s.
　また、比較例として、上記ＣＶ測定の作用電極を、ＰＶＦｃをＭＷＮＴ（多層カーボンナノチューブ）に担持させた電極膜／グラッシーカーボン基板に置き換えた以外は同様にして、ＣＶ測定を行った。その結果を図９に示す。 Further, as a comparative example, CV measurement was performed in the same manner except that the working electrode for the above CV measurement was replaced with an electrode film/glassy carbon substrate in which PVFc was supported on MWNT (multi-walled carbon nanotubes). The results are shown in FIG.
　図８および図９から明らかなように、実施例に係る電極膜を用いた場合、２０サイクル後のフェロセン酸化波ピーク電流値は、１サイクル目のフェロセン酸化波ピーク電流値と比較して、１１％増加していた。一方、比較例に係る電極膜を用いた場合、２０サイクル後のフェロセン酸化波ピーク電流値は、１サイクル目のフェロセン酸化波ピーク電流値と比較して、２９％減少していた。 As is clear from FIGS. 8 and 9, when the electrode film according to the example is used, the peak current value of the ferrocene oxidation wave after 20 cycles is 11% compared to the peak current value of the ferrocene oxidation wave after the first cycle. % increase. On the other hand, when the electrode film according to the comparative example was used, the peak current value of the ferrocene oxidation wave after 20 cycles was reduced by 29% compared to the peak current value of the ferrocene oxidation wave after the first cycle.
　また、実施例に係る電極膜を用いた場合、ピーク電流は減少しなかった。一方、比較例に係る電極膜を用いた場合、ピーク電流は減少した。 Furthermore, when the electrode film according to the example was used, the peak current did not decrease. On the other hand, when the electrode film according to the comparative example was used, the peak current decreased.
　以上の結果より、実施例に係る電極膜を用いた場合、乾燥空気雰囲気下で劣化すること無くレドックス反応を示すことがわかった。一方、比較例に係る電極膜を用いた場合、乾燥空気雰囲気下では、レドックスピーク電流が減少し、酸化による劣化が生じることがわかった。 From the above results, it was found that when the electrode film according to the example was used, a redox reaction was exhibited without deterioration in a dry air atmosphere. On the other hand, when the electrode film according to the comparative example was used, it was found that in a dry air atmosphere, the redox peak current decreased and deterioration due to oxidation occurred.
　以上説明したように、本実施形態の電気化学セル１０１では、対極側活物質１４３が、対極側導電助剤１４４としてのカーボンナノチューブの内部に含有されている。これによれば、カーボンナノチューブにより対極側活物質１４３を保護することができる。このため、対極側活物質１４３が電解質材料１６０であるイオン液体へ溶出することを抑制できるので、対極１４０の電極性能を向上させることができる。また、大気に含まれる酸素により対極側活物質１４３が劣化することを抑制できるので、耐久性を向上させることができる。 As explained above, in the electrochemical cell 101 of this embodiment, the counter electrode side active material 143 is contained inside the carbon nanotube as the counter electrode side conductive agent 144. According to this, the counter electrode active material 143 can be protected by the carbon nanotubes. Therefore, elution of the counter electrode side active material 143 into the ionic liquid that is the electrolyte material 160 can be suppressed, so that the electrode performance of the counter electrode 140 can be improved. Further, since it is possible to suppress deterioration of the counter electrode side active material 143 due to oxygen contained in the atmosphere, durability can be improved.
　本開示は上述の実施形態に限定されることなく、本開示の趣旨を逸脱しない範囲内で、以下のように種々変形可能である。 The present disclosure is not limited to the embodiments described above, and can be modified in various ways as described below without departing from the spirit of the present disclosure.
　例えば、上述した実施形態では、対極側活物質１４３を対極側導電助剤１４４としてのカーボンナノチューブの内部に含有させた例について説明したが、この態様に限定されない。例えば、作用極側導電助剤としてカーボンナノチューブを用いるとともに、作用極１３０の活物質である二酸化炭素吸着材をカーボンナノチューブの内側に含有させてもよい。 For example, in the embodiment described above, an example was described in which the counter electrode side active material 143 was contained inside the carbon nanotube as the counter electrode side conductive agent 144, but the present invention is not limited to this embodiment. For example, carbon nanotubes may be used as the conductive agent on the working electrode side, and a carbon dioxide adsorbent, which is the active material of the working electrode 130, may be contained inside the carbon nanotubes.
　また、上述した実施形態では、電解質材料１６０として、イオン液体を用いた例について説明したが、この態様に限定されない。例えば、電解質材料１６０として、イオン液体をゲル化したイオン液体ゲルを用いてもよい。これによれば、電解質材料１６０が電気化学セル１０１から溶出することを抑制できる。 Furthermore, in the embodiment described above, an example was described in which an ionic liquid was used as the electrolyte material 160, but the present invention is not limited to this embodiment. For example, as the electrolyte material 160, an ionic liquid gel obtained by gelling an ionic liquid may be used. According to this, it is possible to suppress the electrolyte material 160 from being eluted from the electrochemical cell 101.
　また、上述した実施形態では、図５に示すＴＥＭ像に、カーボンナノチューブとして二層カーボンナノチューブが示されているが、カーボンナノチューブは二層カーボンナノチューブに限定されない。カーボンナノチューブとして、単層カーボンナノチューブを用いてもよいし、三層以上のカーボンナノチューブを用いてもよい。 Furthermore, in the embodiment described above, double-walled carbon nanotubes are shown as carbon nanotubes in the TEM image shown in FIG. 5, but carbon nanotubes are not limited to double-walled carbon nanotubes. As the carbon nanotube, a single-walled carbon nanotube or a three- or more-walled carbon nanotube may be used.
　本開示は、実施例に準拠して記述されたが、本開示は当該実施例や構造に限定されるものではないと理解される。本開示は、様々な変形例や均等範囲内の変形をも包含する。加えて、様々な組み合わせや形態、さらには、それらに一要素のみ、それ以上、あるいはそれ以下、を含む他の組み合わせや形態をも、本開示の範疇や思想範囲に入るものである。 Although the present disclosure has been described based on examples, it is understood that the present disclosure is not limited to the examples or structures. The present disclosure also includes various modifications and equivalent modifications. In addition, various combinations and configurations, as well as other combinations and configurations that include only one, more, or fewer elements, are within the scope and scope of the present disclosure.
　本明細書に開示された電気化学セルの特徴を以下の通り示す。
（項目１）
　二酸化炭素を含有する被処理ガスから電気化学反応によって二酸化炭素の吸着と脱離を行う作用極（１３０）と、
　前記作用極との間で電子の授受を行う対極（１４０）と、
　前記作用極および前記対極を覆う電解質材料（１６０）と、を備える電気化学セルであって、
　前記電解質材料は、イオン液体であり、
　前記作用極および前記対極の少なくとも一方は、活物質（１４３）およびカーボンナノチューブを有しており、
　前記活物質は、前記カーボンナノチューブの内部に含有されている電気化学セル。
（項目２）
　前記活物質は、フェロセンの酸化還元電位に対して－１．１Ｖ～＋０．５Ｖの電位範囲内で酸化還元反応する物質を含んでいる項目１に記載の電気化学セル。
（項目３）
　前記活物質は、フェロセン、フェロセン誘導体、メタロセン、フェノチアジンの少なくともいずれかを含んでいる項目１または２に記載の電気化学セル。
（項目４）
　前記イオン液体のカチオンが、イミダゾール、アンモニウムの少なくともいずれかを含んでいる項目１ないし３のいずれか１つに記載の電気化学セル。
（項目５）
　前記イオン液体のアニオンが、トリフルオロメタンスルホニルイミドを含んでいる項目１ないし４のいずれか１つに記載の電気化学セル。 The characteristics of the electrochemical cell disclosed herein are as follows.
(Item 1)
a working electrode (130) that adsorbs and desorbs carbon dioxide from a gas to be treated containing carbon dioxide through an electrochemical reaction;
a counter electrode (140) that exchanges electrons with the working electrode;
An electrochemical cell comprising an electrolyte material (160) covering the working electrode and the counter electrode,
The electrolyte material is an ionic liquid,
At least one of the working electrode and the counter electrode has an active material (143) and carbon nanotubes,
An electrochemical cell in which the active material is contained inside the carbon nanotube.
(Item 2)
The electrochemical cell according to item 1, wherein the active material contains a substance that undergoes a redox reaction within a potential range of -1.1 V to +0.5 V with respect to the redox potential of ferrocene.
(Item 3)
3. The electrochemical cell according to item 1 or 2, wherein the active material contains at least one of ferrocene, ferrocene derivatives, metallocene, and phenothiazine.
(Item 4)
4. The electrochemical cell according to any one of items 1 to 3, wherein the cation of the ionic liquid contains at least one of imidazole and ammonium.
(Item 5)
5. The electrochemical cell according to any one of items 1 to 4, wherein the anion of the ionic liquid contains trifluoromethanesulfonylimide.

Claims (5)

  1. 　二酸化炭素を含有する被処理ガスから電気化学反応によって二酸化炭素の吸着と脱離を行う作用極（１３０）と、
    　前記作用極との間で電子の授受を行う対極（１４０）と、
    　前記作用極および前記対極を覆う電解質材料（１６０）と、を備える電気化学セルであって、
    　前記電解質材料は、イオン液体であり、
    　前記作用極および前記対極の少なくとも一方は、活物質（１４３）およびカーボンナノチューブを有しており、
    　前記活物質は、前記カーボンナノチューブの内部に含有されている電気化学セル。     a working electrode (130) that adsorbs and desorbs carbon dioxide from a gas to be treated containing carbon dioxide through an electrochemical reaction;
    a counter electrode (140) that exchanges electrons with the working electrode;
    An electrochemical cell comprising an electrolyte material (160) covering the working electrode and the counter electrode,
    The electrolyte material is an ionic liquid,
    At least one of the working electrode and the counter electrode has an active material (143) and carbon nanotubes,
    An electrochemical cell in which the active material is contained inside the carbon nanotube.
  2. 　前記活物質は、フェロセンの酸化還元電位に対して－１．１Ｖ～＋０．５Ｖの電位範囲内で酸化還元反応する物質を含んでいる請求項１に記載の電気化学セル。 The electrochemical cell according to claim 1, wherein the active material contains a substance that undergoes a redox reaction within a potential range of -1.1 V to +0.5 V with respect to the redox potential of ferrocene.
  3. 　前記活物質は、フェロセン、フェロセン誘導体、メタロセン、フェノチアジンの少なくともいずれかを含んでいる請求項１または２に記載の電気化学セル。 The electrochemical cell according to claim 1 or 2, wherein the active material contains at least one of ferrocene, ferrocene derivatives, metallocene, and phenothiazine.
  4. 　前記イオン液体のカチオンが、イミダゾール、アンモニウムの少なくともいずれかを含んでいる請求項１または２に記載の電気化学セル。 The electrochemical cell according to claim 1 or 2, wherein the cation of the ionic liquid contains at least one of imidazole and ammonium.
  5. 　前記イオン液体のアニオンが、トリフルオロメタンスルホニルイミドを含んでいる請求項１または２に記載の電気化学セル。 The electrochemical cell according to claim 1 or 2, wherein the anion of the ionic liquid contains trifluoromethanesulfonylimide.
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GUAN, L. SHI, Z. LI, M. GU, Z.: "Ferrocene-filled single-walled carbon nanotubes", CARBON, ELSEVIER OXFORD, GB, vol. 43, no. 13, 1 November 2005 (2005-11-01), GB , pages 2780 - 2785, XP005004228, ISSN: 0008-6223, DOI: 10.1016/j.carbon.2005.05.025 *
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