Carbon dioxide fixation device and battery

Abstract

To provide a carbon dioxide fixation device capable of efficiently fixing atmospheric carbon dioxide while extracting energy.SOLUTION: The carbon dioxide fixation device of the present invention includes an aqueous solution containing a water-soluble polymer compound, and positive and negative electrode materials, and is capable of producing carbon dioxide-derived carbonate after discharge between the electrode materials. Preferably, the water-soluble polymer compound has two or more amino groups in each molecule, has a weight-average molecular weight from 500 to 50,000 inclusive, and is a non-volatile polyamine.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a carbon dioxide fixation device and a battery including a carbon dioxide fixation device. [Background technology]

[0002] Technologies that aim to mitigate or reduce the rise in atmospheric carbon dioxide concentration are collectively called negative emission systems. Negative emission systems currently being considered include BECCS (a technology that captures carbon dioxide emitted when biomass fuel is used and stores it underground) and DACCS (a technology that directly captures and stores carbon dioxide already present in the atmosphere), but both methods require the input of energy in the stage after capturing carbon dioxide from the atmosphere and before storing it.

[0003] For example, Patent Document 1 discloses a method for fixing atmospheric carbon dioxide as an alkaline earth metal carbonate, in which an aqueous solution in which metal ions and polyamines are dissolved is prepared in advance, and the aqueous solution is exposed to the atmosphere to absorb (dissolve) atmospheric carbon dioxide and precipitate it as a carbonate.

[0004] Furthermore, Patent Document 2 discloses a method in which a gas containing carbon dioxide gas is brought into contact with an aqueous alkanolamine solution in an absorption tower to absorb the carbon dioxide gas, and then the carbon dioxide gas absorbing liquid is heated to desorb and recover the carbon dioxide gas in a desorption tower. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2010-194378 A [Patent Document 2] JP 2006-240966 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, in previous studies, as described in Patent Documents 1 and 2, energy input is required during carbon dioxide fixation, and no consideration had been given to extracting energy in some form.

[0007] Therefore, an object of the present invention is to provide a carbon dioxide fixation device that can efficiently fix carbon dioxide in the atmosphere and extract energy. [Means for solving the problem]

[0008] As a result of intensive efforts to solve the above problems, the present inventors have found that a carbon dioxide fixation device that includes an aqueous solution containing a water-soluble polymer compound and positive and negative electrode materials and that can generate carbonates derived from carbon dioxide after passing an electric current through the electrode materials can extract energy during fixation of carbon dioxide. The present invention relates to a device that was completed based on these findings.

[0009] In the carbon dioxide fixation device, carbon dioxide in the atmosphere is precipitated as carbonate and fixed, and energy can be extracted.

[0010] The water-soluble polymer compound is preferably a non-volatile polyamine having two or more amino groups in the molecule, a weight-average molecular weight of 500 to 50,000. The water-soluble polymer compound having the above structure can efficiently absorb carbon dioxide and is also excellent in safety.

[0011] The concentration of the water-soluble polymer compound in the aqueous solution is preferably 1 ppm by mass or more and less than 1000 ppm by mass. The water-soluble polymer compound having the above structure is excellent in safety while absorbing carbon dioxide.

[0012] The pH of the aqueous solution immediately after preparation is preferably 8.6 to 14. When the pH is within the above range, carbon dioxide can be easily absorbed into the aqueous solution.

[0013] It is preferable that the aqueous solution does not substantially contain metal ions before the carbon dioxide fixation device is energized.

[0014] In the carbon dioxide fixation device, the liquid surface of the aqueous solution is preferably in contact with the atmosphere. Since the aqueous solution is highly safe, it can be directly exposed to the atmosphere.

[0015] It is preferable that the carbon dioxide fixation device is capable of dissolving atmospheric carbon dioxide in the aqueous solution up to a saturated concentration before current is applied thereto.

[0016] The negative electrode material preferably contains a metal element other than an alkali metal.

[0017] The negative electrode material preferably contains one or more metal elements selected from the group consisting of zinc, iron, and magnesium.

[0018] The positive electrode material is preferably composed of a material that has a relatively high standard Gibbs energy of formation relative to the negative electrode material.

[0019] The carbon dioxide fixation device is preferably capable of extracting electric energy.

[0020] The aqueous solution preferably has a pH of 5.8 or higher and lower than 8.6 after the carbon dioxide fixation device is energized.

[0021] The present invention also provides a battery including the carbon dioxide fixation device. Effect of the Invention

[0022] The carbon dioxide fixation device of the present invention is capable of efficiently fixing carbon dioxide in the atmosphere and extracting energy. [Brief description of the drawings]

[0023] [Figure 1]1 is a photograph showing an embodiment of a carbon dioxide fixation device of the present invention. [Diagram 2] 4 is a graph showing the transition of voltage in the carbon dioxide fixation device of Example 1. [Diagram 3] 4 is a graph showing the transition of electric current in the carbon dioxide fixation device of Example 1. [Figure 4] 1 is a graph showing the transition of voltage in the carbon dioxide fixation device of Example 2. [Diagram 5] 1 is a graph showing the transition of electric current in the carbon dioxide fixation device of Example 2. [Figure 6] 4 is a graph showing the transition of voltage in the carbon dioxide fixation device of Comparative Example 1. [Figure 7] 4 is a graph showing the transition of electric current in the carbon dioxide fixation device of Comparative Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] [Carbon dioxide fixation device] The carbon dioxide fixation device of the present invention includes at least an aqueous solution containing a water-soluble polymer compound and positive and negative electrode materials. The aqueous solution contains the water-soluble polymer compound, so that it can efficiently absorb carbon dioxide in the atmosphere and generate carbonate ions. In addition, the carbon dioxide fixation device can fix carbon dioxide in the atmosphere while extracting energy by passing electricity through the electrode material. Specifically, the carbon dioxide fixation device can form a circuit through the aqueous solution by connecting the positive and negative electrode materials to an external circuit, and can extract energy through an LED or the like provided in the external circuit. Furthermore, when electricity is passed through the external circuit, the carbon dioxide in the atmosphere absorbed in the aqueous solution reacts to generate carbonate derived from carbon dioxide in the atmosphere and can be fixed. In addition, in the present invention, the "atmosphere" includes gases such as exhaust gas if it includes air and carbon dioxide present in an open system.

[0025] Therefore, the carbon dioxide fixation device can fix carbon dioxide in the atmosphere and extract energy. That is, the carbon dioxide fixation device can be used as a negative emission system that fixes and captures carbon dioxide in the atmosphere, and can simultaneously extract energy.

[0026] In addition, unless otherwise specified in the present invention, this refers to the state before current is applied.

[0027] In addition, the carbon dioxide fixation device preferably includes a separator to separate the positive electrode material from the negative electrode material. By including the separator, it becomes easy to use the device as a battery. As the separator, any known separator used in batteries can be used without any particular limitation, but it is preferable to use a separator made of resin.

[0028] (Aqueous solution containing water-soluble polymer compound) The carbon dioxide fixation device includes an aqueous solution (hereinafter sometimes referred to as "aqueous solution" or "electrolyte") containing a water-soluble polymer compound. The aqueous solution contains the water-soluble polymer compound, and thus can efficiently absorb carbon dioxide in the atmosphere as carbonate ions. As the water-soluble polymer compound in the aqueous solution, only one type may be used, or two or more types may be used.

[0029] The water-soluble polymer compound is preferably a nitrogen atom-containing water-soluble polymer compound, and more preferably a polyamine and / or a salt thereof.

[0030] The weight average molecular weight of the water-soluble polymer compound is preferably 500 or more and 150,000 or less, more preferably 1000 or more and 100,000 or less, and even more preferably 1500 or more and 50,000 or less. The upper limit is particularly preferably 40,000 or less, and may be 30,000 or less, 20,000 or less, or 15,000 or less. By having a weight average molecular weight of 500 or more, it is possible to make it difficult to volatilize, and by having a weight average molecular weight of 150,000 or less, it is possible to suppress the attenuation of the carbon dioxide absorption ability in the atmosphere due to the water-soluble polymer compound being released as a precipitate from the aqueous solution due to the increase in hydrophobicity of the entire molecule caused by the formation of a carboxylate or ester of the water-soluble polymer compound between the water-soluble polymer compound and dissolved carbon dioxide. The weight average molecular weight can be measured by GPC, for example, under the following conditions. Equipment: Gel permeation chromatography (GPC) (equipment name: No. GPC-31) Detector: Differential refractive index detector RI (Showa Denko RI-501, sensitivity 32) Column: TSKgel G6000PWXL-CP x 1, G3000PWXL-CP x 1 (7.8 mm x 30 cm, Tosoh Corporation) Solvent: 0.1M acetate buffer (pH 4) Flow rate: 0.7mL / min Column temperature: 40oC Injection volume: 0.2mL Standard samples: Monodisperse polyethylene oxide (PEO) and polyethylene glycol (PEG) manufactured by Tosoh Corporation and Agilent. Data processing: TRC GPC data processing system

[0031] The water-soluble polymer compound preferably has two or more amino groups in the molecule, more preferably three or more, and even more preferably four or more. By having two or more amino groups in the molecule, the water-soluble polymer compound can easily form a carbamate compound with carbon dioxide in the air, and can efficiently absorb carbon dioxide in the air into the aqueous solution. In addition, spontaneous hydrolysis of the generated carbamate can be induced, and the generation of carbonate ions in the aqueous solution can be promoted.

[0032] In addition, the water-soluble polymer compound is preferably non-volatile. Since the water-soluble polymer compound is non-volatile, the aqueous solution can be excellent in safety even when it is in contact with the air. In the present invention, non-volatile means that the compound is non-volatile at room temperature (25°C) and normal pressure (1 atm).

[0033] The content of the water-soluble polymer compound in the aqueous solution is preferably 1 mass ppm or more and less than 1000 mass ppm, more preferably 3 mass ppm or more and 900 mass ppm or less, even more preferably 5 mass ppm or more and 800 mass ppm or less, particularly preferably 10 mass ppm or more and 700 mass ppm or less, and most preferably 15 mass ppm or more and 600 mass ppm, based on 100 mass% of the aqueous solution. By making the content 1 mass ppm or more, it is possible to easily absorb carbon dioxide. By making the content less than 1000 mass ppm, it is possible to have sufficient safety and facilitate wastewater treatment.

[0034] <Polyamine> The amino group of the polyamine may be any of a primary amine, a secondary amine, and a tertiary amine.

[0035] The polyamine may, for example, be a polyamine represented by the following formula (1). [ka] (In the formula, m represents an integer of 0 to 1000, and R 1 , R 2 each independently represents a linear or branched alkylene group having 2 to 8 carbon atoms. When m is 2 or more, a plurality of R 1 may be the same or different.)

[0036] Above R 1 , R 2 each preferably represents a linear or branched alkylene group having 2 to 6 carbon atoms, and more preferably a linear or branched alkylene group having 3 to 5 carbon atoms.

[0037] The above m is more preferably an integer of 1 to 500, further preferably an integer of 2 to 100, particularly preferably an integer of 3 to 50, and particularly preferably an integer of 5 to 10.

[0038] Among the polyamines represented by the above formula (1), examples of polyamines in which m is 0 include ethylenediamine, 1,2-diaminopropane, 1,3-diaminopropane, 1,4-diaminobutane (putrescine), 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, and 1,8-diaminooctane.

[0039] Among the polyamines represented by the above formula (1), examples of polyamines in which m is 1 or more include spermidine, spermine; polyethyleneamines such as diethylenetriamine, triethylenetetraamine, tetraethylenepentamine, pentaethylenehexamine, hexaethyleneheptamine, heptaethyleneoctamine, octaethylenenonamine, and nonaethylenedecamine; and polypropylenepolyamines such as dipropylenetriamine, tripropylenetetramine, tetrapropylenepentamine, pentapropylenehexamine, hexapropyleneheptamine, heptapropyleneoctamine, octapropylenenonamine, and nonapropyldecamine.

[0040] As the polyamine represented by the above formula (1), commercially available products can be used. Examples of commercially available products are shown in Table 1. [Table 1]

[0041] Furthermore, the polyamine may be, for example, a polymer having a structural unit derived from a cyclic amine represented by the following formula (2) (hereinafter, may be referred to as "polymer A"). This polymer A is obtained by ring-opening polymerization of the cyclic amine represented by the following formula (2). [ka] (In the formula, R 3 , R 4 , R 5 , R 6 each independently represents a hydrogen atom or a methyl group.

[0042] Examples of the cyclic amine represented by the above formula (2) include aziridine (ethyleneimine), 2-methylaziridine, 2,2-dimethylaziridine, 2,3-dimethylaziridine, etc. Examples of the homopolymer of the above polymer A include polyethyleneimine, poly(2-methylaziridine), poly(2,2-dimethylaziridine), poly(2,3-dimethylaziridine), etc.

[0043] Commercially available products can be used as the polymer A. Examples of commercially available products are shown in Table 2. [Table 2]

[0044] Furthermore, the polyamine may be, for example, a polymer having a structural unit derived from an unsaturated amine represented by the following formula (3) (hereinafter, sometimes referred to as "polymer B"). This polymer B is obtained by polymerization of an unsaturated group of an unsaturated amine represented by the following formula (3). [ka] (In the formula, n represents an integer of 0 to 2, p represents an integer of 1 to 3, and R 7 ,R 8 , R 9 each independently represents a hydrogen atom or a methyl group.

[0045] Examples of the unsaturated amine represented by the above formula (3) include vinylamine, divinylamine, trivinylamine, allylamine, diallylamine, triallylamine, methallylamine, dimethallylamine, trimethallylamine, crotylamine, diclotylamine, tricrotylamine, 3-methyl-2-butenylamine, and 3-butenylamine.

[0046] Of the above polymer B, examples of the homopolymer include polyvinylamine, polydivinylamine, polyallylamine, polydiallylamine, polytriallylamine, polymethacrylamine, polycrotylamine, and poly(3-butenylamine).

[0047] Furthermore, the polymer A and the polymer B may be copolymers in addition to the homopolymers. The arrangement of the copolymer may be any of statistical, random, alternating, and periodic copolymers, and the polymer chains may be linked in any of block copolymers and graft copolymers.

[0048] When the polymer A is a copolymer, it may be a copolymer of two or more cyclic amines represented by the above formula (2). When the polymer B is a copolymer, it may be a copolymer of two or more unsaturated amines represented by the above formula (3), or a copolymer of one or more unsaturated amines represented by the above formula (3) and another monomer copolymerizable with the unsaturated amine represented by the formula (3).

[0049] Examples of other monomers copolymerizable with the unsaturated amine represented by the above formula (3) include sulfur dioxide, (meth)acrylamide, (meth)acrylic acid esters, (meth)acrylic acid, and maleic acid.

[0050] When the polymer B is a copolymer, the proportion of the structural units derived from the unsaturated amine represented by the formula (3) (including those in which a substituent has been introduced into the amino group and those in which a salt has been formed) relative to the entire copolymer is, for example, 20 mass % or more, preferably 40 mass % or more, more preferably 60 mass % or more, even more preferably 80 mass % or more, and particularly preferably 90 mass % or more.

[0051] Furthermore, when the polymer B is a copolymer, the proportion of structural units derived from the unsaturated amine represented by the above formula (3) in which no substituent has been introduced into the amino group (including those in which the amino group forms a salt) relative to the entire copolymer is, for example, 20 mass % or more, preferably 40 mass % or more, more preferably 60 mass % or more, even more preferably 80 mass % or more, and particularly preferably 90 mass % or more.

[0052] Representative examples of the polymer having a structural unit derived from the unsaturated amine represented by the above formula (3), i.e., polymer B, include homopolymers such as polyvinylamine, polydivinylamine, polyallylamine, polydiallylamine, polytriallylamine, polymethallylamine, polycrotylamine, poly(3-butenylamine), diallylamine polymers, poly(N,N-dimethylallylamine), and poly(N-acetylallylamine), allylamine-diallylamine copolymers, allylamine-dimethylallylamine copolymers, partially methoxycarbonylated allylamine copolymers, partially ureated allylamine copolymers, and the like. Examples of copolymers include copolymers such as an allylamine polymer, a diallylamine-sulfur dioxide copolymer, a methyldiallylamine-sulfur dioxide copolymer, a diallylamine-acrylamide copolymer, an allylamine-maleic acid copolymer, a diallylamine-maleic acid copolymer, a methyldiallylamine-maleic acid copolymer, a partially formylated allylamine polymer, a partially acetylated allylamine polymer, a partially propionylated allylamine polymer, an allylamine-N,N-dimethylallylamine copolymer, a partially formylated diallylamine polymer, a partially acetylated diallylamine polymer, and a partially propionylated diallylamine polymer.

[0053] In addition, in each of the polyamine represented by the above formula (1), the above polymer A, and the above polymer B, the amino group in the molecule may or may not have a substituent.

[0054] Examples of the substituent include alkyl groups having 1 to 4 carbon atoms, such as methyl and ethyl groups; acyl groups having 1 to 4 carbon atoms, such as formyl, acetyl and propionyl groups; alkoxycarbonyl groups having 1 to 4 carbon atoms in the alkoxy moiety, such as methoxycarbonyl and ethoxycarbonyl groups; and carbamoyl groups. These substituents may be introduced at the monomer stage or after polymerization. The above-mentioned substituents may be used alone or in combination of two or more kinds.

[0055] The polyamine is preferably at least one compound selected from the group consisting of the polyamine represented by the formula (1), the polymer A, or the polymer B. Among these, from the viewpoints of greater economical efficiency and ease of availability, the polyamine is more preferably either the polymer A and / or the polymer B, and most preferably the polymer B.

[0056] Commercially available products can be used as the polymer B. Examples of commercially available products are shown in Table 3. [Table 3]

[0057] The above-mentioned polyamine salt may be either a salt with an acid or a quaternary ammonium salt. Examples of the above-mentioned acid include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, and boric acid; monovalent aliphatic carboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, pentanoic acid, hexanoic acid, octanoic acid, decanoic acid, and dodecanoic acid; divalent aliphatic carboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, and adipic acid; hydroxycarboxylic acids such as glycolic acid, lactic acid, malic acid, and tartaric acid; and sulfonic acids such as methanesulfonic acid and p-toluenesulfonic acid.

[0058] The aqueous solution may contain various additives as other components as long as they do not impair the effects of the present invention. Examples of the other components include one or more of organic solvents, thickening stabilizers, viscosifying agents, preservatives, surfactants, and quality stabilizers.

[0059] The aqueous solution is preferably substantially free of lithium ions, and more preferably substantially free of metal ions. The aqueous solution is substantially free of metal ions, which facilitates wastewater treatment after use. In the present invention, the term "substantially free of metal ions" means that raw materials containing metal elements other than those used to soak the electrode material are not actively added, and the metal ion concentration in the aqueous solution is, for example, 1.0 mol / L or less.

[0060] From the viewpoint of maximizing the function of the polyamine and / or its salt, the content of other components in the aqueous solution other than water, polyamine, and polyamine salt is preferably less than 5% by mass, more preferably less than 3% by mass, and even more preferably less than 1% by mass, relative to 100% by mass of the aqueous solution, and is particularly preferably not blended. When the content of the other components is less than 5% by mass, there is no interference from other components in the aqueous solution, and therefore the effect of the polyamine and / or its salt is more effectively exerted.

[0061] The aqueous solution contains a polyamine and / or a salt thereof as a functional component, and the total content of water, polyamine, and polyamine salt is, for example, 95% by mass or more, preferably 98% by mass or more, 99% by mass or more, more preferably 99.5% by mass or more, even more preferably 99.95% by mass or more, particularly preferably 99.98% by mass or more, and most preferably 100% by mass, relative to 100% by mass of the aqueous solution.

[0062] The pH of the aqueous solution immediately after preparation is preferably 8.6 to 14, more preferably 9 to 13, and even more preferably 9.5 to 12. When the pH is 8.6 or higher, carbon dioxide can be sufficiently absorbed, and when the pH is 14 or lower, the aqueous solution is sufficiently safe and easy to treat in wastewater.

[0063] The aqueous solution is preferably capable of dissolving atmospheric carbon dioxide up to a saturated concentration. By having the above-mentioned configuration, it is possible to efficiently fix atmospheric carbon dioxide.

[0064] In order to dissolve carbon dioxide in the atmosphere to a saturated concentration, the aqueous solution is preferably left to stand for 100 hours or more under conditions of room temperature and normal pressure.

[0065] The pH of the aqueous solution after standing in the air (preferably after standing in the air for 100 hours or more) is preferably 7.5 to 10, more preferably 7.7 to 9.5, and even more preferably 8.1 to 9.0. When the pH of the aqueous solution containing the polymer compound after standing is within the above range, it can be confirmed that carbon dioxide has been sufficiently absorbed.

[0066] (electrode material) The carbon dioxide fixation device includes positive and negative electrode materials. The positive and negative electrode materials may each be made of only one type of raw material, or may contain two or more types of raw materials.

[0067] As the negative electrode material, a known or commonly used negative electrode material can be used. Among them, the negative electrode material is preferably one in which the standard Gibbs energy of formation of the carbonate is lower than the standard Gibbs energy of formation of the hydroxide. If the standard Gibbs energy of formation of the carbonate of the negative electrode material is lower than the standard Gibbs energy of formation of the hydroxide, it becomes easier to generate carbonate after passing electricity through the carbon dioxide fixation device (after discharging).

[0068] In addition, the solubility product in water has a specific value for each salt, and when the product of the molar concentrations of the ionic species constituting the salt exceeds the solubility product, the salt precipitates as crystals. Therefore, when metal ions and carbon dioxide from the atmosphere are continuously supplied to the aqueous solution, carbonates can be continuously precipitated therefrom. When the carbon dioxide fixation device is energized, metal ions are continuously eluted into the aqueous solution due to an oxidation reaction at the negative electrode, and react with carbon dioxide to form carbonates, making it easy to produce carbonates.

[0069] Specifically, the negative electrode material preferably contains a metal element other than an alkali metal, more preferably contains one or more metal elements selected from the group consisting of zinc, iron, copper, and magnesium, even more preferably contains one or more metal elements selected from the group consisting of zinc, iron, and magnesium, and particularly preferably contains zinc. By not containing an alkali metal, the negative electrode material can easily ensure safety. In addition, by containing one or more metal elements selected from the group consisting of zinc, iron, and magnesium, it can easily be fixed as a carbonate after current is applied.

[0070] The content of metals other than alkali metals in the negative electrode material is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 100% by mass, based on 100% by mass of the negative electrode material. By satisfying the above range, carbon dioxide in the aqueous solution (electrolyte) can be easily fixed as carbonate when a current is applied.

[0071] The standard Gibbs energy of formation of hydroxide generated from the negative electrode material is preferably -200 kJ / mol or less, more preferably -300 kJ / mol or less, and even more preferably -400 kJ / mol or less. Although there is no particular lower limit, it is preferably -1000 kJ / mol or more.

[0072] The standard Gibbs energy of formation of the carbonate generated from the negative electrode material is preferably -500 kJ / mol or less, more preferably -600 kJ / mol or less, and even more preferably -700 kJ / mol or less. The standard Gibbs energy of formation of the carbonate is -500 kJ / mol or less, which makes it easy to generate the carbonate. The lower limit is not particularly limited, but is preferably -3000 kJ / mol or more.

[0073] The standard Gibbs energy of formation of the carbonate is preferably at least 100 kJ / mol smaller than the standard Gibbs energy of formation of the hydroxide, more preferably at least 150 kJ / mol smaller, and even more preferably at least 200 kJ / mol smaller. By satisfying the above range, the carbonate can be stably produced when the carbon dioxide fixation device is energized.

[0074] The standard Gibbs energy of formation of the substance generated from the negative electrode material is preferably −300 kJ / mol or less, more preferably −400 kJ / mol or less, and even more preferably −500 kJ / mol or less. By satisfying the above range, it becomes easy to use it as a negative electrode.

[0075] The shape of the negative electrode material is not particularly limited, and may be in the form of a plate, a rod, particles, or the like, depending on the shape of the carbon dioxide fixation device.

[0076] As the positive electrode material, a known or commonly used positive electrode material can be used, and in particular, the positive electrode material is preferably composed of a material that has a relatively high standard Gibbs energy of formation relative to the negative electrode material. Note that, as long as the positive electrode material as a whole has a higher standard Gibbs energy of formation than the negative electrode material, it may contain a material that has a lower standard Gibbs energy of formation than the negative electrode material, but it is preferable that it does not contain such a material. By having the above configuration, it becomes easy to extract energy when the carbon dioxide fixation device is energized.

[0077] The positive electrode material may be, for example, manganese dioxide, carbon, etc. When carbon is used as the positive electrode material, an air electrode is formed in which oxygen in the air is used as the positive electrode.

[0078] Specifically, the standard Gibbs energy of formation of the substance generated from the positive electrode material is preferably -500 kJ / mol or more, more preferably -400 kJ / mol or more, and even more preferably -300 kJ / mol or more. By satisfying the above range, it becomes easy to use it as a positive electrode.

[0079] In addition, the difference in the change in standard Gibbs energy of formation between the negative electrode material and the positive electrode material is preferably 200 kJ / mol or more, more preferably 250 kJ / mol or more, and even more preferably 300 kJ / mol or more. By having the difference in the change in standard Gibbs energy of formation of 200 kJ / mol or more, it becomes easy to obtain a sufficient electromotive force as a battery. In addition, although there is no particular limit to the upper limit, it is preferable that it is 2000 kJ / mol or less.

[0080] The shape of the positive electrode material is not particularly limited, and shapes such as plate, rod, and particle shapes can be used.

[0081] The combination of the negative electrode material and the positive electrode material is not particularly limited, but it is preferable to use zinc or magnesium as the negative electrode material and manganese dioxide as the positive electrode material, or to use zinc or magnesium as the negative electrode material and carbon as the positive electrode material.

[0082] In the carbon dioxide fixation device, it is preferable that the liquid surface of the aqueous solution is in contact with the atmosphere. The aqueous solution is highly safe and can be used even in a state where it is in contact with the atmosphere. If the water-soluble polymer compound is not volatile, it will not volatilize even when it comes into contact with the atmosphere, and can efficiently absorb carbon dioxide in the atmosphere.

[0083] The carbon dioxide fixation device is preferably left to stand before energization in order to stabilize the initial voltage. Thereafter, an external circuit is connected to the carbon dioxide fixation device, and electricity is applied to the device, whereby the carbon dioxide in the aqueous solution reacts, is fixed as a carbonate, and is precipitated while extracting energy.

[0084] The carbonate depends on the type of negative electrode material used, but is preferably a basic carbonate. Specific examples of the carbonate include zinc carbonate, iron carbonate, magnesium carbonate, magnesium carbonate trihydrate, magnesium carbonate pentahydrate, copper carbonate, and basic carbonates thereof. Zinc carbonate and basic zinc carbonate are particularly preferred.

[0085] The pH of the aqueous solution after energization is preferably 5.8 or more and less than 8.6, more preferably 6.0 or more and 8.4 or less, and even more preferably 6.2 or more and 8.2 or less. When the pH of the aqueous solution after energization satisfies the above range, it can be easily discharged into rivers or public sewerage systems, etc., and can be made highly safe.

[0086] Since the carbon dioxide fixation device has the above-mentioned configuration, it can extract energy while fixing carbon dioxide in the atmosphere. The energy is preferably electrical energy. The charge is preferably 108 C or more, more preferably 150 C or more, and even more preferably 200 C or more. Since the electrical energy can be extracted at 108 C or more, it is suitable for use as a battery.

[0087] Furthermore, after energization, the carbon dioxide fixation device can absorb carbon dioxide from the atmosphere again into the aqueous solution, thereby repeatedly fixing and precipitating carbon dioxide and extracting energy.

[0088] Furthermore, since the carbonate is precipitated in the aqueous solution, it can be easily recovered from the carbon dioxide fixation apparatus. The aqueous solution after recovery of the carbonate contains only low concentrations of polyamine and components derived from the electrodes, and therefore is safe and easy to treat as wastewater.

[0089] [battery] One embodiment of the present invention is a battery including the carbon dioxide fixation device. The battery uses the aqueous solution as an electrolyte and can be used as a battery capable of recovering atmospheric carbon dioxide while fixing it as carbonate. In other words, while conventional negative emission systems require the input of energy to fix carbon dioxide, the battery functions as a negative emission system that fixes atmospheric carbon dioxide, does not require the input of energy, and can instead extract electrical energy as a battery.

[0090] Moreover, the battery can function as a negative emission system that repeatedly fixes atmospheric carbon dioxide as carbonate by reabsorbing atmospheric carbon dioxide into the electrolyte after energization. In addition, the electrolyte of the battery is highly safe, so the fixed carbonate can be easily separated and recovered. Therefore, the battery can be continuously used as a battery equipped with a negative emission system that can fix atmospheric carbon dioxide, extract electric energy as a battery, and further, easily separate and recover the fixed carbonate. EXAMPLES

[0091] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0092] Example 1 75 ml of a water-soluble polymer aqueous solution containing polyallylamine with a concentration of 100 ppm by mass and a molecular weight of 1600 was prepared in a glass beaker, and its pH was measured to be 10.18. The above aqueous solution was left to stand in contact with the air at 18 to 22°C for 150 hours, and the pH was measured again to be 8.22, suggesting that carbon dioxide in the air was absorbed into the above water-soluble polymer aqueous solution.

[0093] Reference example 1 A 10-fold concentrated aqueous solution of polyallylamine water-soluble polymer (concentration: 1000 mass ppm) was prepared instead of the aqueous solution of water-soluble polymer of Example 1, and its pH was measured to be 11.19. When the same test was carried out on the concentrated solution of Reference Example 1, it was confirmed that the pH was reduced to 8.60.

[0094] In both Example 1 and Reference Example 1, the pH decreased after standing, and it was confirmed that carbon dioxide in the atmosphere was absorbed. In addition, when Example 1 was compared with Reference Example 1, the error from the pH estimated from the carbon dioxide concentration in the atmosphere was smaller in Example 1, so the aqueous solution of Example 1 was subjected to the following test.

[0095] (Construction of a carbon dioxide fixation device) The carbon rod, terminal, and electrode plate holder of the carbon rod set for electrolysis (product name "B10-2064", manufactured by Narica Co., Ltd.) were used as the positive electrode material, and were set in a separate cup (product name "Daniel Battery DT-B", manufactured by Narica Co., Ltd.). Next, a mixture of granular manganese (IV) oxide (manufactured by Hayashi Pure Chemical Industries Co., Ltd.) crushed to 3 mm and powdered graphite (product name "FK-300", manufactured by Monami Co., Ltd.) was spread in the separate cup to prepare a positive electrode.

[0096] The positive electrode and a zinc plate were set as the negative electrode on the negative electrode side separated from the positive electrode side by the separator cup in a 100 ml beaker (product name "PB-100" manufactured by Niigata Seiki Co., Ltd.). Then, about 50 ml of the aqueous solution of Example 1 was added to prepare the carbon dioxide fixation device of Example 1.

[0097] As shown in Figure 1, two sets of the carbon dioxide fixation device of Example 1 were prepared and connected in series so that the liquid level of the aqueous solution was in contact with air. When the voltage was measured, 2.5 V was output at 1.25 V x 2. After 21 hours, the voltage rose to 2.8 V, and it was still 2.8 V after 24 hours. At this point, it was determined that the initial voltage before discharge had been reached, and the device was subjected to a discharge test described below. In addition, about 10 ml of the aqueous solution was added to compensate for the electrolyte that had permeated the positive electrode side, and the liquid level was adjusted to the 100 ml position on the beaker's scale.

[0098] Regarding the evaluation method of the carbon dioxide fixation device, a red light-emitting diode (hereinafter referred to as LED) that is visible when it is energized was used as the load. The circuit was a series circuit of the LED and an LED current limiting resistor (hereinafter referred to as R) of 326.9 Ω (actual measurement value). The data obtained was the terminal voltage of the carbon dioxide fixation device and the voltage across R, and the current value was calculated by dividing the voltage across R by the resistance value of 326.9 Ω (actual measured value).

[0099] (Discharge test) The pH, voltage, and current of the above aqueous solution were measured during multiple discharge tests under the following conditions, and the average current and charge were calculated. The results are shown in Figures 2 and 3 and Tables 1 and 2. 1. Maintain the powered state until the LED no longer emits light after the first discharge. 2. After discharge, leave the battery to rest. When the voltage exceeds 2.77V, which is 99% of the pre-discharge voltage of 2.8V, recovery is considered complete and a second discharge is initiated. 3. Maintain the powered state for the second discharge until the LED no longer emits light. 4. After the second discharge, leave the battery to rest and check the voltage recovery characteristics. When the voltage exceeds 2.74V, which is 99% of 2.77V, recovery is considered complete. Replace the zinc plate with a new one and repeat the discharge and recovery process.

[0100] [Table 4]

[0101] [Table 5]

[0102] Regarding the carbon dioxide fixation device of Example 1, the standard of the carbon dioxide fixation device was 30 mAh (= 108 C), and because discharge continued beyond this, it was suggested that energy could be extracted and that the device could be used as a battery. It was also suggested that the device could be regenerated as a battery and used repeatedly by setting a recovery period in which carbon dioxide is reabsorbed into the aqueous solution.

[0103] In addition, when the negative electrode zinc plate after the discharge test was subjected to powder X-ray diffraction, zinc oxide was not confirmed, but basic zinc carbonate Zn5(OH)6(CO3)2 was confirmed. In other words, it was confirmed that carbon dioxide in the air was absorbed into the aqueous solution and fixed as a carbonate while acting as a component of the battery electrolyte.

[0104] Example 2 The carbon dioxide fixation device of Example 2 was prepared in the same manner as in Example 1, except that activated carbon (product name "Gas-phase granular activated carbon 4GG", manufactured by AS ONE Corporation) was used instead of granular manganese (IV) oxide (manufactured by Hayashi Pure Chemical Industries, Ltd.) crushed to 3 mm and powdered graphite (product name "FK-300", manufactured by Monami Co., Ltd.) as the positive electrode material.

[0105] Two sets of the carbon dioxide fixation device of Example 2 were prepared, and when the voltage was measured at the stage of connecting them in series so that the liquid surface of the aqueous solution was in contact with air, 1.652 V was output. Since the electrolyte gradually penetrates into the positive electrode (activated carbon) side while passing through the separator, the voltage characteristics were measured while appropriately replenishing the electrolytic water so that the beaker's scale remained at the 100 ml position. In the activated carbon positive electrode of Example 2, it took time for the voltage to rise, and white corrosion products, which are thought to be due to self-discharge, accumulated on the zinc plate of the negative electrode. Finally, after 168 hours (7 days), the voltage was about 1.99 V, and although a further upward trend was observed, it was determined that this was to be set as the initial voltage before discharge, and was subjected to the discharge test described below.

[0106] (Discharge test) A discharge test was performed in which the power supply was maintained until the LED could no longer emit light, and the pH, voltage, and current of the aqueous solution of Example 2 were measured. The results are shown in Figures 4 and 5.

[0107] As shown in Fig. 4, the carbon dioxide fixation device of Example 2 continued discharging for 1824 hours (76 days), and the average voltage during discharging was 1.614 V (maximum value 1.630 V, minimum value 1.578 V). In addition, as shown in Fig. 5, the average current was 157.1 μA, the pH of the electrolyte at the end of discharging was 7.27, and the charge was 1031.5 C.

[0108] Furthermore, when the zinc plate of the carbon dioxide fixation device of Example 2 after the discharge test was subjected to powder X-ray diffraction, basic zinc carbonate Zn5(OH)6(CO3)2 was confirmed. Therefore, the carbon dioxide fixation device of Example 2 was also able to extract energy as a battery. It was also confirmed that carbon dioxide in the atmosphere was absorbed into the aqueous solution and fixed while acting as a component of the battery's electrolyte.

[0109] Comparative Example 1 A 75 ml solution of 0.1 mmol / L potassium hydroxide was prepared in a glass beaker, and its pH was measured and found to be 10.55. The solution was left to stand for 120 hours in contact with the air at 18-22°C, and the pH was measured again and found to be 7.73. It was presumed that carbon dioxide in the air was absorbed into the potassium hydroxide solution.

[0110] A carbon dioxide fixation apparatus of Comparative Example 1 was produced in the same manner as in Example 2, except that the above aqueous potassium hydroxide solution was used instead of the aqueous solution of Example 2.

[0111] Two sets of the carbon dioxide fixation device of Comparative Example 1 were prepared and connected in series so that the liquid surface of the aqueous solution was in contact with air. The voltage was measured and found to be 1.690 V. Since the electrolyte gradually permeates the positive electrode (activated carbon) side while passing through the separator, the voltage characteristics were measured while appropriately refilling the electrolytic water so that the beaker's scale remained at the 100 ml position. Finally, after 168 hours (7 days), the voltage reached 1.986 V, which was determined to be the initial voltage before discharge and subjected to the discharge test described below.

[0112] (Discharge test) A discharge test was performed in which the power supply was maintained until the LED could no longer emit light, and the pH, voltage, and current of the aqueous solution of Comparative Example 1 were measured. The results are shown in Figures 6 and 7.

[0113] As shown in Fig. 6, the carbon dioxide fixation device of Comparative Example 1 continued discharging for 1800 hours (75 days), and the average voltage during discharging was 1.594 V (maximum value 1.660 V, minimum value 1.560 V). In addition, as shown in Fig. 7, the average current was 142.4 μA, the pH of the electrolyte at the end of discharging was 7.08, and the charge was 900 C.

[0114] In addition, when the zinc plate of the carbon dioxide fixation device of Comparative Example 1 after the discharge test was subjected to powder X-ray diffraction, basic zinc carbonate Zn5(OH)6(CO3)2 was confirmed. Therefore, the carbon dioxide fixation device of Comparative Example 1 was also able to extract energy as a battery. It was also confirmed that carbon dioxide in the air was absorbed into the aqueous solution and fixed while acting as a component of the battery's electrolyte.

[0115] Comparing the carbon dioxide fixation devices of Example 2 and Comparative Example 1, the carbon dioxide fixation device of the Example was superior in average voltage, average current, and charge amount, and was able to fix carbon dioxide in the atmosphere more efficiently, resulting in its use as a battery. Furthermore, the carbon dioxide fixation device of Example 2 was superior in safety to Comparative Example 1, which used an aqueous potassium hydroxide solution.

[0116] Variations of the present invention are described below. [Appendix 1] An aqueous solution containing a water-soluble polymer compound and positive and negative electrode materials are provided, A carbon dioxide fixation device capable of generating carbonate derived from carbon dioxide after passing a current through the electrode material. [Appendix 2] 2. The carbon dioxide fixation device according to claim 1, wherein the water-soluble polymer compound has two or more amino groups in the molecule, a weight-average molecular weight of 500 or more and 50,000 or less, and is a non-volatile polyamine. [Appendix 3] 3. The carbon dioxide fixation apparatus according to claim 1 or 2, wherein a concentration of the water-soluble polymer compound in the aqueous solution is 1 ppm by mass or more and less than 1000 ppm by mass. [Appendix 4] 4. The carbon dioxide fixation apparatus according to any one of claims 1 to 3, wherein the aqueous solution has a pH of 8.6 or more and 14 or less immediately after preparation. [Appendix 5] 5. The carbon dioxide fixation apparatus according to any one of claims 1 to 4, wherein the aqueous solution does not substantially contain metal ions before current is applied. [Appendix 6] 6. The carbon dioxide fixation apparatus according to any one of claims 1 to 5, wherein the liquid surface of the aqueous solution is in contact with the atmosphere. [Appendix 7] 7. The carbon dioxide fixation device according to any one of claims 1 to 6, wherein carbon dioxide in the atmosphere can be dissolved in the aqueous solution up to a saturated concentration before current is applied. [Appendix 8] 8. The carbon dioxide fixation device according to any one of claims 1 to 7, wherein the negative electrode material contains a metal element other than an alkali metal. [Appendix 9] 9. The carbon dioxide fixation device according to any one of claims 1 to 8, wherein the negative electrode material contains one or more metal elements selected from the group consisting of zinc, iron, and magnesium. [Appendix 10] 10. The carbon dioxide fixation device according to any one of claims 1 to 9, wherein the positive electrode material is made of a material that has a relatively high standard Gibbs energy of formation as compared with the negative electrode material. [Appendix 11] 11. The carbon dioxide fixation apparatus according to any one of claims 1 to 10, which is capable of extracting electric energy. [Appendix 12] 12. The carbon dioxide fixation apparatus according to any one of claims 1 to 11, wherein the aqueous solution has a pH of 5.8 or more and less than 8.6 after current is applied. [Appendix 13] A battery comprising the carbon dioxide fixation device according to any one of claims 1 to 12.

Claims

1. An aqueous solution containing a water-soluble polymer compound and positive and negative electrode materials are provided, A carbon dioxide fixation device capable of generating carbonate derived from carbon dioxide after passing a current through the electrode material.

2. 2. The carbon dioxide fixation device according to claim 1, wherein the water-soluble polymer compound is a non-volatile polyamine having two or more amino groups in the molecule and a weight average molecular weight of 500 to 50,000.

3. 3. The carbon dioxide fixation device according to claim 1, wherein the concentration of the water-soluble polymer compound in the aqueous solution is equal to or greater than 1 ppm by mass and less than 1000 ppm by mass.

4. 3. The carbon dioxide fixation apparatus according to claim 1, wherein the aqueous solution has a pH of 8.6 or more and 14 or less immediately after preparation.

5. 3. The carbon dioxide fixation device according to claim 1, wherein the aqueous solution does not substantially contain metal ions before application of current.

6. 3. The carbon dioxide fixation apparatus according to claim 1, wherein the liquid surface of the aqueous solution is in contact with the atmosphere.

7. 3. The carbon dioxide fixation device according to claim 1, wherein carbon dioxide in the atmosphere can be dissolved in the aqueous solution up to a saturated concentration before current is applied.

8. 3. The carbon dioxide fixation device according to claim 1, wherein the negative electrode material contains a metal element other than an alkali metal.

9. 3. The carbon dioxide fixation device according to claim 1, wherein the negative electrode material contains one or more metal elements selected from the group consisting of zinc, iron, and magnesium.

10. 3. The carbon dioxide fixation device according to claim 1, wherein the positive electrode material is made of a material that has a relatively high standard Gibbs energy of formation with respect to the negative electrode material.

11. 3. The carbon dioxide fixation device according to claim 1 or 2, which is capable of extracting electric energy.

12. 3. The carbon dioxide fixation apparatus according to claim 1, wherein the aqueous solution has a pH of 5.8 or more and less than 8.6 after the current is applied.

13. A battery comprising the carbon dioxide fixation device according to claim 1 or 2.

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