CN117702148A

CN117702148A - Electrolysis apparatus and electrolysis method

Info

Publication number: CN117702148A
Application number: CN202310153122.3A
Authority: CN
Inventors: 工藤由纪; 小野昭彦; 御子柴智; 北川良太
Original assignee: Toshiba Corp
Current assignee: Toshiba Corp
Priority date: 2022-09-15
Filing date: 2023-02-22
Publication date: 2024-03-15
Also published as: JP2024042579A; EP4339336A3; US20240093395A1; EP4339336A2; AU2023201239A1

Abstract

An electrolytic device according to an embodiment includes: an electrolysis unit (which is provided with a cathode part provided with a reduction electrode, an anode part provided with an oxidation electrode, and a diaphragm arranged between the cathode part and the anode part); a supplied power characteristic obtaining unit (which obtains characteristics of power supplied to the electrolysis unit); an input gas characteristic acquisition unit (which acquires characteristics of gas input to the electrolysis unit); an electric characteristic obtaining unit (which obtains electric characteristics of the electrolysis unit); an output gas characteristic obtaining unit (which obtains the characteristic of the output gas of the electrolysis unit); a temperature acquisition unit (which acquires the temperature of the electrolysis cell); a data storage unit (which stores data from each acquisition unit); and a data processing unit (which transmits data from the data storage unit, processes the data, and determines the state of the electrolytic cell).

Description

Electrolysis apparatus and electrolysis method

The present application is based on Japanese patent application 2022-147380 (filing date: 9/15/2022) and enjoys priority of the above-mentioned application. The present application is incorporated by reference in its entirety into the above application.

Technical Field

Embodiments of the present invention relate to an electrolysis apparatus and an electrolysis method.

Background

In recent years, exhaustion of fossil fuels such as petroleum, coal, and the like has been worried about, and the expectation of sustainable renewable energy has been increasing. As renewable energy sources, there may be mentioned: solar power generation, hydroelectric power generation, wind power generation, geothermal power generation and the like. In these examples, since the amount of power generation depends on weather, natural conditions, and the like, a power source (variable power source) whose output varies has a problem that it is difficult to stably supply electric power. Therefore, attempts have been made to combine a variable power supply with a battery to regulate power. However, there are problems such as the cost of the battery required for storing electric power and the loss of the battery during the storage.

Further, as an attempt to decarbonize, water (H ₂ O) electrolysis to generate hydrogen (H) ₂ ) Is to be used for the electrolysis of carbon dioxide (CO) ₂ ) Electrochemical reduction by electrolysis to convert into carbon monoxide (CO), formic acid (HCOOH), methanol (CH) ₃ OH), methane (CH) ₄ ) Acetic acid (CH) ₃ COOH), ethanol (C) ₂ H ₅ OH), ethane (C) ₂ H ₆ ) Ethylene (C) ₂ H ₄ ) Carbon dioxide electrolysis technology for chemical substances (chemical energy) such as carbon compounds has been attracting attention. By connecting a variable power supply using renewable energy to such an electrolysis apparatus, there is an advantage that electric power adjustment and recycling of hydrogen and carbon dioxide production can be performed simultaneously.

As an electrolyzer for carbon dioxide, for example, a cathode solution and CO are studied ₂ Contacting the gas with the cathode and contacting the anolyte with the anodeIs a structure of (a). Such a structure is referred to herein as an electrolysis cell for carbon dioxide. In using such electrolytic units, e.g. by applying a constant current through the cathode and anode for a long period of time from CO ₂ In the case of a reaction for producing CO, for example, there are the following problems: the output of the electrolysis unit deteriorates with time, such as a decrease in the amount of CO produced or an increase in the voltage of the electrolysis unit. As one of the degradation sites (degradation sites), there is a phenomenon in which salt is deposited in a gas flow path due to an electrolyte of a solution to hinder the flow of gas or the like, and refresh operation for introducing dissolved salt is being studied.

However, in the case of carbon dioxide (CO ₂ ) In an electrolytic device such as a water-jet separator, it is becoming clear that there are various degradation phenomena in addition to the phenomenon that salt is deposited in a flow path. Further, for example, in nitrogen (N) ₂ ) In addition to the electrolysis apparatus with CO ₂ In addition to the same degradation phenomenon as electrolysis, N is also present ₂ Degradation phenomenon peculiar to electrolysis. Therefore, it is necessary to continue the operation according to the electrolyte and the degradation site, to perform the operation stop, maintenance of the electrolysis unit, and the like, and to appropriately cope with the judgment standard according to the type of the electrolyte and the degradation. Therefore, it is required to determine the state of deterioration, the type of the electrolytic cell, and the like.

Disclosure of Invention

The present invention provides an electrolysis apparatus and an electrolysis method capable of determining the state of an electrolysis cell.

An electrolytic device according to an embodiment includes:

an electrolysis unit provided with: a cathode portion to which a gas or a liquid containing a reduced material is supplied and which is provided with a reduction electrode, an anode portion to which a liquid containing an oxide material is supplied and which is provided with an oxidation electrode, and a separator provided between the cathode portion and the anode portion;

a supplied power characteristic obtaining unit that obtains a characteristic of power supplied to the electrolysis unit;

An input gas characteristic obtaining unit for obtaining characteristics of gas input to the electrolysis unit;

an electric characteristic obtaining unit for obtaining electric characteristics of the electrolytic cell;

an output gas characteristic obtaining unit that obtains a characteristic of the output gas of the electrolysis unit;

a temperature control unit for controlling the temperature of the electrolysis unit;

a temperature acquisition unit configured to acquire a temperature of the electrolysis cell;

a data storage unit configured to store data from the supply power characteristic acquisition unit, the input gas characteristic acquisition unit, the electrical characteristic acquisition unit, the output gas characteristic acquisition unit, and the temperature acquisition unit; and

and a data processing unit configured to transmit the data from the data storage unit, process the data, and determine a state of the electrolytic cell.

Drawings

FIG. 1 is a view showing an electrolytic device according to an embodiment.

Fig. 2 is a diagram showing an electrolysis unit in the carbon dioxide electrolysis apparatus according to embodiment 1.

Fig. 3 is a diagram showing a degradation detection process performed by the carbon dioxide electrolysis apparatus according to embodiment 1.

Fig. 4 is a diagram showing an equivalent circuit model of an electrolysis unit in the carbon dioxide electrolysis apparatus according to embodiment 1.

Fig. 5 is a table showing equivalent circuit parameters of the equivalent circuit model of fig. 4.

Fig. 6 is a diagram showing an electrolysis unit in the carbon dioxide electrolysis apparatus according to embodiment 2.

Fig. 7 is a diagram showing an equivalent circuit model of an electrolysis unit in the carbon dioxide electrolysis apparatus according to embodiment 3.

Fig. 8 is a table showing equivalent circuit parameters of the equivalent circuit model of fig. 7.

Fig. 9 is a diagram showing an equivalent circuit model of an electrolytic cell in the nitrogen electrolysis apparatus according to embodiment 4.

FIG. 10 is a view showing a design process of the electrolytic device according to embodiment 5.

FIG. 11 shows the CO partial current density J of example 1 _CO And H ₂ Partial current density J _H2 A graph of measured data and simulated data.

FIG. 12 shows the cell voltage V of example 1 _cell Cathode potential V _cm Anode potential V _am A graph of measured data and simulated data.

FIG. 13 shows the CO Faraday efficiency FE of example 1 _CO And H ₂ Faraday efficiency FE _H2 A graph of measured data and simulated data.

FIG. 14 shows the cathode output gas (CO, H) of example 1 ₂ And CO ₂ ) A graph of measured data and simulated data.

FIG. 15 shows the anode output gas (O) of example 1 ₂ And CO ₂ ) A graph of measured data and simulated data.

(symbol description)

The electrolytic cell 1 …, electrolytic device 2, 2A, 2B …, 3 … supply power control unit, 4 … supply power characteristic acquisition unit, 5 … gas/electrolyte control unit, 6 … input gas characteristic acquisition unit, 7 … electrical characteristic acquisition unit, 8 … output gas characteristic acquisition unit, 9 … temperature control unit, 10 … temperature acquisition unit, 11 … data storage unit, 12 … data processing unit, 21 … st electrolyte, 22 … st housing unit, 23 … reduction electrode (cathode), 24 … cathode unit, 25 … nd electrolyte, 26 … nd housing unit, 27 … oxidation electrode (anode), 28 … anode unit, 29 … diaphragm, 36 … nd 1 flow path, 37 … nd flow path.

Detailed Description

The electrolytic device and the electrolytic method according to the embodiments are described below with reference to the drawings. In the embodiments shown below, substantially the same constituent parts are denoted by the same reference numerals, and a partial description thereof may be omitted. The drawings are merely schematic, and the relationship between the thickness and the planar dimension, the ratio of the thickness of each portion, and the like may be different from those in practice.

Fig. 1 is a view showing an electrolytic device 1 according to an embodiment. The electrolytic device 1 shown in fig. 1 includes:

the electrolytic cell 2 is provided with a gas-liquid separator,

a power supply control unit 3 for controlling the power to be supplied to the electrolysis unit 2,

a supply power characteristic acquisition unit 4 for acquiring characteristics of the supply power,

a gas/electrolyte control unit 5 for controlling the gas and the electrolyte supplied to the electrolytic cell 2,

an input gas characteristic acquisition unit 6 for acquiring the characteristic of the input gas to be supplied,

an electric characteristic obtaining part 7 for obtaining electric characteristics of the electrolysis unit 2,

an output gas characteristic obtaining unit 8 for obtaining the characteristic of the output gas of the electrolysis unit 2,

a temperature control unit 9 for controlling the temperature of the electrolysis unit 2,

a temperature obtaining unit 10 for obtaining the temperature of the electrolysis unit 2,

a data storage unit 11 for storing data from the supply power characteristic acquisition unit 4, the input gas characteristic acquisition unit 6, the electrical characteristic acquisition unit 7, the output gas characteristic acquisition unit 8, and the temperature acquisition unit 10,

A data processing unit 12 for transmitting data from the data storage unit 11 and processing the transmitted data, and

a display unit 13.

Hereinafter, each portion is described in detail.

The electrolysis unit 2 has a structure corresponding to electrolysis of an object to be electrolyzed by the electrolysis apparatus 1, and includes at least: a reducing electrode chamber for supplying a gas or a liquid containing a reduced material and provided with a reducing electrode, an oxidizing electrode chamber for supplying a liquid containing an oxidized material and provided with an oxidizing electrode, and a separator provided between the reducing electrode chamber and the oxidizing electrode chamber. Examples of the object to be electrolyzed in the electrolyzer 1 include: carbon dioxide (CO) ₂ ) Nitrogen (N) ₂ ) Water (H) ₂ O), and the like. CO is processed by ₂ When reduced by electrolysis, carbon monoxide (CO), formic acid (HCOOH) and methane (CH) are produced ₄ ) Methanol (CH) ₃ OH), ethane (C) ₂ H ₆ ) Ethylene (C) ₂ H ₄ ) Ethanol (C) ₂ H ₅ OH), formaldehyde (HCHO), ethylene glycol (C) ₂ H ₆ O ₂ ) And (5) carbon compound. In CO ₂ At the same time as the reduction reaction of (a), sometimes by H ₂ Reduction of O to hydrogen (H) ₂ ). Will N ₂ Upon reduction by electrolysis, ammonia (NH) is formed ₃ )。

(embodiment 1)

As embodiment 1, carbon dioxide (CO) will be described with reference to fig. 1 and 2 ₂ ) Is provided with an electrolysis apparatus 1. In the electrolysis unit 2 shown in fig. 1 for electrolysis of CO ₂ As shown in fig. 2, the electrolysis unit 2 (2A) of (a) includes:

A cathode portion (reduction electrode chamber) 24 having: for accommodating CO-containing materials ₂ A 1 st containing portion (containing groove) 22 of the 1 st electrolyte 21, and a reduction electrode (cathode) 23 disposed in the 1 st containing portion 22;

an anode portion (oxidation electrode chamber) 28 having: a 2 nd containing portion (containing groove) 26 for containing the 2 nd electrolyte 25 containing water; and an oxidation electrode (anode) 27 disposed in the 2 nd housing portion 26; and

and a diaphragm 29 disposed between the 1 st housing portion 22 and the 2 nd housing portion 26.

The 1 st housing portion 22, the 2 nd housing portion 26, and the diaphragm 29 constitute a reaction tank 30.

The reaction tank 30 is configured to allow hydrogen ions (H ⁺ ) Hydroxide ion (OH) ^- ) Bicarbonate ion (HCO) ₃ ^- ) Carbonate ion (CO) ₃ ^2- ) The plasma-movable diaphragm 29 is divided into two chambers, namely, a 1 st housing portion 22 and a 2 nd housing portion 26. The reaction tank 30 may be formed of, for example, quartz white glass, acrylic resin (PMMA), polystyrene (PS), or the like. A light-transmitting material may be used for a part of the reaction tank 5, and a resin material may be used for the remaining part. Examples of the resin material include: polyetheretherketone (PEEK), polyamide (PA), polyvinylidene fluoride (PVDF), polyacetal (POM) (copolymer), polyphenylene ether (PPE), acrylonitrile butadiene styrene copolymer (ABS), polypropylene (PP), polyethylene (PE), and the like.

A reduction electrode 23 is disposed in the 1 st housing portion 22, and further houses CO ₂ 。CO ₂ For example, the 1 st electrolyte 21 containing the electrolyte is stored in the 1 st storage part 22. The 1 st electrolyte 21 functions as a reducing electrode solution (cathode solution) including carbon dioxide (CO ₂ ). Here, CO is present as CO in the 1 st electrolyte 21 ₂ In the form of (2) not necessarily in the form of a gas but in the form of dissolved CO ₂ Or (b)Carbonate ion (CO) ₃ ^2- ) Bicarbonate ion (HCO) ₃ ^- ) And the like. The 1 st electrolyte 21 may contain hydrogen ions, and is preferably an aqueous solution. An oxidation electrode 27 is disposed in the 2 nd housing 26, and further, the 2 nd electrolyte 25 containing water is housed therein. The 2 nd electrolyte 25 functions as an oxidizing electrode solution (anode solution) as a substance to be oxidized, and includes, for example, water (H ₂ O) and chloride ions (Cl) ^- ) Carbonate ion (CO) ₃ ^2- ) Bicarbonate ion (HCO) ₃ ^- ) Etc. The 2 nd electrolyte 25 may be an aqueous alcohol solution or an aqueous organic solution such as amine.

By changing the amounts of water and the electrolyte components contained in the 1 st electrolyte 21 and the 2 nd electrolyte 25, the reactivity, the selectivity of the reduced substances, and the proportion of the chemical substances generated can be changed. The 1 st electrolyte 21 and the 2 nd electrolyte 25 may contain a redox couple as needed. Examples of redox pairs include: fe (Fe) ³⁺ /Fe ²⁺ Or IO (IO) ^3- /I ^- . The 1 st housing portion 22 is connected to a supply unit containing CO ₂ The gas supply passage 31 of the raw material gas and the 1 st liquid supply passage 32 for supplying the 1 st electrolyte 21, and the 1 st gas and liquid discharge passage 33 for discharging the reaction gas and the 1 st electrolyte 21 are connected. The 2 nd liquid supply channel 34 for supplying the 2 nd electrolyte 25 and the 2 nd gas and liquid discharge channel 35 are connected to the 2 nd storage portion 26. The 1 st housing portion 22 and the 2 nd housing portion 26 may have a space portion that houses the reactant and the gas contained in the product.

The pressure in the 1 st accommodation portion 22 and the 2 nd accommodation portion 26 is preferably set so as not to cause CO ₂ The pressure of the liquefaction is preferably adjusted to a range of 0.1MPa or more and 6.4MPa or less. If the pressure in the housing portions 22, 26 is less than 0.1MPa, CO ₂ The reduction reaction efficiency of (a) may be lowered. When the pressure in the housing portions 22, 26 exceeds 6.4MPa, CO ₂ Liquefaction, CO ₂ The reduction reaction efficiency of (a) may be lowered. The diaphragm 29 may be broken or the like due to a differential pressure between the 1 st housing portion 22 and the 2 nd housing portion 26. Therefore, the difference (differential pressure) between the pressure in the 1 st housing portion 22 and the pressure in the 2 nd housing portion 26 is preferably 1MPa or less.

The lower the temperature of the electrolytes 21, 25, the CO ₂ The higher the dissolution but from CO ₂ From the viewpoint of electrolysis, the solution resistance becomes high at low temperature, and the theoretical voltage of the reaction becomes high, and therefore, it is disadvantageous. On the other hand, when the temperature of the electrolytes 21 and 25 is high, although CO ₂ The amount of dissolved (C) becomes low, but for CO ₂ Electrolysis is advantageous. Therefore, the operating temperature condition of the electrolytic cell 2A is preferably in a medium temperature range, for example, a range from above atmospheric temperature to below the boiling point of the electrolytes 21, 25. When the electrolytes 21 and 25 are aqueous solutions, the temperature is preferably 10 ℃ or higher and 100 ℃ or lower, and more preferably 25 ℃ or higher and 80 ℃ or lower. The 1 st accommodation portion 22 is filled with a material containing CO ₂ When the 2 nd housing portion 26 is filled with steam, the operation at a higher temperature can be performed. At this time, the operating temperature is determined in consideration of the heat resistance of the member such as the diaphragm 29. When the separator 29 is an ion exchange membrane or the like, the operating temperature is 180℃at maximum, and when a polymer porous membrane such as Teflon is used as the separator, the maximum temperature is 300 ℃.

The 1 st electrolyte 21 and the 2 nd electrolyte 25 may be electrolytes containing different substances or the same electrolyte containing the same substance. When the 1 st electrolyte 21 and the 2 nd electrolyte 25 contain the same substance and the same solvent, the 1 st electrolyte 21 and the 2 nd electrolyte 25 can be considered as one electrolyte. In addition, the pH of electrolyte 2 may be higher than the pH of electrolyte 1, 21. Thereby, the hydrogen ion and hydroxyl ion plasma easily move through the separator 29. In addition, the oxidation-reduction reaction can be efficiently performed by the inter-liquid potential difference due to the difference in pH.

Electrolyte 1 is preferably CO ₂ Is a solution with high absorptivity. CO ₂ The form of existence in the 1 st electrolyte 21 is not necessarily limited to a dissolved state, and CO in the form of bubbles may be used ₂ The mixture is present in the 1 st electrolyte 21. As a mixture containing CO ₂ Examples of the electrolyte of (a) include: contains lithium bicarbonate (LiHCO) ₃ ) Sodium bicarbonate (NaHCO) ₃ ) Potassium bicarbonate (KHCO) ₃ ) Cesium bicarbonate (CsHCO) ₃ ) Sodium carbonate (Na) ₂ CO ₃ ) Potassium carbonate (K) ₂ CO ₃ ) Such aqueous solutions of bicarbonate or carbonate, phosphoric acid, boric acid, and the like. Containing CO ₂ The electrolyte of (a) may contain alcohols such as methanol, ethanol, and acetone, or may be an alcohol solution. Electrolyte 1 may be a CO-reducing electrolyte 21 ₂ High ionic conductivity, and contains CO absorption ₂ CO of (c) ₂ Electrolyte of the absorbent.

As the 2 nd electrolyte 25, a solution using water (H ₂ O), for example an aqueous solution containing any electrolyte. The solution is preferably an aqueous solution that promotes the oxidation reaction of water. Examples of the aqueous solution containing an electrolyte include: containing phosphate ions (PO) ₄ ^3- ) Borate ion (BO) ₃ ^3- ) Sodium ion (Na) ⁺ ) Potassium ion (K) ⁺ ) Calcium ion (Ca) ²⁺ ) Lithium ion (Li) ⁺ ) Cesium ions (Cs) ⁺ ) Magnesium ions (Mg) ²⁺ ) Chloride ion (Cl) ^- ) Bicarbonate ion (HCO) ₃ ^- ) Carbonate ion (CO) ₃ ^2- ) Hydroxide ion (OH) ^- ) Etc.

As the electrolytes 21 and 25, for example, an imidazole-containing electrolyte can be usedIon, pyridine->Ion plasma cations and BF ₄ ^- Or PF (physical pattern) ₆ ^- Ionic liquids or aqueous solutions thereof of salts of plasmonic anions in a liquid state over a broad temperature range. Further, as another electrolytic solution, there may be mentioned: amine solutions such as ethanolamine, imidazole, pyridine, and the like, or aqueous solutions thereof. Examples of the amine include primary amine, secondary amine, and tertiary amine. These electrolytes have high ion conductivity and carbon dioxide absorbing properties, and may have a property of reducing reduction energy.

Examples of the primary amine include: methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, and the like. The hydrocarbon of the amine may be replaced by an alcohol, halogen, or the like. Examples of amines in which the hydrocarbon of the amine is replaced include: methanolamine, ethanolamine, chloromethylamine, and the like. In addition, an unsaturated bond may be present. The same applies to these hydrocarbons as well as secondary and tertiary amines.

Examples of the secondary amine include: dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentamine, dihexylamine, dimethanol amine, diethanolamine, dipropanol amine, and the like. The hydrocarbon to be replaced may be different. The same is true for tertiary amines. For example, as the amine of different hydrocarbon species, there may be mentioned: methylethylamine, methylpropylamine, and the like.

Examples of the tertiary amine include: trimethylamine, triethylamine, tripropylamine, tributylamine, trihexylamine, trimethanolamine, triethanolamine, tripropanolamine, tributylamine, trihexylamine, methyldiethylamine, methyldipropylamine, and the like.

Examples of the cations of the ionic liquid include: 1-ethyl-3-methylimidazoleIon, 1-methyl-3-propylimidazoleIon, 1-butyl-3-methylimidazole->Ion, 1-methyl-3-pentylimidazole->Ion, 1-hexyl-3-methylimidazole->Ions, and the like.

ImidazoleThe ion may be substituted in the 2-position. As imidazole->Examples of cations having a substitution at the 2-position of the ion include: 1-ethyl-2, 3-dimethylimidazole->Ion, 1, 2-dimethyl-3-propylimidazole +.>Ion, 1-butyl-2, 3-dimethylimidazoleIon, 1, 2-dimethyl-3-pentylimidazole +.>Ion, 1-hexyl-2, 3-dimethylimidazole +.>Ions, and the like.

As pyridineExamples of the ion include: picoline->Ethylpyridine->Propylpyridine->Butylpyridine->Pentylpyridine->Hexyl pyridine->Etc. Imidazole->Ion and pyridine->The ions may be substituted by alkyl groups or unsaturated bonds may be present.

Examples of the anion include: fluoride ion (F) ^- ) Chloride ion (Cl) ^- ) Bromide ion (Br) ^- ) Iodide ion (I) ^- )、BF ₄ ^- 、PF ₆ ^- 、CF ₃ COO ^- 、CF ₃ SO ₃ ^- 、NO ₃ ^- 、SCN ^- 、(CF ₃ SO ₂ ) ₃ C ^- Bis (trifluoromethylsulfonyl) imide, bis (trifluoroethylsulfonyl) imide, bis (perfluoroethylsulfonyl) imide, and the like. May be gemini ions in which the cations and anions of the ionic liquid are linked by hydrocarbons. A buffer solution such as a potassium phosphate solution may be supplied to the storage portions 22 and 26.

The membrane 29 uses a membrane through which anions or cations can selectively pass. Thus, the electrolytes 21 and 25 in contact with the reduction electrode 23 and the oxidation electrode 27 can be made to be electrolytes containing different substances. Further, the reduction reaction or the oxidation reaction can be promoted by the difference in ionic strength, the difference in pH, and the like. Using the separator 29, the 1 st electrolyte 21 can be separated from the 2 nd electrolyte 25. The separator 29 may have a function of transmitting a part of ions contained in the electrolytes 21 and 25 impregnated with the two electrodes 23 and 27, that is, a function of shielding 1 or more kinds of ions contained in the electrolytes 21 and 25. Thus, for example, the pH between the 2 electrolytes 21 and 25 can be made different.

Examples of the separator 29 include a plasma exchange membrane such as neocuptor (registered trademark) of Astom, selemion (registered trademark) of Asahi-sony, aciplex (registered trademark) of Asahi chemical, fumasep (registered trademark) of Fumatech, nafion (registered trademark) which is a fluororesin obtained by sulfonating and polymerizing tetrafluoroethylene of DuPont, lewabrane (registered trademark) of LANXESS, IONSEP (registered trademark) of IONTECH, mustang (registered trademark) of PALL, ralex (registered trademark) of Mega, and GORE-TEX (registered trademark) of GORE-TEX. The ion exchange membrane may be formed using a membrane having a hydrocarbon as a basic skeleton or a membrane having an amine group in anion exchange. When there is a pH difference between the 1 st electrolyte 21 and the 2 nd electrolyte 25, the bipolar membrane in which the cation exchange membrane and the anion exchange membrane are laminated is used, and thus the pH of each electrolyte can be stably maintained.

The separator 29 may be a porous membrane of silicone resin, perfluoroalkoxyalkane (PFA), perfluoroethylene propylene copolymer (FEP), polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), fluorine-based resin such as ethylene-chlorotrifluoroethylene copolymer (ECTFE), polyethersulfone (PES), ceramics, a filler filled with a glass filter or agar, or an insulating porous body such as zeolite or oxide, for example. A hydrophilic porous membrane is preferably used as the separator 29 because clogging due to bubbles is not generated.

The reduction electrode 23 is a reduction electrode for converting carbon dioxide (CO ₂ ) An electrode (cathode) that reduces to produce a carbon compound. The reduction electrode 23 is disposed inside the 1 st housing portion 22 and immersed in the 1 st electrolyte 21. The reduction electrode 23 comprises, for example, for passing CO ₂ A reduction catalyst for producing a carbon compound by the reduction reaction of (a). The reduction catalyst may be reduced in the reduction of CO ₂ Is a material with activation energy. In other words, reduction of the CO passage is exemplified ₂ An overvoltage material when carbon compounds are generated by the reduction reaction.

As the reduction electrode 23, for example, a metal material or a carbon material can be used. As the metal material, for example, there can be used: metals such as gold, aluminum, copper, silver, platinum, palladium, zinc, mercury, indium, nickel, and titanium, and alloys containing the metals. As the carbon material, for example, there can be used: graphene, carbon Nanotubes (CNT), fullerenes, ketjen black, and the like. The reduction catalyst is not limited to this, and for example, a metal complex such as Ru complex or Re complex, or an organic molecule having an imidazole skeleton or pyridine skeleton may be used. The reduction catalyst may be a mixture of materials. The reduction electrode 23 may have a structure in which a reduction catalyst in the form of a film, a lattice, a pellet, a wire, or the like is provided on a conductive substrate, for example.

The carbon compound produced by the reduction reaction in the reduction electrode 23 differs depending on the type of the reduction catalyst and the like, and examples thereof include: carbon monoxide (CO), formic acid (HCOOH), methane (CH) ₄ ) Methanol (CH) ₃ OH), ethane (C) ₂ H ₆ ) Ethylene (C) ₂ H ₄ ) Ethanol (C) ₂ H ₅ OH), formaldehyde (HCHO), ethylene glycol (C) ₂ H ₆ O ₂ ) Etc. In addition, in the reduction electrode 23, carbon dioxide (CO ₂ ) In the course of the reduction reaction, the reaction may be carried out by passing water (H ₂ Reduction of O) to produce hydrogen (H) ₂ ) Is a side reaction of (a).

The oxidation electrode 27 is an electrode (anode) that oxidizes an oxidized substance such as a substance or ion in the 2 nd electrolyte 25. For example, water (H ₂ O) oxidation to form oxygen or hydrogen peroxide water, or chlorine ions (Cl) ^- ) Oxidizing to generate chlorine. The oxidation electrode 27 is disposed inside the 2 nd housing portion 26, and immersed in the 2 nd electrolyte 25. The oxidation electrode 27 contains an oxidation catalyst of an oxidized substance. As the oxidation catalyst, a material that reduces activation energy when oxidizing an oxidized substance, in other words, a material that reduces reaction overvoltage is used.

Examples of such an oxidation catalyst material include: ruthenium, iridium, platinum, cobalt, nickel, iron, manganese, and the like. In addition, binary metal oxides, ternary metal oxides, quaternary metal oxides, and the like can be used. Examples of the binary metal oxide include: manganese oxide (Mn-O), iridium oxide (Ir-O), nickel oxide (Ni-O), cobalt oxide (Co-O), iron oxide (Fe-O), tin oxide (Sn-O), indium oxide (In-O), ruthenium oxide (Ru-O), and the like. Examples of the ternary metal oxide include: ni-Fe-O, ni-Co-O, la-Co-O, ni-La-O, sr-Fe-O, etc. Examples of the quaternary metal oxide include: pb-Ru-Ir-O, la-Sr-Co-O, etc. The oxidation catalyst is not limited thereto, and a metal complex such as a metal hydroxide, ru complex, or Fe complex containing cobalt, nickel, iron, manganese, or the like may be used. In addition, a plurality of materials may be used in combination.

The oxidation electrode 27 may be a composite material containing both an oxidation catalyst and a conductive material. Examples of the conductive material include: carbon materials such as carbon black, activated carbon, fullerene, carbon nanotube, graphene, ketjen black, and diamond, metals such as Indium Tin Oxide (ITO), zinc oxide (ZnO), fluorine-doped tin oxide (FTO), aluminum-doped zinc oxide (AZO), and antimony-doped tin oxide (ATO), and transparent conductive oxides such as Cu, al, ti, ni, ag, W, co, au, and alloys containing at least 1 of these metals. The oxidation electrode 27 may have a structure in which, for example, a thin film-like, lattice-like, granular, wire-like oxidation catalyst is provided on a conductive substrate. As the conductive base material, for example, a metal material containing titanium, a titanium alloy, or stainless steel can be used.

In the electrolytic apparatus 1 shown in fig. 1, the constitution and operation of the data processing section 12 and the like are described. The power supply control unit 3 controls the power generated by the redox reaction in the electrolytic cell 2A, and is electrically connected to the reduction electrode 23 and the oxidation electrode 27 of the electrolytic cell 2A. A power supply, not shown, is connected to the power supply control unit 3. The supply power control unit 3 is provided with electrical devices such as a DC/AC converter, a DC/DC converter, an AC/DC converter, an inverter, a converter, and a switch. The power supply 5 connected to the power supply control unit 3 may be a power supply that converts renewable energy into electric energy and supplies the electric energy, or may be a normal commercial power supply, a battery, or the like. As examples of the power source using renewable energy sources, there are: a power source for converting kinetic energy or potential energy such as wind power, water power, geothermal power, and tidal power into electric energy, a power source such as a solar cell having a photoelectric conversion element for converting light energy into electric energy, a power source such as a fuel cell or a battery for converting chemical energy into electric energy, a power source for converting vibrational energy such as sound into electric energy, and the like.

The supplied power characteristic obtaining unit 4 obtains the voltage and current, which are the power supplied to the electrolysis cell 2A. The supply power characteristics acquired by the supply power characteristic acquisition unit 4 are transmitted to the data storage unit 11 via the signal line. The supply power control unit 3 and the supply power characteristic obtaining unit 4 may be independent or integrated.

The gas/electrolyte control unit 5 controls the CO content input to the electrolysis unit 2A ₂ And the flow rate of the electrolyte. In addition, the dew point, temperature, pressure, etc. of the gas, the pressure, temperature, composition, pH, etc. of the electrolyte may also be controlled. The input gas characteristic obtaining unit 6 obtains the CO-containing gas input to the electrolysis unit 2A ₂ The flow rate and composition of the gas of (a). May also have the function of obtaining CO ₂ The dew point, temperature, pressure, etc. of the gas. The acquired input gas characteristics are supplied to the data storage unit 11 through a signal line. The gas/electrolyte control unit 5 and the input gas characteristic obtaining unit 6 may be independent or integrated.

The electrical characteristic obtaining unit 7 obtains electrical characteristics such as a cell voltage and a cell current of the electrolysis cell 2A. In order to improve the accuracy of the equivalent circuit parameters, it is preferable to assemble a reference electrode in the electrolytic cell 2A and to obtain the potential of the cathode 23 or the anode 27 with respect to the reference electrode. In addition, the function of obtaining the impedance of the electrolytic cell 2A may be provided. The electrical characteristics are supplied to the data storage section 11 through the signal line.

The output gas characteristic obtaining unit 8 obtains the flow rate of the gas output from the cathode 23 side of the electrolysis unit 2A and the flow rate of the gas passing through CO ₂ And CO ₂ The concentration of the various gases produced by the reduction reaction. Can also have the function of obtaining H generated by side reaction ₂ And the concentration of other gases. In addition, O may be obtained from the anode 27 side ₂ And CO ₂ The flow rate of the gas, the concentration of the gas, etc. The output gas characteristic is supplied to the data storage unit 11 through a signal line.

The temperature control unit 9 controls the temperature of the electrolytic cell 2A to a predetermined value, and has a function of controlling the heating of the heater incorporated in the electrolytic cell 2A and the flow of the refrigerant to the cooling water passage. The temperature acquisition unit 10 acquires the temperature of the electrolytic cell 2A. The acquired temperature is sent to the data storage unit 11 through a signal line. The temperature control unit 9 and the temperature acquisition unit 10 may be independent structures or may be integrated structures.

The data storage unit 11 includes a control device such as a computer, and has a function of storing data in a recording medium such as a memory, a hard disk, and an SSD, and a data transmitting/receiving function. The display unit is a display unit having a function of displaying information transmitted from the data storage unit and the degradation detection unit. The data storage unit and the display unit may be independent structures or may be integrated structures such as a computer.

The data processing unit 12 is provided with a computer such as a PC or a microcomputer, for example, and calculates an equivalent circuit model and equivalent circuit parameters based on the data transmitted from the data storage unit 11. The data processing unit 12 estimates the degradation portion and calculates the degradation degree based on the equivalent circuit parameters. Further, CO is performed based on the information of the degradation site and the degradation degree ₂ The determination of the continuation of the operation, the refresh operation, and the stop of the operation of the electrolytic cell 2A is made, and instructions are sent to the supply power control unit 3, the gas/electrolyte control unit 5, and the temperature control unit 9. The data processing unit 12 may be provided near the electrolytic cell 2A or may be provided in the cloud for remote diagnosis. By providing the data processing unit 12 in the cloud, the stored data of the electrolytic cells 2A provided everywhere can be collectively managed, and the accuracy of degradation detection can be improved. Therefore, the data processing section 12 is preferably provided in the cloud.

Next, a degradation detection method of the electrolytic device 1 will be described with reference to fig. 3. First, the equivalent circuit model and the equivalent circuit parameters at the time of designing the electrolytic cell 2A are made into a database, and stored in the data processing unit 12 in advance. Alternatively, the electrolysis cell 2A may be tested by using the supply power control unit 3 and the gas/electrolyte control unit 5, and the equivalent circuit parameters and the calculation of the equivalent circuit model before the main operation may be obtained and the database may be formed (S1). The main operation (this operation) of the electrolysis cell (or the electrolysis cell stack) 2 is started, and the supply power characteristic, the input gas characteristic, the electrical characteristic, the output gas characteristic, and the temperature of the electrolysis cell 2A are acquired, and the data are stored in the data storage unit 11 (S2). These data are sent to the data processing unit 12, and the data processing unit 12 calculates an equivalent circuit model and equivalent circuit parameters (S3).

The data processing unit 12 compares the equivalent circuit model and the equivalent circuit parameters acquired at the time of designing or before the main operation of S1 with the equivalent circuit model and the equivalent circuit parameters during the main operation to estimate the degradation site and calculate the degradation degree. Further, the lifetime until the operation is stopped is predicted from the change in the degradation degree (S4). It is determined whether or not the degree of deterioration exceeds an operation stop criterion (S5), and if the degree of deterioration exceeds the operation stop criterion, the normal operation of the electrolytic cell (or electrolytic cell stack) 2 is stopped (S6). At the time of stopping, maintenance and replacement of the electrolytic cell 2A are performed according to the deteriorated portion (S7). The various characteristic data stored in the data storage unit 11 in S2, the equivalent circuit model and the equivalent circuit parameters calculated in S3, the degradation parts and the degradation degree calculated in S4, and the lifetime until the operation is stopped are transferred to the display unit 13 and displayed (S8).

Next, CO will be described ₂ Is provided for the operation of the electrolysis apparatus 1. Here, the use of a CO-containing catalyst is described ₂ Is mixed with potassium bicarbonate (KHCO) ₃ ) Aqueous solutions were used as electrolytes 21 and 25, and CO was used as a catalyst ₂ Mainly reduces to carbon monoxide (CO) and water (H) ₂ O) or hydroxide ions (OH) ^- ) Oxidation to oxygen. CO ₂ The reduction reaction of (2) is not limited to the CO production reaction, and may be C _x H _y O _z In particular formic acid (HCOOH), methane (CH) ₄ ) Methanol (CH) ₃ OH), ethane (C) ₂ H ₆ ) Ethylene (C) ₂ H ₄ ) Ethanol (C) ₂ H ₅ OH), formaldehyde (HCHO), ethylene glycol (C) ₂ H ₆ O ₂ ) And the formation reaction of an isocarbon.

When a voltage equal to or higher than the electrolysis voltage is applied between the reduction electrode (cathode) 23 and the oxidation electrode (anode) 27, CO is generated in the vicinity of the reduction electrode 23 in contact with the 1 st electrolyte 21 ₂ Is a reduction reaction of (a). As shown in the following formula (1), the electron (e ^- ) CO contained in the 1 st electrolyte 21 ₂ Is reduced to produce CO and OH ^- . As shown in formula (2) or formula (3), OH is formed ^- Part of (C) and CO ₂ React to form bicarbonate ions (HCO) ₃ ^- ) And carbonate ion (CO) ₃ ^2- ). OH by the voltage between the reduction electrode 23 and the oxidation electrode 27 ^- 、HCO ₃ ^- And CO ₃ ^2- And a part of the electrolyte (2) moves into the electrolyte (2) 25 via the separator (29).

2CO ₂ +2H ₂ O+4e ^- →2CO+4OH ^- …(1)

2CO ₂ +2OH ^- →2HCO ₃ ^- …(2)

2HCO ₃ ^- +2OH ^- →CO ₃ ^2- +H ₂ O…(3)

In the vicinity of the oxidation electrode 27 connected to the 2 nd electrolyte 25, water (H ₂ O) oxidation reaction. H contained in the 2 nd electrolyte 25 occurs as shown in the following formula (4) ₂ Oxidation of O, electron disappearance, oxygen generation (O ₂ ) And hydrogen ions (H) ⁺ )。

2H ₂ O→4H ⁺ +O ₂ +4e ^- …(4)

As shown in the following formulas (5) to (7), hydrogen ions (H) are generated ⁺ ) And hydroxide ions (OH) that have moved through the membrane 29 ^- ) Bicarbonate ion (HCO) ₃ ^- ) Carbonate ion (CO) ₃ ^2- ) Part of the reaction to form H ₂ O and CO ₂ 。

2H ⁺ +CO ₃ ^2- →H ₂ O+CO ₂ …(5)

2H ⁺ +2HCO ₃ ^- →2H ₂ O+2CO ₂ …(6)

H ⁺ +OH ^- →H ₂ O…(7)

In the above, it is explained that the reduction electrode 23 is based on OH ^- But may be based on H in the oxidation electrode 27 as described below ⁺ Is used for generating and moving. When a voltage equal to or higher than the electrolysis voltage is applied between the reduction electrode 23 and the oxidation electrode 27, water (H) is generated in the vicinity of the oxidation electrode 27 in contact with the 2 nd electrolyte 25 ₂ O) oxidation reaction. H contained in the 2 nd electrolyte 25 occurs as shown in the following formula (8) ₂ Oxidation of OThe electrons disappear after the reaction, and oxygen (O) is generated ₂ ) And hydrogen ions (H) ⁺ ). Generated hydrogen ions (H) ⁺ ) Part of (2) moves into the 1 st electrolyte 21 through the separator 29.

2H ₂ O→4H ⁺ +O ₂ +4e ^- …(8)

Hydrogen ions (H) generated on the oxidation electrode 27 side ⁺ ) Reaches the vicinity of the reduction electrode 23, and electrons (e) are supplied from the power supply to the reduction electrode 23 ^- ) When carbon dioxide (CO) is generated ₂ ) Is a reduction reaction of (a). As shown in the following formula (9), hydrogen ions (H) moving to the vicinity of the reduction electrode 23 ⁺ ) And electrons supplied from a power source (e ^- ) CO contained in the 1 st electrolyte 21 ₂ Is reduced to produce carbon monoxide (CO).

2CO ₂ +4H ⁺ +4e ^- →2CO+2H ₂ O…(9)

The data storage unit 11 shown in fig. 1 is configured to: the data from the supply power characteristic acquisition unit 4, the input gas characteristic acquisition unit 6, the electrical characteristic acquisition unit 7, the output gas characteristic acquisition unit 8, and the temperature acquisition unit 10 are stored. The data processing unit 12 is configured to: the data are transmitted from the data storage unit 11, and the state of the electrolytic cell 2A is determined by processing the data. That is, the data processing unit 12 calculates the equivalent circuit model and the equivalent circuit parameter of the electrolytic cell 2A based on the processing result of each data, and determines the state of the electrolytic cell 2A based on the calculation result of the equivalent circuit model and the equivalent circuit parameter. Specific examples of the state determination of the electrolytic cell 2A include: the estimated degradation site of the electrolytic cell 2A and the like may be: the degree of degradation of the degraded portion is calculated.

Next, a method for calculating an equivalent circuit model and equivalent circuit parameters, a method for estimating a degradation site, and a method for calculating a degradation degree by the data processing unit 12 will be described with reference to fig. 4. FIG. 4 is CO ₂ An example of an equivalent circuit model of the electrolytic cell 2A. To pass through CO ₂ Is subjected to reduction reaction to form CO ₂ Reduction product (C) _x H _y O _z ) The case of (2) is described as an example. In the case of CO generation, C will be _x H _y O _z The substitution is only needed to be CO. In the cathode portion 24 of the equivalent circuit model, C _x H _y O _z H of the formation part and side reaction ₂ The generating units are connected in parallel, and the cathode resistors are connected in series. The diaphragm portion 29 has a diaphragm resistance. In the anode portion 28, O ₂ The generating section is connected in series with the anode resistor. The cathode portion 24, the separator portion 29, and the anode portion 28 are connected in series.

C _x H _y O _z Generating part, H ₂ Generating part and O ₂ Current density J of generating section _A For example, the electrolytic formula is represented by Tafel (Tafel) of the following formula (10).

[ number 1]

In the subscript A, C is generated _x H _y O _z Time marked as C _x H _y O _z ER(C _x H _y O _z Reaction) in the production of H ₂ Time is denoted as HER (hydrogen evolution reaction), when O is generated ₂ Time is reported as OER (oxygen evolution reaction). J (J) _0,A Representing the exchange current density, B _A Representing Tafil slope, η _A Representing an overvoltage. J is described as _0,A And B _A Is a parameter that varies according to the temperature T. Cathode resistance is represented by R _cathode Expressed, the diaphragm resistance is represented by R _membrane The anode resistance is represented by R _anode And (3) representing. They are parameters that vary according to temperature.

At the time of CO introduction ₂ CO of electrolysis unit 2A ₂ When the flow rate is sufficiently large, the formula (10) may be used. In consideration of CO ₂ Small flow, C _x H _y O _z Is subjected to CO ₂ Restriction of flow, i.e. in the presence of limits, C _x H _y O _z Current density J of generating section _CxHyOz _ER _include _low _CO2 As shown in the following formula (11), the method is represented by Tafil formula (10) and C _x H _y O _z Generating limiting electricityDensity of flow J _CxHyOz _ER,L As a variable. Here, f ₁ Representing a function.

[ number 2]

J _{CxHyOz ER include low CO2} ＝f ₁ (J _{CxHyOz ER} ，J _{CxHyOz ER，L} )...(11)

As shown in the formulas (2), (3), (5) and (6), CO at the cathode side ₂ Is converted into HCO ₃ ^- 、CO ₃ ^2- And moves to the anode side and is converted into CO again ₂ . If the CO moved from the cathode side to the anode side by the ion movement ₂ Flow is expressed as flow _CO2 _from _cathode _to _anode Then when available for generating C _x H _y O _z CO of (c) ₂ CO moving from cathode side to anode side in the flow rate ₂ Flow is reduced, thus C _x H _y O _z Generating limiting current density J _CxHyOz _ER,L As shown in the following formula (12), the variable includes CO introduced into the cathode portion ₂ Flow rate flow _CO2 _{cathode，input} And CO moving from cathode side to anode side ₂ Flow rate flow _CO2 _from _cathode _to _anode Is represented by a relational expression of (2). Here, f ₂ Representing a function.

[ number 3]

J _CxHyOzER，L ＝f ₂ (flow _{cathode，input} ，flow _{CO2 from cathode to anode} )...(12)

The current I flowing through the electrolysis cell shown in FIG. 4 _cell And is used for generating C _x H _y O _z Is greater than the current J of (1) _CxHyOz _ER _include _low _CO2 (may also be J _CxHyOz _ER ) And for generating H ₂ Is greater than the current J of (1) _HER The following relationship is present.

[ number 4]

I _cell ＝(J _{CxHyOz ER include low CO2} +J _HER )A _electrode ...(13)

Here, A _electrode The electrode area of the cathode or the anode is usually the same as the electrode area of the anode. In addition, cell voltage V _cell As shown below.

[ number 5]

Here, E ⁰ _OER And E is ⁰ _CxHyOz Respectively generate O ₂ And generating C _x H _y O _z Is varied according to the temperature. R is R _cathode Is cathode resistance, R _membrane For diaphragm resistance, R _anode Is the anode resistance.

Next, fig. 5 shows equivalent circuit parameters of the equivalent circuit model shown in fig. 4. Using the supply power characteristics, the input gas characteristics, and CO collected before the main operation ₂ Any one or more of the electrical characteristics, the output gas characteristics, and the temperature of the electrolysis cell are calculated by fitting. In the fitting, table calculation software or a circuit simulator may be used. In the normal operation, the equivalent circuit parameters are periodically calculated using the data transferred from the data storage unit 11 to the data processing unit 12, and the degradation site can be estimated by comparing the equivalent circuit parameters before the normal operation or at the time of design with the equivalent circuit parameters during the normal operation.

Further, the degradation degree D can be calculated for each equivalent circuit parameter based on the following equation (15).

[ number 6]

D= [ (equivalent circuit parameter in normal operation) - (equivalent circuit parameter before normal operation or design) ]/(equivalent circuit parameter before normal operation or design) … … (15)

By setting the criterion for the degradation degree D, it is possible to determine whether to stop the operation, refresh the operation, or maintain the operation. The time course of the degradation degree D can be expressed by, for example, a regression equation of a 1 st order function shown in the following equation (16).

[ number 7]

D(t)＝at+b……(16)

Here, a is the variation of D per unit time, and b is the intercept. By using the expression (16), the remaining time until the determination criterion can be estimated. The approximation formula of the time shift of the degradation degree D is not limited to the formula (16), and may be a quadratic formula or a polynomial formula. Further, the remaining time until the determination criterion may be estimated using machine learning based on the equivalent circuit parameters and the degradation degree database of the other electrolytic cells stored in the data processing unit 12.

(embodiment 2)

Next, the structure and degradation detection system of the carbon dioxide electrolysis apparatus according to embodiment 2 will be described with reference to fig. 1 and 6. The degradation detection system of the carbon dioxide electrolysis device 1 according to embodiment 2 is the same as that of embodiment 1. In the carbon dioxide electrolysis apparatus 1 of embodiment 2, CO-containing gas is contained in the electrolysis unit 2B ₂ Is also sometimes referred to as CO ₂ Gas) and the reduction electrode 23, and the aqueous 2 nd electrolyte (anode solution) and the oxidation electrode 27-unlike the electrolytic cell 2A of embodiment 1. The electrolytic cell 2B of the carbon dioxide electrolysis apparatus 1 of embodiment 2 is different from the electrolytic cell 2A of embodiment 1 in structure. The specific constitution of each part other than these, for example, the reducing electrode 23, the oxidizing electrode 27, the separator 29, the 2 nd electrolyte, and the like is the same as that of embodiment 1.

As shown in fig. 9, the electrolytic cell 2B of embodiment 2 includes: reduction electrode 23, oxidation electrode 27, separator 29, and CO-containing electrode ₂ A 1 st flow path 36 through which the 2 nd electrolyte (anode solution) containing water flows, a 2 nd flow path 37 through which the 1 st collector plate 38 electrically connected to the reduction electrode 23, and a 2 nd collector plate 39 electrically connected to the oxidation electrode 27. The reduction electrode 23 and the 1 st flow path 31 facing it constitute a cathode portion (reduction electrode chamber) 24. The oxidation electrode 27 and the 2 nd flow path 32 facing it constitute an anode portion (oxidation electrode chamber) 28.

In embodiment 2, the catalyst may be substituted for CO-containing catalyst ₂ To contain CO by gas of (2) ₂ The 1 st electrolyte of (2) flows through the 1 st flow path 36. In addition, a flow path, not shown, may be provided between the reduction electrode 23 and the separator 29 To contain CO ₂ The gas of (2) flows through the 1 st flow path 36, and the 1 st electrolyte flows through the flow path between the reduction electrode 23 and the separator 29. The 1 st electrolyte used in this case may contain CO ₂ CO may not be contained ₂ . Further, a gas containing water vapor may be used instead of the 2 nd electrolyte containing water.

During operation of the electrolysis unit 2B, CO may be present ₂ The reduced product of (2) or the component of the 2 nd electrolyte moving to the reduction electrode 23 side solidifies and precipitates in the 1 st flow path 36, which may cause the 1 st flow path 36 to be blocked and may contain CO ₂ The supply of the gas is stopped. Therefore, in order to suppress the formation of precipitates, it is preferable to use a catalyst containing CO ₂ Moisture is present in the gas of (a). On the other hand, when CO is contained ₂ If the amount of water in the gas is too large, a large amount of water is supplied to the catalyst surface in the reduction electrode 23, and hydrogen is easily generated, which is not preferable. Thus, as a CO-containing agent ₂ The relative humidity of the gas is preferably 20 to 90%, more preferably 30 to 70%.

The 1 st flow path 36 is connected to supply of CO-containing gas ₂ A 1 st supply passage 31 for gas and a 1 st discharge passage 33 for discharging the generated gas. The 2 nd supply channel 34 and the 2 nd discharge channel 35 for supplying the aqueous electrolyte are connected to the 2 nd channel 37. The 1 st flow path 36 is arranged to face the reduction electrode 23. The 1 st flow path 36 is connected to the 1 st supply flow path 31, and CO-containing gas is supplied from the 1 st supply flow path 31 ₂ Is a gas of (a) a gas of (b). The structure is as follows: when CO ₂ The gas and the 1 st electrolyte (cathode solution) contact the reduction electrode 23 while flowing in the 1 st flow path 36. CO passing through the reduction electrode 23 ₂ CO in gas and cathode solutions ₂ Is reduced by the reduction electrode 23. Containing CO ₂ The gas or solution of the reduction reaction product of (2) is discharged from the 1 st discharge flow path 33.

The 2 nd flow path 37 is arranged to face the oxidation electrode 27. A solution tank or the like, not shown, is connected to the 2 nd flow path 37, and is configured to: the anode solution contacts the oxidation electrode 27 while flowing in the 2 nd flow path 37. H in the anode solution passing through the oxidation electrode 27 ₂ O is oxidized by the oxidation electrode 27.

In the degradation detection system of the carbon dioxide gas electrolysis device according to embodiment 2, the equivalent circuit parameters shown in fig. 5 can be calculated by fitting using the equivalent circuit model shown in fig. 4, as in embodiment 1. In the normal operation, the equivalent circuit parameters are periodically calculated using the data transferred from the data storage unit 11 to the data processing unit 12, and the degradation site can be estimated by comparing the equivalent circuit parameters before the normal operation or at the time of design with the equivalent circuit parameters during the normal operation. Further, by setting a criterion for the degradation degree D, it is possible to determine that the operation is stopped, that the refresh operation is performed, or that the maintenance is performed.

(embodiment 3)

The structure and degradation detection system of the carbon dioxide electrolysis apparatus according to embodiment 3 will be described with reference to fig. 1, 6 and 7. The carbon dioxide electrolysis apparatus according to embodiment 3 includes two H-generating units ₂ Is an equivalent circuit of (a). The electrolytic device according to embodiment 3 is provided with the same configuration and degradation detection system as those of the electrolytic device according to embodiment 1 or embodiment 2. The electrolytic cell of embodiment 3 has the same structure as that of embodiment 2, for example. However, the equivalent circuit model used in the data processing unit of embodiment 3 is different from that of embodiment 1. An equivalent circuit model of the data processing unit 12 according to embodiment 3 will be described with reference to fig. 7.

Fig. 7 is an example of an equivalent circuit model of the carbon dioxide electrolysis unit. Here, by CO ₂ Reduction reaction to form C _x H _y O _z The case of (2) is described as an example. In the case of CO generation, C will be _x H _y O _z The substitution is only needed to be CO. In the cathode part of the equivalent circuit model, C _x H _y O _z Production unit and two side reactions H ₂ The generating units are connected in parallel, and the cathode resistors are connected in series. H ₂ The generating part has H suitable for low current density region ₂ Generating part (low current density) and H suitable for high current density region ₂ Generating parts (high current density) connected in parallel. The diaphragm portion is a diaphragm resistor. In the anode portion, O ₂ The generating section and the anode resistor are connected in series. The cathode portion, the separator portion, and the anode portion are connected in series.

In the parameters of the Taffel formula of formula (10), when subscript A is H ₂ When generating a portion (low current density), HER is used _low When subscript A is H ₂ When generating a portion (high current density), HER is used _high . Fig. 8 shows equivalent circuit parameters of the equivalent circuit model of embodiment 3. These equivalent circuit parameters are calculated by fitting using the supply power characteristics, the input gas characteristics, the electrical characteristics of the electrolysis cell, the output gas characteristics, and the temperature collected before the main operation. In the fitting, table calculation software, a circuit simulator may be used. In the main operation (this operation), the equivalent circuit parameters are periodically calculated using the data transferred from the data storage unit 11 to the data processing unit 12, and the degradation site can be estimated by comparing the equivalent circuit parameters before the main operation or at the time of design with the equivalent circuit parameters during the main operation. Further, by setting a criterion for the degradation degree D, it is possible to determine that the operation is stopped, that the refresh operation is performed, or that the maintenance is performed.

(embodiment 4)

The structure of the electrolytic device and the degradation detection system according to embodiment 4 will be described with reference to fig. 1, 2, 6, and 9. The electrolyzer of embodiment 4 is a electrolyzer for nitrogen (N) ₂ ) Electrolysis and reduction are carried out to produce ammonia (NH) ₃ ) Is provided. However, the electrolytic device according to embodiment 4 differs in the electrolyte and the electrolytic product, but the device configuration itself is the same as the electrolytic device 1 according to embodiment 1 shown in fig. 1. Further, in the electrolytic device according to embodiment 4, the electrolytic cell is also similar to the electrolytic cell 2A shown in fig. 2. In the electrolytic device according to embodiment 4, an electrolytic cell having the same configuration as the electrolytic cell 2B shown in fig. 6 may be used.

In embodiment 4, the substance reduced at the cathode of the electrolytic cell shown in FIG. 2 is nitrogen (N) ₂ ) The case and equivalent circuit model of (2) are different from those of embodiment 1. The 1 st electrolyte contained in the cathode part contains N ₂ As an electrolyte. Alternatively, in the electrolytic cell shown in FIG. 6, N may be ₂ Gas is supplied as an electrolyte to the cathode portion.

At the time of returning toRaw nitrogen (N) ₂ ) In the case of the 1 st electrolyte, the 1 st electrolyte preferably contains N which is different from the electrochemical reaction ₂ An ammonia generating catalyst for generating ammonia by reduction and a reducing agent. As the reducing agent, a halide (II) of a lanthanoid or the like is used. The lanthanoid elements include: lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), and the like, with Sm being preferred. Examples of the halogen include: chlorine (Cl), bromine (Br), iodine (I), of which iodine is preferred. As the halide (II) of the lanthanoid element, samarium (II) iodide (SmI) is more preferable ₂ )。

The ammonia production catalyst is a catalyst that promotes the production of ammonia from nitrogen in the presence of a reducing agent, and for example, molybdenum complexes are used, but the catalyst is not limited thereto. Examples of the ammonia production catalyst include: molybdenum complexes shown in the following (A) to (D).

As example 1, there is given: molybdenum complexes having an N, N-bis (dialkylphosphinomethyl) dihydrobenzimidazole subunit (wherein 2 alkyl groups may be the same or different and at least 1 hydrogen atom of the benzene ring may be substituted with an alkyl group, an alkoxy group or a halogen atom) as (a) PCP ligands.

As example 2, there is given: molybdenum complexes having 2, 6-bis (dialkylphosphinomethyl) pyridine (wherein 2 alkyl groups may be the same or different, and at least 1 hydrogen atom of the pyridine ring may be substituted with an alkyl group, an alkoxy group or a halogen atom) as (B) PNP ligands.

As example 3, there is given: molybdenum complexes having bis (dialkylphosphinomethyl) arylphosphines (wherein 2 alkyl groups may be the same or different) as (C) PPP ligands.

As example 4, there is given: (D) trans-Mo (N) ₂ ) ₂ (R1R2R3P) ₄ (wherein R1, R2 and R3 may be the same or different and are alkyl or aryl groups, and 2R 3 may be linked to each other to form an alkylene chain).

The alkyl group in the molybdenum complex may be, for example, a linear or branched alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, or structural isomers thereof, or a cyclic alkyl group such as a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, or a cyclohexyl group. The carbon number of the alkyl group is preferably 1 to 12, more preferably 1 to 6. The alkoxy group may be, for example, a linear or branched alkoxy group such as methoxy group, ethoxy group, propoxy group, butoxy group, pentoxy group, hexoxy group, or structural isomers thereof, or a cyclic alkoxy group such as cyclopropoxy group, cyclobutoxy group, cyclopentoxy group, cyclohexyloxy group, or the like. The carbon number of the alkoxy group is preferably 1 to 12, more preferably 1 to 6. Examples of the halogen atom include: fluorine atom, chlorine atom, bromine atom, iodine atom, etc.

The amount of the ammonia-generating catalyst to be used may be appropriately selected within the range of 0.00001 to 0.1mol/L equivalent to the electrolyte, and is preferably 0.0001 to 0.05mol/L equivalent, and more preferably 0.0005 to 0.01mol/L equivalent.

Next, description will be made on the case where the number of the N ₂ The operation of the electrolysis device when ammonia is produced by the reduction reaction. When a voltage equal to or higher than the electrolysis voltage is applied between the reduction electrode (cathode) and the oxidation electrode (anode), water (H) in the 2 nd electrolyte is electrochemically generated at the oxidation electrode ₂ O) or hydroxide ions (OH) ^- ) Is a reaction of oxidation. For example, when the hydrogen ion concentration of the 2 nd electrolyte is 7 or less (pH. Ltoreq.7), H is based on the following formula (17) ₂ O is oxidized to produce O ₂ And H ⁺ . In addition, when the hydrogen ion concentration of the 2 nd electrolyte is more than 7 (pH > 7), OH is based on the following formula (18) ^- Is oxidized to produce O ₂ And H ₂ O。

3H ₂ O→3/2O ₂ +6H ⁺ +6e ^- ……(17)

6OH ^- →3/2O ₂ +3H ₂ O+6e ^- ……(18)

In the 1 st housing portion (1 st electrolytic cell) 22, unlike the electrochemical reaction, nitrogen (N) in the 1 st electrolytic solution ₂ ) Is reduced by an ammonia generating catalyst and a reducing agent to generate ammonia (NH) ₃ ). In use of, e.g., smI ₂ In the case of the reducing agent, N in the 1 st electrolyte ₂ Is reduced to produce ammonia (NH) according to the following formula (19) ₃ )。

N ₂ +6SmI ₂ +6H ₂ O→2NH ₃ +6SmI ₂ (OH)……(19)

As shown in the above formula (19), NH is due to ₃ Is used as a reducing agent for SmI ₂ Oxidized, and in this state, the function as a reducing agent is impaired. That is, N in the 1 st electrolyte is generated in the 1 st electrolytic cell having no reduction electrode for electrochemically generating the reduction reaction ₂ In the case of the reduction reaction of (2), the amount of the reducing agent initially charged in the 1 st electrolytic cell is N ₂ Is consumed in the reduction reaction of (a), and as a result, N ₂ Is stopped, NH ₃ Ending the generation of (2). In contrast, in the electrolytic device according to the embodiment, since the reducing electrode that causes the electrochemical reduction reaction is disposed in the 1 st electrolytic cell, the reducing agent that oxidizes the reducing electrode, that is, the SmI, can be obtained by the following formula (20) ₂ (OH) is reduced and regenerated. Therefore, N can be continued continuously ₂ Is a reduction reaction of (a). In order to promote the reaction with the ammonia-generating catalyst, the amount of the reducing agent to be used is preferably 0.01 to 2mol/L, more preferably 0.1 to 1mol/L, relative to the 1 st electrolyte.

6SmI ₂ (OH)+6e ^- →6SmI ₂ +6OH ^- ……(20)

FIG. 9 is a diagram of the use of SmI ₂ NH generation as a reducing agent ₃ Is an equivalent circuit model of the electrolysis cell. As shown in the above formula (20), smI is prepared ₂ (OH) is electrochemically regenerated to SmI ₂ . Therefore, in the cathode portion of the equivalent circuit model, smI ₂ H of regeneration part and side reaction ₂ The generating units are connected in parallel. SmI (smoothie) ₂ The current density of the regeneration unit is represented by the tafel equation of the above equation (10). SmI is described in subscript A of formula (10) ₂ RR(SmI ₂ Regeneration reaction).

(embodiment 5)

A method of designing the electrolysis apparatus and the electrolysis system according to embodiment 5 will be described with reference to fig. 10. The electrolytic system of embodiment 5 is the same as that of embodiments 1 to 2. In the method for designing an electrolytic system according to embodiment 5, the system design is performed using the equivalent circuit models and the equivalent circuit parameters according to embodiments 1 to 4.

First, an electrolysis cell (reference electrolysis cell) is operated as a reference, and supply power characteristics, input gas characteristics, electric characteristics, output gas characteristics, and temperature characteristics are acquired, and actual measurement data is stored in a data storage unit (S1). When acquiring the measured data, it is preferable to perform an aging operation in which a current is supplied in advance in order to stabilize the cell characteristics. The longer the aging operation time, the more stable the characteristics of the electrolytic cell, and therefore, it is preferably 1 hour or more, more preferably 2 hours or more. In the data processing unit, candidates of an equivalent circuit model of the electrolysis cell are selected (S2).

The data processing unit calculates parameters of the equivalent circuit model by fitting so that the square error between the actual measurement data of the reference electrolytic cell at S1 and the analog data of the equivalent circuit model is reduced (S3). A criterion of square error between the measured data and the analog data of the equivalent circuit model is preset, and when the square error is larger than the criterion, the model is replaced with a candidate of the equivalent circuit model of S2. When the square error is smaller than the determination reference, it is determined that the equivalent circuit model of S2 is appropriate (validity, certainty) (S4). The electrolytic system is designed using the equivalent circuit model and the parameters of the equivalent circuit model determined to be appropriate (S5).

Examples

Next, examples and evaluation results thereof are described.

Example 1

A carbon dioxide electrolysis cell having the structure shown in fig. 6 was manufactured. The carbon dioxide electrolysis unit is operated by the degradation detection system of the electrolysis apparatus shown in fig. 1. As the reduction electrode used in the carbon dioxide electrolysis unit, a reduction electrode in which carbon particles carrying gold nanoparticles are coated on carbon paper is used. The average particle diameter of the gold nanoparticles was 2nm, and the loading was 10 mass%. As the oxidation electrode, irO coated on Ti mesh was used ₂ An electrode for nanoparticles. As the separator, an anion exchange membrane was used. The electrode area of the reduction electrode and the oxidation electrode is 16cm ² Is cut and used in a mode of being used. Like the carbon dioxide electrolysis cell having the structure shown in FIG. 6, the 1 st collector plate, the 1 st flow path, and the third flow path are laminated in this order from the left side,The carbon dioxide electrolysis unit is formed by sandwiching a reduction electrode, a separator, an oxidation electrode, a 2 nd flow path, and a 2 nd collector plate between an insulating plate, a cooling water path, and a support plate, not shown. In order to monitor the reduction electrode potential and the oxidation electrode potential easily, a Pt foil, not shown, is brought into contact with the separator on the reduction electrode side as a reference electrode.

CO is introduced into the 1 st flow path of the carbon dioxide electrolysis unit at a flow rate of 80sccm by using a gas/electrolyte control unit ₂ 0.1M KHCO was introduced into the 2 nd channel at a flow rate of 10mL/min ₃ And (3) an electrolyte. The carbon dioxide electrolysis unit uses a temperature control unit and a temperature acquisition unit, and a heater and a cooling water path, not shown, are brought into close contact with the carbon dioxide electrolysis unit to control the temperature to 40 ℃. As the supply power control unit, the supply power acquisition unit, and the electric characteristic acquisition unit, a potentiostat/galvanostat in which these functions are integrated is used. As the output gas obtaining unit, a volumetric flowmeter or a gas chromatograph is used.

The current was allowed to flow through the carbon dioxide electrolysis unit to obtain: the current density dependence of the supply power characteristics (supplied current, voltage), the input gas characteristics (gas flow rate to the cathode), the electrolysis cell temperature, the electrical characteristics (electrolysis cell current, electrolysis cell voltage, cathode potential, anode potential, electrolysis cell resistance), the output gas characteristics (gas flow rates to be output from the cathode and anode, various gas concentrations). In the cathode, CO ₂ CO is generated by reduction reaction, H is generated by side reaction ₂ . In the anode, O is formed by oxidation reaction of water ₂ . Due to H ₂ The behavior of the generation reaction was different between the low current density region and the high current density region, and the CO generation unit and the two H shown in fig. 7 were used as equivalent circuit models ₂ The generating unit is connected in parallel.

Based on the gas flow rate output from the cathode, and CO and H ₂ Calculates the partial current density of CO (current density contributing to CO generation) and H ₂ Partial current density (helping to generate H ₂ As shown in fig. 11 and 12) to make the CO partial current density J _CO 、H ₂ Partial current density J _H2 Electrolysis cell voltage V _cell Cathode potential V _cm Anode potential V _am And determining equivalent circuit parameters in a mode of reducing errors of the measured data and the analog data. As shown in fig. 13, 14 and 15, CO faraday efficiency (FE _CO )、H ₂ Faraday Efficiency (FE) _H2 ) Cathode output gas (CO, H) ₂ And CO ₂ ) Anode output gas (O) ₂ And CO ₂ ) The simulation data of (2) reproduce the measured data well. Therefore, by investigating the change in the equivalent circuit parameter during operation using the equivalent circuit model of fig. 7, degradation can be detected.

The configurations of the above embodiments may be applied in combination, or some of them may be replaced. Although several embodiments of the present invention are described herein, these embodiments are presented by way of example only and are not intended to limit the scope of the invention. These embodiments may be implemented in various other modes, and various omissions, substitutions, changes, and the like may be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and spirit of the present invention, and are also included in the invention described in the claims and their equivalents.

Claims

1. An electrolysis apparatus comprising:

2. The electrolytic device according to claim 1, wherein the data processing section is configured such that: and performing degradation detection based on information of the equivalent circuit parameters by calculating equivalent circuit parameters by fitting using simulation data of an equivalent circuit model of the electrolysis cell and at least 1 kind of actual measurement data from the supply power characteristic acquisition unit, the input gas characteristic acquisition unit, the electrical characteristic acquisition unit, the output gas characteristic acquisition unit, and the temperature acquisition unit.

3. The electrolytic device according to claim 2, wherein the data processing section is configured such that: the degradation site is estimated by comparing the equivalent circuit parameter before the main operation or at the time of design with the equivalent circuit parameter during the main operation.

4. The electrolytic device according to claim 3, wherein the data processing section is configured such that: determining a degree of deterioration of the equivalent circuit parameter, setting a criterion for the degree of deterioration, determining that the operation of the electrolytic cell is stopped,

the degree of degradation of the equivalent circuit parameter is represented by "[ (equivalent circuit parameter in the normal operation) - (equivalent circuit parameter before normal operation or at the time of design) ]/(equivalent circuit parameter before normal operation or at the time of design)".

5. The electrolytic device according to any one of claims 2 to 4, wherein the data processing section is configured such that:

the equivalent circuit model includes:

a cathode section in which a carbon dioxide reducing substance generating section and a hydrogen generating section are connected in parallel and a series resistor is connected in series,

a diaphragm portion, and

an anode section connecting the oxygen generating section and the series resistor in series;

and an equivalent circuit in which the cathode portion, the separator portion, and the anode portion are connected in series is calculated.

6. The electrolytic device according to claim 5, wherein the data processing section is configured such that: the current density of the carbon dioxide reducing substance generating section of the equivalent circuit model is calculated based on a relational expression including a current density expressed by a tafel formula and a generation limit current density of the carbon dioxide reducing substance as variables.

7. The electrolytic device according to claim 6, wherein the data processing section is configured such that: the generation limiting current density of the carbon dioxide reducing substance is calculated based on a relational expression including, as variables, the flow rate of the reduced substance introduced into the cathode portion and the flow rate of the reduced substance moving from the cathode portion to the anode portion.

8. The electrolysis apparatus according to claim 1, wherein the data processing section is provided in the cloud, and the state of the electrolysis cell is remotely determined.

9. The electrolysis apparatus according to any one of claims 1 to 8, wherein the electrolysis unit is configured such that: carbon dioxide is supplied as the reduced material to produce a carbon compound, or nitrogen is supplied as the reduced material to produce ammonia.

10. An electrolysis process comprising the steps of:

a step of supplying a gas or a liquid containing the reduced material to the cathode portion of an electrolysis unit provided with a cathode portion provided with a reduction electrode, an anode portion provided with an oxidation electrode, and a separator provided between the cathode portion and the anode portion, and simultaneously supplying a liquid containing the oxidized material to the anode portion to operate the electrolysis unit,

a step of acquiring, during operation of the electrolysis unit, characteristic data of electric power supplied to the electrolysis unit, characteristic data of gas input to the electrolysis unit, electric characteristic data of the electrolysis unit, characteristic data of output gas of the electrolysis unit, and temperature data of the electrolysis unit, and

And a step of processing the characteristic data of the electric power, the characteristic data of the gas, the electric characteristic data, the characteristic data of the output gas, and the temperature data, and determining the state of the electrolytic cell from an equivalent circuit model and an equivalent circuit parameter of the electrolytic cell.

11. The electrolysis method of claim 10, wherein the degradation state of the electrolysis cell is determined by the equivalent circuit model and the equivalent circuit parameters.

12. The electrolysis method according to claim 10 or 11, wherein the equivalent circuit parameters are calculated by fitting using the acquired data and simulation data of the equivalent circuit model, and degradation detection of the electrolysis cell is performed based on information of the equivalent circuit parameters.

13. The electrolytic method according to any one of claims 10 to 12, wherein the degradation site is estimated by comparing the equivalent circuit parameter before the main operation or at the time of design with the equivalent circuit parameter during the main operation.

14. The electrolytic method according to any one of claims 10 to 13, wherein a degree of deterioration represented by "[ (equivalent circuit parameter in normal operation) - (equivalent circuit parameter before normal operation or at the time of design) ]/(equivalent circuit parameter before normal operation or at the time of design)" is obtained from the equivalent circuit parameters, and a determination criterion is set for the degree of deterioration to determine the operation stop of the electrolytic cell.

15. The electrolysis method according to claim 10, wherein the step of acquiring the data of the electrolysis cell is a step of acquiring data of an electrolysis cell serving as a reference, and the electrolysis cell is designed based on the equivalent circuit model and the equivalent circuit parameters based on the data of the electrolysis cell serving as the reference.

16. The electrolytic method according to claim 15, comprising the steps of:

a step of selecting candidates of the equivalent circuit model,

a step of calculating the equivalent circuit parameters by fitting such that the square error between the data of the electrolytic cell to be the reference and the simulation data of the selected equivalent circuit model is reduced,

a step of determining the adequacy of the equivalent circuit parameter by using the square error between the data of the electrolytic cell serving as the reference and the analog data of the equivalent circuit model, and

and designing the electrolytic cell using the equivalent circuit model and the equivalent circuit parameters determined to be appropriate.