JP2017155337A - Electrochemical reactor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrochemical reactor for heightening an efficiency of conversion to a chemical substance.SOLUTION: The electrochemical reactor includes: an electrolytic liquid tank provided with a first housing part for housing a first electrolytic liquid containing carbon dioxide, and a second housing part for housing a second electrolytic liquid containing water; a reduction electrode having a first surface containing a reduction catalyst and arranged in the first housing part; an oxidation electrode having a second surface containing an oxidation catalyst and arranged in the second housing part; and a power source electrically connected to the reduction electrode and oxidation electrode, in which a region between the first surface in the first housing part and an inner wall of the first housing part is an electrolytic liquid path for conveying at least a part of the first electrolytic liquid, and, the electrolytic liquid path has a maximum part having a maximum value of an area distribution from one end to the other end on a direction of length of a section vertical to a length direction of the electrolytic liquid path and a minimum part having a minimum value of the area distribution.SELECTED DRAWING: Figure 1

Description

  The invention of an embodiment relates to an electrochemical reaction device.

  Artificial photosynthesis is a system that mimics photosynthesis in the biological world in a broad sense, and is a technology that uses sunlight to reduce carbon dioxide and turn it into resources.

  In a highly developed modern society, economic activities are carried out using fossil fuel as the main energy source. However, the consumption of fossil fuels has increased due to population growth and economic activity mainly in emerging countries, and the depletion of fossil fuels is a concern as a realistic and general problem. Effective use of limited resources and energy in modern society is to promote social development and is our duty to live in the present. Artificial photosynthesis technology is a technology that uses infinite solar energy as an energy source, converts carbon dioxide, which is a factor of global warming, and is the final form of fossil fuel after use, into fuel. Therefore, it can be said that it is the ultimate technology that produces green energy.

  In recent years, renewable energy has attracted attention. Of these, solar energy is attractive as an unlimited energy source. As a solar power generation system, there is a large-scale solar power generation system called a mega solar. Since the product of the solar power generation system is electric energy, it is essential to install a transmission system and a power storage system. On the other hand, carbon dioxide resources by artificial photosynthesis are hydrogen, methane, carbon monoxide that can be fueled from sunlight (Fischer-Tropsch synthesis with hydrogen (FT method) or hydrogen for carbon monoxide fuelization), or methanol. Synthesis reaction is required), and fuel gas and liquid such as methanol and ethylene glycol are directly generated. For this reason, if there is a transportation facility, the accompanying equipment is not necessary. The artificial photosynthesis system is suitable for a hydrogen society that is expected to be put into practical use in the future, and has the potential as a plant for producing fuel isolated in the desert.

As an electrochemical reaction device that electrochemically converts sunlight into a chemical substance, for example, an electrode having a reduction catalyst for reducing carbon dioxide (CO ₂ ) and an electrode having an oxidation catalyst for oxidizing water (H ₂ O) And a two-electrode apparatus in which these electrodes are immersed in water in which carbon dioxide is dissolved is known. At this time, each electrode is electrically connected via an electric wire or the like. In an electrode having an oxidation catalyst, H ₂ O is oxidized by light energy to obtain oxygen (1 / 2O ₂ ) and a potential is obtained. In an electrode having a reduction catalyst, formic acid (HCOOH) or the like is generated by reducing carbon dioxide by obtaining a potential from an electrode that causes an oxidation reaction. As described above, in the two-electrode system, the reduction potential of carbon dioxide is obtained by two-stage excitation, so that the conversion efficiency from sunlight to chemical energy is low.

In addition, an electrochemical reaction device using a stacked body (a silicon solar cell or the like) in which a photoelectric conversion body is sandwiched between a pair of electrodes has been studied. In the electrode on the light irradiation side, water (2H ₂ O) is oxidized by light energy to obtain oxygen (O ₂ ) and hydrogen ions (4H ⁺ ). In the opposite electrode, hydrogen (2H ₂ ) or the like is obtained as a chemical substance using the hydrogen ions (4H ⁺ ) generated in the light irradiation side electrode and the potential (e ⁻ ) generated in the photoelectric converter. An electrochemical reaction device in which silicon solar cells are stacked is also known. The electrochemical reaction device preferably has high conversion efficiency.

JP 2012-505310 A JP 2004-236616 A International Publication No. 2000/34026

  The problem to be solved by the invention of the embodiment is to increase the conversion efficiency into a chemical substance.

  An electrochemical reaction device according to an embodiment includes an electrolyte solution including a first storage part that stores a first electrolyte solution containing carbon dioxide, and a second storage part that stores a second electrolyte solution containing water. An oxidation bath having a first surface containing a reduction catalyst and immersed in a first electrolyte and a second electrode containing an oxidation catalyst and immersed in a second electrolyte An electrode, and a power source electrically connected to the reduction electrode and the oxidation electrode. A region between the first surface of the first housing portion and the inner wall of the first housing portion is an electrolyte flow path for feeding at least a part of the first electrolyte solution. The electrolyte flow path has a maximum portion having a maximum value of the area distribution from one end to the other end of the cross section perpendicular to the length direction of the electrolyte flow path, and a minimum portion having a minimum value of the area distribution. And having.

It is a cross-sectional schematic diagram which shows the structural example of an electrochemical reaction apparatus. It is an external appearance schematic diagram which shows the structural example of an electrochemical reaction apparatus. It is a figure which shows the relationship between reaction time and a current density. It is a schematic diagram for demonstrating the thickness of the diffusion layer in real space. It is a figure which shows the relationship between reaction time and the thickness of a diffused layer. It is a figure which shows the relationship between a circular pipe radius and a dimensionless speed. It is a schematic diagram which shows the structural example of a photoelectric conversion cell. It is a cross-sectional schematic diagram which shows the other structural example of an electrochemical reaction apparatus. It is a cross-sectional schematic diagram which shows the other structural example of an electrochemical reaction apparatus. It is a cross-sectional schematic diagram which shows the other structural example of an electrochemical reaction apparatus. It is a cross-sectional schematic diagram which shows the other structural example of an electrochemical reaction apparatus. It is a cross-sectional schematic diagram which shows the other structural example of an electrochemical reaction apparatus. It is a cross-sectional schematic diagram which shows the other structural example of an electrochemical reaction apparatus. It is a cross-sectional schematic diagram which shows the other structural example of an electrochemical reaction apparatus.

  Hereinafter, embodiments will be described with reference to the drawings. The drawings are schematic, and for example, the thickness and width of each component may differ from the actual component dimensions. In the embodiment, substantially the same constituent elements may be assigned the same reference numerals and description thereof may be omitted. In this specification, the term “connecting” is not limited to the case of direct connection, but may include the meaning of indirect connection.

  FIG. 1 is a schematic cross-sectional view showing a configuration example of an electrochemical reaction device. FIG. 2 is a schematic external view of the electrochemical reaction device. As shown in FIGS. 1 and 2, the electrochemical reaction device includes an electrolytic solution tank 11, a reduction electrode 31, an oxidation electrode 32, a photoelectric conversion body 33, and an ion exchange membrane 4.

  The electrolytic solution tank 11 includes a housing part 111 and a housing part 112. The shape of the electrolytic solution tank 11 is not particularly limited as long as it is a three-dimensional shape having a space portion serving as a housing portion. As a material of the electrolytic solution tank 11, for example, glass such as Pyrex glass (registered trademark), blue plate glass, and quartz glass, and organic substances such as polyimide, polyacryl, polymethyl methacrylate, and polyethylene terephthalate can be used. A polyacrylic resin is preferred because strength and durability against flow are required. Light transmittance is required on the light incident surface side of the housing portion 111 and the housing portion 112. Light passage is not required for the flow path opposite to the light irradiation surface, and a general flow path material may be used. For example, it can be arbitrarily selected from polyvinyl chloride, Teflon (registered trademark) -treated polyimide, polyacryl, general glass, ceramics, concrete material, and the like. In this case, it is preferable to select an optimum material from the viewpoint of weight, total cost, and the like.

  The accommodating part 111 accommodates the electrolyte solution 21 containing a to-be-reduced substance. The substance to be reduced is a substance that is reduced by a reduction reaction. The substance to be reduced includes carbon dioxide. Further, the substance to be reduced may contain hydrogen ions. By changing the amount of water contained in the electrolytic solution 21 and the electrolytic solution component, the reactivity can be changed, and the selectivity of the substance to be reduced and the ratio of the generated chemical substance can be changed.

  The accommodating part 112 accommodates the electrolyte solution 22 containing an oxidizable substance. The substance to be oxidized is a substance that is oxidized by an oxidation reaction. The substance to be oxidized includes, for example, water. The substance to be oxidized may contain an organic substance such as alcohol or amine, or an inorganic oxide such as iron oxide. The same material as the electrolytic solution 21 may be contained in the electrolytic solution 22. In this case, the electrolytic solution 21 and the electrolytic solution 22 may be regarded as one electrolytic solution.

  The pH of the electrolytic solution 22 is preferably higher than the pH of the electrolytic solution 21. This facilitates movement of hydrogen ions, hydroxide ions, and the like. In addition, the oxidation-reduction reaction can be effectively advanced by the liquid potential difference due to the difference in pH.

The reduction electrode 31 has a surface 311 including a reduction catalyst. The reduction electrode 31 is immersed in the electrolytic solution 21. At this time, the surface 311 is in contact with the electrolytic solution 21. The compound produced by the reduction reaction varies depending on the type of reduction catalyst. Examples of the compound produced by the reduction reaction include carbon monoxide (CO), formic acid (HCOOH), methane (CH ₄ ), methanol (CH ₃ OH), ethane (C ₂ H ₆ ), and ethylene (C ₂ H ₄ ). , Carbon compounds such as ethanol (C ₂ H ₅ OH), formaldehyde (HCHO), ethylene glycol (HOCH ₂ CH ₂ OH), or hydrogen. The compound produced by the reduction reaction may be recovered, for example, via the product flow path. At this time, the product flow path is connected to the accommodating part 111, for example. The compound produced by the reduction reaction may be recovered via another channel.

  The reduction electrode 31 may have, for example, a thin film, lattice, particle, or wire structure. The reduction catalyst does not necessarily have to be provided on the reduction electrode 31. A reduction catalyst provided other than the reduction electrode 31 may be electrically connected to the reduction electrode 31.

  The oxidation electrode 32 has a surface 321 containing an oxidation catalyst. The oxidation electrode 32 is immersed in the electrolytic solution 22. At this time, the surface 321 is in contact with the electrolytic solution 22. The compound produced by the oxidation reaction varies depending on the type of oxidation catalyst. The compound produced | generated by an oxidation reaction is a hydrogen ion, for example. The compound produced by the oxidation reaction may be recovered, for example, via the product channel. At this time, the product flow path is connected to the accommodating portion 112, for example. The compound produced by the oxidation reaction may be recovered via another channel.

  The oxidation electrode 32 may have, for example, a thin film, lattice, particle, or wire structure. The oxidation electrode 32 does not necessarily have to be provided with the oxidation catalyst. An oxidation catalyst other than the oxidation electrode 32 may be electrically connected to the oxidation electrode 32.

  In the case where the oxidation electrode 32 is laminated and immersed in the electrolytic solution 22, and the oxidation-reduction reaction is performed by irradiating the photoelectric conversion body 33 with light through the oxidation electrode 32, the oxidation electrode 32 is transparent. It is necessary to have sex. The light transmittance of the oxidation electrode 32 is, for example, preferably at least 10% or more, more preferably 30% or more, and still more preferably 80% or more of the amount of light irradiated to the oxidation electrode 32. For example, the photoelectric converter 33 may be irradiated with light via the reduction electrode 31.

  The photoelectric converter 33 has a surface 331 electrically connected to the reduction electrode 31 and a surface 332 electrically connected to the oxidation electrode 32. In FIG. 1, the surface 331 is in contact with the opposite surface of the surface 311, and the surface 332 is in contact with the opposite surface of the surface 321. In addition, between the surface 331 and the surface opposite to the surface 311 and between the surface 332 and the surface opposite to the surface 321 may be connected by a heat transfer member such as a wire having heat transfer properties, for example. When the photoelectric converter and the reduction electrode or the oxidation electrode are connected by wiring or the like, the components are separated for each function, which is advantageous in terms of the system. The photoelectric conversion body 33 may be provided outside the electrolytic solution tank 11. Note that the photoelectric conversion body 33 is not necessarily provided. Another power source may be connected to the oxidation electrode 32 and the reduction electrode 31. As the power source, a power source device such as a system power source or a storage battery, or renewable energy such as wind power, hydraulic power, or geothermal heat may be used. A cell including the reduction electrode 31, the oxidation electrode 32, and the photoelectric conversion body 33 is also referred to as a photoelectric conversion cell.

  The photoelectric conversion body 33 has a function of performing charge separation by the energy of light such as irradiated sunlight. Electrons generated by charge separation move to the reduction electrode side, and holes move to the oxidation electrode side. Thereby, the photoelectric converter 33 can generate an electromotive force. As the photoelectric converter 33, for example, a pn junction type or pin junction type photoelectric converter can be used. The photoelectric conversion body 33 may be fixed to the electrolytic solution tank 11, for example. Note that the photoelectric conversion body 33 may be formed by stacking a plurality of photoelectric conversion bodies. The sizes of the reduction electrode 31, the oxidation electrode 32, and the photoelectric conversion body 33 may be different from each other.

  The ion exchange membrane 4 is provided so as to separate the accommodating portion 111 and the accommodating portion 112. Examples of the ion exchange membrane 4 include Astom Neoceptor (registered trademark), Asahi Glass Selemion (registered trademark), Aciplex (registered trademark), Fumatech Fumasep (registered trademark), fumapem (registered trademark), DuPont's Nafion (registered trademark), which is a fluororesin obtained by sulfonating tetrafluoroethylene, LANWESS® lablane (registered trademark), IONTECH IONSEP (registered trademark), PALL Mustang (registered trademark), mega ralex (Registered trademark), Gore-Tex (registered trademark) manufactured by Gore-Tex Corporation, and the like can be used. In addition, the ion exchange membrane may be configured using a membrane having a basic skeleton of hydrocarbon, or a membrane having an amine group in anion exchange. Note that the ion exchange membrane 4 is not necessarily provided.

  A region between the surface 311 and the inner wall of the accommodating portion 111 in the accommodating portion 111 is an electrolyte flow path 51 for feeding at least a part of the electrolytic solution 21. Ions and other substances contained in the electrolytic solution 21 can move through the electrolytic solution channel 51. A region between the surface 321 and the inner wall of the accommodating portion 112 in the accommodating portion 112 is an electrolyte flow path 52 for feeding at least a part of the electrolytic solution 22. Ions and other substances contained in the electrolytic solution 22 can move through the electrolytic solution channel 52. The white arrow shown in FIG. 1 and FIG. 2 represents the direction in which the electrolyte can move. The electrolyte solution in at least one of the electrolyte solution channel 51 and the electrolyte solution channel 52 may be sent by a pump. As the pump, a tube pump, a plunger pump, a pressure pump, a piston pump, a magnet pump, a screw pump, or the like can be used.

  The electrolyte flow path 51 has a maximum portion 51a and a minimum portion 51b. An area distribution from one end to the other end of the electrolyte channel 51 (opposite part to the surface 311) on the length direction of the area of the cross section perpendicular to the length direction of the electrolyte channel 51 is shown in FIG. As shown in FIG. 1, the maximum cross-sectional area A of the local maximum 51a is larger than the maximum cross-sectional area B of the local minimum 51b. That is, the maximum portion 51a has a maximum value of the area distribution, and the minimum portion 51b has a minimum value of the area distribution. The maximum portion 51 a and the minimum portion 51 b may be provided alternately along the length direction of the electrolyte channel 51, for example.

  The electrolyte flow path 51 has the partition 6 provided so that it may overlap with the minimum part 51b. In FIG. 1, the partition wall 6 is provided between the inner wall of the housing part 111 and the surface 311 of the reduction electrode 31 and is in contact with the inner wall of the housing part 111. As a material of the partition 6, for example, general glass, polyacryl, polyimide, polymer such as vinyl chloride, or the like can be used. In addition, it is good also as the partition 6 by forming a convex part in a part of inner wall of the accommodating part 111. FIG.

  Next, an operation example of the electrochemical reaction device shown in FIGS. 1 and 2 will be described. When light enters the photoelectric converter 33, the photoelectric converter 33 generates photoexcited electrons and holes. At this time, photoexcited electrons gather at the reduction electrode 31 and holes gather at the oxidation electrode 32. Thereby, an electromotive force is generated in the photoelectric conversion body 33. As light, sunlight is preferable, but light such as a light emitting diode or an organic EL may be incident on the photoelectric converter 33.

A case where carbon monoxide is generated using an electrolytic solution containing water and carbon dioxide as the electrolytic solution 21 and the electrolytic solution 22 will be described. In the vicinity of the oxidation electrode 32, an oxidation reaction of water occurs as shown in the following formula (1), the electrons are lost, and oxygen and hydrogen ions are generated. At least one of the generated hydrogen ions moves to the storage unit 111 via the ion exchange membrane 4.
2H ₂ O → 4H ⁺ + O ₂ + 4e ⁻ (1)

In the vicinity of the reduction electrode 31, a reduction reaction of carbon dioxide occurs as in the following formula (2), and hydrogen ions react with carbon dioxide while receiving electrons, thereby generating carbon monoxide and water. Carbon monoxide is dissolved in the electrolytic solution 21 at an arbitrary ratio. In addition to carbon monoxide, hydrogen ions are generated when hydrogen ions receive electrons as shown in the following formula (3). At this time, hydrogen may be generated simultaneously with carbon monoxide.
CO ₂ + 2H ⁺ + 2e ⁻ → CO + H ₂ O (2)
2H ⁺ + 2e ⁻ → H ₂ (3)

  The energy required for the conversion from carbon dioxide to carbon monoxide is estimated to be 1.33 V from the difference in standard chemical energy. However, in the actual reduction of carbon dioxide, a voltage called an overvoltage necessary for the reaction, that is, a voltage larger than the theory is required. Overvoltage is also used in the reaction of oxidizing water to obtain oxygen, and the voltage at this time may reach several hundred mV to less than 2V, for example. Although it depends greatly on the current and voltage curve of the designed photoelectric converter, the overvoltage on the reduction side and the overvoltage on the oxidation side, and a value obtained by adding 1.33 V to the voltage obtained by adding a loss due to the solution resistance is the current voltage. This is the voltage required to operate at the point where it intersects the curve.

  As described above, the electrochemical reaction device of the present embodiment is provided only in the electrolyte solution channel on the reduction electrode side, and has a maximum portion and a minimum portion having different cross-sectional areas perpendicular to the length direction. The flow of the electrolyte in the local minimum is turbulent. The flow of the electrolyte in the maximum portion is, for example, a laminar flow, but is not limited to this.

  The difference between laminar flow and turbulent flow and the diffusion rate control derived from Fick's diffusion equation and the solubility / diffusion coefficient of carbon dioxide will be explained. Carbon dioxide contained in the electrolyte solution on the reduction side is reduced in the electrolyte solution. However, the solubility of carbon dioxide in water is known to be 0.034 mol / l at 25 ° C. The above-mentioned solubility means very low solubility as a main reactant to be reacted on a module or plant scale, and means that the concentration of the reactant is low.

  Examples of the method for transferring a substance in a solution include convection, diffusion, and ion drift. Since carbon dioxide is a neutral molecule, there is no effect of ion drift. Thus, the diffusion of carbon dioxide is governed primarily by Fick's first law and Fick's second law. The physical constants used in Fick's first law and Fick's second law are concentration and diffusion constant. The diffusion constant is physically determined, and considering that the concentration is 0.034 mol / l, which is the solubility limit, Fick's first law (Equation (1)) and Fick's law are used using the following diffusion equation: About the 2nd law (Formula (2)), it can obtain | require about the diffusion amount of carbon dioxide in aqueous solution, and a concentration gradient.

  C is the concentration, D is the diffusion constant, x is the position, J is the amount of movement of the substance, and t is the time. Assuming that the substance diffuses only in the one-dimensional direction, the flow flowing toward the surface of the electrode is positive. It is assumed that carbon dioxide reaching the electrode surface reacts quickly. From the above, it is considered that the solution of this one-dimensional diffusion equation satisfies the following relational expression (Formula (3)).

j is the reaction current density (mA / cm ² ), n is the number of reaction electrons, F is the Faraday constant (96500 c / mol), Cmax (mol / l) is the solubility limit of carbon dioxide, D is the diffusion constant of carbon dioxide ( cm ² / sec) and t is the reaction time (sec). It is known that the diffusion constant of carbon dioxide in an aqueous solution is, for example, 1.92 × 10 ⁻⁵ cm ² / sec. Assuming that carbon dioxide is reduced to carbon monoxide, the number of reaction electrons n on the surface of the electrode is a two-electron reaction, and the current density is positive.

FIG. 3 is a diagram illustrating a relationship between elapsed time and current density obtained by calculating and plotting all parameters. Note that natural convection due to molecular motion is ignored. The current density, which was 16 mA / cm ² after 1 second of the reaction time, drops rapidly, and then changes gradually and becomes almost constant in about 10 seconds. Stated from scientific knowledge, it can be said that there is sufficient carbon dioxide on the surface of the electrode for a reaction time of 1 to 2 seconds, and the surface reaction is rate-limiting. Furthermore, after several seconds, the curve becomes gentle after dropping rapidly and becomes a constant value. This can be interpreted as a process in which the state that is surface reaction-limited is a process in which carbon dioxide on the surface is completely reacted and the diffusion rate is gradually changed as the reaction proceeds. That is, if the carbon dioxide as a reactant changes to diffusion-controlled and a certain amount of time has elapsed, it means that only about 1 to ² mA / cm ² flows. This is a very big problem in electrochemical devices. In order to satisfy the solar energy conversion efficiency of 10%, it is necessary to solve the above-mentioned problem of diffusion rate control.

  Next, the thickness of the diffusion layer in real space will be described with reference to the schematic diagram of FIG. From the definition of the diffusion constant, the mass transfer rate J holds the following relationship (Formula (4)).

  In order to obtain the concentration gradient curve C (x), the diffusion layer thickness is obtained using a first-order (linear) approximation. The differential dc / dx is assumed to be a macroscopic differential. That is, for the limit dx of Δx → 0, the distance from x = 0 to X at which the concentration gradient begins is the diffusion layer thickness δ, and the saturation solubility of carbon dioxide is Cmax. Next, assuming that carbon dioxide reacts quickly on the electrode surface and there is no residual carbon dioxide on the electrode surface, Equation (4) can be expressed as follows (Equation (5)).

  The above approximate expression is significant in terms of considering a concentration boundary layer in which the concentration change of the diffusion layer starts from the electrode surface. When this equation is further solved for δ, Equation (6) is obtained.

  J is the total mass transfer amount. Next, when J in Equation (6) is considered as a mass transfer value per unit area, and the solution of the above-described one-dimensional diffusion equation (Equation (3)) is added to J, the following Equation (7) is obtained.

  Equation (7) has a square root shape with respect to the reaction time t. It is considered that the diffusion layer thickness increases with time.

FIG. 5 is a diagram obtained by actually substituting the diffusion coefficient of carbon dioxide. It can be seen that the thickness of the diffusion layer increases with the reaction time. Assuming a conversion efficiency of 10%, the surface current density to be achieved is less than about 10 mA / cm ² . In 1 to 2 seconds, it can be estimated that the reaction layer thickness is about 100 to 200 μm.

  Next, the fluid will be described. A laminar flow is a flow governed by a viscous force. For example, in an experiment using a stain, the stain flowed in the center flows straight through the center. That is, assuming that the velocity direction with the traveling direction as positive is the X direction and the direction perpendicular to the velocity direction is the Y direction, almost all velocity components are only in the X direction. On the other hand, turbulent flow is a flow governed by inertial force, and after the stain is released to the center, it causes vortices and turbulence, and finally dissolves uniformly in the fluid. This is because the turbulent flow has a velocity component in the Y direction in addition to the velocity component in the X direction, so that a turbulence in the flow, which can also be called a stirring in the fluid, occurs.

  The Navier-Stokes equation, which is the basic fluid equation, is not an equation that provides a smooth general solution at this stage. Limited to laminar flow, that is, very slow flow, solutions are obtained only at limited boundaries. One of them is the velocity distribution in laminar flow. For example, the velocity distribution of the laminar flow flowing in the circular pipe is expressed by the following equation, where R is the center of the circular pipe and r is an arbitrary point from the wall surface (r = 0).

  U represents an arbitrary speed. A is an integral constant for adjusting the entire flow velocity so as to be an average value of U. In the case of a circular pipe, A = 2. Umax is the velocity at the center of the circular pipe where the flow velocity is the highest. The power of U is 2. Therefore, this curve is a parabola where the wall surface r = 0 is 0 and the center r = R is the maximum point. In other words, it can be seen that the flow on the wall surface of the circular pipe is very slow because it is governed by viscosity, while it gradually becomes faster toward the center. Also, in the experiment using a stain, if the laminar flow velocity direction is X, the stain flowed to the center flows almost in a straight line and has almost no flow component in the Y direction perpendicular to the main flow velocity. It has been known.

  Turbulence does not have a solution to the Navier-Stokes equation, and is often derived based on empirical rules. As a formula representing a typical turbulent velocity distribution, there is a formula called a 1 / 7th power law (Formula (9)).

  U is a velocity at an arbitrary r, A is an integral constant that is adjusted so as to be an average value of U over the entire flow velocity, and Umax is a velocity at the point of the center in the circular tube where the flow velocity is the highest. In the flow velocity distribution, the time average is set to the main flow velocity direction X. In the experiment using the above-mentioned stain, the stain at the center of the tube is immediately distributed throughout the tube. That is, the turbulent flow includes many velocity components in the vertical Y direction in addition to the velocity component in the X direction. In this respect, when considering the diffusion of carbon dioxide up to the above, turbulent flow is likely to move due to turbulence due to the velocity component in the Y direction and carbon dioxide to the entire surface of the pipe due to turbulence, as opposed to laminar flow that tends to create a steady state. Conceivable.

  Flows are classified into three types, hydrodynamically laminar and turbulent, and transitional flow located between the two. The index used for classification is a dimensionless number Reynolds number (Re). The reason why the dimensionless Reynolds number can be used as an index is that the only variable in the Navier-Stokes equation, which is the basic fluid equation, is the Reynolds number. The Reynolds number is a dimensionless number, and is also known as an index indicating the similarity of mechanical flow even for flows with different flow velocities. The Reynolds number (Re) is expressed by the following formula (Formula (10)).

  Re is a dimensionless number, d is the density of the solution, v is the flow velocity, L is the representative length, and μ is the viscosity of the solution. There are various units for density, flow rate, and viscosity, but in order to calculate the Reynolds number, the unit must be dimensionless (so that the units of weight, time, length, and mass are erased). , Need to adjust the order and calculate. Although it depends on the shape of the flow path, generally, the flow when the Reynolds number is 2300 or less is a laminar flow, the flow when it is 3000 or more is turbulent, and the flow when it is more than 2300 and less than 3000 Current.

  The representative length L is a length representing the flow path of the fluid, and is generally determined conventionally. For example, in the case of a flow in a circular pipe, it is represented by the diameter of the circular pipe, in the case of a parallel plate, it is represented by twice the distance between the parallel flat plates, and in the case of a flow in a pipe having a rectangular cross-sectional area, The shape is converted into a shape corresponding to a circle, and is represented by the corresponding tube diameter after the conversion. In this embodiment, these conventions are followed.

  The velocity distribution in the laminar flow and the velocity distribution in the turbulent circular pipe is a dimensionless flow velocity obtained by dividing the general flow velocity U by the average flow velocity Uaverage on the vertical axis, and the horizontal axis also indicates the center of the circular tube as R, and the wall surface (r = 0 If an arbitrary point from) is r, the difference in velocity distribution between the two flows is compared as shown in FIG. FIG. 6 is a diagram showing the relationship between the radius of the circular pipe and the dimensionless velocity. In laminar flow, it shows a gentle rise from the wall surface of the tube. On the other hand, in turbulent flow, if applied to a wall surface, that is, a reaction electrode, it shows a very agile rise from the surface of the electrode, and an average flow velocity of 0.5 at a point 1/100 of the center of the circular tube from the surface of the electrode. It can be seen that the flow rate is about 0.6 times.

  Considering the above, turbulent flow is assumed when the radius of the circular tube is 1 cm in the diffusion layer thickness of 100 to 200 μm before the carbon dioxide reaches diffusion rate limiting, that is, the reaction time is a value corresponding to 1 to 2 seconds. The region of 50 to 100 μm where the velocity distribution occurs at a position of 1/100 from the wall surface of the flow path is a velocity boundary layer. It is predicted that this velocity boundary layer exists inside the diffusion layer. That is, by supplying fresh carbon dioxide by a flow field caused by turbulent flow, it is possible to prevent the diffusion layer from forming and expanding with time, and to avoid diffusion rate limiting. This shows that it is necessary to introduce a turbulent flow into the electrolyte flow path for feeding liquid.

  In order to increase reaction efficiency, it is necessary to consider not only turbulent flow but also transport rate limiting. To make it turbulent, simply increase the flow velocity. However, the discharge flow rate of the pump is limited, and in order to form a turbulent flow, a huge amount of electrolyte must be continuously sent. Although the surface of the electrode reacts, most of the mainstream does not react as it is and flows out of the apparatus. Moreover, there is an energy loss due to the pump operation and an increase in cost due to an increase in the size of the pump, which is not preferable. It is preferable that the pump size is small and the flow rate is small under conditions where the pressure is low as long as the reaction is not hindered.

  In order to make a turbulent flow, for example, the channel cross-sectional area may be reduced. Considering the use of a pump that generates a flow with the same volumetric flow rate, the flow path cross-sectional area may be reduced in order to change the flow from laminar flow to turbulent flow. As a result, turbulent flow can be formed by increasing the flow velocity and increasing the Reynolds number. For example, the distance from the surface of the electrode to the wall surface is reduced from 10 cm to 1 mm. At this time, if the flow is from a pump with the same volume flow rate, the Reynolds number increases by two digits, and if the Reynolds number exceeds 3000, turbulence occurs.

However, considering the size when considering commercialization such as planting, and considering a 1 m square device, if the solubility of dissolved carbon dioxide is considered to be 0.034 mol / l at 25 ° C., Since the amount of the electrolyte present is 1 m × 1 m × 0.001 m = 0.001 m ³ = 1 l, the absolute amount of carbon dioxide present in the housing is 0.034 mol. Moreover, if it is made to react by 10 mA / cm < ² >, all the carbon dioxide will be completely reacted in 1 second, and the transport rate of a substance will be reached easily.

  In view of the situation as described above, the problem of transport rate control can be solved by providing a part for storing the electrolyte, that is, a buffer part, in the flow path in addition to the part for reducing the cross-sectional area of the flow path. In the electrochemical reaction device of the present embodiment, the reaction is concentrated in the minimum part of the electrolyte flow path, and then the carbon dioxide consumed in the maximum part which is the pool part is supplemented in the flowing liquid. That is, the local maximum serves as a storage part for carbon dioxide, and serves to supplement the carbon dioxide in the solution rapidly consumed in the turbulent flow part.

  It is only necessary to provide a minimum portion and a maximum portion of the flow path to generate a turbulent flow only on the reduction side. This is because the reactant on the oxidation side is water of the solvent itself and does not become diffusion-limited. Therefore, the electrolyte flowing through the oxidation-side electrolyte flow path may be, for example, a laminar flow.

  In the electrochemical reaction device shown in FIGS. 1 and 2, the electrolyte flow path 52 has a minimum area distribution from one end to the other end in the length direction of a cross section perpendicular to the length direction of the electrolyte flow path 52. It is preferable that the value is larger than the minimum value in the minimum portion of the electrolyte flow path 51. The minimum value may be equal to or greater than the maximum value of the electrolyte channel 51. At this time, the flow of the electrolyte solution 22 in the electrolyte channel 52 is, for example, a laminar flow.

  If a problem occurs due to the pressure difference between the two flow paths, the oxidizing electrolyte may be pressurized. In order to generate turbulent flow in the reduction-side electrolyte flow path, the discharge pressure and discharge amount of the pump must be increased. For this purpose, it is necessary to input energy. However, in this respect, there is no need to input such extra energy in the electrolyte flow path on the oxidation side. Laminar flow may be used.

  When turbulent flow is generated for laminar flow, pressure loss tends to increase. Therefore, it is preferable that the discharge pressure has a surplus. In addition, when the electrochemical reaction device is installed on a slope or has a direct standing structure, acceleration due to gravity can also be used to assist the fluid flow.

  As another method for generating turbulent flow, for example, a packing material is randomly packed or a protruding structure is formed. All of these methods cover the reduction electrode or reduce the effective area. Unlike these methods, the turbulent flow forming method using the minimum portion in the electrochemical reaction apparatus of the present embodiment can expose all the reduction electrodes as reaction surfaces, and can minimize the loss.

  On the other hand, when the reduction electrode 31 has a porous structure, the electrolyte solution 21 may flow inside the porous body. At this time, the structure of the porous body is analyzed, and the Reynolds number can be calculated from the total flow area and the discharge flow rate. When the range in which the Reynolds number is turbulent is satisfied, it is included in the range of the electrochemical reaction device of the present embodiment. In this case, the condition of the turbulent flow is minimal inside the porous body. Therefore, the reduction electrode 31 may be in contact with the inner wall of the housing portion 111. In addition, as long as only the minimum part does not become reaction-controlled, only the minimum part that is the turbulent flow forming part may be included in the range of the electrochemical reaction device of the present embodiment.

  It is preferable that the Reynolds number of the minimal part 51b of the electrolyte flow path 51 is 3000 or more. From the viewpoint of physical destruction of the reducing electrode 31 and protection from destruction of the flow path structure, the Reynolds number of the minimal portion 51b is preferably 200000 or less, and more preferably 20000 or less.

  In order to increase the Reynolds number, it is possible to increase the flow velocity and lengthen the representative length from Equation (10). The flow rate of the electrolytic solution 21 in the minimal portion 51b is preferably 1 m / s or more and 100 m / s or less. If the flow velocity is less than 1 m / s, turbulent flow is unlikely to occur, and laminar flow or transition flow may occur instead of turbulent flow. When the flow rate is higher than 100 m / s, structural stress on the flow path, partition wall, etc. is large, and the flow path may be broken or the partition wall may be peeled off. In particular, when an ion exchange membrane exists between the electrolytes in which both electrodes are immersed, there is a possibility that the membrane may be broken.

  The representative length corresponds to the diameter of a circular tube, for example, but corresponds to the distance between the surface 311 of the reduction electrode 31 and the inner wall of the accommodating portion 111 when a minimal portion is provided. In the case of providing the minimal portion 51b, from the 1 / 100th of the radius of the circular tube, which is the value at which the velocity distribution in the vicinity of the wall surface in the turbulent flow occurs as described above, when considering a 20 cm circular tube, in the length direction in the minimal portion 51b. The maximum diameter of the vertical cross section is preferably 1 mm or more. Further, considering the reaction efficiency of carbon dioxide flowing through the electrolyte flow path 51 (the ratio of carbon dioxide to react in the carbon dioxide in the flow), the maximum diameter of the cross section perpendicular to the length direction in the minimal portion 51b is 50 mm or less. Further, it is preferably 25 mm or less. When the surface 311 comes into contact with the inner wall of the accommodating portion 111 in the electrolyte flow path 51, the reaction current density decreases. For this reason, the surface 311 may be separated from the inner wall of the accommodating portion 111.

  The aspect ratio between the local minimum portion and the local maximum portion is, for example, from the surface 311 of the reduction electrode 31 in the local maximum portion 51a to the minimum distance D2 from the surface 311 of the reduction electrode 31 in the local minimum portion 51b to the inner wall of the storage portion 111. It can be represented by the ratio of the maximum distance D1 to the inner wall. At this time, it is preferable that the aspect ratio between the minimum portion 51b and the maximum portion 51a is 10 or more and 1000 or less. When the aspect ratio is less than 10, the absolute amount of carbon dioxide pooled in the maximum portion 51a decreases, and it is difficult to supply sufficient carbon dioxide to the entire apparatus. When the aspect ratio is more than 1000, the amount of the solution necessary for the pool portion becomes enormous, and the amount of the solution necessary for the reaction rapidly increases.

  As described above, in the electrochemical reaction device of this embodiment, the maximum and minimum portions are provided in the electrolyte flow path on the reduction side, and carbon dioxide is generated on the surface of the reduction electrode by combining turbulent flow and laminar flow. Easy to supply. Therefore, the problem due to diffusion rate control can be solved.

A structural example of each component in the electrochemical reaction device will be further described. As the electrolytic solution containing water applicable to the electrolytic solution, for example, an aqueous solution containing an arbitrary electrolyte can be used. This solution is preferably an aqueous solution that promotes the oxidation reaction of water. Examples of the aqueous solution containing an electrolyte include phosphate ion (PO ₄ ²⁻ ), borate ion (BO ₃ ³⁻ ), sodium ion (Na ⁺ ), potassium ion (K ⁺ ), calcium ion (Ca ²⁺ ), lithium An aqueous solution containing ions (Li ⁺ ), cesium ions (Cs ⁺ ), magnesium ions (Mg ²⁺ ), chloride ions (Cl ⁻ ), hydrogen carbonate ions (HCO ₃ ⁻ ), and the like can be given.

  Examples of the electrolyte solution containing carbon dioxide applicable to the electrolyte include potassium bicarbonate, sodium bicarbonate, potassium carbonate, potassium phosphate, dipotassium phosphate, tripotassium phosphate, sodium phosphate, disodium phosphate, phosphorus Strong base and strong acid or weak acid salt such as trisodium acid, sodium borate, disodium borate, potassium borate, dipotassium borate, sodium sulfate, potassium sulfate, potassium hydrochloride, sodium hydrochloride, potassium nitrate, sodium nitrate, or And acids such as sulfuric acid, hydrochloric acid, boric acid, phosphoric acid, carbonic acid and nitric acid, and strong bases such as sodium hydroxide and potassium hydroxide. The electrolytic solution containing carbon dioxide may contain alcohols or ketones such as methanol, ethanol, and acetone. The electrolytic solution containing water may be the same as the electrolytic solution containing carbon dioxide. However, it is preferable that the amount of carbon dioxide absorbed in the electrolytic solution containing carbon dioxide is high. Therefore, a solution different from the electrolyte solution containing water may be used as the electrolyte solution containing carbon dioxide. The electrolytic solution containing carbon dioxide is preferably an electrolytic solution containing a carbon dioxide absorbent that reduces the reduction potential of carbon dioxide, has high ionic conductivity, and absorbs carbon dioxide.

As the above-mentioned electrolytic solution, for example, an ionic liquid or an aqueous solution thereof which is made of a salt of a cation such as imidazolium ion or pyridinium ion and an anion such as BF ₄ ⁻ or PF ₆ ⁻ and is in a liquid state in a wide temperature range. Can be used. Furthermore, examples of the other electrolyte include amine solutions such as ethanolamine, imidazole, and pyridine, or aqueous solutions thereof. Examples of amines include primary amines, secondary amines, and tertiary amines. These electrolytic solutions may have high ion conductivity, a property of absorbing carbon dioxide, and a property of reducing reduction energy.

  Examples of the primary amine include methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine and the like. The amine hydrocarbon may be substituted with alcohol, halogen or the like. Examples of the substituted amine hydrocarbon include methanolamine, ethanolamine, chloromethylamine and the like. Moreover, an unsaturated bond may exist. These hydrocarbons are the same for secondary amines and tertiary amines.

  Examples of secondary amines include dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, dimethanolamine, diethanolamine, and dipropanolamine. The substituted hydrocarbon may be different. The same applies to tertiary amines. For example, those having different hydrocarbons include methylethylamine, methylpropylamine and the like.

  Tertiary amines include trimethylamine, triethylamine, tripropylamine, tributylamine, trihexylamine, trimethanolamine, triethanolamine, tripropanolamine, tributanolamine, tripropanolamine, triexanolamine, methyldiethylamine, methyl And dipropylamine.

  As the cation of the ionic liquid, 1-ethyl-3-methylimidazolium ion, 1-methyl-3-propylimidazolium ion, 1-butyl-3-methylimidazole ion, 1-methyl-3-pentylimidazolium ion 1-hexyl-3-methylimidazolium ion and the like.

  In addition, the 2-position of the imidazolium ion may be substituted. Examples of the cation substituted at the 2-position of the imidazolium ion include 1-ethyl-2,3-dimethylimidazolium ion, 1,2-dimethyl-3-propylimidazolium ion, 1-butyl-2,3-dimethyl. Examples include imidazolium ion, 1,2-dimethyl-3-pentylimidazolium ion, 1-hexyl-2,3-dimethylimidazolium ion, and the like.

  Examples of the pyridinium ion include methylpyridinium, ethylpyridinium, propylpyridinium, butylpyridinium, pentylpyridinium, hexylpyridinium, and the like. In both the imidazolium ion and the pyridinium ion, an alkyl group may be substituted, and an unsaturated bond may exist.

As anions, fluoride ions, chloride ions, bromide ions, iodide ions, BF ₄ ⁻ , PF ₆ ⁻ , CF ₃ COO ⁻ , CF ₃ SO ₃ ⁻ , NO ₃ ⁻ , SCN ⁻ , (CF ₃ SO _2). ) ₃ C ⁻ , bis (trifluoromethoxysulfonyl) imide, bis (trifluoromethoxysulfonyl) imide, bis (perfluoroethylsulfonyl) imide and the like. It may be a zwitterion in which a cation and an anion of an ionic liquid are connected by a hydrocarbon. In addition, you may supply buffer solutions, such as a potassium phosphate solution, to the accommodating parts 111 and 112. FIG.

  FIG. 7 is a schematic cross-sectional view illustrating a structural example of a photoelectric conversion cell. The photoelectric conversion cell shown in FIG. 7 includes a conductive substrate 30, a reduction electrode 31, an oxidation electrode 32, a photoelectric conversion body 33, a light reflector 34, a metal oxide body 35, and a metal oxide body 36. Prepare.

  The conductive substrate 30 is provided in contact with the reduction electrode 31. The conductive substrate 30 may be regarded as a part of the reduction electrode. Examples of the conductive substrate 30 include a substrate containing at least one or more of Cu, Al, Ti, Ni, Fe, and Ag. For example, a stainless steel substrate containing stainless steel such as SUS may be used. Without being limited thereto, the conductive substrate 30 may be configured using a conductive resin. Moreover, you may comprise the electroconductive board | substrate 30 using semiconductor substrates, such as Si or Ge. Further, a resin film or the like may be used as the conductive substrate 30. For example, a film applicable to the ion exchange membrane 4 may be used as the conductive substrate 30.

  The conductive substrate 30 has a function as a support. The conductive substrate 30 may be provided so as to separate the housing portion 111 and the housing portion 112. By providing the conductive substrate 30, the mechanical strength of the photoelectric conversion unit 3 can be improved. Further, the conductive substrate 30 may be regarded as a part of the reduction electrode 31. Furthermore, the conductive substrate 30 is not necessarily provided.

  The reduction electrode 31 preferably includes a reduction catalyst. The reduction electrode 31 may include both a conductive material and a reduction catalyst. Examples of the reduction catalyst include materials that reduce activation energy for reducing hydrogen ions and carbon dioxide. In other words, a material that reduces the overvoltage when hydrogen or a carbon compound is generated by a reduction reaction of hydrogen ions or carbon dioxide can be used. For example, a metal material or a carbon material can be used. As the metal material, for example, in the case of hydrogen, a metal such as platinum or nickel, or an alloy containing the metal can be used. In the reduction reaction of carbon dioxide, a metal such as gold, aluminum, copper, silver, platinum, palladium, or nickel, or an alloy containing the metal can be used. As the carbon material, for example, graphene, carbon nanotube (CNT), fullerene, ketjen black, Denka Black (registered trademark), Vulcan XC-72, or the like can be used. Note that the present invention is not limited thereto, and for example, a metal complex such as a Ru complex or a Re complex, or an organic molecule having an imidazole skeleton or a pyridine skeleton may be used as a reduction catalyst. A plurality of materials may be mixed.

  The oxidation electrode 32 preferably includes an oxidation catalyst. The oxidation electrode 32 may include both a conductive material and an oxidation catalyst. Examples of the oxidation catalyst include a material that reduces activation energy for oxidizing water. In other words, a material that reduces the overvoltage when oxygen and hydrogen ions are generated by an oxidation reaction of water can be used. For example, iridium, platinum, cobalt, manganese, etc. are mentioned. As the oxidation catalyst, a binary metal oxide, a ternary metal oxide, a quaternary metal oxide, or the like can be used. Examples of binary metal oxides include manganese oxide (Mn—O), iridium oxide (Ir—O), nickel oxide (Ni—O), cobalt oxide (Co—O), iron oxide (Fe—O), Examples thereof include tin oxide (Sn—O), indium oxide (In—O), and ruthenium oxide (Ru—O). Examples of the ternary metal oxide include Ni—Co—O, La—Co—O, Ni—La—O, Ni—Fe—O, and Sr—Fe—O. Examples of the quaternary metal oxide include Pb—Ru—Ir—O and La—Sr—Co—O. Note that the present invention is not limited to this, and a metal complex such as a Ru complex or an Fe complex can also be used as an oxidation catalyst. A plurality of materials may be mixed.

  At least one of the reduction electrode 31 and the oxidation electrode 32 may have a porous structure. Examples of materials applicable to the electrode having a porous structure include, in addition to the above materials, carbon black such as Ketjen Black, Denka Black (registered trademark), and Vulcan XC-72, activated carbon, and fine metal powder. . By having a porous structure, the area of the active surface contributing to the oxidation-reduction reaction can be increased, so that the conversion efficiency can be increased.

  When an electrode reaction with a low current density is performed using a relatively low light irradiation energy, there are a wide range of options for the catalyst material. Therefore, for example, it is easy to perform the reaction using ubiquitous metal or the like, and it is relatively easy to obtain the selectivity of the reaction. On the other hand, when the photoelectric conversion body 33 is not provided in the electrolytic solution tank 11 and the photoelectric conversion body 33 and at least one of the reduction electrode 31 and the oxidation electrode 32 are electrically connected by wiring or the like, the electrolytic solution tank is downsized, etc. For this reason, the electrode area is generally small, and the reaction may be performed at a high current density. In this case, it is preferable to use a noble metal as a catalyst.

  The photoelectric conversion body 33 includes a stacked structure including a photoelectric conversion layer 33x, a photoelectric conversion layer 33y, and a photoelectric conversion layer 33z. The number of stacked photoelectric conversion layers is not limited to FIG.

  The photoelectric conversion layer 33x includes, for example, an n-type semiconductor layer 331n containing n-type amorphous silicon, an i-type semiconductor layer 331i containing intrinsic amorphous silicon germanium, and a p-type semiconductor layer containing p-type microcrystalline silicon. 331p. The i-type semiconductor layer 331i is a layer that absorbs light in a short wavelength region including, for example, 400 nm. Therefore, in the photoelectric conversion layer 33x, charge separation occurs due to light energy in the short wavelength region.

  The photoelectric conversion layer 33y includes, for example, an n-type semiconductor layer 332n containing n-type amorphous silicon, an i-type semiconductor layer 332i containing intrinsic amorphous silicon germanium, a p-type semiconductor layer 332p containing p-type microcrystalline silicon, Have The i-type semiconductor layer 332i is a layer that absorbs light in an intermediate wavelength region including, for example, 600 nm. Therefore, in the photoelectric conversion layer 33y, charge separation occurs due to light energy in the intermediate wavelength region.

  The photoelectric conversion layer 33z includes, for example, an n-type semiconductor layer 333n including n-type amorphous silicon, an i-type semiconductor layer 333i including intrinsic amorphous silicon, and a p-type semiconductor layer 333p including p-type microcrystalline silicon. Have. The i-type semiconductor layer 333i is a layer that absorbs light in a long wavelength region including, for example, 700 nm. Therefore, in the photoelectric conversion layer 33z, charge separation occurs due to light energy in the long wavelength region.

The p-type semiconductor layer or the n-type semiconductor layer can be formed, for example, by adding an element serving as a donor or an acceptor to a semiconductor material. Note that in the photoelectric conversion layer, a semiconductor layer containing silicon, germanium, or the like is used as the semiconductor layer; however, the present invention is not limited thereto, and for example, a compound semiconductor layer or the like can be used. As the compound semiconductor layer, for example, a semiconductor layer containing GaAs, GaInP, AlGaInP, CdTe, CuInGaSe, or the like can be used. In addition, a layer containing a material such as TiO ₂ or WO ₃ may be used as long as photoelectric conversion is possible. Further, each semiconductor layer may be single crystal, polycrystalline, or amorphous. Further, a zinc oxide layer may be provided on the photoelectric conversion layer.

  The light reflector 34 is provided between the conductive substrate 30 and the photoelectric converter 33. As the light reflector 34, for example, a distributed Bragg reflector made of a laminate of a metal layer or a semiconductor layer can be cited. By providing the light reflector 34, the light that could not be absorbed by the photoelectric conversion body 33 can be reflected and incident on either the photoelectric conversion layer 33x or the photoelectric conversion layer 33z, so that light is converted into a chemical substance. Efficiency can be increased. As the light reflector 34, for example, a layer such as a metal such as Ag, Au, Al, or Cu, or an alloy including at least one of these metals can be used.

  The metal oxide body 35 is provided between the light reflector 34 and the photoelectric conversion body 33. The metal oxide body 35 has a function of increasing the light reflectivity by adjusting the optical distance, for example. As the metal oxide body 35, it is preferable to use a material capable of ohmic contact with the n-type semiconductor layer 331n. Examples of the metal oxide body 35 include indium tin oxide (ITO), zinc oxide (ZnO), tin oxide containing fluorine (Fluorine-doped Tin Oxide: FTO), and zinc oxide containing aluminum (Aluminum-doped). A layer of a light-transmitting metal oxide such as Zinc Oxide (AZO) or antimony-containing tin oxide (ATO) can be used.

  The metal oxide body 36 is provided between the oxidation electrode 32 and the photoelectric conversion body 33. The metal oxide body 36 may be provided on the surface of the photoelectric conversion body 33. The metal oxide body 36 has a function as a protective layer that suppresses destruction of the photoelectric conversion unit 3 due to an oxidation reaction. By providing the metal oxide body 36, corrosion of the photoelectric conversion body 33 can be suppressed and the lifetime of the photoelectric conversion unit 3 can be extended. Note that the metal oxide body 36 is not necessarily provided.

As the metal oxide body 36, for example, a dielectric thin film such as TiO ₂ , ZrO ₂ , Al ₂ O ₃ , SiO ₂ , or HfO ₂ can be used. The thickness of the metal oxide body 36 is 10 nm or less, and further 5 nm or less. In order to cause a tunnel effect, it is preferably 2 nm or less, more preferably 1 nm or less. Examples of the metal oxide body 36 include indium tin oxide (ITO), zinc oxide (ZnO), tin oxide containing fluorine (FTO), zinc oxide containing aluminum (AZO), and tin oxide containing antimony (ATO). A metal oxide layer having light properties may be used.

In the case of a TiO ₂ film manufactured at about 150 ° C. by an atomic layer deposition (ALD) method, a film having both transparency and conductivity can be obtained by shortening the precursor exhaust time by the pump. In this case, not the tunnel conduction but the carbon atoms remaining in the TiO ₂ film are considered to act as a dopant, and thus may be considered as normal electron carrier conduction. In this case, the film thickness may be several tens of nm or more and several hundreds of nm or less. However, since multilayering and thickening produce strong wavelength dependence of light, it must be calculated optically and precisely. Specifically, when a wavelength is λ and a refractive index is n, a λ / 4 type antireflection film structure composed of m times λ / 4n and m being an odd number such as 1, 3, 5, or the like can be formed. preferable.

  The metal oxide body 36 has, for example, a structure in which a metal and a transparent conductive oxide are laminated, a structure in which a metal and other conductive materials are combined, or a combination of a transparent conductive oxide and other conductive materials. It may have a structure. With the above structure, the number of parts can be reduced, the weight can be reduced, the manufacturing can be facilitated, and the cost can be reduced. The metal oxide body 36 may have a function as a protective layer, a conductive layer, and a catalyst layer.

  In the photoelectric conversion cell shown in FIG. 7, the surface opposite to the contact surface of the n-type semiconductor layer 331n with the i-type semiconductor layer 331i is the surface 331 of the photoelectric conversion body 33, and the p-type semiconductor layer 333p is in contact with the i-type semiconductor layer 333i. A surface opposite to the contact surface is a surface 332. As described above, the photoelectric conversion cell illustrated in FIG. 7 can absorb light of a wide wavelength of sunlight by stacking the photoelectric conversion layer 33x to the photoelectric conversion layer 33z, thereby more efficiently using solar energy. Can be used. At this time, a high voltage can be obtained because the photoelectric conversion layers are connected in series.

  In FIG. 7, since the electrodes are stacked on the photoelectric conversion body 33, the charge-separated electrons and holes can be directly used for the oxidation-reduction reaction. Further, it is not necessary to electrically connect the photoelectric converter 33 and the electrode by wiring or the like. Therefore, the oxidation-reduction reaction can be performed with high efficiency.

  A plurality of photoelectric converters may be electrically connected in parallel connection. A two-junction type or single layer type photoelectric converter may be used. You may have the lamination | stacking of the photoelectric conversion body of 2 layers or 4 layers or more. Instead of stacking a plurality of photoelectric conversion layers, a single photoelectric conversion layer may be used.

  The electrochemical reaction device of this embodiment is a simplified system in which a reduction electrode, an oxidation electrode, and a photoelectric conversion body are integrated to reduce the number of components. Thus, for example, at least one of manufacture, installation, and maintenance is facilitated. Furthermore, since the wiring etc. which connect a photoelectric conversion body, a reduction electrode, and an oxidation electrode become unnecessary, a light transmittance can be improved and a light-receiving area can be enlarged.

  In some cases, the photoelectric conversion body 33 is corroded because of contact with the electrolytic solution, and the corrosion product is dissolved in the electrolytic solution, thereby causing deterioration of the electrolytic solution. In order to prevent corrosion, a protective layer may be provided. However, the protective layer component may be dissolved in the electrolytic solution. Therefore, deterioration of the electrolytic solution is suppressed by providing a filter such as a metal ion filter in the flow path or the electrolytic solution tank.

  The shape of the partition 6 is not limited to FIG. The electrochemical reaction device shown in FIG. 8 includes a partition wall 6 in which the maximum portion 51a has a rectangular shape in a cross section in the length direction. The electrochemical reaction device shown in FIG. 9 includes a partition wall 6 in which the maximum portion 51a has an inverted triangular shape in a cross section in the length direction. The electrochemical reaction device shown in FIG. 10 includes a partition wall 6 having a semicircular shape in which the maximum portion 51a protrudes downward in a cross section in the length direction.

  The structural example of an electrochemical reaction device is not limited to FIG. FIG. 11 is a schematic view showing another example of an electrochemical reaction device. The electrochemical reaction device shown in FIG. 11 is at least different from the electrochemical reaction device shown in FIG. 1 in that the reduction electrode 31 is not in contact with the surface 331 of the photoelectric conversion body 33. The reduction electrode 31 is electrically connected to the surface 331 through the wiring 81. At this time, a part of the wiring 81 may extend to the outside of the electrolytic solution tank 11.

  FIG. 12 is a schematic view showing another example of an electrochemical reaction device. Compared with the electrochemical reaction device shown in FIG. 1, the electrochemical reaction device shown in FIG. 12 is provided with the photoelectric conversion body 33 in contact with the outer wall of the electrolytic solution tank 11, and the reduction electrode 31 and the oxidation electrode 32 are photoelectric conversion. The configuration that is not in contact with the body 33 is at least different. The reduction electrode 31 is electrically connected to the surface 331 through the wiring 81. The oxidation electrode 32 is electrically connected to the surface 332 via the wiring 82. At this time, a part of the wiring 81 and a part of the wiring 82 may extend outside the electrolytic solution tank 11. When the photoelectric converter and the reduction electrode or the oxidation electrode are connected by wiring or the like, the components are separated for each function, which is advantageous in terms of the system.

  FIG. 13 is a schematic view showing another example of an electrochemical reaction device. Compared with the electrochemical reaction apparatus shown in FIG. 12, the electrochemical reaction apparatus shown in FIG. 13 is a three-junction type of photoelectric conversion layers 33x, 33y, and 33z provided outside the electrolyte bath 11 as the photoelectric conversion body 33. The configuration including the laminate is at least different. For the description of each of the photoelectric conversion layers 33x, 33y, and 33z, the description of the photoelectric conversion layers 33x, 33y, and 33z illustrated in FIG. 7 can be used as appropriate. Note that the photoelectric conversion cell may have a structure shown in FIG. In FIG. 13, the surface on the reduction electrode 31 side of the photoelectric conversion layer 33 x is a surface 331, and the surface on the oxidation electrode 32 side of the photoelectric conversion layer 33 z is a surface 332. The reduction electrode 31 is electrically connected to the surface 331 via the wiring 81 and the conductive layer 83 provided on the surface 331. The oxidation electrode 32 is electrically connected to the surface 332 via the wiring 82 and the conductive layer 84 provided on the surface 332. A unit including the conductive layer 83, the photoelectric conversion layers 33x, 33y, 33z, and the conductive layer 84 is also referred to as the photoelectric conversion unit 3. At this time, a part of the wiring 81 and a part of the wiring 82 may extend outside the electrolytic solution tank 11. The number of photoelectric conversion layers stacked may be 2 or 4 or more.

  FIG. 14 is a schematic view showing another example of an electrochemical reaction device. The electrochemical reaction device illustrated in FIG. 14 is at least different from the electrochemical reaction device illustrated in FIG. 13 in that it includes a plurality of photoelectric conversion units 3 including single-junction photoelectric conversion bodies 33. The description of the photoelectric conversion body 33 can be used as appropriate for the description of the photoelectric conversion body 33, and the description of the photoelectric conversion unit 3 can be used as appropriate for the structure of the other photoelectric conversion unit 3. The plurality of photoelectric conversion units 3 are electrically connected in series with each other. The number of photoelectric conversion units connected in series may be 2 or 4 or more. The voltage used for the oxidation-reduction reaction can be increased by connecting a plurality of photoelectric conversion units 3 in series.

  The above embodiment is presented as an example, and is not intended to limit the scope of the invention. The above embodiment can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. The above-described embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and equivalents thereof.

Example 1
An electrochemical reaction device having a structure was produced. The structure includes a three-junction photoelectric converter having a thickness of 500 nm, a ZnO layer having a thickness of 300 nm provided on the first surface of the three-junction photoelectric converter, and a thickness provided on the ZnO layer. It has a 200 nm Al layer, a 1.5 mm thick SUS substrate provided on the Al layer, and a 70 nm thick ITO layer provided on the second surface of the three-junction photoelectric conversion body. Each layer of the structure has a submicron texture structure for the purpose of obtaining a light confinement effect.

  Similar to the embodiment, the three-junction photoelectric converter includes a first photoelectric conversion layer that absorbs light in a short wavelength region, a second photoelectric conversion layer that absorbs light in a medium wavelength region, and light in a long wavelength region. And a third photoelectric conversion layer that absorbs water. The first photoelectric conversion layer includes a p-type microcrystalline silicon layer, an i-type amorphous silicon layer, and an n-type amorphous silicon layer. The second photoelectric conversion layer includes a p-type microcrystalline silicon layer, an i-type amorphous silicon germanium layer, and an n-type amorphous silicon layer. The third photoelectric conversion layer includes a p-type microcrystalline silicon germanium layer, an i-type amorphous silicon layer, and an n-type amorphous silicon layer.

The open circuit voltage was measured when the structure was irradiated with light using a solar simulator (AM1.5, 1000 W / m ² ). The open circuit voltage was 2.4V.

  Using an atomic layer deposition apparatus, an organic Ni compound was used as a precursor on an ITO layer having a thickness of 100 nm, and pulses were alternately sent to water, followed by repeated deaeration to form a nickel oxide layer having a thickness of about 6 nm at 150 ° C. A copper wire was bonded to the back surface of the SUS substrate with a copper tape as a contact layer. As a reduction electrode, an Au plate having a thickness of 1 mm is used, and a potentio galvanostat is used between a potential at which oxidation of the first wave of two waves ends in 1M sulfuric acid and a potential at which the reduction occurs. A high frequency of 10 kHz was applied. After applying for 3 hours, it was taken out from the solution and reduced in 0.5 M potassium carbonate to obtain a catalyst layer. When confirmed by SEM (Scanning Electron Microscope: SEM), the surface of Au had a shape as etched into particles of several tens of nanometers. Next, it cut out into the square shape of 1 cm square, and sealed the edge part with the chemical-resistant polymer sheet.

  Prepare a 10cm square acrylic flow path cell as the electrolyte flow path on the oxidation side, place and fix an oxidation electrode with a catalyst on the photoelectric converter inside the flow path, and reduce it through an anion exchange membrane (ceremon) An Au plate as an electrode was placed and fixed. The oxidation electrode and the reduction electrode were electrically connected with a copper wire and connected to a potentiostat. A 0.5 M potassium carbonate solution deaerated by argon bubbling was sent to the oxidation side channel at a flow rate of 500 sccm (ml / min) by a plunger pump.

  As the electrolyte channel on the reduction side, a 10 cm square acrylic channel cell was used. It was designed so that the distance from the inner wall of the flow channel cell could be adjusted with an O-ring so as to be 1 mm. A 0.5 M potassium hydrogen carbonate solution saturated with carbon dioxide by bubbling carbon dioxide at a flow rate of 200 sccm in a bubbling tower having a volume of 5 l was fed into the flow channel having a length of 10 cm at a flow rate of 500 sccm by a plunger pump. The Reynolds number in the electrolyte channel when the representative length at this time was 10 cm was Re8333. From this, it is considered that turbulent flow is generated in the electrolyte flow path.

The photoelectric converter was irradiated with light from a solar simulator (AM1.5, 1000 W / m ² ). Bubbles were generated from each of the oxidation electrode and the reduction electrode, and gas chromatography was used for the gas generated from the reduction electrode. As a result, the generated gas was carbon monoxide and hydrogen. In addition, the Faraday efficiency based on carbon monoxide was about 91%. From the obtained current value and current density, and the reaction amount of hydrogen and carbon monoxide, the Faraday constant (96500 C / mol) and the formula of current density (current density = number of reaction electrons (carbon monoxide and hydrogen are 2) × The reaction potential was determined using a relational expression of (Faraday constant × potential). Considering the intersection with the current-voltage curve of the photoelectric converter, the total conversion efficiency from the light irradiation intensity was 3.2%.

(Comparative Example 1)
In the electrochemical reaction apparatus of Example 1, the solution was fed with the distance between the inner wall of the electrolyte channel on the reduction side and the reduction electrode being 10 cm. The Reynolds number in the electrolyte channel when the representative length at this time was 10 cm was Re83.

The photoelectric converter was irradiated with light from a solar simulator (AM1.5, 1000 W / m ² ). Bubbles were generated from each of the oxidation electrode and the reduction electrode, and gas chromatography was used for the gas generated from the reduction electrode. As a result, the generated gas was carbon monoxide and hydrogen. Further, the Faraday efficiency when carbon monoxide was used as a reference was about 80%. From the obtained current value and current density and the reaction amount of hydrogen and carbon monoxide, the reaction potential was determined using the relational expression of the Faraday constant and the current density. The total conversion efficiency from the light irradiation intensity was 0.21%. This shows that the conversion efficiency can be increased by generating turbulent flow in the electrolyte flow path.

(Example 2)
A composite substrate (1.5 × 9 cm square) having a SUS substrate having a thickness of 1.5 mm and a platinum film having a thickness of 100 nm on the SUS substrate connected to a power source through a conductive wire, and a gold foil (1.5 cm × 10 cm) Corner) and prepared. The power source is a solar cell simulation device. An electrolyte flow path was formed on each of the oxidation electrode side and the reduction electrode side of an acrylic frame 3 cm × 11 cm square and 1 cm thick (inner diameter 2 × 10 cm). A composite substrate and gold foil are enclosed in a frame, an ion exchange membrane (Nafion 117, 2 × 10 cm square) is provided between the composite substrate and the gold foil, and a silicon rubber sheet and acrylic on both the outside of the composite substrate and the outside of the platinum foil. A module sandwiched between plates (length 3 cm × width 10 cm × thickness 3 mm) was produced. A potassium carbonate solution deaerated after being bubbled in the module with an argon bubbling tower was supplied at a flow rate of 500 sccm. The composite substrate was a reduction electrode, and the gold foil was an oxidation electrode. A part of the acrylic plate was cut at 3 places every 3 cm at 1 cm × 5 cm with a sculpture machine, and the formed concave part was defined as the maximum part (pool part). Surfaces other than the pool portion were installed using an O-ring so that the distance between the inner wall of the flow channel cell and the reduction electrode was 1 mm. A voltage of 3.6 V was applied between the oxidation electrode and the reduction electrode. The generation of carbon monoxide was confirmed on the reducing electrode side, and it was found that carbon dioxide was being reduced. The current value was 8.3 mA / cm ² .

(Comparative Example 2)
Compared with the electrochemical reaction apparatus of Example 2, an electrochemical reaction apparatus having a different structure without a pool portion was produced. A voltage of 3.6 V was applied between the oxidation electrode and the reduction electrode. The generation of carbon monoxide was confirmed on the reducing electrode side, and it was found that carbon dioxide was being reduced. The current value was 1.6 mA / cm ² . From this, it can be seen that the conversion efficiency is improved by providing the maximum portion as in the second embodiment.

(Example 3)
A photoelectric conversion cell electrically connected in series was installed outside the electrolytic solution tank, and a reduction electrode and an oxidation electrode were set inside the electrolytic solution tank to produce an electrochemical reaction device. As a photoelectric conversion cell, a single-crystal Si type solar cell is cut into 4 cm × 7 mm square so that the transmission line does not come into contact with the outside, and the four solar cells after cutting are connected in series with conductive wires and then sealed with glass. In addition, a photoelectric conversion cell having a total of 4 cm square including the conductor portion was used. The structure of the flow path and the electrolytic solution are the same as those in Example 1.

The open circuit voltage was measured when the photoelectric converter was irradiated with light using a solar simulator (AM1.5, 1000 W / m ² ). The open circuit voltage was 3.6 V, and the photoelectric conversion efficiency was about 13%.

  Each of the positive electrode side and the negative electrode side conductor of the photoelectric converter was electrically connected to an oxidation electrode and a reduction electrode. The oxidation electrode and the reduction electrode were installed in the electrolyte channel in a form in which they were in close contact with an anion exchange membrane interposed therebetween.

  Prepare a 10cm square acrylic flow path cell as the electrolyte flow path on the oxidation side, place and fix an oxidation electrode with a catalyst on the photoelectric converter inside the flow path, and reduce it through an anion exchange membrane (ceremon) An Au plate as an electrode was placed and fixed. The oxidation electrode and the reduction electrode were electrically connected with a copper wire and connected to a potentiostat. A 0.5 M potassium carbonate solution deaerated by argon bubbling was sent to the oxidation side channel at a flow rate of 500 sccm (ml / min) by a plunger pump.

  As the electrolyte channel on the reduction side, a 10 cm square acrylic channel cell was used. It was designed so that the distance from the inner wall of the flow channel cell could be adjusted with an O-ring so as to be 1 mm. A solution in which carbon dioxide was bubbled in a bubbling tower having a volume of 5 l at a flow rate of 200 sccm to saturate the carbon dioxide was fed into the flow channel having a length of 10 cm at a flow rate of 500 sccm by a plunger pump. The Reynolds number in the electrolyte channel when the representative length at this time was 10 cm was Re8333. From this, it is considered that turbulent flow is generated in the electrolyte flow path.

The photoelectric converter was irradiated with light from a solar simulator (AM1.5, 1000 W / m ² ). Bubbles were generated from each of the oxidation electrode and the reduction electrode, and gas chromatography was used for the gas generated from the reduction electrode. As a result, the generated gas was carbon monoxide and hydrogen. In addition, the Faraday efficiency based on carbon monoxide was about 91%. From the obtained current value and current density and the reaction amount of hydrogen and carbon monoxide, the reaction potential was determined using the relational expression of the Faraday constant and the current density. Considering the intersection with the current-voltage curve of the photoelectric converter, the total conversion efficiency from the light irradiation intensity was 4.7%. This shows that the conversion efficiency can be increased by electrically connecting the photoelectric conversion cells in series.

  DESCRIPTION OF SYMBOLS 3 ... Photoelectric conversion unit, 4 ... Ion exchange membrane, 6 ... Partition, 11 ... Electrolyte tank, 21 ... Electrolyte, 22 ... Electrolyte, 30 ... Conductive substrate, 31 ... Reduction electrode layer, 32 ... Oxidation electrode layer, 33 ... Photoelectric conversion layer, 33a ... Photoelectric conversion layer, 33b ... Photoelectric conversion layer, 33c ... Photoelectric conversion layer, 33x ... Photoelectric conversion layer, 33y ... Photoelectric conversion layer, 33z ... Photoelectric conversion layer, 34 ... Light reflecting layer, 35 ... Metal oxide layer, 36 ... Metal oxide layer, 51 ... Electrolyte flow path, 51a ... Maximum part, 51b ... Minimum part, 52 ... Electrolyte flow path, 81 ... Wiring, 82 ... Wiring, 83 ... Conductive layer, 83 ... Wiring, 84 ... Conductive layer, 84 ... Wiring, 111 ... Housing, 112 ... Housing, 311 ... Surface, 321 ... Surface, 331 ... Surface, 332 ... Surface, 331i ... i-type semiconductor layer, 331n ... n-type semiconductor Layer, 331p ... p-type semiconductor layer, 332i ... i-type semiconductor layer, 33 n ... n-type semiconductor layer, 332p ... p-type semiconductor layer, 333i ... i-type semiconductor layer, 333n ... n-type semiconductor layer, 333p ... p-type semiconductor layer.

Claims (17)

An electrolytic solution tank comprising: a first storage unit for storing a first electrolytic solution containing carbon dioxide; and a second storage unit for storing a second electrolytic solution containing water;
A reduction electrode disposed in the first housing portion and having a first surface including a reduction catalyst;
An oxidation electrode disposed in the second housing portion and having a second surface containing an oxidation catalyst;
A power source electrically connected to the reduction electrode and the oxidation electrode,
The region between the first surface of the first housing part and the inner wall of the first housing part is an electrolyte channel for feeding the first electrolyte solution,
The electrolyte flow path includes a maximum portion having a maximum value of an area distribution from one end to the other end of the cross section perpendicular to the length direction of the electrolyte flow path, and a minimum value of the area distribution. An electrochemical reaction device having a minimum portion.   The said power supply is provided with the photoelectric conversion body which has the 3rd surface electrically connected to the said reduction electrode, and the 4th surface electrically connected to the said oxidation electrode. Electrochemical reactor.   The electrochemical reaction device according to claim 2, wherein the photoelectric conversion body is provided inside the electrolytic solution tank or outside the electrolytic solution tank.   The electrochemical reaction device according to any one of claims 1 to 3, wherein the minimum portion has a Reynolds number of 3000 or more and 200000 or less.   The electrochemical reaction device according to any one of claims 1 to 4, wherein an aspect ratio of the maximum portion with respect to an aspect ratio of the minimum portion is 10 or more and 1000 or less.   6. The electricity according to claim 1, wherein a flow rate of the first electrolyte when the first electrolyte flows through the minimum portion is 1 m / s or more and 100 m / s or less. Chemical reactor.   The electrochemical reaction device according to any one of claims 1 to 6, wherein a maximum diameter of a cross section perpendicular to the length direction in the minimum portion is 1 mm or more and 50 mm or less.   A partition provided between the first surface of the first housing portion and the inner wall of the first housing portion so as to be in contact with the inner wall of the first housing portion and further overlapping the minimal portion is further provided. The electrochemical reaction device according to any one of claims 1 to 7. The region between the second surface of the second housing portion and the inner wall of the second housing portion is a second electrolyte flow for feeding at least a part of the second electrolyte solution. Road,
The second electrolyte flow path is a minimum value of an area distribution from one end to the other end in the second length direction of a cross section perpendicular to the second length direction of the second electrolyte flow path. The electrochemical reaction device according to any one of claims 1 to 8, wherein is larger than the minimum value.   The electrochemical reaction device according to any one of claims 1 to 9, wherein the compound produced by the reduction reaction of carbon dioxide contains carbon monoxide.   The electrochemical reaction device according to any one of claims 1 to 9, wherein the compound produced by the reduction reaction of carbon dioxide contains ethylene glycol. An electrolytic solution tank comprising: a first storage unit for storing a first electrolytic solution containing carbon dioxide; and a second storage unit for storing a second electrolytic solution containing water;
A reduction electrode disposed in the first housing portion and having a first surface including a reduction catalyst;
An oxidation electrode disposed in the second housing portion and having a second surface containing an oxidation catalyst;
A power source electrically connected to the reduction electrode and the oxidation electrode,
The region between the first surface of the first housing part and the inner wall of the first housing part is an electrolyte channel for feeding the first electrolyte solution,
The electrolyte flow path has a first area and a second area, and the first area and the second area are juxtaposed along the length direction of the electrolyte flow path,
The electrochemical reaction apparatus, wherein the second region has a partition for generating a turbulent flow in the first electrolyte solution, and the partition is in contact with the inner wall.   The electrochemical reaction device according to claim 12, wherein the Reynolds number of the second region is 3000 or more and 200000 or less.   The said power supply is provided with the photoelectric conversion body which has the 3rd surface electrically connected to the said reduction | restoration electrode, and the 4th surface electrically connected to the said oxidation electrode. 14. The electrochemical reaction device according to 13.   The electrochemical reaction device according to claim 14, wherein the photoelectric conversion body is provided inside the electrolyte bath or outside the electrolyte bath.   The electrochemical reaction device according to any one of claims 12 to 15, wherein the compound produced by the reduction reaction of carbon dioxide contains carbon monoxide.   The electrochemical reaction device according to any one of claims 12 to 15, wherein the compound produced by the reduction reaction of carbon dioxide contains ethylene glycol.

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