JP2024080441A - Electrochemical reaction apparatus and electrochemical reaction apparatus stack - Google Patents

Abstract

To provide an electrochemical reaction apparatus which can improve selectivity of a target compound by reduction reaction of CO2, and can increase a production amount of the target compound, and an electrochemical reaction apparatus stack using the same.SOLUTION: An electrochemical reaction apparatus 1 has a CO2 reduction cell 2, a hydrogen pump cell 3, and a gas flow channel 4 having a gas introduction part 41 to which gas G1 containing CO2 is introduced. The CO2 reduction cell 2 includes an oxide ion conductor 20, a first cathode electrode 21 capable of electrochemically reducing CO2 from the gas G1 containing the CO2, and a first anode electrode 22 capable of emitting oxide ions as oxygen. The hydrogen pump cell 3 includes a hydrogen ion conductor 30, a second anode electrode 32 capable of dissociating hydrogen ions from gas G2 containing hydrogen atoms, and a second cathode electrode 31 to which the hydrogen ions are supplied. The first cathode electrode 21 and the second cathode electrode 31 are provided in the gas flow channel 4 provided with a catalyst body 5 for promoting reduction of CO2.SELECTED DRAWING: Figure 1

Description

The present invention relates to an electrochemical reactor and an electrochemical reactor stack.

2. Description of the Related Art Conventionally, electrochemical reaction devices are known that electrochemically reduce and hydrogenate _CO2 to produce a target compound such as _CH4 .

For example, Patent Document 1 discloses an electrochemical reaction device that includes an anode for oxidizing water to produce oxygen, an electrolyte flow path that faces the anode and is provided for flowing a first electrolyte containing water, a cathode for reducing carbon dioxide to produce a carbon compound, a separator that separates the anode and the cathode, a power source electrically connected to the anode and the cathode, and a flow path plate that includes a first flow path that faces the cathode and is provided for flowing carbon dioxide, and a second flow path that faces the cathode and is provided for flowing a second electrolyte.

JP 2018-154898 A

In the reaction of electrochemically reducing and hydrogenating _CO2 , the element that determines the type of compound obtained is chemical potential. When multiple elements are involved in the reaction, the compound obtained varies depending on the chemical potential of each element. Therefore, in the above-mentioned conventional technology, the chemical potential of each element near the reaction field on the electrode surface is controlled by the partial pressure of the introduced raw material gas and the voltage applied to the electrode, and the compound is selected.

However, there is a limit to the chemical potential that can be controlled by the partial pressure of the raw material gas introduced. Also, in a single electrochemical cell, it is not possible to individually control the chemical potential of each of multiple elements. Therefore, with conventional technology, it is difficult to improve the selectivity of the target compound. Also, it is desirable to produce as much of the target compound as possible by selectively synthesizing it.

The present invention has been made in consideration of such problems, and aims to provide an electrochemical reaction device that can improve the selectivity of a target compound by a reduction reaction of _CO2 and increase the amount of the target compound produced, and an electrochemical reaction device stack using the same.

One aspect of the present invention is
a CO2 reduction cell ( _{2) including: an oxide ion conductor (20) capable of transferring oxide ions; a first cathode electrode (21) provided on one side of the oxide ion conductor and capable of electrochemically reducing the CO2 from} a gas (G1) containing CO2; and a first anode electrode (22) provided on the other side of the oxide ion conductor and capable of releasing the oxide ions that have transferred through the _oxide ion conductor as oxygen;
a hydrogen pump cell (3) including: a hydrogen ion conductor (30) capable of moving hydrogen ions; a second anode electrode (32) provided on one side of the hydrogen ion conductor and capable of dissociating hydrogen ions from a gas (G2) containing hydrogen atoms; and a second cathode electrode (31) provided on the other side of the hydrogen ion conductor and supplied with the hydrogen ions that have moved through the hydrogen ion conductor;
A gas flow path (4) including a gas inlet (41) into which the _CO2 -containing gas is introduced,
The first cathode electrode of the _CO2 reduction cell and the second cathode electrode of the hydrogen pump cell are provided in the gas flow path so as to face each other,
A catalyst (5) for promoting the reduction of the _CO2 is provided in the gas flow path.
Located in an electrochemical reactor (1).

Another aspect of the present invention is
The electrochemical reaction device has a laminated structure (10) in which a plurality of the electrochemical reaction devices are laminated,
The stacked structure includes at least one of a first arrangement structure (101) in which the second anode electrodes of the hydrogen pump cells in the adjacent electrochemical reaction devices are arranged with a gap (101a) between them, and a second arrangement structure (102) in which the first anode electrodes of the _CO2 reduction cells in the adjacent electrochemical reaction devices are arranged with a gap (102a) between them,
the gas flow paths of the adjacent electrochemical reaction devices are connected to each other so that gas discharged from one of the adjacent electrochemical reaction devices is introduced into the gas inlet of the other of the adjacent electrochemical reaction devices;
The gas containing hydrogen atoms is supplied to the gap in the first arrangement structure.
Located in the electrochemical reactor stack (1S).

The electrochemical reaction device has the above configuration. Therefore, the electrochemical reaction device can apply voltages independently to the _CO2 reduction cell and the hydrogen pump cell by electrically connecting a first power source to the first cathode electrode and the first anode electrode of the _CO2 reduction cell and electrically connecting a second power source to the second cathode electrode and the second anode electrode of the hydrogen pump cell. Therefore, according to the electrochemical reaction device, it is possible to independently control the chemical potential of the O element and the chemical potential of the H element in the same gas flow path at the same time. Therefore, the electrochemical reaction device can reduce _CO2 to add or remove any H or O, and selectively synthesize a target compound.

In addition, the electrochemical reaction device is provided with a catalyst that promotes the reduction of CO ₂ in the gas flow path. Therefore, the electrochemical reaction device can improve the conversion rate of CO ₂ and increase the amount of target compound produced. This is considered to be due to the following reasons. That is, according to the electrochemical reaction device, not only can an electrochemical reaction occur in the vicinity of the first cathode electrode and the second cathode electrode, but also a catalytic reaction can occur in the portion where the catalyst is provided. Therefore, the electrochemical reaction device can increase the reaction field in the gas flow path compared to a case where the catalyst is not provided. Furthermore, according to the electrochemical reaction device, the activation energy is reduced by the catalyst and the reaction rate is improved, so that the time until the target compound reaches thermal equilibrium can be shortened. Therefore, the electrochemical reaction device can improve the conversion rate of CO ₂ and increase the amount of target compound produced.

Therefore, according to the above electrochemical reaction device, it is possible to provide an electrochemical reaction device that can improve the selectivity of the target compound by the reduction reaction of _CO2 and increase the amount of the target compound produced.

The electrochemical reactor stack has the above configuration. Therefore, in the electrochemical reactor stack, the gas discharged from the electrochemical reactor is sequentially introduced into the electrochemical reactor arranged in the subsequent stage, so that the total reaction area increases, and in combination with the action and effect of the electrochemical reactor, the production amount of the target compound can be further increased.

The reference characters in parentheses in the claims and the means for solving the problems indicate the corresponding relationship with the specific means described in the embodiments described below, and do not limit the technical scope of the present invention.

FIG. 1 is a diagram showing a schematic configuration of an electrochemical reaction device according to a first embodiment. FIG. 2 is a diagram showing a schematic configuration of an electrochemical reaction device according to the second embodiment. FIG. 3 is a diagram showing a schematic configuration of an electrochemical reaction device according to the third embodiment. FIG. 4 is a diagram showing a schematic configuration of an electrochemical reaction device according to the fourth embodiment. FIG. 5 is a diagram showing a schematic configuration of an electrochemical reaction device according to the sixth embodiment. FIG. 6 is a diagram showing a schematic configuration of an electrochemical reaction device stack according to the seventh embodiment. FIG. 7 is a diagram comparing the CO ₂ transfer rates of the electrochemical reaction devices of Sample 1 and Sample 1R prepared in Experimental Example 1. FIG. 8 is a graph comparing the amounts of _CH4 produced in the electrochemical reaction devices of Sample 1 and Sample 1R prepared in Experimental Example 1. FIG. 9 is a graph comparing the amounts of _CH4 produced in the electrochemical reaction devices of Sample 1, Sample 2, and Sample 1R prepared in Experimental Example 2.

(Embodiment 1)
The electrochemical reaction device of the first embodiment will be described with reference to Fig. 1. As illustrated in Fig. 1, the electrochemical reaction device 1 of the present embodiment has a _CO2 reduction cell 2, a hydrogen pump cell 3, a gas flow passage 4, and a catalyst body 5. This will be described in detail below.

The _CO2 reduction cell 2 includes an oxide ion conductor 20, a first cathode electrode 21 provided on one side of the oxide ion conductor 20, and a first anode electrode 22 provided on the other side of the oxide ion conductor 20.

The oxide ion conductor 20 is capable of moving oxide ions (O ²⁻ ). In other words, the oxide ion conductor 20 has oxide ion conductivity. The oxide ion conductor 20 serves as a separator that separates the first cathode electrode 21 and the first anode electrode 22 so that electrons do not flow between them, and only oxide ions can move within the oxide ion conductor 20. Specifically, the oxide ion conductor 20 can be made of a solid electrolyte having oxide ion conductivity. The oxide ion conductor 20 is usually formed to be dense in order to ensure gas tightness.

As oxide ion conductive materials constituting the oxide ion conductor 20, for example, from the viewpoints of oxide ion conductivity, strength, thermal stability, etc., zirconium oxide oxides such as yttria stabilized zirconia (YSZ) and scandia stabilized zirconia (ScSZ) can be exemplified. These can be used alone or in combination of two or more. As oxide ion conductive materials, yttria stabilized zirconia is preferable from the viewpoints of oxide ion conductivity, mechanical stability, compatibility with other materials, and chemical stability from oxidizing atmospheres to reducing atmospheres. The thickness of the oxide ion conductor 20 can be, for example, 5 μm or more and 2000 μm or less.

The first cathode electrode 21 is an electrode capable of electrochemically reducing CO ₂ contained in the gas G1 containing CO _2. In other words, the first cathode electrode 21 is an electrode capable of electronic conduction and capable of extracting O from CO _2. The gas G1 containing CO ₂ can be, for example, CO ₂ gas, or a gas containing CO ₂ gas and H ₂ gas. The first cathode electrode 21 can be configured in a layered form, and can be configured to include, for example, an electronically conductive material in the first cathode, or an electronically conductive material in the first cathode and an oxide ion conductive material in the first cathode. Examples of the electronically conductive material in the first cathode include platinum group metals such as Pt, Pd, Rh, Ru, Ir, and Os, Au, Ag, Ni, Zn, and Cu. These can be used alone or in combination of two or more. Examples of the oxide ion conductive material in the first cathode include zirconium oxide-based oxides such as yttria-stabilized zirconia and scandia-stabilized zirconia. These can be used alone or in combination of two or more. The oxide ion conductive material in the first cathode can be the same type of material as the oxide ion conductive material used in the oxide ion conductor 20 from the viewpoints of oxide ion conductivity, bonding between the first cathode electrode 21 and the oxide ion conductor 20, manufacturability of the _CO2 reduction cell 2, etc. In the first cathode electrode 21, both the first cathode electronic conductive material and the first cathode oxide ion conductive material can be particulate.

The first cathode electrode 21 can be formed to be porous, including pores, from the viewpoint of improving gas diffusion. Note that if the thickness of the first cathode electrode 21 is thin enough to allow gas to pass through, the first cathode electrode 21 does not necessarily need to be formed to be porous. The thickness of the first cathode electrode 21 can be, for example, 0.1 μm or more and 2000 μm or less.

The first anode electrode 22 is an electrode capable of releasing oxide ions that have moved through the oxide ion conductor 20 as oxygen (O ₂ ). In other words, the first anode electrode 22 is an electrode capable of generating O ₂ from O ^2- . The first anode electrode 22 can be configured in a layered form, and can be configured to include, for example, a first anode electronic conductive material, or a first anode electronic conductive material and a first anode oxide ion conductive material. Examples of the first anode electronic conductive material include platinum group metals such as Pt, Pd, Rh, Ru, Ir, and Os, Au, Ag, Ni, and transition metal perovskite oxides such as lanthanum-strontium-cobalt oxides (LSC), lanthanum-strontium-cobalt-iron oxides (LSCF), and lanthanum-strontium-manganese-iron oxides. These can be used alone or in combination of two or more. Examples of the oxide ion conductive material in the first anode include zirconium oxide-based oxides such as yttria-stabilized zirconia and scandia-stabilized zirconia. These may be used alone or in combination of two or more. The oxide ion conductive material in the first anode may be the same type of material as the oxide ion conductive material used in the oxide ion conductor 20 from the viewpoints of oxide ion conductivity, bonding between the first anode electrode 22 and the oxide ion conductor 20, manufacturability of the _CO2 reduction cell 2, etc. In the first anode electrode 22, both the first anode electronic conductive material and the first anode oxide ion conductive material may be particulate.

The first anode electrode 22 can be formed to be porous, including pores, from the viewpoint of improving gas diffusion. Note that if the thickness of the first anode electrode 22 is thin enough to allow gas to pass through, the first anode electrode 22 does not necessarily need to be formed to be porous. The thickness of the first anode electrode 22 can be, for example, 0.1 μm or more and 2000 μm or less.

The hydrogen pump cell 3 includes a hydrogen ion conductor 30, a second anode electrode 32 provided on one side of the hydrogen ion conductor 30, and a second cathode electrode 31 provided on the other side of the hydrogen ion conductor 30.

The hydrogen ion conductor 30 is capable of moving hydrogen ions (H ⁺ , protons). In other words, the hydrogen ion conductor 30 has proton conductivity. The hydrogen ion conductor 30 serves as a separator that separates the second cathode electrode 31 and the second anode electrode 32 so that electrons do not flow between them, and only hydrogen ions can move within the hydrogen ion conductor 30. Specifically, the hydrogen ion conductor 30 can be made of a solid electrolyte having hydrogen ion conductivity. The hydrogen ion conductor 30 is usually formed to be dense in order to ensure gas tightness.

Examples of the hydrogen ion conductive material constituting the hydrogen ion conductor 30 include, from the viewpoint of hydrogen ion conductivity and material stability, metal oxides containing Ba such as BaZrO ₃ (barium zirconate), BaZrO ₃ in which a portion of the Zr element is substituted with an element such as Y, Sc, Lu, In, Al, Ga, etc. (BaZr _1-x M _x O ₃ , where M is at least one element selected from the group consisting of Y, Sc, Lu, In, Al, and Ga, 0<x<1), BaCeO ₃ , BaCeO ₃ in which a portion of the Ce element is substituted with an element such as Y, Yb, Nb, etc. (BaCe _1-x M _x O ₃ , where M is at least one element selected from the group consisting of Y, Yb, and Nb, 0<x<1); SrZrO ₃ (strontium zirconate), SrZrO Examples of the metal oxides include metal oxides containing Sr, such as those in which a part of the Zr element in SnP ₂ O _{7 is} replaced with an element such as Yb, Y, or In (SrZr _1-x M _x O ₃ , where M is at least one element selected from the group consisting of Yb, Y, and In, 0<x<1); metal oxides containing Sn, such as those in which a part of the Sn element in SnP ₂ O ₇ is replaced with an element such as In, Al, or Mg (Sn _1-x M _x P ₂ O ₇ , where M is at least one element selected from the group consisting of In, Al, and Mg, 0<x<1); and phosphate-based glasses such as Sn _0.9 In _0.1 P ₂ O _7. These can be used alone or in combination of two or more. As the hydrogen ion conductive material, metal oxides containing Ba are suitable from the viewpoints of high hydrogen ion conductivity at 400° C. to 800° C. and material stability. The metal oxide may have oxygen non-stoichiometry. The metal oxide may be a composite metal oxide. The hydrogen ion conductor 30 may have a thickness of, for example, 5 μm or more and 2000 μm or less.

The second cathode electrode 31 is an electrode to which hydrogen ions that have moved through the hydrogen ion conductor 30 are supplied. Specifically, the second cathode electrode 31 can be an electrode capable of releasing hydrogen ions that have moved through the hydrogen ion conductor 30 as hydrogen (H ₂ ) or hydrogen ions. That is, the second cathode electrode 31 can be an electrode capable of generating H ₂ from H ⁺ , or an electrode capable of releasing H ⁺ as it is. The second cathode electrode 31 can be configured to include, for example, an electronically conductive material in the second cathode, or an electronically conductive material in the second cathode and a hydrogen ion conductive material in the second cathode. Examples of the electronically conductive material in the second cathode include platinum group metals such as Pt, Pd, Rh, Ru, Ir, and Os, Au, Ag, Ni, Zn, and Cu. These can be used alone or in combination of two or more. Examples of the hydrogen ion conductive material in the second cathode include the hydrogen ion conductive material constituting the hydrogen ion conductor 30 described above. These materials may be used alone or in combination of two or more. The hydrogen ion conductive material in the second cathode is preferably a metal oxide containing Ba, such as BaZrO ₃ or BaZr _1-x M1 _x O ₃ (where 0<x<1). The hydrogen ion conductive material in the second cathode may be the same type of material as the hydrogen ion conductive material used in the hydrogen ion conductor 30, from the viewpoints of hydrogen ion conductivity, bonding between the second cathode electrode 31 and the hydrogen ion conductor 30, manufacturability of the hydrogen pump cell 3, and the like. In the second cathode electrode 31, both the second cathode electronic conductive material and the second cathode hydrogen ion conductive material may be particulate.

The second cathode electrode 31 can be formed to be porous, including pores, from the viewpoint of improving gas diffusion. Note that if the thickness of the second cathode electrode 31 is thin enough to allow gas to pass through, the second cathode electrode 31 does not necessarily need to be formed to be porous. The thickness of the second cathode electrode 31 can be, for example, 0.1 μm or more and 2000 μm or less.

The second anode electrode 32 is an electrode capable of dissociating hydrogen ions from the gas G2 containing hydrogen atoms. That is, the second anode electrode 32 is an electrode capable of extracting hydrogen ions from the gas G2 containing hydrogen atoms. Examples of the gas G2 containing hydrogen atoms include H ₂ gas, H ₂ O gas (water vapor), or a gas containing H ₂ gas and H ₂ O gas. The second anode electrode 32 can be configured to include, for example, a second anode electronic conductive material, or a second anode electronic conductive material and a second anode hydrogen ion conductive material. Examples of the second anode electronic conductive material include platinum group metals such as Pt, Pd, Rh, Ru, Ir, and Os, Au, Ag, and Ni. These can be used alone or in combination of two or more. Examples of the second anode hydrogen ion conductive material include the hydrogen ion conductive material constituting the hydrogen ion conductor 30 described above. These can be used alone or in combination of two or more. The second anode hydrogen ion conductive material is preferably a metal oxide containing Ba, such as BaZrO ₃ or BaZr _1-x M1 _x O ₃ (where 0<x<1). The second anode hydrogen ion conductive material may be the same type of material as the hydrogen ion conductive material used in the hydrogen ion conductor 30, from the standpoints of hydrogen ion conductivity, bonding between the second anode electrode 32 and the hydrogen ion conductor 30, and manufacturability of the hydrogen pump cell 3. In the second anode electrode 32, both the second anode electron conductive material and the second anode oxide ion conductive material may be in a particulate form.

The second anode electrode 32 can be formed to be porous, including pores, from the viewpoint of improving gas diffusion. Note that if the thickness of the second anode electrode 32 is thin enough to allow gas to pass through, the second anode electrode 32 does not necessarily need to be formed to be porous. The thickness of the second anode electrode 32 can be, for example, 0.1 μm or more and 2000 μm or less.

As illustrated in FIG. 1, the gas flow passage 4 can be disposed between the _CO2 reduction cell 2 and the hydrogen pump cell 3. The gas flow passage 4 is configured so that oxygen ( _O2 ) released from the first anode electrode 22 of the _CO2 reduction cell 2 and the gas G2 containing hydrogen atoms supplied to the second anode electrode 32 of the hydrogen pump cell 3 do not enter the gas flow passage 4. The gas flow passage 4 can be appropriately sealed by a seal member (not shown) or the like as necessary. Examples of the material of the gas flow passage 4 include insulating materials such as alumina, mullite, and quartz, the above-mentioned oxide ion conductive materials, and the above-mentioned hydrogen ion conductive materials. FIG. 1 shows an example in which the oxide ion conductor 20 of the _CO2 reduction cell 2 and the hydrogen ion conductor 30 of the hydrogen pump cell 3 constitute the flow passage wall of the gas flow passage 4.

The gas flow passage 4 has a gas inlet 41 into which a gas G1 containing _CO2 is introduced. In Fig. 1, one end face of the _CO2 reduction cell 2 and the hydrogen pump cell 3 arranged to face each other is configured as the gas inlet 41, and a side end face opposite to the one end face is configured as a gas outlet 40 from which a gas G3 after the reaction is discharged. The gas G3 after the reaction contains gases such as hydrocarbons (including oxygen-containing hydrocarbons containing oxygen atoms).

In the electrochemical reaction device 1, the first cathode electrode 21 of the _CO2 reduction cell 2 and the second cathode electrode 31 of the hydrogen pump cell 3 are provided in the gas flow path 4. That is, the first cathode electrode 21 and the second cathode electrode 31 are both present in the gas flow path 4 and exposed in the gas flow path 4. It is to be noted that the first anode electrode 22 and the second anode electrode 32 are both not exposed in the gas flow path 4.

In this embodiment, the region of the gas flow path 4 where the first cathode electrode 21 and the second cathode electrode 31 are arranged is the chamber section 42. In addition, the region of the gas flow path 4 that is connected to the chamber section 42 and arranged on the upstream side of the chamber section 42 is the upstream flow path section 43. In addition, the region of the gas flow path 4 that is connected to the chamber section 42 and arranged on the downstream side of the chamber section 42 is the downstream flow path section 44. In FIG. 1, an example is shown in which a gas introduction section 41 is provided at the flow path inlet section of the upstream flow path section 43 and a gas discharge section 40 is provided at the flow path outlet section of the downstream flow path section 44. Note that the chamber section 42 includes not only the interelectrode space 420 formed between the first cathode electrode 21 and the second cathode electrode 31, but also the gaps in the first cathode electrode 21 and the second cathode electrode 31.

The electrochemical reaction device 1 can be configured to apply voltages independently to the CO ₂ reduction cell 2 and the hydrogen pump cell 3. FIG. 1 shows an example in which a first power source 51 is electrically connected to the first cathode electrode 21 and the first anode electrode 22 of the CO ₂ reduction cell 2. Specifically, the negative electrode of the first power source 51 is electrically connected to the first cathode electrode 21, and the positive electrode of the first power source 51 is electrically connected to the first anode electrode 22. FIG. 1 also shows an example in which a second power source 52 is electrically connected to the second cathode electrode 31 and the second anode electrode 32 of the hydrogen pump cell 3. Specifically, the negative electrode of the second power source 52 is electrically connected to the second cathode electrode 31, and the positive electrode of the second power source 52 is electrically connected to the second anode electrode 32.

The electrochemical reaction device 1 electrically connects the first power source 51 and the second power source 52, and applies voltages to the CO ₂ reduction cell 2 and the hydrogen pump cell 3 independently via the first power source 51 and the second power source 52, thereby independently and simultaneously controlling the chemical potential of the O element and the chemical potential of the H element in the gas flow path 4. Specifically, as can be understood from the C-H-O phase diagram at a predetermined temperature in the gas flow path 4, the compound obtained changes depending on the combination of the chemical potentials of the C element, the H element, and the O element. The C-H-O phase diagram also changes depending on the temperature of the reaction field in the gas flow path 4, but the electrochemical reaction device 1 fixes the chemical potential of the C element and can independently and simultaneously control the chemical potential of the O element and the chemical potential of the H element in the reaction field in the gas flow path 4 by the CO ₂ reduction cell 2 and the hydrogen pump cell 3. As a result, the electrochemical reaction device 1 can reduce CO ₂ to add or remove any H or O, and selectively synthesize a target compound. Examples of the compound include carbon compounds such as CO, and hydrocarbons such as CH ₄ , C ₂ H ₆ , and CH ₃ OH (including hydrocarbons containing oxygen atoms). Therefore, according to the electrochemical reaction device 1, an electrochemical reaction device 1 that is effective in improving the selectivity of a target compound by a reduction reaction of CO ₂ can be obtained. In addition, according to the electrochemical reaction device 1, it is possible to increase the types of target compounds by a reduction reaction of CO _2. Although it has been difficult to synthesize hydrocarbons with a carbon number of 2 or more, such as C ₂ H ₆ , the electrochemical reaction device 1 can also synthesize hydrocarbons with a carbon number of 2 or more. The operating temperature of the electrochemical reaction device 1 can be, for example, 400° C. or more and 800° C. or less.

_CH4 can be synthesized in the gas flow passage 4 according to the following reaction formula:
_CO2 + _4H2 → _CH4 + _2H2O
Moreover, C ₂ H ₆ can be synthesized in the gas flow passage 4 according to the following reaction formula.
_2CO2 + _7H2 → _{C2H6 + 4H2O}
Moreover, CH ₃ OH can be synthesized in the gas flow passage 4 according to the following reaction formula.
_CO2 + _3H2 → _CH3OH + _H2O

In the electrochemical reaction device 1, the first cathode electrode 21 of the _CO2 reduction cell 2 and the second cathode electrode 31 of the hydrogen pump cell 3 are provided in the gas flow path 4 so as to face each other. Specifically, FIG. 1 shows an example in which the first cathode electrode 21 and the second cathode electrode 31 are provided so as to face each other in the chamber portion 42 in the gas flow path 4. According to this configuration, it is possible to control the chemical potential of the O _element and the chemical potential of the H element in the interelectrode space 420 formed between the first cathode electrode 21 and the second cathode electrode 31 by applying voltages independently to the CO2 reduction cell 2 and the hydrogen pump cell 3. Therefore, according to this configuration, by flowing the gas G1 containing _CO2 into the interelectrode space 420, it is possible to efficiently electrochemically reduce and hydrogenate _CO2 , which makes it easier to improve the selectivity of the target compound.

Note that FIG. 1 shows an example in which the first cathode electrode 21 and the second cathode electrode 31 are arranged to face each other so that they are in the same position when viewed from the side, but the first cathode electrode 21 and the second cathode electrode 31 may be arranged to face each other so that they partially overlap.

In the electrochemical reaction device 1, the distance (shortest distance) between the oxide ion conductor 20 of the _CO2 reduction cell 2 and the hydrogen ion conductor 30 of the hydrogen pump cell 3 can be preferably 10 mm or less, more preferably 6 mm or less, and even more preferably 3 mm or less.

The greater the distance between the oxide ion conductor 20 of the _CO2 reduction cell 2 and the hydrogen ion conductor 30 of the hydrogen pump cell 3, the greater the deviation of the chemical potential of the O element and the chemical potential of the H element from the target chemical potential. In other words, when the distance L is large, the distribution of the chemical potentials is likely to occur. On the other hand, the vicinity of the electrodes is a region where the chemical potential can be controlled with high precision. Therefore, according to the configuration in which the first cathode electrode 21 and the second cathode electrode 31 face each other, the first cathode electrode 21 of the _CO2 reduction cell 2 and the second cathode electrode 31 of the hydrogen pump cell 3 can be brought close to each other without contacting each other so that the region where the chemical potential of the O element can be controlled and the region where the chemical potential of the H element can be controlled are close to each other or overlap each other. Therefore, according to the above configuration, the spatial range in which the chemical potential of the O element and the chemical potential of the H element can be controlled is increased, and the effective reaction field is expanded, thereby obtaining an electrochemical reaction device 1 that is advantageous in terms of improving the selectivity of the target compound.

The electrochemical reaction device 1 has a catalyst 5 that promotes the reduction of _CO2 in the gas flow passage 4. Therefore, the electrochemical reaction device 1 can improve the conversion rate of _CO2 and increase the production amount of the target compound. This is believed to be due to the following reasons.

As described above, the electrochemical reaction device 1 can improve the selectivity of the target compound by controlling the chemical potentials of the O element and the H element by the CO ₂ reduction cell 2 and the hydrogen pump cell 3. However, the region where each chemical potential can be controlled with high precision is near the electrode, and if the catalyst body 5 that promotes the reduction of CO ₂ is not provided in the gas flow path 4, the reaction field is limited to the vicinity of the electrode, and the production amount of the target compound is rate-determined in the reaction field. In addition, the electrochemical reaction proceeds instantly near the electrode, but the further away from the electrode, the more difficult it is to control the chemical potentials of the O element and the H element, so the reaction slows down, and it takes time to reach the thermal equilibrium state of the target compound. Therefore, if the catalyst body 5 that promotes the reduction of CO ₂ is not provided in the gas flow path 4, it is difficult to increase the production amount of the target compound. In contrast, according to the electrochemical reaction device 1 in which the catalyst body 5 that promotes the reduction of CO ₂ is provided in the gas flow path 4, not only can an electrochemical reaction occur near the first cathode electrode 21 and the second cathode electrode 31, but a catalytic reaction can also occur in the part where the catalyst body 5 is provided. Therefore, the electrochemical reaction device 1 can increase the reaction field in the gas flow passage 4 compared to a case where the catalyst body 5 is not provided. Furthermore, according to the electrochemical reaction device 1, the activation energy is reduced by the catalyst body 5, and the reaction rate is improved, so that the time until the target compound reaches thermal equilibrium can be shortened. Therefore, the electrochemical reaction device 1 can improve the conversion rate of _CO2 and increase the production amount of the target compound.

In the electrochemical reaction device 1, the catalyst body 5 may be provided in any of the chamber section 42, the upstream side flow path section 43, and the downstream side flow path section 44, as long as it is provided in the gas flow path 4, or may be provided in all of the chamber section 42, the upstream side flow path section 43, and the downstream side flow path section 44. In this embodiment, the catalyst body 5 is provided in the chamber section 42, as illustrated in FIG. 1. More specifically, in this embodiment, the catalyst body 5 is provided in the interelectrode space 420 in the chamber section 42, as illustrated in FIG. 1. With this configuration, in the interelectrode space 420, which is advantageous for controlling the chemical potential of the O element and the chemical potential of the H element, it is possible to expand the reaction field contributing to the reaction, reduce the activation energy by the catalyst body 5, and improve the reaction rate. Therefore, with this configuration, it is possible to ensure an increase in the amount of production of the target compound.

The catalyst body 5 can have gas diffusibility. In this case, the catalyst body 5 can be formed to be porous. When the catalyst body 5 has gas diffusibility, the contact with the gas is improved, which is advantageous for promoting the catalytic reaction. In FIG. 1, an example is shown in which the catalyst body 5 having gas diffusibility fills the interelectrode space 420. This can also be said to mean that the catalyst body 5 having gas diffusibility is sandwiched between the first cathode electrode 21 and the second cathode electrode 31. In addition, in FIG. 1, an example is shown in which the catalyst body 5 having gas diffusibility is arranged in layers in the interelectrode space 420. If gas flow in the gas flow path 4 can be ensured, the catalyst body 5 itself can be configured not to have gas diffusibility. In this case, for example, in the region where the catalyst body 5 is provided, gaps may be formed in all or part of the outer periphery of the catalyst body 5 so as not to block the flow of gas. However, even if the catalyst body 5 has gas diffusibility, gaps may be formed in all or part of the outer periphery of the catalyst body 5.

The catalyst body 5 may be composed of a single catalyst, or may have a catalyst supported on a carrier. Examples of the carrier include silica, alumina, and glass wool. The catalyst body 5 may be composed of, for example, a powder. The catalyst body 5 may be a compressed powder having a density that allows gas to pass through.

Specifically, the catalyst body 5 can be configured to contain metal elements from Groups 2 to 16 of the periodic table, more specifically, metal elements such as Sn, In, Ga, Ge, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ir, Pt, Au, Ru, Rh, Pd, Ag, Zr, Nb, Mo, Ta, and W. These metal elements can be used alone or in combination of two or more. With this configuration, the reaction promotion effect by the catalytic reaction can be ensured. From the viewpoint of promoting the reduction of CO ₂ , the catalyst body 5 can preferably contain metal elements such as Ni and Cu.

For other configurations and effects, please refer to the descriptions of other embodiments described below.

(Embodiment 2)
The electrochemical reaction device of the second embodiment will be described with reference to Fig. 2. Of the symbols used in the second and subsequent embodiments, those that are the same as those used in the previous embodiments represent the same components, etc., as those in the previous embodiments, unless otherwise specified.

As illustrated in FIG. 2, the electrochemical reaction device 1 of this embodiment has the catalyst 5 provided in the downstream flow path 44. The electrochemical reaction device 1 of the above-mentioned embodiment 1 has the catalyst 5 provided in the chamber 42, so it is necessary to use the electrochemical reaction device 1 in the same state as the cell operating temperature and the catalyst use temperature. In contrast, the electrochemical reaction device 1 of this embodiment has the catalyst 5 provided in the downstream flow path 44, specifically, in the middle of the downstream flow path 44, so that the cell operating temperature and the catalyst use temperature can be distinguished. Therefore, according to the electrochemical reaction device 1 of this embodiment, the cell operating temperature is set to a temperature range in which the performance of the _CO2 reduction cell 2 and the hydrogen pump cell 3 is good, and the catalyst can be set in a temperature range in which the catalytic activity is high and the target compound is easily obtained. Therefore, according to the electrochemical reaction device 1 of this embodiment, an electrochemical reaction device 1 that is easy to increase the amount of the target compound produced can be obtained.

FIG. 2 shows an example in which the downstream flow passage section 44 has a flow passage extension section 440. The flow passage extension section 440 extends from the side end surface on the downstream side in the gas flow direction of the CO ₂ reduction cell 2 and the hydrogen pump cell 3 arranged to face each other. FIG. 2 shows an example in which the catalyst body 5 is arranged in the middle part of the flow passage extension section 440 in the downstream flow passage section 44. In this embodiment, the side end surface on the downstream side in the gas flow direction of the flow passage extension section 440 is the flow passage outlet part, and the gas outlet section 40 is provided in this part. When the downstream flow passage section 44 has the flow passage extension section 440 and the catalyst body 5 is arranged in this flow passage extension section 440, it is easy to ensure the distance from the CO ₂ reduction cell 2 and the hydrogen pump cell 3 to the catalyst body 5, so that it is easy to distinguish the cell operating temperature from the catalyst use temperature. In addition, in this case, by appropriately selecting the arrangement position of the catalyst body 5 in the flow passage extension section 440, it is easy to ensure the temperature zone in which the catalyst use temperature is optimal. In addition, in this case, the degree of freedom in arrangement of the catalyst body 5 can be improved. The electrochemical reaction device 1 may be configured so that the catalyst body 5 can be heated by a catalyst heating source such as a heater (not shown).

For other configurations and effects, please refer to the descriptions of other embodiments as appropriate.

(Embodiment 3)
The electrochemical reaction device of the third embodiment will be described with reference to FIG.

As illustrated in FIG. 3, in the electrochemical reaction device 1 of this embodiment, the catalyst body 5 is disposed on at least one of the first cathode electrode 21 and the second cathode electrode 31. More specifically, in this embodiment, the catalyst body 5 is disposed on at least one of the first cathode electrode 21 and the second cathode electrode 31 provided in the chamber portion 42 in the gas flow path 4.

According to the electrochemical reaction device 1 of this embodiment, the electrochemical action and the catalytic action are combined in the first cathode electrode 21 and/or the second cathode electrode 31, so that an electrochemical reaction device 1 that is easy to increase the amount of the target compound produced is obtained.

In this embodiment, the catalyst body 5 may be present on the surface, inside, or both of the first cathode electrode 21 and/or the second cathode electrode 31.

The catalyst body 5 is preferably included in the first cathode electrode 21 of the _CO2 reduction cell 2. In this case, the reduction of _CO2 by the catalyst body 5 occurs in the first cathode electrode 21, so that the catalytic effect can be increased. Therefore, in this case, it is easier to increase the amount of the target compound produced, compared to the case where the catalyst body 5 is disposed in the interelectrode space 420. Also, in this case, the thickness of the first cathode electrode 21 of the _CO2 reduction cell 2 can be configured to be thicker than the thickness of the second cathode electrode 31 of the hydrogen pump cell 3. According to this configuration, it is easier to increase the catalytic effect in the first cathode electrode 21, so that the above-mentioned effect can be obtained effectively.

In this embodiment, the first cathode electrode 21 and/or the second cathode electrode 31 may function not only as an electrode but also as a catalyst body 5 that promotes the reduction of CO _2. In this case, specifically, the first cathode electrode 21 and/or the second cathode electrode 31 itself may be configured with an electrode/catalyst material that can function as both the first cathode electrode 21 and/or the second cathode electrode 31 and the catalyst body 5. Examples of the electrode/catalyst material include metal elements of Groups 2 to 16 of the periodic table described in the first embodiment. In this case, too, the electrochemical action and the catalytic action are combined in the first cathode electrode 21 and/or the second cathode electrode 31, so that an electrochemical reaction device 1 that is likely to increase the amount of production of the target compound can be obtained.

For other configurations and effects, please refer to the descriptions of other embodiments as appropriate.

(Embodiment 4)
An electrochemical reaction device according to a fourth embodiment will be described with reference to FIG.

The electrochemical reaction device 1 of the present embodiment is configured to be able to circulate at least a portion of the reacted gas G3 that has passed through the chamber section 42 back to the chamber section 42. With this configuration, gas in which the reaction has not reached thermal equilibrium in the chamber section 42 can be circulated back to the reaction field, so that the CO2 conversion efficiency is improved by reusing unreacted _CO2 , and it becomes easier to increase the final production amount of the target compound.

The reacted gas G3 that is circulated back to the chamber section 42 may be all or a part of the reacted gas G3 that has passed through the chamber section 42. Specifically, the electrochemical reaction device 1 of this embodiment may have the following configuration.

As illustrated in FIG. 4, the electrochemical reaction device 1 of this embodiment has a circulation flow path section 61, an exhaust flow path section 62, a switching valve section 63, a hydrogen sensor 64, and an oxygen sensor 65. The circulation flow path section 61 is a flow path that circulates the reacted gas G3 that has passed through the chamber section 42 to the gas inlet section 41. In this embodiment, one end of the circulation flow path section 61 is connected to the switching valve section 63, and the other end of the circulation flow path section 61 is connected to the gas inlet section 41. Although not shown, the gas flow path 4 can be extended upstream of the gas inlet section 41, and the other end of the circulation flow path section 61 can be connected to this extended portion. In addition, the reacted gas G3 that passes through the chamber section 42 and is circulated to the gas inlet section 41 may be introduced into the gas inlet section 41 without being mixed with the new CO ₂ -containing gas G1, or may be mixed with the new CO ₂ -containing gas G1 introduced into the gas inlet section 41.

The exhaust flow passage section 62 is a flow passage that exhausts the gas G3 after the reaction that has passed through the chamber section 42. In this embodiment, one end of the exhaust flow passage section 62 is connected to the switching valve section 63. In this embodiment, the other end of the exhaust flow passage section 62 is a gas exhaust port for exhausting the gas that has flowed through the exhaust flow passage section 62. The switching valve section 63 is a valve into which the gas G3 after the reaction that has passed through the chamber section 42 flows and switches the gas to flow to the circulation flow passage section 61 or the exhaust flow passage section 62. Specifically, the switching valve section 63 can be configured, for example, as a three-way valve. In FIG. 4, an example is shown in which the downstream flow passage section 44 of the gas flow passage 4 has a flow passage extension section 440, and the end of the flow passage extension section 440 on the gas outlet side is connected to the switching valve section 63. This configuration has the advantage that the gas flow passage 4 and the switching valve section 63 can be easily connected. Although not shown, the gas flow passage 4 may be connected to the switching valve section 63 without providing the flow passage extension section 440.

The hydrogen sensor 64 is a sensor for measuring the hydrogen concentration of the gas G3 after the reaction that has passed through the chamber 42. FIG. 4 shows an example in which the hydrogen sensor 64 is provided in the flow path extension 440 in the downstream flow path 44. The oxygen sensor 65 is a sensor for measuring the oxygen concentration of the gas G3 after the reaction that has passed through the chamber 42. FIG. 4 shows an example in which the hydrogen sensor 64 is provided in the flow path extension 440 in the downstream flow path 44. With these configurations, the hydrogen sensor 64 and the oxygen sensor 65 are provided in the flow path extension 440, which improves the freedom of installation of the hydrogen sensor 64 and the oxygen sensor 65.

The electrochemical reaction device 1 illustrated in FIG. 4 is configured to circulate all or a part of the reacted gas G3 that has passed through the chamber 42 to the chamber 42 via the switching valve 63, the circulation flow path 61, and the gas inlet 41 until at least one of the hydrogen concentration measured by the hydrogen sensor 64 and the oxygen concentration measured by the oxygen sensor 65 reaches a predetermined concentration. This configuration ensures the effects of the present embodiment described above. In addition, this configuration allows the reacted gas G3 that has passed through the chamber 42 to be circulated, exhausted, and replaced with a new gas G1 containing CO ₂ for a certain period of time until at least one of the hydrogen concentration measured by the hydrogen sensor 64 and the oxygen concentration measured by the oxygen sensor 65 reaches a desired predetermined concentration. In addition, this configuration allows a certain proportion of the reacted gas G3 that has passed through the chamber 42 to be exhausted from the exhaust flow path 62, and the remaining gas G3 to be circulated via the circulation flow path 61, making it possible to continuously operate the electrochemical reaction device 1 using the new gas G1 containing CO ₂ and the circulated unreacted gas G3.

In this embodiment, as illustrated in FIG. 4, the catalyst body 5 is provided in the chamber portion 42 of the gas flow path 4. However, the electrochemical reaction device 1 of this embodiment may have the catalyst body 5 provided in the downstream flow path portion 44 of the gas flow path 4, as illustrated in FIG. 2. In this case, the hydrogen sensor 64 and the oxygen sensor 65 described above may be provided downstream in the gas flow direction from the catalyst body 5 arranged in the downstream flow path portion 44.

For other configurations and effects, please refer to the descriptions of other embodiments as appropriate.

(Embodiment 5)
An electrochemical reaction device according to a fifth embodiment will be described with reference to FIGS.

In the electrochemical reaction device 1 of this embodiment, the catalyst body 5 is provided in the chamber section 42. The electrochemical reaction device 1 of this embodiment is configured to retain the gas G1 containing CO ₂ for a predetermined time in the chamber section 42. When the gas G1 containing CO ₂ is not retained in the chamber section 42 for a predetermined time and the gas G1 containing CO ₂ is continuously supplied into the chamber section 42, the reaction rate and the gas diffusion rate may be insufficient. In contrast, according to the above configuration, the gas G1 containing CO ₂ is retained until the reaction in the chamber section 42 has progressed sufficiently, and then the gas G3 after the reaction can be output, so that the reaction rate and the gas diffusion rate are easily made sufficient, the CO2 conversion efficiency is improved, and the final production amount of the target compound is easily increased. The electrochemical reaction device 1 of this embodiment is effective for selectively producing the target compound from the gas G1 containing CO ₂ in a batch manner.

Specifically, for example, as illustrated in FIG. 4, the electrochemical reaction device 1 of this embodiment can be configured to provide a hydrogen sensor 64 for measuring the hydrogen concentration of the gas G3 after the reaction that has passed through the chamber section 42, and an oxygen sensor 65 for measuring the oxygen concentration of the gas G3 after the reaction that has passed through the chamber section 42, in the gas flow path 4 downstream of the chamber section 42, such as the flow path extension section 440 in the downstream side flow path section 44, so that the gas G1 containing CO ₂ can be retained in the chamber section 42 for a predetermined time. This configuration can be implemented in the electrochemical reaction device 1 by having, for example, a circulation flow path section ₆₁ , an exhaust flow path section 62, a switching valve section 63, a hydrogen sensor 64, and an oxygen sensor 65, as illustrated in FIG. 4. In this case, the target compound can be selectively generated in a batch manner using the gas G1 containing CO ₂ , or the target compound can be continuously generated using the new gas G1 containing CO 2 and the circulated gas G3 after the reaction containing unreacted CO ₂ . In this case, the reacted gas G3 that has passed through the chamber section 42 may be configured to flow only to the exhaust flow path section 62 via the switching valve section 63, or, if necessary, the reacted gas G3 that has passed through the chamber section 42 may be configured to flow to the circulation flow path section 61 and the exhaust flow path section 62 via the switching valve section 63.

For other configurations and effects, please refer to the descriptions of other embodiments as appropriate.

(Embodiment 6)
An electrochemical reaction device according to a sixth embodiment will be described with reference to FIG.

As illustrated in FIG. 5, in the electrochemical reaction device 1 of this embodiment, the catalyst body 5 is disposed in the interelectrode space 420 between the first cathode electrode 21 and the second cathode electrode 31 facing each other. The chamber section 42 can be configured to have a flow path structure 421 configured so that the gas G1 containing CO ₂ is introduced from the gas inlet section 41 into the first cathode electrode 21, passes through the first cathode electrode 21, flows into the interelectrode space 420, and then is discharged to the downstream flow path section 44. According to this configuration, the electrochemical reduction reaction of CO 2 proceeds first in the first cathode electrode 21 of the CO ₂ reduction cell _{2, and then the reduction reaction of CO 2 proceeds in the interelectrode space 420 due to the catalytic action of the catalyst body 5. Then, hydrogen ions can be supplied to the interelectrode space 420 through the hydrogen pump cell 3 at a place where the conversion of CO 2 to CO} and CO ²⁺ has progressed due to these reduction reactions. Then, the gas G3 after the reaction containing the target compound is discharged to the downstream flow path section 44. Therefore, with the above configuration, it is possible to obtain an electrochemical reaction device 1 that can easily increase the amount of a target compound produced.

Specifically, the electrochemical reaction device 1 of this embodiment can have the following configuration. As illustrated in FIG. 4, the electrochemical reaction device 1 of this embodiment has an upstream sealing portion 451 and a downstream sealing portion 452. The upstream sealing portion 451 is a sealing member that opens the end face of the first cathode electrode 21 on the gas introduction portion 41 side and seals the end faces of the second cathode electrode 31 and the interelectrode space 420 on the gas introduction portion 41 side. The downstream sealing portion 452 is a sealing member that opens the end face of the interelectrode space 420 on the opposite side to the gas introduction portion 41 side and seals the end faces of the first cathode electrode 21 and the second cathode electrode 31 on the opposite side to the gas introduction portion 41 side. The end face of the interelectrode space 420 on the opposite side to the gas introduction portion 41 side can also be called the end face of the downstream flow path portion 44 side in the interelectrode space 420. In this embodiment, the first cathode electrode 21 and the second cathode electrode 31 can be made porous to ensure gas diffusibility.

With the above configuration, the above-mentioned flow path structure 421 can be constructed relatively easily, making it easy to realize an electrochemical reaction device 1 that can easily increase the amount of target compound produced.

For other configurations and effects, please refer to the descriptions of other embodiments as appropriate.

(Embodiment 7)
The electrochemical reaction device stack of the seventh embodiment will be described with reference to FIG.

As illustrated in FIG. 6, the electrochemical reaction device stack 1S of this embodiment has a stacked structure 10 in which multiple electrochemical reaction devices 1 are stacked. FIG. 6 illustrates an electrochemical reaction device stack 1S having a stacked structure 10 in which multiple electrochemical reaction devices 1 of embodiment 3, in which a catalyst body 5 is disposed on at least one of the first cathode electrode 21 and the second cathode electrode 31, are stacked. Note that the electrochemical reaction devices 1 to be stacked are not limited to the electrochemical reaction device 1 of embodiment 3, and may be electrochemical reaction devices 1 of other embodiments or combinations thereof.

The stacked structure 10 includes at least one of a first arrangement structure 101 in which the second anode electrodes 32 of the hydrogen pump cells 3 in adjacent electrochemical reaction devices 1 are arranged with a gap 101a between them, and a second arrangement structure 102 in which the first anode electrodes 22 of the CO ₂ reduction cells 2 in adjacent electrochemical reaction devices 1 are arranged with a gap 102a between them. FIG. 6 shows an example in which the stacked structure 10 has both the first arrangement structure 101 and the second arrangement structure 102. Note that whether the stacked structure 10 has the first arrangement structure 101 or the second arrangement structure 102, or both the first arrangement structure 101 and the second arrangement structure 102, depends on the stacking order and number of layers of the electrochemical reaction device 1.

In the electrochemical reaction device stack 1S, the gas flow paths 4 of adjacent electrochemical reaction devices 1 are connected so that gas discharged from one of the adjacent electrochemical reaction devices 1 is introduced into the gas inlet portion 41 of the other adjacent electrochemical reaction device 1. Therefore, the stacking direction and the gaps 101a in the first arrangement structure 101 are configured to be supplied with gas G2 containing hydrogen atoms. Note that in this embodiment, as illustrated in FIG. 6, the gaps 102a in the second arrangement structure 102 are configured to allow outside air to be present.

According to the electrochemical reaction device stack 1S of this embodiment, the reacted gas G3 discharged from the electrochemical reaction device 1 is sequentially introduced into the electrochemical reaction device 1 arranged in the subsequent stage, so that the total reaction area increases, and in combination with the action and effect of the electrochemical reaction device 1, the production amount of the target compound can be further increased.

For other configurations and effects, please refer to the descriptions of other embodiments as appropriate.

(Experimental Example 1)
_-CO2 reduction cell-
A slurry for forming an oxide ion conductor was prepared, containing yttria-stabilized zirconia (hereinafter, referred to as YSZ) powder (average particle size: 0.3 μm) containing 8 mol % yttria dissolved therein, polyvinyl butyral (binder), and 2-butaisoamyl and ethanol (mixed solvent).

The prepared oxide ion conductor forming slurry was applied in layers onto a plastic substrate using the doctor blade method and then dried to produce an unfired sheet that would become an oxide ion conductor upon firing. The unfired sheet was fired at 1400°C to produce an oxide ion conductor (thickness 480 μm).

An electrode-forming slurry was prepared containing Ni powder (average particle size: 0.5 μm), YSZ powder, and a solvent. The volume ratio of Ni to YSZ was 50:50.

The electrode forming slurry was applied in layers to both sides of the oxide ion conductor using a doctor blade method. This was fired at 1400°C under _N2 flow to form a first cathode electrode (thickness 20 μm) on one side of the oxide ion conductor and a first anode electrode (thickness 20 μm) on the other side of the oxide ion conductor. This resulted in a _CO2 reduction cell.

- Hydrogen pump cell -
A slurry for forming a hydrogen ion conductor was prepared containing SrZr _0.9 Yb _0.1 O _3-δ (hereinafter referred to as SZY) powder (average particle size: 0.5 μm), polyvinyl butyral (binder), and 2-butaisoamyl and ethanol (mixed solvent).

The prepared slurry for forming the hydrogen ion conductor was applied in layers onto a plastic substrate using the doctor blade method and then dried to produce an unfired sheet that would become a hydrogen ion conductor upon firing. The unfired sheet was fired at 1600°C to produce a hydrogen ion conductor (thickness 480 μm).

An electrode-forming slurry was prepared containing Pt powder (average particle size: 1 μm), SZY powder, and a solvent. The volume ratio of Pt to SZY was 50:50.

Using the doctor blade method, the electrode forming slurry was applied in layers on both sides of the hydrogen ion conductor. This was fired at 1450°C under _N2 flow to form a second cathode electrode (thickness 20 μm) on one side of the hydrogen ion conductor and a second anode electrode (thickness 20 μm) on the other side of the hydrogen ion conductor. This resulted in a hydrogen pump cell. The electrode areas of the first cathode electrode of the _CO2 reduction cell and the second cathode electrode of the hydrogen pump cell were the same. In addition, both the first anode electrode and the first cathode electrode were formed to be porous, and both the second anode electrode and the second cathode electrode were formed to be porous.

- Catalyst -
A powdered catalyst body was prepared by supporting Ni particles on alumina powder, where the amount of Ni particles supported relative to the alumina powder was 12 mass %.

-Electrochemical reaction device-
In the alumina gas flow passage, the first cathode electrode of the _CO2 reduction cell and the second cathode electrode of the hydrogen pump cell were arranged facing each other, and a catalyst was arranged in the interelectrode space formed between the first and second cathode electrodes. The first and second cathode electrodes were exposed in the gas flow passage. The distance between the oxide ion conductor of the _CO2 reduction cell and the hydrogen ion conductor of the hydrogen pump cell was 6 mm. Thus, the electrochemical reaction device of sample 1 was produced.

The electrochemical reaction device of sample 1R was produced in the same manner as in the production of the electrochemical reaction device of sample 1, except that no catalyst was placed between the first and second cathode electrodes arranged facing each other in the gas flow path. The electrochemical reaction device of sample 1R is meant as a reference example electrochemical reaction device.

For the electrochemical reaction device thus fabricated, a first power source was electrically connected to the first cathode electrode and the first anode electrode of the _CO2 reduction cell, and a second power source was electrically connected to the second cathode electrode and the second anode electrode of the hydrogen pump cell, so that a voltage could be applied independently to the _CO2 reduction cell and the hydrogen pump cell. Then, at an operating temperature of 500°C, a reaction test was performed by supplying _CO2 to the gas inlet of the gas flow path and supplying _H2 to the second anode electrode of the hydrogen pump cell. At this time, the gas flow rates were _CO2 : 10cc/min and _H2 : 10cc/min. The voltage applied to the _CO2 reduction cell was 5V DC, and the voltage applied to the hydrogen pump cell was 5V DC. The type of the produced gas was analyzed using a gas chromatograph. The reaction test measured the amount of _CH4 produced (ml) and the _CO2 conversion rate (%). The _CO2 conversion rate (%) was calculated from the formula: _CH4 production amount (mol)/input _CO2 (mol) x 100. The results are shown in Figures 7 and 8.

As shown in Figures 7 and 8, in the electrochemical reaction device of sample 1R without a catalyst in the gas flow path, conversion of _CO2 was observed and _CH4 could be selectively generated, but the amount of _CH4 generated was relatively small. In contrast, in the electrochemical reaction device of sample 1 in which a catalyst was arranged in the gas flow path, it was confirmed that the _CO2 conversion rate was high, _CH4 could be selectively generated, and the amount of _CH4 generated could be relatively increased. This is thought to be because the reaction of CO + _3H2 → _CH4 + _H2O , which hardly occurs without the catalyst, occurred in the catalyst part by providing a catalyst that promotes the reduction of _CO2 in the gas flow path. Note that, although not shown, in the electrochemical reaction device of sample 1R according to the reference example, when the above voltage was applied to only one of the _CO2 reduction cell and the hydrogen pump cell, _CO2 conversion was confirmed, but there was almost no generation of _CH4 .

From these results, it can be said that the electrochemical reaction device disclosed herein can improve the selectivity of the target compound through the reduction reaction of _CO2 , thereby making it possible to increase the amount of the target compound produced.

(Experimental Example 2)
The electrochemical reaction devices of Sample 1 and Sample 1R were prepared in the same manner as in Experimental Example 1. In addition, the electrochemical reaction device of Sample 2 was prepared in the same manner as in Experimental Example 1 except that, in the electrochemical reaction device of Sample 1 in Experimental Example 1, a catalyst body was not disposed between the first cathode electrode and the second cathode electrode, the first cathode electrode of the _CO2 reduction cell was made of Ni particles and had a thickness of 500 μm, and the second cathode electrode of the hydrogen pump cell was made of Ni particles and had a thickness of 20 μm. Note that this experimental example is an example in which both the first cathode electrode and the second cathode electrode are made of an electrode/catalyst material.

The amount of _CH4 produced (ml) was measured for the produced electrochemical reaction device in the same manner as in Experimental Example 1. The results are shown in FIG.

As can be seen from the comparison of the test results of the electrochemical reaction device of sample 1 and the electrochemical reaction device of sample 2 shown in Fig. 9, it was confirmed that by disposing a catalyst on at least one of the first and second cathode electrodes present in the gas flow passage, the amount of _CH4 generated can be increased more than by disposing a catalyst in the interelectrode space between the first and second cathode electrodes present in the gas flow passage. This is thought to be because the electrochemical action and catalytic action are combined in the first and/or second cathode electrodes, making it easier to increase the amount of target compound generated.

The present invention is not limited to the above-mentioned embodiments and experimental examples, and various modifications are possible without departing from the gist of the present invention. Furthermore, the configurations shown in the embodiments and experimental examples can be combined in any combination. Furthermore, the claims described in the claims at the time of filing can be combined in any combination.

1 Electrochemical reaction device 2 CO2 reduction cell ₂₀ Oxide ion conductor 21 First cathode electrode 22 First anode electrode 3 Hydrogen pump cell 30 Hydrogen ion conductor 31 Second cathode electrode 32 Second anode electrode 4 Gas flow path 41 Gas inlet 5 Catalyst G1 Gas containing _CO2 G2 Gas containing hydrogen atoms 1S Electrochemical reaction device stack

Claims (10)

a CO2 reduction cell ( _{2) including: an oxide ion conductor (20) capable of transferring oxide ions; a first cathode electrode (21) provided on one side of the oxide ion conductor and capable of electrochemically reducing the CO2 from} a gas (G1) containing CO2; and a first anode electrode (22) provided on the other side of the oxide ion conductor and capable of releasing the oxide ions that have transferred through the _oxide ion conductor as oxygen;
a hydrogen pump cell (3) including: a hydrogen ion conductor (30) capable of moving hydrogen ions; a second anode electrode (32) provided on one side of the hydrogen ion conductor and capable of dissociating hydrogen ions from a gas (G2) containing hydrogen atoms; and a second cathode electrode (31) provided on the other side of the hydrogen ion conductor and supplied with the hydrogen ions that have moved through the hydrogen ion conductor;
A gas flow path (4) including a gas inlet (41) into which the _CO2 -containing gas is introduced,
The first cathode electrode of the _CO2 reduction cell and the second cathode electrode of the hydrogen pump cell are provided in the gas flow path so as to face each other,
A catalyst (5) for promoting the reduction of the _CO2 is provided in the gas flow path.
An electrochemical reactor (1). the gas flow path has a chamber portion (42) constituted by an area portion in which the first cathode electrode and the second cathode electrode are disposed, and a downstream flow path portion (44) communicating with the chamber portion and disposed downstream of the chamber portion,
The catalyst body is provided in at least one of the chamber section and the downstream side flow path section.
Electrochemical reactor (1) according to claim 1. the catalytic body is disposed in an interelectrode space (420) formed between the first and second cathode electrodes; and/or
At least one of the first cathode electrode and the second cathode electrode is disposed on the cathode.
Electrochemical reactor (1) according to claim 1 or 2. The catalyst body is
Contains at least one metal element selected from the group consisting of Sn, In, Ga, Ge, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ir, Pt, Au, Ru, Rh, Pd, Ag, Zr, Nb, Mo, Ta, and W;
Electrochemical reactor (1) according to claim 1 or 2. At least a part of the reacted gas (G3) that has passed through the chamber can be circulated to the chamber.
Electrochemical reactor (1) according to claim 2. a circulation flow path section (61) for circulating the reacted gas (G3) that has passed through the chamber section to the gas inlet section;
an exhaust flow passage section (62) for exhausting the gas after the reaction;
a switching valve unit (63) into which the reacted gas flows and which switches the gas so as to flow into the circulation flow path unit or the exhaust flow path unit;
a hydrogen sensor (64) for measuring the hydrogen concentration of the gas after the reaction;
and an oxygen sensor (65) for measuring the oxygen concentration of the gas after the reaction,
The whole or a part of the gas after the reaction is circulated to the chamber section via the switching valve section, the circulation flow path section and the gas introduction section until at least one of the hydrogen concentration measured by the hydrogen sensor and the oxygen concentration measured by the oxygen sensor reaches a predetermined concentration.
Electrochemical reactor (1) according to claim 2. The catalyst body is provided in the chamber section,
The gas containing _CO2 is configured to remain in the chamber for a predetermined period of time.
Electrochemical reactor (1) according to claim 2. The catalyst body is disposed in an interelectrode space (420) formed between the first cathode electrode and the second cathode electrode;
The chamber section includes:
The gas containing _CO2 is introduced into the first cathode electrode from the gas inlet, passes through the first cathode electrode, flows into the interelectrode space, and then is discharged into the downstream flow path portion.
Electrochemical reactor (1) according to claim 2. an upstream sealing portion (451) that opens an end face of the first cathode electrode on the side of the gas inlet portion and seals the end faces of the second cathode electrode and the interelectrode space on the side of the gas inlet portion;
a downstream sealing portion (452) that opens an end face of the interelectrode space opposite to the gas inlet portion and seals the end faces of the first cathode electrode and the second cathode electrode opposite to the gas inlet portion,
Electrochemical reactor (1) according to claim 8. The electrochemical reaction device according to claim 1 or 2 has a laminated structure (10) in which a plurality of layers are laminated,
The stacked structure includes at least one of a first arrangement structure (101) in which the second anode electrodes of the hydrogen pump cells in the adjacent electrochemical reaction devices are arranged with a gap (101a) between them, and a second arrangement structure (102) in which the first anode electrodes of the _CO2 reduction cells in the adjacent electrochemical reaction devices are arranged with a gap (102a) between them,
The gas flow paths of the adjacent electrochemical reaction devices are connected to each other so that a reacted gas (G3) discharged from one of the adjacent electrochemical reaction devices is introduced into the gas inlet of the other adjacent electrochemical reaction device,
The gas containing hydrogen atoms is supplied to the gap in the first arrangement structure.
Electrochemical reactor stack (1S).

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