Electrolytic cell device, hydrocarbon production system, method for manufacturing an electrolytic cell device, and method for using the same

Abstract

Provided is an electrolytic cell unit (U) which can efficiently perform electrolysis of water and carbon dioxide. The electrolytic cell unit (U) is configured to at least comprise: an electrolytic cell (1) in which an electrode layer (2) and a counterpart electrode layer (3) are formed with an electrolytic layer (1a) therebetween; and a discharge path (5a) for discharging hydrogen generated from the electrode layer (2), wherein the electrolytic cell (1) is formed on a support body (4) in a thin layer shape, and a reverse water gas shift reaction unit (20), which generates carbon monoxide by using carbon dioxide and the hydrogen through a reverse water gas shift reaction, is provided to at least a portion of the discharge path (5a).

Description

Technical Field

[0001] The present invention relates to an electrolytic cell unit including an electrolytic cell configured to include an electrode layer and a counter electrode layer provided with an electrolyte layer interposed therebetween, a method for manufacturing or using the same, an electrolytic cell device configured to include the electrolytic cell unit, and a hydrocarbon production system configured to include this type of electrolytic cell device. This type of hydrocarbon production system is configured as a system for producing hydrocarbons from at least water and carbon monoxide. The electrolytic cell device including the electrolytic cell unit serves for electrolysis (electrolytic decomposition) of a hydrogen source (typically water), and further electrolysis (electrolytic decomposition) of a carbon monoxide source (typically carbon dioxide).

Background Art

[0002] This type of hydrocarbon production system is disclosed in Patent Document 1 or 2. The system disclosed in Patent Document 1 includes a high-temperature electrolyte (HTE) reactor (corresponding to the electrolytic reaction section of the present invention) including a stack of electrolytic single cells (corresponding to the electrolytic cell unit of the present invention) that generate either hydrogen or synthesis feed gas (syngas, representing a mixture of hydrogen and carbon monoxide) from steam and carbon dioxide, and converts the syngas obtained in this electrolytic single cell into a desired combustible gas by heterogeneous catalysis. Therefore, the technique disclosed in this Patent Document 1 provides a hydrocarbon synthesis section downstream of the electrolytic reaction section, and produces hydrocarbons using water and carbon dioxide as starting materials. Referring to FIG. 3 of Patent Document 1, this system is a large cylindrical device.

[0003] On the other hand, the technique disclosed in Patent Document 2 relates to a power-to-gas unit that generates useful gas (specifically, methane) from electric power, and specifically discloses a technique including a methanation reaction catalyst material in the cathode of a stack of basic electrolytic cells of solid oxide (SOEC). Also in the technique disclosed in Patent Document 2, the electrolytic cell serves as the electrolytic reaction section, and the methanation reaction catalyst material provided in the cathode constitutes the hydrocarbon synthesis section.

[0004] In these prior arts, in the electrolysis reaction section, so-called "co-electrolysis" is performed in which water and carbon dioxide are electrolyzed together. For the synthesis of hydrocarbons (so-called methanation), a heterogeneous catalyst is used.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, the inventors have found the following problems regarding co-electrolysis in the electrolysis reaction section and hydrocarbon synthesis in the hydrocarbon synthesis section. 1. Problems of co-electrolysis Since the electrolysis voltage of water is around 1.23 V while the electrolysis voltage of carbon dioxide is around 1.33 V, the electrolysis reaction of carbon dioxide is less likely to occur than that of water. As a result, even when attempting to cause a co-electrolysis reaction, the electrolysis reaction of carbon dioxide is difficult to occur, and it is impossible to sufficiently ensure the concentration of carbon monoxide required for hydrocarbon synthesis.

[0007] 2. Problems in hydrocarbon synthesis Although a heterogeneous catalyst is said to be used, it is difficult to select this type of catalyst, and a technique for stably synthesizing hydrocarbons has not yet been established.

[0008] 3. Furthermore, referring to the apparatus described in Patent Document 1, the apparatus is large, and there is room for improvement in terms of efficiently performing hydrocarbon synthesis without consuming special energy.

[0009] In view of this situation, the main problem of the present invention is to appropriately ensure hydrogen and carbon monoxide required for hydrocarbon synthesis, for example, in an electrolysis cell unit for a gas serving as a hydrogen source or a carbon monoxide source, and to obtain a hydrocarbon production system capable of producing hydrocarbons using the hydrogen and carbon monoxide thus generated.

Means for Solving the Problems

[0010] The first characteristic configuration of the electrolysis cell unit according to the present invention is configured as an electrolysis cell unit including at least an electrolysis cell in which an electrode layer and a counter electrode layer are formed with an electrolyte layer interposed therebetween, and a discharge path for discharging hydrogen generated in the electrode layer, the electrolysis cell being formed in a thin layer on a support, and a reverse water gas shift reaction unit for generating carbon monoxide using carbon dioxide and the hydrogen is provided in at least a part of the discharge path.

[0011] This electrolysis cell unit includes an electrolysis cell. When an electric current flows between the electrode layer and the counter electrode layer of this electrolysis cell, hydrogen is generated from a gas serving as a hydrogen source by an electrolysis reaction. The generated hydrogen is released into the discharge path, but by making at least a part of this part a reverse water gas shift reaction unit, carbon monoxide can be generated using carbon dioxide flowing through the discharge path and hydrogen generated in the electrode layer. In this electrolysis cell unit, since the functional part as the electrolysis reaction part and the functional part as the reverse water gas shift reaction part are configured as separate parts (the former is the electrolysis cell and the latter is the discharge path), by using the optimal material for each part and maintaining an appropriate temperature environment, as a result, carbon dioxide that cannot be sufficiently decomposed in the electrolysis reaction part can be converted into carbon monoxide in the reverse water gas shift reaction part. Furthermore, such an electrolysis reaction and a reverse water gas shift reaction can be carried out within a single electrolysis cell unit. As will be described later, since both reactions require a relatively high temperature, it is preferable to accommodate them within a single unit.

[0012] Furthermore, the electrolytic cell according to the present invention is formed in a thin film shape on a support, and thus exhibits sufficient performance with high efficiency while having a robust structure. In this regard, by forming the electrolytic cell in a thin film shape, it is possible to suppress the internal resistance of the electrolytic cell and realize a high-performance electrolytic cell, and also to reduce the amount of expensive cell materials used and reduce the cost of the electrolytic cell.

[0013] The second characteristic configuration of the present invention lies in the fact that the support is made of metal.

[0014] By adopting metal as the support, the material cost can be suppressed by ensuring the strength with an inexpensive metal material, and since the processability is higher than that of ceramics, the shape selectivity is high.

[0015] The third characteristic configuration of the present invention is that a plurality of through holes penetrating the support are provided, the electrode layer is provided on one surface of the support, the discharge path is provided along the other surface, and the water-repellent gas shift reaction part is provided at least in part on the inner surface of the discharge path.

[0016] According to this characteristic configuration, hydrogen generation can be realized by providing an electrode layer on one surface of the support. The hydrogen thus generated is guided from the electrode layer to the discharge path through a plurality of through holes, and the reaction in the water-repellent gas shift reaction part provided at least in part at this site occurs favorably, and when carbon dioxide is supplied, at least carbon monoxide can be generated.

[0017] The fourth characteristic configuration of the present invention is that the water-repellent gas shift reaction part is provided at least in part inside the through hole.

[0018] According to this characteristic configuration, at least part of the through hole also functions as a water-repellent gas shift reaction part.

[0019] The fifth characteristic configuration of the present invention is that the water-repellent gas shift reaction part is provided on a surface of the support different from the surface on which the electrolytic cell is formed.

[0020] According to this characteristic configuration, on different surfaces of the support (for example, the surface opposite to the surface on which the electrolytic cell is formed, which is the back surface), it is possible to obtain a function as a water-repellent gas shift reaction part.

[0021] The sixth characteristic configuration of the present invention is It includes a separator that separates hydrogen generated in the electrode layer and oxygen generated in the counter electrode layer, and the water-repellent gas shift reaction part is provided at least in part on the hydrogen discharge path side of the separator.

[0022] According to this characteristic configuration, when the electrolytic cell undergoes an electrolytic reaction, hydrogen is generated from the electrode layer and oxygen is generated from the counter electrode layer. By providing a separator, it is possible to cause a water-repellent gas shift reaction using hydrogen and accompanying carbon dioxide in the water-repellent gas shift reaction part.

[0023] The seventh characteristic configuration of the present invention is that the separator is made of metal.

[0024] By adopting metal as the separator, the material cost can be suppressed by ensuring gas separation performance with an inexpensive metal material. Also, it is more workable than ceramics and has a higher shape selectivity.

[0025] The eighth characteristic configuration of the present invention is The water-repellent gas shift catalyst contained in the water-repellent gas shift reaction part is a catalyst in which a metal or metal oxide is supported on a carrier.

[0026] According to this characteristic configuration, it is possible to cause a water-repellent gas shift reaction with a catalyst in which a metal or metal oxide is supported on a carrier.

[0027] The ninth characteristic configuration of the present invention is The water-repellent gas shift catalyst contained in the water-repellent gas shift reaction part is a catalyst containing at least one of platinum, nickel, and iron.

[0028] According to this characteristic configuration, highly active reverse water gas shift performance can be obtained as described later.

[0029] The tenth characteristic configuration of the present invention is that the carrier is a carrier mainly composed of a ceria-based metal oxide or a zirconia-based metal oxide.

[0030] According to this characteristic configuration, highly active reverse water gas shift performance can be obtained as described later, and in the high-temperature environment required for the reverse water gas shift reaction, its catalytic ability and durability can be obtained. Further, when the carrier is a carrier mainly composed of a ceria-based metal oxide or a zirconia-based metal oxide, the thermal expansion coefficient can be made close to that of the materials used for the constituent materials and supports of the electrolytic cell, etc. Therefore, even when the temperature cycle of low temperature and high temperature is repeated, the electrolytic cell unit is less likely to be damaged, and an electrolytic cell unit with excellent reliability and durability can be realized.

[0031] When obtaining a reverse water gas shift catalyst, it is preferably provided with at least a firing step of firing at a temperature of 450 °C or higher.

[0032] For the use of the reverse water gas shift catalyst, in order to cause the target reverse water gas shift reaction, it is necessary to set the reaction temperature range to a relatively high temperature range. However, if the catalyst is obtained by firing in this temperature range, the catalyst can be used stably. It is preferably 450 °C or higher, and more preferably 600 °C or higher and 800 °C or higher because the stability in the high temperature range can be enhanced. For example, even when combined with a solid oxide type electrolytic cell used in a relatively high temperature range (for example, 600 °C to 800 °C), the catalyst can be used stably. Further, if the firing temperature is too high, the cost required for the firing step becomes too high, so the upper limit is about 1200 °C.

[0033] When using the reverse water gas shift catalyst, it is preferable to subject the reverse water gas shift catalyst to a pre-reduction treatment and then use it in the reaction.

[0034] The catalytic active components contained in the water-reverse gas shift catalyst often become at least partially metal oxides in the firing process. However, by performing a pre-reduction treatment (a treatment in which a reduction treatment is performed before use), the catalytic active components in the oxidized state can be reduced to exhibit good catalytic activity.

[0035] The characteristic configuration of the electrolytic cell device according to the present invention is at least including the electrolytic cell unit described so far, an electrolytic raw material supply unit that supplies water or water and carbon dioxide to the electrolytic cell unit, and a power supply unit that supplies power.

[0036] According to this characteristic configuration, an electrolytic raw material is supplied from the electrolytic raw material supply unit to the electrolytic cell unit, and power is supplied from the power supply unit to the electrolytic cell, so that the electrolytic raw material can be electrolyzed by the power. Here, for example, when the electrolytic raw material is water, hydrogen can be generated by the electrolysis. When the electrolytic raw material is carbon dioxide, carbon monoxide is generated by the electrolysis. Further, in the electrolytic cell unit of the present invention, a water-reverse gas shift reaction unit that generates carbon monoxide using carbon dioxide and the hydrogen by a water-reverse gas shift reaction is provided in at least a part of the discharge path, so that carbon monoxide can also be generated by the reaction at this site.

[0037] The characteristic configuration of the hydrocarbon production system according to the present invention is including the electrolytic cell unit or the electrolytic cell device described so far, and a hydrocarbon synthesis reaction unit that reacts at least the hydrogen and the carbon monoxide to generate hydrocarbons.

[0038] According to this characteristic configuration, using the electrolytic cell device described so far, hydrocarbons can be synthesized in the hydrocarbon synthesis reaction unit by receiving the supply of hydrogen and carbon monoxide from this device. Here, since the electrolytic cell unit or the electrolytic cell device according to the present invention includes at least a water-reverse gas shift reaction unit, it is possible to supplement carbon monoxide, which may be insufficient in the electrolysis in the electrolytic reaction unit, with this water-reverse gas shift reaction unit, resulting in a compact and high-performance hydrocarbon production system.

[0039] The characteristic configuration of the method for manufacturing an electrolytic cell unit according to the present invention is that in the step of forming the water-repellent gas shift reaction part provided in this electrolytic cell unit, there is at least a firing step of firing at a temperature of 450°C or higher.

[0040] The electrolytic cell unit according to the present invention includes an electrolytic cell in which an electrode layer, an electrolyte layer, and a counter electrode layer are formed, and includes a water-repellent gas shift reaction part. However, a firing operation is required for the formation of the electrolytic cell and the formation of the water-repellent gas shift reaction part, and the firing steps required for both parts can be performed simultaneously. Further, in the water-repellent gas shift reaction part provided in an electrolytic cell unit that operates in a relatively high temperature range, it is preferable to include a firing step of firing at a temperature of 450°C or higher because the catalyst can be stably used. Further, it is more preferable that the firing temperature is 600°C or higher, and further preferably 800°C or higher. When the firing temperature is such, for example, even in the case of a water-repellent gas shift reaction part provided in a solid oxide type electrolytic cell unit that operates in a temperature range of about 600°C to 800°C, the functions of the electrolytic cell and the water-repellent gas shift reaction part can be stably operated over a long period in such a high temperature range. Note that if the firing temperature is too high, the cost of the firing step becomes too high, so the upper limit is about 1200°C.

[0041] The characteristic configuration of the method of using the electrolytic cell unit according to the present invention is that it is used after performing a reduction pretreatment on the water-repellent gas shift reaction part.

[0042] As will be described later, a catalyst suitable for the water-repellent gas shift reaction part of the electrolytic cell unit according to the present invention has an active metal component that is an oxide in its state before use, and by performing a reduction pretreatment before use, the activity as a water-repellent gas shift catalyst can be enhanced.

Brief Description of the Drawings

[0043]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Embodiments for Carrying Out the Invention

[0044] Embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows the configuration of one form of a hydrocarbon production system 100 recently proposed by the inventors.

[0045] As shown in the figure, this hydrocarbon production system 100 is configured to sequentially include an electrolysis reaction unit 10, a first catalytic reaction unit 20, a second catalytic reaction unit 30, a heavy hydrocarbon separation unit 35 (shown as a CnHm separation unit in the figure), a water separation unit 40 (shown as an H2O separation unit in the figure), and a carbon dioxide separation unit 50 (shown as a CO2 separation unit in the figure).

[0046] The electrolysis reaction unit 10 is a site for electrolyzing at least a part of the inflowing gas. The first catalytic reaction unit 20 is a reverse water gas shift reaction unit for performing a reverse water gas shift reaction on at least a part of the inflowing gas. The second catalytic reaction unit 30 is configured to function as a hydrocarbon synthesis reaction unit for synthesizing at least a part of the inflowing gas into hydrocarbons. Here, the synthesized hydrocarbons are mainly CH4 (hydrocarbons with 1 carbon atom), but also include other lower saturated hydrocarbons with 2 to 4 carbon atoms, etc. Further, as will be shown later, by appropriately selecting the catalyst used in the second catalytic reaction unit 30, heavy hydrocarbons with a larger number of carbon atoms than the above-mentioned lower saturated hydrocarbons, unsaturated hydrocarbons, or oxygen-containing hydrocarbons can also be synthesized. Therefore, in this specification, hydrocarbons are a concept including all of these, and are also collectively referred to as hydrocarbon compounds.

[0047] The heavy hydrocarbon separation unit 35, the water separation unit 40, and the carbon dioxide separation unit 50 are sites for removing at least a part of predetermined components (CnHm, H2O, and CO2 in the described order) from the gas flowing inside. The components removed and recovered by the water separation unit 40 and the carbon dioxide separation unit 50 are returned to a predetermined site of the system and reused via a water return path 41 and a carbon dioxide return path 51, as shown in FIG. 1. The H2O and CO2 returned through the two return paths 41 and 51 are indicated above each path. As a result, this hydrocarbon production system 100 is established as a carbon closed system that substantially does not release CO2 outside the system.

[0048] In the figure, the gas flowing into each part is shown in front of each part, and the gas released from the part is shown behind.

[0049] In the electrolysis reaction section 10, H2O and CO2 as starting materials flow in and are electrolyzed internally. H2O is decomposed into H2 and O2, and a part of CO2 is decomposed into CO and O2 and released.

[0050] The reaction is described as follows. 2H2O → 2H2 + O2 (Equation 1) 2CO2 → 2CO + O2 (Equation 2) These Equations 1 and 2 are also shown inside the box indicating the electrolysis reaction section 10 in Figure 1.

[0051] In the first catalyst reaction section 20 (reverse water gas shift reaction section), H2 and CO2 flow in, and a reverse water gas shift reaction occurs inside, where CO2 becomes CO and H2 becomes H2O and is released.

[0052] The reaction is described as the following equilibrium reaction, but the reverse water gas shift reaction is the reaction in which the reaction described by the following Equation 3 proceeds to the right (the reaction in which CO2 and H2 react to produce CO and H2O). CO2 + H2 ⇔ CO + H2O (Equation 3) This Equation 3 is also shown inside the box indicating the first catalyst reaction section 20 (reverse water gas shift reaction section) in Figure 1. Inside this box, the reverse water gas shift catalyst cat1 used in the reaction is also schematically shown.

[0053] In the second catalyst reaction section 30 (hydrocarbon synthesis reaction section), H2 and CO flow in, and hydrocarbons are synthesized by a catalytic reaction. For example, the reaction of synthesizing CH4 from CO and H2 is described as the following equilibrium reaction, but the reaction of synthesizing CH4 from CO and H2 is the reaction in which the reaction described by the following Equation 4 proceeds to the right (the reaction in which CO and H2 react to produce CH4 and H2O). CO + 3H2 ⇔ CH4 + H2O (Equation 4) This Equation 4 is also shown inside the box indicating the second catalyst reaction section 30 (hydrocarbon synthesis reaction section) in Figure 1. Inside this box, the hydrocarbon synthesis catalyst cat2 used in the reaction is also schematically shown. Furthermore, the equilibrium reaction of (Equation 3) also occurs at this site. Depending on the type of catalyst used in the second catalytic reaction section 30, since it is possible to proceed with a Fischer-Tropsch (FT) synthesis reaction or the like, various hydrocarbons such as ethane, propane, butane, pentane, hexane, etc., paraffins, olefinic hydrocarbons, etc. can be synthesized from CO and H2.

[0054] As will be described later, the inventors have shown an example of a catalyst using ruthenium as its catalytic active component as the hydrocarbon synthesis catalyst cat2 disposed in the second catalytic reaction section 30. However, heavy hydrocarbons are also synthesized with a catalyst containing iron, cobalt, etc. as its catalytic active component, and this type of heavy hydrocarbon can be condensed as the temperature decreases and separated from the carrier gas. Therefore, in the above-described heavy hydrocarbon separation section 35, the hydrocarbon component separated in this way is separated.

[0055] The H2O generated in the water separation section 40 is separated and returned to the upstream side of the electrolysis reaction section 10 via the water return path 41 (water recycle line).

[0056] The CO2 generated in the carbon dioxide separation section 50 is separated and returned to the upstream side of the electrolysis reaction section 10 via the carbon dioxide return path 51 (carbon dioxide recycle line).

[0057] As a result, in this hydrocarbon production system 100, hydrocarbons are finally synthesized and can be supplied to the outside.

[0058] The above is the outline of the hydrocarbon production system 100 described above. Hereinafter, the configuration of each part and its role will be described. 〔Electrolysis reaction section〕 As shown previously, this electrolysis reaction section 10 consumes the electric power supplied according to the above formulas 1 and 2 and decomposes the inflowing H2O and CO2.

[0059] FIG. 2 schematically shows the cross-sectional configuration of this electrolysis reaction section 10. The figure shows an electrolytic cell unit U that is stacked in multiple layers to form an electrolytic stack (not shown). This electrolytic cell unit U includes an electrolytic cell 1, and the electrolytic cell 1 is configured to include an electrode layer 2 on one surface of an electrolyte layer 1a and a counter electrode layer 3 on the other surface. The electrode layer 2 serves as the cathode in the electrolytic cell 1, and the counter electrode layer 3 serves as the anode. Incidentally, this electrolytic cell unit U is supported by a metal support 4. Here, the case where a solid oxide type electrolytic cell is used as the electrolytic cell 1 is exemplified.

[0060] The electrolyte layer 1a can be formed in a thin film state with a thickness of 10 μm or less. As its constituent materials, YSZ (yttria-stabilized zirconia), SSZ (scandia-stabilized zirconia), GDC (gadolinium-doped ceria), YDC (yttrium-doped ceria), SDC (samarium-doped ceria), LSGM (strontium-magnesium-added lanthanum gallate), etc. can be used. In particular, zirconia-based ceramics are preferably used.

[0061] This electrolyte layer 1a is preferably formed by a low-temperature firing method (for example, a wet method using a firing process in a low-temperature range without firing treatment in a high-temperature range exceeding 1100 °C), a spray coating method (methods such as a thermal spraying method, an aerosol deposition method, an aerosol gas deposition method, a powder jet deposition method, a particle jet deposition method, a cold spray method), a PVD method (a sputtering method, a pulsed laser deposition method, etc.), a CVD method, etc. By these film-forming processes that can be used in a low-temperature range, a dense electrolyte layer 1a with high airtightness and gas barrier properties can be obtained without using firing in a high-temperature range exceeding 1100 °C, for example. Therefore, damage to the metal support 4 can be suppressed, and element interdiffusion between the metal support 4 and the electrode layer 2 can be suppressed, and an electrolytic cell unit U with excellent performance and durability can be realized. In particular, using a low-temperature firing method or a spray coating method, etc. is preferable because a low-cost element can be realized. Furthermore, using the spray coating method is even more preferable because a dense electrolyte layer 1a with high airtightness and gas barrier properties can be easily obtained in a low-temperature range.

[0062] Further, the electrolyte layer 1a is densely configured in order to shield gas leakage and exhibit high ionic conductivity. The density of the electrolyte layer 1a is preferably 90% or more, more preferably 95% or more, and still more preferably 98% or more. When the electrolyte layer 1a is a uniform layer, its density is preferably 95% or more, and more preferably 98% or more. Further, when the electrolyte layer 1a is composed of a plurality of layers, it is preferable that at least a part of them includes a layer (dense electrolyte layer) having a density of 98% or more, and more preferably includes a layer (dense electrolyte layer) having a density of 99% or more. When such a dense electrolyte layer is included in a part of the electrolyte layer 1a, even when the electrolyte layer 1a is composed of a plurality of layers, it is possible to easily form a dense, airtight, and highly gas-barrier electrolyte layer 1a.

[0063] The electrode layer 2 can be provided in a thin layer state on the front surface of the metal support 4 in a region larger than the region where the holes 4a are provided. When it is a thin layer, its thickness can be, for example, about 1 μm to 100 μm, preferably 5 μm to 50 μm. With such a thickness, it is possible to reduce the amount of use of an expensive electrode layer material to reduce costs while ensuring sufficient electrode performance. The entire region where the holes (through holes) 4a are provided is covered with the electrode layer 2. That is, the holes 4a are formed inside the region of the metal support 4 where the electrode layer 2 is formed. In other words, all the holes 4a are provided facing the electrode layer 2.

[0064] As the constituent material of this electrode layer 2, composite materials such as NiO-GDC, Ni-GDC, NiO-YSZ, Ni-YSZ, CuO-CeO2, and Cu-CeO2 can be used. In these examples, GDC, YSZ, and CeO2 can be referred to as the aggregates of the composite material. Note that the electrode layer 2 is preferably formed by a low-temperature firing method (for example, a wet method using a firing treatment in a low-temperature range without a firing treatment in a high-temperature range higher than 1100°C), a spray coating method (methods such as a spraying method, an aerosol deposition method, an aerosol gas deposition method, a powder jet deposition method, a particle jet deposition method, and a cold spray method), a PVD method (such as a sputtering method and a pulsed laser deposition method), a CVD method, or the like. By these processes that can be used in a low-temperature range, a good electrode layer 2 can be obtained without using firing in a high-temperature range higher than 1100°C. Therefore, it is preferable because it is possible to realize an electrochemical element excellent in durability without damaging the metal support 4 and suppressing the elemental interdiffusion between the metal support 4 and the electrode layer 2. Furthermore, it is more preferable to use the low-temperature firing method because it facilitates the handling of raw materials.

[0065] The counter electrode layer 3 can be formed in a thin layer state on the surface of the electrolyte layer 1a opposite to the electrode layer 2. When it is a thin layer, the thickness can be, for example, about 1 μm to 100 μm, preferably 5 μm to 50 μm. With such a thickness, it is possible to reduce the amount of use of an expensive counter electrode layer material to reduce costs while ensuring sufficient electrode performance. As the material of the counter electrode layer 3, for example, composite oxides such as LSCF and LSM, ceria-based oxides, and mixtures thereof can be used. In particular, it is preferable that the counter electrode layer 3 contains a perovskite-type oxide containing two or more elements selected from the group consisting of La, Sr, Sm, Mn, Co, and Fe.

[0066] These electrolyte layer 1a, electrode layer 2, and counter electrode layer 3 are formed as thin films as described later, and the inventor refers to this as forming in a thin layer state.

[0067] As shown above, the electrolytic cell unit U has a metal support type, includes a metal support 4 as a support for the electrode layer 2, and is provided with a supply path forming member 5 that forms a U-shaped electrode layer side gas supply path 5a on the side opposite to the electrode layer 2 across the metal support 4. Further, a large number of holes 4a are provided in the metal support 4 so as to penetrate the front and back surfaces. The gases (H2O and CO2) supplied through the electrode layer side gas supply path 5a are subject to electrolysis and are supplied to the electrode layer 2 through the large number of holes 4a. Further, the generated gases (H2, CO) flow out from the holes 4a.

[0068] On the other hand, also with respect to the counter electrode layer 3 side, a supply path forming member 6 for forming a counter electrode layer side gas supply path 6a is provided. As shown in the drawing, this supply path forming member 6 is provided with a large number of grooves on the counter electrode layer 3 side and is configured to supply a transport gas g2 (for example, air or the like) to the counter electrode layer side gas supply path 6a.

[0069] The metal support 4 serves as a support that supports the electrode layer 2, the electrolyte layer 1a, and the counter electrode layer 3 and maintains the strength of the entire electrolytic cell 1 and the electrolytic cell unit U. In this example, a plate-shaped metal support 4 is used as the metal support, but other shapes, such as box-shaped or cylindrical shapes, are also possible. The metal support 4 only needs to have sufficient strength to form the electrolytic cell unit U as a support. For example, those having a thickness of about 0.1 mm to 2 mm, preferably about 0.1 mm to 1 mm, and more preferably about 0.1 mm to 0.5 mm can be used. In the present embodiment, the support is made of metal, but it is also possible to use, for example, ceramics.

[0070] The metal support 4 has, for example, a plurality of holes 4a provided so as to penetrate the front surface and the back surface of the metal plate. For example, the holes 4a can be provided in the metal support 4 by mechanical, chemical, or optical drilling processes. The holes 4a have a function of allowing gas to permeate from the back surface to the front surface of the metal support 4. The holes 4a may be provided inclined in the gas advection direction (the front-back direction of the paper surface in FIG. 2).

[0071] By using a ferrite-based stainless steel material (an example of an Fe-Cr alloy) as the material of the base material of the metal support 4, it is possible to bring the thermal expansion coefficients closer to those of YSZ (yttria-stabilized zirconia), GDC (gadolinium-doped ceria, also referred to as CGO), etc., which are used as the materials of the electrode layer 2 and the electrolyte layer 1a. Therefore, even when the temperature cycle between low and high temperatures is repeated, the electrolytic cell unit U is less likely to be damaged. Thus, it is preferable because an electrolytic cell unit U with excellent long-term durability can be realized.

[0072] The supply path forming members 5 and 6 of the electrolytic cell unit U can employ the same material as the metal support 4, and their thicknesses can also be made substantially the same.

[0073] The metal support 4 and both supply path forming members 5 and 6 have conductivity, but by being configured airtightly, they will function as a separator that separates the respective supply paths 5a and 6a.

[0074] In the electrolytic cell unit U having the above configuration, in the electrolysis operation, DC power is supplied between a pair of electrode layers 2 and 3 provided with the electrolyte layer 1a interposed therebetween from a power supply unit (shown as a battery in FIG. 2). In this embodiment, as shown in the drawing, the case where the electrode layer 2 side is negative and the counter electrode layer 3 side is positive is shown. Note that depending on the configuration of the electrolytic cell unit U, there may be a case where the electrode layer 2 side is positive and the counter electrode layer 3 side is negative. Then, H2O and CO2, which are gases to be electrolyzed, are supplied to the electrode layer 2 from an electrolysis raw material supply unit (the upstream part of the electrolysis reaction part 10 in FIG. 1), and a transport gas g2 is supplied to the counter electrode layer side, so that the reactions shown in Formula 1 and Formula 2 occur in the electrolytic cell 1, and the decomposed gas can be taken out. Here, regarding the supply of H2O, either water or water vapor, or both of them may be used. Therefore, in the present invention, an electrolytic cell device is constructed including at least the electrolytic cell unit U, an electrolysis raw material supply unit that supplies water and / or water vapor and carbon dioxide to the electrolytic cell unit U, and a power supply unit that supplies power.

[0075] In the electrolysis reaction, the gases supplied (H2O, CO2) and the gases released (H2O, H2, CO, O2, CO2) are shown above and below the electrolysis cell unit U in FIG. 2 for ease of understanding. In reality, the above-described gas supply path 5a on the electrode layer side and the gas supply path 6a on the counter electrode layer side are formed to extend in the front-back direction of the paper surface of FIG. 2. For example, the supply-side gases (H2O, CO2) described above the electrolysis cell unit U in FIG. 2 can be recovered from the front side of the paper surface, and the released-side gases (H2O, H2, CO, O2, CO2) described below the electrolysis cell 1 can be recovered from the back side of the paper surface (see FIG. 4 described later). In addition, in order to smoothly discharge the O2 generated in the electrolysis reaction, a carrier gas g2 such as air can also be flowed into the electrolysis cell unit U.

[0076] When H2O and CO2 are supplied to the electrolysis reaction section 10 for electrolysis, the electrolysis voltage of H2O is lower than that of CO2, and it is easier to be electrolyzed. Therefore, if the same amount of H2O and CO2 are supplied to the electrolysis reaction section 10 for electrolysis reaction, the H2 concentration is more likely to be higher than the CO concentration at the outlet of the electrolysis reaction section 10, and unreacted CO2 is likely to remain.

[0077] 〔First Catalytic Reaction Section (Hydrophobic Gas Shift Reaction Section)〕 As shown above, the first catalytic reaction section 20 (hydrophobic gas shift reaction section) causes a hydrophobic gas shift reaction, converts CO2 to CO using the supplied H2, and converts H2 to H2O. That is, in the electrolysis reaction section 10 that supplies H2O and CO2 for electrolysis, the CO2 that remains without being decomposed is converted to CO.

[0078] The reaction here is as shown in Equation 3. This reaction is an endothermic reaction and an equilibrium reaction depending on the reaction temperature conditions. As a result, as described above, it is preferable to use a catalyst that can cause the reaction shown in Equation 3 at as high a temperature as possible (for example, 600°C to 800°C).

[0079] In the description of the catalyst in this specification, the component having activity as a catalyst may be referred to as the "catalytically active component", and the carrier supporting the catalytically active component may be referred to as the "carrier". As will be described later, the inventors examined various combinations of catalytically active components and carriers, and found that a specific combination is preferable. The production of this type of catalyst can easily obtain a carrier-supported catalyst (impregnated support) in which the catalytically active component is distributed on the surface of the carrier by performing an impregnation support step of immersing the carrier in a solution containing the catalytically active component (metal), taking it out, and drying and heat-treating it. This heat treatment is a calcination treatment. The preparation and use of the catalyst will be described with reference to FIGS. 11 and 12.

[0080] The preparation method described here is the same for various combinations of catalytically active components and carriers, except that the starting materials are different. FIG. 11 shows examples of the reverse water gas shift catalyst cat1 and the hydrocarbon synthesis catalyst cat2 according to the present invention. In the figure, the catalytically active component of the reverse water gas shift catalyst cat1 is denoted as ca1, and its carrier is denoted as cb1. On the other hand, for the hydrocarbon synthesis catalyst cat2, its catalytically active component is ca2 and its carrier is cb2.

[0081] As shown in FIG. 11, in catalyst preparation, an aqueous solution of a compound containing the metal components (which are metal catalysts) that become the catalytically active components ca1 and ca2 is obtained, the carriers cb1 and cb2 are added to the aqueous solution, and an impregnation support step (a) of stirring and impregnating is performed. Then, an evaporation to dryness, drying, and then a drying, pulverizing, and forming step (b) of pulverizing and forming are performed, and the obtained formed body is subjected to a calcination step (c) of calcining in air to obtain the target products (cat1, cat2). Therefore, this form of catalyst is also called an impregnation-supported catalyst.

[0082] In this case, as shown in the example of the water-gas shift catalyst cat1 in Fig. 12, it can also be applied to the part where the catalyst is used and then fired. Fig. 12(a) shows the coating and firing process in which the water-gas shift catalyst cat1 is applied to the metal support 4 with holes 4a to form a coating layer 20a and then fired. Fig. 12(b) shows the pre-reduction treatment process in which H2 is passed through for pre-reduction treatment before using this water-gas shift catalyst cat1.

[0083] In addition, when the firing treatment is carried out in air, some or all of the supported catalyst active components ca1 and ca2 are in an oxidized state. Before using the catalyst, so-called pre-reduction treatment can be carried out to reduce the catalyst active components in the oxidized state and sufficiently enhance their activity. Fig. 12(b) shows the state in which a reducing gas (typically H2) is circulated on the surface of the catalyst for pre-reduction treatment.

[0084] (Catalyst to be used) As the water-gas shift catalyst cat1 used in this first catalyst reaction part 20, the inventors have selected a catalyst that satisfies the following requirements.

[0085] A catalyst composed of at least supporting one or both of platinum, nickel, and iron as the catalyst active component ca1 on a carrier cb1 mainly composed of a ceria-based metal oxide or a zirconia-based metal oxide. Here, since the strength of the catalyst cat1 can be increased, the proportion of the carrier cb1 in the whole catalyst is preferably 55 wt% or more, more preferably 60 wt% or more, and still more preferably 65 wt% or more. Also, the upper limit of this proportion can be, for example, 99.5 wt%, but if it exceeds this, it may be difficult to sufficiently support the catalyst active component ca1, and it may be difficult to obtain the effect as the water-gas shift catalyst cat1.

[0086] Furthermore, as the ceria-based metal oxide, ceria doped with at least one of gadolinium, samarium, and yttrium can also be used. Further, as the zirconia-based metal oxide, zirconia stabilized with at least one of yttria and scandia can also be used.

[0087] In addition, since the reverse water gas shift reaction can proceed favorably, the supported amount of the catalyst active component ca1 is preferably 0.5% by weight or more, more preferably 1% by weight or more, and even more preferably 5% by weight or more. Further, even if the supported amount of the catalyst active component ca1 is increased too much, it becomes difficult to support the catalyst active component ca1 with high dispersion, it is difficult to obtain a significant improvement in catalytic activity, and the catalyst cost also increases. Therefore, the supported amount of the catalyst active component ca1 is preferably 35% by weight or less, more preferably 30% by weight or less, and even more preferably 25% by weight or less.

[0088] Furthermore, it is also preferable to add either one or both of platinum, nickel, and iron to the catalyst active component ca1 and support copper as a further catalyst active component ca1. In this configuration, the supported amount of copper is equal to or less than the supported amount of either one or both of nickel and iron as the main catalyst active component ca1.

[0089] Hereinafter, regarding the test results of examples when the catalyst active component ca1 and the carrier cb1 are variously changed as the reverse water gas shift catalyst cat1 used in the first catalyst reaction section 20, an explanation will be given. As the catalyst active component ca1, Ni, Fe were examined and Pt (platinum) was also examined. As the carrier cb1, ZrO2 (zirconia), YSZ (yttria-stabilized zirconia), GDC (gadolinium-doped ceria), CeO2 (ceria) were used as examples, and Al2O3 (alumina) was also examined.

[0090] In the following description, Test Example 1 and Test Example 2 will be introduced. The difference between the two tests is that in the firing of the reverse water gas shift catalyst cat1, the firing temperature in Test Example 1 is set at 450°C, and the firing temperature in Test Example 2 is set on the high temperature side at 600°C to 1000°C.

[0091] (Test Example 1) The test results of Examples (1 to 19) when the carrier is variously changed will be described for the catalyst used in the first catalyst reaction section 20. As the catalyst active components, Ni, Fe were examined and Pt (platinum) was also examined. As carriers, ZrO2 (zirconia), YSZ (yttria-stabilized zirconia), GDC (gadolinium-doped ceria), CeO2 (ceria) were used as examples, and Al2O3 (alumina) was also examined.

[0092] (Catalyst Preparation) In the preparation of the reverse water gas shift catalyst cat1, according to the composition of the target catalyst, a water-soluble nickel compound (nickel nitrate, nickel chloride, nickel sulfate, nickel ammonium sulfate, nickel acetate, nickel oxalate, nickel citrate, etc.), a water-soluble iron compound (iron nitrate, iron chloride, iron sulfate, iron ammonium sulfate, iron acetate, iron oxalate, iron citrate, etc.), or an aqueous solution obtained by dissolving one or both of them in a quantified manner is obtained. Further, when copper is supported as the additional catalyst active component ca1, a water-soluble copper compound (copper nitrate, copper chloride, copper sulfate, copper ammonium sulfate, copper acetate, copper oxalate, copper citrate, etc.) is similarly quantified to obtain a dissolved aqueous solution. A predetermined amount of carrier powder (ceria, zirconia, GDC, YSZ, Al2O3) is added to the aqueous solution, stirred and impregnated, then evaporated to dryness, dried, then pulverized, formed, and fired in air. This impregnation is the "impregnation and support step" referred to in the present invention, and the resulting product is the "impregnation and support product". The catalysts in the following examples were prepared using nickel nitrate hexahydrate, iron nitrate nonahydrate, and copper nitrate trihydrate, respectively. The catalyst using Pt was prepared using tetraammineplatinum hydroxide.

[0093] Regarding the evaporation to dryness, drying, and firing temperatures in the above catalyst preparation, they can be carried out in a generally used temperature range. In Test Example 1, the catalysts in the following examples were set at 80 °C, 80 °C, and 450 °C, respectively.

[0094] Table 1 shows Examples 1 to 19 of the reverse water gas shift catalyst cat1 according to the present invention. The horizontal axis represents the type of the carrier cb1, the metal loading amount as the catalytic active component (weight%; denoted as wt.% in the table), the CO adsorption amount (ml / g), and the BET surface area (m 2 / g). Regarding the CO adsorption amount, after the catalyst was pretreated by reduction in a hydrogen atmosphere at 350°C for 1 hour, the CO adsorption amount was measured.

[0095]

Table 1

[0096] (Catalytic activity test) In the catalytic activity test, a mixed gas of 50% H2 - 50% CO2 (a mixed gas containing H2 and CO2 in a volume ratio of 1:1) was used as the reaction gas, and the reaction temperature was changed in 50°C increments from 600°C to 800°C under the condition of a GHSV (Gas Hourly Space Velocity) of 10000 / h. Before the catalytic activity test, the catalyst was pretreated by reduction at 600°C while flowing hydrogen gas through the catalyst layer. As test results, the CO concentration (%) and CH4 concentration (%) at the outlet of the reaction section were listed in Table 2 together with the CO2 conversion rate (%).

[0097] The CO2 conversion rate (%) was calculated according to the following formula based on the gas analysis results at the outlet of the catalyst layer. 〔CH4 concentration〕 + 〔CO concentration〕 / (〔CH4 concentration〕 + 〔CO concentration〕 + 〔CO2 concentration〕)

[0098] As shown above, as the reverse water gas shift catalyst cat1 used in the first catalytic reaction section 20 (reverse water gas shift reaction section), it is desirable that the CO2 conversion rate (%) is high at the high temperature side (for example, around 600 - 800°C).

[0099]

Table 2

[0100] (Test Example 2) The test results of Examples (20 - 29) of Test Example 2 will be described below. Even in this example, As the catalytic active component, Ni and Fe were examined, and the addition of Cu was also examined. As the carrier, CeO2 (ceria) and ZrO2 (zirconia) were used as examples, and Al2O3 (alumina) was examined.

[0101] (Catalyst Preparation) The reverse water-gas shift catalyst cat1 used in Test Example 2 was prepared in the same manner as in Test Example 1, except that the calcination temperature was changed to 600 °C, 800 °C, and 1000 °C.

[0102] Table 3 shows the respective catalysts of Examples (20 - 29) prepared.

[0103]

Table 3

[0104] (Catalytic Activity Test) The catalytic activity test was carried out while changing the reaction temperature in 50 °C increments from 600 °C to 800 °C under the condition of a GHSV of 10,000 / h, using a mixed gas containing H2 and CO2 in a volume ratio of 1:1 as the reaction gas. Before conducting the catalytic activity test, the catalyst was pretreated by reduction at 600 °C while flowing hydrogen gas through the catalyst layer. As test results, the CO2 conversion rate (%), the CO concentration (%) and the CH4 concentration (%) at the outlet of the reaction section are listed in Table 4.

[0105]

Table 4

[0106] For reference, the equilibrium value (calculated value) of the CO2 conversion rate under the conditions of this experiment is shown in Table 4.

[0107] Iron - zirconia catalyst and iron - alumina catalyst Regarding the iron-zirconia catalyst, the test results when the calcination temperatures were 450°C, 600°C, 800°C, and 1000°C are shown in Example 8, Example 22, Example 26, and Example 29, respectively. On the other hand, regarding the iron-alumina catalyst, the test results when the calcination temperatures were 450°C, 600°C, and 800°C are shown in Example 14, Example 23, and Example 27, respectively. As can be seen from these results, although the metal loadings are slightly different, the iron-zirconia catalyst is superior in activity to the iron-alumina catalyst in performing the water-gas shift reaction. Also, the iron-zirconia catalyst has very high catalytic activity not only when the calcination temperature is 450°C, but also when the calcination temperature is increased to 600°C, 800°C, and 1000°C. In any case of the calcination temperature, the CO2 conversion rate reaches near the equilibrium value.

[0108] Nickel-ceria catalyst The test results when the calcination temperatures were 450°C, 600°C, 800°C, and 1000°C are shown in Example 4, Example 20, Example 24, and Example 28, respectively. As can be seen from these results, the nickel-ceria catalyst has very high catalytic activity not only when the calcination temperature is 450°C, but also when the calcination temperature is increased to 600°C, 800°C, and 1000°C. In any case of the calcination temperature, the CO2 conversion rate reaches near the equilibrium value.

[0109] Nickel-alumina catalyst The test result when the calcination temperature was 450°C is shown in Example 7. In this result, the CO2 conversion rate of the nickel-alumina catalyst was lower compared to the nickel-ceria catalyst described above.

[0110] Nickel-copper-ceria catalyst The test results when the firing temperatures were 450°C, 600°C, and 800°C are shown in Example 6, Example 21, and Example 25, respectively. From these results, in the nickel-copper-ceria catalyst, when the firing temperature becomes high like 600°C or 800°C, there is a tendency for the CO2 conversion rate to slightly decrease, but it is superior to the iron-alumina catalyst with the same firing temperature conditions described above. Also, in the nickel-copper-ceria catalyst with a firing temperature of 450°C, the CO2 conversion rate has reached near the equilibrium value.

[0111] Usefulness as a reverse water-gas shift catalyst As shown above, in the iron-zirconia-based catalyst and the nickel-ceria-based catalyst, even when the firing temperature is variously changed such as 450°C to 1000°C, they exhibit very high reverse water-gas shift catalytic activity. Therefore, for example, even when used in combination with a solid oxide type electrolytic cell used in a high-temperature range around 600°C to 800°C, it is easy to ensure high performance and durability and is useful.

[0112] From the above results, as also shown previously, as the reverse water-gas shift catalyst cat1 used in this first catalyst reaction part 20, on a carrier cb1 mainly composed of a ceria-based metal oxide or a zirconia-based metal oxide, at least one or both of nickel and iron can be used as the catalytic active component ca1 and supported to be configured. Further, if the cost is acceptable, platinum can also be adopted.

[0113] Furthermore, the ceria-based metal oxide as the carrier cb1 can also be ceria doped with at least one of gadolinium, samarium, and yttrium.

[0114] Also, the zirconia-based metal oxide as the carrier cb1 can also be zirconia stabilized with at least one of yttria and scandia.

[0115] Furthermore, in addition to one or both of nickel and iron as the catalytic active component ca1, it is also preferable to support copper as a further catalytic active component ca1.

[0116] And by using the above-mentioned water-gas shift catalyst cat1 in the first catalytic reaction section 20 (water-gas shift reaction section), a water-gas shift reaction can be carried out at a CO2 conversion rate (%) equal to or higher than that of a Pt catalyst, which is highly active but very expensive, in the vicinity of 600 to 1000 °C. Note that since the test of this example was conducted under very high GHSV conditions of 10,000 / h, it is also possible to carry out the water-gas shift reaction at a higher CO2 conversion rate (%) by reducing GHSV to a value smaller than 10,000 / h, that is, by increasing the amount of catalyst used with respect to the amount of gas to be processed.

[0117] 〔Combination of electrolysis reaction section and water-gas shift reaction section〕 In the previous description, according to the system configuration shown in FIG. 1, the electrolysis reaction section 10 and the water-gas shift reaction section 20 have been described separately in the order of description along the gas flow direction. The reaction in the electrolysis reaction section 10 is an exothermic reaction depending on the reaction conditions, and the reaction in the water-gas shift reaction section 20 is an endothermic reaction. Therefore, the thermal efficiency of the system can be improved by integrating these two reaction sections 10 and 20. As shown in FIG. 3, the configuration when these two reaction sections 10 and 20 are combined and integrated is shown, and it is shown that both parts are integrated by surrounding them. In addition, the reaction when integrated in the same box is shown. Basically, the above-mentioned formulas 1, 2, and 3 are carried out. When the electrolysis reaction section 10 and the water-gas shift reaction section 20 are combined and integrated, it is preferable to surround them together with a heat-insulating member because heat transfer between the electrolysis reaction section 10 and the water-gas shift reaction section 20 can be efficiently performed. Also, the electrolysis reaction section 10 and the water-gas shift reaction section 20 may be connected using a heat-conductive member in order to transfer the heat generated in the electrolysis reaction section 10 to the water-gas shift reaction section 20.

[0118] 〔Electrolysis cell unit equipped with both electrolysis reaction section and water-gas shift reaction section〕 Based on the above concept, it is preferable to provide a reverse water gas shift reaction unit 20 in the electrolysis cell unit U that serves as the electrolysis reaction unit 10. This is because when a solid oxide type electrolysis cell that operates at around 600 to 800 °C is used as the electrolysis cell 1, the reverse water gas shift catalyst cat1 of the present application that exhibits high activity at around 600 to 800 °C allows the electrolysis reaction unit 10 and the reverse water gas shift reaction unit 20 to be used in the same temperature range. Also in this case, it is sufficient if the gas that has passed through the electrolysis reaction unit 10 can be led to the reverse water gas shift reaction unit 20 to cause a reverse water gas shift reaction.

[0119] The electrolysis cell unit U provided with such a reverse water gas shift reaction unit 20 is shown in FIG. 4. FIG. 4 is a diagram depicting the electrolysis cell unit U shown in cross-section in FIG. 2, including the direction of gas flow-through.

[0120] As shown in the figure, the cross-section of the electrolysis cell unit U is basically the same. That is, this electrolysis cell unit U also includes an electrolysis cell 1 in which an electrode layer 2 and a counter electrode layer 3 are formed with an electrolyte layer 1a interposed therebetween, a metal support 4 that functions as its support and also serves as a separator, and supply path forming members 5 and 6, and is configured such that an electrode layer side gas supply path 5a and a counter electrode layer side gas supply path 6a are formed. More specifically, as can be seen from the figure, when looking at the metal support 4 in the direction of gas flow-through, holes 4a are provided at the site corresponding to the electrolysis cell 1, but no holes are provided on the downstream side of the electrode layer 2. Therefore, the metal support 4 serves as a separator that effectively separates the gas supplied to and released from the above-mentioned electrode layer 2 and the gas supplied to and released from the counter electrode layer 3 gas.

[0121] However, in this example, the reverse water gas shift catalyst cat1 described above is coated on the inner surface of the electrode layer side gas supply path 5a (the supply path side inner surface of the supply path forming member 5, the surface of the metal support 4 opposite to the surface on which the electrode layer 2 is formed, and the surfaces of the plurality of holes 4a). This coating layer 20a is shown by a thick solid line. Furthermore, the gas supply passage 5a on the electrode layer side extends further beyond the electrolysis reaction section 10, and the coating layer 20a is also provided on this extended side.

[0122] As a result, the gas supply passage 5a on the electrode layer side of the electrolysis cell unit U serves as an exhaust passage for discharging at least H2 generated in the electrode layer 2, and the electrolysis cell unit U is configured to integrally include the electrolysis reaction section 10 and the water-repellent gas shift reaction section 20.

[0123] In this configuration, the metal support 4 functions as a separator that separates H2 generated in the electrode layer 2 and O2 generated in the counter electrode layer 3, and at least a part of the H2 exhaust passage side of this separator is the water-repellent gas shift reaction section 20. By stacking the electrolysis cell units U configured in this way in the left-right direction of FIGS. 2 and 4, a so-called electrolysis cell module (not shown) in which a large number of electrolysis cell units U are stacked and electrically connected can be formed. Naturally, useful gases generated can be obtained over multiple layers.

[0124] Under the concept of combining the above-described electrolysis reaction section 10 and the water-repellent gas shift reaction section 20 (using the gas supply passage 5a on the electrode layer side of the electrolysis reaction section 10 as the water-repellent gas shift reaction section 20), the inventors conducted an experiment by storing the granular water-repellent gas shift catalyst cat1 in the gas supply passage 5a on the electrode layer side. FIG. 5 shows a cross section of the electrolysis cell unit U used in this experiment.

[0125] A specific description will be given below with reference to FIG. 5. The figure shows a cross-sectional view of the electrolysis cell unit U. Here, as the electrolysis cell 1, a metal-supported solid oxide type electrolysis cell was used. As the metal support 4, a plurality of through holes (to become holes 4a) were provided by laser processing on a ferrite-based stainless steel metal plate with a thickness of 0.3 mm to fabricate a metal substrate. On this metal substrate, an electrode layer 2 and an intermediate layer 2a were laminated in sequence, and on the intermediate layer 2a of the metal substrate, an electrolyte layer 1a was laminated so as to cover the intermediate layer 2a. Further, on the electrolyte layer 1a, a reaction prevention layer 7 and a counter electrode layer 3 were laminated in sequence to fabricate the electrolysis cell 1. Note that, as the material for forming the electrode layer 2, a mixture of NiO powder and GDC powder was used, as the material for forming the intermediate layer 2a, GDC powder was used, as the material for forming the electrolyte layer 1a, 8YSZ (8 mol% yttria-stabilized zirconia) powder was used, as the material for forming the reaction prevention layer 7, GDC powder was used, and as the material for forming the counter electrode layer 3, a mixture of GDC powder and LSCF powder was used. Also, the thicknesses of the electrode layer 2, the intermediate layer 2a, the electrolyte layer 1a, the reaction prevention layer 7, and the counter electrode layer 3 were approximately 25 μm, approximately 10 μm, approximately 5 μm, approximately 5 μm, and approximately 20 μm, respectively. By providing the intermediate layer 2a between the electrode layer 2 and the electrolyte layer 1a or providing the reaction prevention layer 7 between the electrolyte layer 1a and the counter electrode layer 3, the performance and durability of the electrolysis cell 1 can be improved. Further, the intermediate layer 2a and the reaction prevention layer 7 are preferably formed by a low-temperature firing method (for example, a wet method using a firing process in a low-temperature range without firing treatment in a high-temperature range higher than 1100 °C), a spray coating method (methods such as a thermal spraying method, an aerosol deposition method, an aerosol gas deposition method, a powder jet deposition method, a particle jet deposition method, a cold spray method), a PVD method (a sputtering method, a pulsed laser deposition method, etc.), a CVD method, etc. By these processes that can be used in a low-temperature range, good intermediate layer 2a and reaction prevention layer 7 can be obtained without using firing in a high-temperature range higher than 1100 °C. Therefore, it is preferable because an electrolysis cell 1 excellent in performance and durability can be realized without damaging the metal support 4. Further, using the low-temperature firing method is more preferable because it facilitates the handling of raw materials.

[0126] Regarding the electrolytic cell unit U obtained as described above, performance improvement was investigated when granular water-repellent gas shift catalyst cat1 was stored in its electrode layer side gas supply passage 5a (which also serves as the discharge passage for the gas electrolyzed in the electrolysis reaction section 10).

[0127] Results when the water-repellent gas shift catalyst cat1 was not stored An electrolysis reaction was carried out while supplying a gas containing H2O and CO2 to the electrolytic cell unit U, and the ratio of H2 to CO in the outlet gas of the electrolytic cell unit U was measured using a gas chromatograph. The results are shown in Table 5 below. These experimental results were described as Comparative Examples A1 and A2.

[0128]

Table 5

[0129] Results when the water-repellent gas shift catalyst cat1 was stored As the water-repellent gas shift catalyst cat1, a granular catalyst obtained by supporting about 10% of Ni on the same 8YSZ carrier as in Example 2 was stored, and an electrolysis reaction was carried out while supplying a gas containing H2O and CO2 to the electrolytic cell unit U. The ratio of H2 to CO in the outlet gas of the electrolytic cell unit U was measured using a gas chromatograph. The results are shown in Table 6. These experimental results were described as Example A1.

[0130]

Table 6

[0131] From the above comparative experiments, in the electrolytic cell unit U in which the electrolytic cell 1 is formed in a thin layer on the metal support 4 and the water-repellent gas shift reaction section 20 that generates CO using CO2 and the H2 by the water-repellent gas shift reaction is provided in the electrode layer side gas supply passage 5a that serves as the discharge passage for the electrolyzed gas, the composition ratio of CO to H2 generated by electrolysis could be increased.

[0132] In comparison with the electrolytic cell unit U that does not store the water-gas shift catalyst cat1 in the electrode layer side gas supply passage 5a (which serves as the discharge passage for the electrolyzed gas), at the outlet, the hydrogen / carbon monoxide ([H2 / CO]) ratio changes from about 10 or more to about 5. By combining the reaction in the electrolysis reaction section 10 and the reaction in the water-gas shift reaction section 20, it is possible to ensure an amount of CO that is advantageous for various hydrocarbon syntheses, which is preferable. In addition, since adopting the methanation reaction of CO rather than the methanation reaction of CO2 can increase the thermal efficiency of the hydrocarbon production system 100, it is preferable that an amount of CO can be ensured by combining the reaction in the electrolysis reaction section 10 and the reaction in the water-gas shift reaction section 20. This is because when 1 mole of CO2 is methanated, 2 moles of H2O are generated, while when 1 mole of CO is methanated, only 1 mole of H2O is generated. Therefore, the hydrocarbon production system 100 that adopts the methanation reaction of CO can suppress the latent heat and sensible heat loss of 1 mole of H2O as a whole system. In addition, by appropriately adjusting the ratio of H2O and CO2 introduced into the electrolysis reaction section 10, the reaction conditions in the electrolysis reaction section 10 (such as electrolysis voltage and reaction temperature), the reaction conditions in the water-gas shift reaction section 20 (such as the amount of catalyst used, GHSV, reaction temperature, etc.), etc., the hydrogen / carbon monoxide ([H2 / CO]) ratio at the outlet of the water-gas shift reaction section 20 can be adjusted to a value suitable for the subsequent second catalyst reaction section 30 (hydrocarbon synthesis reaction section) (for example, H2 / CO = 3, which is the equivalent ratio of the methanation reaction of CO, etc.).

[0133] [Install a heat exchange section between the electrolysis reaction section and the water-gas shift reaction section] In the previous descriptions, the example of integrating the electrolysis reaction section 10 and the first catalyst reaction section (reverse water-gas shift reaction section) 20 has been mainly described. However, a heat exchange section 11 may be provided between the two sections 10 and 20, and a configuration that enables heat transfer between the two sections may be adopted. For example, in the structure of FIG. 4 described above, the reverse water-gas shift reaction section 20 extends to the downstream side. However, a heat exchange layer with high thermal conductivity can also be separately provided between this extended section. This configuration is exemplified in FIG. 6 corresponding to FIG. 1. The hollow double line indicates heat transfer between the two sections. In this configuration, the temperatures of the respective sections 10 and 20 can be appropriately controlled.

[0134] The inventors call the system composed of the electrolysis reaction section 10 and the reverse water-gas shift reaction section 20, which have been described so far, an "electrolysis reaction system".

[0135] 〔Second Catalyst Reaction Section (Hydrocarbon Synthesis Reaction Section)〕 In this second catalyst reaction section 30 (hydrocarbon synthesis reaction section), at least H2 and CO flow in, and hydrocarbons (methane and various hydrocarbons with 2 or more carbon atoms) and the like are generated by the catalytic reaction.

[0136] (Examples of Hydrocarbon Synthesis Catalysts) As the activity test of the catalyst (hydrocarbon synthesis catalyst cat2) used in this second catalyst reaction section 30, the inventors conducted Evaluation Test 1, Evaluation Test 2, and Evaluation Test 3 shown below.

[0137] As examples of the hydrocarbon synthesis catalyst cat2, catalysts were prepared by variously changing the carrier and the catalyst active component. As the catalyst active component ca2, Ru, Ru added with Mo, V, Fe, Co, etc., and Ni were examined. As the carrier cb2, ZrO2, Al2O3, SiO2, MgO, and TiO2 were examined.

[0138] (Catalyst Preparation) The preparation of the hydrocarbon synthesis catalyst cat2 also adopts the method described with reference to FIGS. 11 and 12. That is, according to the composition of the target catalyst, an aqueous solution is obtained by quantifying and dissolving a water-soluble ruthenium compound (ruthenium nitrate, ruthenium chloride, ruthenium sulfate, ammonium ruthenium sulfate, ruthenium acetate, ruthenium oxalate, ruthenium citrate, etc.). Further, when molybdenum, vanadium, iron, and cobalt are supported as additional catalyst active components, these water-soluble metal compounds are similarly quantified to obtain a dissolved aqueous solution. Using the aqueous solution, a catalyst active component is impregnated and supported on a predetermined amount of carrier particles (ZrO2, Al2O3, SiO2, MgO, TiO2), and necessary treatment steps such as drying treatment, calcination treatment, and reduction treatment are performed to obtain a hydrocarbon synthesis catalyst cat2. In addition, the catalysts in the following examples were prepared using an aqueous ruthenium chloride solution, an aqueous ammonium molybdate solution, an aqueous vanadyl oxalate solution, an aqueous iron nitrate solution, and an aqueous cobalt nitrate solution, respectively. When both ruthenium and catalyst active components other than ruthenium are supported, a sequential support method (a two-step support method in which catalyst active components other than ruthenium are first supported on the carrier and then ruthenium is supported) is used.

[0139] (Evaluation Test 1) In Evaluation Test 1, a mixed gas containing 12.4% CO, 24.8% CO2, 37.2% H2, and 12.4% H2O with the balance being N2 was used as the reaction gas, the GHSV was 4000 / h (WET basis), and an activity test of the hydrocarbon synthesis catalyst cat2 was conducted at a reaction temperature between 275°C and 360°C. In this case, the reaction gas is an example of a model in which the co-electrolysis reaction of water and carbon dioxide is carried out in the electrolysis reaction section 10 under conditions where the electrolysis reaction rate of carbon dioxide is low, and then the mixed gas of CO, CO2, H2, and H2O after the reverse water gas shift reaction of carbon dioxide is carried out in the reverse water gas shift reaction section 20 installed in the subsequent stage is introduced into the hydrocarbon synthesis reaction section 30 to carry out the hydrocarbon synthesis reaction.

[0140] When organizing the test results, the following two indicators were adopted.

[0141] 1. Hypothetical hydrocarbon conversion rate for CO2 removal = [Number of carbons in hydrocarbons in the outlet gas] / [Number of carbons in the outlet gas - Number of carbons in the outlet CO2] This index indicates the conversion rate to hydrocarbons when CO2 is removed from the outlet gas of the hydrocarbon synthesis reaction section 30 obtained by the catalytic reaction, and it is preferable that this index is high.

[0142] 2. Calorific value of C1 - C4 (MJ / Nm 3 ) = Σ(Nn × HN) / Σ Nn Nn [mol]: Number of moles of Cn hydrocarbon in the gas of the catalytic reaction section (n = 1 - 4) HN [MJ / m 3 (N)]: Calorific value of Cn hydrocarbon in the gas of the catalytic reaction section 〔H1 = 39.8, H2 = 69.7, H3 = 99.1, H4 = 128.5〕 This index indicates the amount of C1 - C4 components contained in the outlet gas of the hydrocarbon synthesis reaction section 30 obtained by the catalytic reaction. When this value exceeds 39.8, it can be confirmed that hydrocarbons such as ethane, propane, and butane are generated in addition to methane.

[0143] Regarding Evaluation Test 1, Tables 7 and 8 shown below show Examples B1 - B3 of the hydrocarbon synthesis catalyst cat2 in the present invention.

[0144]

Table 7

[0145]

Table 8

[0146] As shown in Tables 7 and 8, it was confirmed that hydrocarbons can be synthesized using a catalyst in which ruthenium is supported on an alumina carrier or a catalyst in which molybdenum or vanadium is supported in addition to ruthenium as the hydrocarbon synthesis catalyst cat2 from a mixed gas of CO, CO2, H2, and H2O. From the above results, it was confirmed that the hydrocarbon production system 100 can produce the high-calorie gas with a calorific value of C1-C4 of 39 MJ / Nm 3 or higher as described above.

[0147] (Evaluation Test 2) In Evaluation Test 2, a mixed gas containing 0.45% CO, 18.0% CO2, 71.55% H2, and 10.0% H2O was used as the reaction gas, the GHSV was set to 5000 / h (DRY basis), and an activity test of the hydrocarbon synthesis catalyst cat2 was conducted at a reaction temperature between about 230°C and about 330°C. Note that the reaction gas in this case is an example assuming a model in which a mixed gas obtained when the co-electrolysis reaction of water and carbon dioxide in the electrolysis reaction unit 10 is carried out under conditions of a low carbon dioxide electrolysis reaction rate is introduced into the hydrocarbon synthesis reaction unit 30 to carry out the hydrocarbon synthesis reaction.

[0148] When organizing the test results, the following two indicators were adopted.

[0149] 1 Hydrocarbon conversion rate = [Number of carbons of hydrocarbons in the outlet gas] / [Number of carbons in the outlet gas] This indicator shows the ratio of the number of carbons converted into hydrocarbons without being converted into CO2 among all the inflowing carbons, and it is preferable that this indicator is high.

[0150] 2 CO2 removal assumed hydrocarbon conversion rate = [Number of carbons of hydrocarbons in the outlet gas] / [Number of carbons in the outlet gas - Number of carbons of outlet CO2] This indicator shows the conversion rate to hydrocarbons when CO2 is removed from the outlet gas of the hydrocarbon synthesis reaction section obtained by the catalytic reaction, and it is also preferable that this indicator is high.

[0151] Regarding Evaluation Test 2, the catalysts used (Examples B4 to B16) are shown in Table 9, and the test results are shown in Table 10, respectively.

[0152]

Table 9

[0153]

Table 10

[0154] The results of Evaluation Test 3 are shown in Table 11.

[0155]

Table 11

[0156] As shown in Table 11, it was confirmed that hydrocarbons can be synthesized from a mixed gas containing H2 and CO using a catalyst in which ruthenium and iron or cobalt are supported on a titania carrier as the hydrocarbon synthesis catalyst cat2.

[0157] It was confirmed that the above hydrocarbon production system 100 can produce a high-calorie gas with a C1-C4 calorific value of 39 MJ / Nm 3 or higher.

[0158] From the above results, as shown previously, a catalyst in which at least ruthenium is supported on the metal oxide carrier cb2 as the catalytically active component ca2 can be used in this second catalytic reaction section 30 (hydrocarbon synthesis reaction section). Further, it is preferable to support at least one of molybdenum, vanadium, iron, and cobalt as the catalytically active component ca2.

[0159] Note that as the hydrocarbon synthesis catalyst cat2, a catalyst in which at least ruthenium is supported on the metal oxide carrier cb2 is used, and the supported amount of ruthenium is preferably 0.1% by weight or more and 5% by weight or less. It has also been found that it is preferable to support at least one of molybdenum, vanadium, iron, and cobalt as the catalytically active component ca2 in addition to ruthenium on the metal oxide carrier cb2.

[0160] Here, the supported amount of at least one of molybdenum, vanadium, iron, and cobalt can be 0.2% by weight or more and 6% by weight or less.

[0161] Also, among such hydrocarbon synthesis catalysts cat2, the carbon monoxide adsorption amount of the highly active catalyst was 0.4 ml / g or more.

[0162] 〔Heavy Hydrocarbon Separation Section〕 The gas reaching this heavy hydrocarbon separation section 35 is cooled, so that the heavy hydrocarbons contained in the gas discharged from the hydrocarbon synthesis reaction section 30 are condensed, and the heavy hydrocarbons can be taken out to the outside. For example, in the hydrocarbon synthesis reaction section 30 using the 2 wt.% Ru / 2 wt.% Fe / TiO2 catalyst shown in Example B17 above, when a mixed gas (H2 / CO = 3) containing H2 and CO in a volume ratio of 3:1 was introduced and the reaction was carried out at 275°C, linear higher aliphatic hydrocarbons with an average carbon chain length of 26 could be taken out in the heavy hydrocarbon separation section 35. When the reaction was carried out at 325°C, linear higher aliphatic hydrocarbons with an average carbon chain length of 18 could be taken out in the heavy hydrocarbon separation section 35.

[0163] 〔Water Separation Section〕 A condenser is arranged in this water separation section 40 to adjust the temperature and pressure of the incoming gas containing H2O to a predetermined value, condense it, and extract water to the outside.

[0164] 〔Carbon dioxide separation section〕 For example, a PSA is arranged in this section 50 to adsorb CO2 from the incoming gas containing CO2 onto an adsorbent under a predetermined temperature and pressure to separate CO2, and desorb the separated CO2 from the adsorbent, thereby separating CO2 well. The separated CO2 can be returned to the front of the electrolysis reaction section 10 via the carbon dioxide return path 51 and reused. Note that the carbon dioxide separation section and the water separation section can be made into the same separation section using a PSA or the like.

[0165] 〔Another embodiment〕 (1) In the above embodiment, the CO2 separated in the carbon dioxide separation section 50 is returned to the front of the electrolysis reaction section 10. However, in the hydrocarbon production system 100 according to the present invention, since the conversion of CO2 to CO is mainly carried out in the reverse water gas shift reaction section 20, the return destination of CO2 may be set in front of the reverse water gas shift reaction section 20. This configuration is shown in FIG. 7.

[0166] (2) In the above embodiment, regarding H2 in the gas obtained from the hydrocarbon synthesis reaction section 30, although not particularly described, a hydrogen separation section (described as the H2 separation section in the figure) 60 that separates H2 using a hydrogen separation membrane or the like may be provided to separate H2 and use it separately. This configuration is shown in FIG. 8. In this example, the return destination of the H2 separated in the hydrogen separation section 60 may be set in front of the reverse water gas shift reaction section 20 and used for the reverse water gas shift reaction.

[0167] (3) In the above embodiment, the water separation section 40 is provided on the lower side of the hydrocarbon synthesis reaction section 30. However, as shown in FIG. 9, the water separation section 40 may be provided between the reverse water gas shift reaction section 20 and the hydrocarbon synthesis reaction section 30. The main function of this water separation section 40 is to facilitate the hydrocarbon synthesis reaction.

[0168] (4) In the above-described embodiment, an example in which both H2O and CO2 are supplied to the electrolysis reaction unit 10 for the electrolysis reaction has been shown. However, as shown in FIG. 10, a system in which only H2O is supplied to the electrolysis reaction unit 10 for the electrolysis reaction may also be used. In this case, the carbon consumed in the hydrocarbon synthesis is introduced as carbon dioxide into the water gas shift reaction unit 20.

[0169] (5) In the above-described embodiment, an example in which a solid oxide type electrolysis cell is used as the electrolysis cell 1 in the electrolysis reaction unit 10 has been shown. However, as the electrolysis cell 1, an alkaline type electrolysis cell, a polymer membrane type electrolysis cell, or the like may be used.

[0170] (6) In the above-described embodiment, a configuration in which the electrolysis reaction unit 10 and the first catalyst reaction unit 20 are integrated has been shown. However, in addition to these reaction units 10 and 20, it is also possible to integrate and configure a second catalyst reaction unit 30. A configuration example in this case is shown in FIG. 13. Incidentally, in this figure, 30a indicates the coating layer of the hydrocarbon synthesis catalyst cat2. Also in the case of this configuration, each of these reaction units 10, 20, and 30 can be configured on the metal support 4 and the supply path forming member 5, and this metal support 4 serves as a separator that separates the generated hydrocarbon and oxygen.

[0171] (7) In the above-described embodiment, an example in which hydrocarbons such as methane are synthesized in the hydrocarbon synthesis reaction unit 30 has been shown. However, depending on the method of selecting the hydrocarbon synthesis catalyst used in the hydrocarbon synthesis reaction unit 30, chemical raw materials can also be synthesized from hydrogen and carbon monoxide introduced into the hydrocarbon synthesis reaction unit 30.

Explanation of Reference Numerals

[0172] 1 Electrolysis cell 1a Electrolyte layer 2 Electrode layer 3 Counter electrode layer 4 Metal support (support / separator) 4a Hole (through hole) 5 Supply path forming member (separator) 6 Supply path forming member (separator) 10 Electrolysis reaction section 20 First catalyst reaction section (reverse water gas shift reaction section) 20a Coating layer 30 Second catalyst reaction section (hydrocarbon synthesis reaction section) 40 Water separation section 50 Carbon dioxide separation section 60 Hydrogen separation section U Electrolytic cell unit cat1 Reverse water gas shift catalyst ca1 Catalytic active component cb1 Carrier cat2 Hydrocarbon synthesis catalyst ca2 Catalytic active component cb2 Carrier

Claims

1. An electrolytic cell unit configured to include at least an electrolytic cell in which an electrode layer and a counter electrode layer are formed with an electrolyte layer interposed therebetween, and a discharge path for discharging hydrogen generated in the electrode layer, wherein the electrolytic cell is formed in a thin layer on a support, and a reverse water gas shift reaction unit for generating carbon monoxide using carbon dioxide and the hydrogen by a reverse water gas shift reaction is provided in at least a part of the discharge path, and an electrolytic cell device including at least an electrolytic raw material supply unit for supplying water and / or steam and carbon dioxide to the electrolytic cell unit, and a power supply unit for supplying power.

2. The electrolytic cell device according to claim 1, wherein the support is a metal.

3. The electrolytic cell device according to claim 1 or 2, wherein a plurality of through holes penetrating the support are provided, the electrode layer is provided on one surface of the support, the discharge path is provided along the other surface, and the reverse water gas shift reaction unit is provided in at least a part of the inner surface of the discharge path.

4. The electrolytic cell device according to claim 3, wherein the reverse water gas shift reaction unit is provided in at least a part of the inside of the through hole.

5. The electrolytic cell device according to any one of claims 1 to 4, wherein the reverse water gas shift reaction unit is provided on a surface of the support different from the surface on which the electrolytic cell is formed.

6. The electrolytic cell device according to any one of claims 1 to 5, further including a separator for separating hydrogen generated in the electrode layer and oxygen generated in the counter electrode layer, and the reverse water gas shift reaction unit is provided in at least a part of the hydrogen discharge path side of the separator.

7. The electrolytic cell device according to claim 6, wherein the separator is a metal.

8. The electrolytic cell device according to any one of claims 1 to 7, wherein the reverse water gas shift catalyst contained in the reverse water gas shift reaction unit is a catalyst in which a metal or a metal oxide is supported on a carrier.

9. The electrolytic cell device according to any one of claims 1 to 8, wherein the reverse water gas shift catalyst contained in the reverse water gas shift reaction unit is a catalyst containing at least one of platinum, nickel, and iron.

10. The electrolytic cell device according to claim 8, wherein the carrier is a carrier mainly composed of a ceria-based metal oxide or a zirconia-based metal oxide.

11. A hydrocarbon production system comprising the electrolytic cell device according to any one of claims 1 to 10 and a hydrocarbon synthesis reaction section that generates hydrocarbons by reacting at least hydrogen and carbon monoxide generated by the electrolytic cell device.

12. A method for manufacturing an electrolytic cell device, comprising at least: an electrolytic cell unit configured to include at least an electrolytic cell in which an electrode layer and a counter electrode layer are formed with an electrolyte layer interposed therebetween, and a discharge path for discharging hydrogen generated in the electrode layer; the electrolytic cell being formed in a thin layer on a support; a reverse water gas shift reaction section for generating carbon monoxide using carbon dioxide and the hydrogen by a reverse water gas shift reaction being provided in at least a part of the discharge path; an electrolytic raw material supply section for supplying water and / or steam and carbon dioxide to the electrolytic cell unit; and a power supply section for supplying power, the method including at least a firing step of firing at a temperature of 450°C or higher in a step of forming the reverse water gas shift reaction section.

13. A method for using an electrolytic cell device, comprising at least: an electrolytic cell unit configured to include at least an electrolytic cell in which an electrode layer and a counter electrode layer are formed with an electrolyte layer interposed therebetween, and a discharge path for discharging hydrogen generated in the electrode layer; the electrolytic cell being formed in a thin layer on a support; a reverse water gas shift reaction section for generating carbon monoxide using carbon dioxide and the hydrogen by a reverse water gas shift reaction being provided in at least a part of the discharge path; an electrolytic raw material supply section for supplying water and / or steam and carbon dioxide to the electrolytic cell unit; and a power supply section for supplying power, the method including using the electrolytic cell device after subjecting the reverse water gas shift reaction section to a pre-treatment for reduction.

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