Laminate, gas decomposition apparatus, and method for decomposing oxygen compound gas

Abstract

To provide a laminate capable of further improving electrolysis efficiency in the electrolysis of an oxygen compound gas such as CO2.SOLUTION: The present invention provides a laminate having an electrolyte layer sandwiched between an anode catalyst layer and a cathode catalyst layer, where the content of a perovskite-type oxide in the cathode catalyst layer is 90.0 to 99.5 mass%; the content of Ni oxide is 0.1 to 9.0 mass%; the content of Co oxide is 0.1 to 9.0 mass%; and the total content of Ni oxide and Co oxide is 0.5 to 10.0 mass%.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a laminate, a gas decomposition device, and a method for decomposing an oxygen compound gas. [Background technology]

[0002] CCU (CO2 Capture and Utilization, a technology for effectively utilizing carbon dioxide) is being considered as one of the methods for reducing emissions of oxygen compound gases, especially carbon dioxide (hereinafter also referred to as CO2). In particular, CO2 electrolysis technology (hereinafter also referred to as electrolysis technology) is attracting attention. In particular, the increase in renewable energy, primarily solar power generation, can result in surplus electricity. With a view to making effective use of such surplus electricity, there are high hopes for power storage using electrolysis technology.

[0003] Carbon monoxide (hereinafter also referred to as CO) generated by the electrolysis of CO2 can be used, for example, as energy in steelworks or as a raw material for chemical products such as methanol. In particular, the blast furnace process is used in the production of steel at steelworks. In the blast furnace process, iron ore is reduced by coal, which inevitably generates CO2. Therefore, it is extremely important to establish electrolysis technology for oxygen compound gases in the blast furnace process as well.

[0004] As an example of an electrolysis technology for such oxygen compound gases, Patent Document 1 discloses a laminate (cell, hereinafter also simply referred to as a laminate) for electrolysis in which nickel oxide (Ni oxide) is used as the main component in the cathode catalyst layer (fuel electrode).

[0005] Furthermore, Non-Patent Document 1 discloses a laminate using a perovskite oxide for the cathode catalyst layer. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5910539 [Non-patent literature]

[0007] [Non-Patent Document 1] Highly active oxide cathode of La(Sr)Fe(Mn)O3 for intermediate temperature CO2 and CO2-H2O co-electrolysis using LSGM electrolyte Summary of the Invention [Problem to be solved by the invention]

[0008] In recent years, due to the effects of global warming worldwide, there has been a demand for further reductions in CO2 emissions. Therefore, there is a strong demand for further improvement in the conversion efficiency from CO2 to CO (hereinafter also simply referred to as electrolysis efficiency) when electrolyzing oxygen compound gases, particularly CO2.

[0009] The present invention has been developed to meet the above-mentioned demands, and aims to provide a laminate that enables further improvement in electrolysis efficiency when electrolyzing oxygen compound gases, such as CO2. Another object of the present invention is to provide a gas decomposition device having the above laminate, and a method for decomposing oxygen compound gases using the above laminate.

[0010] The oxygen compound gas is a gas containing an oxygen compound. The oxygen compound is a gaseous compound that contains oxygen atoms. Examples of such oxygen compounds include CO, HO, NO, and SO. [Means for solving the problem]

[0011] The inventors have conducted extensive research to achieve the above object. As a result, the inventors have found that the above object can be achieved by satisfying the following points in a laminate having a structure in which an electrolyte layer is sandwiched between an anode catalyst layer and a cathode catalyst layer. The cathode catalyst layer contains a perovskite-type oxide, Ni oxide, and Co oxide at the same time. In addition, in the cathode catalyst layer, The content of the perovskite oxide is 90.0 to 99.5 mass%, and The content of Ni oxide is 0.1 to 9.0 mass %, the content of Co oxide is 0.1 to 9.0 mass %, and the total content of Ni oxide and Co oxide is 0.5 to 10.0 mass %. In this specification, any numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits, respectively. The present invention was completed based on the above findings and further investigations.

[0012] That is, the gist and configuration of the present invention are as follows. 1. A laminate comprising an electrolyte layer, an anode catalyst layer, and a cathode catalyst layer, the laminate has a structure in which the electrolyte layer is sandwiched between the anode catalyst layer and the cathode catalyst layer, In the cathode catalyst layer, The content of the perovskite oxide is 90.0 to 99.5 mass %, The content of Ni oxide is 0.1 to 9.0 mass %, The content of Co oxide is 0.1 to 9.0 mass %, the total content of the Ni oxide and the Co oxide is 0.5 to 10.0 mass%; Laminate.

[0013] 2. The perovskite oxide is La α Sr β Fe γ Mn δ The laminate according to 1 above, which is O3. Here, α, β, γ, and δ are 0 to 1, α+β is 1, and γ+δ is 1.

[0014] 3. The laminate according to 1 or 2 above, wherein the electrolyte layer and the anode catalyst layer contain a perovskite-type oxide.

[0015] 4. A raw material gas supply unit that supplies an oxygen compound gas as a raw material gas; an electrolysis unit that generates oxygen and a by-product gas by electrolysis from the oxygen compound gas supplied from the raw material gas supply unit; an oxygen recovery unit that recovers the oxygen; a by-product gas recovery unit that recovers the by-product gas, 4. A gas decomposition device, wherein the electrolysis section comprises the laminate described in any one of 1 to 3 above.

[0016] 5. The gas decomposition apparatus according to 4 above, wherein the raw material gas supply section has a preheating device.

[0017] 6. A supply step of supplying an oxygen compound gas as a raw material gas to the laminate described in any one of 1 to 3 above; an electrolysis step of applying a voltage to the laminate to generate oxygen and a by-product gas from the oxygen compound gas by electrolysis; an oxygen recovery step of recovering the oxygen; a by-product gas recovery step of recovering the by-product gas.

[0018] 7. The method for decomposing an oxygen compound gas according to 6 above, wherein the oxygen compound gas contains CO2 and the by-product gas contains CO.

[0019] 8. The method for decomposing an oxygen compound gas according to 6 above, wherein the oxygen compound gas contains CO2 and H2O, and the by-product gas contains CO and H2.

[0020] 9. The method for decomposing oxygen compound gases according to any one of 6 to 8 above, wherein the temperature at which the raw material gas is supplied is 100°C or higher and 800°C or lower.

[0021] 10. The method for decomposing oxygen compound gases according to any one of 6 to 9 above, wherein the voltage applied in the electrolysis step is 0.6 V or more and 2.0 V or less. [Effects of the Invention]

[0022] According to the present invention, oxygen compound gas, particularly CO2, can be electrolyzed more efficiently, which makes it possible to further reduce CO2 emissions. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is a schematic diagram illustrating an example of a laminate according to one embodiment of the present invention. [Figure 2] 1 is a schematic diagram illustrating an example of a gas decomposition apparatus according to an embodiment of the present invention. [Figure 3] FIG. 1 is a diagram plotting the maximum values ​​of CO generation amounts (μmol / (A·min)) for invention examples and comparative examples 1 to 6. DETAILED DESCRIPTION OF THE INVENTION

[0024] The present invention will be described based on the following embodiments: First, a laminate according to one embodiment of the present invention will be described.

[0025] [1] Laminate As shown in Fig. 1, a stack according to one embodiment of the present invention includes an electrolyte layer, an anode catalyst layer, and a cathode catalyst layer. The stack has a structure in which the electrolyte layer is sandwiched between the anode catalyst layer and the cathode catalyst layer (a so-called sandwich structure). The stack can also be said to be a stack in which an anode catalyst layer is stacked on one side of the electrolyte layer, and a cathode catalyst layer is stacked on the side of the electrolyte layer opposite the side on which the anode catalyst layer is stacked. In FIG. 1, reference numeral 1 denotes a laminate, 11 denotes an anode catalyst layer, 12 denotes an electrolyte layer, 13 denotes a cathode catalyst layer, and 3 denotes a power source.

[0026] First, the principle of electrolyzing CO2 into CO and O2 using a laminate according to one embodiment of the present invention will be described.

[0027] (Principle of CO2 electrolysis) As shown in Figure 1, while a voltage is applied between the anode catalyst layer and the cathode catalyst layer of the laminate, an oxygen compound gas containing CO2 is supplied so that it comes into contact with the laminate, particularly the cathode catalyst layer. This causes the CO2 contained in the oxygen compound gas to be electrolyzed into CO and O2. During this process, the following reactions occur in the cathode catalyst layer and the anode catalyst layer, respectively. Cathode catalyst layer CO2+2e - →CO+O 2- (1) Anode catalyst layer 2O 2- →O2+4e - (2)

[0028] That is, in the cathode catalyst layer, CO2 receives electrons, and the reaction of the above formula (1) occurs. This generates CO. Meanwhile, in the anode catalyst layer, O2 generated in the cathode catalyst layer is converted to CO2. 2- The O diffuses through the electrolyte layer and reaches the anode catalyst layer, where the reaction shown in formula (2) occurs. 2- An electron is removed from the atom to produce O2.

[0029] When electrolyzing H2O, the following reactions occur in the cathode catalyst layer and the anode catalyst layer. Cathode catalyst layer H2O+2e - →H2+O 2- (3) Anode catalyst layer 2O 2- →O2+4e - (4)

[0030] Next, the electrolyte layer, anode catalyst layer, and cathode catalyst layer that constitute the laminate according to one embodiment of the present invention will be described.

[0031] (electrolyte layer) The electrolyte layer is formed by transferring O from the cathode side to the anode side while a voltage is applied between the anode catalyst layer and the cathode catalyst layer. 2- The electrolyte layer of the laminate according to one embodiment of the present invention is not particularly limited in material, and may be made of a material commonly used for electrolysis, such as a spinel oxide or a perovskite oxide. In particular, the electrolyte layer preferably contains a perovskite oxide. Perovskite oxides have high ionic conductivity even at low temperatures. The perovskite oxide is not particularly limited, but a perovskite oxide containing two or more elements selected from La, Sr, Ga, Mg, Zr, and Y is preferred. This allows for high electrolysis efficiency even when a relatively low voltage is applied between the anode catalyst layer and the cathode catalyst layer. The electrolyte layer may contain a spinel oxide or a perovskite oxide alone, or may contain both oxides simultaneously. When a spinel oxide or a perovskite oxide is simultaneously contained, the content of the spinel oxide in the electrolyte layer is preferably 30% by mass or less, and the content of the perovskite oxide is preferably 70% by mass or more. The electrolyte layer may contain a remaining substance other than the spinel oxide or perovskite oxide in a total amount of 10 mass % or less, such as oxides other than the spinel oxide or perovskite oxide, and unavoidable impurities.

[0032] (Anode catalyst layer) The anode catalyst layer is formed on one side of the electrolyte layer. The anode catalyst layer functions as an anode and promotes the reactions shown in the above formulas (2) and (4). In the laminate according to one embodiment of the present invention, the anode catalyst layer is formed of a catalyst that is generally used for electrolysis, i.e., a catalyst that converts oxygen ions (O 2-A highly active substance that quickly recombines cations of cations (Cu, Cu, Cu) into oxygen molecules (O-) is used. In particular, it is preferable that the anode catalyst layer contains a perovskite-type oxide. The perovskite-type oxide is not particularly limited, but a perovskite-type oxide containing one or more elements selected from Ba, La, and Co is preferred. As such a perovskite-type oxide, Ba, m La n Examples of the oxides include CoO3. Here, m and n are 0 to 1, and m+n is 1. Preferably, m is 0.1 to 1. Furthermore, m is more preferably 0.5, as this minimizes electrical resistance. The anode catalyst layer may contain a total of 10 mass% or less of remaining substances other than the perovskite oxide. Examples of the remaining substances include oxides other than the perovskite oxide and unavoidable impurities.

[0033] (Cathode catalyst layer) The cathode catalyst layer is formed on one side of the electrolyte layer opposite the side on which the anode catalyst layer is formed. The cathode catalyst layer functions as a cathode and promotes the reactions represented by the above formulas (1) and (3). As described above, it is extremely important that the cathode catalyst layer of the laminate according to one embodiment of the present invention satisfy the following requirements: The cathode catalyst layer contains a perovskite-type oxide, Ni oxide, and Co oxide at the same time. In addition, in the cathode catalyst layer, The content of the perovskite oxide is 90.0 to 99.5 mass%, and The content of Ni oxide is 0.1 to 9.0 mass %, the content of Co oxide is 0.1 to 9.0 mass %, and the total content of Ni oxide and Co oxide is 0.5 to 10.0 mass %.

[0034] Perovskite oxide content: 90.0 to 99.5 mass% As described above, in order to further improve the electrolysis efficiency when electrolyzing oxygen compound gases, it is important to simultaneously contain a perovskite oxide, Ni oxide, and Co oxide in the cathode catalyst layer and to appropriately control the contents of these. Therefore, the content of the perovskite oxide is set to 90.0 to 99.5 mass%. The content of the perovskite oxide is preferably 93.0 mass% or more. Furthermore, the content of the perovskite oxide is preferably 98.0 mass% or less.

[0035] The perovskite oxide used in the cathode catalyst layer is not particularly limited, but may be La α Sr β Fe γ Mn δ O3 is preferred. Here, α, β, γ, and δ are 0 to 1, α+β is 1, and γ+δ is 1. It is more preferred that α is 0.5 to 1, and γ is 0.05 to 0.3.

[0036] Ni oxide content: 0.1 to 9.0 mass%, Co oxide content: 0.1 to 9.0 mass% As described above, to further improve the electrolysis efficiency during the electrolysis of oxygen compound gases, it is important to incorporate a perovskite-type oxide, Ni oxide, and Co oxide into the cathode catalyst layer and to appropriately control their contents. Therefore, the contents of Ni oxide and Co oxide are each set to 0.1 to 9.0 mass%. The contents of Ni oxide and Co oxide are each preferably 1.0 mass% or more. Furthermore, the contents of Ni oxide and Co oxide are each preferably 5.0 mass% or less.

[0037] Total content of Ni oxide and Co oxide: 0.5 to 10.0 mass% As described above, to further improve the electrolysis efficiency when electrolyzing oxygen compound gases, it is important to incorporate perovskite-type oxides, Ni oxides, and Co oxides into the cathode catalyst layer and to appropriately control their contents. Therefore, the total content of Ni oxide and Co oxide is set to 0.5 to 10.0 mass%. The total content of Ni oxide and Co oxide is preferably 1.0 mass% or more. Furthermore, the total content of Ni oxide and Co oxide is preferably 5.0 mass% or less.

[0038] The cathode catalyst layer may contain a total of 5.0% by mass or less of residual substances other than perovskite-type oxides, Ni oxides, and Co oxides. The content of the residual substances is more preferably 3.0% by mass or less, and even more preferably 1.0% by mass or less. The content of the residual substances may be 0% by mass. Examples of the residual substances include spinel-type oxides, oxides other than those mentioned above, and unavoidable impurities. The content of the unavoidable impurities is preferably 1.0% by mass or less, more preferably 0.5% by mass or less, and even more preferably 0.1% by mass or less. The content of the unavoidable impurities may be 0% by mass. The same applies to the content of unavoidable impurities in the electrolyte layer and the anode catalyst layer.

[0039] Furthermore, as a combination of the electrolyte layer, anode catalyst layer, and cathode catalyst layer, it is preferable that the electrolyte layer and anode catalyst layer are made of perovskite-type oxide, and the cathode catalyst layer is made of perovskite-type oxide, Ni oxide, and Co oxide, which can more effectively improve the electrolysis efficiency.

[0040] The electrolyte layer, anode catalyst layer, and cathode catalyst layer can be formed, for example, by mixing and firing oxides of the metals (elements) that make up each layer to obtain a predetermined composition. Alternatively, nitrates or chlorides of the metals that make up each layer may be used.

[0041] A laminate according to one embodiment of the present invention can be formed, for example, by applying a metal oxide for the anode catalyst layer to one surface of a plate-shaped electrolyte layer and a metal oxide for the cathode catalyst layer to the other surface of the electrolyte layer, followed by firing. Alternatively, the laminate can be formed by processing the electrolyte layer into a cylindrical shape, applying a metal oxide for the cathode catalyst layer to the inner surface of the cylindrical electrolyte layer and a metal oxide for the anode catalyst layer to the outer surface of the cylindrical electrolyte layer, followed by firing.

[0042] Furthermore, the thickness ratio of the electrolyte layer, anode catalyst layer, and cathode catalyst layer is preferably 1:1 for the anode catalyst layer, 0.5 to 5 for the cathode catalyst layer, and 10 to 50 for the electrolyte layer. If the thickness of the electrolyte layer is too small compared to the thickness of the anode catalyst layer or the cathode catalyst layer, it may not be able to withstand the thermal stress and may crack. On the other hand, if the thickness of the electrolyte layer is too large, Joule heat may increase due to increased electrical resistance, which may reduce the electrolysis efficiency.

[0043] Other than the above, there are no particular limitations, and a general configuration of a laminate for electrolysis can be appropriately adopted.

[0044] [2] Gas decomposition equipment Next, a gas decomposition apparatus according to one embodiment of the present invention will be described. As shown in FIG. 2, a gas decomposition apparatus according to one embodiment of the present invention includes: a raw material gas supply unit that supplies an oxygen compound gas as a raw material gas; an electrolysis unit that generates oxygen and a by-product gas by electrolysis from the oxygen compound gas supplied from the raw material gas supply unit; an oxygen recovery unit that recovers the oxygen; a by-product gas recovery unit that recovers the by-product gas, The electrolysis unit has the laminate described in [1] above. In FIG. 2, reference numeral 1 denotes a laminate, 11 denotes an anode catalyst layer, 12 denotes an electrolyte layer, 13 denotes a cathode catalyst layer, 2 denotes a gas decomposition device, 21 denotes an electrolysis unit, 22 denotes a raw material gas supply unit, 23 denotes a sweep gas supply unit, 24 denotes a by-product gas recovery unit, 25 denotes an oxygen recovery unit, and 3 denotes a power source.

[0045] (raw gas supply unit) The raw material gas supply unit supplies an oxygen compound gas serving as a raw material gas to the electrolysis unit, preferably so that the oxygen compound gas contacts the cathode catalyst layer of the stack. The raw material gas supply unit is configured, for example, by a gas flow channel adjacent to the cathode catalyst layer of the stack of the electrolysis unit described below. The gas flow channel is defined, for example, by a casing that houses the stack. Packing or a glass seal may be used to prevent gas leakage from the casing. The gas flow channel may also be configured by piping, ducts, or the like. The raw material gas supply unit may also include a device for pressure-feeding the raw material gas. Examples of such a device include a fan or a blower. The raw material gas supply unit may also include a raw material gas preheater or a separator / recoverer for oxygen compounds such as CO2. The raw material gas preheater and the oxygen compound separator / recoverer may be disposed, for example, in the gas flow channel. From the viewpoint of suppressing a temperature decrease of the raw material gas, it is preferable to dispose the raw material gas preheater immediately before the electrolysis unit, for example, in the gas flow channel defined by the casing that houses the stack, or at a position adjacent to this gas flow channel. Examples of the device for preheating the raw material gas include a burner and a heat exchanger that utilizes exhaust heat.

[0046] The heat source for the heat exchanger can be, for example, waste heat from a steelworks. Examples of waste heat from a steelworks include sensible heat from slag, coke oven gas (COG), and sintered ore. Low-temperature waste heat of around 200°C can also be used, so heating furnace gas or hot stove exhaust gas can be used directly as the heat source for the heat exchanger. Furthermore, if the raw material gas contains CO2, high-temperature CO and O2 are produced by electrolysis, and these can also be used as the heat source for the heat exchanger.

[0047] Furthermore, the oxygen compound gas used as the raw material gas preferably contains CO2, and more preferably contains both CO2 and HO. When the oxygen compound gas contains both CO2 and HO, deterioration of the surface of the cathode catalyst layer is suppressed, contributing to a longer life of the equipment. The ratio of these gases may be set at any ratio depending on the source of the raw material gas, etc. In addition, the oxygen compound gas used as the raw material gas may contain residual gases other than the oxygen compounds. Examples of residual gases include Ar and N2. For example, blast furnace gas, which is a by-product of a blast furnace in the steelmaking process, and combustion exhaust gases from hot stoves and heating furnaces contain 10% or more by volume of CO2, and are therefore suitable as raw material gases. Furthermore, gases obtained by subjecting blast furnace gas to a process to increase the CO2 concentration can also be used. Furthermore, CO2-containing gases generated in other industrial fields can also be used.

[0048] (Electrolysis section) The electrolysis unit has the laminate described in [1] above. As shown in Fig. 2, an oxygen compound gas, such as CO2 or HO, supplied as a raw material gas from the raw material gas supply unit is brought into contact with the cathode catalyst layer of the laminate described in [1] above, whereby electrolysis is carried out according to the above formulas (1) to (4), generating oxygen and by-product gases.

[0049] Here, the electrolysis unit is configured to apply a voltage to the stack described in [1] above. For example, the anode catalyst layer and cathode catalyst layer of the stack are connected to a power source via a cable. The power source may be either a DC power source or an AC power source. However, in the case of an AC power source, the AC power source must be converted to DC power using a converter or the like before current flows through the stack. The electrolysis unit may also have a casing (housing) to house the stack, various measuring instruments such as a voltmeter, a heater for the stack, and the like. The casing may also have a gas distribution (inlet) path for bringing the raw material gas into contact with the cathode catalyst layer of the stack, and a gas distribution (recovery) path for recovering by-product gas and oxygen generated by electrolysis.

[0050] (Oxygen recovery section and by-product gas recovery section) The oxygen recovery unit and the by-product gas recovery unit recover the oxygen and the by-product gas generated in the electrolysis unit, respectively. The oxygen recovery unit and the by-product gas recovery unit are each configured, for example, by gas flow channels adjacent to the anode catalyst layer and the cathode catalyst layer of the stack of the electrolysis unit. The gas flow channels are defined, for example, by a casing that houses the stack. The gas flow channels may also be configured by piping, ducts, or the like. Furthermore, the oxygen recovery unit and the by-product gas recovery unit may each have a device that pressurizes or sucks the oxygen and the by-product gas. Examples of such devices include a fan and a blower. The oxygen and the by-product gas generated in the electrolysis unit may be supplied, for example, to equipment or storage units that use the oxygen and the by-product gas, via the oxygen recovery unit and the by-product gas recovery unit, respectively.

[0051] (others) Additionally, a gas decomposition apparatus according to one embodiment of the present invention may include a sweep gas supply unit that supplies a sweep gas to the anode catalyst layer of the stack in the electrolysis unit. The sweep gas supply unit may be configured, for example, as a gas flow passage adjacent to the anode catalyst layer of the stack in the electrolysis unit. The gas flow passage may be defined, for example, by a casing that houses the stack. The gas flow passage may also be configured as a pipe or duct. The sweep gas supply unit may also include a device for pumping or sucking the sweep gas. Examples of such devices include a fan or a blower. Supplying a sweep gas to the anode catalyst layer can reduce the O2 partial pressure on the surface of the anode catalyst layer (hereinafter also referred to as O2 surface partial pressure), thereby increasing the O2 production rate. This is expected to improve reaction efficiency. For example, supplying air as a sweep gas can produce oxygen-enriched air, which can be used directly for combustion. The sweep gas is not particularly limited and may be an inert gas such as N2 or Ar. Furthermore, by absorbing O2, the surface partial pressure of O2 on the anode catalyst layer can be reduced.

[0052] Other than the above, there are no particular limitations, and a general configuration of a gas decomposition device using electrolysis can be appropriately adopted.

[0053] [3] Method for decomposing oxygen compound gases Next, a method for decomposing an oxygen compound gas according to one embodiment of the present invention will be described. A method for decomposing an oxygen compound gas according to one embodiment of the present invention includes the steps of: a supply step of supplying an oxygen compound gas as a raw material gas to the laminate of the above [1]; an electrolysis step in which a voltage is applied to the laminate of the above [1] to generate oxygen and a by-product gas from the oxygen compound gas by electrolysis; an oxygen recovery step of recovering the oxygen; a by-product gas recovery step of recovering the by-product gas; It has.

[0054] (Supply step) In the supply step, an oxygen compound gas as a raw material gas is supplied to the laminate of the above [1]. Preferably, the oxygen compound gas as a raw material gas is supplied so as to come into contact with the cathode catalyst layer of the laminate of the above [1]. The oxygen compound gas as a raw material gas can be supplied, for example, through a gas flow passage such as a pipe or duct connected to a raw material gas supply source.

[0055] In addition, the supply temperature of the raw material gas to the stack described in [1] above is preferably 100°C or higher and 800°C or lower. The higher the supply temperature of the raw material gas, the more the power required for electrolysis can be reduced. However, from the viewpoint of designing the gas decomposition apparatus, heat generation due to Joule heat from the stack described in [1] above can also be considered. Therefore, the supply temperature of the raw material gas is preferably 400°C or lower. In addition, the supply temperature of the raw material gas is preferably 200°C or higher. The supply temperature of the raw material gas may be measured, for example, in the gas flow passage (upstream of the stack) in the casing that houses the stack or immediately before the casing.

[0056] Furthermore, the raw material gas may be preheated in order to control the supply temperature of the raw material gas, as exemplified in [2] above.

[0057] Furthermore, as explained in [2] above, the oxygen compound gas used as the raw material gas is preferably at a high concentration. For example, the concentration of CO2 is not particularly limited, but is preferably 10% by volume or more from the viewpoint of electrolysis efficiency.

[0058] The gas delivered from the source gas source (hereinafter also referred to as the delivery gas) may be directly supplied to the stack of [1] as the source gas. Alternatively, for example, CO2 and other components may be separated and recovered from the delivery gas in advance, and the separated and recovered gas (hereinafter also referred to as the separated and recovered gas) may be supplied to the stack of [1] as the source gas. The method for separating and recovering CO2 is not particularly limited. Examples include a method of liquefying or solidifying CO2 by pressurization or cooling, a method of absorbing CO2 into a basic aqueous solution such as caustic soda or amine, and then separating and recovering it by heating or reducing pressure, a method of adsorbing CO2 onto activated carbon or zeolite, and then separating and recovering it by heating or reducing pressure, and a method of separating and recovering it using a CO2 separation membrane. The CO2 concentration of the separated and recovered gas is not particularly limited, but is preferably 80% by volume or higher. This is advantageous because it allows for the miniaturization of gas decomposition devices, particularly the stack used during electrolysis, and the associated equipment for the stack.

[0059] Additionally, if desired, the feed gas may be pre-cleaned of harmful components such as sulfur and NOx.

[0060] (Electrolysis step) In the electrolysis step, a voltage is applied to the laminate of the above [1], and oxygen and by-product gases are generated by electrolysis from the oxygen compound gas, which is the raw material gas, in the cathode catalyst layer of the laminate.

[0061] The applied voltage in the electrolysis step (the voltage applied between the anode catalyst layer and the cathode catalyst layer of the laminate in [1] above) is preferably 0.6 V or more and 2.0 V or less. If the applied voltage is less than 0.6 V, the voltage will be lower than the theoretical electrolysis voltage, and the electrolysis reaction may not proceed sufficiently. If the applied voltage exceeds 2.0 V, CO2 will decompose into solid carbon (C) and O2, making it difficult to generate CO2. Furthermore, Joule heat will accumulate in the laminate, which may cause decomposition of the laminate itself.

[0062] Furthermore, it is preferable to control the temperature of the laminate during electrolysis to 100°C or higher and 900°C or lower. The temperature of the laminate during electrolysis is more preferably 600°C or higher. The temperature of the laminate during electrolysis is more preferably 800°C or lower. In other words, it is preferable to control the temperature of the laminate during electrolysis as described above, taking into account Joule heat due to electrical resistance.

[0063] The temperature of the laminate can be controlled by, for example, heating the laminate body with a heater or a heat exchanger using exhaust heat as described above, or by controlling the supply temperature of the raw material gas as described above.

[0064] (Oxygen recovery step and by-product gas recovery step) In the oxygen recovery step and the by-product gas recovery step, the oxygen and by-product gas generated in the electrolysis step are recovered, respectively. The oxygen and by-product gas generated in the electrolysis step can be recovered, for example, via gas flow channels adjacent to the anode catalyst layer and the cathode catalyst layer of the laminate of the electrolysis unit, respectively. The recovered oxygen and by-product gas can be supplied, for example, to equipment or storage units that use the oxygen and by-product gas.

[0065] (others) The method for decomposing oxygen compound gases according to one embodiment of the present invention may further include a sweep gas supply step of supplying a sweep gas to the anode catalyst layer of the electrolysis unit. The sweep gas may be supplied, for example, through a gas flow passage adjacent to the anode catalyst layer of the electrolysis unit. The sweep gas is as described in [2] above.

[0066] Furthermore, the method for decomposing oxygen compound gases according to one embodiment of the present invention can be particularly suitably carried out using, for example, the gas decomposition apparatus described above in [2].

[0067] The conditions other than those mentioned above are not particularly limited, and may be those according to conventional methods. [Example]

[0068] A laminate was prepared in the following manner.

[0069] <Electrolyte layer> The electrolyte layer is made of La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 A perovskite-type oxide with a composition of O3 was used. First, La2O3, SrCO3, Ga2O3, and MgO were mixed in an alumina mortar for 30 minutes in the molar ratios required to obtain the desired composition. The mixture was then placed in an alumina crucible, heated from room temperature to 1000°C over 5 hours, and fired at 1000°C for 6 hours. It was then cooled to room temperature over 5 hours. The resulting powder was mixed in a mortar for 30 minutes. The powder was then uniaxially molded into a 20 mm diameter disk at 20 MPa for 20 minutes. The molded body was then vacuum-packed in a rubber bag and isostatically pressed at 300 MPa for 30 minutes to obtain a pellet. The resulting pellet was then heated from room temperature to 1000°C over 5 hours, further heated to 1500°C over 5 hours, and fired at 1500°C for 6 hours. It was then cooled to 1000°C over 5 hours, further cooled to room temperature over 5 hours, and sintered. In this way, an electrolyte layer with a thickness of 0.3 mm was obtained.

[0070] <Materials for forming the anode catalyst layer> The anode catalyst layer is made of Ba 0.6 La 0.4 A perovskite-type oxide with a composition of CoO3 was used. First, the specified amounts of Ba(NO3)2, La(NO3)3·6H2O, and Co(NO3)2·6H2O were dissolved in water and evaporated to dryness. This was then fired at 400°C in a draft to decompose the nitrates into oxides. The resulting powder was then mixed in a mortar for 30 minutes. This powder was then placed in an alumina crucible and fired at 1200°C for 6 hours. The fired powder was then mixed in the mortar for 30 minutes to obtain the material for forming the anode catalyst layer.

[0071] <Cathode catalyst layer forming materials> The cathode catalyst layer is made of La 0.6 Sr 0.4 Fe 0.9 Mn 0.1 A mixture of a perovskite oxide having a composition of O3 (hereinafter also referred to as LSFM), Ni oxide, and Co oxide in the mass ratio shown in Table 1 was used. Here, the materials used to form the cathode catalyst layer were powdered LSFM and an aqueous solution (hereinafter referred to as the mixed aqueous solution) prepared by mixing predetermined amounts of Ni(NO3)2, Co(NO3)2, and pure water in a molar ratio of 1:1.

[0072] <Formation of anode catalyst layer and cathode catalyst layer (screen printing method)> Using the anode catalyst layer forming material and cathode catalyst layer forming material obtained as described above, an anode catalyst layer was formed on one surface of the electrolyte layer by screen printing, and a cathode catalyst layer was formed on the other surface. Specifically, first, ethyl cellulose and powdered material for forming the anode catalyst layer were mixed in an agate mortar at a mass ratio of 8:100. Similarly, ethyl cellulose and powdered LSFM were mixed at a mass ratio of 8:100. Next, these mixtures were thoroughly mixed until an appropriate viscosity was achieved while adding an appropriate amount of 3-hydroxy-2,2,4-trimethylpentyl dropwise. After stirring for a predetermined time, the mixture was degassed. This resulted in a paste for forming the anode catalyst layer (hereinafter also referred to as the anode paste) and a paste for forming the cathode catalyst layer (hereinafter also referred to as the cathode paste). The resulting anode paste and cathode paste were each applied to the electrolyte layer by screen printing. Screen printing was performed using a 200-mesh stainless steel mesh. The application area was 8 mmφ and the thickness was 5 to 10 μm. In addition, 100 to 900 μL of the above mixed aqueous solution was dropped onto the cathode paste coating to adjust the LSFM, Ni oxide, and Co oxide contents in the cathode catalyst layer. The paste-coated electrolyte layer was then placed on an alumina boat and baked at 1100°C for 30 minutes. At the same time, platinum paste was applied and baked to the edge of the anode paste coating, and a platinum wire (0.1 mm diameter) was attached to the anode catalyst layer (reference electrode). In this way, a laminate for electrolysis (hereinafter also referred to as LSFM-NiCo) was obtained, in which the electrolyte layer was sandwiched between the anode catalyst layer and the cathode catalyst layer.

[0073] For comparison, a cathode catalyst layer was prepared in the same manner as above except for the configuration of the cathode catalyst layer. A laminate in which the cathode catalyst layer is made of Ni oxide (hereinafter, Comparative Example 1, also referred to as Ni type), A laminate in which the cathode catalyst layer was composed of Ni oxide and Cu oxide (Ni oxide / Cu oxide=1 (mass ratio)) (hereinafter, Comparative Example 2, also referred to as NiCu), A laminate in which the cathode catalyst layer was composed of Ni oxide and Co oxide (Ni oxide / Co oxide=9 (mass ratio)) (hereinafter, Comparative Example 3, type may also be referred to as NiCo), The cathode catalyst layer was made of Ni oxide and Fe oxide (Ni oxide / Fe oxide = 9 (mass ratio)) and CMF (Ce 0.6 Mn 0.3 Fe 0.1 O2), in which the total of Ni oxide and Fe oxide was 10 mass % and CMF was 90 mass % (hereinafter, Comparative Example 4, the type may also be referred to as NiFe-CMF), A laminate in which the cathode catalyst layer is made of Co oxide (hereinafter, Comparative Example 5, also referred to as Co type), and A laminate in which the cathode catalyst layer is made of LSFM (hereinafter, Comparative Example 6, type is also referred to as LSFM) obtained.

[0074] The stacks thus obtained were used to fabricate a gas decomposition apparatus as shown in Figure 2. Each stack was sandwiched between an alumina tube and a Pyrex (registered trademark) glass ring from above and below, and the temperature was raised from room temperature to 800°C over two hours. After holding at 800°C for one hour, the Pyrex glass ring was softened and sealed with glass packing. This ensured a flow path for the source gas to the stack, as well as paths for oxygen and by-product gases.

[0075] Next, a voltage of 1.6 V was applied between the anode catalyst layer and the cathode catalyst layer. The raw material gas supply unit supplied oxygen compound gas (30% CO2 / 30% H2O / 40% Ar) to the cathode catalyst layer at a flow rate of 100 mL / min. The sweep gas supply unit supplied air to the anode catalyst layer at a flow rate of 100 mL / min. Electrolysis was performed at four temperatures: 600°C, 700°C, 800°C, and 900°C. By-product gases, such as CO2 generated by CO2 reduction, were recovered from the by-product gas recovery unit, and the generated O2 was recovered from the oxygen gas recovery unit. The electrolysis time (total raw material gas supply time) was 8 hours.

[0076] Then, under each temperature condition, the unit time (min) and unit area (cm) of the cathode catalyst layer were analyzed by gas chromatography. 2CO generation per unit (μmol / (min cm 2 The CO generation rate (μmol / (min cm)) was then calculated. 2 )) is the current density (A / cm 2 ) to determine the amount of CO generated per unit ampere (A) and unit time (min) (μmol / (A·min)). The electrolysis efficiency was then evaluated using the maximum amount of CO generated under each temperature condition, according to the following criteria. The results are also shown in Table 1. Pass (Excellent): Maximum CO emission is 160.0 μmol / (A·min) or more Fail: Maximum CO emission is less than 160.0 μmol / (A·min) For comparison, the maximum values ​​of CO generation (μmol / (A·min)) for Example 1 and Comparative Examples 1 to 6 are plotted in FIG.

[0077] [Table 1]

[0078] As shown in Table 1, extremely high electrolysis efficiency was obtained in the inventive example.

[0079] On the other hand, in all of the comparative examples, sufficient electrolysis efficiency was not obtained.

[0080] Furthermore, when various perovskite-type oxides, Ni oxides, and Co oxides were used in the cathode catalyst layer, and the perovskite-type oxide content was varied within the ranges of 90.0 to 99.5 mass%, the Ni oxide content was varied within the ranges of 0.1 to 9.0 mass%, the Co oxide content was varied within the ranges of 0.1 to 9.0 mass%, and the total content of Ni oxide and Co oxide was varied within the ranges of 0.5 to 10.0 mass%, extremely high electrolysis efficiency was obtained, similar to the above-mentioned inventive examples. [Explanation of symbols]

[0081] 1. Laminate 11 Anode catalyst layer 12 Electrolyte layer 13 Cathode catalyst layer 2. Gas decomposition unit 21 Electrolysis section 22 Raw material gas supply section 23 Sweep gas supply section 24 By-product gas recovery section 25 Oxygen recovery section 3 Power supply

Claims

1. A laminate comprising an electrolyte layer, an anode catalyst layer, and a cathode catalyst layer, the laminate has a structure in which the electrolyte layer is sandwiched between the anode catalyst layer and the cathode catalyst layer, In the cathode catalyst layer, The content of the perovskite oxide is 90.0 to 99.5 mass %, The content of Ni oxide is 0.1 to 9.0 mass %, The content of Co oxide is 0.1 to 9.0 mass %, The total content of the Ni oxide and the Co oxide is 0.5 to 10.0 mass%. Laminate.

2. The perovskite oxide is α Sr β Fe γ Mn δ O ３ The laminate according to claim 1 , Here, α, β, γ, and δ are 0 to 1, α+β is 1, and γ+δ is 1.

3. 3. The laminate according to claim 1, wherein the electrolyte layer and the anode catalyst layer contain a perovskite oxide.

4. a raw material gas supply unit that supplies an oxygen compound gas as a raw material gas; an electrolysis unit that generates oxygen and a by-product gas by electrolysis from the oxygen compound gas supplied from the raw material gas supply unit; an oxygen recovery unit that recovers the oxygen; a by-product gas recovery unit that recovers the by-product gas, A gas decomposition device, wherein the electrolysis section comprises the laminate according to claim 1 or 2.

5. The gas decomposition apparatus according to claim 4 , wherein the raw material gas supply section has a preheating device.

6. a supply step of supplying an oxygen compound gas as a raw material gas to the laminate according to claim 1 or 2; an electrolysis step of applying a voltage to the laminate to generate oxygen and a by-product gas from the oxygen compound gas by electrolysis; an oxygen recovery step of recovering the oxygen; a by-product gas recovery step of recovering the by-product gas.

7. The oxygen compound gas is CO ２ and the by-product gas contains CO.

8. The oxygen compound gas is CO ２ and H ２ and the by-product gas contains CO and H ２ The method for decomposing oxygen compound gases according to claim 6, comprising:

9. 7. The method for decomposing oxygen compound gases according to claim 6, wherein the temperature at which the raw material gas is supplied is 100°C or higher and 800°C or lower.

10. 7. The method for decomposing oxygen compound gases according to claim 6, wherein the voltage applied in the electrolysis step is 0.6 V or more and 2.0 V or less.

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