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

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 apparatus, and a method for decomposing oxygen compound gases. [Background technology]

[0002] One method being considered to reduce emissions of oxygen compound gases, particularly carbon dioxide (hereinafter also referred to as CO2), is CCU (CO2 Capture and Utilization). Among these methods, CO2 electrolysis technology (hereinafter also referred to as electrolysis technology) is attracting particular attention. Especially with the increase in renewable energy sources, primarily solar power, surplus electricity may be generated. With a view to effectively utilizing such surplus electricity, power storage using electrolysis technology is also anticipated.

[0003] Carbon monoxide (hereinafter also referred to as CO), which is produced by the electrolysis of CO2, can be used, for example, as energy in steel mills or as a raw material for chemicals such as methanol. In particular, steel production in steel mills uses the blast furnace process. In the blast furnace process, CO2 is inevitably generated because iron ore is reduced with coal. Therefore, establishing electrolysis technology for oxygen compound gases is extremely important even in the blast furnace process.

[0004] As an electrolysis technology for such oxygen compound gases, for example, Patent Document 1 discloses a laminated body (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 in which a perovskite-type oxide is used as the cathode catalyst layer. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 5910539

Non-Patent Literature

[0007]

Non-Patent Literature 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] By the way, in recent years, due to the influence of global warming, further reduction of CO2 emissions has been demanded. Therefore, when electrolyzing oxygen compound gases, especially CO2, there is a strong demand to further improve the conversion efficiency from CO2 to CO (hereinafter, also simply referred to as electrolysis efficiency).

[0009] The present invention has been developed to meet the above demand, and an object thereof is to provide a laminate that enables further improvement of electrolysis efficiency when electrolyzing an oxygen compound gas represented by CO2. Another object of the present invention is to provide a gas decomposition device having the above laminate and a method for decomposing an oxygen compound gas using the above laminate.

[0010] The oxygen compound gas is a gas containing an oxygen compound. The oxygen compound is a gaseous compound having oxygen atoms as a part thereof. Examples of such oxygen compounds include CO2, H2O, NOx, and SOx.

Means for Solving the Problems

[0011] Now, the inventors have intensively studied to achieve the above object. As a result, in a laminate having a structure in which an electrolyte layer is sandwiched between an anode catalyst layer and a cathode catalyst layer, it has been found that the above object can be achieved by satisfying the following points. · The cathode catalyst layer contains a perovskite-type oxide, Ni oxide, and Co oxide simultaneously. · At this time, in the cathode catalyst layer, the content of the perovskite-type oxide is 90.0 to 99.5% by mass, and the content of Ni oxide is 0.1 to 9.0% by mass, the content of Co oxide is 0.1 to 9.0% by mass, and the total content of Ni oxide and Co oxide is 0.5 to 10.0% by mass. In this specification, any numerical range represented by "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value, respectively. The present invention has been completed through further studies based on the above findings.

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

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

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

[0015] 4. A raw material gas supply unit that supplies oxygen compound gas, which is the raw material gas, An electrolysis unit generates oxygen and by-product gas from the oxygen compound gas supplied from the raw material gas supply unit by electrolysis, An oxygen recovery unit for recovering the aforementioned oxygen, The system includes a by-product gas recovery unit for recovering the aforementioned by-product gas, A gas decomposition apparatus in which the electrolysis unit has the laminate described in any of 1 to 3 above.

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

[0017] 6. A supply step of supplying an oxygen compound gas, which is a raw material gas, to the laminate described in any of 1 to 3 above, An electrolysis step is performed, in which a voltage is applied to the laminate to generate oxygen and byproduct gas from the oxygen compound gas by electrolysis, An oxygen recovery step for recovering the aforementioned oxygen, A method for decomposing an oxygen compound gas, comprising a by-product gas recovery step for recovering the aforementioned by-product gas.

[0018] 7. The method for decomposing an oxygen compound gas according to 6, 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, wherein the oxygen compound gas contains CO2 and H2O, and the by-product gas contains CO and H2.

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

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

[0022] According to the present invention, oxygen compound gases, particularly CO2, can be electrolyzed more efficiently, making it possible to further reduce CO2 emissions. [Brief explanation of the drawing]

[0023] [Figure 1] This is a schematic diagram showing an example of a laminate according to one embodiment of the present invention. [Figure 2] This is a schematic diagram showing an example of a gas decomposition apparatus according to one embodiment of the present invention. [Figure 3] This figure plots the maximum CO generation amounts (μmol / (A·min)) for the inventive example and comparative examples 1 to 6. [Modes for carrying out 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 A laminate according to one embodiment of the present invention comprises an electrolyte layer, an anode catalyst layer, and a cathode catalyst layer, as shown in Figure 1. The laminate 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). Alternatively, the laminate can be described as a laminate in which the anode catalyst layer is laminated on one side of the electrolyte layer, and the cathode catalyst layer is laminated on one side of the electrolyte layer opposite to the side on which the anode catalyst layer is laminated. In Figure 1, reference numeral 1 denotes the laminate, 11 denotes the anode catalyst layer, 12 denotes the electrolyte layer, 13 denotes the cathode catalyst layer, and 3 denotes the power supply.

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

[0027] (Principle of CO2 electrolysis) As shown in FIG. 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 as to contact the laminate, particularly the cathode catalyst layer. Thereby, the CO2 contained in the oxygen compound gas is electrolyzed into CO and O2. At this time, 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. Thereby, CO is generated. On the other hand, in the anode catalyst layer, the O 2- generated in the cathode catalyst layer diffuses through the electrolyte layer and reaches the anode catalyst layer, and the reaction of the above formula (2) occurs. Thereby, electrons are removed from O 2- and O2 is generated.

[0029] When electrolyzing H2O, the following reactions occur in the cathode catalyst layer and the anode catalyst layer, respectively. · 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 constituting the laminate according to an embodiment of the present invention will be described.

[0031] (electrolyte layer) The electrolyte layer is prepared by applying a voltage between the anode catalyst layer and the cathode catalyst layer, with O2 flowing from the cathode side to the anode side. 2- This allows for conductivity. In a laminate according to one embodiment of the present invention, the material of the electrolyte layer is not particularly limited and can be a material commonly used for electrolysis, such as a spinel oxide or a perovskite oxide. In particular, it is preferable that the electrolyte layer contains a perovskite oxide. Perovskite oxides have high ionic conductivity even at low temperatures. The perovskite oxide is not particularly limited, but it is preferable that it contains two or more elements selected from La, Sr, Ga, Mg, Zr, and Y. This makes it possible to achieve high electrolysis efficiency even when the voltage applied between the anode catalyst layer and the cathode catalyst layer is relatively low. In the electrolyte layer, spinel oxides and perovskite oxides can be used individually, or they can be included simultaneously. When spinel oxides and perovskite oxides are included simultaneously, it is preferable that the spinel oxide content in the electrolyte layer be 30% by mass or less, and the perovskite oxide content be 70% by mass or more. Furthermore, the electrolyte layer may contain residual substances other than spinel-type oxides and perovskite-type oxides, provided that their total content is 10% by mass or less. Examples of residual substances include oxides other than spinel-type oxides and perovskite-type oxides, as well as unavoidable impurities.

[0032] (Anode catalyst layer) The anode catalyst layer is formed on one surface of the electrolyte layer. The anode catalyst layer functions as an anode and also promotes the reactions shown in formulas (2) and (4) above. In a laminate according to one embodiment of the present invention, the anode catalyst layer is a common one for electrolysis, namely oxygen ions (O 2-A highly reactive substance is used that rapidly recombines () with oxygen molecules (O-). In particular, the anode catalyst layer preferably 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 CoO3 is one example. Here, m and n are between 0 and 1, and m+n is 1. Furthermore, m is preferably between 0.1 and 1. Moreover, m is more preferably 0.5 because it minimizes electrical resistance. In addition, the anode catalyst layer may contain residual substances other than perovskite-type oxides, as long as the total amount is 10% by mass or less. Examples of residual substances include oxides other than perovskite-type oxides and unavoidable impurities.

[0033] (Cathode catalyst layer) The cathode catalyst layer is formed on one side of the electrolyte layer opposite to the side where the anode catalyst layer is formed. The cathode catalyst layer functions as a cathode and also promotes the reactions shown in formulas (1) and (3) above. As described above, it is extremely important that the cathode catalyst layer of the laminate according to one embodiment of the present invention satisfies the following points. The cathode catalyst layer contains perovskite-type oxides, Ni oxide, and Co oxide simultaneously. Furthermore, in this case, in the cathode catalyst layer, The perovskite-type oxide content is set to 90.0-99.5% by mass, and The Ni oxide content is set to 0.1 to 9.0% by mass, the Co oxide content to 0.1 to 9.0% by mass, and the total content of Ni oxide and Co oxide to 0.5 to 10.0% by mass.

[0034] Perovskite oxide content: 90.0-99.5% by mass As described above, in order to further improve the electrolysis efficiency when electrolyzing oxygen compound gases, it is important to simultaneously contain perovskite-type oxides, Ni oxides, and Co oxides in the cathode catalyst layer and to appropriately control their content. For this reason, the content of perovskite-type oxides is set to 90.0 to 99.5% by mass. Preferably, the content of perovskite-type oxides is 93.0% by mass or more. Also, preferably, the content of perovskite-type oxides is 98.0% by mass or less.

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

[0036] Ni oxide content: 0.1-9.0% by mass, Co oxide content: 0.1-9.0% by mass As described above, in order to further improve the electrolysis efficiency when electrolyzing oxygen compound gases, it is important to simultaneously contain perovskite-type oxides, Ni oxides, and Co oxides in the cathode catalyst layer and to appropriately control their content. For this reason, the content of Ni oxides and Co oxides is set to 0.1 to 9.0% by mass each. Preferably, the content of Ni oxides and Co oxides is 1.0% by mass or more each. Also, preferably, the content of Ni oxides and Co oxides is 5.0% by mass or less each.

[0037] Total content of Ni oxide and Co oxide: 0.5-10.0% by mass As described above, in order to further improve the electrolysis efficiency when electrolyzing oxygen compound gases, it is important to simultaneously contain perovskite-type oxides, Ni oxide, and Co oxide in the cathode catalyst layer, and to appropriately control their content. For this reason, the total content of Ni oxide and Co oxide is set to 0.5 to 10.0% by mass. Preferably, the total content of Ni oxide and Co oxide is 1.0% by mass or more. Also, preferably, the total content of Ni oxide and Co oxide is 5.0% by mass or less.

[0038] The cathode catalyst layer may contain a total of 5.0% by mass or less of the remaining substances other than perovskite-type oxides, Ni oxides, and Co oxides. The content of the remaining substances is more preferably 3.0% by mass or less, and even more preferably 1.0% by mass or less. The content of the remaining substances may be 0% by mass. Examples of the remaining substances include spinel-type oxides, oxides other than those mentioned above, and unavoidable impurities. The content of 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 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, it is preferable that the electrolyte layer and anode catalyst layer be composed of perovskite-type oxides, and the cathode catalyst layer be composed of perovskite-type oxides, Ni oxide, and Co oxide. This allows for a more advantageous improvement in electrolysis efficiency.

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

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

[0042] Furthermore, the preferred ratio of the thicknesses of the electrolyte layer, anode catalyst layer, and cathode catalyst layer is 0.5 to 5 parts for the cathode catalyst layer and 10 to 50 parts for the electrolyte layer, relative to 1 part of the anode catalyst layer. If the thickness of the electrolyte layer is excessively small compared to the anode catalyst layer and even the cathode catalyst layer, it may not be able to withstand thermal stress and may crack. On the other hand, if the thickness of the electrolyte layer is excessively large, the increase in electrical resistance may lead to an increase in Joule heating, 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 adopted as appropriate.

[0044] [2] Gas decomposition apparatus Next, a gas decomposition apparatus according to one embodiment of the present invention will be described. A gas decomposition apparatus according to one embodiment of the present invention is shown in Figure 2, The raw material gas supply unit supplies oxygen compound gas, which is the raw material gas, An electrolysis unit generates oxygen and by-product gas from the oxygen compound gas supplied from the raw material gas supply unit by electrolysis, An oxygen recovery unit for recovering the aforementioned oxygen, The system includes a by-product gas recovery unit for recovering the aforementioned by-product gas, The electrolysis unit has the laminate described in [1] above. In Figure 2, reference numeral 1 denotes the laminate, 11 denotes the anode catalyst layer, 12 denotes the electrolyte layer, 13 denotes the cathode catalyst layer, 2 denotes the gas decomposition apparatus, 21 denotes the electrolysis unit, 22 denotes the raw material gas supply unit, 23 denotes the sweep gas supply unit, 24 denotes the by-product gas recovery unit, 25 denotes the oxygen recovery unit, and 3 denotes the power supply.

[0045] (Raw Gas Supply Department) The raw material gas supply unit supplies an oxygen compound gas, which will be the raw material gas, to the electrolysis unit, preferably in contact with the cathode catalyst layer of the laminate. The raw material gas supply unit is composed of, for example, a gas flow passage adjacent to the cathode catalyst layer of the laminate of the electrolysis unit, which will be described later. The gas flow passage is defined, for example, by a casing that houses the laminate. Packing or glass seals may be used to prevent gas leakage from the casing. The gas flow passage may also be composed of pipes or ducts. Furthermore, the raw material gas supply unit may have a device for pressurizing the raw material gas. Examples of such devices include fans and blowers. The raw material gas supply unit may also have a raw material gas preheating device and a separator and recoverer for oxygen compounds such as CO2. The raw material gas preheating device and the oxygen compound separator and recoverer may be placed, for example, in the gas flow passage described above. Furthermore, from the viewpoint of suppressing a drop in the temperature of the raw material gas, it is preferable to place the raw material gas preheating device immediately before the electrolysis unit, for example, in the gas flow passage defined by the casing that houses the laminate, or in a position adjacent to this gas flow passage. Examples of preheating devices for raw material gases include burners and heat exchangers that utilize waste heat.

[0046] Furthermore, waste heat from a steel mill can be used as a heat source for the heat exchanger. Examples of waste heat from a steel mill include the sensible heat of slag, the sensible heat of coke oven gas (COG), and the sensible heat of sintered ore. Low-temperature waste heat of around 200°C can also be used, so it is possible to use heating furnace gas or hot blast furnace exhaust gas directly as a heat source for the heat exchanger. In addition, if the raw material gas contains CO2, high-temperature CO and O2 will be produced by electrolysis, and these can also be used as a 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 H2O. The presence of both CO2 and H2O in the oxygen compound gas suppresses surface degradation of the cathode catalyst layer, contributing to a longer equipment lifespan. The ratio of these gases can be any ratio depending on the raw material gas source. In addition, the oxygen compound gas used as the raw material gas may contain residual gases other than oxygen compounds. Examples of residual gases include Ar and N2. For example, blast furnace gas produced as a by-product in the steelmaking process, and combustion exhaust gases from hot blast furnaces and heating furnaces, contain 10% or more CO2 by volume, making them suitable as raw material gases. Alternatively, gas obtained by treating blast furnace gas to increase its CO2 concentration can 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 Figure 2, oxygen compound gases, such as CO2 or H2O, supplied as raw material gas from the raw material gas supply unit are brought into contact with the cathode catalyst layer of the laminate described in [1] above, and electrolysis is performed as shown in the above formulas (1) to (4) to generate oxygen and by-product gases.

[0049] Here, the electrolysis unit is configured to apply a voltage to the laminate described in [1] above. For example, the anode catalyst layer and cathode catalyst layer of the laminate are connected to a power supply via a cable. The power supply may be a DC power supply or an AC power supply. However, in the case of an AC power supply, it is necessary to convert it to a DC power supply using a converter or the like before current flows through the laminate. The electrolysis unit may also have a casing to house the laminate, various measuring instruments such as a voltmeter, a heating device for the laminate, etc. The casing may also have a gas flow (introduction) path for bringing the raw material gas into contact with the cathode catalyst layer of the laminate, and a gas flow (recovery) path for recovering by-product gases and oxygen generated by electrolysis.

[0050] (Oxygen recovery unit and by-product gas recovery unit) The oxygen recovery unit and the by-product gas recovery unit recover the oxygen and by-product gases generated in the electrolysis unit, respectively. The oxygen recovery unit and the by-product gas recovery unit are each composed of, for example, gas passages adjacent to the anode catalyst layer and cathode catalyst layer of the electrolysis unit's laminate. The gas passages are defined, for example, by a casing that houses the laminate. Alternatively, the gas passages may be composed of pipes or ducts. Furthermore, the oxygen recovery unit and the by-product gas recovery unit may each have devices for pumping or aspirating the oxygen and by-product gases. Examples of such devices include fans and blowers. The oxygen and by-product gases generated in the electrolysis unit can then be supplied, for example, to equipment or storage units that utilize the oxygen and by-product gases, via the oxygen recovery unit and the by-product gas recovery unit, respectively.

[0051] (others) In addition, a gas decomposition apparatus according to one embodiment of the present invention may have a sweep gas supply unit that supplies sweep gas to the anode catalyst layer of the electrolysis unit's laminate. The sweep gas supply unit is, for example, composed of a gas flow passage adjacent to the anode catalyst layer of the electrolysis unit's laminate. The gas flow passage is defined, for example, by a casing that houses the laminate. The gas flow passage may also be composed of pipes or ducts. Furthermore, the sweep gas supply unit may have a device for pressurizing or sucking the sweep gas. Examples of such devices include fans and blowers. By supplying sweep gas to the anode catalyst layer, the O2 partial pressure on the surface of the anode catalyst layer (hereinafter also referred to as O2 surface partial pressure) can be lowered, and the rate of O2 production can be increased. This is expected to improve reaction efficiency. For example, by supplying air as the sweep gas, oxygen-enriched air can be produced and used directly for combustion. The sweep gas is not particularly limited and may be an inert gas such as N2 or Ar. Furthermore, by aspirating O2, the O2 surface partial pressure of the anode catalyst layer can also be reduced.

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

[0053] [3] Method for decomposing oxygen compound gases Next, a method for decomposing oxygen compound gases 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 is: A supply step involves supplying an oxygen compound gas, which is a raw material gas, to the laminate described in [1] above. An electrolysis step is performed in which a voltage is applied to the laminate of [1] above, and oxygen and by-product gas are generated from the oxygen compound gas by electrolysis. An oxygen recovery step for recovering the aforementioned oxygen, A by-product gas recovery step, which recovers the aforementioned by-product gas, It holds.

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

[0055] Furthermore, the supply temperature of the raw material gas to the laminate described in [1] above is preferably between 100°C and 800°C. The higher the supply temperature of the raw material gas, the less power is required for electrolysis. However, from the standpoint of designing the gas decomposition apparatus, heat generation due to Joule heating from the laminate described in [1] above should also be considered. Therefore, the supply temperature of the raw material gas is preferably 400°C or lower. Also, the supply temperature of the raw material gas is preferably 200°C or higher. The supply temperature of the raw material gas can be measured, for example, in the gas flow passage inside the casing that houses the laminate (upstream of the laminate) or immediately before the casing.

[0056] Furthermore, preheating of the raw material gas may be performed in order to control the supply temperature of the raw material gas. The preheating method and other details are as exemplified in [2] above.

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

[0058] Furthermore, the gas supplied from the raw material gas source (hereinafter also referred to as the supplied gas) may be supplied directly to the laminated structure described in [1] as the raw material gas. Alternatively, for example, CO2 may be separated and recovered from the supplied gas in advance, and the separated and recovered gas (hereinafter also referred to as the separated and recovered gas) may be supplied to the laminated structure described in [1] as the raw material gas. The method for separating and recovering CO2 is not particularly limited. For example, methods include liquefying or solidifying CO2 by pressurization or cooling, absorbing CO2 in a basic aqueous solution such as caustic soda or amine and then separating and recovering it by heating or reduced pressure, adsorbing CO2 on activated carbon or zeolite and then separating and recovering it by heating or reduced pressure, and separating and recovering it using a CO2 separation membrane. The CO2 concentration of the separated and recovered gas described above is not particularly limited, but 80% by volume or higher is preferred. This is advantageous because it allows for miniaturization of the gas decomposition apparatus, particularly the laminated structure used during electrolysis and the equipment associated with this laminated structure.

[0059] Furthermore, harmful components such as sulfur and NOx may be removed from the supplied gas beforehand, if necessary.

[0060] (Electrolysis step) In the electrolysis step, a voltage is applied to the laminate described in [1] above, and oxygen and by-product gases are generated from the oxygen compound gas, which is the raw material gas, by electrolysis 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 described in [1] above) is preferably 0.6V or more and 2.0V or less. If the applied voltage is less than 0.6V, it will be lower than the theoretical electrolysis voltage, and the electrolytic reaction may not proceed sufficiently. If the applied voltage exceeds 2.0V, CO2 will decompose into solid carbon (C) and O2, making it difficult to generate CO. In addition, Joule heat may accumulate in the laminate, and there is a risk that the laminate itself will decompose.

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

[0063] The temperature of the laminate can be controlled, for example, by heating the laminate body with a heater or a heat exchanger using waste heat as described above. Alternatively, the temperature of the laminate can also be controlled 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 gases generated in the electrolysis step are recovered, respectively. The recovery of the oxygen and by-product gases generated in the electrolysis step can be carried out, for example, through gas flow passages adjacent to the anode catalyst layer and cathode catalyst layer of the electrolysis section's laminate. The recovered oxygen and by-product gases can then be supplied, for example, to equipment or a storage unit that uses the oxygen and by-product gases.

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

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

[0067] Other than the conditions mentioned above, there are no particular limitations; you may follow the usual law. [Examples]

[0068] The laminate was fabricated according to the following procedure.

[0069] <Electrolyte layer> As for the electrolyte layer, La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 A perovskite-type oxide having an O3 composition was used. First, La2O3, SrCO3, Ga2O3, and MgO in molar ratios to obtain the predetermined composition were mixed in an alumina mortar for 30 minutes. Next, this mixture was placed in an alumina crucible and heated from room temperature to 1000°C over 5 hours, and then calcined at 1000°C for 6 hours. Next, it was cooled to room temperature over 5 hours. Next, the resulting powder was mixed in a mortar for 30 minutes. Next, this powder was uniaxially molded into a 20 mm diameter disc by applying pressure at 20 MPa for 20 minutes. Next, this molded body was placed in a rubber bag, vacuum-packed, and then hydrostatically pressed at 300 MPa for 30 minutes to obtain pellets. The obtained pellets were heated from room temperature to 1000°C over 5 hours, and then heated to 1500°C over 5 hours, and calcined at 1500°C for 6 hours. Next, it was cooled to 1000°C over 5 hours, and then cooled to room temperature over 5 hours to sinter. In this way, an electrolyte layer with a thickness of 0.3 mm was obtained.

[0070] <Materials for forming anode catalyst layers> As the catalyst layer for the anode, Ba 0.6 La 0.4 A perovskite-type oxide having the composition CoO3 was used. First, predetermined amounts of Ba(NO3)2, La(NO3)3·6H2O, and Co(NO3)2·6H2O were dissolved in water and evaporated to dryness. Next, this was calcined at 400°C in a fume hood to decompose the nitrates into oxides. Then, the resulting powder was mixed in a mortar for 30 minutes. Next, this powder was placed in an alumina crucible and calcined at 1200°C for 6 hours. Finally, the calcined powder was mixed in a mortar for 30 minutes to obtain a material for forming the anode catalyst layer.

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

[0072] <Formation of anode and cathode catalyst layers (screen printing method)> Using the materials for forming the anode catalyst layer and the cathode catalyst layer obtained as described above, an anode catalyst layer was formed on one side of the electrolyte layer and a cathode catalyst layer on the other side by screen printing. Specifically, first, ethylcellulose and powdered anode catalyst layer forming material were mixed in an agate mortar in a ratio of 8:100 (mass ratio). Similarly, ethylcellulose and powdered LSFM were mixed in a ratio of 8:100 (mass ratio). Then, these mixtures were mixed thoroughly while adding an appropriate amount of 3-hydroxy-2,2,4-trimethylpentyl dropwise until a suitable viscosity was achieved, stirred for a predetermined time, and then degassed. This yielded a paste for anode catalyst layer formation (hereinafter also referred to as anode paste) and a paste for cathode catalyst layer formation (hereinafter also referred to as cathode paste). The anode paste and cathode paste thus obtained were applied to the electrolyte layer by screen printing. Here, screen printing was performed using a 200-mesh stainless steel mesh. The application area was 8 mmφ and the thickness was 5-10 μm. Furthermore, 100 to 900 μL of the above mixed aqueous solution was dropped onto the coated area of ​​the cathode paste to adjust the content of LSFM, Ni oxide, and Co oxide in the cathode catalyst layer. Next, the electrolyte layer with the paste applied was 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 coated area of ​​the anode paste, and a platinum wire (0.1 mmφ) 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 is sandwiched between the anode catalyst layer and the cathode catalyst layer.

[0073] Furthermore, for comparison, the configuration is the same as above except for the cathode catalyst layer. • A laminate in which the cathode catalyst layer is composed of Ni oxide (hereinafter referred to as Comparative Example 1, also referred to as Ni type), • A laminate in which the cathode catalyst layer is composed of Ni oxide and Cu oxide (Ni oxide / Cu oxide = 1 (mass ratio)) (hereinafter referred to as Comparative Example 2, also called NiCu), • A laminate in which the cathode catalyst layer is composed of Ni oxide and Co oxide (Ni oxide / Co oxide = 9 (mass ratio)) (hereinafter referred to as Comparative Example 3, also called NiCo), • The cathode catalyst layer is 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 A laminate (hereinafter referred to as Comparative Example 4, also called NiFe-CMF) composed of O2, with a total of 10% by mass of Ni oxide and Fe oxide and 90% by mass of CMF, • A laminate in which the cathode catalyst layer is composed of Co oxide (hereinafter referred to as Comparative Example 5, also referred to as Co), and • A laminate in which the cathode catalyst layer is constructed using LSFM (hereinafter referred to as Comparative Example 6, and the type is also called LSFM) I obtained it.

[0074] Using the resulting laminates, a gas decomposition apparatus as shown in Figure 2 was fabricated. Each laminate was sandwiched from above and below by an alumina tube and a Pyrex® glass ring. The temperature was raised from room temperature to 800°C in 2 hours, and held at 800°C for 1 hour. After that, the Pyrex glass rings were softened and sealed with glass packing. This ensured a flow path for the raw material gas into the laminate, as well as for the flow paths of oxygen and by-product gases.

[0075] Next, a voltage of 1.6V was applied between the anode catalyst layer and the cathode catalyst layer using a power supply, and an oxygen compound gas (30 vol% CO2 / 30 vol% H2O / 40 vol% Ar), which served as the raw material gas, was supplied to the cathode catalyst layer at a flow rate of 100 ml / min from the raw material gas supply unit. In addition, air was supplied to the anode catalyst layer at a flow rate of 100 ml / min as the sweep gas from the sweep gas supply unit. Electrolysis was performed at four different temperature conditions: 600°C, 700°C, 800°C, and 900°C. By-product gases such as CO generated by the reduction of CO2 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 set to 8 hours in all cases.

[0076] Then, under each temperature condition, analysis by gas chromatography was performed to determine the unit time (min) and unit area (cm²) of the cathode catalyst layer. 2CO emissions per unit (μmol / (min·cm)) 2 Next, the amount of CO produced (μmol / (min·cm)) was calculated. 2 )) the current density (A / cm²) during electrolysis 2 By dividing by ( ), the amount of CO generated per unit ampere (A) and unit time (min) (μmol / (A·min)) was determined. Then, the electrolysis efficiency was evaluated based on the maximum value of the CO generated at each temperature condition, according to the following criteria. The results are shown in Table 1. Pass (Excellent): Maximum CO emission is 160.0 μmol / (A·min) or higher. Failure: Maximum CO generation is less than 160.0 μmol / (A·min). Furthermore, for comparison, Figure 3 plots the maximum CO generation amounts (μmol / (A·min)) for Invention Example 1 and Comparative Examples 1-6.

[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 could not be obtained.

[0080] Furthermore, when various perovskite-type oxides, Ni oxides, and Co oxides were used in the cathode catalyst layer, and the content of the perovskite-type oxides was varied within the range of 90.0 to 99.5% by mass, the content of the Ni oxides from 0.1 to 9.0% by mass, the content of the Co oxides from 0.1 to 9.0% by mass, and the total content of Ni oxides and Co oxides from 0.5 to 10.0% by mass, extremely high electrolysis efficiency was obtained, similar to the above-described example of the invention. [Explanation of Symbols]

[0081] 1. Laminate 11 Anode catalyst layer 12 Electrolyte layer 13 Cathode catalyst layer 2. Gas decomposition apparatus 21 Electrolysis section 22 Raw Gas Supply Department 23 Sweep Gas Supply Unit 24 By-product gas recovery unit 25 Oxygen Recovery Unit 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 perovskite-type oxide content is 90.0 to 99.5% by mass. The Ni oxide content is 0.1 to 9.0% by mass. The Co oxide content is 0.1 to 9.0% by mass. The total content of the Ni oxide and the Co oxide is 0.5 to 10.0% by mass. Laminated structure.

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

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

4. The raw material gas supply unit supplies oxygen compound gas, which is the raw material gas, An electrolysis unit generates oxygen and by-product gas from the oxygen compound gas supplied from the raw material gas supply unit by electrolysis, An oxygen recovery unit for recovering the aforementioned oxygen, The system includes a by-product gas recovery unit for recovering the aforementioned by-product gas, A gas decomposition apparatus wherein the electrolysis unit has the laminate described in claim 1 or 2.

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

6. A supply step of supplying an oxygen compound gas, which is a raw material gas, to the laminate according to claim 1 or 2, An electrolysis step is performed, in which a voltage is applied to the laminate to generate oxygen and byproduct gas from the oxygen compound gas by electrolysis, An oxygen recovery step for recovering the aforementioned oxygen, A method for decomposing an oxygen compound gas, comprising a by-product gas recovery step for recovering the aforementioned by-product gas.

7. The oxygen compound gas is CO ２ A method for decomposing an oxygen compound gas according to claim 6, wherein the by-product gas contains CO.

8. The oxygen compound gas contains CO ２ and H ２ O, and the by-product gas contains CO and H ２ The method for decomposing an oxygen compound gas according to claim 6, which contains

9. The method for decomposing an oxygen compound gas according to claim 6, wherein the supply temperature of the raw material gas is 100°C or higher and 800°C or lower.

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

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