WO2021085426A1 - Apparatus for producing carbon monoxide - Google Patents

Apparatus for producing carbon monoxide Download PDF

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WO2021085426A1
WO2021085426A1 PCT/JP2020/040287 JP2020040287W WO2021085426A1 WO 2021085426 A1 WO2021085426 A1 WO 2021085426A1 JP 2020040287 W JP2020040287 W JP 2020040287W WO 2021085426 A1 WO2021085426 A1 WO 2021085426A1
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electrode layer
catalyst
carbon monoxide
solid electrolyte
production apparatus
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PCT/JP2020/040287
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French (fr)
Japanese (ja)
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篤 宇根本
晃平 吉川
杉政　昌俊
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株式会社日立製作所
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/83—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with rare earths or actinides
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/40—Carbon monoxide
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C25B1/02—Hydrogen or oxygen
    • C25B1/04—Hydrogen or oxygen by electrolysis of water
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
    • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B13/00—Diaphragms; Spacing elements
    • C25B13/04—Diaphragms; Spacing elements characterised by the material
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/36—Hydrogen production from non-carbon containing sources, e.g. by water electrolysis

Definitions

  • the present invention relates to a carbon monoxide production apparatus.
  • Carbon monoxide (CO) can extract heat by burning it. Further, electric energy can be extracted by using the fuel gas of the solid oxide fuel cell. Further, since it can be used as a raw material for a liquid fuel such as methanol, an apparatus for efficiently producing CO is required.
  • Patent Document 1 describes oxygen ions and hydrogen (H 2 ) by reducing oxygen-containing molecules such as water (H 2 O), carbon dioxide (CO 2), or a mixture thereof.
  • oxygen-containing molecules such as water (H 2 O), carbon dioxide (CO 2), or a mixture thereof.
  • CO 2 carbon dioxide
  • a cell having a perovskite crystalline structure which is an electron conductive phase or a structure similar thereto has been proposed.
  • Patent Document 1 it is an apparatus for producing H 2 and CO by simultaneously electrolyzing CO 2 and H 2 O.
  • This reaction has a large electrode reaction resistance in order to directly electrolyze CO 2, and needs to be operated at a high temperature of, for example, 750 ° C. or higher. Therefore, there is room for improvement from the viewpoint of heat utilization efficiency. Further, at such a high temperature, the products CO and H 2 O react on the electrode surface to produce CO 2 and H 2 . Therefore, there was room for improvement from the viewpoint of conversion efficiency to CO.
  • the carbon monoxide production apparatus for solving the above problems is between the catalyst electrode layer, the counter electrode layer electrically connected to the catalyst electrode layer by wiring, and the catalyst electrode layer and the counter electrode layer.
  • the solid electrolyte layer comprises an ionic conductor
  • the catalyst electrode layer is an electrode that produces H 2 and a reverse shift reaction catalyst that selectively proceeds the reverse shift reaction. It is characterized in that CO is generated by energizing.
  • FIG. 1 is a cross-sectional view of a CO manufacturing apparatus according to an embodiment of the present invention.
  • the CO manufacturing apparatus includes a catalyst electrode layer 101, a counter electrode layer 102, and a solid electrolyte layer 103 arranged between the catalyst electrode layer 101 and the counter electrode layer 102.
  • the catalyst electrode layer 101 and the counter electrode layer 102 are electrically connected by a wiring 104.
  • the catalyst electrode layer 101 has an electrode that produces H 2 and a reverse shift reaction catalyst that selectively advances the reverse shift reaction.
  • the solid electrolyte layer 103 is an ionic conductor.
  • an electrochemical reaction accompanied by generation of hydrogen selectively occurs at the electrode, and a reverse shift reaction selectively occurs at the reverse shift reaction catalyst.
  • the reverse shift reaction is a reaction that produces carbon monoxide and water vapor (water) from carbon dioxide and hydrogen represented by the reaction formula CO 2 + H 2 ⁇ CO + H 2 O.
  • a catalyst that selectively advances a reverse shift reaction is referred to as a reverse shift reaction catalyst.
  • the CO manufacturing apparatus proposed in the present invention needs to include at least a solid electrolyte layer 103, a catalyst electrode layer 101 including a reverse shift reaction catalyst and an electrode, and a counter electrode layer 102, and needs to have a configuration that maintains mechanical strength. There is.
  • the solid electrolyte layer 103 If the solid electrolyte layer 103 is too thick, the ionic conduction resistance will increase and the amount of CO produced may decrease. On the other hand, if the solid electrolyte layer 103 is too thin, the mechanical strength is weakened, and there is a high possibility that damage such as cracks will occur due to changes in gas composition, temperature, vibration, and the like.
  • As a configuration for thinning the solid electrolyte layer 103 there is a method of applying the solid electrolyte layer 103 to the surface of the thick catalyst electrode layer 101 or the counter electrode layer 102 by a dip coating method or the like.
  • the catalyst electrode layer 101 If the catalyst electrode layer 101 is made too thick, the exchange of gas between the gas phase and the catalyst electrode layer 101 will be delayed, and the amount of CO produced may decrease. On the other hand, if the catalyst electrode layer 101 is made too thin, the current collecting resistance at the electrode becomes large, or the residence time of the gas for sufficiently promoting the reverse shift reaction becomes short, so that the amount of CO produced may decrease. There is.
  • the counter electrode layer 102 If the counter electrode layer 102 is made too thick, the release of oxygen gas from the electrode surface to the gas phase will be delayed, and the amount of CO produced may decrease. On the other hand, if the counter electrode layer 102 is made too thin, the current collecting resistance becomes large, the generation rate of oxygen gas becomes slow, and the amount of CO produced may decrease.
  • a porous support layer may be introduced separately from the solid electrolyte layer 103, the catalyst electrode layer 101, and the counter electrode layer 102.
  • the material used for the support layer is not particularly limited, but it needs to be a porous body in order to improve gas permeability.
  • this support layer is arranged on the catalyst electrode layer 101, the counter electrode layer 102, or both layers, the support layer and the catalyst electrode layer 101, and the support layer and the counter electrode layer 102 during the sintering process or operation. It is desirable to select a material that does not form a resistance layer between them.
  • the solid electrolyte layer 103 needs to be dense so that gases having different compositions introduced into the catalyst electrode layer 101 and the counter electrode layer 102 are not mixed.
  • FIG. 2 shows a schematic diagram illustrating the reaction of the CO production apparatus when an oxide ion conductor is used for the solid electrolyte layer.
  • the electrode contained in the catalyst electrode layer 101 reductive decomposition of water by the electrochemical reaction (H 2 O + 2e - ⁇ H 2 + O 2-) are.
  • a reaction CO 2 + H 2 ⁇ CO + H 2 O
  • the oxide ion O 2- conducts the solid electrolyte layer 103 and is supplied to the counter electrode layer 102.
  • oxygen is generated (O 2- ⁇ 1 / 2O 2 + 2e -).
  • FIG. 3 shows a schematic diagram illustrating the reaction of the CO production apparatus when a proton conductor is used for the solid electrolyte layer.
  • the counter electrode layer 102 water is decomposed to generate oxygen by an electrochemical reaction (H 2 O ⁇ 2H + + 2e ⁇ + 1 / 2O 2 ).
  • the protons generated by this reaction are conducted through the solid electrolyte layer 103 and supplied to the catalyst electrode layer 101.
  • the electrode catalyst electrode layer 101 by an electrochemical reaction, hydrogen is produced from the protons and electrons (2H + + 2e - ⁇ H 2).
  • the reverse shift reaction catalyst of the catalyst electrode layer 101 promotes the reaction of producing carbon monoxide and water from carbon dioxide and hydrogen generated at the electrode (CO 2 + H 2 ⁇ CO + H 2 O).
  • the CO manufacturing apparatus proposed in the present invention is operated at 700 ° C. or lower and 200 ° C. or higher, more preferably 450 ° C. or lower and 300 ° C. or higher. This is because when the temperature is high, the CO 2 gas is decomposed on the electrode surface of the catalyst electrode layer 101 to cause caulking, which reduces the electrochemical reaction activity. Further, the generated CO and H 2 O react with each other to form CO 2 , and the CO production efficiency is lowered. This is because if the operating temperature is too low, the reverse shift reaction does not proceed sufficiently, so that CO cannot be produced efficiently.
  • the solid electrolyte layer 103 is an oxide ion (O 2- ) conductor, a proton (H + ) conductor, and a proton (H +) conductor that conducts oxide ions by energizing between the electrode (catalyst electrode layer 101) and the counter electrode layer 102.
  • oxide ion conductors typically introduce oxygen deficiency into the crystal structure by replacing metal elements of oxides with a fluorite-like structure, such as ZrO 2 and CeO 2, with low valence cations.
  • Oxide ion conductors typically introduce oxygen deficiency into the crystal structure by replacing metal elements of oxides with a fluorite-like structure, such as ZrO 2 and CeO 2, with low valence cations.
  • substitution element for example, an alkaline earth metal, a group 3 element including a lanthanoid, or the like can be selected.
  • Specific examples thereof include (Zr, Y) O 2 in which the Zr site of ZrO 2 is replaced with Y, (Ce, Sm) O 2 in which the Ce site of CeO 2 is replaced with Sm, and the like.
  • Zr, Y Zr, Y
  • Ce, Sm Ce site of CeO 2
  • the chemical formula is Zr 0.84 Y 0.16 O 1.92
  • 0.08 mol of oxygen deficiency is introduced per 1 ml. It becomes an oxide ion carrier.
  • a material having a crystal structure of ZrO 2 and containing a substituent is referred to as a ZrO 2 system.
  • Two or more types having a fluorite-type structure may be solid-solved. Further, the number of substitution elements may be two or more.
  • oxide ion conductors such as LaGaO 3
  • Oxide ion carriers can be introduced by substituting low valence cations for La sites, Ga sites, or both of these sites.
  • substitution element of La site and Ga site for example, alkaline earth metal and the like can be selected. Specific examples thereof include (La, Sr) (Ga, Mg) O 3 in which the La site of LaGaO 3 is replaced with Sr and the Ga site is replaced with Mg.
  • the chemical formula is La 0.95 Sr 0.05 Ga 0.95 Mg 0.05 O 2 It is .95 , and 0.05 mL of oxygen deficiency is introduced per 1 mL to become an oxide ion carrier.
  • the perovskite-type oxides such as LaGaO 3
  • La site A site but the Ga site called the B-site
  • either A-site and B-site may be made relatively excessive composition.
  • Proton conductor is typically such SrZrO 3
  • the B-site element of the oxide has a crystalline structure of perovskite type containing an alkaline earth metal, by replacing low-valent cations, the oxygen deficiency in the crystal structure
  • a Group 3 element including a lanthanoid can be selected.
  • Specific examples thereof include Sr (Zr, Y) O 3 in which the Zr site of SrZrO 3 is replaced with Y.
  • Sr (Zr, Y) O 3 in which the Zr site of SrZrO 3 is replaced with Y.
  • the chemical formula is SrZr 0.9 Y 0.1 O 2.95 , and there is an oxygen deficiency of 0.05 mL per 1 ml. be introduced.
  • water dissolves in this oxygen deficiency 2 mol of proton carriers are introduced per 1 mol of water. This introduction reaction is shown in the Kröger-Vink notation table. H 2 O + V O ...
  • O O X 2 (OH) O ⁇ It is expressed by.
  • V O ⁇ ⁇ is the oxygen deficiency
  • O O X is oxygen ions present in the oxygen site
  • (OH) O ⁇ represent respectively the protons defects present in the oxygen site.
  • proton conductors include rare earth phosphates (LaPO 4 , LaP 3 O 9 , LaP 5 O 14 ), rare earth borates (LaBO 4 ), and Li 1-x Sr x NbO 4 with a shaleite-type structure (LaPO 4). 0 ⁇ x ⁇ 1), LaNbO 4 , LaWO 4, and the like can be mentioned.
  • Proton carriers can be introduced by substituting these rare earth sites with alkaline earth metals. When CO 2 is present in the atmosphere and the alkaline earth metal is contained as the main constituent element, the alkaline earth metal forms a carbonate and decomposes.
  • a proton conductor that does not contain alkaline earth metals as the main constituent material.
  • the water dissolved in the proton conductor is desorbed to reduce the proton defect concentration, and the oxide ion conduction becomes dominant.
  • the movable species is a mixed conduction of protons and oxide ions.
  • Two or more of the above having the same crystal structure may be solid-solved. Further, two or more kinds of these ion conductors may be mixed.
  • La 2 ZrO 2 O 7 based pyrochlore like Form a high resistance layer.
  • a layered structure of two or more layers may be used, such as using another solid electrolyte as a reaction barrier layer.
  • CeO 2 based solid electrolyte may be porous.
  • an oxide ion conductor In order to produce CO with high purity, it is desirable to use an oxide ion conductor.
  • an oxide ion conductor, and electrolyte of H 2 O which is the reaction product of the reverse shift reaction catalyst electrode layer 101 it is possible to using H 2 produced by electrolysis as the raw material for the reverse shift reaction, This is because the concentration of H 2 O, which is an impurity, can be reduced to further increase the CO concentration.
  • the catalyst electrode layer 101 includes a reverse shift reaction catalyst and an electrode.
  • the reverse shift reaction catalyst selectively proceeds the chemical reaction between CO 2 and H 2.
  • the reverse shift reaction catalyst of the catalyst electrode layer 101 is composed of a mixture of a transition metal and an oxide serving as a carrier.
  • the transition metal include V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Ru, Rh and the like. Of these, it is desirable to combine Mn, Co, and Cu, which are D-block elements of the 4th period, which enhance the catalytic activity for the reverse shift reaction.
  • the metal catalyst may be an alloy containing at least one of these metals, or a mixture thereof.
  • the oxide as the carrier it is desirable to select an oxide that is unlikely to react with other constituent materials at the firing or sintering temperature and is stable even in a reducing atmosphere.
  • composite oxides such as CeO 2 , ZrO 2 , Al 2 O 3 , MgO, and LaAlO 3.
  • CeO 2 , ZrO 2 , and Al 2 O 3 which further enhance the catalytic activity for the reverse shift reaction by combining with the transition metal.
  • Some of these oxides may be replaced with other elements. Further, it may be a mixture containing at least one of these oxides.
  • the electrode of the catalyst electrode layer 101 selectively reduces and decomposes water by the following electrochemical reaction. H 2 O + 2e - ⁇ H 2 + O 2-
  • the electrode examples include transition metals such as V, Cr, Mn, Fe, Co, Ni, and Cu, Group 10 elements such as Pt, and Group 11 elements such as Au. Of these, it is desirable to use Ni, Pt or the like, which promotes the reduction decomposition reaction of water.
  • the metal contained in the electrode may be an alloy containing at least one of these metals.
  • the electrode When a proton conductor is used as the solid electrolyte, the electrode selectively generates hydrogen by the following electrochemical reaction. 2H + + 2e - ⁇ H 2
  • the electrode examples include platinum group elements such as Pd and Pt, Au and the like. Of these, it is desirable to use Pd, which has a high activity of hydrogen generation reaction and a high solubility of hydrogen.
  • the metal contained in the electrode may be an alloy containing at least one of these metals. Further, in order to increase the contact area with the solid electrolyte and reduce the reaction resistance, it is desirable to use the mixture in combination with the solid electrolyte.
  • the metal element of the reverse shift reaction catalyst, the metal element of the electrode, and the solid electrolyte particles may be mixed to form one layer. good. Further, a laminated structure having two or more layers in which different metals and oxides are combined may be used.
  • Examples of the counter electrode layer 102 include perovskite-type oxides containing rare earth elements and transition metal elements and having electron conductivity.
  • rare earth elements such as LaMnO 3 , LaCoO 3 , LaFeO 3 , and SmCoO 3 are replaced with alkaline earth metal elements, and the chemical formulas are (La, Sr) MnO 3 , La 1-x Sr x MnO. It is expressed as 3 (0 ⁇ x ⁇ 1) or the like.
  • the substitution element may contain two or more kinds of other alkaline earth metal elements such as Ca and Ba. Further, two or more kinds of transition metal elements may be contained. Further, it may be a mixture containing two or more kinds of these oxides.
  • Examples of the counter electrode layer 102 include platinum group elements such as Pd and Pt, Au and the like. Of these, it is desirable to use Pt, which has a high activity of oxygen evolution reaction.
  • the metal contained in the counter electrode layer 102 may be an alloy containing at least one of these metals. Further, in order to increase the contact area with the solid electrolyte layer 103 and reduce the reaction resistance, it is desirable to use the mixture in combination with the solid electrolyte layer 103.
  • Example 1> ⁇ Preparation of solid electrolyte layer 103>
  • Commercially available Zr 0.84 Y 0.16 O 1.92 (hereinafter, YSZ) powder was weighed to a predetermined weight and pressed with a hydraulic press. By heat-treating this in air at 1350 ° C. for 3 hours, a dense electrolyte membrane having a diameter of 13 mm could be obtained. Both sides of the electrolyte membrane were polished with water-resistant abrasive paper to a thickness of 500 ⁇ m.
  • the electrode slurry was applied to the surface of the solid electrolyte layer 103 with a diameter of 8 mm using a screen printing machine, dried, and then the reverse shift reaction catalyst was further applied to the electrode surface with a diameter of 8 mm. This was heat treated at 1200 ° C. in air for 1 hour. By observing the cross section by SEM, the thickness of the reverse shift reaction catalyst layer and the electrode was 50 ⁇ m, respectively.
  • LSM La 0.8 Sr 0.2 MnO 3- ⁇
  • La 2 CO 3 , SrCO 3 , and Mn 2 O 3 were used as starting materials. These were weighed at a constant ratio composition, mixed with a zirconia mortar and pestle, and heat-treated in air at 1200 ° C. for 5 hours to obtain LSM. The crystal structure was evaluated by X-ray diffraction measurement, and it was confirmed that there was no diffraction peak derived from impurities. LSM was dispersed in a solvent to form a slurry.
  • a slurry of counter electrode was applied using a screen printing machine to a diameter of 8 mm, dried, and then heat-treated in air at 1000 ° C. for 1 hour.
  • the thickness of the counter electrode was 100 ⁇ m.
  • Examples 2 to 8 and Comparative Examples 1 to 6 A CO production cell was prepared in the same manner as in Example 1 except that the compositions of the catalyst electrode layer 101 and the counter electrode layer 102, the introduced gas composition, and the amount of energization were adjusted as shown in Table 1, and the downstream side of the catalyst electrode layer 101 was prepared.
  • the gas composition was analyzed by gas chromatography and the CO concentration was measured.
  • Example 1 a reverse shift reaction catalyst and an electrode were introduced into the catalyst electrode layer 101, and a cell in which the YSZ layer, which is an oxygen ion conductor, was sandwiched between the reverse shift reaction catalyst and the electrode was formed by the oxygen gas generating electrode.
  • a mixed gas of CO 2 and H 2 O was introduced into 101 and energized, CO was detected in the outlet gas of the catalyst electrode layer 101, and the concentration was 0.04%.
  • CO was not detected when the power was not applied.
  • H 2 O when energized, H 2 O is electrochemically reduced and decomposed at the electrode contained in the catalyst electrode layer 101 to produce H 2 and O 2- , and H 2 undergoes a reverse shift reaction with CO 2 to cause CO.
  • O 2- moved the solid electrolyte to reach the counter electrode, indicating that it was released into the gas phase as O 2.
  • Example 2 From Comparative Example 2, in the cell in which the electrode was not introduced into the catalyst electrode layer, the internal resistance increased and energization could not be performed. Since H 2 O electrolysis reaction does not proceed, CO was not detected. In Example 2, the CO concentration was 0.04%, which was about the same as in Example 1. From this, it was found that even if the Ce site of CeO 2 contained in the reverse shift reaction catalyst of the catalyst electrode layer 101 is partially replaced with another element, the catalytic activity is not impaired.
  • Example 3 the CO concentration was 0.081%, which was more than twice that of Example 1.
  • Example 4 the operating temperature was set to 300 ° C. Since the amount of electric current is the same as in Example 1, water electrolysis of H 2 O, i.e., the amount of generated H 2 is the same as in Example 1, CO concentration was reduced to 0.017%. From this, it was found that the higher the operating temperature, the easier the reverse shift reaction to proceed.
  • Example 5 and Example 6 the metal elements contained in the reverse shift reaction catalyst were Mn and Co, respectively.
  • the CO concentrations in Examples 5 and 6 were 0.028% and 0.04%, respectively, depending on the metal element composition. Since CO could be produced, it was found that Cu, Mn, and Co are desirable as the metal elements to be used.
  • Example 7 Ce 0.9 Gd 0.1 O 1.95 (hereinafter referred to as GDC) was used for the solid electrolyte layer 103. Since the CO concentration was 0.04%, which was the same as that of the cell using YSZ (Example 1), it was found that the oxygen ion conductor used as the solid electrolyte layer 103 can be applied regardless of the composition. It was.
  • Example 1 the reverse shift reaction catalyst of the catalyst electrode layer 101 and the electrode have a two-layer structure, whereas in Example 8, the reverse shift reaction catalyst, the metal element contained in the electrode, and GDC are mixed to form one layer. Although it was structured, 0.014% CO was detected. Therefore, the catalyst electrode layer 101 was found that oxide to a metal element to promote the reverse shift reaction and H 2 O electrolyte may be contained in the same layer.
  • Comparative Example 4 although the metal elements contained in the electrode catalyst electrode layer was Cu, H 2 O electrolysis activity is low, the cell can not be energized by high resistance. This is, H 2 O electrolysis activity depends on the metal elements in the electrode, it has been found that it is desirable to use Ni.
  • Comparative Example 5 CeO 2 was used as the oxide in the electrode, but the concentration of the oxide ion carrier was very small because it did not contain a substituent, and the cell resistance was low because the oxide ion conductivity was poor. It was too big to energize. Therefore, in order to increase of H 2 O electrolysis activity it was found to be desirable to use an oxygen ion conductor in the oxide in the electrode.
  • Example 9 when the solid electrolyte layer 103 was energized as the LSN of the proton conductor, 0.008% of CO could be detected. On the other hand, in Comparative Example 7 which was not energized, the CO concentration was less than 0.002%. In Comparative Example 8 the counter electrode layer 102 was lower Au electrode of H 2 O decomposition activity, large cell resistance, it could not be energized.

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Abstract

An apparatus for producing carbon monoxide is characterized by comprising a catalyst electrode layer (101), a counter electrode layer (102) electrically connected to the catalyst electrode layer (101) by wiring (104), and a solid electrolyte layer (103) positioned between the catalyst electrode layer (101) and the counter electrode layer (102), the solid electrolyte including an ion conductor, the catalyst electrode layer (101) having an electrode for generating H2 and a reverse shift reaction catalyst for selectively accelerating a reverse shift reaction, and CO being generated by supplying of electricity to the catalyst electrode layer (101).

Description

一酸化炭素製造装置Carbon monoxide production equipment
　本発明は、一酸化炭素製造装置に関する。 The present invention relates to a carbon monoxide production apparatus.
　一酸化炭素（ＣＯ）は、燃焼させることで熱を取り出すことができる。また、固体酸化物形燃料電池の燃料ガスとすることで電気エネルギーを取り出すことができる。さらに、メタノール等の液体燃料の原料とすることができるため、効率良くＣＯを製造する装置が求められている。 Carbon monoxide (CO) can extract heat by burning it. Further, electric energy can be extracted by using the fuel gas of the solid oxide fuel cell. Further, since it can be used as a raw material for a liquid fuel such as methanol, an apparatus for efficiently producing CO is required.
　従来電解セルの技術として、特許文献１には、水（Ｈ２Ｏ）、二酸化炭素（ＣＯ２）、または、これらの混合物などの含酸素分子を還元して、酸素イオンと水素（Ｈ２）、ＣＯまたは、これらの混合物などの燃料分子を製造する電解セルを提供するため、電子伝導相であるペロブスカイト結晶性構造、またはそれに類似する構造を有するセルが提案されている。 As a conventional electrolytic cell technology, Patent Document 1 describes oxygen ions and hydrogen (H 2 ) by reducing oxygen-containing molecules such as water (H 2 O), carbon dioxide (CO 2), or a mixture thereof. In order to provide an electrolytic cell for producing fuel molecules such as CO or a mixture thereof, a cell having a perovskite crystalline structure which is an electron conductive phase or a structure similar thereto has been proposed.
特表２００９－５４４８４３号公報Special Table 2009-544843
　上記特許文献１では、ＣＯ２とＨ２Ｏを同時に電気分解してＨ２とＣＯを製造する装置である。この反応は、ＣＯ２を直接電気分解するために電極反応抵抗が大きく、例えば７５０℃以上といった高温で動作させる必要があるため、熱利用効率の観点から、改善の余地があった。さらに、このような高温では、生成物であるＣＯとＨ２Ｏが電極表面で反応してＣＯ２とＨ２が生成する。このため、ＣＯへの変換効率の観点から、改善の余地があった。 In Patent Document 1, it is an apparatus for producing H 2 and CO by simultaneously electrolyzing CO 2 and H 2 O. This reaction has a large electrode reaction resistance in order to directly electrolyze CO 2, and needs to be operated at a high temperature of, for example, 750 ° C. or higher. Therefore, there is room for improvement from the viewpoint of heat utilization efficiency. Further, at such a high temperature, the products CO and H 2 O react on the electrode surface to produce CO 2 and H 2 . Therefore, there was room for improvement from the viewpoint of conversion efficiency to CO.
　このような観点から、本発明は、効率良くＣＯを製造する装置を提供することを課題とする。 From this point of view, it is an object of the present invention to provide an apparatus for efficiently producing CO.
　上記課題を解決するための本発明に係る一酸化炭素製造装置は、触媒極層と、前記触媒極層と配線により電気的に接続される対極層と、前記触媒極層と前記対極層の間に配置される固体電解質層と、を備え、前記固体電解質層はイオン伝導体を含み、前記触媒極層は、Ｈ２を生成する電極と、逆シフト反応を選択的に進行させる逆シフト反応触媒とを有し、通電することによりＣＯが生成することを特徴とする。 The carbon monoxide production apparatus according to the present invention for solving the above problems is between the catalyst electrode layer, the counter electrode layer electrically connected to the catalyst electrode layer by wiring, and the catalyst electrode layer and the counter electrode layer. The solid electrolyte layer comprises an ionic conductor, and the catalyst electrode layer is an electrode that produces H 2 and a reverse shift reaction catalyst that selectively proceeds the reverse shift reaction. It is characterized in that CO is generated by energizing.
　本発明によれば、効率よくＣＯを製造する装置を提供することができる。上記した以外の課題、構成及び効果は以下の実施形態の説明により明らかにされる。 According to the present invention, it is possible to provide an apparatus for efficiently producing CO. Issues, configurations and effects other than those described above will be clarified by the following description of the embodiments.
一実施形態に係るＣＯ製造装置の断面図である。It is sectional drawing of the CO manufacturing apparatus which concerns on one Embodiment. 一実施形態に係るＣＯ製造装置の反応を説明する図である。It is a figure explaining the reaction of the CO production apparatus which concerns on one Embodiment. 一実施形態に係るＣＯ製造装置の反応を説明する図である。It is a figure explaining the reaction of the CO production apparatus which concerns on one Embodiment.
　以下、図面等を用いて、本発明の実施形態について説明する。以下の説明は本発明の内容の具体例を示すものであり、本発明がこれらの説明に限定されるものではなく、本明細書に開示される技術的思想の範囲内において当業者による様々な変更及び修正が可能である。また、本発明を説明するための全図において、同一の機能を有するものは、同一の符号を付け、その繰り返しの説明は省略する場合がある。 Hereinafter, embodiments of the present invention will be described with reference to drawings and the like. The following description shows specific examples of the contents of the present invention, and the present invention is not limited to these descriptions, and various works by those skilled in the art will be made within the scope of the technical ideas disclosed in the present specification. It can be changed and modified. Further, in all the drawings for explaining the present invention, those having the same function may be designated by the same reference numerals, and the repeated description thereof may be omitted.
　図１は、本発明の一実施形態に係るＣＯ製造装置の断面図である。ＣＯ製造装置は、触媒極層１０１と、対極層１０２と、触媒極層１０１と対極層１０２の間に配置される固体電解質層１０３とを備える。触媒極層１０１と対極層１０２とは、配線１０４により電気的に接続されている。 FIG. 1 is a cross-sectional view of a CO manufacturing apparatus according to an embodiment of the present invention. The CO manufacturing apparatus includes a catalyst electrode layer 101, a counter electrode layer 102, and a solid electrolyte layer 103 arranged between the catalyst electrode layer 101 and the counter electrode layer 102. The catalyst electrode layer 101 and the counter electrode layer 102 are electrically connected by a wiring 104.
　触媒極層１０１は、Ｈ２を生成する電極と、逆シフト反応を選択的に進行させる逆シフト反応触媒とを有する。固体電解質層１０３は、イオン伝導体である。外部電源１０５を用いて通電することにより、触媒極層１０１においては、電極では、水素の発生を伴う電気化学反応が選択的におこり、逆シフト反応触媒では、逆シフト反応が選択的におこりＣＯが生成する。ここで、逆シフト反応とは、反応式ＣＯ２＋Ｈ２→ＣＯ＋Ｈ２Ｏで表される二酸化炭素と水素から一酸化炭素と水蒸気（水）を生成する反応である。本明細書において、逆シフト反応を選択的に進行させる触媒を逆シフト反応触媒という。 The catalyst electrode layer 101 has an electrode that produces H 2 and a reverse shift reaction catalyst that selectively advances the reverse shift reaction. The solid electrolyte layer 103 is an ionic conductor. By energizing using the external power source 105, in the catalyst electrode layer 101, an electrochemical reaction accompanied by generation of hydrogen selectively occurs at the electrode, and a reverse shift reaction selectively occurs at the reverse shift reaction catalyst. Is generated. Here, the reverse shift reaction is a reaction that produces carbon monoxide and water vapor (water) from carbon dioxide and hydrogen represented by the reaction formula CO 2 + H 2 → CO + H 2 O. In the present specification, a catalyst that selectively advances a reverse shift reaction is referred to as a reverse shift reaction catalyst.
　＜各層の配置＞
　本発明で提案するＣＯ製造装置では、固体電解質層１０３と、逆シフト反応触媒と電極を含む触媒極層１０１と、対極層１０２を少なくとも含む必要があり、機械的強度を保った構成にする必要がある。 <Arrangement of each layer>
The CO manufacturing apparatus proposed in the present invention needs to include at least a solid electrolyte layer 103, a catalyst electrode layer 101 including a reverse shift reaction catalyst and an electrode, and a counter electrode layer 102, and needs to have a configuration that maintains mechanical strength. There is.
　固体電解質層１０３が厚すぎると、イオン伝導抵抗が大きくなり、ＣＯ製造量が少なくなる可能性がある。一方、固体電解質層１０３が薄すぎると、機械強度が弱くなり、ガス組成や温度の変化、振動などによってわれ等の破損が起こる可能性が高くなる。固体電解質層１０３を薄くするための構成として、厚みのある触媒極層１０１、あるいは対極層１０２の表面にディップコート法などで塗布する方法がある。 If the solid electrolyte layer 103 is too thick, the ionic conduction resistance will increase and the amount of CO produced may decrease. On the other hand, if the solid electrolyte layer 103 is too thin, the mechanical strength is weakened, and there is a high possibility that damage such as cracks will occur due to changes in gas composition, temperature, vibration, and the like. As a configuration for thinning the solid electrolyte layer 103, there is a method of applying the solid electrolyte layer 103 to the surface of the thick catalyst electrode layer 101 or the counter electrode layer 102 by a dip coating method or the like.
　触媒極層１０１を厚くしすぎると、気相と触媒極層１０１内のガスの交換が遅くなり、ＣＯ製造量が少なくなる可能性がある。一方、触媒極層１０１を薄くしすぎると、電極での集電抵抗が大きくなる、あるいは、逆シフト反応を十分に促すためのガスの滞留時間が短くなるため、ＣＯ製造量が少なくなる可能性がある。 If the catalyst electrode layer 101 is made too thick, the exchange of gas between the gas phase and the catalyst electrode layer 101 will be delayed, and the amount of CO produced may decrease. On the other hand, if the catalyst electrode layer 101 is made too thin, the current collecting resistance at the electrode becomes large, or the residence time of the gas for sufficiently promoting the reverse shift reaction becomes short, so that the amount of CO produced may decrease. There is.
　対極層１０２を厚くしすぎると、電極表面からの気相への酸素ガスの放出が遅くなり、ＣＯ製造量が少なくなる可能性がある。一方、対極層１０２を薄くしすぎると、集電抵抗が大きくなり、酸素ガスの発生速度が遅くなって、ＣＯ製造量が少なくなる可能性がある。 If the counter electrode layer 102 is made too thick, the release of oxygen gas from the electrode surface to the gas phase will be delayed, and the amount of CO produced may decrease. On the other hand, if the counter electrode layer 102 is made too thin, the current collecting resistance becomes large, the generation rate of oxygen gas becomes slow, and the amount of CO produced may decrease.
　いずれの層も薄膜化した上で機械強度を高めるためには、固体電解質層１０３、触媒極層１０１および対極層１０２とは別に、多孔質の支持層を導入しても良い。支持層に用いる材料に特に制約はないが、ガス通気性を高めるため、多孔質体である必要がある。また、この支持層を、触媒極層１０１、対極層１０２、あるいはこの両方の層上に配置する場合、焼結プロセスや運転中に、支持層と触媒極層１０１、支持層と対極層１０２の間で抵抗層の形成が起こらない材料を選定することが望ましい。固体電解質層１０３は、触媒極層１０１と対極層１０２にそれぞれ導入される、組成の異なるガスが混合しないよう、緻密である必要がある。 In order to increase the mechanical strength after thinning each layer, a porous support layer may be introduced separately from the solid electrolyte layer 103, the catalyst electrode layer 101, and the counter electrode layer 102. The material used for the support layer is not particularly limited, but it needs to be a porous body in order to improve gas permeability. Further, when this support layer is arranged on the catalyst electrode layer 101, the counter electrode layer 102, or both layers, the support layer and the catalyst electrode layer 101, and the support layer and the counter electrode layer 102 during the sintering process or operation. It is desirable to select a material that does not form a resistance layer between them. The solid electrolyte layer 103 needs to be dense so that gases having different compositions introduced into the catalyst electrode layer 101 and the counter electrode layer 102 are not mixed.
　＜動作原理＞
　以下、本発明の一実施形態に係るＣＯ製造装置のＣＯ生成原理を説明する。図２に固体電解質層に酸化物イオン伝導体を用いた場合のＣＯ製造装置の反応を説明する模式図を示す。 <Principle of operation>
Hereinafter, the CO generation principle of the CO production apparatus according to the embodiment of the present invention will be described. FIG. 2 shows a schematic diagram illustrating the reaction of the CO production apparatus when an oxide ion conductor is used for the solid electrolyte layer.
　固体電解質層１０３に酸化物イオン伝導体を用いた場合、触媒極層１０１に含まれる電極では、電気化学反応により水を還元分解（Ｈ２Ｏ＋２ｅ－→Ｈ２＋Ｏ２－）する。逆シフト反応触媒では、二酸化炭素と水の電気分解により生成された水素とから、一酸化炭素と水を生成する反応（ＣＯ２＋Ｈ２→ＣＯ＋Ｈ２Ｏ）が進行する。触媒極層１０１において、逆シフト反応触媒により生成された水は、電極での水の電気分解に利用される。酸化物イオンＯ２－は、固体電解質層１０３を伝導し、対極層１０２に供給される。対極層１０２では、電気化学反応により、酸素が生成する（Ｏ２－→１／２Ｏ２＋２ｅ－）。 If the solid electrolyte layer 103 using an oxide ion conductor, the electrode contained in the catalyst electrode layer 101, reductive decomposition of water by the electrochemical reaction (H 2 O + 2e - → H 2 + O 2-) are. In the reverse shift reaction catalyst, a reaction (CO 2 + H 2 → CO + H 2 O) for producing carbon monoxide and water from carbon dioxide and hydrogen produced by electrolysis of water proceeds. In the catalyst electrode layer 101, the water produced by the reverse shift reaction catalyst is used for electrolysis of water at the electrode. The oxide ion O 2- conducts the solid electrolyte layer 103 and is supplied to the counter electrode layer 102. In the counter electrode layer 102, by the electrochemical reaction, oxygen is generated (O 2- → 1 / 2O 2 + 2e -).
　図３に固体電解質層にプロトン伝導体を用いた場合のＣＯ製造装置の反応を説明する模式図を示す。対極層１０２では、電気化学反応により、水が分解して酸素が発生する（Ｈ２Ｏ→２Ｈ＋＋２ｅ－＋１／２Ｏ２）。この反応により生成したプロトンは、固体電解質層１０３を伝導し、触媒極層１０１に供給される。触媒極層１０１の電極では、電気化学反応により、プロトンと電子とから水素が生成する（２Ｈ＋＋２ｅ－→Ｈ２）。触媒極層１０１の逆シフト反応触媒は、二酸化炭素と電極で生成した水素とから一酸化炭素と水とを生成する反応を促進する（ＣＯ２＋Ｈ２→ＣＯ＋Ｈ２Ｏ）。 FIG. 3 shows a schematic diagram illustrating the reaction of the CO production apparatus when a proton conductor is used for the solid electrolyte layer. In the counter electrode layer 102, water is decomposed to generate oxygen by an electrochemical reaction (H 2 O → 2H + + 2e − + 1 / 2O 2 ). The protons generated by this reaction are conducted through the solid electrolyte layer 103 and supplied to the catalyst electrode layer 101. The electrode catalyst electrode layer 101, by an electrochemical reaction, hydrogen is produced from the protons and electrons (2H + + 2e - → H 2). The reverse shift reaction catalyst of the catalyst electrode layer 101 promotes the reaction of producing carbon monoxide and water from carbon dioxide and hydrogen generated at the electrode (CO 2 + H 2 → CO + H 2 O).
　図２、図３に係るＣＯ製造装置では、上記反応が一段で起こる。電気化学反応と化学反応とを用いることにより、ＣＯ２の還元反応は高温で動作させる必要があるが、高温動作が必要な電気化学反応（ＣＯ２の還元反応）に代り、化学反応（ＣＯ２＋Ｈ２→ＣＯ＋Ｈ２Ｏ）を利用することにより、低温動作が可能となり、熱利用効率が向上する。 In the CO manufacturing apparatus according to FIGS. 2 and 3, the above reaction occurs in one stage. The use of the electrochemical reaction and a chemical reaction, reduction reaction of CO 2 it is necessary to operate at high temperatures, instead the high temperature operation is necessary electrochemical reactions (reduction reaction of CO 2), the chemical reaction (CO 2 By using + H 2 → CO + H 2 O), low temperature operation becomes possible and heat utilization efficiency is improved.
　本発明で提案するＣＯ製造装置では、７００℃以下２００℃以上、より望ましくは４５０℃以下３００℃以上で動作させる。温度が高いとＣＯ２ガスが触媒電極層１０１の電極表面で分解してコーキングが起こり、電気化学反応活性を低下させるためである。また、生成したＣＯとＨ２Ｏが反応してＣＯ２となり、ＣＯ製造効率が低下するためである。動作温度が低すぎると、逆シフト反応が十分に進行しないため、効率良くＣＯが製造できないためである。 The CO manufacturing apparatus proposed in the present invention is operated at 700 ° C. or lower and 200 ° C. or higher, more preferably 450 ° C. or lower and 300 ° C. or higher. This is because when the temperature is high, the CO 2 gas is decomposed on the electrode surface of the catalyst electrode layer 101 to cause caulking, which reduces the electrochemical reaction activity. Further, the generated CO and H 2 O react with each other to form CO 2 , and the CO production efficiency is lowered. This is because if the operating temperature is too low, the reverse shift reaction does not proceed sufficiently, so that CO cannot be produced efficiently.
　＜固体電解質層＞
　固体電解質層１０３は、電極（触媒極層１０１）と対極層１０２間に通電することにより、酸化物イオンを伝導する酸化物イオン（Ｏ２－）伝導体、プロトン（Ｈ＋）伝導体、および酸化物イオンとプロトンの混合伝導体がある。酸化物イオン伝導体は、代表的には、ＺｒＯ２やＣｅＯ２など、蛍石型構造を有する酸化物の金属元素を、低原子価カチオンで置き換えることで、結晶構造に酸素欠損を導入し、この酸素欠損が酸化物イオンキャリアとなる酸化物の材料群がある。 <Solid electrolyte layer>
The solid electrolyte layer 103 is an oxide ion (O 2- ) conductor, a proton (H + ) conductor, and a proton (H +) conductor that conducts oxide ions by energizing between the electrode (catalyst electrode layer 101) and the counter electrode layer 102. There is a mixed conductor of oxide ions and protons. Oxide ion conductors typically introduce oxygen deficiency into the crystal structure by replacing metal elements of oxides with a fluorite-like structure, such as ZrO 2 and CeO 2, with low valence cations. There is a group of oxide materials in which this oxygen deficiency becomes an oxide ion carrier.
　置換元素としては、例えば、アルカリ土類金属や、ランタノイドを含む、第３族元素などを選ぶことができる。具体的には、ＺｒＯ２のＺｒサイトをＹで置換した（Ｚｒ，Ｙ）Ｏ２や、ＣｅＯ２のＣｅサイトをＳｍで置換した（Ｃｅ，Ｓｍ）Ｏ２等が挙げられる。例えば、ＺｒＯ２に０．０８ｍоｌのＹ２Ｏ３を固溶させた場合、化学式はＺｒ０．８４Ｙ０．１６Ｏ１．９２であり、１ｍоｌあたり、０．０８ｍоｌの酸素欠損が導入されて酸化物イオンキャリアとなる。以降、ＺｒＯ２の結晶構造を有しつつ、置換元素を含む材料をＺｒＯ２系と称する。蛍石型構造を有するものを２種類以上、固溶させても良い。また、置換元素は２種類以上であっても良い。 As the substitution element, for example, an alkaline earth metal, a group 3 element including a lanthanoid, or the like can be selected. Specific examples thereof include (Zr, Y) O 2 in which the Zr site of ZrO 2 is replaced with Y, (Ce, Sm) O 2 in which the Ce site of CeO 2 is replaced with Sm, and the like. For example, when 0.08 mol of Y 2 O 3 is dissolved in ZrO 2 , the chemical formula is Zr 0.84 Y 0.16 O 1.92 , and 0.08 mol of oxygen deficiency is introduced per 1 ml. It becomes an oxide ion carrier. Hereinafter, a material having a crystal structure of ZrO 2 and containing a substituent is referred to as a ZrO 2 system. Two or more types having a fluorite-type structure may be solid-solved. Further, the number of substitution elements may be two or more.
　他の酸化物イオン伝導体として、ＬａＧａＯ３など、希土類元素を含むペロブスカイト型構造を有するものもある。Ｌａサイト、Ｇａサイト、あるいは、これらの両サイトに低原子価カチオンを置換することで、酸化物イオンキャリアを導入することができる。ＬａサイトおよびＧａサイトの置換元素として、例えば、アルカリ土類金属などを選ぶことができる。具体的には、ＬａＧａＯ３のＬａサイトをＳｒで、ＧａサイトをＭｇで置換した（Ｌａ，Ｓｒ）（Ｇａ，Ｍｇ）Ｏ３等が挙げられる。例えば、ＬａＧａＯ３のＬａサイトに０．０５ｍоｌのＳｒＯを、Ｇａサイトに０．０５ｍоｌのＭｇＯを固溶させた場合、化学式はＬａ０．９５Ｓｒ０．０５Ｇａ０．９５Ｍｇ０．０５Ｏ２．９５であり、１ｍоｌあたり、０．０５ｍоｌの酸素欠損が導入されて酸化物イオンキャリアとなる。また、ＬａＧａＯ３のようなペロブスカイト型酸化物の場合、ＬａサイトをＡサイト、ＧａサイトをＢサイトと呼ぶが、ＡサイトとＢサイトのいずれかが相対的に過剰組成になっていても良い。 Other oxide ion conductors, such as LaGaO 3 , have a perovskite-type structure containing rare earth elements. Oxide ion carriers can be introduced by substituting low valence cations for La sites, Ga sites, or both of these sites. As the substitution element of La site and Ga site, for example, alkaline earth metal and the like can be selected. Specific examples thereof include (La, Sr) (Ga, Mg) O 3 in which the La site of LaGaO 3 is replaced with Sr and the Ga site is replaced with Mg. For example, when 0.05 mol SrO is dissolved in the La site of LaGaO 3 and 0.05 mol of MgO is dissolved in the Ga site, the chemical formula is La 0.95 Sr 0.05 Ga 0.95 Mg 0.05 O 2 It is .95 , and 0.05 mL of oxygen deficiency is introduced per 1 mL to become an oxide ion carrier. In addition, in the case of the perovskite-type oxides such as LaGaO 3, La site A site, but the Ga site called the B-site, either A-site and B-site may be made relatively excessive composition.
　プロトン伝導体は、代表的には、ＳｒＺｒＯ３など、アルカリ土類金属を含むペロブスカイト型の結晶構造をとる酸化物のＢサイト元素を、低原子価カチオンで置き換えることで、結晶構造に酸素欠損を導入し、さらに、この酸素欠損に雰囲気水蒸気（Ｈ２Ｏ）が溶解することでプロトンキャリアが導入される酸化物の材料群がある。 Proton conductor is typically such SrZrO 3, the B-site element of the oxide has a crystalline structure of perovskite type containing an alkaline earth metal, by replacing low-valent cations, the oxygen deficiency in the crystal structure There is a group of oxide materials that are introduced and further, proton carriers are introduced by dissolving atmospheric water vapor (H 2 O) in this oxygen deficiency.
　置換元素としては、例えば、ランタノイドを含む、第３族元素などを選ぶことができる。具体的には、ＳｒＺｒＯ３のＺｒサイトをＹで置換したＳｒ（Ｚｒ，Ｙ）Ｏ３等が挙げられる。例えば、ＳｒＺｒＯ３のＺｒサイトに０．０５ｍоｌのＹ２Ｏ３を溶解させた場合、化学式は、ＳｒＺｒ０．９Ｙ０．１Ｏ２．９５であり、１ｍоｌあたり、０．０５ｍоｌの酸素欠損が導入される。さらに、この酸素欠損に水が溶解することで水１ｍｏｌあたり、２ｍｏｌのプロトンキャリアが導入される。この導入反応は、Ｋｒoｇｅｒ-Ｖｉｎｋの表記表で、
　　　　　　　　Ｈ２Ｏ＋ＶＯ ・・＋ＯＯ Ｘ　＝　２（ＯＨ）Ｏ ・
で表現される。なお、ＶＯ ・・は、酸素欠損を、ＯＯ Ｘは、酸素サイトに存在する酸素イオンを、（ＯＨ）Ｏ ・は、酸素サイトに存在するプロトン欠陥をそれぞれ表す。 As the substitution element, for example, a Group 3 element including a lanthanoid can be selected. Specific examples thereof include Sr (Zr, Y) O 3 in which the Zr site of SrZrO 3 is replaced with Y. For example, when 0.05 mL of Y 2 O 3 is dissolved in the Zr site of SrZrO 3 , the chemical formula is SrZr 0.9 Y 0.1 O 2.95 , and there is an oxygen deficiency of 0.05 mL per 1 ml. be introduced. Further, when water dissolves in this oxygen deficiency, 2 mol of proton carriers are introduced per 1 mol of water. This introduction reaction is shown in the Kröger-Vink notation table.
H 2 O + V O ... + O O X = 2 (OH) O ・
It is expressed by. Incidentally, V O · · is the oxygen deficiency, O O X is oxygen ions present in the oxygen site, (OH) O · represent respectively the protons defects present in the oxygen site.
　他のプロトン伝導体として、希土類リン酸塩（ＬａＰＯ４、ＬａＰ３Ｏ９、ＬａＰ５Ｏ１４）や希土類ホウ酸塩（ＬａＢＯ４）、シェーライト型構造を有するＬｉ１－ｘＳｒｘＮｂＯ４（０＜ｘ≦１）、ＬａＮｂＯ４、ＬａＷＯ４等が挙げられる。これらの希土類サイトをアルカリ土類金属で置換することにより、プロトンキャリアを導入することができる。雰囲気にＣＯ２が存在する場合、主構成元素としてアルカリ土類金属が含まれると、アルカリ土類金属が炭酸塩を形成して分解する。製造装置の長寿命化の観点から、アルカリ土類金属を主構成材料として含まないプロトン伝導体を用いるのが望ましい。また、プロトン伝導体は、例えば６００℃以上の高温領域では、プロトン伝導体に溶解した水が脱離してプロトン欠陥濃度が減少し、酸化物イオン伝導が支配的になるものもあるが、本発明においては、可動種がプロトンと酸化物イオンの混合伝導であっても成立する。上記、同一結晶構造を有するものを２種類以上固溶させても良い。また、これらイオン伝導体を２種類以上混合させても良い。 Other proton conductors include rare earth phosphates (LaPO 4 , LaP 3 O 9 , LaP 5 O 14 ), rare earth borates (LaBO 4 ), and Li 1-x Sr x NbO 4 with a shaleite-type structure (LaPO 4). 0 <x ≦ 1), LaNbO 4 , LaWO 4, and the like can be mentioned. Proton carriers can be introduced by substituting these rare earth sites with alkaline earth metals. When CO 2 is present in the atmosphere and the alkaline earth metal is contained as the main constituent element, the alkaline earth metal forms a carbonate and decomposes. From the viewpoint of extending the life of the manufacturing equipment, it is desirable to use a proton conductor that does not contain alkaline earth metals as the main constituent material. Further, in some proton conductors, for example, in a high temperature region of 600 ° C. or higher, the water dissolved in the proton conductor is desorbed to reduce the proton defect concentration, and the oxide ion conduction becomes dominant. In, even if the movable species is a mixed conduction of protons and oxide ions. Two or more of the above having the same crystal structure may be solid-solved. Further, two or more kinds of these ion conductors may be mixed.
　例えば、ＺｒＯ２系固体電解質を用いる場合、後述の対極層１０２とＺｒＯ２界面において、焼結過程、あるいは、長時間の動作によって構成元素が相互拡散し、Ｌａ２Ｚｒ２Ｏ７系パイロクロア等の高抵抗層を形成する。このような劣化を促す反応を抑制するため、他の固体電解質を反応バリア層とするなど、２層以上の層状構造としても良い。具体的には、ＺｒＯ２系固体電解質層と対極層１０２の間に、ＣｅＯ２系固体電解質を配置する方法である。この場合、ＣｅＯ２系固体電解質は、多孔質であっても良い。 For example, when a ZrO 2 based solid electrolyte, the counter electrode layer 102 and the ZrO 2 surface will be described later, the sintering process or constitute elements interdiffusion after a long-term operation, La 2 Zr 2 O 7 based pyrochlore like Form a high resistance layer. In order to suppress such a reaction that promotes deterioration, a layered structure of two or more layers may be used, such as using another solid electrolyte as a reaction barrier layer. Specifically, it is a method of arranging a CeO 2 system solid electrolyte between the ZrO 2 system solid electrolyte layer and the counter electrode layer 102. In this case, CeO 2 based solid electrolyte may be porous.
　ＣＯを高純度で製造するためには、酸化物イオン伝導体を用いるのが望ましい。酸化物イオン伝導体を用いる場合、触媒極層１０１の逆シフト反応の反応生成物であるＨ２Ｏを電解し、電解によって生じたＨ２を逆シフト反応の原料として使用することができるので、不純物であるＨ２Ｏの濃度を低減してよりＣＯ濃度を高めることができるためである。 In order to produce CO with high purity, it is desirable to use an oxide ion conductor. When using an oxide ion conductor, and electrolyte of H 2 O which is the reaction product of the reverse shift reaction catalyst electrode layer 101, it is possible to using H 2 produced by electrolysis as the raw material for the reverse shift reaction, This is because the concentration of H 2 O, which is an impurity, can be reduced to further increase the CO concentration.
　＜触媒極層＞
　触媒極層１０１は、前記のとおり、逆シフト反応触媒と電極とを含む。逆シフト反応触媒は、ＣＯ２とＨ２の化学反応を選択的に進行させる。
　　　　　　　　ＣＯ２　＋　Ｈ２　→　ＣＯ　＋　Ｈ２Ｏ <Catalyst electrode layer>
As described above, the catalyst electrode layer 101 includes a reverse shift reaction catalyst and an electrode. The reverse shift reaction catalyst selectively proceeds the chemical reaction between CO 2 and H 2.
CO 2 + H 2 → CO + H 2 O
　触媒極層１０１の逆シフト反応触媒は、遷移金属と担体となる酸化物の混合物からなる。遷移金属としては、Ｖ、Ｃｒ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｍｏ、Ｒｕ、Ｒｈ等が挙げられる。このうち、逆シフト反応に対する触媒活性を高める、第４周期のＤブロック元素であるＭｎ、Ｃｏ、Ｃｕを組み合わせるのが望ましい。金属触媒はこれらの金属を少なくとも１種類以上含む合金、あるいは、混合物としても良い。また、担体となる酸化物としては、焼成や焼結温度において他の構成材料との反応が起こりにくく、還元雰囲気でも安定な酸化物を選ぶのが望ましい。具体的には、ＣｅＯ２、ＺｒＯ２、Ａｌ２Ｏ３、ＭｇＯや、ＬａＡｌＯ３等の複合酸化物等が挙げられる。このうち、遷移金属との組み合わせにより、逆シフト反応に対する触媒活性をより高める、ＣｅＯ２、ＺｒＯ２、Ａｌ２Ｏ３を組み合わせるのが望ましい。これら酸化物は、一部が他の元素に置換されていても良い。また、これら酸化物を少なくとも１種類以上含む混合物としても良い。 The reverse shift reaction catalyst of the catalyst electrode layer 101 is composed of a mixture of a transition metal and an oxide serving as a carrier. Examples of the transition metal include V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Ru, Rh and the like. Of these, it is desirable to combine Mn, Co, and Cu, which are D-block elements of the 4th period, which enhance the catalytic activity for the reverse shift reaction. The metal catalyst may be an alloy containing at least one of these metals, or a mixture thereof. Further, as the oxide as the carrier, it is desirable to select an oxide that is unlikely to react with other constituent materials at the firing or sintering temperature and is stable even in a reducing atmosphere. Specific examples thereof include composite oxides such as CeO 2 , ZrO 2 , Al 2 O 3 , MgO, and LaAlO 3. Of these, it is desirable to combine CeO 2 , ZrO 2 , and Al 2 O 3 , which further enhance the catalytic activity for the reverse shift reaction by combining with the transition metal. Some of these oxides may be replaced with other elements. Further, it may be a mixture containing at least one of these oxides.
　触媒極層１０１の電極は、固体電解質に酸化物イオン伝導体を用いる場合、以下の電気化学反応により、選択的に水を還元分解する。
　　　　　　　　Ｈ２Ｏ　＋　２ｅ－　→　Ｈ２　＋　Ｏ２－ When an oxide ion conductor is used as the solid electrolyte, the electrode of the catalyst electrode layer 101 selectively reduces and decomposes water by the following electrochemical reaction.
H 2 O + 2e - → H 2 + O 2-
　電極としては、Ｖ、Ｃｒ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ等の遷移金属や、Ｐｔ等の第１０族元素やＡｕ等の第１１族元素等が挙げられる。このうち、水の還元分解反応を促進する、ＮｉやＰｔ等を用いるのが望ましい。電極に含まれる金属は、これらの金属を少なくとも１種類以上含む合金としても良い。 Examples of the electrode include transition metals such as V, Cr, Mn, Fe, Co, Ni, and Cu, Group 10 elements such as Pt, and Group 11 elements such as Au. Of these, it is desirable to use Ni, Pt or the like, which promotes the reduction decomposition reaction of water. The metal contained in the electrode may be an alloy containing at least one of these metals.
　また、電極は、固体電解質にプロトン伝導体を用いる場合、以下の電気化学反応により、選択的に水素を発生する。
　　　　　　　　２Ｈ＋　＋　２ｅ－　→　Ｈ２ When a proton conductor is used as the solid electrolyte, the electrode selectively generates hydrogen by the following electrochemical reaction.
2H + + 2e - → H 2
　電極としては、ＰｄやＰｔ等の白金族元素やＡｕ等が挙げられる。このうち、水素発生反応の活性が高く、水素の溶解度が高いＰｄを用いるのが望ましい。電極に含まれる金属は、これらの金属を少なくとも１種類以上含む合金としても良い。さらに、固体電解質との接触面積を増やし、反応抵抗を低減するため、固体電解質と混合して使用するのが望ましい。 Examples of the electrode include platinum group elements such as Pd and Pt, Au and the like. Of these, it is desirable to use Pd, which has a high activity of hydrogen generation reaction and a high solubility of hydrogen. The metal contained in the electrode may be an alloy containing at least one of these metals. Further, in order to increase the contact area with the solid electrolyte and reduce the reaction resistance, it is desirable to use the mixture in combination with the solid electrolyte.
　触媒極層１０１は、逆シフト反応と電気化学反応を選択的に進行させれば良いため、逆シフト反応触媒の金属元素と、電極の金属元素と、固体電解質粒子を混合して１層としても良い。また、異なる金属と酸化物を組み合わせた２層以上の積層構造としても良い。 Since the catalyst electrode layer 101 may selectively proceed with the reverse shift reaction and the electrochemical reaction, the metal element of the reverse shift reaction catalyst, the metal element of the electrode, and the solid electrolyte particles may be mixed to form one layer. good. Further, a laminated structure having two or more layers in which different metals and oxides are combined may be used.
　＜対極層＞
　対極層１０２は、固体電解質に酸化物イオン伝導体を用いる場合、以下の電気化学反応により、酸素ガスが発生する。
　　　　　　　　Ｏ２－　→　１／２Ｏ２　＋　２ｅ－ <Polar layer>
When an oxide ion conductor is used as the solid electrolyte in the counter electrode layer 102, oxygen gas is generated by the following electrochemical reaction.
O 2- → 1 / 2O 2 + 2e -
　対極層１０２としては、希土類元素と遷移金属元素を含み、電子伝導性を有するペロブスカイト型酸化物等が挙げられる。例えば、ＬａＭｎＯ３、ＬａＣｏＯ３、ＬａＦｅＯ３、ＳｍＣｏＯ３等の希土類元素をアルカリ土類金属元素に置換したものが挙げられ、化学式としては、（Ｌａ，Ｓｒ）ＭｎＯ３、Ｌａ１－ｘＳｒｘＭｎＯ３（０＜ｘ≦１）等で表記される。置換元素は、ＣａやＢａ等、他のアルカリ土類金属元素を２種類以上含んでいても良い。また、遷移金属元素を２種類以上含んでいても良い。また、これら酸化物を２種類以上含む混合物であっても良い。 Examples of the counter electrode layer 102 include perovskite-type oxides containing rare earth elements and transition metal elements and having electron conductivity. For example, rare earth elements such as LaMnO 3 , LaCoO 3 , LaFeO 3 , and SmCoO 3 are replaced with alkaline earth metal elements, and the chemical formulas are (La, Sr) MnO 3 , La 1-x Sr x MnO. It is expressed as 3 (0 <x ≦ 1) or the like. The substitution element may contain two or more kinds of other alkaline earth metal elements such as Ca and Ba. Further, two or more kinds of transition metal elements may be contained. Further, it may be a mixture containing two or more kinds of these oxides.
　固体電解質層１０３にプロトン伝導体を用いる場合、以下の電気化学反応により、酸素が発生する。
　　　　　　　　Ｈ２Ｏ　→　２Ｈ＋　＋　２ｅ－　＋　１／２Ｏ２ When a proton conductor is used for the solid electrolyte layer 103, oxygen is generated by the following electrochemical reaction.
H 2 O → 2H + + 2e - + 1 / 2O 2
　対極層１０２としては、ＰｄやＰｔ等の白金族元素やＡｕ等が挙げられる。このうち、酸素発生反応の活性が高いＰｔを用いるのが望ましい。対極層１０２に含まれる金属は、これらの金属を少なくとも１種類以上含む合金としても良い。さらに、固体電解質層１０３との接触面積を増やし、反応抵抗を低減するため、固体電解質層１０３と混合して使用するのが望ましい。 Examples of the counter electrode layer 102 include platinum group elements such as Pd and Pt, Au and the like. Of these, it is desirable to use Pt, which has a high activity of oxygen evolution reaction. The metal contained in the counter electrode layer 102 may be an alloy containing at least one of these metals. Further, in order to increase the contact area with the solid electrolyte layer 103 and reduce the reaction resistance, it is desirable to use the mixture in combination with the solid electrolyte layer 103.
　以下、実施例及び比較例を挙げて本発明をさらに具体的に説明するが、（適宜図１～図３を参照）本発明はこれらの実施例に限定されるものではない。 Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples (see FIGS. 1 to 3 as appropriate).
　＜実施例１＞
　＜固体電解質層１０３の作製＞
　市販のＺｒ０．８４Ｙ０．１６Ｏ１．９２（以下、ＹＳＺ）粉末を所定の重量で秤量し、油圧プレス機にてプレスした。これを、１３５０℃、空気中で３時間熱処理することで、直径１３ｍｍのち密な電解質膜を得ることができた。この電解質膜両面を、耐水研磨紙で研磨して厚み５００μｍとした。 <Example 1>
<Preparation of solid electrolyte layer 103>
Commercially available Zr 0.84 Y 0.16 O 1.92 (hereinafter, YSZ) powder was weighed to a predetermined weight and pressed with a hydraulic press. By heat-treating this in air at 1350 ° C. for 3 hours, a dense electrolyte membrane having a diameter of 13 mm could be obtained. Both sides of the electrolyte membrane were polished with water-resistant abrasive paper to a thickness of 500 μm.
　＜触媒極層１０１の作製＞
　触媒極層１０１の逆シフト反応触媒の出発原料として、ＣｕＯとＣｅＯ２を用いた。これらの粉末を、ＣｕとＣｅＯ２の体積比が５：５となるよう秤量し、遊星ボールミルにてエタノール中で３００ｒｐｍで３時間処理した（以降、５０ｖоｌ％Ｃｕ／ＣｅＯ２と表記する）。また、電極の出発原料として、ＮｉＯとＹＳＺを用いた。これらの粉末を、ＮｉとＹＳＺの体積比が４：６となるよう秤量し、遊星ボールミルにてエタノール中で３００ｒｐｍで３時間処理した。これら粉末を乾燥後、溶媒と混合してスラリーとした。固体電解質層１０３表面に、電極のスラリーをスクリーン印刷機を用いて直径８ｍｍで塗布、乾燥後、さらに、電極表面に逆シフト反応触媒を直径８ｍｍで塗布した。これを１２００℃、空気中で１時間熱処理した。なお、断面ＳＥＭ観察により、逆シフト反応触媒層と電極の厚みはそれぞれ５０μｍであった。 <Preparation of catalyst electrode layer 101>
CuO and CeO 2 were used as starting materials for the reverse shift reaction catalyst of the catalyst electrode layer 101. These powders were weighed so that the volume ratio of Cu and CeO 2 was 5: 5, and treated with a planetary ball mill in ethanol at 300 rpm for 3 hours (hereinafter referred to as 50 vol% Cu / CeO 2 ). In addition, NiO and YSZ were used as starting materials for the electrodes. These powders were weighed so that the volume ratio of Ni and YSZ was 4: 6, and treated with a planetary ball mill in ethanol at 300 rpm for 3 hours. After drying these powders, they were mixed with a solvent to prepare a slurry. The electrode slurry was applied to the surface of the solid electrolyte layer 103 with a diameter of 8 mm using a screen printing machine, dried, and then the reverse shift reaction catalyst was further applied to the electrode surface with a diameter of 8 mm. This was heat treated at 1200 ° C. in air for 1 hour. By observing the cross section by SEM, the thickness of the reverse shift reaction catalyst layer and the electrode was 50 μm, respectively.
　＜対極層１０２の作製＞
　対極層１０２には、Ｌａ０．８Ｓｒ０．２ＭｎＯ３－δ（以下、ＬＳＭ）を用いた。出発原料として、Ｌａ２ＣＯ３、ＳｒＣＯ３、Ｍｎ２Ｏ３を用いた。これらを定比組成で秤量し、ジルコニア製の乳鉢と乳棒で混合し、空気中、１２００℃で５時間熱処理することでＬＳＭを得た。結晶構造は、Ｘ線回折測定で評価し、不純物に由来する回折ピークがないことを確認した。ＬＳＭを溶媒中に分散してスラリーとした。固体電解質層１０３の表面の、触媒極層１０１の逆側に、対極のスラリーをスクリーン印刷機を用いて直径８ｍｍで塗布、乾燥後、１０００℃、空気中で１時間熱処理した。なお、断面ＳＥＭ観察の結果、対極の厚みは１００μｍであった。 <Preparation of counter electrode layer 102>
For the counter electrode layer 102, La 0.8 Sr 0.2 MnO 3-δ (hereinafter, LSM) was used. La 2 CO 3 , SrCO 3 , and Mn 2 O 3 were used as starting materials. These were weighed at a constant ratio composition, mixed with a zirconia mortar and pestle, and heat-treated in air at 1200 ° C. for 5 hours to obtain LSM. The crystal structure was evaluated by X-ray diffraction measurement, and it was confirmed that there was no diffraction peak derived from impurities. LSM was dispersed in a solvent to form a slurry. On the opposite side of the catalyst electrode layer 101 on the surface of the solid electrolyte layer 103, a slurry of counter electrode was applied using a screen printing machine to a diameter of 8 mm, dried, and then heat-treated in air at 1000 ° C. for 1 hour. As a result of cross-sectional SEM observation, the thickness of the counter electrode was 100 μm.
　＜ＣＯ製造速度の評価＞
　作製したセルの表面に、集電体として金のリード線を取り付けた金メッシュを、触媒極層と対極層表面にそれぞれ配置し、触媒極層１０１と対極層１０２で異なるガスを導入できる２室型の評価装置にセッティングした。シーリング材として、パイレックスガラスを使用した。パイレックスガラスを溶解して気密性を付与するため、セルを９００℃で保持した。このとき、触媒極層１０１に還元ガスを導入し、触媒極層１０１内のＣｕＯとＮｉＯを還元処理してＣｕとＮｉとした。セルを徐冷して４５０℃にした後、触媒極層１０１へは３％ＣＯ２－１．７％Ｈ２Ｏ－Ａｒを２０ｃｃｍで、対極層１０２へはＡｒを２０ｃｃｍで導入した。セルに５００ｍＡ／ｃｍ２で通電し、触媒極層１０１の下流側ガス組成をガスクロマトグラフでガス組成を分析してＣＯ濃度を計測した。 <Evaluation of CO production speed>
Two chambers in which a gold mesh having a gold lead wire attached as a current collector is arranged on the surface of the produced cell on the surface of the catalyst electrode layer and the surface of the counter electrode layer, respectively, and different gases can be introduced into the catalyst electrode layer 101 and the counter electrode layer 102. It was set on the mold evaluation device. Pyrex glass was used as the sealing material. The cell was held at 900 ° C. to melt the Pyrex glass and impart airtightness. At this time, a reducing gas was introduced into the catalyst electrode layer 101, and CuO and NiO in the catalyst electrode layer 101 were reduced to obtain Cu and Ni. After the cell was slowly cooled to 450 ° C., 3% CO 2 -1.7% H 2 O-Ar was introduced into the catalyst electrode layer 101 at 20 ccm, and Ar was introduced into the counter electrode layer 102 at 20 ccm. The cell was energized at 500 mA / cm 2 , and the gas composition on the downstream side of the catalyst electrode layer 101 was analyzed by a gas chromatograph to measure the CO concentration.
　＜実施例２～８、及び比較例１～６＞
　触媒極層１０１と対極層１０２の組成、導入ガス組成、通電量を表１に示すように調整した以外は、実施例１と同様にしてＣＯ製造セルを作製し、触媒極層１０１の下流側ガス組成をガスクロマトグラフで分析してＣＯ濃度を計測した。 <Examples 2 to 8 and Comparative Examples 1 to 6>
A CO production cell was prepared in the same manner as in Example 1 except that the compositions of the catalyst electrode layer 101 and the counter electrode layer 102, the introduced gas composition, and the amount of energization were adjusted as shown in Table 1, and the downstream side of the catalyst electrode layer 101 was prepared. The gas composition was analyzed by gas chromatography and the CO concentration was measured.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　＜実施例９＞
　＜固体電解質層１０３の作製＞
　固体電解質層１０３には、プロトン伝導体であるＬａ０．９５Ｓｒ０．０５ＮｂＯ４－δ（以下、ＬＳＮ）を用いた。出発原料として、Ｌａ２Ｏ３、Ｎｂ２Ｏ５、ＳｒＣＯ３を用いた。これらを定比組成で秤量し、ジルコニア製の乳鉢と乳棒で混合し、空気中、１０００℃で１５時間熱処理した。得られた粉末を、遊星ボールミルにてエタノール中で３００ｒｐｍで３時間処理した。乾燥後、油圧プレス機にてプレスした。１５００℃、空気中で５時間熱処理することで、直径１３ｍｍのち密な電解質膜を得ることができた。この電解質膜両面を、耐水研磨紙で研磨して厚み１ｍｍとした。 <Example 9>
<Preparation of solid electrolyte layer 103>
For the solid electrolyte layer 103, La 0.95 Sr 0.05 NbO 4-δ (hereinafter referred to as LSN), which is a proton conductor, was used. La 2 O 3 , Nb 2 O 5 , and SrCO 3 were used as starting materials. These were weighed at a constant ratio composition, mixed with a zirconia mortar and pestle, and heat-treated in air at 1000 ° C. for 15 hours. The obtained powder was treated with a planetary ball mill in ethanol at 300 rpm for 3 hours. After drying, it was pressed with a hydraulic press. By heat-treating at 1500 ° C. in air for 5 hours, a dense electrolyte membrane having a diameter of 13 mm could be obtained. Both sides of the electrolyte membrane were polished with water-resistant abrasive paper to a thickness of 1 mm.
　＜触媒極層１０１の作製＞
　逆シフト反応触媒は、実施例１と同じものを使用した。電極は、ＰｄペーストとＬＳＮの混合物を用いた。ＰｄとＬＳＮの体積比が４：６となるよう秤量し、溶媒とともに混錬してスラリーとした。熱処理方法および、逆シフト反応触媒と電極の厚みはそれぞれ実施例１と同じであった。 <Preparation of catalyst electrode layer 101>
The same reverse shift reaction catalyst as in Example 1 was used. As the electrode, a mixture of Pd paste and LSN was used. Weighed so that the volume ratio of Pd and LSN was 4: 6, and kneaded with a solvent to obtain a slurry. The heat treatment method and the thickness of the reverse shift reaction catalyst and the electrode were the same as in Example 1, respectively.
　＜対極層１０２の作製＞
　対極層１０２には、Ｐｔペーストを用いた。スクリーン印刷機にて、直径８ｍｍで塗布した後、９００℃で３時間熱処理することで対極層を固体電解質表面に焼結した。断面ＳＥＭ観察の結果、対極の厚みは５０μｍであった。 <Preparation of counter electrode layer 102>
Pt paste was used for the counter electrode layer 102. After coating with a screen printing machine having a diameter of 8 mm, the counter electrode layer was sintered on the surface of the solid electrolyte by heat treatment at 900 ° C. for 3 hours. As a result of cross-sectional SEM observation, the thickness of the counter electrode was 50 μm.
　＜ＣＯ製造速度の評価＞
　対極層１０２への導入ガス組成を１．７％Ｈ２Ｏ－Ａｒとした以外は、実施例１と同様にＣＯ濃度を計測した。 <Evaluation of CO production speed>
The CO concentration was measured in the same manner as in Example 1 except that the gas composition introduced into the counter electrode layer 102 was 1.7% H 2 O-Ar.
　＜比較例７＞
　セルに通電しなかった以外は、実施例９と同様にした。 <Comparative Example 7>
The procedure was the same as in Example 9 except that the cell was not energized.
　＜比較例８＞
　対極にＡｕペーストを使用した以外は、実施例９と同様にした。 <Comparative Example 8>
The same procedure as in Example 9 was carried out except that Au paste was used as the counter electrode.
　＜結果と考察＞
　実施例１より、触媒極層１０１に逆シフト反応触媒と電極を導入し、これと酸素ガス発生電極で酸素イオン伝導体であるＹＳＺ層をサンドイッチしたセルを構成し、４５０℃において、触媒極層１０１にＣＯ２とＨ２Ｏ混合ガスを導入して通電した場合、触媒極層１０１の出口ガスでＣＯが検出され、その濃度は０．０４％であった。一方、比較例１より、通電しない場合には、ＣＯは検出されなかった。このことは、通電により、触媒極層１０１に含まれる電極でＨ２Ｏが電気化学的に還元分解してＨ２とＯ２－を生じ、Ｈ２はＣＯ２と逆シフト反応を起こしてＣＯとＨ２Ｏに変換されると同時に、Ｏ２－は固体電解質を移動して対極に到達し、Ｏ２として気相に放出されたことを示している。 <Results and discussion>
From Example 1, a reverse shift reaction catalyst and an electrode were introduced into the catalyst electrode layer 101, and a cell in which the YSZ layer, which is an oxygen ion conductor, was sandwiched between the reverse shift reaction catalyst and the electrode was formed by the oxygen gas generating electrode. When a mixed gas of CO 2 and H 2 O was introduced into 101 and energized, CO was detected in the outlet gas of the catalyst electrode layer 101, and the concentration was 0.04%. On the other hand, from Comparative Example 1, CO was not detected when the power was not applied. This means that when energized, H 2 O is electrochemically reduced and decomposed at the electrode contained in the catalyst electrode layer 101 to produce H 2 and O 2- , and H 2 undergoes a reverse shift reaction with CO 2 to cause CO. At the same time as being converted to H 2 O, O 2- moved the solid electrolyte to reach the counter electrode, indicating that it was released into the gas phase as O 2.
　比較例２より、触媒極層に電極を導入しないセルでは、内部抵抗が増大して通電することができなかった。Ｈ２Ｏ電解反応が進行しないため、ＣＯは検出されなかった。
　実施例２では、ＣＯ濃度は０．０４％であり、実施例１と同程度であった。このことから、触媒極層１０１の逆シフト反応触媒に含まれるＣｅＯ２のＣｅサイトを他の元素で部分置換しても、触媒活性は損なわれないことがわかった。 From Comparative Example 2, in the cell in which the electrode was not introduced into the catalyst electrode layer, the internal resistance increased and energization could not be performed. Since H 2 O electrolysis reaction does not proceed, CO was not detected.
In Example 2, the CO concentration was 0.04%, which was about the same as in Example 1. From this, it was found that even if the Ce site of CeO 2 contained in the reverse shift reaction catalyst of the catalyst electrode layer 101 is partially replaced with another element, the catalytic activity is not impaired.
　実施例３では、ＣＯ濃度は０．０８１％であり、実施例１の２倍以上であった。触媒極層１０１に導入するガスの流速を低減させることで、ＣＯ２の逆シフト反応触媒表面での滞留時間が長くなり、逆シフト反応が促進されたことを示している。 In Example 3, the CO concentration was 0.081%, which was more than twice that of Example 1. By reducing the flow rate of the gas introduced into the catalyst electrode layer 101 , the residence time of CO 2 on the surface of the reverse shift reaction catalyst is lengthened, indicating that the reverse shift reaction is promoted.
　実施例４では、動作温度を３００℃とした。通電電流量が実施例１と同じであることから、Ｈ２Ｏの水電解量、すなわち、Ｈ２の発生量も実施例１と同じであるが、ＣＯ濃度は０．０１７％まで低下した。このことから、動作温度が高いほど、逆シフト反応が進行しやすいことが分かった。 In Example 4, the operating temperature was set to 300 ° C. Since the amount of electric current is the same as in Example 1, water electrolysis of H 2 O, i.e., the amount of generated H 2 is the same as in Example 1, CO concentration was reduced to 0.017%. From this, it was found that the higher the operating temperature, the easier the reverse shift reaction to proceed.
　実施例５と実施例６では、逆シフト反応触媒に含まれる金属元素をそれぞれ、ＭｎとＣｏとした。実施例５と実施例６におけるＣＯ濃度はそれぞれ、０．０２８％、０．０４％と金属元素組成に依存した。ＣＯが製造できたことから、使用する金属元素は、Ｃｕ、Ｍｎ、Ｃｏが望ましいことが分かった。 In Example 5 and Example 6, the metal elements contained in the reverse shift reaction catalyst were Mn and Co, respectively. The CO concentrations in Examples 5 and 6 were 0.028% and 0.04%, respectively, depending on the metal element composition. Since CO could be produced, it was found that Cu, Mn, and Co are desirable as the metal elements to be used.
　実施例７では、固体電解質層１０３にＣｅ０．９Ｇｄ０．１Ｏ１．９５（以降、ＧＤＣと表記する）を使用した。ＣＯ濃度は、ＹＳＺを使用するセル（実施例１）と同じ０．０４％であったことから、固体電解質層１０３として使用する酸素イオン伝導体は、組成に依らず適用可能であることが分かった。 In Example 7, Ce 0.9 Gd 0.1 O 1.95 (hereinafter referred to as GDC) was used for the solid electrolyte layer 103. Since the CO concentration was 0.04%, which was the same as that of the cell using YSZ (Example 1), it was found that the oxygen ion conductor used as the solid electrolyte layer 103 can be applied regardless of the composition. It was.
　比較例３では、逆シフト反応触媒をＣｅＯ２のみとしたが、Ｃｕを含まないために集電抵抗が大きくなり、通電できなかった。 In Comparative Example 3, the reverse shift reaction catalyst was only CeO 2, but since it did not contain Cu, the current collecting resistance became large and energization could not be performed.
　実施例１では、触媒極層１０１の逆シフト反応触媒と電極を２層構造としたのに対し、実施例８では、逆シフト反応触媒と電極に含まれる金属元素とＧＤＣを混合して１層構造としたが、０．０１４％のＣＯが検出された。このことから、触媒極層１０１には逆シフト反応とＨ２Ｏ電解を促す金属元素と酸化物が同一層内に含まれていても良いことがわかった。 In Example 1, the reverse shift reaction catalyst of the catalyst electrode layer 101 and the electrode have a two-layer structure, whereas in Example 8, the reverse shift reaction catalyst, the metal element contained in the electrode, and GDC are mixed to form one layer. Although it was structured, 0.014% CO was detected. Therefore, the catalyst electrode layer 101 was found that oxide to a metal element to promote the reverse shift reaction and H 2 O electrolyte may be contained in the same layer.
　比較例４では、触媒極層内の電極に含まれる金属元素をＣｕとしたが、Ｈ２Ｏ電解活性が低く、セルが高抵抗化して通電できなかった。このことは、Ｈ２Ｏ電解活性は、電極内の金属元素に依存し、Ｎｉを使用するのが望ましいことが分かった。
　比較例５では、電極内の酸化物にＣｅＯ２を使用したが、置換元素を含まないために酸化物イオンキャリアの濃度がごく微量であり、酸化物イオン伝導率の乏しいために、セル抵抗が大きく、通電できなかった。このことから、Ｈ２Ｏ電解活性を高めるためには、電極内の酸化物に酸素イオン伝導体を使用するのが望ましいことが分かった。 In Comparative Example 4, although the metal elements contained in the electrode catalyst electrode layer was Cu, H 2 O electrolysis activity is low, the cell can not be energized by high resistance. This is, H 2 O electrolysis activity depends on the metal elements in the electrode, it has been found that it is desirable to use Ni.
In Comparative Example 5, CeO 2 was used as the oxide in the electrode, but the concentration of the oxide ion carrier was very small because it did not contain a substituent, and the cell resistance was low because the oxide ion conductivity was poor. It was too big to energize. Therefore, in order to increase of H 2 O electrolysis activity it was found to be desirable to use an oxygen ion conductor in the oxide in the electrode.
　比較例６では、対極にＯ２ガス化反応活性の低いＡｕを使用したが、セルの内部抵抗が大きく、通電できなかった。 In Comparative Example 6, but using a low O 2 gasification reaction activity Au counter electrode, the internal resistance of the cell is large, it could not be energized.
　実施例９では、固体電解質層１０３をプロトン伝導体のＬＳＮとして通電した場合、０．００８％のＣＯが検出できた。これに対し、通電しない比較例７では、ＣＯ濃度は０．００２％未満であった。さらに、対極層１０２をＨ２Ｏ分解活性の低いＡｕ電極とした比較例８では、セル抵抗が大きく、通電ができなかった。 In Example 9, when the solid electrolyte layer 103 was energized as the LSN of the proton conductor, 0.008% of CO could be detected. On the other hand, in Comparative Example 7 which was not energized, the CO concentration was less than 0.002%. In Comparative Example 8 the counter electrode layer 102 was lower Au electrode of H 2 O decomposition activity, large cell resistance, it could not be energized.
　以上より、適切な触媒、電極、固体電解質と対極を組み合わせ、低温で通電した場合、ＣＯが製造できることが分かった。さらに、触媒極層で水を生成するプロトン伝導体を用いるセルよりも、水を消費してＣＯをより高濃度化する酸素イオン伝導体を用いるセルの方が、高純度でＣＯを製造できることが分かった。 From the above, it was found that CO can be produced when an appropriate catalyst, electrode, solid electrolyte and counter electrode are combined and energized at a low temperature. Furthermore, it is possible to produce CO with higher purity in a cell using an oxygen ion conductor that consumes water to increase the concentration of CO than a cell using a proton conductor that produces water in the catalyst electrode layer. Do you get it.
　１０１　　　触媒極層
　１０２　　　対極層
　１０３　　　固体電解質層
　１０４　　　配線
　１０５　　　外部電源 101 Catalytic electrode layer 102 Counter electrode layer 103 Solid electrolyte layer 104 Wiring 105 External power supply

Claims (13)

  1. 　触媒極層と、前記触媒極層と配線により電気的に接続される対極層と、前記触媒極層と前記対極層の間に配置される固体電解質層と、を備え、
    　前記固体電解質層はイオン伝導体を含み、
    　前記触媒極層は、Ｈ２を生成する電極と、逆シフト反応を選択的に進行させる逆シフト反応触媒とを有し、
    　通電することによりＣＯが生成することを特徴とする一酸化炭素製造装置。     A catalyst electrode layer, a counter electrode layer electrically connected to the catalyst electrode layer by wiring, and a solid electrolyte layer arranged between the catalyst electrode layer and the counter electrode layer are provided.
    The solid electrolyte layer contains an ionic conductor and contains
    The catalyst electrode layer has an electrode for producing H 2 and a reverse shift reaction catalyst for selectively advancing the reverse shift reaction.
    A carbon monoxide production apparatus characterized in that CO is generated by energizing.
  2. 　前記固体電解質層が酸化物イオン伝導体であり、
    　前記電極では、
    　Ｈ２Ｏ　＋　２ｅ－　→　Ｈ２　＋　Ｏ２－
    　が選択的起こり、
    　前記逆シフト反応触媒では、
    　ＣＯ２　＋　Ｈ２　→　ＣＯ　＋　Ｈ２Ｏ
    　が選択的に起こり、
    　前記対極層では、
    　Ｏ２－　→　１／２Ｏ２　＋　２ｅ－
    　が起こることを特徴とする請求項１に記載の一酸化炭素製造装置。     The solid electrolyte layer is an oxide ion conductor,
    With the electrode
    H 2 O + 2e - → H 2 + O 2-
    Occurs selectively,
    In the reverse shift reaction catalyst,
    CO 2 + H 2 → CO + H 2 O
    Occurs selectively
    In the opposite electrode layer
    O 2- → 1 / 2O 2 + 2e -
    The carbon monoxide production apparatus according to claim 1, wherein
  3. 　前記固体電解質層が、蛍石型構造あるいはペロブスカイト型構造を有する酸化物イオン伝導体を少なくとも１種類以上含むことを特徴とする請求項２に記載の一酸化炭素製造装置。 The carbon monoxide production apparatus according to claim 2, wherein the solid electrolyte layer contains at least one type of oxide ion conductor having a fluorite-type structure or a perovskite-type structure.
  4. 　前記逆シフト反応触媒は、遷移金属と、担体となる酸化物と、を含む混合物であって、
    　前記遷移金属はＣｕ、Ｍｎ、Ｃｏを少なくとも１種類以上含み、
    　前記担体となる酸化物はＣｅＯ２、ＺｒＯ２、Ａｌ２Ｏ３、及び、これらの一部が他の元素に置換されたものを少なくとも１種類以上含むことを特徴とする請求項２又は請求項３に記載の一酸化炭素製造装置。     The reverse shift reaction catalyst is a mixture containing a transition metal and an oxide serving as a carrier.
    The transition metal contains at least one kind of Cu, Mn, and Co, and contains at least one kind.
    Claim 2 or claim, wherein the oxide serving as the carrier contains at least one or more of CeO 2 , ZrO 2 , Al 2 O 3 , and those in which a part thereof is replaced with another element. The carbon monoxide production apparatus according to 3.
  5. 　前記電極は、Ｎｉ、Ｐｔ、又は、これらのいずれかを含む合金を含むことを特徴とする請求項２に記載の一酸化炭素製造装置。 The carbon monoxide production apparatus according to claim 2, wherein the electrode contains Ni, Pt, or an alloy containing any of these.
  6. 　前記対極層は、電子伝導性を有するペロブスカイト型酸化物を含むことを特徴とする請求項２に記載の一酸化炭素製造装置。 The carbon monoxide production apparatus according to claim 2, wherein the counter electrode layer contains a perovskite-type oxide having electron conductivity.
  7. 　前記対極層は、Ｌａ１－ｘＳｒｘＭｎＯ３（０＜ｘ≦１）であることを特徴とする請求項２に記載の一酸化炭素製造装置。 The carbon monoxide production apparatus according to claim 2, wherein the counter electrode layer is La 1-x Sr x MnO 3 (0 <x ≦ 1).
  8. 　前記固体電解質層がプロトン伝導体であり、
    　前記電極では、
    　２Ｈ＋　＋　２ｅ－　→　Ｈ２
    　が選択的に起こり、
    　前記逆シフト反応触媒では、
    　ＣＯ２　＋　Ｈ２　→　ＣＯ　＋　Ｈ２Ｏ
    　が選択的に起こり、
    　前記対極層では、
    　Ｈ２Ｏ　→　２Ｈ＋　＋　２ｅ－　＋　１／２Ｏ２
    　が起こることを特徴とする請求項１に記載の一酸化炭素製造装置。     The solid electrolyte layer is a proton conductor and
    With the electrode
    2H + + 2e - → H 2
    Occurs selectively
    In the reverse shift reaction catalyst,
    CO 2 + H 2 → CO + H 2 O
    Occurs selectively
    In the opposite electrode layer
    H 2 O → 2H + + 2e - + 1 / 2O 2
    The carbon monoxide production apparatus according to claim 1, wherein
  9. 　前記固体電解質層が、シェーライト型構造を有するプロトン伝導体を少なくとも１種類以上含むことを特徴とする請求項８に記載の一酸化炭素製造装置。 The carbon monoxide production apparatus according to claim 8, wherein the solid electrolyte layer contains at least one type of proton conductor having a shaleite type structure.
  10. 　前記固体電解質層が、Ｌｉ１－ｘＳｒｘＮｂＯ４（０＜ｘ≦１）であることを特徴とする請求項８又は請求項９に記載の一酸化炭素製造装置。 The carbon monoxide production apparatus according to claim 8 or 9, wherein the solid electrolyte layer is Li 1-x Sr x NbO 4 (0 <x ≦ 1).
  11. 　前記逆シフト反応触媒は、遷移金属と、担体となる酸化物と、を含む混合物であって、
    　前記遷移金属がＣｕ、Ｍｎ、Ｃｏを少なくとも１種類以上含み、
    　前記担体となる酸化物がＣｅＯ２、ＺｒＯ２、Ａｌ２Ｏ３、及び、これらの一部が他の元素に置換されたものを少なくとも１種類以上含むことを特徴とする請求項８に記載の一酸化炭素製造装置。     The reverse shift reaction catalyst is a mixture containing a transition metal and an oxide serving as a carrier.
    The transition metal contains at least one type of Cu, Mn, and Co.
    The eighth aspect of the present invention, wherein the oxide serving as the carrier contains at least one or more of CeO 2 , ZrO 2 , Al 2 O 3 , and a part thereof substituted with another element. Carbon monoxide production equipment.
  12. 　前記電極は、Ｐｄ、Ｐｔ、Ａｕ、又は、これらのいずれかを含む合金、を含むことを特徴とする請求項８に記載の一酸化炭素製造装置。 The carbon monoxide production apparatus according to claim 8, wherein the electrode contains Pd, Pt, Au, or an alloy containing any of these.
  13. 　前記対極層は、Ｐｄ、Ｐｔ、Ａｕ、又は、これらのいずれかを含む合金、を含むことを特徴とする請求項８に記載の一酸化炭素製造装置。 The carbon monoxide production apparatus according to claim 8, wherein the counter electrode layer contains Pd, Pt, Au, or an alloy containing any of these.
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