US20220220622A1 - Electrode, solid electrolyte electrolysis device, and synthetic gas production method - Google Patents
Electrode, solid electrolyte electrolysis device, and synthetic gas production method Download PDFInfo
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- US20220220622A1 US20220220622A1 US17/605,835 US202017605835A US2022220622A1 US 20220220622 A1 US20220220622 A1 US 20220220622A1 US 202017605835 A US202017605835 A US 202017605835A US 2022220622 A1 US2022220622 A1 US 2022220622A1
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- 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
- C25B1/23—Carbon monoxide or syngas
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- 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
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- 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
- C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
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- 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
- C25B9/17—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof
- C25B9/19—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms
- C25B9/23—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms comprising ion-exchange membranes in or on which electrode material is embedded
Abstract
Techniques may relate to an electrode having high production efficiency of a synthetic gas containing at least CO. Such techniques relating to an electrode may include: a catalyst that produces at least carbon monoxide by a reduction reaction; an electrode material including the catalyst; and a solid base additive provided at least on the electrode material.
Description
- The present disclosure relates to an electrode capable of producing a synthetic gas containing at least carbon monoxide, a solid electrolyte electrolysis device, and a synthetic gas production method.
- Fossil fuels (oil, coal, natural gas) support a modern energy consuming society. However, reserves of such fossil fuel are limited. Thus, various alternative fuels that will replace fossil fuels have been proposed. One of them is Hydrocarbon Fuel (HC). HC can be synthesized, for example, by subjecting a synthetic gas containing at least carbon monoxide (CO) and hydrogen (H2) to Fischer-Tropsch reaction (FT reaction).
- Patent Literature 1 proposes a synthetic gas synthesizing instrument. Specifically, an instrument is disclosed in which carbon dioxide (CO2) is blown into seawater to lower the pH of the seawater from 8 to 5 to 6 in a tank provided separately from an electrolyzer, and the seawater after the pH adjustment is sent from the tank to the electrolyzer for electrolysis.
-
- Patent Literature 1: JP 61-73893 A
- The method of Patent Literature 1 has a problem of poor production efficiency of a synthetic gas due to the low solubility of CO2 in water. Thus, an object of the present disclosure is to provide a technique related to an electrode having high production efficiency of a synthetic gas containing at least CO.
- According to one aspect of the present disclosure, a technique including:
- a catalyst that produces at least carbon monoxide by a reduction reaction;
- an electrode material having the catalyst; and
- a solid base additive provided at least on the electrode material can be provided.
- According to the present disclosure, a technique related to an electrode having high production efficiency of a synthetic gas containing at least CO can be provided.
-
FIG. 1 illustrates a solid electrolyte electrolysis device suitably used in an embodiment of the present disclosure. -
FIG. 2 is a conceptual diagram showing a situation where CO2 can be efficiently adsorbed locally by addition of a solid base additive to a cathode surface in a solid electrolyte electrolysis device suitably used in an embodiment of the present disclosure. -
FIG. 3 is a flowchart showing a synthetic gas production method in which a solid electrolyte electrolysis device suitably used in an embodiment of the present disclosure is used. -
FIG. 4 illustrates use examples of a solid electrolyte electrolysis device suitably used in an embodiment of the present disclosure. - Hereinafter, a solid electrolyte electrolysis device in the present disclosure will be specifically described with reference to one embodiment. The invention according to the present disclosure is not limited to the embodiment described below.
- <<Solid
Electrolyte Electrolysis Device 100>> - The solid electrolyte electrolysis device (also referred to as an electrolysis cell, an electrolysis module) according to the present embodiment will be described with reference to
FIG. 1 . As shown inFIG. 1 , a solidelectrolyte electrolysis device 100 according to the present embodiment includes a cathode (negative electrode) 101; an anode (positive electrode) 102 that constitutes a pair of electrodes with thecathode 101; asolid electrolyte 103 interposed between thecathode 101 and theanode 102 with at least a part of thesolid electrolyte 103 being in contact with the cathode and the anode; acurrent collecting plate 104 in contact with a surface 101-2 that is opposite to a contact surface 101-1 with thesolid electrolyte 103 of thecathode 101; a supportingplate 105 in contact with a surface 102-1 that is opposite to a contact surface 102-2 with thesolid electrolyte 103 of theanode 102; and a voltage application part 106 that applies a voltage between thecurrent collecting plate 104 and the supporting plate 105 (that is, between the cathode and the anode). By a supply source and a supply device (not illustrated), CO2 in a gas phase and the supporting electrolyte H2O are supplied. Though the solidelectrolyte electrolysis device 100 illustrated inFIG. 1 is illustrated in a state where parts such as thecathode 101 and theanode 102 are separated from each other for explanation, actually, each of thecurrent collecting plate 104, thecathode 101, thesolid electrolyte 103, theanode 102, and the supportingplate 105 is bonded each other by a predetermined method and integrally configured. Each part can be removably assembled to constitute one solidelectrolyte electrolysis device 100. Hereinafter, each component will be described in detail. - <Cathode 101>
- (Reduction Reaction at Cathode 101)
- The reduction reaction at the
cathode 101 depends on the type of thesolid electrolyte 103. When a cation exchange membrane is used as thesolid electrolyte 103, reduction reactions of the following formulas (1) and (2) occur, and when an anion exchange membrane is used as the solid electrolyte, reduction reactions of the following formulas (3) and (4) occur. -
Formula 1 -
CO2+2H++2e −→CO+H2O (1) -
2H++2e −→H2 (2) -
H2O±CO2+2e −→CO+2OH− (3) -
2H2O+2e −→H2+2OH− (4) - (Basic Structure and Material of Cathode 101)
- The
cathode 101 is a gas diffusion electrode including a gas diffusion layer. The gas diffusion layer includes, for example, carbon paper or a nonwoven fabric, or a metal mesh. Examples of the electrode material of thecathode 101 include graphite carbon, glassy carbon, titanium, and SUS. The catalyst of the cathode capable of reducing CO2 to CO included in thecathode 101 contains, for example, a metal selected from silver, gold, copper, or a combination thereof. More specifically, the catalyst includes, for example, gold, a gold alloy, silver, a silver alloy, copper, a copper alloy, or a mixed metal containing any one or more of them. The type of the catalyst is not particularly limited as long as the catalyst has a function as a catalyst, and can be determined in consideration of corrosion resistance and the like. For example, when the catalyst does not contain an amphoteric metal such as Al, Sn, or Zn, corrosion resistance can be improved. The catalyst can be supported on the cathode 101 (or the electrode material) by performing a known method such as vapor deposition, deposition, adsorption, sedimentation, adhesion, welding, physical mixing, and spraying. - (Solid Base Additive 107)
- As shown in
FIG. 2 , thecathode 101 has asolid base additive 107. Thesolid base additive 107 is not particularly limited as long as thesolid base additive 107 is a base that is solid at normal temperature (25° C.), and for example, potassium hydrogencarbonate (KHCO3), sodium hydroxide (NaOH), an oxide of an alkaline earth metal, a hydroxide of an alkaline earth metal or a carbide of an alkaline earth metal {for example, magnesium oxide (MgO), magnesium hydroxide (Mg(OH)2), magnesium carbonate (MgCO3), calcium oxide (CaO), calcium hydroxide (Ca(OH)2), calcium carbonate (CaCO3), strontium oxide (SrO), strontium hydroxide (Sr(OH)2), strontium carbonate (SrCO3), barium oxide (BaO), barium hydroxide (Ba(OH)2), barium carbonate (BaCO3)}, an oxide of a rare earth metal, a hydroxide of a rare earth metal or a carbonate of a rare earth metal {for example, yttrium oxide (Y2O3) and lanthanum oxide (La2O3)}, hydrotalcite (for example, metal complex hydroacids, a carbonate, LDH, HT-CO3, HT-OH), zeolite surface-treated with a base, a molecular sieve treated with a base, or porous alumina (KF—Al2O3) surface-treated with a base is preferably used. In particular, as described in Examples described later, a weakly basic solid base additive having a small atomic number is more preferable. An oxide of an alkaline earth metal, a hydroxide of an alkaline earth metal, or a carbide of an alkaline earth metal, an oxide of a rare earth metal, a hydroxide of a rare earth metal, or a carbonate of a rare earth metal, which are water-insoluble solid base additives, is further more preferably used because they are not flowed by water in a gas or water generated by a reaction, and durability of a cathode having thesolid base additive 107 is not deteriorated. The term “water-insoluble” solid base additive refers to one having an insolubility in 100 mL of water at 20° C. of less than 10 mg. Thesolid base additive 107 is suitably present on a side of the contact surface 101-1 with thesolid electrolyte 103 of thecathode 101. The reason for such a configuration is that the interface between thecathode 101 and thesolid electrolyte 103 is a reaction site. Thesolid base additive 107 can be present as a mixture with the material of thecathode 101, or can be present in an integrated state as a compound. Thesolid base additive 107 can be supported on the cathode 101 (or electrode material) by performing a known method such as application, vapor deposition, deposition, and physical mixing. The mass per unit area of the solid base additive is not particularly limited, and is, for example, 0.1 to 10 mg/cm2, and preferably 0.1 to 6 mg/cm2. - The following mechanism of action is presumed to be the reason why the efficiency is increased when the
solid base additive 107 is used. For example, when a gas having a low concentration of CO2 of 10 to 20% such as an exhaust gas in a factory is supplied to the solidelectrolyte electrolysis device 100, CO2 is less likely to be adsorbed on the surface of thecathode 101 because of its low concentration. Thus, as shown inFIG. 2 , it is understood that by adding thesolid base additive 107 to the surface of thecathode 101, CO2 can be efficiently adsorbed locally to a place where the solid base additive is present, and CO2 reduction can be advanced. It is also understood that when a cation exchange membrane is employed as thesolid electrolyte 103, CO2 cannot be sufficiently adsorbed if the surface of thecathode 101 has a large amount of H+. In such a case, the reaction presumably proceeds when thesolid base additive 107 is present (for example, the pH is preferably controlled to pH>2). Meanwhile, when an anion exchange membrane is employed as the solid electrolyte, CO2 is adsorbed because OH− is present on the cathode surface, which is suitable for CO2 reduction. However, it is understood that when the amount of OH− is too large, adsorption occurs in a state of stable CO3 2− and the CO2 reduction reaction does not sufficiently proceed. In such a case, the CO2 reduction reaction presumably further proceeds when the weakly basicsolid base additive 107 is present (for example, the pH is preferably controlled to pH<12). In the present invention, the electrode having such a solid base additive and catalyst can be expressed as “an electrode including a catalyst; an electrode material having the catalyst; and a solid base additive provided at least on the electrode material” (in other words, an electrode including an electrode material having a catalyst and a solid base additive), or “a cathode having a catalyst and further having a solid base additive” or the like. - <
Anode 102> - (Oxidation Reaction at Anode 102)
- The oxidation reaction at the
anode 102 depends on the type of thesolid electrolyte 103. When a cation exchange membrane is used as thesolid electrolyte 103, the oxidation reaction of the following formula (5) occurs, and when an anion exchange membrane is used as thesolid electrolyte 103, the oxidation reaction of the following formulas (6) occurs. -
[Formula 2] -
2H2O→O2+4H++4e − (5) -
4OH−→O2+2H2O+4e − (6) - (Basic Structure and Material of Anode 102)
- The
anode 102 is a gas diffusion electrode including a gas diffusion layer. The gas diffusion layer includes, for example, a metal mesh. Examples of the electrode material of theanode 102 include Ir, IrO2, Ru, RuO2, Co, CoOx, Cu, CuOx, Fe, FeOx, FeOOH, FeMn, Ni, NiOx, NiOOH, NiCo, NiCe, NiC, NiFe, NiCeCoCe, NiLa, NiMoFe, NiSn, NiZn, SUS, Au, and Pt. - <
Solid Electrolyte 103> - The
solid electrolyte 103 is interposed between thecathode 101 and theanode 102 with thesolid electrolyte 103 being in contact with thecathode 101 and theanode 102. Though thesolid electrolyte 103 is not particularly limited to a polymer membrane, a cation exchange membrane or an anion exchange membrane is suitable, and an anion exchange membrane is more suitable. As the cation exchange membrane, for example, a strongly acidic cation exchange membrane in which a sulfone group is introduced into a fluororesin base, Nafion 117, Nafion 115, Nafion 212 or Nafion 350 (manufactured by DuPont), a strongly acidic cation exchange membrane in which a sulfone group is introduced into a styrene-divinylbenzene copolymer base, or NEOSEPTA CMX (manufactured by Tokuyama Soda Co., Ltd.) can be used. Examples of the anion exchange membrane include an anion exchange membrane in which a quaternary ammonium group, a primary amino group, a secondary amino group, a tertiary amino group, or two of more of these ion exchange groups are present. As specific examples, for example, NEOSEPTA (registered trademark) ASE, AHA, AMX, ACS, AFN, and AFX (manufactured by Tokuyama Corporation), SELEMION (registered trademark) AMV, AMT, DSV, AAV, ASV, AHO, AHT, and APS4 (manufactured by AGC Inc.) can be used. - <
Current Collecting Plate 104> - Examples of the
current collecting plate 104 include metal materials such as copper (Cu), nickel (Ni), stainless steel (SUS), nickel-plated steel, and brass, and among them, copper is preferable from the viewpoint of ease of processing and cost. When thecurrent collecting plate 104 is a metal material, examples of the shape of the negative electrode current collecting plate include a metal foil, a metal plate, a metal thin film, an expanded metal, a punching metal, and a foamed metal. - As shown in
FIG. 1 , thecurrent collecting plate 104 is provided with a gas supply hole 104-1 for supplying a gas and a gas collecting hole 104-2 for collecting a gas (raw material gas and produced gas) to thecathode 101. By the gas supply hole 104-1 and the gas collecting hole 104-2, the raw material gas can be uniformly and efficiently fed to thecathode 101 and the produced gas (including the unreacted raw material gas) can be exhausted. Though in this figure, one gas supply hole and one gas collecting hole are provided, the number, place, and size are not limited, and are appropriately set. - In addition, when the
current collecting plate 104 has air permeability, the gas supply hole and the gas collecting hole are not necessarily required. - When the
cathode 101 plays a role of transmitting electrons, thecurrent collecting plate 104 is not necessarily required. - <Supporting
Plate 105> - The supporting
plate 105 supports the anode. Thus, the required rigidity of the supportingplate 105 changes depending on the thickness, rigidity and the like of the anode. The supportingplate 105 needs to have electrical conductivity to receive electrons from the anode. Examples of the material of the supportingplate 105 include Ti, SUS, and Ni. - As shown in
FIG. 1 , the supportingplate 105 is provided with a gas flow path 105-1 for feeding a raw material gas (H2O and the like) to theanode 102. By the gas flow path, the raw material gas can be uniformly and efficiently fed to theanode 102. Though in this figure, eight gas flow paths are provided, the number, place, and size are not limited, and are appropriately set. - Though in the present embodiment, the
anode 102 and the supportingplate 105 are described as separate structures, theanode 102 and the supportingplate 105 can be an integrated structure (that is, theanode 102 and the supportingplate 105 can be anintegrated anode 102 having a support function). - <Voltage Application Part 106>
- As illustrated in
FIG. 1 , the voltage application part 106 plays a role of applying a voltage between thecathode 101 and theanode 102 through application of a voltage to thecurrent collecting plate 104 and the supportingplate 105. As described above, thecurrent collecting plate 104 is a conductor, and thus feeds electrons to thecathode 101, while the supportingplate 105 is also a conductor, and thus receives electrons from theanode 102. When thecurrent collecting plate 104 is not necessary as described above, a voltage is applied between thecathode 101 and the supportingplate 105. To apply an appropriate voltage, a control unit (not illustrated) can be electrically connected to the voltage application part 106. - <Reaction Gas Supply Part>
- The solid
electrolyte electrolysis device 100 in the present disclosure can be provided with a reaction gas supply part (not illustrated) outside the solidelectrolyte electrolysis device 100. That is, it is sufficient that CO2, a reaction gas, is supplied to the surface 101-2, and the reaction gas can be supplied from the reaction gas supply part to the gas supply hole 104-1 via a pipe (not illustrated) or the like, or the reaction gas can be blown to the surface 104-A of thecurrent collecting plate 104 opposite to the contact surface 104-B with thecathode 101. A factory exhaust gas exhausted from a factory is suitably used as the reaction gas from an environmental viewpoint. - <<CO Production Method>>
- A method for producing CO using the solid
electrolyte electrolysis device 100 will be described with reference toFIG. 3 . - <Reaction Gas Supply Step S301>
- CO2, a reaction gas, as a raw material is first supplied to the solid
electrolyte electrolysis device 100 in a gas phase by a reaction gas supply part (not illustrated). At this time, CO2 is supplied to thecathode 101 through the gas supply hole 104-1 provided in the current collecting plate 104 (S301). - <CO, H2 Production Step S302>
- Then, the CO2 supplied to the
cathode 101 undergoes reduction reactions on the surface of the cathode 101: when a cation exchange membrane is used as thesolid electrolyte 103, the reduction reactions of the formulas (1) and (2) described above occur, and when an anion exchange membrane is used as the solid electrolyte, the reduction reactions of the formulas (3) and (4) described above occur. Thereby a synthetic gas containing at least CO and H2 is produced (S302). - <Produced Gas Collecting Step S303>
- Then, the produced synthetic gas containing CO and H2 is sent to a gas collecting device (not illustrated) through a gas collecting hole 104-2 provided in the
current collecting plate 104, and is collected for each predetermined gas (S303). - <<Use>>
- As shown in
FIG. 4 , for example, by using CO2 gas exhausted from a factory as a raw material and utilizing renewable energy of a solar cell or the like to the voltage application part 106 in the solid electrolyte electrolysis device according to the present disclosure as described above, a synthetic gas containing at least CO and H2 can be produced at a desired production rate. From the synthetic gas thus produced, fuel base materials and chemical raw materials can be produced by techniques such as FT synthesis or methanation. - Hereinafter, specific description will be given with reference to Examples and Comparative Examples in which the present embodiments described above is used.
- The solid
electrolyte electrolysis device 100 shown inFIG. 1 was assembled (supporting plate=Ti plate of 3 mm), and the synthetic gas production results for each cathode catalyst and solid base additive material used were shown in Table 1 to 3. -
TABLE 1 Effect of base addition on Ag catalyst (when anion exchange membrane is used) Partial Partial current current density density Material of FE (%) FE (%) (mA/cm2) (mA/cm2) solid base of H2 of CO of H2 of CO Judgement Judgement No addition 3.19 57.62 0.33 6.05 — Criteria 1 Example 1 KHCO3 26.87 54.28 3.07 6.2 Δ Example 2 MgO 20.85 77.19 2.72 10.08 ⊚ Example 3 Sr (OH)3 4.15 54.61 0.71 9.28 ⊚ Example 4 BaCO3 26.36 58.17 3.81 8.25 ◯ Example 5 Y2O3 23.51 58.78 3.43 8.58 ◯ Example 6 La2O3 8.4 64.09 0.88 7.57 ◯ - Table 1 shows experimental data in the solid
electrolyte electrolysis device 100 when an anion exchange membrane was used as thesolid electrolyte 103, silver (Ag) was used as a cathode catalyst, and each solid base additive was added to thecathode 101. - For experimental conditions in Table 1, a platinum mesh was used as an anode material, carbon paper on which Ag was applied to form a thin film was used as a cathode material, a saturated aqueous KHCO3 solution was used as an anode electrolysis solution, and an applied voltage applied to the
current collecting plate 104 and the supportingplate 105 was 3.5 V. The solid base additive was added so that the mass per unit area would be about 5.33 mg/cm2. - The evaluation of the experimental results was performed as follows: the measured value of the partial current density (mA/cm2) of CO when no solid base additive was added was used as a judgment criteria, a symbol of Δ was given to a result in which an improvement of 2% or more was observed, a symbol of ∘ was given to a result in which an improvement of 10% or more was observed, and a symbol of ⊙ was given to a result in which an improvement of 50% or more was observed compared to the measured value, and those conditions that had such results were judged to be capable of improving the production efficiency of a synthetic gas (particularly, CO). The partial current density is a physical quantity representing the amount of electrons used to produce a specific compound, and the larger the value, the larger the production amount.
- In Judgment Criteria 1 in which no solid base additive was added (no addition case), the partial current density of CO was 6.05 mA/cm2. The Faraday Efficiency (FE) of H2 was 3.19%, the FE of CO was 57.62%, and the partial current density of H2 was 0.33 mA/cm2. In this experiment in which an anion exchange membrane was used, these measured values were used as reference values for judgement.
- In Example 1 in which KHCO3 was added, the FE of H2 was 26.87%, the FE of CO was 54.28%, the partial current density of H2 was 3.07 mA/cm2, and the partial current density of CO was 6.2 mA/cm2. Thus, in Example 1, the partial current density of CO increased by about 2.5% compared to that of Judgment Criteria 1, and the production efficiency of CO was not significantly improved. This is presumably because KHCO3 is water-soluble and was dissolved in H2O produced by the reaction in the cathode, so that a sufficient base effect was not obtained.
- Then, in Example 2 in which MgO was added, the FE of H2 was 20.85%, the FE of CO was 77.19%, the partial current density of H2 was 2.72 mA/cm2, and the partial current density of CO was 10.08 mA/cm2. Thus, in Example 2, the partial current density of CO increased by about 66.6% compared to that of Judgment Criteria 1, and the production efficiency of CO was successfully improved.
- Then, in Example 3 in which Sr(OH)2 was added, the FE of H2 was 4.15%, the FE of CO was 54.61%, the partial current density of H2 was 0.71 mA/cm2, and the partial current density of CO was 9.28 mA/cm2. Thus, in Example 3, the partial current density of CO increased by about 53.4% compared to that of Judgment Criteria 1, and the production efficiency of CO was successfully improved.
- Then, in Example 4 in which BaCO3 was added, the FE of H2 was 26.36%, the FE of CO was 58.17%, the partial current density of H2 was 3.81 mA/cm2, and the partial current density of CO was 8.25 mA/cm2. Thus, in Example 4, the partial current density of CO increased by about 36.4% compared to that of Judgment Criteria 1, and the production efficiency of CO was successfully improved.
- Then, in Example 5 in which Y2O3 was added, the FE of H2 was 23.51%, the FE of CO was 58.78%, the partial current density of H2 was 3.43 mA/cm2, and the partial current density of CO was 8.58 mA/cm2. Thus, in Example 5, the partial current density of CO increased by about 41.8% compared to that of Judgment Criteria 1, and the production efficiency of CO was successfully improved.
- Then, in Example 6 in which La2O3 was added, the FE of H2 was 8.4%, the FE of CO was 64.09%, the partial current density of H2 was 0.88 mA/cm2, and the partial current density of CO was 7.57 mA/cm2. Thus, in Example 6, the partial current density of CO increased by about 25.1% compared to that of Judgment Criteria 1, and the production efficiency of CO was successfully improved.
-
TABLE 2 Effect of base addition on Cu and Ag catalyst (when cation exchange membrane is used) Partial Partial current current Production Negative density density activity electrode Material of (mA/cm2) (mA/cm2) (μmol/h) catalyst solid base of H2 of CO of CO Judgement Judgement Cu No addition 711 0 0 — Criteria 2 Example 6 Cu KHCO3 653 2.4 0.2 ◯ Example 7 Cu NaOH 635 16.7 1.4 ◯ Example 8 Cu La2O3 622 66.7 5.6 ⊚ Judgement Ag No addition 763 0 0 — Criteria 3 Example 9 Ag La2O3 610 32.2 2.7 ◯ - Table 2 shows experimental data in the solid
electrolyte electrolysis device 100 when a cation exchange membrane (Nafion 117) was used as thesolid electrolyte 103, copper (Cu) or (Ag) was used as a cathode catalyst, and each solid base additive was added to thecathode 101. - For experimental conditions in Table 2, a platinum mesh was used as an anode material, carbon paper on which Ag was applied to form a thin film was used as a cathode material, 0.1 mol/L of sulfuric acid was used as an anode electrolysis solution, and an applied voltage applied to the
current collecting plate 104 and the supportingplate 105 was 5 V. The solid base additive was added so that the mass per unit area would be about 5.33 mg/cm2. - The evaluation of the experimental results was performed as follows: the measured value of the production amount (μmol/h) of CO per hour when the cathode catalyst was Cu and no solid base additive was added was used as Judgment Criteria 2, the measured value of the production amount (μmol/h) of CO per hour when the cathode catalyst was Ag and no solid base additive was added was used as Judgment Criteria 3, and those conditions that had results of larger production of CO than the measured values were judged to be capable of improving the production efficiency of CO.
- In Judgment Criteria 2 in which Cu was used as a cathode catalyst and no solid base additive was added (no addition case), the production activity of CO was 0 μmol/h.
- Then, in Example 6 in which Cu was used as a cathode catalyst and KHCO3 was added, the production activity of CO was 0.2 μmol/h, and the production efficiency of CO was successfully improved.
- Then, in Example 7 in which Cu was used as a cathode catalyst and NaOH was added, the production activity of CO was 1.4 μmol/h, and the production efficiency of CO was successfully improved.
- Then, in Example 8 in which Cu was used as a cathode catalyst and La2O3 was added, the production activity of CO was 5.6 μmol/h, and the production efficiency of CO was successfully improved.
- Then, in Judgment Criteria 3 in which Ag was used as a cathode catalyst and no solid base additive was added (no addition case), the production activity of CO was 0 μmol/h.
- Then, in Example 9 in which Ag was used as a cathode catalyst and La2O3 was added, the production activity of CO was 2.7 μmol/h, and the production efficiency of CO was successfully improved.
- Table 3 shows experimental data in the solid electrolyte electrolysis device when an anion exchange membrane was used as the solid electrolyte, a cathode catalyst (Cu—In) was used, and a MgO solid base additive was added to the cathode.
-
TABLE 3 Partial Partial current current density density Solid FE (%) FE (%) (mA/cm2) (mA/cm2) Catalyst base of H2 of CO of H2 of CO Judgement Judgement CU-In No addition 32 16 4.49 1.89 — Criteria 3 Example 1 CU-In MgO 56 59 4.50 2.40 ∘ - For experimental conditions, a platinum mesh was used as an anode material, carbon paper on which a thin film of Cu—In was formed in a surface region was used as a cathode material, a saturated aqueous KHCO3 solution was used as an anode electrolysis solution, and a voltage applied to the current collecting plate and the supporting plate were 3.5 V. The solid base additive was added in an amount of 5 mg/cm2.
- For a Cu—In catalyst, when a MgO solid base additive was added, the partial current density of CO increased by 26% compared to no addition case. The effect of base addition is sufficient.
Claims (17)
1. An electrode, comprising:
a catalyst suitable to produce at least carbon monoxide by a reduction reaction;
an electrode material comprising the catalyst; and
a solid base additive provided at least on the electrode material.
2. The electrode of claim 1 , wherein the electrode is a cathode.
3. The electrode of claim 1 , wherein the solid base additive is an oxide of an alkaline earth metal, a hydroxide of an alkaline earth metal, a carbide of an alkaline earth metal, an oxide of a rare earth metal, a hydroxide of a rare earth metal, or a carbonate of a rare earth metal.
4. A solid electrolyte electrolysis device, comprising:
a cathode comprising a catalyst suitable to produce at least carbon monoxide by a reduction reaction;
an anode that constitutes a pair of electrodes with the cathode;
a solid electrolyte interposed between the cathode and the anode with the solid electrolyte being in contact with the cathode and the anode; and
a voltage application part configured to apply a voltage between the cathode and the anode,
wherein the cathode further comprises a solid base additive.
5. The device of claim 4 , wherein the solid base additive is present on a side of a contact surface with the solid electrolyte of the cathode.
6. The device of claim 4 , wherein the solid base additive is an oxide of an alkaline earth metal, a hydroxide of an alkaline earth metal, a carbide of an alkaline earth metal, an oxide of a rare earth metal, a hydroxide of a rare earth metal, or a carbonate of a rare earth metal.
7. The device of claim 4 , wherein the solid electrolyte is an anion exchange membrane.
8. The device of claim 4 , wherein the solid electrolyte is a cation exchange membrane.
9. A synthetic gas production method, comprising:
supplying a reaction gas to a solid electrolyte electrolysis device comprising a cathode comprising a catalyst, an anode that constitutes a pair of electrodes with the cathode, a solid electrolyte interposed between the cathode and the anode with the solid electrolyte being in contact with the cathode and the anode, and a voltage application part configured to apply a voltage between the cathode and the anode, wherein the cathode further comprises a solid base additive;
producing a synthetic gas comprising carbon monoxide by a reduction reaction caused by the reaction gas being brought into contact with the cathode; and
collecting the synthetic gas.
10. The electrode of claim 2 , wherein the solid base additive is an oxide of an alkaline earth metal, a hydroxide of an alkaline earth metal, a carbide of an alkaline earth metal, an oxide of a rare earth metal, a hydroxide of a rare earth metal, or a carbonate of a rare earth metal.
11. The device of claim 5 , wherein the solid base additive is an oxide of an alkaline earth metal, a hydroxide of an alkaline earth metal, a carbide of an alkaline earth metal, an oxide of a rare earth metal, a hydroxide of a rare earth metal, or a carbonate of a rare earth metal.
12. The device of claim 5 , wherein the solid electrolyte is an anion exchange membrane.
13. The device of claim 6 , wherein the solid electrolyte is an anion exchange membrane.
14. The device of claim 11 , wherein the solid electrolyte is an anion exchange membrane.
15. The device of claim 5 , wherein the solid electrolyte is a cation exchange membrane.
16. The device of claim 6 , wherein the solid electrolyte is a cation exchange membrane.
17. The device of claim 11 , wherein the solid electrolyte is a cation exchange membrane.
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