WO2014185068A1 - 酸素を発生させる方法、水の電気分解装置および陽極 - Google Patents
酸素を発生させる方法、水の電気分解装置および陽極 Download PDFInfo
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- WO2014185068A1 WO2014185068A1 PCT/JP2014/002543 JP2014002543W WO2014185068A1 WO 2014185068 A1 WO2014185068 A1 WO 2014185068A1 JP 2014002543 W JP2014002543 W JP 2014002543W WO 2014185068 A1 WO2014185068 A1 WO 2014185068A1
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- 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
- C25B11/073—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material
- C25B11/075—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of a single catalytic element or catalytic compound
- C25B11/081—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of a single catalytic element or catalytic compound the element being a noble metal
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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
- C25B1/02—Hydrogen or oxygen
- C25B1/04—Hydrogen or oxygen by electrolysis of water
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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
- C25B11/073—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material
- C25B11/091—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds
- C25B11/093—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds at least one noble metal or noble metal oxide and at least one non-noble metal oxide
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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
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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
- C25B9/70—Assemblies comprising two or more cells
- C25B9/73—Assemblies comprising two or more cells of the filter-press type
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- 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 method for generating oxygen and a water electrolysis apparatus.
- Patent Document 1 has the chemical formula ABO 2 (where A represents platinum, palladium, silver, or cobalt, and B represents chromium, iron, cobalt, rhodium, aluminum, gadolinium, scandium, indium, thallium, lead, ruthenium, Or a method for generating chlorine by electrolyzing sodium chloride using an anode having a delafossite compound represented on the surface thereof.
- Patent Document 1 does not disclose any method for generating oxygen.
- the present inventors electrolyzed water to generate oxygen using various copper delafossite compounds. As a result, almost all copper delafossite compounds were not suitable for water electrolysis due to their large overvoltage.
- An object of the present invention is to provide a method for efficiently generating oxygen by electrolysis of water using a copper delafossite compound as an anode.
- the object of the present invention is also to provide a water electrolysis apparatus suitable for the method.
- the present invention is a method for generating oxygen comprising the following steps: (A) preparing a water electrolysis apparatus comprising: container, Power supply, anode, The cathode, and the aqueous electrolyte solution, where The anode and the cathode are in contact with the aqueous electrolyte solution;
- the anode has a copper rhodium delafossite compound represented by the chemical formula CuRhO 2 ;
- the copper rhodium delafossite compound is in contact with the aqueous electrolyte solution
- the present invention provides a method for efficiently generating oxygen by electrolysis of water using a copper delafossite compound as an anode.
- the present invention also provides a water electrolysis apparatus suitable for the method.
- FIG. 1 shows a schematic diagram of a water electrolysis apparatus 100 according to Embodiment 1.
- FIG. FIG. 2 is a schematic diagram of a thin film type electrolytic cell.
- Figure 3 is a graph showing the occupation numbers of the calculation results of the e g orbitals in B sites of the copper Delafossite compound.
- FIG. 4 is a graph showing the results of X-ray diffraction measurement.
- FIG. 5 is a graph showing current-potential characteristics measured in Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4.
- FIG. 6 is a graph showing current-potential characteristics measured in Example 1, Reference Example 1, Reference Example 2, and Reference Example 3.
- FIG. 7A is a diagram showing a scanning electron microscope image of the anode substrate according to Example 1 before the potential sweep is started.
- FIG. 7B is a diagram showing a scanning electron microscope image of the anode substrate according to Example 1 after the potential sweep was repeated 1000 times.
- FIG. 8 is a graph showing current-potential characteristics in Example 1 before and after the potential sweep is repeated 1000 times.
- FIG. 9A is a diagram showing a scanning electron microscope image of the anode substrate according to Comparative Example 4 before the potential sweep is started.
- FIG. 9B is a diagram showing a scanning electron microscope image of the anode substrate according to Comparative Example 4 after the potential sweep was repeated 10 times.
- FIG. 10 is a graph showing current-potential characteristics in Comparative Example 4 before and after the potential sweep is repeated 10 times.
- FIG. 1 shows a schematic diagram of a water electrolysis apparatus 100 according to Embodiment 1.
- FIG. A water electrolysis apparatus 100 according to Embodiment 1 includes a container 11, an anode 12, a cathode 13, and a power source 14.
- An electrolyte aqueous solution 15 is stored inside the container 11.
- An example of the aqueous electrolyte solution 15 is an alkaline aqueous solution such as potassium hydroxide or sodium hydroxide.
- electrolyte contained in the aqueous electrolyte solution 15 are sulfuric acid, nitric acid, or perchloric acid. More specifically, examples of the electrolyte cation contained in the aqueous electrolyte solution 15 are protons, alkali metal ions, or alkaline earth metal ions.
- Examples of the anion of the electrolyte contained in the electrolyte aqueous solution 15 are a hydroxide ion represented by the chemical formula OH ⁇ , a sulfate ion represented by the chemical formula SO 4 2 ⁇ , a nitrate ion represented by the chemical formula NO 3 ⁇ , or a chemical formula This is a perchlorate ion represented by ClO 4 ⁇ .
- Halide ions represented by the chemical formula F ⁇ , Cl ⁇ , Br ⁇ , or I ⁇ are excluded from the anion of the electrolyte contained in the aqueous electrolyte solution 15.
- the electrolyte aqueous solution 15 contains halide ions, halogen is generated on the anode 12 instead of oxygen.
- An example of the electrolyte contained in the aqueous electrolyte solution 15 is a salt composed of such cations and anions.
- yet another example of the electrolyte contained in the aqueous electrolyte solution is sodium sulfate, sodium nitrate, or potassium perchlorate.
- the anode 12 and the cathode 13 are disposed inside the container 11 so as to be in contact with the electrolyte aqueous solution 15.
- the anode 12 and the cathode 13 are electrically connected to a power source 14 described later. Oxygen is generated on the anode 12. Hydrogen is generated on the cathode 13.
- the anode 12 has a copper rhodium delafossite compound.
- the anode 12 has a copper rhodium delafossite compound on its surface so that oxygen is generated on the surface of the copper rhodium delafossite compound contained in the anode 12.
- the copper rhodium delafossite compound is represented by the chemical formula CuRhO 2 .
- the copper rhodium delafossite compound means an oxide having a delafossite compound structure in which the A site is copper and the B site is rhodium.
- Copper rhodium delafossite compound has high chemical stability. Therefore, the copper rhodium delafossite compound is hardly decomposed even when used in a wide pH range.
- the method for synthesizing the copper rhodium delafossite compound is not limited.
- An example of a method for synthesizing the copper rhodium delafossite compound is a solid phase reaction method, a hydrothermal synthesis method, or a sputtering method.
- the anode 12 can be formed of a conductive substrate carrying a copper rhodium delafossite compound.
- the method for supporting the copper rhodium delafossite compound is not limited.
- a slurry containing a synthesized copper rhodium delafossite compound is prepared, and then the slurry is applied to a conductive substrate, and the copper rhodium delafossite compound is supported on the conductive substrate.
- the slurry may contain conductive carbon particles, tin oxide, an additive for improving dispersibility, and / or a material for suppressing aggregation of bubbles generated during electrolysis. These are not factors that reduce the catalytic effect of the copper rhodium delafossite compound.
- the conductive substrate can have various shapes such as a plate, a rod, or a mesh.
- the material of the conductive substrate is desirably a material that can maintain its conductivity even when exposed to an oxidizing atmosphere.
- An example of the material of the conductive substrate is a valve metal or carbon.
- the valve metal means a metal having a surface on which a nonconductive film is formed when exposed to an acid. Examples of valve metals are titanium, aluminum, chromium, or alloys thereof.
- the anode 12 does not need to have a conductive substrate.
- Such an anode 12 can be obtained, for example, by pressing or sintering copper rhodium delafossite compound particles.
- Such an anode 12 contains a conductive carbon material for improving conductivity, a flux material for improving adhesion between particles, and / or a material for suppressing aggregation of bubbles generated during electrolysis. obtain.
- the anode 12 is in contact with the aqueous electrolyte solution 15.
- the copper rhodium delafossite compound contained in the anode 12 is in contact with the aqueous electrolyte solution 15.
- the copper rhodium delafossite compound contacts the electrolyte aqueous solution 15
- only a part of the anode 12 can contact the electrolyte aqueous solution 15.
- the cathode 13 is formed from a conductive material. Specifically, the surface of the cathode 13 is formed from a conductive material. Examples of suitable conductive materials are platinum or nickel compounds that have a low overvoltage to generate hydrogen. As long as the conductive substance is not decomposed in the electrolyte aqueous solution 15, the material of the conductive substance is not limited.
- the cathode 13 is in contact with the electrolyte aqueous solution 15. Specifically, the conductive substance contained in the cathode 13 is in contact with the aqueous electrolyte solution 15. As long as the conductive substance is in contact with the aqueous electrolyte solution 15, only a part of the cathode 13 can be in contact with the aqueous electrolyte solution 15.
- the power source 14 is used to apply a predetermined potential difference between the anode 12 and the cathode 13.
- a predetermined potential difference is applied between the anode 12 and the cathode 13 using the power source 14 to electrolyze water contained in the aqueous electrolyte solution. It is desirable to apply a potential difference of 1.6 volts or more and 4.0 volts or less.
- An example of the power source 14 is a potentiostat or a battery.
- the water electrolysis apparatus 100 has a diaphragm 16 between the anode 12 and the cathode 13.
- the diaphragm 16 divides the interior of the container 11 into a first chamber in which the anode 12 is located and a second chamber in which the cathode 13 is located.
- diaphragm 16 examples include a porous ceramic plate such as an unglazed plate, a porous polymer membrane such as a polypropylene film, or an ion exchange membrane such as Nafion (registered trademark).
- the diaphragm 16 is installed so that oxygen generated on the anode 12 does not mix with hydrogen generated on the cathode 13. In the absence of the diaphragm 16, there is no problem with water electrolysis, but oxygen generated on the anode 12 can move to the cathode 13. The oxygen that has moved to the cathode 13 is converted into water. As a result, the oxygen generation efficiency decreases. In order to suppress such a reverse reaction, it is desirable that the diaphragm 16 is provided in the water electrolysis apparatus 100.
- the anode 12, the diaphragm 16, and the cathode 13 are arranged at intervals.
- the water electrolysis apparatus 100 can be composed of an integral electrolysis cell in which the anode 12 and the cathode 13 are in close contact with the front and back surfaces of the diaphragm 16, respectively.
- FIG. 2 shows a thin film type electrolytic cell which is another example of the water electrolysis apparatus.
- the thin-film electrolytic cell shown in FIG. 2 includes an electrolyte membrane 17, an anode 12 formed on the surface of the electrolyte membrane 17, and a cathode 13 formed on the back surface of the electrolyte membrane 17.
- the thin film electrolytic cell includes an electrolyte membrane 17 instead of the container 11 of the water electrolysis apparatus 100.
- An example of the electrolyte 17 is an ion exchange membrane or a ceramic solid electrolyte membrane. Examples of the ion exchange membrane are cation exchange type Nafion (registered trademark), Selemion (registered trademark), or an anion exchange membrane (for example, manufactured by Tokuyama Corporation).
- Ceramic solid electrolyte membranes are zirconia-based ceramics such as yttria stabilized zirconia (YSZ) or scandia stabilized zirconia (ScSZ).
- the thin film type electrolytic cell including the electrolyte membrane 17 formed of an ion exchange membrane is a polymer electrolyte membrane (hereinafter referred to as “PEM”) type electrolytic cell.
- PEM polymer electrolyte membrane
- the electrolytic cell including the electrolyte membrane 17 formed of a ceramic solid electrolyte is a solid electrolyte type electrolytic cell.
- the solid electrolyte type electrolytic cell is also a high temperature steam type electrolytic cell.
- a metal oxide having a delafossite structure is generally represented by the chemical formula ABO 2 .
- Patent document 1 is disclosing the anode containing a delafossite compound. However, it does not disclose that the energy efficiency varies depending on the material of the B site.
- the present inventors diligently studied the possibility that the energy efficiency of a material having a delafossite structure in which the A site is copper differs depending on the material of the B site.
- Non-Patent Document 1 an overvoltage occupation numbers of electrons e g orbitals in the transition metal B sites contained in the perovskite oxide represented by the chemical formula ABO 3 is to be closer to 1, the need to generate oxygen becomes lower.
- the properties of the oxide oxygen evolution catalyst can be related to the electronic structure of the oxide.
- the present inventors predicted that the copper delafossite compound also has a similar relationship, and calculated the electronic state of the copper delafossite compound based on density functional theory.
- Figure 3 shows the occupation numbers of the calculation results of the e g orbitals in B sites of the copper Delafossite compound.
- the vertical axis of FIG. 3 represents the occupation numbers of e g orbitals and the horizontal axis represents the material of the B site.
- the A site is copper
- the B site is aluminum, gallium, iron, yttrium, and rhodium.
- the number of occupied B sites has the following relationship (II).
- the overvoltage necessary for generating oxygen is expected to decrease in the order of rhodium, iron, aluminum, yttrium, and gallium. Since the iron occupancy value is the same as for rhodium, the overvoltage required to generate oxygen when iron is used is expected to be the same as when rhodium is used.
- Example 1 described below with Comparative Example 2
- the present inventors have found that the copper rhodium delafossite compound has a much lower overvoltage than the copper iron delafossite compound. It was.
- the overvoltage of the copper rhodium delafossite compound was thought to be similar to the overvoltage of the copper iron delafossite compound, but actually, from the copper rhodium delafossite compound
- the inventors have found that when the anode formed is used, water is electrolyzed with a much lower overvoltage, i.e. very good energy efficiency, compared to the copper iron delafossite compound.
- Example 1 As apparent from comparison of Example 1 described later with Comparative Examples 1 to 4, by using the anode 12 having a copper rhodium delafossite compound, water can be produced with a low overvoltage, that is, excellent energy efficiency. Electrolyzed.
- the water electrolysis apparatus 100 including the anode 12 formed from the copper rhodium delafossite compound has the same energy efficiency as the water electrolysis apparatus including the anode formed from cobalt oxide Co 3 O 4 having high energy efficiency. See Example 1 and Reference Example 2.
- the present inventors have also found that when a copper delafossite compound other than the copper rhodium delafossite compound is used, the overvoltage necessary for the generation of oxygen by electrolysis of water is high. See Comparative Examples 1 to 4.
- Example 1 (Preparation of anode 12)
- the anode 12 according to Example 1 was manufactured by supporting a copper rhodium delafossite compound on a conductive carbon substrate.
- a copper rhodium delafossite compound was prepared by a solid phase reaction method.
- cuprous oxide represented by the chemical formula Cu 2 O obtained from Wako Pure Chemical Industries, Ltd., 1.17 grams
- rhodium oxide (III) represented by the chemical formula Rh 2 O 3 obtained from Yakuhin Kogyo Co., Ltd., 2.0 grams
- the mixture was supplied to the tablet press. The mixture was then pressed at a pressure of 40 MPa and the tablets that obtained tablets containing cuprous oxide and rhodium oxide had a diameter of 25 millimeters.
- the tablets were baked in a muffle furnace (available from Fulltech Co., Ltd., trade name: FT-101FMW) at a temperature of 1050 degrees Celsius for 12 hours to obtain a baked product.
- the fired product was pulverized in an agate mortar. In this way, particles of a copper rhodium delafossite compound were obtained.
- the obtained copper rhodium delafossite compound particles were subjected to X-ray diffraction using an X-ray diffractometer (obtained from Panalical, X'Pert PRO MPD, target: Cu, acceleration voltage: 45 kV).
- FIG. 4 shows the results of X-ray diffraction measurement.
- the diffraction angle and relative intensity of the peak shown in FIG. 4 were in good agreement with the diffraction angle and relative intensity of the peak determined from the lattice constant of the copper rhodium delafossite compound taught in Non-Patent Document 2. Therefore, the obtained particles were identified as a copper rhodium delafossite compound.
- Copper rhodium delafossite compound particles (60 milligrams) were dispersed in 2 milliliters of pure water to prepare a slurry.
- HPG substrate An isotropic electrographite having an effective reaction area of 0.28 square centimeters (hereinafter referred to as “HPG substrate”, obtained from Toyo Tanso Co., Ltd., trade name: HPG-59) was applied with ultrasonic waves in acetone. The HPG substrate was washed. Next, ultrasonic waves were applied to the HPG substrate in ethanol, and the HPG substrate was washed once more.
- the obtained anode substrate was attached as a working electrode to a rotating disk electrode attachment (manufactured by Nisatsu Kogyo Co., Ltd.) using a cylindrical cap.
- a reversible hydrogen electrode (hereinafter referred to as “RHE”) was used as a reference electrode.
- a platinum electrode was used as the counter electrode.
- As the electrolytic solution an aqueous potassium hydroxide solution having a concentration of 1 mol / L was used. The potential was swept with a potentiostat (available from ALS Co., Ltd., trade name: ALS-760C), and current-potential characteristics were measured.
- Curves (a) in FIGS. 5 and 6 are current-potential characteristics according to Example 1 at a rotational speed of 2000 rpm.
- the overvoltage was defined by the following formula (III).
- EPD1 (volts vs. RHE) ⁇ 1.23 (volts vs. RHE) (III)
- EPD1 represents a potential difference between the reference electrode and the working electrode when a current of 5 mA / cm 2 flows between the counter electrode and the working electrode.
- the anode according to Example 1 had a potential difference EPD1 of 1.62 volts. Therefore, the anode according to Example 1 had an overvoltage of 0.39 volts.
- FIG. 7A is a scanning electron microscope image of the anode substrate according to Example 1 before the potential sweep is started. Using a potentiostat, the potential sweep was repeated 1000 times.
- FIG. 7B is a scanning electron microscope image of the anode substrate according to Example 1 after the potential sweep was repeated 1000 times.
- FIG. 8 is a graph showing current-potential characteristics in Example 1 before and after the potential sweep is repeated 1000 times. As can be understood from FIGS. 7A, 7B, and 8, the anode substrate was not deteriorated. On the contrary, the current-potential characteristics improved after the potential sweep was repeated 1000 times. In other words, after a potential sweep was repeated 1000 times, a higher current density was obtained using a smaller voltage.
- a copper aluminum delafossite compound represented by the chemical formula CuAlO 2 was prepared as follows and its overvoltage was calculated.
- Cupric oxide represented by the chemical formula CuO obtained from High Purity Chemical Laboratory, 6.56 grams
- aluminum oxide represented by the chemical formula Al 2 O 3 obtained from High Purity Chemical Laboratory, 4 .20 grams
- the obtained tablets were placed on a firing boat, and then a firing board having the tablets was placed in a ring furnace (trade name: FKS, manufactured by Fukada Electric Manufacturing Co., Ltd.). After substituting with nitrogen at a flow rate of 200 sccm per hour, the tablets were fired at a firing temperature of 1100 degrees Celsius at a nitrogen flow rate of 50 sccm for 10 hours to obtain a fired product.
- the fired product was pulverized in an agate mortar to obtain particles of a copper aluminum delafossite compound.
- cuprous oxide (5.84 grams) represented by the chemical formula Cu 2 O was used to obtain particles of the same copper aluminum delafossite compound.
- a curve (b) in FIG. 5 is a current-potential characteristic of the anode containing the copper aluminum delafossite compound according to Comparative Example 1.
- the anode according to Comparative Example 1 had a potential difference EPD1 of 1.92 volts. Therefore, the anode according to Comparative Example 1 had an overvoltage of 0.69 volts.
- Cuprous oxide represented by the chemical formula Cu 2 O obtained from Wako Pure Chemical Industries, Ltd., 3.50 grams
- iron oxide represented by the chemical formula Fe 2 O 3 obtained from High Purity Chemical Laboratory, 3.99 g
- a fired product was obtained from the tablet using a ring furnace, as in Comparative Example 1, except that the firing temperature was 1000 degrees Celsius.
- the fired product was pulverized in an agate mortar to obtain particles of a copper iron delafossite compound represented by the chemical formula CuFeO 2 .
- Curve (c) in FIG. 5 is a current-potential characteristic of the anode containing the copper iron delafossite compound according to Comparative Example 2.
- EPD1 potential difference
- Cupric oxide represented by the chemical formula CuO obtained from High Purity Chemical Laboratory, Inc., 7.90 grams
- yttrium oxide represented by the chemical formula Y 2 O 3 (obtained from High Purity Chemical Laboratory, Inc., 11 .29 grams) was ground and mixed in an agate mortar to obtain a mixture.
- a tablet containing cupric oxide and yttrium oxide was obtained.
- a fired product was obtained from the obtained tablet using an annular furnace, as in Comparative Example 1, except that the firing temperature was 1000 degrees Celsius.
- the obtained fired product was pulverized in an agate mortar to obtain copper yttrium oxide particles represented by the chemical formula Cu 2 Y 2 O 5 .
- the obtained copper yttrium oxide particles were supplied again to the tablet press. The particles were then pressed at a pressure of 40 MPa to obtain tablets containing copper yttrium oxide. Except that the firing temperature was 1190 degrees Celsius, a fired product was obtained from the obtained tablet using a ring furnace in the same manner as in Comparative Example 1. The obtained fired product was pulverized in an agate mortar to obtain particles of a copper yttrium delafossite compound represented by the chemical formula CuYO 2 .
- Example 2 As in Example 1, an anode containing copper yttrium delafossite compound particles was prepared, and its oxygen generation characteristics were evaluated.
- a curve (d) in FIG. 6 is a current-potential characteristic of the anode containing the copper yttrium delafossite compound according to Comparative Example 3.
- the anode according to Comparative Example 3 had a potential difference EPD1 of 2.00 volts. Therefore, the anode according to Comparative Example 3 had an overvoltage of 0.77 volts.
- Cupric oxide represented by the chemical formula CuO obtained from High Purity Chemical Laboratory, Inc., 799 grams
- gallium trioxide represented by the chemical formula Ga 2 O 3 obtained from High Purity Chemical Laboratory, 9.37 grams
- Example 1 a tablet containing cupric oxide and gallium trioxide was obtained.
- a fired product was obtained from the obtained tablet using an annular furnace, as in Comparative Example 1, except that the firing temperature was 1000 degrees Celsius.
- the obtained fired product was pulverized in an agate mortar to obtain particles of a copper gallium delafossite compound represented by the chemical formula CuGaO 2 .
- cuprous oxide (7.18 grams) represented by the chemical formula Cu 2 O was used to obtain particles of the same copper gallium delafossite compound.
- an anode containing copper gallium delafossite compound particles was prepared and its oxygen generation characteristics were evaluated.
- the current flowing between the counter electrode and the working electrode increased as the number of sweeps using the potentiostat increased. After the sweep was repeated 10 times, the current was saturated.
- Curve (e) in FIG. 5 is the current-potential characteristic of the electrode according to Comparative Example 4 after the current is saturated. After the current was saturated, the anode according to Comparative Example 4 was observed using an electron microscope. As a result, a part of the copper gallium oxide crystal seemed to be eluted. Therefore, it was considered that the anode according to Comparative Example 4 was deteriorated due to the sweep using the potentiostat.
- FIG. 9A is a scanning electron microscope image of the anode substrate according to Comparative Example 4 before the potential sweep is started. The potential sweep was repeated 10 times using a potentiostat.
- FIG. 9B is a scanning electron microscope image of the anode substrate according to Comparative Example 4 after the potential sweep was repeated 10 times and the current was saturated.
- FIG. 10 is a graph showing current-potential characteristics in Comparative Example 4 before and after the potential sweep is repeated 10 times. As understood from FIGS. 9A, 9B, and 10, the anode substrate was deteriorated. Furthermore, as seen in FIG. 10, in Comparative Example 4, a cathode current due to reprecipitation was observed.
- Cupric oxide represented by the chemical formula CuO obtained from High Purity Chemical Laboratory Co., Ltd., 25 milligrams
- CuO obtained from High Purity Chemical Laboratory Co., Ltd., 25 milligrams
- a curve (b) included in FIG. 6 is a current-voltage characteristic of the anode according to Reference Example 1.
- the electrode according to Reference Example 1 had a potential difference EPD1 of 1.85 volts. Therefore, the anode according to Reference Example 1 had an overvoltage of 0.62 volts.
- Cobalt oxide represented by the chemical formula Co 3 O 4 obtained from Furuuchi Chemical Co., Ltd., 40 milligrams was dispersed in pure water (2 milliliters) to prepare a slurry.
- an anode was prepared using this slurry, and its oxygen generation characteristics were evaluated.
- a curve (c) included in FIG. 6 shows the current-voltage characteristics of the anode according to Reference Example 2.
- the electrode according to Reference Example 2 had a potential difference EPD1 of 1.60 volts. Therefore, the anode according to Reference Example 2 had an overvoltage of 0.37 volts.
- Reference Example 3 In Reference Example 3, the HPG substrate itself used in Example 1 was used as the anode. In other words, the anode according to Reference Example 3 was composed only of the HPG substrate used in Example 1. After the HPG substrate was cleaned as in Example 1, its oxygen evolution characteristics were evaluated. A curve (d) included in FIG. 6 shows the current-voltage characteristics of the anode according to Reference Example 3.
- the electrode according to Reference Example 3 had a potential difference EPD1 of 2.00 volts. Therefore, the anode according to Reference Example 1 had an overvoltage of 0.77 volts.
- Table 1 below shows anode materials, potential difference EPD1, and overvoltage according to Example 1, Comparative Example 1 to Comparative Example 4, and Reference Example 1 to Reference Example 3.
- the present invention provides a method for efficiently generating oxygen by electrolysis of water using a copper delafossite compound as an anode.
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Abstract
Description
(a) 以下を具備する水の電気分解装置を用意する工程、
容器、
電源、
陽極、
陰極、および
電解質水溶液、ここで、
前記陽極および前記陰極は、前記電解質水溶液にに接しており、
前記陽極は、化学式CuRhO2により表される銅ロジウムデラフォサイト化合物を有しており、
前記銅ロジウムデラフォサイト化合物は、前記電解質水溶液に接しており、
(b) 前記電源を用いて前記陰極および前記陽極の間に電位差を印加して、前記銅ロジウムデラフォサイト化合物上で生じる水の電気分解を介して前記陽極上に酸素を発生させる工程。
図1は、実施形態1による水電解装置100の模式図を示す。実施形態1による水電解装置100は、容器11、陽極12、陰極13、および電源14を具備する。
容器11の内部には、電解質水溶液15が貯留されている。電解質水溶液15の例は、水酸化カリウムまたは水酸化ナトリウムのようなアルカリ性水溶液である。アルカリ性水溶液を用いて水を電解することにより、酸素発生の効率を向上させ、かつ電解に必要とされる電力を減少できる。
陽極12及び陰極13は、電解質水溶液15に接するように、容器11の内部に配置される。陽極12及び陰極13は、後述する電源14に電気的に接続されている。陽極12上では、酸素が発生する。陰極13上では、水素が発生する。
陰極13は、導電性物質から形成される。具体的には、陰極13の表面が導電性物質から形成される。好適な導電性物質の例は、水素を発生させるために低い過電圧を有する白金またはニッケル化合物である。導電性物質が電解質水溶液15中で分解されない限り、導電性物質の材料は限定されない。
電源14は、陽極12及び陰極13間に、所定の電位差を印加するために用いられる。電源14を用いて陽極12及び陰極13の間に所定の電位差が印加され、電解質水溶液に含有される水を電気分解する。1.6ボルト以上4.0ボルト以下の電位差が印加されることが望ましい。電源14の例は、ポテンシオスタットまたは電池である。
水電解装置100は、陽極12及び陰極13の間に、隔膜16を有する。隔膜16は、容器11の内部を、陽極12が位置する第1室および陰極13が位置する第2室に分割する。
銅の酸化物は、酸素発生に必要とされる過電圧が高いため、陽極の材料として適さないと考えられる。後述される参考例1を参照せよ。
そのため、酸素を発生させるために必要な過電圧は、ロジウム、鉄、アルミニウム、イットリウム、およびガリウムの順に低くなることが予想される。鉄の占有数の値はロジウムと同じであるため、鉄が用いられた場合の酸素を発生させるために必要な過電圧は、ロジウムが用いられた場合と同じであると予想される。
以下の実験例は、本発明をより詳細に説明する。本発明者らは、水電解装置100に用いられる陽極12の材料および陽極12上で酸素が発生するために必要とされる電圧の間の関係を明らかにするために、以下の実験を行った。
(陽極12の作製)
実施例1による陽極12は、導電性カーボン基体上に銅ロジウムデラフォサイト化合物を担持させることによって製造された。
得られた陽極基板は、円筒状のキャップを用いて、回転ディスク電極アタッチメント(日厚計測社製)に作用電極として取り付けられた。
ここで、電位差EPD1は、5mA/cm2の電流が対極および作用電極の間に流れる時の参照極および作用電極の間の電位差を表す。
化学式CuAlO2により表される銅アルミニウムデラフォサイト化合物が以下のように調製され、その過電圧が計算された。
化学式CuFeO2により表される銅鉄デラフォサイト化合物が以下のように調製され、その過電圧を計算した。
化学式CuYO2により表される銅イットリウムデラフォサイト化合物が以下のように調製され、その過電圧を計算した。
化学式CuGaO2により表される銅ガリウムデラフォサイト化合物が以下のように調製され、その過電圧を計算した。
化学式CuOにより表される酸化銅を担持した陽極が以下のように作成され、その過電圧を計算した。
化学式Co3O4により表される酸化コバルトを担持した陽極が以下のように作成され、その過電圧を計算した。
参考例3では、実施例1において用いられたHPG基板自体が陽極として用いられた。言い換えれば、参考例3による陽極は、実施例1において用いられたHPG基板のみから構成された。HPG基板が実施例1の場合と同様に洗浄された後、その酸素発生特性が評価された。図6に含まれる曲線(d)は、参考例3による陽極の電流-電圧特性を示す。参考例3による電極は、2.00のボルトの電位差EPD1を有していた。従って、参考例1による陽極は、0.77ボルトの過電圧を有していた。
12 陽極
13 陰極
14 電源
15 電解質水溶液
16 隔膜
17 電解質膜
Claims (5)
- 酸素を発生させる方法であって、以下の工程を具備する:
(a) 以下を具備する水の電気分解装置を用意する工程、
容器、
電源、
陽極、
陰極、および
電解質水溶液、ここで、
前記陽極および前記陰極は、前記電解質水溶液にに接しており、
前記陽極は、化学式CuRhO2により表される銅ロジウムデラフォサイト化合物を有しており、
前記銅ロジウムデラフォサイト化合物は、前記電解質水溶液に接しており、
(b) 前記電源を用いて前記陰極および前記陽極の間に電位差を印加して、前記銅ロジウムデラフォサイト化合物上で生じる水の電気分解を介して前記陽極上に酸素を発生させる工程。 - 請求項1に記載の方法であって、
前記容器はさらに隔膜を具備し、
前記隔膜は、容器の内部を、前記陽極を有する第1室および前記陰極を有する第2室に分割している。 - 酸素を発生するために用いられる水の電気分解装置であって、以下を具備する:
容器、
電源、
陽極、および
陰極、ここで、
電解質水溶液は、前記容器に貯留されており、
前記陽極および前記陰極は、前記電源に電気的に接続されており、
前記陽極および前記陰極は、前記電解質水溶液に接しており、
前記陽極は、化学式CuRhO2により表される銅ロジウムデラフォサイト化合物を有しており、
前記銅ロジウムデラフォサイト化合物は、前記電解質水溶液に接している。 - 請求項3に記載の水の電気分解装置であって、
前記容器はさらに隔膜を具備し、
前記隔膜は、容器の内部を、前記陽極を有する第1室および前記陰極を有する第2室に分割している。 - 水の電気分解により酸素を発生するための陽極であって、
化学式CuRhO2により表される銅ロジウムデラフォサイト化合物を有している、陽極。
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JPS5967381A (ja) * | 1982-10-07 | 1984-04-17 | Agency Of Ind Science & Technol | 水電解のための陽極及びその製法 |
JP2009224206A (ja) * | 2008-03-17 | 2009-10-01 | Mitsubishi Electric Corp | 固体高分子電解質膜・触媒金属複合電極及びその製造方法 |
JP2009299111A (ja) * | 2008-06-11 | 2009-12-24 | Nec Corp | 酸素発生電極触媒、酸素発生電極および水電解装置 |
WO2011028262A2 (en) * | 2009-08-27 | 2011-03-10 | Sun Catalytix Corporation | Compositions, electrodes, methods and systems for water electrolysis and other electrochemical techniques |
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JP2009224206A (ja) * | 2008-03-17 | 2009-10-01 | Mitsubishi Electric Corp | 固体高分子電解質膜・触媒金属複合電極及びその製造方法 |
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