JP7725865B2 - Electrode material, and electrodes, fuel cells, and water electrolysis cells using the same - Google Patents

Description

The present invention relates to electrode materials and electrodes, fuel cells, and water electrolysis cells that use the same.

Fuel cells are devices that generate electricity by electrochemically reacting fuels such as hydrogen or alcohol with oxygen. They are classified into polymer electrolyte fuel cells (PEFC), phosphoric acid fuel cells (PAFC), molten carbonate fuel cells (MCFC), solid oxide fuel cells (SOFC), etc. depending on the electrolyte and operating temperature. For example, polymer electrolyte fuel cells are used in stationary power sources and fuel cell vehicles, and are required to maintain the desired power generation performance over the long term.

Among these fuel cells, polymer electrolyte fuel cells (PEFCs) use an ion-conductive polymer membrane (ion exchange membrane) as an electrolyte, and generally use an electrode material in which platinum (Pt) is supported on carbon, a conductive material. In PEFCs, a hydrogen supply shortage can occur due to water clogging of the fuel flow path or freezing of water. When this occurs, the anode potential rises sharply, causing the cell polarity to reverse, resulting in a polarity reversal state. At the anode in a polarity reversal state, instead of the hydrogen oxidation reaction, reactions that decompose water and carbon oxidation (corrosion) supply protons, instantly raising the potential to above 1.5 V vs. RHE, causing carbon oxidation (C + 2H ₂ O → CO ₂ + 4H++ 4e ⁻ ) and resulting in loss of protons, significantly reducing cell performance. To avoid such a decline in battery performance, a method has been proposed in which a non-conductive inorganic oxide such as _TiO2 with a specific surface area of 50 to 400 ^m2 /g coated with a conductive oxide such as _IrO2 is used as a support instead of carbon as a conductive oxide that does not oxidize and disappear (Patent Document 1). Another method has been proposed in which a thin layer of a precious metal such as Pt and hydrophobic molecules such as Teflon (registered trademark) are supported on _SiO2 nanofibers with a specific surface area of 1 ^m2 /g or more (Patent Document 2). Another method has been proposed in which catalyst particles, in which metal particles made of platinum or its alloy are supported on the surface of a catalyst support mainly composed of _SiO2 , are used as electrodes, along with conductive particles such as graphite and a proton-conducting material (Patent Document 3).
Furthermore, water electrolysis, the most practical method for producing hydrogen, is the reverse reaction of a fuel cell, in which water is decomposed into hydrogen and oxygen using electricity. Two types of water electrolysis are mainly used: solid polymer water electrolysis and alkaline electrolysis. Of these, solid polymer water electrolysis can be operated at a higher current density than alkaline electrolysis, which has the advantage of allowing the system to be more compact. Theoretically, a voltage of 1.23 V or more is required for the water electrolysis reaction under standard conditions (25°C, 1 atmosphere), and water electrolysis cells typically use high voltages of up to about 2.0 V. The anode (oxygen-evolving electrode) in a water electrolysis cell requires a catalyst active in the oxygen-evolving reaction, and iridium is known to have high activity (Patent Documents 4 and 5).

International Publication No. 2013/092568 JP 2016-71960 A Patent No. 3576108 Japanese Patent Application Laid-Open No. 2008-274326 Japanese Patent Application Laid-Open No. 2003-166093

Regarding the above-mentioned carbon corrosion that occurs when the potential of a polymer electrolyte fuel cell suddenly rises, there have been reports of electrodes such as those shown in Patent Documents 1 to 3. However, in order to realize fuel cells with even higher performance, it is important to increase the degree of freedom in fuel cell design, and there is a need to develop new electrodes that, when used in polymer electrolyte fuel cells, have high power generation performance and high durability against sudden rises in potential.
Furthermore, when using iridium as an anode catalyst in a polymer electrolyte water electrolysis cell, it is desirable to use iridium supported on a carrier from the standpoint of cost, etc. However, because the anode of a polymer electrolyte water electrolysis cell is used at a potential even higher than the potential to which the electrodes of a polymer electrolyte fuel cell are exposed, there are currently few materials that can be used as an iridium carrier and that have excellent conductivity and potential durability. For this reason, only iridium or iridium oxide without a carrier is usually used as a catalyst. Because a certain catalyst volume is required to form the anode, a large amount of iridium is used. However, because iridium is expensive, there is a need to develop an electrode with high water electrolysis performance that can reduce the amount of iridium used.

In light of the above-mentioned current situation, the present invention aims to provide a new fuel cell electrode material that has high power generation performance and high durability against sudden increases in potential. It also aims to provide a new water electrolysis cell electrode material that has high water electrolysis performance.

The present inventors have discovered that when a material having a predetermined noble metal and/or its oxide supported on spherical _SiO2 is used as an electrode material for a fuel cell, the electrode has high power generation performance and high durability against a sudden rise in potential, and when used as an electrode material for a water electrolysis cell, the cell has high water electrolysis performance. Furthermore, the present inventors have discovered a suitable method for producing such an electrode material, which has led to the completion of the present invention.

That is, the present invention provides an electrode material characterized by having a structure in which at least one noble metal selected from Ru, Ir, Rh, and Pd and/or its oxide is supported on spherical SiO ₂ .

The at least one noble metal selected from Ru, Ir, Rh, and Pd is preferably Ru and/or Ir.

The electrode material preferably has a structure in which at least one noble metal selected from Ru, Ir, Rh, and Pd and/or its oxide is supported on spherical _SiO2 , and then Pt and/or its oxide is further supported thereon.

The above electrode material is preferably an electrode material for a fuel cell or a water electrolysis cell.

The present invention also relates to an electrode constructed from the electrode material of the present invention.

The present invention also relates to a fuel cell comprising the electrode of the present invention.

The present invention also relates to a water electrolysis cell comprising the electrode of the present invention.

The present invention also provides a method for producing the electrode material of the present invention, comprising the steps of:
The production method is also a method for producing an electrode material, characterized by including a step of supporting at least one noble metal selected from Ru, Ir, Rh, and Pd and/or its oxide on spherical SiO2 _.

The present invention further provides a method for producing the electrode material of the present invention, comprising the steps of:
The production method includes a step (1) of supporting at least one noble metal selected from Ru, Ir, Rh, and Pd and/or its oxide on spherical SiO ₂ ;
The method for producing an electrode material is also characterized by comprising, after the step (1), a step (2) of supporting Pt and/or an oxide thereof.

The electrode material of the present invention is a material that can adequately withstand high potentials and can form highly conductive electrodes. Therefore, it is extremely useful as a conductive material for use in electrodes of fuel cells such as polymer electrolyte fuel cells, water electrolysis cells, solar cells, transistors, and displays such as liquid crystal displays, as well as antistatic materials and heat-shielding materials. It is particularly useful as an electrode material for polymer electrolyte fuel cells or polymer electrolyte water electrolysis cells.

1 is a diagram showing the results of electron microscope observation of spherical SiO ₂ (Sciqas 0.15 μm) used in Examples 1 to 3 and 7 and Comparative Example 1. FIG. 1 is a diagram showing the results of electron microscope observation of spherical SiO ₂ (Sciqas 0.4 μm) used in Examples 4 and 8. FIG. 10 is a diagram showing the results of electron microscope observation of spherical SiO ₂ (Sciqas 0.05 μm) used in Example 5. FIG. 1 shows the results of electron microscope observation of spherical SiO ₂ (Quatron SP-03F) used in Example 6. FIG. 1 is a diagram showing the results of electron microscope observation of non-spherical SiO ₂ (Nipsil EL) used in Comparative Example 2. FIG.

The following describes in detail preferred embodiments of the present invention, but the present invention is not limited to the following description and can be modified and applied as appropriate within the scope of the present invention.

1. Electrode Material The electrode material of the present invention has a structure in which at least one noble metal selected from Ru, Ir, Rh, and Pd and/or its oxide is supported on spherical _SiO2 .
When _SiO2 has a spherical shape, when an electrode is formed, the electrode material has the appropriate density necessary for electron conduction and the appropriate voids suitable for the diffusion of reaction gases and moisture, so the properties of the electrode material can be fully exhibited.
The electrode material of the present invention is formed by supporting at least one noble metal selected from Ru, Ir, Rh, and Pd and/or its oxide on such spherical _SiO2 . By using this material, an electrode having high power generation performance and high durability against a sudden rise in potential can be obtained.
Here, spherical _SiO2 is _SiO2 having a circularity of 0.7 or more as shown in the following formula. The circularity takes a value between 0 and 1, and the closer to 1 it is, the closer it is to a circle. The circularity of spherical _SiO2 is preferably 0.75 or more, and more preferably 0.80 or more.
(Circularity) = 4 × π (area of particle) ÷ (perimeter of particle) ²
When a particle contains a hole, the area of the hole is included in the area of the particle. The area and perimeter of a particle can be calculated using image analysis software WinROOF.

The SiO ₂ preferably has a specific surface area of 1 m ² /g or more and 100 m ² /g or less. By supporting at least one noble metal and/or its oxide selected from Ru, Ir, Rh, and Pd, or Pt and/or its oxide, as described below, on spherical SiO ₂ having such a specific surface area and covering the SiO ₂ particle surface, the effect of supporting these metals can be more fully exhibited. Furthermore, the use of such spherical SiO ₂ can improve the performance of the electrode. The specific surface area of SiO ₂ is more preferably 5 m ² /g or more and 80 m ² /g or less, and even more preferably 10 m ² /g or more and 60 m ² /g or less.
The specific surface area of _SiO2 can be measured by the method described in the examples below.

The _SiO2 preferably has an average particle size of 0.01 to 1.0 μm. By using SiO2 with such particle sizes and coating the _SiO2 particle surfaces with at least one noble metal selected from Ru, Ir, Rh, and Pd and/or its oxide, or with Pt and/or its oxide, as described below, the effects of supporting these metals can be more fully realized. Furthermore, the use of such spherical _SiO2 can enhance the performance of the electrode. The average particle size of _SiO2 is more preferably 0.02 to 0.8 μm, and even more preferably 0.03 to 0.5 μm.
The average particle size of _SiO2 can be measured by averaging the particle sizes of 40 randomly selected particles in an image taken with an electron microscope.

The at least one noble metal and/or oxide thereof selected from Ru, Ir, Rh, and Pd may be any of these elements, and may be either a metal or an oxide thereof. However, Ru and/or Ir are preferably used as a metal and/or an oxide thereof. When any of these elements is supported on _SiO2 , an electrode made from the resulting electrode material has better power generation performance and durability against sudden increases in potential. Ru and/or an oxide thereof are more preferably used.

The amount of at least one noble metal and/or oxide thereof selected from Ru, Ir, Rh, and Pd supported in the electrode material of the present invention is preferably 5% by mass or more relative to 100% by mass of the electrode material. With such a supported amount, the effect of supporting these noble metals and/or oxides thereof is more fully exhibited, and the electrode produced from the electrode material has higher performance. The supported amount is more preferably 10% by mass or more relative to 100% by mass of the electrode material, and even more preferably 20% by mass or more relative to 100% by mass of the electrode material. While a larger supported amount is preferable, it is typically 60% by mass or less relative to 100% by mass of the electrode material.
In the electrode material of the present invention, when two or more kinds of noble metals selected from Ru, Ir, Rh, and Pd and/or oxides thereof are supported, it is preferable that the total amount of the two or more kinds of noble metals and/or oxides thereof supported is in the above-mentioned ratio.

The electrode material of the present invention preferably has a structure in which at least one noble metal selected from Ru, Ir, Rh, and Pd and/or its oxide is supported _on spherical SiO2, and then Pt and/or its oxide is further supported on the noble metal. When such an electrode material is used, the electrode using the electrode material has better power generation performance and durability against a sudden rise in potential.

When the electrode material of the present invention is formed by supporting at least one noble metal and/or its oxide selected from Ru, Ir, Rh, and Pd on spherical SiO ₂ , and then further supporting Pt and/or its oxide, the amount of Pt and/or its oxide supported is preferably 5% by mass or more relative to 100% by mass of the electrode material. With such a supported amount, the effect of supporting Pt and/or its oxide is more fully exhibited, and the electrode produced from the electrode material exhibits higher performance. The supported amount is more preferably 8% by mass or more relative to 100% by mass of the electrode material, and even more preferably 10% by mass or more relative to 100% by mass of the electrode material. Although a larger amount is preferable, the supported amount is typically 50% by mass or less relative to 100% by mass of the electrode material.

In the electrode material of the present invention, it is preferable that a material composed only of carbon is not present between the at least one noble metal and/or oxide thereof selected from Ru, Ir, Rh, and Pd supported on the spherical SiO ₂ and the Pt and/or oxide thereof supported thereafter. If this material is present, the voltage after high potential holding described below may decrease. Furthermore, it is preferable that an ion-conductive resin is not present between the at least one noble metal and/or oxide thereof selected from Ru, Ir, Rh, and Pd supported on the spherical SiO ₂ and the Pt and/or oxide thereof supported thereafter. If this material is present, the initial voltage described below may decrease.

When the electrode material of the present invention is used as a material for electrodes of fuel cells or water electrolysis cells, it is possible to obtain electrodes that have high power generation or water electrolysis performance and high durability against sudden increases in potential.
The present invention also includes an electrode made from the electrode material of the present invention, and a fuel cell or water electrolysis cell including the electrode. Because the electrode made using the electrode material of the present invention has high durability against a sudden rise in potential, it is suitable as an electrode material for a polymer electrolyte fuel cell or a polymer electrolyte water electrolysis cell, which are fuel cells and water electrolysis cells in which a sudden rise in potential may occur.
The electrode material of the present invention can be used as an electrode material for various gas electrolysis cells such as _CO2 and _NH3 gas electrolysis cells, solar cells, transistors, liquid crystal and other display devices, and can also be suitably used as an electrically conductive material for use in antistatic materials, heat ray shielding materials, etc., in addition to fuel cells and water electrolysis cells.

2. Manufacturing Method of Electrode Material The manufacturing method of the electrode material of the present invention having a structure in which at least one noble metal selected from Ru, Ir, Rh, and Pd and/or its oxide is supported on spherical SiO2 is not _particularly limited as long as such a structure can be obtained, but the following first manufacturing method and second manufacturing method are preferred.
(First manufacturing method)
The method for producing spherical SiO ₂ supported with at least one noble metal selected from Ru, Ir, Rh, and Pd and/or its oxide (hereinafter also referred to as noble metal 1-supported SiO 2) comprises the steps of: a first step of adding an aqueous solution of at least one noble metal salt selected from Ru, Ir, Rh, and Pd to a spherical SiO ₂ slurry to obtain a mixed solution _{1; a second step of adjusting the pH of the mixed solution 1} obtained in the first step to 5 to 9, and then separating the precipitate; and a third step of calcining the precipitate obtained in the second step.
(Second manufacturing method)
A method for producing SiO2 supported on a precious metal 1, comprising the steps of: a first step of adding an aqueous solution of at least one precious metal salt selected from Ru, Ir, Rh, and Pd to a spherical _SiO2 slurry to obtain a mixed solution 1; a second step of adding a reducing agent to the mixed solution 1 obtained in the first step to precipitate particles of at least one precious metal selected from Ru, Ir, Rh, and Pd, and separating the resulting precipitate; and a third step of calcining the precipitate obtained in the _second step.

In either the first or second manufacturing method, the first to third steps may be repeated multiple times to support at least one kind of noble metal particles selected from Ru, Ir, Rh, and Pd on the spherical _SiO2 multiple times. When repeated multiple times, the same noble metal salt may be used, or different noble metal salts may be used. Furthermore, the third step may not be performed if necessary.

Furthermore, among the electrode materials of the present invention, those having a _structure in which at least one kind of precious metal selected from Ru, Ir, Rh, and Pd and/or an oxide thereof is supported on spherical SiO2, and then Pt and/or an oxide thereof is further supported thereon are not particularly limited to the production method as long as such a structure can be obtained, but a method in which the following third production method or fourth production method is further applied to the slurry of precious metal _1- supported SiO2 obtained by the above-mentioned first or second production method is preferred.
(Third manufacturing method)
This method comprises a first step of adding a Pt salt aqueous solution to a slurry of SiO2 carrying a precious metal ₁ obtained by the first or second manufacturing method to obtain a mixed solution 2, a second step of adjusting the pH of the mixed solution 2 obtained in the first step to 5 to 9, and then separating the precipitate, and a third step of calcining the precipitate obtained in the second step.
(Fourth manufacturing method)
This method includes a first step of adding a Pt salt aqueous solution to a slurry of SiO2 carrying precious metal ₁ obtained by the first or second manufacturing method to obtain a mixed solution 2, a second step of precipitating Pt particles from the mixed solution 2 obtained in the first step using a reducing agent and separating the resulting precipitate, and a third step of calcining the precipitate obtained in the second step.

In either the third or fourth production method, the first to third steps may be repeated multiple times to support Pt and/or its oxide particles on the spherical _SiO2 multiple times. In addition, the third step may not be performed if necessary.

It is preferable not to include a step of coating the electrode material of the present invention, which has a structure in which at least one noble metal selected from Ru, Ir, Rh, and Pd and/or its oxide is supported on spherical SiO ₂ with a material composed only of carbon, before carrying out the third and fourth manufacturing methods. Including this step may result in a decrease in the voltage after high potential holding, as described below. It is also preferable not to include a step of coating the electrode material of the present invention, which has a structure in which at least one noble metal selected from Ru, Ir, Rh, and Pd and/or its oxide is supported on spherical SiO ₂ with an ion conductive resin, before carrying out the third and fourth manufacturing methods. Including this step may result in a decrease in the initial voltage, as described below.

The at least one precious metal salt selected from Ru, Ir, Rh, and Pd used in the first step of the first and second manufacturing methods, and the Pt salt used in the first step of the third and fourth manufacturing methods, may be an inorganic acid salt such as a chloride, sulfate, nitrate, or phosphate, an organic acid salt such as an acetate or oxalate, or a dispersion solution of nano-sized Ru, Ir, Rh, Pd, Pt, or the like. Among these, a chloride solution, a nitrate solution, or the like is preferred.

In the second step of the first and third production methods, the pH of the mixed aqueous solutions 1 and 2 may be adjusted to 5 to 9, but in order to more sufficiently generate a precipitate, the pH is preferably 6 to 8, and more preferably 6.5 to 7.5.
In the second step, the temperature of the mixed aqueous solution when adjusting the pH to 5 to 9 is preferably 50 to 100°C, more preferably 60 to 80°C, from the viewpoints of the rate of precipitation of hydroxides of at least one noble metal selected from Ru, Ir, Rh, and Pd, or Pt, and workability.

In the third step of the first and second production methods, the temperature at which the precipitate is calcined is not particularly limited as long as the precious metal hydroxide precipitate obtained in the second step of the first production method and the precipitate containing the precious metal elemental precipitate and _SiO2 obtained in the second step of the second production method are sufficiently calcined, but is preferably 200 to 750°C, more preferably 250 to 600°C, and even more preferably 300 to 500°C.
The calcination time is not particularly limited as long as the calcination is carried out sufficiently, but is preferably 1 to 8 hours, more preferably 1.5 to 6 hours, and even more preferably 2 to 4 hours.

In the third step of the third and fourth production methods, the temperature for calcining the precipitate is not particularly limited as long as the Pt hydroxide precipitate obtained in the second step of the third production method and the precipitate containing the Pt simple substance precipitate and the precious metal 1-supported SiO ₂ obtained in the second step of the fourth production method are sufficiently calcined, but is preferably 50 to 900°C, more preferably 100 to 700°C, and even more preferably 150 to 600°C.
The calcination time is not particularly limited as long as the calcination is carried out sufficiently, but is preferably 0.1 to 6 hours, more preferably 0.5 to 5 hours, and even more preferably 1 to 4 hours.
The firing is preferably carried out in an atmosphere of a firing gas, such as _N2 gas or _H2 gas, which may be mixed in any ratio.

The second and fourth manufacturing methods involve reducing precious metals using a reducing agent. The reducing agent is not particularly limited, but examples include hydrazine chloride, hydrazine, sodium borohydride, alcohol, hydrogen, sodium thiosulfate, citric acid, sodium citrate, L-ascorbic acid, formaldehyde, ethylene, and carbon monoxide. Among these, ethanol is preferred as the reducing agent.

In the first step of the first and third production methods, a reduction treatment may be carried out as needed by adding a reducing agent to the mixed solution 1. By carrying out the reduction treatment, the valence of the noble metal salt can be adjusted to form a precipitate.
The reducing agent may be the same as those used in the second and fourth production methods, and among them, hydrazine chloride is preferred.
The amount of the reducing agent to be added is not particularly limited, but is preferably 0.1 to 1 times the molar equivalent of the noble metal contained in the mixed solution 1.

The manufacturing method of the electrode material may include other steps in addition to those described above. These steps include washing the precipitate with water after separating it in the second step of the first to fourth manufacturing methods and before firing it in the next step, drying the precipitate, pulverizing the precipitate, and classifying the precipitate.

Specific examples are given below to explain the present invention in detail, but the present invention is not limited to these examples. Unless otherwise specified, "%" and "wt%" mean "% by mass." The methods for measuring each physical property are as follows:

<Supported Pt Amount, Supported Ir Amount, Supported Ru Amount>
The Pt content in the sample was measured using a scanning X-ray fluorescence analyzer ZSX Primus II (manufactured by Rigaku Corporation), and the amount of supported Ir and Ru was calculated.
<Specific surface area (BET-SSA)>
In accordance with the provisions of JIS Z8830 (2013), the sample was heat-treated in a nitrogen atmosphere at 200°C for 60 minutes, and then the specific surface area (BET-SSA) was measured using a specific surface area measuring device (manufactured by Mountech Co., Ltd., product name "Macsorb HM-1220").
<Circularity>
The _SiO2 particles were observed under an electron microscope, and the particle area and perimeter were determined from the particle images using image analysis software WinROOF, and the circularity was calculated using the following formula: When the particles contained holes, the area of the holes was also included in the particle area.
(Circularity) = 4 × π (area of particle) ÷ (perimeter of particle) ²
<Initial power generation test of membrane electrode assembly>
The membrane electrode assembly was placed on the anode side and a Pt-loaded carbon electrode with a Pt basis weight of 0.2 mg Pt/cm ² on the cathode side, and the membrane electrode assembly was incorporated into a single cell (manufactured by Miklab, electrode area 1 cm x 1 cm, Au 10 μm plated Cu separator, straight flow path specification). Using a PEFC single cell evaluation device (manufactured by Toyo Corporation), the cell temperature was set to 80°C, the anode side was set to 77°C and humidified with 100% H ₂ at 500 ml/min, and the cathode side was set to 77°C and humidified with 20% O ₂ /N ₂ at 2000 ml/min. The open circuit voltage was swept from 0.2 V, and the voltage and cell resistance at 1.0 A/cm ² were measured.
<Membrane electrode assembly power generation test after holding high potential>
After the initial power generation test, the single cell was inverted, and the cell temperature was set to 80°C, the anode side was set to 77°C and humidified 100% _H2 at 500 ml/min, and the cathode side was set to 77°C and humidified 100% _N2 at 500 ml/min. After applying 1.7 V for 10 minutes, the single cell was inverted and a power generation test was conducted again, and the voltage at 1.0 A/ ^cm2 was measured.
<Membrane electrode assembly water electrolysis current density measurement>
The electrode using the membrane electrode assembly prepared in the Examples and Comparative Examples was placed on the anode side, and the Pt-supported carbon electrode with a Pt basis weight of 0.2 mg Pt/cm ² was placed on the cathode side, and together with a gas diffusion layer (SIGRACET 28BA manufactured by SGL Carbon), they were assembled into a single cell (manufactured by Miklab, electrode area 1 cm x 1 cm, Au 10 μm plated Cu separator, straight flow path specification). Using a PEFC single cell evaluation device (manufactured by Toyo Corporation), the cell temperature was set to 70°C, the anode side was set to 80°C and humidified at 4% H ₂ /N ₂ 1 L/min, and the cathode side was set to 80°C and humidified at 100% N ₂ 1 L/min. The voltage was swept from 1.0 V to 2.0 V, and the current density at 1.5 V was measured.
<Electron microscope photograph observation>
Observation was carried out using a field emission scanning electron microscope JSM-7000F (manufactured by JEOL Ltd.).

Example 1
(1) Preparation of Ru-supported SiO ₂ powder 8.0 g of spherical SiO ₂ (product name "Sciqas" manufactured by Sakai Chemical Industry Co., Ltd., particle size 0.15 μm) and 1600 ml of ion-exchanged water were weighed into a beaker and mixed with stirring to obtain SiO ₂ slurry 1.
In another beaker, a ruthenic chloride solution (8.369 mass % as Ru, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) was diluted with ion-exchanged water to 2.2 mass % to prepare a solution (hereinafter referred to as "Ru aqueous solution 1").
While stirring the _SiO2 slurry 1, 90.9 g of the above Ru aqueous solution 1 was added, and the mixture was stirred and mixed while heating and maintaining the liquid temperature at 70°C. Furthermore, a 1.0 mol/L potassium hydroxide aqueous solution was added dropwise to adjust the pH to 7, and the mixture was heated and maintained at 70°C for 1 hour. Then, according to the usual method, it was filtered, washed with water, and dried to evaporate all the water. The entire amount of the obtained powder was placed in an alumina boat, heated to 450°C in an electric furnace over 135 minutes, maintained at 450°C for 4 hours, and then naturally cooled to room temperature to obtain Ru-supported _SiO2 powder 1.
(2) Preparation of Pt and Ru-supported SiO ₂ powder 7.0 g of the obtained Ru-supported SiO ₂ powder 1 and 778 g of ion-exchanged water were weighed into a beaker and mixed with stirring to obtain Ru-supported SiO ₂ slurry 1.
In another beaker, 35.4 g of an aqueous solution (referred to as "Pt aqueous solution 1") prepared by diluting a chloroplatinic acid solution (15.343 mass% as Pt, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) with ion-exchanged water to a concentration of 2.2 mass% was added to 0.2 g of hydrazine chloride (manufactured by Tokyo Chemical Industry Co., Ltd., trade name "Hydrazine Dihydrochloride") and stirred to prepare a mixture (referred to as "mixed Pt aqueous solution 1").
While stirring the Ru-supported _SiO2 slurry 1, the above-mentioned mixed Pt aqueous solution 1 prepared in another beaker was added, and then the mixture was stirred and mixed while heating and maintaining the liquid temperature at 70 ° C. Furthermore, 1.0 mol/L sodium hydroxide aqueous solution was added dropwise to adjust the pH to 7, and then the mixture was heated and maintained at 70 ° C for 1 hour, and then filtered, washed with water, and dried according to the usual method to evaporate all water. The entire amount of the obtained powder was placed in an alumina boat, and while flowing 100 vol% hydrogen at 400 mL/min in an atmospheric firing furnace, the temperature was raised to 560 ° C over 60 minutes, and the mixture was maintained at 560 ° C for 3 hours, and then naturally cooled to room temperature to obtain Pt, Ru-supported _SiO2 powder 1.
(3) Preparation of membrane electrode assembly 0.2 g of the obtained Pt, Ru-supported _SiO2 powder 1, 168 μL of 20 mass % Nafion solution (manufactured by Sigma-Aldrich Corporation), 120 μL of t-butyl alcohol (manufactured by Wako Pure Chemical Industries, Ltd.), 24 μL of ion-exchanged water, and 1.4 g of ₂ mmφ ZrO2 beads were placed in a screw tube and dispersed for 150 minutes using an ultrasonic cleaner to obtain Pt, Ru-supported _SiO2 ink 1.
40 μL of the obtained Pt, Ru supported SiO ₂ ink 1 was dropped onto a Teflon (registered trademark) sheet, coated using a bar coater, and then naturally dried to obtain Pt, Ru supported SiO ₂ sheet 1 (Pt amount: 0.05 mg Pt/cm ² ).
0.02 g of commercially available 50% by mass Pt-loaded carbon (manufactured by NE Chemcat Corporation), 61 μL of 20% by mass Nafion solution (manufactured by Sigma-Aldrich Corporation), 179 μL of t-butyl alcohol (manufactured by Wako Pure Chemical Industries, Ltd.), 89 μL of ion-exchanged water, and 1.6 g of ₂ mm diameter ZrO2 beads were placed in a screw tube and dispersed for 150 minutes using an ultrasonic cleaner to obtain Pt-loaded carbon ink 1.
40 μL of the obtained Pt-supported carbon ink 1 was dropped onto a Teflon (registered trademark) sheet, coated using a bar coater, and then allowed to dry naturally to obtain Pt-supported carbon sheet 1 (Pt usage amount 0.2 mgPt/cm ² ).
An electrolyte membrane (manufactured by DuPont, product name NR-212) was cut to a size of 3 cm x 3 cm, and then a Ru/Ir-supported titanium suboxide sheet 1 and a Pt-supported carbon sheet 1 were each cut to a size of 1 cm x 1 cm. The Pt, Ru-supported _SiO2 sheet 1, electrolyte membrane, and Pt-supported carbon sheet 1 were stacked in this order, and hot-pressed at 140°C for 6 minutes using a heated hydraulic press (manufactured by Toyo Seiki Seisakusho, product name Mini Test Press MP-WNH) at a set pressure of 1 MPa.
Thereafter, the Teflon (registered trademark) sheets were peeled off from the Pt- and Ru-supported SiO ₂ sheet 1 and the Pt-supported carbon sheet 1 to obtain a membrane electrode assembly 1.

Example 2
A Pt- and Ru-supported _SiO2 powder ₂ was obtained in the same manner as in Example 1, except that the amount of Ru aqueous solution 1 added to the SiO2 slurry 1 in (1) Preparation of Ru-supported _SiO2 powder in Example 1 was changed to 155.8 g. The obtained Pt- and Ru-supported _SiO2 powder 2 was used to obtain a membrane electrode assembly 2.

Example 3
A Pt- and Ru-supported _SiO2 powder 3 was obtained in the same manner as in Example 1, except that the amount of Ru aqueous solution 1 added to the SiO2 slurry ₁ in (1) Preparation of Ru-supported _SiO2 powder in Example 1 was changed to 363.6 g. Furthermore, a membrane electrode assembly 3 was obtained using the obtained Pt- and Ru-supported _SiO2 powder 3.

Example 4
A Pt and Ru-supported SiO2 _{powder 4} was obtained in the same manner as in Example 2, except that the spherical _SiO2 (manufactured by Sakai Chemical Industry Co., Ltd., product name "Sciqas", particle size 0.15 μm) used in (1) Preparation of Ru-supported SiO2 powder in Example 2 was replaced with spherical SiO2 (manufactured by Sakai Chemical Industry Co., Ltd., product name "Sciqas _" , particle size 0.40 μm). Furthermore, a membrane electrode assembly 4 was obtained using the obtained Pt and Ru-supported SiO2 powder ₄ .

Example 5
A Pt and Ru-supported SiO2 _{powder 5} was obtained in the same manner as in Example 3, except that the spherical _SiO2 (manufactured by Sakai Chemical Industry Co., Ltd., product name "Sciqas", particle size 0.15 μm) used in (1) Preparation of Ru-supported SiO2 powder in Example 3 was changed to spherical SiO2 (manufactured by Sakai Chemical Industry Co., Ltd., product name "Sciqas _" , particle size 0.05 μm). Furthermore, a membrane electrode assembly 5 was obtained using the obtained Pt and Ru-supported SiO2 powder ₅ .

Example 6
A Pt and Ru-supported SiO2 _{powder 6} was obtained in the same manner as in Example 2, except that the spherical SiO2 (manufactured by Sakai Chemical Industry Co., Ltd., product name "Sciqas", particle size 0.15 μm) in (1) Preparation of Ru-supported _SiO2 powder was changed to spherical _SiO2 (manufactured by Fuso Chemical Industry Co., Ltd., product name "Quatron SP-03F") The obtained Pt and Ru-supported _SiO2 powder 6 was used to obtain a membrane electrode assembly 6.

Example 7
In (1) Preparation of Ru-supported _SiO2 powder in Example 1, the addition of 90.9 g of Ru aqueous solution 1 to _SiO2 slurry 1 was changed to the addition of 90.9 g of a chloroiridic acid solution (8.604 mass% Ir, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) diluted with ion-exchanged water to 2.2 mass% (hereinafter referred to as "Ir aqueous solution 1") and 0.55 g of hydrazine chloride (hereinafter referred to as "mixed Ir aqueous solution 1") to _SiO2 slurry 1. Ir-supported _SiO2 powder 1 and Pt, Ir-supported SiO2 powder ₁ were obtained in the same manner as in Example 1. Furthermore, a membrane electrode assembly 7 was obtained using the obtained Pt, Ir-supported SiO2 powder ₁ .

Example 8
The same procedures as in Example 4 were carried out except that (1) in the preparation of Ru-supported _SiO2 powder in Example 4, Ru aqueous solution 1 was replaced with Ir aqueous solution 1, and (2) in the preparation of Pt, Ru-supported _SiO2 powder, mixed Pt aqueous solution 2 was prepared by stirring and mixing 136.4 g of Pt aqueous solution 1 and 0.81 g of hydrazine hydrochloride, and this mixed Pt aqueous solution 2 was used instead. Pt, Ir-supported _SiO2 powder 2 was also obtained using the obtained Pt, Ir-supported _SiO2 powder.

Example 9
A Pt, Ru, and Ir-supported SiO2 powder 1 was obtained in the same manner as in Example 1, except that 103.9 g of Ru aqueous solution 1 was added in (1) Preparation of Ru-supported _SiO2 powder in Example 1, and 51.9 g of Ir aqueous solution 1 in Example ₇ was added at the same time. In addition, a membrane electrode assembly 9 was obtained using the obtained Pt, Ru, and Ir-supported _SiO2 powder 1.

Example 10
A mixture of 79.5 g of Ir aqueous solution 1 and 0.48 g of hydrazine chloride (hereinafter referred to as "mixed Ir aqueous solution 2") was prepared. Example 1 (2) Ir-supported SiO2 powder ₂ was obtained in the same manner as in Example 1 (2), except that the Ru-supported _SiO2 powder used in the preparation of the Pt, Ru-supported _SiO2 powder was changed to the Ir-supported SiO2 powder 1 obtained in Example 7, and the mixed Pt aqueous solution 1 was changed to the mixed Ir aqueous solution ₂ prepared above. Furthermore, a membrane electrode assembly 10 (Ir usage amount 0.1 mgIr/ ^cm2 ) was obtained using the obtained Ir-supported SiO2 powder ₂ .

Example 11
A mixture of 79.5 g of Ru aqueous solution and 0.91 g of hydrazine chloride (referred to as "mixed Ru aqueous solution 1") was prepared. Example 1 (2) Ru- and Ir-supported _SiO2 powder ₁ was obtained in the same manner as in Example 1 (2), except that the Ru-supported SiO2 powder used in the preparation of the Pt and Ru-supported _SiO2 powder was changed to the Ir-supported _SiO2 powder 1 obtained in Example 7, and the mixed Pt aqueous solution 1 was changed to the mixed Ru aqueous solution 1 prepared above. In addition, a membrane electrode assembly 11 was obtained using the obtained Ru and Ir-supported _SiO2 powder 1.

Comparative Example 1
A Pt-supported _SiO2 powder of Comparative Example 1 was obtained in the same manner as in Example 1, except that Ru support in Example 1 was omitted. In addition, a membrane electrode assembly of Comparative Example 1 was obtained using the obtained Pt-supported _SiO2 powder.

Comparative Example 2
A Pt and Ru-supported _SiO2 powder of Comparative Example 2 was obtained in the same manner as in Example 2, except that the spherical _SiO2 (manufactured by Sakai Chemical Industry Co., Ltd., product name "Sciqas", particle size 0.15 μm) in Example 2 was changed to non-spherical _SiO2 (manufactured by Tosoh Silica Corporation, product name "Nipsil EL") The obtained Pt and Ru-supported _SiO2 powder 8 was used to obtain a membrane electrode assembly of Comparative Example 2.

Comparative Example 3
A membrane electrode assembly of Comparative Example 3 was obtained in the same manner as in Example 1, using commercially available 50% by mass Pt-supported carbon (manufactured by NE Chemcat Corporation).

Comparative Example 4
A membrane electrode assembly of Comparative Example 4 was produced in the same manner as in Example 10, except that iridium black (manufactured by Alfa Aesar) was used instead of the Ir-supported SiO ₂ powder 2 of Example 10.

The amount of precious metal supported, the specific surface area, and circularity of the _SiO2 powders used were measured using the methods described above for the precious metal-supported _SiO2 powders obtained in Examples 1 to 11 and Comparative Examples 1 and 2. Furthermore, initial power generation tests and power generation tests after high potential holding were conducted using the membrane electrode assemblies obtained in Examples 1 to 11 and Comparative Examples 1 to 3. The results are shown in Table 1. Furthermore, water electrolysis current density measurements were conducted using the membrane electrode assemblies obtained in Examples 10 and 11 and Comparative Example 4. The results are shown in Table 2. Furthermore, electron microscope observation results for the spherical _SiO2 and non-spherical _SiO2 used in the examples and comparative examples are shown in Figures 1 to 5.

Carrier:
A: Spherical _SiO2 (manufactured by Sakai Chemical Industry Co., Ltd., product name "Sciqas", particle size 0.15 μm)
B: Spherical _SiO2 (manufactured by Sakai Chemical Industry Co., Ltd., product name "Sciqas", particle size 0.4 μm)
C: Spherical _SiO2 (manufactured by Sakai Chemical Industry Co., Ltd., product name "Sciqas", particle size 0.05 μm)
D: Spherical SiO ₂ (manufactured by Fuso Chemical Co., Ltd., product name "Quattron SP-03F")
E: Non-spherical SiO ₂ (manufactured by Tosoh Silica Corporation, product name "Nipsil EL")

From the results in Table 1, it was confirmed that the membrane electrode assemblies of Examples 1 to 11 obtained from the electrode material of the present invention had a high initial voltage, a low cell resistance, and showed a high voltage even after maintaining a high potential, and therefore had high power generation performance and high durability against a high potential, and were effective as an electrode material.
Regarding the voltage difference of 20 mV (0.02 W in terms of power) between Example 9 and Comparative Example 2, this measurement was performed using a single electrode with an electrode area of 1 ^cm2 . However, in the case of a fuel cell vehicle with an output of approximately 100 kW, several hundred membrane electrode assemblies with an electrode area more than a thousand times larger are stacked, resulting in an electrode area more than several hundred thousand times larger, which results in a difference in power of at least several kW, which is an extremely large difference.
Furthermore, it was confirmed from the results in Table 2 that the membrane electrode assemblies of Examples 10 and 11 obtained from the electrode materials of the present invention had a high water electrolysis current density.

Claims (9)

An electrode material characterized by having a structure in which at least one noble metal selected from Ru, Ir, Rh, and Pd and/or its oxide is supported directly on spherical _SiO2 . The electrode material described in claim 1, characterized in that the at least one noble metal selected from Ru, Ir, Rh, and Pd is Ru and/or Ir. 3. The electrode material according to claim ₁ , wherein the electrode material has a structure in which at least one noble metal selected from Ru, Ir, Rh, and Pd and/or an oxide thereof is directly supported on spherical SiO2, and then Pt and/or an oxide thereof is further supported. An electrode material according to any one of claims 1 to 3, characterized in that it is an electrode material for a fuel cell or a water electrolysis cell. An electrode constructed from the electrode material described in any one of claims 1 to 4. A fuel cell comprising the electrode described in claim 5. A water electrolysis cell comprising the electrode described in claim 5. A method for producing the electrode material according to claim 1 or 2, comprising:
The manufacturing method is a method for manufacturing an electrode material, characterized by comprising a step of directly supporting at least one noble metal selected from Ru, Ir, Rh, and Pd and/or its oxide on spherical _SiO2 . A method for producing the electrode material according to claim 3, comprising the steps of:
The production method includes a step ( 1) of directly supporting at least one noble metal selected from Ru, Ir, Rh, and Pd and/or its oxide on spherical _SiO2 ;
The method for producing an electrode material comprises, after the step (1), a step (2) of supporting Pt and/or an oxide thereof.