WO2011136186A1 - Electrode material - Google Patents
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- WO2011136186A1 WO2011136186A1 PCT/JP2011/060084 JP2011060084W WO2011136186A1 WO 2011136186 A1 WO2011136186 A1 WO 2011136186A1 JP 2011060084 W JP2011060084 W JP 2011060084W WO 2011136186 A1 WO2011136186 A1 WO 2011136186A1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
- H01M4/90—Selection of catalytic material
- H01M4/92—Metals of platinum group
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
- H01M4/90—Selection of catalytic material
- H01M4/92—Metals of platinum group
- H01M4/925—Metals of platinum group supported on carriers, e.g. powder carriers
- H01M4/926—Metals of platinum group supported on carriers, e.g. powder carriers on carbon or graphite
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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
- Y02E60/50—Fuel cells
Definitions
- the present invention relates to an electrode material suitable for a fuel cell, an air cell and the like.
- Electrode materials in which a catalyst such as platinum is supported on carbon are often used for electrodes of fuel cells and the like.
- the electrode characteristics of the electrode material vary greatly depending on the catalyst loading method.
- PEFC polymer electrolyte fuel cell
- proposals have been made such that platinum fine particles are supported in a highly dispersed manner see Patent Documents 1 and 2).
- PEFCs for fuel cell vehicles are required to have durability against frequent starting and stopping.
- Conventional carbon-based carriers having a high specific surface area have insufficient durability, particularly oxidation resistance.
- metal oxide carriers such as graphitized carbon and titania have been studied, but there is a problem that the specific surface area is small and it is difficult to increase the loading rate.
- Carbon nanotubes are carriers with excellent oxidation resistance and electron conductivity, but have problems such as water repellency and low specific surface area. For this reason, it has been difficult to support the catalyst using the untreated carbon nanotubes as they are.
- a functional group is formed by treatment with a mixed acid or the like. However, in this case, the activity is not always sufficient, and the oxidation resistance is often not at the expected level.
- An object of the present invention is to provide an electrode material having a high catalyst loading ratio, good durability, and high activity.
- An electrode material obtained by directly supporting platinum on carbon nanotubes (2) The electrode material according to (1), wherein carbon nanotubes are supported with platinum reduced and precipitated in a liquid phase. (3) The electrode material according to (1) or (2), wherein a peak ratio (D / G) of a D band and a G band of a carbon nanotube by Raman spectroscopy is 0.17 or less. (4) The electrode material according to any one of (1) to (3), wherein the reduction deposition in the liquid phase is performed by hydrogen reduction of a platinum salt. (5) The electrode material according to any one of (1) to (4), wherein the carbon nanotube has a diameter of 200 nm or less.
- the electrode material of the present invention is suitable for an electrode (hydrogen electrode or air electrode) of a fuel cell and an air electrode of an air cell, and can also be applied as a cathode of an FED, a flat fluorescent tube, or a cold cathode tube.
- FIG. 1 is a cyclic voltammogram (CV curve) measured using the electrode material of the present invention.
- FIG. 2 is a CV curve measured using an electrode material in which a platinum catalyst is supported on commercially available carbon black.
- FIG. 3 is a CV curve measured using commercially available carbon black.
- FIG. 4 is a CV curve measured using commercially available carbon black.
- FIG. 5 is a CV curve measured using cup-stacked carbon nanofibers.
- FIG. 6 is a CV curve measured using multi-walled carbon nanotubes.
- the potential is a standard hydrogen electrode reference potential.
- CNT carbon nanotubes
- 3 to 6 are cyclic voltammograms (CV curves) showing the comparison.
- the broken line is the case of the gold (Au) substrate only, and the solid line is the CV curve when the carbon-based material is applied.
- the measurement conditions for the CV curve are the same as in the examples described later.
- the method for producing the sample electrode was in accordance with the example, and only the carbon-based material was supported on the gold substrate. In FIG.
- Example 3 commercially available carbon black (Ketjen Black having a specific surface area of 1200 m 2 / g) was used.
- FIG. 4 commercially available carbon black (Vulcan XC-72 having a specific surface area of 250 m 2 / g) was used.
- FIG. 5 cup-stacked carbon nanofibers were used.
- FIG. 6 the same CNT used in Example 1 of the example was used.
- CNTs may be single-walled CNTs or multilayered CNTs, but multilayered CNTs are preferred because they are less susceptible to oxidation and easy to handle.
- CNTs are thought to carry platinum as highly active fine particles compared to carbon nanohorns and the like. This is probably because platinum supported on the CNT surface composed of carbon sp 2 hybrid orbitals exhibits high activity. On the other hand, it is considered that the sp 3 hybrid orbitals increase in the edge portion, and the activity of platinum existing in this portion decreases.
- the CNT used in the present invention preferably has a peak ratio (D / G) of D band to G band by Raman spectroscopy of 0.17 or less, more preferably 0.10 or less.
- the peak of the D band by Raman spectroscopy is a peak near 1350 cm ⁇ 1 , which is caused by a point defect or a crystal edge defect.
- the G band peak is a peak in the vicinity of 1580 cm ⁇ 1 and is a peak commonly observed in graphite.
- a small value of D / G indicates that there are few defects on the surface or end of the CNT. That is, it means that there are many good surfaces with few defects and long CNTs.
- a small number of defects means that there are few defects that are the starting point of the oxidation reaction, which means that the durability is excellent.
- the peak ratio of the D band and the G band by the above Raman spectroscopy is a value when the Raman spectroscopy is measured under the following conditions.
- the diameter of the CNT is preferably 200 nm or less, more preferably 150 nm or less, further preferably 10 to 100 nm, and particularly preferably 10 to 60 nm. If the diameter is in the above range, it is presumed that the electrode activity increases because platinum fine particles are supported on the surface of the CNT while being dispersed as fine particles while maintaining a highly active state.
- the diameter of the CNT is obtained from the result of image analysis of a FE-SEM (Field Emission-Scanning Electron Microscope) or TEM (Transmission Electron Microscope) photograph.
- the aspect ratio of CNT is preferably 10 or more, and more preferably 50 or more. The upper limit of the aspect ratio is not particularly limited, but is generally 1000 or less. If the aspect ratio is large, the D / G value tends to be small.
- the aspect ratio of CNT can be obtained from the result of image analysis of FE-SEM or TEM photograph.
- platinum is directly supported on CNTs.
- directly supporting means that the surface of the CNT is not modified. That is, the surface of the CNT is not modified with, for example, an organic group.
- chemical treatment for the purpose of hydrophilization is not performed. This is because platinum fine particles are supported on a specific surface of CNT, or are supported on a surface on which a metal (metal other than platinum) is supported. Because.
- platinum is preferably supported on the CNT as a catalyst as the electrode material, that is, platinum fine particles are used as the catalyst fine particles.
- platinum fine particles are used as the catalyst fine particles.
- the catalyst only platinum may be used, or platinum and a metal other than platinum may be used in combination. Examples of the metal other than platinum used in combination include nickel, palladium, silver, and gold.
- ⁇ Reduction deposition> it is preferable to use platinum which is reduced and precipitated in the liquid phase.
- the particles When deposited in the liquid phase, it is considered that the particles are easily supported as fine particles on the surface of the CNT.
- the reduction is preferably performed by hydrogen reduction of a platinum salt. It is considered that hydrogen reduction is simple and hardly affected by chemically active species that hinder the expression of the activity of the platinum fine particles.
- a colloid protection method in which colloidal particles of a catalyst are generated and simultaneously supported has been adopted.
- functional groups have been introduced and the surface has been hydrophilized.
- the activity of electrode materials using CNTs with functional groups introduced was low. Its activity was equal to or about half that of the conventional carbon black.
- by introducing a functional group it was easily oxidized at a high potential, resulting in a decrease in the oxidation resistance of CNT at a high potential, which was inappropriate.
- platinum fine particles as a catalyst are preferably deposited on the CNT surface by reducing platinum salt in a liquid phase.
- the use of platinum reduced and precipitated in the liquid phase in this way eliminates the need to introduce functional groups. For this reason, it becomes difficult for CNT to be oxidized at a high potential, and a desirable electrode material can be obtained.
- a predetermined activity is expressed by supporting platinum fine particles and CNTs on a specific surface.
- the platinum salt is preferably one containing no halogen atom.
- the nitro salt (nitro complex) or nitroammine salt (nitroammine complex) of platinum is preferable.
- the nitro salt include K 2 [Pt (NO 2 ) 4 ], Pt (NO 2 ) 3 (OC 2 H 5 ), and [Pt (NO 2 ) 3 (OC 2 H 5 )] H 2 .
- Nitroammine salts include [Pt (NH 3 ) 2 (NO 2 ) 2 ], Pt (NH 3 ) 2 (NO 2 ) 3 (OC 2 H 5 ), Pt (NH 3 ) 2 (NO 2 ) 2 ( OC 2 H 5 ) (NO 3 ), Pt (NH 3 ) (NO 2 ) (OC 2 H 5 ), [Pt (NH 3 ) (NO 2 ) 2 (OC 2 H 5 )] H, Pt (NH 3 ) 2 (NO 2 ) 3 (COCH 3 ), Pt (NH 3 ) 2 (NO 2 ) (COCH 3 ), [Pt (NH 3 ) (NO 2 ) 2 (COCH 3 )] H, Pt (NH 3 ) 2 (NO 2 ) 3 (OCOCH 3 ), Pt (NH 3 ) 2 (NO 2 ) (OCOCH 3 ), [Pt (NH 3 ) (NO 2 ) 2 (OCOCH 3 )] H and the like can be exemplified.
- the liquid phase reduction method when the liquid phase reduction method is adopted, that is, when platinum that is reduced and precipitated in the liquid phase is used, no aggregation inhibitor is used.
- Anti-agglomeration agents are generally used in colloid protection methods. Since no anti-aggregation agent is used, the removal step is also unnecessary. Heating, which is a general removal step, causes coalescence of catalyst fine particles and causes a reduction in catalyst dispersion.
- Examples of the hydrogen reduction method include a method of dispersing CNT in water, adding a platinum salt, and introducing hydrogen gas into water. It is known that it is difficult to stably disperse CNTs, particularly long (high aspect ratio) multilayer CNTs, in a liquid. In the present invention, a permanent distributed state is not necessarily required.
- the concentration at which CNT is dispersed in water is preferably 100 to 900 mg / L, and more preferably 100 to 300 mg / L.
- ultrasonic treatment for the same purpose, alcohols such as ethanol may be added.
- alcohols short-chain alcohols are preferable, and alcohols having 1 to 10 carbon atoms are preferable.
- monools such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-2-propanol, 1-pentanol, 2-ethyl-1-hexanol, etc.
- Polyhydric alcohols such as ethylene glycol and glycerin can be exemplified. Of these, methanol or ethanol is particularly preferred.
- the concentration of the added alcohol is not particularly limited. For example, when ethanol is used, it is preferably 10 to 300 g / L, more preferably 20 to 200 g / L in the solution for depositing the platinum salt.
- the platinum salt may be added as a solid or an aqueous solution to a system in which CNTs are dispersed. It is preferable to add an aqueous solution of a platinum salt to the CNT dispersion because it is easy to operate.
- the concentration of the platinum salt is preferably 10 to 1000 mg / L in the solution for depositing the platinum salt, and more preferably 10 to 100 mg / L. It is considered that highly active platinum fine particles are precipitated by reducing a dilute solution of platinum salt.
- the amount of hydrogen gas introduced is preferably 1 to 20 g / L ⁇ Hr.
- the pressure at the time of introducing hydrogen gas may be a normal pressure or a pressurized pressure.
- the inert gas argon or nitrogen gas is preferable.
- CNT When the electrode material is extremely small, CNT is deposited on an inert substrate (eg, glassy carbon), and then an aqueous platinum salt solution is dropped, followed by exposure to an air stream containing hydrogen. Even manufacture is possible.
- the temperature during the reduction is not particularly limited, but is preferably 5 to 95 ° C, more preferably 20 to 60 ° C. After the reduction is completed, CNTs are collected by filtration and dried to form an electrode material.
- the drying temperature is preferably 20 to 150 ° C, more preferably 50 to 80 ° C.
- the electrode material of the present invention uses the above electrode material. Specifically, for example, an electrode material can be kneaded with a binder and formed into a required shape to obtain an electrode.
- the binder include a fluorinated resin having a sulfonic acid.
- the fluorine-containing resin having a sulfonic acid include a resin (trade name: Flemion) manufactured by Asahi Glass Co., Ltd. and a resin (trade name: Nafion) manufactured by DuPont.
- the electrode of the present invention is suitable for a fuel cell electrode (hydrogen electrode or air electrode). It can also be applied to the air electrode of an air battery. Furthermore, it is expected to be applied to cathodes of FED (Field Emission Display), flat fluorescent tubes, and cold cathode tubes.
- FED Field Emission Display
- Examples 1 to 3 and 8 are examples, and examples 4 to 7 and 9 are comparative examples.
- Example 1 As the CNT, MWNT-7 manufactured by Hodogaya Chemical Co., Ltd. was used. It is a multi-walled CNT having a D / G of 0.08, a diameter of 60 nm, and an aspect ratio of about 120. 3 mg of the CNT was put into 30 mL (liter) of the mixed solvent A and dispersed by irradiation with ultrasonic waves for 15 minutes to obtain a solution 1A.
- the mixed solvent A is a solvent obtained by mixing tetrahydrofuran and HFE-347pc-f (CF 3 CH 2 OCF 2 CF 2 H, manufactured by Asahi Glass Co., Ltd.) at 1: 1 (mass ratio). From this solution 1A, 70 ⁇ L was taken with a pipette, dropped onto the disk electrode of the rotating electrode, and dried to deposit CNTs.
- the disk electrode is an electrode made of glassy carbon having a diameter of 5 mm.
- a platinum salt solution manufactured by Ishifuku Metal Industry Co., Ltd., dinitrodiammine platinum nitric acid solution, platinum concentration 100.93 g / L) ([Pt ( 200 ⁇ L of NH 3 ) 2 (NO 2 ) 2 ] / HNO 3 solution) was added and stirred well to obtain Solution 1B. 15 ⁇ L of this solution 1B was collected using a micropipette and dropped onto the CNT deposited on the disk electrode.
- the disk electrode was set in a reaction tube (made of quartz, cylinder having an inner diameter of 17 mm and a length of 19 cm), and hydrogen gas was introduced at 0.1 g / Hr at normal pressure. The temperature was 25 ° C. The introduction of hydrogen gas was stopped after 1 hour, and the electrode was taken out after replacing with helium gas. The reason for substituting with helium gas is to remove hydrogen on the catalyst surface and prevent overheating and deterioration of the catalyst surface due to oxidation in the air. An ionomer dispersion solution (manufactured by DuPont, Nafion solution) was dropped and dried to obtain a sample electrode 1. This sample electrode 1 was subjected to electrode characteristic evaluation.
- FIG. 1 is a CV curve in the case of using the sample electrode 1 measured according to the conditions described later.
- an adsorption / desorption peak of hydrogen was observed at a considerably lower potential than that of a general catalyst, that is, a portion close to the equilibrium potential of hydrogen.
- the characteristic characteristic of the electrode material of the present invention that the oxidation-reduction potential of platinum was higher than that of a general catalyst was confirmed. From the equilibrium potential of hydrogen that occurs as UPD (underpotential deposition) of hydrogen, an adsorption phenomenon of hydrogen atoms at a noble potential was observed.
- Example 2 A solution 2A was prepared by dispersing 14 mg of the same CNT as in Example 1 in 100 g of the mixed solvent B. The same dinitrodiammine platinum nitric acid solution as in Example 1 was diluted with ultrapure water to obtain a solution 2B containing 0.2 g / L of platinum. 30 mL of Solution 2B was added to Solution 2A. Hydrogen gas was introduced into this mixed solution by bubbling at normal pressure at 0.1 g / Hr. The temperature was 25 ° C. One hour later, the introduction of hydrogen gas was stopped, and the resulting liquid was collected by suction filtration (filter paper: No. 2, manufactured by Advantech, diameter: 110 mm). This was dried in air at 80 ° C.
- Example 2 An electrode material of 30 mass% Pt / CNT (calculated value). 3 mg of this material was dispersed in 30 mL of mixed solvent A. 70 ⁇ L was collected with a micropipette, dropped onto the same disk electrode as in Example 1, treated with an ionomer dispersion solution as in Example 1, and dried to obtain a sample electrode 2. This sample electrode 2 was subjected to electrode characteristic evaluation. The CV curve was the same as in Example 1.
- Example 3 As the CNT, Thin-MWCNT manufactured by Microphase was used. It is a multi-walled CNT having a D / G of 0.08, a diameter of 25 nm, and an aspect ratio of about 30 or more.
- the electrode material of 30 mass% Pt / CNT (calculated value) was obtained in the same manner as in Example 2 except that CNT was changed. This material was treated in the same manner as in Example 2 and 3 mg was dispersed in 30 mL of mixed solvent A. 70 ⁇ L was collected with a micropipette, dropped onto the same disk electrode as in Example 1, treated with an ionomer dispersion solution in the same manner as in Example 1, and dried to obtain a sample electrode 3. This sample electrode 3 was subjected to electrode characteristic evaluation. The CV curve was the same as in Example 1.
- Example 5 instead of CNTs, cup-stacked carbon nanofibers (CNF) were used. D / G is 0.18. The diameter was 50 nm. An electrode material of 30% by mass Pt / CNF (calculated value) was prepared in the same manner as in Example 1 to obtain a sample electrode 5, and the characteristics were evaluated in the same manner. Similar to FIG. 2 of Example 7, the CV curve showed a general shape in which hydrogen adsorption / desorption occurs at a relatively high potential.
- CNF cup-stacked carbon nanofibers
- Example 6 70 mg of CNT (same as Example 3) hydrophilized in the same manner as in Example 4 was dispersed in ethanol, and an ultrasonic wave was irradiated for 30 minutes to prepare a CNT dispersion solution.
- a dinitrodiammine platinum nitrate solution (same as Example 1) manufactured by Ishifuku Metal Industry Co., Ltd. was evaporated to dryness at 80 ° C. using a rotary evaporator to obtain a tan powder. While maintaining the temperature at 50 ° C. or lower, ethanol was gradually added to the tan powder to prepare a platinum ammine ethoxide complex solution having a platinum concentration of 50 g / L.
- This ethanol solution containing 30 mg in terms of platinum amount was added to the CNT dispersion solution and irradiated with ultrasonic waves for 30 minutes. It heated to 60 degreeC using the hot stirrer, and dried slowly. Thereafter, reduction was performed in an argon stream containing 10% hydrogen (volume ratio) to obtain an electrode material of 30% by mass Pt / CNT (calculated value). The temperature during the reduction was slowly raised from room temperature to 60 ° C., then raised to 120 ° C. at a rate of 5 ° C. per minute, and held for 1 hour. Thereafter, the temperature was raised to 200 ° C. at a rate of 5 ° C. per minute, held for 2 hours, and then slowly cooled to room temperature. A sample electrode 6 was obtained using this material, and the characteristics were evaluated in the same manner. Similar to FIG. 2 of Example 7, the CV curve showed a general shape in which hydrogen adsorption / desorption occurs at a relatively high potential.
- Example 7 A sample electrode 7 was obtained using a commercially available catalyst (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., TEC10E50E), and the characteristics were similarly evaluated. As shown in FIG. 2, the CV curve showed a general shape in which hydrogen adsorption / desorption occurs at a relatively high potential. In particular, the oxidation / reduction current peak of hydrogen became broad, and the activity of the catalyst also decreased.
- the peak potential of the reduction current of platinum oxide recognized around 0.6 V (Ag / AgCl electrode reference) has a difference of 70 mV. This is presumably because platinum is hardly oxidized in the electrode material of the present invention.
- the mass activity at 0.85 V when the electrode material shown here was swept cathodic at a rate of 1.2 V to 5 mV / sec was 0.041 A / mg Pt for the electrode material of the present invention, and 0. 0051 A / mg Pt. It can be seen that the electrode material of the present invention provides high oxygen reduction activity.
- the activity was determined by the following electrochemical measurement.
- a cell manufactured by Hokuto Denko Co., Ltd. was used.
- As the working electrode each sample electrode prepared in each of the above examples was used. Glassy carbon was used for the counter electrode.
- As the reference electrode a double junction type silver / silver chloride electrode was used.
- the cell temperature was 60 ° C., 0.5 M sulfuric acid aqueous solution was used, and nitrogen gas was bubbled for measurement. The measurement was performed while rotating the sample electrode at 1000 rpm. In this state, cyclic voltammetry (CV) measurement was performed.
- Table 1 Samples 1 to 7 correspond to Examples 1 to 7 above.
- the mass activity ratio was determined as follows.
- the electrode material of the present invention showed an activity exceeding 2.8 times that of a commercially available catalyst. This is probably because the D / G was as small as 0.1 or less, and the platinum fine particles were directly supported on the CNT without performing the hydrophilic treatment.
- Examples 4 and 6 use CNTs subjected to hydrophilic treatment. For this reason, it is thought that platinum does not express high activity. As shown in Example 5, the activity was low even in CNF having a high D / G.
- Example 8 In the same manner as in Example 1, 30% by mass of platinum was supported on CNTs. Using this electrode, a potential step cycle test was conducted in a 0.5 M sulfuric acid aqueous solution at 60 ° C. under the following conditions. [1.3 V, hold for 30 seconds: 0.9 V, hold for 30 seconds] Repeated 300 times The mass activity before and after this potential step cycle test was compared, and the reduction rate of activity was calculated.
- Example 9 An electrode was prepared and a potential step cycle test was conducted in the same manner as in Example 8 except that ketjen black having a large specific surface area was used instead of CNT as the support.
- Platinum has a small distance between particles on a carrier having a small specific surface area and is likely to deteriorate. Therefore, the potential fluctuation resistance of the electrode material in which platinum was supported on carbon black (KB) having a very large specific surface area by the liquid phase hydrogen reduction method and the electrode material of the present invention were compared by a potential step cycle test. As a result, as shown in Table 2, it was confirmed that the rate of decrease in activity was small even though the specific surface area of CNT was extremely small. In other words, it was shown that the activity as an electrode material hardly decreases and the durability is excellent.
- the electrode material of the present invention is suitable for an electrode (hydrogen electrode or air electrode) of a fuel cell and an air electrode of an air cell. Further, it can be applied as a cathode of FED, flat fluorescent tube, and cold cathode tube. It should be noted that the entire contents of the specification, claims, drawings and abstract of Japanese Patent Application No. 2010-101279 filed on April 26, 2010 are cited herein as disclosure of the specification of the present invention. Incorporated.
Abstract
Disclosed is an electrode material exhibiting a high support rate, good durability, and high activity, and formed by directly supporting platinum on carbon nanotubes. In particular, the platinum supported on carbon nanotubes optimally has been reductively precipitated in the liquid phase. Further, the peak ratio (D/G) of the D band and the G band determined by Raman spectroscopy of the carbon nanotubes is optimally 0.17 or less. Furthermore, when the platinum reductively precipitated in the liquid phase is supported on carbon nanotubes, reductive extraction in the liquid phase is optimally performed by hydrogen reduction of platinum salt.
Description
本発明は、燃料電池、空気電池などに適する電極材料に関する。
The present invention relates to an electrode material suitable for a fuel cell, an air cell and the like.
燃料電池等の電極には、カーボンに白金等の触媒を担持させた電極材料が多く用いられている。特に触媒の担持方法により、電極材料の電極特性は大きく変化する。高出力密度を特徴とする固体高分子形燃料電池（ＰＥＦＣ）においては、反応ガスや生成物の拡散性確保のため、触媒層を薄くする必要が有り、高担持率触媒が使用される。そのため、従来は触媒粒子間距離を大きく確保できる高比表面積のカーボンブラック等の担体が用いられてきた。例えば白金微粒子を高分散に担持させる等の提案がなされている（特許文献１、２参照。）。
Electrode materials in which a catalyst such as platinum is supported on carbon are often used for electrodes of fuel cells and the like. In particular, the electrode characteristics of the electrode material vary greatly depending on the catalyst loading method. In a polymer electrolyte fuel cell (PEFC) characterized by a high power density, it is necessary to make the catalyst layer thin in order to ensure the diffusibility of the reaction gas and product, and a high loading rate catalyst is used. Therefore, conventionally, a carrier such as carbon black having a high specific surface area that can ensure a large distance between catalyst particles has been used. For example, proposals have been made such that platinum fine particles are supported in a highly dispersed manner (see Patent Documents 1 and 2).
しかし、燃料電池自動車用ＰＥＦＣにおいては頻繁な起動停止に対する耐久性が求められている。従来の高比表面積のカーボン系担体では耐久性、特に耐酸化性が不充分であった。このため、グラファイト化したカーボンやチタニア等の金属酸化物担体も検討されているが比表面積が小さく、担持率を高くしにくいという問題があった。
However, PEFCs for fuel cell vehicles are required to have durability against frequent starting and stopping. Conventional carbon-based carriers having a high specific surface area have insufficient durability, particularly oxidation resistance. For this reason, metal oxide carriers such as graphitized carbon and titania have been studied, but there is a problem that the specific surface area is small and it is difficult to increase the loading rate.
カーボンナノチューブは耐酸化性、電子伝導性に優れる担体であるが、撥水性を有し比表面積が低いなどの問題を有する。このため、未処理のカーボンナノチューブをそのまま使用して触媒を担持させることは困難であった。カーボンナノチューブの処理方法としては、混酸等で処理して官能基を形成させることが行われている。しかし、この場合に、活性は必ずしも充分なものではなく、かつ、耐酸化性も期待されるレベルではないことが多い。
Carbon nanotubes are carriers with excellent oxidation resistance and electron conductivity, but have problems such as water repellency and low specific surface area. For this reason, it has been difficult to support the catalyst using the untreated carbon nanotubes as they are. As a method for treating carbon nanotubes, a functional group is formed by treatment with a mixed acid or the like. However, in this case, the activity is not always sufficient, and the oxidation resistance is often not at the expected level.
本発明は、触媒の担持率が高く、耐久性も良好で、高活性である電極材料を提供することを目的とする。
An object of the present invention is to provide an electrode material having a high catalyst loading ratio, good durability, and high activity.
上記の課題を解決するため、以下の発明を提供する。
（１）カーボンナノチューブに直接白金を担持させてなる電極材料。
（２）カーボンナノチューブに、液相で還元析出させた白金を担持させてなる（１）に記載の電極材料。（３）カーボンナノチューブのラマン分光法によるＤバンドとＧバンドのピーク比（Ｄ／Ｇ）が０．１７以下である（１）または（２）に記載の電極材料。（４）前記液相での還元析出が、白金塩の水素還元により行われる（１）～（３）のいずれか一項に記載の電極材料。（５）前記カーボンナノチューブの直径が２００ｎｍ以下である（１）～（４）のいずれか一項に記載の電極材料。（６）前記カーボンナノチューブのアスペクト比が１０以上である（１）～（５）のいずれかに記載の電極材料。（７）（１）～（６）のいずれか一項に記載の電極材料を用いた電極。（８）カーボンナノチューブに親水化処理を施さずに白金を担持させることを特徴とする電極材料の製造方法。 In order to solve the above problems, the following inventions are provided.
(1) An electrode material obtained by directly supporting platinum on carbon nanotubes.
(2) The electrode material according to (1), wherein carbon nanotubes are supported with platinum reduced and precipitated in a liquid phase. (3) The electrode material according to (1) or (2), wherein a peak ratio (D / G) of a D band and a G band of a carbon nanotube by Raman spectroscopy is 0.17 or less. (4) The electrode material according to any one of (1) to (3), wherein the reduction deposition in the liquid phase is performed by hydrogen reduction of a platinum salt. (5) The electrode material according to any one of (1) to (4), wherein the carbon nanotube has a diameter of 200 nm or less. (6) The electrode material according to any one of (1) to (5), wherein the aspect ratio of the carbon nanotube is 10 or more. (7) An electrode using the electrode material according to any one of (1) to (6). (8) A method for producing an electrode material, wherein platinum is supported on a carbon nanotube without subjecting it to a hydrophilic treatment.
（１）カーボンナノチューブに直接白金を担持させてなる電極材料。
（２）カーボンナノチューブに、液相で還元析出させた白金を担持させてなる（１）に記載の電極材料。（３）カーボンナノチューブのラマン分光法によるＤバンドとＧバンドのピーク比（Ｄ／Ｇ）が０．１７以下である（１）または（２）に記載の電極材料。（４）前記液相での還元析出が、白金塩の水素還元により行われる（１）～（３）のいずれか一項に記載の電極材料。（５）前記カーボンナノチューブの直径が２００ｎｍ以下である（１）～（４）のいずれか一項に記載の電極材料。（６）前記カーボンナノチューブのアスペクト比が１０以上である（１）～（５）のいずれかに記載の電極材料。（７）（１）～（６）のいずれか一項に記載の電極材料を用いた電極。（８）カーボンナノチューブに親水化処理を施さずに白金を担持させることを特徴とする電極材料の製造方法。 In order to solve the above problems, the following inventions are provided.
(1) An electrode material obtained by directly supporting platinum on carbon nanotubes.
(2) The electrode material according to (1), wherein carbon nanotubes are supported with platinum reduced and precipitated in a liquid phase. (3) The electrode material according to (1) or (2), wherein a peak ratio (D / G) of a D band and a G band of a carbon nanotube by Raman spectroscopy is 0.17 or less. (4) The electrode material according to any one of (1) to (3), wherein the reduction deposition in the liquid phase is performed by hydrogen reduction of a platinum salt. (5) The electrode material according to any one of (1) to (4), wherein the carbon nanotube has a diameter of 200 nm or less. (6) The electrode material according to any one of (1) to (5), wherein the aspect ratio of the carbon nanotube is 10 or more. (7) An electrode using the electrode material according to any one of (1) to (6). (8) A method for producing an electrode material, wherein platinum is supported on a carbon nanotube without subjecting it to a hydrophilic treatment.
本発明によれば、従来のように親水化処理しなくとも触媒の高い担持率が得られ、また、従来では困難であった高い電極活性と大きい耐久性を有する電極材料が提供される。
本発明の電極材料は、燃料電池の電極（水素極または空気極）、空気電池の空気極に好適であり、さらに、ＦＥＤ、平面蛍光管、冷陰極管のカソードとしても適用できる。 According to the present invention, it is possible to obtain an electrode material having a high catalyst loading even without a hydrophilic treatment as in the prior art, and having a high electrode activity and high durability, which has been difficult in the prior art.
The electrode material of the present invention is suitable for an electrode (hydrogen electrode or air electrode) of a fuel cell and an air electrode of an air cell, and can also be applied as a cathode of an FED, a flat fluorescent tube, or a cold cathode tube.
本発明の電極材料は、燃料電池の電極（水素極または空気極）、空気電池の空気極に好適であり、さらに、ＦＥＤ、平面蛍光管、冷陰極管のカソードとしても適用できる。 According to the present invention, it is possible to obtain an electrode material having a high catalyst loading even without a hydrophilic treatment as in the prior art, and having a high electrode activity and high durability, which has been difficult in the prior art.
The electrode material of the present invention is suitable for an electrode (hydrogen electrode or air electrode) of a fuel cell and an air electrode of an air cell, and can also be applied as a cathode of an FED, a flat fluorescent tube, or a cold cathode tube.
本明細書において、電位は特に記載がない限り標準水素電極基準の電位とする。
In this specification, unless otherwise specified, the potential is a standard hydrogen electrode reference potential.
＜カーボンナノチューブ＞
本発明の電極材料にはカーボンナノチューブ（以下、「ＣＮＴ」と略記することもある。）を用いる。ＣＮＴは、他の炭素系材料（カーボンブラック、カーボンナノホーン等）より耐酸化性に優れている。図３～図６はその比較を示すサイクリックボルタモグラム（ＣＶ曲線）である。図３～図６のいずれも、破線は金（Ａｕ）基板のみの場合であり、実線は炭素系材料を塗布した場合のＣＶ曲線である。ＣＶ曲線の測定条件は後述する実施例と同じである。また試料電極の作製方法は実施例に準じ、金基板に炭素系材料のみを担持させた。なお、図３では市販のカーボンブラック（比表面積が１２００ｍ２／ｇのケッチェンブラック）を用いた。図４では市販のカーボンブラック（比表面積が２５０ｍ２／ｇのバルカンＸＣ－７２）を用いた。図５ではカップ積層型のカーボンナノファイバーを用いた。図６では、実施例の例１で用いたものと同じＣＮＴを用いた。 <Carbon nanotube>
As the electrode material of the present invention, carbon nanotubes (hereinafter sometimes abbreviated as “CNT”) are used. CNT is superior in oxidation resistance to other carbon-based materials (carbon black, carbon nanohorn, etc.). 3 to 6 are cyclic voltammograms (CV curves) showing the comparison. In all of FIGS. 3 to 6, the broken line is the case of the gold (Au) substrate only, and the solid line is the CV curve when the carbon-based material is applied. The measurement conditions for the CV curve are the same as in the examples described later. The method for producing the sample electrode was in accordance with the example, and only the carbon-based material was supported on the gold substrate. In FIG. 3, commercially available carbon black (Ketjen Black having a specific surface area of 1200 m 2 / g) was used. In FIG. 4, commercially available carbon black (Vulcan XC-72 having a specific surface area of 250 m 2 / g) was used. In FIG. 5, cup-stacked carbon nanofibers were used. In FIG. 6, the same CNT used in Example 1 of the example was used.
本発明の電極材料にはカーボンナノチューブ（以下、「ＣＮＴ」と略記することもある。）を用いる。ＣＮＴは、他の炭素系材料（カーボンブラック、カーボンナノホーン等）より耐酸化性に優れている。図３～図６はその比較を示すサイクリックボルタモグラム（ＣＶ曲線）である。図３～図６のいずれも、破線は金（Ａｕ）基板のみの場合であり、実線は炭素系材料を塗布した場合のＣＶ曲線である。ＣＶ曲線の測定条件は後述する実施例と同じである。また試料電極の作製方法は実施例に準じ、金基板に炭素系材料のみを担持させた。なお、図３では市販のカーボンブラック（比表面積が１２００ｍ２／ｇのケッチェンブラック）を用いた。図４では市販のカーボンブラック（比表面積が２５０ｍ２／ｇのバルカンＸＣ－７２）を用いた。図５ではカップ積層型のカーボンナノファイバーを用いた。図６では、実施例の例１で用いたものと同じＣＮＴを用いた。 <Carbon nanotube>
As the electrode material of the present invention, carbon nanotubes (hereinafter sometimes abbreviated as “CNT”) are used. CNT is superior in oxidation resistance to other carbon-based materials (carbon black, carbon nanohorn, etc.). 3 to 6 are cyclic voltammograms (CV curves) showing the comparison. In all of FIGS. 3 to 6, the broken line is the case of the gold (Au) substrate only, and the solid line is the CV curve when the carbon-based material is applied. The measurement conditions for the CV curve are the same as in the examples described later. The method for producing the sample electrode was in accordance with the example, and only the carbon-based material was supported on the gold substrate. In FIG. 3, commercially available carbon black (Ketjen Black having a specific surface area of 1200 m 2 / g) was used. In FIG. 4, commercially available carbon black (Vulcan XC-72 having a specific surface area of 250 m 2 / g) was used. In FIG. 5, cup-stacked carbon nanofibers were used. In FIG. 6, the same CNT used in Example 1 of the example was used.
図３、図４または図５のＣＮＴ以外の炭素系材料では、特に０．６Ｖより高電位において酸化されやすいことを示している。一方、図６に示すようにＣＮＴは基板に用いた金のＣＶ曲線とほぼ同じ特性が得られている。これによりＣＮＴが耐酸化性に優れていることが確認された。
これはＣＮＴの表面のほとんどが、グラファイト構造の基底面に相当する表面であるためと考えられている。またＣＮＴを用いた電極材料は電子伝導性が高く、かつ、ガス透過性も高い。このためＰＥＦＣ用電極（ガス拡散電極）の材料として好適である。さらにＣＮＴはケッチェンブラックのような微細孔の発達したカーボンブラックとは異なり、電極触媒を膜電極接合体（ＭＥＡ）へ適用する際に、イオン交換樹脂等のアイオノマの被覆も容易である点でも好ましい。 This indicates that carbon-based materials other than the CNT of FIG. 3, FIG. 4 or FIG. 5 are likely to be oxidized particularly at a potential higher than 0.6V. On the other hand, as shown in FIG. 6, the CNT has almost the same characteristics as the CV curve of gold used for the substrate. Thereby, it was confirmed that CNT was excellent in oxidation resistance.
This is probably because most of the surface of the CNT is a surface corresponding to the basal plane of the graphite structure. An electrode material using CNTs has high electron conductivity and high gas permeability. For this reason, it is suitable as a material for an electrode for PEFC (gas diffusion electrode). Furthermore, unlike carbon black with fine pores such as ketjen black, CNT is easy to coat ionomers such as ion exchange resins when applying an electrode catalyst to a membrane electrode assembly (MEA). preferable.
これはＣＮＴの表面のほとんどが、グラファイト構造の基底面に相当する表面であるためと考えられている。またＣＮＴを用いた電極材料は電子伝導性が高く、かつ、ガス透過性も高い。このためＰＥＦＣ用電極（ガス拡散電極）の材料として好適である。さらにＣＮＴはケッチェンブラックのような微細孔の発達したカーボンブラックとは異なり、電極触媒を膜電極接合体（ＭＥＡ）へ適用する際に、イオン交換樹脂等のアイオノマの被覆も容易である点でも好ましい。 This indicates that carbon-based materials other than the CNT of FIG. 3, FIG. 4 or FIG. 5 are likely to be oxidized particularly at a potential higher than 0.6V. On the other hand, as shown in FIG. 6, the CNT has almost the same characteristics as the CV curve of gold used for the substrate. Thereby, it was confirmed that CNT was excellent in oxidation resistance.
This is probably because most of the surface of the CNT is a surface corresponding to the basal plane of the graphite structure. An electrode material using CNTs has high electron conductivity and high gas permeability. For this reason, it is suitable as a material for an electrode for PEFC (gas diffusion electrode). Furthermore, unlike carbon black with fine pores such as ketjen black, CNT is easy to coat ionomers such as ion exchange resins when applying an electrode catalyst to a membrane electrode assembly (MEA). preferable.
ＣＮＴとしては、単層ＣＮＴであっても多層ＣＮＴであってもよいが、材料として酸化を受けにくく扱いやすいことから多層ＣＮＴが好ましい。
CNTs may be single-walled CNTs or multilayered CNTs, but multilayered CNTs are preferred because they are less susceptible to oxidation and easy to handle.
ＣＮＴは、カーボンナノホーン等と比較して、白金が高活性の微粒子として担持されると考えられる。これは炭素のｓｐ２混成軌道で構成されるＣＮＴ表面に担持された白金が高い活性を示すためと考えられる。一方、エッジ部分においては、ｓｐ３混成軌道が多くなり、この部分に存在する白金の活性が低下すると考えられる。
CNTs are thought to carry platinum as highly active fine particles compared to carbon nanohorns and the like. This is probably because platinum supported on the CNT surface composed of carbon sp 2 hybrid orbitals exhibits high activity. On the other hand, it is considered that the sp 3 hybrid orbitals increase in the edge portion, and the activity of platinum existing in this portion decreases.
本発明に用いるＣＮＴは、ラマン分光法によるＤバンドとＧバンドのピーク比（Ｄ／Ｇ）が０．１７以下であることが好ましく、０．１０以下がより好ましい。ただしラマン分光法によるＤバンドのピークとは、１３５０ｃｍ－１付近のピークであり、点欠陥や結晶端の欠陥に起因する。またＧバンドのピークとは、１５８０ｃｍ－１付近のピークであり、グラファイトに共通して観測されるピークである。Ｄ／Ｇが小さい値であることは、ＣＮＴの表面または端部の欠陥が少ないことを示す。すなわち欠陥の少ない良好な表面が多く、長いＣＮＴであることを意味する。欠陥が少ないことは、酸化反応の起点となる欠陥が少ないことを意味し、耐久性に優れることを意味する。
The CNT used in the present invention preferably has a peak ratio (D / G) of D band to G band by Raman spectroscopy of 0.17 or less, more preferably 0.10 or less. However, the peak of the D band by Raman spectroscopy is a peak near 1350 cm −1 , which is caused by a point defect or a crystal edge defect. The G band peak is a peak in the vicinity of 1580 cm −1 and is a peak commonly observed in graphite. A small value of D / G indicates that there are few defects on the surface or end of the CNT. That is, it means that there are many good surfaces with few defects and long CNTs. A small number of defects means that there are few defects that are the starting point of the oxidation reaction, which means that the durability is excellent.
なお、上記のラマン分光法によるＤバンドとＧバンドのピーク比は、以下の条件でラマン分光の測定を行った場合の値である。半導体レーザー 波長：５３２ｎｍ、出力：１００ｍＷ、減光率：１０％のときサンプル上でレーザーパワーが約０．６ｍＷ、対物レンズ：１００倍、時間：３０～１８０秒。
In addition, the peak ratio of the D band and the G band by the above Raman spectroscopy is a value when the Raman spectroscopy is measured under the following conditions. Semiconductor laser Wavelength: 532 nm, output: 100 mW, attenuation rate: 10%, laser power is about 0.6 mW on the sample, objective lens: 100 times, time: 30 to 180 seconds.
ＣＮＴの直径は、２００ｎｍ以下が好ましく、１５０ｎｍ以下がより好ましく、１０～１００ｎｍがさらに好ましく、１０～６０ｎｍが特に好ましい。直径が前記範囲であれば、ＣＮＴの表面に白金微粒子が、微粒子として分散したまま高活性の状態を保ちながら担持されることになるため、電極活性が高くなると推定される。
なおＣＮＴの直径は、ＦＥ－ＳＥＭ（Field Emission-Scanning Electron Microscope）またはＴＥＭ（Transmission Electron Microscope）写真の画像解析の結果から求められる。またＣＮＴのアスペクト比は、１０以上が好ましく、５０以上がより好ましい。アスペクト比の上限は特に無いが一般的には１０００以下である。アスペクト比が大きいとＤ／Ｇの値は小さくなりやすい。なおＣＮＴのアスペクト比は、ＦＥ－ＳＥＭまたはＴＥＭ写真の画像解析の結果から求められる。 The diameter of the CNT is preferably 200 nm or less, more preferably 150 nm or less, further preferably 10 to 100 nm, and particularly preferably 10 to 60 nm. If the diameter is in the above range, it is presumed that the electrode activity increases because platinum fine particles are supported on the surface of the CNT while being dispersed as fine particles while maintaining a highly active state.
The diameter of the CNT is obtained from the result of image analysis of a FE-SEM (Field Emission-Scanning Electron Microscope) or TEM (Transmission Electron Microscope) photograph. The aspect ratio of CNT is preferably 10 or more, and more preferably 50 or more. The upper limit of the aspect ratio is not particularly limited, but is generally 1000 or less. If the aspect ratio is large, the D / G value tends to be small. The aspect ratio of CNT can be obtained from the result of image analysis of FE-SEM or TEM photograph.
なおＣＮＴの直径は、ＦＥ－ＳＥＭ（Field Emission-Scanning Electron Microscope）またはＴＥＭ（Transmission Electron Microscope）写真の画像解析の結果から求められる。またＣＮＴのアスペクト比は、１０以上が好ましく、５０以上がより好ましい。アスペクト比の上限は特に無いが一般的には１０００以下である。アスペクト比が大きいとＤ／Ｇの値は小さくなりやすい。なおＣＮＴのアスペクト比は、ＦＥ－ＳＥＭまたはＴＥＭ写真の画像解析の結果から求められる。 The diameter of the CNT is preferably 200 nm or less, more preferably 150 nm or less, further preferably 10 to 100 nm, and particularly preferably 10 to 60 nm. If the diameter is in the above range, it is presumed that the electrode activity increases because platinum fine particles are supported on the surface of the CNT while being dispersed as fine particles while maintaining a highly active state.
The diameter of the CNT is obtained from the result of image analysis of a FE-SEM (Field Emission-Scanning Electron Microscope) or TEM (Transmission Electron Microscope) photograph. The aspect ratio of CNT is preferably 10 or more, and more preferably 50 or more. The upper limit of the aspect ratio is not particularly limited, but is generally 1000 or less. If the aspect ratio is large, the D / G value tends to be small. The aspect ratio of CNT can be obtained from the result of image analysis of FE-SEM or TEM photograph.
本発明においては、白金はＣＮＴに直接担持させる。ここで、直接担持させるとは、ＣＮＴの表面を修飾しないことを意味する。すなわち、ＣＮＴの表面を例えば有機基等で修飾しないことである。特に、親水化を目的とした化学的処理を行わないことである。これは白金の微粒子が、ＣＮＴの特定の表面に担持されているか、または金属（白金以外の金属）が担持された表面に担持されていることで、所定の活性を発現していると考えられるからである。
In the present invention, platinum is directly supported on CNTs. Here, directly supporting means that the surface of the CNT is not modified. That is, the surface of the CNT is not modified with, for example, an organic group. In particular, chemical treatment for the purpose of hydrophilization is not performed. This is because platinum fine particles are supported on a specific surface of CNT, or are supported on a surface on which a metal (metal other than platinum) is supported. Because.
＜触媒微粒子＞
本発明においては、電極材料として、ＣＮＴに触媒として白金を担持させる、すなわち触媒微粒子としては白金微粒子を用いるのが好ましい。ここで触媒としては、白金のみを用いてもよく、白金と白金以外の金属とを併用してもよい。併用する白金以外の金属としては、ニッケル、パラジウム、銀、金等が挙げられる。 <Catalyst fine particles>
In the present invention, platinum is preferably supported on the CNT as a catalyst as the electrode material, that is, platinum fine particles are used as the catalyst fine particles. Here, as the catalyst, only platinum may be used, or platinum and a metal other than platinum may be used in combination. Examples of the metal other than platinum used in combination include nickel, palladium, silver, and gold.
本発明においては、電極材料として、ＣＮＴに触媒として白金を担持させる、すなわち触媒微粒子としては白金微粒子を用いるのが好ましい。ここで触媒としては、白金のみを用いてもよく、白金と白金以外の金属とを併用してもよい。併用する白金以外の金属としては、ニッケル、パラジウム、銀、金等が挙げられる。 <Catalyst fine particles>
In the present invention, platinum is preferably supported on the CNT as a catalyst as the electrode material, that is, platinum fine particles are used as the catalyst fine particles. Here, as the catalyst, only platinum may be used, or platinum and a metal other than platinum may be used in combination. Examples of the metal other than platinum used in combination include nickel, palladium, silver, and gold.
＜還元析出＞
本発明では、液相で還元析出させた白金が用いられることが好ましい。液相で析出させると、ＣＮＴの表面に微粒子として担持されやすいと考えられる。還元は白金塩の水素還元により行うことが好ましい。水素還元であれば、簡便でかつ白金微粒子の活性の発現を妨げる化学的活性種の影響を受けにくいためと考えられる。 <Reduction deposition>
In the present invention, it is preferable to use platinum which is reduced and precipitated in the liquid phase. When deposited in the liquid phase, it is considered that the particles are easily supported as fine particles on the surface of the CNT. The reduction is preferably performed by hydrogen reduction of a platinum salt. It is considered that hydrogen reduction is simple and hardly affected by chemically active species that hinder the expression of the activity of the platinum fine particles.
本発明では、液相で還元析出させた白金が用いられることが好ましい。液相で析出させると、ＣＮＴの表面に微粒子として担持されやすいと考えられる。還元は白金塩の水素還元により行うことが好ましい。水素還元であれば、簡便でかつ白金微粒子の活性の発現を妨げる化学的活性種の影響を受けにくいためと考えられる。 <Reduction deposition>
In the present invention, it is preferable to use platinum which is reduced and precipitated in the liquid phase. When deposited in the liquid phase, it is considered that the particles are easily supported as fine particles on the surface of the CNT. The reduction is preferably performed by hydrogen reduction of a platinum salt. It is considered that hydrogen reduction is simple and hardly affected by chemically active species that hinder the expression of the activity of the platinum fine particles.
従前、触媒微粒子の担持法としては、触媒のコロイド粒子を生成させ、同時に担持させるコロイド保護法等が採用されてきた。コロイド保護法では、比表面積が小さく、撥水性の高い表面を有するＣＮＴに、そのまま未処理の状態で、触媒微粒子を担持させることは困難であった。この担持のために官能基を導入し、表面を親水化処理することが行われてきた。
しかし官能基を導入したＣＮＴを用いた電極材料の活性は低かった。その活性は、従来のカーボンブラックを用いた場合と同等か約半分程度に過ぎなかった。さらに官能基を導入することで高電位において容易に酸化されやすくなり、ＣＮＴの高電位における耐酸化性を低下させる結果となり不適当となっていた。
これに対し、本発明においては、好適には、白金塩を液相で還元させることにより、触媒である白金微粒子をＣＮＴ表面に析出させる。このように液相で還元析出させた白金を用いることにより、官能基を導入する必要がなくなる。このため高電位においてＣＮＴが酸化されにくくなり、電極材料として望ましいものが得られるようになる。また、白金の微粒子とＣＮＴの特定の表面への担持により、所定の活性が発現していると考えられる。 Conventionally, as a method for supporting catalyst fine particles, a colloid protection method in which colloidal particles of a catalyst are generated and simultaneously supported has been adopted. In the colloid protection method, it is difficult to support catalyst fine particles in an untreated state as they are on a CNT having a small specific surface area and a surface with high water repellency. For this support, functional groups have been introduced and the surface has been hydrophilized.
However, the activity of electrode materials using CNTs with functional groups introduced was low. Its activity was equal to or about half that of the conventional carbon black. Furthermore, by introducing a functional group, it was easily oxidized at a high potential, resulting in a decrease in the oxidation resistance of CNT at a high potential, which was inappropriate.
On the other hand, in the present invention, platinum fine particles as a catalyst are preferably deposited on the CNT surface by reducing platinum salt in a liquid phase. The use of platinum reduced and precipitated in the liquid phase in this way eliminates the need to introduce functional groups. For this reason, it becomes difficult for CNT to be oxidized at a high potential, and a desirable electrode material can be obtained. In addition, it is considered that a predetermined activity is expressed by supporting platinum fine particles and CNTs on a specific surface.
しかし官能基を導入したＣＮＴを用いた電極材料の活性は低かった。その活性は、従来のカーボンブラックを用いた場合と同等か約半分程度に過ぎなかった。さらに官能基を導入することで高電位において容易に酸化されやすくなり、ＣＮＴの高電位における耐酸化性を低下させる結果となり不適当となっていた。
これに対し、本発明においては、好適には、白金塩を液相で還元させることにより、触媒である白金微粒子をＣＮＴ表面に析出させる。このように液相で還元析出させた白金を用いることにより、官能基を導入する必要がなくなる。このため高電位においてＣＮＴが酸化されにくくなり、電極材料として望ましいものが得られるようになる。また、白金の微粒子とＣＮＴの特定の表面への担持により、所定の活性が発現していると考えられる。 Conventionally, as a method for supporting catalyst fine particles, a colloid protection method in which colloidal particles of a catalyst are generated and simultaneously supported has been adopted. In the colloid protection method, it is difficult to support catalyst fine particles in an untreated state as they are on a CNT having a small specific surface area and a surface with high water repellency. For this support, functional groups have been introduced and the surface has been hydrophilized.
However, the activity of electrode materials using CNTs with functional groups introduced was low. Its activity was equal to or about half that of the conventional carbon black. Furthermore, by introducing a functional group, it was easily oxidized at a high potential, resulting in a decrease in the oxidation resistance of CNT at a high potential, which was inappropriate.
On the other hand, in the present invention, platinum fine particles as a catalyst are preferably deposited on the CNT surface by reducing platinum salt in a liquid phase. The use of platinum reduced and precipitated in the liquid phase in this way eliminates the need to introduce functional groups. For this reason, it becomes difficult for CNT to be oxidized at a high potential, and a desirable electrode material can be obtained. In addition, it is considered that a predetermined activity is expressed by supporting platinum fine particles and CNTs on a specific surface.
＜白金塩＞
白金塩としては、ハロゲン原子を含まないものが好ましい。白金塩としては、白金のニトロ塩（ニトロ錯体）またはニトロアンミン塩（ニトロアンミン錯体）が好ましい。ニトロ塩としては、Ｋ２［Ｐｔ（ＮＯ２）４］、Ｐｔ（ＮＯ２）３（ＯＣ２Ｈ５）、［Ｐｔ（ＮＯ２）３（ＯＣ２Ｈ５）］Ｈ２が例示できる。ニトロアンミン塩としては、［Ｐｔ（ＮＨ３）２（ＮＯ２）２］、Ｐｔ（ＮＨ３）２（ＮＯ２）３（ＯＣ２Ｈ５）、Ｐｔ（ＮＨ３）２（ＮＯ２）２（ＯＣ２Ｈ５）（ＮＯ３）、Ｐｔ（ＮＨ３）（ＮＯ２）（ＯＣ２Ｈ５）、［Ｐｔ（ＮＨ３）（ＮＯ２）２（ＯＣ２Ｈ５）］Ｈ、Ｐｔ（ＮＨ３）２（ＮＯ２）３（ＣＯＣＨ３）、Ｐｔ（ＮＨ３）２（ＮＯ２）（ＣＯＣＨ３）、［Ｐｔ（ＮＨ３）（ＮＯ２）２（ＣＯＣＨ３）］Ｈ、Ｐｔ（ＮＨ３）２（ＮＯ２）３（ＯＣＯＣＨ３）、Ｐｔ（ＮＨ３）２（ＮＯ２）（ＯＣＯＣＨ３）、［Ｐｔ（ＮＨ３）（ＮＯ２）２（ＯＣＯＣＨ３）］Ｈ等が例示できる。 <Platinum salt>
The platinum salt is preferably one containing no halogen atom. As a platinum salt, the nitro salt (nitro complex) or nitroammine salt (nitroammine complex) of platinum is preferable. Examples of the nitro salt include K 2 [Pt (NO 2 ) 4 ], Pt (NO 2 ) 3 (OC 2 H 5 ), and [Pt (NO 2 ) 3 (OC 2 H 5 )] H 2 . Nitroammine salts include [Pt (NH 3 ) 2 (NO 2 ) 2 ], Pt (NH 3 ) 2 (NO 2 ) 3 (OC 2 H 5 ), Pt (NH 3 ) 2 (NO 2 ) 2 ( OC 2 H 5 ) (NO 3 ), Pt (NH 3 ) (NO 2 ) (OC 2 H 5 ), [Pt (NH 3 ) (NO 2 ) 2 (OC 2 H 5 )] H, Pt (NH 3 ) 2 (NO 2 ) 3 (COCH 3 ), Pt (NH 3 ) 2 (NO 2 ) (COCH 3 ), [Pt (NH 3 ) (NO 2 ) 2 (COCH 3 )] H, Pt (NH 3 ) 2 (NO 2 ) 3 (OCOCH 3 ), Pt (NH 3 ) 2 (NO 2 ) (OCOCH 3 ), [Pt (NH 3 ) (NO 2 ) 2 (OCOCH 3 )] H and the like can be exemplified.
白金塩としては、ハロゲン原子を含まないものが好ましい。白金塩としては、白金のニトロ塩（ニトロ錯体）またはニトロアンミン塩（ニトロアンミン錯体）が好ましい。ニトロ塩としては、Ｋ２［Ｐｔ（ＮＯ２）４］、Ｐｔ（ＮＯ２）３（ＯＣ２Ｈ５）、［Ｐｔ（ＮＯ２）３（ＯＣ２Ｈ５）］Ｈ２が例示できる。ニトロアンミン塩としては、［Ｐｔ（ＮＨ３）２（ＮＯ２）２］、Ｐｔ（ＮＨ３）２（ＮＯ２）３（ＯＣ２Ｈ５）、Ｐｔ（ＮＨ３）２（ＮＯ２）２（ＯＣ２Ｈ５）（ＮＯ３）、Ｐｔ（ＮＨ３）（ＮＯ２）（ＯＣ２Ｈ５）、［Ｐｔ（ＮＨ３）（ＮＯ２）２（ＯＣ２Ｈ５）］Ｈ、Ｐｔ（ＮＨ３）２（ＮＯ２）３（ＣＯＣＨ３）、Ｐｔ（ＮＨ３）２（ＮＯ２）（ＣＯＣＨ３）、［Ｐｔ（ＮＨ３）（ＮＯ２）２（ＣＯＣＨ３）］Ｈ、Ｐｔ（ＮＨ３）２（ＮＯ２）３（ＯＣＯＣＨ３）、Ｐｔ（ＮＨ３）２（ＮＯ２）（ＯＣＯＣＨ３）、［Ｐｔ（ＮＨ３）（ＮＯ２）２（ＯＣＯＣＨ３）］Ｈ等が例示できる。 <Platinum salt>
The platinum salt is preferably one containing no halogen atom. As a platinum salt, the nitro salt (nitro complex) or nitroammine salt (nitroammine complex) of platinum is preferable. Examples of the nitro salt include K 2 [Pt (NO 2 ) 4 ], Pt (NO 2 ) 3 (OC 2 H 5 ), and [Pt (NO 2 ) 3 (OC 2 H 5 )] H 2 . Nitroammine salts include [Pt (NH 3 ) 2 (NO 2 ) 2 ], Pt (NH 3 ) 2 (NO 2 ) 3 (OC 2 H 5 ), Pt (NH 3 ) 2 (NO 2 ) 2 ( OC 2 H 5 ) (NO 3 ), Pt (NH 3 ) (NO 2 ) (OC 2 H 5 ), [Pt (NH 3 ) (NO 2 ) 2 (OC 2 H 5 )] H, Pt (NH 3 ) 2 (NO 2 ) 3 (COCH 3 ), Pt (NH 3 ) 2 (NO 2 ) (COCH 3 ), [Pt (NH 3 ) (NO 2 ) 2 (COCH 3 )] H, Pt (NH 3 ) 2 (NO 2 ) 3 (OCOCH 3 ), Pt (NH 3 ) 2 (NO 2 ) (OCOCH 3 ), [Pt (NH 3 ) (NO 2 ) 2 (OCOCH 3 )] H and the like can be exemplified.
本発明において、液相還元法を採用する場合、つまり、液相で還元析出させた白金を用いる場合は凝集防止剤を用いない。凝集防止剤は一般にコロイド保護法で用いられているものである。凝集防止剤を用いないため、その除去工程も不要となる。一般的な除去工程である加熱は、触媒微粒子の合一の原因となり、触媒分散度の低下の要因となる。
In the present invention, when the liquid phase reduction method is adopted, that is, when platinum that is reduced and precipitated in the liquid phase is used, no aggregation inhibitor is used. Anti-agglomeration agents are generally used in colloid protection methods. Since no anti-aggregation agent is used, the removal step is also unnecessary. Heating, which is a general removal step, causes coalescence of catalyst fine particles and causes a reduction in catalyst dispersion.
＜水素還元＞
水素還元の方法としては、ＣＮＴを水中に分散させ、白金塩を加え、水素ガスを水中に導入する方法が挙げられる。ＣＮＴ、特に長い（アスペクト比の大きい）多層ＣＮＴを液中に安定に分散させることは困難なことが知られている。本発明においては必ずしも永続的な分散状態は必要としない。ＣＮＴを水中に分散させる濃度としては、１００～９００ｍｇ／Ｌが好ましく、１００～３００ｍｇ／Ｌがより好ましい。ＣＮＴの水中への分散を促進するために、超音波処理を行うことが好ましい。また同じ目的のため、エタノール等のアルコール類を添加してもよい。アルコール類としては、短鎖のものが好ましく、炭素数１～１０のアルコール類が好ましい。具体的には、メタノール、エタノール、１－プロパノール、２－プロパノール、１－ブタノール、２－ブタノール、２－メチル－２－プロパノール、１－ペンタノール、２－エチル－１－ヘキサノール等のモノオール類；エチレングリコール、グリセリン等の多価アルコール類が例示できる。このうちメタノールまたはエタノールが特に好ましい。添加されるアルコール類の濃度は、特に制限はない。例えばエタノールを用いる場合に、白金塩を析出させる際の溶液中で１０～３００ｇ／Ｌが好ましく、２０～２００ｇ／Ｌがより好ましい。 <Hydrogen reduction>
Examples of the hydrogen reduction method include a method of dispersing CNT in water, adding a platinum salt, and introducing hydrogen gas into water. It is known that it is difficult to stably disperse CNTs, particularly long (high aspect ratio) multilayer CNTs, in a liquid. In the present invention, a permanent distributed state is not necessarily required. The concentration at which CNT is dispersed in water is preferably 100 to 900 mg / L, and more preferably 100 to 300 mg / L. In order to promote dispersion of CNT in water, it is preferable to perform ultrasonic treatment. For the same purpose, alcohols such as ethanol may be added. As the alcohols, short-chain alcohols are preferable, and alcohols having 1 to 10 carbon atoms are preferable. Specifically, monools such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-2-propanol, 1-pentanol, 2-ethyl-1-hexanol, etc. ; Polyhydric alcohols such as ethylene glycol and glycerin can be exemplified. Of these, methanol or ethanol is particularly preferred. The concentration of the added alcohol is not particularly limited. For example, when ethanol is used, it is preferably 10 to 300 g / L, more preferably 20 to 200 g / L in the solution for depositing the platinum salt.
水素還元の方法としては、ＣＮＴを水中に分散させ、白金塩を加え、水素ガスを水中に導入する方法が挙げられる。ＣＮＴ、特に長い（アスペクト比の大きい）多層ＣＮＴを液中に安定に分散させることは困難なことが知られている。本発明においては必ずしも永続的な分散状態は必要としない。ＣＮＴを水中に分散させる濃度としては、１００～９００ｍｇ／Ｌが好ましく、１００～３００ｍｇ／Ｌがより好ましい。ＣＮＴの水中への分散を促進するために、超音波処理を行うことが好ましい。また同じ目的のため、エタノール等のアルコール類を添加してもよい。アルコール類としては、短鎖のものが好ましく、炭素数１～１０のアルコール類が好ましい。具体的には、メタノール、エタノール、１－プロパノール、２－プロパノール、１－ブタノール、２－ブタノール、２－メチル－２－プロパノール、１－ペンタノール、２－エチル－１－ヘキサノール等のモノオール類；エチレングリコール、グリセリン等の多価アルコール類が例示できる。このうちメタノールまたはエタノールが特に好ましい。添加されるアルコール類の濃度は、特に制限はない。例えばエタノールを用いる場合に、白金塩を析出させる際の溶液中で１０～３００ｇ／Ｌが好ましく、２０～２００ｇ／Ｌがより好ましい。 <Hydrogen reduction>
Examples of the hydrogen reduction method include a method of dispersing CNT in water, adding a platinum salt, and introducing hydrogen gas into water. It is known that it is difficult to stably disperse CNTs, particularly long (high aspect ratio) multilayer CNTs, in a liquid. In the present invention, a permanent distributed state is not necessarily required. The concentration at which CNT is dispersed in water is preferably 100 to 900 mg / L, and more preferably 100 to 300 mg / L. In order to promote dispersion of CNT in water, it is preferable to perform ultrasonic treatment. For the same purpose, alcohols such as ethanol may be added. As the alcohols, short-chain alcohols are preferable, and alcohols having 1 to 10 carbon atoms are preferable. Specifically, monools such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-2-propanol, 1-pentanol, 2-ethyl-1-hexanol, etc. ; Polyhydric alcohols such as ethylene glycol and glycerin can be exemplified. Of these, methanol or ethanol is particularly preferred. The concentration of the added alcohol is not particularly limited. For example, when ethanol is used, it is preferably 10 to 300 g / L, more preferably 20 to 200 g / L in the solution for depositing the platinum salt.
白金塩はＣＮＴが分散された系に、固体として添加されてもよく、水溶液として添加されてもよい。操作が容易であることから白金塩の水溶液をＣＮＴの分散系に添加することが好ましい。白金塩の濃度としては、白金塩を析出させる際の溶液中で１０～１０００ｍｇ／Ｌが好ましく、１０～１００ｍｇ／Ｌがより好ましい。白金塩の希薄溶液を還元することにより、高活性の白金微粒子が析出すると考えられる。
The platinum salt may be added as a solid or an aqueous solution to a system in which CNTs are dispersed. It is preferable to add an aqueous solution of a platinum salt to the CNT dispersion because it is easy to operate. The concentration of the platinum salt is preferably 10 to 1000 mg / L in the solution for depositing the platinum salt, and more preferably 10 to 100 mg / L. It is considered that highly active platinum fine particles are precipitated by reducing a dilute solution of platinum salt.
水素ガスの導入量は、１～２０ｇ／Ｌ・Ｈｒが好ましい。水素ガス導入時の圧力は、常圧であってもよく、加圧であってもよい。また、水素ガスを導入する前に系中の酸素を除去することが好ましい。溶液の場合には、減圧で除去してもよく、不活性ガスでバブリングすることにより酸素を除去してもよい。操作が簡便であることから不活性ガスでバブリングすることが好ましい。不活性ガスとしては、アルゴンまたは窒素ガスが好ましい。
The amount of hydrogen gas introduced is preferably 1 to 20 g / L · Hr. The pressure at the time of introducing hydrogen gas may be a normal pressure or a pressurized pressure. Moreover, it is preferable to remove oxygen in the system before introducing hydrogen gas. In the case of a solution, it may be removed under reduced pressure, or oxygen may be removed by bubbling with an inert gas. Bubbling with an inert gas is preferred because the operation is simple. As the inert gas, argon or nitrogen gas is preferable.
なお電極材料が極少量の場合には、ＣＮＴを不活性な基体（グラッシーカーボン等が例示できる。）の上に堆積させた後、白金塩水溶液を滴下し、その後水素を含む気流中に暴露させることでも製造が可能である。
還元の際の温度は特に制限されないが、５～９５℃が好ましく、２０～６０℃がより好ましい。
還元が終わった後、ろ過でＣＮＴを捕集し、乾燥させて電極材料にできる。乾燥温度は、２０～１５０℃が好ましく、５０～８０℃がより好ましい。 When the electrode material is extremely small, CNT is deposited on an inert substrate (eg, glassy carbon), and then an aqueous platinum salt solution is dropped, followed by exposure to an air stream containing hydrogen. Even manufacture is possible.
The temperature during the reduction is not particularly limited, but is preferably 5 to 95 ° C, more preferably 20 to 60 ° C.
After the reduction is completed, CNTs are collected by filtration and dried to form an electrode material. The drying temperature is preferably 20 to 150 ° C, more preferably 50 to 80 ° C.
還元の際の温度は特に制限されないが、５～９５℃が好ましく、２０～６０℃がより好ましい。
還元が終わった後、ろ過でＣＮＴを捕集し、乾燥させて電極材料にできる。乾燥温度は、２０～１５０℃が好ましく、５０～８０℃がより好ましい。 When the electrode material is extremely small, CNT is deposited on an inert substrate (eg, glassy carbon), and then an aqueous platinum salt solution is dropped, followed by exposure to an air stream containing hydrogen. Even manufacture is possible.
The temperature during the reduction is not particularly limited, but is preferably 5 to 95 ° C, more preferably 20 to 60 ° C.
After the reduction is completed, CNTs are collected by filtration and dried to form an electrode material. The drying temperature is preferably 20 to 150 ° C, more preferably 50 to 80 ° C.
＜電極＞
本発明の電極は、上記電極材料を用いる。具体的には例えば、電極材料をバインダーと混練し必要な形に成形して電極が得られる。バインダーとしては、スルホン酸を有する含フッ素樹脂が例示できる。スルホン酸を有する含フッ素樹脂としては、旭硝子社製の樹脂（商品名：フレミオン）や、デュポン社製の樹脂（商品名：ナフィオン）が例示できる。 <Electrode>
The electrode material of the present invention uses the above electrode material. Specifically, for example, an electrode material can be kneaded with a binder and formed into a required shape to obtain an electrode. Examples of the binder include a fluorinated resin having a sulfonic acid. Examples of the fluorine-containing resin having a sulfonic acid include a resin (trade name: Flemion) manufactured by Asahi Glass Co., Ltd. and a resin (trade name: Nafion) manufactured by DuPont.
本発明の電極は、上記電極材料を用いる。具体的には例えば、電極材料をバインダーと混練し必要な形に成形して電極が得られる。バインダーとしては、スルホン酸を有する含フッ素樹脂が例示できる。スルホン酸を有する含フッ素樹脂としては、旭硝子社製の樹脂（商品名：フレミオン）や、デュポン社製の樹脂（商品名：ナフィオン）が例示できる。 <Electrode>
The electrode material of the present invention uses the above electrode material. Specifically, for example, an electrode material can be kneaded with a binder and formed into a required shape to obtain an electrode. Examples of the binder include a fluorinated resin having a sulfonic acid. Examples of the fluorine-containing resin having a sulfonic acid include a resin (trade name: Flemion) manufactured by Asahi Glass Co., Ltd. and a resin (trade name: Nafion) manufactured by DuPont.
本発明の電極は、燃料電池の電極（水素極または空気極）に好適である。また空気電池の空気極にも適用可能である。さらにＦＥＤ（Field Emission Display）、平面蛍光管、冷陰極管のカソードとしても適用が期待される。
The electrode of the present invention is suitable for a fuel cell electrode (hydrogen electrode or air electrode). It can also be applied to the air electrode of an air battery. Furthermore, it is expected to be applied to cathodes of FED (Field Emission Display), flat fluorescent tubes, and cold cathode tubes.
本発明を以下の実施例で説明するが、本発明はこれら実施例等に限定されない。例１～３、８は実施例、例４～７、９は比較例である。
The present invention will be described in the following examples, but the present invention is not limited to these examples. Examples 1 to 3 and 8 are examples, and examples 4 to 7 and 9 are comparative examples.
（電極材料の調製）
（例１）
ＣＮＴとしては、保土谷化学社製、ＭＷＮＴ－７を用いた。Ｄ／Ｇは０．０８、直径は６０ｎｍ、アスペクト比は約１２０の多層ＣＮＴである。該ＣＮＴの３ｍｇを混合溶媒Ａの３０ｍＬ（リットル）に投入し、超音波を１５分間照射して分散させ溶液１Ａとした。ただし混合溶媒Ａとは、テトラヒドロフランとＨＦＥ－３４７ｐｃ－ｆ（ＣＦ３ＣＨ２ＯＣＦ２ＣＦ２Ｈ、旭硝子社製）を１：１（質量比）で混合した溶媒である。この溶液１Ａからピペットで７０μＬを分取して、回転電極のディスク電極上に滴下し、乾燥させてＣＮＴを堆積させた。ただしディスク電極とは、直径が５ｍｍのグラッシーカーボン製の電極である。 (Preparation of electrode material)
(Example 1)
As the CNT, MWNT-7 manufactured by Hodogaya Chemical Co., Ltd. was used. It is a multi-walled CNT having a D / G of 0.08, a diameter of 60 nm, and an aspect ratio of about 120. 3 mg of the CNT was put into 30 mL (liter) of the mixed solvent A and dispersed by irradiation with ultrasonic waves for 15 minutes to obtain a solution 1A. However, the mixed solvent A is a solvent obtained by mixing tetrahydrofuran and HFE-347pc-f (CF 3 CH 2 OCF 2 CF 2 H, manufactured by Asahi Glass Co., Ltd.) at 1: 1 (mass ratio). From this solution 1A, 70 μL was taken with a pipette, dropped onto the disk electrode of the rotating electrode, and dried to deposit CNTs. However, the disk electrode is an electrode made of glassy carbon having a diameter of 5 mm.
（例１）
ＣＮＴとしては、保土谷化学社製、ＭＷＮＴ－７を用いた。Ｄ／Ｇは０．０８、直径は６０ｎｍ、アスペクト比は約１２０の多層ＣＮＴである。該ＣＮＴの３ｍｇを混合溶媒Ａの３０ｍＬ（リットル）に投入し、超音波を１５分間照射して分散させ溶液１Ａとした。ただし混合溶媒Ａとは、テトラヒドロフランとＨＦＥ－３４７ｐｃ－ｆ（ＣＦ３ＣＨ２ＯＣＦ２ＣＦ２Ｈ、旭硝子社製）を１：１（質量比）で混合した溶媒である。この溶液１Ａからピペットで７０μＬを分取して、回転電極のディスク電極上に滴下し、乾燥させてＣＮＴを堆積させた。ただしディスク電極とは、直径が５ｍｍのグラッシーカーボン製の電極である。 (Preparation of electrode material)
(Example 1)
As the CNT, MWNT-7 manufactured by Hodogaya Chemical Co., Ltd. was used. It is a multi-walled CNT having a D / G of 0.08, a diameter of 60 nm, and an aspect ratio of about 120. 3 mg of the CNT was put into 30 mL (liter) of the mixed solvent A and dispersed by irradiation with ultrasonic waves for 15 minutes to obtain a solution 1A. However, the mixed solvent A is a solvent obtained by mixing tetrahydrofuran and HFE-347pc-f (CF 3 CH 2 OCF 2 CF 2 H, manufactured by Asahi Glass Co., Ltd.) at 1: 1 (mass ratio). From this solution 1A, 70 μL was taken with a pipette, dropped onto the disk electrode of the rotating electrode, and dried to deposit CNTs. However, the disk electrode is an electrode made of glassy carbon having a diameter of 5 mm.
超純水の８０ｇとエタノールの２０ｇとを混合した溶媒（混合溶媒Ｂ）に、白金塩溶液（石福金属興業社製、ジニトロジアンミン白金硝酸溶液、白金濃度１００．９３ｇ／Ｌ）（［Ｐｔ（ＮＨ３）２（ＮＯ２）２］／ＨＮＯ３溶液）の２００μＬを加えよく撹拌し、溶液１Ｂとした。この溶液１Ｂからマイクロピペットを用いて１５μＬを分取し、ディスク電極上に堆積させたＣＮＴ上に滴下した。
To a solvent (mixed solvent B) obtained by mixing 80 g of ultrapure water and 20 g of ethanol, a platinum salt solution (manufactured by Ishifuku Metal Industry Co., Ltd., dinitrodiammine platinum nitric acid solution, platinum concentration 100.93 g / L) ([Pt ( 200 μL of NH 3 ) 2 (NO 2 ) 2 ] / HNO 3 solution) was added and stirred well to obtain Solution 1B. 15 μL of this solution 1B was collected using a micropipette and dropped onto the CNT deposited on the disk electrode.
このディスク電極を反応管内（石英製、内径１７ｍｍ、長さ１９ｃｍの円筒）にセットし、常圧で水素ガスを０．１ｇ／Ｈｒで導入した。温度は２５℃であった。１時間後に水素ガスの導入を停止し、ヘリウムガスで置換した後に電極を取り出した。ヘリウムガスで置換するのは、触媒表面の水素を除去し、空気中の酸化に由来する触媒表面の過熱・劣化を防止するためである。アイオノマ分散溶液（デュポン社製、ナフィオン溶液）を滴下し乾燥して、試料電極１を得た。この試料電極１を電極特性評価に供した。
The disk electrode was set in a reaction tube (made of quartz, cylinder having an inner diameter of 17 mm and a length of 19 cm), and hydrogen gas was introduced at 0.1 g / Hr at normal pressure. The temperature was 25 ° C. The introduction of hydrogen gas was stopped after 1 hour, and the electrode was taken out after replacing with helium gas. The reason for substituting with helium gas is to remove hydrogen on the catalyst surface and prevent overheating and deterioration of the catalyst surface due to oxidation in the air. An ionomer dispersion solution (manufactured by DuPont, Nafion solution) was dropped and dried to obtain a sample electrode 1. This sample electrode 1 was subjected to electrode characteristic evaluation.
図１は後述の条件に従い測定した、試料電極１を用いた場合のＣＶ曲線である。
図１に示すように、ＣＶ曲線からは、水素の吸脱着ピークは、一般的な触媒のそれに比較してかなり低い電位、すなわち水素の平衡電位に近い部分で認められた。さらに、白金の酸化還元電位が、一般的な触媒のそれに対して、高いという本発明の電極材料特有の特徴が確認された。水素のＵＰＤ（アンダーポテンシャルデポジション）として生起する水素の平衡電位より、貴な電位での水素原子の吸着現象が認められた。 FIG. 1 is a CV curve in the case of using the sample electrode 1 measured according to the conditions described later.
As shown in FIG. 1, from the CV curve, an adsorption / desorption peak of hydrogen was observed at a considerably lower potential than that of a general catalyst, that is, a portion close to the equilibrium potential of hydrogen. Furthermore, the characteristic characteristic of the electrode material of the present invention that the oxidation-reduction potential of platinum was higher than that of a general catalyst was confirmed. From the equilibrium potential of hydrogen that occurs as UPD (underpotential deposition) of hydrogen, an adsorption phenomenon of hydrogen atoms at a noble potential was observed.
図１に示すように、ＣＶ曲線からは、水素の吸脱着ピークは、一般的な触媒のそれに比較してかなり低い電位、すなわち水素の平衡電位に近い部分で認められた。さらに、白金の酸化還元電位が、一般的な触媒のそれに対して、高いという本発明の電極材料特有の特徴が確認された。水素のＵＰＤ（アンダーポテンシャルデポジション）として生起する水素の平衡電位より、貴な電位での水素原子の吸着現象が認められた。 FIG. 1 is a CV curve in the case of using the sample electrode 1 measured according to the conditions described later.
As shown in FIG. 1, from the CV curve, an adsorption / desorption peak of hydrogen was observed at a considerably lower potential than that of a general catalyst, that is, a portion close to the equilibrium potential of hydrogen. Furthermore, the characteristic characteristic of the electrode material of the present invention that the oxidation-reduction potential of platinum was higher than that of a general catalyst was confirmed. From the equilibrium potential of hydrogen that occurs as UPD (underpotential deposition) of hydrogen, an adsorption phenomenon of hydrogen atoms at a noble potential was observed.
（例２）
混合溶媒Ｂの１００ｇに例１と同じＣＮＴの１４ｍｇを分散させ溶液２Ａとした。例１と同じジニトロジアンミン白金硝酸液を超純水で希釈し、白金を０．２ｇ／Ｌ含む溶液２Ｂとした。溶液２Ｂの３０ｍＬを溶液２Ａに添加した。この混合溶液に常圧で水素ガスを０．１ｇ／Ｈｒで、バブリングにより導入した。温度は２５℃であった。１時間後に水素ガスの導入を停止し、得られた液を吸引濾過（濾紙：アドバンテック社製Ｎｏ．２、直径：１１０ｍｍ）により捕集した。これを大気中、８０℃で３時間、常圧で乾燥させて、３０質量％Ｐｔ／ＣＮＴ（計算値）の電極材料を得た。この材料の３ｍｇを混合溶媒Ａの３０ｍＬに分散させた。マイクロピペットで７０μＬを分取して、例１と同じディスク電極に滴下し、例１と同様にアイオノマ分散溶液で処理し、乾燥して、試料電極２を得た。この試料電極２を電極特性評価に供した。ＣＶ曲線は例１の場合と同様であった。 (Example 2)
A solution 2A was prepared by dispersing 14 mg of the same CNT as in Example 1 in 100 g of the mixed solvent B. The same dinitrodiammine platinum nitric acid solution as in Example 1 was diluted with ultrapure water to obtain a solution 2B containing 0.2 g / L of platinum. 30 mL of Solution 2B was added to Solution 2A. Hydrogen gas was introduced into this mixed solution by bubbling at normal pressure at 0.1 g / Hr. The temperature was 25 ° C. One hour later, the introduction of hydrogen gas was stopped, and the resulting liquid was collected by suction filtration (filter paper: No. 2, manufactured by Advantech, diameter: 110 mm). This was dried in air at 80 ° C. for 3 hours at normal pressure to obtain an electrode material of 30 mass% Pt / CNT (calculated value). 3 mg of this material was dispersed in 30 mL of mixed solvent A. 70 μL was collected with a micropipette, dropped onto the same disk electrode as in Example 1, treated with an ionomer dispersion solution as in Example 1, and dried to obtain a sample electrode 2. This sample electrode 2 was subjected to electrode characteristic evaluation. The CV curve was the same as in Example 1.
混合溶媒Ｂの１００ｇに例１と同じＣＮＴの１４ｍｇを分散させ溶液２Ａとした。例１と同じジニトロジアンミン白金硝酸液を超純水で希釈し、白金を０．２ｇ／Ｌ含む溶液２Ｂとした。溶液２Ｂの３０ｍＬを溶液２Ａに添加した。この混合溶液に常圧で水素ガスを０．１ｇ／Ｈｒで、バブリングにより導入した。温度は２５℃であった。１時間後に水素ガスの導入を停止し、得られた液を吸引濾過（濾紙：アドバンテック社製Ｎｏ．２、直径：１１０ｍｍ）により捕集した。これを大気中、８０℃で３時間、常圧で乾燥させて、３０質量％Ｐｔ／ＣＮＴ（計算値）の電極材料を得た。この材料の３ｍｇを混合溶媒Ａの３０ｍＬに分散させた。マイクロピペットで７０μＬを分取して、例１と同じディスク電極に滴下し、例１と同様にアイオノマ分散溶液で処理し、乾燥して、試料電極２を得た。この試料電極２を電極特性評価に供した。ＣＶ曲線は例１の場合と同様であった。 (Example 2)
A solution 2A was prepared by dispersing 14 mg of the same CNT as in Example 1 in 100 g of the mixed solvent B. The same dinitrodiammine platinum nitric acid solution as in Example 1 was diluted with ultrapure water to obtain a solution 2B containing 0.2 g / L of platinum. 30 mL of Solution 2B was added to Solution 2A. Hydrogen gas was introduced into this mixed solution by bubbling at normal pressure at 0.1 g / Hr. The temperature was 25 ° C. One hour later, the introduction of hydrogen gas was stopped, and the resulting liquid was collected by suction filtration (filter paper: No. 2, manufactured by Advantech, diameter: 110 mm). This was dried in air at 80 ° C. for 3 hours at normal pressure to obtain an electrode material of 30 mass% Pt / CNT (calculated value). 3 mg of this material was dispersed in 30 mL of mixed solvent A. 70 μL was collected with a micropipette, dropped onto the same disk electrode as in Example 1, treated with an ionomer dispersion solution as in Example 1, and dried to obtain a sample electrode 2. This sample electrode 2 was subjected to electrode characteristic evaluation. The CV curve was the same as in Example 1.
（例３）
ＣＮＴとしては、マイクロフェーズ社製、Ｔｈｉｎ－ＭＷＣＮＴを用いた。Ｄ／Ｇは０．０８、直径は２５ｎｍ、アスペクト比は約３０以上の多層ＣＮＴである。ＣＮＴを変更した以外は例２と同様に処理し３０質量％Ｐｔ／ＣＮＴ（計算値）の電極材料を得た。この材料を例２と同様に処理し、３ｍｇを混合溶媒Ａの３０ｍＬに分散させた。マイクロピペットで７０μＬを分取して、例１と同じディスク電極に滴下し、例１と同様にアイオノマ分散溶液で処理し、乾燥して、試料電極３を得た。この試料電極３を電極特性評価に供した。ＣＶ曲線は例１の場合と同様であった。 (Example 3)
As the CNT, Thin-MWCNT manufactured by Microphase was used. It is a multi-walled CNT having a D / G of 0.08, a diameter of 25 nm, and an aspect ratio of about 30 or more. The electrode material of 30 mass% Pt / CNT (calculated value) was obtained in the same manner as in Example 2 except that CNT was changed. This material was treated in the same manner as in Example 2 and 3 mg was dispersed in 30 mL of mixed solvent A. 70 μL was collected with a micropipette, dropped onto the same disk electrode as in Example 1, treated with an ionomer dispersion solution in the same manner as in Example 1, and dried to obtain a sample electrode 3. This sample electrode 3 was subjected to electrode characteristic evaluation. The CV curve was the same as in Example 1.
ＣＮＴとしては、マイクロフェーズ社製、Ｔｈｉｎ－ＭＷＣＮＴを用いた。Ｄ／Ｇは０．０８、直径は２５ｎｍ、アスペクト比は約３０以上の多層ＣＮＴである。ＣＮＴを変更した以外は例２と同様に処理し３０質量％Ｐｔ／ＣＮＴ（計算値）の電極材料を得た。この材料を例２と同様に処理し、３ｍｇを混合溶媒Ａの３０ｍＬに分散させた。マイクロピペットで７０μＬを分取して、例１と同じディスク電極に滴下し、例１と同様にアイオノマ分散溶液で処理し、乾燥して、試料電極３を得た。この試料電極３を電極特性評価に供した。ＣＶ曲線は例１の場合と同様であった。 (Example 3)
As the CNT, Thin-MWCNT manufactured by Microphase was used. It is a multi-walled CNT having a D / G of 0.08, a diameter of 25 nm, and an aspect ratio of about 30 or more. The electrode material of 30 mass% Pt / CNT (calculated value) was obtained in the same manner as in Example 2 except that CNT was changed. This material was treated in the same manner as in Example 2 and 3 mg was dispersed in 30 mL of mixed solvent A. 70 μL was collected with a micropipette, dropped onto the same disk electrode as in Example 1, treated with an ionomer dispersion solution in the same manner as in Example 1, and dried to obtain a sample electrode 3. This sample electrode 3 was subjected to electrode characteristic evaluation. The CV curve was the same as in Example 1.
（例４）
例３と同じＣＮＴを４０℃の混酸（硫酸：硝酸＝３：１（体積比））中に２４時間浸漬して親水化処理した。その結果、ＢＥＴ表面積は３７ｍ２／ｇ（未処理では２５ｍ２／ｇ）になり、Ｄ／Ｇは０．２３になり未処理のものと比較して約３倍となった。この担体を用いて例１と同様にして３０質量％Ｐｔ／ＣＮＴ（計算値）の電極材料を調製し、試料電極４を得て、活性評価を行った。ＣＶ曲線は、例７の図２と同様に、比較的高い電位で水素の吸脱着が起こる一般的な形状を示した。 (Example 4)
The same CNT as in Example 3 was hydrophilized by immersing it in a mixed acid (sulfuric acid: nitric acid = 3: 1 (volume ratio)) at 40 ° C. for 24 hours. As a result, BET surface area becomes (25 m 2 / g in untreated) 37m 2 / g, D / G was about 3-fold compared to that of untreated becomes 0.23. Using this carrier, an electrode material of 30% by mass Pt / CNT (calculated value) was prepared in the same manner as in Example 1, sample electrode 4 was obtained, and activity evaluation was performed. Similar to FIG. 2 of Example 7, the CV curve showed a general shape in which hydrogen adsorption / desorption occurs at a relatively high potential.
例３と同じＣＮＴを４０℃の混酸（硫酸：硝酸＝３：１（体積比））中に２４時間浸漬して親水化処理した。その結果、ＢＥＴ表面積は３７ｍ２／ｇ（未処理では２５ｍ２／ｇ）になり、Ｄ／Ｇは０．２３になり未処理のものと比較して約３倍となった。この担体を用いて例１と同様にして３０質量％Ｐｔ／ＣＮＴ（計算値）の電極材料を調製し、試料電極４を得て、活性評価を行った。ＣＶ曲線は、例７の図２と同様に、比較的高い電位で水素の吸脱着が起こる一般的な形状を示した。 (Example 4)
The same CNT as in Example 3 was hydrophilized by immersing it in a mixed acid (sulfuric acid: nitric acid = 3: 1 (volume ratio)) at 40 ° C. for 24 hours. As a result, BET surface area becomes (25 m 2 / g in untreated) 37m 2 / g, D / G was about 3-fold compared to that of untreated becomes 0.23. Using this carrier, an electrode material of 30% by mass Pt / CNT (calculated value) was prepared in the same manner as in Example 1, sample electrode 4 was obtained, and activity evaluation was performed. Similar to FIG. 2 of Example 7, the CV curve showed a general shape in which hydrogen adsorption / desorption occurs at a relatively high potential.
（例５）
ＣＮＴに代えて、カップ積層型のカーボンナノファイバー（ＣＮＦ）を用いた。Ｄ／Ｇは０．１８。直径は５０ｎｍであった。例１と同様にして３０質量％Ｐｔ／ＣＮＦ（計算値）の電極材料を調製し、試料電極５を得て、同様にして特性評価を行った。ＣＶ曲線は、例７の図２と同様に、比較的高い電位で水素の吸脱着が起こる一般的な形状を示した。 (Example 5)
Instead of CNTs, cup-stacked carbon nanofibers (CNF) were used. D / G is 0.18. The diameter was 50 nm. An electrode material of 30% by mass Pt / CNF (calculated value) was prepared in the same manner as in Example 1 to obtain a sample electrode 5, and the characteristics were evaluated in the same manner. Similar to FIG. 2 of Example 7, the CV curve showed a general shape in which hydrogen adsorption / desorption occurs at a relatively high potential.
ＣＮＴに代えて、カップ積層型のカーボンナノファイバー（ＣＮＦ）を用いた。Ｄ／Ｇは０．１８。直径は５０ｎｍであった。例１と同様にして３０質量％Ｐｔ／ＣＮＦ（計算値）の電極材料を調製し、試料電極５を得て、同様にして特性評価を行った。ＣＶ曲線は、例７の図２と同様に、比較的高い電位で水素の吸脱着が起こる一般的な形状を示した。 (Example 5)
Instead of CNTs, cup-stacked carbon nanofibers (CNF) were used. D / G is 0.18. The diameter was 50 nm. An electrode material of 30% by mass Pt / CNF (calculated value) was prepared in the same manner as in Example 1 to obtain a sample electrode 5, and the characteristics were evaluated in the same manner. Similar to FIG. 2 of Example 7, the CV curve showed a general shape in which hydrogen adsorption / desorption occurs at a relatively high potential.
（例６）
例４と同様にして親水化処理をした７０ｍｇのＣＮＴ（例３と同じ）をエタノール中に分散し、超音波を３０分間照射してＣＮＴ分散溶液を調製した。石福金属興業社製のジニトロジアンミン白金硝酸溶液（例１と同じ）を、ロータリーエバポレータを用いて、８０℃で蒸発乾固させて黄褐色粉末を得た。温度を５０℃以下に保持しながら、この黄褐色粉末にエタノールを徐々に加えて、白金濃度５０ｇ／Ｌの白金アンミンエトキシド錯体溶液を調製した。白金量で換算して３０ｍｇを含むこのエタノール溶液を、ＣＮＴ分散溶液に添加し、超音波を３０分間照射した。ホットスターラーを用いて６０℃に加温しゆっくり乾燥した。その後水素１０％（体積比）を含むアルゴン気流中で還元して、３０質量％Ｐｔ／ＣＮＴ（計算値）の電極材料を得た。還元の際の温度は、室温からゆっくりと６０℃まで昇温した後、毎分５℃の割合で１２０℃まで昇温して、１時間保持した。その後毎分５℃の割合で２００℃まで昇温し、２時間保持した後、室温までゆっくり冷却した。この材料を用いて試料電極６を得て、同様にして特性評価を行った。ＣＶ曲線は、例７の図２と同様に、比較的高い電位で水素の吸脱着が起こる一般的な形状を示した。 (Example 6)
70 mg of CNT (same as Example 3) hydrophilized in the same manner as in Example 4 was dispersed in ethanol, and an ultrasonic wave was irradiated for 30 minutes to prepare a CNT dispersion solution. A dinitrodiammine platinum nitrate solution (same as Example 1) manufactured by Ishifuku Metal Industry Co., Ltd. was evaporated to dryness at 80 ° C. using a rotary evaporator to obtain a tan powder. While maintaining the temperature at 50 ° C. or lower, ethanol was gradually added to the tan powder to prepare a platinum ammine ethoxide complex solution having a platinum concentration of 50 g / L. This ethanol solution containing 30 mg in terms of platinum amount was added to the CNT dispersion solution and irradiated with ultrasonic waves for 30 minutes. It heated to 60 degreeC using the hot stirrer, and dried slowly. Thereafter, reduction was performed in an argon stream containing 10% hydrogen (volume ratio) to obtain an electrode material of 30% by mass Pt / CNT (calculated value). The temperature during the reduction was slowly raised from room temperature to 60 ° C., then raised to 120 ° C. at a rate of 5 ° C. per minute, and held for 1 hour. Thereafter, the temperature was raised to 200 ° C. at a rate of 5 ° C. per minute, held for 2 hours, and then slowly cooled to room temperature. A sample electrode 6 was obtained using this material, and the characteristics were evaluated in the same manner. Similar to FIG. 2 of Example 7, the CV curve showed a general shape in which hydrogen adsorption / desorption occurs at a relatively high potential.
例４と同様にして親水化処理をした７０ｍｇのＣＮＴ（例３と同じ）をエタノール中に分散し、超音波を３０分間照射してＣＮＴ分散溶液を調製した。石福金属興業社製のジニトロジアンミン白金硝酸溶液（例１と同じ）を、ロータリーエバポレータを用いて、８０℃で蒸発乾固させて黄褐色粉末を得た。温度を５０℃以下に保持しながら、この黄褐色粉末にエタノールを徐々に加えて、白金濃度５０ｇ／Ｌの白金アンミンエトキシド錯体溶液を調製した。白金量で換算して３０ｍｇを含むこのエタノール溶液を、ＣＮＴ分散溶液に添加し、超音波を３０分間照射した。ホットスターラーを用いて６０℃に加温しゆっくり乾燥した。その後水素１０％（体積比）を含むアルゴン気流中で還元して、３０質量％Ｐｔ／ＣＮＴ（計算値）の電極材料を得た。還元の際の温度は、室温からゆっくりと６０℃まで昇温した後、毎分５℃の割合で１２０℃まで昇温して、１時間保持した。その後毎分５℃の割合で２００℃まで昇温し、２時間保持した後、室温までゆっくり冷却した。この材料を用いて試料電極６を得て、同様にして特性評価を行った。ＣＶ曲線は、例７の図２と同様に、比較的高い電位で水素の吸脱着が起こる一般的な形状を示した。 (Example 6)
70 mg of CNT (same as Example 3) hydrophilized in the same manner as in Example 4 was dispersed in ethanol, and an ultrasonic wave was irradiated for 30 minutes to prepare a CNT dispersion solution. A dinitrodiammine platinum nitrate solution (same as Example 1) manufactured by Ishifuku Metal Industry Co., Ltd. was evaporated to dryness at 80 ° C. using a rotary evaporator to obtain a tan powder. While maintaining the temperature at 50 ° C. or lower, ethanol was gradually added to the tan powder to prepare a platinum ammine ethoxide complex solution having a platinum concentration of 50 g / L. This ethanol solution containing 30 mg in terms of platinum amount was added to the CNT dispersion solution and irradiated with ultrasonic waves for 30 minutes. It heated to 60 degreeC using the hot stirrer, and dried slowly. Thereafter, reduction was performed in an argon stream containing 10% hydrogen (volume ratio) to obtain an electrode material of 30% by mass Pt / CNT (calculated value). The temperature during the reduction was slowly raised from room temperature to 60 ° C., then raised to 120 ° C. at a rate of 5 ° C. per minute, and held for 1 hour. Thereafter, the temperature was raised to 200 ° C. at a rate of 5 ° C. per minute, held for 2 hours, and then slowly cooled to room temperature. A sample electrode 6 was obtained using this material, and the characteristics were evaluated in the same manner. Similar to FIG. 2 of Example 7, the CV curve showed a general shape in which hydrogen adsorption / desorption occurs at a relatively high potential.
（例７）
市販触媒（田中貴金属工業社製、ＴＥＣ１０Ｅ５０Ｅ）を用いて試料電極７を得て、同様に特性評価を行った。ＣＶ曲線は、図２に示すように、比較的高い電位で水素の吸脱着が起こる一般的な形状を示した。特に水素の酸化・還元電流ピークはブロードになり、触媒の活性も低くなった。 (Example 7)
A sample electrode 7 was obtained using a commercially available catalyst (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., TEC10E50E), and the characteristics were similarly evaluated. As shown in FIG. 2, the CV curve showed a general shape in which hydrogen adsorption / desorption occurs at a relatively high potential. In particular, the oxidation / reduction current peak of hydrogen became broad, and the activity of the catalyst also decreased.
市販触媒（田中貴金属工業社製、ＴＥＣ１０Ｅ５０Ｅ）を用いて試料電極７を得て、同様に特性評価を行った。ＣＶ曲線は、図２に示すように、比較的高い電位で水素の吸脱着が起こる一般的な形状を示した。特に水素の酸化・還元電流ピークはブロードになり、触媒の活性も低くなった。 (Example 7)
A sample electrode 7 was obtained using a commercially available catalyst (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., TEC10E50E), and the characteristics were similarly evaluated. As shown in FIG. 2, the CV curve showed a general shape in which hydrogen adsorption / desorption occurs at a relatively high potential. In particular, the oxidation / reduction current peak of hydrogen became broad, and the activity of the catalyst also decreased.
図１と図２とを比較すると、０．６Ｖ（Ａｇ／ＡｇＣｌ電極基準）付近に認められる白金酸化物の還元電流のピーク電位は両者で７０ｍＶの差がある。これは本発明の電極材料においては、白金が酸化されにくい状態にあるためと考えられる。
ここに示された電極材料を１．２Ｖから５ｍＶ／秒の速度でカソーディックに掃引した時の０．８５Ｖにおける質量活性は、本発明の電極材料では０．０４１Ａ／ｍｇＰｔ、市販触媒では０．００５１Ａ／ｍｇＰｔであった。本発明の電極材料は高い酸素還元活性が得られることがわかる。 When FIG. 1 and FIG. 2 are compared, the peak potential of the reduction current of platinum oxide recognized around 0.6 V (Ag / AgCl electrode reference) has a difference of 70 mV. This is presumably because platinum is hardly oxidized in the electrode material of the present invention.
The mass activity at 0.85 V when the electrode material shown here was swept cathodic at a rate of 1.2 V to 5 mV / sec was 0.041 A / mg Pt for the electrode material of the present invention, and 0. 0051 A / mg Pt. It can be seen that the electrode material of the present invention provides high oxygen reduction activity.
ここに示された電極材料を１．２Ｖから５ｍＶ／秒の速度でカソーディックに掃引した時の０．８５Ｖにおける質量活性は、本発明の電極材料では０．０４１Ａ／ｍｇＰｔ、市販触媒では０．００５１Ａ／ｍｇＰｔであった。本発明の電極材料は高い酸素還元活性が得られることがわかる。 When FIG. 1 and FIG. 2 are compared, the peak potential of the reduction current of platinum oxide recognized around 0.6 V (Ag / AgCl electrode reference) has a difference of 70 mV. This is presumably because platinum is hardly oxidized in the electrode material of the present invention.
The mass activity at 0.85 V when the electrode material shown here was swept cathodic at a rate of 1.2 V to 5 mV / sec was 0.041 A / mg Pt for the electrode material of the present invention, and 0. 0051 A / mg Pt. It can be seen that the electrode material of the present invention provides high oxygen reduction activity.
＜活性評価＞
活性は以下の電気化学的測定により求めた。セルとしては北斗電工社製のものを用いた。作用極としては上記各例で調製した各試料電極を用いた。対極にはグラッシーカーボンを用いた。参照電極は、ダブルジャンクション型の銀／塩化銀電極を用いた。セルの温度を６０℃とし、０．５Ｍ硫酸水溶液を用い、窒素ガスをバブリングした後に測定した。試料電極を毎分１０００回転で回転させながら測定を行った。この状態でサイクリックボルタンメトリ（ＣＶ）測定を行った。結果を下記表１に示す。なお、各試料１～７は、上記の例１～７に対応する。
質量活性比は以下のように求めた。市販の触媒（例７）を１とした場合の０．８５Ｖにおける同一白金量当たりの電流値の比を活性比として求めた。
例１～３に示されるように本発明の電極材料は、市販触媒の２．８倍を超える活性を示した。Ｄ／Ｇが０．１以下と小さく、かつ、親水化処理などを施さず、ＣＮＴに白金微粒子を直接に担持させたためと考えられる。
一方例４、６は親水化処理を施したＣＮＴを用いている。このため白金が高い活性を発現していないと考えられる。例５に示されるように、Ｄ／Ｇの高いＣＮＦにおいても、活性は低くなっていた。 <Activity evaluation>
The activity was determined by the following electrochemical measurement. A cell manufactured by Hokuto Denko Co., Ltd. was used. As the working electrode, each sample electrode prepared in each of the above examples was used. Glassy carbon was used for the counter electrode. As the reference electrode, a double junction type silver / silver chloride electrode was used. The cell temperature was 60 ° C., 0.5 M sulfuric acid aqueous solution was used, and nitrogen gas was bubbled for measurement. The measurement was performed while rotating the sample electrode at 1000 rpm. In this state, cyclic voltammetry (CV) measurement was performed. The results are shown in Table 1 below. Samples 1 to 7 correspond to Examples 1 to 7 above.
The mass activity ratio was determined as follows. The ratio of the current value per the same amount of platinum at 0.85 V when the commercially available catalyst (Example 7) was 1 was determined as the activity ratio.
As shown in Examples 1 to 3, the electrode material of the present invention showed an activity exceeding 2.8 times that of a commercially available catalyst. This is probably because the D / G was as small as 0.1 or less, and the platinum fine particles were directly supported on the CNT without performing the hydrophilic treatment.
On the other hand, Examples 4 and 6 use CNTs subjected to hydrophilic treatment. For this reason, it is thought that platinum does not express high activity. As shown in Example 5, the activity was low even in CNF having a high D / G.
活性は以下の電気化学的測定により求めた。セルとしては北斗電工社製のものを用いた。作用極としては上記各例で調製した各試料電極を用いた。対極にはグラッシーカーボンを用いた。参照電極は、ダブルジャンクション型の銀／塩化銀電極を用いた。セルの温度を６０℃とし、０．５Ｍ硫酸水溶液を用い、窒素ガスをバブリングした後に測定した。試料電極を毎分１０００回転で回転させながら測定を行った。この状態でサイクリックボルタンメトリ（ＣＶ）測定を行った。結果を下記表１に示す。なお、各試料１～７は、上記の例１～７に対応する。
質量活性比は以下のように求めた。市販の触媒（例７）を１とした場合の０．８５Ｖにおける同一白金量当たりの電流値の比を活性比として求めた。
例１～３に示されるように本発明の電極材料は、市販触媒の２．８倍を超える活性を示した。Ｄ／Ｇが０．１以下と小さく、かつ、親水化処理などを施さず、ＣＮＴに白金微粒子を直接に担持させたためと考えられる。
一方例４、６は親水化処理を施したＣＮＴを用いている。このため白金が高い活性を発現していないと考えられる。例５に示されるように、Ｄ／Ｇの高いＣＮＦにおいても、活性は低くなっていた。 <Activity evaluation>
The activity was determined by the following electrochemical measurement. A cell manufactured by Hokuto Denko Co., Ltd. was used. As the working electrode, each sample electrode prepared in each of the above examples was used. Glassy carbon was used for the counter electrode. As the reference electrode, a double junction type silver / silver chloride electrode was used. The cell temperature was 60 ° C., 0.5 M sulfuric acid aqueous solution was used, and nitrogen gas was bubbled for measurement. The measurement was performed while rotating the sample electrode at 1000 rpm. In this state, cyclic voltammetry (CV) measurement was performed. The results are shown in Table 1 below. Samples 1 to 7 correspond to Examples 1 to 7 above.
The mass activity ratio was determined as follows. The ratio of the current value per the same amount of platinum at 0.85 V when the commercially available catalyst (Example 7) was 1 was determined as the activity ratio.
As shown in Examples 1 to 3, the electrode material of the present invention showed an activity exceeding 2.8 times that of a commercially available catalyst. This is probably because the D / G was as small as 0.1 or less, and the platinum fine particles were directly supported on the CNT without performing the hydrophilic treatment.
On the other hand, Examples 4 and 6 use CNTs subjected to hydrophilic treatment. For this reason, it is thought that platinum does not express high activity. As shown in Example 5, the activity was low even in CNF having a high D / G.
（例８）
例１と同様にし、ＣＮＴに白金を３０質量％担持させた。この電極を用いて６０℃、０．５Ｍ硫酸水溶液中で、以下の条件で電位ステップサイクル試験を行った。
［１．３Ｖ、３０秒保持：０．９Ｖ、３０秒保持］３００回繰り返し
この電位ステップサイクル試験前後の質量活性を比較し、活性の低減率を算出した。 (Example 8)
In the same manner as in Example 1, 30% by mass of platinum was supported on CNTs. Using this electrode, a potential step cycle test was conducted in a 0.5 M sulfuric acid aqueous solution at 60 ° C. under the following conditions.
[1.3 V, hold for 30 seconds: 0.9 V, hold for 30 seconds] Repeated 300 times The mass activity before and after this potential step cycle test was compared, and the reduction rate of activity was calculated.
例１と同様にし、ＣＮＴに白金を３０質量％担持させた。この電極を用いて６０℃、０．５Ｍ硫酸水溶液中で、以下の条件で電位ステップサイクル試験を行った。
［１．３Ｖ、３０秒保持：０．９Ｖ、３０秒保持］３００回繰り返し
この電位ステップサイクル試験前後の質量活性を比較し、活性の低減率を算出した。 (Example 8)
In the same manner as in Example 1, 30% by mass of platinum was supported on CNTs. Using this electrode, a potential step cycle test was conducted in a 0.5 M sulfuric acid aqueous solution at 60 ° C. under the following conditions.
[1.3 V, hold for 30 seconds: 0.9 V, hold for 30 seconds] Repeated 300 times The mass activity before and after this potential step cycle test was compared, and the reduction rate of activity was calculated.
（例９）
担持体として、比表面積が大きなケッチェンブラックをＣＮＴの替わりに使用した他は、例８と同様にして電極の調製および電位ステップサイクル試験を実施した。 (Example 9)
An electrode was prepared and a potential step cycle test was conducted in the same manner as in Example 8 except that ketjen black having a large specific surface area was used instead of CNT as the support.
担持体として、比表面積が大きなケッチェンブラックをＣＮＴの替わりに使用した他は、例８と同様にして電極の調製および電位ステップサイクル試験を実施した。 (Example 9)
An electrode was prepared and a potential step cycle test was conducted in the same manner as in Example 8 except that ketjen black having a large specific surface area was used instead of CNT as the support.
白金は比表面積が小さい担持体上では、粒子間の距離が短く、劣化が起こりやすくなる。そこで比表面積が極めて大きなカーボンブラック（ＫＢ）に液相水素還元法で白金を担持した電極材料と、本発明の電極材料との、電位変動耐性を電位ステップサイクル試験により比較した。その結果、表２に示すように、ＣＮＴでは比表面積が圧倒的に小さいにもかかわらず、活性の低下率は小さいことが確認された。すなわち電極材料として活性は低下しにくく耐久性に優れることが示された。
Platinum has a small distance between particles on a carrier having a small specific surface area and is likely to deteriorate. Therefore, the potential fluctuation resistance of the electrode material in which platinum was supported on carbon black (KB) having a very large specific surface area by the liquid phase hydrogen reduction method and the electrode material of the present invention were compared by a potential step cycle test. As a result, as shown in Table 2, it was confirmed that the rate of decrease in activity was small even though the specific surface area of CNT was extremely small. In other words, it was shown that the activity as an electrode material hardly decreases and the durability is excellent.
本発明の電極材料は、燃料電池の電極（水素極または空気極）、空気電池の空気極に好適である。さらにＦＥＤ、平面蛍光管、冷陰極管のカソードとしても適用できる。
なお、２０１０年４月２６日に出願された日本特許出願２０１０－１０１２７９号の明細書、特許請求の範囲、図面及び要約書の全内容をここに引用し、本発明の明細書の開示として、取り入れるものである。 The electrode material of the present invention is suitable for an electrode (hydrogen electrode or air electrode) of a fuel cell and an air electrode of an air cell. Further, it can be applied as a cathode of FED, flat fluorescent tube, and cold cathode tube.
It should be noted that the entire contents of the specification, claims, drawings and abstract of Japanese Patent Application No. 2010-101279 filed on April 26, 2010 are cited herein as disclosure of the specification of the present invention. Incorporated.
なお、２０１０年４月２６日に出願された日本特許出願２０１０－１０１２７９号の明細書、特許請求の範囲、図面及び要約書の全内容をここに引用し、本発明の明細書の開示として、取り入れるものである。 The electrode material of the present invention is suitable for an electrode (hydrogen electrode or air electrode) of a fuel cell and an air electrode of an air cell. Further, it can be applied as a cathode of FED, flat fluorescent tube, and cold cathode tube.
It should be noted that the entire contents of the specification, claims, drawings and abstract of Japanese Patent Application No. 2010-101279 filed on April 26, 2010 are cited herein as disclosure of the specification of the present invention. Incorporated.
Claims (11)
- カーボンナノチューブに直接白金を担持させてなる電極材料。 An electrode material made of platinum supported directly on carbon nanotubes.
- カーボンナノチューブに、液相で還元析出させた白金を担持させてなる請求項１に記載の電極材料。 The electrode material according to claim 1, wherein platinum reduced and precipitated in a liquid phase is supported on a carbon nanotube.
- カーボンナノチューブのラマン分光法によるＤバンドとＧバンドのピーク比（Ｄ／Ｇ）が０．１７以下である請求項１または２に記載の電極材料。 The electrode material according to claim 1 or 2, wherein a peak ratio (D / G) of D band and G band by Raman spectroscopy of carbon nanotube is 0.17 or less.
- 前記液相での還元析出が、白金塩の水素還元により行われる請求項１～３のいずれか一項に記載の電極材料。 The electrode material according to any one of claims 1 to 3, wherein the reduction deposition in the liquid phase is performed by hydrogen reduction of a platinum salt.
- 前記カーボンナノチューブの直径が２００ｎｍ以下である請求項１～４のいずれか一項に記載の電極材料。 The electrode material according to any one of claims 1 to 4, wherein the carbon nanotube has a diameter of 200 nm or less.
- 前記カーボンナノチューブのアスペクト比が１０以上である請求項１～５のいずれか一項に記載の電極材料。 The electrode material according to any one of claims 1 to 5, wherein an aspect ratio of the carbon nanotube is 10 or more.
- 請求項１～６のいずれか一項に記載の電極材料を用いた電極。 An electrode using the electrode material according to any one of claims 1 to 6.
- 電極が燃料電池用、または空気電池用である請求項７に記載の電極。 The electrode according to claim 7, wherein the electrode is for a fuel cell or an air cell.
- 液相中で白金塩を還元により析出させてカーボンナノチューブに白金を担持させる電極材料の製造方法。 A method for producing an electrode material in which platinum is deposited on a carbon nanotube by depositing platinum salt by reduction in a liquid phase.
- 白金塩を水素還元により析出させる請求項９に記載の電極材料の製造方法。 The method for producing an electrode material according to claim 9, wherein the platinum salt is precipitated by hydrogen reduction.
- カーボンナノチューブに、親水化処理を施さずに白金を担持させる請求項９又は１０に記載の電極材料の製造方法。 The method for producing an electrode material according to claim 9 or 10, wherein platinum is supported on the carbon nanotube without performing hydrophilic treatment.
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| JP2012512835A JPWO2011136186A1 (en) | 2010-04-26 | 2011-04-25 | Electrode material |
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| WO2011136186A1 true WO2011136186A1 (en) | 2011-11-03 |
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| PCT/JP2011/060084 WO2011136186A1 (en) | 2010-04-26 | 2011-04-25 | Electrode material |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2014504428A (en) * | 2010-12-01 | 2014-02-20 | ハイドロ−ケベック | Lithium air battery |
| JP2014504201A (en) * | 2010-11-26 | 2014-02-20 | バイオニア コーポレーション | Hazardous substance removal device |
| WO2016009935A1 (en) * | 2014-07-15 | 2016-01-21 | 東レ株式会社 | Electrode material for metal-air battery |
| JP2019512441A (en) * | 2016-02-12 | 2019-05-16 | フラウンホーファ−ゲゼルシャフト ツァー フォルデルング デア アンゲバンデン フォルシュンク エー． ファオ．Ｆｒａｕｎｈｏｆｅｒ−Ｇｅｓｅｌｌｓｃｈａｆｔ Ｚｕｒ Ｆｏｒｄｅｒｕｎｇ Ｄｅｒ Ａｎｇｅｗａｎｄｔｅｎ Ｆｏｒｓｃｈｕｎｇ Ｅ． Ｖ． | Graphene and Graphene Production |
| WO2023139862A1 (en) * | 2022-01-18 | 2023-07-27 | 恒林日本株式会社 | Multi-walled carbon nanotube catalyst for fuel cell cathode, and method for preparing same |
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| JP2007027096A (en) * | 2005-06-16 | 2007-02-01 | Keio Gijuku | Platinum for fuel cell and manufacturing method of platinum-ruthenium alloy catalyst |
| JP2010140834A (en) * | 2008-12-15 | 2010-06-24 | Fuji Electric Holdings Co Ltd | Catalyst for fuel cell and electrode-electrolyte membrane assembly for fuel cell using the same, and fuel cell |
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- 2011-04-25 JP JP2012512835A patent/JPWO2011136186A1/en not_active Withdrawn
- 2011-04-25 WO PCT/JP2011/060084 patent/WO2011136186A1/en active Application Filing
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| JP2006134835A (en) * | 2004-11-09 | 2006-05-25 | Hitachi Maxell Ltd | Fuel cell and membrane electrode assembly |
| JP2007223891A (en) * | 2006-02-23 | 2007-09-06 | Samsung Sdi Co Ltd | Manufacturing method of carbon nanotube, supported catalyst containing carbon nanotube, and fuel cell using supported catalyst |
| WO2008115753A2 (en) * | 2007-03-16 | 2008-09-25 | Honda Motor Co., Ltd. | Method of preparing carbon nanotube containing electrodes |
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| JP2014504201A (en) * | 2010-11-26 | 2014-02-20 | バイオニア コーポレーション | Hazardous substance removal device |
| JP2014504428A (en) * | 2010-12-01 | 2014-02-20 | ハイドロ−ケベック | Lithium air battery |
| US11398656B2 (en) | 2010-12-01 | 2022-07-26 | Hydro-Quebec | Lithium-air battery |
| WO2016009935A1 (en) * | 2014-07-15 | 2016-01-21 | 東レ株式会社 | Electrode material for metal-air battery |
| CN106471656A (en) * | 2014-07-15 | 2017-03-01 | 东丽株式会社 | Metal-air battery electrode material |
| JPWO2016009935A1 (en) * | 2014-07-15 | 2017-04-27 | 東レ株式会社 | Electrode material for metal-air battery |
| US10249881B2 (en) | 2014-07-15 | 2019-04-02 | Toray Industries, Inc. | Electrode material for metal-air battery |
| JP2019512441A (en) * | 2016-02-12 | 2019-05-16 | フラウンホーファ−ゲゼルシャフト ツァー フォルデルング デア アンゲバンデン フォルシュンク エー． ファオ．Ｆｒａｕｎｈｏｆｅｒ−Ｇｅｓｅｌｌｓｃｈａｆｔ Ｚｕｒ Ｆｏｒｄｅｒｕｎｇ Ｄｅｒ Ａｎｇｅｗａｎｄｔｅｎ Ｆｏｒｓｃｈｕｎｇ Ｅ． Ｖ． | Graphene and Graphene Production |
| JP2022008546A (en) * | 2016-02-12 | 2022-01-13 | アヴァダイン、 エルエルシー | Graphene and production of graphene |
| JP6993343B2 (en) | 2016-02-12 | 2022-01-13 | アヴァダイン、 エルエルシー | Graphene and graphene production |
| WO2023139862A1 (en) * | 2022-01-18 | 2023-07-27 | 恒林日本株式会社 | Multi-walled carbon nanotube catalyst for fuel cell cathode, and method for preparing same |
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| JPWO2011136186A1 (en) | 2013-07-18 |
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