WO2023139862A1 - Multi-walled carbon nanotube catalyst for fuel cell cathode, and method for preparing same - Google Patents

Multi-walled carbon nanotube catalyst for fuel cell cathode, and method for preparing same Download PDF

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WO2023139862A1
WO2023139862A1 PCT/JP2022/039019 JP2022039019W WO2023139862A1 WO 2023139862 A1 WO2023139862 A1 WO 2023139862A1 JP 2022039019 W JP2022039019 W JP 2022039019W WO 2023139862 A1 WO2023139862 A1 WO 2023139862A1
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walled carbon
carbon nanotube
oxygen
fuel cell
metal
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French (fr)
Japanese (ja)
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九廷 陳
源 連
天奇 黄
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恒林日本株式会社
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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
    • H01M4/96—Carbon-based electrodes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • 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

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  • the present invention relates to the field of catalysis, specifically to multi-walled carbon nanotube catalysts for fuel cell cathodes and methods for preparing the same.
  • platinum materials have been used as cathode catalysts for solid polymer electrolyte fuel cells.
  • platinum catalysts have relatively high oxygen reduction catalytic activity, platinum is very expensive and resources are limited, making it difficult for fuel cells using platinum catalysts to be widely used.
  • researchers have hoped to develop platinum-free catalysts for fuel cell cathodes.
  • Carbon nanotubes (hereinafter referred to as CNTs) are currently attracting a great deal of attention as carbon-based catalyst materials that do not contain platinum.
  • Multi-walled carbon nanotubes (hereafter referred to as MWCNTs) have excellent structural properties, have various catalytic activities, and are easier to manufacture than single-walled carbon nanotubes.
  • MWCNTs with holes i.e., defects
  • the preparation of the MWCNT catalyst requires long-term high-temperature and high-pressure treatment, is relatively time-consuming (as long as several days), consumes a lot of energy, and is not suitable for large-scale industrial production.
  • the MWCNT catalysts produced by this method are excessively defective and have lower catalytic activity than platinum catalysts.
  • the purpose of the present invention is to overcome the drawbacks of the prior art and to provide a method for preparing a multi-walled carbon nanotube catalyst for fuel cell cathodes.
  • a multi-walled carbon nanotube catalyst is obtained by directly heating a multi-walled carbon nanotube on which a simple metal, metal alloy, or metal compound is supported on the surface by light irradiation.
  • This method has a short heating time, low energy consumption, completes the formation of multi-walled carbon nanotube surface defects within 24 hours, and even within a few microseconds, and the catalyst prepared by this method has catalytic activity close to that of platinum catalysts.
  • Another object of the present invention is to provide a multi-walled carbon nanotube catalyst having a catalytic activity close to that of the platinum catalyst obtained by the above preparation method.
  • Another object of the present invention is to provide a fuel cell cathode containing the multi-walled carbon nanotube catalyst.
  • a further object of the present invention is to provide a fuel cell including the fuel cell cathode.
  • a further object of the present invention is to provide a fuel cell system including the fuel cell.
  • the present invention provides the following technical aspects.
  • a method for preparing a multi-walled carbon nanotube catalyst comprising: supporting a single metal, metal alloy or metal compound on the surface of the multi-walled carbon nanotube; and obtaining a multi-walled carbon nanotube catalyst by directly heating the multi-walled carbon nanotubes having the single metal, metal alloy or metal compound supported on the surface in an oxygen-containing atmosphere by direct heating with light irradiation.
  • the multi-walled carbon nanotubes are pretreated so that metal impurities in the multi-walled carbon nanotubes are removed.
  • the pretreatment may include heat treatment and acid treatment.
  • the elemental metal is at least one of cobalt, iron, vanadium, tin and nickel.
  • the metal alloy contains at least one element selected from cobalt, iron, vanadium, tin and nickel.
  • the metal compound is at least one of cobalt oxide, iron oxide, vanadium oxide, tin oxide, nickel oxide, cobalt element salt, iron element salt, vanadium element salt, tin element salt and nickel element salt.
  • the metal compound contains at least one of cobalt oxide, iron oxide, vanadium oxide, tin oxide and nickel oxide, and is preferably cobalt oxide.
  • the metal compound is, for example, at least one of cobalt oxide, iron oxide, vanadium oxide, tin oxide and nickel oxide.
  • the metal compound contains at least one of a cobalt element salt, an iron element salt, a vanadium element salt, a tin element salt and a nickel element salt, and is preferably a cobalt element salt.
  • the metal compound is preferably a metal nitrate.
  • the metal nitrate is preferably at least one of cobalt nitrate, iron nitrate, vanadium nitrate, tin nitrate and nickel nitrate.
  • said metal nitrate is at least one of cobalt nitrate, iron nitrate, vanadium nitrate, tin nitrate and nickel nitrate.
  • the elemental metal, metal alloy and metal compound are carried on the surface of the multi-walled carbon nanotube in the form of fine particles.
  • the particle size of the single metal, metal alloy, or fine metal compound particles supported on the surface of the multi-walled carbon nanotube is not particularly limited as long as the particle size of the single metal, metal alloy, or fine metal compound particle is smaller than the tube diameter of the multi-walled carbon nanotube.
  • the particle size of the metal element, metal alloy or metal compound fine particles may be 0.5 to 15 nm, preferably 0.5 to 10 nm. After the oxidation treatment, the metal nitrate microparticles are converted to metal oxide microparticles, and the particle size of the microparticles changes slightly, but not significantly.
  • the amount of the metal element supported on the surface of the multi-walled carbon nanotube may be 5-15% by weight, preferably 10-12% by weight. If the amount of the metal element supported is too small, the effect of promoting pore formation is not significant, and if the amount of the metal element supported is too large, the original structure of the MWCNT is destroyed. Pores with different pore sizes, depths, numbers, or densities can be formed in multi-walled carbon nanotubes by controlling the particle size and the amount of fine particles of a metal, metal alloy, or metal compound supported on the surface of the multi-walled carbon nanotubes.
  • the increase in the amount of the metal element supported can promote the reaction between carbon and oxygen in the multi-walled carbon nanotube in a direction parallel to the axial direction of the multi-walled carbon nanotube, so that the thickness of the multi-walled carbon nanotube can be reduced.
  • the “amount of metal element supported on the surface of the multi-walled carbon nanotube” is the ratio (% by weight) of the “metal element” when the sum of the “multi-walled carbon nanotube (whole)” and the “elementary metal, metal alloy, or metal compound” is 100.
  • the term “metal element” refers to the "metal element” part of "a simple metal, a metal alloy, or a metal compound.”
  • the present invention is not particularly limited to the method for supporting fine metal particles, metal alloys, or metal compound particles on the surface of multi-walled carbon nanotubes.
  • a general method can be used to support fine metal particles, metal alloys, or metal compound particles on a substrate.
  • a method for supporting iron oxide includes adding multi-walled carbon nanotubes to a solvent such as methanol or ethanol, ultrasonically dispersing, and then adding FeCl 3 solution to the mixed solution, and drying after mixing to obtain multi-walled carbon nanotubes supporting iron cations, and heating them in air or an inert atmosphere to obtain MWCNTs supporting iron oxides.
  • a solvent such as methanol or ethanol
  • multi-walled carbon nanotubes are added to cobalt nitrate and a solvent (e.g., methanol or ethanol), sufficiently dispersed, and then dried to obtain multi-walled carbon nanotubes supporting Co(NO 3 ) 2 .
  • a solvent e.g., methanol or ethanol
  • polishing and pulverization are performed to obtain a multi-walled carbon nanotube powder carrying fine Co(NO 3 ) 2 .6H 2 O particles.
  • the rays of light irradiation may be infrared rays, near-infrared rays, or visible rays.
  • the oxidation treatment process of the present invention is a process of forming pores (that is, defects). Light irradiation is essential in this process. Irradiation with light allows the multi-walled carbon nanotubes to form the desired defects more easily rather than generating oxygen-containing functional groups during the oxidation process.
  • the heating temperature may be 100-500°C, and preferably, the heating temperature may be 200-400°C. If the reaction temperature is less than 100°C, the reaction time will be long and not practical. If the reaction temperature exceeds 500° C., the carbon in the multi-walled carbon nanotubes is significantly lost, which is disadvantageous in improving the catalytic activity of the obtained multi-walled carbon nanotube catalyst.
  • the heating time is long, the oxygen concentration in the oxygen-containing atmosphere is correspondingly decreased, and when the heating time is short, the oxygen concentration in the oxygen-containing atmosphere is correspondingly increased, so as to ensure that the number, size and depth of the multi-walled carbon nanotube surface defects are within an appropriate range so that the resulting catalyst has high catalytic performance.
  • the heating time is 1 ⁇ s to 24 hours, and the volume fraction of oxygen in the oxygen-containing atmosphere is greater than 0% and less than or equal to 50%.
  • the volume fraction of oxygen in the oxygen-containing atmosphere is greater than 0% and 45% or less, and the heating time can be 100 ⁇ s to 15 hours. In another embodiment, the volume fraction of oxygen in the oxygen-containing atmosphere is greater than 0% and less than or equal to 40%, and the heating time can be from 0.1s to 10h. In another embodiment, the volume fraction of oxygen in the oxygen-containing atmosphere is greater than 0% and less than or equal to 30%, and the heating time can be 0.1s-1h. For example, in the oxygen-containing atmosphere, the volume fraction of oxygen is greater than 0% and less than or equal to 20%, and the heating time may be 0.1s-10min. For example, the oxygen-containing atmosphere may have a volume fraction of oxygen greater than 0% and less than or equal to 20%, and a heating time of 0.1 s to 60 s.
  • the heating temperature is 100-400° C.
  • the volume fraction of oxygen in the oxygen-containing atmosphere is greater than 5% and 20% or less
  • the heating time is 0.1 s-5 min.
  • the heating temperature is 300-400° C.
  • the volume fraction of oxygen in the oxygen-containing atmosphere is greater than 5% and 20% or less
  • the heating time is 0.1 s-60 s.
  • the presence of oxygen is required, and the progress of the desired reaction can be achieved by heating in an oxygen-containing atmosphere.
  • the concentration of oxygen By changing the concentration of oxygen, the progress of the reaction can be controlled to some extent, and the purpose of reforming can be achieved.
  • the oxidation treatment can be performed in an air atmosphere under atmospheric pressure.
  • the oxidation treatment process of the present invention can maintain the crystallinity of the multi-walled carbon nanotube skeleton and form some pores on its surface. These pores are formed by the loss of carbon moieties on the multi-walled carbon nanotubes. These pores may be formed by partially or completely penetrating the sidewalls of the multi-walled carbon nanotubes.
  • acid cleaning is performed after the oxidation treatment so that metal cations are removed.
  • This can reduce the weight of the catalyst and improve the stability of the catalyst.
  • the acid wash can be performed using sulfuric acid, nitric acid, hydrochloric acid, perchloric acid, or mixtures of two or more thereof.
  • the present invention further provides a multi-walled carbon nanotube catalyst obtained by the above preparation method.
  • the starting potential of the oxygen reduction reaction (ORR) of the fuel cell can be used as an activity index that characterizes the fuel cell cathode catalyst.
  • the ORR onset potential of fuel cells using the multi-walled carbon nanotube catalyst of the present invention can reach more than 0.81 V vs. reversible hydrogen electrode (RHE), which is close to the ORR onset potential of fuel cells using conventional platinum-based catalysts (i.e., 0.98 V vs. RHE).
  • RHE reversible hydrogen electrode
  • OCV open circuit voltage
  • the open circuit voltage of the fuel cell using the multi-walled carbon nanotube catalyst of the present invention can reach 0.85 V or more.
  • the present invention further provides a fuel cell cathode containing the multi-walled carbon nanotube catalyst.
  • the present invention further provides a fuel cell comprising the fuel cell cathode.
  • the present invention further provides a fuel cell system including the fuel cell.
  • the fuel cell is a solid polymer electrolyte fuel cell.
  • the present invention provides a method for preparing a multi-walled carbon nanotube catalyst for a fuel cell cathode, in which a multi-walled carbon nanotube catalyst having a metal simple substance, metal alloy or metal compound supported on the surface is directly heated by light irradiation to obtain a multi-walled carbon nanotube catalyst.
  • MWCNTs are fired in an atmospheric environment at 500°C.
  • the MWCNTs after firing are taken, mixed with concentrated nitric acid (concentration: 69%) and 2M sulfuric acid, put into a treatment tank, and heated and stirred at 120°C. After cooling and diluting, it is filtered and washed to obtain pretreated MWCNT.
  • Formation of pores (defects) An appropriate amount of MWCNT carrying cobalt nitrate fine particles is taken and heated to 400° C. by infrared light irradiation in an atmosphere with an oxygen volume concentration of 20% and maintained for about 5 seconds.
  • the pore formation process is as shown in FIG. Heating by infrared light irradiation was performed using an infrared heating device.
  • MWCNT powder carrying cobalt nitrate fine particles was put into a crucible on a sample stage of an infrared heating device, infrared rays were emitted from the infrared heating device to a lens, and the lens focused the infrared rays within the scope of the sample stage.
  • the MWCNT powder could directly receive the heat generated by the infrared irradiation, thereby realizing the effect of being heated, and was also affected by the light irradiation.
  • the ORR catalytic activity of the DMWCNTs produced in Example 1 was verified by a CV test using a three-electrode system. Using 0.1 M perchloric acid as the electrolyte, graphite as the counter electrode, a silver-silver chloride electrode (vs. Ag/AgCl) as the reference electrode, and the glassy carbon electrode of the DMWCNTs supported as the working electrode, the test is performed at a sweep rate of 5 mV/s and a sweep range of 0.05 V to 0.8 V. As the test results show, the onset potential of oxygen reduction reaction (ORR) can reach 0.81 V vs RHE after using this DMWCNT catalyst.
  • ORR oxygen reduction reaction
  • Example 2 was carried out according to the method described in Example 1, with the difference that an appropriate amount of MWCNTs carrying cobalt nitrate fine particles was taken, heated to 300°C in an atmosphere with an oxygen volume concentration of 5% by infrared light irradiation, and maintained for about 10 seconds.
  • Example 3 Adopting the test method described in Example 1, the DMWCNTs obtained in Example 2 were subjected to an electrochemical performance test (oxygen reduction reaction: ORR), and the test results show that the onset potential of the oxygen reduction reaction (ORR) can reach 0.73 V vs RHE after using this DMWCNT catalyst. (Example 3)
  • Example 3 was carried out according to the method described in Example 1, with the difference that an appropriate amount of MWCNTs carrying cobalt nitrate fine particles was taken, heated to 300°C by infrared light irradiation in an atmosphere with an oxygen volume concentration of 20%, and maintained for about 5 minutes.
  • Example 4 Adopting the test method described in Example 1, the DMWCNTs obtained in Example 3 were subjected to an electrochemical performance test (oxygen reduction reaction: ORR), and the test results show that the onset potential of the oxygen reduction reaction (ORR) can reach 0.58 V vs RHE after using this DMWCNT catalyst. (Example 4)
  • Example 4 was carried out according to the method described in Example 1, with the difference that an appropriate amount of MWCNTs carrying cobalt nitrate fine particles was taken, heated to 300°C in an atmosphere with an oxygen volume concentration of 5% by infrared light irradiation, and maintained for about 25 minutes.
  • Example 5 Adopting the test method described in Example 1, the DMWCNTs obtained in Example 4 were subjected to an electrochemical performance test (oxygen reduction reaction: ORR), and the test results show that the onset potential of the oxygen reduction reaction (ORR) can reach 0.51 V vs RHE after using this DMWCNT catalyst. (Example 5)
  • Example 5 was carried out according to the method described in Example 1, with the difference that an appropriate amount of MWCNTs carrying cobalt nitrate fine particles was taken, heated to 300°C in an atmosphere with an oxygen volume concentration of 50% by infrared light irradiation, and maintained for about 10 seconds.
  • Example 6 Adopting the test method described in Example 1, the DMWCNTs obtained in Example 4 were subjected to an electrochemical performance test (oxygen reduction reaction: ORR), and the test results show that the onset potential of the oxygen reduction reaction (ORR) can reach 0.57 V vs RHE after using this DMWCNT catalyst. (Example 6)
  • Example 6 was carried out according to the method described in Example 1, with the difference that an appropriate amount of MWCNTs carrying cobalt nitrate fine particles was taken, heated to 270°C by infrared light irradiation in an atmosphere with an oxygen volume concentration of 5%, and maintained for about 5 minutes. After that, the MWCNT carrying cobalt ions is directly subjected to an electrochemical performance test without being subjected to an acid cleaning treatment.
  • MWCNTs are sintered for 1 hour in an atmospheric environment at 500°C. 1 g of calcined MWCNT is taken, mixed with 40 ml of concentrated nitric acid (concentration is 69%) and 40 ml of 2M sulfuric acid, and put into a treatment tank. The mixture is heated and stirred at 120° C., cooled, diluted, filtered and washed to obtain pretreated MWCNT.
  • Formation of pores (defects) An appropriate amount of pretreated MWCNT is heated to 270° C. in an atmosphere of 10% oxygen volume concentration by infrared irradiation and maintained for about 3 s.
  • the MWCNT powder was put into a crucible on an infrared heating device sample stage, infrared rays were emitted from the infrared heating device to a lens, and the lens focused the infrared rays within the range of the sample stage.
  • the MWCNT powder could directly receive the heat generated by the infrared irradiation, thereby realizing the effect of being heated, and was also affected by the light irradiation.
  • Comparative Example 2 was carried out according to the method described in Example 1, with the difference that an appropriate amount of MWCNT supporting cobalt nitrate fine particles was taken, heated to 300°C by infrared light irradiation in an atmosphere with an oxygen volume concentration of 5%, and maintained for about 10 seconds. Heating by infrared light irradiation was carried out by employing an infrared heating device. The MWCNT powder supporting cobalt nitrate fine particles was put into a crucible on the sample stage of the infrared heating device, the infrared rays were emitted from the infrared heating device to a lens, and the lens collected the infrared rays within the scope of the sample stage.
  • the crucible is covered with a lid, both the crucible and the lid are made of graphite, so that the crucible can directly receive the heat generated by the infrared irradiation, and efficiently transfer the heat to the sample therein to achieve the effect of heating the sample, but not affected by the light irradiation.
  • Comparative Example 3 was carried out according to the method described in Example 1. The difference was that an appropriate amount of MWCNTs carrying cobalt nitrate fine particles was taken, heated to 270°C by infrared light irradiation in an atmosphere with an oxygen volume concentration of 20%, and maintained for about 25 minutes. Heating by infrared light irradiation was carried out by employing an infrared heating device. The MWCNT powder supporting cobalt nitrate fine particles was put into a crucible on the sample stage of the infrared heating device, the infrared rays were emitted from the infrared heating device to a lens, and the lens collected the infrared rays within the scope of the sample stage.
  • the crucible is covered with a lid, both the crucible and the lid are made of graphite, so that the crucible can directly receive the heat generated by the infrared irradiation, and efficiently transfer the heat to the sample therein to achieve the effect of heating the sample, but not affected by the light irradiation.
  • Comparative Example 4 was carried out according to the method described in Example 1. The difference was that an appropriate amount of MWCNTs carrying cobalt nitrate fine particles was taken, heated to 270°C in an atmosphere with an oxygen volume concentration of 100% by infrared light irradiation, and maintained for about 10 seconds. MWCNT powder carrying cobalt nitrate fine particles was put into a crucible on an infrared heating device sample stage, infrared rays were emitted from the infrared heating device to a lens, and the lens focused the infrared rays within the scope of the sample stage. The MWCNT powder could directly receive the heat generated by the infrared irradiation, thereby realizing the effect of being heated, and was also affected by the light irradiation.
  • Example 2 Using the test method described in Example 1, the DMWCNTs obtained in Comparative Example 4 were subjected to an electrochemical performance test (oxygen reduction reaction: ORR). As the test results show, after using this DMWCNT catalyst, the onset potential of the oxygen reduction reaction (ORR) is 0.56 V vs RHE.
  • the present invention can have the configurations of the items shown below.
  • [Section 1] A method for preparing a multi-walled carbon nanotube catalyst, comprising: supporting a single metal, metal alloy or metal compound on the surface of the multi-walled carbon nanotube; and obtaining a multi-walled carbon nanotube catalyst by directly heating the multi-walled carbon nanotubes having the single metal, metal alloy or metal compound supported on the surface in an oxygen-containing atmosphere by direct heating with light irradiation.
  • Item 2 The preparation method according to Item 1, wherein the light for the light irradiation is infrared rays, near-infrared rays, or visible rays.
  • the heating temperature is 100 to 500°C.
  • the volume fraction of oxygen in the oxygen-containing atmosphere is greater than 0% and 50% or less, and the heating time is 1 ⁇ s to 24 hours.
  • the heating temperature is 100 to 400° C., the volume fraction of oxygen in the oxygen-containing atmosphere is greater than 5% and 20% or less, and the heating time is 0.1 s to 5 min.
  • the elemental metal is at least one of cobalt, iron, vanadium, tin and nickel, the metal alloy comprises at least one element of cobalt, iron, vanadium, tin and nickel; 3.
  • [Section 7] A multi-walled carbon nanotube catalyst obtained by the preparation method according to any one of items 1 to 6 above.
  • [Item 8] 8 8.
  • a fuel cell cathode comprising the multi-walled carbon nanotube catalyst according to item 7 above.
  • [Item 9] 9.
  • a fuel cell comprising the fuel cell cathode according to Item 8 above.
  • a fuel cell system comprising the fuel cell according to Item 9 above.

Abstract

The present invention relates to a method which is for preparing a multi-walled carbon nanotube catalyst for a fuel cell cathode, and with which a multi-walled carbon nanotube catalyst can be obtained by directly heating, by means of light irradiation, a multi-walled carbon nanotube in which a single metal, a metal alloy, or a metal compound is supported on the surface thereof. According to this method, heating time is shortened, energy consumption is lessened, and surface defect formation of the multi-walled carbon nanotube is completed within 24 hours, and even within a few microseconds. In addition, a catalyst prepared by said method has a catalytic activity close to that of a platinum catalyst.

Description

燃料電池カソード用多層カーボンナノチューブ触媒及びその調製方法Multi-walled carbon nanotube catalyst for fuel cell cathode and its preparation method
　本発明は、触媒分野に関し、具体的には、燃料電池カソード用多層カーボンナノチューブ触媒及びその調製方法に関する。 The present invention relates to the field of catalysis, specifically to multi-walled carbon nanotube catalysts for fuel cell cathodes and methods for preparing the same.
　従来、高分子固体電解質燃料電池カソード触媒として白金材料が使用されてきた。しかしながら、白金触媒は、比較的高い酸素還元触媒活性を有するにもかかわらず、白金が非常に高価であり且つ資源に限りがあるため、白金触媒を使用する燃料電池が広く使用されることは困難である。長年にわたり、研究者は、白金を使用しない燃料電池カソード用触媒を開発することを望んでいた。 Conventionally, platinum materials have been used as cathode catalysts for solid polymer electrolyte fuel cells. However, although platinum catalysts have relatively high oxygen reduction catalytic activity, platinum is very expensive and resources are limited, making it difficult for fuel cells using platinum catalysts to be widely used. For many years, researchers have hoped to develop platinum-free catalysts for fuel cell cathodes.
　現在、白金を含まないカーボン系触媒材料として、カーボンナノチューブ（以下、ＣＮＴと称する）が大きな注目を集めている。多層カーボンナノチューブ（以下、ＭＷＣＮＴと称する）は、優れた構造特性を有するので、様々な触媒活性を有し、単層カーボンナノチューブに比べて製造プロセスがより簡単であるので、ＭＷＣＮＴは白金触媒の代替材料として幅広く検討されている。 Carbon nanotubes (hereinafter referred to as CNTs) are currently attracting a great deal of attention as carbon-based catalyst materials that do not contain platinum. Multi-walled carbon nanotubes (hereafter referred to as MWCNTs) have excellent structural properties, have various catalytic activities, and are easier to manufacture than single-walled carbon nanotubes.
　研究者は、側壁を貫通するか、又は貫通しない孔（即ち、欠陥）を有するＭＷＣＮＴは、燃料電池カソード用触媒として使用される際に、一定の触媒活性を示すことを発見した。しかしながら、前記ＭＷＣＮＴ触媒を調製するには長時間の高温高圧処理を必要とし、比較的時間がかかり（数日ほど長い）、エネルギー消耗が大きく、大規模な工業生産が不可能である。なお、この方法で作製されたＭＷＣＮＴ触媒は、欠陥が過度に多く、触媒活性が白金触媒より低い。 Researchers have found that MWCNTs with holes (i.e., defects) that do or do not penetrate the sidewalls exhibit certain catalytic activity when used as catalysts for fuel cell cathodes. However, the preparation of the MWCNT catalyst requires long-term high-temperature and high-pressure treatment, is relatively time-consuming (as long as several days), consumes a lot of energy, and is not suitable for large-scale industrial production. It should be noted that the MWCNT catalysts produced by this method are excessively defective and have lower catalytic activity than platinum catalysts.
　従って、触媒活性が良好で、且つ調製過程にかかる時間が短い多層カーボンナノチューブ触媒及びその調製方法を開発する必要がある。 Therefore, it is necessary to develop a multi-walled carbon nanotube catalyst with good catalytic activity and a short preparation time, and a preparation method thereof.
　本発明は、従来技術の欠点を克服し、燃料電池カソード用多層カーボンナノチューブ触媒の調製方法を提供することを目的とし、この方法は、表面に金属単体、金属合金又は金属化合物が担持されている多層カーボンナノチューブを光照射によって直接加熱することで、多層カーボンナノチューブ触媒が得られるものである。この方法は、加熱時間が短く、エネルギー消耗が少なく、２４時間以内、ひいては数マイクロ秒以内に多層カーボンナノチューブ表面欠陥の形成を完了し、且つこの方法で作製された触媒は白金触媒に近い触媒活性を有する。 The purpose of the present invention is to overcome the drawbacks of the prior art and to provide a method for preparing a multi-walled carbon nanotube catalyst for fuel cell cathodes. In this method, a multi-walled carbon nanotube catalyst is obtained by directly heating a multi-walled carbon nanotube on which a simple metal, metal alloy, or metal compound is supported on the surface by light irradiation. This method has a short heating time, low energy consumption, completes the formation of multi-walled carbon nanotube surface defects within 24 hours, and even within a few microseconds, and the catalyst prepared by this method has catalytic activity close to that of platinum catalysts.
　本発明は、上記の調製方法で得られた白金触媒に近い触媒活性を有する多層カーボンナノチューブ触媒を提供することも目的とする。 Another object of the present invention is to provide a multi-walled carbon nanotube catalyst having a catalytic activity close to that of the platinum catalyst obtained by the above preparation method.
　本発明はまた、前記多層カーボンナノチューブ触媒を含む燃料電池カソードを提供することを目的とする。 Another object of the present invention is to provide a fuel cell cathode containing the multi-walled carbon nanotube catalyst.
　本発明はさらに、前記燃料電池カソードを含む燃料電池を提供することを目的とする。 A further object of the present invention is to provide a fuel cell including the fuel cell cathode.
　本発明はさらに、前記燃料電池を含む燃料電池システムを提供することを目的とする。 A further object of the present invention is to provide a fuel cell system including the fuel cell.
　以上の目的を達成するために、本発明は、以下の技術態様を提供する。 In order to achieve the above objectives, the present invention provides the following technical aspects.
　多層カーボンナノチューブ触媒の調製方法であって、
　多層カーボンナノチューブの表面に金属単体、金属合金又は金属化合物を担持するステップと、
　前記表面に前記金属単体、金属合金又は前記金属化合物が担持されている多層カーボンナノチューブを、酸素含有雰囲気で、光照射によって直接加熱することで酸化処理を行って、多層カーボンナノチューブ触媒を得るステップと、を含む。 A method for preparing a multi-walled carbon nanotube catalyst, comprising:
supporting a single metal, metal alloy or metal compound on the surface of the multi-walled carbon nanotube;
and obtaining a multi-walled carbon nanotube catalyst by directly heating the multi-walled carbon nanotubes having the single metal, metal alloy or metal compound supported on the surface in an oxygen-containing atmosphere by direct heating with light irradiation.
　好ましくは、多層カーボンナノチューブにおける不純物である金属が除去されるように、多層カーボンナノチューブを使用する前に、多層カーボンナノチューブに対して前処理を行う。前記前処理は、熱処理及び酸処理を含んでよい。 Preferably, before using the multi-walled carbon nanotubes, the multi-walled carbon nanotubes are pretreated so that metal impurities in the multi-walled carbon nanotubes are removed. The pretreatment may include heat treatment and acid treatment.
　好ましくは、前記金属単体は、コバルト、鉄、バナジウム、スズ及びニッケルのうちの少なくとも１種であり得る。 Preferably, the elemental metal is at least one of cobalt, iron, vanadium, tin and nickel.
　好ましくは、前記金属合金は、コバルト、鉄、バナジウム、スズ及びニッケルのうちの少なくとも１種の元素を含む。 Preferably, the metal alloy contains at least one element selected from cobalt, iron, vanadium, tin and nickel.
　前記金属化合物は、コバルトの酸化物、鉄の酸化物、バナジウムの酸化物、スズの酸化物、ニッケルの酸化物、コバルト元素の塩、鉄元素の塩、バナジウム元素の塩、スズ元素の塩及びニッケル元素の塩のうちの少なくとも１種である。 The metal compound is at least one of cobalt oxide, iron oxide, vanadium oxide, tin oxide, nickel oxide, cobalt element salt, iron element salt, vanadium element salt, tin element salt and nickel element salt.
　好ましくは、前記金属化合物は、コバルトの酸化物、鉄の酸化物、バナジウムの酸化物、スズの酸化物及びニッケルの酸化物のうちの少なくとも１種を含み、コバルトの酸化物であることが好ましい。前記金属化合物は、例えば酸化コバルト、酸化鉄、酸化バナジウム、酸化スズ及び酸化ニッケルのうちの少なくとも１種である。 Preferably, the metal compound contains at least one of cobalt oxide, iron oxide, vanadium oxide, tin oxide and nickel oxide, and is preferably cobalt oxide. The metal compound is, for example, at least one of cobalt oxide, iron oxide, vanadium oxide, tin oxide and nickel oxide.
　好ましくは、前記金属化合物は、コバルト元素の塩、鉄元素の塩、バナジウム元素の塩、スズ元素の塩及びニッケル元素の塩のうちの少なくとも１種を含み、コバルト元素の塩であることが好ましい。前記金属化合物は、金属硝酸塩であることが好ましい。前記金属硝酸塩は、コバルトの硝酸塩、鉄の硝酸塩、バナジウムの硝酸塩、スズの硝酸塩及びニッケルの硝酸塩のうちの少なくとも１種であることが好ましい。好ましくは、前記金属硝酸塩は、硝酸コバルト、硝酸鉄、硝酸バナジウム、硝酸スズ及び硝酸ニッケルのうちの少なくとも１種である。 Preferably, the metal compound contains at least one of a cobalt element salt, an iron element salt, a vanadium element salt, a tin element salt and a nickel element salt, and is preferably a cobalt element salt. The metal compound is preferably a metal nitrate. The metal nitrate is preferably at least one of cobalt nitrate, iron nitrate, vanadium nitrate, tin nitrate and nickel nitrate. Preferably, said metal nitrate is at least one of cobalt nitrate, iron nitrate, vanadium nitrate, tin nitrate and nickel nitrate.
　好ましくは、前記金属単体、金属合金及び前記金属化合物は、微粒子の形状で多層カーボンナノチューブの表面に担持されている。本発明は、多層カーボンナノチューブの表面に担持されている金属単体、金属合金又は金属化合物微粒子の粒子径のサイズに対して、特に制限せず、金属単体、金属合金又は金属化合物微粒子の粒子径が多層カーボンナノチューブの管径より小さければよい。異なる条件によって、金属単体、金属合金又は金属化合物微粒子の粒子径は、いずれも０．５～１５ｎｍであってもよく、０．５～１０ｎｍが好ましい。酸化処理の後、金属硝酸塩微粒子が金属酸化物微粒子に転換され、微粒子の粒子径はわずかに変化するが、変化はそれほど大きくない。 Preferably, the elemental metal, metal alloy and metal compound are carried on the surface of the multi-walled carbon nanotube in the form of fine particles. In the present invention, the particle size of the single metal, metal alloy, or fine metal compound particles supported on the surface of the multi-walled carbon nanotube is not particularly limited as long as the particle size of the single metal, metal alloy, or fine metal compound particle is smaller than the tube diameter of the multi-walled carbon nanotube. Depending on different conditions, the particle size of the metal element, metal alloy or metal compound fine particles may be 0.5 to 15 nm, preferably 0.5 to 10 nm. After the oxidation treatment, the metal nitrate microparticles are converted to metal oxide microparticles, and the particle size of the microparticles changes slightly, but not significantly.
　前記多層カーボンナノチューブの表面の金属元素の担持量は、５～１５重量％であってもよく、１０～１２重量％が好ましい。金属元素の担持量が少なすぎると、細孔形成を促進する効果が顕著でなく、金属元素の担持量が多すぎると、ＭＷＣＮＴの元の構造が破壊される。多層カーボンナノチューブ表面に担持されている金属単体、金属合金又は金属化合物微粒子の粒子径及び担持量を制御することによって、孔径サイズ、深み、数量又は密度の異なる細孔を多層カーボンナノチューブに形成することができる。なお、金属元素の担持量の増加によって、多層カーボンナノチューブにおけるカーボンと酸素との反応が多層カーボンナノチューブの軸方向に平行な方向で行われることを促進できるので、多層カーボンナノチューブの薄層化が実現される。
　なお、「多層カーボンナノチューブの表面の金属元素の担持量」とは、「多層カーボンナノチューブ（全体）」と「金属単体、金属合金、又は、金属化合物」の合計を１００としたときの、「金属元素」の割合（重量％）である。ここで「金属元素」とは、「金属単体、金属合金、又は、金属化合物」のうちの「金属元素」部分をいう。 The amount of the metal element supported on the surface of the multi-walled carbon nanotube may be 5-15% by weight, preferably 10-12% by weight. If the amount of the metal element supported is too small, the effect of promoting pore formation is not significant, and if the amount of the metal element supported is too large, the original structure of the MWCNT is destroyed. Pores with different pore sizes, depths, numbers, or densities can be formed in multi-walled carbon nanotubes by controlling the particle size and the amount of fine particles of a metal, metal alloy, or metal compound supported on the surface of the multi-walled carbon nanotubes. Note that the increase in the amount of the metal element supported can promote the reaction between carbon and oxygen in the multi-walled carbon nanotube in a direction parallel to the axial direction of the multi-walled carbon nanotube, so that the thickness of the multi-walled carbon nanotube can be reduced.
The “amount of metal element supported on the surface of the multi-walled carbon nanotube” is the ratio (% by weight) of the “metal element” when the sum of the “multi-walled carbon nanotube (whole)” and the “elementary metal, metal alloy, or metal compound” is 100. Here, the term "metal element" refers to the "metal element" part of "a simple metal, a metal alloy, or a metal compound."
　本発明は、多層カーボンナノチューブの表面の金属単体、金属合金又は金属化合物微粒子の担持方法に対して、特に制限されない。金属単体、金属合金又は金属化合物微粒子を基材に担持する方法は、一般的な方法により実現できる。 The present invention is not particularly limited to the method for supporting fine metal particles, metal alloys, or metal compound particles on the surface of multi-walled carbon nanotubes. A general method can be used to support fine metal particles, metal alloys, or metal compound particles on a substrate.
　例えば、鉄の酸化物を担持する方法は、多層カーボンナノチューブをメタノール又はエタノール等の溶媒に添加し、超音波分散した後に、混合溶液にＦｅＣｌ3溶液を添加することと、混合後に乾燥させた後に鉄のカチオンが担持されている多層カーボンナノチューブが得られ、それを空気又は不活性雰囲気で加熱し、鉄の酸化物が担持されているＭＷＣＮＴを得ることとを含む。 For example, a method for supporting iron oxide includes adding multi-walled carbon nanotubes to a solvent such as methanol or ethanol, ultrasonically dispersing, and then adding FeCl 3 solution to the mixed solution, and drying after mixing to obtain multi-walled carbon nanotubes supporting iron cations, and heating them in air or an inert atmosphere to obtain MWCNTs supporting iron oxides.
　例えば、硝酸コバルトを担持する方法は、硝酸コバルト及び溶媒（例えば、メタノール又はエタノール等）に多層カーボンナノチューブを添加し、十分に分散させた後に乾燥させて、Ｃｏ（ＮＯ3）2が担持されている多層カーボンナノチューブが得られる。好ましくは、乾燥後に研磨及び粉砕を行って、Ｃｏ（ＮＯ3）2・６Ｈ2Ｏ微粒子が担持されている多層カーボンナノチューブ粉末が得られる。 For example, in the method of supporting cobalt nitrate, multi-walled carbon nanotubes are added to cobalt nitrate and a solvent (e.g., methanol or ethanol), sufficiently dispersed, and then dried to obtain multi-walled carbon nanotubes supporting Co(NO 3 ) 2 . Preferably, after drying, polishing and pulverization are performed to obtain a multi-walled carbon nanotube powder carrying fine Co(NO 3 ) 2 .6H 2 O particles.
　好ましくは、前記光照射の光線は、赤外線、近赤外線又は可視光線であり得る。本発明の酸化処理過程は、細孔（即ち、欠陥）の形成過程である。この過程において、光照射は必須である。光照射によって、多層カーボンナノチューブが酸化処理過程において酸素含有官能基を生成するのではなく、目的とする欠陥がより容易に形成されるようにすることができる。 Preferably, the rays of light irradiation may be infrared rays, near-infrared rays, or visible rays. The oxidation treatment process of the present invention is a process of forming pores (that is, defects). Light irradiation is essential in this process. Irradiation with light allows the multi-walled carbon nanotubes to form the desired defects more easily rather than generating oxygen-containing functional groups during the oxidation process.
　好ましくは、加熱温度は、１００～５００℃であってもよく、好ましくは、加熱温度は、２００～４００℃であってもよい。反応温度が１００℃未満であると、反応時間が長くなり、実用的ではない。反応温度が５００℃を超えると、多層カーボンナノチューブにおける炭素が著しく消失し、得られる多層カーボンナノチューブ触媒の触媒活性の向上に不利である。 Preferably, the heating temperature may be 100-500°C, and preferably, the heating temperature may be 200-400°C. If the reaction temperature is less than 100°C, the reaction time will be long and not practical. If the reaction temperature exceeds 500° C., the carbon in the multi-walled carbon nanotubes is significantly lost, which is disadvantageous in improving the catalytic activity of the obtained multi-walled carbon nanotube catalyst.
　本発明において、加熱時間及び酸素含有雰囲気における酸素濃度を同時に制御することによって多層カーボンナノチューブ表面欠陥の数量、サイズ及び深みを制御でき、これにより多層カーボンナノチューブ触媒の触媒活性を制御する。加熱時間が長い場合、酸素含有雰囲気における酸素濃度をそれに相応して減少させ、加熱時間が短い場合、酸素含有雰囲気における酸素濃度をそれに相応して増加させることで、得られる触媒が高い触媒性能を有するように多層カーボンナノチューブ表面欠陥の数量、サイズ及び深みが適当な範囲にあることを確保する。加熱時間は、１μｓ～２４ｈであり、且つ前記酸素含有雰囲気で酸素の体積分率は０％より大きく、５０％以下であることが好ましい。 In the present invention, by simultaneously controlling the heating time and the oxygen concentration in the oxygen-containing atmosphere, the number, size and depth of multi-walled carbon nanotube surface defects can be controlled, thereby controlling the catalytic activity of the multi-walled carbon nanotube catalyst. When the heating time is long, the oxygen concentration in the oxygen-containing atmosphere is correspondingly decreased, and when the heating time is short, the oxygen concentration in the oxygen-containing atmosphere is correspondingly increased, so as to ensure that the number, size and depth of the multi-walled carbon nanotube surface defects are within an appropriate range so that the resulting catalyst has high catalytic performance. Preferably, the heating time is 1 μs to 24 hours, and the volume fraction of oxygen in the oxygen-containing atmosphere is greater than 0% and less than or equal to 50%.
　一方の実施態様において、前記酸素含有雰囲気で酸素の体積分率は０％より大きく、４５％以下であり、且つ加熱時間は１００μｓ～１５ｈであり得る。他方の実施態様において、前記酸素含有雰囲気で酸素の体積分率は０％より大きく、４０％以下であり、且つ加熱時間は０．１ｓ～１０ｈであり得る。他方の実施態様において、前記酸素含有雰囲気で酸素の体積分率は０％より大きく、３０％以下であり、且つ加熱時間は０．１ｓ～１ｈであり得る。例えば、前記酸素含有雰囲気で酸素の体積分率は０％より大きく、２０％以下であり、且つ加熱時間は０．１ｓ～１０ｍｉｎであり得る。例えば、前記酸素含有雰囲気で酸素の体積分率は０％より大きく、２０％以下であり、且つ加熱時間は０．１ｓ～６０ｓであり得る。 In one embodiment, the volume fraction of oxygen in the oxygen-containing atmosphere is greater than 0% and 45% or less, and the heating time can be 100 μs to 15 hours. In another embodiment, the volume fraction of oxygen in the oxygen-containing atmosphere is greater than 0% and less than or equal to 40%, and the heating time can be from 0.1s to 10h. In another embodiment, the volume fraction of oxygen in the oxygen-containing atmosphere is greater than 0% and less than or equal to 30%, and the heating time can be 0.1s-1h. For example, in the oxygen-containing atmosphere, the volume fraction of oxygen is greater than 0% and less than or equal to 20%, and the heating time may be 0.1s-10min. For example, the oxygen-containing atmosphere may have a volume fraction of oxygen greater than 0% and less than or equal to 20%, and a heating time of 0.1 s to 60 s.
　ある具体的な実施例において、加熱温度は１００～４００℃であり、前記酸素含有雰囲気で酸素の体積分率は５％より大きく、２０％以下であり、加熱時間は０．１ｓ～５ｍｉｎである。 In a specific embodiment, the heating temperature is 100-400° C., the volume fraction of oxygen in the oxygen-containing atmosphere is greater than 5% and 20% or less, and the heating time is 0.1 s-5 min.
　ある具体的な実施例において、加熱温度は３００～４００℃であり、前記酸素含有雰囲気で酸素の体積分率は５％より大きく、２０％以下であり、加熱時間は０．１ｓ～６０ｓである。 In a specific embodiment, the heating temperature is 300-400° C., the volume fraction of oxygen in the oxygen-containing atmosphere is greater than 5% and 20% or less, and the heating time is 0.1 s-60 s.
　酸化処理過程において、酸素の存在を必要とし、酸素含有雰囲気で加熱することによって目的とする反応の進行を実現できる。酸素の濃度を変えることによって、反応の進行をある程度制御でき、改質の目的を達成できる。通常、大気圧下、空気雰囲気で、酸化処理を行うことができる。 In the oxidation treatment process, the presence of oxygen is required, and the progress of the desired reaction can be achieved by heating in an oxygen-containing atmosphere. By changing the concentration of oxygen, the progress of the reaction can be controlled to some extent, and the purpose of reforming can be achieved. Generally, the oxidation treatment can be performed in an air atmosphere under atmospheric pressure.
　本発明の酸化処理過程は、多層カーボンナノチューブ骨格の結晶化度を維持するとともに、その表面に幾つかの細孔を形成することができる。これらの細孔は、多層カーボンナノチューブ上の炭素部分の損失により形成されたものである。なお、これらの細孔は、多層カーボンナノチューブの側壁を一部又は完全に貫通することによって形成されたものであってもよい。 The oxidation treatment process of the present invention can maintain the crystallinity of the multi-walled carbon nanotube skeleton and form some pores on its surface. These pores are formed by the loss of carbon moieties on the multi-walled carbon nanotubes. These pores may be formed by partially or completely penetrating the sidewalls of the multi-walled carbon nanotubes.
　好ましくは、金属カチオンが除去されるように、酸化処理後に酸洗浄を行う。これにより、触媒の重量を減らし、触媒の安定性を向上できる。例えば、硫酸、硝酸、塩酸、過塩素酸又はこれらの２つ以上の混合物を使用して前記酸洗浄を行うことができる。 Preferably, acid cleaning is performed after the oxidation treatment so that metal cations are removed. This can reduce the weight of the catalyst and improve the stability of the catalyst. For example, the acid wash can be performed using sulfuric acid, nitric acid, hydrochloric acid, perchloric acid, or mixtures of two or more thereof.
　本発明は、前記調製方法で得られた多層カーボンナノチューブ触媒をさらに提供する。 The present invention further provides a multi-walled carbon nanotube catalyst obtained by the above preparation method.
　燃料電池カソード用触媒を特徴付ける活性指標としては、燃料電池の酸素還元反応（ＯＲＲ）の開始電位であり得る。本発明の多層カーボンナノチューブ触媒を使用する燃料電池のＯＲＲ開始電位は０．８１Ｖｖｓ可逆水素電極（ＲＨＥ）以上に到達でき、従来の白金系触媒を使用する燃料電池のＯＲＲ開始電位（即ち、０．９８ＶｖｓＲＨＥ）に近い。膜電極を作製した後に、燃料電池の開回路電圧テストにおける開回路電圧（ＯＣＶ）として特徴づけてもよく、本発明の多層カーボンナノチューブ触媒を使用する燃料電池の開回路電圧は０．８５Ｖ以上に到達できる。 The starting potential of the oxygen reduction reaction (ORR) of the fuel cell can be used as an activity index that characterizes the fuel cell cathode catalyst. The ORR onset potential of fuel cells using the multi-walled carbon nanotube catalyst of the present invention can reach more than 0.81 V vs. reversible hydrogen electrode (RHE), which is close to the ORR onset potential of fuel cells using conventional platinum-based catalysts (i.e., 0.98 V vs. RHE). After fabricating the membrane electrode, it may be characterized as open circuit voltage (OCV) in the fuel cell open circuit voltage test, and the open circuit voltage of the fuel cell using the multi-walled carbon nanotube catalyst of the present invention can reach 0.85 V or more.
　本発明は、前記多層カーボンナノチューブ触媒を含む燃料電池カソードをさらに提供する。 The present invention further provides a fuel cell cathode containing the multi-walled carbon nanotube catalyst.
　本発明は、前記燃料電池カソードを含む燃料電池をさらに提供する。 The present invention further provides a fuel cell comprising the fuel cell cathode.
　本発明は、前記燃料電池を含む燃料電池システムをさらに提供する。 The present invention further provides a fuel cell system including the fuel cell.
　好ましくは、前記燃料電池は高分子固体電解質燃料電池である。 Preferably, the fuel cell is a solid polymer electrolyte fuel cell.
　従来技術に比べて、本発明の有利な効果は、以下の通りである。
　本発明は、燃料電池カソード用多層カーボンナノチューブ触媒の調製方法を提供し、この方法は、表面に金属単体、金属合金又は金属化合物が担持されている多層カーボンナノチューブを光照射によって直接加熱することで、多層カーボンナノチューブ触媒が得られ、この方法は、加熱時間が短く、エネルギー消耗が少なく、２４時間以内、ひいては数マイクロ秒以内に多層カーボンナノチューブ表面欠陥の形成を完了し、且つこの方法で作製された触媒は白金触媒に近い触媒活性を有する。 Advantageous effects of the present invention compared to the prior art are as follows.
The present invention provides a method for preparing a multi-walled carbon nanotube catalyst for a fuel cell cathode, in which a multi-walled carbon nanotube catalyst having a metal simple substance, metal alloy or metal compound supported on the surface is directly heated by light irradiation to obtain a multi-walled carbon nanotube catalyst.
細孔形成過程の模式図である。It is a schematic diagram of a pore formation process.
　以下、実施例を参照して、本発明の実施態様を詳細に説明するが、下記実施例は本発明を説明するためのものにすぎず、本発明の範囲を制限するものではないことを当業者は理解すべきである。実施例において、具体的な条件が明示されていないものは、一般的な条件に従うか、又はメーカーが推奨した条件で行う。使用された試薬又は機器にメーカーが明示されていない場合、いずれも市場から購入できる一般的な製品である。
　（実施例１） Embodiments of the present invention will now be described in detail with reference to examples, but those skilled in the art should understand that the following examples are only for the purpose of illustrating the present invention and do not limit the scope of the present invention. In the examples, where specific conditions are not specified, general conditions are followed or the conditions recommended by the manufacturer are used. If the reagents or instruments used are not marked by manufacturer, they are all common products available on the market.
(Example 1)
　ＭＷＣＮＴの前処理：
　ＭＷＣＮＴを５００℃の大気環境下で焼成する。焼成後のＭＷＣＮＴを取り、濃硝酸（濃度は６９％）及び２Ｍ硫酸と混合して処理槽に投入し、１２０℃で加熱撹拌する。冷却希釈した後に、濾過洗浄して、前処理ＭＷＣＮＴを得る。 Pretreatment of MWCNT:
MWCNTs are fired in an atmospheric environment at 500°C. The MWCNTs after firing are taken, mixed with concentrated nitric acid (concentration: 69%) and 2M sulfuric acid, put into a treatment tank, and heated and stirred at 120°C. After cooling and diluting, it is filtered and washed to obtain pretreated MWCNT.
　硝酸コバルトの担持：
　０．０５４８２ｇの硝酸コバルト六水和物Ｃｏ（ＮＯ3）2・６Ｈ2Ｏ（純度９９．５％）をエタノールに溶解する。前処理したＭＷＣＭＴを０．１ｇ取って溶液に投入し、十分に分散させる。分散液を加熱してエタノールを揮発させ、硝酸コバルト微粒子が担持されているＭＷＣＮＴ粉末を得る。 Support of cobalt nitrate:
0.05482 g of cobalt nitrate hexahydrate Co(NO 3 ) 2 .6H 2 O (purity 99.5%) is dissolved in ethanol. Take 0.1 g of the pretreated MWCMT and put it into the solution and disperse it well. The dispersion liquid is heated to volatilize the ethanol to obtain MWCNT powder supporting fine particles of cobalt nitrate.
　細孔（欠陥）の形成：
　硝酸コバルト微粒子が担持されているＭＷＣＮＴを適量取って、酸素体積濃度が２０％である雰囲気で、赤外光照射の方式により４００℃に加熱し且つ５ｓ程度維持する。細孔形成過程は図１に示す通りである。赤外光照射による加熱は、赤外加熱装置を採用して行った。硝酸コバルト微粒子が担持されているＭＷＣＮＴ粉末を赤外加熱装置の試料台における坩堝に投入し、赤外加熱装置から赤外線をレンズに出射し、レンズが赤外線を試料台の範囲内に集めた。ＭＷＣＮＴ粉末は赤外線照射により発生した熱を直接受けることができ、これにより加熱される効果を実現するとともに、光照射の影響も受けた。 Formation of pores (defects):
An appropriate amount of MWCNT carrying cobalt nitrate fine particles is taken and heated to 400° C. by infrared light irradiation in an atmosphere with an oxygen volume concentration of 20% and maintained for about 5 seconds. The pore formation process is as shown in FIG. Heating by infrared light irradiation was performed using an infrared heating device. MWCNT powder carrying cobalt nitrate fine particles was put into a crucible on a sample stage of an infrared heating device, infrared rays were emitted from the infrared heating device to a lens, and the lens focused the infrared rays within the scope of the sample stage. The MWCNT powder could directly receive the heat generated by the infrared irradiation, thereby realizing the effect of being heated, and was also affected by the light irradiation.
　コバルトイオンの除去：
　加熱終了後、得られた試料を２Ｍ硫酸に投入し、４時間撹拌後、濾過、洗浄、乾燥を行って、コバルトイオンが除去された細孔ＭＷＣＮＴ（即ち、ＤＭＷＣＮＴ）を得る。 Removal of cobalt ions:
After completion of heating, the obtained sample is put into 2M sulfuric acid, stirred for 4 hours, filtered, washed and dried to obtain porous MWCNT (that is, DMWCNT) from which cobalt ions are removed.
　三電極系を使用して、ＣＶテストにより、実施例１で作製されたＤＭＷＣＮＴのＯＲＲ触媒活性に対して検証を行った。０．１Ｍ過塩素酸を電解液として使用し、グラファイトを対電極とし、銀―塩化銀電極（ｖｓ．Ａｇ／ＡｇＣｌ）を基準電極とし、担持されているこのＤＭＷＣＮＴのガラス状炭素電極を作用電極として、掃引速度を５ｍＶ／ｓ、掃引範囲を０．０５Ｖ～０．８Ｖとしてテストを行う。テスト結果が示すように、このＤＭＷＣＮＴ触媒を使用した後に、酸素還元反応（ＯＲＲ）の開始電位は０．８１ＶｖｓＲＨＥに到達できる。 The ORR catalytic activity of the DMWCNTs produced in Example 1 was verified by a CV test using a three-electrode system. Using 0.1 M perchloric acid as the electrolyte, graphite as the counter electrode, a silver-silver chloride electrode (vs. Ag/AgCl) as the reference electrode, and the glassy carbon electrode of the DMWCNTs supported as the working electrode, the test is performed at a sweep rate of 5 mV/s and a sweep range of 0.05 V to 0.8 V. As the test results show, the onset potential of oxygen reduction reaction (ORR) can reach 0.81 V vs RHE after using this DMWCNT catalyst.
　この材料で膜電極を作製した後に燃料電池においてテストすると、開回路電圧は０．８５Ｖ以上に到達できる。
　（実施例２） After fabricating a membrane electrode with this material and testing it in a fuel cell, the open circuit voltage can reach over 0.85V.
(Example 2)
　実施例２は、実施例１で説明した方法に従って実施し、異なる点は、硝酸コバルト微粒子が担持されているＭＷＣＮＴを適量取って、酸素体積濃度が５％である雰囲気で、赤外光照射の方式により３００℃に加熱し且つ１０ｓ程度維持することである。 Example 2 was carried out according to the method described in Example 1, with the difference that an appropriate amount of MWCNTs carrying cobalt nitrate fine particles was taken, heated to 300°C in an atmosphere with an oxygen volume concentration of 5% by infrared light irradiation, and maintained for about 10 seconds.
　実施例１で説明したテスト方法を採用して、実施例２で得られたＤＭＷＣＮＴに対して電気化学性能テスト（酸素還元反応：ＯＲＲ）を行ったところ、テスト結果が示すように、このＤＭＷＣＮＴ触媒を使用した後に、酸素還元反応（ＯＲＲ）の開始電位は０．７３ＶｖｓＲＨＥに到達できる。
　（実施例３） Adopting the test method described in Example 1, the DMWCNTs obtained in Example 2 were subjected to an electrochemical performance test (oxygen reduction reaction: ORR), and the test results show that the onset potential of the oxygen reduction reaction (ORR) can reach 0.73 V vs RHE after using this DMWCNT catalyst.
(Example 3)
　実施例３は、実施例１で説明した方法に従って実施し、異なる点は、硝酸コバルト微粒子が担持されているＭＷＣＮＴを適量取って、酸素体積濃度が２０％である雰囲気で、赤外光照射の方式により３００℃に加熱し且つ５ｍｉｎ程度維持することである。 Example 3 was carried out according to the method described in Example 1, with the difference that an appropriate amount of MWCNTs carrying cobalt nitrate fine particles was taken, heated to 300°C by infrared light irradiation in an atmosphere with an oxygen volume concentration of 20%, and maintained for about 5 minutes.
　実施例１で説明したテスト方法を採用して、実施例３で得られたＤＭＷＣＮＴに対して電気化学性能テスト（酸素還元反応：ＯＲＲ）を行ったところ、テスト結果が示すように、このＤＭＷＣＮＴ触媒を使用した後に、酸素還元反応（ＯＲＲ）の開始電位は０．５８ＶｖｓＲＨＥに到達できる。
　（実施例４） Adopting the test method described in Example 1, the DMWCNTs obtained in Example 3 were subjected to an electrochemical performance test (oxygen reduction reaction: ORR), and the test results show that the onset potential of the oxygen reduction reaction (ORR) can reach 0.58 V vs RHE after using this DMWCNT catalyst.
(Example 4)
　実施例４は、実施例１で説明した方法に従って実施し、異なる点は、硝酸コバルト微粒子が担持されているＭＷＣＮＴを適量取って、酸素体積濃度が５％である雰囲気で、赤外光照射の方式により３００℃に加熱し且つ２５ｍｉｎ程度維持することである。 Example 4 was carried out according to the method described in Example 1, with the difference that an appropriate amount of MWCNTs carrying cobalt nitrate fine particles was taken, heated to 300°C in an atmosphere with an oxygen volume concentration of 5% by infrared light irradiation, and maintained for about 25 minutes.
　実施例１で説明したテスト方法を採用して、実施例４で得られたＤＭＷＣＮＴに対して電気化学性能テスト（酸素還元反応：ＯＲＲ）を行ったところ、テスト結果が示すように、このＤＭＷＣＮＴ触媒を使用した後に、酸素還元反応（ＯＲＲ）の開始電位は０．５１ＶｖｓＲＨＥに到達できる。
　（実施例５） Adopting the test method described in Example 1, the DMWCNTs obtained in Example 4 were subjected to an electrochemical performance test (oxygen reduction reaction: ORR), and the test results show that the onset potential of the oxygen reduction reaction (ORR) can reach 0.51 V vs RHE after using this DMWCNT catalyst.
(Example 5)
　実施例５は、実施例１で説明した方法に従って実施し、異なる点は、硝酸コバルト微粒子が担持されているＭＷＣＮＴを適量取って、酸素体積濃度が５０％である雰囲気で、赤外光照射の方式により３００℃に加熱し且つ１０ｓ程度維持することである。 Example 5 was carried out according to the method described in Example 1, with the difference that an appropriate amount of MWCNTs carrying cobalt nitrate fine particles was taken, heated to 300°C in an atmosphere with an oxygen volume concentration of 50% by infrared light irradiation, and maintained for about 10 seconds.
　実施例１で説明したテスト方法を採用して、実施例４で得られたＤＭＷＣＮＴに対して電気化学性能テスト（酸素還元反応：ＯＲＲ）を行ったところ、テスト結果が示すように、このＤＭＷＣＮＴ触媒を使用した後に、酸素還元反応（ＯＲＲ）の開始電位は０．５７ＶｖｓＲＨＥに到達できる。
　（実施例６） Adopting the test method described in Example 1, the DMWCNTs obtained in Example 4 were subjected to an electrochemical performance test (oxygen reduction reaction: ORR), and the test results show that the onset potential of the oxygen reduction reaction (ORR) can reach 0.57 V vs RHE after using this DMWCNT catalyst.
(Example 6)
　実施例６は、実施例１で説明した方法に従って実施し、異なる点は、硝酸コバルト微粒子が担持されているＭＷＣＮＴを適量取って、酸素体積濃度が５％である雰囲気で、赤外光照射の方式により２７０℃に加熱し且つ５ｍｉｎ程度維持することである。この後、コバルトイオンが担持されているＭＷＣＮＴに対しては酸洗浄処理を行うことなく、直接電気化学性能テストを行う。 Example 6 was carried out according to the method described in Example 1, with the difference that an appropriate amount of MWCNTs carrying cobalt nitrate fine particles was taken, heated to 270°C by infrared light irradiation in an atmosphere with an oxygen volume concentration of 5%, and maintained for about 5 minutes. After that, the MWCNT carrying cobalt ions is directly subjected to an electrochemical performance test without being subjected to an acid cleaning treatment.
　実施例１で説明したテスト方法を採用して、実施例６で得られたＤＭＷＣＮＴに対して電気化学性能テスト（酸素還元反応：ＯＲＲ）を行ったところ、テスト結果が示すように、このＤＭＷＣＮＴ触媒を使用した後に、酸素還元反応（ＯＲＲ）の開始電位は０．５４ＶｖｓＲＨＥに到達できる。
　（比較例１） Adopting the test method described in Example 1, the DMWCNTs obtained in Example 6 were subjected to an electrochemical performance test (oxygen reduction reaction: ORR), and the test results show that the onset potential of the oxygen reduction reaction (ORR) can reach 0.54 V vs RHE after using this DMWCNT catalyst.
(Comparative example 1)
　ＭＷＣＮＴの前処理：
　ＭＷＣＮＴを５００℃の大気環境下で１ｈ焼成する。焼成後のＭＷＣＮＴを１ｇ取り、４０ｍｌ濃硝酸（濃度は６９％）及び４０ｍｌの２Ｍ硫酸と混合して処理槽に投入する。１２０℃で加熱撹拌し、冷却希釈し、濾過洗浄して、前処理ＭＷＣＮＴを得る。 Pretreatment of MWCNT:
MWCNTs are sintered for 1 hour in an atmospheric environment at 500°C. 1 g of calcined MWCNT is taken, mixed with 40 ml of concentrated nitric acid (concentration is 69%) and 40 ml of 2M sulfuric acid, and put into a treatment tank. The mixture is heated and stirred at 120° C., cooled, diluted, filtered and washed to obtain pretreated MWCNT.
　細孔（欠陥）の形成：
　前処理ＭＷＣＮＴを適量取って、酸素体積濃度が１０％である雰囲気で、赤外光照射の方式により２７０℃に加熱し且つ３ｓ程度維持する。ＭＷＣＮＴ粉末を赤外加熱装置試料台における坩堝に投入し、赤外加熱装置から赤外線をレンズに出射し、レンズが赤外線を試料台の範囲内に集めた。ＭＷＣＮＴ粉末は赤外線照射により発生した熱を直接受けることができ、これにより加熱される効果を実現するとともに、光照射の影響も受けた。 Formation of pores (defects):
An appropriate amount of pretreated MWCNT is heated to 270° C. in an atmosphere of 10% oxygen volume concentration by infrared irradiation and maintained for about 3 s. The MWCNT powder was put into a crucible on an infrared heating device sample stage, infrared rays were emitted from the infrared heating device to a lens, and the lens focused the infrared rays within the range of the sample stage. The MWCNT powder could directly receive the heat generated by the infrared irradiation, thereby realizing the effect of being heated, and was also affected by the light irradiation.
　実施例１で説明したテスト方法を採用して、加熱済の前処理ＭＷＣＮＴに対して電気化学性能テスト（酸素還元反応：ＯＲＲ）を行ったところ、テスト結果が示すように、この触媒を使用した後に、酸素還元反応（ＯＲＲ）の開始電位は０．４１ＶｖｓＲＨＥである。
　（比較例２） Adopting the test method described in Example 1, the heated pretreated MWCNTs were subjected to an electrochemical performance test (oxygen reduction reaction: ORR), and the test results show that the onset potential of the oxygen reduction reaction (ORR) is 0.41 V vs RHE after using this catalyst.
(Comparative example 2)
　比較例２は、実施例１で説明した方法に従って実施し、異なる点は、硝酸コバルト微粒子が担持されているＭＷＣＮＴを適量取って、酸素体積濃度が５％である雰囲気で、赤外光照射の方式により３００℃に加熱し且つ１０ｓ程度維持することである。赤外光照射による加熱は、赤外加熱装置を採用して行い、硝酸コバルト微粒子が担持されているＭＷＣＮＴ粉末を赤外加熱装置試料台における坩堝に投入し、赤外加熱装置から赤外線をレンズに出射し、レンズが赤外線を試料台の範囲内に集めた。坩堝は蓋に覆われ、坩堝及び蓋はいずれもグラファイトで作製され、これにより坩堝は赤外線照射により発生した熱を直接受けることができ、熱を効率的にその中の試料に伝達して、試料が加熱される効果を実現するが、光照射の影響を受けることはない。 Comparative Example 2 was carried out according to the method described in Example 1, with the difference that an appropriate amount of MWCNT supporting cobalt nitrate fine particles was taken, heated to 300°C by infrared light irradiation in an atmosphere with an oxygen volume concentration of 5%, and maintained for about 10 seconds. Heating by infrared light irradiation was carried out by employing an infrared heating device. The MWCNT powder supporting cobalt nitrate fine particles was put into a crucible on the sample stage of the infrared heating device, the infrared rays were emitted from the infrared heating device to a lens, and the lens collected the infrared rays within the scope of the sample stage. The crucible is covered with a lid, both the crucible and the lid are made of graphite, so that the crucible can directly receive the heat generated by the infrared irradiation, and efficiently transfer the heat to the sample therein to achieve the effect of heating the sample, but not affected by the light irradiation.
　実施例１で説明したテスト方法を採用して、比較例２で得られたＤＭＷＣＮＴに対して電気化学性能テスト（酸素還元反応：ＯＲＲ）を行ったところ、テスト結果が示すように、このＤＭＷＣＮＴ触媒を使用した後に、酸素還元反応（ＯＲＲ）の開始電位は０．５３ＶｖｓＲＨＥである。
　（比較例３） Adopting the test method described in Example 1, the DMWCNTs obtained in Comparative Example 2 were subjected to an electrochemical performance test (oxygen reduction reaction: ORR), and the test results show that the onset potential of the oxygen reduction reaction (ORR) is 0.53 V vs RHE after using this DMWCNT catalyst.
(Comparative Example 3)
　比較例３は、実施例１で説明した方法に従って実施し、異なる点は、硝酸コバルト微粒子が担持されているＭＷＣＮＴを適量取って、酸素体積濃度が２０％である雰囲気で、赤外光照射の方式により２７０℃に加熱し且つ２５ｍｉｎ程度維持することである。赤外光照射による加熱は、赤外加熱装置を採用して行い、硝酸コバルト微粒子が担持されているＭＷＣＮＴ粉末を赤外加熱装置試料台における坩堝に投入し、赤外加熱装置から赤外線をレンズに出射し、レンズが赤外線を試料台の範囲内に集めた。坩堝は蓋に覆われ、坩堝及び蓋はいずれもグラファイトで作製され、これにより坩堝は赤外線照射により発生した熱を直接受けることができ、熱を効率的にその中の試料に伝達して、試料が加熱される効果を実現するが、光照射の影響を受けることはない。 Comparative Example 3 was carried out according to the method described in Example 1. The difference was that an appropriate amount of MWCNTs carrying cobalt nitrate fine particles was taken, heated to 270°C by infrared light irradiation in an atmosphere with an oxygen volume concentration of 20%, and maintained for about 25 minutes. Heating by infrared light irradiation was carried out by employing an infrared heating device. The MWCNT powder supporting cobalt nitrate fine particles was put into a crucible on the sample stage of the infrared heating device, the infrared rays were emitted from the infrared heating device to a lens, and the lens collected the infrared rays within the scope of the sample stage. The crucible is covered with a lid, both the crucible and the lid are made of graphite, so that the crucible can directly receive the heat generated by the infrared irradiation, and efficiently transfer the heat to the sample therein to achieve the effect of heating the sample, but not affected by the light irradiation.
　実施例１で説明したテスト方法を採用して、比較例３で得られたＤＭＷＣＮＴに対して電気化学性能テスト（酸素還元反応：ＯＲＲ）を行ったところ、テスト結果が示すように、このＤＭＷＣＮＴ触媒を使用した後に、酸素還元反応（ＯＲＲ）の開始電位は０．４２ＶｖｓＲＨＥである。
　（比較例４） Adopting the test method described in Example 1, the DMWCNTs obtained in Comparative Example 3 were subjected to an electrochemical performance test (oxygen reduction reaction: ORR), and the test results show that the onset potential of the oxygen reduction reaction (ORR) is 0.42 V vs RHE after using this DMWCNT catalyst.
(Comparative Example 4)
　比較例４は、実施例１で説明した方法に従って実施し、異なる点は、硝酸コバルト微粒子が担持されているＭＷＣＮＴを適量取って、酸素体積濃度が１００％である雰囲気で、赤外光照射の方式により２７０℃に加熱し且つ１０ｓ程度維持することである。硝酸コバルト微粒子が担持されているＭＷＣＮＴ粉末を赤外加熱装置試料台における坩堝に投入し、赤外加熱装置から赤外線をレンズに出射し、レンズが赤外線を試料台の範囲内に集めた。ＭＷＣＮＴ粉末は赤外線照射により発生した熱を直接受けることができ、これにより加熱される効果を実現するとともに、光照射の影響も受けた。 Comparative Example 4 was carried out according to the method described in Example 1. The difference was that an appropriate amount of MWCNTs carrying cobalt nitrate fine particles was taken, heated to 270°C in an atmosphere with an oxygen volume concentration of 100% by infrared light irradiation, and maintained for about 10 seconds. MWCNT powder carrying cobalt nitrate fine particles was put into a crucible on an infrared heating device sample stage, infrared rays were emitted from the infrared heating device to a lens, and the lens focused the infrared rays within the scope of the sample stage. The MWCNT powder could directly receive the heat generated by the infrared irradiation, thereby realizing the effect of being heated, and was also affected by the light irradiation.
　実施例１で説明したテスト方法を採用して、比較例４で得られたＤＭＷＣＮＴに対して電気化学性能テスト（酸素還元反応：ＯＲＲ）を行ったところ、テスト結果が示すように、このＤＭＷＣＮＴ触媒を使用した後に、酸素還元反応（ＯＲＲ）の開始電位は０．５６ＶｖｓＲＨＥである。 Using the test method described in Example 1, the DMWCNTs obtained in Comparative Example 4 were subjected to an electrochemical performance test (oxygen reduction reaction: ORR). As the test results show, after using this DMWCNT catalyst, the onset potential of the oxygen reduction reaction (ORR) is 0.56 V vs RHE.
　以上の記載は、本発明の好ましい実施形態にすぎず、本発明の保護範囲は、これに制限されず、当業者は、本発明に開示された技術範囲に、容易に想到できる変更又は置換は、いずれも本発明の保護範囲に含まれるべきである。従って、本発明の保護範囲は、請求項の保護範囲を基準とするべきである。 The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited thereto, and any modification or replacement that a person skilled in the art can easily conceive within the technical scope disclosed in the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.
　本発明は以下に示した項目の構成を有し得る。
［項１］
　多層カーボンナノチューブ触媒の調製方法であって、
　多層カーボンナノチューブの表面に金属単体、金属合金又は金属化合物を担持するステップと、
　前記表面に前記金属単体、金属合金又は金属化合物が担持されている多層カーボンナノチューブを、酸素含有雰囲気で、光照射によって直接加熱することで酸化処理を行って、多層カーボンナノチューブ触媒を得るステップと、を含むことを特徴とする多層カーボンナノチューブ触媒の調製方法。
［項２］
　前記光照射の光線は、赤外線、近赤外線又は可視光線であることを特徴とする項１に記載の調製方法。
［項３］
　加熱温度は１００～５００℃であることを特徴とする上記項１又は２に記載の調製方法。
［項４］
　前記酸素含有雰囲気で酸素の体積分率は０％より大きく、５０％以下であり、加熱時間は１μｓ～２４ｈであることを特徴とする上記項１又は２に記載の調製方法。
［項５］
　加熱温度は１００～４００℃であり、前記酸素含有雰囲気で酸素の体積分率は５％より大きく、２０％以下であり、加熱時間は０．１ｓ～５ｍｉｎであることを特徴とする上記項１又は２に記載の調製方法。
［項６］
　前記金属単体は、コバルト、鉄、バナジウム、スズ及びニッケルのうちの少なくとも１種であり、
　前記金属合金は、コバルト、鉄、バナジウム、スズ及びニッケルのうちの少なくとも１種の元素を含み、
　前記金属化合物は、コバルトの酸化物、鉄の酸化物、バナジウムの酸化物、スズの酸化物、ニッケルの酸化物、コバルト元素の塩、鉄元素の塩、バナジウム元素の塩、スズ元素の塩及びニッケル元素の塩のうちの少なくとも１種であることを特徴とする上記項１又は２に記載の調製方法。
［項７］
　上記項１～６のいずれか一行に記載の調製方法で得られる多層カーボンナノチューブ触媒。
［項８］
　上記項７に記載の多層カーボンナノチューブ触媒を含むことを特徴とする燃料電池カソード。
［項９］
　上記項８に記載の燃料電池カソードを含むことを特徴とする燃料電池。
［項１０］
　上記項９に記載の燃料電池を含むことを特徴とする燃料電池システム。 The present invention can have the configurations of the items shown below.
[Section 1]
A method for preparing a multi-walled carbon nanotube catalyst, comprising:
supporting a single metal, metal alloy or metal compound on the surface of the multi-walled carbon nanotube;
and obtaining a multi-walled carbon nanotube catalyst by directly heating the multi-walled carbon nanotubes having the single metal, metal alloy or metal compound supported on the surface in an oxygen-containing atmosphere by direct heating with light irradiation.
[Section 2]
Item 2. The preparation method according to Item 1, wherein the light for the light irradiation is infrared rays, near-infrared rays, or visible rays.
[Section 3]
3. The preparation method according to item 1 or 2, wherein the heating temperature is 100 to 500°C.
[Section 4]
3. The preparation method according to item 1 or 2, wherein the volume fraction of oxygen in the oxygen-containing atmosphere is greater than 0% and 50% or less, and the heating time is 1 μs to 24 hours.
[Section 5]
3. The preparation method according to item 1 or 2, wherein the heating temperature is 100 to 400° C., the volume fraction of oxygen in the oxygen-containing atmosphere is greater than 5% and 20% or less, and the heating time is 0.1 s to 5 min.
[Section 6]
The elemental metal is at least one of cobalt, iron, vanadium, tin and nickel,
the metal alloy comprises at least one element of cobalt, iron, vanadium, tin and nickel;
3. The preparation method according to item 1 or 2, wherein the metal compound is at least one of cobalt oxide, iron oxide, vanadium oxide, tin oxide, nickel oxide, cobalt element salt, iron element salt, vanadium element salt, tin element salt and nickel element salt.
[Section 7]
A multi-walled carbon nanotube catalyst obtained by the preparation method according to any one of items 1 to 6 above.
[Item 8]
8. A fuel cell cathode comprising the multi-walled carbon nanotube catalyst according to item 7 above.
[Item 9]
9. A fuel cell comprising the fuel cell cathode according to Item 8 above.
[Item 10]
10. A fuel cell system comprising the fuel cell according to Item 9 above.

Claims (10)

  1. 　多層カーボンナノチューブ触媒の調製方法であって、
    　多層カーボンナノチューブの表面に金属単体、金属合金又は金属化合物を担持するステップと、
    　前記表面に前記金属単体、金属合金又は金属化合物が担持されている多層カーボンナノチューブを、酸素含有雰囲気で、光照射によって直接加熱することで酸化処理を行って、多層カーボンナノチューブ触媒を得るステップと、を含むことを特徴とする多層カーボンナノチューブ触媒の調製方法。     A method for preparing a multi-walled carbon nanotube catalyst, comprising:
    supporting a single metal, metal alloy or metal compound on the surface of the multi-walled carbon nanotube;
    and obtaining a multi-walled carbon nanotube catalyst by directly heating the multi-walled carbon nanotubes having the single metal, metal alloy or metal compound supported on the surface in an oxygen-containing atmosphere by direct heating with light irradiation.
  2. 　前記光照射の光線は、赤外線、近赤外線又は可視光線であることを特徴とする請求項１に記載の調製方法。 The preparation method according to claim 1, characterized in that the rays of light irradiation are infrared rays, near-infrared rays, or visible rays.
  3. 　加熱温度は１００～５００℃であることを特徴とする請求項１又は２に記載の調製方法。 The preparation method according to claim 1 or 2, wherein the heating temperature is 100 to 500°C.
  4. 　前記酸素含有雰囲気で酸素の体積分率は０％より大きく、５０％以下であり、加熱時間は１μｓ～２４ｈであることを特徴とする請求項１又は２に記載の調製方法。 The preparation method according to claim 1 or 2, characterized in that the volume fraction of oxygen in the oxygen-containing atmosphere is greater than 0% and 50% or less, and the heating time is 1 μs to 24 hours.
  5. 　加熱温度は１００～４００℃であり、前記酸素含有雰囲気で酸素の体積分率は５％より大きく、２０％以下であり、加熱時間は０．１ｓ～５ｍｉｎであることを特徴とする請求項１又は２に記載の調製方法。 The preparation method according to claim 1 or 2, wherein the heating temperature is 100 to 400°C, the volume fraction of oxygen in the oxygen-containing atmosphere is greater than 5% and 20% or less, and the heating time is 0.1 s to 5 min.
  6. 　前記金属単体は、コバルト、鉄、バナジウム、スズ及びニッケルのうちの少なくとも１種であり、
    　前記金属合金は、コバルト、鉄、バナジウム、スズ及びニッケルのうちの少なくとも１種の元素を含み、
    　前記金属化合物は、コバルトの酸化物、鉄の酸化物、バナジウムの酸化物、スズの酸化物、ニッケルの酸化物、コバルト元素の塩、鉄元素の塩、バナジウム元素の塩、スズ元素の塩及びニッケル元素の塩のうちの少なくとも１種であることを特徴とする請求項１又は２に記載の調製方法。     The elemental metal is at least one of cobalt, iron, vanadium, tin and nickel,
    the metal alloy comprises at least one element of cobalt, iron, vanadium, tin and nickel;
    3. The preparation method according to claim 1 or 2, wherein the metal compound is at least one of cobalt oxide, iron oxide, vanadium oxide, tin oxide, nickel oxide, cobalt element salt, iron element salt, vanadium element salt, tin element salt and nickel element salt.
  7. 　請求項１～６のいずれか一項に記載の調製方法で得られる多層カーボンナノチューブ触媒。 A multi-walled carbon nanotube catalyst obtained by the preparation method according to any one of claims 1 to 6.
  8. 　請求項７に記載の多層カーボンナノチューブ触媒を含むことを特徴とする燃料電池カソード。 A fuel cell cathode comprising the multi-walled carbon nanotube catalyst according to claim 7.
  9. 　請求項８に記載の燃料電池カソードを含むことを特徴とする燃料電池。 A fuel cell comprising the fuel cell cathode according to claim 8.
  10. 　請求項９に記載の燃料電池を含むことを特徴とする燃料電池システム。 A fuel cell system comprising the fuel cell according to claim 9.
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