WO2014087894A1 - Platinum-free catalyst for fuel cell cathode and process for producing same - Google Patents

Platinum-free catalyst for fuel cell cathode and process for producing same Download PDF

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WO2014087894A1
WO2014087894A1 PCT/JP2013/081880 JP2013081880W WO2014087894A1 WO 2014087894 A1 WO2014087894 A1 WO 2014087894A1 JP 2013081880 W JP2013081880 W JP 2013081880W WO 2014087894 A1 WO2014087894 A1 WO 2014087894A1
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nitrogen
carbon
catalyst
doped
fuel cell
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PCT/JP2013/081880
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French (fr)
Japanese (ja)
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森　利之
シドゥル ナイドゥ タラパネニ
慶介 府金
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独立行政法人物質・材料研究機構
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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
    • H01M4/9008—Organic or organo-metallic compounds
    • 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
    • H01M2004/8678—Inert electrodes with catalytic activity, e.g. for fuel cells characterised by the polarity
    • H01M2004/8689—Positive electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/10—Fuel cells with solid electrolytes
    • H01M2008/1095—Fuel cells with polymeric electrolytes
    • 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 a non-platinum catalyst used for a cathode of a fuel cell such as a proton exchange membrane (PEM) fuel cell, and more particularly to a non-platinum catalyst using mesoporous carbon doped with nitrogen.
  • a fuel cell such as a proton exchange membrane (PEM) fuel cell
  • PEM proton exchange membrane
  • platinum is used as a catalyst for an electrode of a fuel cell.
  • platinum is not only expensive, but it is a scarce resource and is frequently used as a catalyst in other fields. Therefore, continuing to use platinum as a catalyst may be an obstacle to the spread of fuel cells. Therefore, materials that can replace platinum in the cathode catalyst for fuel cells are being studied.
  • Non-patent Document 1 It has been proposed to use graphene doped with nitrogen as an alternative material for platinum used as an electrode catalyst in fuel cells (Non-patent Document 1).
  • this catalyst contains iron to enhance the activity of graphene. Therefore, when used as a catalyst for a cathode of a fuel cell, a Fenton reagent is formed by hydrogen peroxide generated by oxygen reduction reaction and this iron. Is done. Since the Fenton reagent functions as an oxidizing agent, Nafion (registered trademark) used as a proton exchange membrane and the catalyst itself are oxidized by this.
  • Non-Patent Document 1 when the graphene doped with nitrogen proposed in Non-Patent Document 1 is used as a catalyst for a fuel cell, there is a risk of causing a problem in terms of durability of the fuel cell.
  • Non-Patent Document 2 describes that the ORR (oxygen reduction reaction) activity can be improved by doping carbon nanotubes with nitrogen. However, this improvement in ORR is still insufficient for use as a catalyst for a cathode of a fuel cell.
  • An object of the present invention is to provide a non-platinum catalyst for a cathode of a fuel cell that does not use expensive and rare platinum.
  • the present invention provides a catalyst for a cathode of a fuel cell using nitrogen-doped mesoporous carbon, which does not impair the durability of the fuel cell by not using iron and exhibits high performance. Is an issue.
  • Another object of the present invention is to provide a fuel cell in which the cathode is a nitrogen-doped mesoporous carbon catalyst.
  • the present invention has the following configuration.
  • a method for producing nitrogen-doped mesoporous carbon as a catalyst for a fuel cell cathode comprising impregnating mesoporous silica with a carbon compound and then heating in a nitrogen stream, thereby combining nitrogen-doped carbon and mesoporous silica.
  • a method for producing the nitrogen-doped mesoporous carbon by forming a body and removing the silica component in the composite.
  • the production method according to (1), wherein the carbon compound further contains nitrogen.
  • a catalyst for a cathode of a fuel cell comprising nitrogen-doped mesoporous carbon.
  • a catalyst for a cathode of a fuel cell comprising a nitrogen-doped mesoporous carbon produced by the method according to (1) or (2).
  • the ratio of the peak area I G of the carbon peak area I D and crystalline structure of the carbon in the amorphous structure of the nitrogen-doped mesoporous carbon catalyst (I D / I G) is The catalyst for a cathode of a fuel cell according to any one of (3) to (5), which is less than 1.1.
  • a fuel cell comprising the cathode catalyst according to any one of (3) to (6).
  • a mesoporous silica is impregnated with a carbon compound and then heated in a nitrogen stream to form a composite of nitrogen-doped carbon and mesoporous silica, and the silica component in the composite
  • a method for producing a catalyst for a cathode of a fuel cell wherein the catalyst for a cathode of a fuel cell is made of nitrogen-doped mesoporous carbon, whereby nitrogen-doped mesoporous carbon is obtained by removing.
  • a method for producing nitrogen-doped mesoporous carbon used as a catalyst for a cathode of a fuel cell is provided.
  • the nitrogen-doped mesoporous carbon is formed by impregnating mesoporous silica with a carbon compound and then heating in a nitrogen flow to form a complex of nitrogen-doped carbon and mesoporous silica, and the silica component in the complex Is obtained by removing.
  • nitrogen-doped mesoporous carbon used in the present application means that it contains no substances other than nitrogen-doped mesoporous carbon based on the detection limit, and excludes impurities below the detection limit. It is not a thing.
  • a fuel cell cathode catalyst in which the fuel cell cathode catalyst comprises nitrogen-doped mesoporous carbon.
  • a fuel cell cathode catalyst comprising a nitrogen-doped mesoporous carbon produced by the above method.
  • the nitrogen-doped mesoporous carbon produced by the above-described method for producing nitrogen-doped mesoporous carbon used as a catalyst for a fuel cell cathode is used as a catalyst for a cathode of a fuel cell.
  • a fuel cell is provided in which the cathode is a nitrogen-doped mesoporous carbon catalyst.
  • the mesoporous silica refers to those having fine pores having a pore diameter of 1.5 to 50 nm and a pore volume of 1 cm 3 / g or less.
  • the mesoporous silica used in the present invention is used as, for example, a template of mesoporous carbon nitride called by the name of hard template method. Due to its pore diameter and pore volume, commercially available Santa Barbara amorphous (SBA) -15 Or mesoporous silica such as Korean Institute (KIT) -6 is used as the hard template.
  • the “template” means a mold for using a similar porous structure, that is, a “template”.
  • Examples of the carbon compound impregnated into the mesoporous silica include ethylenediamine, EDTA (ethylenediaminetetraacetic acid), gelatin, and the like, and ethylenediamine and EDTA are preferred for the reason that residual coke hardly occurs after thermal decomposition. Further, as the carbon compound impregnated in the mesoporous silica, those obtained by mixing carbon tetrachloride with these carbon compounds are more preferable from the viewpoint of improving the production rate of carbon nitride. Thus, as the carbon compound impregnated in the mesoporous silica, a nitrogen-containing carbon compound such as ethylenediamine or EDTA may be used.
  • the description “the carbon compound further contains nitrogen” refers to a nitrogen-containing carbon compound such as ethylenediamine or EDTA.
  • a nitrogen-containing carbon compound such as ethylenediamine or EDTA.
  • an adsorbent is used. It is necessary that charge transfer smoothly proceeds between certain oxygen and the electrode surface, and a process (reduction process) in which electrons are given from the electrode surface to oxygen as an adsorbing material needs to proceed smoothly. This charge transfer depends on the crystallinity of the catalyst.
  • the nitrogen-doped mesoporous carbon catalyst for a fuel cell cathode of the present invention needs to have good crystallinity in terms of smooth charge transfer between oxygen as an adsorbent and the electrode surface. . That is, in the nitrogen-doped mesoporous carbon catalyst for the fuel cell cathode of the present invention, it is necessary that the carbon having a crystalline structure exists so as to facilitate the charge transfer.
  • the ratio of the amorphous structure carbon to the crystalline structure carbon in the nitrogen-doped mesoporous carbon catalyst for the fuel cell cathode of the present invention is determined by Raman spectroscopy, the amorphous structure carbon is shown.
  • the ratio of the peak area I G indicating the carbon crystalline structure and the peak area I D (I D / I G ) is preferably less than 1.1.
  • the nitrogen doping amount in the nitrogen-doped mesoporous carbon catalyst for the fuel cell cathode of the present invention may be an amount that can achieve the object of the present invention, but it is 6% or more with respect to the total weight of the nitrogen-doped mesoporous carbon catalyst. Particularly preferred.
  • the nitrogen doping amount is 6% or more with respect to the total weight of the nitrogen-doped mesoporous carbon catalyst, the physical properties of the catalyst are not close to those of ordinary carbon, and it is easy to confirm the physical properties specific to carbon nitride. is there.
  • the nitrogen doping amount is usually used within a range not exceeding the stoichiometric composition in view of the stoichiometric composition being C 3 N 4 .
  • nitrogen-doped mesoporous carbon used as a cathode catalyst for fuel cells has a large proportion of crystalline carbon doped with nitrogen, and it is necessary to have many active sites for the purpose of increasing the slow oxygen reduction reaction rate. Therefore, it is preferable to have a mesopore structure.
  • a non-platinum catalyst for a cathode of a fuel cell that has high redox reaction activity and does not generate a Fenton reagent that adversely affects the durability of the proton exchange membrane or the catalyst was obtained.
  • mesoporous silica as a template is produced.
  • This mesoporous silica is produced by, for example, the method described in Examples of the present application, which is usually called the hard template method. However, it is not limited to such a specific manufacturing method. Moreover, you may use what is marketed as mesoporous silica used as a template. Examples of frequently used mesoporous silica include Santa Barbara Amorphous (SBA) -15 and Korean Institute (KIT) -6, but are not limited thereto. The characteristic values of these two types of mesoporous silica are shown in the table below.
  • mesoporous silica can be used as long as it has characteristic values close to various values shown in Table 1. Also, a value considerably different from this can be used as long as the object of the present invention can be achieved.
  • This mesoporous silica mesopore is impregnated with a mixture of ethylenediamine and carbon tetrachloride, a mixture of EDTA (ethylenediaminetetraacetic acid) and carbon tetrachloride, gelatin, or the like as a carbon source, and then this is mixed in a nitrogen stream. Bake.
  • the temperature is preferably less than 1200 ° C.
  • a preferred calcination temperature range is about 600 ° C to 1100 ° C.
  • the calcination time can be set to 5 hours, for example, but may be shorter. Although calcination can be performed for longer than 5 hours, it is preferably 10 hours or less from the viewpoint of improving the performance.
  • the carbon source may further contain nitrogen by mixing ethylenediamine or the like, so that all or part of the finally doped nitrogen is derived from this carbon source. It can also be supplied.
  • a treatment of the carbon source infiltrating the mesoporous silica when the mesoporous silica is impregnated with the carbon source and the subsequent drying treatment in the following examples, a treatment for raising the temperature after reflux or a treatment for raising the temperature in two stages is performed.
  • various other known permeation / drying treatments may be employed.
  • Examples of a method for producing a nitrogen-doped mesoporous carbon catalyst for a fuel cell cathode according to the present invention as well as examples of the nitrogen-doped mesoporous carbon produced thereby and a fuel cell cathode of the nitrogen-doped mesoporous carbon shown in each of the examples
  • the present invention is not limited to the measurement results regarding the catalyst characteristics.
  • the four types of nitrogen-doped mesoporous materials produced in the following examples are “20% N-MC”, “10% N-MC”, “10% N-MC-800”, and “10% N-MC”, respectively. -1000 ".
  • the notation “10%” or “20%” indicates the nitrogen content
  • the notation “MC” means mesoporous carbon
  • the notation “800” or “1000” The firing temperature is indicated.
  • the amphiphilic triblock copolymer P123 (4 g) was dispersed in a mixed solution of Millipore water (30 g) and HCl solution (12 g, 2M) and stirred for 5 hours. Thereafter, tetraethylorthosilicate (TEOS) (9 g) was added while stirring the uniform solution. The resulting gel was stirred at 40 ° C. for 24 hours and then heated at 150 ° C. for 48 hours. The gel-like material was washed with water several times to obtain a white silica block copolymer composite. After this synthesis, the resulting solid was calcined at 540 ° C. with flowing air to decompose the triblock copolymer. In this way, 2D hexagonal mesoporous silica SBA-15-150 was obtained.
  • TEOS tetraethylorthosilicate
  • the composite of carbon obtained by using silica as a template and having a nitrogen component added thereto (ie, SBA-15-150 encapsulated with a nitrogen-doped carbon (carbon nitride) polymer) was then added to 100 mL. Heat treatment at 600 ° C. in a nitrogen flow per minute. At this time, the temperature rising rate was 3 ° C./min. In order to carbonize, it processed under these conditions for 5 hours. As a result, a composite of mesoporous silica and nitrogen-doped carbon was obtained.
  • This reaction process that is, a process of first forming a carbon compound added with a nitrogen component on a silica template and heating it in a nitrogen stream to obtain nitrogen-doped carbon (carbon nitride) is shown in FIG. It is shown as part of the process of making mesoporous carbon. Note that when the remaining three types of nitrogen-doped mesoporous carbon shown below are produced, nitrogen is not added before heating in a nitrogen stream. Therefore, when producing the remaining three types of nitrogen-doped mesoporous carbon shown below, in the process of mixing calcined mesoporous silica (SBA-15-150) with a carbon compound for the first time, the carbon compound includes ethylenediamine and the like.
  • the temperature rising rate was 3 ° C./min.
  • the silica and the silica in the nitrogen-doped carbon composite were etched with 5 w% hydrofluoric acid.
  • the nitrogen-doped carbon sample was washed several times with ethanol and dried at 100 ° C. overnight to obtain black 10% nitrogen-doped mesoporous carbon 10% N-MC-800.
  • the temperature rising rate was 3 ° C./min.
  • the silica and the silica in the nitrogen-doped carbon composite were etched with 5 w% hydrofluoric acid.
  • the nitrogen-doped carbon sample was washed several times with ethanol and dried at 100 ° C. overnight to obtain black 10% nitrogen-doped mesoporous carbon 10% N-MC-1000.
  • oxygen reduction reaction (ORR) activity and cyclic voltammetry were measured.
  • the conditions are as follows: Electrolyte solution: 0.1M KOH aqueous solution Working electrode: Glassy carbon electrode (GCE) Sweep speed: 50 mV / sec (cyclic voltammetry measurement) 10 mV / sec (ORR activity measurement) (0.2 to -1.4V running, vs. Ag / AgCl))
  • the procedure for measuring ORR activity is to separately measure the electrode performance by the rotating electrode method using nitrogen saturated KOH and oxygen saturated KOH, (ORR measured value in oxygen saturated KOH)-(ORR measurement in nitrogen saturated KOH) Value) was calculated to evaluate the ORR activity (ORR activity (O 2 -N 2 )).
  • ORR activity ORR activity (O 2 -N 2 )
  • the measurement result when the electrode is not rotated is indicated as “No Rotation” in the figure.
  • ORR measurement results of nitrogen-doped mesoporous carbon 20% N-MC, 10% N-MC, 10% N-MC-800, and 10% N-MC-1000 in oxygen saturated and nitrogen saturated KOH are shown in FIG. It is shown in FIG. 3, FIG. 5, and FIG.
  • the results of cyclic voltammetry measurement and the calculated ORR activity (O 2 —N 2 ) for these four types of nitrogen-doped mesoporous carbon are shown in FIG. 2, FIG. 4, FIG. 6, and FIG.
  • FIG. 9 shows the result of comparison of ORR activity when the electrode rotation speed is 900 rpm for the four types of nitrogen-doped mesoporous carbon produced and the commercially available Pt / C catalyst (HiSPEC 3000) to be compared.
  • all of the produced nitrogen-doped mesoporous carbons exhibit a very high ORR activity, although lower than the Pt / C catalyst.
  • 10% N-MC-800 and 10% N— treated at a higher temperature than that.
  • MC-1000 shows higher activity.
  • the heat treatment in a nitrogen flow is preferably 600 ° C. to 1100 ° C.
  • the potential at which activity starts to occur is ⁇ 0.15 V vs. Ag / AgCl, which is reported in Non-Patent Document 1, ⁇ 0.18 V vs. It was found that the potential was lower than the value Ag / AgCl.
  • the nitrogen-doped mesoporous carbon of the present invention has a performance exceeding that of iron-supported nitrogen-doped graphene (specifically, the iron-supported nitrogen-doped graphene reported in Non-Patent Document 1 exhibits ORR activity at a higher potential. ). Therefore, from FIG. 9, the four types of nitrogen-doped mesoporous carbons produced have higher activity (higher performance) than the iron-supported nitrogen-doped graphene reported in Non-Patent Document 1 as a non-platinum catalyst for cathodes of fuel cells. It was confirmed to have.
  • the potential at which the activity reported in Non-Patent Document 2 begins to occur is also higher than that of the nitrogen-doped mesoporous carbon of the present invention, -0.16 V vs. From the value of Ag / AgCl, it was found that the nitrogen-doped mesoporous carbon of the present invention showed activity from a lower potential than the catalyst reported in Non-Patent Document 2. That is, it has been found that the nitrogen-doped mesoporous carbon of the present invention exhibits performance exceeding that of the catalyst reported in Non-Patent Document 2.
  • FIG. 11 shows Raman spectroscopy for identifying amorphous and crystalline carbon in 10% N-MC, 10% N-MC-800, and 10% N-MC-1000.
  • ratio measurements and the carbon peak area I G crystalline structure and the peak area I D carbon of amorphous structure which is calculated from the measurement result by (I D / I G) is shown.
  • a peak peculiar to graphite crystalline carbon, shown as G in FIG. 11
  • Carbon in the structure (denoted as D in FIG. 11) is observed around 1300 cm ⁇ 1 .
  • Ratio of carbon peak area I G of the crystalline structure of the peak area I D carbon having an amorphous structure indicates that the crystallinity is improved as decreases.
  • 10% N-MC-1000 shows higher ORR activity than 10% N-MC
  • 10% N-MC-800 ° C. than 10% N-MC-1000. It shows high ORR activity.
  • the 10% N-MC I D / I G is 1.12
  • I D / I G of 10% N-MC-1000 is 1.09
  • Since I D / I G at 10% N-MC-800 ° C. is 1.07, it was also confirmed that the improvement in crystallinity contributes to the improvement in ORR activity (ie, higher performance).
  • the carbon and nitrogen contents (% by weight) in 10% N-MC, 10% N-MC-800 ° C., and 10% N-MC-1000 ° C. of this example are as shown in the table below. .
  • This nitrogen analysis was carried out by the usual Kjeldahl method. At the time of analysis, loss of ignition occurs due to evaporation of volatile substances as carbon dioxide. Therefore, the reason why the sum of carbon and nitrogen in the analysis results in the following table is not 100% by weight is due to this volatile substance.
  • a catalyst for a cathode of a fuel cell that has a relatively good ORR activity without using a platinum catalyst, and further has no action of damaging the electrolyte membrane or the catalyst itself. Therefore, it is highly expected to be used in the fuel cell field.

Abstract

The present invention addresses the problem of providing a cathode catalyst for fuel cells which has satisfactory characteristics without requiring the use of platinum. The problem is solved by using nitrogen-doped mesoporous carbon produced, for example, by the hard template method, as a cathode catalyst for proton-exchange membrane fuel cells, etc.

Description

燃料電池カソード用非白金触媒及びその製造方法Non-platinum catalyst for fuel cell cathode and method for producing the same
　本発明はプロトン交換膜（ＰＥＭ）燃料電池などの燃料電池のカソードに使用される非白金触媒に関し、より詳細には窒素をドープしたメソポーラスカーボンを用いた非白金触媒に関する。 The present invention relates to a non-platinum catalyst used for a cathode of a fuel cell such as a proton exchange membrane (PEM) fuel cell, and more particularly to a non-platinum catalyst using mesoporous carbon doped with nitrogen.
　燃料電池の電極用触媒としては従来から白金が利用されている。しかしながら、白金は高価であるだけではなく、希少な資源である上に他の分野でも触媒として多用されるため、触媒として白金を使用し続けることは燃料電池の普及にとって障害となりかねない。
　そこで、燃料電池のカソード用触媒においても白金に代わる材料が検討されている。 Conventionally, platinum is used as a catalyst for an electrode of a fuel cell. However, platinum is not only expensive, but it is a scarce resource and is frequently used as a catalyst in other fields. Therefore, continuing to use platinum as a catalyst may be an obstacle to the spread of fuel cells.
Therefore, materials that can replace platinum in the cathode catalyst for fuel cells are being studied.
　燃料電池における電極触媒として利用されている白金の代替材料として窒素をドープしたグラフェンを使用することが提案されている（非特許文献１）。しかし、この触媒は、グラフェンの活性を高めるために鉄を含んでおり、そのため、燃料電池のカソード用触媒として利用すると、酸素の還元反応で生成される過酸化水素とこの鉄によりフェントン試薬が形成される。フェントン試薬は酸化剤として機能するため、これによりプロトン交換膜として使用されるナフィオン（登録商標）や触媒自身が酸化される。従って、非特許文献１で提案されている窒素をドープしたグラフェンは燃料電池の触媒として使用した場合、燃料電池の耐久性の面で問題を引き起こす恐れがあった。
　また、非特許文献２にはカーボンナノチューブに窒素をドープすることでＯＲＲ（酸素還元反応）活性を改善できたことが記載されている。しかし、燃料電池のカソード用触媒として利用するには、このＯＲＲの改善は未だ不十分なものであった。 It has been proposed to use graphene doped with nitrogen as an alternative material for platinum used as an electrode catalyst in fuel cells (Non-patent Document 1). However, this catalyst contains iron to enhance the activity of graphene. Therefore, when used as a catalyst for a cathode of a fuel cell, a Fenton reagent is formed by hydrogen peroxide generated by oxygen reduction reaction and this iron. Is done. Since the Fenton reagent functions as an oxidizing agent, Nafion (registered trademark) used as a proton exchange membrane and the catalyst itself are oxidized by this. Therefore, when the graphene doped with nitrogen proposed in Non-Patent Document 1 is used as a catalyst for a fuel cell, there is a risk of causing a problem in terms of durability of the fuel cell.
Non-Patent Document 2 describes that the ORR (oxygen reduction reaction) activity can be improved by doping carbon nanotubes with nitrogen. However, this improvement in ORR is still insufficient for use as a catalyst for a cathode of a fuel cell.
　本発明は、高価で希少な白金を使用しない燃料電池のカソード用非白金触媒を提供することを課題とする。具体的には、本発明は、鉄を使用しないことにより燃料電池の耐久性を損なうことがなく、また高い性能を発揮する、窒素ドープメソポーラスカーボンを使用した燃料電池のカソード用触媒を提供することを課題とする。
　また、本発明は、カソードが窒素ドープメソポーラスカーボン触媒である燃料電池を提供することを課題とする。 An object of the present invention is to provide a non-platinum catalyst for a cathode of a fuel cell that does not use expensive and rare platinum. Specifically, the present invention provides a catalyst for a cathode of a fuel cell using nitrogen-doped mesoporous carbon, which does not impair the durability of the fuel cell by not using iron and exhibits high performance. Is an issue.
Another object of the present invention is to provide a fuel cell in which the cathode is a nitrogen-doped mesoporous carbon catalyst.
　本発明は、以下の構成を有する。
（１）　燃料電池カソード用触媒の窒素ドープメソポーラスカーボンを製造する方法であって、メソポーラスシリカに炭素化合物を含浸させた後、窒素流中で加熱することにより、窒素ドープカーボンとメソポーラスシリカとの複合体を形成し、前記複合体中のシリカ成分を除去することにより前記窒素ドープメソポーラスカーボンを製造する方法。
（２）　前記炭素化合物は更に窒素を含む、（１）に記載の製造方法。
（３）　窒素ドープメソポーラスカーボンからなる、燃料電池のカソード用触媒。
（４）　（１）または（２）に記載の方法で製造された窒素ドープメソポーラスカーボンからなる、燃料電池のカソード用触媒。
（５）　窒素ドープ量が窒素ドープメソポーラスカーボン触媒の全重量に対して６％以上である、（３）または（４）に記載の燃料電池のカソード用触媒。
（６）　ラマン分光法によって決定される、窒素ドープメソポーラスカーボン触媒中の非晶質構造の炭素のピーク面積ＩＤと結晶質構造の炭素のピーク面積ＩＧの割合（ＩＤ／ＩＧ）が１．１未満である、（３）乃至（５）のいずれか１つに記載の燃料電池のカソード用触媒。
（７）　（３）乃至（６）のいずれか１つに記載のカソード用触媒を含む、燃料電池。 The present invention has the following configuration.
(1) A method for producing nitrogen-doped mesoporous carbon as a catalyst for a fuel cell cathode, comprising impregnating mesoporous silica with a carbon compound and then heating in a nitrogen stream, thereby combining nitrogen-doped carbon and mesoporous silica. A method for producing the nitrogen-doped mesoporous carbon by forming a body and removing the silica component in the composite.
(2) The production method according to (1), wherein the carbon compound further contains nitrogen.
(3) A catalyst for a cathode of a fuel cell, comprising nitrogen-doped mesoporous carbon.
(4) A catalyst for a cathode of a fuel cell, comprising a nitrogen-doped mesoporous carbon produced by the method according to (1) or (2).
(5) The catalyst for a cathode of a fuel cell according to (3) or (4), wherein the nitrogen doping amount is 6% or more with respect to the total weight of the nitrogen-doped mesoporous carbon catalyst.
(6) as determined by Raman spectroscopy, the ratio of the peak area I G of the carbon peak area I D and crystalline structure of the carbon in the amorphous structure of the nitrogen-doped mesoporous carbon catalyst (I D / I G) is The catalyst for a cathode of a fuel cell according to any one of (3) to (5), which is less than 1.1.
(7) A fuel cell comprising the cathode catalyst according to any one of (3) to (6).
　本発明の一側面によれば、メソポーラスシリカに炭素化合物を含浸させた後、窒素流中で加熱することにより、窒素ドープカーボンとメソポーラスシリカとの複合体を形成し、前記複合体中のシリカ成分を除去することにより窒素ドープメソポーラスカーボンを得る、燃料電池のカソード用触媒が窒素ドープメソポーラスカーボンからなる燃料電池のカソード用触媒の製造方法が与えられる。つまり、本発明の一側面によれば、燃料電池のカソード用触媒として使用される窒素ドープメソポーラスカーボンの製造方法が与えられる。そして、この窒素ドープメソポーラスカーボンは、メソポーラスシリカに炭素化合物を含浸させた後、窒素流中で加熱することにより、窒素ドープカーボンとメソポーラスシリカとの複合体を形成し、前記複合体中のシリカ成分を除去することにより得る。
　なお、本願において使用されている「窒素ドープメソポーラスカーボンからなる」という用語は、検出限界を基準として窒素ドープメソポーラスカーボン以外のものを含まないという意味であり、検出限界以下の不純物の混入を排除するものではない。
　本発明の他の側面によれば、燃料電池のカソード用触媒が窒素ドープメソポーラスカーボンからなる燃料電池のカソード用触媒が与えられる。
　本発明の更に他の側面によれば、燃料電池のカソード用触媒が前記方法で製造された窒素ドープメソポーラスカーボンからなる燃料電池のカソード用触媒が与えられる。つまり、本発明の他の側面によれば、前記の、燃料電池カソード用触媒として使用される窒素ドープメソポーラスカーボンの製造方法によって製造された窒素ドープメソポーラスカーボンが燃料電池のカソード用触媒として使用される。
　本発明の他の側面によれば、カソードが窒素ドープメソポーラスカーボン触媒である燃料電池が与えられる。
　ここで、メソポーラスシリカとは、細孔直径が１．５～５０ｎｍの微細な細孔を有し、細孔容積が１ｃｍ３／ｇ以下のものを指す。その中で、吸着特性を向上させる目的に鑑みて、大きな細孔径及び細孔容積を有するものが好ましい。本発明で用いられるメソポーラスシリカは、例えば、ハードテンプレート法という名称で呼ばれるメソポーラス窒化炭素のテンプレートとして用いられるが、その細孔径や細孔容積の大きさから、市販のサンタバーバラアモルファス（ＳＢＡ）－１５やコリアンインスティチート（ＫＩＴ）－６等のメソポーラスシリカが、ハードテンプレートとして用いられる。因みに、「テンプレート」とは、同じような多孔質構造を用いるための型、即ち「鋳型」という意味である。
　また、メソポーラスシリカに含浸させる炭素化合物としては、エチレンジアミン、ＥＤＴＡ（エチレンジアミンテトラ酢酸）、ゼラチン等があり、熱分解後に残留コークが生じにくい等の理由からエチレンジアミン、ＥＤＴＡが好ましい。また、メソポーラスシリカに含浸させる炭素化合物としては、窒化炭素の生成率を向上させる観点から、これらの炭素化合物に四塩化炭素を混合したものがより好ましい。このように、メソポーラスシリカに含浸させる炭素化合物としては、エチレンジアミンやＥＤＴＡのような窒素含有炭素化合物を使用してもよい。したがって、本願における「前記炭素化合物は更に窒素を含む、」という記載は、エチレンジアミンやＥＤＴＡのような窒素含有炭素化合物を指す。
　また、本発明においては、非白金系の窒素ドープメソポーラスカーボン触媒を燃料電池のカソード用電極とするので、ＯＲＲ（酸素還元反応）活性を向上させて高性能化を図るためには、吸着物質である酸素と電極表面上との間で電荷移動が円滑に進行し、吸着物質である酸素に対して電極表面から電子が与える過程（還元過程）が円滑に進行する必要がある。この電荷移動は、触媒の結晶性に依存し、非晶質構造の寄与が大き過ぎると電荷移動が阻害されてしまうが、結晶質構造からの寄与が大きくなるにつれて促進される。そこで、本発明の燃料電池カソード用の窒素ドープメソポーラスカーボン触媒は、吸着物質である酸素と電極表面上との間での円滑な電荷移動という点で、良好な結晶性が備わっている必要がある。つまり、本発明の燃料電池カソード用の窒素ドープメソポーラスカーボン触媒においては、電荷移動を円滑に促進できる程度に結晶質構造の炭素が存在している必要がある。具体的には、本発明の燃料電池カソード用の窒素ドープメソポーラスカーボン触媒における非晶質構造の炭素と結晶質構造の炭素の割合をラマン分光法で決定した場合、非晶質構造の炭素を示すピーク面積ＩＤと結晶質構造の炭素を示すピーク面積ＩＧの割合（ＩＤ／ＩＧ）は１．１未満となるのが好ましい。
　また、本発明の燃料電池カソード用の窒素ドープメソポーラスカーボン触媒における窒素ドープ量は、本発明の目的を達成できる量であればよいが、窒素ドープメソポーラスカーボン触媒の全重量に対して６％以上が特に好ましい。窒素ドープ量が窒素ドープメソポーラスカーボン触媒の全重量に対して６％以上になると、その触媒物性が、通常のカーボンの物性に近い物性ではなくなり、窒化炭素特有の物性の確認が容易になるからである。また、窒素ドープ量は通常、化学両論組成がＣ３Ｎ４であることに鑑みて、この化学両論組成を超えない範囲内で用いる。
　本発明において、燃料電池用カソード触媒として使用される窒素ドープメソポーラスカーボンは、窒素をドープした結晶質カーボンの割合が多く、遅い酸素還元反応速度を高める目的で、その活性サイトを多く持つことが必要であることから、メソポア構造を持つことが好ましい。 According to one aspect of the present invention, a mesoporous silica is impregnated with a carbon compound and then heated in a nitrogen stream to form a composite of nitrogen-doped carbon and mesoporous silica, and the silica component in the composite There is provided a method for producing a catalyst for a cathode of a fuel cell, wherein the catalyst for a cathode of a fuel cell is made of nitrogen-doped mesoporous carbon, whereby nitrogen-doped mesoporous carbon is obtained by removing. That is, according to one aspect of the present invention, a method for producing nitrogen-doped mesoporous carbon used as a catalyst for a cathode of a fuel cell is provided. The nitrogen-doped mesoporous carbon is formed by impregnating mesoporous silica with a carbon compound and then heating in a nitrogen flow to form a complex of nitrogen-doped carbon and mesoporous silica, and the silica component in the complex Is obtained by removing.
The term “consisting of nitrogen-doped mesoporous carbon” used in the present application means that it contains no substances other than nitrogen-doped mesoporous carbon based on the detection limit, and excludes impurities below the detection limit. It is not a thing.
According to another aspect of the present invention, there is provided a fuel cell cathode catalyst in which the fuel cell cathode catalyst comprises nitrogen-doped mesoporous carbon.
According to still another aspect of the present invention, there is provided a fuel cell cathode catalyst comprising a nitrogen-doped mesoporous carbon produced by the above method. That is, according to another aspect of the present invention, the nitrogen-doped mesoporous carbon produced by the above-described method for producing nitrogen-doped mesoporous carbon used as a catalyst for a fuel cell cathode is used as a catalyst for a cathode of a fuel cell. .
According to another aspect of the invention, a fuel cell is provided in which the cathode is a nitrogen-doped mesoporous carbon catalyst.
Here, the mesoporous silica refers to those having fine pores having a pore diameter of 1.5 to 50 nm and a pore volume of 1 cm 3 / g or less. Among them, those having large pore diameters and pore volumes are preferable in view of the purpose of improving adsorption characteristics. The mesoporous silica used in the present invention is used as, for example, a template of mesoporous carbon nitride called by the name of hard template method. Due to its pore diameter and pore volume, commercially available Santa Barbara amorphous (SBA) -15 Or mesoporous silica such as Korean Institute (KIT) -6 is used as the hard template. Incidentally, the “template” means a mold for using a similar porous structure, that is, a “template”.
Examples of the carbon compound impregnated into the mesoporous silica include ethylenediamine, EDTA (ethylenediaminetetraacetic acid), gelatin, and the like, and ethylenediamine and EDTA are preferred for the reason that residual coke hardly occurs after thermal decomposition. Further, as the carbon compound impregnated in the mesoporous silica, those obtained by mixing carbon tetrachloride with these carbon compounds are more preferable from the viewpoint of improving the production rate of carbon nitride. Thus, as the carbon compound impregnated in the mesoporous silica, a nitrogen-containing carbon compound such as ethylenediamine or EDTA may be used. Therefore, in the present application, the description “the carbon compound further contains nitrogen” refers to a nitrogen-containing carbon compound such as ethylenediamine or EDTA.
In the present invention, since a non-platinum-based nitrogen-doped mesoporous carbon catalyst is used as a cathode electrode for a fuel cell, in order to improve the ORR (oxygen reduction reaction) activity and achieve high performance, an adsorbent is used. It is necessary that charge transfer smoothly proceeds between certain oxygen and the electrode surface, and a process (reduction process) in which electrons are given from the electrode surface to oxygen as an adsorbing material needs to proceed smoothly. This charge transfer depends on the crystallinity of the catalyst. If the contribution of the amorphous structure is too great, the charge transfer is inhibited, but is promoted as the contribution from the crystalline structure increases. Therefore, the nitrogen-doped mesoporous carbon catalyst for a fuel cell cathode of the present invention needs to have good crystallinity in terms of smooth charge transfer between oxygen as an adsorbent and the electrode surface. . That is, in the nitrogen-doped mesoporous carbon catalyst for the fuel cell cathode of the present invention, it is necessary that the carbon having a crystalline structure exists so as to facilitate the charge transfer. Specifically, when the ratio of the amorphous structure carbon to the crystalline structure carbon in the nitrogen-doped mesoporous carbon catalyst for the fuel cell cathode of the present invention is determined by Raman spectroscopy, the amorphous structure carbon is shown. the ratio of the peak area I G indicating the carbon crystalline structure and the peak area I D (I D / I G ) is preferably less than 1.1.
Further, the nitrogen doping amount in the nitrogen-doped mesoporous carbon catalyst for the fuel cell cathode of the present invention may be an amount that can achieve the object of the present invention, but it is 6% or more with respect to the total weight of the nitrogen-doped mesoporous carbon catalyst. Particularly preferred. When the nitrogen doping amount is 6% or more with respect to the total weight of the nitrogen-doped mesoporous carbon catalyst, the physical properties of the catalyst are not close to those of ordinary carbon, and it is easy to confirm the physical properties specific to carbon nitride. is there. The nitrogen doping amount is usually used within a range not exceeding the stoichiometric composition in view of the stoichiometric composition being C 3 N 4 .
In the present invention, nitrogen-doped mesoporous carbon used as a cathode catalyst for fuel cells has a large proportion of crystalline carbon doped with nitrogen, and it is necessary to have many active sites for the purpose of increasing the slow oxygen reduction reaction rate. Therefore, it is preferable to have a mesopore structure.
　本発明により、高い酸化還元反応活性を有するとともに、プロトン交換膜や触媒の耐久性に悪影響を及ぼすフェントン試薬を生成することのない燃料電池のカソード用非白金触媒が得られた。 According to the present invention, a non-platinum catalyst for a cathode of a fuel cell that has high redox reaction activity and does not generate a Fenton reagent that adversely affects the durability of the proton exchange membrane or the catalyst was obtained.
２０％窒素ドープメソポーラスカーボン（２０％Ｎ－ＭＣ）についての窒素飽和及び酸素飽和ＫＯＨ中でのＯＲＲ活性を示す図。The figure which shows ORR activity in nitrogen saturation and oxygen saturation KOH about 20% nitrogen dope mesoporous carbon (20% N-MC). ２０％Ｎ－ＭＣについてのサイクリックボルタンメトリー及びＯＲＲ活性を示す図。The figure which shows cyclic voltammetry and ORR activity about 20% N-MC. １０％窒素ドープメソポーラスカーボン（１０％Ｎ－ＭＣ）についての窒素飽和及び酸素飽和ＫＯＨ中でのＯＲＲ活性を示す図。The figure which shows ORR activity in nitrogen saturation and oxygen saturation KOH about 10% nitrogen dope mesoporous carbon (10% N-MC). １０％Ｎ－ＭＣについてのサイクリックボルタンメトリー及びＯＲＲ活性を示す図。The figure which shows the cyclic voltammetry and ORR activity about 10% N-MC. ８００℃で黒鉛化した１０％窒素ドープメソポーラスカーボン（１０％Ｎ－ＭＣ－８００℃）についての窒素飽和及び酸素飽和ＫＯＨ中でのＯＲＲ活性を示す図。The figure which shows ORR activity in nitrogen saturation and oxygen saturation KOH about 10% nitrogen dope mesoporous carbon graphitized at 800 degreeC (10% N-MC-800 degreeC). １０％Ｎ－ＭＣ－８００℃についてのサイクリックボルタンメトリー及びＯＲＲ活性を示す図。The figure which shows the cyclic voltammetry and ORR activity about 10% N-MC-800 degreeC. １０００℃で黒鉛化した１０％窒素ドープメソポーラスカーボン（１０％Ｎ－ＭＣ－１０００℃）についての窒素飽和及び酸素飽和ＫＯＨ中でのＯＲＲ活性を示す図。The figure which shows the ORR activity in nitrogen saturation and oxygen saturation KOH about 10% nitrogen dope mesoporous carbon (10% N-MC-1000 ° C) graphitized at 1000 ° C. １０％Ｎ－ＭＣ－１０００℃についてのサイクリックボルタンメトリー及びＯＲＲ活性を示す図。The figure which shows cyclic voltammetry and ORR activity about 10% N-MC-1000 degreeC. 実施例で作成した４種類の窒素ドープメソポーラスカーボンと市販のＰｔ／Ｃ触媒（ＨｉＳｐｅｃ３０００）のＯＲＲ活性を比較する図。The figure which compares ORR activity of four types of nitrogen dope mesoporous carbon created in the Example, and a commercially available Pt / C catalyst (HiSpec3000). 窒素ドープメソポーラスカーボンを作製する過程の一例を示す図。The figure which shows an example of the process which produces nitrogen dope mesoporous carbon. １０％Ｎ－ＭＣと、１０％Ｎ－ＭＣ－８００℃と、１０％Ｎ－ＭＣ－１０００℃中の非晶質構造の炭素と結晶質構造の炭素を同定するためのラマン分光法による測定結果並びにその非晶質構造の炭素のピーク面積ＩＤと結晶質構造の炭素ピーク面積ＩＧの割合（ＩＤ／ＩＧ）を示す図。Measurement results by Raman spectroscopy to identify amorphous carbon and crystalline carbon in 10% N-MC, 10% N-MC-800 ° C. and 10% N-MC-1000 ° C. and it shows a ratio (I D / I G) of the non-peak area of carbon crystalloid structure I D with the carbon peak area I G crystalline structure.
　本発明の、燃料電池のカソード用触媒が窒素ドープメソポーラスカーボンからなる燃料電池のカソード用触媒を製造するに当たっては、先ずテンプレートとなるメソポーラスシリカを製造する。このメソポーラスシリカは例えば、通常、ハードテンプレート法という名前で呼ばれているところの、本願実施例に記載されている方法で製造される。しかしながら、このような特定の製造方法に限定されるものではない。また、テンプレートとして使用するメソポーラスシリカとして、市販されているものを使用してもよい。よく使用されるメソポーラスシリカとしては、例えばサンタバーバラアモルファス（ＳＢＡ）－１５やコリアンインスティチート（ＫＩＴ）－６等があるが、これらに限定されるものではない。これら２種類のメソポーラスシリカの特性値を下表に示す。 In producing a fuel cell cathode catalyst in which the fuel cell cathode catalyst of the present invention is made of nitrogen-doped mesoporous carbon, first, mesoporous silica as a template is produced. This mesoporous silica is produced by, for example, the method described in Examples of the present application, which is usually called the hard template method. However, it is not limited to such a specific manufacturing method. Moreover, you may use what is marketed as mesoporous silica used as a template. Examples of frequently used mesoporous silica include Santa Barbara Amorphous (SBA) -15 and Korean Institute (KIT) -6, but are not limited thereto. The characteristic values of these two types of mesoporous silica are shown in the table below.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　他のメソポーラスシリカであっても、表１に示す各種の値に近い特性値を持つものであれば使用可能であると考えられる。また、これとはかなり違った値のものでも、本発明の目的を達成できるものであれば使用可能である。 It is considered that other mesoporous silica can be used as long as it has characteristic values close to various values shown in Table 1. Also, a value considerably different from this can be used as long as the object of the present invention can be achieved.
　このメソポーラスシリカのメソポア内に、炭素源として、エチレンジアミンと四塩化炭素の混合物や、ＥＤＴＡ（エチレンジアミンテトラ酢酸）と四塩化炭素の混合物や、ゼラチンなどを含浸させてから、これを窒素気流中でか焼する。か焼温度が高い方が良好な酸素還元活性が得られる。しかしながら、メソポーラスカーボンからの窒素の離脱を考慮すると、１２００℃未満が好ましい。好ましいか焼温度範囲は６００℃～１１００℃程度である。
　また、か焼時間は例えば５時間とすることができるが、これより短時間であってもよい。５時間よりも長時間か焼することもできるが、性能の向上等の観点から１０時間以下が好ましい。 This mesoporous silica mesopore is impregnated with a mixture of ethylenediamine and carbon tetrachloride, a mixture of EDTA (ethylenediaminetetraacetic acid) and carbon tetrachloride, gelatin, or the like as a carbon source, and then this is mixed in a nitrogen stream. Bake. The higher the calcination temperature, the better the oxygen reduction activity. However, considering the detachment of nitrogen from mesoporous carbon, the temperature is preferably less than 1200 ° C. A preferred calcination temperature range is about 600 ° C to 1100 ° C.
The calcination time can be set to 5 hours, for example, but may be shorter. Although calcination can be performed for longer than 5 hours, it is preferably 10 hours or less from the viewpoint of improving the performance.
　また、上記炭素源には、上に例示されている通り、エチレンジアミン等を混合することによって更に窒素を含んでよく、それにより、最終的にドープされる窒素の全部または一部をこの炭素源から供給することもできる。 In addition, as exemplified above, the carbon source may further contain nitrogen by mixing ethylenediamine or the like, so that all or part of the finally doped nitrogen is derived from this carbon source. It can also be supplied.
　また、メソポーラスシリカに炭素源を含浸させる際のメソポーラスシリカへの炭素源の浸透及びその後の乾燥の処理として、以下の実施例では還流後に昇温する処理、あるいは二段階で昇温するという処理を例示しているが、本願発明の目的を達成できるものであれば、その他の既に公知の多様な浸透・乾燥処理を採用することもできる。 In addition, as a treatment of the carbon source infiltrating the mesoporous silica when the mesoporous silica is impregnated with the carbon source and the subsequent drying treatment, in the following examples, a treatment for raising the temperature after reflux or a treatment for raising the temperature in two stages is performed. Although illustrated, as long as the object of the present invention can be achieved, various other known permeation / drying treatments may be employed.
　このようにして製造された窒素ドープメソポーラスカーボンのＯＲＲ活性などを測定した結果、市販のＨｉＳｐｅｃ３０００のＰｔ／Ｃ触媒よりは低いものの、燃料電池のカソード用非白金触媒としては非常に高い活性（高い性能）を有していることが確認された。
　また、本発明の窒素ドープメソポーラスカーボンは非特許文献１で報告されている鉄担持窒素ドープグラフェンを超える性能（具体的には、より高い電位でＯＲＲ活性が発現する）を示すことも確認された。
　なお、本願発明者が知る限り、鉄などを担持していない窒素ドープメソポーラスカーボンのＯＲＲ活性を評価したという報告はないので、本願は窒素ドープメソポーラスカーボンを燃料電池のカソードとして使用する最初の試みであると考えられる。 As a result of measuring the ORR activity and the like of the nitrogen-doped mesoporous carbon produced in this way, it is very high activity (high performance) as a non-platinum catalyst for a cathode of a fuel cell, although it is lower than the commercially available HiSpec 3000 Pt / C catalyst. ).
Moreover, it was also confirmed that the nitrogen-doped mesoporous carbon of the present invention exhibits performance (specifically, ORR activity is expressed at a higher potential) that exceeds the iron-supported nitrogen-doped graphene reported in Non-Patent Document 1. .
As far as the inventors of the present application know, there is no report that the ORR activity of nitrogen-doped mesoporous carbon not supporting iron or the like has been evaluated, so this application is the first attempt to use nitrogen-doped mesoporous carbon as a fuel cell cathode. It is believed that there is.
　本発明の燃料電池カソード用の窒素ドープメソポーラスカーボン触媒の製造方法の実施例、並びにこれにより製造された窒素ドープメソポーラスカーボンの実施例とその各実施例に示された窒素ドープメソポーラスカーボンの燃料電池カソード用触媒特性に関する測定結果を以下に説明するが、本発明はこれに限定されるものでないことに注意しなければならない。
　なお、以下の実施例で製造した４種類の窒素ドープメソポーラスを各々「２０％Ｎ－ＭＣ」、「１０％Ｎ－ＭＣ」、「１０％Ｎ－ＭＣ－８００」、及び「１０％Ｎ－ＭＣ－１０００」と表記している。ここで、「１０％」または「２０％」という表記は窒素含有量を示し、「ＭＣ」という表記はメソポーラスカーボンであることを意味し、「８００」または「１０００」という表記は、製造上の焼成温度を示す。 Examples of a method for producing a nitrogen-doped mesoporous carbon catalyst for a fuel cell cathode according to the present invention, as well as examples of the nitrogen-doped mesoporous carbon produced thereby and a fuel cell cathode of the nitrogen-doped mesoporous carbon shown in each of the examples However, it should be noted that the present invention is not limited to the measurement results regarding the catalyst characteristics.
The four types of nitrogen-doped mesoporous materials produced in the following examples are “20% N-MC”, “10% N-MC”, “10% N-MC-800”, and “10% N-MC”, respectively. -1000 ". Here, the notation “10%” or “20%” indicates the nitrogen content, the notation “MC” means mesoporous carbon, and the notation “800” or “1000” The firing temperature is indicated.
[２Ｄ六方晶系メソポーラスシリカＳＢＡ－１５－１５０の合成]
　窒素ドープメソポーラスカーボン合成のテンプレートとして使用する２Ｄ六方晶系メソポーラスシリカ（hexagonal mesoporous silica）（ＳＢＡ－１５－１５０）が、両親媒性トリブロックコポリマーＰ１２３、ポリ（エチレングリコール）―ブロック―ポリ（プロピレングリコール）（poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol)）（ＥＯ２０ＰＯ７０ＥＯ２０、平均分子量５８００、Aldrich製）をテンプレートとして使用することによって合成された。この合成は以下に示すようにして行った。 [Synthesis of 2D hexagonal mesoporous silica SBA-15-150]
2D hexagonal mesoporous silica (SBA-15-150) used as a template for nitrogen-doped mesoporous carbon synthesis is amphiphilic triblock copolymer P123, poly (ethylene glycol) -block-poly (propylene glycol) ) (Poly (ethylene glycol) -block-poly (propylene glycol) -block-poly (ethylene glycol)) (EO20PO70EO20, average molecular weight 5800, manufactured by Aldrich) was used as a template. This synthesis was performed as follows.
　両親媒性トリブロックコポリマーＰ１２３（４ｇ）をミリポア水（３０ｇ）とＨＣｌ溶液（１２ｇ、２Ｍ）の混合溶液に分散させて５時間攪拌した。その後、この一様な溶液を攪拌しながらオルトケイ酸テトラエチル（tetraethylorthosilicate、ＴＥＯＳ）（９ｇ）を添加した。その結果得られたゲル状物を４０℃で２４時間攪拌し、次に１５０℃で４８時間加熱した。このゲル状物を数回水洗することにより、白色のシリカブロックコポリマー複合体が得られた。この合成後、得られた個体を、空気を流しながら５４０℃でか焼して、トリブロックコポリマーを分解した。このようにして、２Ｄ六方晶系メソポーラスシリカＳＢＡ－１５－１５０を得た。 The amphiphilic triblock copolymer P123 (4 g) was dispersed in a mixed solution of Millipore water (30 g) and HCl solution (12 g, 2M) and stirred for 5 hours. Thereafter, tetraethylorthosilicate (TEOS) (9 g) was added while stirring the uniform solution. The resulting gel was stirred at 40 ° C. for 24 hours and then heated at 150 ° C. for 48 hours. The gel-like material was washed with water several times to obtain a white silica block copolymer composite. After this synthesis, the resulting solid was calcined at 540 ° C. with flowing air to decompose the triblock copolymer. In this way, 2D hexagonal mesoporous silica SBA-15-150 was obtained.
［２０％窒素ドープメソポーラスカーボン（２０％Ｎ－ＭＣ）の合成］
　上述の２Ｄ六方晶系メソポーラスシリカＳＢＡ－１５－１５０を使用して２０％Ｎ－ＭＣを以下の方法によって作製した。
　先ず、か焼したＳＢＡ－１５－１５０（０．５ｇ）をエチレンジアミン（１．３５ｇ）と四塩化炭素（３ｇ）を混合したものに添加した。その結果として得られたこれらの混合物を９０℃で６時間還流させた。得られた暗褐色の固体混合物を次に１００℃の乾燥室内に１２時間置いてから微粉末に破砕した。このようにして得られた、シリカをテンプレートとして窒素成分が添加されたカーボンの複合体（即ち、窒素ドープカーボン（窒化炭素）ポリマーでカプセル化されたＳＢＡ－１５－１５０）を、次に、１００ｍＬ／分の窒素流中で６００℃で熱処理した。この時、昇温速度は３℃／分とした。炭化させるため、この条件下で５時間処理した。これにより、メソポーラスシリカと窒素ドープカーボンとの複合体を得た。この反応過程、すなわち先ず窒素成分を添加した炭素化合物をシリカテンプレート上に形成し、これを窒素流中で加熱することによって窒素ドープカーボン（窒化炭素）を得るという過程が、図１０において、窒素ドープメソポーラスカーボンを作製する過程の一部として示されている。
　なお、以下に示す残り３種類の窒素ドープメソポーラスカーボンを作製する際には、窒素流中での加熱の前の窒素添加を行っていない。よって、以下に示す残り３種類の窒素ドープメソポーラスカーボンを作製する際には、か焼したメソポーラスシリカ（ＳＢＡ－１５－１５０）を初めて炭素化合物と混合させる過程において、その炭素化合物にはエチレンジアミン等のようないかなる窒素含有炭素化合物も添加していない。
　シリカ骨格を除去するため、このシリカと窒素ドープカーボン複合体中のシリカを５ｗ％のフッ化水素酸でエッチングした。窒素ドープカーボン試料をエタノールで数回洗浄して１００℃で一晩乾燥することで、黒色の２０％窒素ドープメソポーラスカーボン２０％Ｎ－ＭＣを得た。 [Synthesis of 20% nitrogen-doped mesoporous carbon (20% N-MC)]
Using the 2D hexagonal mesoporous silica SBA-15-150 described above, 20% N-MC was prepared by the following method.
First, calcined SBA-15-150 (0.5 g) was added to a mixture of ethylenediamine (1.35 g) and carbon tetrachloride (3 g). The resulting mixtures were refluxed at 90 ° C. for 6 hours. The resulting dark brown solid mixture was then placed in a 100 ° C. drying room for 12 hours and then crushed into a fine powder. The composite of carbon obtained by using silica as a template and having a nitrogen component added thereto (ie, SBA-15-150 encapsulated with a nitrogen-doped carbon (carbon nitride) polymer) was then added to 100 mL. Heat treatment at 600 ° C. in a nitrogen flow per minute. At this time, the temperature rising rate was 3 ° C./min. In order to carbonize, it processed under these conditions for 5 hours. As a result, a composite of mesoporous silica and nitrogen-doped carbon was obtained. This reaction process, that is, a process of first forming a carbon compound added with a nitrogen component on a silica template and heating it in a nitrogen stream to obtain nitrogen-doped carbon (carbon nitride) is shown in FIG. It is shown as part of the process of making mesoporous carbon.
Note that when the remaining three types of nitrogen-doped mesoporous carbon shown below are produced, nitrogen is not added before heating in a nitrogen stream. Therefore, when producing the remaining three types of nitrogen-doped mesoporous carbon shown below, in the process of mixing calcined mesoporous silica (SBA-15-150) with a carbon compound for the first time, the carbon compound includes ethylenediamine and the like. No such nitrogen-containing carbon compounds are added.
In order to remove the silica skeleton, the silica and the silica in the nitrogen-doped carbon composite were etched with 5 w% hydrofluoric acid. The nitrogen-doped carbon sample was washed several times with ethanol and dried at 100 ° C. overnight to obtain black 20% nitrogen-doped mesoporous carbon 20% N-MC.
［１０％窒素ドープメソポーラスカーボン（１０％Ｎ－ＭＣ）の合成］
　上述の２Ｄ六方晶系メソポーラスシリカＳＢＡ－１５－１５０を使用して１０％Ｎ－ＭＣを以下の方法によって作製した。
　先ず、ゼラチン（１．０ｇ）と濃硫酸（０．１６８ｇ）をミリポア水（５ｇ）中に溶解して得られる溶液中にか焼したＳＢＡ－１５－１５０（１ｇ）を添加した。この混合物を加熱温度や加熱時間がプログラムされた乾燥室中に１００℃で６時間（０．５時間で１００℃に到達）置き、その後乾燥室温度を１６０℃に上昇させて（０．５時間で１００℃から１６０℃に到達）同じ温度をもう６時間維持した。その後、シリカテンプレートの小孔内のゼラチンを完全に炭化するため、ゼラチン（０．７５ｇ）とＨ２ＳＯ４（０．１２ｇ）をミリポア水（５ｇ）に混ぜたものを前処理された試料にもう一度添加し、この混合物を上述の１００℃及び１６０℃の加熱温度条件を使ってそれぞれ６時間処理した。これにより得られた、シリカをテンプレートとし窒素がドープされた褐色のカーボン複合体（即ち、窒素ドープカーボン（窒化炭素）ポリマーでカプセル化されたＳＢＡ－１５－１５０）を次に１００ｍＬ／分の窒素流中で６００℃で熱処理した。この時、昇温速度は３℃／分とした。炭化させるため、この条件下で５時間処理した。シリカ骨格を除去するため、このシリカと窒素ドープカーボン複合体中のシリカを５ｗ％のフッ化水素酸でエッチングした。窒素ドープカーボン試料をエタノールで数回洗浄して１００℃で一晩乾燥することで、黒色の１０％窒素ドープメソポーラスカーボン１０％Ｎ－ＭＣを得た。 [Synthesis of 10% nitrogen-doped mesoporous carbon (10% N-MC)]
Using the 2D hexagonal mesoporous silica SBA-15-150 described above, 10% N-MC was prepared by the following method.
First, calcined SBA-15-150 (1 g) was added to a solution obtained by dissolving gelatin (1.0 g) and concentrated sulfuric acid (0.168 g) in Millipore water (5 g). This mixture is placed in a drying chamber programmed for heating temperature and heating time at 100 ° C. for 6 hours (reach 100 ° C. in 0.5 hours), and then the drying chamber temperature is increased to 160 ° C. (0.5 hours). The same temperature was maintained for another 6 hours. Thereafter, in order to completely carbonize the gelatin in the small pores of the silica template, a mixture of gelatin (0.75 g) and H 2 SO 4 (0.12 g) in Millipore water (5 g) is used as a pretreated sample. Once again, the mixture was treated for 6 hours each using the 100 ° C. and 160 ° C. heating temperature conditions described above. The resulting brown carbon composite with silica as a template and doped with nitrogen (ie, SBA-15-150 encapsulated with nitrogen-doped carbon (carbon nitride) polymer) was then added at 100 mL / min nitrogen. Heat treated at 600 ° C. in a stream. At this time, the temperature rising rate was 3 ° C./min. In order to carbonize, it processed under these conditions for 5 hours. In order to remove the silica skeleton, the silica and the silica in the nitrogen-doped carbon composite were etched with 5 w% hydrofluoric acid. The nitrogen-doped carbon sample was washed several times with ethanol and dried at 100 ° C. overnight to obtain black 10% nitrogen-doped mesoporous carbon 10% N-MC.
［８００℃で黒鉛化した１０％窒素ドープメソポーラスカーボン（１０％Ｎ－ＭＣ－８００）の合成］
　上述の２Ｄ六方晶系メソポーラスシリカＳＢＡ－１５－１５０を使用して１０％Ｎ－ＭＣ－８００を以下の方法によって作製した。
　先ず、ゼラチン（１．０ｇ）と濃硫酸（０．１６８ｇ）をミリポア水（５ｇ）中に溶解して得られる溶液中にか焼したＳＢＡ－１５－１５０（１ｇ）を添加した。この混合物を加熱温度や加熱時間がプログラムされた乾燥室中に１００℃で６時間（０．５時間で１００℃に到達）置き、その後乾燥室温度を１６０℃に上昇させて（０．５時間で１００℃から１６０℃に到達）同じ温度をもう６時間維持した。その後、シリカテンプレートの小孔内のゼラチンを完全に炭化するため、ゼラチン（０．７５ｇ）とＨ２ＳＯ４（０．１２ｇ）をミリポア水（５ｇ）に混ぜたものを前処理された試料にもう一度添加し、この混合物を上述の１００℃及び１６０℃の加熱温度条件を使ってそれぞれ６時間処理した。これにより得られた、シリカをテンプレートとし窒素がドープされた褐色のカーボン複合体（即ち、窒素ドープカーボン（窒化炭素）ポリマーでカプセル化されたＳＢＡ－１５－１５０）を次に１００ｍＬ／分の窒素流中で８００℃で熱処理した。この時、昇温速度は３℃／分とした。炭化させるため、この条件下で５時間処理した。シリカ骨格を除去するため、このシリカと窒素ドープカーボン複合体中のシリカを５ｗ％のフッ化水素酸でエッチングした。窒素ドープカーボン試料をエタノールで数回洗浄して１００℃で一晩乾燥することで、黒色の１０％窒素ドープメソポーラスカーボン１０％Ｎ－ＭＣ－８００を得た。 [Synthesis of 10% nitrogen-doped mesoporous carbon (10% N-MC-800) graphitized at 800 ° C.]
Using the 2D hexagonal mesoporous silica SBA-15-150 described above, 10% N-MC-800 was prepared by the following method.
First, calcined SBA-15-150 (1 g) was added to a solution obtained by dissolving gelatin (1.0 g) and concentrated sulfuric acid (0.168 g) in Millipore water (5 g). This mixture is placed in a drying chamber programmed for heating temperature and heating time at 100 ° C. for 6 hours (reach 100 ° C. in 0.5 hours), and then the drying chamber temperature is increased to 160 ° C. (0.5 hours). The same temperature was maintained for another 6 hours. Thereafter, in order to completely carbonize the gelatin in the small pores of the silica template, a mixture of gelatin (0.75 g) and H 2 SO 4 (0.12 g) in Millipore water (5 g) is used as a pretreated sample. Once again, the mixture was treated for 6 hours each using the 100 ° C. and 160 ° C. heating temperature conditions described above. The resulting brown carbon composite with silica as a template and doped with nitrogen (ie, SBA-15-150 encapsulated with nitrogen-doped carbon (carbon nitride) polymer) was then added at 100 mL / min nitrogen. Heat treated at 800 ° C. in a stream. At this time, the temperature rising rate was 3 ° C./min. In order to carbonize, it processed under these conditions for 5 hours. In order to remove the silica skeleton, the silica and the silica in the nitrogen-doped carbon composite were etched with 5 w% hydrofluoric acid. The nitrogen-doped carbon sample was washed several times with ethanol and dried at 100 ° C. overnight to obtain black 10% nitrogen-doped mesoporous carbon 10% N-MC-800.
［１０００℃で黒鉛化した１０％窒素ドープメソポーラスカーボン（１０％Ｎ－ＭＣ－１０００）の合成］
　上述の２Ｄ六方晶系メソポーラスシリカＳＢＡ－１５－１５０を使用して１０％Ｎ－ＭＣ－１０００を以下の方法によって作製した。
　先ず、ゼラチン（１．０ｇ）と濃硫酸（０．１６８ｇ）をミリポア水（５ｇ）中に溶解して得られる溶液中にか焼したＳＢＡ－１５－１５０（１ｇ）を添加した。この混合物を加熱温度や加熱時間がプログラムされた乾燥室中に１００℃で６時間（０．５時間で１００℃に到達）置き、その後乾燥室温度を１６０℃に上昇させて（０．５時間で１００℃から１６０℃に到達）同じ温度をもう６時間維持した。その後、シリカテンプレートの小孔内のゼラチンを完全に炭化するため、ゼラチン（０．７５ｇ）とＨ２ＳＯ４（０．１２ｇ）をミリポア水（５ｇ）に混ぜたものを前処理された試料にもう一度添加し、この混合物を上述の１００℃及び１６０℃の加熱温度条件を使ってそれぞれ６時間処理した。これにより得られた、シリカをテンプレートとし窒素がドープされた褐色のカーボン複合体（即ち、窒素ドープカーボン（窒化炭素）ポリマーでカプセル化されたＳＢＡ－１５－１５０）を次に１００ｍＬ／分の窒素流中で１０００℃で熱処理した。この時、昇温速度は３℃／分とした。炭化させるため、この条件下で５時間処理した。シリカ骨格を除去するため、このシリカと窒素ドープカーボン複合体中のシリカを５ｗ％のフッ化水素酸でエッチングした。窒素ドープカーボン試料をエタノールで数回洗浄して１００℃で一晩乾燥することで、黒色の１０％窒素ドープメソポーラスカーボン１０％Ｎ－ＭＣ－１０００を得た。 [Synthesis of 10% nitrogen-doped mesoporous carbon (10% N-MC-1000) graphitized at 1000 ° C.]
Using the 2D hexagonal mesoporous silica SBA-15-150 described above, 10% N-MC-1000 was prepared by the following method.
First, calcined SBA-15-150 (1 g) was added to a solution obtained by dissolving gelatin (1.0 g) and concentrated sulfuric acid (0.168 g) in Millipore water (5 g). This mixture is placed in a drying chamber programmed for heating temperature and heating time at 100 ° C. for 6 hours (reach 100 ° C. in 0.5 hours), and then the drying chamber temperature is increased to 160 ° C. (0.5 hours). The same temperature was maintained for another 6 hours. Thereafter, in order to completely carbonize the gelatin in the small pores of the silica template, a mixture of gelatin (0.75 g) and H 2 SO 4 (0.12 g) in Millipore water (5 g) is used as a pretreated sample. Once again, the mixture was treated for 6 hours each using the 100 ° C. and 160 ° C. heating temperature conditions described above. The resulting brown carbon composite with silica as a template and doped with nitrogen (ie, SBA-15-150 encapsulated with nitrogen-doped carbon (carbon nitride) polymer) was then added at 100 mL / min nitrogen. Heat treated at 1000 ° C. in a stream. At this time, the temperature rising rate was 3 ° C./min. In order to carbonize, it processed under these conditions for 5 hours. In order to remove the silica skeleton, the silica and the silica in the nitrogen-doped carbon composite were etched with 5 w% hydrofluoric acid. The nitrogen-doped carbon sample was washed several times with ethanol and dried at 100 ° C. overnight to obtain black 10% nitrogen-doped mesoporous carbon 10% N-MC-1000.
［作製された窒素ドープメソポーラスカーボンの特性の評価］
　以上のようにして得られた４種類の窒素ドープメソポーラスカーボン、すなわち２０％Ｎ－ＭＣ、１０％Ｎ－ＭＣ、１０％Ｎ－ＭＣ－８００、及び１０％Ｎ－ＭＣ－１０００の特性の評価を行った。また、対比のため、市販のＰｔ／Ｃ触媒（Johnson Matthey Fuel Cells社のＨｉＳＰＥＣ（登録商標）３０００）も評価した。 [Evaluation of characteristics of produced nitrogen-doped mesoporous carbon]
The characteristics of the four types of nitrogen-doped mesoporous carbons obtained as described above, that is, 20% N-MC, 10% N-MC, 10% N-MC-800, and 10% N-MC-1000 were evaluated. went. For comparison, a commercially available Pt / C catalyst (HiSPEC® 3000 from Johnson Matthey Fuel Cells) was also evaluated.
　具体的には、酸素還元反応（oxygen reduction reaction、ＯＲＲ）活性及びサイクリックボルタンメトリーを測定した。その条件は以下のとおりである：
　電解質溶液：０．１Ｍ ＫＯＨ水溶液
　作用電極：ガラス状炭素電極（ＧＣＥ）
　掃引速度：５０ｍＶ／秒（サイクリックボルタンメトリー測定）
　　　　　　１０ｍＶ／秒（ＯＲＲ活性測定）
　　　　　　（０．２～－１．４Ｖ走引、ｖｓ．Ａｇ／ＡｇＣｌ）） Specifically, oxygen reduction reaction (ORR) activity and cyclic voltammetry were measured. The conditions are as follows:
Electrolyte solution: 0.1M KOH aqueous solution Working electrode: Glassy carbon electrode (GCE)
Sweep speed: 50 mV / sec (cyclic voltammetry measurement)
10 mV / sec (ORR activity measurement)
(0.2 to -1.4V running, vs. Ag / AgCl))
　ＯＲＲ活性の測定手順は、窒素飽和ＫＯＨと酸素飽和ＫＯＨを用いて回転電極法により別個に電極性能測定を行い、（酸素飽和ＫＯＨ中でのＯＲＲ測定値）－（窒素飽和ＫＯＨ中でのＯＲＲ測定値）を計算してＯＲＲ活性（ＯＲＲ活性（Ｏ２－Ｎ２））を評価した。
　なお、電極を回転しない場合についての測定結果は図中で「No Rotation」と表記している。 The procedure for measuring ORR activity is to separately measure the electrode performance by the rotating electrode method using nitrogen saturated KOH and oxygen saturated KOH, (ORR measured value in oxygen saturated KOH)-(ORR measurement in nitrogen saturated KOH) Value) was calculated to evaluate the ORR activity (ORR activity (O 2 -N 2 )).
The measurement result when the electrode is not rotated is indicated as “No Rotation” in the figure.
　窒素ドープメソポーラスカーボン２０％Ｎ－ＭＣ、１０％Ｎ－ＭＣ、１０％Ｎ－ＭＣ－８００、及び１０％Ｎ－ＭＣ－１０００の酸素飽和及び窒素飽和ＫＯＨ中でのＯＲＲ測定結果をそれぞれ図１、図３、図５、及び図７に示す。また、これら４種類の窒素ドープメソポーラスカーボンについてのサイクリックボルタンメトリー測定結果及び計算されたＯＲＲ活性（Ｏ２－Ｎ２）をそれぞれ図２、図４、図６、及び図８に示す。 ORR measurement results of nitrogen-doped mesoporous carbon 20% N-MC, 10% N-MC, 10% N-MC-800, and 10% N-MC-1000 in oxygen saturated and nitrogen saturated KOH are shown in FIG. It is shown in FIG. 3, FIG. 5, and FIG. The results of cyclic voltammetry measurement and the calculated ORR activity (O 2 —N 2 ) for these four types of nitrogen-doped mesoporous carbon are shown in FIG. 2, FIG. 4, FIG. 6, and FIG.
　図９は、作製した４種類の窒素ドープメソポーラスカーボン及び比較対象とした市販のＰｔ／Ｃ触媒（ＨｉＳＰＥＣ３０００）についての電極回転数が９００ｒｐｍの場合のＯＲＲ活性を比較した結果である。図９からわかるように、作製した窒素ドープメソポーラスカーボンはいずれも、Ｐｔ／Ｃ触媒よりは低いものの、非常に高いＯＲＲ活性を示す。
　また、窒素流中での熱処理温度が６００℃であった２０％Ｎ－ＭＣ及び１０％Ｎ－ＭＣに比較して、それよりも高温で処理した１０％Ｎ－ＭＣ－８００及び１０％Ｎ－ＭＣ－１０００（それぞれ８００℃及び１０００℃）の方が高い活性を示す。これは高温で熱処理することによって結晶性が向上するからであると考えられる。但し、メソポーラスカーボンからの窒素の離脱等を考慮すると、１２００℃未満の温度が好ましく、特に１１００℃以下が好ましい。従って、窒素流中での熱処理は６００℃～１１００℃とするのが好ましい。
　また、図９より、本発明の窒素ドープメソポーラスカーボンはいずれも、活性が生じ始める電位が－０．１５Ｖ　ｖｓ．　Ａｇ／ＡｇＣｌとなっており、非特許文献１で報告されている－０．１８Ｖ　ｖｓ．　Ａｇ／ＡｇＣｌという値よりも低い電位であることが分かった。つまり、本発明の窒素ドープメソポーラスカーボンは、鉄担持窒素ドープグラフェンを超える性能（具体的には、非特許文献１で報告されている鉄担持窒素ドープグラフェンの方が高い電位でＯＲＲ活性が発現する）を示すことが分かった。
　よって、図９より、作製した４種類の窒素ドープメソポーラスカーボンは、燃料電池のカソード用非白金触媒として、非特許文献１で報告されている鉄担持窒素ドープグラフェンよりも高い活性（高い性能）を有していることが確認された。
　また、非特許文献２で報告されている活性が生じ始める電位も、本発明の窒素ドープメソポーラスカーボンより高い、－０．１６Ｖ　ｖｓ．　Ａｇ／ＡｇＣｌという値であることから、本発明の窒素ドープメソポーラスカーボンは、非特許文献２で報告されている触媒よりも低い電位から活性が現れることが分った。つまり、本発明の窒素ドープメソポーラスカーボンは、非特許文献２で報告されている触媒を超える性能を示すことも分った。 FIG. 9 shows the result of comparison of ORR activity when the electrode rotation speed is 900 rpm for the four types of nitrogen-doped mesoporous carbon produced and the commercially available Pt / C catalyst (HiSPEC 3000) to be compared. As can be seen from FIG. 9, all of the produced nitrogen-doped mesoporous carbons exhibit a very high ORR activity, although lower than the Pt / C catalyst.
Also, compared with 20% N-MC and 10% N-MC where the heat treatment temperature in the nitrogen flow was 600 ° C., 10% N-MC-800 and 10% N— treated at a higher temperature than that. MC-1000 (800 ° C. and 1000 ° C., respectively) shows higher activity. This is considered to be because crystallinity is improved by heat treatment at a high temperature. However, in consideration of nitrogen desorption from mesoporous carbon, a temperature of less than 1200 ° C. is preferable, and 1100 ° C. or less is particularly preferable. Accordingly, the heat treatment in a nitrogen flow is preferably 600 ° C. to 1100 ° C.
In addition, as shown in FIG. 9, in any of the nitrogen-doped mesoporous carbons of the present invention, the potential at which activity starts to occur is −0.15 V vs. Ag / AgCl, which is reported in Non-Patent Document 1, −0.18 V vs. It was found that the potential was lower than the value Ag / AgCl. That is, the nitrogen-doped mesoporous carbon of the present invention has a performance exceeding that of iron-supported nitrogen-doped graphene (specifically, the iron-supported nitrogen-doped graphene reported in Non-Patent Document 1 exhibits ORR activity at a higher potential. ).
Therefore, from FIG. 9, the four types of nitrogen-doped mesoporous carbons produced have higher activity (higher performance) than the iron-supported nitrogen-doped graphene reported in Non-Patent Document 1 as a non-platinum catalyst for cathodes of fuel cells. It was confirmed to have.
The potential at which the activity reported in Non-Patent Document 2 begins to occur is also higher than that of the nitrogen-doped mesoporous carbon of the present invention, -0.16 V vs. From the value of Ag / AgCl, it was found that the nitrogen-doped mesoporous carbon of the present invention showed activity from a lower potential than the catalyst reported in Non-Patent Document 2. That is, it has been found that the nitrogen-doped mesoporous carbon of the present invention exhibits performance exceeding that of the catalyst reported in Non-Patent Document 2.
　図１１には、１０％Ｎ－ＭＣと、１０％Ｎ－ＭＣ－８００と、１０％Ｎ－ＭＣ－１０００中の非晶質構造の炭素と結晶質構造の炭素を同定するためのラマン分光法による測定結果並びにその測定結果から算出された非晶質構造の炭素のピーク面積ＩＤと結晶質構造の炭素ピーク面積ＩＧの割合（ＩＤ／ＩＧ）が示されている。ラマン分光法で計測されたピークのうち、グラファイト（結晶質構造の炭素、図１１中では、Ｇと示される。）特有のピークは、ラマンシフトが１５８１ｃｍ－1付近に観察される一方、非晶質構造の炭素（図１１中ではＤと示される)は、１３００ｃｍ－1付近に観察される。非晶質構造の炭素のピーク面積ＩＤの結晶質構造の炭素ピーク面積ＩＧに対する割合（ＩＤ／ＩＧ）は、小さくなるにつれて結晶性が良くなることを示す。
　図９によれば、１０％Ｎ－ＭＣよりも１０％Ｎ－ＭＣ－１０００の方が高いＯＲＲ活性を示し、この１０％Ｎ－ＭＣ－１０００よりも１０％Ｎ－ＭＣ－８００℃の方が高いＯＲＲ活性を示している。ここで、図１１に示されている通り、１０％Ｎ－ＭＣのＩＤ／ＩＧは１．１２であり、１０％Ｎ－ＭＣ－１０００のＩＤ／ＩＧは１．０９であり、１０％Ｎ－ＭＣ－８００℃のＩＤ／ＩＧは１．０７であることから、結晶性の改善がＯＲＲ活性の向上（即ち、高性能化）に寄与することも確認された。
　なお、本実施例の１０％Ｎ－ＭＣと、１０％Ｎ－ＭＣ－８００℃と、１０％Ｎ－ＭＣ－１０００℃中の炭素及び窒素含有量（重量％）は以下の表の通りである。この窒素の分析は通常のケルダール法（Kjeldahl method）により行った。なお、分析時においては、揮発性物質が二酸化炭素となって蒸発することにより強熱減量が生じる。そのため、以下の表の分析結果における炭素と窒素の合計が１００重量％になっていない原因は、この揮発性物質による。 FIG. 11 shows Raman spectroscopy for identifying amorphous and crystalline carbon in 10% N-MC, 10% N-MC-800, and 10% N-MC-1000. ratio measurements and the carbon peak area I G crystalline structure and the peak area I D carbon of amorphous structure which is calculated from the measurement result by (I D / I G) is shown. Among the peaks measured by Raman spectroscopy, a peak peculiar to graphite (crystalline carbon, shown as G in FIG. 11) is observed in a Raman shift near 1581 cm −1, while being amorphous. Carbon in the structure (denoted as D in FIG. 11) is observed around 1300 cm −1 . Ratio of carbon peak area I G of the crystalline structure of the peak area I D carbon having an amorphous structure (I D / I G) indicates that the crystallinity is improved as decreases.
According to FIG. 9, 10% N-MC-1000 shows higher ORR activity than 10% N-MC, and 10% N-MC-800 ° C. than 10% N-MC-1000. It shows high ORR activity. Here, as shown in Figure 11, the 10% N-MC I D / I G is 1.12, I D / I G of 10% N-MC-1000 is 1.09, Since I D / I G at 10% N-MC-800 ° C. is 1.07, it was also confirmed that the improvement in crystallinity contributes to the improvement in ORR activity (ie, higher performance).
The carbon and nitrogen contents (% by weight) in 10% N-MC, 10% N-MC-800 ° C., and 10% N-MC-1000 ° C. of this example are as shown in the table below. . This nitrogen analysis was carried out by the usual Kjeldahl method. At the time of analysis, loss of ignition occurs due to evaporation of volatile substances as carbon dioxide. Therefore, the reason why the sum of carbon and nitrogen in the analysis results in the following table is not 100% by weight is due to this volatile substance.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　以上説明したように、本発明によれば、白金触媒を用いることなく比較的良好なＯＲＲ活性を有し、更に、電解質膜や触媒自体を損傷する作用を持たない、燃料電池のカソード用触媒が提供されるため、燃料電池分野での利用可能性が大いに期待される。 As described above, according to the present invention, there is provided a catalyst for a cathode of a fuel cell that has a relatively good ORR activity without using a platinum catalyst, and further has no action of damaging the electrolyte membrane or the catalyst itself. Therefore, it is highly expected to be used in the fuel cell field.

Claims (7)

  1. 　燃料電池カソード用触媒の窒素ドープメソポーラスカーボンを製造する方法であって、メソポーラスシリカに炭素化合物を含浸させた後、窒素流中で加熱することにより、窒素ドープカーボンとメソポーラスシリカとの複合体を形成し、前記複合体中のシリカ成分を除去することにより前記窒素ドープメソポーラスカーボンを製造する方法。 A method for producing nitrogen-doped mesoporous carbon as a catalyst for a fuel cell cathode, comprising impregnating mesoporous silica with a carbon compound and then heating in a nitrogen stream to form a composite of nitrogen-doped carbon and mesoporous silica And producing the nitrogen-doped mesoporous carbon by removing the silica component in the composite.
  2. 　前記炭素化合物は更に窒素を含む、請求項１に記載の製造方法。 The method according to claim 1, wherein the carbon compound further contains nitrogen.
  3. 　窒素ドープメソポーラスカーボンからなる、燃料電池のカソード用触媒。 A catalyst for a cathode of a fuel cell made of nitrogen-doped mesoporous carbon.
  4. 　請求項１または２に記載の方法で製造された窒素ドープメソポーラスカーボンからなる、燃料電池のカソード用触媒。 A catalyst for a cathode of a fuel cell, comprising nitrogen-doped mesoporous carbon produced by the method according to claim 1 or 2.
  5. 　窒素ドープ量が窒素ドープメソポーラスカーボン触媒の全重量に対して６％以上である、請求項３又は４に記載の燃料電池のカソード用触媒。 The catalyst for a cathode of a fuel cell according to claim 3 or 4, wherein the nitrogen doping amount is 6% or more with respect to the total weight of the nitrogen-doped mesoporous carbon catalyst.
  6. 　ラマン分光法によって決定される、窒素ドープメソポーラスカーボン触媒中の非晶質構造の炭素のピーク面積ＩＤと結晶質構造の炭素のピーク面積ＩＧの割合（ＩＤ／ＩＧ）が１．１未満である、請求項３乃至５のいずれか一項に記載の燃料電池のカソード用触媒。 The ratio (I D / I G ) between the peak area ID of the amorphous carbon and the peak area I G of the crystalline carbon in the nitrogen-doped mesoporous carbon catalyst as determined by Raman spectroscopy is 1.1. The catalyst for a cathode of a fuel cell according to any one of claims 3 to 5, wherein
  7. 　請求項３乃至６のいずれか一項に記載のカソード用触媒を含む、燃料電池。 A fuel cell comprising the cathode catalyst according to any one of claims 3 to 6.
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