JP2008222486A - Metal-containing carbide and method for manufacturing the same - Google Patents

Metal-containing carbide and method for manufacturing the same Download PDF

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JP2008222486A
JP2008222486A JP2007062275A JP2007062275A JP2008222486A JP 2008222486 A JP2008222486 A JP 2008222486A JP 2007062275 A JP2007062275 A JP 2007062275A JP 2007062275 A JP2007062275 A JP 2007062275A JP 2008222486 A JP2008222486 A JP 2008222486A
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JP5183943B2 (en
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Jun Maruyama
純 丸山
Ikuo Abe
郁夫 安部
Atsushi Okamura
淳志 岡村
Kuninori Miyazaki
邦典 宮碕
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Nippon Shokubai Co Ltd
Osaka City
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal-containing carbide that is inexpensive and exhibits catalytic activity similar to that of a platinum-containing catalyst when used as an electrode catalyst of a solid polymer fuel cell, and to provide a new method for manufacturing the metal-containing carbide. <P>SOLUTION: The method for manufacturing a metal-containing carbide is characterized in that: an organic compound containing a metal is carbonized in two stages; the carbonization temperature in the first stage is controlled to 150 to 500°C; and the carbonization temperature in the second stage is controlled to 600 to 1,200°C. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

本発明は、金属含有炭化物の製造方法、および当該方法で製造される金属含有炭化物に関するものである。また、本発明は、当該金属含有炭化物を用いた電極、酸素還元電極、および固体高分子形燃料電池に関する。   The present invention relates to a method for producing a metal-containing carbide and a metal-containing carbide produced by the method. The present invention also relates to an electrode using the metal-containing carbide, an oxygen reduction electrode, and a polymer electrolyte fuel cell.

燃料電池は、環境に調和した高効率な発電システムとして注目を集めている。特に固体高分子電解質膜を電解質として使用する固体高分子電解質形燃料電池は、常温での作動が可能であり、かつ高出力密度であるため、排気ガスフリーの電気自動車用電源、家庭用電熱併給システムの電源等として幅広い実用化が期待されている。   Fuel cells are attracting attention as a highly efficient power generation system in harmony with the environment. In particular, solid polymer electrolyte fuel cells that use a solid polymer electrolyte membrane as the electrolyte can operate at room temperature and have a high output density. A wide range of practical applications is expected as a power source for systems.

このような燃料電池の実用化と普及のためには、低コスト化が大きな課題となっている。しかし、既存の固体高分子電解質形燃料電池では、一般に電極触媒の成分に高価な白金を含む。よって、固体高分子電解質形燃料電池の低コスト化のためには、白金使用量を低減する工夫が求められる。また白金の埋蔵量や生産量にも限りがあり、将来的に普及が進んだ場合には、白金価格が高騰することも予想される。そこで、白金を用いない安価な電極触媒材料の開発が課題となっている。   In order to put such a fuel cell into practical use and widespread use, cost reduction has become a major issue. However, existing solid polymer electrolyte fuel cells generally contain expensive platinum as a component of an electrode catalyst. Therefore, in order to reduce the cost of the solid polymer electrolyte fuel cell, a device for reducing the amount of platinum used is required. Platinum reserves and production are also limited, and platinum prices are expected to rise as they become more popular in the future. Therefore, the development of an inexpensive electrode catalyst material that does not use platinum has been an issue.

白金を用いない有望な酸素還元電極触媒材料の一つに、資源的に豊富な鉄などを利用した触媒が挙げられる。この触媒は、鉄などの金属イオンが炭素材料表面に窒素原子を介して結合した構造を有し、この部分が触媒の活性点として機能する。かかる触媒は、これまで下記の方法により製造できることが報告されている。   One promising oxygen reduction electrocatalyst material that does not use platinum is a catalyst that uses abundant resources such as iron. This catalyst has a structure in which a metal ion such as iron is bonded to the surface of a carbon material via a nitrogen atom, and this portion functions as an active point of the catalyst. It has been reported that such a catalyst can be produced by the following method.

１． ポルフィリン、フタロシアニンなど、窒素原子を介して鉄イオンが配位している鉄錯体を炭素材料上に担持し、不活性雰囲気下で熱処理する方法（非特許文献１）。
２． ポリピロールやポリアクリロニトリルなど窒素原子を含有する高分子と鉄塩とを混合し、不活性雰囲気下で熱処理する方法（非特許文献２）。
３． 炭素材料に担持した鉄塩を、アンモニアやアセトニトリルなどの窒素含有ガス中で熱処理する方法（非特許文献３）。
４． 窒素原子を含有する炭素材料の表面に鉄塩を担持した後、不活性雰囲気下で熱処理する方法（非特許文献４）。
A．van der Puttenら，ジャーナル・オブ・エレクトロアナリティカル・ケミストリー（J．Electroanal．Chem），第２０５号，第２３３〜２４４頁（１９８６年） S．Guptaら，ジャーナル・オブ・アプライド・エレクトロケミストリー（J．Appl．Electrochem），第１９号，第１９〜２７頁（１９８９年） G．Lalandeら，エレクトロシミカ・アクタ（Electrochim．Acta），第４２号，第１３７９〜１３８８頁（１９８７年） M．Lefevreら，ジャーナル・オブ・フィジカル・ケミストリー（J．Phys．Chem），第１０６号，第８７０５〜８７１３頁（２００２年） 1. A method in which an iron complex in which an iron ion is coordinated through a nitrogen atom, such as porphyrin and phthalocyanine, is supported on a carbon material and heat-treated in an inert atmosphere (Non-patent Document 1).
2. A method in which a polymer containing a nitrogen atom such as polypyrrole or polyacrylonitrile and an iron salt are mixed and heat-treated in an inert atmosphere (Non-patent Document 2).
3. A method of heat-treating an iron salt supported on a carbon material in a nitrogen-containing gas such as ammonia or acetonitrile (Non-patent Document 3).
4). A method in which an iron salt is supported on the surface of a carbon material containing nitrogen atoms and then heat-treated in an inert atmosphere (Non-Patent Document 4).
A. van der Putten et al., Journal of Electroanalytical Chemistry, 205, pp. 233-244 (1986). S. Gupta et al., Journal of Applied Electrochemistry (J. Appl. Electrochem), No. 19, pp. 19-27 (1989) G. Lalande et al., Electrochim. Acta, 42, 1379-1388 (1987). M. Lefevre et al., Journal of Physical Chemistry (J. Phys. Chem), 106, 8705-8713 (2002).

上述した様に、高価な白金含有触媒に代えて、鉄等を含む炭素材料を固体高分子形燃料電池の触媒として用いようとする試みはあった。   As described above, there has been an attempt to use a carbon material containing iron or the like as a catalyst for a polymer electrolyte fuel cell instead of an expensive platinum-containing catalyst.

しかし、上記の従来方法で製造された触媒は、白金を材料として含む炭素材料に比べて性能が劣ることは否めないものである。   However, it cannot be denied that the catalyst produced by the above-described conventional method is inferior in performance to a carbon material containing platinum as a material.

そこで、本発明が解決すべき課題は、安価な上に、固体高分子形燃料電池の電極触媒に用いたとき、白金含有触媒と同様の優れた触媒活性を示す金属含有炭化物を提供することにある。また、本発明では、当該金属含有炭化物を製造するための新規な製造方法を提供することも目的とする。   Therefore, the problem to be solved by the present invention is to provide a metal-containing carbide that is inexpensive and exhibits excellent catalytic activity similar to that of a platinum-containing catalyst when used as an electrode catalyst for a polymer electrolyte fuel cell. is there. Another object of the present invention is to provide a novel production method for producing the metal-containing carbide.

本発明者らは、上記課題を解決すべく鋭意研究を重ねた。その結果、金属を含有する有機化合物を、比較的低温と高温での二段階で炭化処理することによって、白金含有触媒に匹敵するほど触媒活性に優れた金属含有炭化物を、低コストで且つ収率良く製造できることを見出して本発明を完成した。   The inventors of the present invention have made extensive studies to solve the above problems. As a result, metal-containing carbides, which have a catalytic activity comparable to platinum-containing catalysts, are produced at low cost and in a yield by carbonizing organic compounds containing metals in two stages at relatively low and high temperatures. The present invention was completed by finding that it can be manufactured well.

本発明に係る金属含有炭化物の製造方法は、
金属を含有する有機化合物を二段階で炭化処理するものであり；
一段階目の炭化処理の温度を１５０〜５００℃とし；且つ
二段階目の炭化処理の温度を６００〜１２００℃とすることを特徴とする。 The method for producing a metal-containing carbide according to the present invention includes:
Carbonizing organic compounds containing metals in two stages;
The temperature of the first stage carbonization treatment is 150 to 500 ° C; and the temperature of the second stage carbonization treatment is 600 to 1200 ° C.

上記製造方法においては、二段階目の炭化処理を賦活剤の存在下で行うことが好ましい。触媒性能の高い炭化物を、より効率的に製造できるからである。特に、炭化物の細孔を発達させ、表面積を高められる。本発明方法で使用できる賦活剤としては、二酸化炭素、水蒸気、空気、酸素、アルカリ金属水酸化物、塩化亜鉛、およびリン酸からなる群より選択される少なくとも１種を例示することができる。   In the said manufacturing method, it is preferable to perform the carbonization process of the 2nd step in presence of an activator. This is because a carbide having high catalytic performance can be produced more efficiently. In particular, it is possible to develop carbide pores and increase the surface area. Examples of the activator that can be used in the method of the present invention include at least one selected from the group consisting of carbon dioxide, water vapor, air, oxygen, alkali metal hydroxide, zinc chloride, and phosphoric acid.

本発明の金属含有炭化物は、上記本発明方法により製造されることを特徴とする。本発明の金属含有炭化物としては、２価鉄イオンを含むもの、および鉄−窒素結合を有するものが好適である。それぞれ、触媒活性に優れるからである。   The metal-containing carbide of the present invention is produced by the above-described method of the present invention. As the metal-containing carbide of the present invention, those containing divalent iron ions and those having an iron-nitrogen bond are suitable. This is because each has excellent catalytic activity.

本発明の電極および酸素還元電極は、本発明の金属含有炭化物を含むことを特徴とする。また、本発明の固体高分子形燃料電池は、本発明の酸素還元電極を含むことを特徴とする。   The electrode and the oxygen reduction electrode of the present invention are characterized by including the metal-containing carbide of the present invention. The solid polymer fuel cell of the present invention includes the oxygen reduction electrode of the present invention.

本発明方法を用いることで、固体高分子形燃料電池の電極用触媒として、白金含有触媒に匹敵するほど高い酸素還元性能を有する触媒を、低コストで収率良く製造することが可能になる。なお、本発明方法で製造された金属含有炭化物は、特にアルカリ環境下で高い触媒性能を発揮することができるので、例えばアニオン交換型高分子電解質を用いた固体高分子形燃料電池において、高い酸素還元性能を発揮できるものである。従って、本発明の金属含有炭化物を用いた電極、酸素還元電極、および固体高分子形燃料電池は、安価で且つ発電性能に優れるものとして、産業上極めて有用である。   By using the method of the present invention, a catalyst having high oxygen reduction performance comparable to that of a platinum-containing catalyst can be produced at a low cost and in a high yield as an electrode catalyst for a polymer electrolyte fuel cell. In addition, since the metal-containing carbide produced by the method of the present invention can exhibit high catalytic performance particularly in an alkaline environment, for example, in a polymer electrolyte fuel cell using an anion exchange type polymer electrolyte, high oxygen It can exhibit reduction performance. Therefore, the electrode, the oxygen reduction electrode, and the solid polymer fuel cell using the metal-containing carbide of the present invention are extremely useful industrially as being inexpensive and excellent in power generation performance.

本発明に係る金属含有炭化物の製造方法は、
金属を含有する有機化合物を二段階で炭化処理するものであり；
一段階目の炭化処理の温度を１５０〜５００℃とし；且つ
二段階目の炭化処理の温度を６００〜１２００℃とすることを特徴とする。
以下、実際の実施の順番に従って、本発明方法を説明する。 The method for producing a metal-containing carbide according to the present invention includes:
Carbonizing organic compounds containing metals in two stages;
The temperature of the first stage carbonization treatment is 150 to 500 ° C; and the temperature of the second stage carbonization treatment is 600 to 1200 ° C.
Hereinafter, the method of the present invention will be described in the actual order of implementation.

本発明で使用する「金属を含有する有機化合物」の種類は特に制限されず、例えば、天然有機化合物、合成有機化合物、低分子量化合物、高分子量化合物、タンパク質、酵素、芳香族有機化合物など特に制限されない。具体的には、フタロシアニン、ナフタロシアニン、ポルフィリン、ポルフィリン構造を有する化合物、コバラミンなどの天然由来の金属含有有機化合物；ヘモグロビン、カタラーゼ、ペルオキシダーゼ、ヒドロゲナーゼ、ラッカーゼ、チロシナーゼなどの金属含有タンパク質などを例示することができる。   The type of the “organic compound containing a metal” used in the present invention is not particularly limited. For example, natural organic compounds, synthetic organic compounds, low molecular weight compounds, high molecular weight compounds, proteins, enzymes, aromatic organic compounds and the like are not particularly limited. Not. Specifically, examples include phthalocyanine, naphthalocyanine, porphyrin, compounds having a porphyrin structure, naturally-occurring metal-containing organic compounds such as cobalamin; metal-containing proteins such as hemoglobin, catalase, peroxidase, hydrogenase, laccase, and tyrosinase. Can do.

本発明の「金属を含有する有機化合物」は、金属を含む。当該金属は、触媒能を有するものであり、例えば、鉄、コバルト、ニッケル、銅、マンガン、クロムからなる群より選択される少なくとも１種を挙げることができる。好ましくは、鉄、銅、コバルト、またはニッケルを用いる。金属を含有する有機化合物において、基本骨格と金属との結合種は特に制限されないが、例えば配位結合や静電結合などとすることができ、特に制限されない。   The “organic compound containing a metal” of the present invention includes a metal. The metal has catalytic ability, and examples thereof include at least one selected from the group consisting of iron, cobalt, nickel, copper, manganese, and chromium. Preferably, iron, copper, cobalt, or nickel is used. In the organic compound containing a metal, the bond type between the basic skeleton and the metal is not particularly limited, but can be, for example, a coordinate bond or an electrostatic bond, and is not particularly limited.

本発明方法は、金属を含有する有機化合物を二段階で炭化処理することを特徴とし、第一炭化処理では、炭化処理温度を比較的低温である１５０〜５００℃とする。   The method of the present invention is characterized in that an organic compound containing a metal is carbonized in two stages. In the first carbonization, the carbonization temperature is set to 150 to 500 ° C., which is a relatively low temperature.

より具体的には、比較的低温での第一炭化処理を行うことで、金属含有炭化物中の金属を、より活性が高い状態で安定化することができる。例えば鉄イオンを、２価の状態で含むものとすることができる。その結果、高い酸素還元性能を有する金属含有炭化物の製造が可能になった。一方、比較的低温での第一炭化処理を行うことなく、一段階で高温度での炭化処理を行うと、得られる金属含有炭化物中の金属イオンは活性が高い状態を保つことができない。例えば、鉄イオンは、２価よりも活性の低い３価となってしまう。結果として、優れた酸素還元性能を有する金属含有炭化物は得られない。   More specifically, by performing the first carbonization treatment at a relatively low temperature, the metal in the metal-containing carbide can be stabilized in a more active state. For example, iron ions can be included in a divalent state. As a result, it became possible to produce metal-containing carbides having high oxygen reduction performance. On the other hand, if the carbonization treatment at a high temperature is performed in one step without performing the first carbonization treatment at a relatively low temperature, the metal ions in the obtained metal-containing carbide cannot maintain a high activity state. For example, iron ions become trivalent, which is less active than divalent. As a result, a metal-containing carbide having excellent oxygen reduction performance cannot be obtained.

さらに、第一炭化処理を行うことで、続く第二化処理における処理温度を上げることができ、炭素構造の規則性がより高められた金属含有炭化物を得ることが可能になる。その結果、金属含有炭化物の導電性が向上し、高い酸素還元性能が得られ、また、触媒としての耐久性も向上する。一方、比較的低温での第一炭化処理を行うことなく、一段階で高温度での炭化処理を行う場合、金属含有炭化物の収率は著しく低減するため、炭化温度を上げることができない。   Furthermore, by performing the first carbonization treatment, it is possible to increase the treatment temperature in the subsequent second treatment, and it is possible to obtain a metal-containing carbide having a higher regularity of the carbon structure. As a result, the conductivity of the metal-containing carbide is improved, high oxygen reduction performance is obtained, and durability as a catalyst is also improved. On the other hand, when the carbonization treatment at a high temperature is performed in one step without performing the first carbonization treatment at a relatively low temperature, the yield of the metal-containing carbide is remarkably reduced, so that the carbonization temperature cannot be raised.

第一炭化処理温度を１５０℃以上とするのは、処理温度が１５０℃未満であると炭化が進まず、適切な第一炭化物が得られない場合があるからである。一方、５００℃を超えると炭化が過剰に進み、適切な第一炭化物が得られない場合があることに加え、収率が低下するおそれがある。より好ましくは、当該処理温度を２００℃以上、４５０℃以下とし、さらに好ましくは３００℃以上、４００℃以下とする。   The reason why the first carbonization treatment temperature is set to 150 ° C. or higher is that if the treatment temperature is less than 150 ° C., carbonization does not proceed and an appropriate first carbide may not be obtained. On the other hand, when the temperature exceeds 500 ° C., carbonization proceeds excessively, and an appropriate first carbide may not be obtained, and the yield may be reduced. More preferably, the treatment temperature is 200 ° C. or higher and 450 ° C. or lower, and more preferably 300 ° C. or higher and 400 ° C. or lower.

炭化処理は、不活性雰囲気下で行うことが好ましい。本発明で用いる不活性雰囲気は、窒素ガスや希ガス雰囲気下などのガス雰囲気をいう。なお、酸素が含まれていたとしても、被処理物を燃焼させない程度まで酸素量を制限した雰囲気であれば、本発明に係る金属含有炭化物を製造することができる。当該雰囲気は、閉鎖系または新たなガスを流通させる流通系の何れであってもよく、好ましくは流通系とする。流通系とする場合には、被処理物１グラム当たり０．０１〜０．１リットル／分のガスを流通させることが好ましい。   The carbonization treatment is preferably performed in an inert atmosphere. The inert atmosphere used in the present invention refers to a gas atmosphere such as a nitrogen gas or a rare gas atmosphere. Even if oxygen is contained, the metal-containing carbide according to the present invention can be produced in an atmosphere in which the amount of oxygen is limited to such an extent that the workpiece is not burned. The atmosphere may be either a closed system or a distribution system for circulating a new gas, and is preferably a distribution system. In the case of a flow system, it is preferable to flow a gas of 0.01 to 0.1 liter / min per gram of the object to be processed.

第一炭化処理においては、金属含有有機化合物を１５０℃〜５００℃に１〜２０時間保持することが好ましく、さらに好ましくは５〜１５時間程度保持する。１時間以上であれば、第一炭化処理の目的を達することができ、均一な予備炭化物が得られる。一方、２０時間を超えて炭化処理しても、処理時間に相応する効果は得られず不経済である。   In the first carbonization treatment, the metal-containing organic compound is preferably held at 150 ° C. to 500 ° C. for 1 to 20 hours, more preferably about 5 to 15 hours. If it is 1 hour or more, the purpose of the first carbonization treatment can be achieved, and a uniform preliminary carbide can be obtained. On the other hand, even if carbonization is performed for more than 20 hours, an effect corresponding to the treatment time cannot be obtained, which is uneconomical.

当該第一炭化処理は、金属含有有機化合物を炭化装置等に挿入した後に常温から所定温度まで昇温してもよいし、或いは、所定温度の炭化装置等へ金属含有有機化合物を挿入してもよい。好適には、常温から所定温度まで昇温するのがよい。常温から所定温度まで昇温する場合には、昇温温度を一定にすることが好ましい。   In the first carbonization treatment, after the metal-containing organic compound is inserted into the carbonization device or the like, the temperature may be raised from normal temperature to a predetermined temperature, or the metal-containing organic compound may be inserted into the carbonization device or the like at a predetermined temperature. Good. Preferably, the temperature is raised from room temperature to a predetermined temperature. When raising the temperature from room temperature to a predetermined temperature, it is preferable to keep the temperature rise constant.

第一炭化処理の終了後は、そのまま温度を上げて第二炭化処理を行ってもよい。しかし好適には、一旦室温まで冷却した後に温度を上げ、第二炭化処理を行う。また、第一炭化処理後に予備炭化物を室温まで冷却した際には、均一に粉砕してもよいし、さらに成形してもよい。   After the completion of the first carbonization treatment, the second carbonization treatment may be performed by raising the temperature as it is. However, preferably, after cooling to room temperature, the temperature is raised and the second carbonization treatment is performed. Further, when the preliminary carbide is cooled to room temperature after the first carbonization treatment, it may be uniformly pulverized or further molded.

本発明方法では、前述した第一炭化処理に引き続いて、第二炭化処理を行う。第二炭化処理の温度は６００℃〜１２００℃とし、好ましくは８００℃以上、１２００℃以下、さらに好ましくは８５０℃以上、１１００℃以下とする。当該温度を６００℃以上にすることによって、十分に炭化が進んで高い触媒性能を有する金属含有炭化物が得られる。一方、１２００℃超で炭化処理すると炭化物の収率が著しく低減し、炭化物が収率よく製造できない場合がある。   In the method of the present invention, the second carbonization treatment is performed following the first carbonization treatment described above. The temperature of the second carbonization treatment is 600 ° C to 1200 ° C, preferably 800 ° C to 1200 ° C, and more preferably 850 ° C to 1100 ° C. By setting the temperature to 600 ° C. or more, a metal-containing carbide having a high catalytic performance with sufficient carbonization can be obtained. On the other hand, if the carbonization treatment is performed at a temperature exceeding 1200 ° C., the yield of the carbide is significantly reduced, and the carbide may not be produced with a high yield.

第二炭化処理においては、被処理物を６００℃〜１２００℃で、通常３０分〜５時間保持し、より好ましくは１時間〜３時間保持する。３０分以上炭化処理を行えば、炭化が均一に十分進行する。一方、５時間を超えて炭化処理しても処理時間に相応する効果は得られず、不経済である。   In the second carbonization treatment, the object to be treated is held at 600 ° C. to 1200 ° C., usually 30 minutes to 5 hours, more preferably 1 hour to 3 hours. If the carbonization treatment is performed for 30 minutes or more, the carbonization proceeds sufficiently and uniformly. On the other hand, even if carbonization treatment is performed for more than 5 hours, an effect corresponding to the treatment time cannot be obtained, which is uneconomical.

第二炭化処理は、第一炭化処理と同様に不活性雰囲気下で行うことが好ましく、また流通系で行うことが好ましい。流通系とする場合には、被処理物１ｇ当たり０．０１〜０．１Ｌ／分のガスを流通させることが好ましい。   The second carbonization treatment is preferably performed in an inert atmosphere as in the first carbonization treatment, and is preferably performed in a flow system. In the case of a flow system, it is preferable to flow 0.01 to 0.1 L / min of gas per 1 g of the object to be processed.

但し、第二炭化処理は、賦活剤の存在下で行うことが好ましい。賦活剤の存在下、高温で炭化処理することにより、金属含有炭化物の細孔が発達して表面積が増大し、当該金属含有炭化物の表面における金属の露出度が向上することにより、触媒としての性能が向上する。なお、炭化物の表面積は、Ｎ2吸着量により測定することができる。 However, the second carbonization treatment is preferably performed in the presence of an activator. By carbonizing at a high temperature in the presence of an activator, the pores of the metal-containing carbide develop, the surface area increases, and the degree of exposure of the metal on the surface of the metal-containing carbide improves, thereby performance as a catalyst. Will improve. The surface area of the carbide can be measured by the N 2 adsorption amount.

本発明方法で使用できる賦活剤は、特に制限されないが、例えば、二酸化炭素、水蒸気、空気、酸素、アルカリ金属水酸化物、塩化亜鉛、およびリン酸からなる群より選択される少なくとも１種を用いることができ、さらに好ましくは、二酸化炭素、水蒸気、空気、酸素からなる群より選択される少なくとも１種を用いることができる。二酸化炭素や水蒸気などの気体賦活剤は、第二炭化処理の雰囲気中に２〜８０モル％、好ましくは１０〜６０モル％含有させればよい。２モル％以上であれば十分な賦活効果が得られる一方で、８０モル％を超える場合には賦活効果が顕著になり炭化物の収率が著しく低減し、効率よく炭化物を製造することができなくなるおそれがある。また、アルカリ金属水酸化物等の固体賦活剤は、固体の状態で被炭化物と混合してもよく、或いは、水等の溶媒で溶解または希釈した後、被炭化物を含浸するか、或いはスラリー状にして被炭化物に練り込んでもよい。液体賦活剤は、水等で希釈した後、被炭化物を含浸するか或いは被炭化物に練り込めばよい。   The activator that can be used in the method of the present invention is not particularly limited. For example, at least one selected from the group consisting of carbon dioxide, water vapor, air, oxygen, alkali metal hydroxide, zinc chloride, and phosphoric acid is used. More preferably, at least one selected from the group consisting of carbon dioxide, water vapor, air, and oxygen can be used. A gas activator such as carbon dioxide or water vapor may be contained in the atmosphere of the second carbonization treatment in an amount of 2 to 80 mol%, preferably 10 to 60 mol%. If it is 2 mol% or more, a sufficient activation effect can be obtained, while if it exceeds 80 mol%, the activation effect becomes remarkable and the yield of carbide is remarkably reduced, making it impossible to produce carbide efficiently. There is a fear. In addition, the solid activator such as alkali metal hydroxide may be mixed with the carbonized substance in a solid state, or after being dissolved or diluted with a solvent such as water, impregnated with the carbonized substance or in a slurry state. And may be kneaded into the article to be carbonized. The liquid activator may be diluted with water or the like and then impregnated with the carbonized material or kneaded into the carbonized material.

本発明に係る金属含有炭化物の製造方法の具体的な例を以下に示す。
（１）金属含有有機化合物を不活性ガスの存在下に室温から１５０℃〜５００℃まで昇温し、所定時間保持した後、次いで６００〜１２００℃まで昇温し、所定時間保持する方法
（２）金属含有有機化合物を不活性ガスの存在下に室温から１５０℃〜５００℃までに昇温し所定時間保持する。次いで、室温まで冷却した上で粉砕する。次に、所定時間保持した後、６００〜１２００℃まで昇温し、所定時間保持する方法
なお、後炭化処理に際しては、賦活剤を系内に添加することが好ましい。 The specific example of the manufacturing method of the metal containing carbide | carbonized_material which concerns on this invention is shown below.
(1) A method in which a metal-containing organic compound is heated from room temperature to 150 ° C. to 500 ° C. in the presence of an inert gas and held for a predetermined time, and then heated to 600 to 1200 ° C. and held for a predetermined time (2 ) The metal-containing organic compound is heated from room temperature to 150 ° C. to 500 ° C. in the presence of an inert gas and held for a predetermined time. Then, it is pulverized after cooling to room temperature. Next, after holding for a predetermined time, the temperature is raised to 600 to 1200 ° C. and holding for a predetermined time. In the post-carbonization treatment, it is preferable to add an activator to the system.

本発明方法で製造した金属含有炭化物は、特に固体高分子形燃料電池の電極に用いる触媒として、極めて優れた性質を有する。   The metal-containing carbide produced by the method of the present invention has extremely excellent properties particularly as a catalyst used for an electrode of a polymer electrolyte fuel cell.

本発明の金属含有炭化物としては、２価鉄イオンを含むものが好適である。３価鉄イオンの触媒活性は比較的低く、従来の触媒は、固体高分子形燃料電池の電極触媒としては十分ではなかった。しかし、本発明方法で製造された金属含有炭化物は２価鉄イオンを含み、固体高分子形燃料電池の電極触媒として極めて優れている。２価鉄イオンの含有量は、メスバウア分光法により測定することができる。   As the metal-containing carbide of the present invention, those containing divalent iron ions are suitable. The catalytic activity of trivalent iron ions is relatively low, and conventional catalysts have not been sufficient as electrode catalysts for polymer electrolyte fuel cells. However, the metal-containing carbide produced by the method of the present invention contains divalent iron ions and is extremely excellent as an electrode catalyst for a polymer electrolyte fuel cell. The content of divalent iron ions can be measured by Mossbauer spectroscopy.

当該金属含有炭化物は、鉄−窒素結合を有するものが好ましい。窒素原子の孤立電子対に配位した鉄原子は比較的安定であり、且つ良好な触媒活性を発揮することができる。鉄−窒素結合は、メスバウア分光測定や広域Ｘ線吸収微細構造（ＥＸＡＦＳ）により測定することができる。   The metal-containing carbide is preferably one having an iron-nitrogen bond. An iron atom coordinated to a lone pair of nitrogen atoms is relatively stable and can exhibit good catalytic activity. The iron-nitrogen bond can be measured by Mossbauer spectroscopy or wide-area X-ray absorption fine structure (EXAFS).

本発明の金属含有炭化物は、触媒活性が高い上に優れた導電性を有することから、電極、特に酸素還元電極の材料として極めて優れる。本発明の電極は、特にアニオン交換型高分子電解質を用いた燃料電池において、白金触媒を用いた電極に匹敵するほどの高い酸素還元性能を示すことから、空気極の電極として特に有用である。   Since the metal-containing carbide of the present invention has high catalytic activity and excellent conductivity, it is extremely excellent as a material for electrodes, particularly oxygen reduction electrodes. The electrode of the present invention is particularly useful as an electrode for an air electrode because it exhibits high oxygen reduction performance comparable to an electrode using a platinum catalyst, particularly in a fuel cell using an anion exchange type polymer electrolyte.

本発明に係る電極は、本発明の金属含有炭化物の他に、イオン伝導性物質を含有する。カチオン交換型高分子電解質を用いた燃料電池の場合、イオン伝導性物質は、触媒反応により燃料から生じたプロトンを高分子電解質膜へ、さらに高分子電解質膜から正極触媒へ送達する役割を有する。例えば、ナフィオン（デュポン社製）、アシプレックス（旭化成（株）製）、フレミオン（旭硝子（株）製）などのスルホン酸基を有するフッ素樹脂や、タングステン酸、リンタングステン酸などの無機物などを、イオン伝導性物質として使用することができる。   The electrode according to the present invention contains an ion conductive substance in addition to the metal-containing carbide of the present invention. In the case of a fuel cell using a cation exchange type polymer electrolyte, the ion conductive substance has a role of delivering protons generated from the fuel by the catalytic reaction to the polymer electrolyte membrane and further from the polymer electrolyte membrane to the positive electrode catalyst. For example, fluorine resins having a sulfonic acid group such as Nafion (manufactured by DuPont), Aciplex (manufactured by Asahi Kasei Co., Ltd.), Flemion (manufactured by Asahi Glass Co., Ltd.), inorganic substances such as tungstic acid and phosphotungstic acid, It can be used as an ion conductive substance.

アニオン交換型高分子電解質を用いた燃料電池の場合、イオン伝導性物質は、触媒反応により酸素から生じた水酸化物イオンを高分子電解質膜へ、さらに高分子電解質膜から負極触媒へ送達する役割を担っている。例えば、芳香族ポリエーテルスルホン酸と芳香族ポリチオエーテルスルホン酸の共重合体のクロロメチル化物をアミノ化して得られるアニオン交換樹脂や、スルホン酸基を有するパーフルオロカーボンポリマーの末端をジアミンで処理して４級化したポリマーなどを、イオン伝導性物質として使用することができる。   In the case of a fuel cell using an anion exchange type polymer electrolyte, the ion-conducting substance plays a role in delivering hydroxide ions generated from oxygen by a catalytic reaction to the polymer electrolyte membrane and from the polymer electrolyte membrane to the negative electrode catalyst. Is responsible. For example, an anion exchange resin obtained by amination of a chloromethylated copolymer of an aromatic polyether sulfonic acid and an aromatic polythioether sulfonic acid or a perfluorocarbon polymer having a sulfonic acid group is treated with a diamine. A quaternized polymer or the like can be used as the ion conductive substance.

本発明の電極組成物におけるイオン伝導性物質の割合については、電極としたときに必要なプロトン伝導性やアニオン伝導性が得られるように適宜決定すればよい。例えば、金属含有炭化物１００質量部に対してイオン伝導性物質を１０〜４００質量部の割合で適宜配合すればよい。   What is necessary is just to determine suitably about the ratio of the ion conductive substance in the electrode composition of this invention so that the proton conductivity and anion conductivity required when it may be set as an electrode will be obtained. For example, what is necessary is just to mix | blend an ion conductive substance suitably in the ratio of 10-400 mass parts with respect to 100 mass parts of metal containing carbide | carbonized_materials.

本発明に係る固体高分子形燃料電池は、上記電極を含む。   The polymer electrolyte fuel cell according to the present invention includes the electrode.

本発明の固体高分子形燃料電池は、本発明の金属含有炭化物を用いて、常法により製造することができる。固体高分子型燃料電池の電極（アノードとカソード）は、高分子電解質膜側の触媒層と、その外側のガス拡散層からなる。このガス拡散層としては、優れたガス透過性と導電性を有するものとして、厚さ１００〜３００μｍ程度のカーボンペーパーやカーボンクロスが用いられる。これらカーボンペーパー等は、例えばポリテトラフルオロエチレン（ＰＴＦＥ）などで撥水処理を施してもよい。よって、本発明の電極組成物により電極を形成する場合には、本発明の金属含有炭化物およびイオン伝導性物質へ、必要に応じて撥水材やバインダーなどを加え、水やイソプロピルアルコールなどの有機溶媒と均一混合してペーストを調製し、これをカーボンペーパーなどのガス拡散層に塗布後、乾燥することによって、電極を形成することができる。   The polymer electrolyte fuel cell of the present invention can be produced by a conventional method using the metal-containing carbide of the present invention. The electrodes (anode and cathode) of the polymer electrolyte fuel cell are composed of a catalyst layer on the polymer electrolyte membrane side and a gas diffusion layer on the outside thereof. As this gas diffusion layer, carbon paper or carbon cloth having a thickness of about 100 to 300 μm is used as having excellent gas permeability and conductivity. These carbon papers may be subjected to water repellent treatment with, for example, polytetrafluoroethylene (PTFE). Therefore, when an electrode is formed from the electrode composition of the present invention, a water-repellent material or a binder is added to the metal-containing carbide and ion-conducting material of the present invention as necessary, and an organic material such as water or isopropyl alcohol is added. An electrode can be formed by preparing a paste by uniformly mixing with a solvent, applying this to a gas diffusion layer such as carbon paper, and then drying.

得られたアノードとカソードは、高分子電解質膜を間に挟んでホットプレスすることによって、膜電極接合体とすることができる。この際、各電極において、触媒層が高分子電解質膜に接する様に配置する必要がある。また、ホットプレスにおける圧力や温度は、常法の条件に従えばよい。   The obtained anode and cathode can be made into a membrane electrode assembly by hot pressing with a polymer electrolyte membrane interposed therebetween. At this time, in each electrode, it is necessary to dispose the catalyst layer in contact with the polymer electrolyte membrane. Moreover, the pressure and temperature in a hot press should just follow the conditions of a conventional method.

得られた膜電極接合体は、セパレータなどと共に、常法に従って固体高分子型燃料電池とすることができる。こうして得られた本発明の固体高分子型燃料電池は、高性能の電極触媒を有することから発電性能に極めて優れる。よって、本発明の固体高分子型燃料電池は、携帯機器や自動車用の電源、或いは家庭用の発電システムなどに適するものである。   The obtained membrane electrode assembly can be made into a polymer electrolyte fuel cell according to a conventional method together with a separator and the like. The solid polymer fuel cell of the present invention thus obtained has extremely high power generation performance because it has a high-performance electrode catalyst. Therefore, the polymer electrolyte fuel cell of the present invention is suitable for portable devices, automobile power supplies, household power generation systems, and the like.

以下、実施例を挙げて本発明をより具体的に説明するが、本発明はもとより下記実施例により制限を受けるものではなく、前・後記の趣旨に適合し得る範囲で適当に変更を加えて実施することも可能であり、それらはいずれも本発明の技術的範囲に含まれる。   EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. It is also possible to implement, and they are all included in the technical scope of the present invention.

触媒調製例１
金属を含有する有機化合物であるヘモグロビン（１６ｇ）を真空ガス置換炉（デンケン社製、製品名：ＫＤＦ−７５）に入れ、不活性ガスであるアルゴン気流下、昇温速度：５℃／分で３５０℃まで昇温し、３５０℃で１０時間保持して第一炭化処理を行った。その後、室温まで冷却し、得られた第一炭化物を粉砕した。さらに、ＣＯ2を１０％含有するアルゴン気流下、当該第一炭化物を昇温速度５℃／分で９００℃まで昇温し、９００℃で２時間保持して第二炭化処理を行った。次いで、室温まで冷却後、第二炭化物を粉砕した。得られた炭化物粉体を０．５ｍｏｌ／リットルの硫酸水溶液中で１時間煮沸後、超純水で十分に洗浄した。次いで、炭化物を濾別し、真空乾燥することによって、金属成分を含有する炭化物材料Ａを得た。 Catalyst preparation example 1
Hemoglobin (16 g), which is an organic compound containing metal, is placed in a vacuum gas replacement furnace (product name: KDF-75, manufactured by Denken) and heated at a rate of temperature of 5 ° C./min under an argon stream as an inert gas. The temperature was raised to 350 ° C. and held at 350 ° C. for 10 hours to perform the first carbonization treatment. Then, it cooled to room temperature and grind | pulverized the obtained 1st carbide | carbonized_material. Further, in a stream of argon containing 10% CO 2 , the first carbide was heated to 900 ° C. at a temperature increase rate of 5 ° C./min, and held at 900 ° C. for 2 hours to perform a second carbonization treatment. Next, after cooling to room temperature, the second carbide was pulverized. The obtained carbide powder was boiled in a 0.5 mol / liter sulfuric acid aqueous solution for 1 hour, and then sufficiently washed with ultrapure water. Next, the carbide was filtered off and vacuum-dried to obtain a carbide material A containing a metal component.

触媒調製例２
第二炭化処理におけるＣＯ2濃度を２５％と変更した以外は、触媒調製例１と同様にして、金属成分を含有する炭化物材料Ｂを調製した。 Catalyst preparation example 2
A carbide material B containing a metal component was prepared in the same manner as in Catalyst Preparation Example 1, except that the CO 2 concentration in the second carbonization treatment was changed to 25%.

触媒調製例３
第二炭化処理におけるＣＯ2濃度を５０％と変更した以外は、触媒調製例１と同様にして、金属成分を含有する炭化物材料Ｃを調製した。 Catalyst preparation example 3
A carbide material C containing a metal component was prepared in the same manner as in Catalyst Preparation Example 1 except that the CO 2 concentration in the second carbonization treatment was changed to 50%.

触媒調製例４
第二炭化処理におけるＣＯ2濃度を７５％と変更した以外は、触媒調製例１と同様にして、金属成分を含有する炭化物材料Ｄを調製した。 Catalyst preparation example 4
A carbide material D containing a metal component was prepared in the same manner as in Catalyst Preparation Example 1, except that the CO 2 concentration in the second carbonization treatment was changed to 75%.

触媒調製例５
第二炭化処理において、ＣＯ2を用いなかった以外は、触媒調製例１と同様にして、金属成分を含有する炭化物材料Ｅを調製した。 Catalyst preparation example 5
A carbide material E containing a metal component was prepared in the same manner as in Catalyst Preparation Example 1 except that CO 2 was not used in the second carbonization treatment.

触媒調製例６
金属を含有する有機化合物であるヘモグロビン（１６ｇ）を真空ガス置換炉（デンケン社製、製品名：ＫＤＦ−７５）に入れ、不活性ガスであるアルゴン気流下、昇温速度：５℃／分で８５０℃まで昇温し、８５０℃で２時間保持して炭化処理を行った。次いで、室温まで冷却し、得られた炭化物を粉砕した。得られた炭化物粉体を０．５ｍｏｌ／リットルの硫酸水溶液中で１時間煮沸後、超純水で十分に洗浄した。次いで、炭化物を濾別し、真空乾燥することによって、金属成分を含有する炭化物材料Ｆを得た。 Catalyst preparation example 6
Hemoglobin (16 g), which is an organic compound containing metal, is placed in a vacuum gas replacement furnace (product name: KDF-75, manufactured by Denken) and heated at a rate of temperature of 5 ° C./min under an argon stream as an inert gas. The temperature was raised to 850 ° C. and kept at 850 ° C. for 2 hours for carbonization treatment. Subsequently, it cooled to room temperature and grind | pulverized the obtained carbide | carbonized_material. The obtained carbide powder was boiled in a 0.5 mol / liter sulfuric acid aqueous solution for 1 hour, and then sufficiently washed with ultrapure water. Next, the carbide was filtered off and vacuum-dried to obtain a carbide material F containing a metal component.

触媒調製例７
炭化処理温度を８２５℃と変更した以外は、触媒調製例６と同様にして、金属成分を含有する炭化物材料Ｇを調製した。 Catalyst preparation example 7
A carbide material G containing a metal component was prepared in the same manner as in Catalyst Preparation Example 6 except that the carbonization temperature was changed to 825 ° C.

上記触媒調製例１〜７で得られた金属成分を含有する炭化物材料について、炭化処理前後の質量変化から収率を求めた。また、Ｎ2吸着量測定結果より、比表面積を算出した。これらを表１に示す。 About the carbide | carbonized_material containing the metal component obtained in the said catalyst preparation examples 1-7, the yield was calculated | required from the mass change before and behind carbonization. Further, from the N 2 adsorption amount measurement results it was calculated a specific surface area. These are shown in Table 1.

Figure 2008222486
Figure 2008222486

比較的低温での第一炭化処理を行わず、かつ、賦活剤を用いずアルゴン気流下で高温での炭化処理を行った場合、炭化温度を８５０℃とした触媒調製例６では、収率が１．９％と極めて低かった。そこで、触媒調製例７では炭化温度を８２５℃としたところ、１１．５％の収率で炭化物を得ることができた。上記結果より、比較的低温での第一炭化処理を行わずに一段で炭化処理を行うと、８５０℃以上では収率良く炭化物が得られないことがわかる。   In the catalyst preparation example 6 in which the carbonization temperature was 850 ° C. when the first carbonization treatment at a relatively low temperature was not performed and the carbonization treatment was performed at a high temperature under an argon stream without using an activator, the yield was low. It was extremely low at 1.9%. Thus, in Catalyst Preparation Example 7, when the carbonization temperature was set to 825 ° C., a carbide could be obtained with a yield of 11.5%. From the above results, it can be seen that if the carbonization process is performed in a single stage without performing the first carbonization process at a relatively low temperature, a carbide cannot be obtained with a good yield at 850 ° C. or higher.

一方、アルゴン気流下、３５０℃で第一炭化処理を行い、二段階で炭化処理を行った場合、アルゴン気流下、二段階目の炭化処理で温度を９００℃とした触媒調製例５では、収率は１７．５％と高かった。しかし、得られた炭化物材料Ｅでは、細孔発達が不十分であり、比表面積は１３９ｍ2／ｇと低いものとなった。 On the other hand, when the first carbonization treatment was performed at 350 ° C. under an argon stream and the carbonization treatment was performed at two stages, the catalyst preparation example 5 in which the temperature was 900 ° C. at the second stage carbonization treatment under an argon stream was The rate was as high as 17.5%. However, in the obtained carbide material E, pore development was insufficient, and the specific surface area was as low as 139 m 2 / g.

二段階目の高温炭化処理を賦活剤であるＣＯ2存在下で行った触媒調製例１〜４では、賦活により収率は低下傾向にあるが、比表面積は賦活剤を用いない触媒調製例５と比較して大幅に増加した。 In Catalyst Preparation Examples 1 to 4 in which the second stage high-temperature carbonization treatment was performed in the presence of CO 2 as an activator, the yield tends to decrease due to activation, but the specific surface area is a catalyst preparation example 5 using no activator. Compared with the increase.

試験例１ 酸性環境下での酸素還元性能
触媒調製例１〜５および７で得た炭化物材料Ａ〜ＥおよびＧを用いて作成した触媒層の酸素還元反応に対する活性評価を、回転電極法に準拠して行った。回転電極法は、例えば、“ジャーナル・オブ・ザ・エレクトロケミカル・ソサイアティー、第１４５巻、１９９８年、第３７１３頁”や、“ジャーナル・オブ・ザ・エレクトロケミカル・ソサイアティー、第１４６巻、１９９９年、第１２９６頁”等において、固体高分子電解質形燃料電池の電極触媒活性の評価に有効であり、かつ、燃料電池性能と良好な相関性があることが報告されている。 Test Example 1 Oxygen reduction performance in an acidic environment The activity evaluation for the oxygen reduction reaction of the catalyst layer prepared using the carbide materials A to E and G obtained in Catalyst Preparation Examples 1 to 5 and 7 is based on the rotating electrode method. I went there. Examples of the rotating electrode method include “Journal of the Electrochemical Society, Vol. 145, 1998, p. 3713” and “Journal of the Electrochemical Society, Vol. 146, 1999”. , Page 1296 ", etc., are reported to be effective for evaluating the electrocatalytic activity of solid polymer electrolyte fuel cells and to have good correlation with fuel cell performance.

詳しくは、触媒調製例１〜５および７で得た炭化物材料Ａ〜ＥおよびＧと、カーボンブラック（キャボット社製、 商標名：Ｖｕｌｃａｎ ＸＣ−７２Ｒ）を、５重量％パーフルオロスルホン酸樹脂溶液（アルドリッチ社製）に加え、超音波により分散させて触媒ペーストを調製した。当該触媒ペーストを回転グラッシーカーボンディスク電極に塗布し、室温で十分に乾燥させて電極触媒層を形成した。触媒層を形成した回転電極を、酸素で飽和した２５℃の０．１ｍｏｌ／リットル過塩素酸水溶液中に浸漬し、可逆水素電極（ＲＨＥ）を参照極として酸素還元電流と電極電位との関係を測定した。測定結果を図１に示す。   Specifically, the carbide materials A to E and G obtained in Catalyst Preparation Examples 1 to 5 and 7, carbon black (trade name: Vulcan XC-72R, manufactured by Cabot Corporation), and a 5 wt% perfluorosulfonic acid resin solution ( In addition to Aldrich, a catalyst paste was prepared by dispersing with ultrasonic waves. The catalyst paste was applied to a rotating glassy carbon disk electrode and sufficiently dried at room temperature to form an electrode catalyst layer. The rotating electrode on which the catalyst layer was formed was immersed in a 0.1 mol / liter perchloric acid aqueous solution saturated with oxygen at 25 ° C., and the relationship between the oxygen reduction current and the electrode potential was determined using a reversible hydrogen electrode (RHE) as a reference electrode. It was measured. The measurement results are shown in FIG.

図１の通り、二段階で炭化処理した炭化物材料Ｅでは、一段階で炭化処理して製造した炭化物材料Ｇと比較して、酸素還元能が向上した。そしてさらに、二段階の炭化処理を行い、且つ高温での二段階目の炭化処理においてＣＯ2ガスを共存させて製造した炭化物材料Ａ〜Ｄの酸素還元性能は、大幅に優れることがわかった。これら炭化物材料が優れた酸素還元能を有するのは、二段階の炭化により２価の鉄イオンを含むためと考えられる。また、炭化物材料Ａ〜Ｄの酸素還元性能が優れるのは、高温での炭化処理の際に賦活剤を用いたことにより、細孔が発達して表面積が高まったことによると考えられる。 As shown in FIG. 1, in the carbide material E carbonized in two stages, the oxygen reducing ability was improved as compared with the carbide material G manufactured by carbonization in one stage. Furthermore, it was found that the oxygen reduction performance of the carbide materials A to D produced by performing the two-stage carbonization treatment and coexisting CO 2 gas in the second-stage carbonization treatment at a high temperature was greatly improved. The reason why these carbide materials have an excellent oxygen reducing ability is considered to be because they contain divalent iron ions by two-stage carbonization. Further, it is considered that the oxygen reduction performance of the carbide materials A to D is excellent because the pores are developed and the surface area is increased by using the activator during the carbonization treatment at a high temperature.

試験例２ アルカリ環境下での酸素還元性能
触媒調製例２、４および５で得た炭化物材料Ｂ、ＤおよびＥを用いて触媒層を形成し、アルカリ環境下での酸素還元反応に対する活性を評価した。加えて、市販のＰｔ系触媒（Ｅｌｅｃｔｒｏｃｈｅｍ社製、商標名：Ｖｕｌｃａｎ ＸＣ−７２）を、Ｐｔ担持量：２０質量％でカーボンブラック（キャボット社製）に担持したもの、およびＡｇ系触媒（Ｅ−ＴＥＫ社製、商標名：Ｖｕｌｃａｎ ＸＣ−７２）を、Ａｇ担持量：６０質量％でカーボンブラック（キャボット社製）に担持したものについても、同様に酸素還元反応に対する活性を評価した。 Test Example 2 Oxygen reduction performance in an alkaline environment A catalyst layer was formed using the carbide materials B, D and E obtained in Catalyst Preparation Examples 2, 4 and 5, and the activity for an oxygen reduction reaction in an alkaline environment was evaluated. did. In addition, a commercially available Pt-based catalyst (trade name: Vulcan XC-72, manufactured by Electrochem Co., Ltd.) supported on carbon black (manufactured by Cabot) at a Pt loading amount of 20% by mass, and an Ag-based catalyst (E- The activity against the oxygen reduction reaction was similarly evaluated for a product in which TEK, trade name: Vulcan XC-72) was supported on carbon black (manufactured by Cabot) with an Ag loading: 60% by mass.

具体的には、炭化物材料とカーボンブラック（キャボット社製、商標名：Ｖｕｌｃａｎ ＸＣ−７２Ｒ）を、２．５重量％アニオン交換樹脂溶液に加え、超音波により分散させて触媒ペーストを調製した。当該触媒ペーストを回転グラッシーカーボンディスク電極に塗布し、室温で十分に乾燥させて電極触媒層を形成した。触媒層を形成した回転電極を、酸素で飽和した２５℃の１ｍｏｌ／リットル水酸化カリウム水溶液中に浸漬し、可逆水素電極（ＲＨＥ） を参照極として酸素還元電流と電極電位との関係を測定した。なお、市販のＰｔ系、Ａｇ系触媒を用いた触媒層形成では、カーボンブラック（キャボット社製、商標名：Ｖｕｌｃａｎ ＸＣ−７２Ｒ）を加えなかった以外は、上記と同様にして触媒層を形成した。測定結果を図２に示す。   Specifically, a carbide paste and carbon black (trade name: Vulcan XC-72R, manufactured by Cabot Corporation) were added to a 2.5 wt% anion exchange resin solution, and dispersed by an ultrasonic wave to prepare a catalyst paste. The catalyst paste was applied to a rotating glassy carbon disk electrode and sufficiently dried at room temperature to form an electrode catalyst layer. The rotating electrode on which the catalyst layer was formed was immersed in a 1 mol / liter potassium hydroxide aqueous solution saturated with oxygen at 25 ° C., and the relationship between the oxygen reduction current and the electrode potential was measured using a reversible hydrogen electrode (RHE) as a reference electrode. . In the catalyst layer formation using a commercially available Pt-based and Ag-based catalyst, a catalyst layer was formed in the same manner as above except that carbon black (trade name: Vulcan XC-72R, manufactured by Cabot Corporation) was not added. . The measurement results are shown in FIG.

図２の通り、二段階の炭化処理を行い、且つ高温での二段階目の炭化処理においてＣＯ2ガスを共存させて製造した炭化物材料ＢとＤの酸素還元性能は、二段階で炭化処理はしたが賦活剤を用いなかった炭化物材料Ｅよりも、大幅に優れることがわかった。また、その触媒性能は、市販のＡｇ系触媒よりも高く、Ｐｔ系触媒の性能に匹敵するものであった。 As shown in FIG. 2, the oxygen reduction performance of the carbide materials B and D produced by performing the two-stage carbonization treatment and coexisting CO 2 gas in the second-stage carbonization treatment at a high temperature is as follows. However, it was found to be significantly better than the carbide material E that did not use an activator. Moreover, the catalyst performance was higher than that of a commercially available Ag-based catalyst, and was comparable to that of a Pt-based catalyst.

以上の結果より、本発明に係る炭化物材料は、酸素還元反応に対して優れた活性を有しており、特にアルカリ環境下での使用においては、Ｐｔ担持カーボンブラック触媒に匹敵する活性を発揮することが可能である。従って、本発明に係る炭化物材料は、アニオン交換膜を電解質膜とする固体アルカリ形燃料電池での正極触媒として有用である。   From the above results, the carbide material according to the present invention has an excellent activity for the oxygen reduction reaction, and exhibits an activity comparable to that of a Pt-supported carbon black catalyst, particularly when used in an alkaline environment. It is possible. Therefore, the carbide material according to the present invention is useful as a positive electrode catalyst in a solid alkaline fuel cell having an anion exchange membrane as an electrolyte membrane.

本発明に係る金属含有炭化物は、特異的な物性を有することで触媒として作用し、特に固体高分子形燃料電池の電極触媒として用いることができる。   The metal-containing carbide according to the present invention acts as a catalyst by having specific physical properties, and can be used particularly as an electrode catalyst for a polymer electrolyte fuel cell.

図１は試験例１の結果を示すものであり、横軸は触媒層の酸素還元活性の指標となる電流値Ｉｋの対数値であり、縦軸は電極電位である。FIG. 1 shows the results of Test Example 1. The horizontal axis represents the logarithmic value of the current value Ik that serves as an index of the oxygen reduction activity of the catalyst layer, and the vertical axis represents the electrode potential. 図２は試験例２の結果を示すものであり、横軸は触媒層の酸素還元活性の指標となる電流値Ｉｋの対数値であり、縦軸は電極電位である。FIG. 2 shows the results of Test Example 2. The horizontal axis is a logarithmic value of the current value Ik that serves as an index of the oxygen reduction activity of the catalyst layer, and the vertical axis is the electrode potential.

Claims (9)

金属含有炭化物を製造する方法であって、
金属を含有する有機化合物を二段階で炭化処理するものであり；
一段階目の炭化処理の温度を１５０〜５００℃とし；且つ
二段階目の炭化処理の温度を６００〜１２００℃とすることを特徴とする方法。 A method for producing a metal-containing carbide comprising:
Carbonizing organic compounds containing metals in two stages;
The temperature of the carbonization process of the 1st step shall be 150-500 degreeC; and the temperature of the carbonization process of the 2nd step shall be 600-1200 degreeC. 二段階目の炭化処理を、賦活剤の存在下で行う請求項１に記載の方法。   The method according to claim 1, wherein the second stage carbonization is performed in the presence of an activator. 賦活剤として、二酸化炭素、水蒸気、空気、酸素、アルカリ金属水酸化物、塩化亜鉛、およびリン酸からなる群より選択される少なくとも１種を用いる請求項２に記載の方法。   The method according to claim 2, wherein at least one selected from the group consisting of carbon dioxide, water vapor, air, oxygen, alkali metal hydroxide, zinc chloride, and phosphoric acid is used as the activator. 請求項１〜３の何れかに記載の製造方法により得られることを特徴とする金属含有炭化物。   A metal-containing carbide obtained by the production method according to claim 1. ２価鉄イオンを含む請求項４に記載の金属含有炭化物。   The metal-containing carbide according to claim 4, comprising divalent iron ions. 鉄−窒素結合を有する請求項４または５に記載の金属含有炭化物。   The metal-containing carbide according to claim 4 or 5, which has an iron-nitrogen bond. 請求項４〜６の何れか１項に記載の金属含有炭化物を含むことを特徴とする電極。   An electrode comprising the metal-containing carbide according to any one of claims 4 to 6. 請求項４〜６の何れか１項に記載の金属含有炭化物を含むことを特徴とする酸素還元電極。   An oxygen reduction electrode comprising the metal-containing carbide according to any one of claims 4 to 6. 請求項８に記載の酸素還元電極を含むことを特徴とする固体高分子形燃料電池。   A solid polymer fuel cell comprising the oxygen reduction electrode according to claim 8.
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