【発明の詳細な説明】[Detailed description of the invention]
本発明は、空気電池や燃料電池などに使用する
空気極触媒の製造方法に関し、更に詳しくは、優
れた放電特性を有する空気極触媒の製造方法に関
するものである。
従来、カーボンブラツク又は活性炭などの炭素
体に遷移金属の硝酸塩水溶液を含浸させ、次に加
熱処理し、更に必要に応じて還元して、炭素体の
表面に金属もしくは金属酸化物を付着せしめてい
たが、炭素体の表面は多数の気胞が存在するこ
と、一般に疎水性であること、細孔分布が不
均一であること、から金属塩の水溶液を炭素体に
完全に含浸することができないため、金属は炭素
体表面に均一に付着し難い。従つて、触媒の有効
反応面積が小さく、放電特性、特に高放電率の電
導特性が悪い原因となつていた。
そこで、本発明者等は、炭素体表面の性質に着
目し、炭素体表面に金属を均一に付着させる方法
を種々検討の結果遂に本発明を完成したものであ
つて、即ち、本発明は、炭素体に遷移金属塩の少
なくとも１種を溶解した油性溶媒の溶液を含浸さ
せ熱処理し、更に必要に応じて還元し、炭素体の
表面に遷移金属の酸化物もしくは遷移金属を付着
せしめたことを特徴とする空気極触媒の製造方法
を要旨とするものである。
本発明の製造方法で得られる空気極触媒は、遷
移金属塩として、油性溶剤に溶解しやすいものを
使用しており、このため溶媒として水を使用した
場合に比較して、油性溶媒を使用したものは炭素
体の表面の気胞や疎水性に影響されることなく、
均一に炭素体に含浸し、熱処理更には還元するこ
とにより炭素体表面に金属が均一に付着している
ため、放電特性が向上するものと推考される。
以下、本発明について詳細に説明する。
本発明に使用する炭素体として一般に使用され
ているフアーネスブラツク、チヤンネルブラツ
ク、サーマルブラツクなどのカーボンブラツク
や、木材、木炭、ヤシ殻炭、パーム核炭、石炭、
石油調査、合成樹脂、有機廃棄物などを使用して
作られた活性炭、黒鉛などの１種もしくは２種以
上の混合物が挙げられる。
次に本発明の骨子である遷移金属塩は油性溶媒
に溶解する金属塩であり、具体例を挙げるとニツ
ケル、コバルト、クロム、金、銀、白金、パラジ
ウム、マンガンなどのナフテン酸塩やロジン塩な
どがあり特にナフテン酸塩やロジン塩は熱分解し
やすくこれらを単独もしくは混合して使用可能で
あり、その使用量は炭素体に対して５〜40重量％
特に20〜30重量％が好ましい。
油性溶媒としては、ほとんどすべて使用可能で
あるが、特に芳香族系有機溶媒のような無極性溶
媒が好ましく、具体例を挙げるとトルエン、キシ
レン、ベンゼンなどがあり、その使用量は、炭素
体に対して50〜200重量％が好ましい。
上記した物質を使用して、空気極触媒を製造す
るが、まず始めに炭素体を遷移金属塩を溶解した
油性溶媒の溶液に分散させ、１〜３時間撹拌し、
更に炭素体とのなじみをよくするためにその後１
〜２日間放置することが好ましい。
このようにして炭素体に溶液を含浸させた後、
減圧下で油性溶媒を除去する。得られた残留物
を、乳鉢などを使用し粉砕後、該粉砕物を窒素、
ヘリウムなどの不活性ガスの気泡中の電気炉で
300〜400℃で１〜３時間処理することにより炭素
体表面に遷移金属の酸化物を均一に付着させ、更
に必要に応じて還元し空気極触媒を得ることがで
きる。
以下、実施例に従い、本発明を更に詳細に説明
するが、実施例中「部」とあるのは「重量部」を
示す。
実施例 １
粒径0.1〜１μのヤシ殻活性炭10部をトルエン
50部に分散させ、ナフテン酸コバルト（ナフテン
酸ナトリウム100部と塩化コバルト10部より得ら
れる）の５％トルエン溶液50部を添加し、１時間
撹拌後、減圧下でトルエンを除去し、残留物を乳
鉢で粉砕し、窒素気流中の電気炉で300℃２時間
加熱処理後、水素気流中の電気炉で300℃２時間
還元処理することにより活性炭表面にコバルトを
均一に付着せしめた空気極触媒を得た。
比較例 １
粒径0.1〜１μのヤシ殻活性炭10部を実施例１
とコバルトの含有量が同一となるような塩化コバ
ルト水溶液に分散し、１時間撹拌後、水分を除去
し、加熱処理還元処理は実施例１と同様にして活
性炭表面にコバルトを付着せしめた空気極触媒を
得た。
実施例 ２
粒径0.1〜１μのヤシ殻活性炭をベンゼン50部
に分散させ、ナフテン酸銀（ナフテン酸ナトリウ
ム100部と硝酸銀８部から得られる）の５％ベン
ゼン溶液50部を添加し、２時間撹拌後１日間放置
した。その後、減圧下でベンゼンを除去し、残留
物を乳鉢で粉砕し、窒素気流中の電気炉で350℃
３時間加熱処理後、水素気流中の電気炉で350℃
３時間還元処理することにより活性炭表面に銀を
均一に付着せしめた空気極触媒を得た。
比較例 ２
粒径0.1〜１μのヤシ殻活性炭10部を実施例２
と銀の含有量が同一となるような硝酸銀水溶液に
分散し、２時間撹拌後、１日放置し、水分を除去
し、加熱処理還元処理は実施例２と同様にして活
性炭表面に銀を付着せしめた空気極触媒を得た。
実施例 ３
実施例１中のナフテン酸コバルトの代わりにロ
ジン酸コバルト（ロジン酸ナトリウム100部と塩
化コバルト60部より得られる）を使用した他は実
施例１と同様にして空気極触媒を得た。
実施例 ４
実施例２中のナフテン酸銀の代わりにロジン酸
銀（ロジン酸ナトリウム100部と硝酸銀24部より
得られる）を使用した他は実施例２と同様にして
空気極触媒を得た。
実施例 ５
粒径0.1〜１μのヤシ殻活性炭10部をトルエン
50部に分散させ、ナフテン酸マンガン（ナフテン
酸ナトリウム100部と塩化マンガン10部より得ら
れる）の５％トルエン溶液50部、ナフテン酸クロ
ム（ナフテン酸ナトリウム100部と塩化クロム10
部より得られる）の５％トルエン溶液10部を添加
し、１時間撹拌後、減圧下でトルエンを除去し、
残留物を乳鉢で粉砕し、窒素気流中の電気炉で
400℃２時間処理することにより活性炭表面にマ
ンガン酸化物及びクロム酸化物が均一に付着した
空気極触媒を得た。
上述の実施例１〜５、比較例１、２の触媒を用
いて空気極を製造し、その分極特性を測定した結
果を表−１に示す。
The present invention relates to a method for manufacturing an air electrode catalyst used in air cells, fuel cells, etc., and more particularly, to a method for manufacturing an air electrode catalyst having excellent discharge characteristics. Conventionally, a carbon material such as carbon black or activated carbon was impregnated with an aqueous solution of transition metal nitrate, then heat treated, and further reduced if necessary to adhere metals or metal oxides to the surface of the carbon material. However, it is not possible to completely impregnate the carbon body with an aqueous solution of a metal salt because the surface of the carbon body has many gas pores, is generally hydrophobic, and has an uneven pore distribution. Metals are difficult to adhere uniformly to the surface of carbon bodies. Therefore, the effective reaction area of the catalyst is small, which causes poor discharge characteristics, particularly conductivity characteristics at high discharge rates. Therefore, the present inventors focused on the properties of the surface of the carbon body, and as a result of various studies on methods for uniformly depositing metal on the surface of the carbon body, the present invention was finally completed. A carbon body is impregnated with a solution of an oily solvent in which at least one transition metal salt is dissolved, heat-treated, and further reduced as necessary to adhere a transition metal oxide or a transition metal to the surface of the carbon body. The gist of this paper is a method for producing a characteristic air electrode catalyst. The air electrode catalyst obtained by the production method of the present invention uses a transition metal salt that is easily soluble in an oil-based solvent. The material is not affected by the air pores or hydrophobicity on the surface of the carbon body,
It is thought that the discharge characteristics are improved because the metal is evenly attached to the surface of the carbon body by uniformly impregnating the carbon body, heat-treating it, and further reducing the metal. The present invention will be explained in detail below. Carbon blacks such as furnace black, channel black, and thermal black, which are commonly used as carbon bodies used in the present invention, as well as wood, charcoal, coconut shell charcoal, palm kernel charcoal, and coal,
Examples include one or a mixture of two or more of activated carbon, graphite, etc. made from petroleum research, synthetic resin, organic waste, etc. Next, transition metal salts, which are the gist of the present invention, are metal salts that dissolve in oily solvents, and specific examples include naphthenates and rosin salts of nickel, cobalt, chromium, gold, silver, platinum, palladium, manganese, etc. In particular, naphthenates and rosin salts are easily thermally decomposed and can be used alone or in combination, and the amount used is 5 to 40% by weight based on the carbon body.
In particular, 20 to 30% by weight is preferred. Almost all oily solvents can be used, but nonpolar solvents such as aromatic organic solvents are particularly preferred.Specific examples include toluene, xylene, and benzene.The amount used depends on the carbon body. It is preferably 50 to 200% by weight. An air electrode catalyst is manufactured using the above-mentioned substance. First, the carbon body is dispersed in a solution of an oily solvent in which a transition metal salt is dissolved, and the mixture is stirred for 1 to 3 hours.
Furthermore, in order to improve the compatibility with the carbon body,
It is preferable to leave it for ~2 days. After impregnating the carbon body with the solution in this way,
Remove the oily solvent under reduced pressure. After pulverizing the obtained residue using a mortar or the like, the pulverized material is heated with nitrogen,
In an electric furnace in a bubble of inert gas such as helium
By treating at 300 to 400° C. for 1 to 3 hours, transition metal oxides can be uniformly deposited on the surface of the carbon body, and further reduced if necessary to obtain an air electrode catalyst. Hereinafter, the present invention will be described in more detail with reference to Examples, where "parts" in the Examples indicate "parts by weight." Example 1 10 parts of coconut shell activated carbon with a particle size of 0.1 to 1μ was added to toluene.
50 parts of a 5% toluene solution of cobalt naphthenate (obtained from 100 parts of sodium naphthenate and 10 parts of cobalt chloride) was added, and after stirring for 1 hour, the toluene was removed under reduced pressure to form a residue. is ground in a mortar, heated in an electric furnace in a nitrogen stream for 2 hours at 300℃, and then reduced in an electric furnace in a hydrogen stream for 2 hours at 300℃, resulting in an air electrode catalyst with cobalt uniformly adhered to the activated carbon surface. I got it. Comparative Example 1 10 parts of coconut shell activated carbon with a particle size of 0.1 to 1μ was added to Example 1.
An air electrode with cobalt adhered to the surface of the activated carbon was dispersed in an aqueous cobalt chloride solution having the same cobalt content as in Example 1. I got a catalyst. Example 2 Coconut shell activated carbon with a particle size of 0.1 to 1 μm was dispersed in 50 parts of benzene, and 50 parts of a 5% solution of silver naphthenate (obtained from 100 parts of sodium naphthenate and 8 parts of silver nitrate) in benzene was added for 2 hours. After stirring, the mixture was left for one day. Then, the benzene was removed under reduced pressure, the residue was ground in a mortar, and the residue was crushed in an electric furnace at 350°C in a nitrogen stream.
After 3 hours of heat treatment, heat at 350℃ in an electric furnace in a hydrogen stream.
By performing a reduction treatment for 3 hours, an air electrode catalyst with silver uniformly adhered to the surface of the activated carbon was obtained. Comparative Example 2 10 parts of coconut shell activated carbon with a particle size of 0.1 to 1μ was added to Example 2.
Dispersed in a silver nitrate aqueous solution with the same silver content as in Example 2, stirred for 2 hours, left for 1 day, removed water, heated and reduced in the same manner as in Example 2 to adhere silver to the activated carbon surface. An air electrode catalyst was obtained. Example 3 An air electrode catalyst was obtained in the same manner as in Example 1 except that cobalt rosinate (obtained from 100 parts of sodium rosinate and 60 parts of cobalt chloride) was used instead of cobalt naphthenate in Example 1. . Example 4 An air electrode catalyst was obtained in the same manner as in Example 2, except that silver rosinate (obtained from 100 parts of sodium rosinate and 24 parts of silver nitrate) was used instead of silver naphthenate in Example 2. Example 5 10 parts of coconut shell activated carbon with a particle size of 0.1 to 1μ was added to toluene.
50 parts of a 5% toluene solution of manganese naphthenate (obtained from 100 parts of sodium naphthenate and 10 parts of manganese chloride), 50 parts of a 5% toluene solution of manganese naphthenate (obtained from 100 parts of sodium naphthenate and 10 parts of chromium chloride)
Add 10 parts of a 5% toluene solution of (obtained from 1 part) and stir for 1 hour, then remove the toluene under reduced pressure.
The residue was ground in a mortar and then heated in an electric furnace under a nitrogen stream.
By treating at 400°C for 2 hours, an air electrode catalyst was obtained in which manganese oxide and chromium oxide were uniformly adhered to the activated carbon surface. Table 1 shows the results of manufacturing air electrodes using the catalysts of Examples 1 to 5 and Comparative Examples 1 and 2 and measuring their polarization characteristics.
【表】
以上のように本発明による空気極触媒は炭素体
の表面に均一の遷移金属が付着するため、大きい
電流密度においても高い電極電位を維持し、高放
電率の電極特性を改善することができるものであ
る。[Table] As described above, the air electrode catalyst according to the present invention has a uniform transition metal attached to the surface of the carbon body, so it maintains a high electrode potential even at high current density and improves the electrode characteristics at high discharge rates. It is something that can be done.