JP2004261739A - Hydrogen occlusion composite material - Google Patents
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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
Description
【０００１】
【発明の属する技術分野】
本発明は、水素吸蔵性が高く、かつ容易に水素を放出することができる水素吸蔵複合材料に関する。
【０００２】
【従来の技術】
自動車の動力源として、現在はガソリン、軽油を燃料とするレシプロエンジンが主流となっている。しかしながら、大気汚染等の社会問題と燃料の長期安定供給のエネルギー問題に対する対策から、既存のガソリン、軽油を代替する低公害でかつ長期安定供給可能な燃料が検討されている。このような代替燃料のうち、水素燃料は炭素を含まず、燃焼によって生ずるものは水であるため、いわゆる燃料電池自動車等が開発されている。
【０００３】
しかしながら、水素燃料の最大の問題は、その貯蔵法と運搬法にある。すなわち、水素を気体として貯蔵・輸送するには高圧ガスボンベが用いられ、このような高圧貯蔵は単純ではあるが、肉厚の容器が必要であり、そのため容器の重量が重くなり輸送・貯蔵性が低く、車載等への実用化には困難である。また、水素を液体として輸送・貯蔵する場合、気体水素にくらべて輸送・貯蔵性は向上するが、液体水素製造にはガスの液化に１６８ｃａｌの熱を除去しなければならず、液化温度が−２５２．６ ℃という低温であり、このような超低温用の特殊な容器が必要であるため経済的に問題がある。さらに、厳重にシールしても蒸発による消失を避けることはできない。
【０００４】
そこで最近、水素の貯蔵方法として水素吸蔵合金を用いることが提案され、一部実用化されている。水素吸蔵合金とは、適当な温度と圧力の条件において水素と反応し、金属水素化物を形成して、金属容積の数百倍〜１０００倍強もの水素を結晶格子間に貯蔵し、逆の分解反応により水素を放出するように設計された合金である。この水素吸蔵合金を用いた水素貯蔵方法は、安全性、効率、経済性の観点から上記の気体として又は液体として輸送・運搬する方法よりも有利である。
【０００５】
ところが、水素吸蔵合金は、水素を吸蔵・放出することによりその体積が約２０％も膨張・収縮するため、吸蔵−放出の繰り返しによって合金微粉化するという問題がある。このような問題を解決するため、水素吸蔵合金を炭素の海綿状多孔質体で取り囲むことが開示されている（例えば、特許文献１参照。）。
【０００６】
また、水素吸蔵合金は、合金自体の重量が重く、またＭｇ系の軽量な水素貯蔵合金ではその使用温度が２９０℃と高いといった問題があり、燃料として車載するには実用的でないという問題もある。このような問題を解決するため、多孔質炭素材料の表面に、水素分子を水素原子に分離させる機能を有する金属もしくは合金の被膜を形成し、水素原子を吸蔵させる方法が開示されている（例えば、特許文献２参照。）。
【０００７】
【特許文献１】
特開平６−１５８１９４号公報（第２頁、図１）
【特許文献２】
特開平１０−７２２０１号公報（第２〜３頁）
【０００８】
【発明が解決しようとする課題】
しかしながら、水素吸蔵合金単独では、その水素吸蔵量は現状では２ｗｔ％程度であり、更なる大幅軽量化が望まれる。また、炭素材料と水素吸蔵合金を組み合わせた場合には、水素吸蔵能の向上が認められるが、水素吸蔵時には３ＭＰａ以上の高水素圧を必要とし、また低温では常圧で吸蔵した水素を放出しないという問題がある。
【０００９】
本発明は、より常温、常圧に近い条件で水素の吸蔵・放出を可能とする水素吸蔵材を提供することを目的とする。
【００１０】
【課題を解決するための手段】
上記問題点を解決するために１番目の発明によれば、細孔を有する炭素材料の細孔中に、水素吸蔵合金を充填してなる水素吸蔵複合材料が提供される。
【００１１】
また、２番目の発明では上記問題点を解決するために１番目の発明において、前記炭素材料の細孔端部にパラジウム及び／又はバナジウムを担持させている。
【００１２】
また、３番目の発明では上記問題点を解決するために１番目又は２番目の発明において、前記炭素材料の細孔端部に、細孔内に充填された水素吸蔵合金よりも吸蔵圧力の高い水素吸蔵合金を担持させている。
【００１３】
また、４番目の発明では上記問題点を解決するために１〜３番目の発明において、前記炭素材料の細孔端部にニッケルを担持させている。
【００１４】
微構造をもつ炭素材料は弾性を有するものがあり、またある程度の伸びが可能である。従って、このような炭素材料の細孔内に水素吸蔵材料を充填しておくと、水素の吸蔵・放出によって水素吸蔵合金が体積変化を起こしても、その応力を緩和し、水素形状合金の微粉化による形状崩壊を防止することができる。また、炭素材料の細孔端部にパラジウム、バナジウム、ニッケル、あるいは所定の水素吸蔵合金を配置することにより、水素吸蔵・放出の際の圧力及び温度を改善し、並びに水素放出速度を向上させることができる。
【００１５】
【発明の実施の形態】
本発明の水素吸蔵複合材料は、基本的に細孔を有する炭素材料の細孔内に水素吸蔵合金を充填してなるものである。細孔を有する炭素材料としては、活性炭、グラファイト、カーボンナノチューブ等を用いることができる。活性炭は有機物を不活性雰囲気において焼成することにより得られる炭素質を、水蒸気や二酸化炭素と反応させることによって賦活化したものであり、この賦活化によって細孔構造が形成される。グラファイトは、炭素六面網面を基本ユニットとし、これがπ電子により結合した積層構造をとっており、この層間が細孔に相当する。また、カーボンナノチューブは、グラファイトの炭素六面網面を筒状にした形状であり、直径は数ｎｍ〜数十ｎｍ、長さは数μｍに及ぶものであり、このチューブのチューブ内空隙及びチューブ間が細孔に相当する。このカーボンナノチューブとしては、末端が開いた単層カーボンナノチューブを用いることが好ましい。
【００１６】
この炭素材料の細孔の大きさ（カーボンナノチューブの場合、細孔径、グラファイトの場合、層間距離）は、０．６ｎｍ〜２００ｎｍであることが好ましく、２〜５ｎｍであることがより好ましい。これらの炭素材料は、常法により製造することができ、また市販品を用いてもよい。
【００１７】
この炭素材料の細孔内に充填する水素吸蔵合金としては、従来より用いられている各種の水素吸蔵合金、例えばＭｇ、Ｍｇ２ Ｎｉ、Ｍｇ−Ｎｉ合金、ＢＣＣ合金等を用いることができ、このうち、Ｍｇ、Ｍｇ２ Ｎｉを用いることが好ましい。
【００１８】
上記のように、水素吸蔵合金は、水素を吸蔵するとその体積が２０％程度膨張するため、炭素材料の細孔をすべて満たすほど水素吸蔵合金を充填せず、充填率を細孔体積の８０％以下にすることが好ましい。また、十分な水素吸蔵量を確保するため、細孔体積の４０％以上充填することが好ましい。
【００１９】
炭素材料の細孔への水素吸蔵合金の充填は、例えば、水素吸蔵合金の蒸気中に炭素材料を保持することにより行われ、真空蒸着法、スパッタリング法、ＣＶＤ法等を用いることができる。炭素材料の細孔内のポテンシャルは細孔外よりも低いため、水素吸蔵合金の蒸気は細孔内に容易に侵入し、細孔の壁に付着する。
【００２０】
このようにして得られた本発明の水素吸蔵複合材料の構成を図１及び図２に示す。図１は、炭素材料としてカーボンナノチューブを用いた場合の横断面図であり、カーボンナノチューブ１のチューブ内面及びチューブ外面に水素吸蔵合金２が付着し、チューブ内及びチューブ間の空隙を充填している。但し、上記のように水素吸蔵合金の体積膨張を考慮して、チューブ内空隙のすべてを水素吸蔵合金が満たさないよう、８０体積％以下を満たすようにしている。図２は、炭素材料としてグラファイトを用いた場合の断面図であり、グラファイト３の層間に水素吸蔵合金２が層状に充填されている。この場合も、グラファイトの層間の空隙の８０体積％以下を満たすようにしている。
【００２１】
炭素材料は弾性を示し、特にカーボンナノチューブは２０％程度の伸びを示すことが知られている。このような炭素材料に水素吸蔵合金を付着させ、細孔内部を充填した本発明の水素吸蔵複合材料では、水素吸蔵合金が水素を吸蔵・放出する際に体積を変化させても、その応力を緩和し、水素吸蔵合金を単独で用いた場合におけるような構造破壊、微粉化を防ぐことができる。また、この炭素材料の弾性を利用することにより、適切な圧力を水素吸蔵合金に付与することによって適度の歪みを与えることができ、水素放出特性を改善することができる。
【００２２】
このような水素吸蔵複合材料においては、細孔端部から水素が流入し、水素吸蔵合金に吸蔵される。そこで、図２に示すように、この細孔端部にパラジウム及び／又はバナジウム４を担持させると、水素の吸蔵・放出速度を改善することができる。その理由は、このパラジウム等が水素分子の原子解離の触媒として作用すること及び水素の吸蔵・放出を阻害する水や酸素等の付着を防止するからであるからと考えられる。このパラジウム及び／又はバナジウムの担持は、一般的な蒸着法によって行うことができる。その担持量は、水素吸蔵合金１モルに対して好ましくは６×１０−５〜０．２モル、より好ましくは６×１０−５〜１×１０−４モルである。このパラジウム等を担持させる細孔端部とは、細孔の開口部エッジ及び外周を意味する。なお、パラジウム等は細孔内部に担持されてもよい。
【００２３】
また、上記パラジウム等に代えて、もしくはパラジウム等に加えて、細孔端部に細孔内に充填された水素吸蔵合金よりも吸蔵圧力の高い水素吸蔵合金を担持させると、大気圧下における水素放出温度を低下させることができる。例えば、Ｍｇ系水素吸蔵合金では、水素を放出させるために常圧下においては３５０〜４００℃に加熱することが必要であるが、細孔端部にＴｉＭｎを担持させておくと、水素放出温度は約２５０℃にまで低下する。その理由は平衡圧の高いＴｉＭｎ膜が薄膜系全体の平衡圧を上昇させることにより放出を容易にするからであるからと考えられる。この水素吸蔵合金の担持も、一般的な蒸着法によって行うことができ、その担持量は、水素吸蔵合金１モルに対して好ましくは０．００１〜０．１モルである。
【００２４】
さらに、上記パラジウム等に代えて、もしくはパラジウム等に加えて、細孔端部にニッケルを担持させても大気圧下における水素放出温度を低下させることができる。その理由はＮｉが吸蔵・放出阻害元素の付着を防止し、また水素透過性が高いからであるからと考えられる。このニッケルの担持も、一般的な蒸着法によって行うことができ、その担持量は、水素吸蔵合金１モルに対して好ましくは０．００５〜０．１モルである。
【００２５】
こうして形成した水素吸蔵複合材料を所定の容器に収納し、冷却かつ加圧下において水素を吸蔵させる。冷却するのは、水素化物形成時の発熱を除去し、吸蔵を促進するためである。また、圧力は、好ましくは０．１〜３５ＭＰａである。こうして吸蔵された水素は、放出時のみ温度を２００〜２５０℃ほど上げることにより容易に取り出すことができる。
【００２６】
【実施例】
実施例１
径２ｎｍのカーボンナノチューブにＭｇ系水素吸蔵合金（Ｍｇ、Ｍｇ２ Ｎｉ）の蒸気中に保持し、細孔中にカーボンナノチューブ１ｇあたり１〜１．５ｇＭｇ／２．２〜３．３ｇＭｇ２ Ｎｉ充填させた（サンプルＡ）。このサンプルを密閉容器に入れ、室温において水素圧１０ＭＰａに保持し、吸蔵されなかった水素量を測定することにより水素吸蔵量を算出した。また、細孔体積あたりの吸蔵された水素体積より細孔内水素密度を算出した。この結果を表１に示す。
【００２７】
実施例２
カーボンナノチューブとして径２０ｎｍのカーボンナノチューブを用い、Ｍｇ系水素吸蔵合金を細孔中にカーボンナノチューブ１ｇあたり２０〜４０ｇＭｇ／４５〜９０ｇＭｇ２ Ｎｉ充填させることを除き、実施例１と同様にしてサンプルを製造した（サンプルＢ）。このサンプルについて、実施例１と同様にして水素吸蔵量及び細孔内水素密度をもとめ、その結果を表１に示す。
【００２８】
実施例３
カーボンナノチューブの代わりにヤシガラ活性炭を用い、この活性炭１ｇあたりＭｇ系水素吸蔵合金を０．１〜０．５ｇ充填させることを除き、実施例１と同様にしてサンプルを製造した（サンプルＣ）。このサンプルについて、実施例１と同様にして水素吸蔵量及び細孔内水素密度をもとめ、その結果を表１に示す。
【００２９】
実施例４
カーボンナノチューブの代わりにフェノール系活性炭を用い、この活性炭１ｇあたりＭｇ系水素吸蔵合金を０．３〜０．７ｇ充填させることを除き、実施例１と同様にしてサンプルを製造した（サンプルＤ）。このサンプルについて、実施例１と同様にして水素吸蔵量及び細孔内水素密度をもとめ、その結果を表１に示す。
【００３０】
比較例１
水素吸蔵合金を充填していない径５００ｎｍのカーボンナノチューブを水素吸蔵材として用い（サンプルＥ）、このサンプルについて、実施例１と同様にして水素吸蔵量及び細孔内水素密度をもとめ、その結果を表１に示す。
【００３１】
比較例２
水素吸蔵合金を充填していない径２ｎｍのカーボンナノチューブを水素吸蔵材として用い（サンプルＦ）、このサンプルについて、実施例１と同様にして水素吸蔵量及び細孔内水素密度をもとめ、その結果を表１に示す。
【００３２】
比較例３
水素吸蔵合金を充填していないヤシガラ活性炭を水素吸蔵材として用い（サンプルＧ）、このサンプルについて、実施例１と同様にして水素吸蔵量及び細孔内水素密度をもとめ、その結果を表１に示す。
【００３３】
比較例４
Ｍｇ系水素吸蔵合金バルク（５ｇ）を水素吸蔵材として用い（サンプルＨ）、このサンプルについて、実施例１と同様にして水素吸蔵量及び細孔内水素密度をもとめ、その結果を表１に示す。
【００３４】
【表１】
実施例５
上記サンプルＡを用いて、その細孔端部に、表２に示す各種元素を担持させ、水素放出速度及び大気圧水素放出温度を調べた。水素放出速度は、１００〜１５０℃において真空下で調べ、大気圧水素放出温度は、大気圧下で温度を変え、放出温度を調べた。この結果を表２に示す。
【００３６】
【表２】
上記表１の結果より、本発明の水素吸蔵複合材料では明らかに水素吸蔵量の向上が認められた。また、表２に結果より、パラジウム又はバナジウムを細孔端部に担持させることにより、水素放出速度の大幅な向上が認められた。また、ＴｉＭｎを担持させることにより、水素吸蔵圧力が大幅に向上し、それに伴って大気圧水素放出温度がＭｇバルクよりも低下した。ニッケルは水素吸蔵合金ではないが、細孔端部に担持させることにより、大気圧水素放出温度の低下がＴｉＭｎを担持させた場合よりも上回った。また、パラジウム単独よりも、パラジウムとニッケルを組み合わせて担持させた場合の方がサイクル性に優れていた。
【００３８】
【発明の効果】
本発明の水素吸蔵複合材料によれば、より常温、常圧に近い条件で水素の吸蔵・放出を行うことができる。
【図面の簡単な説明】
【図１】本発明の水素吸蔵複合材料の構成を示す断面図である。
【図２】本発明の水素吸蔵複合材料の構成を示す断面図である。
【符号の説明】
１…カーボンナノチューブ
２…水素吸蔵合金
３…グラファイト
４…機能付与元素[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a hydrogen storage composite material having a high hydrogen storage property and capable of easily releasing hydrogen.
[0002]
[Prior art]
At present, reciprocating engines using gasoline or light oil as fuel are the mainstream power sources for automobiles. However, in view of social problems such as air pollution and energy problems of long-term stable supply of fuel, low-pollution and long-term stable fuel that can replace existing gasoline and light oil are being studied. Among such alternative fuels, the hydrogen fuel does not contain carbon and the one produced by combustion is water, so that a so-called fuel cell vehicle or the like has been developed.
[0003]
However, the biggest problem with hydrogen fuel lies in its storage and transportation. In other words, high-pressure gas cylinders are used to store and transport hydrogen as a gas. Such high-pressure storage is simple, but requires a thick container, which increases the weight of the container and increases transport and storability. It is low and is difficult to put into practical use in vehicles. In addition, when hydrogen is transported and stored as a liquid, transport and storage properties are improved as compared with gaseous hydrogen. However, in the production of liquid hydrogen, it is necessary to remove 168 cal of heat to liquefy the gas, and the liquefaction temperature is- Since the temperature is as low as 252.6 ° C. and a special container for such an ultra-low temperature is required, there is an economic problem. Furthermore, even if the seal is tightly sealed, the loss due to evaporation cannot be avoided.
[0004]
Therefore, recently, the use of a hydrogen storage alloy has been proposed as a method for storing hydrogen, and some of them have been put to practical use. Hydrogen storage alloys react with hydrogen under appropriate temperature and pressure conditions to form metal hydrides, store hundreds to 1000 times more than the metal volume of hydrogen between crystal lattices, and reverse decomposition An alloy designed to release hydrogen upon reaction. The hydrogen storage method using the hydrogen storage alloy is more advantageous than the above-mentioned method of transporting or transporting as a gas or a liquid from the viewpoint of safety, efficiency, and economy.
[0005]
However, the hydrogen storage alloy has a problem that the volume of the hydrogen storage alloy expands and contracts by about 20% by absorbing and releasing hydrogen, and the alloy is finely divided by repeated storage and release. In order to solve such a problem, it is disclosed that the hydrogen storage alloy is surrounded by a spongy porous body of carbon (for example, see Patent Document 1).
[0006]
In addition, the hydrogen storage alloy has a problem that the weight of the alloy itself is heavy, and the use temperature of the Mg-based lightweight hydrogen storage alloy is as high as 290 ° C., and it is not practical to be mounted on a vehicle as a fuel. . In order to solve such a problem, a method is disclosed in which a metal or alloy film having a function of separating hydrogen molecules into hydrogen atoms is formed on the surface of a porous carbon material to occlude hydrogen atoms (for example, a method has been disclosed). And
[0007]
[Patent Document 1]
JP-A-6-158194 (
[Patent Document 2]
JP-A-10-72201 (pages 2-3)
[0008]
[Problems to be solved by the invention]
However, the hydrogen storage alloy alone has a hydrogen storage amount of about 2 wt% at present, and further significant weight reduction is desired. In addition, when a carbon material and a hydrogen storage alloy are combined, an improvement in the hydrogen storage ability is recognized, but a high hydrogen pressure of 3 MPa or more is required at the time of hydrogen storage, and hydrogen stored at normal pressure is not released at low temperatures. There is a problem.
[0009]
An object of the present invention is to provide a hydrogen storage material that can store and release hydrogen under conditions close to normal temperature and normal pressure.
[0010]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a hydrogen storage composite material comprising a carbon material having pores filled with a hydrogen storage alloy.
[0011]
In the second invention, in order to solve the above-mentioned problems, in the first invention, palladium and / or vanadium is carried on the end of the pores of the carbon material.
[0012]
According to a third aspect of the present invention, in the first or second aspect of the present invention, in order to solve the above problem, the carbon material has an occlusion pressure higher than that of the hydrogen storage alloy filled in the pores at the pore ends. A hydrogen storage alloy is supported.
[0013]
According to a fourth aspect of the present invention, in order to solve the above-mentioned problems, in the first to third aspects, nickel is carried on the pore ends of the carbon material.
[0014]
Some carbon materials having a microstructure have elasticity and can be stretched to some extent. Therefore, if a hydrogen storage material is filled in the pores of such a carbon material, even if the hydrogen storage alloy causes a volume change due to the storage and release of hydrogen, the stress is relaxed and the fine powder of the hydrogen shape alloy is reduced. It is possible to prevent the shape from being collapsed due to the formation. Also, by disposing palladium, vanadium, nickel, or a predetermined hydrogen storage alloy at the end of the pores of the carbon material, the pressure and temperature during hydrogen storage and release can be improved, and the hydrogen release rate can be improved. Can be.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
The hydrogen storage composite material of the present invention basically comprises a carbon material having pores filled with a hydrogen storage alloy in the pores. Activated carbon, graphite, carbon nanotubes and the like can be used as the carbon material having pores. Activated carbon is obtained by activating carbonaceous material obtained by firing organic matter in an inert atmosphere by reacting with water vapor or carbon dioxide, and the activation forms a pore structure. Graphite has a laminated structure in which a carbon hexahedral plane is used as a basic unit and is bonded by π electrons, and this layer corresponds to pores. Further, the carbon nanotube has a shape in which a carbon hexahedral surface of graphite is formed into a cylindrical shape, the diameter ranges from several nm to several tens of nm, and the length ranges from several μm. The space corresponds to the pore. As this carbon nanotube, it is preferable to use a single-walled carbon nanotube having an open end.
[0016]
The pore size (pore diameter in the case of carbon nanotubes, interlayer distance in the case of graphite) of the carbon material is preferably 0.6 nm to 200 nm, and more preferably 2 nm to 5 nm. These carbon materials can be manufactured by a conventional method, or a commercially available product may be used.
[0017]
As the hydrogen storage alloy to be filled in the pores of the carbon material, various types of conventionally used hydrogen storage alloys, for example, Mg, Mg 2 Ni, Mg-Ni alloy, BCC alloy, and the like can be used. Of these, Mg and Mg 2 Ni are preferably used.
[0018]
As described above, since the volume of the hydrogen storage alloy expands by about 20% when storing hydrogen, the hydrogen storage alloy is not filled to fill all the pores of the carbon material, and the filling rate is reduced to 80% of the pore volume. It is preferable to set the following. Further, in order to secure a sufficient hydrogen storage amount, it is preferable to fill 40% or more of the pore volume.
[0019]
The filling of the hydrogen storage alloy into the pores of the carbon material is performed, for example, by holding the carbon material in the vapor of the hydrogen storage alloy, and a vacuum deposition method, a sputtering method, a CVD method, or the like can be used. Since the potential inside the pores of the carbon material is lower than that outside the pores, the vapor of the hydrogen storage alloy easily penetrates into the pores and adheres to the walls of the pores.
[0020]
FIGS. 1 and 2 show the structure of the hydrogen storage composite material of the present invention thus obtained. FIG. 1 is a cross-sectional view when a carbon nanotube is used as a carbon material. A
[0021]
It is known that carbon materials exhibit elasticity, and in particular, carbon nanotubes exhibit elongation of about 20%. In the hydrogen storage composite material of the present invention in which a hydrogen storage alloy is attached to such a carbon material and the inside of the pores is filled, even when the hydrogen storage alloy changes its volume when storing and releasing hydrogen, its stress is reduced. It can relax and prevent structural destruction and pulverization as in the case where the hydrogen storage alloy is used alone. In addition, by utilizing the elasticity of the carbon material, an appropriate pressure can be applied to the hydrogen storage alloy, whereby an appropriate strain can be given, and the hydrogen release characteristics can be improved.
[0022]
In such a hydrogen storage composite material, hydrogen flows in from the ends of the pores and is stored in the hydrogen storage alloy. Then, as shown in FIG. 2, when palladium and / or vanadium 4 are supported on the end of the pore, the rate of hydrogen absorption and desorption can be improved. This is probably because palladium and the like act as a catalyst for the atomic dissociation of hydrogen molecules and prevent adhesion of water, oxygen, and the like, which hinder the storage and release of hydrogen. The loading of palladium and / or vanadium can be performed by a general vapor deposition method. The supported amount is preferably 6 × 10 −5 to 0.2 mol, more preferably 6 × 10 −5 to 1 × 10 −4 mol, per 1 mol of the hydrogen storage alloy. The end of the pore carrying palladium or the like means the opening edge and outer periphery of the pore. Note that palladium or the like may be supported inside the pores.
[0023]
Further, when a hydrogen storage alloy having a higher storage pressure than the hydrogen storage alloy filled in the pores is carried at the pore ends instead of or in addition to the above-described palladium or the like, hydrogen at atmospheric pressure can be obtained. The release temperature can be reduced. For example, in the case of the Mg-based hydrogen storage alloy, it is necessary to heat to 350 to 400 ° C. under normal pressure in order to release hydrogen. To about 250 ° C. This is probably because the TiMn film having a high equilibrium pressure facilitates release by raising the equilibrium pressure of the entire thin film system. The loading of the hydrogen storage alloy can also be carried out by a general vapor deposition method, and the loading amount is preferably 0.001 to 0.1 mol per 1 mol of the hydrogen storage alloy.
[0024]
Furthermore, the hydrogen release temperature under atmospheric pressure can be lowered even if nickel is supported on the end of the pores instead of or in addition to palladium or the like. It is considered that the reason is that Ni prevents adhesion of the occlusion / release inhibiting element and has high hydrogen permeability. The supporting of nickel can be carried out by a general vapor deposition method, and the supporting amount is preferably 0.005 to 0.1 mol per 1 mol of the hydrogen storage alloy.
[0025]
The hydrogen storage composite material thus formed is housed in a predetermined container, and hydrogen is stored under cooling and pressure. The purpose of cooling is to remove heat generated during hydride formation and promote occlusion. Further, the pressure is preferably 0.1 to 35 MPa. The hydrogen thus occluded can be easily taken out only by releasing the temperature by raising the temperature by about 200 to 250 ° C.
[0026]
【Example】
Example 1
[0027]
Example 2
A sample was produced in the same manner as in Example 1 except that a 20 nm diameter carbon nanotube was used as the carbon nanotube, and a Mg-based hydrogen storage alloy was filled in the pores with 20 to 40 g Mg / 45 to 90 g Mg 2 Ni per 1 g of carbon nanotube. (Sample B). With respect to this sample, the hydrogen storage amount and the hydrogen density in the pores were determined in the same manner as in Example 1, and the results are shown in Table 1.
[0028]
Example 3
A sample was manufactured in the same manner as in Example 1 except that coconut shell activated carbon was used in place of the carbon nanotubes and 0.1 to 0.5 g of the Mg-based hydrogen storage alloy was filled per 1 g of the activated carbon (sample C). With respect to this sample, the hydrogen storage amount and the hydrogen density in the pores were determined in the same manner as in Example 1, and the results are shown in Table 1.
[0029]
Example 4
A sample was manufactured in the same manner as in Example 1 except that phenol-based activated carbon was used instead of the carbon nanotubes, and 0.3 to 0.7 g of the Mg-based hydrogen storage alloy was filled per 1 g of the activated carbon (sample D). With respect to this sample, the hydrogen storage amount and the hydrogen density in the pores were determined in the same manner as in Example 1, and the results are shown in Table 1.
[0030]
Comparative Example 1
A 500 nm-diameter carbon nanotube not filled with a hydrogen storage alloy was used as a hydrogen storage material (sample E). For this sample, the hydrogen storage amount and the hydrogen density in the pores were determined in the same manner as in Example 1, and the results were obtained. It is shown in Table 1.
[0031]
Comparative Example 2
A carbon nanotube having a diameter of 2 nm, which is not filled with a hydrogen storage alloy, was used as a hydrogen storage material (sample F). With respect to this sample, the hydrogen storage amount and the hydrogen density in the pores were determined in the same manner as in Example 1, and the results were obtained. It is shown in Table 1.
[0032]
Comparative Example 3
A coconut shell activated carbon not filled with a hydrogen storage alloy was used as a hydrogen storage material (sample G). For this sample, the hydrogen storage amount and the hydrogen density in the pores were determined in the same manner as in Example 1, and the results are shown in Table 1. Show.
[0033]
Comparative Example 4
Using a Mg-based hydrogen storage alloy bulk (5 g) as a hydrogen storage material (sample H), the hydrogen storage amount and the hydrogen density in the pores of this sample were determined in the same manner as in Example 1, and the results are shown in Table 1. .
[0034]
[Table 1]
Example 5
Using the sample A, various elements shown in Table 2 were supported on the ends of the pores, and the hydrogen release rate and the atmospheric hydrogen release temperature were examined. The hydrogen release rate was examined under vacuum at 100-150 ° C., and the atmospheric hydrogen release temperature was varied under atmospheric pressure to determine the release temperature. Table 2 shows the results.
[0036]
[Table 2]
From the results shown in Table 1, the hydrogen storage composite material of the present invention clearly showed an improvement in the amount of hydrogen storage. In addition, from the results shown in Table 2, it was confirmed that by carrying palladium or vanadium at the end of the pores, the hydrogen release rate was significantly improved. In addition, by supporting TiMn, the hydrogen storage pressure was greatly improved, and the atmospheric pressure hydrogen release temperature was lower than that of the Mg bulk. Although nickel was not a hydrogen storage alloy, the decrease in the atmospheric pressure hydrogen release temperature was larger than that in the case where TiMn was supported by supporting nickel at the ends of the pores. In addition, the case where palladium and nickel were supported in combination was superior to the case of palladium alone in cycleability.
[0038]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the hydrogen storage composite material of this invention, hydrogen can be stored / released under the conditions near normal temperature and normal pressure.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a configuration of a hydrogen storage composite material of the present invention.
FIG. 2 is a cross-sectional view showing a configuration of the hydrogen storage composite material of the present invention.
[Explanation of symbols]
DESCRIPTION OF
Claims (4)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2003055930A JP2004261739A (en) | 2003-03-03 | 2003-03-03 | Hydrogen occlusion composite material |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2003055930A JP2004261739A (en) | 2003-03-03 | 2003-03-03 | Hydrogen occlusion composite material |
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| JP2004261739A true JP2004261739A (en) | 2004-09-24 |
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| JP2003055930A Pending JP2004261739A (en) | 2003-03-03 | 2003-03-03 | Hydrogen occlusion composite material |
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| JP2008062183A (en) * | 2006-09-07 | 2008-03-21 | Toyota Motor Corp | Gas adsorbent material and method for opening cap structure of single-wall carbon nanotube |
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| JP2009512618A (en) * | 2005-10-21 | 2009-03-26 | ワシントン サバンナ リバー カンパニー リミテッド ライアビリティ カンパニー | Hollow glass microspheres with porous walls for hydrogen storage |
| US7951225B2 (en) | 2005-05-03 | 2011-05-31 | Advanced Technology Materials, Inc. | Fluid storage and dispensing systems, and fluid supply processes comprising same |
| US8539781B2 (en) | 2007-06-22 | 2013-09-24 | Advanced Technology Materials, Inc. | Component for solar adsorption refrigeration system and method of making such component |
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| US8282023B2 (en) | 2005-05-03 | 2012-10-09 | Advanced Technology Materials, Inc. | Fluid storage and dispensing systems, and fluid supply processes comprising same |
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| US9132412B2 (en) | 2007-06-22 | 2015-09-15 | Entegris, Inc. | Component for solar adsorption refrigeration system and method of making such component |
| US9468901B2 (en) | 2011-01-19 | 2016-10-18 | Entegris, Inc. | PVDF pyrolyzate adsorbent and gas storage and dispensing system utilizing same |
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