JP2006015291A - Graphite based hydrogen occlusion material and its production method - Google Patents
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本発明は、黒鉛系の水素吸蔵材料及びその製造方法に関するものである。なお、この明細書において、Ｐｔ，Ｐｄ，Ｎｉ，Ｌｉ，Ｋ，Ｃｓ，Ｒｂ，Ｔｉ，Ｃｒ，Ｆｅ，Ｃｕ，Ｃｏ，Ｚｒ，Ｎｂ，Ｂ，Ｓｉ等は元素記号である。 The present invention relates to a graphite-based hydrogen storage material and a method for producing the same. In this specification, Pt, Pd, Ni, Li, K, Cs, Rb, Ti, Cr, Fe, Cu, Co, Zr, Nb, B, Si, etc. are element symbols.
地球温暖化と大気汚染対策、エネルギー供給の安定化と効率化の観点から燃料電池が注目されている。そして、燃料電池を輸送用機器に搭載するためには水素貯蔵法の検討が重要であり、コストが安く、軽量で、体積水素吸蔵密度が高く、水素の充填・放出速度が速く、安全で取り扱いやすい水素貯蔵材料及び貯蔵方法の開発が望まれている。そして、水素吸蔵用の炭素材料としては、例えば、（１）多孔質カーボンの比表面積が１５００ｍ２／ｇ以上、嵩密度０．２５ｇ／ｃｍ３以上の材料であり、炭素原料を含水の水酸化カリウムと混合した後、焼成して製造する構成（特開昭６０−２４７０７３号公報）、（２）炭素１ｇ当たり０．００２２ｇより大きい水素の容量と７９０ＫＰａ及び２５℃で測定して１５Ｖ／Ｖより大きい容積効率を有する炭素モレキュラーシーブに水素を吸着させる水素吸蔵方法で、モレキュラーシーブは塩化ビニリデン共重合体の炭素化により形成する構成（特表平８−５０４３９４号公報）、（３）粘土状無機物マトリックスの隙間に有機重合性先駆物質を満たし、重合炭化により細孔構造を有する活性炭吸着剤を得る構成（特表平８−５０６０４８号公報）が知られている。 Fuel cells are attracting attention from the viewpoints of global warming and air pollution countermeasures, and the stabilization and efficiency of energy supply. In order to mount fuel cells on transportation equipment, it is important to study hydrogen storage methods, which are cheap, lightweight, have a high volumetric hydrogen storage density, have a fast hydrogen filling / release rate, and are safe and handled. Development of easy hydrogen storage materials and storage methods is desired. Examples of the carbon material for storing hydrogen include (1) a material having a specific surface area of porous carbon of 1500 m 2 / g or more and a bulk density of 0.25 g / cm 3 or more. The composition produced by firing after mixing with potassium (Japanese Patent Laid-Open No. 60-247073), (2) From a capacity of hydrogen greater than 0.0022 g per gram of carbon, 790 KPa and 25 ° C., measured from 15 V / V A hydrogen storage method in which hydrogen is adsorbed on a carbon molecular sieve having a large volumetric efficiency. The molecular sieve is formed by carbonization of a vinylidene chloride copolymer (Japanese Patent Publication No. 8-504394), (3) Clay-like inorganic substance A structure in which an activated carbon adsorbent having a pore structure is obtained by polymerizing carbonization in which the gap between the matrix is filled with an organic polymerizable precursor (Japanese Patent Publication No. 8-50604) JP) is known.
ところで、活性炭系の水素吸蔵メカニズムは、活性炭のミクロポアへの水素の吸着により水素吸蔵性を発現させることであり、水素吸蔵量の向上には、活性炭表面への貴金属の担持や細孔径を小さくしたり比表面積を増加させることが必要である。この点に関し、特開平１０−７２２０１号公報には水素分子を原子に分離させる機能を持った金属を表面に有する多孔質炭素質材料について挙げられおり、炭素材料は活性炭、フラーレンまたはカーボンナノチューブ、金属は白金、パラジウムまたは水素吸蔵合金などが記載されている。また、特許文献１には、水素貯蔵用炭素材料として、０．３ｎｍ以上、１．５ｎｍ以下の細孔直径を有する炭素材料で、０．３ｎｍ以上、１．５ｎｍ以下の細孔直径、５０ｍ２／ｇ以上、８００ｍ２／ｇ以下の比表面積、かつ、０．０１ｍｌ／ｇ以上、０．３ｍｌ／ｇ以下の細孔容積を有する材料が特定されている。この材料は２７３〜３７３Ｋの温度領域で高水素吸蔵能を示とされる。特許文献２には、水素吸蔵用炭素材料として、比表面積が３０００ｍ２／ｇ以上であり、細孔を有し、ＢＪＨ法により求めた細孔の細孔モード径が１ｎｍ以上、２ｎｍ以下である材料が特定されている。
By the way, the hydrogen storage mechanism of the activated carbon system is to develop hydrogen storage properties by adsorption of hydrogen to the micropores of the activated carbon. In order to improve the hydrogen storage amount, the loading of precious metals on the activated carbon surface and the pore diameter are reduced. It is necessary to increase the specific surface area. In this regard, Japanese Patent Application Laid-Open No. 10-72201 discloses a porous carbonaceous material having a metal having a function of separating hydrogen molecules into atoms on the surface, and the carbon material is activated carbon, fullerene or carbon nanotube, metal Describes platinum, palladium or hydrogen storage alloys. In Patent Document 1, as a carbon material for hydrogen storage, a carbon material having a pore diameter of 0.3 nm or more and 1.5 nm or less, a pore diameter of 0.3 nm or more and 1.5 nm or less, 50 m 2 / G or more and 800 m 2 / g or less specific surface area and a material having a pore volume of 0.01 ml / g or more and 0.3 ml / g or less. This material has a high hydrogen storage capacity in the temperature range of 273 to 373K. In
上記したような従来の炭素系材料は、活性炭系の炭素を用いミクロ孔の細孔に水素を吸着させようとするものであり貯蔵・放出条件によってはそれなりに高い水素吸蔵能を示すが、常温において水素吸蔵量の多い材料を調製するのが難しかったり、量産性に欠けるなどの問題がある。そこで、本発明の目的は、黒鉛の層間を水素吸蔵用として有効活用できるようにし、例えば、常温で活性炭等の多孔質材料よりも高い水素吸蔵能を有し、製法も容易な黒鉛系水素吸蔵材料と製造方法を提供することにある。 The conventional carbon-based materials as described above are activated carbon-based carbons that try to adsorb hydrogen into the pores of the micropores. However, there is a problem that it is difficult to prepare a material having a large amount of hydrogen occlusion or lack of mass productivity. Therefore, an object of the present invention is to make it possible to effectively utilize the graphite layer for hydrogen storage. For example, it has a higher hydrogen storage capacity than a porous material such as activated carbon at room temperature, and is easy to manufacture. It is to provide a material and a manufacturing method.
本発明者らは、上記した目的を達成するため、原料としては入手及び製造が容易な酸化黒鉛を使用して、黒鉛の層間を如何に利用するかの点から鋭意研究を重ねてきた結果、完成されたものである。すなわち、請求項１の発明は、黒鉛系水素吸蔵材料として、黒鉛の層間に酸素を共有結合した酸化黒鉛であって、前記層間内の酸素を一部または全て取り出すことで、層間内に形成された水素侵入用の空間を有していることを特徴としている。
以上の構成では、層間化合物のうち、特に、層間内に酸素を共有結合した酸化黒鉛を使用する。そして、前記層間内の酸素は、還元等の処理により層間内の酸素を一部または全て取り出すようにしたものである。なお、請求項２〜６の発明は細部ないしは物性を特定したものである。
In order to achieve the above-mentioned object, the present inventors have conducted earnest research from the viewpoint of how to use the graphite layers, using graphite oxide that is easily available and manufactured as a raw material, It has been completed. That is, the invention of claim 1 is graphite oxide in which oxygen is covalently bonded between graphite layers as a graphite-based hydrogen storage material, and is formed in the interlayer by taking out part or all of the oxygen in the interlayer. It is characterized by having a space for hydrogen penetration.
In the above configuration, graphite oxide in which oxygen is covalently bonded in the interlayer is used among the intercalation compounds. The oxygen in the interlayer is obtained by taking out part or all of the oxygen in the interlayer by a treatment such as reduction. The inventions of
これに対し、請求項７の発明は、以上の黒鉛系水素吸蔵材料を製造方法から捉えたもので、黒鉛の層間に共有結合した酸素を有し、かつ粉末Ｘ線回折法による回折角度（２θ）が１３．５〜１６．０°および２６．０〜２６．６°にピークを持つ酸化黒鉛を用いて、前記酸化黒鉛を還元処理することにより前記層間内の酸素を一部または全て取り出して、前記層間内に水素侵入用の空間を形成し、かつ粉末Ｘ線回折法による回折角度（２θ）が前記１３．５〜１６．０°のピークを消失し、２θ＝１９．５〜２０．５°または２１．０〜２３．０に新たなピークを発現していることを特徴とする。
以上の構成では、製造方法として、本発明の完成過程で判明した物性特徴、つまり２θ＝１３．５〜１６．０°および２６．０〜２６．６°にピークを持つ酸化黒鉛であっても、還元処理により層間に空間を創生した試料では１３．５〜１６．０°の規則的な層間が消失し不規則な拡張された層間に変化するとともに、２θ＝１９．５〜２０．５°または２１．０〜２３．０に新たなピークを発現しているという点から特定したものである。
On the other hand, the invention of claim 7 captures the above-mentioned graphite-based hydrogen storage material from the production method, has oxygen covalently bonded between the graphite layers, and has a diffraction angle (2θ by the powder X-ray diffraction method). ) Using graphite oxide having peaks at 13.5 to 16.0 ° and 26.0 to 26.6 °, and by reducing the graphite oxide, part or all of the oxygen in the interlayer is taken out. A space for hydrogen intrusion is formed in the interlayer, and the diffraction angle (2θ) by the powder X-ray diffraction method disappears from the peak of 13.5 to 16.0 °, and 2θ = 19.5 to 20. A new peak is developed at 5 ° or 21.0 to 23.0.
In the above configuration, even if the production method is a physical property characteristic found in the completion process of the present invention, that is, graphite oxide having peaks at 2θ = 13.5 to 16.0 ° and 26.0 to 26.6 °. In the sample in which a space was created between the layers by the reduction treatment, the regular layer of 13.5 to 16.0 ° disappeared and changed to the irregular expanded layer, and 2θ = 19.5 to 20.5. It is specified from the point that a new peak is expressed at ° or 21.0-23.0.
上記した本発明は、黒鉛系水素吸蔵材料として、黒鉛の層間に酸素が共有結合した酸化黒鉛を用い、層間内の酸素を一部または全て取り出すことで、水素が侵入できる空間（ナノスペース）を創生し、より大量の水素を吸蔵できるようにして、軽量で、繰り返し使用できる。製造方法としては、還元処理を主体としているため容易であり、製造費や設備費を抑えて実用化に寄与できる。 The above-described present invention uses graphite oxide in which oxygen is covalently bonded between graphite layers as a graphite-based hydrogen storage material, and by taking out part or all of the oxygen in the interlayer, a space (nanospace) into which hydrogen can enter is obtained. Creates and absorbs a large amount of hydrogen, is lightweight and can be used repeatedly. The manufacturing method is easy because it mainly uses reduction treatment, and can contribute to practical use by suppressing manufacturing costs and equipment costs.
以下、本発明の黒鉛系水素吸蔵材料及びその製造方法を説明した後、実施例を挙げて本発明の有用性を明らかにする。 Hereinafter, after describing the graphite-based hydrogen storage material of the present invention and the production method thereof, the usefulness of the present invention will be clarified by giving examples.
（請求項１の発明について）請求項１の黒鉛系水素吸蔵材料は、黒鉛の層間に酸素を共有結合した酸化黒鉛であって、前記層間内の酸素を一部または全て取り出すことで、層間内に形成されている水素侵入用の空間を有しているという構成である。 (Invention of Claim 1) The graphite-based hydrogen storage material of claim 1 is graphite oxide in which oxygen is covalently bonded between graphite layers, and by taking out part or all of the oxygen in the interlayer, It is the structure of having the space for hydrogen penetration formed in this.
以上の本発明は次のような背景から完成されたものである。まず、水素吸蔵量の多い黒鉛系材料を調整するためには層間に水素が侵入される空間を多く創生する必要がある。この観点から、本発明者らは試験を重ねたところ黒鉛の層間に酸素が共有結合した酸化黒鉛を用い、該層間内の酸素を、加熱または加熱を伴わない還元処理により一部または全てを取り出すことで、層間内に水素侵入用として好適な空間を調整できることを見出した。具体的には、黒鉛粒子内の酸化程度を制御した酸化黒鉛を用い、層間内で共有結合する酸素量を制御することで、還元時に大きく膨脹することなく、層間内に水素侵入用として好適な空間を形成できるようになる。創生した層間内の空間は、水素が侵入できる空間であるが、空間の径が大きくなり過ぎると水素吸着力が弱くなる。なお、吸着力を左右する主なものとしては、Ｌｏｎｄｏｎ分散力相互作用、双極子相互作用、水素結合、静電引力、共有結合の５種類に分類される。Ｌｏｎｄｏｎ分散力は原子と分子、また分子同士が互いに接近したときに瞬間的に電気分極が起き、原子または分子間にごく弱い引力が発生するものである。この分散力は距離が離れると極端に低下する。活性炭が強い吸着力を有するのは細孔径が小さいことに起因する。すなわち、気体分子と同程度の大きさの細孔内では分子は周りの壁からの強い分散力によって吸着する。これは、本発明においても、黒鉛の層間を５〜１０Å程度に均一に広げた空間を確保できれば、該空間内でＬｏｎｄｏｎ分散力等のｖａｎ ｄｅｒ Ｗａａｌｓ力が働き、水素吸蔵量を増加できるものと考えれられる。そして、本発明者らは、水素吸蔵量の多い空間を創生するためには酸化程度を制御した黒鉛を用い、還元時に黒鉛の層間内に形成される空間をできるだけ小さく、かつ多く分布させることが必要であることを確認した。 The present invention as described above has been completed from the following background. First, in order to adjust a graphite-based material with a large amount of hydrogen storage, it is necessary to create a large space for hydrogen to enter between layers. From this point of view, the inventors of the present invention conducted repeated tests and used graphite oxide in which oxygen was covalently bonded between the graphite layers, and part or all of the oxygen in the layers was taken out by reduction treatment without heating or heating. Thus, it has been found that a suitable space for hydrogen penetration can be adjusted in the interlayer. Specifically, by using graphite oxide in which the degree of oxidation in the graphite particles is controlled and controlling the amount of oxygen covalently bonded between the layers, it is suitable for hydrogen intrusion into the layers without greatly expanding during reduction. A space can be formed. The created space between the layers is a space where hydrogen can enter, but if the diameter of the space becomes too large, the hydrogen adsorption force becomes weak. The main factors that influence the adsorption force are classified into five types: London dispersion force interaction, dipole interaction, hydrogen bond, electrostatic attraction, and covalent bond. The London dispersion force is such that when an atom and a molecule, or between molecules, approach each other, electric polarization occurs instantaneously and a very weak attractive force is generated between the atoms or molecules. This dispersive force decreases extremely with increasing distance. The reason why activated carbon has a strong adsorption force is due to the small pore diameter. That is, in the pores of the same size as the gas molecules, the molecules are adsorbed by a strong dispersion force from the surrounding walls. In the present invention, if a space in which the graphite layer is uniformly expanded to about 5 to 10 mm can be secured in this invention, the van der Waals force such as the London dispersion force works in the space, and the hydrogen storage amount can be increased. Conceivable. In order to create a space with a large amount of hydrogen storage, the present inventors use graphite with a controlled degree of oxidation and distribute the space formed between the graphite layers as much as possible during reduction. Confirmed that is necessary.
（請求項２の発明について）この構成は、前記創生した空間の水素吸蔵能力を、更に増加させるため層間内の空間を形成する炭素の六角網面の一部に水素を吸着する活性点を付与するという特定であり、水素吸蔵量のより高い黒鉛系水素吸蔵材料を実現可能にする。ここで、活性点を付与する具体例としては、層間内の空間を形成している炭素の六角網面の一部や、端部に官能基を生成させる。官能基を付与する手法としては、水蒸気やアルカリなどでの賦活や酸を用いた酸化処理が好ましく、カルボキシル基、フェノール性水酸基、カルボン酸無水物、ラクトン等の酸性表面官能基、クロメン型構造、ピロン型構造等の塩基性表面官能基、カルボニル基、キノン型カルボニル基、環状過酸化物等の中性表面官能基が付加される。一例としては、層間内に空間を形成した試料を用い、Ｈ２Ｏ２による酸化処理または不活性雰囲気や真空中で加熱処理を行うことにより、層間内の空間を形成する炭素の六角網面の一部に活性点を発現させて、水素吸蔵量を増加させることができる。 (Invention of Claim 2) In this configuration, in order to further increase the hydrogen storage capacity of the created space, an active point that adsorbs hydrogen to a part of the hexagonal mesh surface of carbon forming a space between layers is provided. It is specific that it is applied, and makes it possible to realize a graphite-based hydrogen storage material having a higher hydrogen storage capacity. Here, as a specific example of providing an active site, a functional group is generated at a part or an end of a hexagonal network surface of carbon forming a space between layers. As a method for imparting a functional group, activation with water vapor or alkali or an oxidation treatment using an acid is preferable, an acidic surface functional group such as a carboxyl group, a phenolic hydroxyl group, a carboxylic acid anhydride, or a lactone, a chromene structure, Basic surface functional groups such as pyrone type structures, neutral surface functional groups such as carbonyl groups, quinone type carbonyl groups, and cyclic peroxides are added. As an example, by using a sample in which a space is formed between layers and performing an oxidation treatment with H 2 O 2 or a heat treatment in an inert atmosphere or vacuum, a carbon hexagonal mesh surface forming a space between layers is formed. It is possible to increase the amount of hydrogen occlusion by expressing an active site in part.
（請求項３と７の発明について）請求項３の構成は、発明の水素吸蔵材料の物性ないしは構造を特定したものであり、前記酸化黒鉛として、粉末Ｘ線回折法による回折角度（２θ）が１３．５〜１６．０°と２６．０〜２６．６°にピークを持つものを用い、還元処理により１３．５〜１６．０°のピークを消失させ、新たに１９．５〜２０．５°または２１．０〜２３．０°にピークを発現しているという特定である。これに対し、請求項７の構成は、以上の物性から発明の黒鉛系水素吸蔵材料の製法特徴を特定したものである。すなわち、製造方法としては、黒鉛の層間に共有結合した酸素を有し、かつ粉末Ｘ線回折法による回折角度（２θ）が１３．５〜１６．０°および２６．０〜２６．６°にピークを持つ酸化黒鉛を用いて、前記酸化黒鉛を還元処理することにより前記層間内の酸素を一部または全て取り出して、前記層間内に水素侵入用の空間を形成し、かつ粉末Ｘ線回折法による回折角度（２θ）が前記１３．５〜１６．０°のピークを消失し、２θ＝１９．５〜２０．５°または２１．０〜２３．０に新たなピークを発現しているという構成である。 (Invention of Claims 3 and 7) The structure of claim 3 specifies the physical properties or structure of the hydrogen storage material of the invention, and the graphite oxide has a diffraction angle (2θ) by a powder X-ray diffraction method. Using peaks having peaks at 13.5 to 16.0 ° and 26.0 to 26.6 °, the peak at 13.5 to 16.0 ° disappeared by reduction treatment, and 19.5 to 20. It is specific that a peak is developed at 5 ° or 21.0 to 23.0 °. On the other hand, the structure of Claim 7 specifies the manufacturing characteristics of the graphite-based hydrogen storage material of the invention from the above physical properties. That is, as a manufacturing method, it has oxygen covalently bonded between graphite layers, and the diffraction angle (2θ) by powder X-ray diffraction method is 13.5 to 16.0 ° and 26.0 to 26.6 °. Using graphite oxide having a peak, the graphite oxide is subjected to reduction treatment to extract part or all of oxygen in the interlayer, thereby forming a space for hydrogen penetration in the interlayer, and a powder X-ray diffraction method The diffraction angle (2θ) due to the above disappears from the peak of 13.5 to 16.0 °, and a new peak is expressed at 2θ = 19.5 to 20.5 ° or 21.0 to 23.0. It is a configuration.
本発明者らは、酸化度合いを変更した酸化黒鉛を用い、層間内に水素侵入用の空間を創生するため検討を重ねた結果、酸化黒鉛内に空間が形成されるメカニズムを明確にした。すなわち、黒鉛の層間に酸素が共有結合した酸化黒鉛は層間が広がっているが、その状態では水素が侵入する空間は創生されていない。そして、加熱または加熱を伴わない還元処理で、層間の酸素の一部または全てを取り出そうとした場合、層間内で共有結合した酸素が還元過程で急激にガス化や分解するため、還元後の粒子は層間の拡張で微粒子化が進み、層間内に水素が侵入できる空間を形成しづらい。しかし、酸化度合いを調製した酸化黒鉛は、層間で共有結合する酸素量を少なくしているため還元時のガス発生量が少なく、それに伴って、還元により過大に拡張する部分が少なくなって微粒子化も起こらない。その結果、層間内に水素侵入用として好適な空間を形成できる。そして、この試料を粉末Ｘ旋回折法（入射Ｘ線：ＣｕＫα）による回折角度（２θ）を測定した結果、還元前の酸化黒鉛は回折角度（２θ）が１３．５〜１６．０°と２６．０〜２６．６°にピークを持ち、還元処理にて１３．５〜１６．０°のピークが消失し、かつ、新たに１９．５〜２０．５°あるいは２１．０〜２３．０°にピークを発現していることが判明した。換言すると、酸化度合いを調製した酸化黒鉛では、回折角度（２θ）が１３．５〜１６．０°と２６．０〜２６．６°にピークを持つことと、その酸化黒鉛を還元処理して層間に空間を創生した試料では、１３．５〜１６．０°のピークが消失し、１９．５〜２０．５°あるいは２１．０〜２３．０°にピークが移行した構造を有し、層間内に水素侵入用の空間が創生される。そして、本発明の製造方法は、以上の現象を指標として具体的な製造条件を設計管理することで容易かつ品質のばらつきを抑えて量産可能となる。 The inventors of the present invention have clarified the mechanism by which a space is formed in the graphite oxide as a result of repeated studies to create a space for hydrogen penetration between the layers using graphite oxide having a different degree of oxidation. That is, the graphite oxide layer in which oxygen is covalently bonded between the graphite layers spreads between the layers, but in that state, no space for hydrogen to enter is created. In addition, when a part or all of oxygen between layers is taken out by heating or reduction treatment without heating, oxygen covalently bonded in the layers is rapidly gasified or decomposed during the reduction process. In the inter-layer expansion, micronization progresses and it is difficult to form a space in which hydrogen can enter the interlayer. However, graphite oxide prepared with a degree of oxidation reduces the amount of oxygen covalently bonded between layers, so there is less gas generation during reduction, and as a result, the portion that is excessively expanded by reduction is reduced and becomes finer Also does not happen. As a result, a space suitable for hydrogen penetration can be formed in the interlayer. And as a result of measuring the diffraction angle (2θ) of this sample by the powder X swirl folding method (incident X-ray: CuKα), the graphite oxide before reduction has a diffraction angle (2θ) of 13.5 to 16.0 ° and 26 It has a peak at 0.0 to 26.6 °, the peak at 13.5 to 16.0 ° disappears in the reduction treatment, and is newly 19.5 to 20.5 ° or 21.0 to 23.0. It was found that a peak was expressed at °. In other words, in the graphite oxide whose oxidation degree is adjusted, the diffraction angles (2θ) have peaks at 13.5 to 16.0 ° and 26.0 to 26.6 °, and the graphite oxide is reduced. The sample that created the space between the layers had a structure in which the peak at 13.5 to 16.0 ° disappeared and the peak shifted to 19.5 to 20.5 ° or 21.0 to 23.0 °. A space for hydrogen intrusion is created between the layers. The manufacturing method of the present invention can be mass-produced easily by suppressing design variations by designing and managing specific manufacturing conditions using the above phenomenon as an index.
なお、本発明者らは、当初、黒鉛の層間を５〜１０Å程度に均一に広げた空間を確保できれば、空間内でＬｏｎｄｏｎ分散力等のｖａｎ ｄｅｒ Ｗａａｌｓ力が働き、水素の吸蔵量が増加すると考えた。ところが、本発明の黒鉛系水素吸蔵材料では、実施例で検証した透過電子顕微鏡による観察から、黒鉛の層間を均一に拡張するまでには至っておらず、不均一な拡張（実施例１〜５の水素吸蔵材料では６０Å以下の不規則な間隔）になっている。つまり、６０Å以上の細孔半径の空間は水素の吸着力がほとんど発現しないため、層間内に形成される空間の半径は６０Å以下にすることが望ましい。換言すると、本発明において、前記層間内に形成された空間は６０Å以下の不規則な間隔からなる点も特徴の一つである。 In addition, if the present inventors can secure a space in which the graphite layers are uniformly spread to about 5 to 10 mm at first, the van der Waals force such as the London dispersion force works and the amount of occlusion of hydrogen increases. Thought. However, in the graphite-based hydrogen storage material of the present invention, the observation by the transmission electron microscope verified in the examples has not led to the uniform expansion of the graphite layers, and the non-uniform expansion (of Examples 1 to 5). The hydrogen storage material has an irregular interval of 60 mm or less. That is, a space having a pore radius of 60 mm or more hardly develops hydrogen adsorption force, and therefore the radius of the space formed between the layers is preferably 60 mm or less. In other words, one of the features of the present invention is that the space formed in the interlayer consists of irregular intervals of 60 mm or less.
（請求項４の発明について）請求項４の構成は、前記酸化黒鉛の還元処理後の比表面積が１００ｍ２／ｇ以下であるという特定である。すなわち、酸化黒鉛のうち、十分に酸化させた酸化黒鉛は、還元により層間が大きく拡張し微粒化が進んで、水素侵入用の空間が形成されず比表面積も大きくなる。これに対し、酸化程度が抑えられた酸化黒鉛は、還元により層間内に水素侵入用として好適な空間が形成され、還元時のガス発生量が少なく層間も大きく拡張されないため微粒子化が進まず比表面積も小さくなっている。つまり、発明の水素吸蔵材料は比表面積が１００ｍ2／ｇ以下である点も特徴の一つである。 (Invention of Claim 4) The structure of claim 4 is specific that the specific surface area of the graphite oxide after the reduction treatment is 100 m 2 / g or less. That is, among the graphite oxides, the graphite oxides that have been sufficiently oxidized are expanded greatly by reduction and the atomization progresses, so that the space for hydrogen penetration is not formed and the specific surface area is also increased. On the other hand, graphite oxide with a reduced degree of oxidation forms a suitable space for hydrogen intrusion in the interlayer by reduction, and the amount of gas generated during reduction is small and the interlayer is not expanded greatly. The surface area is also small. That is, the hydrogen storage material of the invention is also characterized by a specific surface area of 100 m 2 / g or less.
（請求項５の発明について）この構成は、発明の黒鉛層間化合物がＨｅ法で測定された密度で０．２〜１．２ｇ／ｃｍ３の範囲にあるという特定である。黒鉛の層間に創生された水素侵入用の空間は、Ｈｅ法で測定された密度が低いほど多く発生していることを意味する。すなわち、Ｈｅ法で求める試料の密度とは、ボイル・シャルルの法則に基づいてＨｅの圧力が０．２ＭＰａと０．８ＭＰａの条件で算出した試料の密度（平衡圧密度）を表わす。ここで、Ｈｅ法で求めた密度が０．２ｇ／ｃｍ３以下の試料は、嵩高くなっており、単位体積当たりの水素吸蔵量も減少するため実用的ではない。 This configuration is specific that the graphite intercalation compounds of the invention are in the range of 0.2 to 1.2 g / cm 3 as measured by the He method. It means that the space for hydrogen intrusion created between the graphite layers is generated more as the density measured by the He method is lower. In other words, the density of the sample obtained by the He method represents the density of the sample (equilibrium pressure density) calculated under the conditions that the He pressure is 0.2 MPa and 0.8 MPa based on Boyle-Charles' law. Here, a sample having a density of 0.2 g / cm 3 or less determined by the He method is bulky and impractical because the hydrogen storage amount per unit volume is reduced.
（請求項６の発明について）この構成は、前記層間内に形成された前記空間または該空間を形成している炭素の六角網面にＰｔ，Ｐｄ，Ｎｉ，Ｌｉ，Ｋ，Ｃｓ，Ｒｂ，Ｔｉ，Ｃｒ，Ｆｅ，Ｃｕ，Ｃｏ，Ｚｒ，Ｎｂ，Ｂ，Ｓｉのいずれか一種以上の元素を含有したり置換しているという特定である。この点は、これらの元素が層間に創生された空間等にあることで水素の吸着力が増加し水素吸蔵量の増加につながる。 (Invention of Claim 6) In this structure, Pt, Pd, Ni, Li, K, Cs, Rb, Ti are formed on the space formed in the interlayer or the hexagonal mesh surface of carbon forming the space. , Cr, Fe, Cu, Co, Zr, Nb, B, and Si are contained or substituted. In this respect, the hydrogen adsorption force increases due to the presence of these elements in the space created between the layers, leading to an increase in the hydrogen storage capacity.
以下の実施例１〜５は、黒鉛の層間に酸素が共有結合した酸化黒鉛において、層間内の酸素を加熱または加熱を伴わない処理で一部または全て取り出して層間内に水素侵入用の空間を形成させ、水素吸蔵材料の有効性を調べた一例である。また、層間内の空間を形成している炭素の六角網面の一部または前記空間に水素を吸着する活性点を付与した黒鉛系水素吸蔵材料の例も示す。 In the following Examples 1 to 5, in graphite oxide in which oxygen is covalently bonded between graphite layers, oxygen in the layers is partially or completely removed by heating or treatment without heating, and a space for hydrogen intrusion is formed in the layers. This is an example in which the effectiveness of the hydrogen storage material was examined. In addition, an example of a graphite-based hydrogen storage material in which an active site for adsorbing hydrogen in a part of a hexagonal network surface of carbon forming a space between layers or in the space is also shown.
〈１．酸化黒鉛の調製）
（酸化黒鉛の作製）比較例１，２、実施例１〜５の酸化黒鉛は、平均粒径１６μmの天然黒鉛（鱗片状黒鉛）を用い、次の調製法にて酸化度合いをそれぞれ変えたものである。まず、発煙硝酸１５０ｍｌ中に天然黒鉛８ｇを投入し、更に塩素酸カリウムを６４．４ｇ加えて1分から３時間反応させた。反応温度は５５℃とした。反応終了後は、希釈、濾過、乾燥することで酸化黒鉛を調製した。ここでは、反応時間として、比較例１，２のものは３時間、実施例１のものは１０分、実施例２〜５のものは１分に設定して、黒鉛の層間に共有結合する酸素量を制御しそれぞれの酸化黒鉛として調製した。
<1. Preparation of graphite oxide)
(Preparation of graphite oxide) The graphite oxides of Comparative Examples 1 and 2 and Examples 1 to 5 were natural graphite (flaky graphite) having an average particle diameter of 16 μm, and the degree of oxidation was changed by the following preparation methods. It is. First, 8 g of natural graphite was put into 150 ml of fuming nitric acid, and 64.4 g of potassium chlorate was further added to react for 1 minute to 3 hours. The reaction temperature was 55 ° C. After completion of the reaction, graphite oxide was prepared by diluting, filtering and drying. Here, the reaction time is set to 3 hours for Comparative Examples 1 and 2, 10 minutes for Example 1, and 1 minute for Examples 2 to 5, and oxygen bonded covalently between the graphite layers. The amount was controlled to prepare each graphite oxide.
（還元処理など）前記調製された各酸化黒鉛について、次のような条件で層間内の酸素をその一部または全て取り出すようにした。なお、実施例３〜５は層間内の酸素を取り出すとともに活性点を付与するようにした。
・比較例１では、前記調製された酸化黒鉛を、Ｈ２雰囲気中、温度６００℃に加熱することで試料（水素吸蔵材料）とした。
・比較例２、実施例１と２では、前記調製された各酸化黒鉛を、温度３００℃で真空焼成することで試料（水素吸蔵材料）とした。
・実施例３は、Ｈ２Ｏ２で酸化処理し、層間内の空間を形成する炭素の六角網面の一部に水素を吸着する活性点を付与した例である。すなわち、実施例３では、前記調製された酸化黒鉛を温度３００℃で真空焼成した後、更にそれを１５％のＨ２Ｏ２溶液中で１ｈｒ、温度７０°で環流し、洗浄、乾燥した後に試料（水素吸蔵材料）とした。
・実施例４と５は、層間内に形成された空間または空間を形成している炭素の六角網面にＰｔ，Ｐｄ，Ｎｉ，Ｒｂ，Ｔｉ，Ｃｒ，Ｆｅ，Ｃｕ，Ｃｏ，Ｚｒ，Ｎｂ，Ｂ，Ｓｉ，Ｌｉ，Ｋ，Ｃｓのいずれか一種以上の元素を含有したり置換させた試料を作製した一例である。なお、前記調製された酸化黒鉛は、水中では層間が拡張され、微粒子化して分散する。また、乾燥工程においては、強固に凝集し、層間が酸素の共有結合により規則的に拡張した構造となる。この特性を利用して、層間内に形成された空間または空間を形成している炭素の六角網面にＰｔ等の元素を含有したり置換させるようにした。すなわち、実施例４と５の調整法としては、まず、前記調製された酸化黒鉛に対し含有させる元素が５％になるように塩化物（実施例４ではＨ２ＰｔＣｌ４、実施例５ではＰｄＣｌ２）の必要量を溶解した水溶液を用意し、前記調製された酸化黒鉛を入れ攪拌する。温度６０°にて乾燥させて強固に凝集した中間試料を作製した。そして、実施例４では、前記中間試料を、Ｈ２雰囲気中、温度３００℃で１ｈｒ還元した。更に３００℃で真空焼成し、洗浄、乾燥した後に試料（水素吸蔵材料）とした。実施例５では、前記中間試料を、ヒドラジン中に混合し、常温で１０分保持し還元した。その後、３００℃で真空焼成し、洗浄、乾燥した後に試料（水素吸蔵材料）とした。
(Reduction treatment, etc.) For each of the prepared graphite oxides, some or all of the oxygen in the interlayer was taken out under the following conditions. In Examples 3 to 5, oxygen in the interlayer was taken out and active sites were given.
In Comparative Example 1, the prepared graphite oxide was heated to a temperature of 600 ° C. in a H 2 atmosphere to obtain a sample (hydrogen storage material).
In Comparative Example 2 and Examples 1 and 2, each prepared graphite oxide was subjected to vacuum firing at a temperature of 300 ° C. to obtain a sample (hydrogen storage material).
- Example 3, was oxidized with H 2 O 2, it is an example of applying the active sites for adsorption of hydrogen on a part of the hexagonal plane of the carbon to form a space in the interlayer. That is, in Example 3, the prepared graphite oxide was baked in vacuum at a temperature of 300 ° C., and then refluxed in a 15% H 2 O 2 solution for 1 hr at a temperature of 70 °, washed and dried. A sample (hydrogen storage material) was used.
In Examples 4 and 5, Pt, Pd, Ni, Rb, Ti, Cr, Fe, Cu, Co, Zr, Nb, and the like are formed on the hexagonal mesh surface of the carbon forming the space or space formed between the layers. This is an example in which a sample containing or replacing any one or more elements of B, Si, Li, K, and Cs is manufactured. In addition, the prepared graphite oxide expands between layers in water, and is finely dispersed. Further, in the drying process, the structure is agglomerated tightly and the layers are regularly expanded by oxygen covalent bonds. By utilizing this characteristic, an element such as Pt is contained or substituted in the space formed between the layers or the hexagonal mesh surface of carbon forming the space. That is, the adjustment method of Example 4 and 5, firstly, chlorides such element to be contained to the prepared graphite oxide is 5% (Example 4, H 2 PtC l4, in Example 5 PdC An aqueous solution in which the necessary amount of l2 ) is dissolved is prepared, and the prepared graphite oxide is added and stirred. An intermediate sample which was dried at a temperature of 60 ° and strongly agglomerated was produced. In Example 4, the intermediate sample was reduced for 1 hr at a temperature of 300 ° C. in an H 2 atmosphere. Furthermore, after vacuum baking at 300 ° C., washing and drying, a sample (hydrogen storage material) was obtained. In Example 5, the intermediate sample was mixed in hydrazine, held at room temperature for 10 minutes, and reduced. Then, after baking in vacuum at 300 ° C., washing and drying, a sample (hydrogen storage material) was obtained.
〈２．試料の物性〉
以上により作製された実施例１〜５と比較例１，２の各試料（水素吸蔵材料）について粉末Ｘ線回折分析、透過電子顕微鏡による観察、Ｈｅ平衡圧密度を次のようにして測定した。
<2. Sample physical properties>
About each sample (hydrogen storage material) of Examples 1-5 and Comparative Examples 1 and 2 produced as described above, powder X-ray diffraction analysis, observation with a transmission electron microscope, and He equilibrium pressure density were measured as follows.
（粉末Ｘ線回折）この回析では、カウンタ（計数管）による自動記録方式（ディフラクトメータ）を利用したＸ線回折装置として、マックサイエンス社製のＭＸＰ１８ＶＡＨＦを使用した。計測では、Ｘ線管球への印加電圧および電流は４０ｋＶ、１５０ｍＡの条件とし、入射Ｘ線としてはＣｕＫαを用いた。各試料のＸ線粉末図形を測定し、（００２）面の２θ及び（００２）面の層間距離を測定した。 (Powder X-ray diffraction) In this diffraction, MXP18VAHF manufactured by Mac Science Co., Ltd. was used as an X-ray diffraction apparatus utilizing an automatic recording method (diffractometer) using a counter (counter tube). In the measurement, the voltage and current applied to the X-ray tube were 40 kV and 150 mA, and CuKα was used as the incident X-ray. The X-ray powder pattern of each sample was measured, and the 2θ on the (002) plane and the interlayer distance on the (002) plane were measured.
（Ｈｅ平衡圧密度の測定）この測定では、図１に模式化したように、圧力容器１と２からなる測定装置を用い、Ｈｅ平衡圧密度を次のようにして計測した。まず、圧力容器２に測定試料を約１ｇ精量して投入する。次に、圧力容器１と２を真空排気した後、容器２に約０．２ＭＰａのＨｅを入れて正確に圧力Ｐ０．２を測定する。また、圧力容器２側の弁１を閉じた状態で、圧力容器１に圧力０．８ＭＰａのＨｅを入れて正確に圧力Ｐ０．８を測定する。また、圧力容器２の上流側配管部に設けられた弁２を閉じた状態で、弁１と弁３を開き圧力容器１と圧力容器２のＨｅ平衡圧ＰＥを測定する。そして、試料のＨｅ平衡圧密度は以下の式１に基づいてＶ０を求める。
(Measurement of He Equilibrium Pressure Density) In this measurement, as schematically shown in FIG. 1, the He equilibrium pressure density was measured as follows using a measuring apparatus consisting of
（式１）
［（Ｐ０．８・Ｖ２）／Ｔ０．８］＋［（Ｐ０．２・（Ｖ１-Ｖｓ）／Ｔ０．２）＝
［（ＰＥ・Ｖ２）／ＴＥ］＋［ＰＥ・(Ｖ１-Ｖｓ)／ＴＥ］
(Formula 1)
[(P 0.8 · V 2 ) / T 0.8 ] + [(P 0.2 · (V 1 −V s ) / T 0.2 ) =
[(P E · V 2 ) / T E ] + [P E · (V 1 −V s ) / T E ]
そして、Ｈｅ法における密度は試料重量Ｗ／試料容積Ｖ０より求める。ここで、反応容器の容積Ｖ１，Ｖ２はあらかじめ測定しておく。また、それぞれの圧力条件での圧力容器内の温度（Ｔ０．８、Ｔ０．２、ＴＥ）は３０℃に設定したが、Ｈｅ法での密度の測定には実測値を用いた。 The density in the He method obtained from sample weight W / sample volume V 0. Here, the volumes V 1 and V 2 of the reaction vessel are measured in advance. Moreover, although the temperature ( T0.8 , T0.2 , TE ) in the pressure vessel in each pressure condition was set to 30 degreeC, the measured value was used for the measurement of the density by He method.
（その他）各試料の比表面積［ｍ２ ／ｇ］の測定は、窒素吸着法を用い、解析にはBrunauer-Emmett-TellerによるＢＥＴ式より求めた（準拠規格：ＩＳＯ ９２７７）。また、透過電子顕微鏡による観察を行った。この顕微鏡による像観察では、透過型電子顕微鏡としてＥＦＩ製Ｔｅｃｎａｉ Ｇ２を使用し、加速電圧２００ｋＶに設定して各試料の層間の広がりを調べた。 (Others) The specific surface area [m 2 / g] of each sample was measured using a nitrogen adsorption method, and the BET equation by Brunauer-Emmett-Teller was used for analysis (compliance standard: ISO 9277). Moreover, observation with a transmission electron microscope was performed. In the image observation with this microscope, a Tecnai G2 manufactured by EFI was used as a transmission electron microscope, and the acceleration voltage was set to 200 kV, and the spread between the layers of each sample was examined.
〈３．各試料の評価〉実施例１〜５および比較例１，２の各試料はＪＩＳ ７２０１、７２０３に準じた試験方法により、水素吸蔵量と水素放出量の測定を行った。この測定では、各試料を精秤した後、試料管に入れて真空排気した後、１．５ＭＰａまで水素圧を上げて水素吸蔵量［質量％］を容量法で測定した。次に常温まで戻して水素放出量を確認した。表２は以上の実施例１〜３及び比較例１を材料構成・物性とともに評価結果を一覧し、表３は以上の実施例４〜５及び比較例２を材料構成・物性とともに評価結果を一覧したものである。 <3. Evaluation of Samples> The samples of Examples 1 to 5 and Comparative Examples 1 and 2 were measured for hydrogen storage amount and hydrogen release amount by a test method according to JIS 7201 and 7203. In this measurement, each sample was precisely weighed, placed in a sample tube and evacuated, and then the hydrogen pressure was increased to 1.5 MPa, and the hydrogen storage amount [mass%] was measured by the volume method. Next, the temperature was returned to room temperature, and the hydrogen release amount was confirmed. Table 2 lists the evaluation results of Examples 1 to 3 and Comparative Example 1 together with the material constitution / physical properties, and Table 3 lists the evaluation results of Examples 4 to 5 and Comparative Example 2 together with the material constitution / physical properties. It is a thing.
表１から次のようなことが分かる。まず、比較例１の試料（水素吸蔵材料）は、上記した反応時間が３時間の条件で、黒鉛を十分酸化させた酸化黒鉛を調製し、Ｈ２雰囲気−６００℃で還元した例である。この酸化黒鉛は、層間がほとんど均一に酸化されているため、加熱処理により層間内の酸素が一気にガス化し、そしてほぼ均一に大きく膨脹する。その結果、酸化黒鉛は還元により微粒子化し粒子内に空間を作りづらい。この点は、例えば、比較例１の酸化黒鉛中のＸＲＤの２θのピークを強度比で表わすと、２６．０〜２６．６°に現れる黒鉛のピーク１００に対し、酸化黒鉛の層間が広がったピーク(１３．５〜１６．０°)は１６７０であり、黒鉛中のほとんどが酸化されていることが分かる。これに対し、６００℃でＨ２還元することにより、層間の酸素が分解し、層間が不規則に拡張し２θが１３．５〜１６．０°のピークが消失している。しかし、還元時には、一定温度で急激なガス化が起こるため、層間は大きく開き、粒子内に水素が侵入できる空間が創生されていない。つまり、Ｈｅ法での密度は、還元前１．６３ｇ/ｃｍ３に対し、還元後１．３０ｇ/ｃｍ３と比較的低下が少なく、層間内における空間の発生が少ないことが確認できる。また、比表面積が４２５ｍ２／ｇと大きく増加しており、層間の拡張により微粒子化が発生、つまり層間内の空間が大きく開いていることが推察できる。その結果、水素が侵入できる空間は減少し、１．５ＭＰａ時の水素吸蔵量も０．０２mass%と小さくなっている。 Table 1 shows the following. First, the sample of Comparative Example 1 (hydrogen storage material) is an example in which graphite oxide obtained by sufficiently oxidizing graphite was prepared and reduced at H 2 atmosphere at −600 ° C. under the above-described reaction time of 3 hours. Since this graphite oxide is oxidized almost uniformly between the layers, oxygen in the layers is gasified at a stretch by the heat treatment, and expands almost uniformly. As a result, graphite oxide is reduced to fine particles by reduction and it is difficult to create a space in the particles. For example, when the 2θ peak of XRD in the graphite oxide of Comparative Example 1 is expressed as an intensity ratio, the interlayer of the graphite oxide spreads with respect to the peak 100 of graphite appearing at 26.0 to 26.6 °. The peak (13.5 to 16.0 °) is 1670, indicating that most of the graphite is oxidized. On the other hand, oxygen reduction between layers is decomposed by H 2 reduction at 600 ° C., the layers expand irregularly, and a peak at 2θ of 13.5 to 16.0 ° disappears. However, during the reduction, rapid gasification occurs at a constant temperature, so that the layers are greatly opened, and a space in which hydrogen can enter the particles is not created. That is, it can be confirmed that the density in the He method is relatively low, with 1.30 g / cm 3 after reduction compared to 1.63 g / cm 3 before reduction, and there is little generation of space in the interlayer. Further, the specific surface area is greatly increased to 425 m 2 / g, and it can be inferred that fine particles are generated by expansion between layers, that is, a space between layers is greatly opened. As a result, the space where hydrogen can enter is reduced, and the hydrogen storage amount at 1.5 MPa is also as small as 0.02 mass%.
また、比較例２の試料は、比較例１と同一の酸化黒鉛を用い、３００℃真空焼成による還元を行った例である。この酸化黒鉛は、低温で焼成することで、層間内で共有結合した酸素の急激なガス化を抑制することを狙ったものであるが、黒鉛が十分に酸化されているため還元時に大きく膨脹し、微粒子化、比表面積の増加が進み、水素が侵入できる空間の発生が不足する。その結果、１．５ＭＰａ時の水素吸蔵量も０．２５mass％とまだ低い値である。 The sample of Comparative Example 2 is an example in which the same graphite oxide as that of Comparative Example 1 is used and reduction is performed by vacuum firing at 300 ° C. This graphite oxide is intended to suppress rapid gasification of oxygen covalently bonded between layers by firing at a low temperature. However, since graphite is sufficiently oxidized, it expands greatly during reduction. As a result, the formation of fine particles and the increase of the specific surface area are advanced, and the generation of a space where hydrogen can enter is insufficient. As a result, the hydrogen storage amount at 1.5 MPa is still as low as 0.25 mass%.
これに対し、実施例１〜２の試料は酸化黒鉛の酸化度合いを制御した例である。このうち、実施例１の試料は、上記した反応時間が１０分の条件で調製し、ＸＲＤにより２θのピーク強度比を確認しているが、２６．０〜２６．６°に現れる黒鉛のピーク１００に対し、酸化黒鉛の層間が広がったピーク（１３．５〜１６．０°）は１３２９であり、試料中に黒鉛構造部分が少し残っている。同様に、実施例２の試料は、上記した反応時間が１分の試料であるが、２６．０〜２６．６°に現れる黒鉛のピーク強度比１００に対し、酸化黒鉛の層間が広がったピーク（１３．５〜１６．０°）は１９３であり、試料中に黒鉛構造部分と酸化黒鉛部分が混在している構造である。これらの試料は３００℃真空焼成で還元することで、比表面積が６．４又は５．７ｍ２／ｇと小さく、１．５ＭＰａ時の水素吸蔵量が実施例１の場合に１．６０mass%、実施例２の場合に１．２０mass%とそれぞれ大きく向上している。 On the other hand, the samples of Examples 1 and 2 are examples in which the degree of oxidation of graphite oxide is controlled. Among them, the sample of Example 1 was prepared under the above-described reaction time of 10 minutes, and the peak intensity ratio of 2θ was confirmed by XRD, but the peak of graphite appearing at 26.0 to 26.6 °. With respect to 100, the peak (13.5 to 16.0 °) at which the interlayer of graphite oxide spreads is 1329, and a part of the graphite structure remains in the sample. Similarly, the sample of Example 2 is a sample having the above-described reaction time of 1 minute, but the peak in which the interlayer of graphite oxide spreads with respect to the peak intensity ratio 100 of graphite appearing at 26.0 to 26.6 °. (13.5 to 16.0 °) is 193, which is a structure in which a graphite structure portion and a graphite oxide portion are mixed in the sample. These samples are reduced by vacuum baking at 300 ° C., so that the specific surface area is as small as 6.4 or 5.7 m 2 / g, and the hydrogen occlusion amount at 1.5 MPa is 1.60 mass% in Example 1, In the case of Example 2, it is improving significantly with 1.20 mass%.
表２から次のようなことが分かる。実施例３〜５の試料は、層間内に形成された空間または空間を形成している炭素の六角網面に水素を吸着する活性点を付与した例である。このうち、実施例３の試料は、炭素の六角網面の一部をＨ２Ｏ２処理で酸化させ、活性点を付与した例である。また、実施例４、５の試料は、層間や粒子間に形成されて空間にＰｔ，Ｐｄを含有または置換させた試料を調製した例である。なお、実施例３〜５の各試料はともに上記した反応時間が１分の酸化黒鉛を用いており、２６．０〜２６．６°に現れる黒鉛のピーク強度比１００に対し、酸化黒鉛の層間が広がったピーク（１３．５〜１６．０°）は１９３であり、試料中に黒鉛構造部分と酸化黒鉛部分が混在している構造である。そして、実施例３では前記の試料を温度３００℃、真空下での還元後、酸化処理したもので、１３．５〜１６．０°のピークが消失し、２１．０〜２３．０°にピークが発現し、また、層間が大きく広がり過ぎていないため比表面積も５．９ｍ２/gと小さく、酸化処理で活性点を付与していることより水素吸蔵量が１．５５％と向上している。また、実施例４と５では前記の試料を温度３００℃、Ｈ２還元した後、更に温度３００℃で真空焼成したものであるが、１３．５〜１６．０°のピークが消失し、２２．２〜２２．８°にピークが発現し、また、層間が大きく広がり過ぎていないため比表面積も５８．９５ｍ２/gと比較的小さい。また、創生した空間などにＰｔ，Ｐｄが付加され、空間内の吸着力が向上しているため水素吸蔵量は２．１masss%、２．０mass％といずれも向上している。 Table 2 shows the following. The samples of Examples 3 to 5 are examples in which active sites that adsorb hydrogen are imparted to a space formed between layers or a hexagonal mesh surface of carbon forming a space. Among these, the sample of Example 3 is an example in which a part of the hexagonal network surface of carbon is oxidized by H 2 O 2 treatment to give an active site. The samples of Examples 4 and 5 are examples in which samples formed between layers or between particles and containing or replacing Pt and Pd in the space were prepared. Note that each of the samples of Examples 3 to 5 uses graphite oxide having a reaction time of 1 minute as described above, and the graphite peak intensity ratio of 100 that appears at 26.0 to 26.6 ° is 100 nm. Peak (13.5 to 16.0 °) is 193, which is a structure in which a graphite structure portion and a graphite oxide portion are mixed in the sample. In Example 3, the sample was oxidized at a temperature of 300 ° C. after being reduced in vacuum, and the peak at 13.5 to 16.0 ° disappeared, and the value reached 21.0 to 23.0 °. Since the peak appears and the interlayer is not expanded too much, the specific surface area is as small as 5.9 m 2 / g, and the hydrogen storage capacity is improved to 1.55% because the active sites are given by oxidation treatment. ing. In Examples 4 and 5, the sample was subjected to H 2 reduction at a temperature of 300 ° C. and then vacuum baked at a temperature of 300 ° C., but the peak at 13.5 to 16.0 ° disappeared. A peak appears at .2 to 22.8 °, and the interlayer is not too wide, so the specific surface area is relatively small at 58.95 m 2 / g. Further, since Pt and Pd are added to the created space and the like, and the adsorption power in the space is improved, the hydrogen storage amount is improved to 2.1 mass% and 2.0 mass%.
以上の実施例より、粉末Ｘ線回折法による回折角度（２θ）が１３．５〜１６．０°と２６．０〜２６．６°にピークを持つ酸化黒鉛を用い、還元処理などにより１３．５〜１６．０°のピークを消失させ、２１．０〜２３．０°にピークを発現させた黒鉛系水素吸蔵材料とすることで、比表面積が１００ｍ２/g以下と小さく、かつ水素吸蔵能が大きく向上されることが分かった。 From the above examples, graphite oxide having peaks at diffraction angles (2θ) by powder X-ray diffractometry of 13.5 to 16.0 ° and 26.0 to 26.6 ° is used and reduced by a reduction treatment or the like. The specific surface area is as small as 100 m 2 / g or less, and the hydrogen occlusion is made by using a graphite-based hydrogen occlusion material in which the peak at 5 to 16.0 ° disappears and the peak is developed at 21.0 to 23.0 °. It was found that the performance was greatly improved.
１と２は圧力容器
1 and 2 are pressure vessels
Claims (7)
前記酸化黒鉛を還元処理することにより前記層間内の酸素を一部または全て取り出して、前記層間内に水素侵入用の空間を形成し、かつ粉末Ｘ線回折法による回折角度（２θ）が前記１３．５〜１６．０°のピークを消失し、２θ＝１９．５〜２０．５°または２１．０〜２３．０に新たなピークを発現していることを特徴する黒鉛系水素吸蔵材料の製造方法。
Using graphite oxide having oxygen covalently bonded between graphite layers and having peaks at diffraction angles (2θ) by powder X-ray diffraction of 13.5 to 16.0 ° and 26.0 to 26.6 ° And
By reducing the graphite oxide, a part or all of oxygen in the interlayer is taken out to form a space for hydrogen penetration in the interlayer, and the diffraction angle (2θ) by the powder X-ray diffraction method is 13 A graphite-based hydrogen storage material characterized by disappearing a peak of .5 to 16.0 ° and developing a new peak at 2θ = 19.5 to 20.5 ° or 21.0 to 23.0 Production method.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2011500488A (en) * | 2007-10-19 | 2011-01-06 | ユニバーシティー オブ ウロンゴング | Method for producing graphene |
| WO2012173345A3 (en) * | 2011-06-16 | 2013-04-04 | 인하대학교 산학협력단 | Method for preparing graphite powder composite supported by transition metal particles for storing hydrogen |
| JP2013065837A (en) * | 2011-08-26 | 2013-04-11 | Semiconductor Energy Lab Co Ltd | Power storage device |
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2004
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2011500488A (en) * | 2007-10-19 | 2011-01-06 | ユニバーシティー オブ ウロンゴング | Method for producing graphene |
| WO2012173345A3 (en) * | 2011-06-16 | 2013-04-04 | 인하대학교 산학협력단 | Method for preparing graphite powder composite supported by transition metal particles for storing hydrogen |
| KR101273492B1 (en) * | 2011-06-16 | 2013-06-17 | 인하대학교 산학협력단 | Manufacturing method of transition metal nanoparticles loaded graphite composites for the hydrogen storage |
| US20140117279A1 (en) * | 2011-06-16 | 2014-05-01 | Inha-Industry Partnership Institute | Method for preparing graphite powder composite supported by transition metal particles for storing hydrogen |
| US9663359B2 (en) | 2011-06-16 | 2017-05-30 | Inha-Industry Partnership Institute | Method for preparing graphite powder composite supported by transition metal particles for storing hydrogen |
| JP2013065837A (en) * | 2011-08-26 | 2013-04-11 | Semiconductor Energy Lab Co Ltd | Power storage device |
| JP2017208349A (en) * | 2011-08-26 | 2017-11-24 | 株式会社半導体エネルギー研究所 | Production method of power storage device |
| US10748673B2 (en) | 2011-08-26 | 2020-08-18 | Semiconductor Energy Laboratory Co., Ltd. | Power storage device |
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