JP2010275140A - Hydrogen storage carbon material and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrogen storage carbon material and a method for producing the same, the hydrogen storage carbon material having an enhanced hydrogen storage capacity. <P>SOLUTION: In the hydrogen storage material, a portion of stored hydrogen shows a peak having a half-value width of ≤30 ppm at a position in the chemical shift range of -5 to -30 ppm in<SP>1</SP>H-NMR measurement. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a hydrogen storage carbon material and a method for producing the same, and more particularly to a carbon material with improved hydrogen storage capacity.

  In recent years, research and development of fuel cells that extract electric energy using hydrogen have been actively conducted, and their practical application as a self-generated power source or an automotive power source is expected. For example, since a polymer electrolyte fuel cell (PEFC) can be operated in a low temperature region, it is suitable for use in a home cogeneration system or an automobile. In addition, PEFC has attracted attention as a power source and portable power source for electric vehicles because of its high energy conversion efficiency, short start-up time, and small and light system.

  In putting a fuel cell into practical use, it is important how efficiently and safely hydrogen as a fuel can be stored in a limited housing space. One of the hydrogen storage methods is a method using a hydrogen storage material.

  As the hydrogen storage material, for example, the use of an alloy has been studied. However, when a hydrogen storage alloy is used, there is a problem that the weight of the hydrogen storage device increases. Also, depending on the type of metal used, there are problems in terms of price and reserves.

  On the other hand, the use of carbon materials that are relatively inexpensive and are not depleted of resources is being studied. For example, Patent Document 1 describes a carbon material in which the hydrogen storage amount is increased by expanding the interval between carbon layers to 0.5 nm or more.

JP 2005-41742 A

  However, the hydrogen storage capacity of the carbon materials studied so far is not sufficient for practical use as a hydrogen storage material.

  On the other hand, the inventors of the present invention, as a result of repeated independent studies, found a carbon material that occludes hydrogen in a manner not found in conventional hydrogen occlusion carbon materials, and completed the present invention. It was.

  That is, the present invention has been made in view of the above problems, and an object thereof is to provide a hydrogen storage carbon material having improved hydrogen storage capacity and a method for producing the same.

A hydrogen storage carbon material according to an embodiment of the present invention for solving the above-described problem is that a peak of a half-value width of 30 ppm or less at a position where a part of the stored hydrogen is a chemical shift of −5 to −30 ppm in ¹ H-NMR measurement. It is characterized by showing. According to the present invention, it is possible to provide a hydrogen storage carbon material with improved hydrogen storage capacity.

The hydrogen storage carbon material may have an average crystallite size La in the a-axis direction of a carbon structure of 5.0 nm or less and an average crystallite size Lc in the c-axis direction of 0.5 nm or more. The hydrogen storage carbon material may have an average (002) plane distance d ₀₀₂ of a carbon structure of 0.340 to 0.450 nm. Further, the hydrogen storage carbon material has a peak corresponding to the (002) plane reflection with respect to the total area of the peak area corresponding to the (002) plane reflection of the carbon structure and the peak area derived from the amorphous structure in the X-ray diffraction diagram. The area ratio may be 10% or more.

  The hydrogen storage carbon material may be obtained by carbonizing a raw material containing a resin and a metal. In this case, the hydrogen storage carbon material may be obtained by carbonizing the raw material at 700 ° C. or higher.

The method for producing a hydrogen storage carbon material according to an embodiment of the present invention for solving the above-described problem includes performing carbonization of a raw material containing a resin and a metal under a plurality of conditions, and storing the storage among the plurality of conditions. The conditions for obtaining a carbon material having a peak with a half-value width of 30 ppm or less at a position of a chemical shift of -5 to -30 ppm in a ¹ H-NMR measurement in ¹ H-NMR measurement are selected, and the raw material is carbonized under the selected conditions. And producing a hydrogen storage carbon material. ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the hydrogen storage carbon material which improved the hydrogen storage ability can be provided.

  A method for producing a hydrogen storage carbon material according to an embodiment of the present invention for solving the above-described problem is that carbonization of a raw material containing a resin and a metal is performed under a plurality of conditions. In the structure, a condition for obtaining a carbon material having an average crystallite size La in the a-axis direction of 5.0 nm or less and an average crystallite size Lc in the c-axis direction of 0.5 nm or more is selected. The raw material is carbonized to produce a hydrogen storage carbon material. ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the hydrogen storage carbon material which improved the hydrogen storage ability can be provided.

Further, among the plurality of conditions, it is also possible to further average the carbon structure (002) spacing _{d 002} selects a condition wherein the carbon material is 0.340~0.450nm is obtained. Among the plurality of conditions, the (002) plane reflection corresponds to the total area of the peak area corresponding to the (002) plane reflection of the carbon structure and the peak area derived from the amorphous structure in the X-ray diffraction diagram. The conditions for obtaining the carbon material having a peak area ratio of 10% or more may be selected.

  ADVANTAGE OF THE INVENTION According to this invention, the hydrogen storage carbon material which improved hydrogen storage ability, and its manufacturing method can be provided.

It is explanatory drawing which shows an example of the transmission electron micrograph of the carbon material image | photographed in the Example which concerns on one Embodiment of this invention. It is explanatory drawing which shows an example of the transmission electron micrograph of the carbon material image | photographed in the Example which concerns on one Embodiment of this invention. It is explanatory drawing which shows an example of the transmission electron micrograph of the carbon material image | photographed in the Example which concerns on one Embodiment of this invention. It is explanatory drawing which shows an example of the transmission electron micrograph of the carbon material image | photographed in the Example which concerns on one Embodiment of this invention. It is explanatory drawing which shows an example of the transmission electron micrograph of the carbon material image | photographed in the Example which concerns on one Embodiment of this invention. It is explanatory drawing which shows an example of the transmission electron micrograph of the carbon material image | photographed in the Example which concerns on one Embodiment of this invention. It is explanatory drawing about the benzene coronene base model used for the analysis of the crystallite size La distribution in the Example which concerns on one Embodiment of this invention. It is explanatory drawing which shows an example of the X-ray-diffraction figure obtained by the Example which concerns on one Embodiment of this invention. It is explanatory drawing which shows an example of the result of having performed evaluation regarding a carbon structure in the Example which concerns on one Embodiment of this invention. It is explanatory drawing which shows an example of the peak separation of the X-ray-diffraction figure performed when measuring the crystallinity degree of a shell-like structure in the Example which concerns on one Embodiment of this invention. It is explanatory drawing which shows an example of the result of having evaluated the crystallite size La distribution of a carbon structure in the Example which concerns on one Embodiment of this invention. It is explanatory drawing which shows an example of the result of having evaluated the lamination number distribution of the carbon structure in the Example which concerns on one Embodiment of this invention. It is explanatory drawing which shows an example of the NMR spectrum acquired by the Example which concerns on one Embodiment of this invention. It is explanatory drawing which shows an example of the NMR spectrum acquired by the Example which concerns on one Embodiment of this invention. It is explanatory drawing which shows an example of the NMR spectrum acquired by the Example which concerns on one Embodiment of this invention. It is explanatory drawing which shows an example of the NMR spectrum acquired by the Example which concerns on one Embodiment of this invention. It is explanatory drawing which shows an example of the NMR spectrum acquired by the Example which concerns on one Embodiment of this invention. It is explanatory drawing which shows an example of the NMR spectrum acquired by the Example which concerns on one Embodiment of this invention. It is explanatory drawing which shows an example of the NMR spectrum acquired by the Example which concerns on one Embodiment of this invention. It is explanatory drawing which shows an example of the NMR spectrum acquired by the Example which concerns on one Embodiment of this invention. It is explanatory drawing which shows an example of the NMR spectrum acquired by the Example which concerns on one Embodiment of this invention. It is explanatory drawing which shows an example of the result of having evaluated the half value width and peak top position of the peak shown by the NMR spectrum in the Example which concerns on one Embodiment of this invention. It is explanatory drawing which shows an example of the result of having evaluated the temperature dependence of the peak shown by the NMR spectrum in the Example which concerns on one Embodiment of this invention. It is explanatory drawing which shows an example of the result of having evaluated hydrogen storage ability in the Example which concerns on one Embodiment of this invention.

  Hereinafter, an embodiment of the present invention will be described. Note that the present invention is not limited to the present embodiment.

The hydrogen storage carbon material according to the present embodiment (hereinafter referred to as “the present carbon material”) has a hydrogen storage capacity for storing hydrogen in its carbon structure, and a portion of the stored hydrogen is ¹ H-NMR measurement. It is a carbon material that shows a peak with a half-value width of 30 ppm or less at a chemical shift of -5 to -30 ppm.

That is, when ¹ H-NMR measurement is performed by storing hydrogen in the present carbon material, a peak having a half-width of 30 ppm or less (hereinafter, referred to as “half-value width”) caused by a part of the stored hydrogen is located at a position shifted by 5 to 30 ppm toward the high magnetic field side. "Singular peak") appears. In addition, the chemical shift of a peak can prescribe | regulate the peak obtained when hydrogen is introduce | transduced only into the solvent (for example, (alpha) -alumina) used for dispersion | distribution of this carbon material on the basis (0 ppm), for example.

This peculiar peak is peculiar to the present carbon material that is not detected even when activated carbon or carbon black occluded with hydrogen is subjected to ¹ H-NMR measurement. That is, the present carbon material occludes hydrogen in a unique manner that exhibits a specific peak in ¹ H-NMR measurement, which is not found in other carbon materials.

  It is not clear what mechanism the hydrogen storage mode peculiar to this carbon material is, but it is thought to be due to the specific interaction between the carbon structure peculiar to this carbon material and the introduced hydrogen. It is done.

  This carbon material is obtained by carbonizing a raw material containing a resin and a metal, and a defect portion such as an edge portion or a bent portion is formed as an active point on a carbon hexagonal network surface (hereinafter simply referred to as “carbon network surface”). It has a large number of formed carbon structures. That is, the present carbon material has, for example, a turbulent layer structure (hereinafter referred to as “shell structure”) similar to a graphite structure, which has been developed in an onion shape around metal fine particles. It is considered that the edge portion and the bent portion of the carbon network surface included in the shell-like structure function as active points for chemical reactions such as catalytic reactions.

Moreover, this carbon material can be made into the microparticles | fine-particles with an average particle diameter of 3-100 nm, for example, Preferably it is 30-50 nm. When the present carbon material is such a nanoparticle, many active points as described above are formed on the surface having a large curvature. The specific surface area of the present carbon material can be, for example, 100 to 3000 m ² / g.

  In the carbon material, for example, the average crystallite size La in the a-axis direction in the carbon structure is 5.0 nm or less, and the average crystallite size Lc in the c-axis direction is 0.5 nm or more. it can.

  Here, the average crystallite size La (hereinafter, simply referred to as “average La”) corresponds to a diameter when a plane formed by two-dimensionally expanding a carbon network surface included in the carbon structure is approximated to a circle. And the extent of the plane spread. Further, the average crystallite size Lc (hereinafter, simply referred to as “average Lc”) indicates the thickness in the c-axis direction of the carbon network plane group stacked in parallel included in the carbon structure.

  The average La of the present carbon material can be further set to, for example, 4.0 nm or less, and can be set to 3.0 nm or less. The lower limit value of the average La is not particularly limited, but the average La can be set to 1.0 nm or more, for example. Further, the average Lc can be set to 0.6 nm or more, for example. The upper limit value of the average Lc is not particularly limited, but the average Lc can be set to 1.5 nm or less, for example.

  The carbon structure of the present carbon material can be specified by any combination of the average La range and the average Lc range. When the average La is equal to or less than the above-described threshold value, the carbon structure of the present carbon material has a relatively small spread of the carbon network surface in the a-axis direction, and the carbon network surface is frequently interrupted and formed (high density). Of active points).

  In the carbon material, in the distribution of crystallite size La of 7 nm or less on the carbon network surface constituting the carbon structure, for example, the ratio of 1 to 5 nm is 10% or more, and the ratio of 5 to 7 nm is 60%. It can be: The ratio of 5 to 7 nm in the crystallite size La distribution can be, for example, 50% or less, and 40% or less.

  On the other hand, when the average Lc is equal to or greater than the above threshold value, the present carbon material has a carbon structure in which a laminated structure in the c-axis direction is developed. As the average Lc increases, the present carbon material has a carbon structure with a larger number of carbon network layer stacks.

  In addition, the present carbon material can have a carbon structure in which, for example, the ratio of the number of laminations of 3 or more in the distribution of the number of laminations of the carbon network surface in the c-axis direction is 30% or more. In the distribution of the number of layers, the ratio of the number of layers 3 or more can be, for example, 40% or more, and 45% or more.

In addition, for example, the carbon material may have an average (002) plane distance d _{002 of the} carbon structure of 0.340 to 0.450 nm. Here, the average (002) plane spacing d ₀₀₂ (hereinafter simply referred to as “average plane spacing d ₀₀₂ ”) is the average distance between the carbon (002) planes constituting the carbon structure. The average interplanar distance d ₀₀₂ of the present carbon material can be further set to 0.340 to 0.400 nm, for example, and can be set to 0.340 to 0.350 nm.

  Further, the present carbon material has, for example, a peak corresponding to the (002) plane reflection with respect to a total area of a peak area corresponding to the (002) plane reflection of the carbon structure and a peak area derived from the amorphous structure in the X-ray diffraction diagram. The area ratio may be 10% or more.

  Here, in the above X-ray diffraction diagram, when the present carbon material has a developed structure such as a shell-like structure (hereinafter collectively referred to as “shell-like structure”), a diffraction angle (2θ ) Shows a diffraction peak of the carbon (002) plane in the vicinity of 26 °. This peak includes a peak derived from the (002) plane of the shell-like structure carbon (hereinafter referred to as “shell-like structure peak”) and a peak derived from the amorphous structure (hereinafter referred to as “amorphous structure peak”). The two types are mixed.

  Therefore, the peak near 26 ° can be separated into a shell-like structure peak and an amorphous structure peak by peak separation of the X-ray diffraction data. Then, when the ratio of the peak area of the shell-like structure to the sum of these two types of peak areas is calculated, the ratio is an index indicating the degree of development (crystallization) of the shell-like structure (hereinafter referred to as “crystallization of the shell-like structure”). It is called "degree".)

  The degree of crystallinity of the shell-like structure of the present carbon material can be, for example, 15% or more, 20% or more, and 25% or more. When the crystallinity of the shell-like structure is not less than the above-mentioned threshold value, the present carbon material has a carbon structure including a sufficiently developed shell-like structure. As the crystallinity of the shell-like structure increases, the present carbon material has a more developed shell-like structure.

  Note that the crystallinity is determined by the sharp component area and the substantially flat component area in the X-ray diffraction diagram corresponding to the (002) plane reflection of the carbon particles having a shell-like structure described in JP-A-2007-207662. This corresponds to the ratio of the sharp component area to the total area.

The present carbon material occludes hydrogen in an aspect that is observed as a singular peak in ¹ H-NMR measurement and is not found in conventional hydrogen occlusion carbon materials. That is, the present carbon material has a unique aspect considered to be attributable to the above-described carbon structure in addition to an aspect known for a conventional hydrogen storage carbon material (for example, adsorption of molecular hydrogen on the surface). Can store hydrogen.

  In this respect, for example, as described above, the present carbon material has a unique carbon structure in which many active points such as edge portions are formed, a laminated structure is developed, and carbon network surfaces are laminated at appropriate intervals. Thus, it is considered that hydrogen can be occluded in a specific mode represented by the specific peak.

Note that the average interplanar spacing d ₀₀₂ of the present carbon material is larger than that of the graphite crystal, and smaller than the range of 0.5 nm or more, which is a target in the prior art for expanding the interplanar spacing. Therefore, the present carbon material is completely different from the conventionally attempted approach of increasing the interplanar spacing, and is excellent by having a unique carbon structure derived from a turbulent structure while maintaining the interplanar spacing within an appropriate range. The carbon storage ability is demonstrated.

Thus, this carbon material exhibits an excellent hydrogen storage capacity. That is, for example, the hydrogen storage amount per unit surface area of the present carbon material is significantly higher than that of activated carbon. Specifically, the hydrogen storage amount per unit surface area of the present carbon material can be set to, for example, 1.0 × 10 ⁻³ g / m ² or more. The present carbon material having such an excellent hydrogen storage capacity can be applied to various apparatuses and systems that use hydrogen as a raw material.

  Next, a method for producing the hydrogen storage carbon material according to the present embodiment (hereinafter referred to as “the present production method”) will be described.

  In this manufacturing method, the hydrogen storage carbon material which has the carbon structure formed by carbonization of the said resin is manufactured by carbonizing the raw material containing resin and a metal. The present carbon material can be produced efficiently and reliably by this production method.

  The resin used as a part of the raw material is not particularly limited as long as it is a polymer material that can be carbonized. That is, for example, a thermosetting resin or a thermoplastic resin that can be carbonized can be used. Specifically, for example, polyvinyl pyridine, polyacrylonitrile, chelate resin, cellulose, carboxymethyl cellulose, polyvinyl alcohol, polyacrylic acid, polymethyl acrylate, polymethyl methacrylate, polyfurfuryl alcohol, furan resin, phenol resin, phenol formaldehyde resin , Polyimidazole, melamine resin, epoxy resin, pitch, lignite, polyvinylidene chloride, polycarbodiimide, lignin, anthracite, biomass, protein, humic acid, polysulfone, polyaminobismaleimide, polyimide, polyaniline, polypyrrole, ionomer may be used it can. These resins can be used singly or in combination of two or more.

  In addition, the effect similar to the case where nitrogen atom is doped can be acquired by using resin containing a nitrogen atom in a molecule | numerator. The resin may contain a metal atom as long as it is a polymer material that can be carbonized by thermosetting. Moreover, when using resin with poor thermosetting, it is good also as performing infusibilization of the said resin. By this operation, the structure of the resin can be maintained even at a temperature higher than the original melting point or softening point of the resin. The infusibilization method can be performed by a known method. Moreover, even if it is a polymeric material generally considered not suitable for carbonization, carbonization can be performed by mixing or copolymerizing other polymeric materials that promote crosslinking, for example. The shape with the resin is not particularly limited as long as the hydrogen storage ability of the carbon material produced by this production method is not impaired. For example, the shape can be a sheet, a fiber, a block, or a particle.

  The metal used as a part of the raw material is not particularly limited as long as it does not hinder the hydrogen storage ability of the carbon material produced by this production method. That is, as the metal, for example, a transition metal can be preferably used, and a metal belonging to Group 4 to Group 4 of the periodic table can be particularly preferably used.

  These metals can be used individually by 1 type or in combination of 2 or more types. Specifically, for example, one or more selected from the group consisting of cobalt, iron, nickel, manganese, zinc, and copper can be preferably used, and cobalt and iron can be particularly preferably used.

  As the metal, a simple substance of the metal or a compound of the metal can be used. As the metal compound, for example, metal salts, metal hydroxides, metal oxides, metal nitrides, metal sulfides, metal carbonides, metal complexes can be preferably used, and metal chlorides, metal oxides, metal complexes can be used. Can be used particularly preferably.

  Further, for the purpose of increasing the surface area of the present carbon material, other carbon materials, ceramic materials, and metal materials may be added to the raw material. Examples of such other materials include carbon nanotubes, carbon nanofibers, carbon black, ketjen black, acetylene black, graphite, activated carbon, glassy carbon, carbon fibers, mesoporous silica, mesoporous carbon, metal powder, and metal fine particles. One or more of metal fibers and fullerenes can be used. The ratio of these other materials to the raw material can be, for example, 1 to 90% by weight or less, and more preferably 5 to 50% by weight.

  Carbonization is performed by heating a raw material and holding it for a predetermined time at a predetermined temperature at which a resin contained in the raw material can be carbonized (hereinafter referred to as “carbonization temperature”). The carbonization temperature can be appropriately set according to conditions such as the melting point and decomposition point of the resin.

  That is, the carbonization temperature can be, for example, 300 ° C. or higher, and preferably 700 ° C. or higher. More specifically, the carbonization temperature can be, for example, in the range of 300 to 3000 ° C, preferably in the range of 700 to 2000 ° C, and more preferably in the range of 700 to 1500 ° C. Can do. The rate of temperature rise to the carbonization temperature can be, for example, in the range of 0.5 to 300 ° C./min.

  The time for holding the raw material at the above carbonization temperature can be, for example, in the range of 5 minutes to 24 hours, and preferably in the range of 20 minutes to 2 hours. The carbonization treatment is preferably performed under a flow of an inert gas such as nitrogen.

  Moreover, in this manufacturing method, a carbon material can be pulverized and refined. The pulverization method is not particularly limited as long as the surface area of the carbon material can be increased, and any known method can be used. That is, for example, fine particles of a carbon material can be prepared using a pulverizing means such as a ball mill, a bead mill, or a jet mill.

  Moreover, in this manufacturing method, the carbon material can be subjected to a cleaning treatment for reducing the metal content. For this washing treatment, for example, an acid such as hydrochloric acid or sulfuric acid can be preferably used.

  Moreover, in this manufacturing method, activation of a carbon material can also be performed.

  The method for activating the carbon material is not particularly limited, and for example, ammoxidation, carbon dioxide activation, phosphoric acid activation, alkali activation, and water vapor activation can be used.

  In the present manufacturing method, the carbon material can also be subjected to heat treatment. This heat treatment is performed by holding the carbon material obtained by carbonization at a predetermined temperature. The temperature of heat processing can be made into the range of 300-1500 degreeC, for example.

In this production method, for example, carbonization of a raw material containing a resin and a metal is performed under a plurality of conditions, and among the plurality of conditions, a part of the occluded hydrogen is chemically shifted in ¹ H-NMR measurement. A hydrogen storage carbon material can be produced by selecting a condition for obtaining a carbon material having a peak with a half width of 30 ppm or less at a position of −5 to −30 ppm, and carbonizing the raw material under the selected condition.

  That is, in this case, first, a preliminary process for preparing a plurality of carbon materials by carbonizing a raw material under a plurality of different conditions is performed. The carbonization conditions are not particularly limited as long as they can affect the hydrogen storage capacity of the carbon material to be produced. For example, the carbonization temperature, the heating rate, the time for holding at the carbonization temperature, the composition of the raw material (Types and blending ratios of resins and metals, types and blending ratios of other additive components, etc.).

Next, ¹ H-NMR measurement is performed on the plurality of carbon materials obtained in the preliminary process, and conditions are selected based on the result of the measurement. That is, for example, by analyzing the peak derived from hydrogen obtained by ¹ H-NMR measurement, the presence or absence of the above-mentioned specific peak is determined, and the carbonization used for the preparation of the carbon material in which the specific peak is detected Select a condition.

In addition, when there are a plurality of conditions under which a carbon material exhibiting a specific peak can be prepared, for example, the average La, average Lc, average interplanar spacing d ₀₀₂ , and the crystallinity of the shell-like structure described above for the carbon material Conditions can also be selected based on the judgment based on the evaluation result regarding the carbon structure.

  The conditions selected in this way are determined as formal carbonization conditions, and the raw material is carbonized under the determined conditions to produce a hydrogen storage carbon material. Therefore, according to this manufacturing method, the carbon material excellent in hydrogen storage ability can be manufactured efficiently and reliably.

  In this production method, for example, the raw material containing the resin and the metal is carbonized under a plurality of conditions, and among these conditions, the average crystallite size La in the a-axis direction in the carbon structure is 5. Select a condition for obtaining a carbon material having an average crystallite size Lc of 0 nm or less and an average crystallite size Lc in the c-axis direction of 0.5 nm or more, and carbonize the raw material under the selected condition to produce a hydrogen storage carbon material. Can do. That is, in this case, a preliminary process for carbonizing the raw material under a plurality of conditions is performed as described above.

  Next, X-ray diffraction measurement is performed on the plurality of carbon materials obtained in the preliminary process, and conditions are selected based on the measurement results. That is, for example, the diffraction data obtained by the X-ray diffraction measurement is analyzed to determine whether the average La and the average Lc are in the above range, and both the average La and the average Lc are in the above range. The carbonization conditions used for the preparation of a certain carbon material are selected. In addition, as a threshold value which prescribes | regulates the range of average La and average Lc, arbitrary things can be employ | adopted among the various threshold values mentioned above about this carbon material.

  The conditions selected in this way are determined as formal carbonization conditions, and the raw material is carbonized under the determined conditions to produce a hydrogen storage carbon material. Therefore, according to this production method, it is possible to efficiently and reliably produce a carbon material having a specific carbon structure that exhibits an excellent hydrogen storage capacity.

Further, in this case, among the plurality of conditions, a condition for obtaining a carbon material having an average (002) plane distance d _{002 of the} carbon structure of 0.340 to 0.450 nm can be selected. That is, based on the diffraction data obtained by the X-ray diffraction measurement, among the plurality of conditions used in the preliminary process, the average La and the average Lc are each in the above range, and the average interplanar spacing d ₀₀₂ is the above described range. The carbonization conditions used for the preparation of the carbon material in the range are selected. In addition, as a threshold value which prescribes _| regulates the range of average surface space _| interval _d002 , arbitrary things can be employ | adopted among the various ranges mentioned above about this carbon material.

  The conditions selected in this way are determined as formal carbonization conditions, and the raw material is carbonized under the determined conditions to produce a hydrogen storage carbon material. Therefore, according to this production method, a carbon material having a specific carbon structure that exhibits excellent hydrogen storage capacity can be produced efficiently and more reliably.

  In these cases, among the plurality of conditions, the (002) plane reflection with respect to the total area of the peak area corresponding to the (002) plane reflection of the carbon structure and the peak area derived from the amorphous structure in the X-ray diffraction diagram. The conditions for obtaining a carbon material having a peak area ratio corresponding to 1 to 10% or more can be selected.

  That is, for example, based on diffraction data obtained by X-ray diffraction measurement, among a plurality of conditions used in the preliminary process, the average La and the average Lc are in the above-mentioned ranges, respectively, and the crystallization of the shell-like structure The carbonization conditions used for the preparation of the carbon material whose degree is in the above range are selected.

Further, for example, based on diffraction data obtained by X-ray diffraction measurement, among a plurality of conditions used in the preliminary process, the average La and the average Lc are each in the above-described range, and the average surface distance d ₀₀₂ is the above-described range. And the carbonization conditions used for the preparation of the carbon material in which the crystallinity of the shell-like structure is in the above range are selected. In addition, as a threshold value which prescribes | regulates the crystallinity degree of a shell-like structure, arbitrary things can be employ | adopted among the various threshold values mentioned above about this carbon material.

  The conditions selected in this way are determined as formal carbonization conditions, and the raw material is carbonized under the determined conditions to produce a hydrogen storage carbon material. Therefore, according to this production method, a carbon material having a specific carbon structure that exhibits excellent hydrogen storage capacity can be produced efficiently and more reliably.

  Next, specific examples according to the present embodiment will be described.

  Six types of hydrogen storage carbon materials were prepared by heating and carbonizing a raw material containing a resin and a metal.

  [Fe complex / 800 ° C.] First, a precursor composition was prepared. That is, 10 mL of phenol resin was mixed with 100 mL of acetone to prepare a mixed solution. Furthermore, 3.05 g of phthalocyanine iron was added to this mixed solution, and the mixture was stirred for 1 hour at room temperature using a magnetic stirrer. The solvent was removed at 60 ° C. using a rotary evaporator while irradiating this mixture with ultrasonic waves. A precursor composition was thus obtained.

  Next, the precursor composition was carbonized. That is, the precursor composition was put in a quartz tube, and the quartz tube was purged with nitrogen gas for 20 minutes in an elliptical reflection type infrared gold image furnace. Then, heating was started, and the temperature of the gold image furnace was increased from room temperature to 800 ° C. at a temperature increase rate of 10 ° C./min. Thereafter, the quartz tube was held at 800 ° C. for 1 hour. Thus, a carbon material produced by carbonizing the precursor composition was obtained.

  Further, the carbon material was pulverized. That is, a silicon nitride ball having a diameter of 1.5 mm was set in a planetary ball mill (P-7, Fritsch Japan Co., Ltd.), and the carbon material obtained by the carbonization treatment was pulverized for 60 minutes at a rotation speed of 800 rpm. The pulverized carbon material was taken out and classified with a sieve having an aperture of 106 μm. Thus, a powdery carbon material that passed through the sieve was obtained as a hydrogen storage carbon material (hereinafter referred to as “FePc / HT800”).

  [Co salt / 900 ° C.] First, a precursor composition was prepared. That is, 1.5 g of polyacrylonitrile-polymethacrylic acid copolymer was dissolved in 20 g of dimethylformamide. Thereafter, 1.5 g of cobalt chloride hexahydrate and 1.5 g of 2-methylimidazole were added and stirred for 2 hours to obtain a blue solution. Ketjen black (EC600JD, Lion Co., Ltd.) was added to the obtained solution so that it might become 30 weight%, and it mixed using the mortar. A precursor composition was thus obtained.

  Next, the infusibilization process of the precursor composition was performed. That is, the precursor composition was set in a forced circulation dryer. Then, the temperature was raised from room temperature to 150 ° C. in the air for 30 minutes, and then the temperature was raised from 150 ° C. to 220 ° C. over 2 hours. Thereafter, the precursor composition was held at 200 ° C. for 3 hours. Thus, the precursor composition was infusible.

  And the carbonization process of the precursor composition was performed. That is, the infusible precursor composition was put in a quartz tube, and the quartz tube was purged with nitrogen for 20 minutes in an elliptical reflection type infrared gold image furnace. Then, heating was started, and the temperature of the gold image furnace was increased from room temperature to 900 ° C. at a temperature increase rate of 10 ° C./min. Thereafter, the quartz tube was held at 900 ° C. for 1 hour. Thus, a carbon material produced by carbonizing the precursor composition was obtained.

  Further, the carbon material was pulverized in the same manner as in the case of FePc / HT800 described above, and a powdery carbon material was obtained as a hydrogen storage carbon material (hereinafter referred to as “Co / KB / HT900”).

  [Co complex / 1200 ° C.] First, a precursor composition was prepared. That is, 10 mL of phenol resin was mixed with 100 mL of acetone to prepare a mixed solution. Furthermore, 2.09 g of phthalocyanine cobalt was added to this mixed solution, and the mixture was stirred for 1 hour at room temperature using a magnetic stirrer. The solvent was removed at 60 ° C. using a rotary evaporator while irradiating this mixture with ultrasonic waves. A precursor composition was thus obtained.

  Next, the precursor composition was carbonized. That is, a part of the precursor composition was put in a quartz tube, and the quartz tube was purged with nitrogen gas for 20 minutes in an elliptical reflection type infrared gold image furnace. Then, heating was started, and the temperature of the gold image furnace was increased from room temperature to 1200 ° C. at a temperature increase rate of 10 ° C./min. Thereafter, the quartz tube was held at 1200 ° C. for 1 hour. In this way, the carbon material produced | generated by carbonizing a precursor composition at 1200 degreeC was obtained. And similarly to the above-mentioned case of FePc / HT800, the carbon material obtained by the carbonization treatment was pulverized to obtain a powdery carbon material.

  Further, the carbon material was washed. That is, the powdery carbon material was subjected to a pickling treatment for reducing the cobalt content. Specifically, 37% HCl was added to the carbon material and stirred for 2 hours, and then allowed to stand to decant the supernatant. This operation was performed three times. The carbon material was suction filtered, washed with distilled water, and then boiled. In this way, the powdery carbon material subjected to the cleaning treatment was obtained as a hydrogen storage carbon material (hereinafter referred to as “CoPc / HT1200”).

  [Co complex / 1000 ° C.] The same production method as in the case of CoPc / HT1200 was carried out except that the temperature for holding the precursor composition in the carbonization treatment was 1000 ° C. Thus, a powdery carbon material was obtained as a hydrogen storage carbon material (hereinafter referred to as “CoPc / HT1000”).

  [Co complex / 800 ° C.] The same production method as in the case of CoPc / HT1200 described above was carried out except that the temperature at which the precursor composition was maintained in the carbonization treatment was 800 ° C. Thus, a powdery carbon material was obtained as a hydrogen storage carbon material (hereinafter referred to as “CoPc / HT800”).

  [Co complex / 600 ° C.] The same production method as in the case of CoPc / HT1200 described above was carried out except that the temperature for holding the precursor composition in the carbonization treatment was 600 ° C. Thus, a powdery carbon material was obtained as a hydrogen storage carbon material (hereinafter referred to as “CoPc / HT600”).

  The six types of hydrogen storage carbon materials obtained in Example 1 described above were observed with a transmission electron microscope (TEM). Fig. 1 shows FePc / HT800, Fig. 2 shows Co / KB / HT900, Fig. 3 shows CoPc / HT1200, Fig. 4 shows CoPc / HT1000, Fig. 5 shows CoPc / HT800, and Fig. 6 shows TEM photographs obtained for CoPc / HT600. An example is shown respectively.

  3B is an enlarged photograph of a portion surrounded by a broken-line circle shown in FIG. 3A, and FIG. 3D is an enlarged photograph of a portion surrounded by a broken-line circle shown in FIG. 3C. 4B is an enlarged photograph of a portion surrounded by a broken-line circle shown in FIG. 4A, and FIG. 4D is an enlarged photograph of a portion surrounded by a broken-line circle shown in FIG. 4C. 5B is an enlarged photograph of a portion surrounded by a broken-line circle on the left side shown in FIG. 5A, and FIG. 5D is an enlarged photograph of a portion surrounded by a broken-line circle shown in FIG. 5C. 6B is an enlarged photograph of a part surrounded by a broken-line circle shown in FIG. 6A, and FIG. 6D is an enlarged photograph of a part enclosed by a broken-line circle shown in FIG. 6C.

  As shown in FIGS. 1 to 5, in the five kinds of hydrogen storage carbon materials carbonized at a temperature of 800 ° C. or higher, a developed shell-like structure in which distorted graphene was laminated was recognized. This shell-like structure appeared to be crystallized as the carbonization temperature increased.

  Further, not only two types (FePc / HT800 and Co / KB / HT900) that have not been subjected to a cleaning process, but also three types (CoPc / HT1200, CoPc / HT1000, and CoPc / HT800) that have undergone a cleaning process, It was observed that particles of various particle sizes, which seem to be metal compounds, were dispersed unevenly.

  On the other hand, as shown in FIG. 6, in CoPc / HT600 carbonized at 600 ° C., an almost amorphous structure was observed. In this CoPc / HT600, a very slight shell-like structure was observed, but it was not developed as much as the other five types. In CoPc / HT600, no clear dispersion of metal particles as in the other five types was observed.

  The six types of hydrogen storage carbon materials obtained in Example 1 described above were subjected to X-ray diffraction measurement, and their carbon structures were evaluated.

  [X-Ray Diffraction Measurement] First, a sample of the hydrogen storage carbon material was placed in a concave portion of a glass sample plate and pressed with a slide glass, and the concave portion was uniformly filled so that the surface coincided with the reference surface. . Next, the glass sample plate was fixed to a wide-angle X-ray diffraction sample stage so that the shape of the filled sample did not collapse.

  Then, X-ray diffraction measurement of each sample is performed using an X-ray diffractometer (Rigaku RINT2100 / PC, Rigaku Co., Ltd.), diffraction peaks are measured, and integration is performed four times. Diffraction data was obtained.

  The applied voltage and current to the X-ray tube were 50 kV and 300 mA, respectively. The sampling interval was 0.1 ° or 0.01 °, the scanning speed was 1 ° / min, and the measurement angle range (2θ) was 5 to 90 °. CuKα rays were used as incident X-rays.

[Evaluation on the spread of the carbon network surface] The crystallite size La was evaluated based on the obtained X-ray diffraction data. That is, the average La and La distribution were analyzed using the Diamond method. This analysis, software for analysis that has been installed on your computer (Carbon Analyzer D series, Hiroyuki ^{Fujimoto, http: //www.asahi-net.or.jp/ ~ qn6h-fjmt} /) was used. The data to be analyzed was limited to the 11 band intensity of the carbonaceous material measured using a counter graphite monochromator with CuKα ray as an X-ray source. The maximum network surface size that can be analyzed was about 7 nm.

  Here, the procedure of the analysis method proposed by Diamond basically consists of (1) intensity measurement of 11 bands of a sample, (2) correction of measured intensity, and (3) model network surface expected to exist in the sample. (4) Calculation of theoretical scattering intensity from the assumed model network surface, (5) Least square fitting of the obtained measured intensity by the theoretical scattering intensity, (6) Model network surface from the weight of each theoretical scattering intensity It consists of six steps of calculating weight fraction and average network surface size. Therefore, first, data to be analyzed was read, and smoothing processing and absorption correction were performed. The smoothing process was performed 7 times, and the absorption correction was performed using the theoretical absorption coefficient 4.219.

  Next, theoretical scattering intensity calculation was performed. The following formula (I) was used as a calculation formula. In this formula (I), I is an actually measured intensity, w is a mass fraction, B is a theoretical X-ray scattering intensity, P is a deflection factor, and v and s are network surface model factors.

Here, all parameters can be expressed as a function of n (see Hiroyuki Fujimoto, Carbon, 192 (2000) 125-129). In calculating the theoretical scattering intensity, it is necessary to determine the two-dimensional lattice constant a ₀ and the Ruland coefficient and to select the model network surface as initial conditions. The two-dimensional lattice constant is generally set to a value between the lattice constants of benzene and ideal graphite, about 0.240 to 0.24612 nm. The Rule coefficient indicates the integral width of the function representing the pass band of the energy of the used monochromator, and generally takes a value of 0 to 1. In this analysis, 0.24412 nm was selected as an initial set value of the two-dimensional lattice constant a ₀ as a value close to the lattice constant of a general carbonaceous material. 0.05 was selected as the default value of the coefficient of Rand.

Next, the model network surface was selected. With the above software, the theoretical strength can be calculated and executed using three types of model network surfaces: a benzene / coronene base model, a pyrene base model, and a mixed model. In this respect, in this analysis, a benzene / coronene base model as shown in FIG. 7 was used. In the case of this model, the scattering intensity of the model network surface (approximately 0.25 nm to 7 nm) of an odd multiple size (1, 3, 5... 25, 27, 29 times) of the two-dimensional lattice constant a ₀ is calculated. Is possible.

  In this way, all selection conditions were determined, and theoretical scattering intensity calculation was performed. When the calculation was completed, iterative calculation by the least square method based on the following formula (II) was performed 1000 times, and the fitting angle range 2θ was set to 60 to 100 °, and the actual profile and the theoretical profile were fitted. When the fitting was completed, the fitting result, the screen size distribution, and the average screen size were displayed on the computer display.

[Evaluation of Carbon Network Surface Laminated Structure] Further, based on the obtained X-ray diffraction data, an evaluation of the carbon network surface laminated structure in the carbon structure was performed. That is, the average Lc, the number and distribution of carbon network planes, and the average plane spacing d ₀₀₂ are calculated using the above-described analysis software (Carbon Analyzer D series, Hiroyuki Fujimoto, http: //www.asahi-net) installed in a computer. were analyzed .or.jp ^/ ~ qn6h-fjmt ^/) using a.

In the calculation process using this software, (1) diffraction line intensity correction, (2) background correction, (3) Patterson function calculation, (4) validity evaluation by inverse Fourier calculation, (5 ) Five steps of calculating the average Lc, the average number of layers, the distribution of the number of layers, and the average interplanar distance d ₀₀₂ using the Patterson function were performed.

  First, diffraction line intensity correction and background correction were performed on the diffraction data of 5 ° to 40 ° obtained by X-ray diffraction measurement. In the correction of diffraction line intensity, the linear absorption coefficient μ of carbon was 4.219, the sample thickness t was 0.2 mm, the divergence slit width β was 2/3 °, and the goniometer radius R was 285 mm. Background correction was performed by the spline interpolation method with the base point near 15 ° and 35 °.

  Next, the Patterson function was calculated using the corrected data. The integration start angle and end angle were 5 ° and 40 °, respectively, and the inverse Fourier calculation was performed by the Hirsch method while changing the calculation distance u, and the validity was evaluated. This Hirsch method is a method proposed by Hirsch in 1954 in order to evaluate the average number of layers and the distribution of the number of layers in a carbon network surface in a sample having a relatively small surface size such as coal or pitch. is there.

Using the calculated Patterson function, the rest of the calculation process was to calculate the average Lc, the average number of layers, the distribution of the number of layers, and the average interplanar spacing d ₀₀₂ according to the standard procedure of software.

  [Evaluation on the degree of development of the shell-like structure] Further, based on the obtained X-ray diffraction data, the degree of development of the shell-like structure was evaluated. That is, as described above, in the diffraction data obtained by X-ray diffraction measurement of the present carbon material, the diffraction peak of the carbon (002) plane appearing near 26 ° is derived from the (002) plane of the shell-like structure carbon. Two types of peak (shell structure peak) and peak derived from an amorphous structure (amorphous structure peak) are mixed.

  Therefore, peak separation was performed based on diffraction data, and a peak appearing near a diffraction angle of 26 ° was separated into a shell-like structure peak and an amorphous structure peak. For the calculation of peak separation, diffraction data having a diffraction angle of 5 ° to 40 ° subjected to diffraction line intensity correction and background correction similar to the calculation of average Lc described above were used.

  Then, the ratio (%) of the area of the shell-like structure peak to the area of the peak before separation (that is, the total area of the area of the shell-like structure peak and the area of the amorphous structure peak) is calculated, and the ratio is calculated as the shell. The crystallinity of the structure was taken.

  [X-ray diffractogram] FIG. 8 shows an example of X-ray diffractograms obtained for six types of hydrogen storage carbon materials. 8A shows FePc / HT800, FIG. 8B shows Co / KB / HT900, FIG. 8C shows CoPc / HT1200, FIG. 8D shows CoPc / HT1000, FIG. 8E shows CoPc / HT800, and FIG. 8F shows CoPc / HT600 results. In the figure, the horizontal axis indicates the diffraction angle (2θ), and the vertical axis indicates the peak intensity. 8A to 8F, the scales of the vertical axes are not matched, and therefore the corresponding peak intensities cannot be compared from these figures.

  As shown in FIGS. 8A to 8E, five types of hydrogen storage carbon materials carbonized at a temperature of 800 ° C. or higher are attributed to (002), (10), (004) and (11) diffraction of carbon. Diffraction lines were observed at diffraction angles of 26 °, 42 °, 54 ° and 79 °, respectively. In particular, (002) diffraction showed a sharp diffraction line and corresponded to the development of the shell-like structure observed in the TEM image in Example 2 described above.

  In addition, for the four types of hydrogen storage carbon materials using cobalt as a part of the raw material, diffraction lines attributed to metallic cobalt are observed at diffraction angles of 44 °, 51 °, and 75 °, and the above-described examples. 2 confirmed that the non-uniformly dispersed particles observed in the TEM image were metallic cobalt particles. On the other hand, for the hydrogen storage material using iron as a part of the raw material, diffraction lines attributed to iron carbide at diffraction angles of 38 °, 43 °, 44 °, 45 °, 46 °, 48 ° and 49 °, and A diffraction line attributed to metallic iron was observed at 44.5 °.

  In addition, the peak height at a diffraction angle of 26 ° tended to increase as the carbonization temperature increased. This tendency was considered to indicate that the higher the carbonization temperature, the higher the degree of development (crystallinity) of the shell-like structure.

  On the other hand, as shown in FIG. 8F, for PcCo / HT600 carbonized at 600 ° C., only broad peaks were observed in the vicinity of diffraction angles of 26 ° and 42 °. For any of the six types of hydrogen storage carbon materials, no clear peak was observed at a diffraction angle smaller than 26 °.

[Average La, Average Lc, Average Face Distance d ₀₀₂ and Crystallinity] FIG. 9 shows average La, average Lc, average face distance d ₀₀₂ and shell-shaped crystals calculated for six types of hydrogen storage carbon materials. Indicates the degree of conversion. FIG. 10 shows an example of the peak separation result of the X-ray diffraction diagram performed when calculating the crystallinity shown in FIG. FIG. 10A shows the results of peak separation performed for CoPc / HT1000 and FIG. 10B for CoPc / HT600. In FIG. 10, the thin solid line indicates the corrected diffraction data, the thick solid line indicates the shell-like structure peak, and the broken line indicates the amorphous structure peak.

  As shown in FIG. 9, the average La was 1.03 to 2.63 nm for any of the six types of hydrogen storage carbon materials. That is, it was considered that the carbon network surface spread in the a-axis direction of each hydrogen storage carbon material was relatively small, and a large number of edges were formed by the carbon network surface being interrupted.

  On the other hand, for the average Lc, the five types of hydrogen storage carbon materials carbonized at a temperature of 800 ° C. or higher were 0.60 to 0.89 nm, whereas CoPc / HT600 carbonized at 600 ° C. is It was as small as 0.44. That is, as compared with CoPc / HT600, it was confirmed that the other five types have a more developed structure of the carbon network surface.

In addition, regarding the average interplanar distance d ₀₀₂ , five types of hydrogen storage carbon materials carbonized at a temperature of 800 ° C. or higher were 0.342 to 0.345 nm, whereas CoPc carbonized at 600 ° C. / HT600 was as small as 0.335 nm. That is, the average interplanar spacing d ₀₀₂ of CoPc / HT600 was comparable to that of graphite crystals, while the other five types of average interplanar spacing d ₀₀₂ were clearly larger than these.

  Regarding the crystallinity of the shell-like structure, the carbonation at 600 ° C. was 57.8% to 43.7% of the five types of hydrogen storage carbon materials carbonized at a temperature of 800 ° C. or higher. The CoPc / HT600 was significantly smaller at 2.0%. That is, for example, as shown in FIG. 10A, a sharp shell-like structure peak was detected for CoPc / HT1000, whereas an extremely small shell-like structure peak was detected for CoPc / HT600 as shown in FIG. 10B. It was only done.

  As described above, in the five kinds of hydrogen storage carbon materials carbonized at a temperature of 800 ° C. or higher, it was confirmed that the shell-like structure was remarkably developed as compared with CoPc / HT600. This was consistent with the observation result of the TEM image in Example 2.

  [Crystal Size La Distribution] FIG. 11 shows a crystallite size La distribution of 7 nm or less of the carbon network surface obtained for six types of hydrogen storage carbon materials. 11A shows FePc / HT800, FIG. 11B shows Co / KB / HT900, FIG. 11C shows CoPc / HT1200, FIG. 11D shows CoPc / HT1000, FIG. 11E shows CoPc / HT800, and FIG. 11F shows CoPc / HT600 results. In the figure, the horizontal axis represents the crystallite size La (nm), and the vertical axis represents the ratio (%) of each crystallite size La.

  As shown in FIGS. 11A to 11F, the ratio of the crystallite size La of 1 to 5 nm was 10% or more and the ratio of 5 to 7 nm was 40% or less for any of the six types of hydrogen storage carbon materials. That is, each hydrogen storage carbon material was considered to have a carbon structure having many active sites.

  In addition, for CoPc / HT600, the ratio monotonically decreased as the crystallite size La increased, whereas the other five types also showed a difference in distribution tendency such that the distribution was more disordered. Although not shown, when the same analysis is performed on ketjen black, a result that the ratio of 5 nm or more is 60% or more is obtained in the crystallite size La distribution of 7 nm or less on the carbon network surface. It was.

  [Carbon Network Surface Lamination Number Distribution] FIG. 12 shows carbon network surface lamination number distributions obtained for six types of hydrogen storage carbon materials. 12A shows FePc / HT800, FIG. 12B shows Co / KB / HT900, FIG. 12C shows CoPc / HT1200, FIG. 12D shows CoPc / HT1000, FIG. 12E shows CoPc / HT800, and FIG. 12F shows CoPc / HT600 results. In the figure, the horizontal axis indicates the number of stacked layers, and the vertical axis indicates the ratio (%) of each stacked number.

  As shown in FIG. 12F, for CoPc / HT600 carbonized at 600 ° C., the ratio of the number of stacks of 3 or more was as small as less than 35%, whereas, as shown in FIGS. For the other five types of hydrogen storage carbon materials carbonized at the temperature of 3, the ratio of the number of laminated layers of 3 or more was remarkably large, 45% or more. That is, it was confirmed that in the five types of hydrogen storage carbon materials carbonized at a temperature of 800 ° C. or higher, the carbon network surface laminate structure was further developed as compared with CoPc / HT600.

The six types of hydrogen storage carbon materials obtained in Example 1 described above were subjected to high pressure ¹ H-NMR measurement.

[NMR measurement] α-alumina was used as a dispersion medium. That is, a hydrogen storage carbon material sample was diluted with α-alumina so as to be 2% by weight, and placed in a high-pressure NMR quartz sample tube. Next, exhaust and gas introduction pipes and valves were attached, followed by deaeration treatment at a temperature of 573 K and a final ultimate pressure of 1 × 10 ⁻⁴ torr for 24 hours. The sample after the deaeration treatment was quickly placed on the probe in a reduced pressure state, and hydrogen was introduced until the pressure reached 3.0 MPa for measurement. ¹ H-NMR measurement was performed using an FT-NMR apparatus (Apollo Pulse NMR Spectrometer, 38 MHz, Tecmag) equipped with a high-pressure variable temperature probe. The pulse sequence was a 90 ° pulse method. The measurement temperature was 293K. It should be noted that only α-alumina was used as a sample, and the chemical shift was evaluated based on the peak position of hydrogen observed when hydrogen was introduced to 3.0 MPa and the same measurement was performed as a reference (0 ppm). In addition, the following two types of carbon materials were prepared, and NMR measurement was similarly performed.

  [Carbon black / Co] Cobalt powder was added to carbon black (Vulcan (registered trademark) VX72, Cabot Corporation) so as to be 2% by weight and mixed in a mortar. Thus, a carbon material (hereinafter referred to as “CB / Co”) made of a mixed powder of carbon black and metallic cobalt was obtained.

  [Activated carbon] Porous carbon (Maxsorb (registered trademark), Carbontech Co., Ltd.), which is activated carbon activated with alkali, was prepared as a carbon material (hereinafter referred to as “AC”).

  Furthermore, using the analysis software IGOR (Wave Metrics) installed in the computer, peaks contained in the obtained NMR spectrum were separated. In this analysis, peak separation was performed by approximating overlapping peaks by superimposing Lorentzian basic waveforms and further optimizing peak intensity, peak half-value width, and peak position using the least square method.

  [NMR Spectra] FIGS. 13A to I show nine kinds of hydrogen storage carbon materials obtained in Example 1 above, two kinds of carbon materials prepared in Example 4 and a reference alumina solvent. An example of the NMR spectrum obtained by Fourier-transforming the signal for the sample is shown. 13A is FePc / HT800, FIG. 13B is Co / KB / HT900, FIG. 13C is CoPc / HT1200, FIG. 13D is CoPc / HT1000, FIG. 13E is CoPc / HT800, FIG. 13F is CoPc / HT600, and FIG. FIG. 13H shows the results for AC, and FIG. 13I shows the results for the alumina solvent. In the figure, the horizontal axis represents chemical shift (ppm), and the vertical axis represents signal intensity.

  First, as shown in FIG. 13I, hydrogen introduced into an alumina solvent not containing a carbon material showed a single sharp peak (hereinafter referred to as “peak 1”) as in the case of only hydrogen gas. This peak 1 is considered to be caused by gaseous hydrogen (hydrogen gas) present in the voids in the sample because the deviation from the reference frequency is relatively small and the width is narrow.

  Similarly, as shown in FIG. 13H, hydrogen introduced into AC consisting of activated carbon also showed a single peak 1. Furthermore, as shown in FIG. 13F, hydrogen introduced into CoPc / HT600 carbonized at 600 ° C. also showed a single peak 1 as well.

  On the other hand, as shown in FIG. 13G, hydrogen introduced into CB / Co made of a mixed powder of carbon black and metallic cobalt showed two types of peaks with different chemical shifts. That is, in addition to the above-described peak 1, a broad peak shifted to the high magnetic field side (hereinafter referred to as “peak 3”) was observed. This peak 3 was thought to be caused by hydrogen interacting with metallic cobalt, which is a ferromagnetic species, because the chemical shift is relatively large and the width is very wide.

  On the other hand, as shown in FIGS. 13A to 13E, hydrogen introduced into five kinds of hydrogen storage carbon materials carbonized at a temperature of 800 ° C. or higher showed three kinds of peaks having different chemical shifts.

  That is, in addition to the above-described peak 1 and peak 3, a third peak shifted to the high magnetic field side (hereinafter referred to as “peak 2”) was observed. This was thought to be due to the fact that the five types of hydrogen storage carbon materials occlude hydrogen in a manner not found in other carbon materials.

  And since this peak 2 was not observed in CoPc / HT600, the presence or absence of the peak 2 is the structural difference between the CoPc / HT600 and the other five hydrogen storage carbon materials as described above. It was thought to reflect.

  [Specification of Peak 2] FIG. 14 shows four types of hydrogen storage carbon materials (FePc / HT800, Co / KB / HT900, CoPc / HT1000, CoPc / HT800 among the five types in which the above three types of peaks are observed. ) And the CB / Co in which two types of peaks are observed, the half-value width (ppm) and peak top position (ppm) of peak 2 and peak 3 are evaluated. For Co / KB / HT900, the full width at half maximum and peak top of peak 3 could not be specified.

  As shown in FIG. 14, with respect to the peak top position, peak 2 is in the range of −6.9 to −24.8 ppm, peak 3 is in the range of −8.5 to −20.5 ppm, and these ranges overlap. Was. On the other hand, as for the peak half-value width, peak 2 was in the range of 5.9 to 19.6 ppm, while peak 3 was 39.8 to 56.2 ppm. That is, peak 2 was identified as a peak having a remarkably small half width compared to peak 3.

  The temperature dependency of each peak was evaluated for CoPc / HT800, which is one of the five types of hydrogen storage carbon materials in which three types of peaks were observed in Example 4 described above. That is, NMR measurement was performed on the CoPc / HT800 sample in the same manner as in Example 4 except that three different measurement temperatures of 173K, 296K, and 373K were used.

  FIG. 15 shows the peak intensities of peak 1, peak 2 and peak 3 measured at each temperature. In the figure, the horizontal axis represents the measured temperature (K), and the vertical axis represents the peak intensity. The white circle indicates the peak 1, the black triangle indicates the peak 2, and the white diamond indicates the peak 3.

  As shown in FIG. 15, the peak intensity of peak 1 and peak 3 decreased linearly as the measurement temperature increased. That is, as the measurement temperature increased, the amount of hydrogen occluded in the mode showing peak 1 and peak 3 decreased linearly.

  On the other hand, the peak intensity of peak 2 did not decrease even when the measurement temperature increased, and was almost constant. That is, even when the measurement temperature rose, the amount of hydrogen occluded in the mode showing peak 2 was maintained. This indicates that the hydrogen occlusion mode showing peak 2 is different from the modes shown in peak 1 and peak 3 and has a very low temperature dependency and is stable.

  Of the five types of hydrogen storage carbon materials in which peak 2 was observed in Example 4 above, two types of FePc / HT800 and Co / KB / HT900 and AC in which only peak 1 was observed showed hydrogen storage capacity. Was evaluated.

  That is, the hydrogen storage amount of each carbon material was measured according to JIS H7201. First, about 1 g of a carbon material sample was inserted into the sample tube, and evacuated for 18 hours or more. Thereafter, He gas was introduced into the sample tube, and the sample volume was measured. He gas was removed by evacuating for 3 hours or more. And hydrogen gas was introduce | transduced into the sample tube until it became 20 Mpa, and the hydrogen storage amount was measured. The measurement temperature was −30 ° C. (243K).

FIG. 16 shows the results of evaluating the hydrogen storage amount (% by weight), specific surface area (m ² / g), and hydrogen storage amount (g / m ² ) per unit surface area of each carbon material. The specific surface areas of FePc / HT800 and Co / KB / HT900 were measured by the BET method. The specific surface area of AC was the value described in the instructions for the commercial product.

As shown in FIG. 16, the hydrogen storage amounts per unit surface area of FePc / HT800 and Co / KB / HT900 are 1.25 × 10 ⁻³ g / m ² and 1.23 × 10 ⁻³ g / m ^{2, respectively.} It was about 2.5 times higher than that of AC.

  The high hydrogen storage capacity in these FePc / HT800 and Co / KB / HT900 was considered to reflect the hydrogen storage according to the embodiment shown by the above-described peak 2 that is not found in other carbon materials.

Claims (10)

A part of the occluded hydrogen exhibits a peak with a half-value width of 30 ppm or less at a position of a chemical shift of -5 to -30 ppm in ¹ H-NMR measurement. 2. The hydrogen-occluding carbon according to claim 1, wherein the average crystallite size La in the a-axis direction in the carbon structure is 5.0 nm or less and the average crystallite size Lc in the c-axis direction is 0.5 nm or more. material. Hydrogen storage carbon materials according to claim 1 or 2, wherein an average carbon structure (002) spacing _{d 002} is 0.340～0.450Nm. The ratio of the peak area corresponding to the (002) plane reflection to the total area of the peak area corresponding to the (002) plane reflection of the carbon structure and the peak area derived from the amorphous structure in the X-ray diffraction diagram is 10% or more. The hydrogen storage carbon material according to any one of claims 1 to 3. The hydrogen storage carbon material according to any one of claims 1 to 4, which is obtained by carbonizing a raw material containing a resin and a metal. It is obtained by carbonizing the raw material at 700 ° C. or higher. The hydrogen storage carbon material according to claim 5. Perform carbonization of raw materials containing resin and metal under multiple conditions,
Of the plurality of conditions, select a condition in which a part of the occluded hydrogen has a carbon material showing a peak with a half-value width of 30 ppm or less at a chemical shift of -5 to -30 ppm in ¹ H-NMR measurement,
A method for producing a hydrogen storage carbon material, wherein the raw material is carbonized under the selected conditions to produce a hydrogen storage carbon material. Perform carbonization of raw materials containing resin and metal under multiple conditions,
Among the plurality of conditions, a condition for selecting a carbon material having an average crystallite size La in the a-axis direction of the carbon structure of 5.0 nm or less and an average crystallite size Lc in the c-axis direction of 0.5 nm or more is selected. And
A method for producing a hydrogen storage carbon material, wherein the raw material is carbonized under the selected conditions to produce a hydrogen storage carbon material. Among the plurality of conditions are described in claim 8, further average carbon structure (002) spacing _{d 002} is characterized by selecting the conditions under which the carbon material is obtained is 0.340~0.450nm A method for producing a hydrogen storage carbon material. Among the plurality of conditions, the peak area corresponding to the (002) plane reflection with respect to the total area of the peak area corresponding to the (002) plane reflection of the carbon structure and the peak area derived from the amorphous structure in the X-ray diffraction diagram. The method for producing the hydrogen storage carbon material according to claim 8 or 9, wherein a condition for obtaining the carbon material having a ratio of 10% or more is selected.