HYDROGEN STORAGE MATERIAL

Abstract

The present relates to a carbon material having a 3D structure and made of graphene oxide and carbon nanotubes, characterized in that the 3D structure consists in that the carbon nanotubes are located with some agglomeration between the graphene oxide layers so as to extend the spacing between the graphene oxide layers

Claims

1. Carbon material having a 3D structure and made of graphene oxide and carbon nanotubes, characterized in that the 3D structure consists in that the carbon nanotubes are located with some agglomeration between the graphene oxide layers so as to extend the spacing between the graphene oxide layers.

2. Carbon material according to claim 1, characterized in that the carbon nanotubes are multi-walled carbon nanotubes.

3. Hydrogen storage material comprising the carbon material of claim 1.

4. Hydrogen storage material according to claim 3, characterized in that it has a hydrogen storage capacity of 4.5 mass % or greater.

5. Hydrogen storage material according to claim 3, characterized in that it has a hydrogen storage capacity of 5 mass % or greater.

6. Hydrogen storage material according to claim 5, characterized in that the hydrogen was absorbed at p=50 bar and T=298 K.

7. A Carbon material synthesis method for manufacturing a carbon material having a 3D structure and made of graphene oxide and carbon nanotubes, characterized in that the 3D structure consists in that the carbon nanotubes are located with some agglomeration between the graphene oxide layers so as to extend the spacing between the graphene oxide layers, comprising the steps of dispersing graphene oxide and carbon nanotubes in deionized water, mixing, adding an acid and a reduction agent, stirring, and recovering the carbon material.

8. The Carbon material synthesis method according to claim 7, characterized in that the recovering step involves filtering and washing.

9. The Carbon material synthesis method according to claim 7, characterized in that the acid is HCl 1M.

10. The Carbon material synthesis method according to claim 7, characterized in that the reduction agent is Vitamin C.

11. The Carbon material synthesis method according to claim, characterized in that the graphene oxide and the carbon nanotubes are dispersed in a ratio 1:1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Further particular advantages and features of the invention will become more apparent from the following non-limitative description of at least one embodiment of the invention which will refer to the accompanying drawings, wherein

[0029] FIG. 1 represents a schematic diagram of the synthesis of the 3D structure carbon material of the present invention;

[0030] FIG. 2 represents BET adsorption isotherms (at 77K) measured with N.sub.2 in liq. N.sub.2 of various carbon materials;

[0031] FIGS. 3 schematically represents pore size distributions of various carbon materials;

[0032] FIG. 4 schematically represents XRD patterns of various carbon materials;

[0033] FIG. 5 schematically represents XRD patterns of the 3D structure carbon material;

[0034] FIG. 6 schematically represents TEM images of various carbon materials;

[0035] FIG. 7 schematically represent the hydrogen storage capacity of various carbon materials;

[0036] FIG. 8 schematically represents the hydrogen absorption on 3D structure carbon material at different temperatures;

[0037] FIG. 9 schematically represents the thermal hydrogen desorption from various carbon materials.

DETAILED DESCRIPTION OF THE INVENTION

[0038] The present detailed description is intended to illustrate the invention in a non-limitative manner since any feature of an embodiment may be combined with any other feature of a different embodiment in an advantageous manner.

[0039] The present invention relates to a hydrogen storage material having 3D structure of carbon material, which is synthesized from graphene oxide and carbon nanotubes as schematically shown in FIG. 1. Preferably, the hydrogen storage capacity of the 3D carbon material of the present invention is 4.5 mass % or greater, more preferably 5 mass % or greater.

[0040] As shown in FIG. 1, the expression 3D structure means that the graphene oxide and the carbon nanotubes are connected to each other in the material of the present invention so as to provide better and more pathways and spaces for hydrogen adsorbing than conventional materials because the carbon nanotubes which are added to the graphene oxide are agglomerated between the graphene oxide layers so that it extends the spacing between the graphene oxide layers.

[0041] Therefore, carbon nanotubes located at the spacing of graphene oxide layers can form a 3D structure and exhibit improved hydrogen adsorption properties as comparted to the respective graphene oxides and carbon nanotubes alone.

[0042] More particularly, according to a 3D structure carbon material manufacturing method of the present invention, graphene oxide and carbon nanotubes are dispersed in a deionized water and then sonicated. Then acid, such as HCl, preferably HCl 1M, is added and finally a reduction agent, such as Vitamin C is added and the mixture is stirred with low heating such as 323K. Finally, the solution is filtered and the product is washed.

EXAMPLES

[0043] Now an synthesis example of the 3D carbon material will be explained.

[0044] According to this example, one uses graphene oxide that is preferably synthesized by modified Hummer's method and carbon nanotubes, preferably MWCNT, 95.0% that purchased from Plasmachem in USA, for example.

[0045] According to the example, the 3D carbon material was obtained by linking the carbon nanotubes to the graphene oxide with Vitamin C. For the synthesis a 1:1 ratio of graphene oxide and carbon nanotubes (300 mg of each samples) were dispersed in 10 mL of deionized water for 3 h under mixing e.g. by sonication. To the fully dispersed carbon nanotubes and graphene oxide mixture 3-4 drops of acid e.g. 1M HCl were added for the surface treatment. Subsequently 300 mg of a reduction agent (such as vitamin C and HI) were dissolved. The mixture was stirred in an oil bath for 12 h at 323K.

[0046] Finally, the solution was filtered and the product was washed 5 times with 100 mL of deionized water and dried under vacuum at RT.

[0047] FIGS. 2 to 9 show different characteristic of the synthetized product with comparative data of the used material alone. The synthesis product has a specific surface area of A/m=340 m.sup.2/g as shown in FIG. 2 which shows BET adsorption isotherms (at 77K) measured with N.sub.2 in liq. N.sub.2 of various carbon materials at a Conversion A=n(N.sub.2).Math.89833 m.sup.2/mol=V(N.sub.2).Math.4 m.sup.2/cm.sup.3STC, and contains a large amount of pores with a diameter of 4 nm as shown in FIG. 3 showing the pore size distributions of various carbon materials calculated from the BET adsorption isotherms by Barrett-Joyner-Halenda (BJH) Analysis.

[0048] FIG. 4 shows XRD patterns of graphite, Graphene oxide (GO), Carbon nanotubes (CNT) and 3D structure carbon material (3D) that exhibit distinct peaks. The main peak of the stacked layers of graphite is observed at 26 in 2 by C (002). Upon chemical oxidation of graphite using Hummer's method, the C (002) peak was shifted to 11 in 2 due to the expansion of stacked graphite layers by the incorporation of oxygenated functional groups such as epoxy, carboxyl and hydroxyl groups, resulting in GO.

[0049] The broad peak at 20 in 2 shown in FIG. 5 is characteristic for the 3D structure carbon material. This peak is significantly increasing upon hydrogen absorption as represented in the pattern above, indicating that the structural feature that leads to the additional peak, i.e. the fingerprint of the 3D structure carbon material, is also the place where the hydrogen interaction occurs.

[0050] FIG. 6 shows the TEM image of the Graphite oxide (a), the MWCNT (b) and the structure of 3D carbon material (c). We clearly see that the CNT are aggregated on the graphene layer to form a complex, dense structure as compared to the free MWCNT structure.

[0051] FIG. 7 shows the hydrogen storage capacity measured as the hydrogen desorption capacity of the graphite, the graphene oxide, the carbon nanotubes and the 3D carbon material which was measured of the as prepared sample and in the 5.sup.th thermal desorption cycle (303K-573K). In between of these two cycles, hydrogen was absorbed by a constant flow of 5 Ncm.sup.3/min on samples of 50 mg at 303 K until the absorption reached saturation and the pressure increased until 50 bar as shown in FIG. 8 which schematically represents the Hydrogen absorption on 3D structure carbon material at 298 K, 323 K and 353 K (solid line for adsorption, dotted line for desorption).

[0052] Subsequently the sample was evacuated and then thermally desorbed and the amount of desorbed hydrogen was measured by a mass flow controller. Only the 3D graphite material shows a significant hydrogen desorption as represented in FIG. 9 with a maximum flow around 350 K. This indicates that the binding energy for hydrogen in the new 3D graphite material is much higher as compared to the physisorption energy. The hydrogen sorption is therefore reversible and the capacity slightly increased within the first 5 absorption desorption cycles.

[0053] The 3D structure of the 3D carbon material of the present invention can have several applications. More particularly, it can be used as a hydrogen storage material, a support for various catalysts and/or as an adsorbent for all kind of gases. More particularly, the application of the material of the present invention can be used in any reaction in which hydrogen adsorption and desorption are proceeded with a hydrogen storage material.

[0054] While the embodiments have been described in conjunction with a number of embodiments, it is evident that many alternatives, modifications and variations would be or are apparent to those of ordinary skill in the applicable arts. Accordingly, this disclosure is intended to embrace all such alternatives, modifications, equivalents and variations that are within the scope of this disclosure. This is particularly the case for the source of the first material, i.e. the graphene oxide and the CNT, or the type of acid or the type of reduction agent.