Alkyne-rich graphene-based composite hydrogen absorption material and preparation method thereof

Abstract

The invention relates to an alkyne-rich graphene-based composite hydrogen absorption material and a preparation method thereof. The hydrogen absorption material is an irreversible hydrogen absorption material which takes alkynylated graphene oxide (AGO) as a substrate and is compounded with alkynylated polyvinyl alcohol (Alkyne-PVA). The actual loading capacity of the PdO nano particles on the AGO is 35.74%, the average particle size of the PdO nano particles is 9.88 nm, the alkynyl branched chain substitution degree of the polyvinyl alcohol is 63%, and the mass ratio of the AGO-PdO to the Alkyne-PVA is 1: 10. The preparation method comprises the following steps: (1) preparing graphene oxide by adopting a Hummers method; (2) preparing alkynylated graphene oxide by adopting a nucleophilic ring opening method; (3) preparing an AGO-PdO nano composite material by adopting a self-assembly method; (4) preparing alkynylated polyvinyl alcohol by adopting a carbamic acid esterification method; and (5) preparing the alkyne-rich graphene-based composite hydrogen absorption material by adopting a grinding method, namely the AGO-PdO-(Alkyne-PVA) nano composite hydrogen absorption material.

Description

Technical Field

[0001] The present invention relates to the field of vacuum interlayer hydrogen absorbers for cryogenic containers, and in particular to a preparation technology of alkyne-rich graphene-based composite materials. Background Art

[0002] With the rapid development of modern science and technology, cryogenic storage and transportation equipment plays an irreplaceable role in numerous high-tech fields, including superconducting research, space exploration, storage of extremely cold media, and the atomic energy industry. Cryogenic storage and transportation equipment typically utilizes multi-layer insulation (MLI) to enhance thermal insulation. This structure effectively reduces heat transfer through conduction, convection, and radiation, maintaining a low-temperature environment within the container. To achieve good insulation, the interlayer vacuum typically requires a depth of 1×10 -2 Pa or above.

[0003] During actual operation, the pressure stability of the vacuum interlayer faces two challenges: first, the insulating medium continuously desorbs gases in low-temperature environments; second, nanoscale gaps in the container structure can allow for slow gas infiltration. Research has shown that hydrogen accounts for the largest proportion of desorbed gases. Due to its atomic radius of only 0.037 nm and its extremely high diffusion coefficient, hydrogen accumulation during long-term operation significantly increases the interlayer pressure. This pressure increase directly weakens the vacuum insulation effect, exacerbates heat intrusion, and thus affects the service life and performance stability of the cryogenic container.

[0004] Against this backdrop, the introduction of hydrogen getter technology provides an effective solution to these problems. Hydrogen getters can remove hydrogen from the vacuum interlayer, thereby maintaining the low-pressure environment within the interlayer for an extended period. Therefore, hydrogen getters are often added to the vacuum interlayer of cryogenic vessels to ensure stable operation. For example, Yang Xiaojiao (Yang Xiaojiao. Design, Synthesis, and Performance of Supported Alkyne-Functionalized Polyvinyl Alcohol-Metal Gel Nanocatalysts. China Academy of Engineering Physics, 2020) prepared Pd(II)@Alkyne-PVA gels for hydrogen absorption. However, the solid-phase gels exhibited low hydrogen absorption rates, primarily because the gel polymer groups hindered hydrogen diffusion and mass transfer within the composite. Liu Aojie (Liu Aojie. Preparation and Hydrogen Absorption Properties of Palladium / Propargylamine Graphene Composites. Southwest University of Science and Technology, 2021) prepared alkynyl-functionalized graphene / palladium composites (Pd-A-rGO) for hydrogen absorption, but the results were less than ideal. Summary of the Invention

[0005] The purpose of the present invention is to realize the three-time utilization of the precious metal Pd, reduce the preparation cost, reduce the hydrogen concentration in the vacuum interlayer of the cryogenic container, and effectively extend the service life of the cryogenic container.

[0006] The present invention relates to an alkyne-rich graphene-based composite hydrogen-absorbing material and its preparation method. The alkyne-rich graphene-based composite hydrogen-absorbing material is a nanomaterial composed of PdO loaded on alkyne-functionalized graphene oxide (AGO) and composited with alkyne-functionalized polyvinyl alcohol (Alkyne-PVA). The PdO loading is 35.74%, the average particle size is 9.88 nm, and the degree of alkynyl substitution of Alkyne-PVA is 63%. The AGO-PdO and Alkyne-PVA are mixed using a grinding method.

[0007] The preparation method of the alkyne-rich graphene-based composite hydrogen absorbing material of the present invention comprises the following steps: Step (1) preparing graphene oxide by Hummers method; Step (2) preparing alkyne-modified graphene oxide by nucleophilic ring-opening method; Step (3) preparing AGO-PdO nanocomposite materials by self-assembly method; Step (4) preparing acetylated polyvinyl alcohol by carbamate esterification method; In step (5), an alkyne-rich graphene-based composite hydrogen absorption material, namely, an AGO-PdO-(Alkyne-PVA) nanocomposite hydrogen absorption material, is prepared by a grinding method.

[0008] The present invention has the beneficial effects of loading PdO onto AGO and then compounding it with Alkyne-PVA using a grinding method to form an AGO-PdO-(Alkyne-PVA) nanocomposite material. PdO reacts with H2 to generate elemental Pd, which can then act as a catalyst to react with the alkynyl groups on AGO and Alkyne-PVA, achieving triple utilization of the precious metal Pd at the same location and reducing costs. The loose and porous structure of the AGO-PdO-(Alkyne-PVA) nanocomposite material prepared by grinding facilitates hydrogen diffusion, and its excellent hydrogen absorption properties can significantly reduce the hydrogen concentration within the vacuum interlayer of a cryogenic container, effectively extending the service life of the cryogenic container. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 The preparation flow chart of alkyne-rich graphene-based composite materials is as follows: Figure 2 The scanning electron microscope image of the composite material is shown in Figure 2. Figure 3 This is the adsorption isotherm of the alkyne-rich graphene-based composite material prepared in the present invention. DETAILED DESCRIPTION

[0010] The present invention fully utilizes the properties of palladium, loads PdO on alkyne-containing graphene oxide, and adopts a grinding method to prepare an alkyne-rich graphene-based composite hydrogen absorption material (AGO-PdO-(Alkyne-PVA)). PdO can react with H2 to generate Pd and H2O. The product Pd can also act as a catalyst to continue to react with the alkyne groups of alkyne-containing graphene oxide and alkyne-containing polyvinyl alcohol, thus realizing the three-fold utilization of the precious metal Pd. At the same time, the loose and porous structure of the composite material will facilitate hydrogen permeation and improve the hydrogen absorption rate.

[0011] The alkyne-rich graphene-based composite hydrogen absorption material of the present invention uses AGO as the substrate, the PdO nanoparticle loading on AGO is 35.74%, the method of loading PdO on AGO is a self-assembly method, the method of mixing AGO-PdO and Alkyne-PVA is a grinding method, and the alkyne substitution degree of Alkyne-PVA is 63%.

[0012] In the above-mentioned alkyne-rich graphene-based composite hydrogen absorption material, the backing material of the PdO nanoparticles is alkyne-containing graphene oxide.

[0013] The preparation method of the alkyne-rich graphene-based composite hydrogen absorbing material of the present invention comprises the following steps: Step (1) preparing graphene oxide by Hummers method; Step (2) preparing alkyne-modified graphene oxide by nucleophilic ring-opening method; Step (3) preparing AGO-PdO nanocomposite materials by self-assembly method; Step (4) preparing acetylated polyvinyl alcohol by carbamate esterification method; In step (5), an alkyne-rich graphene-based composite hydrogen absorption material, namely, an AGO-PdO-(Alkyne-PVA) nanocomposite hydrogen absorption material, is prepared by a grinding method.

[0014] The advantages of the present invention are as follows: (1) PdO reacts with H2 to generate Pd elemental substance. Pd, as a catalyst, can not only make the alkyne groups on Alkyne-PVA react with H2, but also make the alkyne groups on the substrate AGO react with H2, thus realizing the three-fold utilization of the precious metal Pd at the same position, greatly improving the utilization rate of the Pd element and reducing costs. (2) AGO-PdO and Alkyne-PVA are mixed by a grinding method. The composite material has a loose and porous structure, which is conducive to hydrogen diffusion, significantly reducing the hydrogen concentration in the vacuum interlayer of the cryogenic container, and effectively extending the service life of the cryogenic container. (3) The role of the alkyne-modified graphene oxide substrate is fully utilized, which can not only effectively reduce the agglomeration of PdO nanoparticles, but also participate in the hydrogen absorption reaction as a substrate.

[0015] The present invention uses alkyne-modified graphene oxide as the backing material for PdO nanoparticles, and uses a grinding method to mix AGO-PdO and Alkyne-PVA to form an alkyne-rich graphene-based composite hydrogen absorption material. The material is rich in alkyne functional groups, has a large specific surface area, and has a loose and porous structure. When hydrogen is released in the vacuum interlayer of a low-temperature container, PdO first reacts with hydrogen to generate Pd and H2O. At this time, Pd acts as a catalyst to continue reacting with the alkyne groups of alkyne-modified graphene oxide and alkyne-modified polyvinyl alcohol, achieving three utilizations of the precious metal Pd at the same location, greatly improving the utilization rate of the Pd element and reducing costs. The alkyne-rich graphene-based composite hydrogen absorption material prepared by the present invention is suitable for adsorbing hydrogen at the room temperature end of the vacuum interlayer of low-temperature storage and transportation equipment.

[0016] The preferred embodiments of the present invention are described in detail below so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more precise definition of the protection scope of the present invention.

[0017] The present invention relates to an alkyne-rich graphene-based composite hydrogen absorption material and a preparation method thereof. AGO is a substrate for PdO nanoparticles, the actual loading amount of PdO nanoparticles on AGO is 35.74%, the average particle size of PdO nanoparticles is 9.88 nm, the degree of substitution of alkynyl side chains of polyvinyl alcohol is 63%, and the mixing method of AGO-PdO and Alkyne-PVA is a grinding method.

[0018] The preparation method involves preparing graphene oxide using the Hummers method. In an ice bath, 6 g of KMnO₄ was added in small portions to a round-bottom flask containing 120 ml of concentrated H₂SO₄, 1 g of flake graphite, and 1 g of NaNO₃. The mixture was stirred vigorously for 1 hour, maintaining the temperature below 10°C. The mixture was then transferred to a 35°C water bath and stirred for 5 hours. 100 ml of deionized water was added dropwise to the flask, maintaining the temperature between 80 and 95°C. After the mixture cooled to room temperature, 4 ml of H₂O₂ was added, the mixture allowed to stand, and the supernatant was discarded. The product was washed with 5% dilute hydrochloric acid and deionized water, and freeze-dried to obtain GO.

[0019] Alkynylated graphene oxide (AGO) was prepared by the nucleophilic ring-opening method. 0.4 g of GO powder was weighed and added to an appropriate amount of deionized water to obtain a GO colloidal solution. 1.6 g of propargylamine was added and reacted for 24 h. The solution was washed by centrifugation several times and then dried under vacuum for 10 h to obtain black AGO powder.

[0020] AGO-PdO was prepared by a self-assembly method. AGO was ultrasonically dispersed in anhydrous ethanol to form a 1 mg / mL dispersion. The ultrasonically dispersed PdO dispersion was then added dropwise using a rubber-tipped pipette. The mixture was stirred at room temperature for several hours to ensure uniform loading. The mixture was then centrifuged and washed, and vacuum dried to obtain the AGO-PdO composite material.

[0021] Polyvinyl alcohol (PVA) was modified using the aminoesterification method. 0.7400 g of pre-vacuum-dried PVA with a 78% alcoholysis degree was weighed into a three-necked flask. 20 mL of the organic solvent, N-(N-methylformamide) (DMF), was added. The mixture was alternately evacuated and purged with nitrogen three times. The mixture was then placed in an 85°C water bath and stirred until the PVA was completely dissolved. After the solution cooled to room temperature, 2.4323 g of N-(N-methylcarbonyldiimidazole) (CDI) was added to the three-necked flask. After the reaction proceeded for 3 hours, 0.8262 g of propargylamine was added. Stirring was continued at room temperature for 16 hours, followed by 5 mL of aqueous ammonia, which was stirred continuously for 1 hour. After the reaction was complete, the reaction solution was pipetted dropwise into a beaker containing 200 mL of anhydrous ethanol. The mixture was stirred for 30 minutes and allowed to stand until the product was completely precipitated. The product was then filtered and washed repeatedly with ethanol. The filter residue was dried in a vacuum oven at 70°C for 24 hours to obtain a white, flocculent solid.

[0022] AGO-PdO-(Alkyne-PVA) nanocomposites were prepared by grinding. Weigh 0.3 g of Alkyne-PVA and then add 0.03 g of AGO-PdO. After grinding, a uniform gray solid powder was obtained.

[0023] The hydrogen absorption performance of graphene nanocomposites was tested using a "high and low temperature non-equilibrium getter adsorption performance test device", and the hydrogen absorption performance of the nanocomposites was tested using the static expansion method. The adsorption isotherm of the composite material was drawn. When the equilibrium pressure was 391 Pa, the hydrogen absorption capacity of the AGO-PdO-(Alkyne-PVA) composite material with an Alkyne-PVA grafting degree of 63% was 903.7 Pa.L / g.

[0024] The above description is only the preferred implementation details of the present invention and does not impose any other form of limitation on the present invention. Any equivalent design transformation made with reference to the specification of the present invention, directly or indirectly applied in other related fields, is within the scope of protection required by the present invention.

Claims

1. An alkyne-rich graphene-based composite hydrogen absorbing material, which is a composite material composed of a graphene substrate, PdO nanoparticles, and Alkyne-PVA, characterized in that The substrate is alkyne-containing alkynyl graphene oxide (AGO), with a PdO loading of 35.74%. The method of loading PdO on AGO is self-assembly, and the method of mixing AGO-PdO and Alkyne-PVA is grinding. The degree of alkynyl substitution of Alkyne-PVA is 63%.

2. The alkyne-rich graphene-based composite hydrogen absorption material according to claim 1, characterized in that The backing material of the PdO nanoparticles is alkynylated graphene oxide containing alkynyl groups. The method of mixing AGO-PdO and Alkyne-PVA is a grinding method. The degree of alkynyl substitution of Alkyne-PVA is 63%.

3. The method for preparing the alkyne-rich graphene-based composite hydrogen absorption material according to claim 1, comprising the steps of: Step (1) preparing graphene oxide by Hummers method; Step (2) preparing alkyne-modified graphene oxide by nucleophilic ring-opening method; Step (3) preparing AGO-PdO nanocomposite materials by self-assembly method; Step (4) preparing Alkyne-PVA by carbamate esterification; In step (5), an alkyne-rich graphene-based composite hydrogen absorption material, namely, an AGO-PdO-(Alkyne-PVA) nanocomposite hydrogen absorption material, is prepared by a grinding method.

4. The method for preparing the alkyne-rich graphene-based composite hydrogen absorbing material according to claim 3, characterized in that In the step (1), the Hummers method is used with sodium nitrate and concentrated sulfuric acid as oxidants.

5. The method for preparing the alkyne-rich graphene-based composite hydrogen absorbing material according to claim 3, characterized in that In the step (2), a nucleophilic ring-opening method is adopted, and propargylamine is used as a modifier.

6. The method for preparing the alkyne-rich graphene-based composite hydrogen absorption material according to claim 3, characterized in that In the step (3), a self-assembly method is used to load PdO nanoparticles on AGO.

7. The method for preparing the alkyne-rich graphene-based composite hydrogen absorption material according to claim 3, characterized in that In step (4), polyvinyl alcohol is modified by adding CDI and propargylamine using a carbamate method. The degree of alkynyl substitution of the polyvinyl alcohol is 63%.

8. The method for preparing an alkyne-rich graphene-based composite hydrogen absorbing material according to claim 3, characterized in that In the step (5), grinding is performed using a mortar.

9. The method for preparing an alkyne-rich graphene-based composite hydrogen absorbing material according to claim 3, characterized in that The drying temperature of step (1) and step (4) is 70°C, and the drying temperature of step (2) and step (3) is 50°C, wherein step (2), step (3) and step (4) are all vacuum dried.

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