A one-step preparation process for fluorine-functionalized intercalated graphene materials with adjustable interlayer spacing, along with its products and applications.

Abstract

This invention discloses a one-step preparation process for fluorinated functionalized intercalated graphene materials with adjustable interlayer spacing, comprising: uniformly mixing graphite oxide, an intercalation modifier, and a reaction medium to obtain a mixture; transferring the mixture to a reaction vessel, and undergoing a one-step solvothermal reaction to obtain the fluorinated functionalized intercalated graphene material; the intercalation modifier is selected from perfluorinated rigid symmetrical organic molecules. This invention discloses a one-step process for preparing fluorinated functionalized intercalated graphene materials with adjustable interlayer spacing. The preparation process is simple and flexible, with mild reaction conditions, yet it can efficiently improve the reversible hydrogen adsorption capacity of graphene materials, and is expected to achieve industrial production.

Description

Technical Field

[0001] This invention relates to the technical field of hydrogen storage materials, and in particular to a one-step preparation process for fluorinated functionalized intercalated graphene materials with adjustable interlayer spacing, the resulting products, and their application in adsorption hydrogen storage. Background Technology

[0002] Graphene is a two-dimensional, single-atom-thick layer of sp2 hybrid carbon atoms arranged in a honeycomb pattern, possessing a very high specific surface area (2630 m²). 2 Graphene possesses high mechanical strength and thermal / chemical stability, and exhibits relatively high polarizability due to its π-electron system, theoretically making it a good hydrogen adsorbent. However, it must be acknowledged that current technology cannot achieve large-scale preparation of high-quality monolayer graphene; in practice, few-layer graphene, with a thickness of only a few atoms, is more commonly used. The stacking of graphene sheets drastically reduces the accessible surface area for H2 molecules, significantly hindering H2 adsorption between layers. Furthermore, weak van der Waals interactions further limit graphene's hydrogen adsorption and storage capacity.

[0003] Structural engineering of graphite has been extensively studied to enhance hydrogen adsorption capacity by fully exposing surface adsorption active sites. For example, when using few-layer graphene as an adsorbent, introducing various types of "spacers" such as oxygen-containing groups, fullerenes, or carbon nanotubes between graphene sheets can effectively increase the interlayer distance and improve the accessibility of the inner plane of graphene, thereby increasing the amount of hydrogen adsorption. In addition to structural design, researchers are also committed to improving the hydrogen binding energy of the graphene surface through chemical modification methods such as metal modification and / or heteroatom doping. For example, N or F element doping, due to its strong electron-donating ability or high electronegativity, will greatly change the charge distribution of the graphene plane, enhance the polarization ability for adsorbed gas molecules, and thus lead to an increase in hydrogen binding energy and adsorption capacity (Langmuir, 2012, 28:7826–33; J Am Chem Soc, 2009, 131:17732–3).

[0004] Leveraging the synergistic effect of structural design and chemical modification has become a research hotspot in graphene adsorption and hydrogen storage in recent years. Given the diversity of graphene's structural forms and chemical compositions, many synergistic schemes exist, but most are currently only theoretically feasible. Even those experimentally successful synthesized graphene, such as Pt-modified 3D graphene, N-doped graphene foam, and F-doped porous graphene, typically involve complex operational processes. First, graphene with a specific structure is obtained through activation, etching, intercalation, and self-assembly. Then, chemically modified structured graphene is obtained through precursor impregnation, high-temperature calcination, and chemical reduction. This cumbersome step-by-step preparation method is not only inefficient but also results in significant material loss and poor subsequent modification / doping efficiency, making it unsuitable for practical applications.

[0005] Therefore, there is an urgent need to develop flexible and simple methods to achieve one-step efficient preparation of graphene-based hydrogen storage materials with advanced structures and functions. Summary of the Invention

[0006] To address the aforementioned problems in the existing technology, this invention discloses a one-step process for preparing fluorinated functionalized intercalated graphene materials with adjustable interlayer spacing. The preparation process is simple and flexible, and the reaction conditions are mild, yet it can efficiently improve the reversible hydrogen adsorption capacity of graphene materials, and is expected to achieve industrial production.

[0007] The specific technical solution is as follows:

[0008] A one-step preparation process for fluorine-functionalized intercalated graphene materials with adjustable interlayer spacing includes the following steps:

[0009] After uniformly mixing graphite oxide, intercalation modifier, and reaction medium, a mixture is obtained; the mixture is transferred to a reaction vessel and subjected to a one-step solvothermal reaction to obtain the fluorinated functionalized intercalated graphene material.

[0010] The intercalation modifier is selected from perfluorinated rigid symmetric organic molecules.

[0011] This invention employs a specially structured intercalation modifier to achieve functionalization of graphene through a single solvothermal reaction.

[0012] Experiments revealed that perfluorinated rigid symmetrical organic molecules can ensure the consistency and stability of the "intercalation," avoiding uneven intercalation and subsequent structural collapse; the symmetrical framework structure also helps improve the efficiency of the intercalation reaction. Comparatively, using flexible 1,6-diaminohexane as an intercalation modifier leads to uneven intercalation structures and significant variations in interlayer spacing; while using asymmetric 1,2-diaminotetrafluorobenzene as an intercalation modifier results in low intercalation efficiency, even lower than the efficiency of solvothermal reactions without any intercalation agent.

[0013] Preferably, the intercalation modifier is selected from 1,4-diaminotetrafluorobenzene and / or 4,4'-diaminooctafluorobiphenyl; more preferably, it is 4,4'-diaminooctafluorobiphenyl.

[0014] Experiments revealed that using 4,4'-diaminooctafluorobiphenyl as an intercalation modifier resulted in higher intercalation efficiency and a higher hydrogen adsorption capacity in the final fluorinated functionalized intercalated graphene material.

[0015] Preferably, the reaction medium is selected from one or more of N,N-dimethylformamide, ethanol, and methanol; more preferably, it is N,N-dimethylformamide.

[0016] Preferably, the mass ratio of graphite oxide to intercalation modifier is 1:(2-4); more preferably, it is 1:3.

[0017] Preferably, the mass-to-volume ratio of graphite oxide in the mixture is (2.5–4.0) g / L; more preferably, it is 3.3 g / L.

[0018] In the specific preparation process, graphene oxide can be uniformly dispersed in the reaction medium first, and then an intercalation modifier can be added for uniform dispersion.

[0019] The dispersion can be selected from conventional techniques in the art, such as ultrasonic dispersion.

[0020] Preferably, the temperature of the one-step solvothermal reaction is 90–130°C, and the time is 12–36 h.

[0021] The product after the one-step solvothermal reaction needs to undergo post-processing; the post-processing includes separation, washing and drying.

[0022] This invention also discloses a fluorinated functionalized intercalated graphene material with adjustable interlayer spacing prepared according to the above process, wherein the interlayer spacing is [missing information]. Preferred

[0023] This invention also discloses the application of the fluorinated functionalized intercalated graphene material with adjustable interlayer spacing in hydrogen adsorption and storage. Tests conducted under adsorption conditions of 77 K adsorption temperature and 0–6 MPa H2 pressure showed that the fluorinated functionalized intercalated graphene material prepared in this invention exhibits a high hydrogen adsorption capacity, reaching up to 0.86 wt%.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] The one-step preparation process disclosed in this invention is simple and flexible. It can achieve the control of graphene interlayer spacing and the introduction of functional elements through a one-step solvothermal reaction under mild conditions.

[0026] The preparation process of this invention uses graphite oxide as raw material. Due to the simplification of the process, the loss of raw materials is reduced and the yield is improved. The preparation process of this invention also screens special intercalation modifiers, which not only helps to improve the efficiency of the intercalation reaction, ensure the consistency and stability of the "intercalation", and avoid uneven intercalation and subsequent structural collapse, but also enables efficient F doping.

[0027] The fluorinated intercalated graphene material prepared by this invention has an adjustable interlayer spacing and a high hydrogen absorption capacity, and is expected to be widely used in hydrogen adsorption and storage. Attached Figure Description

[0028] Figure 1Fourier transform infrared spectrum (a) and X-ray diffraction pattern (b) of the product prepared in Example 1;

[0029] Figure 2 X-ray photoelectron spectroscopy of the product prepared in Example 1;

[0030] Figure 3 The scanning electron microscope (SEM) image (a), transmission electron microscope (TEM) image (b), and corresponding EDS elemental distribution map (ce) of the product prepared in Example 1 are shown.

[0031] Figure 4 The hydrogen adsorption-desorption curve of the product prepared in Example 1 is shown below.

[0032] Figure 5 Fourier transform infrared spectrum (a) and X-ray diffraction pattern (b) of the product prepared in Example 2;

[0033] Figure 6 The hydrogen adsorption-desorption curve of the product prepared in Example 2 is shown below.

[0034] Figure 7 Fourier transform infrared spectrum (a) and X-ray diffraction pattern (b) of the product prepared for Comparative Example 1;

[0035] Figure 8 The hydrogen adsorption-desorption curve of the product prepared in Comparative Example 1;

[0036] Figure 9 Fourier transform infrared spectrum (a) and X-ray diffraction pattern (b) of the product prepared for Comparative Example 2;

[0037] Figure 10 The X-ray diffraction pattern of the product prepared in Comparative Example 3;

[0038] Figure 11 Fourier transform infrared spectrum (a) and X-ray diffraction pattern (b) of the product prepared in Comparative Example 4;

[0039] Figure 12 The hydrogen adsorption-desorption curves of the product prepared in Comparative Example 4 are shown. Detailed Implementation

[0040] To further understand the present invention, the present invention will be specifically described below with reference to the embodiments and accompanying drawings. However, the present invention is not limited to these embodiments. Non-essential improvements and adjustments made by those skilled in the art under the core guiding principles of the present invention are still within the protection scope of the present invention.

[0041] Example 1

[0042] 200 mg of graphene oxide was weighed and dispersed in 60 mL of N,N-dimethylformamide and sonicated for 1 h. Then, 600 mg of 4,4'-diaminooctafluorobiphenyl was added to the dispersion and sonicated for 1 h. Subsequently, the mixture was transferred to a 100 mL polytetrafluoroethylene reactor and solvated at 110 °C for 24 h. After cooling, the reaction product was centrifuged and washed three times each with deionized water and ethanol. Finally, it was vacuum dried at 35 °C for 12 h to prepare 4,4'-diaminooctafluorobiphenyl intercalated graphene material.

[0043] Figure 1 The figures (a) and (b) show the Fourier transform infrared spectrum (FTIR) and X-ray diffraction pattern (XRD) of the product prepared in this embodiment, respectively. The presence of NH and CF bond vibration peaks in the FTIR spectrum indicates that 4,4'-diaminooctafluorobiphenyl successfully inserted into the interlayer of graphene through nucleophilic substitution of the oxygen-containing groups in graphene oxide by the NH2 groups at both ends of the molecule. The interlayer spacing of this material can be calculated using the Scherrer formula.

[0044] Figure 2 This is the X-ray photoelectron spectrum of the product prepared in this embodiment. The appearance of the N1s peak at 399.1 eV and the F1s peak at 782.6 eV further demonstrates the successful intercalation of the 4,4'-diaminooctafluorobiphenyl molecule. Specifically, the N atom is grafted onto the graphene carbon plane through the substitution reaction of the oxygen-containing group in the graphene oxide by the NH2 group at the molecule's terminal end, while the F atom is located in the benzene ring skeleton of the intercalated molecule in the graphene interlayer. Therefore, the N1s peak detected by surface XPS is relatively stronger, while the F1s peak is relatively weaker.

[0045] Figure 3 The images shown are a scanning electron microscope (SEM) image (a), a transmission electron microscope (TEM) image (b), and a corresponding EDS elemental distribution map (c) of the product prepared in this embodiment. Its loosely stacked few-layer structure more clearly illustrates the intercalation of organic molecules, and the N and F elements are uniformly distributed in the C matrix.

[0046] In summary, this invention achieves both the control of graphene interlayer spacing and the introduction of functional elements through a simple one-step solvothermal reaction.

[0047] The hydrogen adsorption-desorption curves of the product prepared in this example were measured at 77 K in the range of 0–6 MPa H2 using a BSD 3H-2000PH isothermal high-pressure adsorption instrument. Figure 4 As shown, the hydrogen absorption capacity of this material at 77K / 6MPa H2 can reach 0.86wt%. This is similar to that of 1,4-diaminotetrafluorobenzene intercalated graphene material (Example 2). Figure 6Compared to 4,4'-diaminobiphenyl intercalated graphene material (Comparative Example 1), the hydrogen adsorption capacity increased by 0.42 wt%, indicating that under the same F functionalization modification conditions, increasing the interlayer spacing can improve the hydrogen adsorption capacity of the material. Figure 8 Compared to ), it increased by 0.48 wt%, indicating that under the condition of basically consistent interlayer spacing, F functionalization modification can also improve hydrogen adsorption capacity. Compared to graphene materials treated with solvothermal agents alone (Comparative Example 4), it increased by 0.48 wt%, indicating that under the condition of basically consistent interlayer spacing, F functionalization modification can also improve hydrogen adsorption capacity. Figure 12 Compared to the previous year, the hydrogen adsorption capacity increased by 0.62 wt%, indicating that the synergistic effect of increasing the interlayer spacing and F functionalization modification can more effectively improve the hydrogen adsorption capacity of the material.

[0048] Furthermore, the adsorbed hydrogen gas in the material prepared in this embodiment is almost completely released during the desorption process, indicating its excellent reversibility. However, compared to 4,4'-diaminobiphenyl intercalated graphene material (Comparative Example 1), Figure 8 ) and graphene materials that are solvothermal treated alone (Comparative Example 4, Figure 12 The material exhibits a significant hysteresis effect between its desorption and adsorption curves. This is because the introduction of highly electronegative F element increases the polarization and binding capacity for adsorbed hydrogen molecules, leading to a hysteresis in hydrogen desorption.

[0049] Example 2

[0050] The preparation process is basically the same as in Example 1, except that the intercalation modifier is replaced with an equal mass of 1,4-diaminotetrafluorobenzene. In this example, 1,4-diaminotetrafluorobenzene intercalated graphene material was prepared.

[0051] Figure 5 The figures (a) and (b) are the Fourier transform infrared spectrum and X-ray diffraction pattern of the product prepared in this embodiment, respectively. Similar to Example 1, the appearance of NH and CF bond vibration peaks in the infrared spectrum indicates successful intercalation of the 1,4-diaminotetrafluorobenzene molecule. The interlayer spacing of this material, calculated using the Scherrer formula, is...

[0052] Figure 6 The hydrogen adsorption-desorption curves of the product prepared in this embodiment are shown, and the performance testing methods and conditions are the same as in Example 1. This material can adsorb a maximum of 0.44 wt% H2 at 77 K / 6 MPa H2, and releases it almost completely during desorption. Furthermore, due to the presence of the highly electronegative element F, the adsorption-desorption process of this material also exhibits the hysteresis phenomenon seen in Example 1.

[0053] Comparative Example 1

[0054] The preparation process is basically the same as in Example 1, except that the intercalation modifier is replaced with an equal mass of 4,4'-diaminobiphenyl. This comparative example prepared 4,4'-diaminobiphenyl intercalated graphene material.

[0055] Figure 7 The figures (a) and (b) show the Fourier transform infrared spectrum (FTIR) and X-ray diffraction pattern (XRD) of the product prepared in this comparative example, respectively. Unlike Example 1, only the NH bond vibration peak and no CF bond vibration peak were observed in the FTIR spectrum, indicating the intercalation of fluorine-free 4,4'-diaminobiphenyl molecules. Further calculations using the Scherrer formula yielded the interlayer spacing of this material as follows: Almost identical to Example 1.

[0056] Figure 8 The hydrogen adsorption-desorption curves of the product prepared in this comparative example are shown. The performance testing methods and conditions are the same as in Example 1. This material can adsorb up to 0.38 wt% H2 at 77 K / 6 MPa H2 and completely release it during the desorption process, with no obvious hysteresis loop appearing.

[0057] Comparative Example 2

[0058] The preparation process is basically the same as in Example 2, except that the intercalation modifier is replaced with an equal mass of 1,2-diaminotetrafluorobenzene. This comparative example prepared 1,2-diaminotetrafluorobenzene intercalated graphene material.

[0059] Figure 9 The figures (a) and (b) are the Fourier transform infrared spectrum and X-ray diffraction pattern of the product prepared in this comparative example, respectively. Unlike Example 2, the vibrational peak intensities of NH and CF bonds in this infrared spectrum are relatively weak, and the interlayer spacing of this material is calculated according to the Scherrer formula as follows: Smaller than Example 2 The results show that the intercalation ability of 1,2-diaminotetrafluorobenzene is worse than that of 1,4-diaminotetrafluorobenzene. This may be because the two NH2 groups are located in adjacent positions in the molecular structure of 1,2-diaminotetrafluorobenzene. When one of the NH2 groups undergoes a grafting substitution reaction, the other NH2 group is unable to continue reacting due to steric hindrance, resulting in a decrease in intercalation efficiency.

[0060] Comparative Example 3

[0061] The preparation process is basically the same as in Example 1, except that the intercalation modifier is replaced with an equal mass of 1,6-diaminohexane. This comparative example prepared 1,6-diaminohexane intercalated graphene material.

[0062] Figure 10 This is the X-ray diffraction pattern of the product prepared in this comparative example. Compared to the single peak of Example 1, this material exhibits a unique split peak shape, centered at 9.72° and 11.39°, respectively. The interlayer spacing corresponding to the lower-angle peaks is... Approaching Example 1 The interlayer spacing corresponding to the high-angle peak is The peaks are significantly lower than in Example 1. This peak splitting phenomenon can be explained by the flexible chain structure of the 1,6-diaminohexane molecule, whose two NH2 groups can be grafted onto adjacent graphene sheets to form a bridging configuration, or onto graphene sheets on the same side to form a cyclic configuration, thus leading to the non-uniformity of the intercalation structure.

[0063] Comparative Example 4

[0064] 200 mg of graphene oxide was weighed and dispersed in 60 mL of N,N-dimethylformamide and sonicated for 1 h. The mixture was then transferred to a 100 mL polytetrafluoroethylene reactor and solvothermal treated at 110 °C for 24 h. After cooling, the reaction product was centrifuged and washed three times each with deionized water and ethanol. Finally, it was vacuum dried at 35 °C for 12 h to prepare the solvothermal treated graphene material.

[0065] Figure 11 The figures (a) and (b) are the Fourier transform infrared (FTIR) spectrum and X-ray diffraction (XRD) patterns of the product prepared in this comparative example, respectively. Due to the removal of oxygen-containing groups during solvothermal treatment, no vibrational peaks were observed in the FTIR spectrum. The interlayer spacing of the material was calculated using the Scherrer formula to be... Significantly lower than Example 1 Slightly lower than Example 2 But slightly higher than comparative example 2 This indicates that solvothermal treatment alone can also achieve a certain degree of exfoliation by removing oxygen-containing groups, leading to an increase in interlayer spacing.

[0066] Figure 12 The hydrogen adsorption-desorption curves of the product prepared in this comparative example are shown. The performance testing methods and conditions are the same as in Example 1. This material can adsorb up to 0.24 wt% H2 at 77 K / 6 MPa H2 and completely release it during the desorption process, with no obvious hysteresis loop appearing.

[0067] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. The specific examples used above to illustrate the present invention are only for the purpose of helping to understand the present invention and are not intended to limit the present invention. Those skilled in the art to which this invention pertains can make several simple deductions, modifications, substitutions, or combinations based on the concept of the present invention. These deductions, modifications, substitutions, or combinations also fall within the scope of the claims of the present invention.

Claims

1. The application of a fluorinated functionalized intercalated graphene material with adjustable interlayer spacing in hydrogen adsorption and storage, characterized in that, The fluorine-functionalized intercalated graphene material with adjustable interlayer spacing is prepared using a one-step process, including the following steps: After uniformly mixing graphite oxide, intercalation modifier, and reaction medium, a mixture is obtained; the mixture is transferred to a reaction vessel and subjected to a one-step solvothermal reaction to obtain the fluorinated functionalized intercalated graphene material. The intercalation modifier is selected from 4,4'-diaminooctafluorobiphenyl; The mass ratio of graphite oxide to intercalation modifier is 1:(2~4).

2. The application of the fluorinated functionalized intercalated graphene material with adjustable interlayer spacing according to claim 1 in hydrogen adsorption and storage, characterized in that, The reaction medium is selected from one or more of N,N-dimethylformamide, ethanol, and methanol.

3. The application of the fluorinated functionalized intercalated graphene material with adjustable interlayer spacing according to claim 1 in hydrogen adsorption and storage, characterized in that, The mass-to-volume ratio of graphite oxide in the mixture is (2.5~4.0) g / L.

4. The application of the fluorinated functionalized intercalated graphene material with adjustable interlayer spacing according to claim 1 in hydrogen adsorption and storage, characterized in that, The temperature of the one-step solvothermal reaction is 90~130℃, and the time is 12~36h.

5. The application of the fluorinated functionalized intercalated graphene material with adjustable interlayer spacing according to claim 1 in hydrogen adsorption and storage, characterized in that, The product after the one-step solvothermal reaction still needs to be post-processed; The post-processing includes separation, washing, and drying.

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