Method for improving hydrogen storage efficiency through defective carbon nanotube bundle
By preparing and controlling defective single-walled carbon nanotube bundles, the problems of low hydrogen storage efficiency and insufficient mixed gas separation capacity of single-walled carbon nanotubes were solved, achieving efficient hydrogen adsorption and selective separation, and improving hydrogen storage performance.
Patent Information
- Application Number
- CN202511880587.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-13
- Publication Date
- 2026-03-17
AI Technical Summary
In the existing technology, single-walled carbon nanotubes have limited hydrogen storage efficiency, the positive effects of defects are not fully utilized, and they lack the ability to selectively separate hydrogen from mixed gases.
By preparing hexagonal arrayed single-walled carbon nanotube bundles and introducing vacancy defects of at least the critical size on their walls, adjusting the inter-tube distance, and combining suitable temperature and pressure conditions, efficient adsorption and selective separation of hydrogen can be achieved.
It significantly improved the hydrogen storage efficiency of single-walled carbon nanotube bundles by nearly double, achieving efficient adsorption and selective separation of hydrogen molecules and optimizing the hydrogen storage performance per unit mass.
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Figure CN121672499A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of hydrogen energy storage materials technology, and specifically to a method for improving hydrogen storage efficiency through defective carbon nanotube bundles. Background Technology
[0002] Single-walled carbon nanotubes (SWCNTs) have attracted significant attention in the field of gas adsorption due to their unique hollow tubular structure, ultra-large specific surface area, and excellent chemical stability. Early research on hydrogen storage using SWCNTs primarily focused on structurally perfect SWCNTs, optimizing hydrogen storage performance by controlling parameters such as tube diameter and length. However, related experiments and simulations show that the hydrogen storage capacity of perfectly structured SWCNTs still falls short of industrial application standards. More importantly, in the actual preparation process of SWCNTs, whether using chemical vapor deposition, arc discharge, or laser evaporation, vacancy defects—pore structures formed by the partial loss of carbon atoms—are inevitably generated in the tube walls. The presence of these defects alters the electronic structure and surface energy states of the carbon nanotubes, potentially significantly affecting the adsorption, diffusion, and storage of hydrogen molecules. Therefore, in-depth research into the hydrogen storage mechanism of defective SWCNTs has important theoretical and practical significance.
[0003] In their natural state, single-walled carbon nanotubes (SWCNTs) readily self-assemble into hexagonally tightly packed bundles via van der Waals forces, rather than existing as isolated single nanotubes. Compared to isolated SWCNTs, this bundle structure not only possesses a more complex spatial configuration but also creates two types of potential gas adsorption sites: internal cavities and inter-tube gaps, resulting in significantly different gas adsorption behaviors. Previous studies have confirmed that SWCNT bundles exhibit higher adsorption capacities for inert gases such as neon and xenon, as well as small molecule gases such as nitrogen and methane, compared to isolated SWCNTs. However, existing research still has significant limitations: studies on the hydrogen adsorption performance of single-walled carbon nanotube bundles containing vacancy defects have not been systematically conducted; the comprehensive influence mechanism of key structural parameters such as defect size, bundle diameter, and inter-tube distance, as well as external environmental factors such as temperature and pressure, on hydrogen storage efficiency remains unclear, failing to provide a theoretical basis for targeted optimization of hydrogen storage performance; on the other hand, in practical hydrogen storage scenarios, hydrogen is often mixed with gases such as nitrogen and carbon dioxide, requiring separation and purification before storage, and the application potential of defective single-walled carbon nanotube bundles in the selective adsorption and separation of hydrogen molecules has not yet been effectively explored. Summary of the Invention
[0004] In view of the above-mentioned shortcomings in the prior art, the present invention provides a method for improving hydrogen storage efficiency by using defective carbon nanotube bundles, which solves the problems of limited hydrogen storage efficiency, insufficient utilization of the positive effects of defects, and lack of ability to selectively separate hydrogen from mixed gases in the prior art.
[0005] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows: a method for improving hydrogen storage efficiency through defective carbon nanotube bundles, comprising the following steps:
[0006] S1, Prepare a single-walled carbon nanotube bundle, wherein the single-walled carbon nanotube bundle is composed of multiple single-walled carbon nanotubes arranged in a hexagonal array;
[0007] S2, introduce vacancy defects into the wall of the single-walled carbon nanotube, wherein the size of the vacancy defect is not less than the critical size N. V =8;
[0008] S3, adjust the inter-tube distance between adjacent single-walled carbon nanotubes in the single-walled carbon nanotube bundle to 5.1 Å to 9 Å;
[0009] S4, the single-walled carbon nanotube bundle with vacancy defects is placed in a hydrogen-containing atmosphere, and hydrogen is physically adsorbed under set temperature and pressure conditions.
[0010] Furthermore, in the above method for improving hydrogen storage efficiency through defective carbon nanotube bundles, the size of the vacancy defects in S2 is such that 8 to 12 carbon atoms are removed, and a single single-walled carbon nanotube can be provided with one or more vacancy defects; the multiple vacancy defects include 12 vacancies with a size of 6 carbon atoms removed and 3 vacancies with a size of 9 carbon atoms removed.
[0011] Furthermore, in the above method for improving hydrogen storage efficiency through defective carbon nanotube bundles, the temperature of the hydrogen-containing atmosphere in S4 is 80K to 300K and the pressure is 4MPa to 1219MPa.
[0012] Furthermore, in the above method for improving hydrogen storage efficiency through defective carbon nanotube bundles, the hydrogen-containing atmosphere in S4 is a mixture of hydrogen and nitrogen gas, and the selective adsorption of hydrogen molecules is achieved by adjusting the inter-tube distance between adjacent single-walled carbon nanotubes in the single-walled carbon nanotube bundle.
[0013] Furthermore, the above-mentioned method for improving hydrogen storage efficiency through defective carbon nanotube bundles introduces vacancy defects by means of ion bombardment or focused ion beam patterning technology.
[0014] Furthermore, in the above-mentioned method of improving hydrogen storage efficiency through defective carbon nanotube bundles, the diameter of the single-walled carbon nanotubes ranges from 8.14 Å to 16.27 Å.
[0015] The beneficial effects of this invention are as follows: By introducing vacancy defects, this invention breaks the adsorption limitations of perfect single-walled carbon nanotubes. When the defect size is not less than the critical value of 8 carbon atoms, it can provide a highly efficient adsorption channel for hydrogen molecules. Combined with the dual adsorption sites of the intratube cavity and intertube gap of the single-walled carbon nanotube bundle, the hydrogen storage capacity far exceeds that of isolated single-walled carbon nanotubes. Compared with single-defect structures, the hydrogen storage efficiency of multi-defect single-walled carbon nanotube bundles can be nearly doubled, and by reducing the mass ratio of carbon nanotubes, the hydrogen storage performance per unit mass is further optimized. Attached Figure Description
[0016] Figure 1 A system composed of single-walled carbon nanotube bundles and hydrogen molecules;
[0017] Figure 2 A comparison of H2 adsorption efficiency in single-walled carbon nanotube bundles with single or multiple vacancy defects and isolated single-walled carbon nanotubes;
[0018] Figure 3 The effect of temperature on H2 adsorption in single-walled carbon nanotube bundles and isolated single-walled carbon nanotubes;
[0019] Figure 4 The effect of pressure on H2 adsorption in single-walled carbon nanotube bundles and isolated single-walled carbon nanotubes;
[0020] Figure 5 The relative potential energy E between single-walled carbon nanotube bundles and hydrogen and nitrogen molecules b Comparison;
[0021] Figure 6 The effects of vacancy defect size and carbon nanotube diameter on H2 adsorption in single-walled carbon nanotube bundles and isolated single-walled carbon nanotubes are shown. Detailed Implementation
[0022] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.
[0023] Example 1
[0024] This embodiment provides a method for improving hydrogen storage efficiency using defective carbon nanotube bundles. Based on molecular dynamics simulation technology, this embodiment systematically verifies the hydrogen storage performance and selective hydrogen molecule separation capability of single-walled carbon nanotube bundles containing vacancy defects. The experiment uses a hexagonal array bundle composed of seven single-walled carbon nanotubes as the core adsorbent material. By precisely controlling defect parameters, bundle structure parameters, and external environmental conditions, the influence of various factors on the physical adsorption efficiency of hydrogen molecules is investigated.
[0025] S1: Preparation of single-walled carbon nanotube bundles. Single-walled carbon nanotubes are prepared using chemical vapor deposition (CVD) or arc discharge method, and then self-assembled to form a hexagonal close-packed bundle structure. For example... Figure 1 As shown, the bundle consists of multiple single-walled carbon nanotubes, each with an armchair configuration and a length of 24.6 Å. The nanotube diameter is adjusted by controlling the chiral index between (6,6) and (12,12), corresponding to a diameter range of 8.14 Å to 16.27 Å.
[0026] S2: Vacancy defects are introduced by using focused ion beam patterning or ion bombardment to introduce vacancy defects into the wall of each single-walled carbon nanotube. The size of the vacancy defect is determined by the number of carbon atoms N removed. V In this embodiment, N is set. V =9, meaning removing 9 carbon atoms forms a defect hole. When N V When the energy level is ≥8, hydrogen molecules can overcome the energy barrier and enter the interior of the nanotube, achieving effective adsorption.
[0027] S3: Adjust the inter-tube distance. The center-to-center distance between adjacent single-walled carbon nanotubes is adjusted to be between 5.1 Å and 9 Å through mechanical compression or chemical modification. In this embodiment, the center-to-center distance between adjacent single-walled carbon nanotubes is set to 6 Å. This distance allows hydrogen molecules to enter the inter-tube gap while maintaining the stability of the tube bundle structure.
[0028] S4: Hydrogen adsorption experiment. The treated single-walled carbon nanotube bundles were placed in a high-pressure reactor and a pure hydrogen atmosphere was introduced. The system temperature was set at 300 K, and the hydrogen pressure was in the range of 4 MPa to 1219 MPa. Through molecular dynamics simulation and actual adsorption experiments, it was verified that under these conditions, hydrogen molecules can enter the interior of the nanotubes through vacancy defects and be adsorbed in the inter-tube gaps, achieving dual-site synergistic hydrogen storage.
[0029] In this embodiment, with a single vacancy defect, the average number of hydrogen molecules adsorbed per single-walled carbon nanotube bundle at 300 K and a pressure of 1219 MPa is significantly higher than that of isolated single-walled carbon nanotubes. The adsorption efficiency of the single-walled carbon nanotube bundle (defined as the ratio of the mass of adsorbed hydrogen to the total mass of adsorbed hydrogen plus the single-walled carbon nanotube bundle) reaches approximately 3.09 wt%, far exceeding the 1.91 wt% of isolated single-walled carbon nanotubes.
[0030] Example 2
[0031] This embodiment focuses on the enhancement effect of introducing multiple vacancy defects into single-walled carbon nanotube bundles on hydrogen storage performance. Steps S1, S3, and S4 of this embodiment are the same as in Example 1, except for step S2, which is as follows:
[0032] S2: Introduce vacancy defects. Multiple vacancy defects are introduced into each single-walled carbon nanotube wall. Specifically, 15 defects are set on each tube wall, of which 12 defects have a size of N. V =6, the size of the 3 defects is N V =9. Although this multi-defect structure did not significantly increase the total number of adsorbed hydrogen molecules, it significantly improved the hydrogen storage efficiency per unit mass due to the reduction of the total number of carbon atoms by about 24.8%.
[0033] like Figure 2 As shown, the hydrogen storage efficiency of multi-defect single-walled carbon nanotube bundles reaches 4.04 wt%, while that of single-defect single-walled carbon nanotube bundles is approximately 3.09%. The multi-defect structure not only provides more channels for hydrogen molecules to enter, but also further optimizes the hydrogen storage efficiency due to the reduced mass of the carbon skeleton.
[0034] Example 3
[0035] This embodiment investigates the influence of external parameters (temperature and pressure) on the hydrogen storage performance of single-walled carbon nanotube bundles. Steps S1-S3 of this embodiment are the same as in Example 1, except for step S4, which is as follows:
[0036] Step S4: Temperature and pressure swing adsorption experiment. Under a fixed hydrogen density (corresponding to a pressure of approximately 1 GPa), the system temperature was gradually increased from 80 K to 300 K. The results are as follows: Figure 3 As shown, the number of adsorbed hydrogen molecules gradually decreases with increasing temperature, indicating that low temperature favors physical adsorption. Under a fixed temperature of 300 K, the hydrogen pressure was adjusted from 4 MPa to 1219 MPa. The results are as follows... Figure 4 As shown, the adsorption capacity gradually increases and tends to saturate as the pressure increases, indicating that high pressure is beneficial to improving hydrogen storage density.
[0037] The above results demonstrate that temperature and pressure are effective external parameters for regulating the hydrogen storage behavior of single-walled carbon nanotube bundles. In practical applications, operation should be carried out under low temperature (e.g., 80K–150K) and medium-high pressure (e.g., 4–1219MPa) conditions to balance adsorption efficiency and system energy consumption.
[0038] Example 4
[0039] This embodiment utilizes single-walled carbon nanotube bundles to selectively adsorb hydrogen from an H2 / N2 mixture. Steps S1-S3 in this embodiment are the same as in Example 1, except for step S4, which is as follows:
[0040] Step S4: Selective adsorption experiment. Single-walled carbon nanotube bundles were placed in a mixed gas containing 1500 H2 molecules and 1500 N2 molecules. The system temperature was set to 300 K, and the defect size N was... V =9. The adsorption behavior of H2 and N2 was observed by adjusting the inter-tube distance d between 5.1 Å and 5.9 Å.
[0041] The results show that when d < 5.1 Å, H2 can only enter the tube through defects, while N2 cannot enter any region; when 5.1 ≤ d ≤ 5.4 Å, H2 can enter the inter-tube gap, but N2 still cannot enter; when d ≥ 5.9 Å, N2 can also enter the gap, but the selectivity decreases; the optimal selectivity occurs when d ≈ 5.8 Å, at which point the adsorption amount of H2 is significantly higher than that of N2.
[0042] like Figure 5 As shown, H2 faces a negative energy barrier when entering the gap, which facilitates its entry; while N2 faces a positive barrier, hindering its entry. Efficient separation of H2 / N2 can be achieved by precisely controlling the distance between the tubes.
[0043] Example 5
[0044] This embodiment explores the synergistic effect of single-walled carbon nanotube bundle diameter and defect size on hydrogen storage capacity. Steps S1-S4 of this embodiment are the same as in Example 1, except that the chiral index in step S1 varies from (6,6) to (12,12), corresponding to a diameter range of 8.14 Å to 16.27 Å. The defect size N in step S2... V The variation from 4 to 12 was examined to investigate its effect on the ability of hydrogen molecules to enter.
[0045] The results showed that, Figure 6 As shown in (a), there is a critical defect size N. V =8, when N V When the temperature is below 8, hydrogen molecules cannot enter the tube through the defect; for example... Figure 6 As shown in (b), the hydrogen adsorption capacity gradually increases with the increase of the diameter of the single-walled carbon nanotube bundle.
[0046] This invention achieves highly efficient physical adsorption and selective separation of hydrogen by systematically controlling the structural parameters (defect size, tube diameter, and inter-tube distance) and external conditions (temperature and pressure) of single-walled carbon nanotube bundles. Specifically, vacancies with at least eight carbon atoms are crucial for hydrogen molecule entry into the tube; the optimal range for selective hydrogen adsorption is 5.1 Å to 5.9 Å; the hydrogen storage efficiency per unit mass can be increased to 4.04 wt%; and low temperature and high pressure are beneficial for improving adsorption capacity.
Claims
1. A method for improving hydrogen storage efficiency by using a bundle of defective carbon nanotubes, characterized by, The method comprises the following steps: S1, preparing a single-walled carbon nanotube bundle composed of a plurality of single-walled carbon nanotubes arranged in a hexagonal array; S2, introducing a vacancy defect on the tube wall of the single-walled carbon nanotube, the size of the vacancy defect being not less than a critical size N V = 8; S3, adjusting the inter-tube distance of adjacent single-walled carbon nanotubes in the single-walled carbon nanotube bundle to be 5.1-9 Å; S4, placing the single-walled carbon nanotube bundle with the vacancy defects in a hydrogen-containing atmosphere and performing physical adsorption of hydrogen under a set temperature and pressure condition.
2. The method of claim 1, wherein the carbon nanotube bundle with defects is prepared by a method comprising: The size of the vacancy defects in S2 is the removal of 8-12 carbon atoms, and a single single-walled carbon nanotube can be provided with a single or multiple vacancy defects; the multiple vacancy defects include 12 vacancies with a size of the removal of 6 carbon atoms and 3 vacancies with a size of the removal of 9 carbon atoms. 3. The method of claim 1, wherein the carbon nanotube bundle with defects is prepared by a method comprising: (a) preparing a carbon nanotube bundle; (b) irradiating the carbon nanotube bundle with a laser beam; and (c) removing the carbon nanotube bundle from the irradiated portion. The temperature of the hydrogen-containing atmosphere in S4 is 80-300 K, and the pressure is 4-1219 MPa.
4. The method of claim 1, wherein the carbon nanotube bundle with defects is prepared by a method comprising: (a) preparing a carbon nanotube bundle; (b) applying a chemical treatment to the carbon nanotube bundle; and (c) applying a physical treatment to the carbon nanotube bundle. The hydrogen-containing atmosphere in S4 is a mixed gas of hydrogen and nitrogen, and selective adsorption of hydrogen molecules is achieved by adjusting the inter-tube distance of adjacent single-walled carbon nanotubes in the single-walled carbon nanotube bundle.
5. The method of improving hydrogen storage efficiency by using a bundle of defective carbon nanotubes according to claim 1, wherein, The way of introducing the vacancy defects is ion bombardment or focused ion beam patterning technology.
6. The method of improving hydrogen storage efficiency by using a bundle of defective carbon nanotubes according to claim 1, wherein, The diameter of the single-walled carbon nanotube is 8.14-16.27 Å.