A plasma-irradiated porous MXene membrane, its preparation method and application

Abstract

This invention discloses a plasma-irradiated porous MXene membrane, its preparation method, and its application, belonging to the field of separation membrane material technology. The method includes the following steps: spin-coating an aqueous dispersion of MXene nanosheets onto a substrate, drying it, and then subjecting it to plasma irradiation to create pores. Repeating the spin-coating, drying, and plasma irradiation steps yields the porous MXene membrane. This invention also discloses the porous MXene membrane prepared by the above method and its application in gas separation. The pore size of the porous MXene membrane obtained by plasma irradiation can be controlled within the range of H2 / CO2 molecular dynamic diameters. Effective in-plane and interlayer dual-stage gas sieving channels endow the porous MXene membrane with ultra-high gas permeability and excellent selectivity.

Description

Technical Field

[0001] This invention belongs to the field of separation membrane material technology, and particularly relates to a plasma-irradiated porous MXene membrane, its preparation method and application. Background Technology

[0002] MXene, a two-dimensional transition metal carbide or carbonitride, shows great potential as a membrane material for gas and ion separation due to its abundant functional groups and tunable interlayer spacing. However, MXene membranes also suffer from long interlayer transport paths and low permeability. Therefore, introducing additional transport channels is a necessary condition for improving the separation performance of two-dimensional sheet-like MXene membranes.

[0003] Introducing artificial pores on two-dimensional nanosheets is an effective strategy for shortening mass transfer paths. Currently, a few researchers utilize chemical etching methods (such as Cu) to achieve this. 2+ Porous MXene membranes can be prepared using H2O2 and H2SO4, which shortens the molecular transport path between layers and exhibits better permeability in fields such as dye separation and seawater desalination. However, existing pore-forming methods usually involve the introduction of pollutants, resulting in pores that are generally nanometer-sized, making it difficult to achieve angstrom-sized pores and thus unsuitable for applications requiring more stringent pore sizes, such as gas separation. Furthermore, most pore-forming methods involve first creating pores in MXene nanosheets and then assembling them into a membrane, rather than directly creating pores in the MXene membrane itself.

[0004] Therefore, how to provide a green and simple pore-forming strategy to directly act on MXene membranes and prepare high-performance porous MXene gas separation membranes is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a plasma-irradiated porous MXene membrane, its preparation method, and its application.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing a porous MXene membrane by plasma irradiation includes the following steps:

[0008] After spin-coating and drying the aqueous dispersion of MXene nanosheets onto a substrate, the porous MXene membrane is obtained by plasma irradiation. The spin-coating, drying and plasma irradiation steps are repeated to obtain the porous MXene membrane.

[0009] Preferably, the concentration of the MXene nanosheet aqueous dispersion is 0.1-0.5 mg / mL.

[0010] Preferably, the MXene nanosheets in the MXene nanosheet aqueous dispersion are Ti3C2T.x Ti2CT x Mo2CT x V2CT x Nb2CT x Nb4C3T x One or any of them.

[0011] Preferably, the dispersion medium of the MXene nanosheet aqueous dispersion is at least one of water, ethanol, acetone, and N,N-dimethylformamide.

[0012] More preferably, the MXene nanosheets in the MXene nanosheet aqueous dispersion are Ti3C2T. x Nanosheets.

[0013] More preferably, the Ti3C2T x The nanosheets were prepared by chemical etching.

[0014] Preferably, the pore size of the substrate is 0.1-0.45 nm;

[0015] The substrate is made of at least one of polyethersulfone, nylon, polyvinylidene fluoride, cellulose acetate, polyacrylonitrile, and polysulfone.

[0016] More preferably, the substrate is made of polyethersulfone.

[0017] Preferably, the plasma used in the plasma irradiation is Ar, and the irradiation power is 100-200W, the irradiation time is 2-10min, and the gas flow rate is 100-160mL / min. It should be noted that Ar, He, N2, H2, and SF6 all have physical etching effects and can theoretically create pores in the MXene film.

[0018] Preferably, the repetition is performed 5-20 times.

[0019] A porous MXene membrane prepared by plasma irradiation.

[0020] The pore-forming mechanism of this invention is as follows: This invention utilizes a plasma cleaner to excite gas into plasma using a high-frequency power supply, generating high-energy electrons, positive and negative ions, and neutral particles. These particles then sputter and etch the Ti and C atoms on the surface of MXene nanosheets, thereby penetrating the MXene film layer to prepare a porous MXene film. Mo2CT x V2CT x Nb2CT x Nb4C3T xBoth the metal atoms and Ti atoms in the membrane belong to transition metal elements and, theoretically, can be sputtered away by Ar plasma to form pores. The pore size of the porous MXene membrane in this invention can be adjusted from angstrom to nanometer size by controlling parameters such as plasma power, irradiation time, and gas flow rate, further increasing the transport channels of the MXene membrane. Among them, the angstrom pores can be controlled between the molecular dynamic diameters of H2 and CO2, and the effective interlayer and in-plane dual-stage gas sieving channels realize the high permeability and high selectivity of the porous MXene membrane.

[0021] Preferably, the porous MXene membrane has a thickness of 30-150 nm and a pore size of 0.1-5 nm.

[0022] Application of a plasma-irradiated porous MXene membrane in gas separation.

[0023] Preferably, the gas separation is H2 / CO2 gas separation.

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

[0025] This invention utilizes plasma irradiation technology to directly create pores in MXene membranes. The pore-forming method is simple, low-cost, and allows for pore size adjustment from angstroms to nanometers. The porous MXene membranes obtained by plasma irradiation according to this invention have pore sizes controllable between the molecular dynamic diameters of H2 and CO2. Effective in-plane and interlayer dual-stage gas sieving channels endow the porous MXene membranes with ultra-high gas permeability and excellent selectivity. Attached Figure Description

[0026] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0027] Figure 1 SEM (ad) and TEM (eh) images of MXene nanosheets after Ar plasma irradiation for different times;

[0028] Figure 2 SEM planar (ad) and cross-sectional (eh) images of MXene films after Ar plasma irradiation for different times;

[0029] Figure 3 Raman spectra of MXene films after different times of Ar plasma irradiation, both in their original non-porous state.

[0030] Figure 4 XRD patterns of MXene films after different times of Ar plasma irradiation, both in their original non-porous state.

[0031] Figure 5 H2 permeability (a) and H2 / CO2 selectivity (b) of MXene membranes of different thicknesses after direct irradiation with Ar plasma for different times;

[0032] Figure 6 H2 permeability and H2 / CO2 selectivity of porous MXene membranes (thickness: 100 nm) after repeated Ar plasma irradiation for different times. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] This invention provides a method for preparing a porous MXene membrane by plasma irradiation, comprising the following steps:

[0036] After spin-coating and drying the aqueous dispersion of MXene nanosheets onto a substrate, the porous MXene membrane is obtained by plasma irradiation. The spin-coating, drying and plasma irradiation steps are repeated to obtain the porous MXene membrane.

[0037] In a preferred embodiment, the concentration of the MXene nanosheet aqueous dispersion is 0.1-0.5 mg / mL. A concentration higher than this will result in uneven spin-coating of the nanosheets and a larger thickness, while a concentration lower than this will prevent the nanosheets from effectively covering the polymer substrate.

[0038] In a preferred embodiment, the MXene nanosheets in the MXene nanosheet aqueous dispersion are Ti3C2T. x Ti2CT x Mo2CT x V2CT x Nb2CT x Nb4C3T x One or any of them.

[0039] In a preferred embodiment, the dispersion medium of the MXene nanosheet aqueous dispersion is at least one of water, ethanol, acetone, and N,N-dimethylformamide.

[0040] In a more preferred embodiment, the MXene nanosheets in the MXene nanosheet aqueous dispersion are Ti3C2T. x Nanosheets.

[0041] The Ti3C2T x Nanosheets are prepared by chemical etching, specifically including the following steps:

[0042] 3.75g of lithium fluoride and 3g of Ti3AlC2 powder were mixed with 75ml of 9M hydrochloric acid solution and stirred at 50℃ for 40h. The resulting slurry was repeatedly washed by centrifugation at 5000rpm until the pH reached neutral. Finally, the solution was centrifuged at 5000rpm for 30min, and the supernatant was discarded to remove small flakes. The precipitate was collected by centrifugation at 1500rpm, and the supernatant was obtained, which is the non-porous Ti3C2T. x Aqueous dispersion of nanosheets.

[0043] In a preferred embodiment, the pore size of the substrate is 0.1-0.45 nm; within this pore size range, MXene nanosheets can be completely retained by the substrate to form an MXene film without affecting subsequent separation permeability.

[0044] The substrate is made of at least one of polyethersulfone, nylon, polyvinylidene fluoride, cellulose acetate, polyacrylonitrile, and polysulfone.

[0045] In a more preferred embodiment, the substrate is made of polyethersulfone.

[0046] In a preferred embodiment, the plasma in the plasma irradiation is Ar, and the irradiation power is 100-200W, the irradiation time is 2-10min, and the gas flow rate is 100-160mL / min.

[0047] Under the above irradiation conditions, the membrane pore size is suitable for gas separation. If the irradiation power / time / gas flow rate is higher than this, the pore size will be too large, resulting in poor membrane selectivity. If the irradiation power / time / gas flow rate is lower than this, the membrane pore size will be too small, resulting in lower membrane permeability.

[0048] In a preferred embodiment, the number of repetitions is 5-20. Within this range of repetitions, a porous MXene film with a thickness of 30-150 nm can be obtained.

[0049] This invention also provides a method for preparing porous MXene membranes by plasma irradiation.

[0050] In a preferred embodiment, the porous MXene membrane has a thickness of 30-150 nm and a pore size of 0.1-5 nm.

[0051] This invention also provides an application of a plasma-irradiated porous MXene membrane in gas separation.

[0052] In a preferred embodiment, the gas separation is H2 / CO2 gas separation.

[0053] Unless otherwise specified, all raw materials used in the embodiments of this invention were purchased through commercial channels.

[0054] In the embodiments of this invention, room temperature or ambient temperature refers to 25±3℃.

[0055] Example 1

[0056] A plasma-irradiated porous MXene membrane and its preparation method, comprising the following steps:

[0057] (1) Preparation of pore-free MXene (Ti3C2T) by chemical etching x Nanosheet aqueous dispersion:

[0058] 3.75g of lithium fluoride and 3g of Ti3AlC2 powder were mixed with 75ml of 9M hydrochloric acid solution and stirred at 50℃ for 40h. The resulting slurry was repeatedly washed by centrifugation at 5000rpm until the pH was neutral. Finally, the solution was centrifuged at 5000rpm for 30min, and the supernatant was discarded to remove small flakes. The precipitate was collected by centrifugation at 1500rpm, and the supernatant was obtained, which is the non-porous Ti3C2T. x Aqueous dispersion of nanosheets was prepared, and the concentration of the dispersion was adjusted to 0.5 mg / mL.

[0059] (2) 100 mL of the dispersion with a concentration of 0.2 mg / mL obtained in step (1) was loaded onto a polyethersulfone substrate (pore size: 0.1 μm; size: 2.5 cm diameter disc) by spin coating, and then placed at 80 °C for vacuum drying for 20 min to obtain an ultrathin non-porous MXene membrane with a thickness of ~10 nm. The membrane was further irradiated with Ar plasma (irradiation time: 2 min; irradiation power: 100 W; gas flow rate: 100 mL / min) to obtain an ultrathin porous MXene membrane.

[0060] (3) Further spin-coating the non-porous Ti3C2T obtained in step (1) onto the ultrathin porous MXene film obtained in step (2). x The nanosheet aqueous dispersion (dispersion concentration and volume are the same as in step (2)) was dried and then subjected to plasma irradiation again (drying and irradiation conditions are the same as in step 2). The spin coating and plasma irradiation steps were repeated 10 times to obtain a porous MXene film with a thickness of ~100 nm.

[0061] Example 2

[0062] A porous MXene membrane irradiated by plasma and its preparation method are different from those in Example 1 in that the irradiation time in step (2) is 5 min, while the other process steps and parameters are the same as those in Example 1.

[0063] Example 3

[0064] A plasma-irradiated porous MXene membrane and its preparation method are different from those in Example 1 in that the irradiation time in step (2) is 10 min, while the other process steps and parameters are the same as those in Example 1.

[0065] Comparative Example 1

[0066] (1) Non-porous MXene (Ti3C2T) x The preparation method of the nanosheet aqueous dispersion is the same as in Example 1.

[0067] (2) 100 mL of the dispersion with a concentration of 0.5 mg / mL obtained in step (1) was loaded onto a polyethersulfone substrate (pore size: 0.1 μm; size: 2.5 cm diameter disc) by spin coating, and then vacuum dried at 80 °C for 20 min to obtain an ultrathin porous MXene membrane with a thickness of ~10 nm.

[0068] (3) Further spin-coating the non-porous Ti3C2T obtained in step (1) onto the ultrathin porous MXene film obtained in step (2). x The nanosheet aqueous dispersion (dispersion concentration and volume are the same as in step (2)) is dried, and the spin coating step is repeated 10 times to obtain a non-porous MXene film with a thickness of ~100 nm.

[0069] Technical effect

[0070] Example 1, Example 2, Example 3 and Comparative Example 1 correspond to samples after Ar plasma irradiation for 2 min, 5 min, 10 min and 0 min, respectively.

[0071] 1. Structural characterization of non-porous MXene nanosheets, porous MXene nanosheets, and membranes:

[0072] like Figure 1 As shown in the SEM images of the ad portion, the morphology of MXene nanosheets remained unchanged after Ar plasma irradiation for different times. Further observation... Figure 1 The TEM in the middle section of the eh section shows that when the Ar plasma irradiation time is 2 min, no pore size is observed in the MXene nanosheets; when the irradiation time is extended to 5 min, a large number of 0.3 nm angstrom pores appear on the MXene surface; when the time is further extended to 10 min, the pore size on the MXene surface expands from angstrom pores to nanopores of about 5 nm.

[0073] like Figure 2 As shown in the SEM images, compared with the original non-porous MXene membrane structure in a, the SEM planar and cross-sectional images of the MXene membrane after different Ar plasma irradiations show no significant changes. This is attributed to the fact that the pore size is too small to be observed by SEM.

[0074] Further Raman spectroscopy tests ( Figure 3 The results show that as the irradiation time with Ar plasma increases, the D peak (sp) increases. 3 The amorphous carbon peak gradually increases, which means that the defects on the surface of the MXene film gradually increase. Since the detection depth of Raman spectroscopy is about 10 nm, the results of Raman spectroscopy also indirectly prove that the depth of the film penetrated by Ar plasma irradiation is close to about 10 nm.

[0075] like Figure 4 As shown in the XRD, the 2θ angle gradually increases with the increase of Ar plasma irradiation time. The interlayer spacing of the MXene film under different Ar plasma irradiation times was calculated by Bragg equation to gradually decrease from the original 1.34 nm to 1.3 nm. This may be attributed to the thermal effect of plasma causing interlayer shrinkage of MXene.

[0076] 2. H2 / CO2 gas separation performance of non-porous MXene membranes and porous MXene membranes:

[0077] The MXene membrane obtained in Example 1 was placed in a self-contained gas separation constant pressure device. A mixture of H2 / CO2 gas at a flow rate of 50 mL / min (volume ratio 1:1) was introduced into the feed side. Ar gas at a flow rate of 50 mL / min was then introduced for purging, and the results were analyzed using gas chromatography. To verify the penetration depth of the MXene membrane by Ar plasma irradiation, this invention first tested the H2 permeability and H2 / CO2 selectivity of MXene membranes of different thicknesses after direct Ar plasma irradiation for different times. Figure 5 As shown, it can be observed that the thicker the membrane, the smaller the increase in H2 permeability. Therefore, it is speculated that the depth to which Ar plasma irradiation can penetrate the MXene membrane is approximately 10 nm. Figure 6As shown, this invention employs a spin-coating and irradiation method to continuously increase the membrane thickness to approximately 100 nm, thereby optimizing the gas separation performance of the MXene membrane. Compared to the original non-porous MXene membrane, as the Ar plasma irradiation time is extended to 5 min, the H2 permeability of the porous MXene membrane increases from 481 to 1154 GPU (nearly 3 times). This is attributed to the fact that the pore size of the porous MXene membrane shortens the transport channels for gas molecules. However, the selectivity remains essentially unchanged (from 146 to 138), which is attributed to the fact that the effective in-plane pore size and free interlayer spacing are both between the molecular dynamics of H2 / CO2, serving as a two-stage sieving channel. Further extending the Ar plasma irradiation time to 10 min increases the permeability of the porous MXene membrane to 2978 GPU, while the selectivity decreases to 23. This is attributed to the fact that the MXene membrane generates more non-selective defects under longer irradiation times.

[0078] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for preparing a porous MXene membrane by plasma irradiation for gas separation, characterized in that, Includes the following steps: After spin-coating and drying the aqueous dispersion of MXene nanosheets onto a substrate, the porous MXene membrane is obtained by plasma irradiation. The spin-coating, drying and plasma irradiation steps are repeated to obtain the porous MXene membrane. The plasma used in the plasma irradiation is Ar, and the irradiation power is 100-200W, the irradiation time is 2-10min, and the gas flow rate is 100-160 mL / min. The porous MXene film has a thickness of 30-150 nm and a pore size of 0.1-5 nm.

2. The method for preparing a porous MXene membrane by plasma irradiation for gas separation according to claim 1, characterized in that, The concentration of the MXene nanosheet aqueous dispersion is 0.1-0.5 mg / mL.

3. The method for preparing a porous MXene membrane by plasma irradiation for gas separation according to claim 2, characterized in that, The MXene nanosheets in the aqueous dispersion are Ti3C2T. x Ti2CT x Mo2CT x V2CT x Nb2CT x Nb4C3T x One or any of them.

4. The method for preparing a porous MXene membrane by plasma irradiation for gas separation according to claim 1, characterized in that, The substrate has a pore size of 0.1-0.45 nm; The substrate is made of at least one of polyethersulfone, nylon, polyvinylidene fluoride, cellulose acetate, polyacrylonitrile, and polysulfone.

5. The method for preparing a porous MXene membrane by plasma irradiation for gas separation according to claim 1, characterized in that, The number of repetitions is 5-20 times.

6. The porous MXene membrane prepared by the preparation method according to any one of claims 1-5.

7. The application of the porous MXene membrane as described in claim 6 in gas separation.

8. The application according to claim 7, characterized in that, The gas separation is H2 / CO2 gas separation.

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