A method for rapid heavy ion irradiation treatment of graphene oxide film

Abstract

The present invention relates to a method for treating graphene oxide membranes using rapid heavy ion irradiation, belonging to the field of membrane separation technology. The proposed rapid heavy ion irradiation method can further manipulate the abundant transport channels of graphene oxide (GO) membranes, showing potential for fabricating high-permeability gas separation membranes. Due to the synergistic mass transport between in-plane pores and interlayer thermal channels, as well as the reduction in interlayer spacing caused by irradiation-induced crosslinking, the H2 permeability and H2 / CO2 selectivity of GO membranes after irradiation are enhanced.

Description

Technical Field

[0001] The invention relates to a method for treating a graphene oxide membrane by rapid heavy ion irradiation, and belongs to the technical field of membrane separation. Background Art

[0002] Graphene oxide (GO) is a typical two-dimensional (2D) material that has received considerable attention in the past decade. Since Geim et al. reported unimpeded permeation of water through 46 submicron-thick laminated GO membranes (RR Nair, HA Wu, PN Jayaram, IV Grigorieva, AK Geim, Unimpeded permeation of water through helium-leak-tight graphene-based membranes, Science, 335 (2012) 442-444.), the separation properties of GO membranes have been widely studied.

[0003] Despite the thinness of the membrane, the tortuous mass transfer channels greatly increase the mass transfer resistance, resulting in low gas permeability and uncompetitive separation performance of the membrane. Therefore, in order to fabricate high-permeability GO membranes, it is crucial to introduce additional mass transfer channels. Summary of the Invention

[0004] The present invention addresses the technical problem that graphene oxide membranes, due to their circuitous mass transfer pathways, result in high mass transfer resistance and insufficient permeability. This invention proposes a graphene oxide (GO) layered membrane with abundant direct transfer pathways for the separation of hydrogen (H2) and carbon dioxide (CO2). Unlike conventional methods of treating GO nanosheets with irradiation, this method uses rapid heavy ion irradiation to treat the GO layered membrane, increasing gas permeability by several orders of magnitude.

[0005] A method for treating a graphene oxide film by rapid heavy ion irradiation comprises the following steps:

[0006] Step 1, preparing a graphene oxide separation membrane on the surface of the base film;

[0007] Step 2: The separation membrane obtained in step 1 is treated with rapid heavy ion irradiation.

[0008] In step 2, the rapid heavy ion irradiation process emits 1-10MeV / u 129 Xe ions.

[0009] During the irradiation treatment, the irradiation dose per unit area of ​​the separation membrane surface is controlled to be 10 9 -10 11 ions / cm².

[0010] After the irradiation treatment, the separation membrane is left to relax its structure.

[0011] In step 1, the method for preparing the graphene oxide film includes the following steps:

[0012] A graphene oxide dispersion is prepared and deposited on the surface of a base film, and a graphene oxide film is obtained after removing the solvent.

[0013] The concentration of the graphene oxide dispersion is 0.1-5 mg / L.

[0014] Vacuum suction is used during the deposition process, and the amount of graphene oxide deposited on the surface of the base film is 0.01-0.1 mg / cm 2 .

[0015] The graphene oxide membrane prepared as described above is used for H2 / CO2 separation.

[0016] In the application, the graphene oxide membrane has a permeability of 100-15000 GPU at 0.1 MPa and 25° C., and has an H 2 / CO 2 separation coefficient of 3-10.

[0017] Beneficial effects

[0018] The enhanced H₂ permeability and H₂ / CO₂ selectivity of the irradiated GO membranes are attributed to the synergistic mass transport through in-plane pores and interlayer thermal channels, as well as the reduction in interlayer spacing caused by irradiation-induced cross-linking. Compared with traditional methods, the proposed rapid heavy ion irradiation method can further manipulate the abundant transport channels of GO membranes, showing potential for fabricating high-permeability gas separation membranes. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the transmission channel of GO membrane regulated by rapid heavy ion irradiation.

[0020] Figure 2 SEM images of the cross section (ah) and surface (il) of graphene oxide films irradiated by rapid heavy ions. (a, e, i) GO-0.2; (b, f, j) GO-0.2(I); (c, g, k) GO-0.4(I); (d, h, l) GO-0.8(I).

[0021] Figure 3 (a) XRD patterns of pristine GO film and irradiated GO films with different GO 234 deposition amounts; (b) FT-IR spectra of pristine GO film and irradiated GO film.

[0022] Figure 4The gas separation performances of GO membranes with different deposition amounts and irradiated GO membranes at 0.1 MPa feed pressure and 25 °C. DETAILED DESCRIPTION

[0023] Graphene oxide (GO) is a prominent two-dimensional (2D) material that has been established as an ideal building block for separation membranes due to its unique layered structure and tunable physicochemical properties. Although the ultra-thin nature of GO membranes is believed to minimize transport resistance, the intricate mass transport pathways within the layered GO membranes typically result in moderate permeability. The present invention utilizes rapid heavy ion irradiation to incorporate transport channels with highly enhanced gas permeability into GO membranes. 129 After Xe irradiation, characteristic ion tracks were found on the cross-section of the GO membrane. The irradiation process produced disordered regions and nanopores within the laminate, while promoting cross-linking between GO's oxygen-containing groups, thereby reducing the interlayer spacing and enhancing the molecular sieving ability. The irradiated GO membrane exceeded the performance upper limit of H2 / CO2, and the H2 permeability showed a significant three-order-of-magnitude increase. Figure 1 As shown, 129 The Xe ion beam passes through an electrostatic deflector and undergoes magnetic defocusing. After being filtered through the gap, the ions penetrate the layered GO membrane, leaving a series of ion tracks within the membrane.

[0024] Example 1 Preparation of graphene oxide film

[0025] To prepare a GO dispersion, a certain amount of GO suspension was diluted with deionized water to a concentration of 0.5 mg / mL. Ultrasonic treatment and stirring were used to ensure uniform dispersion of the GO nanosheets in the solution. Each time a GO separation membrane was prepared by deposition, 0.5 mg / mL of GO dispersion was added to deionized water and the final solution volume was adjusted to 200 mL. Subsequently, the dispersion was stirred for 30 minutes. The GO dispersion was then filtered onto a porous PES support using a Buchner funnel and a vacuum pump. Complete filtration and water evaporation took approximately 8-10 hours. A series of GO membranes with different deposition amounts were prepared by vacuum filtration. The original GO membrane was defined as GO-X, where X represents the mass of GO nanosheets deposited on the PES substrate, with an area of ​​12.57 square centimeters. The resulting membrane was cut into circular samples and then irradiated.

[0026] Example 2 GO membrane was irradiated by rapid heavy ion irradiation under vacuum conditions

[0027] During the irradiation process, the GO film is fixed on a sample holder and transferred to the irradiation sample chamber by an automatic sampler, with one side of the GO perpendicular to the ion beam. Once the beam tube reaches the required vacuum level, irradiation begins. The heavy ion accelerator emits 5.98MeV / u 129The high collimation of the ion beam ensures that all ions bombard the membrane in the vertical direction. The irradiation effect on the GO membrane is monitored synchronously by an aluminum foil detector. When the irradiation dose reaches the predetermined 1×10 10 ions / cm2, the ion beam is switched off. The irradiated membrane is then left to stand for several days to allow its structure to fully relax.

[0028] After irradiation, the GO membrane is named GO-X(I). During the irradiation process, the incident ions deposit energy on the GO membrane along their orbits, ionizing and exciting the outer electrons of the membrane atoms. Due to the ordered structure of GO, these hot electrons transfer energy to the membrane atoms through the electron-phonon coupling mechanism, causing strong vibrations of the atoms and a sharp rise in the temperature of the irradiated area, forming the so-called thermal spike. The thermal spike melts the material within a few nanometers of the ion orbit, causing the local volume to expand rapidly and causing the molten material near both sides of the membrane to erupt. At the same time, the rapid expansion of the molten material in the membrane body generates a shock wave, triggering structural changes in a large area of ​​the membrane body.

[0029] Membrane morphology and structural characterization

[0030] The morphology and structure of the GO membrane were characterized before and after irradiation treatment. Figure 2 As shown in a, GO nanosheets were uniformly deposited on the PES substrate to form an ultrathin GO film with a thickness of 50 nm. As observed in other studies, the film surface exhibited a typical wrinkled morphology. After irradiation, the GO-0.2(I) film retained its original morphology but showed a slight decrease in thickness, which may be due to the compression of the interlayer d spacing and the loss of the lamellar layers caused by irradiation. Increasing the amount of GO deposited from 0.2 mg to 0.8 mg increased the film thickness from 50 nm to 200 nm. Figure 2 In the h, the nanopore structure of GO-0.8(I) can be observed, which is generated by the incident fast heavy ion beam along its orbit. This cylindrical pore structure consists of an orbital core and a larger orbital halo extending along the core. It shows that the heavy ions successfully penetrated the entire GO layer, thereby introducing potential molecular transport channels. In addition, a larger wrinkle structure ( Figure 2(l), demonstrating the constrained rearrangement of the GO membrane by the thermal pinning effect and ion bombardment. With increasing membrane thickness, the GO membrane is more susceptible to defect structures after irradiation. Due to the small size of the through-pores, they cannot be directly observed from the surface images. The interlayer d-spacing of the GO membranes was characterized using XRD. The d-spacing of the GO-0.2, GO-0.4, and GO-0.8 membranes was found to be 0.499 nm, 0.498 nm, and 0.501 nm, respectively, indicating good consistency of the d-spacing under vacuum filtration force. In addition, the peak intensity increased significantly with increasing deposition amount. After rapid heavy ion irradiation, the characteristic peak of the GO membrane shifted to the right, indicating a contraction of the interlayer d-spacing. This can be attributed to the effects of thermal pinning, which leads to melting of the material, subsequent cooling and partial recovery of damaged areas, material loss, generation of oxygen-containing species, and interlayer crosslinking. Covalent crosslinking between layers can reduce the interlayer spacing. In the GO-0.2(I) membrane, due to the ultrathin GO layer, this peak was too weak to be detected and judged. Nonetheless, a clear decrease in the d-spacing from 0.501 nm to 0.464 nm was observed in the GO-0.8(I) film, indicating that irradiation not only created pores in the film but also modulated the stacking of GO nanosheets.

[0031] Gas permeation test of GO membranes with different deposition amounts

[0032] Gas separation test methods

[0033] Gas permeation experiments were conducted using a homemade device and measured using the following method. The gas permeation performance of the membrane was evaluated using a constant pressure system. Before the experiment, the membrane assembly and permeation system were purged with the gas to be tested to eliminate air from the device. After the pressure parameters stabilized for 1 hour, the permeation rate was measured using a soap bubble flowmeter (operating pressure set at 0.1 MPa). The gas permeability was calculated as follows:

[0034]

[0035] Where P is the gas permeability (GPU), A is the effective membrane area (cm 2 ), V is the test volume of downstream gas flux (cm 3 ), Δp is the working pressure (MPa), t is the temperature (℃). 1GPU=10 -6 cm 3 (STP) / (cm 2 ·s·cmHg).

[0036] The ideal H2 / CO2 selectivity is calculated based on the gas permeance; it can be calculated as:

[0037] a ij =P i / Pj

[0038] where α ij It is the ideal selectivity of H2 / CO2, P i and P j is the gas permeability.

[0039] like Figure 4 As shown, the 50-nm-thin GO-0.2 membrane exhibited a moderate H2 permeability of 51 gpu, indicating that the transport pathways in the layered membrane are circuitous. For the GO-0.4 and GO-0.8 membranes, the gas permeabilities were even too low to be accurately measured. A significant enhancement in gas permeation was observed after rapid heavy-ion irradiation. The H2 permeability of the GO-0.2 membrane increased from 51 gpu to 10106 gpu, an almost 200-fold increase. Although the irradiation-induced reduction in the interlayer d-spacing facilitates gas sieving, the ultrathin film thickness of approximately 50 nm makes the membrane susceptible to heavy-ion irradiation, and the resulting membrane defects impair the H2 / CO2 selectivity. As the membrane thickness increases, the H2 permeability decreases, while the H2 / CO2 selectivity increases. The irradiated GO-0.8(I) membrane (approximately 200 nm thick) exhibited an H2 permeability of 120 gpu, which is significantly higher than that of the pristine GO-0.2 membrane (approximately 50 nm thick). This result indicates that the channels created by heavy ion irradiation can greatly simplify the mass transport pathway and lead to a significant increase in gas permeability. In addition, the GO-0.8(I) membrane exhibited an H2 / CO2 selectivity of 8.2, demonstrating molecular sieving capability.

Claims

1. Application of a graphene oxide membrane directly obtained by a method of treating a graphene oxide membrane with rapid heavy ion irradiation in H2 / CO2 separation, characterized in that: The method for treating a graphene oxide film by rapid heavy ion irradiation comprises the following steps: Step 1, preparing a graphene oxide separation membrane on the surface of the base film; Step 2, treating the separation membrane obtained in step 1 with rapid heavy ion irradiation; In step 2, the fast heavy ion irradiation process emits 1-10 MeV / u 129 During the irradiation treatment, the irradiation dose per unit area on the surface of the separation membrane is controlled at 10 9 -10 11 ions / cm2; Graphene oxide membranes have a H2 / CO2 separation factor of 3-10.

2. The use according to claim 1, characterized in that After the irradiation treatment, the separation membrane is left to relax its structure.

3. The use according to claim 1, characterized in that In step 1, the method for preparing the graphene oxide film includes the following steps: preparing a graphene oxide dispersion, depositing it on the surface of the base film, and obtaining the graphene oxide film after removing the solvent.

4. The use according to claim 3, characterized in that The concentration of the graphene oxide dispersion is 0.1-5 mg / L.

5. The use according to claim 3, characterized in that Vacuum suction is used during the deposition process, and the amount of graphene oxide deposited on the surface of the base film is 0.01-0.1 mg / cm 2 .

6. The use according to claim 1, characterized in that In the application, the graphene oxide film has a permeability of 100-15000 GPU at 0.1 MPa and 25°C.

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