A MSL membrane with enhanced osmotic energy conversion and preparation method thereof

Abstract

The present invention relates to a MSL membrane with enhanced osmotic energy conversion and a preparation method thereof, belonging to the field of composite material technology. SL is dissolved in water and stirred at room temperature to obtain an SL solution. A MXene nanosheet solution and EGDE are added to the SL solution and mixed. The mixture is stirred under nitrogen, centrifuged, and repeatedly washed until the supernatant reaches neutrality. The precipitate is then redispersed to obtain uniform MSL nanosheets, thereby obtaining a two-dimensional channel MSL membrane. The present invention combines SL, which has abundant functional groups, with MXene, not only addressing the water stability issues of 2D MXene but also providing a larger surface charge for selective ion transport. The ordered MXene skeleton channels provide a shorter permeation path for rapid ion transport, resulting in an MSL membrane with ultra-low resistance.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite materials, and in particular relates to an MSL membrane for enhancing osmotic energy conversion and a preparation method thereof. Background Art

[0002] Two-dimensional (2D) materials have shown great potential in harvesting osmotic energy due to their high membrane selectivity, but the high resistance of the tortuous channels of 2D nanofluidic membranes still hinders further improvement of output performance.

[0003] MXene, a new class of 2D layered materials, is considered a candidate for reverse electrodialysis (RED) membranes because laminated MXene nanochannels with charged functional groups offer excellent ion selectivity and conductivity. However, due to poor bonding between nanosheets, MXene-based ion exchange membranes are mechanically weak and unstable in water, limiting their RED performance. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an MSL membrane with enhanced osmotic energy conversion and a preparation method thereof.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing an MSL membrane with enhanced osmotic energy conversion, comprising the following steps:

[0006] S1. Dissolve sulfonated lignin (SL) in water and stir at room temperature to obtain SL solution;

[0007] S2. MXene nanosheet solution and a drop of ethylene glycol diglycidyl ether (EGDE) were added to the SL solution and mixed. The mixture was stirred under nitrogen, centrifuged, and repeatedly washed until the pH of the supernatant reached neutral. The precipitate was redispersed to obtain uniform MSL nanosheets (i.e., MXene-SL nanosheets).

[0008] S3. Use vacuum-assisted filtration to assemble MSL nanosheets into regular two-dimensional channel MSL membranes.

[0009] Furthermore, in step S2, the MXene nanosheet solution is prepared by etching the Al layer in the Ti3AlC2 powder with HF generated in situ by the reaction of HCl and LiF, and then ultrasonically exfoliating and dispersing it in water to obtain a MXene nanosheet solution, i.e., a Ti3C2Tx nanosheet suspension.

[0010] Furthermore, in step S3, the vacuum-assisted filtration method is as follows: diluting the aqueous solution of MSL nanosheets, then pouring it into a filtration device containing an MCE membrane, letting it stand, and then performing vacuum filtration under pressure.

[0011] Another object of the present invention is to provide a MSL membrane with enhanced osmotic energy conversion.

[0012] Due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0013] The present invention prepares an ultra-low resistance 2D MSL (MXene-SL) layered membrane, which can achieve efficient osmotic energy generation.

[0014] The present invention incorporates sulfonated lignin, a rich source of functional groups, into the MXene membrane. This not only addresses the water stability issues of 2D MXene but also provides a larger surface charge for selective ion transport. The ordered MXene backbone channels provide a shorter permeation path for rapid ion transport, resulting in ultra-low resistance for the MSL membrane.

[0015] Therefore, by mixing artificial seawater and river water, the MSL membrane can reach about 22.15W / m 2 The ultra-high power output of the MSL membrane is 6.78 times higher than that of the pristine MXene membrane. In addition, in terms of output power and internal resistance (9.3 kΩ), the MSL membrane outperforms all reported monolayer 2D nanosheet-based percolation generators under the same experimental conditions.

[0016] It can be seen that the present invention proposes a reliable strategy to stabilize 2D MXene membranes in electrolytes, which opens up a new way to design promising 2D nanofluid membranes for efficient blue energy harvesting (the blue osmotic energy in the ocean is a new type of clean "zero-carbon" energy with extremely abundant reserves and sustainability. The present invention can convert the chemical energy generated by the salinity gradient between natural seawater and river water into electrical energy, thereby realizing the efficient collection and utilization of blue osmotic energy) and ion devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention will be described in detail below with reference to the accompanying drawings and in combination with examples, and the advantages and implementation modes of the present invention will become more apparent. The contents shown in the accompanying drawings are only used to illustrate the present invention and do not constitute any limitation to the present invention. In the accompanying drawings:

[0018] Figure 1 The Ti3AlC2 nanosheets and Ti3C2T x Surface SEM image of nanosheets.

[0019] Figure 2 These are SEM images of the MXene film, MSL film, MXene film cross section, and MSL film cross section of the present invention.

[0020] Figure 3 XPS spectra of the MXene film and MSL film of the present invention.

[0021] Figure 4 Deconvolution of the C1s spectra of the MXene film and MSL film of the present invention.

[0022] Figure 5 FTIR spectra of the MXene film, MSL film and SL of the present invention.

[0023] Figure 6 The Ti3AlC2 nanosheets and Ti3C2T x XRD patterns of nanosheets.

[0024] Figure 7 These are the XRD patterns of the MXene film, MSL1 film, MSL2 film, and MSL3 film of the present invention.

[0025] Figure 8 Graphs showing the IV curves of the MSL membrane of the present invention in neutral KCl electrolytes with different concentrations.

[0026] Figure 9 Graph showing the relationship between the transmembrane ionic conductivity and KCl concentration of a single MSL1 membrane in the present invention.

[0027] Figure 10 10 in the present invention -2 IT curve of MSL1 membrane in MKCl solution.

[0028] Figure 11 Graphs showing the current density and voltage of the MSL membrane in a 50-fold KCl concentration gradient in the forward and reverse diffusion directions of the present invention.

[0029] Figure 12 Schematic diagram of the effect of SL content on output current density in the present invention.

[0030] Figure 13 Schematic diagram of the effect of SL content on output power density in the present invention.

[0031] Figure 14 Schematic diagram of the change in output power density of the MSL membrane of the present invention with increasing external resistance under 5, 50, and 500 times concentration gradients. DETAILED DESCRIPTION

[0032] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with the best embodiment.

[0033] A method for preparing an MSL membrane for enhancing osmotic energy conversion comprises the following steps:

[0034] S1. Dissolve 5 mg of sulfonated lignin (SL) in 8 ml of water and stir at room temperature for 1 h to obtain SL solution;

[0035] S2. 5 ml of MXene nanosheet solution and a drop of ethylene glycol diglycidyl ether (EGDE) were added to the SL solution and mixed. The mixture was stirred under nitrogen for 36 h, centrifuged, and repeatedly washed until the supernatant reached a neutral pH of 7.0. The precipitate was redispersed to obtain uniform MSL1 nanosheets (i.e., MXene-SL nanosheets).

[0036] S3. Use vacuum-assisted filtration to assemble MSL1 nanosheets into regular two-dimensional channel MSL1 membranes.

[0037] In step S2, the preparation method of the MXene nanosheet solution is as follows: the Al layer in the Ti3AlC2 powder is etched by HF generated in situ by the reaction of HCl and LiF, and then ultrasonically exfoliated and dispersed in water to obtain a MXene nanosheet solution, i.e., a Ti3C2Tx nanosheet suspension.

[0038] In step S3, the vacuum-assisted filtration method involves diluting the aqueous solution of MSL1 nanosheets and then pouring it into a filtration device containing an MCE membrane. After standing, the solution is vacuum-filtered under pressure. The filtration process lasts for at least 1 hour to ensure proper compaction of the MSL1 membrane.

[0039] When 10 mg of SL was used, a uniform MSL2 film was obtained through steps S1 to S3.

[0040] When 15 mg of SL was used, a uniform MSL3 film was obtained through steps S1 and S2.

[0041] The MSL membrane in the subsequent examples specifically refers to the MSL2 membrane.

[0042] Another object of the present invention is to provide a MSL membrane with enhanced osmotic energy conversion.

[0043] like Figure 1 As shown, Ti3AlC2 nanosheets and Ti3C2T x The nanosheets were characterized. Figure 1 (a) is the surface SEM image of Ti3AlC2 nanosheets; Figure 1 (b) Ti3C2T x Surface SEM image of nanosheets.

[0044] like Figure 2 As shown, the MXene film, MSL film, MXene film cross section and MSL film cross section were characterized. Figure 2 (a) Surface SEM image of MXene film; Figure 2 (b) Surface SEM image of MSL film; Figure 2(c) SEM image of the cross section of the MXene film; Figure 2 (d) SEM image of the cross section of the MSL membrane.

[0045] like Figure 3 As shown in the full XPS spectrum, the peak positions of C1s of MXene film and MSL film are quite different.

[0046] like Figure 4 and Figure 5 As shown, Figure 4 (a) Deconvolution of the C1s spectrum of the MXene film; Figure 4 (b) Deconvolution of the C1s spectrum of the MSL film. Comparison of the C1s spectrum reveals that the C1s of the MXene film can be decomposed into four peaks at 282.03 eV, 284.71 eV, 286.11 eV, and 288.62 eV, corresponding to CC, CO, C=O, and OC=O, respectively. The C1s of the MSL film can be decomposed into four peaks at 282.03 eV, 284.69 eV, 286.12 eV, and 288.67 eV, corresponding to CC, CO, C=O, and OC=O, respectively. Among them, the peak position difference between CO and C=O is the largest. These results indicate the formation of a strong hydrogen bond network between MXene and SL. In addition, changes in the FTIR spectrum also prove that the MXene nanosheets are successfully modified by SL. The FTIR spectrum proves that the addition of SL not only enhances the interlayer bonding force between MXene sheets, but also promotes the formation of continuous, defect-free composite membranes; the synergistic effect of these functional groups effectively reduces the energy barrier of proton transport, thereby significantly improving the proton conductivity of the membrane.

[0047] like Figure 6 As shown, Ti3AlC2 nanosheets and Ti3C2T x The diffraction peak of the nanosheets can be seen as Ti3C2T x The diffraction peak characteristics of nanosheets are significantly different from those of Ti3AlC2 nanosheets. x The nanosheet has a strong (002) peak in the low-angle region, while the peaks at other angles are relatively weak or insignificant. This diffraction peak characteristic is related to its layered structure and surface functional groups T x Its stronger (002) peak is associated with structural information such as the interlayer distance, reflecting the influence of its layered structure and surface functional groups on diffraction.

[0048] like Figure 7As shown in the figure, the diffraction peak positions of the MSL1, MSL2, and MSL3 films differ from those of the MXene film. The diffraction peak positions are correlated with structural parameters such as the interplanar spacing of the crystals, indicating that the crystal structures of these materials differ: the interplanar spacing of the MSL1 film > the interplanar spacing of the MSL2 film > the interplanar spacing of the MSL3 film > the interplanar spacing of the MXene film.

[0049] The transmembrane ion diffusion characteristics of the MSL membrane were evaluated by measuring the current-voltage (IV) curve. + and Cl - The ion mobility and volume of are very similar, so KCl was chosen as the probe electrolyte.

[0050] like Figure 8 As shown, in KCl electrolyte, the IV curves of MSL1 membrane, MSL2 membrane and MSL3 membrane exhibit linear ohmic behavior with negligible ionic current rectification, which indicates the existence of permanent conductance channels and the symmetrical structure of the composite membranes.

[0051] like Figure 9 As shown in the figure, the ionic conductivity of the MSL membrane was calculated based on the IV curve. The ionic conductivity of the MSL membrane showed two different characteristic behaviors. In the high concentration region (>10 -3 M), the ionic conductivity of the MSL membrane follows the bulk rule and is linear; when the KCl concentration is lower than 10 -3 When M, the ionic conductance of the MSL membrane gradually deviates from the bulk value and tends to a plateau, indicating that the transport of ions in the MSL membrane is mainly controlled by the surface charge of the nanochannel.

[0052] like Figure 10 As shown in Figure 2, the ion transport stability of the MSL membrane was examined by applying AC applied voltages of +0.2 and -0.2 V and measuring the IT curves. Each cycle lasted 16 minutes, and a total of 8 cycles were performed continuously. The negative and positive currents after each voltage polarity switch remained at the same level, indicating that the MSL membrane has excellent ion transport stability.

[0053] The ion transport mechanism was further explored by measuring the current density and voltage curves of the MSL membrane under different salt concentration gradients. - The electrolyte is preferentially transferred from the high concentration side to the low concentration side, generating diffusion current and diffusion potential. The KCl concentration in the low concentration electrolyte pool is fixed at IS 10 -2 M, the concentration gradient is 50 times. Therefore, the values ​​of diffusion current and diffusion potential are equal to the short-circuit current (I SC ) and open circuit voltage (V OC ).like Figure 11As shown, the MSL membrane (SL content is 1:2) was subjected to a 50-fold concentration gradient (10 -2 The current density and voltage curves under the conditions of 0.5 M / 0.5 M KCl) are shown in Figure 3. The similar ion transport behaviors under reverse concentration gradients indicate that the MSL membrane has a symmetrical structure and no preferential direction of ion diffusion.

[0054] In order to evaluate the application prospects of the MSL membrane nanofluid system, standard artificial seawater (0.5M NaCl) and river water (0.01M NaCl) systems were selected for salinity gradient energy conversion tests. Considering the diversity of practical application scenarios, the output current density and power density of the MSL membrane under different SL content conditions (i.e. MXene:SL = 1:1, 1:2 and 1:3) were explored. Figure 12 and Figure 13 When the SL content is 1:1, 1:2, and 1:3, the maximum output power density of MSL1 film, MSL2 film, and MSL3 film is 12.71 Wm -2 、22.15Wm -2 and 19.89Wm -2 ,With the increase of SL content, the power output density of the MSL1 film, MSL2 film, and MSL3 film all showed a trend of first increasing and then decreasing drastically under each load resistance, indicating that the MSL film performs better when the SL content is 1:2.

[0055] like Figure 14 As shown, the present invention also conducted energy conversion tests at 5 times and 500 times salinity gradients, and the maximum output power density was 0.51Wm -2 and 34.54Wm -2 .

[0056] The embodiments of the present invention are described in detail above, but the contents are only preferred embodiments of the present invention and should not be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. A method for preparing a MSL membrane for enhancing osmotic energy conversion, characterized in that: The following steps are involved: S1, dissolving sulfonated lignin in water and stirring to obtain SL solution; S2. MXene nanosheet solution and ethylene glycol diglycidyl ether were added to the SL solution and mixed. The mixture was stirred under nitrogen, centrifuged, and repeatedly washed until the pH of the supernatant reached neutral. The precipitate was redispersed to obtain uniform MSL nanosheets. S3, MSL membrane with enhanced permeability energy conversion by assembling MSL nanosheets into regular two-dimensional channels using vacuum-assisted filtration; In step S2, the MXene nanosheet solution is prepared by etching the Al layer in the Ti3AlC2 powder by in-situ HF generated by the reaction of HCl and LiF, followed by ultrasonic exfoliation and dispersion in water to obtain the MXene nanosheet solution; In step S3, the vacuum-assisted filtration method is as follows: the aqueous solution of MSL nanosheets is diluted and then poured into a filtration device containing an MCE membrane, and after standing, vacuum filtration is performed under pressure; When MXene:SL=1:2, the MSL membrane was applied to standard artificial seawater and river water systems for salinity gradient energy conversion tests. The concentration gradients were 50 and 500 times, and the MSL membrane reached 22.15 and 34.54 W / m 2 Ultra-high power output.

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