A kind of osmosis energy conversion device based on schiff base two-dimensional polymer composite film and its application

Abstract

The application discloses a kind of based on schiff base two-dimensional polymer composite membrane osmotic energy conversion device and its application.Schiff base two-dimensional polymer composite membrane is schiff base two-dimensional polymer / cellulose nanofiber composite membrane, which is prepared by interfacial superassembly strategy, has double nano ion channel and adjustable surface charge characteristics.The composite membrane is assembled between double conductivity cell, and the ion transport and osmotic energy conversion performance are tested under the concentration gradient of simulated seawater (0.5 M NaCl) and river water (0.01 M NaCl).It has a high output power density of 5.62 W / m 2 , and has good durability and cycle stability.The application provides a new intelligent nanochannel platform for efficient capture of blue osmotic energy.

Description

Technical Field

[0001] This invention belongs to the field of intelligent nanochannels and energy conversion, and relates to a permeation energy conversion device based on a Schiff base two-dimensional polymer composite membrane and its application. Background Technology

[0002] Salinity gradient energy (also known as osmotic energy) is a vast renewable energy source located at river estuaries, with a theoretical global reserve of up to 2.6 TW. Reverse electrodialysis (RED) technology directly converts salinity gradients into electrical energy through ion-selective membranes and is considered one of the most promising capture methods. The core of this technology lies in high-performance ion-selective membranes, which must simultaneously possess high ionic conductivity, excellent ion selectivity (especially cation selectivity), good chemical / mechanical stability, and low cost. However, traditional commercial ion exchange membranes (such as Nafion) suffer from low power density, high cost, and susceptibility to fouling in complex water conditions. While nanofluidic membranes (such as graphene oxide membranes and MOF membranes) developed in recent years have demonstrated high power density in the laboratory, they generally face bottlenecks such as complex preparation, difficulty in large-scale production, and poor long-term water stability, hindering their practical application.

[0003] Nanochannel membranes constructed from two-dimensional materials exhibit unique advantages in enhancing ion selectivity and conductivity due to their confinement and surface charge effects. In particular, Schiff base two-dimensional polymers (2DPIs), with their ordered pores and tunable surface chemistry, theoretically serve as ideal ion transport channels. However, integrating them into stable, flexible, and scalable device structures and achieving efficient and sustained energy conversion under real salinity gradients remains a significant challenge. Recent studies have shown that introducing bio-based nanomaterials (such as cellulose nanofibers, CNFs) can effectively improve the processability and stability of 2D material membranes, but the output performance, long-term operational stability, and universality to different electrolyte systems of RED devices constructed based on such composite membranes still lack systematic verification. Therefore, developing a nanofluid permeation energy conversion device based on a novel 2DPI / CNF composite membrane requires not only addressing the structure-performance relationship at the material level but also verifying its feasibility and superiority in practical applications at the device engineering level, providing a reliable solution for next-generation green energy technologies. Summary of the Invention

[0004] The purpose of this invention is to provide a nanofluid permeation energy conversion device based on a 2DPI / CNF composite membrane, which can efficiently and stably convert salinity gradient energy into electrical energy.

[0005] The technical solution of the present invention is described in detail below.

[0006] This invention provides a permeation energy conversion device based on a Schiff base two-dimensional polymer / cellulose nanofiber composite membrane. The device is characterized by using the Schiff base two-dimensional polymer / cellulose nanofiber composite membrane as an ion-selective membrane, which is installed between two conductivity cells. High-concentration and low-concentration electrolyte solutions are added to the two side chambers respectively, and conductive electrodes are inserted to output power. The Schiff base two-dimensional polymer / cellulose nanofiber composite membrane is prepared by the following method: (1) Schiff base two-dimensional polymer 2DPI powder was prepared by Schiff base reaction using melamine MA and trimethylolpropionate BTCA as raw materials. (2) The Schiff base two-dimensional polymer 2DPI powder was dispersed in dimethyl sulfoxide DMSO and exfoliated with trifluoroacetic acid TFA to obtain a dispersion of Schiff base two-dimensional polymer 2DPI nanosheets. (3) The dispersion of Schiff base two-dimensional polymer 2DPI nanosheets and the dispersion of cellulose nanofiber CNF are mixed and then vacuum-assisted filtered and superassembled to obtain the desired product; wherein the CNF dispersion is prepared by dispersing cellulose nanofibers oxidized by TEMPO in dimethyl sulfoxide DMSO.

[0007] In this invention, in step (1), the Schiff base reaction is carried out by N-methylpyrrolidone (NMP) as the solvent, pyridine as the catalyst, calcium chloride as the dehydrating agent, 100-140 °C as the reaction temperature, and 30-50 h as the reaction time.

[0008] In this invention, in step (2), the mass-volume concentration of the dispersion of Schiff base two-dimensional polymer 2DPI nanosheets is 0.8-1.2 mg / mL.

[0009] In this invention, in step (3), the mass volume concentration of CNF dispersion is 0.4-1.0 mg / mL, and the mass ratio of 2DPI nanosheets in the dispersion of Schiff base two-dimensional polymer 2DPI nanosheets to CNF in the dispersion of cellulose nanofiber CNF is 5:3-10:1.

[0010] In this invention, in step (3), 2DPI and CNF dispersions are mixed, distilled water is added for protonation, and after stirring and sonication, the mixture is assembled on a nylon membrane by vacuum-assisted filtration, dried and peeled off to obtain a Schiff base two-dimensional polymer / cellulose nanofiber composite membrane.

[0011] In this invention, in step (3), the thickness of the Schiff base two-dimensional polymer / cellulose nanofiber composite membrane is 10-50 micrometers.

[0012] In this invention, the concentration gradient between the high-concentration electrolyte solution and the low-concentration electrolyte solution is 10-500 times; the electrolyte solution is KCl, NaCl, or LiCl solution; or the high-concentration electrolyte solution and the low-concentration electrolyte solution are natural seawater and natural river water, respectively.

[0013] The present invention also provides an application of the above-mentioned permeation energy conversion device in salinity gradient energy conversion.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: The 2DPI / CNF composite membrane used in the device has excellent cation selectivity and high ionic conductivity, with an ionic conductivity of up to 93.96 µS in 0.1 M KCl solution.

[0015] The nanofluidic device based on this composite membrane exhibits superior performance in permeation energy conversion: under a 50-fold salt concentration gradient (0.5 M NaCl vs 0.01 M NaCl), the open-circuit voltage ( V OC The voltage can reach approximately 112.20 mV, and the short-circuit current ( I SC The maximum output power density can reach approximately 6.59 µA, and the calculated maximum output power density is as high as 5.62 W / m². 2 At a KCl concentration gradient of 50 times, the maximum output power density can reach 9.95 W / m³. 2 In real-world applications, using natural seawater from the East China Sea and river water from urban streams as electrolytes, the maximum output power density of this device was further increased to 5.99 W / m³. 2 .

[0016] The device exhibits good long-term operational stability. After 120 hours of continuous operation without electrolyte replacement, the output current and voltage decayed by only 10.4% and 15.5%, respectively. During a 30-day test, the permeation energy conversion capability remained essentially unchanged. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a permeation energy conversion device based on a 2DPI / CNF composite membrane.

[0018] Figure 2 The IV curves of the 2DPI / CNF composite membrane under 0.5 M and 0.01 M NaCl solution conditions are shown.

[0019] Figure 3The effect of interfacial superassembly on the performance of 2DPI / CNF composite membranes. (a) IV curves, (b) short-circuit current and open-circuit voltage values, (c) current density and (d) power density of 2DPI, CNF and 2DPI / CNF membranes.

[0020] Figure 4 The long-term stability of the 2DPI / CNF composite membrane without changing the electrolyte solution.

[0021] Figure 5 (a) Current density and (b) Power density of 2DPI / CNF composite membrane under a series of NaCl concentration gradients.

[0022] Figure 6 The following figures show the (a) IV curves, (b) short-circuit current and open-circuit voltage values, (c) current density and (d) power density of the 2DPI / CNF composite membrane in a series of electrolyte solutions.

[0023] Figure 7 shows the current density and output power density of the 2DPI / CNF composite membrane in natural seawater and river water.

[0024] Figure 8 Output power density of 2DPI / CNF composite membranes with different CNF contents. Detailed Implementation

[0025] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0026] This invention provides an adsorption-based permeation energy conversion device, which uses a specific Schiff base two-dimensional polymer (2DPI) / cellulose nanofiber (CNF) composite membrane as the core ion-selective separation layer. Electrolyte solutions of different concentrations are injected into the two chambers on either side of the membrane. The salinity gradient (chemical potential difference) across the membrane drives cations to selectively pass through the composite membrane, thereby generating transmembrane potential and current, achieving a direct conversion from salinity gradient energy to electrical energy. This 2DPI / CNF composite membrane is prepared using an interfacial superassembly strategy. The Schiff base two-dimensional polymer (2DPI) provides ordered nanopores and a layered stacked structure, while the cellulose nanofibers (CNF) not only significantly improve the membrane's mechanical flexibility and hydrophilicity but also enhance cation selectivity by synergistically regulating ion transport channels through their surface negative charge. Specific embodiments are described below.

[0027] Example

[0028] 1) Preparation of 2DPI / CNF composite film 1) Synthesis of 2DPI: In a 100 mL three-necked flask, 18 mL of NMP and 2 mL of pyridine were added. Then, 252 mg of melamine and 324 mg of trimesaldehyde were added with stirring, followed by 200 mg of CaCl2. The mixture was refluxed at 120 °C for 48 h. After cooling, the product was washed with ethanol, water, NMP, and acetone, and then dried under vacuum at 80 °C for 24 h to obtain 377 mg of yellow 2DPI powder.

[0029] 2) 2DPI dispersion: 200 mg of 2DPI powder was dispersed in 200 mL of DMSO, 5 mL of TFA was added, and the mixture was stirred at 300 rpm for 7 days to obtain a 1 mg / mL 2DPI / DMSO dispersion.

[0030] 3) CNF dispersion: Take an appropriate amount of TEMPO-oxidized CNF hydrogel (containing about 100 mg dry weight CNF) into DMSO, stir for 4 h, and sonicate for 10 h to obtain a CNF / DMSO dispersion of 0.5 mg / mL.

[0031] 4) Composite membrane preparation: 100 mL of 2DPI dispersion and CNF dispersion were mixed, 20 mL of distilled water was added, and the mixture was stirred at room temperature for 2 h and sonicated for 4 h. The mixture was then filtered through a vacuum-assisted filtration device onto a nylon membrane with a diameter of 50 mm and a pore size of 220 nm to form a membrane. After drying in air for 24 h, the membrane could be easily peeled off from the nylon substrate to obtain the 2DPI / CNF composite membrane.

[0032] (ii) Assembly of nanofluidic devices The prepared 2DPI / CNF composite membrane was mounted in the center of a custom-designed H-type electrochemical cell, with the effective test area consisting of a pair of small holes with an area of ​​3 × 10⁻⁶. -8 m 2 The silicon wafer is controlled. Ag / AgCl electrodes are inserted into both chambers and connected to a Keithley 6487 picoammeter for IV testing.

[0033] (iii) Permeation energy conversion performance test 1) such as Figure 1 As shown, a 2DPI / CNF composite membrane with a CNF content of 25% and a thickness of 17.08 μm was assembled into an H-shaped cell. 0.5 M NaCl (simulated seawater) was injected into one side and 0.01 M NaCl (simulated river water) was injected into the other side for permeation energy conversion performance testing.

[0034] like Figure 2 As shown, two configurations are used. In the first configuration, 0.5 M NaCl is placed on the left side, and 0.01 M NaCl is placed on the other side. Under this configuration, the short-circuit current ( ISC ) and open circuit voltage (V OC The values ​​of ) were 6.50 μA and −110.93 mV, respectively. The second configuration interchanged the positions of the two solutions, resulting in... I SC and V OC The values ​​are basically consistent with the first configuration, with values ​​of −6.59 μA and 112.20 mV, respectively, indicating that the 2DPI / CNF composite film has symmetrical ion diffusion characteristics.

[0035] like Figure 3 As shown, the IV curves of 2DPI / CNF were tested and compared with those of 2DPI / CNF under 0.5 M and 0.01 M NaCl solution conditions. The 2DPI / CNF composite membrane after interfacial superassembly exhibited the best transmembrane ion transport properties. Figure 3 a), and its I SC Value and V OC The values ​​are all higher than those of 2DPI and CNF alone (Figure 3b), indicating that interfacial superassembly can promote its permeation energy conversion capability. Further, the above series of membranes were assembled into nanofluidic devices, and their output current density and power density were studied. The 2DPI / CNF composite membrane exhibited the highest current density and output power density, with values ​​of 217.67 A / m², respectively. 2 ( Figure 3 c) and 5.62 W / m 2 (Figure 3d).

[0036] like Figure 4 As shown, during the 120-hour test, the output voltage showed only a 15.5% decrease, while the output current experienced a 10.4% decrease, indicating that the super-assembled 2DPI / CNF composite membrane has long-term durability in permeation energy conversion; its performance remains basically stable within 30 days.

[0037] 2) A 2DPI / CNF composite membrane with a CNF content of 25% and a thickness of 17.08 μm was assembled into an H-type tank to simulate different types of water resources (urban sewage, salt lake water, etc.) under natural conditions, namely 10 times, 100 times, 200 times, 300 times and 500 times concentration gradients.

[0038] like Figure 5 As shown, with the increase of concentration gradient, the driving force is enhanced, and its output current density and power density increase accordingly.

[0039] 3) A 2DPI / CNF composite membrane with a CNF content of 25% and a thickness of 17.08 μm was assembled into an H-type cell, and K was used to... + Na + Li + The permeation energy conversion performance of the 2DPI / CNF composite membrane was investigated using a salt solution of monovalent cations as the electrolyte (high concentration: 0.5 M, low concentration: 0.01 M, concentration gradient of 50 times).

[0040] like Figure 6 As shown, the above series of K + Na + Li + of I SC The values ​​were 9.55, 6.51, and 5.28 µA, respectively, while the corresponding... V OC The values ​​were 127.12, 110.94, and 98.74 mV, respectively (Figure 6a and 6b). Figure 6 (b) Furthermore, its maximum output current density values ​​are 315.34, 217.00, and 177.67 A / m, respectively. 2 (Figure 6c), with maximum output power densities of 9.95, 5.62, and 4.48 W / m², respectively. 2 (Figure 6d) illustrates the excellent potential of the interfacial super-assembled 2DPI / CNF composite membrane in energy conversion under various salinity gradient conditions.

[0041] 4) A 2DPI / CNF composite membrane with a CNF content of 25% and a thickness of 17.08 μm was assembled into an H-type cell. Real-world environmental conditions were simulated using natural seawater and river water (sourced from the East China Sea and urban streams, respectively). The permeation energy conversion performance of the membrane was tested when connected to an external resistor. Figure 7 It can be seen that the maximum current density of the 2DPI / CNF composite membrane under natural water gradient is 237.97 A / m. 2 And it achieved 5.99 W / m 2 The maximum output power density demonstrates the applicability of the interfacial superassembled 2DPI / CNF composite membrane prepared in this chapter in practical brine gradients.

[0042] 5) Assemble 2DPI / CNF composite membranes with different CNF contents into an H-type tank, inject 0.5 M NaCl (simulated seawater) into one side and 0.01 M NaCl (simulated river water) into the other side.

[0043] Figure 8 Output power density of 2DPI / CNF composite membranes with different CNF contents.

Claims

1. A permeation energy conversion device based on a Schiff base two-dimensional polymer composite membrane, characterized in that, It uses a Schiff base two-dimensional polymer / cellulose nanofiber composite membrane as an ion-selective membrane, which is installed between two conductivity cells. High-concentration and low-concentration electrolyte solutions are added to the two chambers respectively, and conductive electrodes are inserted to output power. The Schiff base two-dimensional polymer / cellulose nanofiber composite membrane is prepared by the following method: (1) Schiff base two-dimensional polymer 2DPI powder was prepared by Schiff base reaction using melamine MA and trimethylolpropionate BTCA as raw materials. (2) The Schiff base two-dimensional polymer 2DPI powder was dispersed in dimethyl sulfoxide DMSO and exfoliated with trifluoroacetic acid TFA to obtain a dispersion of Schiff base two-dimensional polymer 2DPI nanosheets. (3) The dispersion of Schiff base two-dimensional polymer 2DPI nanosheets and the dispersion of cellulose nanofiber CNF are mixed and then vacuum-assisted filtered and superassembled to obtain the desired product; wherein the CNF dispersion is prepared by dispersing cellulose nanofibers oxidized by TEMPO in dimethyl sulfoxide DMSO.

2. The permeation energy conversion device according to claim 1, characterized in that, In step (1), the Schiff base reaction is carried out by N-methylpyrrolidone (NMP) as the solvent, pyridine as the catalyst, calcium chloride as the dehydrating agent, 100-160 °C as the reaction temperature, and 30-50 h as the reaction time.

3. The permeation energy conversion device according to claim 1, characterized in that, In step (2), the mass-volume concentration of the dispersion of Schiff base two-dimensional polymer 2DPI nanosheets is 0.8-1.2 mg / mL.

4. The permeation energy conversion device according to claim 1, characterized in that, In step (3), the mass volume concentration of CNF dispersion is 0.4-1.0 mg / mL, and the mass ratio of 2DPI nanosheets in the dispersion of Schiff base two-dimensional polymer 2DPI nanosheets to CNF in the dispersion of cellulose nanofiber CNF is 5:3-10:

1.

5. The permeation energy conversion device according to claim 1, characterized in that, In step (3), the 2DPI and CNF dispersions are mixed, distilled water is added for protonation, and after stirring and sonication, the mixture is assembled on a nylon membrane by vacuum-assisted filtration. After drying, it is peeled off to obtain the Schiff base two-dimensional polymer / cellulose nanofiber composite membrane.

6. The permeation energy conversion device according to claim 1, characterized in that, In step (3), the thickness of the Schiff base two-dimensional polymer / cellulose nanofiber composite membrane is 10-50 micrometers.

7. The permeation energy conversion device according to claim 1, characterized in that, The concentration gradient between the high-concentration electrolyte solution and the low-concentration electrolyte solution is 10-500 times.

8. The permeation energy conversion device according to claim 1, characterized in that, The electrolyte solution is a KCl, NaCl, or LiCl solution.

9. The permeation energy conversion device according to claim 1, characterized in that, The high-concentration electrolyte solution and the low-concentration electrolyte solution were natural seawater and natural river water, respectively.

10. The application of a permeation energy conversion device as described in any one of claims 1 to 9 in salinity gradient energy conversion.

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