A plasma-electron sponge nanochannel composite membrane, its preparation method and application

Abstract

The application discloses a kind of plasma electron sponge nanochannel composite membranes and preparation method and application thereof, the composite membrane includes a layer of self-assembled arrangement plasma electron sponge film and a layer of membrane material with large pore structure, part of the pore in the self-assembled arrangement plasma electron sponge film and part of the large pore in the membrane material with large pore structure are communicated correspondingly, and electron sponge refers to polyoxometalates (POMs). The application first uses plasma electron sponge nanomaterial as functional material to make nanochannel composite membrane, and plasma electron sponge has excellent and stable performance, mild preparation condition, simple operation and green environmental protection. In addition, the plasma electron sponge nanochannel composite membrane prepared by the application can be used as ion selective membrane in salinity gradient energy conversion, and has the advantages of excellent and stable performance, high conversion power and green environmental protection.

Description

Technical Field

[0001] This invention relates to a plasma electron sponge nanochannel composite membrane, its preparation method and application, belonging to the field of nanochannel composite membranes. Background Technology

[0002] The enormous osmotic energy generated by the salinity gradient between seawater and river water represents a vast potential blue energy source that can be extracted using reverse electrodialysis (RED). This method selectively transports ions between electrodes via ion-selective membranes. In RED systems, ion-selective membranes play a crucial role in osmotic energy harvesting. In recent years, ion-selective membranes based on various emerging materials have significantly advanced the development of osmotic energy conversion. However, due to insufficient ion-selective permeability, current output power densities remain below 5 W / m³. 2 (Standards for commercial membranes). Based on this, previous work has reported on adjusting surface charge through chemical modification and structural regulation to improve the ion selectivity of nanofluidic membranes. However, the complexity of chemical modification and structural regulation still limits their practical application. Therefore, there is an urgent need to find effective strategies to increase the surface charge of nanofluidic membranes, thereby achieving efficient energy conversion.

[0003] Polyoxometalates (POMs), also known as electron sponges, can undergo reversible, rapid, and stepwise multiple electron transfer processes without altering their structure. Based on this, POMs can control charge density while maintaining structural stability, demonstrating great potential for permeation energy harvesting. However, due to their excellent water solubility, POMs have never been used to develop ion-selective membranes for permeation energy harvesting. More importantly, few materials can stably and continuously provide electrons. Fortunately, plasmonic nanoparticles such as Au, Ag, and Cu possess a unique localized surface plasmon resonance (LSPR) effect, providing abundant hot electrons under light irradiation. When combined with POMs, electrons are continuously transferred from plasmonic nanoparticles (NPs) to POMs, significantly enhancing the surface negative charge. Therefore, designing and fabricating a plasmonic electron sponge nanochannel composite membrane holds promise for further advancing the development of high-performance energy conversion. Summary of the Invention

[0004] Objectives of this invention: The first objective is to provide a plasma-electron sponge nanochannel composite membrane, which exhibits stable performance and is environmentally friendly. The second objective is to provide a method for preparing this plasma-electron sponge nanochannel composite membrane, which is simple to operate, operates under mild conditions, and is easily implemented. The third objective is to provide the application of this plasma-electron sponge nanochannel composite membrane in salinity gradient osmosis energy conversion. This membrane can be used in reverse electrodialysis technology to capture salinity gradient osmosis energy and possesses advantages such as stable performance, high conversion power, and wide applicability to various environments.

[0005] Technical solution: The present invention discloses a plasma-electron sponge nanochannel composite membrane, which comprises a self-assembled plasma-electron sponge membrane and a membrane material with a macroporous structure. Some pores in the self-assembled plasma-electron sponge membrane correspond to and communicate with some macropores in the membrane material with a macroporous structure; the electron sponge refers to polyoxometalates (POMs).

[0006] Furthermore, the membrane material with a macroporous structure is an anodic aluminum oxide membrane.

[0007] Furthermore, the pore size of the anodic aluminum oxide (AAO) film is 50-100 nm, preferably 75 nm.

[0008] Furthermore, the plasma electron sponge membrane is composed of plasma nanoparticles and POMs capable of storing electrons.

[0009] Furthermore, the thickness of the plasma electron sponge film is approximately 70-150 nm, preferably 115 nm.

[0010] Furthermore, the plasma nanoparticles are gold nanoparticles (Au NPs), silver nanoparticles (Ag NPs) or copper nanoparticles (Cu NPs), and the electron-storing POMs are phosphotungstic acid, phosphomolybdic acid or silicotungstic acid.

[0011] Furthermore, the preferred POMs are Keggin-type phosphotungstic acid (H3PW). 12 O 40 PW (abbreviated as PW) 12 ).

[0012] The method for preparing the plasma-electron sponge nanochannel composite membrane of the present invention involves using an inducing agent to self-assemble Au@POMs NPs to the water-oil two-phase interface formed by Au@POMs NPs solution and n-hexane to form a plasma-electron sponge nanofilm, and then transferring the plasma-electron sponge nanofilm to the nanochannel end face of a membrane material with a macroporous structure and thermally fixing it to obtain the composite membrane.

[0013] The preparation method of Au@POMs NPs solution includes the following steps:

[0014] (1) Synthesis of gold seeds: Dissolve trisodium citrate in ultrapure water, add HAuCl4 aqueous solution while stirring, mix thoroughly, quickly add sodium borohydride aqueous solution, stir vigorously until the solution turns orange, and obtain gold seed solution.

[0015] (2) Preparation of Au NPs: Boil HAuCl4 aqueous solution, add gold seed solution and trisodium citrate aqueous solution in sequence. Stop heating when the solution gradually changes from colorless to wine red and does not change color. Cool naturally to room temperature under stirring to obtain Au NPs aqueous solution.

[0016] (3) Preparation of Au@POMs NPs: Dissolve phosphotungstic acid in water, add isopropanol, reduce under ultraviolet light, and mix the reduced phosphotungstic acid solution with the Au NPs aqueous solution to obtain the Au@POMs NPs solution.

[0017] Furthermore, plasma-electron sponge nanochannel composite membranes of different thicknesses can be obtained by changing the number of transfers in the plasma-electron sponge nanofilm.

[0018] Furthermore, in steps (1) and (2), the concentration of the HAuCl4 aqueous solution is 5-30 mM, preferably 10 mM.

[0019] Further, in step (1), the mass ratio of trisodium citrate to water is 1-3:20, preferably 1.47:20.

[0020] Further, in step (1), the concentration of the sodium borohydride aqueous solution is 0.05-0.2M, preferably 0.1M.

[0021] Further, in step (1), the volume ratio of the trisodium citrate aqueous solution, HAuCl4 aqueous solution, and sodium borohydride aqueous solution is 20:0.1-1:0.3-1.2, preferably 20:0.5:0.6.

[0022] Furthermore, in step (1), the particle size of the gold seeds is 5-10 nm.

[0023] Further, in step (2), the concentration of the HAuCl4 aqueous solution is 0.1-1 mM, preferably 0.3 mM.

[0024] Furthermore, in step (2), the concentration of the trisodium citrate aqueous solution is 5-20 mg / mL, preferably 10 mg / mL.

[0025] Further, in step (2), the volume ratio of the HAuCl4 aqueous solution, the gold seed solution and the trisodium citrate aqueous solution is 201:1-3:1.6-6.4, preferably 201:1.5:3.2.

[0026] Furthermore, in step (2), the particle size of the Au NPs is 30-40 nm, preferably 35 nm.

[0027] Further, in step (3), the volume ratio of the aqueous phosphotungstic acid solution, isopropanol and the aqueous Au NPs solution is 1-3:0.2-1:8, preferably 2:0.22:8.

[0028] The application of the plasma-electron sponge nanochannel composite membrane described in this invention in salinity gradient osmosis energy conversion.

[0029] Furthermore, during the salinity gradient osmosis energy conversion process, a salinity difference is formed between the concentrated salt solution and the dilute salt solution, converting the salinity difference energy into electrical energy.

[0030] Furthermore, the molar concentration of the concentrated salt solution is 0.1-5M.

[0031] Furthermore, the molar concentration of the dilute salt solution is 0.0001-0.01M.

[0032] Furthermore, the concentrated salt solution and the dilute salt solution are both one of sodium chloride solution, potassium chloride solution, magnesium chloride solution, lithium bromide solution and calcium chloride solution.

[0033] Furthermore, the concentrated salt solution and the dilute salt solution are of the same type.

[0034] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0035] The present invention relates to a plasma-electron sponge nanochannel composite membrane, comprising a self-assembled plasma-electron sponge membrane. The plasma-electron sponge membrane exhibits stable performance, is environmentally friendly, and its preparation method is simple to operate, with mild and easily achievable conditions, overcoming the shortcomings of existing technologies such as complex processes and poor controllability.

[0036] The plasma-electron sponge nanochannel composite membrane of this invention has significant advantages in the application of salinity gradient osmosis energy conversion:

[0037] (1) Under illumination, the hot electrons generated by Au NPs are continuously transferred and stored on POMs, which increases the surface charge density of the plasma electron sponge membrane, greatly reduces the ion penetration energy barrier, thereby improving the interface transport efficiency, significantly improving ion permeability, and greatly enhancing the permeation energy conversion capability.

[0038] (2) The inherent surface charge distribution asymmetry and structural asymmetry enable the asymmetric plasma electron sponge nanochannel composite membrane to have stable ion current rectification characteristics, which greatly improves the cation selectivity of the permeation energy conversion system.

[0039] (3) The plasma-electron sponge nanochannel composite membrane of this invention successfully converts salinity gradient energy into electrical energy in salinity gradient osmosis energy conversion. Under illumination, in a simulated salinity gradient using seawater (0.5M NaCl) and river water (0.01M NaCl), the maximum output energy density reached 15.68 W / m³. 2 It has far exceeded the commercial standard of 5W / m 2 .

[0040] (4) The plasma electron sponge nanochannel composite membrane of the present invention exhibits good stability in the application of salinity gradient permeation energy conversion. After a month of testing, the energy conversion power has almost no decay, laying a solid foundation for practical application. Attached Figure Description

[0041] Figure 1 A schematic diagram of the preparation process of the plasma-electron sponge nanochannel composite membrane prepared in Example 1;

[0042] Figure 2 Transmission electron microscope (TEM) images of individual 35nm Au NPs and Au@POMs NPs in Example 1;

[0043] Figure 3 This is a scanning electron microscope image of the 75nm AAO film in Example 1;

[0044] Figure 4 A scanning electron microscope image of the plasma-electron sponge nanochannel composite membrane with a thickness of 115±5 nm prepared in Example 2;

[0045] Figure 5 This is a diagram of the salinity gradient osmosis energy conversion device in Example 5;

[0046] Figure 6 The graph shows the relationship between current density, power density and external resistance obtained in the salinity gradient osmosis energy conversion of plasma-electron sponge nanochannel composite membranes of different thicknesses in Examples 1-5.

[0047] Figure 7The graph shows the relationship between current density, power density, and external resistance obtained in the salinity gradient osmosis energy conversion of the plasma-electron sponge nanochannel composite membrane and the pure AAO membrane in Example 2 and Comparative Example 1.

[0048] Figure 8 This is a test graph of the salinity gradient permeation energy conversion of the plasma-electron sponge nanochannel composite membrane in Example 6 over one month. Detailed Implementation

[0049] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0050] Example 1: Preparation of Plasma-Electron Sponge Nanochannel Composite Membrane

[0051] (1) Synthesis of gold seeds: 1.47 mg of trisodium citrate was dissolved in 20 mL of ultrapure water. 0.5 mL of 10 mM HAuCl4 aqueous solution was added while stirring. After thorough mixing, 0.6 mL of 0.1 M sodium borohydride aqueous solution was quickly added. The solution was stirred vigorously until it turned orange to obtain a gold seed solution with a gold seed particle size of 5 nm.

[0052] (2) Preparation of Au NPs with a particle size of 35 nm: After boiling 201 mL of 0.3 mM HAuCl4 aqueous solution, 1.5 mL of gold seed solution (1) and 3.2 mL of trisodium citrate aqueous solution with a concentration of 10 mg / mL were added sequentially. After the solution gradually changed from colorless to wine red and did not change color, the heater was turned off and allowed to cool naturally to room temperature under stirring to obtain an aqueous solution of Au NPs. The Au NPs were analyzed by transmission electron microscopy and the particle size of Au NPs was found to be 35 nm.

[0053] Gold nanoparticles of different sizes can be obtained by adjusting the amount of trisodium citrate aqueous solution added.

[0054] (3) Preparation of Au@POMs NPs: 2 mL of 2 mM Keggin-type phosphotungstic acid (H3PW) was prepared. 12 O 40 PW (abbreviated as PW) 12 Dissolve in 220 μl of isopropanol and irradiate under ultraviolet light for 30 minutes for reduction. Mix the blue-black solution of reduced phosphotungstic acid with 8 mL of 35 nm Au NPs aqueous solution to obtain Au@POMs NPs solution.

[0055] (4) Preparation of plasma electron sponge membrane: 5 ml of n-hexane was added to 30 ml of Au@POMs NPs solution to form a two-phase interface. Using ethanol as an inducer, Au@POMs NPs were extracted to the two-phase interface to self-assemble and form a plasma electron sponge membrane. The plasma electron sponge membrane was analyzed by scanning electron microscopy and the thickness of the plasma electron sponge membrane was found to be 70±5 nm.

[0056] (5) Preparation of Aluminum Oxide (AAO): First, aluminum foil was ultrasonically cleaned with acetone and 1M KOH for 10 minutes each, and then rinsed with water. The first anodizing was performed using 0.3M oxalic acid as the electrolyte at 50V for 30 minutes. To remove the irregular oxide layer formed, the aluminum foil was treated with a mixed acid solution of 6wt% H3PO4 and 1.8wt% H2CrO4 at 60°C for 40 minutes. Subsequently, the second anodizing was performed for 4 hours under the same conditions as the first anodizing. The aluminum substrate was removed with a saturated SnCl2 solution. The AAO film was treated with 1.8wt% H3PO4 solution for 40 minutes to remove the barrier layer. The prepared AAO film was then immersed in hydrogen peroxide solution (30% H2O2) and boiled for 30 minutes, generating a large number of hydroxyl groups on the channel surface. Finally, the AAO film was soaked in water overnight and dried. The pore size of the nanochannels in the anodic aluminum oxide film can be controlled by adjusting the oxidation voltage. Scanning electron microscopy analysis of the AAO film revealed that the pore size of the AAO film is 75 nm.

[0057] (6) Preparation of the plasma-electron sponge nanochannel composite membrane: The above-mentioned plasma-electron sponge membrane was transferred to the nanochannel end face of the prepared anodic aluminum oxide membrane and heat-fixed in a 70℃ oven for 2 hours to obtain a plasma-electron sponge nanochannel composite membrane with an anodic aluminum oxide nanochannel pore size of 75nm and a plasma-electron sponge membrane thickness of 70±5nm. The entire preparation process is as follows: Figure 1 As shown.

[0058] Transmission electron microscopy analysis was performed on the 35nm Au NPs and Au@POMs NPs prepared in this embodiment, and the results are as follows: Figure 2 As shown. Figure 2 The images shown are transmission electron microscope (TEM) images of individual 35nm Au NPs and Au@POMs NPs from Example 1. In Figure A, TEM image of a single 35nm Au NP is shown, and in Figure B, TEM image of an Au@POMs NP is shown. Figure 2 It can be seen that Au NPs are spherical nanoparticles with a diameter of 35 nm, and Au@POMs NPs exhibit a core-shell structure with Au NPs at the center and POMs on the outside, indicating the successful preparation of 35 nm Au NPs and Au@POMs NPs.

[0059] Scanning electron microscopy analysis was performed on the AAO film with a pore size of 75 nm prepared in this embodiment, and the results are as follows: Figure 3 As shown. Figure 3 This is a scanning electron microscope image of the AAO film with a pore size of 75 nm in this embodiment (5). Figure 3 It can be seen that the average pore diameter of the AAO membrane is 75 nm, and the pores are evenly distributed.

[0060] Examples 2-4: Preparation of plasma-electron sponge membrane nanochannel composite membranes with different thicknesses

[0061] The experimental procedure is the same as in Example 1. Compared with Example 1, by changing the number of transfers of the plasma-electron sponge membrane in step (6) of Example 1 to 2-4 times, a plasma-electron sponge nanochannel composite membrane with an anodic aluminum nanochannel pore size of 75 nm and plasma-electron sponge membrane thicknesses of 115±5 nm, 150±5 nm and 265±5 nm can be obtained.

[0062] Scanning electron microscopy analysis was performed on the plasma-electron sponge nanochannel composite membrane with a thickness of 115±5 nm prepared in this embodiment. The results are as follows: Figure 4 As shown. Figure 4 The images shown are scanning electron microscope (SEM) images of the plasma-electron sponge nanochannel composite membrane with a thickness of 115 ± 5 nm prepared in Example 2. (A) is the SEM image of the top layer, and (B) is the SEM image of the cross-section. Figure 4 It can be seen that the plasma-electron sponge membrane tightly covers the top of the AAO nanochannel, indicating the successful preparation of the plasma-electron sponge nanochannel composite membrane.

[0063] Example 5: Salinity gradient osmosis energy conversion of plasma-electron sponge nanochannel composite membrane

[0064] 1. Salinity gradient osmosis energy conversion device, such as Figure 5 As shown, the salinity gradient osmosis energy conversion device is a self-made two-chamber electrochemical electrolytic cell. A plasma-electron sponge nanochannel composite membrane is sandwiched between the two cells and fixed with screws. A concentrated salt solution (0.5M NaCl electrolyte solution) is placed at the macropore end of the composite membrane, i.e., the anodic alumina side, and a dilute salt solution (0.01M NaCl electrolyte solution) is placed at the micropore end of the composite membrane, i.e., the plasma-electron sponge membrane side. The two electrolyte solutions are connected to the circuit via an external electrochemical workstation and a load resistor. By adjusting the external resistance value, the relationship curves between current density, power density, and external resistance are measured (under 532nm laser irradiation).

[0065] 2. Permeation energy conversion of plasma-electron sponge composite membranes with different thicknesses

[0066] The plasma-electron sponge nanochannel composite membranes prepared in Examples 1-5 were used to replace the composite membranes in the above-mentioned salinity gradient permeation energy conversion devices, with other conditions remaining unchanged. The effect of the plasma-electron sponge membrane thickness on the salinity gradient permeation energy density was tested, and the results are as follows: Figure 5 As shown.

[0067] Figure 6 The graphs shown in Examples 1-5 depict the relationship between current density, power density, and external resistance obtained during salinity gradient osmosis energy conversion of plasma-electron sponge nanochannel composite membranes of different thicknesses. The larger graph shows the relationship between current density and external resistance, while the graph in the upper right corner of the larger graph shows the relationship between power density and external resistance. Figure 6 It can be observed that when the thickness of the plasma electron sponge film is 70±5nm, 115±5nm, 150±5nm, and 265±5nm, respectively, under 532nm laser irradiation and a 0.01M:0.5M NaCl gradient, the corresponding external circuit power density is 7.87W / m. 2 15.68W / m 2 9.69W / m 2 and 4.12W / m 2 When the thickness of the plasma electron sponge film is within 70-150±5nm, it meets the commercial standard of 5W / m. 2 Furthermore, the salinity gradient permeation energy power is highest when the thickness of the plasma electron sponge membrane is 115nm±5nm.

[0068] Comparative Example 1: Salinity gradient osmosis energy conversion of pure AAO membrane

[0069] The plasma-electron sponge nanochannel composite membrane in Example 5 was replaced with the pure AAO membrane prepared in Example 1, while other conditions remained unchanged, and the salinity gradient osmosis energy conversion was tested. The results are as follows: Figure 7 As shown.

[0070] Figure 7 The graphs show the relationship between current density, power density, and external resistance obtained from the plasma-electron sponge nanochannel composite membranes in Example 2 and Comparative Example 1 during salinity gradient osmosis energy conversion. The larger graph shows the relationship between current density and external resistance, while the graph in the upper right corner of the larger graph shows the relationship between power density and external resistance. Figure 7 Experimental results showed that the pure AAO film, under 532nm laser irradiation and a 0.01M:0.5M NaCl gradient, achieved an external circuit power density of 1.18 W / m. 2The external circuit power density is far lower than that of the plasma-electron sponge membrane with a thickness of 115±5nm in this invention. Since the pure AAO membrane does not have the plasma-electron sponge functional layer to increase the surface charge density, the salinity gradient permeation energy conversion performance of the pure AAO membrane is far inferior to that of the plasma-electron sponge nanochannel composite membrane.

[0071] Example 6: Stability test of salinity gradient osmosis energy conversion of plasma-electron sponge nanochannel composite membrane

[0072] The plasma-electron sponge nanochannel composite membrane with a thickness of 115 nm ± 5 nm, as described in Example 5, was subjected to salinity gradient osmosis energy conversion tests for 1, 3, 5, 7, 9, 11, 13, 15, 18, 21, 24, 27, and 30 days. The subsequent testing procedures were the same as in Example 5, with all other conditions remaining unchanged. The results are as follows: Figure 8 As shown.

[0073] Figure 8 This is a salinity gradient osmosis energy conversion test of the plasma-electron sponge nanochannel composite membrane in Example 6 over one month. Figure 8 Experimental results showed that the plasma-electron sponge nanochannel composite membrane exhibited good stability in the application of salinity gradient osmosis energy conversion. After a month of testing, the energy conversion power showed almost no attenuation, laying a solid foundation for practical applications.

Claims

1. A method for preparing a plasma electron sponge nanochannel composite membrane, characterized in that, The plasma electron sponge nanochannel composite film comprises a self-assembled plasma electron sponge film and a film material with a large pore structure, and part of the pores in the self-assembled plasma electron sponge film correspond to part of the large pores in the film material with a large pore structure. The preparation method of the plasma electron sponge nanochannel composite film comprises the following steps: adding n-hexane to the Au@POMs NPs solution to form a two-phase interface, using ethanol as an inducer to extract Au@POMs NPs to the two-phase interface to self-assemble a plasma electron sponge film, and then transferring the plasma electron sponge nanofilm to the nanochannel end face of the film material with a large pore structure and heat fixing to obtain a composite film. The preparation method of the Au@POMs NPs solution comprises the following steps: (1) Synthesis of gold seeds: dissolve trisodium citrate in ultrapure water, add an aqueous HAuCl4 solution under stirring, mix thoroughly, and then quickly add an aqueous sodium borohydride solution, and stir vigorously until the solution turns orange, to obtain a gold seed solution; (2) Preparation of Au NPs: boil an aqueous HAuCl4 solution, and then add the gold seed solution and an aqueous trisodium citrate solution in sequence, stop heating when the solution gradually changes from colorless to wine red and does not change color, and then naturally cool to room temperature under stirring, to obtain an aqueous Au NPs solution; (3) Preparation of Au@POMs NPs: dissolve phosphotungstic acid in water, add isopropyl alcohol, reduce under ultraviolet light, mix the reduced phosphotungstic acid solution and the aqueous Au NPs solution, and then obtain an Au@POMs NPs solution.

2. The production method according to claim 1, characterized by, Different thicknesses of the plasma electron sponge nanochannel composite film can be obtained by changing the transfer times of the plasma electron sponge nanofilm. In step (1), the concentration of the aqueous HAuCl4 solution is 5-30 mM, the mass ratio of the trisodium citrate to water is 1-3:20, the concentration of the aqueous sodium borohydride solution is 0.05-0.2 M, the volume ratio of the aqueous trisodium citrate solution, the aqueous HAuCl4 solution, and the aqueous sodium borohydride solution is 20:0.1-1:0.3-1.2, and the particle size of the gold seeds is 5-10 nm. In step (2), the concentration of the aqueous HAuCl4 solution is 0.1-1 mM, the concentration of the aqueous trisodium citrate solution is 5-20 mg / mL, the volume ratio of the aqueous HAuCl4 solution, the gold seed solution, and the aqueous trisodium citrate solution is 201:1-3:1.6-6.4, and the particle size of the Au NPs is 30-40 nm. In step (3), the volume ratio of the aqueous phosphotungstic acid solution, isopropyl alcohol, and the aqueous Au NPs solution is 1-3:0.2-1:

8.

3. The plasma electron sponge nanochannel composite film prepared by the preparation method of claim 1 or 2.

4. The plasma electron sponge nanochannel composite membrane of claim 3, wherein, The pore size of the anodic aluminum oxide film is 50-100 nm.

5. The plasma electron sponge nanochannel composite membrane of claim 3, wherein, The thickness of the plasma electron sponge film is 70-150 nm.

6. The use of the plasmonic electron sponge nanochannel composite membrane according to any one of claims 3-5 in a salinity gradient energy conversion.

7. Use according to claim 6, characterized in that, In the process of the salinity gradient energy conversion, a salinity difference is formed between a concentrated salt solution and a dilute salt solution, and the salinity difference is converted into electric energy, wherein the molar concentration of the concentrated salt solution is 0.1-5 M, and the molar concentration of the dilute salt solution is 0.0001-0.01 M.

8. Use according to claim 7, characterized in that, The concentrated salt solution and the dilute salt solution are one of a sodium chloride solution, a potassium chloride solution, a magnesium chloride solution, a lithium bromide solution and a calcium chloride solution.

9. Use according to claim 7, characterized in that, The concentrated salt solution and the dilute salt solution are of the same type.

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