Molybdenum disulfide / graphene oxide composite membrane for osmotic power generation and preparation method thereof

Abstract

The application discloses a preparation method of a molybdenum disulfide / oxidized graphene composite film for osmotic power generation, and specifically comprises the following steps: step 1, taking an oxidized graphene dispersion liquid and a molybdenum disulfide dispersion liquid respectively; the oxidized graphene dispersion liquid and the molybdenum disulfide dispersion liquid are subjected to first ultrasonic treatment respectively, and then are mixed to form a mixed dispersion liquid; step 2, the mixed dispersion liquid is subjected to second ultrasonic treatment, and then the mixed dispersion liquid subjected to the second ultrasonic treatment is subjected to vacuum filtration to obtain a composite film; and step 3, the composite film is subjected to heat treatment to obtain the molybdenum disulfide / oxidized graphene composite film for osmotic power generation. The application further discloses the molybdenum disulfide / oxidized graphene composite film for osmotic power generation. The composite film prepared by the application can solve the problems of poor stability and strength of a single molybdenum disulfide film when collecting salt difference energy.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ocean salinity difference energy generation, and relates to a molybdenum disulfide / oxidized graphene composite film for osmotic power generation, and also relates to a preparation method of the molybdenum disulfide / oxidized graphene composite film for osmotic power generation. BACKGROUND

[0002] The ocean contains abundant sustainable energy, such as wave energy, tidal energy, salinity difference energy and temperature difference energy, and the potential of these energies is huge, which needs to be further developed and utilized. In theory, the salinity difference generated by global river inflow into the sea is as high as 2.4 TW per year, which is enough to meet the energy demand of most regions in the world. The concentration difference between seawater and river water provides a stable energy source for the capture of salinity difference energy. Therefore, it is crucial to develop salinity difference energy conversion technology.

[0003] Reverse electrodialysis technology has attracted much attention due to its great potential in salinity difference power generation, and has made significant progress. By alternately arranging anion exchange membranes and cation exchange membranes, anions and cations are transported in different directions, so that chemical potential energy is directly converted into electrical energy, and the reliability of reverse electrodialysis has also been verified under actual working conditions. Therefore, designing high-performance ion-selective membranes to improve the power generation performance of salinity difference energy has become the first choice for research.

[0004] In recent years, power generation platforms based on two-dimensional materials have been intensively studied. For example, nanopore membranes constructed by two-dimensional nanosheets such as graphene oxide (GO), molybdenum disulfide (MoS2), boron nitride (BN), MXene, black phosphorus, etc. show great potential in salinity difference energy conversion, and their performance gradually reaches and exceeds the basic commercial standard of 5 W / m 2 . Among them, molybdenum disulfide can effectively improve the conversion efficiency of salinity difference energy due to its unique photoelectric effect. However, this single-nanopore-based nanogenerator limits its large-scale use. At the same time, there are relatively few reports on the use of molybdenum disulfide two-dimensional membranes in salinity difference energy collection. This is mainly due to the poor stability and strength of molybdenum disulfide membranes, which makes it difficult to form and easily damaged during reverse electrodialysis. Therefore, it is necessary to improve the physicochemical properties of molybdenum disulfide membranes to improve their salinity difference energy conversion performance. Graphene oxide is widely studied in the field of nanofluids due to its excellent electrical properties and stability. In addition, graphene oxide also has good photothermal effect. Therefore, the introduction of graphene oxide into molybdenum disulfide membranes is expected to enhance the stability of molybdenum disulfide composite membranes, and the application of light during reverse electrodialysis is also expected to improve the salinity difference energy conversion performance. SUMMARY

[0005] The purpose of this invention is to provide a method for preparing a molybdenum disulfide / graphene oxide composite membrane for osmotic power generation. The composite membrane prepared by this method can solve the problem of poor stability and strength of a single molybdenum disulfide membrane during salinity gradient energy harvesting.

[0006] Another object of the present invention is to provide a molybdenum disulfide / graphene oxide composite membrane for osmotic power generation.

[0007] The first technical solution adopted in this invention is a method for preparing a molybdenum disulfide / graphene oxide composite membrane for osmotic power generation, which specifically includes the following steps:

[0008] Step 1: Take graphene oxide dispersion and molybdenum disulfide dispersion separately; subject graphene oxide dispersion and molybdenum disulfide dispersion to a first ultrasonic treatment, and then mix them to form a mixed dispersion.

[0009] Step 2: The mixed dispersion is subjected to a second ultrasonic treatment, and then the mixed dispersion after the second ultrasonic treatment is filtered by vacuum filtration to obtain a composite membrane.

[0010] Step 3: Heat-treat the composite membrane to obtain a molybdenum disulfide / graphene oxide composite membrane for osmotic power generation.

[0011] The first technical solution of this invention is further characterized by:

[0012] The mass ratio of graphene oxide dispersion to molybdenum disulfide dispersion is 1:1.

[0013] The concentration of the graphene oxide dispersion is 0.5-2 mg / ml.

[0014] The concentration of the molybdenum disulfide dispersion is 0.1-5 mg / mL.

[0015] The first ultrasonic treatment should last 15-20 minutes.

[0016] The second ultrasonic treatment lasted 25-30 minutes.

[0017] Vacuum filtration was performed using a 500mL filtration flask. The specific process was as follows: the filtration flask was connected to a vacuum pump with an electrode power of 180W and a maximum vacuum of 0.098MPa via a flexible tube. A polycarbonate film with a diameter of 47mm and a pore size of 200nm was then placed on the filter element of the filtration flask. The mixed dispersion was then poured into the filtration flask and vacuum filtered for 24-48 hours.

[0018] The specific heat treatment method involves placing the composite film in a 60℃ oven for 18-24 hours.

[0019] The second technical solution adopted in this invention is a molybdenum disulfide / graphene oxide composite membrane for osmotic power generation, comprising the following substances: 50% molybdenum disulfide and 50% graphene oxide.

[0020] The second technical solution of the present invention is further characterized by:

[0021] The composite membrane has a two-dimensional layered structure in which nanosheets are stacked on top of each other and ions flow through the interlayered gaps between the nanosheets.

[0022] The beneficial effects of this invention are as follows:

[0023] This invention provides a molybdenum disulfide / graphene oxide composite membrane for osmotic power generation and its preparation method. The molybdenum disulfide / graphene oxide composite membrane is prepared by mixing graphene oxide nanosheets and molybdenum disulfide nanosheets using vacuum-assisted filtration technology. The introduction of graphene oxide nanosheets significantly enhances the stability and electrical performance of the composite membrane, which is crucial for salinity gradient energy conversion. In experiments, a high salinity of 5.86 W / m was achieved by mixing artificial seawater and fresh water. 2 The composite membrane exhibits excellent power density output under various pH, concentration, temperature, and light conditions. Notably, its power density reaches 6.97 W / m³ in an alkaline environment. 2 This surpasses even the most basic commercial output requirements. The molybdenum disulfide composite membrane doped with graphene oxide demonstrates enormous application potential in the field of salinity gradient energy conversion, and proves its ability to operate stably under various working environments while maintaining excellent power density output. Attached Figure Description

[0024] Figure 1 This is a schematic flowchart of the preparation method of the molybdenum disulfide / graphene oxide composite membrane for permeation power generation according to the present invention.

[0025] Figure 2 This is a SEM image of the surface of the molybdenum disulfide / graphene oxide composite film in Example 6 of the present invention;

[0026] Figure 3 This is a microstructure diagram of the first cross-section of the molybdenum disulfide / graphene oxide composite film in Example 6 of the present invention;

[0027] Figure 4 This is a microstructure diagram of the second cross section of the molybdenum disulfide / graphene oxide composite film in Example 6 of the present invention;

[0028] Figure 5 This is the EDX elemental spectrum of the surface elements of the molybdenum disulfide / graphene oxide composite film in Example 6 of the present invention;

[0029] Figure 6This refers to the high-resolution X-ray photoelectron spectroscopy of the molybdenum disulfide / graphene oxide composite film in Example 6 of this invention.

[0030] Figure 7 This is a high-resolution X-ray diffraction pattern of the molybdenum disulfide / graphene oxide composite film in Example 6 of the present invention;

[0031] Figure 8 This is a schematic diagram of the salinity gradient energy conversion system in Embodiment 6 of the present invention;

[0032] Figure 9 This is the IV curve diagram under the combined effect of concentration gradient and potential in Embodiment 6 of the present invention;

[0033] Figure 10 This is a zeta potential diagram of graphene oxide and molybdenum disulfide in Example 6 of the present invention;

[0034] Figure 11 This is an IV curve diagram recorded in neutral KCl electrolyte at different concentrations for the molybdenum disulfide / graphene oxide composite membrane in Example 6 of the present invention;

[0035] Figure 12 This is a schematic diagram showing the changes in concentration and ionic conductivity in Example 6 of the present invention;

[0036] Figure 13 This is a schematic diagram illustrating the effect of graphene oxide content on the power density of the composite membrane under a 50-fold salt gradient in Example 6 of the present invention.

[0037] Figure 14 This is a comparison chart of power densities at different film thicknesses in Embodiment 6 of the present invention;

[0038] Figure 15 This is a power density comparison diagram of the composite membrane in Example 6 of the present invention with that of pure graphene oxide membrane and molybdenum disulfide membrane;

[0039] Figure 16 This is a power density representation of the composite membrane at different pH values ​​in Example 6 of the present invention;

[0040] Figure 17 This is a comparison chart of power densities at different concentrations in Example 6 of the present invention;

[0041] Figure 18 This is a comparison chart of the salinity gradient power generation performance of the composite membrane in Embodiment 6 of the present invention and an existing membrane;

[0042] Figure 19 This is a schematic diagram of the illumination test in Embodiment 6 of the present invention;

[0043] Figure 20 This is a schematic diagram of the surface charge on one side of the light-promoted composite film in Embodiment 6 of the present invention;

[0044] Figure 21 This is the absorption spectrum of the composite membrane in Embodiment 6 of the present invention;

[0045] Figure 22 This is a schematic diagram showing the periodic change of ion current with light irradiation during low-concentration side irradiation in Embodiment 6 of the present invention;

[0046] Figure 23 This is a schematic diagram showing the periodic change of ion current with light irradiation during high-concentration side irradiation in Embodiment 6 of the present invention;

[0047] Figure 24 This is a comparison chart of power density under different illumination conditions in Embodiment 6 of the present invention;

[0048] Figure 25 This is a schematic diagram of the surface charge nanochannels and the concentration distribution of sodium and chloride ions in Embodiment 6 of the present invention;

[0049] Figure 26 This is a schematic diagram of the chloride ion concentration at the inlet of the low-concentration nanochannel in Embodiment 6 of the present invention;

[0050] Figure 27 This is a schematic diagram of the sodium ion concentration at the inlet of the low-concentration nanochannel in Embodiment 6 of the present invention;

[0051] Figure 28 This is a schematic diagram of the chloride ion concentration at the inlet of the high-concentration nanochannel in Embodiment 6 of the present invention;

[0052] Figure 29 This is a schematic diagram of the sodium ion concentration at the inlet of the high-concentration nanochannel in Embodiment 6 of the present invention. Detailed Implementation

[0053] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0054] The present invention relates to a method for preparing a molybdenum disulfide / graphene oxide composite membrane for osmotic power generation, as follows: Figure 1 As shown, the specific steps include the following:

[0055] Step 1: Take graphene oxide dispersion and molybdenum disulfide dispersion separately; subject graphene oxide dispersion and molybdenum disulfide dispersion to a first ultrasonic treatment, and then mix them to form a mixed dispersion.

[0056] The mass ratio of graphene oxide dispersion to molybdenum disulfide dispersion is 1:1;

[0057] The concentration of the graphene oxide dispersion is 0.5-2 mg / ml;

[0058] The concentration of the molybdenum disulfide dispersion is 0.1-5 mg / mL;

[0059] The first ultrasonic treatment should last 15-20 minutes.

[0060] Step 2: The mixed dispersion is subjected to a second ultrasonic treatment, and then the mixed dispersion after the second ultrasonic treatment is filtered by vacuum filtration to obtain a composite membrane.

[0061] The second ultrasonic treatment lasted 25-30 minutes;

[0062] Vacuum filtration was performed using a 500mL filtration flask. The specific process was as follows: the filtration flask was connected to a vacuum pump with an electrode power of 180W and a maximum vacuum of 0.098MPa via a flexible tube. A polycarbonate film with a diameter of 47mm and a pore size of 200nm was then placed on the filter element of the filtration flask. The mixed dispersion was then poured into the filtration flask and vacuum filtered for 24-48 hours.

[0063] Step 3: Heat-treat the composite membrane to obtain a molybdenum disulfide / graphene oxide composite membrane for osmotic power generation; the specific heat treatment method is to place the composite membrane in a 60℃ oven for 18-24 hours.

[0064] The composite membrane can generate 5.86 W / m under both conventional and alkaline environmental testing. 2 and 6.97 W / m 2 The composite membrane exhibits high power density output and maintains stable structural performance while generating higher power density under high-temperature conditions. Furthermore, it demonstrates a certain degree of light response, effectively enhancing power density output under illumination. This highlights the application potential of molybdenum disulfide in osmotic power generation.

[0065] Example 1

[0066] The present invention relates to a method for preparing a molybdenum disulfide / graphene oxide composite membrane for osmotic power generation, as follows: Figure 1 As shown, the specific steps include the following:

[0067] Step 1: Take graphene oxide dispersion and molybdenum disulfide dispersion separately; subject graphene oxide dispersion and molybdenum disulfide dispersion to a first ultrasonic treatment, and then mix them to form a mixed dispersion.

[0068] Step 2: The mixed dispersion is subjected to a second ultrasonic treatment, and then the mixed dispersion after the second ultrasonic treatment is filtered by vacuum filtration to obtain a composite membrane.

[0069] Step 3: Heat-treat the composite membrane to obtain a molybdenum disulfide / graphene oxide composite membrane for osmotic power generation.

[0070] Example 2

[0071] The present invention relates to a method for preparing a molybdenum disulfide / graphene oxide composite membrane for osmotic power generation, as follows: Figure 1 As shown, the specific steps include the following:

[0072] Step 1: Take graphene oxide dispersion and molybdenum disulfide dispersion separately; subject graphene oxide dispersion and molybdenum disulfide dispersion to a first ultrasonic treatment, and then mix them to form a mixed dispersion.

[0073] The mass ratio of graphene oxide dispersion to molybdenum disulfide dispersion is 1:1;

[0074] The concentration of the graphene oxide dispersion is 0.5-2 mg / ml;

[0075] The concentration of the molybdenum disulfide dispersion is 0.1-5 mg / mL;

[0076] Step 2: The mixed dispersion is subjected to a second ultrasonic treatment, and then the mixed dispersion after the second ultrasonic treatment is filtered by vacuum filtration to obtain a composite membrane.

[0077] Step 3: Heat-treat the composite membrane to obtain a molybdenum disulfide / graphene oxide composite membrane for osmotic power generation.

[0078] Example 3

[0079] The present invention relates to a method for preparing a molybdenum disulfide / graphene oxide composite membrane for osmotic power generation, as follows: Figure 1 As shown, the specific steps include the following:

[0080] Step 1: Take graphene oxide dispersion and molybdenum disulfide dispersion separately; subject graphene oxide dispersion and molybdenum disulfide dispersion to a first ultrasonic treatment, and then mix them to form a mixed dispersion.

[0081] The mass ratio of graphene oxide dispersion to molybdenum disulfide dispersion is 1:1;

[0082] The concentration of the graphene oxide dispersion is 0.5-2 mg / ml;

[0083] The concentration of the molybdenum disulfide dispersion is 0.1-5 mg / mL;

[0084] The first ultrasonic treatment should last 15-20 minutes.

[0085] Step 2: The mixed dispersion is subjected to a second ultrasonic treatment, and then the mixed dispersion after the second ultrasonic treatment is filtered by vacuum filtration to obtain a composite membrane.

[0086] The second ultrasonic treatment lasted 25-30 minutes;

[0087] Step 3: Heat-treat the composite membrane to obtain a molybdenum disulfide / graphene oxide composite membrane for osmotic power generation.

[0088] Example 4

[0089] The present invention relates to a method for preparing a molybdenum disulfide / graphene oxide composite membrane for osmotic power generation, as follows: Figure 1 As shown, the specific steps include the following:

[0090] Step 1: Take graphene oxide dispersion and molybdenum disulfide dispersion separately; subject graphene oxide dispersion and molybdenum disulfide dispersion to a first ultrasonic treatment, and then mix them to form a mixed dispersion.

[0091] The mass ratio of graphene oxide dispersion to molybdenum disulfide dispersion is 1:1;

[0092] The concentration of the graphene oxide dispersion is 0.5-2 mg / ml;

[0093] The concentration of the molybdenum disulfide dispersion is 0.1-5 mg / mL;

[0094] The first ultrasonic treatment should last 15-20 minutes.

[0095] Step 2: The mixed dispersion is subjected to a second ultrasonic treatment, and then the mixed dispersion after the second ultrasonic treatment is filtered by vacuum filtration to obtain a composite membrane.

[0096] The second ultrasonic treatment lasted 25-30 minutes;

[0097] Vacuum filtration was performed using a 500mL filtration flask. The specific process was as follows: the filtration flask was connected to a vacuum pump with an electrode power of 180W and a maximum vacuum of 0.098MPa via a flexible tube. A polycarbonate film with a diameter of 47mm and a pore size of 200nm was then placed on the filter element of the filtration flask. The mixed dispersion was then poured into the filtration flask and vacuum filtered for 24-48 hours.

[0098] Step 3: Heat-treat the composite membrane to obtain a molybdenum disulfide / graphene oxide composite membrane for osmotic power generation.

[0099] Example 5

[0100] The present invention relates to a method for preparing a molybdenum disulfide / graphene oxide composite membrane for osmotic power generation, as follows: Figure 1 As shown, the specific steps include the following:

[0101] Step 1: Take graphene oxide dispersion and molybdenum disulfide dispersion separately; subject graphene oxide dispersion and molybdenum disulfide dispersion to a first ultrasonic treatment, and then mix them to form a mixed dispersion.

[0102] The mass ratio of graphene oxide dispersion to molybdenum disulfide dispersion is 1:1;

[0103] The concentration of the graphene oxide dispersion was 1 mg / ml;

[0104] The concentration of the molybdenum disulfide dispersion was 1 mg / mL;

[0105] The first ultrasonic treatment lasted 18 minutes;

[0106] Step 2: The mixed dispersion is subjected to a second ultrasonic treatment, and then the mixed dispersion after the second ultrasonic treatment is filtered by vacuum filtration to obtain a composite membrane.

[0107] The second ultrasonic treatment lasted 28 minutes;

[0108] Vacuum filtration was carried out using a 500mL filtration flask. The specific process of vacuum filtration was as follows: the filtration flask was connected to a vacuum pump with an electrode power of 180W and a maximum vacuum degree of 0.098MPa through a hose. A polycarbonate film with a diameter of 47mm and a pore size of 200nm was then placed on the filter element of the filtration flask. The mixed dispersion was then poured into the filtration flask and vacuum filtered for 36 hours.

[0109] Step 3: Heat-treat the composite membrane to obtain a molybdenum disulfide / graphene oxide composite membrane for osmotic power generation; the specific heat treatment method is to place the composite membrane in a 60℃ oven for 20 hours.

[0110] Example 6

[0111] The present invention relates to a molybdenum disulfide / graphene oxide composite membrane for osmotic power generation, which is prepared according to a method for preparing a molybdenum disulfide / graphene oxide composite membrane for osmotic power generation, and comprises the following substances by mass percentage: 50% molybdenum disulfide and 50% graphene oxide.

[0112] The composite membrane has a two-dimensional layered structure in which nanosheets are stacked on top of each other and ions flow through the interlayered gaps between the nanosheets.

[0113] like Figure 2 As shown, the salinity gradient power generation performance of the composite membrane was tested, where ions can be transported through the gaps between the nanosheets. Scanning electron microscopy (SEM) images show that... Figure 3 , 4 As shown, the composite membrane surface is smooth and uniform, and the cross-section exhibits a typical layered structure. The membrane thickness is approximately 6.2 μm (average value of three consecutive measurements). Figure 5 As shown, EDX analysis revealed a uniform distribution of the four elements, indicating successful preparation of the graphene oxide / molybdenum disulfide composite film. Figure 6XPS results for the composite membrane are shown. (Example) Figure 7 As shown in the XRD pattern, the interlayer spacing of the composite film gradually decreases with increasing graphene oxide content. Furthermore, the composite film exhibits good stability under acidic and alkaline conditions.

[0114] like Figure 8 As shown, the prepared composite membrane was placed between two reservoirs to study ion transmembrane transport and salinity gradient energy conversion performance. KCl solution was used as the electrolyte to study the membrane's voltammetric characteristics (because KCl...). + and Cl - They have similar ion diffusion coefficients. For example... Figure 9 As shown, 0.01M and 0.5M KCl solutions were placed in the reservoirs at both ends, respectively. With opposite concentration gradients, the obtained voltammetric curves showed similar values, but due to the opposite directions of ion diffusion, the values ​​were also opposite in sign. This indicates that the composite membrane has a basically symmetrical structure and no preferential direction of ion transport across the membrane. Figure 10 As shown, the current response of the composite membrane exhibits linear ohmic behavior under different concentrations of KCl solution, further indicating that the composite membrane possesses an approximately symmetrical microchannel structure. Figure 11 As shown, both graphene oxide and molybdenum disulfide exhibit negative zeta potentials under neutral conditions; therefore, the constructed composite membrane possesses cation selectivity. It is noteworthy that, as... Figure 12 As shown, the measured conductivity exhibits different trends with changing electrolyte concentration. At high concentrations (approximately greater than 0.5 M), the conductivity change follows a linear relationship. As the concentration gradually decreases, the conductivity gradually deviates from linearity. This indicates that at low concentrations, the Debye length increases, and the regulatory effect of surface charge becomes dominant. When alternating voltages (+1V and -1V) are applied, the composite membrane can maintain a stable ion current output.

[0115] The power generation performance was tested by connecting an external load to the salinity gradient conversion system. The power generation performance was then assessed based on the external load. R and the detected ion current I The output power density can be calculated. P = I 2 × R As the external load gradually increases, the detected ion current decreases. When the two reach an equilibrium, there is a maximum output power density of approximately 5.86 W / m². Figure 13As shown, the effect of different graphene oxide contents on the output power density of the composite membrane was first investigated. As the graphene oxide content increased from 33.3% to 66.7%, the output power density of the composite membrane first increased and then decreased, reaching a maximum at a content of 50%. This may be due to the excellent electrical properties of graphene oxide itself; its zeta potential is larger than that of molybdenum disulfide. The addition of graphene oxide improves the electrical properties of the composite membrane and enhances ion selectivity. With further increases in the graphene oxide content, the output power density of the composite membrane gradually decreased. This may be attributed to the increased complexity of ion transport pathways due to the increased number of graphene oxide nanosheets, which also reduces the interlayer spacing (6.15 Å–6.13 Å). Therefore, the output power density of the composite membrane decreased from 3.68 W / m². 2 Increased to 5.86 W / m 2 Then reduce it to 3.37 W / m 2 Subsequently, as Figure 14 As shown, the effect of composite membrane thickness on output power density was investigated. With increasing composite membrane thickness, the output power density decreased from 4.77 W / m². 2 Increased to 5.86 W / m 2 Then reduce it to 3.67 W / m 2 This is because increasing the membrane thickness is equivalent to lengthening the nanochannel, reducing concentration polarization at both ends of the membrane, and increasing the effective concentration ratio at both ends. As the membrane thickness further increases, the ion transport path becomes more complex, the ion transport distance increases, and the membrane resistance also increases, reducing ion flux and leading to a decrease in output power density. When the membrane thickness is 6.2 μm, the influence of parameters such as membrane internal resistance and concentration polarization reaches a balance, resulting in the maximum output power density, which is also reflected in the change in current density. Figure 15 As shown, comparing the composite film with pure graphene oxide and molybdenum disulfide, a significant improvement in output power density can be observed. Compared to pure GO films, the interaction between molybdenum disulfide nanosheets is weaker, making film formation more difficult under the same conditions.

[0116] Besides the concentration difference between seawater and freshwater, which constitutes salinity gradient energy, other saline waters or industrial wastewaters also contain abundant salinity gradient energy resources. Therefore, studying the salinity gradient energy conversion performance under different operating conditions is of great significance. For example... Figure 16 As shown, the output power density of the composite membrane increases from pH 3 to 11, reaching a maximum of approximately 6.97 W / m³ at pH 11. 2This enhanced energy conversion behavior can be attributed to changes in the charge density of graphene oxide and molybdenum disulfide. The measured zeta potentials show that both graphene oxide and molybdenum disulfide are sensitive to pH changes. Different pH values ​​lead to changes in the surface charge of the composite membrane, and increasing the channel surface charge gradually increases the ion current. This is mainly due to the significantly enhanced ion selectivity within the channel resulting from the increased surface charge. Figure 17 As shown, the concentration of the solution on the low-concentration side was fixed at 0.01 M, and the salinity gradient energy conversion performance of the composite membrane was studied under conditions of 10 times, 50 times, and 500 times the concentration difference. When the concentration difference across the composite membrane reached 500 times, the output power density could reach 17.68 W / m³. 2 Under high concentration conditions (500 times higher), the composite membrane's output power density is higher than that of some previously reported membranes. Furthermore, the salinity gradient power generation performance of the composite membrane under different temperature conditions was investigated. As the system temperature increases, the output power density of the composite membrane also increases. When the system temperature reaches 338 K, the power density can reach 9.79 W / m³. 2 This is because the ionic conductivity changes linearly with increasing temperature, following the Arrhenius equation. Simultaneously, increasing temperature alters solution properties, such as ion diffusion coefficient, solution viscosity, and conductivity, ultimately leading to increased transmembrane ion flux and power density. Furthermore, the salinity gradient power generation performance of this composite membrane under different electrolyte solutions was investigated. Due to the cation selectivity of this composite membrane, the power output is closely related to the cation diffusion coefficient; a higher diffusion coefficient results in a higher power density. For example, the power density output of the composite membrane in KCl solution is much higher than that in NaCl and LiCl. For divalent ions, such as Mg... 2+ The lowest output power density is caused by factors such as a low diffusion coefficient and uphill transport. When tested with real seawater, the output power density of the composite membrane decreases by approximately 53%. This is due to the presence of a large number of divalent ions (such as Mg²⁺) in seawater. 2+ Ca 2+ SO4 2- (etc.) leads to this. For example... Figure 18 As shown, under the same salt gradient conditions, the power generation performance of the composite membrane was compared with that of existing partial membranes. It can be seen that the power generation performance of the composite membrane is superior to that of existing partial membranes.

[0117] The composite membrane, composed of molybdenum disulfide and graphene oxide, exhibits both photoelectric and photothermal effects. Therefore, as... Figure 19 As shown, the specific impact of sunlight on salinity gradient power generation was investigated in detail. Due to the presence of molybdenum disulfide on the surface of the composite membrane, such as... Figure 20As shown, when light shines on the film surface, photons are absorbed by molybdenum disulfide, generating electron-hole pairs. This leads to further trapping of holes generated in the valence band, causing the Fermi level to shift to the conduction band, resulting in increased surface charge on molybdenum disulfide. Figure 21 As shown, when light is applied, the surface charge on the illuminated side of the composite film increases, while the surface charge on the unilluminated side remains unchanged (because the composite film is thick and opaque, only some molybdenum disulfide nanosheets on the film surface are affected by light). Simultaneously, light exposure causes the temperature on one side of the film to gradually rise, resulting in a certain temperature difference between the two sides. When light is continuously applied to the surface of the composite film (light intensity ~99.52 mW / cm²), the temperature difference is further observed. 2 The surface temperature increased by approximately 1 K during 10 minutes of illumination. Theoretical simulations revealed that a 1 K temperature difference has a relatively small impact on salinity gradient power generation; therefore, the temperature change caused by illumination was ignored in subsequent studies.

[0118] When light shines from the side with low or high concentration, such as Figure 22 , 23 As shown, both methods can increase the transmembrane ion current. By periodically applying light, it can be observed that the composite membrane does not respond instantaneously to light, but rather increases slowly over time. When the light exposure stops, the ion current also gradually decreases. This slow change is mainly related to the photoeffect of the composite membrane. Furthermore, as... Figure 24 The diagram shows a comparison of salinity gradient power generation performance under illumination. When illumination is applied to the low-concentration side, the maximum power density can reach 6.5 W / m². 2 When illumination is applied to the high-concentration side, the maximum power density increases to 6.01 W / m². 2 .

[0119] To explain this phenomenon, a mathematical model was constructed based on the PNP equations. Since illumination primarily affects the surface charge on the illuminated side, the effect of illumination can be simulated by adjusting the surface charge. Figure 25 As shown, three different mathematical models were established: no illumination, illumination on the low-concentration side (with high surface charge on the low-concentration side), and illumination on the high-concentration side (with high surface charge on the high-concentration side). Without illumination, the ion concentration within the nanochannel changes uniformly under the influence of the concentration gradient and ion selectivity. When illumination is applied, the ion selectivity in the high-surface-charge region is more pronounced than in the low-surface-charge region due to the increased double-layer effect. Furthermore, the ions at both ends of the nanochannel were analyzed. Ion concentrations were calculated for two nanometers inside the nanochannel and 10 nanometers at the outlet. Figure 26 , 27As shown, when a high surface charge is located on the low concentration side, the sodium ion concentration within the channel increases significantly due to enhanced ion selectivity, while the effect of chloride ions is relatively small. Due to the repulsive effect, the chloride ion concentration outside the channel is also lower than the ion concentration under the influence of the average surface charge. Figure 28 , 29 As shown, when the high surface charge is located on the high concentration side, the sodium ion concentration in the channel increases, resulting in significant ion enrichment. Regardless of which side the surface charge increases, the ion current passing through the nanochannel also increases. Furthermore, the ion current is even greater when the high surface charge is on the low concentration side, consistent with experimental observations. This phenomenon is primarily related to the thickness of the electrical double layer (the higher the concentration, the thinner the double layer). Under the same surface charge, the double layer on the low concentration side is thicker and has a larger effective area than the high concentration side; a similar phenomenon exists in straight channels. This demonstrates that applying an asymmetric charge distribution can effectively increase transmembrane ion flux and improve energy conversion performance.

[0120] In summary, a molybdenum disulfide composite membrane containing graphene oxide was fabricated via vacuum-assisted filtration. The introduced graphene oxide nanosheets effectively improved the electrical properties and stability of the composite membrane. By adjusting the ratio and membrane thickness, the composite membrane achieved a maximum output power density of 5.86 W / m² under a 50-fold salt gradient. 2 The maximum power density can reach 17.68 W / m² under a salt gradient of 500 times. 2 Furthermore, the salinity gradient power generation performance of the composite membrane under different operating environments was analyzed. It was found that the composite membrane exhibits good power output under both high-temperature and alkaline conditions, providing a new option for salinity gradient energy conversion combined with industrial waste heat and wastewater treatment. In addition, the composite membrane demonstrates excellent photoelectric effect; when light is applied to its surface, its salinity gradient energy conversion performance is enhanced. This provides insights into constructing nanoporous membranes for asymmetric ion transport using light to improve salinity gradient energy conversion performance, demonstrating the application prospects of molybdenum disulfide in the field of salinity gradient energy conversion.

Claims

1. A method for preparing a molybdenum disulfide / graphene oxide composite membrane for osmotic power generation, characterized in that, Specifically, the steps include the following: Step 1: Take graphene oxide dispersion and molybdenum disulfide dispersion separately; subject the graphene oxide dispersion and molybdenum disulfide dispersion to a first ultrasonic treatment, and then mix them to form a mixed dispersion. Step 2: The mixed dispersion is subjected to a second ultrasonic treatment, and then the mixed dispersion after the second ultrasonic treatment is filtered by vacuum filtration to obtain a composite membrane; Step 3: Heat-treat the composite membrane to obtain a molybdenum disulfide / graphene oxide composite membrane for permeation power generation; The mass ratio of the graphene oxide dispersion to the molybdenum disulfide dispersion is 1:1; The concentration of the graphene oxide dispersion is 0.5-2 mg / mL; The concentration of the molybdenum disulfide dispersion is 0.1-5 mg / mL; The duration of the first ultrasonic treatment is 15-20 minutes; The second ultrasonic treatment lasts for 25-30 minutes. The vacuum filtration is specifically performed using a 500mL filtration flask. The specific process of vacuum filtration is as follows: the filtration flask is connected to a vacuum pump with a motor power of 180W and a maximum vacuum degree of 0.098MPa through a hose. A polycarbonate film with a diameter of 47mm and a pore size of 200nm is then placed on the filter element of the filtration flask. The mixed dispersion is then poured into the filtration flask and vacuum filtered for 24-48 hours. The specific heat treatment method involves placing the composite film in a 60°C oven for 18-24 hours.

2. The composite membrane prepared by the method for preparing the molybdenum disulfide / graphene oxide composite membrane for osmotic power generation according to claim 1, characterized in that, By mass percentage, it contains the following substances: 50% molybdenum disulfide and 50% graphene oxide; The composite membrane has a two-dimensional layered structure in which nanosheets are stacked on top of each other and ions flow through the interlayered gaps between the nanosheets.

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