Application of a photoresponsive asymmetric nanofluid membrane in reverse electrodialysis power generation

Abstract

Application of a photoresponsive asymmetric nanofluidic membrane in reverse electrodialysis power generation. This invention belongs to the field of nanofluidic membranes. The purpose of this invention is to solve the technical problems of insufficient ion selectivity and low ion flux in existing ion-selective membranes. The fluid membrane of this invention is composed of a membrane layer with two-dimensional channels formed by stacking a layer of functionalized GO sheets and a membrane layer with three-dimensional channels formed by stacking a layer of one-dimensional MoS2 / CdS nanowires. The two membrane layers have different charges, partially interconnected pores, and different pore sizes. The fluid membrane exhibits excellent performance when applied to photo-assisted or non-photo-assisted salinity gradient power generation systems. Furthermore, the fluid membrane of this invention has practical application value; the series configuration of integrated asymmetric nanofluidic membrane permeation energy cells provides sustainable power for small electronic devices.

Description

Technical Field

[0001] This invention belongs to the field of nanofluid membranes, specifically relating to the application of a photoresponsive asymmetric nanofluid membrane in reverse electrodialysis power generation. Background Technology

[0002] The enormous osmotic energy generated by the salinity gradient between seawater and river water is a promising blue energy source that can be extracted via reverse electrodialysis (RED) and used as a power source for IoT sensing, small portable devices, and maritime rescue systems. A key component of RED is the ion-selective membrane material. Nanofluidic membranes with unique ion transport kinetics enable high-performance salinity gradient power conversion.

[0003] However, existing ion exchange membranes are limited in the field of permeate energy conversion due to their high internal resistance. Current membrane materials suffer from insufficient ion selectivity and low ion flux, resulting in low output power. Therefore, researching how to regulate ion transport to improve permeate energy conversion capacity and efficiency is of great significance. Summary of the Invention

[0004] The purpose of this invention is to solve the technical problems of insufficient ion selectivity and low ion flux of existing ion-selective membranes, and to provide an application of a photoresponsive asymmetric nanofluid membrane in reverse electrodialysis power generation.

[0005] The technical solution of the present invention is as follows:

[0006] One of the objectives of this invention is to provide a photoresponsive asymmetric nanofluid membrane, wherein the nanofluid membrane is composed of a two-dimensional channel membrane layer formed by stacking a functionalized GO sheet and a three-dimensional channel membrane layer formed by stacking a one-dimensional MoS2 / CdS nanowire. The two membrane layers have different charges, some pores are interconnected, and the channel sizes are different.

[0007] To further specify, functionalized GO tablets are GO tablets modified with carboxylated cellulose.

[0008] Further specifying, MoS2 in the MoS2 / CdS nanowires is loaded on the CdS surface.

[0009] Further specifying, the pore size of the membrane with three-dimensional channels is 10-200 nm.

[0010] Further specifying, the gap between the two-dimensional channels in the film layer is 0.5-10 nm.

[0011] Further specified, the thickness of the nanofluidic film is 10-30 μm.

[0012] A second objective of this invention is to provide a method for preparing a photoresponsive asymmetric nanofluidic film, the method comprising the following steps:

[0013] S1: Mix the carboxylated cellulose solution and the GO dispersion evenly to obtain the functionalized GO dispersion;

[0014] S2: Mix sodium molybdate solution, cadmium nitrate solution and thiourea solution, adjust the pH to alkaline, and then transfer to a hydrothermal reactor for hydrothermal reaction. After the reaction is completed, wash the product to obtain MoS2 / CdS nanowires, and then redisperse them in deionized water to obtain MoS2 / CdS nanowire dispersion.

[0015] S3: MoS2 / CdS nanowire dispersion is fixed on the surface of the base film by vacuum filtration to form a film layer with three-dimensional channels. Then, functionalized GO dispersion is fixed on the surface of the film layer with three-dimensional channels by vacuum filtration to form a film layer with two-dimensional channels. Vacuum filtration is continued for 1-5 days, followed by heat treatment to obtain a photoresponsive asymmetric nanofluid membrane.

[0016] Further specified, the concentration of carboxylated cellulose solution in S1 is 0.01-0.06 wt%, and the concentration of GO dispersion is 0.05-0.15 wt%.

[0017] Further specified, the volume ratio of carboxylated cellulose solution to GO dispersion in S1 is 4:(4-5).

[0018] Further specifying, the molar ratio of sodium molybdate to cadmium nitrate and thiourea in S2 is 1:(5-10):(35-40).

[0019] Further specifying, the molar concentrations of sodium molybdate solution, cadmium nitrate solution, and thiourea solution in S2 are 0.005-0.01 mol / L, 0.05-0.1 mol / L, and 0.2-0.5 mol / L, respectively.

[0020] Further specifying, the hydrothermal reaction temperature in S2 is 100-200℃, and the time is 12-48h.

[0021] Further specifying, the concentration of the MoS2 / CdS nanowire dispersion in S2 is 0.05-0.15 wt%.

[0022] Further specified, the heat treatment temperature in S3 is 60-200℃, the time is 2-12h, and the atmosphere is air, nitrogen or argon.

[0023] The third objective of this invention is to provide an application of a photoresponsive asymmetric nanofluid membrane as a separator for a salinity differential battery.

[0024] The fourth objective of this invention is to provide an application of a photoresponsive asymmetric nanofluid membrane in a photocoupled salt gradient power generation system.

[0025] The fifth objective of this invention is to provide a high-efficiency micro-osmotic energy conversion system for power generation. The system uses the aforementioned photoresponsive asymmetric nanofluid membrane as a diaphragm, with electrolyte solutions of different concentrations on both sides of the diaphragm. The membrane layer with two-dimensional channels faces the side with the high concentration solution, while the side exposed to light is a membrane layer with three-dimensional channels formed by stacking one-dimensional MoS2 / CdS nanowires.

[0026] Furthermore, the electrolytes on both sides of the diaphragm are the same.

[0027] Further specified, the electrolyte is KCl, NaCl, MgCl2, LiCl, or CaCl2.

[0028] Furthermore, the pH of the electrolyte solution is specified to be 3-10.

[0029] Furthermore, the concentration difference of the electrolyte solution on both sides of the diaphragm is 5-500 times.

[0030] Further specified, the electrode is a silver / silver chloride electrode, a copper electrode, or a titanium-based ruthenium-coated electrode.

[0031] Further specified, the light source is AM1.5, natural light, full light, ultraviolet light, visible light, or near-infrared light.

[0032] Further specifying, the power of the illumination is 50-600 mW / cm². 2 The duration is 5 minutes to 24 hours.

[0033] The advantages of this invention compared to the prior art are:

[0034] (1) In this invention, the one-dimensional MoS2 / CdS nanowire membrane has three-dimensional nanochannels, which can reduce membrane resistance and increase ion flux; in addition, it can better match the two-dimensional channels formed by GO to form an asymmetric nanoporous nanofluid membrane, reducing concentration polarization. Furthermore, this asymmetric nanoporous nanofluid membrane can effectively utilize sunlight to achieve high-performance permeation energy conversion.

[0035] (2) The method for preparing asymmetric nanofluid membranes provided by the present invention only uses vacuum filtration, which is simple to operate and avoids the disadvantages of complex preparation process, high cost and poor controllability in the prior art.

[0036] (3) The asymmetric nanofluid membrane of the present invention has significant advantages in its application as a separator for salinity gradient batteries and in optically coupled salinity gradient power generation systems. It allows selective passage of cations under different pH conditions, and the asymmetric nanochannels have an ion diode effect, thus reducing concentration polarization and improving ion transport efficiency. Simultaneously, it has high energy conversion efficiency and a wide range of applications: it can be used in electrolyte solutions with pH = 3-11 and various electrolyte solutions. Furthermore, it exhibits high stability; the salinity gradient power generation system containing this asymmetric nanofluid membrane also demonstrates good stability, with no significant decrease in power generation efficiency after one month of continuous testing.

[0037] (4) With practical application value, the series configuration of integrated asymmetric nanofluid membrane permeation energy cells provides sustainable power for small electronic devices. Attached Figure Description

[0038] Figure 1 This is a cross-sectional scanning electron microscope image of the asymmetric nanofluid membrane in Example 1;

[0039] Figure 2 Zeta potential diagrams for functionalized GO and MoS2 / CdS;

[0040] Figure 3 This is a diagram of the device for converting salinity gradient energy into electrical energy according to the present invention;

[0041] Figure 4 The graph showing the relationship between power generation density and external resistance in Example 2;

[0042] Figure 5 The graph shows the relationship between power generation density and external resistance for salinity gradients of 5 and 500 times in Example 3.

[0043] Figure 6 The diagram shows the power generation density at different pH values ​​in Example 4;

[0044] Figure 7 The diagram shows the power generation density under different electrolytes in Example 5;

[0045] Figure 8 The diagram shows the power density of electricity generated under different incident light conditions in Example 6.

[0046] Figure 9 The diagram shows the power generation density under different test areas in Example 7. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0048] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0049] The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof, as used in the following embodiments, are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such a composition, step, method, article, or apparatus.

[0050] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1 to 5” is disclosed, the described range should be interpreted as including ranges “1 to 4”, “1 to 3”, “1 to 2”, “1 to 2 and 4 to 5”, “1 to 3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range. In this specification and claims, range definitions may be combined and / or interchanged, unless otherwise stated, these ranges include all subranges contained therein.

[0051] The indefinite articles “a” and “an” preceding an element or component of this invention do not impose any limitation on the quantity (i.e., number of times) of the element or component. Therefore, “an” or “a” should be interpreted as including one or at least one, and the singular form of an element or component also includes the plural form, unless the quantity clearly refers only to the singular form.

[0052] In this invention, "an embodiment" or "embodiment" refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that excludes other embodiments.

[0053] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0054] Example 1: Preparation of photoresponsive asymmetric nanofluidic films

[0055] (1) Dissolve the TEMPO system oxidized carboxylated cellulose (TOCNF) in deionized water to prepare a carboxylated cellulose solution with a carboxylated cellulose content of 0.05 wt%.

[0056] GO was dispersed in deionized water to prepare a GO dispersion with a GO content of 0.1 wt%.

[0057] Mix 4 mL of carboxylated cellulose solution and 18 mL of GO dispersion, and stir until homogeneous to obtain functionalized GO dispersion;

[0058] (2) Dissolve 0.48 mmol sodium molybdate, 3.46 mmol cadmium nitrate and 18.01 mmol thiourea in 60 mL deionized water to obtain a mixed solution;

[0059] The pH of the mixed solution was adjusted to 11, and then transferred to a hydrothermal reactor. The hydrothermal reaction was carried out at 200℃ for 24 hours. After the reaction was completed, the solution was naturally cooled to room temperature. The product was washed with deionized water and ethanol in sequence to remove unreacted raw materials and by-products. The product was obtained by centrifugation and filtration.

[0060] MoS2 / CdS nanowires were dispersed in deionized water to obtain a dispersion of MoS2 / CdS nanowires with a concentration of 0.1 wt%.

[0061] (3) 20 mL of MoS2 / CdS nanowire dispersion was fixed onto the surface of a polycarbonate filter membrane with a pore size of 0.1 μm by vacuum filtration to form a membrane layer with three-dimensional channels and a pore size of 10-200 nm. Then, 22 mL of functionalized GO dispersion was fixed onto the surface of a three-dimensional porous membrane by vacuum filtration to form a membrane layer with two-dimensional channels and a gap of 0.5-10 nm. Vacuum filtration was then performed for 2 days, followed by heat treatment in an oven at 60 °C for 2 hours. Figure 1 As shown, a photoresponsive asymmetric nanofluid film with a thickness of 10 μm was obtained.

[0062] from Figure 2 The results show that the functionalized GO maintains a high negative charge over a wide pH range, while MoS2 / CdS carries a smaller amount of negative charge, indicating that this photoresponsive asymmetric nanofluid membrane has charge asymmetry characteristics.

[0063] Example 2: Salinity gradient energy converted into electrical energy

[0064] like Figure 3As shown, the device for converting salinity gradient energy into electrical energy is a closed system. The left container contains a 0.5M NaCl electrolyte solution, and the right container contains a 0.01M NaCl electrolyte solution. The electrodes are silver / silver chloride electrodes. The photoresponsive asymmetric nanofluidic membrane prepared in Example 1 is mounted between the two containers and secured with screws. The test area is 28 mm². 2 The smaller pore size end (functionalized GO membrane) faces the high-concentration solution side, while the larger pore size end (MoS2 / CdS membrane) faces the low-concentration solution side. The two electrolyte solutions are connected in the circuit via an external ammeter and a load resistor. Adjusting the electrolyte solution pH to 7 corresponds to an external circuit energy density of 0.142 W / m³. 2 Under simulated sunlight, the light intensity is 100 mW / cm². 2 The result is as follows Figure 4 As shown, the energy density in the external circuit is increased to 0.253 W / m. 2 Compared to no illumination, the power density was increased by 78.2%.

[0065] Example 3: Salinity gradient energy conversion into electrical energy under different salinity gradients

[0066] Compared to Example 1, the effect of different salt solution concentration gradients on the energy density of the external circuit was tested by changing the concentration gradient of the NaCl solution while keeping other conditions constant. When the salt solution concentration gradients were 5 and 500, the corresponding external circuit energy densities were 0.032 and 0.838 W / m², respectively. 2 These figures were 69.9% and 86.6% higher than those under no light, respectively.

[0067] The results are as follows Figure 5 As shown, combined with the results of Example 1, it can be found that the salt gradient energy conversion efficiency is the highest when the salt concentration gradient is 500.

[0068] Example 4: Converting salinity gradient energy into electrical energy using photoresponsive asymmetric nanofluidic membranes at different pH levels.

[0069] Compared to Example 1, the pH of the electrolyte solution was adjusted to 3, 5, 9, and 10, respectively. The results showed that the energy density in the external circuit was 0.146 W / m³ at these values. 2 0.15W / m 2 0.153W / m 2 and 0.17W / m 2 Under simulated sunlight, the light intensity is 100 mW / cm². 2 The energy density was increased to 0.222 W / m³. 2 0.248W / m 2 0.293W / m 2and 0.339W / m 2 .

[0070] The results are as follows Figure 6 As shown in the results of Examples 1-2, the electrolyte solution exhibits the highest energy conversion efficiency at a pH of 10, with an external circuit energy density of 0.339 W / m². 2 .

[0071] Example 5: Converting salinity gradient energy into electrical energy using photoresponsive asymmetric nanofluidic membranes under different electrolyte conditions.

[0072] Compared to Example 1, the solutes in the electrolyte solution were replaced with LiCl, KCl, CaCl2, and MgCl2, respectively, while the concentration remained unchanged. The results showed that the energy density in the external circuit was 0.088 W / m³. 2 0.169W / m 2 0.087W / m 2 and 0.050W / m 2 Under simulated sunlight, the light intensity is 100 mW / cm². 2 The energy density was increased to 0.171 W / m³. 2 0.317W / m 2 0.160W / m 2 and 0.098W / m 2 .

[0073] The results are as follows Figure 7 As shown in the results of Examples 1-2, the highest energy conversion efficiency is achieved when the electrolyte is a KCl solution, with an external circuit energy density of 0.317 W / m². 2 .

[0074] Example 6: Asymmetric nanofluidic membranes with different incident light conditions convert salt gradient energy into electrical energy.

[0075] Compared to Example 1, the illuminance was 100 mW / cm² under incident light at 420 nm and 500 nm. 2 The results showed that the energy density in the external circuit was 0.274 W / m². 2 and 0.265W / m 2 .

[0076] The results are as follows Figure 8 As shown in the figures, and in conjunction with the results of Examples 1-2, when the incident light is 420 nm, the illuminance is 100 mW / cm². 2 It has the highest energy conversion efficiency, with an external circuit energy density of 0.274 W / m. -2 .

[0077] Example 7: Photoresponsive asymmetric nanofluidic membranes with different test areas convert salt gradient energy into electrical energy.

[0078] Compared to Application Example 1, the light intensity was adjusted to 100 mW / cm². 2 The tested areas were 0.03, 3.14, 7, 12.56, 19.6, 50, and 78.5 mm, respectively. 2 and 113mm 2 At that time, the corresponding external circuit energy density was 43.8 W / m. 2 0.296W / m 2 0.224W / m 2 0.160W / m 2 0.143W / m 2 0.128W / m 2 0.116W / m 2 and 0.118W / m 2 Under simulated sunlight, the light intensity is 100 mW / cm². 2 The energy density was increased to 59.5 W / m³. 2 0.584W / m 2 0.450W / m 2 0.339W / m 2 0.299W / m 2 0.237W / m 2 0.186W / m 2 and 0.184W / m 2 .

[0079] The results are as follows Figure 9 As shown in the results of Examples 1-2, the energy conversion efficiency decreases and tends to stabilize as the test area increases. When the test area increases by 113 mm², the energy conversion efficiency reaches a certain level. 2 At this time, the energy density in the external circuit can still reach as high as 0.184 W / m. 2 .

[0080] Example 8: Stability Test of Salinity Gradient Energy Generation System

[0081] The continuous system test in Example 1 showed that, with an electrolyte solution pH of 7 and no external electrolyte added, the current did not decrease after 12 hours of IT testing. Furthermore, after one month of testing, its power generation efficiency showed no decline.

[0082] Tests revealed that, under different lighting conditions, the salinity gradient power generation system containing the photoresponsive heterogeneous nanofluid membrane exhibited stable current output performance and energy conversion efficiency.

[0083] In summary, the one-dimensional MoS2 / CdS nanowire membrane in the asymmetric nanofluid membrane of this invention possesses three-dimensional nanochannels, which can reduce membrane resistance and increase ion flux. Furthermore, it can better match the two-dimensional channels formed by GO, forming an asymmetric nanoporous nanofluid membrane, reducing concentration polarization. It has significant advantages in applications as a separator for salinity gradient batteries and in photocoupled salinity gradient power generation systems. It allows cation selective passage under different pH conditions, and the asymmetric nanochannels exhibit an ion diode effect, thus reducing concentration polarization and improving ion transport efficiency. Simultaneously, it has high energy conversion efficiency and a wide applicability: it can be used in electrolyte solutions with pH = 3-11 and various electrolyte solutions. In addition, it exhibits high stability; the salinity gradient power generation system incorporating this asymmetric nanofluid membrane also demonstrates good stability, with no significant decrease in power generation efficiency after one month of continuous testing. More importantly, the asymmetric nanofluid membrane of this invention has practical application value; the series configuration of the integrated asymmetric nanofluid membrane permeation energy cell provides sustainable power for small electronic devices.

[0084] The above description is merely a preferred embodiment of the present invention. These specific embodiments are different implementations based on the overall concept of the present invention, and the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A light-responsive asymmetric nanofluidic membrane, characterized in that, The nanofluidic membrane is stacked by a membrane layer with two-dimensional channels formed by functionalized GO sheets and a membrane layer with three-dimensional channels formed by one-dimensional MoS2 / CdS nanowires, the two membrane layers have different electric charges, partially intercommunicate and have different channel sizes.

2. The nanofluidic membrane of claim 1, wherein, The functionalized GO sheets are GO sheets modified by carboxylated cellulose, and MoS2 in the MoS2 / CdS nanowires is loaded on the surface of CdS.

3. The nanofluidic membrane of claim 1, wherein, The membrane layer with three-dimensional channels has a pore size of 10-200 nm, the membrane layer with two-dimensional channels has a two-dimensional channel gap of 0.5-10 nm, and the nanofluidic membrane has a thickness of 10-30 μm.

4. The method of claim 1-3 for the preparation of a nanofluidic membrane, characterized in that, The method comprises the following steps: S1: uniformly mixing a carboxylated cellulose solution and a GO dispersion solution to obtain a functionalized GO dispersion solution; S2: mixing a sodium molybdate solution, a cadmium nitrate solution and a thiourea solution, adjusting the pH value to alkaline, then transferring into a hydrothermal reaction kettle, hydrothermal reaction, washing the product after the reaction to obtain MoS2 / CdS nanowires, then re-dispersing the MoS2 / CdS nanowires in deionized water to obtain a MoS2 / CdS nanowire dispersion solution; S3: fixing the MoS2 / CdS nanowire dispersion solution on the surface of a base membrane through suction filtration to form a membrane layer with three-dimensional channels, then fixing the functionalized GO dispersion solution on the surface of the membrane layer with three-dimensional channels through suction filtration to form a membrane layer with two-dimensional channels, continuing vacuum suction filtration for 1-5 days, then performing heat treatment to obtain a photoresponsive asymmetric nanofluidic membrane.

5. The method of claim 4, wherein, In S1, the concentration of the carboxylated cellulose solution is 0.01-0.06 wt%, and the concentration of the GO dispersion solution is 0.05-0.15 wt%, in S2, the molar ratio of sodium molybdate to cadmium nitrate and thiourea is 1:(5-10):(35-40), and in S2, the concentration of the MoS2 / CdS nanowire dispersion solution is 0.05-0.15 wt%.

6. The method of claim 4, wherein, In S2, the hydrothermal reaction temperature is 100-200 ℃, and the time is 12-48 h, and in S3, the heat treatment temperature is 60-200 ℃, and the time is 2-24 h.

7. Application of the nanofluidic membrane of any one of claims 1-3 as a salt difference battery separator.

8. Application of the nanofluidic membrane of any one of claims 1-3 in a photo-coupled salt difference energy power generation system.

9. A micro-osmotic energy conversion system for efficient power generation, characterized by, The system uses the photoresponsive asymmetric nanofluidic membrane of any one of claims 1-3 as a separator, the electrolyte solutions on both sides of the separator have a concentration difference, the membrane layer with two-dimensional channels faces the side of the high-concentration solution, and the side of the light irradiation is the membrane layer with three-dimensional channels formed by one-dimensional MoS2 / CdS nanowires.

10. The system of claim 9, wherein, The electrolyte on both sides of the diaphragm is the same, the concentration difference of the electrolyte solution on both sides of the diaphragm is 5-500 times, the pH of the electrolyte solution is 3-10, the power of the light is 50-600 mW / cm 2 , and the time length is 5 min-24 h.

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