Preparation method and application of a light-responsive heterogeneous nanofluidic membrane

Abstract

The application relates to a preparation method and application of a light response hetero-nanofluid film. The application belongs to the nanofluid film field. The application aims to solve the technical problems of a complex preparation process and poor ion selectivity of an existing ion selective film. The fluid film is formed by layer-by-layer stacking of two kinds of semiconductor materials with band matching to form a heterostructure, one layer is a porous semiconductor film with light response, and the other layer is a porous semiconductor film for promoting charge separation, the porous semiconductor film for promoting charge separation further contains cation nanofibers, the two layers of semiconductor films are opposite in charge, partially interpenetrated in pore channels and different in pore diameter. The fluid film is applied to a light-assisted or non-light-assisted salt differential energy power generation system.

Description

Technical Field

[0001] This invention belongs to the field of nanofluidic membranes, specifically relating to a method for preparing and applying a photoresponsive heterogeneous nanofluidic membrane. Background Technology

[0002] The consumption of fossil fuels has led to a sharp increase in environmental problems, forcing the search for renewable energy alternatives. Photo-assisted salinity gradient (SGR) conversion can simultaneously utilize both salinity gradient energy and solar energy, effectively alleviating the energy crisis. Reverse electrodialysis (RED) technology uses ion-selective membranes to directly convert salinity gradient energy into electricity. Furthermore, by applying external stimuli, ion transport can be modulated to promote salinity gradient energy conversion. Light, as an external stimulus, can reduce the Gibbs free energy of the salinity gradient, promote directional ion transport, and improve the efficiency of salinity gradient power generation systems.

[0003] Currently, ion-selective membranes, as a key factor in RED (reactive energy conversion), still suffer from problems such as expensive raw materials, complex preparation processes, poor ion selectivity, and inability to meet industrial applications. Therefore, it is necessary to design a nanofluidic membrane for the salt gradient energy conversion process that has a simple preparation process, abundant and inexpensive raw materials, can be prepared on a large scale, and has a wide range of applications to solve the existing defects. Summary of the Invention

[0004] The purpose of this invention is to solve the technical problems of complex preparation processes and poor ion selectivity of existing ion-selective membranes, and to provide a method for preparing and applying photoresponsive heterogeneous nanofluid membranes.

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

[0006] One of the objectives of this invention is to provide a photoresponsive heterogeneous nanofluid membrane, wherein the nanofluid membrane is formed by stacking two semiconductor materials with band matching layer by layer to form a heterostructure. One layer is a photoresponsive porous semiconductor membrane, and the other layer is a porous semiconductor membrane that promotes charge separation. The semiconductor membrane that promotes charge separation also contains cationic nanofibers. The two semiconductor membranes have opposite charges, partially interconnected pores, and different pore sizes.

[0007] Further specifying, the content of photoresponsive semiconductor material in the nanofluidic film is 40-70 wt%.

[0008] Further specifying, the content of cationic nanofibers in the semiconductor film that promotes charge separation is 0-3 wt%.

[0009] Furthermore, the photoresponsive semiconductor film is composed of stacked nanowire or nanosheet semiconductor materials.

[0010] Furthermore, the nanowire semiconductor material is tungsten oxide, molybdenum oxide, or titanium dioxide, and the nanosheet semiconductor material is indium zinc sulfide or carbon nitride.

[0011] Furthermore, the semiconductor film that promotes charge separation is composed of stacked nanosheet semiconductor materials.

[0012] Furthermore, the nanosheet semiconductor material is molybdenum sulfide, tungsten sulfide, cobalt hydroxide, or nickel hydroxide.

[0013] Further specified, the thickness of the photoresponsive semiconductor film is 1-15 μm, and the pore size is 2-120 nm.

[0014] Further specified, the thickness of the semiconductor film promoting charge separation is 1-15 μm, and the pore size is 0.2-120 nm.

[0015] A second objective of this invention is to provide a method for preparing a photoresponsive heterogeneous nanofluidic film, the method comprising the following steps:

[0016] A dispersion of a photoresponsive semiconductor material and a dispersion of a charge-separating semiconductor material containing cationic nanofibers are sequentially deposited layer by layer by vacuum filtration, spin coating, or self-assembly, and then subjected to heat treatment to obtain a photoresponsive heterofluidic membrane.

[0017] Further specified, the heat treatment temperature is 60-200℃, the time is 2-24h, and the atmosphere is air, nitrogen or argon.

[0018] The third objective of this invention is to provide an application of a photoresponsive heterogeneous nanofluid membrane in a salinity gradient power generation system.

[0019] The fourth objective of this invention is to provide an application of a photoresponsive heterogeneous nanofluid membrane in a photo-assisted salinity gradient power generation system.

[0020] The fifth objective of this invention is to provide a high-efficiency photovoltaic-assisted or non-photovoltaic-assisted salinity gradient power generation system, wherein the power generation system uses the aforementioned photoresponsive heterogeneous nanofluid membrane as a diaphragm, with electrolyte solutions of different concentrations on both sides of the diaphragm, and the illumination is performed using an asymmetric irradiation method.

[0021] Furthermore, the electrolytes on both sides of the diaphragm are the same.

[0022] Further specified, the electrolyte is KCl, NaCl, MgCl2, LiCl, or CaCl2.

[0023] Furthermore, the pH of the electrolyte solution is specified to be 3-10.

[0024] Furthermore, the concentration difference of the electrolyte solution on both sides of the diaphragm is 5-500 times.

[0025] Further specified, the electrode is a silver / silver chloride electrode, a copper electrode, or a titanium-based ruthenium-coated electrode.

[0026] Further specified, the light source is AM1.5, natural light, full light, ultraviolet light, visible light, or near-infrared light.

[0027] Further specifying, the power of the illumination is 0-600mW / cm². 2 The duration is 0-30 days.

[0028] The advantages of this invention compared to the prior art are:

[0029] (1) The present invention discloses a photoresponsive heterogeneous nanofluid membrane, which is composed of two semiconductors with band matching. Compared with the prior art, the system significantly enhances the ion diode effect of the heterogeneous membrane due to the introduction of the photoresponsive heterostructure, achieving high ion selectivity and permeability, which is beneficial to improving the salt gradient energy conversion efficiency. In addition, the heterostructure also weakens the concentration polarization effect, further improving the ion transport efficiency.

[0030] (2) This invention improves the advantage of unidirectional ion diffusion by constructing an asymmetric nanopore structure; in addition, opposite charges can form a potential gradient to jointly promote unidirectional ion diffusion.

[0031] (3) The present invention also discloses a method for preparing the above-mentioned photoresponsive heterogeneous nanofluid membrane, which can be achieved simply by vacuum filtration. The photoresponsive heterogeneous nanofluid membrane has stable performance, a wide photoresponse range, abundant raw materials, low cost, and a simple preparation process, which can be prepared on a large scale, overcoming the shortcomings of the prior art, such as complex process, high cost, and poor controllability.

[0032] (4) The photoresponsive heterogeneous nanofluid membrane of the present invention has significant advantages in the application of salinity gradient power generation systems. In a salinity gradient power generation system simulating seawater (0.5M NaCl) and river water (0.01M NaCl), the maximum output power density reached 23W / m³. -2 It is more than three times that of a simple tungsten oxide film. After illumination, the power density increased by 58.3%; the energy conversion efficiency increased from 25.5% to 34%.

[0033] (5) The power generation system constructed by this invention has a wide range of applications. It can be used in electrolyte solutions with pH = 3-10. During use, the thickness of the photoresponsive heterogeneous nanofluid membrane can be adjusted according to the pH to maximize the energy conversion efficiency. In addition, the performance is stable. Without external electrolyte, after 8 hours of it test curve, the current decayed by 11.4%. After 1 month of testing, its power generation efficiency only decreased by 6%. Attached Figure Description

[0034] Figure 1 The cross-section of the photoresponsive heterogeneous nanofluidic film in Example 1 and the surface of the Co(OH)2 film and W18 O 49 Scanning electron microscopy images of the membrane surfaces; (a) -Co(OH)₂CNFs membrane, (b) -W 18 O 49 Membrane, (c)-Nanofluidic membrane;

[0035] Figure 2 a is W in Example 1 18 O 49 Zeta potential diagram of Co(OH)2; Figure 2 b is W in Example 1 18 O 49 XRD patterns of Co(OH)2; Figure 2 c represents W in Example 1 18 O 49 BET plot of the membrane;

[0036] Figure 3 This is a diagram of the device for converting salinity gradient energy into electrical energy according to the present invention;

[0037] Figure 4 The graph shows the relationship between current density, power generation density and external resistance under different salt solution concentration gradients in Example 2.

[0038] Figure 5 The graph shows the relationship between power generation density and external resistance at different pH levels in Example 3.

[0039] Figure 6 The graph shows the relationship between power generation density and external resistance under different light intensities in Example 4.

[0040] Figure 7 The graph shows the relationship between current density, power generation density and external resistance under different illumination times in Example 5.

[0041] Figure 8 The graph shows the relationship between power density and external resistance for different cationic nanofiber contents in Example 6.

[0042] Figure 9 For the different W in Example 7 18 O 49 The relationship between power generation density and external resistance at a given content. Detailed Implementation

[0043] 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.

[0044] 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.

[0045] Example 1

[0046] The preparation method of the photoresponsive heterogeneous nanofluid film in this embodiment is carried out according to the following steps:

[0047] (1) Take 0.1g of W 18 O 49 Nanowires (10-45 nm in diameter) were added to 100 mL of water to prepare W 18 O 49 Dispersion of nanowires;

[0048] (2) 0.1g of Co(OH)2 nanosheets (thickness of 2-6nm) and 1mg of cationic nanofibers were added to 100mL of water to prepare a dispersion of Co(OH)2 nanosheets containing cationic nanofibers; wherein the cationic nanofibers were quaternary ammonium salt modified nanofibers purchased from Tianjin Wood Elf Biotechnology Co., Ltd.

[0049] (3) First, a polycarbonate filter membrane with a pore size of 0.1 μm is fixed on the sand core of the vacuum filtration device, and then W 18 O 49 A dispersion of nanowires was fixed onto a polycarbonate filter membrane by vacuum filtration, resulting in a photoresponse W with a thickness of 4 μm and a pore size of 23.4 nm and three-dimensional channel interconnection. 18 O 49 Nanowire films were then formed, and a dispersion of Co(OH)₂ nanosheets containing cationic nanofibers, a semiconductor material whose energy band is matched to that of the photoresponsive semiconductor, was fixed by vacuum filtration on W. 18 O 49 A semiconductor layer with a thickness of 6 μm and a pore size of 0.45 nm, which promotes charge separation, was obtained on the nanowire film.

[0050] (4) The above membrane material was placed in an air atmosphere and heat-treated at 60°C for 8 hours to obtain W. 18 O 49 A photoresponsive heterogeneous nanofluid membrane with a content of 50 wt%.

[0051] In this embodiment, the photoresponsive heterogeneous nanofluid membrane can form a built-in electric field under illumination, promoting the separation of photogenerated charges and the directional transport of ions; wherein W 18 O 49Nanowires possess high surface negative charge, and the constructed nanofluid channels provide a three-dimensional interconnected structure, thus achieving high ion flux and excellent ion selectivity. Furthermore, W 18 O 49 Nanowires exhibit high absorbance across almost the entire spectrum due to surface plasmon resonance. Co(OH)₂ nanosheets possess high positive charge on their surface, which interacts with W... 18 O 49 Nanowire composites form heterostructures with opposite charges and asymmetrical pore sizes. Furthermore, cobalt hydroxide nanosheets and W... 18 O 49 The heterostructure formed by nanowires promotes charge separation, increases ion flux and ion selectivity under illumination, and achieves high salinity gradient energy conversion efficiency.

[0052] Scanning electron microscope image of the Co(OH)2@CNFs film surface as shown below Figure 1 As shown in (a), W 18 O 49 Scanning electron microscope image of the film surface as follows Figure 1 (b) shows a scanning electron microscope image of the cross-section of the nanofluidic membrane. Figure 1 As shown in (c), from Figure 1 As can be seen, the heterofilm is 10 μm thick, W 18 O 49 The side of the film is composed of nanowires and is 4 μm thick, while the side of the Co(OH)2@CNFs film is composed of nanosheets and nanofibers and is 6 μm thick.

[0053] from Figure 2 From a, we can see W 18 O 49 It maintains a high negative charge over a wide pH range, while Co(OH)₂ carries the opposite charge. Figure 2 From b, we can see that the interlayer spacing of Co(OH)₂ can be calculated to be 0.45 nm using the Bragg equation. Figure 2 From c, we can know that W 18 O 49 The average pore size of the layer was measured to be 23.4 nm using BET.

[0054] Application Example 1: Salinity gradient energy converted into electrical energy

[0055] like Figure 3 As 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, corresponding to the right container containing a 0.01M NaCl electrolyte solution. The electrodes are silver / silver chloride electrodes. The photoresponsive heterogeneous nanofluidic membrane prepared in Example 1 is mounted between the two containers and fixed with screws. The W of the photoresponsive heterogeneous nanofluidic membrane... 18 O 49The membrane faces the high-concentration solution side, and the Co(OH)₂CNFs membrane faces the low-concentration solution side. The two electrolyte solutions are connected in a circuit via an external ammeter and a load resistor. Adjusting the pH of the electrolyte solution to 7, the results show that the energy density in the external circuit is 23 W / m² in the absence of light. -2 .

[0056] Application Example 2: The salinity gradient under different salt solution concentration gradients can be converted into electrical energy.

[0057] Compared to Application Example 1, by changing the salt solution concentration gradient while keeping other conditions constant, the effect of different salt solution concentration gradients on the energy density of the external circuit was tested. It was found that when the salt solution concentration gradients were 5 and 500, the corresponding external circuit energy densities were 1.17 W / m², respectively. -2 and 82.3W / m -2 .

[0058] The results are as follows Figure 4 As shown, combined with the results of Application Example 1, it can be found that the salt energy difference is converted into electrical energy most efficiently when the salt solution concentration gradient is 500.

[0059] Application Example 3: Converting salinity gradient energy into electrical energy using photoresponsive heterogeneous nanofluidic membranes at different pH levels.

[0060] Compared to Application Example 1, when the pH of the electrolyte solution was adjusted to 3, 5, 9, and 10, the energy density in the external circuit was found to be 14.5 W / m². -2 15.92W / m -2 21.5W / m -2 and 20.7W / m -2 .

[0061] The results are as follows Figure 5 As shown, and in conjunction with the results of Application Examples 1-2, it can be illustrated that the electrolyte solution has the highest energy conversion efficiency at pH 7, with an external circuit energy density of 23 W / m². -2 .

[0062] Application Example 4: Photoresponsive heterogeneous nanofluidic membranes with different light intensities convert salinity gradient energy into electrical energy.

[0063] Compared to Application Example 1, when irradiated with the full spectrum, the light intensity is 25 mW / cm². -2 50mWcm -2 75mWcm -2 and 100mWcm -2 At that time, the corresponding external circuit energy density was 24.7 W / m. -2 27.3W / m -2 28.9W / m -2 and 36.4W / m-2 .

[0064] The results are as follows Figure 6 As shown, and in conjunction with the results of Application Examples 1-3, when the electrolyte solution pH is 7, the light intensity is 100 mW / cm². -2 It has the highest energy conversion efficiency, with an external circuit energy density of 36.4 W / m. -2 .

[0065] Application Example 5: Photoresponsive heterogeneous nanofluidic membranes with different illumination times convert salinity gradient energy into electrical energy.

[0066] Compared to Application Example 1, the light intensity was adjusted to 100 mW cm⁻¹ -2 When the illumination time is set to 5 min, 10 min, 15 min, and 20 min, the corresponding external circuit energy density is 25.4 W / m². -2 28.6W / m -2 31.7W / m -2 and 36.4W / m -2 .

[0067] The results are as follows Figure 7 As shown, and in conjunction with the results of Application Examples 1-4, when the electrolyte solution pH is 7, the light intensity is 100 mW / cm². -2 It exhibits the highest energy conversion efficiency when the illumination time is 20 minutes, with an external circuit energy density of 36.4 W / m². -2 .

[0068] Examples 2-5: Preparation of photoresponsive heterogeneous nanofluidic films with different cationic nanofiber contents

[0069] The difference between Examples 2-5 and Example 1 is that by changing the content of cationic nanofibers in the Co(OH)2 nanosheet dispersion in step (2), photoresponsive heterofluid membranes with cationic nanofiber contents of 0wt%, 0.5wt%, 3wt%, and 5wt% were obtained.

[0070] Application Example 6: Photoresponsive heterogeneous nanofluidic membranes with different cation nanofiber contents convert salt gradient energy into electricity.

[0071] able

[0072] Compared to Application Example 1, the photoresponsive heterogeneous nanofluidic membrane of Examples 2-5 was used instead of the photoresponsive heterogeneous nanofluidic membrane of Example 1, with other conditions remaining unchanged. The effect of different cationic nanofiber contents on the energy density of the external circuit was tested. It was found that when the cationic nanofiber contents were 0 wt%, 0.5 wt%, 3 wt%, and 5 wt%, the corresponding external circuit energy densities were 15.5 W / m², respectively.-2 18.26W / m -2 13.8W / m -2 and 11.2W / m -2 .

[0073] The results are as follows Figure 8 As shown, combined with the results of Application Example 1, it can be found that when the content of cationic nanofibers is 1 wt%, the efficiency of converting salt energy difference into electrical energy is the highest.

[0074] Examples 6-12, with different W 18 O 49 Preparation of photoresponsive heterogeneous nanofluidic films with high content

[0075] The difference between Examples 6-12 and Example 1 is that W in step (3) is changed. 18 O 49 The amount of nanowire dispersion and Co(OH)2 mixed dispersion used can be used to obtain the W in the photoresponsive heterogeneous nanofluid membrane. 18 O 49 The photoresponsive heterofluidic films were prepared with contents of 0 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, and 100 wt%. The thickness of the photoresponsive heterofluidic films was maintained at 10 μm.

[0076] Application Example 7, with different W 18 O 49 The photoresponsive heterogeneous nanofluidic membrane with high content converts salinity gradient energy into electrical energy.

[0077] Compared with Application Example 1, the samples prepared using Examples 6-12 have different W values. 18 O 49 A photoresponsive heterogeneous nanofluidic membrane with a different content was used instead of the photoresponsive heterogeneous nanofluidic membrane in Example 1, with other conditions remaining unchanged, and different W values ​​were tested. 18 O 49 The effect of content on the energy density of the external circuit was investigated. It was found that when the cationic nanofiber content was 0 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, and 100 wt%, the corresponding external circuit energy densities were 3.2 W / m². -2 7.0W / m -2 12.9W / m -2 18.5W / m -2 10.6W / m -2 and 6.6W / m -2 .

[0078] The results are as follows Figure 9As shown, combined with the results of application example 1, it can be found that when the cationic nanofiber content is 1 wt%, W 18 O 49 When the content is 50wt%, its efficiency in converting salt energy difference into electrical energy is the highest.

[0079] Application Example 8: Stability Testing of Salinity Difference Energy Generation System

[0080] The continuous system test in Application Example 1 showed that, with the electrolyte solution pH at 7 and without added electrolyte, the current decreased by 11.4% after 8 hours of the it test curve. After one month of testing, its power generation efficiency only decreased by 6%.

[0081] 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.

[0082] 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 photoresponsive heterogeneous nanofluidic membrane, characterized in that, The nanofluid membrane is a heterostructure formed by stacking two semiconductor materials with band matching layer by layer. One layer is a porous semiconductor membrane with photoresponse, and the other layer is a porous semiconductor membrane that promotes charge separation. The semiconductor membrane that promotes charge separation also contains cationic nanofibers. The two semiconductor membranes have opposite charges, some channels are interconnected, and the pore sizes are different. The content of photoresponsive semiconductor material in the nanofluidic membrane is 40-70 wt%; The photoresponsive semiconductor film is composed of stacked nanowire or nanosheet semiconductor materials, wherein the nanowire semiconductor material is tungsten oxide, molybdenum oxide or titanium dioxide, and the nanosheet semiconductor material is zinc indium sulfide or carbon nitride. The semiconductor film that promotes charge separation is composed of stacked nanosheet semiconductor materials, wherein the nanosheet semiconductor material is molybdenum sulfide, tungsten sulfide, cobalt hydroxide or nickel hydroxide.

2. The fluid membrane according to claim 1, characterized in that, The semiconductor film with photoresponsiveness has a thickness of 1-15 μm and a pore size of 2-120 nm, while the semiconductor film that promotes charge separation has a thickness of 1-15 μm and a pore size of 0.2-120 nm.

3. The method for preparing the photoresponsive heterogeneous nanofluidic film according to claim 1 or 2, characterized in that, The method described: A dispersion of a photoresponsive semiconductor material and a dispersion of a charge-separating semiconductor material containing cationic nanofibers are sequentially deposited layer by layer by vacuum filtration, spin coating, or self-assembly, and then subjected to heat treatment to obtain a photoresponsive heterofluidic membrane.

4. The method according to claim 3, characterized in that, The heat treatment temperature is 60-200℃, and the time is 2-24h.

5. The application of the photoresponsive heterogeneous nanofluid membrane according to claim 1 or 2 in a salinity gradient power generation system.

6. The application of the photoresponsive heterogeneous nanofluidic membrane according to claim 1 or 2 in a photo-assisted salt gradient power generation system.

7. A high-efficiency solar-assisted or non-solar-assisted salinity gradient energy generation system, characterized in that, The power generation system uses the photoresponsive heterogeneous nanofluid membrane as described in claim 1 or 2 as a diaphragm, with electrolyte solutions of different concentrations on both sides of the diaphragm, and the illumination is performed using an asymmetric irradiation method.

8. The power generation system according to claim 7, characterized in that, The electrolytes on both sides of the membrane are identical, the concentration difference of the electrolyte solutions on both sides of the membrane is 5-500 times, the pH of the electrolyte solutions is 3-10, and the power of the light irradiation is 0-600 mW / cm². 2 The duration is 0-30 days.

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