Preparation method and application of photoresponse heterogeneous nanofluid film

Abstract

The invention discloses a preparation method and application of a photoresponse heterogeneous nanofluid film. The invention belongs to the field of nanofluid films. The invention aims to solve the technical problems of complex preparation process and poor ion selectivity of the existing ion selective membrane. According to the fluid film, two semiconductor materials with matched energy bands are stacked layer by layer to form a heterostructure, one layer is a porous semiconductor film with photoresponse, the other layer is a porous semiconductor film for promoting charge separation, the semiconductor film for promoting charge separation further contains cation nanofibers, and the cation nanofibers can be used for preparing the fluid film. The two layers of semiconductor films are opposite in charge, and partial ducts are communicated and different in aperture. The fluid film is applied to a light-assisted or non-light-assisted salinity gradient energy power generation system.

Description

Technical Field

[0001] The invention belongs to the field of nanofluid films, and in particular relates to a preparation method and application of a light-responsive heterogeneous nanofluid film. Background Art

[0002] The consumption of fossil fuels has led to a sharp increase in environmental problems, forcing the search for renewable energy alternatives. Light-assisted salinity difference energy conversion can simultaneously utilize two green energies, salinity difference energy and solar energy, to effectively alleviate the energy crisis. Reverse electrodialysis (RED) technology uses ion-selective membranes to directly convert salinity difference energy into electrical energy. In addition, by applying external stimuli, ion transport can be regulated to promote salinity difference 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 the salinity difference energy power generation system.

[0003] At present, ion-selective membranes, as the key factor of RED, still have problems such as expensive raw materials, complex preparation process, poor ion selectivity, and inability to meet industrial applications. Therefore, it is necessary to design a nanofluid membrane with a simple preparation process, abundant and low-cost raw materials, large-scale preparation, and a wide range of applications for the salt difference energy conversion process to solve the existing defects. Summary of the invention

[0004] The purpose of the present invention is to solve the technical problems of complex preparation process and poor ion selectivity of existing ion selective membranes, and to provide a preparation method and application of a light-responsive heterogeneous nanofluid membrane.

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

[0006] One of the purposes of the present invention is to provide a light-responsive heterogeneous nanofluid membrane, wherein the nanofluid membrane is formed by stacking two semiconductor materials with energy band matching layer by layer to form a heterogeneous structure, wherein one layer is a porous semiconductor membrane with light response, and the other layer is a porous semiconductor membrane that promotes charge separation, wherein the semiconductor membrane that promotes charge separation also contains cationic nanofibers, and the two semiconductor membranes have opposite charges, partially interconnected pores, and different pore sizes.

[0007] It is further defined that the content of the semiconductor material having light response in the nanofluid film is 40-70 wt %.

[0008] It is further defined that the content of cationic nanofibers in the semiconductor membrane promoting charge separation is 0-3 wt %.

[0009] It is further defined that the semiconductor film with photoresponse is formed by stacking nanowire-shaped or nanosheet-shaped semiconductor materials.

[0010] It is further defined that the nanowire-shaped semiconductor material is tungsten oxide, molybdenum oxide or titanium dioxide, and the nanosheet-shaped semiconductor material is indium zinc sulfide or carbon nitride.

[0011] It is further defined that the semiconductor film promoting charge separation is formed by stacking nanosheet-like semiconductor materials.

[0012] It is further defined that the nanosheet semiconductor material is molybdenum sulfide, tungsten sulfide, cobalt hydroxide or nickel hydroxide.

[0013] It is further defined that the semiconductor film with photoresponse has a thickness of 1-15 μm and a pore size of 2-120 nm.

[0014] It is further defined that the semiconductor film promoting charge separation has a thickness of 1-15 μm and a pore size of 0.2-120 nm.

[0015] The second object of the present invention is to provide a method for preparing a light-responsive heterogeneous nanofluid film, the method being carried out according to the following steps:

[0016] A dispersion of a semiconductor material with light response and a dispersion of a semiconductor material containing cationic nanofibers that promotes charge separation are formed layer by layer in sequence by suction filtration, spin coating or self-assembly, and then heat treated to obtain a light-responsive heterogeneous nanofluid membrane.

[0017] It is further defined that the heat treatment temperature is 60-200° C., the time is 2-24 hours, and the atmosphere is air, nitrogen or argon.

[0018] The third object of the present invention is to provide an application of a light-responsive heterogeneous nanofluid membrane in a salt difference energy power generation system.

[0019] A fourth object of the present invention is to provide an application of a light-responsive heterogeneous nanofluid membrane in a light-assisted salt-difference energy power generation system.

[0020] The fifth object of the present invention is to provide a light-assisted or non-light-assisted salt difference energy power generation system with high efficiency, wherein the power generation system uses the above-mentioned light-responsive heterogeneous nanofluid membrane as a diaphragm, and electrolyte solutions with concentration differences are on both sides of the diaphragm, and light is irradiated in an asymmetric manner.

[0021] It is further defined that the electrolyte on both sides of the separator is the same.

[0022] It is further defined that the electrolyte is KCl, NaCl, MgCl2, LiCl or CaCl2.

[0023] It is further defined that the pH of the electrolyte solution is 3-10.

[0024] It is further defined that the concentration difference of the electrolyte solution on both sides of the separator is 5-500 times.

[0025] It is further defined that the electrode is a silver / silver chloride electrode, a copper electrode or a titanium-based ruthenium-coated electrode.

[0026] It is further defined that the light source is AM1.5, natural light, full light, ultraviolet light, visible light or near infrared light.

[0027] Further defined, the power of the light is 0-600mW / cm 2 , duration is 0-30 days.

[0028] Compared with the prior art, the present invention has the following advantages:

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

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

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

[0032] (4) The application of the light-responsive heterogeneous nanofluid membrane of the present invention in the salt difference energy generation system has obvious advantages. In the salt difference energy generation system simulating seawater (0.5M NaCl) and river water (0.01M NaCl), the maximum output power density reached 23W / m -2 , which 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 the present invention has a wide range of applications and can be used in electrolyte solutions with a pH of 3-10. During use, the thickness of the light-responsive heterogeneous nanofluid film can be adjusted according to the pH, thereby maximizing the energy conversion efficiency. In addition, the performance is stable. In the absence of an external electrolyte, after an 8-hour IT test curve, the current decayed by 11.4%. After 1 month of testing, its power generation efficiency only declined by 6%. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0036] Figure 3 This is a diagram of the system for converting salt difference energy into electrical energy according to the present invention;

[0037] Figure 4 It is the relationship diagram of current density, power generation density and external resistance under different salt solution concentration gradients in Application Example 2;

[0038] Figure 5 The relationship between power generation density and external resistance at different pH values ​​in Application Example 3;

[0039] Figure 6 This is a graph showing the relationship between power generation density and external resistance under different light intensities in Application Example 4;

[0040] Figure 7 The relationship diagram of current density, power generation density and external resistance under different illumination time in Application Example 5;

[0041] Figure 8 The relationship between power generation density and external resistance at different cationic nanofiber contents in Application Example 6;

[0042] Fig. 9 For different W in Application Example 7 18 O 49 Relationship between power generation density and external resistance under different content. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0044] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained through commercial channels by those skilled in the art.

[0045] Example 1

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

[0047] (1) 0.1 g of W 18 O 49 Nanowires (diameter 10-45nm) were added to 100mL of water and configured as W 18 O 49 a dispersion of nanowires;

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

[0049] (3) First, a polycarbonate filter membrane with a pore size of 0.1 μm was fixed on the sand core of the vacuum filtration device, and then W 18 O 49 The dispersion of nanowires was fixed on a polycarbonate filter membrane by suction filtration to obtain a photoresponsive W nanowire with a thickness of 4 μm and a pore size of 23.4 nm and three-dimensional channel interconnection. 18 O 49 The nanowire film is then fixed on the W by filtration, using a semiconductor material that matches the energy band of the photoresponsive semiconductor, namely, a dispersion of Co(OH)2 nanosheets containing cationic nanofibers. 18 O 49 On the nanowire film, a semiconductor layer with a thickness of 6 μm and a pore size of 0.45 nm was obtained, which has the function of promoting charge separation;

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

[0051] The photoresponsive heterogeneous nanofluid film described in this embodiment can form a built-in electric field under light, which promotes the separation of photogenerated charges and directional transport of ions; wherein W 18 O 49The surface of the nanowire has a high surface negative charge, and the constructed nanofluidic channel provides a three-dimensional interconnected structure, thus obtaining high ion flux and excellent ion selectivity. 18 O 49 The nanowires have high light absorption in almost the entire spectrum due to the surface plasmon resonance effect. The surface of Co(OH)2 nanosheets has a high positive charge, which is similar to W 18 O 49 The nanowires form a heterostructure with opposite charges and asymmetric pore sizes. In addition, the cobalt hydroxide nanosheets and W 18 O 49 The heterostructure formed by the nanowires promotes charge separation, increases ion flux and ion selectivity under light irradiation, and achieves high salt difference energy conversion efficiency.

[0052] The scanning electron microscopy image of the Co(OH)2@CNFs film surface is shown in Figure 1 As shown in (a), W 18 O 49 Scanning electron microscope image of the film surface Figure 1 (b) shows the SEM image of the cross section of the nanofluid film. Figure 1 As shown in (c), from Figure 1 It can be seen that the heterogeneous film thickness is 10μm, W 18 O 49 The Co(OH)2@CNFs membrane side is composed of nanowires with a thickness of 4 μm, while the Co(OH)2@CNFs membrane side is composed of nanosheets and nanofibers with a membrane thickness of 6 μm.

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

[0054] Application example 1: Converting salt difference into electrical energy

[0055] like Figure 3 As shown, the device for converting salt difference into electrical energy is a closed system, with a 0.5M NaCl electrolyte solution in the left container and a 0.01M NaCl electrolyte solution in the right container. The electrodes are silver / silver chloride electrodes. The light-responsive heterogeneous nanofluid membrane prepared in Example 1 is installed in the middle of the two containers and fixed with screws. 18 O 49The membrane faces the high concentration solution side, and the Co(OH)2CNFs membrane faces the low concentration side. The two electrolyte solutions are connected through an external ammeter and a load resistor. The pH of the electrolyte solution is adjusted to 7. The results show that when there is no light, the energy density in the external circuit is 23W / m -2 .

[0056] Application Example 2: Salt difference under different salt solution concentration gradients can be converted into electrical energy

[0057] Compared with Application Example 1, by changing the concentration gradient of the salt solution and keeping other conditions unchanged, the influence of different salt solution concentration gradients on the energy density in the external circuit is tested. It can be found that when the salt solution concentration gradients are 500 and 500 respectively, the corresponding external circuit energy density is: 1.17W / m -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 solution concentration gradient is 500, and the efficiency of converting salt energy difference into electrical energy is the highest.

[0059] Application Example 3: Converting salt difference energy into electrical energy using light-responsive heterogeneous nanofluid membranes at different pH values

[0060] Compared with Application 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 14.5 W / m -2 、15.92W / m -2 、21.5W / m -2 and 20.7W / m -2 .

[0061] The results are as follows Figure 5 As shown in Figure 2, combined with the results of Application Examples 1-2, it is shown that when the pH of the electrolyte solution is 7, it has the highest energy conversion efficiency and the external circuit energy density is 23W / m -2 .

[0062] Application Example 4: Photoresponsive heterogeneous nanofluid membranes with different light intensities convert salt difference energy into electrical energy

[0063] Compared with Application Example 1, when full spectrum irradiation is performed, the light intensity is set to 25mWcm -2 , 50mWcm -2 , 75mWcm -2 and 100mWcm -2 When the corresponding external circuit energy density is: 24.7W / 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 in the figure, combined with the results of application examples 1-3, when the pH of the electrolyte solution is 7 and the light intensity is 100mWcm -2 , has the highest energy conversion efficiency, and the external circuit energy density is 36.4W / m -2 .

[0065] Application Example 5: Photoresponsive heterogeneous nanofluid membranes with different illumination times convert salt difference energy into electrical energy

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

[0067] The results are as follows Figure 7 As shown in the figure, combined with the results of application examples 1-4, when the pH of the electrolyte solution is 7 and the light intensity is 100mWcm -2 When the illumination time is 20 minutes, it has the highest energy conversion efficiency and the external circuit energy density is 36.4W / m -2 .

[0068] Example 2-5: Preparation of light-responsive heterogeneous nanofluid membranes with different cationic nanofiber contents

[0069] The difference between Example 2-5 and Example 1 is that by changing the cationic nanofiber content in the Co(OH)2 nanosheet dispersion in step (2), light-responsive heterogeneous nanofluid films with cationic nanofiber contents of 0wt%, 0.5wt%, 3wt% and 5wt% are obtained respectively.

[0070] Application Example 6: Photoresponsive heterogeneous nanofluid membranes with different cationic nanofiber contents convert salt difference energy into electricity

[0071] able

[0072] Compared with Application Example 1, the light-responsive heterogeneous nanofluid membrane of Example 1 is replaced by the light-responsive heterogeneous nanofluid membrane of Example 2-5, and other conditions remain unchanged. The influence of different cationic nanofiber contents on the energy density in the external circuit is tested. It can be found that when the cationic nanofiber contents are 0wt%, 0.5wt%, 3wt%, and 5wt%, respectively, the corresponding external circuit energy densities are: 15.5W / m-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 cationic nanofiber content is 1wt%, the efficiency of converting the salt energy difference into electrical energy is the highest.

[0074] Embodiment 6-12, with different W 18 O 49 Preparation of light-responsive heterogeneous nanofluid films

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

[0076] Application Example 7: With different W 18 O 49 Photoresponsive heterogeneous nanofluid membranes convert salt difference energy into electricity

[0077] Compared with Application Example 1, the samples prepared in Examples 6-12 have different W 18 O 49 The light-responsive heterogeneous nanofluid film with a content of 1 was substituted for the light-responsive heterogeneous nanofluid film of Example 1, and other conditions remained unchanged. 18 O 49 The influence of content on the energy density in the external circuit shows that when the cationic nanofiber content is 0wt%, 30wt%, 40wt%, 50wt%, 60wt%, 70wt% and 100wt%, the corresponding external circuit energy density is 3.2W / m -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 Fig. 9As shown, combined with the results of Application Example 1, it can be found that when the cationic nanofiber content is 1wt%, W 18 O 49 When the content is 50wt%, the efficiency of converting salt energy difference into electrical energy is the highest.

[0079] Application Example 8: Stability test of salt difference energy power generation system

[0080] The system of Application Example 1 was continuously tested. The results showed that the pH of the electrolyte solution was 7. In the absence of an 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 declined by 6%.

[0081] Tests have shown that under different lighting conditions, the salt difference energy generation system containing the photoresponsive heterogeneous nanofluid membrane has stable current output performance and energy conversion efficiency.

[0082] The above are only preferred specific embodiments of the present invention, which are all different implementations based on the overall concept of the present invention, and the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A photoresponsive heterogeneous nanofluid film, characterized in that: The nanofluid membrane is formed by stacking two semiconductor materials with energy band matching layer by layer to form a heterogeneous structure. One layer is a porous semiconductor membrane with light response, 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 layers of semiconductor membranes have opposite charges, some pores are interconnected, and the pore sizes are different.

2. The fluid film according to claim 1, characterized in that The content of semiconductor material with light response in the nanofluid film is 40-70wt%, and the content of cationic nanofiber in the semiconductor film promoting charge separation is 0-3wt%.

3. The fluid film according to claim 1, characterized in that The semiconductor film with light response is formed by stacking nanowire or nanosheet semiconductor materials, wherein the nanowire semiconductor material is tungsten oxide, molybdenum oxide or titanium dioxide, and the nanosheet semiconductor material is indium zinc sulfur or carbon nitride. The semiconductor film promoting charge separation is formed by stacking nanosheet semiconductor materials, and the nanosheet semiconductor material is molybdenum sulfide, tungsten sulfide, cobalt hydroxide or nickel hydroxide.

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

5. The method for preparing the light-responsive heterogeneous nanofluid film according to any one of claims 1 to 4, characterized in that: The method: A dispersion of a semiconductor material with light response and a dispersion of a semiconductor material containing cationic nanofibers that promotes charge separation are formed layer by layer in sequence by suction filtration, spin coating or self-assembly, and then heat treated to obtain a light-responsive heterogeneous nanofluid membrane.

6. The method according to claim 5, characterized in that The heat treatment temperature is 60-200°C and the time is 2-24h.

7. Application of the light-responsive heterogeneous nanofluid membrane according to any one of claims 1 to 4 in a salt difference energy power generation system.

8. Use of the light-responsive heterogeneous nanofluid membrane according to any one of claims 1 to 4 in a light-assisted salt-difference energy generation system.

9. A highly efficient light-assisted or non-light-assisted salt difference energy power generation system, characterized in that: The power generation system uses the light-responsive heterogeneous nanofluid membrane described in any one of claims 1 to 4 as a diaphragm, electrolyte solutions with concentration differences are provided on both sides of the diaphragm, and light is irradiated in an asymmetric manner.

10. The power generation system according to claim 9, characterized in that: The electrolytes on both sides of the diaphragm are 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, and the power of the light is 0-600mW / cm 2 , duration is 0-30 days.

Images