Heterogeneous thin film based on MXene / semiconductor, preparation method of heterogeneous thin film and salinity gradient energy recovery power generation device

Abstract

The invention provides an MXene / semiconductor-based heterogeneous thin film and a preparation method thereof, and a salinity gradient energy recovery power generation device, the heterogeneous thin film comprises a semiconductor layer and an MXene layer which are stacked and connected together, and the semiconductor layer is formed by stacking n-type semiconductor nanosheets. According to the heterogeneous thin film, the photothermal effect of an MXene material and the photoelectric effect of a semiconductor-metal heterojunction can be utilized to promote ion transmission, and the recovery performance of salinity gradient energy is improved; when the MXene / semiconductor-based heterogeneous thin film is used as a semipermeable film, positive ions in a high-salinity solution pass through the heterogeneous thin film under the pushing of salinity difference and migrate into a low-salinity solution so as to form internal current.

Description

Technical Field

[0001] The present invention belongs to the technical field of salt difference energy power generation, and relates to a technology of combining solar energy with salt difference energy and converting them into electrical energy. More specifically, it relates to a MXene / semiconductor-based heterogeneous film and a preparation method thereof, and a salt difference energy recovery power generation device. Background Art

[0002] Environmental pollution, energy shortage and the resulting climate change are the urgent problems to be solved in human development. The development and utilization of new energy sources have become the theme of the times. Developing clean energy and promoting energy transformation are the general trend for human society to achieve sustainable development. Research on the development of salinity difference energy in natural seawater, brackish water, brine and industrial high-salt wastewater has also become an emerging research field towards the goal of carbon neutrality. Among them, reverse electrodialysis (RED) is a promising strategy to obtain electrical energy from salinity difference by using ion-selective membranes. In this technology, the membrane with ion exchange properties is the core element of reverse electrodialysis technology. Due to its inherent surface charge, the two-dimensional nanofluid channel will form an electric double layer (EDL) on both sides of the channel, thereby attracting ions with opposite charges in the solution at the solid-liquid interface, thereby playing a role in the selective permeability of ions. However, the efficiency of recovering salinity difference energy by simple reverse electrodialysis is limited. How to couple reverse electrodialysis technology with other technologies to achieve more effective recovery of salinity difference energy is still lacking. Summary of the invention

[0003] The purpose of the present invention is to provide a MXene / semiconductor-based heterogeneous film and a preparation method thereof and a salt difference energy recovery power generation device, which can utilize the photothermal effect of MXene materials and the photoelectric effect of semiconductor-metal heterojunction to promote ion transport and improve the recovery performance of salt difference energy.

[0004] The present invention is achieved through the following technical solutions: A MXene / semiconductor-based heterogeneous film comprises a semiconductor layer and a MXene layer which are stacked and connected together, wherein the semiconductor layer is formed by stacking n-type semiconductor nanosheets.

[0005] Preferably, the two-dimensional nanosheets are ZnIn2S4 or CdS.

[0006] Preferably, the MXene layer is composed of Ti3C2T x Nanosheets are formed by stacking layer upon layer.

[0007] Preferably, the thickness of the heterogeneous film is 6 to 60 microns, the thickness of the semiconductor layer is 5 to 50 microns, and the thickness of the MXene layer is 1 to 10 microns.

[0008] The method for preparing the MXene / semiconductor-based heterogeneous film of the present invention comprises the following steps: S1, coating the MXene solution on the porous substrate to form a MXene layer; S2, coating the semiconductor nanosheet solution on the MXene layer, drying, forming a semiconductor layer on the MXene layer, and obtaining a heterogeneous film based on MXene / semiconductor materials.

[0009] Preferably, in S1, the porous substrate is a polyvinylidene fluoride membrane, and in S2, after drying, the heterogeneous film is separated from the substrate.

[0010] Preferably, in S1, the preparation method of the MXene solution is: dissolving LiF in hydrochloric acid to obtain a LiF solution, then adding a Ti3AlC2 precursor to the LiF solution and sealing it, stirring and etching; repeatedly washing the etched solution by centrifugation, and after a dark green color appears, centrifuging the solution to obtain an upper layer of MXene solution; wherein the concentration of hydrochloric acid is 9~12 mol / L.

[0011] The present invention also provides a salt difference energy recovery power generation device, comprising a first liquid pool, a second liquid pool and the MXene / semiconductor-based heterogeneous film; one side of the first liquid pool is connected to one side of the second liquid pool through the MXene / semiconductor heterogeneous film, the first liquid pool is located on the semiconductor layer side of the heterogeneous film, and the second liquid pool is located on the MXene layer side of the MXene / semiconductor heterogeneous film; the first liquid pool is used to hold a high-salinity solution, and the second liquid pool is used to hold a low-salinity solution, and the electrolyte concentration of the high-salinity solution is higher than the electrolyte concentration of the low-salinity solution; an anode is provided in the first liquid pool, and a cathode is provided in the second liquid pool. Preferably, the power generation device also includes a light source, the other side of the first liquid pool is optical glass, the light source is connected to an optical fiber, and the light of the optical fiber passes through the optical glass and is vertically incident on one side of the semiconductor layer based on the MXene / semiconductor heterogeneous film.

[0012] Preferably, the low-salinity solution and the high-salinity solution are seawater, salt lake brine or industrial high-salinity wastewater.

[0013] Compared with the prior art, the present invention has the following beneficial effects: The present invention combines a MXene material with extremely high light-to-heat conversion efficiency with a semiconductor material that can produce electron-hole separation under illumination to form a semiconductor-metal heterojunction, which can generate a built-in electric field between the semiconductor and the MXene material. At the same time, since the MXene material itself has excellent conductivity and charge storage capacity, when the semiconductor material is excited under illumination, the electrons can be stored in the MXene material in large quantities, which improves the stability of the built-in electric field, so that the structure can still maintain efficient salt difference energy conversion efficiency when the external illumination conditions are unstable. On the other hand, the MXene material has a plasma resonance effect, which ensures that light energy is converted into heat energy under illumination, thereby forming a temperature difference between the semiconductor and MXene materials. When the MXene / semiconductor heterogeneous film is used as a semipermeable membrane in a salt difference energy recovery power generation device, the transmission of ions in the nanoscale restricted channel is affected by the photothermal effect of the MXene material and the photoelectric effect of the semiconductor material. The temperature difference between the two materials and the built-in electric field play a dual role in promoting ion transmission. In the experiment, it shows excellent salt difference energy conversion characteristics, and produces a higher output power density in the actual salt difference energy recovery system composed of seawater and river water. The present invention combines the advantages of MXene materials and semiconductor materials, solves many problems in the prior art, and has good application prospects in the field of salt difference power generation. In the present invention, although the MXene / semiconductor heterogeneous film has a layered structure, the interlayers are tightly stacked, the mechanical properties are good, the transmission channel is continuous, and a temperature difference system can be effectively formed on both sides; and the heterogeneous film also has the advantages of low production cost, strong stability, and strong self-cleaning ability, and has broad application prospects in the field of recovering salt difference energy by reverse electrodialysis technology.

[0014] Furthermore, the present invention selects a suitable heterogeneous film and a thickness ratio of the semiconductor layer and the MXene layer to promote ion transport and improve the salt difference energy recovery efficiency without increasing the channel path that the cations need to pass through.

[0015] The method for preparing the MXene / semiconductor heterogeneous film of the present invention is simple to operate and easy to implement.

[0016] Furthermore, the porous substrate of the present invention adopts a polyvinylidene fluoride membrane, and the MXene / semiconductor heterogeneous film and the polyvinylidene fluoride membrane can be automatically separated, thereby avoiding the influence of the porous substrate on ion transmission.

[0017] Furthermore, the present invention increases the vacancy defect density on the surface of the Mxene material by increasing the etching solution concentration, which can minimize the electron-hole recombination in a short time to ensure that the intensity of the built-in electric field is stable within a certain range, and further ensure the stability of the built-in electric field.

[0018] The salt difference energy recovery power generation device of the present invention uses the above-mentioned MXene / semiconductor-based heterogeneous film as a semipermeable membrane. The cations in the high-salinity solution pass through the heterogeneous film under the promotion of the salinity difference and migrate to the low-salinity solution to form an internal current. When light is irradiated on the semiconductor material, the excited electrons jump from the valence band to the conduction band and then transfer to the surface of the MXene material to form a built-in electric field, wherein the electric field force provided by the built-in electric field to the cations is the same as the direction in which the cations penetrate due to the salinity difference at this time. At the same time, the MXene material has a good photothermal effect and can convert light energy into thermal energy. After that, a temperature difference is generated between the MXene layer side and the semiconductor layer side. According to the Gibbs free energy formula, the ions will move from the lower temperature side to the higher temperature side, and the promotion direction is consistent with the direction of ion transport promotion caused by the built-in electric field and the salinity difference. Therefore, the heterogeneous film based on MXene / semiconductor promotes ion transport through both temperature difference and built-in electric field, thereby improving the efficiency of salt difference energy recovery. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 This is a scanning electron microscope image of the MXene / semiconductor-based heterogeneous film in Example 1.

[0021] Figure 2 A schematic diagram of the device for recovering power generation from salinity difference energy under illumination used in Example 1 is shown.

[0022] Figure 3 It is the power density generated by the device in artificially simulated seawater / river water test environment. DETAILED DESCRIPTION

[0023] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0024] It should be noted that the process equipment or devices not specifically specified in the following embodiments are all conventional equipment or devices in the art.

[0025] It should be noted that the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or to define the scope of the present invention. Changes or adjustments in their relative relationships should also be regarded as the scope of the present invention without substantially changing the technical content.

[0026] The MXene / semiconductor-based heterogeneous film of the present invention comprises a MXene layer and a semiconductor layer which are stacked and connected together, and the semiconductor layer is formed by stacking n-type semiconductor nanosheets.

[0027] It should be noted that the heterogeneous film of the present invention has a layered structure, but the semiconductor layer and the MXene layer are tightly stacked together, with good mechanical strength, continuous transmission channels and the ability to effectively establish a semiconductor heterojunction and a temperature difference system. The semiconductor layer as the excited electron side can be effectively transmitted to the MXene side to form a built-in electric field, and the MXene material can convert light energy into heat energy through the plasma resonance effect to form a high-temperature side, thereby promoting the transmission of ions to the high-temperature side.

[0028] In the present invention, the thickness of the MXene and n-type semiconductor nanosheets is at the nanometer level, and the lateral dimensions are at the micrometer level.

[0029] In the present invention, the n-type semiconductor nanosheet is a ZnIn2S4 two-dimensional nanosheet or a CdS two-dimensional nanosheet, and other n-type semiconductor materials that have been proven by research can also be selected. x Nanosheets are formed by stacking layer upon layer.

[0030] In the present invention, the thickness of the heterogeneous film is 6 to 60 microns, the thickness of the MXene layer is about 1 to 10 microns, and the thickness of the semiconductor layer is about 5 to 50 microns.

[0031] The method for preparing the MXene / semiconductor-based heterogeneous film of the present invention comprises the following steps: S1, coating a MXene solution on a porous substrate to form a MXene layer on the porous substrate; S2, coating the n-type semiconductor nanosheet solution on the MXene layer, drying, forming a semiconductor layer on the MXene layer, and obtaining a MXene / semiconductor-based heterogeneous film.

[0032] In a specific embodiment of the present invention, the n-type semiconductor nanosheet solution is a single-layer ZnIn2S4 nanosheet solution or a single-layer CdS nanosheet solution; its preparation process is: first, the prepared semiconductor material is centrifuged to remove thicker blocks, and then the solution is ultrasonicated in a water bath ultrasonic instrument for several hours, and then the peeled single-layer nanosheet is further centrifuged to obtain the upper single-layer semiconductor nanosheet solution.

[0033] The preparation materials of the single-layer ZnIn2S4 nanosheet are zinc nitrate, indium trichloride and thioacetamide; the specific molar mass ratio thereof is 1:2:8, and the excess sulfur element is used to enhance the surface electronegativity.

[0034] In a specific embodiment of the present invention, the MXene solution is a single layer Ti3C2T x The preparation process of the nanosheet solution is as follows: weigh 1.6-2.0 g LiF and dissolve it in 9-12 mol / L hydrochloric acid, and stir and dissolve it in a water bath to generate HF; then weigh Ti3AlC2 precursor and add it to the dissolved solution and seal it, and then continue to stir and etch in a water bath; finally, the etched solution is repeatedly washed by low-speed centrifugation, and after a dark green color appears, the upper single-layer Ti3C2Tx nanosheet solution is obtained by low-speed centrifugation.

[0035] In a specific embodiment of the present invention, the porous substrate is a polyvinylidene fluoride membrane. The pore size of the porous substrate is nanometer-level, and the porous substrate can filter out excess water, so that the MXene material and the semiconductor material are deposited on the surface of the porous substrate in sequence. The present invention preferably uses a polyvinylidene fluoride membrane with a pore size of 0.22 microns. After drying, the semiconductor / MXene heterogeneous film is separated from the porous substrate.

[0036] The salt difference energy recovery power generation device of the present invention comprises a first liquid pool, a second liquid pool and the MXene / semiconductor heterogeneous film as described above; one side of the first liquid pool is connected to one side of the second liquid pool through the MXene / semiconductor heterogeneous film, the first liquid pool is located on the semiconductor layer side of the heterogeneous film, and the second liquid pool is located on the MXene layer side of the heterogeneous film; the first liquid pool is used to hold a high-salinity solution, and the second liquid pool is used to hold a low-salinity solution, and the electrolyte concentration of the high-salinity solution is higher than the electrolyte concentration of the low-salinity solution; an anode is provided in the first liquid pool, and a cathode is provided in the second liquid pool, and the cathode and the anode are connected to an external circuit.

[0037] The present invention can be provided with a light source, or can use sunlight as the light source. The light emitted by the light source is vertically incident on one side of the semiconductor layer of the heterogeneous film.

[0038] In a specific embodiment of the present invention, a flow opening is provided on one side of the first liquid pool and one side of the second liquid pool, and the MXene / semiconductor heterogeneous film is arranged between the flow opening of the first liquid pool and the flow opening of the second liquid pool through a gasket.

[0039] In a specific embodiment of the present invention, the other side of the first liquid pool is optical glass, the light source is connected to an optical fiber, and the light of the optical fiber passes through the optical glass and is vertically incident on one side of the semiconductor layer of the MXene / semiconductor heterogeneous film.

[0040] The anode and cathode are two electrodes of the same type that can undergo redox reactions and transfer electrons. The electrodes that can undergo redox reactions are two Ag / AgCl electrodes of the same type.

[0041] The low-salinity solution and the high-salinity solution can be made of salt water such as seawater, salt lake brine, industrial high-salinity wastewater, etc., and the ions contained include Li + 、Na + , K + Mg 2+ , Ca 2+ , Cl - or Br - The concentration of the high salinity solution is 0.1 mol / L to 5 mol / L, preferably 0.5 mol / L, and the concentration of the low salinity solution is 10 -6 ~10 -2 mol / L, preferably 10 -2 mol / L.

[0042] The salt difference energy recovery power generation device of the present invention is a reverse electrodialysis device. A high-salinity solution and a low-salinity solution form a salt difference. The cations in the high-salinity solution pass through the heterogeneous membrane under the impetus of the salinity difference and migrate to the low-salinity solution to form an internal current, thereby converting the salt difference chemical energy between the high-concentration salt solution and the low-concentration salt solution into electrical energy through the device.

[0043] When the salt difference energy recovery power generation device of the present invention is in use, a heterogeneous film having both photoelectric and photothermal effects is placed between two liquid pools, and electrolytes of different concentrations are contained in the liquid pools on both sides to simulate seawater and river water. The high-salinity solution simulating seawater is placed on one side of the semiconductor layer, and the low-salinity solution simulating river water is placed on one side of the MXene layer. The xenon lamp light source is guided to the center of the device facing the membrane through an optical fiber. When the simulated light source is turned on, the light first contacts the semiconductor material, excites electrons to transition from the valence band to the conduction band and then to the surface of the MXene material, so as to form a built-in electric field for electrons to transfer from the semiconductor side to the MXene side, wherein the electric field force provided by the built-in electric field to the cations is the same as the penetration direction of the cations due to the salinity difference at this time. At the same time, the MXene side has a good photothermal effect, which can better convert light energy into heat energy. Then, a temperature difference is generated between the MXene side and the semiconductor layer side. According to the Gibbs free energy formula, ions will move from the lower temperature side to the higher temperature side. The promotion direction is consistent with the direction of ion transport promoted by the built-in electric field and salinity difference mentioned above. Finally, the semiconductor photoelectric heterojunction effect and the MXene photothermal effect are used to jointly promote ion transport in the nanochannel and improve the salt difference energy conversion efficiency.

[0044] Example 1 The present embodiment provides a method for preparing a semiconductor / MXene heterogeneous film, and an application method of the semiconductor / MXene heterogeneous film obtained by the preparation method for salt difference energy recovery and power generation.

[0045] The preparation and testing method comprises the following steps: Step 1: Weigh 1.6 g LiF and dissolve it in 9 mol / L hydrochloric acid. Stir and dissolve it in a 45°C water bath for 15 min. Then weigh 1 g Ti3AlC2 precursor and add it to the dissolved solution and seal it. Stir and etch it in a 45°C water bath for 24 h. Wash the etched solution repeatedly by low-speed centrifugation. After it turns dark green, centrifuge the solution at 4000 rpm for 60 min to obtain Ti3C2T x Nanosheet solution, at this time the solution pH is about 5.

[0046] Step 2: Take the Ti3C2T obtained in step 1 x Nanosheet solution, the nanosheets are stacked in parallel on a polyvinylidene fluoride membrane substrate with a pore size of 0.22µm and a diameter of 43 mm to obtain a MXene layer. The thickness of the film is determined by the Ti3C2T x The nanosheet solution concentration was calculated based on the volume of solution added.

[0047] Step 3: First, synthesize bulk ZnIn2S4 by hydrothermal method. The specific steps are as follows: first, mix 0.33 g zinc sulfate heptahydrate and 0.88 g indium trichloride in a beaker, stir at room temperature for half an hour, then add 0.6 g thioacetamide and continue stirring for half an hour. Then, heat the solution in the beaker to 95°C and stir vigorously for 5 h. Then, centrifuge the solution several times at high speed and wash it until the pH is neutral to obtain a golden ZnIn2S4 block. Then, dissolve it in 200 mL ultrapure water, and use ultrasound to peel off the bulk ZnIn2S4 into a single layer of nanosheets. Finally, centrifuge it at 4000 rpm for 60 min to remove the upper semiconductor nanosheet solution.

[0048] Step 4: Take the semiconductor nanosheet solution prepared in step 3, stack the nanosheets in parallel on the MXene layer that has been stacked in step 2, and then separate the heterogeneous film from the substrate after drying for 24 hours, thereby obtaining a semiconductor / MXene heterogeneous film. The thickness of the heterogeneous film is calculated by the mass concentration of MXene and semiconductor nanosheet solutions and the volume of the added nanosheet colloidal solution.

[0049] like Figure 1 As shown, it is a scanning electron microscope image of the MXene / semiconductor-based heterogeneous film in Example 1. The image results show that the two-dimensional heterogeneous film has a complete cross-section, a uniform layered structure, and no obvious cracks.

[0050] Take the heterogeneous film described in step 4 and place it on Figure 2 The center of the salt difference energy recovery power generation device shown. The semiconductor / MXene heterogeneous film used for ion exchange in the device has a total thickness of 6 µm, of which the MXene layer is 1 µm and the semiconductor layer is 5 µm thick. The electrode uses an Ag / AgCl electrode with a diameter of 1 mm. The liquid pools on both sides are high-salinity solution and low-salinity solution, respectively, using KCl solutions used to simulate seawater and river water. The molar concentration ratio of the high-salinity solution to the low-salinity solution is 50:1, the KCl concentration in the high-salinity solution is 0.5 mol / L, and the KCl concentration in the low-salinity solution is 0.01 mol / L.

[0051] The above-mentioned salt difference energy recovery power generation device is used to generate electricity. Specifically, the power generation process of the heterogeneous film for salt difference energy recovery is promoted under light conditions: K in the high salinity solution + Driven by the salinity difference, it migrates through the heterogeneous film to the low-salinity solution to form an internal current, which is related to K + The migration direction is the same. The specific reaction equation occurring at the anode electrode in the high salinity solution is: , the generated electrons are transmitted to the cathode electrode in the low-salinity solution through an external circuit to form an external current. A variable resistor box is connected to the external circuit. During the test, the maximum power density of the device is obtained when the external resistance is adjusted to be consistent with the internal resistance of the device. The light source is irradiated onto the heterogeneous film in the center of the device using an optical fiber. The light first contacts the semiconductor material, exciting electrons to transition from the valence band to the conduction band and then transfer to the surface of the MXene material to form a built-in electric field. The electric field force provided by the built-in electric field to the cations is the same as the direction in which the cations penetrate due to the salinity difference at this time. At the same time, the MXene material has a good photothermal effect and can better convert light energy into heat energy. After that, a temperature difference is generated between the MXene layer side and the semiconductor layer side. According to the Gibbs free energy formula, ions will move from the lower temperature side to the higher temperature side, and the promotion direction is consistent with the direction of ion transport promotion caused by the built-in electric field and the salinity difference as mentioned above. Figure 3 The results show that when the external resistance is 30 kΩ, the output power density of the salt difference energy recovery power generation device is 5.99 W / m 2 .

[0052] Example 2 The difference between this embodiment and embodiment 1 is that the concentration of the etchant in the preparation of the MXene material in step 1 is: Weigh 2.0 g LiF and dissolve it in 12 mol / L hydrochloric acid. Stir and dissolve it in a 45°C water bath for 15 min. Then weigh 1 g Ti3AlC2 precursor and add it to the dissolved solution and seal it. Stir and etch it in a 45°C water bath for 24 h. Wash the etched solution repeatedly by low-speed centrifugation. After it turns dark green, centrifuge the solution at 4000 rpm for 60 min to obtain Ti3C2T x Nanosheet solution, the solution pH is 5 at this time.

[0053] Since increasing the concentration of the etchant will also change the density of metal vacancies in the MXene material, adjusting the original etchant concentration of about 6 wt% to 8 wt% can obtain more vacancy clusters. When forming a heterostructure with semiconductor materials to build an electric field, it can prevent electron-hole recombination in a short period of time. After stability testing, the output power density of the modified MXene / semiconductor heterostructure used in the salt difference energy recovery power generation device can be maintained at 6.19 W / m within 7 days. 2 About, which is improved compared with Example 1.

[0054] Example 3 The difference between this embodiment and embodiment 1 is the type of semiconductor material and its preparation method in step 3: Preparation steps of bulk CdS precursor: First, add chromium chloride hydrate (0.0732 g), sulfur powder (0.064 g) and diethyltriamine (DETA, 12 mL) into a 30 mL autoclave. The mixture was stirred vigorously for 30 min to form a uniform suspension. Then the autoclave was sealed and placed in an oven and heated at 80°C for 48 hours. After cooling to room temperature, the light yellow precipitate was collected by centrifugation, washed by centrifugation with ethanol and distilled water respectively, and the final product was dried at 60°C for 6 h to obtain a yellow solid powder. After that, the dried CdS precursor powder was dispersed in ultrapure water, cysteic acid was added, and 0.1 mL of DETA was drawn with a 100 µL pipette and dropped into a beaker. After sealing the beaker with plastic wrap, it was placed in a constant temperature water bath sonicator and sonicated in a low-power sonic bath for 4 h to obtain a yellow dispersion. The dispersion was centrifuged at 3500 rpm for 60 min to remove large particles and unpeeled multilayer nanosheets, thereby obtaining a semiconductor nanosheet solution containing a large number of single-layer CdS nanosheets.

[0055] Example 4 This embodiment provides a device and application method for recovering salinity difference energy using a heterogeneous film with high-efficiency light-responsive ion transport.

[0056] See also Figure 2 The salt difference energy recovery power generation device includes a first liquid pool, a second liquid pool, a light source and a semiconductor / MXene heterogeneous film prepared in Example 1; a flow port is provided on one side of the first liquid pool and one side of the second liquid pool, and the semiconductor / MXene heterogeneous film is arranged between the flow port of the first liquid pool and the flow port of the second liquid pool through a gasket. The first liquid pool is located on the semiconductor layer side of the semiconductor / MXene heterogeneous film, and the second liquid pool is located on the MXene layer side of the semiconductor / MXene heterogeneous film; the first liquid pool contains a high-salinity solution, and the second liquid pool contains a low-salinity solution, the KCl concentration in the high-salinity solution is 0.5 mol / L, and the KCl concentration in the low-salinity solution is 0.01 mol / L; the first liquid pool is provided with an Ag / AgCl electrode, and the second liquid pool is provided with an Ag / AgCl electrode, and the cathode and anode are connected to an external circuit, and the external circuit is connected to a variable resistor box and a source meter for testing; the other side of the first liquid pool is optical glass, and the light source is connected to an optical fiber, and the light of the optical fiber is vertically incident on the semiconductor layer side of the semiconductor / MXene heterogeneous film through the optical glass. The light source is a xenon lamp, which is used to simulate actual sunlight.

[0057] Comparative Example 1 The difference between this embodiment and embodiment 1 is that the base material in step 2 is: Take the Ti3C2T obtained in step 1 xThe nanosheet solution was stacked in parallel on a nylon membrane substrate with a pore size of 0.22 µm and a diameter of 43 mm to obtain a MXene layer. The semiconductor / MXene heterogeneous film prepared in this example could not be separated from the substrate after drying for 24 hours, resulting in a decrease in the salt difference energy output power density to 4.91 W / m 2 about.

[0058] Comparative Example 2 The difference between this comparative example and Example 1 is that the thickness of the semiconductor layer in step 4 is: In step 4, the amount of semiconductor nanosheet solution added is increased so that the thickness of the semiconductor layer after stacking is about twice the thickness of the semiconductor layer in Example 1, reaching a size of tens of microns.

[0059] This comparative example increases the channel path that ions need to pass through to pass through the film, reducing the cation flux, and as the semiconductor layer thickens, the transmittance of the simulated light source decreases, making it impossible for the MXene material to absorb enough light energy, and the resulting heat energy converted is also reduced. The lack of obvious temperature difference on both sides and the reduction in ion flux simultaneously lead to a decrease in the salt difference energy conversion performance of the heterogeneous film.

[0060] Comparative Example 3 The salt difference energy recovery power generation device in this comparative example is the same as that in Example 1, except for the test parameters: The liquid pools on both sides are divided into high-salinity solution and low-salinity solution, reducing the salt concentration of the high-salinity solution. The molar concentration ratio of the high-salinity solution to the low-salinity solution is 5:1, the KCl concentration in the high-salinity solution is 0.05 mol / L, and the KCl concentration in the low-salinity solution is 0.01 mol / L. The results show that when the external resistance is 20 kΩ, the maximum output power of the salt difference energy recovery power generation device is 0.298 W / m 2 .

[0061] Comparative Example 4 The difference between this comparative example and Example 1 is that in step 2, the amount of MXene nanosheet solution is increased, and the MXene layer is directly dried after being obtained to separate it from the substrate to obtain a MXene film with a thickness of 6 μm, and steps 3 and 4 are not performed.

[0062] The MXene film was used as the semipermeable membrane to assemble the salt difference energy recovery power generation device according to Example 1 and test it. The results showed that the maximum output power of the salt difference energy recovery power generation device was 5.04 W / m 2 This indicates that using semiconductor / MXene heterojunction film as a semipermeable membrane can improve the ion transport performance compared to using only MXene film as a semipermeable membrane, which is attributed to the built-in electric field formed by the introduction of the semiconductor.

Claims

1. A MXene / semiconductor-based heterogeneous film, characterized in that: The invention comprises a semiconductor layer and a MXene layer which are stacked and connected together, wherein the semiconductor layer is formed by stacking n-type semiconductor nanosheets.

2. The MXene / semiconductor based heterogeneous film according to claim 1, characterized in that: The two-dimensional nanosheets are ZnIn2S4 or CdS.

3. The MXene / semiconductor based heterogeneous film according to claim 1, characterized in that: The MXene layer is composed of Ti3C2T x Nanosheets are formed by stacking layer upon layer.

4. The MXene / semiconductor based heterogeneous film according to claim 1, characterized in that The thickness of the heterogeneous film is 6 to 60 microns, the thickness of the semiconductor layer is 5 to 50 microns, and the thickness of the MXene layer is 1 to 10 microns.

5. The method for preparing a MXene / semiconductor-based heterogeneous film according to any one of claims 1 to 4, characterized in that: The steps include: S1, coating the MXene solution on the porous substrate to form a MXene layer; S2, coating the semiconductor nanosheet solution on the MXene layer, drying, forming a semiconductor layer on the MXene layer, and obtaining a heterogeneous film based on MXene / semiconductor materials.

6. The method for preparing a MXene / semiconductor-based heterogeneous film according to claim 5, characterized in that: In S1, the porous substrate is a polyvinylidene fluoride membrane, and in S2, after drying, the heterogeneous film is separated from the substrate.

7. The method for preparing a MXene / semiconductor-based heterogeneous film according to claim 5, characterized in that: In S1, the preparation method of the MXene solution is: dissolving LiF in hydrochloric acid to obtain a LiF solution, then adding a Ti3AlC2 precursor to the LiF solution and sealing it, stirring and etching; repeatedly washing the etched solution by centrifugation, and after a dark green color appears, centrifuging the solution to obtain an upper layer of MXene solution; wherein the concentration of hydrochloric acid is 9~12 mol / L.

8. A salt difference energy recovery power generation device, characterized in that: It comprises a first liquid pool, a second liquid pool and a MXene / semiconductor-based heterogeneous film according to any one of claims 1 to 5; one side of the first liquid pool is connected to one side of the second liquid pool through the MXene / semiconductor heterogeneous film, the first liquid pool is located on the semiconductor layer side of the heterogeneous film, and the second liquid pool is located on the MXene layer side of the MXene / semiconductor heterogeneous film; the first liquid pool is used to hold a high-salinity solution, and the second liquid pool is used to hold a low-salinity solution, and the electrolyte concentration of the high-salinity solution is higher than the electrolyte concentration of the low-salinity solution; an anode is provided in the first liquid pool, and a cathode is provided in the second liquid pool.

9. The salt difference energy recovery power generation device according to claim 1, characterized in that: The power generation device also includes a light source, the other side of the first liquid pool is optical glass, the light source is connected to an optical fiber, and the light of the optical fiber passes through the optical glass and is vertically incident on one side of the semiconductor layer based on the MXene / semiconductor heterogeneous film.

10. The salt difference energy recovery power generation device according to claim 1, characterized in that: The low-salinity solution and the high-salinity solution are seawater, salt lake brine or industrial high-salinity wastewater.

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