Bifunctional coupling device for synchronously enhancing photo-thermal evaporation water-salt separation and super capacitor performance

Abstract

The invention discloses a dual-function coupling device for synchronously enhancing photo-thermal evaporation water-salt separation and super capacitor performance. An upper electrode, a water conveying layer and a lower electrode are arranged above a water tank from top to bottom and are tightly attached to each other; the front extending section of the water conveying layer penetrates through a heat insulation layer arranged on the top of the water tank to make contact with seawater in the water tank, the rear extending section of the water conveying layer reaches a side salt precipitation layer arranged on the outer side of the water tank, the upper electrode serves as a photo-thermal / evaporation interface, seawater in the water conveying layer serves as electrolyte, and the water conveying layer serves as a diaphragm. The upper electrode, the water conveying layer and the lower electrode are tightly attached to form a supercapacitor structure, the device can synchronously perform solar photo-thermal evaporation water-salt separation and supercapacitor energy storage, and meanwhile, the device shows a synergistic enhancement effect when working; heat generated in the charging and discharging process of the supercapacitor can improve the evaporation rate to promote water-salt separation.

Description

Technical Field

[0001] The present invention belongs to the technical field of seawater desalination and energy storage, and specifically relates to a dual-function coupling device that synchronously enhances photothermal evaporation water-salt separation and supercapacitor performance. Background Art

[0002] Freshwater shortages have become one of the most serious crises threatening human development, and this challenge will continue to intensify. Desalination is one of the most effective ways to address the freshwater resource crisis. Traditional desalination technologies include membrane treatment and multi-stage flash evaporation, but these technologies face challenges such as high energy consumption, high costs, low efficiency, and secondary pollution. In recent years, solar thermal-driven interfacial evaporation, as a new solar desalination technology, has become a research hotspot in the field of desalination due to its environmentally friendly and economically sustainable characteristics, capable of meeting people's daily water needs.

[0003] On the other hand, the limited reserves of traditional fossil fuels and the environmental concerns associated with their large-scale use have prompted the rapid development of renewable energy technologies such as solar, wind, and tidal energy. These clean energy sources play a vital role in green, low-carbon development and energy transition, but their inherent intermittency and instability limit their direct use. Therefore, developing efficient electrical energy storage systems to achieve high-quality development and large-scale application of renewable energy is crucial. Among the various energy storage systems, electrochemical energy storage systems, such as lithium-ion batteries and supercapacitors, are considered the most promising solutions due to their high efficiency, reliability, and practicality.

[0004] Currently, some islands and coastal areas are in urgent need of drinking water and electricity, but lack conventional water supply and energy storage facilities. However, these areas have abundant seawater resources and natural energy sources such as solar energy, wind energy, and tidal energy. Solar-driven interfacial evaporation of seawater can effectively solve the drinking water shortage problem in these areas. Natural energy sources such as solar energy, wind energy, and tides can be used to generate electricity, but their intermittent and unstable nature limits their direct use. Advanced energy storage devices are required. Emerging hydropower combined technologies, which can both generate fresh water and store electricity, have great application value in these areas and can save a lot of manpower and material resources. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a dual-function coupling device that simultaneously enhances the performance of photothermal evaporation water-salt separation and supercapacitor, which can simultaneously perform solar interfacial evaporation and electrochemical energy storage, while achieving effective water-salt separation.

[0006] The present invention is achieved through the following technical solutions:

[0007] A dual-function coupling device for synchronously enhancing photothermal evaporation water-salt separation and supercapacitor performance, comprising a water tank and an upper electrode, a water transfer layer, and a lower electrode arranged from top to bottom and closely attached above the water tank; the upper electrode and the upper electrode are connected to an external circuit, and the lower electrode and the lower electrode are connected to an external circuit; the front and rear ends of the water transfer layer respectively extend downward to form a front extension section and a rear extension section; the front extension section passes through an insulating layer provided at the top of the water tank and contacts the seawater in the water tank; the rear extension section is connected to a side salt precipitation layer provided on the outside of the water tank; the side salt precipitation layer is carried on the rear extension section of the water transfer layer;

[0008] The upper electrode and the lower electrode are made of a membrane material having both light absorption and supercapacitor properties. The electrodes serve as the photothermal / evaporation interface, and the side salt precipitation layer is the location for salt precipitation. The water transport layer transports seawater from the water tank to the side salt precipitation layer through the upper electrode and the lower electrode. The seawater in the water transport layer serves as an electrolyte, and the water transport layer serves as a diaphragm. The upper electrode, the water transport layer, and the lower electrode are tightly attached to form a supercapacitor structure, so that the coupling device has the effect of a supercapacitor during photothermal evaporation.

[0009] Preferably, the upper electrode and the lower electrode are Ti3C2T x MXene / graphene composite film, Ti3C2T x MXene film or graphene film, less than 1mm thick.

[0010] Preferably, a non-membrane material with pseudocapacitance or sodium double layer energy storage performance is added to the membrane material of the upper electrode and the lower electrode, with a content of less than 40%. Preferably, carbon, molybdenum sulfide, iron oxide, Prussian blue compounds, sodium vanadium fluorophosphate, sodium cobaltate or sodium iron sulfate is added to the membrane.

[0011] Preferably, the water transfer layer is made of non-woven fabric or coconut shell cloth, and the thickness of the water transfer layer is less than 2 mm.

[0012] Preferably, the side salt precipitation layer is a plastic plate.

[0013] Preferably, the upper electrode connected to the external circuit and the lower electrode connected to the external circuit are graphite tapes.

[0014] Preferably, the heat insulation layer is a polystyrene foam board; and the water tank is a plastic box.

[0015] Preferably, the upper electrode and the lower electrode are both 1.5 cm long and 2 cm wide; the water transfer layer is 2 cm wide, and the rear extension section of the water transfer layer is an inverted isosceles trapezoid with a lower base of 2 cm, an upper base of 1 cm, and a height of 2.5 cm.

[0016] Preferably, the side salt precipitation layer is arranged at an angle of 10 to 45 degrees to the vertical direction.

[0017] The present invention has the following beneficial effects:

[0018] The present invention comprises an upper electrode, a water transport layer, and a lower electrode arranged from top to bottom above a water tank and closely attached to each other. Under illumination, the upper electrode can serve as a photothermal layer for interface evaporation, closely attached to the lower water transport layer, and can achieve solar-driven interface evaporation. The upper and lower electrodes are made of materials with light absorption and electrochemical energy storage properties. The two electrodes are closely attached to the water transport layer in the middle. The salt water in the water transport layer serves as an electrolyte, and the water transport layer serves as a diaphragm, forming a supercapacitor structure that can achieve electrochemical energy storage. In this way, evaporation and energy storage can be carried out simultaneously. The upper electrode can serve as the photothermal / evaporation interface, and the seawater serves as the electrolyte of the supercapacitor, achieving evaporation and electrical energy storage simultaneously, greatly saving costs. In addition, the device can achieve a water-salt separation effect. During operation, it was found that its evaporation rate and electrochemical performance can be synergistically enhanced. During the charging and discharging process, the evaporation rate is improved to a certain extent. Under illumination, the capacitance of the supercapacitor increases and the resistance decreases, and both effects are enhanced.

[0019] The photothermal layer of an existing photothermal evaporation device for water-salt separation is constructed into two layers: the upper and lower electrodes of the present invention. The upper and lower electrodes also serve as capacitor materials, and seawater serves as the electrolyte. This simultaneously achieves photothermal evaporation for water-salt separation and a supercapacitor. Photothermal energy improves capacitor performance, and the heat generated during the capacitor's charge and discharge process increases the photothermal evaporation rate, mutually reinforcing the effects.

[0020] In order to determine the optimal parameters of the device, the electrode size is designed to be 1.5cm long and 2cm wide, and the electrode mass is designed to be 5mg, 7.5mg, 10mg, and 12.5mg respectively. After the device is illuminated for 24 hours, it is found that their evaporation rates are consistent, but salt crystallizes on the upper electrodes with a mass of 5mg and 7.5mg, so the electrode mass should be 10mg. The angles of the side salting-out layer with the vertical direction are designed to be 15°, 30°, 45°, and 60° respectively. After the device is illuminated for 24 hours, it is found that when the angle with the vertical direction is 30°, the salt will slowly crystallize downward on the side salting-out layer. If the angle is too small, the seawater will flow down on the side salting-out layer, and it is not easy to form salt crystals. If the angle is too large, the salt will slowly crystallize upward on the side salting-out layer, and eventually salt crystals will appear on the upper electrode. Therefore, the angle of the side salting-out layer with the vertical direction should be designed to be 30°. The width of the water transfer layer is 2 cm, and the rear extension section of the water transfer layer is an inverted isosceles trapezoid with a lower base of 2 cm, an upper base of 1 cm, and heights designed to be 1 cm, 2 cm, 2.5 cm, and 3 cm, respectively. After the device was illuminated for 24 hours, it was found that the height of the trapezoid at the tail of the water transfer layer was 2.5 cm. The seawater can be well crystallized slowly downward along the side salt precipitation layer at the end of the non-woven fabric. Therefore, the height of the trapezoid at the tail of the water transfer layer should be designed to be 2.5 cm.

[0021] Under light, the seawater in the water tank is transported upward through the water transfer layer. The salt concentration reaches the highest at the tail of the water transfer layer, and stratified salt is precipitated on the side, achieving synchronous salt extraction and avoiding salt crystallization and precipitation on the top electrode sheet, so that the entire device can operate stably for a long time. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the structure of the dual-function coupling device for simultaneously enhancing the performance of photothermal evaporation water-salt separation and supercapacitor in the present invention;

[0023] Figure 2 a is the device at a scanning rate of 10 mV s -1 Comparison of CV curves under dark and light conditions;

[0024] Figure 2 b is the device at a current density of 2 mA cm -2 Comparison of GCD curves under dark and light conditions;

[0025] Figure 2 c is the comparison of electrochemical impedance spectroscopy (EIS) of the device in the dark and light conditions in the frequency range of 0.01 Hz to 100 kHz;

[0026] Figure 3 dark state, light state, and light state at 2 mA cm -2 Comparison of evaporation rates during charge and discharge at different current densities;

[0027] Figure 4a This is a front view showing the water-salt separation effect of the device after working for 24 hours;

[0028] Figure 4b This is a top view showing the water-salt separation effect of the device after working for 24 hours;

[0029] Figure 5 An experimental diagram reflecting the design process of the present invention;

[0030] Figure numerals: 1-upper electrode, 2-water transport layer, 3-lower electrode, 4-side salt precipitation layer, 5-upper electrode connected to external circuit, 6-lower electrode connected to external circuit, 7-thermal insulation layer, 8-water tank. DETAILED DESCRIPTION

[0031] The present invention will be further described in detail below with reference to specific embodiments, which are intended to explain the present invention rather than to limit it.

[0032] See Figure 1The present invention provides a novel dual-functional coupling device of solar-driven interfacial evaporation and electrochemical energy storage, comprising an upper electrode 1, a water transport layer 2, a lower electrode 3, a side salting-out layer 4, a heat-insulating layer 7, and a water tank 8; the upper electrode 1 and the lower electrode 3 are respectively connected to the upper electrode-connected external circuit 5 and the lower electrode-connected external circuit 6; the upper electrode-connected external circuit 5 and the lower electrode-connected external circuit 6 are respectively tightly connected to the upper electrode 1 and the lower electrode 3, and are made of a conductive material resistant to salt corrosion, preferably graphite tape. The lower end of the water transport layer 2 passes through the heat-insulating layer 7 to contact the seawater, and extends through the ends of the upper electrode 1 and the lower electrode 3 to the side salting-out layer 4, and the side salting-out layer 4 carries the tail of the water transport layer 2. The water transport layer 2 passes through the upper electrode 1 and the lower electrode 3, the seawater in the water transport layer 2 serves as an electrolyte, and the water transport layer serves as a diaphragm. The three are tightly attached to form a supercapacitor structure. The coupled device has the effect of a supercapacitor during photothermal evaporation and exhibits a synergistic enhancement effect during operation: photothermal energy can improve the energy storage performance of the supercapacitor, and the heat generated during the charging and discharging process of the supercapacitor can increase the evaporation rate and promote water-salt separation.

[0033] The electrode 1 can be used as a photothermal / evaporation interface for interface evaporation. The side salt precipitation layer 4 is the location for salt precipitation, so that the coupling device has the effect of water-salt separation during evaporation. The upper electrode 1 and the lower electrode 3 are membrane materials that can form a continuous film, have good light absorption, good conductivity, large specific surface area, good hydrophilicity, and have supercapacitor performance. The membrane material with both light absorption and supercapacitor performance is selected, such as Ti3C2T x MXene film, graphene film, Ti3C2T x MXene / graphene composite films, and materials doped therein with light absorption and electrochemical energy storage properties. Non-membrane materials that can simultaneously enhance the pseudocapacitance of photothermal and supercapacitors and the sodium double-layer energy storage performance can be added, with a content of less than 40%, without compromising film-forming properties. Preferably, the film contains carbon, molybdenum sulfide, iron oxide, Prussian blue compounds, sodium vanadium fluorophosphate, sodium cobaltate, and sodium ferric sulfate.

[0034] The area of ​​the upper electrode 1 and the lower electrode 3 are both 1.5*2cm -2, with a thickness of 5μm. A hydrophilic fabric with excellent water and salt ion transport properties is selected as the water transport layer 2, preferably a non-woven fabric. The water transport layer 2 is 2cm wide and 1mm thick, with its tail mounted on the side salting-out layer 4. The tail of the non-woven fabric is cut into an isosceles trapezoid with a lower base of 2cm, an upper base of 1cm, and a height of 2.5cm. Under light, salt water in the water tank is transported upward through the water transport layer. The salt concentration reaches its highest at the tail of the water transport layer, where salt crystals precipitate in the side salting-out layer 4. These dimensional parameters represent the basic unit. For scaled-up manufacturing, the basic unit is replicated horizontally to form an array. Plastic sheets that facilitate salt crystallization and are corrosion-resistant are selected as the side salting-out layer 4, angled at 30° to the vertical to achieve a relatively balanced and stable operation of the interfacial evaporation rate, salt water transport, and salt crystallization. The thermal insulation layer 7 is a polystyrene foam board, and the water tank 8 is an acrylic box. The device can be used for both interfacial evaporation and electrochemical energy storage, and when it is working, there is a mutually promoting effect between the interfacial evaporation rate and the electrical energy storage.

[0035] The following is implemented as a test method:

[0036] A 300W xenon lamp (CEL-HXF300-T3, Beijing Zhongjiao Jinyuan Technology Co., Ltd.) was used to simulate the solar light source, and an electrochemical workstation (CHI660E, Shanghai Chenhua Instrument Co., Ltd.) was used to test the electrochemical properties of the constructed supercapacitor. The effects of light on the electrochemical properties of the supercapacitor, the effects of supercapacitor charging and discharging on interfacial evaporation, and the water-salt separation effect of the device were explored.

[0037] Example 1:

[0038] Add seawater to the water tank, assemble the device so that the liquid level is lower than the end of the water transfer layer, and connect it to an external electrochemical workstation.

[0039] 1. Place the device in the dark to test the electrochemical performance of the supercapacitor in the device under dark conditions, and then transfer it to a simulated solar intensity (100mW cm -2 ) light source, and after a period of illumination, the effect of illumination on the electrochemical properties of the supercapacitor in the device was tested.

[0040] Calculate the area specific capacitance C of supercapacitors by GCD curve s (mF cm -2 ) is calculated as

[0041]

[0042] Where I is the current (mA cm -2 ), Δt is the discharge time (s), S is the total area of ​​the two electrodes (cm -2), ΔV is the voltage window (V).

[0043] Figure 2 a- Figure 2 c Comparison of the coupled device under one sun intensity illumination and dark conditions with a sweep rate of 10 mV s -1 The area of ​​the CV curve; Figure 2 a is the scanning speed of 10 mV s -1 From the CV curve, it can be seen that the area of ​​the CV curve under light conditions is significantly larger than the area of ​​the CV curve under dark conditions. Figure 2 b is the current density of the coupling device at 2 mA cm -2 From the GCD curve, it can be seen that the discharge time of the supercapacitor in the coupling device under light conditions is longer than that under dark conditions. At this current density, the area specific capacitance under dark conditions is calculated to be 42.5 mF cm-3 through the GCD curve. -2 , while the area capacitance under light conditions is 67.5mF cm -2 , which is 1.6 times that under dark conditions. Figure 2 c is the electrochemical impedance diagram of the device in the dark and light conditions in the frequency range of 0.01Hz to 100kHz. The slope of the impedance under light conditions is significantly larger in the low-frequency region, indicating that photothermal energy can promote the rapid transmission of ions and enable more ions to participate in the reaction, which is also the reason for the increase in capacitance.

[0044] 2. Place the device in a dark place and record the evaporation rate of the device in 1 hour under dark conditions. Then transfer the device to a light source with a simulated sunlight intensity. After stabilization, record the evaporation rate for 1 hour. Finally, charge and discharge the supercapacitor in the device through an electrochemical workstation under a light source with a sunlight intensity of 2 mA cm -2 The evaporation rate for 1 h is also recorded at the current density. Figure 3 As shown, the evaporation rate under dark conditions is 0.77 kg m -2 h -1 The evaporation rate under illumination without charging or discharging is 2.73 kg m -2 h -1 , under illumination and current density of 2 mA cm -2 In the case of charge and discharge, the evaporation rate is 2.90 kg m -2 h -1 The evaporation rate has been improved to a certain extent. The reason for this result is that during the charging and discharging process of the coupling device, there is internal resistance in the electrode. The Joule effect generates heat, which increases the surface temperature of the electrode and promotes evaporation.

[0045] 3. Transfer the device to a light source with simulated sunlight intensity and illuminate it for 24 hours to observe the water-salt separation effect of the device.

[0046] like Figure 4a and Figure 4b As shown, it can be seen that after 24 hours of light exposure, Figure 4a In the front view, salt crystals are precipitated on the side salt precipitation layer. Figure 4b In the top view, Ti3C2T x Only a small amount of salt crystallization occurs at the edge of the MXene membrane, which ensures the long-term and stable operation of the device.

[0047] like Figure 5 As shown, the present invention continuously designs from device 1 to device 6. First, device 1 determines that the entire device structure is a one-way water transmission structure, which can control the water transmission path so that the salt solution concentration reaches the highest at the end of the water transmission layer, achieving the purpose of controllable regional salt crystallization. Then, based on device 1, the structure is designed to try to integrate the interface evaporation structure and the supercapacitor structure; devices 2 and 3 both use coconut shell cloth as the water transmission layer, and use two methods to integrate the interface evaporation structure and the supercapacitor structure into one. One method is to pass the coconut shell cloth through the upper and lower Ti3C2T x film; one is two pieces of Ti3C2T x The membrane was placed parallel to the coconut shell cloth with a certain gap in the middle, which could further increase the photothermal evaporation area. However, no good electrochemical performance was measured on the device. In addition, the coconut shell cloth was used as the water transport layer. During the light evaporation, the upper Ti3C2T x The membrane is prone to salt crystallization; Device 4 and Device 5 are Ti3C2T x The membrane and hydrogel were integrated to form a semi-solid supercapacitor, which was placed directly on top of the coconut shell cloth, or the capacitor was placed horizontally, and the hydrogel was connected to the coconut shell cloth in front and back. It was found that the water transport performance of the hydrogel was not good after a period of light exposure. As the light exposure time increased, the capacitor became wet, which was not conducive to the performance of the electrochemical performance. Device 6 used non-woven fabric as the water transport layer, passing through the upper and lower Ti3C2T x Membrane electrode, this device successfully integrates the interface evaporation structure and supercapacitor structure into one, and both show good performance. However, during the test, it was found that the aluminum sheet was used as the side sheet salt precipitation layer. The crystallized salt easily corroded the aluminum sheet and was not easy to peel off from the aluminum sheet. It was necessary to find a material that was resistant to salt corrosion and easy to peel off the salt. After continuous attempts, we finally got Figure 1 The optimal coupling device is shown.

Claims

1. A dual-function coupling device for synchronously enhancing photothermal evaporation water-salt separation and supercapacitor performance, characterized by: The invention comprises a water tank (8) and an upper electrode (1), a water delivery layer (2) and a lower electrode (3) arranged from top to bottom and closely attached to each other above the water tank (8); the upper electrode (1) is connected to an upper electrode connection external circuit (5), and the lower electrode (3) is connected to a lower electrode connection external circuit (6); the front and rear ends of the water delivery layer (2) respectively extend downward to form a front extension section and a rear extension section; the front extension section passes through a heat insulation layer (7) arranged at the top of the water tank (8) and contacts the seawater in the water tank (8); the rear extension section is connected to a side salt precipitation layer (4) arranged outside the water tank (8); and the side salt precipitation layer (4) is carried on the rear extension section of the water delivery layer (2); The upper electrode (1) and the lower electrode (3) are made of a membrane material having both light absorption and supercapacitor properties. The electrode (1) serves as a photothermal / evaporation interface, and the side salt precipitation layer (4) is the location of salt precipitation. The water transport layer (2) passes through the upper electrode (1) and the lower electrode (3) to transport seawater from the water tank (8) to the side salt precipitation layer (4). The seawater in the water transport layer (2) serves as an electrolyte, and the water transport layer (2) serves as a diaphragm. The upper electrode (1), the water transport layer (2) and the lower electrode (3) are closely attached to each other to form a supercapacitor structure, so that the coupling device has the effect of a supercapacitor during photothermal evaporation.

2. The dual-function coupling device for synchronously enhancing photothermal evaporation water-salt separation and supercapacitor performance according to claim 1 is characterized by: The upper electrode (1) and the lower electrode (3) are Ti3C2T x MXene / graphene composite film, Ti3C2T x MXene film or graphene film, less than 1mm thick.

3. The dual-function coupling device for synchronously enhancing photothermal evaporation water-salt separation and supercapacitor performance according to claim 2 is characterized by: A non-membrane material with pseudocapacitance or sodium double layer energy storage performance is added to the membrane materials of the upper electrode (1) and the lower electrode (3), with the content being less than 40%. Preferably, carbon, molybdenum sulfide, iron oxide, Prussian blue compounds, sodium vanadium fluorophosphate, sodium cobaltate or sodium ferric sulfate are added to the membrane.

4. The dual-function coupling device for synchronously enhancing photothermal evaporation water-salt separation and supercapacitor performance according to claim 1 is characterized by: The water transport layer (2) is made of non-woven fabric or coconut shell cloth, and the thickness of the water transport layer (2) is less than 2 mm.

5. The dual-function coupling device for synchronously enhancing photothermal evaporation water-salt separation and supercapacitor performance according to claim 1 is characterized by: The side salt precipitation layer (4) is a plastic plate.

6. The dual-function coupling device for synchronously enhancing photothermal evaporation water-salt separation and supercapacitor performance according to claim 1 is characterized by: The upper electrode connected to the external circuit (5) and the lower electrode connected to the external circuit (6) are graphite tapes.

7. The dual-function coupling device for synchronously enhancing photothermal evaporation water-salt separation and supercapacitor performance according to claim 1 is characterized by: The heat insulation layer (7) is a polystyrene foam board; and the water tank (8) is a plastic box.

8. The dual-function coupling device for synchronously enhancing photothermal evaporation water-salt separation and supercapacitor performance according to any one of claims 1 to 7, characterized in that: The upper electrode (1) and the lower electrode (3) are both 1.5 cm long and 2 cm wide; the water transport layer (2) is 2 cm wide, and the rear extension section of the water transport layer (2) is an inverted isosceles trapezoid with a lower base of 2 cm, an upper base of 1 cm, and a height of 2.5 cm.

9. The dual-function coupling device for synchronously enhancing photothermal evaporation water-salt separation and supercapacitor performance according to claim 8, characterized in that: The side salt precipitation layer (4) is arranged at an angle of 10 to 45 degrees with respect to the vertical direction.

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