A method for preparing a double-layer polypyrrole deposition foam nickel sodium alginate hydrogel solar evaporator

Abstract

The application relates to a preparation method of a double-layer polypyrrone deposition foam nickel sodium alginate hydrogel solar evaporator, and belongs to the field of solar evaporator preparation. The application aims to solve the problem that salt accumulation on the evaporation surface of an existing solar interface evaporator can reduce the evaporation rate of the evaporator and affect the long-term stability of the evaporator. The method comprises the following steps: 1, preparation of a foam nickel light-absorbing layer of electrodeposited polypyrrone; 2, preparation of a sodium alginate hydrogel; 3, combination of the water-absorbing layer and the light-absorbing layer to prepare a solar seawater evaporation system. The application is used for the preparation of a double-layer polypyrrone deposition foam nickel sodium alginate hydrogel solar evaporator.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of solar evaporator preparation. BACKGROUND

[0002] With the depletion of fresh water resources, people are increasingly urgent to find new technologies to obtain fresh water resources, and seawater desalination is one of the most promising technologies. Traditional seawater desalination technologies include reverse osmosis, multi-stage flash evaporation and electrodialysis, etc., but they have some shortcomings, such as difficult equipment process, high energy consumption, environmental pollution, etc. In recent years, solar photothermal driven interfacial evaporation technology has become a hot spot, which combines photothermal technology and water transport structure, concentrates heat energy on the evaporation surface, reduces loss, and improves evaporation efficiency, with the advantages of sustainability and high energy efficiency.

[0003] A high-performance solar-driven interfacial evaporator water treatment system needs to select a suitable water-absorbing material and design a reasonable structure, which transports water to a solar absorber through capillary force to form a thin water layer. The photothermal component needs to absorb enough light energy and convert it into heat energy to evaporate the thin water layer. However, the existing solar interfacial evaporator has the problem of salt accumulation on the evaporation surface, which reduces the evaporation rate of the evaporator and affects the long-term stability of the evaporator. SUMMARY

[0004] The present application solves the problem of salt accumulation on the evaporation surface of the existing solar interfacial evaporator, which reduces the evaporation rate of the evaporator and affects the long-term stability of the evaporator, and further provides a preparation method of a double-layer polypyrrole deposited foam nickel sodium alginate hydrogel solar evaporator.

[0005] A preparation method of a double-layer polypyrrole deposited foam nickel sodium alginate hydrogel solar evaporator, which is carried out according to the following steps:

[0006] I. Preparation of foam nickel light-absorbing layer of electrodeposited polypyrrole:

[0007] ①Wash and dry the foam nickel to obtain pretreated foam nickel;

[0008] ②Mix pyrrole, acetonitrile and tetrabutylammonium tetrafluoroborate to obtain a mixed solution of pyrrole, acetonitrile and tetrabutylammonium tetrafluoroborate;

[0009] ③Use the pretreated foam nickel as the working electrode, a copper sheet as the counter electrode, silver chloride as the reference electrode, and the mixed solution of pyrrole, acetonitrile and tetrabutylammonium tetrafluoroborate as the electrodeposition solution. Use the chronocoulometry method of the electrochemical workstation, and under the conditions of voltage 1V-4V and temperature 20℃-50℃, electrodeposition for 1000s-2000s. After deposition, wash and dry to obtain the foam nickel light-absorbing layer of electrodeposited polypyrrole;

[0010] II. Preparation of sodium alginate hydrogel:

[0011] ①Sodium alginate is added to distilled water to obtain a sodium alginate solution;

[0012] ②Calcium chloride is added to distilled water to obtain a calcium chloride solution;

[0013] ③The calcium chloride solution is added to the sodium alginate solution and heated to dissolve, to obtain a sodium alginate hydrogel;

[0014] III. A solar sea water evaporation system is prepared by combining the water absorption layer and the light absorption layer:

[0015] The light absorption layer of the polypyrrole-deposited foam nickel is placed at the bottom of a container, the sodium alginate hydrogel is poured from the surface of the light absorption layer of the polypyrrole-deposited foam nickel into the container, a hydrogel layer is formed on the surface of the light absorption layer of the polypyrrole-deposited foam nickel, then the container is placed at room temperature for the first time until the bubbles in the hydrogel are discharged, the calcium chloride solution is added to the hydrogel layer along the inner wall of the container, then the container is placed at room temperature for the second time, the sample is taken out and soaked in distilled water, and finally the excess hydrogel is removed to obtain a double-layer polypyrrole-deposited foam nickel sodium alginate hydrogel solar evaporator;

[0016] The double-layer polypyrrole-deposited foam nickel sodium alginate hydrogel solar evaporator has an upper-lower structure, the light absorption layer is the polypyrrole-deposited foam nickel, and the water absorption layer is the sodium alginate hydrogel.

[0017] The present application has the following advantages:

[0018] The method for preparing the double-layer polypyrrole-deposited foam nickel sodium alginate hydrogel solar evaporator provided by the present application calculates the thickness of the polypyrrole deposition in the light absorption layer, the content of sodium alginate and the content of calcium chloride in the water absorption layer, and the optimal evaporation rate of the prepared double-layer evaporator acting on seawater is 3.22 Kg·m -2 ·h -1 , and the photo-thermal efficiency is 91.8%, which proves that the double-layer structure has higher evaporation rate and photo-thermal conversion efficiency.

[0019] When the double-layer structure is prepared, the light absorption layer of the polypyrrole-deposited foam nickel is immersed in the hydrogel, and the hydrogel layer formed on the side surface and the bottom surface of the foam nickel needs to be removed, so that the double-layer polypyrrole-deposited foam nickel sodium alginate hydrogel solar evaporator has an upper-lower structure, the light absorption layer is the polypyrrole-deposited foam nickel, and the water absorption layer is the sodium alginate hydrogel; the thickness of the hydrogel layer formed on the surface is different, and the evaporation rate of the evaporator will be different.

[0020] The present application prepares the sodium alginate hydrogel in the evaporator, and the calcium chloride is added twice. The first time is added in the process of heating and dissolving sodium alginate, and the calcium ions can be uniformly distributed in the sodium alginate hydrogel by heating and stirring. The second time is added after the sodium alginate hydrogel is placed, and the calcium ions are crosslinked with the gel by soaking in the calcium chloride solution. The step-by-step addition of calcium chloride helps the calcium ions to penetrate into the entire sodium alginate gel, and if a large amount of calcium ions is added at one time, the local calcium ion concentration will be too high, which will cause the crosslinking reaction to proceed rapidly in some positions, while the sodium alginate in other positions may not be fully crosslinked due to insufficient diffusion of calcium ions. The step-by-step crosslinking by adding calcium chloride twice helps to form a more uniform three-dimensional network structure, which can avoid some areas being too soft or too hard, thereby improving the strength and toughness of the hydrogel as a whole.

[0021] The prepared double-layer polypyrrole deposited foam nickel sodium alginate hydrogel solar evaporator has a foam nickel light-absorbing layer on the upper layer and a sodium alginate hydrogel water-absorbing layer on the lower layer. The polypyrrole contains a large amount of double bonds, which can effectively absorb solar energy and convert it into heat energy for water evaporation. The sodium alginate has a large number of hydroxyl and carboxyl groups, which increase the hydrophilic ability, and the micron-sized channels accelerate the transport of water, ensuring the wettability of the evaporation surface.

[0022] The present application is simple to operate and can be mass-produced. The prepared double-layer polypyrrole deposited foam nickel sodium alginate hydrogel solar evaporator has low energy consumption, sufficient strength, and is convenient to use.

[0023] DRAWINGS

[0024] Figure 1 The spectrum is RTIR, 1 is sodium alginate hydrogel, and 2 is polypyrrole prepared in step one of example one;

[0025] Figure 2 The UV-Vis-NIR spectrum and AM1.5G spectrum of the solar radiation spectrum of the double-layer polypyrrole deposited foam nickel sodium alginate hydrogel solar evaporator and the sodium alginate hydrogel prepared in example one;

[0026] Figure 3 The SEM images of the foam nickel and the foam nickel light-absorbing layer of the electrodeposited polypyrrole, a is the foam nickel described in step one of example one, and b is the foam nickel light-absorbing layer of the electrodeposited polypyrrole prepared in step one of example one;

[0027] Figure 4 The SEM image of the sodium alginate hydrogel;

[0028] Figure 5 The contact angle test image of the sodium alginate hydrogel;

[0029] Figure 6 The solar radiation spectrum of the double-layer polypyrrole deposited foam nickel sodium alginate hydrogel solar evaporator under 1kw / m 2Under light intensity, the surface temperature of the light-absorbing layer of the double-layer polypyrrole electrodeposited nickel foam sodium alginate hydrogel solar evaporator prepared in Example 1 is measured.

[0030] Figure 7 To achieve a solar intensity of 1 kW / m 2 The graph shows the relationship between the evaporation rate and photothermal efficiency of the double-layer polypyrrole deposited nickel alginate hydrogel solar evaporators prepared in Examples 1 to 5 and the concentration of calcium chloride in the sodium alginate hydrogel in step 2③ under room temperature conditions.

[0031] Figure 8 To achieve a solar intensity of 1 kW / m 2 The graph shows the relationship between the evaporation rate, photothermal efficiency and hydrogel thickness of the double-layer polypyrrole deposited foam nickel sodium alginate hydrogel solar evaporators prepared in Examples 3, 6 to 9, and at room temperature.

[0032] Figure 9 To achieve a solar intensity of 1 kW / m 2 The evaporation rate of the double-layer polypyrrole deposited foam nickel sodium alginate hydrogel solar evaporator prepared in Example 1 at different concentrations of NaCl solution for 8 hours under room temperature conditions.

[0033] Figure 10 To achieve a solar intensity of 1 kW / m 2 The evaporation rate of the double-layer polypyrrole electrodeposited nickel foam sodium alginate hydrogel solar evaporator prepared in Example 1 was repeatedly evaporated in 25% NaCl solution for 7 days under room temperature conditions.

[0034] Figure 11 To achieve a solar intensity of 1 kW / m 2 A comparison of pH test paper before and after evaporation of 1 mol / L HCl and 1 mol / L NaOH solutions using the double-layer polypyrrole deposited foam nickel sodium alginate hydrogel solar evaporator prepared in Example 1, under room temperature conditions.

[0035] Figure 12 This is a photograph of the double-layer polypyrrole deposited foam nickel sodium alginate hydrogel solar evaporator prepared in Example 1. Detailed Implementation

[0036] Specific Implementation Method 1: This implementation method is a preparation method for a double-layer polypyrrole deposited foam nickel-sodium alginate hydrogel solar evaporator, which is carried out according to the following steps:

[0037] I. Preparation of a nickel foam light-absorbing layer with electrodeposited polypyrrole:

[0038] ① The nickel foam is washed and dried to obtain pretreated nickel foam;

[0039] ②mixing pyrrole, acetonitrile and tetrabutylammonium tetrafluoroborate to obtain a mixed solution of pyrrole, acetonitrile and tetrabutylammonium tetrafluoroborate;

[0040] ③using the pretreated foamed nickel as a working electrode, a copper sheet as a counter electrode, silver chloride as a reference electrode, and the mixed solution of pyrrole, acetonitrile and tetrabutylammonium tetrafluoroborate as an electrodeposition solution, using a chronocoulometry method of an electrochemical workstation, under the conditions of a voltage of 1V-4V and a temperature of 20℃-50℃, electrodeposition for 1000s-2000s, washing and drying after deposition to obtain a foamed nickel light-absorbing layer of electrodeposited polypyrrole;

[0041] II. Preparation of sodium alginate hydrogel:

[0042] ①adding sodium alginate into distilled water to obtain a sodium alginate solution;

[0043] ②adding calcium chloride into distilled water to obtain a calcium chloride solution;

[0044] ③adding the calcium chloride solution into the sodium alginate solution and heating to dissolve to obtain a sodium alginate hydrogel;

[0045] III. Preparation of a solar seawater evaporation system by combining a water-absorbing layer and a light-absorbing layer:

[0046] placing the foamed nickel light-absorbing layer of electrodeposited polypyrrole at the bottom of a container, pouring the sodium alginate hydrogel from the surface of the foamed nickel light-absorbing layer of electrodeposited polypyrrole into the container to form a hydrogel layer on the surface of the foamed nickel light-absorbing layer of electrodeposited polypyrrole, then standing at room temperature for the first time until the air bubbles in the hydrogel are discharged, then adding the calcium chloride solution into the hydrogel layer along the inner wall of the container, and standing at room temperature for the second time, taking out the sample and soaking it in distilled water, and finally removing the excess hydrogel to obtain a double-layer polypyrrole-deposited foamed nickel sodium alginate hydrogel solar evaporator;

[0047] The double-layer polypyrrole-deposited foamed nickel sodium alginate hydrogel solar evaporator has an upper-lower structure, the foamed nickel light-absorbing layer of electrodeposited polypyrrole is the light-absorbing layer, and the sodium alginate hydrogel is the water-absorbing layer.

[0048] The polypyrrole prepared in step one of the specific embodiment is a conjugated conductive polymer with good light absorption performance. Its wide-band light absorption characteristics can effectively absorb the light spectrum from ultraviolet to near-infrared. Depositing it on foamed nickel can significantly improve the light-heat conversion efficiency of the material. The electrodeposition technology can accurately control the thickness and deposition rate of polypyrrole, and can adjust the light absorption efficiency and thermal conductivity performance of the material. This controllability enables the performance of the polypyrrole foamed nickel material to be optimized according to application requirements.

[0049] The sodium alginate in step two of the specific embodiment has strong ion cross-linking ability and good mechanical strength. The sodium alginate can be cross-linked with divalent Ca 2+The cross-linking quickly forms a stable gel structure, and the formed gel has good mechanical stability and durability in environmental changes. The salt deposition resistance is better than other natural or synthetic hydrogels, and the sodium alginate hydrogel has better salt deposition resistance in a high-salt environment, making it more suitable for seawater evaporation purification applications. Environmental protection and biocompatibility: sodium alginate is a natural polymer material derived from seaweed, with good biocompatibility and biodegradability. When used in seawater purification systems, it is harmless to the environment and easy to degrade or recycle in the later stage, meeting environmental protection requirements.

[0050] The water molecules in the hydrogel network in the specific embodiment step three can be divided into three types: water molecules adjacent to the polymer chain are connected by hydrogen bonds and are called bound water, intermediate water has weak hydrogen bond interaction with the polymer chain, and free water is not constrained by the polymer chain. The evaporation enthalpy of intermediate water is lower than that of bound water and free water, so the evaporation enthalpy of water in the hydrogel material is lower than that of pure water.

[0051] The specific embodiment has the following beneficial effects:

[0052] The method for preparing the double-layer polypyrrole-deposited foam nickel sodium alginate hydrogel solar evaporator provided by the specific embodiment calculates the polypyrrole deposition thickness in the light-absorbing layer, the sodium alginate content, the calcium chloride content, etc. in the water-absorbing layer, and the optimal evaporation rate of the prepared double-layer evaporator acting on seawater is 3.22Kg·m -2 ·h -1 , and the photo-thermal efficiency is 91.8%, which proves that the double-layer structure has higher evaporation rate and photo-thermal conversion efficiency.

[0053] When the double-layer structure is prepared in the specific embodiment, the foam nickel light-absorbing layer of the electrodeposited polypyrrole needs to be immersed in the hydrogel, and the hydrogel layer formed on the side and bottom of the foam nickel needs to be removed, so that the double-layer polypyrrole-deposited foam nickel sodium alginate hydrogel solar evaporator is finally in an upside-down structure, the foam nickel of the electrodeposited polypyrrole is the light-absorbing layer, and the sodium alginate hydrogel is the water-absorbing layer; the thickness of the hydrogel layer formed on the surface is different, and the evaporation rate of the evaporator will be different.

[0054] In the embodiment, the calcium chloride is added twice in the preparation of the sodium alginate hydrogel in the evaporator. The first time is during the heating and dissolving of the sodium alginate, and the calcium chloride is uniformly distributed in the sodium alginate hydrogel by heating and stirring. The second time is after the sodium alginate hydrogel is placed, and the calcium ions are cross-linked with the gel by soaking in the calcium chloride solution. The step-by-step addition of calcium chloride helps the calcium ions to gradually penetrate the entire sodium alginate gel. If a large amount of calcium ions is added at once, it may cause the local calcium ion concentration to be too high, leading to rapid cross-linking reaction in some positions, while the sodium alginate in other positions may not be fully cross-linked due to insufficient diffusion of calcium ions. The step-by-step cross-linking by adding calcium chloride twice helps to form a more uniform three-dimensional network structure, which can avoid some areas being too soft or too hard, thereby improving the strength and toughness of the hydrogel as a whole.

[0055] In the embodiment, the upper layer of the double-layer polypyrrole deposited foam nickel sodium alginate hydrogel solar evaporator is a foam nickel light-absorbing layer, and the lower layer is a sodium alginate hydrogel water-absorbing layer. The polypyrrole contains a large number of double bonds that can effectively absorb solar energy and convert it into heat energy for water evaporation. The sodium alginate has a large number of hydroxyl and carboxyl groups, which increase the hydrophilic ability, and the micron-sized pores accelerate water transport, ensuring the wettability of the evaporation surface.

[0056] The embodiment is simple to operate and can be mass-produced. The double-layer polypyrrole deposited in the foam nickel sodium alginate hydrogel solar evaporator has low energy consumption, sufficient strength, and is convenient to use.

[0057] Specific implementation method two: The difference between this embodiment and specific implementation method one is that the thickness of the foam nickel in step one ① is 1mm-5mm, and the porosity is 80%-98%. The others are the same as specific implementation method one.

[0058] Specific implementation method three: The difference between this embodiment and specific implementation method one or two is that the volume ratio of pyrrole to acetonitrile in step one ② is 1:(100-200); and the volume of pyrrole to the mass of tetrabutylammonium tetrafluoroborate in step one ② is 1mL:(1-3)g. The others are the same as specific implementation method one or two.

[0059] Specific implementation method four: The difference between this embodiment and specific implementation method one to three is that the distance between the working electrode and the counter electrode in step one ③ is 2cm-3cm. The others are the same as specific implementation method one to three.

[0060] Specific implementation method five: The difference between this embodiment and specific implementation method one to four is that the mass percentage of the sodium alginate solution in step two ① is 2.5%-4.5%; and the mass percentage of the calcium chloride solution in step two ② is 0.15%-0.30%. The others are the same as specific implementation method one to four.

[0061] Specific embodiment six: different from one of the specific embodiments one to five is that the volume ratio of the calcium chloride solution to the sodium alginate solution in step two ③ is 1:(1.5-3). The others are the same as specific embodiments one to five.

[0062] Specific embodiment seven: different from one of the specific embodiments one to six is that the heating dissolution in step two ③ is specifically heating for 45min-90min at a temperature of 80℃-90℃. The others are the same as specific embodiments one to six.

[0063] Specific embodiment eight: different from one of the specific embodiments one to seven is that the first standing at room temperature in step three is 0.5h-1.5h; the second standing at room temperature in step three is 15h-24h; the distilled water soaking at room temperature in step three is 4h-12h. The others are the same as specific embodiments one to seven.

[0064] Specific embodiment nine: different from one of the specific embodiments one to eight is that the hydrogel layer with a thickness of 1cm-3cm is formed on the surface of the polypyrrole electrodeposited foam nickel light-absorbing layer in step three; the mass percentage of the calcium chloride solution in step three is 0.05%-0.1%. The others are the same as specific embodiments one to eight.

[0065] Specific embodiment ten: different from one of the specific embodiments one to nine is that the volume ratio of the calcium chloride solution to the sodium alginate hydrogel added in the container in step three is 1:(0.5-2). The others are the same as specific embodiments one to nine.

[0066] The beneficial effects of the present application are verified by the following examples:

[0067] Example one:

[0068] A preparation method of a double-layer polypyrrole deposited foam nickel sodium alginate hydrogel solar evaporator, which is carried out according to the following steps:

[0069] I. Preparation of a polypyrrole electrodeposited foam nickel light-absorbing layer:

[0070] ①The foam nickel is washed with distilled water and ethanol in sequence, and then dried at a temperature of 70℃ for 10min to obtain pretreated foam nickel;

[0071] The area of the foam nickel is 3×3cm, the thickness is 1.7mm, and the porosity is 95%;

[0072] ②0.5mL of pyrrole, 60mL of acetonitrile and 0.85g of tetrabutylammonium tetrafluoroborate are mixed to obtain a pyrrole, acetonitrile and tetrabutylammonium tetrafluoroborate mixed solution;

[0073] ③The pre-processed foamed nickel is used as a working electrode, a copper sheet is used as a counter electrode, silver chloride is used as a reference electrode, a pyrrole, acetonitrile and tetrabutylammonium tetrafluoroborate mixed solution is used as an electrodeposition solution, a chronoamperometry method is selected for an electrochemical workstation, electrodeposition is performed at a voltage of 2V and a temperature of 25℃ for 1000s, after deposition, washing is performed with water and ethanol, and drying is performed at a temperature of 70℃, thereby obtaining a foamed nickel light-absorbing layer of electrodeposited polypyrrole;

[0074] The area of the copper sheet is 3*3 cm, and the thickness is 1.7 mm; the distance between the working electrode and the counter electrode is 2 cm;

[0075] II. Preparation of a sodium alginate hydrogel:

[0076] ①1.2 g of sodium alginate is added to 40 mL of distilled water to obtain a sodium alginate solution;

[0077] ②0.042 g of calcium chloride is added to 20 mL of distilled water to obtain a calcium chloride solution;

[0078] ③20 mL of the calcium chloride solution is added to 40 mL of the sodium alginate solution, and heating and dissolution are performed at a temperature of 85℃ for 1 h to obtain a sodium alginate hydrogel; the concentration of calcium chloride in the sodium alginate hydrogel is 0.07 w / v%;

[0079] III. Preparation of a solar seawater evaporation system by combining a water-absorbing layer and a light-absorbing layer:

[0080] The light-absorbing layer of the foamed nickel electrodeposited polypyrrole is placed at the bottom of a container, the sodium alginate hydrogel is poured from the surface of the light-absorbing layer of the foamed nickel electrodeposited polypyrrole into the container, a 2 cm-thick hydrogel layer is formed on the surface of the light-absorbing layer of the foamed nickel electrodeposited polypyrrole, then static standing is performed at room temperature for 1 h, the calcium chloride solution is added to the hydrogel layer along the inner wall of the container, then static standing is performed at room temperature for 16 h, the sample is taken out and soaked in distilled water for 6 h, and finally the excess hydrogel is removed, thereby obtaining a double-layer polypyrrole-deposited foamed nickel sodium alginate hydrogel solar evaporator;

[0081] The mass percentage of the calcium chloride solution is 0.5%; the volume ratio of the calcium chloride solution to the sodium alginate hydrogel added to the container is 1:1; the double-layer polypyrrole-deposited foamed nickel sodium alginate hydrogel solar evaporator has an upper-lower structure, the light-absorbing layer is the foamed nickel electrodeposited polypyrrole, and the water-absorbing layer is the sodium alginate hydrogel.

[0082] The preparation process of step three of the embodiment belongs to the category of foamed nickel immersed in hydrogel, and finally the hydrogel layer formed on the side and bottom of the foamed nickel needs to be removed, so that the double-layer polypyrrole deposited foamed nickel sodium alginate hydrogel solar evaporator is in an upper and lower structure, the foamed nickel with electrodeposited polypyrrole is the light-absorbing layer, and the sodium alginate hydrogel is the water-absorbing layer.

[0083] Example two: The difference between this example and example one is that in step two ②, 0.030 calcium chloride is added to 20 mL distilled water to obtain a calcium chloride solution; in step two ③, the concentration of calcium chloride in the sodium alginate hydrogel is 0.05 w / v%. The others are the same as example one.

[0084] Example three: The difference between this example and example one is that in step two ②, 0.036 calcium chloride is added to 20 mL distilled water to obtain a calcium chloride solution; in step two ③, the concentration of calcium chloride in the sodium alginate hydrogel is 0.06 w / v%. The others are the same as example one.

[0085] Example four: The difference between this example and example one is that in step two ②, 0.048 calcium chloride is added to 20 mL distilled water to obtain a calcium chloride solution; in step two ③, the concentration of calcium chloride in the sodium alginate hydrogel is 0.08 w / v%. The others are the same as example one.

[0086] Example five: The difference between this example and example one is that in step two ②, 0.054 calcium chloride is added to 20 mL distilled water to obtain a calcium chloride solution; in step two ③, the concentration of calcium chloride in the sodium alginate hydrogel is 0.09 w / v%. The others are the same as example one.

[0087] Example six: The difference between this example and example one is that the sodium alginate hydrogel is poured from the surface of the light-absorbing layer of the foamed nickel with electrodeposited polypyrrole into a container to form a hydrogel layer with a thickness of 3 cm on the surface of the light-absorbing layer of the foamed nickel with electrodeposited polypyrrole. The others are the same as example one.

[0088] Example seven: The difference between this example and example one is that the sodium alginate hydrogel is poured from the surface of the light-absorbing layer of the foamed nickel with electrodeposited polypyrrole into a container to form a hydrogel layer with a thickness of 2.5 cm on the surface of the light-absorbing layer of the foamed nickel with electrodeposited polypyrrole. The others are the same as example one.

[0089] Example eight: The difference between this example and example one is that the sodium alginate hydrogel is poured from the surface of the light-absorbing layer of the foamed nickel with electrodeposited polypyrrole into a container to form a hydrogel layer with a thickness of 1.5 cm on the surface of the light-absorbing layer of the foamed nickel with electrodeposited polypyrrole. The others are the same as example one.

[0090] Example 9: The difference between this example and example 1 is that the sodium alginate hydrogel is poured from the surface of the polypyrrole electrodeposited foam nickel light-absorbing layer into a container, and a 1 cm-thick hydrogel layer is formed on the surface of the polypyrrole electrodeposited foam nickel light-absorbing layer. The other steps are the same as in example 1.

[0091] Comparative experiment 1: The difference between this example and example 1 is that in step three, the polypyrrole electrodeposited foam nickel light-absorbing layer is placed at the bottom of the container and put into a mold, and the sodium alginate hydrogel is poured from the surface of the polypyrrole electrodeposited foam nickel light-absorbing layer into the container, forming a 2 cm-thick hydrogel layer on the surface of the polypyrrole electrodeposited foam nickel light-absorbing layer. Due to the control of the mold, half of the foam nickel is immersed in the hydrogel, and the other half is not immersed in the hydrogel. Finally, the excess hydrogel is removed. The other steps are the same as in example 1.

[0092] Comparative experiment 2: The difference between this example and example 1 is that the sodium alginate hydrogel prepared in step two is poured into a container, and then left to stand at room temperature for 1 hour. Then, a calcium chloride solution is added to the hydrogel layer along the inner wall of the container, and then left to stand at room temperature for 16 hours. The sample is then taken out and soaked in distilled water for 6 hours. Then, the polypyrrole electrodeposited foam nickel prepared in step one is placed on the surface of the 2 cm-thick hydrogel, resulting in a solar evaporator in which the foam nickel is not immersed in the sodium alginate hydrogel. The other steps are the same as in example 1.

[0093] Figure 1 2 The sodium alginate hydrogels described in examples 4 and 5 are prepared according to the following steps: the sodium alginate hydrogel prepared in step two of example one is poured into a container, and then left to stand at room temperature for 1 hour. Then, a calcium chloride solution is added to the hydrogel layer along the inner wall of the container, and then left to stand at room temperature for 16 hours. The sample is then taken out and soaked in distilled water for 6 hours, resulting in a sodium alginate hydrogel. The mass percentage of the calcium chloride solution is 0.5%. The volume ratio of the calcium chloride solution to the sodium alginate hydrogel added to the container is 1:1.

[0094] The foam nickel part of the polypyrrole electrodeposited foam nickel light-absorbing layer prepared in step one of example one is removed, and the remaining polypyrrole is subjected to RTIR testing. Figure 1 The figure is the spectrum of RTIR, 1 is the sodium alginate hydrogel, and 2 is the polypyrrole prepared in step one of example one. As can be seen from the figure, in the spectrum of the sodium alginate hydrogel, the stretching vibration at 3429 cm -1 is O-H, the asymmetric and symmetric stretching vibrations at 1621 and 1423 cm -1 are C=O, indicating the successful curing of sodium alginate with calcium ions; in the spectrum of polypyrrole, the stretching of C=C in the pyrrole ring and the stretching of C-N are at 1545 and 1461 cm -1 , respectively. The stretching of C=C in the pyrrole ring and the stretching of C-N are at 1042 and 902 cm​-1 are C-H in-plane vibration and C-H ring deformation, which indicates the successful synthesis of polypyrrole.

[0095] Figure 2 UV-Vis-NIR spectrum and AM1.5G spectrum of the solar evaporator of the double-layer polypyrrole electrodeposited foam nickel alginate hydrogel prepared in Example One and the absorbance test of the wavelength range of 300-2500 nm. It is observed that the absorbance of the alginate hydrogel itself is relatively low, below 15%, and compared with the lower one, the absorbance of the evaporator in the wavelength range of 300-2500 nm is significantly improved due to the presence of the electrodeposited polypyrrole, reaching 94%-99%.

[0096] Figure 3 SEM images of the foam nickel and the foam nickel light-absorbing layer of the electrodeposited polypyrrole. a is the foam nickel described in step one ① of Example One, and b is the foam nickel light-absorbing layer of the electrodeposited polypyrrole prepared in step one ③ of Example One. As can be seen from the figure, the original foam nickel shows a rich inter-connected large gap structure, and after the electrodeposition of polypyrrole on the surface, it still maintains the inter-connected large gap structure.

[0097] Figure 4 SEM image of the alginate hydrogel. As can be seen from the figure, the alginate hydrogel contains many microporous channels to provide water for the upper light-absorbing material.

[0098] Figure 5 Contact angle test figure of the alginate hydrogel. As can be seen from the figure, the surface 10 uL water droplets can be quickly absorbed in 0.1 s, indicating that the alginate hydrogel has strong water absorption, and there are a large number of hydrophilic groups in the alginate chain, which quickly transport water to the evaporation interface during evaporation.

[0099] Figure 6 Absorbing layer surface temperature test figure of the double-layer polypyrrole electrodeposited foam nickel alginate hydrogel solar evaporator prepared in Example One under the light intensity of 1 kw / m 2 Absorbing layer surface temperature test figure of the double-layer polypyrrole electrodeposited foam nickel alginate hydrogel solar evaporator prepared in Example One under the light intensity of 1 kw / m

[0100] 1. The evaporation rate test is a key parameter to describe the energy efficiency of the evaporator, and the evaporation rate test is carried out according to the following steps: place the double-layer polypyrrole electrodeposited foam nickel alginate hydrogel solar evaporator into a beaker, add water, and fill the empty water surface with PS foam, and the light intensity is 1 kw / m 2, temperature is room temperature, water weight change is recorded every 5 minutes, and evaporation rate (R) is calculated according to the formula.

[0101]

[0102] In the formula, M: water mass change (Kg);

[0103] S: evaporator area (area of electrodeposited polypyrrole nickel foam) (m 2 );

[0104] h: irradiation time (h).

[0105] 2. Determination of evaporator equivalent enthalpy:

[0106] The evaporator is placed on the surface of pure water and then placed in a constant temperature and humidity chamber as the experimental group; pure water with the same surface area as the evaporator is used as the control group and placed in a constant temperature and humidity chamber; the temperature is set to 22℃, the relative humidity is set to 45%, and the test is conducted under normal atmospheric pressure and dark environment, which can ensure that the heat absorbed by the evaporator and pure water is consistent. After 6h, the equivalent evaporation enthalpy value (△Hequ, J / g) of the evaporator is calculated according to the formula.

[0107] △Hvap×m0=△Hvau×m1

[0108] In the formula, △Hvap: evaporation enthalpy of pure water at 25℃ (2246J / g);

[0109] m0: mass change of pure water (g);

[0110] m1: mass change of water in the evaporator (g).

[0111] 3. Photothermal efficiency test:

[0112] Photothermal efficiency is an important indicator to evaluate the performance of the evaporator, and the photothermal efficiency (η) is calculated according to the formula.

[0113] η=R1×(△Hequ) / (q×Copt)

[0114] In the formula, R1: relative evaporation rate (kgm -2 h -1 ), evaporation rate (R) minus dark evaporation rate of water;

[0115] △Hequ: equivalent evaporation enthalpy (jg -1 )

[0116] q: density of sunlight (w / m 2 );

[0117] Copt: optical concentration of the evaporator surface.

[0118] wherein Figure 7 and Figure 8 The evaporation rate test was carried out by using natural seawater from the Yellow Sea (Weihai, Shandong); Figure 9 The evaporation rate test was carried out by using NaCl solution with mass percentage of 3.5% to 25%; Figure 10 The evaporation rate test was carried out by using NaCl solution with mass percentage of 25%; Figure 11 The evaporation rate test was carried out by using 1 mol / L HCL solution or 1 mol / L NaOH solution;

[0119] The evaporation rate of the foam nickel was tested under the condition of solar intensity of 1 kw / m 2 and room temperature, and the foam nickel was immersed in the hydrogel with half thickness (comparative experiment 1), not immersed in the hydrogel (comparative experiment 2), and completely immersed in the hydrogel (example 1). The seawater was taken from the Yellow Sea (Weihai, Shandong), and the evaporation rates were 3.06 Kg·m -2 ·h -1 , 2.83 Kg·m -2 ·h -1 and 3.22 Kg·m -2 ·h -1 respectively. It can be seen that the evaporator prepared by immersing the whole structure of the foam nickel in the hydrogel has the highest evaporation rate.

[0120] Figure 7 The evaporation rate and photo-thermal efficiency of the double-layer polypyrrole deposited foam nickel sodium alginate hydrogel solar evaporator prepared in examples 1 to 5 were tested under the condition of solar intensity of 1 kw / m 2 and room temperature, and the relationship between the evaporation rate and the concentration of calcium chloride in the sodium alginate hydrogel in step 2③. The calcium ions in the calcium chloride will exchange with the sodium ions in the sodium alginate to form cross-linking bonds between the calcium ions and the sodium alginate molecules. These cross-linking bonds connect the sodium alginate molecules together to form a three-dimensional network structure. Increasing the amount of calcium chloride can enhance the strength of the hydrogel, but will reduce the pore structure and affect the water transport function. It was found that the 0.07wt% CaCl solution still has an observable evaporation rate under good hydrogel effect, and the evaporation rate is 3.22 Kg·m -2 ·h -1 and the photo-thermal efficiency is 91.8%.

[0121] Figure 8 The evaporation rate and photo-thermal efficiency of the double-layer polypyrrole deposited foam nickel sodium alginate hydrogel solar evaporator prepared in examples 1 to 5 were tested under the condition of solar intensity of 1 kw / m 2The graph shows the relationship between the evaporation rate, photothermal efficiency, and hydrogel thickness of the double-layer polypyrrole deposited nickel foam sodium alginate hydrogel solar evaporators prepared in Examples 3, 6, to 9, under room temperature conditions. The thickness of the hydrogel in the evaporator affects the water transport rate; the thicker the hydrogel, the greater the force required for water transport. However, the hydrogel thickness provides a certain degree of insulation at the photothermal interface, reducing heat loss in the evaporation system. Measurements show that a thickness of 2 cm is suitable for the sodium alginate hydrogel in this evaporation system, with an evaporation rate of 3.22 kg·m⁻². -2 ·h -1 The photothermal efficiency is 91.8%.

[0122] Figure 9 To achieve a solar intensity of 1 kW / m 2 The evaporation rate of the double-layer polypyrrole deposited nickel alginate hydrogel solar evaporator prepared in Example 1 was plotted at room temperature and in different concentrations of NaCl solution for 8 hours. The figure shows that, in the 8-hour water evaporation experiment with solutions of different salinities ranging from 3.5% to 25% by mass, stable evaporation rates of 3.22 kg·m³ were observed in saline solutions of 3.5%, 7%, 10.5%, and 15% by mass. -2 ·h -1 3.18 kg·m -2 ·h -1 3.15 kg·m -2 ·h -1 3.09 kg·m -2 ·h -1 The evaporation rate decreased slightly in brine with a mass percentage of 20% and 25%, but still reached 2.94 kg·m³. -2 ·h -1 and 2.83 kg·m -2 ·h -1 This indicates that the evaporator has good salt resistance.

[0123] Figure 10 To achieve a solar intensity of 1 kW / m 2 The evaporation rate of the double-layer polypyrrole electrodeposited nickel foam sodium alginate hydrogel solar evaporator prepared in Example 1 was repeatedly evaporated in a 25% NaCl solution for 7 days under room temperature conditions. Evaporation was carried out for 8 hours per day, indicating that the evaporator has good stability and reusability in high-concentration NaCl solution.

[0124] Figure 11 To achieve a solar intensity of 1 kW / m 2The pH test paper before and after the evaporation of 1 mol / L HCL and 1 mol / L NaOH solution by the double-layer polypyrrole deposited foam nickel sodium alginate hydrogel solar evaporator prepared in Example 1 at room temperature is compared; the pH values before and after the evaporation of the solution are detected by the pH test paper, the pH value of the 1 mol / L HCL solution after the evaporation is about 6.0, the pH value of the 1 mol / L NaOH solution after the evaporation is about 7, and the solution after the evaporation and purification is close to neutral, which proves that the evaporator has a good purification effect on strong acid and strong alkali solution.

[0125] Figure 12 The physical map of the double-layer polypyrrole deposited foam nickel sodium alginate hydrogel solar evaporator prepared in Example 1 is shown.

Claims

1. A method for preparing a double-layer polypyrrole deposited nickel foam sodium alginate hydrogel solar evaporator, characterized in that... It is done in the following steps: Step 1: Preparation of the electrodeposited polypyrrole nickel foam light-absorbing layer: ① The nickel foam is washed and dried to obtain pretreated nickel foam; The thickness of the nickel foam is 1mm to 5mm, and the porosity is 80% to 98%. ② Pyrrole, acetonitrile and tetrabutylammonium tetrafluoroborate are mixed to obtain a mixed solution of pyrrole, acetonitrile and tetrabutylammonium tetrafluoroborate; ③ Using pretreated nickel foam as the working electrode, copper sheet as the counter electrode, silver chloride as the reference electrode, and a mixed solution of pyrrole, acetonitrile and tetrabutylammonium tetrafluoroborate as the electrodeposition solution, the electrochemical workstation was set to the chronoamperometry method. Under the conditions of voltage of 1V~4V and temperature of 20℃~50℃, the electrodeposition was carried out for 1000s~2000s. After deposition, the material was washed and dried to obtain a light-absorbing layer of nickel foam with electrodeposited polypyrrole. Step 2: Preparation of sodium alginate hydrogel: ① Add sodium alginate to distilled water to obtain sodium alginate solution; The sodium alginate solution has a mass percentage of 2.5% to 4.5%. ② Add calcium chloride to distilled water to obtain a calcium chloride solution; The calcium chloride solution has a mass percentage of 0.15% to 0.30%. ③ Add calcium chloride solution to sodium alginate solution and heat to dissolve, thus obtaining sodium alginate hydrogel; Step 3: Assemble the water-absorbing layer and light-absorbing layer to prepare a solar-powered seawater evaporation system: Electrodeposited nickel foam light-absorbing layer of polypyrrole was placed at the bottom of the container. Sodium alginate hydrogel was poured into the container from the surface of the electrodeposited nickel foam light-absorbing layer of polypyrrole, forming a hydrogel layer with a thickness of 1 cm to 3 cm on the upper surface of the electrodeposited nickel foam light-absorbing layer of polypyrrole. The sample was then allowed to stand at room temperature until the air bubbles in the hydrogel were expelled. Calcium chloride solution was added to the hydrogel layer along the inner wall of the container. The sample was then allowed to stand at room temperature for a second time. The sample was then removed and soaked in distilled water. Finally, the excess hydrogel was removed to obtain a double-layer polypyrrole deposited nickel foam sodium alginate hydrogel solar evaporator. The aforementioned double-layer polypyrrole deposited nickel foam and sodium alginate hydrogel solar evaporator has an upper and lower structure, with the electrodeposited polypyrrole nickel foam serving as the light-absorbing layer and the sodium alginate hydrogel serving as the water-absorbing layer. The calcium chloride solution has a mass percentage of 0.05% to 0.1%.

2. The method for preparing a double-layer polypyrrole deposited nickel foam sodium alginate hydrogel solar evaporator according to claim 1, characterized in that... The volume ratio of pyrrole to acetonitrile in step 1② is 1:(100~200); the volume ratio of pyrrole to tetrabutyltetrafluoroborate in step 1② is 1mL:(1~3)g.

3. The method for preparing a double-layer polypyrrole deposited nickel foam sodium alginate hydrogel solar evaporator according to claim 1, characterized in that... The distance between the working electrode and the counter electrode mentioned in step 1③ is 2cm~3cm.

4. The method for preparing a double-layer polypyrrole deposited nickel foam sodium alginate hydrogel solar evaporator according to claim 1, characterized in that... The volume ratio of calcium chloride solution to sodium alginate solution mentioned in step 2③ is 1:(1.5~3).

5. The method for preparing a double-layer polypyrrole deposited foam nickel alginate sodium hydrogel solar evaporator according to claim 1, characterized in that... The heating and dissolving process described in step 2③ specifically involves heating at a temperature of 80℃~90℃ for 45min~90min.

6. The method for preparing a double-layer polypyrrole deposited nickel foam sodium alginate hydrogel solar evaporator according to claim 1, characterized in that... In step three, let it stand at room temperature for 0.5h to 1.5h once; in step three, let it stand at room temperature for 15h to 24h a second time; in step three, soak it in distilled water at room temperature for 4h to 12h.

7. The method for preparing a double-layer polypyrrole deposited nickel foam sodium alginate hydrogel solar evaporator according to claim 1, characterized in that... The volume ratio of the calcium chloride solution mentioned in step three to the sodium alginate hydrogel added to the container is 1:(0.5~2).

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