Solar interface evaporator and method of making the same

Abstract

This application provides a solar interface evaporator and its preparation method, relating to the field of evaporator technology. The evaporator includes: a photothermal layer for photothermal conversion and steam escape, comprising a first fiber material; a water transport layer for drawing water from bulk water and transporting it to the photothermal layer, comprising a second fiber material; and an interface layer located between the photothermal layer and the water transport layer, comprising an interpenetrating network structure formed by the first and second fiber materials. The pore size of the interpenetrating network structure varies gradient along the thickness direction. This evaporator utilizes the interpenetrating network structure to reduce the capillary ingress pressure barrier, ensuring continuous low-resistance transport of water from the water transport layer to the photothermal layer and reducing salt ion retention in the interface layer.

Description

Technical Field

[0001] This application relates to the field of evaporator technology, specifically to a solar interface evaporator and its preparation method. Background Technology

[0002] Solar-driven interfacial evaporation (SDIE) is a low-energy water production technology that utilizes photothermal materials to concentrate solar energy on the evaporation surface, enabling seawater desalination, brackish water purification, and wastewater resource recovery. Compared with traditional processes such as reverse osmosis and multi-stage flash evaporation, interfacial evaporation has advantages such as operating at atmospheric pressure, simple equipment, and easy off-grid deployment, making it particularly suitable for distributed freshwater acquisition scenarios.

[0003] In the field of solar interfacial evaporation technology, achieving continuous, high-flux water supply, efficient salt management, and environmental sustainability of materials are the core requirements driving the technology towards practical application. However, the aforementioned performance characteristics of solar evaporators using related technologies need further improvement. Summary of the Invention

[0004] In order to overcome the technical problems mentioned in the background, this application provides a solar interface evaporator and its preparation method.

[0005] In a first aspect, embodiments of this application provide a solar interface evaporator, comprising: a photothermal layer for photothermal conversion and steam escape, the photothermal layer comprising a first fiber material; a water transport layer for absorbing water from bulk water and transporting water to the photothermal layer, the water transport layer comprising a second fiber material; and an interface layer located between the photothermal layer and the water transport layer, the interface layer comprising an interpenetrating network structure formed by the first fiber material and the second fiber material; wherein the pore size of the interpenetrating network structure varies gradient along the thickness direction.

[0006] In conjunction with the first aspect, in some implementations, the pore size of the interpenetrating network structure gradually decreases from the water transport layer to the photothermal layer along the thickness direction, wherein the pore size of the interpenetrating network structure ranges from 2 to 150 nanometers; and / or, the thickness of the interface layer ranges from 100 to 300 micrometers, preferably from 100 to 200 micrometers.

[0007] In conjunction with the first aspect, in some implementations, the photothermal layer includes a fiber matrix composed of a first fiber material, photothermal particles loaded on the surface of the fiber matrix, and a coating layer covering the photothermal particles; wherein the material of the photothermal particles includes at least one of MOF, MOF-derived materials, carbon nanotubes, graphene / graphene oxide, MXene, and metal oxides; and / or, the material of the coating layer includes a polydopamine layer.

[0008] In conjunction with the first aspect, in some implementations, the water conveyance layer includes a first channel and a second channel, wherein the first channel is oriented along the thickness direction; preferably, the pore size of the first channel is in the range of 50 to 80 micrometers, and the pore size of the second channel is in the range of 5 to 30 nanometers.

[0009] In conjunction with the first aspect, in some implementations, the first fiber material and the second fiber material include bio-based materials; wherein, the bio-based material includes bamboo, the first fiber material includes bamboo microfibers, and the second fiber material includes bamboo nanofibers; preferably, the diameter of the first fiber material is in the range of 15 to 22 micrometers, and the diameter of the second fiber material is in the range of 5 to 50 nanometers.

[0010] Secondly, embodiments of this application also provide a method for preparing a solar interface evaporator, comprising: preparing a photothermal layer preform, the photothermal layer preform including a first fiber material; preparing a water transport layer precursor, the water transport layer precursor including a second fiber material; placing the photothermal layer preform at the gas-liquid interface of the water transport layer precursor and applying pressure, so that a portion of the first fiber material is inserted into the water transport layer precursor to obtain an intermediate part; performing directional pore forming treatment on the intermediate part, so that the second fiber material forms a first channel oriented along the thickness direction, and forms an interpenetrating network structure including the first fiber material and the second fiber material; and performing freeze-drying treatment to form a solar interface evaporator.

[0011] In conjunction with the second aspect, in some implementation methods, the directional hole forming process is selected from at least one of the following: liquid nitrogen freezing method, ice template method, electric field induction method, magnetic field induction method, and template-assisted method.

[0012] In conjunction with the second aspect, in some implementation methods, the intermediate component undergoes directional pore forming treatment, including: placing the intermediate component in a liquid nitrogen environment for directional freezing treatment; wherein the directional freezing treatment time is 20 min to 40 min, the freezing distance of the directional freezing treatment is 1.5 cm to 2.5 cm, and the temperature gradient of the directional freezing treatment is 50℃ to 200℃; preferably, the pressure is greater than or equal to 10 kPa and less than or equal to 100 kPa; preferably, the vacuum degree of the freeze-drying treatment is less than or equal to 0.01 MPa, the temperature range of the freeze-drying treatment is -90℃ to -70℃, and the time range of the freeze-drying treatment is 40 h to 60 h.

[0013] In conjunction with the second aspect, in some implementation methods, the preparation of the photothermal layer preform includes: obtaining a first fiber material; immersing the first fiber material in a cobalt salt solution, adding 2-methylimidazole for ultrasonic-assisted in-situ growth, so that ZIF-67 particles are loaded on the surface of the first fiber material, and drying at 70℃~90℃ for 20h~24h to obtain a first intermediate product; dispersing the first intermediate product and dopamine hydrochloride in a Tris-HCl buffer solution, and magnetically stirring at 20℃~30℃ for 2min~10min to coat the ZIF-67 particles with a polydopamine layer to obtain a second intermediate product; vacuum filtering the second intermediate product and washing it with deionized water to remove unreacted substances; and drying at 70℃~90℃. The photothermal layer preform is obtained by drying under temperature conditions for 20-24 hours; preferably, the cobalt salt solution includes cobalt nitrate solution; preferably, the mass ratio of ZIF-67 particles to polydopamine layer is in the range of 10:3-10:8; preferably, the first fiber material includes bamboo fiber microfiber, and the first fiber material is obtained by: treating bamboo raw material with delignification using chlorite solution to obtain treated bamboo substrate; then treating bamboo substrate with alkaline solution to remove hemicellulose to obtain bamboo fiber microfiber; preferably, the chlorite solution includes sodium chlorite solution, and the pH of the chlorite solution is 4.5-4.6; the delignification treatment temperature is 70℃-90℃; preferably, the alkaline solution includes sodium hydroxide solution, and the alkaline treatment temperature is 70℃-90℃.

[0014] In conjunction with the second aspect, in some implementations, the preparation of the aquifer precursor includes: obtaining a hydrogel of a second fiber material; mixing the hydrogel of the second fiber material with a metal ion solution and mechanically stirring for 5 min to 20 min to obtain the aquifer precursor; wherein the metal ions include at least one of aluminum ions, calcium ions, and copper ions; preferably, the second fiber material includes bamboo nanofibers, and obtaining the hydrogel of the second fiber material includes: subjecting the bamboo nanofibers to TEMPO oxidation and high-pressure homogenization treatment to obtain the hydrogel of the second fiber material.

[0015] Compared to related technologies where abrupt changes in fiber and pore size at the interface between the photothermal layer and the water delivery layer in a double-layer evaporator cause a sudden increase in capillary entry pressure barrier, leading to discontinuous water supply and salt ion retention, this application's embodiment addresses these issues by setting an interface layer between the photothermal layer and the water delivery layer. This interface layer contains an interpenetrating network structure formed by a first fiber material and a second fiber material, with the pore size of the interpenetrating network structure varying gradually along the thickness direction. This transforms the sudden change in capillary pressure caused by the abrupt change in pore size into a continuous and gentle capillary pressure gradient, reducing the capillary entry pressure barrier and enabling continuous, low-resistance water transport from the water delivery layer to the photothermal layer. Simultaneously, it avoids localized salt ion retention, providing a reliable structural basis for achieving high evaporation flux and active salt removal in solar interface evaporators. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the structure of a solar interface evaporator provided in an embodiment of this application.

[0018] Figure 2a This is a schematic diagram of the water flow at the abrupt change in pore size in a double-layer evaporator of a related technology.

[0019] Figure 2b This is a schematic diagram of water flow at the interface of the double-layer evaporator in this embodiment of the application.

[0020] Figure 2c This is a schematic diagram showing the salt ion enrichment at the interface of related technologies.

[0021] Figure 2d This is a schematic diagram of salt ion enrichment at the interface in an embodiment of this application.

[0022] Figure 3a This is a schematic diagram of the interpenetrating network structure of the interface layer.

[0023] Figures 3b to 3d Renderings of scanning electron microscope images of interface layers of different thicknesses.

[0024] Figure 3e This is a rendered image of the scanning electron microscope (SEM) image of the interface layer.

[0025] Figure 4 This is a schematic diagram of the photothermal layer and water transport layer of a solar interface evaporator provided in an embodiment of this application.

[0026] Figure 5 This is a schematic flowchart illustrating a method for preparing a solar interface evaporator according to an embodiment of this application.

[0027] Figure 6 A schematic diagram of a test apparatus for a solar interface evaporator under natural light conditions provided in an embodiment of this application. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0029] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0030] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. It should be noted that, unless otherwise specified, different features in the embodiments of this application can be combined with each other.

[0031] In solar interfacial evaporation technology, to achieve the goal of transporting bulk water to the evaporation surface and completing photothermal conversion, the related technology employs a double-layer stacked evaporator design. Specifically, a photothermal layer for broadband light absorption and interfacial heating is prepared, along with a hydrophilic porous water-transporting layer that continuously replenishes water from the bulk water using capillary action and provides thermal insulation. The two layers are then combined together by physical bonding or simple pressing.

[0032] However, when this stacked double-layer evaporator is applied to continuous, high-flux evaporation conditions, especially when treating water bodies with high salinity, its water supply stability and salinity management capabilities become significantly insufficient. This is because the structure, which involves separate preparation and reassembly, makes it difficult to form a continuously varying pore structure at the interface between the photothermal layer and the water transport layer, resulting in abrupt discontinuities in pore size within an extremely narrow space. This abrupt change in pore size creates a steep capillary ingress pressure barrier at the interface, restricting the continuous, low-resistance transport of water from the water transport layer to the photothermal layer. Furthermore, in applications such as marine or brackish water desalination, the abrupt change at the interface not only disrupts hydraulic connectivity, making the evaporation surface prone to drying out due to insufficient water supply under high light conditions, but also causes the retention and accumulation of salt ions at the interface, ultimately leading to salt crystallization and pore blockage, causing the evaporator's evaporation rate to continuously decline over time.

[0033] To address the aforementioned technical problems, this application provides a novel technical approach. The core concept involves deep mechanical interpenetration of the fiber materials constituting the photothermal layer and the water supply layer, forming an interface layer with a gradient in pore size along the thickness direction. This transforms the originally steep capillary entry pressure barrier into a smooth capillary pressure gradient, resolving the problems of discontinuous water supply and ion retention caused by interfacial discontinuities. Thus, while maintaining interfacial hydraulic continuity, it provides a structural basis for high evaporation flux and active desalination.

[0034] Figure 1 This is a schematic diagram of the structure of a solar interface evaporator provided in an embodiment of this application.

[0035] In some implementations, a solar interface evaporator may include any device or system capable of concentrating solar energy at the gas-liquid interface, heating the liquid through photothermal conversion, and vaporizing it at the interface. For example, it may include, but is not limited to, a bilayer structure consisting of a photothermal layer and a water-conducting layer, an integrated structure with an interface transition layer between the bilayer structures, or an integral structure formed from a single material through gradient processing. In the embodiments of this application, the solar interface evaporator may include a photothermal layer made of a first fiber material, a water-conducting layer made of a second fiber material, and an interface layer located between the photothermal layer and the water-conducting layer.

[0036] When a solar-powered interfacial evaporator is in operation, it is placed on top of the water body to be treated. It draws water from the bulk water through capillary action and converts the water into steam at the evaporation surface using solar energy. Specifically, the bottom of the water transport layer contacts the bulk water, and water is transported upwards through its internal channels. After entering the interfacial layer, the water continues to migrate towards the photothermal layer via capillary action within the gradient-changing pore structure of the interfacial layer, eventually reaching the evaporation surface of the photothermal layer. The solar energy absorbed by the photothermal layer is converted into heat at the evaporation surface, causing the water reaching the evaporation surface to vaporize. The steam escapes from the evaporation surface, completing the evaporation process.

[0037] like Figure 1 As shown, the solar interface evaporator has a layered structure, mainly consisting of a photothermal layer 110, an interface layer 120, and a water conveyance layer 130 from top to bottom. The interface layer 120, the photothermal layer 110, and the water conveyance layer 130 are integrally formed, so there is no independent interlayer bonding interface between the photothermal layer 110 and the water conveyance layer 130.

[0038] The photothermal layer 110 is used for photothermal conversion and vapor escape. Specifically, it can be a functional layer capable of absorbing solar energy and efficiently converting it into heat energy to drive liquid vaporization at the interface and allow vapor escape. For example, the photothermal layer 110 may include, but is not limited to, a composite layer formed by loading photothermal particles onto a fiber matrix, a porous film with intrinsic photothermal effect, or a light-absorbing layer with a blackened surface. In the embodiments of this application, the photothermal layer 110 has an evaporation surface facing sunlight for receiving solar energy and converting it into heat energy, while providing a channel for vapor escape. Exemplarily, the photothermal layer 110 includes a first fiber material that forms a fiber network with specific pores within the photothermal layer 110 to carry the photothermal conversion functional components and maintain a vapor diffusion path.

[0039] The water-conducting layer 130 is used to draw water from the bulk water and transport it to the photothermal layer 110. Specifically, it can be any functional layer with a porous structure capable of drawing liquid from the bulk water using capillary action and continuously and with low resistance transporting the liquid to the photothermal layer 110. The water-conducting layer 130 typically also has a thermal insulation function, limiting downward heat conduction and reducing energy loss. For example, the water-conducting layer 130 may include, but is not limited to, fibrous aerogels with vertically oriented channels, hierarchical porous materials with a dual-level pore size distribution, or porous matrices with high porosity and hydrophilicity. In the embodiments of this application, the water-conducting layer 130 is in direct or indirect contact with the underlying bulk water for drawing water from the bulk water and transporting it to the photothermal layer 110. Preferably, the water-conducting layer 130 includes a second fibrous material with channels oriented along the thickness direction internally. These channels provide a low-resistance path for the transport of liquid water to the photothermal layer 110 and simultaneously structurally block reverse heat conduction, suppressing the dissipation of heat generated by the photothermal layer 110 into the bulk water.

[0040] The interface layer 120 may be a structural transition region located between the photothermal layer 110 and the water conveyance layer 130, used to establish and improve the hydraulic continuity between the two layers and eliminate or significantly reduce interfacial water conveyance resistance. Unlike the abrupt pore interface of a double-layer evaporator in related technologies, in this embodiment, the interface layer 120 is composed of interwoven materials from the photothermal layer 110 and the water conveyance layer 130. Specifically, the interface layer 120 is located between the photothermal layer 110 and the water conveyance layer 130, and it is not a separate prefabricated layer, but rather an integrated transition region formed by a first fiber material from the photothermal layer 110 and a second fiber material from the water conveyance layer 130. In one implementation, the interface layer 120 includes an interpenetrating network structure formed by the first and second fiber materials. The pore size of the interpenetrating network structure varies continuously along the thickness direction, thus creating a gradient of capillary pressure between the photothermal layer 110 and the water conveyance layer 130. Specifically, the thickness direction can be characterized by the direction perpendicular to the main surface of the solar interface evaporator, downwards to the side towards the water transport layer 130, and upwards to the side towards the photothermal layer 110.

[0041] Figure 2a This is a schematic diagram of the water flow at the abrupt change in pore size in a double-layer evaporator of a related technology. Figure 2b This is a schematic diagram of water flow at the interface of the double-layer evaporator in this embodiment of the application. Figure 2c This is a schematic diagram showing the salt ion enrichment at the interface of related technologies. Figure 2d This is a schematic diagram of salt ion enrichment at the interface in an embodiment of this application.

[0042] In related technologies, abrupt pore size changes at the interface between the photothermal layer and the water supply layer of a double-layer evaporator. According to the Yang-Laplace equation, a steep capillary ingress pressure barrier is generated at this interface. This barrier hinders the continuous upward transport of water, causing backflow or vortices, resulting in energy loss and thus forming a bottleneck in the water supply. Figure 2a As shown, a convex liquid surface is formed at this interface, indicating a large capillary pressure at this interface, which hinders the upward transport of water. Figure 2c As shown, due to the low water flux of related technologies, salt ions tend to accumulate at the interface, leading to severe salt ion enrichment and affecting the performance of the solar interface evaporator. In this embodiment, by constructing the interface layer 120, the sudden change in capillary pressure caused by abrupt pore size can be transformed into a continuous and gentle capillary pressure gradient, thereby reducing the capillary entry pressure barrier and ensuring that water can be supplied uninterruptedly and with low resistance from the water supply layer 130 to the photothermal layer 110. Figure 2b As shown, a concave liquid surface forms at the interface where the gradient changes, indicating that the capillary pressure at this interface is relatively low, which is conducive to the upward transport of water. Figure 2d As shown, due to the large water flux in this embodiment, it is beneficial for the reflux of salt ions, which helps to suppress the accumulation of salt on the evaporation surface and salt blockage, and can adapt to high salinity conditions.

[0043] Compared to related technologies where abrupt changes in pore size at the interface between the photothermal layer and the water delivery layer in a double-layer evaporator cause a sudden increase in capillary ingress pressure barrier, leading to discontinuous water supply and salt ion retention, this application's embodiment addresses these issues by setting an interface layer between the photothermal layer and the water delivery layer. This interface layer comprises an interpenetrating network structure formed by a first fiber material and a second fiber material, with the pore size of the interpenetrating network structure varying gradually along the thickness direction. This transforms the sudden change in capillary pressure caused by abrupt pore size changes into a continuous and gentle capillary pressure gradient, reducing the capillary ingress pressure barrier and enabling continuous, low-resistance water transport from the water delivery layer to the photothermal layer. Simultaneously, it avoids localized salt ion retention, providing a reliable structural basis for achieving high evaporation flux and active salt removal in solar interface evaporators.

[0044] In some implementations, the pore size of the interpenetrating network structure gradually decreases along the thickness direction from the water transport layer to the photothermal layer.

[0045] Specifically, on the side near the water transport layer 130, the second fiber material dominates, and the second fiber material is arranged to form a first channel (see subsequent description for details). The first channel has a large pore size (e.g., up to the micrometer level). Therefore, the pores on the side of the interface layer 120 near the water transport layer 130 are relatively large, which can provide a large capillary driving force to absorb and transport water. On the side near the photothermal layer 110, the first fiber material dominates, and the surface of the first fiber material is loaded with nanoparticles with a pore size at the nanometer level. Therefore, the pores on the side of the interface layer 120 near the photothermal layer 110 are relatively small. In the embodiments of this application, when preparing the mechanically interpenetrating interface layer 120, pressure needs to be applied to the photothermal layer 110 side. As the pressure is transmitted downwards, it gradually decreases. Therefore, along the direction from the photothermal layer 110 to the water transport layer 130, the first fiber material in the interface layer 120 gradually decreases, so the pores in the interface layer 120 can exhibit a gradient change. In other words, the pore size of the interpenetrating network structure gradually decreases from the water transport layer to the photothermal layer along the thickness direction. The gradient change in pore size helps to reduce the capillary entry pressure barrier, which can guide water to be transported smoothly and continuously to the photothermal layer 110 side, thereby achieving efficient and low-resistance directional water transport.

[0046] Figure 3a This is a schematic diagram of the interpenetrating network structure of the interface layer. Figures 3b to 3d Renderings of scanning electron microscope images of interface layers of different thicknesses. Figure 3e This is a rendered image of the scanning electron microscope (SEM) image of the interface layer.

[0047] like Figure 3aAs shown, the first fiber material extends primarily laterally, while the first channel formed by the second fiber material extends vertically. At the interface layer, the laterally extending first fiber material and the vertically extending second fiber material mechanically interpenetrate, forming an interpenetrating network structure. Figure 3e In the magnified image, the interpenetrating network structure of the first fiber material and the second fiber material can be clearly seen, where blue represents the second fiber material and red represents the first fiber material.

[0048] In some embodiments, the porosity of the interpenetrating network structure ranges from 2 to 150 nanometers, for example, 2 nanometers, 10 nanometers, 50 nanometers, 100 nanometers, 150 nanometers, etc.; and / or, the thickness of the interface layer ranges from 100 to 300 micrometers, preferably from 100 to 200 micrometers, for example, 100 micrometers, 150 micrometers, 200 micrometers, 250 micrometers, 300 micrometers, etc.

[0049] When the thickness of the interface layer is too small (e.g., less than 100 micrometers), the rate of change of pore size along the thickness is too large, and a large capillary ingress pressure barrier may still exist. Conversely, when the thickness of the interface layer is too large (e.g., more than 300 micrometers), although a relatively gentle capillary ingress pressure gradient can be formed, the excessively long transport path will increase the viscous frictional resistance of the water flow, and the excessively thick interface layer may reduce the mechanical strength of the overall structure due to the weakening of the interfiber bonding force.

[0050] By controlling the thickness of the interface layer within the range of 100–300 micrometers, particularly when the thickness is approximately 200 micrometers, optimal values ​​can be simultaneously achieved for both mechanical strength and evaporation rate. In some implementations, the thickness parameter achieving the same balance can be adjusted according to the specific type, diameter, and weaving density of the first and second fiber materials, for example, fine-tuning can be performed within the range of 100–300 micrometers.

[0051] By limiting the thickness of the interface layer to 100-300 micrometers (preferably 100-200 micrometers), sufficient space is provided for a smooth transition and the capillary entry pressure barrier is reduced. This avoids the problems that may result from an excessively thick interface layer (greater than 300 micrometers), such as an excessively long mass transfer path and increased viscous resistance, as well as the problems that may result from an excessively thin interface layer (less than 100 micrometers), such as an excessively large porosity change rate, residual local barriers, or insufficient mechanical strength. This achieves simultaneous optimization of hydraulic continuity and interface mechanical strength.

[0052] In some implementations, the photothermal layer 110 includes a fiber matrix composed of a first fiber material, photothermal particles loaded on the surface of the fiber matrix, and a coating layer covering the photothermal particles; wherein the material of the photothermal particles includes at least one of a metal-organic framework (MOF), MOF-derived materials, carbon nanotubes, graphene / graphene oxide, two-dimensional transition metal carbides (MXene), and metal oxides; and / or, the material of the coating layer includes a polydopamine layer.

[0053] Specifically, the fiber matrix composed of the first fiber material serves as a three-dimensional framework, providing a large specific surface area for the attachment of photothermal particles. Preferably, the photothermal particles can be zeolitic imidazolate framework-67 (ZIF-67) particles. In one implementation, ZIF-67 particles can be uniformly and firmly anchored to the surface of the first fiber material through in-situ growth. Further, coating the ZIF-67 particles with a polydopamine (PDA) layer can form a core-shell structure. The PDA layer not only covers the 700-2500 nm infrared region through π-π transitions, complementing the spectral absorption of the ZIF-67 particles to achieve full-spectrum absorption, but also synergistically constructs nano-hydrophilic pores between the PDA layer and the ZIF-67 particles. For example, the interfacial voids between the shell and core of PDA@ZIF-67 particles, as well as the molecular channels within the PDA layer itself, can form nano-hydrophilic pores with a size of approximately 1-2 nanometers. These nano-hydrophilic pores can alter the state of water, significantly increasing the proportion of intermediate-state water. This allows water molecules to evaporate without completely breaking all hydrogen bonds, thus reducing the equivalent enthalpy of evaporation from 2406 ohms for pure water. Significantly reduced to approximately 1825 The decrease could reach approximately 24.2%.

[0054] Through the synergistic effect of photothermal particles (such as ZIF-67 particles) and coating layers (such as PDA), efficient solar energy capture and conversion are achieved, significantly increasing the surface temperature of the photothermal layer, providing sufficient heat source for steam generation, improving the conversion efficiency of solar energy to steam, and reducing the equivalent enthalpy required for water evaporation.

[0055] When the water supply layer 130 of a solar interface evaporator needs to simultaneously meet the requirements of high-flux water supply and low thermal conductivity insulation, how to synergistically resolve the contradiction between the pursuit of rapid water supply and the exacerbated downward heat conduction is another issue that needs attention. To address this issue, this application further provides a preferred scheme for the internal microstructure of the water supply layer 130.

[0056] In some implementations, the water conveyance layer 130 includes a first channel and a second channel, with the first channel oriented along the thickness direction. Optionally, the pore size of the first channel ranges from 50 to 80 micrometers, for example, 50 micrometers, 60 micrometers, 70 micrometers, 80 micrometers, etc.; the pore size of the second channel ranges from 5 to 30 nanometers, for example, 5 nanometers, 10 nanometers, 20 nanometers, 30 nanometers, etc.

[0057] Specifically, the first vertically oriented channel, with a pore size of 50–80 micrometers, provides a low-torsion macrochannel for the upward transport of bulk water. Since the viscous flow resistance within the channel is inversely proportional to the square of the channel radius, the macrochannel reduces water transport resistance, ensuring a sufficient and continuous water supply to the evaporation surface under high evaporation flux. Simultaneously, the second channel, with a pore size of 5–30 nanometers, generates a large capillary driving force and has a strong water absorption capacity, rapidly drawing water from the bulk water and replenishing it to the first channel.

[0058] Figure 4 This is a schematic diagram of the photothermal layer and water transport layer of a solar interface evaporator provided in an embodiment of this application.

[0059] like Figure 4 As shown, the black dashed arrows in the photothermal layer 110 indicate the transverse channels within this layer, primarily responsible for the escape of steam, allowing the generated water vapor to diffuse smoothly. The water transport layer 130 contains axial / vertical channels, also known as the first channel, which is a low-resistance, high-speed pathway for bulk water to be transported from the water transport layer 130 to the photothermal layer 110. The interface layer (not shown) is located between the photothermal layer and the water transport layer.

[0060] By constructing a bilevel porous structure consisting of a vertically oriented first channel (50~80 μm) and a second channel (5~30 nm), the water supply and heat insulation functions are decoupled. The first channel provides a high-speed water transport path with low tortuosity and low viscous resistance, ensuring high-flux water supply. The second channel absorbs water with its strong capillary driving force and effectively suppresses solid-phase heat conduction through its large amount of air filling and low tortuosity structure, achieving low thermal conductivity and effectively localizing heat on the evaporation surface to avoid downward dissipation.

[0061] In order to address the environmental burden caused by the non-degradability and difficulty in recycling of synthetic polymer solar interface evaporators after their lifespan, while pursuing high performance of solar interface evaporators, this application provides a more environmentally friendly material.

[0062] In some implementations, the first fiber material and the second fiber material include bio-based materials; wherein, the bio-based material includes bamboo, the first fiber material includes bamboo microfibers, and the second fiber material includes bamboo nanofibers.

[0063] Specifically, both the photothermal layer 110 and the water-conducting layer 130 are derived from the same bio-based material—bamboo. In one implementation, natural bamboo is deconstructed using chemical and mechanical means to obtain bamboo cellulose microfibers and bamboo nanofibers with specific dimensions, which are then reconstructed according to preset functional requirements. Optionally, the diameter range of the first fiber material can be 15–22 micrometers, for example, 15 micrometers, 16 micrometers, 17 micrometers, 18 micrometers, 19 micrometers, 20 micrometers, 21 micrometers, 22 micrometers, etc. The diameter range of the second fiber material can be 5–50 nanometers, for example, 5 nanometers, 10 nanometers, 20 nanometers, 30 nanometers, 40 nanometers, 50 nanometers, etc.

[0064] By using bamboo, the solar interface evaporator can be rapidly biodegraded through soil landfill or composting after its service life, avoiding secondary pollution such as microplastics generated during the decomposition of polymer evaporators in related technologies.

[0065] Figure 5 This is a schematic flowchart illustrating a method for preparing a solar interface evaporator according to an embodiment of this application. Figure 5 As shown, the preparation method includes the following steps.

[0066] Step S510: Prepare the photothermal layer preform.

[0067] In some embodiments, the photothermal layer preform can characterize a thin material layer that has undergone photothermal particle loading and coating treatment on a fiber matrix, but has not yet been integrally formed with the water transport layer. In one implementation, the photothermal layer preform may include a first fiber material.

[0068] Step S520: Prepare the aquifer precursor.

[0069] In one implementation, the water-conducting layer precursor can characterize an intermediate-state material or molded body formed during the preparation process that has not yet undergone final shaping treatment (such as directional freezing or freeze-drying). The water-conducting layer precursor may include a second fiber material. Optionally, the water-conducting layer precursor may be in a gel state.

[0070] Step S530: Place the photothermal layer preform at the gas-liquid interface of the water transport layer precursor and apply pressure to insert part of the first fiber material into the water transport layer precursor to obtain the intermediate part.

[0071] For example, a water-conveying layer precursor containing a second fiber material can be injected into a mold. A pre-formed photothermal layer preform is then laid flat and placed on the upper surface / gas-liquid interface of the water-conveying layer precursor, and pressure is applied to insert a portion of the first fiber material into the water-conveying layer precursor, resulting in an intermediate part. In some embodiments, the thickness of the formed interface layer can be adjusted by changing the applied pressure. Optionally, the pressure is greater than or equal to 10 kPa and less than or equal to 100 kPa, for example, 10 kPa, 30 kPa, 50 kPa, 80 kPa, 100 kPa, etc. Preferably, the pressure is greater than or equal to 10 kPa and less than or equal to 50 kPa. Within this thickness range, an interface layer of suitable thickness can be formed. It should be noted that since the pressure is applied from the photothermal layer side, the pressure gradually decreases as it extends towards the water-conveying layer, reducing the amount of the first fiber material inserted into the water-conveying layer precursor. That is, along the direction from the photothermal layer to the water-conveying layer, the amount of the first fiber material in the interface layer gradually decreases, allowing for a gradient change in pore size.

[0072] Step S540: The intermediate part is subjected to directional hole forming process so that the second fiber material forms a first channel oriented along the thickness direction and forms an interpenetrating network structure containing the first fiber material and the second fiber material.

[0073] By performing directional hole forming on the intermediate component, the second fiber material can form a first channel oriented along the thickness direction and form an interpenetrating network structure.

[0074] Step S550 involves freeze-drying to form a solar interface evaporator.

[0075] A solar interface evaporator with an interpenetrating network structure can be formed through freeze-drying.

[0076] After stacking the photothermal layer preform onto the water transport layer precursor, pressure is applied to insert the first fiber material into the water transport layer precursor and oriented to form pores, thus forming an interface layer with an interpenetrating network structure and a vertically oriented first channel. This avoids the problems of poor interface bonding and complex processes in the separate preparation and physical bonding channels of related technologies, simplifies the production process, and improves product consistency and interface bonding strength.

[0077] In some embodiments, the directional pore-forming process is selected from at least one of liquid nitrogen freezing, ice template method, electric field induction method, magnetic field induction method, and template-assisted method. All of the above methods can form vertical channels in the water-carrying layer and form an interface layer.

[0078] By employing various directional pore-forming methods, the fabrication process of solar interface evaporators has been made more flexible.

[0079] In some embodiments, the intermediate component is subjected to directional pore forming treatment, which includes: placing the intermediate component in a liquid nitrogen environment and performing directional freezing treatment; wherein the directional freezing treatment time is 20 min to 40 min, the freezing distance of the directional freezing treatment is 1.5 cm to 2.5 cm, and the temperature gradient of the directional freezing treatment is 50°C to 200°C; wherein the vacuum degree of the freeze-drying treatment is less than or equal to 0.01 MPa, the temperature range of the freeze-drying treatment is -90°C to -70°C, and the time range of the freeze-drying treatment is 40 h to 60 h.

[0080] In the directional freezing process, by controlling parameters such as the freezing time, freezing distance, and temperature gradient, the pore size, orientation, and the thickness and pore gradient of the interface layer formed in the first channel can be effectively controlled. In some implementations, the directional freezing time can be controlled within the range of 20 to 40 minutes, for example, 20 minutes, 30 minutes, or 40 minutes, to ensure the formation of a vertically oriented first channel.

[0081] The freezing distance (i.e., the vertical distance between the sample and the liquid nitrogen surface) for directional freezing treatment can be controlled within the range of 1.5 cm to 2.5 cm, for example, 1.5 cm, 2.0 cm, 2.5 cm, etc. The geometry of the first channel can be adjusted by changing the freezing distance. This application provides several examples and comparative examples. Example 1 uses liquid nitrogen directional freezing treatment with a freezing distance of 2 cm; Comparative Example 1 uses liquid nitrogen directional freezing treatment with a freezing distance of 0 cm (i.e., the sample is in contact with liquid nitrogen); Comparative Example 2 uses liquid nitrogen directional freezing treatment with a freezing distance of 1 cm; Comparative Example 3 uses liquid nitrogen directional freezing treatment with a freezing distance of 3 cm; and Comparative Example 4 uses isotropic freezing treatment. All other conditions are the same for Examples 1 to Comparative Example 4.

[0082] In Example 1, when the freezing distance is 2 cm, an oriented first channel can be formed, achieving low resistance and efficient water delivery. In Comparative Example 1, when the freezing distance is 0 cm, a highly tortuous first channel with a small aperture can be formed, resulting in high water delivery resistance. In Comparative Example 2, when the freezing distance is 1 cm, a moderately tortuous first channel can be formed, resulting in relatively high water delivery resistance. In Comparative Example 3, when the freezing distance is 3 cm, a first channel with an excessively large aperture can be formed, which is prone to collapse. In Comparative Example 4, isotropic freezing treatment is used, resulting in a disordered and non-directional porous structure, which is difficult to provide rapid water delivery and lacks the thermal insulation performance provided by oriented channels.

[0083] In one implementation, the vacuum degree of the freeze-drying process can be set to less than or equal to 0.01 MPa, and the processing temperature range can be controlled from -90℃ to -70℃, for example, -90℃, -85℃, -80℃, -75℃, -70℃, etc. The processing time range can be controlled from 40 hours to 60 hours, for example, 40 hours, 45 hours, 50 hours, 55 hours, 60 hours, etc.

[0084] By limiting the key process parameters (time, distance, temperature gradient, vacuum degree, temperature, and time) of directional freezing and freeze-drying, the formation of the first channel and the uniformity of the interpenetrating network structure are ensured, providing a reliable process guarantee for obtaining a stable solar interface evaporator with strong industrial applicability.

[0085] To illustrate the preparation process of the photothermal layer preform in more detail, this application provides the following more detailed embodiments.

[0086] In some embodiments, the preparation of a photothermal layer preform includes: obtaining a first fiber material; immersing the first fiber material in a cobalt salt solution, adding 2-methylimidazole for ultrasonic-assisted in-situ growth, so that ZIF-67 particles are loaded onto the surface of the first fiber material, and drying at 70°C~90°C for 20h~24h to obtain a first intermediate product; dispersing the first intermediate product and dopamine hydrochloride in a Tris-HCl buffer solution, and magnetically stirring at 20°C~30°C for 2min~10min to coat the ZIF-67 particles with a polydopamine layer to obtain a second intermediate product; vacuum filtering the second intermediate product and washing it with deionized water to remove unreacted substances; and drying at 70°C~90°C. The material is dried for 20-24 hours to obtain a photothermal layer preform; wherein the cobalt salt solution includes cobalt nitrate solution; and / or, the mass ratio of ZIF-67 particles to polydopamine layer is in the range of 10:3-10:8; wherein the first fiber material includes bamboo fiber microfibers, and the first fiber material is obtained by: treating bamboo raw material with delignification using chlorite solution to obtain treated bamboo substrate; then treating bamboo substrate with alkaline solution to remove hemicellulose to obtain bamboo fiber microfibers; wherein the chlorite solution includes sodium chlorite solution, and the pH of the chlorite solution is 4.5-4.6; the delignification treatment temperature is 70℃-90℃; and / or, the alkaline solution includes sodium hydroxide solution, and the alkaline treatment temperature is 70℃-90℃.

[0087] Specifically, after removing the outer skin and inner yellow layer of bamboo, bamboo raw material is obtained. This raw material is then treated with a chlorite solution to induce delignification, resulting in treated bamboo substrate. For example, a sodium chlorite solution can be used, with the pH adjusted to a weakly acidic range of 4.5 to 4.6 using glacial acetic acid. The delignification treatment temperature can be between 70°C and 90°C, for example, 70°C, 80°C, or 90°C. Delignification treatment can selectively remove lignin components from the bamboo.

[0088] Then, the delignified bamboo substrate is subjected to alkali treatment with an alkaline solution to remove hemicellulose, thereby obtaining bamboo cellulose microfibers (BCFs). Sodium hydroxide solution can be used as the alkaline solution, and the alkali treatment temperature can be between 70℃ and 90℃, for example, 70℃, 80℃, 90℃, etc. Through alkali treatment, the natural hierarchical structure of bamboo is broken down, retaining cellulose microfibers with excellent mechanical properties and a diameter mainly distributed in the range of 15~22 micrometers.

[0089] The first fiber material is impregnated in a cobalt salt solution, and 2-methylimidazole is added for ultrasonic-assisted in-situ growth, allowing ZIF-67 particles to be loaded onto the surface of the first fiber material. For example, a cobalt nitrate solution can be used as the cobalt salt solution. The ultrasonic cavitation effect effectively improves the uniformity and adhesion density of the ZIF-67 particles on the surface of the first fiber material. Drying at a temperature of 70°C to 90°C for 20 to 24 hours, for example, 70°C, 80°C, or 90°C, yields the first intermediate product, ZIF-67@BCFs.

[0090] The first intermediate product and dopamine hydrochloride were dispersed in a Tris(hydroxymethyl)aminomethane hydrochloride (Tris-HCl) buffer solution and magnetically stirred at a temperature of 20°C to 30°C for a stirring time of 2 to 10 minutes, for example, 2 minutes, 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, 10 minutes, etc., to form a polydopamine layer on the surface of ZIF-67 particles through self-etching and in-situ polymerization, thus obtaining the second intermediate product.

[0091] This application includes embodiments and comparative examples. In embodiment 2, ZIF-67 particles are coated to form a polydopamine layer, and in comparative example 5, ZIF-67 particles are not coated to form a polydopamine layer. In Example 1, ZIF-67 particles are coated to form a polydopamine layer. The polydopamine layer not only covers the 700-2500 nm infrared region through π-π transitions, complementing the ZIF-67 particles in spectral absorption, thus achieving full-spectrum absorption capability, but also synergistically constructs nano-hydrophilic pores between the polydopamine layer and the ZIF-67 particles. These nano-hydrophilic pores can change the state of water, significantly increasing the proportion of intermediate water, so that water molecules do not need to completely break all hydrogen bonds before evaporation, thereby reducing the equivalent enthalpy of vaporization. In Comparative Example 5, ZIF-67 particles are not coated to form a polydopamine layer, and can only cover ultraviolet-visible light (300~700 nm). The absorption in the infrared region (>700 nm) is extremely weak, resulting in a significant reduction in the utilization rate of sunlight.

[0092] To achieve better spectral absorption complementarity and reduce enthalpy of evaporation, the mass ratio of ZIF-67 particles to the polydopamine layer can be controlled within the range of 10:3 to 10:8, such as 10:3, 10:4, 10:5, 10:6, 10:7, and 10:8, to construct a hierarchical structure with a clear core-shell structure and key interface voids. Within this mass ratio range, good light absorption is achieved.

[0093] The second intermediate product was vacuum filtered and washed with deionized water to remove unreacted substances. Then, it was dried at 70°C to 90°C for 20 to 24 hours, for example, 20 hours, 21 hours, 22 hours, 23 hours, 24 hours, etc., to obtain the photothermal layer preform (PDA@ZIF-67@BCFs), abbreviated as PZ / BCFs.

[0094] A two-step process, which involves ultrasonic-assisted in-situ growth of ZIF-67 particles and coating them with a polydopamine layer, can stably form a second intermediate product, achieving a synergistic effect of broad-spectrum absorption and reduced enthalpy of vaporization.

[0095] In some embodiments, the preparation of the water transport layer precursor includes: obtaining a hydrogel of a second fiber material; mixing the hydrogel of the second fiber material with a metal ion solution and mechanically stirring for 5 min to 20 min to obtain the water transport layer precursor; wherein the metal ion includes at least one of aluminum ion, calcium ion and copper ion; wherein the second fiber material includes bamboo nanofibers, and obtaining the hydrogel of the second fiber material includes: subjecting the bamboo nanofibers to TEMPO oxidation and high-pressure homogenization treatment to obtain the hydrogel of the second fiber material.

[0096] Bamboo nanofibers were subjected to 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) oxidation and high-pressure homogenization. TEMPO oxidation selectively oxidizes the primary hydroxyl groups on the surface of cellulose microfibers to carboxyl groups, thereby introducing a negative charge and promoting fiber dissociation. High-pressure homogenization, through strong hydrodynamic shear forces, completely dissociates the oxidized fibers into nanoscale fibers, ultimately yielding a hydrogel of a second fiber material stably dispersed in water in a gel state.

[0097] The hydrogel of the second fiber material is mixed with a metal ion solution and mechanically stirred for various times, such as 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20 minutes, to obtain the aquifer precursor. The introduction of metal ions aims to achieve ionic cross-linking of the bamboo nanofiber network, enhancing its structural stability and elasticity, and endowing it with the ability to electrostatically conduct ions. The metal ions used may include aluminum ions (…). ), calcium ions ( ) and copper ions ( At least one of the following.

[0098] By introducing Ionic crosslinking of bamboo nanofiber networks with isovalent metal ions enhances the mechanical strength and structural stability of the hydrogel, preventing network collapse during subsequent directional freezing. Simultaneously, ionic crosslinking introduces a negative surface charge into the water-transporting layer, providing a crucial functional basis for subsequent active electrostatic repulsion of salt ions (in synergy with the positively charged photothermal layer). Furthermore, TEMPO oxidation and high-pressure homogenization allow for efficient dissociation of bamboo nanofibers, yielding a hydrogel of a second fiber material with high specific surface area, abundant carboxyl functional groups, and good water dispersibility, providing a high-quality raw material for constructing high-performance water-transporting layers.

[0099] In one specific implementation, bamboo raw material is obtained by removing the outer skin and inner yellow layer of bamboo. The bamboo raw material is then treated with a chlorite solution to achieve delignification, resulting in a treated bamboo substrate. The delignified bamboo substrate is then treated with an alkaline solution to obtain bamboo cellulose microfibers (BCFs). The first fiber material may include bamboo microfibers. The first fiber material is impregnated in a cobalt salt solution, and 2-methylimidazole is added for ultrasonic-assisted in-situ growth, allowing ZIF-67 particles to be loaded onto the surface of the first fiber material. The material is then dried at 80°C for 24 hours to obtain a first intermediate product. The first intermediate product and dopamine hydrochloride (PDA) are dispersed in a Tris-HCl buffer solution and magnetically stirred at 25°C for 6 minutes to coat the ZIF-67 particles with a polydopamine layer, resulting in a second intermediate product. The second intermediate product is vacuum filtered and washed with deionized water to remove unreacted substances. Finally, it is dried at 80°C for 24 hours to obtain a photothermal layer preform (PZ / BCFs). The second fiber material includes bamboo nanofibers. The bamboo nanofibers are subjected to TEMPO oxidation and high-pressure homogenization to obtain a hydrogel of the second fiber material. The hydrogel of the second fiber material is then reacted with metal ions (e.g., metal nanofibers). The solution is mixed and mechanically stirred for 10 minutes to obtain the water transport layer precursor. The photothermal layer preform is placed at the gas-liquid interface of the water transport layer precursor and pressure is applied, causing part of the first fiber material to insert into the water transport layer precursor to obtain the intermediate part. The intermediate part is subjected to directional pore forming treatment so that the second fiber material forms a first channel oriented along the thickness direction, and an interpenetrating network structure of the fiber material and the second fiber material is formed. The intermediate part is then freeze-dried to form a solar interface evaporator. The solar interface evaporator (PZ / BCFs-BNFA) is placed on the sea surface and exposed to sunlight to generate clean steam.

[0100] Figure 6 A schematic diagram of a test apparatus for a solar interface evaporator under natural light conditions provided in an embodiment of this application.

[0101] like Figure 6As shown, the solar interface evaporator 601 is located above the container holding seawater 602, meaning that the solar interface evaporator 601 floats directly or is placed on the surface of the seawater 602, utilizing sunlight for interface evaporation. An infrared thermometer 603 is used to monitor the surface temperature distribution of the solar interface evaporator 601 in real time, verifying its photothermal conversion and thermal localization effects. The water collection area on the right side of the container holding seawater 602 is used to collect the desalinated water 604 formed by condensation. A light power meter 605, a thermocouple 606, and a temperature and humidity meter 607 are used to measure the intensity of sunlight, ambient / water temperature, and humidity, respectively, ensuring the quantifiability and repeatability of the test conditions. This verifies that the solar interface evaporator is effective not only under ideal laboratory conditions but also under real outdoor conditions such as sunlight, ambient temperature, and wind speed, achieving a water production efficiency of approximately 3.52 ppm under strong sunlight. The evaporation rate and efficiency of 177.12% remained at approximately 3.37% under 20 wt% sodium chloride conditions. It has excellent evaporation performance and stable operation for more than 100 days.

[0102] The basic principles of this application have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this application are merely examples and not limitations, and should not be considered as essential features of each embodiment of this application. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the application to the necessity of employing the aforementioned specific details for implementation.

[0103] The block diagrams of devices, apparatuses, devices, and systems involved in this application are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, apparatuses, devices, and systems can be connected, arranged, and configured in any manner. Words such as “comprising,” “including,” “having,” etc., are open-ended terms meaning “including but not limited to,” and are used interchangeably with them. The terms “or” and “and” as used herein refer to the terms “and / or,” and are used interchangeably with them unless the context clearly indicates otherwise. The term “such as” as used herein refers to the phrase “such as but not limited to,” and is used interchangeably with it.

[0104] It should also be noted that in the apparatus, equipment, and methods of this application, the components or steps can be disassembled and / or recombined. These disassemblies and / or recombinations should be considered as equivalent solutions of this application.

[0105] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use this application. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects without departing from the scope of this application. Therefore, this application is not intended to be limited to the aspects shown herein, but rather to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0106] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of this application to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

[0107] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A solar interface evaporator, characterized in that, include: A photothermal layer for photothermal conversion and steam escape, the photothermal layer comprising a first fiber material; A water-conducting layer for drawing water from bulk water and supplying water to the photothermal layer, the water-conducting layer comprising a second fiber material; An interface layer is located between the photothermal layer and the water transport layer, and the interface layer comprises an interpenetrating network structure formed by the first fiber material and the second fiber material. The pore size of the interpenetrating network structure varies with a gradient along the thickness direction.

2. The solar interface evaporator according to claim 1, characterized in that, The pore size of the interpenetrating network structure gradually decreases from the water transport layer to the photothermal layer along the thickness direction, wherein the pore size of the interpenetrating network structure ranges from 2 to 150 nanometers; and / or, The thickness of the interface layer ranges from 100 to 300 micrometers, preferably from 100 to 200 micrometers.

3. The solar interface evaporator according to claim 1, characterized in that, The photothermal layer includes a fiber matrix made of the first fiber material, photothermal particles loaded on the surface of the fiber matrix, and a coating layer covering the photothermal particles. The photothermal particles are made of at least one of MOF, MOF-derived materials, carbon nanotubes, graphene / graphene oxide, MXene, and metal oxides; and / or, The coating material includes a polydopamine layer.

4. The solar interface evaporator according to claim 1, characterized in that, The water conveyance layer includes a first channel and a second channel, wherein the first channel is oriented along the thickness direction; Preferably, the pore size of the first channel is in the range of 50 to 80 micrometers, and the pore size of the second channel is in the range of 5 to 30 nanometers.

5. The solar interface evaporator according to claim 1, characterized in that, The first fiber material and the second fiber material include bio-based materials; The bio-based material includes bamboo, the first fiber material includes bamboo microfiber, and the second fiber material includes bamboo nanofiber. Preferably, the diameter of the first fiber material is in the range of 15 to 22 micrometers, and the diameter of the second fiber material is in the range of 5 to 50 nanometers.

6. A method for preparing a solar interface evaporator, characterized in that, include: A photothermal layer preform is prepared, the photothermal layer preform comprising a first fiber material; A water-conveying layer precursor is prepared, wherein the water-conveying layer precursor comprises a second fiber material; The photothermal layer preform is placed at the gas-liquid interface of the water transport layer precursor and pressure is applied, so that part of the first fiber material is inserted into the water transport layer precursor to obtain an intermediate part. The intermediate component is subjected to directional hole forming process so that the second fiber material forms a first channel oriented along the thickness direction and forms an interpenetrating network structure containing the first fiber material and the second fiber material; The solar interface evaporator is formed by freeze-drying.

7. The method for preparing a solar interface evaporator according to claim 6, characterized in that, The directional hole-forming process is selected from at least one of the following: liquid nitrogen freezing method, ice template method, electric field induction method, magnetic field induction method, and template-assisted method.

8. The method for preparing a solar interface evaporator according to claim 6, characterized in that, The directional hole forming process for the intermediate component includes: The intermediate component was placed in a liquid nitrogen environment for directional freezing. The directional freezing treatment time is 20 min to 40 min, the freezing distance of the directional freezing treatment is 1.5 cm to 2.5 cm, and the temperature gradient of the directional freezing treatment is 50℃ to 200℃. Preferably, the pressure is greater than or equal to 10 kPa and less than or equal to 100 kPa; Preferably, the vacuum degree of the freeze-drying process is less than or equal to 0.01 MPa, the temperature range of the freeze-drying process is -90℃ to -70℃, and the time range of the freeze-drying process is 40h to 60h.

9. The method for preparing a solar interface evaporator according to claim 6, characterized in that, The preparation of the photothermal layer preform includes: Obtain the first fiber material; The first fiber material was immersed in a cobalt salt solution, and 2-methylimidazole was added for ultrasonic-assisted in-situ growth, so that ZIF-67 particles were loaded on the surface of the first fiber material. The material was then dried at 70℃~90℃ for 20h~24h to obtain the first intermediate product. The first intermediate product and dopamine hydrochloride were dispersed in a Tris-HCl buffer solution and magnetically stirred at 20°C to 30°C for 2 to 10 minutes to coat the ZIF-67 particles with a polydopamine layer, thus obtaining the second intermediate product. The second intermediate product was vacuum filtered and washed with deionized water to remove unreacted substances; it was then dried at 70°C to 90°C for 20 to 24 hours to obtain the photothermal layer preform. Preferably, the cobalt-containing salt solution includes a cobalt nitrate solution; Preferably, the mass ratio of the ZIF-67 particles to the polydopamine layer is in the range of 10:3 to 10:8; Preferably, the first fiber material comprises bamboo fiber microfibers, and the process of obtaining the first fiber material comprises: treating the bamboo raw material with a chlorite solution to remove hemicellulose, thereby obtaining the treated bamboo substrate; and then treating the bamboo substrate with an alkaline solution to remove hemicellulose, thereby obtaining the bamboo fiber microfibers. Preferably, the chlorite solution comprises a sodium chlorite solution, and the pH of the chlorite solution is 4.5-4.6; the delignification treatment temperature is 70℃-90℃; Preferably, the alkaline solution comprises a sodium hydroxide solution, and the alkaline treatment temperature is 70°C to 90°C.

10. The method for preparing a solar interface evaporator according to claim 6, characterized in that, The preparation of the aquifer precursor includes: Obtain the hydrogel of the second fiber material; The hydrogel of the second fiber material is mixed with a metal ion solution and mechanically stirred for 5 min to 20 min to obtain the water transport layer precursor. The metal ions include at least one of aluminum ions, calcium ions, and copper ions; Preferably, the second fiber material comprises bamboo nanofibers, and the process of obtaining the hydrogel of the second fiber material comprises: subjecting the bamboo nanofibers to TEMPO oxidation and high-pressure homogenization to obtain the hydrogel of the second fiber material.

Images