Solar-driven photo-thermal water-power cogeneration system and preparation method thereof

Abstract

The invention provides a solar-driven photo-thermal water-power cogeneration system and a preparation method thereof, according to the system, Fe3O4 and an MAX phase material are firstly combined through a unique material design, and then the combined material is coupled with super-hydrophobic SiO2, so that a super-hydrophobic MAX-Fe3O4 coated SiO2 photo-thermal composite material is prepared. The composite material is sprayed on the hot end of a thermoelectric module to efficiently absorb solar energy. And the cold end of the thermoelectric module is respectively connected with the foamy copper radiator and a water delivery channel made of a melamine sponge material. According to the design, on one hand, waste heat transferred to the cold end can be used for seawater evaporation; on the other hand, the temperature of the cold end can be further reduced through water evaporation, a continuous temperature difference is formed between the cold end and the hot end, and finally efficient solar-driven water and electricity cogeneration is achieved. By means of the design, multiple functions are integrated, the energy utilization efficiency is greatly improved, and a brand new thought is provided for research, development and application of a seawater desalination coupling electric energy production system.

Description

Technical Field

[0001] This invention relates to the field of solar-powered cogeneration technology, specifically to a solar-driven solar-powered cogeneration system and its preparation method. Background Technology

[0002] Freshwater scarcity has become a global problem, particularly in arid coastal areas and islands, where seawater desalination has become a core means of ensuring water supply security. Traditional mainstream seawater desalination technologies, such as reverse osmosis and multi-stage flash distillation, while capable of large-scale freshwater production, have significant drawbacks. Reverse osmosis relies on high-voltage electricity, resulting in extremely high energy consumption, and its membrane modules are easily fouled. Multi-stage flash distillation requires a continuous supply of low- and medium-temperature heat energy, generally relying on fossil fuel boilers, leading to high operating costs and significantly increased carbon emissions. Furthermore, existing technologies are difficult to apply in remote, power-deficient areas, severely hindering the promotion of sustainable freshwater supply. Therefore, developing seawater desalination technologies with low energy consumption, low carbon emissions, and the ability to operate off-grid is urgently needed.

[0003] Against the backdrop of a global energy transition, electricity demand continues to rise. However, approximately 780 million people still face the hardship of lacking or being without electricity, particularly in developing countries and off-grid areas. Traditional thermal power generation relies on fossil fuels, further exacerbating greenhouse gas emissions and resource depletion. While renewable energy sources such as wind and solar power have clean advantages, their intermittent power generation requires high-cost energy storage systems. In existing solar power technologies, photovoltaic modules can only utilize about 15-20% of the spectral energy, and waste heat reduces efficiency. Although concentrated solar power (CSP) can store thermal energy, its systems are complex and have high investment thresholds, making it difficult to meet the actual needs of distributed energy.

[0004] To address the aforementioned dual crisis of water and electricity, solar-driven solar thermal desalination and combined power generation technology has become a breakthrough direction. For example, He Jianbo et al. (Chinese Patent CN119391222A) used a hydrophobic coating made of multi-walled carbon nanotubes and polydimethylsiloxane to cover the hot end of a thermoelectric module for heating; an aluminum heat sink with good thermal conductivity was used below the thermoelectric module to transfer heat to the evaporation zone; the evaporation zone was made of chitosan and waterborne polyurethane crosslinked to form an aerogel, thereby reducing the enthalpy of vaporization and achieving effective evaporation, carrying away heat and thus reducing the cold end temperature, ultimately synergistically improving power generation and evaporation efficiency.

[0005] Although full-spectrum utilization of solar energy can simultaneously achieve power generation in the high-calorific-value band and water production in the medium- and low-calorific-value bands, existing systems still have many limitations. Firstly, single-function systems (power generation only or desalination only) result in low solar energy utilization rates and fail to achieve cascaded recovery of waste heat. Secondly, the coupling between solar thermal and desalination modules is not tight enough, leading to significant heat transfer losses and a lack of power peak-shaving capabilities. Thirdly, distributed integrated design is inadequate, making it difficult to adapt to miniaturized and mobile application scenarios. Therefore, there is an urgent need to develop a highly synergistic solar "solar-thermal-electricity-water" cogeneration system. By leveraging spectral frequency division, cascaded utilization of thermal energy, and modular integration, this system can simultaneously improve energy conversion efficiency and freshwater production, providing an innovative solution for sustainable water-electricity co-management. Summary of the Invention

[0006] The purpose of this invention is to overcome the above-mentioned technical deficiencies and provide a solar-driven solar-thermal cogeneration system and its preparation method, which solves a series of problems faced by existing technologies in the fields of seawater desalination and power generation, such as low energy utilization efficiency, poor system integration, and difficulty in adapting to complex application scenarios. Through innovative system design and preparation process, it achieves efficient and sustainable solar-thermal cogeneration.

[0007] To achieve the above-mentioned technical objectives, the technical solution of the present invention first provides a solar-driven photothermal power generation system, including a thermoelectric module, a copper foam radiator, and an evaporator support with a water supply channel. The hot end of the thermoelectric module is coated with a superhydrophobic MAX-Fe3O4@SiO2 photothermal coating, the cold end of the thermoelectric module is connected to the upper end of the copper foam radiator, and the lower end of the copper foam radiator is connected to the evaporator support. The evaporator support is made of a porous mesh structure of melamine sponge anchored with MAX-Fe3O4@SiO2 particles.

[0008] Preferably, the thermoelectric module is a Seebeck thermoelectric generator; the water contact angle of the superhydrophobic MAX-Fe3O4@SiO2 photothermal coating is 155.7° and the roll-off angle is 1.5°; the thickness of the foamed copper heat sink is 1-10 mm and the pore size is 300-1200 μm.

[0009] Preferably, the evaporator support body consists of a base and multiple water supply channels located above the base, with each water supply channel connected to the base; the height of the evaporator support body above the water surface is greater than 0 and does not exceed 10 mm.

[0010] Accordingly, the present invention also provides a method for preparing a solar-driven solar-thermal cogeneration system as described above, comprising the following steps: S10, the superhydrophobic MAX-Fe3O4@SiO2 photothermal coating is sprayed onto the hot end of the thermoelectric module; S20 connects the cold end of the thermoelectric module to the upper end of the foamed copper heat sink with thermally conductive adhesive, and connects the lower end of the foamed copper heat sink to the evaporator support, thus obtaining a solar-driven photothermal power cogeneration system; the evaporator support is made of a melamine sponge porous mesh structure anchored by MAX-Fe3O4@SiO2 particles.

[0011] Preferably, step S10 specifically includes the following steps: S101, The resin is stirred and dissolved in an organic solvent to obtain a resin-based paint dispersion; S102, MAX phase material and Fe3O4 are ultrasonically dispersed in alcohol solution, and then alkali solution and organosilicon compound are added in sequence to carry out hydrolysis reaction to obtain hydroxyl-modified MAX-Fe3O4@SiO2 dispersion; S103, a low surface energy modifier was added to the hydroxyl-modified MAX-Fe3O4@SiO2 dispersion, and the reaction was continued by stirring to obtain a superhydrophobic MAX-Fe3O4@SiO2 photothermal composite material. S104, the resin base paint dispersion and the superhydrophobic MAX-Fe3O4@SiO2 photothermal composite material dispersion are sequentially sprayed onto the hot end of the thermoelectric module, so that the hot end of the thermoelectric module is coated with a superhydrophobic MAX-Fe3O4@SiO2 photothermal coating.

[0012] Preferably, in step S101: the resin is at least one of alkyd resin, polypropylene resin, acrylic resin, epoxy resin, fluorocarbon resin and polyurethane, and the organic solvent is any one of butyl acetate, ethyl acetate and methyl acetate.

[0013] Preferably, in step S102: the MAX phase material has a layered structure with a particle size of 20-50 μm, and the layered structure is at least one of Ti3AlC2, Ti3AlCN, Ti2AlC, Ti2AlN, V2AlC, Nb2AlC, Ta2AlC, Cr2AlC, Ti3SnC2, and Ti3SiC2; the Fe3O4 has a particle size of 100-500 nm; the alcohol solution includes organic ethanol, and the solid-liquid ratio of the MAX phase material, Fe3O4, and alcohol solution is (0.5-3) g:(0.1-2) g:(10-20) ml; the alkaline solution is NaOH solution, KOH solution, or ammonia water. The concentrations of NaOH and KOH solutions are both 1–1.8 mol / L, and the concentration of ammonia is 25–29 wt%; the organosilicon compound is any one of methyl silicate, tetraethyl orthosilicate, propyl silicate, and butyl silicate; the volume ratio of alkali solution to organosilicon compound is (1–1.5):5; the reaction time of the hydrolysis reaction is 12–48 h.

[0014] Preferably, in step S103: the low surface energy modifier includes at least one of hexamethyldisilazane, trimethoxy(1H,1H,2H,2H-heptadecylfluorodecyl)silane and triethoxy-1H,1H,2H,2H-tetrafluoron-octylsilane; the volume ratio of the organosilicon compound to the low surface energy modifier is 1:(1-2); the mass ratio of the MAX phase material, Fe3O4, organosilicon compound and low surface energy modifier is (0.5-3):(0.1-2):1.88:(1.54-3.08); and the reaction time of the stirring reaction is 4-24 h.

[0015] Preferably, the foamed copper radiator in step S20 is prepared using a template cryogenic casting method, the preparation method of which includes: Using ethanol as a binder, copper powder with an average diameter of 75 μm was uniformly adhered to the surface of K2CO3 particles with an average diameter of 300–1200 μm to obtain a mixed powder; wherein the volume fraction of K2CO3 powder was 50%–85%. The mixed powder is poured into a mold and compacted at 200 MPa to obtain a compacted block. The compacted block is removed from the mold and placed in a vacuum furnace for sintering at 850°C for 30–60 minutes. Then, the temperature is raised to 950°C for further sintering for 2–4 hours to obtain a foamed copper radiator.

[0016] Preferably, the method for preparing the evaporator support in step S20 includes: First, the hydroxyl-modified MAX-Fe3O4@SiO2 dispersion was mixed with a dopamine solution and stirred under weakly alkaline conditions to promote the formation of a polydopamine adhesion layer on the surface of the MAX-Fe3O4@SiO2 particles. Then, glutaraldehyde is added as a crosslinking agent, and the aldehyde group reacts with the amino group of polydopamine and the hydroxyl group on the surface of MAX-Fe3O4@SiO2 particles to form a dispersion with a covalent crosslinking network. Subsequently, the melamine sponge was immersed in a dispersion with a covalently cross-linked network to obtain a porous mesh structure of melamine sponge anchored by MAX-Fe3O4@SiO2 particles. Finally, the porous mesh structure of the melamine sponge was cut with a cutting tool to obtain an evaporator support with different fractal structures.

[0017] Compared with existing technologies, the beneficial effects of this invention include: This invention provides a solar-driven solar-powered photothermal cogeneration system and its preparation method. This system achieves efficient energy conversion and utilization through a unique material design and structural combination. Specifically, Fe3O4 is first combined with MAX phase materials, and then coupled with superhydrophobic SiO2 to create a superhydrophobic MAX-Fe3O4@SiO2 photothermal composite material. This composite material is sprayed onto the hot end of the thermoelectric module, enabling efficient absorption of solar energy. At the cold end of the thermoelectric module, a copper foam radiator and a water delivery channel made of melamine foam are connected. This design allows waste heat transferred to the cold end to be used for seawater evaporation; furthermore, water evaporation further reduces the temperature at the cold end, creating a continuous temperature difference with the hot end. This design not only achieves multifunctional integration and greatly improves energy utilization efficiency, but also provides a new approach for the research and application of seawater desalination coupled with power generation systems. Furthermore, the preparation method involved in this invention is simple to operate, has mild reaction conditions, and is environmentally friendly, possessing the potential for large-scale application. Attached Figure Description

[0018] Figure 1 Optical photographs and water contact angle photographs of the surface of the superhydrophobic MAX-Fe3O4@SiO2 photothermal coating obtained in Example 1; Figure 2 To simulate sunlight (light intensity 100mW / cm²) using a xenon lamp light source (model CEL-S500-T5). 2 The photothermal power system obtained in Example 1 was irradiated; wherein, the foamed copper was cut into different thicknesses to investigate the effect of the foamed copper thickness on the evaporation rate and power output of the hydropower system: (a) simulated seawater quality changes; (b) evaporation rate; (c) voltage changes; (d) current changes; Figure 3 To simulate sunlight (light intensity 100mW / cm²) using a xenon lamp light source (model CEL-S500-T5). 2 The photothermal power system obtained in Example 1 was irradiated; wherein, the copper foam was cut into different areas to investigate the effect of the copper foam area on the evaporation rate and power output of the power system: (a) simulated seawater quality changes; (b) evaporation rate; (c) voltage changes; (d) current changes; Figure 4 To simulate different sunlight conditions (light intensity 100mW / cm²) using a xenon lamp light source (model CEL-S500-T5). -2 150mWcm -2 200mWcm -2 250mWcm -2The photothermal power system obtained in Example 1 was irradiated; wherein, (a) simulated changes in seawater quality; (b) evaporation rate; (c) voltage changes; and (d) current changes; Figure 5 To simulate sunlight (light intensity 100mW / cm²) using a xenon lamp light source (model CEL-S500-T5). 2 The photothermal power system obtained in Example 1 was irradiated; different salt concentration environments (3.5 wt% NaCl, 10 wt% NaCl, and 20 wt% NaCl) were set up to investigate the evaporation rate and power output performance of the hydropower system under complex saline-alkali environment: (a) simulated seawater quality changes; (b) evaporation rate; (c) voltage changes; (d) current changes; Figure 6 To simulate sunlight (light intensity 100mW / cm²) using a xenon lamp light source (model CEL-S500-T5). 2 The photothermal power system obtained in Example 1 was irradiated; different salt concentration environments (3.5 wt% NaCl, 10 wt% NaCl, 20 wt% NaCl) were set up, and the system was continuously run for 6 hours to investigate the evaporation rate and power output performance of the hydropower system under long-term complex saline-alkali environment: (a) simulated seawater quality changes; (b) evaporation rate; (c) voltage changes; (d) current changes; Figure 7 To simulate sunlight (light intensity 100mW / cm²) using a xenon lamp light source (model CEL-S500-T5). 2 The photothermal power combined system obtained in Examples 1, 2, and 3 were respectively irradiated; wherein: (a) simulated seawater quality changes; (b) evaporation rate; (c) voltage changes; (d) current changes; Figure 8 To simulate sunlight (light intensity 100mW / cm²) using a xenon lamp light source (model CEL-S500-T5). 2 Inclined 45 degrees o The simulated seawater quality changes of the solar-thermal-power cogeneration systems obtained in Example 1 and Comparative Example 1 were observed by irradiating them at different angles. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0020] The main objective of this invention is to address the problems and shortcomings of existing technologies by providing a solar-driven solar-thermal cogeneration system and its preparation method. This system utilizes Fe3O4 and MAX materials (a type of ternary carbide or nitride with a layered structure, chemical formula M...). n+1 AX n M is a transition metal element, A is a main group element, X is a carbon or nitrogen element, n=1, 2, 3, combining the good electrical and thermal conductivity of metals with the high modulus, high temperature resistance, and corrosion resistance of ceramics, and couples it with superhydrophobic SiO2 to prepare a superhydrophobic photothermal composite material. This composite material is then sprayed onto the hot end of a thermoelectric module (Sebeck thermoelectric generator) to achieve efficient absorption of sunlight. By connecting a foamed copper radiator and a melamine sponge water transport channel to the cold end of the generator, the waste heat from the cold end is used for seawater evaporation, while further reducing the temperature of the cold end and forming a larger temperature gradient with the hot end. This achieves a design for efficient solar-driven hydropower cogeneration, realizing multi-functional integration and efficient energy utilization. This provides a reference and expands new ideas for the research and development and application of seawater desalination coupled with power generation systems. Moreover, the preparation method involved is simple and easy to implement, the reaction conditions are mild and environmentally friendly, and it can be scaled up and applied.

[0021] In a first aspect, the present invention provides a solar-driven photothermal combined heat and power system, comprising a thermoelectric module, a copper foam radiator, and an evaporator support with a water delivery channel. The hot end of the thermoelectric module is coated with a superhydrophobic MAX-Fe3O4@SiO2 photothermal coating, the cold end of the thermoelectric module is connected to the upper end of the copper foam radiator, and the lower end of the copper foam radiator is connected to the evaporator support. The evaporator support is made of a porous mesh structure of melamine sponge anchored with MAX-Fe3O4@SiO2 particles.

[0022] Specifically, this solar-driven solar-thermal-power cogeneration system utilizes a superhydrophobic MAX-Fe3O4@SiO2 photothermal coating on the hot end of the thermoelectric module, which can efficiently absorb solar energy. The cold end connects a foamed copper radiator and an evaporator support made of a specific material, which can utilize the waste heat at the cold end for seawater evaporation, thereby reducing the temperature at the cold end to create a larger temperature difference and achieve efficient power generation. This achieves solar-thermal-power cogeneration, realizing multi-functional integration and efficient energy utilization, and providing a new approach for seawater desalination coupled with power generation.

[0023] The photothermal power cogeneration system prepared according to the above scheme is characterized by the following: the upper end (hot end) of the thermoelectric module is a superhydrophobic MAX-Fe3O4@SiO2 photothermal coating obtained by sequentially spraying a resin base coat and a superhydrophobic MAX-Fe3O4@SiO2 topcoat, with a water contact angle of up to 155.7°. o The roll angle can reach 1.5. oThe lower end (cold end) of the thermoelectric module uses a foamed copper radiator with good thermal conductivity and a porous structure, which can effectively transfer waste heat to the evaporation zone. Its porous structure also provides numerous steam escape channels, preventing excessively high local steam pressure from inhibiting seawater evaporation and desalination. The lower part of the cogeneration system employs a dopamine and glutaraldehyde synergistic crosslinking technology to firmly anchor hydroxyl-modified MAX-Fe3O4@SiO2 superhydrophilic nanoparticles onto melamine sponge, constructing a seawater desalination evaporation module. Dopamine forms a polydopamine transition layer on the sponge surface through the strong adhesion of its catechol groups, while glutaraldehyde reacts with the amino groups of polydopamine and the hydroxyl groups on the nanoparticle surface through its aldehyde groups, forming a covalent crosslinked network that effectively prevents nanoparticle detachment. Its abundant hydrophilic groups and capillary structure provide numerous water transport channels, pumping seawater to the evaporation zone for rapid evaporation, absorbing heat, and further reducing the cold end temperature, thereby increasing the output voltage. Meanwhile, the anchored MAX-Fe3O4@SiO2 exhibits broad-spectrum light absorption characteristics, enabling it to efficiently capture light energy and convert it into heat energy even under non-perpendicular sunlight conditions such as oblique sunlight, significantly increasing the seawater evaporation rate. It also possesses the advantages of resistance to salt spray corrosion and structural stability. This combined hydropower system utilizes waste heat from thermoelectric power generation for seawater desalination, efficiently recovering low-grade heat energy, reducing desalination energy costs, and minimizing thermal pollution, thus achieving synergistic effects between energy cascade utilization and freshwater resource production.

[0024] In this embodiment of the invention, the thermoelectric module is a Seebeck thermoelectric generator; the superhydrophobic MAX-Fe3O4@SiO2 photothermal coating has a water contact angle of 155.7° and a roll-off angle of 1.5°; the former utilizes the temperature difference to achieve efficient thermoelectric conversion, while the latter, with its superhydrophobic properties of high water contact angle and low roll-off angle, can not only efficiently absorb solar energy, but also prevent surface water accumulation, ensuring stable photothermal conversion, thereby improving the energy conversion efficiency and operational stability of the entire solar-driven solar-thermal cogeneration system.

[0025] In this embodiment of the invention, the thickness of the foamed copper radiator is 1–10 mm, and the pore size is 300–1200 μm. If the foamed radiator is too thin, although heat conduction is faster, heat is easily lost through radiation and convection, resulting in low waste heat utilization. If the foamed radiator is too thick, steam needs to travel a longer escape path, which may lead to local steam saturation and inhibit evaporation. Similarly, for foamed radiators with smaller pore sizes, although the specific surface area can be increased to accelerate evaporation, the resistance to steam escape is greater when the pore size is too small, hindering steam escape and thus inhibiting the evaporation rate. For evaporators with larger pore sizes, the solid-phase skeleton is more continuous, the thermal conductivity is higher, and steam escapes faster, but the evaporation area is reduced. Therefore, it is necessary to select foamed radiators with a certain range of thickness and pore size.

[0026] In this embodiment of the invention, to ensure the rapid and continuous transport of seawater from the water body to the evaporation zone of the solar-thermal-power cogeneration system and the efficient utilization of waste heat, the height of the evaporator support above the water surface is greater than 0 and not more than 10 mm. When the height of the evaporator support is insufficient, there is too much water in the evaporation zone, making it difficult to achieve rapid evaporation of a small amount of water and reducing the evaporation rate. When the height of the evaporator support is too high, it is difficult to transport water to the evaporation zone of the solar-thermal-power cogeneration system, and the multi-stage energy utilization of the integrated hydropower system cannot be realized.

[0027] In this embodiment of the invention, the evaporator support can be constructed by cutting to form an evaporator support with different numbers of water delivery channels (columnar), forming a special "trunk-branch" fractal structure with water storage at the base and water delivery through the columns. This significantly improves the water delivery rate through capillary pressure surge driven by pore gradient and the Marangoni effect, and avoids the water retention problem present in uncut uniform sponge blocks. At the same time, cutting introduces additional evaporation side area. For example, a 3cm×3cm×3cm block has an evaporation area of ​​only 3cm×3cm on the top surface, but if it is cut into a 3cm×3cm×1cm base plus four 1cm×1cm×2cm columns, the evaporation area is 1cm×1cm×4 on the top surface plus 1cm×2cm×4×4 on the side surface, totaling 36cm. 2 It is four times the evaporation area of ​​an uncut sponge. These additional evaporation side areas absorb waste heat from the cold end of the thermoelectric module and receive heat from the surrounding air convection, significantly increasing the evaporation rate and achieving efficient hydropower cogeneration.

[0028] The superhydrophobic MAX-Fe3O4@SiO2 photothermal coating prepared by this invention has excellent superhydrophobic properties and photothermal conversion performance. The designed photothermal power generation system has high voltage output and excellent seawater desalination evaporation capacity, and is expected to be used in the fields of seawater desalination or wastewater treatment co-generation.

[0029] Secondly, the present invention also provides a method for preparing any of the above-mentioned solar-driven solar-thermal cogeneration systems, comprising the following steps: S10, the superhydrophobic MAX-Fe3O4@SiO2 photothermal coating is sprayed onto the hot end of the thermoelectric module; S20 connects the cold end of the thermoelectric module to the upper end of the foamed copper heat sink with thermally conductive adhesive, and connects the lower end of the foamed copper heat sink to the evaporator support, thus obtaining a solar-driven photothermal power cogeneration system; the evaporator support is made of a melamine sponge porous mesh structure anchored by MAX-Fe3O4@SiO2 particles.

[0030] Specifically, the method for preparing a solar-driven photothermal cogeneration system provided by this invention has simple and clear steps. First, a superhydrophobic MAX-Fe3O4@SiO2 photothermal coating is sprayed onto the hot end of the thermoelectric module. Then, the cold end of the thermoelectric module is connected to the upper end of the foamed copper radiator through thermally conductive adhesive. The lower end of the foamed copper radiator is connected to an evaporator support made of a porous melamine sponge structure anchored by MAX-Fe3O4@SiO2 particles. The operation is simple and easy, the reaction conditions are mild, and no complex processes or special equipment are required. This facilitates large-scale production and lays the foundation for the widespread application of the system, thus strongly promoting the application of solar photothermal cogeneration technology.

[0031] Specifically, step S10 includes the following steps: S101, The resin is stirred and dissolved in an organic solvent to obtain a resin-based paint dispersion; S102, the MAX phase material and Fe3O4 were ultrasonically dispersed in an alcohol solution, and then an alkaline solution and an organosilicon compound were added sequentially to carry out a hydrolysis reaction to obtain a hydroxyl-modified MAX-Fe3O4@SiO2 dispersion (superhydrophilic). S103, a low surface energy modifier was added to the hydroxyl-modified MAX-Fe3O4@SiO2 dispersion, and the reaction was continued by stirring to obtain a superhydrophobic MAX-Fe3O4@SiO2 photothermal composite material. S104, the resin base paint dispersion and the superhydrophobic MAX-Fe3O4@SiO2 photothermal composite material dispersion are sequentially sprayed onto the hot end of the thermoelectric module, so that the hot end of the thermoelectric module is coated with a superhydrophobic MAX-Fe3O4@SiO2 photothermal coating.

[0032] Furthermore, the preparation method in step S10 involves dissolving the resin to obtain a base paint dispersion, ultrasonically dispersing the MAX phase material and Fe3O4, and hydrolyzing them to obtain a hydroxyl-modified dispersion. A low surface energy modifier is then added to obtain a superhydrophobic photothermal composite material. Finally, both are sequentially sprayed onto the hot end of the thermoelectric module. This process is clearly defined, uses common raw materials, and operates under mild reaction conditions. It can accurately prepare a superhydrophobic MAX-Fe3O4@SiO2 photothermal coating, endowing the hot end of the thermoelectric module with efficient photothermal conversion and superhydrophobic properties. Moreover, this method is simple to operate, easy to control, and suitable for large-scale production, providing a feasible and efficient solution for the preparation of key components in solar-thermal-power cogeneration systems.

[0033] In step S101: the resin is at least one of alkyd resin, polypropylene resin, acrylic resin, epoxy resin, fluorocarbon resin and polyurethane, and the organic solvent is any one of butyl acetate, ethyl acetate and methyl acetate; wherein, the resin-based paint dispersion prepared by the above resin materials not only ensures good adhesion and compatibility between the superhydrophobic MAX-Fe3O4@SiO2 photothermal coating and the hot end of the thermoelectric module, but also takes into account the diverse performance requirements of the coating such as flexibility, wear resistance and corrosion resistance under different conditions, which greatly broadens the applicability of the preparation method and the application field of the product.

[0034] In step S102, the MAX phase material is a layered structure with a particle size of 20~50μm, and the layered structure is at least one of Ti3AlC2, Ti3AlCN, Ti2AlC, Ti2AlN, V2AlC, Nb2AlC, Ta2AlC, Cr2AlC, Ti3SnC2 and Ti3SiC2.

[0035] Specifically, the specific particle size range ensures that the MAX phase material has suitable dispersibility and reactivity in the reaction system, facilitating full contact and reaction with other substances. MAX phase materials with various layered structures differ in electrical conductivity, thermal conductivity, and stability, enabling them to meet the different performance requirements of solar-thermal-power cogeneration systems.

[0036] In step S102, the particle size of Fe3O4 is 100~500nm; the alcohol solution includes organic ethanol, and the solid-liquid ratio of MAX phase material, Fe3O4 and alcohol solution is (0.5~3)g:(0.1~2)g:(10~20)ml.

[0037] Specifically, the suitable particle size range allows Fe3O4 to be well dispersed in the reaction system and to form appropriate interactions with the MAX phase material and subsequent reactants, which helps to form a uniform and stable structure during the composite process. The precise solid-liquid ratio of the MAX phase material, Fe3O4 and alcohol solution ensures that the reactant concentration is within a suitable range, which is beneficial to controlling the reaction process and the composition and structure of the products, thereby ensuring the consistency and stability of the reaction and making the prepared material stable and reproducible.

[0038] In step S102, the alkaline solution is NaOH solution, KOH solution, or ammonia water; the concentration of NaOH solution and KOH solution is 1-1.8 mol / L, and the concentration of ammonia water is 25-29 wt%; the organosilicon compound is any one of methyl silicate, tetraethyl orthosilicate, propyl silicate, and butyl silicate; the volume ratio of alkaline solution to organosilicon compound is (1-1.5):5.

[0039] Specifically, the aforementioned appropriate concentration of alkaline solution ensures that the alkaline solution provides a sufficiently alkaline environment to promote the hydrolysis of organosilicon compounds during the hydrolysis reaction, without causing the reaction to be too vigorous due to excessive alkalinity, which would affect the quality and performance of the product. The aforementioned precise volume ratio ensures the stoichiometric relationship between the alkaline solution and organosilicon compounds during the hydrolysis reaction, which is beneficial for controlling the degree of hydrolysis and the product structure, ensuring that the reaction proceeds in the direction of generating the expected hydroxyl-modified MAX-Fe3O4@SiO2 dispersion, thereby ensuring the stability and consistency of the final material properties.

[0040] In step S102, the hydrolysis reaction takes 12 to 48 hours. This appropriate reaction time range provides sufficient time for the hydrolysis reaction to proceed, while avoiding problems such as side reactions or excessive polymerization of products that may result from an excessively long reaction time.

[0041] In step S103, the low surface energy modifier includes at least one of hexamethyldisilazane, trimethoxy(1H,1H,2H,2H-heptadecylfluorodecyl)silane, and triethoxy-1H,1H,2H,2H-tetrafluoron-octylsilane; the volume ratio of the organosilicon compound to the low surface energy modifier is 1:(1-2); the mass ratio of the MAX phase material, Fe3O4, organosilicon compound, and low surface energy modifier is (0.5-3):(0.1-2):1.88:(1.54-3.08); and the reaction time of the stirred reaction is 4-24 h.

[0042] Specifically, a well-defined volume ratio of organosilicon compounds to low surface energy modifiers, and the mass ratio of each component, such as the MAX phase material, ensures that the reaction proceeds according to a specific stoichiometry, precisely controlling the composition of the superhydrophobic MAX-Fe3O4@SiO2 photothermal composite material. A stirring reaction time of 4–24 hours ensures sufficient reaction of each component while preventing excessive reaction and side reactions, contributing to the acquisition of a stable photothermal composite material with excellent superhydrophobic properties, providing a highly efficient and stable photothermal conversion component for solar-thermal-power cogeneration systems.

[0043] Specifically, in step S20, foamed copper heat sinks with different porosities and pore sizes are prepared using a template cryogenic casting (LCS) method, the preparation method of which includes: Using ethanol as a binder, copper powder with an average diameter of 75 μm was uniformly adhered to the surface of K2CO3 particles with an average diameter of 300–1200 μm to obtain a mixed powder; wherein the volume fraction of K2CO3 powder was 50%–85%. The mixed powder is poured into a mold and compacted at 200 MPa to obtain a compacted block. The compacted block is removed from the mold and placed in a vacuum furnace for sintering at 850°C for 30–60 minutes. Then, the temperature is raised to 950°C for further sintering for 2–4 hours to obtain a foamed copper radiator.

[0044] Specifically, during the sintering stage, Cu particles in the preform gradually combine, while K2CO3 particles decompose to form open-cell copper foam. The porosity of the sintered copper foam is close to the volume fraction of the K2CO3 powder, and the pore size is approximately the particle size of the K2CO3 powder.

[0045] Furthermore, the aforementioned method for preparing foamed copper radiators employs a template-based cryogenic casting method to produce foamed copper radiators with different porosities and pore sizes. Ethanol is used as a binder to uniformly mix copper powder of a specific particle size with K2CO3 particles. By precisely controlling the volume fraction of the K2CO3 powder, combined with a two-step sintering process involving 200MPa compaction and specific temperature and time, the porosity and pore size of the foamed copper can be precisely controlled, making them close to the volume fraction and particle size of the K2CO3 powder, respectively. This method is simple and can stably produce foamed copper radiators that meet the different heat dissipation requirements of solar-thermal-power cogeneration systems, providing a strong guarantee for the efficient operation of the system.

[0046] Specifically, the preparation method of the evaporator support in step S20 includes: First, the hydroxyl-modified MAX-Fe3O4@SiO2 dispersion (superhydrophilic) was mixed with a dopamine solution and stirred under weakly alkaline conditions to promote the formation of a polydopamine adhesion layer on the surface of MAX-Fe3O4@SiO2 particles. Then, glutaraldehyde is added as a crosslinking agent, and the aldehyde group reacts with the amino group of polydopamine and the hydroxyl group on the surface of MAX-Fe3O4@SiO2 particles to form a dispersion with a covalent crosslinking network. Subsequently, the melamine sponge was immersed in a dispersion with a covalent cross-linked network. Through the strong adhesion of dopamine and the cross-linking effect of glutaraldehyde, the binding stability of MAX-Fe3O4@SiO2 particles was effectively improved, thereby firmly anchoring the MAX-Fe3O4@SiO2 particles in the porous mesh structure of the melamine sponge. Finally, the porous mesh structure of the melamine sponge was cut with a cutting tool to obtain an evaporator support with different fractal structures.

[0047] The solar-driven photothermal cogeneration system and its preparation method provided by the present invention will be described in detail below through specific embodiments.

[0048] Example 1: Example 1 provides a solar-driven solar-powered combined solar thermal power system and its preparation method. The preparation method includes the following steps: Step (1): Dissolve 3g alkyd resin, 3g polypropylene resin and 1g fluorocarbon resin in 15ml butyl acetate to obtain resin base paint dispersion. Step (2): 0.2 g of MAX phase and 0.6 g of Fe3O4 were ultrasonically dispersed in 10 ml of ethanol, and then 0.4 ml of 1.8 M NaOH solution and 2 ml of tetraethyl orthosilicate were added in sequence. The hydrolysis reaction was carried out for 24 h to obtain hydroxyl-modified MAX-Fe3O4@SiO2 dispersion (superhydrophilic). Step (3): Add 2 ml of hexamethyldisilazane (HMDS) to the MAX-Fe3O4@SiO2 dispersion obtained in step (2), and continue stirring for 4 h to obtain the superhydrophobic MAX-Fe3O4@SiO2 photothermal composite material; Step (4): The resin base paint obtained in step (1) and the superhydrophobic MAX-Fe3O4@SiO2 photothermal composite material dispersion obtained in step (3) are sprayed onto the hot end of the thermoelectric module in sequence, that is, the superhydrophobic MAX-Fe3O4@SiO2 photothermal coating is obtained by spraying. Step (5): Preparation of a 3cm×3cm×3cm foamed copper radiator using the LCS method: Using ethanol as a binder, copper powder with an average diameter of 75μm was uniformly adhered to the surface of K2CO3 particles with an average diameter of 500μm (K2CO3 powder volume fraction was 60%). The mixed powder was poured into a mold and compacted at 200MPa. The compacted block was removed from the mold and placed in a vacuum furnace at 850°C. o Sinter at C for 30 minutes. Then raise the temperature to 950°C. o C is further sintered for 2 hours. During the sintering stage, the Cu particles in the preform gradually combine, and the K2CO3 particles decompose to form open-cell copper foam. The porosity of the sintered copper foam is close to the volume fraction of the K2CO3 powder, and the pore size is approximately the particle size of the K2CO3 powder. Step (6): The hydroxyl-modified MAX-Fe3O4@SiO2 dispersion (superhydrophilic) obtained in step (2) is mixed with a dopamine solution and stirred under weakly alkaline conditions to form a polydopamine adhesion layer on the surface of the MAX-Fe3O4@SiO2 particles. Then, glutaraldehyde is added as a crosslinking agent, and a covalent crosslinking network is formed by the reaction of the aldehyde group with the amino group of polydopamine and the hydroxyl group on the particle surface. Finally, the melamine sponge is immersed in the above dispersion. Through the strong adhesion of dopamine and the crosslinking effect of glutaraldehyde, the binding stability of the particles is effectively improved, thereby firmly anchoring the particles in the porous mesh of the melamine sponge. Step (7): Cut the 3cm×3cm×3cm melamine sponge obtained in step (6) into a 3cm×3cm×1cm main base and nine 0.6cm×0.6cm×2cm branch sponge columns to obtain the evaporator support body; Step (8): Place a 3cm×3cm×3cm foamed copper radiator at the lower end of the thermoelectric module obtained in step (4), and place the evaporator support obtained in step (7) at the lower end of the radiator to obtain the solar-thermal-power cogeneration system.

[0049] Please see Figure 1 , Figure 1 These are optical photographs and water contact angle photographs of the surface of the superhydrophobic MAX-Fe3O4@SiO2 photothermal coating obtained in Example 1. It can be seen that the surface of the methylene blue-stained water droplet thermoelectric module exhibits a contracted state, with a water contact angle of 155.7°. o It exhibits excellent superhydrophobic properties.

[0050] Please see Figure 2 , Figure 2 To simulate sunlight (light intensity 100mW / cm²) using a xenon lamp light source (model CEL-S500-T5). 2 The photothermal power system obtained in Example 1 was irradiated. The copper foam was cut into different thicknesses to investigate the effect of copper foam thickness on the evaporation rate and power output of the cogeneration system: (a) simulated seawater quality changes; (b) evaporation rate; (c) voltage changes; (d) current changes. Figure 2 It can be seen that the evaporation rate first increases and then decreases with increasing copper foam thickness. The results show that the evaporation rate of 3 mm thick copper foam is the highest, reaching 5.11 kgm³. 2 h 1 This is because if the radiator is too thin, although the heat conduction is faster, the heat is easily lost through radiation and convection, resulting in low waste heat utilization. If the radiator is too thick, the steam needs to pass through a longer escape path, which may cause local steam saturation and thus inhibit evaporation. At the same time, it can be seen that the evaporation rate is the lowest when no copper foam is added (thickness is 0 mm), which shows the important role of the copper foam radiator: it can not only achieve efficient conduction of waste heat to the evaporation zone, but also build a low-resistance steam channel through the through-pores, avoid the blockage of the evaporation interface, and maintain the continuity of the evaporation process.

[0051] Please see Figure 3 , Figure 3 To simulate sunlight (light intensity 100mW / cm²) using a xenon lamp light source (model CEL-S500-T5). 2 The photothermal power system obtained in this embodiment was irradiated. The copper foam was cut into different areas to investigate the effect of the copper foam area on the evaporation rate and power output of the cogeneration system: (a) simulated seawater quality changes; (b) evaporation rate; (c) voltage changes; (d) current changes. Figure 3It can be seen that the evaporation rate first increases and then decreases with the increase of the copper foam area. The results show that the evaporation rate of the 3cm×3cm copper foam is the highest, reaching 4.378 kgm³. 2 h 1 Increasing the heat dissipation area can provide more evaporation surfaces and improve the evaporation rate, but if the area is too large, the resistance to steam escape will increase, which will reduce efficiency.

[0052] Please see Figure 4 , Figure 4 To simulate different sunlight conditions (light intensity 100mW / cm²) using a xenon lamp light source (model CEL-S500-T5). -2 150mWcm -2 200mWcm -2 250mWcm -2 The solar-thermal-power cogeneration system obtained in this embodiment was irradiated. (a) simulated seawater quality changes; (b) evaporation rate; (c) voltage changes; and (d) current changes. Figure 4 It can be seen that the evaporation rate gradually increases with increasing light intensity, reaching a maximum at 250 mW / cm². -2 The evaporation rate was highest under these conditions, reaching 7.226 kg / m³. 2 h 1 . Figure 4 As can be seen from (c) and (d), light intensity directly affects the temperature difference between the hot and cold ends. Higher light intensity results in a greater temperature difference and higher thermoelectric output power. At 250mW / cm²... -2 Under light intensity, the voltage is 263.7mV and the current is 20.248mA.

[0053] Please see Figure 5 , Figure 5 To simulate sunlight (light intensity 100mW / cm²) using a xenon lamp light source (model CEL-S500-T5). 2The photohydropower cogeneration system obtained in Example 1 was irradiated. Different salt concentration environments (3.5 wt% NaCl, 10 wt% NaCl, and 20 wt% NaCl) were set up to investigate the evaporation rate and power output performance of the cogeneration system under complex saline-alkali environments: (a) simulated seawater mass changes; (b) evaporation rate; (c) voltage changes; (d) current changes. Figures (a) and (b) show that the cogeneration system can achieve efficient seawater desalination under different NaCl concentration environments. In 3.5 wt% NaCl, less salt crystallization occurs; instead, the increased concentration gradient may promote water transport. During evaporation, NaCl accumulates to form a localized high-concentration zone, generating osmotic pressure between it and the low-concentration solution at the bottom, driving the solution to flow continuously from bottom to top, thereby accelerating evaporation efficiency. Therefore, the evaporation rate is highest at 3.5 wt% NaCl concentration, reaching 5.793 kg / m³. 2 h 1 When the NaCl concentration increased from 3.5 wt% to 20 wt%, the evaporation rate of the evaporator decreased to 4.411 kg / m³. - ²h - ¹ indicates that the salt crystals formed by the evaporation of high-concentration brine block the copper water transport channels of the sponge foam, reducing the evaporation area and decreasing the evaporation rate.

[0054] Please see Figure 6 , Figure 6 To simulate sunlight (light intensity 100mW / cm²) using a xenon lamp light source (model CEL-S500-T5). 2 The photohydropower cogeneration system obtained in this embodiment was irradiated. Different salt concentration environments (3.5 wt% NaCl, 10 wt% NaCl, and 20 wt% NaCl) were set up, and the system was continuously operated for 6 hours to investigate the evaporation rate and power output performance of the cogeneration system under long-term complex saline-alkali environment: (a) simulated seawater mass changes; (b) evaporation rate; (c) voltage changes; (d) current changes. Evaporation performance is as follows: Figure 6 As shown in (a) and (b), the mass loss due to evaporation changes uniformly with time during this process, with a remaining mass of 5.548 kgm in the 3.5 wt% NaCl environment. 2 h 1 The evaporation rate indicates that this combined hydropower system can maintain excellent photothermal evaporation performance even after long-term operation on the ocean surface. Electrical performance test results are as follows: Figure 6As shown in (c) and (d), after 6 hours of experimentation, the electrical performance of the combined hydropower system was not affected, and the voltage remained at around 140mV.

[0055] Example 2: Example 2 provides a solar-driven solar-thermal cogeneration system and its preparation method. The preparation method provided in Example 2 is roughly the same as that in Example 1, except that: in step (7), the 3cm×3cm×3cm melamine sponge obtained is directly used as the evaporator support.

[0056] Example 3: Example 3 provides a solar-driven photothermal power generation system and its preparation method. The preparation method provided in Example 3 is roughly the same as that in Example 1, except that in step (7), the 3cm×3cm×3cm melamine sponge is cut into a 3cm×3cm×1cm main base and four 0.6cm×0.6cm×2cm branch sponge columns to obtain the evaporator support.

[0057] Please see Figure 7 , Figure 7 To simulate sunlight (light intensity 100mW / cm²) using a xenon lamp light source (model CEL-S500-T5). 2 The photothermal power combined systems obtained in Examples 1, 2, and 3 were respectively irradiated. Among them: (a) simulated seawater quality changes; (b) evaporation rate; (c) voltage changes; (d) current changes. Figure 7 As can be seen from (a) and (b), the evaporator support with different fractal structures has a significant impact on the evaporation rate. The evaporation rate of fresh water increases with the increase of the evaporation area on the side of the sponge. The evaporation rate of the sponge evaporation system in Example 1 is 6.094 kg / m³. 2 h 1 The evaporation rate is much greater than that of Examples 2 and 3. This is because the additional evaporation side area absorbs waste heat from the cold end of the thermoelectric module and receives heat from the surrounding air convection, which significantly increases the evaporation rate and achieves efficient combined hydropower.

[0058] Comparative Example 1: Comparative Example 1 provides a solar-driven solar-thermal cogeneration system and its preparation method. The preparation method provided by Comparative Example 1 is roughly the same as that of Example 1, except that: Comparative Example 1 removes step (6), that is, it does not immerse the sponge in a mixed solution of hydroxyl-modified MAX-Fe3O4@SiO2 dispersion (superhydrophilic) with dopamine solution and glutaraldehyde, and directly cuts the untreated 3×3×3cm melamine sponge into a 3cm×3cm×1cm main base and nine 0.6×0.6×2cm branch sponge columns to obtain the evaporator support.

[0059] Please see Figure 8 , Figure 8 To simulate sunlight (light intensity 100mW / cm²) using a xenon lamp light source (model CEL-S500-T5). 2 Inclined 45 degrees o The simulated seawater quality changes of the combined solar-thermal-power systems obtained in Example 1 and Comparative Example 1 were observed by irradiating them at different angles. Figure 8 It can be seen that the evaporation rate of Example 1 is much greater than that of Comparative Example 1. This demonstrates the important role of MAX-Fe3O4@SiO2 anchored on melamine sponge. Due to its broad-spectrum light absorption characteristics, it can still efficiently capture light energy and effectively increase the seawater evaporation rate even under non-vertical light conditions such as oblique sunlight.

[0060] Compared with existing technologies, the present invention has the following advantages: (1) This invention breaks through the spectral response limitations of traditional single-component photothermal materials. It utilizes the broad-spectrum absorption characteristics of the MAX phase layered structure and the synergistic coupling of the Fe3O4 near-infrared LSPR (Localized Surface Plasmon Resonance in Near –Infrared) effect to achieve full-spectrum response coverage of 300-2500nm, which significantly improves the photothermal conversion efficiency compared with traditional materials. (2) The hot end coating (superhydrophobic MAX-Fe3O4@SiO2 photothermal coating) of the thermoelectric module of the present invention forms a self-cleaning and anti-salting property through the design of high contact angle and low roll-off angle, effectively inhibiting salt deposition in seawater evaporation and ensuring long-term stability of photothermal conversion efficiency; (3) Multi-porous heat dissipation synergistic design of foamed copper radiator: The cold end is connected to high thermal conductivity porous foamed copper, which not only realizes the efficient conduction of waste heat to the evaporation zone (evaporator support), but also constructs a low-resistance steam channel through the through-pores to avoid the blockage of the evaporation interface and maintain the continuity of the evaporation process. (4) The evaporator support of the present invention uses dopamine-glutaraldehyde covalent cross-linking technology to firmly anchor superhydrophilic nanoparticles to the sponge matrix, and combines capillary structure to form directional water transport channels, thereby improving seawater transport and evaporation efficiency. It also shows excellent adaptability to sunlight at different angles and reduces the attenuation of photothermal conversion efficiency when the incident light is not perpendicular. (5) This invention innovatively directs the waste heat from the cold end of the thermoelectric generator to the seawater evaporation module (evaporator support). Through the "thermoelectric-evaporation" coupling design, it improves the overall energy utilization rate, realizes the integration of power generation and seawater desalination functions, reduces desalination energy consumption and reduces thermal pollution emissions. The equipment has a compact structure and is suitable for energy-water synergistic supply in space-constrained scenarios such as islands and ships.

[0061] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A solar-driven photothermal combined heat and power system, characterized in that, The device includes a thermoelectric module, a copper foam radiator, and an evaporator support with water delivery channels. The hot end of the thermoelectric module is coated with a superhydrophobic MAX-Fe3O4@SiO2 photothermal coating. The cold end of the thermoelectric module is connected to the upper end of the copper foam radiator, and the lower end of the copper foam radiator is connected to the evaporator support. The evaporator support is made of a porous melamine sponge structure anchored with MAX-Fe3O4@SiO2 particles.

2. The solar-driven photothermal combined heat and power system according to claim 1, characterized in that, The thermoelectric module is a Seebeck thermoelectric generator; the water contact angle of the superhydrophobic MAX-Fe3O4@SiO2 photothermal coating is 155.7° and the roll-off angle is 1.5°; the thickness of the foamed copper heat sink is 1-10 mm and the pore size is 300-1200 μm.

3. The solar-driven photothermal combined heat and power system according to claim 1, characterized in that, The evaporator support is composed of a base and a plurality of water supply channels located above the base, each of which is connected to the base; the height of the evaporator support above the water surface is greater than 0 and does not exceed 10 mm.

4. A method for preparing a solar-driven photothermal combined heat and power system as described in any one of claims 1 to 3, characterized in that, Includes the following steps: S10, the superhydrophobic MAX-Fe3O4@SiO2 photothermal coating is sprayed onto the hot end of the thermoelectric module; S20, the cold end of the thermoelectric module is connected to the upper end of the foamed copper heat sink with thermally conductive adhesive, and the lower end of the foamed copper heat sink is connected to the evaporator support, thus obtaining a solar-driven photothermal power generation system; the evaporator support is made of a melamine sponge porous mesh structure anchored by MAX-Fe3O4@SiO2 particles.

5. The method for preparing a solar-driven photothermal cogeneration system according to claim 4, characterized in that, Step S10 specifically includes the following steps: S101, The resin is stirred and dissolved in an organic solvent to obtain a resin-based paint dispersion; S102, MAX phase material and Fe3O4 are ultrasonically dispersed in alcohol solution, and then alkali solution and organosilicon compound are added in sequence to carry out hydrolysis reaction to obtain hydroxyl-modified MAX-Fe3O4@SiO2 dispersion; S103, a low surface energy modifier is added to the hydroxyl-modified MAX-Fe3O4@SiO2 dispersion, and the reaction is continued by stirring to obtain a superhydrophobic MAX-Fe3O4@SiO2 photothermal composite material. S104, the resin base paint dispersion and the superhydrophobic MAX-Fe3O4@SiO2 photothermal composite material dispersion are sequentially sprayed onto the hot end of the thermoelectric module, so that the hot end of the thermoelectric module is coated with the superhydrophobic MAX-Fe3O4@SiO2 photothermal coating.

6. The method for preparing a solar-driven photothermal cogeneration system according to claim 5, characterized in that, In step S101: the resin is at least one of alkyd resin, polypropylene resin, acrylic resin, epoxy resin, fluorocarbon resin and polyurethane, and the organic solvent is any one of butyl acetate, ethyl acetate and methyl acetate.

7. The method for preparing a solar-driven photothermal cogeneration system according to claim 5, characterized in that, In step S102: the MAX phase material is a layered structure with a particle size of 20-50 μm, and the layered structure is at least one of Ti3AlC2, Ti3AlCN, Ti2AlC, Ti2AlN, V2AlC, Nb2AlC, Ta2AlC, Cr2AlC, Ti3SnC2, and Ti3SiC2; the Fe3O4 has a particle size of 100-500 nm; the alcohol solution includes organic ethanol, and the solid-liquid ratio of the MAX phase material, Fe3O4, and the alcohol solution is (0.5-3) g:(0.1-2) g:(10-20) ml; the alkaline solution is NaOH solution, KOH solution, or ammonia water. The concentrations of both NaOH and KOH solutions are 1–1.8 mol / L, and the concentration of ammonia is 25–29 wt%; the organosilicon compound is any one of methyl silicate, tetraethyl orthosilicate, propyl silicate, and butyl silicate; the volume ratio of the alkaline solution to the organosilicon compound is (1–1.5):5; and the reaction time of the hydrolysis reaction is 12–48 h.

8. The method for preparing a solar-driven photothermal cogeneration system according to claim 5, characterized in that, In step S103: the low surface energy modifier includes at least one of hexamethyldisilazane, trimethoxy(1H,1H,2H,2H-heptadecylfluorodecyl)silane, and triethoxy-1H,1H,2H,2H-tetrafluoron-octylsilane; the volume ratio of the organosilicon compound to the low surface energy modifier is 1:(1-2); the mass ratio of MAX phase material, Fe3O4, the organosilicon compound, and the low surface energy modifier is (0.5-3):(0.1-2):1.88:(1.54-3.08); the reaction time of the stirring reaction is 4-24 h.

9. The method for preparing a solar-driven photothermal cogeneration system according to claim 5, characterized in that, The foamed copper radiator in step S20 is prepared using a template cryogenic casting method, the preparation method of which includes: Using ethanol as a binder, copper powder with an average diameter of 75 μm was uniformly adhered to the surface of K2CO3 particles with an average diameter of 300–1200 μm to obtain a mixed powder; wherein the volume fraction of K2CO3 powder was 50%–85%. The mixed powder is poured into a mold and compacted at 200 MPa to obtain a compacted block. The compacted block is removed from the mold and placed in a vacuum furnace for sintering at 850°C for 30-60 minutes. Then, the temperature is raised to 950°C for further sintering for 2-4 hours to obtain the foamed copper radiator.

10. The method for preparing a solar-driven photothermal cogeneration system according to claim 5, characterized in that, The method for preparing the evaporator support in step S20 includes: First, the hydroxyl-modified MAX-Fe3O4@SiO2 dispersion is mixed with a dopamine solution and stirred under weakly alkaline conditions to promote the formation of a polydopamine adhesion layer on the surface of MAX-Fe3O4@SiO2 particles. Then, glutaraldehyde is added as a crosslinking agent, and the aldehyde group reacts with the amino group of polydopamine and the hydroxyl group on the surface of MAX-Fe3O4@SiO2 particles to form a dispersion with a covalent crosslinking network. Subsequently, the melamine sponge was immersed in the dispersion with the covalent cross-linked network to obtain the porous mesh structure of the melamine sponge anchored by MAX-Fe3O4@SiO2 particles; Finally, the porous mesh structure of the melamine sponge is cut with a cutting tool to obtain the evaporator support with different fractal structures.

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