Laser carbonization evaporator with three-dimensionally fluctuant surface as well as preparation method and application of laser carbonization evaporator

Abstract

The invention relates to the field of solar seawater desalination, and discloses a laser carbonization evaporator with a three-dimensionally fluctuant surface as well as a preparation method and application of the laser carbonization evaporator. A staggered hexagonal honeycomb array is formed on the top surface of the evaporator and comprises platforms and valleys; a surface carbonization layer is formed on the exposed surface except the bottom surface in situ, and the surface carbonization layer is continuously transited from outside to inside and does not penetrate through the bottom surface, so that a hydrophilic and hydrophobic seamless integrated structure is formed. The preparation method comprises the steps of laser etching forming and laser-induced carbonization. The evaporator is used for solar-driven interface evaporation desalination / water purification, and has high evaporation rate and long-term anti-salt crystallization stability. The evaporator is used for solar-driven interface evaporation desalination / water purification, the evaporation rate reaches 2.78 kg.m <-2 >. H <-1 > under 1 sun, the efficiency is 97.95%, and the evaporator is still stable and free of obvious salt crystallization after continuous operation for more than 100 h under the condition of 20 wt% NaCl.

Description

A laser carbonization evaporator with three-dimensional surface undulations, its fabrication method and application Technical Field

[0001] This invention relates to the field of solar-powered seawater desalination, and more specifically, to a laser carbonization evaporator with a three-dimensional undulating surface, its preparation method, and its application. Background Technology

[0002] The global freshwater crisis is rapidly escalating. Biomass-derived materials, such as natural wood, are increasingly becoming ideal platforms for constructing environmentally friendly solar evaporators. However, wood-based evaporators still face two major challenges: (i) the photothermal conversion efficiency is limited due to the weak light absorption capacity of raw wood; and (ii) salt accumulation is prone to occur during long-term operation, with salt crystals gradually blocking light-harvesting sites and reducing system stability. To address these challenges, various surface modification strategies have been reported, such as forming graphite coatings through spraying, depositing hydrophobic photothermal nanoparticles to create asymmetric wettability, or first deligninating followed by solvent-assisted lignin recoating, to improve light absorption performance and alleviate salt deposition. Although these methods are effective, they typically require additional chemical reagents and involve multiple processing steps, increasing preparation complexity, hindering large-scale deployment, and potentially introducing environmental burdens.

[0003] In existing technologies, Wang et al. reported forming a carbonized porous layer on the surface of wood using laser treatment to enhance light absorption and for interfacial evaporation. However, this is a modification route mainly based on surface laser carbonization. The original pore structure of the wood surface is significantly altered after laser treatment, and the wettability of the treated surface also differs from that of the original wood. Therefore, the integrity of the continuous water supply channel and the long-term salt accumulation behavior under high-salt, long-term operating conditions remain uncertain. Patent CN119217491A further introduces multiple external components and a multi-step preparation process, such as iron tannic acid ink pretreatment, GO / CNT composite coating, and stearic acid phase change heat storage, on the basis of laser-engraved wood to form a carbon layer. Although it can improve evaporation efficiency and performance under low light conditions, the process involves many steps and is highly dependent on chemical materials. The consistency of large-scale production and the long-term adhesion reliability of the coating in a saltwater environment may still be limiting factors. Moreover, its description of salt suppression relies more on macroscopic structure and material superposition, lacking more controllable and verifiable salt ion migration and crystal suppression mechanisms.

[0004] In summary, existing wood-based solar interface desalination evaporators may still face stability issues such as shading and pore blockage due to salt enrichment and crystallization, and evaporation performance degradation under high salt and long-term operation. At the same time, surface modification affects the original continuous water supply channels and wettability of wood, making it difficult to achieve both efficient evaporation and continuous water supply. In addition, the schemes that rely on multiple chemical components and multi-step coating are complex in process, and the consistency and durability of the coating are still insufficient. Therefore, there is an urgent need for a simpler construction strategy that is low in material burden and can stably suppress salt in the long term. Summary of the Invention

[0005] To overcome the shortcomings of existing wood-based photothermal evaporators, such as complex preparation, insufficient durability, and susceptibility to salt crystallization affecting stable operation, this invention provides a laser carbonization evaporator with a three-dimensional undulating surface. Another objective of this invention is to provide a method for preparing a laser carbonization evaporator with a three-dimensional undulating surface. A further objective is to provide an application of this laser carbonization evaporator with a three-dimensional undulating surface. Finally, a solar-powered interfacial water desalination device is provided.

[0006] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows: a laser carbonization evaporator with three-dimensional undulations on the surface, wherein the three-dimensional undulation structure is located on the upper part of the laser carbonization evaporator and is an interlaced hexagonal array structure, including platforms and valleys of several regularly oriented hexagonal units; the valleys are embedded in the gap area between the hexagonal units of two adjacent rows of platforms, thereby forming a honeycomb array in which platforms and valleys are interlaced.

[0007] The regular hexagonal cells in this application are arranged in a regular array to form a continuous "platform-valley-sidewall" three-dimensional topology. The honeycomb structure causes uneven heat distribution on the surface, which easily forms and maintains temperature / salinity differences, thereby driving the interfacial Marangoni circulation to complete the transport and dilution of salt.

[0008] Furthermore, all exposed surfaces of the laser carbonization evaporator, except for the bottom surface, are formed with a hydrophobic carbonization layer that continuously transitions into the interior of the substrate without penetrating to the bottom surface.

[0009] Furthermore, the platform height is 0.5~3.0 cm, the spacing between adjacent regular hexagonal units is 0.02~0.30 cm, and the distance between the outermost regular hexagonal unit and its nearest evaporator substrate boundary is 0.02~0.30 cm.

[0010] Preferably, the platform height is 1.5 cm, the spacing between adjacent regular hexagonal units is 0.1 cm, and the distance between the outermost regular hexagonal unit and its nearest evaporator substrate boundary is 0.1 cm.

[0011] The height, cell spacing, and peripheral boundary gap of the cellular array in this application have a synergistic effect: if the height is too low, the sidewall area will be insufficient, the platform and valley partitions will be indistinct, the temperature / salt gradient will be difficult to establish, and the Marangoni circulation range will be limited; if the height is too high, the processing burden will increase, and it may lead to a decrease in structural stability and an increase in water supply resistance. The three factors together determine whether the continuous sidewall network is sufficient and whether the valleys have concentrated brine collection and buffer space, thereby supporting long-term salt-resistant operation.

[0012] Furthermore, the evaporator substrate has microchannels perpendicular to the top surface.

[0013] Preferably, the evaporator is made of wood or bamboo with microchannels perpendicular to the top surface; preferably, the material has a density of 0.10-0.20 g·cm³. -3 Timber with a moisture content of 10%-15%.

[0014] Preferably, the sidewalls of the platform do not converge or diverge along the height direction.

[0015] A method for preparing a laser carbonization evaporator with three-dimensional undulations on the surface includes the following steps: laser etching the top surface of the evaporator material substrate to form a platform and valley of several regularly oriented hexagonal units; laser carbonization treatment is performed on all exposed surfaces except the bottom surface to form a hydrophobic carbonization layer, thereby obtaining the laser carbonization evaporator with three-dimensional undulations on the surface.

[0016] Furthermore, the laser power for laser etching is 10-15W, and the scanning speed is 600-800 mm / s. -1 The repetition frequency is 100-120 kHz.

[0017] Preferably, the number of laser etching scans is 950-1050.

[0018] Preferably, the laser etching has a laser power of 12W and a scanning speed of 700 mm·s. -1 The repetition frequency is 110kHz.

[0019] Furthermore, the laser power for laser carbonization is 15-20W, and the scanning speed is 800-1000 mm·s. -1 The repetition frequency is 120-150 kHz.

[0020] Preferably, the number of laser carbonization scans is 1080-1150.

[0021] Preferably, the laser power for laser carbonization is 17.5 W, and the scanning speed is 900 mm / s. -1 The repetition frequency is 130kHz.

[0022] The parameter settings for the two-stage laser processing in this application have a clear division of labor and matching relationship: The first stage is laser etching, the core of which is to form a three-dimensional honeycomb undulating structure with clear boundaries and regular geometry without damaging the wood water supply skeleton, thereby establishing a stable "platform-valley-sidewall" three-dimensional topological structure; therefore, the etching parameters need to fall within the window of uniform material removal without excessive ablation, so as to avoid pattern deformation or damage to longitudinal microchannels, which would lead to a decrease in water supply capacity. The second stage is laser-induced carbonization, the purpose of which is to generate a continuous porous carbon layer in situ on the formed top surface and exposed sidewalls, to achieve photothermal absorption and wettability functionalization, and to maintain a continuous transition and firm bond with the uncarbonized wood skeleton; the parameters in this stage directly affect the continuity, pore structure and carbonization depth of the carbon layer. Too weak a parameter will lead to discontinuous carbon layer and insufficient light absorption / hydrophobicity, while too strong a parameter may lead to excessive ablation, causing embrittlement or interface defects and affecting the patency of microchannels.

[0023] An application of the laser carbonization evaporator with three-dimensional undulations on the surface for solar-driven interface evaporation.

[0024] Furthermore, it is used for water purification.

[0025] A solar-powered interfacial water desalination device includes a liquid container, a condensation chamber, and a freshwater collection unit. The liquid container is equipped with a laser carbonization evaporator with a three-dimensional undulating surface.

[0026] The overall performance improvement of the RW-HL evaporator in this application stems from the synergistic effect of the three-dimensional interface structure, surface carbonization, and temperature / concentration gradient-driven circulation transport. The evaporation interface is constructed by laser to form an interlaced honeycomb array with a macroscopic three-dimensional topology of "platform-valley-sidewall." The interconnected sidewalls of each unit form a continuous sidewall network, causing multiple scattering and reflection of incident light near the interface, improving broadband absorption and photothermal coupling, and expanding the effective evaporation interface. The laser-induced porous carbonized layer provides a highly efficient photothermal conversion surface, while the low thermal conductivity of the wood matrix helps to localize heat at the evaporation interface and suppress heat loss to the bulk water phase. Meanwhile, the Janus configuration, formed by the seamless integration of a hydrophobic carbon photothermal layer and vertically oriented hydrophilic wood microchannels, can continuously replenish water while returning ions to the bulk solution, thus avoiding surface salt accumulation. Under the influence of the temperature and concentration gradients formed by the platform, valleys, and their sidewall network structures, the interface generates Marangoni-driven circulating flow and superimposed density reflux, causing salt to be dynamically redistributed at the interface and continuously carried away from the main evaporation zone. This allows for stable evaporation and inhibits salt crystallization even under high-salt, long-term operating conditions.

[0027] Compared with the prior art, the beneficial effects of the technical solution of the present invention are: the evaporator of this application achieves an evaporation rate of 2.78 kg·m³ under 1 sun conditions. -2 ·h-1 The solar-to-steam conversion efficiency reaches 97.95%, with an environmental heat loss of approximately 6.52%. It maintains stable evaporation and shows no significant salt crystallization even after continuous operation for over 100 hours under high-salt conditions (20 wt% NaCl). It can stably evaporate and produce significantly purified condensate from various water sources (including dye-contaminated water containing CR, MB, MO, and RhB, rainwater, pond water, etc.). The concentration of major ions in the condensate is significantly reduced after desalination (e.g., Mg). 2+ Ca 2+ K + Na + The levels decreased to 0.85, 0.68, 1.12, and 1.66 mg·L, respectively. -1 (Scale), it can produce condensate with a near-neutral pH even with strong acid (pH=1) and strong alkali (pH=14) feed water; in outdoor testing, the cumulative water production in 12 hours was 20.73 kg·m³. -2 The cumulative water production over 10 days was approximately 198.7 kg·m³. -2 This demonstrates good actual water production capacity and environmental adaptability. Attached Figure Description

[0028] Figure 1 shows the SEM images of RW-HL: (a) a photograph of the RW object; (b) a photograph of the RW-FL object; (c) a photograph of the RW-HL object; (d) a cross-sectional SEM image of the RW-HL object; and (e) cross-sections at different magnifications.

[0029] Figure 2 shows the photothermal and evaporation performance of the RW-HL evaporator. (a) Absorption spectra and standard solar spectrum (AM 1.5 G) of RW, RW-FL and RW-HL; (b) Surface temperature variation curves of RW, RW-FL and RW-HL (platform and valley) under 1 sun illumination; (c) Infrared thermal images of the top (upper) and side (lower) surfaces under 1 sun illumination; (d) Changes in the mass of pure water and water in different evaporators under dark conditions and 1 sun illumination; (e) Evaporation rate and corresponding solar-to-steam conversion efficiency of each evaporator under 1 sun illumination; (f) Mass change of the RW-HL evaporator under different solar irradiance; (g) Relationship between the evaporation rate and efficiency of the RW-HL evaporator and the solar irradiance.

[0030] Figure 3 shows the salt resistance and long-term stability of the RW-HL evaporator under continuous sunlight and the test results. (a) Top-view optical photograph and schematic diagram of the RW-HL evaporator during seawater evaporation under 1 sun illumination; (b) Mass change curve of the RW-HL evaporator during long-term operation; (c) Top-view optical photograph and schematic diagram of the RW-FL evaporator during seawater evaporation under 1 sun illumination; (d) Mass change curve of the RW-FL evaporator during long-term operation; (e) Evaporation rate of the RW-HL evaporator when treating different water sources under 1 sun condition; (f) UV-vis absorption spectra and digital photographs of CR, MB, MO and RhB dye-contaminated influent and their corresponding condensate; (g) Mg before and after desalination. 2+ Ca 2+ K + with Na + (h) pH values ​​of strongly acidic and strongly alkaline wastewater before purification and pH values ​​of condensate obtained after solar-driven purification; (i) Comparison of red bean seed germination irrigated with untreated wastewater (left) and condensate (right).

[0031] Figure 4 shows the performance of the RW-HL evaporator under outdoor conditions and the test results of solar-driven water purification. (a) Schematic diagram of the RW-HL evaporator under real outdoor conditions in Fuzhou, China; (b) Changes in solar irradiance, ambient temperature, relative humidity, instantaneous evaporation rate, and cumulative water production during 12 hours of continuous operation; (c) Cumulative freshwater production of the RW-HL evaporator over 10 consecutive days under fluctuating weather conditions; (d) Main cations (Mg) in the influent and condensate before and after desalination. 2+ Ca 2+ K + Na + Concentration comparison. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0033] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0034] The density of raw balsa wood is 0.10-0.20 g·cm³. -3 The moisture content is 10%-15%.

[0035] Example 1: Pre-cut to obtain dimensions of 20×20×20 mm 3The original balsa wood was used. A pulsed fiber laser (JX-YLP-50MD) with a galvanometer scanning optical system was employed to convert the designed honeycomb pattern (4×4, 16 units; height 1.5 cm; spacing 0.1 cm; boundary spacing 0.1 cm; sidewalls of equal width) into a vector scanning path. Laser etching was then performed on the top surface of the sample using a raster scanning method. During etching, the laser power was set to 24%, and the scanning speed was 700 mm / s. -1 The repetition frequency was 110 kHz and the number of scans was 1000 to achieve uniform material removal and form a well-defined honeycomb cavity, while preserving the inherent vertical orientation microchannel structure of the wood as much as possible.

[0036] After etching, the etched top surface and four sidewalls were subjected to uniform planar scanning carbonization. The laser power during the carbonization stage was set to 35%, and the scanning speed was 900 mm / s. -1 The repetition frequency was 130 kHz, and the number of scans was 1100, thereby generating a porous carbon layer that is firmly bonded and continuous to the surface of the wooden skeleton, and avoiding excessive ablation caused by excessive energy. The final product is honeycomb laser-carbonized balsa wood (RW-HL), which is an evaporator containing a honeycomb laser-carbonized layer.

[0037] Example 2 (RW-HL-EL) Example 2 is the same as Example 1, except that the laser power was set to 18% during the honeycomb etching stage, while the other etching parameters remained the same as in Example 1, resulting in a honeycomb carbonized sample, RW-HL-EL, with lower etching energy. The scanning speed during the etching stage was 700 mm / s. -1 The repetition frequency was 110 kHz, and the number of scans was 1000; the carbonization stage was the same as in Example 1 (35% / 900 mm·s). -1 / 130 kHz, 1100 scans).

[0038] Example 3 (RW-HL-CH) Example 3 is the same as Example 1, except that the laser power is set to 45% in the second stage carbonization process, and the other carbonization parameters are the same as in Example 1, resulting in a honeycomb carbonized sample RW-HL-CH with higher carbonization energy.

[0039] The scanning speed during the carbonization stage was 900 mm / s. -1 The repetition frequency was 130 kHz, and the number of scans was 1000; the etching stage was the same as in Example 1 (24% / 700 mm·s). -1 / 110 kHz, 1100 scans); the cellular array and geometric parameters are consistent with those of Example 1.

[0040] Example 4 (RW-HL-SS) Example 4 is the same as Example 1, except that the spacing between adjacent regular hexagonal honeycomb cells is set to 0.01 cm, and the other geometric parameters are the same as in Example 1, resulting in a sample RW-HL-SS with a smaller honeycomb spacing.

[0041] The honeycomb protrusions have a height of 1.5 cm, a boundary spacing of 0.1 cm, and an array of 16 units in a 4×4 configuration with straight, uniform sidewalls. The two-stage laser parameters are consistent with those in Example 1: etching stage 24% / 700 mm·s. -1 / 110 kHz, 1000 scans; carbonization stage 35% / 900 mm·s⁻¹ / 130 kHz, 1100 scans.

[0042] Example 5 (RW-HL-SL) Example 5 is the same as Example 1, except that the spacing between adjacent hexagonal honeycomb cells is set to 0.40 cm, while the other geometric parameters remain the same as in Example 1, resulting in the RW-HL-SL sample with a larger honeycomb spacing. The two-stage laser parameters are the same as in Example 1: etching stage 24% / 700 mm·s -1 / 110 kHz, 1000 scans; carbonization stage 35% / 900 mm·s -1 / 130 kHz, 1100 scans.

[0043] Example 6 (RW-HL-LH) Example 6 is the same as Example 1, except that the honeycomb protrusion height is set to 0.30 cm, while the other geometric parameters remain the same as in Example 1, resulting in the RW-HL-LH sample with excessively low honeycomb height. The spacing between adjacent cells is 0.1 cm, and the boundary spacing is 0.1 cm. The two-stage laser parameters are the same as in Example 1: etching stage 24% / 700 mm·s. -1 / 110 kHz, 1000 scans; carbonization stage 35% / 900 mm·s -1 / 130 kHz, 1100 scans.

[0044] Comparative Example 1 (RW-FL) was the same as Example 1, except that the honeycomb pattern laser etching was not performed on the top surface of the sample; instead, only the top surface and four sidewalls were subjected to planar uniform scanning carbonization (the bottom surface was not treated), resulting in a planar laser-carbonized layer of balsa wood, RW-FL. The laser power during the carbonization stage was set to 35%, and the scanning speed was 900 mm·s. -1 The repetition frequency is 130 kHz and the number of scans is 1100.

[0045] Comparative Example 2 (RW-H) is the same as Example 1, except that after laser etching of the honeycomb structure, a second-stage carbonization process is not performed, resulting in balsa wood RW-H with only a honeycomb etched structure. The laser power during the etching stage is 24%, and the scanning speed is 700 mm·s. -1 The repetition frequency is 110 kHz and the number of scans is 1000.

[0046] Comparative Example 3 (RW-HL-T) is the same as Example 1, except that after the honeycomb etching is completed, only the top surface (platform surface) of the honeycomb structure is scanned and carbonized. Exposed surfaces such as the honeycomb sidewalls, valley areas, and outer edge sidewalls of the device are not carbonized, resulting in a honeycomb sample RW-HL-T with only the top surface carbonized. The etching stage is 24% / 700 mm·s. -1 10 kHz, 1000 scans; carbonization stage 35% / 900 mm·s -1 / 130 kHz, 1100 scans.

[0047] Test Method 1: Solar Interface Evaporation and Photothermal Performance Testing. Raw balsa wood (RW), balsa wood with a planar laser-carved surface (RW-FL), and balsa wood with a honeycomb laser-carved surface (RW-HL) were directly floated on the surface of simulated seawater in a glass container. Testing was conducted under simulated illumination using a solar simulator (Sol3A Model 90943A, Newport Oriel Inc., USA), with the illumination intensity set to one standard solar intensity (1 kW·m²). -2 During the experiment, the ambient temperature was maintained at around 25℃, and the relative humidity was controlled at 30%-40%. An infrared thermal imager (HIKMICRO, Hikvision, China) was used to monitor the surface temperature changes of the evaporator in real time, while a high-precision electronic balance (ME204, METTLER TOLEDO, USA) was used to record the mass loss caused by water evaporation.

[0048] 2. Solar Desalination and Water Purification Performance Testing: A transparent condensation chamber is installed above the evaporator to capture and collect the water vapor generated during evaporation. The water vapor liquefies upon contact with the inner surface of the condensation chamber and flows along the chamber wall to an independent collection unit. The collected condensate is used for subsequent water quality analysis. Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES, Agilent 5110, Agilent Technologies, USA) was used to quantitatively detect the ion concentrations of the simulated seawater and the condensed freshwater. The resistivity of the condensate was measured using a digital multimeter (Model 2450, Keithley, USA) to evaluate the desalination performance of the device.

[0049] To further explore the universality of the device's water purification capabilities, various model pollutant aqueous solutions were selected as water samples to be treated under the same experimental conditions. These included solutions of four organic dyes: Congo Red (CR), Methylene Blue (MB), Methyl Orange (MO), and Rhodamine B (RhB), as well as two extreme pH solutions: sulfuric acid solution (pH=1) and sodium hydroxide solution (pH=14). All evaporation performance tests were repeated four times (n=4) to ensure the reliability of the experimental data.

[0050] 3. Outdoor Solar Desalination Experiment: Under real-world environmental conditions, a self-built SIWD device was used to evaluate the solar desalination performance of the RW-HL evaporator. The device consisted of an RW-HL evaporator, a container for holding brine, and a transparent condensation chamber. The condensation chamber contained a steam condensation zone and a freshwater collection unit (Figure 4a). The outdoor experiment was conducted in Fuzhou, China, on June 10, 2025 (06:00-18:00), on a sunny day. Environmental conditions were recorded over time during the experiment, and the device's water production performance was characterized by water production per unit area and evaporation rate. Simultaneously, condensate samples were collected for ion concentration detection to evaluate the desalination effect.

[0051] To assess long-term operational reliability, continuous outdoor operation tests were conducted under variable weather conditions, including some cloudy days, for a period of 10 days, and the cumulative water production was recorded.

[0052] Analysis and Explanation 1. Structural and Interface Characteristics As seen in the SEM image of RW-HL (Figure 1d), laser-induced carbonization forms a continuous porous carbon layer on the balsa wood surface, while effectively preserving the vertically oriented microchannels within the wood. This allows water to be rapidly transported from the bottom to the evaporation surface under capillary action, achieving a continuous water supply. Structural observation and preliminary testing indicate that the microchannel system is intact and has stable water supply capacity. The morphology of the RW-HL sample prepared under these process conditions is consistent with the carbonization quality and exhibits good repeatability, demonstrating the high robustness of this laser preparation process. Compared to RW (Figure 1a), the honeycomb structure and carbon layer porosity of RW-HL increase the specific surface area from 0.16 m² / s². 2 ·g -1 Significantly increased to 26.79 m 2 ·g -1 The total pore volume also increased from 0.0003 cm³. 2 ·g -1 Increased to 0.0968 cm 2 ·g -1 .

[0053] Based on this, the prepared Janus structure consists of a hydrophobic carbon top layer and a hydrophilic wood substrate, with a seamless connection between the two (Figure 1e). Compared with other processes used to prepare Janus solar evaporators (such as attaching the photothermal layer to the substrate by coating or injection), this seamless connection is crucial to ensuring the high strength and stability of the overall structure.

[0054] 2. Photothermal and interfacial evaporation performance of the RW-HL evaporator: Compared to the RW-FL evaporator, which only underwent laser-induced carbonization without laser etching (Figure 1b), the RW-HL evaporator utilizes laser etching of a three-dimensional honeycomb pattern on the top surface of the wood, while preserving vertically oriented microchannels and interconnected valley structures. These geometric features enhance light-harvesting capabilities and increase the effective evaporation area. The RW-HL achieves an average broadband solar absorptivity of 96.79% in the 250-2500 nm wavelength range, significantly higher than the RW's 25.06% (Figure 2a). In contrast, the RW-FL has a lower solar absorptivity of only 79.20%.

[0055] As seen in the side-view infrared image (Fig. 2c), the RW-HL evaporator exhibits significant thermal characteristics: strong surface heating and enhanced lateral thermal diffusion at the three-dimensional interface. The laser-induced honeycomb structure achieves localized photothermal confinement while promoting multidirectional heat conduction, thereby accelerating water vapor escape.

[0056] As shown in Figures 2b-c, the RW-HL evaporator can more efficiently convert absorbed solar energy into latent heat required for evaporation. Under 1 sun illumination, the RW-HL evaporator reaches a steady-state surface temperature of 42.5°C within 10 minutes, lower than the RW's 33.7°C and the RW-FL's 46.4°C. Furthermore, the temperature in the valley region of the RW-HL evaporator surface remains stable at 42.5°C, while the higher plateau region is slightly lower at 41.3°C, exhibiting spatial thermal nonuniformity. This resulting temperature gradient promotes lateral energy redistribution, which is crucial for its salt resistance.

[0057] In an evaporation test under 1 sun condition, the RW-HL evaporator achieved 2.78 kg·m³. -2 ·h -1 Its high evaporation rate and 97.95% solar-to-steam conversion efficiency are significantly better than RW-FL (1.54 kg·m³). -2 ·h -1 ,70.29%), RW (0.83 kg·m -2 ·h -1 45.91%) and pure water (0.31 kg·m -2 ·h -1The energy efficiency of the RW-HL evaporator is 18.65% (Figure 2d-e), and the total ambient heat loss is only 6.52%. This indicates that the RW-HL evaporator has higher energy utilization efficiency and steam generation capacity, and can effectively improve the interfacial evaporation performance.

[0058] Under variable light intensity (0.5–3 sun), the mass change of the RW-HL evaporator increases nearly linearly with increasing light intensity (Figure 2f); when the light intensity is 3 sun, its evaporation rate can reach 8.30 kg·m³. -2 ·h -1 The corresponding efficiency is 96.41% (Figure 2g). These results indicate that the RW-HL evaporator has good scalability and robustness, and still has the potential to be applied to solar desalination under actual operating conditions with fluctuating solar irradiance.

[0059] 3. Salt Resistance and Long-Term Stability of the RW-HL Evaporator: Under high-salt conditions, the honeycomb structure of the RW-FL evaporator exhibits strong evaporation in the platform area, initially increasing local salinity. Surface temperature differences induce thermal Marangoni convection, and differences in surface tension drive the liquid upwards along the sidewalls. The high salinity in the valleys induces solute Marangoni convection, further enhancing the upward flow from low-salinity areas to high-salinity areas. Simultaneously, density-driven convection causes high-density concentrated brine to settle within the valleys, forming a closed loop that redistributes and carries away the salt-rich solution from the platform area.

[0060] Through this cycle, concentrated brine gradually accumulates in the valley, while the platform area receives a continuous supply of lower salinity water. Even under long-term high-salinity conditions, the evaporation interface at the platform remains free of salt deposition. This dynamic redistribution mechanism effectively inhibits interfacial salt crystallization, thereby achieving long-term stable evaporation performance.

[0061] Based on the above principles, the RW-HL evaporator can maintain a stable evaporation rate of 2.78 kg·m³ even after continuous operation for over 100 hours under 20 wt% NaCl conditions. -2 ·h -1 Furthermore, no obvious salt crystallization was observed (Figures 3a-b). As shown in Figures 3c-d, the evaporation rate of the RW-FL evaporator was only 1.54 kg·m³ in the first 20 hours. -2 ·h -1 Its structure is merely a Janus configuration consisting of a hydrophobic carbon top layer and a hydrophilic woody substrate. Due to the lack of a temperature concentration gradient, an effective interfacial mass transfer process cannot be formed, leading to the gradual accumulation of salt at the evaporation interface during operation. After 44 hours of continuous operation, visible salt crystals appeared, and the evaporation performance rapidly declined.

[0062] Furthermore, the RW-HL evaporator also exhibits stable evaporation performance (approximately 2.78 kg·m³) when handling various types of influent.-2 ·h -1 This includes water contaminated with dyes containing CR, MB, MO, and RhB, rainwater, and pond water (Figure 3e). UV-vis spectroscopy confirmed that CR, MB, MO, and RhB dyes could be effectively removed, and the photographs showed that the condensate was clear, transparent, and colorless (Figure 3f). ICP-OES results showed that Mg in the condensate... 2+ Ca 2+ K + with Na + The concentration decreased by about 3-4 orders of magnitude (Figure 3g) and was below the limits set by the WHO and EPA.

[0063] For strongly acidic (H2SO4, pH=1) or strongly alkaline (NaOH, pH=14) influent, the resulting condensate had a near-neutral pH of 6.95 and 7.06, respectively (Fig. 3h). Red bean seed germination experiments further verified the safety of the produced water (Fig. 3i).

[0064] 4. Real-world environmental performance evaluation of the RW-HL evaporator: During the 12-hour test, environmental conditions fluctuated over time, with the temperature peaking at 44.3℃ around noon (Figure 4b). Under these conditions, the peak evaporation rate of the RW-HL evaporator reached 2.78 kg·m³. -2 ·h -1 The total daily water production was 20.73 kg·m³. -2 This is sufficient to meet the daily drinking water needs of 8 adults (calculated at 2.5 L per adult per day).

[0065] During 10 days of continuous outdoor testing in variable weather, the cumulative freshwater production reached 198.7 kg·m³. -2 (Figure 4c) shows that the device has good adaptability and stable water production performance in the natural environment.

[0066] Water quality analysis results show that it has a highly efficient ion removal capacity: Mg in the influent 2+ Ca 2+ K + with Na + The concentrations were 2,210, 3,041, 2,716 and 6,951 mg·L, respectively. -1 The concentrations in the collected condensate decreased significantly to 0.85, 0.68, 1.12, and 1.66 mg·L⁻¹, respectively. -1 (Figure 4d). These results demonstrate that the RW-HL evaporator can stably and efficiently produce high-quality potable freshwater under real-world environmental conditions.

[0067] 5. Effects of Preparation Conditions on Evaporator Performance Comparative Example 1: Due to the lack of a macroscopic three-dimensional topology (platform-valley-sidewall) and a continuous sidewall network, the RW-FL is not conducive to maintaining a stable temperature / salt gradient and cyclic transport. Therefore, its salt resistance stability during long-term high-salt operation is generally lower than that of the honeycomb structure sample, with light absorption and water evaporation efficiency decreasing by 18.1% and 28.2% respectively compared to Example 1. Comparative Example 2: Due to the absence of a continuous porous carbon layer, the sample is not conducive to achieving effective photothermal absorption and wettability functionalization. Its overall evaporation and stable operation performance is significantly weaker than that of the honeycomb sample that has undergone carbonization treatment. Comparative Example 3: Due to the absence of a continuous carbon layer at key interfaces such as the sidewall network / valleys, the synergistic effect of the honeycomb structure's "sidewall network-gradient maintenance-cyclic transport" is easily weakened, thus hindering long-term salt-resistant stable operation.

[0068] Example 2: Insufficient etching energy results in an incomplete honeycomb pattern or unclear three-dimensional topology, weakening the establishment of the platform-valley-sidewall structure and subsequent salt resistance synergy. Example 3: Increased carbonization energy can lead to excessive ablation, embrittlement, or interface defects, affecting microchannel patency and negatively impacting the quality of continuous carbon layers and long-term stable operation. Example 4: Reduced cell spacing compresses lateral migration / recirculation channels and weakens valley buffer space, hindering gradient maintenance and circulation transport, and easily reducing salt resistance stability. Example 5: Increased cell spacing weakens the effectiveness of the continuous sidewall network and cell synergy, making it difficult to maintain a stable gradient, thus hindering long-term salt resistance operation. Example 6: Reduced height results in insufficient sidewall area, unclear platform and valley partitioning, difficulty in establishing temperature / salt gradients, and limited Marangoni circulation range, thus negatively impacting salt resistance stability.

[0069] Table 1. At a solar irradiance of 1 kW m -2 Performance of different samples under (1 sun) conditions

[0070] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A laser carbonization evaporator with three-dimensional surface undulations, characterized in that, The three-dimensional undulating structure is located on the upper part of the laser carbonization evaporator. It is an interlaced hexagonal array structure, including platforms and valleys of several regularly oriented hexagonal units. The valleys are embedded in the gaps between the hexagonal units of two adjacent rows of platforms, thus forming a honeycomb array in which platforms and valleys are interlaced.

2. The laser carbonization evaporator with three-dimensional surface undulations according to claim 1, characterized in that, The laser carbonization evaporator forms a hydrophobic carbonization layer on all exposed surfaces except the bottom surface, and transitions continuously into the interior of the substrate without penetrating to the bottom surface.

3. The laser carbonization evaporator with three-dimensional surface undulations according to claim 1, characterized in that, The platform height is 0.5~3.0 cm, the spacing between adjacent regular hexagonal units is 0.02~0.30 cm, and the distance between the outermost regular hexagonal unit and its nearest evaporator substrate boundary is 0.02~0.30 cm.

4. The laser carbonization evaporator with three-dimensional surface undulations according to claim 1, characterized in that, The evaporator has microchannels perpendicular to its top surface inside its substrate.

5. A method for preparing a laser carbonization evaporator with three-dimensional surface undulations as described in any one of claims 1 to 4, characterized in that, Includes the following steps: The top surface of the evaporator material substrate is laser-etched to form platforms and valleys of several regularly oriented hexagonal units; all exposed surfaces except the bottom surface are laser-carbonized to form a hydrophobic carbonized layer, resulting in a laser-carbonized evaporator with three-dimensional undulations on the surface.

6. The method for preparing a laser carbonization evaporator with three-dimensional surface undulations according to claim 5, characterized in that, The laser etching process uses a laser power of 10-15W and a scanning speed of 600-800 mm / s. -1 The repetition frequency is 100-120 kHz.

7. The method for preparing a laser carbonization evaporator with three-dimensional surface undulations according to claim 5, characterized in that, Laser carbonization uses a laser power of 15-20W and a scanning speed of 800-1000 mm / s. -1 The repetition frequency is 120-150 kHz.

8. An application of the laser carbonization evaporator with three-dimensional surface undulations as described in any one of claims 1 to 4, characterized in that, Used for solar-driven interface evaporation.

9. The application of the laser carbonization evaporator with three-dimensional surface undulations according to claim 8, characterized in that, Used for water purification.

10. A solar-powered interfacial water desalination device, characterized in that, It includes a liquid container, a condensation chamber and a freshwater collection unit, wherein the liquid container is provided with a laser carbonization evaporator with three-dimensional surface undulations as described in any one of claims 1 to 4.

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