Wood-based photo-thermal moisture absorption sponge device and preparation method thereof

Abstract

The invention discloses a wood-based photo-thermal moisture absorption sponge device and a preparation method thereof. The method comprises the following steps: by taking natural balsa wood as a raw material, sequentially carrying out deep eutectic solvent (DES) selective delignification treatment, sodium chlorite-acetic acid buffer solution bleaching, chloroacetic acid carboxymethylation modification introduction of hydrophilic functional groups, lithium chloride moisture absorption treatment and modified lignin loading to construct a photo-thermal response layer; the obtained photo-thermal moisture absorption wood sponge retains an anisotropic micro-channel structure of natural wood, and is endowed with excellent capillary driving and water vapor transmission capabilities. Under the environment humidity condition, the material can rapidly adsorb moisture in air, and rapid desorption is achieved through temperature rise of the photo-thermal coating under sunlight illumination, so that continuous water vapor flow is formed; and charges are driven to directionally flow by utilizing an interface charge and microchannel ion migration mechanism, so that stable voltage and current output in the whole moisture absorption-desorption process is realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of biomass functional materials and energy conversion devices, and particularly relates to a light-heat-hygroscopic wood sponge material taking natural light wood as a substrate and a device construction method thereof, which can realize stable current and voltage output in the process of environmental humidity adsorption and solar desorption, and is suitable for atmospheric water collection, moisture energy collection, low-power electronic device power supply and other fields. BACKGROUND

[0002] Under the current global water resource and renewable energy dual tension background, the development of integrated environmental energy collection system has become a research hotspot. Atmospheric water resources are widely distributed but exist in low concentration, and traditional condensation / membrane distillation methods are high in energy consumption and low in efficiency. At the same time, environmental humidity gradient, capillary driven and photothermal response can cooperatively realize multi-functional processes such as evaporation, moisture absorption and power generation, forming an environmental energy self-driven system.

[0003] Natural wood has a longitudinally penetrating water guide microchannel structure, which is a natural capillary material; and through structure and surface modification, it can be endowed with moisture absorption and photothermal response capability. However, the current wood-based moisture or solar energy conversion system usually disperses the functional units, has poor structural integration, and the electrical output is unstable, making it difficult to realize efficient moisture absorption, atmospheric water release and water-driven power generation at the same time under actual conditions.

[0004] Therefore, it is urgent to develop a wood-based power generation material system with a porous skeleton, strong interface regulation ability, high photothermal response efficiency, and stable output of voltage and current during the process of moisture absorption / desorption. SUMMARY

[0005] The present application aims to overcome the technical difficulties of structural fragility, unstable electrical output and poor environmental adaptability in existing wood-based water vapor energy conversion devices, and provides a wood-based light-heat-hygroscopic sponge device and a preparation method thereof, which is stable in structure, integrated in function, stable in output and green and sustainable.

[0006] The present application first proposes a wood-based light-heat-hygroscopic sponge type water-driven device structure design scheme which integrates atmospheric moisture absorption, solar desorption and stable electrical output. Natural balsa wood is used as a substrate to construct a porous sponge-like wood structure with high specific surface area and high hydrophilicity, which endows it with excellent moisture absorption performance and interfacial water vapor migration ability. Innovatively, lignin is no longer discharged as a waste by-product, but is recovered from the wood delignification liquid, purified and subjected to chemical modification treatment, including demethylation and metal coordination processes, to prepare a modified lignin (D-Lignin-Fe) photothermal coating with good photothermal response capability, which is used as a functional component to load back on the surface of the wood sponge in situ, realizing closed-loop high-value utilization of wood resources.

[0007] To achieve the above-mentioned purposes, the present application adopts the following technical solutions: In a first aspect, a preparation method of a wood-based photothermal moisture absorption sponge device is provided, comprising: S1. Pre-treating natural Bashan wood as a matrix to obtain a Bashan wood block; S2. Using a deep eutectic solvent with choline chloride and oxalic acid as components to perform partial delignification treatment on the Bashan wood block to extract lignin and retain the longitudinal vessel structure of the wood, thereby obtaining partially delignified wood and a deep eutectic solvent waste liquid rich in lignin; S3. Using sodium chlorite-acetic acid buffer solution to perform bleaching treatment on the partially delignified wood to obtain white wood; S4. Placing the white wood in a water / ethanol system, adding chloroacetic acid and NaOH for heating reaction to introduce carboxymethyl functional groups into the white wood, thereby obtaining carboxymethylated wood; S5. Soaking the carboxymethylated wood in a LiCl solution and then drying to obtain a moisture absorption wood sponge; S6. Adding deionized water to the deep eutectic solvent waste liquid rich in lignin as an anti-solvent to deposit, centrifuge, and dry to obtain lignin; S7. Dissolving the lignin in anhydrous CH2Cl2, adding boron tribromide to perform demethylation treatment on the lignin to increase the content of phenolic hydroxyl groups, thereby obtaining demethylated lignin; S8. Dissolving the demethylated lignin in deionized water, adjusting the pH to 11-13 with a strong base, and then adding a FeCl3 solution to perform cross-linking to obtain a demethylated lignin-Fe 3+ complex; S9. Dropping the demethylated lignin-Fe 3+ complex on the upper surface of the moisture absorption wood sponge to form a photothermal coating, thereby obtaining a photothermal moisture absorption wood sponge; S10. Assembling the photothermal moisture absorption wood sponge using a double-sided carbon film electrode to construct a wood-based photothermal moisture absorption sponge device with moisture absorption-desorption synergistic water-powered generation function.

[0008] In some embodiments, step S1 specifically comprises: selecting natural Bashan wood as a raw material, performing size cutting, and performing acetone pre-treatment to remove surface impurities.

[0009] In some embodiments, in step S2, the deep eutectic solvent with choline chloride and oxalic acid as components is used to perform selective delignification treatment on the Bashan wood block, which comprises: mixing choline chloride and oxalic acid to form a homogeneous transparent liquid to obtain a deep eutectic solvent DES; immersing the Bashan wood block in the deep eutectic solvent DES and heating at 80-100°C for reaction to dissolve out lignin; and washing with deionized water to neutralization after the reaction is completed to obtain partially delignified wood.

[0010] Further, in step S2, at least any one of the following is satisfied: The thickness of the beech wood block is 8-12 mm, preferably 10 mm; In the preparation of the DES, choline chloride and oxalic acid are mixed at a molar ratio of 1:1 to form a homogeneous transparent liquid at 50-70 °C; preferably, a homogeneous transparent liquid is formed at 60 °C; The mass ratio of the basswood block to the DES is 1: (18-22), preferably 1:20; The heating reaction includes: 80-100 °C for 4-6 hours, preferably 90 °C for 5 hours.

[0011] It should be noted that basswood has a natural anisotropic microchannel structure, and the water transmission mainly occurs in the longitudinal direction. If the thickness is less than 8 mm, the mechanical stability is reduced, and the processing process (delignification, bleaching) is easy to cause warping and cracking; if the thickness is greater than 12 mm, the internal reactant penetration and thermal diffusion are uneven, and incomplete delignification or insufficient carboxylation is easy to occur. The thickness of 10 mm can balance the chemical penetration efficiency and mechanical stability, and at the same time ensure that the cross-sectional light and heat layer coverage matches the core ion migration efficiency, and improves the overall output balance of the device.

[0012] It should be noted that the amount of solvent determines the driving concentration gradient and the reactant coverage of the delignification reaction. If the proportion is too low, the delignification will not be complete due to insufficient wood absorption, and if the proportion is too high, it will cause resource waste and increase the pressure of post-processing. The mass ratio of the basswood block to the DES is 1: (18-22), which can ensure that the wood block is fully soaked and maintain the stability of the system's reactive concentration, and is the best ratio for delignification effect and wood structure preservation in the experiment.

[0013] It should be noted that the DES delignification process is a diffusion-reaction coupling process. Below 80 °C, the reaction rate is slow and the lignin is not fully dissolved; above 100 °C, the wood may be carbonized and the anisotropic microstructure may be damaged. If the time is less than 4 h, the reaction is not complete, and if it exceeds 6 h, the cellulose may be degraded and the pore wall may be brittle.

[0014] More preferably, 90 °C for 5 h, which can ensure that the lignin is fully dissolved while the mechanical structure of the wood is maximally protected, and 5 h is the best time point for the maximum lignin release and high cellulose retention in the experiment, which ensures the integrity of the subsequent moisture absorption and conductive functional substrate.

[0015] In some embodiments, step S3 specifically includes: immersing part of the delignified wood in a sodium chlorite-acetic acid buffer solution, and after the bleaching reaction is completed, white wood DW is obtained.

[0016] Further, in step S3, at least any one of the following is satisfied: The sodium chlorite-acetic acid buffer solution is obtained by adding acetic acid solution dropwise into 1-3 wt% sodium chlorite aqueous solution until the pH is 4.6. More preferably, the concentration of sodium chlorite is 2 wt%. The bleaching reaction temperature is 80-90°C, preferably 85°C. It should be noted that when the concentration of sodium chlorite is less than 1 wt%, the amount of active ClO2 generated is insufficient, and residual hemicellulose and lignin cannot be effectively removed, resulting in incomplete bleaching and affecting the functional group exposure of wood. When it is higher than 3 wt%, the system is too oxidizing, which may damage the wood cell wall, damage the original longitudinal channel structure and mechanical stability, and reduce the subsequent moisture absorption and water conductivity. At a concentration of 2 wt%, the ClO2 generation rate is moderate, which can ensure sufficient bleaching while gently treating the wood microstructure, maintaining the integrity of the anisotropic water-conducting network and microporous skeleton.

[0017] It should be noted that sodium chlorite (NaClO2) as a selective oxidant is most stable under slightly acidic conditions (pH ≈4.5–5.0), which can effectively and selectively degrade the benzene quinone and quinone methyl structures in residual lignin without significantly damaging the cellulose skeleton; If the pH is too low (<4), the chlorite will decompose prematurely to generate ClO2 gas, causing oxidant loss and unsafe treatment; If the pH is too high (>5.5), the oxidation ability will be reduced, resulting in low bleaching efficiency and residual wood color. pH 4.6 is the standard working point of the classic NaClO2 / acetic acid buffer system, which can maintain the stability of the oxidation system and balance the lignin removal efficiency and cellulose retention rate; The wood bleached under this condition in the experiment is uniform ivory white, which is beneficial to the subsequent comparison and functional construction of the photo-thermal layer.

[0018] It should be noted that the bleaching efficiency of NaClO2 under acidic conditions increases with increasing temperature, but its upper limit of thermal stability is about 90–95°C; If the temperature is too low (<80°C), the reaction rate will be significantly reduced and the lignin cannot be completely degraded; If the temperature is too high (>90°C), ClO2 will volatilize rapidly, the reaction will be out of control, and cellulose degradation and wood brittleness will occur. 85°C is the critical point of the balance between delignification speed and structure preservation in sodium chlorite bleaching; Under this temperature, the residual lignin can be removed to the greatest extent, the wood whiteness and adsorbent uniform loading capacity can be improved, and the water-conducting microchannels are not damaged, providing an ideal substrate for the subsequent penetration of moisture absorbent (such as LiCl) and photo-thermal coating.

[0019] In some embodiments, in step S4, specifically comprising: using chloroacetic acid and NaOH in a water / ethanol system to perform a carboxymethylation reaction on the white wood to introduce carboxyl groups, to obtain carboxymethylated wood CW.

[0020] Further, in step S4, at least any one of the following is satisfied: The water / ethanol system uses 90wt% ethanol; The mass ratio of chloroacetic acid and NaOH is 1:(0.6-1.6), preferably 1:1.1; The reaction temperature is 80-100°C, preferably 90°C.

[0021] It should be noted that carboxymethylation is a process of introducing -CH2COOH groups into wood through nucleophilic substitution reaction; the reaction relies on the substitution of chloroacetic acid (ClCH2COOH) and alkoxide group (-O-) generated under alkaline conditions to form carboxymethyl cellulose (CMC) structure; the role of NaOH is: ① promote the deprotonation of hydroxyl groups in wood, ② promote the activity enhancement of ClCH2COOH, ③ neutralize the byproduct hydrochloric acid. Insufficient NaOH (<0.6) will result in insufficient alkoxide generation, low reaction efficiency, and small amount of carboxyl group introduction; excessive NaOH (>1.6) will lead to alkaline degradation of wood, such as cellulose chain breakage or pore structure damage; the mass ratio of chloroacetic acid and NaOH is preferably 1:1.1, which is the best ratio to obtain maximum -COOH introduction efficiency, structure retention and uniform modification effect, taking into account reaction activity and material mechanics retention.

[0022] It should be noted that carboxymethylation is a liquid phase diffusion + interface reaction controlled process, the higher the temperature, the faster the reaction rate; but above 100°C, the modification uniformity will be affected due to rapid evaporation of ethanol, severe pH fluctuation, and increased risk of wood thermal degradation; below 80°C, the reaction rate is limited, resulting in insufficient carboxyl group introduction. At 90°C, ClCH2COOH has good solubility in ethanol-water medium, and NaOH has moderate activity; it can greatly improve the carboxyl density (i.e. surface charging capacity) while maintaining the integrity of the wood microchannels; enhance the electrostatic adsorption capacity of Li⁺, improve the moisture response speed and subsequent interface ion migration efficiency.

[0023] In some embodiments, in step S5, at least any one of the following is satisfied: The concentration of LiCl solution is 5wt%-25wt%, preferably 15wt%; The soaking is vacuum impregnation for 10-14 hours, preferably 12 hours; The drying temperature is 90-110°C, preferably 100°C.

[0024] In some embodiments, in step S7, at least any one of the following is satisfied: The amount of anhydrous CH2Cl2 used per 1 gram of lignin is 90-110 mL; The amount of boron tribromide used is 10-30 mL, preferably 20 mL, per 1 gram of lignin; The demethylation reaction is performed for 12-36 hours, preferably 24 hours.

[0025] It should be noted that by using boron tribromide (BBr3) to demethylate natural lignin in anhydrous dichloromethane system, the surface polarity and metal coordination ability of the lignin can be significantly improved, thereby enhancing the photothermal response performance and surface loading stability. When the dosage of boron tribromide is less than 10 mL, the methoxy group is not completely removed, and the lignin still exhibits hydrophobic characteristics and poor surface activity. When the dosage exceeds 30 mL, the risk of system reaction heat and side reactions is significantly increased, and there is no obvious performance improvement.

[0026] It should be noted that the BBr3 demethylation reaction is performed under anhydrous conditions. As the reaction time increases, the methoxy groups in the lignin structure are gradually broken, and the hydroxyl groups increase. However, excessive treatment may cause degradation of the molecular skeleton, affecting the photothermal and film-forming performance. When the reaction time is less than 12 h, the methoxy removal rate is insufficient. When the reaction time is too long, the lignin molecular polymerization degree decreases, the dispersibility becomes poor, and self-polymerization and sedimentation easily occur.

[0027] In some embodiments, step S8 specifically includes, after 1 gram of demethylated lignin is dissolved in 20 mL of deionized water, adjusting the pH to 11-13 (preferably 12) using a strong base (sodium hydroxide solution), and then adding 10 mL of FeCl3 solution. After thorough stirring, centrifugation and drying are performed. The concentration of the FeCl3 solution should be 0.3-0.7 M, preferably 0.5 M.

[0028] It should be noted that the main functional groups present in demethylated lignin include phenolic hydroxyl groups (–OH), carboxyl groups (–COOH), and part of the quinone structure. In an alkaline environment, these groups are more prone to deprotonation to form anion active sites such as –O⁻ and –COO⁻, which can undergo multi-coordination reactions with Fe³⁺.

[0029] A pH of 11-13 (preferably 12) significantly improves the coordination ability of the lignin, promotes stable complexation between Fe³⁺ and the lignin, forms a tannin-iron-like structure, and enhances the photothermal response and film-forming stability of the thin film.

[0030] It should be noted that if the concentration of Fe³⁺ is too low (<0.3 M), the system complexation is not complete, and part of the lignin remains in a free state, affecting the compactness and light absorption performance of the film. If the concentration is too high (>0.7 M), colloidal precipitates such as Fe(OH)3 are easily formed, which can damage the lignin structure and reduce the stability of the coating. Within the concentration range of 0.3-0.7 M, Fe³⁺ can fully complex with –OH / –COO⁻ in the lignin molecules, achieving stable coordination crosslinking and uniform distribution, and forming a compact and strongly adherent photothermal coating.

[0031] In some embodiments, step S9 specifically comprises, drop-coating the demethylated lignin-Fe 3+ The complex photo-thermal coating needs to meet the demethylated lignin-Fe 3+ The loading amount of the complex is 40-80 mg / 9 cm 2 , preferably 60 mg / 9 cm 2 ; It should be noted that when the loading amount is too low, the surface photo-thermal coating is not uniformly covered, resulting in reduced light absorption rate, insufficient thermal response, insufficient surface temperature rise shown in the infrared thermal image, and difficulty in effectively driving the interface water vapor evaporation, thereby affecting the continuity of potential formation and voltage output. When the loading amount is too high, the thick coating will hinder water vapor transmission and heat diffusion, forming local heat accumulation, which is easy to cause surface drying and salt crystallization accumulation, and at the same time increase the risk of coating falling off, thereby affecting the stability and cycle performance of the device. The preferred amount is 60 mg / 9 cm 2 , which can form a uniform and dense photo-thermal functional layer on the surface of the wood sponge, realize optimal light absorption and interface evaporation coupling, and at the same time maintain the balance between moisture absorption, water vapor transport and the overall flexibility of the device.

[0032] In some embodiments, S6, a double-sided carbon film electrode is used to assemble a photo-thermal moisture-absorbing wood sponge, and a wood-based photo-thermal moisture-absorbing sponge device is constructed, comprising: A polyethylene terephthalate (PET) mesh electrode coated with carbon conductive paste is attached to the upper and lower surfaces of the photo-thermal moisture-absorbing wood sponge, respectively, and then the electrodes are connected to an external circuit using carbon tape to obtain a wood-based photo-thermal moisture-absorbing sponge device.

[0033] In a second aspect, a wood-based photo-thermal moisture-absorbing sponge device is provided, which is prepared by the above preparation method and has the following structural characteristics: The porous cellulose framework formed after delignification: the natural Bashan wood treated by the eutectic solvent and sodium chlorite-acetic acid buffer solution forms a loose and porous cellulose framework, effectively improving the specific surface area and hydrophilic ability; The internal longitudinal conductive microchannels that retain the natural wood: the anisotropic structure of the original wood is maintained to realize the directional migration of water vapor under capillary driving; The surface is covered with a modified lignin photo-thermal response coating: the coating is derived from lignin extracted from raw materials, which is modified by demethylation and metal coordination to construct a surface layer with both light absorption and hydrophobic functions; The two carbon electrodes embedded on the upper and lower surfaces form a closed water-voltage structure: carbon conductive paste is coated on the two surfaces of the device using a PET mesh to ensure the integrity of the conductive network and the compatibility of the flexible structure; With stable DC output capability: can be in the absence of external bias, only rely on ambient humidity and solar light driven output stable voltage and current.

[0034] Further, under the condition of 25°C, 70% RH, the device can absorb environmental moisture up to 1.89g / g; under 1 sun solar irradiation, the surface temperature rises rapidly to 68.8°C, realizing rapid water vapor desorption and continuous power generation output.

[0035] Compared with the prior art, the present application has the following beneficial effects: The wood-based light-heat moisture absorption sponge device and the preparation method thereof have the following advantages: (1) green controllable and complete structure: the natural light wood is subjected to delignification extraction by using a green low eutectic solvent (DES) system composed of choline chloride and lactic acid, and is subjected to bleaching treatment by using sodium chlorite-acetic acid buffer solution, so that the natural duct system is retained, and the structural stability and continuous transmission performance are ensured; (2) gradient regulation and interface optimization: the hydrophilicity of the substrate is enhanced by carboxymethylation, and at the same time, a modified lignin light-heat coating is coated only on the surface, so that an interface structure with a biomimetic gradient hydrophilicity and a light-heat asymmetric interface is constructed, and the evaporation efficiency and ion migration rate are significantly improved; (3) light-heat coupling and continuous power generation: the light-heat coating constructed by the modified lignin has high light absorption efficiency and strong heat conversion capability, and can form a local high temperature area under solar light conditions, so as to drive the interface to evaporate efficiently and generate stable voltage, and the power generation process does not depend on mechanical pumps or external electric fields, and has the characteristics of self-driving; (4) high stability and environmental adaptability: the device can continuously cycle and work under the condition of relative humidity of 30%-90%, and still maintains the moisture absorption performance and stable voltage output, so that it is suitable for the atmospheric water collection and energy collection demand in the tropical or coastal humid area; (5) wide application and strong expandability: the device can be integrated in series or in parallel, realizes an output of up to 3-4V, can directly drive small electronic devices such as LED, electronic watch, temperature and humidity sensor, and is suitable for distributed energy systems, environmental monitoring terminals and low-power wearable device power supply scenes. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 It is a working mechanism schematic diagram of the wood-based device with moisture absorption-desorption synergistic water-driven power generation function of the present application; Figure 2 It is a real object diagram and microstructure diagram of the wood-based device with moisture absorption-desorption synergistic water-driven power generation function in the embodiment of the present application; Figure 3 It is a surface water drop contact angle test diagram of the wood-based light-heat moisture absorption sponge device material in the embodiment of the present application; Figure 4A schematic diagram of the moisture absorption kinetics curve of the material under different environmental humidity conditions in the embodiment of the present application; Figure 5 A schematic diagram of the moisture absorption kinetics curve under different temperature conditions in the embodiment of the present application; Figure 6 A schematic diagram of the infrared thermal imaging of the device surface under light conditions in the embodiment of the present application; Figure 7 A schematic diagram of the desorption rate change curve of the device under different light intensities in the embodiment of the present application; Figure 8 A schematic diagram of the mass change curve of the moisture absorption and desorption process in different humidity environments in the embodiment of the present application; Figure 9 A schematic diagram of the atmospheric water collection system device in the embodiment of the present application, including the structure schematic and actual photo schematic of the moisture absorption-desorption circulation device; Figure 10 The ion chromatography detection results of cations (Na⁺, K⁺, etc.) contained in the collected moisture in the embodiment of the present application; Figure 11 A schematic diagram of the open-circuit voltage change curve of the device in the moisture absorption and desorption processes in the embodiment of the present application; Figure 12 A schematic diagram of the open-circuit voltage output curve of a plurality of devices connected in series in the desorption stage in the embodiment of the present application; Figure 13 A schematic diagram of the voltage-time curve of the series-connected device in the process of charging the capacitor in the embodiment of the present application; Figure 14 A photo actual shot of the digital temperature and humidity meter directly driven by the series-connected device in the embodiment of the present application; Figure 15 A functional demonstration diagram of the LED lamp bead lit by the series-connected device after energy storage by the capacitor in the embodiment of the present application; Figure 16 A functional demonstration diagram of the calculator driven by the series-connected device after energy storage by the capacitor in the embodiment of the present application. DETAILED DESCRIPTION

[0037] The present application will be further described below in conjunction with the drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present application, and cannot be used to limit the protection scope of the present application.

[0038] The endpoints of the ranges and any values in the ranges disclosed herein are not limited to the precise values stated. The ranges and values should be construed to be approximations that can vary depending on the intended application. For numerical ranges, the endpoints are included in the ranges, and the ranges between the endpoints are also included in the ranges. The ranges and endpoints between the ranges can be combined with each other to form one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0039] For the purposes of this specification and the appended claims, unless otherwise stated, all expressions, percentages, or proportions, and other numerical values ​​used in this specification and the appended claims, are to be understood to be modified by the term "about" in all cases. Furthermore, all scopes disclosed herein include their endpoints and can be combined independently.

[0040] In this embodiment of the application, the method for preparing the sodium chlorite-acetic acid buffer solution includes: adding acetic acid dropwise to a 2wt% sodium chlorite aqueous solution until the pH is adjusted to 4.6.

[0041] Example 1: A method for preparing a wood-based photothermal moisture-absorbing sponge device, comprising the following steps: S1. Log Pretreatment Take natural balsa wood blocks (size: 30mm×30mm×10mm), soak them in acetone solution for 12 hours to remove surface oils and terpenes, rinse them with deionized water, and dry them in a vacuum oven at 45°C for later use.

[0042] S2. Partial delignification treatment with eutectic solvent (DES) A DES solution of choline chloride and oxalic acid (molar ratio 1:1) was prepared and formed into a homogeneous transparent liquid under magnetic stirring at 80°C. Dried balsa wood blocks were immersed in a eutectic solvent (DES) at 90°C for 5 hours. After removal, the blocks were thoroughly washed with deionized water until neutral to obtain partially delignified wood with a significantly darker color.

[0043] S3. Bleaching with sodium chlorite-acetic acid buffer solution Part of the delignified wood was immersed in a sodium chlorite-acetic acid buffer solution with a pH of 4.6 and reacted at 85°C for 12 hours to further remove impurities and purify the wood, removing residual lignin and obtaining white wood (DW).

[0044] S4. Carboxymethylation modification White wood was reacted in 90wt% ethanol with chloroacetic acid and NaOH (mass ratio 1:1.1) at 93°C for 5 hours to introduce carboxymethyl functional groups, which enhanced hydrophilicity and ion exchange capacity, thus obtaining carboxymethylated wood. S5. Lithium chloride impregnation with moisture-absorbing modification Carboxymethylated wood was soaked in a 15 wt% LiCl solution and vacuum impregnated for 12 hours, followed by drying at 100°C for 12 hours to form highly hydrophilic moisture-absorbing wood sponge AMW.

[0045] S6. Lignin extraction from delignification waste liquid To the eutectic solution waste liquid rich in lignin, slowly add lignin antisolvent deionized water to precipitate lignin, and after precipitation, centrifugal drying obtains lignin Lignin.

[0046] S7. Lignin demethylation The extracted lignin Lignin is dissolved in 100 mL anhydrous CH2Cl2, and then boron tribromide is added (the amount of boron tribromide is 20 mL per 1 gram of lignin). After 24 hours of demethylation reaction at room temperature, the obtained demethylated lignin D-Lignin is centrifugally dried.

[0047] S8. Demethylated lignin and Fe 3+ Coordination crosslinking The demethylated lignin D-Lignin is dissolved in 20 mL deionized water, and then a 0.5M FeCl3 solution is added (the amount of FeCl3 solution is 10 mL per 1 gram of demethylated lignin) after adjusting the pH to 12 with a sodium hydroxide solution. After stirring, the obtained demethylated lignin-Fe D-Lignin-Fe is centrifugally dried. 3+ complex D-Lignin-Fe.

[0048] S9. Hygroscopic wood sponge photothermal coating loading demethylated lignin-Fe 3+ The complex is made into a coating solution of 25 mg / mL. 200 μL of the coating solution is repeatedly dropped on the upper surface of the wood sponge, and the loading amount is 60 mg. After drying, a photothermal coating is formed, and a photothermal hygroscopic wood sponge PAMW is obtained.

[0049] S10. Photothermal hygroscopic wood sponge device assembly and series connection A PET mesh electrode coated with a carbon conductive paste (CH-8) is attached to the upper and lower surfaces of the photothermal hygroscopic wood sponge, respectively. The carbon tape is connected to the external circuit to form a single wood-based photothermal hygroscopic sponge device. Several wood-based photothermal hygroscopic sponge devices are connected in series, exposed to air, and tested for voltage output, power density, and load relationship during the hygroscopic and photothermal desorption processes. The wood-based photothermal hygroscopic sponge device can drive a low-power temperature and humidity meter to operate.

[0050] Embodiment 2: A preparation method of a wood-based photothermal hygroscopic sponge device, comprising the following steps: S1. Raw wood pretreatment A natural Bashan wood block (size: 30 mm x 30 mm x 10 mm) is taken, soaked in an acetone solution for 12 h to remove surface grease and terpenes, washed clean with deionized water, and dried in a vacuum oven at 45°C for standby use.

[0051] S2. Deep eutectic solvent (DES) partial delignification treatment A DES solution of choline chloride and oxalic acid (molar ratio 1:1) was prepared and formed a homogeneous transparent liquid under magnetic stirring at 80 °C. Dry balsa wood blocks were immersed in the DES at 90 °C for 5 h, and after removal, washed thoroughly with deionized water until neutral to obtain partially delignified wood, which was significantly darker in color.

[0052] S3. Bleaching with sodium chlorite-acetic acid buffer solution The partially delignified wood was immersed in a sodium chlorite-acetic acid buffer solution at pH 4.6 at 90 °C for 12 h, and further purified to remove residual lignin to obtain white wood DW.

[0053] S4. Carboxymethylation modification The white wood was immersed in 90 wt% ethanol with chloroacetic acid and NaOH (mass ratio 1:1.1) at 95 °C for 5 h to introduce carboxymethyl functional groups, which enhanced the hydrophilicity and ion exchange capacity, to obtain carboxymethylated wood. S5. Lithium chloride impregnation for moisture absorption modification The carboxymethylated wood was immersed in a 17 wt% LiCl solution and vacuum-impregnated for 12 h, followed by drying at 100 °C for 12 h to form a highly hydrophilic moisture-absorbing wood sponge AMW.

[0054] S6. Lignin extraction from delignification waste liquid A lignin antisolvent was slowly added to the lignin-rich DES waste liquid to precipitate lignin, and after complete precipitation, lignin was obtained by centrifugal drying.

[0055] S7. Lignin demethylation The extracted lignin was dissolved in 100 mL anhydrous CH2Cl2, and then boron tribromide was added (10 mL per 1 g of lignin). After 24 h of demethylation at room temperature, the demethylated lignin D-Lignin was obtained by centrifugal drying.

[0056] S8. Demethylated lignin coordination with Fe 3+ Coordination crosslinking The demethylated lignin D-Lignin was dissolved in 20 mL deionized water, and then a 0.5 M FeCl3 solution was added (10 mL per 1 g of demethylated lignin) after adjusting the pH to 12 with a sodium hydroxide solution. After stirring, the demethylated lignin-Fe D-Lignin-Fe complex was obtained by centrifugal drying. 3+ complex D-Lignin-Fe.

[0057] S9. Moisture-absorbing wood sponge photo-thermal coating loading A 50 mg / mL coating solution was prepared using the demethylated lignin-Fe3+ complex D-Lignin-Fe. 200 μL of the coating solution was repeatedly drop-coated onto the surface of the wood sponge, with a loading of 50 mg. After drying, a photothermal coating was formed, yielding a photothermal hygroscopic wood sponge (PAMW).

[0058] S10 Photothermal Moisture Absorbing Wood Sponge Device Assembly and Series Connection PET mesh electrodes coated with carbon conductive paste (CH-8) are attached to the upper and lower surfaces of a photothermal absorbing wood sponge, respectively, and connected to an external circuit using carbon tape to form a single wood-based photothermal absorbing sponge device. Several wood-based photothermal absorbing sponge devices are connected in series and exposed to air. Tests are performed on voltage output, power density, and load relationship during the moisture absorption and photodesorption processes, which can drive the operation of a low-power thermo-hygrometer.

[0059] Example 3: A method for preparing a wood-based photothermal moisture-absorbing sponge device, comprising the following steps: S1. Log Pretreatment Take natural balsa wood blocks (size: 30mm×30mm×15mm), soak them in acetone solution for 12 hours to remove surface oils and terpenes, rinse them with deionized water, and dry them in a vacuum oven at 45°C for later use.

[0060] S2. Partial delignification treatment with eutectic solvent (DES) A DES solution of choline chloride and oxalic acid (molar ratio 1:1) was prepared and formed into a homogeneous transparent liquid under magnetic stirring at 80°C. Dried balsa wood blocks were immersed in a eutectic solvent (DES) at 90°C for 5 hours. After removal, the blocks were thoroughly washed with deionized water until neutral to obtain partially delignified wood with a significantly darker color.

[0061] S3. Bleaching with sodium chlorite-acetic acid buffer solution Part of the delignified wood was immersed in a 1wt% sodium chlorite aqueous solution, and acetic acid was added dropwise to adjust the pH to 4.6. The reaction was carried out at 85°C for 12 hours to further remove impurities and purify the wood, removing residual lignin and obtaining white wood (DW).

[0062] S4. Carboxymethylation modification White wood was reacted in 90wt% ethanol with chloroacetic acid and NaOH (mass ratio 1:1.2) at 95°C for 5 hours to introduce carboxymethyl functional groups, which enhanced hydrophilicity and ion exchange capacity, thus obtaining carboxymethylated wood. S5. Lithium chloride impregnation with moisture-absorbing modification Carboxymethylated wood was soaked in a 13 wt% LiCl solution and vacuum impregnated for 12 hours, followed by drying at 100°C for 12 hours to form highly hydrophilic and hygroscopic wood sponge AMW.

[0063] S6. Extraction of lignin from delignification waste liquor To the eutectic solution waste liquor rich in lignin, slowly add lignin antisolvent for the precipitation of lignin, after precipitation, centrifugal drying to obtain lignin Lignin.

[0064] S7. Demethylation of lignin The extracted lignin Lignin is dissolved in 100 mL anhydrous CH2Cl2, then add boron tribromide (boron tribromide dosage is 30 mL per 1 gram of lignin), after 24 hours of demethylation reaction at room temperature, centrifugal drying to obtain demethylated lignin D-Lignin.

[0065] S8. Demethylated lignin and Fe 3+ coordination crosslinking The demethylated lignin D-Lignin is dissolved in 20 mL deionized water, and then the pH is adjusted to 12 with sodium hydroxide solution, then 0.5 M FeCl3 solution is added (FeCl3 solution dosage is 10 mL per 1 gram of demethylated lignin), after stirring, centrifugal drying to obtain demethylated lignin-Fe 3+ complex D-Lignin-Fe.

[0066] S9. Hygroscopic wood sponge photo-thermal coating loading demethylated lignin-Fe 3+ The demethylated lignin-Fe complex D-Lignin-Fe is made into a coating solution of 25 mg / mL. 200 μL of the coating solution is repeatedly dropped on the upper surface of the wood sponge, with a loading of 62 mg, and then dried to form a photo-thermal coating, obtaining a photo-thermal hygroscopic wood sponge PAMW.

[0067] S10 Photo-thermal hygroscopic wood sponge device assembly and series connection A PET mesh electrode coated with carbon conductive paste (CH-8) is attached to the upper and lower surfaces of the photo-thermal hygroscopic wood sponge, respectively, and connected to an external circuit using carbon tape, forming a single wood-based photo-thermal hygroscopic sponge device. Several wood-based photo-thermal hygroscopic sponge devices are connected in series, exposed to air, and tested for voltage output, power density, and load relationship during the hygroscopic and photothermal desorption processes, which can drive a low-power temperature and humidity meter to operate.

[0068] Comparative Example 1: (different from Example 1, lacking the steps of modifying lignin by demethylation and Fe 3+ coordination) A preparation method of a wood-based photo-thermal hygroscopic sponge device, comprising the following steps: S1. Raw wood pretreatment Take natural balsa wood blocks (size: 30 mm x 30 mm x 10 mm), soak in acetone solution for 12 h to remove surface grease and terpenes, rinse with deionized water after taking out, and dry in a vacuum oven at 45 °C for standby.

[0069] S2. Deep eutectic solvent (DES) partial delignification treatment Prepare a DES solution of choline chloride and oxalic acid (molar ratio 1:1), and form a homogeneous transparent liquid under magnetic stirring at 80 °C. Dry balsa wood blocks are immersed in the deep eutectic solvent (DES) at 90 °C for 5 hours, and washed with deionized water to neutral after taking out, to obtain partially delignified wood, which is significantly darker in color.

[0070] S3. Sodium chlorite-acetic acid buffer bleaching Immerse the partially delignified wood in a sodium chlorite-acetic acid buffer solution at pH 4.6, and react at 85 °C for 12 hours, further purify and remove residual lignin to obtain white wood DW.

[0071] S4. Carboxymethylation modification Carboxymethylated wood is obtained by adding chloroacetic acid and NaOH (mass ratio 1:1.1) in 90 wt% ethanol at 93 °C for 5 hours to introduce carboxymethyl functional groups, enhance hydrophilicity and ion exchange capacity; S5. Lithium chloride impregnation for moisture absorption modification Carboxymethylated wood is soaked in a 15 wt% LiCl solution, vacuum impregnated for 12 hours, and then dried at 100 °C for 12 hours to form a highly hydrophilic moisture-absorbing wood sponge AMW.

[0072] S6. Lignin extraction from delignification waste liquid Slowly add lignin antisolvent to the lignin-rich deep eutectic solution waste liquid to precipitate lignin, and obtain lignin Lignin by centrifugal drying after complete precipitation.

[0073] S7. Moisture-absorbing wood sponge photo-thermal coating loading Demethylated lignin-Fe 3+ Prepare a 25 mg / mL coating solution of complex D-Lignin-Fe. Drop 200 μL of the coating solution onto the surface of the moisture-absorbing wood sponge AMW multiple times, with a loading of 60 mg, and dry to form a photo-thermal coating, obtaining a photo-thermal moisture-absorbing wood sponge PAMW.

[0074] S8. Assembly and series connection of photo-thermal moisture-absorbing wood sponge devices The PET mesh electrode coated with carbon conductive paste (CH-8) is attached to the upper and lower surfaces of the photo-thermal hygroscopic wood sponge, and is connected with an external circuit by using a carbon tape to form a single wood-based photo-thermal hygroscopic sponge device. A plurality of wood-based photo-thermal hygroscopic sponge devices are connected in series, exposed to air, and tested for voltage output, power density and load relationship during the hygroscopic and desorption processes, which can drive a low-power temperature and humidity meter to operate.

[0075] Figure 1 is a schematic diagram of the overall working mechanism of the wood-based device with hygroscopic-desorption synergistic water power generation function obtained in Example 1, which shows the hygroscopic process of the device under atmospheric humidity conditions and the desorption process achieved by heating the surface photo-thermal coating under solar radiation; at the same time, the water vapor driven ion migration process is realized by using the interface water vapor flow, and the water vapor driven potential generation and stable electric output are realized.

[0076] Figure 2 is a real object image and a scanning electron microscope image of the microstructure of the photo-thermal hygroscopic wood sponge obtained in Example 1. It can be observed that the material has a porous structure and typical longitudinal conductive microchannels, which lay a structural foundation for directional adsorption and transmission of water and interfacial evaporation.

[0077] Figure 3 is the water drop contact angle test result of the photo-thermal hygroscopic wood sponge obtained in Example 1. The results show that after carboxymethylation and LiCl hygroscopic modification, the hydrophilicity of the sample surface is significantly improved, which is beneficial to rapid hygroscopicity under high humidity conditions.

[0078] Figure 4 is a comparison curve of the hygroscopic properties of the photo-thermal hygroscopic wood sponge obtained in Example 1 under different relative humidity conditions, which shows that the material has a significant water vapor adsorption capacity under low humidity and high humidity environments.

[0079] Figure 5 is the hygroscopic kinetics behavior of the photo-thermal hygroscopic wood sponge obtained in Example 1 under different environmental temperature conditions, which reflects that the increase of temperature helps to speed up the hygroscopic rate and improve the water vapor migration efficiency.

[0080] Figure 6 is an infrared thermal imaging image of the surface of the photo-thermal hygroscopic wood sponge obtained in Example 1 under 1 sun sunlight. The temperature of the sample surface rises significantly, indicating that the photo-thermal coating has good light absorption and heat conversion capacity.

[0081] Figure 7 is a curve of the desorption rate of the surface of the photo-thermal hygroscopic wood sponge device obtained in Example 1 under different light intensities (0.5, 1, 2 sun). The results show that the increase of light intensity can effectively accelerate the water vapor desorption and improve the interfacial evaporation efficiency.

[0082] Figure 8is the mass change curve of the light-heat hygroscopic wood-based sponge device obtained in Example 1 in the process of hygroscopicity-desorption under different humidity environments (30%, 50%, 70% RH), which further illustrates that the device has good hygroscopicity-desorption cycle stability and reversibility.

[0083] Figure 9 is the structure of the atmospheric water collection system device designed in Example 1, which includes a wood-based hygroscopic sponge module, a top condensation collector, an electrode packaging structure, and a liquid water collection container. The system can continuously operate in a natural environment to realize the cycle function of water collection during the day and water storage at night.

[0084] Figure 10 is the ion chromatography detection result of the main cations (Na⁺, K⁺) contained in the moisture collected by the device obtained in Example 1, which verifies the fresh water collection capacity of the system.

[0085] Figure 11 is the open-circuit voltage (Voc) change curve of the device obtained in Example 1 in the process of hygroscopicity and desorption. It shows that the hygroscopicity process can output about 220-250 mV, and the light desorption can be increased to 350-410 mV, and the output is stable.

[0086] Figure 12 is the output voltage curve of the device obtained in Example 1 after being connected in series, which shows that the device can increase the total voltage output through modular integration and has system expansion capability.

[0087] Figure 13 is the voltage-time curve of the capacitor charged by the device obtained in Example 1 after being connected in series, which reflects that the device has certain energy storage driving capacity.

[0088] Figure 14 is a photo of the digital temperature and humidity meter directly driven by the device obtained in Example 1 connected in series, which proves that it can be used for actual low-power environmental monitoring equipment power supply.

[0089] Figure 15 is a real photo of the LED lamp bead driven by the device obtained in Example 1 connected in series through capacitor energy storage, which shows its indirect energy storage application scenario.

[0090] Figure 16 is a process photo of the portable calculator successfully driven by the device obtained in Example 1 connected in series through capacitor energy storage, which verifies the adaptability of the device to low-power electronic products.

[0091] The above only describes the preferred embodiments of the present application, and it should be noted that for ordinary skilled persons in the art, without departing from the technical principles of the present application, a number of improvements and modifications can be made, and these improvements and modifications should be considered as the protection scope of the present application.

Claims

1. A method for preparing a wood-based photothermal hygroscopic sponge device, characterized in that, The method comprises the following steps: S1, pretreating natural balsa wood to obtain balsa wood blocks; S2, using a deep eutectic solvent with choline chloride and oxalic acid as components to partially delignify the balsa wood blocks, extracting lignin and retaining the longitudinal vessel structure of the wood, to obtain partially delignified wood and a deep eutectic solvent waste liquid rich in lignin; S3, bleaching the partially delignified wood with a sodium chlorite-acetic acid buffer solution to obtain white wood; S4, placing the white wood in a water / ethanol system, adding chloroacetic acid and NaOH for heating reaction, introducing carboxymethyl functional groups into the white wood to obtain carboxymethylated wood; S5, soaking the carboxymethylated wood in a LiCl solution and then drying to obtain a hygroscopic wood sponge; S6, adding deionized water to the deep eutectic solvent waste liquid rich in lignin as an anti-solvent, and then depositing, centrifuging and drying to obtain lignin; S7, dissolving the lignin in anhydrous CH2Cl2, and then adding boron tribromide to demethylate the lignin to increase the content of phenolic hydroxyl groups, to obtain demethylated lignin; S8, after demethylated lignin is dissolved in deionized water, the pH is adjusted to 11-13 by strong base, FeCl3 solution is added, and crosslinking is carried out to obtain demethylated lignin-Fe 3+ complexes; S9, drop-coating on the surface of the hygroscopic wood sponge with Lignin-Fe 3+ complex, forming a photo-thermal coating, obtaining a photo-thermal hygroscopic wood sponge; S10, assembling a photo-thermal hygroscopic wood sponge with a double-sided carbon film electrode to construct a wood-based photo-thermal hygroscopic sponge device with a hygroscopic-desorption synergistic water-vapor power generation function.

2. The method for preparing the wood-based photothermal moisture-absorbing sponge device according to claim 1, characterized in that, In step S2, the balsa wood blocks are selectively delignified using a deep eutectic solvent with choline chloride and oxalic acid as components, which comprises: Mixing choline chloride and oxalic acid to form a homogeneous transparent liquid to obtain a deep eutectic solvent DES; immersing the balsa wood blocks in the deep eutectic solvent DES and heating at 80-100°C to dissolve lignin; after the reaction is completed, washing with deionized water until neutral to obtain partially delignified wood.

3. The method for preparing the wood-based photothermal moisture-absorbing sponge device according to claim 2, characterized in that, In step S2, at least one of the following conditions is met: The thickness of the balsa wood blocks is 8-12 mm, preferably 10 mm; In the preparation process of the deep eutectic solvent DES, choline chloride and oxalic acid are mixed at a molar ratio of 1:1 to form a homogeneous transparent liquid at 50-70°C; preferably, a homogeneous transparent liquid is formed at 60°C; The mass ratio of the balsa wood blocks to the deep eutectic solvent DES is 1:(18-22), preferably 1:20; The heating reaction includes: reacting at 80-100°C for 4-6 hours, preferably reacting at 90°C for 5 hours.

4. The method for preparing the wood-based photothermal moisture-absorbing sponge device according to claim 1, characterized in that, Step S3 specifically includes: immersing the partially delignified wood in a sodium chlorite-acetic acid buffer solution, and after the bleaching reaction is completed, white wood is obtained; Further, the preparation method of the sodium chlorite-acetic acid buffer solution comprises: adding acetic acid dropwise in a 1-3wt% sodium chlorite aqueous solution until the pH is adjusted to 4.6; And / or, the bleaching reaction temperature is 80-90°C, preferably 85°C.

5. The method for preparing the wood-based photothermal moisture-absorbing sponge device according to claim 1, characterized in that, In step S4, at least one of the following conditions is met: The water / ethanol system uses 90wt% ethanol; The mass ratio of chloroacetic acid to NaOH is 1:(0.6-1.6), preferably 1:1.1; The reaction temperature is 80-100°C, preferably 90°C.

6. The method for preparing the wood-based photothermal moisture-absorbing sponge device according to claim 1, characterized in that, In step S5, at least one of the following conditions is met: The concentration of the LiCl solution is 5wt%-25wt%, preferably 15wt%. The soaking is vacuum impregnation for 10-14 hours, preferably 12 hours; The drying temperature is 90-110°C, preferably 100°C.

7. The method for preparing the wood-based photothermal moisture-absorbing sponge device according to claim 1, characterized in that, In step S7, at least any one of the following is satisfied: The amount of boron tribromide is 10-30 mL per 1 gram of lignin, preferably 20 mL; The demethylation reaction is 12-36 hours, preferably 24 hours.

8. The method for preparing the wood-based photothermal moisture-absorbing sponge device according to claim 1, characterized in that, In step S8, at least any one of the following is satisfied: After 1 gram of demethylated lignin is dissolved in 20 mL of deionized water, the pH is adjusted to 11-13 with sodium hydroxide solution, 10 mL of FeCl3 solution is added, and after stirring, centrifugation and drying; The concentration of FeCl3 solution is 0.3-0.7 M, preferably 0.5 M.

9. The method for preparing the wood-based photothermal moisture-absorbing sponge device according to claim 1, characterized in that, In step S9, the demethylated lignin-Fe on the upper surface of the hygroscopic wood sponge 3+ The loading of the complex is 40-80 mg / 9 cm 2 , preferably 60 mg / 9 cm 2 .

10. A wood-based photothermal hygroscopic sponge device, characterized in that, The wood-based photothermal and hygroscopic sponge device is prepared by the preparation method of any one of claims 1-9.

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