Wood-based evaporation-driven photovoltaic power generation device and preparation method thereof

Abstract

The invention discloses a wood-based evaporation-driven photovoltaic power generation device and a preparation method thereof.The preparation method comprises the steps that natural beech serves as a matrix, and a surface gradient hydrophilic structure is constructed through pretreatment, deep eutectic solvent DES selective delignification treatment, citric acid modification carboxyl introduction and surface silane modifier spraying in sequence; directional transmission of water is realized through an anisotropic micro-channel reserved in wood, and stable water vapor flow induction potential is generated by combining ion selective migration induced by surface fixed charges and an interface evaporation process driven by a top photo-thermal layer, so that electric energy is continuously output. The device has good environmental adaptability, can stably output voltage and power in a high-humidity or high-salt environment, and shows excellent durability and expansibility. The method is environmentally friendly, the process is simple, functional high-value utilization of wood can be achieved, and the method is suitable for flexible electronic or distributed energy supply systems such as low-power-consumption sensors and environment energy collectors.

Description

Technical Field

[0001] This invention belongs to the field of biomass energy and functional materials technology, and relates to a wood-based evaporation-driven hydrovoltaic power generation device and its preparation method. Specifically, it relates to a wood-based evaporation-driven hydrovoltaic power generation device with a hydrophilic gradient and photothermal enhancement structure and its preparation method. Background Technology

[0002] With the increasing demand for low-carbon energy and the rapid development of distributed energy systems, novel energy harvesting technologies based on the natural water-energy conversion mechanism have attracted widespread attention. Water-Evaporation-Induced Generators (WEIGs) are a class of devices that generate electricity by inducing interfacial charge migration through water evaporation. They have the advantage of continuous operation without external light or wind power, making them particularly suitable for micro-energy harvesting in low-energy-consumption, uninhabited, or humid and hot environments.

[0003] Wood, as a natural anisotropic porous material, possesses a rich network of longitudinal microchannels, making it an ideal structural substrate for evaporation-driven devices. However, natural wood contains a large amount of hydrophobic lignin, which hinders the rise of moisture and the migration of ions, limiting its application in high-efficiency WEIG. In addition, wood has a low surface charge density and poor interfacial ion regulation ability, making it difficult to maintain stable power generation under complex electrolysis environments.

[0004] Currently, the main methods to improve the performance of wood-based WEIGs include delignification treatment, surface coating modification and carbonization enhancement, but the following problems are common: (1) Traditional delignification methods are drastic and easily damage the structure; (2) Multi-step organic synthesis modification is complex and has a heavy environmental burden; (3) Carbonization will destroy the wood channel structure, reduce the water vapor transport capacity, and affect the stability of the device.

[0005] Therefore, there is an urgent need for a green, controllable, and structurally friendly modification strategy to achieve multifunctional integration of wood and endow it with efficient and stable energy conversion capabilities. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and address the problems of fragile structure, limited hydrophilicity, unstable power output, and poor environmental adaptability of existing wood-based water vapor energy conversion devices. This invention provides a wood-based evaporation-driven water photovoltaic power generation device and its preparation method. The prepared wood-based evaporation-driven water photovoltaic power generation device can maintain stable power output in complex environments (such as high humidity and high salinity), and has excellent water vapor driving capability, photothermal conversion performance, interfacial ion migration efficiency, and environmental tolerance. It is suitable for environmental energy harvesting and powering small electronic devices.

[0007] This invention proposes a wood-based evaporation-driven hydrovoltaic power generation device that mimics the transpiration mechanism of trees. It employs selective delignification with a green, low-eutectic solvent, combined with gradient hydrophilic structure construction and interfacial photothermal enhancement, to achieve the synergistic effect of directional water migration and interfacial charge regulation, thereby significantly improving the device's power generation capacity, environmental stability, and practical application prospects.

[0008] To achieve the above objectives, the present invention is implemented using the following technical solution: In a first aspect, a method for preparing a wood-based evaporation-driven water photovoltaic power generation device is provided, comprising the following steps: S1, beech wood blocks are obtained by pre-treating natural beech wood as the matrix; S2, using the eutectic solvent DES composed of choline chloride and oxalic acid, selectively delignified beech wood blocks to remove hydrophobic lignin while retaining the longitudinal vascular structure of the wood, resulting in delignified wood DB. S3, carboxylation treatment of delignified wood was carried out using a citric acid-triethylamine modification system to introduce fixed carboxyl groups on the surface, enhance the interfacial charge density and hydrophilicity, and obtain carboxylated wood CB; S4, a silane modifier is sprayed onto the surface of carboxylated wood CB to form a heterogeneous interface structure with a hydrophobic surface and a hydrophilic inner layer, resulting in a vertically gradient hydrophilic wood AWCB from a hydrophobic surface to a hydrophilic bottom; wherein the silane modifier is a mixed solution of triethoxy-1H,1H,2H,2H-tridecylfluoro-N-octylsilane (FS) and N-aminoethyl-γ-aminopropyltrimethoxysilane (AS); S5, vertical gradient hydrophilic wood AWCB is vacuum freeze-dried to obtain functionalized wood with gradient hydrophilicity and photothermal response properties; S6 uses double-sided carbon film electrodes to assemble functionalized wood, thus constructing a wood-based evaporation-driven hydrovoltaic power generation device.

[0009] In some embodiments, step S1 specifically includes: selecting natural beech wood as raw material, cutting it to size and pretreating it with acetone to remove surface impurities.

[0010] In some embodiments, in step S2, selective delignification treatment of beech wood blocks is performed using a eutectic solvent DES composed of choline chloride and oxalic acid, including: The preparation method of the eutectic solvent DES includes: mixing choline chloride and oxalic acid to form a homogeneous transparent liquid at 60~100°C; Beech wood blocks are immersed in the eutectic solvent DES and heated to 80-100°C to remove lignin. After the reaction is complete, wash with deionized water until neutral to obtain delignified wood (DB).

[0011] Furthermore, in step S2, at least one of the following conditions must be met: The thickness of the beech wood block is 8-12mm, preferably 10mm; In the preparation of the eutectic solvent DES, choline chloride and oxalic acid are mixed in a molar ratio of 1:1 and a homogeneous transparent liquid is formed at 60~100°C; preferably, a homogeneous transparent liquid is formed at 80°C. The mass ratio of beech wood blocks to the eutectic solvent DES is 1:(18~22), preferably 1:20; The heating reaction includes reacting at 80~100°C for 4-8 hours, preferably at 90°C for 6 hours.

[0012] It should be noted that controlling the solid-liquid ratio (mass ratio) of the eutectic solvent for delignification is a key parameter for achieving efficient lignin extraction and subsequent lignin reuse. A mass ratio of beech block to eutectic solvent DES of 1:(18~22) ensures sufficient solvent penetration into the wood cell walls while maintaining a suitable solution viscosity, which is beneficial for diffusion and heat transfer. At higher concentrations, the solvent molecules are insufficient to complete the lignin complexation and release, resulting in an incomplete reaction; while excessive dilution will increase energy consumption and processing difficulty, and also dilute the lignin concentration, which is detrimental to subsequent extraction and modification.

[0013] It should be noted that the reaction temperature has a significant impact on the dissolution rate and selectivity of lignin. At excessively low temperatures, lignin release is slow, and the reaction equilibrium tends towards in-situ binding, making significant delignification difficult to achieve. At excessively high temperatures, oxalic acid is prone to decomposition, which also accelerates the degradation of cellulose and hemicellulose, damaging the structural integrity of the wood. The reaction temperature of 80–100°C is chosen because the kinetics of the complexation reaction between oxalic acid and lignin are moderate; it can effectively promote the breaking of aromatic bonds while maintaining structural conservatism; and it is also the active range of the DES system without inducing degradation reactions.

[0014] It should be noted that if the delignification treatment time is less than 4 hours, the amount of lignin dissolution will be insufficient, while after 6 hours, the lignin removal will be close to the plateau period and the cellulose degradation will not be significant. If the treatment time exceeds 8 hours, the excessively long treatment time will damage the microstructure of the wood and affect the final performance. Therefore, it is recommended to react at 80~100°C for 4-8 hours, preferably at 90°C for 6 hours.

[0015] In some embodiments, step S3 specifically includes: immersing delignified wood in a citric acid-triethylamine modification system, and after the reaction is complete, heat-treating to obtain carboxylated wood CB.

[0016] Furthermore, in step S3, at least one of the following conditions must be met: The concentration of citric acid is 70 wt%; In the citric acid-triethylamine modified system, the mass ratio of triethylamine to citric acid is 1:(18~22), preferably 1:20; The reaction temperature is 80~90°C, preferably 85°C; The heat treatment is performed at 118~122°C for 4~8 hours, preferably at 120°C for 6 hours.

[0017] It should be noted that the mechanism of the citric acid-triethylamine system in carboxylating wood is that when citric acid reacts with hydroxyl groups (–OH) on the wood cell walls under heating conditions, an esterification reaction occurs, introducing –COOH groups onto the walls of cellulose, hemicellulose, and wood micropores, thereby enhancing their surface polarity, hygroscopicity, and ion fixation capacity. Triethylamine can form a complex intermediate with citric acid, enhancing the affinity of citric acid for wood hydroxyl groups, accelerating the carboxyl transfer rate, and promoting the reaction towards esterification.

[0018] It should be noted that a mass ratio of citric acid to triethylamine of 1:(18~22) is the optimal neutral ratio verified in experiments. This ratio can control the pH of the system within the range of 3.5–4.0, ensuring the partial ionization of the tricarboxylic acid groups while inhibiting the hydrolysis of the wood backbone. Below this ratio, a large amount of residual triethylamine may lead to alkalization, yellowing, and decreased mechanical properties of the material; above this ratio, the system becomes too acidic, with a pH below 3, which may trigger cellulose degradation.

[0019] It should be noted that after esterification, some intermediate ester bonds are unstable and need to be dehydrated and condensed to form stable ester bonds during the heat treatment stage. At the same time, heat treatment at 118~122°C can further promote the cross-linking reaction of citric acid with wood hydroxyl groups on the microporous surface and enhance the structural bonding force. If the temperature is below 100°C, the reaction is incomplete; if it is above 130°C, brittleness and cracking will occur.

[0020] In some embodiments, in step S4, the volume ratio of triethoxy-1H,1H,2H,2H-tridecylfluoro-N-octylsilane (FS) to N-aminoethyl-γ-aminopropyltrimethoxysilane (AS) in the silane modifier is 1:(1.4~1.6), preferably 1:1.5; The sidewalls of carboxylated wood CB are sealed, and a silane modifier is sprayed onto the surface of the carboxylated wood CB 8-12 times to form a gradient distribution. After spraying, it is heat-cured at 30-50°C to obtain vertical gradient hydrophilic wood AWCB.

[0021] It should be noted that the mechanism of constructing a hydrophilic gradient using triethoxy-1H,1H,2H,2H-tridecylfluoro-N-octylsilane (FS) and N-aminoethyl-γ-aminopropyltrimethoxysilane (AS) is to simultaneously introduce FS and AS onto the wood surface, which can form an asymmetric chemical functional layer on the surface: that is, the top region is dominated by FS (hydrophobic), while the bottom or uncoated areas retain AS or the original carboxyl groups (hydrophilic), thereby achieving a change in the surface free energy gradient.

[0022] It should be noted that FS and AS, as low molecular weight silanes, have a limited hydrophobic thickness on the wood surface; a single spray only forms a sparse distribution, which is insufficient to constitute a complete chemical barrier, resulting in hydrophilic leakage or an unclear gradient; while excessive spraying will cause excessive hydrophobicity, hindering the upward transport of water; experiments have shown that 8-12 sprays are the most effective.

[0023] In some embodiments, in step S5, the temperature for vacuum freeze drying is -70°C to -50°C, preferably -60°C.

[0024] In some embodiments, S6, functionalized wood is assembled using double-sided carbon film electrodes to construct a wood-based evaporation-driven hydrovoltaic power generation device, including: Polyethylene terephthalate (PET) mesh electrodes coated with carbon conductive paste are attached to the upper and lower surfaces of functionalized wood, and then the electrodes are connected to an external circuit using carbon tape to obtain a wood-based evaporation-driven hydrovoltaic power generation device.

[0025] Secondly, a wood-based evaporation-driven hydrovoltaic power generation device is provided, which is prepared by the above-mentioned method and has the following structural features: It has a gradient hydrophilic structure that transitions from hydrophobic at the top to hydrophilic at the bottom; The interior retains the longitudinally oriented microchannel structure of natural wood; A coating with photothermal responsiveness on top; It incorporates double-sided carbon electrodes and is capable of outputting a stable open-circuit voltage.

[0026] Furthermore, it can operate for more than 100 hours in 1M NaCl solution, and the open circuit voltage remains stable at 360-410mV during operation, with an output power density of 92-96μW / cm².

[0027] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: The present invention provides a wood-based evaporation-driven hydrovoltaic power generation device and its preparation method, which has the following advantages: (1) Green and controllable, with complete structure: The beech block is selectively delignified by using a green eutectic solvent (DES) composed of choline chloride and oxalic acid to remove hydrophobic lignin and retain the longitudinal vascular structure of the wood, avoiding the damage to the wood structure caused by traditional acid and alkali treatment, while maintaining the natural multi-level pores and water and ion conduction capabilities of the wood. (2) Gradient regulation and interface optimization: Construct a biomimetic gradient hydrophilic structure to simulate the water potential gradient and interface asymmetry in plant transpiration, and promote a significant increase in water evaporation rate and ion migration efficiency. (3) Photothermal coupling and continuous power generation: The top is redeposited with lignin to form a light absorption layer, which, combined with the surface hydrophobic salt inhibition function, achieves efficient photothermal conversion and clean interface continuous evaporation; (4) High stability and environmental adaptability: It can maintain a stable voltage output of 360–410mV after working continuously for 115 hours in 1M NaCl, with an output power density of up to 96μW / cm², which is significantly better than most existing WEIG devices. (5) Wide range of applications and strong scalability: It can be connected in series or in parallel to achieve a voltage output of 2-3V, directly driving temperature and humidity sensors, electronic watches, etc., and is suitable for power supply of distributed energy systems, environmental monitoring terminals and wearable devices. Attached Figure Description

[0028] Figure 1 This is a schematic diagram illustrating the principle of the wood-based evaporation-driven hydrovoltaic power generation device in an embodiment of the present invention; Figure 2 The images show the physical and microscopic structures of the wood-based evaporation-driven hydrovoltaic power generation device in this embodiment of the invention. Figure 3 This is a schematic diagram of the contact angles of the top, middle, and bottom of the wood-based evaporation-driven hydrovoltaic power generation device in an embodiment of the present invention; Figure 4 This is an infrared thermal imaging diagram of the wood-based evaporation-driven hydrovoltaic power generation device under different illumination times during the evaporation process in an embodiment of the present invention. Figure 5 This is a schematic diagram of the evaporation rate curve of the wood-based evaporation-driven hydrovoltaic power generation device in an embodiment of the present invention; Figure 6 A schematic diagram of the electrical output performance test curve of the wood-based evaporation-driven hydrovoltaic power generation device in an embodiment of the present invention; Figure 7 A schematic diagram of the power density versus load resistance curve of the wood-based evaporation-driven hydrovoltaic power generation device in an embodiment of the present invention; Figure 8 A schematic diagram of the positive and negative electrode voltage curves of the wood-based evaporation-driven hydrovoltaic power generation device in an embodiment of the present invention; Figure 9 Schematic diagram of voltage curves of a wood-based evaporation-driven water-voltaic power generation device in different solutions in an embodiment of the present invention; Figure 10 A schematic diagram of the voltage curves of the wood-based evaporation-driven hydrovoltaic power generation device under different light intensities in an embodiment of the present invention; Figure 11 A schematic diagram of the salt resistance performance of the wood-based evaporation-driven hydrovoltaic power generation device in simulated seawater under light conditions in an embodiment of the present invention; Figure 12 A schematic diagram of the voltage output curves of different numbers of wood-based evaporation-driven water-voltaic power generation devices connected in series in an embodiment of the present invention; Figure 13 In this embodiment of the invention, the charging curves and physical images of capacitors are shown after different numbers of wood-based evaporation-driven hydrovoltaic power generation devices are connected in series. Figure 14 A schematic diagram of a series wood-based evaporation-driven water-voltaic power generation device illuminating a small electronic device (temperature and humidity sensor) in an embodiment of the present invention; Figure 15 The output voltage curve of the wood-based evaporation-driven hydrovoltaic power generation device in this embodiment of the invention during long-term power generation in a 1 M NaCl solution. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0030] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and should be understood to include values ​​close to those ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0031] 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.

[0032] Example 1: A method for preparing a wood-based evaporation-driven hydrovoltaic power generation device, comprising the following steps: S1. Log Pretreatment Take natural beech wood blocks (size: 50mm×50mm×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.

[0033] S2. Selective delignification treatment using 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 beech wood blocks were immersed in the eutectic solvent (DES) at 90°C for 8 hours. After removal, the wood was thoroughly washed with deionized water until neutral to obtain delignified wood (DB), which significantly darkened the color.

[0034] S3. Citric acid carboxylation modification Delignified wood (DB) was immersed in a 70 wt% aqueous citric acid solution with triethylamine added as a catalyst. The mass ratio of citric acid to triethylamine in this system was 20:1, and the reaction was carried out at 85°C for 4 hours. Subsequently, the sample was heat-treated at 120°C for 6 hours to induce carboxylation, yielding carboxylated wood (CB).

[0035] S4. Constructing a surface gradient hydrophilic structure A mixed solution of triethoxy-1H,1H,2H,2H-tridecylfluoro-N-octylsilane (FS) and N-aminoethyl-γ-aminopropyltrimethoxysilane (AS) in a volume ratio of 1:1.5 was prepared as a silane modifier. The sidewalls of the carboxylated wood (CB) were sealed at a distance of 10 cm from the top surface, and the solution was sprayed only onto the top surface 10 times to create a gradient distribution. After spraying, the wood was dried at 40°C for 2 hours to obtain vertically gradient hydrophilic wood (AWCB).

[0036] S5. Freeze-drying and electrode encapsulation Vertical gradient hydrophilic wood (AWCB) was dried at -60°C for 24 hours in a vacuum freeze dryer to retain its porous structure and hydrophobic top layer, resulting in functionalized wood. Subsequently, PET mesh electrodes coated with carbon conductive paste (CH-8) were attached to the upper and lower surfaces of the functionalized wood, and connected to an external circuit using carbon tape to form a single wood-based evaporation-driven hydrovoltaic power generation device.

[0037] S6. Series Assembly and Output Test Three wood-based evaporation-driven hydrovoltaic power generation devices were connected in series. The lower end was immersed in a 1M NaCl solution to a depth of 1cm, while the top was exposed to air. Infrared thermal imaging, voltage output, power density and load relationship tests were conducted under 1sun light conditions. The device can drive a low-power electronic watch.

[0038] Example 2: A method for preparing a wood-based evaporation-driven water photovoltaic power generation device, comprising the following steps: S1. Log Pretreatment Take natural beech wood blocks (size: 50mm×50mm×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.

[0039] S2. Selective delignification treatment using 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 beech wood blocks were immersed in a eutectic solvent (DES) at 100°C for 8 hours. After removal, the wood was thoroughly washed with deionized water until neutral to obtain delignified wood (DB), which significantly darkened the color.

[0040] S3. Citric acid carboxylation modification Delignified wood (DB) was immersed in a 70 wt% citric acid aqueous solution with triethylamine added as a catalyst. The mass ratio of citric acid to triethylamine in this system was 20:1, and the reaction was carried out at 85°C for 4 hours. Subsequently, the sample was heat-treated at 120°C for 4 hours to induce carboxylation, obtaining carboxylated wood (CB).

[0041] S4. Constructing a surface gradient hydrophilic structure A mixed solution of triethoxy-1H,1H,2H,2H-tridecylfluoro-N-octylsilane (FS) and N-aminoethyl-γ-aminopropyltrimethoxysilane (AS) in a volume ratio of 1:1.5 was prepared as a silane modifier. The sidewalls of the carboxylated wood (CB) were sealed at a distance of 10 cm from the top surface, and the solution was sprayed only onto the top surface 10 times to create a gradient distribution. After spraying, the wood was dried at 40°C for 2 hours to obtain vertically gradient hydrophilic wood (AWCB).

[0042] S5. Freeze-drying and electrode encapsulation Vertical gradient hydrophilic wood (AWCB) was dried at -60°C for 24 hours in a vacuum freeze dryer to retain its porous structure and hydrophobic top layer, resulting in functionalized wood. Subsequently, PET mesh electrodes coated with carbon conductive paste (CH-8) were attached to the upper and lower surfaces of the functionalized wood, and connected to an external circuit using carbon tape to form a single wood-based evaporation-driven hydrovoltaic power generation device.

[0043] S6. Series Assembly and Output Test Six wood-based evaporation-driven hydrovoltaic power generation devices were connected in series. The lower end was immersed in a 1M NaCl solution to a depth of 1cm, while the top was exposed to air. Infrared thermal imaging, voltage output, power density and load relationship tests were conducted under 1sun light conditions. The device can drive a low-power electronic watch.

[0044] Example 3: A method for preparing a wood-based evaporation-driven water photovoltaic power generation device, comprising the following steps: S1. Log Pretreatment Take natural beech wood blocks (size: 50mm×50mm×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.

[0045] S2. Selective delignification treatment using 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 beech wood blocks were immersed in the eutectic solvent (DES) at 80°C for 8 hours. After removal, the wood was thoroughly washed with deionized water until neutral to obtain delignified wood (DB), which significantly darkened the color.

[0046] S3. Citric acid carboxylation modification Delignified wood (DB) was immersed in a 70 wt% citric acid aqueous solution with triethylamine added as a catalyst. The mass ratio of citric acid to triethylamine in this system was 20:1, and the reaction was carried out at 85°C for 4 hours. Subsequently, the sample was heat-treated at 120°C for 8 hours to induce carboxylation, obtaining carboxylated wood (CB).

[0047] S4. Constructing a surface gradient hydrophilic structure A mixed solution of triethoxy-1H,1H,2H,2H-tridecylfluoro-N-octylsilane (FS) and N-aminoethyl-γ-aminopropyltrimethoxysilane (AS) in a volume ratio of 1:1.5 was prepared as a silane modifier. The sidewalls of the carboxylated wood (CB) were sealed at a distance of 10 cm from the top surface, and the solution was sprayed only onto the top surface 10 times to create a gradient distribution. After spraying, the wood was dried at 40°C for 2 hours to obtain vertically gradient hydrophilic wood (AWCB).

[0048] S5. Freeze-drying and electrode encapsulation Vertical gradient hydrophilic wood (AWCB) was dried at -60°C for 24 hours in a vacuum freeze dryer to retain its porous structure and hydrophobic top layer, resulting in functionalized wood. Subsequently, PET mesh electrodes coated with carbon conductive paste (CH-8) were attached to the upper and lower surfaces of the functionalized wood, and connected to an external circuit using carbon tape to form a single wood-based evaporation-driven hydrovoltaic power generation device.

[0049] S6. Series Assembly and Output Test Nine wood-based evaporation-driven hydrovoltaic power generation devices were connected in series. The lower end was immersed in a 1M NaCl solution to a depth of 1cm, while the top was exposed to air. Infrared thermal imaging, voltage output, power density and load relationship tests were conducted under 1sun light conditions. The device can drive the operation of low-power electronic watches.

[0050] Comparative Example 1: (Unlike Example 1, the step of constructing a surface gradient hydrophilic structure using a silane modifier is missing) A method for preparing a wood-based evaporation-driven hydrovoltaic power generation device, comprising the following steps: S1. Log Pretreatment Take natural beech wood blocks (size: 50mm×50mm×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.

[0051] S2. Selective delignification treatment using 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 beech wood blocks were immersed in the eutectic solvent (DES) at 90°C for 8 hours. After removal, the wood was thoroughly washed with deionized water until neutral to obtain delignified wood (DB), which significantly darkened the color.

[0052] S3. Citric acid carboxylation modification Delignified wood (DB) was immersed in a 70 wt% aqueous citric acid solution with triethylamine added as a catalyst. The mass ratio of citric acid to triethylamine in this system was 20:1, and the reaction was carried out at 85°C for 4 hours. Subsequently, the sample was heat-treated at 120°C for 6 hours to induce carboxylation, yielding carboxylated wood (CB).

[0053] S4. Freeze-drying and electrode encapsulation Carboxylated wood (CB) is dried at -60°C for 24 hours in a vacuum freeze dryer. Then, PET mesh electrodes coated with carbon conductive paste (CH-8) are attached to the upper and lower surfaces of the carboxylated wood. The carbon tape is used to connect it to an external circuit to form a single wood-based evaporation-driven hydrovoltaic power generation device.

[0054] S5. Series Assembly and Output Test Nine wood-based evaporation-driven hydrovoltaic power generation devices were connected in series. The lower end was immersed in a 1M NaCl solution to a depth of 1cm, while the top was exposed to air. Infrared thermal imaging, voltage output, power density and load relationship tests were conducted under 1sun light conditions. The device can drive the operation of low-power electronic watches.

[0055] Figure 1This is a schematic diagram of the principle of the hydrophilic gradient photothermal wood-based evaporation-driven hydrovoltaic power generation device obtained in Example 1. It shows that the device consists of a layered structure of natural water-conducting wood at the bottom, a carboxylated hydrophilic interface, a microchannel structure in the middle, and a hydrophobic photothermal layer at the top. This structure is conducive to realizing directional water transport, enhanced interface evaporation, and selective ion migration.

[0056] Figure 2 The images show the physical diagram and material microstructure diagram of the power generation device in Example 1. The scanning electron microscope image shows that the wood retains a complete longitudinal duct structure after delignification, with good channel connectivity and continuous water transport capability.

[0057] Figure 3 These are contact angle images of the top, middle, and bottom of the device obtained in Example 1. The contact angles show a gradient distribution from large to small, namely 82.3° (top), 60.4° (middle), and 41.4° (bottom), indicating that the constructed hydrophilic gradient structure significantly modulates the surface wettability and provides a power basis for water vapor drive.

[0058] Figure 4 The image shows an infrared thermal image of the device obtained in Example 1 under continuous 1 Sun illumination. The surface temperature of the device rapidly rises to 46.2°C, demonstrating that it has good photothermal response capability and can effectively promote the evaporation of interfacial moisture.

[0059] Figure 5 The curves show the water evaporation rates of the devices obtained in Example 1 and Comparative Example 1. The evaporation rate of Example 1 (with a gradient structure) reached 2.42 kg / m²·h, which was better than that of the comparative example (2.39 kg / m²·h) without a hydrophilic gradient, indicating that the gradient structure significantly improves the evaporation capacity.

[0060] Figure 6 This is the electrical output performance curve of the device prepared in Example 1, with open-circuit voltage ( V oc The voltage stabilized at 410mV, and the short-circuit current ( I sc The voltage is 4.3 μA, indicating that the device has a significant water vapor-driven electrogenerated effect.

[0061] Figure 7 This is the power density versus load resistance curve of the device obtained in Example 1. The maximum power density occurs when the load resistance is 10. 5 At Ω, it reaches 96μW / cm², which is a relatively high level among similar natural-based water-based photovoltaic devices.

[0062] Figure 8 The voltage reversal curve is the result of the device obtained in Example 1 after the positive and negative electrode connection methods are changed, indicating that the potential originates from the electrostatic field driven by the migration of interface ions rather than the redox electrochemical reaction of the electrode material.

[0063] Figure 9 The voltage response curves of the device obtained in Example 1 in different ionic solutions show a good linear enhancement trend, verifying the coupling mechanism between photothermal enhancement, water evaporation, and electrical output.

[0064] Figure 10 The voltage response curves of the device obtained in Example 1 under different solar light intensities (0.5-2.0 sun) show a good linear enhancement trend, verifying the coupling mechanism between photothermal enhancement, water evaporation, and electrical output.

[0065] Figure 11 The devices obtained in Example 1 and Comparative Example 1 exhibit salt resistance under simulated seawater (1M NaCl) illumination conditions, demonstrating their strong salt tolerance in high-salt environments and suitability for complex working conditions such as coastal and saline water environments.

[0066] Figure 12 The figures show the voltage output curves of different numbers of devices connected in series, as obtained in Example 1. Three devices connected in series can output a voltage of over 0.8V, which can meet the operating voltage requirements of electronic devices such as micro sensors.

[0067] Figure 13 The images show the charge-discharge curves and photographs of the device obtained in Example 1 connected in series to charge a capacitor, illustrating that the system has short-term energy storage and power supply capabilities and has preliminary application value.

[0068] Figure 14 The image shows a physical diagram of the device driven by the temperature and humidity sensor obtained in Example 1, which intuitively demonstrates the feasibility and practicality of the device of the present invention in energy harvesting in actual environments.

[0069] Figure 15 The voltage curve of the device obtained in Example 1 over a long period in 1 M NaCl solution demonstrates the long-term stable power generation of the device in a high-salinity environment. From... Figure 15 As can be seen from the data, the device obtained in Example 1 can operate for 115 hours in 1M NaCl solution, and the open circuit voltage remains stable at 360-410mV during operation.

[0070] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a wood-based evaporation-driven hydrovoltaic power generation device, characterized in that, Includes the following steps: S1, beech wood blocks are obtained by pre-treating natural beech wood as the matrix; S2, using a eutectic solvent composed of choline chloride and oxalic acid, selectively delignifies beech wood blocks to remove hydrophobic lignin while retaining the longitudinal vascular structure of the wood, resulting in delignified wood. S3 uses a citric acid-triethylamine modification system to carboxylate delignified wood, introducing fixed carboxyl groups on the surface to enhance interfacial charge density and hydrophilicity, thus obtaining carboxylated wood. S4, a silane modifier is sprayed onto the surface of carboxylated wood to form a heterogeneous interface structure with a hydrophobic surface and a hydrophilic inner layer, resulting in hydrophilic wood with a vertical gradient from hydrophobic surface to hydrophilic bottom; wherein the silane modifier is a mixed solution of triethoxy-1H,1H,2H,2H-tridecylfluoro-N-octylsilane and N-aminoethyl-γ-aminopropyltrimethoxysilane; S5, vertical gradient hydrophilic wood is vacuum freeze-dried to obtain functionalized wood with gradient hydrophilicity and photothermal response properties; S6 uses double-sided carbon film electrodes to assemble functionalized wood, thus constructing a wood-based evaporation-driven hydrovoltaic power generation device.

2. The method for preparing a wood-based evaporation-driven hydrovoltaic power generation device according to claim 1, characterized in that, In step S2, a eutectic solvent consisting of choline chloride and oxalic acid is used to selectively delignify the beech wood blocks, including: The preparation method of the eutectic solvent includes: mixing choline chloride and oxalic acid to form a homogeneous transparent liquid at 60~100°C; Beech wood blocks are immersed in the eutectic solvent DES and heated to 80-100°C to remove lignin. After the reaction is complete, wash with deionized water until neutral to obtain delignified wood (DB).

3. The method for preparing a wood-based evaporation-driven hydrovoltaic power generation device according to claim 2, characterized in that, In step S2, at least one of the following conditions must be met: The thickness of the beech wood block is 8-12mm, preferably 10mm; In the preparation of the eutectic solvent DES, choline chloride and oxalic acid are mixed in a molar ratio of 1:1 and a homogeneous transparent liquid is formed at 60~100°C; preferably, a homogeneous transparent liquid is formed at 80°C. The mass ratio of beech wood blocks to the eutectic solvent DES is 1:(18~22), preferably 1:20; The heating reaction includes reacting at 80~100°C for 4-8 hours, preferably at 90°C for 6 hours.

4. The method for preparing a wood-based evaporation-driven hydrovoltaic power generation device according to claim 1, characterized in that, Step S3 specifically includes: immersing delignified wood in a citric acid-triethylamine modification system, and after the reaction is complete, heat treatment to obtain carboxylated wood CB.

5. The method for preparing a wood-based evaporation-driven hydrovoltaic power generation device according to claim 4, characterized in that, In step S3, at least one of the following conditions must be met: The concentration of citric acid is 70 wt%; In the citric acid-triethylamine modified system, the mass ratio of triethylamine to citric acid is 1:(18~22), preferably 1:20; The reaction temperature is 80~90°C, preferably 85°C; The heat treatment is performed at 118~122°C for 4~8 hours, preferably at 120°C for 6 hours.

6. The method for preparing a wood-based evaporation-driven hydrovoltaic power generation device according to claim 1, characterized in that, In step S4, at least one of the following conditions must be met: The volume ratio of triethoxy-1H,1H,2H,2H-tridecylfluoro-N-octylsilane to N-aminoethyl-γ-aminopropyltrimethoxysilane in the silane modifier is 1:(1.4~1.6), preferably 1:1.5; The sidewalls of carboxylated wood are sealed, and a silane modifier is sprayed onto the surface of the carboxylated wood 8-12 times to form a gradient distribution. After spraying, it is heat-cured at 30-50°C to obtain vertical gradient hydrophilic wood.

7. The method for preparing a wood-based evaporation-driven hydrovoltaic power generation device according to claim 1, characterized in that, In step S5, the temperature for vacuum freeze drying is -70°C to -50°C, preferably -60°C.

8. The method for preparing a wood-based evaporation-driven hydrovoltaic power generation device according to claim 7, characterized in that, S6, using double-sided carbon film electrodes to assemble functionalized wood, constructs a wood-based evaporation-driven hydrovoltaic power generation device, including: Polyethylene terephthalate (PET) mesh electrodes coated with carbon conductive paste are attached to the upper and lower surfaces of functionalized wood, and then the electrodes are connected to an external circuit using carbon tape to obtain a wood-based evaporation-driven hydrovoltaic power generation device.

9. A wood-based evaporation-driven hydrovoltaic power generation device, characterized in that, It is prepared by the method of any one of claims 1 to 8 for the preparation of a wood-based evaporation-driven water photovoltaic power generation device; and has the following structural features: It has a gradient hydrophilic structure that transitions from hydrophobic at the top to hydrophilic at the bottom; The interior retains the longitudinally oriented microchannel structure of natural wood; A coating with photothermal responsiveness on top; It incorporates double-sided carbon electrodes and is capable of outputting a stable open-circuit voltage.

10. The wood-based evaporation-driven hydrovoltaic power generation device according to claim 9, characterized in that, It can operate for more than 100 hours in 1M NaCl solution, and the open circuit voltage remains stable at 360-410mV during operation, with an output power density of 92-96μW / cm².

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