Biomass nitrogen-doped derived porous carbon material and preparation method and application thereof

Abstract

The application discloses biomass nitrogen-doped derived porous carbon material and a preparation method and application thereof, and belongs to the technical field of photo-thermal atmospheric water collection. The preparation method comprises the following steps: placing a carbon source and a nitrogen source into water for ultrasonic reaction, and performing hydrothermal treatment on the reactants to obtain a solid product; performing vapor etching and high-temperature annealing treatment on the solid product and a metal salt in an inert atmosphere, and then sequentially performing acidification treatment, grinding and drying to prepare the biomass nitrogen-doped derived porous carbon material. The biomass nitrogen-doped derived porous carbon material prepared by the method has rich pore structure and high adsorption-desorption performance, can replace expensive MOFs material, optimizes a preparation path, improves nitrogen-doping efficiency and material stability, significantly reduces cost and environmental burden while guaranteeing excellent atmospheric water collection performance, and has a more superior industrialization prospect and sustainable development value.

Description

Technical Field

[0001] This invention belongs to the field of photothermal atmospheric water collection technology, and particularly relates to a biomass nitrogen-doped derived porous carbon material, its preparation method and application. Background Technology

[0002] Water is a fundamental resource for life, and water scarcity has become a global challenge worldwide. Therefore, addressing water scarcity has become a global focus. Traditional methods of freshwater acquisition, such as groundwater extraction, water distillation, and seawater desalination, while effective, are difficult to widely implement due to high energy consumption, complex equipment, and poor environmental adaptability. Against this backdrop, atmospheric water harvesting technology has emerged. Atmospheric water harvesting is a method of addressing water scarcity by capturing moisture from the atmosphere. This means the atmosphere is a vast potential water source. The core of atmospheric water harvesting technology lies in the efficient adsorption and extraction of water vapor from the atmosphere and its conversion into liquid water under appropriate conditions. Therefore, designing and developing efficient and renewable adsorption materials has become a key technology for realizing atmospheric water harvesting. Currently, commonly used atmospheric water harvesting technologies include mist collection, water condensation, and adsorption-based water collection. Mist collection technology relies on specially structured mesh materials to collect water droplets from the air and condense them into water; however, this technology has demanding application conditions, typically requiring high altitude, high humidity, and high wind speeds, thus limiting its versatility. Condensation water collection technology collects moisture by condensing water vapor in the atmosphere. Its advantages include mature equipment technology and the ability to collect large quantities of water. However, it has extremely high energy consumption and equipment costs, is sensitive to ambient temperature and humidity, and has limited applicability. Adsorption water collection technology has received widespread attention in recent years, especially for its excellent performance under low humidity conditions. This technology uses an adsorbent to adsorb water vapor from the air and then releases the adsorbed moisture through light or heat sources, ultimately achieving water collection.

[0003] Currently, research on adsorption-based water collection technology mainly focuses on the development of novel hygroscopic materials. Common hygroscopic materials include hygroscopic salts, zeolites, metal-organic frameworks (MOFs), porous silica-based materials, and carbon-based materials. Among these, hygroscopic salts can adsorb large amounts of water, up to 95% of their mass. However, hygroscopic salts are prone to crystallization and aggregation during water absorption, and their water absorption capacity decreases due to surface passivation. Hygroscopic salts also have poor regenerability, making it difficult to maintain high-efficiency water absorption performance through multiple cycles. Zeolites are natural porous materials with high adsorption capacity and relatively stable pore structure. Their disadvantages include high regeneration requirements at high temperatures and poor thermal conductivity, leading to significant energy consumption and limiting their application in atmospheric water collection. MOFs are widely studied due to their high specific surface area, tunable pore structure, and rich chemical functions. MOFs can provide a large number of water-absorbing active sites, but their photothermal conversion efficiency is low, and they require high temperatures and energy during dehydration. Furthermore, the pore structure of MOFs is easily affected by environmental factors, leading to poor stability and limiting their long-term application in atmospheric water collection. Porous silicon-based materials are inexpensive, have a large specific surface area, and exhibit fast adsorption-desorption kinetics, but their desorption energy consumption is high, and they may encounter pore structure collapse during long-term use, affecting their long-term performance. Carbon-based materials, especially porous carbon, have become a research focus in recent years due to their tunable structure, large specific surface area, low cost, and environmental friendliness. However, existing biomass nitrogen-doped porous carbon materials lack research on optimizing the type and amount of hydrophilic nitrogen doping and precisely controlling the pore structure to further improve the adsorption-desorption kinetics of novel porous carbon materials. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a biomass nitrogen-doped derived porous carbon material, its preparation method, and its applications. The preparation method of this biomass nitrogen-doped derived porous carbon material is simple, and it can effectively adsorb water vapor. Furthermore, under certain light conditions, it exhibits excellent thermal conversion capabilities, thereby achieving rapid water desorption.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for preparing biomass nitrogen-doped derived porous carbon materials includes the following steps:

[0007] Carbon and nitrogen sources are added to water, and the mixture is first subjected to ultrasonic reaction, followed by hydrothermal treatment to obtain a solid product.

[0008] The solid product and metal salt are mixed and ground, then subjected to vapor etching and high-temperature annealing under an inert atmosphere, followed by acidification, grinding and drying to prepare the biomass nitrogen-doped derived porous carbon material.

[0009] Optionally, the carbon source is selected from at least one of chitosan, cellulose, peanut meal, algae, or biomass waste; and / or,

[0010] The nitrogen source is selected from at least one of urea, melamine, aniline or imidazole.

[0011] Furthermore, the carbon source is chitosan, and the nitrogen source is urea.

[0012] Beneficial Effects: This invention starts from the design of hydrophilic adsorption molecules on the surface of activated carbon. Firstly, it uses abundant and inexpensive chitosan as a carbon-based precursor material, urea as a nitrogen-doping source, and metal salts as nitrogen-fixing and pore-forming agents. Then, carbonization products are obtained through ultrasonic dispersion, hydrothermal pyrolysis, vapor etching, and high-temperature annealing. Afterward, acid treatment removes the metal clusters, resulting in derived porous carbon with a quantitative nitrogen doping amount and high specific surface area. The derived porous carbon material synthesized using this method can rapidly capture atmospheric water molecules through the synergistic effect of highly active adsorption sites such as pyrrole nitrogen and pyridine nitrogen, as well as irregular pores, giving the derived carbon material excellent water adsorption performance.

[0013] Furthermore, the raw materials of this invention are abundant and economical, the synthesis is simple and the yield is high, and the derived carbon porous materials have the advantages of high water absorption, fast adsorption and desorption rate and strong recyclability.

[0014] Furthermore, the mass ratio of the carbon source to the nitrogen source is 1:(1-5).

[0015] Optionally, the ultrasonic treatment conditions are: ultrasonic treatment for 30-60 minutes at 25-30℃ and 30-40kHz.

[0016] Optionally, the hydrothermal treatment conditions are: hydrothermal treatment at a temperature of 160-200℃ for 15-25 hours.

[0017] Furthermore, the hydrothermal treatment conditions are: hydrothermal treatment at 180°C for 24 hours.

[0018] Optionally, the metal salt is zinc chloride hexahydrate.

[0019] This invention uses zinc chloride hexahydrate as a metal salt. The bound water in zinc chloride hexahydrate itself is used for steam etching. The specific reaction mechanism is as follows: during heating and carbonization, the water of crystallization turns into water vapor, generating instantaneous high-pressure steam. The steam expands from the inside to the outside, thereby producing an etching effect.

[0020] Furthermore, the mass ratio of the solid product to zinc chloride hexahydrate is 1:(1-5); preferably 1:3.

[0021] Optionally, the conditions for the vapor etching and high-temperature annealing treatment are as follows: heating to 600-900℃ (preferably 600℃, 700℃ and 800℃) at a heating rate of 2-7℃ / min, and then performing vapor etching and high-temperature annealing treatment at this temperature for 1-2 hours.

[0022] Optionally, the inorganic acid used in the acidification process is selected from at least one of hydrochloric acid, nitric acid, and hydrofluoric acid.

[0023] Furthermore, the concentration of the inorganic acid is 1-5 mol / L; preferably 2 mol / L.

[0024] A biomass nitrogen-doped derived porous carbon material is prepared by the above-described preparation method.

[0025] Optionally, the molar percentage of nitrogen in the biomass nitrogen-doped derived porous carbon material (i.e., the percentage of nitrogen in the total amount of nitrogen, oxygen, and carbon) is 5.6-8.36%; the molar percentage of pyridine nitrogen and pyrrole nitrogen in the total elements is 3%; and the micropore volume is 0.16-0.61 cm³. 3 / g; specific surface area is 343.16-1041.28m² 2 / g.

[0026] The above-mentioned biomass nitrogen-doped porous carbon materials are used in atmospheric water collection.

[0027] Compared with the prior art, the present invention has the following advantages and technical effects:

[0028] (1) The biomass nitrogen-doped derived porous carbon material prepared in this invention achieves the regulation of nitrogen atoms in the carbon skeleton by introducing nitrogen-doped organic precursors, which significantly increases the amount of nitrogen doping while maintaining a high specific surface area, thereby enhancing the adsorption selectivity of the material for polar molecules. The percentage of strong water-absorbing groups such as pyridine nitrogen and pyrrole nitrogen in the total elements can reach more than 3%, and excellent wettability and interfacial hydrophilicity can be achieved without additional surface modification. The high specific surface area provides a large number of active sites and attachment points for the adsorption and aggregation of water molecules, thereby achieving efficient water vapor capture and collection.

[0029] (2) The biomass nitrogen-doped porous carbon material prepared by the present invention is derived from renewable biomass resources. The raw materials are inexpensive and widely available. No harmful byproducts are generated during the preparation process. It has good environmental friendliness, adaptability and sustainable development advantages.

[0030] (3) The biomass nitrogen-doped derived porous carbon material prepared by the present invention is a black powder material with extremely high light absorption rate and excellent photothermal conversion ability. It can reach a surface temperature of 85°C within 15 minutes (that is, after the material is pressed into a sheet, the absorption of sunlight in the 200–2500 nm band is measured by a UV–Vis–NIR spectrophotometer), which provides sufficient energy for the efficient thermal desorption of adsorbed water molecules.

[0031] (4) The biomass nitrogen-doped derived porous carbon powder material prepared by the present invention has good dispersibility and can be further processed into thin films, bulk materials or composite coatings to meet the structural design and functional requirements of different devices.

[0032] (5) The atmospheric water collection system of the biomass nitrogen-doped porous carbon material of the present invention can operate efficiently in low humidity environment. The adsorption and desorption process can be completely driven by natural light energy and has self-powered characteristics. At the same time, its construction and operation are simple and convenient, and it has excellent water vapor condensation and liquid water generation capabilities, which can realize efficient and stable water production process. It can be applied to remote or power-deficient areas.

[0033] (6) The biomass nitrogen-doped porous carbon material prepared by this invention maintains a stable structure and performance during cyclic adsorption-desorption tests, indicating that it has good chemical stability, hydrolysis resistance, cycle durability, and long-term reliability. It is suitable for atmospheric water collection applications under different climatic and humidity conditions. This material can work stably in a variety of environments, demonstrating wide applicability and is expected to provide a feasible solution to the water shortage problem in different regions. Attached Figure Description

[0034] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0035] Figure 1 Water contact angle diagrams of porous carbon materials prepared in Examples 1, 2, 4, Comparative Example 1, and Comparative Example 2 of this invention;

[0036] Figure 2 In diagram a, the simplified atmospheric water collection device used in this invention is shown in the figure. In diagram b, c, and d, the top, left, and front views of diagram a are shown in the figure, respectively.

[0037] Figure 3 This is a graph showing the adsorption and desorption rates of the biomass nitrogen-doped derived porous carbon material prepared in Example 4 of this invention.

[0038] Figure 4 This is a cycle diagram of the biomass nitrogen-doped derived porous carbon material prepared in Example 4 of the present invention during indoor testing;

[0039] Figure 5 The graph shows the actual water collection rate outdoors of the biomass nitrogen-doped porous carbon material prepared in Example 4 of this invention. Detailed Implementation

[0040] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0041] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0042] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0043] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0044] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0045] The first aspect of this invention discloses a biomass nitrogen-doped derived porous carbon material, comprising carbon, oxygen, hydrogen, and nitrogen. Based on the total molar amount of the elements, the molar content of pyrrole nitrogen and pyridine nitrogen is above 3%, and the micropore volume of the material is 0.13-0.61 cm³. 3 / g.

[0046] The high pyrrole nitrogen and pyridine nitrogen content of the biomass nitrogen-doped derived porous carbon material provided by this invention is beneficial for rapid water vapor capture in low humidity areas. Unless otherwise specified, the carbon, nitrogen, oxygen, pyrrole nitrogen, and pyridine nitrogen content are obtained by analyzing the photoelectrons excited by the sample using X-ray photoelectron spectroscopy with an energy analyzer.

[0047] The nitrogen-doped porous carbon material prepared in this invention significantly enhances its water absorption capacity by introducing abundant hydrophilic sites through nitrogen doping, demonstrating great potential for atmospheric water collection. By introducing nitrogen atoms, the electronic structure and surface properties of the carbon material are optimized. Nitrogen atoms effectively enhance the hydrophilicity of the carbon material, thereby improving its adsorption capacity for water vapor. Furthermore, nitrogen doping increases the surface polarity of the porous carbon material, further improving its adsorption capacity and regeneration performance. The nitrogen-doped porous carbon material not only possesses a high specific surface area and abundant pore structure, but also exhibits superior kinetics in the adsorption-desorption process. Compared with MOFs, the synthesis process of biomass nitrogen-doped derived porous carbon materials is simpler and more convenient, the material acquisition cost is lower, and biomass carbon materials are more environmentally friendly. In addition, due to its high photothermal conversion capacity, the biomass nitrogen-doped derived porous carbon material can effectively convert solar energy while adsorbing water vapor, accelerating the release of water vapor, which results in higher water collection efficiency under sunlight. More importantly, biomass nitrogen-doped porous carbon materials can effectively adsorb water vapor under low humidity and low temperature conditions, and release moisture through photothermal or other means at appropriate temperatures. They are highly adaptable and can be used in a variety of environments around the world.

[0048] In some alternative embodiments, the specific surface area of ​​the biomass nitrogen-doped derived porous carbon material reaches as high as 1041.28 m². 2 / g. This means that the derived carbon porous material provided by this invention possesses excellent microporous properties and a high specific surface area, which is more conducive to the rapid capture of water molecules from the atmosphere. Unless otherwise specified, the specific surface area and micropore volume of the biomass nitrogen-doped derived porous carbon material are obtained using a specific surface area and porosity analyzer.

[0049] The second aspect of this invention discloses a method for preparing biomass nitrogen-doped derived porous carbon materials, comprising the following steps:

[0050] The carbon source (chitosan), nitrogen source (urea), and metal salt (acting as nitrogen fixative and pore-forming agent) are dispersed by ultrasonic reaction, followed by hydrothermal pyrolysis, vapor etching, annealing and carbonization, and then acidification treatment to obtain derived nanoporous carbon; the specific process is as follows:

[0051] The two sources (carbon source and nitrogen source) are mixed in 50-150 mL of water at a mass ratio of 1:1-1:5 and ultrasonically dispersed in a 30 kHz ultrasonic oscillator for 30-60 min. The reactants are then subjected to hydrothermal treatment at 160-200 °C for 15-25 h. After mixing with a metal salt at a ratio of 1:1-1:5, the mixture is heated to 600-900 °C at a rate of 2-7 °C / min under an inert atmosphere. Vapor etching and annealing are then performed at this temperature for 1-2 h. The acidification treatment conditions include acid treatment with an inorganic acid solution at a concentration of 1-5 mol / L.

[0052] The reaction principle is as follows: High-proportion nitrogen-rich urea is incorporated into chitosan, a carbon source with abundant reserves and nanopores. Metal salts serve as nitrogen-fixing agents and pore-forming agents. The carbonized product is then obtained through ultrasonic dispersion, hydrothermal pyrolysis, vapor etching, and high-temperature annealing. Subsequently, acid treatment removes the metal clusters, yielding a biomass nitrogen-doped derived porous carbon material with a quantitative nitrogen doping level and high specific surface area. The prepared derived porous carbon material exhibits excellent water absorption, adsorption-desorption rates, and recyclability.

[0053] In some optional embodiments, there are no particular limitations on the specific selection of the carbon source chitosan and the nitrogen source urea. Any nitrogen-rich organic matter conventionally used in the art can be used in this invention. Carbon sources include, but are not limited to, chitosan, cellulose, soybean flour, peanut meal, algae, and biomass waste; nitrogen sources include, but are not limited to, urea, melamine, aniline, and imidazole. Preferably, this invention uses chitosan as the carbon source and urea as the nitrogen source. This preferred embodiment is more conducive to adjusting the nitrogen-doped structure type, thereby optimizing the water absorption, adsorption-desorption rate, and recycling performance of the resulting biomass nitrogen-doped derived porous carbon material.

[0054] It should be noted that the biomass nitrogen-doped derived porous carbon material provided by this invention may also contain residual metals (such as Zn), and their content is not particularly limited. It is understood that the sum of the contents of all elements present in the nitrogen-doped derived porous carbon material is 100%.

[0055] In some optional embodiments, the conditions for ultrasonic reaction dispersion, hydrothermal pyrolysis, and high-temperature annealing include: mixing the carbon source and nitrogen source at a mass ratio of 1:1.25-1:5, ultrasonically reacting the mixture in 50-150 mL of water for 30-60 min at an ultrasonic frequency of 30-40 kHz, followed by hydrothermal treatment at 160-200 °C for 15-25 h; then, under an inert atmosphere, heating at a rate of 3-6 °C / min to 600-900 °C, followed by vapor etching and annealing for 1-2 h at this temperature. This preferred embodiment is more conducive to the synergistic improvement of the specific surface area and water adsorption sites of biomass nitrogen-doped porous carbon materials. If the nitrogen source doping concentration is too low, it is not conducive to increasing the number of hydrophilic nitrogen doping sites in biomass nitrogen-doped porous carbon materials. If the nitrogen source doping concentration is too high, it may lead to an increase in the types of non-hydrophilic nitrogen atoms such as graphitic nitrogen, resulting in graphitization of the carbon structure. If the high-temperature pyrolysis temperature is too low, it will be detrimental to increasing the types and quantities of hydrophilic nitrogen in biomass nitrogen-doped porous carbon materials, as well as their hydrophilic specific surface area and porosity. If the high-temperature pyrolysis temperature is too high, it may cause a decrease in the number of water adsorption sites for hydrophilic nitrogen and graphitization of the carbon structure.

[0056] In some optional embodiments, the mass ratio of chitosan to urea is 1:1.25, 1:2.5, 1:3.75, 1:5, or any range thereof. The preferred embodiment of the present invention is 1:2.5 or 1:5, which will be used as an example for illustration.

[0057] In some alternative embodiments, the mass ratio of hydrothermal carbon (solid product) to metal salt is 1:2, 1:3, 1:4, or any range thereof. The present invention uses zinc chloride hexahydrate, preferably at a ratio of 1:3, as an example for illustrative purposes, but the present invention is not limited thereto.

[0058] In some alternative embodiments, the ultrasonic response takes 30-60 minutes and has a frequency of 30-40 kHz.

[0059] In some alternative embodiments, the hydrothermal reaction is carried out at a temperature of 160-200°C for a reaction time of 20-26 hours.

[0060] In some optional embodiments, the temperature of vapor etching and high-temperature annealing is 600°C, 700°C, 800°C, 900°C, or any range thereof. The embodiments of the present invention preferably use 600°C, 700°C, or 800°C as an example for illustrative purposes.

[0061] In some alternative embodiments, the vapor etching and high-temperature annealing treatment time is 1-3 hours, for example, 1 hour, 2 hours, 3 hours, or any range between the two, preferably 1-2 hours.

[0062] In some alternative embodiments, the inert atmosphere includes at least one of helium, argon, and neon. This invention uses argon as an example for illustrative purposes, but is not limited thereto.

[0063] In some alternative embodiments, vapor etching and high-temperature annealing are performed in a flowing inert gas atmosphere. The present invention does not impose any particular limitations on the amount of vapor etching, the time, or the rate of the flowing inert gas.

[0064] In some optional embodiments, the inorganic acid is selected from at least one of hydrochloric acid, nitric acid, and hydrofluoric acid, more preferably hydrochloric acid. This preferred embodiment is more conducive to the removal of metal oxides and the improvement of porosity in biomass-derived porous carbon. The present invention has a wide range of acid solution concentration options; preferably, the acid solution concentration is 1-5 mol / L, more preferably 2-3 mol / L. This preferred embodiment is more conducive to ensuring the yield of synthesized biomass-derived porous carbon and improving acid washing efficiency. Specifically, analytical grade hydrochloric acid solution can be diluted with deionized water to obtain a hydrochloric acid aqueous solution with a concentration of 2-3 mol / L. The present invention has a wide range of acid treatment time options, aiming to achieve complete removal of metal oxides from the biomass nitrogen-doped derived porous carbon material; preferably, the acid treatment time is 20-30 hours, more preferably 22-26 hours. The present invention has a wide range of specific acid treatment methods; preferably, the carbonized porous carbon is added to the acid solution for impregnation and stirring, followed by vacuum filtration.

[0065] In some optional embodiments, the preparation process of the present invention further includes washing the precipitate obtained after hydrothermal pyrolysis and carbonization with water, and washing the precipitate obtained after steam etching, high-temperature annealing, acid treatment, and filtration with water. The present invention does not particularly limit the washing conditions; for example, the precipitate can be added to deionized water, stirred, and then filtered to obtain the final product. The number of washing cycles is not particularly limited; for example, it can be 2-6 times.

[0066] In some optional embodiments, the preparation process of the present invention further includes drying the washed product. Preferably, the vacuum drying temperature is 60°C, and the time can be 12-48 hours.

[0067] In some optional embodiments, the preparation process of the present invention further includes pulverizing the washed and dried product, preferably grinding the washed and dried product for 1-5 minutes. The grinding tool is preferably made of quartz.

[0068] The third aspect of this invention discloses the application of the aforementioned biomass nitrogen-doped derived porous carbon material in atmospheric water collection. The biomass nitrogen-doped derived porous carbon material provided by this invention exhibits highly efficient atmospheric water collection performance during atmospheric water collection.

[0069] A fourth aspect of the present invention discloses an atmospheric water collection device, the device comprising:

[0070] Water collection structure, water condensation unit, thermoelectric module, heat dissipation module, voltage regulator and solar panel;

[0071] The water collection structure includes a water adsorption unit and a photothermal desorption unit;

[0072] This atmospheric water collection device can adsorb moisture in the air and achieve rapid desorption and condensation through photothermal and thermoelectric cooling, ultimately producing liquid water. The device boasts advantages such as low energy consumption, strong recyclability, and wide applicability, showing significant application prospects in arid and water-scarce regions.

[0073] The water adsorption unit supports at least one adsorbent; when the adsorbent is in the adsorption unit, it absorbs water from the surrounding air, and when the adsorbent is in the desorption mode of the water desorption unit, it desorbs water in the form of water vapor; at least one water condensation unit is used to condense the water vapor into liquid water.

[0074] The adsorbent is selected from the biomass nitrogen-doped derived porous carbon material of the first aspect or the biomass nitrogen-doped derived porous carbon material prepared by the preparation method described in the second aspect.

[0075] The atmospheric water collection device provided by this invention can achieve excellent light collection and efficient atmospheric water condensation, and has the characteristics of low energy consumption, high energy utilization rate and high water production rate.

[0076] The water absorption and water desorption units have different working modes for absorbing and desorbing water, respectively. The present invention does not have any particular limitation on their specific settings, as long as it can be ensured that when the water absorption unit is in absorption mode, the adsorbent can absorb water from the surrounding air, and when the water desorption unit is in desorption mode, it can desorb water in the form of water vapor.

[0077] This invention does not impose any particular limitations on the location or type of the water condensation unit, as long as it can condense the water vapor desorbed by the absorption / desorption unit into liquid water. The water condensation unit can be a condenser. The water condensation unit can be installed on the wall of the atmospheric water collection device.

[0078] In some alternative embodiments, the photothermal desorption unit in the device is configured to achieve photothermal desorption of moisture captured by the adsorbent. This preferred embodiment enables atmospheric water collection via sunlight irradiation.

[0079] The preferred angle of the bevel of the light-transmitting cover of the photothermal desorption unit is 5-25°. This preferred embodiment is more conducive to concentrating sunlight onto the surface of the adsorbent while reducing the obstruction of sunlight by the desorbed water vapor.

[0080] This invention does not impose any particular limitations on the material selection for the atmospheric water collection device, but glass is preferred. The device is mainly assembled from transparent glass materials, resulting in low raw material and processing costs. The device is easy to operate, allows for easy replacement of the adsorbent, and has strong compatibility with various adsorbents. Through optimization of the device's thermodynamic and kinetic parameters, high water production efficiency can be achieved.

[0081] Because the biomass nitrogen-doped derived porous carbon provided by this invention exhibits strong hydrolytic stability and chemical stability, temperature, humidity, and other conditions have almost no impact on the adsorbent's efficiency. This material is widely applicable to water production in various environments, addressing water shortage problems in different regions.

[0082] Unless otherwise specified, "room temperature" in this invention refers to 20-30℃.

[0083] All raw materials used in this invention were purchased from the market.

[0084] The technical solution of the present invention will be further illustrated by the following embodiments.

[0085] Example 1

[0086] A method for preparing biomass nitrogen-doped derived porous carbon includes the following steps:

[0087] First, 1.0 g of chitosan and 2.5 g of urea were completely mixed. This mixture was then added to 60 mL of deionized water and stirred at 700 rpm for 1 h. Next, the mixture was placed in a 100 mL PTFE-lined container and subjected to ultrasonic dispersion at 30 kHz for 30 min. After cooling, the reactants were transferred to a stainless steel autoclave and placed in a drying oven for hydrothermal reaction at 180 °C for 24 h. After cooling to room temperature, the product was washed repeatedly with deionized water using ultrasonication (5 min) and then filtered. The product was then dried in a vacuum drying oven at 60 °C for 12 h. The solid product was mixed with zinc chloride hexahydrate at a mass ratio of 1:3 by grinding for 2 min. The mixture was transferred to an alumina crucible and heated from room temperature to 600 °C at a rate of 5 °C / min in a tube furnace under flowing argon gas. It was then subjected to vapor etching and high-temperature annealing at 600 °C for 1 h. After natural cooling to room temperature, the carbonized product was obtained. Finally, the product was washed with 2 mol / L hydrochloric acid solution and deionized water until the washing water was neutral. After drying at 60°C overnight, it was ground for 2 min to obtain biomass nitrogen-doped derived porous carbon.

[0088] Example 2

[0089] A method for preparing biomass nitrogen-doped derived porous carbon includes the following steps:

[0090] First, 1.0 g of chitosan and 5 g of urea were completely mixed. This mixture was then added to 60 mL of deionized water and stirred at 700 rpm for 1 hour. Next, the mixture was placed in a 100 mL PTFE-lined container and subjected to ultrasonic dispersion at 30 kHz for 30 minutes. After cooling, the reactants were transferred to a stainless steel autoclave and placed in a drying oven for hydrothermal reaction at 180°C for 24 hours. After cooling to room temperature, the product was washed repeatedly with deionized water using ultrasonication (5 minutes each time) and then filtered. The product was then dried in a vacuum drying oven at 60°C for 12 hours. The solid product was mixed with zinc chloride hexahydrate at a mass ratio of 1:3 by grinding for 2 minutes. The mixture was transferred to an alumina crucible and heated from room temperature to 600°C at a rate of 5°C / min in a tube furnace under flowing argon gas. It was then subjected to vapor etching and high-temperature annealing at 600°C for 1 hour. After natural cooling to room temperature, the carbonized product was obtained. Finally, the product was washed with 2 mol / L hydrochloric acid solution and deionized water until the washing water was neutral. After drying at 60°C overnight, it was ground for 2 min to obtain biomass nitrogen-doped derived porous carbon.

[0091] Example 3

[0092] A method for preparing biomass nitrogen-doped derived porous carbon includes the following steps:

[0093] First, 1.0 g of chitosan and 2.5 g of urea were completely mixed. This mixture was then added to 60 mL of deionized water and stirred at 700 rpm for 1 h. Next, the mixture was placed in a 100 mL PTFE-lined container and subjected to ultrasonic dispersion at 30 kHz for 30 min. After cooling, the reactants were transferred to a stainless steel autoclave and placed in a drying oven for hydrothermal reaction at 180 °C for 24 h. After cooling to room temperature, the product was washed repeatedly with deionized water using ultrasonication (5 min) and then filtered. The product was then dried in a vacuum drying oven at 60 °C for 12 h. The solid product was mixed with zinc chloride hexahydrate at a mass ratio of 1:3 by grinding for 2 min. The mixture was transferred to an alumina crucible and heated from room temperature to 800 °C at a rate of 5 °C / min in a tube furnace under flowing argon gas. It was then subjected to vapor etching and high-temperature annealing at 800 °C for 1 h. After natural cooling to room temperature, the carbonized product was obtained. Finally, the product was washed with 2 mol / L hydrochloric acid solution and deionized water until the washing water was neutral. After drying at 60°C overnight, it was ground for 2 min to obtain biomass nitrogen-doped derived porous carbon.

[0094] Example 4

[0095] A method for preparing biomass nitrogen-doped derived porous carbon includes the following steps:

[0096] First, 1.0 g of chitosan and 2.5 g of urea were completely mixed. This mixture was then added to 60 mL of deionized water and stirred at 700 rpm for 1 h. Next, the mixture was placed in a 100 mL PTFE-lined container and subjected to ultrasonic dispersion at 30 kHz for 30 min. After cooling, the reactants were transferred to a stainless steel autoclave and placed in a drying oven for hydrothermal reaction at 180 °C for 24 h. After cooling to room temperature, the product was washed repeatedly with deionized water using ultrasonication (5 min) and then filtered. The product was then dried in a vacuum drying oven at 60 °C for 12 h. The solid product was mixed with zinc chloride hexahydrate at a mass ratio of 1:3 by grinding for 2 min. The mixture was transferred to an alumina crucible and heated from room temperature to 700 °C at a rate of 5 °C / min in a tube furnace under flowing argon gas. It was then subjected to vapor etching and high-temperature annealing at 700 °C for 1 h. After natural cooling to room temperature, the carbonized product was obtained. Finally, the product was washed with 2 mol / L hydrochloric acid solution and deionized water until the washing water was neutral. After drying at 60°C overnight, it was ground for 2 min to obtain biomass nitrogen-doped derived porous carbon.

[0097] Example 5

[0098] A method for preparing biomass nitrogen-doped derived porous carbon includes the following steps:

[0099] First, 1.0 g of cellulose and 2.5 g of 1-methylimidazole (CAS No. 616-47-7) were thoroughly mixed. This mixture was then added to 60 mL of deionized water and stirred at 700 rpm for 1 h. Next, the mixture was placed in a 100 mL polytetrafluoroethylene-lined container and subjected to ultrasonic dispersion at 30 kHz for 30 min. After cooling, the reactants were transferred to a stainless steel autoclave and placed in a drying oven for hydrothermal reaction at 180 °C for 24 h. After cooling to room temperature, the product was washed repeatedly with deionized water using ultrasonication (5 min each time) and then filtered. The product was then dried in a vacuum drying oven at 60 °C for 12 h. The solid product was then mixed with zinc chloride hexahydrate at a mass ratio of 1:3 by grinding for 2 min. The mixture was transferred to an alumina crucible and heated from room temperature to 700°C at a rate of 5°C / min in a tube furnace under flowing argon. It was then subjected to vapor etching and high-temperature annealing at 700°C for 1 hour. After natural cooling to room temperature, the carbonized product was obtained. Finally, the product was washed with 2 mol / L hydrochloric acid solution and deionized water until the wash water was neutral. After drying at 60°C overnight, it was ground for 2 minutes to obtain biomass nitrogen-doped derived porous carbon.

[0100] Example 6

[0101] A method for preparing biomass nitrogen-doped derived porous carbon includes the following steps:

[0102] First, 1.0 g of cellulose and 2.5 g of ethylenediamine were completely mixed. This mixture was then added to 60 mL of deionized water and stirred at 700 rpm for 1 h. Next, the mixture was placed in a 100 mL PTFE-lined container and subjected to ultrasonic dispersion at 30 kHz for 30 min. After cooling, the reactants were transferred to a stainless steel autoclave and placed in a drying oven for hydrothermal reaction at 180 °C for 24 h. After cooling to room temperature, the product was washed repeatedly with deionized water using ultrasonication (5 min) and then filtered. The product was then dried in a vacuum drying oven at 60 °C for 12 h. The solid product was mixed with zinc chloride hexahydrate at a mass ratio of 1:3 by grinding for 2 min. The mixture was transferred to an alumina crucible and heated from room temperature to 700 °C at a rate of 5 °C / min in a tube furnace under flowing argon gas. It was then subjected to vapor etching and high-temperature annealing at 700 °C for 1 h. After natural cooling to room temperature, the carbonized product was obtained. Finally, the product was washed with 2 mol / L hydrochloric acid solution and deionized water until the washing water was neutral. After drying at 60°C overnight, it was ground for 2 min to obtain biomass nitrogen-doped derived porous carbon.

[0103] Example 7

[0104] A method for preparing biomass nitrogen-doped derived porous carbon includes the following steps:

[0105] First, 1.0 g of peanut shells and 2.5 g of methylimidazole were thoroughly mixed. This mixture was then added to 60 mL of deionized water and stirred at 700 rpm for 1 h. Next, the mixture was placed in a 100 mL PTFE-lined container and subjected to ultrasonic dispersion at 30 kHz for 30 min. After cooling, the reactants were transferred to a stainless steel autoclave and placed in a drying oven for hydrothermal reaction at 180 °C for 24 h. After cooling to room temperature, the product was washed repeatedly with deionized water using ultrasonication (5 min) and then filtered. The product was then dried in a vacuum drying oven at 60 °C for 12 h. The solid product was mixed with zinc chloride hexahydrate at a mass ratio of 1:3 by grinding for 2 min. The mixture was transferred to an alumina crucible and heated from room temperature to 700 °C at a rate of 5 °C / min in a tube furnace under flowing argon gas. It was then subjected to vapor etching and high-temperature annealing at 700 °C for 1 h. After natural cooling to room temperature, the carbonized product was obtained. Finally, the product was washed with 2 mol / L hydrochloric acid solution and deionized water until the washing water was neutral. After drying at 60°C overnight, it was ground for 2 min to obtain biomass nitrogen-doped derived porous carbon.

[0106] Comparative Example 1

[0107] A method for preparing biomass-derived porous carbon includes the following steps:

[0108] First, 1.0 g of chitosan was added to 60 mL of deionized water and stirred at 700 rpm for 1 h. Then, the mixture was placed in a 100 mL PTFE-lined container and ultrasonically dispersed at 30 kHz for 30 min. After cooling, the reactants were transferred to a stainless steel autoclave and placed in a drying oven at 180 °C for 24 h. After cooling to room temperature, the product was washed repeatedly with deionized water using ultrasonication (5 min) and filtered. The product was then dried in a vacuum drying oven at 60 °C for 12 h. The solid product was mixed with zinc chloride at a mass ratio of 1:3 by grinding for 2 min. The mixture was transferred to an alumina crucible and heated from room temperature to 600 °C at a rate of 5 °C / min in a tube furnace under flowing argon gas. It was then etched and carbonized at 600 °C for 1 h. After natural cooling to room temperature, the carbonized product was obtained. Finally, the product was washed with 2 mol / L hydrochloric acid solution and deionized water until the washing water was neutral. After drying at 60°C overnight, it was ground for 2 minutes to obtain biomass-derived porous carbon.

[0109] Comparative Example 2

[0110] A method for preparing biomass-derived porous carbon includes the following steps:

[0111] First, 1.0 g of glucose was added to 60 mL of deionized water and stirred at 700 rpm for 1 h. Then, the mixture was placed in a 100 mL PTFE-lined container and ultrasonically dispersed at 30 kHz for 30 min. After cooling, the reactants were placed in a stainless steel autoclave and reacted at 180 °C for 24 h in a drying oven. The product was washed repeatedly with deionized water by ultrasonication (5 min) and filtered. Then, the product was dried in a vacuum drying oven at 60 °C for 12 h. The solid product was mixed with zinc chloride at a mass ratio of 1:3 by grinding for 2 min. The mixture was transferred to an alumina crucible and heated from room temperature to 600 °C at a rate of 5 °C / min in a tube furnace under flowing argon gas. The mixture was then etched and carbonized at 600 °C for 1 h. After naturally cooling to room temperature, the carbonized product was obtained. Finally, the product was washed with 2 mol / L hydrochloric acid solution and deionized water until the washing water was neutral. After drying at 60°C overnight, it was ground for 2 minutes to obtain biomass-derived porous carbon.

[0112] Comparative Example 3

[0113] A method for preparing biomass-derived porous carbon includes the following steps:

[0114] First, 1.0 g of cellulose and 1.0 g of ethylenediamine were completely mixed and added to 60 mL of deionized water, and stirred at 700 rpm for 1 h. Then, the mixture was placed in a 100 mL PTFE-lined container and ultrasonically dispersed at 30 kHz for 30 min. After cooling, the reactants were transferred to a stainless steel autoclave and placed in a drying oven at 180 °C for 24 h. After cooling to room temperature, the product was washed repeatedly with deionized water using ultrasonication (5 min) and filtered. The product was then dried in a vacuum drying oven at 60 °C for 12 h. The solid product was mixed with zinc chloride at a mass ratio of 1:3 by grinding for 2 min. The mixture was transferred to an alumina crucible and heated from room temperature to 600 °C in a tube furnace under flowing argon at a heating rate of 5 °C / min. The mixture was then etched and carbonized at 600 °C for 1 h. After natural cooling to room temperature, the carbonized product was obtained. Finally, the product was washed with 2 mol / L hydrochloric acid solution and deionized water until the washing water was neutral. After drying at 60°C overnight, it was ground for 2 minutes to obtain biomass-derived porous carbon.

[0115] Comparative Example 4

[0116] See Chitosan-derived N-doped porous carbon with enhanced nitrogenconcentration and tailored nitrogen configuration. J Mater Sci (2022) 57:8739–8751;

[0117] The specific preparation process is as follows:

[0118] 1.0 g of chitosan and 2.5 g of urea were thoroughly mixed. The mixture was added to 60 mL of deionized water under vigorous stirring. The mixture was then placed in a 100 mL stainless steel autoclave lined with PTFE and maintained at 180°C for 24 hours. After cooling to room temperature, the resulting black solid product was washed with deionized water by centrifugation. It was then dried in an oven at 80°C for 4 hours. The solid product was mixed with ZnCl2 at a mass ratio of 1:3. The mixture was transferred to a quartz crucible and heated in a tube furnace under a nitrogen atmosphere from room temperature to 600°C for 1 hour at a heating rate of 10°C / min. Finally, the product was washed with 1 M HCl solution and deionized water until the wash water was neutral.

[0119] Nitrogen-doped porous carbon materials are prepared by hydrothermal reaction of a mixture of chitosan and urea, followed by activation with zinc chloride. While this method can introduce certain nitrogen-containing structures, it suffers from problems such as insufficient material synthesis, low carbonization temperature, rapid heating rate, and excessively high drying temperature. This results in materials with a simple pore structure, thin pore walls, and nitrogen species predominantly pyrrole nitrogen, which has poor thermal stability. Such materials exhibit shortcomings in air-to-water collection applications, including slow adsorption rates, poor cycle stability, and high desorption energy consumption. In contrast, the preparation method proposed in this invention has the following advantages:

[0120] 1. Introducing an ultrasonic step before hydrothermal treatment, the high-frequency micro-perturbation flow generated by ultrasonic dispersion can suppress phase separation or sedimentation during the static process, effectively promoting the uniform dispersion of carbon and nitrogen sources at the molecular scale. This allows carbon sources (such as chitosan molecular chains) to fully expand and nitrogen sources (such as urea particles) to be uniformly linked and distributed throughout the system, significantly improving the system's homogeneity. Ultrasonic treatment results in a higher micropore ratio and a more uniform distribution of nitrogen functional groups, ultimately yielding porous carbon exhibiting superior adsorption performance, hydrophilicity regulation ability, and atmospheric water collection capacity.

[0121] 2. The drying process adopts a low-temperature long-time drying method, which can effectively prevent excessive pore wall tension caused by rapid vaporization in the precursor after hydrothermal impregnation, and avoid microporous structure collapse or pore closure.

[0122] 3. By employing a grinding process and a slow heating (5 ℃ / min) to above 600 ℃ vapor etching and high-temperature annealing process, the nitrogen element configuration can be effectively fixed while the template activation effect of the metal salt is more complete, forming a multi-level pore structure with micropores, mesopores and macropores, which helps to control the pore size distribution and increase the specific surface area.

[0123] 4. A 2 mol / L hydrochloric acid solution was used during the pickling process to thoroughly remove residual metal salts and improve the purity of the pores;

[0124] 5. By combining the synergistic doping effects of pyridine nitrogen, pyrrole nitrogen and graphitic nitrogen, a composite hydrophilic active surface with high polarity and high thermal conductivity was constructed.

[0125] The comparison shows that the nitrogen-doped hierarchical porous carbon material prepared by this invention exhibits significantly superior air water collection performance:

[0126] (1) The hierarchical porous structure significantly enhances the adsorption and diffusion rate of water molecules;

[0127] (2) Increased surface polarity allows nitrogen sites to form stable hydrogen bonds with water molecules, thereby increasing hygroscopic capacity;

[0128] (3) High thermal conductivity promotes energy transfer in the adsorption-desorption cycle, enabling low-energy regeneration;

[0129] (4) The material structure is stable and its performance remains good during multiple moisture absorption and desorption cycles.

[0130] In summary, the method of the present invention can obtain porous carbon materials with more hierarchical pore structure, more stable nitrogen-containing functional groups, and better adsorption-desorption performance, which are especially suitable for the fields of efficient air water collection and environmental humidity control.

[0131] The composition and property parameters of the porous carbon prepared in Examples 1-7 and Comparative Examples 1-4 are shown in Table 1.

[0132] Table 1

[0133]

[0134] Test Example 1

[0135] To verify the surface hydrophilicity of biomass nitrogen-doped porous carbon materials, water contact angle tests were conducted on some examples (Example 1, Example 2, Example 4) and comparative examples (Comparative Example 1, Comparative Example 2). A contact angle meter was used for the tests, with an ambient temperature of 27±2 ℃ and a relative humidity of 45±5%. The sample powder was pressed into a disc with a diameter of 10 mm and a thickness of approximately 1 mm, and fixed onto a glass substrate. A 3 μL droplet of deionized water was dropped onto the sample surface using an automated liquid injection needle. The change in the contact angle between the water droplet and the sample surface was recorded using an optical imaging system, and the static contact angle was measured using the accompanying software.

[0136] Figure 1 The water contact angle diagrams are shown for the porous carbon materials prepared in Examples 1, 2, 4, Comparative Example 1, and Comparative Example 2 of this invention; [The diagrams show the water contact angles of the porous carbon materials prepared in Examples 1, 2, 4, Comparative Example 1, and Comparative Example 2.] Figure 1 The test results show that the water contact angles of Comparative Example 1 and Comparative Example 2 are approximately 36.8° and 111.2°, respectively. The water contact angles of Examples 1, 2, and 4 are significantly smaller than those of Comparative Example 1 and Comparative Example 2, indicating a substantial improvement in surface hydrophilicity. This demonstrates that the biomass nitrogen-doped derived porous carbon of the present invention exhibits excellent hydrophilic properties, providing a structural and chemical basis for its rapid water absorption and efficient dehydration during atmospheric water collection.

[0137] Test Example 2

[0138] The test subjects were the biomass nitrogen-doped derived porous carbon prepared in Examples 1-7 and the undoped nitrogen-derived porous carbon prepared in Comparative Examples 1-4. The sample dish in the test apparatus had a bottom area of ​​6.15 cm². 2 The height is 1.2cm. The specifications of the designed atmospheric water collection device are as follows: Figure 2As shown in Table 2, a constant temperature and humidity chamber was used to simulate the temperature and humidity environment for the moisture absorption performance test. To test the moisture absorption effect of the sample under different humidity conditions, 100 mg of porous carbon material was placed in a sample dish and placed in a constant temperature and humidity chamber at 25°C to simulate outdoor testing. Specific values ​​are shown in Table 2.

[0139] Table 2

[0140]

[0141] Test Example 3

[0142] To fully demonstrate the water adsorption and desorption performance of biomass nitrogen-doped porous carbon, this invention tested the porous carbon prepared in all examples and comparative examples. Water saturation was achieved in a constant temperature and humidity chamber with a humidity range of 90% RH. The water desorption performance of the biomass nitrogen-doped porous carbon prepared in Example 4 was tested using simulated sunlight at a temperature of 27°C and a humidity of 40% RH. Temperature and mass changes during the testing process were recorded using a temperature monitoring instrument and a balance, respectively.

[0143] First, a glass dish (6.15 cm² bottom area) containing 100 mg of biomass nitrogen-doped derived porous carbon was placed... 2 The sample (1.2 cm in height) was placed in a constant temperature and humidity chamber with a humidity range of 90% RH for 60 minutes to absorb moisture. The weight gain of the sample was recorded before and after moisture absorption. During the atmospheric dehydration stage, the sample was placed under a solar simulator with a light intensity of 1.0 kw / m². 2 Water desorption was performed at an ambient temperature of 27°C and a humidity of approximately 30% RH. The change in adsorbed mass per unit mass of sample at different times was recorded to reflect the adsorption rate. The dehydration rates and temperature rise of the adsorbents obtained in each embodiment and comparative example under the above conditions are shown in Table 3.

[0144] Table 3

[0145]

[0146] As can be seen from Table 3, the desorption rate and temperature rise in the same time period of the embodiments of the present invention are superior to those of the comparative examples, indicating that the embodiments of the present invention have high light absorption rate and excellent thermal response characteristics, providing sufficient energy for rapid desorption of water.

[0147] Figure 3The graph shows the surface temperature and internal water desorption performance of the biomass nitrogen-doped porous carbon material prepared in Example 4 of this invention under simulated sunlight. When the sample is exposed to light, water molecules are rapidly released, and the curve shows a rapid downward trend. It can basically recover to its initial mass in just 15 minutes, indicating that the material has high light absorption rate and excellent thermal response characteristics, allowing the surface temperature of the material to rise to about 80°C within 20 minutes of light exposure, providing sufficient energy for rapid water desorption.

[0148] Test Example 4

[0149] To fully demonstrate the excellent cycle durability and long-term operational reliability of biomass nitrogen-doped porous carbon, this invention tested the porous carbon prepared in all examples and comparative examples. Water was absorbed for 1 hour in a constant temperature and humidity chamber with a selected humidity range of 90% RH. The water desorption performance of the biomass nitrogen-doped porous carbon prepared in Example 4 was tested using simulated sunlight in an environment with a temperature of 27℃ and a humidity of approximately 40% RH. The change in adsorption mass per unit mass sample at different times was recorded using a balance.

[0150] First, glass dishes containing biomass nitrogen-doped derived porous carbon were placed in a constant temperature and humidity chamber with a humidity range of 90% RH for 60 minutes to absorb moisture. The weight gain of the samples before and after moisture absorption was recorded. During the atmospheric dehydration stage, the samples were placed under a solar simulator with a light intensity of 1.0 kW / m². 2 Water desorption was performed at an ambient temperature of 27°C and a humidity of approximately 30% RH, and the change in adsorption mass per unit mass sample at different times was recorded. Table 4 shows the adsorption-desorption cycles of the adsorbents obtained in each example and comparative example under the above conditions for 10 cycles.

[0151] Table 4

[0152]

[0153] As can be seen from Table 4, after 10 cycles, the water collection performance of the comparative embodiment of the present invention decreased, while the adsorption capacity of the embodiment of the present invention remained almost unchanged, indicating that the embodiment of the present invention has good chemical stability, hydrolysis resistance, cycle durability and long-term reliability.

[0154] Figure 4The graph shows the cyclic performance of the biomass nitrogen-doped derived porous carbon material prepared in Example 4 of this invention, after repeated water absorption for 1 hour in a constant temperature and humidity chamber with a humidity range of 90% RH, followed by dehydration under sunlight. As can be seen from the graph, the adsorption and desorption capacities of the sample remained almost constant during multiple cycles, with a high degree of overlap in the curves, indicating that the material can maintain stable adsorption-desorption capacity under repeated use conditions. After 10 cycles, the adsorption capacity remained almost constant, and the desorption recovery rate was close to 100%, demonstrating that the material has excellent structural stability and chemical reversibility.

[0155] Test Example 5

[0156] To fully demonstrate the water collection performance of the adsorbent and the device, the biomass nitrogen-doped porous carbon prepared in Example 4 was selected for outdoor atmospheric water production testing, with an average humidity range of 30-50% RH. Temperature, humidity, and solar intensity were recorded regularly during the test using a thermometer / hygrometer and a light intensity meter, respectively.

[0157] First, a glass dish containing biomass nitrogen-doped derived porous carbon is placed in a dark environment with a certain level of humidity for atmospheric water absorption, which takes 20-50 minutes. After absorption, the sample is weighed and the weight gain is recorded. During the atmospheric dehydration stage, the sample is placed in a sealed water collection device with a transparent lid and a 5-15° angled slope. The angle affects the light intensity irradiated onto the sample surface by influencing the water vapor enrichment zone; a 15° angle is preferred for this device. The device is then placed under sunlight and the condenser assembly is turned on. Liquid water begins to condense on the device walls, taking 10-30 minutes. After water production, the derived porous carbon material is removed and weighed. Simultaneously, the condensed liquid water is collected and weighed, and the water production during this process is recorded.

[0158] Figure 5The graph shows the actual water collection volume of the biomass nitrogen-doped porous carbon material prepared in Example 4 of this invention outdoors. As can be seen from the graph, the material exhibits significant cyclic adsorption-desorption characteristics during the test period from 9:36 AM to 4:48 PM. During the moisture absorption phase (9:36 AM - 12:00 PM), as the ambient humidity gradually increased, the water absorption of the material continued to rise, reaching a peak of approximately 0.5 g / g at 10:48 AM, indicating its extremely strong ability to capture water vapor in the air. Subsequently, after 12:00 PM, it entered the light-driven desorption phase. Although the ambient humidity decreased, the material rapidly heated up under sunlight, triggering the desorption of adsorbed water. From 12:00 PM onwards, the water absorption gradually decreased, dropping below 0.18 g / g by 3:36 PM, indicating that the adsorbent achieved efficient water release under light conditions. Meanwhile, the line graph shows that the actual water absorption of the material continuously increases over time, finally reaching approximately 4.8 g at 16:48, indicating that the material can achieve multiple continuous adsorption and desorption cycles throughout the entire test period, demonstrating good reusability. Combined with the liquid water data collected by the device's condensation, it can be seen that the material can still efficiently produce water in a dry environment with an average relative humidity of 30-50%, verifying its practicality under low-humidity conditions. In short, the above fully demonstrates that the biomass nitrogen-doped derived porous carbon material prepared in this invention not only possesses a high specific surface area and abundant nitrogen active sites, but also exhibits excellent photothermal conversion capabilities, enabling efficient and stable outdoor atmospheric water collection under natural light and low humidity environments, showcasing excellent practical application potential.

[0159] In summary, this invention leverages the superior properties of biomass nitrogen-doped porous carbon, employing efficient carbonization and acid treatment strategies to regulate both chemical properties and pore structure through quantitative changes in nitrogen content. This results in a biomass-derived porous carbon material with excellent hygroscopic properties and photothermal conversion capabilities, demonstrating significant application potential in atmospheric water collection. Furthermore, by combining this porous carbon material with a rapid atmospheric water collection device, atmospheric moisture can be effectively collected in arid regions. Moreover, this method is convenient to operate, inexpensive to manufacture, easily scalable, and highly practical.

[0160] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing biomass nitrogen-doped derived porous carbon materials, characterized in that, Includes the following steps: A carbon source and a nitrogen source are added to water and subjected to an ultrasonic reaction, followed by hydrothermal treatment to obtain a solid product; the mass ratio of the carbon source to the nitrogen source is 1:(2-5). The solid product and metal salt were mixed and ground, and then vapor etched and high-temperature annealed under an inert atmosphere. Then, acid treatment, grinding and drying were performed in sequence to prepare the biomass nitrogen-doped derived porous carbon material. The carbon source is selected from chitosan or cellulose; The nitrogen source is selected from at least one of urea, melamine, aniline or imidazole; The metal salt is zinc chloride hexahydrate; the mass ratio of the solid product to zinc chloride hexahydrate is 1:(1-5). The conditions for the hydrothermal treatment are: hydrothermal treatment at a temperature of 160-200℃ for 15-25 hours; The conditions for vapor etching and high-temperature annealing are as follows: the temperature is increased to 600-900℃ at a heating rate of 2-7℃ / min, and then vapor etching and high-temperature annealing are performed at this temperature for 1-2 hours.

2. The method for preparing a biomass nitrogen-doped derived porous carbon material according to claim 1, characterized in that, The carbon source is chitosan, and the nitrogen source is urea.

3. The method for preparing a biomass nitrogen-doped derived porous carbon material according to claim 1, characterized in that, The conditions for the ultrasonic response are: ultrasonication at a frequency of 30-40 kHz for 30-60 minutes.

4. A biomass nitrogen-doped derived porous carbon material, characterized in that, Prepared by the preparation method according to any one of claims 1-3; The biomass nitrogen-doped derived porous carbon material contains 5.6-8.36% nitrogen by molar percentage and has a micropore volume of 0.16-0.61 cm³. 3 / g; specific surface area is 343.16-1041.28m² 2 / g.

5. The application of the biomass nitrogen-doped porous carbon material as described in claim 4 in the field of atmospheric water collection.

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