Preparation method of alumina-loaded hydrogen-substituted graphdiyne composite material

Abstract

The invention relates to a preparation method of an alumina-loaded hydrogen-substituted graphdiyne composite material, and belongs to the technical field of gas sensors. According to the prepared aluminum oxide loaded hydrogen-substituted graphite alkyne composite material, aluminum oxide powder is uniformly and discretely distributed on hydrogen-substituted graphite alkyne through the anchoring effect of an alkyne bond, and the composite material with a large specific surface area is formed. The structure is beneficial to adsorption of more gas molecules and transmission of carriers in a gas sensitive test process, and more active sites are provided for target gas, so that the detection sensitivity of NH3 gas is remarkably improved.

Description

Technical Field

[0001] This application relates to the field of gas sensor technology, and in particular to a method for preparing an alumina-supported hydrogen-substituted graphite monoacetylene composite material. Background Technology

[0002] The core of a gas sensor is the sensing material. In recent years, two-dimensional (2D) materials, represented by graphene, have attracted widespread attention in the field of gas sensing due to their huge specific surface area and high electron mobility. Hydrogen-substituted graphitic monoacetylene (HsGY), as a novel two-dimensional carbon material, consists of a planar network structure composed of sp and sp² hybridized carbon atoms. First-principles calculations show that HsGY exhibits stronger adsorption energy and charge transfer ability for small molecule gases such as NH3 than graphene, indicating its excellent gas sensing potential. Experimental studies have also confirmed that HsGY has a high intrinsic conductivity and has been preliminarily applied to the detection of NH3 at room temperature. However, the response signal of pure HsGY material to gases is still limited; for example, its response value to 100 ppm NH3 is only about 4.9.

[0003] On the other hand, alumina (Al2O3) is another classic gas-sensitive material. Alumina possesses excellent thermal stability, chemical stability, and a large specific surface area, providing abundant active sites for gas molecule adsorption. However, pure alumina nanoparticles are prone to agglomeration during preparation and use, leading to a significant decrease in effective specific surface area; simultaneously, its intrinsic conductivity is poor. These factors combined result in sensors based on pure alumina typically exhibiting low sensitivity, high operating temperatures, or slow response recovery speeds.

[0004] To overcome the performance limitations of single materials, constructing heterojunction composites has become an effective strategy. Theoretically, combining highly conductive HsGY with alumina, which has rich surface properties, holds promise for achieving complementary advantages. However, how to achieve uniform and highly dispersed loading of alumina on the HsGY surface through a simple and controllable preparation method, thereby maximizing the heterojunction interface effect and ultimately obtaining a high-performance NH3 gas-sensitive material at room temperature, remains a technical challenge that needs to be solved. Summary of the Invention

[0005] This application provides a method for preparing an alumina-supported hydrogen-substituted graphitic monoacetylene composite material to solve the following technical problem: how to achieve high dispersion loading of alumina on the HsGY surface. This application provides a method for preparing an alumina-supported hydrogen-substituted graphene monoacetylene composite material, the method comprising: An organic phase containing 1,3,5-triethynylbenzene and an aqueous phase containing 1,3,5-tribromobenzene are brought into contact to carry out an interfacial polymerization reaction to obtain hydrogen-substituted graphitic monoacetylene. The hydrogen-substituted graphitic monoacetylene was ground to obtain hydrogen-substituted graphitic monoacetylene nanopowder. Aluminum chloride hexahydrate, carbonate, glycerol, and solvent are mixed to obtain an aluminum chloride solution; Polyvinylpyrrolidone and the hydrogen-substituted graphitic monoacetylene nanoparticles were added to the aluminum chloride solution to obtain a first mixture. The first mixture was subjected to a first hydrothermal reaction, ultrasonic treatment, and a second hydrothermal reaction in sequence to obtain a second reaction product. The second reaction product was washed and vacuum dried sequentially to obtain the dried product. The dried product was calcined to obtain an alumina-supported hydrogen-substituted graphite monoacetylene composite material.

[0006] Optionally, the organic phase is prepared by dissolving 1,3,5-triethynylbenzene in chloroform; the aqueous phase is prepared by adding cuprous iodide, palladium dichloride of bis(triphenylphosphine)phosphine and 1,3,5-tribromobenzene to pure water.

[0007] Optionally, the mass ratio of the 1,3,5-triethynylbenzene to the volume ratio of the chloroform is (1-3) mg: 1 mL; The mass ratio of the bis(triphenylphosphine)-phosphine-palladium dichloride to the 1,3,5-triethynylbenzene is (0.25–0.5):1; The mass ratio of cuprous iodide to 1,3,5-triethynylbenzene is (0.1-0.2):1; The mass ratio of the 1,3,5-tribromobenzene to the 1,3,5-triethynylbenzene is (2-2.1):1.

[0008] Optionally, the interfacial polymerization reaction time is 72h to 96h.

[0009] Optionally, the aluminum chloride solution is prepared by mixing and stirring aluminum trichloride hexahydrate, carbonate, glycerol and distilled water for 3 to 5 hours; wherein the weight ratio of aluminum trichloride hexahydrate, carbonate, glycerol and distilled water is (20 to 25): (15 to 20): (5 to 7): (100 to 105).

[0010] Optionally, the step of mixing aluminum trichloride hexahydrate, carbonate, glycerol, and a solvent to obtain an aluminum chloride solution includes: Aluminum chloride hexahydrate, carbonate, glycerol, and solvent are mixed to obtain an aluminum chloride solution; The pH of the aluminum chloride solution is adjusted to 8–8.5 using a sodium hydroxide solution; wherein the molar concentration of the sodium hydroxide solution is 0.05 mol / L–0.15 mol / L.

[0011] Optionally, the mass ratio of the polyvinylpyrrolidone to the hydrogen-substituted graphitic monoacetylene nanopowder is (50-100):1.

[0012] Optionally, the temperature of the first hydrothermal reaction is 155℃~175℃, and the time of the first hydrothermal reaction is 36h~60h.

[0013] Optionally, the ultrasonic treatment time is 30 min to 60 min.

[0014] Optionally, the temperature of the second hydrothermal reaction is 200℃~250℃, and the time of the second hydrothermal reaction is 18h~30h.

[0015] Optionally, the washing includes washing the second reaction product with ethanol 3 to 5 times, and then washing the second reaction product with distilled water 3 to 5 times.

[0016] Optionally, the vacuum drying temperature is 80℃~120℃, and the vacuum drying time is 12h~36h.

[0017] Optionally, the calcination temperature is 300℃~500℃, and the calcination time is 5h~7h.

[0018] The technical solutions provided in this application have the following advantages compared with the prior art: This application provides a method for preparing an alumina-supported hydrogen-substituted graphitic monoacetylene composite material. The method includes: contacting an organic phase containing 1,3,5-triethynylbenzene and an aqueous phase containing 1,3,5-tribromobenzene to perform an interfacial polymerization reaction to obtain hydrogen-substituted graphitic monoacetylene; grinding the hydrogen-substituted graphitic monoacetylene to obtain hydrogen-substituted graphitic monoacetylene nanoparticles; mixing aluminum trichloride hexahydrate, carbonate, glycerol, and a solvent to obtain an aluminum chloride solution; adding polyvinylpyrrolidone and the hydrogen-substituted graphitic monoacetylene nanoparticles to the aluminum chloride solution to obtain a first mixture; subjecting the first mixture to a first hydrothermal reaction, ultrasonic treatment, and a second hydrothermal reaction sequentially to obtain a second reaction product; washing and vacuum drying the second reaction product sequentially to obtain a dried product; and calcining the dried product to obtain the alumina-supported hydrogen-substituted graphitic monoacetylene composite material. The carbon-carbon triple bonds in the two-dimensional carbon network of hydrogen-substituted graphitic monoacetylene (HsGY) have high π electron density and reactivity, and can serve as Lewis base sites. In a hydrothermal reaction system, aluminum source precursors (such as Al produced by the hydrolysis of aluminum trichloride hexahydrate) 3+Aluminum oxide ions (or the formed aluminum hydroxyl clusters) act as Lewis acids, preferentially engaging in strong coordination interactions or chemisorption with these high-electron-density carbon-carbon triple bond sites. This interaction specifically and firmly anchors aluminum species to the two-dimensional framework of HsGY at the molecular level. This chemical anchoring mechanism fundamentally inhibits the spontaneous aggregation of alumina nanoparticles due to their high surface energy, forcing the alumina nanoparticles to undergo in-situ crystallization growth centered on the anchored location of the aluminum source precursor. Ultimately, this achieves high-density loading of alumina particles on the HsGY surface in a uniform size and spatially discrete state. This composite material not only solves the problem of low sensitivity of HsGY but also overcomes the defect of easy alumina powder aggregation, providing a new and effective approach for high-sensitivity detection of NH3. Attached Figure Description

[0019] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 The SEM image provided in Embodiment 1 of this application. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0023] The range descriptions used herein, such as numerical ranges and proportional ranges, include all possible sub-ranges and single numerical values ​​within that range. For example, the range descriptions of "1 to 6" or "1~6" cover all sub-ranges (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6) between 1 and 6. Unless otherwise specified, the terms "including" and "contains" as used herein mean "including but not limited to"; relational terms such as "first" and "second" are used only to distinguish different entities or operations and do not imply an actual order or relationship; "and / or" indicates that multiple situations can exist individually or simultaneously; expressions such as "at least one," "multiple," and "at least one" refer to any combination of the corresponding objects, including combinations of single or multiple objects. The proportional relationships mentioned herein, such as mass ratios and molar ratios, should be understood as the correspondence between the first and second terms of a proportional formula, according to the order of description. The raw materials, reagents, instruments, and equipment used herein can all be obtained through commercial purchase or prepared using existing methods.

[0024] This application provides a method for preparing an alumina-supported hydrogen-substituted graphene monoacetylene composite material, the method comprising: An organic phase containing 1,3,5-triethynylbenzene and an aqueous phase containing 1,3,5-tribromobenzene are brought into contact to carry out an interfacial polymerization reaction to obtain hydrogen-substituted graphitic monoacetylene. The hydrogen-substituted graphitic monoacetylene was ground to obtain hydrogen-substituted graphitic monoacetylene nanopowder. Aluminum chloride hexahydrate, carbonate, glycerol, and solvent are mixed to obtain an aluminum chloride solution; Polyvinylpyrrolidone and the hydrogen-substituted graphitic monoacetylene nanoparticles were added to the aluminum chloride solution to obtain a first mixture. The first mixture was subjected to a first hydrothermal reaction, ultrasonic treatment, and a second hydrothermal reaction in sequence to obtain a second reaction product. The second reaction product was washed and vacuum dried sequentially to obtain the dried product. The dried product was calcined to obtain an alumina-supported hydrogen-substituted graphite monoacetylene composite material.

[0025] This application utilizes the alkyne bonds in hydrogen-substituted graphitic monoacetylene (HsGY) as anchoring points to uniformly and discretely fix alumina powder onto the HsGY surface, forming an alumina-supported hydrogen-substituted graphitic monoacetylene composite material. This structure not only prevents alumina agglomeration but also maximizes the interfacial contact between alumina and HsGY, effectively improving carrier density and charge transfer efficiency. The large specific surface area of ​​the alumina-supported hydrogen-substituted graphitic monoacetylene composite material provides more adsorption sites for NH3 molecules, while the synergistic effect between HsGY and alumina enhances the material's response to NH3, significantly improving the sensor's sensitivity.

[0026] In some embodiments, the organic phase is prepared by dissolving 1,3,5-triethynylbenzene in chloroform; and the aqueous phase is prepared by adding cuprous iodide, palladium dichloride of bis(triphenylphosphine)phosphine and 1,3,5-tribromobenzene to pure water.

[0027] One monomer (1,3,5-triethynylbenzene) is dissolved in the organic solvent chloroform, while another monomer (1,3,5-tribromobenzene) and a catalyst are dissolved in water. Since chloroform and water are immiscible, a clear physical interface naturally forms when the organic and aqueous phases come into contact. 1,3,5-Triethynylbenzene and 1,3,5-tribromobenzene are respectively confined to the organic and aqueous bulk phases on either side of the interface. The polymerization reaction can only occur at the interface between the two phases, which is a prerequisite for achieving controllable interfacial polymerization.

[0028] In some embodiments, the mass ratio of the 1,3,5-triethynylbenzene to the volume ratio of the chloroform is (1-3) mg: 1 mL; The mass ratio of the bis(triphenylphosphine)-phosphine-palladium dichloride to the 1,3,5-triethynylbenzene is (0.25–0.5):1; The mass ratio of cuprous iodide to 1,3,5-triethynylbenzene is (0.1-0.2):1; The mass ratio of the 1,3,5-tribromobenzene to the 1,3,5-triethynylbenzene is (2-2.1):1.

[0029] The mass-to-volume ratio of 1,3,5-triethynylbenzene to chloroform (1–3) mg:1 mL defines the concentration range of 1,3,5-triethynylbenzene monomer in the organic phase, ensuring that the concentration of 1,3,5-triethynylbenzene in the organic phase is at an appropriate level. This concentration level is fundamental to ensuring the efficient progress of subsequent interfacial polymerization. When the mass-to-volume ratio of 1,3,5-triethynylbenzene to chloroform is (1–3) mg:1 mL, the 1,3,5-triethynylbenzene in the organic phase can migrate to the interface of the two phases at an appropriate diffusion rate when the organic phase containing 1,3,5-triethynylbenzene is contacted with the aqueous phase containing 1,3,5-tribromobenzene. This diffusion rate is conducive to a full and orderly reaction with the 1,3,5-tribromobenzene monomer from the aqueous phase at the interface, thereby promoting the formation of structurally regular and quality-stable hydrogen-substituted graphitic monoacetylene. If the mass-to-volume ratio of 1,3,5-triethynylbenzene to chloroform is less than 1 mg to 1 mL, the monomer concentration in the organic phase is too low, which may lead to a slow interfacial polymerization rate or insufficient yield of the generated hydrogen-substituted graphitic monoacetylene. If the mass-to-volume ratio of 1,3,5-triethynylbenzene to chloroform is higher than 3 mg to 1 mL, the monomer concentration in the organic phase is too high, which may lead to an overly rapid interfacial polymerization reaction, uneven product structure, or side reactions. Furthermore, controlling the mass-to-volume ratio of 1,3,5-triethynylbenzene to chloroform helps optimize the physical morphology of the hydrogen-substituted graphitic monoacetylene. When the mass-to-volume ratio of 1,3,5-triethynylbenzene to chloroform is (1–3) mg:1 mL, the thickness and size of the generated hydrogen-substituted graphitic monoacetylene are more easily converted into well-dispersed hydrogen-substituted graphitic monoacetylene nanoparticles through grinding in subsequent steps.

[0030] The mass ratio of palladium dichloride to 1,3,5-triethynylbenzene was (0.25–0.5):1, directly determining the concentration of the palladium dichloride catalyst in the aqueous phase. Palladium dichloride is the core catalyst for the coupling reaction (Sonogashira reaction) between 1,3,5-triethynylbenzene and 1,3,5-tribromobenzene. When the organic phase is in contact with the aqueous phase, the palladium dichloride at the interface effectively catalyzes the polymerization of 1,3,5-triethynylbenzene from the organic phase and 1,3,5-tribromobenzene from the aqueous phase, producing hydrogen-substituted graphitic monoyne. Maintaining the mass ratio of palladium dichloride to 1,3,5-triethynylbenzene within the range of (0.25–0.5):1 ensures a sufficient and appropriate amount of catalytically active centers. This ratio ensures that the interfacial polymerization reaction has a sufficient reaction rate, which can be carried out efficiently and fully within a reaction time of 72h to 96h, thereby obtaining hydrogen-substituted graphitic monoacetylene with high yield and high structural regularity.

[0031] The concentration of cuprous iodide in the aqueous phase was determined by a mass ratio of cuprous iodide to 1,3,5-triethynylbenzene of (0.1–0.2):1. Cuprous iodide is an indispensable co-catalyst in interfacial polymerization reactions, synergistically acting with palladium dichloride dichloride to catalyze the coupling reaction between 1,3,5-triethynylbenzene and 1,3,5-tribromobenzene. When the organic phase comes into contact with the aqueous phase, cuprous iodide assists in the generation and recycling of active species, thereby promoting the efficient synthesis of hydrogen-substituted graphitic monoacetylene. If the mass ratio of cuprous iodide to 1,3,5-triethynylbenzene is less than 0.1:1, the amount of cuprous iodide used is relatively insufficient, which may lead to a decrease in catalytic efficiency, a slowdown in the interfacial polymerization rate, or insufficient degree of polymerization of the product. If the mass ratio of cuprous iodide to 1,3,5-triethynylbenzene is greater than 0.2:1, excess cuprous iodide may lead to increased side reactions, higher costs, and may introduce more metal impurities into the final product.

[0032] 1,3,5-Tribromobenzene is a comonomer that undergoes a coupling reaction with 1,3,5-triethynylbenzene in an organic phase to construct a hydrogen-substituted graphitic monoacetylene network. When the organic phase comes into contact with the aqueous phase, 1,3,5-tribromobenzene migrates to the interface and reacts with 1,3,5-triethynylbenzene in the presence of a catalyst. The mass ratio of 1,3,5-tribromobenzene to 1,3,5-triethynylbenzene is controlled within the range of (2–2.1):1 to provide a near-stoichiometric, slightly surplus, amount of 1,3,5-tribromobenzene monomer. This quantitative relationship helps drive the interfacial polymerization reaction as completely as possible towards the formation of hydrogen-substituted graphitic monoacetylene, thereby obtaining higher yields and more complete chemical structures of hydrogen-substituted graphitic monoacetylene. If the mass ratio of 1,3,5-tribromobenzene to 1,3,5-triethynylbenzene is less than 2:1, then there will be a relative deficiency of 1,3,5-tribromobenzene, which may lead to incomplete interfacial polymerization. Some 1,3,5-triethynylbenzene will fail to participate in the reaction, affecting the degree of polymerization and structural integrity of the hydrogen-substituted graphitic monoacetylene. If the mass ratio of 1,3,5-tribromobenzene to 1,3,5-triethynylbenzene is greater than 2.1:1, then there will be an excessive amount of 1,3,5-tribromobenzene, which will not only waste raw materials but may also increase the burden of subsequent purification or introduce unnecessary by-products.

[0033] In some embodiments, the interfacial polymerization reaction takes 72 to 96 hours.

[0034] After preparing the organic and aqueous phases, they were transferred to a reaction vessel to form a stable interface. The interfacial polymerization reaction was continued while maintaining contact between the organic and aqueous phases, with the total reaction time controlled within the range of 72 to 96 hours. This 72- to 96-hour reaction time provides sufficient time for the catalytic coupling reaction between 1,3,5-triethynylbenzene in the organic phase and 1,3,5-tribromobenzene in the aqueous phase at the interface. This reaction is a stepwise polymerization process, requiring sufficient time for monomer molecules to diffuse fully to the interface, react, and for the resulting polymer chains / networks to extend and grow in an orderly manner, thereby forming a hydrogen-substituted graphitic monoacetylene film or solid with a regular two-dimensional structure. Furthermore, controlling the interfacial polymerization reaction time within the range of 72 to 96 hours is a necessary condition for obtaining hydrogen-substituted graphitic monoacetylene with high molecular weight and high structural integrity. If the interfacial polymerization reaction time is less than 72 hours, the reaction may be incomplete, resulting in low degree of polymerization, numerous structural defects, or a significant decrease in yield of the generated hydrogen-substituted graphitic monoacetylene. If the interfacial polymerization reaction time exceeds 96 hours, although the reaction may be more complete, the benefit of extending the time to improve the product structure and quality is limited. At the same time, it will reduce process efficiency, increase energy consumption, and long-term reactions may be accompanied by unnecessary side reactions or solvent evaporation.

[0035] In some embodiments, the aluminum chloride solution is prepared by mixing and stirring aluminum trichloride hexahydrate, carbonate, glycerol and distilled water for 3 to 5 hours; wherein the weight ratio of aluminum trichloride hexahydrate, carbonate, glycerol and distilled water is (20 to 25): (15 to 20): (5 to 7): (100 to 105).

[0036] Aluminum trichloride hexahydrate serves as a precursor for providing aluminum ions, and its weight percentage determines the potential loading of alumina. The optimized homogeneous solution system, consisting of aluminum trichloride hexahydrate, carbonate, glycerol, and distilled water at a weight ratio of (20–25):(15–20):(5–7):(100–105), lays the foundation for effective subsequent composite with hydrogen-substituted graphitic monoacetylene nanoparticles. A mixing and stirring time of 3 to 5 hours is necessary to ensure complete dissolution and full interaction of all components, forming a homogeneous and stable aluminum chloride solution. Sufficient stirring time ensures complete ionization of aluminum trichloride hexahydrate, and sufficient dispersion and function of carbonate and glycerol, avoiding localized concentration differences due to uneven mixing. This ensures uniform loading and growth of the alumina precursor on the hydrogen-substituted graphitic monoacetylene nanoparticles in subsequent steps. If the ratio of aluminum trichloride hexahydrate, carbonate, glycerol, and distilled water, or the stirring time deviates from the range required in the embodiments of this application, it may adversely affect subsequent steps. For example, if the amount of aluminum trichloride hexahydrate is too low or the amount of distilled water is too high, the solution concentration will be too dilute, which may lead to insufficient alumina loading in the final composite material. Conversely, it may lead to supersaturation of the solution, resulting in uneven precipitation when preparing or subsequently adding hydrogen-substituted graphitonium nanoparticles. If the stirring time is insufficient, the solution will be uneven, affecting the uniformity of the composite material; if the stirring time is too long, the process efficiency will be reduced.

[0037] In some embodiments, the mixing of aluminum trichloride hexahydrate, carbonate, glycerol, and solvent to obtain an aluminum chloride solution includes: Aluminum chloride hexahydrate, carbonate, glycerol, and solvent are mixed to obtain an aluminum chloride solution; The pH of the aluminum chloride solution is adjusted to 8–8.5 using a sodium hydroxide solution; wherein the molar concentration of the sodium hydroxide solution is 0.05 mol / L–0.15 mol / L.

[0038] Precisely adjusting the pH of the aluminum chloride solution to a weakly alkaline range of 8–8.5 is a crucial step in controlling the hydrolysis behavior of aluminum species and their subsequent precipitation forms. Under pH conditions of 8–8.5, the aluminum ions (Al2O3) in the aluminum chloride solution... 3+Controllable hydrolysis and preliminary condensation begin, forming specific aluminum hydroxide complexes or sols, but large-scale precipitation has not yet occurred. This provides an ideal thermodynamic starting point and reaction precursor state for the uniform and slow deposition of the alumina precursor on the surface of the hydrogen-substituted graphitic monoacetylene nanoparticles in the subsequent first hydrothermal reaction. If the final pH of the aluminum chloride solution is below 8, the degree of hydrolysis of aluminum species is insufficient, which may lead to incomplete alumina formation or weak binding force with hydrogen-substituted graphitic monoacetylene in the subsequent hydrothermal reaction; if the final pH of the aluminum chloride solution is above 8.5, aluminum species may prematurely form precipitates that are difficult to redisperse, destroying the homogeneity of the solution and affecting the uniformity of the composite material. Adjustment with a sodium hydroxide solution of concentrations from 0.05 mol / L to 0.15 mol / L is used to achieve precise and gradual pH control. Sodium hydroxide solutions with concentrations of 0.05 mol / L to 0.15 mol / L allow for a slower and more uniform rate of alkali addition, avoiding the instantaneous rapid precipitation of aluminum species or the formation of uneven coarse particles due to excessively high local pH, thereby ensuring the homogeneity and stability of the aluminum chloride solution system.

[0039] In some embodiments, the mass ratio of the polyvinylpyrrolidone to the hydrogen-substituted graphitic monoacetylene nanoparticles is (50-100):1.

[0040] Polyvinylpyrrolidone (PVP), as a high-molecular-weight surfactant, primarily functions by adsorbing onto the surface of hydrogen-substituted graphitic monoacetylene nanoparticles. Through steric hindrance, it prevents the aggregation of these nanoparticles, thereby achieving uniform and stable dispersion in aluminum chloride solution. Maintaining the mass ratio of PPVP to hydrogen-substituted graphitic monoacetylene nanoparticles within the range of 50:1 to 100:1 ensures a sufficient number of PPVP molecules completely coat the surface of each nanoparticle, achieving optimal dispersion and creating a uniform physical environment for the subsequent hydrothermal reaction and the uniform nucleation and growth of alumina on the surface of the hydrogen-substituted graphitic monoacetylene nanoparticles. If the mass ratio of polyvinylpyrrolidone (PVP) to hydrogen-substituted graphitic monoacetylene nanoparticles is less than 50:1, the amount of dispersant (PVP) may be relatively insufficient, failing to adequately prevent the agglomeration of the hydrogen-substituted graphitic monoacetylene nanoparticles. This results in uneven dispersion of the hydrogen-substituted graphitic monoacetylene nanoparticles in the first mixture, thus affecting the uniformity of the two-phase distribution in the final composite material. If the mass ratio of PPVP to hydrogen-substituted graphitic monoacetylene nanoparticles is greater than 100:1, although the dispersion effect may be better, excessive PPVP not only increases costs but may also generate more decomposition products during subsequent calcination, potentially having a complex impact on the purity and structure of the final alumina-supported hydrogen-substituted graphitic monoacetylene composite material.

[0041] In some embodiments, the temperature of the first hydrothermal reaction is 155°C to 175°C, and the time of the first hydrothermal reaction is 36h to 60h.

[0042] After the first mixture is prepared, it can be placed in a polytetrafluoroethylene (PTFE) high-pressure reactor. The reactor is then placed in a heating device to heat the reaction system and maintain it at a constant temperature between 155°C and 175°C, the initial hydrothermal reaction temperature. At this temperature, the first hydrothermal reaction is maintained for 36 to 60 hours.

[0043] The combination of a first hydrothermal reaction temperature of 155℃ to 175℃ and a first hydrothermal reaction time of 36 to 60 hours provides the necessary energy and time for the complete hydrolysis and condensation of the aluminum source (from aluminum chloride solution). The first hydrothermal reaction process promotes the gradual formation and uniform loading of amorphous alumina precursors on the surface and in the gaps between hydrogen-substituted graphitic monoacetylene nanoparticles. A first hydrothermal reaction temperature of 155℃ to 175℃ and a first hydrothermal reaction time of 36 to 60 hours are key steps in achieving effective and stable composite formation of alumina and hydrogen-substituted graphitic monoacetylene nanoparticles, laying the foundation for subsequent ultrasonic treatment and the second hydrothermal reaction step. If the first hydrothermal reaction temperature is below 155℃ or the first hydrothermal reaction time is less than 36 hours, incomplete hydrolysis of the aluminum source may occur, resulting in a loose composite structure; if the first hydrothermal reaction temperature is above 175℃ or the first hydrothermal reaction time is longer than 60 hours, excessive energy consumption or unnecessary phase transitions and agglomeration may occur.

[0044] In some embodiments, the ultrasonic treatment time is 30 min to 60 min.

[0045] After the first hydrothermal reaction is completed, the first hydrothermal reaction product is obtained. The first hydrothermal reaction product is placed in an ultrasonic treatment device, the ultrasonic treatment device is started, and ultrasonic waves are continuously applied to the first hydrothermal reaction product, with the ultrasonic treatment time controlled within the range of 30 to 60 minutes.

[0046] Ultrasonic treatment utilizes cavitation and mechanical vibration to redisperse solid particles that may agglomerate during the first hydrothermal reaction. An ultrasonic treatment time of 30 to 60 minutes provides the necessary duration to fully disperse agglomerates, allowing the hydrogen-substituted graphitic monoacetylene nanoparticles and alumina precursor to achieve a uniform distribution in the liquid phase. Secondly, thorough dispersion helps increase the active surface area. After 30 to 60 minutes of ultrasonic treatment, the contact interface between the hydrogen-substituted graphitic monoacetylene nanoparticles and the alumina precursor is optimized, creating more uniform starting conditions for further bonding and crystal growth in the subsequent second hydrothermal reaction step. If the ultrasonic treatment time is less than 30 minutes, incomplete dispersion may result in some agglomerates remaining, affecting the uniformity and performance of the final alumina-supported hydrogen-substituted graphitic monoacetylene composite. If the ultrasonic treatment time exceeds 60 minutes, excessive ultrasonic energy input may cause structural damage to the hydrogen-substituted graphitic monoacetylene nanoparticles or unnecessary phase transitions in the alumina precursor, and increase process energy consumption. Therefore, the ultrasonic treatment time is controlled between 30 and 60 minutes to achieve a balance between effective dispersion and material integrity.

[0047] In some embodiments, the temperature of the second hydrothermal reaction is 200°C to 250°C, and the time of the second hydrothermal reaction is 18h to 30h.

[0048] The combination of a second hydrothermal reaction temperature of 200℃ to 250℃ and a second hydrothermal reaction time of 18 to 30 hours creates a high-temperature and high-pressure crystallization and maturation environment. This environment promotes the complete dehydration, condensation, and phase transformation of the amorphous or low-crystallinity alumina precursor formed in the first hydrothermal reaction, transforming it into an alumina phase with higher crystallinity and greater thermodynamic stability. Simultaneously, the high-temperature and high-pressure environment further strengthens the interfacial bonding between alumina and hydrogen-substituted graphitic monoacetylene nanoparticles. If the second hydrothermal reaction temperature is below 200℃ or the second hydrothermal reaction time is less than 18 hours, it may lead to incomplete alumina crystallization, excessively small grain size, or insufficient structural stability, affecting the final properties of the composite material. If the second hydrothermal reaction temperature is above 250℃ or the second hydrothermal reaction time exceeds 30 hours, it may lead to undesirable phase transformations in alumina (such as transformation to the α-phase), excessive grain growth, or thermal damage to the carbon framework structure of the hydrogen-substituted graphitic monoacetylene nanoparticles.

[0049] In some embodiments, the washing includes washing the second reaction product with ethanol 3 to 5 times, and then washing the second reaction product with distilled water 3 to 5 times.

[0050] The initial ethanol washing aims to effectively remove residual organic solvents, unreacted organic monomers, polymeric dispersants (polyvinylpyrrolidone), and other organic byproducts from the second reaction product. Ethanol, as a polar organic solvent, has excellent solubility for these organic compounds. Subsequent distilled water washing aims to thoroughly remove residual inorganic salt ions (such as chloride ions, sodium ions, etc.), water-soluble small molecules, and other water-soluble impurities from the second reaction product. Distilled water washing avoids introducing new impurities. The number of washes, ranging from 3 to 5, strikes a balance between cleaning effectiveness and operational efficiency. Three washes are the minimum effective number, ensuring basic impurity removal; five washes achieve more thorough cleaning, ensuring the purity of the final product. Fewer than three washes may result in incomplete cleaning, with residual impurities affecting subsequent drying and calcination steps and impairing the performance of the final alumina-supported hydrogen-substituted graphene monoacetylene composite. More than five washes offer limited improvement in cleaning effectiveness but significantly increase solvent consumption and process time, reducing efficiency.

[0051] In some embodiments, the vacuum drying temperature is 80°C to 120°C, and the vacuum drying time is 12h to 36h.

[0052] The combination of vacuum drying temperatures of 80°C to 120°C and vacuum drying times of 12 to 36 hours provides the necessary conditions for the thorough and gentle removal of physically adsorbed moisture and ethanol solvent from washed solids. In a vacuum environment, the boiling point of the solvent decreases, allowing for effective evaporation within the 80°C–120°C temperature range, while avoiding thermal shock or damage to the material structure that could occur due to excessively high temperatures. If the vacuum drying temperature is below 80°C or the vacuum drying time is less than 12 hours, incomplete solvent removal may occur, and residual solvent or moisture may cause adverse reactions or affect product purity in subsequent calcination steps. If the vacuum drying temperature is above 120°C, although the drying rate may be accelerated, excessively high temperatures may cause localized oxidation or structural changes in hydrogen-substituted graphitic monoacetylene nanoparticles. If the vacuum drying time exceeds 36 hours, the increase in drying efficiency is limited, but the process efficiency will be significantly reduced.

[0053] In some embodiments, the calcination temperature is 300℃ to 500℃, and the calcination time is 5h to 7h.

[0054] After vacuum drying, the dried product is obtained. The dried product is then placed in a calcination apparatus. Under an air or oxygen atmosphere, the calcination apparatus is started, and the furnace temperature is raised to a calcination temperature range of 300°C to 500°C, and maintained at this temperature for 5 to 7 hours. After calcination, the product is naturally cooled to room temperature to obtain the final alumina-supported hydrogen-substituted graphitic monoacetylene composite material. The combination of a calcination temperature of 300°C to 500°C and a calcination time of 5 to 7 hours provides the necessary thermal oxidation conditions for the complete decomposition and removal of residual organic components (such as polyvinylpyrrolidone, carbonates, glycerol, etc.) from the dried product. The calcination process completely burns away the organic template agents and additives in the composite material, leaving a pure inorganic / carbon composite skeleton. Secondly, the calcination temperature is 300℃~500℃, and the calcination time is 5h~7h. This promotes the final dehydration and crystal transformation of the alumina precursor in the dried product, forming an alumina component with a stable crystalline phase (such as γ-Al2O3) and a high specific surface area. Simultaneously, the temperature range of 300℃~500℃ ensures that the carbon framework structure of the hydrogen-substituted graphdiyne nanoparticles is not destroyed by excessively high temperatures (graphdiyne materials have limited high-temperature stability), thus achieving a stable composite of alumina and the carbon network. If the calcination temperature is below 300℃ or the calcination time is less than 5 hours, it may lead to residual organic matter, insufficient alumina crystallization, or insufficient structural stability of the composite material. If the calcination temperature is above 500℃, it may severely damage or even ablate the carbon network structure of the hydrogen-substituted graphdiyne, leading to the loss of key properties such as conductivity in the composite material; a calcination time exceeding 7 hours may cause excessive alumina grain growth or phase transformation, and unnecessarily increase energy consumption.

[0055] The present application is further illustrated below with reference to specific embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national / industry standards; if there is no corresponding national / industry standard, they are performed according to general international standards, conventional conditions, or conditions recommended by the manufacturer.

[0056] Example 1 Step 1: Preparation of hydrogen-substituted graphitic monoacetylene (HsGY) powder: 200 mg of 1,3,5-triethynylbenzene was uniformly dissolved in 150 mL of chloroform to form an organic phase. 150 mL of pure water was slowly poured along the inner wall of the reactor, forming a clear two-phase interface. Subsequently, an aqueous solution containing 100 mg of palladium dichloride bis(triphenylphosphine), 30 mg of cuprous iodide, and 420 mg of 1,3,5-tribromobenzene was added to the aqueous phase. The entire system was allowed to react in air at room temperature (25 °C) for 96 hours. After the reaction was complete, the product at the interface was collected. The product was then ground in a mortar for 5 min to obtain HsGY powder.

[0057] Step 2: Synthesis of alumina-supported hydrogen-substituted graphite monoacetylene composite material: Weigh 25 g of aluminum trichloride hexahydrate, 15 g of carbonate, and 5 g of glycerol, dissolve them in 100 mL of distilled water, and stir for 3 h to obtain an aluminum chloride solution. Adjust the pH of the solution to 8 with 0.05 mol / L NaOH. Then, add 0.5 g of polyvinylpyrrolidone and 10 mg of HsGY powder prepared in step one to the solution. Transfer the mixture to a high-pressure reactor lined with polytetrafluoroethylene and carry out the first hydrothermal reaction at 155 °C for 36 h. After the reaction, allow it to cool naturally to obtain a milky white suspension. Sonicate the suspension at room temperature for 30 minutes, then transfer it to a stainless steel high-pressure vessel and carry out the second hydrothermal reaction at 200 °C for 18 h. After cooling to room temperature, wash the product three times with anhydrous ethanol and deionized water, and dry it in a vacuum drying oven at 80 °C for 12 h. Finally, calcine the dried solid in a muffle furnace at 300 °C for 5 h. After natural cooling, the alumina-supported hydrogen-substituted graphitic monoacetylene composite material is obtained.

[0058] Example 2: Preparation of composite materials with varying HsGY addition amounts The preparation steps were basically the same as in Example 1, except that in step two, the amount of polyvinylpyrrolidone added was 0.75 g, and the amount of HsGY powder added was 20 mg. All other parameters (pH, temperature, time, reagent dosage) remained the same as in Example 1.

[0059] Example 3: Preparation of composite materials with altered hydrothermal reaction conditions The preparation steps are basically the same as in Example 1, except for the hydrothermal parameters in step two: the hydrothermal reaction temperature in the first step is 165℃ and the reaction time is 48 hours; the hydrothermal reaction temperature in the second step is 225℃ and the time is 24 hours; the calcination temperature is 400℃ and the time is 6 hours.

[0060] Comparative Example 1: Preparation of pure HsGY Pure HsGY powder was prepared by performing only step one of Example 1.

[0061] Comparative Example 2: Preparation of Pure Alumina The preparation steps are basically the same as step two of Example 1, except that no HsGY powder is added. All other conditions are exactly the same. Pure alumina powder is obtained.

[0062] The samples prepared in the above embodiments and comparative examples were subjected to a series of characterization and gas-sensing performance tests, and the results are as follows: Specific surface area analysis (BET): The specific surface area of ​​the sample in Example 1 reached 176.27 m². 2 / g, the specific surface area of ​​the sample in Example 2 reached 215.82 m². 2 / g, the specific surface area of ​​the sample in Example 3 reached 155.36 m². 2 / g, the specific surface area of ​​the sample in Comparative Example 1 reached 35.64 m². 2 / g, the specific surface area of ​​the sample in Comparative Example 2 reached 12.30 m² / g. 2 / g, the specific surface area of ​​the example is much higher than that of pure alumina in Comparative Example 2, which proves that the introduction of HsGY effectively inhibits the agglomeration of alumina and greatly increases the effective active surface of the material.

[0063] Gas-sensitive performance test: The sample powders from the examples and comparative examples were mixed with deionized water to form a slurry, which was then coated onto a ceramic tube with interdigitated electrodes to fabricate a side-heated gas-sensitive element. NH3 gas sensing tests were conducted at room temperature (25°C, 50% relative humidity). The response value S is defined as... Ra / Rg (For reducing gas NH3), where Ra For air resistance, Rg The resistance is the resistance when the target gas is introduced.

[0064] At a NH3 concentration of 100 ppm, the response value of the sample in Example 1 reached 4.86, the response value of the sample in Example 2 reached 6.19, and the response value of the sample in Example 3 reached 4.9. In contrast, the response value of Comparative Example 1 (pure HsGY) was 3.35, and Comparative Example 2 (pure alumina) had extremely high resistance at room temperature and its response was negligible (S was close to 1).

[0065] Appendix Figure 1 Detailed explanation: Appendix Figure 1 The image provided in Example 1 of this application shows that alumina nanoparticles are attached to the surface of HsGY in a discrete, non-aggregated state with high density.

[0066] Furthermore, one or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages: The synergistic effect between HsGY and alumina enables the composite material to achieve complementary advantages in gas-sensing properties, reaching an effect that cannot be achieved by a single material.

[0067] The composite material sensor of this invention can operate stably at room temperature without the need for an additional heating device, thus reducing energy consumption and simplifying the sensor structure.

[0068] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed in this application.

Claims

1. A method for preparing an alumina-supported hydrogen-substituted graphite monoacetylene composite material, characterized in that, The method includes: An organic phase containing 1,3,5-triethynylbenzene and an aqueous phase containing 1,3,5-tribromobenzene are brought into contact to carry out an interfacial polymerization reaction to obtain hydrogen-substituted graphitic monoacetylene. The hydrogen-substituted graphitic monoacetylene was ground to obtain hydrogen-substituted graphitic monoacetylene nanopowder. Aluminum chloride hexahydrate, carbonate, glycerol, and solvent are mixed to obtain an aluminum chloride solution; Polyvinylpyrrolidone and the hydrogen-substituted graphitic monoacetylene nanoparticles were added to the aluminum chloride solution to obtain a first mixture. The first mixture was subjected to a first hydrothermal reaction, ultrasonic treatment, and a second hydrothermal reaction in sequence to obtain a second reaction product. The second reaction product was washed and vacuum dried sequentially to obtain the dried product. The dried product was calcined to obtain an alumina-supported hydrogen-substituted graphite monoacetylene composite material.

2. The method according to claim 1, characterized in that, The organic phase is prepared by dissolving 1,3,5-triethynylbenzene in chloroform; the aqueous phase is prepared by adding cuprous iodide, palladium dichloride of bis(triphenylphosphine)phosphine and 1,3,5-tribromobenzene to pure water.

3. The method according to claim 2, characterized in that, The mass ratio of the 1,3,5-triethynylbenzene to the volume ratio of the chloroform is (1-3) mg: 1 mL; The mass ratio of the bis(triphenylphosphine)-phosphine-palladium dichloride to the 1,3,5-triethynylbenzene is (0.25–0.5):1; The mass ratio of cuprous iodide to 1,3,5-triethynylbenzene is (0.1-0.2):1; The mass ratio of the 1,3,5-tribromobenzene to the 1,3,5-triethynylbenzene is (2-2.1):

1.

4. The method according to claim 1, characterized in that, The interfacial polymerization reaction takes 72 to 96 hours.

5. The method according to claim 1, characterized in that, The aluminum chloride solution is prepared by mixing and stirring aluminum trichloride hexahydrate, carbonate, glycerol and distilled water for 3 to 5 hours; wherein the weight ratio of aluminum trichloride hexahydrate, carbonate, glycerol and distilled water is (20 to 25): (15 to 20): (5 to 7): (100 to 105).

6. The method according to claim 1, characterized in that, The process of mixing aluminum trichloride hexahydrate, carbonate, glycerol, and a solvent to obtain an aluminum chloride solution includes: Aluminum chloride hexahydrate, carbonate, glycerol, and solvent are mixed to obtain an aluminum chloride solution; The pH of the aluminum chloride solution is adjusted to 8–8.5 using a sodium hydroxide solution; wherein the molar concentration of the sodium hydroxide solution is 0.05 mol / L–0.15 mol / L.

7. The method according to claim 1, characterized in that, The mass ratio of the polyvinylpyrrolidone to the hydrogen-substituted graphitic monoacetylene nanopowder is (50-100):

1.

8. The method according to claim 1, characterized in that, The temperature of the first hydrothermal reaction is 155℃~175℃, and the time of the first hydrothermal reaction is 36h~60h; and / or, The ultrasonic treatment time is 30 min to 60 min; and / or, The temperature of the second hydrothermal reaction is 200℃~250℃, and the time of the second hydrothermal reaction is 18h~30h.

9. The method according to claim 1, characterized in that, The washing process includes washing the second reaction product with ethanol 3 to 5 times, followed by washing it with distilled water 3 to 5 times; and / or, The vacuum drying temperature is 80℃~120℃, and the vacuum drying time is 12h~36h.

10. The calcination temperature is 300℃~500℃, and the calcination time is 5h~7h.

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