Hydrogen sensor and preparation method thereof

Abstract

The invention relates to a gas sensor, and discloses a hydrogen sensor and a preparation method thereof, and the hydrogen sensor comprises a packaging shell and a substrate. The packaging shell is provided with an air inlet and an air outlet which are symmetrically arranged, and the air inlet and the air outlet are located on the two sides of the packaging shell. The substrate is arranged at the bottom in the packaging shell, the upper end of the substrate is coated with a sensing material layer, the upper surfaces of the two ends of the sensing material layer are provided with two electrodes, the ends, away from each other, of the two electrodes are connected with connecting ends respectively, the two connecting ends are connected with an external measuring circuit, the upper end of the sensing material layer is provided with a heterojunction, and the heterojunction is connected with the external measuring circuit. The heterojunction is arranged between the two electrodes, the heterojunction is flush with the upper surfaces of the two electrodes, the upper surfaces of the heterojunction and the two electrodes are covered with inorganic gas filtering membranes, and the gas inlet and the gas outlet are located above the inorganic gas filtering membranes. The inorganic gas filtering membrane is matched with the heterojunction, so that the sensitivity of the sensor is improved from two aspects of physical screening and chemical specific reaction.

Description

Technical Field

[0001] The present invention relates to a gas sensor, in particular to a hydrogen sensor and a preparation method thereof. Background Art

[0002] Currently, hydrogen energy has broad prospects as a substitute for fossil fuels, but the flammable and explosive properties of hydrogen make safe monitoring of sensors crucial.

[0003] Existing hydrogen sensor structures mainly include limiting current type hydrogen sensors, concentration cell type hydrogen sensors, and resistance type hydrogen sensors. Resistive type hydrogen sensors detect hydrogen concentration by measuring the resistance change of metal oxide semiconductor materials under different hydrogen concentrations. Their advantages are low cost and easy integration, but they have slow response speeds. The flammable and explosive nature of hydrogen makes sensitivity a non-negligible factor.

[0004] Therefore, how to improve the sensitivity of metal oxide semiconductor materials has become the current research and development focus in the field. Summary of the Invention

[0005] The technical problem to be solved by the present invention is: how to improve the sensitivity of metal oxide semiconductor materials.

[0006] In order to solve the above technical problems, the present invention provides a hydrogen sensor and a preparation method thereof.

[0007] According to a first aspect of the present invention, a hydrogen sensor is provided, comprising: a packaging shell, the packaging shell being provided with a symmetrically arranged air inlet and air outlet, the air inlet and air outlet being located on both sides of the packaging shell; a substrate, the substrate being placed at the bottom of the packaging shell, the upper end of the substrate being coated with a sensing material layer, the upper surfaces of both ends of the sensing material layer being provided with two electrodes, the ends of the two electrodes being respectively connected to connecting ends that are away from each other, the two connecting ends being connected to an external measurement circuit, the upper end of the sensing material layer being provided with a heterojunction, the heterojunction being placed between the two electrodes, the heterojunction being flush with the upper surfaces of the two electrodes, and the upper surfaces of the heterojunction and the two electrodes being covered with an inorganic gas filter membrane, the air inlet and air outlet being located above the inorganic gas filter membrane.

[0008] In one embodiment, the sensing material layer includes tin dioxide and palladium, wherein the mass proportion of tin dioxide in the sensing material layer ranges from 90% to 99%, and palladium is doped in the tin dioxide, wherein the mass proportion of palladium in the sensing material layer ranges from 0.1% to 5%.

[0009] In one embodiment, the heterojunction includes graphene and tin dioxide, the graphene covers the surface of the tin dioxide, the mass proportion of tin dioxide in the heterojunction ranges from 90% to 99%, and the mass proportion of graphene in the heterojunction ranges from 1% to 10%.

[0010] In one embodiment, the inorganic gas filtration membrane includes: aluminosilicate and a template agent, the aluminosilicate includes aluminosilicate ions and cations, the aluminosilicate ions are a three-dimensional network structure formed by silicon-oxygen tetrahedrons and aluminum-oxygen tetrahedrons sharing oxygen atoms, the cations are used to balance the negative charge of the aluminosilicate ions, and the template agent is used to guide the aluminosilicate ions to form a regular pore structure during the crystal growth process of the aluminosilicate.

[0011] The second aspect of the present invention provides a method for preparing a hydrogen sensor, the method comprising: S101, ultrasonically cleaning a silicon wafer, drying the silicon wafer to obtain a substrate; S102, adding a dopant to a tin dioxide sol and stirring the mixture evenly, coating the tin dioxide sol on the upper surface of the substrate, drying and sintering the tin dioxide sol to obtain a sensing material layer; S103, preparing electrodes on the upper surfaces of both ends of the sensing material layer; S104, mixing aluminosilicate and a template to prepare a precursor solution, and sintering the precursor solution and the covering layer; The substrate with the sensing material layer and the electrode is subjected to a hydrothermal reaction, and the precursor solution after the hydrothermal reaction is washed with water and calcined to form an inorganic gas filter membrane; S105, graphene is grown on the copper foil, the copper foil with the grown graphene is transferred to the cavity formed by the sensing material layer, the electrode and the inorganic gas filter membrane, and the copper foil is annealed to form a heterojunction; S106, the substrate with the sensing material layer, the electrode, the inorganic gas filter membrane and the heterojunction is placed in a packaging shell, the packaging shell is sealed and an air inlet and an air outlet are reserved on the packaging shell.

[0012] In one embodiment, in step S102, the step of adding a dopant to the tin dioxide sol and stirring it uniformly includes: dissolving tin tetrachloride in ethanol, adding water and hydrochloric acid as catalysts, and stirring uniformly to cause the tin tetrachloride to undergo hydrolysis and polycondensation reactions to form a transparent tin dioxide sol containing a tin dioxide precursor; dissolving palladium nitrate in a solvent to prepare a doping solution, adding the doping solution to the tin dioxide sol, and continuously stirring to uniformly disperse the palladium nitrate in the tin dioxide sol.

[0013] In one embodiment, the step of coating the tin dioxide sol on the upper surface of the substrate includes: immersing the substrate in the tin dioxide sol and pulling it up at a constant speed of 1 to 5 cm per minute so that the tin dioxide sol is evenly coated on the surface of the substrate; the step of obtaining the sensing material layer by drying and sintering includes: drying the substrate with the tin dioxide sol to evaporate the solvent to form a gel film, and sintering the substrate with the gel film to convert the tin dioxide precursor in the tin dioxide sol into a crystalline sensing material layer.

[0014] In one embodiment, step S104 includes: dissolving silica sol, sodium aluminate, and a template in water according to a preset proportion, and stirring evenly to form a transparent precursor solution; placing a substrate with a sensing material layer and an electrode into a reactor, adding the precursor solution into the reactor, sealing the reactor, placing the reactor into an oven, and performing a hydrothermal reaction to allow the substance in the precursor solution to crystallize and grow on the surface of the substrate to form a zeolite film; cooling the reactor to room temperature, removing the substrate, and rinsing the substrate with deionized water several times to remove residual impurities on the surface of the substrate and unreacted substances in the precursor solution, and then calcining the substrate for several hours to remove the residual template in the zeolite film to obtain an inorganic gas filtration membrane.

[0015] In one embodiment, step S105 includes: placing a copper foil in a reaction chamber of a chemical vapor deposition device, introducing hydrogen and methane into the reaction chamber, and causing carbon atoms produced by the decomposition of methane to deposit on the surface of the copper foil and grow into graphene; transferring the graphene from the copper foil to a substrate containing a sensing material layer and an electrode by chemical etching, and placing the substrate with the transferred graphene in a high-temperature annealing furnace for annealing for 1 to 2 hours to form a heterojunction between the graphene and the sensing material layer.

[0016] In one embodiment, when carbon atoms generated by the decomposition of methane are deposited on the surface of the copper foil and grow into graphene, the growth quality and number of growth layers of the graphene on the copper foil are controlled by controlling the flow rates of the introduced hydrogen and methane and the temperature of the reaction chamber.

[0017] Compared with the prior art, the hydrogen sensor and its preparation method according to the embodiment of the present invention have the following advantages:

[0018] The hydrogen sensor of the present invention utilizes a combination of an inorganic gas filter membrane and a heterojunction. The inorganic gas filter membrane has a unique physical structure or chemical properties that enable it to screen gas molecules, preferentially allowing the target gas to pass through while blocking interfering gases. The heterojunction, due to the unique band structure formed at the interface of two different semiconductor materials, alters the electron distribution and chemical reactivity on the sensing material surface, resulting in the sensor having stronger specific adsorption and reaction capabilities for the target gas. The combination of the two greatly improves the sensor's selectivity for the target gas from both physical screening and chemical specific reaction perspectives, effectively resolving the issue of existing resistive hydrogen sensors being susceptible to interference from other gases and consequently enhancing sensitivity. Furthermore, the present invention provides a simpler preparation method for the inorganic gas filter membrane and heterojunction, effectively shortening the preparation process and addressing the complex and inefficient preparation of deposited inorganic gas filter membranes and the difficult and costly preparation of heterojunctions. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 FIG. 1 is a schematic structural diagram of a hydrogen sensor exemplarily shown in an embodiment of the present invention.

[0020] Figure 2 FIG. 1 is an enlarged schematic diagram of the structure of a hydrogen sensor at position A, exemplarily shown in an embodiment of the present invention.

[0021] Figure 3 The figure is a flow chart of a method for preparing a hydrogen sensor according to an embodiment of the present invention.

[0022] Figure 4 FIG1 is a flow chart of another method for preparing a hydrogen sensor according to an embodiment of the present invention.

[0023] Figure 5 FIG1 is a flow chart of another method for preparing a hydrogen sensor according to an embodiment of the present invention.

[0024] Reference numerals:

[0025] 1. Substrate, 2. Sensing material layer, 3. Heterojunction, 4. Electrode, 5. Inorganic gas filter membrane, 6. Connection end, 7. Packaging shell, 71. Air inlet, 72. Air outlet. DETAILED DESCRIPTION

[0026] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0027] Hydrogen energy has broad prospects as a substitute for fossil fuels, but hydrogen is flammable and explosive, and requires high-sensitivity, low-operating-temperature sensors to ensure safety.

[0028] Existing hydrogen sensor structures mainly include limiting current type hydrogen sensors, concentration cell type hydrogen sensors, and resistance type hydrogen sensors. Resistive type hydrogen sensors detect hydrogen concentration by measuring the resistance change of metal oxide semiconductor materials under different hydrogen concentrations. Because the main structure of resistive type hydrogen sensors, MOS (metal oxide semiconductor), is low-cost and long-lasting, resistive type hydrogen sensors have become the preferred sensor type.

[0029] However, the flammable and explosive nature of hydrogen makes it extremely demanding on sensitivity. Therefore, it is necessary to specifically enhance the sensitivity of MOS to improve the overall performance of the resistive hydrogen sensor.

[0030] like Figure 1 As shown, a hydrogen sensor according to a preferred embodiment of the present invention includes a packaging shell 7 and a substrate 1.

[0031] The packaging shell 7 is provided with an air inlet 71 and an air outlet 72 which are symmetrically arranged. The air inlet 71 and the air outlet 72 are located on both sides of the packaging shell 7 .

[0032] The substrate 1 is placed at the bottom of the packaging shell 7, and the upper end of the substrate 1 is coated with a sensing material layer 2. Two electrodes 4 are provided on the upper surfaces of the two ends of the sensing material layer 2. The ends of the two electrodes 4 that are away from each other are respectively connected to connection ends 6, and the two connection ends 6 are connected to the external measurement circuit. A heterojunction 3 is provided on the upper end of the sensing material layer 2. The heterojunction 3 is placed between the two electrodes 4. The heterojunction 3 is flush with the upper surfaces of the two electrodes 4, and the upper surfaces of the heterojunction 3 and the two electrodes 4 are both covered with an inorganic gas filter membrane 5. The air inlet 71 and the air outlet 72 are located above the inorganic gas filter membrane 5.

[0033] In the above scheme, the hydrogen sensor of the present invention achieves improved performance through innovative structural design. Specifically, the symmetrically arranged air inlet 71 and air outlet 72 of the package housing 7 ensure uniform gas flow. The inorganic gas filter membrane 5 has a unique physical structure or chemical properties that can screen gas molecules, preferentially allowing the target gas to pass through while blocking interfering gases. The heterojunction 3, due to the unique band structure formed at the interface of two different semiconductor materials, changes the electron distribution and chemical reactivity on the surface of the sensing material, making the sensor more specific in adsorption and reaction to the target gas.

[0034] The combination of the inorganic gas filter membrane 5 and the heterojunction 3 significantly improves the sensor's selectivity for the target gas through both physical screening and chemically specific reactions, effectively resolving the issue of existing resistive hydrogen sensors being susceptible to interference from other gases. Furthermore, the device provides a simpler preparation method for the inorganic gas filter membrane 5 and the heterojunction 3, effectively shortening the preparation process and addressing the complex and inefficient preparation of the deposited inorganic gas filter membrane 5 and the difficult and costly preparation of the heterojunction 3. This effectively addresses the insufficient sensitivity and stability of existing resistive hydrogen sensors, making it suitable for use in scenarios requiring extremely high hydrogen safety.

[0035] In one embodiment of the present invention, the sensing material layer 2 may include tin dioxide and palladium, the mass proportion of tin dioxide in the sensing material layer 2 ranges from 90% to 99%, and palladium is doped in the tin dioxide, and the mass proportion of palladium in the sensing material layer 2 ranges from 0.1% to 5%.

[0036] Tin dioxide (SnO2) is the main component (90%-99% by mass). As a typical n-type metal oxide semiconductor, it has abundant oxygen vacancies and a large specific surface area, providing sufficient active sites for hydrogen adsorption.

[0037] Palladium (Pd) doping accounts for 0.1%-5% by mass. On the one hand, Pd nanoparticles are highly dispersed in the SnO2 matrix, which can catalyze the dissociation of hydrogen into hydrogen atoms, accelerate the reaction of hydrogen and oxygen species on the SnO2 surface, and significantly improve the sensor's adsorption rate and sensitivity to hydrogen.

[0038] On the other hand, Pd forms a heterojunction interface with SnO2, which modulates the band structure and optimizes electron transfer efficiency, enabling the sensor to generate a significant resistance change signal even when detecting low concentrations of hydrogen. Furthermore, this mass ratio ensures that SnO2 maintains stable semiconductor properties as the main component while also enabling the catalytic and synergistic sensing effects of palladium. This avoids the aggregation and cost increases associated with excessive palladium content, achieving a balance between sensing performance and economic efficiency, effectively meeting the hydrogen sensor's requirements for high sensitivity, rapid response, and stability.

[0039] Furthermore, the present invention combines graphene and tin dioxide to form a heterojunction 3, with their mass ratios strictly controlled, further enhancing the performance of the hydrogen sensor. In one embodiment, heterojunction 3 can include graphene and tin dioxide, with the graphene covering the surface of the tin dioxide. The tin dioxide mass ratio of heterojunction 3 ranges from 90% to 99%, and the graphene mass ratio ranges from 1% to 10%.

[0040] Based on 90%-99% tin dioxide by mass, its inherent semiconductor properties and abundant oxygen vacancies provide conditions for hydrogen adsorption and electrochemical reactions; while graphene, accounting for 1%-10% by mass, covers the surface of tin dioxide and can build an efficient electron transmission channel with its excellent conductivity and two-dimensional sheet structure, greatly reducing the interface resistance of the heterojunction 3 and significantly improving the response speed and signal strength of the sensor.

[0041] At the same time, graphene's high specific surface area and chemical stability can not only help tin dioxide capture more hydrogen molecules and enhance its adsorption capacity, but also protect tin dioxide from erosion by environmental impurities, thereby improving the sensor's anti-interference and long-term stability.

[0042] In the present invention, in addition to using other inorganic gas filter membranes 5 that can be produced, the inorganic gas filter membrane 5 exemplarily provided by the present invention can also be used. Specifically, the inorganic gas filter membrane 5 can include aluminosilicate and a template.

[0043] Among them, aluminosilicates include aluminosilicate ions and cations. Aluminosilicate ions are three-dimensional network structures formed by silicon-oxygen tetrahedrons and aluminum-oxygen tetrahedrons sharing oxygen atoms. Cations are used to balance the negative charge of aluminosilicate ions. Templates are used to guide aluminosilicate ions to form regular pore structures during the crystal growth of aluminosilicates.

[0044] Aluminosilicates form a three-dimensional network skeleton composed of silicon-oxygen tetrahedra and aluminum-oxygen tetrahedra, with cations balancing the charge and ensuring structural stability. The template precisely guides the formation of regular pores, leveraging a molecular sieving effect to preferentially allow hydrogen to pass through while blocking interfering gases, significantly improving detection selectivity. Furthermore, the membrane material exhibits excellent chemical and thermal stability, effectively resisting environmental corrosion, protecting the underlying sensing material layer, and extending the sensor's lifespan.

[0045] In addition, by adjusting the template parameters, the pore characteristics of the membrane material can be flexibly customized to adapt to the needs of different detection scenarios, thereby enhancing the adaptability and reliability of the sensor in complex environments.

[0046] Based on the structure of any embodiment of the present invention, such as Figure 3 As shown, the present invention also provides a method for preparing a hydrogen sensor, which may include:

[0047] S101 , ultrasonically clean the silicon wafer and dry the silicon wafer to obtain a substrate 1 .

[0048] S102 , adding a dopant to the tin dioxide sol and stirring the mixture evenly, coating the tin dioxide sol on the upper surface of the substrate 1 , and drying and sintering the tin dioxide sol to obtain the sensing material layer 2 .

[0049] S103 , forming electrodes 4 on the upper surfaces of both ends of the sensing material layer 2 .

[0050] S104, mixing aluminosilicate and a template to prepare a precursor solution, subjecting the precursor solution and the substrate 1 covered with the sensing material layer 2 and the electrode 4 to a hydrothermal reaction, and washing and calcining the precursor solution after the hydrothermal reaction to form an inorganic gas filter membrane 5.

[0051] S105 , growing graphene on the copper foil, transferring the copper foil with the graphene grown thereon into the cavity formed by the sensing material layer 2 , the electrode 4 and the inorganic gas filter membrane 5 , and annealing the copper foil to form a heterojunction 3 .

[0052] S106 , placing the substrate 1 with the sensing material layer 2 , the electrode 4 , the inorganic gas filter membrane 5 and the heterojunction 3 in the packaging shell 7 , sealing the packaging shell 7 and reserving an air inlet 71 and an air outlet 72 on the packaging shell 7 .

[0053] In an exemplary embodiment of the present invention, a silicon wafer can be deep ultrasonically cleaned with acetone, ethanol, and deionized water in sequence, and then dried to obtain a substrate 1. During coating, a tin dioxide sol can be applied to the upper surface of the substrate 1 by pulling or spin coating to obtain a uniform coating effect. The prepared electrode can be operated on the substrate 1 by screen printing or physical vapor deposition. Graphene can also be grown on copper foil by chemical vapor deposition. Through the steps of the above-mentioned preparation method of the present invention, according to the order of the steps and the materials used, several components of the hydrogen sensor can be stably prepared, and a complete hydrogen sensor can be obtained.

[0054] It can be understood that since the preparation method of the present invention includes all the technical features of the hydrogen sensor of the present invention, the embodiments of the hydrogen sensor in the present invention and their beneficial effects are all applicable to the preparation method in the present invention, and the present invention will not elaborate on them one by one.

[0055] Based on this, combined with the structure of the hydrogen sensor in the present invention, the preparation method in the present invention can also adopt the content of the following embodiment.

[0056] In one embodiment of the present invention, Figure 4 As shown, after the step of drying the silicon wafer to obtain the substrate 1 in step S101, in step S102, the step of adding a dopant to the tin dioxide sol and stirring it uniformly may include:

[0057] S201. Dissolve tin tetrachloride in ethanol, add water and hydrochloric acid as catalysts, and stir evenly for 1 to 3 hours to allow the tin tetrachloride to undergo hydrolysis and polycondensation reactions to form a uniform and transparent tin dioxide sol containing a tin dioxide precursor.

[0058] S202. Dissolve palladium nitrate in a solvent to prepare a doping solution, slowly add the doping solution into the tin dioxide sol, and continue stirring for 1 to 2 hours to uniformly disperse the palladium nitrate in the tin dioxide sol.

[0059] In the steps of the above embodiment, a more detailed process for preparing the tin dioxide sol is provided. By strictly controlling the stirring sequence, stirring time and doping sequence, it is convenient to prepare the sensing material layer 2 with better performance.

[0060] Moreover, in another embodiment of the present invention, Figure 5 As shown, in S102 of the present invention, the step of coating the tin dioxide sol on the upper surface of the substrate 1 by pulling or spin coating may include: S1021, immersing the substrate 1 in the tin dioxide sol, and pulling it at a uniform speed of 1 to 5 cm per minute so that the tin dioxide sol is evenly coated on the surface of the substrate 1.

[0061] The steps of obtaining the sensing material layer 2 by drying and sintering may include: S1022, drying the substrate 1 with the tin dioxide sol at 80 to 120 degrees Celsius for 1 to 2 hours to evaporate the solvent to form a gel film, and finally placing the substrate 1 with the gel film in a high-temperature furnace and sintering it at 500 to 700 degrees Celsius for 2 to 4 hours to convert the tin dioxide precursor in the tin dioxide sol into a crystalline sensing material layer 2.

[0062] The time, temperature, etc. in the above embodiments are all exemplary. Those skilled in the art can also appropriately adjust and adopt other parameters such as time and temperature according to the above embodiments.

[0063] Of course, by strictly controlling the stirring order, time and doping order of the tin dioxide sol, it is possible to ensure that dopants such as palladium are evenly dispersed in the sol, avoid agglomeration, and obtain better results, laying the foundation for the subsequent formation of a sensing material layer 2 with uniform performance.

[0064] Other pulling techniques can also achieve the purpose of the present invention. According to the coating method using a uniform pulling speed of 1 to 5 cm per minute, the thickness and uniformity of the tin dioxide sol on the surface of the substrate 1 can be accurately controlled to avoid problems such as sagging or uneven thickness of the film layer.

[0065] During the drying process, the solvent is gently evaporated at 80 to 120 degrees Celsius for 1 to 2 hours, forming a dense and crack-free gel film, thereby preventing the film from cracking due to rapid evaporation of the solvent.

[0066] The sintering process at 500 to 700 degrees Celsius for 2 to 4 hours can not only promote the full crystallization of the tin dioxide precursor into a nanocrystalline structure with a high specific surface area, but also avoid coarsening of grains or structural collapse caused by excessively high temperatures. The resulting sensing material layer 2 has excellent electrical conductivity and gas adsorption capacity, and works synergistically with the heterojunction 3 and the inorganic gas filter membrane 5 to significantly improve the detection sensitivity, response speed and long-term stability of the hydrogen sensor.

[0067] In another embodiment of the present invention, in S104, the step of mixing aluminosilicate and template to form a precursor solution may include: S1041, dissolving silica sol, sodium aluminate, and template in water according to a preset ratio, and stirring evenly for 2 to 4 hours to form a transparent precursor solution.

[0068] The step of placing the precursor solution and the substrate 1 with the sensing material layer 2 and the electrode 4 into a reactor for a hydrothermal reaction may include: S1042, placing the substrate 1 with the sensing material layer 2 and the electrode 4 into the reactor, adding the precursor solution to the reactor, sealing the reactor, placing the reactor in an oven, and performing a hydrothermal reaction at 150 to 200 degrees Celsius for 1 to 3 days, so that the substance in the precursor solution crystallizes and grows on the surface of the substrate 1 to form a zeolite film.

[0069] The steps of washing and calcining the product of the hydrothermal reaction to form the inorganic gas filter membrane 5 may include: S1043, cooling the reactor to room temperature, taking out the substrate 1, rinsing the substrate 1 with deionized water several times to remove residual impurities on the surface of the substrate 1 and substances in the unreacted precursor solution, and then calcining the substrate 1 at 550 to 650 degrees Celsius for several hours to remove the residual template in the zeolite film to obtain the inorganic gas filter membrane 5.

[0070] Likewise, the temperatures, times, and equipment given in the above embodiment and other embodiments of the present invention are merely exemplary and are not intended to limit the scope of protection of the present invention. Other known technical means may also be used to achieve the technical effects required by the present invention.

[0071] The present invention achieves both enhanced filtration performance and structural stability by optimizing the preparation process of the inorganic gas filtration membrane 5. During the precursor preparation stage, silica sol, sodium metaaluminate, and a template are dissolved in appropriate proportions and uniformly stirred for 2 to 4 hours to ensure sufficient interaction between the aluminosilicate ions and the template, providing a uniform reaction system for subsequent crystal growth and avoiding pore defects caused by uneven composition.

[0072] During the hydrothermal reaction, a temperature of 150 to 200 degrees Celsius and a constant temperature treatment for 1 to 3 days provide a suitable growth environment for aluminosilicate crystals, promoting their directional crystallization on the surface of substrate 1 to form a continuous zeolite film. The film layer generated under these conditions is tightly bonded to substrate 1, and the pore structure has a high regularity and a significant molecular sieving effect.

[0073] The water washing process effectively removes residual impurities and unreacted precursors, preventing contaminants from clogging the pores. Calcination at 550 to 650 degrees Celsius precisely removes the template and further crystallizes the zeolite, forming a stable three-dimensional network. This not only ensures the regularity of the pore structure but also enhances the chemical and thermal stability of the inorganic gas filtration membrane.

[0074] The preparation process is controlled by multiple steps, so that the inorganic gas filter membrane 5 has high selectivity, high density and environmental adaptability, and cooperates with the sensing material layer 2 to optimize the detection performance of the hydrogen sensor.

[0075] Furthermore, in one embodiment of the present invention, the step of growing graphene on copper foil using chemical vapor deposition may include: placing the copper foil in a reaction chamber of a chemical vapor deposition device, introducing hydrogen and methane into the reaction chamber, and at 900 to 1100 degrees Celsius, carbon atoms produced by the decomposition of methane are deposited on the surface of the copper foil and grow into graphene.

[0076] Based on this, the step of transferring the copper foil with grown graphene to the substrate 1 and then annealing to form a heterojunction 3 may include: transferring the graphene from the copper foil to the substrate 1 containing the sensing material layer 2 and the electrode 4 by chemical etching, placing the substrate 1 with the transferred graphene in a high-temperature annealing furnace, and annealing at 300 to 500 degrees Celsius for 1 to 2 hours to form a heterojunction 3 between the graphene and the sensing material layer 2.

[0077] In one embodiment, when carbon atoms generated by the decomposition of methane are deposited on the surface of the copper foil and grow into graphene, the growth quality and number of growth layers of the graphene on the copper foil are controlled by controlling the flow rates of the introduced hydrogen and methane and the temperature of the reaction chamber.

[0078] Through the above steps, the controllable growth of the graphene structure was successfully achieved. The growth quality and number of growth layers of graphene on the copper foil can be properly adjusted according to the specifications of other structures in the hydrogen sensor, thereby achieving better technical effects.

[0079] Compared with the prior art, the hydrogen sensor and its preparation method according to the embodiment of the present invention have the following advantages:

[0080] The hydrogen sensor of the present invention utilizes a combination of an inorganic gas filter membrane 5 and a heterojunction 3. The inorganic gas filter membrane 5 has a unique physical structure or chemical properties that enable it to screen gas molecules, preferentially allowing the target gas to pass through while blocking interfering gases. The heterojunction 3, due to the unique band structure formed at the interface of two different semiconductor materials, alters the electron distribution and chemical reactivity on the sensing material surface, resulting in the sensor having stronger specific adsorption and reaction capabilities for the target gas. The combination of the two greatly improves the sensor's selectivity for the target gas through both physical screening and chemical specific reaction, effectively resolving the issue of existing resistive hydrogen sensors being susceptible to interference from other gases and consequently enhancing sensitivity. Furthermore, the present invention provides a simpler preparation method for the inorganic gas filter membrane 5 and the heterojunction 3, effectively shortening the preparation process and addressing the complex and inefficient preparation of the deposited inorganic gas filter membrane 5 and the difficult and costly preparation of the heterojunction 3.

[0081] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. A hydrogen sensor, characterized in that: The hydrogen sensor comprises: A packaging shell (7), wherein the packaging shell (7) is provided with an air inlet (71) and an air outlet (72) that are symmetrically arranged, and the air inlet (71) and the air outlet (72) are located on both sides of the packaging shell (7); A substrate (1) is placed at the bottom of the packaging shell (7); the upper end of the substrate (1) is coated with a sensing material layer (2); the upper surfaces of both ends of the sensing material layer (2) are provided with two electrodes (4); the ends of the two electrodes (4) that are away from each other are respectively connected to connection ends (6); the two connection ends (6) are connected to an external measurement circuit; the upper end of the sensing material layer (2) is provided with a heterojunction (3); the heterojunction (3) is placed between the two electrodes (4); the heterojunction (3) is flush with the upper surfaces of the two electrodes (4); and the upper surfaces of the heterojunction (3) and the two electrodes (4) are both covered with an inorganic gas filter membrane (5); the air inlet (71) and the air outlet (72) are located above the inorganic gas filter membrane (5).

2. The hydrogen sensor according to claim 1, characterized in that The sensing material layer (2) comprises tin dioxide and palladium, wherein the mass proportion of the tin dioxide in the sensing material layer (2) ranges from 90% to 99%, and the palladium is doped in the tin dioxide, wherein the mass proportion of the palladium in the sensing material layer (2) ranges from 0.1% to 5%.

3. The hydrogen sensor according to claim 1, characterized in that The heterojunction (3) includes graphene and tin dioxide, the graphene covers the surface of the tin dioxide, the mass proportion of the tin dioxide in the heterojunction (3) ranges from 90% to 99%, and the mass proportion of the graphene in the heterojunction (3) ranges from 1% to 10%.

4. The hydrogen sensor according to claim 1, characterized in that The inorganic gas filtration membrane (5) comprises: aluminosilicate and a template agent, wherein the aluminosilicate comprises aluminosilicate ions and cations, wherein the aluminosilicate ions are a three-dimensional network structure formed by connecting silicon-oxygen tetrahedrons and aluminum-oxygen tetrahedrons with shared oxygen atoms, the cations are used to balance the negative charge of the aluminosilicate ions, and the template agent is used to guide the aluminosilicate ions to form a regular pore structure during the crystal growth process of the aluminosilicate.

5. A method for preparing a hydrogen sensor, characterized in that: The preparation method comprises: S101, ultrasonically cleaning the silicon wafer, and drying the silicon wafer to obtain a substrate (1); S102, adding a dopant to the tin dioxide sol and stirring the mixture uniformly, coating the tin dioxide sol on the upper surface of the substrate (1), and drying and sintering the tin dioxide sol to obtain a sensing material layer (2); S103, forming electrodes (4) on the upper surfaces of both ends of the sensing material layer (2); S104, mixing aluminosilicate and a template to form a precursor solution, subjecting the precursor solution and the substrate (1) covered with the sensing material layer (2) and the electrode (4) to a hydrothermal reaction, and washing and calcining the precursor solution after the hydrothermal reaction to form an inorganic gas filter membrane (5); S105, growing graphene on a copper foil, transferring the copper foil on which the graphene is grown into a cavity formed by the sensing material layer (2), the electrode (4), and the inorganic gas filter membrane (5), and annealing the copper foil to form a heterojunction (3); S106. Place the substrate (1) with the sensing material layer (2), the electrode (4), the inorganic gas filter membrane (5) and the heterojunction (3) in a packaging shell (7), seal the packaging shell (7) and reserve an air inlet (71) and an air outlet (72) on the packaging shell (7).

6. The preparation method according to claim 5, characterized in that In step S102, the step of adding a dopant to the tin dioxide sol and stirring the sol uniformly includes: Dissolve tin tetrachloride in ethanol, add water and hydrochloric acid as catalysts, and stir evenly to allow the tin tetrachloride to undergo hydrolysis and polycondensation reactions to form a transparent tin dioxide sol containing a tin dioxide precursor; Palladium nitrate is dissolved in a solvent to prepare a doping solution, and the doping solution is added to the tin dioxide sol, and the mixture is continuously stirred to uniformly disperse the palladium nitrate in the tin dioxide sol.

7. The preparation method according to claim 6, characterized in that The step of coating the tin dioxide sol on the upper surface of the substrate (1) comprises: immersing the substrate (1) in the tin dioxide sol, and uniformly pulling it up at a speed of 1 to 5 cm per minute, so that the tin dioxide sol is uniformly coated on the surface of the substrate (1); The steps of obtaining the sensing material layer (2) through drying and sintering include: The substrate (1) with the tin dioxide sol is dried to volatilize the solvent to form a gel film, and the substrate (1) with the gel film is sintered to convert the tin dioxide precursor in the tin dioxide sol into a crystalline sensing material layer (2).

8. The preparation method according to claim 5, characterized in that Step S104 includes: Dissolve silica sol, sodium metaaluminate and template in water according to a preset ratio and stir evenly to form a transparent precursor solution; Placing the substrate (1) with the sensing material layer (2) and the electrode (4) into a reactor, adding the precursor solution into the reactor, sealing the reactor, placing the reactor into an oven, and performing a hydrothermal reaction to allow the substance in the precursor solution to crystallize and grow on the surface of the substrate (1) to form a zeolite film; The reactor is cooled to room temperature, the substrate (1) is taken out, and the substrate (1) is rinsed several times with deionized water to remove residual impurities on the surface of the substrate (1) and unreacted substances in the precursor solution. The substrate (1) is then calcined for several hours to remove the template agent remaining in the zeolite film, thereby obtaining the inorganic gas filtration membrane (5).

9. The preparation method according to claim 5, characterized in that Step S105 includes: placing the copper foil in a reaction chamber of a chemical vapor deposition device, introducing hydrogen and methane into the reaction chamber, and allowing carbon atoms generated by decomposition of the methane to deposit on the surface of the copper foil and grow into the graphene; The graphene is transferred from the copper foil to the substrate (1) containing the sensing material layer (2) and the electrode (4) by chemical etching, and the substrate (1) with the transferred graphene is placed in a high-temperature annealing furnace and annealed for 1 to 2 hours to form the heterojunction (3) between the graphene and the sensing material layer (2).

10. The preparation method according to claim 9, characterized in that When the carbon atoms generated by the decomposition of methane are deposited on the surface of the copper foil and grow into the graphene, the growth quality and the number of growth layers of the graphene on the copper foil are controlled by controlling the flow rates of the hydrogen and methane introduced and the temperature of the reaction chamber.

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