A Tunable Hydrogen Sensor and Its Preparation Process

Abstract

The present invention belongs to the technical field of photochemical sensors and relates to a tunable hydrogen sensor and its preparation process, which includes a hydrogen-sensitive metal film and a piezoelectric sheet; the hydrogen-sensitive metal film is a structural layer formed by multiple hydrogen-sensitive metal bodies in an array manner, the hydrogen-sensitive metal body is a nanoscale bowl-shaped structure, two of the hydrogen-sensitive metal films are pressed together with the bowl tops of the hydrogen-sensitive metal bodies facing each other, two of the hydrogen-sensitive metal films are respectively connected to one of the piezoelectric sheets, and the two piezoelectric sheets adjust the distance between the two hydrogen-sensitive metal films through deformation. The present invention can achieve precise control of the nanoscale distance between the hydrogen-sensitive metal films through the piezoelectric sheet, enhance the electromagnetic field coupling at low concentrations, amplify weak signals, and achieve highly sensitive detection of low-concentration hydrogen. At high concentrations, the coupling is weakened to avoid signal saturation, and it can meet the hydrogen detection requirements from as low as 100 ppm to high concentrations, and is suitable for various application scenarios such as fuel cells and industrial gas detection.

Description

Technical Field

[0001] The present invention belongs to the technical field of photochemical sensors, and particularly relates to a tunable hydrogen sensor and a preparation process thereof. Background Art

[0002] Hydrogen sensor: As a clean energy source, hydrogen has the advantages of high combustion efficiency and less pollution, and is widely used in fuel cells, energy storage, chemical industry and other fields. However, hydrogen has extremely high flammability and explosiveness, and even a very low concentration of leakage can cause serious safety accidents. Therefore, it is particularly important to develop a hydrogen sensor with high sensitivity and high stability for ensuring safety.

[0003] The current mainstream hydrogen sensing technologies include semiconductor metal oxide sensors, catalytic combustion sensors, electrochemical sensors, etc. Although these technologies have been applied in practice, they have limitations in terms of sensitivity, response time, operating temperature, selectivity, etc.: semiconductor metal oxide sensors usually require high-temperature heating, with large energy consumption and limited applicability; catalytic combustion sensors have low sensitivity and slow response speed; electrochemical sensors are easily affected by humidity and have poor stability. Summary of the Invention

[0004] Aiming at the defects in the prior art, the purpose of the present invention is to provide a tunable hydrogen sensor and a preparation process thereof.

[0005] According to the tunable hydrogen sensor provided by the present invention, it includes a hydrogen-sensitive metal film and a piezoelectric sheet;

[0006] The hydrogen-sensitive metal film is a nanoscale structural layer formed by a plurality of hydrogen-sensitive metal bodies in an array manner. The hydrogen-sensitive metal body is in a bowl shape. Two of the hydrogen-sensitive metal films are pressed together with the bowl tops of the hydrogen-sensitive metal bodies facing each other. Two of the hydrogen-sensitive metal films are respectively connected to one piezoelectric sheet, and the two piezoelectric sheets adjust the distance between the two hydrogen-sensitive metal films through deformation.

[0007] In some embodiments, the hydrogen-sensitive metal body includes a base film, and a hydrogen-sensitive metal layer is deposited on the base film.

[0008] In some embodiments, the material of the base film is an alloy formed by one or more of aluminum, copper, silver, and gold.

[0009] In some embodiments, the material of the hydrogen-sensitive metal layer is palladium or platinum.

[0010] In some embodiments, the material of the piezoelectric sheet is lead zirconate titanate, sodium potassium niobate, barium titanate, lanthanum lead zirconate titanate, or polyvinylidene fluoride and its copolymers.

[0011] In some embodiments, it further includes a packaging layer. The material of the packaging layer is polyvinyl alcohol or silica gel. The piezoelectric sheet is encapsulated within the packaging layer, and the thickness of the packaging layer is 1 - 5 μm.

[0012] In some embodiments, it further includes a protective coating. The material of the protective coating is silicon dioxide or titanium dioxide. The protective coating is coated on the outer surface of the piezoelectric sheet, or when the piezoelectric sheet is externally encapsulated with a packaging layer, the protective coating is coated on the outer surface of the packaging layer.

[0013] The present invention also provides a preparation process for a tunable hydrogen sensor, including the following steps:

[0014] A1, ultrasonically clean the substrate with acetone, isopropyl alcohol, absolute ethanol, and deionized water in sequence for 5 - 20 min, and then perform a drying treatment;

[0015] A2, deposit a polystyrene microsphere suspension on the substrate processed in step A1 by self - assembly to form an ordered polystyrene sphere array;

[0016] A3, sputter - deposit a base film on the surface of the polystyrene spheres on the surface of the intermediate obtained in step A2 by magnetron sputtering. The base film is in the shape of an open semi - circle, and the thickness of the base film is 270 - 350 nm;

[0017] A4, deposit a hydrogen - sensitive metal layer on the surface of the base film on the surface of the intermediate obtained in step A3 by electrodeposition. The structure formed by the base film and the hydrogen - sensitive metal layer covering a single polystyrene sphere is denoted as a hydrogen - sensitive metal body;

[0018] A5, place the intermediate obtained in step A4 in an organic solvent capable of dissolving polystyrene spheres for cleaning. After the polystyrene spheres are dissolved, the hydrogen - sensitive metal bodies form a hydrogen - sensitive metal film in a layer - structured state in an array manner;

[0019] A6, drop a polyvinyl alcohol solution on the surface of the hydrogen - sensitive metal film in the layer - structured state obtained in step A5. After curing, peel it off to form a film - like hydrogen - sensitive metal film. Press two pieces of the hydrogen - sensitive metal films together with the bowl tops of the hydrogen - sensitive metal bodies facing each other;

[0020] A7, coat an adhesive on the surface of the piezoelectric sheet to form an adhesive layer. Place the two pieces of hydrogen - sensitive metal films that have been pressed together in step A6 between two piezoelectric sheets. The hydrogen - sensitive metal films are adhesively fixed to the piezoelectric sheets in a manner that the bowl mouths of the hydrogen - sensitive metal bodies are buckled, and the piezoelectric sheet adjusts the distance between the two pieces of hydrogen - sensitive metal films by deformation.

[0021] In some embodiments, it further includes A8, package the sample obtained in step A7 to form a packaging layer. The material of the packaging layer is polyvinyl alcohol or silica gel, and the thickness of the packaging layer is 1 - 5 μm.

[0022] In some embodiments, A9 is further included. A protective layer is coated on the surface of the sample obtained in step A7 or on the surface of the sample obtained in step A8, and the material of the protective layer is silicon dioxide or titanium dioxide.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The tunable hydrogen sensor of the present invention can precisely control the nanoscale distance between hydrogen-sensitive metal films through a piezoelectric sheet, enhance the electromagnetic field coupling at low concentrations, amplify weak signals, and achieve highly sensitive detection of low-concentration hydrogen. At high concentrations, the coupling is weakened to avoid signal saturation, and it can adapt to the hydrogen detection requirements from as low as 100 ppm to high concentrations, and is suitable for various application scenarios such as fuel cells and industrial gas detection.

[0025] 2. The tunable hydrogen sensor of the present invention effectively increases the specific surface area of the sensing material through the semi-circular concave structure of the hydrogen-sensitive metal film, significantly increases the contact area with hydrogen molecules, and enhances the adsorption effect. This structural characteristic enables the hydrogen sensor to more quickly and accurately sense low-concentration hydrogen, significantly improving the sensitivity of the sensor.

[0026] 3. The preparation process of the tunable hydrogen sensor of the present invention is prepared by mature processes such as the polystyrene template method and electrodeposition, and has the advantages of low cost and stable process. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] By reading the following detailed description of non-limiting embodiments with reference to the accompanying drawings, other features, objects, and advantages of the present invention will become more apparent:

[0028] Figure 1 is a schematic diagram of polystyrene spheres densely arranged on a glass slide;

[0029] Figure 2 is for Figure 1 a schematic diagram after coating;

[0030] Figure 3 is for Figure 2 a schematic diagram after electrodepositing palladium (Pd);

[0031] Figure 4 is for Figure 3 a schematic diagram after removing the polystyrene spheres;

[0032] Figure 5 is a template schematic diagram of the completed silver-palladium nanobowl preparation;

[0033] Figure 6 is a schematic diagram of the silver-palladium nanobowl fixed on the piezoelectric sheet;

[0034] Figure 7 is the manufacturing flow chart of the present invention. Specific embodiments

[0035] The present invention will be described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that those of ordinary skill in the art can make several changes and improvements without departing from the concept of the present invention. These all belong to the protection scope of the present invention. Embodiment

[0036] This embodiment provides a tunable hydrogen sensor, as Figure 1-7 shown, mainly including a hydrogen-sensitive metal film 1 and a piezoelectric sheet 2. Among them: the hydrogen-sensitive metal film 1 is a structure of two sheets pressed together, and the piezoelectric sheet 2 is also two sheets, which are respectively glued and fixed to the two hydrogen-sensitive metal films 1 and located on the outside, and the distance between the two hydrogen-sensitive metal films 1 is adjusted by the deformation of the piezoelectric sheet 2.

[0037] The hydrogen-sensitive metal film 1 is used as a sensing element for hydrogen detection. In this embodiment, it is a double-layer structure, including a base film 11 and a hydrogen-sensitive metal layer 12 located on the base film 11. The material of the base film 11 is one or more alloys of aluminum, copper, silver, and gold. In this embodiment, silver is taken as an example for illustration. The material of the hydrogen-sensitive metal layer 12 is palladium or platinum. In this embodiment, palladium is taken as an example for illustration. The double-layer structure of the hydrogen-sensitive metal film 1 is not a flat layer structure, but a film structure formed by an array of a plurality of semi-circular hydrogen-sensitive metal bodies 10. Each hydrogen-sensitive metal body 10 is a semi-circular structure formed by the base film 11 and the hydrogen-sensitive metal layer 12 located thereon. The hydrogen-sensitive metal film 1 formed by the semi-circular hydrogen-sensitive metal bodies 10 can effectively increase the specific surface area of the sensing material, significantly increase the contact area with hydrogen molecules, and enhance the adsorption effect. This structural characteristic enables the hydrogen sensor to more quickly and accurately sense low-concentration hydrogen, and can significantly improve the sensitivity of the sensor.

[0038] The method for forming the hydrogen-sensitive metal body 10 of the array structure is as follows: First, a polystyrene (PS) microsphere suspension is deposited on a pretreated substrate by self-assembly to form an ordered polystyrene (PS) microsphere array. Then, a silver (Ag) film is deposited on the surface of the polystyrene (PS) microsphere array by magnetron sputtering to form a base film 11, and the thickness of the base film 11 is 270 - 350 nm. Subsequently, a palladium (Pd) layer is electroplated on the base film 11 by a three-electrode direct current deposition method to form a hydrogen-sensitive metal layer 12. Then, the polystyrene spheres are dissolved by placing the sample in a tetrahydrofuran solvent that can dissolve the polystyrene spheres, forming a hydrogen-sensitive metal film 1 in a layer structure state. Finally, a polyvinyl alcohol solution is dropped on the surface of the hydrogen-sensitive metal film 1 in the layer structure state, and after curing, it is peeled off to form a hydrogen-sensitive metal film 1 in a film state. Two hydrogen-sensitive metal films 1 with basically the same structure prepared by this method are pressed together with the bowl tops of their hydrogen-sensitive metal bodies 10 facing each other to form a sensing element for hydrogen detection.

[0039] The material of the piezoelectric sheet 2 is lead zirconate titanate (PZT), sodium potassium niobate (KNN), barium titanate (BaTiO3), lanthanum lead zirconate titanate (PLZT), or polyvinylidene fluoride (PVDF) and its copolymers. A UV-curable adhesive or thermosetting epoxy resin is coated on the piezoelectric sheet 2 to form an adhesive layer, and the hydrogen-sensitive metal film 1 is coated on the adhesive layer by spin coating and positioned by an external pressure or alignment device to improve the alignment uniformity and structural stability of the hydrogen-sensitive metal film 1. The thickness of the adhesive layer is between 100 - 500 nm to ensure the stability and firmness of the bonding of the hydrogen-sensitive metal film 1 to the piezoelectric sheet 2. In some embodiments, two piezoelectric sheets 2 are used to adjust the amount of deformation through a control circuit. The control circuit includes a feedback adjustment system that can adjust the voltage on the piezoelectric sheet in real time according to the hydrogen concentration, automatically control the distance between the upper and lower hydrogen-sensitive metal films 1, and thus achieve adaptive sensitivity regulation under different concentration conditions. The voltage adjustment circuit in the control circuit uses a digital-to-analog converter (DAC) to adjust the voltage to precisely control the amount of deformation, thereby precisely adjusting the distance between the upper and lower hydrogen-sensitive metal films 1. The control circuit includes a signal processing circuit and a data transmission interface for real-time transmission of hydrogen concentration data to a microcontroller or display device. The thickness of the piezoelectric sheet 2 is usually relatively thin, generally between a few hundred micrometers and a few millimeters, and the deformation range is precisely controllable. On the one hand, it can achieve precise regulation of the nanoscale distance between the hydrogen-sensitive metal films 1, and at the same time, the overall structure of the sensor can be made very compact, which is beneficial to the miniaturization of the sensor.

[0040] The working principle of the tunable hydrogen sensor provided in this embodiment is as follows: the nanoscale bowl-shaped structure of the upper and lower hydrogen-sensitive metal films 1 will form two independent electromagnetic fields. When the distance between the upper and lower hydrogen-sensitive metal films 1 is within the nanometer range, the electromagnetic fields generated by them will overlap, thereby inducing electromagnetic field coupling and forming a local enhanced electromagnetic field. The strength of the electromagnetic field coupling is nonlinear with the distance between the two hydrogen-sensitive metal films 1. The smaller the distance, the stronger the coupling strength. When the distance increases to a certain extent, the coupling effect will be quickly disconnected. The silver-palladium material in the hydrogen-sensitive metal film 1 has excellent catalytic and adsorption properties for hydrogen. When hydrogen molecules enter the surface of the hydrogen-sensitive metal film 1, the distribution of the local enhanced electromagnetic field between the hydrogen-sensitive metal films 1 will be significantly changed, thereby enhancing the detection sensitivity of hydrogen. At the same time, by arranging piezoelectric sheets 2 on the upper and lower parts of the hydrogen-sensitive metal film 1, the piezoelectric sheets 2 can produce mechanical deformation under the action of external voltage, thereby changing the distance between the upper and lower hydrogen-sensitive metal films 1. When the hydrogen concentration is high, the control circuit reduces the voltage applied to the piezoelectric sheet 2, and controls the deformation of the piezoelectric sheet 2 within a small range or without deformation, so that the distance between the upper and lower hydrogen-sensitive metal films 1 is at a larger position, so that the electromagnetic field coupling effect between the two hydrogen-sensitive metal films 1 is weakened, thereby avoiding the problem of electromagnetic field signal saturation under high hydrogen concentration, ensuring that the output signal of the sensor will not lose linear response due to excessive coupling, and making the detection result more accurate and reliable. When the hydrogen concentration is low, the control system increases the voltage on the piezoelectric sheet 2, and by increasing the deformation, the distance between the upper and lower hydrogen-sensitive metal films 1 is shortened, and the electromagnetic field coupling strength between the upper and lower hydrogen-sensitive metal films 1 is enhanced. The enhancement of the electromagnetic field coupling strength means that the response of the electromagnetic field to the weak hydrogen signal is amplified, so that the sensor can detect the changes caused by the adsorption of weak hydrogen molecules under low hydrogen concentration, and can even respond quickly to changes in hydrogen concentration below 100 ppm. Example

[0041] This embodiment 2 is formed on the basis of embodiment 1, and by forming a packaging layer and / or a protective layer on the tunable hydrogen sensor, the stability of the tunable hydrogen sensor structure is improved and the interference of the external environment on the sensor performance is reduced. Specifically:

[0042] Two piezoelectric sheets 2 sandwich and connect two hydrogen-sensitive metal films 1 that are joined and pressed together. An encapsulation layer is formed by wrapping around the outside of the piezoelectric sheets 2. The thickness of the encapsulation layer is controlled between 1 - 5 μm, which can effectively ensure the structural stability and sealing of the tunable hydrogen sensor, and avoid interference from the external environment to the performance of the tunable hydrogen sensor. In this embodiment, the material of the encapsulation layer is polyvinyl alcohol (PVA) or silica gel. Taking the encapsulation with polyvinyl alcohol (PVA) material as an example, the encapsulation material is mainly evenly distributed on the outside of the tunable sensor by spin coating to form an encapsulation layer. Its main technological process is as follows: First, dissolve polyvinyl alcohol (PVA) in deionized water to prepare a 4% concentration polyvinyl alcohol (PVA) solution. Secondly, fix the tunable sensor on the spin coating equipment and rotate it at a low speed of 500 rpm for 10 s to evenly distribute the liquid. Then gradually increase the rotation speed to 3000 rpm for 45 s to spin dry the waste material and form a uniform thin film. Finally, put the sensor after the workpiece into an oven and heat it to 80 °C for curing to shape the encapsulation layer.

[0043] In some embodiments, a protective layer is coated on the tunable hydrogen sensor. When the tunable hydrogen sensor has no encapsulation structure, the protective layer is coated on the two piezoelectric sheets 2. When the tunable hydrogen sensor is provided with an encapsulation layer, the protective layer is coated on the encapsulation layer. The material of the protective layer is silicon dioxide (SiO2) or titanium dioxide (TiO2) coating. Utilize its antioxidant and photocatalytic self-cleaning properties to enhance the durability and environmental tolerance of the device. Example

[0044] This Example 3 provides a preparation process for a tunable hydrogen sensor, including the following steps:

[0045] A1. Cleaning of the substrate: The substrate 4 is a conductive glass, a common glass sheet deposited with metal, or a metal sheet. First, cut the substrate 4 into pieces with a size of 2 cm * 4 cm, and ultrasonically clean it with acetone, isopropanol, absolute ethanol, and deionized water in sequence for 10 minutes, and finally dry it under a nitrogen gas flow.

[0046] A2: First, use a pipette to suck 300 μL of a polystyrene (PS) microsphere 3 solution with a diameter of 300 nm, and centrifuge it with counterweight for 15 minutes. Subsequently, add 20 μL of deionized water and 20 μL of absolute ethanol in sequence, and perform vortex mixing for 1 minute respectively. Then add 5 μL of n-butanol and vortex for 1 minute. Place the solution in an ultrasonic wave and oscillate it for 2 to 4 hours to fully disperse the polystyrene (PS) microspheres, and complete the preparation of the polystyrene (PS) microsphere suspension. Deposit the obtained polystyrene (PS) microsphere suspension on the substrate pretreated in step A1 by self-assembly method to form an ordered PS sphere array, as Figure 1 shown.

[0047] A3: Place the sample obtained in step A2 into a magnetron sputtering chamber, and sputter a layer of silver (Ag) with a thickness of about 300 nm on the surface of the sample obtained in step A2 to form a base film 11, as Figure 2 shown. The sputtering current is 15 mA, the power is 46 W, the sputtering is carried out at a rate of 10 nm / min, and the sputtering time is 30 min.

[0048] A4: Electrodeposit a layer of palladium (Pd) on the surface of the sample obtained in step A3 by a three-electrode direct current electrodeposition method to form a hydrogen-sensitive metal layer 12, as Figure 3 shown. The configuration of the basic plating solution is as follows: the palladium precursor is palladium chloride (PdCl2) with a concentration of 5 - 10 mmol / L; the auxiliary electrolyte is potassium chloride (KCl) with a concentration of 0.1 - 0.5 M; the buffer is acetic acid (CH3COOH) with a concentration of 0.05 - 0.1 M. Add 60 g of palladium chloride (PdCl2), 2 g of potassium chloride (KCl), and 7 g of acetic acid (CH3COOH) to every 200 mL of distilled water. When preparing the electroplating solution, first dissolve palladium chloride in a small amount of deionized water to ensure complete dissolution, and then gradually add potassium chloride (KCl), acetic acid (CH3COOH), and deionized water to the required volume, and slowly stir until the solution is uniform. Then place the basic plating solution in a thermostatic bath. Take the silver-plated base as the working electrode, silver chloride (AgCl) as the reference electrode, and a high-purity platinum electrode as the counter electrode, insert them into the basic plating solution in the thermostatic bath for the electrodeposition reaction, control the potential at -0.3 V to -0.5 V, the current density is 2 - 10 mA / cm², and electroplate at a temperature of 80 °C for 20 min. After the deposition is completed, gently rinse the sample with deionized water to remove the residual electroplating solution on the surface. The entire electrodeposition process should be carried out in an environment with good temperature and vibration control to ensure the density and surface quality of the palladium coating.

[0049] A5: Place the sample obtained in step A4 into a beaker containing tetrahydrofuran (THF), and let it stand for 1 hour. Subsequently, take out the sample and rinse it thoroughly with absolute ethanol, and finally dry it under a nitrogen stream to form a layered hydrogen-sensitive metal film 1, as Figure 4 shown. Repeat the above steps to prepare two hydrogen-sensitive metal films 1 with basically the same nanostructure.

[0050] A6: Drop a polyvinyl alcohol (PVA) solution on the surfaces of the two samples obtained in step A5. After it is completely cured, peel off the sample structure to form a hydrogen-sensitive metal film 1 in a film structure state, and press the two hydrogen-sensitive metal films 1 together, as Figure 5 shown.

[0051] A7: Ultrasonically clean each of the two piezoelectric wafers 2 with acetone, absolute ethanol, and deionized water for 15 min to remove surface oil stains, dust, and other impurities. Use a spin coater to evenly coat the surface of the piezoelectric wafer 2 with UV glue. The spin coating conditions can be set to 2800 rpm and the spin coating time to 45 seconds to obtain a uniform nano-scale adhesive thin layer of 500 nm. Under a microscope, gently place the hydrogen-sensitive metal film 1 on the surface of the piezoelectric wafer 2 coated with the adhesive and ensure its correct position. Using UV curable glue, place the piezoelectric wafer 2 with the hydrogen-sensitive metal film 1 placed thereon into a UV curing box and irradiate it with ultraviolet light at a wavelength of 300 - 400 nm for 30 - 60 seconds to ensure that the adhesive is fully cured, forming a tunable hydrogen sensor, as Figure 6 shown.

[0052] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application.

[0053] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Without conflict, the embodiments of the present application and the features in the embodiments can be arbitrarily combined with each other.

Claims

1. A tunable hydrogen sensor, characterized in that, It includes a hydrogen-sensitive metal film (1) and a piezoelectric sheet (2); The hydrogen-sensitive metal film (1) is a nanoscale structural layer formed by a plurality of hydrogen-sensitive metal bodies (10) in an array manner. The hydrogen-sensitive metal body (10) has a bowl-shaped structure. Two pieces of the hydrogen-sensitive metal film (1) are pressed together with the bowl tops of the hydrogen-sensitive metal bodies (10) facing each other. Two pieces of the hydrogen-sensitive metal film (1) are respectively connected to one piece of the piezoelectric sheet (2). The two pieces of the piezoelectric sheet (2) are adjusted for the amount of deformation through a control circuit. The control circuit includes a feedback adjustment system, which can adjust the voltage on the piezoelectric sheet (2) in real time according to the hydrogen concentration, and automatically control the distance between the upper and lower two pieces of the hydrogen-sensitive metal film (1), so as to achieve adaptive sensitivity control under different concentration conditions.

2. The tunable hydrogen sensor according to claim 1, wherein, The hydrogen-sensitive metal body (10) includes a base film (11), and a hydrogen-sensitive metal layer (12) is deposited on the base film (11).

3. The tunable hydrogen sensor according to claim 2, wherein, The material of the base film (11) is an alloy formed by one or more of aluminum, copper, silver, and gold.

4. The tunable hydrogen sensor according to claim 2, wherein The material of the hydrogen-sensitive metal layer (12) is palladium or platinum.

5. The tunable hydrogen sensor according to claim 1, wherein The material of the piezoelectric sheet (2) is lead zirconate titanate, sodium potassium niobate, barium titanate, lanthanum lead zirconate titanate, or polyvinylidene fluoride and its copolymer.

6. The tunable hydrogen sensor according to any one of claims 1-5, characterized in that, It also includes a packaging layer. The material of the packaging layer is polyvinyl alcohol or silica gel. The piezoelectric sheet (2) is encapsulated in the packaging layer, and the thickness of the packaging layer is 1 - 5 μm.

7. The tunable hydrogen sensor according to claim 6, wherein It also includes a protective coating. The material of the protective coating is silicon dioxide or titanium dioxide. The protective coating is coated on the outer surface of the piezoelectric sheet (2), or when the piezoelectric sheet (2) is externally encapsulated with a packaging layer, the protective coating is coated on the outer surface of the packaging layer.

8. A preparation process of a tunable hydrogen sensor, characterized in that, It includes the following steps: A1. Ultrasonically clean the substrate with acetone, isopropyl alcohol, absolute ethanol, and deionized water for 5 - 20 min in sequence, and then perform a drying treatment; A2. Deposit a polystyrene microsphere suspension on the substrate treated in step A1 through a self-assembly method to form an ordered polystyrene sphere array; A3. On the surface of the intermediate obtained in step A2, sputter a base film (11) on the surface of the polystyrene spheres through a magnetron sputtering method. The base film (11) is in the shape of an open semi-circle, and the thickness of the base film (11) is 270 - 350 nm; A4. On the surface of the intermediate obtained in step A3, deposit a hydrogen-sensitive metal layer (12) on the surface of the base film (11) through an electrodeposition method. The structure formed by the base film (11) and the hydrogen-sensitive metal layer (12) covering a single polystyrene sphere is denoted as the hydrogen-sensitive metal body (10); A5. Place the intermediate obtained in step A4 in an organic solvent capable of dissolving the polystyrene spheres for cleaning. After the polystyrene spheres are dissolved, the hydrogen-sensitive metal bodies (10) form a layer-structured hydrogen-sensitive metal film (1) in an array manner; A6. Drop a polyvinyl alcohol solution on the surface of the hydrogen-sensitive metal film (1) in the layer-structured state obtained in step A5. After curing, peel it off to form a film-shaped hydrogen-sensitive metal film (1). Two pieces of the hydrogen-sensitive metal film (1) are pressed together with the bowl tops of the hydrogen-sensitive metal bodies (10) facing each other for treatment; A7. A bonding layer is formed by coating an adhesive on the surface of the piezoelectric sheet (2). The two hydrogen-sensitive metal films (1) that are subjected to the alignment and pressing treatment in step A6 are placed between the two piezoelectric sheets (2). The hydrogen-sensitive metal film (1) is adhesively fixed to the piezoelectric sheet (2) in a way that the bowl opening of the hydrogen-sensitive metal body (10) is buckled. The two piezoelectric sheets (2) are used to adjust the amount of deformation through a control circuit. The control circuit includes a feedback adjustment system that can adjust the voltage on the piezoelectric sheet (2) in real time according to the hydrogen concentration, and automatically control the distance between the upper and lower hydrogen-sensitive metal films (1), so as to achieve adaptive sensitivity regulation under different concentration conditions.

9. The preparation process of the tunable hydrogen sensor according to claim 8, characterized in that, It further includes A8. The sample obtained in step A7 is encapsulated to form an encapsulation layer. The material of the encapsulation layer is polyvinyl alcohol or silica gel, and the thickness of the encapsulation layer is 1 - 5 μm.

10. The preparation process of the tunable hydrogen sensor according to claim 9, characterized in that, It further includes A9. A protective layer is coated on the surface of the sample obtained in step A7 or on the surface of the sample obtained in step A8. The material of the protective layer is silicon dioxide or titanium dioxide.

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