Tunable hydrogen sensor and preparation process thereof

Abstract

The invention belongs to the technical field of photochemical sensors, and relates to a tunable hydrogen sensor and a preparation process thereof. The tunable hydrogen sensor comprises a hydrogen-sensitive metal film and a piezoelectric plate, each hydrogen-sensitive metal film is a structural layer formed by a plurality of hydrogen-sensitive metal bodies in an array mode, each hydrogen-sensitive metal body is of a nanoscale bowl-shaped structure, the two hydrogen-sensitive metal films are oppositely combined and pressed in the mode that the bowl tops of the hydrogen-sensitive metal bodies are opposite, the two hydrogen-sensitive metal films are connected to the piezoelectric plates respectively, and the piezoelectric plates are arranged on the piezoelectric plates. And the two piezoelectric patches adjust the distance between the two hydrogen-sensitive metal films through deformation. According to the invention, accurate regulation and control of the nano-scale distance between the hydrogen-sensitive metal films can be realized through the piezoelectric plate, electromagnetic field coupling is enhanced and weak signals are amplified under low concentration, high-sensitivity detection of low-concentration hydrogen is realized, coupling is weakened and signal saturation is avoided under high concentration, the detection requirements of hydrogen with the concentration from 100 ppm to high concentration can be met, and the method is suitable for large-scale popularization and application. The method is suitable for various application scenes such as fuel cells and industrial gas detection.

Description

Technical Field

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

[0002] Hydrogen sensor: As a clean energy, hydrogen has the advantages of high combustion efficiency and low pollution, and is widely used in fuel cells, energy storage, chemical industry and other fields. However, hydrogen is highly flammable and explosive, and leakage at extremely low concentrations can cause serious safety accidents. Therefore, the development of hydrogen sensors with high sensitivity and high stability is particularly important 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 sensitivity, response time, operating temperature, selectivity, etc.: semiconductor metal oxide sensors usually require high-temperature heating, consume a lot of energy and have 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] In view of the defects in the prior art, an object of the present invention is to provide a tunable hydrogen sensor and a preparation process thereof.

[0005] A tunable hydrogen sensor provided according to the present invention comprises a hydrogen-sensitive metal film and a piezoelectric sheet; 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 a bowl-shaped structure. Two hydrogen-sensitive metal films are pressed together with the bowl tops of the hydrogen-sensitive metal bodies facing each other. The two hydrogen-sensitive metal films are respectively connected to one piezoelectric sheet. The distance between the two piezoelectric sheets is adjusted by deformation.

[0006] In some embodiments, the hydrogen-sensitive metal body includes a base film, and a hydrogen-sensitive metal layer is deposited on the base film.

[0007] In some embodiments, the material of the base film is an alloy formed by one or more of aluminum, copper, silver, and gold.

[0008] In some embodiments, the material of the hydrogen sensitive metal layer is palladium or platinum.

[0009] In some embodiments, the material of the piezoelectric film is lead zirconate titanate, potassium sodium niobate, barium titanate, lead lanthanum zirconate titanate or polyvinylidene fluoride and copolymers thereof.

[0010] In some embodiments, a packaging layer is further included. The material of the packaging layer is polyvinyl alcohol or silica gel. The piezoelectric sheet is packaged in the packaging layer. The thickness of the packaging layer is 1 to 5 μm.

[0011] In some embodiments, a protective coating is further included. The material of the protective coating is silicon dioxide or titanium dioxide. The protective coating is coated on the outer surface of the piezoelectric piece, or, when the piezoelectric piece is encapsulated with an encapsulation layer, the protective coating is coated on the outer surface of the encapsulation layer.

[0012] The present invention also provides a preparation process of a tunable hydrogen sensor, comprising the following steps: A1, ultrasonically clean the substrate with acetone, isopropanol, anhydrous ethanol, and deionized water for 5 to 20 minutes, and then dry it; A2, depositing the polystyrene microsphere suspension on the substrate treated in step A1 by a self-assembly method to form an ordered polystyrene sphere array; A3, sputtering the surface of the intermediate obtained in step A2 on the surface of the polystyrene sphere by magnetron sputtering to form a base film, wherein the base film is in the shape of an open semicircle and has a thickness of 270 to 350 nm; A4, forming a hydrogen-sensitive metal layer on the surface of the intermediate obtained in step A3 by electrodeposition on the surface of the base film, and the structure formed by the base film and the hydrogen-sensitive metal layer covering the single polystyrene ball is recorded as a hydrogen-sensitive metal body; A5, washing the intermediate obtained in step A4 in an organic solvent capable of dissolving polystyrene balls, wherein the hydrogen-sensitive metal bodies are arrayed to form a hydrogen-sensitive metal film in a layered structure after the polystyrene balls are dissolved; A6, adding polyvinyl alcohol solution to the surface of the hydrogen-sensitive metal film in the layered structure obtained in step A5, peeling off the hydrogen-sensitive metal film after solidification to form a film-like hydrogen-sensitive metal film, and pressing the two hydrogen-sensitive metal films together in a manner that the bowl tops of the hydrogen-sensitive metal body are opposite to each other; A7, coating adhesive on the surface of the piezoelectric sheet to form an adhesive layer, placing the two hydrogen-sensitive metal films pressed together in step A6 between the two piezoelectric sheets, the hydrogen-sensitive metal films are bonded and fixed to the piezoelectric sheet in the bowl-shaped buckle manner of the hydrogen-sensitive metal body, and the piezoelectric sheet adjusts the distance between the two hydrogen-sensitive metal films by deformation.

[0013] In some embodiments, the method further comprises A8, encapsulating the sample obtained in step A7 to form an encapsulation layer, wherein the material of the encapsulation layer is polyvinyl alcohol or silica gel, and the thickness of the encapsulation layer is 1 to 5 μm.

[0014] In some embodiments, the method further comprises A9, coating a protective layer on the surface of the sample obtained in step A7 or on the surface of the sample obtained in step A8, wherein the material of the protective layer is silicon dioxide or titanium dioxide.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The tunable hydrogen sensor of the present invention can achieve precise regulation of the nanometer-level distance between hydrogen-sensitive metal films through piezoelectric sheets, enhance electromagnetic field coupling at low concentrations, amplify weak signals, and achieve high-sensitivity detection of low-concentration hydrogen, while weakening coupling at high concentrations to avoid signal saturation. It can adapt to hydrogen detection needs from as low as 100 ppm to high concentrations, and is suitable for various application scenarios such as fuel cells and industrial gas detection.

[0016] 2. The tunable hydrogen sensor of the present invention effectively increases the specific surface area of ​​the sensing material through the semicircular 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 sense low-concentration hydrogen more quickly and accurately, significantly improving the sensitivity of the sensor.

[0017] 3. The preparation process of the tunable hydrogen sensor of the present invention is prepared by mature processes such as polystyrene template method and electrodeposition, and has the advantages of low cost and stable process. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings: Figure 1 This is a schematic diagram of densely arranged polystyrene spheres on a glass slide; Figure 2 Yes Figure 1 Schematic diagram after coating; Figure 3 Yes Figure 2 Schematic diagram after electrodeposition of palladium (Pd); Figure 4 Yes Figure 3 Schematic diagram after the polystyrene balls are removed; Figure 5 This is a schematic diagram of the template for preparing the silver-palladium nanobowl; Figure 6 It is a schematic diagram of the silver palladium nanobowl fixed on the piezoelectric sheet; Figure 7 It is a production flow chart of the present invention. DETAILED DESCRIPTION

[0019] The present invention is 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 are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention. Example

[0020] This embodiment provides a tunable hydrogen sensor, such as Figure 1-7 As shown, it mainly includes a hydrogen-sensitive metal film 1 and a piezoelectric sheet 2. The hydrogen-sensitive metal film 1 is a two-piece pressed structure, and the piezoelectric sheet 2 is also two pieces, which are 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.

[0021] 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 used as an example for illustration. The material of the hydrogen-sensitive metal layer 12 is palladium or platinum. In this embodiment, palladium is used 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 arrangement of multiple semicircular hydrogen-sensitive metal bodies 10. Each hydrogen-sensitive metal body 10 is a semicircular structure formed by a base film 11 and a hydrogen-sensitive metal layer 12 located thereon. The hydrogen-sensitive metal film 1 formed by the semicircular hydrogen-sensitive metal body 10 can effectively increase the specific surface area of ​​the sensing material, significantly increase the contact area with the hydrogen molecules, and enhance the adsorption effect. This structural characteristic enables the hydrogen sensor to sense low-concentration hydrogen more quickly and accurately, and can significantly improve the sensitivity of the sensor.

[0022] 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 a self-assembly method to form an ordered polystyrene (PS) microsphere array. Then, a layer of silver (Ag) is plated on the surface of the polystyrene (PS) microsphere array by magnetron sputtering technology to form a base film 11, and the thickness of the base film 11 is 270-350nm. 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 balls are dissolved by placing the sample in a tetrahydrofuran solvent that can dissolve polystyrene balls to form a hydrogen-sensitive metal film 1 in a layer structure state. Finally, a polyvinyl alcohol solution is dripped on the surface of the hydrogen-sensitive metal film 1 in a layer structure state, and the hydrogen-sensitive metal film 1 in a film state is peeled off after solidification. Through this method, two hydrogen-sensitive metal films 1 with substantially the same structure are pressed together in a manner that the bowl tops of the hydrogen-sensitive metal bodies 10 are relative to each other to form a sensing element for hydrogen detection.

[0023] The material of the piezoelectric sheet 2 is lead zirconate titanate (PZT), potassium sodium niobate (KNN), barium titanate (BaTiO3), lead lanthanum zirconate titanate (PLZT) or polyvinylidene fluoride (PVDF) and its copolymers. UV curing glue or heat curing 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 external pressure or alignment equipment to improve the arrangement uniformity and structural stability of the hydrogen-sensitive metal film 1. The thickness of the adhesive layer is between 100-500nm, which ensures the stability and firmness of the hydrogen-sensitive metal film 1 bonded to the piezoelectric sheet 2. In some embodiments, the two piezoelectric sheets 2 adjust the deformation amount through the control circuit, and the control circuit includes a feedback adjustment system, which can adjust the voltage on the piezoelectric sheet in real time according to the hydrogen concentration, and automatically control the distance between the upper and lower hydrogen-sensitive metal films 1, thereby realizing adaptive sensitivity regulation under different concentration conditions. The voltage regulating circuit in the control circuit uses a digital analog converter (DAC) to adjust the voltage and implement precise control of the deformation, thereby accurately 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 transmitting the hydrogen concentration data to a microcontroller or a display device in real time. The thickness of the piezoelectric sheet 2 is usually thin, generally between a few hundred microns and a few millimeters, and the deformation range is precisely controllable. On the one hand, it can achieve precise control of the nanometer-level distance between the hydrogen-sensitive metal films 1, and at the same time, it can make the overall structure of the sensor very compact, which is conducive to the miniaturization of the sensor.

[0024] 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

[0025] 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: The two piezoelectric sheets 2 are sandwiched to connect the two closely pressed hydrogen-sensitive metal films 1, and the piezoelectric sheets 2 are wrapped to form an encapsulation layer. 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 the interference of the external environment on 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 of polyvinyl alcohol (PVA) material as an example, the encapsulation material is evenly distributed on the outside of the tunable sensor by spin coating to form an encapsulation layer. The main process procedure is: first, polyvinyl alcohol (PVA) is dissolved in deionized water to prepare a 4% concentration of polyvinyl alcohol (PVA) solution, and then the tunable sensor is fixed on the spin coating equipment, and the low speed is rotated at 500 rpm for 10 seconds to evenly distribute the liquid, and the rotation speed is gradually increased to 3000 rpm for 45 seconds, and the waste material is dried to form a uniform film. Finally, the sensor behind the workpiece is placed in an oven and heated and cured at 80°C to shape the encapsulation layer.

[0026] In some embodiments, a protective layer is coated on the tunable hydrogen sensor. When the tunable hydrogen sensor has no packaging structure, the protective layer is coated on the two piezoelectric sheets 2. When the tunable hydrogen sensor has a packaging layer, the protective layer is coated on the packaging layer. The material of the protective layer is a silicon dioxide (SiO2) or titanium dioxide (TiO2) coating, which utilizes its anti-oxidation and photocatalytic self-cleaning properties to enhance the durability and environmental tolerance of the device. Example

[0027] This embodiment 3 provides a preparation process of a tunable hydrogen sensor, comprising the following steps: A1. Cleaning of the substrate: The substrate 4 is a conductive glass, a common glass sheet with deposited metal, or a metal sheet. First, the substrate 4 is cut into 2cm*4cm pieces, and ultrasonically cleaned with acetone, isopropanol, anhydrous ethanol, and deionized water for 10 minutes in sequence, and finally dried under nitrogen flow.

[0028] A2: First, use a pipette to draw 300 μL of a 300 nm diameter polystyrene (PS) microsphere 3 solution, and centrifuge it for 15 minutes. Then, add 20 μL of deionized water and 20 μL of anhydrous ethanol in turn, and vortex mix them for 1 minute respectively, and then add 5 μL of n-butanol and vortex for 1 minute. Place the solution in an ultrasonic oscillation for 2 to 4 hours to fully disperse the polystyrene (PS) microspheres to complete the preparation of the polystyrene (PS) microsphere suspension. The obtained polystyrene (PS) microsphere suspension is deposited on the substrate pretreated in step A1 by self-assembly method to form an ordered PS ball array, such as Figure 1 shown.

[0029] 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, such as Figure 2 The sputtering current is 15 mA, the power is 46 W, the sputtering is performed at a rate of 10 nm / min, and the sputtering time is 30 min.

[0030] A4: A layer of palladium (Pd) is deposited on the surface of the sample obtained in step A3 by a three-electrode direct current deposition method to form a hydrogen-sensitive metal layer 12, such as Figure 3 As shown. The configuration of its basic plating solution is: the palladium precursor is palladium chloride (PdCl2) with a concentration of 5-10mmol / 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 60g of palladium chloride (PdCl2), 2g of potassium chloride (KCl) and 7g of acetic acid (CH3COOH) to every 200mL of distilled water. When preparing the plating solution, first dissolve the palladium chloride in a small amount of deionized water to ensure complete dissolution, then gradually add potassium chloride (KCl), acetic acid (CH3COOH) and deionized water to the required volume, and stir slowly until the solution is uniform. Then put the base plating solution into a thermostatic bath, take the silver-plated base as the working electrode, silver chloride (AgCl) as the reference electrode, and the high-purity platinum electrode as the counter electrode, insert it into the base plating solution of the thermostatic bath for electrodeposition reaction, control the potential at -0.3 V to -0.5 V, the current density is 2 to 10 mA / cm², and electroplate at 80°C for 20 minutes. After the deposition is completed, gently rinse the sample with deionized water to remove the residual plating solution on the surface. The entire electroplating 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.

[0031] A5: Place the sample obtained in step A4 in a beaker containing tetrahydrofuran (THF) and let it stand for 1 hour. Then, take out the sample and rinse it thoroughly with anhydrous ethanol, and finally dry it under a nitrogen flow to form a layered hydrogen-sensitive metal film 1, such as Figure 4 Repeat the above steps to prepare two hydrogen-sensitive metal films 1 having substantially the same nanostructure.

[0032] A6: Add polyvinyl alcohol (PVA) solution to the surfaces of the two samples obtained in step A5, and after the solution is completely solidified, peel off the sample structure to form a hydrogen-sensitive metal film 1 in a membrane structure state, and then align and press the two hydrogen-sensitive metal films 1, as shown in FIG. Figure 5 shown.

[0033] A7: Use acetone, anhydrous ethanol and deionized water to ultrasonically clean the two piezoelectric sheets 2 for 15 minutes each to remove surface oil, dust and other impurities. Use a spin coater to evenly apply UV glue on the surface of the piezoelectric sheet 2. The spin coating conditions can be set to 2800rpm, and the spin coating time is 45 seconds to obtain a uniform nanoscale adhesive thin layer of 500 nanometers. Under a microscope, gently place the hydrogen-sensitive metal film 1 on the surface of the piezoelectric sheet 2 coated with the adhesive, and ensure that it is positioned correctly. If using UV curing glue, place the piezoelectric sheet 2 with the hydrogen-sensitive metal film 1 in a UV curing box and irradiate it under ultraviolet light with a wavelength of 300-400 nm for 30-60 seconds to ensure that the adhesive is fully cured to form a tunable hydrogen sensor, such as Figure 6 shown.

[0034] In the description of the present application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0035] The above describes the specific embodiments of the present invention. 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 does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A tunable hydrogen sensor, characterized in that: It comprises a hydrogen-sensitive metal film (1) and a piezoelectric sheet (2); The hydrogen-sensitive metal film (1) is a nano-scale structural layer formed by a plurality of hydrogen-sensitive metal bodies (10) in an array manner. The hydrogen-sensitive metal body (10) is a bowl-shaped structure. Two hydrogen-sensitive metal films (1) are pressed together in a manner such that the bowl tops of the hydrogen-sensitive metal bodies (10) are opposite to each other. The two hydrogen-sensitive metal films (1) are respectively connected to a piezoelectric sheet (2). The distance between the two hydrogen-sensitive metal films (1) is adjusted by deformation.

2. The tunable hydrogen sensor according to claim 1, characterized in that: The hydrogen-sensitive metal body (10) comprises a base film (11), on which a hydrogen-sensitive metal layer (12) is deposited.

3. The tunable hydrogen sensor according to claim 2, characterized in that: 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, characterized in that: The material of the hydrogen-sensitive metal layer (12) is palladium or platinum.

5. The tunable hydrogen sensor according to claim 1, characterized in that: The material of the piezoelectric sheet (2) is lead zirconate titanate, potassium sodium niobate, barium titanate, lead lanthanum zirconate titanate or polyvinylidene fluoride and copolymers thereof.

6. The tunable hydrogen sensor according to any one of claims 1 to 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 packaged in the packaging layer, and the thickness of the packaging layer is 1 to 5 μm.

7. The tunable hydrogen sensor according to claim 1, characterized in that: It also includes a protective coating, the material of which is silicon dioxide or titanium dioxide, and the protective coating is coated on the outer surface of the piezoelectric sheet (2), or, when the piezoelectric sheet (2) is encapsulated with an encapsulation layer, the protective coating is coated on the outer surface of the encapsulation layer.

8. A process for preparing a tunable hydrogen sensor, characterized in that: The steps include: A1, the substrate was ultrasonically cleaned with acetone, isopropanol, anhydrous ethanol, and deionized water for 5 to 20 minutes, and then dried; A2, depositing the polystyrene microsphere suspension on the substrate treated in step A1 by a self-assembly method to form an ordered polystyrene sphere array; A3, sputtering the surface of the intermediate obtained in step A2 on the surface of the polystyrene sphere by magnetron sputtering to form a base film (11), wherein the base film (11) is in the shape of an open semicircle, and the thickness of the base film (11) is 270 to 350 nm; A4, depositing a hydrogen-sensitive metal layer (12) on the surface of the intermediate obtained in step A3 by electrodeposition on the surface of the base film (11), and the structure formed by the base film (11) and the hydrogen-sensitive metal layer (12) covering the single polystyrene ball is recorded as a hydrogen-sensitive metal body (10); A5, washing the intermediate obtained in step A4 in an organic solvent capable of dissolving polystyrene balls, wherein the hydrogen-sensitive metal bodies (10) are arrayed to form a hydrogen-sensitive metal film (1) in a layered structure after the polystyrene balls are dissolved; A6, adding a polyvinyl alcohol solution to the surface of the hydrogen-sensitive metal film (1) in the layered structure obtained in step A5, peeling off the hydrogen-sensitive metal film (1) after solidification to form a film-like film, and pressing the two hydrogen-sensitive metal films (1) together in a manner that the bowl tops of the hydrogen-sensitive metal body (10) face each other; A7, an adhesive is coated on the surface of the piezoelectric sheet (2) to form an adhesive layer, and the two hydrogen-sensitive metal films (1) that have been pressed together in step A6 are placed between the two piezoelectric sheets (2). The hydrogen-sensitive metal film (1) is bonded and fixed to the piezoelectric sheet (2) in a bowl-shaped buckle manner of the hydrogen-sensitive metal body (10), and the piezoelectric sheet (2) adjusts the distance between the two hydrogen-sensitive metal films (1) by deformation.

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

10. The preparation process of the tunable hydrogen sensor according to claim 8 or 9, characterized in that: The method further comprises A9, coating a protective layer on the surface of the sample obtained in step A7 or on the surface of the sample obtained in step A8, wherein the material of the protective layer is silicon dioxide or titanium dioxide.

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