A hydrogen sensor and a method of manufacturing the same

Abstract

The application discloses a hydrogen sensor and a preparation method thereof, and relates to the technical field of sensors. The preparation method of the hydrogen sensor comprises the following steps: providing a substrate with a first electrode and a second electrode arranged at intervals on the surface of the substrate; providing a precursor solution comprising the following components in the following contents: a palladium source 0.01-0.2 mol / L, a complexing agent 0.02-8 mol / L, a reduction auxiliary agent 0.002-0.2 mol / L, a dispersing agent 0.001-0.02 mol / L and water; applying the precursor solution to the substrate between the first electrode and the second electrode, performing laser direct writing in a preset pattern, forming a hydrogen-sensitive sensing element connected with the first electrode and the second electrode, and obtaining the hydrogen sensor. The laser liquid-phase direct writing technology is adopted, the synthesis and patterning of the hydrogen-sensitive sensing element are completed in one step, the steps are simple and flexible, the preparation period is short, the cost is low, and the prepared hydrogen sensor has a relatively fast response speed.

Description

Technical Field

[0001] This invention relates to the field of sensor technology, and in particular to a hydrogen sensor and its preparation method. Background Technology

[0002] Hydrogen is a clean energy source, and its leak detection is crucial. Palladium (Pd) is a recognized ideal hydrogen-sensitive material, as it reacts with hydrogen to produce a reversible change in electrical resistance. Traditional palladium hydrogen sensors typically use dense, continuous palladium films as the sensing element. However, due to the low specific surface area and limited hydrogen diffusion paths (hydrogen diffuses much faster in dense lattices), existing hydrogen sensors using palladium films as the sensing element suffer from slow response times (typically tens of seconds to minutes), insufficient sensitivity, or inadequate stability.

[0003] In addition, the existing hydrogen sensor manufacturing usually relies on complex semiconductor micro-nano processing technology, including cumbersome steps such as spin coating of photoresist, mask exposure, development, high vacuum magnetron sputtering coating (or physical vapor deposition), stripping or etching, and the equipment used is expensive and the preparation cycle is long.

[0004] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a hydrogen sensor and its preparation method, which aims to solve the problems of complicated preparation steps and long cycle of existing hydrogen sensors.

[0006] The technical solution of the present invention is as follows:

[0007] In a first aspect, the present invention provides a method for preparing a hydrogen sensor, wherein the method for preparing the hydrogen sensor includes the following steps:

[0008] A substrate having a first electrode and a second electrode spaced apart on its surface is provided;

[0009] A precursor solution is provided, the precursor solution comprising the following components in varying amounts:

[0010] The mixture consists of a first metal source (0.01–0.2 mol / L), a complexing agent (0.02–8 mol / L), a reducing agent (0.002–0.2 mol / L), a dispersant (0.001–0.02 mol / L), and water; the first metal source is a palladium source.

[0011] The precursor solution is applied to a substrate between the first and second electrodes, and laser direct writing is performed according to a preset pattern to form a hydrogen-sensitive sensing element connecting the first and second electrodes, thus obtaining the hydrogen sensor.

[0012] Optionally, the laser direct writing includes femtosecond laser direct writing, picosecond laser direct writing, or nanosecond laser direct writing.

[0013] Optionally, the preset pattern includes one of the following patterns:

[0014] A straight line, several parallel straight lines, a serpentine shape, a spiral shape, a forked shape, and a grid shape.

[0015] Optionally, the laser wavelength used in the femtosecond laser direct writing is 515~800 nm.

[0016] Optionally, laser direct writing is performed along a straight line to form a palladium line connecting the first electrode and the second electrode, i.e., a hydrogen-sensitive sensing element; the linewidth of the palladium line is 600 nm to 10 μm.

[0017] Optionally, before forming the hydrogen-sensitive sensing element connecting the first and second electrodes after laser direct writing according to a preset pattern, the following steps are also included:

[0018] Soak in a cleaning solvent at 40-80°C for 30-60 minutes, then moisten with ethanol and blow dry; then place at 180-300°C for 10-30 minutes.

[0019] Optionally, the palladium source includes at least one of palladium chloride, sodium chloropalladium, potassium chloropalladium, palladium acetate, and palladium nitrate.

[0020] The complexing agent includes ammonia;

[0021] The reducing aid includes at least one of potassium sodium tartrate, sodium citrate, ascorbic acid, ethylene glycol, and formic acid;

[0022] The dispersant includes at least one of polyvinylpyrrolidone, hexadecyltrimethylammonium bromide, sodium dodecyl sulfate, and polyethylene glycol.

[0023] Optionally, the materials of the first electrode and the second electrode are each independently selected from at least one of metal, conductive metal oxide, conductive polymer and carbon material;

[0024] The substrate can be a rigid substrate or a flexible substrate. The material of the rigid substrate is selected from glass or quartz, and the material of the flexible substrate is selected from flexible polymer materials, including at least one of polyethylene terephthalate, polyimide, and polydimethylsiloxane.

[0025] Optionally, the precursor solution further includes at least one of the following components:

[0026] Viscosity modifier, second metal source, and conductive material;

[0027] The viscosity modifier accounts for 5% to 30% of the volume of the precursor solution;

[0028] In the precursor solution, the content of the second metal source is 0.01~0.2 mol / L, and the second metal source includes at least one of silver source, gold source, nickel source and copper source;

[0029] The conductive material in the precursor solution has a content of 0.01~0.2 mol / L, and the conductive material includes at least one of carbon nanotubes and graphene oxide.

[0030] In a second aspect, the present invention provides a hydrogen sensor, wherein the hydrogen sensor is prepared by the preparation method of the present invention as described above.

[0031] Beneficial Effects: This invention employs laser liquid phase direct writing technology to directly draw palladium onto a substrate in the precursor solution, completing the synthesis and patterning of the hydrogen-sensitive sensing element in one step between the first and second electrodes. The process is simple, flexible, and has a short preparation cycle. Furthermore, the method provided by this invention completely eliminates the need for expensive photolithography machines, photomasks, and high-vacuum coating equipment, and does not require a cleanroom environment, significantly reducing costs. This invention consumes the precursor solution only in the laser scanning area, greatly reducing the waste of precious palladium compared to the traditional full-coverage etching process.

[0032] Furthermore, traditional palladium thin film patterns are limited by physical masks, requiring re-fabrication of the mask to modify the pattern. The method of this invention, however, allows for software-controlled laser scanning paths, offering high printing freedom. It can draw arbitrarily complex two-dimensional geometric shapes (such as straight lines, serpentine patterns, and grids) on any substrate, facilitating rapid customization for different electrode spacings. It also possesses excellent point-to-point interconnection capabilities, enabling precise bridging between various pre-fabricated electrodes, unrestricted by electrode material properties, and achieving flexible integration of sensing elements and circuits.

[0033] The hydrogen-sensitive sensing elements (such as palladium wires, palladium sheets, palladium grids, etc.) prepared by the preparation method provided by the present invention have a large specific surface area, and therefore have a faster response speed (response time can be less than 4 s) and better sensing response performance. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the hydrogen sensor in an embodiment of the present invention.

[0035] Figure 2 This is a schematic diagram of the fabrication process of the hydrogen sensor in an embodiment of the present invention.

[0036] Figure 3 This is an optical microscope image of the hydrogen sensor in Example 1.

[0037] Figure 4 The graph shows the hydrogen response test results of the hydrogen sensor in Example 1. Detailed Implementation

[0038] This invention provides a hydrogen sensor and its preparation method. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0040] If the embodiments of the present invention involve descriptions such as "first" or "second", such descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated.

[0041] This invention provides a method for preparing a hydrogen sensor, wherein, as shown in the embodiments, Figure 1 As shown, the hydrogen sensor includes a substrate 1, a first electrode 2 and a second electrode 3 spaced apart on the substrate 1, and a hydrogen-sensitive sensing element 4 connecting the first electrode 2 and the second electrode 3; as shown Figure 2 As shown, the method for preparing the hydrogen sensor includes the following steps:

[0042] S1. A substrate on which a first electrode and a second electrode are spaced apart;

[0043] S2. Provide a precursor solution, wherein the precursor solution comprises the following components in varying amounts:

[0044] The mixture consists of a first metal source (0.01–0.2 mol / L), a complexing agent (0.02–8 mol / L), a reducing agent (0.002–0.2 mol / L), a dispersant (0.001–0.02 mol / L), and water; the first metal source is a palladium source.

[0045] S3. The precursor solution is applied to the substrate between the first electrode and the second electrode, and laser direct writing is performed according to a preset pattern to form a hydrogen-sensitive sensing element connecting the first electrode and the second electrode, thereby obtaining the hydrogen sensor.

[0046] In this invention, a hydrogen sensor with a fast response speed is prepared by employing a specific precursor solution formulation and a laser direct writing process (laser-induced reduction). A good crystal structure can be obtained by controlling the composition of the precursor solution. The complexing agent can react with the palladium source in situ to form a complex (e.g., a palladium-amine complex), which has high solubility and good thermodynamic stability. The dispersant enables the formation of smooth lines during the laser direct writing process. During laser direct writing, under the high energy density of the laser focal point, the palladium-amine complex in the precursor solution along the laser scanning path undergoes multiphoton absorption and photothermal dissociation, and is simultaneously reduced to metallic palladium nanoparticles under the action of the reduction aid, forming a hydrogen-sensitive sensing element. Therefore, the hydrogen-sensitive sensing element is composed of stacked metallic palladium nanoparticles.

[0047] In this invention, the working mechanism of the hydrogen sensor is as follows: When hydrogen permeates into the palladium lattice of the hydrogen-sensitive sensing element to form palladium hydride, the hydrogen atoms, acting as scattering centers, increase the probability of electron scattering, leading to an increase in the material's resistivity. At this point, the electron scattering effect (leading to increased resistance) outweighs the contact improvement effect brought about by lattice expansion (leading to decreased resistance), macroscopically manifesting as increased resistance. Therefore, hydrogen can be detected by observing the change in resistance. The hydrogen-sensitive sensing element (such as a palladium wire) has a large specific surface area, which is more conducive to the instantaneous permeation of hydrogen into its interior, thus achieving a response speed of less than 4 seconds. Furthermore, as the linewidth of the hydrogen-sensitive sensing element (such as a palladium wire) decreases, the response speed is expected to decrease further.

[0048] This invention employs laser liquid phase direct writing technology to directly draw palladium onto a substrate in a precursor solution, completing the synthesis and patterning of the hydrogen-sensitive sensing element in one step between the first and second electrodes. The process is simple, flexible, and has a short preparation cycle. Furthermore, the method provided by this invention completely eliminates the need for expensive photolithography machines, photomasks, and high-vacuum coating equipment, and does not require a cleanroom environment, significantly reducing costs. This invention consumes the precursor solution only in the laser scanning area, greatly reducing the waste of precious palladium compared to the traditional full-coverage etching process.

[0049] Furthermore, traditional palladium thin film patterns are limited by physical masks, requiring re-fabrication of the mask to modify the pattern. The method of this invention, however, allows for software-controlled laser scanning paths, offering high printing freedom. It can draw arbitrarily complex two-dimensional geometric shapes (such as straight lines, serpentine patterns, and grids) on any substrate, facilitating rapid customization for different electrode spacings. It also possesses excellent point-to-point interconnection capabilities, enabling precise bridging between various pre-fabricated electrodes, unrestricted by electrode material properties, and achieving flexible integration of sensing elements and circuits.

[0050] The hydrogen-sensitive sensing elements (such as palladium wires, palladium sheets, palladium grids, etc.) prepared using the preparation method provided by the present invention have a much larger specific surface area than palladium thin films. Therefore, they have a faster response speed (response time can be less than 4 s) and better sensing response performance.

[0051] Furthermore, in some embodiments of the present invention, by controlling the laser wavelength, microbubbles can be induced at the laser spot based on the laser thermal effect to form a porous structure of palladium nanoparticles. This results in a porous continuous network structure for the hydrogen-sensitive sensing element (with good physical continuity between palladium nanoparticles forming a continuous network). Consequently, the hydrogen-sensitive sensing element has a large specific surface area and abundant gas diffusion channels, allowing hydrogen to instantly penetrate into the material, achieving a rapid response and giving the hydrogen sensor better hydrogen sensing performance.

[0052] In this embodiment, the distance between the first electrode and the second electrode on the substrate can be set according to actual needs. For example, the distance between the first electrode and the second electrode on the substrate can be 2 μm to 1 mm, specifically, it can be 2 μm, 5 μm, 10 μm, 50 μm, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm or 1 mm, etc.

[0053] In this embodiment, as an example, the concentration of the first metal source can be 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.15 mol / L, or 0.2 mol / L, etc. The concentration of the complexing agent can be 0.02 mol / L, 0.03 mol / L, 0.05 mol / L, 0.08 mol / L, 0.1 mol / L, 0.2 mol / L, 0.5 mol / L, 0.8 mol / L, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, or 8 mol / L, etc. The concentration of the reducing agent can be 0.002 mol / L, 0.005 mol / L, 0.008 mol / L, 0.01 mol / L, 0.02 mol / L, 0.05 mol / L, 0.08 mol / L, 0.1 mol / L, 0.12 mol / L, 0.15 mol / L, 0.18 mol / L, or 0.2 mol / L, etc. The concentration of the dispersant can be 0.001 mol / L, 0.002 mol / L, 0.005 mol / L, 0.008 mol / L, 0.01 mol / L, 0.12 mol / L, 0.15 mol / L, 0.18 mol / L, or 0.02 mol / L, etc.

[0054] In step S1, in some embodiments, the substrate is a rigid substrate or a flexible substrate. The method provided by this invention has a wide range of applications, applicable to both rigid and flexible substrates. Specifically, this invention does not require photolithography and masks, therefore it can be printed not only on rigid planar glass, but also directly fabricated on fiber end faces, microfluidic channel inner walls, or flexible curved surfaces (such as the surface of contact lenses).

[0055] In some embodiments, the material of the rigid substrate is selected from glass or quartz, but is not limited thereto.

[0056] In some embodiments, the material of the flexible substrate is selected from flexible polymer materials, including at least one of polyethylene terephthalate (PET), polyimide (PI), and polydimethylsiloxane (PDMS).

[0057] In some embodiments, the materials of the first electrode and the second electrode are each independently selected from at least one of metals, conductive metal oxides, conductive polymers and carbon materials, but are not limited thereto.

[0058] Among them, the metal includes at least one of silver (Ag) and copper (Cu), and the specific preparation materials can be conductive silver paste, copper foil, etc.; the conductive metal oxide includes indium tin oxide (ITO), etc.; the carbon material includes graphene, conductive carbon, etc., and the preparation materials can be carbon paste, etc., but are not limited to these.

[0059] Since the preparation method provided by this invention does not involve high-temperature sintering, it is particularly suitable for the preparation of fully transparent hydrogen sensors based on indium tin oxide.

[0060] In step S2, in some embodiments, the palladium source includes at least one of palladium chloride (PdCl2), sodium chloropalladium, potassium chloropalladium, palladium acetate, and palladium nitrate, but is not limited thereto.

[0061] In some embodiments, the complexing agent includes ammonia water, i.e., the concentration of NH3 in the ammonia water in the precursor solution is 0.02~8 mol / L, for example, it can be 0.02 mol / L, 0.05 mol / L, 0.08 mol / L, 0.1 mol / L, 0.2 mol / L, 0.5 mol / L, 0.8 mol / L, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L or 8 mol / L, etc.

[0062] In some embodiments, the reducing agent includes at least one of potassium sodium tartrate, sodium citrate, ascorbic acid, ethylene glycol, and formic acid, but is not limited thereto.

[0063] In some embodiments, the dispersant includes, but is not limited to, at least one of polyvinylpyrrolidone (PVP), hexadecyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), and polyethylene glycol (PEG).

[0064] In some embodiments, the precursor solution further includes at least one of the following components:

[0065] Viscosity modifier, second metal source, and conductive material.

[0066] The volume of the viscosity modifier accounts for 5% to 30% of the volume of the precursor solution (for example, it can be 5%, 6%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28% or 30%).

[0067] In some embodiments, the viscosity modifier is glycerin.

[0068] In the precursor solution, the concentration of the second metal source is 0.01~0.2 mol / L (e.g., 0.01 mol / L, 0.02 mol / L, 0.05 mol / L, 0.08 mol / L, 0.1 mol / L, 0.12 mol / L, 0.15 mol / L, 0.18 mol / L, or 0.2 mol / L, etc.). The second metal source includes at least one of the following: a silver source (e.g., silver salts, specifically silver nitrate, silver chlorate, etc.), a gold source (e.g., gold salts), a nickel source (e.g., nickel salts, specifically nickel sulfate, nickel chloride, etc.), and a copper source (e.g., copper salts, specifically copper sulfate, copper chloride, etc.). This allows for the preparation of Pd-Ag, Pd-Au, and Pd-Ni alloy hydrogen-sensitive sensing elements. For example, Pd-Ag alloys can effectively suppress hydrogen embrittlement.

[0069] In the precursor solution, the concentration of the conductive material is 0.01–0.2 mol / L (e.g., 0.01 mol / L, 0.02 mol / L, 0.05 mol / L, 0.08 mol / L, 0.1 mol / L, 0.12 mol / L, 0.15 mol / L, 0.18 mol / L, or 0.2 mol / L, etc.). The conductive material includes at least one of carbon nanotubes and graphene oxide. These conductive materials are co-deposited with palladium using a laser to form a composite sensing network.

[0070] In step S3, it is understood that when the precursor solution is applied to the substrate between the first electrode and the second electrode, the precursor solution on the substrate needs to cover the laser direct writing path (i.e., the laser scanning path).

[0071] In this invention, a hydrogen-sensitive sensing element can be formed by laser direct writing according to a preset pattern, or an array of hydrogen-sensitive sensing elements can be formed by laser direct writing according to multiple identical or different patterns (e.g., multiple straight lines with different line widths) to achieve the detection of hydrogen gas in a wide concentration range.

[0072] In step S3, in some embodiments, the laser direct writing includes femtosecond laser direct writing, picosecond laser direct writing, or nanosecond laser direct writing, etc.

[0073] In some embodiments, the laser wavelength used for femtosecond laser direct writing is 515~800 nm, for example, it can be 515 nm, 520 nm, 530 nm, 540 nm, 550 nm, 560 nm, 570 nm, 580 nm, 590 nm, 600 nm, 610 nm, 620 nm, 630 nm, 640 nm, 650 nm, 660 nm, 670 nm, 680 nm, 690 nm, 700 nm, 710 nm, 720 nm, 730 nm, 740 nm, 750 nm, 760 nm, 770 nm, 780 nm, 790 nm or 800 nm, etc.

[0074] This invention does not limit the specific pattern of the hydrogen-sensitive sensing element; it can be any desired shape. As an example, the preset pattern includes one of the following patterns:

[0075] A straight line, several parallel straight lines, a serpentine shape, a spiral shape, a forked shape, and a grid shape.

[0076] These different patterns can change the initial resistance of the hydrogen sensor to match different detection circuits.

[0077] In some embodiments, laser direct writing is performed along a straight line to form a palladium line connecting the first electrode and the second electrode, i.e., a hydrogen-sensitive sensing element; the linewidth of the palladium line is 600 nm to 10 μm (for example, it can be 600 nm, 700 nm, 800 nm, 900 nm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm, etc.).

[0078] In some embodiments, before forming the hydrogen-sensitive sensing element connecting the first and second electrodes after laser direct writing according to a preset pattern, the following steps are also included:

[0079] The sample is immersed in a cleaning solvent at 40–80 °C (e.g., 40 °C, 50 °C, 60 °C, 70 °C, or 80 °C) for 30–60 minutes (e.g., 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes, or 60 minutes), then moistened with ethanol and dried. This cleaning process removes residual complexing agents, unreacted ions, and excess dispersants. After cleaning, the hydrogen-sensitive sensing element, such as the palladium wire, is no longer affected by ionic conductivity and exhibits its intrinsic metallic conductivity.

[0080] Then, place the product at a temperature of 180–300 °C (e.g., 180 °C, 190 °C, 200 °C, 220 °C, 250 °C, 280 °C, or 300 °C) for 10–30 minutes (e.g., 10 minutes, 15 minutes, 20 minutes, 25 minutes, or 30 minutes). This is a drying process to remove water and stabilize the contact between palladium nanoparticles. This process can be carried out in air, or in a vacuum, nitrogen atmosphere, or dilute hydrogen atmosphere to adjust the degree of oxidation of the final product.

[0081] In some embodiments, the cleaning solvent includes deionized water, a mixed solution of ethanol and deionized water, acetic acid solution, or sodium borohydride solution, but is not limited to these.

[0082] This invention also provides a hydrogen sensor, wherein the hydrogen sensor is prepared by the preparation method described above. The hydrogen sensor includes a substrate, a first electrode and a second electrode spaced apart on the substrate, and a hydrogen-sensitive sensing element connecting the first electrode and the second electrode. The hydrogen-sensitive sensing element can be a palladium wire (specifically, palladium nanowires, palladium microwires, etc.; if the line width is sufficiently wide, it can be considered as a palladium nanosheet), a palladium grid, etc., and both the palladium wire and the palladium grid are composed of stacked palladium nanoparticles.

[0083] In this embodiment, the hydrogen-sensitive sensing element (such as a palladium wire) has a large specific surface area, which is more conducive to the instantaneous penetration of hydrogen into its interior, resulting in a fast response speed of less than 4 seconds. Furthermore, as the linewidth of the hydrogen-sensitive sensing element (such as a palladium wire) decreases, the response speed is expected to decrease further.

[0084] The present invention will be further described below through specific embodiments.

[0085] In the following embodiments, unless otherwise specified, the raw materials and equipment used are all commercially available products.

[0086] In the following embodiments, the equipment used for laser direct writing is the Prome-Uni lithography equipment from Magic Nanotechnology.

[0087] Example 1

[0088] This embodiment provides a method for preparing a hydrogen sensor, including the following steps:

[0089] (1) Preparation of precursor solution: Mix 0.1 mol palladium chloride, a certain volume of ammonia water (the mass content of NH3 in the ammonia water is 28%; that is, add a certain volume of ammonia water so that the concentration of NH3 in the precursor solution is 2 mol / L) and a certain amount of water (make up to 800 mL) (to form palladium-ammonium complex), then add 0.1 mol potassium sodium tartrate, 0.01 mol polyvinylpyrrolidone and 100 mL glycerol, and finally add water to make up to 1000 mL (i.e. 1 L) to obtain the precursor solution.

[0090] (2) Laser direct writing to prepare hydrogen-sensitive sensing element: Two spaced first gold electrodes and second gold electrodes (30 μm apart) are prepared on a quartz substrate. The precursor solution prepared in step (1) is dropped onto the substrate between the first gold electrodes and the second gold electrodes and laser direct writing is performed (equipment setting parameters: center wavelength is 515 nm) to form a palladium line connecting the first gold electrodes and the second gold electrodes, which is the hydrogen-sensitive sensing element.

[0091] (3) Cleaning: Immerse the sample prepared in step (2) in deionized water at 60 °C, let it stand for 60 minutes, then wet it with ethanol and blow it dry.

[0092] (4) Drying: Place the sample prepared in step (3) in the air and heat it on a 200 ℃ heating stage for 30 minutes to complete the device preparation.

[0093] test:

[0094] (1) The optical microscope image of the hydrogen sensor prepared above is shown in Figure 1. Figure 3 As shown, the linewidth of the palladium line is approximately 4.778 μm.

[0095] (2) The hydrogen sensor prepared above was placed in a gas chamber, and hydrogen gas with a volume concentration of 4% was introduced at room temperature for testing. The results are as follows. Figure 4 As shown, the results indicate that the hydrogen sensor exhibits excellent response characteristics:

[0096] Positive resistance response: When 4% hydrogen gas is introduced at room temperature, the resistance value of the hydrogen sensor increases rapidly.

[0097] Ultrafast response speed: The response time of the hydrogen sensor (i.e., the time Δt required for the resistance change to reach 90% of its maximum change). 90 (less than 4 seconds)

[0098] Reversibility: After the hydrogen flow is stopped and air is introduced, the resistance can be restored to the initial baseline level.

[0099] Example 2

[0100] This embodiment provides a method for preparing a hydrogen sensor, including the following steps:

[0101] (1) Preparation of precursor solution: Mix 0.2 mol palladium chloride, a certain volume of ammonia water (the mass content of NH3 in the ammonia water is 28%; that is, add a certain volume of ammonia water so that the concentration of NH3 in the precursor solution is 8 mol / L) and a certain amount of water (make up to 800 mL) (to form palladium-ammonium complex), then add 0.2 mol potassium sodium tartrate, 0.02 mol polyvinylpyrrolidone and 200 mL glycerol, and finally add water to make up to 1000 mL (i.e. 1 L) to obtain the precursor solution.

[0102] (2) Laser direct writing to prepare hydrogen-sensitive sensing element: Same as step (2) in Example 1.

[0103] (3) Cleaning: Immerse the sample prepared in step (2) in deionized water at 60 °C, let it stand for 50 minutes, then wet it with ethanol and blow it dry.

[0104] (4) Drying: Place the sample prepared in step (3) in the air and treat it on a heating stage at 200 °C for 20 minutes to complete the device preparation.

[0105] The hydrogen sensor prepared in this embodiment has similar performance to the hydrogen sensor prepared in Example 1, and has a faster response speed.

[0106] Example 3

[0107] This embodiment provides a method for preparing a hydrogen sensor, including the following steps:

[0108] (1) Preparation of precursor solution: Mix 0.01 mol palladium chloride, a certain volume of ammonia water (the mass content of NH3 in the ammonia water is 28%; that is, add a certain volume of ammonia water so that the concentration of NH3 in the precursor solution is 0.02 mol / L) and a certain amount of water (make up to 800 mL) (to form palladium-ammonium complex), then add 0.002 mol potassium sodium tartrate, 0.001 mol polyvinylpyrrolidone and 100 mL glycerol, and finally add water to make up to 1000 mL (i.e. 1 L) to obtain the precursor solution.

[0109] (2) Laser direct writing to prepare hydrogen-sensitive sensing element: Same as step (2) in Example 1.

[0110] (3) Cleaning: Immerse the sample prepared in step (2) in deionized water at 60 °C, let it stand for 60 minutes, then wet it with ethanol and blow it dry.

[0111] (4) Drying: The sample prepared in step (3) is heated on a 200 ℃ heating stage for 10 minutes to complete the device preparation.

[0112] The hydrogen sensor prepared in this embodiment has similar performance to the hydrogen sensor prepared in Example 1, and has a faster response speed.

[0113] Comparative Example 1

[0114] This comparative example provides a method for preparing a hydrogen sensor, comprising the following steps:

[0115] (1) Preparation of precursor solution: Mix 0.1 mol palladium chloride, a certain volume of ammonia water (the NH3 content in the ammonia water is the same as in Example 1, and the concentration of NH3 in the precursor solution is the same as in Example 1) and a certain amount of water (to a final volume of 800 mL) (to form a palladium-ammonium complex), then add 0.001 mol potassium sodium tartrate, 0.01 mol polyvinylpyrrolidone and 100 mL glycerol, and finally add water to a final volume of 1000 mL (i.e. 1 L) to obtain the precursor solution.

[0116] (2) Laser direct writing to prepare hydrogen-sensitive sensing element: Same as step (2) in Example 1.

[0117] (3) Cleaning: Same as step (3) in Example 1.

[0118] (4) Drying: Same as step (4) in Example 1.

[0119] This method cannot be used to prepare a hydrogen sensor with hydrogen sensing capabilities.

[0120] In summary, this invention provides a hydrogen sensor and its fabrication method. This invention employs laser liquid-phase direct writing technology to directly draw palladium onto a substrate in a precursor solution, completing the synthesis and patterning of the hydrogen-sensitive element in one step between the first and second electrodes. The process is simple, flexible, and has a short fabrication cycle. Furthermore, the method provided by this invention completely eliminates the need for expensive photolithography machines, photomasks, and high-vacuum coating equipment, and does not require a cleanroom environment, significantly reducing costs. This invention consumes the precursor solution only in the laser scanning area, greatly reducing the waste of precious palladium compared to the traditional full-coverage etching process.

[0121] Furthermore, traditional palladium thin film patterns are limited by physical masks, requiring re-fabrication of the mask to modify the pattern. The method of this invention, however, allows for software-controlled laser scanning paths, offering high printing freedom. It can draw arbitrarily complex two-dimensional geometric shapes (such as straight lines, serpentine patterns, and grids) on any substrate, facilitating rapid customization for different electrode spacings. It also possesses excellent point-to-point interconnection capabilities, enabling precise bridging between various pre-fabricated electrodes, unrestricted by electrode material properties, and achieving flexible integration of sensing elements and circuits.

[0122] The hydrogen-sensitive sensing elements (such as palladium wires, palladium sheets, palladium grids, etc.) prepared by the preparation method provided by the present invention have a large specific surface area, and therefore have a faster response speed (response time can be less than 4 s) and better sensing response performance.

[0123] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for preparing a hydrogen sensor, characterized in that, The method for preparing the hydrogen sensor includes the following steps: A substrate having a first electrode and a second electrode spaced apart on its surface is provided; A precursor solution is provided, the precursor solution comprising the following components in varying amounts: The mixture consists of a first metal source (0.01–0.2 mol / L), a complexing agent (0.02–8 mol / L), a reducing agent (0.002–0.2 mol / L), a dispersant (0.001–0.02 mol / L), and water; the first metal source is a palladium source. In the precursor solution, the complexing agent reacts with the palladium source to form a complex in situ; The precursor solution is applied to the substrate between the first electrode and the second electrode, and laser direct writing is performed according to a preset pattern. The complex in the precursor solution along the laser scanning path undergoes multiphoton absorption and photothermal dissociation, and is simultaneously reduced to palladium nanoparticles under the action of a reducing agent, forming a hydrogen-sensitive sensing element connecting the first electrode and the second electrode, thus obtaining the hydrogen sensor. The hydrogen-sensitive sensing element is composed of stacked palladium nanoparticles.

2. The method for preparing a hydrogen sensor according to claim 1, characterized in that, The laser direct writing includes femtosecond laser direct writing, picosecond laser direct writing, or nanosecond laser direct writing.

3. The method for preparing a hydrogen sensor according to claim 1, characterized in that, The preset pattern includes one of the following patterns: A straight line, several parallel straight lines, a serpentine shape, a spiral shape, a forked shape, and a grid shape.

4. The method for preparing a hydrogen sensor according to claim 2, characterized in that, The femtosecond laser direct writing uses a laser wavelength of 515~800 nm.

5. The method for preparing a hydrogen sensor according to claim 1, characterized in that, Laser direct writing is performed along a straight line to form a palladium line connecting the first electrode and the second electrode, which is a hydrogen-sensitive sensing element; the linewidth of the palladium line is 600 nm to 10 μm.

6. The method for preparing a hydrogen sensor according to claim 1, characterized in that, Before forming the hydrogen-sensitive sensing element connecting the first and second electrodes after laser direct writing according to the preset pattern, the following steps are also included: Soak in a cleaning solvent at 40-80°C for 30-60 minutes, then moisten with ethanol and dry; then place at 180-300°C for 10-30 minutes.

7. The method for preparing a hydrogen sensor according to any one of claims 1-6, characterized in that, The palladium source includes at least one of palladium chloride, sodium chloropalladium, potassium chloropalladium, palladium acetate, and palladium nitrate. The complexing agent includes ammonia; The reducing aid includes at least one of potassium sodium tartrate, sodium citrate, ascorbic acid, ethylene glycol, and formic acid; The dispersant includes at least one of polyvinylpyrrolidone, hexadecyltrimethylammonium bromide, sodium dodecyl sulfate, and polyethylene glycol.

8. The method for preparing a hydrogen sensor according to any one of claims 1-6, characterized in that, The materials of the first electrode and the second electrode are each independently selected from at least one of metal, conductive metal oxide, conductive polymer and carbon material; The substrate can be a rigid substrate or a flexible substrate. The material of the rigid substrate is selected from glass or quartz, and the material of the flexible substrate is selected from flexible polymer materials, including at least one of polyethylene terephthalate, polyimide, and polydimethylsiloxane.

9. The method for preparing a hydrogen sensor according to claim 1, characterized in that, The precursor solution further includes at least one of the following components: Viscosity modifier, second metal source, and conductive material; The viscosity modifier accounts for 5% to 30% of the volume of the precursor solution; In the precursor solution, the content of the second metal source is 0.01~0.2 mol / L, and the second metal source includes at least one of silver source, gold source, nickel source and copper source; The conductive material in the precursor solution has a content of 0.01~0.2 mol / L, and the conductive material includes at least one of carbon nanotubes and graphene oxide.

10. A hydrogen sensor, characterized in that, The hydrogen sensor is prepared by the preparation method according to any one of claims 1-9.

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