A palladium-doped ZnO-SnO2 heterostructure hydrogen sensor and its preparation method

Abstract

This invention provides a palladium-doped ZnO-SnO2 heterostructure hydrogen sensor and its preparation method, belonging to the field of hydrogen sensor technology. The preparation method includes: mixing SnO2 nanosheets with ZIF-8 in a certain proportion, drying and calcining to obtain a ZnO-SnO2 heterostructure material with a clear phase interface; mixing the ZnO-SnO2 heterostructure material with palladium nitrate dihydrate in deionized water in a certain proportion, stirring, centrifuging, drying and calcining under an argon atmosphere to obtain a PdOx / ZnO-SnO2 composite material, wherein PdOx contains both PdO and PdO2 forms; finally, depositing the composite material onto interdigitated electrodes using a drop-coating method to obtain the hydrogen sensor. The hydrogen sensor obtained by this invention provides a more efficient charge transport path for hydrogen reactions, while effectively solving the problem of volume expansion of metallic palladium in hydrogenation / dehydrogenation cycles.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen sensor technology, specifically relating to a palladium-doped ZnO-SnO2 heterostructure hydrogen sensor and its preparation method. Background Technology

[0002] Hydrogen, as a clean and efficient new energy source, is widely used in hydrogen fuel cell vehicles, distributed power generation, and chemical industries. However, hydrogen is colorless and odorless, has a high diffusion coefficient, and a wide explosion limit; it is flammable at concentrations of 4%-75% by volume. Leaks are difficult to detect and can easily lead to explosions, posing a serious challenge to the safe operation of the hydrogen energy industry chain. To prevent hydrogen leaks, hydrogen sensors are generally required for detection. Existing technologies include hydrogen sensors loaded with palladium, which utilize the catalytic overflow effect to reduce the activation energy, thereby improving the sensitivity and response speed of hydrogen detection and lowering the operating temperature. However, this type of hydrogen sensor has the following drawbacks: (1) Single metal oxide carriers have poor electron transport capabilities and mainly rely on the chemical sensitization effect of palladium. The reaction path is simple, resulting in insufficient response of the sensor to low concentration of hydrogen and slow response speed. (2) The volume of palladium particles expands significantly during hydrogenation / dehydrogenation cycles, which can easily lead to structural pulverization, thereby exacerbating migration and agglomeration, causing irreversible performance degradation and affecting the detection stability of the sensor.

[0003] Therefore, it is necessary to provide a palladium-doped ZnO-SnO2 heterostructure hydrogen sensor and its preparation method to solve the above problems. Summary of the Invention

[0004] This invention provides a palladium-doped ZnO-SnO2 heterostructure hydrogen sensor and its preparation method, which provides a more efficient charge transport path for hydrogen reactions and effectively solves the problem of volume expansion of metallic palladium in hydrogenation / dehydrogenation cycles.

[0005] To solve the above-mentioned technical problems, the present invention is implemented as follows: A method for fabricating a palladium-doped ZnO-SnO2 heterostructure hydrogen sensor includes the following steps: Step S1: SnO2 nanosheets and ZIF-8 are mixed in anhydrous ethanol at a molar ratio of 10:1, stirred evenly, dried thoroughly, and then calcined in a muffle furnace to obtain ZnO-SnO2 heterostructure material. Step S2: Dissolve the ZnO-SnO2 heterostructure material and palladium nitrate dihydrate in deionized water at a mass ratio of 5:1, stir thoroughly, collect the product by centrifugation, wash with deionized water, dry, and calcine the product in a tube furnace under an argon atmosphere to obtain PdO. x / ZnO-SnO2 composite material, wherein PdO x It includes both PdO and PdO2 forms; Step S3: Using the drop-coating method, PdO is applied... x The ZnO-SnO2 composite material was dissolved in deionized water and sonicated. Then, it was dropped onto the middle of the interdigitated electrodes with a pipette and dried at a certain temperature for a period of time to obtain a palladium-doped ZnO-SnO2 heterostructure hydrogen sensor.

[0006] As a preferred improvement, in step S1, SnO2 nanosheets are prepared by the following method: Dissolve 0.96 g of sodium hydroxide and 1.99 g of terephthalic acid in 300 mL of deionized water and stir thoroughly to obtain solution A; Dissolve 3.45 g of stannous chloride dihydrate in 60 mL of deionized water and stir thoroughly to obtain solution B; Solution B was added dropwise to solution A at room temperature and with magnetic stirring to obtain a mixed solution. The mixture was stirred for 1 hour, centrifuged and dried. The resulting product was calcined in a muffle furnace at 500℃ for 3 hours to obtain SnO2 nanosheets.

[0007] As a preferred improvement, in step S1, ZIF-8 is prepared in the following manner: 0.67 g of zinc nitrate hexahydrate and 0.167 g of 2-methylimidazole were mixed in 50 mL of DMF and stirred vigorously until a clear solution was obtained. The solution was then transferred to a 100 mL reaction vessel with a polytetrafluoroethylene liner and heated in an oven at 140 °C for 24 hours. The product was filtered, washed with DMF, stored in methanol for 3 days, and then dried at 50 °C for 24 hours to obtain ZIF-8.

[0008] As a preferred improvement, step S1 specifically includes the following process: Mix 3 mmol SnO2 nanosheets and 0.3 mmol ZIF-8 in 20 mL anhydrous ethanol, stir well, and dry thoroughly. The dried product was calcined at 350℃ for 2 hours, and then heated to 400℃ for 1 hour to obtain ZnO-SnO2 heterostructure material.

[0009] As a preferred improvement, step S2 specifically includes the following process: 100 mg of ZnO-SnO2 heterostructure material and 20 mg of palladium nitrate dihydrate were dissolved in 40 mL of deionized water and stirred thoroughly at 35 °C for 24 hours. The product was collected by centrifugation, washed twice with deionized water, dried at 60 °C for 2 hours, and then calcined at 350 °C for 2 hours in a tube furnace under an argon atmosphere to obtain PdO. x / ZnO-SnO2 composite material.

[0010] As a preferred improvement, PdO x PdO accounted for 67.52% and PdO2 accounted for 32.48%.

[0011] As a preferred improvement, step S3 specifically includes the following process: 10 mg of PdO was applied using a drop-coating method. x The ZnO-SnO2 composite material was dissolved in 0.5 mL of deionized water and sonicated for 30 minutes. Then, it was dropped onto the middle of the interdigitated electrode with a pipette and dried at 80 °C for 2 hours to obtain a palladium-doped ZnO-SnO2 heterostructure hydrogen sensor.

[0012] A palladium-doped ZnO-SnO2 heterostructure hydrogen sensor was prepared using the method described above.

[0013] As a preferred improvement, the sensor has a hydrogen concentration detection range of 0.1-50 ppm.

[0014] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention adopts the construction strategy of “pre-fabricated SnO2 nanosheets + ZIF-8 stepwise pyrolysis”, which is different from the traditional one-pot method. It can form a ZnO-SnO2 heterostructure with a clear and stable phase interface, effectively avoiding the generation of ternary impurities such as Zn2SnO4 or excessive solid solutions, thereby ensuring the electronic control capability of the heterojunction interface and providing a more effective charge transport path for hydrogen reaction. (2) PdO introduced in this invention x The active component is not simply supported palladium, but rather Pd. 2+ Main, Pd 4+ The presence of PdO in its secondary oxidation state effectively reduces the volume expansion of palladium during the hydrogenation / dehydrogenation cycle; XPS results show that PdO... x / ZnO-SnO2 composite material with strong adsorption of oxygen (O V The proportion of 46.89% indicates that this structure can significantly enhance the adsorption and activation capacity of oxygen species on the material surface, providing more reaction sites for hydrogen molecules, which is the key to realizing low-temperature and low-concentration hydrogen detection. (3) The hydrogen sensor prepared by the present invention can achieve a high response value of about 80% for 50ppm hydrogen at a low operating temperature (such as 120℃), and exhibits excellent selectivity for hydrogen. It has extremely low response to interfering gases such as ethanol, nitric oxide, formaldehyde, ammonia, and nitrogen dioxide, and has strong anti-interference ability. (4) The sensor of the present invention has small response fluctuations to hydrogen in the range of relative humidity from 0 to 75%, and has good moisture resistance. At the same time, the response value decays only slightly in the long-term stability test of 40 days, and the consistency between multiple batches of devices is good, indicating that it has good repeatability, reliability and environmental adaptability. (5) The preparation method of the present invention has good process compatibility and strong controllability of operation steps, and is suitable for industrial mass production. The sensor obtained has important practical application value in the hydrogen energy industry chain fields such as hydrogen fuel cell vehicles, distributed power generation, and chemical safety. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein: Figure 1 This is a SEM image of the intermediate Sn-MOF from Example 3; Figure 2 This is a SEM image of the intermediate SnO2 nanosheets from Example 3. Figure 3 PdO obtained in Example 3 x SEM image of the ZnO-SnO2 composite material; Figure 4 PdO obtained in Example 3 x TEM image of the ZnO-SnO2 composite material; Figure 5 PdO obtained in Example 3 x EDS energy spectrum of Sn element in ZnO-SnO2 composite material; Figure 6 PdO obtained in Example 3 x EDS energy spectrum of Zn element in ZnO-SnO2 composite material; Figure 7 PdO obtained in Example 3 x EDS energy spectrum of Pd element in ZnO-SnO2 composite material; Figure 8 PdO obtained in Example 3 x EDS energy spectrum of O element in ZnO-SnO2 composite material; Figure 9 PdO obtained in Example 3 x XRD pattern of ZnO-SnO2 composite material; Figure 10The nitrogen adsorption-desorption curve of the hydrogen sensor obtained in Example 3 is shown. Figure 11 PdO obtained in Example 3 x XPS image of O1s in ZnO-SnO2 composite material; Figure 12 The response graphs of the hydrogen sensors obtained in Examples 1-4 to 50 ppm hydrogen at 40-160°C are shown. Figure 13 The repeatability curve of the hydrogen sensor obtained in Example 3 at 120°C for 50 ppm hydrogen is shown. Figure 14 The resistance curve of the hydrogen sensor obtained in Example 3 to 50 ppm hydrogen at 120°C is a single-cycle curve. Figure 15 The single-cycle response curves of five hydrogen sensors prepared from the same materials obtained in Example 3 to 50 ppm hydrogen at 120°C are shown. Figure 16 This is a linear fitting graph of the response of the hydrogen sensor obtained in Example 3 as a function of different hydrogen concentrations; Figure 17 The selectivity of the hydrogen sensor obtained in Example 3 to six gases at the same concentration of 50 ppm: hydrogen, ethanol, nitric oxide, formaldehyde, ammonia, and nitrogen dioxide. Figure 18 The response of the hydrogen sensor obtained in Example 3 to 50 ppm hydrogen under conditions of 0-75% relative humidity is shown in the figure. Figure 19 The graph shows the response changes of the hydrogen sensor obtained in Example 3 during a long-term stability test over 40 days. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] A method for fabricating a palladium-doped ZnO-SnO2 heterostructure hydrogen sensor includes the following steps: Step S1: SnO2 nanosheets and ZIF-8 (zeolite imidazole ester framework-8) are mixed in anhydrous ethanol at a molar ratio of 10:1, stirred evenly, dried thoroughly, and then calcined in a muffle furnace to obtain ZnO-SnO2 heterostructure material. Step S2: Dissolve ZnO-SnO2 and palladium nitrate dihydrate in deionized water at a mass ratio of 5:1, stir thoroughly, collect the product by centrifugation, wash with deionized water, dry, and calcine the product in a tube furnace under an argon atmosphere to obtain PdO. x / ZnO-SnO2 composite material, wherein PdO x It includes both PdO and PdO2 forms; Step S3: Using the drop-coating method, PdO is applied... x The ZnO-SnO2 composite material was dissolved in deionized water and sonicated. Then, it was dropped onto the middle of the interdigitated electrodes with a pipette and dried at a certain temperature for a period of time to obtain a palladium-doped ZnO-SnO2 heterostructure hydrogen sensor.

[0018] In step S1, SnO2 nanosheets are prepared as follows: Dissolve 0.96 g of sodium hydroxide and 1.99 g of terephthalic acid in 300 mL of deionized water and stir thoroughly to obtain solution A; Dissolve 3.45 g of stannous chloride dihydrate in 60 mL of deionized water and stir thoroughly to obtain solution B; Solution B was added dropwise to solution A at room temperature and with magnetic stirring to obtain a mixed solution. The mixture was stirred for 1 hour, centrifuged and dried. The resulting product was calcined in a muffle furnace at 500℃ for 3 hours to obtain SnO2 nanosheets.

[0019] In step S1, ZIF-8 is prepared as follows: 0.67 g of zinc nitrate hexahydrate and 0.167 g of 2-methylimidazole were mixed in 50 mL of DMF (N,N-dimethylformamide) and stirred vigorously until a clear solution was obtained. The solution was then transferred to a 100 mL reaction vessel with a polytetrafluoroethylene liner and heated in an oven at 140 °C for 24 hours. The product was filtered, washed with DMF, stored in methanol for 3 days, and then dried at 50 °C for 24 hours to obtain ZIF-8.

[0020] Step S1 specifically includes the following process: 3 mmol SnO2 nanosheets and 0.3 mmol ZIF-8 were mixed in 20 mL of anhydrous ethanol, stirred evenly, and dried thoroughly. The mixture was first calcined at 350 °C for 2 hours, and then calcined at 400 °C for 1 hour to obtain ZnO-SnO2 heterostructure material.

[0021] Step S2 specifically includes the following process: 100 mg of ZnO-SnO2 heterostructure material and 20 mg of palladium nitrate dihydrate were dissolved in 40 mL of deionized water and stirred thoroughly at 35 °C for 24 hours. The product was collected by centrifugation, washed twice with deionized water, dried at 60 °C for 2 hours, and then calcined at 350 °C for 2 hours in a tube furnace under an argon atmosphere to obtain PdO. x / ZnO-SnO2 composite material, PdO x PdO accounted for 67.52% and PdO2 accounted for 32.48%.

[0022] Step S3 specifically includes the following process: 10 mg of PdO was applied using a drop-coating method. x The ZnO-SnO2 composite material was dissolved in 0.5 mL of deionized water and sonicated for 30 minutes. Then, it was dropped onto the middle of the interdigitated electrode with a pipette and dried at 80 °C for 2 hours to obtain a palladium-doped ZnO-SnO2 heterostructure hydrogen sensor.

[0023] The preparation principle of this invention is as follows: Unlike the traditional one-pot method that assembles zinc salts, tin salts, and organic ligands into a Sn-Zn-ZIF-8 precursor followed by direct calcination to obtain SnO2-ZnO heterostructure materials, this invention employs a stepwise construction strategy involving the pre-preparation of SnO2 nanosheets, followed by compositing with the ZIF-8 precursor and pyrolysis. This method does not simply change the feeding order; instead, it uses independent SnO2 nanosheets as Sn sources and heterostructure interface building units. This allows ZnO and SnO2 to form a ZnO-SnO2 heterostructure with a clear phase interface during pyrolysis, while preserving the MOF-derived hierarchical channels and hollow framework morphology. It also effectively suppresses the formation of ternary composite phases such as Zn2SnO4 or excessive solid solution in the Zn / Sn component during heat treatment. This structure is beneficial for forming a stable n-n heterojunction electronic control interface and provides continuous gas diffusion channels and more surface reaction sites, thereby improving the adsorption, diffusion, and reaction efficiency of low-concentration hydrogen.

[0024] Furthermore, this invention introduces oxidized PdO into the surface and pores of the ZnO-SnO2 heterojunction framework. x The active component is not simply loaded Pd nanoparticles. XPS characterization results show that PdO is an active component, not just a load of metallic Pd nanoparticles. x Pd is mainly composed of Pd 2+ It exists in form and is accompanied by a small amount of Pd. 4+ The Pd 2+ / Pd 4+ Coexisting oxidation state PdO xIt can undergo interfacial electronic coupling with ZnO-SnO2 heterojunctions, modulating the electron depletion layer and band bending on the material surface, while simultaneously promoting the adsorption and activation of oxygen molecules and increasing the surface adsorption of oxygen (O). V Content. That is, the sensitive material of the present invention not only relies on the catalytic effect of Pd on hydrogen, but more importantly, on the catalytic effect of PdO. x Valence state regulation enhances the ability of reactive oxygen species on the ZnO-SnO2 surface to participate in hydrogen reactions.

[0025] Furthermore, PdO x The introduction of [a specific technology] can synergistically adjust the electron depletion layer depth and surface strong adsorption of oxygen O at the ZnO-SnO2 heterojunction interface. V The concentration of H2 in the atmosphere causes the sensor to maintain a high resistivity in an air background, while in a hydrogen atmosphere, the rapid reaction of H2 with strongly adsorbed oxygen releases electrons, leading to a significant decrease in the material's resistance and thus exhibiting a clear on / off hydrogen-sensitive response. XPSO1s peak separation results indicate that PdO2... x Strongly adsorbed oxygen O in ZnO-SnO2 composite materials V The proportion reached 46.89%, indicating that the composite structure can provide more oxygen adsorption / activation sites and hydrogen reaction sites, which is an important reason for realizing low-temperature ppb-level hydrogen detection.

[0026] In summary, the palladium-doped ZnO-SnO2 heterostructure hydrogen sensor provided by this invention can achieve rapid response to low concentrations of hydrogen at relatively low operating temperatures, and also possesses advantages such as low power consumption, low detection concentration, significant response, and relatively simple fabrication process. Compared with simple MOF-derived SnO2-ZnO composites, conventional Pd-modified SnO2 hydrogen sensing materials, and general MOF-doped gas-sensitive materials, the difference of this invention lies in: the stepwise construction of the ZnO-SnO2 heterostructure interface through "prefabricated SnO2 nanosheets / ZIF-8" and "Pd-doped ZnO2 heterostructure interface through "prefabricated ZnO2 nanosheets / ZIF-8". 2+ Main, Pd 4+ PdO as a secondary component x The combination of "active component-induced strong adsorption oxygen enrichment" enables synergistic regulation of hydrogen adsorption, oxygen activation, and interfacial electron transport processes, thereby improving the applicability of the material in ppb-level hydrogen detection.

[0027] This embodiment also provides a palladium-doped ZnO-SnO2 heterostructure hydrogen sensor, which is prepared using the above-described preparation method.

[0028] To more clearly demonstrate the technical solution of the present invention, specific embodiments are described below: Example 1 This embodiment provides a method for preparing a palladium-doped ZnO-SnO2 heterostructure hydrogen sensor, comprising the following steps: (1) Dissolve 0.96 g of sodium hydroxide and 1.99 g of terephthalic acid in 300 mL of deionized water and stir thoroughly; (2) Dissolve 3.45 g of stannous chloride dihydrate in 60 mL of deionized water and stir thoroughly; (3) At room temperature, the latter is added dropwise to the former under magnetic stirring to obtain a mixed solution. Stir for 1 hour, centrifuge and dry.

[0029] (4) The obtained product was calcined in a muffle furnace at 500℃ for 3 hours to obtain SnO2 nanosheets; (5) Mix 0.67 g of zinc nitrate hexahydrate and 0.167 g of 2-methylimidazole in 50 mL of DMF and stir vigorously until a clear solution is obtained; (6) Transfer the clear solution into a 100 mL reaction vessel with a polytetrafluoroethylene liner and heat it in an oven at 140 °C for 24 hours. (7) The product was filtered, washed several times with DMF, stored in methanol for 3 days, and then dried at 50°C for 24 hours to obtain ZIF-8; (8) Mix 3 mmol SnO2 nanosheets and ZIF-8 in 20 mL of anhydrous ethanol at a molar ratio of 10:1, stir, and dry thoroughly; (9) Then, ZnO-SnO2 heterostructure material was obtained by calcining it in a muffle furnace at 400℃ for 3 hours. (10) Dissolve 100 mg of ZnO-SnO2 heterostructure material in 40 mL of deionized water and stir thoroughly at 35 °C for 24 hours; (11) Centrifuge to collect the product, wash twice with deionized water, and dry at 60°C for 2 hours; (12) The product was calcined in a tube furnace at 350°C for 2 hours in an argon atmosphere to obtain PdOx / ZnO-SnO2 composite material; (13) Using the drop-coating method, 10 mg of PdOx / ZnO-SnO2 composite material was dissolved in 0.5 mL of deionized water and sonicated for 30 minutes. Then, it was dropped onto the middle of the interdigitated electrode with a pipette and dried at 80 °C for 2 hours to obtain a palladium-doped ZnO-SnO2 heterostructure hydrogen sensor.

[0030] Example 2 The difference between this embodiment and Embodiment 1 lies only in step (10): (10) Dissolve 100 mg of ZnO-SnO2 heterostructure material and 10 mg of palladium nitrate dihydrate in 40 mL of deionized water and stir thoroughly at 35 °C for 24 hours.

[0031] The remaining steps are consistent with those in Example 1.

[0032] Example 3 The difference between this embodiment and Embodiment 1 lies only in step (10): (10) Dissolve 100 mg of ZnO-SnO2 heterostructure material and 20 mg of palladium nitrate dihydrate in 40 mL of deionized water and stir thoroughly at 35 °C for 24 hours.

[0033] Example 4 The difference between this embodiment and Embodiment 1 lies only in step (10): (10) Dissolve 100 mg of ZnO-SnO2 heterostructure material and 30 mg of palladium nitrate dihydrate in 40 mL of deionized water and stir thoroughly at 35 °C for 24 hours.

[0034] That is, in Examples 1-4, the only difference is that the mass ratio of ZnO-SnO2 heterostructure material to palladium nitrate dihydrate differs in step (10). In Examples 1-4, the mass ratio is 10:0, 10:1, 10:2, and 10:3 respectively.

[0035] The samples obtained in Examples 1-4 were subjected to relevant performance tests, and the results are as follows: Figures 1-4 Morphological images of the intermediate product and the final sample of Example 3 are shown, wherein: Figure 1 SEM image of the intermediate Sn-MOF; Figure 2 SEM image of the intermediate SnO2 nanosheets; Figure 3 SEM image of PdOx / ZnO-SnO2 composite material; Figure 4 The image shows a TEM image of the PdOx / ZnO-SnO2 composite material. As can be seen from the attached image, the PdOx / ZnO-SnO2 composite material is porous and loose, with PdO... x It is evenly distributed in the material.

[0036] Figures 5-8 The EDS spectrum of the PdOx / ZnO-SnO2 composite material obtained in Example 3 is shown, indicating the distribution of each element in the material. Figure 5 EDS energy spectrum of Sn element Figure 6 EDS energy spectrum of Zn element Figure 7 EDS spectrum of Pd element Figure 8 This represents the EDS energy spectrum of element O.

[0037] Figure 9 The XRD pattern of the sample from Example 3 is shown. The figure shows independent ZnO and SnO2 peaks, but no Zn2SnO4 characteristic peak.

[0038] Figure 10 The nitrogen adsorption-desorption curves of the sample in Example 3 are shown; as can be seen from the figure, the sample has a nitrogen adsorption-desorption rate as high as 84.2 m. 2 The specific surface area of ​​ / g and the average pore size of 12.7nm indicate that the sample is conducive to the adsorption of hydrogen molecules.

[0039] Figure 11 The O1s XPS plot of the sample from Example 3 is shown, and the plot shows strong adsorption of oxygen (O1s). V The proportion of 46.89% indicates that the sample can provide more reaction sites for hydrogen molecules.

[0040] Figure 12 The response graphs of the samples in Examples 1-4 to 50 ppm hydrogen at 40-160°C are shown. It can be seen from the graph that Example 3 has the maximum response value of 80% at 120°C.

[0041] Figure 13 The response repeatability curve of the hydrogen sensor prepared in Example 3 to 50 ppm hydrogen at 120°C is shown. The graph shows that the sensor has good repeatability.

[0042] Figure 14 The graph shows the single-cycle resistance curve of the hydrogen sensor prepared in Example 3 at 120°C for 50 ppm hydrogen. It can be seen from the graph that the sensor responds very quickly to hydrogen, with a response time as low as 3 seconds.

[0043] Figure 15 The single-cycle response curves of five hydrogen sensors prepared from five identical samples of Example 3 to 50 ppm hydrogen at 120 °C are shown. As can be seen from the figure, the five hydrogen sensors have almost the same response to hydrogen under the same experimental conditions, which proves that the material properties are stable and eliminates the device dependence.

[0044] Figure 16 The graph shows the linear fit of the response S of the hydrogen sensor prepared in Example 3 as a function of different hydrogen concentrations C. It can be seen from the graph that the experimental value is very close to the fitted line, which proves that the hydrogen sensor has good linearity.

[0045] Figure 17 The selectivity of the hydrogen sensor prepared in Example 3 to six gases at the same concentration of 50 ppm: hydrogen, ethanol, nitric oxide, formaldehyde, ammonia, and nitrogen dioxide is shown. As can be seen from the figure, the sensor has the highest response to hydrogen and a weaker response to other gases, which proves that the sensor has good hydrogen selectivity.

[0046] Figure 18The response graph of the hydrogen sensor prepared in Example 3 to 50 ppm hydrogen under 0-75% relative humidity conditions is shown. It can be seen from the graph that the hydrogen sensor still has a good response at 75% relative humidity, which proves that the sensor has good humidity resistance.

[0047] Figure 19 The graph shows the response change of the hydrogen sensor prepared in Example 3 during a long-term stability test over 40 days. The graph shows that the hydrogen sensor's response to hydrogen decreases little over 40 days, proving that the sensor has good long-term stability.

[0048] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of the present invention.

Claims

1. A method for preparing a palladium-doped ZnO-SnO2 heterostructure hydrogen sensor, characterized in that, Includes the following steps: Step S1: SnO2 nanosheets and ZIF-8 are mixed in anhydrous ethanol at a molar ratio of 10:1, stirred evenly, dried thoroughly, and then calcined in a muffle furnace to obtain ZnO-SnO2 heterostructure material. Step S2: Dissolve the ZnO-SnO2 heterostructure material and palladium nitrate dihydrate in deionized water at a mass ratio of 5:1, stir thoroughly, collect the product by centrifugation, wash with deionized water, dry, and calcine the product in a tube furnace under an argon atmosphere to obtain PdO. x / ZnO-SnO2 composite material, wherein PdO x It includes both PdO and PdO2 forms; Step S3: Using the drop-coating method, PdO is applied... x The ZnO-SnO2 composite material was dissolved in deionized water and sonicated. Then, it was dropped onto the middle of the interdigitated electrodes with a pipette and dried at a certain temperature for a period of time to obtain a palladium-doped ZnO-SnO2 heterostructure hydrogen sensor.

2. The preparation method according to claim 1, characterized in that, In step S1, SnO2 nanosheets are prepared as follows: Dissolve 0.96 g of sodium hydroxide and 1.99 g of terephthalic acid in 300 mL of deionized water and stir thoroughly to obtain solution A; Dissolve 3.45 g of stannous chloride dihydrate in 60 mL of deionized water and stir thoroughly to obtain solution B; Solution B was added dropwise to solution A at room temperature and with magnetic stirring to obtain a mixed solution. The mixture was stirred for 1 hour, centrifuged and dried. The resulting product was calcined in a muffle furnace at 500℃ for 3 hours to obtain SnO2 nanosheets.

3. The preparation method according to claim 1, characterized in that, In step S1, ZIF-8 is prepared as follows: 0.67 g of zinc nitrate hexahydrate and 0.167 g of 2-methylimidazole were mixed in 50 mL of DMF and stirred vigorously until a clear solution was obtained. The solution was then transferred to a 100 mL reaction vessel with a polytetrafluoroethylene liner and heated in an oven at 140 °C for 24 hours. The product was filtered, washed with DMF, stored in methanol for 3 days, and then dried at 50 °C for 24 hours to obtain ZIF-8.

4. The preparation method according to claim 1, characterized in that, Step S1 specifically includes the following process: Mix 3 mmol SnO2 nanosheets and 0.3 mmol ZIF-8 in 20 mL anhydrous ethanol, stir well, and dry thoroughly. The dried product was calcined at 350℃ for 2 hours, and then heated to 400℃ for 1 hour to obtain ZnO-SnO2 heterostructure material.

5. The preparation method according to claim 1, characterized in that, Step S2 specifically includes the following process: 100 mg of ZnO-SnO2 heterostructure material and 20 mg of palladium nitrate dihydrate were dissolved in 40 mL of deionized water and stirred thoroughly at 35 °C for 24 hours. The product was collected by centrifugation, washed twice with deionized water, dried at 60 °C for 2 hours, and then calcined at 350 °C for 2 hours in a tube furnace under an argon atmosphere to obtain PdO. x / ZnO-SnO2 composite material.

6. The preparation method according to claim 1, characterized in that, PdO x PdO accounted for 67.52% and PdO2 accounted for 32.48%.

7. The preparation method according to claim 1, characterized in that, Step S3 specifically includes the following process: 10 mg of PdO was applied using a drop-coating method. x The ZnO-SnO2 composite material was dissolved in 0.5 mL of deionized water and sonicated for 30 minutes. Then, it was dropped onto the middle of the interdigitated electrode with a pipette and dried at 80 °C for 2 hours to obtain a palladium-doped ZnO-SnO2 heterostructure hydrogen sensor.

8. A palladium-doped ZnO-SnO2 heterostructure hydrogen sensor, characterized in that, It is prepared by the preparation method according to any one of claims 1-7.

9. The palladium-doped ZnO-SnO2 heterostructure hydrogen sensor according to claim 8, characterized in that, The sensor has a hydrogen concentration detection range of 0.1-50 ppm.

Images