A pdpt alloy loaded in2o3 hollow micrometer tube, a preparation method thereof and a hydrogen sensor application

Abstract

The application belongs to the technical field of gas sensitive elements and its preparation, and discloses a PdPt alloy loaded In2O3 hollow microtubule, a preparation method thereof and a hydrogen sensor application, and solves the technical problems of low sensitivity and poor stability of the hydrogen sensor. An indium nitrate hydrate compound and terephthalic acid are dissolved in N,N-dimethylformamide, and after hydrothermal reaction and high-temperature calcination, In2O3 hollow microtubules are obtained; potassium chloroplatinate, sodium chloroplatinate, potassium bromide, potassium iodide and polyvinylpyrrolidone are added to deionized water, and hydrochloric acid solution is added until the pH value of the solution is 2.5-3.5, and then PdPt alloy powder is obtained through hydrothermal reaction; the dispersion liquid containing the In2O3 hollow microtubules is mixed with the dispersion liquid containing the PdPt alloy powder to obtain solution B, and after stirring, ultrasonic treatment and removal of the solvent, the PdPt alloy loaded In2O3 hollow microtubule is obtained. The resistance type hydrogen sensor based on the PdPt alloy loaded In2O3 hollow microtubule shows a low detection lower limit, a fast response-recovery speed and good stability.

Description

Technical Field

[0001] This invention belongs to the field of gas-sensitive elements and their preparation technology, and particularly relates to a method for preparing a composite material. Background Technology

[0002] Hydrogen (H2), as a high-energy-density and clean energy carrier, has wide applications in industrial production, the hydrogen energy industry chain, fuel cell research and development, and chemical synthesis. However, hydrogen is a nonpolar, homonuclear diatomic molecule with a kinetic diameter of only 0.289 nm, is colorless and odorless, and has a high diffusion coefficient (0.61 cm⁻¹). 2 With an explosive limit as low as 4.0% in air, the development of highly sensitive, fast-response, and highly stable hydrogen detection technology is of great significance for ensuring the safe application and process monitoring of hydrogen energy.

[0003] Currently, resistive sensors based on metal-oxide-semiconductor (MOS) technology have attracted much attention due to their advantages such as high sensitivity, small size, low cost, and easy integration. Palladium (Pd)-based materials are widely used to enhance the gas-sensing performance of MOS-based H2 sensors because they can effectively adsorb and dissociate hydrogen molecules. However, traditional Pd-sensitized MOS sensors still face challenges in complex real-world operating conditions. Pd is prone to phase transition upon contact with H2, leading to volume expansion and structural degradation, which in turn causes response drift and decreased stability, limiting their application in practical leak monitoring scenarios.

[0004] Currently, most MOS-based hydrogen-sensitive materials employ an impregnation co-reduction method to simultaneously load noble metal precursors such as palladium and platinum onto the MOS surface (e.g., CN117929487A), thereby utilizing the synergistic catalytic effect of bimetals to improve the sensor's sensitivity to hydrogen. However, due to the differences in reduction potentials among different noble metal ions, the co-reduction process struggles to precisely control the particle size, composition, and spatial distribution of bimetallic nanoparticles. This can easily lead to the agglomeration of some noble metals in the product and an unclear noble metal structure, resulting in low sensor sensitivity, poor repeatability, and difficulty in ensuring stability.

[0005] Therefore, it is crucial to develop a fabrication process that improves the stability and sensitivity of Pd-based MOS hydrogen sensors. Summary of the Invention

[0006] To address the technical problems of low sensitivity and poor stability caused by the easy phase transition between Pd and H2 and the uncontrollable bimetallic load structure in Pd-based MOS hydrogen sensors, this invention proposes a PdPt alloy-loaded In2O3 hollow microtube, its preparation method, and its application in hydrogen sensors.

[0007] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0008] A method for preparing PdPt alloy-supported In2O3 hollow microtubes, comprising the following steps:

[0009] (1) Dissolve indium nitrate hydrate and terephthalic acid in N,N-dimethylformamide and stir at 20-30°C for 10-30 min. Then transfer the resulting mixture to a high-pressure reactor lined with polytetrafluoroethylene. Place the reactor in an oven and react at 115-125°C for 2-3 h. After the reaction, centrifuge the resulting solution. Wash the centrifuged product 3-6 times with N,N-dimethylformamide and dry it under vacuum at 60-70°C for 10-12 h to obtain a white metal-organic framework MIL-68(In) powder. The mass ratio of indium nitrate hydrate to terephthalic acid is 1:(0.9-1.1).

[0010] (2) The white powder of MIL-68(In) obtained in step (1) is evenly spread in a crucible, heated to 115-125℃ in an air atmosphere in a muffle furnace at 1-2℃ / min, and calcined for 2-3 h. Then, the temperature is increased to 490-510℃ at 1-2℃ / min and calcined for 2-3 h. The sample is naturally cooled to room temperature, and the calcined sample is collected to obtain In2O3 powder, i.e. In2O3 hollow microtube.

[0011] (3) Add potassium chloroplatinate, sodium chloropalladium, potassium bromide, potassium iodide, and polyvinylpyrrolidone to deionized water and stir at 20-30℃ for 10-30 min. During stirring, add hydrochloric acid solution (1 mol / L) dropwise to the solution until the pH of the solution is 2.5-3.5 to obtain solution A. The molar ratio of potassium chloroplatinate, sodium chloropalladium, potassium bromide, and potassium iodide is 1:(0.9-1.2):(90-120):(0.1-0.3), and 90-110 mg of polyvinylpyrrolidone is required for every 0.03 mol of potassium chloroplatinate.

[0012] (4) The solution A obtained in step (3) is transferred to a high-pressure reactor with a polytetrafluoroethylene liner. The reactor is heated hydrothermally at 155-165°C for 4-5 h. After naturally cooling to room temperature, 35-45 mL of acetone is added to the solution and centrifuged for 10-15 min. The centrifuged product is washed 3-6 times with a 1:1 ethanol / cyclohexane mixture and dried under vacuum at 60-70°C for 10-12 h to obtain PdPt alloy powder.

[0013] (5) Dispersion I containing In2O3 hollow microtubes and dispersion II containing PdPt alloy powder are mixed to obtain solution B; mixture B is stirred at 20-30℃ for 15-20 min and then sonicated for 10-15 min to obtain PdPt-loaded In2O3 solution, and then the solvent is evaporated to obtain PdPt alloy-loaded In2O3 hollow microtubes. The mass ratio of In2O3 hollow microtubes to PdPt alloy powder in solution B is (180-220):1.

[0014] PdPt alloy-supported In2O3 hollow microtubes were prepared using the above-described preparation method.

[0015] The above-mentioned PdPt alloy-supported In2O3 hollow microtubes are used in resistive hydrogen sensors.

[0016] A resistive hydrogen gas sensor comprises, from bottom to top: a ruthenium dioxide film printed on the lower surface of a ceramic sheet, a ceramic sheet, a pair of interdigitated electrodes printed on the upper surface of the ceramic sheet, and a gas-sensitive film coated on the upper surface of the ceramic sheet and the surfaces of the interdigitated electrodes; wherein the gas-sensitive film is a PdPt alloy-supported In2O3 hollow microtube as described above. The ceramic sheet can be an alumina ceramic sheet; the interdigitated electrodes can be gold interdigitated electrodes.

[0017] The aforementioned resistive hydrogen sensor also includes two wires led out from the interdigitated electrodes and two wires led out from both ends of the ruthenium dioxide film. Platinum wires are led out from the gold electrode and the ruthenium dioxide film and connected to the base. The sensor operates at different temperatures by controlling the current in the heating layer. The gas-sensitive film is an In₂O₃ hollow microtube derived from a PdPt alloy-supported MOF. The resistance of this gas-sensitive film changes significantly before and after contact with the test gas. By measuring the resistance change between the gold electrodes, the sensor's sensitivity to the target gas can be obtained. The sensitivity of this invention is defined as the ratio of the resistance of the gas-sensitive film in air to its resistance in a specific concentration of the test gas.

[0018] The preparation method of the above-mentioned resistive hydrogen sensor includes the following steps:

[0019] S1. Using an alumina ceramic sheet as a substrate, the ceramic sheet has a width and length of 1.2-1.8 mm and a thickness of 0.2-0.3 mm; a pair of interdigitated gold electrodes with a width of 0.2-0.3 mm and a thickness of 15-35 μm are printed on the upper surface of the ceramic sheet using screen printing; a ruthenium dioxide film with a thickness of 20-30 μm is printed on the lower surface of the ceramic sheet as a heating layer; the platinum wires leading out from the gold electrodes and the ruthenium dioxide film have a length of 4-7 mm;

[0020] S2. Take 10-20 mg of PdPt alloy-supported MOF-derived In2O3 hollow microtube powder and 0.1-0.2 mL of deionized water and put them into an agate mortar. Grind for 10-30 min to form a uniform slurry. Use a brush to apply the slurry evenly to the surface of the ceramic sheet and the surface of the gold electrode as a gas-sensitive film. Then heat treat at 80-130℃ for 1-4 h. The thickness of the PdPt alloy-supported MOF-derived In2O3 hollow microtube film is 12-30 μm.

[0021] S3. The device obtained in step S2 is aged at 250-300°C for 12-24 h to obtain a resistive hydrogen sensor based on PdPt alloy-supported MOF-derived In2O3 hollow microtube, i.e., a resistive hydrogen sensor.

[0022] The beneficial effects of this invention are:

[0023] (1) The MOF-derived In2O3 supported on the PdPt alloy prepared in this invention has a high specific surface area and a rough, porous hollow tubular structure, providing abundant surface active sites for hydrogen adsorption and surface reactions, which is beneficial to improving the sensor sensitivity and response recovery speed. Compared with the traditional impregnation co-reduction method, the pre-synthesized PdPt alloy nanoparticles with controllable composition and uniform particle size can precisely control the atomic ratio of Pd and Pt and the degree of alloying. This not only effectively optimizes the electronic structure of Pd and ensures the stable performance of the electronic synergistic effect between the two metals, but also suppresses the sensor response resistance reversal caused by the phase transition after Pd comes into contact with H2, thereby significantly improving the long-term stability of the sensor. In addition, there is a synergistic enhancement between the hollow tubular structure and the PdPt alloy. The open channels facilitate the rapid diffusion of H2 to the alloy active sites, while the Schottky barrier formed at the interface between In2O3 and the PdPt alloy amplifies the resistance change signal, further enhancing the hydrogen-sensitive response.

[0024] (2) The resistive hydrogen sensor based on PdPt alloy supported MOF-derived In2O3 hollow microtube prepared in this invention exhibits a low detection limit (500 ppb), fast response-recovery speed (3 s and 4 s) and excellent stability.

[0025] (3) The planar electrode structure used in this invention has uniform heat distribution, low power consumption, low cost and small size, and is suitable for mass production and system integration. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art 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.

[0027] Figure 1 This is a scanning electron microscope image of the PdPt alloy-supported In2O3 hollow microtube prepared in Example 1 of the present invention.

[0028] Figure 2 X-ray energy dispersive spectroscopy (EDS-mapping) analysis of the PdPt alloy-supported In2O3 hollow microtube prepared in Example 1 of this invention.

[0029] Figure 3 These are the X-ray diffraction patterns of the materials prepared in Example 1 and Comparative Example 1.

[0030] Figure 4 Sensitivity curves of a resistive hydrogen sensor fabricated based on the materials prepared in Example 1 and Comparative Example 1 of this invention for 100 ppm H2 at 220-280°C.

[0031] Figure 5 The dynamic response recovery curve of a resistive hydrogen sensor fabricated based on the materials prepared in Example 2 and Comparative Example 1 of this invention to 100 ppm H2 at 250°C.

[0032] Figure 6 The sensing performance of the resistive hydrogen sensor made based on the materials prepared in Comparative Examples 2 and 3 of this invention is shown; wherein (a, b) are the sensitivity curves for 100 ppm H2 at 220-290℃; and (c, d) are the dynamic response recovery curves for 100 ppm H2 at 250℃.

[0033] Figure 7 The resistance hydrogen sensor fabricated based on the material prepared in Example 2 of this invention exhibits the concentration response curve of 0.5-8 ppm H2 at 250°C.

[0034] Figure 8 The resistance hydrogen sensor fabricated based on the materials prepared in Example 2 and Comparative Example 1 of this invention exhibits the response curves of 10-2000 ppm H2 concentrations at 250°C.

[0035] Figure 9The selectivity bar graph (a) of a resistive hydrogen sensor fabricated based on the material prepared in Example 3 of the present invention for 20 ppm of different types of gases at 250 °C and the response repeatability curve of 100 ppm H2 at 250 °C are shown.

[0036] Figure 10 The long-term stability curve of a resistive hydrogen sensor fabricated based on the material prepared in Example 1 of this invention against 100 ppm H2 at 250°C.

[0037] Figure 11 The long-term stability curve of a resistive hydrogen sensor fabricated based on the material prepared in Comparative Example 2 of this invention against 100 ppm H2 at 250°C is shown. Detailed Implementation

[0038] 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 embodiments of the present invention, and not all embodiments. 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.

[0039] Example 1

[0040] The preparation method of a PdPt alloy-supported In2O3 hollow microtube in this embodiment includes the following steps:

[0041] (1) Dissolve 0.6 g of indium nitrate hydrate and 0.6 g of terephthalic acid in 60 mL of N,N-dimethylformamide and stir at 25 °C for 30 min to obtain a mixed solution. Transfer the mixed solution to a high-pressure reactor lined with polytetrafluoroethylene and place the reactor in an oven. React at 120 °C for 2 h. After the reaction, centrifuge the obtained solution and wash the centrifuged product 4 times with N,N-dimethylformamide. Dry it under vacuum at 60 °C for 12 h to obtain a white powder of metal-organic framework MIL-68(In).

[0042] (2) The MIL-68(In) powder obtained in step (1) is evenly spread in a crucible, heated to 120°C at 2°C / min in an air atmosphere in a muffle furnace, calcined for 2 h, then heated to 500°C at 2°C / min, calcined for 2 h, and naturally cooled to room temperature. The calcined sample is collected to obtain In2O3 powder, also known as In2O3 hollow microtube.

[0043] (3) Add 12.45 mg potassium chloroplatinate, 8.83 mg sodium chloropalladium, 357 mg potassium bromide, 1.0 mg potassium iodide and 100 mg polyvinylpyrrolidone to 10 mL of deionized water and stir at 25°C for 30 min. During stirring, add 1 mol / L hydrochloric acid solution dropwise to the solution until the pH of the solution stabilizes at about 3.

[0044] (4) Transfer the solution prepared in step (3) to a high-pressure reactor with a 25 mL polytetrafluoroethylene liner, and heat it at 160°C for 4 h for hydrothermal reaction. After naturally cooling to room temperature, add 40 mL of acetone to the obtained solution and centrifuge for 15 min. Wash the centrifuged product 5 times with a 1:1 volume ratio of ethanol / cyclohexane mixture and dry it under vacuum at 60 °C for 12 h to obtain PdPt alloy powder.

[0045] (5) Add the PdPt alloy powder obtained in step (4) to 9 mL of ethanol and sonicate for 10 min to prepare a 1 mg / mL PdPt alloy dispersion; add 100 mg of In2O3 powder obtained in step (2) to 20 mL of anhydrous ethanol, stir at 25 °C for 15 min, and then sonicate for 8 min to obtain an In2O3 carrier solution.

[0046] (6) Add 0.5 mL of the PdPt alloy dispersion obtained in step (5) to the In2O3 support solution, stir at 25°C for 20 min, and then sonicate for 10 min to obtain a PdPt-loaded In2O3 solution; then evaporate the solvent of the PdPt-loaded In2O3 solution at 60°C to obtain a PdPt alloy-loaded In2O3 hollow microtube.

[0047] Example 2

[0048] The preparation method of a PdPt alloy-supported In2O3 hollow microtube in this embodiment includes the following steps:

[0049] (1) Dissolve 0.55 g of indium nitrate hydrate and 0.55 g of terephthalic acid in 60 mL of N,N-dimethylformamide and stir at 25 °C for 30 min to obtain a mixed solution. Transfer the mixed solution to a high-pressure reactor lined with polytetrafluoroethylene and place the reactor in an oven. React at 120 °C for 2 h. After the reaction, centrifuge the obtained solution and wash the centrifuged product 4 times with N,N-dimethylformamide. Dry it under vacuum at 60 °C for 12 h to obtain a white powder of metal-organic framework MIL-68(In).

[0050] (2) The MIL-68(In) powder obtained in step (1) is evenly spread in a crucible, heated to 120°C at 2°C / min in an air atmosphere in a muffle furnace, calcined for 2 h, then heated to 500°C at 2°C / min, calcined for 2 h, and naturally cooled to room temperature. The calcined sample is collected to obtain In2O3 powder, also known as In2O3 hollow microtube.

[0051] (3) Add 12 mg potassium chloroplatinate, 8 mg sodium chloropalladium, 345 mg potassium bromide, 0.95 mg potassium iodide and 95 mg polyvinylpyrrolidone to 10 mL of deionized water and stir at 25°C for 30 min. During stirring, add 1 mol / L hydrochloric acid solution dropwise to the solution until the pH of the solution stabilizes at about 3.

[0052] (4) Transfer the solution prepared in step (3) to a high-pressure reactor with a 25 mL polytetrafluoroethylene liner, and heat it at 160°C for 4 h for hydrothermal reaction. After naturally cooling to room temperature, add 40 mL of acetone to the obtained solution and centrifuge for 15 min. Wash the centrifuged product 5 times with a 1:1 volume ratio of ethanol / cyclohexane mixture and dry it under vacuum at 60 °C for 12 h to obtain PdPt alloy powder.

[0053] (5) Add the PdPt alloy powder obtained in step (4) to 9 mL of ethanol and sonicate for 10 min to prepare a 1 mg / mL PdPt alloy dispersion; add 100 mg of In2O3 powder obtained in step (2) to 20 mL of anhydrous ethanol, stir at 25 °C for 15 min, and then sonicate for 8 min to obtain an In2O3 carrier solution.

[0054] (6) Add 0.5 mL of the PdPt alloy dispersion obtained in step (5) to the In2O3 support solution, stir at 25°C for 20 min, and then sonicate for 10 min to obtain a PdPt-loaded In2O3 solution; then evaporate the solvent of the PdPt-loaded In2O3 solution at 60°C to obtain a PdPt alloy-loaded In2O3 hollow microtube.

[0055] Example 3

[0056] The preparation method of a PdPt alloy-supported In2O3 hollow microtube in this embodiment includes the following steps:

[0057] (1) Dissolve 0.7 g of indium nitrate hydrate and 0.7 g of terephthalic acid in 60 mL of N,N-dimethylformamide and stir at 25 °C for 30 min to obtain a mixed solution. Transfer the mixed solution to a high-pressure reactor lined with polytetrafluoroethylene and place the reactor in an oven. React at 120 °C for 2 h. After the reaction, centrifuge the obtained solution and wash the centrifuged product 4 times with N,N-dimethylformamide. Dry the product under vacuum at 60 °C for 12 h to obtain a white powder of metal-organic framework MIL-68(In).

[0058] (2) The MIL-68(In) powder obtained in step (1) is evenly spread in a crucible, heated to 120°C at 2°C / min in an air atmosphere in a muffle furnace, calcined for 2 h, then heated to 500°C at 2°C / min, calcined for 2 h, and naturally cooled to room temperature. The calcined sample is collected to obtain In2O3 powder, also known as In2O3 hollow microtube.

[0059] (3) Add 13 mg potassium chloroplatinate, 9 mg sodium chloropalladium, 355 mg potassium bromide, 1.05 mg potassium iodide and 105 mg polyvinylpyrrolidone to 10 mL of deionized water and stir at 25°C for 30 min. During stirring, add 1 mol / L hydrochloric acid solution dropwise to the solution until the pH of the solution stabilizes at about 3.

[0060] (4) Transfer the solution prepared in step (3) to a high-pressure reactor with a 25 mL polytetrafluoroethylene liner, and heat it at 160°C for 4 h for hydrothermal reaction. After naturally cooling to room temperature, add 40 mL of acetone to the obtained solution and centrifuge for 15 min. Wash the centrifuged product 5 times with a 1:1 volume ratio of ethanol / cyclohexane mixture and dry it under vacuum at 60 °C for 12 h to obtain PdPt alloy powder.

[0061] (5) Add the PdPt alloy powder obtained in step (4) to 9 mL of ethanol and sonicate for 10 min to prepare a 1 mg / mL PdPt alloy dispersion; add 100 mg of In2O3 powder obtained in step (2) to 20 mL of anhydrous ethanol, stir at 25 °C for 15 min, and then sonicate for 8 min to obtain an In2O3 carrier solution.

[0062] (6) Add 0.5 mL of the PdPt alloy dispersion obtained in step (5) to the In2O3 support solution, stir at 25°C for 20 min, and then sonicate for 10 min to obtain a PdPt-loaded In2O3 solution; then evaporate the solvent of the PdPt-loaded In2O3 solution at 60°C to obtain a PdPt alloy-loaded In2O3 hollow microtube.

[0063] Example 4

[0064] The preparation method of a PdPt alloy-supported In2O3 hollow microtube in this embodiment includes the following steps:

[0065] (1) Dissolve 0.65 g of indium nitrate hydrate and 0.58 g of terephthalic acid in 60 mL of N,N-dimethylformamide and stir at 25 °C for 30 min to obtain a mixed solution. Transfer the mixed solution to a high-pressure reactor lined with polytetrafluoroethylene and place the reactor in an oven. React at 115 °C for 3 h. After the reaction, centrifuge the obtained solution and wash the centrifuged product 4 times with N,N-dimethylformamide. Dry it under vacuum at 60 °C for 12 h to obtain a white powder of metal-organic framework MIL-68(In).

[0066] (2) The MIL-68(In) powder obtained in step (1) is evenly spread in a crucible, heated to 115°C at 1°C / min in an air atmosphere in a muffle furnace, calcined for 3 h, then heated to 510°C at 2°C / min, calcined for 2.5 h, and naturally cooled to room temperature. The calcined sample is collected to obtain In2O3 powder, also known as In2O3 hollow microtube.

[0067] (3) Add 14.58 mg potassium chloroplatinate, 7.9 mg sodium chloropalladium, 321 mg potassium bromide, 1.4 mg potassium iodide and 110 mg polyvinylpyrrolidone to 10 mL of deionized water and stir at 25°C for 30 min. During stirring, add 1 mol / L hydrochloric acid solution dropwise to the solution until the pH value of the solution stabilizes at about 2.5.

[0068] (4) Transfer the solution prepared in step (3) to a high-pressure reactor lined with 25 mL of polytetrafluoroethylene, and heat it at 165°C for 4.5 h for hydrothermal reaction. After naturally cooling to room temperature, add 40 mL of acetone to the obtained solution and centrifuge for 15 min. Wash the centrifuged product 5 times with a 1:1 volume ratio of ethanol / cyclohexane mixture and dry it under vacuum at 60 °C for 12 h to obtain PdPt alloy powder.

[0069] (5) Add the PdPt alloy powder obtained in step (4) to 9 mL of ethanol and sonicate for 10 min to prepare a 1 mg / mL PdPt alloy dispersion; add 90 mg of In2O3 powder obtained in step (2) to 20 mL of anhydrous ethanol, stir at 25 °C for 15 min, and sonicate for 8 min to obtain an In2O3 carrier solution.

[0070] (6) Add 0.5 mL of the PdPt alloy dispersion obtained in step (5) to the In2O3 support solution, stir at 25°C for 20 min, and then sonicate for 10 min to obtain a PdPt-loaded In2O3 solution; then evaporate the solvent of the PdPt-loaded In2O3 solution at 60°C to obtain a PdPt alloy-loaded In2O3 hollow microtube.

[0071] Example 5

[0072] The preparation method of a PdPt alloy-supported In2O3 hollow microtube in this embodiment includes the following steps:

[0073] (1) Dissolve 0.68 g of indium nitrate hydrate and 0.74 g of terephthalic acid in 60 mL of N,N-dimethylformamide and stir at 25 °C for 30 min to obtain a mixed solution. Transfer the mixed solution to a high-pressure reactor lined with polytetrafluoroethylene and place the reactor in an oven. React at 125 °C for 2.5 h. After the reaction is completed, centrifuge the obtained solution and wash the centrifuged product 4 times with N,N-dimethylformamide. Dry the product under vacuum at 60 °C for 12 h to obtain a white powder of metal-organic framework MIL-68(In).

[0074] (2) The MIL-68(In) powder obtained in step (1) is evenly spread in a crucible, heated to 125°C at 2°C / min in an air atmosphere in a muffle furnace, calcined for 2.5 h, then heated to 490°C at 1°C / min, calcined for 3 h, and naturally cooled to room temperature. The calcined sample is collected to obtain In2O3 powder, also known as In2O3 hollow microtube.

[0075] (3) Add 14.58 mg potassium chloroplatinate, 10.6 mg sodium chloropalladium, 428 mg potassium bromide, 0.5 mg potassium iodide and 90 mg polyvinylpyrrolidone to 10 mL of deionized water and stir at 25°C for 30 min. During stirring, add 1 mol / L hydrochloric acid solution dropwise to the solution until the pH value of the solution stabilizes at about 3.5.

[0076] (4) Transfer the solution prepared in step (3) to a high-pressure reactor with a 25 mL polytetrafluoroethylene liner, and heat it at 155°C for 5 h for hydrothermal reaction. After naturally cooling to room temperature, add 40 mL of acetone to the obtained solution and centrifuge for 15 min. Wash the centrifuged product 5 times with a 1:1 volume ratio of ethanol / cyclohexane mixture, and dry it under vacuum at 60 °C for 12 h to obtain PdPt alloy powder.

[0077] (5) Add the PdPt alloy powder obtained in step (4) to 9 mL of ethanol and sonicate for 10 min to prepare a 1 mg / mL PdPt alloy dispersion; add 110 mg of In2O3 powder obtained in step (2) to 20 mL of anhydrous ethanol, stir at 25 °C for 15 min, and then sonicate for 8 min to obtain an In2O3 carrier solution.

[0078] (6) Add 0.5 mL of the PdPt alloy dispersion obtained in step (5) to the In2O3 support solution, stir at 25°C for 20 min, and then sonicate for 10 min to obtain a PdPt-loaded In2O3 solution; then evaporate the solvent of the PdPt-loaded In2O3 solution at 60°C to obtain a PdPt alloy-loaded In2O3 hollow microtube.

[0079] Comparative Example 1

[0080] The preparation method of Pd-supported In2O3 hollow microtubes in this comparative example includes the following steps:

[0081] (1) Dissolve 0.6 g of indium nitrate hydrate and 0.6 g of terephthalic acid in 60 mL of N,N-dimethylformamide and stir at 25 °C for 30 min to obtain a mixed solution. Transfer the mixed solution to a high-pressure reactor lined with polytetrafluoroethylene and place the reactor in an oven. React at 120 °C for 2 h. After the reaction, centrifuge the obtained solution and wash the centrifuged product 4 times with N,N-dimethylformamide. Dry it under vacuum at 60 °C for 12 h to obtain a white powder of metal-organic framework MIL-68(In).

[0082] (2) The MIL-68(In) powder obtained in step (1) is evenly spread in a crucible, heated to 120°C at 2°C / min in an air atmosphere in a muffle furnace, calcined for 2 h, then heated to 500°C at 2°C / min, calcined for 2 h, and naturally cooled to room temperature. The calcined sample is collected to obtain In2O3 powder, also known as In2O3 hollow microtube.

[0083] (3) Add 8.83 mg sodium chloropalladium, 357 mg potassium bromide, 1.0 mg potassium iodide and 100 mg polyvinylpyrrolidone to 10 mL of deionized water and stir at 25°C for 30 min. During stirring, add 1 mol / L hydrochloric acid solution dropwise to the solution until the pH value of the solution stabilizes at about 3.

[0084] (4) Transfer the solution prepared in step (3) to a high-pressure reactor lined with 25 mL of polytetrafluoroethylene, and heat it at 160°C for 4 h for hydrothermal reaction. After naturally cooling to room temperature, add 40 mL of acetone to the obtained solution and centrifuge for 15 min. Wash the centrifuged product 5 times with a 1:1 volume ratio of ethanol / cyclohexane mixture and dry it under vacuum at 60 °C for 12 h to obtain Pd powder.

[0085] (5) Add the Pd powder obtained in step (4) to 9 mL of ethanol and sonicate for 10 min to prepare a Pd dispersion of 1 mg / mL; add 100 mg of In2O3 powder obtained in step (2) to 20 mL of anhydrous ethanol, stir at 25 °C for 15 min, and then sonicate for 8 min to obtain an In2O3 carrier solution.

[0086] (6) Add 0.5 mL of the Pd dispersion obtained in step (5) to the In2O3 carrier solution, stir at 25°C for 20 min, and then sonicate for 10 min to obtain the Pd-loaded In2O3 solution; then evaporate the solvent of the Pd-loaded In2O3 solution at 60°C to obtain the Pd-loaded In2O3 hollow microtube.

[0087] Comparative Example 2

[0088] The preparation method of Pd@Pt@In2O3 in this comparative example differs from that in Example 1 in that a PdPt alloy was not synthesized first. The specific steps are as follows:

[0089] (1) Dissolve 0.6 g of indium nitrate hydrate and 0.6 g of terephthalic acid in 60 mL of N,N-dimethylformamide and stir at 25 °C for 30 min to obtain a mixed solution. Transfer the mixed solution to a high-pressure reactor lined with polytetrafluoroethylene and place the reactor in an oven. React at 120 °C for 2 h. After the reaction, centrifuge the obtained solution and wash the centrifuged product 4 times with N,N-dimethylformamide. Dry it under vacuum at 60 °C for 12 h to obtain a white powder of metal-organic framework MIL-68(In).

[0090] (2) The MIL-68(In) powder obtained in step (1) is evenly spread in a crucible, heated to 120°C at 2°C / min in an air atmosphere in a muffle furnace, calcined for 2 h, then heated to 500°C at 2°C / min, calcined for 2 h, and naturally cooled to room temperature. The calcined sample is collected to obtain In2O3 powder, also known as In2O3 hollow microtube.

[0091] (3) Add 12.45 mg potassium chloroplatinate, 8.83 mg sodium chloropalladium, 357 mg potassium bromide, 1.0 mg potassium iodide and 100 mg polyvinylpyrrolidone to 10 mL of deionized water and stir at 25°C for 30 min. During stirring, add 1 mol / L hydrochloric acid solution dropwise to the solution until the pH value of the solution stabilizes at about 3, and obtain solution A.

[0092] (4) Add 100 mg of In2O3 powder obtained in step (2) to 20 mL of anhydrous ethanol, stir at 25 °C for 15 min, and then sonicate for 8 min to obtain In2O3 carrier solution.

[0093] (5) Add 0.61 mL of solution A obtained in step (3) to the In2O3 carrier solution, stir at 25°C for 20 min, and then sonicate for 10 min to obtain Pd@Pt@In2O3 solution; then evaporate the solvent of Pd@Pt@In2O3 solution at 60°C to obtain Pd@Pt@In2O3.

[0094] Comparative Example 3

[0095] The preparation method of PdPt-supported In2O3 nanoparticles in this comparative example differs from that in Example 1 in that the In2O3 is in nanoparticle form. The specific steps are as follows:

[0096] (1) Preparation of In2O3 nanoparticles: First, prepare 0.1 mol•L -1 An InCl3 solution and a NaOH solution were prepared. Then, 4 mL of the InCl3 solution was transferred to a 100 mL Erlenmeyer flask. Subsequently, 12 mL of deionized water and 24 mL of NaOH solution were added sequentially to the InCl3 solution, and the mixture was stirred at room temperature for 3 hours. The resulting white solid precipitate was centrifuged and washed repeatedly with anhydrous ethanol to obtain a white solid product. This white solid product was dried in an 80°C oven. After grinding, a white powder was obtained as an In2O3 precursor. The white powder was then calcined in a muffle furnace at a temperature of 2°C·min. -1 The temperature was gradually increased to 500 °C, and the annealing process was carried out at this temperature for 2 hours. Finally, a yellow In₂O₃ powder was obtained.

[0097] (2) Add 12.45 mg potassium chloroplatinate, 8.83 mg sodium chloropalladium, 357 mg potassium bromide, 1.0 mg potassium iodide and 100 mg polyvinylpyrrolidone to 10 mL of deionized water and stir at 25°C for 30 min. During stirring, add 1 mol / L hydrochloric acid solution dropwise to the solution until the pH of the solution stabilizes at about 3.

[0098] (4) Transfer the solution prepared in step (3) to a high-pressure reactor with a 25 mL polytetrafluoroethylene liner, and heat it at 160°C for 4 h for hydrothermal reaction. After naturally cooling to room temperature, add 40 mL of acetone to the obtained solution and centrifuge for 15 min. Wash the centrifuged product 5 times with a 1:1 volume ratio of ethanol / cyclohexane mixture and dry it under vacuum at 60 °C for 12 h to obtain PdPt alloy powder.

[0099] (5) Add the PdPt alloy powder obtained in step (4) to 9 mL of ethanol and sonicate for 10 min to prepare a PdPt alloy dispersion of 1 mg / mL; add 100 mg of In2O3 nanosheets obtained in step (2) to 20 mL of anhydrous ethanol, stir at 25 °C for 15 min, and then sonicate for 8 min to obtain an In2O3 carrier solution.

[0100] (6) Add 0.5 mL of the PdPt alloy dispersion obtained in step (5) to the In2O3 support solution, stir at 25°C for 20 min, and then sonicate for 10 min to obtain a PdPt-loaded In2O3 solution; then evaporate the solvent of the PdPt-loaded In2O3 solution at 60°C to obtain PdPt-In2O3 nanosheets.

[0101] Application examples

[0102] The materials prepared in the above embodiments and comparative examples were applied to a resistive hydrogen sensor, and the specific preparation method is as follows:

[0103] S1. Using an alumina ceramic sheet as a substrate, the ceramic sheet has a width and length of 1.5 mm and a thickness of 0.25 mm; a pair of interdigitated gold electrodes with a width of 0.25 mm and a thickness of 20 μm are printed on the upper surface of the ceramic sheet using screen printing; a ruthenium dioxide film with a thickness of 25 μm is printed on the lower surface of the ceramic sheet as a heating layer; and platinum wires with a length of 5 mm are drawn from the gold electrodes and the ruthenium dioxide film.

[0104] S2. Take 15 mg of the materials prepared in the above examples and comparative examples and 0.2 mL of deionized water respectively and put them into an agate mortar. Grind for 20 min to form a uniform slurry. Use a brush to dip the slurry and coat it evenly on the surface of the ceramic sheet and the surface of the gold electrode as a gas-sensitive film. Then heat treat at 100℃ for 4 h. The film thickness is 20 μm.

[0105] S3. The device obtained in step S2 is aged at 300°C for 24 h to obtain a resistive hydrogen sensor.

[0106] Figure 1 The scanning electron microscope (SEM) image of the PdPt alloy-supported In2O3 hollow microtubes prepared for this invention shows that the material has a tubular structure with a size of approximately 2-3 µm. The rough and porous surface is beneficial for detecting gas diffusion.

[0107] Figure 2 X-ray energy dispersive spectroscopy (EDS) analysis was performed on the PdPt alloy-supported In₂O₃ hollow microtubes prepared for this invention. The analysis revealed that the material possesses a hollow microtube structure with a size of approximately 2-3 µm. Pd, Pt, In, and O elements are uniformly distributed within the hollow microtubes, demonstrating the uniform loading of the PdPt alloy onto the In₂O₃ hollow microtubes.

[0108] Figure 3 These are the X-ray diffraction patterns of the materials prepared in Example 1 and Comparative Example 1. It can be seen that the materials have a series of diffraction peaks, which are characteristic diffraction peaks belonging to the cubic phase In₂O₃. Due to the extremely low PdPt loading, no PdPt peaks were detected.

[0109] Figure 4 The sensitivity curves of the resistive hydrogen sensor assembled using the materials prepared in Example 1 and Comparative Example 1 of this invention for 100 ppm H2 are shown at 220-280°C. It can be seen that the sensitivity of the H2 sensor based on the PdPt alloy-supported MOF-derived In2O3 hollow microtube for 100 ppm H2 first increases and then decreases with increasing operating temperature, with the highest sensitivity of 9.5 at an operating temperature of 250°C. In contrast, the device in Comparative Example 1 has a sensitivity of 2.6 at an operating temperature of 250°C, which is significantly lower than that of this application.

[0110] Figure 5 The dynamic response recovery curves of the resistive hydrogen sensors assembled using the materials prepared in Example 2 and Comparative Example 1 of this invention are shown in the figure at 250°C to 100 ppm H2. It can be seen that when the sensor assembled in Example 2 is exposed to H2, the sensor resistance decreases significantly. When switched back to an air atmosphere, the sensor resistance returns to its initial state, indicating that the sensor has good response recovery characteristics to H2, with response recovery times of 3 s and 4 s, respectively. In contrast, the sensor based on Comparative Example 1 shows a significant increase in resistance after contact with H2 under the same conditions, with response recovery times of 4 s and 4 s, respectively. This is because the Pd in ​​Comparative Example 1 reacts with H2 to form PdH2. x This phase leads to enhanced electron scattering, which in turn causes an increase in resistance.

[0111] Figure 6The performance of resistive hydrogen sensors fabricated using the materials prepared in Comparative Examples 2 and 3 of this invention is shown; wherein (a, b) are sensitivity curves for 100 ppm H2 at 220-290°C; and (c, d) are dynamic response recovery curves for 100 ppm H2 at 250°C. Figure 6 As can be seen, the optimal operating temperature of the sensors based on the materials of Comparative Example 2 and Comparative Example 3 is 250℃, and their sensitivities to 100 ppm H2 are 3.2 and 2.6, respectively, both lower than those of this application. Their response recovery times are 8 s / 6 s and 7 s / 6 s, respectively, both greater than those of this application.

[0112] Figure 7 The image shows the response curves of a resistive hydrogen sensor assembled using the materials prepared in Example 2 of this invention to concentrations of 0.5-8 ppm H2 at 250°C. It can be seen that as the H2 concentration increases, the sensitivity of the H2 sensor based on a PdPt alloy-supported MOF-derived In2O3 hollow microtube gradually increases, and the sensor's detection limit for H2 gas can reach 500 ppb. Even at 500 ppb H2, the sensor still exhibits a significant response (approximately 1.4).

[0113] Figure 8 The graph shows the response curves of resistive hydrogen sensors assembled using the materials prepared in Example 2 and Comparative Example 1 to concentrations of 10-2000 ppm H2 at 250°C. As can be seen from the graph, the sensitivity of the sensor based on Example 2 gradually increases with increasing H2 concentration, reaching a response value of 32 at 2000 ppm H2. However, the sensor based on Comparative Example 1, due to the PdH... x There is competition between generated and surface-adsorbed oxygen, and its sensitivity gradually decreases with increasing H2 concentration. In addition, the sensor resistance fluctuates greatly, making it difficult to effectively detect different concentrations of H2.

[0114] Figure 9 The figures show a bar graph (a) of the selectivity of the resistive hydrogen sensor assembled with the material prepared in Example 3 of this invention to 20 ppm of different gases at 250°C and a repeatability curve (b) of the response to 100 ppm H2 at 250°C. It can be seen that the sensor has good selectivity for H2, and after multiple cycles of H2-air testing, the sensor's sensitivity remains relatively consistent, indicating that the sensor has good response repeatability.

[0115] Figure 10 The image shows the long-term stability curve of the resistive hydrogen sensor assembled using the material prepared in Example 1 of this invention against 100 ppm H2 at 250°C. It can be seen that after 35 days of testing, the sensor's sensitivity did not significantly decrease, indicating that the sensor has good long-term stability.

[0116] Figure 11 The image shows the long-term stability curve of the resistive hydrogen sensor assembled using the material prepared in Comparative Example 2 of this invention against 100 ppm H2 at 250°C. It can be seen that after 35 days of testing, the sensor's sensitivity decreased significantly, with a decrease of approximately 20%, indicating poor long-term stability and unsuitability for H2 detection in practical applications.

[0117] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a PdPt alloy-supported In2O3 hollow microtube, characterized in that, The steps are as follows: (1) Indium nitrate hydrate and terephthalic acid were dissolved in N,N-dimethylformamide, and after hydrothermal reaction I and high-temperature calcination, In2O3 hollow microtubes were obtained; (2) Add potassium chloroplatinate, sodium chloropalladium, potassium bromide, potassium iodide and polyvinylpyrrolidone to deionized water, and add hydrochloric acid solution under stirring until the pH of the solution is 2.5-3.5 to obtain solution A; (3) Solution A obtained in step (2) undergoes hydrothermal reaction II to obtain PdPt alloy powder; (4) Mix the dispersion I containing In2O3 hollow microtubes with the dispersion II containing PdPt alloy powder to obtain solution B. After stirring, ultrasonic treatment and solvent removal, PdPt alloy supported In2O3 hollow microtubes are obtained.

2. The method for preparing a PdPt alloy-supported In2O3 hollow microtube according to claim 1, characterized in that, In step (1), the mass ratio of indium nitrate hydrate to terephthalic acid is 1:(0.9-1.1), the temperature of hydrothermal reaction I is 115-125℃, and the time is 2-3 h.

3. The method for preparing a PdPt alloy-supported In2O3 hollow microtube according to claim 2, characterized in that, In step (1), high-temperature calcination refers to first raising the temperature to 115-125℃ at 1-2℃ / min and calcining for 2-3 hours, and then raising the temperature to 490-510℃ at 1-2℃ / min and calcining for 2-3 hours.

4. The method for preparing a PdPt alloy-supported In2O3 hollow microtube according to claim 3, characterized in that, In step (2), the molar ratio of potassium chloroplatinate, sodium chloropalladium, potassium bromide, and potassium iodide is 1:(0.9-1.2):(90-120):(0.1-0.3).

5. The method for preparing a PdPt alloy-supported In2O3 hollow microtube according to claim 4, characterized in that, In step (3), the temperature of hydrothermal reaction II is 155-165℃ and the time is 4-5 h.

6. The method for preparing a PdPt alloy-supported In2O3 hollow microtube according to claim 5, characterized in that, In step (4), the mass ratio of In2O3 hollow microtubes to PdPt alloy powder in solution B is (180-220):

1.

7. A PdPt alloy-supported In2O3 hollow microtube prepared by the preparation method according to any one of claims 1-6.

8. The application of the PdPt alloy-supported In2O3 hollow microtube as described in claim 7 in a resistive hydrogen sensor.

9. A resistive hydrogen sensor, characterized in that, The resistive hydrogen sensor comprises, from bottom to top: a ruthenium dioxide film printed on the lower surface of a ceramic sheet, a ceramic sheet, a pair of interdigitated electrodes printed on the upper surface of the ceramic sheet, and a gas-sensitive film coated on the upper surface of the ceramic sheet and the surface of the interdigitated electrodes; wherein, the gas-sensitive film is a PdPt alloy-supported In2O3 hollow microtube as described in claim 7.

10. The resistive hydrogen sensor according to claim 9, wherein the resistive hydrogen sensor further comprises two wires led out from the interdigitated electrode and two wires led out from both ends of the ruthenium dioxide film.

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