Au-Pt bimetallic co-modified In₂O₃ nanoflower material for resistive hydrogen sensors, preparation method, and application in hydrogen sensing.

Abstract

The application discloses an Au-Pt bimetal co-modified In2O3 nanoflower material for a resistance hydrogen sensor, a preparation method and application thereof in hydrogen sensing. In order to improve the problems of low hydrogen response value, slow response recovery speed and poor selectivity of pure indium oxide material, the overall effect and ligand effect of a gold-platinum bimetal system are utilized, a modification method is started from two aspects of chemical sensitization and electronic sensitization, the optimal doping ratio of the bimetal catalyst is determined, and a gold-platinum bimetal modified indium oxide ternary material with excellent morphology, large specific surface area, high response and low response-recovery time is prepared. The hydrogen response value of the ternary material obtained by the method under the optimal working condition is 17 times that before modification, great improvement in response is realized, and the ternary material has the advantages of good repeatability, high stability, short response recovery time and low detection lower limit, and has great research potential and space in the research and development of subsequent high-performance advanced hydrogen sensors.

Description

Technical Field

[0001] This invention belongs to the technical field of gas-sensitive materials and electrochemical devices, specifically relating to an Au-Pt bimetallic co-modified In2O3 nanoflower material for resistive hydrogen sensors, its preparation method, and its application in hydrogen sensing. The Au-Pt bimetallic co-modified In2O3 nanoflower material is a ternary material of Au-Pt bimetallic co-modified In2O3 nanoflowers for use in semiconductor oxide (MOS) based resistive hydrogen sensors. Background Technology

[0002] With the continuous development of modernization, the energy shortage and environmental pollution problems brought about by social progress have become increasingly serious and have received widespread attention, giving rise to the concept of sustainable development. Hydrogen energy, as a clean and efficient alternative energy source, has attracted much attention. Compared with other flammable gases, such as methane, propane, and petroleum gas, its combustion process produces only water and negligible hydrogen nitride, without generating additional environmental pollutants. Therefore, the use of hydrogen energy is also conducive to reducing the negative impacts of greenhouse gas emissions. Currently, hydrogen energy has been widely used in aerospace, transportation, nuclear energy, and other fields, showing broad application prospects and development potential. It is worth noting that hydrogen, as the main form of hydrogen energy, carries the risk of leakage, combustion, and explosion in all aspects of its production, storage, transportation, and application. Due to the rapid diffusion of hydrogen in the air, once a leak occurs, it will quickly form an explosive mixture with oxygen, causing related safety problems. In addition, hydrogen, as a common product in typical chemical reactions, can also be used as an indicator to measure whether a reaction has occurred and the extent of the reaction, such as the thermal runaway process of lithium-ion batteries, which releases flammable gases such as H2 and CH4. However, the colorless and odorless nature of hydrogen makes it difficult for human senses to detect its presence. To address the safety concerns arising from this, the need for precise and rapid hydrogen detection equipment has emerged. Among these, metal-oxide-semiconductor (MOS) sensors, as one of the earliest commercially available hydrogen sensors, have remained a research hotspot in the field of gas sensing due to their advantages such as low cost, all-solid-state operation, and moderate power consumption.

[0003] Indium oxide (In₂O₃), a typical n-type semiconductor material, has a wide bandgap of 3.6 eV at room temperature. Its excellent conductivity, superior catalytic properties, and high stability make it widely used in optoelectronics, catalysis, and gas sensing. Especially in gas sensing, its response characteristics to gases such as CO, NO₂, C₂H₅OH, and H₂ have been extensively studied and reported, reflecting its promising future in this field. However, a review of previous research revealed that traditional single In₂O₃ materials often suffer from insufficient response values, long response recovery times, high operating temperatures, weak long-term stability, and poor selectivity for hydrogen. These shortcomings make it difficult to meet the requirements for accurate and rapid hydrogen detection technologies in ensuring hydrogen safety. Therefore, modifying traditional single metal oxide semiconductor materials to obtain better gas-sensing performance has become an important approach for developing high-performance advanced hydrogen sensors.

[0004] Mechanism studies and experiments have revealed that In₂O₃ materials can be modified through improving their microstructure and structure, noble metal doping, and the construction of heterojunctions. Regarding noble metal doping, bimetallic catalysts can effectively improve the gas sensing performance of the substrate material through alloying effects and synergistic interactions. Pt is a recognized highly active catalyst with good catalytic effects on hydrogen, but its irreversible adsorption of hydrogen results in a weak response to hydrogen. Au, on the other hand, is a catalyst with long-term stability and high activity and strong electron affinity, but its promoting effect on the hydrogen adsorption process is weak. Compared to monometallic catalysis, Au-Pt bimetallic catalysts can leverage the strengths of both, thereby improving the catalytic ability, selectivity, and durability for hydrogen. Currently, domestic modifications to gas sensing materials mainly focus on single noble metal doping or doping with other elements; there is little development of metal oxide semiconductor composite materials modified with bimetallic catalysts specifically for improving hydrogen sensing performance.

[0005] This invention aims to expand the practical application range of sensors and improve their hydrogen sensing performance. It also considers the need for simple fabrication processes to meet industrial production requirements and lower operating temperatures to reduce safety hazards. Combining mechanistic research and experimental design, this invention proposes a method for preparing Au-Pt bimetallic co-modified nanoflower ternary materials for MOS-based resistive hydrogen sensors. This method modifies traditional single metal oxide semiconductor materials from the perspectives of microstructure and bimetallic catalysis, successfully achieving the expected effects of improved hydrogen response, shortened response recovery time, reduced operating temperature, and increased hydrogen selectivity. Summary of the Invention

[0006] To address the aforementioned issues, this invention provides an Au-Pt bimetallic co-modified In₂O₃ nanoflower material for resistive hydrogen sensors, its preparation method, and its application in hydrogen sensing. The preparation method is a simple template-free hydrothermal synthesis approach, employing both Au and Pt noble metals as dopants to achieve synergistic catalytic effects. Based on the metal oxide semiconductor material In₂O₃ as the core substrate, a template-free solvothermal method is used to synthesize the precursor. Through a series of subsequent treatments including washing and sintering, a nanoflower-like ternary composite material co-modified with an Au-Pt bimetallic catalyst on an In₂O₃ metal oxide semiconductor substrate is obtained. This modification of traditional single metal oxide semiconductor materials from the perspectives of microstructure and bimetallic catalysis successfully achieves the expected effects of improved hydrogen response, shortened response recovery time, reduced operating temperature, and improved hydrogen selectivity, providing a new method for the preparation of high-performance resistive hydrogen sensors based on In₂O₃.

[0007] This invention first proposes a nanoflower-like ternary composite material co-modified with an Au-Pt bimetallic catalyst on an In2O3 metal oxide semiconductor substrate. The material morphology is a nanoflower structure composed of nanosheets with a porous structure, exhibiting a coral reef crack shape and a grooved surface. The catalytic metals Au and Pt are distributed on the surface and inside the indium oxide nanoflowers.

[0008] The present invention adopts the following technical solution:

[0009] An Au-Pt bimetallic co-modified In₂O₃ nanoflower material for resistive hydrogen sensors is disclosed. The material has a micron-scale Au-Pt bimetallic catalyst co-modified indium oxide nanoflower structure, wherein gold and platinum, two noble metal elements, are doped into the indium oxide nanoflower lattice via a hydrothermal method and uniformly dispersed. Preferably, based on the total mass of the Au-Pt bimetallic co-modified In₂O₃ nanoflower material, the mass percentage of Au is 3-6%, and the mass percentage of Pt is 0.1-2%; preferably, the balance is In₂O₃ nanoflowers; preferably, the diameter of the In₂O₃ nanoflowers is 1.2-1.6 μm. For example, the diameter of the In₂O₃ nanoflowers is 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, or 1.6 μm.

[0010] For example, based on the total mass of Au-Pt bimetallic co-modified In₂O₃ nanoflower materials, the mass percentage of Au is 3%, 3.2%, 3.4%, 3.6%, 3.8%, 34%, 4.2%, 4.4%, 4.6%, 4.8%, 5%, 5.2%, 5.4%, 5.6%, 5.8%, or 6%. For example, based on the total mass of Au-Pt bimetallic co-modified In₂O₃ nanoflower materials, the mass percentage of Pt is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, or 2%.

[0011] The preparation method of Au-Pt bimetallic co-modified In2O3 nanoflower materials as described above includes the following steps:

[0012] Step 1: Add urea, sodium dodecyl sulfate and indium salt to deionized water, stir, and react at 40-60°C (e.g. 40°C, 45°C, 50°C, 55°C or 60°C) to obtain a uniform white suspension.

[0013] Step 2: Weigh out chloroplatinic acid and chloroauric acid in an inert atmosphere, then add them to the white suspension and stir continuously until they are mixed evenly to obtain a uniform yellow suspension.

[0014] Step 3: Transfer the uniform yellow suspension to a hydrothermal reactor. After confirming the seal, react at 140–200°C (e.g., 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, 180°C, 185°C, 190°C, 195°C, or 200°C) for 20–40 hours (e.g., 20 hours, 24 hours, 25 hours, 30 hours, 35 hours, or 40 hours), then cool to room temperature. Separate the supernatant and precipitate in the reactor by centrifugation. Wash the obtained precipitate repeatedly until the supernatant is no longer turbid. Dry the washed precipitate to obtain the precursor powder. Preferably, after confirming the seal, react at 160°C for 24 hours, then cool to room temperature.

[0015] Step 4: The precursor powder is heated to 550-650℃ (e.g., 550℃, 555℃, 560℃, 565℃, 570℃, 580℃, 590℃, 600℃, 610℃, 620℃, 630℃, 640℃ or 650℃) in air at a rate of 3-5℃ / min, and sintered for 1-4 hours. It is then naturally cooled to room temperature. The final product obtained is the Au-Pt bimetallic catalyst co-modified In2O3 substrate nanoflower-like ternary composite material. Preferably, the precursor powder is heated to 600℃ in air at a rate of 3-5℃ / min and sintered for 2 hours.

[0016] Further, in step 1, the molar ratio of indium salt, sodium dodecyl sulfate, and urea is 0.1–2:1–5:6. For example, the molar ratio of indium salt, sodium dodecyl sulfate, and urea is 0.1:1–5:6, 0.2:1–5:6, 0.4:1–5:6, 0.6:1–5:6, 0.8:1–5:6, 1:1–5:6, 1.2:1–5:6, 1.4:1–5:6, 1.6:1–5:6, 1.8:1–5:6, 2:1–5:6, or 1:3.5:6. Preferably, the indium salt is indium nitrate.

[0017] Further, in step 2, the molar ratio of chloroplatinic acid to chloroauric acid is 1:4 to 6; for example, the molar ratio of chloroplatinic acid to chloroauric acid is 1:4, 1:4.5, 1:5, 1:5.5 or 1:6.

[0018] Further, in step 2, the molar ratio of chloroplatinic acid to indium salt is 0.008 to 0.012:1; for example, the molar ratio of chloroplatinic acid to indium salt is 0.008:1, 0.009:1, 0.01:1, 0.011:1 or 0.012:1.

[0019] Furthermore, in step 3, the centrifugation speed is set to 7000-9000 rpm and the centrifugation time is 10-20 min; preferably, the centrifugation speed is 8000 rpm and the centrifugation time is 15 min to achieve the best separation effect.

[0020] Specifically, this invention describes the preparation method of the above-mentioned Au-Pt bimetallic catalyst co-modified In2O3 metal oxide semiconductor substrate nanoflower-like ternary composite material, and the specific steps are as follows:

[0021] Step 1: Weigh 6 mmol of urea, 3.5 mmol of sodium dodecyl sulfate and 1 mmol of In(NO3)3·4.5H2O, add them to 60 mL of deionized water, and stir continuously at 550 rpm for 6 hours at 40 °C to obtain a uniform white suspension.

[0022] Step 2: Weigh 0.01 mmol of crystalline chloroplatinic acid and 0.05 mmol of crystalline chloroauric acid in an argon atmosphere, then add the white suspension and continue stirring for 3 hours. Remove the foam on the surface of the solution to obtain a uniform yellow suspension.

[0023] Step 3: Transfer the uniform yellow suspension to a 100ml stainless steel high-pressure reactor with a polytetrafluoroethylene core. After confirming the seal, react at 160℃ for 24 hours. After the oven temperature naturally cools to room temperature, open the reactor. Separate the supernatant and precipitate in the reactor by centrifugation. Wash the obtained precipitate repeatedly with deionized water and anhydrous ethanol until the supernatant is no longer turbid during the washing process. Dry the washed precipitate at 60℃ for 12 hours to obtain a light yellow powder precursor product.

[0024] Step 4: Place the dried precursor powder into a muffle furnace and heat it to 600°C at a rate of 5°C / min in an air atmosphere. Sinter for 2 hours and allow it to cool naturally to room temperature. The final product obtained is the nanoflower-like ternary composite material of Au-Pt bimetallic catalyst co-modified In2O3 substrate.

[0025] Preferably, in step 1, the molar ratio of In(NO3)3·4.5H2O to sodium dodecyl sulfate and urea is 1:3.5:6, and the order of addition is In(NO3)3·4.5H2O, urea, and sodium dodecyl sulfate.

[0026] Preferably, in step 2, the ratio of HPtCl6 to AuCl4H is 1:5.

[0027] Preferably, in step 3, the centrifugation speed during the washing process is typically set to 7000-9000 rpm, and the centrifugation time is 10-20 min; preferably, the centrifugation speed is 8000 rpm, and the centrifugation time is 15 min to achieve the best separation effect.

[0028] Furthermore, the Au-Pt bimetallic co-modified In2O3 nanoflower material hydrogen sensor for resistive hydrogen sensors has an Al2O3 as a planar substrate, on which gold interdigitated electrodes are formed by thick film screen printing. The prepared nanocomposite material is uniformly coated on the gold interdigitated electrodes, and two pairs of platinum electrodes are connected to both ends of the gold interdigitated electrodes for the transmission and measurement of electrical signals.

[0029] Furthermore, the specific fabrication steps of the Au-Pt bimetallic co-modified In2O3 nanoflower material for resistive hydrogen sensors are as follows:

[0030] Step 1: Take a certain mass of nanocomposite material, mix it with terpineol, and disperse it evenly by ultrasonic dispersion. Use a pipette to take a fixed volume of the dispersion solution and drop it onto the interdigital electrodes. Place them stably in an 80℃ oven to dry, and scrape off the coating material on both electrodes with a blade.

[0031] Step 2: Place the dried interdigitated electrodes into a muffle furnace, heat to 350°C at a heating rate of 2°C / min, and sinter at 350°C for a period of time, then allow to cool naturally to room temperature;

[0032] Step 3: Connect the exposed portions of the gold interdigitated electrodes coated with composite material after sintering to the platinum electrodes, and age them in an air environment at 300-400℃ for a period of time to obtain a stable hydrogen sensor based on Au-Pt bimetallic co-modified In2O3 nanoflower material.

[0033] Preferably, in step 1, the mass of the material taken is usually 10-50 mg; the amount of terpineol used is 0.5-1.5 mL; and the amount taken by the pipette is usually 15-50 μL. By controlling the same amount of sample taken each time, the uniformity of the detector preparation is ensured.

[0034] Preferably, in step 2, the sintering time in the muffle furnace is typically controlled to be between 3 and 6 hours.

[0035] Preferably, in step 3, the detector aging time is typically controlled within 3 to 7 days. Further, the performance testing of the Au-Pt bimetallic co-modified In2O3 nanoflower material hydrogen sensor for resistive hydrogen sensors is conducted by placing the prepared sensor loaded with the sensitive material in a sealed gas chamber with precise temperature control, maintaining the temperature between 20 and 440°C, then introducing customized dry hydrogen and air. The resistance data is measured in real-time through four platinum pins. The obtained resistance data is processed to obtain characteristic values ​​such as the sensor's response value and response time.

[0036] Furthermore, the test temperature range is 20–440°C; preferably, the test temperature is 240°C.

[0037] Furthermore, the response value is calculated as follows:

[0038]

[0039] Among them, R a R is the sensor's fundamental resistance in air. g It is the resistance value measured by the sensor in hydrogen gas.

[0040] Furthermore, the response time uses T 90 The standard, and its calculation method is as follows:

[0041]

[0042]

[0043] Among them, tr es The resistance value is from R a To R g The time required for a 90% change, t rec The resistance value is from R g Restore to R a The time required for a 90% change.

[0044] The advantages of this invention compared to the prior art are:

[0045] This invention provides a method for preparing Au-Pt bimetallic co-modified ternary nanoflower materials for MOS-based resistive hydrogen sensors. The method employs a simple and easy-to-implement template-free solvothermal approach, enabling the controlled design of microstructure. This yields ternary nanoflower materials with a large specific surface area and porous structure assembled from nanosheets. Simultaneously, the addition of Au and Pt, two noble metals, further enhances the sensitization of the substrate material through the synergistic effect of the bimetallic catalyst. The hydrogen sensor prepared using the ternary material obtained by this invention effectively improves the response value limitations when using pure indium oxide as the core gas-sensitive material. Overcoming the problems of low sensitivity, slow response and recovery, and poor selectivity, the modified sensor achieves a response value 17 times higher than its unmodified counterpart under optimal operating conditions. For 500 ppm hydrogen, the response value reaches 32, with response and recovery times reduced by 48.08% and 71.91%, respectively. Simultaneously, the optimal operating temperature is lowered, successfully improving the gas sensing performance for hydrogen. This provides a new method for fabricating high-performance resistive hydrogen sensors based on In₂O₃ substrate material, further expanding the sensor's application range in practical production and daily life, and paving the way for the subsequent development of more advanced metal-oxide-semiconductor resistive hydrogen sensors. Specifically:

[0046] (1) The preparation method of the ternary material proposed in this invention is mainly through a template-free solvothermal method. This method has the advantages of simple operation and can synthesize the precursor in one step, which is conducive to the realization of subsequent industrial production. At the same time, there is no gas generation in the reactor during the reaction process, which can reduce the risk of opening the reactor and improve the operational safety of the synthesis process.

[0047] (2) The ternary material obtained by the preparation method proposed in this invention has excellent morphology. It is a relatively regular nanoflower morphology with an average diameter of 1.4 μm, which is formed by the self-assembly of nanosheets. This morphology has a large specific surface area and a large number of pore structures. At the same time, the surface has cracks and grooves similar to coral reefs, which increases the reaction area.

[0048] (3) In the preparation method proposed in this invention, two noble metals, Au and Pt, were selected for doping, thereby forming a bimetallic catalyst with higher catalytic activity, better catalytic effect, higher selectivity and stronger durability compared with single metal catalysts. The gas-sensing performance was enhanced through the overall effect. Specifically, the addition of Au diluted Pt, changed the number of Pt atoms in a specific direction, caused the lattice ratio of Pt to be unbalanced, and changed the Pt-Pt metal bond distance, thereby enhancing the selectivity of the material for hydrogen and promoting the adsorption of hydrogen in the reaction process.

[0049] (4) The preparation method proposed in this invention enhances the gas-sensing performance through the ligand effect of the Au-Pt bimetallic system. Specifically, Au has a higher electron affinity and tends to attract electrons from the s and p orbitals of Pt. Pt, on the other hand, has a higher catalytic activity and tends to acquire electrons from the d orbitals of Au, thereby causing the d band center to shift. The charge transfer between Au and Pt helps to improve the gas-sensing performance for hydrogen.

[0050] (5) By uniformly doping with two noble metals, Au and Pt, the overflow effect of the two on the surface of the metal oxide improves the reaction efficiency of hydrogen in the process, while adjusting the grain boundary barrier at the material contact, further enhancing the hydrogen sensing performance of the composite material.

[0051] (6) The optimal operating temperature of the sensor made from the material obtained by the preparation method proposed in this invention is 240°C. Compared with the operating temperature of pure indium oxide material above 300°C, the sensor made from the material obtained by the preparation method proposed in this invention has a milder operating environment and lower power consumption.

[0052] (7) The detector made by the method described in this invention has good repeatability and high long-term stability, which is conducive to the use of the sensor in multiple scenarios in daily production and life and has high practical value.

[0053] (8) The sensor prepared by the preparation method proposed in this invention has a response value of 32 to 500ppm hydrogen, which is 17 times that of the indium oxide material before modification. The sensor prepared by the preparation method proposed in this invention is more sensitive to hydrogen.

[0054] This invention provides a method for preparing Au-Pt bimetallic co-modified nanoflower ternary materials for semiconductor oxide (MOS)-based resistive hydrogen sensors. While improving the hydrogen sensing performance of the substrate material, it also addresses the need for a simple and easy-to-operate preparation process conducive to subsequent industrial production, and a low optimal operating temperature to reduce energy consumption and safety hazards. Given the urgent market demand for accurate, fast, low-power, highly selective, and inexpensive hydrogen sensors, this method has significant development potential and application prospects. Attached Figure Description

[0055] The present invention will now be described in further detail with reference to the accompanying drawings.

[0056] Figure 1 Scanning electron microscope image of In2O3 nanoflowers modified with Au-Pt bimetallic catalyst prepared in Example 2 of this invention.

[0057] Figure 2 Transmission electron microscopy (TEM) image of In2O3 nanoflowers modified with Au-Pt bimetallic catalyst prepared in Example 2 of this invention.

[0058] Figure 3 The image shows an elemental scan of the In2O3 nanoflowers modified with the Au-Pt bimetallic catalyst prepared in Example 2 of this invention. It can be seen that Au and Pt are uniformly distributed in the In2O3 nanoflowers.

[0059] Figure 4 The image shows the XRD data of the In2O3 nanoflower material co-modified with pure-phase In2O3 and Au-Pt bimetallic catalyst prepared in Example 1 of this invention.

[0060] Figure 5 The image shows the BET curve of the In2O3 nanoflower material co-modified with the Au-Pt bimetallic catalyst prepared in Example 2 of this invention.

[0061] Figure 6 The response recovery sensitivity of the pure-phase In2O3 nanoflower material and the In2O3 nanoflower material co-modified with Au-Pt bimetallic catalyst prepared in Examples 1 and 2 of this invention to 500ppm hydrogen gas at 240℃ was tested.

[0062] Figure 7 The continuous change of response recovery sensitivity of the pure phase In2O3 nanoflower material and the In2O3 nanoflower material co-modified with Au-Pt bimetallic catalyst prepared in Examples 1 and 2 of this invention was tested at 240 °C for different concentration gradients of hydrogen gas from 200 to 1000 ppm. Detailed Implementation

[0063] 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 preferred 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 protection scope of the present invention.

[0064] Example 1:

[0065] First, weigh 6 mmol of urea, 3.5 mmol of sodium dodecyl sulfate and 1 mmol of In(NO3)3·4.5H2O, add them to 60 mL of deionized water, and stir continuously at 550 rpm for 6 hours at 40 °C to obtain a uniform white suspension.

[0066] The uniform white suspension was transferred to a 100ml stainless steel high-pressure reactor with a polytetrafluoroethylene core. After confirming the seal, the reactor was reacted at 160℃ for 24 hours. The reactor was then opened after the oven temperature had naturally cooled to room temperature. The supernatant and precipitate in the reactor were separated by centrifugation (8000rpm for 15 minutes). The precipitate was repeatedly washed with deionized water and anhydrous ethanol until the supernatant was no longer cloudy. The washed precipitate was dried at 60℃ for 12 hours to obtain a white powder precursor product.

[0067] The dried precursor powder was placed in a muffle furnace and heated to 600°C at a rate of 5°C / min in air atmosphere. After sintering for 2 hours, it was naturally cooled to room temperature. The final product obtained was the pure phase In2O3 nanoflower material.

[0068] Example 2:

[0069] Weigh 6 mmol of urea, 3.5 mmol of sodium dodecyl sulfate and 1 mmol of In(NO3)3·4.5H2O, and add them sequentially to 60 mL of deionized water. Stir continuously at 550 rpm for 6 hours at 40 °C to obtain a uniform white suspension.

[0070] Weigh 0.01 mmol of crystalline chloroplatinic acid and 0.05 mmol of crystalline chloroauric acid into a white suspension under an argon atmosphere, continue stirring for 3 hours, remove the foam on the surface of the solution, and obtain a uniform yellow suspension.

[0071] The uniform yellow suspension was transferred to a 100ml stainless steel high-pressure reactor with a polytetrafluoroethylene core. After confirming the seal, the reactor was reacted at 160℃ for 24 hours. The reactor was opened after the oven temperature naturally cooled to room temperature. The supernatant and precipitate in the reactor were separated by centrifugation. The precipitate was repeatedly washed with deionized water and anhydrous ethanol until the supernatant was no longer turbid. The washed precipitate was dried at 60℃ for 12 hours to obtain a pale yellow powder precursor product.

[0072] The dried precursor powder was placed in a muffle furnace and heated to 600°C at a rate of 5°C / min in air atmosphere, sintered for 2 hours, and then naturally cooled to room temperature. The final product obtained was a nanoflower-like ternary composite material co-modified with Au-Pt bimetallic catalyst on an In2O3 substrate. Based on the total mass of the nanoflower-like ternary composite material co-modified with Au-Pt bimetallic catalyst on an In2O3 substrate, the mass percentage of Au was 5% and the mass percentage of Pt was 1%.

[0073] Figure 1 The image shows a scanning electron microscope (SEM) image of the Au-Pt bimetallic catalyst-modified In2O3 nanoflowers prepared in Example 2 of this invention. The morphology is a relatively regular nanoflower structure with an average diameter of 1.4 μm, which is self-assembled from nanosheets. It has a large specific surface area and a large number of pore structures. At the same time, the surface has cracks and grooves similar to coral reefs, which further increases the reaction area with hydrogen.

[0074] Figure 2 The image shows a transmission electron microscope (TEM) image of the In2O3 nanoflowers modified with the Au-Pt bimetallic catalyst prepared in Example 2 of this invention. The presence of a cavity structure inside the morphology further indicates that it has a large specific surface area.

[0075] Figure 3 The image shows an elemental scan of the In2O3 nanoflowers modified with the Au-Pt bimetallic catalyst prepared in Example 2 of this invention. It can be seen that Au and Pt are uniformly distributed in the In2O3 nanoflowers.

[0076] Figure 4 The image shows the XRD data of the In2O3 nanoflower material co-modified with pure-phase In2O3 and Au-Pt bimetallic catalyst prepared in Example 1 of this invention. The characteristic peaks are obvious, the peak values ​​are high and there are no impurity peaks, indicating that the nanomaterial obtained by the preparation method proposed in this invention has good crystallinity and purity. The comparison with the standard card shows that the positions of the characteristic peaks can be matched one by one, indicating that the material is a cubic In2O3 material co-catalyzed by Au-Pt bimetallic catalyst.

[0077] Figure 5The BET curve of the In2O3 nanoflower material co-modified with Au-Pt bimetallic catalyst prepared in Example 2 of this invention shows that the ternary material has a large surface area, and the inconsistency between adsorption and desorption branches indicates that its structure has many pores.

[0078] The Au-Pt bimetallic co-modified In2O3 nanoflower material hydrogen sensor for resistive hydrogen sensors has a structure with Al2O3 as a planar substrate. Gold interdigitated electrodes are formed on the substrate using a thick-film screen printing process. The prepared nanocomposite material is uniformly coated on the gold interdigitated electrodes, and two pairs of platinum electrodes are connected to both ends of the gold interdigitated electrodes for electrical signal transmission and measurement. Specifically, the application of the Au-Pt bimetallic co-modified In2O3 nanoflower material in resistive hydrogen sensors, and the specific fabrication steps of the sensor are as follows:

[0079] Step 1: Take 50 mg of Au-Pt bimetallic catalyst-modified In2O3 nanoflower composite material, mix it with 1.5 mL of terpineol, and disperse it evenly by ultrasonic dispersion. Use a pipette to take a fixed volume of dispersion solution and drop it onto the interdigital electrodes. By controlling the sample amount (50 μL each time) to be the same, the uniformity of detector preparation is ensured. Place it stably in an 80℃ oven to dry, and scrape off the coating material on both electrodes with a blade.

[0080] Step 2: Place the dried interdigitated electrodes into a muffle furnace, heat to 350°C at a heating rate of 2°C / min, and sinter at 350°C for 6 hours, then allow to cool naturally to room temperature;

[0081] Step 3: Connect the exposed portions of the gold interdigitated electrodes coated with composite material after sintering to the platinum electrodes, and age them in air at 400°C for 7 days to obtain a stable hydrogen sensor based on Au-Pt bimetallic co-modified In2O3 nanoflower material. Figure 6 The response recovery sensitivity tests of the pure-phase In2O3 nanoflower materials and the Au-Pt bimetallic catalyst-modified In2O3 nanoflower materials prepared in Examples 1 and 2 of this invention to 500 ppm hydrogen at 240 °C showed that the ternary materials prepared by the method provided by this invention have a response value to hydrogen that is 17 times that of the pure-phase materials before modification, and the response and recovery times are shortened by 48.08% and 71.91%, respectively, demonstrating the superiority and advancement of the method described in this invention.

[0082] Figure 7The response recovery sensitivity of the pure-phase In2O3 nanoflower material and the In2O3 nanoflower material co-modified with Au-Pt bimetallic catalyst prepared in Examples 1 and 2 of this invention was continuously tested at 240℃ for different concentration gradients of hydrogen from 200 to 1000 ppm. The images show that for different concentrations of hydrogen, the ternary material prepared by the method of this invention has a significant improvement in performance (including response value, response time, etc.) compared with the pure-phase indium oxide material. The response value for 500 ppm hydrogen is 32, which is 17 times that before modification. This proves that the method of this invention can successfully modify the substrate material, thereby further optimizing the application of indium oxide substrate hydrogen sensors in actual industrial production and daily life.

[0083] The parts of this invention not described in detail are well-known in the field.

[0084] Although the illustrative specific embodiments of the present invention have been described above to enable those skilled in the art to understand the invention, it should be understood that the invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the invention as defined and determined by the appended claims, and all inventions utilizing the concept of the present invention are protected.

Claims

1. An Au-Pt bimetallic co-modified In2O3 nanoflower material for resistive hydrogen sensors, characterized in that: The material morphology is an indium oxide nanoflower structure co-modified with an Au-Pt bimetallic catalyst, wherein gold and platinum, two noble metal elements, are doped into the indium oxide nanoflower lattice by a hydrothermal method and uniformly dispersed. The Au-Pt bimetallic co-modified In2O3 nanoflower material, based on its total mass, contains 3-6% Au and 0.1-2% Pt; the balance is In2O3 nanoflowers; the diameter of the In2O3 nanoflowers is 1.2-1.6 μm; the Au-Pt bimetallic co-modified In2O3 nanoflower material is prepared by the following method: Step 1: Add urea, sodium dodecyl sulfate and indium salt to deionized water, stir, and react at 40~60℃ to obtain a uniform white suspension; Step 2: Weigh out chloroplatinic acid and chloroauric acid in an inert atmosphere, then add them to the white suspension and stir continuously until they are mixed evenly to obtain a uniform yellow suspension. Step 3: Transfer the uniform yellow suspension to a hydrothermal reactor, confirm that it is sealed, and react at 140~200℃ for 20~40 hours, then cool to room temperature; separate the supernatant and precipitate in the reactor by centrifugation, wash the obtained precipitate repeatedly until the supernatant is no longer turbid during the washing process, and dry the washed precipitate to obtain the precursor powder. Step 4: Heat the precursor powder to 550-650℃ in air at a rate of 3-5℃ / min, sinter for 1-4 hours, and then cool naturally to room temperature. The final product is the nanoflower-like ternary composite material of Au-Pt bimetallic catalyst co-modified In2O3 substrate.

2. The Au-Pt bimetallic co-modified In₂O₃ nanoflower material for resistive hydrogen sensors according to claim 1, characterized in that, In step 1, the molar ratio of indium salt, sodium dodecyl sulfate, and urea is 0.1~2:1~5:

6.

3. The Au-Pt bimetallic co-modified In₂O₃ nanoflower material for resistive hydrogen sensors according to claim 1, characterized in that, In step 2, the molar ratio of chloroplatinic acid to chloroauric acid is 1:4~6; the molar ratio of chloroplatinic acid to indium salt is 0.008~0.012:

1.

4. The Au-Pt bimetallic co-modified In₂O₃ nanoflower material for resistive hydrogen sensors according to claim 1, characterized in that, In step 3, the centrifugation speed is set to 7000~9000 rpm and the centrifugation time is 10~20 min.

5. The application of the nanoflower material according to claim 1 in hydrogen sensing, characterized in that: Using Al2O3 as a planar substrate, gold interdigitated electrodes are formed on it through thick film screen printing. The prepared nanocomposite material is uniformly coated on the gold interdigitated electrodes. Two pairs of platinum electrodes are connected to the two ends of the gold interdigitated electrodes for the transmission and measurement of electrical signals.

6. The application according to claim 5, characterized in that: Simultaneously using Au and Pt as selective enhancement elements for hydrogen, the morphology of the core sensitive metal oxide semiconductor material In2O3 is improved by utilizing the synergistic effect between the two elements. A high-performance Au-Pt bimetallic co-modified In2O3 nanoflower composite material that can be used for hydrogen sensors is synthesized. Based on this, a high-performance hydrogen sensor is prepared and applied to hydrogen gas detection.

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