Pd-In co-modified MoO3 nanocomposites, preparation methods and applications

Abstract

This invention discloses a Pd-In synergistic modification of MoO3 nanocomposite materials, its preparation method, and its applications, relating to the fields of gas-sensitive materials and electrochemical devices. The nanocomposite material is prepared by hydrothermal reaction of palladium, indium, and molybdenum sources, followed by drying and calcination. The morphology of the nanocomposite material is a nanorod composite structure with micron-sized nanoparticles grown in situ on the surface. Palladium and indium are incorporated into the MoO3 lattice, with some indium particles agglomerated on the molybdenum oxide surface. This invention not only achieves breakthrough optimization of the microstructure morphology and core gas-sensing performance of traditional hydrogen detection materials but also significantly improves the sensor's specific response to hydrogen and overall gas-sensing characteristics in practical applications. Ultimately, it provides a novel technical path that is innovative, practical, and operable for the design and preparation of new functional materials in the field of room-temperature gas sensing.

Description

Technical Field

[0001] This invention relates to the field of gas-sensitive materials and electrochemical devices, and particularly to Pd-In synergistically modified MoO3 nanocomposites, their preparation methods, and applications. Background Technology

[0002] Hydrogen energy, as a clean and efficient secondary energy source, has been applied on a large scale in fuel cell vehicles, energy storage systems, and industrial synthesis, becoming one of the core carriers of energy transition. However, the unique physicochemical properties of hydrogen pose significant safety risks, casting a shadow over its industrialization process. Compared to traditional fuels, hydrogen has extremely high diffusivity (diffusion coefficient reaches 1.29 cm⁻¹). 2 With its extremely high explosive capacity (up to 8 times that of natural gas), wide explosion limits (4%~75% by volume), and extremely low ignition energy (only 0.017mJ, less than 1 / 18th that of natural gas), coupled with its colorless and odorless properties, hydrogen leaks cannot be detected by human senses. Therefore, developing room-temperature hydrogen detection technology with high sensitivity and strong anti-interference capabilities, and constructing a comprehensive safety early warning system, has become an urgent need to ensure the safe and sustainable development of the hydrogen energy industry.

[0003] In recent years, metal-oxide-semiconductor (MOS) hydrogen sensors have attracted widespread attention due to their superior performance, long lifespan, ease of miniaturization, and low cost. However, most MOS gas sensors typically operate at temperatures above 200°C, leading to issues such as high power consumption and potential safety hazards. Therefore, the development of room-temperature hydrogen sensors is becoming increasingly important. Compared to common metal oxide materials such as SnO2, In2O3, ZnO, and WO3, MoO3 possesses a unique layered structure with a band gap of 2.39–3.0 eV, exhibiting high stability, excellent thermal conductivity, carrier mobility, and abundant surface active sites. MoO3 is an n-type semiconductor with three crystal forms: orthorhombic α-MoO3 (thermodynamically stable phase), monoclinic β-MoO3 (low-temperature metastable state), and hexagonal h-MoO3. Among these, α-MoO3 exhibits the best thermal stability and is therefore widely used in catalysis, energy storage, and gas sensing. Particularly in the detection of reducing gases, MoO3 has garnered significant attention due to its excellent gas-sensing performance. However, while pure MoO3 gas sensors possess the fundamental advantage of surface active sites due to their layered structure, their inherent characteristics result in significant shortcomings in stability, selectivity, and response recovery time, severely hindering their practical application. Regarding stability, the crystal structure and surface chemical state of pure MoO3 materials are easily affected by the external environment. During long-term operation, repeated adsorption and desorption of gas molecules lead to the gradual occupation of surface active sites by carbon deposits or impurities. Simultaneously, under high-temperature operating conditions, crystal transformation or particle agglomeration may occur, causing the sensor's response signal to continuously decay, making it difficult to maintain stable detection performance. This instability is particularly pronounced in complex industrial environments. As a key clean energy source, the rapid development of hydrogen energy places higher demands on hydrogen detection technology, making the development of highly sensitive detection materials for room-temperature hydrogen leak detection of great significance.

[0004] To further improve the sensing performance of gas-sensitive materials, researchers have proposed various methods, including noble metal modification, heterostructure construction, and photoexcitation. In heterostructure construction, In₂O₃ itself is a wide-bandgap sensing material commonly used for room-temperature hydrogen detection. Using In as a modifier in heterostructure construction plays a crucial role in modifying the core sensing material of the sensor. Pd itself has a catalytic activity enhancement effect; Pd exhibits excellent catalytic cracking ability for reducing gases such as hydrogen, which can accelerate the adsorption and dissociation of gas molecules on the surface of the sensing material, improving the reaction kinetic rate, and thus has significant advantages in the preparation of hydrogen sensing materials. Currently, in the field of gas sensing material modification research in China, the focus is mostly on single noble metal doping or other single-element doping methods, while research specifically targeting the needs of room-temperature hydrogen detection and developing composite nanomaterials with multi-element synergistic modification is relatively scarce. Summary of the Invention

[0005] Based on the technical problems existing in the background technology, this invention proposes a Pd-In synergistic modification of MoO3 nanocomposite material, its preparation method and application. It not only achieves breakthrough optimization of the microstructure morphology and core gas-sensing performance of traditional hydrogen detection materials, but also significantly improves the sensor's specific response capability to hydrogen and comprehensive gas-sensing characteristics in practical application scenarios. Ultimately, it provides a new technical path that is innovative, practical and operable for the design and preparation of novel functional materials in the field of room temperature gas sensing.

[0006] The present invention proposes a Pd-In synergistic modification of MoO3 nanocomposite material, which is prepared by hydrothermal reaction of palladium source, indium source and molybdenum source, followed by drying and calcination;

[0007] The morphology of the nanocomposite material is a nanorod composite structure of micron-sized nanoparticles grown in situ on the surface.

[0008] In the nanocomposite material, palladium and indium are incorporated into the MoO3 lattice, and some indium particles agglomerate and grow on the surface of molybdenum oxide.

[0009] The present invention proposes a method for preparing Pd-In synergistically modified MoO3 nanocomposite material. The method steps are as follows: a molybdenum source is dispersed in deionized water, an indium source and a palladium source are added sequentially, and a hydrothermal reaction is carried out under acidic conditions. After the reaction, the product is washed, dried and sintered to obtain the Pd-In synergistically modified MoO3 nanocomposite material.

[0010] The morphology of the nanocomposite material is a nanorod composite structure of micron-sized nanoparticles grown in situ on the surface.

[0011] In the nanocomposite material, palladium and indium are incorporated into the MoO3 lattice, and some indium particles agglomerate and grow on the surface of molybdenum oxide.

[0012] Preferably, the molybdenum source is Na2MoO4·2H2O; the indium source is In(NO3)3·4.5H2O; and the palladium source is PdCl2.

[0013] Preferably, the molar ratio of the molybdenum source, indium source, and palladium source is 1:3-7:80-120.

[0014] Preferably, the hydrothermal reaction conditions are: temperature 180-200℃, time 10-12h.

[0015] Preferably, the pH of the hydrothermal reaction system is 1.5-2.

[0016] Preferably, the sintering conditions are as follows: heating to 250-350°C at a heating rate of 1-3°C / min under an inert atmosphere and holding for 2-3 hours; then naturally cooling to room temperature and then heating to 350-450°C at a heating rate of 2-4°C / min under an oxygen-containing atmosphere and holding for 2-3 hours.

[0017] Preferably, the inert atmosphere is nitrogen and / or argon.

[0018] Preferably, the oxygen-containing atmosphere is air or a mixture of oxygen and an inert atmosphere; the oxygen content of the oxygen-containing atmosphere is 10%-30%.

[0019] This invention proposes the application of a Pd-In co-modified MoO3 nanocomposite material in a hydrogen sensor, the nanocomposite material being described above; the hydrogen sensor can detect hydrogen at room temperature.

[0020] Beneficial technical effects of the present invention:

[0021] This invention develops a Pd-In co-modified MoO3 nanocomposite material preparation process suitable for room temperature hydrogen sensors. It synthesizes a bimetallic co-modified gas-sensitive material with controllable microstructure and ultra-large specific surface area through a simple one-pot hydrothermal preparation strategy. This material possesses advantages such as a heterostructure formed by In and MoO3, uniform distribution of the catalytic element Pd, and a large specific surface area. By utilizing the catalytic metal Pd doping to enhance the specific response to hydrogen, it achieves high sensitivity, wide detection range, and strong selectivity for hydrogen at room temperature without heating. This represents a breakthrough improvement in the microstructure and gas-sensing performance of traditional MoO3-based detection materials, significantly enhancing the targeted response capability and overall gas-sensing performance for hydrogen in practical applications. This opens up an innovative technical path for the preparation of core materials and device applications of metal oxide semiconductor-based hydrogen sensors. Specifically:

[0022] (1) First, the Pd-In synergistic modified MoO3 nanocomposite material prepared by one-pot hydrothermal method has the advantages of simple and easy operation and strong reproducibility in synthesis process. It does not require complex equipment and cumbersome post-processing steps, which lowers the preparation threshold and facilitates the transformation of laboratory research and development into large-scale production.

[0023] (2) A special ternary composite nanomaterial with one-dimensional MoO3 nanorods as the framework, In elements to construct a heterogeneous substrate, and noble metal Pd nanoparticles uniformly loaded on the surface is formed. This hierarchical structure can fully expose gas-sensitive active sites and provide sufficient contact interfaces for gas-sensitive reactions.

[0024] (3) By synergistic modification of Pd and In, the response performance of the composite material to hydrogen is synergistically enhanced: Pd, as a catalytic noble metal, forms an "overflow effect" on the surface of MoO3, which accelerates the adsorption, dissociation and activation process of hydrogen molecules, and has excellent targeting response to hydrogen. At the same time, it can adjust the contact barrier at the material interface. The introduction of In constructs a MoO3-In heterojunction, regulates the electronic band structure of the material, enhances the adsorption affinity for hydrogen and inhibits the adsorption of other interfering gases. The synergistic effect of the two greatly improves the gas sensitivity and selectivity.

[0025] (4) The heterostructure constructed by In element and the semiconductor properties of MoO3 form a synergy, combined with the dispersion effect of Pd nanoparticles, so that the composite material has both excellent electrical conductivity and ultra-large specific surface area, which can significantly optimize the gas adsorption / desorption kinetics in hydrogen detection, shorten the response / recovery time, and effectively broaden the detection concentration range to meet the needs of different scenarios from low concentration leak monitoring to high concentration detection.

[0026] (5) The hydrogen detector made by the method described in this invention has excellent consistency and high long-term stability. After a standardized sintering and aging process, it not only has reliable mechanical strength and can withstand environmental vibrations in practical applications, but also has significantly improved hydrogen detection response speed, sensitivity and cycle repeatability compared with traditional commercial MoO3-based sensors, making it suitable for harsh application scenarios such as industry and new energy.

[0027] The method of this invention has the advantages of simple material preparation, high response to hydrogen at room temperature and low detection limit, providing a new approach for the future preparation of room temperature hydrogen sensors. Attached Figure Description

[0028] Figure 1 This is a flowchart of the preparation method of Pd-In synergistically modified MoO3 nanocomposite material proposed in this invention;

[0029] Figure 2 This is a scanning electron microscope image of the control group one-dimensional MoO3 nanorod nanomaterial prepared in Example 1 of this invention;

[0030] Figure 3 This is a scanning electron microscope image of the Pd-In synergistically modified MoO3 nanocomposite material prepared in Example 3 of the present invention;

[0031] Figure 4 Transmission electron microscope (TEM) images of the Pd-In synergistically modified MoO3 nanocomposite material prepared in Example 3 of this invention at different magnifications; where (a) is 1 μm and (b) is 200 nm.

[0032] Figure 5This is a scanning electron microscope image of the Pd-In synergistically modified MoO3 nanocomposite material prepared in Example 4 of the present invention;

[0033] Figure 6 The images show the XRD data of the pure-phase MoO3 nanomaterials and Pd-In synergistically modified MoO3 nanocomposites prepared in Examples 1 and 3 of this invention.

[0034] Figure 7 The BET curves of the MoO3 nanomaterials proposed in this invention are shown below; where (a) is the nanomaterial prepared in Example 1, (b) is the nanomaterial prepared in Example 2, and (c) is the nanomaterial prepared in Example 3.

[0035] Figure 8 The graph shows a comparison of the room temperature response / recovery of the pure-phase MoO3 nanomaterials and Pd-In co-modified MoO3 nanocomposites prepared in Example 5 of this invention at a hydrogen concentration of 500 ppm.

[0036] Figure 9 The graph shows a comparison of the room temperature response / recovery of the pure-phase MoO3 nanomaterials and Pd-In co-modified MoO3 nanocomposites prepared in Example 5 of this invention under continuously varying hydrogen concentrations from 200 to 1000 ppm.

[0037] Figure 10 The graph shows a comparison of the room temperature response / recovery of the pure-phase MoO3 nanomaterial and the Pd-In co-modified MoO3 nanocomposite material prepared in Example 5 of this invention under continuously varying hydrogen concentrations from 5000 to 10000 ppm.

[0038] Figure 11 The graph shows the repeatability test of pure phase MoO3 nanomaterials and Pd-In synergistically modified MoO3 nanocomposites prepared in Example 5 of this invention against 500ppm hydrogen gas at room temperature in 5 cycles.

[0039] Figure 12 The graph shows the long-term stability test of pure-phase MoO3 nanomaterials and Pd-In co-modified MoO3 nanocomposites prepared in Example 5 of this invention against 500ppm hydrogen at room temperature for 15 days.

[0040] Figure 13 The graph shows the hydrogen selectivity test results of pure-phase MoO3 nanomaterials and Pd-In synergistically modified MoO3 nanocomposites prepared in Example 5 of this invention at room temperature for 500 ppm of interfering gas. Detailed Implementation

[0041] The present invention will be further explained below with reference to specific embodiments.

[0042] Example 1

[0043] Reference Figure 1 Weigh 2.4195 g (10 mmol) of Na2MoO4·2H2O, put it into 33 mL of deionized water, stir at 25 °C for 30 min, then add 7 mL of 65% concentrated nitric acid dropwise, and stir for 30 min.

[0044] The stirred and homogeneous solution was poured into a 100 mL stainless steel high-pressure reactor lined with polytetrafluoroethylene. The reaction was carried out at 200 °C for 12 hours and then allowed to cool naturally to room temperature. The resulting mixture was centrifuged and then washed repeatedly with deionized water and anhydrous ethanol, with the centrifugation operation repeated 3 times. The lower precipitate was collected and placed in a vacuum oven to dry at 80 °C for 12 hours.

[0045] The dried solid powder was placed in a tube furnace and heated to 400°C at a rate of 2°C / min under an argon atmosphere for 2 hours for carbonization and sintering. After natural cooling to room temperature, it was then placed in a muffle furnace and heated to 300°C at a rate of 2°C / min for oxidation and sintering for 2 hours. After natural cooling to room temperature, one-dimensional MoO3 nanorod materials were obtained.

[0046] Figure 2 The image shows a scanning electron microscope (SEM) image of the control group one-dimensional MoO3 nanorod nanomaterials prepared in this embodiment. As can be seen from the image, the MoO3 nanomaterials are mainly in the form of one-dimensional rods. These nanorods have a diameter of about 200-500 nanometers and a relatively smooth and uniformly distributed surface.

[0047] Figure 7 Part (a) shows the BET curve of the MoO3 nanomaterials prepared in this embodiment. The results indicate that the specific surface area of ​​pure-phase MoO3 is 8.8847 m². 2 / g, and the adsorption-desorption isotherm exhibits type IV isotherm characteristics, accompanied by H3 type hysteresis loop, indicating the presence of mesoporous structure in the material.

[0048] Example 2

[0049] Weigh 2.4195 g (10 mmol) of Na2MoO4·2H2O and 0.23 g (0.5 mmol) of In(NO3)3·4.5H2O, put them into 33 mL of deionized water, stir at 25 °C for 50 min, then add 7 mL of concentrated nitric acid with a volume ratio of 65%, and stir for 1 h.

[0050] The stirred and homogeneous solution was poured into a 100 mL stainless steel high-pressure reactor lined with polytetrafluoroethylene. The reaction was carried out at 200 °C for 12 hours and then allowed to cool naturally to room temperature. The resulting mixture was centrifuged and then washed repeatedly with deionized water and anhydrous ethanol, with the centrifugation operation repeated 3 times. The lower precipitate was collected and placed in a vacuum oven to dry at 80 °C for 12 hours.

[0051] The dried solid powder was placed in a tube furnace and heated to 400°C at a rate of 2°C / min under an argon atmosphere for 2 hours for carbonization and sintering. After natural cooling to room temperature, it was then placed in a muffle furnace and heated to 300°C at a rate of 2°C / min for oxidation and sintering for 2 hours. After natural cooling to room temperature, an In-modified MoO3 nanorod material was obtained.

[0052] Figure 7 Part (b) shows the BET curve of the In-modified MoO3 nanocomposite prepared in this embodiment. The results show that the specific surface area of ​​the In-modified MoO3 nanocomposite is 6.4487 m² / g, and the doping of In reduces the specific surface area of ​​the material.

[0053] Example 3

[0054] Weigh 2.4195 g (10 mmol) of Na2MoO4·2H2O and 0.23 g (0.5 mmol) of In(NO3)3·4.5H2O, add them to 33 mL of deionized water, stir at 25 °C for 50 min, then add 0.018 g (0.1 mmol) of PdCl2, stir at 25 °C for 1 h, then add 7 mL of 65% concentrated nitric acid dropwise, and stir for 1 h.

[0055] The stirred and homogeneous solution was poured into a 100 mL stainless steel high-pressure reactor lined with polytetrafluoroethylene. The reaction was carried out at 200 °C for 12 hours and then allowed to cool naturally to room temperature. The resulting mixture was centrifuged and then washed repeatedly with deionized water and anhydrous ethanol, with the centrifugation operation repeated 3 times. The lower precipitate was collected and placed in a vacuum oven to dry at 80 °C for 12 hours.

[0056] The dried solid powder was placed in a tube furnace and heated to 400°C at a rate of 2°C / min under an argon atmosphere for 2 hours for carbonization and sintering. After natural cooling to room temperature, it was then placed in a muffle furnace and heated to 300°C at a rate of 2°C / min for oxidation and sintering for 2 hours. After natural cooling to room temperature, a Pd and In synergistically modified MoO3 nanorod material was obtained.

[0057] Figure 3This is a scanning electron microscope (SEM) image of the Pd-In synergistically modified MoO3 nanocomposite material prepared in this embodiment. Observation shows that a micron-sized Pd and In synergistically modified MoO3 composite structure was formed, in which palladium and some indium are incorporated into the molybdenum oxide lattice, and a small number of indium particles grow on the surface of molybdenum oxide.

[0058] Figure 4 This is a transmission electron microscope (TEM) image of the Pd-In co-modified MoO3 nanocomposite material prepared in this embodiment. The image shows that In and Pd nanoparticles are uniformly distributed inside the one-dimensional nanorods, confirming the successful loading of these two metals. Furthermore, some nanoparticles grown on the surface of the nanorods mainly contain In, indicating that some In has been successfully deposited on the pure MoO3 surface.

[0059] Figure 6 The images show XRD data of the pure-phase MoO3 nanomaterials prepared in Example 1 of this invention and the Pd-In synergistically modified MoO3 nanocomposites prepared in this example. The images show that the prepared nanomaterials have good crystallinity, corresponding to PDF standard cards 05-0508 for MoO3 and 65-7421 for In, demonstrating the successful modification of In and the phase structure of MoO3.

[0060] Figure 7 Part (c) shows the BET curve of the Pd-In synergistically modified MoO3 nanocomposite material prepared in this embodiment. The results show that the specific surface area is improved compared to traditional nanomaterials; using the synthesis method described in this invention, the specific surface area can be increased to 9.8947 m². 2 / g, which improves the gas-sensitive detection performance of the composite material.

[0061] Example 4

[0062] Weigh 2.4195 g (10 mmol) of Na2MoO4·2H2O and 0.23 g (0.5 mmol) of In(NO3)3·4.5H2O, add them to 33 mL of deionized water, stir at 25 °C for 50 min, then add 0.124 g (0.7 mmol) of PdCl2, stir at 25 °C for 1 h, then add 7 mL of 65% concentrated nitric acid dropwise, and stir for 1 h.

[0063] The stirred and homogeneous solution was poured into a 100 mL stainless steel high-pressure reactor lined with polytetrafluoroethylene. The reaction was carried out at 200 °C for 12 hours and then allowed to cool naturally to room temperature. The resulting mixture was centrifuged and then washed repeatedly with deionized water and anhydrous ethanol, with the centrifugation operation repeated 3 times. The lower precipitate was collected and placed in a vacuum oven to dry at 80 °C for 12 hours.

[0064] The dried solid powder was placed in a tube furnace and heated to 400°C at a rate of 2°C / min under an argon atmosphere for 2 hours for carbonization and sintering. After natural cooling to room temperature, it was then placed in a muffle furnace and heated to 300°C at a rate of 2°C / min for oxidation and sintering for 2 hours. After natural cooling to room temperature, a Pd and In synergistically modified MoO3 nanocomposite material was obtained.

[0065] Figure 5 This is a scanning electron microscope (SEM) image of the Pd-In co-modified MoO3 nanocomposite material prepared in this embodiment. Observations show that when the palladium doping concentration increases to 7%, the nanorod structure undergoes significant changes; the nanorod surface becomes rougher and agglomeration becomes more severe.

[0066] Take 10 mg of the Pd and In synergistically modified MoO3 nanocomposite material prepared in Examples 1-4, mix it with 1 mL of terpineol, and then sonicate it for 1 h to disperse it evenly. Take 150 μL of the dispersion solution and drop it onto the gold interdigital electrode, and place it in an oven at 60 °C to dry for 12 h.

[0067] The dried gold interdigitated electrode with the above-mentioned nanocomposite material was placed in a muffle furnace and sintered at 400°C for 2 hours in air at a heating rate of 2°C / min, and then naturally cooled to room temperature.

[0068] After scraping off the excess covering material at both ends of the sintered gold interdigitated electrode, it is aged in air at 350°C for 5 days to obtain a hydrogen sensor.

[0069] Figure 8 The dynamic response-recovery curves of hydrogen sensors prepared using pure-phase MoO3 nanomaterials from Example 1 and Pd-In synergistically modified MoO3 nanocomposites from Example 3 at a hydrogen concentration of 500 ppm are shown. It can be seen that the hydrogen sensor prepared using pure-phase MoO3 nanomaterials has a response value of 4.6, a response time of 142 s, and a recovery time of 150 s for 500 ppm hydrogen. After doping with 5.0 at% In and 1.0 at% Pd, the hydrogen sensor prepared using the Pd-In synergistically modified MoO3 nanocomposites from Example 3 has a response value of 31.2, a response time of 163 s, and a recovery time of 237 s for 500 ppm hydrogen, respectively, with the response value being 6.8 times that of the pure-phase MoO3 nanomaterials. In the Pd-In synergistically modified MoO3 nanocomposite system, In... 3+ Replace Mo 6+The generation of oxygen vacancies creates more active reaction sites on the material surface, introduces charge carriers (electrons), and optimizes surface reactivity, thereby enhancing hydrogen response / recovery kinetics and improving hydrogen sensing performance at room temperature. Simultaneously, the catalytic overflow effect of Pd nanoparticles efficiently dissociates hydrogen molecules into active hydrogen atoms, promoting their overflow to the MoO3 surface. Overall, In and Pd doping alters the band structure and electronic properties of MoO3, optimizing baseline conductivity and enhancing the response signal. This provides a feasible solution and a complete design reference for the engineering design of high-performance room-temperature hydrogen-sensitive materials.

[0070] Figure 9 The graph shows a comparison of the room temperature response / recovery of hydrogen sensors prepared using pure-phase MoO3 nanomaterials from Example 1 and Pd-In synergistically modified MoO3 nanocomposites from Example 3, under continuously varying hydrogen concentrations from 250 to 1000 ppm. Figure 10 This image shows a comparative test of the room temperature response / recovery of hydrogen sensors prepared using pure-phase MoO3 nanomaterials (Example 1) and Pd-In synergistically modified MoO3 nanocomposites (Example 3) under continuously varying hydrogen concentrations from 5000 to 10000 ppm. The results indicate that the hydrogen sensors prepared using both pure-phase MoO3 nanomaterials and Pd-In synergistically modified MoO3 nanocomposites exhibit good dynamic response and recovery performance for hydrogen over a wide concentration range. The sensitivity of all samples to hydrogen gradually increases with increasing concentration. The 1.0Pd-5.0In-MoO3 sensor shows a response value as high as 9.9 for 250 ppm hydrogen, enabling early warning of hydrogen leakage. Furthermore, the response intensity of 1.0Pd-5.0In-MoO3 is 4-7 times that of pure MoO3. Furthermore, 300 data points were selected from the initial resistance (Ra) baseline of the sensor as samples to calculate its standard deviation, and the concentration-response curve was linearly fitted. Substituting these values ​​into equations (1) and (2), the theoretical estimate of the detection limit of the 1.0Pd-5.0In-MoO3 sensor was obtained, which is 3.749 ppm. This demonstrates that the Pd-In synergistically modified MoO3 nanocomposite material proposed in this invention has great application potential in low-concentration hydrogen detection scenarios at room temperature.

[0071] (1)

[0072] (2)

[0073] Figure 11The graph shows the repeatability of a hydrogen sensor prepared using the pure-phase MoO3 nanomaterial of Example 1 and the Pd-In synergistically modified MoO3 nanocomposite material of Example 3 for five rounds of testing at 500 ppm hydrogen. Throughout the five cycles, the hydrogen sensor prepared using the pure-phase MoO3 nanomaterial of Example 1 and the Pd-In synergistically modified MoO3 nanocomposite material of Example 3 maintained a relatively consistent response. Figure 12 The graph shows the long-term stability test results of hydrogen sensors prepared using pure-phase MoO3 nanomaterials from Example 1 and Pd-In synergistically modified MoO3 nanocomposite materials from Example 3 against 500 ppm hydrogen for 15 days. The results indicate that during a series of long-term tests lasting approximately 15 days, the average response values ​​of the sensors based on pure-phase MoO3 nanomaterials and Pd-In synergistically modified MoO3 nanocomposite materials were 4.36 and 29.87, respectively, with maximum fluctuations of 8.26% and 4.45% during repeated tests. For the 1.0Pd-5.0In-MoO3 nanocomposite sensor, the response fluctuation range was controlled within 5%, demonstrating good stability and repeatability.

[0074] Figure 13 The figure shows the hydrogen selectivity test results for 500 ppm interfering gases using hydrogen sensors prepared with pure-phase MoO3 nanomaterials (Example 1), In-modified MoO3 nanocomposites (Example 2), and Pd-In synergistically modified MoO3 nanocomposites (Example 3). As can be seen from the figure, the sensor prepared based on the Pd-In synergistically modified MoO3 nanocomposites proposed in this invention exhibits an extremely high response value to 500 ppm hydrogen at room temperature, with a sensitivity far exceeding that of other gases at the same high concentration, achieving high selectivity for hydrogen at room temperature. For scenarios where it is urgent to eliminate interference from other gases and achieve specific detection of hydrogen, the method proposed in this invention has great application potential.

[0075] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application. The scope of this application is defined by the appended claims and their equivalents, all of which should be included within the protection scope of this application.

Claims

1. A Pd-In synergistically modified MoO3 nanocomposite material, characterized in that, The nanocomposite material is prepared by hydrothermal reaction of palladium source, indium source and molybdenum source, followed by drying and calcination; The morphology of the nanocomposite material is a nanorod composite structure of micron-sized nanoparticles grown in situ on the surface. In the nanocomposite material, palladium and indium are incorporated into the MoO3 lattice, and some indium particles agglomerate and grow on the surface of molybdenum oxide.

2. A method for preparing a Pd-In synergistically modified MoO3 nanocomposite material, characterized in that, The method steps are as follows: Molybdenum source is dispersed in deionized water, indium source and palladium source are added in sequence, and hydrothermal reaction is carried out under acidic conditions. After the reaction, the product is washed, dried and sintered to obtain Pd-In synergistic modified MoO3 nanocomposite material. The morphology of the nanocomposite material is a nanorod composite structure of micron-sized nanoparticles grown in situ on the surface. In the nanocomposite material, palladium and indium are incorporated into the MoO3 lattice, and some indium particles agglomerate and grow on the surface of molybdenum oxide.

3. The method for preparing Pd-In synergistically modified MoO3 nanocomposite materials according to claim 2, characterized in that, The molybdenum source is Na2MoO4·2H2O; the indium source is In(NO3)3·4.5H2O; and the palladium source is PdCl2.

4. The method for preparing Pd-In synergistically modified MoO3 nanocomposite materials according to claim 2, characterized in that, The molar ratio of molybdenum source, indium source and palladium source is 1:3-7:80-120.

5. The method for preparing Pd-In synergistically modified MoO3 nanocomposite materials according to claim 2, characterized in that, The conditions for the hydrothermal reaction are: temperature 180-200℃, time 10-12h.

6. The method for preparing Pd-In synergistically modified MoO3 nanocomposite materials according to claim 2, characterized in that, The pH of the hydrothermal reaction system is 1.5-2.

7. The method for preparing Pd-In synergistically modified MoO3 nanocomposite materials according to claim 2, characterized in that, The sintering conditions are as follows: heat to 250-350℃ at a heating rate of 1-3℃ / min under an inert atmosphere and hold for 2-3 hours; after naturally cooling to room temperature, heat to 350-450℃ at a heating rate of 2-4℃ / min under an oxygen-containing atmosphere and hold for 2-3 hours.

8. The method for preparing Pd-In synergistically modified MoO3 nanocomposite materials according to claim 7, characterized in that, The inert atmosphere is nitrogen and / or argon.

9. The method for preparing Pd-In synergistically modified MoO3 nanocomposite materials according to claim 7, characterized in that, The oxygen-containing atmosphere is air or a mixture of oxygen and an inert atmosphere; the oxygen content of the oxygen-containing atmosphere is 10%-30%.

10. The application of a Pd-In synergistically modified MoO3 nanocomposite material in a hydrogen sensor, characterized in that, The nanocomposite material is as described in claim 1; the hydrogen sensor can detect hydrogen at room temperature.

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