A hydrogen-sensitive sensor material and a method for its production and use

Abstract

The application relates to the technical field of new energy safety monitoring and microelectronic sensor technology, and particularly relates to a hydrogen-sensitive sensor material and a preparation method and use method thereof, the preparation method comprising the following steps: adding tungsten source, palladium source and silver source into a mixed solvent of dimethylformamide and ethanol, then adding a high-molecular binder, continuously stirring at normal temperature until the solute is fully dispersed and uniform, and obtaining a precursor solution; loading the precursor solution into a syringe with a stainless steel nozzle, spraying the nanoscale fiber bundle from the syringe in an electrostatic spinning machine to a receiving plate covered with aluminum foil paper; collecting the nanoscale fiber bundle on the receiving plate, placing and drying, then placing in a muffle furnace, and performing programmed temperature calcination in an air atmosphere to obtain Pd-Ag / WO3 nanofiber powder; and dissolving the Pd-Ag / WO3 nanofiber powder with ethanol to complete the preparation. The application greatly simplifies the preparation process and guarantees high batch consistency.

Description

Technical Field

[0001] This invention relates to the fields of new energy safety monitoring and microelectronic sensor technology, specifically to a material for a hydrogen-sensitive sensor and its preparation and usage methods. Background Technology

[0002] The widespread application of hydrogen energy has placed stringent demands on early safety warnings for hydrogen leaks. Semiconductor metal oxide gas sensors have become an ideal choice for detecting trace amounts of hydrogen due to their advantages such as low cost and ease of miniaturization. Among them, tungsten trioxide (WO3), as a typical n-type semiconductor, has a good basic response to reducing gases. However, pure-phase WO3 materials face performance bottlenecks in practical hydrogen detection, such as high operating temperature, insufficient sensitivity to low concentrations of hydrogen, and insufficient selectivity.

[0003] To enhance the ability of gas-sensitive materials to capture specific gases, surface modification with noble metals has become an important direction for improving gas-sensing performance. Particularly in the field of hydrogen detection, Pd, with its "hydrogen spillover effect," is widely used. While single-metal Pd can improve the basic sensitivity of the sensor, it is prone to "hydrogen embrittlement" or catalytic poisoning due to excessive adsorption during continuous detection, leading to baseline drift. Therefore, introducing Ag and Pd to form a bimetallic modification system, utilizing the modulation effect of Ag on the electronic structure of Pd, can not only effectively improve the cycling stability of the material but also further reduce the dissociation activation energy of the target gas. This is a crucial technical route for developing high-efficiency hydrogen sensors.

[0004] However, extensive device testing shows that although Pd-Ag bimetallic modification theoretically possesses excellent hydrogen-sensing potential, in practical fabrication, conventional processes often struggle to fully translate it into the final macroscopic sensing performance. Existing technologies mostly employ a traditional multi-step process of "first synthesizing the support framework, then secondary impregnation / deposition of the loading material." This non-in-situ multi-step modification method has significant limitations in improving gas-sensing performance, mainly in the following aspects:

[0005] (1) Due to the thermodynamic barriers in the multiple wet chemical treatments and subsequent annealing processes, the noble metal phase formed by the later attachment is difficult to form a deep electronic coupling with the WO3 substrate. This weak interfacial interaction means that the dissociated hydrogen atoms cannot be efficiently and quickly injected into the semiconductor depletion layer. Macroscopically, this directly leads to the sensor's response value to trace amounts of hydrogen gas being difficult to achieve a breakthrough of orders of magnitude, and thus cannot meet the timeliness requirements of real-time alarm for hydrogen gas leakage.

[0006] (2) The poor bonding force of the heterogeneous interface caused by the multi-step method makes the device prone to catalytic phase deactivation or stripping under long-term high-temperature operation. This is reflected in the gas sensing performance, namely, poor anti-interference ability of the sensor and a significant decrease in long-term working stability (i.e., cycle test life).

[0007] (3) The cumbersome multi-step liquid phase processing inevitably introduces too many process variables, which greatly increases the difficulty of batch consistency control. Sensor elements prepared by this method are prone to sensitivity fluctuations when facing complex environments, making it difficult to meet the standards for large-scale industrial applications.

[0008] Therefore, the core technical problem that urgently needs to be solved in the current field of high-efficiency hydrogen sensor fabrication is: how to break through the limitations of the traditional multi-step process of "synthesis first and modification later" in terms of interfacial electronic transport and performance conversion, and explore a preparation path that can achieve single-step continuous molding and in-situ construction of strong interfacial chemical coupling, so as to maximize the release of the specific catalytic potential of Pd-Ag bimetal for hydrogen, and finally obtain a next-generation gas-sensitive device with high hydrogen responsiveness, high selectivity and excellent stability. Summary of the Invention

[0009] To address the technical challenges of existing semiconductor gas-sensitive materials in the detection of trace amounts of hydrogen, such as weak interfacial chemical coupling and high electron transfer barriers caused by traditional multi-step non-in-situ modification processes, which lead to difficulties in achieving high hydrogen response sensitivity, poor anti-interference capabilities, and batch-to-batch inconsistencies in devices, this invention proposes a method for preparing materials for hydrogen-sensitive sensors, specifically including the following steps:

[0010] Tungsten, palladium, and silver sources were added to a mixed solvent of dimethylformamide and ethanol, followed by the addition of a polymer binder. The mixture was stirred continuously at room temperature until the solute was fully and uniformly dispersed to obtain a precursor solution.

[0011] The precursor solution is loaded into a syringe with a stainless steel nozzle, and the syringe sprays nanofiber bundles onto a receiving plate covered with aluminum foil in an electrospinning machine.

[0012] The nanofiber bundles on the receiving plate were collected, dried, and then placed in a muffle furnace for programmed calcination in an air atmosphere to obtain Pd-Ag / WO3 nanofiber powder.

[0013] The Pd-Ag / WO3 nanofiber powder was dissolved in ethanol to complete the preparation.

[0014] The present invention also proposes a material for a hydrogen sensor, which is prepared according to a method for preparing a hydrogen sensor material.

[0015] This invention also proposes a method for using a hydrogen-sensitive sensor material. The material is prepared by a method for preparing a hydrogen-sensitive sensor material and uniformly coated on the surface of a ceramic tube with a metal electrode sensor. After natural drying, it is subjected to high-temperature aging treatment to finally obtain a sensor with high hydrogen sensitivity.

[0016] Compared with existing technologies, this invention abandons the traditional cumbersome multi-step non-in-situ wet chemical modification process and innovatively introduces a synthesis mechanism that couples single-step electrospinning technology with in-situ pyrolysis reduction. While the macroscopic one-dimensional nanofiber skeleton is formed, the in-situ precipitation and anchoring of the microscopic Pd-Ag bimetallic phase is spontaneously completed. The in-situ construction strategy of this invention not only significantly simplifies the preparation process and ensures extremely high batch consistency, but more importantly, the strong heterogeneous interface chemical coupling constructed between the metal phase and the WO3 substrate deeply excites the catalytic "spillover effect" of the Pd-Ag bimetallic compound. By eliminating the interfacial electron transport barrier and utilizing the in-situ modulation of the Pd electronic structure by Ag, this invention greatly reduces the dissociation activation energy of hydrogen molecules, effectively passivating interfering gases such as methane and carbon monoxide while achieving extremely high response amplitude and specific and accurate identification of trace amounts of hydrogen. In addition, thanks to the stable strong interaction anchoring between the Pd-Ag clusters and the WO3 lattice, this invention fundamentally overcomes the problem of active phase shedding caused by secondary loading, endowing the device with excellent baseline anti-drift capability and long-term working stability, and possessing extremely high industrial mass production and application potential. Attached Figure Description

[0017] Figure 1 A schematic flowchart of a method for preparing a material for a hydrogen-sensitive sensor according to the present invention;

[0018] Figure 2 The response curve of the sensor coated with the Pd-Ag / WO3 material of this invention to 5 ppm H2.

[0019] Figure 3 The response curve of the sensor coated with the Pd-Ag / WO3 material of this invention to 10 ppm H2;

[0020] Figure 4 The response curves of the sensor coated with the Pd-Ag / WO3 material of this invention to different concentrations of H2;

[0021] Figure 5 The response curve of the sensor coated with the Pd-Ag / WO3 material of this invention to 10 ppm CH4.

[0022] Figure 6 The response curve of the sensor coated with the Pd-Ag / WO3 material of this invention to 10 ppm CO2;

[0023] Figure 7 A bar chart showing the response values ​​of the sensor coated with the Pd-Ag / WO3 material of this invention to different gases;

[0024] Figure 8 This is a schematic diagram of the repeatability dynamic response curve of the sensor coated with the Pd-Ag / WO3 material of the present invention. Detailed Implementation

[0025] 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.

[0026] This invention aims to effectively solve the technical problems in the preparation of high-performance semiconductor gas-sensitive composite materials. Traditional multi-step in-situ modification processes, due to weak interfacial chemical coupling and high electron transfer barriers, struggle to fully activate the synergistic effect of multiple components, resulting in limited device sensitivity to low-concentration hydrogen, weak specific anti-interference capabilities, and poor batch-to-batch consistency. This invention introduces a one-step electrospinning combined with in-situ pyrolysis-reduction synthesis mechanism, enabling deep co-fusion of the single-phase precursor during high-voltage electrostatic stretching. In subsequent heat treatment, a Pd-Ag / WO3 heterostructure with strong interfacial electronic interactions is spontaneously constructed in-situ. This organically unifies the single-step forming of the macroscopic one-dimensional nanofiber framework with the catalytic "overflow effect" that reduces the hydrogen dissociation activation energy at the microscopic level. To achieve the above-mentioned objectives, as follows... Figure 1 The specific technical solution adopted in this invention is as follows:

[0027] Tungsten, palladium, and silver sources are added to a mixed solvent containing DMF (dimethylformamide) and ethanol in a preset stoichiometric ratio. Then, a polymer binder PVP (polyvinylpyrrolidone) is added, and the mixture is continuously stirred at room temperature until the solute is fully and uniformly dispersed to form a clear precursor solution with specific viscosity and conductivity.

[0028] The prepared precursor solution was then loaded into a syringe with a stainless steel nozzle. The appropriate electrospinning parameters were set, and the Coulomb repulsion generated by the high voltage electrostatic field was used to overcome the surface tension to form a Taylor cone. The nanofiber bundles were then ejected onto a receiving plate covered with aluminum foil. During the solvent evaporation and electric field stretching process, the metal ions in the precursor were wrapped in the PVP fiber skeleton, achieving uniform blending at the atomic level.

[0029] After spinning, the collected nascent composite nanofiber films were dried and then placed in a muffle furnace for programmed calcination in air atmosphere (heating rate: 2℃ / min; constant temperature: 600℃; natural cooling after 3 hours). During calcination, the PVP molecular chains decomposed thermally, the tungsten source was transformed in situ into an n-type semiconductor WO3 lattice, and the palladium and silver sources were thermally decomposed and reduced in situ to Pd-Ag metal clusters while the WO3 crystal nuclei grew. This process utilized the thermochemical stress generated in situ to anchor Pd-Ag nanoparticles on the surface and pores of WO3 nanofibers, forming a heterogeneous interface with strong chemical bonding.

[0030] Finally, the Pd-Ag / WO3 nanofiber powder obtained after calcination was mixed with ethanol to form a slurry, which was then evenly coated onto the surface of a ceramic tube with a metal electrode. After natural drying, it was subjected to high-temperature aging treatment to finally obtain a Pd-Ag / WO3 sensor with high hydrogen sensitivity.

[0031] As an optional implementation, in this embodiment, the total mass of elemental Pd and Ag in the Pd-Ag / WO3 nanofiber powder is 5wt% of the mass of WO3, and the mass ratio of Pd to Ag is 1:1. Tungsten source, palladium source and silver source are added to a mixed solvent of dimethylformamide and ethanol according to this mass ratio.

[0032] As an optional implementation, the electrospinning machine in this embodiment operates at a voltage of 20kV, and the entire spinning process is carried out at room temperature and in an environment with a relative humidity of less than 50%.

[0033] As an optional implementation, the distance from the syringe needle to the receiving plate covered with aluminum foil is 15cm. In this embodiment, the syringe uses a 21G injection needle and the injection speed is 1mL / h.

[0034] To verify the actual working performance of the present invention, a systematic gas-sensing performance evaluation was conducted on the sensor element prepared according to this example. All the following tests were performed under a heating condition of 200°C, which was used as the base operating temperature for evaluating its comprehensive gas-sensing characteristics.

[0035] (1) High sensitivity detection and wide resolution characteristics of low concentration hydrogen

[0036] Early and accurate capture of low-concentration hydrogen and a wide detection range are two core indicators for evaluating the practical application level of advanced hydrogen sensors. To examine the absolute sensitivity of the sensor prepared in this invention to low-concentration hydrogen, the device's sensitivity to 5 ppm (… Figure 2 ) and 10 ppm ( Figure 3The gas-sensitive response behavior of hydrogen was examined. Test results showed that even in the presence of extremely low hydrogen concentrations (5 ppm), the sensor element's resistance exhibited a sharp and clear decrease. When the gas concentration was slightly increased to 10 ppm, the decrease in resistance became even more significant, demonstrating an extremely high signal-to-noise ratio. This intuitive phenomenon strongly proves that, thanks to the extremely high specific surface area resulting from the one-step electrospinning in-situ construction technology, and the high-throughput, uniform distribution of Pd-Ag bimetals on the surface of WO3 nanofibers, this sensor possesses extremely high basic sensitivity and an extremely low limit of detection (LOD) for trace amounts of hydrogen, making it perfectly capable of accurately predicting early, minute hydrogen leaks.

[0037] After confirming its excellent ability to detect low-concentration gases, the sensor's response was further tested over a wide concentration range of 5 ppm to 300 ppm. Figure 4 Test results show that the sensor exhibits exceptionally superior wide-range concentration gradient resolution. With a continuous increase in the concentration of hydrogen in the environment, the sensor's response value shows a stable, continuous, and significant increasing trend—steadily increasing from 1.85 at 5 ppm to 3.4 at 100 ppm, and further climbing to 10.67 at a high concentration of 300 ppm. This large-scale response growth indicates that the in-situ anchored Pd-Ag catalytic structure of this invention not only possesses extremely high activity but also sufficient surface gas adsorption capacity. No obvious early catalytic saturation phenomenon was observed when facing high concentrations of target gas, endowing the device with the ability to accurately quantitatively assess the degree of hydrogen leakage over a wide concentration range.

[0038] (2) High selectivity for trace amounts of hydrogen

[0039] The ability to resist cross-interference in complex multi-component gas environments is the core of evaluating sensor reliability and false alarm prevention. To verify the high selectivity advantage of this invention, the sensor prepared in this example was exposed to the same concentration (10 ppm) of hydrogen (H2) and common background interfering gases—methane (CH4) and carbon dioxide (CO2)—for cross-comparison tests.

[0040] From the real-time dynamic response curve of the gas-sensitive test, when 10 ppm hydrogen gas is introduced into the test chamber ( Figure 3 When CH4 (CH4) is introduced, the sensor's resistance rapidly breaks the baseline equilibrium and drops sharply, exhibiting an extremely strong signal response; however, when the same concentration of CH4 (CH4) is introduced, the resistance drops evenly. Figure 5 ) and CO2 ( Figure 6When the device's dynamic resistance curve exhibits only minimal baseline-level fluctuations (noise level), it does not show a significant unidirectional decreasing trend in resistance caused by gas adsorption reactions. This dynamic characteristic intuitively demonstrates that the sensor exhibits extremely strong physicochemical inertness to the aforementioned interfering gases.

[0041] Furthermore, the resistance changes observed in the aforementioned dynamic tests are extracted for quantitative comparison. For example... Figure 7 Test results show that the sensor has a response value of 2.425 to 10 ppm hydrogen; however, when faced with the same concentration of methane and carbon dioxide interfering gases, its response value is greatly suppressed, only 0.013 and 0.014 respectively, and it is basically in a "passivated" and unresponsive state to interfering gases.

[0042] This highly specific and precise identification of hydrogen, along with its anti-interference performance, fully demonstrates the superiority of the in-situ synthesis mechanism of this invention: during the single-step spinning and in-situ pyrolysis processes, the strong heterogeneous interface constructed between the Pd-Ag bimetallic compound and the WO3 lattice deeply excites a unique "hydrogen spillover effect." This effect specifically reduces the dissociation activation energy of H2 molecules on the material surface, while lacking catalytic activity for methane with high CH bond energy and chemically stable carbon dioxide. Therefore, the sensor prepared by this invention can achieve efficient and specific capture of target hydrogen in complex working conditions where multiple reducing or inert gases coexist, greatly reducing the false alarm rate.

[0043] (3) Excellent cyclic stability and reproducibility

[0044] To evaluate the structural stability of the device during long-term operation, the sensor underwent continuous multi-cycle dynamic gas-sensitive cycling tests. The sensor was alternately placed in clean air and a 10 ppm hydrogen environment for three consecutive response-recovery cycles. Figure 8 The test results showed that the resistance change trajectory of the sensor maintained a high degree of consistency across multiple test cycles. After each introduction of 10 ppm hydrogen gas, its resistance steadily and accurately decreased to approximately the same level, with no significant attenuation or irregular drift in the response amplitude.

[0045] This data strongly confirms the technological advantages of this invention—a one-step electrospinning process combined with programmed high-temperature pyrolysis promotes a robust chemical bond anchoring between the Pd-Ag clusters and the WO3 lattice. In the continuous gas adsorption-desorption and high-temperature catalytic reaction, this in-situ anchoring structure effectively resists the problems of noble metal nanoparticle aggregation, migration, or interface delamination commonly found in traditional multi-step modification methods, thus endowing the sensor with extremely excellent operational reproducibility and a long service life for industrial applications.

[0046] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a material for a hydrogen-sensitive sensor, characterized in that, Specifically, the following steps are included: Tungsten, palladium, and silver sources were added to a mixed solvent of dimethylformamide and ethanol, followed by the addition of a polymer binder. The mixture was stirred continuously at room temperature until the solute was fully and uniformly dispersed to obtain a precursor solution. The precursor solution is loaded into a syringe with a stainless steel nozzle, and the syringe sprays nanofiber bundles onto a receiving plate covered with aluminum foil in an electrospinning machine. The nanofiber bundles on the receiving plate were collected, dried, and then placed in a muffle furnace for programmed calcination in an air atmosphere to obtain Pd-Ag / WO3 nanofiber powder. The Pd-Ag / WO3 nanofiber powder was dissolved in ethanol to complete the preparation.

2. The method for preparing a material for a hydrogen-sensitive sensor according to claim 1, characterized in that, In the Pd-Ag / WO3 nanofiber powder, the total mass of elemental Pd and Ag is 5wt% of the mass of WO3, and the mass ratio of Pd to Ag is 1:

1.

3. The method for preparing a material for a hydrogen-sensitive sensor according to claim 1, characterized in that, The electrospinning machine operates at a voltage of 20kV, and the entire spinning process is carried out at room temperature and in an environment with a relative humidity of less than 50%.

4. The method for preparing a material for a hydrogen-sensitive sensor according to claim 1, characterized in that, When performing programmed calcination in an air atmosphere, the heating rate is 2℃ / min, and after the temperature reaches 600℃, it is kept at a constant temperature for 3 hours and then allowed to cool down naturally.

5. The method for preparing a material for a hydrogen-sensitive sensor according to claim 1, characterized in that, The polymer binder is polyvinylpyrrolidone.

6. A method for preparing a material for a hydrogen-sensitive sensor according to any one of claims 1 to 5, characterized in that, The distance from the syringe needle to the receiving plate covered with aluminum foil is 15cm.

7. A method for preparing a material for a hydrogen-sensitive sensor according to any one of claims 6, characterized in that, The syringe uses a 21G needle and the injection rate is 1 mL / h.

8. A material for a hydrogen-sensitive sensor, characterized in that, The material for a hydrogen-sensitive sensor is prepared according to any one of claims 1 to 7.

9. A method of using a material for a hydrogen-sensitive sensor, characterized in that, The material prepared by the method of preparing a hydrogen-sensitive sensor according to any one of claims 1 to 7 is uniformly coated on the surface of a ceramic tube with a metal electrode sensor. After natural drying, it is subjected to high-temperature aging treatment to finally obtain a sensor with high hydrogen sensitivity.

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