A novel room-temperature hydrogen sensor based on ion semiconductor and a preparation method thereof

Abstract

The present application relates to a kind of novel hydrogen sensor based on ion semiconductor and its preparation method.The present application uses ammonia salt type heteropolyacid salt as gas sensitive material, is prepared by room temperature liquid phase precipitation method combined with gas-solid phase ammoniation treatment, solve the existing hydrogen sensor needs heating work, poor selectivity, detection limit and other problems.The present application has room temperature work, high sensitivity, good selectivity, response fast and other characteristics, in 200 ppb to 10 ppm wide concentration range, it shows excellent detection performance to hydrogen, while ammonia, ethanol, toluene, isopropanol and other interfering gases have good anti-interference ability.Compared with phosphotungstic acid, silver phosphotungstate and other metal substituted phosphotungstate, the response of heteropolyacid salt after ammoniation to hydrogen is the strongest.

Description

Technical Field

[0001] This invention belongs to the field of gas sensor technology, specifically relating to a novel hydrogen sensor based on ion semiconductors and its preparation method, and particularly to a hydrogen sensor that uses silver phosphotungstic acid as the sensitive material and can operate at room temperature. Background Technology

[0002] Hydrogen, as the gas with the lowest density, possesses extremely high energy density, and its combustion product is only water, making it an ideal clean energy source. With the rapid development of the hydrogen energy industry, hydrogen is increasingly widely used in fuel cell vehicles, distributed power generation, and chemical synthesis. However, the small diameter of hydrogen molecules, their rapid diffusion, colorlessness, and odorlessness make leaks difficult to detect, and their wide flammability and explosiveness range (4%-75% by volume) pose serious challenges to the safe use of hydrogen. Therefore, developing highly sensitive, highly selective, and fast-response hydrogen sensors is of significant practical importance.

[0003] Existing hydrogen sensor technologies mainly include catalytic combustion, electrochemical, and semiconductor types. Catalytic combustion sensors detect changes in heat generated by the combustion of hydrogen on the surface of a catalytic element, but suffer from high power consumption and poor selectivity. Electrochemical sensors generate electrical signals through the redox reaction of hydrogen on electrodes, but have drawbacks such as slow response speed, short lifespan, and potential for electrical sparks. Semiconductor sensors detect changes in resistance based on metal oxides (such as SnO2, ZnO, WO3, etc.), offering advantages such as simple structure and low cost, but typically require heating to 200-400 °C to operate, resulting in high energy consumption and safety risks associated with heating in a hydrogen environment.

[0004] Polyoxometalates (POMs) are a class of inorganic nanomaterials composed of transition metal-oxygen clusters, exhibiting reversible multi-electron redox properties, strong acidity, and high stability. Phosphotungstic acid (H3PW) is one such example. 12 O 40 It is a typical Keggin-type polyoxometalate, and its silver salt derivative, silver phosphotungstate (Ag3PW), is also known as silver phosphotungstate. 12 O 40 Silver phosphotungstenate (SPP) possesses both ionic and electronic conductivity, showing potential for application in gas sensing. However, pure SPP exhibits limited selectivity and sensitivity to hydrogen, and its room-temperature response is weak. Ammoniation of SPP introduces amino functional groups onto the material surface, allowing for the modulation of its surface electronic structure and acid-base properties, thereby enhancing its selective adsorption of hydrogen and room-temperature response. Currently, no room-temperature hydrogen sensors using ammonized SPP have been reported. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an ammonium salt-type heteropolyacid salt silver gas-sensitive material, its preparation method, and a room-temperature hydrogen sensor based on this material. Unlike the two-step route of "precipitation followed by gas-solid phase ammoniation," this invention introduces NH3 / NH4⁺ in a single step through inorganic metal ammonium complex ions during the room-temperature liquid-phase co-precipitation stage, eliminating the need for subsequent gas-solid phase ammoniation. The resulting material exhibits excellent hydrogen detection performance at room temperature, with a simpler process, more uniform amino distribution, and significantly improved response speed and stability.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for fabricating a novel ion semiconductor sensor includes the following steps:

[0008] (1) Dissolve the heteropolyacid in anhydrous ethanol;

[0009] (2) Dissolve the inorganic metal salt in deionized water and stir at room temperature until completely dissolved;

[0010] (3) Under stirring conditions at room temperature, add the ammonia solution dropwise to the inorganic metal salt solution, with the dropping rate controlled at 1-5 mL / min, until the brown precipitate just disappears and a silver ammonia complex ion solution is formed;

[0011] (4) Mix the heteropolyacid alcohol solution obtained in (1) with the inorganic metal ammonium complex ion solution obtained in (3) uniformly, stir at room temperature for 0.5-1 h, and obtain the ammonium salt type heteropolyacid precursor by standing, centrifugation and solid-liquid separation;

[0012] (5) The precursor obtained in (4) is placed in a vacuum drying oven and dried at 30–40 °C and −0.08 MPa for 8–12 h to obtain the ammonium salt type heteropoly acid salt gas-sensitive material.

[0013] Preferably, the concentration of the phosphotungstic acid solution in step (1) is 0.01 mol / L.

[0014] Preferably, the concentration of the silver nitrate solution in step (2) is 0.041 mol / L.

[0015] Preferably, the stirring reaction time in step (3) is 0.4 h.

[0016] Preferably, the stirring reaction time in step (4) is 0.6 h.

[0017] Preferably, the heteropolyacids in step (1) include phosphomolybdic acid, phosphotungstic acid, silicotungstic acid, etc.

[0018] Preferably, the inorganic metal salt in step (2) includes calcium nitrate, silver nitrate, sodium nitrate, copper nitrate, zinc nitrate, etc.

[0019] The present invention also provides a hydrogen sensor, comprising an insulating substrate, interdigitated electrodes disposed on the surface of the substrate, and an ammonium phosphotungstic acid silver gas-sensitive material layer coated on the surface of the interdigitated electrodes. The insulating substrate is preferably an alumina ceramic sheet, and the interdigitated electrodes are preferably made of gold, platinum, or silver, with an electrode spacing and width of 50-200 μm.

[0020] The method for preparing the hydrogen sensor of the present invention is as follows: mixing and grinding ammonium heteropolyacid salt powder with ethanol into a uniform slurry, coating it on the surface of a ceramic substrate with interdigitated electrodes, and drying it at room temperature.

[0021] The working principle of this invention is as follows: the metal ions in the aminated heteropolyacid salt material have reversible redox properties. When exposed to a hydrogen atmosphere, hydrogen molecules are adsorbed on the material surface and undergo a redox reaction with the metal ions, resulting in a change in the material's electrical resistance. The introduction of amino functional groups enhances the material's selective adsorption capacity for hydrogen and promotes the charge transfer process, enabling the material to produce a significant electrical response at room temperature.

[0022] Compared with the prior art, the beneficial effects of the present invention include: (1) it operates at room temperature without heating, with low power consumption and high safety; (2) it has a low detection limit and a significant response to ppb-level hydrogen; (3) it has a wide detection range, covering a concentration range from 200 ppb to 10 ppm; (4) it has good selectivity and good anti-interference ability against interfering gases such as ammonia, ethanol, toluene, and isopropanol; (5) it has a fast response, with short response and recovery times; and (6) it has a simple preparation process, readily available raw materials, and is suitable for large-scale production. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0024] Example 1

[0025] This embodiment provides an ammonified silver phosphotungstenate gas-sensitive material and its preparation method, including the following steps:

[0026] (1) Dissolve 0.3 g of phosphotungstic acid in 10 mL of anhydrous ethanol to prepare a 0.01 mol / L phosphotungstic acid solution;

[0027] (2) Dissolve 0.055 g of silver nitrate in 8 mL of deionized water to prepare a silver nitrate solution of 0.041 mol / L;

[0028] (3) Under the conditions of room temperature (25℃) and magnetic stirring (400 rpm), 5% ammonia solution was added dropwise to silver nitrate solution at a rate of 2 mL / min. The addition was continuously observed during the addition process, and the addition was stopped immediately after the precipitate just disappeared.

[0029] (4) Mix the phosphotungstic acid solution obtained in step (1) and the aminated silver nitrate solution obtained in step (3) evenly, let stand for 30 minutes, and then use a centrifuge to rotate at high speed to separate the solid and liquid. Discard the supernatant to obtain the aminated silver phosphotungstic acid precursor.

[0030] (5) The silver phosphotungsten precursor obtained in step (4) is dried in a vacuum oven at a set temperature of 60 °C for 7 hours to form silver phosphotungsten gas-sensitive material.

[0031] Take 0.05 mg of the above gas-sensitive material, add 1 mL of ethanol, grind into a uniform slurry, coat it on the surface of an alumina ceramic substrate with gold interdigitated electrodes, and dry at room temperature for 1 h to obtain a room temperature hydrogen sensor of ion semiconductor.

[0032] The fabricated sensor was placed in a gas-sensitive testing system, and its response performance to hydrogen was tested under room temperature (25℃) and relative humidity (30% RH). The test results show that the sensor has a good response to hydrogen at concentrations of 200-1000 ppb, with the response value increasing with increasing concentration; the response is even more significant for hydrogen at concentrations of 2-10 ppm. Figure 2 As shown, at a hydrogen concentration of 200 ppb, the response value is 1.086%, the response time is 3.6 s, and the recovery time is 6.3 s; at a hydrogen concentration of 10 ppm, the response value is 45.213%, the response time is 14 s, and the recovery time is 16.2 s.

[0033] Example 2

[0034] The difference between this embodiment and Embodiment 1 is that: after the phosphotungstic acid solution is left to stand for 30 minutes, the solid and liquid are separated by high-speed centrifugation. The supernatant is then discarded to obtain the phosphotungstic acid precursor. Other conditions are the same, and there is no need to add aminated silver nitrate solution.

[0035] Test results show that the hydrogen sensor has a response value of 3.63% to 10 ppm hydrogen at room temperature.

[0036] Example 3

[0037] The difference between this embodiment and embodiment 1 is that step (3) is removed, and silver nitrate is not ammoniated to obtain the silver phosphotungstate precursor, while other conditions remain the same.

[0038] Test results show that the hydrogen sensor has a response value of 9.93% to 10 ppm hydrogen at room temperature.

[0039] Example 4

[0040] The difference between this embodiment and embodiment 1 is that step (3) is removed, and phosphotungstic acid and silver nitrate are physically mixed according to stoichiometric ratio, while other conditions remain the same.

[0041] Test results show that the hydrogen sensor has a response value of 11.21% to 10 ppm hydrogen at room temperature.

[0042] Example 5

[0043] The difference between this embodiment and embodiment 1 is that in step (2), silver nitrate is replaced with calcium nitrate, and 0.026 g of calcium nitrate is dissolved in 10 ml of deionized water to prepare a calcium nitrate solution of 0.016 mol / L. Other conditions are the same.

[0044] Test results show that the hydrogen sensor has a response value of 9.22% to 10 ppm hydrogen at room temperature.

[0045] Example 6

[0046] The difference between this embodiment and embodiment 1 is that in step (2), silver nitrate is replaced with sodium nitrate, and 0.026 g of sodium nitrate is dissolved in 10 ml of deionized water to prepare a sodium nitrate solution of 0.031 mol / L. Other conditions are the same.

[0047] Test results show that the hydrogen sensor has a response value of 7.68% to 10 ppm hydrogen at room temperature.

[0048] Example 7

[0049] The difference between this embodiment and embodiment 1 is that in step (2), silver nitrate is replaced with copper nitrate, and 0.038 g of copper nitrate is dissolved in 10 ml of deionized water to prepare a 0.016 mol / L copper nitrate solution. Other conditions are the same.

[0050] Test results show that the hydrogen sensor has a response value of 13.31% to 10 ppm hydrogen at room temperature.

[0051] Example 8

[0052] The difference between this embodiment and embodiment 1 is that in step (2), silver nitrate is replaced with zinc nitrate, and 0.046 g of zinc nitrate is dissolved in 10 ml of deionized water to prepare a 0.016 mol / L zinc nitrate solution. Other conditions are the same.

[0053] Test results show that the hydrogen sensor has a response value of 11.89% to 10 ppm hydrogen at room temperature.

[0054] Example 9

[0055] This embodiment tests the selectivity of the sensor prepared in Example 1 to hydrogen and common interfering gases. Under the same test conditions, 10 ppm hydrogen (H2), 10 ppm ammonia (NH3), 10 ppm ethanol (C2H6O), 10 ppm toluene (C7H8), and 10 ppm isopropanol (C3H8O) were introduced respectively, and the response value of the sensor was tested.

[0056] The test results were as follows: hydrogen response value 45.213%, ammonia response value 6.99%, ethanol response value 13.54%, toluene response value 6.62%, and isopropanol response value 12.08%.

[0057] The results of the above embodiments are as follows: Figure 3 , Figure 4 As shown;

[0058] pass Figure 2 , 3 As can be seen from Figure 4, the aminated silver phosphotungsten gas-sensitive material has the highest responsiveness to hydrogen at room temperature, which is 45.213%.

[0059] This invention employs a static gas mixing method to test the gas-sensing performance of the sensor. The sensor sensitivity is defined as (R... a -R g ) / R g *100%, where R a R is the resistance value of the sensor in air. g This represents the resistance value of the sensor in the gas being measured. Response time is defined as the time required for the sensor resistance to reach 90% of its final change, and recovery time is defined as the time required for the sensor resistance to recover to 10% of its final change from the gas.

[0060] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention should still fall within the scope of the present invention. Attached Figure Description Figure 1 This is a schematic diagram of the structure of the ammonium salt type heteropoly acid salt gas-sensitive material of the present invention; Figure 2 This is a response curve of the sensor in Embodiment 1 of the present invention under different hydrogen concentrations. Figure 3 This is a graph showing the selective test results of the sensor of the present invention for hydrogen and interfering gases; Figure 4 This figure shows a comparison of the hydrogen response performance of different material systems.

Claims

1. A method for preparing an ammonified heteropolyacid acid gas-sensitive material, characterized in that, Includes the following steps: (1) Dissolve the heteropolyacid in anhydrous ethanol and stir at room temperature until clear to obtain a heteropolyacid solution; (2) Dissolve the inorganic metal salt in deionized water and stir at room temperature until clear to obtain an inorganic metal salt solution; (3) Under continuous stirring, ammonia solution is added to inorganic metal salt solution to carry out ion coordination reaction and generate metal ammonia complex solution; (4) The metal ammonia complex solution obtained in step (3) is slowly added dropwise to the heteropolyacid solution prepared in step (1), and the mixture is stirred continuously at room temperature to generate a white precipitate. (5) The precipitate obtained in step (4) is allowed to stand and centrifuged, and then vacuum dried to obtain an ammonium salt type heteropoly acid salt gas-sensitive material.

2. The application according to claim 1, characterized in that, The inorganic metal salts mentioned in step (1) include calcium nitrate, silver nitrate, sodium nitrate, copper nitrate, zinc nitrate, etc.

3. The preparation method according to claim 1, characterized in that, In step (1), the mass and volume ratio of heteropolyacid to anhydrous ethanol in the heteropolyacid solution is 1-3 g: 5-15 ml.

4. The preparation method according to claim 1, characterized in that, In step (2), the mass and volume ratio of inorganic metal salt to deionized water in the inorganic metal salt solution is 2-3 g: 20-50 ml.

5. The preparation method according to claim 1, characterized in that, The ammonia concentration in step (3) is 5%.

6. The preparation method according to claim 1, characterized in that, The standing time in step (5) is 1-2.5 h, the vacuum drying time is 4-8 h, and the drying temperature is 50-80 ℃.

7. A hydrogen sensor, characterized in that, include: An insulating substrate, interdigitated electrodes disposed on the surface of the substrate, and an ammonium salt type heteropoly acid salt gas-sensitive material layer coated on the surface of the interdigitated electrodes as described in claim 1.

8. The hydrogen sensor according to claim 7, characterized in that, The insulating substrate is an alumina ceramic sheet, and the interdigitated electrodes are made of gold, platinum, or silver.

9. The hydrogen sensor according to claim 7, characterized in that, The thickness of the ammonium salt type heteropoly acid salt gas-sensitive material layer is 5-30 μm.

10. The application of the hydrogen sensor according to claim 7 in hydrogen detection, characterized in that, The sensor operates at room temperature and has a detection response for hydrogen gas in the concentration range of 200 ppb-10 ppm. The response time of hydrogen at a concentration of 200 ppb was 3.6 s, the recovery time was 6.3 s, and the sensitivity was 1.086%; the response time of hydrogen at a concentration of 10 ppm was 14 s, the recovery time was 16.2 s, and the sensitivity was 45.213%.

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