Preparation method of PdPt / ZnO microflower and hydrogen sensing application of PdPt / ZnO microflower
By preparing PdPt/ZnO micron gas-sensitive material, the problem of high temperature operation and low selectivity of hydrogen sensors is solved, and rapid and highly selective detection of hydrogen at low temperatures is achieved, thereby improving the performance and stability of the sensor.
Patent Information
- Application Number
- CN202510583703.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-07
- Publication Date
- 2025-08-05
AI Technical Summary
The existing hydrogen sensors have high operating temperature and low selectivity, making it difficult to achieve rapid and highly selective detection of hydrogen under low temperature conditions.
ZnO microns were prepared by solvothermal reaction and calcination treatment, and loaded Pd and Pt through a water bath reaction to form PdPt/ZnO micron gas-sensitive material, reducing the sensing temperature and increasing the carrier transport rate.
A rapid and highly selective detection of hydrogen at 75°C was achieved, with a response time of 1 s and a response value of 623, showing a good linear relationship to hydrogen concentration, reducing sensor power consumption and extending service life.
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Figure CN120423595A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a preparation method of a PdPt / ZnO micron flower and hydrogen sensing application thereof, belonging to the technical field of hydrogen detection. Background Art
[0002] As a renewable secondary energy carrier with zero carbon emissions, hydrogen plays a vital role in ensuring energy supply security and promoting the realization of carbon emission reduction targets. However, hydrogen has a small molecular diameter (0.289 nm) and a high diffusion coefficient (0.61 cm 2 Characteristics such as hydrogen's high concentration (1000 t / s) and low explosion limit (4.0 vol.%) make it prone to leaking from equipment and leading to catastrophic accidents. For safety reasons, the use of hydrogen sensors during hydrogen production, transportation, and use is crucial to detect hydrogen leak concentrations and provide early warning.
[0003] Metal oxide semiconductor sensors have attracted widespread attention from researchers both domestically and internationally due to their excellent gas-sensing performance, compact size, and low cost. However, traditional gas-sensing materials require high temperatures (200-400°C) to generate sufficient energy for surface redox reactions. Long-term high-temperature operation of the device can cause microstructural changes in the sensitive material, leading to a decrease in hydrogen-sensing performance and stability. Furthermore, higher operating temperatures increase sensor power consumption, shortening its service life and limiting its application in explosive environments. Furthermore, metal oxide semiconductor materials have an inherent defect of cross-sensitivity. The presence of volatile organic compounds and other reactive gases in the detection environment, besides hydrogen, can strongly interfere with or completely disable the sensing material's ability to detect hydrogen. Therefore, there is a great need to develop highly selective hydrogen-sensitive materials that operate near room temperature. Summary of the Invention
[0004] The purpose of the present invention is to solve the problems of high operating temperature and low selectivity of hydrogen sensors, and to provide a preparation method of PdPt / ZnO micron flowers and their hydrogen sensing application, so as to achieve rapid and highly selective detection of hydrogen at lower operating temperature conditions.
[0005] To achieve the above object, the present invention provides the following technical solutions:
[0006] A method for preparing PdPt / ZnO micron flowers, comprising the following steps:
[0007] Step S1: zinc nitrate hexahydrate, urea and ethylene glycol are uniformly mixed, the product of the solvothermal reaction is alternately centrifuged and washed with deionized water and ethanol, and calcined to obtain ZnO microflowers;
[0008] The usage ratio of zinc nitrate hexahydrate, urea and ethylene glycol is (58-62) mg: (48-52) mg: 1 mL;
[0009] Step S2: The ZnO microflowers prepared in step S1 are dispersed in deionized water, and ascorbic acid, polyvinyl pyrrolidone, and potassium bromide are added. The resulting solution is transferred to a water bath and reacted in a water bath for 0.5 h. Then, a sodium chloropalladate solution is added and reacted in a water bath for 3 h. Subsequently, a citric acid solution and a potassium tetrachloroplatinate solution are added and reacted in a water bath for 5 h. The reaction product is washed alternately by centrifugation with deionized water and acetone, and dried to obtain PdPt / ZnO microflowers.
[0010] The dosage ratio of ascorbic acid, polyvinyl pyrrolidone, potassium bromide, sodium chloropalladate solution, citric acid solution and potassium tetrachloroplatinate solution is (490-510) mg: (390-410) mg: (2900-3100) mg: (20-100) mL: 1 mL: (9-11) mL; the molar concentrations of sodium chloropalladate solution, citric acid solution and potassium tetrachloroplatinate solution are 19-20 mM, 795-805 mM and 4-6 mM, respectively;
[0011] The molar ratio of Pd atoms to Zn atoms in the PdPt / ZnO micron flowers is not greater than 5%.
[0012] Preferably, the solvent thermal reaction in step S1 is a constant temperature reaction at 90-110° C. for 10-14 h.
[0013] Preferably, the calcination treatment in step S1 is calcination at 380-420° C. for 1-1.5 h.
[0014] Preferably, the water bath reaction in step S2 is carried out at 75-85°C.
[0015] Preferably, during the water bath reaction in step S2, the precursor solution is stirred at a stirring speed of 700-800 rpm / min.
[0016] The present invention also provides a PdPt / ZnO micron flower gas-sensitive material obtained by the above preparation method.
[0017] The present invention also provides the application of PdPt / ZnO micron flowers in hydrogen detection.
[0018] Furthermore, the operating temperature of the gas-sensitive material is 75-100°C.
[0019] A hydrogen sensor comprises the above-mentioned gas-sensitive material.
[0020] Beneficial effects of the present invention:
[0021] The present invention uses zinc nitrate hexahydrate, urea, and ethylene glycol as reaction raw materials. After a solvent thermal reaction and calcination, a self-assembled micron-flower of ZnO nanosheets is produced. The ZnO micron-flower is then mixed with sodium chloropalladate and potassium tetrachloroplatinate and reacted in a water bath to obtain a PdPt / ZnO micron-flower gas-sensitive material. The present invention modifies ZnO with Pd and Pt elements. The combination of Pd and Pt not only reduces the sensing temperature but also accelerates carrier transport and shortens detection time. Specifically, the PdPt / ZnO micron-flower gas-sensitive material produced by the present invention has good selectivity for hydrogen, with an optimal operating temperature of 75°C, a response value of 623 to 1000 ppm of hydrogen, and a response time of 1 s. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Figure 1 This is the SEM image of the PdPt / ZnO microflower prepared in Example 1.
[0023] Figure 2 3 is a graph showing the relationship between the response value of the gas-sensitive materials prepared in the examples and comparative examples to 1000 ppm hydrogen and the operating temperature.
[0024] Figure 3 3 is a transient response curve of the PdPt / ZnO micron flower prepared in Example 1 to 10-1000 ppm hydrogen.
[0025] Figure 4 1 is a response-recovery time diagram of the PdPt / ZnO microflower prepared in Example 1 to 1000 ppm hydrogen.
[0026] Figure 5 1 is a dynamic resistance diagram of the PdPt / ZnO micron flower prepared in Example 1 to 1000 ppm of different gases. DETAILED DESCRIPTION
[0027] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described below in conjunction with specific embodiments. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.
[0028] The experimental materials used in the examples of the present invention are all conventional experimental materials in the field and can be purchased through commercial channels.
[0029] The names and symbols used in the present invention are commonly used in the art. For example, mM is a concentration unit, and 1 mM means a concentration of 1 millimole per liter.
[0030] Example 1
[0031] The PdPt / ZnO micron flower of this embodiment is prepared according to a Pd loading concentration of 1.0%, and the preparation method specifically includes the following steps:
[0032] Step S1: 2400 mg of zinc nitrate hexahydrate, 2000 mg of urea, and 40 mL of ethylene glycol were stirred at room temperature for 0.5 h, and then transferred to a 100 mL autoclave for reaction at 100°C for 12 h. The reaction product was then washed alternately with deionized water and ethanol by centrifugation six times and dried in a 60°C oven for 12 h. The resulting precursor was transferred to a high-temperature muffle furnace and calcined at 400°C for 1 h to obtain ZnO microflowers.
[0033] Step S2: 4600 mg of ZnO microflowers prepared in step S1 were dispersed in 50 mL of deionized water, followed by the addition of 0.5 mg of ascorbic acid, 0.4 mg of polyvinylpyrrolidone, and 3 mg of potassium bromide, and stirred for 0.5 h. The resulting solution was transferred to a water bath and reacted at 80°C for 0.5 h. Then, 30 μL of 19 mM sodium chloropalladate solution was added and reacted at 80°C for 3 h. Subsequently, 1 μL of 800 mM citric acid solution and 10 μL of 5 mM potassium tetrachloroplatinate solution were added and reacted at 80°C for 5 h. Finally, the reaction product was washed alternately by centrifugation with deionized water and acetone, and dried in an oven at 60°C for 12 h to obtain PdPt / ZnO microflowers.
[0034] Example 2
[0035] The PdPt / ZnO microflowers of this example were prepared with a Pd loading concentration of 2.0%. The only difference from Example 1 was the addition of 60 μL of a 19 mM sodium chloropalladate solution and 20 μL of a 5 mM potassium tetrachloroplatinate solution in step S2. All other parameters were the same as in Example 1 and are not further described.
[0036] Example 3
[0037] The PdPt / ZnO microflowers of this example were prepared with a Pd loading concentration of 3.0%. The only difference from Example 1 was that in step S2, 90 μL of a 19 mM sodium chloropalladate solution and 30 μL of a 5 mM potassium tetrachloroplatinate solution were added. All other parameters were the same as in Example 1 and are not further described.
[0038] Comparative Example 1
[0039] The preparation method of the ZnO micron flower of this comparative example specifically comprises the following steps:
[0040] Step S1: 2400 mg of zinc nitrate hexahydrate, 2000 mg of urea, and 40 mL of ethylene glycol were stirred at room temperature for 0.5 h, and then transferred to a 100 mL autoclave for reaction at 100°C for 12 h. The reaction product was then washed alternately with deionized water and ethanol by centrifugation six times and dried in a 60°C oven for 12 h. The resulting precursor was transferred to a high-temperature muffle furnace and calcined at 400°C for 1 h to obtain ZnO microflowers.
[0041] Comparative Example 2
[0042] The preparation method of the Pd / ZnO micron flower of this comparative example specifically comprises the following steps:
[0043] Step S1: 2400 mg of zinc nitrate hexahydrate, 2000 mg of urea, and 40 mL of ethylene glycol were stirred at room temperature for 0.5 h, and then transferred to a 100 mL autoclave for reaction at 100°C for 12 h. The reaction product was then washed alternately with deionized water and ethanol by centrifugation six times and dried in a 60°C oven for 12 h. The resulting precursor was transferred to a high-temperature muffle furnace and calcined at 400°C for 1 h to obtain ZnO microflowers.
[0044] Step S2: 4600 mg of ZnO microflowers prepared in step S1 were dispersed in 50 mL of deionized water, followed by the addition of 0.5 mg of ascorbic acid, 0.4 mg of polyvinylpyrrolidone, and 3 mg of potassium bromide, and stirred for 0.5 h. The resulting solution was transferred to a water bath and reacted at 80°C for 0.5 h. Then, 30 μL of 19 mM sodium chloropalladate solution was added and reacted at 80°C for 3 h. Subsequently, 1 μL of 800 mM citric acid solution was added and reacted at 80°C for 5 h. Finally, the reaction product was washed alternately by centrifugation with deionized water and acetone, and dried in an oven at 60°C for 12 h to obtain Pd / ZnO microflowers.
[0045] Comparative Example 3
[0046] The preparation method of the Pt / ZnO micron flower of this comparative example specifically comprises the following steps:
[0047] Step S1: 2400 mg of zinc nitrate hexahydrate, 2000 mg of urea, and 40 mL of ethylene glycol were stirred at room temperature for 0.5 h, and then transferred to a 100 mL autoclave for reaction at 100°C for 12 h. The reaction product was then washed alternately with deionized water and ethanol by centrifugation six times and dried in a 60°C oven for 12 h. The resulting precursor was transferred to a high-temperature muffle furnace and calcined at 400°C for 1 h to obtain ZnO microflowers.
[0048] Step S2: 4600 mg of ZnO microflowers prepared in step S1 were dispersed in 50 mL of deionized water, followed by the addition of 0.5 mg of ascorbic acid, 0.4 mg of polyvinylpyrrolidone, and 3 mg of potassium bromide, and stirred for 0.5 h. The resulting solution was transferred to a water bath and reacted at 80°C for 0.5 h. Then, 10 μL of 5 mM potassium tetrachloroplatinate solution was added and reacted at 80°C for 3 h. Subsequently, 1 μL of 800 mM citric acid solution was added and reacted at 80°C for 5 h. Finally, the reaction product was washed alternately by centrifugation with deionized water and acetone, and dried in an oven at 60°C for 12 h to obtain Pt / ZnO microflowers.
[0049] The material characterization and hydrogen sensitivity test results of the above examples and comparative examples are shown below:
[0050] Figure 1 This is a SEM image of the PdPt / ZnO micron flower prepared in Example 1 of the present invention. Figure 1 The PdPt / ZnO microflowers prepared by the solvothermal and water-bath methods are assembled from porous nanosheets 2-3 μm long. The pores within the nanosheets serve as transport channels for gas molecules, enhancing the hydrogen-sensitive response rate. EDS elemental mapping of the PdPt / ZnO microflowers reveals a uniform distribution of Pd and Pt on the surface of the microflowers, indicating that the PdPt bimetallic material is uniformly loaded on the ZnO microflowers.
[0051] Figure 2 is a graph showing the relationship between the response value of the gas-sensitive materials prepared in Examples 1 to 3 of the present invention and Comparative Examples 1 to 3 to 1000 ppm of hydrogen and the operating temperature, Figure 2 As can be seen, the response values of all gas-sensitive materials to hydrogen show a volcano-like trend with increasing temperature. Among them, the ZnO prepared in Comparative Example 1 has the highest response value to 1000 ppm hydrogen at 200°C. The optimal operating temperature of the Pd / ZnO prepared in Comparative Example 2 and the Pt / ZnO prepared in Comparative Example 3 decreases from 200°C to 150°C, and the optimal operating temperature of the PdPt / ZnO prepared in Examples 1-3 decreases to 75°C. The results show that the loading of precious metals reduces the activation energy of surface molecular reactions, and bimetallic materials exhibit superior catalytic activity compared to monometallic materials. Lowering the optimal operating temperature of gas-sensitive materials can reduce sensor power consumption and extend their service life.
[0052] Figure 3 The figure is a transient response curve of the PdPt / ZnO micron flower prepared in Example 1 of the present invention to 10-1000 ppm hydrogen, and the inset is a calibration curve of the PdPt / ZnO micron flower to 10-1000 ppm hydrogen. Figure 3As can be seen, the response of the gas-sensitive material increases linearly as the hydrogen concentration increases from 10 ppm to 1000 ppm. The response of the PdPt / ZnO microflower exhibits a good linear relationship with the hydrogen concentration between 10 and 1000 ppm. The linear fit equation is: lnS = 1.343 ‧ lnC – 2.904. Here, S is defined as the gas-sensitive material's response to hydrogen, and C is defined as the hydrogen concentration.
[0053] Figure 4 The response-recovery time diagram of the PdPt / ZnO micron flower prepared in Example 1 to 1000 ppm hydrogen is shown in FIG. Figure 4 As can be seen, the response time of the PdPt / ZnO microflower to 1000 ppm of hydrogen at 75°C is 2 s, and the recovery time is 4 s, indicating that the PdPt / ZnO microflower prepared in Example 1 of the present invention can quickly detect hydrogen leakage concentration. The response time is defined as the time required for hydrogen to contact the gas-sensitive material and for the material resistance to drop to 90% of the steady-state resistance, while the recovery time is defined as the time required for hydrogen to desorb from the gas-sensitive material and for the material resistance to return to 90% of the baseline resistance.
[0054] Figure 5 The dynamic resistance diagram of the PdPt / ZnO micron flower prepared in Example 1 to 1000 ppm of different gases is shown in FIG. Figure 5 It can be seen that PdPt / ZnO micron flowers are insensitive to ethanol at 75°C, and have only weak response signals to ammonia and methanol, and their response amplitude is much smaller than the response amplitude to hydrogen of the same concentration; compared with other interfering gases, PdPt / ZnO micron flowers not only have the highest response value to hydrogen, but also have the shortest response time to hydrogen.
[0055] The above description is only a preferred embodiment of the present application and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made by ordinary technicians in the relevant technical field without departing from the spirit and scope of the present invention also fall within the scope of the present invention. The scope of patent protection of the present invention shall be defined by the claims.
Claims
1. A method for preparing PdPt / ZnO micron flowers, characterized in that: The preparation method comprises the following steps: Step S1: uniformly mixing zinc nitrate hexahydrate, urea and ethylene glycol, washing the product of the solvent thermal reaction, and calcining to obtain ZnO micron flowers; The usage ratio of zinc nitrate hexahydrate, urea and ethylene glycol is (58-62) mg: (48-52) mg: 1 mL; Step S2: Dispersing the ZnO microflowers prepared in step S1 in deionized water, adding ascorbic acid, polyvinyl pyrrolidone, and potassium bromide, transferring the resulting solution to a water bath for reaction, then adding a sodium chloropalladate solution and reacting in a water bath, followed by adding a citric acid solution and a potassium tetrachloroplatinate solution and reacting in a water bath, washing and drying the reaction product to obtain PdPt / ZnO microflowers; The dosage ratio of ascorbic acid, polyvinyl pyrrolidone, potassium bromide, sodium chloropalladate solution, citric acid solution and potassium tetrachloroplatinate solution is (490-510) mg: (390-410) mg: (2900-3100) mg: (20-100) mL: 1 mL: (9-11) mL; the molar concentrations of sodium chloropalladate solution, citric acid solution and potassium tetrachloroplatinate solution are 19-20 mM, 795-805 mM and 4-6 mM, respectively; The molar ratio of Pd atoms to Zn atoms in the PdPt / ZnO micron flowers is not greater than 5%.
2. The method for preparing PdPt / ZnO microflowers according to claim 1, wherein: In step S1, the solvent thermal reaction is carried out at a constant temperature of 90-110° C. for 10-14 h.
3. The method for preparing PdPt / ZnO microflowers according to claim 1, wherein: In step S1, the calcination treatment is performed at 380-420° C. for 1-1.5 h.
4. The method for preparing PdPt / ZnO microflowers according to claim 1, wherein: In step S2, the temperature of the water bath reaction is 75-85°C.
5. A PdPt / ZnO micron flower gas-sensitive material, characterized in that: The method is prepared according to any one of claims 1 to 4.
6. Use of the PdPt / ZnO micron flower gas-sensitive material according to claim 5 in hydrogen detection.
7. The use according to claim 6, characterized in that: The working temperature of the gas-sensitive material is 75-100°C.
8. A hydrogen sensor, characterized in that: The sensor comprises the gas-sensitive material according to claim 7.