CN117929487B - Pd@Pt/In2O3Nanomaterial and hydrogen sensor - Google Patents
Pd@Pt/In2O3Nanomaterial and hydrogen sensor Download PDFInfo
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- 229910052739 hydrogen Inorganic materials 0.000 title claims abstract description 65
- 239000001257 hydrogen Substances 0.000 title claims abstract description 65
- 125000004435 hydrogen atom Chemical class [H]* 0.000 title claims description 4
- KDLHZDBZIXYQEI-UHFFFAOYSA-N palladium Substances [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 claims abstract description 102
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 58
- 239000007789 gas Substances 0.000 claims abstract description 38
- CIWBSHSKHKDKBQ-JLAZNSOCSA-N Ascorbic acid Chemical compound OC[C@H](O)[C@H]1OC(=O)C(O)=C1O CIWBSHSKHKDKBQ-JLAZNSOCSA-N 0.000 claims abstract description 28
- 239000002086 nanomaterial Substances 0.000 claims abstract description 26
- 239000002105 nanoparticle Substances 0.000 claims abstract description 21
- XURCIPRUUASYLR-UHFFFAOYSA-N Omeprazole sulfide Chemical compound N=1C2=CC(OC)=CC=C2NC=1SCC1=NC=C(C)C(OC)=C1C XURCIPRUUASYLR-UHFFFAOYSA-N 0.000 claims abstract description 17
- PIBWKRNGBLPSSY-UHFFFAOYSA-L palladium(II) chloride Chemical compound Cl[Pd]Cl PIBWKRNGBLPSSY-UHFFFAOYSA-L 0.000 claims abstract description 17
- 229960005070 ascorbic acid Drugs 0.000 claims abstract description 14
- 235000010323 ascorbic acid Nutrition 0.000 claims abstract description 14
- 239000011668 ascorbic acid Substances 0.000 claims abstract description 14
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims abstract description 12
- 239000002253 acid Substances 0.000 claims abstract description 12
- 235000011114 ammonium hydroxide Nutrition 0.000 claims abstract description 12
- 239000000919 ceramic Substances 0.000 claims abstract description 11
- 239000000758 substrate Substances 0.000 claims abstract description 11
- 238000000034 method Methods 0.000 claims abstract description 5
- 239000008367 deionised water Substances 0.000 claims description 41
- 229910021641 deionized water Inorganic materials 0.000 claims description 41
- 238000006243 chemical reaction Methods 0.000 claims description 31
- 238000001035 drying Methods 0.000 claims description 22
- IOLCXVTUBQKXJR-UHFFFAOYSA-M potassium bromide Chemical compound [K+].[Br-] IOLCXVTUBQKXJR-UHFFFAOYSA-M 0.000 claims description 22
- 238000005406 washing Methods 0.000 claims description 22
- 238000002360 preparation method Methods 0.000 claims description 12
- 239000001267 polyvinylpyrrolidone Substances 0.000 claims description 11
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 claims description 11
- 229920000036 polyvinylpyrrolidone Polymers 0.000 claims description 11
- 239000011248 coating agent Substances 0.000 claims description 7
- 238000000576 coating method Methods 0.000 claims description 7
- 125000004429 atom Chemical group 0.000 claims description 4
- 238000003760 magnetic stirring Methods 0.000 claims description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 abstract description 36
- 150000002431 hydrogen Chemical class 0.000 abstract description 28
- 229910052763 palladium Inorganic materials 0.000 abstract description 24
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 abstract description 21
- PJXISJQVUVHSOJ-UHFFFAOYSA-N indium(iii) oxide Chemical compound [O-2].[O-2].[O-2].[In+3].[In+3] PJXISJQVUVHSOJ-UHFFFAOYSA-N 0.000 abstract description 19
- 238000001514 detection method Methods 0.000 abstract description 18
- 229910052697 platinum Inorganic materials 0.000 abstract description 13
- 239000001301 oxygen Substances 0.000 abstract description 11
- 229910052760 oxygen Inorganic materials 0.000 abstract description 11
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 abstract description 10
- 230000001965 increasing effect Effects 0.000 abstract description 10
- 238000007598 dipping method Methods 0.000 abstract description 8
- 239000000463 material Substances 0.000 abstract description 6
- 229910000510 noble metal Inorganic materials 0.000 abstract description 6
- 230000035945 sensitivity Effects 0.000 abstract description 5
- 150000004687 hexahydrates Chemical class 0.000 abstract description 4
- 229910052738 indium Inorganic materials 0.000 abstract description 4
- 238000011068 loading method Methods 0.000 abstract description 4
- 230000009467 reduction Effects 0.000 abstract description 4
- 239000004065 semiconductor Substances 0.000 abstract description 4
- 229910003437 indium oxide Inorganic materials 0.000 abstract 2
- 239000003638 chemical reducing agent Substances 0.000 abstract 1
- APFVFJFRJDLVQX-UHFFFAOYSA-N indium atom Chemical compound [In] APFVFJFRJDLVQX-UHFFFAOYSA-N 0.000 abstract 1
- 239000012716 precipitator Substances 0.000 abstract 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 31
- 230000004044 response Effects 0.000 description 30
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- 239000011540 sensing material Substances 0.000 description 5
- 230000000694 effects Effects 0.000 description 4
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 3
- 230000001680 brushing effect Effects 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 3
- 230000002431 foraging effect Effects 0.000 description 3
- 238000005470 impregnation Methods 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- 238000006722 reduction reaction Methods 0.000 description 3
- 230000002195 synergetic effect Effects 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 238000003915 air pollution Methods 0.000 description 2
- 239000003054 catalyst Substances 0.000 description 2
- 230000003197 catalytic effect Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 125000004430 oxygen atom Chemical group O* 0.000 description 2
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- MGWGWNFMUOTEHG-UHFFFAOYSA-N 4-(3,5-dimethylphenyl)-1,3-thiazol-2-amine Chemical compound CC1=CC(C)=CC(C=2N=C(N)SC=2)=C1 MGWGWNFMUOTEHG-UHFFFAOYSA-N 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 108091006149 Electron carriers Proteins 0.000 description 1
- 240000006829 Ficus sundaica Species 0.000 description 1
- 230000009471 action Effects 0.000 description 1
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- 230000004888 barrier function Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
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- 239000002803 fossil fuel Substances 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
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- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- JCXJVPUVTGWSNB-UHFFFAOYSA-N nitrogen dioxide Inorganic materials O=[N]=O JCXJVPUVTGWSNB-UHFFFAOYSA-N 0.000 description 1
- 230000009965 odorless effect Effects 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- -1 oxygen ions Chemical class 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 238000006479 redox reaction Methods 0.000 description 1
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- 238000001179 sorption measurement Methods 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
- G01N27/12—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid
- G01N27/125—Composition of the body, e.g. the composition of its sensitive layer
- G01N27/127—Composition of the body, e.g. the composition of its sensitive layer comprising nanoparticles
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Abstract
A Pd@Pt/In 2O3 nano material and a hydrogen sensor belong to the technical field of semiconductor gas sensitive materials. According to the method, indium nitrate is used as an indium source, ammonia water is used as a precipitator, and a water bath method is adopted to obtain indium oxide nano particles; palladium chloride and chloroplatinic acid hexahydrate are respectively used as a palladium source and a platinum source, ascorbic acid is used as a reducing agent, the prepared indium oxide is loaded with Pd and Pt noble metals by using a dipping method, and Pd@Pt/In 2O3 is coated on a ceramic substrate to obtain the hydrogen sensitive element. The active site of the In 2O3 nano-particles is increased by loading Pd and Pt double noble metals, and the oxygen vacancies are increased by the cooperation of the double noble metals and the hydrogen reduction, so that a heterojunction is formed, and the hydrogen sensitivity of the Pd@Pt/In 2O3 nano-material is further improved. The invention can realize ultra-fast (1 s) low detection limit (400 ppb) and high-selectivity hydrogen detection at 200 ℃.
Description
Technical Field
The invention relates to a Pd@Pt/In 2O3 nano material and a hydrogen sensor, and belongs to the technical field of semiconductor gas-sensitive materials.
Background
Hydrogen (H 2) is used as a sustainable, clean and efficient secondary energy carrier with zero carbon emission, is a renewable clean energy carrier, and can solve the problems of fossil fuel reduction, air pollution, global warming and the like. Hydrogen (H 2) has the greatest potential for use in renewable and clean energy, and can prevent the problem of harmful air pollution associated with conventional fuel sources. However, H 2 is a colorless, odorless, flammable, explosive gas that is undetectable by the human eyes and nose even at high concentrations. H 2 has low ignition energy, high diffusion coefficient, broad explosion limits, and can lead to catastrophic results in the event of accidental leakage.
Among various hydrogen gas detection methods, metal Oxide Semiconductor (MOS) gas sensors are a promising hydrogen gas detection technology because of their low cost, stable sensing performance, ease of manufacture, and the like. However, the conventional MOS semiconductor sensor has the disadvantages of low response speed, high detection lower limit and high operating temperature. How to improve the defects of the MOS-based sensor and further reduce the power consumption to detect the low-concentration hydrogen is of great significance. Therefore, the MOS type H 2 sensor with low detection lower limit and high response speed is researched, the application range of H 2 can be expanded, and the real-time monitoring and leakage-proof alarm technology applied to hydrogen safety production can be measured in a key, accurate and rapid manner.
Disclosure of Invention
The invention aims to solve the problems of slow response, high detection lower limit and poor selectivity of a hydrogen sensor, and provides a Pd@Pt/In 2O3 nano material and the hydrogen sensor so as to realize the purpose of rapidly and selectively detecting the leakage concentration of low-concentration hydrogen.
In order to achieve the above purpose, the present invention provides the following technical solutions:
A preparation method of Pd@Pt/In 2O3 nano-material, which comprises the following steps:
Step S1: centrifugally washing a product of the reaction of indium nitrate, polyvinylpyrrolidone, potassium bromide, ammonia water and deionized water bath, and drying to obtain In 2O3 nano particles;
the mass ratio of the indium nitrate to the polyvinylpyrrolidone to the potassium bromide is 3 (5-6) to 2-3 respectively; the mass ratio of the indium nitrate to the ammonia water to the deionized water is 1 (400-500) (2100-2200);
Step S2: dispersing In 2O3 nano particles prepared In the step S1 In deionized water, adding a palladium chloride solution and a hexahydrated chloroplatinic acid solution to carry out magnetic stirring, and then adding an ascorbic acid solution to carry out reaction; after the reaction is finished, centrifugally washing and drying the product to obtain Pd@Pt/In 2O3 nano material;
Wherein the molar concentrations of the palladium chloride solution, the hexahydrated chloroplatinic acid solution and the ascorbic acid solution are 9-11 mM, 9-11 mM and 100-105 mM respectively; the molar ratio of indium nitrate to palladium chloride is 2:100; the mole ratio of Pd atoms to Pt atoms In the Pd@Pt/In 2O3 nano-material is 1:1.
The water bath reaction conditions in the step S1 are as follows: the reaction temperature is 60-70 ℃ and the reaction time is 1-2 hours;
The drying treatment is as follows: and drying at 60-80 ℃ for 12-20 h in an air atmosphere.
The reaction condition in the step S2 is that the reaction is carried out for 20-24 hours at 20-25 ℃.
And in the step S2, centrifugal washing is carried out at a centrifugal speed of 10000r/min for 5-10min and washing times of 3-6 times.
The Pd@Pt/In 2O3 nano material is prepared by the preparation method.
An application of Pd@Pt/In 2O3 nano-material, wherein the nano-material is applied to the preparation of a hydrogen sensor.
Further, the nano material is uniformly coated on an A1 2O3 ceramic substrate printed with Ag-Pd interdigital electrodes, so that the Pd@Pt/In 2O3 gas sensor for the hydrogen sensor is obtained.
Mixing the In 2O3 nano material with absolute ethyl alcohol, and grinding to obtain paste; a certain amount of paste is dipped by a zero-number writing brush and uniformly coated on an A1 2O3 ceramic substrate printed with Ag-Pd interdigital electrodes, and the assembled device is placed in a baking oven at 200 ℃ for aging for 6 hours to obtain the hydrogen sensitive element.
Preferably, in 2O3 gas sensors are reacted In palladium chloride solution, chloroplatinic acid solution hexahydrate and ascorbic acid solution for 22 hours In step S2.
The invention has the beneficial effects that:
The Pd@Pt/In 2O3 gas-sensitive composite material provided by the invention firstly adopts a water bath method to prepare In 2O3 nano particles, then adopts an impregnation method to load double noble metals Pd and Pt on the In 2O3 nano particles to obtain the Pd@Pt/In 2O3 composite material, The active site of the In 2O3 nano-particles is increased, and the oxygen vacancies are increased by the load of the double noble metal and hydrogen reduction, so that the hydrogen sensitivity performance of the double noble metal is improved. The synergistic increase In hydrogen sensitivity to In 2O3 of Pd and Pt has three main causes: the overflow effect and the catalytic effect of Pd and Pt are firstly; secondly, oxygen vacancies are increased; and thirdly, heterojunction formation. First, the overflow effect of the two promotes dissociation and adsorption of oxygen molecules and hydrogen molecules, thereby leading to rapid capture and release of electron carriers. Oxygen molecules are preferentially adsorbed on the surfaces of Pd and Pt and dissociated into oxygen atoms, and under the action of the overflow effect of the two bimetallic materials, the oxygen atoms overflow to the surface of In 2O3 and are captured to form O -, so that more oxygen ions are adsorbed on the surface of the sensor to accelerate the electron transfer rate, and the sensing performance of the sensing material on hydrogen is improved. meanwhile, pd and Pt can dissociate hydrogen molecules into hydrogen atoms and overflow to the surface of In 2O3 to participate In oxidation-reduction reaction, and In addition, H 2 molecules can be directly adsorbed on active sites of Pt and Pd and then migrate to the surface of In 2O3 to react with adsorbed oxygen. H 2 is therefore susceptible to oxidation, enhancing the gas response. And the number of adsorbed oxygen molecules increases with increasing oxygen vacancy concentration according to the OVs model. In conclusion, due to the synergistic effect of Pd and Pt, the bimetallic catalyst has stronger catalytic performance than a single-metal catalyst. The work function of In 2O3 (Φ=4.80 eV) is lower than that of Pd (Φ=5.12 eV) and Pt (Φ=5.65 eV), electrons flow from In 2O3 to the Pd and Pt bimetallic, causing the contact interface In 2O3 to be bent upwards, Until the fermi levels of the three reach equilibrium, a schottky barrier is formed at the interface between In 2O3 and Pd and Pt, and a larger electron depletion layer is formed on the In 2O3 side, so that the baseline resistance of In 2O3 is increased, and the resistance change is increased. the Pd@Pt/In 2O3 gas-sensitive composite material provided by the invention has excellent hydrogen sensing performance, has a response value of 1.70 to low-concentration 0.4ppm hydrogen at an optimal working temperature of 200 ℃, has a response/recovery time of 1s/7s, and has good hydrogen selectivity.
Drawings
FIG. 1 is a bar graph of the selectivity of the gas sensor prepared in the examples for 1000ppm of different gases at an operating temperature of 200 ℃.
FIG. 2 is a graph of dynamic resistance of a Pd@Pt/In 2O3 gas sensor prepared In the example to 0.4-6000 ppm hydrogen at an operating temperature of 200 ℃.
FIG. 3 is a graph showing the recovery of the response of the Pd@Pt/In 2O3 gas sensor prepared In the example to 0.4 to 6000ppm hydrogen at an operating temperature of 200 ℃.
FIG. 4 is a graph of the response recovery time of the Pd@Pt/In 2O3 gas sensor prepared In example 2 to 0.4ppm hydrogen at an operating temperature of 200 ℃.
Detailed Description
The following describes in further detail the embodiments of the present invention with reference to the drawings and examples. It is apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments, and that other embodiments obtained by those skilled in the art without inventive effort are within the scope of the present invention based on the embodiments of the present invention.
The names and symbols used in the invention are common names and symbols in the field. For example, mM is a concentration unit, and 1mM means a concentration of 1 millimole per liter.
The preparation method of the Pd@Pt/In 2O3 gas-sensitive composite material comprises the following steps:
Step S1: uniformly stirring indium nitrate, polyvinylpyrrolidone, potassium bromide, ammonia water and deionized water, transferring to a water bath kettle for water bath reaction, centrifugally washing a reaction product with deionized water and ethanol, and drying to obtain In 2O3 nano particles;
Step S2: dispersing In 2O3 nano particles prepared In the step S1 In deionized water by ultrasonic, adding a palladium chloride solution and a hexahydrated chloroplatinic acid solution after uniformly mixing, transferring the obtained solution to a magnetic stirrer, adding an ascorbic acid solution to enable the mixture to carry out an impregnation reaction, alternately centrifugally washing the product with deionized water and ethanol for three times, and drying to obtain the Pd@Pt/In 2O3 composite material;
the atomic mole ratio of Pd and In the Pd@Pt/In 2O3 composite material is not more than 2.00%;
Step S3: and (3) uniformly coating the Pd@Pt/In 2O3 composite material prepared In the step (S2) on an A1 2O3 ceramic substrate printed with Ag-Pd interdigital electrodes, and placing the assembled device In a baking oven at 200 ℃ for aging for 6 hours to obtain the hydrogen sensitive element.
Step S4: and (3) reducing the Pd@Pt/In 2O3 composite material prepared In the step (S3) In a hydrogen atmosphere to obtain oxygen vacancies.
The mass ratio of the indium nitrate to the polyvinylpyrrolidone to the potassium bromide is 3:5-6:2-3 respectively.
In the step S1, the dosage ratio of the indium nitrate, the ammonia water and the deionized water is 1:467-468:2125-2126, for example, the dosage ratio is 150mg:70000mg:318500mg, 300mg:140000mg:637000mg, or 375mg, 175000mg:796250mg.
In the step S1, the water bath reaction is as follows: and (3) carrying out constant temperature reaction for 1-2 h (such as 1h, 1.5h or 2 h) at 60-70 ℃ (such as 60 ℃, 65 ℃ or 70 ℃).
In step S1, the drying process is: drying at 60-80 ℃ (e.g. 60 ℃, 70 ℃ or 80 ℃) for 12-20 hours (e.g. 12 hours, 15 hours or 20 hours) under an air atmosphere.
In the step S2, the volume ratio of the palladium chloride solution, the hexahydrated chloroplatinic acid solution and the ascorbic acid solution is (1-2): (20-25) (for example, 1:2:20,1:2:25 or 1:1:20), wherein the molar concentrations of the palladium chloride solution, the hexahydrated chloroplatinic acid solution and the ascorbic acid solution are 9-11 mM, 9-11 mM and 100-105 mM respectively.
In the step S2, the addition amount of the palladium chloride solution is as follows: the atomic molar ratio of Pd and In is not more than 2.00%, for example, the atomic molar ratio of Pd and In is 1.00%, 1.50% or 2.00%.
In step S2, the impregnation reaction is: and (3) carrying out constant-temperature reaction for 20-24 h (for example, 20h, 22h or 24 h) at 20-25 ℃ (for example, 20 ℃, 23 ℃ or 25 ℃).
In step S1 and step S2, the centrifugal washing is: the centrifugal speed is 10000r/min, and the time is 5-10 min (for example, 5min, 7min or 10 min); the number of washing is 3 to 6 (e.g., 3,4,5 or 6).
In the step S3, mixing the Pd@Pt/In 2O3 composite material prepared In the step S2 with absolute ethyl alcohol, and grinding to obtain a paste; a certain amount of paste is dipped by a zero-number writing brush and uniformly coated on an A1 2O3 ceramic substrate printed with Ag-Pd interdigital electrodes, and the assembled device is placed in a 200 ℃ oven for aging for 6 hours to obtain the A1 2O3 gas sensor.
In the step S4, the Pd@Pt/In 2O3 composite material prepared In the step S3 is reduced In a hydrogen atmosphere to obtain oxygen vacancies. The reduction time is 2-4 hours (e.g., 2 hours, 3 hours or 4 hours).
The Pd@Pt/In 2O3 gas-sensitive composite material can be used for rapidly and selectively detecting hydrogen leakage at 200 ℃.
The invention is further described below in connection with specific examples.
Example 1
The preparation method of the Pd 1@Pt1/In2O3 nano material in the embodiment specifically comprises the following steps:
S1, uniformly stirring 150mg of indium nitrate, 250mg of polyvinylpyrrolidone, 100mg of potassium bromide and 20mL of deionized water, transferring to a water bath kettle, adding 3.5mL of ammonia water and 50mL of deionized water to carry out hydrothermal reaction at 60 ℃ for 1h, centrifugally washing a reaction product with deionized water for 6 times, and drying In a 60 ℃ oven for 12h to obtain In 2O3 nano particles;
S2, ultrasonically dispersing In 2O3 nano particles prepared In the step S1 In 20mL of deionized water, uniformly mixing, adding 1mL of 10mM palladium chloride solution, 1mL of 10mM chloroplatinic acid solution hexahydrate and 20mL of deionized water, uniformly stirring, transferring the obtained solution to a magnetic stirrer for water bath reaction at 20 ℃, adding 20mL of 100mM ascorbic acid solution, carrying out dipping reaction for 22 hours, alternately centrifuging and washing the reaction product with deionized water and ethanol for 6 times, and drying In an oven at 60 ℃ for 12 hours to obtain Pd@Pt/In 2O3 composite material;
And S3, mixing the Pd@Pt/In 2O3 composite material prepared In the step S2 with absolute ethyl alcohol, grinding to obtain paste, brushing a certain amount of paste with a zero-number writing brush, uniformly coating the paste on an A1 2O3 ceramic substrate printed with Ag-Pd interdigital electrodes, and aging the assembled device In an oven at 200 ℃ for 6 hours to obtain the hydrogen sensitive element.
The sensor had a response value of 159 to 6000ppm hydrogen at 200℃operating temperature, with a lower detection limit of 0.4ppm.
The results of the performance test of the above embodiment are shown below:
And testing by using a CGS-MT photoelectric comprehensive test platform manufactured by Beijing Zhonghua high-tech limited company. To investigate the selectivity, 1000ppm of hydrogen, carbon dioxide, methane, nitrogen dioxide, ammonia, methanol and ethanol were injected into a 100mL test chamber at 200 ℃ operating temperature, respectively, and the response of the gas sensor to the different gases was recorded after 100 s. FIG. 1 is a bar graph showing the selectivity of the gas sensor prepared In the embodiment of the invention to 1000ppm of different gases at the working temperature of 200 ℃, and as can be seen from FIG. 1, the Pd@Pt/In 2O3 composite material has higher response to hydrogen and has negligible response to other gases, which indicates that the Pd@Pt/In 2O3 gas sensor composite material has higher selectivity to hydrogen.
At 200 ℃ working temperature, 0.4, 0.5, 1, 2, 5, 10, 50, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 2000, 4000 and 6000ppm hydrogen are sequentially injected into the test cavity, and dynamic response curves of the gas sensor to different concentrations of hydrogen in 100s are recorded in real time. FIG. 2 is a graph showing the dynamic resistance of the Pd@Pt/In 2O3 gas sensor prepared by the embodiment of the invention to 0.4-6000 ppm hydrogen at the working temperature of 200 ℃, and FIG. 3 shows that the response value of the Pd@Pt/In 2O3 gas sensor is positively correlated with the concentration of hydrogen, and the response value is rapidly increased and does not reach saturation along with the increase of the concentration of hydrogen, so that the Pd@Pt/In 2O3 gas sensor can detect the hydrogen with the concentration range of 0.4-6000 ppm. Its response to 6000ppm hydrogen was 159. The response value is the ratio of the resistance value R a of the gas sensor in the air to the resistance value R g of the gas to be measured, namely R a/Rg.
At 200 ℃, 1000ppm of hydrogen is injected into a 100L test cavity of a CGS-MT photoelectric comprehensive test platform manufactured by Beijing Zhonggao science and technology Co., ltd, and a dynamic resistance curve of a gas sensor to hydrogen in 100s is recorded in real time.
FIG. 4 is a graph showing response recovery time of the Pd@Pt/In 2O3 gas sensor prepared by the embodiment of the invention to 0.4ppm hydrogen at the working temperature of 200 ℃, and as can be seen from FIG. 4, the response time of the Pd@Pt/In 2O3 gas sensor to 0.4ppm hydrogen at 200 ℃ is 1s, the recovery time is 7s, and the ultra-fast response rate can realize rapid detection of hydrogen leakage. The response time is defined as the time required for the gas to be measured to start contacting the gas sensor until the resistance of the element drops to 90% of the stable resistance, and the recovery time is defined as the time required for the gas to be measured to separate from the gas sensor and desorb from the gas sensor until the resistance of the element returns to the baseline resistance.
Comparative example 1
The preparation method of the Pd 1@Pt0.5/In2O3 nano material of the comparative example specifically comprises the following steps:
S1, uniformly stirring 150mg of indium nitrate, 250mg of polyvinylpyrrolidone, 100mg of potassium bromide and 20mL of deionized water, transferring to a water bath kettle, adding 3.5mL of ammonia water and 50mL of deionized water to carry out hydrothermal reaction at 60 ℃ for 1h, centrifugally washing a reaction product with deionized water for 6 times, and drying In a 60 ℃ oven for 12h to obtain In 2O3 nano particles;
S2, ultrasonically dispersing In 2O3 nano particles prepared In the step S1 In 20mL of deionized water, uniformly mixing, adding 1mL of 10mM palladium chloride solution, 0.5mL of 10mM chloroplatinic acid solution and 20mL of deionized water, uniformly stirring, transferring the obtained solution to a magnetic stirrer for water bath reaction at 20 ℃, adding 20mL of 100mM ascorbic acid solution, carrying out dipping reaction for 22 hours, alternately centrifuging and washing the reaction product with deionized water and ethanol for 6 times, and drying In an oven at 60 ℃ for 12 hours to obtain a Pd 1@Pt0.5/In2O3 composite material;
And S3, mixing and grinding the Pd 1@Pt0.5/In2O3 composite material prepared in the step S2 with absolute ethyl alcohol to obtain paste, brushing a certain amount of paste with a zero-number writing brush, uniformly coating the paste on the A1 2O3 ceramic substrate printed with the Ag-Pd interdigital electrode, and aging the assembled device in a baking oven at 200 ℃ for 6 hours to obtain the hydrogen sensitive element.
The response value of the sensor to 6000ppm hydrogen at the working temperature of 200 ℃ is 12.31, and the detection lower limit is 50ppm.
Comparative example 2
The preparation method of the Pd 1@Pt1.5/In2O3 nano material of the comparative example specifically comprises the following steps:
S1, uniformly stirring 150mg of indium nitrate, 250mg of polyvinylpyrrolidone, 100mg of potassium bromide and 20mL of deionized water, transferring to a water bath kettle, adding 3.5mL of ammonia water and 50mL of deionized water to carry out hydrothermal reaction at 60 ℃ for 1h, centrifugally washing a reaction product with deionized water for 6 times, and drying In a 60 ℃ oven for 12h to obtain In 2O3 nano particles;
s2, ultrasonically dispersing In 2O3 nano particles prepared In the step S1 In 20mL of deionized water, uniformly mixing, adding 1mL of 10mM palladium chloride solution, 1.5mL of 10mM chloroplatinic acid solution hexahydrate and 20mL of deionized water, uniformly stirring, transferring the obtained solution to a magnetic stirrer for water bath reaction at 20 ℃, adding 20mL of 100mM ascorbic acid solution, carrying out dipping reaction for 22 hours, alternately centrifuging and washing the reaction product with deionized water and ethanol for 6 times, and drying In an oven at 60 ℃ for 12 hours to obtain a Pd 1@Pt1.5/In2O3 composite material;
and S3, mixing and grinding the Pd 1@Pt1.5/In2O3 composite material prepared in the step S2 with absolute ethyl alcohol to obtain paste, brushing a certain amount of paste with a zero-number writing brush, uniformly coating the paste on the A1 2O3 ceramic substrate printed with the Ag-Pd interdigital electrode, and aging the assembled device in a baking oven at 200 ℃ for 6 hours to obtain the hydrogen sensitive element.
The response value of the sensor to 6000ppm hydrogen at the working temperature of 200 ℃ is 14.22, and the detection lower limit is 5ppm.
The small knot:
TABLE 1 In 2O3 sensing Performance at different Pd to Pt loading ratios at 200℃
| Sensing material | Response value (6000 ppm) | Lower detection limit/ppm |
| Pd1@Pt0.5/In2O3 | 12.31 | 50 |
| Pd1@Pt1.0/In2O3 | 159 | 0.4 |
| Pd1@Pt1.5/In2O3 | 14.22 | 5 |
With the increase of the proportion of Pt, the sensing performance of the sensing material shows a trend of increasing and then decreasing, and the response value of Pd 1@Pt1.0/In2O3 to 6000ppm hydrogen at 200 ℃ is 12.97 times that of Pd 1@Pt0.5/In2O3 and 11.18 times that of Pd 1@Pt1.5/In2O3; the lower detection limit is 8 per mill of Pd 1@Pt0.5/In2O3 and 8 percent of Pd 1@Pt1.5/In2O3; in summary, it can be seen that when the ratio of Pd to Pt is 1: the response value is maximum and the detection lower limit is minimum when 1.
Comparative example 3
The preparation method of the 2.00 at% Pd/In 2O3 nanometer material of the comparative example specifically comprises the following steps:
S1, uniformly stirring 150mg of indium nitrate, 250mg of polyvinylpyrrolidone, 100mg of potassium bromide and 20mL of deionized water, transferring to a water bath kettle, adding 3.5mL of ammonia water and 50mL of deionized water to carry out hydrothermal reaction at 60 ℃ for 1h, centrifugally washing a reaction product with deionized water for 6 times, and drying In a 60 ℃ oven for 12h to obtain In 2O3 nano particles;
S2, ultrasonically dispersing In 2O3 nano particles prepared In the step S1 In 20mL of deionized water, uniformly mixing, adding 1mL of 10mM palladium chloride solution and 20mL of deionized water, uniformly stirring, transferring the obtained solution to a magnetic stirrer for water bath reaction at 20 ℃, adding 20mL of 100mM ascorbic acid solution, carrying out dipping reaction for 22 hours, alternately centrifuging and washing the reaction product with deionized water and ethanol for 6 times, and drying In a 60 ℃ oven for 12 hours to obtain a 1.00 at% Pd/In 2O3 composite material;
And S3, mixing the 2.00 at% Pd/In 2O3 composite material prepared In the step S2 with absolute ethyl alcohol, grinding to obtain paste, dipping a certain amount of paste by using a zero-number writing brush, uniformly coating the paste on an A1 2O3 ceramic substrate printed with Ag-Pd interdigital electrodes, and aging the assembled device In an oven at 200 ℃ for 6 hours to obtain the hydrogen sensitive element.
The sensor had a response value of 87.48 to 6000ppm hydrogen at 250℃operating temperature, with a lower detection limit of 0.5ppm.
The small knot:
TABLE 2 comparison of In 2O3 sensing Performance with whether optimum proportion Pt is supported at optimum load Pd proportion
| Sensing material | Response value (6000 ppm) | Operating temperature/. Degree.C | Lower detection limit/ppm |
| Pd1@Pt1.0/In2O3 | 159 | 200 | 0.4 |
| 2.00 at% Pd/In2O3 | 87.48 | 250 | 0.5 |
Comparison of the results according to example 1 and comparative example 3 shows that with addition of Pt In the appropriate proportion, the optimum operating temperature was reduced by 50 ℃ and was twice the response value of 2.00 at% Pd/In 2O3 to 6000ppm hydrogen, and the lower detection limit was reduced by 0.1ppm. The synergistic effect of Pt and Pd is proved to successfully improve the hydrogen sensitivity of the sensing material.
Comparative example 4
The preparation method of the 2.50 at% Pd/In 2O3 nanometer material of the comparative example specifically comprises the following steps:
S1, uniformly stirring 150mg of indium nitrate, 250mg of polyvinylpyrrolidone, 100mg of potassium bromide and 20mL of deionized water, transferring to a water bath kettle, adding 3.5mL of ammonia water and 50mL of deionized water to carry out hydrothermal reaction at 60 ℃ for 1h, centrifugally washing a reaction product with deionized water for 6 times, and drying In a 60 ℃ oven for 12h to obtain In 2O3 nano particles;
S2, ultrasonically dispersing In 2O3 nano particles prepared In the step S1 In 20mL of deionized water, uniformly mixing, adding 1.25mL of 10mM palladium chloride solution and 20mL of deionized water, uniformly stirring, transferring the obtained solution to a magnetic stirrer for water bath reaction at 20 ℃, adding 20mL of 100mM ascorbic acid solution, carrying out dipping reaction for 22 hours, alternately centrifuging and washing the reaction product with deionized water and ethanol for 6 times, and drying In an oven at 60 ℃ for 12 hours to obtain a 1.00 at% Pd/In 2O3 composite material;
And S3, mixing the 2.50 at% Pd/In 2O3 composite material prepared In the step S2 with absolute ethyl alcohol, grinding to obtain paste, dipping a certain amount of paste by using a zero-number writing brush, uniformly coating the paste on an A1 2O3 ceramic substrate printed with Ag-Pd interdigital electrodes, and aging the assembled device In an oven at 200 ℃ for 6 hours to obtain the hydrogen sensitive element.
The response value of the sensor to 6000ppm hydrogen at the working temperature of 250 ℃ is 40.87, and the detection lower limit is 10ppm.
The small knot: when the Pd loading is greater than 2%, the particles are more likely to agglomerate on the surface of In 2O3 so as to reduce the active sites, and the hydrogen sensitive material sensitivity is reduced, and when the Pd loading is greater than 2%, the Pd particles are more likely to agglomerate, so that the sensing performance can be greatly improved by selecting Pd with proper concentration to be loaded on In 2O3. The effect of example 1 is better than that of the comparative example.
The above embodiments are only for illustrating the present invention, not for limiting the present invention, and various changes and modifications may be made by one of ordinary skill in the relevant art without departing from the spirit and scope of the present invention, and therefore, all equivalent technical solutions are also within the scope of the present invention, and the scope of the present invention is defined by the claims.
Claims (5)
1. The preparation method of the Pd@Pt/In 2O3 nano material is characterized by comprising the following steps of:
Step S1: centrifugally washing a product of the reaction of indium nitrate, polyvinylpyrrolidone, potassium bromide, ammonia water and deionized water bath, and drying to obtain In 2O3 nano particles;
The mass ratio of the indium nitrate to the polyvinylpyrrolidone to the potassium bromide is 3:5:2 respectively; the dosage ratio of the indium nitrate, the ammonia water and the deionized water is 150mg:3.5ml:50ml;
Step S2: dispersing In 2O3 nano particles prepared In the step S1 In deionized water, adding a palladium chloride solution and a hexahydrated chloroplatinic acid solution to carry out magnetic stirring, and then adding an ascorbic acid solution to carry out reaction; after the reaction is finished, centrifugally washing and drying the product to obtain Pd@Pt/In 2O3 nano material;
Wherein the molar concentrations of the palladium chloride solution, the chloroplatinic acid solution and the ascorbic acid solution are 10mM, 10mM and 100mM, respectively; the molar ratio of indium nitrate to palladium chloride is 2:100, wherein the atomic ratio of Pd atoms to Pt atoms In the Pd@Pt/In 2O3 nano-material is 1:1;
the water bath reaction conditions in the step S1 are as follows: the reaction temperature is 60 ℃, and the reaction is carried out for 1h;
The drying treatment is as follows: drying at 60deg.C in air atmosphere for 12 hr;
the reaction conditions in the step S2 are that the reaction is carried out for 22 hours at 20 ℃.
2. The method for preparing the Pd@Pt/In 2O3 nano material according to claim 1, which is characterized by comprising the following steps: and in the step S2, centrifugal washing is carried out at a centrifugal speed of 10000r/min for 5-10min and washing times of 3-6 times.
3. A Pd@Pt/In 2O3 nano material is characterized In that: the nanomaterial is prepared by the preparation method of claim 1 or 2.
4. The use of a pd@pt/In 2O3 nanomaterial according to claim 3, wherein: the nanomaterial is applied to the preparation of a hydrogen sensor.
5. The application of the Pd@Pt/In 2O3 nanomaterial according to claim 4, wherein: and uniformly coating the nano material on an A1 2O3 ceramic substrate printed with Ag-Pd interdigital electrodes to obtain the Pd@Pt/In 2O3 gas sensor for the hydrogen sensor.
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