CN109368706B - Pd-modified three-dimensional hierarchical porous alpha-Fe2O3Material, preparation method and application thereof - Google Patents
Pd-modified three-dimensional hierarchical porous alpha-Fe2O3Material, preparation method and application thereof Download PDFInfo
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- 239000000463 material Substances 0.000 claims abstract description 42
- 239000002105 nanoparticle Substances 0.000 claims abstract description 35
- 238000001514 detection method Methods 0.000 claims abstract description 31
- 229910003145 α-Fe2O3 Inorganic materials 0.000 claims abstract description 31
- 229910000859 α-Fe Inorganic materials 0.000 claims abstract description 21
- KDLHZDBZIXYQEI-UHFFFAOYSA-N palladium Substances [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 claims description 60
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 claims description 36
- 239000002243 precursor Substances 0.000 claims description 24
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 19
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- 238000001354 calcination Methods 0.000 claims description 10
- 229910052742 iron Inorganic materials 0.000 claims description 9
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 8
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- 239000000843 powder Substances 0.000 claims description 4
- JRMUNVKIHCOMHV-UHFFFAOYSA-M tetrabutylammonium bromide Chemical compound [Br-].CCCC[N+](CCCC)(CCCC)CCCC JRMUNVKIHCOMHV-UHFFFAOYSA-M 0.000 claims description 4
- 229910021578 Iron(III) chloride Inorganic materials 0.000 claims description 3
- RBTARNINKXHZNM-UHFFFAOYSA-K iron trichloride Chemical compound Cl[Fe](Cl)Cl RBTARNINKXHZNM-UHFFFAOYSA-K 0.000 claims description 3
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- C01G49/00—Compounds of iron
- C01G49/02—Oxides; Hydroxides
- C01G49/06—Ferric oxide [Fe2O3]
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- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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- G01N27/127—Composition of the body, e.g. the composition of its sensitive layer comprising nanoparticles
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Abstract
The invention discloses Pd-modified three-dimensional hierarchical porous alpha-Fe2O3The material and the preparation method thereof, and the application of the material in detecting ethylene gas. The invention greatly improves alpha-Fe through the catalytic action of noble metal nano-particle Pd2O3The material has detection sensitivity to ethylene gas, and simultaneously reduces detection limit, thereby realizing high-sensitivity and low-detection-limit detection to ethylene gas. Three-dimensional grading porous alpha-Fe2O3The structure not only provides more adsorption sites for adsorbing Pd nano-particles, but also is beneficial to adsorbing more ethylene gas due to the large specific surface area. So Pd nanoparticles and three-dimensionally graded porous alpha-Fe2O3The synergistic effect of (A) realizes high sensitivity and low detection limit detection of ethylene gas.
Description
Technical Field
The invention relates to Pd modified three-dimensional porous alpha-Fe2O3A structural material and a preparation method and application thereof belong to the field of new materials.
Background
The ethylene gas is used as a plant hormone, and the judgment of the maturity grade of the fruits by detecting the ethylene gas released by the fruits has very important significance for fruit picking, processing and storage. Meanwhile, ethylene is flammable and explosive gas, and can form an explosive mixture when being mixed with air, and if the ethylene meets open fire, high heat or contacts with an oxidant, the ethylene has the danger of causing combustion and explosion. And the method can also be used for analyzing lipid peroxidation of cells in the human body by detecting the content of ethylene in the exhaled air of the human body, further analyzing pathological changes of organs in the human body, researching pathogenesis of related diseases and achieving the aim of effective prevention through early detection. Efficient and rapid detection of ethylene gas is therefore of great importance to industry, agriculture and biological health.
The detection difficulty of ethylene gas is high, the sensitivity is low, and high-temperature detection is mostly adopted. The traditional method for detecting ethylene mainly adopts chromatographic analysis, which is time-consuming and labor-consuming and has poor use flexibility. Although the sensor technology, the optical detection technology, the fluorescence detection technology and the like are also reported for ethylene detection, the detection limit is not high, the sensitivity is poor, and the rapid high-sensitivity detection of low-concentration ethylene is difficult to realize. Therefore, it is necessary and meaningful to develop a rapid and highly sensitive detection technique and method for low concentration ethylene.
Metal oxide semiconductor nanomaterials are widely used in gas sensitive research due to their unique advantages, such as alpha-Fe2O3As an n-type semiconductor having a band gap width of 2.1eV, it is commonly used for detecting liquefied petroleum gas, ethanol gas, acetone gas, and hydrogen sulfide gas, but it has a problem of low sensitivity and cross-sensitivity.
Disclosure of Invention
The invention aims to provide Pd modified three-dimensional hierarchical porous alpha-Fe2O3The material and the preparation method thereof, and the application of the material in detecting ethylene gas.
The invention relates to Pd-modified three-dimensional hierarchical porous alpha-Fe2O3Material of alpha-Fe2O3alpha-Fe with a structure of flake2O3Self-assembled and stacked flower-shaped alpha-Fe2O3Pd nanoparticles modified on alpha-Fe2O3On the sheet layer, Pd nano-particle rulerCun is distributed between 10-30 nm.
The invention relates to Pd-modified three-dimensional hierarchical porous alpha-Fe2O3The preparation method of the material comprises the steps of preparing an amorphous iron-containing precursor, preparing Pd nanoparticles, adsorbing the Pd nanoparticles onto the precursor and calcining.
The Pd modified three-dimensional hierarchical porous alpha-Fe2O3In the preparation method of the material, preferably, the preparation step of the amorphous iron-containing precursor comprises:
(1) FeCl is added3·6H2Dissolving O, urea and tetrabutylammonium bromide in ethylene glycol, fully stirring and dissolving, heating to 170-200 ℃, and waiting until the color of the solution turns green completely;
(2) and centrifuging, washing and drying the product to obtain the amorphous iron-containing precursor.
The Pd modified three-dimensional hierarchical porous alpha-Fe2O3In the method for preparing a material, preferably, the step of preparing the Pd nanoparticles includes:
(1) dissolving palladium chloride in hydrochloric acid, dissolving polyvinylpyrrolidone in ethylene glycol, and slowly adding the two solutions into the ethylene glycol at the temperature of 100-150 ℃;
(2) after the solution reacts for 10-20min, adding NaOH solution, and continuously stirring at the temperature of 100-150 ℃ for 8-10h to obtain the solution containing Pd nano-particles.
The Pd modified three-dimensional hierarchical porous alpha-Fe2O3In the preparation method of the material, preferably, the step of adsorbing the Pd nanoparticles onto the amorphous iron-containing precursor is to take the Pd-nanoparticle-containing solution obtained in the preparation step of the Pd nanoparticles, add the iron-containing precursor, and perform table shaking reaction at a temperature of 40-60 ℃ to enable the Pd nanoparticles to be uniformly adsorbed onto the sheet layer of the precursor.
The Pd modified three-dimensional hierarchical porous alpha-Fe2O3In the preparation method of the material, preferably, the calcination step is calcination at 300-400 ℃ for 1-3 h.
The Pd-modified three-dimensional hierarchical porous structureα-Fe2O3In the preparation method of the material, the following steps are preferably included:
step 1: 0.5-0.8g FeCl3·6H2Dissolving 1.2-1.5g of urea and 3-4g of tetrabutylammonium bromide in 80-100mL of ethylene glycol, fully stirring and dissolving, heating to 170-;
step 2: centrifuging, washing and drying the product to obtain an amorphous iron-containing precursor;
and step 3: dissolving 0.07-0.09g of palladium chloride in 2mL of 0.15-0.2g/mL hydrochloric acid, dissolving 0.08-0.1g of polyvinylpyrrolidone in 4-6mL of ethylene glycol, and slowly adding the two solutions into 100-150 ℃ ethylene glycol at the same time;
and 4, step 4: after the solution reacts for 10-20min, 6-7mL of 0.006-0.007g/mL NaOH solution is added, and the solution containing Pd nano-particles is prepared after continuous stirring at the temperature of 100-150 ℃ for 8-10 h;
and 5: taking the precursor powder prepared in the step 2, adding a solution containing Pd nano-particles, and carrying out table shaking reaction for 4-6 hours at the temperature of 40-60 ℃ to ensure that the Pd nano-particles are uniformly adsorbed on the sheet layer of the amorphous precursor; the rotating speed of the shaking table is 200-300 rmp;
step 6: calcining the amorphous precursor adsorbed with the Pd nano-particles at the temperature of 300-400 ℃ for 1-3h to obtain the Pd-modified three-dimensional hierarchical porous alpha-Fe2O3And (5) structure.
The Pd modified three-dimensional hierarchical porous alpha-Fe2O3In the preparation method of the material, preferably, in the step 2, the rotation speed during the centrifugal treatment is 5000-7000 r/min, and the washing treatment is alternately and respectively washing with water and ethanol for 3-5 times; the drying temperature is 50-70 ℃, and the drying time is 10-13 h.
The Pd modified three-dimensional hierarchical porous alpha-Fe2O3In the preparation method of the material, preferably, in the step 6, the temperature rising speed is 1-3 ℃/min, and the temperature is reduced to room temperature along with the furnace during temperature reduction.
The Pd-modified three-dimensional hierarchical porous alpha-Fe provided by the invention2O3The material can be applied to the detection of ethylene gas. In detection applicationsCan be used for three-dimensional grading porous alpha-Fe modified by Pd2O3The material is applied to the surface of a ceramic tube of a commonly used gas detection sensor. The invention realizes the high-sensitivity detection of the structure on the ethylene gas by utilizing the catalytic action of Pd on the carbon-carbon double bond fracture of the ethylene gas. The specific implementation mode is as follows: taking a proper amount of the materials, dispersing the materials in an ethanol solution, and taking 5-10 mu L of Pd modified three-dimensional hierarchical porous alpha-Fe by using a liquid-transferring gun2O3And (3) coating the suspension of the material on the ceramic tube of the sensor to ensure that the material is uniformly coated on the surface of the ceramic tube. And then putting the sensor coated with the material into a gas chamber, heating to 300 ℃, aging for 2-5h, introducing ethylene gas with a certain concentration into the gas chamber, reacting for 2-4min, introducing air, expelling the ethylene gas out of the gas chamber, and detecting the sensitivity of the gas by the ratio of the resistance change of the material before and after the gas introduction, wherein the specific test result is shown in figure 4.
The flower-shaped three-dimensional hierarchical structure self-assembled by the porous ultrathin nano sheets is beneficial to the adsorption and diffusion of gas, and meanwhile, the noble metal nano particles are modified on the surface of the hierarchical structure through electrostatic action, so that the catalytic action of the noble metal nano particles can be effectively utilized. The invention constructs a new material made of alpha-Fe2O3The three-dimensional hierarchical porous structure self-assembled by the porous nanosheets is modified with Pd nanoparticles on the lamellar structure, and the response sensitivity of the three-dimensional hierarchical porous structure is improved by utilizing the synergistic effect of the Pd nanoparticles and the Pd nanoparticles.
The invention has the beneficial effects that: the alpha-Fe can be greatly improved by the catalytic action of noble metal nano-particle Pd (the catalytic action of Pd is beneficial to the carbon-carbon double bond fracture of ethylene gas)2O3The material has the detection sensitivity to ethylene gas, reduces the detection limit, realizes the detection of ethylene gas with high sensitivity and low detection limit, and leads the Pd-modified three-dimensional porous alpha-Fe of the invention2O3The material is more suitable to be used as a gas sensitive material for ethylene gas detection. Three-dimensional grading porous alpha-Fe2O3The structure not only provides more adsorption sites for adsorbing Pd nano-particles, but also is beneficial to adsorbing more ethylene gas due to the large specific surface area. So Pd nanoparticles and three-dimensional porous graded alpha-Fe2O3The synergistic effect of (A) realizes high sensitivity and low detection limit detection of ethylene gas. Meanwhile, the invention discovers that when the adsorption capacity (detected by EDS energy spectrum) of Pd is 2% -3.5%, the catalytic action of Pd is strongest, the detection sensitivity is about 46 for 1000ppm of ethylene gas, the test temperature is 300 ℃, and the specific detection performance is shown in attached figures 4 and 5.
Drawings
FIG. 1 is this Pd-modified three-dimensional porous alpha-Fe2O3The material synthesis flow chart comprises the steps of firstly preparing a precursor by a simple hydrothermal method, then adsorbing Pd nano particles on a sheet layer with a three-dimensional hierarchical structure, and finally calcining to convert the phase of the precursor into alpha-Fe with a crystalline state from an amorphous state2O3While at the same time, due to the gas generation during the calcination, in alpha-Fe2O3A large number of pores are generated on the sheet layer, and finally Pd modified three-dimensional porous alpha-Fe is formed2O3And (5) structure.
FIG. 2 is an SEM image of the product obtained during the synthesis of the material of the present invention, wherein (a) is an SEM image of a precursor obtained by hydrothermal method, and the flower-like structure formed by stacking sheets can be clearly seen; (b) the figure is three-dimensional grading porous alpha-Fe obtained after calcining the precursor2O3The flower-like alpha-Fe is clearly seen in the SEM picture2O3A large number of holes are produced in the sheets of the structure; (c) the figure shows that the three-dimensional grading porous alpha-Fe2O3SEM images after Pd nanoparticles were modified on the sheets of the structure.
Figure 3 is an XRD spectrum. As can be seen, the initial hydrothermal precursor is an amorphous (non-crystalline) structure, and the alpha-Fe with good crystallinity is obtained by calcination2O3When the amount of the modified Pd is less, the XRD spectrum has no peak corresponding to Pd, but when the content of the modified Pd reaches 4.65%, the peak of Pd can be obviously seen in the XRD spectrum, as shown in FIG. 2.
FIG. 4 is a graph showing the sensitivity characteristics of the product obtained in the example in an ethylene gas atmosphere having a concentration of 100 to 1500ppm, at a working temperature of 300 ℃. It can be seen from the figure that the product obtained in the example has fast response speed to ethylene, good recovery performance, and response sensitivity as high as 46 to 1000ppm of ethylene, and the response sensitivity is the ratio of the resistance of the material before and after reaction. When the concentration of ethylene gas reached 1500ppm, the response value tended to be saturated.
FIG. 5 is a graph of three-dimensional grading of alpha-Fe with different Pd modification amounts at an optimum working temperature of 300 deg.C2O3The line graph of the response sensitivity of the structure to 500ppm ethylene gas. As can be seen, when this three-dimensional grading of alpha-Fe is carried out2O3After the Pd nano-particles are structurally modified, the response sensitivity of the Pd nano-particles to ethylene gas is greatly improved, and the sensitivity is highest when the modification amount of Pd is 2-3.5%. In the graph, the response curve of Pd to 1ppm of ethylene gas is shown when the amount of Pd modification is 2-3.5%, and it can be seen that the response is still obtained when the concentration of ethylene gas is 1ppm, and the response value is about 2. Therefore, 2-3.5% Pd modified three-dimensional grading alpha-Fe2O3The lowest detection limit of the structure on ethylene gas can reach 1 ppm.
Detailed Description
Examples
The Pd-modified three-dimensional hierarchical porous alpha-Fe of the invention2O3The preparation method of the material comprises the following steps:
step 1: 0.6g FeCl3·6H2Dissolving 1.35g of urea and 3.6g of tetrabutylammonium bromide in 90mL of ethylene glycol, fully stirring and dissolving, and heating to 170 ℃ until the color of the solution is completely changed to green.
Step 2: and centrifuging, washing and drying the product to obtain flower-shaped amorphous iron-containing precursor powder.
And step 3: 0.085g of palladium chloride was dissolved in 2mL of hydrochloric acid at 0.2g/mL, 0.08g of polyvinylpyrrolidone was dissolved in 5mL of ethylene glycol, and both solutions were slowly added to ethylene glycol at 120 ℃.
And 4, step 4: after the solution reacts for 15min, 6.5mL of NaOH solution with the concentration of 0.007g/mL is added, and the solution containing the Pd nano-particles is prepared after continuous stirring for 9h at the temperature of 120 ℃.
And 5: and (3) taking a certain amount of the precursor powder prepared in the step (2), respectively adding different amounts of solutions containing the Pd nano-particles, and carrying out shaking table reaction for 5 hours at the temperature of 50 ℃, wherein the rotation speed of the shaking table is 250rpm, so that the Pd nano-particles are uniformly adsorbed on the flower-shaped precursor sheet layer.
Step 6: calcining the flower-like precursor adsorbed with the Pd nano-particles with different contents at 350 ℃ for 2h to obtain the three-dimensional hierarchical porous alpha-Fe with different Pd modification amounts2O3And (5) structure.
Application example
Pd-modified three-dimensional graded porous alpha-Fe prepared in example2O3The material is uniformly dispersed in an ethanol solution, and a liquid-transfering gun is used for taking three-dimensional hierarchical porous alpha-Fe modified by 5-10 mu LPd2O3And the suspension of the material is coated on the surface of the ceramic tube of the sensor, so that the material is uniformly coated on the surface of the ceramic tube. And (3) placing the sensor coated with the sensitive material in an air chamber, heating to the test temperature of 300 ℃, aging for 2-5h, introducing ethylene gas for detection, introducing air after reacting for 2-4min, expelling the ethylene gas, and expressing the response sensitivity to the ethylene gas by the ratio of the resistance values of the material before and after the ethylene gas is adsorbed. Test results show that 2-3.5% of Pd modified three-dimensional hierarchical porous alpha-Fe2O3The material has the highest detection sensitivity to ethylene gas, the response sensitivity to 1000ppm of ethylene gas at the working temperature of 300 ℃ is about 46, and the lowest detection limit can reach 1 ppm.
Claims (3)
1. Pd-modified three-dimensional hierarchical porous alpha-Fe2O3Material of alpha-Fe2O3alpha-Fe with a structure of flake2O3Self-assembled and stacked flower-shaped alpha-Fe2O3Pd nanoparticles modified on alpha-Fe2O3The size of the Pd nano-particles is distributed between 10 nm and 30nm, and the modification amount of Pd is 2-3.5%.
2. The Pd-modified three-dimensional hierarchical porous alpha-Fe as defined in claim 12O3The preparation method of the material is characterized by comprising the following steps:
step 1: 0.5-0.8g FeCl3•6H2Dissolving 1.2-1.5g of urea and 3-4g of tetrabutylammonium bromide in 80-100mL of ethylene glycol, fully stirring and dissolving, heating to 170-;
step 2: centrifuging, washing and drying the product to obtain an amorphous iron-containing precursor;
and step 3: dissolving 0.07-0.09g of palladium chloride in 2mL of 0.15-0.2g/mL hydrochloric acid, dissolving 0.08-0.1g of polyvinylpyrrolidone in 4-6mL of ethylene glycol, and slowly adding the two solutions into 100-150 ℃ ethylene glycol;
and 4, step 4: after the solution reacts for 10-20min, 6-7mL of 0.006-0.007g/mL NaOH solution is added, and the solution containing Pd nano-particles is prepared after continuous stirring at the temperature of 100-150 ℃ for 8-10 h;
and 5: taking the precursor powder prepared in the step 2, adding a solution containing Pd nano-particles, and carrying out table shaking reaction for 4-6 hours at the temperature of 40-60 ℃ to ensure that the Pd nano-particles are uniformly adsorbed on the amorphous iron-containing precursor sheet layer; the rotating speed of the shaking table is 200-300 rpm;
step 6: calcining the precursor adsorbed with the Pd nano-particles at the temperature of 300-400 ℃ for 1-3h to obtain the Pd-modified three-dimensional hierarchical porous alpha-Fe2O3And (5) structure.
3. The Pd-modified three-dimensionally fractionated porous α -Fe as set forth in claim 12O3Material or Pd-modified three-dimensional graded porous alpha-Fe obtained by the preparation method of claim 22O3The application of the material in ethylene gas detection.
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| CN1228535A (en) * | 1998-03-05 | 1999-09-15 | 中国科学院大连化学物理研究所 | Ethylene sensor for fire alarm of coal mine |
| CN100494076C (en) * | 2004-10-21 | 2009-06-03 | 北京大学 | Transition metal-magnetic ferric oxide nano-composite material, its production and uses |
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