A micro-flower-like manganese cobalt oxide composite catalyst, its preparation method and application
By preparing the micro-flower-like manganese cobalt oxide composite catalyst Pt@δ-MnO2@MnCo2O4, the problems of complex preparation and poor performance of existing catalysts were solved, and the effect of efficient catalytic oxidation of formaldehyde and benzene series compounds at room temperature was achieved, improving the stability and activity of the catalyst.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- TIANJIN POLYTECHNIC UNIV
- Filing Date
- 2024-01-08
- Publication Date
- 2026-05-05
AI Technical Summary
Existing composite catalysts have complex preparation processes, poor catalytic degradation performance, and high raw material costs, making it difficult to efficiently catalyze the oxidation of formaldehyde and benzene compounds such as toluene at room temperature.
A spinel-structured MnCo2O4 support was prepared by using a micro-flower-like manganese cobalt oxide composite catalyst Pt@δ-MnO2@MnCo2O4 via a solvothermal method and heat treatment. δ-MnO2 and Pt nanoparticles were then loaded onto its surface to form a heterojunction, thereby improving the catalytic activity.
It significantly reduces the concentration of formaldehyde and benzene compounds at room temperature, improves catalytic efficiency by more than 80%, has a simple preparation process, mild reaction conditions, provides more contact sites, and improves catalytic performance.
Smart Images
Figure CN117943053B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of composite catalysts, and more specifically to a micro-flower-like manganese cobalt oxide composite catalyst Pt@δ-MnO2@MnCo2O4, its preparation method, and its application in the catalytic degradation of organic pollutants. Background Technology
[0002] Indoor air pollution poses a significant threat to human health, with formaldehyde and benzene compounds (such as toluene) among the main harmful substances. Catalytic degradation technology is considered an effective and environmentally friendly method for treating these pollutants. Currently, various catalysts have been developed, such as those supported on transition metal oxides (MnO2, Co3O4, CeO2, etc.) and those supported on noble metals (such as Au, Pt, Pd, etc.). Transition metal oxide catalysts, such as MnO2, typically require relatively high temperatures (>150℃) to achieve a good catalytic effect on formaldehyde and benzene compounds, thus completely removing the pollutants. In contrast, noble metal catalysts often exhibit good catalytic effects at lower temperatures or even room temperature; however, they are more expensive.
[0003] To address the above problems, there is an urgent need for a composite catalyst capable of efficiently catalytically degrading formaldehyde and benzene compounds at room temperature. Spinel ferrites are widely used as catalyst supports, among which n-type semiconductor MnCo2O4 possesses advantages such as narrow band gap, high catalytic activity, good chemical stability, and environmental friendliness. These unique advantages make it a promising candidate material for the catalytic degradation of pollutants. MnCo2O4 has attracted widespread attention because it can effectively combine transition metal oxide particles and noble metal nanoparticles, enhancing the catalytic degradation effect through the generation of atomic vacancies and occupied sites. Therefore, this patent discloses a stable and simple composite catalyst material and its preparation method using micro-flower-like MnCo2O4 as the active support, aiming to solve the problem of efficient catalytic degradation of formaldehyde and benzene compounds at room temperature. Summary of the Invention
[0004] Therefore, the technical problem to be solved by the present invention is that existing composite catalysts have problems such as complex preparation processes, poor catalytic degradation performance of pollutants, and high raw material costs.
[0005] To address the aforementioned technical problems, this invention proposes a micro-flower-like composite catalyst material and its preparation method, which can significantly catalyze the oxidation of formaldehyde and benzene compounds at room temperature, thereby reducing the concentration of formaldehyde and benzene compounds.
[0006] This invention provides the following technical solution:
[0007] A micro-flower-like manganese cobalt oxide composite catalyst, Pt@δ-MnO2@MnCo2O4, is a spinel-structured transition metal oxide, MnCo2O4, composed of oxygen ions arranged in a cubic close-packed pattern. 2+ Filling one-eighth of the tetrahedral voids, Co 3+ The Pt@δ-MnO2@MnCo2O4 composite catalyst, which fills half of the octahedral voids, has a micro-flower-like morphology. The "petals" are 10 nm to 15 nm thick and uniformly distributed. The micro-flower diameter is 1.5 μm to 2 μm. The MnCo2O4 support has a micro-flower-like morphology with abundant voids and a large specific surface area, providing more contact sites. δ-MnO2 particles and Pt nanoparticles are uniformly loaded on the surface of the micro-flower. δ-MnO2 particles are plate-like microspheres aggregated on the surface of the MnCo2O4 micro-flower, with a diameter of 90 nm to 120 nm. Pt nanoparticles are fine particles uniformly loaded on the surface of the MnCo2O4 micro-flower, with a diameter of 1 nm to 2 nm. The surface of the above micro-flower-like manganese cobalt oxide composite catalyst is rough, and a heterojunction is formed between δ-MnO2 and MnCo2O4.
[0008] The above-mentioned micro-flower-like manganese cobalt oxide composite catalyst Pt@δ-MnO2@MnCo2O4 was prepared by solvothermal method and heat treatment. This composite catalyst has both high catalytic activity and high stability.
[0009] A method for preparing the micro-flower-like composite catalyst Pt@δ-MnO2@MnCo2O4, which is composed of micro-flower-like MnCo2O4 stably supported δ-MnO2 particles and Pt nanoparticles, includes the following steps:
[0010] Step 1: Preparation of MnCo2O4 support:
[0011] Using Mn(CH3COO)2·4H2O and Co(CH3COO)2·4H2O as Mn and Co sources, and PVP as a surface protectant, MnCo2O4 nanosheet precursors were prepared by solvothermal method. The obtained precursor solution was then transferred to a stainless steel high-pressure reactor for heat treatment reaction, and finally naturally cooled to room temperature to obtain MnCo2O4 microflowers.
[0012] Step 2: Preparation of Pt@δ-MnO2@MnCo2O4:
[0013] Using KMnO4 and MnSO4·H2O as Mn sources, δ-MnO2 was loaded onto MnCo2O4 microflowers by deposition-precipitation method, while heterojunctions were formed between δ-MnO2 and MnCo2O4. After centrifugation, washing and vacuum drying, Pt@δ-MnO2@MnCo2O4 was obtained.
[0014] Step 3: Preparation of Pt@δ-MnO2@MnCo2O4:
[0015] Pt nanoparticles were synthesized in situ on the surface of δ-MnO2@MnCo2O4 using H2PtCl6·6H2O as the Pt source and NaBH4 as the reducing agent, thus preparing a Pt@δ-MnO2@MnCo2O4 micro-flower-like composite catalyst.
[0016] In step one, the temperature inside the stainless steel high-pressure reactor is kept constant at 180°C for 12 hours.
[0017] In step two, by controlling the mass ratio of MnCo2O4 to KMnO4 and MnSO4·H2O, the former to the sum of the latter two is controlled at 2.0∶1 to 10.0∶1, so that the mass ratio of the product MnCo2O4 to δ-MnO2 is controlled at 2.7∶1 to 13.6∶1.
[0018] In step two, the deposition-precipitation method involves heating and stirring in a 60°C water bath for 3 hours.
[0019] In step three, the concentration range of H2PtCl6·6H2O is 0.09M to 0.10M, and the mass fraction of the loaded Pt in Pt@δ-MnO2@MnCo2O4 is controlled between 0.1wt% and 1wt%.
[0020] The microflora-like catalyst Pt@δ-MnO2@MnCo2O4 according to the present invention can significantly reduce the formaldehyde concentration when used for catalytic oxidation of formaldehyde at room temperature.
[0021] The microflora-like catalyst Pt@δ-MnO2@MnCo2O4 according to the present invention is used for the catalytic degradation of substances other than formaldehyde. The catalytic degradation of substances other than formaldehyde can be the catalytic degradation of benzene series compounds. Specifically, the catalytic degradation of benzene series compounds can be the catalytic degradation of toluene.
[0022] The present invention discloses the following technical effects:
[0023] (1) The micro-flower-like catalyst Pt@δ-MnO2@MnCo2O4 synthesized in this invention has both high stability and catalytic activity, and has a large specific surface area to provide more contact sites, which provides good conditions for subsequent catalysis.
[0024] (2) The catalytic performance of the Pt@δ-MnO2@MnCo2O4 micro-flower-like composite catalyst for low concentrations of formaldehyde and toluene was studied at room temperature (25℃) with different ratios and initial concentrations. The results showed that the catalyst with a mass ratio of MnCo2O4 to KMnO4 and MnSO4·H2O of 4.0:1 exhibited good formaldehyde and toluene removal performance. The catalytic performance was significantly improved after loading Pt nanoparticles, and the catalytic efficiency was also improved with the increase of Pt loading.
[0025] (3) The preparation route of this invention is simple and the reaction conditions are mild. The reaction process is highly controllable, and materials with different properties can be obtained as needed by changing the reaction conditions and various experimental variables. Attached Figure Description
[0026] Figure 1 This is a scanning electron microscope image of the Pt@δ-MnO2@MnCo2O4 microflora catalyst prepared in Example 1 of the present invention.
[0027] Figure 2 This is a field emission high-resolution transmission electron microscope image of the Pt@δ-MnO2@MnCo2O4 microflora catalyst prepared in Example 1 of the present invention. Detailed Implementation
[0028] Specific embodiments of the present invention are given below. These specific embodiments are only used to further illustrate the present invention in detail and do not limit the scope of protection of the claims of the present invention.
[0029] A micro-flower-like manganese cobalt oxide composite catalyst Pt@δ-MnO2@MnCo2O4,
[0030] Spinel-structured transition metal oxide MnCo2O4 is composed of oxygen ions arranged in a cubic close-packed manner. 2+ Filling one-eighth of the tetrahedral voids, Co 3+ The Pt@δ-MnO2@MnCo2O4 composite catalyst, which fills half of the octahedral voids, has a micro-flower-like morphology. The "petals" are 10 nm to 15 nm thick and uniformly distributed. The micro-flower diameter is 1.5 μm to 2 μm. The MnCo2O4 support has a micro-flower-like morphology and abundant voids, providing more contact sites due to its large specific surface area. δ-MnO2 particles and Pt nanoparticles are uniformly loaded on the surface of the micro-flower. δ-MnO2 particles are plate-like microspheres aggregated on the surface of the MnCo2O4 micro-flower, with a diameter of 90 nm to 120 nm. Pt nanoparticles are fine particles uniformly loaded on the surface of the MnCo2O4 micro-flower, with a diameter of 1 nm to 2 nm. The surface of the above micro-flower-like manganese cobalt oxide composite catalyst is rough, and a heterojunction is formed between δ-MnO2 and MnCo2O4.
[0031] A method for preparing a micro-flower-like manganese cobalt oxide composite catalyst (Pt@δ-MnO2@MnCo2O4) (hereinafter referred to as the method), the method comprising the following steps:
[0032] Step 1: Preparation of MnCo2O4 support
[0033] First, using manganese acetate (Mn(CH3COO)2·4H2O) and cobalt acetate (Co(CH3COO)2·4H2O) as Mn and Co sources, and polyvinylpyrrolidone (PVP) as a surface protectant, MnCo2O4 nanosheet precursors were prepared by a solvothermal method. Then, the obtained precursor solution was transferred to a stainless steel high-pressure reactor for heat treatment reaction. Finally, after natural cooling to room temperature, MnCo2O4 microflowers were obtained.
[0034] Step 2: Preparation of δ-MnO2@MnCo2O4
[0035] Using potassium permanganate (KMnO4) and manganese sulfate hydrate (MnSO4·H2O) as Mn sources, δ-MnO2 was loaded onto MnCo2O4 microflowers by deposition-precipitation method. At the same time, heterojunctions were formed between δ-MnO2 and MnCo2O4. After centrifugation, washing and vacuum drying, δ-MnO2@MnCo2O4 was obtained.
[0036] Step 3: Preparation of Pt@δ-MnO2@MnCo2O4
[0037] Using chloroplatinic acid hexahydrate (H2PtCl6·6H2O) as the Pt source and sodium borohydride (NaBH4) as the reducing agent, Pt nanoparticles were synthesized in situ on the surface of δ-MnO2@MnCo2O4 to prepare a Pt@δ-MnO2@MnCo2O4 micro-flower-like composite catalyst.
[0038] Furthermore, the MnCo2O4 microflowers described in step one have a diameter of 1.5–2 μm, a petal thickness of 10–15 nm, and good morphology;
[0039] Furthermore, the temperature inside the stainless steel high-pressure reactor described in step one is kept constant at 180°C for 12 hours.
[0040] Furthermore, in step two, by controlling the mass ratio of MnCo2O4 to KMnO4 and MnSO4·H2O, the former to the sum of the latter two is controlled at 2.0∶1 to 10.0∶1, the mass ratio of the product MnCo2O4 to δ-MnO2 is controlled at 2.7∶1 to 13.6∶1.
[0041] Furthermore, the deposition-precipitation method described in step two involves heating and stirring in a 60°C water bath for 3 hours;
[0042] Furthermore, the concentration range of H2PtCl6·6H2O in step two is 0.09M to 0.10M, and the mass fraction of the loaded Pt in Pt@δ-MnO2@MnCo2O4 is controlled between 0.1wt% and 1wt%.
[0043] Furthermore, the micro-flower-like composite catalyst Pt@δ-MnO2@MnCo2O4 prepared through the above steps is characterized by its ability to significantly reduce formaldehyde concentration when used for catalytic oxidation of formaldehyde at room temperature.
[0044] Furthermore, the micro-flower-like composite catalyst Pt@δ-MnO2@MnCo2O4 prepared through the above steps can be used for the catalytic degradation of substances other than formaldehyde.
[0045] Furthermore, the micro-flower-like composite catalyst Pt@δ-MnO2@MnCo2O4 prepared through the above steps can be used for the catalytic degradation of substances other than formaldehyde into benzene compounds.
[0046] Furthermore, the micro-flower-like composite catalyst Pt@δ-MnO2@MnCo2O4 prepared through the above steps is used for the catalytic degradation of the benzene series compounds, specifically the catalytic degradation of toluene.
[0047] In the embodiments of this invention, the catalytic oxidation of formaldehyde was tested and analyzed as follows: The Pt@δ-MnO2@MnCo2O4 micro-flower composite catalyst exhibited significant catalytic performance for low-concentration formaldehyde at room temperature (25℃) under different ratios, initial concentrations, and relative humidity. The catalyst with MnCo2O4 / δ-MnO2 (2∶1) showed good formaldehyde removal performance. After loading Pt nanoparticles, the catalytic performance was significantly improved (>94%), and the formaldehyde catalytic performance gradually increased (94%, 95%, 96%, 98%) with increasing Pt loading (0.1wt%, 0.2wt%, 0.5wt%, 1wt%). Compared to pure MnCo2O4 micro-flowers, the catalytic efficiency was increased by up to 80% at an initial concentration of 1 mg / m³. 3 At 0.8 ppm, the formaldehyde removal rate reached 94% within 120 minutes, and after 4 cycles of experiment, the formaldehyde removal rate still reached 92%.
[0048] In the embodiments of the present invention, the catalytic oxidation of toluene was tested and analyzed as follows: The Pt@δ-MnO2@MnCo2O4 micro-flower-like composite catalyst exhibited significant catalytic performance for low concentrations of toluene at room temperature (25°C) under different ratios, different initial concentrations, and different relative humidity. The catalyst with MnCo2O4 / δ-MnO2 (2∶1) showed better toluene removal performance. The catalytic performance was significantly improved after loading Pt nanoparticles, and the toluene catalytic performance gradually increased (70%, 72%, 74%, 76%) with the increase of Pt loading (0.1wt%, 0.2wt%, 0.5wt%, 1wt%).
[0049] The morphology characterization methods for the Pt@δ-MnO2@MnCo2O4 micro-flower-like composite catalyst were transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron surface energy dispersive spectroscopy (XPS), and specific surface area analysis (BET).
[0050] Catalysis tests: Formaldehyde catalytic performance was tested using a fully mixed batch mode, and toluene catalytic performance was tested using a micro-fixed bed stainless steel reaction tube apparatus.
[0051] Example 1
[0052] (1) First, take a clean 250mL round-bottom flask and add 2.5mL of deionized water and 200mL of ethylene glycol. Weigh 0.6125g of manganese acetate (Mn(CH3COO)2·4H2O) and 1.245g of cobalt acetate (Co(CH3COO)2·4H2O) and add them to the round-bottom flask. Seal the round-bottom flask with sealing glue and stir it on a magnetic stirrer until a transparent solution is obtained. Add 0.5475g of polyvinylpyrrolidone (PVP) to the above solution and transfer the resulting solution to a Teflon-lined stainless steel high-pressure reactor. Place it in an oven and react at a constant temperature of 180℃ for 12h. After naturally cooling to room temperature, remove the reactor and pour the solution in the liner into a centrifuge tube. Set the speed to 10000r / min and centrifuge for 10min to obtain the cobalt-manganese compound. Wash the compound four times with distilled water and ethanol. Dry the precipitate in air at 80℃ for 10h. The temperature was increased to 500℃ in air at a heating rate of 2℃ / min, and then heat-treated at that temperature for 4 hours (a total of 8 hours and 10 minutes). After that, it was naturally cooled to room temperature to obtain micro-flower-like MnCo2O4.
[0053] (2) Weigh 0.2 g of the synthesized micro-flower-like MnCo2O4 powder into a 50 mL round-bottom flask, add 30 mL of deionized water, and stir magnetically for 15 min to disperse it evenly. After even dispersion, add 0.05 g of KMnO4 and MnSO4·H2O, heat and stir in a 60 °C water bath for 3 h, transfer the precipitate generated after the reaction to a 50 mL centrifuge tube, centrifuge at 10000 r / min for 10 min, wash with deionized water 4 times, and transfer the material after the last centrifugation to a vacuum drying oven and vacuum dry at 25 °C for 12 h.
[0054] (3) Dissolve 1g of chloroplatinic acid hexahydrate (H2PtCl6·6H2O) in 20mL of water to obtain a chloroplatinic acid solution with a concentration of 0.09654mol / L. Weigh 0.5g of MnCo2O4 powder loaded with δ-MnO2 in the above steps into a 50mL round-bottom flask, and disperse it in 10mL of deionized water by magnetic stirring for 15min. Measure a certain volume of 0.09654mol / L chloroplatinic acid solution (Pt loading is 0.1wt%), insert a needle below the liquid surface of the round-bottom flask and add it. Seal and protect from light, and stir magnetically for 12h. Weigh 0.0189g of NaBH4 and 0.02g of NaOH into a 50mL beaker, add 5mL of deionized water, stir thoroughly to dissolve, and then quickly add to the round-bottom flask. Seal and protect from light, and stir for 30min. The above solution was centrifuged at 10,000 r / min and washed four times with deionized water. The solution was ultrasonically dispersed for 10 min between each wash. After the last centrifugation, the supernatant was discarded and the product was placed in an oven and dried at 80°C for 8 h.
[0055] The overall morphology of the obtained catalyst particles was analyzed using field emission scanning electron microscopy, such as... Figure 1 As shown, the composite catalyst exhibits a unique micro-flower-like morphology, with "petals" 10.5 nm thick, uniformly distributed, and 2.1 μm in diameter, showing good dispersion.
[0056] High-resolution transmission electron microscopy images characterize the catalyst surface supported structure and the crystal form of nanoparticles, such as... Figure 2As shown, δ-MnO2 particles and Pt nanoparticles are uniformly loaded on the surface of the micro-flower-like MnCo2O4. The diameter of the δ-MnO2 particles is 91.50 nm, and the diameter of the Pt nanoparticles is 1.15 nm. The interplanar spacings are 0.48 nm and 0.25 nm, corresponding to the (111) and (311) lattice planes of MnCo2O4, respectively. The interplanar spacing is 0.36 nm, corresponding to the (002) plane of δ-MnO2. The interplanar spacing is 0.226 nm, corresponding to the (111) lattice plane of metallic Pt. The intersecting lattice stripes (circled in yellow) are visible in the figure, indicating the formation of heterojunctions. Loading δ-MnO2 and Pt nanoparticles onto the micro-flower-like MnCo2O4 does not change the crystal structure of MnCo2O4.
[0057] Effect Experiment:
[0058] The prepared Pt@δ-MnO2@MnCo2O4 micro-flower-like composite catalyst was tested at 25℃, 50% humidity, and an initial formaldehyde concentration of 0.1 mg / m³. 3 The catalytic performance of formaldehyde was tested under the following conditions. The catalytic efficiency for formaldehyde was 94% within 120 minutes. Furthermore, the initial concentration was 1 mg / m³. 3 At 0.8 ppm, the formaldehyde removal rate reached 94% within 120 minutes, and after 4 cycles of experiment, the formaldehyde removal rate still reached 92%.
[0059] In addition, the prepared Pt@δ-MnO2@MnCo2O4 micro-flower-like composite catalyst can also catalytically degrade benzene series compounds such as toluene, with a toluene removal rate of 70%.
[0060] Example 2
[0061] (1) First, take a clean 250mL round-bottom flask and add 2.5mL of deionized water and 200mL of ethylene glycol. Weigh 0.6125g of manganese acetate (Mn(CH3COO)2·4H2O) and 1.245g of cobalt acetate (Co(CH3COO)2·4H2O) and add them to the round-bottom flask. Seal the round-bottom flask with sealing glue and stir it on a magnetic stirrer until a transparent solution is obtained. Add 0.5475g of polyvinylpyrrolidone (PVP) to the above solution and transfer the resulting solution to a Teflon-lined stainless steel high-pressure reactor. Place it in an oven and react at a constant temperature of 180℃ for 12h. After naturally cooling to room temperature, remove the reactor and pour the solution in the liner into a centrifuge tube. Set the speed to 10000r / min and centrifuge for 10min to obtain the cobalt-manganese compound. Wash the compound four times with distilled water and ethanol. Dry the precipitate in air at 80℃ for 10h. The temperature was increased to 500℃ in air at a heating rate of 2℃ / min, and then heat-treated at that temperature for 4 hours (a total of 8 hours and 10 minutes). After that, it was naturally cooled to room temperature to obtain micro-flower-like MnCo2O4.
[0062] (2) Weigh 0.2 g of the synthesized micro-flower-like MnCo2O4 powder into a 50 mL round-bottom flask, add 30 mL of deionized water, and stir magnetically for 15 min to disperse it evenly. After even dispersion, add 0.05 g of KMnO4 and MnSO4·H2O, heat and stir in a 60 °C water bath for 3 h, transfer the precipitate generated after the reaction to a 50 mL centrifuge tube, centrifuge at 10000 r / min for 10 min, wash with deionized water 4 times, and transfer the material after the last centrifugation to a vacuum drying oven and vacuum dry at 25 °C for 12 h.
[0063] (3) Dissolve 1g of chloroplatinic acid hexahydrate (H2PtCl6·6H2O) in 20mL of water to obtain a chloroplatinic acid solution with a concentration of 0.09654mol / L. Weigh 0.5g of MnCo2O4 powder loaded with δ-MnO2 in the above steps into a 50mL round-bottom flask, and disperse it in 10mL of deionized water by magnetic stirring for 15min. Measure a certain volume of 0.09654mol / L chloroplatinic acid solution (Pt loading is 0.2wt%), insert a needle below the liquid surface of the round-bottom flask and add it. Seal and protect from light, and stir magnetically for 12h. Weigh 0.0189g of NaBH4 and 0.02g of NaOH into a 50mL beaker, add 5mL of deionized water, stir thoroughly to dissolve, and then quickly add to the round-bottom flask. Seal and protect from light, and stir for 30min. The above solution was centrifuged at 10,000 r / min and washed four times with deionized water. The solution was ultrasonically dispersed for 10 min between each wash. After the last centrifugation, the supernatant was discarded and the product was placed in an oven and dried at 80°C for 8 h.
[0064] Effect Experiment:
[0065] The prepared Pt@δ-MnO2@MnCo2O4 micro-flower-like composite catalyst was tested at 25℃, 50% humidity, and an initial formaldehyde concentration of 0.1 mg / m³. 3 The catalytic performance of formaldehyde was tested under the specified conditions. The catalytic efficiency for formaldehyde was 95% within 120 minutes.
[0066] In addition, the prepared Pt@δ-MnO2@MnCo2O4 micro-flower-like composite catalyst can also catalytically degrade benzene series compounds such as toluene, with a toluene removal rate of 72%.
[0067] Example 3
[0068] (1) First, take a clean 250mL round-bottom flask and add 2.5mL of deionized water and 200mL of ethylene glycol. Weigh 0.6125g of manganese acetate (Mn(CH3COO)2·4H2O) and 1.245g of cobalt acetate (Co(CH3COO)2·4H2O) and add them to the round-bottom flask. Seal the round-bottom flask with sealing glue and stir it on a magnetic stirrer until a transparent solution is obtained. Add 0.5475g of polyvinylpyrrolidone (PVP) to the above solution and transfer the resulting solution to a Teflon-lined stainless steel high-pressure reactor. Place it in an oven and react at a constant temperature of 180℃ for 12h. After naturally cooling to room temperature, remove the reactor and pour the solution in the liner into a centrifuge tube. Set the speed to 10000r / min and centrifuge for 10min to obtain the cobalt-manganese compound. Wash the compound four times with distilled water and ethanol. Dry the precipitate in air at 80℃ for 10h. The temperature was increased to 500℃ in air at a heating rate of 2℃ / min, and then heat-treated at that temperature for 4 hours (a total of 8 hours and 10 minutes). After that, it was naturally cooled to room temperature to obtain micro-flower-like MnCo2O4.
[0069] (2) Weigh 0.2 g of the synthesized micro-flower-like MnCo2O4 powder into a 50 mL round-bottom flask, add 30 mL of deionized water, and stir magnetically for 15 min to disperse it evenly. After even dispersion, add 0.05 g of KMnO4 and MnSO4·H2O, heat and stir in a 60 °C water bath for 3 h, transfer the precipitate generated after the reaction to a 50 mL centrifuge tube, centrifuge at 10000 r / min for 10 min, wash with deionized water 4 times, and transfer the material after the last centrifugation to a vacuum drying oven and vacuum dry at 25 °C for 12 h.
[0070] (3) Dissolve 1g of chloroplatinic acid hexahydrate (H2PtCl6·6H2O) in 20mL of water to obtain a chloroplatinic acid solution with a concentration of 0.09654mol / L. Weigh 0.5g of MnCo2O4 powder loaded with δ-MnO2 in the above steps into a 50mL round-bottom flask, and disperse it in 10mL of deionized water by magnetic stirring for 15min. Measure a certain volume of 0.09654mol / L chloroplatinic acid solution (Pt loading is 0.5wt%), insert a needle below the liquid surface of the round-bottom flask and add it. Seal and protect from light, and stir magnetically for 12h. Weigh 0.0189g of NaBH4 and 0.02g of NaOH into a 50mL beaker, add 5mL of deionized water, stir thoroughly to dissolve, and then quickly add to the round-bottom flask. Seal and protect from light, and stir for 30min. The above solution was centrifuged at 10,000 r / min and washed four times with deionized water. The solution was ultrasonically dispersed for 10 min between each wash. After the last centrifugation, the supernatant was discarded and the product was placed in an oven and dried at 80°C for 8 h.
[0071] Effect Experiment:
[0072] The prepared Pt@δ-MnO2@MnCo2O4 micro-flower-like composite catalyst was tested at 25℃, 50% humidity, and an initial formaldehyde concentration of 0.1 mg / m³. 3 The catalytic performance of formaldehyde was tested under the specified conditions. The catalytic efficiency for formaldehyde was 96% within 120 minutes.
[0073] In addition, the prepared Pt@δ-MnO2@MnCo2O4 micro-flower-like composite catalyst can also catalytically degrade benzene series compounds such as toluene, with a toluene removal rate of 74%.
[0074] Example 4
[0075] (1) First, take a clean 250mL round-bottom flask and add 2.5mL of deionized water and 200mL of ethylene glycol. Weigh 0.6125g of manganese acetate (Mn(CH3COO)2·4H2O) and 1.245g of cobalt acetate (Co(CH3COO)2·4H2O) and add them to the round-bottom flask. Seal the round-bottom flask with sealing glue and stir it on a magnetic stirrer until a transparent solution is obtained. Add 0.5475g of polyvinylpyrrolidone (PVP) to the above solution and transfer the resulting solution to a Teflon-lined stainless steel high-pressure reactor. Place it in an oven and react at a constant temperature of 180℃ for 12h. After naturally cooling to room temperature, remove the reactor and pour the solution in the liner into a centrifuge tube. Set the speed to 10000r / min and centrifuge for 10min to obtain the cobalt-manganese compound. Wash the compound four times with distilled water and ethanol. Dry the precipitate in air at 80℃ for 10h. The temperature was increased to 500℃ in air at a heating rate of 2℃ / min, and then heat-treated at that temperature for 4 hours (a total of 8 hours and 10 minutes). After that, it was naturally cooled to room temperature to obtain micro-flower-like MnCo2O4.
[0076] (2) Weigh 0.2 g of the synthesized micro-flower-like MnCo2O4 powder into a 50 mL round-bottom flask, add 30 mL of deionized water, and stir magnetically for 15 min to disperse it evenly. After even dispersion, add 0.05 g of KMnO4 and MnSO4·H2O, heat and stir in a 60 °C water bath for 3 h, transfer the precipitate generated after the reaction to a 50 mL centrifuge tube, centrifuge at 10000 r / min for 10 min, wash with deionized water 4 times, and transfer the material after the last centrifugation to a vacuum drying oven and vacuum dry at 25 °C for 12 h.
[0077] (3) Dissolve 1g of chloroplatinic acid hexahydrate (H2PtCl6·6H2O) in 20mL of water to obtain a chloroplatinic acid solution with a concentration of 0.09654mol / L. Weigh 0.5g of MnCo2O4 powder loaded with δ-MnO2 in the above steps into a 50mL round-bottom flask, and disperse it in 10mL of deionized water by magnetic stirring for 15min. Measure a certain volume of 0.09654mol / L chloroplatinic acid solution (Pt loading is 1wt%), insert a needle below the liquid surface of the round-bottom flask and add it. Seal and protect from light, and stir magnetically for 12h. Weigh 0.0189g of NaBH4 and 0.02g of NaOH into a 50mL beaker, add 5mL of deionized water, stir thoroughly to dissolve, and then quickly add to the round-bottom flask. Seal and protect from light, and stir for 30min. The above solution was centrifuged at 10,000 r / min and washed four times with deionized water. The solution was ultrasonically dispersed for 10 min between each wash. After the last centrifugation, the supernatant was discarded and the product was placed in an oven and dried at 80°C for 8 h.
[0078] Effect Experiment:
[0079] The prepared Pt@δ-MnO2@MnCo2O4 micro-flower-like composite catalyst was tested at 25℃, 50% humidity, and an initial formaldehyde concentration of 0.1 mg / m³. 3 The catalytic performance of formaldehyde was tested under the specified conditions. The catalytic efficiency for formaldehyde was 98% within 120 minutes.
[0080] In addition, the prepared Pt@δ-MnO2@MnCo2O4 micro-flower-like composite catalyst can also catalytically degrade benzene series compounds such as toluene, with a toluene removal rate of 76%.
[0081] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of this application. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technical content disclosed in this invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of this invention.
Claims
1. A micro-flower-like manganese cobalt oxide composite catalyst Pt@δ-MnO2@MnCo2O4, characterized in that: Spinel-structured transition metal oxide MnCo2O4 is composed of oxygen ions arranged in a cubic close-packed manner. 2+ Filling one-eighth of the tetrahedral voids, Co 3+ The Pt@δ-MnO2@MnCo2O4 composite catalyst, which fills half of the octahedral voids, has a micro-flower-like morphology with "petals" of 10 nm to 15 nm thickness, uniform distribution, and a micro-flower diameter of 1.5 μm to 2 μm. The MnCo2O4 support has a micro-flower-like morphology and abundant porosity, providing more contact sites due to its large specific surface area. δ-MnO2 particles and Pt nanoparticles are uniformly loaded on the surface of the micro-flowers. δ-MnO2 particles are plate-like microspheres aggregated on the surface of the MnCo2O4 micro-flowers with a diameter of 90 nm to 120 nm, while Pt nanoparticles are fine particles uniformly loaded on the surface of the MnCo2O4 micro-flowers with a diameter of 1 nm to 2 nm. The surface of the above-mentioned micro-flower-like manganese cobalt oxide composite catalyst is rough, and a heterojunction is formed between δ-MnO2 and MnCo2O4.
2. A method for preparing the micro-flower-like composite catalyst Pt@δ-MnO2@MnCo2O4 according to claim 1, wherein the micro-flower-like composite catalyst is composed of micro-flower-like MnCo2O4 stably supported δ-MnO2 particles and Pt nanoparticles, and the specific preparation method includes the following steps: Step 1: Preparation of MnCo2O4 support: Using Mn(CH3COO)2·4H2O and Co(CH3COO)2·4H2O as Mn and Co sources, and PVP as a surface protectant, MnCo2O4 nanosheet precursors were prepared by solvothermal method. The obtained precursor solution was then transferred to a stainless steel high-pressure reactor for heat treatment reaction, and finally naturally cooled to room temperature to obtain MnCo2O4 microflowers. Step 2, Preparation of δ-MnO2@MnCo2O4: Using KMnO4 and MnSO4·H2O as Mn sources, δ-MnO2 was loaded onto MnCo2O4 microflowers by deposition-precipitation method, while heterojunctions were formed between δ-MnO2 and MnCo2O4. After centrifugation, washing and vacuum drying, δ-MnO2@MnCo2O4 was obtained. Step 3: Preparation of Pt@δ-MnO2@MnCo2O4: Pt nanoparticles were synthesized in situ on the surface of δ-MnO2@MnCo2O4 using H2PtCl6·6H2O as the Pt source and NaBH4 as the reducing agent, thus preparing a Pt@δ-MnO2@MnCo2O4 micro-flower-like composite catalyst.
3. The preparation method according to claim 2, characterized in that: In step one, the temperature inside the stainless steel high-pressure reactor is kept constant at 180°C for 12 hours.
4. The preparation method according to claim 2, characterized in that: In step two, by controlling the mass ratio of MnCo2O4 to KMnO4 and MnSO4·H2O, the former to the sum of the latter two is controlled at 2.0:1 to 10.0:1, so that the mass ratio of the product MnCo2O4 to δ-MnO2 is controlled at 2.7:1 to 13.6:
1.
5. The preparation method according to claim 2, characterized in that: In step two, the deposition-precipitation method involves heating and stirring in a 60°C water bath for 3 hours.
6. The preparation method according to claim 2, characterized in that: In step three, the concentration range of H2PtCl6·6H2O is 0.09M to 0.10M, and the mass fraction of the loaded Pt in Pt@δ-MnO2@MnCo2O4 is controlled between 0.1wt% and 1wt%.
7. The use of the micro-flower-like composite catalyst Pt@δ-MnO2@MnCo2O4 according to claim 1, characterized in that: It is used to catalytically oxidize formaldehyde at room temperature, which can significantly reduce formaldehyde concentration.
8. The use of the micro-flower-like composite catalyst Pt@δ-MnO2@MnCo2O4 according to claim 1, which is used for the catalytic degradation of substances other than formaldehyde.
9. The use of the micro-flower-like composite catalyst Pt@δ-MnO2@MnCo2O4 according to claim 8, wherein the catalytic degradation of substances other than formaldehyde is the catalytic degradation of benzene series compounds.
10. The use of the micro-flower-like composite catalyst Pt@δ-MnO2@MnCo2O4 according to claim 9, wherein the catalytic degradation of the benzene series compounds is the catalytic degradation of toluene.