Preparation and Application of a MOF-Derived ZnO / C-Supported Carbon-Bridged Atomically Dispersed Pt Catalyst

Abstract

The invention discloses the preparation and application of a MOF-derived ZnO / C-supported carbon-bridged atomically dispersed Pt catalyst, which relates to the technical field of photocatalyst synthesis. The process of this method is simple and easy to operate. The prepared Pt-ZnO / C photocatalyst has high photocatalytic performance in the degradation of NO, providing technical support for the wide application of ZnO catalysts. The atomically dispersed Pt catalyst is loaded on MOF-derived ZnO / C by chemical impregnation. The Pt-ZnO / C catalyst obtained by this method is simple and easy to operate. In addition, C doping of the ZnO / C support can narrow the band gap of the catalyst, which is beneficial to the separation of photo-generated electron-hole pairs. Moreover, the interaction between C and Pt also contributes to the stability of the Pt-ZnO / C catalyst. Therefore, the Pt-ZnO / C catalyst has good photocatalytic activity.

Description

Technical Field

[0001] The present invention relates to the technical field of photocatalyst synthesis, and particularly relates to a method for carbon-bridged atomically dispersed Pt on a MOF-derived ZnO / C catalyst. Background Art

[0002] Air pollution has become a global challenge faced by modern society. The large emission of NOx will cause a series of environmental problems and health problems. And the content of NO in NOx is as high as 90%-95%. Therefore, reducing the emission of NO is the key to controlling air pollution. Visible light photocatalysis technology is an economical and effective strategy for using sustainable solar energy to solve NO pollutants. The core of photocatalysis technology is the photocatalyst.

[0003] Zinc oxide (ZnO) is often used in the fields of energy storage, degradation of organic dyes, degradation of volatile organic compounds, nitrogen monoxide, etc. due to its chemical stability, easy synthesis, high cost-effectiveness, environmental friendliness and other advantages. However, pure zinc oxide has poor visible light absorption due to its wide bandgap (3.37 eV) and rapid photoelectron-hole recombination, resulting in low photocatalytic activity of the photocatalyst. Researchers have enhanced the light absorption ability of the catalyst and inhibited the separation of photogenerated electron-hole pairs by optimizing the morphology of ZnO, doping other atoms, introducing defects and depositing noble metals on the catalyst surface, thereby improving its photocatalytic activity. However, these existing catalysts can only remove NO at the ppb level, and the removal efficiency is low. Especially the low reserves and high cost of noble metals limit the wide application of ZnO. Therefore, new strategies are needed to improve the photocatalytic activity of ZnO to expand its engineering applications.

[0004] In recent years, noble metal nanoclusters and single atoms have unique properties and relatively high atomic utilization rates compared to nanoparticles, which can significantly improve the activity of the catalyst and reduce the cost of the catalyst, and have been widely used in the field of photocatalysis. In addition, the interaction between metal single atoms and the support can also change the electronic structure on the catalyst surface, accelerating the transfer of photogenerated carriers, thereby improving the photocatalytic activity. Considering that C doping can not only narrow the bandgap of the catalyst, which is beneficial to the separation of photogenerated electron-hole pairs. Moreover, the interaction between C and Pt can also stabilize the Pt atoms in ZnO / C. Therefore, we attempt to synthesize a Pt-ZnO / C catalyst by carbon-bridged atomically dispersed Pt on MOF-derived ZnO / C to improve the photocatalytic activity of the catalyst. Summary of the Invention

[0005] In view of the above problems, the present invention provides a preparation method and application of carbon-bridged atomically dispersed Pt on MOF-derived ZnO / C catalyst. The MOF-derived ZnO / C supported atomically dispersed Pt catalyst is prepared by a chemical impregnation method. This method has a simple process and is easy to operate. The prepared Pt-ZnO / C photocatalyst has high photocatalytic performance in the degradation of NO, providing technical support for the wide application of ZnO catalysts.

[0006] The technical solution of the present invention is as follows: The atomically dispersed P catalyst is supported on MOF-derived ZnO / C by a chemical impregnation method, and the steps are as follows:

[0007] Step 1: Ultrasonically disperse Zn(NO3)2·6H2O in methanol to form solution A;

[0008] Step 2: Ultrasonically disperse 2-methylimidazole in a methanol solution to form solution B;

[0009] Step 3: Then mix solution A and B in a ratio of 1:1 and magnetically stir for 24 h to obtain ZIF-8 solid;

[0010] Step 4: The obtained ZIF-8 solid is calcined in a tube furnace at 450 °C in an air atmosphere for 3 h to obtain a ZnO / C sample;

[0011] Step 5: Ultrasonically disperse ZnO / C into ultrapure water to obtain solution C;

[0012] Step 6: Add H2PtCl6 to ultrapure water to obtain solution D;

[0013] Step 7: Drop the D solution in Step 6 into the C solution in Step 5 at a ratio of 1:11 and keep magnetic stirring for 12 h;

[0014] Step 8: Centrifuge 3 times with ultrapure water and absolute ethanol respectively, and dry the obtained precipitate in a vacuum oven at 60 °C for 8 h;

[0015] Step 9: Calcinate the dried powder in a tube furnace at a heating rate of 5 °C / min in a N2 atmosphere at 125 °C for 1 h to obtain a Pt-ZnO / C catalyst.

[0016] Further, in Step 1, 6.03 g of Zn(NO3)2·6H2O is placed in every 144 ml of methanol.

[0017] Further, in Step 2, 13.32 g of 2-methylimidazole is placed in every 144 ml of methanol.

[0018] Further, in Step 5, 0.4 g of ZnO / C is placed in every 100 mL of ultrapure water.

[0019] Further, in step 6, 10 - 50 μL of H2PtCl6 is placed in every 10 mL of ultrapure water, and the concentration of H2PtCl6 is 1 g / 3 mL.

[0020] Regarding the application method, 0.08 g of the catalyst is dispersed in 10 ml of ultrapure water, sonicated for 2 min, and the dispersed suspension is transferred to a glass slide of 10×5×0.1 cm 3 by pipette, dried in an oven at 60 °C to make a glass slide loaded with the photocatalyst, and placed in a photocatalytic reactor.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] First, the C doping in the MOF-derived ZnO / C supporting atomically dispersed Pt-ZnO / C used in the present invention can narrow the band gap of the catalyst, which is beneficial to the separation of photogenerated electron-hole pairs, thus improving the activity of the catalyst.

[0023] Second, the present invention uses ZnO / C as a carrier, and the C therein can bridge Pt, which is beneficial to the dispersion of Pt atoms and the stability of the catalyst, thus inhibiting the deactivation of the catalyst.

[0024] Third, the present invention prepares the MOF-derived ZnO / C supported catalyst by a simple chemical impregnation method. The synthesized catalyst shows very good photocatalytic activity in the photocatalytic degradation of the gas pollutant NO. And small-sized Pt single atoms and nanoclusters are synthesized, which can improve the utilization rate of noble metals, thus reducing costs.

[0025] The present invention is not only conducive to the in-depth study of the modification of ZnO photocatalysts, but also has guiding significance for the modification research of designing other oxide catalysts and the rational design of highly efficient catalysts. Description of the Drawings

[0026] Figure 1 It is the X-ray diffraction pattern (the abscissa is the angle and the ordinate is the diffraction intensity) of the prepared ZIF-8, ZnO / C, Pt-ZnO / C, and PtNPs-ZnO / C catalysts.

[0027] Figure 2 It is the scanning electron microscopy image of the prepared ZIF-8, ZnO / C, Pt-ZnO / C, and PtNPs-ZnO / C catalysts.

[0028] Figure 3 It is the high-angle annular dark-field scanning transmission electron microscopy (AC-HAADF-STEM) image of the Pt-ZnO / C catalyst

[0029] Figure 4XPS comparison chart of Pt in the prepared Pt-ZnO / C and PtNPs-ZnO / C catalysts.

[0030] Figure 5 Photocatalytic degradation effect diagrams of ZnO / C, Pt-ZnO / C, 30-Pt-ZnO / C, 40-Pt-ZnO / C, 50-Pt-ZnO / C and PtNPs-ZnO / C samples for NO. Specific implementation manners

[0031] To clearly illustrate the technical features of this patent, the following will elaborate on this patent in detail through specific implementation manners and in combination with its attached drawings.

[0032] The Pt-ZnO / C catalyst obtained by this method is simple and easy to operate. Moreover, C doping of the ZnO / C support can narrow the band gap of the catalyst, which is beneficial to the separation of photogenerated electron-hole pairs. In addition, the interaction between C and Pt also contributes to the stability of the Pt-ZnO / C catalyst. Therefore, the Pt-ZnO / C catalyst has good photocatalytic activity.

[0033] Example 1:

[0034] Weigh 6.03 g of Zn(NO3)2·6H2O and ultrasonically disperse it in 144 mL of methanol to form solution A; weigh 13.32 g of 2-methylimidazole and ultrasonically disperse it in 144 mL of methanol solution to form solution B. Then, mix solutions A and B and stir magnetically for 24 h to obtain ZIF-8 solid. Calcinate the obtained ZIF-8 solid in a tube furnace at 450 °C in an air atmosphere for 3 h to obtain the ZnO / C sample. Subsequently, weigh 0.4 g of ZnO / C and ultrasonically disperse it into 100 mL of ultrapure water to obtain a C solution. Then, add 40 μL of H2PtCl6 solution to 10 mL of ultrapure water, ultrasonicate for 5 min, and add it to the above mixed ZnO / C solution, and keep stirring magnetically for 12 h. Centrifuge 3 times with ultrapure water and absolute ethanol respectively, and dry the obtained precipitate in a vacuum oven at 60 °C for 8 h. Then, calcinate it in a tube furnace at a heating rate of 5 °C / min in a N2 atmosphere at 125 °C for 1 h to obtain the Pt-ZnO / C catalyst.

[0035] Example 2:

[0036] The difference between this example and Example 1 is only that the content of H2PtCl6 in the H2PtCl6 solution in step 6 is 30 μL, and the obtained catalyst is named 30-Pt-ZnO / C catalyst.

[0037] Example 3:

[0038] The difference between this example and Example 1 is only that the content of H2PtCl6 in the H2PtCl6 solution in step 6 is 50 μL, and the obtained catalyst is named 50-Pt-ZnO / C catalyst.

[0039] Example 4:

[0040] The preparation of the ZnO / C catalyst in this example is the same as that in Example 1. 0.4 g of ZnO / C was dispersed in 100 mL of ultrapure water, and then ultrasonicated for 5 min to form suspension C; 40 μL of H2PtCl6 solution was injected into 10 mL of water to generate solution D; solution D was added dropwise to solution C;

[0041] Then, 0.0336 g of NaBH4 was dissolved in 10 mL of water to generate solution E. Solution E was added to the previous mixed solution, and then magnetically stirred for 2 h. The obtained solid was centrifuged and washed twice with ultrapure water and ethanol respectively. The washed solid was heated in an oven at 60 °C for 12 h to obtain the Pt NPs-ZnO / C catalyst sample.

[0042] Combined with Figure 1 the X-ray diffraction results and Figure 2 the scanning electron microscopy results, it can be seen that the characteristic diffraction peaks of the ZIF-8 sample were not found in the X-ray diffraction patterns of the ZnO / C, Pt-ZnO / C, and PtNPs-ZnO / C samples. In addition, the morphology of ZIF-8 is regular octahedron, while the morphologies of the ZnO / C, Pt-ZnO / C, and PtNPs-ZnO / C samples are irregular nanoparticles. These results indicate that ZIF-8 has been completely derived into the ZnO / C sample after calcination.

[0043] According to Figure 3 the results, Pt species in the Pt-ZnO / C catalyst exist in the form of Pt single atoms and nanoclusters. Figure 4 The results show that Pt in the PtNPs-ZnO / C catalyst mainly exists as metallic Pt. While Pt in the Pt-ZnO / C catalyst mainly exists in the form of Pt 2+ and contains a small amount of metallic Pt, which further illustrates that the Pt-ZnO / C catalyst contains a large number of Pt single atoms and a small amount of nanoclusters.

[0044] Application example:

[0045] The catalytic activities of the ZnO / C, 30-Pt-ZnO / C, Pt-ZnO / C, 50-Pt-ZnO / C, and Pt NPs-ZnO / C catalysts prepared by the method of the present invention were evaluated by photocatalytic oxidation of NO under visible light irradiation.

[0046] Specific steps of the photocatalytic experiment:

[0047] 1. Disperse about 0.08 g of the catalyst in 10 ml of ultrapure water, sonicate for 2 min, and transfer the well-dispersed suspension to a glass slide of 10×5×0.1 cm 3 and dry it in an oven at 60 °C;

[0048] 2. Place the glass slide loaded with the photocatalyst in a photocatalytic reactor, and introduce a gas containing a certain concentration of NO and 5% O2 with N2 as the carrier gas, and the gas flow rate is 200 ml / min;

[0049] 3. After introducing the gas, perform physical adsorption until the catalyst is saturated with NO adsorption in the gas. Use a 300 W xenon lamp (λ>380 nm) with an ultraviolet light filter as the light source to irradiate the glass slide through quartz glass, and connect a Fourier transform infrared spectrometer (flue gas analyzer) at the reactor outlet to detect the concentrations of NO and NO2 in real time;

[0050] 4. Calculate the conversion rate of NO based on the recorded concentrations of NO and NO2 as follows.

[0051] The experimental results are as Figure 5 shown. Under visible light irradiation, the degradation rate of NO of the Pt-ZnO / C catalyst is higher than that of the ZnO / C and PtNPs-ZnO / C catalysts. Therefore, under visible light irradiation, the Pt-ZnO / C catalyst loaded with atomically dispersed Pt has better photocatalytic activity.

[0052] There are many specific implementation ways of the present invention. The above description is only the preferred implementation manner of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements can be made, and these improvements should also be regarded as the protection scope of the present invention.

Claims

1. Preparation method of MOF-derived ZnO / C supported carbon-bridged atomically dispersed Pt catalyst, characterized in that, The steps are as follows: Step 1: Ultrasonically disperse Zn(NO3)2·6H2O in methanol to form solution A; Step 2: Ultrasonically disperse 2-methylimidazole in a methanol solution to form solution B; Step 3: Then mix solution A and B in a volume ratio of 1:1 and magnetically stir for 24 h to obtain ZIF-8 solid; Step 4: Calcinate the obtained ZIF-8 solid in a tubular furnace at 450 °C in an air atmosphere for 3 h to obtain a ZnO / C sample; Step 5: Ultrasonically disperse ZnO / C into ultrapure water to obtain solution C; Step 6: Add the H2PtCl6 solution to ultrapure water to obtain solution D; put 10-50 µL of the H2PtCl6 solution into every 10 mL of ultrapure water, and the concentration of the H2PtCl6 solution is 1 g / 3 mL; Step 7: Drop the D solution in Step 6 into the C solution in Step 5 and keep magnetic stirring for 12 h, where the volume ratio of the D solution to the C solution is 1:10; Step 8: Centrifuge 3 times with ultrapure water and absolute ethanol respectively, and dry the obtained precipitate in a vacuum oven at 60 °C for 8 h; Step 9: Calcinate the dried powder in a tubular furnace in a N2 atmosphere at a heating rate of 5 °C / min to 125 °C for 1 h to obtain a Pt-ZnO / C catalyst.

2. The preparation method of a MOF-derived ZnO / C-supported carbon-bridged atomically dispersed Pt catalyst according to claim 1, characterized in that, In Step 1, 6.03 g of Zn(NO3)2·6H2O is put into every 144 mL of methanol.

3. The preparation method of a MOF-derived ZnO / C-supported carbon-bridged atomically dispersed Pt catalyst according to claim 1, characterized in that, In Step 2, 13.32 g of 2-methylimidazole is put into every 144 mL of methanol.

4. The preparation method of a MOF-derived ZnO / C-supported carbon-bridged atomically dispersed Pt catalyst according to claim 1, characterized in that, In Step 5, 0.4 g of ZnO / C is put into every 100 mL of ultrapure water.

5. Use of the MOF-derived ZnO / C-supported carbon-bridged atomically dispersed Pt catalyst prepared by the preparation method according to any one of claims 1-4 in photocatalysis, characterized in that, Disperse 0.08 g of the catalyst in 10 mL of ultrapure water, sonicate for 2 min, and transfer the well-dispersed suspension to a glass slide with dimensions of 10×5×0.1 cm 3 using a pipette. Dry it in an oven at 60 °C to prepare a glass slide loaded with the catalyst, and place it in a photocatalytic reactor.

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