Manganese dioxide / graphdiyne composite material and preparation method and application thereof

Abstract

The invention discloses a manganese dioxide / graphdiyne composite material as well as a preparation method and application thereof, and belongs to the technical field of catalytic materials. The preparation method of the manganese dioxide / graphdiyne composite material comprises the following steps: mixing a manganese salt solution and graphdiyne to obtain a solution a, mixing a potassium permanganate solution and the solution a to obtain a suspension, and reacting the suspension at 130-180 DEG C to obtain the manganese dioxide / graphdiyne composite material. In addition, the invention also provides an application of the manganese dioxide / graphdiyne composite material prepared by the preparation method in catalytic ozonolysis. The composite material provided by the invention can effectively decompose ozone.

Description

Technical Field

[0001] The present invention relates to the technical field of catalytic materials, and in particular to a manganese dioxide / graphene composite material and a preparation method and application thereof. Background Art

[0002] With the continuous development of industry and the economy, and the accelerating pace of urbanization, the emission of large amounts of industrial gaseous pollutants has led to increasingly severe atmospheric pollution problems. Among these, ozone pollution has attracted the attention of scientists and the public due to its extremely harmful nature. Although the ozone layer, approximately 30 kilometers above the Earth's surface, absorbs ultraviolet radiation and serves as a protective shield for life on Earth, ozone in the troposphere near the surface can pose a threat to the environment and human health. For example, it can affect plant growth and inhibit photosynthesis, leading to lower crop yields and decreased species diversity. Furthermore, long-term exposure can lead to respiratory illnesses such as asthma, emphysema, and bronchitis. In severe cases, it can also cause health problems such as immune system disorders and neurological damage. Therefore, reducing ozone pollution in the atmosphere is essential.

[0003] With the increasing harm caused by ozone, scholars at home and abroad have developed and studied many ozone removal methods, including activated carbon adsorption, thermal decomposition, electromagnetic wave radiation conversion, liquid absorption and catalytic decomposition. Among them, the catalytic decomposition method has been widely studied in recent years due to its simple technical operation and low energy consumption. Among them, the catalytic conversion of manganese dioxide catalysts has attracted widespread attention due to its high efficiency, safety and low cost. However, in a humid environment, traditional manganese dioxide catalysts are prone to water poisoning and deactivation. The main reason is that water molecules compete with ozone for the adsorption of metal active sites or oxygen vacancies, resulting in a significant decrease in the adsorption and activation efficiency of ozone molecules, which seriously reduces the conversion performance of the catalyst under wet conditions. Therefore, it is of great significance to develop a catalyst that is resistant to moisture environments to achieve efficient ozone decomposition. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above technical deficiencies, provide a manganese dioxide / graphene composite material and its preparation method and application, and solve the technical problem of how to effectively decompose ozone under wet conditions in the prior art.

[0005] To achieve the above technical objectives, the technical solution of the present invention provides a method for preparing a manganese dioxide / graphene composite material, comprising the following steps: mixing a manganese salt solution and graphene to obtain a solution a, then mixing a potassium permanganate solution and a solution a to obtain a suspension, and then subjecting the suspension to a hydrothermal reaction at 130-180 ° C to obtain a manganese dioxide / graphene composite material.

[0006] In any embodiment, the manganese salt solution is a manganese sulfate solution.

[0007] In any embodiment, the mixing of the potassium permanganate solution and the solution a to obtain a suspension comprises: dropwise adding the potassium permanganate solution to the solution a to obtain the suspension.

[0008] In any embodiment, the suspension is hydrothermally reacted at 130-180° C. for 10-15 hours.

[0009] In any embodiment, the manganese sulfate solution is prepared by the following steps: dissolving MnSO4•H2O in water.

[0010] In addition, the present invention also provides a manganese dioxide / graphene composite material, which is prepared by the above preparation method.

[0011] In any embodiment, the mass fraction of C / Mn in the manganese dioxide / graphene composite material is 3.75%-15%.

[0012] In any embodiment, the mass fraction of C / Mn in the manganese dioxide / graphene composite material is 7.5%.

[0013] In addition, the present invention also proposes a manganese dioxide / graphene composite material prepared by the above preparation method or the use of the above manganese dioxide / graphene composite material in ozone catalytic decomposition.

[0014] In any embodiment, the ozone catalytic decomposition is carried out under a humidity condition of 0%-60%.

[0015] Compared with the prior art, the beneficial effects of the present invention include: the preparation method of the manganese dioxide / graphene composite material proposed in the present invention introduces manganese dioxide on graphene with an ultra-high specific surface area, successfully prepares the manganese dioxide / graphene composite material, and applies it to ozone decomposition at room temperature and high humidity, which can effectively decompose ozone; the synthesis of the present invention is simple and the graphene loading amount is controllable within a certain range, the catalytic process is stable, the catalyst structure and active sites are maintained under room temperature catalysis, and the catalytic ozone decomposition activity can be maintained for more than 100 hours. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the XRD pattern of the MnO2 / GDY catalyst with different doping amounts prepared in Example 1 of the present invention.

[0017] Figure 2 The Raman graphs of the MnO2 / GDY catalysts with different doping amounts prepared in Example 1 of the present invention are shown;

[0018] Figure 3 This is the SEM image of the 3.75%-MnO2 / GDY catalyst prepared in Example 1 of the present invention.

[0019] Figure 4 This is the SEM image of the 7.5%-MnO2 / GDY catalyst prepared in Example 1 of the present invention.

[0020] Figure 5 This is the SEM image of the 15%-MnO2 / GDY catalyst prepared in Example 1 of the present invention.

[0021] Figure 6 Schematic diagram of the testing device of the present invention.

[0022] Figure 7 This is the room temperature catalytic ozone decomposition activity diagram of the MnO2 / GDY catalyst with different doping amounts of the present invention.

[0023] Figure 8 This is a stability diagram of the 7.5%-MnO2 / GDY catalyst of the present invention during catalytic ozone decomposition at room temperature for 100 hours.

[0024] Figure 9 This is the ozone decomposition activity diagram of the 7.5%-MnO2 / GDY catalyst of the present invention under different humidity.

[0025] Figure 10 This is an ozone decomposition activity diagram of the 7.5%-MnO2 / GDY catalyst of the present invention under dry-wet gas switching conditions at a relative humidity of 3% to 60%.

[0026] Figure 11 This is a comparison chart of the ozone decomposition activities of the 7.5%-MnO2 / GDY catalyst of the present invention and the MnO2+GDY mechanical mixed catalyst. DETAILED DESCRIPTION

[0027] The "range" disclosed in this application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The range defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. For example, if a range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that a range of 60 to 110 and 80 to 120 is also expected. In addition, if the minimum range values ​​listed are 1 and 2, and if the maximum range values ​​listed are 3, 4, and 5, then the following ranges can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise specified, the numerical range "a to b" represents an abbreviation of any real number combination between a and b, wherein a and b are both real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, stating that a parameter is an integer ≥ 2 is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0028] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0029] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0030] This specific embodiment provides a method for preparing a manganese dioxide / graphene oxide (GDY) composite material, comprising the following steps: mixing a manganese salt solution and graphene oxide (GDY) to obtain a solution a, then mixing a potassium permanganate solution and the solution a to obtain a suspension, and then reacting the suspension at 130-180 ° C for 10-15 hours to obtain the manganese dioxide / graphene oxide composite material.

[0031] In some embodiments, the manganese salt solution is a manganese sulfate solution; the manganese sulfate solution is prepared by the following steps: dissolving MnSO4•H2O in water.

[0032] In some embodiments, mixing the potassium permanganate solution and the a solution to obtain a suspension comprises: dropwise adding the potassium permanganate solution to the a solution to obtain the suspension.

[0033] This specific embodiment further provides a manganese dioxide / graphene composite material, which is prepared by the above preparation method, wherein the mass fraction of C / Mn in the manganese dioxide / graphene composite material is 3.75%-15%.

[0034] In some embodiments, the mass fraction of C / Mn in the manganese dioxide / graphene composite material is 7.5%.

[0035] This specific embodiment also proposes a manganese dioxide / graphene composite material prepared by the above preparation method or the use of the above manganese dioxide / graphene composite material in ozone catalytic decomposition.

[0036] In some embodiments, the ozone catalytic decomposition is performed at a humidity of 0%-60%.

[0037] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0038] In the present invention, references to “some embodiments”, “this embodiment”, examples, etc. describe a subset of all possible embodiments, but it can be understood that “some embodiments” may be the same subset or different subsets of all possible embodiments, and may be combined with each other without conflict.

[0039] If similar descriptions of "first / second" appear in the application documents, the following explanation is added. In the following description, the terms "first\second\third" are merely used to distinguish similar objects and do not represent a specific order of the objects. It can be understood that "first\second\third" can be interchanged with the specific order or sequence where permitted, so that the embodiments described herein can be implemented in an order other than that illustrated or described herein.

[0040] In this embodiment, the term "and / or" is merely a description of the association relationship between associated objects, indicating that three relationships may exist. For example, object A and / or object B may represent three situations: object A exists alone, object A and object B exist at the same time, and object B exists alone.

[0041] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0042] In the following examples, the MnO2 / GDY catalyst was placed in a quartz glass fixed bed reactor with an inner diameter of 6 mm and an outer diameter of 8 mm, loaded with 100 mg of catalyst sample, and the total gas flow rate was controlled at 1.2 L / min, with a mass space velocity of 720,000 mL g -1 h -1 , the ozone concentration is 17 ppm. The ozone concentration in the exhaust gas is detected by an ozone detector, and the humidity is detected by a hygrometer.

[0043] The Graphdiyne (GDY) carrier used in this embodiment is derived from a method for preparing Graphdiyne in a paper published in 2010 (Chem. Commun. 2010, 46, 3256-3258). The synthesis method and steps will not be elaborated in detail here.

[0044] Example 1

[0045] This embodiment provides a MnO2 / GDY catalyst, which is prepared by the following steps:

[0046] 1.166 g of MnSO4•H2O was dissolved in 80 mL of deionized water to obtain solution a. The mixture was stirred continuously, and then graphyne was added to solution a. Finally, 0.727 g of KMnO4 was dissolved in 20 mL of deionized water to obtain solution b. Solution b was added dropwise into solution a to form a uniform suspension. The mixture was stirred continuously for 20 min, and the suspension was transferred to a polytetrafluoroethylene reactor and kept at 150 °C for 12 h. After the reaction was completely cooled, the mixture was washed with deionized water and then transferred to a vacuum oven and kept at 60 °C for 12 h. According to this method, MnO2 / GDY catalysts with C / Mn mass fractions of 3.75%, 7.5%, and 15% and manganese dioxide catalysts without graphyne were prepared by adding different masses of graphyne.

[0047] First, the synthesized catalyst needs to be structurally characterized to confirm whether the target material is accurately synthesized.

[0048] like Figure 1XRD structural analysis shows that the synthesized MnO2 powder has obvious characteristic peaks at diffraction angles of 2θ = 28.7°, 37.5°, 41.9°, 49.8°, 65.3°, and 71.9°, which are consistent with the PDF 44-0141 standard card of MnO2, corresponding to the (310), (400), (211), (301), (411), (002), and (312) crystal plane MnO2 diffraction peaks, respectively. The above proves that MnO2 has been successfully synthesized. Comparing the XRD spectra of MnO2 and 7.50%-MnO2 / GDY samples, it is found that both samples show similar α-MnO2 characteristic peaks, and the peak intensities are comparable, indicating that the crystallinity of MnO2 remains unchanged. Furthermore, no obvious characteristic peaks of gydne were observed in the 7.50%-MnO2 / GDY sample, indicating that the gydne film attached to the MnO2 surface not only did not alter the crystalline phase of α-MnO2 but also that this species was evenly distributed and highly dispersed on the MnO2 surface. However, the 3.75%-MnO2 / GDY and 15%-MnO2 / GDY samples exhibited more pronounced characteristic peaks of gydne, with the intensities of the MnO2 peaks significantly increased and some peaks shifted. This suggests that the strong coordination with gydne significantly altered the crystal structure of MnO2 in the 3.75%-MnO2 / GDY and 15%-MnO2 / GDY samples.

[0049] Furthermore, the synthesized samples were analyzed using Raman spectroscopy, and the position and intensity of the characteristic peaks can reflect the structure of the material. Figure 2 As shown in the Raman spectra of the four samples of MnO2, 3.75%-MnO2 / GDY, 7.5%-MnO2 / GDY and 15%-MnO2 / GDY, the typical Raman vibration of MnO2 is shown at 384 cm -1 、574 cm -1 、639 cm -1 It is a characteristic peak. Among them, 639 cm -1 The peak at 1345 cm is caused by the stretching vibration of the MnO2 octahedron and is an important indicator of the MnO2 structure. -1 and 1570 cm -1 The characteristic peaks of sp2 hybridized carbon breathing vibration and unidirectional stretching vibration in aromatic rings, 1984 cm -1 and 2118 cm -1 It is the characteristic vibration peak of conjugated acetylenic bond, indicating that the MnO2 / GDY catalyst was successfully prepared. Further observation of the Raman shift shows that compared with pure MnO2, the Raman shift at 384 cm -1 and 574 cm -1The band shifts slightly to higher frequencies. This is likely due to the electronic interaction between GDY and MnO2, which changes the local electronic structure of MnO2 and affects the energy of its vibrational modes, manifesting as a shift in the Raman peak. This indicates a strong interaction between the graphyne film and MnO2. The surface morphology of the prepared MnO2 / GDY sample was analyzed using SEM. Figure 3 , Figure 4 and Figure 5 The SEM images of the 3.75%-MnO2 / GDY catalyst, the 3.75%-MnO2 / GDY catalyst, and the 3.75%-MnO2 / GDY catalyst respectively, show the microstructure of the composite materials with different mass fractions of MnO2 loaded on GDY. It can be clearly observed that graphyne is uniformly covered in the form of a thin film on the MnO2 surface, and the elemental distribution map shows that carbon and manganese are evenly distributed, confirming the successful synthesis of MnO2 / GDY catalysts with different doping levels.

[0050] Comparative Example 1

[0051] The catalyst proposed in this comparative example is obtained by mixing MnO2 and graphyne according to a C / Mn mass fraction of 7.5%, that is, a MnO2+GDY mechanically mixed catalyst.

[0052] Comparative Example 2

[0053] The catalyst proposed in this comparative example is graphyne alone.

[0054] Application Example 1

[0055] The application of MnO2 / GDY catalyst for room-temperature catalytic decomposition of ozone specifically includes: loading 100 mg of the above catalyst sample in a quartz tube glass fixed-bed reactor with an inner diameter of 6 mm and an outer diameter of 8 mm, controlling the total gas flow rate to 1.2 L / min and the mass space velocity to 720,000 mL g -1 h -1 , ozone concentration is 16 ppm, humidity is ≤ 3%. Test equipment such as Figure 6 The room temperature catalytic ozone decomposition activities of 3.75%, 7.5%, and 15% MnO2 / GDY catalysts and manganese dioxide catalysts are shown in Figure 2. Figure 7As shown in the figure, the 7.5%-MnO2 / GDY catalyst has 100% ozone decomposition activity and maintains it stably for 12 hours; the 3.75%-MnO2 / GDY and 15%-MnO2 / GDY catalysts drop to 65% and 70% respectively after 12 hours; while the ozone decomposition activity of the manganese dioxide catalyst not doped with graphyne drops rapidly to below 13% after 12 hours. The above results prove that the 7.5%-MnO2 / GDY catalyst has excellent ozone decomposition activity. The ozone decomposition stability test of the 7.5%-MnO2 / GDY catalyst was further carried out under the same conditions, as shown in the figure. Figure 8 As shown in the figure, under the same test conditions, the ozone decomposition activity of the 7.5%-MnO2 / GDY catalyst can be stably maintained for 100 hours, indicating that the catalyst has significant room temperature ozone decomposition stability.

[0056] Application Example 2

[0057] The present embodiment further proposes the application of manganese dioxide / graphene composite materials under different humidity conditions, simulates real environment, and tests the room temperature ozone decomposition activity of 7.5%-MnO2 / GDY catalyst under relative humidity RH=20%, 40%, and 60% respectively.Specific experimental device and test method are with specific embodiment 2, and humidity is controlled by bubbling bottle adjusting flow rate, and humidity is controlled to RH=20%, 40%, and 60% respectively.After 6 hours of activity test results, 7.5%-MnO2 / GDY catalyst under 20% relative humidity condition its ozone decomposition activity will slightly drop to 95%, and when relative humidity is increased to 40%, its ozone decomposition activity will further decline, and can only maintain about 80% after 6 hours, further if relative humidity is increased to 60%, ozone decomposition activity will then rapidly drop to about 45%.The above results show that 7.5%-MnO2 / GDY catalyst has certain water resistance, but ozone decomposition efficiency will be seriously affected under higher humidity environment. In order to verify the water resistance of the catalyst, a dry-wet gas switching test of 7.5%-MnO2 / GDY catalyst was carried out. The results are as follows Figure 10 As shown in the figure, under the condition of relative humidity RH = 0%, the catalyst can maintain 100% ozone decomposition activity. After 3 hours, when it is switched to the first round of humid conditions of RH = 60%, the decomposition efficiency of the catalyst drops rapidly to 53%; when it is switched back to the condition of relative humidity RH = 0%, the ozone decomposition activity of the catalyst rises rapidly to 100%; four rounds of dry-wet switching tests are repeated in this way. In the fourth round of testing under RH = 60% humid conditions, the ozone decomposition activity of the catalyst drops severely to 22%, indicating that water has occupied a part of the active sites on the catalyst surface, thereby affecting the decomposition of ozone.

[0058] Furthermore, the catalytic performance of the MnO2+GDY mechanical mixed catalyst of Comparative Example 1, MnO2 alone, and GDY alone of Comparative Example 2 were tested according to the test conditions and methods of Application Example 1. The results are as follows: Figure 11 As shown, it can be seen that the 7.5%-MnO2 / GDY catalyst proposed in the present invention is significantly better than other catalysts.

[0059] The specific embodiments of the present invention described above do not limit the scope of protection of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a manganese dioxide / graphene composite material, characterized in that: The following steps are involved: A manganese salt solution and graphyne are mixed to obtain a solution a, and then a potassium permanganate solution and the solution a are mixed to obtain a suspension, and then the suspension is hydrothermally reacted at 130-180 ° C to obtain a manganese dioxide / graphyne composite material.

2. The method for preparing the manganese dioxide / graphene composite material according to claim 1, wherein: The manganese salt solution is a manganese sulfate solution.

3. The method for preparing the manganese dioxide / graphene composite material according to claim 1, wherein: The mixing of the potassium permanganate solution and the solution a to obtain the suspension comprises: dropwise adding the potassium permanganate solution to the solution a to obtain the suspension.

4. The method for preparing the manganese dioxide / graphene composite material according to claim 1, wherein: The suspension is hydrothermally reacted at 130-180° C. for 10-15 hours.

5. The method for preparing the manganese dioxide / graphene composite material according to claim 2, wherein: The manganese sulfate solution is prepared by the following steps: dissolving MnSO4•H2O in water.

6. A manganese dioxide / graphene composite material, characterized in that: Prepared by the preparation method according to any one of claims 1 to 5.

7. The manganese dioxide / graphene composite material according to claim 6, characterized in that The mass fraction of C / Mn in the manganese dioxide / graphene composite material is 3.75%-15%.

8. The manganese dioxide / graphene composite material according to claim 7, characterized in that: The mass fraction of C / Mn in the manganese dioxide / graphene composite material is 7.5%.

9. Use of the manganese dioxide / graphene composite material prepared by the preparation method according to any one of claims 1 to 5 or the manganese dioxide / graphene composite material according to any one of claims 6 to 8 in ozone catalytic decomposition.

10. The use according to claim 9, characterized in that Ozone catalytic decomposition is carried out under humidity conditions of 0%-60%.

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