Preparation method and application of MOF-derived multilayer carbon material catalyst

Abstract

The invention is applicable to the technical field of hydrogen production, and provides a preparation method and application of an MOF-derived multilayer carbon material catalyst, and the catalyst is prepared by taking cobalt-based MOF as a precursor, roasting at high temperature, and then carrying out DBD plasma treatment under specific conditions. DBD treatment can effectively reduce the particle size of the catalyst, increase exposure of active sites and improve the dispersity of cobalt species. The obtained catalyst is used for ammonia borane methanol decomposition hydrogen production reaction, efficient hydrogen production can be achieved under mild conditions, and the catalytic activity of the catalyst is equivalent to that of part of noble metal catalysts. The preparation method is simple in preparation process, low in energy consumption and environment-friendly, and a new way is provided for development of non-noble metal catalysts and application of ammonia borane hydrogen storage materials.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen production technology, and particularly relates to a method for preparing MOF-derived multilayer carbon material catalysts and their applications. Background Technology

[0002] With the rapid development of the global economy, the demand for clean energy is becoming increasingly urgent. Hydrogen, as a clean and efficient energy carrier, has shown great application potential in many fields. However, hydrogen faces numerous challenges in storage and transportation, which limits its large-scale application and promotion. Ammonia borane (NH3BH3, abbreviated as AB) is a promising new hydrogen storage material. It has the following significant advantages: the theoretical hydrogen storage density of ammonia borane is as high as 19.6 wt%, a value far exceeding that of many traditional hydrogen storage materials, enabling it to store more hydrogen with the same mass.

[0003] Currently, there are three routes for producing hydrogen from ammonia borane: pyrolysis, hydrolysis, and alcoholysis. Pyrolysis requires very high temperatures and generates polymers and gaseous byproducts, making it difficult to apply practically. Compared to pyrolysis, hydrolysis and alcoholysis can produce 3 equivalents of hydrogen at room temperature by adding suitable catalysts. During the hydrolysis of ammonia borane, NH3 is produced as a byproduct, which is toxic to batteries, and the hydrolysis products are difficult to recover. Therefore, researching catalysts for hydrogen production from methanol decomposition of ammonia borane has practical application significance. The hydrogen production from the alcoholysis of ammonia borane is under mild conditions, but the molecular weight of CH3OH is larger than that of H2O, resulting in relatively slow adsorption kinetics and reactivity, requiring the presence of a suitable catalyst. By adjusting the active components, particle size, dispersion, and electronic structure of the catalyst, the hydrogen production rate from the alcoholysis of ammonia borane can be significantly improved.

[0004] Dielectric barrier discharge (DBD) is a non-equilibrium gas plasma discharge technique that inserts an insulating dielectric into the discharge space. Compared with traditional heat treatment methods, DBD plasma technology has significant advantages: the large number of high-energy species generated during the process can greatly accelerate the nucleation rate of nanoparticle precursors; the system temperature is close to room temperature, effectively suppressing crystal nucleus growth, thereby obtaining smaller catalyst particle sizes; and high-energy particle bombardment can enhance the interaction between the active component and the support. Therefore, DBD technology is a green, efficient, and advanced method suitable for the preparation and modification of supported nanocatalysts. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing MOF-derived multilayer carbon material catalysts and their applications, aiming to solve the problems mentioned in the background art.

[0006] The present invention is implemented as follows: a method for preparing a MOF-derived multilayer carbon material catalyst includes the following steps: Step 1: Dissolve terephthalic acid and cobalt nitrate hexahydrate in DMF and stir for 10-200 min to form solution A; the molar ratio of terephthalic acid to cobalt nitrate hexahydrate in solution A is 1:1, and the mass percentage of solution A is 10-40% of DMF. Step 2: Add sodium hydroxide solution dropwise to solution A under stirring to form solution B, and stir for 5-720 minutes; Step 3: Transfer solution B to the reaction vessel and react at 100~200℃ for 2-48h. After cooling, take the solid at the bottom of the vessel, centrifuge it, and then dry it in an oven at 70-150℃ for 2-48h until the mass is constant. Step 4: Transfer the dried solid obtained in Step 3 to a quartz boat and, under a stable Ar gas flow, heat it at 0.5-10℃·min. -1 The heating rate is increased to 400~600℃ for 1-48h, and Ar atmosphere is continuously introduced into the tube furnace, followed by natural cooling to room temperature. Step 5: Place the solid obtained in Step 4 into the DBD reactor. Set the device voltage to 24-80V and the frequency to 8.9-9.3kHz, and the concentration to 0.1-20.0 mL·g. -1 ·s -1 DBD treatment is performed in an air atmosphere for 0.5-10 minutes each time, and the number of treatments is 1-10 times; the treated sample is the catalyst.

[0007] In a further technical solution, the reaction temperature in the reactor is 158°C in step 3.

[0008] In a further technical solution, in step 4, the calcination temperature of the tubular furnace is 500°C.

[0009] In a further technical solution, in step 5, the DBD frequency is set to 9.0 kHz.

[0010] Another objective of this invention is to provide an application of a MOF-derived multilayer carbon material catalyst, wherein the catalyst prepared by the above method is used to catalyze the hydrogen production reaction of ammonia borane.

[0011] In a further technical solution, the reaction medium for the hydrogen production reaction is anhydrous methanol, the reaction temperature is 25-60℃, and the mass ratio of the catalyst to ammonia borane is (0.05-2.00):1.

[0012] The present invention provides a method for preparing a MOF-derived multilayer carbon material catalyst and its application, the beneficial effects of which are as follows: (1) High efficiency and energy saving: The catalyst precursor is processed by DBD plasma technology at near room temperature, which consumes far less energy than traditional high temperature heat treatment. It is a green and efficient catalyst modification method.

[0013] (2) Excellent performance: DBD treatment can effectively reduce the particle size of the cobalt-based active component in the catalyst, improve its dispersion, and expose more active sites, thereby significantly enhancing the intrinsic activity of the catalyst in the ammonia borane alcoholysis reaction. After DBD treatment under specific conditions (such as 9.0 kHz), the catalyst's transition frequency (TOF) can reach 1.92 mol H2·mol Metal. -1 ·min -1 Its performance is comparable to that of some precious metal catalysts.

[0014] (3) Low cost: The catalyst uses non-precious metal cobalt as the active center, which has low raw material cost and is suitable for large-scale preparation and practical application.

[0015] (4) Mild reaction conditions: The catalyst can efficiently catalyze the alcoholysis of ammonia borane to produce hydrogen under mild conditions from room temperature to 60°C, which reduces the energy consumption and requirements of the reaction system. Attached Figure Description

[0016] Figure 1 Images showing the activity of the catalysts obtained in each embodiment; Figure 2 XRD patterns and corresponding PDF cards of the catalysts obtained in each example; Figure 3 The image is a transmission electron microscope image of the catalyst obtained after DBD processing at 9.0 kHz. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the 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 merely illustrative and not intended to limit the invention.

[0018] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0019] An embodiment of the present invention provides a method for preparing a MOF-derived multilayer carbon material catalyst, comprising the following steps: Step 1: Dissolve terephthalic acid and cobalt nitrate hexahydrate in DMF and stir for 10-200 min to form solution A; the molar ratio of terephthalic acid to cobalt nitrate hexahydrate in solution A is 1:1, and the mass percentage of solution A is 10-40% of DMF. Step 2: Add sodium hydroxide solution dropwise to solution A under stirring to form solution B, and stir for 5-720 minutes; Step 3: Transfer solution B to the reaction vessel and react at 100~200℃ for 2-48h. After cooling, take the solid at the bottom of the vessel, centrifuge it, and then dry it in an oven at 70-150℃ for 2-48h until the mass is constant. Step 4: Transfer the dried solid obtained in Step 3 to a quartz boat and, under a stable Ar gas flow, heat it at 0.5-10℃·min. -1 The heating rate is increased to 400~600℃ for 1-48h, and Ar atmosphere is continuously introduced into the tube furnace, followed by natural cooling to room temperature. Step 5: Place the solid obtained in Step 4 into the DBD reactor. Set the device voltage to 24-80V and the frequency to 8.9-9.3kHz, and the concentration to 0.1-20.0 mL·g. -1 ·s -1 DBD treatment is performed in an air atmosphere for 0.5-10 minutes each time, and the number of treatments is 1-10 times; the treated sample is the catalyst.

[0020] In a preferred embodiment of the present invention, the sodium hydroxide solution is formed by dissolving 1-10 mmol of sodium hydroxide (NaOH) in 1-10 mL of deionized water and ultrasonically vibrating for 1-60 min.

[0021] Several specific embodiments are provided below to verify the effectiveness of this method.

[0022] Example 1: Step 1: Dissolve 5 mmol of terephthalic acid and 5 mmol of cobalt nitrate hexahydrate in DMF and stir for 15 min to form solution A; Step 2: Add sodium hydroxide solution dropwise to solution A under stirring to form solution B, and stir for 30 minutes; Step 3: Transfer the B solution to the reaction vessel and react at 158°C for 24 hours. After cooling, take the solid from the bottom of the vessel, centrifuge it three times, and then dry it in a 70°C oven until the mass is constant. Step 4: Take 2g of the dried solid obtained in Step 3 and place it in a quartz boat. Under a stable Ar gas flow, incubate at 2℃·min. -1 The product was heated to 500℃ at a heating rate for 2 hours, and Ar atmosphere was continuously introduced into the tube furnace. Then it was cooled to room temperature by natural cooling. The product obtained was the target product and named Co-MIL-500℃. When 50 mg of the obtained powder is placed in a methanol solution of 50 mg of ammonia borane as a catalyst, approximately 13.3 mL of hydrogen gas can be produced in 1 minute.

[0023] Example 2: Step 1: Dissolve 5 mmol of terephthalic acid and 5 mmol of cobalt nitrate hexahydrate in DMF and stir for 15 min to form solution A; Step 2: Add sodium hydroxide solution dropwise to solution A under stirring to form solution B, and stir for 30 minutes; Step 3: Transfer the B solution to the reaction vessel and react at 158°C for 24 hours. After cooling, take the solid from the bottom of the vessel, centrifuge it three times, and then dry it in a 70°C oven until the mass is constant. Step 4: Take 2g of the dried solid obtained in Step 3 and place it in a quartz boat. Under a stable Ar gas flow, incubate at 2℃·min. -1 The temperature was heated to 500°C for 2 hours, and Ar atmosphere was continuously introduced into the tube furnace. Then the temperature was cooled to room temperature by natural cooling. Step 5: Take 0.1g of the solid obtained in Step 4 and put it into the DBD reactor. Set the voltage of the device to 60V and the frequency to 8.9kHz. Perform DBD treatment 6 times in air atmosphere, 5min each time, for a total of 30min. The resulting powder is the target product, named Co-MIL-500℃-DBD-8.9. When 50 mg of the obtained powder is placed in a methanol solution of 50 mg of ammonia borane as a catalyst, approximately 11.2 mL of hydrogen gas can be produced in 1 minute.

[0024] Example 3: Step 1: Dissolve 5 mmol of terephthalic acid and 5 mmol of cobalt nitrate hexahydrate in DMF and stir for 15 min to form solution A; Step 2: Add sodium hydroxide solution dropwise to solution A under stirring to form solution B, and stir for 30 minutes; Step 3: Transfer the B solution to the reaction vessel and react at 158°C for 24 hours. After cooling, take the solid from the bottom of the vessel, centrifuge it three times, and then dry it in a 70°C oven until the mass is constant. Step 4: Take 2g of the dried solid obtained in Step 3 and place it in a quartz boat. Under a stable Ar gas flow, incubate at 2℃·min. -1 The temperature was heated to 500°C for 2 hours, and Ar atmosphere was continuously introduced into the tube furnace. Then the temperature was cooled to room temperature by natural cooling. Step 5: Place the solid obtained in Step 4 into the DBD reactor. Set the voltage to 60V and the frequency to 9.0kHz. Perform DBD treatment 6 times in an air atmosphere, 5 minutes each time, for a total of 30 minutes. The resulting powder is the target product, named Co-MIL-500℃-DBD-9.0. When 50 mg of the obtained powder is placed in a methanol solution of 50 mg of ammonia borane as a catalyst, approximately 42.3 mL of hydrogen gas can be produced in 1 minute.

[0025] Example 4: Step 1: Dissolve 5 mmol of terephthalic acid and 5 mmol of cobalt nitrate hexahydrate in DMF and stir for 15 min to form solution A; Step 2: Add sodium hydroxide solution dropwise to solution A under stirring to form solution B, and stir for 30 minutes; Step 3: Transfer the B solution to the reaction vessel and react at 158°C for 24 hours. After cooling, take the solid from the bottom of the vessel, centrifuge it three times, and then dry it in a 70°C oven until the mass is constant. Step 4: Take 2g of the dried solid obtained in Step 3 and place it in a quartz boat. Under a stable Ar gas flow, incubate at 2℃·min. -1 The temperature was heated to 500°C for 2 hours, and Ar atmosphere was continuously introduced into the tube furnace. Then the temperature was cooled to room temperature by natural cooling. Step 5: Place the solid obtained in Step 4 into the DBD reactor. Set the voltage to 60V and the frequency to 9.1kHz. Perform DBD treatment 6 times in an air atmosphere, 5 minutes each time, for a total of 30 minutes. The resulting powder is the target product, named Co-MIL-500℃-DBD-9.1. When 50 mg of the obtained powder is placed in a methanol solution of 50 mg of ammonia borane as a catalyst, approximately 14.7 mL of hydrogen gas can be produced in 1 minute.

[0026] Example 5: Step 1: Dissolve 5 mmol of terephthalic acid and 5 mmol of cobalt nitrate hexahydrate in DMF and stir for 15 min to form solution A; Step 2: Add sodium hydroxide solution dropwise to solution A under stirring to form solution B, and stir for 30 minutes; Step 3: Transfer the B solution to the reaction vessel and react at 158°C for 24 hours. After cooling, take the solid from the bottom of the vessel, centrifuge it three times, and then dry it in a 70°C oven until the mass is constant. Step 4: Take 2g of the dried solid obtained in Step 3 and place it in a quartz boat. Under a stable Ar gas flow, incubate at 2℃·min. -1 The temperature was heated to 500°C for 2 hours, and Ar atmosphere was continuously introduced into the tube furnace. Then the temperature was cooled to room temperature by natural cooling. Step 5: Place the solid obtained in Step 4 into the DBD reactor. Set the voltage to 60V and the frequency to 9.2kHz. Perform DBD treatment 6 times in an air atmosphere, 5 minutes each time, for a total of 30 minutes. The resulting powder is the target product, named Co-MIL-500℃-DBD-9.2. When 50 mg of the obtained powder is placed in a methanol solution of 50 mg of ammonia borane as a catalyst, approximately 13.3 mL of hydrogen gas can be produced in 1 minute.

[0027] Example 6: Step 1: Dissolve 5 mmol of terephthalic acid and 5 mmol of cobalt nitrate hexahydrate in DMF and stir for 15 min to form solution A; Step 2: Add sodium hydroxide solution dropwise to solution A under stirring to form solution B, and stir for 30 minutes; Step 3: Transfer the B solution to the reaction vessel and react at 158°C for 24 hours. After cooling, take the solid from the bottom of the vessel, centrifuge it three times, and then dry it in a 70°C oven until the mass is constant. Step 4: Take 2g of the dried solid obtained in Step 3 and place it in a quartz boat. Under a stable Ar gas flow, incubate at 2℃·min. -1 The temperature was heated to 500°C for 2 hours, and Ar atmosphere was continuously introduced into the tube furnace. Then the temperature was cooled to room temperature by natural cooling. Step 5: Place the solid obtained in Step 4 into the DBD reactor. Set the voltage to 60V and the frequency to 9.3kHz. Perform DBD treatment 6 times in an air atmosphere, 5 minutes each time, for a total of 30 minutes. The resulting powder is the target product, named Co-MIL-500℃-DBD-9.3. When 50 mg of the obtained powder is placed in a methanol solution of 50 mg of ammonia borane as a catalyst, approximately 7.6 mL of hydrogen gas can be produced in 1 minute.

[0028] Activity images of the catalysts prepared in each embodiment are shown below. Figure 1 As shown, based on Figure 1 It is evident that the hydrogen production rates of some Co-MIL-500℃ series catalysts (Co-MIL-500℃-DBD-9.0 to Co-MIL-500℃-DBD-9.2) modified by DBD are significantly better than those of the unmodified Co-MIL-500℃ catalyst. Among them, the performance improvement of the Co-MIL-500℃-DBD-9.0 catalyst is the most prominent. When the reaction proceeds to about 3 minutes, its hydrogen production volume is already far greater than that of the unmodified Co-MIL-500℃ catalyst, and it maintains a better hydrogen production efficiency throughout the entire reaction cycle. This fully demonstrates that the DBD modification process used in this invention can effectively improve the catalytic hydrogen production activity of Co-based catalysts.

[0029] The TOF values ​​of Examples 1, 2, and some existing catalysts are shown in Table 1 below.

[0030] Table 1

[0031] As shown in Table 1, the DBD-modified Co-based material (Co-MIL-500℃-DBD-9.0) of this invention achieves a catalytic conversion frequency (TOF) of 1.92. Compared to the baseline Co-based material (Co-MIL-500℃) without DBD modification, this TOF value represents an increase of approximately 2.2 times, significantly improving the utilization efficiency of the active sites. In contrast, the typical Co-based composite catalyst Co-Ni-P / Pd-TiO2 in the prior art has a TOF value of 0.3. Although the overall TOF level of Co-based materials is lower than that of Ag-based and Pd-based noble metal materials, this invention, through the regulation of the DBD modification process, effectively improves the efficiency of the active sites in Co-based materials, providing a feasible path for the performance upgrade of low-cost Co-based catalysts.

[0032] based on Figure 2 It is known that the active species in the unmodified catalyst is mainly elemental cobalt, while the crystalline phases in the modified catalyst are elemental cobalt, cobalt monoxide, and cobalt tetroxide. The degree of catalyst oxidation can be controlled by adjusting the frequency of the DBD reactor. At a discharge frequency of 9.0 kHz, this type of cobalt species is most favorable for the decomposition of ammonia borane into methanol to produce hydrogen, which is consistent with the literature reports.

[0033] based on Figure 3 It can be seen that the diameter of the catalyst particles after DBD modification is 40-60 nm, indicating that the active sites of the catalyst after DBD modification have been redispersed and some of the multilayer carbon wrapped on the active sites have been eliminated, so that the active sites are more fully exposed and the rate of ammonia borane alcoholysis reaction is improved.

[0034] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a MOF-derived multilayer carbon material catalyst, characterized in that, Includes the following steps: Step 1: Dissolve terephthalic acid and cobalt nitrate hexahydrate in DMF and stir for 10-200 min to form solution A; the molar ratio of terephthalic acid to cobalt nitrate hexahydrate in solution A is 1:1, and the mass percentage of solution A is 10-40% of DMF. Step 2: Add sodium hydroxide solution dropwise to solution A under stirring to form solution B, and stir for 5-720 minutes; Step 3: Transfer solution B to the reaction vessel and react at 100~200℃ for 2-48h. After cooling, take the solid at the bottom of the vessel, centrifuge it, and then dry it in an oven at 70-150℃ for 2-48h until the mass is constant. Step 4: Transfer the dried solid obtained in Step 3 to a quartz boat and, under a stable Ar gas flow, heat it at 0.5-10℃·min. -1 The heating rate is increased to 400~600℃ for 1-48h, and Ar atmosphere is continuously introduced into the tube furnace, followed by natural cooling to room temperature. Step 5: Place the solid obtained in Step 4 into the DBD reactor. Set the device voltage to 24-80V and the frequency to 8.9-9.3kHz, and the concentration to 0.1-20.0 mL·g. -1 ·s -1 DBD treatment is performed in an air atmosphere for 0.5-10 minutes each time, and the number of treatments is 1-10 times; the treated sample is the catalyst.

2. The method for preparing the MOF-derived multilayer carbon material catalyst according to claim 1, characterized in that, In step 2, the sodium hydroxide solution is formed by dissolving 1-10 mmol of sodium hydroxide in 1-10 mL of deionized water and then ultrasonically vibrating for 1-60 min.

3. The method for preparing the MOF-derived multilayer carbon material catalyst according to claim 1, characterized in that, In step 3, the reaction temperature in the reactor is 158°C.

4. The method for preparing the MOF-derived multilayer carbon material catalyst according to claim 1, characterized in that, In step 4, the calcination temperature of the tubular furnace is 500°C.

5. The method for preparing the MOF-derived multilayer carbon material catalyst according to claim 1, characterized in that, In step 5, the DBD frequency is set to 9.0 kHz.

6. The method for preparing the MOF-derived multilayer carbon material catalyst according to claim 1, characterized in that, In step 5, DBD is performed 6 times, each time for 5 minutes, for a total of 30 minutes.

7. An application of a MOF-derived multilayer carbon material catalyst, based on the preparation method of the MOF-derived multilayer carbon material catalyst according to any one of claims 1-6, wherein the prepared catalyst is characterized in that, The catalyst was used to catalyze the hydrogen production reaction of ammonia borane.

8. The application of the MOF-derived multilayer carbon material catalyst according to claim 7, characterized in that, The reaction medium for the hydrogen production reaction is anhydrous methanol, the reaction temperature is 25-60℃, and the mass ratio of catalyst to ammonia borane is (0.05-2.00):1.

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