Co-based non-noble metal catalyst as well as preparation method and application thereof

Abstract

The invention provides a Co-based non-noble metal catalyst as well as a preparation method and application thereof, and belongs to the technical field of catalyst preparation. The preparation method of the Co-based non-noble metal catalyst comprises the following steps: uniformly dispersing ZIF-67, a conductive medium and a molybdenum source in a solvent, and then heating to obtain slurry; and coating the surface of a conductive substrate with the slurry, and then obtaining the Co-based non-noble metal catalyst through a carbon thermal shock method. The preparation method provided by the invention can be used for preparation in an atmospheric environment without a high-pressure environment; a rapid carbon thermal shock method is used, the preparation efficiency is high, and particles are uniformly dispersed. The obtained catalyst has good catalytic activity, improves the hydrolysis activity of catalyzing ammonia borane, has good stability, and can be repeatedly used.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst preparation, and particularly relates to a Co-based non-noble metal catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] At present, the energy supply is becoming increasingly scarce, and finding green and clean energy is a major challenge faced currently. Compared with fossil energy, hydrogen energy has prominent advantages such as being green, efficient, and renewable, and is considered an important direction for future energy development. And the safe and efficient storage and transportation of hydrogen energy are important challenges determining its future development. Among many hydrogen storage materials, ammonia borane has received extensive attention and research because of its high hydrogen storage capacity (19.6 wt%), non-toxicity, stability at room temperature, and good solubility in solvents, which is an important research direction for future hydrogen energy development.

[0003] Due to the slow hydrolysis kinetics of ammonia borane itself, the hydrolysis dehydrogenation of ammonia borane needs to be carried out under the action of a catalyst, and a highly efficient and stable catalyst is the key factor determining its hydrolysis performance. The hydrolysis catalysts of ammonia borane are mainly divided into two categories: noble metals and non-noble metals. Noble metal catalysts such as ruthenium (Ru), rhodium (Rh), palladium (Pd), etc. have high catalytic activity in the hydrolysis of ammonia borane to produce hydrogen, but the scarcity and high cost of noble metals greatly hinder their practical applications in the hydrolysis of ammonia borane. Compared with noble metals, non-noble metals such as cobalt (Co), nickel (Ni), copper (Cu), etc., which are low in price and rich in resources, show great potential in the practical applications of ammonia borane hydrolysis. However, there is still a large gap in the catalytic activity between non-noble metals and noble metals, and at the same time, the currently reported non-noble metal catalysts also have the following disadvantages: unstable at room temperature and long preparation time. Therefore, improving the catalytic activity and room temperature stability of non-noble metals and simplifying the preparation process of non-noble metal catalysts have important scientific significance for the development of efficient and economical hydrolysis of ammonia borane to produce hydrogen. Summary of the Invention

[0004] Based on the above, the purpose of the present invention is to provide a Co-based non-noble metal catalyst, a preparation method thereof, and an application thereof.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] One of the technical solutions of the present invention, a preparation method of a Co-based non-noble metal catalyst, includes the following steps:

[0007] Disperse ZIF-67, a conductive medium, and a molybdenum source uniformly in a solvent, and then heat to obtain a slurry;

[0008] Coat the slurry on the surface of a conductive substrate, and then obtain the Co-based non-noble metal catalyst through a carbothermal shock method.

[0009] The second technical solution of the present invention is a Co-based non-noble metal catalyst prepared by the above preparation method.

[0010] The third technical solution of the present invention is an application of the above Co-based non-noble metal catalyst in catalyzing the hydrolysis of ammonia borane to produce hydrogen.

[0011] The present invention discloses the following technical effects:

[0012] The preparation method provided by the present invention can be carried out in an atmospheric environment without a high-pressure environment.

[0013] The present invention uses a rapid carbon thermal shock method, with high preparation efficiency and uniform particle dispersion.

[0014] The present invention uses ZIF-67 as a carrier and provides a Co source, and anchors the Mo 2+ metal precursor on ZIF-67 through π-π conjugation. The addition of Mo 2+ can improve the catalytic activity of ammonia borane hydrolysis. Among them, a cobalt-based catalyst doped with a small amount of Mo has good catalytic activity and improves the hydrolysis activity of catalyzing ammonia borane.

[0015] The Co-based non-noble metal catalyst prepared by the present invention has good stability and can be reused. Description of the Drawings

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0017] Figure 1 SEM image of the CoO-MoO 2 @C catalyst prepared in Example 1;

[0018] Figure 2 Particle size distribution diagram of the CoO-MoO 2 @C catalyst prepared in Example 1;

[0019] Figure 3 BET diagram of the CoO-MoO 2 @C catalyst prepared in Example 1;

[0020] Figure 4 Hydrolysis performance diagram of the CoO-MoO 2 @C catalyst prepared in Example 1 for catalyzing ammonia borane;

[0021] Figure 5Catalytic hydrolysis performance diagram of the catalyst obtained in Comparative Example 1;

[0022] Figure 6 Catalytic hydrolysis performance diagrams of the catalysts obtained in Comparative Examples 2 and 3;

[0023] Figure 7 Catalytic hydrolysis performance diagrams of the catalysts obtained in Comparative Examples 4 and 5;

[0024] Figure 8 Catalytic hydrolysis performance diagram of the catalyst obtained in Comparative Example 6. Detailed Description of the Invention

[0025] The various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation manners of the present invention.

[0026] It should be understood that the terms used in the present invention are only for describing specific embodiments and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0027] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0028] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific implementation manners of the present invention specification, which are obvious to those skilled in the art. Other implementation manners obtained from the specification of the present invention are obvious to those skilled in the art. The specification and examples of the present invention are merely exemplary.

[0029] Regarding the use of "comprising", "including", "having", "containing", etc. in this article, they are all open-ended terms, meaning including but not limited to.

[0030] The present invention uses ZIF-67 as a carrier and Co source, and through π-π conjugation, Mo 2+The metal precursor is anchored on ZIF-67, and through the electronic synergy between the bimetals, the catalytic activity of the cobalt-based catalyst is enhanced to meet the actual application requirements of hydrogen production by ammonia borane hydrolysis.

[0031] In the first aspect of the present invention, a preparation method of a Co-based non-precious metal catalyst is provided, including the following steps:

[0032] Disperse ZIF-67, a conductive medium, and a molybdenum source evenly in a solvent, and then heat to obtain a slurry;

[0033] Coat the slurry on the surface of a conductive substrate, and then obtain the Co-based non-precious metal catalyst through a carbothermal shock method.

[0034] In a preferred embodiment of the present invention, the preparation method of the ZIF-67 is: mix a Co source, cetyltrimethylammonium bromide (CTAB), 2-methylimidazole, and water evenly, and then stir and react; after the stirring reaction ends, centrifuge, wash, and dry to obtain the ZIF-67.

[0035] In the present invention, the Co source is cobalt nitrate hexahydrate (Co(NO 3 ) 2 ·6H 2 O); the mass ratio of Co(NO 3 ) 2 ·6H 2 O, CTAB, and 2-methylimidazole is 58:1:900.

[0036] In the present invention, the temperature of the stirring reaction is room temperature, and the time is 50 min; the stirring speed during the stirring reaction is 800 revolutions per minute.

[0037] In a preferred embodiment of the present invention, the conductive medium is conductive carbon black (BP2000); the molybdenum source is molybdenum acetylacetonate; the solvent is ethanol; the mass ratio of ZIF-67, the conductive medium, and the molybdenum source is 7:7:1.

[0038] In the present invention, if the addition of the molybdenum source is omitted, the catalytic performance of the obtained catalyst is not good; if the addition amount of the molybdenum source is too much, the catalytic performance will also decrease. Only by adding a trace amount of the molybdenum source (under the parameter conditions of the present invention), the catalytic performance can reach the best.

[0039] In a preferred embodiment of the present invention, the heating temperature is 30 - 75 °C, preferably 35 °C. In the present invention, after ZIF-67, the conductive medium, and the molybdenum source are evenly dispersed in ethanol, heat at 30 - 75 °C to volatilize ethanol until the solution becomes viscous.

[0040] In a preferred embodiment of the present invention, the conductive substrate is carbon cloth; the voltage of the carbon thermal shock method is 22.8 V. After applying the voltage in the present invention, the duration is about 1 second, and the preparation of the Co-based non-precious metal catalyst can be completed. When the applied voltage is 22.8 V, the instantaneous central temperature is about 850 °C.

[0041] The second aspect of the present invention provides a Co-based non-precious metal catalyst prepared by the above preparation method.

[0042] The third aspect of the present invention provides an application of the above Co-based non-precious metal catalyst in catalyzing the hydrolysis of ammonia borane to produce hydrogen.

[0043] The technical solutions of the present invention, unless otherwise specified, are all conventional solutions in the art. The reagents or raw materials used, unless otherwise specified, are all purchased from commercial channels or are publicly available.

[0044] To better understand the present invention, the content of the present invention will be further clarified below in conjunction with embodiments, but the content of the present invention is not limited to the following embodiments.

[0045] Example 1

[0046] Step 1. Add 9.08 g of 2-methylimidazole and 140 mL of deionized water to a 250 mL beaker, and slowly pour it into Co(NO 3 ) 2 ·6H 2 O (0.58 g) and 0.01 g of CTAB solution dissolved in 20 mL of deionized water. Stir and react at 800 rpm at room temperature for 50 min, centrifuge in a centrifuge (9500 rpm / 3 min), and then wash 3 times with deionized water and ethanol respectively, and vacuum dry at 75 °C for 12 h to obtain ZIF-67.

[0047] Step 2. Ultrasonically disperse 90 mg of ZIF-67, 90 mg of BP2000, and 0.04 mmol of molybdenum acetylacetonate in 25 mL of ethanol, and then evaporate the ethanol at 35 °C. When the solution becomes viscous, brush it on the surface of a 5×6 cm carbon cloth with a brush. After the carbon cloth surface is dried, cut the carbon cloth into a 1×2 cm rectangle, and then clamp it at both ends of a carbon thermal shock instrument. Perform carbon thermal shock at 22.8 V (duration about 1 second, instantaneous central temperature about 850 °C) to obtain a CoO-MoO 2 @C catalyst.

[0048] The SEM image of the catalyst prepared in this example is as Figure 1 shown, indicating that uniformly dispersed nanoparticles are prepared after carbon thermal shock. The corresponding particle size distribution Figure 2 shows that the average particle size of this catalyst is 26.8 nm. BET Figure 3The results show that this catalyst has a high specific surface area.

[0049] The catalytic performance of the prepared catalyst was evaluated by the water displacement method at room temperature. First, 40 mg of the above catalyst was weighed and placed in a 25 mL round-bottom flask. Then, 5 mL of 1 M aqueous sodium hydroxide solution was added, and the mixture was sonicated for 2 min. After that, 200 μL of 1 mmol aqueous ammonia borane solution was injected into the round-bottom flask using a microsyringe. The hydrolysis performance of ammonia borane catalyzed by this catalyst is as Figure 4 . During the first hydrolysis, ammonia borane completely released hydrogen within 1.7 min, and the catalyst still had excellent catalytic performance after 8 cycles.

[0050] Comparative Example 1

[0051] Step 1. The same as Step 1 of Example 1.

[0052] Step 2. 90 mg of ZIF-67 and 90 mg of BP2000 were ultrasonically dispersed in 25 mL of ethanol. Then, the ethanol was evaporated at 35 °C. When the solution became viscous, it was brushed onto the surface of a 5×6 cm carbon cloth using a brush. After the carbon cloth surface was dried, the carbon cloth was cut into a 1×2 cm rectangle, and then it was clamped at both ends of a carbon thermal shock instrument and subjected to carbon thermal shock at 22.8 V (the duration was about 1 second, and the instantaneous center temperature was about 850 °C) to prepare the catalyst.

[0053] The catalytic performance of the prepared catalyst was evaluated by the water displacement method at room temperature. First, 40 mg of the above catalyst was weighed and placed in a 25 mL round-bottom flask. Then, 5 mL of 1 M aqueous sodium hydroxide solution was added, and the mixture was sonicated for 2 min. After that, 200 μL of 1 mmol aqueous ammonia borane solution was injected into the round-bottom flask using a microsyringe. The hydrolysis performance of ammonia borane catalyzed by this catalyst is as Figure 5 (In the figure, CTS represents carbon thermal shock, CTS ZIF-67 + 0.04 mmol Mo 2+ represents the catalyst of Example 1, and CTS ZIF-67 represents the catalyst of Comparative Example 1), and ammonia borane completely released hydrogen within 3.5 min.

[0054] Comparative Example 2

[0055] Step 1. The same as Step 1 of Example 1.

[0056] Step 2. Ultrasonically disperse 90 mg of ZIF-67 and 90 mg of BP2000 in 25 mL of ethanol, then evaporate the ethanol at 35 °C. When the solution becomes viscous, brush it onto the surface of a 5×6 cm carbon cloth. After the carbon cloth surface dries, cut the carbon cloth into a 1×2 cm rectangle, then clamp it at both ends of a carbon thermal shock instrument and perform carbon thermal shock at 20.4 V (duration about 1 second) to obtain the catalyst. (That is, the difference from Comparative Example 1 is that the voltage of carbon thermal shock is adjusted from 22.8 V to 20.4 V)

[0057] The catalytic performance of the prepared catalyst was evaluated by the water displacement method at room temperature. First, weigh 40 mg of the above catalyst, put it into a 25 mL round-bottom flask, add 5 mL of 1 M sodium hydroxide aqueous solution, ultrasonicate for 2 min, and then inject 200 μL of 1 mmol ammonia borane aqueous solution into the round-bottom flask with a micro syringe. The hydrolysis performance of ammonia borane catalyzed by this catalyst is as Figure 6 (In the figure, 20.4 V represents Comparative Example 2, and 22.8 V represents Comparative Example 1), and ammonia borane completely releases hydrogen in 2.48 min.

[0058] Comparative Example 3

[0059] Step 1. The same as Step 1 of Example 1.

[0060] Step 2. Ultrasonically disperse 90 mg of ZIF-67 and 90 mg of BP2000 in 25 mL of ethanol, then evaporate the ethanol at 35 °C. When the solution becomes viscous, brush it onto the surface of a 5×6 cm carbon cloth. After the carbon cloth surface dries, cut the carbon cloth into a 1×2 cm rectangle, then clamp it at both ends of a carbon thermal shock instrument and perform carbon thermal shock at 25.2 V (duration about 1 second) to obtain the catalyst. (That is, the difference from Comparative Example 1 is that the voltage of carbon thermal shock is adjusted from 22.8 V to 25.2 V)

[0061] The catalytic performance of the prepared catalyst was evaluated by the water displacement method at room temperature. First, weigh 40 mg of the above catalyst, put it into a 25 mL round-bottom flask, add 5 mL of 1 M sodium hydroxide aqueous solution, ultrasonicate for 2 min, and then inject 200 μL of 1 mmol ammonia borane aqueous solution into the round-bottom flask with a micro syringe. The hydrolysis performance of ammonia borane catalyzed by this catalyst is as Figure 6 , and ammonia borane completely releases hydrogen in 2.43 min.

[0062] Comparative Example 4

[0063] Step 1. The same as Step 1 of Example 1.

[0064] Step 2. Ultrasonically disperse 90 mg of ZIF-67, 90 mg of BP2000, and 0.04 mmol of manganese acetylacetonate in 25 mL of ethanol. Then evaporate the ethanol at 35 °C. When the solution becomes viscous, brush it onto the surface of a 5×6 cm carbon cloth. After the carbon cloth surface dries, cut the carbon cloth into a 1×2 cm rectangle, and then clamp it at both ends of a carbon thermal shock instrument. Perform carbon thermal shock at 22.8 V (duration about 1 second) to obtain the catalyst. (That is, different from Example 1 in that molybdenum acetylacetonate is replaced by manganese acetylacetonate)

[0065] Evaluate the catalytic performance of the prepared catalyst by the water displacement method at room temperature. First, weigh 40 mg of the above catalyst and put it into a 25 mL round-bottom flask. Add 5 mL of 1 M sodium hydroxide aqueous solution and ultrasonicate for 2 min. Then inject 200 μL of 1 mmol ammonia borane aqueous solution into the round-bottom flask using a microsyringe. The hydrolysis performance of ammonia borane catalyzed by this catalyst is as Figure 7 , and ammonia borane releases hydrogen completely in 5 min.

[0066] Comparative Example 5

[0067] Step 1. The same as Step 1 of Example 1.

[0068] Step 2. Ultrasonically disperse 90 mg of ZIF-67, 90 mg of BP2000, and 0.04 mmol of zirconium acetylacetonate in 25 mL of ethanol. Then evaporate the ethanol at 35 °C. When the solution becomes viscous, brush it onto the surface of a 5×6 cm carbon cloth. After the carbon cloth surface dries, cut the carbon cloth into a 1×2 cm rectangle, and then clamp it at both ends of a carbon thermal shock instrument. Perform carbon thermal shock at 22.8 V (duration about 1 second) to obtain the catalyst. (That is, different from Example 1 in that molybdenum acetylacetonate is replaced by zirconium acetylacetonate)

[0069] Evaluate the catalytic performance of the prepared catalyst by the water displacement method at room temperature. First, weigh 40 mg of the above catalyst and put it into a 25 mL round-bottom flask. Add 5 mL of 1 M sodium hydroxide aqueous solution and ultrasonicate for 2 min. Then inject 200 μL of 1 mmol ammonia borane aqueous solution into the round-bottom flask using a microsyringe. The hydrolysis performance of ammonia borane catalyzed by this catalyst is as Figure 7 (In the figure, 0.04 mmol Mo represents Example 1, 0.04 mmol Mn represents Comparative Example 4, and 0.04 mmol Zr represents Comparative Example 5), and ammonia borane releases hydrogen completely in 3.35 min.

[0070] Comparative Example 6

[0071] The difference from Example 1 is only that 90 mg of ZIF-67 and 0.04 mmol of molybdenum acetylacetonate are replaced with 90 mg of ZIF-67 and 0.02 mmol of molybdenum acetylacetonate, and other steps and parameters are the same as those in Example 1.

[0072] The catalytic performance of the prepared catalyst was evaluated by the water displacement method at room temperature. First, 40 mg of the above catalyst was weighed and placed in a 25 mL round-bottom flask. 5 mL of 1 M aqueous sodium hydroxide solution was added, and it was ultrasonically treated for 2 min. Then, 200 μL of 1 mmol aqueous ammonia borane solution was injected into the round-bottom flask with a micro syringe. The hydrolysis performance of ammonia borane catalyzed by this catalyst is as Figure 8 (In the figure, 0.04 mmol Mo 2+ ZIF-67 represents Example 1, and 0.02 mmol Mo 2+ ZIF-67 represents Comparative Example 6). When the addition amount of Mo is too low, the catalytic performance of the catalyst will be reduced.

[0073] The above are only the preferred embodiments 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 and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a Co-based non-precious metal catalyst, characterized in that: The following steps are involved: The ZIF-67, the conductive medium and the molybdenum source are uniformly dispersed in a solvent, and then heated to obtain a slurry; The slurry is coated on the surface of a conductive substrate, and then the Co-based non-precious metal catalyst is obtained by a carbon thermal shock method.

2. The preparation method according to claim 1, characterized in that: The preparation method of ZIF-67 is as follows: after uniformly mixing Co source, hexadecyltrimethylammonium bromide, 2-methylimidazole and water, stirring for reaction; after the stirring reaction is completed, centrifuging, washing and drying to obtain the ZIF-67.

3. The preparation method according to claim 2, characterized in that: The Co source is cobalt nitrate hexahydrate; the mass ratio of cobalt nitrate hexahydrate, hexadecyltrimethylammonium bromide and 2-methylimidazole is 58:1:

900.

4. The preparation method according to claim 2, characterized in that: The stirring reaction was carried out at room temperature for 50 minutes. The stirring speed during the stirring reaction was 800 revolutions per minute.

5. The preparation method according to claim 1, characterized in that: The conductive medium is conductive carbon black; the molybdenum source is molybdenum acetylacetonate; the solvent is ethanol; and the mass ratio of the ZIF-67, the conductive medium and the molybdenum source is 7:7:

1.

6. The preparation method according to claim 1, characterized in that: The heating temperature is 30-75°C.

7. The preparation method according to claim 1, characterized in that: The conductive substrate is carbon cloth; the voltage of the carbon thermal shock method is 22.8V.

8. A Co-based non-precious metal catalyst prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the Co-based non-precious metal catalyst according to claim 8 in catalyzing the hydrolysis of ammonia borane to produce hydrogen.

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