A simple preparation method and application of a high-loading oxygen ligand nickel monatomic composite graphene base catalyst

Abstract

The application belongs to the technical field of catalytic materials, and discloses a simple preparation method and application of a high-load oxygen ligand nickel monatomic composite graphene base catalyst. The catalyst is prepared by using the graphene oxide peeled off by the improved Hummer method as a carrier to load highly dispersed monatomic nickel salt under the condition of no high temperature and high pressure, using the energy change of graphene reduction to connect the nickel metal and the carrier, and using a simple one-step co-reduction method to obtain the high-load oxygen ligand nickel monatomic composite graphene base catalyst. The catalyst has high catalytic activity, excellent metal dispersion, high specific surface area, and high metal monatomic load, and can be used for catalytic oxidation of various volatile organic pollutants, and has high practical significance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalytic materials, and particularly relates to a simple preparation method of a high-load oxygen ligand nickel monatomic composite graphene base catalyst and application. BACKGROUND

[0002] Volatile organic compounds (VOCs) are the main precursors of urban haze and photochemical smog and other air pollution. They are toxic, irritating, teratogenic and carcinogenic, posing a great threat to human health. Catalytic oxidation is currently one of the most effective means to eliminate VOCs, because it has the outstanding advantages of high removal rate, low reaction temperature and less secondary pollution. Atomic-level catalysts are used for low-temperature catalytic oxidation of VOCs due to their special structure and significant activity, selectivity and stability. However, exploring a simple method to synthesize a catalyst with high load and good stability is the biggest challenge in the controllable preparation of atomic-level catalysts. Atomic dispersed metals are prone to migration and aggregation, and it can be further understood that the interaction between the metal and the support and the atomic-level coordination environment are necessary conditions to improve the atomic dispersion and stability. Reduced graphene oxide (RGO) is obtained by reducing graphene oxide and has important application prospects in materials science, energy, biomedical and drug delivery, etc. Its large specific surface area and rich surface unsaturated atoms can be used as a catalyst carrier to load various atomic-level metals, which is of great significance for the design and development of high-performance metal catalysts. Based on RGO, graphene-based composite materials are formed by compounding with other materials, mainly including compounding with metals and their oxides. Metal-graphene composite materials have been widely studied and applied due to their high strength, high corrosion resistance, excellent electrical and thermal properties, etc. Therefore, in order to reduce the amount of metal and cost and obtain better comprehensive performance, it is very meaningful to develop a simple, economical and efficient method for preparing atomic-level metal-graphene composite material catalysts and applications. SUMMARY

[0003] In order to overcome the shortcomings and deficiencies of the prior art, the primary purpose of the present application is to provide a simple preparation method of a high-load oxygen ligand nickel monatomic composite graphene base catalyst; the method is to prepare a high-load oxygen ligand nickel monatomic transition metal composite graphene base catalyst by a simple one-step co-reduction, further reducing the dispersion of metal atoms and the amount of metal material.

[0004] Another purpose of the present application is to provide a high-load oxygen ligand nickel monatomic composite graphene base catalyst prepared by the above preparation method; the catalyst has good catalytic activity for various VOCs and excellent metal dispersion.

[0005] Another object of the present application is to provide an application of the above-mentioned high-loading oxygen ligand nickel monatomic composite graphene base catalyst.

[0006] The object of the present application is achieved by the following technical solutions:

[0007] A simple preparation method of a high-loading oxygen ligand nickel monatomic composite graphene base catalyst comprises the following operation steps:

[0008] S1, flake graphite and NaNO3 with a mass ratio of 1:1 to 1:1.5 are weighed and mixed to obtain a mixture;

[0009] S2, concentrated sulfuric acid is added to the mixture obtained in step S1, and stirring is performed under the condition of an ice bath not exceeding 5℃ to obtain a mixed solution;

[0010] S3, potassium permanganate is weighed and added to the mixed solution obtained in step S1 in multiple times, and stirring is maintained during the addition; after the addition of potassium permanganate is completed, stirring is continued in the ice bath to obtain a dark green solution;

[0011] S4, the dark green solution is removed from the ice bath and stirred in a water bath to obtain a brown solution;

[0012] S5, the brown solution is removed from the water bath, deionized water is added to the brown solution under normal temperature conditions, and stirring is continued; then the solution is transferred to the water bath for continuous stirring to obtain a mixed solution;

[0013] S6, the mixed solution is removed from the water bath, deionized water is added to the mixed solution and stirred, hydrogen peroxide is then added and stirring is continued; at this time, gas bubbles are generated in the solution and the solution turns bright yellow; further stirring is performed to obtain solution A;

[0014] S7, solution A obtained in step S6 is washed with dilute hydrochloric acid to remove residual metal atoms, and then washed with deionized water until neutral; the reaction product A is collected by freeze-drying;

[0015] S8, the reaction product A is dispersed in an aqueous solution to obtain solution B, and a nickel salt is ultrasonically mixed to obtain solution C;

[0016] S9, solution B and solution C are mixed and stirred, sodium borohydride solution is added under stirring, and stirring is continued until the reaction is complete to obtain solution D; the composite is separated by suction filtration, washed with deionized water, dried, and a high-loading oxygen ligand nickel monatomic composite graphene base catalyst is obtained.

[0017] The amount of concentrated sulfuric acid in step S2 is 35-50 milliliters per gram of flake graphite in step S1, and the stirring time is 0.5-1.5 hours.

[0018] The amount of potassium permanganate in step S3 is 10-15 grams of potassium permanganate per gram of flake graphite in step S1;The said multiple additions are specifically as follows: each addition time is 2-5 minutes, and the interval between each two additions is 5-10 minutes.

[0019] The temperature of the water bath in step S4 is 35-40 DEG C, and the stirring time is 2-2.5 hours.

[0020] The amount of deionized water in step S5 is 40-50 milliliters of deionized water per gram of flake graphite in step S1, and the water addition process lasts for 10-15 minutes;The water bath temperature in the water bath transferred to is 95 DEG C, and the continuous stirring time is 30-40 minutes.

[0021] The amount of deionized water in step S6 is 50-100 milliliters of deionized water per gram of flake graphite in step S1, and the amount of hydrogen peroxide is 20-40 milliliters of hydrogen peroxide per gram of flake graphite in step S1.

[0022] The dilute hydrochloric acid in step S7 is prepared by mixing and stirring concentrated hydrochloric acid and deionized water in a volume ratio of 1:10-1:15;The washing with deionized water is centrifuged at a speed of 10000-12000 revolutions per minute for 5-10 minutes.

[0023] The sodium borohydride solution in step S9 is prepared on site and used on site;The continuous stirring time is 60-90 minutes.

[0024] A high-load oxygen ligand nickel monatomic composite graphene base catalyst prepared by the above preparation method, the nickel load of the catalyst reaches 10.16% by mass percentage at most.

[0025] The application of the above high-load oxygen ligand nickel monatomic composite graphene base catalyst in the catalytic oxidation of volatile organic pollutants.

[0026] The volatile organic pollutants include toluene, ethyl acetate, n-hexane and various VOCs.

[0027] The present application has the following advantages and effects relative to the prior art:

[0028] (1) Compared with the traditional high temperature and high pressure method, the present application uses a simple room temperature reaction to prepare monatomic, and the carrier and metal precursor are co-reduced in one step, which further improves the stability of the material by using the energy change of graphene reduction to connect the nickel metal and the carrier.

[0029] (2) The synthesis method has excellent dispersity, high metal single-atom loading, high specific surface area, and the obtained catalyst has high catalytic activity compared with other synthesis methods.

[0030] (3) The high-loading oxygen ligand nickel single-atom composite graphene base catalyst obtained by the method can completely degrade ethyl acetate, toluene and n-hexane at a low temperature, and has a good application prospect in the field of atmospheric pollutant treatment. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 Atomic force microscope image of graphene prepared for Example 1.

[0032] Figure 2 Transmission electron microscope image of the oxygen ligand nickel single-atom composite graphene base catalyst prepared for Example 1.

[0033] Figure 3 Spherical aberration electron microscope image of the oxygen ligand nickel single-atom composite graphene base catalyst prepared for Example 1.

[0034] Figure 4 Degradation efficiency diagram of the oxygen ligand nickel single-atom composite graphene base catalyst prepared for Example 1 on different organic matters (ethyl acetate, toluene, n-hexane).

[0035] Figure 5 Degradation efficiency diagram of the oxygen ligand nickel single-atom composite graphene base catalyst prepared for Example 1 on the typical organic matter ethyl acetate doped with water vapor.

[0036] Figure 6 Long-time degradation efficiency diagram of the oxygen ligand nickel single-atom composite graphene base catalyst prepared for Example 1 on the typical organic matter ethyl acetate. DETAILED DESCRIPTION

[0037] The application will be further described in detail below in combination with examples and drawings, but the embodiments of the application are not limited thereto.

[0038] Example 1

[0039] This example is the preparation of a high-loading oxygen ligand nickel single-atom composite graphene base catalyst.

[0040] (1) Take 1 gram of flake graphite (300 mesh) and 1 gram of NaNO3 into a dry beaker to obtain a mixture. Measure 48 milliliters of concentrated sulfuric acid and add it to the mixture, stirring for 30 minutes under ice bath conditions (not exceeding 5°C) to obtain a mixed solution. Weigh 6 grams of potassium permanganate and add it to the mixed solution in 12 portions, stirring continuously, with each addition taking 2 minutes and a 5-minute interval between each addition. After the potassium permanganate is added, continue stirring in the ice bath for 90 minutes to obtain a dark green solution. Move the dark green solution out of the ice bath and stir in a 35°C water bath for 2 hours to obtain a brown solution. Move the brown solution out of the water bath and slowly add 40 milliliters of deionized water to the brown solution, with the water addition process lasting 10 minutes and continuous stirring. Then transfer the solution to a 90°C water bath and continue stirring for 30 minutes to obtain a mixed solution. Move the mixed solution out of the water bath, add 100 milliliters of deionized water to the mixed solution and stir, then add 5 milliliters of hydrogen peroxide (30%) and continue stirring. At this time, a large amount of bubbles are generated in the solution and the solution turns bright yellow. Continue stirring for another 30 minutes to obtain solution A. Slowly pour 50 milliliters of concentrated hydrochloric acid (HCl) into a container containing 500 milliliters of deionized water and stir to obtain dilute hydrochloric acid. Wash the previously obtained solution A with dilute hydrochloric acid to remove residual metal atoms, then wash with deionized water until neutral. Centrifugal wash for 5 minutes at a speed of 10,000 revolutions per minute, and collect the reaction product A by freeze-drying. The atomic force microscope image of the reaction product A is shown in Figure 1 .

[0041] (2) Redispersed the reaction product A in an aqueous solution to obtain a 10 milligram / milliliter solution B. Ultrasonically mixed the nickel salt with water to obtain solution C. Took the solution C prepared as required and mixed it with 20 milliliters of solution B, stirring for 60-90 minutes. Added 5 milliliters of freshly prepared sodium borohydride solution under stirring, and continued stirring until the reaction was complete to obtain solution D. Separated the composite by suction filtration with a 0.26 μm water filter membrane, and repeatedly washed the composite with deionized water. Vacuum dried to obtain a high-dispersion and high-loading oxygen ligand nickel monatomic composite graphene-based catalyst. The highest nickel monatomic loading was 10.16% by mass, and the transmission electron microscope image and spherical aberration electron microscope image are shown in Figure 2 and Figure 3 .

[0042] Example 2

[0043] This example uses the high-loading oxygen ligand nickel monatomic composite graphene-based catalyst provided in Example 1 to test the degradation of ethyl acetate for comparison.

[0044] Catalyst activity evaluation was carried out in a fixed-bed continuous flow reactor, the reactor was a quartz glass tube with an inner diameter of 6 mm, the catalyst loading was 20 mg, the raw gas concentration was 500 ppm, the gas flow rate was 20 ml / min, and the reaction time was 1-2 hours. The volatile organic pollutants in the product gas were analyzed online by a Kechuang GC-9800 gas chromatograph equipped with a hydrogen ion flame detector. The reaction activity was represented by the conversion rate of VOCs. The activity test proved that the high-loading oxygen ligand nickel monatomic composite graphene-based catalyst prepared by the method had an ethyl acetate conversion rate of 100% at 280°C, and the results are shown in Table 1. Figure 4 The high-loading oxygen ligand nickel monatomic composite graphene-based catalyst also had excellent water resistance. When doped with different gradients of water vapor, the material still maintained a 100% degradation effect on ethyl acetate at 280°C, and the results are shown in Table 2. Figure 5 Meanwhile, the material could completely degrade ethyl acetate at 280°C and maintain stable performance for 150 hours, and the results are shown in Table 3. Figure 6

[0045] Example 3

[0046] This example used the high-loading oxygen ligand nickel monatomic composite graphene-based catalyst provided in Example 1 to test the degradation of n-hexane. The catalyst evaluation method was the same as in Example 2. The activity test proved that the bimetallic Pt-Co / UiO-66 catalyst prepared by the method had a n-hexane conversion rate of 100% at 280°C. The results are shown in Table 4. Figure 4

[0047] Example 4

[0048] This example used the high-loading oxygen ligand nickel monatomic composite graphene-based catalyst provided in Example 1 to test the degradation of toluene. The catalyst evaluation method was the same as in Example 2. The activity test proved that the high-loading oxygen ligand nickel monatomic composite graphene-based catalyst prepared by the method had a toluene conversion rate of 93% at 320°C. The results are shown in Table 5. Figure 4

[0049] The high-loading oxygen ligand nickel monatomic composite graphene-based catalyst prepared in Example 1 was tested by transmission electron microscopy and spherical aberration electron microscopy. The test results are analyzed as follows.

[0050] As shown in the transmission electron microscope image, the clear graphene framework is a thin transparent yarn. The bright spots in the AC-STEM image correspond to single-atom nickel. As can be clearly seen, the single-atom nickel is uniformly distributed within the graphene framework, and no nickel clusters are observed. Therefore, the high-loading oxygen ligand nickel monatomic composite graphene-based catalyst prepared in Example 1 has the following advantages:

[0051] ​​​1. The metal active sites are highly dispersed; 2. The degradation effect on various volatile organic compounds is excellent; 3. It has excellent water resistance and durability.

[0052] The above examples are the preferred embodiments of the present application, but the embodiments of the present application are not limited to the above examples, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application should be equivalent replacement methods, and are included in the protection scope of the present application.

Claims

1. A simple preparation method of a high loading amount oxygen ligand nickel monatomic composite graphene base catalyst, characterized in that The method comprises the following steps: S1, scale graphite and NaNO3 with a mass ratio of 1:1-1:1.5 are weighed and mixed to obtain a mixture; S2, concentrated sulfuric acid is added to the mixture obtained in step S1, and stirring is performed under the condition of an ice bath with a temperature not higher than 5°C for 0.5-1.5 hours to obtain a mixed solution; the amount of the concentrated sulfuric acid is 35-50 ml per gram of the scale graphite in step S1; S3, potassium permanganate is weighed and added to the mixed solution obtained in step S1 in multiple times, each time for 2-5 minutes, and the interval between two times is 5-10 minutes, and stirring is maintained during the addition; after the addition of the potassium permanganate is completed, stirring is continued in the ice bath to obtain a dark green solution; the amount of the potassium permanganate is 10-15 g per gram of the scale graphite in step S1; S4, the dark green solution is removed from the ice bath and stirred in a water bath with a temperature of 35-40°C for 2-2.5 hours to obtain a brown solution; S5, the brown solution is removed from the water bath, and deionized water is added to the brown solution under the condition of normal temperature, the amount of the deionized water is 40-50 ml per gram of the scale graphite in step S1, the water adding process lasts for 10-15 minutes, and stirring is continued, and then the solution is transferred to a water bath with a temperature of 95°C for continuous stirring for 30-40 minutes to obtain a mixed solution; S6, the mixed solution is removed from the water bath, and deionized water is added to the mixed solution, the amount of the deionized water is 50-100 ml per gram of the scale graphite in step S1, stirring is performed, hydrogen peroxide is further added and stirring is maintained, the amount of the hydrogen peroxide is 20-40 ml per gram of the scale graphite in step S1, at this time, gas bubbles are generated in the solution and the solution turns bright yellow, and then stirring is continued to obtain a solution A; S7, the solution A obtained in step S6 is washed with dilute hydrochloric acid to remove residual metal atoms, and then washed with deionized water until neutral, and the reaction product A is collected by freeze-drying; S8, the reaction product A is dispersed in an aqueous solution to obtain a solution B, and a nickel salt is ultrasonically mixed to obtain a solution C; S9, the solution B and the solution C are mixed and stirred, a sodium borohydride solution is added under the condition of stirring, and stirring is continued until the reaction is completed to obtain a solution D; the solution D is separated by suction filtration to obtain a composite, the composite is washed with deionized water and dried to obtain a high-loading oxygen ligand nickel monatomic composite graphene base catalyst; the loading amount of the nickel monatomic of the catalyst is 10.16% by mass.

2. The method of claim 1, wherein: The dilute hydrochloric acid in step S7 is prepared by mixing concentrated hydrochloric acid and deionized water with a volume ratio of 1:10-1:15 under stirring; the washing with deionized water is performed under the condition of centrifugal washing with deionized water at a rotation speed of 10,000-12,000 rpm for 5-10 minutes.

3. The method of claim 1, wherein: The sodium borohydride solution in step S9 is prepared on site and used on site; the time for continuous stirring is 60-90 minutes.

4. The high-loading oxygen-ligand nickel single-atom graphitic catalyst prepared by the method of any one of claims 1-3, wherein: The loading amount of the nickel monatomic of the catalyst is 10.16% by mass.

5. Use of the high loading oxygen ligand nickel single atom composite graphene base catalyst according to claim 4 in the catalytic oxidation of volatile organic pollutants.

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