Preparation method of a nickel trioxide doped carbon nanotube catalyst

Abstract

The application relates to a preparation method of a carbon nanotube doped with nickel trioxide, and steps include: firstly, ultrasonic treatment of carbon nanotubes for 20-40 minutes, then adding the carbon nanotubes into a mixed solution composed of concentrated sulfuric acid and concentrated nitric acid, and ultrasonic stirring reaction for 3-5 hours; then, adding hydrogen peroxide and potassium permanganate into the reaction product after ultrasonic treatment in step (1), and continuing to stir for 1-3 hours, filtering, and taking out after freeze drying overnight; dispersing the oxidized carbon nanotubes treated in step (2) in ultrasonic treatment for 20-40 minutes, then adding an aqueous solution of nickel nitrate hexahydrate, and ultrasonic treatment for 20-40 minutes, then adding a sodium hydroxide sodium hypochlorite solution, and stirring for 1-3 hours to obtain a black colloidal suspension, and filtering and drying to obtain a carbon nanotube doped with nickel trioxide; the application has the advantages of being capable of increasing the electron conduction capacity so as to improve the catalytic efficiency, and effectively reducing the agglomeration of nanoparticles.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of doped catalysts, in particular to a preparation method of a carbon nanotube doped with nickel sesquioxide. BACKGROUND

[0002] Now carbon nanotube (CNT) doping is a very effective method for improving the stability and catalytic performance of catalysts, and has been widely applied to different catalysts, such as titanium dioxide, nickel oxide (II nickel) and other composite catalysts, and obvious improvement of photocatalytic performance can be observed after the carbon nanotubes are doped.

[0003] Nickel sesquioxide is widely used in photocatalysis and electrocatalysis due to its unique crystal structure and photosensitive range, and is often used as a cocatalyst in combination with other catalysts, but there are few reports on the preparation of catalysts by directly doping carbon nanotubes with nickel sesquioxide. SUMMARY

[0004] In view of the above problems of the prior art, the application provides a preparation method of a carbon nanotube doped with nickel sesquioxide, which can increase the electron conduction capacity and improve the catalytic efficiency, and can effectively reduce the agglomeration of nanoparticles.

[0005] In order to solve the above technical problems, the technical scheme adopted by the application is as follows: a preparation method of a carbon nanotube doped with nickel sesquioxide, the preparation steps comprising:

[0006] (1) first ultrasonic the carbon nanotubes for 20-40 minutes, and then add them to a mixed solution composed of concentrated sulfuric acid and concentrated nitric acid, and ultrasonic stir and react for 3-5 hours;

[0007] (2) then add hydrogen peroxide and potassium permanganate to the reaction product after ultrasonic in step (1), continue to stir for 1-3 hours, filter, and take out after freeze-drying overnight;

[0008] (3) disperse the oxidized carbon nanotubes treated in step (2) in ultrasonic for 20-40 minutes, then add an aqueous solution of nickel nitrate hexahydrate, ultrasonic for 20-40 minutes again, then add a sodium hydroxide sodium hypochlorite solution, stir for 1-3 hours, obtain a black colloidal suspension, filter and dry to obtain a carbon nanotube doped with nickel sesquioxide catalyst.

[0009] Further, the mixed solution of concentrated sulfuric acid and concentrated nitric acid in step (1) of the application has a volume ratio of concentrated sulfuric acid to concentrated nitric acid of 3:1.

[0010] Further, the second ultrasonic stirring time in step (1) of the application is 3.5-4.5 hours.

[0011] Further, the power of the ultrasonic treatment described in the present application is 1-1.5 kw.

[0012] Further, the stirring time described in step (2) of the present application is 1.5-2.5 hours.

[0013] Further, the hydrogen peroxide and potassium permanganate described in step (2) of the present application are added, specifically 1-2 g of potassium permanganate is first added, then after stirring for 25-40 minutes, 8-15 ml of hydrogen peroxide is added.

[0014] Further, the oxidized carbon nanotubes described in step (3) of the present application are dispersed in ultrasonic for 25-35 minutes, and an aqueous solution of nickel nitrate hexahydrate is added, and ultrasonic is performed for 25-35 minutes.

[0015] Further, the sodium hydroxide sodium hypochlorite solution described in step (3) of the present application is stirred for 1.5-2.5 hours.

[0016] Further, the drying described in step (3) of the present application is dried at 85-95 degrees for 10-12 hours.

[0017] Further, the mass concentration of the aqueous solution of nickel nitrate hexahydrate described in step (3) of the present application is 55-70 g / L.

[0018] Further, the sodium hydroxide sodium hypochlorite solution described in step (3) of the present application is formed by dissolving 1-3 g of sodium hydroxide in 15-25 ml of 4% available chlorine sodium hypochlorite solution.

[0019] Advantages and beneficial effects of the present application:

[0020] 1. The present application directly uses trivalent nickel as carbon nanotube doping to prepare a catalyst for the first time. Compared with divalent nickel (nickel oxide), the trivalent nickel has great advantages in stability, catalytic potential, and photosensitive interval. The catalyst obtained can increase the electron conduction ability to improve the catalytic efficiency, and can effectively reduce the agglomeration of nanoparticles. This is because carbon nanotubes have excellent electron conduction ability and high surface area ratio. The introduction of carbon nanotubes and trivalent nickel interaction can enhance the conductivity and increase the contact area, promote the reaction rate and reduce agglomeration. The trivalent nickel nanoparticles grown on the carbon nanotubes will reduce agglomeration.

[0021] 2. The present application uses trivalent nickel as carbon nanotube doping to prepare a catalyst. The catalyst shows that the surface of CNTs is loaded with nickel oxide nanoparticles. Through the comparison of the effect of photocatalytic hydrogen production, it is shown that with the increase of the doping amount, the photocatalytic effect of the catalyst of the present application is also significantly improved.

[0022] 3. The present application adopts multiple ultrasonic treatments in the carbon nanotube treatment process. The first ultrasonic treatment is to disperse the oxidized multi-walled carbon nanotubes, so that they can fully and uniformly contact with the reactants. The second ultrasonic stirring is to ensure that the reactants are uniformly dispersed during the reaction process, so that the prepared product is uniform and dispersed enough and is not easy to agglomerate. The aqueous solution of nickel nitrate hexahydrate in the present application is used as a precursor and a reactant, which reacts with sodium hydroxide and sodium hypochlorite, and the reaction process can grow on the carbon nanotube at the same time, and finally a nickel oxide doped carbon nanotube catalyst is obtained.

[0023] 4. The present application adopts a freeze-drying scheme in step (2) of the preparation process. The freeze-drying can not only not damage the hydroxyl group on the surface of the product, but also effectively dry the product. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 Transmission electron microscope (TEM) results of the carbon nanotube-nickel oxide composite material prepared in the example.

[0025] Figure 2 Photocatalytic hydrogen production results of the catalyst prepared by the carbon nanotube-nickel oxide composite material and the catalyst without CNT in the example.

[0026] Figure 3 Gas chromatography hydrogen production results (one hour) of the catalyst prepared by the divalent nickel doped CNT in the comparative example.

[0027] Figure 4 Gas chromatography hydrogen production results (2 hours of light exposure) of the catalyst prepared by the divalent nickel doped CNT in the comparative example. DETAILED DESCRIPTION

[0028] The technical solutions in the examples of the present application will be described clearly and completely in combination with the examples and the drawings. Obviously, the described examples are only preferred examples, not all examples. Based on the examples in the present application, all other examples obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0029] Example 1

[0030] (1) After ultrasonic treatment (ultrasonic power 1.5kw) of carbon nanotubes for 35 minutes, add a 3:1 volume ratio of concentrated sulfuric acid and concentrated nitric acid solution, and ultrasonic stir (ultrasonic power 1.5kw) for 5 hours:

[0031] (2) Add hydrogen peroxide and potassium permanganate to step (1). Specifically, add 1.5g of potassium permanganate, stir for 30 minutes, then add 10ml of hydrogen peroxide and stir. Continue stirring for 2.5 hours, filter, and freeze-dry overnight.

[0032] (3) The oxidized carbon nanotubes from step (2) were dispersed in an ultrasonic bath (ultrasonic power 1.5 kw) for 40 minutes, an aqueous solution of nickel nitrate hexahydrate (1 g of nickel nitrate hexahydrate dissolved in 15 ml of deionized water) was added and ultrasonicated for 35 minutes, then an aqueous solution of sodium hydroxide in sodium hypochlorite (1.6 g of sodium hydroxide dissolved in 20 ml of 4% available chlorine sodium hypochlorite solution) was added and stirred for 2.5 hours to obtain a black colloidal suspension which was filtered and dried in an oven at 90 degrees for 12 hours; this example is 10% CNT doped nickelous oxide nanoparticles.

[0033] Example 2

[0034] (1) The carbon nanotubes were ultrasonicated (ultrasonic power 1.5 kw) for 30 minutes, then added to a 3:1 ratio of concentrated sulfuric acid to concentrated nitric acid solution and ultrasonicated (ultrasonic power 1.5 kw) and stirred for 4 hours;

[0035] (2) To step (1) was added hydrogen peroxide and potassium permanganate (1.2 g of potassium permanganate was added first, then 10 ml of hydrogen peroxide was added after 30 minutes of stirring), and stirring was continued for 2 hours, then filtered and lyophilized overnight;

[0036] (3) The oxidized carbon nanotubes from step (2) were dispersed in an ultrasonic bath (ultrasonic power 1.5 kw) for 30 minutes, an aqueous solution of nickel nitrate hexahydrate (1.2 g of nickel nitrate hexahydrate dissolved in 18 ml of deionized water) was added and ultrasonicated for 30 minutes, then an aqueous solution of sodium hydroxide in sodium hypochlorite (1.5 g of sodium hydroxide dissolved in 18 ml of 4% available chlorine sodium hypochlorite solution) was added and stirred for 2 hours to obtain a black colloidal suspension which was filtered and dried in an oven at 90 degrees for 12 hours; this example is 5% CNT doped nickelous oxide nanoparticles.

[0037] Example 3

[0038] (1) The carbon nanotubes were ultrasonicated for 40 minutes, then added to a 3:1 ratio of concentrated sulfuric acid to concentrated nitric acid solution and ultrasonicated (ultrasonic power 1.1 kw) and stirred for 4.5 hours;

[0039] (2) To step (1) was added hydrogen peroxide and potassium permanganate (1.5 g of potassium permanganate was added first, then 10 ml of hydrogen peroxide was added after 30 minutes of stirring), and stirring was continued for 3 hours, then filtered and lyophilized overnight;

[0040] (3) The oxidized carbon nanotubes of step (2) were dispersed in ultrasonic (ultrasonic power 1.1kw) for 35 minutes, an aqueous solution of nickel nitrate hexahydrate (1g of nickel nitrate hexahydrate dissolved in 15ml of deionized water to form an aqueous solution) was added, ultrasonic for 40 minutes, then an aqueous solution of sodium hydroxide and sodium hypochlorite (2.0g of sodium hydroxide dissolved in 25ml of 4% available chlorine sodium hypochlorite solution to form a solution) was added, stirred for 3 hours, to obtain a black colloidal suspension, filtered, dried in an oven at 90 degrees for 12 hours; this example is 8% CNT doped nickelous oxide nanoparticles.

[0041] As shown in the TEM picture of the composite material CNT-Ni2O3 prepared in Example 2 of the present application, from the attached Figure 1 , it can be known that Ni2O3 nanoparticles are successfully synthesized on the prepared CNT, and the size is very small, about 10 nanometers, and are uniformly dispersed without agglomeration. Figure 1

[0042] Photocatalytic hydrogen production experiment verifies the efficiency of the catalyst: pure nickelous oxide nanoparticles (without the participation of CNT, as a comparative example), 5% CNT doped nickelous oxide nanoparticles (Example 1), 10% CNT doped nickelous oxide nanoparticles (Example 2). Take 10ml of triethanolamine as a sacrificial agent (the sacrificial agent acts as an electron donor, can consume photo-generated holes, and leaves electrons to react with water to produce hydrogen, the oxidation potential of the sacrificial agent is higher than that of H2O, which increases the driving force of the oxidation half-reaction, thereby reducing the recombination of photo-generated electrons), 40ml of deionized water, 100mg of catalyst, stirring and light for 4 hours, and then comparing the hydrogen production, refer to the attached Figure 2 , the comparative curves of the attached Figure 2 are pure nickelous oxide (without the participation of CNT), 5% CNT doped nickelous oxide nanoparticles, and 10% doped nickelous oxide nanoparticles, the results prove that the introduction of CNT has obvious improvement on the hydrogen production effect, and the 5% doped effect is the best.

[0043] Figures 3-4 The test results of the hydrogen production efficiency of the catalyst obtained after doping CNT with divalent nickel, wherein Figure 3 is the 1 hour light result, Figure 4 is the 2 hour light result, Figures 3-4 the horizontal axis in the attached Figures 3-4 , the vertical axis is the peak value, that is, the existence of substances in the gas is analyzed quantitatively; it can be seen from the attached Figures 3-4 that when divalent nickel and CNT are doped, the hydrogen production is detected, and no hydrogen peak can be seen.The two peaks are respectively peaks of oxygen and nitrogen, and there is no peak of hydrogen; it can be known that the hydrogen production efficiency of the catalyst after the CNT is doped with divalent nickel is not ideal, so the catalyst obtained by doping CNT with trivalent nickel relative to divalent nickel has more excellent catalytic performance.

[0044] It can be known from the above examples and experimental detection results that the catalyst obtained by introducing trivalent nickel in the method has better catalytic potential and effect, and the photosensitive property is obviously improved.

Claims

1. A method for preparing a nickel trioxide-doped carbon nanotube catalyst, characterized in that: The preparation steps include: (1) First, sonicate the carbon nanotubes for 20-40 minutes, then add them to a mixed solution of concentrated sulfuric acid and concentrated nitric acid, and sonicate and stir for 3-5 hours. (2) Then add hydrogen peroxide and potassium permanganate to the reaction mixture after sonication in step (1), continue stirring for 1-3 hours, filter, freeze dry overnight and take out; (3) Disperse the oxidized carbon nanotubes after step (2) in ultrasound for 20-40 minutes, then add an aqueous solution of nickel nitrate hexahydrate, and sonicate for another 20-40 minutes. Then add a sodium hypochlorite solution of sodium hydroxide and stir for 1-3 hours to obtain a black colloidal suspension. Filter and dry to obtain carbon nanotube-doped nickel oxide catalyst. The drying in step (3) is to dry at 85-95 degrees for 10-12 hours. The mass concentration of the aqueous solution of nickel nitrate hexahydrate in step (3) is 55-70 g / L. The sodium hypochlorite solution of sodium hydroxide is formed by dissolving 1-3 g of sodium hydroxide in 15-25 ml of sodium hypochlorite solution with 4% available chlorine.

2. The method for preparing the nickel trioxide-doped carbon nanotube catalyst according to claim 1, characterized in that: The mixed solution of concentrated sulfuric acid and concentrated nitric acid described in step (1) has a volume ratio of 3:1 between concentrated sulfuric acid and concentrated nitric acid.

3. The method for preparing the nickel trioxide-doped carbon nanotube catalyst according to claim 1, characterized in that: Step (1) The second ultrasonic stirring time is 3.5-4.5 hours.

4. The method for preparing the nickel trioxide-doped carbon nanotube catalyst according to claim 1, characterized in that: The power of the ultrasound is 1-1.5kw.

5. The method for preparing the nickel trioxide-doped carbon nanotube catalyst according to claim 1, characterized in that: The stirring time described in step (2) is 1.5-2.5 hours.

6. The method for preparing the nickel trioxide-doped carbon nanotube catalyst according to claim 1, characterized in that: In step (2), hydrogen peroxide and potassium permanganate are added. Specifically, 1-2g of potassium permanganate is added first, and then 8-15ml of hydrogen peroxide is added after stirring for 25-40 minutes.

7. The method for preparing the nickel trioxide-doped carbon nanotube catalyst according to claim 1, characterized in that: In step (3), the oxidized carbon nanotubes are dispersed in ultrasound for 25-35 minutes, and an aqueous solution of nickel nitrate hexahydrate is added and ultrasonicated for 25-35 minutes.

8. The method for preparing the nickel trioxide-doped carbon nanotube catalyst according to claim 1, characterized in that: The sodium hypochlorite solution containing sodium hydroxide, as described in step (3), is stirred for 1.5-2.5 hours.

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