Method for preparing carbon material loaded beta-Co (OH) 2 in NH3 plasma auxiliary solution

Abstract

The invention discloses a method for preparing carbon material loaded beta-Co (OH) 2 in an NH3 plasma auxiliary solution, and belongs to the technical field of nano material preparation. Atmospheric pressure surface dielectric barrier discharge cold plasma is adopted, mixed gas of NH3 and Ar is used as working gas, and the carbon material loaded beta-Co (OH) 2 is prepared in a solution by regulating and controlling the plasma. According to the method, other toxic and harmful chemical reagents and tedious operation procedures do not need to be used, the carbon material loaded beta-Co (OH) 2 can be obtained in a short time only by mixing the carbon material carrier with the Co (NO3) 2 solution, adding a small amount of deionized water and adopting plasma treatment, and the problem that alkali metal ion impurities are generated in a traditional preparation method does not exist. Besides, atmospheric pressure NH3 plasma is adopted, a certain alkaline environment can be provided, the alkaline intensity can be adjusted in time and reasonably through plasma regulation and control, and therefore the carbon material loaded beta-Co (OH) 2 can be prepared in a solution in a green, rapid, flexible and safe mode.

Description

Technical Field

[0001] The invention belongs to the technical field of nano material preparation, and in particular relates to a method for preparing carbon material loaded with beta-Co(OH)2 in an NH3 plasma-assisted solution. Background Art

[0002] Co(OH)2 is a two-dimensional layered hydroxide, which mainly has two crystalline phases: α-Co(OH)2 and β-Co(OH)2. α-Co(OH)2 has a structure similar to hydrotalcite, while β-Co(OH)2 has a structure similar to brucite. Compared with α-Co(OH)2, β-Co(OH)2 has good stability and a larger interlayer spacing (more than 0.46nm). The expanded interlayer spacing gives it more active sites, which can promote ion transfer at the interface between electroactive materials and electrolytes, improve conductivity and accelerate electrolyte penetration, showing great application advantages in the fields of electrochemistry, magnetism and catalysis.

[0003] The preparation of β-Co(OH)2 is mainly carried out by chemical precipitation method (Co 2+ +2OH - =Co(OH)2↓+2H + ). Chinese patent CN104261489B discloses a method for preparing hexagonal β-Co(OH)2 nanosheets. First, ethylene glycol, methanol and alkali are mixed to prepare a system solvent (the alkali is one or more of sodium hydroxide and potassium hydroxide); then, a water-soluble cobalt salt is mixed with the system solvent to prepare a system mixture (the water-soluble cobalt salt is cobalt nitrate hexahydrate); finally, hydrazine hydrate is added to the system mixture to react and obtain hexagonal β-Co(OH)2 nanosheets.

[0004] Since chemical preparation methods usually require the addition of a variety of chemical reagents, the operation process is cumbersome, and a large number of impurities are easily generated during the preparation process, resulting in impure products. Therefore, it is urgent to develop a simple, fast, and green preparation method for β-Co(OH)2.

[0005] Plasma is the fourth state of matter besides solid, liquid and gas. It is a non-condensed system with a certain degree of ionization and macroscopically neutral charge. Cold plasma is a typical non-thermodynamic equilibrium plasma. Its electron temperature (T e , 1-10eV, 1eV=11605K)>>gas temperature (T g , close to room temperature) Ion temperature (T i ), which is very suitable for the preparation and processing of nanomaterials under mild conditions, and has attracted increasing attention in the field of nanocatalytic material preparation.

[0006] Chinese patent CN117486265A discloses a method for preparing carbon material loaded α-Co(OH)2 in a plasma-assisted solution. The invention adopts atmospheric pressure surface dielectric barrier discharge cold plasma, and uses a mixed gas of H2 and Ar as the working gas to treat the cobalt nitrate aqueous solution. The entire discharge process lasts for 5-30 minutes, and finally α-Co(OH)2 loaded with carbon material can be obtained. Since the generation mechanism of β-Co(OH)2 is obviously different from that of α-Co(OH)2, it requires both a strong alkaline environment and timely and reasonable regulation of the alkalinity strength. Therefore, using a mixed gas of H2 and Ar as the working gas, only α-Co(OH)2 can be obtained by regulating the discharge. At present, there is no report on the preparation of β-Co(OH)2 by plasma regulation. Summary of the invention

[0007] In order to overcome the deficiencies of the prior art, the present invention provides a method for preparing carbon material loaded β-Co(OH)2 in NH3 plasma-assisted solution. The advantage of the present invention is that it adopts atmospheric pressure surface dielectric barrier discharge cold plasma that is easy to scale up, and uses a mixed gas of NH3 and Ar as the working gas, which can not only provide a certain alkaline environment, but also timely and reasonably adjust the alkalinity strength by regulating the plasma, so that carbon material loaded β-Co(OH)2 can be prepared in the solution. In addition, the method has a simple operation process, and there is no need to add any other chemical reagents to the solution. It only needs to mix the carbon material carrier with the Co(NO3)2 solution, add a small amount of deionized water, and treat it with atmospheric pressure NH3 plasma to obtain carbon material loaded β-Co(OH)2 in a short time. The preparation process has the advantages of being green, fast, flexible and safe, and the product will not have the problem of introducing other impurities that are usually introduced by traditional preparation methods.

[0008] The above object of the present invention is achieved through the following technical solutions:

[0009] A method for preparing carbon material loaded with β-Co(OH)2 in an NH3 plasma-assisted solution, comprising:

[0010] S1. Prepare a mixture containing a carbon material carrier, Co(NO3)2 solution and deionized water;

[0011] S2. In an atmospheric pressure surface dielectric barrier discharge cold plasma reactor, a working gas is introduced to generate plasma, and the mixture described in step S1 is processed;

[0012] S3. Filter, dry and grind the mixture obtained by the treatment in step S2 to obtain a sample of carbon material loaded with β-Co(OH)2.

[0013] Furthermore, the step S1 is specifically as follows: using a pipette, 40-300 μL of Co(NO 3 ) 2 solution, 1-5 mL of deionized water and 5-50 mg of the carbon material carrier are mixed in a watch glass.

[0014] Furthermore, in step S1, the carbon material carrier is any one of multi-walled carbon nanotubes, multi-layer graphene, and activated carbon, preferably multi-walled carbon nanotubes.

[0015] Furthermore, in step S1, the final concentration of the Co(NO3)2 solution in the mixture is 0.5-1.5 mol·L -1 .

[0016] Furthermore, the step S2 specifically includes: placing the watch dish containing the mixture in step S1 into an atmospheric pressure surface dielectric barrier discharge cold plasma reactor, wherein the depth of the mixture is 4-10 mm; stirring the mixture with a magnetic stirrer, wherein the speed of the magnetic stirrer is 200-800 r·min -1 The distance between the solution and the discharge electrode in the reactor is 2-5 mm. A mixed gas of NH3 and Ar is introduced as the working gas, and the plasma discharge frequency and discharge voltage are adjusted to treat the mixed solution through the generated plasma.

[0017] Furthermore, in the atmospheric pressure surface dielectric barrier discharge cold plasma reactor used in step S2, the medium is quartz glass or alumina (thickness is 1-2 mm), and the metal electrode is silver or tungsten.

[0018] Furthermore, in step S2, the volume content of NH3 in the working gas is 50%.

[0019] Furthermore, in step S2, the plasma discharge frequency is 5-15 kHz, the discharge voltage is sinusoidal high voltage, the peak-to-peak value is 4-8 kV, and the discharge treatment time of the mixture is 5-15 min.

[0020] Furthermore, the step S3 is specifically as follows: filtering the mixture obtained in step S2, and then drying and grinding it in an oven at 100° C. to obtain a sample of carbon material loaded with β-Co(OH)2.

[0021] The beneficial effects of the present invention compared with the prior art are:

[0022] Atmospheric pressure surface dielectric barrier discharge cold plasma is used, and a mixed gas of NH3 and Ar is used as the working gas to prepare β-Co(OH)2 loaded on carbon materials in a solution. This method does not require the use of other toxic and harmful chemical reagents and cumbersome operating procedures. It only requires mixing the carbon material carrier with the Co(NO3)2 solution, adding a small amount of deionized water, and using plasma treatment to obtain β-Co(OH)2 loaded on carbon materials in a short time. The problem of alkali metal ion impurities produced by traditional preparation methods does not exist. In addition, since the generation mechanism of β-Co(OH)2 is obviously different from that of α-Co(OH)2, it requires both a strong alkaline environment and timely and reasonable regulation of the alkalinity strength. Therefore, the existing plasma discharge regulation treatment can only obtain α-Co(OH)2, and there has been no report on the preparation of β-Co(OH)2 by plasma regulation. This patent uses atmospheric pressure surface dielectric barrier discharge cold plasma, with a mixture of NH3 and Ar as the working gas, which can not only provide a certain alkaline environment, but also timely and reasonably adjust the alkalinity strength through plasma regulation, so that carbon material loaded with β-Co(OH)2 can be prepared in solution. In short, the preparation process reported in this patent will not introduce other impurities, and the timely and reasonable regulation of the alkalinity strength of the solution by plasma provides a green, fast, flexible and safe new method for the preparation of pure β-Co(OH)2 loaded on carbon materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will be further described below in conjunction with the accompanying drawings and specific implementations.

[0024] Figure 1 This is the XRD pattern of the sample prepared using multi-walled carbon nanotubes as a carrier in Example 1;

[0025] Figure 2 The XRD pattern of the sample prepared with multilayer graphene as the carrier in Example 2;

[0026] Figure 3 This is the XRD pattern of the sample prepared using activated carbon as a carrier in Example 3;

[0027] Figure 4 This is the XRD pattern of the sample prepared by using multi-walled carbon nanotubes as carriers and introducing an equal amount of NH3 but without plasma discharge.

[0028] Figure 5 and Figure 6 The XRD patterns of samples prepared using non-carbon inorganic materials (Al2O3 and TiO2) as carriers in Comparative Examples 2 and 3, respectively;

[0029] Figure 7 XRD patterns of Co(OH)2 prepared using different NH3 / Ar ratios in Comparative Example 4;

[0030] Figure 8 XRD diagram of Co(OH)2 prepared in different discharge atmospheres in Comparative Example 5;

[0031] Fig. 9 XRD diagram of Co(OH)2 prepared by using different discharge voltages for comparative example 6;

[0032] Fig.10 The XRD patterns of Co(OH)2 prepared by using different discharge times are shown in Comparative Example 7. DETAILED DESCRIPTION

[0033] The present invention is described in detail below by specific examples, but the protection scope of the present invention is not limited. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can be obtained from commercial channels.

[0034] Example 1

[0035] A method for preparing carbon material loaded with β-Co(OH)2 in NH3 plasma-assisted solution, specifically comprising:

[0036] Plasma-assisted solution treatment of a mixture of multi-walled carbon nanotubes and Co(NO3)2 solution:

[0037] The plasma-assisted solution treatment of a mixture of multi-walled carbon nanotubes and Co(NO3)2 solution was carried out as follows: First, 30 mg of multi-walled carbon nanotubes were placed in a quartz reactor (4 cm in diameter and 6 mm in depth). Then, 60 μL of 0.94 mol·L -1 3 mL of Co(NO3)2 solution and 3 mL of deionized water were transferred to the quartz reactor. Then, the position of the quartz reactor was adjusted so that the liquid level was 2 mm away from the discharge electrode. The device was sealed and the circuit was connected. A mixed gas of NH3 and Ar (V NH3 :V Ar =1:1), the total gas flow rate is 100 mL min -1 , set the magnetic stirrer speed in the solution to 500 r·min -1 , the discharge frequency was adjusted to 10kHz, the sinusoidal discharge voltage peak-to-peak value was 6.0kV, and the discharge time was 10min. After the discharge, the treated mixture was filtered, dried in an oven at 100℃ for 10h, then ground and placed in a glass reagent bottle and stored in a desiccator.

[0038] Example 2

[0039] A method for preparing carbon material loaded with β-Co(OH)2 in NH3 plasma-assisted solution, specifically comprising:

[0040] Plasma-assisted solution treatment of a mixture of multilayer graphene and Co(NO3)2 solution:

[0041] The mixture of multilayer graphene and Co(NO3)2 solution is treated in a plasma-assisted solution, and the specific steps are the same as those in Example 1, except that the multi-walled carbon nanotubes are replaced with multilayer graphene.

[0042] Example 3

[0043] A method for preparing carbon material loaded with β-Co(OH)2 in NH3 plasma-assisted solution, specifically comprising:

[0044] Treatment of a mixture of activated carbon and Co(NO3)2 solution in plasma-assisted solution:

[0045] The mixture of activated carbon and Co(NO3)2 solution was treated in NH3 plasma-assisted solution, and the specific steps were the same as those in Example 1, except that the multi-walled carbon nanotubes were replaced with activated carbon.

[0046] Comparative Example 1

[0047] Treatment of a mixture of multi-walled carbon nanotubes and Co(NO3)2 solution in NH3-assisted solution:

[0048] The mixture of multi-walled carbon nanotubes and Co(NO3)2 solution was treated in NH3-assisted solution, and the specific steps were the same as those in Example 1, but no plasma discharge treatment was performed.

[0049] Comparative Example 2

[0050] Treatment of a mixture of non-carbon inorganic support Al2O3 and Co(NO3)2 solution in NH3 plasma-assisted solution:

[0051] A mixture of a non-carbon inorganic carrier Al2O3 and a Co(NO3)2 solution is treated in an NH3 plasma-assisted solution. The specific steps are the same as those in Example 1, except that the multi-walled carbon nanotubes are replaced with Al2O3.

[0052] Comparative Example 3

[0053] Treatment of a mixture of non-carbon inorganic support TiO2 and Co(NO3)2 solution in NH3 plasma-assisted solution:

[0054] The mixture of non-carbon inorganic carrier TiO2 and Co(NO3)2 solution is treated in NH3 plasma-assisted solution, and the specific steps are the same as those in Example 1, except that the multi-walled carbon nanotubes are replaced by TiO2.

[0055] Comparative Example 4

[0056] A method for preparing carbon material loaded with β-Co(OH)2 in NH3 plasma-assisted solution, specifically comprising:

[0057] Treatment of a mixture of multi-walled carbon nanotubes and Co(NO3)2 solution in NH3 plasma-assisted solution:

[0058] The specific steps are the same as those in Example 1, except that the ratio of the mixed gas of NH3 and Ar is changed to 1:3, 1:2, and 2:1.

[0059] Comparative Example 5

[0060] A method for preparing carbon material loaded with β-Co(OH)2 in NH3 plasma-assisted solution, specifically comprising:

[0061] Treatment of a mixture of multi-walled carbon nanotubes and Co(NO3)2 solution in NH3 plasma-assisted solution:

[0062] The specific steps are the same as those in Example 1, except that the mixed gas of NH3 and Ar is changed to a mixed gas of H2 and Ar and pure Ar.

[0063] Comparative Example 6

[0064] A method for preparing carbon material loaded with β-Co(OH)2 in NH3 plasma-assisted solution, specifically comprising:

[0065] A mixture of multi-walled carbon nanotubes and Co(NO3)2 solution treated in an NH3 plasma-assisted solution:

[0066] The specific steps are the same as those in Example 1, except that the discharge voltage is changed to 4 kV and 8 kV.

[0067] Comparative Example 7

[0068] A method for preparing carbon material loaded with β-Co(OH)2 in NH3 plasma-assisted solution, specifically comprising:

[0069] Treatment of a mixture of multi-walled carbon nanotubes and Co(NO3)2 solution in NH3 plasma-assisted solution:

[0070] The specific steps are the same as those in Example 1, except that the discharge time is changed to 5 min and 15 min.

[0071] like Figure 1 It can be seen that the XRD pattern of the experimentally treated multi-walled carbon nanotubes shows obvious characteristic diffraction peaks of β-Co(OH)2 at 19.1°, 32.5°, 37.9° and 51.4°, indicating that the atmospheric pressure surface dielectric barrier discharge cold plasma successfully prepared the β-Co(OH)2 sample loaded on the multi-walled carbon nanotubes. Figure 2It can be seen that when multilayer graphene is used as a carrier, weak β-Co(OH)2 characteristic diffraction peaks appear at 19.1°, 32.5°, 37.9° and 51.4° in the XRD graph. Figure 3 It can be seen that when activated carbon is used as a carrier, a weak characteristic diffraction peak of β-Co(OH)2 appears at 37.9° in the XRD graph. This shows that the mixture of carbon material and Co(NO3)2 solution treated in plasma-assisted solution can generate β-Co(OH)2, but the amount generated is closely related to the carbon material carrier, and the carbon carrier is preferably multi-walled carbon nanotubes. Figure 4 It can be seen that only by introducing NH3 without plasma discharge treatment, only cobalt ammonia complex can be generated after vacuum drying and forced air drying, and no characteristic diffraction peak of β-Co(OH)2 appears in the XRD diagram, indicating that plasma regulation is the key to the generation of β-Co(OH)2. Figure 5 and Figure 6 It can be seen that when non-carbon inorganic carriers Al2O3 and TiO2 are used, no characteristic diffraction peak of β-Co(OH)2 appears in the XRD graph. Figure 7 It can be seen that too much or too little NH3 will affect the formation of β-Co(OH)2, and its characteristic diffraction peaks are very weak. Figure 8 It can be seen that when H2 and Ar are introduced, α-Co(OH)2 will be generated, and when only Ar is introduced, no β-Co(OH)2 is generated. Fig. 9 It can be seen that the characteristic diffraction peaks of β-Co(OH)2 are very weak. When the discharge voltage is too high or too low, the generation of β-Co(OH)2 cannot be effectively regulated. Fig.10 It can be seen that when the discharge time is too short, β-Co(OH)2 cannot be effectively generated, and when the discharge time is too long, β-Co(OH)2 will cause decomposition.

[0072] In Comparative Examples 8-15, the amount of NH3 introduced is too much, and the alkalinity is too strong, which will convert the generated β-Co(OH)2 into an ammonia-cobalt complex; the amount of NH3 introduced is too little, and the alkalinity is weak, which is not enough to completely generate β-Co(OH)2. The discharge voltage or discharge frequency is low, the input power is small, the plasma reactor is not fully discharged, and the energy required to generate β-Co(OH)2 is not reached. Under this discharge parameter, β-Co(OH)2 cannot be completely generated; the discharge voltage or discharge frequency is high, the input power is large, and the energy is too high, resulting in β-Co(OH)2 being generated and decomposed. The discharge time is short, the pH is too low, and the generated β-Co(OH)2 is incomplete; the discharge treatment time is too long, and the pH is too high, which will convert the generated β-Co(OH)2 into an ammonia-cobalt complex. Therefore, the use of atmospheric pressure surface dielectric barrier discharge cold plasma, with a mixture of NH3 and Ar as the working gas (ammonia volume content of 50%), a discharge voltage of 4-8kV, a discharge frequency of 5-15kHz, and a discharge time of 5-15min is a suitable condition for the generation of β-Co(OH)2.

[0073] Table 1 Description of samples prepared in Comparative Examples 8-15

[0074]

[0075]

[0076] The above-described embodiments are only preferred embodiments of the present invention, but not all feasible embodiments of the present invention. For those skilled in the art, any obvious changes made thereto without departing from the principles and spirit of the present invention should be considered to be included in the scope of protection of the claims of the present invention.

Claims

1. A method for preparing carbon material loaded with β-Co(OH)2 in NH3 plasma-assisted solution, characterized in that the steps include: S1. Prepare a mixture containing a carbon material carrier, Co(NO3)2 solution and deionized water; S2. In an atmospheric pressure surface dielectric barrier discharge cold plasma reactor, a working gas is introduced to generate plasma, and the mixture described in step S1 is processed; S3. Filter, dry and grind the mixture obtained by the treatment in step S2 to obtain a sample of carbon material loaded with β-Co(OH)2.

2. The method for preparing carbon material loaded with β-Co(OH)2 in an NH3 plasma-assisted solution according to claim 1, characterized in that: Step S1 is specifically as follows: use a pipette to mix 40-300 μL of Co(NO 3 ) 2 solution, 1-5 mL of deionized water and 5-50 mg of the carbon material carrier in a watch glass.

3. The method for preparing carbon material loaded with β-Co(OH)2 in an NH3 plasma-assisted solution according to claim 1, characterized in that: In step S1, the carbon material carrier is any one of multi-walled carbon nanotubes, multi-layer graphene, and activated carbon, preferably multi-walled carbon nanotubes.

4. The method for preparing carbon material loaded with β-Co(OH)2 in an NH3 plasma-assisted solution according to claim 1, characterized in that the steps The final concentration of Co(NO3)2 solution in S1 is 0.5-1.5 mol·L -1 .

5. The method for preparing carbon material loaded with β-Co(OH)2 in a NH3 plasma-assisted solution according to claim 1, characterized in that: Step S2 specifically includes: placing the watch dish containing the mixture in step S1 into an atmospheric pressure surface dielectric barrier discharge cold plasma reactor, wherein the depth of the mixture is 4-10 mm; stirring the mixture with a magnetic stirrer, wherein the speed of the magnetic stirrer is 200-800 r·min -1 ; The distance between the solution and the discharge electrode in the reactor is 2-5 mm. A mixed gas of NH3 and Ar is introduced as the working gas, and the plasma discharge frequency and discharge voltage are adjusted to treat the mixed solution through the generated plasma.

6. The method for preparing carbon material loaded with β-Co(OH)2 in a NH3 plasma-assisted solution according to claim 1, characterized in that: The atmospheric pressure surface dielectric barrier discharge cold plasma reactor used in step S2, wherein the medium is quartz glass or alumina (thickness is 1-2 mm), and the metal electrode is silver or tungsten.

7. The method for preparing carbon material loaded with β-Co(OH)2 in a NH3 plasma-assisted solution according to claim 1, characterized in that: In step S2, the volume content of NH3 in the working gas is 50%.

8. The method for preparing carbon material loaded β-Co(OH)2 in a NH3 plasma-assisted solution according to claim 1, characterized in that: In step S2, the plasma discharge frequency is 5-15 kHz, the discharge voltage is sinusoidal high voltage, the peak-to-peak value is 4-8 kV, and the discharge treatment time of the mixture is 5-15 min.

9. The method for preparing carbon material loaded with β-Co(OH)2 in a NH3 plasma-assisted solution according to claim 1, characterized in that: Step S3 specifically comprises: filtering the mixture obtained in step S2, and then drying and grinding it in an oven at 100° C. to obtain a sample of carbon material loaded with β-Co(OH)2.

10. The method for preparing carbon material loaded with β-Co(OH)2 in a NH3 plasma-assisted solution according to claim 1, characterized in that: In step S1, the carbon material carrier is a multi-walled carbon nanotube.

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