A method for preparing carbon-supported α-Co(OH)2 in plasma-assisted solution

Abstract

The application discloses a method for preparing carbon material loaded alpha-Co(OH)2 in a solution with plasma assistance, and belongs to the technical field of nanometer material preparation. The method adopts atmospheric pressure surface dielectric barrier discharge cold plasma, uses a mixed gas of H2 and Ar as working gas, and prepares carbon material loaded alpha-Co(OH)2 in a solution. The plasma device adopts a surface dielectric barrier discharge form, the discharge is stable and easy to control, liquid material can be processed in a flowing state, and large-scale amplification processing can be realized. The method has the advantages of simple operation process, no need to add any other chemical reagent, and the like. Only by mixing a carbon material carrier with Co(NO3)2 solution, adding a small amount of deionized water, and processing with atmospheric pressure surface dielectric barrier discharge cold plasma, carbon material loaded alpha-Co(OH)2 can be obtained in a short time, and the preparation process has the advantages of green, rapid, flexible and safe.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterial preparation technology, specifically relating to a method for preparing carbon-supported α-Co(OH)2 in a plasma-assisted solution. Background Technology

[0002] Co(OH)₂ is a layered hydroxide with two crystalline phases: α and β. The α phase has a structure similar to hydrotalcite, while the β phase has a structure similar to brucite. The interlayer distances of the α and β phases exceed 0.7 nm and 0.46 nm, respectively. The expanded interlayer distance of Co(OH)₂ provides more active sites, which can promote ion transfer at the interface between electroactive materials and electrolytes, improve conductivity, and accelerate electrolyte penetration. Compared with the β phase, the α phase has a larger interlayer distance, showing greater application advantages in electrochemistry, magnetism, catalysis, and other fields.

[0003] The preparation of α-Co(OH)₂ mainly employs a chemical precipitation method (Co... 2+ +2OH - =Co(OH)2↓+2H + Since α-Co(OH)₂ is metastable, its preparation conditions are quite demanding, requiring control of the pH and Co content of the reaction. 2+ With OH - The ratio of urea, PVP, or other reagents is added to act as precipitants or stabilizers. Chinese patent CN113134361A discloses a method for preparing an Ag / α-Co(OH)2 oxygen evolution catalyst. Cobalt chloride hexahydrate, sodium chloride, and hexamethylenetetramine are dissolved sequentially in a mixed solution of deionized water and ethanol according to a specific ratio. The mixed solution is then stirred and heated in an oil bath. After heating, a suspension containing green particles is produced. The solid product is collected by centrifugation, washed, and air-dried at room temperature to finally prepare α-Co(OH)2.

[0004] Chemical preparation methods typically require the addition of numerous reagents, involve complex procedures, and easily generate impurities, resulting in impure products. Therefore, there is an urgent need to develop a simple, rapid, and environmentally friendly method for preparing α-Co(OH)₂.

[0005] Plasma is the fourth state of matter, after solid, liquid, and gas. It is a non-condensed state system with a certain degree of ionization and macroscopically neutral charge. Cold plasma is a typical non-thermodynamically equilibrium plasma. It is well-suited for the preparation and processing of nanomaterials under mild conditions, and has attracted increasing attention in the field of metal nanomaterial preparation.

[0006] Chinese patent CN107473272B discloses a method for preparing sheet-like nano-β-Co(OH)2 using liquid-phase cathode glow discharge plasma. This invention uses a cobalt sheet as the anode, a needle-shaped platinum wire as the cathode, and NaNO3 solution as the electrolyte to prepare sheet-like nano-β-Co(OH)2 using liquid-phase cathode glow discharge plasma. The entire process lasts 0.5-2 hours. Because the liquid-phase cathode glow discharge plasma discharges inside the solution, the discharge time is relatively long, and the solution conductivity has a significant impact on the discharge, leading to uneven discharge, making the discharge process difficult to control, and α-Co(OH)2 is not obtained. Summary of the Invention

[0007] To overcome the shortcomings of existing technologies, this invention provides a method for preparing carbon-supported α-Co(OH)₂ in a plasma-assisted solution. The method employs atmospheric pressure surface dielectric barrier discharge (SDPD) cold plasma, using a mixture of H₂ and Ar as the working gas, to prepare carbon-supported α-Co(OH)₂ in solution. The plasma reactor utilizes SPD discharge, which provides stable and easily controlled discharge, allowing for the flow of liquid materials and scalable processing. Furthermore, this method is simple to operate, requiring no additional chemical reagents. Simply mix the carbon material support with a Co(NO₃)₂ solution, add a small amount of deionized water, and treat with atmospheric pressure SPD cold plasma to obtain carbon-supported α-Co(OH)₂ in a short time. The preparation process is green, rapid, flexible, and safe.

[0008] The above-mentioned objective of this invention is achieved through the following technical solution: a method for preparing carbon-supported α-Co(OH)2 in a plasma-assisted solution, comprising the following steps:

[0009] S1. Prepare a mixture containing a carbon material carrier, a Co(NO3)2 solution, and deionized water;

[0010] S2. In an atmospheric pressure surface dielectric barrier discharge cold plasma reactor, a working gas is introduced to generate plasma and process the mixture described in step S1;

[0011] S3. Filter, dry and grind the mixture obtained in step S2 to obtain a carbon-supported α-Co(OH)2 sample.

[0012] Furthermore, step S1 specifically involves using a pipette to mix 50-500 μL of Co(NO3)2 solution, 1-10 mL of deionized water, and 2-50 mg of carbon material carrier in a petri dish.

[0013] Furthermore, in step S1, the carbon material carrier can be multi-walled carbon nanotubes, single-walled carbon nanotubes, graphene, activated carbon, etc., and any one of them can be selected, with multi-walled carbon nanotubes or single-walled carbon nanotubes being preferred.

[0014] Furthermore, the final concentration of the Co(NO3)2 solution in step S1 is 0.005-0.07 mol·L⁻¹. -1 .

[0015] Further, step S2 specifically involves: placing the petri dish containing the mixture from step S1 into an atmospheric pressure surface dielectric barrier discharge cold plasma reactor, with the mixture depth being 4-10 mm; and stirring the mixture using a magnetic stirrer at a speed of 200-800 r·min. -1 The distance between the solution and the discharge electrode in the reactor is 2-5 mm. A mixture of H2 and Ar is introduced as the working gas. The plasma discharge frequency and discharge voltage are adjusted, and the generated plasma is used to process the mixed solution.

[0016] Furthermore, the atmospheric pressure surface dielectric barrier discharge cold plasma reactor used in step S2 has a dielectric material of quartz glass or alumina and a metal electrode of silver or tungsten.

[0017] Furthermore, the volume content of H2 in step S2 is 5%-100%.

[0018] Furthermore, in step S2, the plasma discharge frequency is 5kHz-15kHz, the discharge voltage is a sinusoidal high voltage with a peak-to-peak value of 4.0-12.0kV, and the treatment time for the mixture is 5-30min.

[0019] Furthermore, step S3 specifically involves filtering the mixture obtained in step S2, then drying and grinding it in a 100°C oven to obtain a carbon-loaded α-Co(OH)2 sample.

[0020] The advantages of this invention compared to existing technologies are as follows: It employs atmospheric pressure surface dielectric barrier discharge cold plasma, using a mixture of H2 and Ar as the working gas, to prepare carbon-supported α-Co(OH)2 in solution. This method eliminates the need for other toxic or harmful chemical reagents and cumbersome procedures. Simply mixing the carbon material carrier with a Co(NO3)2 solution, adding a small amount of deionized water, and then treating with plasma allows for the rapid preparation of carbon-supported α-Co(OH)2. The preparation process is green, rapid, flexible, and safe, providing a flexible and safe new method for the preparation of α-Co(OH)2. Attached Figure Description

[0021] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0022] Figure 1 The image shows the XRD pattern of the sample prepared using multi-walled carbon nanotubes as a carrier in Example 1.

[0023] Figure 2 XRD patterns of samples prepared in Example 2, Example 3, and Comparative Example 1;

[0024] Figure 3 The XRD patterns of samples prepared using non-carbon inorganic materials as supports in Comparative Examples 2 and 3 are shown.

[0025] Figure 4 The XRD pattern of Co(OH)2 prepared by chemical method for Comparative Example 4 is shown. Detailed Implementation

[0026] The present invention is described in detail below through specific embodiments, but this does not limit the scope of protection of the present invention. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can all be obtained commercially.

[0027] Example 1

[0028] A method for preparing carbon-supported α-Co(OH)2 in a plasma-assisted solution, specifically comprising:

[0029] Plasma-assisted solution treatment of mixtures of multi-walled carbon nanotubes and Co(NO3)2 solution:

[0030] The specific steps for treating a mixture of multi-walled carbon nanotubes and Co(NO3)2 solution in plasma-assisted solution are as follows: First, 30 mg of multi-walled carbon nanotubes are placed in a quartz reactor, and 135 μL of a 0.94 mol·L⁻¹ solution is transferred using a pipette. -1 Add 3 mL of Co(NO3)2 solution and 3 mL of deionized water to a quartz reactor (4 cm in diameter, 6 mm deep). Adjust the position of the quartz reactor so that the liquid surface is 2 mm from the discharge electrode. Seal the device, connect the circuit, and introduce a mixture of H2 and Ar gas (V). H2 :V Ar =1:1), the total gas flow rate is 100 mL·min -1 The magnetic stirrer speed in the solution was set to 500 r·min. -1 The discharge frequency was adjusted to 10.3 kHz, the peak-to-peak sinusoidal discharge voltage was 6.0 kV, and the discharge time was 15 min. After the discharge was completed, the treated mixture was filtered, dried in an oven at 100 ℃ for 12 h, then ground and placed in a glass reagent bottle for storage in a desiccator.

[0031] Example 2

[0032] A method for preparing carbon-supported α-Co(OH)2 in a plasma-assisted solution, specifically comprising:

[0033] Plasma-assisted solution treatment of a mixture of multilayer graphene and Co(NO3)2 solution:

[0034] The treatment of a mixture of multilayer graphene and Co(NO3)2 solution in plasma-assisted solution follows the same steps as in Example 1, except that the multi-walled carbon nanotubes are replaced with multilayer graphene.

[0035] Example 3

[0036] A method for preparing carbon-supported α-Co(OH)2 in a plasma-assisted solution, specifically comprising:

[0037] Plasma-assisted solution treatment of a mixture of activated carbon and Co(NO3)2 solution:

[0038] The treatment of a mixture of activated carbon and Co(NO3)2 solution in plasma-assisted solution follows the same steps as in Example 1, except that multi-walled carbon nanotubes are replaced with activated carbon.

[0039] Comparative Example 1

[0040] Treatment of a mixture of graphite oxide and Co(NO3)2 solution in plasma-assisted solution:

[0041] The mixture of graphite oxide and Co(NO3)2 solution was treated in a plasma-assisted solution using the same steps as in Example 1, except that the multi-walled carbon nanotubes were replaced with graphite oxide.

[0042] Comparative Example 2

[0043] Plasma-assisted solution treatment of a mixture of non-carbon inorganic support TiO2 and Co(NO3)2 solution:

[0044] The treatment of a mixture of non-carbon inorganic carrier TiO2 and Co(NO3)2 solution in plasma-assisted solution follows the same steps as in Example 1, except that multi-walled carbon nanotubes are replaced with TiO2.

[0045] Comparative Example 3

[0046] Plasma-assisted solution treatment of a mixture of non-carbon inorganic carriers Al2O3 and Co(NO3)2 solution:

[0047] The treatment of a mixture of non-carbon inorganic carrier Al2O3 and Co(NO3)2 solution in plasma-assisted solution follows the same steps as in Example 1, except that the multi-walled carbon nanotubes are replaced with Al2O3.

[0048] Comparative Example 4

[0049] Chemical preparation of Co(OH)2:

[0050] The chemical method for preparing Co(OH)₂ involves the following steps: 30 mg of multi-walled carbon nanotubes and 135 μL of a solution with a molar concentration of 1 mol·L⁻¹. -1 The concentration of Co(NO3)2 and 270 μL is 2 mol·L⁻¹. -1 NaOH was mixed in a crucible and magnetically stirred for 30 minutes. After the reaction, the mixture was dried in an oven at 100°C and then ground to obtain Co(OH)2 prepared by chemical method.

[0051] like Figure 1 As can be seen, the XRD patterns of the experimentally treated multi-walled carbon nanotubes show obvious peaks at 13° (main peak), 22.7°, 33.9°, and 60.1°, which correspond to the (003), (006), (012), and (018) crystal planes of α-Co(OH)₂, respectively. This proves that atmospheric pressure surface dielectric barrier discharge cold plasma successfully prepared α-Co(OH)₂ samples loaded on carbon nanotubes. Figure 2 As can be seen, when graphite oxide is used as the support, no characteristic diffraction peak of α-Co(OH)₂ was clearly observed in the XRD pattern. However, when multilayer graphene or activated carbon is used as the support, a characteristic diffraction peak of α-Co(OH)₂ of a certain intensity appears at 13° in the XRD pattern. This indicates that treating a mixture of carbon materials and Co(NO₃)₂ solution in plasma-assisted solution can generate α-Co(OH)₂, but the amount generated is closely related to the carbon material support; multi-walled carbon nanotubes are preferred as the support. Figure 3 As can be seen, when using non-carbon inorganic supports TiO2 and Al2O3, no characteristic diffraction peaks of α-Co(OH)2 were detected in the XRD patterns. Figure 4 It is evident that by using chemical precipitation with multi-walled carbon nanotubes as a carrier, β-Co(OH)2 is generated through the reaction of NaOH and Co(NO3)2, but α-Co(OH)2 is not generated. Furthermore, the generated β-Co(OH)2 is impure and contains residual NaNO3.

[0052] Comparative Examples 5-11 show that when the discharge voltage or frequency is too high, the energy in the plasma reactor is high, leading to the simultaneous generation and decomposition of α-Co(OH)2; when the discharge voltage or frequency is too low, the plasma reactor does not discharge sufficiently, resulting in insufficient energy and preventing the generation of α-Co(OH)2; when the discharge treatment time is too long, the generated α-Co(OH)2 will decompose; when the discharge treatment time is too short, the energy in the plasma reactor is low, preventing the generation of α-Co(OH)2. Without hydrogen, species that produce α-Co(OH)2 cannot be generated. Therefore, using atmospheric pressure surface dielectric barrier discharge cold plasma, with a mixture of H2 and Ar as the working gas (hydrogen volume content of 5%-100%), a discharge voltage of 4-12 kV, a discharge frequency of 5-15 kHz, and a discharge time of 5-30 min, are suitable conditions for the generation of α-Co(OH)2.

[0053] Table 1. Description of sample preparation for Comparative Example 5-11

[0054]

[0055]

[0056]

[0057] The embodiments described above are merely preferred embodiments of the present invention, and not all feasible embodiments of the present invention. Any obvious modifications made by those skilled in the art without departing from the principles and spirit of the present invention should be considered to be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing carbon-supported α-Co(OH)₂ in a plasma-assisted solution, characterized in that the steps include... include: S1. Prepare a mixture containing a carbon material carrier, a 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 process the mixture described in step S1; S3. Filter, dry and grind the mixture obtained in step S2 to obtain a carbon-supported α-Co(OH)2 sample; In step S1, the carbon material carrier is any one of multi-walled carbon nanotubes, single-walled carbon nanotubes, graphene, and activated carbon. In step S2, a mixture of H2 and Ar is used as the working gas. The plasma discharge frequency in step S2 is 5kHz-15kHz, the discharge voltage is a sinusoidal high voltage with a peak-to-peak value of 4.0-12.0 kV, and the discharge processing time is 5-30 min.

2. The method for preparing carbon-supported α-Co(OH)₂ in a plasma-assisted solution according to claim 1, characterized in that, Step S1 specifically involves using a pipette to mix 50-500 μL of Co(NO3)2 solution, 1-10 mL of deionized water, and 2-50 mg of carbon material in a petri dish.

3. The method for preparing carbon-supported α-Co(OH)₂ in a plasma-assisted solution according to claim 1, characterized in that, In step S1, the final concentration of the Co(NO3)2 solution in the mixture is 0.005-0.07 mol∙L. -1 .

4. The method for preparing carbon-supported α-Co(OH)₂ in a plasma-assisted solution according to claim 1, characterized in that, Step S2 specifically involves: placing the petri dish containing the mixture from step S1 into an atmospheric pressure surface dielectric barrier discharge cold plasma reactor, with the mixture depth being 4-10 mm; and stirring the mixture using a magnetic stirrer at a speed of 200-800 r·min. -1 The distance between the mixture in the reactor and the discharge electrode is 2-5 mm.

5. The method for preparing carbon-supported α-Co(OH)₂ in a plasma-assisted solution according to claim 1, characterized in that, The atmospheric pressure surface dielectric barrier discharge cold plasma reactor used in step S2 has a dielectric material of quartz glass or alumina and a metal electrode of silver or tungsten.

6. The method for preparing carbon-supported α-Co(OH)₂ in a plasma-assisted solution according to claim 1, characterized in that, In step S2, the total flow rate of the working gas is 20-200 mL·min. -1 The volume content of H2 in the working gas is 5%-100%.

7. The method for preparing carbon-supported α-Co(OH)₂ in a plasma-assisted solution according to claim 1, characterized in that, Step S3 specifically involves filtering the mixture obtained in step S2, then drying and grinding it in a 100 ℃ oven to obtain a carbon-loaded α-Co(OH)2 sample.

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