Preparation and application of a carbon-metal-silicate composite material

Abstract

The invention discloses a method for preparing a carbon-metal-silicate composite material, which comprises mixing an oxygen-rich functional carbon-based material, silicon oxide, a transition metal and deionized water, and then subjecting the mixture to a hydrothermal reaction at 100°C to 200°C for 20 to 24 hours; cooling the reaction to room temperature and performing solid-liquid separation, and washing the resulting solid product with a mixed solution of deionized water and acetone and drying it to obtain a solid powder; then treating the solid powder with ammonia water, filtering, washing and drying it to obtain a carbon-metal-silicate composite material. This composite material not only includes the structural advantages of carbon-based materials but also is compatible with the properties of layered silicate materials. The synergistic effect of the two has a broader application prospect.

Description

Technical Field

[0001] The present invention relates to the preparation of a carbon silicate composite material, in particular to a method for preparing a carbon-metal-silicate composite material, which is mainly used as a battery electrode, catalytic material, and adsorption material, and belongs to the field of new materials and new energy technology applications. Background Art

[0002] Carbon-based materials and layered silicates, typical inorganic materials, exhibit broad application prospects and potential in a wide range of fields due to their unique physical and chemical properties. They play a vital role in human life and economic development, and are attracting increasing attention. Carbon-based materials possess exceptional mechanical and electrical properties, such as high electrical and thermal conductivity, high mechanical strength, and ease of modification. They can be used as functional additives to enhance polymer matrices, holding significant application prospects in the information, medical, materials, environmental, energy, electrochemistry, textile, and semiconductor industries. Layered silicates, with their advantages of heat resistance, acid and alkali resistance, insulation, high strength, and chemical stability, have been widely used in adsorption, catalysis, corrosion protection, and flame retardancy research. Furthermore, layered silicates contain a large number of exchangeable ions, allowing inorganic or organic ions to be inserted into the interlamellar space through ion exchange to form ionic composites. Silicon-carbon composites, through silicon-carbon coupling, combine the high specific capacity of silicon with the high electrical conductivity of carbon, minimizing silicon volume changes during cycling and thus maintaining the integrity of the electrode structure. At present, research on silicon-carbon composites at home and abroad mainly focuses on the effective combination of elemental silicon / silicon oxide and carbon-based materials. The coupling of carbon and silicate is also physical compounding (such as grinding and mixing), while there is no literature record of research on uniformly mixed and chemically bonded carbon silicate composites. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for preparing a carbon-metal-silicate composite material, which uses transition metals as bridging agents to easily connect carbon-based materials and layered silicate materials, making the carbon silicate more stable, with good controllable performance, and more green and economical.

[0004] The preparation method of the carbon-metal-silicate composite material of the present invention comprises the following steps: mixing an oxygen-rich functional carbon-based material, silicon oxide, a transition metal and deionized water, and then subjecting the mixture to a hydrothermal reaction; cooling the mixture to room temperature after the reaction, and subjecting the mixture to solid-liquid separation; washing the obtained solid product with a mixed solution of deionized water and acetone, and drying the mixture to obtain a solid powder; and then treating the solid powder with aqueous ammonia, filtering, washing and drying the mixture to obtain the carbon-metal-silicate composite material.

[0005] The oxygen-rich functional carbon-based material is selected from carbon nanotubes, carbon fibers, nanodiamonds, graphite or graphene, activated carbon, biomass-derived carbon, etc. 2Carbon-based materials; the thickness of the carbon-based material depends on the choice of carbon-based material, and the carbon-silicate composite material can have various structural morphologies, including spherical and layered. Silicon oxides are selected from SBA-15 amorphous silica, commercial glass, waste silicon-based photovoltaic materials, sand, and other materials. Layered silicates are obtained by dissolving and rearranging silicon oxides during the reaction process. The transition metals are selected from iron, nickel, cobalt, and manganese. The mass ratio of oxygen-rich functional carbon-based material, silicon oxide, and transition metal is controlled within the range of 1:(0.05-50):(0.001-0.9). The ratio of carbon-based material, silicon oxide, and transition metal significantly influences the morphology, structure, and properties of the carbon-based material.

[0006] The hydrothermal reaction temperature is 100°C to 200°C and the reaction time is 20 to 24 hours. In the hydrothermal reaction, a higher temperature will produce a more uniform product than a lower temperature for the same time.

[0007] The solid product from the hydrothermal reaction is a mixture of a carbosilicate complex and unconverted silicon oxide, so it needs to be purified with ammonia. The ammonia concentration is 2-8 mol / L, the liquid-to-solid ratio of ammonia to solid powder is 75:1-300:1, and the treatment temperature is 40-50°C for 12-16 hours.

[0008] Figure 1 Schematic diagram of the synthesis process of the carbon-metal-silicate composite material prepared by the present invention. In the hydrothermal reaction, the carbon-based material will be cut to form graphene, the silicon oxide will be stripped, hydrolyzed and rearranged to form layered silicate, and the transition metal ions will connect the layered silicate and the carbon-based material to form a carbon-metal-silicate composite material. Since the surfaces of the carbon-based material and the silicate lack functional groups that can directly form bonds, the doping of transition metals can successfully bridge the two. In addition, as a cross-linking agent, the content and type of metal ions have a significant impact on the properties of the carbon-silicate composite material. If the metal content is low, a small amount of a mixture of carbon silicate and reactants will be formed; and sufficient metal content will completely bridge the layered silicate to the carbon surface to form a better carbon silicate structure. The unzipping / cutting process of the carbon-based material is actually an oxidation-reduction process from C(0) to C(oxide), and the metal M ion (Fe 3+ 、Ni 2+ 、Mn 2+ ) is considered the main debonding agent. The ring opening energy of the first carbon-carbon bond without metal participation (3.3 eV) is five times that of the metal participation (0.06 eV) (in other words, the presence of metal makes the C-C bond break easier). In addition, the functional groups on the surface of carbon-based materials have also been shown to facilitate the debonding process. The exposed open carbon edges need to consume OH - Forming a carbon positive surface (COM) with metal ions +To stabilize. OH - Produced by the reaction of water and iron, it is also the main ion that reacts with silicon oxide. - Reacts with Si-O-Si of silicon oxide to form silicate ions. Silicate ions are on the positive carbon surface (COM) + Compared to the individual materials, carbon and silicate retain their primary structure and properties in the composite, despite forming chemical bonds via metal and oxygen.

[0009] Figure 2 N2 adsorption-desorption curve (a) and pore size distribution (b) of the carbon-metal-silicate composite material prepared in the present invention. Figure 2 The surface area of ​​carbon nanotubes (CNTs) is 232 m 2 / g, the tailoring process has no significant effect on its specific surface area. However, with the formation of carbon silicate composites, their surface areas increase to 289 m 2 / g(2.1Fe-CSiOx) and 312m 2 / g (10Fe-CSiOx). Moreover, with the increase of metal content (2.1 wt% to 10 wt%), BJH found that a mesoporous structure gradually formed (pore size of about 2nm, Figure 2 b), therefore, this type of composite material has an ultra-high specific surface area and higher electrochemical performance. Since the carbon-based skeleton and silicate in the composite material form chemical bonds through metal and oxygen, the composite carbon silicate has the characteristics of both. The introduction of layered silicates can greatly enhance the high temperature resistance and corrosion resistance of graphene, and the presence of graphene not only gives the silicon-based composite matrix electrical conductivity, but also improves the thermal conductivity. It is also of great significance for increasing the glass transition temperature and improving the mechanical properties of the composite material. Compared with traditional silicon-carbon materials, the new carbon silicate is more stable, has good controllable performance, and is greener and more economical. Since the oxygen element acts as a volume buffer in the process of lithium ion insertion and extraction, it exhibits better volume effect and cycle performance than pure silicon negative electrode materials. It can be used as a high-quality catalytic carrier and adsorbent, and has potential prospects in other applications.

[0010] In summary, the carbon silicate composite material prepared by the present invention includes a carbon-based material skeleton and a transition metal connected to the edge of the carbon skeleton and a layered silicate connected by a bridging oxygen bond. Therefore, the structure and thickness of the carbon silicate composite material depend on the selection of the carbon-based material, and it has a variety of structural morphologies such as spherical and layered. By changing the types of carbon-based materials, transition metals and silicon oxide materials, the in-situ introduction of different heteroatoms and different structural components can be achieved to adapt to various chemical environments. In addition, the composition ratio of carbon-based materials, transition metals and silicates can be adjusted within a specified range, and the structure of the carbon silicate composite material can be easily regulated, providing unlimited possibilities for the compatibility of the superior performance of silicates and carbon-based materials. The carbon silicate composite material not only includes the structural advantages of carbon-based materials, but also is compatible with the properties of layered silicate materials. The synergistic effect of the two has a broader application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 Schematic diagram of the “cutting and bridging” synthesis process of the carbon-metal-silicate composite material of the present invention.

[0012] Figure 2 N2 adsorption-desorption curves (a) and pore size distributions (b) of the carbon-metal-silicate composite materials prepared in Examples 1 and 2;

[0013] Figure 3 These are the potential-current curves of the carbon-metal-carbon silicate composite materials prepared in Examples 1 and 3.

[0014] Figure 4 This is the charge and discharge diagram of the 10Fe-CSiOx carbon silicate composite material prepared in Example 2 as the anode of a lithium-ion battery.

[0015] Figure 5 Comparison of current density tests between the 0.4Ni-CSiOx carbon silicate prepared in Example 3 and the commercial IrOx catalyst. DETAILED DESCRIPTION

[0016] The preparation and application performance of the carbon-metal-silicate composite material of the present invention are further described below through specific examples.

[0017] Example 1

[0018] (1) Multi-walled carbon nanotubes (MCNT), amorphous silica (SBA-15), and metallic iron powder were mixed in an autoclave at a weight ratio of 1:1:0.021 (MCNT 100 mg, SBA-15 100 mg, metallic iron powder 2.1 mg) along with an appropriate amount of deionized water (5 ml).

[0019] (2) Setting the temperature of the autoclave to 200°C and subjecting the autoclave to hydrothermal treatment for 24 hours under stirring, stopping the heating and cooling the autoclave to room temperature; separating the liquid-solid mixture of the reaction product, wherein the obtained solid is a mixture of a carbon silicate complex (2.1Fe-CSiOx) and unconverted SBA-15 silicon oxide; washing with a mixed solution of deionized water and acetone and drying to obtain a solid powder, which is the carbon silicate complex 2.1Fe-CSiOx;

[0020] (3) The carbon silicate composite 2.1Fe-CSiOx was treated with an ammonia solution (concentration 6 mol / L, liquid-to-solid mass ratio 1:10) at 40°C~50°C for 16 hours, and then filtered, washed and dried to obtain a pure carbon silicate material (2.1Fe-CSiOx). Its N2 adsorption-desorption curve and pore size distribution are shown in Figure 2 ;

[0021] (4) The carbon silicate material 2.1Fe-CSiOx was used as a catalyst to test the oxygen evolution reaction. The solvent selected for the reaction process was potassium hydroxide solution. The working electrode was a 5 mm diameter glassy carbon disc electrode. The electrode needed to be ground and polished before use to ensure a smooth surface. The electrode coated with 2.1Fe-CSiOx was then placed in ethanol and water for ultrasonic treatment for 5 minutes, rinsed and dried (60°C). The catalyst was evenly dispersed in a specific mixed solvent (4 ml IPA, 960 μl H2O and 40 μl Nafion solution) through ultrasonic treatment. The catalyst will gradually precipitate from the dispersion. The catalyst loading on the electrode is 50 μg / cm². The potential-current curve of the carbon silicate material 2.1Fe-CSiOx is shown in Figure 3 .

[0022] Example 2

[0023] The amount of iron powder added was 10 mg, and the rest was the same as in Example 1. The obtained product was a carbon silicate material 10Fe-CSiOx. Its N2 adsorption-desorption curve and pore size distribution are shown in Figure 2 With increasing metal content (2.1 wt% to 10 wt%), the surface area of ​​the carbon silicate composites increased to 289 m 2 / g(2.1Fe-CSiOx) and 312m 2 / g (10Fe-CSiOx). Moreover, BJH found that 10Fe-CSiOx has a mesoporous structure ( Figure 2b). The obtained carbon silicate material (10Fe-CSiOx) was applied to lithium-ion battery anode materials: the lithium-ion battery anode material used 10Fe-CSiOx carbon silicate material and polyvinylidene fluoride were mixed with N-methyl-2-pyrrolidone in a weight ratio of 85:15 to form a slurry. The slurry was cast onto copper foil, dried under vacuum, cut into discs, and transferred to an argon-filled glove box for battery assembly. The separator was soaked with LiPF6 (concentration 1 mol / L) in a 1:1 mixed solvent of ethylene carbonate (EC) and dimethyl carbonate (DMC). The reaction temperature was 25°C, the biocirculator operating current was 66 μA, and the operating voltage range was 1 mV to 2.5 V. Figure 4 This is the charge and discharge diagram of 10Fe-CSiOx as the anode of lithium-ion battery. Figure 4 The 10Fe-CSiOx electrode was tested through 11 electrochemical charge-discharge cycles, with the first discharge capacity reaching 1684 mAh / g and the first charge capacity reaching 448 mAh / g. The capacity gradually stabilized at around 300 mAh / g over 10 cycles, demonstrating good cycling stability.

[0024] Experiments show that when the multi-walled carbon nanotubes in Example 1 are replaced with carbon fibers, activated carbon, nanodiamonds, graphite or graphene, or biomass-derived carbon, the structure and properties of the resulting carbon silicate material are similar to those in Example 1.

[0025] Example 3

[0026] (1) Multi-walled carbon nanotubes (MCNT), amorphous silica (SBA-15), and metallic nickel were mixed in an autoclave at a weight ratio of 1:1:0.004 (or specifically 100 mg of MCNT, 100 mg of SBA-15, and 0.4 mg of metallic nickel powder) along with an appropriate amount of deionized water (5 ml);

[0027] (2) Setting the temperature of the autoclave to 200°C, stopping the heating after the hydrothermal treatment under stirring for 24 hours, and cooling the autoclave to room temperature; separating the liquid-solid mixture of the reaction product, and the resulting solid is a mixture of the carbon silicate complex (0.4Ni-CSiOx) and unconverted SBA-15 silicon oxide; washing with a mixed solution of deionized water and acetone and drying to obtain a solid powder, which is the carbon silicate complex 0.4Ni-CSiOx;

[0028] (3) The carbon silicate composite 0.4Ni-CSiOx was treated with an ammonia solution (concentration 6 mol / L, liquid-to-solid mass ratio 1:10) at 40°C~50°C for 16 hours, and then filtered, washed, and dried to obtain a pure carbon silicate material 0.4Ni-CSiOx.

[0029] (4) Carbon silicate material 0.4Ni-CSiOx is used as a catalyst for oxygen evolution reaction: The operation process is the same as in Example 1. The potential-current curve of 0.4Ni-CSiOx is shown in Figure 3 , the potential-current curves obtained by different metal doping are obviously different, and the effect of nickel metal doping is better than that of iron metal. Figure 5 Comparison of current density stability between the prepared 0.4Ni-CSiOx carbosilicate and commercial IrOx catalysts. The 0.4Ni-CSiOx carbosilicate catalyst achieved a more stable and higher current density, demonstrating heterogeneous catalysis and achieving higher oxygen evolution reaction efficiency than commercial NiCoOx and IrOx catalysts.

[0030] The metal nickel powder in Example 3 was replaced by cobalt powder, and the structure and performance of the obtained carbon silicate material were similar to those in Example 3.

[0031] The SBA-15 amorphous SiO2 in Example 3 is replaced by glass, photovoltaic silicon material, and the structure and performance of the obtained carbon silicate material are similar to those in Example 3.

Claims

1. A method for preparing a carbon-metal-silicate composite material, comprising mixing an oxygen-rich functional carbon-based material, silicon oxide, a transition metal, and deionized water, and subjecting the mixture to a hydrothermal reaction at 100°C to 200°C for 20 to 24 hours. After the reaction, the mixture is cooled to room temperature and subjected to solid-liquid separation. The resulting solid product is washed with a mixed solution of deionized water and acetone and dried to obtain a solid powder. The solid powder is then treated with aqueous ammonia, filtered, washed, and dried to obtain the carbon-metal-silicate composite material. The oxygen-rich functional carbon-based material is selected from carbon nanotubes, carbon fibers, nanodiamonds, graphite or graphene, activated carbon, and biomass-derived carbon; the silicon oxide is selected from SBA-15 amorphous silicon dioxide, commercial glass, waste silicon-based photovoltaic materials, and sand; the transition metal is selected from iron, nickel, cobalt, and manganese; and the mass ratio of the oxygen-rich functional carbon-based material, silicon oxide, and transition metal is 1:(0.05~50):(0.001~0.9).

2. The method for preparing a carbon-metal-silicate composite material according to claim 1, wherein: In the ammonia treatment, the concentration of the ammonia is 2-8 mol / L, the liquid-solid mass ratio of the ammonia to the solid powder is 75:1-300:1, the treatment temperature is 40° C.-50° C., and the treatment time is 12-16 hours.

3. Use of the carbon-metal-silicate composite material prepared by the method of claim 1 as a catalyst in oxygen evolution reaction.

4. Use of the carbon-metal-silicate composite material prepared by the method according to claim 1 as a negative electrode material for lithium-ion batteries.

Images