Preparation method of graphitized carbon-coated transition metal silicide composite nanomaterial and application thereof

Abstract

The application discloses a preparation method and application of a graphitized carbon-coated transition metal silicide composite nanomaterial, and has the characteristics that SiO2 nanospheres are prepared first; then the prepared SiO2 nanospheres and a transition metal amino complex are reacted to obtain a transition metal silicate compound; finally, the transition metal silicate compound is reduced by hydrogen and then carbon-coated by a chemical vapor deposition method, so that a graphitized carbon shell is formed on the surface of transition metal silicide nanoparticles to obtain a core-shell structure composite nanomaterial of the graphitized carbon-coated transition metal silicide; the graphitized carbon-coated transition metal silicide composite nanomaterial prepared by the method has a typical capsule structure, a graphitized carbon shell is formed on the surface of the transition metal silicide nanoparticles, the graphitized carbon-coated transition metal silicide composite nanomaterial has good conductivity and durability, and when used as an electrode material of a super capacitor, the graphitized carbon-coated transition metal silicide composite nanomaterial has excellent specific capacity performance and prolongs the service life of the super capacitor.

Description

Technical Field

[0001] This invention relates to the technical field of supercapacitor electrode materials, and in particular to a method for preparing graphitized carbon-coated transition metal silicide composite nanomaterials and their applications. Background Technology

[0002] Supercapacitors are a new type of energy storage device that falls between traditional capacitors and rechargeable batteries. They store charge by generating pseudocapacitance through an electrochemical reaction between electrodes and an electrolyte, with capacities ranging from hundreds to thousands of farads. Compared to traditional capacitors, they have larger capacity, specific energy or specific power density, and a wider operating temperature range; while compared to batteries, they have higher specific power and are environmentally friendly.

[0003] Currently, the electrode materials for supercapacitors are mainly transition metal oxides, sulfides, hydroxides, and phosphides. However, these materials have poor conductivity, and during long-term cyclic charging and discharging, the electrode materials are prone to structural changes or even breakage, resulting in poor durability and reduced service life of supercapacitors. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing graphitized carbon-coated transition metal silicide composite nanomaterials. The resulting composite nanomaterials have good conductivity, good durability, and high specific capacitance, making them suitable for use as electrode materials for supercapacitors. Furthermore, the entire preparation method is simple to operate, has good repeatability, and can be prepared on a large scale.

[0005] The technical solution adopted by this invention to solve the above-mentioned technical problems is: a method for preparing graphitized carbon-coated transition metal silicide composite nanomaterials, comprising the following specific steps:

[0006] A method for preparing graphitized carbon-coated transition metal silicide composite nanomaterials, characterized by the following specific steps:

[0007] (1) Preparation of SiO2 nanospheres;

[0008] (2) The prepared SiO2 nanospheres and the amino complex of the transition metal were reacted to obtain the transition metal silicate compound;

[0009] (3) After reducing the transition metal silicate compound with hydrogen, carbon coating is carried out by chemical vapor deposition to form a graphitized carbon shell on the surface of the transition metal silicide nanoparticles, thus obtaining a core-shell structured composite nanomaterial of graphitized carbon-coated transition metal silicide.

[0010] Further, in step (1), the specific preparation process of SiO2 nanospheres is as follows: Ethanol, deionized water and ammonia water with a concentration of 28wt% are poured into a beaker at a volume ratio of 1:20:3-6 and mixed evenly to obtain a solution. Then, tetraethyl orthosilicate is added dropwise to the above solution at a volume of 0.2-0.3 times that of ammonia water. The mixture is magnetically stirred at room temperature and aged for 5-8 hours. The white precipitate is washed several times with deionized water, filtered, and dried at 60-80℃ to obtain SiO2 nanospheres.

[0011] Furthermore, the transition metal is cobalt, nickel, or copper, etc.

[0012] Furthermore, the specific preparation process of step (2) is as follows:

[0013] (2-1) Mix ethanol and water at a volume ratio of 1:1 to obtain an ethanol aqueous solution. Then, add SiO2 nanospheres to the ethanol aqueous solution at a ratio of 5-6 mg SiO2 per milliliter of ethanol aqueous solution and disperse them with an ultrasonic disperser for 1 hour to obtain solution A.

[0014] (2-2) Dissolve nickel chloride hexahydrate / cobalt chloride hexahydrate and ammonium chloride in deionized water until completely dissolved (here, nickel chloride hexahydrate / cobalt chloride hexahydrate means nickel chloride hexahydrate or cobalt chloride hexahydrate), wherein: the molar ratio of nickel chloride hexahydrate / cobalt chloride hexahydrate to ammonium chloride is 1:5-6, and the molar ratio of nickel chloride hexahydrate / cobalt chloride hexahydrate to SiO2 in (2-1) above is 1.5-2:1. Then add ammonia water with a concentration of 28wt%, the amount of ammonia water added is 2-4 ml of 28wt% ammonia water per 100 mg of SiO2 in (2-1) above, to form solution B;

[0015] (2-3) Mix solution A and solution B, transfer to a hydrothermal reactor, and place in an oven at 150-200°C for 10-15 hours. After the hydrothermal reaction, wash the powdered product with deionized water and dry to obtain nickel silicate or cobalt silicate.

[0016] Further, the specific preparation process of step (3) is as follows: the transition metal silicate compound is placed in a quartz crucible and placed in the chemical vapor deposition reaction chamber of a tube furnace. It is heated to 800°C in a hydrogen atmosphere of 50 sccm and 1.5 Torr, and the heating rate is controlled at 5°C / min. After 3 hours, the transition metal silicate compound is fully reduced by hydrogen. The temperature is then raised to 1000°C, and acetylene gas is introduced at 50 sccm for 30 minutes. After that, the acetylene is turned off, and the furnace is cooled to room temperature in a hydrogen atmosphere to obtain a core-shell structured composite nanomaterial of graphitized carbon-coated transition metal silicide.

[0017] The prepared graphitized carbon-coated transition metal silicide composite nanomaterials are used as electrode materials for supercapacitors.

[0018] Furthermore, graphitized carbon-coated transition metal silicide composite nanomaterials and PVDF (polyvinylidene fluoride) are added to N-methylpyrrolidone in a mass ratio of 3 to 4:1:5, and the mixture is prepared into a slurry and coated onto the surface of a graphite plate to form an electrode.

[0019] Compared with the prior art, the advantages of this invention are that the graphitized carbon-coated transition metal silicide composite nanomaterials prepared by this method have a typical capsule structure, in which highly crystalline graphitized carbon is formed on the surface of the transition metal silicide, that is, a graphitized carbon shell is formed on the surface of the transition metal silicide nanoparticles, which makes it have good conductivity and durability. When used as an electrode material for supercapacitors, it exhibits excellent specific capacitance performance and extends the service life of supercapacitors. Moreover, the entire preparation method is simple to operate, has good repeatability, and can be prepared in large quantities. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the preparation process of the present invention;

[0021] Figure 2 The images shown are SEM images (a) of silicon dioxide and TEM images (b) of nickel silicate of the present invention.

[0022] Figure 3 The XRD diffraction pattern of graphitized carbon-coated nickel silicide according to the present invention;

[0023] Figure 4 This is a TEM image of the graphitized carbon-coated nickel silicide nanoparticles of the present invention.

[0024] Figure 5 This is an HR-TEM image (i.e., a high-resolution transmission electron microscope image) of the graphitized carbon-coated nickel silicide nanoparticles of the present invention.

[0025] Figure 6 The three-electrode volt-ampere cycle test curves are for Ni2Si@GC as the electrode material of the supercapacitor. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0027] Example 1: A method for preparing graphitized carbon-coated nickel silicide composite nanomaterials, comprising the following specific steps:

[0028] (1) Preparation of SiO2 nanospheres: Ethanol, deionized water and ammonia water with a concentration of 28wt% were poured into a beaker at a volume ratio of 1:20:3 and mixed evenly to obtain a solution. Then, tetraethyl orthosilicate was added dropwise to the above solution at a volume of 0.2 times that of ammonia water. The mixture was magnetically stirred at room temperature and aged for 5 hours. The white precipitate was washed several times with deionized water, filtered, and dried at 60℃ to obtain SiO2 nanospheres.

[0029] (2-1) Ethanol and water were mixed at a volume ratio of 1:1 to obtain an ethanol aqueous solution. Then, SiO2 nanospheres were added to the ethanol aqueous solution at a ratio of 5 mg SiO2 per milliliter of ethanol aqueous solution, and dispersed with an ultrasonic disperser for 1 hour to obtain solution A.

[0030] (2-2) Dissolve nickel chloride hexahydrate and ammonium chloride in deionized water until completely dissolved, wherein the molar ratio of nickel chloride hexahydrate to ammonium chloride is 1:5, and the molar ratio of nickel chloride hexahydrate to SiO2 in (2-1) above is 1.5:1. Then add ammonia water with a concentration of 28wt%, the amount of ammonia water added is 2 ml of 28wt% ammonia water per 100 mg of SiO2 in (2-1) above, to form solution B;

[0031] (2-3) Mix solution A and solution B, transfer to a hydrothermal reactor, place in an oven at 160°C for 15 hours, after hydrothermal reaction, wash the light green powder with deionized water, and dry to obtain nickel silicate;

[0032] (3) Nickel silicate was placed in a quartz crucible and placed in the chemical vapor deposition reaction chamber of a tube furnace. It was heated to 800°C in a hydrogen atmosphere of 50 sccm and 1.5 Torr, and the heating rate was controlled at 5°C / min. After 3 hours, the nickel silicate was fully reduced by hydrogen. The temperature was then raised to 1000°C and acetylene gas was introduced at 50 sccm for 30 minutes. After that, the acetylene was turned off and the furnace was cooled to room temperature in a hydrogen atmosphere, so that a graphitized carbon shell was formed on the surface of the nickel silicide nanoparticles, and a core-shell structured composite nanomaterial of graphitized carbon-coated nickel silicide (Ni2Si@GC) was obtained.

[0033] Example 2: A method for preparing graphitized carbon-coated cobalt silicide composite nanomaterials, comprising the following specific steps:

[0034] (1) Preparation of SiO2 nanospheres: Ethanol, deionized water and ammonia water with a concentration of 28wt% were poured into a beaker at a volume ratio of 1:20:5 and mixed evenly to obtain a solution. Then, tetraethyl orthosilicate was added dropwise to the above solution at a volume of 0.3 times that of ammonia water. The mixture was magnetically stirred at room temperature and aged for 8 hours. The white precipitate was washed several times with deionized water, filtered, and dried at 70℃ to obtain SiO2 nanospheres.

[0035] (2-1) Ethanol and water were mixed at a volume ratio of 1:1 to obtain an ethanol aqueous solution. Then, SiO2 nanospheres were added to the ethanol aqueous solution at a ratio of 6 mg SiO2 per milliliter of ethanol aqueous solution, and dispersed with an ultrasonic disperser for 1 hour to obtain solution A.

[0036] (2-2) Dissolve cobalt chloride hexahydrate and ammonium chloride in deionized water until completely dissolved, wherein the molar ratio of cobalt chloride hexahydrate to ammonium chloride is 1:6, and the molar ratio of cobalt chloride hexahydrate to SiO2 in (2-1) above is 2:1. Then add ammonia water with a concentration of 28wt%, the amount of ammonia water added is 3 ml of 28wt% ammonia water per 100 mg of SiO2 in (2-1) above, to form solution B;

[0037] (2-3) Mix solution A and solution B, transfer to a hydrothermal reactor, place in an oven at 180°C for 12 hours, after hydrothermal reaction, wash the coral red powder with deionized water, and dry to obtain cobalt silicate;

[0038] (3) Cobalt silicate was placed in a quartz crucible and placed in the chemical vapor deposition reaction chamber of a tube furnace. It was heated to 800°C in a hydrogen atmosphere of 50 sccm and 1.5 Torr, and the heating rate was controlled at 5°C / min. After 3 hours, the cobalt silicate was fully reduced by hydrogen. The temperature was then raised to 1000°C and acetylene gas was introduced at 50 sccm for 30 minutes. After that, the acetylene was turned off and the furnace was cooled to room temperature in a hydrogen atmosphere, so that a graphitized carbon shell was formed on the surface of cobalt silicate nanoparticles, and a core-shell structured composite nanomaterial of cobalt silicate coated with graphitized carbon was obtained.

[0039] The graphitized carbon-coated nickel silicide (Ni2Si@GC) composite nanomaterials prepared in Example 1 were subjected to diffraction peak analysis, and the results are as follows: Figure 3 The image shows its X-ray diffraction spectrum. Based on the diffraction peak analysis, the synthesized nickel silicide belongs to Ni₂Si (corresponding to JCPDS 3-0943). The diffraction peak at 26.5°, marked by the red line, is a typical absorption peak of graphitized carbon, proving the presence of graphitized carbon. Furthermore... Figure 4 TEM images of graphitized carbon-coated nickel silicide nanoparticles, from... Figure 4 (a) It can be seen that the Ni2Si particles are tightly coated with a carbon layer; while after treatment with hydrofluoric acid, as... Figure 4 As shown in (b), after the Ni2Si core is etched away, the empty shell of graphite layer is revealed.

[0040] The graphitized carbon-coated nickel silicide (Ni2Si@GC) composite nanomaterial was analyzed using high-resolution transmission electron microscopy (HR-TEM) to obtain the following images: Figure 5 As shown, nickel silicide is clearly encapsulated by a layer of graphitized carbon, indicating that the material has a core-shell structure.

[0041] Furthermore, the graphitized carbon-coated nickel silicide composite nanomaterials and PVDF prepared above were added to N-methylpyrrolidone in a mass ratio of 3:1:5, and a slurry was prepared. This slurry was then coated onto the surface of a graphite plate to form an electrode, which served as the electrode material for a supercapacitor. A three-electrode voltammetric cycle test was then performed, and the three-electrode voltammetric cycle test curve was obtained, as shown below. Figure 6 As shown, when the scanning voltage window is -0.9V to 0.1V and the scanning speed is 10 mV / s, the specific capacitance value calculated by the curve integral method is 286.9F / g.

[0042] The scope of protection of this invention includes, but is not limited to, the above embodiments. The scope of protection is defined by the claims. Any substitutions, modifications, or improvements to this technology that are easily conceived by those skilled in the art fall within the scope of protection of this invention.

Claims

1. A method for preparing graphitized carbon-coated transition metal silicide composite nanomaterials, characterized in that... The specific steps include the following: (1) Preparation of SiO2 nanospheres; (2) The prepared SiO2 nanospheres and the amino complex of the transition metal were reacted to obtain the transition metal silicate compound; (3) After reducing the transition metal silicate compound with hydrogen, carbon coating is performed by chemical vapor deposition. The specific preparation process is as follows: The transition metal silicate compound is placed in a quartz crucible and then placed in the chemical vapor deposition reaction chamber of a tube furnace. It is heated to 800℃ in a hydrogen atmosphere of 50 sccm and 1.5 Torr, with the heating rate controlled at 5℃ / min. After 3 hours, the transition metal silicate compound is fully reduced by hydrogen. The temperature is then raised to 1000℃, and acetylene gas is introduced at 50 sccm for 30 minutes. After that, the acetylene is turned off, and the furnace is cooled to room temperature in a hydrogen atmosphere, so that a graphitized carbon shell is formed on the surface of the transition metal silicide nanoparticles, thus obtaining a core-shell structured composite nanomaterial of graphitized carbon-coated transition metal silicide.

2. The method for preparing graphitized carbon-coated transition metal silicide composite nanomaterials as described in claim 1, characterized in that: In step (1), the specific preparation process of SiO2 nanospheres is as follows: Ethanol, deionized water and ammonia water with a concentration of 28wt% are poured into a beaker at a volume ratio of 1:20:3-6 and mixed evenly to obtain a solution. Then, tetraethyl orthosilicate is added dropwise to the above solution at a volume of 0.2-0.3 times that of ammonia water. The mixture is magnetically stirred at room temperature and aged for 5-8 hours. The white precipitate is washed several times with deionized water, filtered, and dried at 60-80℃ to obtain SiO2 nanospheres.

3. The method for preparing graphitized carbon-coated transition metal silicide composite nanomaterials as described in claim 1, characterized in that: The transition metal is cobalt, nickel, or copper.

4. The method for preparing graphitized carbon-coated transition metal silicide composite nanomaterials as described in claim 3, characterized in that: The specific preparation process of step (2) is as follows: (2-1) Mix ethanol and water at a volume ratio of 1:1 to obtain an ethanol aqueous solution. Then, add SiO2 nanospheres to the ethanol aqueous solution at a ratio of 5-6 mg SiO2 per milliliter of ethanol aqueous solution and disperse them with an ultrasonic disperser for 1 hour to obtain solution A. (2-2) Dissolve nickel chloride hexahydrate / cobalt chloride hexahydrate and ammonium chloride in deionized water until completely dissolved, wherein the molar ratio of nickel chloride hexahydrate / cobalt chloride hexahydrate to ammonium chloride is 1:5-6, and the molar ratio of nickel chloride hexahydrate / cobalt chloride hexahydrate to SiO2 in (2-1) above is 1.5-2:

1. Then add ammonia water with a concentration of 28wt%, the amount of ammonia water added is 2-4 ml of 28wt% ammonia water per 100 mg of SiO2 in (2-1) above, to form solution B; (2-3) Mix solution A and solution B, transfer to a hydrothermal reactor, and place in an oven at 150-200°C for 10-15 hours. After the hydrothermal reaction, wash the powdered product with deionized water and dry to obtain nickel silicate or cobalt silicate.

5. The application of the graphitized carbon-coated transition metal silicide composite nanomaterial prepared according to claim 1 as a supercapacitor electrode material.

6. The application of the graphitized carbon-coated transition metal silicide composite nanomaterial as described in claim 5 as a supercapacitor electrode material, characterized in that: Graphitized carbon-coated transition metal silicide composite nanomaterials and PVDF were added to N-methylpyrrolidone in a mass ratio of 3-4:1:5 and mixed into a slurry, which was then coated onto the surface of a graphite plate to form an electrode.

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