CN103436904B - A kind of fused salt electrolysis process is prepared the method for carbide-derived carbon - Google Patents

Abstract

A method for preparing carbide-derived carbon by molten salt electrolysis, which mainly includes: using metal carbide as a raw material, molding and sintering to form a metal carbide sheet as a positive electrode, using molten salt as an electrolyte, and using a high-purity and high-density graphite rod As the negative electrode, perform molten salt electrolysis in an electrolytic furnace with an argon atmosphere. The electrolysis temperature is 400-1300°C, the electrolysis voltage is 1.8V-3.2V, and the electrolysis time is 2-60 hours. After the electrolysis, the positive electrode product is taken out and washed with water-ultrasonic Auxiliary pickling-water washing-drying treatment to obtain carbide-derived carbon. In the present invention, through the method of molten salt electrolysis, cheap metal carbides can be used as raw materials to prepare carbide-derived carbon, which simplifies the preparation process and reduces the cost. The prepared carbide-derived carbon has a high specific capacity as an electrode material for a supercapacitor, and Good cycle stability.

Description

A method for preparing carbide-derived carbon by molten salt electrolysis

technical field

The invention relates to a preparation method of carbide-derived carbon.

technical background

Carbide-derived carbons have excellent properties such as relatively high specific surface area, tunable pore size distribution, and good electronic conductivity, so they are used in gas storage, molecular sieves, catalyst supports, adsorbents, electrodes for batteries and supercapacitors, water/air filtration and Potential applications in fields such as medical devices have become very important. At present, the main preparation methods of carbide-derived carbon are: high temperature pyrolysis method, halogen erosion method, supercritical fluid erosion method, etc. These methods are intermittent, the preparation process is complicated, the production cycle is long and the energy consumption is high; the environmental pollution is relatively serious; thus resulting in the high price of carbide-derived carbon, which limits the wide application of carbide-derived carbon.

Contents of the invention

The object of the present invention is to provide a method for preparing carbide-derived carbon by molten salt electrolysis, which has a simple preparation method, low cost, no pollution, and is convenient for industrial production.

The technical scheme adopted in the present invention is as follows:

1. Metal carbide powder, which is titanium carbide, silicon carbide, boron carbide, tungsten carbide, chromium carbide, etc., preferably industrial grade, with an average particle size of 2 μm, is pressed into a tablet with a pressure of 3-15 MPa in a mold.

2. Sintering at a temperature of 800-1000°C for 2-8 hours under the protection of an inert gas.

3. Use the sintered metal carbide sheet as the positive electrode, and the high-purity high-density graphite rod (carbon content>99.99%, density 1.5g/cm ³ ) as the negative electrode, put the positive and negative electrodes into the ceramic crucible, and use the ceramic crucible As an electrolytic cell, the heating equipment is a crucible resistance furnace, the power supply is a DC stabilized power supply, and the molten salt is used as the electrolyte in the electrolytic furnace under the protection of argon. The electrolysis temperature is 400-1300 ° C, the electrolysis voltage is 1.8V-3.2V, and the electrolysis time 2-60 hours; the molten salt is calcium chloride, magnesium chloride, potassium chloride, sodium chloride, and mixed molten salts thereof.

4. After the electrolysis is over, take out the positive electrode electrolysis product and cool it down to room temperature. The whole process of electrolysis is protected by argon gas. The electrolysis product is washed with deionized water, pickled with 36% hydrochloric acid, preferably ultrasonic-assisted pickling, washed with deionized water, and dried in air at 120°C. The obtained product is carbide-derived carbon.

Compared with the prior art, the present invention has the following advantages:

1. The present invention uses cheap industrial-grade metal carbides as raw materials and uses a pollution-free and simplified preparation process. The prepared carbide-derived carbon products have high purity, uniform pore size distribution, and large specific surface area. Excellent chemical properties, high specific capacity.

2. The electrolysis equipment adopted in the present invention can make the electrolysis process stable, easy to control, and low in preparation cost.

Description of drawings

Fig. 1 is a schematic diagram of the front section of the molten salt electrolysis equipment of the present invention.

Fig. 2 is an XRD pattern of carbide-derived carbon prepared from industrial titanium carbide as raw material in the present invention.

Fig. 3 is the XRD diagram of the carbide-derived carbon prepared from industrial boron carbide as raw material in the present invention.

Fig. 4 is an XRD pattern of carbide-derived carbon prepared from industrial silicon carbide as raw material in the present invention.

Fig. 5 is an XRD pattern of carbide-derived carbon prepared from industrial tungsten carbide as raw material in the present invention.

Fig. 6 is an XRD pattern of carbide-derived carbon prepared from industrial chromium carbide as raw material in the present invention.

Fig. 7 is a TEM image of carbide-derived carbon prepared from industrial titanium carbide as raw material in the present invention.

Fig. 8 is the TEM figure of the carbide-derived carbon prepared by the present invention with industrial boron carbide as raw material

Fig. 9 is a TEM image of carbide-derived carbon prepared from industrial silicon carbide as raw material in the present invention.

Fig. 10 is a TEM image of carbide-derived carbon prepared from industrial tungsten carbide as raw material in the present invention.

Fig. 11 is a TEM image of the carbide-derived carbon prepared from industrial chromium carbide in the present invention.

Fig. 12 is the charging and discharging curves under different current densities of the porous carbon prepared by using titanium carbide as the raw material and electrolyzing the porous carbon at 3.2V molten salt for 60h under the protection of argon at 400°C.

Fig. 13 is the charging and discharging curves under different current densities of the porous carbon prepared by using boron carbide as the raw material and electrolyzing the porous carbon at 3.0V molten salt for 45h under the protection of argon at 750°C.

Figure 14 is the charge and discharge curves of porous carbon prepared by electrolysis of 2.6V molten salt for 30 hours under the protection of argon at 900°C under different current densities, using silicon carbide as the raw material.

Fig. 15 is the charge and discharge curves of porous carbon prepared by electrolysis of 2.2V molten salt for 15 hours under the protection of argon at 1100°C under different current densities, using tungsten carbide as the raw material.

Fig. 16 is the charging and discharging curves under different current densities of the porous carbon prepared by electrolysis of 1.8V molten salt under the protection of argon at 1300°C for 2h using chromium carbide as raw material.

In the figure: 1. Crucible resistance furnace, 2. Graphite rod negative electrode, 3. Molten salt electrolyte, 4. Argon gas bottle, 5. Flow meter, 6. Argon gas inlet, 7. Cooling water, 8. Electrode extension line , 9, thermocouple, 10, argon gas outlet, 11, DC power supply, 12, stainless steel electrolytic furnace, 13, cooling water jacket, 14, metal carbide positive electrode, 15, ceramic crucible electrolytic cell.

In the schematic diagram of the front view of the molten salt electrolysis equipment shown in Figure 1, a stainless steel electrolysis furnace is provided in the crucible-type resistance furnace, which has a groove-shaped shell with an upper opening. The sealed upper cover connected by the firmware, the inner bottom of the electrolytic furnace shell is provided with refractory bricks, and the ceramic crucible electrolytic cell is placed on the refractory brick layer, and the metal carbide positive electrode, graphite rod negative electrode and molten salt electrolyte are arranged in the tank. The wires connected with the above-mentioned positive and negative poles pass through the through holes of the upper cover of the electrolytic furnace respectively and are connected with the DC stabilized voltage power supply. Argon gas inlet and outlet pipes are respectively arranged on the upper cover of the electrolytic furnace, wherein the argon gas inlet pipe is connected with the argon gas bottle through a pipeline provided with a flow meter. The upper cover of the electrolytic furnace is also provided with a part of thermocouples placed in the electrolytic furnace. There is a jacket for cooling water in and out of the electrolytic furnace body.

Example 1

Weigh 1.5g of titanium carbide powder (2μm, 98%), mold it into a sheet under 3MPa pressure, then put it into a sintering furnace, fill it with argon, heat it up to 800°C for 8h, put the sintered titanium carbide sheet into Use an electronically conductive material to connect and lead out as the positive electrode, use a high-purity high-density graphite rod (carbon content >99.99%, density 1.5g/cm ³ ) as the negative electrode, use a ceramic crucible as the electrolytic cell in the electrolytic furnace, and weigh potassium chloride 48 grams, 120 grams of magnesium chloride, 72 grams of sodium chloride (potassium chloride: magnesium chloride: sodium chloride = 0.2: 0.5: 0.3) with a total weight of 240 grams are placed in a ceramic crucible, and argon gas is introduced into the crucible resistance furnace to raise the temperature Melt it at 400°C, put the positive and negative electrodes into a ceramic crucible, connect the positive and negative electrodes to a 3.2V DC stabilized power supply, and perform electrolysis for 60 hours. After the reaction, the product obtained from the positive electrode was sequentially washed with deionized water, ultrasonically assisted with 36% hydrochloric acid pickling, washed with deionized water, dried in air at 120°C, and then tested. Fig. 2 is the XRD pattern of the prepared titanium carbide derived carbon. Fig. 7 is a TEM image of the prepared carbide-derived carbon, from which the flake structure can be seen. Figure 12 is the charge-discharge curve of the prepared titanium carbide-derived carbon under different current densities. It can be seen from the figure that: under the charge-discharge test of 300mA/g, the discharge specific capacity of the prepared sample after 10 cycles is 110F/ g, at 500mA/g, the discharge specific capacity of the prepared sample is 90F/g, and at 1000mA/g, the discharge specific capacity of the prepared sample is 75F/g; through the low-temperature nitrogen adsorption test BETSurfaceArea=602.196m ² /g.

Example 2

Weigh 1.5 grams of boron carbide powder (2μm, 98%), mold it into a tablet under a pressure of 5 MPa, then put it into a sintering furnace, fill it with argon, heat it up to 850 ° C for 7 hours, and put the sintered boron carbide sheet into The positive pole basket is used as the positive pole, and the high-purity high-density graphite rod (carbon content>99.99%, density 1.5g/cm ³ ) is used as the negative pole. In the electrolytic furnace, the ceramic crucible is used as the electrolytic cell, and 240 grams of magnesium chloride is weighed into the ceramic In the crucible, argon gas was introduced into the crucible resistance furnace, and after the temperature was raised to 750°C and stabilized, the positive and negative electrodes were placed in the ceramic crucible, and the DC stabilized power supply was connected to the positive and negative electrodes with 3.0V for electrolysis for 45 hours. After the reaction, the product obtained from the positive electrode was sequentially washed with deionized water, ultrasonically assisted with 36% hydrochloric acid pickling, washed with deionized water, dried in air at 120°C, and then tested. Figure 3 is the XRD pattern of the prepared boron carbide derived carbon. Figure 8 is a TEM image of the prepared boron carbide derived carbon, from which we can see the flake structure and pore structure. Figure 13 is the charge-discharge curve of the prepared boron carbide-derived carbon under different current densities. It can be seen from the figure that: under the charge-discharge test of 300mA/g, the discharge specific capacity of the prepared sample after 10 cycles is 123.5F /g, at 500mA/g, the discharge specific capacity of the prepared sample is 102F/g, at 1000mA/g, the discharge specific capacity of the prepared sample is 77.7F/g; by low temperature nitrogen adsorption test BETSurfaceArea=763.843 m ² /g.

Example 3

Weigh 1.5 grams of silicon carbide powder (2μm, 98%), mold it into a tablet under a pressure of 8MPa, then put it into a sintering furnace, fill it with argon, heat it up to 900 ° C for 5 hours, and put the sintered silicon carbide chip into The positive pole basket is used as the positive pole, and the high-purity high-density graphite rod (carbon content>99.99%, density 1.5g/cm ³ ) is used as the negative pole. In the electrolytic furnace, the ceramic crucible is used as the electrolytic cell, and 240 grams of calcium chloride is weighed. Put it into a ceramic crucible, pass argon gas into the crucible resistance furnace, heat up to 900°C and stabilize, put the positive and negative electrodes into the crucible, connect the positive and negative electrodes to 2.6V with a DC stabilized voltage power supply, and perform electrolysis for 30 hours. After the reaction, the product obtained from the positive electrode was sequentially washed with deionized water, ultrasonically assisted with 36% hydrochloric acid pickling, washed with deionized water, dried in air at 120°C, and then tested. Fig. 4 is an XRD pattern of the prepared silicon carbide derived carbon. Fig. 9 is a TEM image of the prepared silicon carbide-derived carbon, and an obvious pore structure can be seen. Figure 14 is the charge-discharge curve of the prepared silicon carbide-derived carbon under different current densities. It can be seen from the figure that: under the charge-discharge test of 300mA/g, the discharge specific capacity of the prepared sample after 10 cycles is 143.8F /g, at 500mA/g, the discharge specific capacity of the prepared sample is 123F/g, and at 1000mA/g, the discharge specific capacity of the prepared sample is 97.2F/g; by low temperature nitrogen adsorption test BETSurfaceArea=988.5522 m ² /g.

Example 4

Weigh 1.5 grams of tungsten carbide powder (2μm, 98%), mold it into a sheet under a pressure of 10MPa, then put it into a sintering furnace, fill it with argon, heat it up to 950°C for 3 hours, and sinter the sintered tungsten carbide sheet with an electronic The conductive material is connected and drawn as the positive electrode, and the high-purity high-density graphite rod (carbon content>99.99%, density 1.5g/cm ³ ) is used as the negative electrode. In the electrolytic furnace, the ceramic crucible is used as the electrolytic cell, and 240 grams of potassium chloride is weighed. Put it into a ceramic crucible, pass argon gas into the crucible resistance furnace, heat up to 1100°C and stabilize, put the positive and negative electrodes into the crucible, connect the positive and negative electrodes to 2.2V with a DC stabilized voltage power supply, and perform electrolysis for 15 hours. After the reaction, the product obtained from the positive electrode was sequentially washed with deionized water, ultrasonically assisted with 36% hydrochloric acid pickling, washed with deionized water, dried in air at 120°C, and then tested. Figure 5 is the XRD pattern of the prepared tungsten carbide derived carbon. Figure 10 is a TEM image of the prepared tungsten carbide-derived carbon, from which it can be seen that there is an obvious pore structure. Figure 15 is the charge-discharge curve of the prepared tungsten carbide derived carbon under different current densities. It can be seen from the figure that: under the charge-discharge test of 300mA/g, the discharge specific capacity of the prepared sample after 10 cycles is 160F/ g, at 500mA/g, the discharge specific capacity of the prepared sample is 138.89F/g, and at 1000mA/g, the discharge specific capacity of the prepared sample is 111.1F/g; by low temperature nitrogen adsorption test BETSurfaceArea=1137.7433 m ² /g.

Example 5

Weigh 1.5 grams of chromium carbide powder (2μm, 98%), mold it into a sheet under a pressure of 15MPa, then put it into a sintering furnace, fill it with argon, heat it up to 1000°C for sintering for 2 hours, and put the sintered chromium carbide sheet into The positive pole is drawn from the positive pole basket as the positive pole, and the high-purity high-density graphite rod (carbon content>99.99%, density 1.5g/cm ³ ) is used as the negative pole. In the electrolytic furnace, the ceramic crucible is used as the electrolytic cell, and 240 grams of sodium chloride is weighed. Put it into a ceramic crucible, pass argon gas into the crucible resistance furnace, heat up to 1300°C and stabilize, put the positive and negative electrodes into the crucible, connect the positive and negative electrodes to 1.8V with a DC stabilized voltage power supply, and perform electrolysis for 2 hours. After the reaction, the product obtained from the positive electrode was sequentially washed with deionized water, ultrasonically assisted with 36% hydrochloric acid pickling, washed with deionized water, dried at 120°C in air, and tested. Figure 6 is the XRD pattern of the prepared chromium carbide derived carbon. Figure 11 is a TEM image of the prepared chromium carbide-derived carbon, from which we can see the sheet structure and pore structure. Figure 16 is the charge-discharge curve of the prepared chromium carbide-derived carbon under different current densities. It can be seen from the figure that: under the charge-discharge test of 300mA/g, the discharge specific capacity of the prepared sample after 10 cycles is 114.22F /g, at 500mA/g, the discharge specific capacity of the prepared sample is 88.89F/g, at 1000mA/g, the discharge specific capacity of the prepared sample is 54.165F/g; by low temperature nitrogen adsorption test BETSurfaceArea= 640.6837m ² /g.

Claims (4)

1. A method for preparing carbide-derived carbon by molten salt electrolysis, characterized in that: the metal carbide powder is molded and pressed into sheets under a pressure of 3-15MPa, and sintered at a temperature of 800-1000°C under the protection of an inert gas For 2-8 hours, the sintered metal carbide sheet is used as the positive electrode, the high-purity high-density graphite rod is used as the negative electrode, the ceramic crucible is used as the electrolytic cell, the heating equipment is a crucible resistance furnace, and the power supply is a DC stabilized power supply. The molten salt is used as the electrolyte in the lower electrolysis furnace, the electrolysis temperature is 400-1300°C, the electrolysis voltage is 1.8V-3.2V, and the electrolysis time is 2-60 hours. The product is successively washed with water, pickled with water, washed with water and dried, and the obtained product is carbide-derived carbon. 2. The method for preparing carbide-derived carbon by molten salt electrolysis according to claim 1, characterized in that: the positive electrode is a metal carbide sheet put into the positive pole basket or drawn out as the positive pole with an electronically conductive material. 3. The method for preparing carbide-derived carbon by molten salt electrolysis according to claim 1 or 2 is characterized in that: the metal carbide raw material is industrial-grade titanium carbide, boron carbide, silicon carbide, tungsten carbide, Chromium carbide. 4. the device that the molten salt electrolysis method of claim 1 prepares carbide derivative carbon is characterized in that: the crucible type electric resistance furnace furnace is provided with stainless steel electrolysis furnace, and it has an upper opening groove-shaped shell, and on the opening of this shell There is a sealed upper cover connected by fasteners, refractory bricks are arranged at the bottom of the electrolytic furnace shell, and a ceramic crucible electrolytic cell is placed on the refractory brick layer, and metal carbide sheets are installed in the tank as positive electrodes, graphite rod negative electrodes and molten salt. Electrolyte, the wires connected with the above-mentioned positive and negative poles pass through the through holes of the upper cover of the electrolytic furnace to connect with the DC stabilized voltage power supply, and the upper cover of the electrolytic furnace is also provided with inlet and outlet pipes for argon gas, of which the inlet pipes for argon gas It is connected to the argon cylinder through the pipeline with flowmeter, and a part of the thermocouple placed in the electrolytic furnace is arranged on the upper cover of the electrolytic furnace, and a jacket for cooling water in and out is provided outside the electrolytic furnace.