CN107572517A - Alginic acid alkali three-dimensional network layered activated carbon and one step charing preparation method - Google Patents

Abstract

Alginate-based three-dimensional network layered activated carbon and its one-step carbonization preparation method, comprising: reacting alginic acid with sodium ions to obtain soluble sodium alginate, then preparing sodium alginate into a solution, adding CaCl ₂ to fully stir to obtain sodium alginate Calcium complex precursor. Finally, the obtained precursor is fully washed and dried in an oven; the obtained precursor is placed in a quartz boat, placed in a tube furnace, fed with nitrogen, and heated from room temperature to the final carbonization temperature; After the carbonization process is completed and the temperature drops to room temperature, the obtained insoluble alginate-based porous activated carbon is acid-washed, washed with water to remove the metal compounds, and finally placed in an oven at 110°C to fully dry. Grinding and placing in a dry environment, the alginate-based three-dimensional network layered activated carbon can be obtained. The preparation process of the invention is clean, the steps are simple, the product structure is various and adjustable, the capacitance performance is high, and the manufacturing cost is low.

Description

Alginate-based three-dimensional network layered activated carbon and its one-step carbonization preparation method

technical field

The invention relates to an alginate-based three-dimensional network layered activated carbon and a one-step carbonization preparation method thereof, in particular to the preparation of composite alginate raw materials and precursors, and the one-step carbonization process conditions.

Background technique

Supercapacitors have the characteristics of fast charging speed, high power density, and long life. They are the most effective way to solve the power supply for electric vehicles. It can be used not only as the sole power source for electric vehicles, but also as an auxiliary power source for electric vehicles. Supercapacitors can also be used for power devices such as photovoltaic battery storage, grid stabilization, and radio transmission, as well as starting energy for tanks and rocket traction; the United States, Europe, Japan, etc. are also conducting research on supercapacitors.

The alginate used in this experiment has a wide range of sources and is easy to extract and prepare. However, alginate has a mutual substitution effect between monovalent and divalent metal ions, which can flexibly change the type and content of metal ions in the precursor, thereby changing the structure of the precursor, and finally obtaining carbon materials with different pore size distributions. At the same time, because it contains a large number of metal atoms, it does not need to add any additional chemical activation reagents, which breaks the shackles of the traditional chemical method to activate activated carbon and overcomes the shortcomings of the traditional chemical method to prepare activated carbon materials. The preparation process is simple and will not cause corrosion to production equipment, and finally the metal can be easily recovered without polluting the environment. And the obtained insoluble alginate-based porous activated carbon has a controllable pore size distribution range, and the pore size of the final activated carbon sample can be adjusted by simply changing the type of metal elements in the precursor and the ratio of different metal contents. The obtained activated carbon sample has a large specific surface area and total pore volume, and also has a super large bulk density, which can reach 0.9 cm ³ /g. Therefore, this kind of activated carbon material also has a super large volume specific capacitance as an electrode material of a supercapacitor, which can greatly reduce the volume occupied by the electrode material of a supercapacitor, and has great application prospects.

Zhongrong Gen et al. (Geng Z, Wang H, Wang R, et al. Facile synthesis of hierarchical porous carbon for supercapacitor with enhanced electrochemical performance [J]. Materials Letters, 2016, 182:1-5.) found that alginic acid The activated carbon electrode material obtained by sodium carbonization at low temperature and then activated by NaOH has a very high specific capacitance, which can reach 451 F/g, and has a long and stable cycle life.

Raymundo et al. (E. Raymundo-Piñero, Leroux F, Béguin F. A High‐Performance Carbon for Supercapacitors Obtained by Carbonization of a Seaweed Biopolymer[J]. Advanced Materials, 2006, 18(14):1877-1882.) through simple Sodium alginate was carbonized at a low temperature of 600 °C to obtain a three-dimensional porous carbon material. And analyzed its electrochemical performance, found that the carbon material prepared by this precursor has a very high oxygen content, and under the premise of high packing density, it has a very high volume as an electrode material for aqueous supercapacitors. Specific capacitance. However, the researchers only focused on the analysis of the surface properties, and only prepared a sodium alginate-based porous carbon material.

Ma et al. (Ma G F, Mu J J, Zhang Z G, et al. Preparation of Polypyrrole/Sodium Alginate Nanospheres and Their Application for High-Performance Supercapacitors[J]. Acta Physico-Chimica Sinica, 2013, 29(11):2385-2391 (7).) The sodium alginate/polypyrrole composite material was prepared, with a specific capacity of 347 F/g, and good cycle performance for 500 cycles, but the long-term cycle stability was poor, and the composite material used was expensive, so it did not have practical application value.

Ma L et al. (Ma L, Xu LM, Zhou XP, et al. Biopolymer-assisted hydrothermal synthesis of flower-like MoS2, microspheres and their supercapacitive properties[J]. Materials Letters, 2014, 132:291-294.) used sodium alginate As a carrier, composite MoS ₂ metal sulfides are used as supercapacitor electrode materials, but their performance is general, and expensive metal materials are used, so there is no application prospect.

In summary, although some people have used one of the alginates-sodium alginate for carbonization, activation and compounding with conductive polymers, compounding with metal compounds, etc. However, they all have certain limitations, and the use of chemical reagents for activation is too corrosive, the investment in equipment is too large, continuous production cannot be performed, and a large amount of toxic gases and liquids are produced in the end, which cannot be recovered. Expensive conductive polymers and Compounding of metal compounds requires many steps, large pollution, and general performance, resulting in low actual application value

Contents of the invention

Technical problem to be solved: In order to solve the problems of serious pollution in the preparation process, many steps, single product structure, low capacitance performance and high cost in the prior art, the present invention proposes an alginate-based three-dimensional network layered activated carbon and its One-step carbonization preparation method, the preparation process is clean, the steps are simple, the product structure is diverse and adjustable, the capacitance performance is high, and the manufacturing cost is low.

Technical solution: One-step carbonization preparation method of alginate-based three-dimensional network layered activated carbon, the preparation steps are: the first step, the preparation of the precursor: react alginic acid with sodium ions to obtain soluble sodium alginate, and then prepare sodium alginate as Solution, add CaCl ₂ and stir thoroughly to prepare the precursor of sodium calcium alginate complex, and finally wash the obtained precursor fully and dry it in an oven; the second step, carbonization: place the obtained precursor in a quartz boat, Put it into a tube furnace, feed nitrogen, and raise the temperature from room temperature to the final carbonization temperature at a rate of 10°C/min; the third step, washing and drying: after the carbonization process is completed, the temperature is lowered to room temperature, and the obtained insoluble seaweed is Alginate-based porous activated carbon was acid-washed, then washed with water to remove the metal compounds, and finally placed in an oven at 110 °C for sufficient drying and placed in a dry environment to obtain alginate-based three-dimensional network layered activated carbon.

In the above-mentioned first step, the mass concentration of calcium chloride is 1%-10%, and the mass ratio of sodium alginate to calcium chloride is 1:0.02.

The carbonization in the above second step is under the protection of inert gas, the flow rate is 1L/min, the final carbonization temperature is 700-1000°C, and the carbonization time is 30-120 min.

The above pickling is first washed with 1+9 hydrochloric acid, and then washed 2-4 times with deionized water.

The alginate-based three-dimensional network layered activated carbon prepared by the above method.

The alginate-based three-dimensional network layered activated carbon has a specific surface area of 400-1400 m ² /g, a mass specific capacitance of 100-300 F/g, and a volume specific capacitance of 100-300 F/cm ³ .

Beneficial effects: the corresponding composite alginate-based porous activated carbon material is prepared by one-step carbonization, the steps are simple and the operation is simple, and the pore size distribution of the obtained activated carbon sample can be artificially adjusted only by changing the type and content of metal ions in the precursor As an electrode material for a supercapacitor, it can have high specific capacitance, good rate performance, excellent cycle performance, etc., so it can be applied to different needs. The whole process does not need to add any chemical activation reagents, and only needs a simple one-step temperature rise carbonization to obtain the final activated carbon sample.

Description of drawings

Fig. 1 is the sodium calcium alginate composite material base activated carbon _N2 adsorption-desorption isotherm prepared by the embodiment.

Fig. 2 is the pore size distribution range of the sodium-calcium alginate composite material-based activated carbon prepared in the embodiment.

Figure 3 Galvanostatic charge-discharge curves of Alg-Na-Ca 900 composite-based activated carbon.

Fig. 4 Cyclic voltammetry curves of Alg-Na-Ca 900 composite-based activated carbon.

Figure 5 Alg-Na-Ca 900 Na-Ca alginate composite-based activated carbon rate performance.

Fig. 6 Alg-Na-Ca 900 Alginate-calcium composite material-based activated carbon impedance performance.

detailed description

The present invention is as follows to the test method of a kind of alginate-based three-dimensional network layered activated carbon material performance:

(1) Determination of specific surface area and pore volume: The adsorption isotherm of activated carbon to nitrogen was measured under liquid nitrogen conditions, and the specific surface area was calculated according to the BET formula.

(2) The surface morphology was observed with a Hitachi S-4800 cold field emission electron microscope.

(3) Determination of specific capacitance: use electrochemical workstation to measure under constant current.

An alginate-based three-dimensional network layered activated carbon and a one-step carbonization preparation method thereof, comprising the following steps:

The first step is the preparation of the precursor: react alginic acid with sodium hydroxide to obtain sodium alginate. Then sodium alginate is configured as a solution, and a certain concentration of CaCl ₂ is added and fully stirred to prepare a sodium-calcium alginate composite precursor. Finally, the obtained samples were fully washed and dried in an oven.

The second step, carbonization: the obtained precursor is placed in a quartz boat, put into a tube furnace, and nitrogen gas is introduced. Raise the temperature from room temperature to the final carbonization temperature at a heating rate of 10 °C/min;

The third step, washing and drying: after the first carbonization process is completed, the temperature drops to room temperature, the insoluble alginate-based porous activated carbon is acid-washed, washed with water several times to remove the metal compounds, and finally placed in an oven at 110 ° C After drying for 12 hours, the dried activated carbon sample was fully ground and placed in a dry environment to obtain a three-dimensional network layered activated carbon material based on alginate.

In the method of the present invention, the mass concentration of calcium chloride is 1-10%, and the mass ratio of sodium/potassium alginate to calcium chloride is 1:0.0.2. Carbonization is under the protection of inert gas, the flow rate is 1L/min, the final temperature of carbonization is 700-1000°C, the carbonization time is 30-120min, and the inert atmosphere is nitrogen or argon. The obtained activated carbon sample was first washed with 1+9 hydrochloric acid, then washed 2-4 times with deionized water, and finally dried in an oven, cooled, and pulverized to obtain an insoluble alginate-based activated carbon material for supercapacitors.

The alginate-based three-dimensional network layered activated carbon and the activated carbon material obtained by the one-step carbonization preparation method thereof are characterized in that the specific surface area is 400-1400 m ² /g, the mass specific capacitance is 100-300 F/g, and the volume The specific capacitance can reach 100-300 F/cm ³ . The activated carbon materials prepared by different precursors have different pore size distribution ranges, and the activated carbon materials with large medium pores and large pores can be obtained respectively.

The specific surface area, pore size distribution, and pore volume of the composite alginate-based activated carbon material for supercapacitors of the present invention can be quantitatively regulated by changing the type and content of metal ions in the precursor. At the same time, the structure of activated carbon samples obtained from the same precursor is controlled by the temperature and time of one-step carbonization. The present invention only selects sodium calcium alginate as an example, and this method is used for one-step carbonization of any insoluble alginate to prepare porous carbon materials with different pore size distribution ranges. The alginic acid extracted from seaweed is purified, washed to remove impurities, and dried; the obtained alginic acid is reacted with corresponding alkali to obtain soluble sodium alginate. Then configure it as a solution, add a certain concentration of CaCl ₂ and stir thoroughly to prepare the precursor of sodium calcium alginate complex. Finally, the obtained samples were fully washed and dried in an oven. The obtained precursor was placed in a quartz boat, put into a tube furnace, and nitrogen gas was introduced. Raise the temperature from room temperature to the final carbonization temperature at a heating rate of 10 ℃/min; after the one-step carbonization process is completed, the temperature is lowered to room temperature, and the obtained insoluble alginate-based porous activated carbon is acid-washed, and the metal compounds in it are removed by repeated washing. Finally, it was fully dried in an oven at 110 °C for 12 h, and the dried activated carbon samples were fully ground and placed in a dry environment to obtain insoluble alginate-based activated carbon materials for supercapacitors with different pore size distributions.

Example 1

(1) Precursor preparation: soak alginic acid with NaOH first to prepare sodium alginate, then soak sodium alginate and 1wt.% calcium chloride, wash, and dry to obtain sodium calcium alginate precursor.

(2) Carbonization: put sodium calcium alginate in a quartz boat and put it into a tube furnace, feed nitrogen at a flow rate of 1L/min, raise the temperature from room temperature to 700°C at a heating rate of 10°C/min, keep it for 60min, and cool down naturally to room temperature.

(3) After one-step carbonization is completed, the cooled activated carbon sample is washed with 1+9 hydrochloric acid, then washed 2-4 times with deionized water, and finally dried in an oven, cooled, and ground to obtain supercapacitor alginic acid Soda calcium based activated carbon material. It has a specific surface area of 456 m ² /g, a total pore volume of 0.54 cm ³ /g, and a specific capacitance of 86 F/g at a current density of 0.5 A/g.

Example 2

(1) Precursor preparation: Sodium alginate was obtained by soaking alginic acid with NaOH first, and then sodium alginate was soaked with 5 wt.% calcium chloride, washed and dried to obtain a sodium calcium alginate precursor.

(2) Carbonization: put sodium calcium alginate in a quartz boat and put it into a tube furnace, feed nitrogen at a flow rate of 1L/min, raise the temperature from room temperature to 800°C at a heating rate of 10°C/min, keep it for 60min, and cool down naturally to room temperature.

(3) After one-step carbonization is completed, the cooled activated carbon sample is washed with 1+9 hydrochloric acid, then washed 2-4 times with deionized water, and finally dried in an oven, cooled, and ground to obtain supercapacitor alginic acid Soda calcium based activated carbon material. It has a specific surface area of 899 m ² /g, a total pore volume of 0.92 cm ³ /g, and a specific capacitance of 158 F/g at a current density of 0.5 A/g.

Example 3

(1) Precursor preparation: Sodium alginate was obtained by soaking alginic acid with NaOH first, and then sodium alginate was soaked with 5 wt.% calcium chloride, washed and dried to obtain a sodium calcium alginate precursor.

(2) Carbonization: put sodium calcium alginate in a quartz boat and put it into a tube furnace, feed nitrogen at a flow rate of 1L/min, raise the temperature from room temperature to 900°C at a heating rate of 10°C/min, keep it for 60min, and cool down naturally to room temperature.

(3) After one-step carbonization is completed, the cooled activated carbon sample is washed with 1+9 hydrochloric acid, then washed 2-4 times with deionized water, and finally dried in an oven, cooled, and ground to obtain supercapacitor alginic acid Soda calcium based activated carbon material. It has a specific surface area of 1295 m ² /g, a total pore volume of 1.79 cm ³ /g, and a specific capacitance of 170 F/g at a current density of 0.5 A/g.

Example 4

(1) Precursor preparation: soak alginic acid with NaOH to prepare sodium alginate, then soak sodium alginate and 10 wt.% calcium chloride, wash, and dry to obtain sodium calcium alginate precursor.

(2) Carbonization: put sodium calcium alginate in a quartz boat and put it into a tube furnace, feed nitrogen at a flow rate of 1L/min, raise the temperature from room temperature to 1000°C at a heating rate of 10°C/min, keep it for 60min, and cool down naturally to room temperature.

(3) After the one-step carbonization is completed, the cooled activated carbon sample is washed with 1+9 hydrochloric acid, then washed 2-4 times with deionized water, and finally dried in an oven, cooled, and pulverized to obtain supercapacitor alginic acid Soda calcium based activated carbon material. It has a specific surface area of 479 m ² /g, a total pore volume of 0.57 cm ³ /g, and a specific capacitance of 79 F/g at a current density of 0.5 A/g.

Claims (6)

1. A one-step carbonization preparation method of alginate-based three-dimensional network layered activated carbon, characterized in that the preparation steps are: The first step is the preparation of the precursor: react alginic acid with sodium ions to obtain soluble sodium alginate, then prepare sodium alginate into a solution, add CaCl ₂ and stir thoroughly to prepare the precursor of sodium calcium alginate complex, and finally The obtained precursor is fully washed and placed in an oven to dry; The second step, carbonization: put the obtained precursor in a quartz boat, put it into a tube furnace, pass nitrogen gas, and raise the temperature from room temperature to the final carbonization temperature at a heating rate of 10 ℃/min; The third step, washing and drying: after the carbonization process is completed, the temperature drops to room temperature, the obtained insoluble alginate-based porous activated carbon is acid-washed, and then washed with water to remove the metal compounds in it, and finally placed in an oven at 110 ℃ for full drying , placed in a dry environment, the alginate-based three-dimensional network layered activated carbon can be obtained. 2. according to the described alginate-based three-dimensional network layered activated carbon one-step carbonization preparation method of claim 1, it is characterized in that, in the first step, calcium chloride mass concentration 1%-10%, the quality of sodium alginate and calcium chloride The ratio is 1:0.02. 3. according to the described alginate-based three-dimensional network layered activated carbon one-step carbonization preparation method of claim 1, it is characterized in that, in the second step, carbonization is under the protection of inert gas, flow rate: 1L/min, carbonization final temperature is 700- 1000°C, carbonization time 30-120 min. 4. The one-step carbonization preparation method of alginate-based three-dimensional network layered activated carbon according to claim 1, characterized in that pickling is first washed with 1+9 hydrochloric acid, and then washed 2-4 times with deionized water. 5. The alginate-based three-dimensional network layered activated carbon prepared by any one of claims 1-4. 6. The alginate-based three-dimensional network layered activated carbon according to claim 5, characterized in that, the specific surface area is 400-1400 m ² /g, the mass specific capacitance is 100-300 F/g, and the volume specific capacitance is 100-300 F/g. cm ³ .