CN107190367A - The preparation method of nitrogen sulphur codope porous carbon fiber - Google Patents

Abstract

The invention discloses a method for preparing nitrogen-sulfur co-doped porous carbon fibers for supercapacitors with good mechanical properties by using cotton as a carbon source. It specifically relates to a new method for preparing porous carbon fibers for supercapacitors with good mechanical properties by using cotton as a raw material, through carbonization, introduction of nitrogen and sulfur, and a chemical activation method. The invention includes the following specific steps: first, high-temperature carbonization of cotton into fibers, mixing carbon fibers with activating reagents and nitrogen-sulfur compounds according to a certain mass ratio, then adding an appropriate amount of distilled water to the mixture, soaking for a certain period of time, drying, and then activating in a tube furnace After processing for a certain period of time, the solid is washed and dried to obtain nitrogen-sulfur co-doped porous carbon fibers for supercapacitors.

Description

Preparation method of nitrogen and sulfur co-doped porous carbon fiber

technical field

The invention relates to a preparation method of nitrogen-sulfur co-doped porous carbon fiber, in particular to a method of firstly carbonizing cotton to prepare carbon fiber, then mixing it with nitrogen, sulfur source, and activation reagent, and high-temperature treatment to prepare nitrogen-sulfur co-doping for supercapacitors A new approach to heteroporous carbon fibers.

Background technique

Supercapacitors have become energy storage devices that are widely concerned by researchers because of their fast charge and discharge rates, high capacity density and power density, excellent cycle stability, and high stability. According to different energy storage mechanisms, supercapacitors can be divided into electric double layer capacitors and pseudocapacitors. Electrode materials are one of the key factors determining the performance of supercapacitors. Porous carbons are widely used as electrode materials for supercapacitors due to their stable chemical properties, large specific surface area, well-developed pores, and adjustable pore sizes. At present, there are many kinds of porous carbon materials used in supercapacitors, such as spherical carbon, granular carbon, and fibrous carbon. Among them, the porous carbon fiber is light in weight, excellent in tensile strength and thermal stability, and its surface is distributed with rich pore structure, which can increase its contact area with the electrolyte and shorten the ion transport path. These properties have facilitated the extensive research of porous carbon fibers to improve energy storage efficiency. At the same time, the research results show that heteroatom (N, B, P, S, F, Ni, Co, etc.) doping is an effective way to improve the electrochemical performance of carbon materials. For example, in the field of capacitor electrode materials, the doping of nitrogen and sulfur elements can affect the formation of electric double layers by affecting the electron accepting or donating characteristics of carbon materials. In addition, nitrogen doping can also enhance the conductivity of carbon materials, promote the rapid migration of ions, and introduce pseudocapacitance, thereby improving the performance of carbon materials on supercapacitor electrode materials. Therefore, the preparation of nitrogen-sulfur co-doped porous carbon materials has important research value.

Patent CN105931855A discloses a synthesis method of nitrogen and sulfur co-doped carbon-polyaniline composite materials for supercapacitors. It involves the synthesis of poly(aniline-sophene) composite materials by aqueous solution method, the synthesis of nitrogen-sulfur co-doped carbon materials by high-temperature pyrolysis method, the synthesis of nitrogen-sulfur co-doped carbon-polyaniline composite materials by chemical oxidation and their use in the research of supercapacitors, The method comprises the following steps: preparing poly(aniline-sophene) composite material, preparing nitrogen-sulfur co-doped carbon material, and preparing nitrogen-sulfur co-doped carbon-polyaniline composite material electrode. The beneficial effect of the invention is that the composite material has better electrical conductivity, smaller electrode resistance, better capacitance performance and better cycle stability. Patent CN105776178A discloses a nitrogen-sulfur co-doped porous carbon prepared by direct liquefaction of heavy organic matter from coal, its preparation method and application. The method comprises the following steps: (1) grinding heavy organic matter directly liquefied from coal into powder, and obtaining a hydrophilic first product through alkylation, shuttle acidification or sulfonation; (2) mixing the first product with formaldehyde and thiourea (3) mechanically mixing the second product with a certain proportion of magnesium source, and then placing it in a carbonization furnace for carbonization to obtain a magnesium oxide and nitrogen-sulfur co-doped porous carbon mixture; Nitrogen-sulfur co-doped porous carbon was obtained by removing magnesium oxide by acid washing. The nitrogen-sulfur co-doped porous carbon prepared by the invention has excellent electrochemical properties, and is a high-performance supercapacitor electrode material. Patent CN105084358A discloses a method for preparing nitrogen-sulfur co-doped activated carbon for supercapacitors. Nitrogen-sulfur co-doped activated carbon is mainly prepared from the following composition according to the ratio of parts by weight, through carbonization and activation process; the composition is: powdery 1- 2 parts; 1-4 parts of alkaline activator; the preparation method includes the following steps, (1) carbonization: ① soaking: ② hydrothermal treatment: ③ centrifugal filtration; ④ drying; ⑤ grinding; (2) activation: ① using Stage heating and heat preservation: ②Slow cooling; ③Soaking in hydrochloric acid solution: ④Washing; ⑤Drying; after drying, it becomes nitrogen-sulfur co-doped activated carbon for supercapacitors. Patent CN106492749A discloses a preparation method of nitrogen and sulfur co-doped microporous-mesoporous carbon microspheres. The invention relates to a method for preparing nitrogen and sulfur co-doped microporous-mesoporous carbon microspheres. Aminophenol, formaldehyde solution, L-cysteine, surfactant, silica sol, ethanol and water are mixed according to a certain mass ratio. Mix water and ethanol at 20-35°C and add the rest of the raw materials in sequence. After 24 hours of reaction, hydrothermally treat at 100°C for 24 hours. In a nitrogen atmosphere, the temperature rises from room temperature to 2-10°C/min. Carbonize at 600-900°C, remove silicon dioxide with NaOH, and obtain nitrogen and sulfur co-doped mesoporous carbon microspheres.

Most of the raw materials in the above patents are organic compounds, and the synthesis process is relatively complicated. The prepared nitrogen-sulfur co-doped carbon materials are not fibrous. Therefore, it is of great research significance to prepare nitrogen-sulfur co-doped porous carbon fibers from renewable biomass. . Cotton is a natural biomass resource with a fibrous structure, which can maintain its fibrous structure after carbonization and has good mechanical properties. Therefore, it is of certain research value to use cotton as raw material to prepare supercapacitor electrode materials with high specific surface area and good mechanical properties through carbonization, activation, and nitrogen-sulfur co-doping.

This patent uses cotton as raw material, carbonizes it into fibers, and then introduces nitrogen and sulfur combined with chemical activation to prepare nitrogen-sulfur co-doped porous carbon fibers for supercapacitors with good mechanical properties. This route has a wide range of sources of raw materials and a simple synthesis method. By adjusting the amount of activating reagents and nitrogen and sulfur, the degree of pore development and the amount of nitrogen and sulfur doping in porous carbon fibers are controlled, and nitrogen and sulfur co-doped porous carbon fibers for supercapacitors with good mechanical properties are finally prepared. .

Contents of the invention

The purpose of the invention is to provide a new method for preparing nitrogen-sulfur co-doped porous carbon fibers for supercapacitors with good mechanical properties using cotton as a carbon source.

In the present invention, cotton is firstly carbonized into fibers at 700-950°C, carbon fibers are mixed with activating reagents and thiourea in a mass ratio of 1:2:2 to 1:7:6 (g/g/g), and an appropriate amount of distilled water is added therein for mixing Uniform, soak the mixture for 12 hours and dry it in an oven at 105°C for 5 hours, activate the mixture in a tube furnace at 700-1000°C for 0.5-3 hours, wash and dry the solids, and test the electrochemical performance of the obtained nitrogen-sulfur co-doped porous carbon fiber test.

The present invention is characterized in that: the activator is a mixture of potassium bicarbonate and potassium hydroxide or a mixture of potassium bicarbonate and sodium hydroxide.

detailed description

Embodiment 1: First cotton is carbonized at 850° C. in a tube furnace for 1 h, and the obtained carbon fiber is mixed with an activation reagent (KHCO ₃ : the mass ratio of KOH is 1: 2), thiourea in a mass ratio of 1: 5: 4 ( g/g/g) were mixed, an appropriate amount of distilled water was added therein and mixed evenly, the mixture was soaked for 14 hours and dried in an oven at 105°C for 5 hours, the mixture was activated in a tube furnace at 800°C for 1.5 hours, the solid was washed and dried, and the obtained Nitrogen-sulfur co-doped porous carbon fiber was tested for electrochemical performance. Using 6mol/L potassium hydroxide as the electrolyte, the measured specific capacity was 338F/g, and the capacity retention rate was about 98% after 5000 cycles.

Embodiment 2: change carbon fiber and activation reagent (KHCO ₃ : the mass ratio of KOH is 1: 2), the mass ratio of thiourea 1: 4: 5 (g/g/g), other conditions are the same as embodiment 1, obtain The specific capacitance of the nitrogen-sulfur co-doped porous carbon fiber is 315F/g, and the capacity retention rate after 5000 cycles is about 97%.

Embodiment 3: change carbon fiber and activation reagent (KHCO ₃ : the mass ratio of KOH is 1: 2), the mass ratio of thiourea 1: 6: 3 (g/g/g), other conditions are the same as embodiment 1, obtained The specific capacitance of the nitrogen-sulfur co-doped porous carbon fiber is 323F/g, and the capacity retention rate after 5000 cycles is about 97%.

Example 4: Change the activation treatment time of the mixture in a tube furnace at 800°C to 2h, and other conditions are the same as in Example 1. The specific capacitance of the obtained nitrogen-sulfur co-doped porous carbon fiber is 309F/g, and the capacity retention rate after 5000 cycles is 97 %about.

Example 5: Change the activation treatment time of the mixture in a tube furnace at 800°C to 1h, and other conditions are the same as in Example 1. The specific capacitance of the obtained nitrogen-sulfur co-doped porous carbon fiber is 318F/g, and the capacity retention rate after 5000 cycles is 96 %about.

Example 6: Change the mixture in a tube furnace to activate the treatment at a temperature of 900° C. and an activation time of 1 h. Other conditions are the same as in Example 1. The specific capacitance of the obtained nitrogen-sulfur co-doped porous carbon fiber is 298 F/g, and the cycle is 5000 times. The capacity retention rate is about 97%.

Embodiment 7: change carbon fiber and activation reagent (KHCO ₃ : the mass ratio of NaOH is 1: 3), the mass ratio of thiourea 1: 5: 4 (g/g/g), mix the mixture in 800 ℃ tube furnace Activation treatment was performed for 2 hours, and other conditions were the same as in Example 1. The obtained nitrogen-sulfur co-doped porous carbon fiber had a specific capacitance of 315 F/g and a capacity retention rate of about 97% after 5000 cycles.

Embodiment 8: Change carbon fiber and activation reagent (KHCO ₃ : The mass ratio of NaOH is 1:3), the mass ratio of thiourea 1:6:3 (g/g/g), the mixture is heated in 850 ℃ tube furnace After activating for 1.5 hours, the other conditions were the same as in Example 1. The specific capacitance of the obtained nitrogen-sulfur co-doped porous carbon fiber was 328 F/g, and the capacity retention rate after 5000 cycles was about 97%.

Claims (2)

1. a kind of ultracapacitor preparation method of nitrogen sulphur codope porous carbon fiber, it is comprised the following steps that：First by cotton It is fiber to spend 700~950 DEG C of carbonizations, and carbon fiber and activating reagent, thiocarbamide in mass ratio 1: 2: 2~1: 7: 6 (g/g/g) are mixed Close, appropriate distilled water is added thereto and is well mixed, 5h will be dried after impregnation mixture 12h in 105 DEG C of baking ovens, by mixture 0.5~3h of activation process in 700~1000 DEG C of tube furnaces, solid washing, dry, obtained nitrogen sulphur codope porous carbon fiber Carry out electrochemical property test.

2. a kind of preparation method of nitrogen sulphur codope porous carbon fiber as claimed in claim 1, it is characterised in that：The activation Agent is the mixture or saleratus and the mixture of sodium hydroxide of saleratus and potassium hydroxide.