阅读说明：本技术 一种利用木质素制备碳电极的方法 (Method for preparing carbon electrode by using lignin ) 是由 闵斗勇 迟明超 罗斌 张清桐 李明富 王双飞 于 2019-09-02 设计创作，主要内容包括：本发明公开了一种利用木质素制备碳电极的方法。该方法采用木质素为原料,将木质素与乙炔黑混合,经过模具压制后在惰性气体氛围下高温加热脱除含氧基团,碳化后的木质素具有固定形状和较低电阻率。本发明方法,利用生物炼制或制浆造纸废弃物木质素为原料制备出高强度、低电阻的碳电极材料,具有原料来源丰富、价格低廉、应用范围广等优势。碳电极材料制备过程中未添加任何粘合剂,利用碳化过程中碳原子之间的化学键连接成型,具有绿色环保的优势和广泛应用的潜力。(The invention discloses a method for preparing a carbon electrode by using lignin. The method adopts lignin as a raw material, the lignin and acetylene black are mixed, oxygen-containing groups are removed by high-temperature heating in an inert gas atmosphere after mould pressing, and the carbonized lignin has a fixed shape and lower resistivity. The method of the invention prepares the high-strength and low-resistance carbon electrode material by using the lignin which is the waste of biological refining or pulping and papermaking as the raw material, and has the advantages of rich raw material source, low price, wide application range and the like. The carbon electrode material is not added with any adhesive in the preparation process, is formed by utilizing chemical bond connection among carbon atoms in the carbonization process, and has the advantages of environmental protection and wide application potential.)

1. A method for preparing a carbon electrode by using lignin is characterized by comprising the following steps:

(1) lignin pretreatment: drying the enzymolysis lignin raw material for 24h at 60 ℃, weighing 50g of lignin, carrying out primary grinding treatment, screening by a 80-mesh screen, and refining particles in the raw material;

(2) preparation of lignin/acetylene black mixed material: mixing the lignin raw material pretreated in the step (1) with acetylene black according to a fixed proportion, then weighing 40g of the mixture, putting the mixture into a 100ml ball milling tank, adjusting the rotation speed to 300rpm, and carrying out ball milling for 48 hours to obtain a lignin/acetylene black mixed material;

(3) pressure forming: putting the lignin/acetylene black mixed material into a customized metal nickel mold, applying 5MPa pressure and keeping for 10min, and fixing and molding the lignin/acetylene black mixed material;

(4) high-temperature carbonization: putting the formed mixed material of the lignin and the acetylene black into a tubular furnace, carbonizing in an Ar atmosphere, and introducing Ar for 30min to discharge air in the tube; then heating, heating to 150 ℃ at the heating rate of 3 ℃/min, preserving heat for 60min at the temperature of 150 ℃, heating to 800-1000 ℃ at the heating rate of 3 ℃/min, and preserving heat for 3h at the temperature of 800-1000 ℃ to obtain a low-resistance carbon electrode;

the ratio of the lignin to the acetylene black in the step (2) is 5: 1-20: 1, and the carbon electrode with high strength and low resistivity can be prepared under the conditions, wherein the resistivity is 0.10132-0.11732 omega/cm.

2. The method for preparing the carbon electrode by using the lignin according to claim 1, wherein the lignin in the step (1) is one of enzymatic lignin and pulping black liquor lignin.

3. The method for preparing the carbon electrode by using the lignin according to claim 2, wherein the maximum sintering temperature in the step (4) is 800-1000 ℃.

Technical Field

The invention belongs to the technical field of green preparation of electrode materials. The invention relates to a method for preparing a carbon electrode by using lignin.

Background

The lignin-based carbon electrode as a non-metallic conductive material has excellent mechanical properties, extremely low resistance, high specific surface area and the like, and also has good biocompatibility, so the lignin-based carbon electrode is widely applied to the fields of preparation of lithium ion electrode materials, electromagnetic protection, heavy metal adsorption and the like.

The lignin-based carbon electrode is prepared by carbonizing lignin under high temperature inert gas condition, and mixing the carbonized lignin with mixed polytetrafluoroethylene adhesive and acetylene black conductive agent. But because the addition of the polytetrafluoroethylene can cause the resistance of the conductive material to be increased, the energy consumption can be increased in the actual use process; these problems limit the development of lignin-based carbon electrodes when the binder and the conductive agent are mixed during the manufacturing process, and the carbon electrode becomes more resistant if the conductive agent content is low, and is less likely to be formed if the binder content is low.

The lignin-based carbon electrode has the excellent performances of wide raw material source, good conductivity, light weight, corrosion resistance and the like, and is applied to the aspects of oxidative degradation treatment of organic matters such as toluene and the like, preparation of battery electrode materials, heavy metal ion adsorption and the like at present. The carbon electrode has the characteristics of excellent conductivity, corrosion resistance and the like, so that the carbon electrode has higher degradation efficiency and longer service life when being used as an electrode for oxidizing and degrading toxic organic matters; when the conductive carbon is used as a battery electrode, the porous characteristic of the conductive carbon provides a channel for ion exchange, and the carbon electrode is a preferred material for preparing a capacitor due to the high specific surface area. All the materials mentioned above suffer from the problems of difficult formation, difficult preparation, etc. during the preparation process, and the application range of the carbon electrode is greatly limited.

Chinese patent publication No. CN107623105A describes a method for preparing a negative electrode and a conductive agent material of a lithium ion battery using biomass. According to the method, taro head and neck, rice hulls, peanut shells and the like are used as biomass raw materials, carbonization is carried out at high temperature of 900 ℃, activation is carried out by utilizing different methods such as acid, alkali, salt and the like after carbonization, and activated biomass-based active substances are mixed with substances such as a conductive agent, an adhesive and the like in a ball milling mode to obtain negative electrode slurry of a lithium ion battery; and uniformly coating the obtained slurry on a copper foil, baking the copper foil in a vacuum environment for 10-36 hours, and finally rolling and slitting to obtain the lithium ion battery negative electrode material. The lithium ion electrode cathode prepared by the method has the advantages of good conductive three-dimensional channel, higher specific discharge capacity, extremely long cycle service life and the like. However, when the lithium ion battery electrode prepared by the method is used, the internal resistance of the electrode material is increased due to the existence of the adhesive, and the adhesive also has a certain barrier effect on an ion conduction channel in the electrode material.

Chinese patent publication No. CN103265025A describes a method for preparing an electromagnetic shielding material using biomass. The method uses agricultural wastes such as straws, wheat straws, corn stalks and the like as biomass materials, the biomass materials are put into a 500 ℃ condition for low-temperature carbonization, and the carbonized biomass materials are mixed with ferronickel and calcium-based compounds according to a certain proportion to obtain a mixed material. The obtained mixed material is carbonized at 1000 ℃. And obtaining the biomass conductive carbon after acid washing. And uniformly mixing the obtained conductive carbon and resin according to a ratio, pouring the mixture into a mold, and molding under high pressure to obtain the biomass electromagnetic shielding material. Compared with the traditional metal electromagnetic shielding material, the electromagnetic shielding material prepared by the method has the characteristics of low cost, corrosion resistance, environmental friendliness and the like. However, the introduction of the resin during use may result in an increase in electrical resistance, which may reduce the electromagnetic shielding ability.

Chinese patent publication No. CN101671069A describes a method for treating low-concentration metal wastewater by using biomass conductive carbon. The double-fluidized bed reactor assembled by utilizing the biomass conductive carbon mainly comprises a wastewater purification reaction bed and a metal recovery reaction bed. According to the invention, the biomass conductive carbon is adopted to replace the traditional metal particles and activated carbon to treat sewage, so that the current density is improved, the reaction area is increased, and the metal adsorption efficiency is improved. However, the conductive carbon prepared by the method can be dissolved into waste liquid in the subsequent treatment process, and the treatment difficulty of waste water is increased.

The lignin is a natural high polymer with a three-dimensional network structure and composed of phenylpropane structural units, and is the second largest renewable natural polymer which is second only to cellulose. Lignin is a waste of pulping and papermaking industry, the annual lignin yield is about 5000 ten thousand tons in the world, the main utilization approach of lignin at present is to generate heat energy by combustion for an alkali recovery section, and only less than 2% of lignin is used for producing low-value commercial products such as an adhesive, a cement water reducing agent, a dispersing agent, a surfactant and the like. The lignin structure contains various functional groups, including benzene rings, methoxy groups, phenolic hydroxyl groups, side-chain carbonyl groups, alcoholic hydroxyl groups, carbon-carbon double bonds and the like. Compared with other biomass materials, the lignin has the characteristics of higher strength and better conductivity after carbonization due to the characteristic that the lignin forms more carbon-carbon double bonds during carbonization due to the rich carbon element content, and the carbonized lignin has very stable carbon-carbon bond connection and good corrosion resistance.

Disclosure of Invention

The invention mainly aims to provide a method for preparing a carbon electrode by using lignin, which aims to solve the problems of increased resistance and increased product cost after adding a binder in the existing process for preparing a lignin-based carbon electrode.

The technical scheme of the invention for solving the technical problems is as follows.

A method for preparing a carbon electrode using lignin, comprising the steps of:

1. lignin pretreatment: drying the lignin raw material for 24h at the temperature of 60 ℃, weighing 80g of lignin, carrying out primary grinding treatment, screening by a 200-mesh screen, and refining particles in the raw material;

2. preparation of lignin/acetylene black mixed material: mixing the preliminarily treated lignin raw material and acetylene black according to a fixed proportion, then weighing 40g of the mixture, putting the mixture into a 100ml ball milling tank, adjusting the rotation speed to 300rpm, and carrying out ball milling for 48 hours to obtain the lignin/acetylene black mixed material.

3. Pressure forming: putting the lignin/acetylene black mixed material into a customized metal nickel mold, applying pressure for 10min, and fixing and molding the lignin/acetylene black mixed material.

4. High-temperature carbonization: and (2) putting the formed mixed material of the lignin and the acetylene black into a tubular furnace, carbonizing in an Ar atmosphere, introducing Ar for 30min, discharging air in the tube, heating to 150 ℃ at the heating rate of 3 ℃/min, preserving heat at the temperature of 150 ℃ for 60min, heating to 800-1000 ℃ at the heating rate of 3 ℃/min, and preserving heat at the temperature of 800-1000 ℃ for 3h to obtain the carbon electrode material.

The lignin in the step 1 is one of enzymatic hydrolysis lignin, bagasse black liquor lignin and other lignin;

in the step 2, the ball milling mixing ratio of the lignin to the acetylene black is 5: 1-20: 1; in the step 4, the highest carbonization temperature is 800-1000 ℃.

Compared with the prior art, the method has the following advantages:

1. the lignin has the characteristics of wide source, reproducibility, no harm to the environment and human health and the like, and can realize the high-efficiency utilization of resources by taking the lignin as a raw material;

2. the lignin used in the process of preparing the carbon electrode is unpurified industrial lignin, and the direct use of the industrial lignin as a raw material is beneficial to reducing the preparation cost of the conductive carbon;

3. the process for preparing the carbon electrode by utilizing the lignin is simple, safe and reliable in technology, economical, environment-friendly and easy to industrialize.

4. The prepared lignin carbon electrode does not use any adhesive, and has the advantages of low resistance, good stability and the like.

Drawings

FIG. 1 is a pictorial representation of a carbon electrode made in accordance with the present invention.

In the figure, left: a physical map of the carbon electrode of example 2; and (3) right: physical representation of the carbon electrode of example 3.

Fig. 2 is an image of cyclic voltammetry curves of a carbon electrode prepared according to the present invention.

In the figure, cyclic voltammogram images of the carbon electrode of example 1. A working electrode: a lignin carbon electrode; counter electrode: a platinum electrode; reference electrode: a saturated calomel electrode; electrolyte solution: saturated sodium chloride solution.

Detailed Description

The present invention will now be described with reference to specific examples. The following examples are presented as preferred embodiments of the present disclosure, and are intended only to illustrate and explain the present invention, and are not intended to limit the present invention.