Carbon nanofiber aerogel as well as preparation method and application thereof

[0034] The invention discloses a preparation method of carbon nanofiber aerogel, which comprises the following steps:

[0035] Step a) Soak the bacterial cellulose block in deionized water to remove acid to obtain a neutral bacterial cellulose block. The function of this step is to remove the acid liquid in the bacterial cellulose block to prevent the acidic substance from reacting with the bacterial cellulose aerogel in the subsequent high-temperature pyrolysis step. Since bacterial cellulose has a three-dimensional network structure and can be produced on a large scale, it is an ideal precursor for preparing carbon nanofiber aerogels. In order to make the pH value of the bacterial cellulose block close to neutral, the bacterial cellulose block may preferably be soaked in deionized water that is replaced every day for 3-7 days, more preferably for 5-6 days. Those skilled in the art can easily imagine that for the convenience of subsequent operations, the bacterial cellulose block after deacidification can be cut so as to be easily immersed in deionized water.

[0036] Step b) Use liquid nitrogen to freeze the neutral bacterial cellulose block, and then dry it in a freeze dryer to obtain a white bacterial cellulose aerogel. The freeze-drying method used in this step to dry the neutral bacterial cellulose block can keep the original three-dimensional network structure of the bacterial cellulose from being destroyed. Preferably, the neutral bacterial cellulose block is placed in liquid nitrogen and frozen for 20-30 minutes, and then the neutral bacterial cellulose block is taken out and dried in a freeze dryer for 3 to 5 days. More preferably, the freezing time is 25 minutes and the drying time is 4 days.

[0037] Step c) After heating the bacterial cellulose aerogel, perform high-temperature pyrolysis to obtain a black carbon nanofiber aerogel. Among them, the selection of a suitable heating rate and pyrolysis temperature is one of the important factors that affect the properties of the final carbon nanofiber aerogel. A suitable heating rate is conducive to the maintenance of the carbon nanofiber network structure, and different pyrolysis temperatures The lipophilicity of the carbon nanofiber aerogels prepared below is different. In order to prevent gases such as oxygen from reacting with the bacterial cellulose aerogel during the pyrolysis process, the heating and high-temperature pyrolysis process can also be carried out under an inert atmosphere. Those skilled in the art can easily imagine that the inert atmosphere can include argon and nitrogen. And many other options. The heating rate and pyrolysis temperature in step c) are selected according to the required properties of the carbon nanofiber aerogel. Preferably, the bacterial cellulose aerogel is heated to 600-1400 at a rate of 1 to 6°C/min ℃, pyrolysis for 1~7h. More preferably, the bacterial cellulose aerogel is heated to 400-500°C at a rate of 1 to 3°C/min, then kept for 1 to 3 hours, and then heated to 600 to 1400°C at a rate of 4 to 6°C/min. Solution 2~4h. Further, in order to completely maintain the structure of the prepared carbon nanofiber aerogel, the bacterial cellulose aerogel is cooled to 400-500°C at a rate of 4-6°C/min after the pyrolysis is completed, and then naturally cooled to room temperature . The present invention has no particular limitation on the furnace used for high-temperature pyrolysis. Apparatuses known to those skilled in the art can be used, preferably continuous furnaces or batch furnaces of metal resistance heating type, graphite resistance heating type or silicon molybdenum rod resistance heating type. .

[0038] The preparation method provided by the present invention is simple and easy to implement, has good repeatability, and the density of the prepared carbon nanofiber aerogel is 4-6 mg/cm 3 , Which is composed of a three-dimensional network structure of carbon fibers with a diameter of 10-20 nm. The carbon nanofiber aerogel prepared by the present invention can still be restored to its original volume after being compressed to 10% of its original volume, and remains inert and its original appearance on the flame of an alcohol lamp (400-500°C). In addition, it is extremely resistant to organic liquids Good absorption performance, capable of absorbing organic liquids 106 to 312 times its own mass.

[0042] Example 1

[0043] Take a commercially purchased 320×240×12mm 3 Bacterial cellulose flakes, soak in deionized water for 5 days, and replace the deionized water every day. Cut the large pieces of neutral bacterial cellulose after deacidification into 50×20×12mm 3 The small pieces are ready for use.

[0044] The small pieces of neutral bacterial cellulose were frozen in liquid nitrogen for 25 minutes, and then transferred to a freeze dryer for 4 days.

[0045] The bacterial cellulose aerogel obtained by freeze drying was placed in a ceramic boat, and then transferred to a tube furnace. Pyrolysis in an argon atmosphere, starting from room temperature 20°C, heating at a rate of 2°C/min, reaching 500°C after 4h, holding at 500°C for 1h, and then heating up to 1300°C at a rate of 5°C/min. Keep at 1300℃ for 2h to fully pyrolyze. Then the temperature is lowered to 500°C at 5°C/min, and finally the temperature is naturally lowered to obtain a black carbon nanofiber aerogel.

[0046] The density of carbon nanofiber aerogel prepared by testing is 4~6mg/cm 3 , And has excellent flexibility. Such as figure 1 As shown, the diameter of the carbon nanofiber aerogel is 10-20 nm. Such as figure 2 As shown, the contact angle of the carbon nanofiber aerogel is 128.64°, the contact angle of the carbon nanofiber aerogel is relatively large, and the lipophilicity is relatively high, and it can be used as an organic reagent absorbent.

[0047] The prepared carbon nanofiber aerogel is used as the absorbent of organic reagents to absorb various organic reagents. The results show that the carbon nanofiber aerogel has excellent absorption performance for organic reagents, and its absorption capacity can reach its own 106 to 312 times the quality.

[0048] Example 2

[0049] Take a commercially purchased 320×240×12mm 3 Bacterial cellulose flakes, soak in deionized water for 4 days, and replace the deionized water every day. Cut the large pieces of neutral bacterial cellulose after deacidification into 50×20×12mm 3 The small pieces are ready for use.

[0050] The small pieces of neutral bacterial cellulose were frozen in liquid nitrogen for 20 minutes, and then transferred to a freeze dryer for 5 days.

[0051] The bacterial cellulose aerogel obtained by freeze drying was placed in a ceramic boat, and then transferred to a tube furnace. Pyrolysis in a nitrogen atmosphere, starting from room temperature 20°C, heating at a rate of 1°C/min to 400°C, holding at 400°C for 2h, then heating at a rate of 4°C/min to 1000°C, and keeping it at 1000°C for 3h Come full pyrolysis. Then the temperature is lowered to 500°C at 4°C/min, and finally the temperature is naturally lowered to obtain a black carbon nanofiber aerogel.

[0052] Such as image 3 As shown, the diameter of the carbon nanofiber aerogel is 10-20 nm. Such as Figure 4 As shown, the contact angle of the carbon nanofiber aerogel is 120.18°, the contact angle of the carbon nanofiber aerogel is relatively large, and the lipophilicity is relatively high, and it can be used as an organic reagent absorbent.