CHITIN REGENERATIVE HYDROGEL AND PREPARATION METHOD AND APPLICATION THEREOF

Abstract

The present invention discloses a chitin regenerative hydrogel and a preparation method and application thereof, which belong to the technical field of energy materials. The preparation method of the chitin regenerative hydrogel comprises the following steps: 1, performing heating dissolution and cooling molding on chitin and ionic liquid to obtain chitin-ionic liquid gel; and S2, soaking the chitin-ionic liquid gel into alkaline solution to obtain the chitin regenerative hydrogel. The chitin-ionic liquid gel and the chitin regenerative hydrogel that are prepared in the present invention have good restoring capacity and thixotropy capacity. The chitin-ionic liquid gel is soaked into potassium hydroxide aqueous solution for replacement to obtain the chitin-based regenerative hydrogel, the chitin-based regenerative hydrogel is taken as a polymer electrolyte diaphragm for assembling a supercapacitor, and the obtained capacitor has higher specific capacitance and charging/discharging efficiency, and good rate capability and reversibility.

Claims

1. A preparation method of chitin regenerative hydrogel, comprising the following steps: S1, performing heating dissolution and cooling molding on chitin and ionic liquid to obtain chitin-ionic liquid gel; S2, soaking the chitin-ionic liquid gel into alkaline solution to obtain the chitin regenerative hydrogel.

2. The preparation method according to claim 1, wherein in the step S1, the chitin is from at least one of shrimp shells and crab shells.

3. The preparation method according to claim 1, wherein in the step S1, the ionic liquid is at least one of 1-butyl-3-methylimidazolium acetate, 1-ethyl-3-methylimidazolium acetate and 1-allyl-3-methylimidazolium bromide.

4. The preparation method according to claim 1, wherein in the step S1, the mass ratio of the chitin and the ionic liquid is 0.5-5:100.

5. The preparation method according to claim 1, wherein in the step S1, the heating refers to oil bath heating; the temperature of the oil bath heating is 60-80° C., and the time of the oil bath heating is 1-3 h.

6. The preparation method according to claim 1, wherein in the step S2, the alkaline solution is at least one of potassium hydroxide solution, LiOH solution and sodium hydroxide solution.

7. A chitin regenerative hydrogel, which is prepared by the preparation method of claim 1.

8. An application of the chitin regenerative hydrogel of claim 7 in an energy material.

9. An application of the chitin regenerative hydrogel of claim 7 in a polymer electrolyte.

10. A supercapacitor, taking the chitin regenerative hydrogel of claim 7 as the polymer electrolyte.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0057] FIG. 1 shows strain step curve charts of chitin/[BMIM]Ac gel with the chitin contents of 1 wt %, 1.5 wt %, 2 wt % and 3 wt % respectively;

[0058] FIG. 2 shows cyclic voltammetry curve charts of regenerative chitin hydrogel with the chitin content of 2 wt % and a commercial aqueous diaphragm made of a PP/PE material;

[0059] FIG. 3 shows alternating-current impedance curve charts of regenerative chitin hydrogel with the chitin contents of 1.5 wt %, 2 wt % and 3 wt % respectively and the commercial aqueous diaphragm made of the PP/PE material; and

[0060] FIG. 4 is a diagram (a) of rate capability of the regenerative chitin hydrogel with the chitin content of 2 wt % and the commercial aqueous diaphragm made of the PP/PE material and a diagram (b) of a changing curve of discharge capacity in a cyclic process, wherein a is charging and discharging curve charts of a regenerative hydrogel diaphragm with the chitin content of 2 wt % and the commercial aqueous diaphragm made of the PP/PE material under different working current densities; b is a changing diagram of discharge capacity after a capacitor with the chitin content of 2 wt % circulates 1000 times under the current density of 100 mA.Math.g.sup.−1; and blank represents the commercial aqueous diaphragm made of the PP/PE material.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0061] The present invention is further described in detail below through combination with embodiments and the drawings, but implementation manners of the present invention are not limited to this.

[0062] Reagents and methods involved in the embodiments are all commonly used reagents and methods in the field unless stated, and any immaterial change and replacement made by those skilled in the art based on the present invention belongs to the protection scope required by the present invention.

Embodiment 1: Preparation of Chitin-Ionic Liquid Gel and Chitin-Ionic Liquid Regenerative Hydrogel

[0063] 3 g of 1-butyl-3-methylimidazolium acetate is weighed and then is put into a 25 mL eggplant-shaped flask, oil bath is performed at 100° C. for 10 min, and twin exhaust pipes are utilized for repeated air exhaust and air inflation to remove moisture and oxygen; 30 mg of dry chitin is quickly added into the above flask, oil bath is performed at 80° C., and the mixture is stirred for 3 h, so as to obtain clear and bright chitin ionic solution with 1 wt % of chitin; the chitin ionic solution is poured into a culture vessel with the diameter of 35 mm, the culture vessel is put into a dryer for natural cooling and film forming; the prepared chitin-ionic liquid gel is soaked into anhydrous ethanol for 1 h to remove most ionic liquid, then a thin film is soaked into deionized water for 24 h to thoroughly remove the ionic liquid, and the thin film is cut into a wafer with the suitable size; and the thin film is soaked into 6 M KOH solution for 3 h under the vacuum condition, so as to obtain the chitin regenerative hydrogel.

[0064] According to the above same operation, 45 mg, 60 mg and 90 mg of chitin are respectively added to prepare chitin ionic solution with 1.5 wt %, 2 wt % and 3 wt % of chitin respectively, and cooling molding and alkaline liquid replacement are performed to obtain the chitin regenerative hydrogel.

[0065] An advanced rotational rheometer is used for characterizing the gel performance of the chitin-ionic liquid gel and performing a continuous stepped deformation scanning test in a dynamic mode, and the testing frequency is 1 rad/s; and the advanced rotational rheometer maintains 120 s under 100% of strain and then maintains 180 s under 1% of strain, and the above operations are repeated once. Additionally, in order to ensure that the structure of the gel is destroyed, the maximum strain value selected in a strain step test is 100%, which is much greater than the maximum value (3%) of a linear viscoelasticity region in a dynamic strain scanning test. Results are shown as FIG. 1.

[0066] It can be seen from FIG. 1 that, when the strain amplitude is larger, the structure of the gel is destroyed (G″>G′); when the applied strain is the smaller value (1%), the structure of the gel can be restored quickly (G′>G″), and the modulus is not decreased, which indicates that the chitin-ionic liquid gel has certain restoring capacity and good thixotropy. The reasons of generating the phenomenon may be: in one aspect, a local network in chitin/[BMIM]Ac gel is not destroyed under big strain possibly, only the connection between gel networks is broken, and therefore, the chitin-ionic liquid gel can be quickly restored when the strain is decreased. In the other aspect, the ionic liquid carries charges, an imino group (—NH—) on the chitin has electropositivity, and the electrostatic force between the charges and the imino group can enable the chitin-ionic liquid gel obtained finally to have restoring capacity. Compared with a hydrogen bond, the electrostatic force is long-distance acting force, which can provide support for quick reconstruction of the structure of the gel networks, so that the deformation restoring capacity of the chitin-ionic liquid gel is improved. Additionally, due to the combined action of the hydrogen bond and the electrostatic interaction, the transient state network structure between the chitin and [BMIM]Ac can be stabilized, so as to form the physically cross-linked gel.

Embodiment 2 Assembling of Supercapacitor by Taking Chitin Regenerative Hydrogel as Polymer Electrolyte

[0067] Preparation methods of chitin-ionic liquid gel and chitin regenerative hydrogel in the embodiment are the same as the preparation method of the chitin regenerative hydrogel in Embodiment 1.

[0068] 0.85 g of TF-supercapacitor activated carbon and 0.1 g of conductive additive: Timcal graphite are weighed, and 0.05 g of PTFE concentrated emulsion and 10 mL of anhydrous ethanol are added, wherein the mass ratio of the TF-supercapacitor activated carbon, the Timcal graphite and the PTFE is 85:10:5; the mixture is uniformly stirred and then is ground for 1 h with a quartz mortar into a plasticine state, the plasticine state mixture is ground into a thin film with a glass rod, and then the thin film is cut into a wafer with the suitable size by a puncher; and the wafer is pressed on a cut foamed nickel wafer by a manual oil press with 100 Mpa of force and is dried at the temperature of 80° C. for 24 h under the vacuum condition. The total weight of a diaphragm minus the weight of a nickel sheet is multiplied by 85% which is the proportion of active substances (the TF-supercapacitor activated carbon and the conductive additive: Timcal graphite) to obtain the mass of the active substances loaded on a single electrode plate. The model of a used button capacitor is CR2032, foamed nickel electrode plates with the mass close to the active substances are selected as a group of electrodes of a supercapacitor and are soaked into 6 M KOH solution for 3 h in a vacuum environment before assembling; and the cut chitin thin film for absorbing potassium hydroxide solution is taken as a polymer electrolyte. The following tests are conducted respectively:

[0069] (1) A Zahner Zennium electrochemical workstation (Germany) is utilized for conducting a cyclic voltammetry test. The testing conditions are: the scanning voltage range is 0-0.8 V, the scanning rates are 5 mV/s, 10 mV/s, 50 mV/s and 100 mV/s respectively, and the scanning times are 5 times. Results are shown as FIG. 2.

[0070] A cyclic voltammetry research in FIG. 2 indicates that compared with a commercial aqueous diaphragm (Celgard) made of a PP/PE material, a chitin regenerative hydrogel diaphragm with the chitin content of 2 wt % shows higher specific capacitance and better rate capability.

[0071] (2) The Zahner Zennium electrochemical workstation (Germany) is utilized for conducting an alternating-current impedance test. The testing conditions are: the frequency is 100 KHz-100 mHz, the voltage amplitude is 5 mV, and the open-circuit voltage is 1 V.

[0072] The ionic conductivity σ of the polymer electrolyte is calculated by the equation: σ=d/(SR), wherein d represents the thickness of a gel electrolyte, S represents the effective contact area of the gel electrolyte and the electrode plate, and R represents the volume resistance obtained from an alternating-current impedance spectrogram (the real axis intercept of a high frequency part of the impedance spectrogram). Results are shown as FIG. 3.

[0073] The alternating-current impedance test in FIG. 3 indicates that compared with the commercial aqueous diaphragm made of the PP/PE material, the hydrophilic nature of networks of the chitin regenerative hydrogel and the loose porous structure therein are conductive to transmission of the electrolyte therein, thereby showing greater capacitance.

[0074] (3) The Zahner Zennium electrochemical workstation (Germany) is utilized for testing the capacitance, the rate capability and other indexes of the supercapacitor made by taking the chitin regenerative hydrogel with the chitin content of 2 wt % as the polymer electrolyte of the supercapacitor. The testing conditions are: the current densities are 0, 100 mA.Math.g.sup.−1, 200 mA.Math.g.sup.−1, 300 mA.Math.g.sup.−1, 400 mA.Math.g.sup.−1 and 500 mA.Math.g.sup.−1 respectively; and the charging/discharging times are 0, 2.0×10.sup.2, 4.0×10.sup.2, 6.0×10.sup.2, 8.0×10.sup.2 and 1.0×10.sup.3 respectively. Results are shown as FIG. 4.

[0075] It can be seen from FIG. 4a that the capacitance of the chitin regenerative hydrogel diaphragm with the chitin content of 2 wt % is 92 F.Math.g.sup.−1 under the working current of 50 mA.Math.g.sup.−1, the rate retention rate is 92% under the current density of 500 mA.Math.g.sup.−1, which are the same as the results of the above cyclic voltammetry test and the above alternating-current impedance test and indicate that the chitin regenerative hydrogel diaphragm prepared in the present invention has better rate retention performance.

[0076] The results in FIG. 4b indicate that compared with the commercial aqueous diaphragm made of the PP/PE material, the discharge capacity of the supercapacitor made by taking the chitin regenerative hydrogel with the chitin content of 2 wt % as the polymer electrolyte of the supercapacitor is attenuated more slowly with the increase of the charging/discharging times.

Embodiment 3 Preparation of Chitin-Ionic Liquid Gel and Chitin-Ionic Liquid Regenerative Hydrogel

[0077] Preparation methods of chitin-ionic liquid gel and chitin-ionic liquid regenerative hydrogel in the embodiment are the same as the preparation method in Embodiment 1, and the differences are that: in the embodiment, the temperature of oil bath heating before mixing of ionic liquid and chitin is 120° C., and the time of oil bath heating is 12 min; the temperature of oil bath heating of chitin and 1-ethyl-3-methylimidazolium acetate ([EMIM]Cl) is 70° C., and the time of oil bath heating is 2 h; the time of soaking the prepared chitin-ionic liquid gel with an alcohol solvent is 0.5 h, and the time of soaking the prepared chitin-ionic liquid gel with distilled water is 18 h; and the prepared chitin-ionic liquid gel is soaked into LiOH with the concentration of 8 M for 4 h.

[0078] The chitin regenerative hydrogel with good performance, which is as described in Embodiment 1, is also prepared by the above method.

Embodiment 4 Preparation of Chitin-Ionic Liquid Gel and Chitin-Ionic Liquid Regenerative Hydrogel

[0079] Preparation methods of chitin-ionic liquid gel and chitin-ionic liquid regenerative hydrogel in the embodiment are the same as the preparation method in Embodiment 1, and the differences are that: in the embodiment, the temperature of oil bath heating before mixing of ionic liquid and chitin is 80° C., and the time of oil bath heating is 8 min; the temperature of oil bath heating of chitin and 1-allyl-3-methylimidazolium bromide ([AMIM]Br) is 60° C., and the time of oil bath heating is 1 h; the time of soaking the prepared chitin-ionic liquid gel with an alcohol solvent is 2 h, and the time of soaking the prepared chitin-ionic liquid gel with distilled water is 12 h; and the prepared chitin-ionic liquid gel is soaked into NaOH with the concentration of 3 M for 2 h.

[0080] The chitin regenerative hydrogel with good performance, which is as described in Embodiment 1, is also prepared by the above method.

[0081] The above embodiments are better implementation manners of the present invention, but the implementation manners of the present invention are not limited by the above embodiments. Any other changes, modifications, replacements, combinations and simplifications made without departing from the spiritual essence and the principle of the present invention should be equivalent substitutions and shall be concluded in the protection scope of the present invention.