CN112233914B

CN112233914B - Preparation method and application of micronized cellulose/MXene composite film

Info

Publication number: CN112233914B
Application number: CN202011106596.5A
Authority: CN
Inventors: 姚忠平; 张志荣; 姜兆华
Original assignee: Harbin Institute of Technology
Current assignee: Harbin Institute of Technology
Priority date: 2020-10-15
Filing date: 2020-10-15
Publication date: 2022-01-18
Anticipated expiration: 2040-10-15
Also published as: CN112233914A

Abstract

A preparation method and application of a micronized cellulose/MXene composite film relate to a preparation method and application of an MXene composite film. The invention aims to solve the problems that the mechanical property and the capacitance of the existing MXene composite film are poor, and the conductivity of the MXene cellulose composite film is in a linear reduction trend along with the increase of nano-cellulose. The method comprises the following steps: first, prepare dark green few-layer Ti₃C₂T_xA colloidal supernatant; II, preparing MFC @ Ti₃C₂T_xMicrogel; thirdly, adding MFC @ Ti₃C₂T_xAnd (3) carrying out vacuum filtration on the microgel through a mixed cellulose membrane with the aperture of 0.22 mu m, and drying at room temperature to obtain the independently supported microfibrillated cellulose/MXene composite membrane. An independently supported microfibrillated cellulose/MXene composite film is used as a negative electrode material of a capacitor. The invention can obtain a micro cellulose/MXene composite film.

Description

Preparation method and application of micronized cellulose/MXene composite film

Technical Field

The invention relates to a preparation method and application of an MXene composite film.

Background

Ti₃C₂T_xAs a new super capacitor electrode material, the super capacitor electrode material has strong hydrophilicity, high conductivity and high theoretical capacity, thereby attracting people's attention. Ti with a thickness of about 3 μm is reported₃C₂T_xThe tensile strength of the film is 22MPa, the Young modulus can reach 3.52GPa, and the tensile elongation is about 1%. Due to Ti₃C₂T_xThe surface contains a large number of negatively charged-OH, -F, -O groups and can therefore be linked to the organic polymer by hydrogen bonds. The plasticity of the composite material can be improved by compounding the composite material with a polymer, and the tensile strength of the composite material can also be greatly improved. However, the conductivity of most cellulose composite films shows a linear decreasing trend with the increase of the nano-cellulose, which will cause the reduction of electrochemical performance. This may be due to the intercalation of nanocellulose into Ti₃C₂T_xThe interlayer electron conductivity is rapidly reduced, and the electron transport in the vertical direction is greatly reduced due to the presence of the polymer, which is used for Ti₃C₂T_xThe use of the supercapacitor of (a) is detrimental.

Disclosure of Invention

The invention aims to solve the problems that the mechanical property and the capacitance of the existing MXene composite film are poor, and the conductivity of the MXene cellulose composite film is in a linear reduction trend along with the increase of nano-cellulose, and provides a preparation method of an independently supported microfibrillated cellulose/MXene composite film.

A preparation method of an independently supported microfibrillated cellulose/MXene composite film is completed according to the following steps:

first, prepare dark green few-layer Ti₃C₂T_xAnd (3) colloid supernatant fluid:

adding LiF into HCl solution, stirring at room temperature until the LiF is completely dissolved, and then adding Ti under the condition of ice-water bath₃AlC₂Reacting for 18-28 h at 30-35 ℃ in nitrogen atmosphere to obtain reaction liquid;

② firstly, deionized water is used as cleaning agent, the reaction liquid is centrifugally cleaned to pH value under the centrifugal speed of 3500 r/min-4000 r/min>6, pouring out the supernatant to obtain a precipitate; adding deionized water into the sediment, then carrying out ultrasonic treatment, centrifuging for 1-1.2 h at the centrifugal speed of 3500-4000 r/min, and collecting the supernatant to obtain dark green few-layer Ti₃C₂T_xA colloidal supernatant;

secondly, a small number of greenish black Ti layers₃C₂T_xAdding the colloid supernatant into the micronized cellulose solution, and shaking to obtain MFC @ Ti₃C₂T_xMicrogel;

thirdly, adding MFC @ Ti₃C₂T_xAnd (3) carrying out vacuum filtration on the microgel through a mixed cellulose membrane with the aperture of 0.22 mu m, and drying at room temperature to obtain the independently supported microfibrillated cellulose/MXene composite membrane.

An independently supported microfibrillated cellulose/MXene composite film is used as a negative electrode material of a capacitor.

The principle and the advantages of the invention are as follows:

firstly, the invention selects micron-sized Microfibrillated Cellulose (MFC) with diameter as Ti₃C₂T_xReinforcing agent for mechanical properties, known as Ti₃C₂T_xThe lateral dimension of the nanosheets is only a few microns at most, so when the two are combined, Ti₃C₂T_xThe nanoplatelets can be attached to the one-dimensional cellulose to form a one-dimensional conductive channel, so that Ti is not influenced₃C₂T_xElectronic transmission in the one-dimensional and two-dimensional directions of the nanosheets is realized, and the celluloses are mutually connected and built, so that the formed film has enhanced mechanical properties;

secondly, the invention adds the micro cellulose to ensure Ti₃C₂T_xUnder the condition that the tensile strength is improved by 2-3 times, the conductivity and capacitance of the composite material can still be ensured not to be reduced; when the mass fraction of the microfibrillated cellulose (MFC) in the independently supported microfibrillated cellulose/MXene composite film is 10%, the capacitance can be increased from 362F/g to 451F/g, so that the addition of the easily-obtained microfibrillated cellulose for increasing Ti₃C₂T_xThe combination of properties of the film is of great significance.

Drawings

FIG. 1 shows Ti in the second step of the example₃C₂T_xThe microgel formation process is shown in figure 1, which shows a greenish black few-layer Ti₃C₂T_xThe supernatant of colloid, 2 is a micronized cellulose solution, 3 is Ti₃C₂T_xMicrogel;

FIG. 2 shows Ti prepared in comparative example₃C₂T_xFilms and MFC @ Ti prepared in example one₃C₂T_xComparative figures for thin films;

FIG. 3 is MFC @ Ti prepared in example one₃C₂T_xA schematic diagram of the self-assembly of microgels;

FIG. 4 is a Zeta potential comparison diagram, in which 1 is Ti prepared in comparative example₃C₂T_xFilm, 2 MFC @ Ti prepared in example one₃C₂T_xA film;

FIG. 5 shows Ti prepared in comparative example₃C₂T_xSEM image of the film;

FIG. 6 is an SEM image of MFC;

FIG. 7 is MFC @ Ti prepared in example one₃C₂T_xSEM image of the film;

FIG. 8 is MFC @ Ti prepared in example one₃C₂T_xTEM image of the thin film;

FIG. 9 is a graph showing tensile properties, in which 1 is Ti prepared in comparative example₃C₂T_xFilm, 2 MFC @ Ti prepared in example one₃C₂T_xFilm, 3 MFC @ Ti prepared in example two₃C₂T_xFilm, 4 MFC @ Ti prepared in example III₃C₂T_xA film;

FIG. 10 is an EIS diagram, in which 1 is Ti prepared in a comparative example₃C₂T_xFilm, 2 MFC @ Ti prepared in example one₃C₂T_xFilm, 3 MFC @ Ti prepared in example two₃C₂T_xFilm, 4 MFC @ Ti prepared in example III₃C₂T_xA film;

FIG. 11 is an enlarged view taken at A in FIG. 10;

FIG. 12 is a GCD curve of different films at a current density of 1A/g, wherein 1 is Ti prepared in comparative example₃C₂T_xFilm, 2 MFC @ Ti prepared in example one₃C₂T_xFilm, 3 MFC @ Ti prepared in example two₃C₂T_xFilm, 4 MFC @ Ti prepared in example III₃C₂T_xA film;

FIG. 13 is a CV diagram of 5mV/s sweep rate for various films, where 1 is Ti prepared in a comparative example₃C₂T_xFilm, 2 MFC @ Ti prepared in example one₃C₂T_xFilm, 3 MFC @ Ti prepared in example two₃C₂T_xFilm, 4 MFC @ Ti prepared in example III₃C₂T_xA film.

Detailed Description

The following examples further illustrate the present invention but are not to be construed as limiting the invention. Modifications and substitutions to methods, procedures, or conditions of the invention may be made without departing from the spirit of the invention.

The first embodiment is as follows: the embodiment is a preparation method of an independently supported microfibrillated cellulose/MXene composite film, which is completed by the following steps:

firstly, deionized water is used as a cleaning agent, reaction liquid is centrifugally cleaned at a centrifugal speed of 3500 r/min-4000 r/min until the pH value is more than 6, and supernatant liquid is poured out to obtain a precipitate; deionized water was added to the precipitated material,

then carrying out ultrasonic treatment, centrifuging for 1-1.2 h at the centrifugal speed of 3500 r/min-4000 r/min, and collecting supernatant fluid to obtain dark green few-layer Ti₃C₂T_xA colloidal supernatant;

The principle and advantages of the embodiment are as follows:

first, in the present embodiment, Microfibrillated Cellulose (MFC) with a micron-sized diameter is selected as Ti₃C₂T_xReinforcing agent for mechanical properties, known as Ti₃C₂T_xThe lateral dimension of the nanosheets is only a few microns at most, so when the two are combined,Ti₃C₂T_xthe nanoplatelets can be attached to the one-dimensional cellulose to form a one-dimensional conductive channel, so that Ti is not influenced₃C₂T_xElectronic transmission in the one-dimensional and two-dimensional directions of the nanosheets is realized, and the celluloses are mutually connected and built, so that the formed film has enhanced mechanical properties;

secondly, the embodiment adds the micro cellulose to ensure Ti₃C₂T_xUnder the condition that the tensile strength is improved by 2-3 times, the conductivity and capacitance of the composite material can still be ensured not to be reduced; when the mass fraction of the microfibrillated cellulose (MFC) in the independently supported microfibrillated cellulose/MXene composite film is 10%, the capacitance can be increased from 362F/g to 451F/g, so that the addition of the easily-obtained microfibrillated cellulose for increasing Ti₃C₂T_xThe combination of properties of the film is of great significance.

The second embodiment is as follows: the present embodiment differs from the present embodiment in that: the concentration of the HCl solution in the first step is 8-10 mol/L. Other steps are the same as in the first embodiment.

The third concrete implementation mode: the present embodiment differs from the first or second embodiment in that: the ratio of the mass of LiF to the volume of HCl solution in the first step (1 g-2 g) is 20 mL. The other steps are the same as in the first or second embodiment.

The fourth concrete implementation mode: the difference between this embodiment and one of the first to third embodiments is as follows: ti described in step one₃AlC₂The ratio of the mass of (1) to the volume of the HCl solution (0.5g to 1.5g) was 20 mL. The other steps are the same as those in the first to third embodiments.

The fifth concrete implementation mode: the difference between this embodiment and one of the first to fourth embodiments is: the ultrasonic power is 100W-300W, and the ultrasonic time is 50 min-70 min; the small layer of greenish black Ti in the step one₃C₂T_xThe concentration of the colloid supernatant is 5 mg/mL-6 mg/mL. The other steps are the same as those in the first to fourth embodiments.

The sixth specific implementation mode: the difference between this embodiment and one of the first to fifth embodiments is as follows: the mass fraction of the microfibrillated cellulose solution in the second step is 0.5-0.8%, and the solvent is water. The other steps are the same as those in the first to fifth embodiments.

The seventh embodiment: the difference between this embodiment and one of the first to sixth embodiments is: the shaking time in the step two is 5 min-10 min. The other steps are the same as those in the first to sixth embodiments.

The specific implementation mode is eight: the difference between this embodiment and one of the first to seventh embodiments is: the mass fraction of the microfibrillated cellulose in the independently supported microfibrillated cellulose/MXene composite film in the third step is 10-30%. The other steps are the same as those in the first to seventh embodiments.

The specific implementation method nine: the difference between this embodiment and the first to eighth embodiments is: the mass fraction of the microfibrillated cellulose in the independently supported microfibrillated cellulose/MXene composite film in the third step is 10-20%. The other steps are the same as those in the first to eighth embodiments.

The detailed implementation mode is ten: in the present embodiment, an independently supported microfibrillated cellulose/MXene composite film is used as a negative electrode material for a capacitor.

The following examples were used to demonstrate the beneficial effects of the present invention:

the first embodiment is as follows: a preparation method of an independently supported microfibrillated cellulose/MXene composite film is completed according to the following steps:

adding 1.6g LiF into 20mL of 9mol/L HCl solution, stirring at room temperature until the LiF is completely dissolved, and then adding 1g Ti under the condition of ice-water bath₃AlC₂Reacting for 24 hours at 35 ℃ in nitrogen atmosphere to obtain reaction liquid;

② firstly, deionized water is used as cleaning agent, the reaction liquid is centrifugally cleaned to pH value at 3500r/min of centrifugal speed>6, pouring out the supernatant to obtain a precipitate; adding deionization to the precipitated materialWater, performing ultrasonic treatment, centrifuging at 3500r/min for 1 hr, and collecting supernatant to obtain dark green Ti with few layers₃C₂T_xA colloidal supernatant;

the ultrasonic power in the first step is 100W, and the ultrasonic time is 60 min;

the small layer of greenish black Ti in the step one₃C₂T_xThe concentration of the colloid supernatant is 5 mg/mL;

secondly, a small number of greenish black Ti layers₃C₂T_xAdding the colloid supernatant into the micronized cellulose solution, and shaking for 10min to obtain MFC @ Ti₃C₂T_xMicrogel;

the mass fraction of the microfibrillated cellulose solution in the second step is 0.5 percent;

thirdly, adding MFC @ Ti₃C₂T_xVacuum filtering the microgel through a mixed cellulose membrane with the aperture of 0.22 mu m, and drying at room temperature to obtain an independently supported microfibrillated cellulose/MXene composite membrane;

the mass fraction of the microfibrillated cellulose in the independently supported microfibrillated cellulose/MXene composite film described in step three is 10%.

Example two: a preparation method of an independently supported microfibrillated cellulose/MXene composite film is completed according to the following steps:

② firstly, deionized water is used as cleaning agent, the reaction liquid is centrifugally cleaned to pH value at 3500r/min of centrifugal speed>6, pouring out the supernatant to obtain a precipitate; adding deionized water into the precipitate, performing ultrasonic treatment, centrifuging at 3500r/min for 1 hr, and collecting supernatant to obtain dark green Ti with few layers₃C₂T_xA colloidal supernatant;

the mass fraction of the microfibrillated cellulose in the independently supported microfibrillated cellulose/MXene composite film described in step three is 20%.

Example three: a preparation method of an independently supported microfibrillated cellulose/MXene composite film is completed according to the following steps:

the mass fraction of the microfibrillated cellulose in the independently supported microfibrillated cellulose/MXene composite film described in step three is 30%.

Comparative example: ti₃C₂T_xThe preparation method of the film is completed according to the following steps:

secondly, a small number of greenish black Ti layers₃C₂T_xFiltering the colloid supernatant with 0.22 μm mixed cellulose membrane under vacuum, and drying at room temperature to obtain Ti₃C₂T_xA film.

Example two in one step a few layers of Ti of greenish black color were applied₃C₂T_xAdding the colloidal supernatant into the microfibrillated cellulose solution, shaking for 10min, and then finding that the solution becomes a microgel visible to the naked eye within one minute, as shown in figure 1;

FIG. 1 shows Ti in the second step of the example₃C₂T_xThe microgel formation process is shown in figure 1, which shows a greenish black few-layer Ti₃C₂T_xThe supernatant of colloid, 2 is a micronized cellulose solution, 3 is Ti₃C₂T_xMicrogels.

This indicates that Ti₃C₂T_xThe nano-sheets are completely combined with cellulose due to strong electrostatic attraction and hydrogen bonding, and the self-assembly schematic diagram is shown in FIG. 3;

as can be seen from a comparison of FIG. 2, the original Ti₃C₂T_xThe film surface is smooth, and MFC @ Ti₃C₂T_xThe film surface is rough due to the inter-weaving of cellulose, which slows down the layer-to-layer stacking to some extent.

Testing of the original Ti₃C₂T_xZeta potentials of the colloidal solution and the self-assembled microgel solution are shown in FIG. 4.

as can be seen from FIG. 4, the original Ti₃C₂T_xThe colloidal solution was-23 mV, due to Ti₃C₂T_xAnd (3) existence of a functional group with negative electricity on the surface of the nanosheet. When Ti is present₃C₂T_xThe Zeta potential of the colloidal solution after complexing with MFC was-3 mV, demonstrating that these functional groups have bonded to a large number of hydroxyl groups on MFC and that the entire solution becomes electrically neutral.

FIG. 5 shows Ti prepared in comparative example₃C₂T_xSEM image of the film;

as can be seen from FIG. 5, Ti produced in comparative example₃C₂T_xIs a thin nano-sheet structure.

FIG. 6 is an SEM image of MFC;

from the microscopic appearance of MFC observed in FIG. 6, it can be found that the micron-sized large framework of MFC is composed of a piece of cellulose with a super-long length-diameter ratio and a diameter of tens of nanometers, and the smaller cellulose is Ti₃C₂T_xThe enhancement of the mechanical property of the film provides guarantee.

FIG. 7 is MFC @ Ti prepared in example one₃C₂T_xSEM image of the film;

from fig. 7 it can be seen that one piece of cellulose is cross-linked to each other and agglomerated.

FIG. 8 is MFC @ Ti prepared in example one₃C₂T_xTEM image of the thin film;

from the TEM image of FIG. 8, it can be seen that the cellulose outer layer having a diameter of about 2 μm is coated with a layer of Ti₃C₂T_xNanosheets, from which Ti was known₃C₂T_xThe nanosheets have been attached to the surface of the microfibrillated cellulose by means of hydrogen bonding or the like.

it can be seen from FIG. 9 that as the MFC content increases, the tensile strength Ti₃C₂T_xThe stress and strain of the film are increased, the strain is mainly due to the existence of hydrogen bonds, the film can act as a 'movable pulley' to increase the sliding between the sheets and further increase the plasticity, and when the MFC content reaches 30%, MFC @ Ti is added₃C₂T_xThe tensile strength of the film is virgin Ti₃C₂T_xThree times as much film.

FIG. 11 is an enlarged view taken at A in FIG. 10;

as can be seen from fig. 10 and 11, the high frequency region still appears as a negligible semicircle after adding MFC, demonstrating its excellent conductivity. Compared with the slope of the straight line in the high-frequency region, the slope is found to be smaller and the Weber impedance is reduced due to the introduction of the cellulose. This is because the addition of MFC alleviates the stacking phenomenon between sheets to greatly shorten the ion transport path, so that the utilization rate of the material is increased.

it can be seen from FIG. 12 that the film discharge time for 10% MFC content is longer than the original Ti₃C₂T_xThe film is grown and its capacitance, Ti, is calculated₃C₂T_xThe specific capacities of 10% MFC, 20% MFC and 30% MFC were 362F/g, 451F/g, 367F/g and 333F/g, respectively. The increase in film capacitance for 10% MFC content is not only due to the increase in interlayer spacing, but also due to the reduced ion channels due to the mitigation of stacking phenomena.

As can be seen in FIG. 13, MFC @ Ti₃C₂T_xThe film had the largest area, consistent with the GCD curve results.

Table 1 shows the comparison of the conductivities of composite films with different MFC contents, and it can be seen that the conductivity is smaller than that of the original Ti when the content is smaller₃C₂T_xThe film is higher, which is different from the fact that the addition of the nano-cellulose immediately reduces the conductivity, which also shows the advantage of the micro-cellulose in improving the overall performance of the film: the mechanical property is improved under the condition of not reducing the conductivity.

TABLE 1

Claims

1. A preparation method of a microfibrillated cellulose/MXene composite film is characterized in that the preparation method of the microfibrillated cellulose/MXene composite film is completed according to the following steps:

adding LiF into HCl solution, stirring at room temperature until the LiF is completely dissolved, and then adding Ti under the condition of ice-water bath₃AlC₂Then reacting at 30-35 ℃ in nitrogen atmosphere for 18 DEG Ch to 28h to obtain reaction liquid;

the mass fraction of the microfibrillated cellulose solution in the step two is 0.5-0.8%, and the solvent is water;

the shaking time in the step two is 5min to 10 min;

thirdly, adding MFC @ Ti₃C₂T_xAnd (3) passing the microgel through a mixed cellulose membrane with the aperture of 0.22 mu m, performing vacuum filtration, and drying at room temperature to obtain the microfibrillated cellulose/MXene composite membrane.

2. The method for preparing a micronized cellulose/MXene composite film according to claim 1, wherein the HCl solution has a concentration of 8mol/L to 10mol/L in the first step.

3. The method for preparing the microfibrillated cellulose/MXene composite film according to claim 1, wherein the ratio of the mass of LiF to the volume of HCl solution in the first step (1 g-2 g) is 20 mL.

4. The method for preparing a micronized cellulose/MXene composite film according to claim 1, wherein Ti is as described in step one >₃AlC₂The ratio of the mass of (1) to the volume of the HCl solution (0.5g to 1.5g) was 20 mL.

5. The method of claim 1The preparation method of the microfibrillated cellulose/MXene composite film is characterized in that the ultrasonic power in the first step is 100W-300W, and the ultrasonic time is 50 min-70 min; the small layer of greenish black Ti in the step one₃C₂T_xThe concentration of the colloid supernatant is 5 mg/mL-6 mg/mL.

6. The method for preparing the microfibrillated cellulose/MXene composite film according to claim 1, wherein the mass fraction of the microfibrillated cellulose in the microfibrillated cellulose/MXene composite film in the step three is 10-30%.

7. The method for preparing the microfibrillated cellulose/MXene composite film according to claim 6, wherein the mass fraction of the microfibrillated cellulose in the microfibrillated cellulose/MXene composite film in the step three is 10-20%.

8. The use of a microfibrillated cellulose/MXene composite film according to claim 1 for producing a capacitor negative electrode material.