CN111233037A - Nb-shaped alloy2O5Preparation method and application of nanorod - Google Patents

Nb-shaped alloy2O5Preparation method and application of nanorod Download PDF

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CN111233037A
CN111233037A CN202010057287.7A CN202010057287A CN111233037A CN 111233037 A CN111233037 A CN 111233037A CN 202010057287 A CN202010057287 A CN 202010057287A CN 111233037 A CN111233037 A CN 111233037A
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mxenes
solution
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niobium
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CN111233037B (en
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原长洲
秦理
刘洋
侯林瑞
徐森炀
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University of Jinan
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    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/04—Hybrid capacitors
    • H01G11/06—Hybrid capacitors with one of the electrodes allowing ions to be reversibly doped thereinto, e.g. lithium ion capacitors [LIC]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
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    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
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    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H01G11/50—Electrodes characterised by their material specially adapted for lithium-ion capacitors, e.g. for lithium-doping or for intercalation
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Abstract

The invention belongs to the technical field of nano material preparation and the field of new energy, and particularly relates to Nb2O5A preparation method and application of the nano-rod. The Nb2O5The diameter and the length of the nano rod are 20-100 nm and 100-900 nm respectively. The preparation method comprises the steps of putting multiple layers of MXenes into a tetramethylammonium hydroxide solution, heating and stirring to obtainThe obtained upper layer solution is the few-layer MXenes solution. And transferring the small-layer niobium-based MXenes solution into a reaction kettle, heating, cooling, centrifuging and drying to obtain the final product. The invention adopts a simple hydrothermal method to convert the two-dimensional MXenes material into the one-dimensional nanorod, and the nanorod has uniform structure and extremely high crystallization degree. When the material is used as a negative electrode material of a lithium ion capacitor, an ion diffusion path can be shortened due to a nano-sized structure, so that a faster charge and discharge process and excellent cycle performance are shown.

Description

Nb-shaped alloy2O5Preparation method and application of nanorod
Technical Field
The invention belongs to the technical field of nano materials and the field of new energy, and particularly relates to Nb2O5A preparation method and application of the nano-rod.
Technical Field
The lithium ion capacitor is a novel electrochemical energy storage device, the positive electrode adopts a double electric layer capacitor porous carbon material, and the negative electrode adopts an embedded lithium ion battery negative electrode material, so that the lithium ion capacitor has the dual characteristics of a battery and a capacitor. It has higher power density and more stable cycle performance than a lithium ion battery, and has higher energy density than an electric double layer capacitor. At present, the biggest problem of lithium ion capacitors is unbalanced reaction kinetics between positive and negative electrodes, and the key for solving the problem is to find a high-power negative electrode material.
The two-dimensional transition metal carbide or nitride (MXenes) has high chemical stability, conductivity, hydrophilicity and specific surface area, and has attractive application prospect in the fields of energy, photoelectricity, biology and the like. However, the MXenes materials are further applied due to the defects of no obvious discharge platform, low coulombic efficiency for the first time, easy stacking of nano-layer sheets and the like. And Nb derived from niobium-based MXenes2O5As a typical semiconductor material, the material has excellent physicochemical properties, is applied to the fields of catalysis, gas sensors, microelectronics, solar energy and the like, particularly has the characteristic of quick charge and discharge when being used as a negative electrode material of a lithium ion capacitor, can solve the problem of unmatched dynamics of a positive electrode and a negative electrode when being used as the negative electrode material of the lithium ion capacitor, and has potential commercial value. At present about Nb2O5The reports of nanorod synthesis are relatively few, such as the synthesis of Huang Meng in 2013 with NbCl5Is a niobium source and is reacted by a solvothermal method 7The method needs a plurality of solvents and has longer reaction time for preparing the nano rod within 2 hours. For another example, 2018 Severe Hai et al, Nb prepared by hydrothermal method using potassium fluoroniobate as niobium source2O5Although the method adopts a single reagent, the temperature required in the process is overhigh, and the requirement on instruments is severe. Overall, current Nb2O5The synthesis method of the nano-rod is generally complicated and has the characteristics of high cost or high energy consumption, and the synthesized Nb2O5The nanorods are less uniform. This limits Nb to some extent2O5The application and popularization of the nano-rod in industrial production.
Disclosure of Invention
In order to overcome the defects, the invention derives Nb from few-layer niobium-based MXenes2O5Nanorod, compared with the existing synthesized Nb2O5In the method of the nanorod, the nanorod only needs a few layers of MXenes as a niobium source to perform simple hydrothermal reaction, no other reagent needs to be added, and the prepared nanorod has a stable structure, good uniformity, high crystallization degree and low cost.
The purpose of the invention is realized by the following scheme:
nb-shaped alloy2O5The preparation method of the nano-rod comprises the following steps:
(1) placing multilayer niobium-based MXenes in a tetramethylammonium hydroxide solution, heating to 25-55 ℃, and stirring for 6-24 hours;
(2) centrifuging the solution obtained in the step (1), pouring out the upper layer liquid, adding deionized water, shaking to disperse the lower layer MXenes, and centrifuging to obtain an upper layer solution, namely a few-layer MXenes solution;
(3) putting the few-layer niobium-based MXenes solution obtained in the step (2) into a reaction kettle;
(4) carrying out hydrothermal reaction on the reaction kettle in the step (3), wherein the temperature of the hydrothermal reaction is 100-220 ℃, and the reaction time is 6-24 h;
(5) after the hydrothermal reaction in the step (4) is finished, the solution is naturally cooled to room temperature, the solution is centrifuged, and the precipitate is dried to obtain pseudo-hexagonal crystal form Nb2O5And (4) nanorods.
Preferably, the multilayer niobium-based mxenees in step (1) is prepared by the following method:
(1) mixing Nb with2Placing AlC in hydrofluoric acid with the mass fraction concentration of 50%, and etching at normal temperature for 90 hours;
(2) centrifuging the etched solution in the step (1), and cleaning until the pH value is 6;
(3) and (3) pouring out the supernatant of the product obtained in the step (2), and drying the lower-layer precipitate to obtain the multilayer niobium-based MXenes.
Preferably, the concentration of the niobium-based MXenes with a small layer in the step (1) is 0.1-10 mol/L.
Preferably, the filling volume of the solution in the reaction kettle in the step (3) is 40-80% of the volume of the container.
Preferably, the specific preparation method adopts the following steps:
(1) firstly 2g of Nb2Placing AlC in 20ml of hydrofluoric acid with the mass fraction concentration of 50%, and etching at normal temperature for 90 hours;
(2) centrifuging the etched liquid in the step (1), and repeatedly cleaning with deionized water and absolute ethyl alcohol until the pH value is 6;
(3) pouring out supernatant liquor of the product obtained in the step (2), taking the lower-layer precipitate, and placing the lower-layer precipitate in a vacuum drying oven for drying to obtain multiple layers of MXenes;
(4) putting 1 g of the multilayer niobium-based MXenes obtained in the step (3) into 10 ml of 25% tetramethylammonium hydroxide solution, heating to 25-55 ℃, and stirring for 6-24 hours;
(5) centrifuging the solution obtained in the step (4) by using a centrifugal machine, pouring the upper layer liquid obtained for the first time, adding deionized water into the centrifugal tube, then ultrasonically or forcibly shaking to re-disperse the lower layer MXenes, and centrifuging by using the centrifugal machine to obtain the upper layer solution, namely the lower layer MXenes solution;
(6) putting 20 ml-40 ml of the few-layer niobium-based MXenes obtained in the step (5) into a 50ml reaction kettle;
(7) placing the reaction kettle in the step (6) in an oven, and reacting for 6-24 hours at 100-220 ℃;
(8) naturally cooling to room temperature, taking out the solution obtained in the step (7) to a centrifuge tube, centrifuging to collect white precipitate, and drying in an oven to obtain the pseudo hexagonal crystal form Nb2O5And (4) nanorods.
Nb prepared by the method2O5Nanorods, said Nb2O5The nano-rods are in a pseudo-hexagonal crystal form; the Nb2O5The diameter of the nano rod is 20-100 nm; the length is 100 to 900 nm.
One kind of Nb2O5Application of nano-rod, the described Nb2O5The nano-rod is used as the cathode material of the lithium ion capacitor. Advantageous effects
On the basis of the few-layer niobium-based MXenes, no other solvent is needed to be added, only the few-layer niobium-based MXenes are needed to be used as a niobium source, a simple hydrothermal reaction is carried out, the conversion from a two-dimensional nanosheet to a one-dimensional nanorod structure is realized, and the Nb is2O5The diameter and the length of the nanorod are 20-100 nm and 100-900 nm respectively, and the nanorod is uniform in structure and high in crystallization degree. When the nano-sized lithium ion capacitor cathode material is used as a lithium ion capacitor cathode material, compared with a micron-sized nanorod, a nano-sized structure can shorten an ion diffusion path, so that a faster charge and discharge process and excellent cycle performance are shown.
Description of the drawings fig. 1 is an XRD image of few-layer niobium-based MXenes, examples and comparative examples;
FIG. 2 is an SEM image (a) and a TEM image (b) of a less niobium-based MXenes solution used in example 1;
FIG. 3 shows Nb prepared in example 12O5SEM image (a) and TEM image (b) of nanorods;
FIG. 4 shows Nb prepared in example 22O5SEM image of the nano-rod;
FIG. 5 shows Nb prepared in example 32O5SEM image of the nano-rod;
FIG. 6 is a graph of Nb prepared in comparative example 12O5SEM image of the nano-rod;
fig. 7 is a few-layer niobium-based MXenes image prepared in comparative example 2;
FIG. 8 is an image of the nanorod prepared in comparative example 2;
FIG. 9 shows Nb prepared in comparative example 32O5A bar image;
fig. 10 is a graph of cycle performance for each example and comparative example.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Example 1
This embodiment provides a Nb2O5The preparation method of the nano rod comprises the following steps:
(1) firstly 2g of Nb2Placing AlC in 20ml of hydrofluoric acid with the mass fraction concentration of 50%, and etching at normal temperature for 90 hours;
(2) centrifuging the etched liquid in the step (1), and repeatedly cleaning with deionized water and absolute ethyl alcohol until the pH value is 6;
(3) pouring out supernatant liquor of the product obtained in the step (2), taking the lower-layer precipitate, and placing the lower-layer precipitate in a vacuum drying oven for drying to obtain multiple layers of MXenes;
(4) placing the multilayer niobium-based MXenes obtained in the step (3) in a tetramethylammonium hydroxide solution, and heating and stirring for 24 hours at 25 ℃;
(5) centrifuging the solution obtained in the step (4) by using a centrifugal machine, pouring the upper layer liquid obtained for the first time, adding deionized water into the centrifugal tube, then ultrasonically or forcibly shaking to re-disperse the lower layer MXenes, and centrifuging by using the centrifugal machine to obtain the upper layer solution, namely the lower layer MXenes solution;
(6) and (3) putting 20ml of the small-layer niobium-based MXenes obtained in the step (5) into a 50ml reaction kettle.
(7) Placing the reaction kettle in the step (6) in an oven, and reacting for 6 hours at 240 ℃;
(8) naturally cooling to room temperatureAnd (3) taking out the solution obtained in the step (7) into a centrifugal tube, centrifuging at 10000 r/min to collect white precipitate, and drying in an oven to obtain the pseudo-hexagonal crystal form Nb with the diameter of 20-50 nm and the length of 100-500 nm2O5And (4) nanorods.
Example 2
This embodiment provides a Nb2O5The preparation method of the nano rod comprises the following steps:
(1) firstly 2g of Nb2And placing the AlC in 20ml of hydrofluoric acid with the mass fraction concentration of 50%, and etching at normal temperature for 90 hours.
(2) Centrifuging the etched liquid in the step (1), and repeatedly cleaning with deionized water and absolute ethyl alcohol until the pH value is 6;
(3) pouring out supernatant liquor of the product obtained in the step (2), taking the lower-layer precipitate, and placing the lower-layer precipitate in a vacuum drying oven for drying to obtain multiple layers of MXenes;
(4) placing the multilayer niobium-based MXenes obtained in the step (3) in a tetramethylammonium hydroxide solution, and heating and stirring for 24 hours at the temperature of 35 ℃;
(5) centrifuging the solution obtained in the step (4) by using a centrifugal machine, pouring the upper layer liquid obtained for the first time, adding deionized water into the centrifugal tube, then ultrasonically or forcibly shaking to re-disperse the lower layer MXenes, and centrifuging by using the centrifugal machine to obtain the upper layer solution, namely the lower layer MXenes solution;
(6) and (3) putting 40ml of the small-layer niobium-based MXenes obtained in the step (5) into a 50ml reaction kettle.
(7) Placing the reaction kettle in the step (6) in an oven, and reacting for 24 hours at 180 ℃;
(8) naturally cooling to room temperature, taking out the solution obtained in the step (7) to a centrifugal tube, centrifuging at 10000 r/min to collect white precipitate, and drying in an oven to obtain pseudo-hexagonal crystal Nb with the diameter of 50-100 nm and the length of 500-900 nm2O5And (4) nanorods.
Example 3
This embodiment provides a Nb2O5The preparation method of the nano rod comprises the following steps:
(1) firstly 2g of Nb2Placing AlC in 20ml of hydrofluoric acid with the mass fraction concentration of 50%, and etching at normal temperature for 90 hours;
(2) centrifuging the etched liquid in the step (1), and repeatedly cleaning with deionized water and absolute ethyl alcohol until the pH value is 6;
(3) pouring out supernatant liquor of the product obtained in the step (2), taking the lower-layer precipitate, and placing the lower-layer precipitate in a vacuum drying oven for drying to obtain multiple layers of MXenes;
(4) placing the multilayer niobium-based MXenes obtained in the step (3) in a tetramethylammonium hydroxide solution, and heating and stirring for 6 hours at the temperature of 55 ℃;
(5) centrifuging the solution obtained in the step (4) by using a centrifugal machine, pouring the upper layer liquid obtained for the first time, adding deionized water into the centrifugal tube, then ultrasonically or forcibly shaking to re-disperse the lower layer MXenes, and centrifuging by using the centrifugal machine to obtain the upper layer solution, namely the lower layer MXenes solution;
(6) putting 40ml of the few-layer niobium-based MXenes obtained in the step (5) into a 50ml reaction kettle;
(7) placing the reaction kettle in the step (6) in an oven, and reacting for 12 hours at 100 ℃;
(8) naturally cooling to room temperature, taking out the solution obtained in the step (7) to a centrifugal tube, centrifuging at 10000 r/min to collect white precipitate, and drying in an oven to obtain the pseudo-hexagonal crystal form Nb with the diameter of 20-50 nm and the length of 300-600 nm2O5And (4) nanorods.
Comparative example 1
(1) Firstly 2g of Nb2Placing AlC in 20ml of hydrofluoric acid with the mass fraction concentration of 50%, and etching at normal temperature for 90 hours;
(2) centrifuging the etched liquid in the step (1), and repeatedly cleaning with deionized water and absolute ethyl alcohol until the pH value is 6;
(3) pouring out supernatant liquor of the product obtained in the step (2), taking the lower-layer precipitate, and placing the lower-layer precipitate in a vacuum drying oven for drying to obtain multiple layers of MXenes;
(4) placing the multilayer niobium-based MXenes obtained in the step (3) in a tetramethylammonium hydroxide solution, and heating and stirring for 24 hours at the temperature of 35 ℃;
(5) centrifuging the solution obtained in the step (4) by using a centrifugal machine, pouring the upper layer liquid obtained for the first time, adding deionized water into the centrifugal tube, then ultrasonically or forcibly shaking to re-disperse the lower layer MXenes, and centrifuging by using the centrifugal machine to obtain the upper layer solution, namely the lower layer MXenes solution;
(6) and (3) putting 40ml of the small-layer niobium-based MXenes obtained in the step (5) into a 50ml reaction kettle.
(7) Placing the reaction kettle in the step (6) in an oven, and reacting for 3 hours at 180 ℃;
(8) after naturally cooling to room temperature, taking out the solution in the step (7) in a centrifuge tube, centrifuging at 10000 r/min to collect precipitates and drying in an oven. Nb prepared from this example2O5The nanometer rod SEM image shows that the few-layer niobium-based MXenes is in a transition state after being hydrothermal for 3 hours, and the few-layer niobium-based MXenes is converted into Nb2O5The nanorods are transformed and do not grow completely into rod-like structures.
Comparative example 2
(1) Firstly 2g of Nb2Placing AlC in 20ml of hydrofluoric acid with the mass fraction concentration of 50%, and etching at normal temperature for 90 hours;
(2) centrifuging the etched liquid in the step (1), and repeatedly cleaning with deionized water and absolute ethyl alcohol until the pH value is 6;
(3) pouring out supernatant liquor of the product obtained in the step (2), taking the lower-layer precipitate, and placing the lower-layer precipitate in a vacuum drying oven for drying to obtain multiple layers of MXenes;
(4) placing the multilayer niobium-based MXenes obtained in the step (3) in a tetramethylammonium hydroxide solution, and heating and stirring for 3 hours at the temperature of 35 ℃;
(5) centrifuging the solution obtained in the step (4) by using a centrifugal machine, pouring the upper layer liquid obtained for the first time, adding deionized water into the centrifugal tube, then ultrasonically or forcibly shaking to re-disperse the lower layer MXenes, and centrifuging by using the centrifugal machine to obtain the upper layer solution, namely the lower layer MXenes solution;
(6) putting 40ml of the few-layer niobium-based MXenes obtained in the step (5) into a 50ml reaction kettle;
(7) placing the reaction kettle in the step (6) in an oven, and reacting for 6 hours at 180 ℃;
(8) after naturally cooling to room temperature, taking out the solution in the step (7) in a centrifuge tube, then centrifuging at 10000 r/min to collect precipitates and drying in an oven. From the SEM image of this comparative example it can be seen that the multilayer MXenes were not completely converted to few layers of MXenes, with partially disordered and thicker lamellae. The few-layer niobium-based MXenes are not completely converted into Nb2O5Nanorods and MXenes are agglomerated.
Comparative example 3
(1) Firstly 2g of Nb2Placing AlC in 20ml of hydrofluoric acid with the mass fraction concentration of 50%, and etching at normal temperature for 90 hours;
(2) centrifuging the etched liquid in the step (1), and repeatedly cleaning with deionized water and absolute ethyl alcohol until the pH value is 6;
(3) pouring out supernatant liquor of the product obtained in the step (2), taking the lower-layer precipitate, and placing the lower-layer precipitate in a vacuum drying oven for drying to obtain multiple layers of MXenes;
(4) placing the multilayer niobium-based MXenes obtained in the step (3) in a tetramethylammonium hydroxide solution, and heating and stirring for 24 hours at the temperature of 35 ℃;
(5) centrifuging the solution obtained in the step (4) by using a centrifugal machine, pouring the upper layer liquid obtained for the first time, adding deionized water into the centrifugal tube, then ultrasonically or forcibly shaking to re-disperse the lower layer MXenes, and centrifuging by using the centrifugal machine to obtain the upper layer solution, namely the lower layer MXenes solution;
(6) putting 40ml of the few-layer niobium-based MXenes obtained in the step (5) into a 50ml reaction kettle;
(7) placing the reaction kettle in the step (6) in an oven, and reacting for 36 hours at 180 ℃;
(8) after naturally cooling to room temperature, taking out the solution in the step (7) in a centrifuge tube, and then centrifuging at 10000 r/min to collect white precipitate and drying in an oven. Nb prepared by this comparative example2O5The rod image reveals that the length of the rod grows from nanometer scale to micrometer scale.
Fig. 1 is an XRD pattern of few-layer niobium-based MXenes, example 1, example 2, and comparative example 1. Firstly, the figure shows that few-layer niobium-based MXenes are successfully prepared, and nanorods derived from the niobium-based MXenes are pseudo hexagonal Nb crystals2O5. Examples 1 and 2 prolong the hydrothermal reaction time to produce Nb2O5And (4) nanorods. The XRD pattern of the comparative example shows that few niobium based MXenes were gradually oxidized to Nb after 3 hours of hydrothermal treatment2O5，But some diffraction peaks are not evident.
FIG. 2 shows SEM images (a) and TEM images (b) of the niobium-less group MXenes used in example 1.
FIG. 3 is an SEM image (a) and a TEM image (b) of a less niobium-based MXenes solution used in example 1; from FIG. 3, it can be seen that Nb is produced2O5The nano-rod has the advantages of uniform structure, small size, good dispersibility and high crystallization degree.
FIG. 4 shows Nb prepared in example 22O5SEM image of the nano-rod; compared with the embodiment 1, the size of the nano rod is increased by prolonging the hydrothermal time of the niobium-based MXenes solution with few layers, the structure of the nano rod is uniform and has good dispersibility, and the crystallization degree is very high.
FIG. 5 shows Nb prepared in example 32O5SEM image of the nano-rod; compared with the embodiment 1, the nano-rod can still be obtained by changing the temperature of the hydrothermal reaction, and the obtained nano-rod has the advantages of uniform structure, small size, good dispersibility and high crystallization degree.
FIG. 6 is a graph of Nb prepared in comparative example 12O5SEM image of the nano-rod; it can be seen that the small-layer niobium-based MXenes is in a transition state after being hydrothermal for 3 hours, and the small-layer niobium-based MXenes is converted into Nb2O5The nanorods are transformed and do not grow completely into rod-like structures.
FIG. 7 is an image of intercalated niobium-based MXenes of comparative example 2; it can be seen that instead of converting the multi-layer MXenes completely to less-layer MXenes, there are partially disordered and thicker plies.
FIG. 8 is an image of the nanorod prepared in comparative example 2; it can be seen thatThe few-layer niobium-based MXenes are not completely converted into Nb due to the influence of the few-layer niobium-based MXenes2O5Nanorods and MXenes are agglomerated.
FIG. 9 shows Nb prepared in comparative example 32O5A bar image; it can be seen that the length of the rods grew from the nanometer scale to the micrometer scale due to the prolonged hydrothermal reaction time.
Performance test of lithium ion capacitor cathode material
And (4) performing a performance test on the lithium ion capacitor cathode material by using a button type half cell. To prepare the working electrode, an active material, acetylene black and PVDF in a mass ratio of 7:2:1 were mixed in NMP to prepare a uniform slurry. The resulting slurry was then coated onto a copper foil and vacuum dried at 110 ℃ for 11 hours. The half cell was assembled using lithium metal as the counter electrode, followed by Ar atmosphere glove box.
To highlight the conversion of two-dimensional MXenes to one-dimensional Nb2O5Advantages of nanorod Performance We performed performance tests on nanorods of each example and comparative example, which are active materials, respectively (see FIG. 10). The current density used in the test was 100mA g-1It can be clearly seen that the Nb prepared by the invention2O5Compared with a comparative example, the nanorod has higher specific capacity and higher first coulombic efficiency.
The technical features of the above examples and comparative examples can be arbitrarily combined, and for the sake of brevity of description, reduction of the variables of the comparative experiment, and increase of the reliability of the results of the comparative experiment, all the possible technical features in the examples are not described, but should be considered as the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express the centralized implementation mode of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims (7)

1. Nb-shaped alloy2O5The preparation method of the nano-rod is characterized by comprising the following steps:
(1) placing multilayer niobium-based MXenes in a tetramethylammonium hydroxide solution, heating to 25-55 ℃, and stirring for 6-24 hours;
(2) centrifuging the solution obtained in the step (1), pouring out the upper layer liquid, adding deionized water, vibrating to disperse the lower layer MXenes, and centrifuging to obtain the upper layer solution, namely the less layer MXenes solution;
(3) putting the few-layer niobium-based MXenes solution obtained in the step (2) into a reaction kettle;
(4) carrying out hydrothermal reaction on the reaction kettle in the step (3), wherein the temperature of the hydrothermal reaction is 100-220 ℃, and the reaction time is 6-24 h; (ii) a
(5) After the hydrothermal reaction in the step (4) is finished, the solution is naturally cooled to room temperature for centrifugation, and the precipitate is dried to obtain Nb2O5And (4) nanorods.
2. Nb in accordance with claim 12O5The preparation method of the nanorod is characterized in that the multilayer niobium-based MXenes prepared in the step (1) is prepared by adopting the following method:
(1) mixing Nb with2Placing AlC in hydrofluoric acid to etch for 90 hours at normal temperature;
(2) centrifuging the etched solution in the step (1), and cleaning until the pH value is 6;
(3) and (3) pouring out the supernatant of the product obtained in the step (2), and drying the lower-layer precipitate to obtain the multilayer niobium-based MXenes.
3. Nb in accordance with claim 12O5The preparation method of the nanorod is characterized in that the concentration of the few-layer niobium-based MXenes in the step (1) is 0.1-10 mol/L.
4. According to the claimsNb in accordance with claim 12O5The preparation method of the nano-rod is characterized in that the filling volume of the solution in the reaction kettle in the step (3) is 40-80% of the volume of the container.
5. The method according to any one of claims 1 to 4, characterized in that the specific preparation method comprises the following steps:
(1) firstly 2g of Nb2Placing AlC in 20ml of hydrofluoric acid with the mass fraction concentration of 50%, and etching at normal temperature for 90 hours;
(2) centrifuging the etched liquid in the step (1), and repeatedly cleaning with deionized water and absolute ethyl alcohol until the pH value is 6;
(3) pouring out supernatant liquor of the product obtained in the step (2), taking the lower-layer precipitate, and placing the lower-layer precipitate in a vacuum drying oven for drying to obtain multiple layers of MXenes;
(4) taking 1 g of the multilayer niobium-based MXenes obtained in the step (3), placing the multilayer niobium-based MXenes in 10 ml of tetramethylammonium hydroxide solution with the mass fraction concentration of 25%, and heating and stirring the mixture at the temperature of 35 ℃ for 24 hours;
(5) centrifuging the solution obtained in the step (4) by using a centrifugal machine, pouring the upper layer liquid obtained for the first time, adding deionized water into the centrifugal tube, then ultrasonically or forcibly shaking to re-disperse the lower layer MXenes, and centrifuging by using the centrifugal machine to obtain the upper layer solution, namely the less layer MXenes solution;
(6) putting 20 ml-40 ml of the few-layer niobium-based MXenes obtained in the step (5) into a 50ml reaction kettle;
(7) placing the reaction kettle in the step (6) in an oven, and reacting for 6-24 hours at 100-220 ℃;
(8) naturally cooling to room temperature, taking out the solution obtained in the step (7) to a centrifuge tube, centrifuging to collect white precipitate, and drying in an oven to obtain the pseudo hexagonal crystal form Nb2O5And (4) nanorods.
6. Nb prepared by the method of any one of claims 1 to 52O5Nanorods, characterized in that the Nb is2O5The nano-rods are in a pseudo-hexagonal crystal form; the Nb2O5The diameter of the nano rod is 20-100 nm; the length is 100 to 900 nm.
7. An Nb in accordance with claim 62O5The application of the nano-rod is characterized in that the Nb is2O5The nano-rod is used as the cathode material of the lithium ion capacitor.
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