CN114039060B - N-TiO 2 /Ti 3 C 2 T x Heterogeneous MXene structural material, preparation and application thereof - Google Patents
N-TiO 2 /Ti 3 C 2 T x Heterogeneous MXene structural material, preparation and application thereof Download PDFInfo
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Abstract
The invention provides an N-TiO 2 /Ti 3 C 2 T x Heterogeneous MXene structural material, microstructure of which is accordion-shaped and N-doped nano TiO 2 The particles are uniformly distributed in the accordion shape Ti 3 C 2 T x And interlaminar surfaces. N-TiO prepared by the invention 2 /Ti 3 C 2 T x The specific surface area of the structure is large, the structure contains mesoporous structure, and Ti is used as 3 C 2 T x As a substrate, the electron transfer is fast, and the conductivity is strong; N-TiO grown on a substrate 2 The nano structure has small size and uniform particle size, can not self-aggregate in the running process of the battery, and the catalytic active sites of oxygen evolution reaction (ORR) and oxygen reduction reaction (OER) are highly exposed, so that the composite material has high-efficiency catalytic activity, and in addition, N-TiO 2 The nano structure also has isolation effect and prevents Ti from 3 C 2 T x The accumulation of the nano sheets can provide enough storage space for discharge products and can greatly improve Li-O 2 Electrochemical performance of the cell. The preparation method has the advantages of environment friendliness, simplicity, high efficiency, low cost and the like.
Description
Technical Field
The invention belongs to the technical field of electrode materials, and in particular relates to N-TiO 2 /Ti 3 C 2 T x Heterogeneous MXene structural materials, preparation and application thereof.
Background
With the gradual popularization of new energy technology, the fields of power transportation and power grid energy storage are rapidly developed. Rechargeable lithium-air batteries due to their extremely high theoretical specific energy density (11400 Wh kg -1 ) The electric vehicle can meet the driving mileage requirement of the electric vehicle and is widely paid attention to. Although lithium air batteries store energy in the next generationThe device has remarkable application potential, but some problems still need to be solved to realize commercial application. For example, the development prospects of lithium-air batteries are limited by their slow kinetics, resulting in excessive overpotential, low round trip efficiency, poor rate capability, limited cycling stability, and the like. In order to solve the problem of slow dynamics of the lithium-air battery and improve the battery performance, researchers propose that developing a cathode electrode reaction catalyst with high catalytic activity is a key to promoting the development to the application of the lithium-air battery.
MXene is a two-dimensional material emerging in recent years, the precursor of which is a MAX phase, from which a is removed by selective etching to obtain a graphene-like two-dimensional structure material, and thus MXene is essentially a transition metal carbo/nitride (TMC/TMN). Hydrophilic functional groups such as-OH, -F, -O and the like and some defects can be generated in the preparation process of the MXene by etching, and the surface functional groups endow the MXene with hydrophilicity and surface structure adjustability, namely the MXene not only has the characteristics of high specific surface area, abundant surface pi electrons and catalytic active sites of the conventional two-dimensional material, but also has the advantages of certain hydrophilicity and surface structure adjustability, based on the characteristics, scientific researches on MXene are greatly conducted by scientific researchers, including the utilization of the characteristic of high specific surface area of the MXene as a lithium-air battery cathode reaction catalyst carrier, the preparation of a high-efficiency lithium-air battery cathode catalyst by utilizing the surface functional groups for modification, the preparation of the high-efficiency lithium-air battery cathode reaction catalyst by compounding other catalysts, and the like.
The prior art has patent CN202110479555.9 discloses a Co 3 O 4 MXene composite catalyst, preparation method and application thereof, co 3 O 4 The preparation method of the/MXene composite catalyst comprises the following steps: preparation of Co by MXene, cobalt salt and precipitant through in-situ hydrothermal method 3 O 4 MXene composite catalytic material. Patent CN202010922696.9 discloses an ultrathin flexible air electrode material, a lithium air battery and a preparation method thereof, wherein the ultrathin flexible air electrode material is formed by carrying out electrostatic self-assembly on a two-dimensional Co-MOF nano sheet and a two-dimensional MXene through an intercalation finite field engineering technology. The technology is to prepare the negative electrode material of the lithium-air battery by using MXeneThe prepared anode material not only has good conductivity, but also has rich active sites, namely, the diffusion rate of lithium ions is improved, and the anode material also has good catalytic activity. However, the structural characteristics of MXene itself are prone to collapse and pile up, and as an electrode material, battery performance is affected. In addition, the presence of metastable Ti atoms and inert functional groups on the two-dimensional MXene surface greatly limits its application in electrocatalytic reactions. Therefore, improvement is needed for the MXene, so that an MXene-based negative electrode material which is not easy to collapse and accumulate is prepared, catalytic active sites are increased, the material has high catalytic activity and conductivity, and the prepared lithium-air battery has good electrochemical performance.
Disclosure of Invention
To solve the above problems, an object of the present invention is to provide an N-TiO 2 /Ti 3 C 2 T x Heterogeneous MXene structural material, preparation and application thereof, wherein the material has an accordion-shaped microstructure and is N-doped with nano TiO 2 The particles are uniformly distributed in the accordion shape Ti 3 C 2 T x Is provided between the surface and the layer; the invention uses Ti 3 C 2 T x As raw material, the surface metastable Ti atoms are oxidized in situ to make the surface possess TiO 2 The nanocrystalline is then doped with N element in environment-friendly urea atmosphere to prepare the material; the heterostructure material is used as Li-O 2 The battery of the battery anode catalyst not only has high-efficiency catalytic activity and conductivity, but also has good electrochemical performance.
In order to achieve the above purpose, the invention adopts the specific technical scheme that:
N-TiO 2 /Ti 3 C 2 T x Heterogeneous MXene structural material, wherein the microstructure of the heterogeneous MXene structural material is accordion-shaped, and N-doped nano TiO 2 The particles are uniformly distributed in the accordion shape Ti 3 C 2 T x And interlaminar surfaces.
And T is a surface functional group, x is the number of the surface functional groups, and the T comprises at least one of-O, -OH, -F and-Cl.
The XRD of the heterogeneous MXene structural material has diffraction peaks of 25.3+/-0.3 degrees, 37.8+/-0.3 degrees, 48.0+/-0.3 degrees, 53.9+/-0.3 degrees, 60.8+/-0.3 degrees and 62.7+/-0.3 degrees; peaks 455.13 + -0.5 eV, 456.05 + -0.5 eV, 456.98 + -0.5 eV and 458.72 + -0.5 eV of Ti-O of Ti 2p exist in XPS of the material.
The specific surface area of the heterogeneous MXene structural material is 30-60m 2 g -1 Preferably 40-50m 2 g -1 The average pore diameter is 2 to 6nm, preferably 3 to 5nm.
N-TiO in the heterogeneous MXene structural material 2 (101) The lattice spacing of the crystal faces is 0.353-0.357nm.
The doping amount of N in the heterogeneous MXene structural material is 0.50-0.80%.
The invention also provides the N-TiO 2 /Ti 3 C 2 T x The preparation method of the heterogeneous MXene structural material comprises the following steps:
1) Ti is mixed with 3 AlC 2 Mixing powder and organic alcohol, ball milling, filtering, drying, adding HF solution into the dried powder, stirring at room temperature to react, centrifuging, washing and drying to obtain Ti 3 C 2 T x ；
2) Ti prepared in step 1) 3 C 2 T x Adding organic reducing acid into the mixed solution of water and organic alcohol, performing ultrasonic treatment, heating to react, cooling to room temperature, alternately centrifuging with organic alcohol and water, washing, and drying to obtain TiO 2 /Ti 3 C 2 T x ；
3) Urea and step 2) TiO 2 /Ti 3 C 2 T x Uniformly mixing, calcining under inert atmosphere to obtain nitrogen-doped TiO 2 /Ti 3 C 2 T x Heterojunction, i.e. N-TiO 2 /Ti 3 C 2 T x 。
Ti 3 AlC 2 Is the most representative material in MAX, and can synthesize multi-layer Ti through acid etching reaction 3 C 2 T x 。
The organic alcohol in the step 1) and the step 2) is fatty alcohol of C1-C6.
Step 1) the Ti 3 AlC 2 The mass volume ratio of the powder to the organic alcohol is 1:200-400 (g: ml); the drying is not particularly limited, and is generally used in the art, and includes at least one of vacuum drying and freeze drying, preferably vacuum drying, wherein the vacuum drying temperature is 60-90 ℃ and the drying time is 6-24h; the grinding mode is not particularly limited, and comprises at least one of planetary ball milling, drum ball milling and stirring ball milling, preferably planetary ball milling, wherein the rotating speed of the planetary ball milling is 100-800r/min, and the ball milling time is 6-24h.
HF is fuming corrosive liquid, has severe pungent smell, and is used in places with good ventilation, such as fume hood, special gloves for preventing HF, etc.
The mass-volume ratio of the dried powder to the HF solution in the step 1) is 1-3:30-50 (g: ml), preferably 1-3:50, the concentration of the HF solution is 30-50wt%, the stirring reaction time is 10-30h, the washing is carried out by using deionized water until the pH of the washing solution is 5-6, the washing solution and the centrifuged supernatant are concentrated HF solution before the pH is 5-6, water is required to be added for dilution until the pH is 5-7, then the concentrated HF solution is poured into a waste liquid barrel, and the vacuum drying temperature is 60-90 ℃ for 12-24h.
Step 2) the organic reducing acid includes, but is not limited to, at least one of citric acid, ammonium citrate, oxalic acid, ammonium oxalate, L-ascorbic acid, D-ascorbic acid methanesulfonic acid, ammonium methylsulfonate; the Ti is 3 C 2 T x The weight ratio of organic reducing acid, water and organic alcohol is 1:4-6:200-800:200-400, wherein the ultrasonic time is 1-3h, the ultrasonic power is 20-50W, the temperature is raised to 150-200 ℃, the heating reaction time is 6-12h, the times of alternating washing of ethanol and deionized water is 3-5 times, the drying is vacuum drying, the vacuum drying temperature is 60-100 ℃, and the drying time is 6-12h.
Step 3) the urea and TiO 2 /Ti 3 C 2 T x The mass ratio of (2) is 40-60:1, the calcination temperature is 300-500 ℃, and the calcination time is1-3h。
The invention also provides the N-TiO 2 /Ti 3 C 2 T x Application of heterostructures as Li-O 2 Cathode electrode material of the battery.
Compared with the prior art, the invention has the beneficial effects that:
N-TiO prepared by the invention 2 /Ti 3 C 2 T x The specific surface area of the structure is large, the structure contains mesoporous structure, and Ti is used as 3 C 2 T x As a substrate, the electronic transmission is fast, and the conductivity is strong; N-TiO grown on a substrate 2 The nano structure has small size and uniform particle size, can not self-aggregate in the running process of the battery, and the catalytic active sites of oxygen evolution reaction (ORR) and oxygen reduction reaction (OER) are highly exposed, so that the composite material has high-efficiency catalytic activity, and in addition, N-TiO 2 The nano structure also has isolation effect and prevents Ti from 3 C 2 T x The accumulation of the nano sheets can provide enough storage space for discharge products and can greatly improve Li-O 2 Electrochemical performance of the cell.
The preparation method has the advantages of environment friendliness, simplicity, high efficiency, low cost and the like.
Drawings
FIG. 1 is N-TiO prepared in preparation example 1 2 /Ti 3 C 2 T x XRD test results of heterostructures;
FIG. 2 is N-TiO prepared in preparation example 1 2 /Ti 3 C 2 T x Microscopic photograph of heterostructure material, SEM (a), TEM (b), HRTEM (c);
FIG. 3 is the result of XPS analysis of preparation example 1;
FIG. 4 is N-TiO prepared in preparation example 1 2 /Ti 3 C 2 T x Nitrogen adsorption and desorption isotherms of heterostructures (aperture distribution diagram in inset);
FIG. 5 is a graph showing the results of the electrochemical performance test of example 1.
Detailed Description
The invention is further illustrated below in connection with specific examples, but is not limited to the disclosure. If no special description exists, the parts are parts by weight in the embodiment of the invention. All reagents used are those commercially available in the art.
N-TiO 2 /Ti 3 C 2 T x Preparation of electrode composite material
Preparation example 1
1) First, 5g of Ti 3 AlC 2 Mixing the powder with 1000ml of absolute ethyl alcohol, ball milling for 6 hours at a rotating speed of 500r/min, filtering, vacuum drying at 80 ℃ for 12 hours to obtain dry powder, adding 3 batches of 1.2g of dry powder into 20ml of 40wt% HF solution in a fume hood, stirring and reacting for 24 hours at room temperature, centrifuging after the reaction is finished, flushing centrifugal solid precipitate with deionized water for 3 times till the pH value is 5, mixing centrifugal liquid and washing liquid, diluting the centrifugal liquid and washing liquid with water till the pH value is 6, pouring the washing liquid into a waste liquid barrel together, and finally placing the centrifugal precipitate into a vacuum oven at 70 ℃ for drying for 24 hours to obtain Ti 3 C 2 T x ；
2) 0.1g of Ti prepared in step 1) was reacted with 3 C 2 T x Adding 0.6g of ascorbic acid into a mixed solution of 30g of ionized water and 30g of ethanol, performing ultrasonic treatment for 2 hours at the power of 40W, then pouring the mixed solution into a 100ml autoclave, heating to 180 ℃ for reaction for 10 hours, cooling to room temperature, filtering, alternately centrifuging and washing with ethanol and deionized water for 3 times, and performing vacuum drying at 100 ℃ for 10 hours to obtain TiO 2 /Ti 3 C 2 T x ；
3) 6g of urea and 0.1g of TiO from step 2) are reacted with 2 /Ti 3 C 2 T x Mixing uniformly, placing in a tube furnace, calcining at 500 ℃ for 2 hours under argon atmosphere to obtain nitrogen-doped TiO 2 /Ti 3 C 2 T x Heterojunction, i.e. N-TiO 2 /Ti 3 C 2 T x 。
Preparation example 2
The remainder was the same as in preparation example 1 except that step 1) 1.2g of the dry powder was added in an average of 3 batches to 60ml of 40wt% HF solution in a fume hood.
Preparation example 3
The remainder was the same as in preparation example 1 except that the amount of ascorbic acid was 0.4g.
Preparation example 4
The remainder was the same as in preparation example 1 except that the deionized water was used in an amount of 40g and ethanol was used in an amount of 20g in step 2).
Preparation example 5
The remainder was the same as in preparation example 1, except that the urea was used in an amount of 4g in step 3).
Preparation example 6
The remainder is the same as in preparation example 1, except that in step 3) urea is used in an amount of 1g.
Preparation example 7
The remainder was the same as in preparation example 1, except that in step 3) urea was used in an amount of 7g.
Preparation example 8
The remainder was the same as in preparation example 1 except that the calcination temperature in step 3) was 300 ℃.
Comparative preparation example 1
The remainder was the same as in preparation example 1 except that there was no step 3), tiO was obtained 2 /Ti 3 C 2 T x 。
Comparative preparation example 2
The remainder is the same as in preparation 1, except that there is no step 2), i.e
1) Will 5g Ti 3 AlC 2 Mixing the powder with 25ml absolute ethyl alcohol, ball milling for 6 hours at a rotating speed of 500r/min, filtering, vacuum drying at 80 ℃ for 12 hours to obtain dry powder, adding 3 batches of 1.2g of dry powder into 20ml of 40wt% HF solution in a fume hood, stirring and reacting for 24 hours at room temperature, centrifuging after the reaction is finished, flushing the centrifugal solid precipitate with deionized water for 3 times till the pH value is 5, mixing the centrifugal liquid and the washing liquid, diluting the mixture with water till the pH value is 6, pouring the washing liquid into a waste liquid barrel together, and finally placing the centrifugal precipitate into a vacuum drying box for drying at 70 ℃ for 24 hours to obtain Ti 3 C 2 T x ；
2) 6g of urea and 0.1g of Ti from step 1) 3 C 2 T x Mixing uniformly, placing in a tube furnace, calcining at 500 ℃ for 2 hours under argon atmosphere to obtain N-Ti 3 C 2 T x A composite material.
Comparative preparation example 3
The remainder being identical to preparation 1, except that there is no step 2), step 3), i.e
First, 5g of Ti 3 AlC 2 Mixing the powder with 1000ml of absolute ethyl alcohol, ball milling for 6 hours at a rotating speed of 500r/min, filtering, vacuum drying at 80 ℃ for 12 hours to obtain dry powder, adding 3 batches of 1.2g of dry powder into 20ml of 40wt% HF solution in a fume hood, stirring and reacting for 24 hours at room temperature, centrifuging after the reaction is finished, flushing centrifugal solid precipitate with deionized water for 3 times till the pH value is 5, mixing a centrifugal liquid and a washing liquid, adding water to dilute until the pH value is 6, pouring the washing liquid into a waste liquid barrel together, and finally drying the centrifugal precipitate for 24 hours at 70 ℃ in a vacuum oven to obtain Ti 3 C 2 T x 。
Examples 1-8, comparative examples 1-3 lithium oxygen batteries were assembled
The heterogeneous MXene structural materials prepared in the above preparation examples and comparative preparation examples were respectively used as positive electrode active catalysts for the assembly of lithium oxygen batteries with reference to the following method steps.
(1) Preparation of cathode Material
Li-O 2 The positive electrode of the battery consists of 45 weight percent of positive electrode active catalyst, 45 weight percent of Keqin Black (KB) and 10 weight percent of polyvinylidene fluoride (PVDF) binder, the materials are weighed according to the mass ratio, are mixed with N-2-methyl pyrrolidone (NMP) solvent, are uniformly dispersed by ultrasound, a liquid-transferring gun is used for transferring 40 mu L of slurry to cut carbon paper with the diameter of 14mm, the obtained pole piece is placed in a vacuum oven for drying at the temperature of 100 ℃ for 12 hours, the quality of the pole piece is accurately weighed after drying, and then the quality of a pure carbon piece is subtracted, so that each position of the active catalyst of 0.45mg cm is obtained -2 Li-O of (2) 2 And a positive electrode.
(2) Battery assembly
Li-O 2 The assembly of the cell was performed in a Labstar-ECO (1250/780) glove box filled with argon, ensuring water and oxygen contents below 0.5ppm. The positive electrode material is used as a positive electrode, a lithium sheet is used as a negative electrode, a glass fiber diaphragm is used as a diaphragm for separating the positive electrode from the negative electrode, an electrolyte is 1M LiTFSI-TEGDME, a battery-negative electrode shell-elastic sheet-gasket-lithium sheet-electrolyte-diaphragm-electrolyte-positive electrode sheet-positive electrode shell is assembled in sequence, and a CR2032 button type anode shell is adoptedThe battery, wherein the positive electrode shell is provided with a plurality of small holes, so that the battery can be diffused with oxygen, and the newly-assembled battery is required to be placed in a glove box for standing for 12 hours and then placed in an oxygen box for electrochemical performance test.
The following performance tests were performed for the above preparation:
x-ray powder diffraction (XRD): x-ray powder diffractometer of model X' pert ProMPD of Royal Philips, netherlands, by using Cu Ka ray source (wavelength 1.54056A) to set tube voltage and tube current at 40kV and 40mA, respectively, scanning with 2θ=5-80 °, and selecting appropriate scanning speed of 12 ° min -1 。
X-ray photoelectron spectroscopy (XPS): k-alpha type X-ray photoelectron spectrometer produced by Thermofisher.
Specific surface area and pore size distribution: the principle of the oxygen adsorption and desorption test is that the adsorption and desorption characteristics of nitrogen on the surface of a sample to be tested are tested at the temperature of liquid nitrogen, and then the BET method and BJH model are utilized to calculate the specific surface area, pore size distribution and other information of the sample.
Transmission Electron Microscope (TEM): a high-resolution transmission electron microscope model TECNAI G2F 20 of FEI company in the United states, photographs a high-resolution image of the sample, and selects an electron diffraction pattern to observe the fine microstructure thereof.
Electrochemical performance test:
charging and discharging for the first time: the voltage is 2.0-4.5V, and the current is 100mA g -1 。
And (3) multiplying power performance test: current density 100mA g -1 ，200mA g -1 ，500mA g -1 The voltage is 2.0-4.5V, and the full capacity discharge is realized.
And (3) testing the cycle performance: current density 500mA g -1 Limiting capacity 500mAh g -1 。
TABLE 1
Table 1 shows the results of the electrochemical performance tests of the examples and comparative examples at a current density of 100mA g -1 Under the condition of carrying out full capacity discharge test, the electrolyte shows good electrochemical performance, and example 1 shows that the maximum discharge capacity is 15290mAh g -1 The lowest overpotential is 0.49V; at a current density of 500mA g -1 And limiting capacity 500mAh g -1 The cycle performance was measured under the conditions of 190 cycles at the maximum. The larger discharge capacity shows that the higher the capacity of the positive electrode material is, the surface catalytic active site is supposed to be completely exposed, and the active site can improve the electronic structure and reduce the adsorption energy, so that the overpotential is reduced, the cycle life can reach 190 circles, the optimal state of the performance of the MXene-based transition metal oxide-based lithium oxygen battery is already approached, and the stability of the battery can be intuitively shown.
FIG. 1 shows XRD test results of the electrode composite material prepared in preparation example 1, and it can be seen from FIG. 1 that TiO of the present invention 2 /Ti 3 C 2 T x Can clearly identify anatase TiO in XRD patterns of (C) 2 Characteristic peaks of (JCPDS No. 21-1272) indicating that metastable Ti atoms are oxidized to TiO 2 . Diffraction peaks appearing at 2θ=25.26 °, 37.83 °, 48.04 °, 53.87 °, 62.66 ° with Ti 3 C 2 T x TiO generated by in-situ oxidation of nano-sheet 2 The (101), (004), (200), (105), (204) crystal planes. N-TiO prepared 2 /Ti 3 C 2 T x No peaks associated with nitride were found in the XRD pattern of the heterojunction structure, indicating that nitrogen has been successfully doped into TiO 2 /Ti 3 C 2 T x In a heterostructure.
FIG. 2 is N-TiO in preparation example 1 2 /Ti 3 C 2 T x As can be seen from the electron microscope photograph of the heterostructure material, combining the SEM image of FIG. 2 (a), the TEM image of FIG. 2 (b) and the HRTEM image of FIG. 2 (c), the accordion-like Ti 3 C 2 T x Surface of the bodyBy N-TiO 2 Nanoparticle coating, N-TiO 2 Nanocrystalline is uniformly grown on Ti 3 C 2 T x And interlaminar surfaces. N-TiO in FIG. 2 (c) 2 /Ti 3 C 2 T x The high resolution transmission electron microscope results of (2) showed the presence of TiO with a lattice spacing of 0.355nm 2 (101) Ti with crystal face and lattice spacing of 0.251nm 3 C 2 Tx (012) crystal plane. N-TiO 2 /Ti 3 C 2 T x TiO of (C) 2 (101) Lattice spacing of crystal face is 0.355nm, and the crystal face is equal to pure TiO 2 /Ti 3 C 2 T x Compared to 0.352 of TiO 2 (101) The lattice spacing of the crystal planes tends to increase mainly due to doping of N element, nitrogen ions (N 3- ) Substituted oxygen ion (O) 2- ) The lattice spacing is increased.
FIG. 3 is a study of N-doped vs. TiO 2 /Ti 3 C 2 T x Further characterization of the elemental composition and state of the heterostructure material prepared in preparation 1 by XPS, in FIG. 3a, the characteristic peak of Ti, C, O, N is most pronounced in the measured spectrum, indicating that the nitrogen element has been successfully doped into TiO 2 /Ti 3 C 2 T x In the heterojunction. To clarify the chemical states of these elements, spectra of Ti 2p, and N1s were further studied. As shown in FIG. 3b, at Ti 2p 3/2 The peaks at 455.13, 456.05, 456.98 and 458.72 eV of (c) are respectively attributed to Ti-C, ti 2+ 、Ti 3+ And the presence of Ti-O. As shown in FIG. 3c, the peaks at 398.77 and 400.22eV are significantly higher than the typical binding energy of Ti-N bonds (397.20 eV), considered to be the presence of Ti-O-N and/or Ti-N-O bonds. The electronic state of nitrogen generated by atomic rearrangement after the doping of urea is anion (N - ) It was concluded that nitrogen was successfully doped into TiO 2 。
FIG. 4 is N-TiO 2 /Ti 3 C 2 T x Nitrogen adsorption and desorption isotherms (pore size distribution diagram) of heterostructures can be seen in the figure at type IV N 2 Typical hysteresis loops are presented in adsorption isotherms (FIG. 4), indicating the presence of mesopores, N-TiO, in the heterostructure 2 /Ti 3 C 2 T x Is 48.307m 2 g -1 Far greater than the simple accordion-shaped Ti 3 C 2 T x Is a specific surface area of (a). The increase in specific surface area facilitates sufficient exposure of the active site to enhance ORR and OER activity. The pore size distribution shows N-TiO 2 /Ti 3 C 2 T x The pore size distribution of (2) is 4.050nm, which indicates that larger mesopores exist in the heterojunction structure, and the surface functionalization strategy is beneficial to increase of pore volume. The presence of such relatively high specific surface area and mesoporous structure can provide more active sites and store more discharge products, and can not only reduce the overpotential in the battery reaction but also increase the specific capacity, which is one of the reasons why electrochemical performance tests are superior.
FIG. 5 shows the application of example 1 to Li-O 2 Electrochemical performance test curve of battery positive electrode material, specifically, FIG. 5a is N-TiO 2 /Ti 3 C 2 T x Heterostructure-prepared Li-O 2 The discharge capacity of the first circle of the battery reaches 15290mAh g -1 Indicating N-TiO 2 /Ti 3 C 2 T x The conversion of the cathode reaction can be catalyzed more effectively. In FIG. 5b, N-TiO 2 /Ti 3 C 2 T x The electrode has a low overpotential of 0.49V. In FIG. 5c, N-TiO 2 /Ti 3 C 2 T x The electrode can stably circulate for 190 circles, and the circulation stability is strong. To sum up, surface-functionalized N-TiO 2 /Ti 3 C 2 T x Heterostructures exhibit higher ORR and OER catalytic activity and better cycling stability during cell operation, i.e., N-TiO 2 /Ti 3 C 2 T x Heterostructure pair Li-O 2 The battery reaction of the battery has very good catalytic activity, can greatly improve the overall performance of the battery, and has better application value.
The foregoing detailed description is directed to one of the possible embodiments of the present invention, which is not intended to limit the scope of the invention, but rather is intended to cover all modifications and variations within the scope of the present invention.
Claims (7)
1. N-TiO 2 /Ti 3 C 2 T x Heterogeneous MXene structural material as Li-O 2 The application of the cathode electrode material of the battery is characterized in that the microstructure of the heterogeneous MXene structural material is accordion-shaped, and N-doped TiO 2 The nano particles are uniformly distributed in the accordion-shaped Ti 3 C 2 T x Is provided between the surface and the layer; the T is a surface functional group, x is the number of the surface functional groups, and the T is at least one selected from-O-, -OH, -F and-Cl;
the specific surface area of the heterogeneous MXene structural material is 30-60m 2 g -1 The average pore diameter is 3-5nm, and the doping amount of N is 0.50-0.80%.
2. The use according to claim 1, wherein diffraction peaks of 25.3±0.3°,37.8±0.3°,48.0±0.3°,53.9±0.3°,60.8±0.3° and 62.7±0.3° are present in XRD of the heterogeneous MXene structural material; peaks of 455.13 + -0.5 eV, 456.05 + -0.5 eV, 456.98 + -0.5 eV and 458.72 + -0.5 eV of Ti 2p exist in XPS of the heterogeneous MXene structural material.
3. The use according to claim 1, wherein the heterogeneous MXene structural material is N-TiO 2 (101) The lattice spacing of the crystal faces is 0.353-0.357nm.
4. The use according to any one of claims 1 to 3, wherein the N-TiO 2 /Ti 3 C 2 T x The preparation method of the heterogeneous MXene structural material comprises the following steps:
1) Ti is mixed with 3 AlC 2 Mixing powder and organic alcohol, ball milling, filtering, drying, adding the dried powder into HF solution in batches, stirring at room temperature for reaction, centrifuging, washing and drying after the reaction is finished to obtain Ti 3 C 2 T x ；
2) Ti prepared in step 1) 3 C 2 T x Organic reducibilityAdding acid into the mixed solution of water and organic alcohol, performing ultrasonic treatment, heating to react, cooling to room temperature, alternately centrifuging with organic alcohol and water, washing, and drying to obtain TiO 2 /Ti 3 C 2 T x The method comprises the steps of carrying out a first treatment on the surface of the The organic reducing acid is at least one selected from citric acid, ammonium citrate, oxalic acid, ammonium oxalate, L-ascorbic acid, D-ascorbic acid methanesulfonic acid and ammonium methylsulfonate;
3) Urea and the TiO from step 2) 2 /Ti 3 C 2 T x Uniformly mixing, calcining under inert atmosphere to obtain nitrogen-doped TiO 2 /Ti 3 C 2 T x Heterojunction, i.e. N-TiO 2 /Ti 3 C 2 T x 。
5. The method according to claim 4, wherein step 1) the Ti 3 AlC 2 The mass volume ratio of the powder to the organic alcohol is 1g (200-400 mL); the mass volume ratio of the dried powder to the HF solution is (1-3) g: (30-50) mL, the concentration of the HF solution is 30-50wt%.
6. The method according to claim 4, wherein step 2) the Ti 3 C 2 T x The weight ratio of organic reducing acid, water and organic alcohol is 1:4-6:200-800:200-400; heating to 150-200 ℃ for 6-12h.
7. The use according to claim 4, wherein step 3) the urea and TiO 2 /Ti 3 C 2 T x The mass ratio of (2) is 40-60:1, the calcination temperature is 300-500 ℃, and the calcination time is 1-3h.
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