High-valence metal tungsten doped molybdenum selenide coupling catalyst as well as preparation method and application thereof

Abstract

The invention provides a high-valence metal tungsten doped molybdenum selenide coupling catalyst and a preparation method and application thereof, and the method comprises the following steps: (1) dissolving ammonium molybdate tetrahydrate, sodium tungstate dihydrate and selenium dioxide in a Ti3C2MXene solution, carrying out ultrasonic treatment, adding an ethylenediamine solution into the solution, and stirring to obtain a uniform precursor solution; (2) transferring the precursor solution into a hydrothermal kettle, and then carrying out solvothermal reaction; (3) after the reaction is finished, cooling, respectively centrifugally washing the precipitate with deionized water and alcohol for several times, and drying the obtained material overnight; and (4) placing the dried and collected material in a tubular heating furnace in a nitrogen atmosphere, and then carrying out annealing treatment to prepare the catalyst. The prepared catalyst shows significantly reduced charge-discharge overpotential and excellent high-current-density cycling stability when applied to the lithium-oxygen battery, and a new thought is provided for developing an efficient lithium-oxygen battery positive electrode catalyst.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of batteries, and specifically discloses a high-valence metal tungsten-doped molybdenum selenide coupled Ti3C2 MXene catalyst, a preparation method and application BACKGROUND

[0002] Lithium-oxygen (Li-O2) batteries have extremely high theoretical energy density (~3500 Wh kg -1 ) and a unique open system structure of the oxygen cathode, and are considered as a candidate for the next generation of clean energy devices to meet the growing global energy demand. However, the inherent slow kinetics of the oxygen cathode leads to large overpotential, poor rate capability and limited cycle stability, hindering the practical application of lithium-oxygen batteries. To solve the above problems, researchers have developed bifunctional electrocatalysts with unique morphology and excellent catalytic activity to accelerate the oxygen reduction / evolution reaction (ORR / OER) kinetics and optimize the intermediate adsorption energy, including noble metals, transition metal compounds (such as oxides and phosphides, etc.) and carbon-based catalysts.

[0003] Two-dimensional (2D) materials, such as transition metal chalcogenides, MXenes, and graphene, are widely used in the field of energy conversion and storage due to their high aspect ratio, tunable surface chemistry, and excellent mechanical flexibility. However, their practical application is often limited by obvious self-stacking and inherent limitations of single material systems. Efficient construction of 2D / 2D heterostructures is crucial to overcome the limitations of single-component systems. In recent years, the bridge oxygen bond of M1-O-M2 configuration has attracted widespread attention due to its excellent electrical conductivity and structural stability, which helps to regulate the generation / decomposition pathway of Li2O2 and strengthen the reaction kinetics. For example, a 2D / 2D MoS2 / Ti3C2 MXene heterostructure with an interconnected network has been successfully constructed. Based on the strong coupling of high-capacitance MoS2 and high-rate Ti3C2 MXene, the flexible capacitor device exhibits excellent electrochemical performance. By constructing an interfacial oxygen bridge between MoO x and the MXene matrix, a MoO x @Ti3C2 MXene composite material is prepared as an efficient positive electrode catalyst for lithium-oxygen batteries. The Li-O2 battery assembled based on the MoO x @Ti3C2 MXene catalyst exhibits smaller charge-discharge polarization (0.75 V) and enhanced cycle stability (more than 300 cycles). Density functional theory (DFT) analysis shows that the bridge oxygen bond maximizes the advantages of electronic structure regulation and Li2O2 formation.

[0004] High-valence metal doping (M = Zr 4+ , Nb 5+ , Mo 6+Strategies such as these can effectively modulate local electron density and induce spatial charge redistribution while simultaneously serving as active sites for oxygen electrode reactions to optimize intermediate adsorption and lower energy barriers to accelerate reaction kinetics. Researchers introduced high-valent metal sites (e.g., Zr 4+ , Mo 6+ ) to produce abundant unoccupied antibonding orbitals through optimized hybridization of high-valent metal d orbitals and nonmetal p orbitals. Based on this unique electronic arrangement, it is beneficial to reduce the charge transfer barrier and lower the free energy of the rate-determining step (O*→OOH*). Thus, the synergistic coupling of high-valent metal centers and interfacial oxygen bridge bonds can effectively regulate the electronic structure and local coordination environment of the catalyst. However, the relevance between specific high-valent metals and interfacial bridge oxygen bonds in 2D / 2D metal selenides and MXene heterostructures and the potential synergistic mechanism have not been revealed. SUMMARY

[0005] In view of this, the present application provides a high-valent metal tungsten-doped molybdenum selenide coupled Ti3C2 MXene catalyst, a preparation method and applications thereof. The Li-O2 battery assembled with the prepared catalyst shows high discharge specific capacity and long-term cycle stability at large current density. The first object of the present application is to provide a preparation method of a high-valent metal tungsten-doped molybdenum selenide coupled Ti3C2 MXene catalyst, comprising the following steps:

[0006] (1) Dissolve a certain amount of ammonium molybdate tetrahydrate, sodium tungstate dihydrate and selenium dioxide in a certain amount of Ti3C2 MXene solution and perform ultrasonic treatment, then add a certain amount of ethylenediamine solution to the above solution and stir at room temperature to obtain a uniform precursor solution;

[0007] (2) Transfer the precursor solution to an autoclave and perform solvothermal reaction under certain temperature and time conditions;

[0008] (3) After the reaction is completed and cooled to room temperature, the precipitate is washed several times by centrifugation with water and alcohol, respectively, and the obtained material is placed in a vacuum oven for drying overnight;

[0009] (4) Collect the dried material and perform annealing treatment in a tube furnace under a nitrogen atmosphere at certain temperature and time conditions to obtain a high-valent metal tungsten-doped molybdenum selenide coupled Ti3C2 MXene composite catalyst.

[0010] Preferably, in step (1), the molar ratio of ammonium molybdate tetrahydrate, sodium tungstate dihydrate and selenium dioxide is 1:1.2:1.4.

[0011] Preferably, in step (1), the total volume of Ti3C2 MXene solution x and ethylenediamine solution y is 40 mL, i.e. x+y=40.

[0012] Preferably, the volume of the Ti3C2 MXene solution is x = 15 mL, and the volume of the ethylenediamine solution is y = 25 mL.

[0013] Preferably, in step (2), the precursor mixed solution is transferred to a hydrothermal kettle, and kept at 190-210℃ for 19-21h.

[0014] Preferably, in step (2), after cooling to room temperature, centrifugal washing is performed with deionized water and anhydrous ethanol, and the rotation speed during centrifugation is 7500-8500 rpm, and the centrifugation time is 7 minutes.

[0015] Preferably, in step (3), the drying temperature in the vacuum oven is 50-70℃, and after drying overnight, the precursor material of the target catalyst is obtained.

[0016] Preferably, in step (4), the annealing temperature in the tube furnace under a nitrogen atmosphere is 450-550℃, and the annealing time is 1-3h, and after the treatment is completed, the target catalyst (W-MoSe2@MXene) is obtained.

[0017] The second object of the present application is to provide a lithium-oxygen battery positive electrode catalyst, which is prepared by the preparation method of the high-valence metal tungsten-doped molybdenum selenide coupled Ti3C2 MXene (W-MoSe2@MXene) catalyst as described above.

[0018] The third object of the present application is to provide an application of the above-mentioned electrocatalyst in a lithium-oxygen battery.

[0019] Compared with the prior art, the present application has the following technical advantages:

[0020] The present application provides a preparation method of a high-valence W-doped MoSe2 nanosheet anchored in a two-dimensional layered Ti3C2 MXene matrix (W-MoSe2@MXene) with abundant oxygen bridge bonds, and the prepared catalyst has a unique porous and vertically staggered nanosheet array network structure, which is beneficial to expose abundant active sites and accelerate the electrolyte penetration and material transport processes in the lithium-oxygen battery reaction process, thereby showing low charge-discharge polarization potential, high discharge specific capacity and enhanced cycle stability. The present application provides a new way for the rational design and development of high-rate lithium-oxygen battery positive electrode catalysts.

[0021] Drawings of the specification

[0022] Appendix Figure 1Scanning electron micrographs of a) MXene, b) MoSe2@MXene and c) W-MoSe2@MXene catalysts; X-ray diffraction patterns of d) MXene, e) MoSe2@MXene and f) W-MoSe2@MXene catalysts;

[0023] Figure 1 Figure 2 Transmission electron micrographs of a) and b) W-MoSe2@MXene catalysts; High resolution transmission electron micrographs of c) - f).

[0024] Figure 2 Figure 3 X-ray photoelectron spectrograms of a) Mo 3d, b) Se 3d, c) W 4f and d) O 1s of MoSe2@MXene and W-MoSe2@MXene catalysts.

[0025] Figure 3 Figure 4 Lithium-oxygen battery performance of MXene, MoSe2@MXene and W-MoSe2@MXene catalysts: a) cyclic voltammograms, b) initial discharge / charge curves at 100 mA g -1 current density; c) constant current discharge / charge curves of lithium-oxygen batteries at 1 Ag -1 current density; d) rate and cycle stability performance at ultra-high current density. DETAILED DESCRIPTION

[0026] The present application provides a preparation method of high-valence metal tungsten doped molybdenum selenide coupled Ti3C2 MXene catalyst, an electrocatalyst and application thereof.

[0027] The high-valence metal tungsten doped molybdenum selenide coupled Ti3C2 MXene catalyst is W-MoSe2@MXene.

[0028] Example 1

[0029] The preparation process of the W-MoSe2@MXene catalyst comprises the following steps:

[0030] (1) Ammonium molybdate tetrahydrate, sodium tungstate dihydrate and selenium dioxide are added to 25 mL of ethylenediamine solution according to a feeding molar ratio of 1:1.2:1.4 and 15 mL of Ti3C2 MXene solution (concentration of 2 mg mL -1 ) is stirred uniformly to obtain a precursor solution for reaction;

[0031] (2) The precursor solution is transferred to a stainless steel hydrothermal kettle lined with para-polyphenyl, and kept at 190-210℃ for 20 h. After cooling to room temperature, centrifugal washing is performed with deionized water and anhydrous ethanol at a rotation speed of 7500-8500 rpm.

[0032] (3) The above material is placed in a vacuum oven (50-70°C) for drying overnight to obtain a precursor powder material of the target catalyst.

[0033] (4) The dried precursor material collected is placed in a tube furnace under a nitrogen atmosphere and annealed at 450-550°C for 2h to prepare a high-valence metal tungsten-doped molybdenum selenide coupled Ti3C2 MXene composite catalyst (W-MoSe2@MXene).

[0034] Example 2

[0035] A method for preparing a molybdenum selenide coupled Ti3C2 MXene composite catalyst, referring to Example 1, the only difference is that no sodium tungstate dihydrate is added to the precursor solution in step 1, and other conditions including the mass ratio of each raw material, reaction steps, reaction temperature and time are unchanged, i.e. a molybdenum selenide nanosheet coupled two-dimensional layered Ti3C2 MXene composite material (MoSe2@MXene) can be prepared.

[0036] The application of the above-prepared electrocatalyst in lithium-oxygen batteries, the specific application steps are as follows:

[0037] (1) The prepared composite catalyst is used as the positive active material of lithium-oxygen battery. Super P is used as the conductive additive, and polyvinylidene fluoride is used as the binder; the active material, Super P and polyvinylidene fluoride are added to NMP in a mass ratio of 7:2:1, and then ultrasonic treatment and stirring are performed;

[0038] (2) The obtained slurry is uniformly sprayed on carbon paper and dried in a vacuum oven at 60°C overnight;

[0039] (3) The prepared electrode is assembled into a 2032 type button lithium-oxygen battery in a glove box, and the battery assembly includes: lithium foil negative electrode, glass fiber separator and electrolyte (1.0M bis(trifluoromethanesulfonyl) imide lithium dissolved in DMSO) and the positive electrode with the catalyst sprayed on the carbon paper, gasket and spring. The blue electric battery test system is used to test the galvanostatic charge-discharge curves and cycle stability under the conditions of 1 Ag -1 large current density and 1000mAhg -1 high cut-off specific capacity.

[0040] The Al layer in Ti3AlC2 MAX can be etched using a lithium fluoride and hydrochloric acid mixed solution to synthesize Ti3C2 MXene with a smooth surface and a multi-layer nanosheet structure. Figure 1 a). As Figure 1 b and Figure 1c, the scanning electron microscope images of MoSe2@MXene and W-MoSe2@MXene materials show that the vertically interconnected MoSe2and W-MoSe2nanosheets are randomly distributed on the surface of Ti3C2MXene, forming a three-dimensional hierarchical porous structure. X-ray diffraction was used to evaluate the material composition and crystal structure information of MXene, MoSe2@MXene and W-MoSe2@MXene materials. As shown in Figure 1 d, the diffraction peaks of MXene at 8.9°, 18.6°, 27.9°, 36.3°, 42.1° and 62.7° correspond to the (002), (004), (008), (111), (200) and (220) planes of typical Ti3C2MXene, respectively. In addition, MoSe2@MXene shows four characteristic diffraction peaks at 12.3°, 32.4°, 38.2° and 56.3°, corresponding to the (002), (100), (103) and (110) crystal planes of MoSe2, respectively Figure 1 e). The diffraction peaks of W-MoSe2@MXene are basically consistent with those of MoSe2@MXene material, but slightly negatively shifted, indicating the successful doping of W element and the formation of a new phase Figure 1 f). Based on the above research results, it is further proved that the W-doped MoSe2is successfully anchored on the layered MXene matrix.

[0041] The transmission electron microscope images of W-MoSe2@MXene catalyst further confirm that the sample has a three-dimensional porous interconnected nanosheet array structure Figure 2 a and Figure 2 b), in which the unique porous nanosheet network helps to promote mass transport and charge transfer. High-resolution transmission electron microscope images show that there is a unique multiphase coexisting heterostructure in the W-MoSe2@MXene catalyst, indicating the existence of abundant heterojunction interfaces Figure 2 c). In addition, the characteristic lattice spacing is 0.64 and 0.26 nm, corresponding to the (002) crystal plane of 2H-MoSe2phase and the (002) crystal plane of Ti3C2MXene, respectively Figure 2 d-f), proving the successful preparation of W-MoSe2@MXene composite catalyst.

[0042] X-ray photoelectron spectroscopy was used to analyze the surface chemical composition and element valence of MoSe2@MXene and W-MoSe2@MXene samples. As shown in Figure 3 a, the high-resolution Mo 3d XPS spectra of MoSe2@MXene and W-MoSe2@MXene can be deconvoluted into two pairs of characteristic peaks, which are respectively Mo 4+ (228.7, 231.8 eV) and Mo 6+(229.5, 232.2 eV) corresponding. It is worth noting that the W-MoSe2@MXene Mo 3d orbital binding energy moves ~0.3 eV to the high binding energy direction after the addition of W doping, indicating that the introduction of W will capture Mo atoms, thus causing the redistribution of the surrounding electron cloud and space charge. This is mainly due to the relatively high electronegativity of W (2.36) compared to Mo (2.16), thus regulating the electronic structure of the catalyst. For Se 3d XPS spectra of W-MoSe2@MXene (c), Figure 3 b), two characteristic peaks at 54.2 and 55.1 eV are in high agreement with Se 3d 5 / 2 and Se 3d 3 / 2 of MoSe2@MXene. For W 4f XPS spectra of W-MoSe2@MXene (c), Figure 3 c), the peaks fitted at 37.8 and 35.9 eV can be attributed to W 6+ species of W 4f 7 / 2 and W4f 5 / 2 , indicating the successful introduction of high-valence W elements. As shown in Figure 3 d, O 1s XPS spectrum fitting four peaks located at 529.8, 530.8, 531.5 and 533.2 eV, which can d correspond to Ti-O, Ti-OH, Mo-O-Ti and surface adsorbed H2O. It is worth noting that the formation of bridging metal-oxygen active chains (Mo-O-Ti) indicates the successful construction of the heterojunction between W-MoSe2 and MXene, which is conducive to promoting the interface charge transfer and reducing the polarization overpotential of Li-O2 battery.

[0043] The catalytic performance of W-MoSe2@MXene cathode was evaluated by assembling the button lithium-oxygen battery, and MXene and MoSe2@MXene catalysts were used as controls. The cyclic voltammetry curves of the samples are shown in Figure 4 a, W-MoSe2@MXene shows higher oxygen reduction reaction onset potential (2.89 V) and lower oxygen evolution reaction onset potential (3.61 V) than MXene and MoSe2@MXene, indicating that it has good bifunctional catalytic performance. In addition, the larger positive electrode reduction peak area and negative electrode oxidation peak area mean that the lithium-oxygen battery assembled by W-MoSe2@MXene cathode has higher specific capacity. As shown in Figure 4 b, the galvanostatic charge-discharge curves show that W-MoSe2@MXene has a higher discharge capacity than MXene and MoSe2@MXene at 100 mAg -1The W-MoSe2@MXene exhibited a smaller charge-discharge overpotential (0.61V), significantly lower than that of MoSe2@MXene (0.87V) and MXene (1.11V), indicating that the formation of interfacial oxygen bridges and the high-valence metal doping sites induce faster charge transfer channels and excellent electrochemical performance. The Li-O2 battery assembled with the W-MoSe2@MXen cathode achieved a current density of 1000 mAg. -1 It exhibits a larger specific capacity (12442.6 mAh g). -1 ), namely MoSe2@MXene (5568.3mAh g -1 ) and MXene (4823.2mAh g) -1 The rate performance was ~2.23 times and ~2.56 times that of [other components]. Meanwhile, to evaluate the high-rate performance of the battery, lithium-oxygen batteries assembled with W-MoSe2@MXene as the positive electrode were tested at 1-5 Ag [amount missing]. -1 Charge-discharge tests were conducted at high current densities. For example... Figure 4 As shown in Figure d, the charging potential plateau rises only slightly from 4.12V to 4.31V, and eventually returns to 4.18V, demonstrating excellent high-rate performance. Simultaneously, it can operate at 1Ag... -1 The battery demonstrated excellent cycling stability after continuous operation for 127 q cycles at high current densities. Based on the above electrochemical performance tests, the high-valence metal W-doped molybdenum selenide coupled layered Ti3C2MXene exhibits favorable lithium-oxygen battery performance, proving the positive role of high-valence metal sites and heterostructure.

[0044] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing a high-valent tungsten-doped molybdenum selenide coupled catalyst, characterized in that, Includes the following steps: (1) A certain amount of ammonium molybdate tetrahydrate, sodium tungstate dihydrate and selenium dioxide were dissolved in a certain amount of Ti3C2 MXene solution and subjected to ultrasonic treatment. Then a certain amount of ethylenediamine solution was added to the above solution and stirred at room temperature to obtain a uniform precursor solution. (2) The precursor solution is transferred to a hydrothermal reactor and subjected to a solvothermal reaction under certain temperature and time conditions; (3) After the reaction is complete and cooled to room temperature, the precipitate is washed several times by centrifugation with water and alcohol respectively, and the obtained material is dried in a vacuum oven overnight. (4) The dried material was annealed in a tube furnace under a nitrogen atmosphere at a certain temperature and time to obtain a high-valence tungsten-doped molybdenum selenide coupled Ti3C2 MXene composite catalyst.

2. The method for preparing a high-valent tungsten-doped molybdenum selenide coupled catalyst according to claim 1, characterized in that, In step (1), the molar ratio of ammonium molybdate tetrahydrate, sodium tungstate dihydrate, and selenium dioxide is 1:1.2:1.

4.

3. The method for preparing a high-valent tungsten-doped molybdenum selenide coupled catalyst according to claim 1, characterized in that, In step (1), the total volume of Ti3C2 MXene solution x and ethylenediamine solution y added is 40 mL, i.e., x + y = 40.

4. The method for preparing a high-valent tungsten-doped molybdenum selenide coupled catalyst according to claim 3, characterized in that, The volume of the Ti3C2 MXene solution is x = 15 mL, and the volume of the ethylenediamine solution is y = 25 mL.

5. The method for preparing a high-valent tungsten-doped molybdenum selenide coupled catalyst according to claim 1, characterized in that, In step (2), the precursor mixture solution is transferred to a hydrothermal reactor and kept at 190-210°C for 19-21 hours.

6. The method for preparing a high-valent tungsten-doped molybdenum selenide coupled catalyst according to claim 1, characterized in that, In step (2), after cooling to room temperature, wash with deionized water and anhydrous ethanol by centrifugation at a speed of 7500-8500 rpm for 7 minutes.

7. The method for preparing a high-valent tungsten-doped molybdenum selenide coupled catalyst according to claim 1, characterized in that, In step (3), the drying temperature in the vacuum oven is 50-70℃, and the precursor material of the target catalyst is obtained after drying overnight.

8. The method for preparing a high-valent tungsten-doped molybdenum selenide coupled catalyst according to claim 1, characterized in that, In step (4), the annealing temperature in a tube furnace under a nitrogen atmosphere is 450-550℃ and the annealing time is 1-3h.

9. A high-valence tungsten-doped molybdenum selenide coupled catalyst prepared by the method according to any one of claims 1-8.

10. The application of a high-valence tungsten-doped molybdenum selenide coupled catalyst according to claim 9 in a lithium-oxygen battery.

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