A preparation method of molybdenum rare earth niobium aluminum carbide and two-dimensional derived molybdenum niobium carbide
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NORTHEASTERN UNIV CHINA
- Filing Date
- 2024-05-08
- Publication Date
- 2026-05-12
AI Technical Summary
Existing two-dimensional materials have problems with insufficient service life and charging/discharging speed in energy storage devices, and the research on in-plane and out-of-plane ordered structures in the MAX phase family has not been fully explored.
A molybdenum rare earth niobium aluminum carbide (s-MAX) was prepared by mixing Mo, R, Nb, Al and C in a specific ratio and treating it at high temperature to form an orthorhombic crystal structure. Subsequently, it was etched with a fluorine ion solution to form a two-dimensional derivative s-MXene, and then treated with an intercalating agent to obtain nanosheets with more than one layer.
The electrochemical performance of the two-dimensional derivative was improved, which significantly enhanced the capacitance performance of the energy storage device.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of nanomaterials for energy storage, and in particular to a method for preparing molybdenum rare earth niobium aluminum carbides and their two-dimensional derivatives. Background Technology
[0002] The overuse of fossil fuels has exacerbated environmental problems, creating an urgent need for clean and renewable energy. Designing and developing energy storage devices is crucial for storing new energy sources. Currently, the most widely used commercial energy storage technologies are lithium-ion batteries and supercapacitors. Due to inherent limitations of traditional fuel cells and lithium-ion batteries, such as lifespan and charging / generating speed, recent research on energy storage devices has increasingly shifted towards supercapacitors. Two-dimensional materials, such as graphene, have wide applications in energy storage.
[0003] In recent years, a novel type of two-dimensional transition metal carbide / nitride (MXene) has emerged. This two-dimensional material is prepared by chemical etching from its precursor, the MAX phase. In 2011, the aluminum atom layer in the Ti3AlC2 MAX phase was successfully etched away for the first time using an aqueous HF solution, yielding accordion-shaped multilayer MXene. Further intercalation can yield monolayer or higher MXenes. Two-dimensional MXenes exhibit great application potential in energy storage, electromagnetic shielding, and electrocatalysis due to their metallic conductivity, abundant surface functional groups (-F, -OH, and =O, etc.), satisfactory hydrophilicity, and exposed electronegativity. (M. Naguib, M. Kurtoglu, V. Presser, J. Lu, J. Niu, M. Heon, L. Hultman, Y. Gogotsi, MW Barsoum, Adv. Mater. 2011, 23, 4248).
[0004] Within the MAX phase family, there are two types of ordered-site MAX (o-MAX and i-MAX). The chemical formula for o-MAX is (M', M”). n+1 AlC n (n = 2 or 3), M' atoms preferentially occupy the outer layer of the transition metal carbide, and M” atoms preferentially occupy the inner layer of the transition metal carbide. M' and M” atoms are distributed in an orderly out-of-plane configuration. The i-MAX chemical formula is (M' 2 / 3 ,M” 1 / 3 In AlC, M' atoms and M” atoms are arranged in an ordered ratio of 2:1. Considering that in-plane ordering currently only exists in the 211 type MAX phase, while out-of-plane ordering only exists in the 312 or 413 type o-MAX, whether a novel ordered MAX phase with both in-plane and out-of-plane ordering exists and can be experimentally confirmed is of great significance for further exploration of such MAX phases. Summary of the Invention
[0005] This invention provides a method for preparing molybdenum rare earth niobium aluminum carbide (s-MAX) and its two-dimensional derivative molybdenum niobium carbide (s-MXene), and the series of two-dimensional derivatives have excellent capacitance performance.
[0006] The technical solution of this invention is as follows: A molybdenum rare earth niobium aluminum carbide, composed of molybdenum (Mo), rare earth element R, niobium (Nb), aluminum (Al), and carbon (C), has an orthorhombic crystal structure, and its chemical formula is Mo. 3.33-x R 0.67 Nb x AlC3, 1≤x≤2.5, where R is Sc, Y, or a lanthanide element.
[0007] The molybdenum rare earth niobium aluminum carbide is formed by alternating stacking of metal carbide layers and Al atom layers along the c-axis, with one metal carbide layer between every two adjacent Al atom layers. The metal carbide layer contains four transition metal layers, with Mo and R atoms preferentially occupying the outer layer of the metal carbide layer and Nb atoms preferentially occupying the inner layer. Mo and R atoms are arranged in an ordered ratio of 2:1, with R atoms occupying the center of the hexagon formed by Mo atoms, thus forming a layered structure in which Mo and R atoms are ordered in-plane and Mo and Nb atoms are ordered out-of-plane.
[0008] The x = 2.
[0009] A method for preparing molybdenum rare earth niobium aluminum carbide involves mixing Mo:R:Nb:Al:C = (3.33-x):0.67:x:1.2:2.7, cold pressing the mixture into sheets, heating it at a rate of 5–20 °C / min, holding it under vacuum at 1300 °C–1600 °C for 0.5–10 hours, and then naturally cooling it to room temperature to obtain the molybdenum rare earth niobium aluminum carbide.
[0010] A method for preparing two-dimensional derived molybdenum-niobium carbide from molybdenum rare earth niobium aluminum carbide, wherein the molybdenum rare earth niobium aluminum carbide is etched by a fluorine-containing ion solution to form a non-stoichiometric two-dimensional derivative; the two-dimensional derivative contains corresponding vacancies formed by the etching of ordered rare earth atoms, and negative ion functional groups are bonded to the surface of the two-dimensional derivative during the etching process; after intercalation treatment with an intercalating agent, a suspension of molybdenum-niobium carbide nanosheets with more than one layer is obtained, and after freeze-drying, two-dimensional derived molybdenum-niobium carbide powder is obtained.
[0011] The fluoride-containing solution is an aqueous solution of HF or a mixed solution of a fluoride salt and hydrochloric acid; the intercalating agent is tetramethylammonium hydroxide or tetrabutylammonium hydroxide.
[0012] The beneficial effects of this invention are as follows: A molybdenum rare-earth niobium aluminum carbide (s-MAX) is synthesized for the first time, adding a new branch to the MAX phase family and greatly stimulating researchers to further explore MAX phases. Furthermore, the obtained s-MAX phase is chemically etched to further intercalate and obtain monolayer or multilayer s-MXene. Due to the presence of ordered vacancies, its electrochemical performance is significantly improved compared to Mo2Nb2C3 o-MXene. Attached Figure Description
[0013] Figure 1 for Mo 3.33-x R 0.67 Nb x XRD spectra of AlC3 (x = 0.75, 1, 2, 2.5 and 2.75) s-MAX phases;
[0014] Figure 2(a) shows Mo 1.33 Lu 0.67 A bright-field image of the Nb2AlC3 s-MAX phase from a transmission electron microscope, with the inset showing the corresponding selected area electron diffraction image;
[0015] Figure 2(b) shows Mo 1.33 Lu 0.67 Transmission electron microscopy high-angle annular dark-field image of Nb2AlC3 s-MAX phase;
[0016] Figure 3(a) shows Mo 1.33 Lu 0.67 Secondary electron micrograph of Nb2AlC3 s-MAX phase before etching and X-ray energy dispersive spectra of Mo, Lu, Nb and Al;
[0017] Figure 3(b) shows Mo 1.33 Lu 0.67 Secondary electron micrographs of Nb2AlC3 s-MAX phase after etching and X-ray energy dispersive spectra of Mo, Lu, Nb and Al;
[0018] Figure 3(c) shows Mo 1.33 Digital photographs of the Tyndall effect in Nb2C3 s-MXene suspensions;
[0019] Figure 3(d) is Mo 1.33 Scanning electron microscope image of the cross section of the filter plate for Nb2C3 s-MXene suspension;
[0020] Figure 3(e) shows Mo 1.33 Bright-field image of Nb2C3 s-MXene lyophilized powder under a transmission electron microscope;
[0021] Figure 3(f) is Mo 1.33Diffraction of the bright-field image of Nb2C3 s-MXene lyophilized powder under a transmission electron microscope;
[0022] Figure 4(a) shows Mo 1.33 CV curves of Nb2C3 s-MXene;
[0023] Figure 4(b) shows Mo 1.33 GCD curve of Nb2C3 s-MXene. Detailed Implementation
[0024] The technical solution of the present invention will be further described below with reference to the accompanying drawings.
[0025] Example 1
[0026] Powder with a molar ratio of Mo:Lu:Nb:Al:C = 1.33:0.67:2:1.2:2.7 was placed in a ball mill jar and ball-milled for 7 hours. After the powder was uniformly mixed, it was cold-pressed into sheets, then heated at a heating rate of 10℃ / min and vacuum-held at 1500℃ for 1 hour. The sheets were then naturally cooled to room temperature to obtain the molybdenum rare earth niobium aluminum carbide. Figure 1 As shown, XRD at x=2 indicates the formation of the corresponding phase and crystal structure. Observation and calibration by transmission electron microscopy, as shown in Figures 2(a) and 2(b), reveal orthogonal symmetry, forming a layered structure with in-plane ordering of Mo and R atoms and out-of-plane ordering of Mo and Nb atoms.
[0027] Example 2
[0028] Powder with a molar ratio of Mo:Lu:Nb:Al:C = 2.33:0.67:1:1.2:2.7 was placed in a ball mill jar and ball-milled for 7 hours. After the powder was uniformly mixed, it was cold-pressed into sheets, then heated at a heating rate of 10℃ / min and vacuum-held at 1500℃ for 1 hour. The sheets were then naturally cooled to room temperature to obtain the molybdenum rare earth niobium aluminum carbide. Figure 1 As shown, XRD at x=1 indicates the formation of the corresponding phase and crystal structure.
[0029] Example 3
[0030] Powder with a molar ratio of Mo:Lu:Nb:Al:C = 0.83:0.67:2.5:1.2:2.7 was placed in a ball mill jar and ball-milled for 7 hours. After the powder was uniformly mixed, it was cold-pressed into sheets, then heated at a heating rate of 10℃ / min and vacuum-held at 1500℃ for 1 hour. The sheets were then naturally cooled to room temperature to obtain the molybdenum rare earth niobium aluminum carbide. Figure 1 As shown, XRD at x = 2.5 indicates the formation of the corresponding phase and crystal structure.
[0031] When x < 1 or x > 2.5, taking x = 0.75 and x = 2.75 as examples, the XRD of the prepared molybdenum rare earth niobium aluminum carbide ( Figure 1 This indicates that the corresponding phase and crystal structure have not been formed.
[0032] Take 1g of Mo ground into powder 1.33 Lu 0.67 Nb₂AlC₃ was placed in a polytetrafluoroethylene bottle containing 10 ml of HF aqueous solution, and then placed in a stainless steel reactor. The mixture was kept at 120°C for 2 days in a forced-air drying oven to selectively etch away the Al and Lu atomic layers, as shown in Figures 3(a) and 3(b). After the reaction, the mixture was washed five times with deionized water, and the resulting precipitate was ML-MXene. Scanning electron microscopy revealed the characteristic step-like morphology of the s-MAX phase before etching, and a distinct "accordion" morphology after etching. Combined with X-ray energy dispersive spectroscopy (EDS) before and after etching, this indicates that the s-MAX phase was successfully etched into ML-MXene.
[0033] Add 5 ml of 40 wt% TBAOH to the obtained precipitate and stir in a water bath at 55 °C for 1 day. After the reaction is complete, wash three times with anhydrous ethanol, add deionized water to the obtained precipitate, and sonicate for 1 hour to obtain a stable s-MXene suspension exhibiting a significant Tyndall effect (Figure 3(c)). This colloidal solution is composed of Mo 1.33 Lu 0.67 Two-dimensional Mo derived from the Nb2AlC3 type s-MAX phase 1.33 The nanosheets are composed of Nb2C3-type s-MXene nanosheets. After vacuum filtration, the cross-section of the fragments still shows a mesoscale layered stacking morphology (Figure 3(d)). The aerogel powder obtained by freeze-drying the colloidal solution can be clearly observed as layered flakes under a transmission electron microscope (Figure 3(e)). The selected area electron diffraction of the zone axis also matches the simulation results (Figure 3(f)).
[0034] Take 16 mg of lyophilized powder, 2 mg of binder (PVDF) and 2 mg of conductive agent (acetylene black), mix them evenly, add an appropriate amount of 1-methyl-2-pyrrolidone solution, stir evenly and then coat it on a 1*1 cm surface. 2 The electrode was vacuum dried at 60℃ for 12 hours on a stainless steel mesh. The electrode was then removed, flattened with a manual tablet press, and weighed. The electrochemical performance of the electrode was tested in 1M H2SO4 solution with Pt as the counter electrode and Ag / AlCl as the reference electrode.
[0035] The freeze-dried powder was used for testing as a negative electrode material for supercapacitors, 2mV s -1 It has 115F g -1 The capacitance is shown in Figure 4(a) and Figure 4(b).
Claims
1. A molybdenum rare earth niobium aluminum carbide, characterized in that, The molybdenum rare-earth niobium aluminum carbide is composed of molybdenum (Mo), rare-earth element R, niobium (Nb), aluminum (Al), and carbon (C), and has an orthorhombic crystal structure. Its chemical formula is Mo. 3.33-x R 0.67 Nb x AlC3, 1 ≤ x ≤ 2.5, where R is Sc, Y, or a lanthanide element; the molybdenum rare earth niobium aluminum carbide is formed by alternating stacking of metal carbide layers and Al atom layers along the c-axis, with one metal carbide layer between every two adjacent Al atom layers; the metal carbide layer contains four transition metal layers, with Mo and R atoms preferentially occupying the outer layer of the metal carbide layer and Nb atoms preferentially occupying the inner layer of the metal carbide layer; Mo and R atoms are arranged in an ordered ratio of 2:1, with R atoms occupying the center of the hexagon formed by Mo atoms, thus forming a layered structure in which Mo and R atoms are ordered in-plane and Mo and Nb atoms are ordered out-of-plane.
2. The molybdenum rare earth niobium aluminum carbide according to claim 1, characterized in that, The x=2.
3. A method for preparing the molybdenum rare earth niobium aluminum carbide according to claim 1 or 2, characterized in that, After being mixed evenly according to the ratio of Mo:R:Nb:Al:C = (3.33-x):0.67:x:1.2:2.7, the mixture was cold-pressed into sheets, then heated at a heating rate of 5~20℃ / min and vacuum-held at 1300℃~1600℃ for 0.5~10 hours, and then naturally cooled to room temperature to obtain the molybdenum rare earth niobium aluminum carbide.
4. A method for preparing two-dimensional derived molybdenum-niobium carbides from molybdenum rare-earth niobium aluminum carbides according to claim 1 or 2, characterized in that, The molybdenum rare earth niobium aluminum carbide is etched by a fluorine ion-containing solution to form a non-stoichiometric two-dimensional derivative; the two-dimensional derivative contains corresponding vacancies formed by the etching of ordered rare earth atoms, and negative ion functional groups are bonded to the surface of the two-dimensional derivative during the etching process. After intercalation treatment with an intercalating agent, a suspension of molybdenum-niobium carbide nanosheets with more than one layer was obtained, which was then freeze-dried to obtain two-dimensional derived molybdenum-niobium carbide powder.