A method for obtaining S-intercalated MXene by in-situ vapor phase sulfidation etching of MAX phase.
By etching the MAX phase using in-situ vapor phase sulfidation and reacting MAX powder with thioacetamide, selective etching of the A layer and uniform sulfur intercalation were achieved. This solved the safety and complexity issues of wet chemical etching, yielded high-performance S-intercalated MXene materials, and expanded their application range.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- WUHAN UNIV
- Filing Date
- 2026-03-16
- Publication Date
- 2026-05-26
AI Technical Summary
In the preparation of MXene materials, existing wet chemical etching methods are highly toxic and corrosive, and it is difficult to achieve uniform intercalation of functional elements, resulting in performance degradation and process complexity. Vapor phase etching methods have not completely avoided fluorine termination and stacking problems.
The in-situ gas-phase sulfidation method uses thioacetamide as a solid sulfur source, which reacts with MAX powder in a tube furnace. Through heating and heat preservation treatment, selective etching of the A layer and in-situ, uniform intercalation of sulfur are achieved, avoiding the use of high-risk liquid chemicals and simplifying the process.
A safe and simplified MXene preparation process was achieved, resulting in S-intercalated MXene materials with stable structure and excellent electrochemical performance, which broadens their application prospects in high-performance energy storage and catalysis.
Smart Images
Figure CN122079164A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of novel two-dimensional materials technology, specifically to a method for obtaining S-intercalated MXene by in-situ vapor phase sulfidation etching of the MAX phase. Background Technology
[0002] MXenes are a new class of two-dimensional layered transition metal carbides / nitrides / carbonitrides, with the general chemical formula M. n+1 X n Tx, where M represents an early transition metal (such as Ti, V, Nb, Mo, etc.), X is carbon and / or nitrogen, Tx represents a surface functional group (such as -O, -OH, -F, -Cl, etc.), and n is usually 1, 2, or 3. MXenes, due to their unique metallic conductivity, hydrophilicity, tunable surface chemistry, and excellent electrochemical performance, have shown great application potential in energy storage (such as lithium-ion batteries and supercapacitors), electromagnetic shielding, catalysis, sensing, and composite materials.
[0003] Currently, the most mainstream method for large-scale preparation of MXene is through selective etching of the precursor MAX phase ceramic. The MAX phase is a type of ternary layered compound with the molecular formula M0. n+1 AX n In this process, A primarily consists of group III or IV elements (such as Al, Ga, and Si). The chemical bonds between the A and M atomic layers are relatively weak, allowing the etchant to selectively remove the A atomic layer, thereby transforming the three-dimensional MAX phase into a two-dimensional MXene. To date, the most mature and widely used etching method is wet chemical etching, typically performed at room temperature or with moderate heating using an acidic solution containing fluoride ions (such as hydrofluoric acid HF, or HF generated in situ from hydrochloric acid and lithium fluoride). For example, selectively etching away the Al layer in Ti3AlC2 using an HF solution yields Ti3C2Tx MXene with surface terminations of -O, -OH, and -F.
[0004] However, the aforementioned traditional wet chemical etching method has several significant drawbacks, restricting the further development and application of MXene materials: First, high concentrations of hydrofluoric acid (HF) are extremely corrosive and toxic, posing a serious safety threat to experimental operators and requiring extremely strict protective measures and wastewater treatment processes, increasing production costs and environmental risks. Second, MXene prepared in fluorine-containing etchants inevitably has a large number of -F terminals on its surface. Numerous studies have shown that the high electronegativity of -F terminals may lead to strong dipole-dipole repulsion between MXene sheets. Although this is beneficial for dispersion, excessive -F terminals are believed to reduce the intrinsic conductivity and electrochemical active sites of MXene, hindering its performance in electrochemical energy storage and other fields. Furthermore, while MXene nanosheets obtained by wet etching exhibit good dispersibility in water or polar solvents, strong van der Waals forces during subsequent drying or electrode film preparation easily cause nanosheets to recombine and aggregate, significantly reducing the available specific surface area and active sites, hindering ion transport, and thus causing performance degradation. In addition to the above disadvantages, the wet process involves multiple centrifugation and washing steps to remove residual acid and byproducts, which is cumbersome and time-consuming, and generates a large amount of acidic wastewater containing heavy metal ions and fluorides, resulting in high subsequent treatment costs.
[0005] To overcome the drawbacks of wet etching, researchers have begun exploring vapor phase etching (VPE). For example, high-temperature fluoride vapors (such as HF vapor or gases produced by the decomposition of NH4HF2) have been reported for etching the MAX phase. While these methods avoid generating significant amounts of liquid waste to some extent, they still rely on fluorides and face challenges related to fluorine terminal introduction and equipment corrosion. More importantly, traditional VPE primarily focuses on removing the A-layer, and the resulting MXene often requires additional intercalation treatments (such as using organic bases or metal ions) to widen the interlayer spacing and prevent stacking. This increases the complexity and uncertainty of the process.
[0006] In recent years, sulfur has attracted attention due to its large atomic radius, moderate electronegativity, and its positive role in energy storage (such as lithium-sulfur batteries) and catalysis. Theoretical calculations and preliminary experiments show that introducing sulfur as an intercalating agent into the interlayer of MXene can not only effectively widen the interlayer spacing, inhibit stacking, and promote ion transport, but also optimize the electronic structure of MXene and introduce additional redox active sites, thereby potentially significantly improving its electrochemical performance. Currently, the preparation of sulfur-intercalated MXenes mostly adopts post-processing methods, that is, adding sulfur-containing compounds (such as Na2S, thiourea, etc.) to the prepared MXene suspension for reaction or treating MXene powder by high-temperature gas-phase sulfidation. This method involves separate steps, low efficiency, and difficulty in controlling the uniform intercalation of sulfur and its binding state with the MXene matrix.
[0007] Therefore, given the limitations of existing vapor phase etching techniques, which can only achieve halogen surface terminalization and cannot simultaneously complete the intercalation of functional elements, there is an urgent need in this field to develop a method for MXene preparation that can overcome the step-by-step limitation of "etching-intercalation". This method should be able to: completely eliminate the use of high-risk fluorine / halogen reagents, achieving an inherently safe vapor phase reaction process; and, while selectively etching the MAX phase A layer, utilize the chemical affinity between active species and transition metals to achieve directional, in-situ, and uniform intercalation of A-layer vacancies in one step. This would simplify the process while endowing the material with unique electrochemical activity and structural stability, broadening its application prospects in high-performance energy storage and catalysis. Summary of the Invention
[0008] To address the shortcomings of the existing technologies, this invention provides a method for obtaining S-intercalated MXene by in-situ vapor-phase sulfidation etching of the MAX phase. This method achieves directional, in-situ, and uniform intercalation of A-layer vacancies in one step, yielding MXene materials with functional S-intercalation. Furthermore, the process is simple, avoids the use of highly hazardous fluorine / halogen-containing reagents, and is conducive to large-scale production.
[0009] To achieve the above objectives, the specific technical solution of the present invention is as follows:
[0010] In a first aspect, the present invention provides a method for obtaining S-intercalated MXene by in-situ vapor-phase etching of the MAX phase, comprising the following steps:
[0011] MAX powder and thioacetamide powder are placed in a tube furnace, with the thioacetamide powder placed upstream and the MAX powder placed downstream; the chamber is evacuated to below 3 Pa; a carrier gas is introduced and heated and kept warm to obtain MXene with S intercalation.
[0012] Furthermore, the mass ratio of the MAX powder to the thioacetamide powder is 1:(20-60).
[0013] Furthermore, the MAX includes, but is not limited to, at least one of V2AlC, Ti2AlC, Ti3AlC2, and Mo2GaC.
[0014] Furthermore, inside the tubular furnace, the distance between the thioacetamide powder and the MAX powder is 15-40 cm.
[0015] Furthermore, the flow rate of the carrier gas is 70-100 sccm.
[0016] Furthermore, the carrier gas is an inert gas, including but not limited to nitrogen (N2) or argon (Ar).
[0017] Furthermore, the heating and heat preservation temperature is 400-600℃, and the time is 2-5 hours.
[0018] Secondly, the present invention provides MXene with functional element S intercalation prepared by the method described above.
[0019] Thirdly, the present invention provides the application of MXene with functional element S intercalation in energy storage (such as lithium-ion batteries, supercapacitors), electronic devices, catalysis, and sensing.
[0020] Compared with the prior art, the advantages of the present invention are:
[0021] 1. This invention completely eliminates the use of highly toxic and corrosive hydrofluoric acid (HF), fluorine-containing mixed acids, or halogens in traditional wet etching. Instead, it uses a solid sulfur source (thioacetamide) in a closed reactor to generate in-situ etching through controlled heating. This etching process is completed under gas phase conditions, avoiding the risks of using, storing, and transporting large amounts of highly hazardous liquid chemicals, and greatly improving the inherent safety level of the process.
[0022] 2. The method of this invention completes the two key steps of selective removal (etching) of the A layer and expansion of the interlayer domain (intercalation) in situ and simultaneously; wherein, while the gas-phase sulfurizing agent etches away the weakly bonded A atomic layer (such as Al) in the MAX phase, the active sulfur species (S) are simultaneously... 2- The S-terminator reacts immediately with the exposed highly reactive transition metal (M) layer, anchoring itself chemically to the surface and interlayer of MXene. This not only completely eliminates harmful -F terminals but also introduces uniformly distributed S-intercalation in one step. This integrated design simplifies the process flow of functional element S-intercalated MXene materials, reduces production costs, and solves the complexity and inhomogeneity problems of the traditional stepwise process of "wet etching first, then physical / chemical intercalation," thus broadening the application prospects of MXene in high-performance devices. Attached Figure Description
[0023] Figure 1 X-ray diffraction patterns of V2AlC MAX and V2CS MXene prepared in this invention;
[0024] Figure 2 Scanning electron microscope images of V2AlC MAX and V2CS MXene prepared in this invention;
[0025] Figure 3 This is a scanning transmission electron microscope image of V2AlC MAX.
[0026] Figure 4 and Figure 5This is a scanning transmission electron microscope image of the V2CS MXene prepared in this invention. Detailed Implementation
[0027] To enable those skilled in the art to clearly and completely understand the technical solution of the present invention, the present invention will be further described in detail below with reference to embodiments. Obviously, the embodiments described herein are only for explaining the present invention and are not intended to limit the scope of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.
[0028] This invention provides a method for obtaining S-intercalated MXene by in-situ vapor phase sulfidation etching of the MAX phase, comprising the following steps:
[0029] MAX powder and thioacetamide powder are placed in a tube furnace, with the thioacetamide powder placed upstream and the MAX powder placed downstream; the chamber is evacuated to below 3 Pa; a carrier gas is introduced and heated and kept warm to obtain MXene with S intercalation.
[0030] In some examples, the mass ratio of the MAX powder to the thioacetamide powder is 1:(20-60).
[0031] In some examples, the MAX includes, but is not limited to, at least one of V2AlC, Ti2AlC, Ti3AlC2, and Mo2GaC.
[0032] In some examples, the carrier gas flow rate is 70-100 sccm.
[0033] In some examples, the carrier gas is an inert gas, including but not limited to nitrogen or argon.
[0034] In some examples, the heating and heat preservation temperature is 400-600℃, and the time is 2-5 h.
[0035] Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods and equipment used in this invention are conventional reagents, methods and equipment in the art.
[0036] Example 1
[0037] An MXene with functional element S intercalation is prepared by the following steps:
[0038] S1: Spread 0.05 g of V2AlC MAX powder and 1 g of thioacetamide powder separately in a rectangular crucible for later use.
[0039] S2: Low-pressure in-situ vapor etching of the V2AlC MAX phase: Using a single-temperature tube furnace, V2AlC MAX powder and thioacetamide powder were placed separately inside the furnace, with the thioacetamide powder positioned upstream and the V2AlC MAX powder downstream, with a distance of 20 cm between them. Before heating, the chamber was evacuated to below 3 Pa, and then the carrier gas (N2) was turned on at a flow rate of 70 sccm; simultaneously, the temperature was raised to 500℃ and held for 5 h. The furnace was then allowed to undergo a natural cooling process, ultimately yielding V2CS MXene with S intercalation.
[0040] The X-ray diffraction patterns of the V2AlC MAX and the V2CS MXene prepared in this embodiment are as follows: Figure 1 As shown. From Figure 1 It can be seen that the V2AlC MAX phase is located at approximately 14 o (002) and about 41 o The characteristic diffraction peak (103) almost completely disappears in V2CS MXene, proving that the Al layer has been successfully removed. At the same time, a new diffraction peak (002) belonging to V2CS MXene appears in the low-angle region, and its peak position is significantly shifted to the left compared with the (002) peak of V2AlC MAX phase. Combined with the disappearance of the Al characteristic peak, it is confirmed that sulfur species have been directionally inserted into the original A layer lattice site, forming a structurally stable S intercalated MXene.
[0041] Scanning electron microscope images of the V2AlC MAX and the V2CS MXene prepared in this embodiment are shown below. Figure 2 As shown. From Figure 2 As can be seen, V2AlC MAX exhibits a dense, blocky, layered structure; after etching, the product transforms into a typical accordion-like layered exfoliation morphology, with obvious openings between the layers. This morphological change intuitively indicates that the Al layer has been selectively removed, and the adjacent VC layers have been separated. Simultaneously, the full exposure of the interlayer region confirms that sulfur species have been inserted in situ into the interlayer during etching, forming V2CS MXene with a layered interlayer structure.
[0042] The scanning transmission electron microscope images of V2AlC MAX and V2CS MXene are shown below. Figure 3-5 As shown. From Figure 3 As can be seen, based on the difference in atomic number contrast, the periodically arranged V, Al, and C atomic layers can be clearly distinguished, with a stacking sequence of …CV-Al-VC…, perfectly matching the ternary layered crystal structure of V2AlC MAX. This image visually confirms that the Al atomic layer (A layer) exists as an independent layer between the VC layers, providing a clear structural basis for subsequent selective etching and directional sulfur insertion. Figure 4-5 It can be seen that V2CS MXene maintains a complete layered morphology, with clear layers and no structural collapse, as shown in the high-resolution images ( Figure 5 This reveals the structural evolution at the atomic scale: with the precursor V2AlC MAX ( Figure 3 Compared to the original, clearly discernible Al atomic layer, it has completely disappeared; in the original Al layer location, a new set of atomic columns with a contrast characteristic of S element appears; the new atomic columns, together with the V and C atomic columns, form a regular…VCSCV… periodic arrangement. These characteristics collectively confirm that the Al layer has been successfully etched away, and sulfur species have been directionally inserted and orderly occupy the vacancies in the original A layer, forming a structurally stable A-site selective sulfur insertion V2CS MXene.
[0043] Example 2
[0044] An MXene with functional element S intercalation is prepared by the following steps:
[0045] S1: Spread 0.02 g of V2AlC MAX powder and 1 g of thioacetamide powder separately in a rectangular crucible for later use.
[0046] S2: Low-pressure in-situ vapor etching of V2AlC MAX phase: Using a single-temperature tube furnace, V2AlC MAX powder and thioacetamide powder were placed separately inside the tube furnace, with the thioacetamide powder placed upstream and the V2AlC MAX powder downstream, with a distance of 20 cm between them. Before heating, the chamber was evacuated to below 3 Pa, and then the carrier gas (N2) was turned on at a flow rate of 70 sccm. Simultaneously, the temperature was raised to 500℃ and held for 5 h, followed by a natural cooling process, ultimately yielding V2CS MXene with S intercalation.
[0047] Example 3
[0048] An MXene with functional element S intercalation is prepared by the following steps:
[0049] S1: Spread 0.02 g of V2AlC MAX powder and 1 g of thioacetamide powder separately in a rectangular crucible for later use.
[0050] S2: Low-pressure in-situ vapor etching of V2AlC MAX phase: Using a single-temperature tube furnace, V2AlC MAX powder and thioacetamide powder were placed separately inside the tube furnace, with the thioacetamide powder placed upstream and the V2AlC MAX powder downstream, with a distance of 20 cm between them. Before heating, the chamber was evacuated to below 3 Pa, and then the carrier gas (N2) was turned on at a flow rate of 100 sccm; simultaneously, the temperature was raised to 500℃ and held for 5 h, followed by a natural cooling process, ultimately yielding V2CS MXene with S intercalation.
[0051] Example 4
[0052] An MXene with functional element S intercalation is prepared by the following steps:
[0053] S1: Spread 0.02 g of V2AlC MAX powder and 1 g of thioacetamide powder separately in a rectangular crucible for later use.
[0054] S2: Low-pressure in-situ vapor etching of V2AlC MAX phase: Using a single-temperature tube furnace, V2AlC MAX powder and thioacetamide powder were placed separately inside the tube furnace, with the thioacetamide powder placed upstream and the V2AlC MAX powder downstream, with a distance of 20 cm between them. Before heating, the chamber was evacuated to below 3 Pa, and then the carrier gas (N2) was turned on at a flow rate of 100 sccm. Simultaneously, heating was started to 500℃ and held for 2 h, followed by a natural cooling process of the furnace, ultimately yielding V2CS MXene with S intercalation.
[0055] Example 5
[0056] An MXene with functional element S intercalation is prepared by the following steps:
[0057] S1: Spread 0.02 g of V2AlC MAX powder and 1.2 g of thioacetamide powder separately in a rectangular crucible for later use.
[0058] S2: Low-pressure in-situ vapor etching of V2AlC MAX phase: Using a single-temperature tube furnace, V2AlC MAX powder and thioacetamide powder were placed separately inside the furnace, with the thioacetamide powder positioned upstream and the V2AlC MAX powder downstream, with a distance of 20 cm between them. Before heating, the chamber was evacuated to below 3 Pa, and then the carrier gas (N2) was turned on at a flow rate of 70 sccm. Simultaneously, heating was initiated to 400℃ and held for 5 h, followed by natural cooling of the furnace, ultimately yielding V2CS MXene with S intercalation.
[0059] It has been verified that the sulfur species in Examples 2-5 are all oriented and uniformly inserted into the original A-layer lattice sites, forming structurally stable S-intercalated MXene.
[0060] In summary, this invention places thioacetamide powder upstream of a tube furnace and MAX powder downstream of the tube furnace. Under heating conditions, the MAX phase is etched using an in-situ vapor-phase sulfidation method to obtain MXene with functional element S intercalation. Compared to the wet etching and re-intercalation methods in the prior art, this invention eliminates the use of high-risk fluorine / halogen reagents, avoiding the risks of using, storing, and transporting large quantities of high-risk liquid chemicals, and greatly improving the intrinsic safety level of the process. Furthermore, this invention achieves in-situ, uniform intercalation of functional sulfur elements while etching the MAX phase, resulting in S-intercalated MXene materials with expanded interlayer spacing, controllable termination, and excellent electrochemical performance, thus broadening the application prospects of MXene in high-performance devices.
[0061] The above detailed embodiments describe the implementation of the present invention; however, the present invention is not limited to the specific details described in the above embodiments. Within the scope of the claims and technical concept of the present invention, various simple modifications and changes can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.
Claims
1. A method for obtaining S-intercalated MXene by in-situ vapor phase sulfidation etching of the MAX phase, characterized in that, Includes the following steps: MAX powder and thioacetamide powder are placed in a tube furnace, with the thioacetamide powder placed upstream and the MAX powder placed downstream. After evacuating the chamber, a carrier gas is introduced and the furnace is heated and kept warm to obtain MXene with S intercalation.
2. The method for obtaining S-intercalated MXene by in-situ vapor-phase etching of the MAX phase according to claim 1, characterized in that, The mass ratio of MAX powder to thioacetamide powder is 1:(20-60).
3. The method for obtaining S-intercalated MXene by in-situ vapor phase sulfidation etching of the MAX phase according to claim 2, characterized in that, The MAX includes, but is not limited to, at least one of V2AlC, Ti2AlC, Ti3AlC2, and Mo2GaC.
4. The method for obtaining S-intercalated MXene by in-situ vapor-phase etching of the MAX phase according to claim 1, characterized in that, The heating and heat preservation temperature is 400-600℃, and the time is 2-5 hours.
5. The method for obtaining S-intercalated MXene by in-situ vapor-phase etching of the MAX phase according to claim 1, characterized in that, Inside the tubular furnace, the distance between the thioacetamide powder and the MAX powder is 15-40 cm.
6. The method for obtaining S-intercalated MXene by in-situ vapor-phase etching of the MAX phase according to claim 1, characterized in that, The flow rate of the carrier gas is 70-100 sccm.
7. The method for obtaining S-intercalated MXene by in-situ vapor-phase etching of the MAX phase according to claim 6, characterized in that, The carrier gas is an inert gas, including but not limited to nitrogen or argon.
8. MXene with functional element S intercalation prepared by the method according to any one of claims 1-7.
9. The application of MXene with functional element S intercalation as described in claim 8 in energy storage, electronic devices, catalysis, and sensing.