Preparation method of MoS2 / MXene moire heterogeneous synergistic catalyst

Abstract

The invention provides a preparation method of a MoS2 / MXene moire heterogeneous synergistic catalyst, which comprises the following preparation steps: selectively etching a Ti3AlC2 precursor by adopting LiF and HCl to obtain a two-dimensional MXene nanosheet; the preparation method comprises the following steps: mixing an MXene solution with Na2MoO4, CH4N2S and citric acid in proportion, and ultrasonically dispersing in a water solvent to form a precursor solution; by regulating and controlling the proportion of the 1T / 2H-MoS2 phase, the conductivity and the stability are both considered, and the synergistic effect of the MoS2 as an electrocatalytic active phase is improved; the orientation and the torsional angle of MoS2 are regulated and controlled on a two-dimensional MXene substrate, a periodic Moire superlattice structure is constructed, and electron coupling and energy band alignment are enhanced; by constructing a collaborative interface system, the transmission rate of interface carriers is increased, the reaction overpotential is reduced, and the durability and cycling stability under high current density are enhanced; the invention provides an extensible and universal flexible preparation method which is suitable for a low-temperature-condition controllable synthesis process for constructing a two-dimensional MoS2 / MXene heterostructure in a large area.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst preparation, and specifically to a method for preparing a MoS2 / MXene moiré heterogeneous synergistic catalyst. Background Art

[0002] As the global demand for green energy transformation continues to increase, hydrogen production by electrolysis of water as a clean and renewable way to produce hydrogen energy has received more and more attention. Among them, the catalyst performance of the electrocatalytic hydrogen evolution reaction (HER) is the core factor that determines its efficiency and economy. Molybdenum disulfide (MoS2) is a typical two-dimensional layered transition metal sulfide. Due to its low cost, good chemical stability and abundant edge active sites, it has been widely studied as a HER catalyst material. Studies have shown that MoS2 mainly exists in two crystalline phases, namely the thermodynamically stable 2H phase (semiconductor phase) and the kinetically metastable 1T phase (metallic). Among them, the 1T phase has higher electronic conductivity and is suitable as an electrocatalytic active phase. In order to further improve its catalytic performance, in recent years, the academic community has begun to try to combine MoS2 with two-dimensional MXene materials (such as Ti3C2T x ) constructs a heterojunction, and by introducing a highly conductive interface and abundant active sites, it achieves a dual improvement in charge transfer ability and catalytic activity.

[0003] However, existing MoS2 / MXene heterojunction catalysts still have many shortcomings in terms of structural regulation and interface coupling. First, in most studies, MoS2 is a single phase, lacking a 1T / 2H synergistic regulation strategy, making it difficult to balance high conductivity and structural stability. Second, the heterojunctions prepared so far are mostly disordered stacking or simple accumulation, with random interface orientation and lattice matching relationships, failing to effectively control the lattice twist angle to form a periodic moiré superlattice structure, making it difficult to systematically improve the electronic behavior of the interface. In addition, the two-dimensional MoS2 and MXene are mostly bound by physical adsorption or weak van der Waals interactions, resulting in loose interface coupling, which limits the interfacial charge transfer and energy band reconstruction capabilities. This leads to a significant performance degradation of existing catalysts under high current density conditions, poor cycling stability, and a lack of precise regulation of the catalytic mechanism. Summary of the Invention

[0004] (1) Technical problems solved

[0005] In response to the shortcomings of the existing technology, the present invention provides a method for preparing a MoS2 / MXene moiré heterogeneous synergistic catalyst, which solves the problems of single phase, weak interface bonding, and low charge transfer efficiency in existing catalysts.

[0006] (2) Technical solution

[0007] To achieve the above objectives, the present invention is implemented by the following technical solution: a method for preparing a MoS2 / MXene moiré heterogeneous synergistic catalyst, comprising the following preparation steps:

[0008] (1) Selective etching of Ti3AlC2 precursor using LiF and HCl to obtain MXene nanosheets;

[0009] (2) mixing the MXene solution with Na2MoO4, CH4N2S and citric acid in proportion and ultrasonically dispersing the mixture in an aqueous solvent to form a precursor solution;

[0010] Exfoliation and preparation of MXene precursors

[0011] Ti3AlC2MAX phase is selected as raw material, and hydrofluoric acid (HF) or LiF / HCl mixture is used for selective etching to remove the Al layer and form Ti3C2T x MXene is then subjected to ultrasonic exfoliation, centrifugation, and solvent dispersion to obtain a single layer or a few layers of Ti3C2T x dispersion.

[0012] Phase-regulated synthesis of MoS2

[0013] Using a solution, hydrothermal, or in-situ growth method, a Mo source (such as Na₂MoO₄) and a sulfur source (such as thiourea) react in the presence of a suitable reducing agent (such as citric acid). The 1T / 2H phase ratio in MoS₂ is controlled by adjusting the reaction temperature (e.g., 180–220°C), reaction time, and precursor concentration. The 1T phase is typically maintained at 30–60%.

[0014] (3) placing the obtained precursor solution and the substrate simultaneously into a hydrothermal reactor for hydrothermal reaction, cooling naturally after the reaction, and removing the catalyst;

[0015] (4) Under an inert atmosphere, the catalyst is first preheated at low temperature and then pyrolyzed at high temperature to form a two-dimensional MoS2 and MXene heterojunction with a 1T / 2H phase coexistence structure;

[0016] (5) A periodic moiré superlattice structure is formed between two-dimensional MoS2 and MXene, forming a synergistic interface.

[0017] Heterojunction interface construction and moiré superlattice formation

[0018] The regulated MoS2 is deposited on two-dimensional MXene nanosheets. By adjusting the deposition direction or spin coating angle (3–7°), the lattice directions of the two are misaligned to form a periodic moiré superlattice structure. Electrostatic self-assembly or liquid-phase spin coating can be used to achieve orderly stacking of the two two-dimensional materials.

[0019] Preferably, the preparation method of MXene in step (1) is as follows:

[0020] S1. Weigh 1 to 2 g of Ti3AlC2 powder and slowly add it to a 15 to 20 mL, 9 to 12 M HCl solution containing 1 to 2 g of LiF. The mixture is stirred magnetically in a polytetrafluoroethylene reactor at room temperature for 48 hours.

[0021] S2. After the reaction, the product was centrifuged several times (3500 rpm, 10 min) and washed with deionized water until the pH was close to 6-7;

[0022] S3. Finally, gray-black multilayer MXene nanosheets were precipitated and freeze-dried for 48 hours for later use.

[0023] Preferably, in the step (ii), the precursor solution

[0024] 0.106-0.206 g Na2MoO4, 0.14-0.304 g CH4N2S, 0.13 g citric acid (CA) and 15-30 mL Ti3C2T x The suspension was added to 50 mL of polytetrafluoroethylene liner and ultrasonically treated for 30 min to form a uniform mixture.

[0025] Preferably, the heat treatment step in step (iv) is as follows:

[0026] First, perform a hydrothermal reaction at 160-200℃ for 12-24 hours, and then anneal in an inert atmosphere at 600-800℃ for 30-45 minutes.

[0027] Preferably, in step (iv), MoS2 comprises 1T phase and 2H phase and the operation is as follows:

[0028] The ratio of 1T phase of MoS2 to 2H phase of MoS2 can be adjusted by regulating the hydrothermal reaction temperature and time.

[0029] Preferably, the lattice period range of the moiré superlattice in step (5) is as follows:

[0030] The lattice period of the moiré superlattice is 0.6–0.8 nm.

[0031] Post-processing and structural stabilization

[0032] The constructed heterostructure is vacuum annealed (200–300°C) to enhance interface bonding and structural stability; a small amount of reducing agent (such as NaBH4) can be selectively introduced to adjust the MoS2 phase ratio, ultimately forming a stable and uniform synergistic catalytic heterostructure.

[0033] The heterojunction sample is prepared into an electrode, and its hydrogen evolution performance is tested in 0.5M H2SO4 electrolyte. A three-electrode system (a Pt sheet as a counter electrode, an Ag / AgCl reference electrode) is adopted, and the working electrode is the active material drop-coated on the surface of a glassy carbon electrode. Linear sweep voltammetry tests show that the catalyst requires only 78mV overpotential at a current density of 10mA·cm -2 , the Tafel slope is 43mV·dec -1 , the charge transfer resistance is about 20Ω, and the electrocatalytic performance is excellent. In addition, the double-layer capacitance C dl of the catalyst is 56mF·cm -2 , indicating that the interface charge storage capacity is strong and the active sites are rich.

[0034] The following improvements are obtained through the three strategies of phase engineering, heterostructure construction and interface regulation:

[0035] (1) The catalytic performance is significantly improved

[0036] By constructing a MoS2 / MXene heterojunction moire superlattice structure and combining the 1T / 2H phase synergistic regulation strategy, the problems of low charge transfer efficiency, few active sites and unstable structure in traditional two-dimensional catalysts are significantly improved. Experimental results show that in a typical electrocatalytic hydrogen evolution reaction (HER) system, the overpotential of the catalyst is only 78mV at a current density of 10mA·cm -2 , the Tafel slope is 43mV·dec -1 , which is significantly better than MoS2 (~180mV, ~85mV·dec -1 ) without structure regulation or MXene nanosheets alone. Therefore, the present application can realize lower reaction energy barrier and faster reaction kinetics, and effectively improve the catalytic activity.

[0037] (2) The structure regulation mechanism is optimized

[0038] The multi-level regulation mechanism has a significant synergistic effect. Specifically, 1T-MoS2 provides high electronic conductivity, 2H-MoS2 provides abundant edge active sites, the built-in electric field generated by the heterojunction interface and the moire potential regulation mechanism promote the rapid transfer of interface electrons and enhance the adsorption capacity of reactants. In addition, the two-dimensional MXene layered structure provides a high-speed electron channel and enhances the stability of the overall structure. Electrochemical impedance spectroscopy (EIS) shows that the interface charge transfer resistance of the structure is about 20Ω, which is significantly better than the comparative sample without moire structure, indicating that the present application scheme significantly improves the electron / proton transport efficiency and electrocatalytic kinetic performance.

[0039] (3) Green, low-cost, scalable preparation process and practical application

[0040] The two-dimensional MXene nanosheet preparation process is liquid phase etching, which is completed under mild conditions (about 40 DEG C), avoiding high temperature annealing and vacuum conditions. The MoS2 deposition process adopts low-temperature solution assembly (<200 DEG C) or hydrothermal method, which is suitable for glass, flexible plastic substrate. Compared with the traditional Pt / C noble metal catalyst, the cost of the heterojunction system is reduced by more than 80%. It has good flexibility and bendability, and is suitable for future wearable energy devices, portable hydrogen energy systems. Promote the development of low-carbon, green hydrogen energy economy, and have important support for the national strategy of "carbon neutralization".

[0041] (III) beneficial effects

[0042] The application provides a preparation method of a MoS2 / MXene moire heterojunction synergistic catalyst.

[0043] 1. By adjusting the 1T / 2H-MoS2 phase ratio, the conductivity and stability are considered, and the synergistic effect of the electrocatalytic active phase is improved.

[0044] 2. The orientation and torsion angle of the MoS2 nanosheet on the two-dimensional MXene nanosheet are adjusted, a periodic moire superlattice structure is constructed, and the electronic coupling and energy band alignment are enhanced.

[0045] 3. The intrinsic activity and stability of the catalyst in the electrocatalytic hydrogen evolution reaction are improved, the interface carrier transport rate is improved by constructing a synergistic interface system, the reaction overpotential is reduced, and the durability and cycle stability under high current density are enhanced.

[0046] 4. A scalable and universal flexible preparation method is provided, which is suitable for controllable synthesis process of two-dimensional MoS2 / MXene heterojunction under low temperature conditions, and is convenient for popularization in flexible devices, wearable energy systems and other practical applications. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 It is a MoS2 / MXene heterojunction and moire superlattice formation schematic diagram of the preparation method of the MoS2 / MXene moire heterojunction synergistic catalyst provided by the application;

[0048] Figure 2 It is XRD and Raman spectrum of MoS2 / MXene heterojunction prepared at different temperatures and different Mxene concentrations of the preparation method of the MoS2 / MXene moire heterojunction synergistic catalyst provided by the application;

[0049] Figure 3 It is a scanning electron microscope image of MoS2@Mxene prepared by different Mxene concentrations of the preparation method of the MoS2 / MXene moire heterojunction synergistic catalyst provided by the application;

[0050] Figure 4 High-magnification transmission electron microscope image of the MoS2@Mxene catalyst prepared at 180 DEG C according to the preparation method of the MoS2 / MXene Moiré heterojunction synergistic catalyst proposed in the application;

[0051] Figure 5 X-ray photoelectron spectrogram of the MoS2@Mxene catalyst prepared at 180 DEG C according to the preparation method of the MoS2 / MXene Moiré heterojunction synergistic catalyst proposed in the application;

[0052] Figure 6 Polarization curve and Tafel slope diagram of the MoS2@Mxene catalyst prepared at 180 DEG C according to the preparation method of the MoS2 / MXene Moiré heterojunction synergistic catalyst proposed in the application. DETAILED DESCRIPTION

[0053] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0054] Embodiment one:

[0055] The embodiment of the present application provides a preparation method of a MoS2 / MXene Moiré heterojunction synergistic catalyst, including the following preparation steps:

[0056] (1) LiF and HCl are used to selectively etch Ti3AlC2 precursor to obtain MXene nanosheets;

[0057] (2) MXene solution, Na2MoO4, CH4N2S and citric acid are mixed in proportion and ultrasonically dispersed in an aqueous solvent to form a precursor solution;

[0058] (3) the obtained precursor solution and the substrate are simultaneously put into a hydrothermal reaction kettle for hydrothermal reaction, and the catalyst is taken out after natural cooling;

[0059] (4) under an inert atmosphere, the catalyst is first subjected to low-temperature preheating treatment, and then subjected to high-temperature pyrolysis to form a two-dimensional MoS2 and MXene heterojunction with 1T / 2H phase coexistence structure;

[0060] (5) a periodic Moiré superlattice structure is formed between the two-dimensional MoS2 and MXene, forming a synergistic interface.

[0061] The preparation method of MXene in step (1) is as follows:

[0062] S1. Weigh 1 g of Ti3AlC2 powder and slowly add it to a 15 mL, 12 M HCl solution containing 1 g of LiF. The reaction was stirred magnetically in a polytetrafluoroethylene reactor at room temperature for 48 hours.

[0063] S2. After the reaction, the product was centrifuged several times (3500 rpm, 10 min) and washed with deionized water until the pH was close to 7;

[0064] S3. Finally, a gray-black multilayer MXene precipitate was obtained, which was freeze-dried for 48 hours for later use.

[0065] In step (2), the precursor solution

[0066] The concentration of the two-dimensional MXene nanosheet solution was 1-5 mg / mL. 0.106 g Na2MoO4, 0.14 g CH4N2S, 0.13 g citric acid (CA) and 15 mL Ti3C2T x The suspension was added to 50 mL of polytetrafluoroethylene liner and ultrasonicated for 10 minutes.

[0067] The heat treatment steps in step (iv) are as follows:

[0068] The reaction was first hydrothermally reacted at 180 °C for 12 h, and then annealed in an inert atmosphere at 600–800 °C for 30–45 min.

[0069] In step (iv), MoS2 contains 1T phase and 2H phase and the operation is as follows:

[0070] The ratio of 1T phase of MoS2 to 2H phase of MoS2 can be adjusted by regulating the heat treatment temperature and time.

[0071] The lattice period range of the moiré superlattice in step (5) is as follows:

[0072] The lattice period of the moiré superlattice is 0.6–0.8 nm.

[0073] This method can induce the in situ growth of MoS2 on the surface of MXene nanosheets at low temperature to form a clear heterogeneous structure.

[0074] Example 2:

[0075] The difference between this embodiment and the first embodiment is that the preparation steps are as follows:

[0076] (1) Selective etching of Ti3AlC2 precursor using LiF and HCl to obtain MXene nanosheets;

[0077] (2) mixing the MXene solution with Na2MoO4, CH4N2S and citric acid in proportion and ultrasonically dispersing the mixture in an aqueous solvent to form a precursor solution;

[0078] (3) placing the obtained precursor solution and the substrate simultaneously into a hydrothermal reactor for hydrothermal reaction, cooling naturally after the reaction, and removing the catalyst;

[0079] (4) Under an inert atmosphere, the catalyst is first preheated at low temperature and then pyrolyzed at high temperature to form a two-dimensional MoS2 and MXene heterojunction with a 1T / 2H phase coexistence structure;

[0080] (5) A periodic moiré superlattice structure is formed between two-dimensional MoS2 and MXene, forming a synergistic interface.

[0081] The preparation method of MXene in step (1) is as follows:

[0082] S1. Weigh 2 g of Ti3AlC2 powder and slowly add it to a 2 g LiF (20 mL, 9 M) HCl solution. The reaction was stirred magnetically in a polytetrafluoroethylene reactor at room temperature for 48 hours.

[0083] S2. After the reaction, the product was centrifuged several times (3500 rpm, 10 min) and washed with deionized water until the pH was close to 6;

[0084] S3. Finally, gray-black multilayer MXene nanosheets were precipitated and freeze-dried for 48 hours for later use.

[0085] In step (2), the precursor solution

[0086] The concentration of the two-dimensional MXene nanosheet solution was 1-5 mg / mL. 0.106 g Na2MoO4, 0.14 g CH4N2S, 0.13 g citric acid (CA) and 30 mL Ti3C2T x The suspension was added to 50 mL of polytetrafluoroethylene liner and ultrasonically treated for 30 minutes.

[0087] The heat treatment steps in step (iv) are as follows:

[0088] The samples were hydrothermally reacted at 200 °C for 18 h, followed by annealing at 600–800 °C in an inert atmosphere for 30–45 min.

[0089] In step (iv), MoS2 contains 1T phase and 2H phase and the operation is as follows:

[0090] The ratio of 1T phase of MoS2 to 2H phase of MoS2 can be adjusted by regulating the heat treatment temperature and time.

[0091] The lattice period range of the moiré superlattice in step (5) is as follows:

[0092] The lattice period of the moiré superlattice is 0.6–0.8 nm.

[0093] Experiments show that at higher temperatures, MoS2 x Obvious periodic overlapping areas are formed on the surface of the nanosheets, producing a moiré-like superlattice structure, which helps to enhance electronic interactions and catalytic activity.

[0094] Example 3:

[0095] The difference between this embodiment and the first embodiment is that the preparation steps are as follows:

[0096] (1) Selective etching of Ti3AlC2 precursor using LiF and HCl to obtain MXene nanosheets;

[0097] (2) mixing the MXene solution with Na2MoO4, CH4N2S and citric acid in proportion and ultrasonically dispersing the mixture in an aqueous solvent to form a precursor solution;

[0098] (3) placing the obtained precursor solution and the substrate simultaneously into a hydrothermal reactor for hydrothermal reaction, cooling naturally after the reaction, and removing the catalyst;

[0099] (4) Under an inert atmosphere, the catalyst is first preheated at low temperature and then pyrolyzed at high temperature to form a two-dimensional MoS2 and MXene heterojunction with a 1T / 2H phase coexistence structure;

[0100] (5) A periodic moiré superlattice structure is formed between two-dimensional MoS2 and MXene, forming a synergistic interface.

[0101] The preparation method of MXene in step (1) is as follows:

[0102] S1. Weigh 2 g of Ti3AlC2 powder and slowly add it to a 2 g LiF (20 mL, 9 M) HCl solution. The reaction was stirred magnetically in a polytetrafluoroethylene reactor at room temperature for 48 hours.

[0103] S2. After the reaction, the product was centrifuged several times (3500 rpm, 10 min) and washed with deionized water until the pH was close to 6;

[0104] S3. Finally, gray-black multilayer MXene nanosheets were precipitated and freeze-dried for 48 hours for later use.

[0105] In step (2), the precursor solution

[0106] The concentration of MXene is 1-5 mg / mL, 0.206 g Na2MoO4, 0.304 g CH4N2S, 0.13 g citric acid (CA) and 30 mL Ti3C2T x The suspension was added into a 50 mL polytetrafluoroethylene liner and sonicated for 30 minutes.

[0107] The heat treatment step in step (four) is as follows:

[0108] Firstly, hydrothermal reaction at 180 °C for 24 hours, then annealing in inert atmosphere at 600-800 °C for 30-45 minutes.

[0109] The MoS2 in step (four) contains 1T phase and 2H phase and its operation is as follows:

[0110] The ratio of 1T and 2H phase of MoS2 can be adjusted by controlling the hydrothermal reaction temperature and time.

[0111] The lattice period of the moire superlattice in step (five) is as follows:

[0112] The lattice period of the moire superlattice is 0.6-0.8 nm.

[0113] Under this condition, coexisting 1T-MoS2 and 2H-MoS2 crystal phases can be obtained, and both of them are uniformly distributed on the Ti3C2T x The conductive property of 1T phase and the semiconductor property of 2H phase jointly act on the catalytic process, realizing the synergistic effect of fast electron transfer and selective activation of reaction interface.

[0114] Although embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, replacements and changes can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a MoS2 / MXene moiré heterogeneous synergistic catalyst, characterized by: The preparation steps are as follows: (1) Selective etching of Ti3AlC2 precursor using LiF and HCl to obtain two-dimensional MXene nanosheets; (2) mixing the MXene solution with Na2MoO4, CH4N2S and citric acid in proportion and ultrasonically dispersing the mixture in an aqueous solvent to form a precursor solution; (3) placing the obtained precursor solution and the substrate simultaneously into a hydrothermal reactor for hydrothermal reaction, cooling naturally after the reaction, and removing the catalyst; (4) Under an inert atmosphere, the catalyst is first preheated at low temperature and then pyrolyzed at high temperature to form a MoS2 and MXene heterojunction with a 1T / 2H phase coexistence structure; (5) A periodic moiré superlattice structure is formed between two-dimensional MoS2 and MXene, forming a synergistic interface.

2. The method for preparing a MoS2 / MXene moiré heterogeneous synergistic catalyst according to claim 1, characterized in that: The preparation method of MXene in step (1) is as follows: S1. Weigh 1 to 2 g of Ti3AlC2 powder and slowly add it to a 15 to 20 mL, 9 to 12 M HCl solution containing 1 to 2 g of LiF. The mixture is stirred magnetically in a polytetrafluoroethylene reactor at room temperature for 48 hours. S2. After the reaction, the product was centrifuged several times (3500 rpm, 10 min) and washed with deionized water until the pH was close to 6-7; S3. Finally, gray-black multilayer MXene nanosheets were precipitated and freeze-dried for 48 hours for later use.

3. The method for preparing a MoS2 / MXene moiré heterogeneous synergistic catalyst according to claim 1, characterized in that: In the step (ii), the precursor solution 0.106-0.206 g Na2MoO4, 0.14-0.304 g CH4N2S, 0.13 g citric acid (CA) and 15-30 mL Ti3C2T x The suspension was added to 50 mL of polytetrafluoroethylene liner and ultrasonically treated for 30 min to form a uniform mixture.

4. The method for preparing a MoS2 / MXene moiré heterogeneous synergistic catalyst according to claim 1, characterized in that: The heat treatment steps in step (iv) are as follows: First, perform a hydrothermal reaction at 160-200℃ for 12-24 hours, and then anneal in an inert atmosphere at 600-800℃ for 30-45 minutes.

5. The method for preparing a MoS2 / MXene moiré heterogeneous synergistic catalyst according to claim 1, characterized in that: In the step (iv), MoS2 contains 1T phase and 2H phase and the operation is as follows: The ratio of 1T and 2H phases of MoS2 can be adjusted by regulating the hydrothermal reaction temperature and time.

6. The method for preparing a MoS2 / MXene moiré heterogeneous synergistic catalyst according to claim 1, characterized in that: The lattice period range of the moiré superlattice in step (5) is as follows: The lattice period of the moiré superlattice is 0.6–0.8 nm.

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