A method and application of high-pressure puffing-ultrasonic assisted exfoliation of two-dimensional materials and in-situ loading of metals

Abstract

The application discloses a method for high-pressure puffing-ultrasonic assisted exfoliation of two-dimensional materials and in-situ loading of metals and application. The method places uniformly dispersed layered raw materials in a pressure-resistant reaction device, uses water as a medium, and realizes interlayer intercalation and loosening under subcritical conditions through low-frequency medium-pressure pretreatment. After dilution, main exfoliation is carried out through ultrasonic high frequency and high pressure. The operation is a cycle, which promotes the exfoliation of the layered material into two-dimensional nanosheets. Then, metal precursors are introduced to puff the two-dimensional nanosheets and complete the in-situ reduction and uniform loading of the nanometer metal precursors through ultrasonic circulation. The application only uses water as a medium, and through multi-cycle puffing-ultrasonic synergistic effect, the efficient exfoliation of two-dimensional materials and the in-situ loading of nanometer metals are simultaneously completed, realizing the high dispersity of metal particles and the interface bonding strength with two-dimensional materials. The obtained metal-loaded two-dimensional material has important application value in the fields of catalytic reaction, energy storage, conductive ink and the like.

Description

Technical Field

[0001] This invention belongs to the field of advanced nanomaterial green preparation technology, specifically relating to a method and application of high-pressure expansion-ultrasound-assisted exfoliation of two-dimensional materials and in-situ metal loading. In particular, through multi-cycle "expansion-ultrasound," layered two-dimensional materials are first gradually exfoliated into thin two-dimensional nanosheets less than 5 nm thick. Then, a metal precursor is introduced, and the in-situ reduction and uniform loading of the nanometal are completed in the "expansion-ultrasound" process. The resulting metal-loaded two-dimensional materials can be widely used in electrocatalysis, energy storage, conductive inks, electromagnetic shielding, and biomedicine, offering significant advantages such as simple process, absence of organic solvents, and ease of continuous scale-up. Background Technology

[0002] Since the advent of graphene, two-dimensional materials have attracted widespread attention due to their atomic-level thickness, large specific surface area, and excellent electrical, thermal, and chemical properties. However, in layered precursors, strong van der Waals forces and π–π stacking interactions result in low efficiency and difficulty in controlling defects during the material exfoliation process. To expand their applications, it is often necessary to uniformly load nanomaterials such as Pt, Pd, Au, Ag, Cu, and Fe onto the surface of two-dimensional materials to improve interfacial catalytic activity or enhance electron and ion transport performance. The traditional two-step process of exfoliation followed by loading is complex and prone to causing layer re-stacking, metal particle agglomeration, and insufficient interfacial bonding strength. Furthermore, it is often accompanied by residual organic solvents and strong reducing agents, making it difficult to meet the requirements of green and large-scale production.

[0003] Among existing exfoliation technologies, mechanical ball milling and ultrasonic treatment are energy-intensive, have low yields, and easily introduce lattice defects. Chemical oxidation-reduction routes require strong oxidants such as potassium permanganate and persulfate, as well as large amounts of organic solvents, generating wastewater that is difficult to treat, and oxidation defects are difficult to repair. Ion / molecular intercalation methods require long-term infiltration and are supplemented by high-temperature expansion or solvent exchange, resulting in complex processes and serious intercalator residues. Although supercritical water or fluid exfoliation can obtain high-quality nanosheets, the operating window is harsh (temperature ≥374℃, pressure ≥22.1 MPa), requiring large equipment investment, making safety control difficult, and it is impossible to simultaneously achieve in-situ metal loading. On the other hand, conventional metal loading methods such as wet chemical reduction, photo / thermal reduction, or physical vapor deposition generally require additional reducing agents, surfactants, or high vacuum conditions, resulting in wide metal particle size distribution, severe interface contamination, high energy consumption, and difficulty in scale-up. In terms of metal loading, wet chemical reduction commonly uses hazardous reducing agents such as sodium borohydride and hydrazine hydrate, as well as high-boiling-point organic solvents such as DMF and NMP, resulting in a wide particle size distribution and severe agglomeration of metal particles. Although physical vapor deposition or chemical vapor deposition can obtain a clean interface, the high vacuum and high temperature conditions cause a sharp increase in cost and make it difficult to handle powders. Photothermal reduction strategies require additional energy input, have poor uniformity, and are difficult to scale up.

[0004] In recent years, periodic pulsed pressurization technology has demonstrated advantages in polymer processing and micromixing by inducing local cavitation, shearing, and microjets through transient high-pressure gradients. However, it has not yet been systematically applied to the green exfoliation and in-situ metal loading of two-dimensional materials. How to precisely couple pulsed energy to the interlayer dissociation and metal reduction processes under mild conditions of aqueous phase, non-supercritical, and additive-free conditions to achieve one-step preparation of high-quality two-dimensional materials with uniform metal loading remains a key technological bottleneck that urgently needs to be overcome in this field. Summary of the Invention

[0005] This invention discloses a method and application for high-pressure expansion-ultrasound-assisted exfoliation of two-dimensional materials and in-situ metal loading, aiming to solve problems in existing technologies such as step-by-step exfoliation and metal loading, severe layer damage, metal agglomeration and weak interfacial bonding, high energy consumption, and complex processes. This invention uses water as the sole reaction medium and employs a multi-cycle "expansion-ultrasound synergy" mechanism to gradually exfoliate layered raw materials. Simultaneously, metal is in-situ reduced and uniformly loaded onto the newly formed layer surfaces, achieving simultaneous exfoliation of two-dimensional materials and metal loading.

[0006] This invention defines a method for high-pressure expansion-ultrasound-assisted exfoliation of two-dimensional materials and in-situ loading of metal, specifically including the following steps:

[0007] 1) Disperse the layered two-dimensional material precursor in water to prepare a dispersion with a concentration of 2-20 wt%, and mechanically stir to form a uniform dispersion system;

[0008] 2) Inject the mixed dispersion obtained in step 1) into a high-pressure resistant reaction device, raise the temperature of the chamber from room temperature to 250-300℃, and keep it at a constant temperature and pressure of 15-20 MPa for 30-100 minutes to allow water molecules to enter the interlayer of the layered two-dimensional material precursor and induce the expansion of the interlayer structure; after the heat preservation is completed, reduce the pressure of the reaction chamber to normal pressure by rapid depressurization, and cool it to room temperature under cooling water or natural cooling conditions to obtain a high-viscosity expanded slurry;

[0009] 3) Add water to the high-viscosity expanded slurry in step 2) to dilute it until the concentration of the two-dimensional material is halved; transfer the diluted slurry to an ultrasonic bath and treat it continuously for 12-24 hours with an ultrasonic power of 200-600 W and an ultrasonic frequency of 20-40 kHz, so that the expanded layer is gradually peeled off into two-dimensional nanosheets.

[0010] 4) Taking the expansion-dilution ultrasonic process of step 2)-3) as one process cycle, repeat the process cycle of step 2)-3) 5-20 times to gradually peel off the layered two-dimensional material into two-dimensional nanosheets with a thickness of less than 5 nm.

[0011] 5) Before the ultrasonic treatment in the penultimate process cycle of step 4), add the metal precursor solution, and obtain a uniformly dispersed mixture by ultrasonication. Then, after the expansion-dilution ultrasonic treatment in the last process cycle, obtain a dispersion of metal-supported two-dimensional material uniformly dispersed on the surface or edge of the two-dimensional nanosheet.

[0012] 6) The dispersion obtained in step 5) is centrifuged at a speed of 8000~15000 rpm, and the supernatant is collected to remove the unpeeled layered material and agglomerated particles; the supernatant is reduced by heat treatment or chemical reduction to convert the metal precursor into nano-metal particles, which are uniformly loaded on the surface or edge of the two-dimensional material sheets, and then freeze-dried to obtain the metal-loaded two-dimensional material.

[0013] Furthermore, the present invention further specifies that the layered two-dimensional material precursor in step 1) is selected from at least one of the following: multilayer natural graphite, expanded graphite, hexagonal boron nitride, MXene (Ti3C2 / Ti2C), molybdenum disulfide (MoS2), molybdenum diselenide (MoSe2), molybdenum carbide (Mo2C), and niobium carbide (Nb2C).

[0014] Furthermore, the present invention also specifies that the stirring time in step 1) to form a uniformly dispersed system is 20-60 minutes.

[0015] Furthermore, the present invention further specifies that the high-pressure resistant reaction chamber in step 2) is a closed high-temperature and high-pressure resistant reactor with a pressure range of 15–25 MPa and a reaction temperature range of 25–300°C. The reaction uses water as the only medium, and under these specified conditions, the temperature of the water does not exceed its supercritical condition and is in the subcritical condition.

[0016] Furthermore, the present invention also specifies that the heating rate of the cavity in step 2) is 2–8℃ / min, so that water molecules gradually enter the interlayer structure and form a swollen state; the rapid depressurization process reduces the pressure to normal pressure within 1–5 seconds to induce rapid expansion of the interlayer.

[0017] Furthermore, the present invention also limits the amount of water used for dilution in step 3) to be equal to the volume of the expanded slurry, so that the total volume of the system reaches twice that of the original expanded system.

[0018] Furthermore, the present invention also specifies that the ultrasonic treatment in step 3) is carried out under cooling water circulation conditions to keep the system temperature not higher than 50°C and avoid the fragmentation or agglomeration of the sheets.

[0019] Furthermore, the present invention also specifies that the pressurization method in step 2) is pulse pressurization, the waveform is square wave, sine wave or triangle wave, and the pulse pressure amplitude is 5%–20% of the set pressure.

[0020] Furthermore, the present invention further specifies that the high-pressure resistant reaction device in step 2) is equipped with a stirring system, a heating system, a pulse pressurization system, and a data acquisition and control system. The pulse pressurization system is used to periodically apply a set pressure, and the data acquisition and control system records and adjusts the pulse pressure, pulse frequency, and temperature. The data acquisition and control system is used to monitor and adjust the temperature, pressure, pulse frequency, and duration in real time. The heating system precisely heats or keeps the pressure-resistant chamber warm according to the instructions of the data acquisition and control system. The pulse pressurization system applies precise pressure to the pressure-resistant chamber through a servo hydraulic or pneumatic booster according to the instructions of the data acquisition and control system.

[0021] Furthermore, the present invention further specifies that in step 5), after adding the metal precursor, stirring is continued for 10–30 minutes at a stirring speed of 300–800 r / min to ensure that the metal precursor is uniformly penetrated into the interlayer; the metal precursor is selected from at least one of nickel nitrate, chloroplatinic acid, palladium chloride, copper nitrate, silver nitrate, zinc nitrate, and ruthenium chloride.

[0022] Furthermore, the present invention also specifies that the centrifugation speed in step 6) is 8000~15000 rpm and the centrifugation time is 5–15 minutes.

[0023] Furthermore, the present invention also specifies that when the reduction method in step 6) is heat treatment, the heat treatment temperature is 200–400°C and the holding time is 0.5–4 hours.

[0024] Furthermore, the present invention also specifies that when the reduction method in step 6) is chemical reduction, the reducing agent is NaBH4, sodium citrate or ascorbic acid, wherein the amount of reducing agent is 1–3 times the molar amount of the metal precursor.

[0025] Furthermore, the present invention also limits the particle size of the reduced metal nanoparticles in step 6) to 1–50 nm, and they are uniformly loaded on the surface or edge of the two-dimensional material sheet without obvious agglomeration.

[0026] Furthermore, the present invention also defines the two-dimensional material with in-situ metal loading obtained in step 6) as a powder, film or sheet-like solid after freeze-drying, wherein the sheet thickness is 0.3–10 nm and the sheet diameter is 0.1–20 μm.

[0027] Furthermore, the present invention also defines the application of metal-supported two-dimensional materials prepared by a defined method in electrocatalysis, energy storage, conductive inks, electromagnetic shielding, and flexible devices.

[0028] The concept of this invention is as follows: using water as the sole reaction medium, a layered two-dimensional material precursor is dispersed and injected into a pressure-resistant reaction chamber. Through expansion treatment, water molecules enter the interlayer and induce the interlayer structure to open, forming an expanded slurry. Subsequently, the expanded slurry is diluted and ultrasonically applied under cooling water circulation conditions, causing the expanded layers to gradually peel off into two-dimensional nanosheets. This invention uses "expansion-dilution ultrasound" as a complete process cycle. By repeating multiple cycles until the interlayer structure gradually loosens and the sheets continuously peel off, and after introducing a metal precursor, the metal is simultaneously introduced into the sheet interface during the peeling process, thereby improving the uniformity of metal loading. Finally, heat treatment or chemical reduction is used to convert the metal precursor into nano-metal particles, and freeze-drying yields a two-dimensional material with in-situ metal loading. This invention, through multi-cycle synergistic operation, has a simple overall process flow and is applicable to various layered precursors and various metal systems.

[0029] By employing the technology defined in this invention, compared with existing methods that separate stripping and loading into multiple independent steps, this invention has the following advantages:

[0030] (1) This invention uses water as the only reaction medium and does not involve organic solvents. Water enters the interlayer at high temperature to form a swollen structure, and is gradually peeled off through rapid pressure relief and ultrasonic treatment. The process conditions are mild and the system is highly safe, making it suitable for conventional operation of pressure-resistant reaction equipment.

[0031] (2) In this invention, water molecules are introduced into the interlayer through the expansion process, which opens the layered structure and forms a high-viscosity expanded slurry. Then, the layered two-dimensional material is gradually peeled off to two-dimensional nanosheets with a thickness of less than 5 nm by dilution ultrasound. After the metal precursor is introduced, the metal is synchronously introduced into the layer interface during the peeling process, thereby improving the uniformity of metal loading. Finally, the metal precursor is converted into nano metal particles by heat treatment or chemical reduction.

[0032] (3) The present invention adopts a process cycle repetition method, and through multiple cycles of "expansion-dilution ultrasound", the peeling process is more thorough, and the metal precursor is gradually distributed on the surface or edge as the sheets are peeled off, thereby improving the uniformity of the final product.

[0033] (4) The present invention removes unpeeled layered materials and agglomerated particles by centrifugation under limited conditions, and converts metal precursors into nano-metal particles by heat treatment or chemical reduction. The final product with metal nanoparticles of 1-50 nm in diameter is uniformly distributed on the surface or edge of two-dimensional material sheets. The final product is morphologically stable and easy to use in subsequent applications.

[0034] (5) The preparation process of the present invention consists of dispersion, expansion, dilution and ultrasonication, repeated cycles and reduction. The operation steps are continuous and the material is widely applicable. It can be used for precursors such as graphite, hexagonal boron nitride, MXene, transition metal sulfides, carbides and layered oxides. The obtained metal in-situ loaded two-dimensional materials have application potential in the fields of electrocatalysis, energy storage, conductive inks, electromagnetic shielding and flexible devices. Attached Figure Description

[0035] Figure 1 TEM image of the Pd / Graphene nanocomposite powder obtained in Example 1;

[0036] Figure 2 SEM image of the Pd / Graphene nanocomposite powder obtained in Example 1;

[0037] Figure 3 TEM image of Pt / Graphene nanocomposite powder obtained in Example 2;

[0038] Figure 4 SEM image of Ru / Ti3C2 MXene composite powder obtained in Example 3;

[0039] Figure 5 Here is a SEM image of the Ag / NB composite powder obtained in Example 4;

[0040] Figure 6 SEM image of the Ag / Graphene composite powder obtained in Example 5;

[0041] Figure 7 The image shows the SEM image of the Ni / Ti3C2 MXene composite powder obtained in Example 6. Detailed Implementation

[0042] The present invention will be further described below with reference to the embodiments and accompanying drawings, but the scope of protection of the present invention is not limited thereto:

[0043] Example 1: Preparation of Pd / Graphene Nanocomposite Powder

[0044] 8 g of natural graphite was added to deionized water to prepare a 10 wt% dispersion. The mixture was mechanically stirred for 30 min to form a homogeneous system, which was then injected into a pressure-resistant cavity. The temperature was raised to 300℃ and maintained at 20 MPa for 30 min. After rapid depressurization (reducing to atmospheric pressure within 1 second), an expanded slurry was obtained. This slurry was diluted with an equal volume of deionized water to a concentration of 5 wt%. Under cooling water circulation, the slurry was sonicated at 20–40 kHz and approximately 300 W for 24 h to gradually peel off the sheets. This "expansion-dilution sonication" process was repeated 10 times. Before the sonication process in the 9th cycle, a palladium acetate solution (equivalent to 0.4 g of Pd mass, target load 5 wt%, meaning the metal precursor loading is equal to the mass of the two-dimensional material precursor, the same below) was added to form a homogeneous dispersion system of two-dimensional graphite sheets and palladium acetate. The "expansion-dilution sonication" process was then repeated 10 times, allowing the Pd precursor to gradually disperse during the peeling process and be reduced in situ to nanoparticles under local cavitation conditions. The nanoparticles were then centrifuged at 12000 rpm for 10 minutes. The supernatant was collected and heat-treated at 300℃ for 1 h, followed by freeze-drying to obtain two-dimensional graphene-supported Pd powder, Pd / Graphene. Its SEM and TEM images are shown below. Figure 1 , Figure 2 As shown in the figure, the graphene sheets have a diameter of about 4–6 μm and a thickness of about 1 nm, while the Pd particles have a diameter of about 2–5 nm and are uniformly distributed. This material exhibits excellent activity and stability in selective hydrogenation, electrocatalysis, and fuel cell cathode catalysis.

[0045] Example 2: Preparation of Pt / Graphene Nanocomposite Powder

[0046] 8 g of natural graphite was dispersed in deionized water to form a 10 wt% slurry. The mixture was stirred for 30 min to form a homogeneous system, which was then injected into a pressure-resistant cavity. The cavity was heated to 280°C, subjected to 18 MPa, and held for 30 min. The pressure was then rapidly released within 3 seconds to obtain an expanded system. The expanded slurry was diluted with an equal volume of water to approximately 5 wt%, and then subjected to continuous ultrasonication at 20–40 kHz and approximately 300 W for 24 h under cooling conditions to exfoliate the sheets. This process was repeated 12 times as one cycle. Before the ultrasonication process in the 11th cycle, a chloroplatinic acid solution (equivalent to 0.2 g of Pt, with a target load of 2.5 wt%) was added to form a homogeneous dispersion of two-dimensional graphite sheets and chloroplatinic acid. The 12th "expansion-dilution ultrasonication" process was then repeated, allowing the Pt precursor to be reduced in situ to nanoparticles at the continuously exposed new interfaces of the sheets. The supernatant was collected after centrifugation at 12000 rpm for 10 min and then heat-treated at 200°C for 2 seconds. After reduction, freeze-drying yielded Pt / Graphene composite powder with a flake diameter of approximately 4–6 μm and a thickness of approximately 1.5 nm. The Pt particles were approximately 2–4 nm in size and uniformly anchored. This material exhibited excellent catalytic efficiency in alcohol oxidation, hydrogen evolution reaction, and fuel cell electrodes. Its TEM image is shown below. Figure 3 As shown.

[0047] Example 3: Preparation of Ru / Ti3C2 MXene nanocomposite powder

[0048] 7 g of etched Ti3C2 was added to deionized water to form a 12 wt% dispersion. After stirring for 30 min, a homogeneous system was formed and injected into a pressure-resistant cavity. The temperature was raised to 250℃ and held at 20 MPa for 30 min. After rapid depressurization within 2 seconds, an expanded slurry was obtained. The slurry was diluted with an equal volume of water to approximately 6 wt% and sonicated at 20–40 kHz for 20 h in a cooling ultrasonic bath to gradually peel off the layered structure. The "expansion-dilution ultrasonication" process was repeated 10 times as one cycle. Before the ultrasonication process of the 9th cycle, a RuCl3 solution (equivalent to 0.08 g of Ru, target load 1.1 wt%) was added to form a homogeneous dispersion system of two-dimensional MXene and RuCl3. Then, the "expansion-dilution ultrasonication" process was repeated 10 times to allow Ru to gradually peel off the layered structure. 3+ As the lamellae peeled off, they were gradually reduced in situ to nanoparticles on the surface. The supernatant was collected by centrifugation at 12000 rpm and treated at 300℃ for 1 h, followed by freeze-drying to obtain Ru / Ti3C2 powder. The resulting MXene lamellae had a diameter of approximately 2–4 μm and a thickness of approximately 1.2–1.5 nm, with Ru particles of approximately 1–4 nm uniformly loaded. This material exhibited high activity and excellent cycling stability in electrocatalytic hydrogen evolution, hydrogen isotope exchange, and electrochemical energy storage. Its SEM images are shown below. Figure 4 As shown.

[0049] Example 4: Preparation of Ag / h-BN nanocomposite powder

[0050] 15 g of hexagonal boron nitride was added to deionized water to form a 15 wt% dispersion. After stirring for 30 min, a homogeneous system was injected into a pressure-resistant cavity, heated to 250℃, and held at 18 MPa for 30 min. After rapid depressurization within 5 seconds, an expanded slurry was obtained. The expanded system was diluted 2 times and sonicated at 20–40 kHz for 24 h in a cooling ultrasonic bath to gradually exfoliate h-BN and Ag. + In-situ reduction to nanoparticles was performed, and this process was repeated 8 times as one cycle. Before the ultrasonic process in the 7th cycle, a silver carbonate solution (equivalent to 0.50 g of Ag, target loading 3.3 wt%) was added to form a uniform dispersion system of two-dimensional h-BN and silver carbonate. Subsequently, the "expansion-dilution ultrasonication" process was repeated once to reduce the Ag content to nanoparticles. + In-situ reduction to nanoparticles, followed by centrifugation at 12000 rpm for 10 min to collect the supernatant, heat treatment at 250℃ for 1 h, and freeze-drying to obtain Ag / h-BN composite powder with a flake diameter of approximately 3 μm and a thickness of approximately 2.2 nm. The Ag particles have a diameter of approximately 4–8 nm and are uniformly dispersed. This material exhibits excellent performance in thermally conductive composites, conductive inks, and electromagnetic shielding. Its SEM image is shown below. Figure 5 As shown.

[0051] Example 5: Preparation of Ag / Graphene Nanocomposite Powder

[0052] 20 g of natural graphite was dispersed in deionized water to form a 10 wt% slurry. After stirring for 30 min, the slurry was injected into a pressure-resistant chamber, heated to 250 °C, subjected to 16 MPa, and held for 30 min. The pressure was then rapidly released within 4 seconds to obtain an expanded system. The expanded slurry was diluted with an equal volume of water to approximately 5 wt%, and then subjected to continuous sonication at 20–40 kHz and approximately 600 W for 12 h under cooling conditions to exfoliate the sheets. This "expansion-dilution sonication" process was repeated 5 times. Before the sonication process in the 4th cycle, a silver carbonate solution (equivalent to 2 g of Ag, with a target loading of 10 wt%) was added to form a uniform dispersion system of two-dimensional graphene and silver carbonate. The 5th "expansion-dilution sonication" process was then repeated, allowing the Ag precursor to be reduced in situ at the newly exposed interfaces of the sheets to generate nanoparticles. After centrifugation at 8000 rpm for 15 min, the supernatant was collected and reduced with sodium citrate, followed by freeze-drying to obtain Ag / Graphene composite powder with a sheet diameter of approximately 6–12 mm. With a particle size of approximately μm and a thickness of approximately 1.2 nm, and uniformly anchored Ag particles of approximately 2–4 nm, this material exhibits excellent performance in photodegradation, conductive inks, and electromagnetic shielding. Its SEM image is shown below. Figure 6 As shown.

[0053] Example 6: Preparation of Ni / Ti3C2 MXene nanocomposite powder

[0054] 7.00 g of etched Ti3C2 was dispersed in deionized water to form a suspension of approximately 10 wt%. After mechanical stirring for 30 min, the mixture was transferred to a pressure-resistant chamber, heated to 280 °C, and held at 20 MPa for 30 min. The pressure was then rapidly released within 1 second to obtain an expanded slurry. An equal volume of deionized water was added to dilute the slurry to 5 wt%, and the slurry was placed in a cooling ultrasonic bath and sonicated at 20–40 kHz and 200–500 W for 24 h to further open and gradually peel off the interdomain structures. This "expansion-dilution ultrasonication" process was repeated 5 times as one cycle. Before the ultrasonication process in the 4th cycle, a nickel nitrate hexahydrate solution (equivalent to 0.20 g of Ni mass, with a target loading of approximately 2.8 wt%) was added to form two-dimensional MXene and Ni. + A uniformly dispersed system was formed, and then the "expansion-dilution ultrasound" process was repeated for the fifth time to allow the Ni precursor to be converted into nano-metal particles in situ under local reduction conditions. The supernatant was collected by centrifugation at 12,000 rpm, reduced at 300℃ for 1 h, and freeze-dried to obtain Ni / Ti3C2 black composite powder. The obtained MXene sheets had a diameter of approximately 2–4 μm and a thickness of approximately 1.5 nm, and the Ni particles had a diameter of approximately 3–6 nm and were uniformly loaded. This material exhibited high conductivity and excellent cycling stability in hydrogenation of nitro compounds, electromagnetic shielding, and supercapacitor electrodes. Its SEM image is shown below. Figure 7 As shown.

[0055] Example 7: Preparation of Cu / Graphene Nanocomposite Powder

[0056] 8.00 g of natural flake graphite was dispersed in deionized water to form a 10 wt% slurry. After stirring for 30 min, the slurry was injected into a pressure-resistant cavity, heated to 250℃, and held at 20 MPa for 30 min. The pressure was then rapidly released within 3 seconds to induce expansion, resulting in a thick slurry. This slurry was diluted to 5 wt% with an equal volume of deionized water and placed in a cooling circulating ultrasonic bath for continuous sonication at 20–40 kHz for 24 h. This process was repeated 15 times as one cycle to efficiently exfoliate graphite into few-layer graphene. Before the 14th cycle of ultrasonication, a copper acetate solution (equivalent to 0.80 g of Cu, with a target loading of approximately 10 wt%) was added to form a uniform dispersion system of two-dimensional graphene and copper acetate, allowing Cu to... 2+The process involves complete contact with the flakes, followed by a 15th iteration of the "expansion-dilution ultrasound" process. This process promotes the in-situ generation of nano-metal particles from the Cu precursor under local cavitation and water reduction. The supernatant is collected by centrifugation at 12,000 rpm and calcined at 250 °C for 1 h. After freeze-drying, Cu / Graphene composite powder is obtained, with flake diameters of approximately 4–8 μm and thicknesses of approximately 1.5 nm. The Cu particles are approximately 3–6 nm in size and are well dispersed. This material exhibits excellent thermal conductivity and electrical conductivity in high thermal conductivity coatings, conductive inks, and heat dissipation composite materials.

[0057] Example 8: Preparation of Pd / Ti3C2 MXene nanocomposite powder

[0058] 6.00 g of etched Ti3C2 was added to deionized water to form a uniform dispersion of approximately 6 wt%. After stirring for 30 min, the mixture was injected into a pressure-resistant cavity, heated to 250 °C, and held at 20 MPa for 30 min. The pressure was then rapidly released within 3 seconds to obtain the expanded system. The system was diluted to 3 wt% with an equal volume of water and continuously sonicated at 20–40 kHz for 24 h in a cooling water circulating ultrasonic bath to gradually peel off the layers and expose new interfaces. This "expansion-dilution ultrasonication" process was repeated 8 times as one cycle. Before the ultrasonication process in the 7th cycle, a palladium acetate solution (equivalent to 0.23 g of Pd, target loading 3.8 wt%) was added to form a uniform dispersion of two-dimensional MXene and palladium acetate. The 8th "expansion-dilution ultrasonication" process was then repeated to further disperse the Pd... 2+ During the process, the particles were reduced in situ to 2–4 nm and uniformly anchored on the surface of the sheet. After centrifugation at 12,000 rpm for 10 min, calcination at 300 °C for 1 h, and freeze-drying, Pd / Ti3C2 black powder was obtained with a sheet diameter of about 2–4 μm and a thickness of about 1–1.5 nm. The Pd nanoparticles were highly dispersed and firmly bonded. This material exhibited excellent activity and long-term durability in methanol electro-oxidation, hydrogen evolution reaction, and coupling catalysis.

[0059] Example 9: Preparation of Ru / Graphene Nanocomposite Powder

[0060] 8.00 g of natural graphite was dispersed in deionized water and stirred for 30 min to form a 10 wt% dispersion. This dispersion was injected into a pressure-resistant chamber, heated to 250°C, subjected to 20 MPa, and held for 30 min. The pressure was then rapidly released within 2 seconds to obtain an expanded slurry. The slurry was diluted with an equal volume of deionized water to 5 wt% and continuously sonicated at 20–40 kHz for 24 h in a cooling ultrasonic bath. This process was repeated 15 times as one cycle to exfoliate the graphite into few-layer graphene. Before the 14th cycle of ultrasonication, a RuCl3 solution (equivalent to 0.09 g of Ru, with a target loading of approximately 1.1 wt%) was added to form a uniform dispersion system of two-dimensional graphene and RuCl3. This process was then repeated 15 times using the "expansion-dilution ultrasonication" process to exfoliate and promote the Ru... 3+ Nanoparticles were formed by in-situ reduction in aqueous phase. After centrifugation at 12,000 rpm to remove the precipitate, the supernatant was heat-treated at 250 °C for 1 h and then freeze-dried to obtain Ru / Graphene powder with a particle size of 4–6 μm and a thickness of about 1 nm. The Ru particles were uniformly anchored at 2–5 nm. This material exhibited high activity and excellent cycle life in selective hydrogenation, hydrogen isotope exchange and electrocatalytic oxygen reduction.

[0061] Example 10: Preparation of Pt / h-BN nanocomposite powder

[0062] 10.00 g of h-BN was dispersed in deionized water and stirred for 30 min to form a 12 wt% dispersion. This dispersion was injected into a pressure-resistant cavity, heated to 250 °C, subjected to 20 MPa, and held for 30 min. The pressure was then rapidly released within 3 seconds to obtain an expanded slurry. This slurry was diluted to 6 wt% and continuously sonicated at 20–40 kHz for 24 h in a cooling ultrasonic bath. This process was repeated 5 times as one cycle to exfoliate the h-BN sheets. Before the fourth cycle of ultrasonication, palladium acetate solution and chloroplatinic acid solution (equivalent to 0.50 g of Pt, target loading 5 wt%) were added to form a uniform dispersion system of two-dimensional h-BN nanosheets and Pt. The fifth "expansion-dilution ultrasonication" process was then repeated to reduce the Pt precursor to nanoparticles in situ at a fresh interface. After centrifugation at 12000 rpm, heat treatment at 250 °C for 1 h, and freeze-drying, Pt / h-BN powder was obtained, with a sheet diameter of approximately 3 μm, a thickness of 0.8–1.0 nm, and Pt particles of 3–6 μm. With a uniform nm distribution, this material exhibits excellent performance in nitrobenzene hydrogenation, fuel cell catalysis, and high-temperature electromagnetic shielding.

[0063] Example 11: Preparation of Zn / h-BN nanocomposite powder

[0064] 10 g of h-BN was dispersed in deionized water to prepare a 10 wt% suspension system. After stirring for 30 min, the suspension was injected into a pressure-resistant cavity, heated to 250℃, and held at 18 MPa for 30 min. The pressure was rapidly released within 5 seconds to obtain an expanded slurry. This slurry was diluted to 5 wt% and sonicated at 20–40 kHz for 24 h under cooling cycling conditions. One cycle was repeated 8 times to exfoliate h-BN. Before the sonication process in the 7th cycle, a zinc nitrate hexahydrate solution (equivalent to 0.08 g of Zn, target loading 0.8 wt%) was added to form a uniform dispersion system of two-dimensional h-BN nanosheets and Zn. The "expansion-dilution sonication" process was then repeated once more to allow Zn to dissipate. 2+ 3–6 nm nanoparticles were generated in situ. After centrifugation to remove the precipitate, the powder was heat-treated at 200 °C for 1 h and then freeze-dried to obtain Zn / h-BN composite powder with a particle size of about 3 μm and a thickness of about 2 nm. The metal was uniformly dispersed. This material exhibits excellent antibacterial properties and biocompatibility in antibacterial coatings and biomedical materials.

[0065] Example 12: Preparation of Pd / h-BN nanocomposite powder

[0066] 10 g of h-BN was dispersed in deionized water to prepare an 8 wt% dispersion. After stirring for 30 min, the dispersion was injected into a pressure-resistant cavity, heated to 250 °C, and subjected to a pressure of 20 MPa for 30 min. The pressure was then rapidly released within 3 seconds to obtain an expanded slurry. This slurry was diluted to 4 wt% and treated in a cooling ultrasonic bath at 20–40 kHz for 24 h. This process was repeated 10 times as one cycle to ensure complete exfoliation of the sheets. Before the ultrasonic process in the 9th cycle, a palladium acetate solution (equivalent to 0.20 g of Pd, with a target loading of 2 wt%) was added to form a uniform dispersion system of two-dimensional h-BN nanosheets and Pd. Subsequently, the "expansion-dilution ultrasonic" process was repeated once more to allow Pd to fully dissipate. 2+ The material was reduced in situ to nanoparticles on the newly exposed surface. After centrifugation at 12,000 rpm for 10 min, the supernatant was collected and calcined at 250 °C for 1 h and freeze-dried to obtain Pd / h-BN powder with a sheet diameter of about 5 μm and a thickness of 1.5–3 nm. The Pd particles were highly dispersed at 3–6 nm. This material showed excellent catalytic efficiency and stability in fuel cell electrocatalysis, electrochemical sensing and electromagnetic shielding.

[0067] Example 13: Preparation of Pt / Nb2C MXene nanocomposite powder

[0068] 6.00 g of Nb₂C MXene was dispersed in deionized water to form a suspension of approximately 20 wt%. After stirring for 30 min, the suspension was injected into a pressure-resistant chamber and heated to 250 °C. A pressure of 20 MPa was applied and held for 30 min. The pressure was rapidly released within 3 seconds, followed by expansion. The slurry was diluted to 10 wt% with an equal volume of deionized water and continuously sonicated at 20–40 kHz in a cooling ultrasonic bath for 24 h. This process was repeated 12 times as one cycle to exfoliate the Nb₂C sheets. Before the 11th cycle of ultrasonication, a chloroplatinic acid solution (equivalent to 0.18 g of Pt, with a target loading of 3 wt%) was added to form a uniform dispersion of two-dimensional MXene nanosheets and Pt. The 12th cycle of the "expansion-dilution ultrasonication" process was then repeated to allow the Pt precursor to generate 2–4 nm nanoparticles in situ under reducing conditions. The supernatant was collected by centrifugation at 12000 rpm and calcined at 200–300 °C. Pt / Nb2C black powder was obtained by freeze-drying. The MXene flakes were about 1–3 μm in diameter and about 1.5 nm thick. The Pt particles were highly dispersed and firmly bonded. This material exhibited high specific capacitance and excellent rate performance in supercapacitors, electrocatalytic hydrogen evolution and lithium battery systems.

[0069] Application Example 1: Application of Ag / Graphene nanocomposite powder prepared in Example 5 in the photocatalytic treatment of tetracycline hydrochloride wastewater

[0070] The Ag / Graphene nanocomposite powder obtained in Example 5 was added to a simulated wastewater system containing tetracycline hydrochloride (initial concentration 50 mg / L), with a catalyst dosage of 0.2 g / L. The reaction was carried out in a quartz reactor under simulated visible light irradiation by a 300 W xenon lamp, maintaining room temperature and magnetic stirring (600 r / min) to ensure uniform contact. Samples were taken periodically after 2 h of reaction, and the tetracycline hydrochloride degradation rate was measured by UV-Vis spectrophotometer, reaching 93.0%, approximately 35 times higher than the blank system. Further extending the reaction to 3 h further increased the degradation rate to over 97%. To verify recyclability, after the reaction, the catalyst was centrifuged (8000 r / min, 10 min), washed once with deionized water and once with ethanol, and then freeze-dried. The catalyst was then added to wastewater under the same conditions for repeated reaction. After five consecutive cycles, the degradation rate remains above 85%, and the catalytic efficiency decays very little, proving that it has excellent structural stability, catalytic persistence and reusability, and is suitable for green deep treatment of antibiotic pharmaceutical wastewater, livestock and poultry breeding wastewater and highly recalcitrant organic pollutants.

[0071] Application of Ni / Ti3C2 MXene nanocomposite powder prepared in Example 2 of Example 6 in the hydrogenation of nitrobenzene to p-aminophenol

[0072] 50 mL of ethanol solution containing nitrobenzene (0.10 mol / L) was added to 0.2 g of Ni / Ti3C2MXene nanocomposite powder (Ni mass fraction approximately 2.4 wt%) prepared in Example 6 as a catalyst. The system was placed in a 100 mL high-pressure stainless steel reactor. After purging the reactor three times with hydrogen gas to remove air, the hydrogen pressure was maintained at 0.1 MPa. The reactor was magnetically stirred at 30 °C for 4 h (500 r / min). After the reaction, samples were taken and analyzed by high-performance liquid chromatography. The nitrobenzene conversion rate reached 99.2%, the selectivity of the target product to aminophenol reached 98.5%, and the byproducts were mainly trace amounts of aniline and trace amounts of coupling byproducts, indicating that the catalyst has a significant advantage in the selective hydrogenation of aromatic nitro groups. After the reaction, the catalyst was recovered by centrifugation, washed with ethanol, and vacuum dried at 60 °C before being reused in the next reaction. After eight consecutive uses, the nitrobenzene yield remained at 92.1%, showing excellent cycle stability and industrial scale-up potential. It can be used for the green preparation of fine chemicals, dyes, and pharmaceutical intermediates. Similarly, the Pd / Ti3C2 MXene nanocomposite powder prepared in Example 8 was used to replace the Ni / Ti3C2 MXene nanocomposite powder in Example 6. Other operations were the same as in Application Example 2. Finally, the conversion rate of nitrobenzene reached 93.2%, the selectivity of para-aminophenol reached 96.9%, and the yield reached 90.4%.

[0073] Application Example 3: Application of Ni / Ti3C2 MXene nanocomposite powder prepared in Example 6 in the selective hydrogenation of phenylacetylene to styrene.

[0074] 50 mL of phenylacetylene cyclohexane solution (concentration 0.05 mol / L) was added to a 100 mL three-necked flask. 0.15 g of the Ni / Ti3C2 MXene nanocomposite powder catalyst prepared in Example 6 was weighed, hydrogen gas was introduced (flow rate 20 mL / min), and the reaction was stirred at 50 °C (600 r / min) for 2 h. Gas chromatography analysis of the reaction solution showed that the phenylacetylene conversion reached 97.3%, the styrene selectivity was as high as 96.1%, while the content of the over-hydrogenation product ethylbenzene was only 1.2%, proving that the catalyst can effectively inhibit further C=C hydrogenation and is a highly selective double-bond-retaining catalytic system. Catalyst separation and reuse results showed that after centrifugation and reintroduction into the system, the selectivity remained above 92% after 5 cycles, and the activity retention rate was significantly higher than that of the traditional Raney Ni catalyst. This makes it suitable for the clean preparation of high-value-added products such as styrene monomers, engineering plastics, and rubber additives. Similarly, the Pd / Ti3C2 MXene nanocomposite powder prepared in Example 8 was used to replace the Ni / Ti3C2 MXene nanocomposite powder in Example 6. Other operations were the same as in Application Example 3. Finally, the phenylacetylene conversion rate reached 95.6%, the styrene selectivity was as high as 98.6%, and the yield reached 94.3%.

[0075] Application Example 4: Application of Ni / Ti3C2 MXene nanocomposite powder prepared in Example 6 in the selective hydrogenation of methyl acrylate to methyl propionate.

[0076] 0.25 g of the Ni / Ti3C2 MXene nanocomposite powder obtained in Example 6 was added to 60 mL of a methanol solution containing methyl acrylate (0.20 mol / L). The reactor was purged with hydrogen to 0.5 MPa, and the reaction was carried out at 80 °C and 400 r / min for 3 h with stirring. Gas chromatography-mass spectrometry analysis showed that the methyl acrylate conversion rate reached 95.6%, with selective formation of methyl propionate (94.3%). The product did not contain significant C–O bond cleavage or hydrogenolysis byproducts, indicating that the catalytic system has high selectivity for double bond hydrogenation. After centrifugation, washing, and vacuum drying to recover the catalyst, the conversion rate remained at 88.7% and the selectivity at 92.7% after six consecutive uses. The catalytic activity showed low decay and good structural stability, making it highly suitable for the industrial-grade hydrogenation preparation of unsaturated esters in coatings, plasticizers, fragrances, and pharmaceutical intermediates.

[0077] Application of Pd / Ti3C2 MXene nanocomposite powder prepared in Example 5 and Example 8 in the coupling reaction of iodobenzene and phenylboronic acid

[0078] 0.05 g of the Pd / Ti3C2 MXene powder prepared in Example 8 (Pd mass fraction approximately 3 wt%) was weighed and added to an ethanol-water solution (volume ratio 1:1, total volume 20 mL) containing iodobenzene (1 mmol) and phenylboronic acid (1.2 mmol). K2CO3 (2 mmol) was added as a base, and the reaction was carried out under magnetic stirring at 80 °C for 2 h. Gas chromatography analysis showed that the iodobenzene conversion rate reached 99.5%, and the biphenyl selectivity was as high as 99.2%. After the reaction, the catalyst could be recovered by centrifugation and simply washed for reuse. After 10 consecutive cycles, the activity retention rate was still 92%, and the biphenyl selectivity was approximately 98%. This indicates that the Pd / Ti3C2 MXene possesses excellent anti-sintering properties, anti-detachment ability, and electron migration stability, making it suitable for the green synthesis of C–C bond couplings, Suzuki reactions, and fine chemicals and pharmaceutical intermediates. Similarly, replacing the Pd / Ti3C2 MXene nanocomposite powder prepared in Example 8 with the Ni / Ti3C2 MXene nanocomposite powder of Example 6, and performing the same other operations as in Application Example 5, the final iodobenzene conversion rate was only 34.2%, while the biphenyl selectivity was as high as 23.4%, indicating that the Ni / Ti3C2 MXene nanocomposite powder of Example 6 was not effective in the coupling reaction of iodobenzene and phenylboronic acid.

[0079] Application Example 6: Application of Pd / Graphene nanocomposite powder prepared in Example 1 in the preparation of enalapril intermediates

[0080] 500 mg of N-(1-(S)-ethoxycarbonyl-3-phenylpropyl)-L-alanyl-N-carboxycyanide substrate was mixed with 4.4 mL of anhydrous ethanol, and 84 μL of concentrated sulfuric acid was added as a co-catalyst. Then, 150 mg of Pd / Graphene nanocomposite powder prepared in Example 1 was added, and the mixture was placed in a stainless steel high-pressure reactor. After purging with hydrogen three times to remove air, the hydrogen pressure was maintained at 0.4 MPa, and the reaction was carried out at 30 °C and 1000 r / min for 6 h. After the reaction, the pressure was reduced by cooling, and the catalyst was recovered by filtration. Liquid chromatography analysis of the filtrate showed a conversion rate of 90%, a target product selectivity of 90.5%, and byproducts mainly consisting of trace amounts of unconverted substrate and a very small amount of hydrogenated excess product. The catalyst, after being washed with ethanol and vacuum dried at 60°C, can be reused six times, maintaining a final conversion rate above 85% and a selectivity above 90%, demonstrating good structural stability and recyclability. It is suitable for high-selectivity green hydrogenation routes for enalapril and other drug intermediates, significantly reducing the use of precious metals and the burden of wastewater treatment. Similarly, replacing the Pd / Graphene nanocomposite powder prepared in Example 1 with the Pt / Graphene nanocomposite powder prepared in Example 2, with other operations the same as in Application Example 6, resulted in a reaction conversion rate of 3.2% and a target product selectivity of 10.8%, indicating that the Pt / Graphene nanocomposite powder prepared in Example 2 is not effective in the preparation of enalapril intermediates.

[0081] Application of Pd / Ti3C2 MXene nanocomposite powder prepared in Example 7 and Example 8 in the electrocatalytic oxidation of methanol.

[0082] The Pd / Ti3C2MXene nanocomposite powder prepared in Example 8 was used to fabricate a catalytic electrode. The catalyst was loaded onto the surface of a glassy carbon electrode as the working electrode, and a three-electrode system was constructed using a saturated calomel electrode and a platinum wire counter electrode. Cyclic voltammetry was performed in an electrolyte (0.50 mol / L H2SO4 + 1.00 mol / L CH3OH). At 0.6 V (vs Ag / AgCl), a methanol oxidation peak current density of 320 mA / mg Pd was detected, which is 1.8 times that of commercial Pd / C, indicating that Pd / Ti3C2MXene has higher active site exposure and carrier transport efficiency. After 1000 cycles of stability testing, the peak current retention rate remained at 78%, with no obvious particle agglomeration or exfoliation, demonstrating its excellent resistance to poisoning, structural stability, and electrochemical durability. It can be used in the preparation of electrode catalytic materials for direct methanol fuel cells (DMFC), exhibiting significant advantages in energy density and cycle life.

[0083] Application Example 8: Application of Pd / Graphene nanocomposite powder prepared in Example 1 in electrodes of flexible electronic devices.

[0084] The Pd / Graphene nanocomposite powder prepared in Example 1 was dispersed in anhydrous ethanol at a mass ratio of 1:19 and ultrasonicated for 30 min to prepare a uniform slurry with a solid content of 5%. This slurry was then spin-coated onto the surface of a flexible polyimide substrate (3000 r / min, 60 s), followed by drying at 60 °C for 1 h to form a continuous conductive film. 200 nm thick silver electrodes were deposited at both ends by magnetron sputtering, and the film was then cured by hot pressing at 80 °C and 0.5 MPa for 30 min. After bending cycle testing (1000 repeated bends from 0°–180°), the film resistivity change rate was less than 5%. The film operated stably within a temperature range of -20 °C to 80 °C without significant detachment, breakage, or conductive failure. It maintained conductive continuity even under a 10 V surge current. This demonstrates that the Pd / Graphene film possesses excellent mechanical flexibility, strain resistance, and long-term reliability in flexible displays, wearable devices, and flexible sensors.

[0085] Application Example 9: Application of Pd / Graphene nanocomposite powder prepared in Example 1 in a hydrogen sensor

[0086] The Pd / Graphene powder prepared in Example 1 was dispersed in ethanol (3% solid content), ultrasonicated for 1 h, and then coated onto a ceramic substrate using a scraper to form a wet film with a thickness of approximately 8 μm. After drying at 120°C for 2 h, it was reduced at 300°C for 2 h in an H2 atmosphere to obtain a dense sensing layer. This layer was then encapsulated with silver paste leads, with a 2 mm gas exposure window reserved for sensing testing. Results show that the sensor exhibits rapid response characteristics to hydrogen gas at concentrations of 1–1000 ppm (response time <5 s, recovery time <10 s). It operates continuously for 30 days under 60% humidity conditions with signal fluctuations of less than 3%. It shows almost no response to interfering gases such as CO, CH4, and NH3, demonstrating excellent selectivity and stability. This makes it suitable for hydrogen leak alarms, fuel cell safety monitoring, and online detection of industrial pipelines. Similarly, the Ru / Graphene nanocomposite powder prepared in Example 9 was used to replace the Pd / Graphene nanocomposite powder prepared in Example 1, and other operations were the same as in Example 9. The Ru / Graphene prepared in Example 9 had a response time of about 10 s and a recovery time of about 15 s in a hydrogen sensor at hydrogen concentrations of 1–1000 ppm.

[0087] Application Example 10: Application of Pd / Graphene nanocomposite powder prepared in Example 1 in conductive coatings for lithium batteries

[0088] Pd / Graphene powder was mixed with N-methylpyrrolidone (NMP) and sonicated for 2 h to prepare a uniform coating slurry with a solid content of 5%. After vacuum drying of a lithium iron phosphate cathode at 120 °C, the slurry was coated onto the cathode using a doctor blade method to form a wet film (approximately 10 μm thick), which was then dried at 80 °C and rolled. The modified electrode was assembled into a CR2032 button cell (using lithium metal as the negative electrode and 1 mol / L LiPF6 / EC:DMC = 1:1 electrolyte). Charge-discharge tests were conducted, and the specific capacity reached 132 mAh / g under 10C high-rate discharge conditions, with a capacity retention of approximately 85%, representing an improvement of approximately 25% compared to the unmodified electrode. After 500 cycles at 1C, the capacity decay was only 8.3%, and the electrochemical impedance was significantly reduced. This indicates that the Pd / Graphene coating can effectively improve the electrode conductive network, reduce interfacial impedance, and enhance structural stability, making it suitable for power batteries and high-rate energy storage applications.

[0089] Application Example 11: Application of Pd / Graphene nanocomposite powder prepared in Example 1 in the preparation of medical antibacterial materials.

[0090] The Pd / Graphene nanocomposite powder prepared in Example 1 was dispersed in deionized water at a mass fraction of 0.5%, and ultrasonicated for 40 min to obtain a uniform dispersion. Medical nonwoven fabric was immersed in this dispersion for 30 min to allow the fiber structure to fully adsorb the catalytic particles. Then, it was dried at 60℃ for 1 h, and the immersion-drying process was repeated twice to achieve a final powder loading of 1.5 g / m³. 2 The treated nonwoven fabric was then sterilized with ethylene oxide, and its antibacterial properties against typical Gram-negative / positive bacteria such as Escherichia coli and Staphylococcus aureus were evaluated. Test results showed that the treated material was effective against bacterial concentrations of 10... 6 The antibacterial rate against Escherichia coli and Staphylococcus aureus (CFU / mL) reached 99.9%, with a significantly expanded sterile zone, demonstrating a significant and stable antibacterial effect. Biocompatibility testing showed a grade 0, with no cytotoxic reaction. After aging under damp heat cycling (40℃, 90% humidity, 100 h) and repeated bending 2000 times, it maintained good antibacterial properties and mechanical integrity. This indicates that the material can be used in medical dressings, surgical instrument wrapping, and long-term contact medical protective materials, offering advantages such as sustained antibacterial activity, resistance to shedding, and low cost.

[0091] Application Example 12: Application of Ag / Graphene nanocomposite powder prepared in Example 5 in electromagnetic shielding coatings

[0092] The Ag / Graphene nanocomposite powder prepared in Example 1 was mixed with epoxy resin at a mass ratio of 1:4. After adding a curing agent, the mixture was mechanically stirred for 30 min to obtain a uniform shielding coating with a solid content of approximately 40%. The coating was sprayed onto the surface of a polycarbonate substrate using an air spraying process to form a wet film with a thickness of approximately 50 μm, and then cured at room temperature for 24 h to obtain an electromagnetic shielding layer. The shielding effectiveness of the sample was tested in the 1–18 GHz frequency band, and the average shielding effectiveness reached 45 dB, with absorption loss accounting for approximately 65%, showing good high-frequency attenuation capability and interface loss effect. After 200 cycles in an environment ranging from -20 ℃ to 80 ℃, the shielding effectiveness changed by less than 3 dB, indicating that the material still has a stable conductive path and structural integrity under thermal shock. Further aging at 40 ℃ and 90% humidity for 1000 h, the shielding effectiveness decreased by less than 3 dB, with no obvious cracking, peeling, or resistance drift. It is suitable for electromagnetic interference protection applications in the housing of precision electronic devices, shielding layers of flexible wearable circuits, and humid and hot working environments.

[0093] Application Example 13: Application of Ag / Graphene nanocomposite powder prepared in Example 5 in conductive inks

[0094] The Ag / Graphene powder prepared in Example 5 was added to a mixed solvent (deionized water: ethanol = 3:1) at a solid content of 30%, and 1% sodium carboxymethyl cellulose was added as a dispersant and binder. The mixture was ultrasonically treated at 300 W for 60 min and stirred at 800 r / min for 30 min to obtain a uniform conductive ink. The ink was then screen-printed onto a PET flexible substrate (200 mesh, squeegee pressure 0.3 MPa, printing speed 50 mm / s), and dried with hot air at 120℃ for 30 min to form a continuous conductive pattern. Test results show that the sheet resistance of the obtained conductive film is as low as 13 Ω / sq, which is significantly lower than that of conventional carbon-based conductive inks. In 500 cycles of thermal cycling from -40℃ to 120℃, the sheet resistance change rate is <5%, and after repeated bending 1000 times (radius 5 mm), it still maintains >90% conductivity. In a humid and hot environment (40℃, RH 90%, 200 h), there is no oxidation discoloration or sudden increase in resistance, indicating that the ink has high conductivity, mechanical flexibility and environmental stability, and can be used in applications such as flexible circuit boards, RFID tags, wearable electronic skin and printed sensors.

[0095] Application Example 14: Application of Cu / Graphene nanocomposite powder prepared in Example 7 in corrosion-resistant electroplating layers

[0096] 0.02 g of the Cu / Graphene composite powder prepared in Example 7 was added to an electroplating solution containing 200 g / L copper sulfate and 50 g / L sulfuric acid. The powder was ultrasonically dispersed at 200 W for 30 min and stirred at 500 r / min to form a stable dispersion. Using copper as the anode and brass or aluminum as the cathode, a current density of 2 A / dm³ was maintained at 25°C. 2 Electroplating for 30 min. After electroplating, rinse with deionized water and dry at 60℃. The resulting coating has a uniform thickness of 8–10 μm and a resistivity of 1.645 × 10⁻⁶. -8 With a Ω·m value close to that of high-purity electrolytic copper, the coating exhibits high conductivity and low interface defects. After a neutral salt spray corrosion test (5% NaCl, 35℃, 48 h), the coating showed no pinholes, blisters, or obvious corrosion spots; in a mechanical stress test involving 50 180° bends, the coating showed no cracking or peeling. This indicates that the introduction of Cu / Graphene improves the coating's density, conductivity, and corrosion resistance, making it widely applicable for surface treatment of high-end electronic connectors, precision parts, and high-reliability circuit components.

[0097] Application Example 15: Application of Cu / Graphene nanocomposite powder prepared in Example 7 in heat dissipation and protective coatings

[0098] The Cu / Graphene powder prepared in Example 7 was added to acrylic resin at a solid-liquid ratio of 1:10, and 2% polyethylene glycol was added as a dispersant. The mixture was ultrasonicated at 300 W for 40 min and stirred for 1 h to obtain a uniform thermally conductive coating. The coating was then applied to the surface of an LED aluminum-based heat sink using air spraying to form a wet film of approximately 30 μm, which was then cured at 60 °C for 30 min. Tests showed that the thermal conductivity of the cured coating reached 18 W / (m·K), approximately 8 times that of the pure resin-based coating. After 2 h of continuous operation of a 10 W LED, the substrate temperature using this coating was approximately 12 °C lower than the untreated substrate, and the thermal resistance decreased to 0.8 °C / W, effectively suppressing heat accumulation and the risk of thermal failure. After 500 cycles of thermal cycling from -40 °C to 120 °C, the coating did not exhibit cracking, peeling, or thermal conductivity degradation (retention rate exceeding 90%), indicating that this material can be used in high-power LEDs, chip heat dissipation modules, and power battery thermal management, offering advantages such as low cost, easy processing, and high reliability.

[0099] Application Example 16: Application of Ru / Graphene nanocomposite powder prepared in Example 9 in hydrogen-deuterium exchange reaction

[0100] 0.10 g of Ru / Graphene nanocomposite powder (Ru loading approximately 1.0 wt%) prepared in Example 9 was placed in a 50 mL sealed reactor. 10 mmol of toluene and 20 mL of heavy water (D₂O) were added sequentially. After purging with nitrogen three times to remove air, the reaction was carried out at 80 °C with magnetic stirring at 500 r / min for 4 h. After the reaction, the catalyst was separated by centrifugation, and the reaction was analyzed using hydrogen nuclear magnetic resonance (HNMR). 1 Analysis of the product by ¹H NMR revealed significant hydrogen-deuterium exchange at both the benzene ring and side chain positions in toluene, with a total exchange rate of 92% and excellent selectivity at the exchange sites. After washing with ethanol and vacuum drying at 60°C, the catalyst was reused six times, maintaining an exchange rate of approximately 90%, without significant sintering deactivation or loss of active metal. This indicates that the composite catalyst can achieve highly selective deuteration under mild conditions, making it suitable for the preparation of pharmaceutical intermediates, tracer molecules, and stable isotope fine chemical products, while also possessing advantages such as high activity, low energy consumption, and long cycle life.

[0101] Application Example 17: Application of Pt / h-BN nanocomposite powder prepared in Example 10 in the selective hydrogenation of nitrobenzene to aniline.

[0102] 0.30 g of Pt / h-BN composite powder (Pt mass fraction approximately 5 wt%) prepared in Example 10 was added to 50 mL of an ethanol solution containing nitrobenzene (0.05 mol / L). The solution was placed in a high-pressure reactor, and after three H2 purgings, the pressure was maintained at 0.3 MPa. The reaction was carried out at 50 °C with magnetic stirring at 600 r / min for 2 h. After the reaction, the catalyst was recovered by centrifugation, and the solution was analyzed by gas chromatography. The nitrobenzene conversion rate reached 99%, the aniline selectivity reached 98.5%, and the byproducts were minimal. The recovered catalyst was washed with ethanol and dried at 60 °C for reuse. After 8 cycles, it still maintained a conversion efficiency of over 90%, demonstrating excellent anti-sintering and antioxidant stability. Due to the insulating and chemically resistant properties of the h-BN sheets and the uniform dispersion of Pt nanoparticles, which are not prone to aggregation or detachment, this material is suitable for green preparation processes of aniline and its derivatives in the fine chemical, dye, and pharmaceutical industries, with mild operating conditions and high safety.

[0103] Application Example 18: Application of Ag / h-BN nanocomposite powder prepared in Example 4 in electromagnetic shielding coatings

[0104] The Ag / h-BN composite powder (Ag mass fraction approximately 4.3%) prepared in Example 4 was mixed with epoxy resin at a mass ratio of 2:5. A curing agent was added, and the mixture was mechanically stirred for 30 min to obtain a uniform shielding coating. The coating was then uniformly sprayed onto an ABS plastic shell using a spray gun to form a wet film thickness of approximately 60 μm, and cured at room temperature for 24 h. Tests showed that the coating achieved a shielding effectiveness of 42 dB in the 1–18 GHz frequency band, mainly due to the combined effects of conductive absorption loss and multi-interface scattering. After 1000 bending tests (bending radius 5 mm), it still maintained 88% of its shielding effectiveness, indicating that the coating possesses both flexibility and structural stability. Furthermore, the sample did not show any conductivity degradation or silver migration after being placed in a salt spray and humid heat environment for 200 h, indicating that the Ag / h-BN nanocomposite material forms a good interfacial bond with the resin and can be applied to lightweight shielding layers for smartphone casings, precision instrument cavities, and electromagnetically sensitive devices.

[0105] Application Example 19: Application of Zn / h-BN nanocomposite powder prepared in Example 11 in antibacterial medical device coatings

[0106] The Zn / h-BN composite powder (Zn mass fraction approximately 0.75 wt%) prepared in Example 11 was dispersed in deionized water to prepare a dispersion with a solid content of 1.5%. This dispersion was then mixed with medical silica gel at a mass ratio of 1:10. After ultrasonication for 40 min, the mixture was uniformly coated onto the surface of surgical forceps to form a coating of approximately 15 μm. The coating was then sterilized at 120°C for 2 h to solidify. Antibacterial experiments were conducted against Staphylococcus aureus, with an initial bacterial concentration of 10... 6 CFU / mL, 24-hour plate count results showed an antibacterial rate of 99.8% with a clear inhibition zone. After 30 days of continuous use and multiple high-temperature sterilizations, the antibacterial performance showed no significant attenuation, and the coating did not peel or crack. The cytotoxicity test met the medical material standard 6. This indicates that the Zn / h-BN coating possesses excellent and long-lasting antibacterial ability, biocompatibility, and sterilization resistance, and can be used for surface protection of surgical instruments, dental tools, and long-term contact medical materials.

[0107] Application Example 20: Application of Pd / h-BN nanocomposite powder prepared in Example 12 in fuel cell cathode catalysis

[0108] The Pd / h-BN powder (Pd mass fraction approximately 1.9 wt%) prepared in Example 12 was mixed with a 5% Nafion solution at a mass ratio of 1:4, and ultrasonically dispersed for 20 min to prepare a catalyst ink. This ink was then drop-coated onto the surface of a carbon paper electrode to achieve a Pd loading of approximately 0.08 mg / cm³. 2 The material was dried at 80℃ for 30 min and used as the cathode material. The electrode was assembled into a hydrogen-oxygen fuel cell, and test results showed a peak power density of 620 mW / cm². 2This catalyst exhibits approximately 1.5 times higher performance than commercial Pd / C catalysts. After 1500 cycles under constant current conditions, it retains 82% of its activity, indicating that h-BN provides a stable support for Pd nanoparticles, inhibiting sintering and migration, and improving durability and resistance to poisoning. This catalyst features low precious metal content, high power density, and long cycle life, making it suitable for applications such as automotive, portable power supplies, and stationary fuel cells.

[0109] Application Example 21: Application of Pt / Nb2C nanocomposite powder prepared in Example 13 in supercapacitor electrodes

[0110] The Pt / Nb2C composite powder (Pt mass fraction approximately 2.9 wt%) prepared in Example 13 was mixed with acetylene black and polytetrafluoroethylene at a mass ratio of 8:1:1. Anhydrous ethanol was added and the mixture was ground thoroughly for 30 min until a paste was formed. The paste was then uniformly coated onto a nickel foam current collector to achieve an active material loading of approximately 2 mg / cm³. 2 The electrode was then vacuum-dried at 80℃ for 12 h and pressed into a working electrode under 10 MPa pressure. A three-electrode system was assembled and tested using 6 mol / L KOH as the electrolyte and Hg / HgO as the reference electrode. The results showed that the electrode achieved a specific capacitance of 680 F / g at a current density of 1 A / g, which is about 45% higher than that of the pure Nb2C electrode. Under high-rate conditions of 10 A / g, the capacitance retention rate was 82%, and only about 5% capacitance decayed after 10,000 cycles, demonstrating excellent rate performance and cycle stability. The assembled symmetrical supercapacitor achieved an energy density of 42 Wh / kg (power density of 1000 W / kg), making it suitable for use in new energy vehicles, energy storage systems, and high-frequency charge and discharge scenarios.

Claims

1. A method for high-pressure expansion-ultrasound-assisted exfoliation of two-dimensional materials and in-situ loading of metal, characterized in that... Includes the following steps: 1) Disperse the layered two-dimensional material precursor in water and stir until homogeneous to obtain a dispersion system; 2) Inject the dispersion system obtained in step 1) into a high-pressure resistant reactor and maintain it at 250-300℃ and 15-20 MPa for 30-100 minutes under constant temperature and pressure to allow water molecules to enter the interlayer of the layered two-dimensional material precursor and induce the expansion of the interlayer structure; then rapidly depressurize to normal pressure and then to room temperature to obtain a high-viscosity expanded slurry. The pressurization method is pulse pressurization, and the waveform is a square wave, sine wave, or triangular wave. The pulse pressure amplitude is 5%-20% of the set pressure. 3) Add water to the high-viscosity expanded slurry from step 2) to dilute it until the concentration of the two-dimensional material is halved, then transfer it to an ultrasonic bath for ultrasonic treatment to gradually peel off the expanded layer into two-dimensional nanosheets. 4) Taking the expansion-dilution ultrasonic process of step 2)-3) as one process cycle, repeat the process cycle of step 2)-3) 5-20 times to gradually peel off the layered two-dimensional material into two-dimensional nanosheets with a thickness of less than 5 nm. 5) Before the ultrasonic treatment in the penultimate process cycle of step 4), add the metal precursor solution, and obtain a uniformly dispersed mixture by ultrasonication. Then, after the expansion-dilution ultrasonic treatment in the last process cycle, obtain a dispersion of metal-supported two-dimensional material uniformly dispersed on the surface or edge of the two-dimensional nanosheet. 6) Centrifuge the dispersion obtained in step 5), and reduce the supernatant to convert the metal precursor into nano-metal particles, which are then uniformly loaded onto the surface or edge of the two-dimensional material sheet. Freeze-dry the two-dimensional material with metal in situ loaded in situ. The centrifugation speed is 8000~15000 rpm and the centrifugation time is 5–15 minutes.

2. The method for high-pressure expansion-ultrasound-assisted exfoliation of two-dimensional materials and in-situ loading of metal according to claim 1, characterized in that... The layered two-dimensional material precursor in step 1) is selected from at least one of natural graphite, expanded graphite, hexagonal boron nitride, MXene, molybdenum disulfide, molybdenum diselenide, molybdenum carbide, and niobium carbide.

3. The method for high-pressure expansion-ultrasound-assisted exfoliation of two-dimensional materials and in-situ loading of metal according to claim 1, characterized in that... In step 1), the stirring time until a uniform dispersion system is formed is 20-60 minutes, and the concentration of the layered two-dimensional material precursor in the dispersion system is 2-20 wt%.

4. The method for high-pressure expansion-ultrasound-assisted exfoliation of two-dimensional materials and in-situ loading of metal according to claim 1, characterized in that... The high-pressure resistant reaction device in step 2) is a sealed high-temperature and high-pressure resistant reactor with a pressure range of 15–25 MPa and a reaction temperature of 25–300℃.

5. A method for high-pressure expansion-ultrasound-assisted exfoliation of two-dimensional materials and in-situ loading of metal according to claim 1, characterized in that... In step 2), the heating rate of the reaction chamber is 2–8 °C / min, which allows water molecules to gradually enter the interlayer structure and form a swollen state; rapid depressurization is used to induce rapid swollen interlayers.

6. The method for high-pressure expansion-ultrasound-assisted exfoliation of two-dimensional materials and in-situ loading of metal according to claim 1, characterized in that... The amount of water used for dilution in step 3) is equal to the volume of the high-viscosity expanded slurry.

7. The method for high-pressure expansion-ultrasound-assisted exfoliation of two-dimensional materials and in-situ loading of metal according to claim 1, characterized in that... The ultrasonic treatment in step 3) is carried out under cooling water circulation to keep the system temperature below 50°C and avoid the fragmentation or agglomeration of the sheets; the ultrasonic power is 200~600 W, the ultrasonic frequency is 20-40 kHz, and the ultrasonic treatment time is 12-24 hours, so that the expanded layer is gradually peeled off into two-dimensional nanosheets.

8. The method for high-pressure expansion-ultrasound-assisted exfoliation of two-dimensional materials and in-situ loading of metal according to claim 1, characterized in that... The metal precursor in step 5) is selected from at least one of nickel nitrate, chloroplatinic acid, palladium chloride, copper nitrate, silver nitrate, palladium acetate, silver carbonate, copper acetate, zinc nitrate, and ruthenium chloride.

9. The method for high-pressure expansion-ultrasound-assisted exfoliation of two-dimensional materials and in-situ loading of metal according to claim 1, characterized in that... When the reduction treatment in step 6) is heat treatment, the heat treatment temperature is 200–400℃ and the holding time is 0.5–4 hours.

10. The method for high-pressure expansion-ultrasound-assisted exfoliation of two-dimensional materials and in-situ loading of metal according to claim 1, characterized in that... When the reduction treatment in step 6) is a chemical reduction, the reducing agent is NaBH4, sodium citrate, or ascorbic acid, and the amount of reducing agent used is 1–3 times the molar amount of the metal precursor.

11. The method for high-pressure expansion-ultrasound-assisted exfoliation of two-dimensional materials and in-situ loading of metal according to claim 1, characterized in that... The reduced metal nanoparticles in step 6) have a particle size of 1–50 nm and are uniformly loaded on the surface or edge of the two-dimensional material sheet without obvious agglomeration.

12. The method for high-pressure expansion-ultrasound-assisted exfoliation of two-dimensional materials and in-situ loading of metal according to claim 1, characterized in that... After freeze-drying in step 6), a two-dimensional material with in-situ metal loading is obtained in the form of powder, thin film or sheet solid, wherein the sheet thickness is 0.3–10 nm and the sheet diameter is 0.1–20 μm.

13. The application of the metal-supported two-dimensional material prepared by the method according to claim 1 in catalysis, energy storage, conductive inks, electromagnetic shielding and flexible devices.

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