A controllable loading method of 6d transition metal monatomic atoms based on titanium carbide MXene two-dimensional material

Abstract

The application discloses a 6d transition metal single-atom controllable loading method based on titanium carbide MXene two-dimensional material, and belongs to the technical field of electrocatalytic electrode material preparation and application, namely, by adjusting 12-14 M HCl / LiF etching liquid conditions, titanium vacancy defects with different densities are constructed on the surface of MXene, and then the precise anchoring of 6d transition metal single atoms is realized. The obtained single-atom metal loaded titanium carbide MXene two-dimensional material has a clear single-atom coordination structure, significantly optimizes the surface charge distribution, and improves the hydrogen evolution reaction kinetics. Moreover, the method is simple in process, low in energy consumption and capable of batch production. The prepared electrode shows better catalytic activity and stability than a commercial Pt / C, is suitable for water decomposition to produce hydrogen, and provides a new path for the development of non-noble metal efficient electrocatalysts.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalytic electrode material preparation and application technology, and particularly relates to a method for controllable loading of 6d transition metal single atoms based on titanium carbide MXene two-dimensional material. Background Technology

[0002] Electrocatalytic water splitting for hydrogen evolution refers to the electrochemical process of splitting water into hydrogen and oxygen using an electrocatalyst under an applied electric field. In this process, the catalyst reduces the hydrogen evolution overpotential and improves reaction efficiency by controlling charge transfer on the electrode surface, adsorption energy of reaction intermediates, and hydrogen evolution reaction kinetics. By optimizing the electronic structure, interfacial characteristics, and active site distribution of the catalyst, proton reduction can be effectively promoted, achieving efficient and stable hydrogen production. This technology is an important pathway for clean energy conversion and storage, and is of great significance for promoting the utilization of renewable energy and achieving carbon neutrality goals.

[0003] Currently, the performance of transition metals, noble metals, and alloys in the electrocatalytic hydrogen evolution reaction (HER) has been extensively studied. Two-dimensional layered MXene materials, with their unique intrinsic physicochemical properties, exhibit distinctive advantages in electrocatalytic HER performance. Single-atom modification strategies, by constructing highly dispersed active sites on the MXene surface, can precisely control the electronic structure and hydrogen adsorption free energy of the material, providing a new approach to improve its HER performance. However, the supporting configuration, stability, charge regulation mechanism between the single-atom sites and the MXene substrate, as well as long-term catalytic activity, remain key challenges for achieving efficient and stable HER applications.

[0004] Therefore, developing a single-atom modification method that can synergistically enhance activity and stability is of great significance for promoting the commercialization of MXene-based electrocatalysts. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a single-atom controllable loading method for 6d transition metals (transition metals in Group 6 of the periodic table) based on titanium carbide MXene two-dimensional materials. Specifically, this invention utilizes precise control of the atomic-level surface structure of titanium carbide MXene two-dimensional materials. By precisely controlling the etching conditions, titanium atom vacancies of varying densities are obtained on the surface, providing sites for transition metal loading. This enables charge rearrangement on the surface of the titanium carbide MXene two-dimensional material, fundamentally improving reaction kinetics, reducing the reaction barrier, and enhancing catalytic performance.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for controllable loading of 6d transition metal single atoms based on titanium carbide MXene two-dimensional material includes the following steps: (1) Add aluminum titanium carbide to an etching solution for etching, wash, and then mechanically peel off and centrifuge to prepare a single-layer / few-layer titanium carbide MXene two-dimensional material; the etching solution is obtained by mixing and dissolving HCl solution with LiF at a concentration of 12-14 M. (2) The monolayer / few-layer titanium carbide MXene two-dimensional material is added to deionized water and dispersed evenly. Then, a 6d transition metal salt solution is added to it for reaction and washing to obtain a single-atom metal-supported titanium carbide MXene two-dimensional material (composite electrocatalyst).

[0007] Beneficial effects: This invention precisely controls the concentration of hydrochloric acid etching solution (12M-14M) to directionally regulate the titanium vacancy density on the surface of monolayer / few-layer titanium carbide MXene, and uses these vacancies as anchoring points to achieve controllable and constant-density loading of 6d transition metal single atoms under mild aqueous phase conditions.

[0008] Optionally, in step (1), the ratio of the amount of HCl solution to LiF is 20 mL: 1.5 g.

[0009] Furthermore, the concentration of the HCl solution is 12M.

[0010] Optionally, in step (1), the ratio of the amount of aluminum titanium carbide to the amount of etching solution is 1.0g:12mL.

[0011] Optionally, in step (1), the etching conditions are: stirring at 35 °C for 24 h.

[0012] Optionally, in step (1), the washing conditions are as follows: wash with deionized water 6-8 times, 15 min each time, centrifuge at 10,000 rad / min until the pH test paper shows that it has been washed to neutral.

[0013] Optionally, in step (1), the mechanical stripping conditions are: the washed product is mechanically stripped at 300 W for 2 hours.

[0014] Optionally, in step (1), the centrifugation screening conditions are as follows: the blended titanium carbide MXene two-dimensional material after mechanical exfoliation is centrifuged at 5000 rad min. -1 The upper liquid layer was used to obtain monolayer / few-layer titanium carbide MXene two-dimensional materials.

[0015] Optionally, in step (2), the 6d transition metal salt solution is selected from salt solutions of (NH4)2HfF6, K2TaF7 or Na2WO4·2H2O.

[0016] Optionally, in step (2), the reaction conditions are: reacting at a temperature of 30~55 °C for 8 h.

[0017] A single-atom metal-supported titanium carbide MXene two-dimensional material was prepared by the above-described preparation method.

[0018] The above-mentioned single-atom metal-supported titanium carbide MXene two-dimensional material is used in the electrocatalytic water splitting for hydrogen production.

[0019] An electrode for electrocatalytic water splitting to produce hydrogen includes carbon cloth and a slurry containing the single-atom metal-supported titanium carbide MXene two-dimensional material.

[0020] Optionally, the preparation process of the slurry is as follows: The monoatomic metal-supported titanium carbide MXene two-dimensional material was dispersed with carbon black in a mixture of Nafion solution and isopropanol, and then ultrasonically treated for 30 min to obtain the final product.

[0021] Furthermore, the mass ratio of the single-atom metal-supported titanium carbide MXene two-dimensional material to carbon black is 3 mg: 7 μg.

[0022] Compared with the prior art, the present invention has the following advantages and technical effects: (1) The present invention can realize titanium metal vacancy defects of different densities on the surface of single-layer / few-layer titanium carbide MXene two-dimensional materials, providing a definite configuration and density positioning for the loading of 6d metal single atoms, which plays an important role in the theoretical revelation of the mechanism of action. Moreover, the method can be achieved simply by controlling the acidity of the etching solution, and is convenient to operate and easy to prepare in batches.

[0023] (2) This invention achieves surface loading of different types of 6d transition metals through a simple temperature-controlled loading process. By precisely controlling the temperature within the range of 30-55 °C, in-situ surface vacancy loading of different 6d transition metals (Hf, Ta, W) can be achieved at different temperatures. This process has the significant advantages of controllable metal single-atom coordination structure and easy expansion of the types of metal single atoms. Moreover, the entire loading process is short in time, low in energy consumption, and easy to prepare in batches.

[0024] (3) The electrode assembly process of this invention is simple, consumes few materials, has a high yield, and generates virtually no waste. Through electrochemical testing, a composite configuration sample with comprehensive performance (catalytic activity and catalytic stability) superior to commercial Pt / C electrodes was selected, providing a feasible alternative for noble metal-based commercial electrodes, with great application value. Attached Figure Description

[0025] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a diagram of the aluminum titanium carbide unit cell structure in step 1.2 of the method for supporting aluminum carbide in this invention. Figure 2 This is a diagram of the monolayer / few-layer titanium carbide MXene unit cell structure after centrifugation, screening, and etching in step 1.4 of the loading method of this invention; Figure 3 The cell structure diagrams of titanium carbide MXene two-dimensional materials with different etching degrees in step 2.1 of the support method of the present invention are shown. Figure 4 The cell structure diagrams of different single-atom metal loadings implemented in step 2.2 of the loading method of the present invention on monolayer / few-layer titanium carbide MXene two-dimensional materials with the same etching degree are shown. Figure 5 The image is a transmission electron microscope image of titanium carbide MXene two-dimensional material obtained after etching with 12 M etching solution in step 1.2 of Example 1. Figure 6 These are high-resolution transmission electron microscope images of titanium carbide MXene two-dimensional materials obtained under different etching solution concentrations in steps 1.2 of Examples 1-3; Figure 7 These are high-resolution transmission electron microscopy comparison images of in-situ loading of titanium carbide MXene with different Ti vacancy defect densities under the action of Ta salt in step 2 of Examples 1-3. Figure 8 The activity diagrams for water splitting to produce hydrogen are shown for the two-dimensional titanium carbide MXene materials with different Ti vacancy densities loaded with Ta single atoms in Application Examples 1-3, the commercial electrode in Comparative Example 1, and the untreated aluminum titanium carbide in Comparative Example 2. Detailed Implementation

[0026] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0027] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0028] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0029] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0030] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0031] The purpose of this invention is to provide a method for controllable surface loading of 6d transition metal single atoms based on monolayer / few-layer titanium carbide MXene two-dimensional materials. This method achieves site-specific loading and surface loading density of 6d transition metal single atoms by controlling the distribution and number of titanium atom vacancies on the MXene surface. The rearrangement of surface atomic configurations leads to the redistribution of surface charge, activating surface atoms and improving the overall electrocatalytic hydrogen evolution performance.

[0032] This invention discloses a method for controllable loading of 6d transition metal single atoms based on monolayer / few-layer titanium carbide MXene two-dimensional materials, comprising the following steps: Step 1: Preparation of monolayer / few-layer titanium carbide MXene two-dimensional materials Step 1.1: Prepare the etching solution Weigh a certain amount of concentrated hydrochloric acid and prepare HCl solutions of different concentrations; mix and dissolve a certain amount of HCl solution with a certain amount of LiF to prepare mixed solutions of different concentrations for later use.

[0033] Step 1.2: Etching aluminum titanium carbide A certain mass of titanium aluminum carbide was added to the etching solution, and the mixture was stirred for 24 h at a certain temperature to obtain two-dimensional titanium carbide MXene materials with different etching degrees.

[0034] Step 1.3: Mechanically exfoliate the two-dimensional titanium carbide MXene material The cleaned titanium carbide MXene two-dimensional material was mechanically exfoliated using a high-power ultrasonic instrument. After ultrasonication for 2 hours, it was washed twice with deionized water to obtain titanium carbide MXene two-dimensional materials with different numbers of layers.

[0035] Step 1.4: Centrifuge screening of monolayer / few-layer titanium carbide MXene two-dimensional materials The exfoliated and blended titanium carbide MXene two-dimensional materials were ultrasonically dispersed to achieve uniform dispersion. The layers of the titanium carbide MXene two-dimensional materials with different layer numbers were screened using a centrifuge at 5000 rad / min. -1 The upper liquid layer was removed to obtain monolayer / few-layer titanium carbide MXene two-dimensional materials. The lower liquid layer was removed, and the above ultrasonic, washing, and centrifugation steps were repeated to improve the sample yield. The sample was retained in deionized water, and solid samples could be obtained by freeze-drying.

[0036] Step 2: Single-atom metal-supported titanium carbide MXene two-dimensional material (composite electrocatalyst) Step 2.1: Implement the same single-atom metal support on titanium carbide MXene two-dimensional materials with different etching degrees. 100 mg of titanium carbide MXene two-dimensional material with different etching degrees (10 M, 12 M, 14 M hydrochloric acid solution) was added to 100 mL of deionized water. After sonication for 1 hour, 25 mL of 1 mM 6d transition metals ((NH4)2HfF6, K2TaF7, Na2WO4·2H2O) was added. The reaction temperature was controlled at 30–55 °C and the reaction time was 8 h. After the reaction, the mixture was washed twice with acetone and deionized water, respectively. The reaction was carried out in a three-necked flask.

[0037] Step 2.2: Implement different single-atom metal loading on monolayer / few-layer titanium carbide MXene two-dimensional materials with the same etching degree. 100 mg of titanium carbide MXene two-dimensional material (etched sample with 12 M hydrochloric acid etching solution) was added to 100 mL of deionized water. After sonication for 1 hour, 25 mL of different types of 6d transition metals ((NH4)2HfF6, K2TaF7, Na2WO4·2H2O) were added. The reaction temperature was controlled at 30–55 °C and the reaction time was 8 h. After the reaction, the sample was washed twice with acetone. The reaction was carried out in a three-necked flask.

[0038] Step 3: Assemble the electrodes and test their performance. Step 3.1: Preparation of slurry 3 mg of the composite electrocatalyst and 7 μg of carbon black were dispersed in a mixture of 35 μL of Nafion (5%) solution and 925 μL of isopropanol, and the mixture was sonicated for 30 min. 100 μL of this solution was then uniformly coated onto a 0.5 × 0.5 cm layer of carbon cloth. 2 Place both sides of the container on the floor and allow them to dry at room temperature.

[0039] Step 3.2: Electrode system assembly Electrode performance was tested using a standard three-electrode system on an electrochemical workstation. A graphite electrode and a saturated calomel electrode were used as the counter and reference electrodes, respectively. The electrolyte was a 1.0 M KOH solution. Linear sweep voltammetry (LSV) was performed at a scan rate of 5 mV / s. -1 All test potentials were referenced to the reversible hydrogen electrode (RHE).

[0040] Furthermore, in step 1.1, the solid-liquid mixing must be carried out in a well-ventilated kitchen. LiF must be added slowly, and safety must be taken into account during stirring and transfer steps to prevent damage from the acidic liquid.

[0041] Furthermore, in step 1.2, after adding a certain mass of aluminum titanium carbide to etching solutions of different concentrations (etching solutions prepared with 10 M, 12 M, and 14 M hydrochloric acid solutions respectively), care should be taken to keep the container sealed during the heating and stirring process to avoid prolonged stirring increasing the acidity of the solution, which could lead to over-etching of the aluminum titanium carbide and collapse of its two-dimensional structure. The aluminum titanium carbide cell structure is as follows: Figure 1 As shown.

[0042] Furthermore, in step 1.3, after etching, the titanium carbide MXene is cleaned 6-8 times, using 20 mL of deionized water each time, until the solution is neutral. The ultrasonic instrument power is 300 W, and the solution temperature must be kept constant below 30 ℃ during the ultrasonic process.

[0043] Furthermore, in step 1.4, the single-layer / few-layer titanium carbide MXene unit cell structure after centrifugal screening and etching is as follows: Figure 2 As shown.

[0044] Furthermore, in step 2.1, the same single-atom metal support is applied to titanium carbide MXene two-dimensional materials with different etching degrees, and the cell structure is as follows: Figure 3 As shown (from top to bottom, these correspond to etching solutions including 10, 12, and 14 M HCl solutions).

[0045] Furthermore, in step 2.2, different single-atom metal supports are implemented on monolayer / few-layer titanium carbide MXene two-dimensional materials with the same etching degree, and the cell structure is as follows: Figure 4 As shown.

[0046] In summary, this invention discloses a method for controllable loading of 6d transition metal single atoms onto the surface of two-dimensional titanium carbide MXene. This method enables the controllable loading of 6d transition metal single atoms onto the surface of two-dimensional titanium carbide MXene. Through the electronic synergistic modulation of different 6d metals and titanium carbide MXene coordinating atoms, the performance of electrocatalytic water splitting electrodes can be significantly improved, making it a promising alternative material for noble metal electrodes. Specifically, it offers the following advantages: (1) This invention achieves Ti metal defects of different densities on the surface of single-layer / few-layer titanium carbide MXene two-dimensional materials by controlling the process parameters of the acid etching process. This method is convenient to operate and easy to prepare in batches. (2) The present invention achieves surface loading of different types of 6d transition metals through a special temperature-controlled loading process, which has the significant advantages of uniform metal single-atom coordination structure and easy expansion of metal single-atom types; (3) This invention uses electrode assembly to test the electrocatalytic water splitting hydrogen production performance of single-atom supported monolayer / few-layer titanium carbide MXene two-dimensional material composites, and screens out composite configurations with comprehensive performance superior to commercial Pt / C electrodes, providing a feasible alternative to noble metal-based commercial electrodes, with great application value.

[0047] Unless otherwise specified, "room temperature" in this invention refers to 20-30℃.

[0048] All raw materials used in this invention were purchased from the market.

[0049] The technical solution of the present invention will be further illustrated by the following embodiments.

[0050] Example 1 Taking Ta single-atom-supported monolayer / few-layer MXene two-dimensional materials (sample etched with 12 M hydrochloric acid etching solution) as an example, a Ta SA@MXene composite was constructed. By determining the electronic synergistic modulation of the configuration of the 6d Ta transition metal and the titanium carbide MXene coordinating atoms, the overall performance of the electrocatalytic water splitting electrode was improved.

[0051] A method for controllable Ta single-atom loading based on titanium carbide MXene two-dimensional material includes the following steps: Step 1: Preparation of monolayer / few-layer titanium carbide MXene two-dimensional materials Step 1.1: Prepare the etching solution Weigh 20 mL of concentrated hydrochloric acid and add a certain amount of deionized water to prepare a 12 M hydrochloric acid solution. Slowly mix and stir 1.5 g of HCl aqueous solution to dissolve the solution, preparing an etching solution of a specific concentration. The etching solution preparation process must be carried out in a fume hood. LiF must be added slowly, and safety precautions must be taken during stirring and transfer. Avoid contact with or inhalation of the generated white fumes (aerosol formed by HF and HCl). After the solid has completely dissolved, continue stirring for 15 minutes, then seal the container for later use. The optimal usage time for the prepared etching solution is within 24 hours.

[0052] Step 1.2: Etching aluminum titanium carbide Take 12 mL of etching solution, add 1.0 g of aluminum titanium carbide, maintain at 35 ℃ and stir for 24 h to obtain titanium carbide MXene two-dimensional material with appropriate etching degree.

[0053] Step 1.3: Mechanically exfoliate the two-dimensional titanium carbide MXene material The etched titanium carbide MXene two-dimensional material samples were washed 6-8 times with deionized water, adding 20 mL of deionized water each time, for 15 min each time, and centrifuged at 10,000 rad / min until the pH paper showed neutrality. After collecting the solid samples, 20 mL of deionized water was added, and the mixture was ultrasonically dispersed at 300 W for 2 h. The titanium carbide MXene two-dimensional materials with different layer numbers were screened using a centrifuge, and the layer number was determined at 5000 rad / min. -1 The upper liquid layer was used to obtain monolayer / few-layer titanium carbide MXene two-dimensional materials. The lower liquid layer was removed, and the above ultrasonic, washing, and centrifugation steps were repeated to improve the sample yield. The sample was retained in deionized water, and solid samples could be obtained by freeze-drying. The number of sample layers, the relative and absolute amounts of surface Ti defects in the upper liquid layer were obtained by high-resolution transmission electron microscopy, electron spin spectroscopy, and aberration-corrected high-resolution transmission electron microscopy.

[0054] Step 2: Single-atom 6d transition metal-supported titanium carbide MXene two-dimensional material (composite electrocatalyst) 100 mg of etched titanium carbide MXene two-dimensional material (etched with 12 M hydrochloric acid etching solution) was added to 100 mL of deionized water. After sonication for 1 hour, 25 mL of 1 mM 6d transition metal tantalum salt (K2TaF7) was added while maintaining the system temperature at 55 °C. The reaction was carried out with stirring for 8 hours. After the reaction, the sample was washed twice with 20 mL of acetone and deionized water, respectively, and centrifuged for 15 min at 5500 rad / min. The sample was sealed and stored in sample tubes for later use (before use, it was dried in a vacuum oven at 50 °C for 8 hours to obtain solid powder, which was then directly used for electrode assembly testing). The loading reaction was carried out in a three-necked flask with a reflux condenser. The single-atom loading density of the sample was obtained directly by aberration-corrected high-resolution transmission electron microscopy.

[0055] Example 2 The only difference from Example 1 is that in step 1.1, "weigh 20 mL of concentrated hydrochloric acid, add a certain amount of deionized water, and prepare a 12 M hydrochloric acid solution" is replaced with "weigh 20 mL of concentrated hydrochloric acid, add a certain amount of deionized water, and prepare a 14 M hydrochloric acid solution". The other steps are the same as in Example 1.

[0056] Example 3 The only difference from Example 1 is that in step 1.1, "weigh 20 mL of concentrated hydrochloric acid, add a certain amount of deionized water, and prepare a 12 M hydrochloric acid solution" is replaced with "weigh 20 mL of concentrated hydrochloric acid, add a certain amount of deionized water, and prepare a 10 M hydrochloric acid solution". The other steps are the same as in Example 1.

[0057] Example 4 The only difference from Example 1 is that in step 2, the metal tantalum salt (K2TaF7) is replaced with a metal salt solution of (NH4)2HfF6 of equal concentration.

[0058] Example 5 The only difference from Example 1 is that in step 2, the tantalum salt (K2TaF7) is replaced with a Na2WO4·2H2O tantalum salt solution of equal concentration.

[0059] Effect verification Application Examples 1-3 Electrode systems were prepared using the single-atom 6d transition metal-supported titanium carbide MXene two-dimensional materials (composite electrocatalysts) obtained in Examples 1-3. The specific preparation process is as follows: (1) Preparation of slurry 3 mg of the composite electrocatalyst and 7 μg of carbon black were dispersed in a mixture of 35 μL of Nafion (5%) solution and 925 μL of isopropanol, and the mixture was sonicated for 30 min. 100 μL of this mixture was then uniformly coated onto a 0.5 × 0.5 cm layer of carbon cloth. 2 Place both sides of the container on the floor and dry at room temperature (20 ℃).

[0060] (2) Electrode system assembly Electrode performance was tested using a standard three-electrode system on an electrochemical workstation. A graphite electrode and a saturated calomel electrode were used as the counter and reference electrodes, respectively, with a 1.0 M KOH solution as the electrolyte. Linear sweep voltammetry (LSV) was performed at a scan rate of 5 mV / s. -1 The scanning range was between -0.6 and 0.1 V. All test potentials were referenced to a reversible hydrogen electrode (RHE). Stability tests were conducted at -200 mV for 50 hours.

[0061] Application Comparative Example 1 Commercially available 20% Pt / C electrode (Accelerate) was used as the working electrode, and the electrode HER performance, including electrode catalytic activity (LSV) and catalytic stability, was tested under the same test conditions as in Application Examples 1-3.

[0062] Application Comparative Example 2 Directly applying untreated titanium carbide (Ti) 3-x C2X y The electrode HER performance, including electrode catalytic activity (LSV) and catalytic stability, was tested under the same test conditions as in Application Examples 1-3, using it as the working electrode.

[0063] Figure 5 The image shows a transmission electron microscope image of the titanium carbide MXene two-dimensional material obtained after etching with 12 M etchant in step 1.2 of Example 1. As can be seen from the image, the titanium carbide MXene after etching with 12 M HCl has a size of 300-500 nm and a uniform thickness in the range of 5-10 nm. This indicates that the etching conditions not only obtained an ultrathin MXene two-dimensional material, but also preserved the uniformity of thickness.

[0064] Figure 6 These are high-resolution transmission electron microscope images of titanium carbide MXene two-dimensional materials obtained under different etching solution concentrations in steps 1.2 of Examples 1-3. The image comparison shows that as the HCl concentration in the etching solution increases (10 M→12 M→14 M), the density of Ti atomic defects (marked by circles) shows an increasing trend.

[0065] Figure 7 These are in-situ high-resolution transmission electron microscopy (HRTEM) images comparing the loading of Ta single atoms onto titanium carbide MXene with different Ti vacancy defect densities under the influence of Ta salt in steps 2 of Examples 1-3. The relatively large and brighter circles in the images represent Ta atoms and are marked with circles. The comparison clearly shows that samples with different Ti vacancy densities can provide more loading vacancies for Ta atoms, thus obtaining composite samples with higher Ta single-atom vacancy densities.

[0066] Figure 8 The graphs show the water splitting hydrogen production activity of the electrode systems prepared using the two-dimensional titanium carbide MXene materials with different Ti vacancy densities supported by Ta single atoms in Examples 1-3, the commercial electrode in Comparative Example 1, and the untreated aluminum titanium carbide electrode in Comparative Example 2. As can be seen from the graphs, the water splitting activity of the composite electrodes made of Ta single atoms supported by MXene with different densities is significantly higher than that of the unsupported Ti single atoms. 3-x C2X y Both showed significant improvements. The performance of the sample treated with the etchant prepared with 14 M HCl (Ta-14 M) was comparable to that of the commercial 20% Pt / C electrode, while the performance of the sample treated with the etchant prepared with 12 M HCl (Ta-12 M) was significantly better than that of the commercial 20% Pt / C electrode.

[0067] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for controllable loading of 6d transition metal single atoms based on titanium carbide MXene two-dimensional material, characterized in that, Includes the following steps: (1) Add aluminum titanium carbide to the etching solution for etching, wash it, and then perform mechanical peeling and centrifugal screening to prepare single-layer / few-layer titanium carbide MXene two-dimensional materials; The etching solution is obtained by mixing and dissolving a 12-14 M HCl solution with LiF. (2) The monolayer / few-layer titanium carbide MXene two-dimensional material is added to water and dispersed evenly. Then, a 6d transition metal salt solution is added to it for reaction and washing to obtain a single-atom metal-supported titanium carbide MXene two-dimensional material.

2. The method for controllable loading of 6d transition metal single atoms based on titanium carbide MXene two-dimensional material according to claim 1, characterized in that, In step (1), the concentration of the HCl solution is 12M.

3. The method for controllable loading of 6d transition metal single atoms based on titanium carbide MXene two-dimensional material according to claim 1, characterized in that, In step (1), the etching conditions are: stirring at 35 °C for 24 h.

4. The method for controllable loading of 6d transition metal single atoms based on titanium carbide MXene two-dimensional material according to claim 1, characterized in that, In step (1), the washing conditions are as follows: wash with deionized water 6-8 times, 15 min each time, centrifuge at 10,000 rad / min until the pH test paper shows that it has been washed to neutral; The conditions for mechanical stripping are as follows: the washed product is mechanically stripped at 300 W for 2 hours. The centrifugation screening conditions are as follows: the mechanically exfoliated blended titanium carbide MXene two-dimensional material is centrifuged at 5000 rad / min. -1 The upper liquid layer is used to obtain the monolayer / few-layer titanium carbide MXene two-dimensional material.

5. The method for controllable loading of 6d transition metal single atoms based on titanium carbide MXene two-dimensional material according to claim 1, characterized in that, In step (2), the 6d transition metal in the 6d transition metal salt solution is selected from Hf, Ta or W.

6. The method for controllable loading of 6d transition metal single atoms based on titanium carbide MXene two-dimensional material according to claim 5, characterized in that, The 6d transition metal in the 6d transition metal salt solution is Ta.

7. The method for controllable loading of 6d transition metal single atoms based on titanium carbide MXene two-dimensional material according to claim 1, characterized in that, In step (2), the reaction conditions are: reacting at a temperature of 30~55 °C for 8 h.

8. A single-atom metal-supported titanium carbide MXene two-dimensional material, characterized in that, It is prepared by the method described in any one of claims 1-7.

9. The application of a single-atom metal-supported titanium carbide MXene two-dimensional material as described in claim 8 in electrocatalytic water splitting for hydrogen production.

10. An electrode for electrocatalytic water splitting to produce hydrogen, characterized in that, This includes a slurry coated on carbon cloth containing the single-atom metal-supported titanium carbide MXene two-dimensional material as described in claim 8; The preparation process of the slurry is as follows: The single-atom metal-supported titanium carbide MXene two-dimensional material was dispersed with carbon black in a mixture of Nafion solution and isopropanol, and then subjected to ultrasonic treatment.

Images