A single-atom Pt catalyst supported on the edge sites of monolayer MoS2, and its preparation method and application

Abstract

The present invention discloses a single-atom Pt catalyst supported on the edge sites of monolayer MoS2, its preparation method and application. The carrier of this catalytic material is monolayer MoS2 exfoliated by lithium intercalation, and single-atom Pt is selectively loaded on the edge defect sites of MoS2. The present invention discloses a synthesis strategy for a novel single-atom catalyst with simple preparation process and mild synthesis conditions, which is suitable for large-scale production applications. In addition, the electrochemical test on a rotating ring-disk electrode shows that the single-atom Pt catalyst supported on the edge sites of monolayer MoS2 obtained in the present invention can be applied to the two-electron oxygen reduction reaction to hydrogen peroxide.

Description

Technical Field

[0001] The present invention relates to the technical field of single-atom supported catalysis, and relates to a single-atom Pt catalyst supported on the edge sites of monolayer MoS2, a preparation method thereof, and an application thereof. Background Art

[0002] As an environmentally friendly and highly efficient oxidant, hydrogen peroxide (H2O2) has a variety of industrial applications, including the bleaching of pulp and paper, chemical synthesis, and wastewater treatment. However, today's commercial production of hydrogen peroxide is accomplished through the high-energy-consuming and highly polluting indirect anthraquinone process. In order to meet China's "carbon neutrality" goal, electrochemical hydrogen peroxide synthesis via a two-electron oxygen reduction pathway using renewable electricity is considered a potentially viable alternative for the green synthesis of hydrogen peroxide.

[0003] In recent years, various novel two-dimensional materials with unique structures and electronic properties, such as graphene, hexagonal boron nitride, layered oxides, and other two-dimensional layered transition metal dichalcogenides, have attracted great research interest in heterogeneous catalysis. Moreover, it is generally believed that layered transition metal dichalcogenides, including MoS2 and WS2, can be chemically exfoliated into monolayer two-dimensional materials in solution by intercalation (using Li). Due to the change in orbital interaction, their band structures are adjusted, endowing them with a series of special optical and electromagnetic properties. In addition, the chemically exfoliated monolayer MoS2 molecular layer contains a large number of sulfur vacancies at its surface edges, which is due to the charge transfer from Li to this layer, resulting in S 2- leaching. These sulfur vacancies constitute atomic-level interfaces with high surface free energy, to which small molecules can attach with high affinity, thus serving as anchoring sites for metal atoms or clusters. Summary of the Invention

[0004] In view of this, the present invention provides a single-atom Pt catalyst supported on the edge sites of monolayer MoS2, a preparation method thereof, and an application thereof. The synthesis conditions are mild, the procedure is simple, it can be used for large-scale production, and its application in the electrochemical reduction of oxygen to hydrogen peroxide is realized.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A single-atom Pt catalyst supported on the edge sites of monolayer MoS2 includes monolayer MoS2 and Pt atoms selectively supported on the edge sites of MoS2.

[0007] As a preferred technical solution, the mass ratio of Pt atoms to monolayer MoS2 is 0.3 - 5:95 - 105.

[0008] As a preferred technical solution, the supported single atoms include but are not limited to Pt, Pd, Au, Ag, Ir, Rh.

[0009] A preparation method of a single-atom Pt catalyst supported on the edge sites of monolayer MoS2 comprises the following steps: uniformly disperse the exfoliated monolayer MoS2 in deionized water to obtain a mixed solution A; add dilute hydrochloric acid dropwise to the mixed solution A to adjust the pH to 2-3 to obtain a mixed solution B; slowly dropwise add a chloroplatinic acid solution to the mixed solution B, fully stir and react to obtain a mixed solution C; perform suction filtration, water washing and vacuum drying on the mixed solution C for 12 h to obtain the single-atom Pt catalyst supported on the edge sites of the monolayer MoS2.

[0010] As a preferred technical solution, the mass-volume ratio of the monolayer MoS2 to the deionized water is: 500-600 (mg): 50-80 (ml). The Pt atom concentration of the chloroplatinic acid solution is 0.5-5 mg / ml, and the added volume is: 3-5 ml.

[0011] As a preferred technical solution, the dropping rate of the chloroplatinic acid solution is 20-25 ml / h, the stirring reaction time is 3-5 h, and the rotation speed of the magnetic stirrer is 800-1200 r / min.

[0012] In the above steps, the monolayer MoS2 exfoliation step is as follows: in a glove box, add a n-hexane solution of n-butyllithium to the nano-MoS2 powder to obtain a mixed solution D. After the mixed solution D stands for 2-3 days, pour it into 500 ml of deionized water, add dilute hydrochloric acid dropwise to adjust the pH to 3-5 to obtain a mixed solution E. Centrifuge and collect the mixed solution E, and the obtained reaction product is washed and dried to obtain the monolayer MoS2.

[0013] As a preferred technical solution, the mass-volume ratio of the nano-MoS2 powder to the n-hexane solution of n-butyllithium is 400-600 (mg): 4-6 (ml).

[0014] As a preferred technical solution, the washing treatment uses deionized water and ethanol, and the specific operation is as follows: perform centrifugal separation on the mixed solution E after the reaction, ultrasonically wash the product obtained by centrifugal separation with deionized water and ethanol, then continue centrifugal separation, and ultrasonically wash the product obtained by centrifugation with deionized water and ethanol again, repeating 3-5 times. The ultrasonic washing time each time is 4-6 min, the rotation speed of each centrifugal separation is 12000-13000 r / min, and the time of each centrifugal separation is 5-7 min.

[0015] The application of the single-atom Pt catalyst supported on the edge sites of monolayer MoS2 in the electrochemical reduction of oxygen to hydrogen peroxide is realized in a rotating ring-disk electrode.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] (1) In the present invention, Pt single atoms are selectively loaded on the edge sites of monolayer MoS2 to construct a novel single-atom catalyst structure system.

[0018] (2) The Pt single-atom catalyst loaded on the edge sites of monolayer MoS2 in the present invention has a controllable metal loading amount and a wide range of single atoms for loading (Pt, Pd, Au, Ag, Ir, Rh).

[0019] (3) The synthesis strategy of the present invention is an electrostatic adsorption loading method, with simple synthesis steps and strong repeatability; mild reaction conditions, safe operation, and low equipment loss; low energy consumption, green and clean, and environmentally friendly; the carrier, components, loading amount, etc. of the catalyst all have a flexible and wide regulation range, providing a new synthesis method for single-atom catalysts.

[0020] (4) The Pt single-atom catalyst loaded on the edge sites of monolayer MoS2 in the present invention realizes the application in the two-electron oxygen reduction to hydrogen peroxide. Description of the Drawings

[0021] Figure 1 It is the transmission electron microscope photograph of the monolayer MoS2 carrier obtained in Example 1 of the present invention.

[0022] Figure 2 It is the aberration-corrected high-resolution transmission electron microscope photograph of the Pt single-atom catalyst loaded on the edge sites of monolayer MoS2 obtained in Example 2 of the present invention.

[0023] Figure 3 It is the X-ray absorption near-edge spectrum of the Pt single-atom catalyst loaded on the edge sites of monolayer MoS2 obtained in Example 2 of the present invention.

[0024] Figure 4 It is the X-ray absorption fine structure spectrum of the Pt single-atom catalyst loaded on the edge sites of monolayer MoS2 obtained in Example 2 of the present invention.

[0025] Figure 5 It is the X-ray diffraction pattern of the monolayer MoS2 carrier in Example 1, the Pt single-atom catalyst loaded on the edge sites of monolayer MoS2 in Example 2, and the Pt single-atom catalyst loaded on the edge sites of monolayer MoS2 in Example 3 of the present invention.

[0026] Figure 6 It is the rotating ring-disk electrode electrochemical data of the Pt single-atom catalyst loaded on the edge sites of monolayer MoS2 with a Pt atomic mass fraction of 1.8 wt% at different rotation speeds in Example 4 of the present invention.

[0027] Figure 7This is the selectivity of the Pt single-atom catalyst loaded on the edge sites of monolayer MoS2 with a Pt atomic mass fraction of 1.8 wt% at different rotation speeds in Example 4 for the electrochemical reduction of oxygen to hydrogen peroxide at different potentials. Detailed implementation mode

[0028] To further understand the present invention, the preferred implementation schemes of the present invention will be described below in conjunction with embodiments. However, it should be understood that these descriptions are only for further explaining the features and advantages of the present invention, rather than limiting the claims of the invention.

[0029] For all raw materials of the present invention, there is no special limitation on their sources, and they can be purchased on the market or prepared according to the conventional methods well-known to those skilled in the art.

[0030] For all raw materials of the present invention, there is no special limitation on their purity. The present invention preferably adopts analytical pure or the conventional purity requirements in the field of atomic layer deposition.

[0031] For all raw materials and process procedures of the present invention, their trademarks or abbreviations all belong to the conventional trademarks or abbreviations in the field. Each trademark or abbreviation is clear and definite in the field of its related uses. Those skilled in the art can purchase or prepare them by conventional methods according to the trademark, abbreviation and corresponding uses, or implement them using the corresponding equipment.

[0032] Example 1

[0033] In this example, a monolayer MoS2 support was prepared, which specifically included the following steps:

[0034] Step 1: In a glove box filled with nitrogen, 500 mg of nano-molybdenum disulfide and 6 ml of a hexane solution of n-butyllithium were added to a 20-ml glass vial, and the mixture was left to stand in the dark for 2 days to obtain a precursor mixed solution with lithium intercalation.

[0035] Step 2: The mixed solution obtained in Step 1 was poured into 500 ml of deionized water. The intercalated lithium reacted with water between the MoS2 layers to generate H2, thereby realizing the exfoliation of MoS2. 5 M dilute hydrochloric acid was added dropwise to the above monolayer MoS2 solution to adjust the pH value to 3 to obtain a monolayer MoS2 suspension.

[0036] Step 3: The monolayer MoS2 suspension obtained in Step 2 was ultrasonically treated at room temperature for 1 h, centrifuged, washed 3 times with deionized water, and dried in a vacuum oven at 50 °C for 12 h to obtain the monolayer MoS2 support.

[0037] The monolayer MoS2 support obtained in this example was characterized.

[0038] Figure 1This is the transmission electron microscope photograph of the monolayer MoS2 support obtained in this example, indicating that MoS2 has been successfully exfoliated into monolayer MoS2.

[0039] Example 2

[0040] In this example, a single-atom Pt catalyst supported on the edge sites of monolayer MoS2 was prepared, which specifically included the following steps:

[0041] Step 1: 500 mg of the exfoliated monolayer MoS2 support was evenly dispersed in deionized water, and stirred at a magnetic stirring speed of 1000 rpm for 0.5 h to obtain a homogeneous solution.

[0042] Step 2: 5 M dilute hydrochloric acid was added dropwise to the homogeneous solution obtained in Step 1 to adjust the pH value to 2, and stirring was continued for 0.5 h. Step 3: 3 ml of chloroplatinic acid solution with a Pt atomic concentration of 1 mg / ml was slowly added dropwise to the monolayer MoS2 solution obtained in Step 2 at a dropping rate of 20 ml / h, and stirring was continued for 5 h.

[0043] Step 4: The solution obtained in Step 3 was filtered by suction, washed 3 times with deionized water, and dried in a vacuum oven at 50 °C for 12 h to obtain the single-atom Pt catalyst supported on the edge sites of monolayer MoS2.

[0044] The single-atom Pt catalyst supported on the edge sites of monolayer MoS2 obtained in this example was characterized.

[0045] Detected by an inductively coupled plasma spectrometer, the mass fraction of Pt atoms in the single-atom Pt catalyst supported on the edge sites of monolayer MoS2 obtained in this example was 0.5 wt%.

[0046] Figure 2 This is the aberration-corrected high-resolution transmission electron microscope photograph of the single-atom Pt catalyst supported on the edge sites of monolayer MoS2 obtained in this example, indicating that Pt is loaded on the monolayer MoS2 support as isolated single atoms and only on the edge sites of the monolayer MoS2 support.

[0047] Figure 3 This is the X-ray absorption near-edge spectrum of the single-atom Pt catalyst supported on the edge sites of monolayer MoS2 obtained in this example. From the position of the absorption edge and the intensity of the white line peak, it can be seen that the valence state of Pt in the single-atom Pt catalyst supported on the edge sites of monolayer MoS2 is between 0 and +4;

[0048] Figure 4 This is the X-ray absorption fine structure spectrum of the single-atom Pt catalyst supported on the edge sites of monolayer MoS2 obtained in this example. It can be seen from the figure that Pt is coordinated with S.

[0049] Example 3

[0050] In this example, a single-atom Pt catalyst supported on the edge sites of monolayer MoS2 was prepared, which specifically includes the following steps:

[0051] Step 1: Uniformly disperse 500 mg of the exfoliated monolayer MoS2 support in deionized water, and stir it at a magnetic stirring speed of 1000 revolutions / min for 0.5 h to obtain a uniform solution.

[0052] Step 2: Add 5 M dilute hydrochloric acid to the uniform solution obtained in Step 1 to adjust the pH value to 2, and continue stirring for 0.5 h.

[0053] Step 3: Slowly drop 3 ml of chloroplatinic acid solution with a Pt atomic concentration of 5 mg / ml into the monolayer MoS2 solution obtained in Step 2 at a dropping rate of 20 ml / h, and continue stirring for 5 h.

[0054] Step 4: Filter the solution obtained in Step 3 by suction filtration, wash it 3 times with deionized water, and dry it in a vacuum oven at 50 °C for 12 h to obtain a single-atom Pt catalyst supported on the edge sites of monolayer MoS2.

[0055] Characterize the single-atom Pt catalyst supported on the edge sites of monolayer MoS2 obtained in this example.

[0056] Detected by an inductively coupled plasma spectrometer, the mass fraction of Pt atoms in the single-atom Pt catalyst supported on the edge sites of monolayer MoS2 obtained in this example is 2.3 wt%.

[0057] Figure 5 X-ray diffraction patterns of the monolayer MoS2 support in Example 1, the single-atom Pt catalyst supported on the edge sites of monolayer MoS2 in Example 2, and the single-atom Pt catalyst supported on the edge sites of monolayer MoS2 in this example. It can be seen therefrom that the platinum atom loading amount in the single-atom Pt catalyst supported on the edge sites of monolayer MoS2 of the present invention is controllable.

[0058] Example 4

[0059] In this example, a single-atom Pt catalyst supported on the edge sites of monolayer MoS2 was prepared, which specifically includes the following steps:

[0060] Step 1: Uniformly disperse 500 mg of the exfoliated monolayer MoS2 support in deionized water, and stir it at a magnetic stirring speed of 1000 revolutions / min for 0.5 h to obtain a uniform solution.

[0061] Step 2: Add 5 M dilute hydrochloric acid to the uniform solution obtained in Step 1 to adjust the pH value to 2, and continue stirring for 0.5 h.

[0062] Step 3: Slowly add 2 ml of chloroplatinic acid solution with a Pt atomic concentration of 5 mg / ml dropwise to the monolayer MoS2 solution obtained in Step 2 at a dropping rate of 20 ml / h, and continue stirring for 5 h.

[0063] Step 4: Filter the solution obtained in Step 3 by suction filtration, wash it 3 times with deionized water, and dry it in a vacuum oven at 50 °C for 12 h to obtain a monolayer MoS2 edge-site supported Pt single-atom catalyst.

[0064] Detected by an inductively coupled plasma spectrometer, the mass fraction of Pt atoms in the monolayer MoS2 edge-site supported Pt single-atom catalyst obtained in this example is 1.8 wt%.

[0065] Test the catalytic performance of the monolayer MoS2 edge-site supported Pt single-atom catalyst with a Pt atomic mass fraction of 1.8 wt% obtained in this example using a rotating ring-disk electrode.

[0066] Using the glassy carbon ring-disk electrode loaded with the monolayer MoS2 edge-site supported Pt single-atom catalyst obtained in this example as the working electrode, a platinum wire as the counter electrode, and a silver / silver chloride electrode as the reference electrode, and using 0.1 mol / L potassium hydroxide as the electrolyte, perform the oxygen electroreduction performance test in a single electrolytic cell. The disk electrode is tested by the potential linear sweep method, and the applied potential range is 0.9 - 0.2 V (relative to the reversible hydrogen electrode); the ring electrode is tested by the constant potential method, and the applied potential is 1.2 V (relative to the reversible hydrogen electrode). Obtain the catalytic performance data according to the collection coefficient of the ring-disk electrode: 37% and the data recorded by the electrochemical workstation at different rotation speeds.

[0067] Figure 6 This is the rotating ring-disk electrode electrochemical data of the monolayer MoS2 edge-site supported Pt single-atom catalyst with a Pt atomic mass fraction of 1.8 wt% at different rotation speeds in this example. It can be seen that the monolayer MoS2 edge-site supported Pt single-atom catalyst has dual-electron oxygen reduction electrochemical activity.

[0068] Figure 7 This is the selectivity of the monolayer MoS2 edge-site supported Pt single-atom catalyst with a Pt atomic mass fraction of 1.8 wt% for the electrochemical reduction of hydrogen peroxide from oxygen at different potentials at different rotation speeds in this example. It can be obtained that at a cathode potential of 0.45 - 0.7 V (relative to the reversible hydrogen electrode), the monolayer MoS2 edge-site supported Pt single-atom catalyst with a Pt atomic mass fraction of 1.8 wt% has a hydrogen peroxide selectivity of ~45% for dual-electron oxygen reduction.

[0069] Example 5

[0070] In this example, a monolayer MoS2 edge-site supported Pd single-atom catalyst was prepared, which specifically includes the following steps:

[0071] Step 1: Uniformly disperse 500 mg of the exfoliated monolayer MoS2 support in deionized water, and magnetically stir at a speed of 1000 revolutions / min for 0.5 h to obtain a uniform solution.

[0072] Step 2: Add 5M dilute hydrochloric acid to the uniform solution obtained in Step 1 to adjust the pH value to 2, and continue stirring for 0.5 h.

[0073] Step 3: Slowly add 2 ml of a chloropalladic acid solution with a Pd atomic concentration of 5 mg / ml to the monolayer MoS2 solution obtained in Step 2 at a dropping rate of 20 ml / h, and continue stirring for 5 h.

[0074] Step 4: Filter the solution obtained in Step 3 by suction filtration, wash it 3 times with deionized water, and dry it in a vacuum oven at 50 °C for 12 h to obtain a monolayer MoS2 edge-site supported Pd single-atom catalyst.

[0075] Characterize the monolayer MoS2 edge-site supported Pt single-atom catalyst obtained in this example.

[0076] Detected by an inductively coupled plasma spectrometer, the mass fraction of Pt atoms in the monolayer MoS2 edge-site supported Pt single-atom catalyst obtained in this example is 1.8 wt%. Thus, it can be seen that the supported single atoms in the monolayer MoS2 edge-site supported single-atom catalyst of the present invention are controllable.

[0077] It should be understood that the examples and embodiments described herein are for illustrative purposes only and are not intended to limit the present invention. Those skilled in the art can make various modifications or changes based on it. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A single-atom Pt catalyst supported on the edge sites of monolayer MoS2, characterized in that, The invention comprises a single layer of MoS2 and Pt atoms selectively loaded on the edge sites of MoS2, wherein the mass ratio of Pt atoms to the single layer of MoS2 is 0.3-5:95-105; the preparation method of the single layer of MoS2 edge site loaded Pt single atom catalyst comprises the following steps: the peeled single layer of MoS2 is uniformly dispersed in deionized water to obtain a mixed solution A; dilute hydrochloric acid is added dropwise to the mixed solution A to adjust the pH to 2-3 to obtain a mixed solution B; chloroplatinic acid solution is slowly added dropwise to the mixed solution B, and the reaction is fully stirred to obtain a mixed solution C; the mixed solution C is filtered, washed with water, and vacuum dried for 12 hours to obtain the single layer of MoS2 edge site loaded Pt single atom catalyst; The stripping of a single layer of MoS2 includes the following steps: in a glove box, adding an n-hexane solution of n-butyl lithium to nano MoS2 powder to obtain a mixed solution D; after the mixed solution D is allowed to stand for 2 to 3 days, pouring it into 500 ml of deionized water, adding dilute hydrochloric acid dropwise to adjust the pH to 3 to 5 to obtain a mixed solution E; collecting the mixed solution E by centrifugation, and washing and drying the obtained reaction product to obtain the single layer of MoS2.

2. The single-atom Pt-loaded catalyst on the edge sites of monolayer MoS2 according to claim 1, wherein The mass volume ratio of monolayer MoS2 to deionized water is 500~600mg:50~80ml; the Pt atomic concentration of chloroplatinic acid solution is 0.5~5mg / ml, and the added volume is 3~5ml.

3. A single-atom Pt catalyst supported on the edge sites of monolayer MoS2 according to claim 1, wherein, The dropping rate of chloroplatinic acid solution is 20-25 ml / h, the stirring reaction time is 3-5 h, and the speed of the magnetic stirrer for stirring is set to 800-1200 rpm.

4. The single-atom Pt-loaded catalyst on the edge sites of monolayer MoS2 according to claim 1, wherein The mass volume ratio of nano-MoS2 powder to n-butyl lithium n-hexane solution is 400~600mg:4~6ml.

5. The single-atom Pt catalyst supported on the edge sites of monolayer MoS2 according to claim 1, wherein Deionized water and ethanol are used for washing treatment. The specific operation is as follows: the mixed solution E after the reaction is centrifuged, the product obtained by centrifugation is ultrasonically washed with deionized water and ethanol, and then centrifugation is continued. The product obtained by centrifugation is ultrasonically washed with deionized water and ethanol, and the process is repeated 3 to 5 times. The ultrasonic washing time for each time is 4 to 6 minutes. The speed of each centrifugation is 12000 to 13000 rpm, and the time for each centrifugation is 5 to 7 minutes.

6. The application of a single-atom Pt catalyst supported on the edge sites of monolayer MoS2 as described in claim 1, wherein The catalyst is used in the electrochemical reduction of oxygen to produce hydrogen peroxide.

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