Carbon-based material loaded with magnesium single atoms, its preparation method and application

Abstract

The present invention discloses a carbon-based material loaded with a single magnesium atom, and a preparation method and application thereof. The preparation method comprises reacting a mixed reaction system comprising a carbon source and a complexing agent, a magnesium source, and a template agent to obtain a carbon-based material precursor, and calcining and washing the carbon-based material precursor to obtain a carbon-based material loaded with a single magnesium atom. The preparation method of the carbon-based material loaded with a single magnesium atom provided by the present invention is simple, the raw materials are readily available, the product structure is clear and stable, and it can efficiently catalyze a two-electron oxygen reduction reaction to generate hydrogen peroxide, especially with good selectivity under the support of a high overpotential, and is a heterogeneous catalyst with a wide voltage window, high efficiency, and environmental protection.

Description

Technical Field

[0001] The present invention belongs to the field of catalytic technology, and relates to a carbon-based material loaded with single magnesium atoms, its preparation method and application, and particularly to a carbon-based catalyst loaded with single magnesium atoms that selectively generates hydrogen peroxide in a two-electron oxygen reduction reaction occurring in an electrolytic cell and still has high reaction activity and reaction selectivity when applying a relatively high overpotential, as well as its preparation method and application. Background Art

[0002] Hydrogen peroxide, also known as hydrogen dioxide (H2O2), is a very important environmentally friendly chemical. In recent years, its demand in various applications has increased rapidly. Currently, the anthraquinone process is used industrially to produce hydrogen peroxide on a large scale. This multi-step process has high energy consumption, serious pollution and requires large production equipment. At the same time, high-concentration H2O2 is unstable and prone to decomposition, and there are great safety hazards during its transportation. Electrochemical two-electron oxygen reduction reaction (2e-ORR) as a low-cost, small-scale, distributed, green and environmentally friendly alternative technology for preparing H2O2 has attracted more and more attention.

[0003] Oxygen molecules can be reduced to H2O through a 4e- pathway in an aqueous solution, or reduced to H2O2 through a 2e- pathway. The key to developing an efficient 2e-ORR catalyst lies in the appropriate binding strength between the reaction catalytic center and the reaction intermediate OOH*. Too strong an interaction will lead to difficult desorption of OOH*, and it will be more inclined to the 4e- path to generate H2O, while too weak an interaction will lead to a decrease in activity or even the inability to produce H2O2. Therefore, an ideal 2e- catalyst should have a suitable electronic structure to have a suitable adsorption / desorption strength between OOH* and the catalytic active site, and have good activity while also having excellent selectivity and stability.

[0004] In the process of traditional electrocatalysts catalyzing oxygen to undergo two-electron reduction to generate hydrogen peroxide, the common problem is that when applying a relatively high overpotential, that is, when the system passes a relatively large current density, the competition between two electrons and four electrons will shift towards the direction of four electrons generating H2O, and the selectivity of hydrogen peroxide will be greatly reduced, resulting in a relatively narrow selectable voltage window, a relatively small current density in the system, and the inability to achieve high-selectivity generation of H2O2 at a relatively large current density. Therefore, developing an electrocatalyst that still has high selectivity at a high overpotential is an urgent problem to be solved. Summary of the Invention

[0005] The main object of the present invention is to provide a carbon-based material loaded with single magnesium atoms, its preparation method and application to overcome the deficiencies of the prior art.

[0006] To achieve the foregoing invention object, the technical solutions adopted by the present invention include:

[0007] The present invention provides a method for preparing a carbon-based material loaded with single magnesium atoms, which includes:

[0008] Reacting a mixed reaction system containing a carbon source, a complexing agent, a magnesium source, and a templating agent to obtain a carbon-based material precursor.

[0009] Calcining and washing the carbon-based material precursor to obtain a carbon-based material loaded with single magnesium atoms.

[0010] Another object of the present invention is to provide a carbon-based material loaded with single magnesium atoms prepared by the above preparation method.

[0011] The present invention also provides the application of the carbon-based material loaded with single magnesium atoms as a catalyst in the reaction for preparing hydrogen peroxide.

[0012] In addition, the present invention also provides a catalyst for electrocatalytic oxygen reduction to generate hydrogen peroxide, which includes the carbon-based material loaded with single magnesium atoms.

[0013] Compared with the prior art, the beneficial effects of the present invention are at least as follows:

[0014] 1) The carbon-based material loaded with single magnesium atoms provided by the present invention does not contain precious metals, and uses cheap and non-toxic tannic acid and sucrose to replace expensive compounds such as acetylacetone, significantly reducing the preparation cost of the catalyst.

[0015] 2) The atomic distribution of magnesium elements in the carbon-based material loaded with single magnesium atoms provided by the present invention maximizes the utilization efficiency of magnesium atoms, effectively changes the electronic configuration of adjacent C, effectively changes the adsorption energy of the intermediate OOH*, making the catalyst exhibit excellent ORR catalytic performance, especially maintaining high selectivity even at high overpotentials. Description of the Drawings

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0017] Figure 1 It is the XRD pattern of the carbon-based material Mg-O-C loaded with single magnesium atoms in Example 1 of the present invention.

[0018] Figure 2 It is the SEM pattern of the carbon-based material Mg-O-C loaded with single magnesium atoms in Example 1 of the present invention.

[0019] Figure 3It is the TEM image of the carbon-based material Mg-O-C loaded with single magnesium atoms in Example 1 of the present invention.

[0020] Figure 4 It is the aberration-corrected transmission image of the carbon-based material Mg-O-C loaded with single magnesium atoms in Example 1 of the present invention.

[0021] Figure 5 It is the current curve graph of the carbon-based materials Mg-O-C and SUC-Mg-O-C loaded with single magnesium atoms in 0.1M NaOH (pH = 13) in Example 1 and Example 4 of the present invention.

[0022] Figure 6 It is the selectivity graph of the carbon-based materials Mg-O-C and SUC-Mg-O-C loaded with single magnesium atoms in 0.1M NaOH (pH = 13) in Example 1 and Example 4 of the present invention.

[0023] Figure 7 It is the electron transfer number graph of the carbon-based materials Mg-O-C and SUC-Mg-O-C loaded with single magnesium atoms in 0.1M NaOH (pH = 13) in Example 1 and Example 4 of the present invention. Detailed implementation manners

[0024] In view of the defects of the prior art, through long-term research and a large number of practices by the inventors of this case, the technical solution of the present invention can be proposed. The technical solution of the present invention will be described clearly and completely below. It mainly makes the carbon source, complexing agent, magnesium source, and templating agent react, and calcines and washes the carbon-based material precursor after freeze-drying to obtain the carbon-based material loaded with single magnesium atoms.

[0025] The following will further explain the technical solution, its implementation process, principle, etc. However, it should be understood that within the scope of the present invention, the above-mentioned technical features of the present invention and the technical features specifically described below (in the examples) can be combined with each other to form new or preferred technical solutions. Due to space limitations, they will not be repeated one by one here.

[0026] As an aspect of the technical solution of the present invention, a preparation method of a carbon-based material loaded with single magnesium atoms includes:

[0027] Reacting a mixed reaction system containing a carbon source, a complexing agent, a magnesium source, and a templating agent to obtain a carbon-based material precursor;

[0028] Calcining and washing the carbon-based material precursor to obtain a carbon-based material loaded with single magnesium atoms.

[0029] In some specific embodiments, the preparation method of the carbon-based material loaded with single magnesium atoms specifically includes:

[0030] Dissolve the carbon source and complexing agent in water, and stir at 15 - 30 °C for 1 - 2 h to obtain a carbon source and complexing agent solution;

[0031] Mix the magnesium source with the carbon source and complexing agent solution, and ultrasonically disperse for 1 - 2 h to obtain a uniform mixed solution;

[0032] Add the template agent aqueous solution to the mixed solution and ultrasonically disperse for 1 - 2 h, and then perform freeze - drying treatment on the obtained reaction product to prepare the carbon - based material precursor.

[0033] In some specific embodiments, the carbon source and complexing agent include any one or a combination of two of tannic acid and sucrose. Taking tannic acid as the carbon source and complexing agent, the tannic acid - magnesium complex formed by the complexation of tannic acid and magnesium ions can effectively avoid the agglomeration and oxidation of magnesium in subsequent processing.

[0034] Further, the template agent includes any one or a combination of two of sodium chloride and potassium chloride. Utilizing the confinement effect of the template agent can prevent agglomeration during the pyrolysis process, and after washing away the NaCl and KCl templates by water, the generated macropores can reduce the mass transfer resistance, which is beneficial to kinetics.

[0035] Further, the magnesium source includes any one or a combination of two or more of magnesium chloride and magnesium acetate.

[0036] In some specific embodiments, the molar ratio of water to the carbon source and complexing agent in the mixed solution is 400 - 500∶1.

[0037] Further, the molar ratio of water to the magnesium source in the carbon source and complexing agent solution is 1200 - 1400∶1.

[0038] Further, the molar ratio of water to the template agent in the template agent aqueous solution is 4.5 - 7∶1.

[0039] In some specific embodiments, the calcination temperature of the carbon material precursor is 650 - 750 °C, and the calcination time is 1 - 3 h.

[0040] Further, the preparation method further includes soaking the product obtained by the calcination treatment in water for 5 - 10 h.

[0041] The embodiment of the present invention also provides a carbon - based material loaded with single - atom magnesium prepared by the above - mentioned preparation method.

[0042] Specifically, the magnesium atoms in the carbon - based material loaded with single - atom magnesium are uniformly dispersed in the carbon - based material in a single - atom state.

[0043] Further, the content of magnesium atoms in the carbon - based material loaded with single - atom magnesium is 0.8 - 1.2 wt%.

[0044] Furthermore, the magnesium atoms in the carbon-based material loaded with single magnesium atoms are connected to oxygen atoms by covalent bonds, having a Mg-O-C structure.

[0045] The embodiment of the present invention also provides an application of the carbon-based material loaded with single magnesium atoms as a catalyst in the reaction for preparing hydrogen peroxide.

[0046] The embodiment of the present invention also provides a catalyst for electrocatalytic oxygen reduction to generate hydrogen peroxide, which includes the carbon-based material loaded with single magnesium atoms.

[0047] In some more specific embodiments, the preparation method of the carbon-based material loaded with single magnesium atoms of the present invention includes:

[0048] Reacting a reaction system containing a carbon source, a complexing agent, a magnesium source, and a sodium chloride templating agent to obtain a carbon-based material precursor;

[0049] And, calcining and washing the obtained carbon-based precursor to obtain a carbon-based material loaded with single magnesium atoms (denoted as Mg-O-C).

[0050] And, the inventors of this case also performed the following performance tests on the obtained Mg-O-C:

[0051] (1) Morphology test: Scanning electron microscope, model: Hitachi S-4800 field emission scanning electron microscope.

[0052] Transmission electron microscope, model: Tecnai F20.

[0053] Spherical aberration corrected transmission electron microscope, model: JEM-ARM200F.

[0054] (2) Structure test: X-ray powder diffractometer, model: D8 ADVANCE DAVINCI.

[0055] (3) ORR performance test:

[0056] Instrument model: Rotating ring-disk test system: American pine rotating ring-disk device (AFCPRBE).

[0057] Electrochemical workstation: Shanghai Chenhua, 760E.

[0058] The test method adopted is as follows:

[0059] On a rotating ring-disk test system, a three-electrode test system was used to test the oxygen reduction catalytic performance of the material described in the present invention. Among them, the ring-disk electrode, carbon rod, and mercury / mercuric oxide electrode were used as the working electrode, counter electrode, and reference electrode, respectively. 3.3 mg of the carbon-based material loaded with magnesium single atoms described in the present invention was dispersed in 1.05 ml of a solvent. The solvent consisted of 1 ml of ethanol and 50 μl of a 5% Nafion solution by mass. The uniformly dispersed mixed solution was drop-coated onto the ring-disk electrode, and the loading amount of the material on the ring-disk electrode was 0.077 mg cm -2 . During the test, the rotation speed of the rotating ring-disk system was set at 1600 rpm, and the scanning speed was 5 mV s -1 . The test was carried out in a 0.1 M NaOH solution (pH = 13).

[0060] The technical solution of the present invention will be further described in detail below in conjunction with several preferred embodiments. These embodiments are implemented on the premise of the technical solution of the invention, and the detailed implementation manners and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0061] The experimental materials used in the following embodiments can be purchased from conventional biochemical reagent companies without special instructions.

[0062] Example 1

[0063] The specific steps for synthesizing the carbon-based material loaded with magnesium single atoms in this example are as follows:

[0064] First, a carbon-based material precursor is synthesized, specifically including: adding 1.11 mmol of tannic acid to 10 ml of deionized water, loading into a 50 ml centrifuge tube, adding a magnetic stirrer into the centrifuge tube, stirring at 20°C until completely dissolved to obtain a tannic acid solution, adding 0.46 mmol of magnesium chloride hexahydrate to the aforementioned centrifuge tube, and continuing to stir for 1 hour to obtain a mixed solution; taking another 50 ml centrifuge tube, adding 5 ml of deionized water to dissolve 3 g of sodium chloride, adding the sodium chloride solution to the above mixed solution, continuing to stir for 1 hour to obtain a clear brown-yellow solution, and placing the solution in a freeze dryer for freeze drying for two days to obtain a carbon material precursor. Then, heat treatment is carried out, and an appropriate amount of the obtained carbon-based material precursor is placed in a porcelain boat, placed in a tube furnace and calcined at 700°C for 2h in an inert gas atmosphere, with a heating rate of 5°C / min. After naturally cooling to room temperature, the obtained black powder is taken out, and finally the black powder is washed with water, 100mg of black powder is taken and ground thoroughly in a mortar, and stirred in 100ml of deionized water for 8h, and then washed twice with deionized water and ethanol respectively, and the solid matter is filtered out and placed in a vacuum drying oven at 60°C overnight to obtain a carbon-based material loaded with magnesium single atoms (hereinafter also referred to as Mg-OC). The purpose of the water washing step is to remove the NaCl template in the black powder. The ICP test of the obtained sample shows that the magnesium single atom loading is about 1.2wt%.

[0065] Example 2

[0066] The specific steps for synthesizing the carbon-based material supporting magnesium single atoms in this embodiment are as follows:

[0067] First, a carbon-based material precursor is synthesized, specifically including: adding 1.30 mmol of tannic acid to 10 ml of deionized water, loading into a 50 ml centrifuge tube, adding a magnetic stirrer into the centrifuge tube, stirring at 15°C until completely dissolved to obtain a tannic acid solution, adding 0.42 mmol of magnesium chloride hexahydrate to the aforementioned centrifuge tube, and continuing to stir for 1 hour to obtain a mixed solution; taking another 50 ml centrifuge tube, adding 5 ml of deionized water to dissolve 3.6 g of sodium chloride, adding the sodium chloride solution to the above mixed solution, continuing to stir for 1 hour to obtain a clear brown-yellow solution, and placing the solution in a freeze dryer for freeze drying for two days to obtain a carbon material precursor. Then, a heat treatment is performed, and an appropriate amount of the obtained carbon-based material precursor is placed in a porcelain boat, placed in a tube furnace and calcined at 650°C for 3 hours in an inert gas atmosphere, with a heating rate of 5°C / min. After naturally cooling to room temperature, the obtained black powder is taken out, and finally the black powder is washed with water, 100 mg of the black powder is taken and ground thoroughly in a mortar, and stirred in 100 ml of deionized water for 10 hours, and then washed twice with deionized water and ethanol respectively, and the solid matter is filtered out and placed in a vacuum drying oven at 60°C overnight to obtain a carbon-based material loaded with magnesium single atoms (hereinafter also referred to as Mg-OC). The purpose of the water washing step is to remove the NaCl template in the black powder. The ICP test of the obtained sample shows that the magnesium single atom loading is about 0.98wt%.

[0068] Example 3

[0069] The specific steps for synthesizing the carbon-based material supporting magnesium single atoms in this embodiment are as follows:

[0070] First, a carbon-based material precursor is synthesized, specifically including: adding 1.39 mmol of tannic acid to 10 ml of deionized water, loading into a 50 ml centrifuge tube, adding a magnetic stirrer into the centrifuge tube, stirring at 30°C until completely dissolved to obtain a tannic acid solution, adding 0.4 mmol of magnesium chloride hexahydrate to the aforementioned centrifuge tube, and continuing to stir for 1 hour to obtain a mixed solution; taking another 50 ml centrifuge tube, adding 5 ml of deionized water to dissolve 2.32 g of sodium chloride, adding the sodium chloride solution to the above mixed solution, continuing to stir for 1 hour to obtain a clear brown-yellow solution, and placing the solution in a freeze dryer for freeze drying for two days to obtain a carbon material precursor. Then, a heat treatment is performed, and an appropriate amount of the obtained carbon-based material precursor is placed in a porcelain boat, placed in a tube furnace and calcined at 750°C for 1 hour in an inert gas atmosphere, with a heating rate of 5°C / min. After naturally cooling to room temperature, the obtained black powder is taken out, and finally the black powder is washed with water, 100 mg of the black powder is taken and ground thoroughly in a mortar, and stirred in 100 ml of deionized water for 5 hours, and then washed twice with deionized water and ethanol respectively, and the solid matter is filtered out and placed in a vacuum drying oven at 60°C overnight to obtain a carbon-based material loaded with magnesium single atoms (hereinafter also referred to as LC-Mg-OC). The purpose of the water washing step is to remove the NaCl template in the black powder. The ICP test of the obtained sample shows that the magnesium single atom loading is about 0.8wt%.

[0071] Example 4

[0072] The specific steps for synthesizing the carbon-based material loaded with magnesium single atoms in this comparative example are as follows:

[0073] First, synthesize the carbon-based material precursor, specifically including: Add 1.3 mmol of sucrose to 10 ml of deionized water, place it in a 50-ml centrifuge tube, add a magnetic stir bar to the centrifuge tube, stir at 20 °C until completely dissolved to obtain a tannic acid solution, add 0.32 mmol of magnesium chloride hexahydrate to the aforementioned centrifuge tube, and continue stirring for 1 h to obtain a mixed solution; Take another 50-ml centrifuge tube, dissolve 3 g of sodium chloride in 5 ml of deionized water, add this sodium chloride solution to the above mixed solution, and continue stirring for 1 h to obtain a clear brownish-yellow solution. Place this solution in a freeze dryer and freeze-dry for two days to obtain the carbon material precursor. Subsequently, perform heat treatment. Place an appropriate amount of the obtained carbon-based material precursor in a porcelain boat, put it into a tube furnace, calcine at 700 °C for 2 h in an inert gas atmosphere, with a heating rate of 5 °C / min. After naturally cooling to room temperature, take out the obtained black powder. Finally, wash this black powder. Take 100 mg of the black powder, grind it thoroughly in a mortar, place it in 100 ml of deionized water and stir for 10 h, then wash it twice with deionized water and ethanol respectively, and filter out the solid matter by suction filtration and place it in a vacuum drying oven to dry overnight at 60 °C to obtain the comparative sample (hereinafter also referred to as SUC-Mg-O-C). The purpose of the water washing step is to remove the NaCl template agent in the black powder. The magnesium single-atom loading amount of the obtained sample measured by ICP is about 1.2 wt%.

[0074] Example 5

[0075] In this example, the synthesis of the carbon-based material loaded with magnesium single atoms is specifically carried out as follows:

[0076] First, synthesize the carbon-based material precursor, which specifically includes: adding 1.39 mmol of sucrose into 10 ml of deionized water, loading it into a 50-ml centrifuge tube, adding a magnetic stir bar into the centrifuge tube, stirring at 15 °C for 2 h until completely dissolved to obtain a sucrose solution, adding 0.4 mmol of magnesium acetate into the aforementioned centrifuge tube, and continuing to stir for 2 h to obtain a mixed solution; separately taking a 50-ml centrifuge tube, adding 5 ml of deionized water to dissolve 2.32 g of potassium chloride, adding this potassium chloride solution into the above mixed solution, and continuing to stir for 2 h to obtain a clear brownish-yellow solution. Freeze-dry this solution in a freeze dryer for two days to obtain the carbon material precursor. Subsequently, perform heat treatment. Place an appropriate amount of the obtained carbon-based material precursor in a porcelain boat, put it into a tube furnace, and calcine it at 750 °C for 2 h in an inert gas atmosphere with a heating rate of 5 °C / min. After naturally cooling to room temperature, take out the obtained black powder. Finally, wash this black powder. Take 100 mg of the black powder, grind it thoroughly in a mortar, place it in 100 ml of deionized water, stir for 5 h, wash it twice with deionized water and ethanol respectively, filter out the solid matter by suction filtration, and place it in a vacuum drying oven at 60 °C for overnight drying to obtain the carbon-based material loaded with single magnesium atoms (hereinafter also referred to as SUC-Mg-O-C). The purpose of the water washing step is to remove the KCl template agent in the black powder.

[0077] Example 6

[0078] In this example, the specific steps for synthesizing the carbon-based material loaded with single magnesium atoms are as follows:

[0079] First, synthesize the carbon-based material precursor, which specifically includes: adding 1.39 mmol of sucrose into 10 ml of deionized water, loading it into a 50-ml centrifuge tube, adding a magnetic stir bar into the centrifuge tube, stirring at 30 °C for 1 h until completely dissolved to obtain a sucrose solution, adding 0.4 mmol of magnesium acetate into the aforementioned centrifuge tube, and continuing to stir for 1 h to obtain a mixed solution; separately taking a 50-ml centrifuge tube, adding 5 ml of deionized water to dissolve 2.32 g of potassium chloride, adding this potassium chloride solution into the above mixed solution, and continuing to stir for 1 h to obtain a clear brownish-yellow solution. Freeze-dry this solution in a freeze dryer for two days to obtain the carbon material precursor. Subsequently, perform heat treatment. Place an appropriate amount of the obtained carbon-based material precursor in a porcelain boat, put it into a tube furnace, and calcine it at 750 °C for 1 h in an inert gas atmosphere with a heating rate of 5 °C / min. After naturally cooling to room temperature, take out the obtained black powder. Finally, wash this black powder. Take 100 mg of the black powder, grind it thoroughly in a mortar, place it in 100 ml of deionized water, stir for 5 h, wash it twice with deionized water and ethanol respectively, filter out the solid matter by suction filtration, and place it in a vacuum drying oven at 60 °C for overnight drying to obtain the carbon-based material loaded with single magnesium atoms (hereinafter also referred to as SUC-Mg-O-C). The purpose of the water washing step is to remove the KCl template agent in the black powder.

[0080] Result analysis

[0081] The carbon-based materials loaded with single-atom magnesium prepared in Examples 1-6 were subjected to X-ray powder diffraction testing (XRD). The XRD results of the carbon-based materials loaded with single-atom magnesium prepared in Example 1 are as Figure 1 shown. The results show that only the diffraction peaks of graphitized carbon exist, and there are no diffraction peaks of metallic Mg and other derivatives, proving the single-atom distribution of magnesium atoms. The XRD results of the carbon-based materials loaded with single-atom magnesium prepared in Examples 2, 3, 4, 5, and 6 are similar to those in Example 1.

[0082] The carbon-based materials loaded with single-atom magnesium prepared in Examples 1-6 were subjected to scanning electron microscopy (SEM) testing. The SEM testing results of the carbon-based materials loaded with single-atom magnesium prepared in Example 1 are as Figure 2 shown. The results show that the morphology of the material is a lamellar structure. The SEM testing results of the carbon-based materials loaded with single-atom magnesium prepared in Examples 2, 3, 4, 5, and 6 are similar to those in Example 1.

[0083] The carbon-based materials loaded with single-atom magnesium prepared in Examples 1-6 were subjected to transmission electron microscopy (TEM) testing. The TEM testing results of the carbon-based materials loaded with single-atom magnesium prepared in Example 1 are as Figure 3 shown. The results show that no clusters and nanoparticles were observed in the material, proving the successful preparation of the carbon-based materials loaded with single-atom magnesium. The TEM testing results of the carbon-based materials loaded with single-atom magnesium prepared in Examples 2, 3, 4, 5, and 6 are similar to those in Example 1.

[0084] The carbon-based materials loaded with single-atom magnesium prepared in Examples 1-6 were subjected to aberration-corrected transmission electron microscopy (ACTEM) testing. The ACTEM testing results of the carbon-based materials loaded with single-atom magnesium prepared in Example 1 are as Figure 4 shown. It can be seen that a large number of white bright spots can be observed in the figure, which are magnesium atoms distributed at the atomic level. TEM and ACTEM testing confirmed the atomic-level distribution of magnesium atoms and the successful synthesis of the carbon-based materials loaded with single-atom magnesium. The ACTEM testing results of the carbon-based materials loaded with single-atom magnesium prepared in Examples 2, 3, 4, 5, and 6 are similar to those in Example 1.

[0085] The carbon-based materials loaded with single-atom magnesium prepared in Examples 1-6 were subjected to ORR testing. The ORR testing results of the carbon-based materials loaded with single-atom magnesium prepared in Example 1 are as Figures 5 to 7As shown, under alkaline conditions, the starting potential of the sample Mg-O-C in Example 1 is 0.7493 V, and the starting potential of the sample SUC-Mg-O-C in Example 4 is 0.6563 V. The selectivity of the sample Mg-O-C in Example 1 remains above 90% within a relatively wide voltage window (0.7 - 0.2 V), and the number of electron transfers is below 2.25. Especially at a relatively high overpotential of 0.2 V, the selectivity is still 90%, showing good ORR catalytic performance. The overall selectivity of the sample SUC-Mg-O-C in Example 4 is below 90% within this voltage window, the number of electron transfers is between 2.25 and 2.4, and at a relatively high overpotential of 0.2 V, the selectivity is 81%. Among them, the performance of Example 1 is the best.

[0086] It should be understood that although this specification is described according to each embodiment, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0087] The above is an exemplary description of the present invention. Obviously, the implementation of the present invention is not limited by the above methods. Without improvement, directly applying the concept and technical solution of the present invention to other occasions, or equivalent implementation schemes or changes made without departing from the method concept and technical solution of the present invention, such as the combination, division, or repetition of features, are within the protection scope of the present invention.

Claims

1. A preparation method of a carbon-based material loaded with single magnesium atoms, characterized in that Comprising: Reacting a mixed reaction system containing a carbon source, a complexing agent, a magnesium source, and a templating agent to obtain a carbon-based material precursor, wherein the carbon source and the complexing agent are selected from any one or a combination of tannic acid and sucrose, and the templating agent is selected from any one or a combination of sodium chloride and potassium chloride; Calcining and washing the carbon-based material precursor to obtain a carbon-based material loaded with single magnesium atoms.

2. The preparation method according to claim 1, characterized in that, Comprising: Dissolve the carbon source and the complexing agent in water, and stir at 15 - 30 °C for 1 - 2 h to obtain a carbon source and complexing agent solution; Mix the magnesium source with the carbon source and complexing agent solution, and ultrasonically disperse for 1 - 2 h to obtain a homogeneous mixed solution; Add an aqueous solution of the templating agent to the mixed solution and ultrasonically disperse for 1 - 2 h, and then perform freeze-drying treatment on the obtained reaction product to obtain the carbon-based material precursor.

3. The preparation method according to claim 2, characterized in that: The magnesium source is selected from any one or a combination of magnesium chloride and magnesium acetate.

4. The preparation method according to claim 2, wherein: The molar ratio of water to the carbon source and the complexing agent is 400 - 500:

1.

5. The preparation method according to claim 2, characterized in that: The molar ratio of water to the magnesium source in the carbon source and complexing agent solution is 1200 - 1400:

1.

6. The preparation method according to claim 2, characterized in that: The molar ratio of water to the templating agent in the aqueous solution of the templating agent is 4.5 - 7:

1.

7. The preparation method according to claim 1, characterized in that: The temperature of the calcination is 650 - 750 °C, and the time of the calcination is 1 - 3 h.

8. The preparation method according to claim 1, characterized in that, The preparation method further includes: soaking the product obtained by calcination in water for 5 - 10 h for the washing treatment.

9. A carbon-based material loaded with single magnesium atoms prepared by the preparation method according to any one of claims 1 - 8.

10. The carbon-based material loaded with single magnesium atoms according to claim 9, characterized in that: The magnesium atoms in the carbon-based material loaded with single magnesium atoms are uniformly dispersed in the carbon-based material in a single-atom state.

11. The carbon-based material loaded with single magnesium atoms according to claim 10, characterized in that: The magnesium atoms in the carbon-based material loaded with single magnesium atoms are connected to oxygen atoms by covalent bonds and have a Mg - O - C structure.

12. The carbon-based material loaded with single magnesium atoms according to claim 10, wherein: The content of magnesium atoms in the carbon-based material loaded with single magnesium atoms is 0.8 - 1.2 wt%.

13. Use of the carbon-based material loaded with single magnesium atoms according to any one of claims 9 - 12 as a catalyst in the reaction for preparing hydrogen peroxide.

14. A catalyst for electrocatalytic oxygen reduction to produce hydrogen peroxide, characterized in that, Comprising the carbon-based material loaded with single magnesium atoms according to any one of claims 9 - 12.

Images