Preparation method of monatomic catalyst for oxygen reduction reaction

Abstract

The invention belongs to the technical field of material preparation, and relates to a preparation method of a monatomic catalyst for oxygen reduction reaction, the preparation method comprises the following steps: placing metal salt and 4, 4 '-dipyridyl in a methanol or ethanol solution, stirring, and filtering to obtain a precursor; and placing the obtained precursor in a tubular furnace, carrying out temperature programming calcination in an inert atmosphere, naturally cooling to room temperature, and carrying out acid pickling and filtration to obtain the target catalyst. The preparation method provided by the invention is simple and convenient, is easy for large-scale production, has excellent oxygen reduction reaction catalytic activity, and can effectively replace Pt / C for oxygen reduction reaction.

Description

Technical Field

[0001] The present invention relates to the technical field of material preparation, and in particular to a method for preparing a single-atom catalyst for oxygen reduction reaction. Background Art

[0002] As a new type of energy technology, fuel cells are not limited by the Carnot cycle, have high conversion efficiency, produce pollution-free products, have a wide range of raw materials, and are safe and reliable. They are recognized as efficient and clean energy batteries.

[0003] During the operation of hydrogen-oxygen fuel cells, fuels such as hydrogen are catalytically cracked into protons and electrons at the anode. The protons pass through the electrolyte to the cathode and react with oxygen to generate water and electricity. So far, fuel cell technology has not yet been commercialized on a large scale. One of the important reasons limiting the commercialization of fuel cells is the slow kinetics of the cathode oxygen reduction reaction, which requires the use of precious metal catalysts to increase the reaction rate, resulting in expensive fuel cells. The oxygen reduction catalyst currently used in fuel cells is precious metal platinum. Surveys show that platinum catalysts account for 56% of the overall price of fuel cells. Moreover, even with the use of precious metal platinum catalysts, the cathode oxygen reduction reaction still lags significantly behind the anode oxidation reaction. In addition, platinum catalysts also have the problem of poor durability. During use, metal platinum is easy to aggregate, dissolve, and fall off from the carbon support agent, thereby shortening the service life of the fuel cell. At present, the actual working life of fuel cells is only 1,900 hours at most, while the service life target of commercial mobile fuel cell systems set by the U.S. Department of Energy is more than 5,000 hours. Therefore, the development of fuel cell technology urgently requires the development of cheap, efficient, and stable cathode oxygen reduction catalysts.

[0004] Single-atom catalysts have the characteristics of maximizing atomic utilization and isolating active sites, and have become a very prosperous branch of catalytic research in recent years. Single-atom catalysts provide an ideal model for in-depth understanding of the active site structure and catalytic mechanism, and have shown excellent performance in many catalytic applications. However, the current preparation methods of single-atom catalysts are complex, and the methods reported so far mostly focus on the preparation of a certain type of single-atom catalyst, lacking efficient and general synthetic strategies. At the same time, in the existing technology, the demand for single-atom catalysts is more focused on improving the reaction rate, and there are fewer improvements in the higher catalytic activity and selectivity required in the oxygen reduction reaction. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a method for preparing a single atom catalyst for oxygen reduction reaction.

[0006] A method for preparing a single-atom catalyst for oxygen reduction reaction comprises the following steps:

[0007] Step 1: Place a certain amount of metal salt and 4,4'-bipyridine in methanol or ethanol, stir and filter to obtain a precursor;

[0008] Step 2: The precursor obtained in step 1 is heated to 600-1000° C. under a preset gas atmosphere, calcined for 0.5-4 h, and then cooled to 20-25° C. to obtain a product;

[0009] Step 3: The product is acid-washed, water-washed and then filtered to obtain a single-atom catalyst.

[0010] Note: The above preparation method is relatively simple and easy to mass-produce single-atom catalysts. The obtained single-atom catalysts have excellent catalytic activity in oxygen reduction reactions.

[0011] Furthermore, the metal type in the metal salt in step 1 is any one of V, Cr, Mn, Fe, Ni, Cu, Zn, Nb, Mo, and W; and the metal salt is any one of metal chloride, metal acetate, and metal nitrate.

[0012] Description: The method of this scheme can be used in single-atom catalysts of the above-mentioned various metals and has wide applicability.

[0013] Furthermore, in step 1, the molar ratio of the metal salt to 4,4'-bipyridine is 1:3 to 3:1, and the stirring time is 10 to 50 minutes.

[0014] Note: The catalytic activity of the single-atom catalyst prepared with the above parameters is more preferred.

[0015] Furthermore, the preset gas in step 2 is any one of nitrogen or argon.

[0016] Furthermore, the acid used in the pickling process in step 3 is any one of hydrochloric acid, sulfuric acid, and nitric acid, and the concentration of the acid is 1 to 6 mol / L. -1 ; The temperature of the product during the pickling process is 22 to 90°C.

[0017] Note: The above parameter settings can improve the catalytic effect of single atom catalysts.

[0018] Further, the stirring process includes:

[0019] Stir at a speed of 600-700 r / min for 5-10 minutes, then apply 40-50 V DC with a current of 0.1-0.5 A. After applying the current for 10-15 minutes, stop applying DC, then heat to 80-100°C and stir at a speed of 300-500 r / min for 5-10 minutes.

[0020] Description: The above stirring treatment method can accelerate the contact and mixing between the reactants, increase the rate of chemical reactions, and reduce local concentration gradients, thereby increasing the reaction conversion rate and improving the mass transfer efficiency, so that the metal salt and 4,4'-bipyridine can quickly form a three-dimensional structure with good active sites.

[0021] Furthermore, the method further comprises: using a dielectric material with a high dielectric constant to perform surface modification on the single atom catalyst.

[0022] Description: Dielectric materials with high dielectric constants can enhance charge separation, reduce electron-hole recombination, and thus improve catalytic efficiency. These materials can also promote the rapid transport of electrons and stabilize the active sites of single-atom catalysts, which is crucial for improving the electronic conductivity and catalytic activity of catalysts.

[0023] Furthermore, the high dielectric constant dielectric material is HfO 2 .

[0024] Furthermore, the method of using a dielectric material with a high dielectric constant to modify the surface of the single atom catalyst includes:

[0025] Prepare single atom catalyst and HfCl in a mass ratio of 10-15:1:20-30. 4 , H 2 O;

[0026] First, place the prepared single-atom catalyst into the atomic layer deposition reaction chamber.

[0027] Then HfCl 4 Divide into 25 equal parts, 2 O is divided into 25 parts, and HfCl is alternately introduced into the atomic layer deposition reaction chamber 4 , H 2 O, each time a portion is passed, each time HfCl is passed 4 The pulse was applied for 1 second, followed by a 5 second interval, and then H 2 O pulses were applied for 0.5 seconds, and after a 5-second interval, HfCl was introduced again. 4 , and the cycle is repeated until the treatment is completed to obtain the deposited single-atom catalyst;

[0028] The deposited single-atom catalyst is then heated and maintained at a constant temperature of 400-500° C. for 1-2 hours to obtain a surface-modified single-atom catalyst.

[0029] Note: The above HfCl 4It can be attached to the single-atom catalyst, and can improve the stability and catalytic performance of the single-atom catalyst without changing the original structure of the catalyst; the introduction of hafnium atoms can adjust the electronic properties of the catalyst surface and affect the activity and selectivity of the catalyst; that is, it provides the higher catalytic activity and selectivity required for the oxygen reduction reaction. At the same time, the introduction of hafnium atoms can help other metal atoms to be better dispersed on the carrier, avoiding the aggregation of metal atoms into larger particles, thereby improving the atomic utilization of the catalyst.

[0030] Furthermore, the surface-modified single-atom catalyst is subjected to plasma treatment, and the plasma treatment method includes:

[0031] At 0-5°C, the surface-modified single-atom catalyst is placed in a plasma reaction chamber, and any one of ethylene, propylene or styrene with a volume concentration of 0.1-5% is introduced for plasma treatment; the power of the plasma treatment is 100W, the time is 10 minutes, and the gas flow rate is 10sccm; then it is placed at a constant temperature of 400-500°C for 15-30 minutes to complete the plasma treatment.

[0032] Note: The above plasma treatment can activate the catalyst surface and increase the number of active sites, thereby improving the catalytic activity of the catalyst, improving the dispersion of metal atoms on the carrier, and improving the selectivity and activity of the catalyst.

[0033] The present invention also discloses an application of a single-atom catalyst for oxygen reduction reaction. The single-atom catalyst obtained by the above preparation method is used to catalyze oxygen reduction reaction, and the half-wave potential of the oxygen reduction reaction is 0.84-0.91V.

[0034] Note: The above half-wave potential refers to the potential corresponding to when the current of the redox peak reaches half of the maximum value in the cyclic voltammetry curve. The half-wave potential is usually used to describe the activity and stability of catalysts (i.e. single-atom catalysts) in electrochemical reactions. The larger the half-wave potential, the easier it is for the redox reaction of the catalyst to proceed, and the higher the activity of the catalyst.

[0035] The beneficial effects of the present invention are:

[0036] The present invention is relatively simple through the above-mentioned preparation method, and is easy to large-scale production of single-atom catalysts, and the prepared single-atom catalyst can efficiently catalyze oxygen reduction reaction, such as Fe single-atom catalyst for oxygen reduction reaction half-wave potential up to 0.90V, better than the precious metal Pt / C catalyst. In addition, by setting the stirring treatment method, it is possible to accelerate the contact and mixing between the reactants, increase the rate of the chemical reaction, reduce the local concentration gradient, thereby increasing the conversion rate of the reaction, improving the mass transfer efficiency, so that the metal salt and 4,4'-bipyridine quickly form a three-dimensional structure. At the same time, the dielectric material with a high dielectric constant can enhance charge separation, reduce electron-hole recombination, and thus improve the catalytic efficiency, and these materials can promote the rapid transmission of electrons, stabilize the active sites of the single-atom catalyst, and further improve the electronic conductivity and catalytic activity of the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a scanning electron microscope image of the “Fe single atom catalyst” in Example 1.

[0038] Figure 2 This is a high-angle annular dark field scanning transmission image of the “Fe single atom catalyst” in Example 1.

[0039] Figure 3 This is the polarization curve of the oxygen reduction reaction of the “Fe single atom catalyst” in Example 1.

[0040] Figure 4 This is the polarization curve of the oxygen reduction reaction of the “Co single atom catalyst” in Example 2.

[0041] Figure 5 This is a scanning electron microscope image of the “Co single atom catalyst” in Example 2.

[0042] Figure 6 This is a high-angle annular dark field scanning transmission image of the “Co single atom catalyst” in Example 2.

[0043] Figure 7 This is a scanning electron microscope image of the “Ni single atom catalyst” in Example 3.

[0044] Figure 8 This is a high-angle annular dark field scanning transmission image of the “Ni single atom catalyst” in Example 3. DETAILED DESCRIPTION

[0045] The present invention is further described below in conjunction with specific embodiments. These embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. Simple replacement or improvement made by those skilled in the art to the present invention belongs to the technical solution protected by the present invention.

[0046] Example 1

[0047] 0.6 g FeCl 3 ·3H 2 O was placed in 20 ml of methanol, stirred, and then 1.0 g of 4,4'-bipyridine was added. After stirring at 500 r / min for 10 minutes, the resulting precipitate was filtered, washed several times with methanol and deionized water, and dried in a vacuum oven. Then, the above precursor was placed in a tube furnace and heated at N 2 In the atmosphere, 800°C was maintained for 2h, with a heating rate of 5°C / min. Finally, the obtained product was acid-washed with 2M HCl solution for 1h, then filtered and dried to finally obtain the Fe single atom catalyst.

[0048] Figure 1 This is a scanning electron microscope image of the Fe single-atom catalyst precursor obtained in this embodiment. It can be seen that it is a small-sized capsule structure with a size between 100 and 200 nm. Because the concentration of the reaction solution is relatively high, it is slightly agglomerated. Figure 2 The high-angle annular dark-field image of the spherical aberration-corrected scanning transmission electron microscope clearly shows that a large number of iron atoms are evenly distributed in the carbon substrate. Figure 3 This is the polarization curve of the oxygen reduction reaction catalyzed by the Fe single atom catalyst. Its half-wave potential is 0.90V, which is better than that of the precious metal Pt / C catalyst.

[0049] Example 2

[0050] 0.6 g CoCl 2 6H 2 O was placed in 20 ml of methanol, stirred and then 1.0 g of 4,4'-bipyridine was added. After stirring for 10 minutes, the resulting precipitate was filtered, washed several times with methanol and deionized water, and dried in a vacuum oven. Then, the above precursor was placed in a tube furnace and heated at N 2 In the atmosphere, 800°C was maintained for 2h with a heating rate of 5°C / min. Finally, the obtained product was acid-washed with 2M HCl solution for 1h, then filtered and dried to finally obtain the Co single atom catalyst.

[0051] Figure 5 This is a scanning electron microscope image of the Co single atom catalyst precursor obtained in this embodiment. It can be seen that it is a small-sized capsule structure with a length of 400 nm. Due to the high concentration of the reaction solution, there is slight agglomeration. Figure 4 This is the polarization curve of the oxygen reduction reaction catalyzed by the Co single atom catalyst, and its half-wave potential is 0.88V. Figure 6 This is a high-angle annular dark field image of a spherical aberration-corrected scanning transmission electron microscope. It can be clearly seen that a large number of Co atoms are evenly distributed in the carbon substrate.

[0052] Example 3

[0053] 0.6 g NiCl 2 6H 2 O was placed in 20 ml of methanol, stirred and then 1.0 g of 4,4'-bipyridine was added. After stirring for 10 minutes, the resulting precipitate was filtered, washed several times with methanol and deionized water, and dried in a vacuum oven. Then, the above precursor was placed in a tube furnace and heated at N 2 In the atmosphere, 800°C was maintained for 2h, with a heating rate of 5°C / min. Finally, the obtained product was acid-washed with 2M HCl solution for 1h, then filtered and dried to finally obtain the Ni single atom catalyst.

[0054] Figure 7 This is a scanning electron microscope image of the Ni single-atom catalyst precursor obtained in this embodiment. It can be seen that it is a small-sized capsule-like structure with a length of 400 nm. Due to the high concentration of the reaction solution, there is slight agglomeration. Figure 8 This is a high-angle annular dark field image of a spherical aberration-corrected scanning transmission electron microscope. It can be clearly seen that a large number of Ni atoms are evenly distributed in the carbon substrate.

[0055] Example 4

[0056] Place 0.6g of ferric acetate in 20ml of methanol, stir and add 1.0g of 4,4'-bipyridine, stir for 10 minutes, filter the resulting precipitate, wash it with methanol and deionized water several times, and put it into a vacuum oven to dry. Then, put the above precursor into a tube furnace, keep it at 800℃ for 2h in a N2 atmosphere, and the heating rate is 5℃ / min. Finally, the obtained product is acid-washed with 2MHCl solution for 1h, then filtered and dried to finally obtain the Fe single atom catalyst.

[0057] Example 5

[0058] 0.6 g FeCl 3 ·3H 2 O was placed in 20 ml of methanol, stirred and then 1.0 g of 4,4'-bipyridine was added. After stirring for 10 minutes, the resulting precipitate was filtered, washed several times with methanol and deionized water, and dried in a vacuum oven. Then, the above precursor was placed in a tube furnace, maintained at 1000 ° C for 2 h in a N2 atmosphere, and the heating rate was 5 ° C / min. Finally, the obtained product was acid-washed with 2M HCl solution for 1 h, then filtered and dried to finally obtain the Fe single atom catalyst.

[0059] Example 6

[0060] 0.6 g FeCl 3 ·3H 2O was placed in 20 ml of methanol, stirred and then 1.0 g of 4,4'-bipyridine was added. After stirring for 10 minutes, the resulting precipitate was filtered, washed several times with methanol and deionized water, and dried in a vacuum oven. Then, the above precursor was placed in a tube furnace and heated at N 2 In the atmosphere, 600°C was maintained for 4 hours with a heating rate of 5°C / min. Finally, the obtained product was acid-washed with 2M HCl solution for 1 hour, then filtered and dried to finally obtain the Fe single atom catalyst.

[0061] Example 7

[0062] This embodiment is substantially the same as embodiment 2, except that, in step 2, the temperature is raised to 1000° C. and calcined for 0.5 h at a heating rate of 6° C. / min, and then cooled to 20° C. to obtain a product.

[0063] Example 8

[0064] This embodiment is substantially the same as embodiment 2, except that, in step 2, the temperature is raised to 600° C. and calcined for 4 h at a heating rate of 4° C. / min, and then cooled to 25° C. to obtain a product.

[0065] Example 9

[0066] This embodiment is substantially the same as embodiment 2, except that the stirring time is 50 min; the preset gas is nitrogen; the acid used in the pickling process in step 3 is hydrochloric acid, and the concentration of the acid is 1 mol / L -1 ; The temperature of the product during the pickling process is 22°C.

[0067] Example 10

[0068] This embodiment is substantially the same as embodiment 2, except that the stirring time is 10 min; the preset gas is nitrogen; the acid used in the pickling process in step 3 is nitric acid, and the concentration of the acid is 6 mol / L -1 ; The temperature of the product during the pickling process is 90°C.

[0069] Embodiment 11

[0070] This embodiment is substantially the same as Embodiment 2, except that the stirring treatment includes: stirring at a speed of 650 r / min for 8 min, then applying a 45 V direct current with a current of 0.3 A, and after applying the current for 12 min, stopping applying the direct current, and then heating to 90° C. and stirring at a speed of 400 r / min for 8 min.

[0071] Example 12

[0072] This embodiment is substantially the same as Embodiment 11, except that the stirring treatment includes: stirring at a speed of 600 r / min for 5 min, then applying a 40 V direct current with a current of 0.1, and after applying the current for 10 min, stopping applying the direct current, and then heating to 80°C and stirring at a speed of 500 r / min for 10 min.

[0073] Example 13

[0074] This embodiment is substantially the same as Embodiment 11, except that the stirring treatment includes: stirring at a speed of 700 r / min for 10 min, then applying a 50 V direct current with a current of 0.5 A, and after applying the current for 15 min, stopping applying the direct current, and then heating to 100°C and stirring at a speed of 300 r / min for 5 min.

[0075] Embodiment 14

[0076] This embodiment is substantially the same as embodiment 2, except that a dielectric material with a high dielectric constant is used to modify the surface of the single atom catalyst; the dielectric material with a high dielectric constant is HfO 2 ;

[0077] The method for surface modification of the single atom catalyst comprises:

[0078] Prepare single atom catalyst and HfCl at a mass ratio of 14:1:25. 4 , H 2 O;

[0079] First, place the prepared single-atom catalyst into the atomic layer deposition reaction chamber.

[0080] Then HfCl 4 Divide into 25 equal parts, 2 O is divided into 25 parts, and HfCl is alternately introduced into the atomic layer deposition reaction chamber 4 , H 2 O, each time a portion is passed, each time HfCl is passed 4 The pulse was applied for 1 second, followed by a 5 second interval, and then H 2 O pulses were applied for 0.5 seconds, and after a 5-second interval, HfCl was introduced again. 4 , and the cycle is repeated until the treatment is completed to obtain the deposited single-atom catalyst;

[0081] The deposited single-atom catalyst is then heated and maintained at a constant temperature of 450° C. for 1.5 h to obtain a surface-modified single-atom catalyst.

[0082] Embodiment 15

[0083] This embodiment is substantially the same as embodiment 14, except that the method for surface modification of the single atom catalyst comprises:

[0084] Prepare single atom catalyst and HfCl at a mass ratio of 10:1:20. 4 , H 2 O;

[0085] First, place the prepared single-atom catalyst into the atomic layer deposition reaction chamber.

[0086] Then HfCl 4 Divide into 25 equal parts, 2 O is divided into 25 parts, and HfCl is alternately introduced into the atomic layer deposition reaction chamber 4 , H 2 O, each time a portion is passed, each time HfCl is passed 4 The pulse was applied for 1 second, followed by a 5 second interval, and then H 2 O pulses were applied for 0.5 seconds, and after a 5-second interval, HfCl was introduced again. 4 , and the cycle is repeated until the treatment is completed to obtain the deposited single-atom catalyst;

[0087] The deposited single-atom catalyst is then heated and maintained at a constant temperature of 400°C for 2 hours to obtain a surface-modified single-atom catalyst.

[0088] Example 16

[0089] This embodiment is substantially the same as embodiment 14, except that the method for surface modification of the single atom catalyst comprises:

[0090] Prepare single atom catalyst and HfCl at a mass ratio of 15:1:30. 4 , H 2 O;

[0091] First, place the prepared single-atom catalyst into the atomic layer deposition reaction chamber.

[0092] Then HfCl 4 Divide into 25 equal parts, 2 O is divided into 25 parts, and HfCl is alternately introduced into the atomic layer deposition reaction chamber 4 , H 2 O, each time a portion is passed, each time HfCl is passed 4 The pulse was applied for 1 second, followed by a 5 second interval, and then H 2 O pulses were applied for 0.5 seconds, and after a 5-second interval, HfCl was introduced again. 4 , and the cycle is repeated until the treatment is completed to obtain the deposited single-atom catalyst;

[0093] The deposited single-atom catalyst is then heated and maintained at a constant temperature of 500° C. for 1 hour to obtain a surface-modified single-atom catalyst.

[0094] Embodiment 17

[0095] This embodiment is substantially the same as Embodiment 14, except that the surface-modified single-atom catalyst is subjected to plasma treatment, and the plasma treatment method comprises: placing the surface-modified single-atom catalyst into a plasma reaction chamber at 3°C, introducing any one of ethylene, propylene or styrene at a volume concentration of 2%, and conducting plasma treatment; the plasma treatment power is 100 W, the time is 10 min, and the gas flow rate is 10 sccm; and then the plasma treatment is completed after being placed at a constant temperature of 450°C for 20 min.

[0096] Embodiment 18

[0097] This embodiment is substantially the same as Embodiment 17, except that the surface-modified single-atom catalyst is subjected to plasma treatment, and the plasma treatment method comprises: placing the surface-modified single-atom catalyst into a plasma reaction chamber at 0°C, introducing any one of ethylene, propylene or styrene at a volume concentration of 5%, and conducting plasma treatment; the power of the plasma treatment is 100 W, the time is 10 min, and the gas flow rate is 10 sccm; and then placing it at a constant temperature of 400°C for 15 min to complete the plasma treatment.

[0098] Embodiment 19

[0099] This embodiment is substantially the same as Embodiment 17, except that the surface-modified single-atom catalyst is subjected to plasma treatment, and the plasma treatment method comprises: placing the surface-modified single-atom catalyst into a plasma reaction chamber at 5°C, introducing any one of ethylene, propylene or styrene with a volume concentration of 0.1% for plasma treatment; the power of the plasma treatment is 100 W, the time is 10 min, and the gas flow rate is 10 sccm; and then placing it at a constant temperature of 500°C for 30 min to complete the plasma treatment.

[0100] Experimental example

[0101] The half-wave potentials of Example 2, Example 11, Example 14 and Example 17 were obtained. It was found that compared with Example 2, the half-slope potentials of the Co single atom catalysts in Example 11 and Example 14 were increased by 0.02, that is, 0.90. The reason may be that the electronic structures and electrochemical properties of the two metals Co and Fe are different, resulting in the need to further improve the Co single atom catalyst. Specifically, the catalytic activity can be improved by the coordination environment, the stirring conditions in Example 11, and the surface modification in Example 14. Furthermore, the treatment method of Example 17 can increase the half-slope potential of the Co single atom catalyst to 0.91 on the basis of Example 14.

Claims

1. A method for preparing a single-atom catalyst for oxygen reduction reaction, characterized in that: The following steps are involved: Step 1: placing a metal salt and 4,4'-bipyridine in a molar ratio of 1:3 to 3:1 in a methanol or ethanol liquid, stirring and filtering to obtain a precursor; Step 2: The precursor obtained in step 1 is heated to 600-1000° C. under a preset gas atmosphere, and then calcined for 0.5-4 h at a heating rate of 4-6° C. / min, and then cooled to 20-25° C. to obtain a product; Step 3: The product is acid-washed, water-washed and then filtered to obtain a single-atom catalyst.

2. The method for preparing a single-atom catalyst for oxygen reduction reaction according to claim 1, characterized in that: The metal in the metal salt in step 1 is any one of V, Cr, Mn, Fe, Ni, Cu, Zn, Nb, Mo, and W; and the metal salt is any one of metal chloride, metal acetate, and metal nitrate.

3. The method for preparing a single-atom catalyst for oxygen reduction reaction according to claim 1, characterized in that: The stirring time in step 1 is 10 to 50 minutes.

4. The method for preparing a single-atom catalyst for oxygen reduction reaction according to claim 1, characterized in that: The preset gas in step 2 is either nitrogen or argon.

5. The method for preparing a single-atom catalyst for oxygen reduction reaction according to claim 1, characterized in that: The acid used in the pickling process of step 3 is any one of hydrochloric acid, sulfuric acid and nitric acid, and the concentration of the acid is 1-6 mol / L -1 ; The temperature of the product during the pickling process is 22 to 90°C.

6. The method for preparing a single-atom catalyst for oxygen reduction reaction according to claim 1, characterized in that: The stirring process comprises: Stir at a speed of 600-700 r / min for 5-10 minutes, then apply 40-50 V DC with a current of 0.1-0.5 A. After applying the current for 10-15 minutes, stop applying DC, then heat to 80-100°C and stir at a speed of 300-500 r / min for 5-10 minutes.

7. The method for preparing a single-atom catalyst for oxygen reduction reaction according to claim 1, characterized in that: Also includes: The single atom catalyst is surface modified by using a dielectric material with a high dielectric constant.

8. The method for preparing a single-atom catalyst for oxygen reduction reaction according to claim 7, characterized in that: The high dielectric constant dielectric material is HfO2.

9. The method for preparing a single-atom catalyst for oxygen reduction reaction according to claim 8, characterized in that: The method of using a dielectric material with a high dielectric constant to modify the surface of the single atom catalyst comprises: Prepare single atom catalyst, HfCl4, and H2O in a mass ratio of 10-15:1:20-30; First, place the prepared single-atom catalyst into the atomic layer deposition reaction chamber. Then, HfCl4 is divided into 25 parts, and H2O is divided into 25 parts, and HfCl4 and H2O are alternately introduced into the atomic layer deposition reaction chamber, one part each time, and a pulse of 1 second is applied each time when HfCl4 is introduced, and after a 5-second interval, H2O is introduced and a pulse of 0.5 second is applied, and after a 5-second interval, HfCl4 is introduced again, and this cycle is repeated until the treatment is completed to obtain a deposited single-atom catalyst; The deposited single-atom catalyst is then heated and maintained at a constant temperature of 400-500° C. for 1-2 hours to obtain a surface-modified single-atom catalyst.

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