A method for preparing a single-atom catalyst for oxygen reduction reaction

Abstract

The application belongs to the technical field of material preparation and relates to a preparation method of a single-atom catalyst for an oxygen reduction reaction, which comprises the following steps: firstly, placing a metal salt and 4,4'-dipyridyl in a methanol or ethanol solution, stirring and filtering to obtain a precursor; then placing the obtained precursor in a tube furnace, performing programmed temperature calcination under an inert atmosphere, naturally cooling to room temperature, and then performing acid pickling and filtering to obtain a target catalyst. The preparation method provided in the application is simple in synthesis method, easy to mass-produce, has excellent oxygen reduction reaction catalytic activity, and can effectively replace Pt / C for oxygen reduction reactions.

Description

Technical Field

[0001] This invention relates to the field of materials preparation technology, specifically to a method for preparing a single-atom catalyst for oxygen reduction reaction. Background Technology

[0002] As a novel energy technology, fuel cells are not limited by the Carnot cycle, have high conversion efficiency, produce no pollution, use a wide range of raw materials, and are safe and reliable. They are recognized as highly efficient and clean energy batteries.

[0003] In the operation of a hydrogen-oxygen fuel cell, fuel such as hydrogen is catalytically cracked into protons and electrons at the anode. The protons travel through the electrolyte to the cathode, where they react with oxygen to produce water and generate electricity. To date, fuel cell technology has not yet achieved large-scale commercial application. One of the major reasons limiting the commercialization of fuel cells is the slow kinetics of the cathode oxygen reduction reaction, requiring the use of precious metal catalysts to increase the reaction rate, thus making fuel cells expensive. Currently, the oxygen reduction catalyst used in fuel cells is the precious metal platinum; surveys show that platinum catalysts account for 56% of the overall price of fuel cells. Furthermore, even with the use of platinum catalysts, the cathode oxygen reduction reaction still lags significantly behind the anodic oxidation reaction. In addition, platinum catalysts also suffer from poor durability. During use, platinum is prone to aggregation, dissolution, and detachment from the carbon support, thus shortening the lifespan of the fuel cell. Currently, the longest actual operating life of fuel cells is only 1900 hours, while the U.S. Department of Energy's target for the lifespan of commercial mobile fuel cell systems is over 5000 hours. Therefore, the development of fuel cell technology urgently requires the development of inexpensive, efficient, and stable cathode oxygen reduction catalysts.

[0004] Single-atom catalysts, characterized by maximized atom utilization and isolated active sites, have become a rapidly developing branch of catalysis research in recent years. They provide ideal models for a deeper understanding of active site structure and catalytic mechanisms, exhibiting superior performance in many catalytic applications. However, current methods for preparing single-atom catalysts are complex, and most reported methods focus on the preparation of specific single-atom catalysts, lacking efficient and universal synthetic strategies. Furthermore, existing technologies prioritize increasing reaction rates for single-atom catalysts, with less emphasis on improvements targeting the higher catalytic activity and selectivity required for oxygen reduction reactions. Summary of the Invention

[0005] To address the above problems, this 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 includes 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 the precursor;

[0008] Step 2: The precursor obtained in Step 1 is calcined at 600-1000℃ for 0.5-4h in a preset gas atmosphere, and then cooled to 20-25℃ to obtain the 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 oxygen reduction reaction catalytic activity.

[0011] Furthermore, the metal in the metal salt mentioned 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] Note: The method described in this scheme can be used in single-atom catalysts of the above-mentioned 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 single-atom catalyst prepared with the above parameters has the best catalytic activity.

[0015] Furthermore, the preset gas mentioned in step 2 is either nitrogen or argon.

[0016] Furthermore, the acid used in the pickling process described in 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 22–90°C.

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

[0018] Further, the stirring process includes:

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

[0020] Note: The above stirring treatment can accelerate the contact and mixing between reactants, increase the rate of chemical reaction, and reduce local concentration gradients, thereby improving the conversion rate and mass transfer efficiency of the reaction, so as to facilitate the rapid formation of a stereostructure between the metal salt and 4,4'-bipyridine, and this stereostructure has good active sites.

[0021] Furthermore, the method further includes: surface modification of the single-atom catalyst using a dielectric material with a high dielectric constant.

[0022] Note: High dielectric constant dielectric materials can enhance charge separation, reduce electron-hole recombination, and thus improve catalytic efficiency. In addition, these materials can promote rapid electron transport 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 dielectric material with the high dielectric constant is HfO2.

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

[0025] Prepare a single-atom catalyst, HfCl4, and H2O in a mass ratio of 10–15:1:20–30.

[0026] First, the prepared single-atom catalyst is placed in the atomic layer deposition reaction chamber.

[0027] The HfCl4 and H2O were then divided into 25 equal parts and 25 equal parts respectively. HfCl4 and H2O were alternately introduced into the atomic layer deposition reaction chamber, one part at a time. Each time HfCl4 was introduced, a pulse of 1 second was applied, followed by a 5-second interval. Then H2O was introduced with a pulse of 0.5 seconds, followed by a 5-second interval. HfCl4 was introduced again, and this cycle was repeated until the process was completed, resulting in the deposited single-atom catalyst.

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

[0029] Note: The HfCl4 mentioned above can be attached to single-atom catalysts, improving their stability and catalytic performance without altering their original structure. The introduction of hafnium atoms can modulate the electronic properties of the catalyst surface, affecting its activity and selectivity. This provides the oxygen reduction reaction with the required high catalytic activity and selectivity. Furthermore, the introduction of hafnium atoms can help other metal atoms to be better dispersed on the support, preventing them from agglomerating into larger particles, thereby improving the atom utilization rate of the catalyst.

[0030] Furthermore, the surface-modified single-atom catalyst described above is subjected to plasma treatment, the plasma treatment method including:

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

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

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

[0034] Note: The half-wave potential mentioned above refers to the potential corresponding to half the maximum current of the redox peak in a cyclic voltammetry curve. Half-wave potential is commonly used to describe the activity and stability of catalysts (i.e., single-atom catalysts) in electrochemical reactions. A larger half-wave potential indicates that the redox reaction proceeds more easily, and the catalyst has higher activity.

[0035] The beneficial effects of this invention are:

[0036] The preparation method described above is relatively simple and facilitates the large-scale production of single-atom catalysts. The prepared single-atom catalysts can efficiently catalyze the oxygen reduction reaction. For example, the Fe single-atom catalyst exhibits a half-wave potential of up to 0.90 V for the oxygen reduction reaction, which is superior to the noble metal Pt / C catalyst. Furthermore, the designed stirring process accelerates the contact and mixing of reactants, increases the chemical reaction rate, and reduces local concentration gradients, thereby improving the reaction conversion rate and mass transfer efficiency, facilitating the rapid formation of a stereostructure between the metal salt and 4,4'-bipyridine. Simultaneously, the use of high dielectric constant mediating materials enhances charge separation, reduces electron-hole recombination, and further improves catalytic efficiency. These materials also promote rapid electron transport and stabilize the active sites of the single-atom catalyst, further enhancing the catalyst's electronic conductivity and catalytic activity. Attached Figure Description

[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 oxygen reduction reaction polarization curve of the "Fe single-atom catalyst" in Example 1.

[0040] Figure 4 This is the oxygen reduction reaction polarization curve 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 Implementation

[0045] The present invention will be further illustrated below with reference to specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Simple substitutions or modifications made to the present invention by those skilled in the art are all within the scope of the technical solutions protected by the present invention.

[0046] Example 1

[0047] 0.6 g of FeCl3·3H2O was placed in 20 ml of methanol, stirred, and then 1.0 g of 4,4'-bipyridine was added. After stirring at 500 rpm for 10 minutes, the resulting precipitate was filtered, washed several times with methanol and deionized water, and then dried in a vacuum oven. The precursor was then placed in a tube furnace and heated at 800 °C for 2 hours in a N2 atmosphere at a heating rate of 5 °C / min. Finally, the product was acid-washed with 2 M HCl solution for 1 hour, followed by filtration and drying to obtain the Fe single-atom catalyst.

[0048] Figure 1 The image shows 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 capsule-like structure with a size between 100 and 200 nm. Due to the high concentration of the reaction solution, it is slightly aggregated. Figure 2 A high-angle annular dark-field image from a spherical aberration-corrected scanning transmission electron microscope clearly shows a large number of iron atoms uniformly distributed in the carbon substrate. Figure 3 The figure shows the polarization curve of the oxygen reduction reaction catalyzed by the Fe single-atom catalyst, with a half-wave potential of 0.90 V, which is superior to that of the noble metal Pt / C catalyst.

[0049] Example 2

[0050] 0.6 g of CoCl₂·6H₂O 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 then dried in a vacuum oven. The precursor was then placed in a tube furnace and heated to 800 °C for 2 hours in a N₂ atmosphere at a heating rate of 5 °C / min. Finally, the product was acid-washed with 2 M HCl solution for 1 hour, followed by filtration and drying to obtain the final Co single-atom catalyst.

[0051] Figure 5 The image shows 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 capsule-like structure with a length of 400 nm. Due to the high concentration of the reaction solution, it is slightly aggregated. Figure 4 This is the polarization curve of the oxygen reduction reaction catalyzed by a Co single-atom catalyst, with a half-wave potential of 0.88V. Figure 6 This is a high-angle annular dark-field image from a spherical aberration-corrected scanning transmission electron microscope, which clearly shows a large number of Co atoms uniformly distributed in the carbon substrate.

[0052] Example 3

[0053] 0.6 g of NiCl₂·6H₂O 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 then dried in a vacuum oven. The precursor was then placed in a tube furnace and heated to 800 °C for 2 hours in a N₂ atmosphere at a heating rate of 5 °C / min. Finally, the product was acid-washed with 2 M HCl solution for 1 hour, followed by filtration and drying to obtain the Ni single-atom catalyst.

[0054] Figure 7 The image shows 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 capsule-like structure with a length of 400 nm. Due to the high concentration of the reaction solution, it is slightly aggregated. Figure 8 This is a high-angle annular dark-field image from a spherical aberration-corrected scanning transmission electron microscope, which clearly shows a large number of Ni atoms uniformly distributed in the carbon substrate.

[0055] Example 4

[0056] 0.6 g of ferric acetate 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 then dried in a vacuum oven. The precursor was then placed in a tube furnace and heated to 800 °C for 2 hours in a N2 atmosphere at a heating rate of 5 °C / min. Finally, the product was acid-washed with 2 M HCl solution for 1 hour, followed by filtration and drying to obtain the Fe single-atom catalyst.

[0057] Example 5

[0058] 0.6 g of FeCl3·3H2O 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 then dried in a vacuum oven. The precursor was then placed in a tube furnace and heated at 1000 °C for 2 hours in a N2 atmosphere at a heating rate of 5 °C / min. Finally, the product was acid-washed with 2 M HCl solution for 1 hour, followed by filtration and drying to obtain the Fe single-atom catalyst.

[0059] Example 6

[0060] 0.6 g of FeCl3·3H2O 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 then dried in a vacuum oven. The precursor was then placed in a tube furnace and heated to 600 °C for 4 hours in a N2 atmosphere at a heating rate of 5 °C / min. Finally, the product was acid-washed with 2 M HCl solution for 1 hour, followed by filtration and drying to obtain the Fe single-atom catalyst.

[0061] Example 7

[0062] This embodiment is largely the same as Embodiment 2, except that in step 2: after heating to 1000℃, calcination is carried out for 0.5h at a heating rate of 6℃ / min, and then cooled to 20℃ to obtain the product.

[0063] Example 8

[0064] This embodiment is largely the same as Embodiment 2, except that in step 2: after heating to 600°C, calcination is carried out for 4 hours at a heating rate of 4°C / min, and then the product is obtained by cooling to 25°C.

[0065] Example 9

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

[0067] Example 10

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

[0069] Example 11

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

[0071] Example 12

[0072] This embodiment is largely the same as Embodiment 11, except that the stirring process includes: stirring at 600 r / min for 5 min, then applying 40V DC current with a current of 0.1, applying the current for 10 min, then stopping the application of DC current, then heating to 80℃, and stirring at 500 r / min for 10 min.

[0073] Example 13

[0074] This embodiment is largely the same as Embodiment 11, except that the stirring process includes: stirring at 700 r / min for 10 min, then applying 50V DC current with a current of 0.5A for 15 min, then stopping the application of DC current, then heating to 100℃, and stirring at 300 r / min for 5 min.

[0075] Example 14

[0076] This embodiment is largely the same as Embodiment 2, except that a medium material with a high dielectric constant is used to modify the surface of the single-atom catalyst; the medium material with a high dielectric constant is HfO2.

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

[0078] Prepare a single-atom catalyst, HfCl4, and H2O in a mass ratio of 14:1:25;

[0079] First, the prepared single-atom catalyst is placed in the atomic layer deposition reaction chamber.

[0080] The HfCl4 and H2O were then divided into 25 equal parts and 25 equal parts respectively. HfCl4 and H2O were alternately introduced into the atomic layer deposition reaction chamber, one part at a time. Each time HfCl4 was introduced, a pulse of 1 second was applied, followed by a 5-second interval. Then H2O was introduced with a pulse of 0.5 seconds, followed by a 5-second interval. HfCl4 was introduced again, and this cycle was repeated until the process was completed, resulting in the deposited single-atom catalyst.

[0081] The deposited single-atom catalyst was then heated and kept at a constant temperature of 450℃ for 1.5 hours to obtain the surface-modified single-atom catalyst.

[0082] Example 15

[0083] This embodiment is largely the same as Embodiment 14, except that the method for surface modification of the single-atom catalyst includes:

[0084] Prepare a single-atom catalyst, HfCl4, and H2O in a mass ratio of 10:1:20;

[0085] First, the prepared single-atom catalyst is placed in the atomic layer deposition reaction chamber.

[0086] The HfCl4 and H2O were then divided into 25 equal parts and 25 equal parts respectively. HfCl4 and H2O were alternately introduced into the atomic layer deposition reaction chamber, one part at a time. Each time HfCl4 was introduced, a pulse of 1 second was applied, followed by a 5-second interval. Then H2O was introduced with a pulse of 0.5 seconds, followed by a 5-second interval. HfCl4 was introduced again, and this cycle was repeated until the process was completed, resulting in the deposited single-atom catalyst.

[0087] The deposited single-atom catalyst was then heated and kept at 400℃ for 2 hours to obtain the surface-modified single-atom catalyst.

[0088] Example 16

[0089] This embodiment is largely the same as Embodiment 14, except that the method for surface modification of the single-atom catalyst includes:

[0090] Prepare a single-atom catalyst, HfCl4, and H2O in a mass ratio of 15:1:30;

[0091] First, the prepared single-atom catalyst is placed in the atomic layer deposition reaction chamber.

[0092] The HfCl4 and H2O were then divided into 25 equal parts and 25 equal parts respectively. HfCl4 and H2O were alternately introduced into the atomic layer deposition reaction chamber, one part at a time. Each time HfCl4 was introduced, a pulse of 1 second was applied, followed by a 5-second interval. Then H2O was introduced with a pulse of 0.5 seconds, followed by a 5-second interval. HfCl4 was introduced again, and this cycle was repeated until the process was completed, resulting in the deposited single-atom catalyst.

[0093] The deposited single-atom catalyst was then heated and kept at 500℃ for 1 hour to obtain the surface-modified single-atom catalyst.

[0094] Example 17

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

[0096] Example 18

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

[0098] Example 19

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

[0100] Experimental Example

[0101] Half-wave potentials were obtained for Examples 2, 11, 14, and 17. The results showed that, compared to Example 2, the half-wave potentials of the Co single-atom catalysts in Examples 11 and 14 were increased by 0.02, i.e., 0.90. The principle behind this may be that the electronic structures and electrochemical properties of Co and Fe are different, which leads to the need for further improvement of the Co single-atom catalyst. Specifically, the catalytic activity can be improved by adjusting the coordination environment, the stirring conditions in Example 11, and the surface modification in Example 14. Furthermore, the treatment method in Example 17 can increase the half-wave potential of the Co single-atom catalyst to 0.91 based on that in Example 14.

Claims

1. A method for preparing a single-atom catalyst for oxygen reduction reaction, characterized in that, Includes the following steps: Step 1: Place a metal salt with a molar ratio of 1:3 to 3:1 and 4,4'-bipyridine in methanol or ethanol, stir, filter, and obtain the precursor. Step 2: The precursor obtained in Step 1 is calcined in a preset gas atmosphere at a temperature of 600-1000℃ for 0.5-4 hours at a heating rate of 4-6℃ / min, and then cooled to 20-25℃ to obtain the product. Step 3: The product is acid-washed, water-washed, and then filtered to obtain a single-atom catalyst; then, the surface of the single-atom catalyst is modified using HfO2, a medium with a high dielectric constant. The method for surface modification of the single-atom catalyst using HfO2 includes: Prepare a single-atom catalyst, HfCl4, and H2O in a mass ratio of 10~15:1:20~30; First, the prepared single-atom catalyst is placed in the atomic layer deposition reaction chamber. The HfCl4 and H2O were then divided into 25 equal parts and 25 equal parts respectively. HfCl4 and H2O were alternately introduced into the atomic layer deposition reaction chamber, one part at a time. Each time HfCl4 was introduced, a pulse of 1 second was applied, followed by a 5-second interval. Then H2O was introduced with a pulse of 0.5 seconds, followed by a 5-second interval. HfCl4 was introduced again, and this cycle was repeated until the process was completed, resulting in the deposited single-atom catalyst. The deposited single-atom catalyst is then heated and kept at a constant temperature of 400-500°C for 1-2 hours to obtain the surface-modified single-atom catalyst.

2. The method for preparing a single-atom catalyst for oxygen reduction reaction as described in claim 1, characterized in that, The metal in the metal salt mentioned in step 1 is any one of V, Cr, Mn, Fe, Ni, Cu, Zn, Nb, Mo, and W; 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 as described in claim 1, characterized in that, The stirring time in step 1 is 10~50 minutes.

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

5. The method for preparing a single-atom catalyst for oxygen reduction reaction as described in claim 1, characterized in that, The acid used in step 3, pickling, is any one of hydrochloric acid, sulfuric acid, or nitric acid, with a concentration of 1-6 mol / L; the temperature of the product during pickling is 22-90℃.

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

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