Oxygen-doped carbon hollow sphere anchored metal palladium monatomic catalyst, and preparation method and application thereof

Abstract

The present application relates to the field of nanomaterials, and aims at the problem that H2O2 electrocatalysts are difficult to have high activity and high selectivity, and provides an oxygen-doped carbon hollow sphere anchoring metal palladium monatomic catalyst, a preparation method and application thereof, wherein palladium is anchored on the surface of the oxygen-doped carbon hollow sphere in the form of a single atom, the preparation method comprises the following steps: adding tetraethyl orthosilicate into a mixed solvent of water, ethanol and ammonia water to form a silica nanosphere template through hydrolysis reaction, adding resorcinol and formaldehyde to perform polymerization reaction, forming a carbon precursor on the surface of the silica, collecting the initial product after filtration and drying treatment; removing the silica through acid washing after first heat treatment of the initial product, drying to obtain oxygen-doped carbon hollow spheres, immersing in a metal palladium salt solution, drying, and then performing second heat treatment to obtain the product. The catalyst is applied to the reaction of electrocatalytic oxygen reduction to prepare H2O2 in an alkaline solution, and has good electrocatalytic selectivity and activity.

Description

Technical Field

[0001] This invention relates to the field of nanomaterials, and in particular to an oxygen-doped carbon hollow sphere anchored palladium single-atom catalyst, its preparation method, and its application. Background Technology

[0002] Hydrogen peroxide (H2O2), as a green and environmentally friendly oxidant, is widely used in papermaking, printing and dyeing, medical treatment, water treatment, and chemical synthesis. Currently, the anthraquinone oxidation method is the main method for producing H2O2 both domestically and internationally. However, the anthraquinone method for H2O2 production requires technological innovation to significantly reduce energy consumption and organic waste emissions. Furthermore, the chemical instability of H2O2 poses certain risks during its transportation and storage. In recent years, the two-electron pathway for H2O2 production via electrocatalytic oxygen reduction has attracted widespread attention from researchers. This technology offers advantages such as a green synthesis process, high H2O2 purity, and low energy consumption, and it allows for in-situ synthesis of H2O2. Therefore, electrocatalytic oxygen reduction for H2O2 production is one of the important technological approaches to replace the anthraquinone method in industrial hydrogen peroxide production.

[0003] The technical challenge of electrocatalytic oxygen reduction to H2O2 production lies in designing and preparing electrocatalysts that possess both high activity and high selectivity. Noble metal catalysts (such as Pd and Pt) have been extensively studied due to their high activity in oxygen reduction; however, the four-electron pathway-dominated oxygen reduction reaction is typically designed as the cathode material for fuel cells. The active sites of noble metal catalysts can be appropriately modulated to control the oxygen reduction reaction pathway, thereby promoting the two-electron pathway to H2O2 production. However, the high cost of noble metal catalysts limits their large-scale industrial application. Currently, reported Pd-based catalysts are mostly in nanoparticle form on electrocatalyst supports, exhibiting poor dispersion of active sites and low atom utilization.

[0004] Compared to nanoparticles, single-atom metal catalysts, with their active atoms uniformly dispersed on the support surface in single-atom form, achieve maximum atom utilization efficiency in catalytic reactions, exhibiting excellent activity and selectivity in electrocatalysis, photocatalysis, and thermocatalysis. For example, patent CN108786921A discloses a single-atom Pd@UiO-66 catalyst, which obtains the single-atom Pd@UiO-66 catalyst by impregnating a palladium source onto a zirconium-based metal-organic framework UiO-66; patent CN109806903A discloses a single-atom Pd-supported nitrogen-doped graphene catalyst, which obtains the single-atom Pd catalyst by dissolving a Pd precursor, a carbon source, and a nitrogen source in a solvent and then performing a high-temperature reduction treatment.

[0005] Currently, single-atom metal catalysts have made some progress in thermocatalysis, electrocatalytic hydrogen evolution, and electrocatalytic carbon dioxide reduction. However, research on their activity and selectivity regulation in the oxygen reduction reaction to achieve efficient H2O2 production remains limited. Therefore, by loading Pd single atoms onto oxygen-doped carbon hollow nanospheres, it is hoped to achieve H2O2 production via the two-electron pathway of electrocatalytic oxygen reduction. The oxygen-containing functional groups on the surface of the oxygen-doped carbon hollow spheres can effectively regulate the electronic structure of Pd atoms, and their hollow carbon structure provides abundant reaction sites with a high specific surface area, thereby promoting the activity and selectivity of H2O2, which is highly beneficial for its industrial production. Summary of the Invention

[0006] To overcome the problem that H2O2 electrocatalysts struggle to simultaneously achieve high activity and high selectivity, this invention provides an oxygen-doped carbon hollow sphere-anchored palladium single-atom catalyst, its preparation method, and its application. The hollow spherical carbon nanoparticles in the catalyst possess a high specific surface area, which facilitates high atomic dispersion of Pd loading. The abundant oxygen-containing functional groups on their surface promote selective oxygen reduction to H2O2 production, while their defect sites facilitate the dispersion and loading of Pd in ​​single-atom form. Through the loading of Pd single atoms, the selectivity and activity of the catalyst are further improved. When applied to the electrocatalytic oxygen reduction to H2O2 reaction in alkaline solution, this electrocatalyst exhibits excellent electrocatalytic selectivity and activity.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] An oxygen-doped carbon hollow sphere anchored palladium single-atom catalyst, wherein Pd is anchored in the form of single atoms on the surface of the oxygen-doped carbon hollow sphere.

[0009] The present invention also provides a method for preparing the catalyst, comprising the following steps:

[0010] (1) Tetraethyl orthosilicate was added to a mixed solvent of water, ethanol and ammonia to carry out hydrolysis reaction to form silica nanosphere template, and then resorcinol and formaldehyde were added to carry out polymerization reaction to form carbon precursor on silica surface. The initial product was collected after filtration and drying.

[0011] (2) The initial product obtained in step (1) is subjected to a first heat treatment. The product after heat treatment is acid washed to remove silicon dioxide, and then dried to obtain oxygen-doped carbon hollow spheres.

[0012] (3) The oxygen-doped carbon hollow spheres obtained in step (2) are immersed in a metal palladium salt solution, dried, and then subjected to a second heat treatment to obtain an oxygen-doped carbon hollow sphere-supported Pd single-atom catalyst.

[0013] This invention selects resorcinol and formaldehyde, organic compounds containing oxygen elements, as the oxygen and carbon sources for the reaction, and deionized water, ethanol, and ammonia as reaction solvents. Tetraethyl orthosilicate, which can form silica nanosphere structures, is used as a catalyst to prepare a structure inducing agent. The silica in the spherical structure after high-temperature carbonization is etched away by acid washing to form a carbon hollow sphere structure with a high specific surface area, which provides abundant active sites for the reaction. Palladium salt is used as an atomically dispersed Pd metal precursor to provide metal single atoms.

[0014] Preferably, in step (1), the mass ratio of hydroquinone, formaldehyde, and tetraethyl orthosilicate is 0.2–0.5:0.05–0.25:0.5–3.5.

[0015] Preferably, in step (1), the volume ratio of deionized water, ethanol, and ammonia is 5–20:50–100:1–5, wherein the volume ratio of tetraethyl orthosilicate to the three solvents is 40–60 mL of solvent per 1 mL of tetraethyl orthosilicate. Tetraethyl orthosilicate undergoes hydrolysis to form silica nanospheres. These nanospheres have a higher specific surface area, which is more conducive to oxygen mass transfer and oxygen reduction reactions. During the hydrolysis of tetraethyl orthosilicate, linear oligomers are easily formed under acidic conditions, leading to gel formation, and nanosphere structures are less likely to form. Therefore, it is necessary to control the proportion of ammonia in the mixed solvent.

[0016] Preferably, the hydrolysis reaction in step (1) is carried out at a temperature of 10–40°C and for a time of 5–20 min. If the reaction time is too short, a silica template cannot be formed. If the reaction time is too long, the silica template formed will have an excessively large diameter. When the silica template particle size is too large, the stability of the resulting nano-carbon sphere structure decreases, resulting in poor dispersibility of the catalyst in the solution.

[0017] Preferably, the polymerization reaction in step (1) is carried out at a temperature of 10–40°C for 10–48 hours. If the polymerization temperature is too low, the polymerization rate will be slow; if the reaction temperature is too high, the ammonia in the solvent will evaporate, affecting the pH environment of the solution.

[0018] Preferably, the first heat treatment in step (2) is calcination at 700–900℃ for 1–6 hours in an inert gas atmosphere; the second heat treatment in step (3) is calcination at 100–400℃ for 1–4 hours in an inert gas atmosphere. During the heat treatment, the polymer formed by resorcinol and formaldehyde provides carbon and oxygen sources. By controlling the heat treatment temperature, the graphitization degree and oxygen content of the carbon nanospheres are adjusted, thereby achieving selective regulation of the electrocatalytic H2O2 production of oxygen-doped carbon hollow spheres. As a further preferred option, the first heat treatment temperature is 780–830℃ (e.g., 780℃, 785℃, 790℃, 800℃, 820℃, etc.) and the time is 2–4 hours; the second heat treatment temperature is 300℃ and the time is 2 hours. If the first heat treatment temperature is too low, it will easily lead to a low degree of graphitization and poor conductivity; if the temperature is too high, it will lead to a decrease in oxygen content, thereby reducing catalytic activity.

[0019] Preferably, the pickling is performed using a hydrofluoric acid solution with a molar concentration of 0.1–20 M for 1–6 hours. If the pickling solution concentration is too low or the time is too short, the silica template cannot be effectively removed; if the pickling solution concentration is too high or the pickling time is too long, the structure of the carbon hollow spheres may be damaged. More preferably, the hydrofluoric acid solution concentration is 7 M and the etching time is 2 hours. At this concentration and etching time, the silica template in the carbon spheres can be effectively removed.

[0020] Preferably, the amount of palladium salt added in step (3) is calculated as 0.1% to 1.0% of the mass of Pd relative to the mass of the oxygen-doped carbon hollow spheres. The palladium salt is preferably palladium chloride.

[0021] Preferably, the impregnation in step (3) is performed by stirring for 1 to 4 hours, adjusting the pH to 9 to 11, and then stirring for another 1 to 4 hours. More preferably, the impregnation in step (3) is performed by stirring for 2 hours, adjusting the pH to 10.5, and then stirring for another 2 hours.

[0022] The present invention also provides the application of the catalyst in the electrocatalytic reduction of oxygen to H2O2 in alkaline solution. The catalyst has excellent electrocatalytic activity and selectivity. As a catalyst for the electrocatalytic reduction of oxygen to produce H2O2, the oxygen reduction onset potential is 0.84V and the H2O2 selectivity can reach 76%.

[0023] Therefore, the beneficial effects of the present invention are as follows: (1) an oxygen-doped carbon hollow sphere anchored Pd single-atom catalyst was obtained by means of phenolic polymerization reaction, high temperature heat treatment, acid etching and impregnation. The catalyst has a hollow spherical structure with uniform size, rich oxygen-containing functional groups, and single-atom dispersed Pd sites, which further improves the catalytic activity and selectivity of the catalyst and reduces the content of metal Pd in ​​the catalyst.

[0024] (2) The reaction potential of oxygen-doped carbon hollow sphere anchored Pd single-atom electrocatalyst for the electrocatalytic reduction of oxygen to H2O2 in alkaline solution is 0.84V, and the H2O2 selectivity can reach 76%, with both catalytic activity and selectivity being high.

[0025] (3) The oxygen-doped carbon hollow sphere-anchored Pd single-atom electrocatalyst of the present invention has Pd supported on the surface of the oxygen-doped carbon hollow spheres in a single dispersed form, which helps to improve the utilization rate of metallic Pd. In addition, the abundant oxygen-containing functional groups also help to improve the selectivity in the electrocatalytic reduction of oxygen to H2O2, which is conducive to realizing industrial application. Attached Figure Description

[0026] Figure 1 Here is a scanning electron microscope image of the catalyst prepared in Example 1;

[0027] Figure 2 This is a transmission electron microscope image of the catalyst prepared in Example 1;

[0028] Figure 3 This is the XRD pattern of the catalyst prepared in Example 1;

[0029] Figure 4 The figures show the electrocatalytic reduction curves of O2 to H2O2 produced by the catalysts prepared in Examples 1-3 and Comparative Example 1 in alkaline solution. Detailed Implementation

[0030] The technical solution of the present invention will be further described below through specific embodiments.

[0031] In this invention, unless otherwise specified, the raw materials and equipment used can be purchased from the market or are commonly used in the field. The methods in the embodiments, unless otherwise specified, are conventional methods in the field.

[0032] General Implementation Examples

[0033] An oxygen-doped carbon hollow sphere anchored palladium single-atom catalyst, wherein Pd is anchored in the form of single atoms on the surface of the oxygen-doped carbon hollow sphere.

[0034] The method for preparing the catalyst includes the following steps:

[0035] (1) Tetraethyl orthosilicate was added to a mixed solvent of water, ethanol and ammonia (volume ratio 5-20:50-100:1-5) to carry out hydrolysis reaction to form silica nanosphere template. The hydrolysis reaction temperature was 10-40℃ and the time was 5-20 min. Then resorcinol and formaldehyde were added to carry out polymerization reaction. The mass ratio of resorcinol, formaldehyde and tetraethyl orthosilicate was 0.2-0.5:0.05-0.25:0.5-3.5. The polymerization reaction temperature was 10-40℃ and the time was 10-48 h. A carbon precursor was formed on the silica surface. The initial product was collected after filtration and drying.

[0036] (2) The initial product obtained in step (1) is subjected to a first heat treatment under the conditions of calcination at 700-900℃ for 1-6 hours in an inert gas atmosphere. The product after heat treatment is etched with hydrofluoric acid solution with a molar concentration of 0.1-20M for 1-6 hours to remove silicon dioxide, and then dried to obtain oxygen-doped carbon hollow spheres.

[0037] (3) The oxygen-doped carbon hollow spheres obtained in step (2) are immersed in a palladium salt solution, stirred for 1 to 4 hours, the pH is adjusted to 9 to 11, and stirred for another 1 to 4 hours. The amount of palladium salt added is calculated as 0.1 to 1.0% of the mass of Pd in ​​the oxygen-doped carbon hollow spheres. After drying, a second heat treatment is performed under the condition of calcination at 100 to 400°C for 1 to 4 hours in an inert gas atmosphere to obtain an oxygen-doped carbon hollow sphere supported Pd single-atom catalyst.

[0038] The catalyst is used in the electrocatalytic reduction of oxygen to produce H2O2 in alkaline solution. The catalyst has excellent electrocatalytic activity and selectivity. As a catalyst for the electrocatalytic reduction of oxygen to produce H2O2, the oxygen reduction initiation potential is 0.84V and the H2O2 selectivity can reach 76%.

[0039] Example 1

[0040] A method for preparing an oxygen-doped carbon hollow sphere-anchored palladium single-atom catalyst, comprising the following steps:

[0041] (1) At room temperature (20℃), 210 mL of ethanol, 30 mL of deionized water, 9 mL of ammonia, and 5.19 mL of tetraethyl orthosilicate were added to a beaker and stirred for 15 min. Then, 1.2 g of resorcinol and 1.68 mL of formaldehyde were added, and stirring was continued for 24 h. After stirring, the product was washed multiple times by centrifugation with ethanol and deionized water, dried under vacuum at 60℃ for 12 h, and the initial product was collected.

[0042] (2) The initial product obtained in step (1) was placed in a tube furnace and calcined at 800°C for 2 hours under an argon atmosphere. After cooling to room temperature, the sample was collected and then thoroughly stirred and etched for 2 hours in a mixed solution of hydrofluoric acid, ethanol and water (volume ratio 1:1:1). After centrifugation and washing several times, the sample was vacuum dried to obtain oxygen-doped carbon hollow spheres.

[0043] (3) Dissolve a certain amount of PdCl2 solution (Pd content is 1 mg / mL) in 20 mL of water, add the oxygen-doped carbon nanotube hollow spheres prepared in step (2), wherein the mass of Pd added is 0.5% of the mass of the oxygen-doped carbon nanotube hollow spheres, stir thoroughly for 2 h, adjust the pH of the solution to 10.5, stir for another 2 h, centrifuge and dry, and place in a tube furnace under an argon atmosphere at 5 °C·min. -1 The temperature was increased to 300℃ at a certain rate, heat-treated for 2 hours, and then cooled to finally obtain an oxygen-doped carbon hollow sphere anchored Pd single-atom catalyst.

[0044] The surface morphology of the obtained catalyst was observed using scanning electron microscopy and transmission electron microscopy, and the results are as follows: Figure 1 and 2 As shown, the catalyst exhibits a hollow spherical structure with uniform diameter and good dispersibility, showing no obvious metal particles. Its structure was characterized by XRD, and the results are as follows. Figure 3 As shown, the catalyst exhibits only characteristic peaks of carbon at 20–30°, with no signal peaks observed from palladium particles, demonstrating that palladium supported on the carbon hollow sphere substrate has good dispersibility.

[0045] Example 2

[0046] The difference from Example 1 is that the mass of Pd added in step (3) is 0.1% of the mass of the oxygen-doped carbon hollow spheres.

[0047] Example 3

[0048] The difference from Example 1 is that the mass of Pd added in step (3) is 1% of the mass of the oxygen-doped carbon hollow spheres.

[0049] Comparative Example 1

[0050] Comparative Example 1 uses oxygen-doped carbon hollow spheres, and the steps are as follows:

[0051] (1) At room temperature (20℃), 210 mL of ethanol, 30 mL of deionized water, 9 mL of ammonia, and 5.19 mL of tetraethyl orthosilicate were added to a beaker and stirred for 15 min. Then, 1.2 g of resorcinol and 1.68 mL of formaldehyde were added, and stirring was continued for 24 h. After stirring, the product was washed multiple times by centrifugation with ethanol and deionized water, dried under vacuum at 60℃ for 12 h, and the initial product was collected.

[0052] (2) The initial product obtained in step (1) was placed in a tube furnace and calcined at 800°C for 2 hours under an argon atmosphere. After cooling to room temperature, the sample was collected and then thoroughly stirred and etched for 2 hours in a mixed solution of hydrofluoric acid, ethanol and water (volume ratio 1:1:1). After centrifugation and washing several times, the sample was vacuum dried to obtain oxygen-doped carbon hollow spheres.

[0053] Comparative Example 2

[0054] Comparative Example 2 uses oxygen-doped carbon hollow spheres, and the steps are as follows:

[0055] (1) At room temperature (20℃), 210 mL of ethanol, 30 mL of deionized water, 9 mL of ammonia, and 5.19 mL of tetraethyl orthosilicate were added to a beaker and stirred for 15 min. Then, 1.2 g of resorcinol and 1.68 mL of formaldehyde were added, and stirring was continued for 24 h. After stirring, the product was washed multiple times by centrifugation with ethanol and deionized water, dried under vacuum at 60℃ for 12 h, and the initial product was collected.

[0056] (2) The initial product obtained in step (1) was placed in a tube furnace and calcined at 600°C for 2 hours under an argon atmosphere. After cooling to room temperature, the sample was collected and then thoroughly stirred and etched for 2 hours in a mixed solution of hydrofluoric acid, ethanol and water (volume ratio 1:1:1). After centrifugation and washing several times, the sample was vacuum dried to obtain oxygen-doped carbon hollow spheres.

[0057] Application example: Catalyst used for electrocatalytic reduction of O2 to H2O2

[0058] The specific steps are as follows: First, the catalyst dispersion was prepared by mixing ethanol and 0.5 wt.% Nafion solution at a volume ratio of 9:1. Then, 1 μL of the dispersion containing the catalysts prepared in Examples 1-3 and Comparative Example 1 was drop-coated onto a rotating disk electrode. After air drying, it was used as the working electrode for testing. A silver / silver chloride electrode was used as the reference electrode, and a platinum column was used as the counter electrode. Electrochemical performance was tested in 0.1 M KOH electrolyte.

[0059] Cyclic voltammetry (CV) activation: Testing was performed using a Shanghai Chenhua CHI 660E electrochemical workstation. Oxygen was bubbled into the electrolyte for at least 0.5 hours before testing. A CV program was used, with a scan rate of 100 mV·s in the range of 0–1.2 V (vs. RHE). -1 The catalyst on the disc electrode and the Pt ring on the ring electrode were electrochemically activated by 50 CV cycles to bring the electrodes to a stable state.

[0060] Linear sweep voltammetry (LSV) test: After the working electrode is activated by CV, switch to the LSV program. The test range is 0–1.2 V (vs. RHE), and the scan rate is 10 mV·s.-1 The potential of the Pt ring is set to 1.2V (vs. RHE).

[0061]

[0062] The result is as follows Figure 4 As shown in the table above, the catalyst prepared in Example 1 exhibits excellent electrocatalytic performance in the electrocatalytic reduction of oxygen to H2O2 in alkaline solution. The catalyst of Example 1 has an onset potential of 0.84 V and an H2O2 selectivity of 76%; the catalyst of Example 2 has an onset potential of 0.84 V and an H2O2 selectivity of 64%; and the catalyst of Example 3 has an onset potential of 0.84 V and an H2O2 selectivity of 69%. The catalyst of Comparative Example 1, without palladium loading, has an onset potential of 0.84 V and an H2O2 selectivity of 60%, which is inferior to that of Example 1. The catalyst of Comparative Example 2 has an onset potential of 0.80 V and an H2O2 selectivity of 63%, but its carbonization temperature is insufficient, resulting in poor conductivity, and its onset potential is more negative.

[0063] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing an oxygen-doped carbon hollow sphere-anchored palladium single-atom catalyst, characterized in that, include: S1: Tetraethyl orthosilicate is added to a mixed solvent of water, ethanol and ammonia to carry out a hydrolysis reaction to form SiO2 nanosphere templates. Then, resorcinol and formaldehyde are added to carry out a polymerization reaction to form a carbon precursor on the surface of SiO2. The initial product is collected after filtration and drying. S2: The initial product is subjected to a first heat treatment, then acid washing to remove SiO2, and then dried to obtain oxygen-doped carbon hollow spheres. S3: Oxygen-doped carbon hollow spheres are impregnated in a metallic palladium salt solution, dried, and then calcined at 100~400℃ for 1~4h under an inert gas atmosphere to obtain an oxygen-doped carbon hollow sphere-supported Pd single-atom catalyst.

2. The method for preparing an oxygen-doped carbon hollow sphere-anchored palladium single-atom catalyst according to claim 1, characterized in that, In step S1, the mass ratio of hydroquinone, formaldehyde, and tetraethyl orthosilicate is 0.2~0.5:0.05~0.25:0.5~3.

5.

3. A method for preparing an oxygen-doped carbon hollow sphere-anchored palladium single-atom catalyst according to claim 1 or 2, characterized in that, In step S1, the volume ratio of deionized water, ethanol, and ammonia is 5~20:50~100:1~5, wherein the volume ratio of tetraethyl orthosilicate to the three solvents is 40~60 mL of solvent per 1 mL of tetraethyl orthosilicate.

4. The method for preparing an oxygen-doped carbon hollow sphere-anchored palladium single-atom catalyst according to claim 1, characterized in that, The hydrolysis reaction in step S1 is carried out at a temperature of 10~40 ℃ and for a time of 5~20 min.

5. A method for preparing an oxygen-doped carbon hollow sphere-anchored palladium single-atom catalyst according to claim 1 or 4, characterized in that, The polymerization reaction in step S1 is carried out at a temperature of 10~40 °C for 10~48 h.

6. The method for preparing an oxygen-doped carbon hollow sphere-anchored palladium single-atom catalyst according to claim 1, characterized in that, The conditions for the first heat treatment in step S2 are calcination at 700~900 ℃ for 1~6 h in an inert gas atmosphere.

7. The method for preparing an oxygen-doped carbon hollow sphere-anchored palladium single-atom catalyst according to claim 1, characterized in that, The amount of palladium salt added in step S3 is calculated as 0.1 to 1.0% of the mass of Pd relative to the mass of the oxygen-doped carbon hollow spheres.

8. The method for preparing an oxygen-doped carbon hollow sphere-anchored palladium single-atom catalyst according to claim 1, characterized in that, The impregnation process in step (3) is as follows: first stir for 1-4 hours, adjust the pH to 9-11, and then stir for 1-4 hours.

9. An oxygen-doped carbon hollow sphere-anchored palladium single-atom catalyst prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the oxygen-doped carbon hollow sphere anchored palladium single-atom catalyst according to claim 9 in the electrocatalytic reduction of oxygen to H2O2 in alkaline solution.

Images