CN115386906A

CN115386906A - Carbon-supported nickel monoatomic catalyst and preparation method and application thereof

Info

Publication number: CN115386906A
Application number: CN202210909919.7A
Authority: CN
Inventors: 李宇航; 李春忠; 肖楚倩; 王雅婷; 刘锦泽; 陈容振
Original assignee: East China University of Science and Technology
Current assignee: East China University of Science and Technology
Priority date: 2022-07-29
Filing date: 2022-07-29
Publication date: 2022-11-25

Abstract

The invention discloses a carbon-supported nickel monoatomic catalyst and a preparation method and application thereof. The preparation method comprises the following steps: (1) reacting the raw material liquid to obtain a mixed liquid; the raw material liquid comprises a carbon nano tube, a nickel source, a nitrogen source and a solvent; (2) removing the solvent in the mixed solution to obtain a solid; (3) Carrying out heat treatment on the solid under inert gas to obtain a precursor; (4) And treating the precursor with acid to obtain the carbon-supported nickel monatomic catalyst. In the carbon-supported nickel monatomic catalyst provided by the invention, the nickel monatomic has a super-coordination structure, and the nickel monatomic is monodisperse on the surface of the carbon nanotube, so that the carbon-supported nickel monatomic catalyst has excellent stability of good Faraday efficiency of hydrogen peroxide when the current density is high in the reaction of preparing hydrogen peroxide through electrocatalysis two-electron oxygen reduction reaction.

Description

Carbon-supported nickel monoatomic catalyst and preparation method and application thereof

Technical Field

The invention relates to a carbon-supported nickel monoatomic catalyst and a preparation method and application thereof.

Background

Hydrogen peroxide (H) ₂ O ₂ ) As an environment-friendly oxidant and potential energy carrier, the compound has been widely applied. Current industrial production of hydrogen peroxide involves hazardous transportation of hydrogen peroxide and additional use of hydrogen gas, which is often centralized and energy intensive, limiting its implementation in remote areas. Electrochemical synthesis is carried out through a double-electron transfer oxygen reduction reaction way, and a promising alternative solution is provided for small-scale on-site generation of hydrogen peroxide. However, the noble metal catalysts currently used for electrochemical synthesis of hydrogen peroxide work in acidic or alkaline electrolytes, resulting in high cost and environmental problems. Thus, there is increasing interest in non-noble metal (e.g., nickel) electrocatalysts, some of which exhibit satisfactory activity.

Among them, carbon supported metal Single Atom Catalysts (SACs) have become a popular new approach for the development of catalysts for two electron transfer oxygen reduction reaction in recent years, and research has mainly focused on the production of catalysts having M-N ₄ Metal SACs of active sites. However, to achieve high faradaic current efficiencies of greater than 90%, the operating current density is limited to a lower level (less than 100mA cm) ^-2 ). This prompted us to find a way to further tune the coordination structure of metal monatomic catalysts to achieve high activity and faraday efficiency at high current densities.

Disclosure of Invention

The invention aims to solve the technical problem that a non-noble metal monoatomic catalyst in the prior art cannot have the defects of high current density, high hydrogen peroxide Faraday efficiency and high catalytic activity in the electrocatalysis double-electron transfer oxygen reduction reaction process, and provides a carbon-supported nickel monoatomic catalyst and a preparation method and application thereof. In the carbon-supported nickel monatomic catalyst provided by the invention, the nickel monatomic has a super-coordination structure, and the nickel monatomic is monodisperse on the surface of the carbon nano tube, so that the carbon-supported nickel monatomic catalyst has excellent Faraday efficiency and better stability of hydrogen peroxide when the current density is high in the reaction of preparing hydrogen peroxide through electrocatalytic two-electron oxygen reduction reaction.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention provides a preparation method of a carbon-supported nickel monoatomic catalyst, which comprises the following steps:

(1) Reacting the raw material liquid to obtain a mixed liquid; the raw material liquid comprises a carbon nano tube, a nickel source, a nitrogen source and a solvent;

(2) Removing the solvent in the mixed solution to obtain a solid;

(3) Carrying out heat treatment on the solid under inert gas to obtain a precursor;

(4) And treating the precursor with acid to obtain the carbon-supported nickel monatomic catalyst.

In the present invention, the nickel source may be a nickel source conventionally used in the art, and may generally have NiN ₄ Structural nickel sources such as nickel phthalocyanine and/or nickel porphyrin.

In the present invention, the nitrogen source may be a nitrogen source conventionally used in the art, and may be one or more of dicyandiamide, cysteine, glutamic acid, lysine, melamine, ethylenediamine, urea, aniline or polyethyleneimine, and preferably melamine.

In the present invention, the carbon nanotube may be a carbon nanotube conventionally used in the art, preferably a multi-walled carbon nanotube or a single-walled carbon nanotube.

In the present invention, the carbon nanotube is preferably a carboxyl carbon nanotube, and more preferably a carboxyl multi-walled carbon nanotube.

In the step (1), the amount of the carbon nanotubes may be the amount conventionally used in the art, and may be generally 100 to 300g.

In the step (1), the molar ratio of the nickel source to the nitrogen source may be 1: (6.5X 10) ⁵ ～13×10 ⁵ ) Preferably 1: (8X 10) ⁵ ～12×10 ⁵ ) E.g. 1 (10X 10) ⁵ )。

In the step (1), the mass of the nickel source corresponding to the carbon nanotube can be 1 × 10 ⁵ ～5×10 ⁵ g/mol, preferably 3X 10 ⁵ g/mol。

In the step (1), the raw material solution may be prepared by a conventional method in the art, and the carbon nanotube, the nickel source, the nitrogen source, and the solvent may be mixed.

Preferably, the preparation method of the raw material liquid comprises the following steps: firstly, dispersing the carbon nano tube and the nitrogen source in a solvent, and then adding the nickel source for mixing.

The dispersion process is preferably carried out under ultrasonic conditions; wherein, the frequency of the ultrasonic wave is preferably 10-50 KHz, such as 40KHz; the time of the ultrasound is preferably 0.5 to 1 hour, for example 0.8 hour.

The mixing is preferably by stirring.

In the step (1), the reaction time is 24-48 h, such as 36h.

In step (1), the temperature of the reaction is 20 to 30 ℃, for example 25 ℃.

In the step (1), the reaction is carried out under stirring, and the stirring speed is preferably 700 to 1200rpm/min.

In the step (1), the solvent may be conventional in the art, and may be capable of dispersing the carbon nanotubes and the nitrogen source, and is preferably a mixed solution of water and ethanol; more preferably, the volume ratio of water to ethanol in the water-ethanol mixture is 1.

In the step (2), the method for removing the solvent in the mixed solution comprises centrifugation and drying.

Wherein the rate of centrifugation may be 8000 to 10000r/min, for example 10000r/min.

Wherein the drying temperature may be 50 to 80 ℃, such as 60 ℃ or 70 ℃.

Wherein the pressure of the drying may be 1 to 10Pa.

Wherein the drying time can be 20-24 h, such as 22h.

In the step (3), the inert gas may be argon.

In step (3), the heating rate of the heat treatment may be 2 to 10 ℃/min, preferably 4 to 8 ℃/min, for example 5 ℃/min.

In the step (3), the temperature of the heat treatment may be 800 to 1000 ℃, for example, 900 ℃. And (3) performing heat treatment to ensure that the solid obtained in the step (2) is subjected to pyrolysis to generate a coordination reaction.

In the step (3), the time of the heat treatment may be 0.5 to 1.5 hours, for example, 1 hour.

In the step (4), the acid used in the acid treatment is a strong inorganic acid, preferably one or more of sulfuric acid, hydrochloric acid and nitric acid. In the acid treatment process, the simple nickel substance in the precursor can be removed, and only nickel monoatomic atoms are ensured in the carbon-supported nickel monoatomic catalyst.

Wherein the concentration of the strong inorganic acid can be 0.5-1 mol/L, such as 0.7mol/L.

In step (4), the temperature of the acid treatment may be 60 to 100 ℃, for example, 80 ℃.

The invention also provides a carbon-supported nickel monoatomic catalyst prepared by the preparation method.

The invention also provides a carbon-supported nickel monoatomic catalyst which comprises a carbon nano tube and a nickel monoatomic catalyst supported on the surface of the carbon nano tube, wherein the nickel monoatomic catalyst has N ₄ -Ni ₁ -O _x Wherein said N is ₄ -Ni ₁ -O _x Wherein X is in the range of 0.5-2.5; the mass content of the nickel monoatomic is 0.1-0.5%, and the percentage is the percentage of the total mass of the carbon-supported nickel monoatomic catalyst.

In the present invention, said N ₄ -Ni ₁ -O _x Wherein X may be 1, 1.5 or 2.

In the invention, the mass content of the nickel monoatomic atom can be 0.2%, 0.3% or 0.4%, and the percentage is the percentage of the total mass of the carbon-supported nickel monoatomic catalyst.

The invention also provides an application of the carbon-supported nickel monoatomic catalyst in a double-electron transfer oxygen reduction reaction.

In the present invention, the application is preferably an application in the preparation of hydrogen peroxide by a two-electron transfer oxygen reduction reaction.

The reagents and starting materials used in the present invention are commercially available.

On the basis of the common knowledge in the field, the above preferred conditions can be combined randomly to obtain the preferred embodiments of the invention.

The positive progress effects of the invention are as follows:

1. the carbon-supported nickel monoatomic catalyst and the preparation method thereof provided by the invention can realize the nickel monoatomic (N) with an oxygen atom coordination structure by taking the carbon nanotube as a substrate ₄ -Ni ₁ -O _x ). The method has the characteristics of high utilization rate of non-noble metal monatomic, good stability and the like; the obtained material is easy to apply and is beneficial to popularization and application in industrial production.

2. The carbon-supported nickel monatomic catalyst provided by the invention has good catalytic performance, and realizes higher faradic efficiency of hydrogen peroxide while having high current density. Provides a new idea and method for the design and synthesis of electrocatalytic materials, so that the electrocatalytic materials can simultaneously realize higher hydrogen peroxide Faraday efficiency and higher catalytic activity under high current density, thereby further improving the application prospect of the nickel monatomic catalyst in the industrial preparation of hydrogen peroxide. In a preferred embodiment, the current density is 300mA cm ^-2 The faradaic efficiency of hydrogen peroxide is over 90%.

Drawings

FIG. 1 shows N prepared in example 1 ₄ -Ni ₁ -O ₂ Energy dispersive X-ray spectroscopy (EDX) elemental analysis of/OCNTs. Wherein FIG. 1a is N prepared in example 1 ₄ -Ni ₁ -O ₂ High resolution scanning electron microscope images of/OCNTs, FIG. 1b is a elemental scan of C, and FIG. 1C is a elemental scan of NiAnd FIG. 1d is an element scan of N.

FIG. 2 shows N prepared in example 1 ₄ -Ni ₁ -O ₂ Transmission electron micrograph corrected spherical aberration of/OCNTs material, nickel monoatomic in the circle.

FIG. 3 is N prepared in example 1 ₄ -Ni ₁ -O ₂ OCNTs and N prepared in example 2 ₄ -Ni ₁ -O ₁ Fourier transform spectra of Ni K-edge EXAFS spectra for/MCNTs and NiPc for comparative example 2.

FIG. 4 shows N prepared in example 1 ₄ -Ni ₁ -O ₂ Fourier transform fit spectra of Ni K-edge EXAFS spectra of/OCNTs.

FIG. 5 is a graph showing the Faraday efficiencies of hydrogen peroxide at different current densities for the catalysts prepared in examples 1-2 and comparative examples 1-2.

FIG. 6 is N prepared in example 1 ₄ -Ni ₁ -O ₂ The stability test chart of hydrogen peroxide prepared by electrocatalysis two-electron oxygen reduction of/OCNTs.

Detailed Description

The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention. The experimental methods without specifying specific conditions in the following examples were selected according to the conventional methods and conditions, or according to the commercial instructions.

Example 1

Step (1): dispersing 200mg of carboxyl purified multi-walled carbon nanotubes and 500mg of melamine in 120mL of a mixed solvent of water and ethanol, wherein the volume ratio of the water to the ethanol is 1:1. then, the mixture was subjected to ultrasonic treatment at a frequency of 40KHz for 0.5 hour. Then, 140 mu L of NiPc ethanol solution with the concentration of 25mg/mL is dripped into the solution under stirring, and the solution is stirred and reacts for 24 hours at the temperature of 25 ℃ to obtain mixed solution;

step (2): centrifuging the mixed solution obtained in the step (1) by using a centrifuge at a centrifugation speed of 1000r/min, and drying the solid after centrifugation at a drying temperature of 80 ℃ for 24 hours;

and (3): grinding the black solid obtained in the step (2), and then carrying out heat treatment for 1h at the temperature rise rate of 5 ℃/min at 1000 ℃ in Ar atmosphere;

and (4): treating the heat-treated sample in 0.5mol/L sulfuric acid at 80 ℃ for 12h, washing the sample to be neutral by deionized water, and drying the sample at 80 ℃ for 12h to obtain N ₄ -Ni ₁ -O ₂ the/OCNTs super-coordinated single atom catalyst.

Example 2

Step (1): dispersing 200mg of multi-walled carbon nanotubes and 500mg of melamine in 120mL of a mixed solvent of water and ethanol, wherein the volume ratio of the water to the ethanol is 1:1. then, the mixture was subjected to ultrasonic treatment at a frequency of 40KHz for 0.5 hour. Then, 140. Mu.L of NiPc ethanol solution with a concentration of 25mg/mL was added dropwise to the above solution under stirring, and the reaction was carried out at 25 ℃ for 24 hours under stirring to obtain a mixed solution.

and (3): and (3) grinding the black solid obtained in the step (2), and then carrying out heat treatment for 1h at the temperature rise rate of 5 ℃/min at 1000 ℃ in Ar atmosphere.

And (4): treating the sample subjected to the heat treatment in the step (3) in 0.5mol/L sulfuric acid at 80 ℃ for 12h, washing the sample to be neutral by using deionized water, and drying the sample at 80 ℃ for 12h to obtain the N ₄ -Ni ₁ -O ₁ Pentacoordinate monatomic catalyst, noted N ₄ -Ni ₁ -O ₁ /MCNTs。

Example 3

and (3): grinding the black solid obtained in the step (2), and then carrying out heat treatment for 1h at the temperature rise rate of 2 ℃/min at 1000 ℃ in Ar atmosphere;

Comparative example 1

Step (1): dispersing 200mg of carboxyl purified multi-walled carbon nano-tubes and 500mg of melamine in 120ml of a mixed solvent of water and ethanol, wherein the volume ratio of the water to the ethanol is 1:1. then ultrasonic treatment is carried out for 0.5 hour, the frequency of ultrasonic treatment is 40KHz, and then stirring is carried out for 24 hours at room temperature, thus obtaining a mixed solution.

and (3): and (3) grinding the black solid obtained in the step (2), and then carrying out heat treatment for 1h at the temperature rise rate of 5 ℃/min at 1000 ℃ in Ar atmosphere to obtain the carboxyl carbon nano tube without the nickel source, which is marked as OCNTs.

Comparative example 2

Commercially available nickel phthalocyanine was used as a comparative example, and is designated as NiPc.

Effect example 1

For N obtained in example 1 ₄ -Ni ₁ -O ₂ the/OCNTs nickel monoatomic catalyst is subjected to TEM characterization, EDX elemental analysis and spherical aberration correction transmission electron microscope analysis. In FIGS. 1 and 2, N can be seen ₄ -Ni ₁ -O ₂ The morphology of the/OCNTs nickel monoatomic atoms still maintains the morphology of the carboxyl carbon nano-tubes, and energy dispersive X-ray spectroscopy (EDS) mapping confirms that Ni, N, O and C elements are uniformly distributed on the carboxyl carbon nano-tubes. The spherical aberration corrected scanning transmission electron microscope image confirmed that the Ni atoms were monodisperse on the surface of the carboxycarbon nanotube.

Effect example 2

FIG. 3 is a Fourier transform spectrum of the Ni K-edge EXAFS spectrum of the catalysts obtained in examples 1,2 and comparative example 2. As can be seen from FIG. 3, catalyst N ₄ -Ni ₁ -O ₂ OCNT and N ₄ -Ni ₁ -O ₁ The results of the peaks corresponding to Ni-N/O bonds in/MCNT, and the peaks corresponding to Ni-Ni bonds in Ni Foil alone and Ni-O bonds in NiO alone showed that N is present ₄ -Ni ₁ -O ₂ OCNT and N ₄ -Ni ₁ -O ₁ Ni in/MCNT exists in a monoatomic form. NiO and Ni Foil, commercial products, were purchased.

FIG. 4 is a Fourier transform fit of the Ni K-edge EXAFS spectrum of the catalyst obtained in example 1, from which FIG. 4 it can be derived: the structure of the nickel monoatomic site is N ₄ -Ni ₁ -O ₂ 。

Effect example 3

Electrocatalytic two-electron oxygen reduction performance detection

The test method comprises the following steps: (1) Mixing 10mg of the catalyst obtained in example 1 with 0.96mL of ethanol and 0.04mL5wt% of Nafion117 solution to obtain a catalyst dispersion; dripping the catalyst dispersion liquid on a gas diffusion electrode, and drying in the air to finally obtain the catalyst loading of 0.1mg/cm ² N of (A) ₄ -Ni ₁ -O ₂ an/OCNT working electrode;

(2) The above load N ₄ -Ni ₁ -O ₂ The gas diffusion electrode of/OCNT, porous nickel foam and saturated Ag/AgCl electrode were used as cathode, anode and reference electrode, respectively, for testing.

Oxygen flow was constant at 50mL min throughout the test ^-1 The rate of the KOH solution is introduced into an electrolytic cell, and 1mol/L of KOH electrolyte is respectively circulated between the cathode and the anode of the electrolytic cell.

When testing linear sweep voltammetry, the electrochemical workstation uses 5mV s ^-1 The scan rate of (a) was used to collect the data and the results are shown in table 1. It can be seen that: n is a radical of ₄ -Ni ₁ -O ₂ the/OCNT is used as a gas diffusion electrode and shows great catalytic activity, N ₄ -Ni ₁ -O ₂ OCNTs reached at 0.65VTo 350mA cm ^-2 Is greater than that of example 2 (98.47 mA cm) ^-2 ) And much larger than comparative example 1 (74.6 mA cm) ^-2 ) And comparative example 2 (48.3 mA cm) ^-2 ) The resulting electrode was prepared.

TABLE 1

Effect example 4

N obtained in example 1 ₄ -Ni ₁ -O ₂ the/OCNTs catalyst is in the range of 100 to 350mA cm ^-2 Constant current electrolysis was performed at different current densities to test the faradaic efficiency of the product hydrogen peroxide. The hydrogen peroxide concentration was determined by cerium sulfate titration.

FIG. 5 is a graph showing the Faraday efficiencies of hydrogen peroxide at different current densities for the catalysts prepared in examples 1-2 and comparative examples 1-2. As can be seen from FIG. 5 and Table 2, N obtained in example 1 ₄ -Ni ₁ -O ₂ the/OCNTs catalyst is in the range of 100 to 350mA cm ^-2 The wide application current range of the (2) can keep good Faraday efficiencies of hydrogen peroxide, which are all more than 86%; at 100 and 200mA cm ^-2 The maximum hydrogen peroxide faradaic efficiency is over 96%. At 100 to 350mA cm ^-2 The catalyst prepared in example 1 has a higher faradaic efficiency of hydrogen peroxide than the catalysts of comparative examples 1 and 2 over a wide range of applied currents.

TABLE 2

Effect example 5

FIG. 6 is N prepared in example 1 ₄ -Ni ₁ -O ₂ Preparation of peroxide by electrocatalysis two-electron oxygen reduction with/OCNTs nickel monoatomic catalystHydrogen stability test chart. The test condition is 200mA cm of heavy current ^-2 Next 1M KOH solution. It can be seen that when the overpotential is stabilized at 0.3V (without resistance compensation) during the test, the faradaic efficiency of preparing hydrogen peroxide is maintained above 80%. Meanwhile, the Faraday efficiency of the hydrogen peroxide does not obviously decrease after 24 hours of reaction, which indicates that the hydrogen peroxide has very good stability.

Effect example 6

The example 3 in which the temperature rise rate in the step (3) of example 1 was changed was obtained, and the electrocatalytic two-electron oxygen reduction for the preparation of hydrogen peroxide was slightly inferior to the nickel monoatomic catalysts obtained in examples 1 and 2, but superior to the tetradentate Ni-N catalyst represented by NiPc in comparative examples 1 and 2 ₄ Faradaic efficiency performance of hydrogen peroxide in a coordinated structure.

Claims

1. A preparation method of a carbon-supported nickel monatomic catalyst is characterized by comprising the following steps:

(2) Removing the solvent in the mixed solution to obtain a solid;

2. The method of claim 1, wherein the nickel source is a catalyst having NiN ₄ Structural nickel sources, such as nickel phthalocyanine and/or nickel porphyrin;

and/or the nitrogen source is one or more of dicyandiamide, cysteine, glutamic acid, lysine, melamine, ethylenediamine, urea, aniline or polyethyleneimine, preferably melamine;

and/or the carbon nano tube is a multi-wall carbon nano tube or a single-wall carbon nano tube;

and/or the carbon nano tube is a carboxyl carbon nano tube, preferably a carboxyl multi-wall carbon nano tube;

and/or the solvent is a mixed solution of water and ethanol; preferably, the volume ratio of water to ethanol in the water-ethanol mixture is 1;

and/or the dosage of the carbon nano tube is 100-300 g;

and/or the molar ratio of the nickel source to the nitrogen source is 1 (6.5 x 10) ⁵ ～13×10 ⁵ ) Preferably 1 (8X 10) ⁵ ～12×10 ⁵ ) E.g. 1 (10X 10) ⁵ )；

And/or the mass of the nickel source corresponding to the carbon nano tube is 1 multiplied by 10 ⁵ ～5×10 ⁵ g/mol, preferably 3X 10 ⁵ g/mol。

3. The method for producing a carbon-supported nickel monatomic catalyst according to claim 1, wherein in the step (1), the method for producing the raw material liquid comprises: firstly, dispersing the carbon nano tube and the nitrogen source in a solvent, and then adding the nickel source for mixing;

preferably, the dispersion process is carried out under ultrasonic conditions; wherein, the frequency of the ultrasonic wave is preferably 10-50 KHz, such as 40KHz; the time of the ultrasound is preferably 0.5 to 1 hour, for example 0.8 hour;

preferably, the mixing mode is stirring.

4. The method of preparing a carbon-supported nickel monatomic catalyst of claim 1 wherein in step (1), the reaction time is between 24 and 48 hours, such as 36 hours;

and/or, in step (1), the temperature of the reaction is 20 to 30 ℃, for example 25 ℃;

and/or, in step (1), the reaction is carried out under stirring; the stirring rate is preferably 700 to 1200rpm/min.

5. The method for preparing a carbon-supported nickel monatomic catalyst according to claim 1, wherein in the step (2), the method for removing the solvent in the mixed liquid comprises centrifugation and drying;

the rate of centrifugation is preferably 8000 to 10000r/min, for example 10000r/min;

the temperature of the drying is preferably 50 to 80 ℃, for example 60 ℃ or 70 ℃;

the drying pressure is preferably 1 to 10Pa;

the drying time is preferably 20 to 24 hours, for example 22 hours.

6. The method for preparing a carbon-supported nickel monatomic catalyst according to claim 1, wherein in step (3), the inert gas is argon;

and/or, in the step (3), the heating rate of the heat treatment is 2 to 10 ℃/min, preferably 4 to 8 ℃/min, such as 5 ℃/min;

and/or, in step (3), the temperature of the heat treatment is 800-1000 ℃, such as 900 ℃;

and/or, in step (3), the time of the heat treatment is 0.5 to 1.5 hours, such as 1 hour;

and/or in the step (4), the acid used in the acid treatment is strong inorganic acid, preferably one or more of sulfuric acid, hydrochloric acid and nitric acid; preferably, the concentration of the strong inorganic acid is 0.5 to 1mol/L, such as 0.7mol/L;

and/or, in step (4), the temperature of the acid treatment is 60 to 100 ℃, for example 80 ℃.

7. A carbon-supported nickel monatomic catalyst produced by the production method according to any one of claims 1 to 6.

8. A carbon-supported nickel monoatomic catalyst, comprising a carbon nanotube and a nickel monoatomic catalyst supported on the surface of the carbon nanotube, the nickel monoatomic catalyst having N ₄ -Ni ₁ -O _x Wherein said N is ₄ -Ni ₁ -O _x Wherein X is in the range of 0.5-2.5;

the mass content of the nickel monoatomic is 0.1-0.5%, and the percentage is the percentage of the total mass of the carbon-supported nickel monoatomic catalyst.

9. The carbon-supported nickel monatomic catalyst of claim 8 wherein said N is ₄ -Ni ₁ -O _x Wherein X is 1, 1.5 or 2;

and/or the mass content of the nickel single atom is 0.2%, 0.3% or 0.4%, and the percentage is the percentage of the total mass of the carbon-supported nickel single atom catalyst.

10. Use of a carbon-supported nickel monatomic catalyst as defined in any one of claims 7 to 9 in a two-electron transfer oxygen reduction reaction.