WO2017028520A1 - C2n graphene-precious metal composite nanometer catalyst and preparation method therefor - Google Patents

Abstract

Embodiments of the present invention provide a C₂N graphene-precious metal composite nanometer catalyst, comprising a C₂N graphene carrier and catalytically active precious metal nanoparticles attached to a surface of the C₂N graphene carrier. The precious metal nanoparticles are uniformly distributed on the surface of the C₂N graphene carrier by coordinating with nitrogen atoms in the C₂N graphene carrier. The C₂N graphene is used as a carrier in the catalyst, and therefore, the precious metal nanoparticles can be uniformly dispersed on the surface of the graphene by a high-loading amount, so that the catalyst has excellent performances such as high activity, high thermal stability, and high mechanical strength, thereby finally improving power performances and prolonging service lives of fuel battery and metal air battery. The embodiments of the present invention further provide a preparation method for the C₂N graphene-precious metal composite nanometer catalyst.

Description

C2N graphene composite noble metal nano catalyst and preparation method thereof

The present application claims priority to Chinese Patent Application No. 201510506908.4, entitled "C ₂ N Graphene Composite Precious Metal Nanocatalyst and Preparation Method thereof", filed on August 18, 2015, the entire disclosure of which is incorporated herein by reference. The content is incorporated herein by reference.

Technical field

The invention relates to the field of nanocatalysts for electrocatalytic reduction, in particular to a C ₂ N graphene composite precious metal nanocatalyst and a preparation method thereof.

Background technique

At present, noble metals (Pt, Au, Pd, Ru, Ag, etc.) and alloy nanoparticles formed thereof with Fe, Co, Cr, Ni, Sn, Re, etc., have excellent oxygen reduction catalytic properties as fuel cells and metal air. The electrocatalyst of the battery has been widely used and studied. In practical applications, the catalyst needs to act in combination with the carrier, and the dispersibility and loading of the noble metal nanoparticles on the carrier have a great influence on the catalytic performance. To a certain extent, the better the dispersibility and the higher the load, the larger the contact area between the catalyst and the reactant per unit area, and the more oxygen is reduced per unit time. Correspondingly, the fuel cell or the metal air battery The better the power performance.

Graphene is a monoatomic layer-thick two-dimensional nanomaterial composed of carbon atoms. It is an ideal precious metal due to its ultra-high specific surface area (2650 m ² /g) and electrical conductivity (10 ⁴ -10 ⁵ S/m). Nanocatalytic support material. However, there is no active site on the surface of the graphene, and the catalyst particles cannot be anchored, resulting in poor dispersibility of the catalyst and low loading. Moreover, in the electrocatalytic oxygen reduction process, since the catalyst nanoparticles are easily detached from the graphene surface and aggregated, the catalytic performance is further lowered.

In order to solve the above problem of the graphene carrier, the patent application 201310457005.2 proposes a cationic polymer functionalization of graphene. Although the method improves the dispersibility of the catalyst, the introduction of the cationic polymer greatly reduces the loading amount of the noble metal nanoparticles, and Lead to a decrease in the electrical conductivity of the graphene body. In addition, the patent application 201310170468.0 proposes to utilize nitrogen-doped graphene as a carrier, and the stability of the catalyst obtained by the method is improved, but the nitrogen atom distribution in the nitrogen-doped graphene is not uniform, resulting in the dispersibility of the noble metal nanocatalyst; The nitrogen atom content is usually less than 10%, resulting in a low loading of the precious metal nanocatalyst.

Summary of the invention

In view of this, the first aspect of the present invention provides a C ₂ N graphene composite precious metal nano catalyst, which solves the problem that the precious metal nanoparticles in the prior precious metal nano catalyst technical solution have low loading on the graphene carrier, poor dispersion and catalyst Poor stability.

In a first aspect, an embodiment of the present invention provides a C ₂ N graphene composite noble metal nano catalyst, comprising a C ₂ N graphene carrier and catalytically active noble metal nanoparticles attached to the surface of the C ₂ N graphene carrier, The noble metal nanoparticles are uniformly distributed on the surface of the C ₂ N graphene carrier by coordination bonding with a nitrogen atom in the C ₂ N graphene carrier.

The C ₂ N graphene is a special graphene having a nitrogen atom content of 33.3% (the structure is as shown in FIG. 1 ), and has a regular porous structure, and the pore diameter of each pore is 0.83 nm, and Six nitrogen atoms are evenly distributed around the pores. The nitrogen orbital has a pair of lone pairs of electrons in the P orbital, which can form a coordination chemical bond with the empty d orbital or f orbital of the noble metal atom, and anchor the noble metal atom to the surface of the graphene. Since the nitrogen atoms in the C ₂ N graphene are densely distributed and uniformly distributed throughout the two-dimensional plane of graphene, the noble metal nanoparticles can be uniformly dispersed on the surface of the C ₂ N graphene carrier by coordination with nitrogen atoms. Finally, a C ₂ N graphene composite noble metal nano catalyst with good dispersibility, high loading and good stability is obtained.

Preferably, the mass ratio of the catalytically active noble metal nanoparticles to the C ₂ N graphene carrier is from 0.2 to 5:1.

Preferably, the catalytically active noble metal nanoparticle is an alloy formed of one or more metals of Pt, Au, Pd, Ru, Ag, or one or more of Pt, Au, Pd, Ru, Ag An alloy formed with one or more of Fe, Co, Cr, Ni, Sn, and Re.

Preferably, the catalytically active noble metal nanoparticles have a diameter of from 0.4 nm to 0.9 nm.

A C ₂ N graphene composite noble metal nano catalyst provided by the first aspect of the present invention uses C ₂ N graphene as a catalyst carrier, because the nitrogen atom in the C ₂ N graphene is highly dense and uniformly distributed throughout the graphene II Dimensional plane, thus the noble metal nanoparticles can be uniformly dispersed on the graphene surface by coordination with nitrogen atoms, so that the catalyst has excellent properties such as high activity, good thermal stability and high mechanical strength, and finally can be improved. The power performance and service life of the fuel cell and the metal air battery solve the problems of low loading, poor dispersibility and poor catalyst stability of the noble metal nanoparticles on the graphene carrier in the prior art.

In a second aspect, an embodiment of the present invention provides a method for preparing the above C ₂ N graphene composite noble metal nano catalyst, comprising the following steps:

Step 1: placing C ₂ N graphene in a solvent, and obtaining a C ₂ N graphene dispersion after sonication;

Step 2: adding a noble metal precursor to the C ₂ N graphene dispersion obtained above to obtain a mixed dispersion under an inert atmosphere, heating the mixed dispersion to 60-200 ° C, and then adding a reducing agent, wherein the precious metal precursor: C ₂ N graphene: reducing agent mass ratio = 0.5-20: 1: 0.3-15, after 1-24 hours of reaction, centrifugation, washing, drying to obtain C ₂ N graphene composite precious metal nanocatalyst, said C _{The 2} N graphene composite precious metal nanocatalyst comprises a C ₂ N graphene carrier and catalytically active noble metal nanoparticles attached to the surface of the C ₂ N graphene carrier, the noble metal nanoparticles passing through the C ₂ N graphene The nitrogen atoms in the carrier are coordinately bonded to be uniformly distributed on the surface of the C ₂ N graphene carrier.

Preferably, in the step 1, the solvent comprises ethanol, acetone, tetrahydrofuran, water or N-methylpyrrolidone.

Preferably, in the step 1, the concentration of the C ₂ N graphene dispersion is 0.1 to 2.0 mg/mL.

Preferably, in the step 2, the noble metal precursor is one or more of an ionic salt or an acid of Pt, Au, Pd, Ru or Ag, or an ionic salt or acid of Pt, Au, Pd, Ru, Ag. One or more of the mixture of one or more of ionic salts or acids of Fe, Co, Cr, Ni, Sn, Re.

Preferably, in the step 2, the reducing agent is one of sodium borohydride, hydrazine hydrate and ascorbic acid.

The preparation method provided by the second aspect of the present invention has a simple process, and the prepared C ₂ N graphene composite precious metal nano catalyst has high activity and stable performance.

In a third aspect, an embodiment of the present invention provides a fuel cell or a metal air battery, which comprises the C ₂ N graphene composite noble metal nano catalyst provided by the above first aspect of the invention as a catalyst.

The fuel cell and the metal air battery provided by the third aspect of the embodiments of the present invention have good power performance and service life.

The advantages of the embodiments of the present invention will be set forth in part in the description which follows.

DRAWINGS

Figure 1 is a schematic diagram showing the composition and structure of C ₂ N graphene.

detailed description

The following is a preferred embodiment of the embodiments of the present invention, it should be noted that Many modifications and refinements can be made by those skilled in the art without departing from the principles of the embodiments of the present invention. These modifications and refinements are also considered as the scope of protection of the embodiments of the present invention.

The first aspect of the present invention provides a C ₂ N graphene composite precious metal nano catalyst, which solves the problem that the precious metal nanoparticles in the prior precious metal nano catalyst technical solution have low loading on the graphene carrier, poor dispersion and stable catalyst stability. Good question.

In a first aspect, an embodiment of the present invention provides a C ₂ N graphene composite noble metal nano catalyst, comprising a C ₂ N graphene carrier and catalytically active noble metal nanoparticles attached to the surface of the C ₂ N graphene carrier, The noble metal nanoparticles are uniformly distributed on the surface of the C ₂ N graphene carrier by coordination bonding with a nitrogen atom in the C ₂ N graphene carrier.

The C ₂ N graphene is a special graphene having a nitrogen atom content of 33.3% (the structure is as shown in FIG. 1 ), and has a regular porous structure, and the pore diameter of each pore is 0.83 nm, and Six nitrogen atoms are evenly distributed around the pores. The nitrogen orbital has a pair of lone pairs of electrons in the P orbital, which can form a coordination chemical bond with the empty d orbital or f orbital of the noble metal atom, and anchor the noble metal atom to the surface of the graphene. Since the nitrogen atoms in the C ₂ N graphene are densely distributed and uniformly distributed throughout the two-dimensional plane of graphene, the noble metal nanoparticles can be uniformly dispersed on the surface of the C ₂ N graphene carrier by coordination with nitrogen atoms. Finally, a C ₂ N graphene composite precious metal nanocatalyst with good dispersibility, high loading and good stability is obtained.

Preferably, the mass ratio of the noble metal nanoparticles to the C ₂ N graphene carrier is 0.2-5:1.

Preferably, the catalytically active noble metal nanoparticle is an alloy formed of one or more metals of Pt, Au, Pd, Ru, Ag, or one or more of Pt, Au, Pd, Ru, Ag An alloy formed with one or more of Fe, Co, Cr, Ni, Sn, and Re.

Preferably, the catalytically active noble metal nanoparticles have a diameter of from 0.4 nm to 0.9 nm.

A C ₂ N graphene composite noble metal nano catalyst provided by the first aspect of the present invention uses C ₂ N graphene as a catalyst carrier, because the nitrogen atom in the C ₂ N graphene is densely distributed and uniformly distributed throughout the graphene II. Dimensional plane, thus the noble metal nanoparticles can be uniformly dispersed on the graphene surface by coordination with nitrogen atoms, so that the catalyst has excellent properties such as high activity, good thermal stability and high mechanical strength, and finally can be improved. The power performance and service life of the fuel cell and the metal air battery solve the problems of low loading, poor dispersibility and poor catalyst stability of the noble metal nanoparticles on the graphene carrier in the prior art.

In a second aspect, an embodiment of the present invention provides a method for preparing the above C ₂ N graphene composite noble metal nano catalyst, comprising the following steps:

Step 1: placing C ₂ N graphene in a solvent, and obtaining a C ₂ N graphene dispersion after sonication;

Step 2: adding a noble metal precursor to the C ₂ N graphene dispersion obtained above to obtain a mixed dispersion under an inert atmosphere, heating the mixed dispersion to 60-200 ° C, and then adding a reducing agent, wherein the precious metal precursor : C ₂ N graphene: reducing agent mass ratio = 0.5-20: 1: 0.3-15, after 1-24 hours of reaction, centrifugation, washing, drying to obtain C ₂ N graphene composite precious metal nanocatalyst, The C ₂ N graphene composite noble metal nanocatalyst comprises a C ₂ N graphene carrier and catalytically active noble metal nanoparticles attached to the surface of the C ₂ N graphene carrier, the noble metal nanoparticles passing through the C ₂ N graphite The nitrogen atom in the olefinic carrier is coordinately bonded to be uniformly distributed on the surface of the C ₂ N graphene carrier.

In the step 1, the solvent may be ethanol, acetone, tetrahydrofuran, water or N-methylpyrrolidone (NMP), but is not limited thereto. The power of the sonication is generally 50-400 W, and the ultrasonic dispersion time is 0.5-5 hours depending on the solvent.

Preferably, in the step 1, the concentration of the C ₂ N graphene dispersion is 0.1 to 2.0 mg/mL.

Preferably, in the step 2, the noble metal precursor is one or more of an ionic salt or an acid of Pt, Au, Pd, Ru or Ag, or an ionic salt or acid of Pt, Au, Pd, Ru, Ag. a mixture of one or more of the ionic salts or acids of Fe, Co, Cr, Ni, Sn, Re or one or more of the acids. Specific The ionic salt may be a halogen salt, a nitrate salt, and the acid is a halogen acid.

Preferably, the inert atmosphere may be nitrogen, helium, argon or the like.

Preferably, in the step 2, the reducing agent is one of sodium borohydride, hydrazine hydrate and ascorbic acid.

In the step 2, the operation of heating the mixed dispersion to 60-200 ° C can be determined according to the solvent selected, and is lower than the boiling point of the solvent.

The C ₂ N graphene of the present invention can be obtained by the following production method, but is not limited thereto:

Method 1: Under argon protection, hexaphenylamine trihydrochloride (2 g, 7.20 mmol) and hexaketone cyclohexane (2.248 g, 7.20 mmol) were placed in a three-necked round bottom flask, ice bath, and stirred; Add 2 drops of concentrated sulfuric acid to 80 mL of NMP, and vacuum to remove oxygen; then add the above NMP solution dropwise to the three-necked round bottom flask; after the dropwise addition, the mixture in the three-necked round bottom flask was warmed to room temperature and stored for 2 hours; The mixture was heated to 175 ° C with an oil bath, incubated for 8 hours, cooled to room temperature, 200 mL of water was added and stirred for 0.5 hours; the mixture was suction filtered, washed several times with methanol and water; finally, the black solid residue was at -120 The C ₂ N graphene sample was obtained by freeze-drying at ° C and 0.05 mmHg for 3 days.

Method 2: Under argon protection, hexaphenylamine trihydrochloride (2g, 7.20mmol) and hexaketone cyclohexane (2.248g, 7.20mmol) were placed in a three-necked round bottom flask, ice bath, and stirred; Distilled 80 mL of trifluoromethanesulfonic acid was added dropwise to the three-necked flask; after the completion of the dropwise addition, the mixture in the three-necked flask was warmed to room temperature and stored for 2 hours; then the mixture was heated to 175 ° C in an oil bath for 8 hours. Cool to room temperature, add 200mL of water, stir for 0.5 hours; then mix and filter, wash with methanol and water several times; finally, freeze the black solid residue at -120 ° C, 0.05mmHg pressure for 3 days, you can A C ₂ N graphene sample was obtained.

The preparation method provided by the second aspect of the present invention has a simple process, and the prepared C ₂ N graphene composite precious metal nano catalyst has high activity and stable performance.

In a third aspect, an embodiment of the present invention provides a fuel cell or a metal-air battery using the C ₂ N graphene composite noble metal nanocatalyst provided by the above first aspect of the present invention as a catalyst.

The fuel cell and the metal air battery provided by the third aspect of the embodiments of the present invention have good power performance and service life.

The embodiments of the present invention are further described below in various embodiments. The embodiments of the present invention are not limited to the following specific embodiments. Changes can be implemented as appropriate within the scope of the invariable primary rights.

Embodiment 1

20 mg of C ₂ N graphene was weighed and added to 200 mL of acetone, and ultrasonically irradiated at 200 W for 30 minutes to obtain a 0.1 mg/mL C ₂ N graphene dispersion. Then, 42 mg of chloroplatinic acid was added to the above C ₂ N graphene dispersion under a nitrogen atmosphere to obtain a mixed dispersion. After heating the mixed dispersion to 50 ° C, 4 mg of sodium borohydride was added to carry out a reaction for 24 hours. Subsequently, the reaction product was centrifuged, washed, and dried to obtain a C ₂ N graphene composite platinum nanocatalyst.

Embodiment 2

20 mg of C ₂ N graphene was weighed into 10 mL of N-methylpyrrolidone, and 300 minutes of ultrasonication for 20 minutes gave a C ₂ N graphene dispersion having a concentration of 2 mg/mL. Then, 65 mg of chloroplatinic acid and 52 mg of chloroauric acid were added to the above C ₂ N graphene dispersion under a nitrogen atmosphere. After the mixed solution was heated to 200 ° C, 28 mg of ascorbic acid was added and reacted for 1 hour. Next, the reactant was centrifuged, washed, and dried to obtain a C ₂ N graphene-complex platinum binary noble metal nanocatalyst.

Embodiment 3

20 mg of C ₂ N graphene was weighed into 10 mL of N-methylpyrrolidone, and 400 W was ultrasonicated for 10 minutes to obtain a 2 mg/mL C ₂ N graphene dispersion. Then, under the protection of a nitrogen atmosphere, 164 mg of chloroplatinic acid and 51 mg of iron dichloride were added to the above C ₂ N graphene dispersion. After the mixed solution was heated to 150 ° C, 13 mg of hydrazine hydrate was added and reacted for 12 hours. Next, the reactant was centrifuged, washed, and dried to obtain a C ₂ N graphene composite platinum iron binary metal nanocatalyst.

Embodiment 4

20 mg of C ₂ N graphene was weighed into 10 mL of N-methylpyrrolidone, and ultrasonically irradiated at 250 W for 20 minutes to obtain a 2 mg/mL C ₂ N graphene dispersion. Then, 2 mg of chloroplatinic acid, 1.6 mg of chloroauric acid, and 1.2 mg of iron dichloride were added to the above C ₂ N graphene dispersion under a nitrogen atmosphere. After the mixed solution was heated to 150 ° C, 0.25 mg of sodium borohydride was added and reacted for 20 hours. Next, the reactant was centrifuged, washed, and dried to obtain a C ₂ N graphene composite platinum-gold iron ternary metal nanocatalyst.

Embodiment 5

20 mg of C ₂ N graphene was weighed into 10 mL of N-methylpyrrolidone, and 200 W was ultrasonicated for 30 minutes to obtain a 2 mg/mL C ₂ N graphene dispersion. Then, 52 mg of chloroplatinic acid, 60 mg of nickel dichloride and 20 mg of iron dichloride were added to the above C ₂ N graphene dispersion under a nitrogen atmosphere. After the mixed solution was heated to 150 ° C, 4.4 mg of hydrazine hydrate was added and reacted for 12 hours. Next, the reactant was centrifuged, washed, and dried to obtain a C ₂ N graphene-composite platinum-nickel-iron ternary metal nanocatalyst.

Embodiment 6

20 mg of C ₂ N graphene was weighed into 10 mL of water, and ultrasonication was carried out for 30 minutes to obtain a 2 mg/mL C ₂ N graphene dispersion. Then, under the protection of a nitrogen atmosphere, 26 mg of chloroauric acid, 60 mg of nickel dichloride and 20 mg of iron dichloride were added to the above C ₂ N graphene dispersion. After the mixed solution was heated to 90 ° C, 25 mg of ascorbic acid was added and reacted for 2 hours. Next, the reactant was centrifuged, washed, and dried to obtain a C ₂ N graphene-composite gold-iron-nickel ternary metal nanocatalyst.

Example 7

20 mg of C ₂ N graphene was weighed into 10 mL of ethanol, and ultrasonication was carried out for 30 minutes to obtain a 2 mg/mL C ₂ N graphene dispersion. Then, under the protection of a nitrogen atmosphere, 32 mg of chloroplatinic acid, 26 mg of chloroauric acid, 60 mg of nickel dichloride and 20 mg of iron dichloride were added to the above C ₂ N graphene dispersion. After the mixed solution was heated to 80 ° C, 30 mg of ascorbic acid was added and reacted for 3 hours. Next, the reactant was centrifuged, washed, and dried to obtain a C ₂ N graphene composite platinum gold iron nickel quaternary metal nanocatalyst.

Effect embodiment

In order to strongly support the beneficial effects brought by the technical solutions of the embodiments of the present invention, the following performance tests are provided:

1, load rate

The elemental composition of the product was analyzed by inductively coupled plasma emission spectroscopy (ICP) to determine the loading ratio of the C ₂ N graphene composite noble metal nano catalyst obtained in the first to seventh embodiments of the present invention, that is, the mass ratio of the noble metal nanoparticles to the C ₂ N graphene carrier. . The results are shown in Table 1:

Table 1

	Embodiment 1	Embodiment 2	Embodiment 3	Embodiment 4	Embodiment 5	Embodiment 6	Example 7
Load rate	1:1	3:1	5:1	0.2:1	1.4:1	1.6:1	2.2:1

2, precious metal nanoparticle size

The average size of the noble metal nanoparticles in the C ₂ N graphene-complex noble metal nano-catalyst obtained in Examples 1 to 7 of the present invention was obtained by analyzing the morphology of the product by transmission electron microscopy (TEM). The results are shown in Table 2:

Table 2

3. Catalytic activity and cycle performance

The C ₂ N graphene composite precious metal nanocatalyst obtained in the above Examples 1 to 7 was ultrasonically dispersed in N-methylpyrrolidone to prepare a dispersion of 1.0 mg/mL, and 5 μl of the above dispersion was spin-coated to be polished and cleaned. The surface of the glassy carbon electrode is allowed to dry. The electrode was placed in an oxygen-saturated 0.5 M sulfuric acid at 50 mV/s for cyclic voltammetry scanning using a conventional three-electrode system to determine the ultimate exchange current density. After 20,000 seconds of operation, the limit exchange current density attenuation was known. The measurement results are shown in Table 3:

table 3

It can be seen from the above Table 3 that the C ₂ N graphene composite noble metal nano catalyst obtained in Examples 1 to 7 has high catalytic activity, and the first ultimate exchange current density mA/cm ² reaches 1-5 times of the commercial platinum carbon catalyst, and the work is 20,000 seconds. After that, the attenuation is small and the cycle performance is good.

4, stability

The C ₂ N graphene composite noble metal nanocatalyst after the above work was observed under a transmission electron microscope. The results show that the noble metal nanoparticles in the catalyst are uniformly dispersed, no aggregation occurs, and the size does not change significantly, so the catalyst has good stability.

In summary, the C ₂ N graphene composite noble metal nano catalyst provided by the above embodiment of the present invention uses C ₂ N graphene as a catalyst carrier, because the nitrogen atom in the C ₂ N graphene is densely distributed and uniformly distributed throughout the graphene two-dimensional. The plane, thus the noble metal nanoparticles can be uniformly dispersed on the graphene surface by coordination with nitrogen atoms, so that the catalyst has excellent properties such as high activity, good thermal stability, high mechanical strength, etc., and finally can improve fuel. The power performance and service life of the battery and the metal air battery solve the problems of low loading, poor dispersion and poor catalyst stability of the noble metal nanoparticles on the graphene carrier in the prior art.

Claims (10)

1. A C ₂ N graphene composite noble metal nanocatalyst, comprising: a C ₂ N graphene carrier and a catalytically active noble metal nanoparticle attached to a surface of the C ₂ N graphene carrier, the noble metal nanoparticle passing uniformly distributed in the carrier C ₂ N graphene surface-bound ligand with the nitrogen atom C ₂ N graphene carrier.
2. The C ₂ N graphene composite noble metal nanocatalyst according to claim 1 , wherein a mass ratio of the noble metal nanoparticles to the C ₂ N graphene carrier is 0.2-5:1.
3. The C ₂ N graphene composite noble metal nanocatalyst according to claim 1 , wherein the catalytically active noble metal nanoparticles are formed of one or more metals of Pt, Au, Pd, Ru, and Ag. An alloy, or an alloy of one or more of Pt, Au, Pd, Ru, Ag, and one or more of Fe, Co, Cr, Ni, Sn, Re.
4. The C ₂ N graphene-complex noble metal nanocatalyst according to claim 1, wherein the catalytically active noble metal nanoparticles have a diameter of 0.4 nm to 0.9 nm.
5. A preparation method of a C ₂ N graphene composite noble metal nano catalyst comprises the following steps:

   Step 1: placing C ₂ N graphene in a solvent, and obtaining a C ₂ N graphene dispersion after sonication;

   Step 2: adding a noble metal precursor to the C ₂ N graphene dispersion obtained above to obtain a mixed dispersion under an inert atmosphere, heating the mixed dispersion to 60-200 ° C, and then adding a reducing agent, wherein the precious metal precursor: C ₂ N graphene: reducing agent mass ratio = 0.5-20: 1: 0.3-15, after 1-24 hours of reaction, centrifugation, washing, and drying to obtain a C ₂ N graphene composite noble metal nanocatalyst, the C _{The 2} N graphene composite noble metal nanocatalyst comprises a C ₂ N graphene carrier and catalytically active noble metal nanoparticles attached to the surface of the C ₂ N graphene carrier, the noble metal nanoparticles passing through the C ₂ N graphene The nitrogen atoms in the carrier are coordinately bonded to be uniformly distributed on the surface of the C ₂ N graphene carrier.
6. The preparation method according to claim 5, wherein in the step 1, the solvent comprises ethanol, acetone, tetrahydrofuran, water or N-methylpyrrolidone.
7. The preparation method according to claim 5, wherein in the step 1, the concentration of the C ₂ N graphene dispersion is 0.1 to 2.0 mg/mL.
8. The preparation method according to claim 5, wherein in the step 2, the noble metal precursor is one or more of an ionic salt or an acid of Pt, Au, Pd, Ru or Ag, or Pt, Au a mixture of one or more of an ionic salt or an acid of Pd, Ru, Ag and one or more of an ionic salt or an acid of Fe, Co, Cr, Ni, Sn, Re.
9. The preparation method according to claim 5, wherein in the step 2, the reducing agent is one of sodium borohydride, hydrazine hydrate and ascorbic acid.
10. A fuel cell or a metal-air battery characterized by using the C ₂ N graphene-complex noble metal nano catalyst according to any one of claims 1 to 4 as a catalyst.

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