CN113996325B - Nitrogen-doped graphene copper-based bimetallic monatomic catalyst and preparation method and application thereof - Google Patents

Nitrogen-doped graphene copper-based bimetallic monatomic catalyst and preparation method and application thereof Download PDF

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CN113996325B
CN113996325B CN202111228665.4A CN202111228665A CN113996325B CN 113996325 B CN113996325 B CN 113996325B CN 202111228665 A CN202111228665 A CN 202111228665A CN 113996325 B CN113996325 B CN 113996325B
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陈海群
何光裕
赵宜涛
陈群
李乐
朱俊武
付永胜
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Changzhou University
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Abstract

The invention discloses a nitrogen-doped graphene copper-based bimetallic monatomic catalyst as well as a preparation method and application thereof, wherein the catalyst is composed of nitrogen-doped graphene loaded monatomic copper and transition metal, the loading amount of the metal copper in the catalyst is 0.5-6.0%, and the loading amount of the transition metal M is 0.1-3.0%; wherein the transition metal M comprises chromium, iron, cobalt, nickel, manganese, vanadium and molybdenum. The nitrogen-doped graphene with a large specific surface area is used as a carrier, so that the dispersion and fixation of a monatomic catalyst are facilitated, the porous structure is further provided, the rapid mass and energy transfer can be realized, the rich N atoms are used as anchoring centers, the anchoring and the dispersion of the monatomic Cu/M centers are facilitated, a large number of N atoms can form a coordination effect with metal Cu/M in a high-temperature treatment process, the anchoring amount of the monatomic Cu/M is improved, the monatomic Cu/M species are strongly anchored and confined on the derived nitrogen-doped graphene by the N atoms, and the problem of dissolution and desorption cannot occur.

Description

Nitrogen-doped graphene copper-based bimetallic monatomic catalyst and preparation method and application thereof
Technical Field
The invention belongs to the technical field of heterogeneous catalysts, and particularly relates to a nitrogen-doped graphene copper-based bimetallic monatomic catalyst as well as a preparation method and application thereof.
Background
Phenol is an important organic chemical raw material and is widely applied to the fields of dyes, polymers, plastics, medicines, pesticides and the like. The current industrial production method of phenol is mainly an isopropyl benzene method, but the process flow is complex, the reaction steps are multiple, and the development of the process is limited by the parallel product of acetone.
In recent years, people begin with the aspects of improving atom economy, saving energy, protecting environment and the like, gradually shift attention to the preparation of phenol by directly catalyzing benzene hydroxylation, and directly catalyze the benzene hydroxylation to prepare phenol, so that the method has the advantages of simple process, short reaction steps and low pollution, is an environment-friendly catalytic synthesis process, and has wide industrial application prospect.
However, this is a reaction for directly introducing a hydroxyl group into an aromatic ring to produce a hydroxyl compound by activating an inert C — H bond, and is a challenging problem in synthetic chemistry, and the key is the development of a highly active and highly selective catalyst.
Disclosure of Invention
This section is for the purpose of summarizing some aspects of embodiments of the invention and to briefly introduce some preferred embodiments. In this section, as well as in the abstract and the title of the invention of this application, simplifications or omissions may be made to avoid obscuring the purpose of the section, the abstract and the title, and such simplifications or omissions are not intended to limit the scope of the invention.
The present invention has been made keeping in mind the above and/or other problems occurring in the prior art.
Therefore, the invention aims to overcome the defects in the prior art and provide a nitrogen-doped graphene copper-based bimetallic monatomic catalyst.
In order to solve the technical problems, the invention provides the following technical scheme: the nitrogen-doped graphene copper-based bimetallic single-atom catalyst is composed of nitrogen-doped graphene loaded single-atom copper and transition metal, wherein the loading amount of the metal copper in the catalyst is 0.5-6.0%, and the loading amount of the transition metal M is 0.1-3.0%; wherein the transition metal M comprises chromium, iron, cobalt, nickel, manganese, vanadium and molybdenum.
The invention further aims to overcome the defects in the prior art and provide a preparation method of the nitrogen-doped graphene copper-based bimetallic monatomic catalyst.
In order to solve the technical problems, the invention provides the following technical scheme: a preparation method of a nitrogen-doped graphene copper-based bimetallic monatomic catalyst comprises the following steps,
preparing a graphene oxide dispersion liquid;
adding dicyandiamide (DCD) and soluble salt of transition metal M into the graphene oxide dispersion liquid, stirring at room temperature for 10-12 h, and freeze-drying to obtain an M/DCD/GO precursor;
wrapping the obtained M/DCD/GO precursor with a copper mesh, putting the wrapped precursor into a quartz boat, and putting the quartz boat in N2Heating to 600 ℃ under the atmosphere, treating for 2-3 h, treating for 1-2 h at 800 ℃, and cooling to room temperature to obtain black powder;
adding H into the obtained black powder2SO4And (3) completely immersing the solution in the material, stirring at a constant temperature of 60-80 ℃ for 10-12 h, filtering and washing to be neutral, and drying the obtained solid in a vacuum drying oven to obtain the catalyst.
As a preferred scheme of the preparation method of the nitrogen-doped graphene copper-based bimetallic single-atom catalyst, the preparation method comprises the following steps: the transition metal M includes chromium, iron, cobalt, nickel, manganese, vanadium and molybdenum.
As a preferred scheme of the preparation method of the nitrogen-doped graphene copper-based bimetallic monatomic catalyst, the preparation method comprises the following steps: adding dicyandiamide (DCD) and soluble salt of transition metal M into graphene oxide dispersion liquid, wherein,
the mass ratio of the dicyandiamide DCD to the graphene oxide is 3: 1-21: 1, and the transition metal M soluble salt accounts for 0.1-5% of the total mass of the dicyandiamide DCD and the graphene oxide.
As a preferred scheme of the preparation method of the nitrogen-doped graphene copper-based bimetallic monatomic catalyst, the preparation method comprises the following steps: said H2SO4Solution, concentration 0.5M.
As a preferred scheme of the preparation method of the nitrogen-doped graphene copper-based bimetallic monatomic catalyst, the preparation method comprises the following steps: and heating to 600 ℃, wherein the heating rate is 5 ℃/min.
As a preferred scheme of the preparation method of the nitrogen-doped graphene copper-based bimetallic monatomic catalyst, the preparation method comprises the following steps: the loading amount of the metal copper in the catalyst is 0.5-6.0%.
The invention also aims to overcome the defects in the prior art and provide the application of the nitrogen-doped graphene copper-based bimetallic single-atom catalyst in the preparation of phenol by directly oxidizing benzene.
The invention has the beneficial effects that:
(1) the invention provides a preparation method of a nitrogen-doped graphene copper-based bimetallic monatomic catalyst, which takes nitrogen-doped graphene with a larger specific surface area as a carrier, is beneficial to the dispersion and fixation of the monatomic catalyst, has a porous structure, and can realize rapid mass and energy transfer and an adjustable chemical coordination environment;
(2) according to the invention, nitrogen-doped graphene is taken as a carrier, N atoms rich in the nitrogen-doped graphene are taken as an anchoring center, so that the anchoring and dispersion of a monoatomic Cu/M center are facilitated, a large number of N atoms can form a coordination effect with metal Cu/M in a high-temperature treatment process, the anchoring amount of the monoatomic Cu/M is increased, even if a small number of nano particles are inevitably formed, and the monoatomic Cu/M is subjected to a subsequent acid leaching process (diluted H) to form a nano-particle2SO4) The method can remove the nitrogen-doped graphene, and monoatomic Cu/M species are strongly anchored and limited on the derived nitrogen-doped graphene by N atoms, so that the problem of dissolution and desorption cannot occur;
(3) the SA-Cu/M-NRGO catalyst provided by the invention is expected to show high catalytic performance in the reaction of preparing high value-added phenolic compounds by hydroxylation of aromatic hydrocarbons.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise. Wherein:
FIG. 1 is an XRD pattern of the SA-Cu/M-NRGO composite material prepared by the present invention.
FIG. 2 is an SEM image of the SA-Cu/M-NRGO composite material prepared in example 6 of the invention.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention more comprehensible, specific embodiments thereof are described in detail below with reference to examples of the specification.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, the present invention may be practiced otherwise than as specifically described herein, and it will be appreciated by those skilled in the art that the present invention may be practiced without departing from the spirit and scope of the present invention and that the present invention is not limited by the specific embodiments disclosed below.
Furthermore, reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one implementation of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments.
The copper mesh is a T1 pure copper mesh, and is 30-600 meshes;
the Cr soluble salt is chromium nitrate; other raw materials, which are not specifically described, are all commercially available.
Example 1:
(1) carrying out ultrasonic stripping on graphite oxide to obtain Graphene Oxide (GO), and uniformly mixing and dispersing the graphite oxide and water to obtain a graphene oxide dispersion liquid, wherein the concentration of the graphene oxide dispersion liquid is 4 mg/mL;
(2) adding dicyandiamide (DCD) into the mixture obtained in the step (1), wherein the mass ratio of DCD to pure GO is 3:1, the mass ratio of the soluble salt of the transition metal Cr is 0.1% of the total mass of DCD and GO, stirring for 10h at normal temperature, and then freezing and drying to obtain the Cr/DCD/GO precursor.
(3) Wrapping the precursor obtained in the step (2) with a copper mesh, placing the wrapped precursor into a quartz boat, processing the precursor at 600 ℃ for 2h and 800 ℃ for 1h at a heating rate of 5 ℃/min under the atmosphere of N2, and cooling the precursor to room temperature to obtain black powder;
(4) adding 0.5M H to the black powder obtained in (3)2SO4The solution is stirred at a constant temperature of 80 ℃ until the material is completely immersedAfter 10 hours, filtering and washing to be neutral, and putting the solid in a vacuum drying oven for drying to obtain the catalyst, wherein the loading capacity of metal copper in the catalyst is 0.86%, and the loading capacity of metal chromium in the catalyst is 0.12%;
the metal loading was determined by ICP, weighing the catalyst-digestion-dilution-measurement-calibration standard curve-calculation to give the content.
10mg of the SA-Cu/Cr-NRGO catalyst is applied to the reaction of preparing phenol by directly oxidizing benzene: 0.1mL of reactant benzene, 2mL of oxidant hydrogen peroxide, 2mL of solvent acetonitrile, and 25 ℃ of reaction temperature, reacting for 24h, wherein the reaction result is as follows: the yield of phenol was 7.24%.
Example 2:
(1) carrying out ultrasonic stripping on graphite oxide to obtain Graphene Oxide (GO), and uniformly mixing and dispersing the graphite oxide and water to obtain a graphene oxide dispersion liquid, wherein the concentration of the graphene oxide dispersion liquid is 4 mg/mL;
(2) adding dicyandiamide (DCD) into the mixture obtained in the step (1), wherein the mass ratio of DCD to pure GO is 6:1, the mass ratio of the soluble salt of the transition metal Cr is 0.3% of the total mass of DCD and GO, stirring for 10h at normal temperature, and then freezing and drying to obtain the Cr/DCD/GO precursor.
(3) Wrapping the precursor obtained in the step (2) with a copper mesh, placing the wrapped precursor into a quartz boat, processing the precursor at 600 ℃ for 2h and 800 ℃ for 1h at a heating rate of 5 ℃/min under the atmosphere of N2, and cooling the precursor to room temperature to obtain black powder;
(4) and (3) adding 0.5M H2SO4 solution into the black powder obtained in the step (3) until the material is completely immersed, stirring at the constant temperature of 80 ℃ for 10 hours, filtering and washing to be neutral, and drying the solid in a vacuum drying oven to obtain the catalyst, wherein the loading capacity of metallic copper in the catalyst is 1.73%, and the loading capacity of metallic chromium in the catalyst is 0.21%.
10mg of the SA-Cu/Cr-NRGO catalyst is applied to the reaction of preparing phenol by directly oxidizing benzene: 0.1mL of reactant benzene, 2mL of oxidant hydrogen peroxide, 2mL of solvent acetonitrile, and 25 ℃ of reaction temperature, reacting for 24h, wherein the reaction result is as follows: the phenol yield was 9.32%.
Example 3:
(1) carrying out ultrasonic stripping on graphite oxide to obtain Graphene Oxide (GO), and uniformly mixing and dispersing the graphite oxide and water to obtain a graphene oxide dispersion liquid, wherein the concentration of the graphene oxide dispersion liquid is 4 mg/mL;
(2) adding dicyandiamide (DCD) into the mixture obtained in the step (1), wherein the mass ratio of DCD to pure GO is 9:1, the mass ratio of the soluble salt of the transition metal Cr is 0.5% of the total mass of DCD and GO, stirring for 10h at normal temperature, and then freezing and drying to obtain the Cr/DCD/GO precursor.
(3) Wrapping the precursor obtained in the step (2) with a copper mesh, placing the wrapped precursor into a quartz boat, processing the precursor at 600 ℃ for 2h and 800 ℃ for 1h at a heating rate of 5 ℃/min under the atmosphere of N2, and cooling the precursor to room temperature to obtain black powder;
(4) adding 0.5M H to the black powder obtained in (3)2SO4And (3) completely immersing the solution in the material, stirring at the constant temperature of 80 ℃ for 10 hours, filtering and washing to be neutral, and drying the solid in a vacuum drying oven to obtain the catalyst, wherein the loading capacity of the metal copper in the catalyst is 3.30%.
10mg of 3.30% SA-Cu-N/G catalyst was applied to the reaction of preparing phenol by direct oxidation of benzene: 0.1mL of reactant benzene, 2mL of oxidant hydrogen peroxide, 2mL of solvent acetonitrile, and 25 ℃ of reaction temperature, reacting for 24h, wherein the reaction result is as follows: the phenol yield was 8.24%.
Example 4:
(1) carrying out ultrasonic stripping on graphite oxide to obtain Graphene Oxide (GO), and uniformly mixing and dispersing the graphite oxide and water to obtain a graphene oxide dispersion liquid, wherein the concentration of the graphene oxide dispersion liquid is 4 mg/mL;
(2) adding dicyandiamide (DCD) into the mixture obtained in the step (1), wherein the mass ratio of DCD to pure GO is 12:1, the mass ratio of the soluble salt of the transition metal Cr is 0.7% of the total mass of DCD and GO, stirring for 10h at normal temperature, and then freezing and drying to obtain the Cr/DCD/GO precursor.
(3) Wrapping the precursor obtained in the step (2) with a copper mesh, placing the wrapped precursor into a quartz boat, processing the precursor at 600 ℃ for 2h and 800 ℃ for 1h at a heating rate of 5 ℃/min under the atmosphere of N2, and cooling the precursor to room temperature to obtain black powder;
(4) and (3) adding 0.5M H2SO4 solution into the black powder obtained in the step (3) until the material is completely immersed, stirring at the constant temperature of 80 ℃ for 10 hours, filtering and washing to be neutral, and drying the solid in a vacuum drying oven to obtain the catalyst, wherein the loading capacity of metallic copper in the catalyst is 4.79%, and the loading capacity of metallic chromium in the catalyst is 0.46%.
10mg of the SA-Cu/Cr-NRGO catalyst is applied to the reaction of preparing phenol by directly oxidizing benzene: 0.1mL of reactant benzene, 2mL of oxidant hydrogen peroxide, 2mL of solvent acetonitrile, and 25 ℃ of reaction temperature, reacting for 24h, wherein the reaction result is as follows: the phenol yield was 10.69%.
Example 5:
(1) carrying out ultrasonic stripping on graphite oxide to obtain Graphene Oxide (GO), and uniformly mixing and dispersing the graphite oxide and water to obtain a graphene oxide dispersion liquid, wherein the concentration of the graphene oxide dispersion liquid is 4 mg/mL;
(2) adding dicyandiamide (DCD) into the mixture obtained in the step (1), wherein the mass ratio of DCD to pure GO is 15:1, the mass ratio of the soluble salt of the transition metal Cr is 0.9% of the total mass of DCD and GO, stirring for 10h at normal temperature, and then freezing and drying to obtain the Cr/DCD/GO precursor.
(3) Wrapping the precursor obtained in the step (2) with a copper mesh, placing the wrapped precursor into a quartz boat, processing the precursor at 600 ℃ for 2h and 800 ℃ for 1h at a heating rate of 5 ℃/min under the atmosphere of N2, and cooling the precursor to room temperature to obtain black powder;
(4) and (3) adding 0.5M H2SO4 solution into the black powder obtained in the step (3) until the material is completely immersed, stirring at the constant temperature of 80 ℃ for 10 hours, filtering and washing to be neutral, and drying the solid in a vacuum drying oven to obtain the catalyst, wherein the loading capacity of metallic copper in the catalyst is 4.96%, and the loading capacity of metallic chromium in the catalyst is 0.67%.
10mg of the SA-Cu/Cr-NRGO catalyst is applied to the reaction of preparing phenol by directly oxidizing benzene: 0.1mL of reactant benzene, 2mL of oxidant hydrogen peroxide, 2mL of solvent acetonitrile, and 25 ℃ of reaction temperature, reacting for 24h, wherein the reaction result is as follows: the yield of phenol was 11.32%.
Example 6:
(1) carrying out ultrasonic stripping on graphite oxide to obtain Graphene Oxide (GO), and uniformly mixing and dispersing the graphite oxide and water to obtain a graphene oxide dispersion liquid, wherein the concentration of the graphene oxide dispersion liquid is 4 mg/mL;
(2) adding dicyandiamide (DCD) into the mixture obtained in the step (1), wherein the mass ratio of DCD to pure GO is 18:1, the mass ratio of the soluble salt of the transition metal Cr is 1.1% of the total mass of DCD and GO, stirring for 10h at normal temperature, and then freezing and drying to obtain a DCD/GO precursor.
(3) Wrapping the precursor obtained in the step (2) with a copper mesh, placing the wrapped precursor into a quartz boat, processing the precursor at 600 ℃ for 2h and 800 ℃ for 1h at a heating rate of 5 ℃/min under the atmosphere of N2, and cooling the precursor to room temperature to obtain black powder;
(4) and (4) adding 0.5M H2SO4 solution into the black powder obtained in the step (3) until the material is completely immersed, stirring at the constant temperature of 80 ℃ for 10 hours, filtering and washing to be neutral, and drying the solid in a vacuum drying oven to obtain the catalyst, wherein the metal copper loading in the catalyst is 5.47%, and the metal chromium loading in the catalyst is 0.69%.
10mg of the SA-Cu/Cr-NRGO catalyst is applied to the reaction of preparing phenol by directly oxidizing benzene: 0.1mL of reactant benzene, 2mL of oxidant hydrogen peroxide, 2mL of solvent acetonitrile, and 25 ℃ of reaction temperature, reacting for 24h, wherein the reaction result is as follows: the yield of phenol was 13.01%.
Adding dicyandiamide DCD and soluble salt of transition metal M (M is iron, cobalt, nickel, manganese, vanadium and molybdenum) into graphene oxide dispersion liquid, stirring at room temperature for 10-12 h, and freeze-drying to obtain an M/DCD/GO precursor; wrapping the obtained M/DCD/GO precursor with a copper mesh, putting the wrapped precursor into a quartz boat, and putting the quartz boat in N2Heating to 600 ℃ under the atmosphere, treating for 2-3 h, treating for 1-2 h at 800 ℃, and cooling to room temperature to obtain black powder; adding H into the obtained black powder2SO4And (3) completely immersing the solution in the material, stirring at a constant temperature of 60-80 ℃ for 10-12 h, filtering and washing to be neutral, putting the obtained solid in a vacuum drying oven for drying, and obtaining the catalyst, wherein the XRD (X-ray diffraction) pattern of the prepared SA-Cu/M-NRGO composite material is shown in figure 1.
An SEM image of the SA-Cu/M-NRGO composite material prepared in the embodiment 6 of the invention is shown in figure 2.
Example 7:
(1) carrying out ultrasonic stripping on graphite oxide to obtain Graphene Oxide (GO), and uniformly mixing and dispersing the graphite oxide and water to obtain a graphene oxide dispersion liquid, wherein the concentration of the graphene oxide dispersion liquid is 4 mg/mL;
(2) adding dicyandiamide (DCD) into the mixture obtained in the step (1), wherein the mass ratio of DCD to pure GO is 21:1, the mass ratio of the soluble salt of the transition metal Cr is 1.3% of the total mass of DCD and GO, stirring for 10h at normal temperature, and then freezing and drying to obtain the Cr/DCD/GO precursor.
(3) Wrapping the precursor obtained in the step (2) with a copper mesh, placing the wrapped precursor into a quartz boat, processing the precursor at 600 ℃ for 2h and 800 ℃ for 1h at a heating rate of 5 ℃/min under the atmosphere of N2, and cooling the precursor to room temperature to obtain black powder;
(4) and (3) adding 0.5M H2SO4 solution into the black powder obtained in the step (3) until the material is completely immersed, stirring at the constant temperature of 80 ℃ for 10 hours, filtering and washing to be neutral, and drying the solid in a vacuum drying oven to obtain the catalyst, wherein the loading capacity of metallic copper in the catalyst is 3.90%, and the loading capacity of metallic chromium in the catalyst is 0.53%.
10mg of SA-Cu-N/G catalyst is applied to the reaction for preparing phenol by directly oxidizing benzene: 0.1mL of reactant benzene, 2mL of oxidant hydrogen peroxide, 2mL of solvent acetonitrile, and 25 ℃ of reaction temperature, reacting for 24h, wherein the reaction result is as follows: the phenol yield was 9.38%.
Example 8:
(1) carrying out ultrasonic stripping on graphite oxide to obtain Graphene Oxide (GO), and uniformly mixing and dispersing the graphite oxide and water to obtain a graphene oxide dispersion liquid, wherein the concentration of the graphene oxide dispersion liquid is 4 mg/mL;
(2) adding dicyandiamide (DCD) into the mixture obtained in the step (1), wherein the mass ratio of DCD to pure GO is 21:1, the mass ratio of the soluble salt of the transition metal Cr is 1.1% of the total mass of DCD and GO, stirring for 10h at normal temperature, and then freezing and drying to obtain a DCD/GO precursor.
(3) Wrapping the precursor obtained in the step (2) with a copper mesh, placing the wrapped precursor into a quartz boat, processing the precursor at 600 ℃ for 2h and 800 ℃ for 1h at a heating rate of 5 ℃/min under the atmosphere of N2, and cooling the precursor to room temperature to obtain black powder;
(4) adding 0.5M H to the black powder obtained in (3)2SO4And (3) completely immersing the solution in the material, stirring at the constant temperature of 80 ℃ for 10 hours, filtering and washing to be neutral, and drying the solid in a vacuum drying oven to obtain the catalyst, wherein the loading capacity of the metal copper in the catalyst is 2.53%, and the loading capacity of the metal chromium in the catalyst is 0.41%.
10mg of the SA-Cu/Cr-NRGO catalyst is applied to the reaction of preparing phenol by directly oxidizing benzene: 0.1mL of reactant benzene, 2mL of oxidant hydrogen peroxide, 2mL of solvent acetonitrile, and 25 ℃ of reaction temperature, reacting for 24h, wherein the reaction result is as follows: the phenol yield was 7.84%.
It can be seen that the amount of DCD is too large, which has a poor influence on the catalytic effect, and destroys the electronic structure of N-doped graphene, resulting in a decrease in the metal loading and a decrease in the activity.
Comparative example 1:
(1) carrying out ultrasonic stripping on graphite oxide to obtain Graphene Oxide (GO), and uniformly mixing and dispersing the graphite oxide and water to obtain a graphene oxide dispersion liquid, wherein the concentration of the graphene oxide dispersion liquid is 4 mg/mL;
(2) and (3) directly freezing and drying the (1) to obtain a GO precursor.
(3) Wrapping the precursor obtained in the step (2) with a copper mesh, placing the wrapped precursor into a quartz boat, processing the precursor at 600 ℃ for 2h and 800 ℃ for 1h at a heating rate of 5 ℃/min under the atmosphere of N2, and cooling the precursor to room temperature to obtain black powder;
(4) and (3) adding the black powder obtained in the step (3) into a 0.5M H2SO4 solution until the material is completely immersed, stirring at the constant temperature of 80 ℃ for 10 hours, filtering and washing to be neutral, and drying the solid in a vacuum drying oven to obtain the catalyst, wherein the copper loading amount in the catalyst is 0.
Taking 10mg of Cu-RGO catalyst to be applied to the reaction for preparing phenol by directly oxidizing benzene: 0.1mL of reactant benzene, 2mL of oxidant hydrogen peroxide, 2mL of solvent acetonitrile, and 25 ℃ of reaction temperature, reacting for 24h, wherein the reaction result is as follows: the yield of phenol was 0.1%.
Comparative example 2:
(1) carrying out ultrasonic stripping on graphite oxide to obtain Graphene Oxide (GO), and uniformly mixing and dispersing the graphite oxide and water to obtain a graphene oxide dispersion liquid, wherein the concentration of the graphene oxide dispersion liquid is 4 mg/mL;
(2) adding a 1.1% transition metal Cr soluble salt based on the weight of GO into the solution obtained in the step (1), stirring for 10 hours at normal temperature, and then freeze-drying to obtain a Cr/GO precursor.
(3) Directly putting the precursor obtained in the step (2) into a quartz boat, processing at 600 ℃ for 2h and 800 ℃ for 1h at the heating rate of 5 ℃/min under the atmosphere of N2, and cooling to room temperature to obtain black powder;
(4) and (3) adding the black powder obtained in the step (3) into a 0.5M H2SO4 solution until the material is completely immersed, stirring at the constant temperature of 80 ℃ for 10 hours, filtering and washing to be neutral, and drying the solid in a vacuum drying oven to obtain the catalyst, wherein the chromium loading capacity of the catalyst is 0 Cr-RGO.
Taking 10mg of Cr-RGO catalyst to be applied to the reaction for preparing phenol by directly oxidizing benzene: 0.1mL of reactant benzene, 2mL of oxidant hydrogen peroxide, 2mL of solvent acetonitrile, and 25 ℃ of reaction temperature, reacting for 24h, wherein the reaction result is as follows: the yield of phenol was 0.1%.
Comparative example 3:
(1) carrying out ultrasonic stripping on graphite oxide to obtain Graphene Oxide (GO), and uniformly mixing and dispersing the graphite oxide and water to obtain a graphene oxide dispersion liquid, wherein the concentration of the graphene oxide dispersion liquid is 4 mg/mL;
(2) adding 1.1% of transition metal Cr soluble salt with the mass of GO into the mixture obtained in the step (1), stirring for 10 hours at normal temperature, and then freezing and drying to obtain a Cr/GO precursor.
(3) Wrapping the precursor obtained in the step (2) with a copper mesh, putting the wrapped precursor into a quartz boat, processing the precursor at 600 ℃ for 2h and 800 ℃ for 1h at a heating rate of 5 ℃/min under the atmosphere of N2, and cooling the precursor to room temperature to obtain black powder.
(4) And (3) adding the black powder obtained in the step (3) into a 0.5M H2SO4 solution until the material is completely immersed, stirring at the constant temperature of 80 ℃ for 10 hours, filtering and washing to be neutral, and drying the solid in a vacuum drying oven to obtain the catalyst, wherein the chromium loading in the catalyst is 0 Cu/Cr-RGO.
Taking 10mg of Cu/Cr-RGO catalyst to be applied to the reaction of preparing phenol by directly oxidizing benzene: 0.1mL of reactant benzene, 2mL of oxidant hydrogen peroxide, 2mL of solvent acetonitrile, and 25 ℃ of reaction temperature, reacting for 24h, wherein the reaction result is as follows: the yield of phenol was 0.1%.
The loading capacity of the metal copper is controlled by adjusting the content of DCD (dicyandiamide), CDC (chemical vapor deposition) pyrolysis generates nitrogen-containing gas, the quantity of the nitrogen-containing gas generated by different DCD contents is different, and the gases are based on strong Lewis acid-base interaction and directly capture Cu atoms to generate middle when passing through a compact Cu netSubstance Cu (NH)3) And x, capturing the intermediate substance by Graphene Oxide (GO) with a charged functional group on the surface to form a single-atom nitrogen-doped reduced graphene oxide graphene-based single-copper catalyst precursor, and removing nanoparticles, namely the target catalyst by acid washing.
Compared with the existing single-atom catalyst with a focusing single-active site, the monodisperse double-active site catalyst can submit metal loading capacity and increase the synergistic effect among sites; the preparation process is simple and universal; the larger nano particles generated in the preparation process can effectively increase the specific surface area. According to the invention, nitrogen-doped graphene is taken as a carrier, N atoms rich in the nitrogen-doped graphene are taken as an anchoring center, so that the anchoring and dispersion of a monoatomic Cu/M center are facilitated, a large number of N atoms can form a coordination effect with metal Cu/M in a high-temperature treatment process, the anchoring amount of the monoatomic Cu/M is increased, even if a small number of nano particles are inevitably formed, and the monoatomic Cu/M is subjected to a subsequent acid leaching process (diluted H) to form a nano-particle2SO4) The metal can be removed, and the monoatomic Cu/M species are strongly anchored and limited on the derived nitrogen-doped graphene by N atoms, so that the problem of dissolution cannot occur.
It should be noted that the above-mentioned embodiments are only for illustrating the technical solutions of the present invention and not for limiting, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, which should be covered by the claims of the present invention.

Claims (5)

1. A preparation method of a nitrogen-doped graphene copper-based bimetallic monatomic catalyst is characterized by comprising the following steps: comprises the steps of (a) preparing a mixture of a plurality of raw materials,
preparing a graphene oxide dispersion liquid;
adding dicyandiamide DCD and soluble salt of transition metal M into graphene oxide dispersion liquid, stirring at room temperature for 10-12 h, and freeze-drying to obtain an M/DCD/GO precursor;
wrapping the obtained M/DCD/GO precursor with a copper mesh, putting the wrapped precursor into a quartz boat, and putting the quartz boat in N2Heating under the atmosphereTreating at 600 ℃ for 2-3 h, treating at 800 ℃ for 1-2 h, and cooling to room temperature to obtain black powder;
adding H into the obtained black powder2SO4The solution is stirred for 10-12 hours at a constant temperature of 60-80 ℃ until the material is completely immersed, then the solution is filtered and washed to be neutral, and the obtained solid is placed in a vacuum drying oven to be dried, so that the catalyst is obtained; wherein the content of the first and second substances,
the loading capacity of the metal copper in the catalyst is 0.5-6.0%, and the loading capacity of the transition metal M is 0.1-3.0%;
the transition metal M includes chromium, iron, cobalt, nickel, manganese, vanadium and molybdenum.
2. The method for preparing the nitrogen-doped graphene copper-based bimetallic monatomic catalyst according to claim 1, wherein the method comprises the following steps: adding dicyandiamide DCD and soluble salt of transition metal M into graphene oxide dispersion liquid, wherein,
the mass ratio of the dicyandiamide DCD to the graphene oxide is 3: 1-21: 1, and the transition metal M soluble salt is 0.1-5% of the total mass of the dicyandiamide DCD and the graphene oxide.
3. The method for preparing the nitrogen-doped graphene copper-based bimetallic monatomic catalyst according to claim 1, wherein the method comprises the following steps: said H2SO4Solution, concentration 0.5M.
4. The method for preparing the nitrogen-doped graphene copper-based bimetallic monatomic catalyst according to claim 1, wherein the method comprises the following steps: and heating to 600 ℃, wherein the heating rate is 5 ℃/min.
5. The application of the nitrogen-doped graphene copper-based bimetallic single-atom catalyst prepared by the preparation method of any one of claims 1-4 in preparing phenol by directly oxidizing benzene.
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