CN116237077B

CN116237077B - Method for synthesizing metal single-atom catalyst by using metal phthalocyanine compound

Info

Publication number: CN116237077B
Application number: CN202310268054.5A
Authority: CN
Inventors: 刘学良; 杨慧敏; 孙金萍; 丁宏卫; 靳林
Original assignee: Zhoukou Normal University
Current assignee: Zhoukou Normal University
Priority date: 2023-03-20
Filing date: 2023-03-20
Publication date: 2023-10-17
Anticipated expiration: 2043-03-20
Also published as: CN116237077A

Abstract

The application provides a method for synthesizing a metal monoatomic catalyst by using a metal phthalocyanine compound, which belongs to the technical field of catalysts, wherein the metal monoatomic catalyst is obtained by taking the metal phthalocyanine compound and ammonium salt as raw materials and then pyrolyzing under the protection of inert gas.

Description

Method for synthesizing metal single-atom catalyst by using metal phthalocyanine compound

Technical Field

The application belongs to the technical field of catalysts, and particularly relates to a method for synthesizing a metal monoatomic catalyst by using a metal phthalocyanine compound.

Background

Monoatomic catalysts are catalysts in which isolated individual metal atoms are dispersed on a support material, with the isolated metal atoms as active centers. As an advanced novel catalyst, the single-atom catalyst has the advantages of clear structure, high catalytic activity, high selectivity and the like, and has great application prospect in industrial production of petroleum, chemical industry, biological medicine and the like. In the preparation method of the single-atom material, compared with methods such as atomic layer deposition, an impregnation method, photochemical reduction and the like, the high-temperature pyrolysis method is to carry out pyrolysis carbonization on a metal organic ligand, carbon, a template carrier and the like at a high temperature (600-1000 ℃) in an inert atmosphere, and metal atoms coordinate with heteroatoms such as N, P and the like in the carbon material to form isolated M-N-C (M refers to metal atoms) structure active centers, so that the preparation method is the most main method for preparing the single-atom catalyst at present. However, there are still many problems to be solved in the preparation process, such as low content of metal active center (generally less than 1.5 wt.%), easy aggregation of metal atoms to generate metal nano particles, difficulty in large-scale preparation, and the like, which limit the practical application of the single-atom catalyst.

Patent CN115672375a discloses a method for preparing a tungsten-molybdenum supported nitrogen-doped carbon single-atom catalyst, which comprises the steps of respectively placing tungsten or molybdenum oxide and ZIF-8 in the same porcelain boat without contact, and forming a metal single-atom catalyst through high-temperature atom migration, wherein the prepared single-atom catalyst has high activity in electrocatalytic reactions such as oxygen reduction, hydrogen evolution and the like; but the loading of metal atoms in the product is low, and the product needs dilute sulfuric acid washing, which is unfavorable for large-scale production. Patent CN111905794B provides another method for preparing a high-density iron monoatomic catalyst, which comprises pre-reacting ferric salt, sucrose, melamine and pore-forming agent to form a precursor, carbonizing at high temperature to form an iron monoatomic catalyst, removing the pore-forming agent with high-concentration sodium hydroxide, and obtaining the catalyst Fe-N ₄ The metal content of the catalyst is 5-12 wt%, high concentration sodium hydroxide is needed in the later stage of the patent, and the pollution is serious.

Disclosure of Invention

In order to solve the technical problems, the application provides a method for synthesizing a metal single-atom catalyst by using a metal phthalocyanine compound, and particularly relates to a method for synthesizing a metal single-atom-supported nitrogen-doped carbon catalyst of iron, cobalt, manganese, nickel, copper, zinc and the like.

In order to achieve the above object, the present application provides a method for synthesizing a metal monoatomic catalyst from a metal phthalocyanine compound, comprising the steps of:

(1) Mixing a metal phthalocyanine compound and an ammonium salt, and grinding to obtain a mixture;

(2) And (3) carrying out high-temperature pyrolysis on the mixture, and washing and drying the obtained product to obtain the metal monoatomic catalyst.

The metal phthalocyanine compound has high chemical stability and bright color, is widely used in the printing and dyeing industry, has a chemical structure in which metal atoms coordinate with nitrogen atoms in phthalocyanine and are positioned in the center of phthalocyanine molecules, has an active center structure similar to that of a single-atom catalyst, and is an excellent precursor for preparing the high-load metal single-atom catalyst. In the application, during the pyrolysis process of the metal phthalocyanine compound, partial metal atoms can migrate and aggregate into metal nano particles, the hydrogen halide gas generated by the decomposition of ammonium salt reacts with the migrated metal atoms to generate corresponding metal salts (metal chlorides or metal bromides), the metal nano particles are etched in situ or inhibited from forming, and finally the generated metal salts are removed by washing with water, so that the metal single-atom-supported nitrogen-doped carbon catalyst (metal single-atom catalyst) is obtained.

Further, the mass ratio of the metal phthalocyanine compound to the ammonium salt is 1:1-1:10, and the ammonium salt is excessively small and can be completely decomposed and sublimated before being raised to a specified temperature; excessive amounts result in waste of ammonium salts and reduced product yields.

Further, the metal phthalocyanine compound includes one of iron phthalocyanine, copper phthalocyanine, cobalt phthalocyanine, nickel phthalocyanine, zinc phthalocyanine and manganese phthalocyanine.

Further, the ammonium salt is ammonium chloride, ammonium bromide or a mixture thereof, and the ammonium salt is decomposed at high temperature to generate hydrogen halide gas (hydrogen chloride and hydrogen bromide), so that metal atoms migrating at high temperature can be etched in situ to generate metal halides, and the formation of metal nano particles is avoided.

Further, the high-temperature pyrolysis is performed under the protection of inert gas, and the inert gas is nitrogen or argon.

Further, the high-temperature pyrolysis is carried out at 550-700 ℃ for 2-4 hours, and the heating rate is 1-10 ℃/min, preferably 2-5 ℃/min.

A metal monoatomic catalyst synthesized according to the synthesis method described above.

The application of the metal monoatomic catalyst in catalytic oxidation and catalytic reduction.

Compared with the prior art, the application has the following advantages and technical effects:

the synthesis method is adopted to convert the metal phthalocyanine compound into the metal single-atom-supported nitrogen-doped carbon catalyst, and the metal single-atom-supported nitrogen-doped carbon catalyst comprises metal single-atom catalysts such as iron, cobalt, nickel, copper, manganese, zinc and the like, and the metal phthalocyanine compound is very easy to obtain as an industrial product; the preparation method has the advantages that no metal nano particles are formed in the product, strong acid washing is not needed, the method is simple, and the macro preparation of the metal monoatomic catalyst can be realized; the ammonium salt used can be recycled (after a very small amount of hydrogen halide reacts with metal, generated metal salt is remained in the sample, and the rest ammonium salt is decomposed at high temperature to generate hydrogen halide and ammonia gas, and the hydrogen halide and the ammonia gas are combined again in a low-temperature area to generate ammonium salt to be condensed in the low-temperature area, so that the recovery rate is approximately 90 percent), and the environment is friendly.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the application. In the drawings:

FIG. 1 is a scanning transmission electron microscope image of the spherical aberration correcting iron single atom catalyst prepared in example 1;

FIG. 2 is an EDS spectrum of the iron monoatomic catalyst prepared in example 1;

FIG. 3 is a synchrotron radiation analysis chart of the iron monoatomic catalyst prepared in example 1, wherein A is Fe K-side X-ray absorption near-side spectrum, and B is Fourier transform spectrum Fe K edge expansion X-ray absorption fine structure spectrum;

FIG. 4 is an X-ray diffraction pattern of the iron monoatomic catalyst prepared in example 3;

FIG. 5 is a transmission electron microscope image of the supported iron catalyst prepared in example 5;

FIG. 6 is a magnetic comparison of the iron catalysts prepared in example 1 and example 5;

FIG. 7 shows the color change of the solution before and after the reduction of 4-nitrophenol by using the iron single-atom catalyst obtained in example 1;

FIG. 8 is an absorption curve of the iron single-atom catalyst of example 1 in the front and rear solutions of 4-nitrophenol;

FIG. 9 is a UV-visible absorption spectrum of the iron monoatomic catalyst obtained in example 1 in catalytic oxidation of 3,3', 5' -Tetramethylbenzidine (TMB), showing TMB solution and TMB+H in this order from left to right in the left-hand inset ₂ O ₂ Solution and TMB+H ₂ O ₂ And (5) carrying out solution picture after the reaction of the reaction solution of the +iron monoatomic catalyst for 5 min.

Detailed Description

Various exemplary embodiments of the application will now be described in detail, which should not be considered as limiting the application, but rather as more detailed descriptions of certain aspects, features and embodiments of the application.

It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. In addition, for numerical ranges in this disclosure, it is understood that each intermediate value between the upper and lower limits of the ranges is also specifically disclosed. Every smaller range between any stated value or stated range, and any other stated value or intermediate value within the stated range, is also encompassed within the application. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned in this specification are incorporated by reference for the purpose of disclosing and describing the methods and/or materials associated with the documents. In case of conflict with any incorporated document, the present specification will control.

It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the application described herein without departing from the scope or spirit of the application. Other embodiments will be apparent to those skilled in the art from consideration of the specification of the present application. The specification and examples of the present application are exemplary only.

As used herein, the terms "comprising," "including," "having," "containing," and the like are intended to be inclusive and mean an inclusion, but not limited to.

The room temperature of the present application means 25.+ -. 2 ℃.

Example 1

The embodiment provides a preparation method of an iron single-atom-supported nitrogen-doped carbon catalyst, which comprises the following steps:

respectively weighing 10g of iron phthalocyanine and 50g of ammonium bromide, adding into a mortar, grinding and mixing, loading into a quartz bottle, transferring into a vacuum tube furnace, setting the heating rate to be 2 ℃/min, heating to 650 ℃ under the protection of argon, preserving heat for 4 hours, naturally cooling to room temperature, washing the obtained product with pure water until no bromide ions are generated (the nitrate test solution acidified by nitric acid detects no bromide ions in the washed water), and finally drying to obtain 8.2g of black iron single-atom catalyst.

The spherical aberration correction scanning transmission electron microscope image of the iron monoatomic catalyst obtained in this example is shown in fig. 1, white bright spots in fig. 1 represent iron atoms, and it can be observed that in the iron monoatomic catalyst prepared in example 1, iron is distributed in nitrogen-doped carbon in a monoatomic form, the EDS spectrum is shown in fig. 2, and the EDS test load is 9.6%, which proves that the scheme of example 1 can be used to successfully prepare the iron monoatomic catalyst. The analysis of synchrotron radiation of the iron monoatomic catalyst obtained in this example is shown in FIG. 3, and it is clear that iron exists in the catalyst in the form of Fe-N-C, and does not exist in the form of Fe-Fe or Fe-O, indicating the formation of monoatomic active sites.

Example 2

The embodiment provides a preparation method of a cobalt monoatomic load nitrogen-doped carbon catalyst, which comprises the following steps:

respectively weighing 1g of cobalt phthalocyanine and 10g of ammonium chloride, adding into a mortar, grinding and mixing, loading into a quartz bottle, transferring into a vacuum tube furnace, setting the heating rate to be 5 ℃/min, heating to 620 ℃ under the protection of nitrogen, preserving heat for 2 hours, naturally cooling to room temperature, washing the obtained product with pure water until no chloride ions are generated (the nitric acid acidified silver nitrate test solution detects no chloride ions in the washed water), and finally drying to obtain the black cobalt monoatomic catalyst.

Example 3

respectively weighing 3.0g of iron phthalocyanine and 15g of ammonium chloride, adding into a mortar, grinding and mixing, loading into a quartz bottle, transferring into a vacuum tube furnace, setting the heating rate to 5 ℃/min, heating to 700 ℃ under the protection of nitrogen, preserving heat for 2 hours, naturally cooling to room temperature, washing the obtained product with pure water until no chloride ions exist, and finally drying to obtain the black iron single-atom catalyst.

The X-ray diffraction pattern of the black iron monoatomic catalyst prepared in this example is shown in fig. 4, and it can be seen that the X-ray diffraction pattern of the iron monoatoms and the iron phthalocyanine raw material is obviously changed, and meanwhile, there is no X-ray diffraction peak of metallic iron and iron oxide, which indicates that no iron nano particles and iron oxide particles exist in the prepared iron monoatomic catalyst.

Example 4

The embodiment provides a preparation method of a zinc monoatomic load nitrogen-doped carbon catalyst, which comprises the following steps:

weighing 4g of zinc phthalocyanine and 20g of ammonium chloride respectively, adding into a mortar, grinding and mixing, loading into a quartz bottle, transferring into a vacuum tube furnace, setting the heating rate to 10 ℃/min, heating to 700 ℃ under the protection of nitrogen, preserving heat for 2 hours, naturally cooling to room temperature, washing the obtained product with pure water until no chloride ions exist, and finally drying to obtain the zinc monoatomic catalyst.

Example 5

In contrast, in this example, no ammonium salt was added during the preparation of the iron monoatomic catalyst, and the specific method was as follows: 3.0g of iron phthalocyanine is weighed and added into a mortar, grinding is carried out, the mixture is transferred into a vacuum tube furnace, the heating rate is set to be 5 ℃/min, the temperature is raised to 700 ℃ under the protection of nitrogen, the heat is preserved for 2 hours, and after the mixture is naturally cooled to room temperature, the black catalyst (supported iron catalyst) is obtained. The transmission electron microscope image of the supported iron catalyst prepared in this example is shown in fig. 5, and it can be known that the iron catalyst obtained by directly pyrolyzing iron phthalocyanine in the absence of ammonium salt can clearly observe the existence of iron nanoparticles.

The magnetic comparison of the iron catalysts prepared in example 1 and example 5 is shown in fig. 6, and it is known that the iron monoatomic catalyst prepared in example 1 cannot be adsorbed by magnet at all, and is nonmagnetic, which means that an iron monoatomic material is formed, whereas the iron catalyst prepared in example 5 has strong magnetism, is easily adsorbed by magnet, and means that iron nanoparticles exist therein.

Application example 1

The use of the iron single-atom catalyst obtained in example 1 in catalytic reduction (for example catalytic reduction of sodium borohydride).

To 25mL of a solution of 4-nitrophenol (0.1 mmol/L), 30mg of sodium borohydride was added, the solution turned bright yellow, 2mg of iron monoatomically catalyzed was added, and after 30 minutes of reaction, the solution turned colorless (FIG. 7), indicating that 4-nitrophenol was reduced to 4-aminophenol. In contrast, the reaction is difficult to carry out without a change in solution color in the absence of an iron monoatomic catalyst. Further confirming the catalysis of the iron monoatomic catalyst on the 4-nitrophenol catalytic hydrogenation reduction reaction through an ultraviolet-visible absorption spectrum, wherein after the catalysis reaction, the absorption peak of the 4-nitrophenol disappears, and meanwhile, the absorption peak of the 4-aminophenol appears (figure 8); and in the comparison experiment without the catalyst, the ultraviolet visible absorption curve is not changed obviously.

Application example 2

The iron monoatomic catalyst obtained in example 1 is used in catalytic oxidation (3, 3', 5' -tetramethylbenzidine is used as an example in catalytic oxidation).

The 3,3', 5' -tetramethyl benzidine (TMB) turns from colorless to blue after being oxidized, and the reaction is difficult to carry out under the condition of no catalyst, so that the method can be used for testing the catalytic activity of the catalyst. Taking 0.5mL of sodium dihydrogen phosphate-sodium phosphate buffer solution (ph=4) in a 1.5mL centrifuge tube, adding 10 μl of TMB solution, 10 μl of hydrogen peroxide (20 mmol/L) and 10 μl of iron monoatomic catalyst dispersion (0.5 mg/mL), shaking, standing for 5min, and observing the reaction solution from colorless to blue, which exhibits a maximum absorption peak at 652nm in the uv-visible absorption spectrum (fig. 9). The TMB solution is not oxidized in the buffer solution; after the hydrogen peroxide solution is added, the oxidation reaction of TMB is still difficult to carry out, the solution is colorless, and the comparison between the ultraviolet and visible absorption spectrum and TMB is not obviously changed; it can be seen that the iron monoatomic catalyst is capable of effectively catalyzing the progress of the TMB oxidation reaction.

The present application is not limited to the above-mentioned embodiments, and any changes or substitutions that can be easily understood by those skilled in the art within the technical scope of the present application are intended to be included in the scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for synthesizing a metal monoatomic catalyst by using a metal phthalocyanine compound, which is characterized by comprising the following steps:

(1) Mixing a metal phthalocyanine compound and an ammonium salt, and grinding to obtain a mixture, wherein the ammonium salt is ammonium chloride, ammonium bromide or a mixture thereof;

(2) And (3) carrying out high-temperature pyrolysis on the mixture, washing and drying the obtained product to obtain the metal monoatomic catalyst, wherein the temperature of the high-temperature pyrolysis is 550-700 ℃, the time is 2-4 h, and the heating rate is 1-10 ℃/min.

2. The method for synthesizing a metal monoatomic catalyst by using a metal phthalocyanine compound according to claim 1, wherein the mass ratio of the metal phthalocyanine compound to the ammonium salt is 1:1-1:10.

3. The method for synthesizing a metal single-atom catalyst according to claim 2, wherein the metal phthalocyanine compound comprises one of iron phthalocyanine, copper phthalocyanine, cobalt phthalocyanine, nickel phthalocyanine, zinc phthalocyanine and manganese phthalocyanine.

4. The method for synthesizing a metal monoatomic catalyst according to claim 1, wherein the pyrolysis is performed under the protection of inert gas.

5. A metal monoatomic catalyst, characterized in that it is synthesized according to the method of any one of claims 1 to 4.

6. The use of the metal monoatomic catalyst according to claim 5 for catalytic oxidation and catalytic reduction.