CN115337947B

CN115337947B - Metal atom high-doping-amount monoatomic catalyst, preparation method and application thereof

Info

Publication number: CN115337947B
Application number: CN202210872587.XA
Authority: CN
Inventors: 俞豪杰; 黄志坤; 王立
Original assignee: Zhejiang University ZJU
Current assignee: Zhejiang University ZJU
Priority date: 2022-07-19
Filing date: 2022-07-19
Publication date: 2024-04-05
Anticipated expiration: 2042-07-19
Also published as: CN115337947A

Abstract

The invention discloses a metal atom high doping amount monoatomic catalyst, a preparation method and application thereof. The metal atom high doping amount monoatomic catalyst is obtained by heat treatment of a metallocene modified two-dimensional material, and the metallocene modified two-dimensional material is obtained by chemical reaction of a metallocene derivative and the two-dimensional material through covalent bond connection; preparing a two-dimensional material with functional groups, weighing a metallocene derivative and the two-dimensional material, performing ultrasonic dispersion in absolute ethyl alcohol to obtain a uniform dispersion liquid, reacting in a protective atmosphere, naturally cooling, performing centrifugal separation to obtain the metallocene modified two-dimensional material, and performing heat treatment to obtain the metal atom high doping amount monoatomic catalyst. The photocatalyst has high metal atom doping amount and excellent catalytic activity, and has high application value in the field of sewage treatment.

Description

Metal atom high-doping-amount monoatomic catalyst, preparation method and application thereof

Technical Field

The invention relates to a preparation method of a metal atom catalyst, in particular to a preparation method of an iron-nitrogen-carbon single-atom catalyst and application of the iron-nitrogen-carbon single-atom catalyst in water pollution treatment.

Background

Tetracyclines are a commonly used broad-spectrum antibiotic and are widely used as therapeutic agents, particularly in the animal industry for the treatment of infections. However, since tetracycline has a stable chemical structure and is not easily biodegradable, most of the non-metabolized tetracycline molecules in the living body are easily discharged into the water environment through food chains, biological metabolism and the like, causing great harm to the surrounding environment and organisms, such as inhibition of growth of aquatic organisms, gene exchange, increase of bacterial resistance, biotoxicity and the like. However, the traditional physical method, chemical method or biological method is insufficient to thoroughly remove the tetracycline in the water environment due to limited degradation capacity and the like. Therefore, the design of a catalytic system has important significance in effectively degrading antibiotics such as tetracycline. In recent years, the monoatomic catalyst has ultrahigh catalytic activity due to the fact that the monoatomic catalyst has the catalytic active sites dispersed in an atomic level, and the utilization rate of the active sites can reach 100% in theory. However, the preparation of monoatomic catalysts with high doping levels of metal atoms still presents a great challenge. On the one hand, highly dispersed metal atoms tend to migrate and aggregate during the preparation process, making it easier to obtain metal nanoparticles rather than monoatomic catalysts; on the other hand, the metal doping amount in the monoatomic catalyst is usually very limited, so that the catalytic activity of the system is low. To overcome the above difficulties, the transition metal is introduced onto the surface of the two-dimensional carbon material by directional covalent grafting, which has a number of points: firstly, the directional covalent grafting mode can effectively improve the dispersibility of transition metal and the stability of a system, and prevent aggregation of the transition metal; secondly, the doping amount of the transition metal can be accurately controlled so as to achieve the optimal catalytic performance; and the preparation method has certain universality and can be applied to the preparation of other single-atom catalysts.

Disclosure of Invention

In view of the existing problems, the invention aims to provide an iron-nitrogen-carbon single-atom catalyst with high doping of iron atoms, a preparation method and application thereof in water pollution treatment. The preparation method disclosed by the invention is simple in process, can be popularized to other systems, and the catalytic performance of the system can meet the actual application requirements. The iron-nitrogen-carbon prepared by the method can obtain higher catalytic activity without illumination, can reduce the energy consumption of a catalytic system, and can effectively degrade the tetracycline dissolved in the water body within 30 minutes.

The technical scheme adopted by the invention is as follows:

1. a metal atom high doping amount monoatomic catalyst:

the metal atom high doping amount monoatomic catalyst is obtained by heat treatment of a metallocene modified two-dimensional material, and the metallocene modified two-dimensional material is obtained by chemical reaction of a metallocene derivative and the two-dimensional material through covalent bond connection.

Preferably, the metallocene is any one or a combination of two or more of ferrocene, cobaltocene, nickelocene, zirconocene, titanocene and manganese cobaltocene;

preferably, the two-dimensional material is any one or a combination of two or more of graphite-phase carbon nitride, graphene oxide, reduced graphene oxide and boron nitride;

preferably, the metallocene derivative is any one or a combination of two or more of metallocene formaldehyde, 1' -metallocene dicarboxaldehyde, metallocene formic acid, 1' -metallocene dicarboxyl acid, metallocene methanol and 1,1' -metallocene dimethanol.

2. A preparation method of a metal atom high doping amount monoatomic catalyst comprises the following steps:

(1) Preparing a two-dimensional material with functional groups;

(2) Respectively weighing the metallocene derivative and the two-dimensional material obtained in the step (1) according to a certain mass ratio, and ultrasonically dispersing the two-dimensional material in absolute ethyl alcohol to obtain uniform dispersion liquid;

(3) Reacting the uniform dispersion liquid obtained in the step (2) in a protective atmosphere, naturally cooling, and obtaining metallocene-modified two-dimensional material powder as powder through centrifugal separation;

(4) And (3) carrying out heat treatment on the metallocene modified powder obtained in the step (3) in a protective atmosphere to obtain the metal atom high doping amount single-atom catalyst.

Preferably, the functional group is any one or a combination of two or more of amino, aldehyde, carboxyl, hydroxyl, sulfo, halogen atom and epoxy group.

Preferably, the mass ratio of the two-dimensional material to the metallocene derivative in step (2) is in the range of 1:0.01 to 1:100.

Preferably, in the step (3), the reaction temperature is in the range of 20-200 ℃ and the reaction time is in the range of 0.5-108 h.

Preferably, in the step (4), the protective atmosphere is any one or a combination of two or more of nitrogen, helium, neon, argon, krypton and radon, the heat treatment temperature is in the range of 200-1000 ℃, and the heat preservation time is in the range of 0.5-20 h. It is preferable to heat from ambient temperature to 500 c at a rate of 5 c/min.

A typical preparation process is: the preparation of the single-atom catalyst is mainly formed by heat treatment of graphitized carbon nitride modified by ferrocene. Placing urea into a quartz boat with a cover, slowly heating to 550 ℃ from normal temperature in an air environment, preserving heat for 4 hours, and cooling along with a furnace to obtain graphitized carbon nitride; weighing a certain amount of graphitized carbon nitride and ferrocene formaldehyde according to a preset mass ratio, mixing and dispersing in absolute ethyl alcohol, heating to 100 ℃, and reacting for 24 hours to obtain ferrocene modified graphitized carbon nitride; and (3) treating the graphitized carbon nitride modified by ferrocene for 2 hours at 550 ℃ in a protective atmosphere to finally obtain the iron atom high doping amount monoatomic catalyst.

3. An application method of a metal atom high doping amount monoatomic catalyst in sewage treatment comprises the following steps:

and (3) ultrasonically dispersing the monoatomic catalyst in sewage with the pH value of between 2 and 13, stirring for 0 to 24 hours to obtain uniform dispersion, and adding an oxidant to start reaction for a certain time to realize sewage treatment.

Wherein stirring for 0h means no stirring.

The sewage is a solution containing organic pollutants, and the organic pollutants comprise any one or a combination of at least two of organic dyes, tetracyclines and analogues thereof, volatile organic compounds, antibiotics and pesticides.

The oxidant is any one or the combination of two or more of hydrogen peroxide, peroxymonosulfate and persulfate, and the reaction time is 0.01-3h.

In the specific implementation, a sample is obtained by sampling after the reaction, and after the quenching agent is added into the sample and is quenched and separated, the content of organic pollutants in the water body is tested. The water body can be sampled at intervals so as to further contain organic pollutants.

The quenching agent is any one or the combination of two or more of ethanol, methanol, isopropyl alcohol and tert-butyl alcohol.

The water body organic matter content is tested by adopting equipment of an ultraviolet visible light spectrometer, a liquid chromatograph or a liquid chromatograph-mass spectrometer.

According to the method, the iron atoms dispersed in atomic scale are directionally and covalently doped on graphite-phase carbon nitride, so that the agglomeration effect of the iron atoms is effectively relieved, and the content of the iron atoms in the obtained single-atom catalyst is accurately controlled by changing the introduction amount of an iron source in a precursor material, so that the problems in the background technology are effectively overcome. The graphite phase carbon nitride is a two-dimensional organic semiconductor, has the advantages of simple preparation, easy expansion production, higher specific surface area, high chemical stability, high nitrogen content and the like, and can be used as a photocatalyst and has higher application prospect in the field of environmental remediation. However, the photo-generated electron-hole pairs generated by the graphite-phase carbon nitride are very easy to recombine under the illumination condition, so that the number of available photo-generated carriers is low. In addition, graphite-phase carbon nitride catalytic systems generally require external light sources, and their practical application value is yet to be examined. Therefore, graphite-phase carbon nitride is used as a matrix material, and atomic-level transition metal is doped in a two-dimensional network in a directional covalent grafting mode, so that the two-dimensional structure of the transition metal can be reserved, and additional catalytic active sites can be introduced, so that the dependence of the system on external energy is reduced. According to the invention, the ferrocenyl formaldehyde is covalently grafted at the tail end of graphite phase carbon nitride through Schiff base reaction, so that the distance between the ferrocenyl groups is far due to the huge two-dimensional network, the interaction between the ferrocenyl groups is effectively reduced, and the agglomeration is prevented. After heat treatment, the ferrocene molecular structure is decomposed, and the iron atoms in the ferrocene molecular structure are immediately coordinated with surrounding nitrogen atoms and doped in a graphite-phase carbon nitride network, so that the iron-nitrogen-carbon single-atom catalyst is obtained in situ. The invention tests the performance of the iron-nitrogen-carbon single-atom catalyst on tetracycline degradation in specific implementation.

The preparation method of the concrete typical composite material comprises the following steps: (1) Weighing 5g of urea, placing the weighed 5g of urea in a quartz boat with a cover, heating the quartz boat to 550 ℃ from normal temperature in an air environment, reacting for 4 hours, and naturally cooling to obtain light yellow solid; (2) Grinding the solid obtained in the step (1) to obtain graphite-phase carbon nitride powder; (3) Respectively weighing a certain amount of graphite-phase carbon nitride obtained in the step (2) and ferrocenyl formaldehyde to be dispersed in absolute ethyl alcohol for reaction to obtain ferrocene-modified carbon nitride-X (X represents the mass ratio of carbon nitride to ferrocenyl formaldehyde); (4) And (3) carrying out heat treatment on the ferrocene modified carbon nitride-X obtained in the step (3) in a protective atmosphere to obtain the iron-nitrogen-carbon-X-T single-atom catalyst (T represents the heat treatment temperature).

Compared with the prior art, the invention has the following beneficial effects:

1. the invention prepares the iron-nitrogen-carbon-X-T single-atom catalyst by a simple and effective process, and can effectively avoid the agglomeration of iron atoms.

2. According to the invention, the doping amount of the iron atoms in the iron-nitrogen-carbon-X-T single-atom catalyst can be accurately regulated and controlled through the Schiff base reaction.

3. The iron-nitrogen-carbon-X-T single-atom catalyst prepared by the invention has higher catalytic activity under the condition of no illumination, and widens the application range of the system.

4. The preparation process is simple and can be popularized to other systems.

In summary, the photocatalyst provided by the invention can realize higher metal atom doping amount and excellent catalytic activity, and has very high application value in the field of sewage treatment.

Drawings

FIG. 1 is a transmission electron microscope image of an Fe-N-C-0.1-500 single-atom catalyst prepared according to the invention and a corresponding elemental distribution diagram.

FIG. 2 is a graph showing the variation of iron content in the iron-nitrogen-carbon-X-500 single-atom catalyst prepared according to the present invention.

FIG. 3 is a graph showing the results of the performance of the iron-nitrogen-carbon-X-500 single-atom catalyst prepared by the invention on tetracycline degradation.

FIG. 4 shows the performance of the iron-nitrogen-carbon-0.1-500 single-atom catalyst prepared by the invention in the degradation of tetracycline under the condition of illumination.

The present invention will be described in further detail below. The following examples are merely illustrative of the present invention and are not intended to represent or limit the scope of the invention as defined in the claims.

Detailed Description

The technical scheme of the invention is further described below by the specific embodiments with reference to the accompanying drawings.

The following examples are merely illustrative of the present invention and are not intended to represent or limit the scope of the invention as defined in the claims. It will be apparent to those skilled in the art that the examples are merely to aid in understanding the invention and are not to be construed as a specific limitation thereof.

Embodiments of the invention are as follows:

example 1

Weighing 5g of urea, placing in a quartz boat with a cover, heating from normal temperature to 550 ℃ at a speed of 2.5 ℃/min in an air environment, reacting for 4 hours to obtain a light yellow solid, and grinding to obtain carbon nitride powder. 20mg of ferrocene formaldehyde and 100mg of carbon nitride (the mass ratio of ferrocene formaldehyde to carbon nitride is 1:5) are respectively weighed and ultrasonically dispersed in 160mL of absolute ethyl alcohol to obtain a uniform dispersion liquid. Heating the dispersion liquid to 100 ℃ in Ar, reacting for 24 hours, naturally cooling, and centrifugally separating to obtain ferrocene modified carbon nitride-5 powder. And (3) placing the obtained ferrocene modified carbon nitride-5 powder into a quartz boat with a cover, heating the powder to 500 ℃ from normal temperature at a speed of 5 ℃/min in an argon protection atmosphere, and preserving the heat for 2 hours to obtain the iron-nitrogen-carbon-5-500 monoatomic catalyst.

Example 2

This example differs from example 1 in that the mass ratio of ferrocene formaldehyde to carbon nitride is 1:1 to give a catalyst of iron-nitrogen-carbon-1-500.

Example 3

The difference between this example and example 1 is that the mass ratio of ferrocene formaldehyde to carbon nitride is 1:0.5, and the resulting catalyst is iron-nitrogen-carbon-0.5-500.

Example 4

The difference between this example and example 1 is that the mass ratio of ferrocene formaldehyde to carbon nitride is 1:0.1, and the resulting catalyst is iron-nitrogen-carbon-0.1-500.

Fig. 1 is a transmission electron microscope image of iron-nitrogen-carbon-0.1-500 prepared in example 4, and it can be seen that the morphology of the obtained catalyst is two-dimensional, and signals of iron, nitrogen and carbon elements can be observed at the same time, and the three elements are uniformly distributed, which indicates that the catalyst can successfully introduce iron atoms and can avoid agglomeration of the iron atoms.

Example 5

100mg of the catalyst obtained in example 1 was accurately weighed into a 50mL polytetrafluoroethylene digestion tube. The masses m1, m2, m3, m4 are recorded separately. And (3) respectively adding about 6mL of concentrated nitric acid and 1mL of hydrogen peroxide into the weighed sample digestion tube, covering a cover, putting the cover into a stainless steel reaction kettle, putting the stainless steel reaction kettle into a 180 ℃ oven, preserving heat for 8 hours, and stopping heating and cooling. The cooled solution was transferred to a 25mL plastic volumetric flask and finally, deionized water was used to determine the volume. Preparing a standard test solution, wherein the standard solution is a national standard substance, and the concentration points of the curve are respectively: 0. 0.5, 1.0, 2.0, 5.0, 10.0mg/L. A standard solution calibration curve is firstly prepared through an apparatus with model number Varian (720-ES) of American AES company, the mass and the volume of a sample are input, then the digested solution is sequentially tested, and the solution is tested after dilution beyond the curve range. And determining the final content of the iron element in each sample according to the test result through a spectrogram, and obtaining the test result.

Example 6

This example differs from example 5 in that the test sample was the catalyst obtained in example 2.

Example 7

This example differs from example 5 in that the test sample was the catalyst obtained in example 3.

Example 8

This example differs from example 5 in that the test sample was the catalyst obtained in example 5.

FIG. 2 shows the results of the tests of examples 5, 6, 7 and 8, and shows that the iron content of the obtained catalyst gradually increases with the addition amount of ferrocene dicarboxaldehyde, and the highest mass ratio can reach 2.7%. The method shows that the content of iron atoms in the catalyst can be accurately regulated.

Example 9

Weighing 5g of urea, placing in a quartz boat with a cover, heating from normal temperature to 550 ℃ at a speed of 2.5 ℃/min in an air environment, reacting for 4 hours to obtain a light yellow solid, and grinding to obtain carbon nitride powder, wherein the carbon nitride powder has a large amount of amino groups. 20mg of ferrocene formaldehyde and 100mg of carbon nitride are respectively weighed and ultrasonically dispersed in 160mL of absolute ethyl alcohol to obtain a uniform dispersion liquid. Heating the dispersion liquid to 100 ℃ in Ar, reacting for 24 hours, naturally cooling, and centrifugally separating to obtain ferrocene modified carbon nitride-5 powder. And (3) placing the obtained ferrocene modified carbon nitride-5 powder into a quartz boat with a cover, heating the powder to 500 ℃ from normal temperature at a speed of 5 ℃/min in an argon protection atmosphere, and preserving the heat for 2 hours to obtain the iron-nitrogen-carbon-5-500 monoatomic catalyst.

2.5mg of ferrocene modified carbon nitride-5 powder is weighed and dispersed in a solution with pH=6 and 50mL of tetracycline concentration of 20mg/L by ultrasonic, and stirred for 1h at 25 ℃ to reach adsorption-desorption balance. Subsequently, 10.0mg of potassium hydrogen peroxymonosulfate complex was added to the above solution to initiate the reaction. 2mL of the sample is immediately quenched with 2mL of methanol at a specific time, filtered through a 0.22 mu m hydrophilic PTFE membrane, tested by an ultraviolet spectrometer, the absorbance at 357nm is measured, and the residual tetracycline concentration in the sample can be calculated according to a standard curve.

Experimental results show that the residual tetracycline concentration after 30min of treatment with Fe-N-C-5-500 is 47.5%.

Example 10

This example differs from example 9 in that the catalyst is iron-nitrogen-carbon-1-500.

Experimental results show that the residual tetracycline concentration after 30min of treatment with iron-nitrogen-carbon-1-500 is 39.2%.

Example 11

This example differs from example 9 in that the catalyst is iron-nitrogen-carbon-0.5-500.

Experimental results show that the concentration of residual tetracycline is 35.1% after 30min of treatment with iron-nitrogen-carbon-0.5-500.

Example 12

This example differs from example 9 in that the catalyst is iron-nitrogen-carbon-0.1-500.

Experimental results show that the residual tetracycline concentration is 19.6% after 30min of treatment with iron-nitrogen-carbon-0.1-500.

FIG. 3 shows the tetracycline degradation performance of the catalysts of examples 9, 10, 11 and 12 of the present invention. It can be seen from the figure that the catalytic activity of the system is significantly improved with increasing iron doping amount in the iron-nitrogen-carbon-X-500.

Example 13

This example differs from example 12 in that the system degrades tetracycline under light conditions.

Experimental results show that the residual tetracycline concentration after 30min of treatment under illumination is 10.6%.

FIG. 4 shows the tetracycline degradation performance of examples 12 and 13 of the invention. From this figure, it can be seen that the catalytic performance of the system is further improved under light conditions.

Example 14

This example differs from example 12 in that the catalyst is iron-nitrogen-carbon-0.1-300.

Experimental results indicate that the residual tetracycline concentration after 30min of treatment with iron-nitrogen-carbon-0.1-300 is about 35%.

Example 15

This example differs from example 12 in that the catalyst is iron-nitrogen-carbon-0.1-400.

Experimental results indicate that the residual tetracycline concentration after 30min of treatment with iron-nitrogen-carbon-0.1-400 is about 30%.

Example 16

This example differs from example 12 in that the catalyst is iron-nitrogen-carbon-0.1-600.

Experimental results indicate that the residual tetracycline concentration after 30min of treatment with iron-nitrogen-carbon-0.1-600 is about 20%.

Example 17

This example differs from example 12 in that the catalyst is iron-nitrogen-carbon-0.1-700.

Experimental results indicate that the residual tetracycline concentration after 30min of treatment with iron-nitrogen-carbon-0.1-700 is about 18%.

The detailed process equipment and process flow of the present invention are described by the above embodiments, but the present invention is not limited to, i.e., it does not mean that the present invention must be practiced depending on the detailed process equipment and process flow. It should be apparent to those skilled in the art that any modification of the present invention, equivalent substitution of raw materials for the product of the present invention, addition of auxiliary components, selection of specific modes, etc., falls within the scope of the present invention and the scope of disclosure.

Claims

1. An application method of a metal atom high doping amount monoatomic catalyst in sewage treatment is characterized in that:

the application method comprises the following steps:

ultrasonically dispersing the monoatomic catalyst in sewage with pH=2-13, stirring for 0-24 and h to obtain uniform dispersion, and adding an oxidant to start reaction for a certain time to realize sewage treatment;

the metal atom high doping amount monoatomic catalyst is obtained by heat treatment of a metallocene modified two-dimensional material, and the metallocene modified two-dimensional material is obtained by chemical reaction of a metallocene derivative and the two-dimensional material through covalent bond connection;

the metallocene is ferrocene, the two-dimensional material is graphite phase carbon nitride, and the metallocene derivative is metallocene formaldehyde;

the monoatomic catalyst is prepared in the following manner:

(1) Preparing a two-dimensional material with functional groups;

(3) Reacting the uniform dispersion liquid obtained in the step (2) in a protective atmosphere, naturally cooling, and obtaining metallocene modified two-dimensional material powder through centrifugal separation;

2. The application method according to claim 1, wherein:

3. The application method according to claim 1, wherein: the functional group is any one or the combination of two or more of amino, aldehyde, carboxyl, hydroxyl, sulfo, halogen atom and epoxy group.

4. The application method according to claim 1, wherein: the mass ratio of the two-dimensional material to the metallocene derivative in the step (2) is in the range of 1:0.01-1:100.

5. The application method according to claim 1, wherein: in the step (3), the reaction temperature is in the range of 20-200 ℃ and the reaction time is in the range of 0.5-108 h.

6. The application method according to claim 1, wherein: in the step (4), the protective atmosphere is any one or the combination of two or more of nitrogen, helium, neon, argon, krypton and radon, the heat treatment temperature is in the range of 200-1000 ℃, and the heat preservation time is in the range of 0.5-20 h.