CN115337947A

CN115337947A - Metal atom high-doping-amount monatomic catalyst, preparation method and application thereof

Info

Publication number: CN115337947A
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: 2022-11-15
Anticipated expiration: 2042-07-19
Also published as: CN115337947B

Abstract

The invention discloses a metal atom high-doping-amount single-atom catalyst, a preparation method and application thereof. The metal atom high-doping-amount single-atom catalyst is obtained by carrying out heat treatment on a metallocene-modified two-dimensional material, wherein the metallocene-modified two-dimensional material is obtained by connecting a metallocene derivative and the two-dimensional material through a covalent bond through a chemical reaction; preparing a two-dimensional material with functional groups, weighing the metallocene derivative and the two-dimensional material, ultrasonically dispersing the metallocene derivative and the two-dimensional material 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 thermal treatment to obtain the metal atom high-doping-amount monatomic catalyst. The photocatalyst has higher metal atom doping amount and excellent catalytic activity, and has very high application value in the field of sewage treatment.

Description

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

Technical Field

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

Background

Tetracycline is a commonly used broad spectrum antibiotic used widely as a therapeutic agent, particularly in the animal husbandry for the treatment of infections. However, since tetracycline has a stable chemical structure and is not easily biodegradable, most of the unmetabolized tetracycline molecules in organisms are easily discharged to the water environment through the food chain and biological metabolism, causing great harm to the surrounding environment and organisms, such as inhibition of growth of aquatic organisms, gene exchange, increase of bacterial resistance, and biotoxicity. The traditional physical method, chemical method or biological method is not enough to thoroughly remove the tetracycline in the water body environment due to the limited degradation capability and the like. Therefore, the technology that a catalytic system can effectively degrade antibiotics such as tetracycline and the like is designed to have important significance. In recent years, a monatomic catalyst has ultrahigh catalytic activity due to the fact that the monatomic catalyst has catalytic active sites dispersed at an atomic level, and the active site utilization rate can reach 100% in theory. However, the preparation of monatomic catalysts with high doping levels of metal atoms still faces significant challenges. 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 monatomic catalysts; on the other hand, the amount of metal doping in the monatomic catalyst is usually very limited, resulting in a system with low catalytic activity. In order to overcome the above difficulties, the transition metal is introduced onto the surface of the two-dimensional carbon material by means of directional covalent grafting, which has many advantages: firstly, the directional covalent grafting mode can effectively improve the dispersibility of the transition metal and the stability of a system and prevent the transition metal from agglomerating; secondly, the doping amount of the transition metal can be accurately controlled so as to achieve the best catalytic performance; thirdly, the preparation method has certain universality and can be applied to the preparation of other monatomic catalysts.

Disclosure of Invention

In view of the existing problems, the invention aims to provide an iron-nitrogen-carbon single-atom catalyst with high doped iron atom, a preparation method and application thereof in water pollution treatment. The preparation method has simple process, can be popularized to other systems, and the catalytic performance of the system can meet the actual application requirement. 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 tetracycline dissolved in water within 30 minutes.

The technical scheme adopted by the invention is as follows:

1. a metal atom high-doping-capacity single-atom catalyst:

the metal atom high-doping-quantity single-atom catalyst is obtained by carrying out heat treatment on a metallocene-modified two-dimensional material, wherein the metallocene-modified two-dimensional material is obtained by connecting a metallocene derivative and a two-dimensional material through a covalent bond through a chemical reaction.

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

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 diformaldehyde, metallocene formic acid, 1' -metallocene dicarboxylic acid, metallocene methanol and 1,1' -metallocene dimethanol.

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

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

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

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

(4) And (3) carrying out heat treatment on the metallocene modified powder obtained in the step (3) under a protective atmosphere to obtain the metal atom high-doping-amount monatomic 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 the step (2) is in the range of 1.

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 within the range of 200-1000 ℃, and the heat preservation time is within the range of 0.5-20 h. Heating from ambient temperature to 500 c at a rate of 5 c/min is preferred.

One typical preparation process is: the preparation of the monatomic catalyst is mainly formed by performing heat treatment on ferrocene-modified graphitized carbon nitride. Placing urea in a quartz boat with a cover, slowly heating the quartz boat to 550 ℃ from normal temperature in an air environment, preserving heat for 4 hours, and cooling the quartz boat with the urea in a furnace to obtain graphitized carbon nitride; weighing a certain amount of graphitized carbon nitride and ferrocene formaldehyde according to a predetermined 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 treating the ferrocene-modified graphitized carbon nitride at 550 ℃ for 2h under the protective atmosphere to finally obtain the iron atom high-doping-amount monatomic catalyst.

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

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

Wherein 0h of stirring means that stirring was not carried out.

The sewage is a solution containing organic pollutants, and the organic pollutants comprise any one or the combination of at least two of organic dyes, tetracycline 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 specific implementation, a sample is obtained after reaction, and after a quenching agent is added into the sample and is quenched and separated, the content of organic pollutants in a water body is tested. And the sampling can be carried out at intervals and in fixed time, so that the content of the organic pollutants in the water body is reduced.

The quenching agent is any one or the combination of two or more of ethanol, methanol, isopropanol and tert-butanol.

The method for testing the content of the organic matters in the water body is to test by adopting an ultraviolet visible spectrometer, a liquid chromatograph or a liquid chromatogram-mass spectrometer.

According to the invention, iron atoms with dispersed atomic levels are directionally and covalently doped on graphite-phase carbon nitride, so that the agglomeration effect of the iron atoms is effectively relieved, and the iron atom content in the obtained monatomic catalyst is accurately controlled by changing the iron source introduction amount in the precursor material, so that the problems in the background art are effectively overcome. The graphite phase carbon nitride is a two-dimensional organic semiconductor, has the advantages of simple preparation, easy expanded production, higher specific surface area, high chemical stability, high nitrogen content and the like, and can be used as a photocatalyst to have 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 susceptible to recombination under illumination conditions, resulting in a low number of available photo-generated carriers. In addition, the graphite phase carbon nitride catalyst system usually requires an external lamp source, and the practical application value of the system is still to be investigated. Therefore, graphite-phase carbon nitride is used as a matrix material, and the atomic-level transition metal is doped in the two-dimensional network in a directional covalent grafting manner, so that the two-dimensional structure of the transition metal can be retained, and additional catalytic active sites can be introduced to reduce the dependence of the system on external energy. According to the invention, ferrocene formaldehyde is covalently grafted to the tail end of graphite-phase carbon nitride through Schiff base reaction, and the large two-dimensional network enables the distance between introduced ferrocene groups to be long, so that the interaction between the ferrocene groups is effectively reduced, and the aggregation of the ferrocene groups is prevented. After heat treatment, the ferrocene molecular structure is decomposed, and iron atoms in the ferrocene molecular structure are immediately coordinated with surrounding nitrogen atoms to be doped in a graphite phase carbon nitride network so as to obtain the iron-nitrogen-carbon single atom catalyst in situ. The invention tests the degradation performance of the iron-nitrogen-carbon single atom catalyst on tetracycline in specific implementation.

The preparation method of the specific typical composite material comprises the following steps: (1) Weighing 5g of urea, placing the urea in a quartz boat with a cover, heating the quartz boat to 550 ℃ from the normal temperature in an air environment, reacting for 4 hours, and naturally cooling to obtain a 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 ferrocene formaldehyde, dispersing the graphite-phase carbon nitride and ferrocene formaldehyde in absolute ethyl alcohol, and reacting to obtain ferrocene-modified carbon nitride-X (X represents the mass ratio of carbon nitride to ferrocene formaldehyde); (4) And (4) carrying out heat treatment on the ferrocene-modified carbon nitride-X obtained in the step (3) under 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. The invention can realize the accurate regulation and control of the doping amount of the iron atom in the iron-nitrogen-carbon-X-T single-atom catalyst through the Schiff base reaction.

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

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

In conclusion, the photocatalyst 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 the Fe-N-C-0.1-500 monatomic catalyst prepared by the method and a corresponding element distribution diagram.

FIG. 2 is a graph showing the change in the iron content of the iron-nitrogen-carbon-X-500 monatomic catalyst prepared in accordance with the present invention.

FIG. 3 is a graph showing the results of the performance of the Fe-N-C-X-500 monatomic catalyst prepared by the present invention on tetracycline degradation.

FIG. 4 shows the tetracycline degradation performance of the Fe-N-C-0.1-500 monatomic catalyst prepared in accordance with the present invention under light conditions.

The present invention is described in further detail below. The following examples are merely illustrative of the present invention and do not represent or limit the scope of the claims, which are defined by the claims.

Detailed Description

The technical scheme of the invention is further explained by the specific implementation mode in combination with the attached drawings.

The following examples are merely illustrative of the present invention and do not represent or limit the scope of the claims, which are defined by the claims. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.

The examples of the invention are as follows:

example 1

Weighing 5g of urea, placing the urea in a quartz boat with a cover, heating the urea to 550 ℃ from the normal temperature at the speed of 2.5 ℃/min in an air environment, reacting for 4h to obtain a light yellow solid, and grinding to obtain carbon nitride powder. Respectively weighing 20mg of ferrocenecarboxaldehyde and 100mg of carbon nitride (the mass ratio of the ferrocenecarboxaldehyde to the carbon nitride is 1. And heating the dispersion liquid in Ar to 100 ℃, reacting for 24h, naturally cooling, and then performing centrifugal separation to obtain the ferrocene-modified carbon nitride-5 powder. And (3) placing the obtained ferrocene modified carbon nitride-5 powder in a quartz boat with a cover, heating the quartz boat to 500 ℃ from the normal temperature at the speed of 5 ℃/min in the argon protection atmosphere, and preserving the temperature for 2 hours to obtain the iron-nitrogen-carbon-5-500 monatomic catalyst.

Example 2

This example differs from example 1 in that a weight ratio of ferrocenecarboxaldehyde to carbon nitride of 1 gives a catalyst of iron-nitrogen-carbon-1-500.

Example 3

This example differs from example 1 in that a weight ratio of ferrocenecarboxaldehyde to carbon nitride of 1.5 gives a catalyst of iron-nitrogen-carbon-0.5 to 500.

Example 4

This example differs from example 1 in that a weight ratio of ferrocenecarboxaldehyde to carbon nitride of 1.1 gives a catalyst of iron-nitrogen-carbon-0.1 to 500.

Fig. 1 is a transmission electron microscope image of fe-n-c-0.1-500 prepared in example 4, which shows that the morphology of the obtained catalyst is two-dimensional, and signals of fe, n and c elements can be observed and obtained simultaneously, and the three elements are uniformly distributed, which indicates that the catalyst successfully introduces fe atoms and can avoid the agglomeration of fe atoms.

Example 5

100mg of the catalyst obtained in example 1 was weighed out accurately into a 50mL polytetrafluoroethylene digestion tube. The masses m1, m2, m3, m4 were recorded, respectively. Adding about 6mL of concentrated nitric acid and 1mL of hydrogen peroxide into the weighed sample digestion tube respectively, covering a cover, putting the mixture into a stainless steel reaction kettle, putting the stainless steel reaction kettle into an oven at 180 ℃, preserving heat for 8 hours, and stopping heating and cooling. The cooled solution was transferred to a 25mL plastic volumetric flask and finally made to volume with deionized water. Preparing a standard test solution, wherein the standard solution is a national standard substance, and the curve concentration points are respectively as follows: 0. 0.5, 1.0, 2.0, 5.0 and 10.0mg/L. A standard solution calibration curve is firstly made by an American AES (American advanced encryption Standard) instrument with the model number of Varian (720-ES), the mass and the volume of a sample are input, then the digested solution is sequentially tested, and the test is carried out after the solution is diluted beyond the curve range. And determining the final content of the iron element in each sample according to the test result through a spectrogram to obtain 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 examples 5, 6, 7 and 8, according to which the iron content of the obtained catalyst gradually increases with the increase of the amount of ferrocene dialdehyde, and the maximum mass ratio can reach 2.7%. The iron atom content in the catalyst can be accurately regulated and controlled.

Example 9

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

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

Experimental results show that the concentration of residual tetracycline is 47.5% after the treatment of iron-nitrogen-carbon-5-500 for 30 min.

Example 10

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

Experimental results show that the concentration of residual tetracycline after being treated by iron-nitrogen-carbon-1-500 for 30min is 39.2%.

Example 11

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

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

Example 12

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

The experimental result shows that the concentration of residual tetracycline is 19.6 percent after the treatment of iron-nitrogen-carbon-0.1-500 min.

FIG. 3 is a graph showing the tetracycline degradation performance of the catalysts of examples 9, 10, 11 and 12 of this invention. It can be seen from the figure that the catalytic activity of the system is obviously improved along with the increase of the 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.

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

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

Example 14

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

Experimental results show that the concentration of residual tetracycline after being treated by iron-nitrogen-carbon-0.1-300 for 30min is about 35%.

Example 15

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

Experimental results show that the concentration of residual tetracycline is about 30% after being treated by Fe-N-C-0.1-400 for 30 min.

Example 16

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

Experimental results show that the concentration of residual tetracycline is about 20% after 30min treatment with Fe-N-C-0.1-600.

Example 17

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

Experimental results show that the concentration of residual tetracycline after being treated by iron-nitrogen-carbon-0.1-700 for 30min is about 18%.

The present invention is illustrated by the above-mentioned examples, but the present invention is not limited to the above-mentioned detailed process equipment and process flow, i.e. it is not meant to imply that the present invention must rely on the above-mentioned detailed process equipment and process flow to be practiced. It should be understood by those skilled in the art that any modifications of the present invention, equivalent substitutions of the raw materials of the product of the present invention, and the addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.

Claims

1. A metal atom high-doping-quantity monatomic catalyst is characterized in that:

the metal atom high-doping-amount single-atom catalyst is obtained by carrying out heat treatment on a metallocene-modified two-dimensional material, wherein the metallocene-modified two-dimensional material is obtained by connecting a metallocene derivative and the two-dimensional material through a covalent bond through a chemical reaction.

2. The metal atom high doping amount monatomic catalyst according to claim 1, wherein: the metallocene is any one or the combination of two or more of ferrocene, cobaltocene, nickelocene, zirconocene, titanocene and manganocene;

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

the metallocene derivative is any one or the combination of two or more of metallocene formaldehyde, 1' -metallocene diformaldehyde, metallocene formic acid, 1' -metallocene dicarboxylic acid, metallocene methanol and 1,1' -metallocene dimethanol.

3. A method for preparing a metal atom high doping amount monatomic catalyst as recited in any one of claims 1 to 2, wherein: the method comprises the following steps:

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

(2) Respectively weighing metallocene derivatives and the two-dimensional material obtained in the step (1) according to a certain mass ratio, and ultrasonically dispersing the metallocene derivatives and 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 performing centrifugal separation to obtain metallocene-modified two-dimensional material powder;

4. The method for preparing the metal atom high doping amount monatomic catalyst according to claim 3, wherein: the functional group is any one or the combination of two or more of amino, aldehyde group, carboxyl, hydroxyl, sulfo, halogen atom and epoxy group.

5. The method for preparing the metal atom high doping amount monatomic catalyst according to claim 3, wherein: the mass ratio of the two-dimensional material to the metallocene derivative in the step (2) is in the range of 1.

6. The method for preparing the metal atom high doping amount monatomic catalyst according to claim 3, wherein: in the step (3), the reaction temperature is within the range of 20-200 ℃, and the reaction time is within the range of 0.5-108 h.

7. The method for preparing the metal atom high doping amount monatomic catalyst according to claim 3, 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 within the range of 200-1000 ℃, and the heat preservation time is within the range of 0.5-20 h.

8. Use of the metal atom highly doped monatomic catalyst as recited in any one of claims 1 to 2 or the metal atom highly doped monatomic catalyst produced by the production method as recited in any one of claims 3 to 7, wherein: the application in sewage treatment.

9. A method for using the metal atom high-doping-amount monatomic catalyst as recited in any one of claims 1 to 2 or the metal atom high-doping-amount monatomic catalyst produced by the production method as recited in any one of claims 3 to 7 in sewage treatment, characterized in that: the application method comprises the following steps:

the monatomic catalyst of any one of claims 1 to 5 is ultrasonically dispersed in sewage with the pH =2-13, and is stirred for 0-24h to obtain a uniform dispersion liquid, and then an oxidizing agent is added to start reaction for a certain time to realize sewage treatment.

10. The use according to any one of claim 8 or the use method according to claim 9, characterized in that: