阅读说明：本技术 配位原子掺杂多孔碳纤维限域过渡金属单原子材料及其制备方法 (Coordination atom doped porous carbon fiber confinement transition metal monoatomic material and preparation method thereof ) 是由 于静 李�杰 王君 刘琦 刘婧媛 陈蓉蓉 朱佳慧 于 2021-09-20 设计创作，主要内容包括：本发明公开了一种配位原子掺杂多孔碳纤维限域过渡金属单原子材料及其制备方法,其制备方法包括如下步骤：S1.将过渡金属源溶于N,N-二甲基甲酰胺溶剂中,然后将正硅酸乙酯、高分子聚合物、配位原子源加入,水浴搅拌；S2.将配制好的前驱体纺丝溶液进行静电纺丝,制得前驱体纤维膜,真空干燥；S3.将前驱体纤维膜置于空气氛围下预氧化处理；随后在惰性气体保护下,升温碳化,保温,最后在惰性气体保护下冷却至室温；S4.将碳化后的纤维用氢氟酸刻蚀去除SiO-(2)硬模板,再用酸浸泡处理,离心分离即得。本发明材料中的过渡金属单原子与配位原子之间具有较强的电子耦合作用,通过调节配位环境可以实现过渡金属单原子性能的优化。(The invention discloses a coordination atom doped porous carbon fiber confinement transition metal monoatomic material and a preparation method thereof, wherein the preparation method comprises the following steps: s1, dissolving a transition metal source in an N, N-dimethylformamide solvent, adding tetraethoxysilane, a high-molecular polymer and a coordination atom source, and stirring in a water bath; s2, performing electrostatic spinning on the prepared precursor spinning solution to prepare a precursor fiber film, and performing vacuum drying; s3, placing the precursor fiber film in an air atmosphere for pre-oxidation treatment; then under the protection of inert gas, heating up for carbonization, preserving heat, and finally cooling to room temperature under the protection of inert gas; s4, etching the carbonized fiber by hydrofluoric acid to remove SiO 2 And (3) soaking the hard template by using acid, and performing centrifugal separation to obtain the template. Transition Metal sheets in the Material of the inventionThe atoms and the coordination atoms have stronger electronic coupling effect, and the optimization of the performance of the transition metal monoatomic atoms can be realized by adjusting the coordination environment.)

1. A preparation method of a coordination atom doped porous carbon fiber confinement transition metal monatomic material is characterized by comprising the following steps:

s1, dissolving a transition metal source in an N, N-dimethylformamide solvent, adding tetraethoxysilane, a high-molecular polymer and a coordination atom source, and stirring in a water bath to prepare a precursor spinning solution;

s2, performing electrostatic spinning on the precursor spinning solution prepared in the S1 to prepare a precursor fiber film, and drying the precursor fiber film in vacuum;

s3, placing the dried precursor fiber film in S2 in an air atmosphere for pre-oxidation treatment; then under the protection of inert gas, heating up for carbonization, preserving heat, and finally cooling to room temperature under the protection of inert gas to obtain carbonized fibers;

s4, etching the carbonized fiber in S3 by hydrofluoric acid to remove SiO₂And soaking the hard template in acid, and performing centrifugal separation to obtain the coordination atom doped porous carbon fiber confinement transition metal monoatomic material.

2. The method for preparing the coordination atom doped porous carbon fiber confinement transition metal monatomic material according to claim 1, wherein in S1, the metal source is any one of a Ni source, a Co source, a Fe source, a Cu source, a Mo source, a W source, and a Mn source.

3. The method for preparing the coordination atom doped porous carbon fiber confinement transition metal monatomic material according to claim 1, wherein in S1, the high molecular polymer is any one or a combination of more than two of polyvinylpyrrolidone, polyacrylonitrile, polyvinyl alcohol and polytetrafluoroethylene.

4. The method for preparing the coordination atom doped porous carbon fiber confinement transition metal monatomic material according to claim 1, wherein in S1, the coordination atom source is any one of urea, thiourea, thioacetamide, phosphoric acid and boric acid.

5. The preparation method of the coordination atom doped porous carbon fiber confinement transition metal monatomic material according to claim 1, wherein in S1, the dosage of the transition metal source is 0.1 to 2mmol, the dosage of tetraethoxysilane is 1 to 4mL, the dosage of the high molecular polymer is 1.5 to 3g, the dosage of the coordination atom source is 0.1 to 1g, and the dosage of the solvent is 10 to 20 mL.

6. The preparation method of the coordination atom doped porous carbon fiber confinement transition metal monatomic material according to claim 1, wherein in S1, the material is stirred in a water bath at 40-70 ℃ for 4-10 h.

7. The method for preparing the coordination atom doped porous carbon fiber confinement transition metal monatomic material according to claim 1, wherein in S2, the spinning voltage is controlled to be 15-20kV during electrospinning, the vertical distance between an injector and a receiving plate is 10-24cm, and the pushing rate of the injector is 0.5-1.5 mL/h.

8. The method for preparing the coordination atom doped porous carbon fiber confinement transition metal monatomic material according to claim 1, wherein in S3, the precursor fiber film is placed in a porcelain boat, the porcelain boat is placed in the middle of a tube furnace, air is introduced for pre-oxidation, the temperature of the tube furnace is raised to 250-300 ℃, the temperature raising rate is 2-2.5 ℃/min, and the temperature is maintained for 1-4 h; and then under the protection of inert gas, heating to 600-1200 ℃, keeping the heating rate at 4-5 ℃/min for 2-5h, and finally cooling to room temperature under the protection of inert gas to obtain the carbonized fiber.

9. The method for preparing the coordination atom doped porous carbon fiber confinement transition metal monatomic material according to claim 1, wherein in S4, the carbonized fiber in S3 is etched with hydrofluoric acid with the concentration of 10-20 wt% for 4-15h to remove SiO₂And (3) soaking the hard template by using sulfuric acid, hydrochloric acid or nitric acid with the concentration of 3-6 mol/L.

10. A coordination atom doped porous carbon fiber confinement transition metal monatomic material, characterized in that it is produced by the production method according to any one of claims 1 to 9.

Technical Field

The invention relates to the technical field of new energy materials, in particular to a coordination atom doped porous carbon fiber confinement transition metal monoatomic material and a preparation method thereof.

Background

The single atom has the highest atom utilization rate and unsaturated coordinated active center, so that the active site can be fully exposed, and the number of the active site is increased; furthermore, the monatomic material has a uniform structure, the active sites are highly dispersed at the atomic level, and the enhanced interaction and charge transfer between the monatomic material and the carrier can obviously improve the intrinsic activity of the active sites. However, the monoatomic material has very high surface energy and mobility, and is easy to agglomerate to form nanoparticles with larger size and more stability, so that the performance of the nanoparticles is reduced, the prevention of the agglomeration of metal monoatomic atoms is still an important challenge for preparing monoatomic metals, and the search for a suitable carrier for supporting the monoatomic material is an effective means for solving the problem. The stable existence of a single atom is premised on a certain strength of interaction with the carrier, which generally allows the single atom to exist in an ionic form rather than an atomic form, i.e., generally the single atom will have a certain oxidation state.

The microstructure and coordination environment of the metal monoatomic atoms on the electronic and atomic scale is critical. The activity of the active site of the single atom is closely related to the coordination environment of the active site, and the single atom can be synthesized by designing a coordination site or a coordination group on the surface of the carrier, capturing and limiting the transition metal single atom by utilizing the strong interaction between the coordination site or the coordination group and the transition metal single atom, preventing the single atom from migrating and agglomerating. The coordinating atoms used to anchor the monatomic atoms can affect the localized electronic structure of the active center, which in turn affects the performance of the monatomic material. Transition metal single atoms and peripheral different atoms can establish various coupling structures to form a specific overall coordination configuration, and the clear coordination structure is important for further understanding the single atom action mechanism. In conclusion, the regulation and control of the coordination environment of the transition metal monoatomic atom and the carrier hetero atom and the elucidation of the action mechanism of the coordination atom have important research values for coordinating the stability of the monoatomic atom and enhancing the performance of the monoatomic atom.

The inventors have found that carbon fibers have a large surface area, high electrical conductivity, and stable chemistry, and are common substrates for supporting a single metal atom. Another advantage of carbon fibers is that electronic interactions can be modulated by incorporating precise heteroatoms (e.g., boron, nitrogen, sulfur, phosphorus) on the support. The design of highly loaded, highly stable monatomic materials is best designed with the monatomic and its surrounding chemical environment as a whole. The design of constructing porous carbon fiber confinement transition metal single atoms based on different coordination environments can improve the conductivity to the maximum extent, and can also improve the long-term durability by preventing the movement and aggregation of the single atoms. Compared with strategies such as a hydrothermal method, an in-situ growth method, nucleation crystallization and the like, electrostatic spinning can directly construct a porous carbon fiber structure with a porous structure, the porous carbon fiber structure has the advantages of simple process and good controllability, and the efficient load and performance optimization of transition metal monoatomic atoms can be realized by constructing porous carbon fiber confinement transition metal monoatomic atoms based on different coordination environments by using an electrostatic spinning technology.

It is noted that the above information disclosed in this background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information constitutes prior art already known to a person skilled in the art.

In addition, only one Chinese patent document is found to have certain correlation through search. The chinese patent document CN111346640A discloses a transition metal monoatomic supported electrolyzed water catalyst and a preparation method thereof, the invention utilizes electrostatic spinning fiber and phthalocyanine to jointly limit domain to synthesize highly dispersed transition metal monoatomic, the electrolyzed water catalyst is composed of a carrier and a catalytic active component, the carrier is ultrafine carbon nanofiber, and the catalytic active component is transition metal monoatomic. The fiber-supported transition metal monoatomic water electrolysis catalyst prepared by the method has the characteristics of high active site performance and good dispersibility, has good alkaline water electrolysis hydrogen evolution activity, and can be used as a self-supporting electrode material to be directly used for electrocatalytic hydrogen production.

However, the transition metal monoatomic-supported electrolytic water catalyst does not incorporate precise heteroatoms (such as boron, nitrogen, sulfur and phosphorus) on the carrier to regulate the electronic interaction, and does not construct porous carbon fiber confinement transition metal monoatomic based on different coordination environments. But also the raw materials used are different. The phthalocyanine complex and the phthalocyanine ligand used in the invention are obviously different from the present application.

Disclosure of Invention

In view of the above, in order to solve the above technical problems, an object of the present invention is to provide a coordination atom doped porous carbon fiber confinement transition metal monatomic material and a preparation method thereof, wherein coordination atoms in carbon fibers, such as carbon, nitrogen, sulfur, phosphorus, boron, and other atomic confinement transition metal monatomic atoms, are utilized to disperse the coordination atoms into porous carbon fibers at an atomic level, so as to improve the loading of the monatomic atoms and regulate and control the performance of the monatomic atoms.

The adopted technical scheme is as follows:

the invention relates to a preparation method of a coordination atom doped porous carbon fiber confinement transition metal monatomic material, which comprises the following steps:

s1, dissolving a transition metal source in an N, N-dimethylformamide solvent, adding tetraethoxysilane, a high-molecular polymer and a coordination atom source, and stirring in a water bath to prepare a precursor spinning solution;

s2, performing electrostatic spinning on the precursor spinning solution prepared in the S1 to prepare a precursor fiber film, and drying the precursor fiber film in vacuum;

s3, placing the dried precursor fiber film in S2 in an air atmosphere for pre-oxidation treatment; then under the protection of inert gas, heating up for carbonization, preserving heat, and finally cooling to room temperature under the protection of inert gas to obtain carbonized fibers;

s4, etching the carbonized fiber in S3 by hydrofluoric acid to remove SiO₂Hard form, thenAnd (3) carrying out acid soaking treatment and centrifugal separation to obtain the coordination atom doped porous carbon fiber confinement transition metal monoatomic material.

In S1, the metal source is any one of a Ni source, a Co source, an Fe source, a Cu source, a Mo source, a W source, and an Mn source.

In S1, the high molecular polymer is any one or a combination of two or more of polyvinylpyrrolidone, polyacrylonitrile, polyvinyl alcohol, and polytetrafluoroethylene.

Further, in S1, the source of the coordinating atom is any one of urea, thiourea, thioacetamide, phosphoric acid, and boric acid.

Furthermore, in S1, the dosage of the transition metal source is 0.1-2mmol, the dosage of the tetraethoxysilane is 1-4mL, the dosage of the high molecular polymer is 1.5-3g, the dosage of the coordination atom source is 0.1-1g, and the dosage of the solvent is 10-20 mL.

Further stirring in water bath at 40-70 ℃ for 4-10h in S1.

Further, in S2, the spinning voltage is controlled to be 15-20kV during electrostatic spinning, the vertical distance between the injector and the receiving plate is 10-24cm, and the pushing rate of the injector is 0.5-1.5 mL/h.

Further, in S3, placing the precursor fiber film in a porcelain boat, placing the porcelain boat in the middle of a tube furnace, introducing air for pre-oxidation, raising the temperature of the tube furnace to 300 ℃ at the temperature of 250-; and then under the protection of inert gas, heating to 600-1200 ℃, keeping the heating rate at 4-5 ℃/min for 2-5h, and finally cooling to room temperature under the protection of inert gas to obtain the carbonized fiber.

Further, in S4, the carbonized fiber in S3 is etched by hydrofluoric acid with the concentration of 10-20 wt% for 4-15h to remove SiO₂And (3) soaking the hard template by using sulfuric acid, hydrochloric acid or nitric acid with the concentration of 3-6 mol/L.

The coordination atom doped porous carbon fiber confinement transition metal monatomic material is prepared by the preparation method of any scheme.

The invention has the following beneficial technical effects:

the invention provides a prepared coordination atom-doped porous carbon fiber confinement transition metal monoatomic material, and develops a method for doping a heteroatom-doped porous carbon fiber confinement transition metal monoatomic material, wherein a porous carbon fiber carrier has high specific surface area and porosity, and the provided porous structure can realize high-efficiency loading of the transition metal monoatomic material and avoid aggregation of the transition metal monoatomic material in a high-temperature carbonization process; the transition metal monoatomic atom has a strong electronic coupling effect with the coordination atom, and the optimization of the transition metal monoatomic atom performance can be realized by adjusting the coordination environment.

The invention provides a preparation method of a coordination atom doped porous carbon fiber confinement transition metal monatomic material and a universal strategy for optimizing the performance of the coordination atom doped porous carbon fiber confinement transition metal monatomic material, and the preparation method is suitable for popularization and application.

Drawings

FIG. 1 is a TEM image of the Ni-based material with sulfur-doped porous carbon fiber confinement prepared in example 1;

FIG. 2 is a spherical aberration electron microscope photograph of the nitrogen-doped porous carbon fiber confinement Ni monatomic material prepared in example 2;

FIG. 3 is a TEM image of the Fe monatomic material in the boron-doped porous carbon fiber confinement prepared in example 3.

Detailed Description

The technical solution of the present invention is further described below by using specific examples and with reference to the drawings, but the scope of the present invention is not limited thereto.

In the invention, the raw materials, equipment and the like are all available from the market or are commonly used in the field, if not specially.

Example 1

A preparation method of a sulfur-doped porous carbon fiber confinement Ni monatomic material comprises the following steps:

(1) dissolving 1.2mmol of nickel nitrate in 20mL of N, N-dimethylformamide, slowly adding 2mL of tetraethoxysilane, 1.5g of polyvinylpyrrolidone and 0.2g of thiourea for multiple times respectively, and magnetically stirring the mixture for 8 hours in a water bath at 60 ℃ to obtain a sol solution, namely a precursor spinning solution. And then preparing a precursor fiber membrane by adopting an electrostatic spinning method, wherein the spinning voltage is controlled to be 18kV during electrostatic spinning, the distance from a receiving device to a spinning needle head is 20cm, the feeding rate is 0.8mL/h, and aluminum foil receiving is carried out. Specifically, the spinning voltage is controlled to be 18kV, the vertical distance between the injector and the receiving plate is 20cm, and the pushing rate of the injector is 0.8 mL/h.

(2) Placing the fiber membrane in a porcelain boat, placing the porcelain boat in the middle position of a tube furnace, introducing air for pre-oxidation, heating the temperature of the tube furnace to 250 ℃, heating at a rate of 2.5 ℃/min, and keeping the temperature for 1 h; and then, under the protection of nitrogen, heating to 800 ℃, keeping the temperature for 2h at the heating rate of 5 ℃/min, and finally cooling to room temperature under the protection of inert gas.

(3) Etching the fiber carbonized at high temperature by using 20 wt% hydrofluoric acid for 12h to remove SiO₂And (3) treating the hard template with 4mol/L sulfuric acid for 6h, and performing centrifugal separation to obtain the sulfur-doped porous carbon fiber confinement Ni monatomic material, which is shown in figure 1.

As can be seen from fig. 1, the prepared material exhibits a porous fibrous morphology, and no significant agglomeration or larger nanoclusters are found.

Example 2

A preparation method of a nitrogen-doped porous carbon fiber confinement Ni monatomic material comprises the following steps:

(1) dissolving 1mmol of nickel nitrate in 18mL of N, N-dimethylformamide, slowly adding 2.35mL of tetraethoxysilane, 1.8g of polyvinylpyrrolidone and 0.3g of urea for multiple times respectively, and magnetically stirring the mixture for 8 hours in a water bath at 50 ℃ to obtain a sol solution, namely a precursor spinning solution. And then preparing a precursor fiber membrane by adopting an electrostatic spinning method, wherein the spinning voltage is controlled to be 20kV during electrostatic spinning, the distance from a receiving device to a spinning needle head is 20cm, the feeding rate is 0.8mL/h, and aluminum foil is received. Specifically, the spinning voltage is controlled to be 18kV, the vertical distance between the injector and the receiving plate is 20cm, and the pushing rate of the injector is 0.8 mL/h.

(2) Placing the fiber membrane in a porcelain boat, placing the porcelain boat in the middle position of a tube furnace, introducing air for pre-oxidation, heating the temperature of the tube furnace to 250 ℃, heating at a rate of 2.5 ℃/min, and keeping the temperature for 1 h; and then, under the protection of nitrogen, heating to 800 ℃, keeping the temperature for 2h at the heating rate of 5 ℃/min, and finally cooling to room temperature under the protection of inert gas.

(3) Etching the fiber carbonized at high temperature by using 20 wt% of HF for 12h to remove SiO₂And (3) treating the hard template with 4mol/L sulfuric acid for 6h, and performing centrifugal separation to obtain the nitrogen-doped porous carbon fiber confinement Ni monatomic material, which is shown in figure 2.

As can be seen from FIG. 2, the white bright spots circled in the high-resolution spherical aberration electron microscope are the atomically dispersed nickel monoatomic spots.

Example 3

A preparation method of a boron-doped porous carbon fiber confinement Fe monatomic material comprises the following steps:

(1) 1mmol of iron acetylacetonate was dissolved in 20mL of N, N-dimethylformamide, and then 2.5mL of ethyl orthosilicate, 1.6g of polyacrylonitrile, and 0.5mL of boric acid (boric acid density of 1.435 g/cm)³) And slowly adding the mixture for multiple times respectively, and magnetically stirring the mixture for 6 hours in a water bath at 65 ℃ to obtain a sol solution, namely a precursor spinning solution. The precursor fiber membrane is prepared by adopting an electrostatic spinning method, the spinning voltage is controlled to be 18kV during electrostatic spinning, the distance from a receiving device to a spinning needle head is 20cm, the feeding rate is 0.8mL/h, and aluminum foil receiving is carried out. Specifically, the spinning voltage is controlled to be 18kV, the vertical distance between the injector and the receiving plate is 20cm, and the pushing rate of the injector is 0.8 mL/h.

(2) Placing the fiber membrane in a porcelain boat, placing the porcelain boat in the middle of a tube furnace, introducing air for pre-oxidation, heating the temperature of the tube furnace to 250 ℃, heating at a rate of 2.5 ℃/min, keeping the temperature for 1h, heating to 1000 ℃ under the protection of argon, heating at a rate of 5 ℃/min, keeping the temperature for 2h, and finally cooling to room temperature under the protection of inert gas.

(3) Etching the fiber carbonized at high temperature by using 15 wt% HF for 10h to remove SiO₂And (3) treating the hard template with 4mol/L nitric acid for 6h to remove Fe nanoparticles, and performing centrifugal separation to obtain the boron-doped porous carbon fiber confinement Fe monatomic material, which is shown in figure 3.

As can be seen from fig. 3, the prepared material has a porous fibrous morphology, has an obvious hierarchical pore structure characteristic, and does not find obvious agglomeration or larger nanoclusters.

The detailed description set forth herein is merely a detailed description of possible embodiments of the invention and is not intended to limit the scope of the invention, which is intended to include within the appended claims all equivalent embodiments or modifications that do not depart from the spirit of the invention.