阅读说明：本技术 高选择性太阳能驱动二氧化碳转化的复合材料及其制备 (High-selectivity composite material for driving carbon dioxide conversion by solar energy and preparation method thereof ) 是由 胡俊蝶 阳婷玉 李长明 于 2021-07-19 设计创作，主要内容包括：本发明涉及一种高选择性太阳能驱动二氧化碳转化的复合材料及其制备,属于环境及新能源材料领域。本发明首先通过溶剂剥离法将块状黑磷材料剥离成二维的黑磷纳米薄片；再将磷化钴的前驱体加入到黑磷纳米片溶液中分散均匀,在惰性气体保护下制备磷化钴@黑磷；以碳氮化合物为前驱体,通过高温煅烧和热剥离法制备薄层石墨相氮化碳纳米片；最后采用自组装法将石墨相氮化碳纳米片与黒磷@磷化钴薄片进行复合,得到磷化钴@黑磷/石墨相氮化碳纳米复合材料。本发明制备的磷化钴@黑磷/石墨相氮化碳纳米复合材料在光照条件下具有良好的还原二氧化碳性能；且合成步骤简单,产一氧化碳选择性高等优点,在二氧化碳减排、清洁能源生产方面很有工业应用前景。(The invention relates to a composite material for high-selectivity solar-driven carbon dioxide conversion and a preparation method thereof, belonging to the field of environmental and new energy materials. Firstly, stripping a blocky black phosphorus material into a two-dimensional black phosphorus nano sheet by a solvent stripping method; adding a precursor of cobalt phosphide into the black phosphorus nanosheet solution, uniformly dispersing, and preparing cobalt phosphide @ black phosphorus under the protection of inert gas; preparing a thin-layer graphite phase carbon nitride nanosheet by using a carbon nitride compound as a precursor through high-temperature calcination and thermal stripping; and finally, compounding the graphite-phase carbon nitride nanosheet with the black phosphorus @ cobalt phosphide sheet by adopting a self-assembly method to obtain the cobalt phosphide @ black phosphorus/graphite-phase carbon nitride nanocomposite. The cobalt phosphide @ black phosphorus/graphite phase carbon nitride nanocomposite prepared by the method has good carbon dioxide reduction performance under the illumination condition; and the synthesis steps are simple, the selectivity of the produced carbon monoxide is high, and the like, and the method has industrial application prospects in the aspects of carbon dioxide emission reduction and clean energy production.)

1. A preparation method of a cobalt phosphide @ black phosphorus/graphite phase carbon nitride nanocomposite is characterized by comprising the following steps:

(1) stripping the block black phosphorus by using a solvent to obtain a two-dimensional black phosphorus nanosheet;

(2) uniformly dispersing a precursor of cobalt phosphide and the two-dimensional black phosphorus nanosheet in the step (1) in an organic solvent, and heating in a protective atmosphere to obtain cobalt phosphide @ black phosphorus;

(3) calcining and stripping a carbon nitride compound serving as a precursor to obtain a graphite-phase carbon nitride nanosheet;

(4) and (3) uniformly mixing the cobalt phosphide @ black phosphorus in the step (2) and the graphite-phase carbon nitride nanosheet in the step (3) to obtain the cobalt phosphide @ black phosphorus/graphite-phase carbon nitride nanocomposite.

2. The method for preparing the cobalt phosphide @ black phosphorus/graphite-phase carbon nitride nanocomposite material according to claim 1, wherein the method comprises the following steps: in the step (1), the mass ratio of the black phosphorus to the solvent is 1: 1000-5000.

3. The method for preparing the cobalt phosphide @ black phosphorus/graphite-phase carbon nitride nanocomposite material according to claim 1, wherein the method comprises the following steps: in the step (1), the power of stripping is 10-200W; the stripping time is 1-5 days.

4. The method for preparing the cobalt phosphide @ black phosphorus/graphite-phase carbon nitride nanocomposite material according to claim 1, wherein the method comprises the following steps: in the step (2), the mass ratio of the cobalt phosphide precursor to the two-dimensional black phosphorus nanosheet is 1: 20-50.

5. The method for preparing the cobalt phosphide @ black phosphorus/graphite-phase carbon nitride nanocomposite material according to claim 1, wherein the method comprises the following steps: in the step (2), the heating is carried out at the temperature of 150 ℃ and 200 ℃ for 3-5 h.

6. The method for preparing the cobalt phosphide @ black phosphorus/graphite-phase carbon nitride nanocomposite material according to claim 1, wherein the method comprises the following steps: in the step (3), the carbon nitrogen compound is one or more of dicyandiamide, urea, thiourea, cyanamide and tricyanamide.

7. The method for preparing the cobalt phosphide @ black phosphorus/graphite-phase carbon nitride nanocomposite material according to claim 1, wherein the method comprises the following steps: in the step (3), the calcination is 400-600 ℃ calcination for 2-6 h; the stripping is carried out at the temperature of 400 ℃ and 600 ℃ for 1-4 h.

8. The method for preparing the cobalt phosphide @ black phosphorus/graphite-phase carbon nitride nanocomposite material according to claim 1, wherein the method comprises the following steps: in the step (4), the mass ratio of the cobalt phosphide @ black phosphorus to the graphite-phase carbon nitride nanosheet is 1: 1-100.

9. The cobalt phosphide @ black phosphorus/graphite phase carbon nitride nanocomposite prepared according to the process of any one of claims 1 to 8.

10. The use of the cobalt phosphide @ black phosphorus/graphite phase carbon nitride nanocomposite as defined in claim 9 in solar-driven carbon dioxide conversion, clean energy production.

Technical Field

The invention relates to the technical field of environment and new energy materials, in particular to a composite material for driving carbon dioxide conversion by high-selectivity solar energy and a preparation method thereof.

Background

Carbon dioxide (CO) in the atmosphere due to excessive consumption of fossil fuels₂) The concentration of the compound is continuously increased, and 400ppm of the compound is broken through, so that the global energy crisis and the ecological environment problem are caused. In order to solve the problems, a series of countermeasures such as 'carbon peak value' and 'carbon neutralization' targets, vigorous development of clean new energy and the like are recently proposed in China. Therefore, the development of clean energy and the reduction of carbon dioxide content have become one of the problems to be solved in the world. At present, the conversion of carbon dioxide into high-value fuel or chemical by utilizing solar energy based on semiconductor materials has become a feasible method. The method has the advantages of energy conservation, environmental protection, green, mild reaction conditions and the like, and can effectively solve the two problems.

In the field of solar-driven carbon dioxide conversion, two-dimensional materials have received much attention due to their excellent in-plane carrier mobility, catalytic active sites, and ease of constructing interfacial heterojunctions. The graphite phase carbon nitride material has the advantages of high photocatalytic activity, proper band gap (2.7 eV), low cost, good chemical stability, easiness in preparation and the like, and is widely applied to photocatalytic carbon dioxide reduction. However, the graphite phase carbon nitride material itself has many disadvantages, such as fast recombination of photogenerated carriers, poor charge transfer efficiency, and narrow absorption range of visible light. Therefore, constructing a suitable heterojunction is an effective way to overcome its limitations. The black phosphorus nanosheet has unique photoelectric characteristics, and has excellent light absorption capacity, a proper band gap and a high electron migration rate. Therefore, the construction of the black phosphorus/graphite phase carbon nitride heterojunction can effectively improve the photocatalytic activity, but the black phosphorus nanosheet is extremely unstable in the environment and is easy to oxidize, so that the photocatalytic activity is limited. In addition, the products in the process of converting carbon dioxide driven by solar energy are more, which is not beneficial to the industrial application. Therefore, increasing the selectivity of solar driven carbon dioxide conversion and enhancing the stability of black phosphorus based composites is a serious challenge at present.

Disclosure of Invention

Therefore, the technical problem to be solved by the invention is to overcome the selectivity of solar-driven carbon dioxide conversion and the stability of the black phosphorus-based composite material in the prior art.

In order to solve the technical problems, the invention provides a composite material for driving carbon dioxide conversion by high-selectivity solar energy and a preparation method thereof. The invention constructs a stable black phosphorus-based solar-driven carbon dioxide conversion material by a solvent stripping method, a hydrothermal method and a hydrothermal method. The material has excellent visible light responsiveness, high carrier mobility and good stability, and realizes high activity and high selectivity of the material in the conversion of solar-driven carbon dioxide.

The invention aims to provide a preparation method of a cobalt phosphide @ black phosphorus/graphite phase carbon nitride nanocomposite, which comprises the following steps:

(1) stripping the block black phosphorus by using a solvent to obtain a two-dimensional black phosphorus nanosheet;

(2) uniformly dispersing a precursor of cobalt phosphide and the two-dimensional black phosphorus nanosheet in the step (1) in an organic solvent, and heating in a protective atmosphere to obtain cobalt phosphide @ black phosphorus;

(3) calcining and stripping a carbon nitride compound serving as a precursor to obtain a graphite-phase carbon nitride nanosheet;

(4) and (3) uniformly mixing the cobalt phosphide @ black phosphorus in the step (2) and the graphite-phase carbon nitride nanosheet in the step (3) to obtain the cobalt phosphide @ black phosphorus/graphite-phase carbon nitride nanocomposite.

Further, in the step (1), the mass ratio of the black phosphorus to the solvent is 1: 1000-5000.

Further, in the step (1), the power of stripping is 10-200W; the stripping time is 1-5 days. The two-dimensional flaky material can be obtained by adopting a simple solution stripping method, the specific surface area of the black phosphorus material can be effectively increased, the active sites can be increased, and the catalytic effect of the photocatalyst can be enhanced.

Further, in the step (2), the mass ratio of the cobalt phosphide precursor to the two-dimensional black phosphorus nanosheet is 1: 20-50.

Further, in the step (2), the heating is 150-.

Further, in the step (3), the carbon nitrogen compound is one or more of dicyandiamide, urea, thiourea, cyanamide and tricyanamide.

Further, in the step (3), the calcination is 400-600 ℃ for 2-6h to obtain the bulk graphite phase carbon nitride.

Further, in the step (3), the stripping is to strip the bulk graphite phase carbon nitride by a thermal stripping method, and the stripping is to strip for 1-4h at the temperature of 400-.

Further, in the step (4), the mass ratio of the cobalt phosphide @ black phosphorus to the graphite-phase carbon nitride nanosheets is 1: 1-100; the reaction time is 10-16 h.

Further, after the reaction in the step (4) is finished, the cobalt phosphide @ black phosphorus/graphite phase carbon nitride nanocomposite is washed with water and ethanol for 2-5 times respectively, and then is dried in vacuum at 50-70 ℃. The two-dimensional cobalt phosphide @ black phosphorus is successfully modified on the surface of the graphite-phase carbon nitride nanosheet, a perfect heterojunction structure is formed, and the method plays a vital role in improving the efficiency of solar-driven carbon dioxide conversion.

The second purpose of the invention is to provide a cobalt phosphide @ black phosphorus/graphite phase carbon nitride nanocomposite.

The third purpose of the invention is to provide the application of the cobalt phosphide @ black phosphorus/graphite phase carbon nitride nanocomposite in the production of clean fuel.

The fourth purpose of the invention is to provide the application of the cobalt phosphide @ black phosphorus/graphite phase carbon nitride nanocomposite material in solar-driven carbon dioxide conversion.

Further, the cobalt phosphide @ black phosphorus/graphite phase carbon nitride nanocomposite is added into a sacrificial agent solution, and carbon dioxide is introduced to carry out a solar-driven carbon dioxide conversion reaction.

Further, the temperature of the reaction is 5-20 ℃; the pressure is 60-100 kPa.

According to the invention, a carbon nitrogen compound is used as a precursor, and a thin-layer graphite phase carbon nitride nanosheet is prepared by calcining under the air condition; stripping the massive black phosphorus into a two-dimensional black phosphorus sheet by using a solvent stripping method, and modifying cobalt phosphide on the black phosphorus nanosheet; and finally, preparing the stable cobalt phosphide @ black phosphorus/graphite phase carbon nitride nanocomposite by adopting a self-assembly method. The modification of cobalt phosphide improves the stability of black phosphorus and the selectivity of converting carbon dioxide into carbon monoxide by solar drive, and the introduction of cobalt phosphide @ black phosphorus enables the material to have strong absorption capacity for visible light. Therefore, the invention discloses the application of the cobalt phosphide @ black phosphorus/graphite phase carbon nitride nanocomposite material in solar-driven carbon dioxide conversion; meanwhile, the invention also discloses application of the cobalt phosphide @ black phosphorus/graphite phase carbon nitride nanocomposite in energy production, in particular application of solar-driven carbon dioxide to conversion of clean energy such as carbon monoxide.

The principle of the invention is as follows: the graphite phase carbon nitride material has a conduction band value of about-1.0V (relative to a standard hydrogen electrode) and a valence band value of about 2.0V (relative to a standard hydrogen electrode); the black phosphorus material has a conduction band value of about-0.8V (relative to a standard hydrogen electrode) and a valence band value of about-0.7V (relative to a standard hydrogen electrode). Their conduction band values are all more negative than the standard potentials for the reduction of carbon dioxide to carbon monoxide (-0.53V versus standard hydrogen electrode) and methane (-0.24V versus standard hydrogen electrode). Therefore, after the cobalt phosphide @ black phosphorus/graphite-phase carbon nitride forms a heterojunction, the solar energy is favorable for driving the carbon dioxide conversion reaction.

Compared with the prior art, the technical scheme of the invention has the following advantages:

(1) the solar energy drives the carbon dioxide to convert, is clean, environment-friendly, energy-saving and efficient, and has good large-scale industrial application prospect. The preparation method of the cobalt phosphide @ black phosphorus/graphite phase carbon nitride nanocomposite is simple, raw materials are easy to obtain, and the operation is simple and convenient, so that the method is very key to industrial application.

(2) The graphite-phase carbon nitride related by the invention has higher efficiency in the solar-driven carbon dioxide conversion, but the application of the graphite-phase carbon nitride is limited by the rapid recombination of photogenerated carriers, the unsatisfactory sunlight absorption capacity and the poor charge transfer efficiency, and the activity of the graphite-phase carbon nitride solar-driven carbon dioxide conversion can be improved by constructing the heterojunction.

(3) The black phosphorus nanosheet has unique photoelectric characteristics, such as strong sunlight absorption capacity, adjustable band gap and high charge mobility, and is also the most suitable solar-driven carbon dioxide conversion material. Therefore, the introduction of the two-dimensional black phosphorus nanosheet can greatly improve the electron transmission efficiency, improve the utilization rate of the graphite phase carbon nitride to visible light and further improve the conversion activity of the solar-driven carbon dioxide.

(4) The cobalt-based material has high carbon monoxide selectivity, and the cobalt phosphide is used for modifying the black phosphorus material, so that the selectivity of the composite material to carbon monoxide can be greatly improved. The cobalt phosphide is modified on the surface of the black phosphorus material through a cobalt-phosphorus bond, thereby occupying lone pair electrons of the black phosphorus and overcoming the defect that the black phosphorus is easy to oxidize in the environment, thereby improving the stability of the composite material in the process of converting the solar-driven carbon dioxide, being beneficial to the recovery and the reutilization of the material, simultaneously increasing the efficiency and the selectivity of converting the solar-driven carbon dioxide into carbon monoxide, and having good application prospect.

(5) The cobalt phosphide @ black phosphorus/graphite phase carbon nitride nanocomposite disclosed by the invention is a novel composite material with high visible light absorption efficiency, good catalytic effect and stable performance, has the selectivity of producing carbon monoxide by converting solar-driven carbon dioxide, can reach 95%, and can be used for producing carbon monoxide in a visible light environment.

Drawings

In order that the present disclosure may be more readily and clearly understood, reference is now made to the following detailed description of the present disclosure taken in conjunction with the accompanying drawings, in which:

fig. 1 is a Transmission Electron Micrograph (TEM) of two-dimensional black phosphorus nanoplates of example 1 of the present invention.

FIG. 2 is a Transmission Electron Micrograph (TEM) of cobalt phosphide @ black phosphorus of example 1 of the present invention.

FIG. 3 is a Transmission Electron Micrograph (TEM) of graphitic carbon nitride according to example 1 of the present invention.

FIG. 4 is a Transmission Electron Micrograph (TEM) of the cobalt phosphide @ black phosphorus/graphite phase carbon nitride nanocomposite of example 1 of the present invention.

FIG. 5 is a graph showing the effect of solar-driven carbon dioxide conversion to carbon monoxide in example 2 of the present invention.

FIG. 6 is a graph showing the effect of the solar-driven carbon dioxide reforming to methane in example 2 of the present invention.

FIG. 7 is a graph showing the selective effect of solar-driven carbon dioxide conversion in example 2 of the present invention.

FIG. 8 is a graph showing the effect of the solar-driven cycle on carbon dioxide conversion in example 2 of the present invention.

Detailed Description

The present invention is further described below in conjunction with the following figures and specific examples so that those skilled in the art may better understand the present invention and practice it, but the examples are not intended to limit the present invention.

Example 1

1. Preparation of two-dimensional black phosphorus material

Dispersing 20mg of blocky black phosphorus materials into 25 mLN-methyl pyrrolidone, and carrying out ultrasonic pulverization by using a cell pulverizer for 3d at the power of 160W to obtain an N-methyl pyrrolidone solution of the two-dimensional black phosphorus.

Fig. 1 is a TEM image of two-dimensional black phosphorus, which is seen to have a thin plate-like structure.

2. Preparation of cobalt phosphide @ black phosphorus nanosheet

Taking 10mL of N-methylpyrrolidone solution of two-dimensional black phosphorus, washing the solution with N, N-dimethylformamide solution for three times to obtain 10mL of N, N-dimethylformamide solution of two-dimensional black phosphorus, adding 35.6mg of cobalt (II) acetylacetonate into the solution, uniformly dispersing the solution, adding the solution into a reaction kettle, introducing argon into the reaction kettle, heating the solution at 180 ℃ for 4 hours, washing the product with ethanol for 3 times after the screening is finished, and drying the product in a vacuum oven for 12 hours to obtain the cobalt phosphide @ black phosphorus nanosheet.

Fig. 2 is a TEM image of a two-dimensional cobalt phosphide @ black phosphorus nanosheet, and it can be observed through the picture that the prepared cobalt phosphide is uniformly dispersed on the black phosphorus nanosheet.

3. Preparation of graphite phase carbon nitride nanosheet

Adding 3g of dicyandiamide into a crucible, putting the crucible into a muffle furnace, and setting the program to heat up to 550 ℃ from 20 ℃ at the heating rate of 2.5 ℃/min, preserving the heat for 4h, and then naturally cooling to obtain bulk graphite-phase carbon nitride nanosheets; and flatly spreading the blocky graphite-phase carbon nitride at the bottom of the flat-bottomed porcelain boat, putting the flat-bottomed porcelain boat into a muffle furnace, setting the temperature to rise from 20 ℃ to 550 ℃ at the temperature rise speed of 5 ℃/min, and naturally cooling after heat preservation for 2h to obtain the graphite-phase carbon nitride nanosheet. And adding the product into a beaker filled with a mixed solution of concentrated sulfuric acid and concentrated nitric acid, wherein each 100mg of graphite-phase carbon nitride nanosheet corresponds to a mixed solution of 5mL of concentrated sulfuric acid and 10mL of concentrated nitric acid. Acidifying for 10min, pouring the solution into a beaker containing 150mL of water, stirring, washing, standing, extracting, pouring out supernatant, adding 200mL of water, repeating the extraction for 5 times, washing the bottom turbid solution twice with ethanol, and vacuum drying at 60 ℃.

Fig. 3 is a TEM image of graphite phase carbon nitride, which shows a thin plate-like structure of the black phosphorus.

4. Preparation of cobalt phosphide @ black phosphorus/graphite phase carbon nitride nanocomposite

Dispersing 10mg of black phosphorus nano-sheets and 100mg of cobalt phosphide @ black phosphorus nano-sheets into 30mL of ethanol solution, performing ultrasonic treatment for 10min to uniformly disperse the black phosphorus nano-sheets and the cobalt phosphide @ black phosphorus nano-sheets, stirring the mixture at room temperature for 12h, after the reaction is finished, performing centrifugal separation on the product, then washing the product twice with ethanol, and finally drying the product in a vacuum oven at 60 ℃ to obtain the cobalt phosphide @ black phosphorus/graphite phase carbon nitride nano-composite material.

Fig. 4 is a TEM image of the cobalt phosphide @ black phosphorus/graphite phase carbon nitride nanocomposite from which it can be clearly and intuitively seen that the graphite phase carbon nitride nanosheets successfully formed a perfect heterojunction structure with the cobalt phosphide @ black phosphorus.

Example 2

A photocatalytic reactor was used for the photocatalytic reduction of carbon dioxide: uniformly mixing 10mg of cobalt phosphide @ black phosphorus/graphite phase-based carbon nitride nanocomposite prepared in example 1 with 12mL of mixed solution (acetonitrile: deionized water: triethanolamine: 3: 2: 1), putting the mixture into the photocatalytic reactor, introducing condensed water to keep the temperature at 5 ℃, turning on a xenon lamp light source, introducing carbon dioxide to enable the pressure in the reaction system to reach 80kPa, and starting to perform solar-driven carbon dioxide conversion reaction; the cobalt phosphide @ black phosphorus/graphite phase carbon nitride nanocomposite has high carbon dioxide reduction efficiency and high selectivity for generating carbon monoxide.

FIGS. 5 and 6 are a representation of the solar-driven carbon dioxide conversion of cobalt phosphide @ black phosphorus/graphite phase carbon nitride nanocomposite to produce carbon monoxide (CO) and methane (CH), respectively₄) The effect diagram of (1). Fig. 7 is a graph of the selective effect of solar-driven carbon dioxide conversion, and fig. 8 is a graph of the cyclic effect of solar-driven carbon dioxide conversion. As can be seen from the figure, the main product of the carbon dioxide reduction is carbon monoxide, and the byproduct is methane. The efficiency of the cobalt phosphide @ black phosphorus/graphite phase carbon nitride nanocomposite material for driving carbon dioxide to convert by solar energy is obviously superior to that of a graphite phase carbon nitride material and the cobalt phosphide @ black phosphorus material, wherein the yield of carbon monoxide can reach 16.21 mu molg at most^-1h^-1Is 5 times higher than the carbon monoxide produced by graphite phase carbon nitride material and 4 times higher than cobalt phosphide @ black phosphorus material. The selectivity of the cobalt phosphide @ black phosphorus/graphite phase carbon nitride nanocomposite to carbon monoxide is also obviously superior to that of the graphite phase carbon nitride material, and the selectivity of the composite material with the best performance to carbon monoxide reaches about 95%. In particular, the selectivity of the cobalt phosphide @ black phosphorus/graphite-phase carbon nitride nanocomposite to carbon monoxide is increased along with the increase of the proportion of the cobalt phosphide @ black phosphorus nanosheets, and the selectivity is the greatest when the proportion of the cobalt phosphide @ black phosphorus is 10%, so that the modification of the cobalt phosphide @ black phosphorus can effectively improve the selectivity of the graphite-phase carbon nitride to carbon monoxide. Through a cycle experiment, after four cycles, the cobalt phosphide @ black phosphorus/graphite phase carbon nitride nanocomposite has a stable efficiency of solar-driven carbon dioxide conversion, the yield of carbon monoxide and methane is slightly changed, the selectivity of carbon dioxide reduction is basically unchanged, and after four cycles, the selectivity of the composite to carbon monoxide can be maintained at 95%And on the left and right, the stability is proved to be good and the product can be recycled.

Through the analysis, the cobalt phosphide @ black phosphorus/graphite phase carbon nitride nanocomposite prepared by the simple and effective method has higher solar-driven carbon dioxide conversion efficiency and selectivity; the preparation method has the advantages of simple preparation process, easily obtained production raw materials and the like, and has application prospect in the aspect of solar-driven carbon dioxide conversion.

It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.