阅读说明：本技术 一种氧化钴/二硒化钴异质结构负载碳三氮四复合材料的制备方法 (Preparation method of cobalt oxide/cobalt diselenide heterostructure loaded carbon-nitrogen-carbon four-composite material ) 是由 张丰发 布和巴特尔 谭雪飞 董媛媛 王巍 张晓萌 史鹏 刘超 张晓晨 齐海群 于 2021-07-19 设计创作，主要内容包括：一种氧化钴/二硒化钴异质结构负载碳三氮四复合材料的制备方法,属于碳三氮四基复合材料制备领域。所述方法为：将Se粉分散在高沸点有机溶剂中,得到Se粉分散液；将钴源分散到低沸点有机溶剂中,再放入高沸点有机溶剂中,加热去除低沸点溶剂；将Se粉分散液加热得到反应液Ⅰ；g-C-3N-4加入低沸点有机溶剂,再加入到高沸点有机溶剂中,将低沸点溶剂全部去除,得到反应液Ⅲ；将钴源溶液加热得到反应液Ⅳ；将反应液Ⅰ、Ⅲ、和Ⅳ溶液混合水热；加入庚烷后,进行抽滤,清洗,真空干燥。本发明制备的材料的介电性能适合做电磁波吸收材料,可以通过调整负载量和尺寸来调控其对电磁波的吸收性能。(A preparation method of a cobalt oxide/cobalt diselenide heterostructure loaded carbon-nitrogen-tetrad composite material belongs to the field of carbon-nitrogen-tetrad composite material preparation. The method comprises the following steps: dispersing Se powder in a high-boiling-point organic solvent to obtain Se powder dispersion liquid; dispersing a cobalt source into a low-boiling-point organic solvent, then putting into a high-boiling-point organic solvent, and heating to remove the low-boiling-point solvent; heating the Se powder dispersion liquid to obtain a reaction liquid I; g-C 3 N 4 Adding a low-boiling-point organic solvent, adding the mixture into a high-boiling-point organic solvent, and completely removing the low-boiling-point solvent to obtain a reaction solution III; heating the cobalt source solution to obtain a reaction solution IV; mixing the reaction solution I, III and IV solution to obtain a mixture(ii) a After heptane was added, suction filtration, washing and vacuum drying were carried out. The dielectric property of the material prepared by the invention is suitable for being used as an electromagnetic wave absorption material, and the absorption property of the material to electromagnetic waves can be regulated and controlled by adjusting the load capacity and the size.)

1. A preparation method of a cobalt oxide/cobalt diselenide heterostructure loaded carbon-nitrogen-carbon four-composite material is characterized by comprising the following steps: the method comprises the following specific steps:

dispersing Se powder in a high-boiling-point organic solvent by using an ultrasonic disperser to obtain Se powder dispersion liquid;

step two, dispersing a cobalt source into a low-boiling-point organic solvent to obtain a cobalt dispersion liquid, then putting the cobalt dispersion liquid into a high-boiling-point organic solvent, and heating to remove the low-boiling-point organic solvent;

thirdly, heating the Se powder dispersion liquid obtained in the first step to 50-100 ℃, and ultrasonically dispersing for 30-200 min to obtain a reaction liquid I;

② take g-C₃N₄Adding the mixture into a low-boiling-point organic solvent, performing ultrasonic treatment at the temperature of 50-60 ℃ for 30-100 min to obtain a reaction solution II, adding the reaction solution II into a high-boiling-point organic solvent, stirring at the temperature of 50-100 ℃ and the stirring speed of 50-400 r/min for 10-200 min, and removing all the low-boiling-point organic solvent to obtain a reaction solution III;

thirdly, stirring the cobalt source solution obtained in the second step for 30-60 min at 50-100 ℃ under the stirring condition of 50-100 r/min to obtain a reaction solution IV;

mixing the reaction solutions I, III and IV and stirring for 10-100 min at 40-100 ℃ under the stirring condition of 50-100 r/min to obtain a reaction solution V; transferring the mixture into a hydrothermal reaction kettle, reacting for 120-240 min at 100-150 ℃, and then raising the reaction temperature to 150-200 ℃ for further reaction for 120-240 min;

adding heptane into the reaction liquid V, heating to 40-50 ℃, stirring for 10-100 min at the stirring speed of 50-100 r/min to obtain a reaction liquid VI, performing suction filtration on the reaction liquid VI by using a Buchner funnel, extracting a liquid part, filtering and cleaning solid matters by using heptane for five times, and collecting the solid matters; vacuum drying at 40-60 ℃ for 240-600 min to obtain CoO/CoSe₂Heterostructure loading g-C₃N₄A composite material.

2. The preparation method of the cobalt oxide/cobalt diselenide heterostructure loaded carbon-nitrogen-carbon four-composite material according to claim 1, characterized by comprising the following steps: in the first step, in the Se powder dispersion liquid, the mass fraction of Se powder is 5-15%.

3. The preparation method of the cobalt oxide/cobalt diselenide heterostructure loaded carbon-nitrogen-carbon four-composite material according to claim 1, characterized by comprising the following steps: in the first step, the high-boiling-point organic solvent is one or a mixed solution of more than two of octadecene, oleic acid, oleylamine and octadecanol.

4. The preparation method of the cobalt oxide/cobalt diselenide heterostructure loaded carbon-nitrogen-carbon four-composite material according to claim 1, characterized by comprising the following steps: step III, g-C in the finally obtained solution₃N₄The mass fraction of (A) is 0.01-3%.

5. The preparation method of the cobalt oxide/cobalt diselenide heterostructure loaded carbon-nitrogen-carbon four-composite material according to claim 1, characterized by comprising the following steps: in the second step and the third step, the high-boiling-point organic solvent is one or a mixed solution of more than two of octadecene, oleic acid, oleylamine and octadecanol; the low-boiling-point organic solvent is one of ethanol, acetic acid, ethyl acetate, n-butanol, tetrahydrofuran and methyl formate; the volume ratio of the low-boiling-point organic solvent to the high-boiling-point organic solvent is 1:2 to 5.

6. The preparation method of the cobalt oxide/cobalt diselenide heterostructure loaded carbon-nitrogen-carbon four-composite material according to claim 1, characterized by comprising the following steps: in the second step, the cobalt source is one of cobalt acetylacetonate, cobalt acetate, cobalt sulfate and cobalt chloride.

7. The preparation method of the cobalt oxide/cobalt diselenide heterostructure loaded carbon-nitrogen-carbon four-composite material according to claim 1, characterized by comprising the following steps: in the second step, the mass fraction of the cobalt source in the finally obtained solution is 10-20%.

8. The preparation method of the cobalt oxide/cobalt diselenide heterostructure loaded carbon-nitrogen-carbon four-composite material according to claim 1, characterized by comprising the following steps: in the third step, g-C in the reaction liquid II₃N₄And the weight ratio of the low-boiling-point organic solvent to the low-boiling-point organic solvent is 1-10: 100, respectively; g-C in the reaction liquid III₃N₄The weight ratio of the organic solvent to the high-boiling-point organic solvent is 1-10: 100.

9. the preparation method of the cobalt oxide/cobalt diselenide heterostructure loaded carbon-nitrogen-carbon four-composite material according to claim 1, characterized by comprising the following steps: in the step III, the volume ratio of the reaction solution I, the reaction solution III and the reaction solution IV is 1-2: 1: 1-2.

10. The preparation method of the cobalt oxide/cobalt diselenide heterostructure loaded carbon-nitrogen-carbon four-composite material according to claim 1, characterized by comprising the following steps: in the fourth step, the volume ratio of the reaction liquid V to heptane is 0.1-1: 1; the weight ratio of the heptane to the solid matter is 1-10: 1.

Technical Field

The present invention belongs to carbon three nitrogen four (g-C)₃N₄) The field of preparation of base composite materials, in particular to cobalt oxide/cobalt diselenide (CoO/CoSe)₂) Heterostructure supported carbon three nitrogen four (g-C)₃N₄) A method for preparing a composite material.

Background

Graphitized carbon nitride (g-C)₃N₄) Due to its unique structure and excellent performance, it is widely concerned in research and application, and its potential value in the fields of energy, catalysis, sensing, etc. is continuously developed, and its application in the fields of chemistry, material, physics, biology, environment, energy, etc. has achieved important achievements. g-C₃N₄Can further improve the physical and chemical properties of the product after being effectively compounded with other different materials, thereby leading the g-C to be₃N₄The application field is wider.

Chinese patent three-dimensional porous Co-C₃N₄Preparation method of (1) (publication No. CN110120514B) g-C was prepared by sintering a raw material containing N and C elements under a nitrogen atmosphere₃N₄Then doping Co element to g-C while forming pores₃N₄To obtain Co-C with high specific capacity₃N₄Can be used inThe field of lithium batteries. Chinese patent' A simple calcination method for preparing BaTiO₃/g-C₃N₄Method for preparing composite photocatalyst (publication No. CN112275306A) BaTiO with fiber-sheet composite structure is prepared by simple calcination method_3/g-C₃N₄The material enhances active sites and improves photocatalytic efficiency. Chinese patent three-dimensional/two-dimensional Ni-Co bimetal oxide/g-C₃N₄Nano composite material, preparation method and application thereof (publication No. CN112138702A), and three-dimensional/two-dimensional Ni-Co bimetallic oxide/g-C is prepared by using urea, nickel salt and cobalt salt as raw materials₃N₄The material has high-efficiency degradation performance. Chinese patent' A boron doped nano g-C₃N₄The electrocatalytic hydrogen production material coated with nano Co and its preparation method (publication No. CN112080757A) uses triisopropyl borate as boron source, and adopts hydrothermal synthesis method and thermal decomposition method to prepare boron-doped nano g-C with high specific surface area and pore structure₃N₄Nanosheets having a high specific surface area and high conductivity.

Heterostructure materials have quantum effects, large mobility and unusual two-dimensional characteristics and are widely applied to the fields of photodetectors, solar cells, standard resistors or photoelectric modulators and the like. Zhang et al prepared CoSe₂CoO and Nitrogen-doped carbon fiber composites (Electrochimica Acta, Volume 356,1October 2020,136822), in which CoSe is due to the heterostructure₂The addition of the-CoO material improves its catalytic performance.

In summary, there are many g-C₃N₄Patents on base composite materials, compounding of other materials effectively increases g-C₃N₄The physical and chemical properties of the heterostructure material are unique electron migration and interface effect, and the heterostructure material can change and optimize the properties after being compounded with other structural materials. But g-C in patent and literature reports₃N₄The preparation method of the composite material mainly adopts a high-temperature thermal decomposition method with higher cost, influences the large-area use of the composite material due to the higher cost, mainly adopts the photoelectric property research, and prepares the heterostructure material and the g-C by a simple method₃N₄CompoundingAnd reports on the study of electromagnetic properties are rare.

Disclosure of Invention

The invention aims to solve the problem that the prior method for preparing the heterostructure load g-C by a one-step method under the low-temperature condition is difficult to prepare₃N₄The problem of the composite material is that the method for preparing the cobalt oxide/cobalt diselenide heterostructure loaded carbon-nitrogen-carbon four composite material is that g-C is used₃N₄The cobalt salt and the selenium powder are used as main raw materials, are prepared by a simple solvothermal method at a lower cost under the condition of stepwise gradient temperature rise, and the dielectric property of the cobalt salt and the selenium powder is improved through the interface polarization effect, so that the cobalt salt and the selenium powder have excellent electromagnetic wave loss characteristics and become a novel electromagnetic wave absorbent.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a preparation method of a cobalt oxide/cobalt diselenide heterostructure loaded carbon-nitrogen-carbon four-composite material comprises the following specific steps:

dispersing Se powder in a high-boiling-point organic solvent by using an ultrasonic disperser to obtain Se powder dispersion liquid;

step two, dispersing a cobalt source into a low-boiling-point organic solvent to obtain a cobalt dispersion liquid, then putting the cobalt dispersion liquid into a high-boiling-point organic solvent, and heating to remove the low-boiling-point solvent;

thirdly, heating the Se powder dispersion liquid obtained in the first step to 50-100 ℃, and ultrasonically dispersing for 30-200 min to obtain a reaction liquid I; se powder is adsorbed by double bonds or functional groups of a high-boiling-point polar solvent, and a uniformly dispersed Se powder solution is obtained by an ultrasonic means, and the uniformly dispersed Se powder is favorable for forming small-size selenides.

② take g-C₃N₄Adding the mixture into a low-boiling-point organic solvent, performing ultrasonic treatment at the temperature of 50-60 ℃ for 30-100 min to obtain a reaction solution II, adding the reaction solution II into a high-boiling-point organic solvent, stirring at the temperature of 50-100 ℃ and the stirring speed of 50-400 r/min for 10-200 min, and removing all the low-boiling-point organic solvent to obtain a reaction solution III; by this method, a uniformly dispersed g-C can be obtained₃N₄The dispersion liquid avoids direct dispersion at high boiling pointThe phenomenon of uneven dispersion in organic solvent is favorable for uniform loading of selenide nano-particles on g-C₃N₄A surface.

Thirdly, stirring the cobalt source solution obtained in the second step for 30-60 min at 50-100 ℃ under the stirring condition of 50-100 r/min to obtain a reaction solution IV;

mixing the reaction solutions I, III and IV and stirring for 10-100 min at 40-100 ℃ under the stirring condition of 50-100 r/min to obtain a reaction solution V; transferring the mixture into a hydrothermal reaction kettle, reacting for 120-240 min at 100-150 ℃, and then raising the reaction temperature to 150-200 ℃ for further reaction for 120-240 min; first generating CoO/g-C by a gradient reaction method₃N₄The composite material (100-150 ℃) is heated, then partial CoO is selenized or Co ions which are not completely reacted at low temperature are selenized after the reaction temperature is raised, and the heterostructure CoO/CoSe is obtained₂/g-C₃N₄A composite material. By adjusting the reaction temperature and the reaction time, heterostructure materials with different proportions can be obtained, and CoO/g-C can also be obtained₃N₄Composite materials or CoSe₂/g-C₃N₄A composite material.

Adding heptane into the reaction liquid V, heating to 40-50 ℃, stirring for 10-100 min at the stirring speed of 50-100 r/min to obtain a reaction liquid VI, performing suction filtration on the reaction liquid VI by using a Buchner funnel, extracting a liquid part, filtering and cleaning solid matters by using heptane for five times, and collecting the solid matters; vacuum drying at 40-60 ℃ for 240-600 min to obtain CoO/CoSe₂Heterostructure loading g-C₃N₄Composite material, wherein the resulting CoO/CoSe₂The size is 5 to 100 nm.

The invention can effectively control the growth speed of the particles by the surfactant due to the reaction in the organic solvent, thereby obtaining the product with smaller particles. Uniformly growing the nanoparticles in g-C by physical-chemical adsorption at high temperature and high pressure₃N₄The surface is beneficial to the transmission of electron energy and improves the absorption performance of electromagnetic waves.

Further, in the first step, the mass fraction of the Se powder in the Se powder dispersion liquid is 5-15%.

Further, in the first step, the high-boiling-point organic solvent is one or a mixed solution of more than two of octadecene, oleic acid, oleylamine and octadecanol.

Further, in the third step, g-C in the finally obtained solution₃N₄The mass fraction of (A) is 0.01-3%.

Further, in the second and third steps, the high-boiling-point organic solvent is one or a mixed solution of more than two of octadecene, oleic acid, oleylamine and octadecanol; the low-boiling-point organic solvent is one of ethanol, acetic acid, ethyl acetate, n-butanol, tetrahydrofuran and methyl formate; the volume ratio of the low-boiling-point organic solvent to the high-boiling-point organic solvent is 1:2 to 5.

Further, in the second step, the cobalt source is one of cobalt acetylacetonate, cobalt acetate, cobalt sulfate and cobalt chloride.

Further, in the second step, the mass fraction of the cobalt source in the finally obtained solution is 10-20%.

Further, in the third step, g-C in the reaction liquid II₃N₄And the weight ratio of the low-boiling-point organic solvent to the low-boiling-point organic solvent is 1-10: 100, respectively; g-C in the reaction liquid III₃N₄The weight ratio of the organic solvent to the high-boiling-point organic solvent is 1-10: 100.

furthermore, in the third step, the volume ratio of the solutions of the reaction liquid I, III and IV is 1:1: 1.

Further, in the fourth step, the volume ratio of the reaction liquid V to heptane is 0.1-1: 1; the weight ratio of the heptane to the solid matter is 1-10: 1.

compared with the prior art, the invention has the beneficial effects that: in the invention, Se powder reacts with a cobalt source to generate CoO/CoSe₂Heterostructure and g-C₃N₄A composite material. Resulting from a reaction carried out in a solvent, the resulting CoO/CoSe₂The heterostructure particles are uniform in size and can be regulated and controlled in size, shape and structure through temperature and reaction time; the dielectric property of the prepared material is suitable for being used as an electromagnetic wave absorption material and can be used for preparing a materialThe absorption performance of the material on electromagnetic waves is regulated and controlled by adjusting the loading amount and the size;

the material prepared by the invention contains CoO/CoSe₂The heterostructure material has quantum effect, large mobility and singular two-dimensional space characteristics. CoO/CoSe in materials₂Heterostructures can dissipate a significant amount of electromagnetic wave energy through interfacial polarization. CoO/CoSe prepared by the invention₂Heterostructure loading g-C₃N₄CoO/CoSe obtained from composite material₂The size is 5 to 100 nm. And no agglomeration phenomenon exists. The invention firstly prepares the CoO material by a sectional heating method, and then partially selenizes the CoO to obtain the CoO/CoSe₂A heterostructure. The raw material is dispersed in the low-boiling point solvent and then transferred to the high-boiling point solvent, so that the problem of poor dispersibility when the raw material is directly dispersed in the high-boiling point solvent is solved.

Drawings

FIG. 1 is CoO/CoSe prepared in example 1₂/g-C₃N₄A transmission electron microscope image of the composite material;

FIG. 2 is CoO/CoSe prepared in example 1₂/g-C₃N₄Composite XRD pattern;

FIG. 3 is CoO/CoSe prepared in example 1₂/g-C₃N₄Composite electromagnetic wave absorption pattern;

FIG. 4 is CoO/CoSe prepared in example 2₂/g-C₃N₄A transmission electron microscope image of the composite material;

FIG. 5 is CoO/CoSe prepared in example 2₂/g-C₃N₄Electromagnetic wave absorption diagram of composite material.

Detailed Description

The technical solutions of the present invention are further described below with reference to the drawings and the embodiments, but the present invention is not limited thereto, and modifications or equivalent substitutions may be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

The innovation points of the invention are as follows: (1) preparation of CoO/CoSe by gradient heating method through one-pot method (solvothermal reaction)₂Heterostructure loadg-C₃N₄A composite material; (2) CoO loading g-C by first stage reaction₃N₄Selenizing part of CoO to obtain CoO/CoSe by raising reaction temp and elongating reaction time₂Heterostructure loading g-C₃N₄A composite material; (3) CoO and CoSe can be obtained by adjusting the reaction temperature and time₂Heterostructure materials in different proportions; (4) first-time CoO/CoSe₂Heterostructure loading g-C₃N₄The composite material is applied to electromagnetic wave absorption; (5) CoO/CoSe regulation and control through proportion of organic solvent₂The size of the heterostructure material; (6) by regulating CoO and CoSe₂And g-C₃N₄Obtaining composite materials with different electromagnetic wave properties according to the proportion; (7) by phase transfer of g-C₃N₄The material is uniformly dispersed in the organic solvent.

Example 1:

the preparation method of the cobalt oxide/cobalt diselenide heterostructure loaded carbon-nitrogen-carbon four-composite material is completed according to the following steps:

dispersing Se powder in octadecene by an ultrasonic disperser to obtain Se powder organic solvent dispersion liquid. The Se powder-octadecylene solution contains 10% of Se powder by mass and has a dispersion time of 60 min;

II, mixing g-C₃N₄Dispersing in ethanol, dispersing in octadecene, and heating to remove ethanol. Said g-C₃N₄The mass fraction of (A) is 1%; the volume ratio of the ethanol to the octadecene is 1: 2;

thirdly, dispersing a cobalt source into oleylamine to obtain a cobalt dispersion solution; the cobalt source is cobalt acetate. The mass fraction of the cobalt acetate is 10 percent;

fourthly, heating the Se powder solution to 80 ℃ to obtain reaction liquid I;

② will g-C₃N₄Heating the dispersion liquid to 80 ℃ to obtain reaction liquid II;

thirdly, heating the cobalt acetate solution to 80 ℃ to obtain reaction liquid III;

mixing the solutions I, II and III, stirring for 30min at 100 ℃ and 100r/min at a stirring speed to obtain a mixed solution IV, cooling to 50 ℃, transferring to a hydrothermal reaction kettle, reacting for 400min at 150 ℃, then increasing the reaction temperature to 200 ℃, reacting for 960min, and cooling to room temperature to obtain a reaction solution V; the volume ratio of the solutions of the reaction liquid I, the reaction liquid II and the reaction liquid III is 2:1: 2;

and fifthly, adding heptane into the reaction solution V to obtain a reaction solution VI, heating the reaction solution to 60 ℃, stirring for 30min at the stirring speed of 60r/min, performing suction filtration on the reaction solution VI by using a Buchner funnel, extracting a liquid part, and filtering and washing the liquid part by using heptane five times. Vacuum drying at 65 deg.C for 100min to obtain CoO/CoSe₂Heterostructure loading g-C₃N₄A composite material. The volume ratio of the reaction liquid V to heptane is 1: 1. The CoO/CoSe₂Heterostructure loading g-C₃N₄CoO/CoSe obtained from composite material₂The size is 10-20 nm.

As can be seen from FIG. 1, CoO @ CoSe prepared in example 1₂The size of the heterostructure is basically about 10-20 nanometers, and the heterostructure is embedded in the hetero g-C₃N₄A surface.

As shown in FIG. 2, the diffraction peaks at 30.775, 34.523, and 53.482 ° for 2 θ correspond to CoSe, respectively₂The (101), (111) and (031) crystal planes of the crystal, which are compatible with CoSe₂(PDF #53-0499) Standard cards matched, indicating that the product produced was indeed CoSe₂. The diffraction peaks at 36.4, 42.3 and 61.4 ° for 2 θ correspond to the (111), (200) and (220) crystallographic planes of the CoO crystal, respectively, which is consistent with the CoO (PDF #48-1719) standard card, indicating that the product produced is indeed CoO. 2 theta has a weak 002 characteristic peak of C at 26.2 degrees, but CoSe is loaded on the surface₂Resulting in less distinct peaks.

As shown in fig. 3, the sample was mixed with liquid paraffin in a weight ratio of 1:4 to prepare a hollow cylinder, and then the electromagnetic wave absorption performance was measured using a vector network analyzer. CoO @ CoSe can be seen from the reflectance graph (FIG. 3)₂/g-C₃N₄The composite material has good absorption effect at the thickness of 1-5mm (all the thicknesses exceed-10 dB), and the most excellent effect isThe excellent reflectivity is at 4.28GHz with the thickness of 4mm, which can reach-26.86 dB, and the frequency band which can absorb more than 90% of the electromagnetic wave energy is arranged in all thickness ranges.

Example 2:

the preparation method of the cobalt oxide/cobalt diselenide heterostructure loaded carbon-nitrogen-carbon four-composite material is completed according to the following steps:

dispersing Se powder in octadecene by an ultrasonic disperser to obtain Se powder organic solvent dispersion liquid. The Se powder-octadecylene solution contains 10% of Se powder by mass and has a dispersion time of 60 min;

II, mixing g-C₃N₄Dispersing in ethanol, adding into octadecene, and heating to remove ethanol. Said g-C₃N₄The mass fraction of (A) is 1%; the volume ratio of the ethanol to the octadecene is 1: 2;

thirdly, dispersing a cobalt source into oleylamine to obtain a cobalt dispersion solution; the cobalt source is cobalt acetate. The mass fraction of the cobalt acetate is 10 percent;

fourthly, heating the Se powder solution to 80 ℃ to obtain reaction liquid I;

② will g-C₃N₄Heating the dispersion liquid to 80 ℃ to obtain reaction liquid II;

thirdly, heating the cobalt acetate solution to 80 ℃ to obtain reaction liquid III;

mixing the solutions I, II and III, stirring for 30min at 100 ℃ and 100r/min to obtain a mixed solution IV, cooling to 50 ℃, transferring to a hydrothermal reaction kettle, reacting for 600min at 150 ℃, then increasing the reaction temperature to 200 ℃, reacting for 840min, and cooling to room temperature to obtain a reaction solution V; the volume ratio of the solutions of the reaction liquid I, the reaction liquid II and the reaction liquid III is 2:1: 2;

fifthly, adding heptane into the reaction solution V to obtain a reaction solution VI, heating the reaction solution to 60 ℃, stirring for 30min at the stirring speed of 60r/min, performing suction filtration on the reaction solution VI by using a Buchner funnel, extracting a liquid part, filtering and washing the reaction solution VI by using heptane five times, and performing vacuum drying for 100min at the temperature of 65 ℃ to obtain the CoO/CoSe₂Heterostructure loading g-C₃N₄A composite material. The volume ratio of the reaction liquid V to heptane is 1:1, and the CoO/CoSe is₂Heterostructure loading g-C₃N₄CoO/CoSe obtained from composite material₂The size is 30-50 nm.

As can be seen from FIG. 4, the CoO @ CoSe2 heterostructure prepared in example 2 has a size of about 30-50 nm and is embedded in the hetero-g-C₃N₄A surface.

As shown in fig. 5, the sample was mixed with liquid paraffin in a weight ratio of 1:4, and the electromagnetic wave absorption performance was measured using a vector network analyzer after hollow cylindrical. From the reflectance map (FIG. 5), it can be seen that CoO @ CoSe₂/g-C₃N₄The composite material has good absorption effect when the thickness is 1-5mm, the optimal reflectivity of the composite material is at 6.53GHz with the thickness of 3mm, the reflectivity can reach-34.75 dB, and the composite material can absorb more than 90% of the frequency band of electromagnetic wave energy.