Potassium / ytterbium diatomic co-doped carbon nitride photocatalytic material, preparation method and application

Abstract

The application belongs to the field of photocatalytic functional materials, and discloses a potassium / ytterbium double-atom co-doped carbon nitride photocatalytic material, a preparation method and application. The potassium / ytterbium double-atom is co-doped into the carbon nitride structure through a one-step molten salt method, and transmission electron microscopy morphology observation is carried out on the catalyst material. It is found that the catalyst with a good crystallinity two-dimensional sheet structure is generated. Under the irradiation of visible light, a photocatalytic water decomposition hydrogen production experiment is carried out, and it is found that the material has good photocatalytic activity and stability. The new catalyst material and the preparation method have certain significance for enriching the types and sources of existing photocatalytic materials.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic functional materials, specifically relating to a potassium / ytterbium diatomic co-doped carbon nitride photocatalytic material, its preparation method and application. Background Technology

[0002] With the rapid growth of the global population and the rapid development of industry, the consumption of traditional fossil fuels is increasing year by year, and the energy shortage problem is becoming increasingly prominent. Finding new technologies to solve this problem is now urgent. Among many promising technologies, photocatalysis is considered one of the most promising for addressing energy shortages.

[0003] Carbon nitride, as a structurally tunable semiconductor photocatalyst, has attracted widespread attention due to its advantages such as low cost and availability, visible light response, suitable band structure, and chemical stability. However, carbon nitride semiconductor catalysts suffer from problems such as poor crystallinity, easy recombination of photogenerated electrons and holes, and a narrow light response range, resulting in unsatisfactory photocatalytic performance. Therefore, researchers have made great efforts and proposed corresponding strategies to improve the activity of photocatalytic materials, such as morphology control, elemental doping, construction of semiconductor heterojunctions, co-catalyst loading, and surface photosensitization.

[0004] Diatomic co-doping is considered an emerging method for preparing modified carbon nitride because diatomic catalysts exhibit high atomic utilization and synergistic catalytic effects at their two atomic sites, and also demonstrate strong electronic coupling with surrounding atoms. Diatomic-doped carbon nitride can improve its catalytic activity by controlling its spectral response range, light absorption capacity, and redox potential through tuning its electronic and band structures. Furthermore, existing literature primarily reports transition metals as the types of diatomic dopants in carbon nitride, with limited coverage of alkali metal and rare earth metal diatomic doping. This significantly restricts the types and sources of doped diatomic atoms. Therefore, it is urgent to explore a method for alkali metal and rare earth metal diatomic doping to achieve efficient doping of carbon nitride, thereby broadening the types and sources of diatomic metals. Summary of the Invention

[0005] This invention aims to enrich the types and sources of existing photocatalytic materials, providing a potassium / ytterbium diatomic co-doped carbon nitride photocatalytic material and its preparation method, and applying it to the field of photocatalytic water splitting for hydrogen production. The inventive concept involves incorporating potassium / ytterbium diatomic atoms into the carbon nitride structure via a one-step molten salt method to obtain a photocatalytic material with high hydrogen production performance and good stability.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] First, a certain amount of melamine, ytterbium oxide, potassium chloride, and lithium chloride were weighed and placed in an agate mortar, and repeatedly ground until homogeneous. The mixture was then dried in an oven. Next, the dried sample was placed in a square alumina crucible, which was then placed in a tube furnace. The furnace was heated to 500-600°C at a heating rate of 3-5°C / min for 3-5 hours. In the inert environment provided by potassium chloride and lithium chloride, potassium / ytterbium diatomic particles were incorporated into the carbon nitride structure to form a new catalytic material. Finally, the mixture was allowed to cool naturally to room temperature, yielding a pale yellow powder. The powder was collected, washed with hot deionized water, centrifuged, and dried to obtain the potassium / ytterbium diatomic co-doped carbon nitride photocatalytic material.

[0008] The mass ratio of melamine to ytterbium oxide is 1.5 to 2.5.

[0009] The total mass of melamine and ytterbium oxide is: potassium chloride:lithium chloride = 1:1.1:0.9.

[0010] Preferably, the reaction temperature is 550℃ and the heating time is 3 hours.

[0011] In a preferred embodiment of the present invention, 1.5g of melamine and ytterbium oxide, 1.65g of potassium chloride and 1.35g of lithium chloride were weighed and placed in an agate mortar, ground until uniform, and then dried in an oven. The dried sample was placed in a square alumina crucible and sealed with tin foil, heated to 550°C at a heating rate of 3°C / min, and held at that temperature for 3 hours. Then, heating was stopped, and the sample was allowed to cool to room temperature, and a pale yellow powder sample was collected. The sample was washed and centrifuged several times with hot deionized water, dried, and the pale yellow precipitate was collected, finally yielding potassium / ytterbium diatomic co-doped carbon nitride.

[0012] Another objective of this invention is to protect the application of potassium / ytterbium diatomic co-doped carbon nitride. Specifically, this material decomposes water to generate hydrogen gas under visible light irradiation, making it an excellent photocatalyst material that can be applied to visible light semiconductor photocatalytic materials.

[0013] Compared with the prior art, the beneficial effects of the present invention are:

[0014] (1) Using lithium chloride and potassium chloride as high-temperature liquid solvents, potassium / ytterbium diatoms are incorporated into two-dimensional layered carbon nitride materials. Potassium / ytterbium diatoms can serve as active sites for photocatalytic reactions, reducing electron localization and prolonging the influence of π-conjugation.

[0015] (2) Under visible light irradiation, through photocatalytic water splitting to produce hydrogen, it was found that the hydrogen production rate of the photocatalyst of the present invention (1377.12 μmol g) was significantly higher than that of the photocatalyst of the present invention. -1 h -1 The pure component is carbon nitride (440.59 μmol g). -1 h -1It is 3 times that of the photocatalyst material. Furthermore, through 20 cycles of stability testing, it was found that the hydrogen production activity did not significantly decrease after introducing potassium / ytterbium diatoms into the carbon nitride structure, proving that the photocatalyst material of this invention exhibits good stability during photocatalytic hydrogen production.

[0016] (3) The introduction of potassium / ytterbium diatoms into the carbon nitride structure mainly improves the charge transfer rate by reducing the electron density, thereby significantly enhancing the photocatalytic hydrogen evolution performance.

[0017] This invention synthesizes photocatalyst materials via a simple one-step molten salt method, characterized by simple experimental steps, short synthesis time, and high yield. This invention provides a new technical pathway for developing the types and sources of visible light semiconductor photocatalyst materials, which is of great significance for solving the increasingly serious energy problem. Attached Figure Description

[0018] Figure 1 These are transmission electron microscope images of the product of this invention, wherein the scale bars in (A) are 500 nm and the scale bars in (B) are 100 nm.

[0019] Figure 2 This is a comparison chart showing the rate of hydrogen production from water decomposition of the product of this invention and carbon nitride under visible light irradiation.

[0020] Figure 3 This is a cycle stability diagram of the product of the present invention for hydrogen production by water decomposition under visible light irradiation. Detailed Implementation

[0021] To more clearly illustrate the purpose, technical solutions, and advantages of this disclosure, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the following description of the embodiments is intended to explain and illustrate the overall concept of the present invention and should not be construed as limiting the invention. Unless otherwise specified, the experimental methods used in this invention are conventional methods, and the experimental equipment, materials, reagents, etc., used can all be purchased commercially.

[0022] Example 1

[0023] Weigh 1g of melamine, 0.5g of ytterbium oxide, 1.65g of potassium chloride, and 1.35g of lithium chloride into an agate mortar and grind until homogeneous. Dry the mixture in an oven. Place the dried sample into a square alumina crucible and seal it with tin foil. Heat the crucible to 550℃ at a rate of 3℃ / min and hold for 3 hours. Then, stop heating and allow the sample to cool to room temperature. Collect the pale yellow powder sample. Wash the sample repeatedly with hot deionized water and centrifuge. Dry the sample and collect the pale yellow precipitate. The final catalyst obtained is potassium / ytterbium diatomic co-doped carbon nitride with a mass ratio of x=2 (where x=2 is the mass ratio of melamine to ytterbium oxide, the same below).

[0024] Example 2

[0025] The preparation method of this embodiment is basically the same as that of Example 1, except that the mass of melamine and ytterbium oxide added in step (1) is adjusted to 0.9g and 0.6g respectively, and the final catalyst is potassium / ytterbium diatomic co-doped carbon nitride with x=1.5.

[0026] Example 3

[0027] The preparation method of this embodiment is basically the same as that of Example 1, except that the mass of melamine and ytterbium oxide added in step (1) is adjusted to 1.07g and 0.43g respectively, and finally, the catalyst is potassium / ytterbium diatomic co-doped carbon nitride with x=2.5.

[0028] Example 4

[0029] The preparation method of this embodiment is basically the same as that of Example 1, except that the mass of melamine and ytterbium oxide added in step (1) is adjusted to 1.5g and 0g respectively, and the catalyst obtained is pure carbon nitride.

[0030] Performance testing

[0031] like Figure 1 The image shown is a transmission electron microscope image of the product of the present invention. It can be observed from the transmission electron microscope image that the morphology of the product of the present invention is a two-dimensional sheet-like structure.

[0032] like Figure 2 The figure shows a comparison of the hydrogen production rates of the product of this invention and carbon nitride under visible light irradiation. The photocatalytic water splitting experiment shows that the hydrogen production rate of the product of this invention (1377.12 μmol g / L) is [missing data]. -1 h -1 The pure component is carbon nitride (440.59 μmol g). -1 h -1 This demonstrates that the photocatalytic activity of the product of this invention is three times that of carbon nitride.

[0033] like Figure 3 The diagram shows the cyclic stability of the product of this invention in water splitting to produce hydrogen under visible light irradiation. After 20 cycles of stability testing under visible light irradiation, no significant change in the hydrogen production activity of the product of this invention was observed, demonstrating that the photocatalyst material of this invention exhibits good stability in the photocatalytic hydrogen production process.

[0034] The potassium / ytterbium diatomic co-doped carbon nitride photocatalyst material prepared in this invention exhibits excellent water-splitting performance for hydrogen production under visible light irradiation. This is mainly attributed to the synergistic effect of the potassium / ytterbium diatomic material and the carbon nitride material, primarily in two aspects: Firstly, the incorporation of potassium / ytterbium diatomic atoms into the carbon nitride structure accelerates the separation of photoelectrons and holes, promoting electron transfer from carbon nitride to the diatomic potassium / ytterbium. Secondly, it provides more active sites for the photocatalytic reaction, shortening the diffusion distance of charge carriers to the interface, thereby improving the carrier transport efficiency. Compared with existing ytterbium single-atom doped graphitic carbon nitride materials and carbon nitride, the product of this invention has better photocatalytic activity and stability. The catalytic material and preparation method prepared in this invention are significant for enriching the types and sources of existing photocatalytic materials.

[0035] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a potassium / ytterbium diatomic co-doped carbon nitride photocatalytic material, characterized in that, The preparation method includes the following steps: First, a certain amount of melamine, ytterbium oxide, potassium chloride, and lithium chloride are weighed and ground evenly in an agate mortar, then dried. Next, the dried sample is reacted in a tube furnace, heated to 500-600℃ at a rate of 3-5℃ / min, and heated for 3-5 hours, allowing potassium / ytterbium diatomic doping into the carbon nitride structure to form a catalytic material. Finally, the mixture is cooled to room temperature, the powder is collected, washed with hot deionized water, centrifuged, and dried to obtain the potassium / ytterbium diatomic co-doped carbon nitride photocatalytic material. The raw materials are weighed according to the following mass ratio: the total mass of melamine and ytterbium oxide is 1:1.1:0.9, and the mass ratio of melamine to ytterbium oxide is 1.5~2.

5.

2. The preparation method according to claim 1, characterized in that, The reaction temperature in the preparation method is 550℃, and the heating time is 3 hours.

3. The preparation method according to claim 1, characterized in that, In the preparation method described above, 1.5 g of melamine and ytterbium oxide, 1.65 g of potassium chloride and 1.35 g of lithium chloride were weighed and placed in an agate mortar, ground until uniform, and then dried in an oven. The dried sample was placed in a square alumina crucible and sealed with tin foil. The temperature was increased to 550 °C at a heating rate of 3 °C / min and held at that temperature for 3 hours. Then, the heating was stopped, and the sample was allowed to cool to room temperature. The pale yellow powder sample was collected, washed with hot deionized water and centrifuged multiple times, dried, and the pale yellow precipitate was collected to finally obtain potassium / ytterbium diatomic co-doped carbon nitride.

4. A potassium / ytterbium diatomic co-doped carbon nitride photocatalytic material, characterized in that, It is prepared according to the preparation method according to any one of claims 1-3.

5. The application of the potassium / ytterbium diatomic co-doped carbon nitride photocatalytic material according to claim 4, characterized in that, It is applied to photocatalytic water splitting for hydrogen production under visible light.

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