阅读说明：本技术 一种多孔g-C3N4纳米薄片的制备方法及其应用 (Porous g-C3N4Preparation method and application of nano-sheet ) 是由 关荣锋 田亚西 高岩 石文艳 张海成 李正恩 于 2021-08-03 设计创作，主要内容包括：本发明属于多孔纳米材料的制备技术领域,具体涉及一种多孔g-C-(3)N-(4)纳米薄片的制备方法及其应用。本发明的制备方法包括以下步骤：(1)将三聚氰胺、葡萄糖酸盐、去离子水混合均匀,得乳浊液；(2)将所述乳浊液置于高压釜中进行水热反应,得悬浮液；(3)将所述悬浮液固液分离,将所得固体洗涤、干燥,得水热前驱体；(4)将所述水热前驱体在空气中煅烧,得多孔g-C-(3)N-(4)纳米薄片。本发明制备的多孔g-C-(3)N-(4)纳米薄片与体相g-C-(3)N-(4)相比,具有更大的比表面积,电子转移速率加快,且有效抑制了电子空穴对的复合；二维纳米片和多孔形貌的成功制备,使其具有更多的活性位点,解决了块状的团聚和堆叠问题,拥有更好的光催化活性。(The invention belongs to the technical field of preparation of porous nano materials, and particularly relates to porous g-C 3 N 4 A preparation method and application of nano-flakes. The preparation method comprises the following steps: (1) uniformly mixing melamine, gluconate and deionized water to obtain emulsion; (2) placing the emulsion in a high-pressure kettle for hydrothermal reaction to obtain a suspension; (3) carrying out solid-liquid separation on the suspension, washing and drying the obtained solid to obtain a hydrothermal precursor; (4) calcining the hydrothermal precursor in air to obtain porous g-C 3 N 4 And (4) nano flakes. Porous g-C prepared by the invention 3 N 4 Nanoplatelets and bulk g-C 3 N 4 Compared with the prior art, the material has larger specific surface area, the electron transfer rate is accelerated, and the recombination of electron hole pairs is effectively inhibited; successful preparation of two-dimensional nanoplates and porous morphologies to render them more viableThe sexual locus solves the problems of agglomeration and stacking of blocks and has better photocatalytic activity.)

1. Porous g-C₃N₄The preparation method of the nano-flake is characterized by comprising the following steps of:

(1) uniformly mixing melamine, gluconate and deionized water to obtain emulsion;

(2) placing the emulsion in a high-pressure kettle for hydrothermal reaction to obtain a suspension;

(3) carrying out solid-liquid separation on the suspension, washing and drying the obtained solid to obtain a hydrothermal precursor;

(4) calcining the hydrothermal precursor in air to obtain porous g-C₃N₄And (4) nano flakes.

2. The porous g-C of claim 1₃N₄The preparation method of the nano-flake is characterized in that in the step (1), the gluconic acidThe salt is potassium gluconate or sodium gluconate.

3. The porous g-C of claim 1₃N₄The preparation method of the nano-flake is characterized in that in the step (1), the mass ratio of melamine to potassium gluconate is 7.2: (0.025 to 0.2); or the mass ratio of the melamine to the sodium gluconate is 4: (0.05-0.2).

4. The porous g-C of claim 1₃N₄The preparation method of the nano-flake is characterized in that in the step (1), every 60mL of deionized water corresponds to 4-7.2 g of melamine.

5. The porous g-C of claim 1₃N₄The preparation method of the nano sheet is characterized in that in the step (2), the temperature of the hydrothermal reaction is 160-200 ℃, and the time of the hydrothermal reaction is 10-14 h.

6. The porous g-C of claim 1₃N₄The preparation method of the nano sheet is characterized in that in the step (4), the calcining temperature is 500-650 ℃;

preferably, the calcining time is 3-6 h.

7. The porous g-C of claim 1₃N₄The preparation method of the nano sheet is characterized in that the temperature rise rate of the calcination is 3-10 ℃/min.

8. The porous g-C of claim 1₃N₄The preparation method of the nano-sheet is characterized in that in the step (4), the gluconate is potassium gluconate, and secondary calcination is performed after the calcination is finished, wherein the temperature of the secondary calcination is 500-650 ℃.

9. Porous g-C according to claim 7₃N₄Method for preparing nano-flake, and the sameCharacterized in that in the step (4), the secondary calcination time is 3-6 h;

preferably, the temperature rise rate of the secondary calcination is 3-10 ℃/min.

10. Use of a porous g-C according to any of claims 1 to 9₃N₄Porous g-C prepared by preparation method of nano-sheet₃N₄The application of the nano-flake as a photocatalytic material.

Technical Field

The invention belongs to the technical field of preparation of porous nano materials, and particularly relates to porous g-C₃N₄A preparation method and application of nano-flakes.

Background

In the modern society, along with the rapid development of modern industrial technology, the problem of energy shortage is increasingly outstanding and needs to be solved urgently. The use of a large amount of traditional energy causes various environmental problems such as floating dust, acid rain, greenhouse effect and the like, so that the survival and development of human beings meet unprecedented challenges, and the energy structure needs to be adjusted urgently. With the gradual depletion of fossil fuels, the development of new energy sources is imminent, people explore various methods to search for new energy sources, the developed new energy sources comprise solar energy, hydroenergy, wind energy, ocean energy, tidal energy, biomass energy and the like, the proportion of the clean energy sources in a primary energy structure is gradually increased, and if the clean energy sources are utilized, the new energy sources have important practical significance for solving the energy problem. The hydrogen energy is clean and efficient secondary energy, has good heat conductivity and combustibility and high utilization rate, and compared with other fuels, the combustion product is nontoxic and nuisanceless.

For the acquisition of hydrogen energy, the photocatalyst is considered as one of the most promising energy conversion modes, has outstanding performances in the aspects of environmental pollution treatment, clean energy and the like, and can utilize solar energy as a light source to drive catalytic water decomposition to prepare hydrogen.

In 2009, Wang et al discovered for the first time graphite-like carbon nitride (g-C₃N₄) The catalyst has strong oxidation-reduction capability, so that the catalyst can crack water and separate hydrogen under visible light. g-C₃N₄Is a polymer with 3-s-triazine structure as a unit, and the sp is arranged among C, N molecules²The hybrid orbital forms conjugated pi bonds with good chemical and thermal stability, and thus, g-C₃N₄As a hydrogen evolution photocatalyst, it has been widely studied. Semiconductor photocatalyst g-C₃N₄With its own unique advantages, the band gap E is fixed_g2.70eV, has a proper energy band structure, has a good response to visible light, has outstanding performance in the aspect of hydrogen production by photocatalytic water splitting, and has attracted the worldwide attention. But bulk phases g-C₃N₄Poor conductivity, small specific surface area, high recombination rate of photo-generated electron-hole pairs, low photocatalytic efficiency and the like, and the block body g-C₃N₄The number of centers and adsorption centers is very small and its photocatalytic activity is far from satisfactory.

The former adjusts g-C by various methods such as changing morphology, increasing specific surface area, doping elements, compounding heterojunction and the like₃N₄The band gap of (3) widens the response range to light and the separation efficiency of photon-generated carriers. Numerous attempts have been made before methods such as morphology control, heteroatom doping, metal loading, etc., and the development of new synthetic materials and the significant improvement of the photocatalytic performance of nitrogen carbide are problems which are urgently needed to be solved at present.

Therefore, there is a need to provide an improved solution to the above-mentioned deficiencies of the prior art.

Disclosure of Invention

The invention aims to provide a brand new porous g-C₃N₄The preparation method of the nano-sheet aims to solve the problem that the existing nitrogen carbide material is low in photocatalytic activity.

In order to achieve the purpose, the invention provides the following technical scheme:

porous g-C₃N₄The preparation method of the nano-flake comprises the following steps:

(1) uniformly mixing melamine, gluconate and deionized water to obtain emulsion;

(2) placing the emulsion in a high-pressure kettle for hydrothermal reaction to obtain a suspension;

(3) carrying out solid-liquid separation on the suspension, washing and drying the obtained solid to obtain a hydrothermal precursor;

(4) calcining the hydrothermal precursor in air to obtain porous g-C₃N₄And (4) nano flakes.

Preferably, in the step (1), the gluconate is potassium gluconate or sodium gluconate.

Preferably, in the step (1), the mass ratio of melamine to potassium gluconate is 7.2: (0.025 to 0.2); or the mass ratio of the melamine to the sodium gluconate is 4: (0.05-0.2).

Preferably, in the step (1), 4-7.2 g of melamine is added to every 60mL of deionized water.

Preferably, in the step (2), the temperature of the hydrothermal reaction is 160-200 ℃, and the time of the hydrothermal reaction is 10-14 h.

Preferably, in the step (4), the calcining temperature is 500-650 ℃.

Preferably, the calcining time is 3-6 h.

Preferably, the temperature rise rate of the calcination is 3-10 ℃/min.

Preferably, in the step (4), the gluconate is potassium gluconate, and the secondary calcination is performed after the calcination is finished, wherein the temperature of the secondary calcination is 500-650 ℃.

Preferably, in the step (4), the time of the secondary calcination is 3-6 h.

Preferably, the temperature rise rate of the secondary calcination is 3-10 ℃/min.

The present invention also provides the above porous g-C₃N₄The application of the nano-flake as a photocatalytic material.

Has the advantages that:

the performance of the carbon nitride prepared by the invention far exceeds that of blocky g-C₃N₄Is g-C₃N₄The change of the appearance and the performance provides a new way of thinking. The invention is provided withThe following advantages are:

(1) firstly utilizes the characteristics of gluconate and adopts a two-step method to synthesize porous g-C₃N₄A nanoflake;

(2) porous g-C prepared by the invention₃N₄Nanoplatelets and bulk g-C₃N₄Compared with the prior art, the material has larger specific surface area, the electron transfer rate is accelerated, and the recombination of electron hole pairs is effectively inhibited; the two-dimensional nanosheets and the porous shapes are successfully prepared, so that the nanosheets have more active sites, and the problems of lumpy agglomeration and stacking are solved, so that the nanosheets have better photocatalytic activity;

(3) novel g-C prepared by the invention₃N₄The hydrogen production rate of the photocatalytic material can reach 3441 mu mol/g/h, and the bulk phase g-C₃N₄The hydrogen production rate is only 130 mu mol/g/h, the former hydrogen production rate is 26 times of the latter hydrogen production rate, namely the invention has excellent visible light catalytic performance;

(4) porous g-C of the invention₃N₄The preparation process of the nano-sheet is simple, the operation is easy, the repeatability is good, the green and environment-friendly effects are achieved, and the prepared material is good in stability and high in hydrogen production rate.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention. Wherein:

FIG. 1 is a schematic representation of a cell g-C according to example 3 of the present invention₃N₄Scanning Electron Microscope (SEM) images of the nanoplatelets;

FIG. 2 is a schematic representation of a porous g-C of example 3 of the present invention₃N₄Transmission Electron Microscopy (TEM) images of the nanoplatelets;

FIG. 3 shows a porous g-C of example 3 of the present invention₃N₄Nanoplatelets and comparative example 1 bulk phase g-C₃N₄A fluorescence spectrum (PL) test pattern of (a);

FIG. 4 shows a porous g-C of example 3 of the present invention₃N₄UV-VIS absorption spectra of nanoflakes and comparative example 1 bulk g-C3N 4;

FIG. 5 shows a porous g-C of example 3 of the present invention₃N₄Nanoplatelets and comparative example 1 bulk phase g-C₃N₄A band gap diagram of;

FIG. 6 shows a porous g-C of example 3 of the present invention₃N₄Nanoplatelets and comparative example 1 bulk phase g-C₃N₄Hydrogen production under visible light irradiation;

FIG. 7 shows sodium gluconate-modified g-C of example 7 in accordance with the present invention₃N₄Scanning Electron Microscope (SEM) images of (a);

FIG. 8 shows the bulk phases g-C of comparative example 2 of the present invention₃N₄Scanning Electron Microscope (SEM) images of (a);

FIG. 9 shows sodium gluconate-modified g-C of example 7 in accordance with the present invention₃N₄And comparative example 2 bulk phases g-C₃N₄X-ray diffraction (XRD) pattern of (a);

FIG. 10 shows sodium gluconate-modified g-C of example 7 in accordance with the present invention₃N₄And comparative example 2 bulk phases g-C₃N₄The amount of hydrogen produced by visible light.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments that can be derived by one of ordinary skill in the art from the embodiments given herein are intended to be within the scope of the present invention.

The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings. It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.

The nano sheet changes the morphological structure of carbon nitride to make the carbon nitride nano, and is generally used for increasing g-C₃N₄The specific surface area of the photocatalyst enables more active sites to be provided and the photocatalytic activity to be increased. Currently, glucose is often used as a precursor for synthesizing C quantum dots. The patent firstly prepares g-C by adopting a sodium gluconate hydrothermal method₃N₄Nanosheets, greatly improved g-C₃N₄To solve the above-mentioned g-C₃N₄The invention provides a brand new g-C₃N₄Preparation method of increasing g-C₃N₄The photocatalytic activity of the photocatalyst has important practical significance.

The two-dimensional nano-flake has high aspect ratio, large specific surface area, high charge transfer rate, high stacking property and mechanical flexibility, which is the improvement of g-C₃N₄One of the most effective methods for photocatalytic activity. The nano structure is beneficial to accelerating the transport of electrons, shortening the diffusion path of the photo-excited electron hole pair from the body to the surface of the catalyst, providing abundant reaction sites, enhancing charge transport and inhibiting the recombination of charge carriers. 2D g-C₃N₄The ultrathin thickness of the photocatalytic material provides wider space for water molecule adhesion, a porous shape is prepared on the nano-chip, and the change obviously increases the number of reactive sites, and is more beneficial to improving g-C₃N₄Photocatalytic activity of (1). The porous structure not only can obviously improve the charge transport efficiency in the photocatalysis process, but also can greatly reduce the recombination and aggregation of electron holes through interaction sites. Therefore, the development of efficient and environment-friendly photocatalyst has important practical significance.

Porous g-C of the invention₃N₄The preparation method of the nano-flake comprises the following steps:

(1) uniformly mixing melamine, gluconate and deionized water to obtain emulsion;

(2) placing the emulsion in a high-pressure kettle for hydrothermal reaction to obtain a suspension;

(3) carrying out solid-liquid separation on the suspension, washing and drying the obtained solid to obtain a hydrothermal precursor;

(4) calcining the hydrothermal precursor in air to obtain porous g-C₃N₄And (4) nano flakes.

In the step (1), the gluconate is potassium gluconate or sodium gluconate.

For potassium gluconate, in the step (1), the mass ratio of melamine to potassium gluconate is 7.2: (0.025 to 0.2), for example, 7.2: 0.025, 7.2: 0.05, 7.2: 0.075, 7.2: 0.1, 7.2: 0.2, 7.2: 0.4, 7.2: 0.6 or 7.2: 0.8.

for sodium gluconate, in the step (1), the mass ratio of melamine to sodium gluconate is 4: (0.05 to 0.2), for example, 4: 0.05, 4: 0.1 or 4: 0.2, wherein the optimal ratio is 4: 0.1.

in the step (1), each 60mL of deionized water corresponds to 4-7.2 g of melamine.

In the step (1), various modes can be selected for uniform mixing, preferably, ultrasonic-assisted dispersion is adopted, and the ultrasonic time is 10-60 min, such as 10min, 20min, 30min, 40min, 50min or 60min, preferably 30 min.

In the step (2), the temperature of the hydrothermal reaction is 160-200 ℃, for example 160 ℃, 165 ℃, 170 ℃, 175 ℃, 180 ℃, 185 ℃, 190 ℃, 195 ℃ or 200 ℃, preferably 180 ℃, and the time of the hydrothermal reaction is 10-14 h, for example 10h, 11h, 12h, 13h or 14h, preferably 12 h.

In the step (3), various operations commonly used in the experimental field can be selected for solid-liquid separation, and in order to facilitate the experiment, a centrifugation mode is selected, the obtained solid is washed 3-5 times (for example, 3 times, 4 times or 5 times), preferably 5 times, by deionized water after centrifugation, and then dried for 12-24 hours (for example, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours or 24 hours) at 60-80 ℃ (for example, 60 ℃, 70 ℃ or 80 ℃).

In the step (4), the calcining temperature is 500-650 ℃ (for example, 500 ℃, 520 ℃, 540 ℃, 560 ℃, 580 ℃, 600 ℃, 620 ℃ or 650 ℃), preferably 550 ℃, the calcining time is 3-6 h (for example, 3h, 4h, 5h, 6h), preferably 4h, wherein the heating rate is 3-10 ℃/min (for example, 3 ℃/min, 4 ℃/min, 5 ℃/min, 6 ℃/min, 7 ℃/min, 8 ℃/min, 9 ℃/min or 10 ℃/min), preferably 5 ℃/min; the potassium gluconate is preferably subjected to secondary calcination after the calcination is completed (after the first calcination is completed, the temperature is reduced to room temperature, and then the secondary calcination is performed), the temperature of the secondary calcination is 500 to 650 ℃ (for example, 500 ℃, 510 ℃, 5240 ℃, 530 ℃, 540 ℃ or 550 ℃), preferably 520 ℃, the time of the secondary calcination is 3 to 6 hours (for example, 3 hours, 4 hours, 5 hours or 6 hours), preferably 4 hours, wherein the temperature rise rate is 3 to 10 ℃/min (for example, 3 ℃/min, 4 ℃/min, 5 ℃/min, 6 ℃/min, 7 ℃/min, 8 ℃/min, 9 ℃/min or 10 ℃/min), preferably 5 ℃/min.

Example 1

Porous g-C of the example₃N₄The preparation method of the nano-flake comprises the following steps:

(1) respectively weighing 7.2g of melamine and 25mg of potassium gluconate, dispersing in 60mL of deionized water, and carrying out ultrasonic treatment for 30min to obtain emulsion;

(2) transferring the emulsion into a 100mL autoclave with a tetrafluoroethylene lining, and heating at 180 ℃ for 12h to obtain a suspension;

(3) centrifuging the suspension, washing the suspension for several times by deionized water, and drying the suspension for 12 hours at the temperature of 60 ℃ to obtain a hydrothermal precursor;

(4) putting the hydrothermal precursor into a 50mL crucible, covering the crucible with a cover, putting the crucible into a muffle furnace, calcining the hydrothermal precursor in static air for 4 hours at 550 ℃, wherein the heating rate is 5 ℃/min, and the calcined product is g-C₃N₄Nanosheets.

(5) The g-C obtained₃N₄The nano-sheet is subjected to secondary calcination at 520 ℃ for 4h at a heating rate of 5 ℃/min to obtain porous g-C₃N₄Nanoflakes (labeled CNNs).

Example 2

This example differs from example 1 in that: the amount of potassium gluconate in step (2) was 50mg, and other steps and process parameters were kept the same as those in example 1 and will not be described again.

Example 3

This example differs from example 1 in that: the amount of potassium gluconate in step (2) is 100mg, and other steps and process parameters are consistent with those in example 1 and are not described again.

Example 4

This example differs from example 1 in that: the amount of potassium gluconate in step (2) was 150mg, and the other steps and process parameters were kept the same as in example 1 and will not be described again.

Example 5

This example differs from example 1 in that: the amount of potassium gluconate in step (2) was 200mg, and the other steps and process parameters were kept the same as in example 1 and will not be described again.

Comparative example 1

To examine the invention for comparison, porous g-C was prepared₃N₄Properties of the Nanoflexs, g-C of bulk phase was prepared according to the procedure in example 1₃N₄The preparation method is different from the preparation method of the embodiment 1 in that: the hydrothermal reaction process does not use potassium gluconate, and specifically comprises the following steps:

(1) weighing 7.2g of melamine, dispersing in 60mL of deionized water, and carrying out ultrasonic treatment for 30min to obtain emulsion;

(2) transferring the emulsion into a 100mL autoclave with a tetrafluoroethylene lining, and heating at 180 ℃ for 12h to obtain a suspension;

(3) centrifuging the suspension, washing the suspension with deionized water for several times, and drying the suspension at the temperature of 60 ℃ for 12 hours to obtain a hydrothermal precursor;

(4) finally, putting the hydrothermal precursor into a 50mL crucible, covering the crucible with a cover, putting the crucible into a muffle furnace, and calcining the hydrothermal precursor in static air at 550 ℃ for 4 hours at the heating rate of 5 ℃/min; the calcined product is bulk phase g-C₃N₄(labeled as BCN).

Test example 1

In this test example, SEM and TEM images of the product obtained in example 3 were measured, and the results of the test are shown in fig. 1 and 2.

As shown in fig. 1 and fig. 2, SEM images of sample CNNs in example 3 clearly show a nano sheet-like structure, TEM images show a porous structure on the nano sheet, the photographed size is 100nm, and g-C can be seen from TEM₃N₄The thickness is very thin, with no bulk build-up.

Test example 2

In this test example, the products obtained in example 3 and comparative example 1 were used as test samples, the fluorescence spectra of the samples were measured, and the results of the measurement were measured by a Cary Eclipse fluorescence spectrometer, and are shown in fig. 3.

As shown in fig. 3, the CNNs of the sample of example 3 has the weakest peak in the PL spectrum, and the peak of BCN is much higher than that of CNNs, which indicates that the porous nano-sheet structure effectively promotes the separation of electron-hole pairs.

Test example 3

In this test example, the products obtained in example 3 and comparative example 1 were used as test samples, and the ultraviolet-visible absorption spectra of the samples were measured by using an ultraviolet-visible spectrophotometer UV-2600, and the specific test results are shown in fig. 4.

As shown in fig. 4, the absorption sidebands of the CNNs of the sample of example 3 are slightly red-shifted compared with those of BCN, which indicates that the CNNs have stronger light absorption capability in the visible light region, and the change of the porous structure morphology enhances the light absorption capability thereof.

Test example 4

In this test example, the products obtained in example 3 and comparative example 1 were used as test samples, a band gap spectrum of the samples was measured, and a band gap value was calculated according to the Kubelka-Munk formula, and the specific result is shown in fig. 5.

As shown in fig. 5, in the sample of example 3, the band gap of CNNs is 2.57eV, the band gap of BCN is 2.67eV, CNNs have smaller band gap structures and wider absorption spectrum bands, the separation efficiency and transfer speed of electron-hole pairs are greatly improved, porous structures and nanosheets provide more reaction sites, and the photocatalytic activity of carbon nitride is significantly increased.

Test example 5

In this test example, the products obtained in example 3 and comparative example 1 were used as test samples, the hydrogen production amounts of the samples were measured, the reaction was performed using a parallel light reaction apparatus, and the hydrogen production amounts were measured by a gas chromatograph, and the specific test results are shown in fig. 6.

As shown in FIG. 6, the hydrogen production of CNNs of example 3 is much greater than that of BCN, and the experimental result shows that the porous g-C prepared by the method₃N₄The nano-flake has a significant photocatalytic effect.

The photocatalytic hydrogen production experiment test method comprises the following steps: the hydrogen production experiment is carried out in a parallel light reactor. Dispersing 10mg of photocatalyst in 10 vol% triethanolamine-containing aqueous solution, sonicating for 20min, and thenThen adding H₂PtCl₆. An LED with power of 10W is used as a light source for irradiation. Analysis of the H produced using a gas chromatograph (SP-7890)₂。

Example 6

Porous g-C of the example₃N₄The preparation method of the nano-flake comprises the following steps:

(1) respectively weighing 4g of melamine and 50mg of sodium gluconate, dispersing in 60mL of deionized water, and carrying out ultrasonic treatment for 30min to obtain emulsion;

(2) transferring the emulsion into a 100mL autoclave with a tetrafluoroethylene lining, and heating at 180 ℃ for 12h to obtain a suspension;

(3) centrifuging the suspension, washing the suspension for several times by deionized water, and drying the suspension for 12 hours at the temperature of 60 ℃ to obtain a hydrothermal precursor;

(4) putting the hydrothermal precursor into a 50mL crucible, covering the crucible with a cover, putting the crucible into a muffle furnace, calcining the hydrothermal precursor in static air for 4 hours at 550 ℃, wherein the heating rate is 5 ℃/min, and the calcined product is g-C₃N₄Nanoplatelets (labeled CCN).

Example 7

This example differs from example 6 in that: the amount of sodium gluconate in step (2) was 100mg, and other steps and process parameters were kept the same as those in example 6 and will not be described again.

Example 8

This example differs from example 6 in that: the amount of sodium gluconate in step (2) was 200mg, and other steps and process parameters were kept the same as those in example 6, and are not described again.

Comparative example 2

To compare the properties of the photocatalysts prepared according to the present invention, bulk phases g-C were prepared using the same procedure as in example 6₃N₄The preparation method is different from the preparation method of the embodiment 6 in that: modification of g-C by sodium gluconate during hydrothermal reaction₃N₄The method specifically comprises the following steps:

(1) weighing 4g of melamine, dispersing in 60mL of deionized water, and performing ultrasonic action for 30min to obtain emulsion;

(2) transferring the obtained emulsion into a 100mL autoclave with a tetrafluoroethylene lining, and heating at 180 ℃ for 12h to obtain a suspension;

(3) centrifuging the suspension, washing the suspension with deionized water for several times, and then drying the suspension at 60 ℃ for 12 hours to obtain a hydrothermal precursor;

(4) finally, the hydrothermal precursor is placed into a 50mL crucible and covered with a cover, and the crucible is placed into a muffle furnace to be calcined for 4 hours in static air at the temperature of 550 ℃, the heating rate is 5 ℃/min, and the calcined product is bulk phase g-C₃N₄(labeled as BCN).

Test example 6

In this test example, SEM images of samples were measured using the products obtained in example 7 and comparative example 2 as test samples, and the specific test results are shown in fig. 7 and 8.

As shown in fig. 7 and 8, the SEM image of the sample BCN of comparative example 2 is a bulk structure, and the SEM image of the sample CCN of example 7 can clearly show that the sample BCN is an ultrathin nanosheet structure, is thinner and wider in a sheet structure, and effectively increases g-C₃N₄Provides more reactive active sites, thereby greatly increasing the photocatalytic activity.

Test example 8

In this test example, the products obtained in example 7 and comparative example 2 were used as test samples, and the X-ray diffraction (XRD) patterns of the samples were measured by using an X-ray diffractometer, and the specific measurement results are shown in fig. 9.

As shown in FIG. 9, the XRD diffraction peak positions of comparative example 2 and example 7 are consistent, indicating that the addition of sodium gluconate does not alter the g-C₃N₄The original structure of the structure is as follows; the (002) diffraction peak of BCN of the sample of comparative example 2 is obviously higher than the (002) diffraction peak of CCN of the sample of example 7, which shows that sodium gluconate influences g-C in the reaction process₃N₄Resulting in a decrease in crystallinity.

Test example 3

In this test example, the products obtained in example 7 and comparative example 2 were used as test samples, the hydrogen production amounts of the samples were measured, the reaction was performed using a parallel light reaction apparatus, and the hydrogen production amounts were measured by a gas chromatograph, and the specific test results are shown in fig. 10.

As shown in FIG. 10, the hydrogen production of CCN of example 7 is much greater than that of BCN of comparative example 2, the hydrogen production (3441. mu. mol/g/h) of CCN is 26 times that of BCN (130. mu. mol/g/h), and the experimental results show that the g-C can be effectively increased by using sodium gluconate for assisting modification₃N₄The photocatalytic performance of (a).

The hydrogen production experiment test method specifically comprises the following steps:

the hydrogen production experiment is carried out in a photocatalysis type parallel reaction instrument (WP-TEC-1020HSL), 10mg of photocatalyst is weighed in a quartz glass tube, 16mL of triethanolamine is added, ultrasonic treatment is carried out for 20min, and a cocatalyst H is added₂PtCl₆. Using 10W LED lamp as visible light source (lambda)>420nm), H was measured using a gas chromatograph₂The yield is measured by adopting a TCD detector and a TDX-01 stainless steel packed column as a chromatographic column.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.