Photocatalyst and preparation method thereof
阅读说明：本技术 光催化剂及其制备方法 (Photocatalyst and preparation method thereof ) 是由 翟赟璞 张帅阳 卢思宇 刘永刚 于 2021-09-24 设计创作，主要内容包括：一种光催化剂及其制备方法,属于光催化剂制氢领域。光催化剂为片状结构,光催化剂中含有石墨相氮化碳、碳量子点和红磷量子点,碳量子点和红磷量子点在石墨相氮化碳的骨架中。光催化剂的制备方法包括：将碳量子点与石墨相氮化碳前驱体的混合物在惰性气氛及400～600℃的温度下进行煅烧得到碳量子点/石墨相氮化碳复合物；将碳量子点/石墨相氮化碳复合物与红磷量子点混合,在预设温度进行热处理得到光催化剂；预设温度低于红磷量子点的沸点。该光催化剂具有良好的光催化制氢性能。(A photocatalyst and a preparation method thereof, belonging to the field of hydrogen production by photocatalysts. The photocatalyst is of a sheet structure, and contains graphite-phase carbon nitride, carbon quantum dots and red phosphorus quantum dots, wherein the carbon quantum dots and the red phosphorus quantum dots are arranged in a framework of the graphite-phase carbon nitride. The preparation method of the photocatalyst comprises the following steps: calcining the mixture of the carbon quantum dots and the graphite phase carbon nitride precursor in an inert atmosphere at the temperature of 400-600 ℃ to obtain a carbon quantum dot/graphite phase carbon nitride compound; mixing the carbon quantum dot/graphite phase carbon nitride compound with the red phosphorus quantum dot, and carrying out heat treatment at a preset temperature to obtain a photocatalyst; the preset temperature is lower than the boiling point of the red phosphorus quantum dots. The photocatalyst has good photocatalytic hydrogen production performance.)
1. The photocatalyst is characterized in that the photocatalyst is of a sheet structure, the photocatalyst contains graphite-phase carbon nitride, carbon quantum dots and red phosphorus quantum dots, and at least part of the carbon quantum dots and the red phosphorus quantum dots are in the framework of the graphite-phase carbon nitride.
2. A method for preparing the photocatalyst of claim 1, comprising:
calcining the mixture of the carbon quantum dots and the graphite phase carbon nitride precursor in an inert atmosphere at the temperature of 400-600 ℃ to obtain a carbon quantum dot/graphite phase carbon nitride compound;
mixing the carbon quantum dot/graphite phase carbon nitride compound with the red phosphorus quantum dot, and carrying out heat treatment at a preset temperature to obtain the photocatalyst; the preset temperature is lower than the boiling point of the red phosphorus quantum dots.
3. The method for preparing the photocatalyst according to claim 2, wherein the predetermined temperature is 150 to 250 ℃.
4. The method for producing a photocatalyst as claimed in claim 2 or 3, wherein the heat treatment is carried out in an inert atmosphere.
5. The method for preparing a photocatalyst according to claim 2 or 3, wherein the mass of the carbon quantum dots is 0.01 to 20% of the mass of the graphite-phase carbon nitride precursor.
6. The method for preparing a photocatalyst according to claim 2 or 3, wherein the mass of the red phosphorus quantum dots is 0.1 to 20% of the mass of the carbon quantum dot/graphite phase carbon nitride composite.
7. The method of claim 2 or 3, wherein the step of preparing the mixture of the carbon quantum dots and the graphite-phase carbon nitride precursor comprises: and mixing the carbon quantum dots and the graphite phase carbon nitride precursor with water, and drying to obtain a mixture of the carbon quantum dots and the graphite phase carbon nitride precursor.
8. The method of claim 7, wherein the drying is freeze-drying.
9. The method of claim 2 or 3, wherein the carbon quantum dots are doped with at least one of nitrogen, sulfur and phosphorus.
10. The method of claim 2 or 3, wherein the graphite-phase carbon nitride precursor comprises at least one of urea, thiourea, cyanamide, dicyandiamide, and melamine.
Technical Field
The application relates to the field of hydrogen production by using a photocatalyst, in particular to a photocatalyst and a preparation method thereof.
Background
Hydrogen, an ideal clean energy source, is generated by solar energy decomposing water, and plays a vital role in solving energy and environmental problems. As a powerful solution, photocatalysis is an energy conversion process that utilizes inexhaustible green solar energy to produce the desired hydrogen fuel.
In the prior art, the water is favorably decomposed by the graphite-phase carbon nitride in a photocatalytic manner under the irradiation of visible light, however, in the actual photocatalytic process, the forbidden band width of the graphite-phase carbon nitride is large, the visible light is difficult to be fully utilized, and the photo-generated electron-hole recombination is serious, so that the feasibility of the graphite-phase carbon nitride as a high-efficiency photocatalyst is limited.
Disclosure of Invention
The application provides a photocatalyst and a preparation method thereof, and the photocatalyst has good photocatalytic hydrogen production performance.
The embodiment of the application is realized as follows:
in a first aspect, an embodiment of the present application provides a photocatalyst, where the photocatalyst has a sheet structure, and the photocatalyst contains graphite-phase carbon nitride, carbon quantum dots, and red phosphorus quantum dots, and at least a part of the carbon quantum dots and the red phosphorus quantum dots are in a framework of the graphite-phase carbon nitride.
In a second aspect, embodiments of the present application provide a method for preparing a photocatalyst according to embodiments of the first aspect, including:
calcining the mixture of the carbon quantum dots and the graphite phase carbon nitride precursor in an inert atmosphere at the temperature of 400-600 ℃ to obtain a carbon quantum dot/graphite phase carbon nitride compound;
mixing the carbon quantum dot/graphite phase carbon nitride compound with the red phosphorus quantum dot, and carrying out heat treatment at a preset temperature to obtain a photocatalyst; the preset temperature is lower than the boiling point of the red phosphorus quantum dots.
The photocatalyst and the preparation method thereof provided by the embodiment of the application have the following beneficial effects:
the photocatalyst of the embodiment of the application is of a sheet structure, at least part of carbon quantum dots and red phosphorus quantum dots is arranged in the framework of graphite phase carbon nitride, the carbon quantum dots and the red phosphorus quantum dots are firmly combined with the graphite phase carbon nitride, and the carbon quantum dots and the red phosphorus quantum dots are not easy to fall off from the framework of the graphite phase carbon nitride in the process of carrying out photocatalytic hydrogen production on water. The photocatalyst provided by the embodiment of the application has good photocatalytic hydrogen production performance through the synergistic effect of the carbon quantum dots and the red phosphorus quantum dots.
In the preparation method of the photocatalyst of the embodiment of the application, a mixture of the carbon quantum dots and the graphite phase carbon nitride precursor is calcined at a temperature of 400-600 ℃, the graphite phase carbon nitride precursor becomes graphite phase carbon nitride after being calcined, so that the carbon quantum dots/graphite phase carbon nitride compound is prepared, then the carbon quantum dots/graphite phase carbon nitride compound is mixed with the red phosphorus quantum dots, heat treatment is carried out at a temperature lower than the boiling point of the red phosphorus quantum dots, the red phosphorus quantum dots cannot volatilize, so that the carbon quantum dots/red phosphorus quantum dots/graphite phase carbon nitride photocatalyst is prepared, and at least part of the carbon quantum dots and the red phosphorus quantum dots are in the framework of the graphite phase carbon nitride.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained from the drawings without inventive effort.
FIG. 1 is an XRD pattern of carbon quantum dots NCDs-en prepared at step S1 and red phosphorus quantum dots RPDs prepared at step S3 of example 2 of the present application;
FIG. 2 is a TEM image of carbon quantum dots NCDs-en prepared at step S1 in example 2 of the present application;
FIG. 3 is a TEM image of red phosphorus quantum dots RPDs obtained in step S3 of example 2 of the present application;
FIG. 4 is an XRD pattern of CN/RPDs/NCDs-en photocatalyst prepared in example 2 of the present application;
FIG. 5 is a TEM image and elemental distribution chart of CN/RPDs/NCDs-en photocatalyst prepared in example 2 of the present application;
FIG. 6 is a graph showing the evaluation of the photocatalytic hydrogen production performance of the photocatalyst produced in example 1 of the present application;
FIG. 7 is a graph showing the evaluation of the photocatalytic hydrogen production performance of the photocatalyst produced in example 2 of the present application;
FIG. 8 is a graph showing the evaluation of the photocatalytic hydrogen production performance of the photocatalyst produced in example 3 of the present application;
FIG. 9 is a graph showing the evaluation of the photocatalytic hydrogen production performance of the photocatalyst prepared in comparative example 1 of the present application;
FIG. 10 is a graph showing the evaluation of the photocatalytic hydrogen production performance of the photocatalyst prepared in comparative example 2 of the present application;
fig. 11 is a graph showing the photocatalytic hydrogen production performance evaluation of the photocatalyst produced in comparative example 3 of the present application.
Detailed Description
Embodiments of the present application will be described in detail below with reference to examples, but those skilled in the art will appreciate that the following examples are only illustrative of the present application and should not be construed as limiting the scope of the present application. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
The following description will be made specifically for the photocatalyst and the preparation method thereof in the embodiments of the present application:
in a first aspect, an embodiment of the present application provides a photocatalyst, where the photocatalyst has a sheet structure, and the photocatalyst contains graphite-phase carbon nitride, carbon quantum dots, and red phosphorus quantum dots, and at least a part of the carbon quantum dots and the red phosphorus quantum dots are in a framework of the graphite-phase carbon nitride.
The carbon quantum dots are carbon materials with the particle size of below 10nm and can emit fluorescence under the illumination condition, and the carbon quantum dots have the characteristics of good charge transmission capability and easiness in processing and modification due to conjugated pi structures and abundant surface functional groups. The red phosphorus quantum dots are red phosphorus particles with the particle size of less than 10nm, have good visible light absorption capacity, and can be used for photocatalytic decomposition of water under the irradiation of visible light. According to the photocatalyst provided by the embodiment of the application, the carbon quantum dots and the red phosphorus quantum dots are arranged in the framework of the graphite-phase carbon nitride, and the photocatalyst has good photocatalytic hydrogen production performance through the synergistic effect of the carbon quantum dots and the red phosphorus quantum dots. According to the photocatalyst provided by the embodiment of the application, at least part of the carbon quantum dots and the red phosphorus quantum dots are in the framework of the graphite phase carbon nitride, the carbon quantum dots and the red phosphorus quantum dots are firmly combined with the graphite phase carbon nitride, and the carbon quantum dots and the red phosphorus quantum dots are not easy to fall off from the framework of the graphite phase carbon nitride in the process of photocatalytic hydrogen production of water.
The carbon quantum dots and the red phosphorus quantum dots are at least partially in the graphite phase carbon nitride skeleton, and all the carbon quantum dots and the red phosphorus quantum dots may be in the graphite phase carbon nitride skeleton, or some of the carbon quantum dots and the red phosphorus quantum dots may be in the graphite phase carbon nitride skeleton.
In a second aspect, embodiments of the present application provide a method for preparing a photocatalyst according to embodiments of the first aspect, including:
(1) and calcining the mixture of the carbon quantum dots and the graphite phase carbon nitride precursor in an inert atmosphere at the temperature of 400-600 ℃ to obtain the carbon quantum dot/graphite phase carbon nitride compound.
In the preparation method of the photocatalyst of the embodiment of the application, a mixture of the carbon quantum dots and the graphite phase carbon nitride precursor is calcined in an inert atmosphere at a temperature of 400-600 ℃, the graphite phase carbon nitride precursor becomes graphite phase carbon nitride after being calcined, so that the carbon quantum dots/graphite phase carbon nitride compound is prepared, and the carbon quantum dots are doped in a framework of the graphite phase carbon nitride and are firmly combined with the graphite phase carbon nitride. Alternatively, the calcination temperature is any one of 400 ℃, 450 ℃, 500 ℃, 550 ℃ and 600 ℃ or a range between any two.
Optionally, the inert atmosphere comprises at least one of nitrogen, helium, and argon.
In some embodiments, the graphite phase carbon nitride precursor includes at least one of urea, thiourea, cyanamide, dicyandiamide, and melamine.
In some embodiments, the mass of the carbon quantum dots is 0.01 to 20% of the mass of the graphite phase carbon nitride precursor.
When the amount of the carbon quantum dots and the amount of the graphite-phase carbon nitride precursor satisfy the proportion, the photocatalytic hydrogen production effect of the photocatalyst is improved.
Illustratively, the mass of the carbon quantum dots is 0.01%, 0.1%, 0.5%, 1%, 2%, 4%, 6%, 8%, 10%, 12%, 15%, 18%, or 20% of the mass of the graphite phase carbon nitride precursor.
In some embodiments, the step of preparing the mixture of carbon quantum dots and graphite phase carbon nitride precursor comprises: and mixing the carbon quantum dots and the graphite phase carbon nitride precursor with water, and drying to obtain a mixture of the carbon quantum dots and the graphite phase carbon nitride precursor.
The carbon quantum dots and the graphite phase carbon nitride precursor are mixed with water, so that the carbon quantum dots and the graphite phase carbon nitride precursor are mixed more uniformly, and in the mixture of the carbon quantum dots and the graphite phase carbon nitride precursor obtained after drying, the carbon quantum dots and the graphite phase carbon nitride precursor are distributed more uniformly, and the photocatalytic stability of the photocatalyst is improved.
In other embodiments, the carbon quantum dots and the graphite phase carbon nitride precursor may also be mixed and stirred directly to improve the uniformity of mixing of the carbon quantum dots and the graphite phase carbon nitride precursor.
Further, in some embodiments, the step of preparing the carbon quantum dots comprises: mixing a carbon source and water, reacting at the temperature of 80-240 ℃ to obtain a first solution, and extracting carbon quantum dots from the first solution after the reaction is finished.
According to the preparation method of the carbon quantum dots, other impurities cannot be introduced, and the prepared carbon quantum dots are purer. Illustratively, the above reaction may be carried out under water bath conditions.
Alternatively, the carbon source comprises a polyhydroxycarboxylic acid, a saccharide compound, an amino acid compound. The polyhydroxycarboxylic acid comprises at least one of citric acid, malic acid, gluconic acid and tartaric acid. The saccharide compound includes at least one of glucose, fructose, sucrose and cellulose. The amino acid compound comprises at least one of glycine, alanine, tryptophan and serine.
Alternatively, the temperature at which the reaction is carried out after mixing the carbon source with water is any one of 80 ℃, 100 ℃, 120 ℃, 140 ℃, 160 ℃, 180 ℃, 200 ℃, 220 ℃ and 240 ℃ or a range between any two of them.
Optionally, the reaction time after the carbon source is mixed with water is 5-20 h, for example, 5h, 8h, 10h, 12h, 15h, 18h or 20 h.
In some embodiments, the step of extracting the carbon quantum dots from the first solution comprises: and cooling the first solution, and then dialyzing and drying to obtain the carbon quantum dots. The drying method is, for example, freeze drying or natural drying.
In the present embodiment, the carbon quantum dots may be directly purchased carbon quantum dots.
Further, in some embodiments, the carbon quantum dots are doped with at least one of nitrogen, sulfur, and phosphorus.
When the carbon quantum dots are doped with at least one of nitrogen, sulfur and phosphorus, the carbon source is doped with at least one of a nitrogen source, a sulfur source and a phosphorus source when the carbon quantum dots are prepared.
When the carbon quantum dots are doped with at least one of nitrogen, sulfur and phosphorus, the photocatalytic hydrogen production effect of the photocatalyst is favorably improved. In addition, the inventors of the present application have found in their studies that when carbon quantum dots are prepared, the yield of the carbon quantum dots is higher when at least one of a nitrogen source, a sulfur source, and a phosphorus source is doped in a carbon source.
Optionally, the nitrogen source comprises at least one of ethylenediamine, dicyandiamide, urea, thiourea, and cystine. Optionally, the sulfur source comprises at least one of thiourea and cystine. Optionally, the phosphorus source comprises at least one of phosphorous acid and phytic acid.
(2) Mixing the carbon quantum dot/graphite phase carbon nitride compound with the red phosphorus quantum dot, and carrying out heat treatment at a preset temperature to obtain a photocatalyst; the preset temperature is lower than the boiling point of the red phosphorus quantum dots.
The carbon quantum dot/graphite phase carbon nitride compound is mixed with the red phosphorus quantum dot, and heat treatment is carried out at the temperature lower than the boiling point of the red phosphorus quantum dot, so that the red phosphorus quantum dot can not volatilize, and the carbon quantum dot/red phosphorus quantum dot/graphite phase carbon nitride photocatalyst is prepared, and the carbon quantum dot and the red phosphorus quantum dot are in the framework of the graphite phase carbon nitride. Optionally, the preset temperature is 150 to 250 ℃, for example, 150 ℃, 180 ℃, 200 ℃, 220 ℃ or 250 ℃.
In the research of the inventor of the present application, it is found that if the graphite phase carbon nitride precursor and the red phosphorus quantum dots are mixed and calcined first, in order to ensure that the graphite phase carbon nitride precursor is converted into the graphite phase carbon nitride in the calcining process, the calcining temperature also needs to be maintained at 400-600 ℃, at this temperature, the red phosphorus quantum dots are volatilized, and the finally prepared photocatalyst does not contain the red phosphorus quantum dots.
In addition, if the red phosphorus is pulverized to nano-scale red phosphorus particles by ultrasonic treatment, and the nano-scale red phosphorus particles are loaded on graphite-phase carbon nitride to form a red phosphorus/graphite-phase carbon nitride composite, the red phosphorus particles with larger particle size cover the active sites of the carbon nitride, affecting the catalytic activity. The photocatalyst is formed by the red phosphorus quantum dots and the carbon quantum dots/graphite phase carbon nitride compound, the carbon quantum dots and the red phosphorus quantum dots are arranged in the framework of the graphite phase carbon nitride, the active sites of the carbon nitride cannot be influenced, and the obtained carbon quantum dots/red phosphorus quantum dots/graphite phase carbon nitride photocatalyst has good catalytic activity.
Illustratively, the heat treatment is performed in an inert atmosphere. Wherein the inert atmosphere is optionally at least one of nitrogen, helium, and argon.
In some embodiments, the mass of the red phosphorus quantum dots is 0.1 to 20% of the mass of the carbon quantum dot/graphite phase carbon nitride composite.
When the dosage of the red phosphorus quantum dot and the carbon quantum dot/graphite phase carbon nitride compound meets the proportion, the photocatalytic hydrogen production effect of the photocatalyst is more favorably improved.
Illustratively, the mass of the red phosphorus quantum dots is 0.1%, 0.3%, 0.5%, 1%, 2%, 5%, 8%, 10%, 12%, 15%, 18%, or 20% of the mass of the carbon quantum dot/graphite phase carbon nitride composite.
In some embodiments, the carbon quantum dot/graphite phase carbon nitride composite, the red phosphorus quantum dot, and the solvent are mixed, then dried, and then heat treated after drying. Optionally, the solvent comprises ethanol and/or water.
Because the carbon quantum dots are doped in the framework of the graphite phase carbon nitride in the carbon quantum dot/graphite phase carbon nitride compound and are firmly combined with the graphite phase carbon nitride, the carbon quantum dots are not easy to fall off when being mixed with the solvent alcohol. Optionally, the drying is by freeze drying or natural drying.
In some embodiments, the step of preparing the red phosphorus quantum dots comprises: dispersing red phosphorus in water, reacting at 120-240 ℃ to obtain a second solution, and extracting red phosphorus quantum dots from the second solution after the reaction is finished.
According to the preparation method of the red phosphorus quantum dot, other impurities cannot be introduced, and the prepared red phosphorus quantum dot is purer. Illustratively, the above reaction may be carried out under water bath conditions.
Alternatively, the temperature at which the reaction is carried out after the red phosphorus is dispersed in water is any one of 120 ℃, 140 ℃, 160 ℃, 180 ℃, 200 ℃, 220 ℃ and 240 ℃ or a range between any two of them.
Optionally, the reaction time after the red phosphorus is dispersed in water is 12-36 h, for example, 12h, 15h, 18h, 20h, 25h, 30h, 33h or 36 h.
In some embodiments, the step of extracting the red phosphorus quantum dots from the second solution comprises: and cooling the second solution, then carrying out ultrasonic treatment, standing, taking supernatant, and drying to obtain the red phosphorus quantum dots. Alternatively, the drying is performed by, for example, freeze drying or vacuum drying.
Compared with a heat treatment drying mode, the freeze drying and vacuum drying mode can avoid the red phosphorus quantum dots from being oxidized in the drying process.
It is understood that the steps of the ultrasonic treatment and the supernatant taking after standing can be performed in a cycle, for example, the supernatant taking after the first standing is performed with the second ultrasonic treatment, then the supernatant taking after the second standing is performed, the cycle is performed in a cycle, and the supernatant taking after the last standing is performed with the drying to obtain the red phosphorus quantum dots.
The photocatalyst and the preparation method thereof of the present application are further described in detail with reference to examples below.
Example 1
This embodiment provides a method for preparing a photocatalyst, which includes:
s1: adding 0.02mol of citric acid into 40mL of water, uniformly dispersing to obtain a dispersion, placing the dispersion into a 100mL reaction kettle, carrying out hydrothermal reaction at the temperature of 180 ℃ for 5 hours, cooling to room temperature to obtain a light yellow first solution, dialyzing the first solution, and freeze-drying to obtain a white carbon quantum dot, which is recorded as CDs.
S2: 0.5mg of the above CDs, 3.0g of urea and 20mL of water were mixed, and the mixture was freeze-dried to obtain a white powder, and the white powder was calcined in a tube furnace at 550 ℃ for 3 hours under an argon atmosphere, and cooled to room temperature to obtain a dark yellow powder, i.e., a carbon quantum dot/graphite phase carbon nitride composite, which was designated CN/CDs.
S3: putting 2.0g of ground commercial red phosphorus into 80mL of deionized water, putting the commercial red phosphorus into a hydrothermal reaction kettle, reacting for 24 hours at 200 ℃ to obtain a second solution, cooling the second solution, performing ultrasonic treatment for 2 hours, standing for 1 hour, performing ultrasonic treatment on the supernatant again, circulating for 4 times, finally performing vacuum drying on the supernatant to obtain yellowish red powder, and obtaining red phosphorus quantum dots which are marked as RPDs.
S4: and (3) dispersing 100mg of CN/CDs and 2mg of RPDs in 50% ethanol aqueous solution, ultrasonically stirring for 2 hours, rotationally evaporating to obtain red yellow powder, and placing the red yellow powder in a tube furnace under the argon atmosphere to carry out heat treatment at the temperature of 250 ℃ for 2 hours to obtain the carbon quantum dot/red phosphorus quantum dot/graphite phase carbon nitride photocatalyst which is marked as CN/RPDs/CDs.
Example 2
This embodiment provides a method for preparing a photocatalyst, which includes:
s1: adding 0.02mol of citric acid and 0.02mol of ethylenediamine into 40mL of water, uniformly dispersing to obtain a dispersion solution, placing the dispersion solution into a 100mL reaction kettle, carrying out hydrothermal reaction at 180 ℃ for 5 hours, cooling to room temperature to obtain a brownish black first solution, dialyzing and freeze-drying the first solution to obtain golden nitrogen-doped carbon quantum dots, and marking the golden nitrogen-doped carbon quantum dots as NCDs-en.
S2: and mixing 0.5mg of NCDs-en and 3.0g of urea with 20mL of water, freezing and drying to obtain white powder, putting the white powder into a tube furnace under the atmosphere of argon gas, calcining at 550 ℃ for 3 hours, and cooling to room temperature to obtain dark yellow powder, namely the nitrogen-doped carbon quantum dot/graphite phase carbon nitride compound, which is marked as CN/NCDs-en.
S3: putting 2.0g of ground commercial red phosphorus into a proper amount of deionized water, putting the commercial red phosphorus into a hydrothermal reaction kettle, reacting for 24 hours at 200 ℃ to obtain a second solution, cooling the second solution, performing ultrasonic treatment for 2 hours, standing for 1 hour, performing ultrasonic treatment on the supernatant again, circulating for 4 times, finally performing vacuum drying on the supernatant to obtain yellowish red powder, and obtaining red phosphorus quantum dots which are marked as RPDs.
S4: and dispersing 100mg of CN/NCDs-en and 2mg of RPDs in 50% ethanol water solution, ultrasonically stirring for 2 hours, rotationally evaporating to obtain yellowish red powder, and placing the yellowish red powder in a tube furnace under the argon atmosphere to carry out heat treatment at the temperature of 250 ℃ for 2 hours to obtain the nitrogen-doped carbon quantum dot/red phosphorus quantum dot/graphite-phase carbon nitride photocatalyst which is marked as CN/RPDs/NCDs-en.
Example 3
This embodiment provides a method for preparing a photocatalyst, which includes:
s1: adding 0.02mol of citric acid and 0.02mol of urea into 40mL of water, uniformly dispersing to obtain a dispersion solution, placing the dispersion solution into a 100mL reaction kettle, carrying out hydrothermal reaction at the temperature of 180 ℃ for 5 hours, cooling to room temperature to obtain a black and green first solution, dialyzing and freeze-drying the first solution to obtain black nitrogen-doped carbon quantum dots, and marking the black nitrogen-doped carbon quantum dots as NCDs-ur.
S2: and mixing 0.5mg of NCDs-ur and 3.0g of urea with 20mL of water, freezing and drying to obtain white powder, putting the white powder into a tube furnace under the argon atmosphere, calcining at 550 ℃ for 3 hours, and cooling to room temperature to obtain dark yellow powder, namely the nitrogen-doped carbon quantum dot/graphite-phase carbon nitride compound, which is marked as CN/NCDs-ur.
S3: putting 2.0g of ground commercial red phosphorus into a proper amount of deionized water, putting the commercial red phosphorus into a hydrothermal reaction kettle, reacting for 24 hours at 200 ℃ to obtain a second solution, cooling the second solution, performing ultrasonic treatment for 2 hours, standing for 1 hour, performing ultrasonic treatment on the supernatant again, circulating for 4 times, finally performing vacuum drying on the supernatant to obtain yellowish red powder, and obtaining red phosphorus quantum dots which are marked as RPDs.
S4: and dispersing 100mg of CN/NCDs-ur and 2mg of RPDs in 50% ethanol water solution, ultrasonically stirring for 2 hours, rotationally evaporating to obtain yellowish red powder, and placing the yellowish red powder in a tube furnace under the argon atmosphere to perform heat treatment at the temperature of 250 ℃ for 2 hours to obtain the nitrogen-doped carbon quantum dot/red phosphorus quantum dot/graphite-phase carbon nitride photocatalyst which is marked as CN/RPDs/NCDs-ur.
Examples 4 to 7
Examples 4 to 7 each provide a method for producing a photocatalyst, which comprises the steps of producing a photocatalyst differing from example 2 only in the amount of NCDs-en used in step S2, and examples 4 to 7 wherein the amounts of NCDs-en are 0.2mg, 1mg, 3mg and 5mg, respectively.
Examples 8 to 11
Examples 8 to 11 each provide a method for producing a photocatalyst, which comprises the steps of producing the photocatalyst in a manner different from that of example 2 only in the amount of RPDs used in step S4, and the amounts of RPDs used in examples 8 to 11 were 0.5mg, 1mg, 3mg and 4mg, respectively, in this order.
Comparative example 1
This comparative example provides a photocatalyst, which was prepared by the steps of:
3.0g of urea is put into a corundum porcelain boat with a cover, aluminum foil is used for sealing for many times, the corundum porcelain boat is put into a tube furnace under the protection of argon gas and calcined for 3 hours at 550 ℃, and light yellow powder, namely graphite-phase carbon nitride photocatalyst, is obtained after the calcining for 3 hours is cooled to room temperature and is marked as CN.
Comparative example 2
This comparative example provides a method for preparing a photocatalyst, which is different from example 1 only in that steps S3 and S4 of example 1 are omitted.
Comparative example 3
The present comparative example provides a method for preparing a photocatalyst, comprising the steps of:
s1: 3.0g of urea is put into a corundum porcelain boat with a cover, aluminum foil is used for sealing for many times, the corundum porcelain boat is put into a tube furnace under the protection of argon gas and calcined for 3 hours at 550 ℃, and light yellow powder, namely graphite-phase carbon nitride, is obtained after the corundum porcelain boat is cooled to room temperature and is marked as CN.
S2: putting 2.0g of ground commercial red phosphorus into a proper amount of deionized water, putting the commercial red phosphorus into a hydrothermal reaction kettle, reacting for 24 hours at 200 ℃ to obtain a second solution, cooling the second solution, performing ultrasonic treatment for 2 hours, standing for 1 hour, performing ultrasonic treatment on the supernatant again, circulating for 4 times, finally performing vacuum drying on the supernatant to obtain yellowish red powder, and obtaining red phosphorus quantum dots which are marked as RPDs.
S3: and dispersing 100mg of CN and 2mg of RPDs in 50% ethanol water, ultrasonically stirring for 2 hours, rotationally evaporating to obtain yellowish red powder, and placing the yellowish red powder in a tubular furnace under the argon atmosphere to carry out heat treatment at the temperature of 250 ℃ for 2 hours to obtain the red phosphorus quantum dot/graphite phase carbon nitride photocatalyst which is marked as CN/RPDs.
Test example 1
(1) XRD tests were carried out on the carbon quantum dots NCDs-en prepared in the step S1 of example 2 and the red phosphorus quantum dots RPDs prepared in the step S3, and XRD patterns obtained are shown in FIG. 1.
As can be seen from FIG. 1, the XRD pattern of NCDs-en has a diffraction peak at 23 °, which corresponds to the (002) plane of the carbon quantum dot; the XRD pattern of RPDs has a diffraction peak at 15 degrees, which corresponds to the (102) crystal plane of red phosphorus quantum dots.
(2) The carbon quantum dots NCDs-en prepared in the step S1 in example 2 and the red phosphorus quantum dots RPDs prepared in the step S3 were observed under a transmission electron microscope, and TEM images thereof were respectively shown in fig. 2 and 3.
As can be seen from FIGS. 2 and 3, the carbon quantum dots NCDs-en and the red phosphorus quantum dots RPDs are both spherical particles with a size of <10nm, which illustrates that the carbon quantum dots and the red phosphorus quantum dots are successfully prepared in example 1.
(3) XRD testing was performed on the CN/RPDs/NCDs-en photocatalyst prepared in example 2, and the XRD pattern obtained is shown in FIG. 4.
As can be seen from FIG. 4, the XRD pattern of the CN/RPDs/NCDs-en photocatalyst has a weak diffraction peak at 13 degrees, which corresponds to the (100) crystal plane of the graphite-phase carbon nitride, and a slightly strong diffraction peak at 27 degrees, which corresponds to the (002) crystal plane of the graphite-phase carbon nitride.
(4) The CN/RPDs/NCDs-en photocatalyst prepared in example 2 was observed under a transmission electron microscope, and the obtained TEM images are shown in FIG. 5, respectively.
As can be seen from FIG. 5, the basic morphology of the CN/RPDs/NCDs-en photocatalyst prepared in example 2 is lamellar, and some quantum dots are found, wherein the lamellar structure is graphite phase carbon nitride, and the small black particles attached to the circles of the lamellar structure are quantum dots. Moreover, the element map also shows that the carbon element, the nitrogen element, the oxygen element and the phosphorus element are uniformly distributed, which indicates that the carbon quantum dots and the red phosphorus quantum dots are successfully doped into the graphite phase carbon nitride.
Test example 2
10mg of each of the photocatalysts of examples 1 to 11 and comparative examples 1 to 3 was taken, and the photocatalysts were mixed with 5mL of triethanolamine and 1.0mL of H with a concentration of 0.8mg/mL14Cl6O6The Pt solutions were mixed to obtain 14 sets of dispersion solutions, and then the 16 sets of solutions were subjected to photo-reduction for 30min and then subjected to catalytic evaluation, which was continuously performed for 4 hours, to finally obtain the hydrogen production capacity of each photocatalyst, and the results thereof are recorded in table 1. Among them, the photocatalytic hydrogen production performance evaluation graphs corresponding to the photocatalysts of examples 1 to 3 are shown in FIGS. 6 to 6Fig. 8 shows photocatalytic hydrogen production performance evaluation graphs corresponding to the photocatalysts of comparative examples 1 to 3, as shown in fig. 9 to 11.
TABLE 1 photocatalytic Hydrogen production Performance of photocatalyst
Hydrogen production Performance/μmol g-1h-1
Example 1
2874
Example 2
3731
Example 3
3576
Example 4
2803
Example 5
3272
Example 6
2726
Example 7
2175
Example 8
2251
Example 9
3361
Example 10
2647
Example 11
2156
Comparative example 1
570
Comparative example 2
2037
Comparative example 3
2447
From the results in table 1, it can be seen that all of the photocatalysts of the examples of the present application have better photocatalytic hydrogen production capability. In addition, it can be seen from the results of comparing example 1 with examples 2 and 3 that doping nitrogen in the carbon quantum dots can improve the photocatalytic hydrogen production capability of the photocatalyst.
It can be seen from the results of comparing example 2 with examples 4 to 7 that the hydrogen production effect of the photocatalyst of example 4 is inferior to that of examples 2 and 5, which indicates that when the mass of the nitrogen-doped carbon quantum dots is 0.01 to 1% of that of the graphite-phase carbon nitride precursor, the photocatalytic hydrogen production capability of the photocatalyst is more favorably improved.
It can be seen from the results of comparing example 2 with examples 8 to 11 that the hydrogen production effect of the photocatalysts of examples 2 and 9 is better than that of examples 8, 10 and 11, and it is demonstrated that when the mass of the red phosphorus quantum dot is 1 to 2% of that of the carbon quantum dot/graphite phase carbon nitride composite, the photocatalytic hydrogen production capability of the photocatalyst is more favorably improved.
The foregoing is illustrative of the present application and is not to be construed as limiting thereof, as numerous modifications and variations will be apparent to those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.