CN114345379A - Catalyst modification method and photocatalyst - Google Patents
Catalyst modification method and photocatalyst Download PDFInfo
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- CN114345379A CN114345379A CN202210040867.4A CN202210040867A CN114345379A CN 114345379 A CN114345379 A CN 114345379A CN 202210040867 A CN202210040867 A CN 202210040867A CN 114345379 A CN114345379 A CN 114345379A
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Abstract
A catalyst modification method and a photocatalyst belong to the field of photocatalysis. The modification method is realized by compounding a modifier and a catalyst. Wherein the modifier and the catalyst are two different semiconductor materials, and the band gaps of the modifier and the catalyst have an overlapping region; the valence band of the modifier is at the top of the valence band of the catalyst and the conduction band bottom of the modifier is at the bottom of the conduction band of the catalyst. The modification method can improve the catalytic activity of the catalyst.
Description
Technical Field
The application relates to the field of photocatalysis, in particular to a catalyst modification method and a photocatalyst.
Background
As the name implies, photocatalysis is a catalytic reaction that occurs under the action of light. Among them, a photocatalyst (photocatalyst) is a special substance. The photocatalyst does not undergo chemical changes under light, but causes chemical reactions of surrounding substances.
Specifically, the photocatalyst makes O around it by light energy2And H2O molecules are converted into-OH or negative ions, the-OH or negative ions and organic pollutants are subjected to chemical reaction, and the organic pollutants are degraded to generate CO2And water. Thus, photocatalytic technology can degrade organic contaminants.
Titanium dioxide nanoparticles are a substance which is researched and used in a photocatalyst, and how to further improve the catalytic effect of the photocatalyst is a difficult problem to be solved urgently.
Disclosure of Invention
Based on the above disadvantages, the present application provides a method for modifying a catalyst and a photocatalyst, so as to improve, even solve, the problem of how to improve the photocatalytic effect of titanium dioxide.
The application is realized as follows:
in a first aspect, examples of the present application provide a modification method for increasing the catalytic activity of a catalyst. The modification method is realized by compounding a modifier and a catalyst, wherein the modifier and the catalyst are two different semiconductor materials, and the band gaps of the modifier and the catalyst have an overlapping region. The valence band of the modifier is at the top of the valence band of the catalyst and the conduction band bottom of the modifier is at the bottom of the conduction band of the catalyst.
In some examples of the present application, the catalyst is a photocatalyst.
In some examples of the present application, catalytic activity is increased by broadening the absorption spectrum bandwidth of the modified photocatalyst.
In some examples of the present application, the photocatalyst is titanium dioxide and the modifier is cadmium selenide quantum dots; by modification, the absorption spectrum bandwidth of titanium dioxide is broadened from a violet region of less than 400nm to a visible region.
In a second aspect, the present application exemplifies a modification method for increasing the photocatalytic activity of titanium dioxide. The modification method comprises the following steps: in the process of preparing titanium dioxide by a solvothermal method, quantum dots are used as modifiers to participate in solvothermal reaction.
In some examples of the present application, the quantum dots are added to the reaction system in the form of a finished product.
In some examples of the present application, the quantum dots are water soluble.
Optionally, the quantum dot is cadmium selenide.
Alternatively, the quantum dots are cadmium selenide dispersed in an organic solvent.
In some examples of the present application, cadmium selenide is prepared as follows:
mixing cadmium oxide, oleic acid and octadecene in a container with inert atmosphere conditions; reacting at a first temperature to enable cadmium element to form cadmium oleate; and at a second temperature, adding a selenium precursor for reaction, and then cooling to room temperature.
Optionally, the first temperature is 240 ℃ and the temperature is continuously raised to 320 ℃ after cadmium element forms cadmium oleate, and the second temperature is 280 ℃.
Optionally, at the second temperature, after adding the selenium precursor to react for 5 minutes, rapidly cooling to room temperature.
Alternatively, after cooling to room temperature, an organic solvent is added to keep the liquid clear, and a solid is obtained by extraction and then dissolved in hexane.
In some examples of the present application, the method of modifying comprises: dissolving a titanium source in an acidic reagent, and then sequentially adding alcohol, deionized water and quantum dots to form a reaction solution; sealing the reaction solution in a reaction kettle for carrying out dissolution thermal reaction to form a product solution; the dried solid was separated from the product liquor and calcined.
Alternatively, the calcination temperature is 350 ℃.
In a third aspect, the present application example provides a photocatalyst. It is in the shape of a nanometer flower and contains titanium dioxide and cadmium selenide quantum dots.
In the above implementation process, the catalyst modification method provided in the embodiment of the present application uses the modifier and the catalyst both of which are semiconductor materials. The simultaneous selection of the energy level position and the band gap width of the two semiconductor materials allows for a wider "band gap" of the materials to which they are combined, and also allows for better separation of charges (electrons and holes). As such, the recombination rate of electron-hole pairs in the composite material is lower, thereby achieving higher catalytic performance relative to that of the catalyst alone.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments or the prior art of the present application, the drawings used in the description of the embodiments or the prior art will be briefly described below.
FIG. 1 is a schematic diagram showing a scanning electron microscope image of a single titanium dioxide nanoflower and a scanning electron microscope image of quantum dot-modified titanium dioxide in example 1 of the present application in comparison;
fig. 2 shows a graph of the efficiency of degradation of MO for the samples prepared in example 1, example 2 and 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 method of modifying a catalyst and a photocatalyst in the examples of the present application:
titanium dioxide, as a photocatalyst, has a number of advantages. However, as a result of practice, the inventors have found that the existing titanium dioxide photocatalyst still has room and room for improvement.
For example, to the inventors' knowledge, titanium dioxide (TiO)2) The absorption spectrum of the photocatalyst is also limitedThe ultraviolet light region, thus making its use of sunlight less efficient. Therefore, one important direction for improving the titanium dioxide photocatalyst is to expand the absorption spectrum range thereof so as to improve the utilization rate of sunlight.
At present, the improvement of titanium dioxide mainly adopts surface modification (such as chelation and derivatization), transition metal doping, non-metal doping, dye sensitization and the like; alternatively, the particle diameter is controlled so as to utilize its quantum size effect or the like.
Through research, the inventors chose to implement modification measures that are different from the above-described schemes. The solution is mainly based on semiconductor compounding. Namely, on the basis of using titanium dioxide, another semiconductor material is selected and compounded, so that the modulation of the charge distribution is realized. Such a solution enables better separation of electron and hole pairs (reduction of recombination rate) in the obtained modified titanium dioxide material.
On this basis, the inventors believe, by further verification, that the above scheme is equally applicable to other catalysts. Such as other metal oxide catalysts, including but not limited to Bi2O3、ZnO、CuO、In2O3(ii) a Non-oxide catalysts include, but are not limited to, CdS series, CuS series, nitride series.
Therefore, in the present application, the inventors propose a method for modifying a catalyst for improving the catalytic activity of the catalyst. The increased catalytic activity can be reflected, for example, from the width of the absorption spectrum determined for the photocatalyst.
Illustratively, when the photocatalyst is titanium dioxide, its absorption spectrum extends from the ultraviolet region to the visible region. That is, the absorption spectrum of the composite titanium dioxide photocatalyst modified in the above manner is a spectral region extending from the visible light region to the ultraviolet light region. As a more specific alternative example, when the photocatalyst is titanium dioxide, the modifier may be selected to be a cadmium selenide quantum dot. And the modification of the titanium dioxide by the quantum dots is realized through the matching of the quantum dots and the titanium dioxide, so that the absorption spectrum bandwidth of the titanium dioxide is widened from a purple light region of less than 400nm to a visible light region.
Generally, the modification method is mainly realized by compounding a modifier and a catalyst. And, in particular, wherein the modifier and the catalyst are two different semiconductor materials. Meanwhile, from the energy level structures of the two, the band gap of the modifier and the band gap of the catalyst have an overlapping region, the valence band top of the modifier is above the valence band top of the catalyst, and the conduction band bottom of the modifier is above the conduction band bottom of the catalyst.
Through the selection of the energy level structures of the catalyst and the modifier, the catalyst and the modifier are enabled to generate coupled interaction on the energy level, so that the catalyst and the modifier can play a specific role in charge in the catalytic reaction process. That is, the coupling of the energy levels of the two enables the generated electron-hole pairs to be better separated (rather than recombined) -the electrons and holes are independently dispersed in the catalyst and modifier, respectively-thus facilitating the catalytic reaction to proceed.
In some examples of the present application, the titanium dioxide as the photocatalyst is optionally modified with quantum dots to obtain a quantum dot modified titanium dioxide photocatalyst. This is in view of the fact that quantum dots, as the aforementioned modifiers with specifically selected energy level structures, have typical quantum effects, and thus the selection of quantum dots is fully useful for modifying TiO2Photocatalytic efficiency.
To the best of the inventors' knowledge, can now be adopted to modify TiO by quantum dots2Most procedures of the preparation method are complicated, conditions are harsh, repeatability is poor, and difficulty in controlling experiment operation is increased.
For example, a method for preparing quantum dot modified nano titanium dioxide emulsion currently exists. The preparation method slowly drops titanium tetrachloride into deionized water to obtain titanium dioxide precursor solution. Then, adding a quantum dot cation precursor and a quantum dot anion precursor into the titanium dioxide precursor solution respectively, and stirring until the precursors are completely dissolved to form a mixed solution. Then, adjusting the pH value of the mixed solution to 7-9 by using ammonia water, and generating a precipitate. Then, the filter cake obtained after vacuum filtration is washed clean by deionized water. Clean and cleanAnd pulping the filter cake by using carboxylic acid, an emulsifier and deionized water, and stirring for 10-80 h to obtain a transparent complex solution. And heating and refluxing the obtained transparent complex solution to obtain the quantum dot modified nano titanium dioxide emulsion. Obviously, the method has the defects of more complicated synthesis process, poorer process repeatability and longer manufacturing period, and experiments show that the synthesized TiO is2The appearance of the particles in the emulsion is not uniform, and the photocatalysis performance is poor.
As a specific application example of the scheme of the present application, the present application also proposes a catalyst modification method. Which is a method for substantially increasing the photocatalytic activity of titanium dioxide, mainly by using TiO2The nano-flower structure has the characteristics of uniformity, large specific surface area and the like, and the quantum dots can be effectively and uniformly distributed on the surface of the nano-flower structure, so that the nano-flower structure can be effectively contacted with pollutants, and the photocatalytic performance of the nano-flower structure is enhanced. And which comprises: in the process of preparing titanium dioxide by a solvothermal method, quantum dots are used as modifiers to participate in solvothermal reaction.
The scheme is different from the method of directly compounding the conventional titanium dioxide photocatalyst and the quantum dots serving as the finished product, and the quantum dots and the titanium dioxide are compounded by a one-step method. I.e. quantum dots are implanted into the TiO2The composite prepared in (1) (i.e. the titanium dioxide is not extracted from the reaction system as a pure substance, but reacts with the reaction raw material of the titanium dioxide in a same system) is reacted and compounded. The quantum dot modified titanium dioxide photocatalyst obtained by the scheme has stable performance, good experimental repeatability, convenient operation and simple and easy operation. Thus, in this approach, the titanium dioxide is grown in situ in an environment containing the quantum dots, and thus grown in such a way as to complex the titanium dioxide and the quantum dots.
For the quantum dots of the modified titanium dioxide, different types of quantum dots can be selected according to different application modes, and the preparation mode of the quantum dots can be correspondingly regulated and controlled. Of course, since quantum dots are used directly as modifiers in the present application, they can of course be marketed products rather than having to be formulated in situ.
From the class of quantum dots, quantum dots can be water soluble, or lipid soluble (can be modified to be water soluble). The specific components can be selected from one or more of cadmium selenide, CdS, CdTe, ZnS, ZnSe, ZnTe, HgS, HgSe, HgTe, PbS, PbSe, PbTe and other binary, ternary and quaternary II-VI compounds. As alternative examples, the quantum dot material may include, but is not limited to, one or more of GaP, GaAs, InP, InAs, and other binary, ternary, quaternary III-V compounds. In a specific use, the quantum dots may be optionally dispersed in an organic solvent to be used in a dispersion.
For example, cadmium selenide can be prepared by means of a thermal injection process. Illustratively, cadmium oxide, oleic acid (which may serve as a ligand for cadmium), and octadecene (which may serve as a non-ligand solvent) are mixed in a vessel with inert atmosphere conditions and then reacted at a first temperature to form cadmium oleate from the cadmium element. And then adding a selenium precursor into the cadmium oleate for reaction at a second temperature, and then cooling to room temperature. Briefly, the reaction is conducted in a heated environment in a non-coordinating solvent environment of a cadmium source and a selenium source.
In the process of preparing the CdS quantum dots by a thermal injection method, the following reaction process is mainly involved.
Cadmium oxide and oleic acid are mixed and heated to react to form cadmium oleate, so that the cadmium simple substance is changed into Cd2+。
Trioctylphosphine dissolves elemental selenium powder at normal temperature, and selenium exists in trioctylphosphine in atomic form.
The solution containing selenium simple substance at normal temperature is injected into the hot solution containing cadmium ion rapidly, and the cadmium ion reacts with S atom to form fine CdS particles (seed crystal, namely the formation process of nucleus).
As the reaction proceeds, Ostwald ripening occurs and CdS particles grow gradually. The quantum dots are stable in solution. The Ostwald ripening refers to the later stage of precipitation phase of supersaturated solid solution, the particle sizes of the precipitation phase are different, and the average particle size is increased because smaller particles dissolve and larger particles continue to grow.
For example, cadmium oxide, Oleic Acid (OA), and Octadecene (ODE) are mixed in a vessel having an inert atmosphere, and then reacted at 240 ℃ to form cadmium oleate from cadmium element. And continuously heating to 320 ℃, cooling to 280 ℃, adding a selenium precursor (such as TOP-Se, trioctylphosphine selenium which is a product of dissolving simple substance selenium by trioctylphosphine) into cadmium oleate for reaction, and then cooling to room temperature. Since cadmium oleate coagulates at 60 ℃, the formation of solid precipitates due to the coagulation thereof can make it difficult to remove impurities mixed therein. Cadmium oleate may therefore be selected to be dissolved in an organic solvent (such as chloroform) at room temperature so that impurities therein, such as a cadmium source, may be removed.
In order to control the particle size, uniformity and the like of the quantum dots, the selenium precursor is added, and then the mixture is selected to react for 5 minutes and then is rapidly cooled to room temperature. Furthermore, the cadmium selenide quantum dots can be separated and purified from the reaction system, so that the cadmium selenide quantum dots can be used later, and the influence of other substances in the reaction system on the preparation of the modified titanium dioxide can be reduced. For example, the various substances are dissolved in an organic solvent to form a clear solution, which is then extracted and then prepared into a solution for use. For the scheme of the cadmium selenide, chloroform is used for keeping a reaction system after reaction clear, then n-hexane and ethanol are used for extracting to obtain solid, and the n-hexane is used for dissolving. In other words, in the process of extracting the normal hexane and the ethanol, the cadmium selenide is separated out as a solid to form a precipitate, and then the precipitate of the solid can be obtained by centrifuging and removing the supernatant. The solid, namely the cadmium selenide, is prepared into a solution by using normal hexane, so that the solid is conveniently added into a reaction system and participates in the reaction in the process of preparing titanium dioxide by using the re-solution heat.
After the cadmium selenide quantum dots are obtained, the cadmium selenide quantum dots can be applied to a scheme for preparing modified titanium dioxide in the following manner. In an example of the present application, a method includes the following steps.
Dissolving a titanium source (such as tetrabutyl titanate) in an acidic reagent (for inhibiting the hydrolysis rate), and then sequentially adding alcohol, deionized water and quantum dots to form a reaction solution; sealing the reaction solution in a reaction kettle for carrying out dissolution thermal reaction to form a product solution; the dried solid was separated from the product liquor and calcined. The reaction mechanism is as follows:
the hydrolysis reaction process is as follows:
Ti(O-CH4)4+H2O→Ti(O-CH4)3(OH)+C4H9OH；
Ti(O-CH4)3(OH)+H2O→Ti(O-CH4)2(OH)2+C4H9OH；
Ti(O-CH4)2(OH)2+H2O→Ti(O-CH4)(OH)3+C4H9OH；
Ti(O-CH4)(OH)3+H2O→Ti(OH)4+C4H9OH；
hydrolysis of tetrabutyl titanate to Ti (OH)4Then annealed (e.g. 350 deg.C) to dehydrate it to TiO2。
In the present example, titanium dioxide was prepared by a solvothermal method, and the n-hexane solution of the above-mentioned cadmium selenide quantum dots was introduced during the preparation process so that the quantum dots participated in the reaction. After the reaction is complete, a rinse is performed, followed by an anneal (e.g., 350 ℃) to adjust the crystalline phase as desired. Annealing at 350 ℃ results in titanium dioxide which is predominantly in the anatase phase. Anatase type TiO2Belongs to a tetragonal system, and the band gap width is 3.2 eV. The photocatalyst has the advantages of low energy consumption, high activity, high electron mobility and the like, and has good photocatalytic performance. The rutile phase is also tetragonal due to the para-O2The adsorption capacity of the composite material is poor, and the photocatalytic performance of the composite material is poor due to easy recombination of photo-generated electron hole pairs.
In this way, a photocatalyst with the size of nanometer and the shape of nanometer can be obtained, wherein the photocatalyst contains titanium dioxide and cadmium sulfide quantum dots. The photocatalyst can generate light absorption spectra in an ultraviolet region and a visible light region, so that sunlight can be efficiently utilized, and good photocatalytic efficiency is shown.
Adding the prepared quantum dots into a reaction system in the process of preparing titanium dioxide, and enabling the quantum dots to participate in reaction, thereby forming the titanium dioxide modified by the quantum dots; wherein the main body is titanium dioxide, and the modification component is quantum dots. Since the titanium dioxide particles are large and the quantum dot particles are small, the quantum dot particles are supported on the surface of the titanium dioxide particles. The scheme can effectively improve the quality of the prepared quantum dot modified titanium dioxide product.
On the contrary, if TiO is synthesized first2Then adding TiO2Adding into the process of synthesizing quantum dots. Then, what will be TiO in the product obtained in this way will be2And modifying the quantum dots. I.e. the bulk in the product is quantum dots, and TiO2Only as a small amount of improver. In this process scheme, TiO2The size of the particles is much larger than the size of the quantum dots, and therefore, the two cannot be modified substantially, but only by simple mechanical mixing.
The method for modifying the catalyst and the photocatalyst of the present application are described in further detail below with reference to examples.
Example 1
A modified photocatalyst is prepared by the following steps:
(1) preparation of modifier (CdSe quantum dots)
8mmol of cadmium oxide, 8mL of Oleic Acid (OA), and 72mL of Octadecene (ODE) were weighed and charged into a three-necked flask. And vacuumizing the three-neck flask by using a vacuum pump, filling argon, and repeating for many times to fill the three-neck flask with the argon. Then, slowly raising the temperature to 240 ℃ to completely convert the cadmium oleate into the cadmium oleate solution. If the temperature is raised too fast in the process, acid, water, oxygen and the like cannot be effectively removed, so that the performance of the cadmium oleate is reduced.
And continuously heating the cadmium oleate solution to 320 ℃, then quickly injecting a TOP-Se (trioctylphosphine solution of selenium elementary substance) precursor into the reaction kettle at 280 ℃, reacting for about 5min, and quickly cooling to room temperature to obtain the mixture containing the cadmium selenide quantum dots. In this step, the temperature control device was set at 320 ℃ and the temperature of the injected Se was 280 ℃. The formation of CdSe is favored at temperatures of 280 ℃. The rapid injection can accelerate the growth rate of CdSe and improve the uniformity of particle size. The rapid reduction can improve the working efficiency.
Adding chloroform to prevent the mixture from forming solid, adding n-hexane and ethanol for extraction, centrifuging after the generated precipitate, removing supernatant, and dissolving the obtained precipitate in n-hexane again to prepare cadmium selenide quantum dot solution (oil-soluble quantum dot solution) for later use. Wherein, the dosage ratio of the normal hexane and the cadmium selenide can be adjusted according to the actual needs, and the concentration of the experiment is 20 mg/ml.
The n-hexane solution is an oily solution, and is firstly subjected to phase inversion to be converted into water-soluble quantum dots. The transformation method comprises the following steps: dissolving mercaptoethylamine in water, and ultrasonically stirring until the mercaptoethylamine is completely dissolved to prepare a mercaptoethylamine solution; adding an oil-soluble quantum dot solution into a mercaptoethylamine solution, stirring and reacting for a certain time under the controlled temperature and atmosphere, and completely volatilizing an organic solvent to obtain the water-soluble quantum dot.
(2) CdSe modified TiO2Preparation of the nanoflower composite
1mL of tetrabutyltitanate and 25mL of acetic acid were weighed out and mixed in a beaker.
Performing ultrasonic stirring for 50min, and sequentially dropwise adding 20ml of ethanol and water-soluble quantum dots in the ultrasonic process to obtain a mixed solution.
After the ultrasonic stirring was completed, the mixed solution was transferred to a 100mL stainless steel autoclave lined with Teflon.
And (3) placing the reaction kettle in a drying oven at the temperature of 150 ℃ for keeping the temperature for 10 hours, and taking out after natural cooling environment temperature such as heating is finished.
And (3) respectively centrifuging and cleaning the mixed solution in the polytetrafluoroethylene lining after the reaction is finished by using deionized water and absolute ethyl alcohol (removing water-soluble and fat-soluble substances).
After the cleaning, the mixture is placed in a constant temperature box and dried for 10 hours at the temperature of 75 ℃. Annealing the powder in an annealing furnace at 350 ℃ for 3 hours after drying is finished to obtain CdSe modified TiO2Nanoflower, denoted as S1. CdSe modified TiO2The morphology of the nanoflower (b), and the morphology of the single titanium dioxide nanocrystallization as a contrast (a) are shown in fig. 1. As can be seen from FIG. 1, TiO2Nanometer flower, uniform size, and no agglomerationLike; the CdSe quantum dots are uniformly modified on TiO2 petals, and the size of the CdSe quantum dots is about 10nm basically.
Example 2
(1) Preparation of modifier (ZnSe quantum dot)
Adding 5mmol Zn (OAc)2Adding into a three-neck flask containing 3ml of OA and 3.6ml of ODE, exhausting gas at 170 ℃ for 30min to remove acetic acid, heating to 300 ℃, adding 1mmol of Se-TOP, reacting for 5min, cooling to room temperature, and cleaning to obtain ZnSe quantum dot solution.
(2) ZnSe modified Bi2WO6Preparation of the Complex of
Adding Bi (NO)3)3·5H2O and Na2WO4·2H2Preparing Bi according to the atomic ratio of Bi to W being 2 to 12WO65mmol of Bi (NO)3)3·5H2O and 2.5mmol of Na2WO4·2H2O is added into a beaker containing 90mL of deionized water for magnetic stirring, and 5mL of glacial acetic acid is slowly dripped into the beaker by a burette during the stirring process.
After 2h, a white suspension was formed. Then, the white suspension and the prepared ZnSe quantum dots are added into a 100ml high-pressure reaction kettle with a polytetrafluoroethylene lining, and the mixture is placed in a forced air drying oven to react for 20 hours at the constant temperature of 140 ℃.
And naturally cooling to room temperature after the reaction is finished. Taking out the sample, washing the sample with distilled water, drying the sample with cold air, annealing the sample in a muffle furnace at 400 ℃ for 3 hours (the heating rate is 3 ℃/min), and naturally cooling the sample to room temperature to obtain ZnSe/Bi2WO6A composite photocatalyst, designated as S2.
Example 3
(1) Preparation of modifier (ZnS quantum dots)
Adding 5mmol Zn (OAc)2 into a three-neck flask with 3ml OA and 3.6ml ODE, exhausting gas at 170 ℃ for 30min to remove acetic acid, heating to 300 ℃, adding 2mmol S-TOP, reacting for 5min, cooling to room temperature, and cleaning to obtain ZnSe quantum dot solution.
(2) Preparation of ZnS modified MoS2 composite
Weighing 90mg of sodium molybdate and 180mg of thioacetamide, dissolving in 20mL of water, adding ZnS quantum dots into the solution, carrying out ultrasonic stirring for 1h, transferring the mixed solution to a 100mL stainless steel high-pressure reaction kettle with a polytetrafluoroethylene lining after the ultrasonic stirring is finished, and then placing the reaction kettle in a drying box for keeping the temperature for 20h at 200 ℃. And naturally cooling to the ambient temperature, taking out, respectively cleaning the mixed solution with deionized water and absolute ethyl alcohol, centrifuging and cleaning for multiple times, drying for 12 hours at the temperature of 75 ℃, and obtaining black powder which is the ZnS/MoS2 composite photocatalyst after drying, and marking as S3.
Test example 1
Photocatalytic degradation experiment:
the photocatalytic performance of the synthesized sample is analyzed by degrading a pollutant Methyl Orange (MO) solution to obtain: the concentration of the methyl orange solution in a certain range is directly proportional to the absorbance of the characteristic peak. Namely, the characteristic peak light absorption intensity of methyl orange in different time is measured, the concentration change value of the methyl orange solution is calculated, and the photocatalytic effect of the sample is deduced.
From Lambert Law (Beer-Lambert Law), the degradation efficiency of methyl orange can be calculated by the following formula:
in the above formula, c represents the residual concentration of the methyl orange solution when the illumination time is t, and c0 represents the initial concentration of the methyl orange solution. The results of the experiment are shown in FIG. 2.
The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by 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.
Claims (10)
1. A modification method of a catalyst is used for improving the catalytic activity of the catalyst and is characterized in that the modification method is realized by compounding a modifier and the catalyst;
the modifier and the catalyst are two different semiconductor materials;
there is an overlap region between the band gaps of the modifier and the catalyst, the valence band top of the modifier is above the valence band top of the catalyst, and the conduction band bottom of the modifier is above the conduction band bottom of the catalyst.
2. The method of modifying a catalyst according to claim 1, wherein the catalyst is a photocatalyst.
3. The method of modifying a catalyst according to claim 2, wherein the catalytic activity is increased by broadening an absorption spectrum bandwidth of the modified photocatalyst.
4. The method of claim 3, wherein the photocatalyst is titanium dioxide, and the modifier is cadmium selenide quantum dots;
by modification, the absorption spectrum bandwidth of the titanium dioxide is widened from a purple light region of less than 400nm to a visible light region.
5. A method of modifying a catalyst for increasing the photocatalytic activity of titanium dioxide, the method comprising: in the process of preparing titanium dioxide by a solvothermal method, quantum dots are used as modifiers to participate in solvothermal reaction.
6. The method of claim 5, wherein the quantum dots are added to the reaction system in the form of a finished product.
7. The method of modifying a catalyst according to claim 6, wherein the quantum dot is water-soluble;
optionally, the quantum dot is cadmium selenide;
optionally, the quantum dot is cadmium selenide dispersed in an organic solvent.
8. The method for modifying a catalyst according to claim 7, wherein the cadmium selenide is prepared by the following steps:
mixing cadmium oxide, oleic acid and octadecene in a container with inert atmosphere conditions;
reacting at a first temperature to enable cadmium element to form cadmium oleate;
at a second temperature, adding a selenium precursor for reaction, and then cooling to room temperature;
optionally, the first temperature is 240 ℃, and after the cadmium element forms cadmium oleate, the temperature is continuously increased to 320 ℃, and the second temperature is 280 ℃;
optionally, at a second temperature, adding a selenium precursor, reacting for 5 minutes, and then rapidly cooling to room temperature;
alternatively, after cooling to room temperature, an organic solvent is added to keep the liquid clear, and a solid is obtained by extraction and then dissolved in hexane.
9. The method of modifying a catalyst according to claim 7 or 8, characterized in that it comprises:
dissolving a titanium source in an acidic reagent, and then sequentially adding alcohol, deionized water and the quantum dots to form a reaction solution;
sealing the reaction solution in a reaction kettle for carrying out dissolution thermal reaction to form a product solution;
separating and drying the product liquid to obtain a solid, and calcining the solid;
alternatively, the calcination temperature is 350 ℃.
10. The photocatalyst is characterized by being in a nanometer flower shape and containing titanium dioxide and cadmium selenide quantum dots.
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| CN114904541A (en) * | 2022-06-02 | 2022-08-16 | 华侨大学 | CdSe quantum dot/three-dimensional layered Ti 3 C 2 Preparation method of composite photocatalyst |
| CN115121266A (en) * | 2022-07-27 | 2022-09-30 | 辽宁大学 | Two-dimensional sulfide self-assembly composite photocatalyst and preparation method and application thereof |
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| CN101181978A (en) * | 2007-11-15 | 2008-05-21 | 合肥工业大学 | Method for synthesizing cadmium selenide or zinc selenide quantum-dot by selenium dioxide |
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| CN114904541A (en) * | 2022-06-02 | 2022-08-16 | 华侨大学 | CdSe quantum dot/three-dimensional layered Ti 3 C 2 Preparation method of composite photocatalyst |
| CN115121266A (en) * | 2022-07-27 | 2022-09-30 | 辽宁大学 | Two-dimensional sulfide self-assembly composite photocatalyst and preparation method and application thereof |
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