CN115155643A - Photocatalytic composite material and preparation method and application thereof - Google Patents
Photocatalytic composite material and preparation method and application thereof Download PDFInfo
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- CN115155643A CN115155643A CN202210899843.4A CN202210899843A CN115155643A CN 115155643 A CN115155643 A CN 115155643A CN 202210899843 A CN202210899843 A CN 202210899843A CN 115155643 A CN115155643 A CN 115155643A
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- VZSRBBMJRBPUNF-UHFFFAOYSA-N 2-(2,3-dihydro-1H-inden-2-ylamino)-N-[3-oxo-3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propyl]pyrimidine-5-carboxamide Chemical compound C1C(CC2=CC=CC=C12)NC1=NC=C(C=N1)C(=O)NCCC(N1CC2=C(CC1)NN=N2)=O VZSRBBMJRBPUNF-UHFFFAOYSA-N 0.000 description 1
- PUAQLLVFLMYYJJ-UHFFFAOYSA-N 2-aminopropiophenone Chemical compound CC(N)C(=O)C1=CC=CC=C1 PUAQLLVFLMYYJJ-UHFFFAOYSA-N 0.000 description 1
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Classifications
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- B01J35/39—
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
- B01J27/24—Nitrogen compounds
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
- C01B3/02—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen
- C01B3/04—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by decomposition of inorganic compounds, e.g. ammonia
- C01B3/042—Decomposition of water
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/36—Hydrogen production from non-carbon containing sources, e.g. by water electrolysis
Abstract
The invention discloses a photocatalytic composite material and a preparation method and application thereof. The photocatalytic composite material comprises the following raw materials: graphite phase carbon nitride and thiophene-2,5-dicarboxaldehyde. In the photocatalytic composite material, the aromatic rings in-C = N-and thiophene-2,5-dialdehyde structures can enhance the delocalization of pi electrons of the photocatalytic composite material, so that the enhancement of light absorption and the rapid migration of photogenerated electrons are facilitated; in the photocatalytic composite material, the carrier migration rate is obviously increased, the recombination rate of electrons and holes is reduced, the electron hole separation rate is improved, the rapid recombination of photon-generated carriers is further inhibited, and the remarkable improvement of the photocatalytic hydrogen production performance is promoted.
Description
Technical Field
The invention relates to the technical field of photocatalytic materials, in particular to a photocatalytic composite material and a preparation method and application thereof.
Background
The photocatalysis technology is a technology for catalytic reaction under the condition of illumination by using a photocatalyst, and is a green technology with important application prospect in the fields of energy and environment. Since the 21 st century, the excessive use of fossil energy has caused global energy crisis and environmental crisis, and the establishment of clean energy systems is urgent. The hydrogen plays an important role in the system as a renewable clean energy source, and can be used for fuel cells and also can be used in the chemical industry. The existing method for producing hydrogen mainly comprises the step of producing hydrogen by photolysis of water, which is an important way for converting solar energy into usable energy and is also an effective way for storing solar energy. Because the performance of photolysis water is directly influenced by the photo-generated charge transfer, the band gap structure and the stability of the catalyst, the hydrogen production efficiency of the existing method is not high, and therefore, the design of a novel efficient environment-friendly photocatalyst is the key for improving the hydrogen production efficiency.
Graphite phase carbon nitride (g-C) 3 N 4 ) The conjugated polymer is a conjugated polymer with a two-dimensional lamellar structure, has stable property and is similar to a graphite structure. g-C 3 N 4 As a novel metal-free polymerization photocatalyst, the photocatalyst has the advantages of being green, economical, good in stability, good in optical performance and electronic performance and the like, and is widely concerned in the field of photocatalysis; g-C 3 N 4 Can be applied to the fields of photocatalytic degradation of pollutants, photocatalytic water splitting hydrogen production and photocatalytic reduction of CO 2 The field and the field of selective organic synthesis reaction. g-C 3 N 4 As a typical representative of graphene-like materials, the graphene-like material has a band gap of 2.7eV, can absorb visible light, has good chemical and thermodynamic stability due to Van der Waals force connection between layers, and is g-C 3 N 4 It also has the characteristics of no toxicity, rich sources, low price, simple preparation and the like. However, g-C 3 N 4 In practical applications, due to the pure phase of g-C 3 N 4 Has a plurality of defects to influence the improvement of the photocatalytic performance, so that the g-C 3 N 4 Limited by rapid charge carrier recombination, low surface area and limited absorption of visible light, particularly g-C 3 N 4 Has higher electron-hole recombinationThe rate of synthesis, so that the photocatalytic efficiency is severely limited.
Therefore, it is highly desirable to find a composite material for improving g-C 3 N 4 The photocatalysis performance, the photoresponse range is widened, and the electron hole separation rate is improved.
Disclosure of Invention
The first technical problem to be solved by the invention is as follows:
a photocatalytic composite material is provided.
The second technical problem to be solved by the invention is:
provides a preparation method of the photocatalytic composite material.
The third technical problem to be solved by the invention is:
the application of the photocatalytic composite material.
In order to solve the first technical problem, the invention adopts the technical scheme that:
a photocatalytic composite material, comprising the following raw materials:
graphite phase carbon nitride and thiophene-2,5-dicarboxaldehyde.
In the photocatalytic composite material, the thiophene-2,5-diformaldehyde is grafted to the graphite phase carbon nitride.
According to an embodiment of the present invention, the photocatalytic composite material comprises at least one of the following structural formulas:
the mass ratio of TDA in the photocatalytic composite material is different, so that the structure of the photocatalytic composite material is influenced, and therefore, the photocatalytic composite material is named UCN-xTDA in the invention.
According to the embodiment of the invention, one of the technical solutions has at least one of the following advantages or beneficial effects:
in the graphite phase of nitrogen carbide (g-C) 3 N 4 ) KnotAn organic monomer thiophene-2,5-dicarboxaldehyde is introduced into the structure, so that thiophene-2,5-dicarboxaldehyde is grafted to a carbon nitride network structure. In the network structure, the aromatic rings in the-C = N-and thiophene-2,5-dialdehyde structures can enhance the pi electron delocalization of the photocatalytic composite material, thereby being beneficial to enhancing light absorption and rapid migration of photo-generated electrons; in the photocatalytic composite material, the carrier migration rate is obviously increased, the recombination rate of electrons and holes is reduced, the electron hole separation rate is improved, the rapid recombination of photon-generated carriers is further inhibited, and the remarkable improvement of the photocatalytic hydrogen production performance is promoted.
According to one embodiment of the invention, the weight ratio of the thiophene-2,5-dicarboxaldehyde in the photocatalytic composite material is 0.003-0.006%.
The different mass ratios of the thiophene-2,5-diformaldehyde in the photocatalytic composite material can influence the structure of the photocatalytic composite material, so that the photocatalytic efficiency, the hydrogen production yield and the catalytic stability of the photocatalytic composite material are influenced.
In order to solve the second technical problem, the invention adopts the technical scheme that:
a method of preparing the photocatalytic composite material, comprising the steps of:
mixing the graphite-phase carbon nitride with the thiophene-2,5-dicarboxaldehyde to obtain a mixture;
calcining the mixture to obtain the photocatalytic composite material.
One of the technical solutions has at least one of the following advantages or beneficial effects:
the preparation of the photocatalytic composite material by the method can improve g-C 3 N 4 The photocatalysis performance of the (graphite phase carbon nitride) widens the photoresponse range of the material and improves the electron hole separation rate; the method utilizes a high-temperature one-step thermal polymerization method to prepare the visible-light-responsive thiophene-2,5-dialdehyde-grafted CN network structure photocatalytic composite material, and has the advantages of simple operation and reaction efficiencyHigh performance of the prepared material and the like.
According to one embodiment of the invention, the polymerization reaction is a thermal shrinkage polymerization process. The thermal shrinkage polymerization method is to prepare g-C by the pyrolysis treatment of a nitrogen-rich precursor 3 N 4 . The method has the characteristics of cheap raw materials, simple preparation process and good crystal form of the product.
According to an embodiment of the invention, the method further comprises the step of grinding the mixture after cooling the mixture. The reaction will be more complete with the milled mixture.
According to one embodiment of the invention, the temperature of the calcination is 530 to 560 ℃. Different nitrogen-containing organics, and different mass ratios of the nitrogen-containing organics to the thiophene-2,5-dialdehyde, will affect the pyrolysis temperature and thus the temperature of calcination.
According to one embodiment of the invention, the calcination is carried out for a period of 4 to 5 hours. Different calcination temperatures require different calcination times.
According to one embodiment of the invention, the temperature increase rate of the calcination is 5-15 ℃/min. The temperature is raised to the specified calcining temperature by a program with the temperature-raising rate of 5-15 ℃/min. The rate of temperature rise ensures that the reaction proceeds.
According to one embodiment of the present invention, a method of preparing a photocatalytic composite material includes the steps of:
mixing nitrogen-containing organic matter with thiophene-2,5-dicarboxaldehyde to obtain a mixture;
calcining the mixture to obtain the photocatalytic composite material.
After the nitrogen-containing organic matter is heated, graphite-phase carbon nitride can be obtained through polymerization reaction, wherein the graphite-phase carbon nitride has a 3-s-triazine structural unit; and the thiophene-2,5-diformaldehyde obtained by Schiff base reaction of the graphite-phase carbon nitride and the thiophene-2,5-diformaldehyde is grafted on the photocatalytic composite material of the 3-s-triazine, and the obtained photocatalytic composite material can be further subjected to thermal polymerization with the graphite-phase carbon nitride or other structural units with the 3-s-triazine to obtain the photocatalytic material.
According to one embodiment of the invention, the nitrogen-containing organic compound comprises at least one of urea, melamine and dicyandiamide.
The nitrogen-containing organic substance may be any raw material that can react to obtain graphite-phase carbon nitride.
According to one embodiment of the invention, the mass ratio of the nitrogen-containing organic compound to the thiophene-2,5-dicarboxaldehyde is 10000:3-6.
The ratio of urea to thiophene-2,5-dicarboxaldehyde is adjusted to cause the thiophene-2,5-dicarboxaldehyde in the final high polymer to change in a CN network structure, so that the photocatalytic composite material under different ratios is obtained.
The invention also relates to application of the photocatalytic composite material in hydrogen production reaction by photolysis of water under visible light. Comprising a photocatalytic composite material as described in the embodiment of aspect 1 above. Since the application adopts all the technical solutions of the photocatalytic composite material of the above embodiments, at least all the advantages brought by the technical solutions of the above embodiments are achieved.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
Drawings
The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
FIG. 1 is a process flow diagram for preparing the photocatalytic composite material according to examples 1-6.
FIG. 2 is a graph showing the UV-visible diffuse reflectance of the materials obtained in examples 1 to 4 and comparative example.
FIG. 3 is a graph showing the photocatalytic hydrogen production rate of the materials obtained in examples 1 to 4 and comparative example.
FIG. 4 is a graph showing the results of experiments on photocatalytic degradation of BPA for materials obtained in examples 1 to 4 and comparative example.
FIG. 5 is a photoluminescence spectrum of the materials obtained in example 3 and comparative example.
Fig. 6 is a graph showing the photocatalytic stability test of the photocatalytic composite material obtained in example 3.
FIG. 7 is a nuclear magnetic resonance spectrum of the photocatalytic composite material obtained in example 3.
Detailed Description
Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.
In the description of the present invention, if there are first, second, etc. described, it is only for the purpose of distinguishing technical features, and it is not understood that relative importance is indicated or implied or that the number of indicated technical features is implicitly indicated or that the precedence of the indicated technical features is implicitly indicated.
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the scope of the present invention.
Example 1
The method for preparing the photocatalytic composite material is shown in figure 1 and comprises the following steps:
(1) Weighing 20g of urea, heating to a molten state, adding 3mg of thiophene-2,5-dialdehyde, stirring, cooling to room temperature, grinding the raw materials until powdery particles are uniformly mixed to obtain a mixture of the two;
(2) Placing the mixture in a 100ml aluminum oxide crucible with a cover, placing the crucible in a muffle furnace, gradually heating to 550 ℃ at a heating rate of 10 ℃/min, and then heating at 550 ℃ for 4 hours;
(3) Naturally cooling to room temperature, and fully grinding the obtained sample again.
The photocatalytic composite material is prepared through the steps, and a sample is named UCN-3-TDA.
As shown in FIG. 1, in which urea is polymerized to obtain g-C 3 N 4 ，g-C 3 N 4 Possess the structural unit of 3-s-triazine.
Wherein, thiophene-2,5-diformaldehyde which can be obtained by performing Schiff base reaction on urea and thiophene-2,5-diformaldehyde is grafted on a structural unit of 3-s-triazine, the unit is a photocatalytic composite material, when urea is further added, the photocatalytic composite material can further repeat the reaction to obtain a new thiophene-2,5-diformaldehyde which is grafted on the structural unit of 3-s-triazine, namely the new photocatalytic composite material is obtained; when other substances with 3-s-triazine structures are further added, the photocatalytic composite material can further repeat the reaction to obtain a new structural unit of thiophene-2,5-diformaldehyde grafted on 3-s-triazine, namely the new photocatalytic composite material.
Example 2
The method for preparing the photocatalytic composite material as shown in figure 1 comprises the following steps:
(1) Weighing 20g of urea, heating to a molten state, adding 4mg of thiophene-2,5-dialdehyde, stirring, cooling to room temperature, grinding the raw materials until powdery particles are uniformly mixed to obtain a mixture of the two;
(2) Placing the mixture in a 100ml alumina crucible with a cover, placing the crucible in a muffle furnace, gradually heating to 550 ℃ at a heating rate of 10 ℃/min, and then heating at 550 ℃ for 4 hours;
(3) Naturally cooling to room temperature, and fully grinding the obtained sample again.
Compared with example 1, the difference is that thiophene-2,5-dicarboxaldehyde is added in an amount of 4mg, and the prepared sample is named UCN-4-TDA.
Example 3
The method for preparing the photocatalytic composite material as shown in figure 1 comprises the following steps:
(1) Weighing 20g of urea, heating to a molten state, adding 5mg of thiophene-2,5-dialdehyde, stirring, cooling to room temperature, grinding the raw materials until powdery particles are uniformly mixed to obtain a mixture of the two;
(2) Placing the mixture in a 100ml aluminum oxide crucible with a cover, placing the crucible in a muffle furnace, gradually heating to 550 ℃ at a heating rate of 10 ℃/min, and then heating at 550 ℃ for 4 hours;
(3) Naturally cooling to room temperature, and fully grinding the obtained sample again.
Compared with example 1, the difference is that thiophene-2,5-dicarboxaldehyde is added in an amount of 5mg, and the prepared sample is named UCN-5-TDA.
Example 4
The method for preparing the photocatalytic composite material as shown in figure 1 comprises the following steps:
(1) Weighing 20g of urea, heating to a molten state, adding 6mg of thiophene-2,5-dialdehyde, stirring, cooling to room temperature, grinding the raw materials until powdery particles are uniformly mixed to obtain a mixture of the two;
(2) Placing the mixture in a 100ml alumina crucible with a cover, placing the crucible in a muffle furnace, gradually heating to 550 ℃ at a heating rate of 10 ℃/min, and then heating at 550 ℃ for 4 hours;
(3) Naturally cooling to room temperature, and fully grinding the obtained sample again.
Compared with example 1, the difference is that the addition amount of thiophene-2,5-dicarboxaldehyde is 6mg, and the prepared sample is named UCN-6-TDA.
Examples 1-4 differ only in the amount of thiophene-2,5-dicarboxaldehyde added. The invention grafts g-C by thiophene-2,5-dialdehyde 3 N 4 The network structure can obtain the photocatalytic composite material. The obtained material has different proportions of thiophene-2,5-diformaldehyde in the composite material of the CN network due to different addition amounts of thiophene-2,5-diformaldehyde, so that the chemical properties and the catalytic efficiency of the material are different. By adjusting the ratio of urea to thiophene-2,5-dicarboxaldehyde, the thiophene-2,5-dicarboxaldehyde in the final high polymer is induced to be in g-C 3 N 4 The network structure is changed, and then the photocatalytic composite material under different proportions is obtained.
Example 5
The method for preparing the photocatalytic composite material as shown in figure 1 comprises the following steps:
(1) Weighing 20g of urea, heating to a molten state, adding 3mg of thiophene-2,5-dialdehyde, stirring, cooling to room temperature, grinding the raw materials until powdery particles are uniformly mixed to obtain a mixture of the two;
(2) Placing the mixture in a 100ml aluminum oxide crucible with a cover, placing the crucible in a muffle furnace, gradually heating to 530 ℃ at a heating rate of 10 ℃/min, and then heating at the constant temperature of 530 ℃ for 4 hours;
(3) Naturally cooling to room temperature, and fully grinding the obtained sample again.
The only difference compared to example 1 is that the calcination temperature and the constant temperature are 530 ℃.
Example 6
The method for preparing the photocatalytic composite material as shown in figure 1 comprises the following steps:
(1) Weighing 20g of urea, heating to a molten state, adding 3mg of thiophene-2,5-dialdehyde, stirring, cooling to room temperature, grinding the raw materials until powdery particles are uniformly mixed to obtain a mixture of the two;
(2) Placing the mixture in a 100ml aluminum oxide crucible with a cover, placing the crucible in a muffle furnace, gradually heating to 550 ℃ at a heating rate of 5 ℃/min, and then heating at 550 ℃ for 4 hours;
(3) Naturally cooling to room temperature, and fully grinding the obtained sample again.
The difference is only that the temperature is gradually increased at a temperature increase rate of 5 deg.C/min, compared to example 1.
Example 7
The method for preparing the photocatalytic composite material comprises the following steps:
(1) Weighing 42g of melamine, heating to a molten state, adding 3mg of thiophene-2,5-dialdehyde, stirring, cooling to room temperature, grinding the raw materials until powdery particles are uniformly mixed to obtain a mixture of the two;
(2) Placing the mixture in a 100ml aluminum oxide crucible with a cover, placing the crucible in a muffle furnace, gradually heating to 550 ℃ at a heating rate of 10 ℃/min, and then heating at 550 ℃ for 4 hours;
(3) Naturally cooling to room temperature, and fully grinding the obtained sample again.
The difference compared to example 1 is that only 42g of melamine was weighed out.
Example 8
The method for preparing the photocatalytic composite material comprises the following steps:
(1) Weighing 28g of dicyandiamide, heating to a molten state, adding 3mg of thiophene-2,5-dialdehyde, stirring, cooling to room temperature, grinding the raw materials until powdery particles are uniformly mixed to obtain a mixture of the two;
(2) Placing the mixture in a 100ml aluminum oxide crucible with a cover, placing the crucible in a muffle furnace, gradually heating to 550 ℃ at a heating rate of 10 ℃/min, and then heating at 550 ℃ for 4 hours;
(3) Naturally cooling to room temperature, and fully grinding the obtained sample again.
The only difference compared to example 1 was that 28g of dicyandiamide had been weighed out.
The organic monomer thiophene-2,5-dialdehyde prepared by the above example was grafted with g-C 3 N 4 The D-A structure and pi electron delocalization of the composite material constructed by the network structure are enhanced, so that the light absorption enhancement and the rapid migration of photo-generated electrons are facilitated; the recombination rate of electrons and holes is reduced, so that the rapid recombination of photon-generated carriers is inhibited, and the remarkable improvement of the photocatalytic hydrogen production performance is promoted. The conjugated structure of the nanosheet layer is regulated and controlled through copolymerization, the band gap width of a semiconductor is reduced while the mass transfer process of the surface of the catalyst is enhanced, the separation and migration of photo-generated carriers are promoted, the utilization rate of solar energy is improved, and the method has a wide application prospect in the field of photocatalysis.
Comparative example
Pure phase g-C 3 N 4 The preparation method of the photocatalyst comprises the following steps:
weighing 20g of urea, heating to a molten state, cooling to room temperature, grinding the urea until powdery particles are placed in a 100ml aluminum oxide crucible with a cover, placing the crucible in a muffle furnace, gradually heating to 550 ℃ at a heating rate of 10 ℃/min, and then heating at the constant temperature of 550 ℃ for 4 hours; naturally cooling to room temperature, and fully grinding the obtained sample again.
In comparison to example 1, except that no thiophene-2,5-dicarboxaldehyde was added, the sample prepared was designated as UCN.
And (3) performance testing:
test example 1:
ultraviolet visible diffuse reflection experiment:
the photocatalytic composite materials obtained in examples 1 to 4 and the comparative example were subjected to ultraviolet-visible diffuse reflection spectroscopy, and the test is shown in fig. 2.
Wherein, the used instrument of ultraviolet visible diffuse reflectance spectrum test is: hitachi U-3010UV-vis spectrometer using BaSO 4 As a reference.
As can be seen from FIG. 2, it is obvious that with the gradual increase of the concentration of thiophene-2,5-dialdehyde, the absorption of the photocatalytic composite material to visible light is gradually enhanced to show a red shift phenomenon, a strong absorption peak appears at 420-650nm, and the response of a sample to visible light is enhanced.
The absorption range of the photocatalytic composite material prepared by the method for visible light is gradually widened, so that the photocatalytic hydrogen production performance of the material is greatly improved.
Test example 2:
photocatalytic hydrogen production rate experiment:
the specific experimental conditions and method are as follows: an on-line Labsolar-6A photocatalytic analysis system of Beijing Pofilly technologies, inc. was used.
Wherein, the specific reaction solution: photocatalytic composite 20mg was added to 100mL of aqueous solution containing 10mL of triethanolamine as a sacrificial agent, and 3wt% Pt was used as a co-catalyst, light source PLS-SXE 300/300UV, light intensity: 100mW/cm 2 ，λ>420nm。
The photocatalytic hydrogen production rates of the photocatalytic composite materials obtained in examples 1 to 4 and the comparative example were tested by the above experimental conditions and methods, and the results are shown in fig. 3.
As can be seen from FIG. 3, the UCN was compared to the original sample (prepared by comparative example)To the material), almost all thiophene-2,5-dialdehyde grafted g-C 3 N 4 The composite material comprises the following components: UCN-x-TDA has obvious improvement on the performance of photocatalytic hydrogen production.
Specifically, the hydrogen production rate of the sample UCN prepared in the comparative example is 42 mu mol h -1 g -1 Significantly lower than 186. Mu. Mol h of UCN-3-TDA prepared in sample example 1 -1 g -1 ；
The hydrogen production rate of UCN-4-TDA prepared in example 2 was 212. Mu. Mol h -1 g -1 Higher than UCN-3-TDA prepared in example 1;
the hydrogen production rate of UCN-5-TDA prepared in example 3 was 247. Mu. Mol h -1 g -1 Higher than UCN-4-TDA prepared in example 2.
The hydrogen production rate of UCN-6 thiophene-2,5-dicarboxaldehyde prepared in example 4 is 200 mu mol h -1 g -1 Higher than the UCN of the sample prepared in the comparative example, the UCN-3-TDA prepared in example 1 and the UCN-4-TDA prepared in example 2, but lower than the UCN-5-TDA prepared in example 3.
In conclusion, the UCN-5-TDA sample obtained by grafting a proper amount of thiophene-2,5-diformaldehyde on a CN network structure has the highest photocatalytic hydrogen production performance, namely the photocatalytic hydrogen production rate of the photocatalytic composite material prepared in the embodiment 3 is the best. With the further increase of the dosage of thiophene-2,5-dicarboxaldehyde, the hydrogen production performance of the prepared photocatalytic composite material sample is gradually reduced, which may be due to excessive doping, damage to some characteristics of the semiconductor and influence on the photocatalytic performance of the material.
Test example 3:
photocatalytic degradation experiment of BPA:
the specific experimental conditions and method are as follows: the filtrate was analyzed by High Performance Liquid Chromatography (HPLC) and fluorescence detector (Waters e2695 Alliance, USA) at 245 nm.
Wherein, the specific reaction solution: 50mg of the photocatalytic composite material was dispersed in 100mL of an aqueous solution of BPA (bisphenol A) (20 mg L) -1 ) And stirring is continued for 60min to perform dark pre-adsorption experiments. Then theThe system was exposed to the radiation of a 300W xenon lamp (PLS-SXE 300D, beijing Perfectlight technologies ltd) fitted with a 420nm cut-off filter. 2mL of the reaction solution (filtrate) was periodically extracted using a 0.45 μm membrane.
The photocatalytic degradation curves of the samples obtained in examples 1 to 4 and comparative example were tested by the above experimental conditions and methods, and the results are shown in fig. 4.
As can be seen from fig. 4, the adsorption efficiency was only 0.4% after the dark treatment for 60 minutes using raw UCN as a catalyst, and the removal rate was 22.4% at 180 minutes under visible light irradiation. However, UCN-x thiophene-2,5-dicarboxaldehyde significantly improved BPA removal efficiency compared to UCN. The photodegradation efficiencies of UCN-3 thiophene-2,5-dicarboxaldehyde, UCN-4 thiophene-2,5-dicarboxaldehyde, UCN-5 thiophene-2,5-dicarboxaldehyde and UCN-6 thiophene-2,5-dicarboxaldehyde were 92.6%, 94.1%, 100% and 96.5%, respectively. The significant improvement in photodegradation efficiency may result from the formation of D-a structures (donor-acceptor covalent organic framework structures) and increased adsorption capacity in UCN-x-TDA. In addition, a sample UCN-5 thiophene-2,5-dialdehyde obtained by grafting a proper amount of thiophene-2,5-dialdehyde onto a CN network structure has the highest photocatalytic degradation efficiency.
Test example 4:
photoluminescence spectrum test:
wherein, the specific experimental conditions are as follows: at room temperature, FLS-980 spectrofluorometer was used.
The photoluminescence spectra of the samples obtained in example 3 and comparative example are shown in fig. 5.
As can be seen in FIG. 5, the amount of thiophene-2,5-dialdehyde increased to 5mg, significant fluorescence quenching of the sample was observed, and in addition, an additional peak was observed at 577nm, which is the charge transfer between the D-A structures. With the addition of the thiophene-2,5-dialdehyde, the composite material obtained by grafting the thiophene-2,5-dialdehyde on the CN network structure can effectively promote the separation of sample photo-generated electrons and photo-generated holes. The reason is that pi electron delocalization is enhanced and photo-generated electrons are rapidly transferred along with the CN network structure grafted by organic monomer thiophene-2,5-dialdehyde. Thereby inhibiting the rapid recombination of photogenerated holes and photogenerated electrons and promoting the photocatalytic hydrogen production activity of the catalyst.
Test example 5:
photocatalytic stability experiment:
the photocatalytic stability test of the UCN-5-TDA sample obtained in example 3 is shown in FIG. 6.
As can be seen from FIG. 6, after 5 cycles of continuous illumination for 20h (every 4h, the generated hydrogen is evacuated and discharged, and one cycle is calculated), the hydrogen production activity of the sample UCN-5-TDA is not attenuated basically, and the catalyst is proved to have good stability and good application prospect in practical application.
Test example 6:
nuclear magnetic resonance spectroscopy experiment:
the NMR spectrum 7 of UCN-5-TDA obtained as a sample in example 3 is shown.
It can be observed from FIG. 7 that the main peaks at 156.1ppm and 164.3ppm are from CN in UCN 3 And CN 2 -NH 2 This indicates that the frame of the CN network structure is well preserved after thiophene-2,5-dialdehyde is added, and more importantly a new peak is observed at 114.4ppm, corresponding to aromatic-C = C-in thiophene-2,5-dicarboxaldehyde. Based on these characterization results, it can be concluded that thiophene-2,5-dicarboxaldehyde is grafted as a molecule into the CN network by schiff base reaction. In addition, aromatic rings in-C = C-and thiophene-2,5-dicarboxaldehyde can enhance pi electron delocalization, which is beneficial to the enhancement of light absorption and the rapid migration of photo-generated electrons and promotes the photocatalytic hydrogen production activity of the catalyst.
The above description is only an example of the present invention and is not intended to limit the scope of the present invention, and all equivalent modifications made by the present invention in the specification or the related technical fields, which are directly or indirectly applied, are included in the scope of the present invention.
Claims (10)
1. A photocatalytic composite material characterized by: the photocatalytic composite material comprises the following raw materials:
graphite phase carbon nitride and thiophene-2,5-dicarboxaldehyde.
2. A method of preparing a photocatalytic composite material as set forth in claim 1, characterized in that: the method comprises the following steps:
mixing the graphite-phase carbon nitride with the thiophene-2,5-dicarboxaldehyde to obtain a mixture;
calcining the mixture to obtain the photocatalytic composite material.
3. The method of claim 2, wherein: the temperature of the calcination is 530-560 ℃.
4. The method of claim 2, wherein: the calcination time is 4-5 hours.
5. The method of claim 2, wherein: the temperature rise rate of the calcination is 5-15 ℃/min.
6. The method of claim 2, wherein: further comprising the step of preparing the graphite phase carbon nitride:
and heating the nitrogen-containing organic matter to a molten state to obtain the graphite-phase carbon nitride.
7. The method of claim 6, wherein: the nitrogen-containing organic matter comprises at least one of urea, melamine and dicyandiamide.
8. The method of claim 6, wherein: the mass ratio of the nitrogen-containing organic matter to the thiophene-2,5-dicarboxaldehyde is 10000:3-6.
9. Use of a photocatalytic composite material as set forth in claim 1 in a hydrogel photocatalytic membrane.
10. The use of the photocatalytic composite material as set forth in claim 1 in hydrogen production reaction by photolysis of water under visible light.
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| CN107413378A (en) * | 2016-05-23 | 2017-12-01 | 中国科学院上海硅酸盐研究所 | A kind of preparation method for the graphite phase carbon nitride visible light catalyst that combined polymerization is modified |
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