CN111790423A - Composite photocatalyst with edge-modified non-metallic functional group and preparation method and application thereof - Google Patents
Composite photocatalyst with edge-modified non-metallic functional group and preparation method and application thereof Download PDFInfo
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- 239000002131 composite material Substances 0.000 title claims abstract description 32
- 238000002360 preparation method Methods 0.000 title claims abstract description 25
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- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims abstract description 36
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 36
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- 125000003118 aryl group Chemical group 0.000 claims description 12
- 238000001354 calcination Methods 0.000 claims description 10
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- 229910052786 argon Inorganic materials 0.000 claims description 7
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- 239000000725 suspension Substances 0.000 claims description 7
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- 239000007864 aqueous solution Substances 0.000 claims description 6
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- 239000007789 gas Substances 0.000 description 10
- 230000000630 rising effect Effects 0.000 description 10
- 125000001997 phenyl group Chemical group [H]C1=C([H])C([H])=C(*)C([H])=C1[H] 0.000 description 9
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- 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
-
- B01J35/39—
-
- 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
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
- C01B2203/02—Processes for making hydrogen or synthesis gas
- C01B2203/0266—Processes for making hydrogen or synthesis gas containing a decomposition step
- C01B2203/0277—Processes for making hydrogen or synthesis gas containing a decomposition step containing a catalytic decomposition step
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- 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 belongs to the technical field of nano material synthesis, relates to a non-metal functional group edge modified composite photocatalyst and a preparation method and application thereof, and particularly relates to g-C3N4a/4-PTSC composite photocatalyst and a preparation method and application thereof; in the invention, g-C is synthesized in one step by utilizing an efficient and convenient thermal polycondensation method3N44-PTSC nanosheets forming structurally stable g-C3N4The 4-PTSC photocatalyst realizes stable and efficient hydrogen production by photolysis of water; the photocatalyst prepared by the invention has better stability and repeatability, and has the advantages of high separation efficiency of photo-generated electron-hole pairs, simple and quick preparation method, low cost, no environmental pollution, excellent hydrogen production performance and the like.
Description
Technical Field
The invention belongs to the technical field of nano material synthesis, and relates to a non-metal functional group edge modified composite photocatalyst, and a preparation method and application thereof.
Background
In the modern society, the requirement of people on the environment quality which depends on the survival is higher and higher, and hydrogen energy has the advantages of high combustion heat value, clean and pollution-free combustion process and the like, and is a secondary energy with good future prospect. Meanwhile, a photolysis water hydrogen production technology for converting solar energy into usable energy is considered as one of the most promising green technologies for relieving the global energy crisis, and has attracted extensive attention across disciplines. The key to this technology is to develop a high efficiency, low cost photocatalyst to be a viable alternative.
Graphite-like phase carbon nitride (g-C)3N4) The method has the unique advantages of abundant raw materials, convenient synthesis, proper electronic band structure, high physical and chemical stability and environmental friendliness, and becomes one of the research hotspots in the field of solar energy conversion, however, because the photoproduction electron-hole pair has high recombination rate in the process of transferring the photoproduction current carrier to the surface, pure g-C is used3N4The photocatalyst used for photohydrogen evolution cannot be further applied, and a material capable of improving the separation efficiency of photogenerated carriers to enhance H is urgently required to be searched2Thereby increasing the g-C3N4Photocatalytic activity.
Disclosure of Invention
The invention aims to provide a non-metal functional group edge-modified composite photocatalyst and a preparation method and application thereof, and particularly provides an aromatic C = C and amino synergetic edge-modified composite photocatalyst and a preparation method and application thereof, wherein the catalyst can be recorded as g-C3N44-PTSC composite photocatalyst. The preparation steps of the composite material are simple, and the prepared 2D photocatalyst has good photocatalytic H production2And (4) performance.
In the invention, the nonmetal functional group is modified at g-C by a simple and rapid thermal polycondensation method3N4And the edge of the composite photocatalyst system is modified by the edge of the non-metal functional group, so that the hydrogen production performance of the photocatalysis is more efficient, and the hydrogen production performance is optimized by controlling the doping amount of the non-metal material.
The invention firstly provides a non-metal functional group edge modificationThe composite photocatalyst of (1), i.e. g-C3N4a/4-PTSC composite photocatalyst, wherein the catalyst is aromatic C = C and amino edge modified g-C cooperatively3N4。
The mass ratio of urea to 4-PTSC (4-phenyl-3-thiosemicarbazide) was 20g:5-35mg, and the samples prepared were respectively designated as g-C3N4/4-PTSC-a（a=5,15,25,35）。
The invention also provides a g-C3N4The preparation method of the/4-PTSC composite photocatalyst comprises the following steps:
putting urea and 4-PTSC with certain mass into a mortar and grinding to uniformly disperse the 4-PTSC in the urea, then putting the urea and the PTSC into a crucible and compacting, heating the mixture from room temperature to 500-600 ℃ in a muffle furnace, and calcining for 2-4 h; then cooling to room temperature to obtain g-C3N4/4-PTSC。
In the selection of the calcination temperature, the calcination at the temperature lower than 500 ℃ is tried in the invention, and the crystallinity of the obtained product is not enough; while calcining at a temperature of more than 600 ℃ and finding that g-C3N4Is easy to decompose.
Wherein the mass ratio of the urea to the 4-PTSC is 20g:5-35mg, and the prepared samples are respectively marked as g-C3N44-PTSC-a (a represents the amount of 4-PTSC, a =5~ 35).
Wherein the heating rate is 2.5 ℃ min-1。
The invention also provides the non-metal functional group edge modified composite photocatalyst (g-C)3N44-PTSC composite photocatalyst) in photocatalytic hydrogen production, and the specific catalytic method comprises the following steps:
first, 50mg of g-C3N4the/4-PTSC composite photocatalyst was uniformly dispersed in 100mL of TEOA (triethanolamine) aqueous solution (concentration 20 vol%, pH = 11.4), and 3% of H was added2PtCl6·H2O (chloroplatinic acid, 1.5mL, 1 mg/mLPt) in water. The suspension prepared above was poured into a glass apparatus and sealed. Thereafter, the air in the reactor was purged with argon gas, and a 300W xenon lamp equipped with a 420nm filter was usedAs a visible light source and measuring the generated H by an on-line gas chromatography system2The amount of (c).
The invention has the beneficial effects that:
typical covalent semiconducting polymers have sp2p-conjugation, g-C3N4The charge transfer in the nanoplatelets is anisotropic, which limits the transfer of photogenerated charge to the 2D plane, resulting in different charge densities between the central and edge regions of the nanoplatelet structure. As n-type semiconductors, g-C3N4Most likely in g-C3N4Near the edges of the nanoplatelets. Therefore, if the edge is modified with a non-metallic electron acceptor, it is possible to induce an anisotropic built-in electric field inside the molecule, thereby effectively separating carriers. The aromatic C ═ C bond has high electronegativity, and can significantly enhance the electron attracting and electron capturing ability of the material. In particular, in g-C by using a simple wet chemistry method3N4Preparation of edge-functionalized g-C by edge-selective introduction of electron-withdrawing groups into the edges of the nanoplates3N4. The prepared catalyst film shows excellent disinfection efficiency of more than 99.9999% under the irradiation of visible light. The results show that in g-C3N4The exposed-COOH and C = O groups at the edges of the nanosheets can obviously cause upward band bending and enhance the separation efficiency of photo-generated electron-hole pairs, thereby improving the catalytic performance. From this perspective, it is particularly important to select a potential edge-lining agent with an appropriate electron acceptor. In our work, we prepared edge-functionalized g-C by selective introduction of electron-withdrawing groups3N4。
The electron-withdrawing group represents a group in which the electron cloud density on the benzene ring is reduced after the hydrogen on the aromatic benzene ring is substituted with the substituent. And the groups with the increased electron cloud density on the benzene ring are called electron donating groups. One group is an electron-withdrawing group or an electron-donating group at all, and the sum of the induction effect, the conjugation effect and the hyperconjugation effect of the group on the benzene ring is obtained. The experimental results show that atoms directly connected with carbon atoms have the electron-withdrawing capability decreasing with the increase of atomic number in the same group, and the electron-withdrawing capability increasing with the increase of atomic number in the same period. Meanwhile, the greater the degree of unsaturation of the group directly attached to a carbon atom, the stronger the electron-withdrawing ability thereof.
Non-metals of the invention g-C3N44-PTSC nanoplatelets in g-C3N4Providing aromatic C = C and amino for 4-PTSC as raw materials, adopting a thermal polycondensation method to synthesize a high-efficiency and stable non-metal functional group edge-modified composite system in one step, and coupling the benzene ring and the amino of the 4-PTSC at g-C under the high-temperature condition3N4An edge. The amino group is connected to the benzene ring to activate the benzene ring, so that the electron cloud density on the benzene ring is reduced, and the electron attracting and capturing ability of the aromatic C ═ C bond is remarkably enhanced due to the high electronegativity of the aromatic C ═ C bond, so that the electrophilic substitution reaction is very easy to occur. Therefore, the photocatalyst modified by the aromatic C = C and the amino group can enable photo-generated electrons to be rapidly transferred to the edges of the nanosheets, so that the recombination of photo-generated electron-hole pairs is inhibited. At the same time, g-C is introduced due to non-metallic functional groups3N4The light absorption capacity of the/4-PTSC nano sheet is obviously enhanced, and the absorption capacity is from g to C3N4459nm to 600 nm. g-C3N4The fluorescence intensity of the/4-PTSC is obviously lower than that of the g-C3N4The compound nano-sheet is proved to have better migration rate of photon-generated carriers under illumination, so that the hydrogen production activity of the compound nano-sheet is enhanced.
By testing the hydrogen production performance, g-C3N4The hydrogen production rate of the/4-PTSC is 2390.6 mu mol.h-1·g-1Specific g-C3N4The improvement is about 4 times. The quantum efficiency at 420nm was 8.3%. The preparation method of the catalyst is simple and rapid, the cost is low, and the obtained catalyst has excellent hydrogen production performance. Meanwhile, through detection, the nano sheet only contains C, N and O elements, does not contain metal ions harmful to the environment, and does not generate organic matters harmful to the environment.
Description of the drawings:
FIG. 1 shows g-C3N4(a) And g-C3N4TE of/4-PTSC-25 (b)And (5) an M diagram.
FIG. 2 shows g-C3N4And g-C3N4Fourier infrared spectrum of/4-PTSC-25.
FIG. 3 is g-C3N4And g-C3N4XRD pattern of/4-PTSC-25.
FIG. 4 shows g-C3N4、g-C3N4Ultraviolet-visible diffuse reflection absorption spectrum chart (a) of/4-PTSC-25, Kubelka-Munk function and g-C3N4And g-C3N4A graph (b) relating the optical energy of the 4-PTSC-25.
FIG. 5 is g-C3N4、g-C3N4/4-PTSC-5、 g-C3N4/4-PTSC-15、g-C3N4/4-PTSC-25、g-C3N4The performance diagram of photocatalytic water splitting hydrogen production of 4-PTSC-35.
FIG. 6 is a graph of the performance of the g-C3N4/4-PTSC-25 sample in continuous circulation for 24 h for hydrogen production by photolysis of water.
FIG. 7 is g-C3N4、g-C3N4a/4-PTSC-25 PL spectrum (a) and a time-resolved transient PL decay curve (b).
Example 1: g-C3N4Preparation of photocatalyst and hydrogen production by photolysis of water
(1) Preparation of g-C3N4Nanosheet:
drying a certain amount of urea in an oven at 70 deg.C overnight, grinding the dried urea into powder, placing into a crucible with a cover, and placing in a muffle furnace at room temperature for 2.5 deg.C for min-1The temperature rising rate of (2) is increased to 550 ℃, and the calcination is carried out for 4 hours. After cooling to room temperature, g-C is obtained3N4. At the same time, an attempt was made to work at 2.5 ℃ for min-1The temperature rise rate of (2) is increased to 500 ℃ and calcined for 4h and 2.5 ℃ min-1The temperature rising rate is increased to 600 ℃ to calcine for 2 hours to prepare g-C3N4。
（2）g-C3N4The composite photocatalyst photolyzes water to produce hydrogen:
50mg of g-C3N4The nanoplatelets are homogeneously dispersed in 100ml 20 vol% Triethanolamine (TEOA) pH =11.4In an aqueous solution, and adding g-C3N4Adding H accounting for 3 percent of the mass of the nanosheet2PtCl6·H2O (1.5 ml, 1mg/ml Pt) in water. Then, the uniformly mixed suspension was poured into a glass reactor having a volume of about 250ml, and air in the reactor was discharged with argon gas to fill the entire reactor with Ar, and then 500 μ L of gas in the reactor was extracted every hour using a 300W xenon lamp equipped with a 420nm cutoff filter as a visible light source, and was injected into an on-line gas chromatography system to measure H generated2The amount of (c). The hydrogen production was 614.9. mu. mol. h as determined by chromatography-1·g-1。
Example 2: g-C3N4Preparation of/4-PTSC-5 photocatalyst and hydrogen production by photolysis of water
(1) Preparation of g-C3N44-PTSC-5 photocatalyst:
20g of dried urea and 5mg of 4-PTSC were weighed, ground in a mortar, and the 4-PTSC was uniformly dispersed in the urea, which was then placed in a crucible, and heated from room temperature in a muffle furnace for 2.5 ℃ min-1The temperature rising rate of (2) is increased to 550 ℃, and the calcination is carried out for 4 hours. After cooling to room temperature, g-C is obtained3N44-PTSC-5. At the same time, an attempt was made to work at 2.5 ℃ for min-1The temperature rise rate of (2) is increased to 500 ℃ and calcined for 4h and 2.5 ℃ min-1The temperature rising rate is increased to 600 ℃ to calcine for 2 hours to prepare g-C3N4/4-PTSC-5。
（2）g-C3N4The 4-PTSC-5 composite photocatalyst is used for photolyzing water to prepare hydrogen:
50mg of g-C3N4the/4-PTSC-5 nanoplates were uniformly dispersed in 100ml of a 20 vol% aqueous Triethanolamine (TEOA) solution at pH =11.4, and as added g-C3N43% of the mass of the/4-PTSC-5 nanosheet, H2PtCl6·H2O (1.5 ml, 1mg/ml Pt) in water. Thereafter, the uniformly mixed suspension was poured into a glass reactor having a volume of about 250ml, and the air in the reactor was purged with argon gas to fill the entire reactor with Ar, followed by using a 300W xenon lamp equipped with a 420nm cut-off filter as a visible light source to simulate sunlight, and 50 was extracted every hourGas in the 0 mu L reactor is pumped into an online gas chromatography system to measure generated H2The amount of (c). The hydrogen production was 1293.9. mu. mol. h as determined by chromatography-1·g-1。
Example 3: g-C3N4Preparation of/4-PTSC-15 photocatalyst and hydrogen production by photolysis of water
(1) Preparation of g-C3N44-PTSC-15 photocatalyst:
20g of dried urea and 15mg of 4-PTSC were weighed, ground in a mortar, and the 4-PTSC was uniformly dispersed in the urea, which was then placed in a crucible, and heated from room temperature in a muffle furnace for 2.5 ℃ min-1The temperature rising rate of (2) is increased to 550 ℃, and the calcination is carried out for 4 hours. After cooling to room temperature, g-C is obtained3N44-PTSC-15. At the same time, an attempt was made to work at 2.5 ℃ for min-1The temperature rise rate of (2) is increased to 500 ℃ and calcined for 4h and 2.5 ℃ min-1The temperature rising rate is increased to 600 ℃ to calcine for 2 hours to prepare g-C3N4/4-PTSC-15。
（2）g-C3N4The 4-PTSC-15 composite photocatalyst is used for photolyzing water to prepare hydrogen:
50mg of g-C3N4the/4-PTSC-15 nanoplates were uniformly dispersed in 100ml of a 20 vol% aqueous Triethanolamine (TEOA) solution at pH =11.4, and as added g-C3N43% of the mass of the/4-PTSC-15 nanosheet is added with H2PtCl6·H2O (1.5 ml, 1mg/ml Pt) in water. Then, the uniformly mixed suspension was poured into a glass reactor having a volume of about 250ml, and air in the reactor was discharged with argon gas to fill the entire reactor with Ar, and then, a 300W xenon lamp equipped with a 420nm cutoff filter was used as a visible light source to simulate sunlight, and 500 μ L of gas in the reactor was extracted every hour and injected into an on-line gas chromatography system to measure H generated2The amount of (c). The hydrogen production was 1604.9. mu. mol. h as determined by chromatography-1·g-1。
Example 4: g-C3N4Preparation of/4-PTSC-25 photocatalyst and hydrogen production by photolysis of water
(1) Preparation of g-C3N44-PTSC-25 photocatalyst：
20g of dried urea and 25mg of 4-PTSC were weighed, ground in a mortar, and the 4-PTSC was uniformly dispersed in the urea, which was then placed in a crucible, and heated from room temperature in a muffle furnace for 2.5 ℃ min-1The temperature rising rate of (2) is increased to 550 ℃, and the calcination is carried out for 4 hours. After cooling to room temperature, g-C is obtained3N44-PTSC-25. At the same time, an attempt was made to work at 2.5 ℃ for min-1The temperature rise rate of (2) is increased to 500 ℃ and calcined for 4h and 2.5 ℃ min-1The temperature rising rate is increased to 600 ℃ to calcine for 2 hours to prepare g-C3N4/4-PTSC-25。
（2）g-C3N4The 4-PTSC-25 composite photocatalyst is used for photolyzing water to prepare hydrogen:
50mg of g-C3N4the/4-PTSC-25 nanoplates were uniformly dispersed in 100ml of a 20 vol% aqueous Triethanolamine (TEOA) solution with pH =11.4, and as added g-C3N43% of the mass of the/4-PTSC-25 nanosheet, H was added2PtCl6·H2O (1.5 ml, 1mg/ml Pt) in water. Then, the uniformly mixed suspension was poured into a glass reactor having a volume of about 250ml, and air in the reactor was discharged with argon gas to fill the entire reactor with Ar, and then, a 300W xenon lamp equipped with a 420nm cutoff filter was used as a visible light source to simulate sunlight, and 500 μ L of gas in the reactor was extracted every hour and injected into an on-line gas chromatography system to measure H generated2The amount of (c). The hydrogen production was 2390.6. mu. mol. h as determined by chromatography-1·g-1。
Example 5: g-C3N4Preparation of 4-PTSC-35 photocatalyst
(1) Preparation of g-C3N44-PTSC-35 photocatalyst:
20g of dried urea and 35mg of 4-PTSC were weighed, ground in a mortar, and the 4-PTSC was uniformly dispersed in the urea, which was then placed in a crucible, and heated from room temperature in a muffle furnace for 2.5 ℃ min-1The temperature rising rate of (2) is increased to 550 ℃, and the calcination is carried out for 4 hours. After cooling to room temperature, g-C is obtained3N44-PTSC-35. At the same time, an attempt was made to work at 2.5 ℃ for min-1The temperature rise rate of (2) is increased to 500 ℃ and calcined for 4h and 2.5 ℃ min-1The temperature rising rate is increased to 600 ℃ to calcine for 2 hours to prepare g-C3N4/4-PTSC-35。
（2）g-C3N4The 4-PTSC-35 composite photocatalyst is used for photolyzing water to prepare hydrogen:
50mg of g-C3N4the/4-PTSC-35 nanoplates were uniformly dispersed in 100ml of a 20 vol% aqueous Triethanolamine (TEOA) solution at pH =11.4, and as added g-C3N4Adding H to 3 percent of mass of 4-PTSC-35 nanosheet2PtCl6·H2O (1.5 ml, 1mg/ml Pt) in water. Then, the uniformly mixed suspension was poured into a glass reactor having a volume of about 250ml, and air in the reactor was discharged with argon gas to fill the entire reactor with Ar, and then, a 300W xenon lamp equipped with a 420nm cutoff filter was used as a visible light source to simulate sunlight, and 500 μ L of gas in the reactor was extracted every hour and injected into an on-line gas chromatography system to measure H generated2The amount of (c). The hydrogen production was 2156.4. mu. mol. h as determined by chromatography-1·g-1。
The invention relates to a method for measuring g-C by means of X-ray diffraction (XRD), a Transmission Electron Microscope (TEM), a Fourier infrared spectrometer, an ultraviolet-visible absorption spectrometer and the like3N4And g-C3N4Characterization was performed on the/4-PTSC-25 photocatalyst.
FIG. 1 (a) shows g-C prepared in example 13N4From which g-C can be seen3N4Presenting a typical two-dimensional nanosheet structure. FIG. 1 (b) shows g-C prepared in example 43N4TEM image of/4-PTSC-25, from which it can be seen that the thickness is g-C3N4Small and the surface curves upwards. The thinner structure shows that the nano-sheet has larger specific surface area, and because the thickness of the nano-sheet is reduced, more electrons in the inner layer can be exposed, and more active sites are provided for the photocatalytic hydrogen evolution reaction.
(3) FIG. 2 shows g-C prepared in example 13N4g-C prepared in example 43N4Fourier infrared spectrum of/4-PTSC-25. In pure g-C3N4In the case of (2), a spectrum corresponding to 1200-1650cm was found-1Regioaromatic CN heterocycles are characteristic of strong bands in the stretch mode. 1562 and 1639cm-1Nearby absorption bands due to C = N stretch, 1240, 1319, 1410 and 1456cm-1The other four absorption bands at (a) are due to aromatic C-N stretching. In addition, at 808cm-1Characteristic absorption patterns of the triazine units are observed. At 3100cm-1A broad band corresponding to the terminal NH at the defect of the aromatic ring was also observed nearby2Or a stretching mode of the NH group. In g-C3N41543cm in the/4-PTSC-25 nanosheet-1One is observed at g-C3N4The peak absent in (C) is attributable to stretching vibration of the aromatic C = C.
FIG. 3 is a graph of g-C prepared in example 13N4g-C prepared in example 43N4X-ray diffraction (XRD) pattern of/4-PTSC-25. As can be seen, the addition of the benzene ring and the amino group of the nonmetal group does not change the position of the peak, which indicates that the doping of the nonmetal group does not change the original g-C3N4And (5) structure. But with pure g-C3N4Comparative example g-C3N4The peak at/4-PTSC-25 became broader and weaker. This indicates that 4-PTSC is at g-C3N4The addition of (A) can change the chemical environment and reduce the g-C to a certain extent3N4But its main chemical skeleton has been preserved.
FIG. 4 is a graph of g-C prepared in example 13N4g-C prepared in example 43N4The ultraviolet-visible diffuse reflection absorption spectrum (a) of the/4-PTSC-25 and the corresponding estimated band gap spectrum (b). To study g-C3N4Source of excellent Activity of/4-PTSC-25, g-C estimated by UV-absorption Spectroscopy3N4The light absorption ability of 4-PTSC-25. Pure g-C in the figure3N4Exhibiting typical semiconductor light absorption. g-C3N4the/4-PTSC-25 nanosheet has strong absorption capacity in a visible light region (300-600 nm), shows strong light absorption and corresponds to an energy band of 2.85 eV. In contrast, pure g-C3N4At a wavelength of about 459nmThere is an absorption edge on the right, corresponding to a band gap energy of 2.99 eV. The expansion of the light absorption of such a composite material allows maximum use of the spectrum, thereby creating additional electron-hole pairs.
As shown in fig. 5 as g-C3N4、g-C3N4/4-PTSC-5、 g-C3N4/4-PTSC-15、g-C3N4/4-PTSC-25、g-C3N4The performance diagram of photocatalytic water splitting hydrogen production of 4-PTSC-35. As seen from the figure, when the doping amount of the non-metallic material 4-PTSC reaches 25mg, the hydrogen production performance is best, and the hydrogen production amount is 2390.6 mu mol.h-1·g-1. With the increase of the doping amount, the hydrogen production amount increases first and then decreases. When the doping amount is 35mg, it is possible that the recombination center of the photogenerated carrier is newly formed at the edge thereof due to the large amount of 4-PTSC.
FIG. 6 shows g-C3N4And the performance diagram of the/4-PTSC-25 sample for continuous circulation for 24 h for hydrogen production by photolysis of water. H was obtained as the reaction time was extended throughout the 6-cycle experiment2The amounts are substantially the same, total H2The reduction in amount was not significant. Thus showing good stability and repeatability.
As shown in figure 7 as g-C3N4、g-C3N4a/4-PTSC-25 PL spectrum (a) and a time-resolved transient PL decay curve (b). Original g-C3N4The sample showed a strong emission peak at 460nm, which is measured by g-C3N4The recombination of excited electron-hole pairs in the photocatalyst. However, with the introduction of 4-PTSC, the emission peak was significantly reduced, indicating efficient separation and rapid transfer of photo-generated charge. g-C in FIG. 6b3N4The average lifetime of the/4-PTSC-25 (2.86ns) is much shorter than that of g-C3N4(4.38ns), which means that additional non-radiative decay channels can be opened for electron transfer. The results show that the recombination of photogenerated electron-hole pairs can be inhibited through certain edge modification, so that the hydrogen production performance is improved.
Claims (10)
1. g-C3N4The preparation method of the/4-PTSC composite photocatalyst is characterized in thatThe method comprises the following steps:
putting urea and 4-PTSC into a mortar and grinding to uniformly disperse the 4-PTSC in the urea, then putting the urea and the 4-PTSC into a container and compacting, heating to 500-600 ℃, and calcining for 2-4 h; then cooling to room temperature to obtain g-C3N4/4-PTSC。
2. A g-C according to claim 13N4The preparation method of the/4-PTSC composite photocatalyst is characterized in that the dosage ratio of the urea to the 4-PTSC is 20g:5-35 mg.
3. A g-C according to claim 13N4The preparation method of the/4-PTSC composite photocatalyst is characterized in that the heating rate is 2.5 ℃ for min-1。
4. g-C prepared according to the method of any one of claims 1 to 33N4The 4-PTSC composite photocatalyst is characterized in that g-C is3N4the/4-PTSC composite photocatalyst is a composite photocatalyst with a non-metal functional group edge modified, and specifically comprises aromatic C = C and amino edge modified g-C cooperatively3N4。
5. g-C as claimed in claim 43N4The application of the/4-PTSC composite photocatalyst in photocatalytic hydrogen production.
6. Use according to claim 5, characterized in that it comprises:
g to C3N4the/4-PTSC composite photocatalyst is uniformly dispersed in TEOA aqueous solution, and H is added2PtCl6·H2O aqueous solution, pouring the suspension into a container, sealing, discharging air, and measuring the generated H with xenon lamp as visible light source2The amount of (c).
7. Use according to claim 6, wherein the aqueous TEOA solution has a concentration of 20% and a pH = 11.4.
8. Use according to claim 6, wherein H is2PtCl6·H2The Pt content of the O aqueous solution was 1 mg/mL.
9. Use according to claim 6, wherein the exhaust air is exhausted using argon.
10. Use according to claim 6, wherein H is2PtCl6·H2The dosage of the O aqueous solution is g-C3N43% of the/4-PTSC composite photocatalysis mass.
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