Preparation method and application of metal nanocluster modified ultrathin 2D g-c3n4 / znin2s4 heterojunction photocatalyst

Abstract

The application discloses a metal nanocluster modified ultrathin 2D g-C3N4 / ZnIn2S4 heterojunction photocatalyst and a preparation and application thereof, and belongs to the field of photocatalytic hydrogen production. In the application, the ultrathin ZnIn2S4 is anchored on the metal nanocluster modified ultrathin 2D g-C3N4 by using an electrostatic self-assembly method, so that efficient and stable water photolysis hydrogen production under visible light is realized. The heterojunction photocatalyst is characterized in that the metal nanoclusters are distributed in the layers of the ultrathin g-C3N4 and ZnIn2S4 nanosheets in a decorative manner, and the average thickness of the photocatalyst is 1.5-2.0 nm. In addition, the application explores the influence of introduction of different metal nanoclusters into the layers of the ultrathin g-C3N4 and ZnIn2S4 nanosheets on the photocatalytic hydrogen evolution performance, so as to further optimize the activity of the catalyst in the photocatalytic hydrogen evolution reaction. The catalyst has the advantages of low cost, no pollution and the like, and has a wide application prospect in the field of photocatalytic hydrogen production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of hydrogen production catalysts for water splitting, and particularly relates to a preparation method and application of a metal nanocluster modified ultrathin 2D g-C3N4 / ZnIn2S4 heterojunction water splitting hydrogen production catalyst. BACKGROUND

[0002] In recent years, energy shortage and environmental pollution have become increasingly serious, and hydrogen energy, as an ideal clean energy, has attracted widespread attention. Developing carbon-free hydrogen energy and optimizing industrial energy structure are expected to become one of the feasible ways to replace traditional fuels and achieve carbon neutrality. Photocatalytic hydrogen production technology based on semiconductors is an ideal energy conversion strategy, which can directly convert solar energy into hydrogen energy by using efficient photocatalysts. However, most of the current research photocatalysts still face problems such as low visible light absorption efficiency, poor charge separation efficiency, easy recombination of photo-generated electrons and holes, and slow kinetics of surface redox reactions. Therefore, the development and design of efficient photocatalysts have become a research hotspot in the field of water splitting.

[0003] Graphitic carbon nitride (g-C3N4) is a promising metal-free conjugated polymer semiconductor, which has been widely used in photocatalytic water splitting due to its unique electronic structure, excellent thermal and chemical stability, and easily controllable band structure. However, g-C3N4 still faces problems such as insufficient visible light utilization, low carrier mobility, and rapid recombination of photo-generated carriers in practical applications. In order to solve these problems, researchers have adopted various strategies to improve the photocatalytic performance of g-C3N4, such as morphology control, metal and non-metal element doping, heterojunction construction, and defect engineering. Among them, nanocrystallization of g-C3N4 by morphology control to prepare two-dimensional sheet structure with ultrathin structure can effectively improve its specific surface area and promote the surface redox reaction. In addition, constructing heterojunction with other semiconductors is also an effective method to improve the photocatalytic performance. Semiconductor ZnIn2S4 (ZIS) is a chalcogenide with good photoelectric performance, low toxicity, and good structural stability. However, due to its limited electron-hole separation efficiency and slow carrier transfer kinetics, the photocatalytic hydrogen production efficiency of pure ZIS is not ideal. In order to improve the photocatalytic efficiency, constructing heterojunction based on ZIS is a promising strategy.

[0004] At present, the research on the heterojunction of g-C3N4 and ZIS has been reported, however, due to the similar conduction band and valence band structure of the two, most of them form type II heterostructure, which reduces the redox ability of the charge transfer process. The Z-type heterojunction has stronger redox ability than the type II heterojunction, because in the Z-type heterojunction, electrons accumulate on the high energy level, and holes accumulate on the low energy level. Therefore, how to construct a Z-type heterojunction between the two is still a difficult problem.

[0005] In view of the above technical defects, the present application provides a simple and feasible preparation method of a metal nanocluster modified ultrathin 2D g-C3N4 / ZnIn2S4 Z-type heterojunction photocatalyst.

[0006] The present application uses twice calcination method to obtain ultrathin 2D g-C3N4 sheet structure, which improves the specific surface area of g-C3N4, and uses a large number of N atoms in g-C3N4 to anchor metal clusters. By introducing metal nanoclusters (Fe, Co, Ni, Pd, Ag, Pt, Au) on the ultrathin 2D g-C3N4, the catalytic active sites are increased, and the ultrathin 2D / 2D full solid Z-type heterojunction is precisely constructed by electrostatic self-assembly of 2D ultrathin ZnIn2S4. The combination of g-C3N4 and ZnIn2S4 can significantly improve the light absorption efficiency and charge separation ability. More importantly, in the process of photocatalytic reaction, the metal nanoclusters act as an electron transfer bridge, helping the interface charge to transfer quickly and accelerating the separation of photo-generated holes and photo-generated electrons. The metal nanocluster modified ultrathin 2D g-C3N4 / ZnIn2S4 heterojunction catalyst constructed by the present application not only has abundant charge transfer channels, but also effectively shortens the charge transfer path of the atomically thick ultrathin two-dimensional structure, accelerates the charge transfer efficiency, and improves the photocatalytic activity. SUMMARY

[0007] In view of the above research status, the present application provides a green and simple preparation method of a metal nanocluster modified ultrathin 2D g-C3N4 / ZnIn2S4 heterojunction photocatalyst, which loads metal active sites (Fe, Co, Ni, Pd, Ag, Pt, Au) on the ultrathin 2D g-C3N4, and precisely constructs an ultrathin 2D / 2D full solid Z-type heterojunction by electrostatic self-assembly of 2D ultrathin ZnIn2S4. The influence of different metal layers introduced into the g-C3N4 / ZnIn2S4 heterojunction on the photocatalytic hydrogen evolution performance is discussed and studied. The present application uses different metal nanocluster modified ultrathin 2D g-C3N4 / ZnIn2S4 heterojunction photocatalyst for photocatalytic water splitting experiment, which has good photocatalytic hydrogen evolution performance due to the advantages of abundant charge transfer channels and active sites, and is a photocatalytic hydrogen evolution material with application prospect.

[0008] To achieve the above object, the application discloses the following technical scheme.

[0009] The preparation method of the metal nanocluster modified ultrathin 2D g-C3N4 / ZnIn2S4 heterojunction photocatalyst includes the following steps:

[0010] 1) Put 30 g of urea into a crucible with a lid, heat at a temperature increasing rate of 2.3 ℃ / min under static air at 550 ℃ for 4 h, place the collected powder in an open crucible, and increase the temperature to 500 ℃ at a temperature increasing rate of 5 ℃ / min for further heating for 4 h, after cooling to room temperature, centrifugal washing with deionized water and ethanol for three times respectively, and drying in a vacuum oven at 60 ℃ overnight to obtain g-C3N4 nanosheets;

[0011] 2) Ultrasonically disperse 150 mg of g-C3N4 nanosheets in 30 mL of anhydrous ethanol under stirring to form a uniform suspension (solution 1), measure 1 mL of MPA and add to 10 mL of methanol, and use NaOH to adjust to pH=13 (solution 2), pour solution 2 into solution 1 under stirring, stir for 3 h, centrifugal washing with deionized water and ethanol for three times respectively, and drying in a vacuum oven at 60 ℃ overnight to obtain the required ultrathin g-C3N4 nanosheets, marked as UCN;

[0012] 3) Weigh a certain amount of metal salt, dissolve in 50 mL of ultrapure water under different conditions, and stir for 1 h (solution 3), weigh 500 mg of ultrathin g-C3N4 in 100 mL of ultrapure water, ultrasonically disperse for 30 min (solution 4), add solution 3 to solution 4 under stirring, continue ultrasonic dispersion for 15 min, stir for 6 h under different conditions, after stirring, quickly freeze with liquid nitrogen, and perform freeze-drying treatment, place the freeze-dried powder in a crucible, put it into a tube furnace, increase the temperature to a certain temperature at a temperature increasing rate of 5 ℃ / min under argon atmosphere, keep the temperature constant for 2 h, after cooling to room temperature, collect the powder, and mark it as M-UCN;

[0013] In the step 3), the loading amount of the metal salt is 3% by mass ratio;

[0014] In the step 3), the noble metal (Pd, Ag, Pt, Au) needs to be dissolved and stirred in the dark, and the transition metal (Fe, Co, Ni) does not need to be dissolved in the dark;

[0015] In the step 3), the freezing temperature is -50 ℃, and the drying time is 72 h;

[0016] In the step 3), the room temperature is 20-25 ℃, the temperature is increased from the room temperature to a certain temperature at a temperature increasing rate of 5 ℃ / min, and the temperature is 130-400 ℃;

[0017] 4) Zn(CH3COO)2·2H2O, InCl3, TAA were weighed according to the molar ratio of 1:2:8 and dissolved in 30 mL of a mixed solution of ultrapure water and anhydrous ethanol (1:1), stirred for 30 min, transferred to a 100 mL polytetrafluoroethylene high-pressure reaction kettle, hydrothermal at 180℃ for 24 h, cooled to room temperature, washed with deionized water and ethanol three times respectively, and placed in a vacuum oven at 60℃ overnight to obtain the desired ultrathin ZnIn2S4 nanosheets, marked as ZIS;

[0018] 5) The prepared ZIS and M-UCN were mixed at a mass ratio of 2:1, ultrasonically dispersed in anhydrous ethanol for 30 min to obtain a uniform suspension (1 mg / mL), stirred for 12 h, centrifuged and washed with anhydrous ethanol three times, and placed in a vacuum oven at 60℃ overnight to obtain the desired metal nanocluster modified ultrathin 2D g-C3N4 / ZnIn2S4 composite material, marked as ZIS-M / UCN;

[0019] The application further discloses application of the metal nanocluster modified ultrathin 2D g-C3N4 / ZnIn2S4 heterojunction photocatalyst in photocatalytic hydrogen evolution, which is described in detail as follows:

[0020] (1) In the technical scheme, the metal nanocluster modified ultrathin 2D g-C3N4 / ZnIn2S4 heterojunction ZIS-M / UCN is used as a photocatalyst.

[0021] (2) In the technical scheme, 20 mg of the photocatalyst is ultrasonically dispersed in 60 mL of a triethanolamine (TEOA) aqueous solution (20 vol%), a light source is a 300 W xenon lamp, and a carrier gas is argon.

[0022] The metal nanocluster modified ultrathin 2D g-C3N4 / ZnIn2S4 heterojunction photocatalyst disclosed by the application has the beneficial effects compared with the prior art, which are as follows:

[0023] (1) The metal nanocluster modified ultrathin 2D g-C3N4 / ZnIn2S4 heterojunction photocatalyst disclosed by the application has an ultrathin atomic two-dimensional structure, and the thickness of a sheet layer is 1.5-2.0 nm. The ultrathin structure can effectively shorten an electron transmission path, improve a charge transmission efficiency, and accelerate electron transmission between the ultrathin g-C3N4 and ZnIn2S4.

[0024] (2) The metal nanocluster modified ultrathin 2D g-C3N4 / ZnIn2S4 heterojunction photocatalyst disclosed by the application has a metal cluster size of 1.5-2.4 nm. The atomic nanocluster improves atomic utilization rate, acts as an electron transmission channel, and accelerates electron transmission.

[0025] (3) The metal nanocluster modified ultrathin 2D g-C3N4 / ZnIn2S4 composite material disclosed in the application is a brand-new full solid Z-type heterojunction catalyst, which can maximize the retention of strong oxidation hole and reduction electron capacity in the semiconductor in the photocatalytic reaction, and significantly improves the light absorption efficiency and charge separation capacity.

[0026] (4) The metal nanocluster modified ultrathin 2D g-C3N4 / ZnIn2S4 heterojunction catalyst ZIS-M / UCN disclosed in the application has high catalytic activity as a photocatalytic hydrogen evolution reaction catalyst, and has a wide application prospect in the field of water splitting. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 A transmission electron microscope (TEM) image of a metal nanocluster modified ultrathin 2D Co / UCN prepared by the application;

[0028] Figure 2 A Co nanocluster particle size distribution graph of a metal nanocluster modified ultrathin 2D Co / UCN prepared by the application;

[0029] Figure 3 A transmission electron microscope (TEM) image of a metal nanocluster modified ultrathin 2D g-C3N4 / ZnIn2S4 heterojunction catalyst ZIS-Co / UCN prepared by the application;

[0030] Figure 4 An atomic force microscope (AFM) image of a metal nanocluster modified ultrathin 2D g-C3N4 / ZnIn2S4 heterojunction catalyst ZIS-Co / UCN prepared by the application;

[0031] Figure 5 A photocatalytic hydrogen evolution performance graph of a metal nanocluster modified ultrathin 2D g-C3N4 / ZnIn2S4 heterojunction catalyst ZIS-Co / UCN in a triethanolamine (TEOA) aqueous solution (20vol%) under visible light prepared by the application;

[0032] Figure 6 A photocatalytic stability test graph of a metal nanocluster modified ultrathin 2D g-C3N4 / ZnIn2S4 heterojunction catalyst ZIS-Co / UCN under a 420nm filter prepared by the application.

[0033] The application further investigates the influence of different transition metals on the photocatalytic performance of the metal nanocluster modified ultrathin 2D g-C3N4 / ZnIn2S4 heterojunction catalyst, taking ZIS-Fe / UCN; ZIS-Co / UCN; ZIS-Ni / UCN; ZIS-Pd / UCN; ZIS-Ag / UCN; ZIS-Pt / UCN; ZIS-Au / UCN as typical examples for further description. DETAILED DESCRIPTION

[0034] The application is described below through specific embodiments. Unless otherwise specified, the technical means used in the application are methods known to those skilled in the art. In addition, the embodiments should be understood as illustrative, rather than limiting the scope of the application, and the essence and scope of the application are limited only by the claims. For those skilled in the art, various changes or modifications to the composition and amount of the materials in these embodiments without departing from the essence and scope of the application also fall within the protection scope of the application. The technical solutions of the application are further described below in combination with specific examples.

[0035] Example 1

[0036] The preparation method of the metal nanocluster modified ultrathin 2D g-C3N4 / ZnIn2S4 heterojunction photocatalyst ZIS-Co / UCN includes the following steps:

[0037] 1) Put 30 g of urea into a covered crucible, heat at a temperature increasing rate of 2.3℃ / min under static air at 550℃ for 4 h, place the collected powder in an open crucible, and increase the temperature to 500℃ at a temperature increasing rate of 5℃ / min, further heat for 4 h, after cooling to room temperature, centrifugal wash with deionized water and ethanol for three times respectively, and place in a vacuum oven for drying overnight at 60℃, to obtain g-C3N4 nanosheets;

[0038] 2) Ultrasonically disperse 150 mg of g-C3N4 nanosheets in 30 mL of anhydrous ethanol under stirring to form a uniform suspension (solution 1), measure 1 mL of MPA and add to 10 mL of methanol, and use NaOH to adjust to pH=13 (solution 2), pour (solution 2) into the suspension (solution 1) under stirring, stir for 3 h, centrifugal wash with deionized water and ethanol for three times respectively, and place in a vacuum oven for drying overnight at 60℃, to obtain the required ultrathin g-C3N4 nanosheets, marked as UCN;

[0039] 3) 0.0808 g of Co(N03)2-6H20 was weighed into 50 mL of ultrapure water and stirred for 1 h (solution 3), 500 mg of ultra-thin g-C3N4 was weighed into 100 mL of ultrapure water and ultrasonically dispersed for 30 min (solution 4), (solution 3) was added to (solution 4) under stirring, ultrasonic dispersion was continued for 15 min, stirring was continued for 6 h, after stirring, rapid freezing was carried out with liquid nitrogen, freeze-drying treatment was carried out, the powder after freeze-drying was placed in a crucible and placed in a tube furnace, the temperature was raised to 150°C at a rate of 5°C / min under an argon atmosphere, the temperature was kept constant for 2 h, the powder was collected after cooling to room temperature, and was labeled as Co-UCN;

[0040] In the step 3), the freezing temperature was -50°C, and the drying time was 72 h;

[0041] Figure 1 The transmission electron microscope (TEM) image of the ultra-thin 2D g-C3N4 modified with Co nanoclusters (Co-UCN), Co nanoparticles are distributed on the ultra-thin 2D g-C3N4 in a decorative manner;

[0042] Figure 2 The particle size distribution diagram of the Co nanoclusters of the ultra-thin 2D g-C3N4 modified with Co nanoclusters (Co-UCN), analysis shows that the size of the Co nanoclusters is 1.5-2.4 nm, and the average size is 1.8 nm;

[0043] 4) Zn(CH3COO)2-2H20, InCl3, and TAA were weighed according to a molar ratio of 1:2:8 and dissolved in a mixed solution of 30 mL of ultrapure water and anhydrous ethanol (1:1), stirred for 30 min, transferred to a 100 mL polytetrafluoroethylene high-pressure reaction kettle, hydrothermally treated at 180°C for 24 h, cooled to room temperature, washed with deionized water and ethanol three times respectively, and placed in a vacuum oven at 60°C overnight to obtain the desired ultra-thin ZnIn2S4 nanosheet, labeled as ZIS;

[0044] 5) The prepared ZIS and M-UCN were mixed in anhydrous ethanol at a mass ratio of 2:1 and ultrasonically dispersed for 30 min to obtain a uniform suspension (1 mg / mL), stirred for 12 h, washed with anhydrous ethanol three times by centrifugation, and placed in a vacuum oven at 60°C overnight to obtain the desired ultra-thin 2D g-C3N4 / ZnIn2S4 composite material modified with Co nanoparticles, labeled as ZIS-Co / UCN;

[0045] Figure 3The transmission electron microscope (TEM) image of the Co-nanocluster-modified ultrathin 2D g-C3N4 / ZnIn2S4 composite material (ZIS-Co / UCN) shows that the flaky ZIS is uniformly anchored on the ultrathin g-C3N4 nanosheet and forms a clear heterojunction interface; it can be clearly seen that the interface is distributed with obvious ZIS lattice fringes and amorphous g-C3N4 on both sides, and through measurement, the ZIS lattice fringe spacing is 0.320 nm, which corresponds to the (102) crystal plane of the hexagonal ZIS, indicating that the ultrathin ZIS-Co / UCN composite material is successfully prepared.

[0046] Figure 4 The atomic force microscope (AFM) image of the Co-nanocluster-modified ultrathin 2D g-C3N4 / ZnIn2S4 heterojunction catalyst ZIS-Co / UCN shows that the ZIS-Co / UCN has an ultrathin atomic-level two-dimensional structure, and the sheet thickness is 1.5-2.0 nm.

[0047] The Co-nanocluster-modified ultrathin 2D g-C3N4 / ZnIn2S4 composite material (ZIS-Co / UCN) obtained in Example 1 was tested as a photocatalyst:

[0048] The photocatalytic activity evaluation system: 20 mg of the ZIS-Co / UCN photocatalyst obtained in Example 1 was ultrasonically dispersed in 60 mL of a triethanolamine (TEOA) aqueous solution (20 vol%), the light source was a 300 W xenon lamp, the carrier gas was argon, and the testing instrument was a CEL-SPH2N photocatalytic activity evaluation system, a GC7920-TA gas chromatograph, a THA3L air generator, and a LX-300 cooling water circulating machine.

[0049] Photocatalytic performance research:

[0050] Figure 5 The photocatalytic hydrogen production rate of the Co-nanocluster-modified ultrathin 2D g-C3N4 / ZnIn2S4 composite material (ZIS-Co / UCN) in a triethanolamine (TEOA) aqueous solution (20 vol%) is shown in the figure. The ZIS-Co / UCN composite material has good photocatalytic hydrogen evolution performance, and the photocatalytic hydrogen production rate under visible light is 15999.43 μmol·g -1 ·h -1 .

[0051] Figure 6The photocatalytic stability test of the Co nanocluster modified ultrathin 2D g-C3N4 / ZnIn2S4 composite material (ZIS-Co / UCN) under a 420 nm filter. As can be seen from the figure, the hydrogen evolution amount of the composite material ZIS-Co / UCN has no obvious attenuation trend within four cycles, proving that the composite material ZIS-Co / UCN has excellent photocatalytic hydrogen evolution activity and stability, and has potential practical application value.

[0052] Example 2

[0053] The preparation method of the metal nanocluster modified ultrathin 2D g-C3N4 / ZnIn2S4 composite material (ZIS-Fe / UCN) is the same as that of Example 1, except that:

[0054] 3) 0.1122g Fe(NO3)·9H2O was weighed into 50mL ultrapure water and stirred for 1h (solution 3), 500mg ultrathin g-C3N4 was weighed into 100mL ultrapure water and ultrasonically dispersed for 30min (solution 4), (solution 3) was added to (solution 4) under stirring, and ultrasonic dispersion was continued for 15min, stirring was continued for 6h, after stirring, rapid freezing with liquid nitrogen was performed, freeze-drying treatment was performed, the powder after freeze-drying was placed in a crucible, and the powder was collected after cooling to room temperature, and was labeled as Fe-UCN;

[0055] In the step 3), the freezing temperature is -50℃, and the drying time is 72h;

[0056] Steps (1), (2), (4) and (5) are the same as those of Example 1, and the obtained sample is labeled as ZIS-Fe / UCN.

[0057] Example 3

[0058] The preparation method of the metal nanocluster modified ultrathin 2D g-C3N4 / ZnIn2S4 composite material (ZIS-Ni / UCN) is the same as that of Example 1, except that:

[0059] 3) 0.0808 g Ni(NO3)2·6H2O was weighed into 50 mL ultrapure water and stirred for 1 h (solution 3), 500 mg of ultra-thin g-C3N4 was weighed into 100 mL ultrapure water and ultrasonically dispersed for 30 min (solution 4), (solution 3) was added to (solution 4) under stirring, ultrasonic dispersion was continued for 15 min, stirring was continued for 6 h, after stirring, rapid freezing was performed with liquid nitrogen, freeze-drying treatment was performed, the powder after freeze-drying was placed in a crucible, and was placed in a tube furnace, and was heated to 140°C at a heating rate of 5°C / min under an argon atmosphere, and was kept at 140°C for 2 h, and the powder was collected after cooling to room temperature, and was marked as Ni-UCN;

[0060] In the step 3), the freezing temperature was -50°C, and the drying time was 72 h;

[0061] Steps (1), (2), (4) and (5) were the same as in Example 1, and the obtained sample was marked as ZIS-Ni / UCN.

[0062] Example 4

[0063] A preparation method of a metal nanocluster modified ultra-thin 2D g-C3N4 / ZnIn2S4 composite material (ZIS-Pd / UCN) was the same as in Example 1, except that:

[0064] 3) 0.0290 g PdCl2 was weighed into 50 mL ultrapure water and stirred for 1 h under light shielding (solution 3), 500 mg of ultra-thin g-C3N4 was weighed into 100 mL ultrapure water and ultrasonically dispersed for 30 min (solution 4), (solution 3) was added to (solution 4) under stirring, ultrasonic dispersion was continued for 15 min, stirring was continued for 6 h under light shielding, after stirring, rapid freezing was performed with liquid nitrogen, freeze-drying treatment was performed, the powder after freeze-drying was placed in a crucible, and was placed in a tube furnace, and was heated to 500°C at a heating rate of 5°C / min under an argon atmosphere, and was kept at 500°C for 2 h, and the powder was collected after cooling to room temperature, and was marked as Pd-UCN;

[0065] In the step 3), the freezing temperature was -50°C, and the drying time was 72 h;

[0066] Steps (1), (2), (4) and (5) were the same as in Example 1, and the obtained sample was marked as ZIS-Pd / UCN.

[0067] Example 5

[0068] A preparation method of a metal nanoparticle modified ultra-thin 2D g-C3N4 / ZnIn2S4 composite material (ZIS-Ag / UCN) was the same as in Example 1, except that:

[0069] 3) 0.0236 g AgN03 was dissolved in 50 mL ultrapure water, stirred for 1 h under dark condition (solution 3), 500 mg ultrathin g-C3N4 was dissolved in 100 mL ultrapure water, ultrasonic dispersed for 30 min (solution 4), (solution 3) was added into (solution 4) under stirring, ultrasonic dispersed for 15 min, stirred for 6 h under dark condition, quickly frozen with liquid nitrogen after stirring, freeze-dried, the freeze-dried powder was placed in a crucible, put into a tube furnace, heated to 420 ℃ at a rate of 5 ℃ / min under argon atmosphere, kept for 2 h, the powder was collected after cooling to room temperature, marked as Ag-UCN;

[0070] In the step 3), the freezing temperature was -50 ℃, and the drying time was 72 h;

[0071] The steps (1), (2), (4) and (5) were the same as those in Example 1, and the obtained sample was marked as ZIS-Ag / UCN.

[0072] Example 6

[0073] The preparation method of the metal nanoparticle modified ultrathin 2D g-C3N4 / ZnIn2S4 composite material (ZIS-Pt / UCN) was the same as that in Example 1, except that:

[0074] 3) 2.847 mL H2PtCl6 solution (20 mg / mL) was measured and dissolved in 50 mL ultrapure water, stirred for 1 h under dark condition (solution 3), 500 mg ultrathin g-C3N4 was dissolved in 100 mL ultrapure water, ultrasonic dispersed for 30 min (solution 4), (solution 3) was added into (solution 4) under stirring, ultrasonic dispersed for 15 min, stirred for 6 h under dark condition, quickly frozen with liquid nitrogen after stirring, freeze-dried, the freeze-dried powder was placed in a crucible, put into a tube furnace, heated to 500 ℃ at a rate of 5 ℃ / min under argon atmosphere, kept for 2 h, the powder was collected after cooling to room temperature, marked as Pt-UCN;

[0075] In the step 3), the freezing temperature was -50 ℃, and the drying time was 72 h;

[0076] The steps (1), (2), (4) and (5) were the same as those in Example 1, and the obtained sample was marked as ZIS-Pt / UCN.

[0077] Example 7

[0078] The preparation method of the metal nanoparticle modified ultrathin 2D g-C3N4 / ZnIn2S4 composite material (ZIS-Pt / UCN) was the same as that in Example 1, except that:

[0079] 3) 47.21 mL of HAuCl4 solution (1 mg / mL) was measured and dissolved in 50 mL of ultrapure water, and stirred for 1 h under dark condition (solution 3), 500 mg of ultra-thin g-C3N4 was weighed in 100 mL of ultrapure water, and ultrasonic dispersed for 30 min (solution 4), (solution 3) was added to (solution 4) under stirring, and ultrasonic dispersed for 15 min, and stirred for 6 h under dark condition, and then quickly frozen with liquid nitrogen after stirring, and freeze-dried, and the powder after freeze-drying was placed in a crucible, and placed in a tube furnace, and heated to 400 ℃ at a heating rate of 5 ℃ / min under argon atmosphere, and kept for 2 h, and the powder was collected after cooling to room temperature, and marked as Au-UCN;

[0080] In the step 3), the freezing temperature is -50 ℃, and the drying time is 72 h;

[0081] The steps (1), (2), (4) and (5) are the same as those in Example 1, and the obtained sample is marked as ZIS-Au / UCN.

[0082] The application discloses the application prospect of metal nanocluster modified ultra-thin 2D g-C3N4 / ZnIn2S4 composite material (ZIS-M / UCN) in the field of photocatalytic hydrogen evolution:

[0083] The catalysts obtained in Examples 1-7 are subjected to photocatalytic performance test:

[0084] The photocatalytic activity evaluation system: 20 mg of the composite material (ZIS-M / UCN) is ultrasonic dispersed in 60 mL of a triethanolamine (TEOA) aqueous solution (20 vol%), the light source is a 300 W xenon lamp, the carrier gas is argon, the testing instrument is a CEL-SPH2N photocatalytic activity evaluation system, a GC7920-TA gas chromatograph, a THA3L air generator and a LX-300 cooling water circulating machine.

[0085] Comparative Example 1

[0086] This comparative example provides a preparation method of ultra-thin 2D g-C3N4 (UCN), and the steps are the same as those in steps (1) and (2) of Example 1; the obtained sample is marked as UCN.

[0087] Comparative Example 2

[0088] This comparative example provides a preparation method of ultra-thin 2D ZnIn2S4 (ZIS), and the steps are the same as those in step (4) of Example 1; the obtained sample is marked as ZIS.

[0089] Comparative Example 3

[0090] The comparative example provides a preparation method of an ultrathin 2D g-C3N4 / ZnIn2S4 composite material (ZIS-UCN), which has the same steps as those of Example 1, and the difference is that:

[0091] 5) The prepared ZIS and UCN are mixed in a mass ratio of 2:1, ultrasonically dispersed in anhydrous ethanol for 30 min to obtain a uniform suspension (1 mg / mL), stirred for 12 h, washed with anhydrous ethanol by centrifugation for three times, and placed in a vacuum oven at 60°C for drying overnight, thereby obtaining the required ultrathin 2D g-C3N4 / ZnIn2S4 composite material, which is marked as ZIS-UCN.

[0092] The catalysts obtained in Comparative Examples 1-3 are subjected to photocatalytic performance testing, and the photocatalytic performance is compared with that of Examples 1-7:

[0093] The photocatalytic activity evaluation system: 20 mg of the ultrasonically dispersed catalysts in Comparative Examples 1-3 are placed in 60 mL of a triethanolamine (TEOA) aqueous solution (20 vol%), the light source is a 300W xenon lamp, the carrier gas is argon, the testing instrument is a CEL-SPH2N photocatalytic activity evaluation system, a GC7920-TA gas chromatograph, a THA3L air generator, and a LX-300 cooling water circulating machine.

[0094] The prepared composite material is subjected to photocatalytic performance research:

[0095] Table 1 is a comparison of the photocatalytic hydrogen evolution rates of ZIS-Co / UCN (Example 1), ZIS-Fe / UCN (Example 2), ZIS-Ni / UCN (Example 3), ZIS-Pd / UCN (Example 4), ZIS-Ag / UCN (Example 5), ZIS-Pt / UCN (Example 6), ZIS-Au / UCN (Example 7), UCN (Comparative Example 1), ZIS (Comparative Example 2), and ZIS-UCN (Comparative Example 3) under visible light:

[0096] Table 1 is a comparison of the photocatalytic hydrogen evolution rates of ZIS-Co / UCN (Example 1), ZIS-Fe / UCN (Example 2), ZIS-Ni / UCN (Example 3), ZIS-Pd / UCN (Example 4), ZIS-Ag / UCN (Example 5), ZIS-Pt / UCN (Example 6), ZIS-Au / UCN (Example 7), UCN (Comparative Example 1), ZIS (Comparative Example 2), and ZIS-UCN (Comparative Example 3) under visible light:

[0097]

[0098] The above results show that the metal nanocluster modified ultrathin 2D g-C3N4 / ZnIn2S4 heterojunction catalyst prepared in the present application exhibits excellent hydrogen production activity, and is significantly better than UCN, ZIS, and ZIN-UCN comparative examples.

Claims

1. A method for preparing a metal-nanocluster-modified ultrathin 2D g-C 3 N 4 / ZnIn 2 S 4 all-solid-state Z-type heterojunction photocatalyst, characterized in that, Preparation according to the following steps: 1) Put 30 g of urea into a covered crucible, heat at a static air temperature of 550℃ for 4 h at a heating rate of 2.3℃ / min, place the collected powder into an open crucible, and heat at a heating rate of 5℃ / min to 500℃ for 4 h, after cooling to room temperature, centrifugal washing with deionized water and ethanol for three times respectively, and drying in a vacuum oven at 60℃ overnight to obtain g-C3N4 nanosheets; 2) Ultrasonic dispersion of 150 mg of g-C3N4 nanosheets in 30 mL of anhydrous ethanol under stirring to form a uniform suspension as solution 1, measure 1 mL of MPA and add to 10 mL of methanol, and use NaOH to adjust to PH = 13 to obtain solution 2, pour solution 2 into solution 1 under stirring for 3 h, centrifugal washing with deionized water and ethanol for three times respectively, and drying in a vacuum oven at 60℃ overnight to obtain the required ultrathin g-C3N4 nanosheets, marked as UCN; 3) Weigh a certain amount of metal salt and dissolve in 50 mL of ultrapure water under different conditions to obtain solution 3, the metal is Pd, Ag, Pt, Au, Fe, Co or Ni, weigh 500 mg of ultrathin g-C3N4 and place in 100 mL of ultrapure water, ultrasonic dispersion for 30 min to obtain solution 4, add solution 3 to solution 4 under stirring, continue ultrasonic dispersion for 15 min, stirring for 6 h under different conditions, after stirring, rapid freezing with liquid nitrogen, freeze-drying treatment, place the freeze-dried powder in a crucible and put it into a tube furnace, heat to a certain temperature at a heating rate of 5℃ / min under argon atmosphere, keep constant temperature for 2 h, after cooling to room temperature, collect the powder, marked as M-UCN; 4) Weigh Zn(CH3COO)2·2H2O, InCl3, TAA according to the molar ratio of 1:2:8 and dissolve in 30 mL of a 1:1 mixed solution of ultrapure water and anhydrous ethanol, stir for 30 min, transfer to a 100 mL polytetrafluoroethylene high-pressure reaction kettle, hydrothermal at 180℃ for 24 h, after cooling to room temperature, wash with deionized water and ethanol for three times respectively, and dry in a vacuum oven at 60℃ overnight to obtain the required ultrathin ZnIn2S4 nanosheets, marked as ZIS; 5) Mix the prepared ZIS and M-UCN in anhydrous ethanol at a mass ratio of 2:1 and ultrasonic dispersion for 30 min to obtain a uniform suspension of 1 mg / mL, stir for 12 h, centrifugal washing with anhydrous ethanol for three times, and dry in a vacuum oven at 60℃ overnight to obtain the required metal nanocluster decorated ultrathin 2D g-C3N4 / ZnIn2S4 full solid Z-type heterojunction photocatalyst, marked as ZIS-M / UCN; the metal nanoclusters are distributed in the interlayer of ultrathin 2D g-C3N4 and ZnIn2S4; the average thickness of the full solid Z-type heterojunction photocatalyst is 1.5-2.0 nm.

2. The method of claim 1, wherein: In the step 3), the noble metals Pd, Ag, Pt, Au need to be dissolved and stirred in the dark, and the transition metals Fe, Co, Ni do not need to be dissolved in the dark.

3. The method of claim 1, wherein: In the step 3), the freezing temperature is -50℃, and the drying time is 72h.

4. The method of claim 1, wherein: In the step 3), the room temperature is 20-25℃, the temperature is raised from room temperature to a certain temperature of 130-400℃, and the temperature raising rate is 5℃ / min.

5. Application of the metal nanocluster modified ultrathin 2D g-C3N4 / ZnIn2S4 full solid Z-type heterojunction photocatalyst prepared by the preparation method of any one of claims 1-4 in a water splitting reaction.

6. Use according to claim 5, characterized in that: 20mg photocatalyst is ultrasonically dispersed in 60mL 20vol% triethanolamine aqueous solution, the light source is a 300W xenon lamp, and the carrier gas is argon.

7. Use according to claim 5, characterized in that: The metal nanocluster modified ultrathin 2D g-C3N4 / ZnIn2S4 full solid Z-type heterojunction photocatalyst has a hydrogen production rate superior to that of pure g-C3N4, pure ZnIn2S4 and g-C3N4 / ZnIn2S4 composite under visible light.

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