A ZnIn2S4-MOF heterojunction photocatalyst, its preparation method and application

Abstract

This invention discloses a ZnIn2S4-MOF homojunction photocatalyst, its preparation method, and its applications. The process of this invention is simple, low-cost, and environmentally friendly. The prepared ZnIn2S4-MOF homojunction photocatalyst not only exhibits high stability but also demonstrates excellent photocatalytic hydrogen production performance, showing broad application prospects in the field of photocatalysis.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of photocatalysis, in particular to a ZnIn2S4-MOF heterojunction photocatalyst and a preparation method and application thereof. BACKGROUND

[0002] As a non-renewable energy source, the large use of petrochemical fuels has brought problems such as air pollution and energy shortage. Developing a green new energy source that is pollution-free, renewable, low-cost and widely available is a great challenge facing the world today. H2 combustion only produces water, which is an excellent clean energy. The water production technology by photolysis can obtain energy from solar energy, which is a clean, pollution-free, low-cost and inexhaustible natural energy. Therefore, replacing petrochemical energy with hydrogen energy as the global energy foundation is a way to effectively solve the current energy crisis and environmental problems.

[0003] Zinc indium sulfide (ZnIn2S4) is a ternary sulfide with good visible light absorption, chemical stability and photoelectric performance, and is a new type of photocatalytic water splitting material with good development prospects. However, the low specific surface area and high carrier recombination rate of ZnIn2S4 limit its industrial application. Therefore, modification of ZnIn2S4 is an important means to improve its photocatalytic activity.

[0004] As disclosed in the patent with the application publication number CN 115709079 A, a Mo-modified zinc indium sulfide photocatalyst is prepared by doping Mo into the zinc indium sulfide lattice to generate a unit cell dipole. The unit cell dipole is positively superimposed to form an internal electric field by taking advantage of the periodic arrangement of the unit cell, thereby reducing the carrier recombination rate and inhibiting the probability of oxidation of sulfur ions, so as to improve the hydrogen production activity and catalytic life of the catalyst. However, the photocatalyst has a high cost and is not suitable for industrial production.

[0005] As disclosed in the patent with the application publication number CN 113209990 A, a willow catkin-shaped copper-doped zinc indium sulfide photocatalyst is prepared. First, zinc acetate is added to a mixed solvent of dimethylformamide and ethylene glycol, and stirred at room temperature to form a uniform transparent solution. Then, copper nitrate, indium trichloride tetrahydrate and thioacetamide are sequentially added and stirred, and the mixture is reacted at 180℃ for 24h. After washing and drying, a copper-doped zinc indium sulfide sample powder is obtained. Compared with pure zinc indium sulfide, the copper-doped zinc indium sulfide has enhanced hydrophilicity, improved dispersibility, and a larger specific surface area. The catalyst has a simple preparation operation and a low cost, but its photocatalytic hydrogen production performance is poor and the hydrogen production rate is not high. SUMMARY

[0006] To solve the above problems, the present application provides a ZnIn2S4-MOF heterojunction photocatalyst, which not only has high stability, but also exhibits excellent photocatalytic hydrogen production performance.

[0007] The technical scheme for solving the above problems of the present application is as follows:

[0008] A preparation method of a ZnIn2S4-MOF heterojunction photocatalyst, comprising the following steps:

[0009] S1, 1, 4-benzenedicarboxylic acid, and an indium-containing compound are sequentially added into DMF, stirred and uniformly dispersed, and ultrasonically dispersed to obtain a reaction dispersion liquid;

[0010] S2, the reaction dispersion liquid is reacted for 3.5-4.5 hours, and cooled to room temperature to obtain an In-MIL-68 initial product, which is washed and dried to obtain In-MIL-68;

[0011] S3, after the zinc-containing compound is added into water and stirred until dissolved, a sulfur-containing compound is added and stirred until completely dispersed, and reacted for 1.5-2.5 hours, and then washed and dried to obtain ZnIn M S4.

[0012] Preferably, the indium-containing compound is selected from one or more of indium chloride, indium nitrate, indium acetate, and indium sulfate.

[0013] Preferably, the zinc-containing compound is selected from one or more of zinc nitrate, zinc chloride, zinc acetate, zinc carbonate, and zinc sulfate.

[0014] Preferably, the sulfur-containing compound is selected from one or more of sulfur powder, thiourea, thioacetamide, and ammonium sulfide.

[0015] Preferably, the molar ratio of indium: zinc: sulfur in the indium-containing compound, the zinc-containing compound, and the sulfur-containing compound is (0.5-1.2) : (1.5-3) : (4-5.5).

[0016] Preferably, the washing in steps S2 and S3 refers to washing with deionized water and ethanol.

[0017] Preferably, the drying in steps S2 and S3 refers to drying at 40-80℃ for 6-10 hours.

[0018] Preferably, the reaction temperature of the reaction dispersion liquid in step S2 is 90-110℃, and the reaction temperature in step S3 is 70-90℃.

[0019] Another object of the present application is to provide a ZnIn2S4-MOF heterojunction photocatalyst prepared by the above preparation method.

[0020] Another object of the present application is to provide an application of the above ZnIn2S4-MOF heterojunction photocatalyst in photocatalytic hydrogen production.

[0021] Metal organic frameworks (MOFs) have the advantages of super-high specific surface area, low crystal density, adjustable pore size and functional structure, and can be applied to the field of photocatalysis. Among them, In-MIL-68 is a MOFs material with super-high specific surface area, low cost and easy preparation. ZnIn2S4 is a classic ternary sulfide with the advantages of suitable band edge position, narrow band gap, low toxicity and low cost, and is a photocatalytic material with great application prospect. However, ZnIn2S4 also has the defects of limited light response range, low specific surface area and easy recombination of photo-generated carriers, which greatly limits its industrial application. Therefore, the application synthesizes ZnIn2S4-MOF heterojunction photocatalyst (named as ZnIn M S4) by taking In-MIL-68 as a template and an indium source, and the catalyst can be used for photocatalytic decomposition of water to produce hydrogen by solar energy.

[0022] The application has the following beneficial effects:

[0023] 1. The ZnIn2S4-MOF heterojunction photocatalyst synthesized by the in-situ synthesis method of the application can overcome the problem of charge transfer at the heterojunction interface, accelerate the charge transfer, and improve the photocatalytic performance.

[0024] 2. The ZnIn2S4-MOF heterojunction photocatalyst prepared by the application has large specific surface area and high stability, and exhibits excellent visible light catalytic water decomposition hydrogen production performance.

[0025] 3. The preparation process of the application is simple, does not contain noble metal, is low in price, and is conducive to industrial production. DETAILED DESCRIPTION

[0026] Figure 1 XRD patterns of Examples 1-4 and Comparative Examples 1-2;

[0027] Figure 2 SEM patterns of Comparative Example 1, Comparative Example 2 and Example 2;

[0028] Figure 3 TEM pattern of Example 2;

[0029] Figure 4 XPS pattern of Example 2;

[0030] Figure 5 Transient photocurrent patterns of Example 2 and Comparative Example 2;

[0031] Figure 6 Hydrogen production rate patterns of Examples 1-4 and Comparative Example 2;

[0032] Figure 7 Stability test pattern of Example 2. DETAILED DESCRIPTION

[0033] The specific embodiments are only intended for explaining the present application, and are not intended to limit the present application. Any change made by those skilled in the art after reading the specification of the present application will be protected by the patent law as long as it is within the scope of the claims.

[0034] Example 1

[0035] The 120 mg of 1,4-benzenedicarboxylic acid and 312 mg of indium nitrate tetrahydrate were sequentially added into 40 ml of DMF, and the obtained reaction mixture was stirred and ultrasonically dispersed to obtain a reaction dispersion. The reaction dispersion was transferred into a 50 ml hydrothermal reaction kettle, and then reacted in a 100°C oven for 4 h. After the reaction was completed, the reaction mixture was cooled to room temperature to obtain an In-MIL-68 initial product. The In-MIL-68 initial product was washed with deionized water and ethanol three times by a vacuum filtration pump, and then dried in a 60°C vacuum drying oven for 8 h to obtain the In-MIL-68.

[0036] Into a conical flask containing 60 ml of water with a pH of 2.5, 272 mg of ZnCl2 was added and stirred until completely dissolved. Then, 168 mg of In-MIL-68 was added and stirred until completely dispersed. Then, 300 mg of thioacetamide was added and stirred until completely dispersed. The obtained reaction dispersion was placed in an 80°C oil bath, and reacted for 2 h to obtain a light yellow product. The product was washed with deionized water and ethanol three times by a vacuum filtration pump, and then dried in a 60°C vacuum drying oven for 8 h to obtain ZnIn M S4-1.

[0037] Example 2

[0038] The 120 mg of 1,4-benzenedicarboxylic acid and 312 mg of indium nitrate tetrahydrate were sequentially added into 40 ml of DMF, and the obtained reaction mixture was stirred and ultrasonically dispersed to obtain a reaction dispersion. The reaction dispersion was transferred into a 50 ml hydrothermal reaction kettle, and then reacted in a 100°C oven for 4 h. After the reaction was completed, the reaction mixture was cooled to room temperature to obtain an In-MIL-68 initial product. The In-MIL-68 initial product was washed with deionized water and ethanol three times by a vacuum filtration pump, and then dried in a 60°C vacuum drying oven for 8 h to obtain the In-MIL-68.

[0039] Into a flask containing 60 ml of water with pH of 2.5, 272 mg of ZnCl2 was added, stirred until completely dissolved, 252 mg of In-MIL-68 was added, stirred until completely dispersed, then 300 mg of thioacetamide was added, the obtained reaction dispersion was placed in an oil bath at 80°C, reacted for 2 hours, a light yellow product was obtained, which was washed with deionized water, ethanol three times by vacuum filtration pump, and dried in a vacuum drying oven at 60°C for 8h to obtain ZnIn M S4-2.

[0040] Example 3

[0041] Into a flask containing 60 ml of water with pH of 2.5, 272 mg of ZnCl2 was added, stirred until completely dissolved, 252 mg of In-MIL-68 was added, stirred until completely dispersed, then 300 mg of thioacetamide was added, the obtained reaction dispersion was placed in an oil bath at 80°C, reacted for 2 hours, a light yellow product was obtained, which was washed with deionized water, ethanol three times by vacuum filtration pump, and dried in a vacuum drying oven at 60°C for 8h to obtain ZnIn

[0042] Into a flask containing 60 ml of water with pH of 2.5, 272 mg of ZnCl2 was added, stirred until completely dissolved, 252 mg of In-MIL-68 was added, stirred until completely dispersed, then 300 mg of thioacetamide was added, the obtained reaction dispersion was placed in an oil bath at 80°C, reacted for 2 hours, a light yellow product was obtained, which was washed with deionized water, ethanol three times by vacuum filtration pump, and dried in a vacuum drying oven at 60°C for 8h to obtain ZnIn M S4-3.

[0043] Example 4

[0044] Into a flask containing 60 ml of water with pH of 2.5, 272 mg of ZnCl2 was added, stirred until completely dissolved, 252 mg of In-MIL-68 was added, stirred until completely dispersed, then 300 mg of thioacetamide was added, the obtained reaction dispersion was placed in an oil bath at 80°C, reacted for 2 hours, a light yellow product was obtained, which was washed with deionized water, ethanol three times by vacuum filtration pump, and dried in a vacuum drying oven at 60°C for 8h to obtain ZnIn

[0045] Into a flask containing 60 ml of water with pH of 2.5, 272 mg of ZnCl2was added, stirred until completely dissolved, 502 mg of In-MIL-68 was added, stirred until completely dispersed, then 300 mg of thioacetamide was added, stirred until completely dispersed, the obtained reaction dispersion was placed in an oil bath at 80°C, reacted for 2 hours, a light yellow product was obtained, which was washed with deionized water, ethanol and deionized water by vacuum filtration pump for three times respectively, and dried in a vacuum drying oven at 60°C for 8h to obtain ZnIn M S4-5.

[0046] Comparative Example 1

[0047] Into a flask containing 40 ml of DMF, 120 mg of 1,4-benzenedicarboxylic acid and 312 mg of indium nitrate tetrahydrate were sequentially added, the obtained reaction mixture was stirred and ultrasonically dispersed to obtain a reaction dispersion. The reaction dispersion was transferred to a 50 ml hydrothermal reactor, and then reacted in a 100°C oven for 4h. After the reaction was completed, it was cooled to room temperature to obtain an In-MIL-68 initial product. The In-MIL-68 initial product was washed with deionized water, ethanol and deionized water by vacuum filtration pump for three times respectively, and dried in a vacuum drying oven at 60°C for 8h to obtain In-MIL-68 (In MOF ).

[0048] Comparative Example 2

[0049] Into a flask containing 60 ml of water with pH of 2.5, 272 mg of ZnCl2was added, stirred until completely dissolved, 442 mg of InCl3was added, stirred until completely dispersed, then 300 mg of thioacetamide was added, stirred until completely dispersed, the obtained reaction dispersion was placed in an oil bath at 80°C, reacted for 2 hours, a light yellow product was obtained, which was washed with deionized water, ethanol and deionized water by vacuum filtration pump for three times respectively, and dried in a vacuum drying oven at 60°C for 8h to obtain ZnIn2S4.

[0050] The performance of the photocatalysts of Examples 1-4 and Comparative Examples 1-2 was tested by hydrogen production reaction through water decomposition in an online photocatalytic H2system. 50 mg of ZnIn M S4-1, ZnIn M S4-2, ZnIn M S4-3, ZnIn MS4-5, In-MIL-68, ZnIn2S4 was dispersed in 100 ml distilled water containing 10 ml triethanolamine, and a 300 w xenon lamp (λ>420 nm) was used as a visible light source. The air dispersed in the water was removed before the reaction, and the reaction was continuously stirred during the reaction, and the cooling water was circulated to maintain the reaction temperature at 12℃. GC7900 online gas chromatography (N2 carrier, 5A molecular sieve column, TCD detector) was used to detect the gaseous product H2, and the hydrogen production rate was as follows.

[0051] Table 1: Hydrogen production rate table of examples 1-4 and comparative examples 1-2

[0052]

[0053]

[0054] According to table 1, the hydrogen production rate of comparative example 1 (In-MIL-68) under light irradiation is 0, and the hydrogen production rate of comparative example 2 (ZnIn2S4) is also lower than that of examples 1-4, which shows that the composite structure ZnIn M S4 has a greater improvement in photocatalytic hydrogen production activity than In-MIL-68 and pure ZnIn2S4;

[0055] According to table 1, the hydrogen production rate of example 2 (ZnIn M S4-2) is the best, reaching 70 μmol·h -1 -1, which is 3.2 times that of pure ZnIn2S4;

[0056] According to examples 1-4, comparative examples 1-2, table 1 and Figure 6 It can also be seen that with the increase of In-MIL-68 addition amount, the hydrogen production rate of examples 1-4 first increases and then decreases, because pure In-MIL-68 cannot catalyze water photolysis to produce hydrogen, and too much In-MIL-68 covers the visible light absorption of ZnIn2S4, thereby affecting the performance of the catalyst;

[0057] According to Figure 1 It can be seen that examples 1 (ZnIn M S4-1), example 2 (ZnIn M S4-2), example 3 (ZnIn M S4-3), example 4 (ZnIn M S4-5) all have ZnIn2S4 characteristic peaks and In-MOF characteristic peaks, according to Figure 2 and Figure 3 It can be seen that the sheet-like ZnIn2S4 structure with rod-like MOF structure as substrate, according to Figure 4It can be seen that, in addition to the traditional Zn-In-S chemical bond, there is also a Zn-O chemical bond that is conducive to charge transfer, and the above conclusions all show that ZnIn M S4 is successfully prepared;

[0058] According to Figure 5 It can be seen that the photocurrent of example 2 (ZnIn M S4-2) is much higher than that of comparative example 2 (ZnIn2S4), which shows that example 2 (ZnIn M S4-2) has higher photocatalytic activity;

[0059] According to Figure 7 It can be seen that the photocurrent of example 2 (ZnIn M S4-2) still has higher photocatalytic activity at 16h, which shows that it has good stability.

[0060] The process is simple, low in cost and green and environmentally friendly, the prepared ZnIn2S4-MOF heterojunction photocatalyst not only has higher stability, but also shows excellent photocatalytic hydrogen production performance.

Claims

1. A method for preparing a ZnIn2S4-MOF heterojunction photocatalyst, characterized in that, The method comprises the following steps: S1, 1,4-benzenedicarboxylic acid, indium-containing compound is added to DMF in turn, stirred uniformly and ultrasonically dispersed to obtain a reaction dispersion liquid; S2, the reaction dispersion liquid is reacted for 3.5-4.5 h, cooled to room temperature to obtain an In-MIL-68 initial product, which is washed and dried to obtain In-MIL-68; S3, after stirring to dissolve the zinc-containing compound in water, the sulfur-containing compound is added and stirred until completely dispersed, and then reacted for 1.5-2.5 h, washed and dried to obtain ZnIn M S4.

2. The method for preparing a ZnIn2S4-MOF heterojunction photocatalyst according to claim 1, characterized in that, The indium-containing compound is selected from one or more of indium chloride, indium nitrate, indium acetate and indium sulfate.

3. The method according to claim 1, wherein the method comprises the following steps: 1) preparing ZnIn2S4 quantum dots; 2) preparing MOF; 3) mixing ZnIn2S4 quantum dots and MOF to obtain ZnIn2S4-MOF heterojunction photocatalyst. The zinc-containing compound is selected from one or more of zinc nitrate, zinc chloride, zinc acetate, zinc carbonate and zinc sulfate.

4. The method according to claim 1, wherein the method comprises the following steps: 1) preparing ZnIn2S4 quantum dots; 2) preparing MOF; 3) mixing ZnIn2S4 quantum dots and MOF to obtain ZnIn2S4-MOF heterojunction photocatalyst. The sulfur-containing compound is selected from one or more of sulfur powder, thiourea, thioacetamide and ammonium sulfide.

5. The method according to claim 1, wherein the method comprises the following steps: 1) preparing ZnIn2S4 quantum dots; 2) preparing MOF; 3) mixing ZnIn2S4 quantum dots and MOF to obtain ZnIn2S4-MOF heterojunction photocatalyst. The molar ratio of indium: zinc: sulfur in the indium-containing compound, the zinc-containing compound and the sulfur-containing compound is (0.5-1.2):(1.5-3):(4-5.5).

6. The method for preparing a ZnIn2S4-MOF heterojunction photocatalyst according to claim 1, characterized in that, The washing in the steps S2 and S3 refers to washing with deionized water or ethanol.

7. The method according to claim 1, wherein the method comprises the following steps: 1) preparing ZnIn2S4 quantum dots; 2) preparing MOF; 3) mixing ZnIn2S4 quantum dots and MOF to obtain ZnIn2S4-MOF heterojunction photocatalyst. The drying in the steps S2 and S3 refers to drying at 40-80℃ for 6-10h. 8.The method for preparing a ZnIn 2S 4-MOF heterojunction photocatalyst according to claim 1, characterized in that, The reaction temperature of the reaction dispersion liquid in the step S2 is 90-110℃, and the reaction temperature in the step S3 is 70-90℃.

9. The ZnIn2S4-MOF heterojunction photocatalyst prepared by the preparation method in any one of claims 1-8.

10. The application of the ZnIn2S4-MOF heterojunction photocatalyst in claim 9 in photocatalytic hydrogen production.

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