ZnO (at) ZnS (at) CuS ternary nano composite material as well as preparation method and application thereof

Abstract

The invention discloses a ZnO (at) ZnS (at) CuS ternary nano composite material as well as a preparation method and application thereof. The ZnO (at) ZnS (at) CuS ternary nano composite material comprises ZnO, a ZnS layer and CuS nano particles, wherein the ZnS layer grows on the ZnO in situ through vulcanization reaction, and the CuS nano particles grow on the ZnS layer in situ. The preparation method of the ZnO (at) ZnS (at) CuS ternary nano composite material comprises the following steps: (1) ultrasonically dispersing ZnO in water, after uniformly dispersing, adding thioacetamide for reaction, and after reaction, centrifuging, washing and drying to obtain ZnO (at) ZnS; and (2) mixing ZnO (at) ZnS, copper nitrate and thiourea, reacting, centrifuging, washing and drying to obtain the ZnO (at) ZnS (at) CuS ternary nano composite material. When the composite material is used as a photocatalyst in the aspect of hydrogen production by photocatalytic water splitting, the composite material has high hydrogen production capacity and good cycle stability.

Description

Technical Field

[0001] The invention relates to a ZnO@ZnS@CuS ternary nanocomposite material, and also relates to a preparation method of the composite material and application of the composite material as a photocatalyst in photocatalytic decomposition of water to produce hydrogen. Background Art

[0002] In the past few decades, hydrogen energy has been considered as the best candidate energy to replace traditional fossil fuels such as coal, oil and natural gas due to its sustainability and good cleanliness. Therefore, many hydrogen production technologies have emerged. Among them, photocatalytic water decomposition to produce H 2 The reaction has the advantages of low cost, environmental friendliness, and simple experimental equipment. 2 Existing photocatalysts have problems such as easy recombination of photogenerated carriers and holes, narrow utilization range of visible light by some materials, and easy corrosion, which lead to poor catalytic activity of photocatalytic water splitting to produce hydrogen. Therefore, solving the above problems is of great significance to the development of photocatalytic water splitting to produce hydrogen technology. Summary of the invention

[0003] Purpose of the invention: The purpose of the present invention is to provide a ZnO@ZnS@CuS ternary nanocomposite material, which, when used as a photocatalyst in the photocatalytic decomposition of water to produce hydrogen, has a high hydrogen production capacity and good cycle stability; another purpose of the present invention is to provide a method for preparing the above-mentioned composite material and its use as a photocatalyst in the photocatalytic decomposition of water to produce hydrogen.

[0004] Technical solution: The ZnO@ZnS@CuS ternary nanocomposite material of the present invention comprises ZnO, ZnS formed on the outer surface of ZnO by a sulfurization reaction, and CuS nanoparticles grown in situ on ZnS.

[0005] Wherein, the particle size of ZnO particles is about 250nm.

[0006] The thickness of the ZnS shell formed by sulfurization is about 40nm. If the sulfurization time is too long, ZnO will be completely sulfurized into ZnS and lose the core-shell structure.

[0007] Wherein, the loading amount of the CuS nanoparticles is about 2 wt.% (relative to the mass of the composite material).

[0008] The preparation method of the above ZnO@ZnS@CuS ternary nanocomposite material comprises the following steps:

[0009] (1) Ultrasonic dispersion of ZnO in water, after uniform dispersion, adding thioacetamide (TAA) thereto for hydrothermal reaction, centrifuging, washing, and drying to obtain ZnO@ZnS;

[0010] (2) ZnO@ZnS, copper nitrate and thiourea (TU) are mixed, subjected to a hydrothermal reaction, centrifuged, washed and dried to obtain a ZnO@ZnS@CuS ternary nanocomposite material.

[0011] Wherein, in step (1), the mass ratio of ZnO to thioacetamide is 1:1-2.

[0012] Wherein, in step (1), the reaction temperature is 180-200° C. and the reaction time is 1-2 h.

[0013] Wherein, in step (2), the mass ratio of ZnO@ZnS, copper nitrate and thiourea is 50:1-2:4-8.

[0014] Wherein, in step (2), the reaction temperature is 160-180° C. and the reaction time is 24-48 h.

[0015] The above-mentioned ZnO@ZnS@CuS ternary nanocomposite material is used as a photocatalyst in the photocatalytic decomposition of water to produce hydrogen.

[0016] ZnS is a semiconductor with a high reduction potential, and ZnS and ZnO also have the same metal elements, which is conducive to the in-situ growth of ZnS on ZnO. In addition, ZnS and ZnO have similar crystal structures, which reduces the lattice mismatch problem between them and is conducive to the rapid transmission of charge carriers. At the same time, the narrow band gap characteristics of CuS (p-type semiconductor) are used to expand the visible light absorption spectrum of ZnO-based photocatalysts and construct np heterojunctions, which can effectively promote charge separation and thus enhance the photocatalytic hydrogen production activity. At the same time, the S vacancies in CuS and the SO between ZnO and ZnS can act as fast migration channels for photogenerated carriers, thereby greatly improving the hydrogen production rate.

[0017] Beneficial effects: Compared with the prior art, the present invention has the following significant effects: when the composite material of the present invention is used as a photocatalyst in the photocatalytic decomposition of water to produce hydrogen, it has high hydrogen production capacity and good cycle stability; ZnS and CuS can promote the rapid generation and rapid migration of photogenerated carriers under light excitation, inhibit the generation of electron-hole pairs, and promote the electron to H + The transfer of hydrogen can achieve a considerable hydrogen yield, and the hydrogen production rate can reach 15.70 μmol·mg -1 ·h -1 . BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a scanning electron microscope image of the ZnO@ZnS@CuS ternary nanocomposite prepared in Example 1;

[0019] Figure 2This is a scanning electron microscope image of the ZnO@ZnS@CuS ternary nanocomposite prepared in Example 2;

[0020] Figure 3 This is a scanning electron microscope image of the ZnO@ZnS@CuS ternary nanocomposite prepared in Example 3;

[0021] Figure 4 This is a diagram showing the hydrogen production effect of the ZnO@ZnS@CuS ternary nanocomposite material prepared in Example 1;

[0022] Figure 5 This is a cyclic stability diagram of the ZnO@ZnS@CuS ternary nanocomposite prepared in Example 1;

[0023] Figure 6 This is a hydrogen production effect diagram of ZnO@CuS@ZnS prepared in Comparative Example 1;

[0024] Figure 7 This is the cyclic stability diagram of the ZnO@CuS@ZnS ternary nanocomposite material prepared in Comparative Example 1. DETAILED DESCRIPTION

[0025] Example 1

[0026] The preparation method of the ZnO@ZnS@CuS ternary nanocomposite material of the present invention comprises the following steps:

[0027] (1) 0.25 g ZnO powder was added to 30 mL distilled water, ultrasonicated for 10 min, and then 0.25 g TAA was added thereto. After stirring for 10 min, the mixture was hydrothermally reacted at 180 °C for 1 h. After the reaction, the mixture was naturally cooled to room temperature, centrifuged, washed three times with distilled water and ethanol, and dried in vacuum to obtain ZnO@ZnS.

[0028] (2) The above 0.25 g ZnO@ZnS particles, 5 mg copper nitrate and 20 mg TU were added to 40 mL distilled water, stirred for 10 min, and then hydrothermally reacted at 160 °C for 24 h. After the reaction, it was naturally cooled to room temperature, centrifuged, washed three times with distilled water and ethanol respectively, and vacuum dried to obtain a ZnO@ZnS@CuS ternary nanocomposite material.

[0029] The ZnO@ZnS@CuS ternary nanocomposite material prepared in Example 1 has a core-shell structure, wherein ZnO is the core, ZnS is the shell, and CuS particles are loaded in the outermost layer. Figure 1 It can be clearly seen that in Example 1, small CuS particles are attached to the surface of ZnO@ZnS.

[0030] The ZnO@ZnS@CuS ternary nanocomposite material prepared in Example 1 produces hydrogen by photocatalytic hydrolysis under visible light, specifically:

[0031] 50 mg of the ZnO@ZnS@CuS ternary nanocomposite material of Example 1 was added to 50 mL of 0.25 M Na 2 SO 3 +0.35M Na 2 The aqueous solution of S was balanced in a dark environment for 30 minutes. A 300W xenon lamp was used as the light source. The photocatalytic hydrogen production reaction was carried out at 6°C. Samples were taken every 1 hour and the concentration of the product was measured using gas chromatography. The results are as follows: Figure 4 shown. Figure 4 The left figure shows that the hydrogen production rate of the catalyst under full spectrum conditions is 15.70 μmol·mg -1 ·h -1 , under the condition of λ>420nm, the hydrogen production rate is 2.34μmol·mg -1 ·h -1 . Figure 4 The right figure shows that when the sacrificial agent is Na 2 SO 3 / Na 2 S, the catalyst has the best hydrogen production effect.

[0032] Figure 4 This is the hydrogen production effect diagram of Example 1. Under visible light conditions, the sacrificial agent is 0.25M Na 2 SO 3 +0.35MNa 2 S, ZnO@ZnS@CuS has a hydrogen production capacity of 15.70 μmol·mg -1 ·h -1 .

[0033] The cyclic stability test results of Example 1 are shown in Figure 5 After 4 cycles (20 h), the catalyst produced hydrogen at a rate of 12.78 μmol·mg -1 ·h -1 , indicating that it has a certain stability.

[0034] Example 2

[0035] The preparation method of the ZnO@ZnS@CuS ternary nanocomposite material of the present invention comprises the following steps:

[0036] (1) 0.25 g ZnO powder was added to 30 mL distilled water, ultrasonicated for 10 min, and then 0.375 g TAA was added thereto. After stirring for 10 min, the mixture was hydrothermally reacted at 190 °C for 1.5 h. After the reaction, the mixture was naturally cooled to room temperature, centrifuged, washed three times with distilled water and ethanol, and dried in vacuum to obtain ZnO@ZnS.

[0037] (2) The above 0.25 g ZnO@ZnS particles, 7.5 mg copper nitrate and 30 mg TU were added to 40 mL distilled water, stirred for 10 min, and then hydrothermally reacted at 170 °C for 36 h. After the reaction, it was naturally cooled to room temperature, centrifuged, washed three times with distilled water and ethanol respectively, and vacuum dried to obtain a ZnO@ZnS@CuS ternary nanocomposite material.

[0038] The ZnO@ZnS@CuS ternary nanocomposite material prepared in Example 2 has a core-shell structure, wherein ZnO is the core, ZnS is the shell, and CuS particles are loaded in the outermost layer. Figure 2 It can be clearly seen that in Example 2, small CuS particles are attached to the surface of ZnO@ZnS.

[0039] The ZnO@ZnS@CuS ternary nanocomposite material prepared in Example 2 produces hydrogen by photocatalytic hydrolysis under visible light, specifically:

[0040] 50 mg of the ZnO@ZnS@CuS ternary nanocomposite material of Example 2 was added to 50 mL of 0.25 M Na 2 SO 3 +0.35M Na 2 The aqueous solution of S was balanced in a dark environment for 30 minutes. A 300W xenon lamp was used as the light source. The photocatalytic hydrogen production reaction was carried out at 6°C. Samples were taken every 1 hour and the concentration of the product was determined by gas chromatography. The hydrogen production rate was 12.57 μmol·mg -1 ·h -1 .

[0041] Example 3

[0042] The preparation method of the ZnO@ZnS@CuS ternary nanocomposite material of the present invention comprises the following steps:

[0043] (1) 0.25 g ZnO powder was added to 30 mL distilled water, ultrasonicated for 10 min, and then 0.5 g TAA was added thereto. After stirring for 10 min, the mixture was hydrothermally reacted at 200 °C for 2 h. After the reaction was completed, the mixture was naturally cooled to room temperature, centrifuged, washed three times with distilled water and ethanol, and dried in vacuum to obtain ZnO@ZnS.

[0044] (2) The above 0.25 g ZnO@ZnS particles, 10 mg copper nitrate and 40 mg TU were added to 40 mL distilled water, stirred for 10 min, and then hydrothermally reacted at 180 °C for 48 h. After the reaction, it was naturally cooled to room temperature, centrifuged, washed three times with distilled water and ethanol respectively, and vacuum dried to obtain a ZnO@ZnS@CuS ternary nanocomposite material.

[0045] The ZnO@ZnS@CuS ternary nanocomposite material prepared in Example 3 has a core-shell structure, wherein ZnO is the core, ZnS is the shell, and CuS particles are loaded in the outermost layer. Figure 3 It can be clearly seen that in Example 3, small CuS particles are attached to the surface of ZnO@ZnS.

[0046] The ZnO@ZnS@CuS ternary nanocomposite material prepared in Example 3 produces hydrogen by photocatalytic hydrolysis under visible light, specifically:

[0047] 50 mg of the ZnO@ZnS@CuS ternary nanocomposite material of Example 3 was added to 50 mL of 0.25 M Na 2 SO 3 +0.35M Na 2 The aqueous solution of S was balanced in a dark environment for 30 minutes. A 300W xenon lamp was used as the light source. The photocatalytic hydrogen production reaction was carried out at 6°C. Samples were taken every 1 hour and the concentration of the product was determined by gas chromatography. The hydrogen production rate was 10.19 μmol·mg -1 ·h -1 .

[0048] Comparative Example 1

[0049] A method for preparing a ZnO@CuS@ZnS composite material comprises the following steps:

[0050] (1) 0.25 g ZnO powder, 5 mg copper nitrate and 20 mg TU were added to 40 mL distilled water, stirred for 10 min, and then hydrothermally reacted at 160 °C for 24 h. After the reaction, the mixture was naturally cooled to room temperature, centrifuged, washed three times with distilled water and ethanol, and dried in vacuum to obtain ZnO@CuS.

[0051] (2) The above 0.25 g ZnO@CuS particles were added to 30 mL distilled water, ultrasonicated for 10 min, and then 0.25 g TAA was added. After stirring for 10 min, the mixture was hydrothermally reacted at 180 °C for 1 h. After the reaction was completed, the mixture was naturally cooled to room temperature, centrifuged, washed three times with distilled water and ethanol, and vacuum dried to obtain ZnO@CuS@ZnS.

[0052] The ZnO@CuS@ZnS composite material prepared in Comparative Example 1 produces hydrogen by photocatalytic hydrolysis under visible light, specifically:

[0053] 50 mg of the ZnO@CuS@ZnS composite material of Comparative Example 1 was added to 50 mL of 0.25 M Na 2 SO 3 +0.35M Na 2 The aqueous solution of S was balanced in a dark environment for 30 minutes. A 300W xenon lamp was used as the light source. The photocatalytic hydrogen production reaction was carried out at 6°C. Samples were taken every 1 hour and the concentration of the product was measured using gas chromatography. The results are as follows: Figure 6 As shown, the hydrogen production rate of the catalyst under full spectrum conditions is 2.79 μmol·mg -1 ·h -1 , under the condition of λ>420nm, the hydrogen production rate is 0.44μmol·mg -1 ·h -1 .

[0054] The cyclic stability test results of Comparative Example 1 are shown in Figure 7 After 4 cycles (20 h), the hydrogen production rate of the catalyst was 2.80 μmol·mg -1 ·h -1 , indicating that it has a certain stability.

[0055] Comparative Example 2

[0056] A preparation method of a ZnO@ZnS composite material comprises the following steps: adding 0.25 g ZnO powder to 30 mL distilled water, ultrasonicating for 10 min, adding 0.25 g TAA thereto, stirring for 10 min, hydrothermally reacting at 180° C. for 1 h, naturally cooling to room temperature after the reaction, centrifuging, washing three times with distilled water and ethanol, and vacuum drying to obtain ZnO@ZnS.

[0057] The ZnO@ZnS composite material prepared in Comparative Example 2 produces hydrogen by photocatalytic hydrolysis under visible light, specifically:

[0058] 50 mg of the ZnO@ZnS composite material of Comparative Example 2 was added to 50 mL of 0.25 M Na 2 SO 3 +0.35M Na 2 The aqueous solution of S was balanced in a dark environment for 30 minutes. A 300W xenon lamp was used as the light source. The photocatalytic hydrogen production reaction was carried out at 6°C. Samples were taken every 1 hour and the concentration of the product was determined by gas chromatography. The hydrogen production rate was 2.3 μmol·mg -1 ·h -1 .

[0059] Comparative Example 3

[0060] A preparation method of a ZnO@CuS composite material, specifically comprising: adding 0.25g ZnO powder, 5mg copper nitrate and 20mg TU to 40mL distilled water, stirring for 10min, hydrothermally reacting at 160°C for 24h, naturally cooling to room temperature after the reaction, centrifuging, washing three times with distilled water and ethanol, and vacuum drying to obtain ZnO@CuS.

[0061] The ZnO@CuS composite material prepared in Comparative Example 3 produces hydrogen by photocatalytic hydrolysis under visible light, specifically:

[0062] 50 mg of the ZnO@ZnS composite material of Comparative Example 3 was added to 50 mL of 0.25 M Na 2 SO 3 +0.35M Na 2 The aqueous solution of S was balanced in a dark environment for 30 minutes. A 300W xenon lamp was used as the light source. The photocatalytic hydrogen production reaction was carried out at 6°C. Samples were taken every 1 hour and the concentration of the product was determined by gas chromatography. The hydrogen production rate was 9.9 μmol·mg -1 ·h -1 .

Claims

1. A ZnO@ZnS@CuS ternary nanocomposite material, characterized in that: The invention comprises ZnO, a ZnS layer in situ grown on the ZnO by sulfidation, and CuS nanoparticles in situ grown on the ZnS layer.

2. The ZnO@ZnS@CuS ternary nanocomposite material according to claim 1, characterized in that: The particle size of the ZnO particles is not more than 250 nm.

3. The ZnO@ZnS@CuS ternary nanocomposite material according to claim 1, characterized in that: The thickness of the ZnS shell formed by sulfidation is 38-40 nm.

4. The ZnO@ZnS@CuS ternary nanocomposite material according to claim 1, characterized in that: The loading amount of the CuS nanoparticles is 1.8-2% of the mass of the composite material.

5. The method for preparing the ZnO@ZnS@CuS ternary nanocomposite material according to claim 1, characterized in that: The steps include: (1) Ultrasonic dispersion of ZnO in water, after uniform dispersion, adding thioacetamide to the water for reaction, centrifuging, washing, and drying to obtain ZnO@ZnS; (2) ZnO@ZnS, copper nitrate and thiourea are mixed, reacted, centrifuged, washed and dried to obtain a ZnO@ZnS@CuS ternary nanocomposite material.

6. The preparation method according to claim 5, characterized in that: In step (1), the mass ratio of ZnO to thioacetamide is 1:1-2.

7. The preparation method according to claim 5, characterized in that: In step (1), the reaction temperature is 180-200° C. and the reaction time is 1-2 h.

8. The preparation method according to claim 5, characterized in that: In step (2), the mass ratio of ZnO@ZnS, copper nitrate and thiourea is 50:1-2:4-8.

9. The preparation method according to claim 5, characterized in that: In step (2), the reaction temperature is 160-180° C. and the reaction time is 24-48 h.

10. Use of the ZnO@ZnS@CuS ternary nanocomposite material according to claim 1 as a photocatalyst in photocatalytic water decomposition to produce hydrogen.

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