Preparation and Application of an Indium Zinc Sulfide / Dopamine / Polyacid Composite Photocatalyst

Abstract

This invention relates to the preparation and application of an indium zinc sulfide / dopamine / polyacid composite photocatalyst. The composite material obtained by this invention is used for photocatalytic water splitting to produce hydrogen under ambient temperature and pressure. This invention can obtain ZnIn2S4 / PDA composite materials and ZnIn2S4 / PDA / SiW9Ni3 composite materials. This invention combines ZnIn2S4 flower-like microspheres with a trinickel-substituted polyacid (SiW9Ni3) with good stability and photocatalytic activity through a PDA binder. The resulting flower-like microsphere composite material exhibits significantly improved photocatalytic hydrogen production performance. The addition of PDA enhances the transfer of photogenerated charges between ZnIn2S4 and SiW9Ni3, while also overcoming the problems of SiW9Ni3's easy agglomeration and water solubility. The ZnIn2S4 nanoflower surface is loaded with SiW9Ni3, which has reversible redox properties, suppressing the recombination of photogenerated electrons and holes, allowing the photogenerated electrons generated by the composite material under illumination to act more effectively on the photocatalytic water splitting to produce hydrogen. The indium zinc sulfide / dopamine / polyacid nanocomposite material shows great promise for application in photocatalytic water splitting to produce hydrogen under normal temperature and pressure.

Description

Technical Field

[0001] This invention relates to the preparation and application of an indium zinc sulfide / dopamine / polyacid composite photocatalyst. Background Technology

[0002] Photocatalysis, as a zero-carbon emission technology, has attracted much attention due to its advantages such as high energy efficiency and environmental friendliness. Among its components, the photocatalyst is one of the key factors in improving photocatalytic performance. Indium zinc sulfide (ZnIn2S4, or ZIS) is considered a high-performance visible-light-responsive photocatalyst due to its non-toxicity, suitable band gap, ease of synthesis, high physicochemical stability, and durability. Its structure can be easily modified or coupled with other semiconductor catalysts to prepare various morphologies such as nanoparticles, nanoribbons, and flower-like microspheres. Due to its good and suitable band gap (2.34–2.55 eV) and its physical and chemical stability, flower-like ZnIn2S4 microspheres with a hexagonal crystal phase exhibit excellent photocatalytic performance. Dopamine (PDA) is an effective surface functionalization material in the field of photocatalysis. With abundant functional groups such as primary amines, tertiary amines, and catechols, PDA can form covalent and non-covalent bonds on the surface of semiconductor photocatalysts, creating an attraction-adhesion effect.

[0003] Sub-nanometer-sized polyoxometalates (POMs) are a large class of inorganic anionic clusters, mainly formed by the oxidation bridging of early transition metals (TMs) such as tungsten, molybdenum, and vanadium (Mo, W, V, Nb, Ta) in their highest oxidation states. Transition metal-substituted polyoxometalates are widely used in photocatalysis due to their expanded absorption range and high activity. The composition, charge, and structure of transition metal-substituted polyoxometalates can be adjusted by changing the type and number of transition metal atoms. However, polyoxometalates also suffer from the critical problems of easy aggregation and high water solubility. This invention introduces a silicotungsten polyoxometalate α-[SiW9O] substituted with nickel, a transition metal with good proton migration ability. 37 {Ni(H2O)}3] 10- (abbreviated as SiW9Ni3) is attached to the surface of ZIS nanoflowers by PDA, a binder with π-π* electron delocalization effect, to form a novel and high-performance ZnIn2S4 / PDA / SiW9Ni3 composite photocatalyst. Summary of the Invention

[0004] The purpose of this invention is to solve the problems of poor light absorption, narrow band gap and easy recombination of photogenerated carriers caused by polyacid aggregation in existing polyacid-based materials, and to prepare nanoflower-like composite materials to improve the photocatalytic efficiency of hydrogen production materials.

[0005] This invention provides a method for preparing a ZnIn2S4 / PDA / SiW9Ni3 composite material by adding a conductive binder, dopamine, to polyoxometalates and indium zinc sulfide at room temperature. The composite material exhibits a three-dimensional flower-shaped structure and is used for photocatalytic water splitting to produce hydrogen.

[0006] Preparation of composite material ZnIn2S4 / PDA / SiW9Ni3:

[0007] I. Preparation of dispersions for each sample: Different amounts of nickel-substituted silicotungstic polyacid (SiW9Ni3), different amounts of dopamine hydrochloride (PDA), and the same amount of zinc indium sulfide (ZnIn2S4, abbreviated as ZIS) were added to buffer solutions of the same pH, and the mixtures were sonicated and stirred until the samples were uniformly dispersed.

[0008] II. Preparation of composite material: PDA dispersion was added to ZnIn2S4 dispersion, ultrasonicated, stirred and mixed evenly to obtain ZnIn2S4 / PDA dispersion. Then SiW9Ni3 dispersion was added, ultrasonicated and stirred. After several hours, centrifuged and dried to obtain ZnIn2S4 / PDA / SiW9Ni3 composite material.

[0009] In the preparation of the above composite material, the buffer solution with the same pH mentioned in step one is a Tris-HCl buffer solution with pH = 8.47 to 8.53.

[0010] In the preparation of the above composite material, the different amounts of nickel-substituted silicotungstic polyacid (SiW9Ni3) mentioned in step one have a molar ratio of 0:9~11:19~21:29~31:39~41 (unit μmol).

[0011] In the preparation of the above composite material, the molar ratio of different amounts of dopamine hydrochloride mentioned in step one is 0:4~6:9~11:14~16:19~21 (unit μmol).

[0012] In the preparation of the above composite material, the same amount of indium zinc sulfide mentioned in step one has a molar amount of 0.23 to 0.27 mmol.

[0013] In the preparation of the above composite material, the dispersion in step two refers to a SiW9Ni3 solution ranging from light green to dark green, a PDA solution ranging from light to dark, and a ZnIn2S4 suspension that is uniformly dispersed in yellow or golden yellow.

[0014] In the preparation of the above composite material, the ZnIn2S4 / PDA dispersion described in step two is stirred for 50-70 minutes, centrifuged, washed with deionized water and ethanol, and dried under vacuum at 60-70°C for 8-12 hours to obtain the ZnIn2S4 / PDA composite material (abbreviated as ZP).

[0015] In the preparation of the above composite material, in step two, the ZnIn2S4 / PDA dispersion is stirred for 11 to 16 minutes, the SiW9Ni3 dispersion is added, ultrasonicated, stirred, and after 6.5 to 7.5 hours, it is centrifuged and dried to obtain the ZnIn2S4 / PDA / SiW9Ni3 composite material (abbreviated as ZPS).

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] This invention yields ZnIn2S4 / PDA composite materials and ZnIn2S4 / PDA / SiW9Ni3 composite materials. Using ZIS nanoflowers as a substrate, highly conductive and viscous PDA is used to bond SiW9Ni3, which exhibits excellent photocatalytic performance, to their surface. The resulting ZnIn2S4 / PDA / SiW9Ni3 composite materials show a significant improvement in photocatalytic hydrogen production performance. Scanning electron microscopy (SEM) reveals that the appropriate addition of SiW9Ni3 not only does not significantly alter the morphology and structure of the ZIS nanoflowers, but also, under the action of the PDA with its π-π* electron delocalization effect, enhances the transfer of photogenerated carriers between ZIS and SiW9Ni3 under illumination, thereby improving photocatalytic hydrogen production performance.

[0018] This invention utilizes highly conductive PDA to bond sub-nanostructured SiW9Ni3 onto the surface of ZIS nanoflowers to achieve a photocatalytic composite material with high natural light response. This invention is the first to attach nickel-substituted Keggin-type silicotungstic polyacid (SiW9Ni3) to the surface of indium zinc sulfide (ZIS), setting a precedent for preparing indium zinc sulfide / dopamine / polyacid (ZnIn2S4 / PDA / POMs) composite photocatalytic materials using PDA as a conductive binder. Attached Figure Description

[0019] Figure 1 The image shows a ZIS monomer scanning electron microscope image prepared for Comparative Example 1 of the present invention.

[0020] Figure 2 The images are scanning electron microscope images of the ZnIn2S4 / PDA composite material (ZP) provided by the present invention, wherein (a) is the ZP-1 composite material with an added PDA amount of 4-6 μmol as described in Comparative Example 2; (b) is the ZP-2 composite material with an added PDA amount of 9-11 μmol as described in Comparative Example 3; (c) is the ZP-3 composite material with an added PDA amount of 14-16 μmol as described in Comparative Example 3; and (d) is the ZP-4 composite material with an added PDA amount of 19-21 μmol as described in Comparative Example 4.

[0021] Figure 3The images show scanning electron microscope (SEM) images of the ZnIn2S4 / PDA / SiW9Ni3 composite material (ZPS) provided by this invention. (a) is the ZPS-1 composite material with 9-11 μmol of SiW9Ni3 added as described in Comparative Example 5; (b) is the ZPS-2 composite material with 19-21 μmol of SiW9Ni3 added as described in Example 2; (c) is the ZPS-3 composite material with 29-31 μmol of SiW9Ni3 added as described in Comparative Example 6; and (d) is the ZPS-4 composite material with 39-41 μmol of SiW9Ni3 added as described in Comparative Example 7.

[0022] Figure 4 This is a comparison diagram of the composite material ZP-2 provided in Comparative Example 3 of the present invention with ZIS and PDA monomer FT-IR.

[0023] Figure 5 The image shows a comparison of the composite material ZPS-2 provided in Example 1 of this invention with ZIS and SiW9Ni3 monomers via FT-IR.

[0024] Figure 6 The following are FT-IR comparison images of several composite materials described in this invention: (a) shows the four ZnIn2S4 / PDA composite materials provided; (b) shows the four ZnIn2S4 / PDA / SiW9Ni3 composite materials provided.

[0025] Figure 7 The images show XRD comparisons of several composite materials described in this invention. (a) shows the four ZnIn2S4 / PDA composite materials provided; (b) shows the four ZnIn2S4 / PDA / SiW9Ni3 composite materials provided.

[0026] Figure 8 This is a comparison chart of the photocatalytic hydrogen production performance of the ZPS-2 composite material provided in Example 2 of the present invention and several catalysts under normal temperature and pressure.

[0027] Figure 9 The figures show a comparison of the photocatalytic hydrogen production performance of several composite materials described in this invention under ambient temperature and pressure. (a) shows the four ZnIn2S4 / PDA composite materials provided by this invention; (b) shows the four ZnIn2S4 / PDA / SiW9Ni3 composite materials provided by this invention. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0029] Implementation Case 1

[0030] This embodiment provides an indium zinc sulfide / dopamine / polyacid composite photocatalyst, which is prepared according to the following method:

[0031] Preparation of dispersions for each sample: 0.25 mmol of zinc indium sulfide (ZIS) was added to a buffer solution of pH 8.51, and the mixture was sonicated and stirred until the sample was uniformly dispersed. The mixture was stirred for 7 hours, centrifuged, washed three times with ethanol and deionized water, and vacuum dried at 60°C for 12 hours to obtain ZIS monomer material impregnated in buffer solution of pH 8.51.

[0032] Implementation Case 2

[0033] This embodiment provides an indium zinc sulfide / dopamine / polyacid composite photocatalyst, which is prepared according to the following method:

[0034] I. Preparation of dispersions for each sample: 20 μmol of SiW9Ni3, 10 μmol of PDA and 0.25 mmol of ZIS were added to 10 mL of pH 8.51 Tris-HCl buffer solution, and the mixture was sonicated and stirred until the samples were uniformly dispersed.

[0035] II. Preparation of composite material: PDA dispersion was added to ZnIn2S4 dispersion, ultrasonicated, stirred and mixed evenly to obtain ZnIn2S4 / PDA dispersion. Then SiW9Ni3 dispersion was added, ultrasonicated and stirred for 7 hours, centrifuged and dried to obtain ZnIn2S4 / PDA / SiW9Ni3 composite material.

[0036] Comparison Case 1

[0037] The comparative case provides an indium zinc sulfide / dopamine / polyacid composite photocatalyst that differs from Example 2 in that 0 μmol of SiW9Ni3 and 5 μmol of PDA are added to 10 mL of pH 8.51 buffer solution.

[0038] Comparison Case 2

[0039] The indium zinc sulfide / dopamine / polyacid composite photocatalyst provided in this comparative case differs from that in Example 2 in that 0 μmol of SiW9Ni3 and 15 μmol of PDA are added to 10 mL of pH 8.51 buffer solution.

[0040] The indium zinc sulfide / dopamine / polyacid composite photocatalyst provided in this comparative case differs from that in Example 2 in that 0 μmol of SiW9Ni3 and 20 μmol of PDA are added to 10 mL of pH 8.51 buffer solution.

[0041] The indium zinc sulfide / dopamine / polyacid composite photocatalyst provided in this comparative case differs from that in Example 2 in that 10 μmol of SiW9Ni3 and 10 μmol of PDA are added to 10 mL of pH 8.51 buffer solution.

[0042] The comparative case provides an indium zinc sulfide / dopamine / polyacid composite photocatalyst that differs from Example 2 in that 30 μmol of SiW9Ni3 and 10 μmol of PDA are added to 10 mL of pH 8.51 buffer solution.

[0043] The comparative case provides an indium zinc sulfide / dopamine / polyacid composite photocatalyst that differs from Example 2 in that 40 μmol of SiW9Ni3 and 10 μmol of PDA are added to 10 mL of pH 8.51 buffer solution.

[0044] The invention will be further described below with reference to the accompanying drawings:

[0045] Figure 1 The image shows a scanning electron microscope image of the ZIS monomer prepared for Comparative Example 1 of the present invention. A distinct nanoflora-like structure was observed.

[0046] Figure 2 The images shown are scanning electron microscope images of the ZnIn2S4 / PDA composite material (ZP) provided by this invention. (a), (b), (c), and (d) are SEM images of the ZP composite materials provided in comparative cases 1, 2, 3, and 4, respectively. It can be observed that the ZIS nanoflower structure does not change significantly with the increase of PDA input.

[0047] Figure 3 The scanning electron microscope images of the ZnIn2S4 / PDA / SiW9Ni3 composite material (ZPS) provided by this invention are shown in (b), (a), (c), and (d), respectively. They are SEM images of the ZPS composite material provided in Example 2 and Comparative Examples 5, 6, and 7. It can be observed that as the amount of SiW9Ni3 added increases, the morphology of the ZPS nanoflower structure does not change significantly.

[0048] Figure 4 The figure shows a comparison of the composite material ZP-2 provided in Comparative Example 3 of the present invention with ZIS and PDA monomers via FT-IR. As can be seen from the figure, ZP-2 has obvious infrared characteristic peaks of ZIS and PDA, indicating that PDA is loaded onto the surface of ZIS nanoflowers.

[0049] Figure 5The figure shows a comparison of the composite material ZPS-2 provided in Example 1 of this invention with ZIS and SiW9Ni3 monomers FT-IR. As can be seen from the figure, ZPS-2 has obvious infrared characteristic peaks of ZIS and SiW9Ni3, indicating that the surface of ZIS nanoflowers is loaded with SiW9Ni3.

[0050] Figure 6 The following are FT-IR comparison images of several composite materials described in this invention. (a) is the infrared image of ZP composite material. As shown in the figure, the infrared characteristic peak of ZP composite material becomes stronger with the increase of PDA input. (b) is the infrared image of ZPS composite material. As shown in the figure, the infrared characteristic peak of SiW9Ni3 in ZPS composite material becomes stronger with the increase of SiW9Ni3 input, indicating the increase of SiW9Ni3 loading on the ZIS nanoflower surface.

[0051] Figure 7 The images show XRD comparisons of several composite materials described in this invention. (a) and (b) are XRD comparisons of ZP composite material and ZPS composite material, respectively. By comparing with the ZIS standard card (PDF#72-0773), the synthesis of ZIS is confirmed. In both composite materials, the XRD characteristic peaks of PDA and SiW9Ni3 cannot be clearly observed.

[0052] Figure 8 The graph shows a comparison of the photocatalytic hydrogen production performance of the ZPS-2 composite material provided in Example 2 of this invention with several catalysts under ambient temperature and pressure. The graphs show the photocatalytic hydrogen production rates of each material under ambient temperature and pressure, with 10 vol% TEOA as the sacrificial reagent, and irradiation by a 300W (λ = 300nm ~ 1100nm) xenon lamp for 5 hours. The five-hour photocatalytic hydrogen production performance of the ZPS-2 composite material provided in Example 2 is 13.99 mmol·g. -1 ·h -1 Indium zinc sulfide / dopamine / polyacid nanoflower-like materials can serve as a highly efficient photocatalytic water splitting catalyst.

[0053] Figure 9 This is a comparison chart of the photocatalytic hydrogen production performance of several composite materials described in this invention, such as... Figure 9 As shown in Figure a, with the addition of PDA, the photocatalytic hydrogen production performance is enhanced, reaching its highest level in ZP-2; however, as the amount of PDA added increases, the catalytic performance decreases. Figure 9 As shown in b, the addition of polyacid SiW9Ni3 enhances the photocatalytic hydrogen production performance of the composite material. However, the photocatalytic performance of the ZPS composite material decreases as the amount of polyacid added continues to increase.

[0054] In summary, this invention can prepare an indium zinc sulfide-supported polyacid nanoflower-shaped composite photocatalyst, which can be used for photocatalytic water splitting to produce hydrogen. The addition of polyacid enhances the photocatalytic hydrogen production efficiency of the flower-shaped material, and PDA, as a high-performance conductive binder, strengthens the transfer of photogenerated carriers and improves the separation of photogenerated electrons and holes. An indium zinc sulfide / dopamine / polyacid composite photocatalyst has great potential in photocatalytic water splitting.

Claims

1. A method for preparing an indium zinc sulfide / dopamine / polyacid composite photocatalyst, characterized in that: (1) Preparation of dispersions of each sample: 20 μmol of SiW9Ni3, 10 μmol of PDA and 0.25 mmol of ZnIn2S4 were added to 10 mL of pH 8.51 Tris-HCl buffer solution, and the mixture was sonicated and stirred until the sample was uniformly dispersed. (2) Preparation of composite material: PDA dispersion was added to ZnIn2S4 dispersion, ultrasonicated, stirred and mixed evenly to obtain ZnIn2S4 / PDA dispersion, then SiW9Ni3 dispersion was added, ultrasonicated and stirred for 7 hours, centrifuged and dried to obtain ZnIn2S4 / PDA / SiW9Ni3 composite material.

2. The indium zinc sulfide / dopamine / polyacid composite photocatalyst prepared by the preparation method according to claim 1 is applied to photocatalytic water splitting for hydrogen production at room temperature and pressure.

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