Twin crystal zinc cadmium sulfide nanosheet, composite photocatalyst and preparation method and application thereof
By constructing a composite photocatalyst of twinned zinc cadmium sulfide nanosheets and metal tungstate, the problem of limited photocatalytic activity and stability of traditional zinc cadmium sulfide nanoparticles was solved, and the dual functions of efficient photocatalytic hydrogen production and waste plastic degradation were achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- XI'AN PETROLEUM UNIVERSITY
- Filing Date
- 2026-03-10
- Publication Date
- 2026-04-17
AI Technical Summary
Traditional zinc cadmium sulfide nanoparticles suffer from problems such as easy recombination of photogenerated electrons and holes, limited surface active sites, and severe photocorrosion in the field of photocatalysis, which limit their photocatalytic activity and stability. Furthermore, existing methods have shortcomings such as insufficient interfacial contact, obstructed carrier migration paths, complex structures, and high costs.
Twinned zinc cadmium sulfide nanosheets were constructed using a solvent coordination molecular template method and formed a composite photocatalyst with metal tungstate. The built-in electric field in the twinned structure and the band matching of the heterojunction drive the directional migration of charge carriers, achieving a dual-function integration of photocatalytic water splitting for hydrogen production and synergistic degradation of waste plastics.
It improves the photocatalytic hydrogen production rate and stability, realizes the dual-function integration of photocatalytic water splitting for hydrogen production and co-degradation of waste plastics, and enhances carrier separation efficiency and reaction rate.
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Figure CN121869394A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of photocatalyst technology, specifically relating to twinned zinc cadmium sulfide nanosheets, a composite photocatalyst, its preparation method, and its application. Background Technology
[0002] Currently, zinc cadmium sulfide (CdZnS), as a visible-light-responsive group II-VI semiconductor material, has attracted widespread attention due to its tunable band structure and simple preparation process. It has potential applications in photocatalytic water splitting for hydrogen production, CO2 reduction, and degradation of organic pollutants. However, traditional CdZnS nanoparticles generally suffer from problems such as easy recombination of photogenerated electrons and holes, limited surface active sites, and severe photocorrosion, which restrict both their photocatalytic activity and stability.
[0003] To enhance the photocatalytic performance of CdZnS, current research often employs methods such as ion doping, noble metal deposition, or heterojunction construction to modulate the band structure and promote carrier separation. However, these methods typically suffer from drawbacks such as insufficient interfacial contact, obstructed carrier migration pathways, complex structures, and high costs.
[0004] Two-dimensional nanosheet structures exhibit unique advantages in photocatalysis due to their high specific surface area, short carrier diffusion distance, and abundant surface active sites. Constructing two-dimensional CdZnS nanosheets can significantly increase the contact area at the reaction interface and shorten the electron-hole migration path, thereby contributing to improved carrier separation efficiency and reaction rate. However, the controllable construction of CdZnS nanosheets and the optimization of their internal electronic structure still face challenges, particularly in how to further control crystal defects and internal electric fields within the two-dimensional structure to achieve stable and efficient photocatalytic performance. Summary of the Invention
[0005] To address the aforementioned technical problems, this invention provides twinned zinc cadmium sulfide nanosheets, a composite photocatalyst, its preparation method, and its application.
[0006] A method for preparing twinned zinc cadmium sulfide nanosheets includes the following steps: A zinc source, a diethylenetriamine aqueous solution, and a sulfur source were mixed and subjected to a first solvothermal reaction to obtain a zinc sulfide-diethylenetriamine composite precursor; the ratio of the zinc source, the diethylenetriamine aqueous solution, and the sulfur source was 1 mmol: 30 mL: 1~6 mmol. The zinc sulfide-diethylenetriamine composite precursor, cadmium source, and organic solvent are mixed and subjected to a second solvothermal reaction, in which cadmium ions replace some of the zinc ions in the zinc sulfide-diethylenetriamine composite precursor lattice, to obtain the zinc sulfide-cadmium-diethylenetriamine composite precursor; the ratio of the zinc sulfide-diethylenetriamine composite precursor, cadmium source, and organic solvent is 1~2 mmol:2 mmol:60 mL. The zinc cadmium sulfide-diethylenetriamine composite precursor was dispersed in water, and a hydrothermal reaction was carried out to remove the diethylenetriamine molecules, resulting in twinned zinc cadmium sulfide nanosheets.
[0007] In the above method, Zn 2+ First, a ZnS-DETA precursor is formed with a sulfur source under the action of diethylenetriamine. Subsequently, during the solvothermal reaction, some Zn... 2+ Being Cd 2+ Replacement to generate Cd 0.5 Zn 0.5 In the S-DETA composite precursor, some diethylenetriamine molecules gradually escape. During the hydrothermal treatment stage, the diethylenetriamine in the precursor is removed, accompanied by twinning structure regulation within the crystal, thus forming Cd with a two-dimensional lamellar morphology and twinning interfaces. 0.5 Zn 0.5 S nanosheets, with their twinned interfaces, provide preferential carrier migration channels, further promoting photogenerated electron-hole separation and improving photocatalytic hydrogen production performance.
[0008] Preferably, the zinc source is zinc acetate dihydrate; The sulfur source is thioacetamide; The cadmium source is cadmium acetate dihydrate.
[0009] Preferably, the temperature of the first solvothermal reaction is 140~180℃ and the time is 6~24h; the temperature of the second solvothermal reaction is 140~180℃ and the time is 0.5~16h; and the temperature of the hydrothermal reaction is 120~160℃ and the time is 3~6h.
[0010] The twinned zinc cadmium sulfide nanosheets prepared by the method described above.
[0011] A composite photocatalyst is obtained by supporting metal tungstate on twinned zinc cadmium sulfide nanosheets as described above.
[0012] Preferably, the mass fraction of metal tungstate in the composite photocatalyst is 2% to 10%.
[0013] Preferably, the metal is selected from any one of nickel, cobalt, silver, bismuth, barium, zinc, cadmium, copper, iron, and manganese.
[0014] Preferably, the preparation steps of the composite photocatalyst are as follows: Metal tungstate and twinned zinc cadmium sulfide nanosheets were separately dispersed in water and mixed to obtain a dispersion. The resulting dispersion was then mixed to obtain a mixed dispersion. The mixed dispersion was heated at 60℃~80℃ until the solvent was completely evaporated to obtain the composite photocatalyst. The mass ratio of metal tungstate to twinned zinc cadmium sulfide nanosheets is 2~10:90~98.
[0015] The application of the composite photocatalyst in photocatalytic water splitting for hydrogen production.
[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: The twinned zinc cadmium sulfide nanosheets of the present invention, by constructing a two-dimensional nanosheet morphology with a characteristic crystal structure, can achieve a high hydrogen production rate under illumination, and are suitable for clean energy utilization such as solar hydrogen production.
[0017] This invention constructs a metal tungstate / twinned CdZnS (MWO4 / T-CZS-S) synergistic system by solvent evaporation induction method, so that the built-in electric field in the twinned structure and the band matching of the heterostructure interface jointly drive the directional migration of charge carriers, realizing the dual-function integration of photocatalytic water splitting to produce hydrogen and synergistic degradation of waste plastics. Attached Figure Description
[0018] Figure 1 This is a schematic diagram of the preparation process of NiWO4 / T-CZS-S.
[0019] Figure 2 XRD patterns of the materials are shown below, where (a) is the XRD pattern of NiWO4, T-CZS-S and 6% NiWO4 / T-CZS-S, (b) is the XRD pattern of NiWO4, T-CZS and 6% NiWO4 / T-CZS, (c) is the XRD pattern of CoWO4 and Ag2WO4, (d) is the XRD pattern of Bi2WO6 and BaWO4, (e) is the XRD pattern of ZnWO4 and CdWO4, and (f) is the XRD pattern of CuWO4, FeWO4 and MnWO4.
[0020] Figure 3 The images are SEM images of the materials, where (a) and (d) are SEM images of T-CZS-S at scales of 1 μm and 200 nm, respectively; (b) is the SEM image of NiWO4; (e) is a magnified view of (b); (c) and (f) are SEM images of 6% NiWO4 / T-CZS-S at scales of 1 μm and 200 nm, respectively; (g) is the elemental distribution map of 6% NiWO4 / T-CZS-S; and (h) is the EDS spectrum of 6% NiWO4 / T-CZS-S.
[0021] Figure 4The images show the morphology and elemental distribution characteristics of T-CZS and the composite sample NiWO4 / T-CZS. (a) and (c) are T-CZS with scale bars of 500 nm and 200 nm, respectively. (b) and (d) are SEM images of 6% NiWO4 / T-CZS with scale bars of 500 nm and 200 nm, respectively. (e) is the elemental distribution map of 6% NiWO4 / T-CZS.
[0022] Figure 5 The morphology and elemental distribution characteristics of T-CZS-S are shown in (a) SEM image, (b-d) elemental distribution map, and (e) EDS spectrum.
[0023] Figure 6 SEM images of other MWO4 are shown, where (a) is CoWO4, (b) is Ag2WO4, (c) is Bi2WO6, (d) is BaWO4, (e) is ZnWO4, (f) is CdWO4, (g) is CuWO4, (h) is FeWO4, and (i) is MnWO4.
[0024] Figure 7 The images are TEM images of T-CZS-S, where (a) is a TEM image at the 1μm size, (b) is a TEM image of another part at the 1μm size, (c) is an enlarged view of (b), (d) is an enlarged view of (c), (e) is an enlarged view of (d), and (f) is an enlarged view of (e).
[0025] Figure 8 The images are TEM images of 6% NiWO4 / T-CZS-S, where (a) is the image at 2 μm, (b) is the TEM image at 100 nm, (c) is the image at 10 nm, (d) is a magnified view of (c), (e) is a TEM image of another part at 100 nm, and (f) is a magnified view of (e).
[0026] Figure 9 The images are TEM images of 6% NiWO4 / T-CZS, where (a) is a TEM image at a size of 200 nm, (b) is a TEM image at a size of 10 nm, (c) is a magnified view of (b), (d) is a TEM image of another part at a size of 10 nm, (e) is a magnified view of (d), and (f) is a TEM image of yet another part at a size of 10 nm.
[0027] Figure 10 (a) N2 adsorption-desorption isotherms of T-CZS and T-CZS-S, (b) Zeta potential of T-CZS-S and NiWO4, and (c) WCA of T-CZS-S and 6% NiWO4 / T-CZS-S.
[0028] Figure 11The images show the high-resolution XPS spectra of T-CZS, NiWO4, and 6% NiWO4 / T-CZS-S, where (a) is the S 2 p (b) is Zn 2 p (c) is Cd 3 d (d) is W 4 f (e) is O 1 s (f) is Ni 2 p .
[0029] Figure 12 The results show the light absorption and photothermal properties, where (a) is the UV−Vis−NIR RDS plot of T-CZS-S, NiWO4 and 6% NiWO4 / T-CZS-S, (b) is the K−M curve of T-CZS-S and NiWO4, and (c−h) is the infrared thermal image of 6% NiWO4 / T-CZS-S under 300W xenon lamp irradiation.
[0030] Figure 13 To assess hydrogen production and plastic degradation performance, (a) shows the T-CZS-S series samples in PLA solution. r H2 (b) shows the T-CZS series samples in PLA solution. r H2 (c) 6% NiWO4 / T-CZS-S in different sacrificial agents r H2 (d) represents MWO4 / T-CZS-S in the PLA. r H2 (e) represents hydrogen production under NIR light, and (f) represents the AQE of 6% NiWO4 / T-CZS-S.
[0031] Figure 14 The results show the cyclic stability of 6% NiWO4 / T-CZS-S, where (a) is the cyclic experiment of 6% NiWO4 / T-CZS-S, and (b) are the XRD patterns before and after the reaction.
[0032] Figure 15The results are as follows: (a) i−t curves of T-CZS-S, NiWO4, 6%NiWO4 / T-CZS and 6%NiWO4 / T-CZS-S in the full spectrum; (b) i−t curves of NiWO4, 6%NiWO4 / T-CZS and 6%NiWO4 / T-CZS-S in near-infrared light (2000nm>λ>800nm); (c) LSV curves of 6% NiWO4 / T-CZS and 6% NiWO4 / T-CZS-S; (d) LSV curve of 6% MWO4 / T-CZS-S; (e) EIS spectrum; and (f) PL spectrum. Figure 16 The photoelectrochemical performance is shown in section II, where (a) is the Tafel curve of T-CZS-S, NiWO4, 6% NiWO4 / T-CZS and 6% NiWO4 / T-CZS-S, (b-e) are the CV curves at different scan rates, and (f) is the linear relationship curve between current density and corresponding scan rate.
[0033] Figure 17 The results of the photocatalytic hydrogen production coupled plastic degradation mechanism analysis are shown in the following figures: (a) is the M-S curve of T-CZS-S, (b) is the M-S curve of NiWO4, (c) is the M-S curve of 6% NiWO4 / T-CZS-S, and (d) is the band structure diagram.
[0034] Figure 18 The EPR characterization results are shown below, where (a) is the DMPO−·O2 signal of T-CZS-S, (b) is the DMPO−·O2 signal of NiWO4, (c) is the DMPO−·O2 signal of 6% NiWO4 / T-CZS-S, and (d) is the NBT−·O2 signal of T-CZS-S. − UV–Vis spectrum, (e) is the NBT−·O2 of NiWO4. − UV–Vis spectrum, (f) is NBT−·O2 of 6% NiWO4 / T-CZS-S − UV–Vis spectrum.
[0035] Figure 19 The results are for the analysis of the catalytic mechanism, where (a) is the band gap of T-CZS-S, (b) is the band gap of NiWO4, (c) is the skewed density of T-CZS-S, (d) is the skewed density of NiWO4, (e) is the work function of T-CZS-S, and (f) is the work function of NiWO4. Figure 20 The charge transfer mechanism is that of the NiWO4 / T-CZS-S homo-heterojunction.
[0036] Figure 21 The photocatalytic hydrogen production coupled with the degradation mechanism of waste plastics in the NiWO4 / T-CZS-S homo-heterojunction is investigated.
[0037] Figure 22 The non-twinned CdZnS nanosheets in Comparative Example 4 are shown in the TEM. Detailed Implementation
[0038] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. Unless otherwise specified, the experimental methods described in the embodiments of the present invention are conventional methods.
[0039] Firstly, this invention provides zinc cadmium sulfide nanosheets with a twinned structure and a method for preparing the same. This method uses diethylenetriamine (DETA) as a structure-directing agent and employs a solvent coordination molecular template method to achieve the controllable construction of two-dimensional twinned CdZnS nanosheets. The process is simple, highly operable, and reproducible. The resulting nanosheets exhibit a sheet-like two-dimensional structure with a high specific surface area, abundant structural active sites, and excellent bulk charge separation capability originating from the twinned interface, demonstrating excellent reactivity and stability in photocatalytic water splitting for hydrogen production.
[0040] In this invention, the reactions that occur during the preparation process are shown in Equations 1-3: Zn 2+ First, a ZnS-DETA precursor is formed with a sulfur source under the action of diethylenetriamine. Then, during the solvothermal reaction, as the temperature increases, some ZnS... 2+ Being Cd 2+ Replacement to generate Cd 0.5 Zn 0.5 S-DETA composite precursor. Simultaneously, some diethylenetriamine molecules gradually escape. During the hydrothermal treatment stage, the diethylenetriamine in the precursor is removed, accompanied by twinning structure regulation within the crystal, thus forming Cd with a two-dimensional lamellar morphology and twinning interfaces. 0.5 Zn 0.5 S-nanosheets (T-CZS-S). This twinned interface provides a preferential carrier migration channel, further promoting photogenerated electron-hole separation and improving photocatalytic hydrogen production performance.
[0041] Secondly, while traditional CdZnS photocatalytic systems can achieve water splitting for hydrogen production, they suffer from several drawbacks in actual reactions: rapid recombination of photogenerated carriers and low quantum efficiency; the need for expensive or unsustainable sacrificial agents (such as Na2S / Na2SO3); the prevalence of heterogeneous composite materials designed for single reactions (hydrogen production or degradation only), lacking multifunctional synergistic systems; and significant kinetic differences between plastic degradation and hydrogen production processes, making efficient coupling within the same system difficult. This invention constructs a metal tungstate / twinned CdZnS (MWO4 / T-CZS-S) synergistic system via solvent evaporation induction. This allows the built-in electric field in the twinned structure and bandgap matching at the heterogeneous interface to jointly drive the directional migration of carriers, achieving a dual-function integration of photocatalytic water splitting for hydrogen production and synergistic degradation of waste plastics.
[0042] This invention proposes a novel "homo-heterojunction" system by synergistically constructing twinned and heterojunction structures. The twinned interfaces within the twinned CdZnS nanosheets (T-CZS-S) can form a homojunction, generating a built-in electric field under the same chemical composition, achieving spatial separation of electrons and holes. After coupling with external metal tungstate (MWO4), a heterojunction is further constructed, and the direction of electron transfer at the interface is controlled by the band difference. This coupling enables dual-field driving and multi-level charge migration channels within the same system, effectively improving the separation efficiency of photogenerated carriers and the interfacial reactivity. Therefore, constructing a homo-heterojunction between MWO4 and T-CZS-S can achieve band complementarity and the synergistic effect of the built-in electric field at the interface, promoting directional electron / hole migration and improving the photocatalytic water splitting performance for hydrogen production.
[0043] Example 1 The preparation method of twinned CdZnS nanosheets (T-CZS-S) includes the following steps: T-CZS-S was prepared using a solvent coordination molecular template method. First, ZnS-DETA inorganic-organic hybrid materials were synthesized via a solvothermal method using diethylenetriamine (DETA) as a structure-directing agent. Subsequently, a cation exchange process was introduced using ethylene glycol as a solvent to allow Cd... 2+ Replacing part of Zn in the ZnS-DETA lattice 2+ At the same time, some DETA molecules escape, forming Cd. 0.5 Zn 0.5 S-DETA hybrid materials. Finally, by means of hydrothermal treatment, DETA molecules are removed to obtain T-CZS-S with a mesoporous structure, as follows:
[0044] (1) Synthesis of ZnS-diethylenetriamine inorganic-organic hybrid materials 2 mmol Zn(CH3COO)2·2H2O was dissolved in 60 mL of a mixed solution and sonicated for 15 min. The 60 mL mixed solution consisted of 5 mL water and 55 mL diethylenetriamine (DETA). Then, 3 mmol TAA (thioacetamide) was added and stirred until completely dissolved. The resulting mixed solution was transferred to a hydrothermal tank and incubated at 160 °C for 16 h. After natural cooling, the resulting white precipitate was washed three times alternately by centrifugation with water and ethanol, and dried at 60 °C to obtain the ZnS-DETA hybrid material.
[0045] (2) Cd 0.5 Zn 0.5 Preparation of S-diethylenetriamine inorganic-organic hybrid materials 1–2 mmol of the obtained ZnS-DETA hybrid material was slowly added to 60 mL of ethylene glycol and ultrasonically dispersed until homogeneous. Then, 2 mmol of Cd(CH3COO)2·2H2O was weighed and added to the above solution. After stirring for 15 min, the mixture was transferred to a hydrothermal reactor and reacted at 160 °C for 8 h. After cooling to room temperature, the resulting yellow precipitate was washed three times by alternating centrifugation with water and ethanol, and dried at 60 °C to obtain Cd. 0.5 Zn 0.5 S-DETA hybrid materials.
[0046] (3) Twin Cd 0.5 Zn 0.5 Preparation of S nanosheets Weigh 100 mg of the above Cd 0.5 Zn 0.5 S-DETA hybrid material was dispersed in 60 mL of water and sonicated for 30 min. The dispersion was then transferred to a hydrothermal tank and incubated at 160 °C for 3 h. After natural cooling, the resulting precipitate was washed three times by alternating centrifugation with water and ethanol to finally obtain twinned Cd. 0.5 Zn 0.5 S nanosheets (T-CZS-S).
[0047] Comparative Example 1 A method for preparing cubic zinc sphalerite zinc cadmium sulfide nanoparticles includes the following steps: Cubic zinc sphalerite zinc cadmium sulfide nanoparticles were prepared by a hydrothermal method. 2 mmol each of Zn(CH3COO)2·2H2O and Cd(CH3COO)2·2H2O were weighed and dissolved in 50 mL of deionized water, then sonicated and stirred until homogeneous. 6 mmol of sodium sulfide (Na2S) was added, and the mixture was then transferred to a hydrothermal synthesis reactor. After sealing, the reactor was heated to 180 °C for 24 h. After natural cooling to room temperature, the mixture was centrifuged and dried to obtain yellow cubic zinc sphalerite zinc cadmium sulfide powder.
[0048] Comparative Example 2 The preparation method of hexagonal fibrous zinc cadmium sulfide nanoparticles includes the following steps: 2 mmol of Zn(CH3COO)2·2H2O and 2 mmol of Cd(CH3COO)2·2H2O were weighed out and dissolved in 50 mL of deionized water. After sonication and stirring until homogeneous, 6 mmol of thiourea was added. The reaction was then carried out at 180 °C for 24 h. After the reaction was completed, the product was centrifuged and dried to obtain a yellow WZ-CZS powder.
[0049] Comparative Example 3 The preparation method of twinned zinc cadmium sulfide nanoparticles includes the following steps: 2 mmol Zn(CH3COO)2·2H2O and 2 mmol Cd(CH3COO)2·2H2O were dissolved in 50 mL of water. NaOH solution was then added dropwise with continuous stirring. Next, 6 mmol thioacetamide (TAA) was added to the suspension, stirred for 15 min, and then ultrasonically dispersed for 15 min. The mixture was then transferred to a hydrothermal flask, sealed, and reacted at 180 °C for 24 h. After cooling, the resulting yellow precipitate was washed three times by alternating centrifugation with water and ethanol, and finally dried at 70 °C to obtain yellow T-CZS powder.
[0050] The photocatalytic hydrogen production rate of the materials in Example 1 and Comparative Examples 1-3 was detected, and the results are as follows: Twin Cd in Example 1 0.5 Zn 0.5 The photocatalytic hydrogen production rate of S nanosheets (22.5 mmol∙h⁻¹) −1 ∙g −1 () is approximately the same as the Cd in Comparative Example 1 0.5 Zn 0.5 S nanoparticles (13.1 mmol∙h) −1 ∙g −1 It is 1.7 times that of the single six-directional Cd in Comparative Example 2, and approximately 1.7 times that of the single six-directional Cd in Comparative Example 2. 0.5 Zn 0.5 S nanoparticles (5.2 mmol∙h) −1 ∙g −1 4.3 times that of Comparative Example 3, approximately equal to the single-direction Cd. 0.5 Zn 0.5 S nanoparticles (5.8 mmol∙h) −1 ∙g −1 3.9 times that of ). Comparative Example 4 The preparation method of non-twinned CdZnS nanosheets differs from that in Example 1 in that diethylenetriamine (DETA) is replaced with ethylenediamine, as detailed below: (1) Dissolve 2 mmol Zn(CH3COO)2·2H2O in a mixed solution of 5 mL water and 55 mL ethylenediamine (en) and sonicate for 15 min. Then, add 3 mmol thioacetamide (TAA) and stir until completely dissolved. Transfer the resulting mixed solution to a hydrothermal tank and keep it at 160 °C for 16 h. After natural cooling, wash the resulting white precipitate three times by alternating centrifugation with water and ethanol, and dry at 60 °C to obtain the ZnS-en hybrid material.
[0051] (2) The obtained ZnS-en hybrid material was slowly added to 60 mL of ethylene glycol and ultrasonically dispersed until homogeneous. Then, 2 mmol of Cd(CH3COO)2·2H2O was weighed and added to the above solution. After stirring for 15 min, the mixture was transferred to a hydrothermal tank and reacted at 160 °C for 8 h. After cooling to room temperature, the resulting yellow precipitate was washed three times by alternating centrifugation with water and ethanol, and dried at 60 °C to obtain Cd. 0.5 Zn 0.5 S-en hybrid materials.
[0052] (3) Weigh 100 mg of the above Cd 0.5 Zn 0.5 S-en hybrid material was dispersed in 60 mL of water and sonicated for 30 min. The dispersion was then transferred to a hydrothermal tank and incubated at 160 °C for 3 h. After the system cooled naturally, the resulting precipitate was washed three times by alternating centrifugation with water and ethanol to obtain Cd. 0.5 Zn 0.5 S nanosheets.
[0053] Comparative Example 4: TEM testing of non-twinned CdZnS nanosheets Figure 22 As shown, there are no zigzag twin lattice fringes, indicating no twin structure.
[0054] The photocatalytic hydrogen production rate of the materials in Example 1 and Comparative Example 4 was detected, and the results are as follows: The twinned Cd in Example 1... 0.5 Zn 0.5 The photocatalytic hydrogen production rate of S nanosheets is 21.3 mmol∙h⁻¹. −1 ∙g −1 The photocatalytic hydrogen production rate of the non-twinned CdZnS nanosheets in Comparative Example 4 was 15.2 mmol∙h⁻¹. −1 ∙g −1 Example 2 1. A series of metal tungstates (MWO4, M = Ni, Co, Cu, Bi, Fe, Mn, etc.) were synthesized using a combination of controlled deposition, hydrothermal crystallization, and slow-heat calcination. Taking NiWO4 as an example, the specific steps are as follows:
[0055] 2 mol of Na₂WO₄·2H₂O and 2 mol of Ni(NO₃)₂·6H₂O were dissolved in 60 mL of water. After stirring for 30 min, the solution was transferred to a 100 mL hydrothermal flask and reacted at 140 °C for 6 h. After cooling to room temperature, the resulting precipitate was washed three times by alternating centrifugation with water and ethanol, dried, and then incubated in a muffle furnace at 5 °C·min⁻¹. −1 Heating to 400℃ and calcining for 2 hours yields NiWO4 powder with good crystallization and uniform particle size.
[0056] 2. Preparation of composite photocatalysts A certain mass of NiWO4 and T-CZS-S powder were dispersed in 10 mL of water, stirred for 15 min, and then mixed. After sonication for 30 min, the resulting dispersion was heated at 70 °C. After the solvent was completely evaporated, x% NiWO4 / T-CZS-S composite sample was obtained (where x represents the theoretical mass fraction of MWO4, x = 2, 4, 6, 8 and 10). Wherein, when x=2, the mass of NiWO4 is 2mg and the mass of T-CZS-S powder is 98mg; when x=4, the mass of NiWO4 is 4mg and the mass of T-CZS-S powder is 96mg; when x=6, the mass of NiWO4 is 6mg and the mass of T-CZS-S powder is 94mg; when x=8, the mass of NiWO4 is 8mg and the mass of T-CZS-S powder is 92mg; when x=10, the mass of NiWO4 is 10mg and the mass of T-CZS-S powder is 90mg, with 2~10wt% metal tungstate and 90~98wt% zinc cadmium sulfide.
[0057] By adjusting the type of metal precursor, other metal tungstates (CoWO4, Ag2WO4, Bi2WO6, BaWO4, ZnWO4, CdWO4, CuWO4, FeWO4, MnWO4, etc.) can be obtained. Different metal ions can introduce local lattice distortion and band structure differences, thereby controlling the position of the light absorption edge and conduction band of MWO4.
[0058] Comparative Example 5 The T-CZS nanoparticles of Comparative Example 3 were combined with MWO4 to obtain MWO4 / T-CZS, as follows: 6 mg of NiWO4 and 94 mg of T-CZS nanoparticles were dispersed in 10 mL of water respectively, stirred for 15 min, and then mixed. After sonication for 30 min, the resulting dispersion was heated at 70 °C. After the solvent was completely evaporated, a 6% NiWO4 / T-CZS composite sample was obtained.
[0059] Effect verification To investigate the effect of nanosheet structures on photocatalytic performance.
[0060] 1. Material structure characterization from Figure 2 The XRD pattern in (a) shows that the diffraction peaks of T-CZS-S are slightly shifted compared to the standard PDF cards for CdS and ZnS, indicating that Cd and Zn form a solid solution in the crystal lattice. Furthermore, its characteristic peaks are close to the cubic phase crystal structure, suggesting that the cubic phase may be the dominant crystalline phase. The characteristic peaks of NiWO4 perfectly match those of the standard PDF card (JCPDS No. 15-0755). In the 6% NiWO4 / T-CZS-S composite sample, diffraction peaks of both T-CZS-S and NiWO4 can be observed. Although the NiWO4 content is low, its characteristic diffraction peaks can still be detected, such as 15.70° (010), 19.32° (100), 24.02° (011), 24.94° (110), and 31°. The 36.64° (-111), 31.50° (020), 36.64° (002), 37.34° (120), 39.24° (200), 41.74° (-102), 44.80° (-112), 46.48° (-211), 52.46° (130), 54.68° (-202), 62.38° (-113), 65.80° (-311), and 72.54° (-302) are also observed. This indicates that the introduction of NiWO4 did not alter the crystal structure of T-CZS-S. Figure 2 (b) The XRD pattern shows that NiWO4 and T-CZS were also successfully composited.
[0061] Depend on Figure 3 The SEM images (a, d) show that T-CZS-S has a sheet-like structure, while NiWO4 consists of nanoparticles. Figure 3 (b, e)). Figure 3 In (c, f), NiWO4 particles are loaded on the surface of T-CZS-S, and the introduction of NiWO4 does not change the plate-like structure of T-CZS-S. T-CZS-S provides good adhesion sites for NiWO4 particles. Figure 3 The elemental distribution diagram and EDS spectrum of NiWO4 / T-CZS-S in (g, h) show that S, Zn, Cd, W, O and Ni are uniformly distributed on the surface of the composite sample, indicating that NiWO4 / T-CZS-S was successfully prepared.
[0062] Figure 4 The figures show the morphology and elemental distribution characteristics of T-CZS and the composite sample NiWO4 / T-CZS. Both NiWO4 and T-CZS have granular structures. The elemental distribution diagram shows that Zn, Cd, S, Ni, W and O are uniformly dispersed, indicating that NiWO4 / T-CZS was successfully prepared.
[0063] Figure 5 (a) is a SEM image of T-CZS-S, showing that the sample has a sheet-like structure. Figure 5The elemental distribution diagram (b−d) shows that Zn, S and Cd elements are uniformly distributed on the sample surface. Figure 5 In the EDS spectrum of (e), the elemental ratio of S, Zn, and Cd is approximately 2:1.5:1. The Zn atomic content is relatively high, which may be attributed to the presence of additional Zn-related species on the sample surface, considering the Zn content during the synthesis of the ZnS precursor. 2+ High concentration, some Zn 2+ It may not have been completely doped into the T-CZS-S lattice, but rather enriched on the surface, forming Zn particles or Zn-related compounds.
[0064] Figure 6 SEM images of different metal tungstates (MWO4, M = Co, Ag, Bi, Ba, Zn, Cd, Cu, Fe, Mn) show significant differences in their microstructures. Specifically, CoWO4 and CdWO4 are uniformly dispersed nanoparticles, Ag2WO4 and Bi2WO6 exhibit plate-like or flower-like structures, BaWO4 is a cluster of nanoparticles, ZnWO4 is rod-shaped crystals, and CuWO4 is blocky. FeWO4 and MnWO4 both exhibit irregular rod-shaped morphologies.
[0065] The metal ion radius, coordination number, and charge density of MWO4 can affect its interaction with WO4. 2− The bonding mode of these molecules affects the crystal growth rate and nucleation process, resulting in unique micromorphologies. These morphological differences not only influence the specific surface area and active site distribution of the material, but can also further modulate the photoelectrochemical properties of metal tungstates.
[0066] Figure 7 TEM image of T-CZS-S Figure 7 In (a, b), the T-CZS-S structure is plate-like, which not only helps to enhance multiple scattering of light and improve photon absorption efficiency, but also shortens the diffusion path of photogenerated carriers, thereby reducing e − -h + The probability of compounding. Furthermore, by... Figure 7 HRTEM images (c, d) show that the nanosheet surface is relatively rough, which may be due to uneven nucleation during crystal growth, leading to the precipitation of some particles. This surface structure can provide more catalytic active sites. During the synthesis process, due to Zn 2+ and Cd 2+ There are differences in ionic radii, when Cd 2+ When rapidly entering the ZnS-diethylenetriamine lattice, lattice expansion induces local distortion and promotes the formation of void structures. Furthermore, Figure 7 The HRTEM images of (e, f) show clear zigzag lattice fringes, indicating the successful construction of a twinned structure. The ordered crystal orientation not only helps to reduce e −-h + The recombination rate is high, and the twin interface, as a unique structural defect, can provide additional active sites, promoting catalytic reaction activity.
[0067] Figure 8 (a−c) are TEM images of the 6% NiWO4 / T-CZS-S composite sample. NiWO4 nanoparticles are distributed on the surface of T-CZS-S nanosheets, and the two have been successfully composited. Figure 8 In the HRTEM image of (d), the 0.334 nm lattice spacing corresponds to the (111) crystal plane of T-CZS-S, while the 0.370 nm lattice spacing corresponds to the (011) crystal plane of NiWO4. Figure 8 (f)). Furthermore, in Figure 8 In (d, f), zigzag lattice fringes can be observed in local areas, indicating that the T-CZS bulk phase has a twinned structure, and the tight interfacial contact formed with NiWO4 helps to promote the separation and migration of photogenerated carriers and improve photocatalytic performance.
[0068] Figure 10 The N2 adsorption-desorption isotherm in (a) shows that T-CZS-S has a higher specific surface area (86.78 m²). 2 ·g −1 ), approximately T-CZS (18.67m) 2 ·g −1 The specific surface area of T-CZS is 4.5 times that of T-CZS and it exhibits significant mesoporous characteristics. This indicates that T-CZS possesses a richer pore structure and a larger specific surface area, which helps to provide more active sites, thereby enhancing the adsorption and catalytic activity of reactant molecules during photocatalysis. Furthermore, the mesoporous structure reduces mass transfer resistance, facilitating the diffusion of reactants and products, further improving catalytic efficiency. Therefore, compared to T-CZS, T-CZS-S not only provides more active sites but also optimizes carrier migration and reaction kinetics.
[0069] Figure 10 In (b), NiWO4 has a surface potential of −9.0 mV, exhibiting negative charge, while T-CZS-S has a surface potential of +11.0 mV, exhibiting positive charge. The two can self-assemble through electrostatic forces to achieve a tight bond. Figure 10 (c) The WCA of T-CZS-S decreased from 23.9° to 15.1° (6%NiWO4 / T-CZS-S). The smaller water contact angle means that the construction of the heterojunction enhances the surface hydrophilicity of the composite sample, which can promote the adsorption and diffusion of water molecules on the catalyst surface, thereby improving the water dissociation efficiency, providing more reaction sites for photocatalytic reaction, and helping to enhance the interaction between the catalyst and water molecules.
[0070] Figure 11The image shows the XPS spectrum of the sample. Figure 11 In (a), the two characteristic peaks at 161.48 eV (161.13 eV) and 162.88 eV (162.33 eV) correspond to S, respectively. 2- The presence of S2p3 / 2 and S2p1 / 2 orbitals indicates that S mainly exists in the form of sulfides. Figure 11 The binding energies of 1021.73 eV (1021.48 eV) and 1044.83 eV (1044.78 eV) in (b) are attributed to Zn. 2+ The Zn2p3 / 2 and Zn2p1 / 2 orbitals. Figure 11 In (c), the peak signals at 404.93 eV (404.53 eV) and 411.63 eV (411.33 eV) are attributed to the Cd3d5 / 2 and Cd3d3 / 2 orbitals, respectively, which is consistent with the reported Cd values in the literature. 2+ The peak values match.
[0071] Figure 11 In (d), the peak signals of 34.43 eV (34.72 eV) and 36.55 eV (36.85 eV) correspond to the W4f5 / 2 and W4f7 / 2 orbitals, respectively, indicating that W mainly orbits WO4. 2− It exists in the form of. Figure 11 The characteristic peaks at 529.58 eV (529.78 eV), 530.93 eV (531.03 eV), and 532.18 eV (532.68 eV) in (e) belong to lattice oxygen (Olatt), adsorbed oxygen (Oads), and free water in NiWO4, respectively. Figure 11 In (f), the peaks at 854.62 eV (855.04 eV) and 872.17 eV (871.89 eV) correspond to Ni, respectively. 2+ The Ni 2p3 / 2 and Ni 2p1 / 2 orbitals are located therein, while the characteristic peaks at 855.91 eV (856.72 eV) and 873.57 eV (873.71 eV) correspond to Ni. 3+ The composite material contains Ni2p3 / 2 and Ni2p1 / 2 orbitals. Analysis shows that compared to T-CZS-S, the binding energies of Zn, Cd, and S in 6%NiWO4 / T-CZS-S are slightly increased, while the binding energies of W, O, and Ni are slightly decreased compared to NiWO4. The electron density of NiWO4 in the composite sample is increased. This indicates an interaction between NiWO4 and T-CZS-S, leading to charge transfer from T-CZS-S to NiWO4.
[0072] 2. Light absorption and photothermal properties Depend on Figure 12(a) The UV-Vis-NIRDRS plot shows that NiWO4 has strong light absorption capacity. T-CZS-S and T-CZS have similar light absorption characteristics, with a clear absorption band edge at 520 nm. Due to the LSPR effect of NiWO4, the 6% NiWO4 / T-CZS-S composite material also exhibits light absorption capacity in the NIR region, which is beneficial for expanding the spectral response range and enhancing the utilization efficiency of solar energy. Based on the K-M formula, the Eg values of T-CZS-S and NiWO4 are 2.43 and 2.63 eV, respectively. Figure 12 (b)). Figure 12 (c−h) shows the infrared thermographic image of 6% NiWO4 / T-CZS-S. After illumination, the surface temperature of the sample increased from 25.1℃ to 48.1℃. This is because the LSPR effect of NiWO4 enables the composite sample to absorb NIR and generate high-energy "hot electrons" under illumination. These electrons can migrate to the CB of T-CZS to participate in HER. At the same time, the photothermal conversion caused by the LSPR effect can effectively increase the sample surface temperature. The synergistic effect of light and heat energy is beneficial to improving the catalytic performance of the system.
[0073] 3. Hydrogen production and plastic degradation performance Figure 13 In (a), NiWO4 / T-CZS-S r H2 The loading of NiWO4 first increases and then decreases, reaching a minimum at a loading of 6%. r H2 Reaching 141.5 mmol∙h −1 ∙g −1 The values are T-CZS-S (21.3 mmol∙h⁻¹). −1 ∙g −1 ) 6.6 times that of NiWO4 (2.4 mmol∙h −1 ∙g −1 The loading was 59.0 times that of the T-CZS-S nanosheets, indicating that excessive loading may obscure active sites and cause charge migration imbalance. As shown in 7.13(b), the T-CZS-S nanosheets... r H2 (21.3 mmol∙h) −1 ∙g −1 The content is approximately equal to that of T-CZS nanoparticles (13.1 mmol∙h⁻¹). −1 ∙g −1 The 1.6-fold increase in NiWO4 / T-CZS-S indicates that the sheet-like T-CZS-S has an advantage in promoting surface reactions. Furthermore, the 6% NiWO4 / T-CZS-S... r H2 (141.5 mmol∙h) −1 ∙g −1Compared to T-CZS and T-CZS-S, it increased by 9.8 times and 5.6 times respectively, and was also higher than 6% NiWO4 / T-CZS (96.7 mmol∙h⁻¹). −1 ∙g −1 The platy structure of T-CZS-S may be more conducive to the dispersion of NiWO4 and carrier migration. In addition, the hydrogen evolution performance of 6% NiWO4 / T-CZS-S in different sacrificial agents was investigated. Figure 13 (c)), where, compared to PBS (76.8 mmol∙h −1 ∙g −1 ), PET (89.7 mmol∙h) −1 ∙g −1 ), PBAT (82.5 mmol∙h) −1 ∙g −1 PBT (78.3 mmol∙h) −1 ∙g −1 ) and TEOA (129.8 mmol∙h −1 ∙g −1 Sacrificial agent solution, in PLA depolymerization solution sacrificial agent r H2 The highest concentration is due to the fact that lactic acid, a degradation product of PLA, can interact with the active sites on the catalyst surface, rapidly consuming h. + . Figure 13 (d) T-CZS-S modified with different MWO4 in PLA depolymerization solution r H2 6% MWO4 / T-CZS-S r H2 The values were all higher than those of T-CZS-S, indicating that the introduction of MWO4 can improve the catalytic activity of T-CZS-S.
[0074] Figure 14 (a) Cyclic stability test of 6% NiWO4 / T-CZS-S: After three consecutive reaction cycles, the sample performance gradually decreased. After adding 10 mL of sacrificial agent before the fourth cycle, rH2 recovered to its initial level, indicating that 6% NiWO4 / T-CZS-S possesses excellent stability. Figure 14 As can be seen from the XRD pattern in (b), the position and intensity of the diffraction peaks of the catalyst remain basically unchanged before and after the reaction, indicating that the catalyst has good structural stability.
[0075] 4. Photoelectrochemical performance analysis like Figure 15 As shown in (a), the photocurrent density of 6%NiWO4 / T-CZS-S reaches approximately 200 μA·cm. -2The levels were significantly higher than those of T-CZS-S and 6% NiWO4 / T-CZS, indicating that the twinned nanosheet structure and NiWO4 loading can generate more photogenerated electrons. − . Figure 15 (b) shows the transient photocurrent curves of the samples under NIR irradiation. In the figure, NiWO4, 6%NiWO4 / T-CZS, and 6%NiWO4 / T-CZS-S all have photocurrent responses, while T-CZS has no NIR response. The introduction of NiWO4 enables the composite material to promote hydrogen production using NIR, but the increase in NIR wavelength means a decrease in photon energy, so the photocurrent is relatively low under this condition.
[0076] Figure 15 In (c), at 1 mA·cm -2 At the given current density, the hydrogen evolution overpotential of 6%NiWO4 / T-CZS-S (−1.29V vs. SCE) is lower than that of 6%NiWO4 / T-CZS (−1.43V vs. SCE), T-CZS-S (−1.56V vs. SCE), and NiWO4 (−1.89V vs. SCE), indicating that the synergy between NiWO4 loading and the nanosheet structure helps to reduce the hydrogen evolution overpotential of the system and improve catalytic performance. Figure 15 (d) shows the LSV curves of 6% MWO4 / T-CZS-S. The hydrogen evolution overpotentials of the composite samples were all lower than those of T-CZS-S, indicating that the introduction of MWO4 effectively lowered the reaction barrier. Among them, 6% NiWO4 / T-CZS-S had the lowest hydrogen evolution overpotential, thus exhibiting the best hydrogen production activity. Figure 15 The EIS curve in (e) shows that 6% NiWO4 / T-CZS-S has the smallest Nyquist radius of curvature, indicating that both the twinned nanosheet structure and the NiWO4 loading contribute to the transport of photogenerated carriers and reduce charge migration resistance. Simultaneously, the NiWO4 loading weakens the recombination of photogenerated carriers, thereby reducing the fluorescence intensity of the system. Figure 15 (f) indicates that the introduction of NiWO4 helps to improve the charge separation efficiency of the 6%MWO4 / T-CZS-S surface, which is beneficial to promoting the photocatalytic hydrogen evolution kinetics.
[0077] Figure 16 In (a), the corrosion current density of 6% NiWO4 / T-CZS-S is 2.537 × 10⁻⁶. −5 A, higher than other samples, indicates its effective charge transport capability. Figure 16 (b−e) represents the CV curves of the sample at different scan rates. Figure 16(f) shows the linear relationship fitting curve between the current density of the sample and the corresponding scan rate. Based on the curve slope, the Cdl values of NiWO4, T-CZS-S, 6%NiWO4 / T-CZS, and 6%NiWO4 / T-CZS-S are calculated to be 17.85, 32.78, 22.52, and 46.14 μF·cm, respectively. -2 r, calculated per unit specific surface area using ECSA H2 The values were 134.4, 649.8, 4293.9, and 3066.8 mol·h⁻¹. -1 ·g -1 ·F -1 ·cm 2 The composite material has a larger electrochemically active specific surface area, indicating that it has more hydrogen-producing active sites.
[0078] 5. Analysis of the photocatalytic hydrogen production coupled with plastic degradation mechanism because Figure 17 In (a, b), the positive slope of the M-S curve of T-CZS-S indicates it is an n-type semiconductor, while the opposite slope of NiWO4 indicates it is a p-type semiconductor. Tests at different frequencies yielded Efb values of -1.14V and 1.74V for T-CZS-S and NiWO4 (vs. SCE), respectively. Calculations based on the Nernst equation show the CB potential of T-CZS-S to be -0.49V (vs. RHE) and the VB potential of NiWO4 to be 2.39V (vs. RHE). Using the formula E... g =E VB -E CB The VB potential of T-CZS-S was found to be 1.94V, and the CB potential of NiWO4 was −0.24V (vs. RHE). Figure 17 The inverted "V"-shaped M-S curve in (c) shows that 6%NiWO4 / T-CZS-S exhibits both p-type and n-type semiconductor characteristics. Figure 17 The band structure diagram in (d) shows that T-CZS-S and NiWO4 have an interlaced band structure, which is conducive to the construction of an S-type heterojunction.
[0079] EPR characterization was used to indirectly analyze the carrier migration path, and the ·O of the system was detected by DMPO. 2− Signal. After 2 minutes of light exposure, the reaction solution containing T-CZS-S exhibited a ·O signal. 2− Characteristic peaks ( Figure 18 (a) indicates that its CB position (−0.49V) is relative to O2 / ·O 2− The reduction potential (−0.33V) is more negative. In contrast, the CB site of NiWO4 (−0.24V) prevents it from forming ·O. 2− Therefore, ·O was not detected. 2−Signal( Figure 18 (b)). And the 6% NiWO4 / T-CZS-S·O 2− The signal is stronger than that of T-CZS-S ( Figure 18 (c) indicates that the composite sample has a superior O2 reduction ability.
[0080] Using NBT as a trap to detect ·O under illumination 2− concentration( Figure 18 (d−e)), a decrease in absorption intensity indicates that ·O 2− With increased concentration, it was found that 6% NiWO4 / T-CZS-S could produce more O. 2− This is consistent with the EPR detection results. The above phenomenon can be attributed to the strong reducing agent e in 6% NiWO4 / T-CZS-S. − The electrons are retained, providing more electrons to participate in the hydrogen evolution reaction, thus enhancing the efficiency of the reduction reaction.
[0081] Using VASP 5.4.4 software, the electronic structure of semiconductors was calculated based on density functional theory to reveal their catalytic mechanism. The calculation employed the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional under the generalized gradient approximation (GGA), with the Gamma scheme used for Brillouin zone sampling. The computational accuracy was set to 0.04 eV, the energy convergence criterion was 10⁻⁶ eV, and the force convergence criterion was −2 × 10⁻⁶ eV. −2 eV / Å. The estimated band gaps for T-CZS-S and NiWO4 are 1.315 eV and 1.125 eV, respectively. Figure 19 (a, b)). Figure 19 (c, d) are the PDOS plots of T-CZS-S and NiWO4, showing that the electronic structure of both is mainly contributed by p orbitals. The Φ values of T-CZS-S(111) and NiWO4(020) were calculated to be 4.448 eV and 4.611 eV, respectively. Figure 19 (e, f)), the structural model is shown in the illustration. Φ is the difference between the Fermi level and the vacuum level. It can be seen that the EF of T-CZS-S(111) is higher than that of NiWO4(020). When the two are in contact, e − It will spontaneously migrate from T-CZS-S to NiWO4 until EF balance is achieved at the interface.
[0082] Based on the above analysis Figure 20 A possible carrier transfer path between T-CZS-S and NiWO4 is proposed. T-CZS-S is an n-type semiconductor with its EF (electron convexity) adjacent to CB (conductivity, convexity, and ductility), while NiWO4 is a p-type semiconductor with its EF close to VB (conductivity, convexity, and ductility). When the two come into contact, due to the higher EF of T-CZS-S, the electron transport in T-CZS-S... −They will spontaneously migrate to NiWO4 in order to achieve EF balance. NiWO4 gains e − At its interface, negative charges accumulate, causing the energy band to bend downwards. T-CZS-S, due to e − The loss of positive charge causes the energy band to bend upwards. At the same time, a built-in electric field is formed at the NiWO4 / T-CZS-S heterojunction interface, pointing from T-CZS-S towards NiWO4.
[0083] Under illumination, the combined effects of band bending, built-in electric field, and Coulomb force contribute to the relatively weak reduction ability of NiWO4 on CB. − Compared to T-CZS-S, h has a relatively weaker oxidizing ability on VB. + Composite. Simultaneously, the CB of T-CZS-S possesses a strong reducing ability of e. − Effectively preserved, enabling participation in HER H + Reduced to H2. NiWO4 has a strong oxidizing ability on its VB surface. + It can then undergo oxidation reactions with lactic acid and other components of PLA depolymerization to produce small molecule chemicals such as pyruvic acid and acetic acid. Therefore, the charge transfer between T-CZS-S and NiWO4 follows an S-type heterojunction transport mechanism. Furthermore, in NiWO4 / T-CZS-S, the LSPR effect of NiWO4 can excite the generation of "hot electrons," which can overcome the potential barrier and inject CBs into T-CZS-S to participate in the reduction and hydrogen production, achieving efficient utilization of UV−Vis−NIR and enhancing catalytic activity.
[0084] like Figure 21 In the bulk phase of T-CZS-S, the interlaced band structure formed between WZ-CZS and ZB-CZS constructs an S-type homojunction. In summary, the synergistic effect of the LSPR effect and the double S-type heterojunction, the advantages of the sheet-like structure of T-CZS-S, and the effective participation of PLA depolymerization compounds jointly achieve excellent catalytic performance.
[0085] The composite photocatalyst of this invention, under illumination, utilizes the synergistic effect of band bending, built-in electric field, and Coulomb force to promote the reduction of relatively weak e-bands on NiWO4 at CB. − Compared to T-CZS-S, h has a relatively weaker oxidizing ability on VB. + Composite. Simultaneously, the CB of T-CZS-S possesses a strong reducing ability of e. − Effectively preserved, enabling participation in HER H + Reduced to H2. NiWO4 has a strong oxidizing ability on its VB surface. +It can then undergo oxidation reactions with lactic acid and other components of PLA depolymerization to produce small molecule chemicals such as pyruvic acid and acetic acid. Therefore, the charge transfer between T-CZS-S and NiWO4 follows an S-type heterojunction transport mechanism. Furthermore, in NiWO4 / T-CZS-S, the LSPR effect of NiWO4 can excite the generation of "hot electrons," which can overcome the potential barrier and inject CBs into T-CZS-S to participate in the reduction and hydrogen production, achieving efficient utilization of UV−Vis−NIR and enhancing catalytic activity.
[0086] It should be noted that when numerical ranges are mentioned in the claims of this invention, it should be understood that the two endpoints of each numerical range and any value between the two endpoints can be selected. To avoid redundancy, the present invention describes preferred embodiments.
[0087] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.
[0088] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.
Claims
1. A method for preparing a twinned zinc cadmium sulfide nanoplate, characterized in that, Includes the following steps: A zinc source, a diethylenetriamine aqueous solution, and a sulfur source were mixed and subjected to a first solvothermal reaction to obtain a zinc sulfide-diethylenetriamine composite precursor; the ratio of the zinc source, the diethylenetriamine aqueous solution, and the sulfur source was 1 mmol: 30 mL: 1~6 mmol. The zinc sulfide-diethylenetriamine composite precursor, cadmium source, and organic solvent are mixed and subjected to a second solvothermal reaction, in which cadmium ions replace some of the zinc ions in the zinc sulfide-diethylenetriamine composite precursor lattice, yielding the zinc sulfide-cadmium-diethylenetriamine composite precursor; the ratio of the zinc sulfide-diethylenetriamine composite precursor, cadmium source, and organic solvent is 1-2 mmol: 2 mmol: 60 mL. The zinc cadmium sulfide-diethylenetriamine composite precursor was dispersed in water, and a hydrothermal reaction was carried out to remove the diethylenetriamine molecules, resulting in twinned zinc cadmium sulfide nanosheets.
2. The production method according to claim 1, characterized by, The zinc source is zinc acetate dihydrate; The sulfur source is thioacetamide; The cadmium source is cadmium acetate dihydrate.
3. The preparation method according to claim 1, characterized in that, The temperature of the first solvothermal reaction is 140~180℃ and the time is 6~24h; the temperature of the second solvothermal reaction is 140~180℃ and the time is 0.5~16h; the temperature of the hydrothermal reaction is 120~160℃ and the time is 3~6h.
4. Twinized zinc cadmium sulfide nanosheets prepared by the preparation method according to any one of claims 1-3.
5. A composite photocatalyst, characterized in that, It is obtained by loading metal tungstate onto twinned zinc cadmium sulfide nanosheets as described in claim 4.
6. The composite photocatalyst according to claim 5, characterized in that, The mass fraction of metal tungstate in the composite photocatalyst is 2% to 10%.
7. The composite photocatalyst according to claim 5, characterized in that, The metal is selected from any one of nickel, cobalt, silver, bismuth, barium, zinc, cadmium, copper, iron, and manganese.
8. The composite photocatalyst according to claim 5, characterized in that, The preparation steps of the composite photocatalyst are as follows: Metal tungstate and twinned zinc cadmium sulfide nanosheets were separately dispersed in water and mixed to obtain a dispersion. The resulting dispersion was then mixed to obtain a mixed dispersion. The mixed dispersion was heated at 60℃~80℃ until the solvent was completely evaporated to obtain the composite photocatalyst. The mass ratio of metal tungstate to twinned zinc cadmium sulfide nanosheets is 2~10:90~98.
9. The application of the composite photocatalyst according to claim 5 in photocatalytic water splitting for hydrogen production.