Preparation method and application of z-type heterojunction znCdS / nife LDH composite catalyst for hydrogen production by waste plastic photoreforming coupled with water decomposition

Abstract

This invention discloses a method for preparing and applying a Z-type heterojunction ZnCdS / NiFeLDH composite catalyst for hydrogen evolution through photoreforming of waste plastics coupled with water decomposition, relating to the field of photocatalyst technology for hydrogen evolution through water decomposition. The invention involves ultrasonically dispersing NiFeLDH in anhydrous ethanol solution, followed by ultrasonically dispersing ZnCdS nanoparticles; thoroughly stirring the mixture to form a Z-type heterojunction ZnCdS / NiFeLDH through electrostatic interaction; washing the mixture several times by centrifugation with ethanol; and drying the resulting yellow powder to obtain a powdered Z-type heterojunction ZnCdS / NiFeLDH composite catalyst. The preparation method of this invention is simple, the reaction conditions are mild, and it is economical, efficient, and environmentally friendly. The resulting composite catalyst exhibits excellent catalytic performance, efficiently decomposing water to generate hydrogen, and maintains good performance and stability even after multiple cycles of recycling.

Description

Technical Field

[0001] This invention relates to the field of water desorption hydrogen photocatalyst technology, specifically to a method for preparing and applying a Z-type heterojunction ZnCdS / NiFeLDH composite catalyst for hydrogen evolution through water decomposition coupled with photoreforming of waste plastics. Background Technology

[0002] Transforming recalcitrant waste plastics into clean energy and high-value-added chemicals has become a crucial issue in the fields of environmental catalysis and resource recycling. Polylactic acid (PLA), a typical bio-based biodegradable plastic, can hydrolyze and degrade under specific conditions, but in real-world environments, it may exhibit slow degradation and high end-of-life disposal costs due to differences in crystallinity, additive systems, and water conditions. Meanwhile, hydrogen energy is considered a key carrier for future low-carbon energy systems, and its green production still heavily relies on efficient conversion pathways driven by renewable energy. Therefore, developing visible-light-responsive photocatalytic systems to simultaneously achieve resource-based conversion and hydrogen production from waste plastics under mild conditions using solar energy not only aligns with the technological direction of low energy consumption and low emissions but also provides new solutions and engineering possibilities for the closed-loop cycle of plastics "from waste to energy, from waste to chemical." In recent years, photocatalytic reforming has received widespread attention as a cutting-edge direction connecting solid waste treatment and clean energy production. Existing research has confirmed that semiconductor photocatalysts can generate electron-hole pairs under light irradiation. The holes can oxidize organic substrates such as alcohols, organic acids, and polymer hydrolysis products, while the photogenerated electrons can reduce water to produce hydrogen, thus achieving a redox coupling reaction. This technology relies on the photoelectric conversion effect of semiconductor materials, using the absorption of photon energy to cause electrons to jump from the valence band to the conduction band, forming electron-hole pairs with strong redox activity, thereby driving the water splitting reaction to produce hydrogen. Therefore, developing catalytic materials with high photocatalytic activity, strong stability, and the ability to fully utilize visible light response has become a core research topic for promoting the practical application of photocatalytic hydrogen production technology.

[0003] Metal sulfide semiconductors are considered ideal candidates for visible light-driven hydrogen evolution reactions due to their tunable narrow bandgap, broad spectral response, and designable surface electronic structure. However, under illumination, the photogenerated holes in MS interact with the lattice S... 2- An auto-oxidation reaction occurs between them, leading to S 2-Oxidized to elemental sulfur, the precipitated sulfur layer not only covers active sites but also induces lattice vacancies to extend into the bulk phase, thereby destroying crystal integrity and significantly reducing photocatalytic efficiency and stability. The photocorrosion problem of CdS can completely destroy its structure, from the surface to the interior, accompanied by sulfur oxidation and cadmium loss, leading to complete particle deactivation. To suppress this self-oxidation pathway, heterovalent doping, defect chemistry, or heterostructure construction are commonly used to address the photocorrosion problem. In contrast, ZnS exhibits superior resistance to photocorrosion due to its higher Zn-S bond energy, but its wide bandgap almost completely blocks visible photons, severely limiting spectral utilization. By constructing Zn... x Cd 1-x S-materials can introduce high-bond-energy Zn-S units while maintaining the visible light absorption edge, forming a "narrow bandgap-high bond energy" synergistic framework, thereby simultaneously optimizing photon capture and photostability.

[0004] Patent application CN121695891A, entitled "Double-Vacancy ZnCdS Solid Solution Photocatalyst, Its Preparation Method and Application," describes the preparation of powdered ZnCdS solid solution under low-temperature water bath conditions. It utilizes NaOH to establish an alkaline reducing environment, successfully constructing surface defects in the ZnCdS solid solution. Ultrasound is then used to further accelerate and solidify the formation of these surface defects. While ultrasound does indeed facilitate the separation of vacancies and atoms within the ZnCdS catalyst, potentially improving its performance to some extent, significant breakthroughs in hydrogen production are unlikely. This may still be related to electron-hole pair recombination. Therefore, there is an urgent need for a method and application of a Z-type heterojunction ZnCdS / NiFeLDH composite catalyst for photoreforming of waste plastics coupled with water splitting and hydrogen evolution to address this problem. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing and applying a Z-type heterojunction ZnCdS / NiFeLDH composite catalyst for photo-reforming of waste plastics coupled with water decomposition and hydrogen evolution, so as to improve the photocatalytic activity of water decomposition and hydrogen evolution and generate hydrogen gas efficiently.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a Z-type heterojunction ZnCdS / NiFeLDH composite catalyst for photo-reforming of waste plastic coupled with water decomposition and hydrogen evolution, comprising the following steps: adding NiFeLDH to anhydrous ethanol solution and ultrasonically dispersing it evenly, then adding ZnCdS nanoparticles and ultrasonically dispersing them evenly; thoroughly stirring the mixture to form a Z-type heterojunction ZnCdS / NiFeLDH through electrostatic interaction; centrifuging and washing with ethanol several times; drying the resulting yellow powder to obtain a powdered Z-type heterojunction ZnCdS / NiFeLDH composite catalyst;

[0007] ZnCdS nanoparticles were prepared by hydrothermal synthesis of zinc-based compounds, cadmium-based compounds, and sulfur-based compounds in the required atomic ratio; NiFeLDH was prepared by hydrothermal synthesis of nickel-based compounds and iron-based compounds in the designed ratio.

[0008] Preferably, the molar ratio of zinc atoms, cadmium atoms and sulfur atoms in the above ZnCdS nanoparticles is 1:1:1; and the molar ratio of nickel to iron in the nickel source compound and iron source compound is 9:1.

[0009] Preferably, the zinc source compound is zinc acetate dihydrate, the cadmium source compound is cadmium acetate dihydrate, the sulfur source compound is thioacetamide, the nickel source compound is nickel nitrate hexahydrate, and the iron source compound is ferric nitrate nonahydrate; the mass ratio of the zinc source compound to NiFeLDH used in the ZnCdS nanoparticle preparation process is (3.3~20):1.

[0010] Optionally, the preparation method of ZnCdS nanoparticles includes: adding sufficient zinc source compound, sufficient cadmium source compound, excess sulfur source compound and sufficient triethylene glycol into a container and stirring thoroughly; after stirring, the mixture is subjected to hydrothermal reaction at 200℃; after the reaction is completed, centrifugation and washing with ethanol several times are performed, and the precipitate is vacuum dried to obtain ZnCdS nanoparticles.

[0011] Optionally, the preparation method of NiFeLDH includes: adding a nickel source compound, an iron source compound, sufficient urea and sufficient deionized water into a container and ultrasonically dispersing until uniform, so that the total concentration of metal ions in the resulting mixed solution is 20 mM; subjecting the mixed solution to a hydrothermal reaction at 150℃, allowing it to stand and age in the mother liquor after the reaction is complete, centrifuging, washing with water several times and washing with ethanol once after aging, and drying the resulting powder to obtain NiFeLDH.

[0012] In the preferred method for preparing NiFeLDH described above, the mass ratio of ZnCdS to NiFeLDH in the Z-type heterojunction ZnCdS / NiFeLDH composite catalyst preparation process is 50:(2.5~15).

[0013] Optionally, the mixture is stirred at 600 rpm / min for 8 hours using a magnetic stirrer, and the resulting yellow powder is dried in a vacuum drying oven at 60°C.

[0014] A Z-type heterojunction ZnCdS / NiFeLDH composite catalyst for hydrogen evolution by photo-reforming of waste plastic coupled with water splitting using the above preparation method.

[0015] The above-mentioned Z-type heterojunction ZnCdS / NiFeLDH composite catalyst was applied to the photo-reforming of waste plastics coupled with water splitting to generate hydrogen, using PLA plastic particle hydrolysis solution as a sacrificial reagent. The catalytic hydrogen production rate of the composite catalyst reached 80 mmol g.-1 h -1 above.

[0016] Preferably, the Z-type heterojunction ZnCdS / NiFeLDH composite catalyst is reused after each use in the photo-reforming of waste plastics to couple water splitting to generate hydrogen. After centrifugation, washing with ethanol, and drying, the hydrogen yield of the fifth use can reach 97.53% of the first use.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] 1. In this Z-type heterojunction ZnCdS / NiFeLDH composite catalyst for hydrogen evolution by photoreforming of waste plastic coupled with water splitting, the presence of NiFeLDH makes the stacked ZnCdS nanoparticles more uniformly dispersed, effectively increasing the specific surface area of ​​the material. This significantly shortens the diffusion path of photogenerated carriers, exposes a large number of active sites, and effectively suppresses electron-hole recombination, which is beneficial to improving the photocatalytic hydrogen evolution activity. This composite photocatalyst is low in cost, controllable and easy to operate, and can efficiently generate hydrogen.

[0019] 2. In the application of the Z-type heterojunction ZnCdS / NiFeLDH composite catalyst for hydrogen evolution by photo-reforming of waste plastic coupled with water splitting, the composite catalyst showed high efficiency in hydrogen evolution and stability for repeated use, which greatly improved the upper limit of the catalytic performance of ZnCdS and expanded its future possibilities. Moreover, the sacrificial reagent is a hydrolysis solution of PLA material, which can simultaneously realize the resource utilization of waste plastic and the preparation of green hydrogen energy.

[0020] 3. The preparation method of the Z-type heterojunction ZnCdS / NiFeLDH composite catalyst for photo-reforming of waste plastic coupled with water decomposition and hydrogen evolution: Both nickel-iron layered double hydroxide and ZnCdS are prepared by hydrothermal synthesis. Then, ZnCdS nanoparticles are composited on the surface of nickel-iron layered double hydroxide using anhydrous ethanol as solvent. The two form a Z-type heterojunction through electrostatic interaction. The preparation method is mild, simple, low cost, controllable and easy to operate, and the obtained photocatalyst has strong stability. Attached Figure Description

[0021] Figure 1 The X-ray diffraction patterns of ZnCdS / NiFeLDH composite catalysts with different loadings in the embodiments of the present invention are shown below.

[0022] Figure 2 A scanning electron microscope image of the ZnCdS nanoparticles prepared in step 1 of Example 1 of this invention;

[0023] Figure 3 A scanning electron microscope image of the NiFeLDH nickel-iron layered double hydroxide prepared in step 2 of Example 1 of this invention;

[0024] Figure 4 Scanning electron microscope image of the Z-type heterojunction ZnCdS / NiFeLDH composite catalyst prepared in Example 2 of this invention;

[0025] Figure 5 The hydrogen generation rate diagram is shown for the Z-type heterojunction ZnCdS / NiFeLDH composite catalyst prepared in Example 2 of this invention.

[0026] Figure 6 This is a schematic diagram of the hydrogen evolution cycle performance of the Z-type heterojunction ZnCdS / NiFeLDH composite catalyst prepared in Example 2 of the present invention. Detailed Implementation

[0027] To enable the ZnCdS catalyst to fully exert its hydrogen evolution performance, this invention conceived and designed numerous schemes. After countless experiments, adjustments, and scheme modifications, a method for preparing a Z-type heterojunction ZnCdS / NiFeLDH composite catalyst for hydrogen evolution through waste plastic photoreforming coupled with water splitting was finally obtained. This method yields a composite photocatalyst with good stability and catalytic performance, capable of efficiently splitting water to generate hydrogen. The specific preparation method includes the following:

[0028] NiFeLDH was added to anhydrous ethanol solution and ultrasonically dispersed evenly. Then, ZnCdS nanoparticles were added and ultrasonically dispersed evenly. The mixture was stirred thoroughly to form a Z-type heterojunction ZnCdS / NiFeLDH through electrostatic interaction. The mixture was washed several times by centrifugation with ethanol, and the resulting yellow powder was dried to obtain a powdered Z-type heterojunction ZnCdS / NiFeLDH composite catalyst. Optionally, the stirring was carried out using a magnetic stirrer at a speed of 600 rpm / min for 8 hours, and the resulting yellow powder was dried in a vacuum drying oven at 60°C.

[0029] ZnCdS nanoparticles were prepared by hydrothermal synthesis of zinc-based compounds, cadmium-based compounds, and sulfur-based compounds in the required atomic ratio; NiFeLDH was prepared by hydrothermal synthesis of nickel-based compounds and iron-based compounds in the designed ratio.

[0030] In a preferred embodiment, the molar ratio of zinc, cadmium, and sulfur atoms in the ZnCdS nanoparticles is 1:1:1; the molar ratio of nickel to iron in the nickel and iron source compounds is 9:1. Further optionally, the zinc source compound is zinc acetate dihydrate, the cadmium source compound is cadmium acetate dihydrate, the sulfur source compound is thioacetamide, the nickel source compound is nickel nitrate hexahydrate, and the iron source compound is ferric nitrate nonahydrate; the mass ratio of the zinc source compound to NiFeLDH used in the ZnCdS nanoparticle preparation process can be further preferably (3.3–20):1.

[0031] For reference, if preparing ZnCdS nanoparticles yourself, the following hydrothermal method can be used: Add sufficient zinc source compound, sufficient cadmium source compound, excess sulfur source compound and sufficient triethylene glycol to a container and stir thoroughly. After stirring, the mixture is subjected to hydrothermal reaction at 200°C. After the reaction, centrifuge and wash several times with ethanol, and vacuum dry the precipitate to obtain ZnCdS nanoparticles.

[0032] For reference, if preparing NiFeLDH yourself, the following hydrothermal method can be used: Add a nickel source compound, an iron source compound, sufficient urea, and sufficient deionized water to a container and sonicate until uniformly dispersed. The total metal ion concentration of the resulting mixed solution is 20 mM. The mixed solution is then subjected to a hydrothermal reaction at 150°C. After the reaction, the solution is allowed to stand and age in the mother liquor. After aging, the solution is centrifuged, washed several times with water, and washed once with ethanol. The resulting powder is then dried to obtain NiFeLDH. This invention will test the hydrogen evolution performance of the prepared catalyst using the above NiFeLDH preparation method through several examples. Specifically, in the following examples, during the preparation of the Z-type heterojunction ZnCdS / NiFeLDH composite catalyst, the mass ratio of ZnCdS to NiFeLDH is 50:(2.5~15).

[0033] The following examples further illustrate the content of the present invention, but these examples are not all of the embodiments of the present invention, and the scope of protection of the present invention should not be absolutely limited thereto.

[0034] For ease of description and distinction, the following uses ZnCdS / NiFeLDH-X to describe the mass ratio of ZnCdS to NiFeLDH used in the preparation of the composite catalyst, where X represents a mass ratio of 50:X.

[0035] Example 1:

[0036] Step 1: Preparation of ZnCdS nanoparticles

[0037] 0.6146 g of zinc acetate dihydrate, 0.7463 g of cadmium acetate dihydrate, 0.525 g of thioacetamide, and 59.5 mL of triethylene glycol were added to a flask and stirred continuously for 30 minutes, resulting in a pale yellow solution. After stirring, the reaction solution was transferred to a 100 mL autoclave lined with polytetrafluoroethylene and placed in an oven for hydrothermal heating at 200 °C for 12 hours. After the reaction, the solution was transferred to a 50 mL centrifuge tube, washed three times with ethanol, and a yellow precipitate was obtained. The yellow precipitate was then placed in a vacuum drying oven and dried under vacuum at 60 °C for 12 hours to obtain yellow ZnCdS nanoparticles.

[0038] Step 2: Preparation of NiFeLDH (NiFe-Iron Layered Hydroxide)

[0039] 0.3141 g of nickel nitrate hexahydrate, 0.0485 g of ferric nitrate nonahydrate, 0.1261 g of urea, and 60 mL of deionized water were added to a beaker. The beaker was ultrasonicated for 20 minutes to ensure uniform dispersion of nickel nitrate hexahydrate and ferric nitrate nonahydrate in the deionized water. The mixture was transferred to a stainless steel autoclave with a polytetrafluoroethylene liner. The autoclave was placed in an oven and hydrothermally heated at 150°C for 48 hours. After the hydrothermal reaction, the mixture was allowed to stand and age in the mother liquor for 48 hours. After aging, the solution was transferred to 50 mL centrifuge tubes, washed three times with water and once with ethanol. The resulting yellow-brown powder was dried in a drying oven at 50°C.

[0040] Step 3: Preparation of Z-type heterojunction ZnCdS / NiFeLDH composite catalyst

[0041] Add 30 mL of anhydrous ethanol solution and 2.5 mg of NiFeLDH nickel-iron layered double hydroxide prepared in step 2 to a 50 mL beaker. Mix the mixture and sonicate for 30 min to disperse it evenly. Then add 50 mg of ZnCdS nanoparticles prepared in step 1. Mix the mixture and sonicate for 30 min to disperse it evenly. Add a magnetic stir bar to transfer the beaker to a stirring table and stir at 600 rpm / min for 8 hours.

[0042] Step 4: Wash and dry

[0043] The Z-type heterojunction ZnCdS / NiFeLDH-2.5 composite catalyst powder obtained in step 3 was washed repeatedly by centrifugation with anhydrous ethanol, and then the powder sample was vacuum dried to obtain the Z-type heterojunction ZnCdS / NiFeLDH-2.5 composite catalyst.

[0044] Example 2

[0045] Step 1: Preparation of ZnCdS nanoparticles

[0046] The preparation process in this step is the same as in Example 1.

[0047] Step 2: Preparation of NiFeLDH (NiFe-Iron Layered Hydroxide)

[0048] The preparation process in this step is the same as in Example 1.

[0049] Step 3: Preparation of Z-type heterojunction ZnCdS / NiFeLDH-5 composite catalyst

[0050] Add 30 ml of anhydrous ethanol solution and 5 mg of NiFeLDH nickel-iron layered double hydroxide prepared in step 2 to a 50 mL beaker. Mix and sonicate the mixture for 30 min to disperse it evenly. Then add 50 mg of ZnCdS nanoparticles prepared in step 1. Mix and sonicate the mixture for 30 min to disperse it evenly. Add a magnetic stir bar to transfer the beaker to a stirring table and stir at 600 rpm / min for 8 hours.

[0051] Step 4: Wash and dry

[0052] The preparation process in this step is the same as in Example 1.

[0053] Example 3:

[0054] Step 1: Preparation of ZnCdS nanoparticles

[0055] The preparation process in this step is the same as in Example 1.

[0056] Step 2: Preparation of NiFeLDH (NiFe-Iron Layered Hydroxide)

[0057] The preparation process in this step is the same as in Example 1.

[0058] Step 3: Preparation of Z-type heterojunction ZnCdS / NiFeLDH-10 composite catalyst

[0059] Add 30 ml of anhydrous ethanol solution and 10 mg of the NiFeLDH nickel-iron layered double hydroxide prepared in step 2 to a 50 mL beaker. Mix and sonicate the mixture for 30 min to disperse it evenly. Then add 50 mg of the ZnCdS nanoparticles prepared in step 1. Mix and sonicate the mixture for 30 min to disperse it evenly. Add a magnetic stir bar to transfer the beaker to a stirring table and stir at 600 rpm / min for 8 hours.

[0060] Step 4: Wash and dry

[0061] The preparation process in this step is the same as in Example 1.

[0062] Example 4

[0063] Step 1: Preparation of ZnCdS nanoparticles

[0064] The preparation process in this step is the same as in Example 1.

[0065] Step 2: Preparation of NiFeLDH (NiFe-Iron Layered Hydroxide)

[0066] The preparation process in this step is the same as in Example 1.

[0067] Step 3: Preparation of Z-type heterojunction ZnCdS / NiFeLDH-15 composite catalyst

[0068] Add 30 ml of anhydrous ethanol solution and 15 mg of the NiFeLDH nickel-iron layered double hydroxide prepared in step 2 to a 50 mL beaker. Mix and sonicate the mixture for 30 min to disperse it evenly. Then add 50 mg of the ZnCdS nanoparticles prepared in step 1. Mix and sonicate the mixture for 30 min to disperse it evenly. Add a magnetic stir bar to transfer the beaker to a stirring table and stir at 600 rpm / min for 8 hours.

[0069] Step 4: Wash and dry

[0070] The preparation process in this step is the same as in Example 1.

[0071] Hydrogen evolution performance test

[0072] The photocatalytic hydrogen evolution performance of the Z-type heterojunction ZnCdS / NiFeLDH-X composite catalysts prepared in Examples 1-5 and the catalysts in Comparative Examples 1-2 using only ZnCdS and NiFeLDH as catalysts was tested under the same time and light intensity. Specifically, 5 mg of photocatalyst and 6 mL of aqueous solution from the hydrolysis of PLA plastic particles were added to the photocatalytic reactor. The reactor was evacuated for 30 min to maintain the system under vacuum. The reactor temperature was maintained at 25°C using a reflux condenser, and the sealed reactor was irradiated with a 300 W xenon lamp (MC-XF300, λ > 420 nm). During the photocatalytic hydrogen evolution process, 1 mL of gas was extracted from the reactor every 0.5 h, and the hydrogen production was detected and recorded using gas chromatography. Before the cycle stability test, the system was evacuated to remove residual gas. The test results are shown in the table below.

[0073] Hydrogen evolution performance test results

[0074] project Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 <![CDATA[Hydrogen production amount mmol g -1 / h]]> 32.424 80.816 55.406 41.537 17.616 0.002

[0075] The performance test results of the above photocatalytic water splitting for hydrogen show that the Z-type heterojunction ZnCdS / NiFeLDH-5 composite catalyst of this invention can generate up to 80.816 mmol g of hydrogen per hour through photocatalytic water splitting. -1 It is ZnCdS (17.616 mmol g) -1 h -1 ) and NiFeLDH (0.002 mmol g) -1 h -1The hydrogen evolution performance is 4.6 and 40408 times that of the original performance, which is a significant improvement. It can generate hydrogen gas efficiently, which far exceeds the hydrogen evolution capacity that ZnCdS catalysts can achieve using general methods.

[0076] In addition, the Z-type heterojunction ZnCdS / NiFeLDH composite catalyst of the present invention can be reused. After each use for 2 hours, the catalyst is taken out, centrifuged, washed with ethanol and dried, and then used for photocatalytic water evolution hydrogen release under the same conditions as above. The operation is repeated, and after five cycles, the hydrogen evolution performance is retained to 97.53% of the first time.

[0077] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

[0078] Any aspects of this invention not described in detail are well-known to those skilled in the art.

Claims

1. A method for preparing a Z-type heterojunction ZnCdS / NiFeLDH composite catalyst for photo-reforming of waste plastics coupled with water splitting and hydrogen evolution, characterized in that, The process includes the following: NiFeLDH is added to anhydrous ethanol solution and ultrasonically dispersed until uniform; then ZnCdS nanoparticles are added and ultrasonically dispersed until uniform. The mixture was thoroughly stirred to form a Z-type heterojunction ZnCdS / NiFeLDH through electrostatic interaction. After being washed several times by centrifugation with ethanol, the resulting yellow powder was dried to obtain a powdered Z-type heterojunction ZnCdS / NiFeLDH composite catalyst. ZnCdS nanoparticles were prepared by hydrothermal synthesis of zinc-based compounds, cadmium-based compounds, and sulfur-based compounds in the required atomic ratio; NiFeLDH was prepared by hydrothermal synthesis of nickel-based compounds and iron-based compounds in the designed ratio.

2. The preparation method of the Z-type heterojunction ZnCdS / NiFeLDH composite catalyst for photo-reforming of waste plastics coupled with water splitting and hydrogen evolution according to claim 1, characterized in that: The molar ratio of zinc, cadmium, and sulfur atoms in the ZnCdS nanoparticles is 1:1:1; the molar ratio of nickel to iron in the nickel source compound and iron source compound is 9:

1.

3. The preparation method of the Z-type heterojunction ZnCdS / NiFeLDH composite catalyst for photo-reforming of waste plastics coupled with water splitting and hydrogen evolution according to claim 2, characterized in that: The zinc source compound is zinc acetate dihydrate, the cadmium source compound is cadmium acetate dihydrate, the sulfur source compound is thioacetamide, the nickel source compound is nickel nitrate hexahydrate, and the iron source compound is ferric nitrate nonahydrate; the mass ratio of the zinc source compound to NiFeLDH used in the ZnCdS nanoparticle preparation process is (3.3~20):

1.

4. A method for preparing a Z-type heterojunction ZnCdS / NiFeLDH composite catalyst for photo-reforming of waste plastics coupled with water splitting and hydrogen evolution according to any one of claims 1 to 3, characterized in that, The method for preparing ZnCdS nanoparticles includes: adding sufficient zinc source compound, sufficient cadmium source compound, excess sulfur source compound and sufficient triethylene glycol into a container and stirring thoroughly; after stirring, the mixture is subjected to hydrothermal reaction at 200°C; after the reaction, centrifugation and washing with ethanol several times are performed, and the precipitate is vacuum dried to obtain ZnCdS nanoparticles.

5. A method for preparing a Z-type heterojunction ZnCdS / NiFeLDH composite catalyst for photo-reforming of waste plastics coupled with water splitting and hydrogen evolution according to any one of claims 1 to 3, characterized in that, The preparation method of NiFeLDH includes: adding a nickel source compound, an iron source compound, sufficient urea and sufficient deionized water into a container and ultrasonically dispersing until uniform, the total concentration of metal ions in the resulting mixed solution is 20 mM; hydrothermally reacting the mixed solution at 150℃, aging it in the mother liquor after the reaction is completed, centrifuging, washing with water several times and washing with ethanol once after aging, and drying the resulting powder to obtain NiFeLDH.

6. The preparation method of the Z-type heterojunction ZnCdS / NiFeLDH composite catalyst for photo-reforming of waste plastics coupled with water splitting and hydrogen evolution according to claim 5, characterized in that: In the preparation process of the Z-type heterojunction ZnCdS / NiFeLDH composite catalyst, the mass ratio of ZnCdS to NiFeLDH is 50:(2.5~15).

7. The preparation method of the Z-type heterojunction ZnCdS / NiFeLDH composite catalyst for photo-reforming of waste plastics coupled with water splitting and hydrogen evolution according to claim 1, characterized in that: The stirring was performed using a magnetic stirrer at a speed of 600 rpm / min for 8 hours, and the resulting yellow powder was dried in a vacuum drying oven at 60°C.

8. A Z-type heterojunction ZnCdS / NiFeLDH composite catalyst for hydrogen evolution by photo-reforming of waste plastic coupled with water splitting using any one of claims 1 to 7.

9. The application of the Z-type heterojunction ZnCdS / NiFeLDH composite catalyst as described in claim 8 in the coupled water splitting of waste plastic photo-reforming to generate hydrogen, characterized in that: Using PLA plastic particle hydrolysis solution as a sacrificial reagent, the composite catalyst can achieve a hydrogen production rate of 80 mmol g. -1 h -1 above.

10. The application according to claim 9, characterized in that: The Z-type heterojunction ZnCdS / NiFeLDH composite catalyst is used to generate hydrogen from water through photo-reforming of waste plastics. After centrifugation, washing with ethanol, and drying, it can be reused. The hydrogen yield of the fifth use can reach 97.53% of the first use.

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