Preparation method of Zn0. 3Cd0. 7S (at) CFR heterojunction photocatalyst

Abstract

The invention discloses a preparation method of a Zn0. 3Cd0. 7S (at) CFR heterojunction photocatalyst, which comprises the following steps: firstly, preparing a Zn0. 3Cd0. 7S catalyst by a hydrothermal method, and dispersing the Zn0. 3Cd0. 7S catalyst in ultrapure water; then, catechol, ammonia water and formaldehyde are sequentially added into the dispersion liquid, CFR evenly grows on the surface of Zn0. 3Cd0. 7S through a hydrothermal reaction, a coating layer is formed, and a final product is obtained after washing and drying. The preparation method is simple, the process is easy to control, and the prepared photocatalyst shows excellent H2O2 yield and good cycle stability under the condition that a sacrificial agent is not added.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic preparation of H2O2, and relates to a Zn 0.3 Cd 0.7 Preparation method of S@CFR heterojunction photocatalyst. Background Technology

[0002] Hydrogen peroxide (H2O2), as a green, efficient, and environmentally friendly multifunctional oxidant, has been widely used in chemical, medical, energy, and environmental protection fields. With the advancement of global sustainable development goals, the demand for H2O2 is expected to continue to grow. The anthraquinone process is currently a relatively mature production technology, but the process is complex, requires a large amount of energy input, and is often accompanied by high pollution problems. Therefore, there is an urgent need to develop green, clean, and sustainable alternative technologies. Solar-driven photocatalytic H2O2 production relies solely on solar energy, water, and oxygen to achieve green synthesis of H2O2, possessing the dual characteristics of "zero carbon energy input" and "mild reaction conditions," which better aligns with the requirements of economic, environmental, and sustainable development.

[0003] Among many photocatalysts, Zn x Cd 1-x Zn(II) exhibits excellent photocatalytic potential due to its tunable band structure, superior visible light response, strong reducing properties, and good electron mobility. However, in practical applications, it is still constrained by some key issues, such as insufficient O2 adsorption activity and mismatch between electron and proton transfer kinetics, which limit the overall reaction process. Therefore, promoting the effective separation and migration of photogenerated electrons and holes, enhancing the adsorption and activation capacity of O2, and regulating the surface proton microenvironment are crucial for improving the photocatalytic activity of Zn(II). x Cd 1-x The efficiency and stability of H2O2 generation in S-based photocatalysts are crucial. Furthermore, existing Zn... x Cd 1-x The S photocatalytic system still faces the following scientific problems that urgently need to be solved: First, the heterojunction interface has poor contact quality, which hinders carrier transport; second, a single modification strategy is difficult to achieve synergistic optimization of efficient separation and migration of photogenerated carriers and matching of interfacial proton supply kinetics; third, the photocatalytic system has poor stability in long-term operation and is prone to photocorrosion, which affects its recycling performance.

[0004] Based on this, the present invention achieves efficient synergistic optimization of surface reaction pathways and active sites by constructing an organic-inorganic coating interface, thereby significantly improving Zn x Cd 1-x The photocatalytic performance of S photocatalysts. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a Zn0.3 Cd 0.7 A method for preparing S@CFR heterojunction photocatalysts, which first involves preparing Zn via a hydrothermal method. 0.3 Cd 0.7 S catalyst was dispersed in ultrapure water; then catechol, ammonia, and formaldehyde were added sequentially to the dispersion, and CFR was achieved in Zn via a hydrothermal reaction. 0.3 Cd 0.7 The S surface grows uniformly and forms a coating layer. After washing and drying, the final product is obtained. The preparation method of this invention is simple and the process is easy to control. The photocatalyst obtained exhibits excellent H2O2 yield and good cycle stability without the addition of sacrificial agents.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A type of Zn 0.3 Cd 0.7 The preparation method of S@CFR heterojunction photocatalyst is carried out in the following order: S1. Preparation of Zn using a hydrothermal method 0.3 Cd 0.7 S catalyst S11. Place zinc acetate and cadmium acetate in a 40 mL mixture of deionized water and ethylenediamine, with a volume ratio of deionized water to ethylenediamine of 1:1. Stir at room temperature for 20-30 min, then add thioacetamide and continue stirring for 10-15 min to obtain the precursor. S12. The precursor is placed in a hydrothermal reactor for hydrothermal reaction. After cooling, the precipitate is collected by centrifugation. The precipitate is washed 3-5 times with deionized water and anhydrous ethanol, respectively. After drying, it is ground to 100-200 mesh to obtain bright yellow Zn. 0.3 Cd 0.7 S powder, i.e., Zn 0.3 Cd 0.7 S catalyst; S2. Preparation of Zn using a hydrothermal method 0.3 Cd 0.7 S@CFR heterojunction photocatalyst Zn 0.3 Cd 0.7 The S catalyst was ultrasonically dispersed in ultrapure water, and catechol, ammonia, and formaldehyde were added sequentially. After mixing thoroughly, the mixture was hydrothermally reacted at 140-160℃ for 6-8 h. After cooling, the precipitate was collected by centrifugation, washed 3-5 times with deionized water and anhydrous ethanol, respectively, dried, and ground to 100-200 mesh to obtain Zn. 0.3 Cd 0.7 S@CFR heterojunction photocatalyst.

[0007] As a limitation of the present invention, in step S11, the molar ratio between zinc acetate, cadmium acetate, and thioacetamide is 0.3:0.7:1.25.

[0008] As another limitation of the present invention, in step S12, the temperature of the hydrothermal reaction is 200-205°C and the time is 22-24 h.

[0009] As a third limitation of the present invention, in step S12, the drying temperature is 60-70°C and the time is 24-30 h.

[0010] As a fourth limitation of the present invention, in step S2, the Zn 0.3 Cd 0.7 The mass ratio of catalyst S to catechol is 5:(1-3).

[0011] As a fifth limitation of the present invention, in step S2, the mass-to-volume ratio of catechol to ammonia is (40-120):(24-72) mg / uL; and the mass fraction of ammonia is 25-28 wt.%.

[0012] As a sixth limitation of the present invention, in step S2, the mass-to-volume ratio of catechol to formaldehyde is (40-120):(60-180) mg / uL; and the formaldehyde is an aqueous solution of formaldehyde with a mass fraction of 37 wt.%.

[0013] In this invention, Zn 0.3 Cd 0.7 The mass-to-volume ratio of S catalyst to catechol to ammonia and formaldehyde affects the growth thickness of the CFR layer. Within this ratio range, catechol and formaldehyde can be mixed in Zn... 0.3 Cd 0.7 The S surface undergoes a condensation reaction, which is conducive to the formation of a continuous, dense, and controllable-thickness CFR coating layer; if Zn 0.3 Cd 0.7 If the mass ratio of S catalyst to CFR precursor is greater than this range, the CFR precursor will be relatively insufficient and unable to completely cover Zn. 0.3 Cd 0.7 S-surfaces can easily lead to discontinuous or incomplete CFR layer growth, thereby reducing interfacial charge transport efficiency; if Zn 0.3 Cd 0.7 If the mass ratio of S catalyst to CFR precursor is less than this range, then the CFR precursor is in relative excess, which easily leads to an imbalance in Zn. 0.3 Cd 0.7 Excessive condensation occurs on the S surface, forming an excessively thick CFR layer, which inhibits efficient light transmission and increases carrier transport resistance.

[0014] As a seventh limitation of the present invention, in step S2, the drying temperature is 60-70°C and the time is 24-30h.

[0015] As a final limitation of the present invention, the obtained Zn 0.3 Cd 0.7 The S@CFR heterojunction photocatalyst exhibits a core-shell structure with uniform thickness.

[0016] This invention uses Zn 0.3 Cd 0.7 A CFR coating layer rich in catechol groups was constructed on the S surface to prepare a Zn alloy that integrates continuous proton supply, charge transport channel, and structural stability protection barrier. 0.3 Cd 0.7 The S@CFR composite catalyst achieves synergistic coupling of multiple functions on a single catalyst. On one hand, Zn... 0.3 Cd 0.7 The tight heterojunction interface formed between S and CFR drives the directional migration of photogenerated electrons to the CFR surface, which not only effectively inhibits electron-hole recombination but also ensures that electrons can continuously participate in the surface reduction reaction. On the other hand, the highly retained catechol groups in CFR exhibit multifunctional integrated characteristics in this composite system: (1) catechol groups can act as reaction sites for O2 adsorption and activation, participate in the two-electron oxygen reduction reaction, and promote the generation of H2O2; (2) the enrichment of photogenerated electrons on the CFR surface induces the catechol groups to undergo a reversible deprotonation process of proton-electron coupling, making them act as dynamic proton donors and effectively regulate the proton microenvironment on the catalyst surface. Thus, O2 activation and proton supply occur synergistically at the same spatial site, significantly enhancing the kinetics of the two-electron oxygen reduction reaction. In addition, the -CH2- motif in CFR constructs a continuous electron transport channel through bridging, promoting the rapid migration of electrons along the resin skeleton; at the same time, the presence of this bridging structure significantly enhances the structural integrity and stability of the CFR coating layer, making Zn 0.3 Cd 0.7 S can effectively suppress photocorrosion during the reaction process, thus providing structural protection for the long-term and stable operation of this synergistic mechanism.

[0017] The above-mentioned technical solution of the present invention is a whole in which each step is closely related and mutually influential, and together they determine the morphological characteristics and performance of the product.

[0018] The above technical solution has the following advantages or beneficial effects: 1. This invention successfully applied Zn 0.3 Cd 0.7A CFR coating layer rich in catechol groups was constructed in situ on the S surface. This active layer has multiple functions, including catalytic active interface, promoting charge transport, and protective barrier. It can simultaneously promote the effective separation and migration of photogenerated electrons and holes, enhance the adsorption and activation of O2, and regulate Zn. 0.3 Cd 0.7 The effect of the proton microenvironment on the S surface; 2. The Zn prepared by this invention 0.3 Cd 0.7 The S@CFR heterojunction photocatalyst can achieve an H2O2 yield of 6.22 mmol·g under sacrificial agent-free conditions. -1 ·h -1 ; 3. The preparation method of this invention is simple, the process is easy to control, and it is suitable for large-scale industrial production.

[0019] This invention is applicable to the preparation of Zn 0.3 Cd 0.7 S@CFR heterojunction photocatalyst.

[0020] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0021] Figure 1 The XRD patterns of the photocatalysts prepared in Example 1 and Comparative Example 1 of this invention are shown below. Figure 2 Fourier transform infrared images of the photocatalysts prepared in Examples 1-3, Comparative Example 1, and Comparative Example 6 of the present invention. Figure 3 The solid-state photocatalysts prepared in Example 1 and Comparative Example 6 of this invention are respectively... 13 C NMR spectrum; Figure 4 The images shown are transmission electron microscope (TEM) images of the photocatalysts prepared in Examples 1-3 of the present invention, wherein: (a) and (d) are TEM images of Example 2 at 50 nm and 5 nm, respectively; (b) and (e) are TEM images of Example 1 at 50 nm and 5 nm, respectively; and (c) and (f) are TEM images of Example 3 at 50 nm and 5 nm, respectively. Figure 5 The graphs show the H2O2 yield changes over time under visible light (λ>420nm) irradiation for the photocatalysts prepared in Examples 1-3, Comparative Examples 1 and 6 of this invention. Figure 6 The cyclic stability test results are shown for the photocatalysts prepared in Example 1 and Comparative Example 1 of this invention. Figure 7The graphs show the H2O2 yield changes over time under visible light (λ>420nm) irradiation for the photocatalysts prepared in Comparative Examples 1 and 2 of this invention. Figure 8 The graphs show the H2O2 yield changes over time under visible light (λ>420nm) irradiation for the photocatalysts prepared in Comparative Examples 1 and 3 of this invention. Figure 9 The graphs show the H2O2 yield of the photocatalysts prepared in Comparative Examples 4-5 of this invention as a function of time under visible light (λ>420nm) irradiation. Detailed Implementation

[0022] The following embodiments are merely some, not all, of the embodiments of the present invention. Therefore, the detailed descriptions of the embodiments provided below are not intended to limit the scope of the claimed invention, but merely to illustrate selected 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.

[0023] In this invention, unless otherwise specified, all equipment and raw materials are commercially available or commonly used in the industry. The methods described in the following embodiments are conventional methods in the art, unless otherwise specified.

[0024] Example 1 This embodiment prepares a Zn 0.3 Cd 0.7 The preparation process and steps of the S@CFR heterojunction photocatalyst are as follows: S1. Preparation of Zn using a hydrothermal method 0.3 Cd 0.7 S catalyst S11. 0.5268 g (2.4 mmol) of zinc acetate and 1.4926 g (5.6 mmol) of cadmium acetate were placed in a mixed solution of 40 mL of deionized water and ethylenediamine, with a volume ratio of deionized water to ethylenediamine of 1:1. After stirring at room temperature for 20 min, 0.752 g (10 mmol) of thioacetamide was added and stirring was continued for 10 min to obtain the precursor. S12. The precursor was placed in a hydrothermal reactor and reacted at 200℃ for 24 h. After cooling, the precipitate was collected by centrifugation. The precipitate was washed four times with deionized water and anhydrous ethanol, respectively. It was then dried at 60℃ for 24 h and ground to 100-200 mesh to obtain bright yellow Zn. 0.3 Cd 0.7 S powder, i.e., Zn 0.3 Cd 0.7 S catalyst; S2. Preparation of Zn using a hydrothermal method 0.3 Cd 0.7 S@CFR heterojunction photocatalyst 200 mg Zn 0.3 Cd 0.7 The S catalyst was ultrasonically dispersed in 20 mL of ultrapure water at 800 r / min and stirred for 20 min. Then, 80 mg of catechol, 48 μL of 25 wt.% ammonia water, and 120 μL of 37 wt.% formaldehyde aqueous solution were added sequentially. After stirring the mixture for 10 min, it was transferred to a 50 mL hydrothermal reactor for hydrothermal reaction. The hydrothermal temperature was set at 140℃ and the holding time was 6 h. After cooling, the precipitate was collected by centrifugation. The precipitate was washed three times with deionized water and anhydrous ethanol, respectively, dried at 60℃ for 24 h, and ground to 100-200 mesh to obtain Zn. 0.3 Cd 0.7 S@CFR heterojunction photocatalyst, Zn 0.3 Cd 0.7 The mass ratio of S to CFR is 2:1, denoted as Z@C 2:1.

[0025] Example 2 This embodiment prepares a Zn 0.3 Cd 0.7 The preparation process and steps of the S@CFR heterojunction photocatalyst are as follows: S1. Preparation of Zn using a hydrothermal method 0.3 Cd 0.7 S catalyst S11. 0.5268 g (2.4 mmol) of zinc acetate and 1.4926 g (5.6 mmol) of cadmium acetate were placed in a 40 mL mixture of deionized water and ethylenediamine, with a volume ratio of deionized water to ethylenediamine of 1:1. After stirring at room temperature for 25 min, 0.752 g (10 mmol) of thioacetamide was added, and stirring was continued for 12 min to obtain the precursor. S12. The precursor was placed in a hydrothermal reactor and reacted at 202℃ for 23 h. After cooling, the precipitate was collected by centrifugation. The precipitate was washed three times with deionized water and anhydrous ethanol, respectively. It was then dried at 65℃ for 28 h and ground to 100-200 mesh to obtain bright yellow Zn. 0.3 Cd 0.7 S powder, i.e., Zn 0.3 Cd 0.7 S catalyst; S2. Preparation of Zn using a hydrothermal method 0.3 Cd 0.7 S@CFR heterojunction photocatalyst 200 mg Zn0.3 Cd 0.7 The S catalyst was ultrasonically dispersed in 20 mL of ultrapure water at 800 r / min and stirred for 20 min. Then, 40 mg of catechol, 24 μL of 27 wt.% ammonia water, and 60 μL of 37 wt.% formaldehyde aqueous solution were added sequentially. After stirring the mixture for 10 min, it was transferred to a 50 mL hydrothermal reactor for hydrothermal reaction. The hydrothermal temperature was set at 150℃ and the holding time was 7 h. After cooling, the precipitate was collected by centrifugation. The precipitate was washed four times with deionized water and anhydrous ethanol, respectively, dried at 65℃ for 28 h, and ground to 100-200 mesh to obtain Zn. 0.3 Cd 0.7 S@CFR heterojunction photocatalyst, Zn 0.3 Cd 0.7 The mass ratio of S to CFR is 4:1, denoted as Z@C 4:1.

[0026] Example 3 This embodiment prepares a Zn 0.3 Cd 0.7 The preparation process and steps of the S@CFR heterojunction photocatalyst are as follows: S1. Preparation of Zn using a hydrothermal method 0.3 Cd 0.7 S catalyst S11. 0.5268 g (2.4 mmol) of zinc acetate and 1.4926 g (5.6 mmol) of cadmium acetate were placed in a 40 mL mixture of deionized water and ethylenediamine, with a volume ratio of deionized water to ethylenediamine of 1:1. After stirring at room temperature for 30 min, 0.752 g (10 mmol) of thioacetamide was added, and stirring was continued for 15 min to obtain the precursor. S12. The precursor was placed in a hydrothermal reactor and reacted at 205℃ for 22 h. After cooling, the precipitate was collected by centrifugation. The precipitate was washed five times with deionized water and anhydrous ethanol, respectively. It was then dried at 70℃ for 30 h and ground to 100-200 mesh to obtain bright yellow Zn. 0.3 Cd 0.7 S powder, i.e., Zn 0.3 Cd 0.7 S catalyst; S2. Preparation of Zn using a hydrothermal method 0.3 Cd 0.7 S@CFR heterojunction photocatalyst 200 mg Zn 0.3 Cd 0.7The S catalyst was ultrasonically dispersed in 20 mL of ultrapure water at 800 r / min and stirred for 20 min. Then, 120 mg of catechol, 72 μL of ammonia solution with a mass fraction of 28 wt.%, and 180 μL of formaldehyde solution with a mass fraction of 37 wt.% were added sequentially. After stirring the mixture for 10 min, it was transferred to a 50 mL hydrothermal reactor for hydrothermal reaction. The hydrothermal temperature was set at 160℃ and the holding time was 8 h. After cooling, the precipitate was collected by centrifugation. The precipitate was washed five times with deionized water and anhydrous ethanol, respectively, dried at 70℃ for 30 h, and ground to 100-200 mesh to obtain Zn. 0.3 Cd 0.7 S@CFR heterojunction photocatalyst, Zn 0.3 Cd 0.7 The mass ratio of S to CFR is 4:3, denoted as Z@C 4:3.

[0027] Comparative Example To investigate the influence of different raw materials on the performance of the product during the preparation process of this invention, the following comparative experiments were conducted. Different photocatalysts were prepared in the following comparative examples: Comparative Example 1 In this comparative example, a photocatalyst was prepared. The preparation process was similar to that in Example 1, except that step S2 was omitted. The resulting catalyst was Zn. 0.3 Cd 0.7 S catalyst.

[0028] Comparative Example 2 In this comparative example, a photocatalyst was prepared. The preparation process was similar to that in Example 1, except that the molar ratio of zinc acetate to cadmium acetate and thioacetamide was different in step S1, and step S2 was not performed. The details are as follows: Group A: The molar ratio of zinc acetate to cadmium acetate and thioacetamide was 0:1:1.25, and the resulting sample was denoted as CdS; Group B: The molar ratio of zinc acetate to cadmium acetate and thioacetamide was 0.1:0.9:1.25, and the resulting sample was denoted as Zn. 0.1 Cd 0.9 S; Group C: The molar ratio of zinc acetate to cadmium acetate and thioacetamide was 0.5:0.5:1.25, and the resulting sample was denoted as Zn. 0.5 Cd 0.5 S; Group D: The molar ratio of zinc acetate to cadmium acetate and thioacetamide was 0.7:0.3:1.25, and the resulting sample was denoted as Zn. 0.7 Cd 0.3 S; Group E: The molar ratio of zinc acetate to cadmium acetate and thioacetamide was 0.9:0.1:1.25, and the resulting sample was denoted as Zn. 0.9 Cd 0.1 S; Group F: The molar ratio of zinc acetate to cadmium acetate and thioacetamide was 1:0:1.25, and the resulting sample was denoted as ZnS.

[0029] Comparative Example 3 This comparative example uses dopamine hydrochloride (DA), which is rich in catechol groups, to treat Zn. 0.3 Cd 0.7 S was used to coat Zn to prepare a Zn 0.3 Cd 0.7 The specific preparation process of the S@PDA catalyst is as follows: Group G: (1) Preparation of Zn by hydrothermal method 0.3 Cd 0.7 S catalyst The preparation process is the same as step S1 in Example 1; (2) Preparation of Zn 0.3 Cd 0.7 S@PDA catalyst 200 mg of Zn 0.3 Cd 0.7 S was added to Tris-HCl buffer solution (100 mL, pH=8.5), and sonicated for 30 min. 50 mg of DA was slowly added to the mixture, and the mixture was stirred continuously for 12 h at room temperature and in the dark. The resulting mixture was collected by centrifugation, washed four times with water and four times with anhydrous ethanol, dried in a 60°C oven, and ground to 100-200 mesh to obtain Zn. 0.3 Cd 0.7 S@PDA catalyst, denoted as Z@P-12 h; Group H: The preparation method is the same as that of Group G. The only difference is that in step (2), the mixture solution is stirred continuously for 12 h at room temperature and in the dark, instead of stirring for 24 h. The resulting sample is recorded as Z@P-24 h. Group I: The preparation method is the same as that of Group G. The only difference is that in step (2), the mixture solution is stirred continuously at room temperature and in the dark for 12 h instead of stirring for 48 h. The resulting sample is recorded as Z@P-48 h.

[0030] Comparative Example 4 In this comparative example, a photocatalyst was prepared. The preparation process was similar to that in Example 1, except that catechol was not added in step S2.

[0031] Comparative Example 5 In this comparative example, a photocatalyst was prepared. The preparation process was similar to that in Example 1, except that formaldehyde was not added in step S2.

[0032] Comparative Example 6 In this comparative example, a photocatalyst was prepared. The preparation process was similar to that in Example 1, except that Zn was not added in step S2. 0.3 Cd 0.7 S, denoted as CFR.

[0033] Performance testing A series of tests were conducted on the catalysts prepared in Examples 1-3 and Comparative Examples 1-6 of the present invention, as detailed below: like Figure 1 The figures show the XRD patterns of the photocatalysts prepared in Example 1 and Comparative Example 1 of this invention. It can be seen from the figures that Zn... 0.3 Cd 0.7 S catalyst sample at 25.5 ° 27.1 ° 28.8 ° 37.4 ° 44.8 ° 48.9 ° and 52.2 ° Seven distinct diffraction peaks appeared at the location, corresponding to Zn. 2.77 Cd 7.23 S 10 (JCPDS No. 40-0836) crystal planes (100), (002), (101), (102), (110), (103) and (200), and Zn 0.3 Cd 0.7 The diffraction peaks of the S@CFR heterojunction photocatalyst are similar to those of pure Zn in both peak position and peak shape. 0.3 Cd 0.7 The high consistency of S indicates that during the CFR coating process, Zn 0.3 Cd 0.7 The crystal structure of S did not change significantly, and no new crystal phase was formed, indicating that the prepared Zn... 0.3 Cd 0.7 S@CFR heterojunctions exhibit good structural stability.

[0034] like Figure 2 The figures show the Fourier transform infrared (FTIR) images of the photocatalysts prepared in Examples 1-3, Comparative Examples 1 and 6 of this invention. It can be seen from the figures that at approximately 3400 cm⁻¹... -1 The broad absorption band at 2996 cm⁻¹ -1 The nearby absorption peaks correspond to the OH stretching vibration and the methylene CH stretching vibration, respectively. (1620 cm⁻¹)-1 The absorption peak at approximately 1450 cm⁻¹ is attributed to the C=C stretching vibration of the aromatic ring, indicating that the benzene ring structure is preserved. -1 The absorption reflects the presence of aromatic rings and partially bridged (-CH) structures, indicating the involvement of formaldehyde in the reaction and the formation of methylene bridges between catechol units. CFR and Zn 0.3 Cd 0.7 All S@CFR samples exhibited characteristic absorption peaks originating from catechol and linking groups, and the intensity of these characteristic peaks gradually increased with the increase of CFR content.

[0035] like Figure 3 The solid-state photocatalysts prepared in Example 1 and Comparative Example 6 of this invention are respectively... 13 C10 NMR spectra. As can be seen from the figures, both Z@C 2:1 and CFR show clear carbon signals (ag): ortho-aromatic carbon at the phenolic hydroxyl position (145.4 ppm, a), unsubstituted aromatic carbon (131.9 ppm, b), para-carbon at the bridging position (121.1 ppm, c), trace ether bond carbon (66.2 ppm, d), characteristic peaks of the methylene bridge (31.7 ppm, e; 47.3 ppm, f), and terminal methyl carbon (15.8 ppm, g). These signals correspond to the aromatic structure, bridging unit, and residual side chain, respectively, and are highly consistent with the characteristic structures observed in the FTIR spectra.

[0036] like Figure 4 The figures show transmission electron microscopy (TEM) images of the photocatalysts prepared in Examples 1-3 of this invention. As can be seen from the images, the obtained catalysts all exhibit a core-shell structure with a diameter less than 50 nm, wherein the CFR layer is uniformly grown on Zn. 0.3 Cd 0.7 S surface. With increasing CFR content, the coating thickness gradually increases: Z@C 4:1 is approximately 0.8 nm, Z@C 2:1 is approximately 2 nm, while Z@C 4:3 reaches as high as 5 nm. Too thin a coating will result in insufficient catalytic active sites, while too thick a coating will obscure Zn. 0.3 Cd 0.7 Irradiation by S increases electron migration resistance. Only at an appropriate thickness can the CFR layer fully exert its synergistic effect and significantly improve catalytic efficiency.

[0037] like Figure 5 The graphs show the H2O2 yield changes over time under visible light (λ>420nm) irradiation for the photocatalysts prepared in Examples 1-3, Comparative Examples 1 and 6 of this invention. As can be seen from the graphs, Zn... 0.3 Cd 0.7The photocatalytic efficiencies of S, Z@C 4:1, Z@C 2:1, Z@C 4:3, and CFR were 2.81 mmol·g⁻¹. -1 ·h -1 5.29 mmol·g -1 ·h -1 6.22 mmol·g -1 ·h -1 4.12 mmol·g -1 ·h -1 and 0.25 mmol·g -1 ·h -1 CFR-modified Zn 0.3 Cd 0.7 The performance of S@CFR photocatalysts has been significantly improved.

[0038] like Figure 6 The figures show the cycle stability test results of the photocatalysts prepared in Example 1 and Comparative Example 1 of this invention. As can be seen from the figures, after four cycles, the Z@C 2:1 photocatalyst still maintains good stability, while the Zn... 0.3 Cd 0.7 The activity of the S catalyst gradually decreases during multiple cycles, indicating a certain degree of deactivation. Its cycle stability is significantly lower than that of the Z@C 2:1 photocatalyst.

[0039] like Figure 7 The figures show the H2O2 yield changes over time under visible light (λ>420nm) irradiation for the photocatalysts prepared in Comparative Example 2 and Comparative Example 1, respectively. It can be seen from the figures that the Zn prepared in Comparative Example 1... 0.3 Cd 0.7 The S catalyst exhibits the best H2O2 yield (2.81 mmol·g). -1 ·h -1 The efficiency is significantly higher than that of CdS and ZnS photocatalysts with other doping ratios and single components.

[0040] like Figure 8 The figures show the H2O2 yield changes over time under visible light (λ>420nm) irradiation for the photocatalysts prepared in Comparative Examples 1 and 3 of this invention. As can be seen from the figures, compared with pure Zn... 0.3 Cd 0.7Compared to S, the composite photocatalysts modified with dopamine hydrochloride all exhibited enhanced photocatalytic activity for H2O2 generation. In contrast, while PDA also contains a large number of catechol groups, its complex amine structure and strong basicity weaken the effective local proton concentration, thus affecting the protonation step of the key intermediate in the two-electron reduction of O2, leading to insufficient matching of electron and proton transfer kinetics. In contrast, CFR, with its highly active catechol structure, can rapidly donate protons, enhancing the 2e-proton transfer activity. - The selectivity and stability of the ORR pathway make it more suitable as a functional coating layer to promote H2O2 generation.

[0041] like Figure 9 The figures show the H2O2 yield of the photocatalysts prepared in Comparative Examples 4-5 of this invention under visible light (λ>420nm) irradiation as a function of time. It can be seen from the figures that when no catechol was added during the CFR coating process, the H2O2 production in the system after 1 hour was slightly lower than that of pure Zn. 0.3 Cd 0.7 S indicates that formaldehyde itself is unlikely to provide an effective proton supply to the catalyst. In contrast, the catalyst prepared without formaldehyde showed a higher H2O2 formation rate in the early stage of the reaction, indicating that catechol played a positive role in promoting O2 activation and proton supply; however, the H2O2 formation rate of this system tended to plateau in the later stage of the reaction, and the amount of H2O2 produced after 1 hour was similar to that of pure Zn. 0.3 Cd 0.7 The near-perfect S-value is mainly attributed to the lack of structural fixation in catechol, making it difficult to form a stable functional layer, thus limiting its long-term effectiveness. In summary, this result clearly demonstrates that the synergistic construction of catechol and formaldehyde is a key factor in achieving a highly efficient CFR functional coating layer and significantly improving the performance of photocatalytic H2O2 production.

[0042] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A type of Zn 0.3 Cd 0.7 The preparation method of S@CFR heterojunction photocatalyst is characterized by, Follow these steps in sequence: S1. Preparation of Zn using a hydrothermal method 0.3 Cd 0.7 S catalyst S11. Place zinc acetate and cadmium acetate in a mixed solution of 40 mL deionized water and ethylenediamine, with a volume ratio of deionized water to ethylenediamine of 1:

1. Stir at room temperature for 20-30 min, then add thioacetamide and continue stirring for 10-15 min to obtain the precursor. S12. The precursor is placed in a hydrothermal reactor for hydrothermal reaction. After cooling, the precipitate is collected by centrifugation. The precipitate is washed 3-5 times with deionized water and anhydrous ethanol, respectively. After drying, it is ground to 100-200 mesh to obtain bright yellow Zn. 0.3 Cd 0.7 S powder, i.e., Zn 0.3 Cd 0.7 S catalyst; S2. Preparation of Zn using a hydrothermal method 0.3 Cd 0.7 S@CFR heterojunction photocatalyst Zn 0.3 Cd 0.7 The S catalyst was ultrasonically dispersed in ultrapure water, and catechol, ammonia, and formaldehyde were added sequentially. After mixing thoroughly, the mixture was hydrothermally reacted at 140-160℃ for 6-8 h. After cooling, the precipitate was collected by centrifugation, washed 3-5 times with deionized water and anhydrous ethanol, respectively, dried, and ground to 100-200 mesh to obtain Zn. 0.3 Cd 0.7 S@CFR heterojunction photocatalyst.

2. A Zn according to claim 1 0.3 Cd 0.7 The preparation method of S@CFR heterojunction photocatalyst is characterized by, In step S11, the molar ratio of zinc acetate to cadmium acetate and thioacetamide is 0.3:0.7:1.

25.

3. A Zn according to claim 1 0.3 Cd 0.7 The preparation method of S@CFR heterojunction photocatalyst is characterized by, In step S12, the temperature of the hydrothermal reaction is 200-205℃ and the time is 22-24 h.

4. A Zn according to claim 1 0.3 Cd 0.7 The preparation method of S@CFR heterojunction photocatalyst is characterized by, In step S12, the drying temperature is 60-70℃ and the drying time is 24-30 h.

5. A Zn according to claim 1 0.3 Cd 0.7 The preparation method of S@CFR heterojunction photocatalyst is characterized by, In step S2, the Zn 0.3 Cd 0.7 The mass ratio of catalyst S to catechol is 5:(1-3).

6. A Zn according to claim 1 0.3 Cd 0.7 The preparation method of S@CFR heterojunction photocatalyst is characterized by, In step S2, the mass-to-volume ratio of catechol to ammonia is (40-120):(24-72) mg / µL; the mass fraction of ammonia is 25-28 wt.%.

7. A Zn according to claim 1 0.3 Cd 0.7 The preparation method of S@CFR heterojunction photocatalyst is characterized by, In step S2, the mass-to-volume ratio of catechol to formaldehyde is (40-120):(60-180) mg / µL; the formaldehyde is an aqueous solution of formaldehyde with a mass fraction of 37 wt.%.

8. A Zn according to claim 1 0.3 Cd 0.7 The preparation method of S@CFR heterojunction photocatalyst is characterized by, In step S2, the drying temperature is 60-70℃ and the drying time is 24-30 h.

9. A Zn according to any one of claims 1-8 0.3 Cd 0.7 The preparation method of S@CFR heterojunction photocatalyst is characterized by, The obtained Zn 0.3 Cd 0.7 The S@CFR heterojunction photocatalyst has a core-shell structure.

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